L-Carnitine

availability_state

nutrient_deficiency Imported condition classification; unverified.

evidence_span

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experimental_model

Two-factor biotin/carnitine depletion and carnitine repletion in human HepG2 cells

exposure

Separate and combined biotin and carnitine depletion

limitations

This is a cell-culture demonstration of marker masking; it does not validate a diagnostic correction formula in pregnancy or the general population.

nutrient_topic

Biotin research collection; topical membership is not evidence of a direct dietary effect. · Biotin

organism

Homo sapiens

plain_language

A second shortage can hide the laboratory signature of the first.

primary_references

[b7-p25527659] In HepG2 cells, coexisting carnitine deficiency masks important indicators of marginal biotin deficiency. (2015). https://pubmed.ncbi.nlm.nih.gov/25527659/ DOI: 10.3945/jn.114.201343

tissue_or_cell_type

HepG2 hepatoma cells

trigger_kind

nutrient_deficiency Imported condition classification; unverified.

Biotin: carboxylases, recycling, deficiency and nutrient interactions (2026-09-17) · lines 962–973

AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Two-factor biotin/carnitine depletion and carnitine repletion in human HepG2 cells · source_derived_draft · unverified_draft

### b7-carnitine-hides-c5oh Combined biotin and carnitine deficiency largely masked the increase in substrate-derived acylcarnitines observed with isolated biotin deficiency in HepG2 cells. Condition category: nutrient_deficiency nutrient_topic: Biotin research collection; topical membership is not evidence of a direct dietary effect. plain_language: A second shortage can hide the laboratory signature of the first. organism: Homo sapiens tissue_or_cell_type: HepG2 hepatoma cells experimental_model: Two-factor biotin/carnitine depletion and carnitine repletion in human HepG2 cells limitations: This is a cell-culture demonstration of marker masking; it does not validate a diagnostic correction formula in pregnancy or the general population. exposure: Separate and combined biotin and carnitine depletion evidence_span: {"source_cache": "artifacts/biotin-research/25527659.abstract.txt", "locator": "Exact primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "4a368eb2fa2020bb1cabc99b31a3420870a8256886d5934d3d834c90b078238f", "start_char": 0, "end_char": 2372, "text_sha256": "4a368eb2fa2020bb1cabc99b31a3420870a8256886d5934d3d834c90b078238f"} [b7-p25527659] In HepG2 cells, coexisting carnitine deficiency masks important indicators of marginal biotin deficiency. (2015). https://pubmed.ncbi.nlm.nih.gov/25527659/ DOI: 10.3945/jn.114.201343

availability_state

nutrient_deficiency Imported condition classification; unverified.

evidence_span

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experimental_model

Two-factor biotin/carnitine depletion and carnitine repletion in human HepG2 cells

exposure

Separate and combined biotin and carnitine depletion

limitations

This is a cell-culture demonstration of marker masking; it does not validate a diagnostic correction formula in pregnancy or the general population.

nutrient_topic

Biotin research collection; topical membership is not evidence of a direct dietary effect. · Biotin

organism

Homo sapiens

plain_language

Restoring carnitine exposed the unresolved biotin-related bottleneck.

primary_references

[b7-p25527659] In HepG2 cells, coexisting carnitine deficiency masks important indicators of marginal biotin deficiency. (2015). https://pubmed.ncbi.nlm.nih.gov/25527659/ DOI: 10.3945/jn.114.201343

tissue_or_cell_type

HepG2 hepatoma cells

trigger_kind

nutrient_deficiency Imported condition classification; unverified.

Biotin: carboxylases, recycling, deficiency and nutrient interactions (2026-09-17) · lines 975–986

AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Two-factor biotin/carnitine depletion and carnitine repletion in human HepG2 cells · source_derived_draft · unverified_draft

### b7-carnitine-unmasking Carnitine repletion of doubly deficient HepG2 cells increased acetylcarnitine, propionylcarnitine and 3-hydroxyisovalerylcarnitine each by more than 50-fold. Condition category: nutrient_deficiency nutrient_topic: Biotin research collection; topical membership is not evidence of a direct dietary effect. plain_language: Restoring carnitine exposed the unresolved biotin-related bottleneck. organism: Homo sapiens tissue_or_cell_type: HepG2 hepatoma cells experimental_model: Two-factor biotin/carnitine depletion and carnitine repletion in human HepG2 cells limitations: This is a cell-culture demonstration of marker masking; it does not validate a diagnostic correction formula in pregnancy or the general population. exposure: Separate and combined biotin and carnitine depletion evidence_span: {"source_cache": "artifacts/biotin-research/25527659.abstract.txt", "locator": "Exact primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "4a368eb2fa2020bb1cabc99b31a3420870a8256886d5934d3d834c90b078238f", "start_char": 0, "end_char": 2372, "text_sha256": "4a368eb2fa2020bb1cabc99b31a3420870a8256886d5934d3d834c90b078238f"} [b7-p25527659] In HepG2 cells, coexisting carnitine deficiency masks important indicators of marginal biotin deficiency. (2015). https://pubmed.ncbi.nlm.nih.gov/25527659/ DOI: 10.3945/jn.114.201343

evidence_access

Primary abstract

experimental_model

Human nonketotic-hyperglycinemia case series.

limitations

Do not infer a general glycine/carnitine supplement combination or a dosing recommendation.

nutrient_topic

Glycine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · Glycine

plain_language

A measured treatment-associated nutrient deficit responded to replacement.

primary_references

Benzoate therapy and carnitine deficiency in non-ketotic hyperglycinemia. · 1995 · https://pubmed.ncbi.nlm.nih.gov/8585564/ · DOI 10.1002/ajmg.1320590410

Glycine: supply, one-carbon allocation, receptors and cross-nutrient mechanisms (2026-09-19) · lines 322–328

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Human nonketotic-hyperglycinemia case series. · source_derived_draft · unverified_draft

## glycine-benzoate-carnitine-repletion A measured treatment-associated nutrient deficit responded to replacement. L-carnitine treatment normalized plasma free carnitine in the reported benzoate-treated patients; increased glycine conjugation was a tendency rather than a definitive outcome. Model: Human nonketotic-hyperglycinemia case series. Limitations: Do not infer a general glycine/carnitine supplement combination or a dosing recommendation. Evidence access: Primary abstract Benzoate therapy and carnitine deficiency in non-ketotic hyperglycinemia. · 1995 · https://pubmed.ncbi.nlm.nih.gov/8585564/ · DOI 10.1002/ajmg.1320590410

evidence_access

Primary full-text Figure 4

experimental_model

Isolated mouse muscle mitochondria; pyruvate-only respiratory context and direct PDH assay.

limitations

The effect is context-dependent; liver mitochondria also lacked the stimulation.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

Carnitine needs the acetyl-transfer enzyme to relieve this brake on glucose oxidation.

primary_references

Muscle-specific deletion of carnitine acetyltransferase compromises glucose tolerance and metabolic flexibility. · 2012 · https://pubmed.ncbi.nlm.nih.gov/22560225/ · DOI 10.1016/j.cmet.2012.04.005

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 162–168

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Isolated mouse muscle mitochondria; pyruvate-only respiratory context and direct PDH assay. · source_derived_draft · unverified_draft

## l-carnitine-crat-pdh Carnitine needs the acetyl-transfer enzyme to relieve this brake on glucose oxidation. Adding carnitine stimulated PDH activity 1.8-fold in control muscle mitochondria but did not stimulate it in Crat-null mitochondria. Model: Isolated mouse muscle mitochondria; pyruvate-only respiratory context and direct PDH assay. Limitations: The effect is context-dependent; liver mitochondria also lacked the stimulation. Evidence access: Primary full-text Figure 4 Muscle-specific deletion of carnitine acetyltransferase compromises glucose tolerance and metabolic flexibility. · 2012 · https://pubmed.ncbi.nlm.nih.gov/22560225/ · DOI 10.1016/j.cmet.2012.04.005

evidence_access

Primary abstract

experimental_model

Same human trial, higher-intensity exercise phase.

limitations

Different workload explains the different direction; this is not a contradiction.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

At higher demand, the same intervention supported glucose oxidation.

primary_references

Chronic oral ingestion of L-carnitine and carbohydrate increases muscle carnitine content and alters muscle fuel metabolism during exercise in humans. · 2011 · https://pubmed.ncbi.nlm.nih.gov/21224234/ · DOI 10.1113/jphysiol.2010.201343

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 202–208

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Same human trial, higher-intensity exercise phase. · source_derived_draft · unverified_draft

## l-carnitine-high-work-pdc At higher demand, the same intervention supported glucose oxidation. At 80% exercise intensity after loading, muscle PDC activation was 38% higher and lactate was lower than in controls. Model: Same human trial, higher-intensity exercise phase. Limitations: Different workload explains the different direction; this is not a contradiction. Evidence access: Primary abstract Chronic oral ingestion of L-carnitine and carbohydrate increases muscle carnitine content and alters muscle fuel metabolism during exercise in humans. · 2011 · https://pubmed.ncbi.nlm.nih.gov/21224234/ · DOI 10.1113/jphysiol.2010.201343

evidence_access

Primary abstract

experimental_model

157 participants with metabolic syndrome and pre-existing plaque; randomized trial.

limitations

A six-month imaging endpoint is not a lifetime clinical-event result.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

The human trial did not show a plaque-volume benefit or increase.

primary_references

Progression of atherosclerosis with carnitine supplementation: a randomized controlled trial in the metabolic syndrome. · 2022 · https://pubmed.ncbi.nlm.nih.gov/35366920/ · DOI 10.1186/s12986-022-00661-9

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 426–432

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · 157 participants with metabolic syndrome and pre-existing plaque; randomized trial. · source_derived_draft · unverified_draft

## l-carnitine-human-plaque-null The human trial did not show a plaque-volume benefit or increase. Two grams/day carnitine for six months did not significantly change the primary total-carotid-plaque-volume outcome versus placebo. Model: 157 participants with metabolic syndrome and pre-existing plaque; randomized trial. Limitations: A six-month imaging endpoint is not a lifetime clinical-event result. Evidence access: Primary abstract Progression of atherosclerosis with carnitine supplementation: a randomized controlled trial in the metabolic syndrome. · 2022 · https://pubmed.ncbi.nlm.nih.gov/35366920/ · DOI 10.1186/s12986-022-00661-9

evidence_access

Primary abstract

experimental_model

Same 157-participant randomized trial; secondary endpoints.

limitations

Different endpoints are not a contradiction; the study does not isolate TMAO as the mediator.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

A different vascular endpoint showed a concerning signal.

primary_references

Progression of atherosclerosis with carnitine supplementation: a randomized controlled trial in the metabolic syndrome. · 2022 · https://pubmed.ncbi.nlm.nih.gov/35366920/ · DOI 10.1186/s12986-022-00661-9

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 434–440

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Same 157-participant randomized trial; secondary endpoints. · source_derived_draft · unverified_draft

## l-carnitine-human-stenosis A different vascular endpoint showed a concerning signal. The carnitine arm in the same trial had greater progression of carotid stenosis than placebo, reported as a 9.3% difference; total and LDL cholesterol also increased. Model: Same 157-participant randomized trial; secondary endpoints. Limitations: Different endpoints are not a contradiction; the study does not isolate TMAO as the mediator. Evidence access: Primary abstract Progression of atherosclerosis with carnitine supplementation: a randomized controlled trial in the metabolic syndrome. · 2022 · https://pubmed.ncbi.nlm.nih.gov/35366920/ · DOI 10.1186/s12986-022-00661-9

evidence_access

Primary abstract

experimental_model

Same 24-week trial; muscle biopsies during cycling.

limitations

Glycogen sparing is compatible with more fat use, but is not proof of body-fat loss.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

The fuel effect changed with exercise demand.

primary_references

Chronic oral ingestion of L-carnitine and carbohydrate increases muscle carnitine content and alters muscle fuel metabolism during exercise in humans. · 2011 · https://pubmed.ncbi.nlm.nih.gov/21224234/ · DOI 10.1113/jphysiol.2010.201343

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 194–200

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Same 24-week trial; muscle biopsies during cycling. · source_derived_draft · unverified_draft

## l-carnitine-low-work-glycogen The fuel effect changed with exercise demand. After the loading regimen, muscle glycogen use at 50% exercise intensity was 55% lower than in carbohydrate-only controls. Model: Same 24-week trial; muscle biopsies during cycling. Limitations: Glycogen sparing is compatible with more fat use, but is not proof of body-fat loss. Evidence access: Primary abstract Chronic oral ingestion of L-carnitine and carbohydrate increases muscle carnitine content and alters muscle fuel metabolism during exercise in humans. · 2011 · https://pubmed.ncbi.nlm.nih.gov/21224234/ · DOI 10.1113/jphysiol.2010.201343

evidence_access

Primary abstract

experimental_model

Omnivores and vegans/vegetarians; labeled oral substrates, cultures and antibiotics.

limitations

This host-microbe direction differs from human BBOX1 synthesis of carnitine; no single universal flux.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

Gut microbes can send carnitine into a different chemical pathway.

primary_references

l-Carnitine in omnivorous diets induces an atherogenic gut microbial pathway in humans. · 2019 · https://pubmed.ncbi.nlm.nih.gov/30530985/ · DOI 10.1172/JCI94601

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 346–352

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Omnivores and vegans/vegetarians; labeled oral substrates, cultures and antibiotics. · source_derived_draft · unverified_draft

## l-carnitine-microbial-first-step Gut microbes can send carnitine into a different chemical pathway. Human tracer, fecal culture and antibiotic studies supported microbial conversion of carnitine to gamma-butyrobetaine, occurring rapidly in both dietary groups. Model: Omnivores and vegans/vegetarians; labeled oral substrates, cultures and antibiotics. Limitations: This host-microbe direction differs from human BBOX1 synthesis of carnitine; no single universal flux. Evidence access: Primary abstract l-Carnitine in omnivorous diets induces an atherogenic gut microbial pathway in humans. · 2019 · https://pubmed.ncbi.nlm.nih.gov/30530985/ · DOI 10.1172/JCI94601

evidence_access

Primary abstract

experimental_model

Human isotope challenges before/after at least two months of supplementation.

limitations

A metabolite-production study does not prove cardiovascular events from a given supplement dose.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

The response depends partly on microbial adaptation and diet.

primary_references

l-Carnitine in omnivorous diets induces an atherogenic gut microbial pathway in humans. · 2019 · https://pubmed.ncbi.nlm.nih.gov/30530985/ · DOI 10.1172/JCI94601

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 354–360

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Human isotope challenges before/after at least two months of supplementation. · source_derived_draft · unverified_draft

## l-carnitine-microbial-induction The response depends partly on microbial adaptation and diet. Chronic carnitine exposure increased microbial gamma-butyrobetaine-to-TMA conversion; baseline labeled TMAO generation was greater in omnivores. Model: Human isotope challenges before/after at least two months of supplementation. Limitations: A metabolite-production study does not prove cardiovascular events from a given supplement dose. Evidence access: Primary abstract l-Carnitine in omnivorous diets induces an atherogenic gut microbial pathway in humans. · 2019 · https://pubmed.ncbi.nlm.nih.gov/30530985/ · DOI 10.1172/JCI94601

evidence_access

Primary abstract

experimental_model

Atherosclerosis-prone mice; dietary intervention with microbiota suppression comparison.

limitations

Human cohort associations in the same paper are not randomized supplement effects.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

One mouse study linked carnitine metabolism to more arterial lesions.

primary_references

Intestinal microbiota metabolism of L-carnitine, a nutrient in red meat, promotes atherosclerosis. · 2013 · https://pubmed.ncbi.nlm.nih.gov/23563705/ · DOI 10.1038/nm.3145

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 410–416

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Atherosclerosis-prone mice; dietary intervention with microbiota suppression comparison. · source_derived_draft · unverified_draft

## l-carnitine-mouse-atheroma-increase One mouse study linked carnitine metabolism to more arterial lesions. Chronic dietary carnitine increased atherosclerosis in the studied mice; concurrent microbial suppression prevented that increase. Model: Atherosclerosis-prone mice; dietary intervention with microbiota suppression comparison. Limitations: Human cohort associations in the same paper are not randomized supplement effects. Evidence access: Primary abstract Intestinal microbiota metabolism of L-carnitine, a nutrient in red meat, promotes atherosclerosis. · 2013 · https://pubmed.ncbi.nlm.nih.gov/23563705/ · DOI 10.1038/nm.3145

evidence_access

Primary abstract

experimental_model

Fourteen healthy men; 2 g L-carnitine L-tartrate plus 80 g carbohydrate twice daily.

limitations

Tartrate mass is not pure carnitine mass; the study does not isolate carnitine without carbohydrate.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

Human muscle loading depended on the tested intake pattern and time.

primary_references

Chronic oral ingestion of L-carnitine and carbohydrate increases muscle carnitine content and alters muscle fuel metabolism during exercise in humans. · 2011 · https://pubmed.ncbi.nlm.nih.gov/21224234/ · DOI 10.1113/jphysiol.2010.201343

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 186–192

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Fourteen healthy men; 2 g L-carnitine L-tartrate plus 80 g carbohydrate twice daily. · source_derived_draft · unverified_draft

## l-carnitine-muscle-loading Human muscle loading depended on the tested intake pattern and time. Twice-daily carnitine tartrate plus carbohydrate for 24 weeks increased muscle total carnitine by 21%; carbohydrate-only controls did not show loading. Model: Fourteen healthy men; 2 g L-carnitine L-tartrate plus 80 g carbohydrate twice daily. Limitations: Tartrate mass is not pure carnitine mass; the study does not isolate carnitine without carbohydrate. Evidence access: Primary abstract Chronic oral ingestion of L-carnitine and carbohydrate increases muscle carnitine content and alters muscle fuel metabolism during exercise in humans. · 2011 · https://pubmed.ncbi.nlm.nih.gov/21224234/ · DOI 10.1113/jphysiol.2010.201343

evidence_access

Primary abstract

experimental_model

Six healthy adults on a low-carnitine diet; oral and IV comparisons.

limitations

Supplement boluses do not establish food bioavailability or tissue loading.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

A larger oral dose did not yield proportionally more circulating carnitine.

primary_references

Pharmacokinetics of bolus intravenous and oral doses of L-carnitine in healthy subjects. · 1988 · https://pubmed.ncbi.nlm.nih.gov/3220097/ · DOI 10.1007/BF00555510

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 34–40

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Six healthy adults on a low-carnitine diet; oral and IV comparisons. · source_derived_draft · unverified_draft

## l-carnitine-oral-dose A larger oral dose did not yield proportionally more circulating carnitine. Single oral L-carnitine doses had estimated bioavailability of 16% at 2 g and 5% at 6 g, with similar plasma exposure despite the higher dose. Model: Six healthy adults on a low-carnitine diet; oral and IV comparisons. Limitations: Supplement boluses do not establish food bioavailability or tissue loading. Evidence access: Primary abstract Pharmacokinetics of bolus intravenous and oral doses of L-carnitine in healthy subjects. · 1988 · https://pubmed.ncbi.nlm.nih.gov/3220097/ · DOI 10.1007/BF00555510

evidence_access

Primary abstract

experimental_model

Small human metabolic intervention; three healthy comparison subjects excreted mainly acetylcarnitine.

limitations

Restoration of mitochondrial free CoA was a proposed mechanism, not directly measured.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

Acyl-group disposal can consume and export carnitine.

primary_references

L-carnitine enhances excretion of propionyl coenzyme A as propionylcarnitine in propionic acidemia. · 1984 · https://pubmed.ncbi.nlm.nih.gov/6725560/ · DOI 10.1172/JCI111387

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 250–256

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Small human metabolic intervention; three healthy comparison subjects excreted mainly acetylcarnitine. · source_derived_draft · unverified_draft

## l-carnitine-organic-acid-export Acyl-group disposal can consume and export carnitine. Giving L-carnitine to three patients with propionic acidemia increased urinary propionylcarnitine, verified by mass spectrometry. Model: Small human metabolic intervention; three healthy comparison subjects excreted mainly acetylcarnitine. Limitations: Restoration of mitochondrial free CoA was a proposed mechanism, not directly measured. Evidence access: Primary abstract L-carnitine enhances excretion of propionyl coenzyme A as propionylcarnitine in propionic acidemia. · 1984 · https://pubmed.ncbi.nlm.nih.gov/6725560/ · DOI 10.1172/JCI111387

availability_state

machinery_impairment Imported condition classification; unverified.

evidence_access

Primary abstract

experimental_model

Single human case and long-term follow-up.

limitations

One case, no untreated comparator; not proof of general cardiovascular benefit.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

Treating a confirmed transport disorder can have a different role from general supplementation.

primary_references

Primary systemic carnitine deficiency: a Turkish case with a novel homozygous SLC22A5 mutation and 14 years follow-up. · 2015 · https://pubmed.ncbi.nlm.nih.gov/26030785/ · DOI 10.1515/jpem-2014-0528

trigger_kind

machinery_impairment Imported condition classification; unverified.

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 82–88

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Single human case and long-term follow-up. · source_derived_draft · unverified_draft

## l-carnitine-primary-heart Treating a confirmed transport disorder can have a different role from general supplementation. In a reported patient with homozygous SLC22A5-associated primary carnitine deficiency and a cardiac presentation, cardiac function remained normal during 14 years of oral carnitine treatment. Model: Single human case and long-term follow-up. Limitations: One case, no untreated comparator; not proof of general cardiovascular benefit. Evidence access: Primary abstract Primary systemic carnitine deficiency: a Turkish case with a novel homozygous SLC22A5 mutation and 14 years follow-up. · 2015 · https://pubmed.ncbi.nlm.nih.gov/26030785/ · DOI 10.1515/jpem-2014-0528

evidence_access

Primary abstract

experimental_model

Five groups of ten; randomized, double-blind placebo-controlled treatment periods.

limitations

Specific iatrogenic hyperthyroidism context; does not justify changing thyroid medication or establish universal safety.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

A small clinical trial tested peripheral thyroid-hormone effects.

primary_references

Usefulness of L-carnitine, a naturally occurring peripheral antagonist of thyroid hormone action, in iatrogenic hyperthyroidism: a randomized, double-blind, placebo-controlled clinical trial. · 2001 · https://pubmed.ncbi.nlm.nih.gov/11502782/ · DOI 10.1210/jcem.86.8.7747

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 306–312

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Five groups of ten; randomized, double-blind placebo-controlled treatment periods. · source_derived_draft · unverified_draft

## l-carnitine-thyroid-clinical A small clinical trial tested peripheral thyroid-hormone effects. In a six-month trial of 50 women on fixed TSH-suppressive thyroxine, 2 or 4 g/day carnitine reduced or limited several hyperthyroid symptoms during treatment periods. Model: Five groups of ten; randomized, double-blind placebo-controlled treatment periods. Limitations: Specific iatrogenic hyperthyroidism context; does not justify changing thyroid medication or establish universal safety. Evidence access: Primary abstract Usefulness of L-carnitine, a naturally occurring peripheral antagonist of thyroid hormone action, in iatrogenic hyperthyroidism: a randomized, double-blind, placebo-controlled clinical trial. · 2001 · https://pubmed.ncbi.nlm.nih.gov/11502782/ · DOI 10.1210/jcem.86.8.7747

evidence_access

Primary abstract

experimental_model

Human HepG2 uptake assay; high millimolar exposures.

limitations

No direct inhibition of T3 binding to isolated nuclei was observed; not proof of iodine depletion or routine-dose hypothyroidism.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

Carnitine can affect thyroid-hormone access to the nucleus in cell experiments.

primary_references

Carnitine is a naturally occurring inhibitor of thyroid hormone nuclear uptake. · 2000 · https://pubmed.ncbi.nlm.nih.gov/11201848/ · DOI 10.1089/thy.2000.10.1043

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 298–304

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Human HepG2 uptake assay; high millimolar exposures. · source_derived_draft · unverified_draft

## l-carnitine-thyroid-nuclear Carnitine can affect thyroid-hormone access to the nucleus in cell experiments. Adding 10 mM carnitine reduced nuclear T3 uptake in human HepG2 cells by about 35%; 50 mM produced a larger reduction. Model: Human HepG2 uptake assay; high millimolar exposures. Limitations: No direct inhibition of T3 binding to isolated nuclei was observed; not proof of iodine depletion or routine-dose hypothyroidism. Evidence access: Primary abstract Carnitine is a naturally occurring inhibitor of thyroid hormone nuclear uptake. · 2000 · https://pubmed.ncbi.nlm.nih.gov/11201848/ · DOI 10.1089/thy.2000.10.1043

availability_state

nutrient_deficiency Imported condition classification; unverified.

evidence_access

Primary abstract

experimental_model

Cachectic 69-year-old woman, 12 years after gastric bypass; supervised diagnostic fast.

limitations

Single case; impaired mitochondrial transport was inferred. This is not a general carnitine supplement recommendation.

nutrient_topic

Fasting physiological-state collection; human protocols, cellular deprivation and refeeding are distinguished. · Fasting / abstention from energy intake

plain_language

Fat release was not enough when the next transport step appeared limited.

primary_references

Fasting hypoglycaemia secondary to carnitine deficiency: a late consequence of gastric bypass. · 2021 · https://pubmed.ncbi.nlm.nih.gov/34281938/ · DOI 10.1136/bcr-2021-241703

trigger_kind

nutrient_deficiency Imported condition classification; unverified.

Fasting: fuel switching, nutrient sensing, ketone signaling, nutrient dependencies and refeeding (2026-09-18) · lines 168–174

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Cachectic 69-year-old woman, 12 years after gastric bypass; supervised diagnostic fast. · source_derived_draft · unverified_draft

## fast-carnitine-case Fat release was not enough when the next transport step appeared limited. A post-bypass patient had fasting hypoglycemia, low BHB and high free fatty acids; carnitine replacement resolved fasting hypoglycemia. Model: Cachectic 69-year-old woman, 12 years after gastric bypass; supervised diagnostic fast. Limitations: Single case; impaired mitochondrial transport was inferred. This is not a general carnitine supplement recommendation. Evidence access: Primary abstract Fasting hypoglycaemia secondary to carnitine deficiency: a late consequence of gastric bypass. · 2021 · https://pubmed.ncbi.nlm.nih.gov/34281938/ · DOI 10.1136/bcr-2021-241703

cross_nutrient

true

experimental_model

Human PANK2 in 293T-cell lysates and purified enzyme assays

exposure

Primary Fig. 4B purified-enzyme assay; carnitine concentration range not extracted.

limitations

The same paper observed free-carnitine activation in lysate preparations at higher concentrations, so the purified-enzyme negative result must not be generalized to every lysate condition. Neither assay tests clinical carnitine supplementation.

nutrient_topic

Pantothenic acid (vitamin B5) research collection; topical membership is not evidence of a direct dietary effect. · Pantothenate (vitamin B5)

organism

Homo sapiens

plain_language

The purified enzyme did not respond directly to free carnitine.

primary_references

[b5-bio-pank2reg] Activation of human mitochondrial pantothenate kinase 2 by palmitoylcarnitine. (2007). https://pubmed.ncbi.nlm.nih.gov/17242360/ DOI: 10.1073/pnas.0607621104

tissue_or_cell_type

Purified recombinant protein; no intact tissue

Pantothenic acid (vitamin B5): coenzyme A, deficiency and nutrient interactions (2026-09-17) · lines 626–637

AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Human PANK2 in 293T-cell lysates and purified enzyme assays · source_derived_draft · unverified_draft

### b5-bio-pank2-free-carnitine Free carnitine did not activate purified human PANK2 in the experiment shown in Fig. 4B. Condition category: normal nutrient_topic: Pantothenic acid (vitamin B5) research collection; topical membership is not evidence of a direct dietary effect. plain_language: The purified enzyme did not respond directly to free carnitine. organism: Homo sapiens tissue_or_cell_type: Purified recombinant protein; no intact tissue experimental_model: Human PANK2 in 293T-cell lysates and purified enzyme assays limitations: The same paper observed free-carnitine activation in lysate preparations at higher concentrations, so the purified-enzyme negative result must not be generalized to every lysate condition. Neither assay tests clinical carnitine supplementation. exposure: Primary Fig. 4B purified-enzyme assay; carnitine concentration range not extracted. cross_nutrient: true [b5-bio-pank2reg] Activation of human mitochondrial pantothenate kinase 2 by palmitoylcarnitine. (2007). https://pubmed.ncbi.nlm.nih.gov/17242360/ DOI: 10.1073/pnas.0607621104

evidence_span

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experimental_model

Cloning and functional expression

exposure

Radiolabeled carnitine uptake and sodium dependence

limitations

Expression assay; dietary sodium intake, mitochondrial fatty-acid oxidation and clinical supplementation were not directly tested.

nutrient_topic

Sodium research collection; topical membership is not evidence of a direct dietary effect. · Sodium

organism

Human OCTN2 in HEK293 cells

plain_language

The sodium gradient helps bring carnitine into cells.

primary_references

[sodium-p9685390] Molecular and functional identification of sodium ion-dependent, high affinity human carnitine transporter OCTN2. (1998). https://pubmed.ncbi.nlm.nih.gov/9685390/ DOI: 10.1074/jbc.273.32.20378

tissue_or_cell_type

Cell plasma membrane

transport_effect

raises Expression increased sodium-dependent carnitine uptake.

transport_pool

the expressing cell Expression increased sodium-dependent carnitine uptake.

Sodium: gradients, nutrient transport, fluid regulation and loss states (2026-09-17) · lines 616–627

AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Cloning and functional expression · source_derived_draft · unverified_draft

### sodium-octn2-carnitine Human OCTN2 expression increased sodium-dependent carnitine uptake with an apparent Km of 4.34 micromolar. Condition category: normal nutrient_topic: Sodium research collection; topical membership is not evidence of a direct dietary effect. plain_language: The sodium gradient helps bring carnitine into cells. organism: Human OCTN2 in HEK293 cells tissue_or_cell_type: Cell plasma membrane experimental_model: Cloning and functional expression limitations: Expression assay; dietary sodium intake, mitochondrial fatty-acid oxidation and clinical supplementation were not directly tested. exposure: Radiolabeled carnitine uptake and sodium dependence evidence_span: {"source_cache": "artifacts/sodium-research/9685390.abstract.txt", "locator": "Exact primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "08cdedaad32299795a52b81183d565d2b476b7a190b2af7b950c829f8c11ddf6", "start_char": 0, "end_char": 1549, "text_sha256": "08cdedaad32299795a52b81183d565d2b476b7a190b2af7b950c829f8c11ddf6"} [sodium-p9685390] Molecular and functional identification of sodium ion-dependent, high affinity human carnitine transporter OCTN2. (1998). https://pubmed.ncbi.nlm.nih.gov/9685390/ DOI: 10.1074/jbc.273.32.20378

evidence_access

Primary abstract

experimental_model

Metabolomic screening and uptake assays in transfected human cells.

limitations

Higher Km for ergothioneine, carnitine and carnosine than their established carriers; substrate sharing does not prove competition at dietary exposures.

nutrient_topic

Ergothioneine collection; molecular form, preparation, species, exposure and manipulation remain explicit. · L-Ergothioneine

plain_language

An additional carrier connects carnitine to the transport network.

primary_references

Deorphaning a solute carrier 22 family member, SLC22A15, through functional genomic studies. · 2020 · https://pubmed.ncbi.nlm.nih.gov/33124720/ · DOI 10.1096/fj.202001497R

transport_effect

raises Expression enabled uptake in HEK293 substrate assays.

transport_pool

the expressing cell Expression enabled uptake in HEK293 substrate assays.

Ergothioneine: transport, redox chemistry and cross-nutrient mechanisms (2026-09-19) · lines 64–70

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Metabolomic screening and uptake assays in transfected human cells. · source_derived_draft · unverified_draft

## ergothioneine-slc22a15-carnitine An additional carrier connects carnitine to the transport network. Human SLC22A15 expression enabled uptake of carnitine in HEK293 substrate assays. Model: Metabolomic screening and uptake assays in transfected human cells. Limitations: Higher Km for ergothioneine, carnitine and carnosine than their established carriers; substrate sharing does not prove competition at dietary exposures. Evidence access: Primary abstract Deorphaning a solute carrier 22 family member, SLC22A15, through functional genomic studies. · 2020 · https://pubmed.ncbi.nlm.nih.gov/33124720/ · DOI 10.1096/fj.202001497R

evidence_access

Primary abstract

experimental_model

Wild-type human SLC22A4/SLC22A5 transport comparison.

limitations

Assay-specific discrimination; engineered mutants have different properties.

nutrient_topic

Ergothioneine collection; molecular form, preparation, species, exposure and manipulation remain explicit. · L-Ergothioneine

plain_language

The historical carrier name does not mean carnitine uses this route.

primary_references

Substrate discrimination by ergothioneine transporter SLC22A4 and carnitine transporter SLC22A5: gain-of-function by interchange of selected amino acids. · 2009 · https://pubmed.ncbi.nlm.nih.gov/19814996/ · DOI 10.1016/j.bbamem.2009.09.019

Ergothioneine: transport, redox chemistry and cross-nutrient mechanisms (2026-09-19) · lines 32–38

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Wild-type human SLC22A4/SLC22A5 transport comparison. · source_derived_draft · unverified_draft

## ergothioneine-slc22a4-not-carnitine The historical carrier name does not mean carnitine uses this route. Wild-type human SLC22A4 did not mediate carnitine transport in the comparative HEK293 expression assay. Model: Wild-type human SLC22A4/SLC22A5 transport comparison. Limitations: Assay-specific discrimination; engineered mutants have different properties. Evidence access: Primary abstract Substrate discrimination by ergothioneine transporter SLC22A4 and carnitine transporter SLC22A5: gain-of-function by interchange of selected amino acids. · 2009 · https://pubmed.ncbi.nlm.nih.gov/19814996/ · DOI 10.1016/j.bbamem.2009.09.019

evidence_access

Primary abstract

experimental_model

Mouse colon transporter expressed in human retinal pigment epithelial cells and frog oocytes.

limitations

The transporter is mouse-derived even in a human host cell; dietary sodium/chloride effects were not tested.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

A second uptake route couples carnitine to both salt ions.

primary_references

Na+- and Cl--coupled active transport of carnitine by the amino acid transporter ATB(0,+) from mouse colon expressed in HRPE cells and Xenopus oocytes. · 2001 · https://pubmed.ncbi.nlm.nih.gov/11306651/ · DOI 10.1111/j.1469-7793.2001.0297f.x

transport_effect

raises Carnitine transport requiring both sodium and chloride, which is inward.

transport_pool

the expressing cell Carnitine transport requiring both sodium and chloride, which is inward.

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 466–472

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Mouse colon transporter expressed in human retinal pigment epithelial cells and frog oocytes. · source_derived_draft · unverified_draft

## l-carnitine-atb-carnitine A second uptake route couples carnitine to both salt ions. Expressing mouse ATB0,+ in HRPE cells enabled carnitine transport requiring both sodium and chloride; activation analysis was consistent with two sodium ions and one chloride ion. Model: Mouse colon transporter expressed in human retinal pigment epithelial cells and frog oocytes. Limitations: The transporter is mouse-derived even in a human host cell; dietary sodium/chloride effects were not tested. Evidence access: Primary abstract Na+- and Cl--coupled active transport of carnitine by the amino acid transporter ATB(0,+) from mouse colon expressed in HRPE cells and Xenopus oocytes. · 2001 · https://pubmed.ncbi.nlm.nih.gov/11306651/ · DOI 10.1111/j.1469-7793.2001.0297f.x

evidence_access

Primary abstract

experimental_model

Recombinant rat carrier and proteoliposomes.

limitations

Transport reconstitution is not a human flux measurement.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

A separate carrier moves the loaded molecule across the inner membrane.

primary_references

Bacterial overexpression, purification, and reconstitution of the carnitine/acylcarnitine carrier from rat liver mitochondria. · 1998 · https://pubmed.ncbi.nlm.nih.gov/9731180/ · DOI 10.1006/bbrc.1998.9197

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 98–104

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Recombinant rat carrier and proteoliposomes. · source_derived_draft · unverified_draft

## l-carnitine-cact-exchange A separate carrier moves the loaded molecule across the inner membrane. Purified rat mitochondrial CACT reconstituted into liposomes exchanged carnitine and transported acylcarnitines of several chain lengths. Model: Recombinant rat carrier and proteoliposomes. Limitations: Transport reconstitution is not a human flux measurement. Evidence access: Primary abstract Bacterial overexpression, purification, and reconstitution of the carnitine/acylcarnitine carrier from rat liver mitochondria. · 1998 · https://pubmed.ncbi.nlm.nih.gov/9731180/ · DOI 10.1006/bbrc.1998.9197

evidence_access

Primary abstract

experimental_model

Purified bacterial enzyme complex, spectroscopy and mutagenesis.

limitations

This aerobic chemistry is not assumed to dominate the anoxic colon.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

A separate microbial route needs oxygen.

primary_references

Carnitine metabolism in the human gut: characterization of the two-component carnitine monooxygenase CntAB from Acinetobacter baumannii. · 2020 · https://pubmed.ncbi.nlm.nih.gov/32694223/ · DOI 10.1074/jbc.RA120.014266

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 386–392

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Purified bacterial enzyme complex, spectroscopy and mutagenesis. · source_derived_draft · unverified_draft

## l-carnitine-cnta-cleavage A separate microbial route needs oxygen. Acinetobacter baumannii CntA/CntB catalyzed oxygen-dependent carnitine cleavage to TMA and malic semialdehyde. Model: Purified bacterial enzyme complex, spectroscopy and mutagenesis. Limitations: This aerobic chemistry is not assumed to dominate the anoxic colon. Evidence access: Primary abstract Carnitine metabolism in the human gut: characterization of the two-component carnitine monooxygenase CntAB from Acinetobacter baumannii. · 2020 · https://pubmed.ncbi.nlm.nih.gov/32694223/ · DOI 10.1074/jbc.RA120.014266

evidence_access

Primary abstract and reviewed UniProt catalytic-reaction record

experimental_model

Human heart/muscle isoform in Pichia mitochondria; canonical reaction also recorded in UniProt Q92523/Rhea 12661.

limitations

This isoform assay does not measure whole-body fat loss.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

The outer-membrane enzyme loads a fatty-acid group onto carnitine.

primary_references

Functional studies of yeast-expressed human heart muscle carnitine palmitoyltransferase I. · 1997 · https://pubmed.ncbi.nlm.nih.gov/9344464/ · DOI 10.1006/abbi.1997.0314

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 90–96

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Human heart/muscle isoform in Pichia mitochondria; canonical reaction also recorded in UniProt Q92523/Rhea 12661. · source_derived_draft · unverified_draft

## l-carnitine-cpt1-transfer The outer-membrane enzyme loads a fatty-acid group onto carnitine. Human CPT1B expressed in yeast catalyzed transfer from palmitoyl-CoA onto carnitine, forming palmitoylcarnitine and releasing CoA. Model: Human heart/muscle isoform in Pichia mitochondria; canonical reaction also recorded in UniProt Q92523/Rhea 12661. Limitations: This isoform assay does not measure whole-body fat loss. Evidence access: Primary abstract and reviewed UniProt catalytic-reaction record Functional studies of yeast-expressed human heart muscle carnitine palmitoyltransferase I. · 1997 · https://pubmed.ncbi.nlm.nih.gov/9344464/ · DOI 10.1006/abbi.1997.0314

evidence_access

Primary abstract

experimental_model

Human transporter cloning, oocyte transport and tissue immunohistochemistry.

limitations

Transport/localization do not establish improved fertility from carnitine supplements.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

A distinct transporter connects carnitine with the reproductive tract.

primary_references

Molecular identification of a novel carnitine transporter specific to human testis. Insights into the mechanism of carnitine recognition. · 2002 · https://pubmed.ncbi.nlm.nih.gov/12089149/ · DOI 10.1074/jbc.M203883200

transport_effect

raises High-affinity carnitine transport measured in expressing oocytes.

transport_pool

the expressing cell High-affinity carnitine transport measured in expressing oocytes.

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 482–488

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Human transporter cloning, oocyte transport and tissue immunohistochemistry. · source_derived_draft · unverified_draft

## l-carnitine-ct2-transport A distinct transporter connects carnitine with the reproductive tract. Human CT2 expressed in Xenopus oocytes mediated high-affinity carnitine transport; tissue staining located CT2 in epididymal luminal membranes and Sertoli cells. Model: Human transporter cloning, oocyte transport and tissue immunohistochemistry. Limitations: Transport/localization do not establish improved fertility from carnitine supplements. Evidence access: Primary abstract Molecular identification of a novel carnitine transporter specific to human testis. Insights into the mechanism of carnitine recognition. · 2002 · https://pubmed.ncbi.nlm.nih.gov/12089149/ · DOI 10.1074/jbc.M203883200

evidence_access

Primary abstract

experimental_model

Human OCTN2 expressed in HEK293 cells.

limitations

Does not imply that eating more salt improves carnitine uptake.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

Cell entry depends on a sodium-coupled transporter.

primary_references

Na(+)-dependent carnitine transport by organic cation transporter (OCTN2): its pharmacological and toxicological relevance. · 1999 · https://pubmed.ncbi.nlm.nih.gov/10525100/

transport_effect

raises Sodium-coupled, with about one sodium ion accompanying each carnitine molecule inward.

transport_pool

the expressing cell Sodium-coupled, with about one sodium ion accompanying each carnitine molecule inward.

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 42–48

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Human OCTN2 expressed in HEK293 cells. · source_derived_draft · unverified_draft

## l-carnitine-octn2-sodium Cell entry depends on a sodium-coupled transporter. Human OCTN2 transport measurements were consistent with approximately one sodium ion accompanying each carnitine molecule. Model: Human OCTN2 expressed in HEK293 cells. Limitations: Does not imply that eating more salt improves carnitine uptake. Evidence access: Primary abstract Na(+)-dependent carnitine transport by organic cation transporter (OCTN2): its pharmacological and toxicological relevance. · 1999 · https://pubmed.ncbi.nlm.nih.gov/10525100/

evidence_access

Primary abstract

experimental_model

Transporter expression assay.

limitations

D-carnitine is an experimental comparator, not a substitute.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

The two mirror-image molecules are handled differently.

primary_references

Na(+)-dependent carnitine transport by organic cation transporter (OCTN2): its pharmacological and toxicological relevance. · 1999 · https://pubmed.ncbi.nlm.nih.gov/10525100/

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 58–64

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Transporter expression assay. · source_derived_draft · unverified_draft

## l-carnitine-octn2-stereo The two mirror-image molecules are handled differently. Human OCTN2 transported D-carnitine with lower affinity than L-carnitine: reported Km values were 10.9 versus 4.3 micromolar. Model: Transporter expression assay. Limitations: D-carnitine is an experimental comparator, not a substitute. Evidence access: Primary abstract Na(+)-dependent carnitine transport by organic cation transporter (OCTN2): its pharmacological and toxicological relevance. · 1999 · https://pubmed.ncbi.nlm.nih.gov/10525100/

experimental_model

Human cDNA expression and human tissue activity assays

limitations

Do not generalize full carnitine-synthesis capacity to every tissue.

organism

Homo sapiens

plain_language

BBOX1 completes carnitine synthesis.

primary_references

[vaz1998] Carnitine biosynthesis: identification of the cDNA encoding human gamma-butyrobetaine hydroxylase (1998). https://pubmed.ncbi.nlm.nih.gov/9753662/ DOI: 10.1006/bbrc.1998.9343 [rebouche1980] Tissue distribution of carnitine biosynthetic enzymes in man (1980). https://pubmed.ncbi.nlm.nih.gov/6770910/ DOI: 10.1016/0304-4165(80)90133-6

tissue_or_cell_type

Kidney, liver and brain; abundance differs

L-Lysine: mechanism-first literature curation (2026-09-17) · lines 207–216

AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Human cDNA expression and human tissue activity assays · source_derived_draft · unverified_draft

### bbox1-carnitine-formation BBOX1 hydroxylates gamma-butyrobetaine to L-carnitine using oxygen, 2-oxoglutarate and ferrous iron. Plain language: BBOX1 completes carnitine synthesis. Condition category: normal organism: Homo sapiens tissue_or_cell_type: Kidney, liver and brain; abundance differs experimental_model: Human cDNA expression and human tissue activity assays limitations: Do not generalize full carnitine-synthesis capacity to every tissue. [vaz1998] Carnitine biosynthesis: identification of the cDNA encoding human gamma-butyrobetaine hydroxylase (1998). https://pubmed.ncbi.nlm.nih.gov/9753662/ DOI: 10.1006/bbrc.1998.9343 [rebouche1980] Tissue distribution of carnitine biosynthetic enzymes in man (1980). https://pubmed.ncbi.nlm.nih.gov/6770910/ DOI: 10.1016/0304-4165(80)90133-6

availability_state

nutrient_deficiency Imported condition classification; unverified.

evidence_span

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experimental_model

Two-factor biotin/carnitine depletion and carnitine repletion in human HepG2 cells

exposure

Separate and combined biotin and carnitine depletion

limitations

This is a cell-culture demonstration of marker masking; it does not validate a diagnostic correction formula in pregnancy or the general population.

nutrient_topic

Biotin research collection; topical membership is not evidence of a direct dietary effect. · Biotin

organism

Homo sapiens

plain_language

When carnitine is available, the biotin-related bottleneck produces a strong side-product signal.

primary_references

[b7-p25527659] In HepG2 cells, coexisting carnitine deficiency masks important indicators of marginal biotin deficiency. (2015). https://pubmed.ncbi.nlm.nih.gov/25527659/ DOI: 10.3945/jn.114.201343

tissue_or_cell_type

HepG2 hepatoma cells

trigger_kind

nutrient_deficiency Imported condition classification; unverified.

Biotin: carboxylases, recycling, deficiency and nutrient interactions (2026-09-17) · lines 949–960

AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Two-factor biotin/carnitine depletion and carnitine repletion in human HepG2 cells · source_derived_draft · unverified_draft

### b7-c5oh-biotin-low Biotin-deficient but carnitine-sufficient HepG2 cells had more than tenfold higher intracellular 3-hydroxyisovalerylcarnitine than doubly sufficient cells. Condition category: nutrient_deficiency nutrient_topic: Biotin research collection; topical membership is not evidence of a direct dietary effect. plain_language: When carnitine is available, the biotin-related bottleneck produces a strong side-product signal. organism: Homo sapiens tissue_or_cell_type: HepG2 hepatoma cells experimental_model: Two-factor biotin/carnitine depletion and carnitine repletion in human HepG2 cells limitations: This is a cell-culture demonstration of marker masking; it does not validate a diagnostic correction formula in pregnancy or the general population. exposure: Separate and combined biotin and carnitine depletion evidence_span: {"source_cache": "artifacts/biotin-research/25527659.abstract.txt", "locator": "Exact primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "4a368eb2fa2020bb1cabc99b31a3420870a8256886d5934d3d834c90b078238f", "start_char": 0, "end_char": 2372, "text_sha256": "4a368eb2fa2020bb1cabc99b31a3420870a8256886d5934d3d834c90b078238f"} [b7-p25527659] In HepG2 cells, coexisting carnitine deficiency masks important indicators of marginal biotin deficiency. (2015). https://pubmed.ncbi.nlm.nih.gov/25527659/ DOI: 10.3945/jn.114.201343

availability_state

nutrient_deficiency Imported condition classification; unverified.

evidence_span

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experimental_model

Leucine challenge during biotin depletion in two cohorts of 5 and 7 healthy adults

exposure

28-day egg-white depletion; weekly oral leucine challenge

limitations

The challenge was sensitive but not diagnostically superior to 24-hour urine measurements; no validated universal threshold follows.

nutrient_topic

Biotin research collection; topical membership is not evidence of a direct dietary effect. · Biotin

organism

Homo sapiens

plain_language

The carnitine-linked side product also increased as biotin became limited.

primary_references

[b7-p21918059] Urinary excretion of 3-hydroxyisovaleric acid and 3-hydroxyisovaleryl carnitine increases in response to a leucine challenge in marginally biotin-deficient humans. (2011). https://pubmed.ncbi.nlm.nih.gov/21918059/ DOI: 10.3945/jn.111.146126

tissue_or_cell_type

Urine

trigger_kind

nutrient_deficiency Imported condition classification; unverified.

Biotin: carboxylases, recycling, deficiency and nutrient interactions (2026-09-17) · lines 923–934

AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Leucine challenge during biotin depletion in two cohorts of 5 and 7 healthy adults · source_derived_draft · unverified_draft

### b7-leucine-challenge-c5oh Challenge-induced urinary 3-hydroxyisovalerylcarnitine rose more than twofold by day 14 in both biotin-depleted cohorts. Condition category: nutrient_deficiency nutrient_topic: Biotin research collection; topical membership is not evidence of a direct dietary effect. plain_language: The carnitine-linked side product also increased as biotin became limited. organism: Homo sapiens tissue_or_cell_type: Urine experimental_model: Leucine challenge during biotin depletion in two cohorts of 5 and 7 healthy adults limitations: The challenge was sensitive but not diagnostically superior to 24-hour urine measurements; no validated universal threshold follows. exposure: 28-day egg-white depletion; weekly oral leucine challenge evidence_span: {"source_cache": "artifacts/biotin-research/21918059.abstract.txt", "locator": "Exact primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "5cf1d7e25ae7bdfeb2ac3225cee8e4e660723d5197fc057f63327b3ad9eb3aaf", "start_char": 0, "end_char": 1723, "text_sha256": "5cf1d7e25ae7bdfeb2ac3225cee8e4e660723d5197fc057f63327b3ad9eb3aaf"} [b7-p21918059] Urinary excretion of 3-hydroxyisovaleric acid and 3-hydroxyisovaleryl carnitine increases in response to a leucine challenge in marginally biotin-deficient humans. (2011). https://pubmed.ncbi.nlm.nih.gov/21918059/ DOI: 10.3945/jn.111.146126

evidence_span

{"source_cache": "artifacts/biotin-research/10651636.abstract.txt", "locator": "Exact primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "e99728ef83700f17a810421385b71ea243576419df807dc4749b588beb01d400", "start_char": 0, "end_char": 1542, "text_sha256": "e99728ef83700f17a810421385b71ea243576419df807dc4749b588beb01d400"}

experimental_model

Human CPT1B wild type and N-terminal deletions expressed in yeast mitochondria

exposure

Malonyl-CoA binding and activity assays

limitations

Expression host is yeast; these data concern human CPT1B, not every CPT1 isoform or a biotin supplementation outcome.

nutrient_topic

Biotin research collection; topical membership is not evidence of a direct dietary effect. · Biotin

organism

Homo sapiens

plain_language

Malonyl-CoA links the carboxylase pathway to the carnitine-dependent fat-entry step.

primary_references

[b7-p10651636] The first 28 N-terminal amino acid residues of human heart muscle carnitine palmitoyltransferase I are essential for malonyl CoA sensitivity and high-affinity binding. (2000). https://pubmed.ncbi.nlm.nih.gov/10651636/ DOI: 10.1021/bi9918700

tissue_or_cell_type

Recombinant human muscle/heart CPT1B

Biotin: carboxylases, recycling, deficiency and nutrient interactions (2026-09-17) · lines 741–752

AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Human CPT1B wild type and N-terminal deletions expressed in yeast mitochondria · source_derived_draft · unverified_draft

### b7-malonyl-cpt1b Wild-type human CPT1B showed high-affinity malonyl-CoA binding and inhibition in recombinant mitochondrial assays. Condition category: normal nutrient_topic: Biotin research collection; topical membership is not evidence of a direct dietary effect. plain_language: Malonyl-CoA links the carboxylase pathway to the carnitine-dependent fat-entry step. organism: Homo sapiens tissue_or_cell_type: Recombinant human muscle/heart CPT1B experimental_model: Human CPT1B wild type and N-terminal deletions expressed in yeast mitochondria limitations: Expression host is yeast; these data concern human CPT1B, not every CPT1 isoform or a biotin supplementation outcome. exposure: Malonyl-CoA binding and activity assays evidence_span: {"source_cache": "artifacts/biotin-research/10651636.abstract.txt", "locator": "Exact primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "e99728ef83700f17a810421385b71ea243576419df807dc4749b588beb01d400", "start_char": 0, "end_char": 1542, "text_sha256": "e99728ef83700f17a810421385b71ea243576419df807dc4749b588beb01d400"} [b7-p10651636] The first 28 N-terminal amino acid residues of human heart muscle carnitine palmitoyltransferase I are essential for malonyl CoA sensitivity and high-affinity binding. (2000). https://pubmed.ncbi.nlm.nih.gov/10651636/ DOI: 10.1021/bi9918700

availability_state

nutrient_deficiency Imported condition classification; unverified.

evidence_span

{"source_cache": "artifacts/biotin-research/20943794.abstract.txt", "locator": "Exact primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "1351a960b61efdce767a72da73d9ad8755e52f935e98b9510b4f68c2d5b83c9a", "start_char": 0, "end_char": 1877, "text_sha256": "1351a960b61efdce767a72da73d9ad8755e52f935e98b9510b4f68c2d5b83c9a"}

experimental_model

Depletion/repletion in 10 healthy adults, 8 women

exposure

28 days of undenatured egg white, followed by repletion

limitations

The study-specific reference interval and 10 participants do not define a universally diagnostic blood cutoff.

nutrient_topic

Biotin research collection; topical membership is not evidence of a direct dietary effect. · Biotin

organism

Homo sapiens

plain_language

A blood marker tracked depletion in most, but not all, participants.

primary_references

[b7-p20943794] Plasma concentration of 3-hydroxyisovaleryl carnitine is an early and sensitive indicator of marginal biotin deficiency in humans. (2010). https://pubmed.ncbi.nlm.nih.gov/20943794/ DOI: 10.3945/ajcn.110.002543

tissue_or_cell_type

Plasma

trigger_kind

nutrient_deficiency Imported condition classification; unverified.

Biotin: carboxylases, recycling, deficiency and nutrient interactions (2026-09-17) · lines 936–947

AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Depletion/repletion in 10 healthy adults, 8 women · source_derived_draft · unverified_draft

### b7-plasma-c5oh Plasma 3-hydroxyisovalerylcarnitine was above the study reference interval in 7 of 10 adults by day 14 and 9 of 10 by day 28 of depletion, then fell with repletion. Condition category: nutrient_deficiency nutrient_topic: Biotin research collection; topical membership is not evidence of a direct dietary effect. plain_language: A blood marker tracked depletion in most, but not all, participants. organism: Homo sapiens tissue_or_cell_type: Plasma experimental_model: Depletion/repletion in 10 healthy adults, 8 women limitations: The study-specific reference interval and 10 participants do not define a universally diagnostic blood cutoff. exposure: 28 days of undenatured egg white, followed by repletion evidence_span: {"source_cache": "artifacts/biotin-research/20943794.abstract.txt", "locator": "Exact primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "1351a960b61efdce767a72da73d9ad8755e52f935e98b9510b4f68c2d5b83c9a", "start_char": 0, "end_char": 1877, "text_sha256": "1351a960b61efdce767a72da73d9ad8755e52f935e98b9510b4f68c2d5b83c9a"} [b7-p20943794] Plasma concentration of 3-hydroxyisovaleryl carnitine is an early and sensitive indicator of marginal biotin deficiency in humans. (2010). https://pubmed.ncbi.nlm.nih.gov/20943794/ DOI: 10.3945/ajcn.110.002543

availability_state

biomarker_context Imported condition classification; unverified.

evidence_span

{"source_cache": "artifacts/biotin-research/25122647.abstract.txt", "locator": "Exact primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "6066b007a013c3c0c69336e7aba0e51baa39e3a24b6eb918cb4778e792376a9b", "start_char": 0, "end_char": 2354, "text_sha256": "6066b007a013c3c0c69336e7aba0e51baa39e3a24b6eb918cb4778e792376a9b"}

experimental_model

Controlled feeding: 26 pregnant, 28 lactating and 21 control women

exposure

57 micrograms dietary biotin per day for 10–12 weeks

limitations

Groups differed in reproductive state. Marker changes do not establish fetal outcomes, universal deficiency or a treatment dose.

nutrient_topic

Biotin research collection; topical membership is not evidence of a direct dietary effect. · Biotin

organism

Homo sapiens

plain_language

Two related markers moved in opposite directions during pregnancy.

primary_references

[b7-p25122647] Pregnancy and lactation alter biomarkers of biotin metabolism in women consuming a controlled diet. (2014). https://pubmed.ncbi.nlm.nih.gov/25122647/ DOI: 10.3945/jn.114.194472

tissue_or_cell_type

Urine and plasma

trigger_kind

biomarker_context Imported condition classification; unverified.

Biotin: carboxylases, recycling, deficiency and nutrient interactions (2026-09-17) · lines 988–999

AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Controlled feeding: 26 pregnant, 28 lactating and 21 control women · source_derived_draft · unverified_draft

### b7-pregnancy-3hia At the controlled intake, pregnant women excreted 69% more 3-HIA than controls, while urinary 3-HIA-carnitine was 27% lower. Condition category: biomarker_context nutrient_topic: Biotin research collection; topical membership is not evidence of a direct dietary effect. plain_language: Two related markers moved in opposite directions during pregnancy. organism: Homo sapiens tissue_or_cell_type: Urine and plasma experimental_model: Controlled feeding: 26 pregnant, 28 lactating and 21 control women limitations: Groups differed in reproductive state. Marker changes do not establish fetal outcomes, universal deficiency or a treatment dose. exposure: 57 micrograms dietary biotin per day for 10–12 weeks evidence_span: {"source_cache": "artifacts/biotin-research/25122647.abstract.txt", "locator": "Exact primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "6066b007a013c3c0c69336e7aba0e51baa39e3a24b6eb918cb4778e792376a9b", "start_char": 0, "end_char": 2354, "text_sha256": "6066b007a013c3c0c69336e7aba0e51baa39e3a24b6eb918cb4778e792376a9b"} [b7-p25122647] Pregnancy and lactation alter biomarkers of biotin metabolism in women consuming a controlled diet. (2014). https://pubmed.ncbi.nlm.nih.gov/25122647/ DOI: 10.3945/jn.114.194472

evidence_span

{"source_cache": "artifacts/mangiferin-research/21348301.abstract.txt", "locator": "Primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "7c27a677db4a27cc088cfd83ce3506ffdfd866ef91250732b1dd2287d4cf4b58", "start_char": 0, "end_char": 1981, "text_sha256": "7c27a677db4a27cc088cfd83ce3506ffdfd866ef91250732b1dd2287d4cf4b58"}

experimental_model

Seven-day potassium-oxonate hyperuricemia model

exposure

Mangiferin 50, 100 or 200 mg/kg orally

limitations

Animal expression findings; no human carnitine-retention or gout-treatment conclusion.

nutrient_topic

Mangiferin research collection; topical membership is not evidence of a direct dietary effect. · Mangiferin

organism

Mus musculus

plain_language

A transporter linked to carnitine also responded.

primary_references

[mangiferin-p21348301] [Mangiferin promotes uric acid excretion and kidney function improvement and modulates related renal transporters in hyperuricemic mice]. (2010). https://pubmed.ncbi.nlm.nih.gov/21348301/

tissue_or_cell_type

Kidney

Mangiferin: metabolism, signaling and nutrient connections (2026-09-17) · lines 1004–1015

AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Seven-day potassium-oxonate hyperuricemia model · source_derived_draft · unverified_draft

### mangiferin-mouse-slc22a5 Mangiferin increased renal Mouse carnitine transporter Octn2 / Slc22a5 expression in the hyperuricemic mice. Condition category: normal nutrient_topic: Mangiferin research collection; topical membership is not evidence of a direct dietary effect. plain_language: A transporter linked to carnitine also responded. organism: Mus musculus tissue_or_cell_type: Kidney experimental_model: Seven-day potassium-oxonate hyperuricemia model limitations: Animal expression findings; no human carnitine-retention or gout-treatment conclusion. exposure: Mangiferin 50, 100 or 200 mg/kg orally evidence_span: {"source_cache": "artifacts/mangiferin-research/21348301.abstract.txt", "locator": "Primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "7c27a677db4a27cc088cfd83ce3506ffdfd866ef91250732b1dd2287d4cf4b58", "start_char": 0, "end_char": 1981, "text_sha256": "7c27a677db4a27cc088cfd83ce3506ffdfd866ef91250732b1dd2287d4cf4b58"} [mangiferin-p21348301] [Mangiferin promotes uric acid excretion and kidney function improvement and modulates related renal transporters in hyperuricemic mice]. (2010). https://pubmed.ncbi.nlm.nih.gov/21348301/

evidence_span

{"source_cache": "artifacts/mangiferin-research/25989216.abstract.txt", "locator": "Primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "2f57445ffe1eb20de3c2bf1170d152c358be1d7763cef2a091c0b3052040e539", "start_char": 0, "end_char": 1522, "text_sha256": "2f57445ffe1eb20de3c2bf1170d152c358be1d7763cef2a091c0b3052040e539"}

experimental_model

Double-blind randomized placebo-controlled trial

exposure

Mangiferin 150 mg/day for 12 weeks

limitations

One trial in a selected population; biomarkers do not demonstrate clinical outcomes or directly measure fatty-acid flux.

nutrient_topic

Mangiferin research collection; topical membership is not evidence of a direct dietary effect. · Mangiferin

organism

Overweight adults with hyperlipidemia; 97 completers

plain_language

A metabolite used in fatty-acid handling was higher in blood.

primary_references

[mangiferin-p25989216] Mangiferin supplementation improves serum lipid profiles in overweight patients with hyperlipidemia: a double-blind randomized controlled trial. (2015). https://pubmed.ncbi.nlm.nih.gov/25989216/ DOI: 10.1038/srep10344

tissue_or_cell_type

Serum metabolic measurements

Mangiferin: metabolism, signaling and nutrient connections (2026-09-17) · lines 1199–1210

AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Double-blind randomized placebo-controlled trial · source_derived_draft · unverified_draft

### mangiferin-trial-carnitine Serum L-carnitine increased compared with placebo. Condition category: normal nutrient_topic: Mangiferin research collection; topical membership is not evidence of a direct dietary effect. plain_language: A metabolite used in fatty-acid handling was higher in blood. organism: Overweight adults with hyperlipidemia; 97 completers tissue_or_cell_type: Serum metabolic measurements experimental_model: Double-blind randomized placebo-controlled trial limitations: One trial in a selected population; biomarkers do not demonstrate clinical outcomes or directly measure fatty-acid flux. exposure: Mangiferin 150 mg/day for 12 weeks evidence_span: {"source_cache": "artifacts/mangiferin-research/25989216.abstract.txt", "locator": "Primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "2f57445ffe1eb20de3c2bf1170d152c358be1d7763cef2a091c0b3052040e539", "start_char": 0, "end_char": 1522, "text_sha256": "2f57445ffe1eb20de3c2bf1170d152c358be1d7763cef2a091c0b3052040e539"} [mangiferin-p25989216] Mangiferin supplementation improves serum lipid profiles in overweight patients with hyperlipidemia: a double-blind randomized controlled trial. (2015). https://pubmed.ncbi.nlm.nih.gov/25989216/ DOI: 10.1038/srep10344

evidence_access

Primary abstract

experimental_model

Small treated human case series.

limitations

No untreated comparator; association does not quantify an ordinary food-preservative effect.

nutrient_topic

Glycine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · Glycine

plain_language

Using one conjugation route can be accompanied by loss of another nutrient.

primary_references

Benzoate therapy and carnitine deficiency in non-ketotic hyperglycinemia. · 1995 · https://pubmed.ncbi.nlm.nih.gov/8585564/ · DOI 10.1002/ajmg.1320590410

Glycine: supply, one-carbon allocation, receptors and cross-nutrient mechanisms (2026-09-19) · lines 314–320

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Small treated human case series. · source_derived_draft · unverified_draft

## glycine-benzoate-carnitine Using one conjugation route can be accompanied by loss of another nutrient. During sodium-benzoate treatment of five neonatal-onset nonketotic-hyperglycinemia patients, three of four tested had plasma carnitine deficiency and benzoylcarnitine was detected. Model: Small treated human case series. Limitations: No untreated comparator; association does not quantify an ordinary food-preservative effect. Evidence access: Primary abstract Benzoate therapy and carnitine deficiency in non-ketotic hyperglycinemia. · 1995 · https://pubmed.ncbi.nlm.nih.gov/8585564/ · DOI 10.1002/ajmg.1320590410

evidence_access

Primary abstract

experimental_model

Human wild-type transporters expressed in HEK293 cells.

limitations

Related sequence does not establish substrate interchangeability.

nutrient_topic

Ergothioneine collection; molecular form, preparation, species, exposure and manipulation remain explicit. · L-Ergothioneine

plain_language

The main carnitine carrier cannot be assumed to carry ergothioneine.

primary_references

Substrate discrimination by ergothioneine transporter SLC22A4 and carnitine transporter SLC22A5: gain-of-function by interchange of selected amino acids. · 2009 · https://pubmed.ncbi.nlm.nih.gov/19814996/ · DOI 10.1016/j.bbamem.2009.09.019

Ergothioneine: transport, redox chemistry and cross-nutrient mechanisms (2026-09-19) · lines 40–46

AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Human wild-type transporters expressed in HEK293 cells. · source_derived_draft · unverified_draft

## ergothioneine-slc22a5-not-ergo The main carnitine carrier cannot be assumed to carry ergothioneine. Wild-type human SLC22A5 did not transport ergothioneine in the comparative expression assay. Model: Human wild-type transporters expressed in HEK293 cells. Limitations: Related sequence does not establish substrate interchangeability. Evidence access: Primary abstract Substrate discrimination by ergothioneine transporter SLC22A4 and carnitine transporter SLC22A5: gain-of-function by interchange of selected amino acids. · 2009 · https://pubmed.ncbi.nlm.nih.gov/19814996/ · DOI 10.1016/j.bbamem.2009.09.019

evidence_access

Primary abstract

experimental_model

Human U87MG culture, isotope tracing.

limitations

Does not show that oral acetylcarnitine causes or treats cancer.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

The acetylated form can deliver carbon for cellular synthesis.

primary_references

Carnitine octanoyltransferase is important for the assimilation of exogenous acetyl-L-carnitine into acetyl-CoA in mammalian cells. · 2023 · https://pubmed.ncbi.nlm.nih.gov/36587768/ · DOI 10.1016/j.jbc.2022.102848

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 210–216

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Human U87MG culture, isotope tracing. · source_derived_draft · unverified_draft

## l-carnitine-acetyl-carbon The acetylated form can deliver carbon for cellular synthesis. Isotope-labeled acetylcarnitine supplied acetyl-CoA and fatty-acid carbon in glucose-limited human U87MG glioma cells. Model: Human U87MG culture, isotope tracing. Limitations: Does not show that oral acetylcarnitine causes or treats cancer. Evidence access: Primary abstract Carnitine octanoyltransferase is important for the assimilation of exogenous acetyl-L-carnitine into acetyl-CoA in mammalian cells. · 2023 · https://pubmed.ncbi.nlm.nih.gov/36587768/ · DOI 10.1016/j.jbc.2022.102848

evidence_access

Primary abstract and full-text PBMC exposure methods and results

experimental_model

Human PBMCs with 5 mg/ml human serum albumin, given 30 minutes before or alongside the four-hour exposure.

limitations

This comparison does not by itself prove a binding mechanism or clinical efficacy.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

The surrounding protein environment changed the observed effect.

primary_references

Palmitoylcarnitine impairs immunity in decompensated cirrhosis. · 2024 · https://pubmed.ncbi.nlm.nih.gov/39524205/ · DOI 10.1016/j.jhepr.2024.101187

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 522–528

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Human PBMCs with 5 mg/ml human serum albumin, given 30 minutes before or alongside the four-hour exposure. · source_derived_draft · unverified_draft

## l-carnitine-acyl-albumin The surrounding protein environment changed the observed effect. Albumin reduced palmitoylcarnitine-associated oxidative stress and membrane-potential impairment in donor leukocytes. Model: Human PBMCs with 5 mg/ml human serum albumin, given 30 minutes before or alongside the four-hour exposure. Limitations: This comparison does not by itself prove a binding mechanism or clinical efficacy. Evidence access: Primary abstract and full-text PBMC exposure methods and results Palmitoylcarnitine impairs immunity in decompensated cirrhosis. · 2024 · https://pubmed.ncbi.nlm.nih.gov/39524205/ · DOI 10.1016/j.jhepr.2024.101187

evidence_access

Primary abstract and full-text PBMC exposure methods and results

experimental_model

Human PBMCs; 2.5-25 micromolar dose range, four-hour exposure.

limitations

Does not prove a clinical inflammatory effect of carnitine supplements.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

The acylated molecule can promote an inflammatory response in cells.

primary_references

Palmitoylcarnitine impairs immunity in decompensated cirrhosis. · 2024 · https://pubmed.ncbi.nlm.nih.gov/39524205/ · DOI 10.1016/j.jhepr.2024.101187

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 514–520

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Human PBMCs; 2.5-25 micromolar dose range, four-hour exposure. · source_derived_draft · unverified_draft

## l-carnitine-acyl-immune-cytokine The acylated molecule can promote an inflammatory response in cells. Palmitoylcarnitine exposure increased CXCL8 expression and IL-8 release in human donor leukocytes. Model: Human PBMCs; 2.5-25 micromolar dose range, four-hour exposure. Limitations: Does not prove a clinical inflammatory effect of carnitine supplements. Evidence access: Primary abstract and full-text PBMC exposure methods and results Palmitoylcarnitine impairs immunity in decompensated cirrhosis. · 2024 · https://pubmed.ncbi.nlm.nih.gov/39524205/ · DOI 10.1016/j.jhepr.2024.101187

evidence_access

Primary abstract and full-text PBMC exposure methods and results

experimental_model

Human donor leukocytes ex vivo; a separate cohort comparison measured acylcarnitines in decompensated cirrhosis.

limitations

PBMCs were exposed to 2.5-25 micromolar palmitoylcarnitine for four hours; this is not equivalent to taking free L-carnitine.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

A loaded carnitine molecule can have effects beyond carrying fuel.

primary_references

Palmitoylcarnitine impairs immunity in decompensated cirrhosis. · 2024 · https://pubmed.ncbi.nlm.nih.gov/39524205/ · DOI 10.1016/j.jhepr.2024.101187

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 506–512

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Human donor leukocytes ex vivo; a separate cohort comparison measured acylcarnitines in decompensated cirrhosis. · source_derived_draft · unverified_draft

## l-carnitine-acyl-immune-respiration A loaded carnitine molecule can have effects beyond carrying fuel. Adding palmitoylcarnitine impaired mitochondrial membrane potential and spare respiratory capacity in leukocytes from healthy donors. Model: Human donor leukocytes ex vivo; a separate cohort comparison measured acylcarnitines in decompensated cirrhosis. Limitations: PBMCs were exposed to 2.5-25 micromolar palmitoylcarnitine for four hours; this is not equivalent to taking free L-carnitine. Evidence access: Primary abstract and full-text PBMC exposure methods and results Palmitoylcarnitine impairs immunity in decompensated cirrhosis. · 2024 · https://pubmed.ncbi.nlm.nih.gov/39524205/ · DOI 10.1016/j.jhepr.2024.101187

evidence_access

Primary abstract

experimental_model

Same randomized trial; prespecified secondary follow-up.

limitations

Not a demonstrated molecular explanation of the harm; keep the clinical outcome visible.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

Longer follow-up revealed harm in that setting.

primary_references

Randomized double-blind placebo-controlled trial of acetyl-L-carnitine for the prevention of taxane-induced neuropathy in women undergoing adjuvant breast cancer therapy. · 2013 · https://pubmed.ncbi.nlm.nih.gov/23733756/ · DOI 10.1200/JCO.2012.44.8738

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 338–344

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Same randomized trial; prespecified secondary follow-up. · source_derived_draft · unverified_draft

## l-carnitine-alc-neuropathy-harm Longer follow-up revealed harm in that setting. At 24 weeks in the same taxane trial, the acetyl-L-carnitine arm had worse neuropathy scores and more severe neurotoxicity than placebo. Model: Same randomized trial; prespecified secondary follow-up. Limitations: Not a demonstrated molecular explanation of the harm; keep the clinical outcome visible. Evidence access: Primary abstract Randomized double-blind placebo-controlled trial of acetyl-L-carnitine for the prevention of taxane-induced neuropathy in women undergoing adjuvant breast cancer therapy. · 2013 · https://pubmed.ncbi.nlm.nih.gov/23733756/ · DOI 10.1200/JCO.2012.44.8738

evidence_access

Primary abstract

experimental_model

Women with breast cancer; 3 g/day acetyl-L-carnitine versus placebo.

limitations

A finding for this derivative and treatment context, not every carnitine use.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

A plausible nerve-protection idea failed its main clinical test.

primary_references

Randomized double-blind placebo-controlled trial of acetyl-L-carnitine for the prevention of taxane-induced neuropathy in women undergoing adjuvant breast cancer therapy. · 2013 · https://pubmed.ncbi.nlm.nih.gov/23733756/ · DOI 10.1200/JCO.2012.44.8738

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 330–336

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Women with breast cancer; 3 g/day acetyl-L-carnitine versus placebo. · source_derived_draft · unverified_draft

## l-carnitine-alc-neuropathy-null A plausible nerve-protection idea failed its main clinical test. In a 409-patient randomized trial during adjuvant taxane chemotherapy, acetyl-L-carnitine did not significantly improve the primary 12-week neuropathy endpoint. Model: Women with breast cancer; 3 g/day acetyl-L-carnitine versus placebo. Limitations: A finding for this derivative and treatment context, not every carnitine use. Evidence access: Primary abstract Randomized double-blind placebo-controlled trial of acetyl-L-carnitine for the prevention of taxane-induced neuropathy in women undergoing adjuvant breast cancer therapy. · 2013 · https://pubmed.ncbi.nlm.nih.gov/23733756/ · DOI 10.1200/JCO.2012.44.8738

evidence_access

Primary abstract

experimental_model

Recombinant human ALDH9 compared with purified and recombinant rat enzyme.

limitations

NAD+ dependence does not establish benefit from niacin supplementation.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

A niacin-derived coenzyme participates in making carnitine.

primary_references

Molecular and biochemical characterization of rat gamma-trimethylaminobutyraldehyde dehydrogenase and evidence for the involvement of human aldehyde dehydrogenase 9 in carnitine biosynthesis. · 2000 · https://pubmed.ncbi.nlm.nih.gov/10702312/ · DOI 10.1074/jbc.275.10.7390

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 18–24

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Recombinant human ALDH9 compared with purified and recombinant rat enzyme. · source_derived_draft · unverified_draft

## l-carnitine-aldehyde-step A niacin-derived coenzyme participates in making carnitine. Expressing human ALDH9 in bacteria produced NAD+-dependent trimethylaminobutyraldehyde dehydrogenase activity, completing the aldehyde-to-gamma-butyrobetaine step. Model: Recombinant human ALDH9 compared with purified and recombinant rat enzyme. Limitations: NAD+ dependence does not establish benefit from niacin supplementation. Evidence access: Primary abstract Molecular and biochemical characterization of rat gamma-trimethylaminobutyraldehyde dehydrogenase and evidence for the involvement of human aldehyde dehydrogenase 9 in carnitine biosynthesis. · 2000 · https://pubmed.ncbi.nlm.nih.gov/10702312/ · DOI 10.1074/jbc.275.10.7390

evidence_access

Primary abstract

experimental_model

Mouse Slc6a14 heterologous expression assays.

limitations

This finding concerns ATB0,+, not OCTN2; in vitro competition does not establish a meal or supplement interaction.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

Some amino acids share and compete for this transport route.

primary_references

Na+- and Cl--coupled active transport of carnitine by the amino acid transporter ATB(0,+) from mouse colon expressed in HRPE cells and Xenopus oocytes. · 2001 · https://pubmed.ncbi.nlm.nih.gov/11306651/ · DOI 10.1111/j.1469-7793.2001.0297f.x

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 474–480

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Mouse Slc6a14 heterologous expression assays. · source_derived_draft · unverified_draft

## l-carnitine-atb-competition Some amino acids share and compete for this transport route. Amino-acid substrates inhibited carnitine transport through expressed mouse ATB0,+. Model: Mouse Slc6a14 heterologous expression assays. Limitations: This finding concerns ATB0,+, not OCTN2; in vitro competition does not establish a meal or supplement interaction. Evidence access: Primary abstract Na+- and Cl--coupled active transport of carnitine by the amino acid transporter ATB(0,+) from mouse colon expressed in HRPE cells and Xenopus oocytes. · 2001 · https://pubmed.ncbi.nlm.nih.gov/11306651/ · DOI 10.1111/j.1469-7793.2001.0297f.x

evidence_access

Primary full-text Figure 3 and enzyme experiments

experimental_model

E. timonensis enzymes; recombinant expression and reconstitution.

limitations

Acetyl-CoA was preferred among tested donors; in vivo donor use can differ.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

The microbial route first activates its substrate with CoA.

primary_references

Elucidation of an anaerobic pathway for metabolism of l-carnitine-derived γ-butyrobetaine to trimethylamine in human gut bacteria. · 2021 · https://pubmed.ncbi.nlm.nih.gov/34362844/ · DOI 10.1073/pnas.2101498118

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 370–376

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · E. timonensis enzymes; recombinant expression and reconstitution. · source_derived_draft · unverified_draft

## l-carnitine-bbu-coa The microbial route first activates its substrate with CoA. Purified BbuB and BbuC together transferred CoA onto gamma-butyrobetaine; neither component alone reproduced the tested activity. Model: E. timonensis enzymes; recombinant expression and reconstitution. Limitations: Acetyl-CoA was preferred among tested donors; in vivo donor use can differ. Evidence access: Primary full-text Figure 3 and enzyme experiments Elucidation of an anaerobic pathway for metabolism of l-carnitine-derived γ-butyrobetaine to trimethylamine in human gut bacteria. · 2021 · https://pubmed.ncbi.nlm.nih.gov/34362844/ · DOI 10.1073/pnas.2101498118

evidence_access

Primary full text and pathway reconstitution

experimental_model

E. timonensis BbuA biochemical characterization.

limitations

Flavin participation is supported; detailed catalytic chemistry remained proposed in this paper.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

A microbial enzyme releases the trimethylamine group.

primary_references

Elucidation of an anaerobic pathway for metabolism of l-carnitine-derived γ-butyrobetaine to trimethylamine in human gut bacteria. · 2021 · https://pubmed.ncbi.nlm.nih.gov/34362844/ · DOI 10.1073/pnas.2101498118

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 378–384

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · E. timonensis BbuA biochemical characterization. · source_derived_draft · unverified_draft

## l-carnitine-bbua-lyase A microbial enzyme releases the trimethylamine group. BbuA converted gamma-butyrobetainyl-CoA to TMA and crotonyl-CoA in the reconstituted anaerobic pathway. Model: E. timonensis BbuA biochemical characterization. Limitations: Flavin participation is supported; detailed catalytic chemistry remained proposed in this paper. Evidence access: Primary full text and pathway reconstitution Elucidation of an anaerobic pathway for metabolism of l-carnitine-derived γ-butyrobetaine to trimethylamine in human gut bacteria. · 2021 · https://pubmed.ncbi.nlm.nih.gov/34362844/ · DOI 10.1073/pnas.2101498118

evidence_access

Primary abstract

experimental_model

Rat depression-model hippocampus and prefrontal cortex.

limitations

Histone acetylation differs from DNA methylation; this is not proof of human antidepressant efficacy.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

The acetylated form altered a glutamate-signaling pathway in a rodent model.

primary_references

L-acetylcarnitine causes rapid antidepressant effects through the epigenetic induction of mGlu2 receptors. · 2013 · https://pubmed.ncbi.nlm.nih.gov/23382250/ · DOI 10.1073/pnas.1216100110

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 314–320

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Rat depression-model hippocampus and prefrontal cortex. · source_derived_draft · unverified_draft

## l-carnitine-brain-acetylation The acetylated form altered a glutamate-signaling pathway in a rodent model. Acetyl-L-carnitine treatment increased Grm2-associated H3K27 acetylation and mGlu2 expression in Flinders Sensitive Line rats. Model: Rat depression-model hippocampus and prefrontal cortex. Limitations: Histone acetylation differs from DNA methylation; this is not proof of human antidepressant efficacy. Evidence access: Primary abstract L-acetylcarnitine causes rapid antidepressant effects through the epigenetic induction of mGlu2 receptors. · 2013 · https://pubmed.ncbi.nlm.nih.gov/23382250/ · DOI 10.1073/pnas.1216100110

evidence_access

Primary abstract

experimental_model

Mouse knockout and stress-behavior experiments.

limitations

Behavioral tests are not human depression outcomes.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

Removing the receptor tested whether the rodent effect depended on it.

primary_references

L-acetylcarnitine causes rapid antidepressant effects through the epigenetic induction of mGlu2 receptors. · 2013 · https://pubmed.ncbi.nlm.nih.gov/23382250/ · DOI 10.1073/pnas.1216100110

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 322–328

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Mouse knockout and stress-behavior experiments. · source_derived_draft · unverified_draft

## l-carnitine-brain-receptor-required Removing the receptor tested whether the rodent effect depended on it. Acetyl-L-carnitine did not produce the reported behavioral benefit in mGlu2-knockout mice exposed to chronic unpredictable stress. Model: Mouse knockout and stress-behavior experiments. Limitations: Behavioral tests are not human depression outcomes. Evidence access: Primary abstract L-acetylcarnitine causes rapid antidepressant effects through the epigenetic induction of mGlu2 receptors. · 2013 · https://pubmed.ncbi.nlm.nih.gov/23382250/ · DOI 10.1073/pnas.1216100110

availability_state

machinery_impairment Imported condition classification; unverified.

evidence_access

Primary abstract

experimental_model

Functional variant study within a six-patient CACT-deficiency report.

limitations

CACT deficiency is distinct from OCTN2 deficiency; supplying substrate does not replace a transporter.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

A second transport defect can block the mitochondrial shuttle even when carnitine exists.

primary_references

Molecular and functional analysis of SLC25A20 mutations causing carnitine-acylcarnitine translocase deficiency. · 2004 · https://pubmed.ncbi.nlm.nih.gov/15365988/ · DOI 10.1002/humu.20085

trigger_kind

machinery_impairment Imported condition classification; unverified.

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 122–128

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Functional variant study within a six-patient CACT-deficiency report. · source_derived_draft · unverified_draft

## l-carnitine-cact-loss A second transport defect can block the mitochondrial shuttle even when carnitine exists. The human SLC25A20 p.Arg133Trp substitution impaired carrier activity after bacterial expression and liposome reconstitution. Model: Functional variant study within a six-patient CACT-deficiency report. Limitations: CACT deficiency is distinct from OCTN2 deficiency; supplying substrate does not replace a transporter. Evidence access: Primary abstract Molecular and functional analysis of SLC25A20 mutations causing carnitine-acylcarnitine translocase deficiency. · 2004 · https://pubmed.ncbi.nlm.nih.gov/15365988/ · DOI 10.1002/humu.20085

evidence_access

Primary abstract

experimental_model

Acinetobacter enzyme redox spectroscopy and site-directed mutants.

limitations

Bacterial cofactor dependence does not show that human B2 or iron supplementation increases TMAO.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

Riboflavin-derived FMN, iron centers and NADH connect to microbial carnitine chemistry.

primary_references

Carnitine metabolism in the human gut: characterization of the two-component carnitine monooxygenase CntAB from Acinetobacter baumannii. · 2020 · https://pubmed.ncbi.nlm.nih.gov/32694223/ · DOI 10.1074/jbc.RA120.014266

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 394–400

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Acinetobacter enzyme redox spectroscopy and site-directed mutants. · source_derived_draft · unverified_draft

## l-carnitine-cntb-redox Riboflavin-derived FMN, iron centers and NADH connect to microbial carnitine chemistry. CntB passed NADH-derived electrons through FMN and iron-sulfur centers to support CntA oxygen activation. Model: Acinetobacter enzyme redox spectroscopy and site-directed mutants. Limitations: Bacterial cofactor dependence does not show that human B2 or iron supplementation increases TMAO. Evidence access: Primary abstract Carnitine metabolism in the human gut: characterization of the two-component carnitine monooxygenase CntAB from Acinetobacter baumannii. · 2020 · https://pubmed.ncbi.nlm.nih.gov/32694223/ · DOI 10.1074/jbc.RA120.014266

evidence_access

Primary abstract

experimental_model

Native rat-liver carrier; recombinant cysteine mutants supported involvement of C136 and C155.

limitations

Free copper in an assay is not dietary copper exposure; no clinical deficiency or toxicity threshold follows.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

Metal exposure can interfere with the carrier in a controlled assay.

primary_references

Effect of Copper on the Mitochondrial Carnitine/Acylcarnitine Carrier Via Interaction with Cys136 and Cys155. Possible Implications in Pathophysiology. · 2020 · https://pubmed.ncbi.nlm.nih.gov/32070004/ · DOI 10.3390/molecules25040820

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 138–144

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Native rat-liver carrier; recombinant cysteine mutants supported involvement of C136 and C155. · source_derived_draft · unverified_draft

## l-carnitine-copper-carrier Metal exposure can interfere with the carrier in a controlled assay. Copper inhibited rat-liver CACT carnitine exchange in proteoliposomes, with a native-protein IC50 of 1.6 micromolar. Model: Native rat-liver carrier; recombinant cysteine mutants supported involvement of C136 and C155. Limitations: Free copper in an assay is not dietary copper exposure; no clinical deficiency or toxicity threshold follows. Evidence access: Primary abstract Effect of Copper on the Mitochondrial Carnitine/Acylcarnitine Carrier Via Interaction with Cys136 and Cys155. Possible Implications in Pathophysiology. · 2020 · https://pubmed.ncbi.nlm.nih.gov/32070004/ · DOI 10.3390/molecules25040820

availability_state

machinery_impairment Imported condition classification; unverified.

evidence_access

Primary abstract

experimental_model

Human patient-derived iPSC myocytes; heat challenge.

limitations

A cellular disease model, not a universal plasma threshold or a supplement trial.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

A downstream block can leave more loaded carnitine behind.

primary_references

Functional analysis of iPSC-derived myocytes from a patient with carnitine palmitoyltransferase II deficiency. · 2014 · https://pubmed.ncbi.nlm.nih.gov/24780397/ · DOI 10.1016/j.bbrc.2014.04.084

trigger_kind

machinery_impairment Imported condition classification; unverified.

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 130–136

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Human patient-derived iPSC myocytes; heat challenge. · source_derived_draft · unverified_draft

## l-carnitine-cpt2-heat A downstream block can leave more loaded carnitine behind. Myocytes derived from a CPT2-deficient patient accumulated palmitoylcarnitine; incubation at 38 degrees C accentuated accumulation relative to control myocytes. Model: Human patient-derived iPSC myocytes; heat challenge. Limitations: A cellular disease model, not a universal plasma threshold or a supplement trial. Evidence access: Primary abstract Functional analysis of iPSC-derived myocytes from a patient with carnitine palmitoyltransferase II deficiency. · 2014 · https://pubmed.ncbi.nlm.nih.gov/24780397/ · DOI 10.1016/j.bbrc.2014.04.084

evidence_access

Primary abstract and reviewed UniProt catalytic-reaction record

experimental_model

Human CPT2 in yeast homogenates; physiological direction from reviewed UniProt P23786/Rhea 12663.

limitations

The experiment directly measured the reverse reaction; direction in a cell depends on compartment and substrates.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

The inner enzyme unloads the fatty-acid group and recycles carnitine.

primary_references

Carnitine palmitoyltransferase 2: New insights on the substrate specificity and implications for acylcarnitine profiling. · 2010 · https://pubmed.ncbi.nlm.nih.gov/20538056/ · DOI 10.1016/j.bbadis.2010.06.002

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 106–112

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Human CPT2 in yeast homogenates; physiological direction from reviewed UniProt P23786/Rhea 12663. · source_derived_draft · unverified_draft

## l-carnitine-cpt2-return The inner enzyme unloads the fatty-acid group and recycles carnitine. Expressed human CPT2 formed medium- and long-chain acylcarnitines from acyl-CoAs; its physiological matrix-side reaction reconverts incoming acylcarnitines to acyl-CoAs plus free carnitine. Model: Human CPT2 in yeast homogenates; physiological direction from reviewed UniProt P23786/Rhea 12663. Limitations: The experiment directly measured the reverse reaction; direction in a cell depends on compartment and substrates. Evidence access: Primary abstract and reviewed UniProt catalytic-reaction record Carnitine palmitoyltransferase 2: New insights on the substrate specificity and implications for acylcarnitine profiling. · 2010 · https://pubmed.ncbi.nlm.nih.gov/20538056/ · DOI 10.1016/j.bbadis.2010.06.002

evidence_access

Primary abstract

experimental_model

Recombinant human CPT2 substrate panel.

limitations

No claim that every acylcarnitine originates from CPT2.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

The long-chain shuttle is not the same enzyme system as short-chain buffering.

primary_references

Carnitine palmitoyltransferase 2: New insights on the substrate specificity and implications for acylcarnitine profiling. · 2010 · https://pubmed.ncbi.nlm.nih.gov/20538056/ · DOI 10.1016/j.bbadis.2010.06.002

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 114–120

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Recombinant human CPT2 substrate panel. · source_derived_draft · unverified_draft

## l-carnitine-cpt2-specificity The long-chain shuttle is not the same enzyme system as short-chain buffering. Human CPT2 had activity with C8-C18 acyl-CoAs but virtually none with short-chain acyl-CoAs or branched-chain amino-acid oxidation intermediates. Model: Recombinant human CPT2 substrate panel. Limitations: No claim that every acylcarnitine originates from CPT2. Evidence access: Primary abstract Carnitine palmitoyltransferase 2: New insights on the substrate specificity and implications for acylcarnitine profiling. · 2010 · https://pubmed.ncbi.nlm.nih.gov/20538056/ · DOI 10.1016/j.bbadis.2010.06.002

evidence_access

Primary abstract and full-text Figures 1-4

experimental_model

Muscle-specific mouse knockout, enzyme assays and metabolomics.

limitations

Crat buffer function depends on tissue and substrate conditions.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

Carnitine can carry excess acetyl groups as well as long fatty-acid groups.

primary_references

Muscle-specific deletion of carnitine acetyltransferase compromises glucose tolerance and metabolic flexibility. · 2012 · https://pubmed.ncbi.nlm.nih.gov/22560225/ · DOI 10.1016/j.cmet.2012.04.005

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 154–160

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Muscle-specific mouse knockout, enzyme assays and metabolomics. · source_derived_draft · unverified_draft

## l-carnitine-crat-buffer Carnitine can carry excess acetyl groups as well as long fatty-acid groups. Muscle Crat deletion reduced short-chain acyltransferase activity and acetylcarnitine pools, supporting transfer of acetyl groups from acetyl-CoA to carnitine. Model: Muscle-specific mouse knockout, enzyme assays and metabolomics. Limitations: Crat buffer function depends on tissue and substrate conditions. Evidence access: Primary abstract and full-text Figures 1-4 Muscle-specific deletion of carnitine acetyltransferase compromises glucose tolerance and metabolic flexibility. · 2012 · https://pubmed.ncbi.nlm.nih.gov/22560225/ · DOI 10.1016/j.cmet.2012.04.005

evidence_access

Primary full-text Figure 6 and methods

experimental_model

Human myotubes; adenoviral silencing, approximately 60% lower enzyme activity.

limitations

Cell culture, not human supplementation.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

An independent enzyme controls acetyl-group export from muscle cells.

primary_references

Muscle-specific deletion of carnitine acetyltransferase compromises glucose tolerance and metabolic flexibility. · 2012 · https://pubmed.ncbi.nlm.nih.gov/22560225/ · DOI 10.1016/j.cmet.2012.04.005

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 170–176

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Human myotubes; adenoviral silencing, approximately 60% lower enzyme activity. · source_derived_draft · unverified_draft

## l-carnitine-crat-knockdown-export An independent enzyme controls acetyl-group export from muscle cells. Silencing CRAT in primary human myotubes reduced acetylcarnitine export by 47%. Model: Human myotubes; adenoviral silencing, approximately 60% lower enzyme activity. Limitations: Cell culture, not human supplementation. Evidence access: Primary full-text Figure 6 and methods Muscle-specific deletion of carnitine acetyltransferase compromises glucose tolerance and metabolic flexibility. · 2012 · https://pubmed.ncbi.nlm.nih.gov/22560225/ · DOI 10.1016/j.cmet.2012.04.005

evidence_access

Primary full-text Figure 6

experimental_model

Primary human myotube loss-of-function experiment.

limitations

No universal reciprocal rule for all tissues.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

More fat oxidation did not mean better glucose handling in this experiment.

primary_references

Muscle-specific deletion of carnitine acetyltransferase compromises glucose tolerance and metabolic flexibility. · 2012 · https://pubmed.ncbi.nlm.nih.gov/22560225/ · DOI 10.1016/j.cmet.2012.04.005

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 178–184

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Primary human myotube loss-of-function experiment. · source_derived_draft · unverified_draft

## l-carnitine-crat-knockdown-glucose More fat oxidation did not mean better glucose handling in this experiment. Silencing CRAT in human myotubes reduced glucose uptake by 13% while increasing oleate oxidation. Model: Primary human myotube loss-of-function experiment. Limitations: No universal reciprocal rule for all tissues. Evidence access: Primary full-text Figure 6 Muscle-specific deletion of carnitine acetyltransferase compromises glucose tolerance and metabolic flexibility. · 2012 · https://pubmed.ncbi.nlm.nih.gov/22560225/ · DOI 10.1016/j.cmet.2012.04.005

evidence_access

Primary full text and cell-line methods

experimental_model

Mouse HCC cell genetic perturbation and carbon tracing.

limitations

Dependence arises in the specified metabolic background.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

The acetyl shuttle can supply lipid synthesis when a usual route is missing.

primary_references

Acetylcarnitine shuttling links mitochondrial metabolism to histone acetylation and lipogenesis. · 2023 · https://pubmed.ncbi.nlm.nih.gov/37134161/ · DOI 10.1126/sciadv.adf0115

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 242–248

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Mouse HCC cell genetic perturbation and carbon tracing. · source_derived_draft · unverified_draft

## l-carnitine-crat-lipogenesis The acetyl shuttle can supply lipid synthesis when a usual route is missing. Removing Crat impaired glucose-derived lipid synthesis in ACLY-deficient mouse HCC cells. Model: Mouse HCC cell genetic perturbation and carbon tracing. Limitations: Dependence arises in the specified metabolic background. Evidence access: Primary full text and cell-line methods Acetylcarnitine shuttling links mitochondrial metabolism to histone acetylation and lipogenesis. · 2023 · https://pubmed.ncbi.nlm.nih.gov/37134161/ · DOI 10.1126/sciadv.adf0115

evidence_access

Primary abstract and full-text genetic/pharmacologic experiments

experimental_model

Mouse macrophages; pharmacologic exposure exceeding concentrations needed to inhibit CPT1.

limitations

Etomoxiryl-CoA formation was the proposed depletion mechanism; not evidence that carnitine depletes CoA.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

The experiment exposed a CoA-related off-target effect.

primary_references

Etomoxir Inhibits Macrophage Polarization by Disrupting CoA Homeostasis. · 2018 · https://pubmed.ncbi.nlm.nih.gov/30043752/ · DOI 10.1016/j.cmet.2018.06.001

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 450–456

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Mouse macrophages; pharmacologic exposure exceeding concentrations needed to inhibit CPT1. · source_derived_draft · unverified_draft

## l-carnitine-etomoxir-coa The experiment exposed a CoA-related off-target effect. High etomoxir exposure depleted free CoA and inhibited IL-4 macrophage polarization even without Cpt1a or Cpt2 expression. Model: Mouse macrophages; pharmacologic exposure exceeding concentrations needed to inhibit CPT1. Limitations: Etomoxiryl-CoA formation was the proposed depletion mechanism; not evidence that carnitine depletes CoA. Evidence access: Primary abstract and full-text genetic/pharmacologic experiments Etomoxir Inhibits Macrophage Polarization by Disrupting CoA Homeostasis. · 2018 · https://pubmed.ncbi.nlm.nih.gov/30043752/ · DOI 10.1016/j.cmet.2018.06.001

evidence_access

Primary abstract

experimental_model

Rat-liver CACT proteoliposome assay.

limitations

Does not demonstrate oral glutathione-carnitine synergy.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

The redox environment can change whether the carrier works.

primary_references

Effect of Copper on the Mitochondrial Carnitine/Acylcarnitine Carrier Via Interaction with Cys136 and Cys155. Possible Implications in Pathophysiology. · 2020 · https://pubmed.ncbi.nlm.nih.gov/32070004/ · DOI 10.3390/molecules25040820

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 146–152

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Rat-liver CACT proteoliposome assay. · source_derived_draft · unverified_draft

## l-carnitine-gsh-carrier The redox environment can change whether the carrier works. Adding reduced glutathione reversed copper inhibition of the reconstituted native rat carnitine-acylcarnitine carrier. Model: Rat-liver CACT proteoliposome assay. Limitations: Does not demonstrate oral glutathione-carnitine synergy. Evidence access: Primary abstract Effect of Copper on the Mitochondrial Carnitine/Acylcarnitine Carrier Via Interaction with Cys136 and Cys155. Possible Implications in Pathophysiology. · 2020 · https://pubmed.ncbi.nlm.nih.gov/32070004/ · DOI 10.3390/molecules25040820

evidence_access

Primary full-text Figure 6 and cell-line methods

experimental_model

Mouse hepatocellular carcinoma double-knockout cells; supplementation and isotope tracing.

limitations

An engineered cancer-cell bypass is not a general epigenetic benefit.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

Acetyl-group transport can connect energy metabolism to chromatin chemistry.

primary_references

Acetylcarnitine shuttling links mitochondrial metabolism to histone acetylation and lipogenesis. · 2023 · https://pubmed.ncbi.nlm.nih.gov/37134161/ · DOI 10.1126/sciadv.adf0115

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 234–240

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Mouse hepatocellular carcinoma double-knockout cells; supplementation and isotope tracing. · source_derived_draft · unverified_draft

## l-carnitine-histone-carbon Acetyl-group transport can connect energy metabolism to chromatin chemistry. Adding acetylcarnitine increased histone acetylation in lipid-depleted mouse HCC cells lacking both ACLY and ACSS2. Model: Mouse hepatocellular carcinoma double-knockout cells; supplementation and isotope tracing. Limitations: An engineered cancer-cell bypass is not a general epigenetic benefit. Evidence access: Primary full-text Figure 6 and cell-line methods Acetylcarnitine shuttling links mitochondrial metabolism to histone acetylation and lipogenesis. · 2023 · https://pubmed.ncbi.nlm.nih.gov/37134161/ · DOI 10.1126/sciadv.adf0115

evidence_access

Primary full-text Table 1 and recombinant enzyme methods

experimental_model

Human CRAT expressed in E. coli; steady-state kinetic substrate panel.

limitations

Purified-enzyme capacity does not identify the dominant flux in every compartment.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

The human enzyme directly connects carnitine and the CoA pool.

primary_references

Carnitine octanoyltransferase is important for the assimilation of exogenous acetyl-L-carnitine into acetyl-CoA in mammalian cells. · 2023 · https://pubmed.ncbi.nlm.nih.gov/36587768/ · DOI 10.1016/j.jbc.2022.102848

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 498–504

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Human CRAT expressed in E. coli; steady-state kinetic substrate panel. · source_derived_draft · unverified_draft

## l-carnitine-human-crat-reaction The human enzyme directly connects carnitine and the CoA pool. Purified recombinant human CRAT transferred short-chain acyl groups including acetyl from acyl-CoA substrates to carnitine in enzyme assays. Model: Human CRAT expressed in E. coli; steady-state kinetic substrate panel. Limitations: Purified-enzyme capacity does not identify the dominant flux in every compartment. Evidence access: Primary full-text Table 1 and recombinant enzyme methods Carnitine octanoyltransferase is important for the assimilation of exogenous acetyl-L-carnitine into acetyl-CoA in mammalian cells. · 2023 · https://pubmed.ncbi.nlm.nih.gov/36587768/ · DOI 10.1016/j.jbc.2022.102848

evidence_access

Primary abstract and full-text mouse macrophage methods

experimental_model

Mouse macrophage genetic and pharmacologic comparisons.

limitations

Context-specific immune result, not a statement that fatty-acid oxidation never matters.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

A drug effect did not prove that the carnitine shuttle was required.

primary_references

Etomoxir Inhibits Macrophage Polarization by Disrupting CoA Homeostasis. · 2018 · https://pubmed.ncbi.nlm.nih.gov/30043752/ · DOI 10.1016/j.cmet.2018.06.001

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 442–448

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Mouse macrophage genetic and pharmacologic comparisons. · source_derived_draft · unverified_draft

## l-carnitine-macrophage-cpt-loss A drug effect did not prove that the carnitine shuttle was required. Genetic loss of Cpt1a or Cpt2 did not reproduce the strong block of IL-4-driven macrophage polarization caused by high-dose etomoxir. Model: Mouse macrophage genetic and pharmacologic comparisons. Limitations: Context-specific immune result, not a statement that fatty-acid oxidation never matters. Evidence access: Primary abstract and full-text mouse macrophage methods Etomoxir Inhibits Macrophage Polarization by Disrupting CoA Homeostasis. · 2018 · https://pubmed.ncbi.nlm.nih.gov/30043752/ · DOI 10.1016/j.cmet.2018.06.001

evidence_access

Primary abstract

experimental_model

Cultured human fecal commensals under anaerobic conditions.

limitations

Community capability does not establish the abundance or activity in every person.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

Different microbes can carry out consecutive steps.

primary_references

l-Carnitine in omnivorous diets induces an atherogenic gut microbial pathway in humans. · 2019 · https://pubmed.ncbi.nlm.nih.gov/30530985/ · DOI 10.1172/JCI94601

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 362–368

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Cultured human fecal commensals under anaerobic conditions. · source_derived_draft · unverified_draft

## l-carnitine-microbial-coculture Different microbes can carry out consecutive steps. Adding E. timonensis in coculture completed the carnitine-to-TMA conversion using other microbes' gamma-butyrobetaine production. Model: Cultured human fecal commensals under anaerobic conditions. Limitations: Community capability does not establish the abundance or activity in every person. Evidence access: Primary abstract l-Carnitine in omnivorous diets induces an atherogenic gut microbial pathway in humans. · 2019 · https://pubmed.ncbi.nlm.nih.gov/30530985/ · DOI 10.1172/JCI94601

evidence_access

Primary abstract

experimental_model

Twelve-week carnitine and/or methimazole study; hCETP-expressing ApoE-null mice.

limitations

The inverse correlation does not establish TMAO protection; genotype, sex and co-treatment differ.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

Another mouse model did not show the same adverse relationship.

primary_references

L-Carnitine intake and high trimethylamine N-oxide plasma levels correlate with low aortic lesions in ApoE(-/-) transgenic mice expressing CETP. · 2016 · https://pubmed.ncbi.nlm.nih.gov/26584136/ · DOI 10.1016/j.atherosclerosis.2015.10.108

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 418–424

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Twelve-week carnitine and/or methimazole study; hCETP-expressing ApoE-null mice. · source_derived_draft · unverified_draft

## l-carnitine-mouse-atheroma-inverse Another mouse model did not show the same adverse relationship. In male ApoE-null mice expressing human CETP, carnitine raised TMAO but higher TMAO correlated with smaller aortic lesions across treatment groups. Model: Twelve-week carnitine and/or methimazole study; hCETP-expressing ApoE-null mice. Limitations: The inverse correlation does not establish TMAO protection; genotype, sex and co-treatment differ. Evidence access: Primary abstract L-Carnitine intake and high trimethylamine N-oxide plasma levels correlate with low aortic lesions in ApoE(-/-) transgenic mice expressing CETP. · 2016 · https://pubmed.ncbi.nlm.nih.gov/26584136/ · DOI 10.1016/j.atherosclerosis.2015.10.108

evidence_access

Primary abstract

experimental_model

Gnotobiotic mouse transplantation with defined communities.

limitations

Not a human clinical-event trial.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

A microbial addition tested a downstream vascular consequence.

primary_references

The microbial gbu gene cluster links cardiovascular disease risk associated with red meat consumption to microbiota L-carnitine catabolism. · 2022 · https://pubmed.ncbi.nlm.nih.gov/34949826/ · DOI 10.1038/s41564-021-01010-x

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 402–408

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Gnotobiotic mouse transplantation with defined communities. · source_derived_draft · unverified_draft

## l-carnitine-mouse-microbial-thrombosis A microbial addition tested a downstream vascular consequence. Adding E. timonensis to defined microbial communities in gnotobiotic mice completed carnitine-to-TMA conversion, raised TMAO and enhanced thrombosis after arterial injury. Model: Gnotobiotic mouse transplantation with defined communities. Limitations: Not a human clinical-event trial. Evidence access: Primary abstract The microbial gbu gene cluster links cardiovascular disease risk associated with red meat consumption to microbiota L-carnitine catabolism. · 2022 · https://pubmed.ncbi.nlm.nih.gov/34949826/ · DOI 10.1038/s41564-021-01010-x

evidence_access

Primary abstract

experimental_model

Human OCTN2 in HEK293 cells.

limitations

A kinetic constant is not a treatment target.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

The transporter also carries the acetylated form.

primary_references

Na(+)-dependent carnitine transport by organic cation transporter (OCTN2): its pharmacological and toxicological relevance. · 1999 · https://pubmed.ncbi.nlm.nih.gov/10525100/

transport_effect

raises Sodium-dependent acetylcarnitine transport with a measured Km of 8.5 micromolar.

transport_pool

the expressing cell Sodium-dependent acetylcarnitine transport with a measured Km of 8.5 micromolar.

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 50–56

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Human OCTN2 in HEK293 cells. · source_derived_draft · unverified_draft

## l-carnitine-octn2-acetyl The transporter also carries the acetylated form. Expressed human OCTN2 transported acetyl-L-carnitine in a sodium-dependent manner with a measured Km of 8.5 micromolar. Model: Human OCTN2 in HEK293 cells. Limitations: A kinetic constant is not a treatment target. Evidence access: Primary abstract Na(+)-dependent carnitine transport by organic cation transporter (OCTN2): its pharmacological and toxicological relevance. · 1999 · https://pubmed.ncbi.nlm.nih.gov/10525100/

availability_state

machinery_impairment Imported condition classification; unverified.

evidence_access

Primary abstract

experimental_model

Human primary-carnitine-deficiency patient fibroblasts and variant expression.

limitations

Genetic transport failure differs from low dietary intake.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

A broken cell-entry mechanism can produce primary carnitine deficiency.

primary_references

Mutations in the organic cation/carnitine transporter OCTN2 in primary carnitine deficiency. · 1999 · https://pubmed.ncbi.nlm.nih.gov/10051646/ · DOI 10.1073/pnas.96.5.2356

trigger_kind

machinery_impairment Imported condition classification; unverified.

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 66–72

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Human primary-carnitine-deficiency patient fibroblasts and variant expression. · source_derived_draft · unverified_draft

## l-carnitine-octn2-loss A broken cell-entry mechanism can produce primary carnitine deficiency. Fibroblasts carrying truncating OCTN2 variants from two unrelated patients lacked mediated carnitine transport. Model: Human primary-carnitine-deficiency patient fibroblasts and variant expression. Limitations: Genetic transport failure differs from low dietary intake. Evidence access: Primary abstract Mutations in the organic cation/carnitine transporter OCTN2 in primary carnitine deficiency. · 1999 · https://pubmed.ncbi.nlm.nih.gov/10051646/ · DOI 10.1073/pnas.96.5.2356

availability_state

machinery_impairment Imported condition classification; unverified.

evidence_access

Primary abstract

experimental_model

Patient fibroblast gene-complementation experiment.

limitations

This is experimental gene complementation, not a clinical gene-therapy result.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

Replacing the missing transport function rescued uptake in cells.

primary_references

Mutations in the organic cation/carnitine transporter OCTN2 in primary carnitine deficiency. · 1999 · https://pubmed.ncbi.nlm.nih.gov/10051646/ · DOI 10.1073/pnas.96.5.2356

trigger_kind

machinery_impairment Imported condition classification; unverified.

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 74–80

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Patient fibroblast gene-complementation experiment. · source_derived_draft · unverified_draft

## l-carnitine-octn2-rescue Replacing the missing transport function rescued uptake in cells. Transfecting patient fibroblasts with normal OCTN2 cDNA partially restored carnitine transport. Model: Patient fibroblast gene-complementation experiment. Limitations: This is experimental gene complementation, not a clinical gene-therapy result. Evidence access: Primary abstract Mutations in the organic cation/carnitine transporter OCTN2 in primary carnitine deficiency. · 1999 · https://pubmed.ncbi.nlm.nih.gov/10051646/ · DOI 10.1073/pnas.96.5.2356

evidence_access

Primary abstract

experimental_model

Human OCTN2 structures in ligand-free, carnitine/sodium-bound and ipratropium-bound conformations; 2025 primary study.

limitations

Structural coupling does not show that more sodium intake increases transport.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

Sodium supports transport through a separate coupled binding site.

primary_references

Structural basis of sodium ion-dependent carnitine transport by OCTN2. · 2025 · https://pubmed.ncbi.nlm.nih.gov/41318751/ · DOI 10.1038/s41467-025-66867-6

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 490–496

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Human OCTN2 structures in ligand-free, carnitine/sodium-bound and ipratropium-bound conformations; 2025 primary study. · source_derived_draft · unverified_draft

## l-carnitine-octn2-structure Sodium supports transport through a separate coupled binding site. Human OCTN2 cryo-EM structures identified a sodium-binding cavity separate from the carnitine site, with allosteric coupling supported by electrophysiology. Model: Human OCTN2 structures in ligand-free, carnitine/sodium-bound and ipratropium-bound conformations; 2025 primary study. Limitations: Structural coupling does not show that more sodium intake increases transport. Evidence access: Primary abstract Structural basis of sodium ion-dependent carnitine transport by OCTN2. · 2025 · https://pubmed.ncbi.nlm.nih.gov/41318751/ · DOI 10.1038/s41467-025-66867-6

availability_state

nutrient_deficiency Imported condition classification; unverified.

evidence_access

Primary abstract

experimental_model

Two PA and two MMA cases; plasma, urine and selected muscle measurements.

limitations

Export-driven tissue depletion is the authors' mechanism; these inherited conditions are not synonymous with dietary B12 deficiency.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

A metabolic block can tie up carnitine and lead to its loss in urine.

primary_references

Propionylcarnitine excretion in propionic and methylmalonic acidurias: a cause of carnitine deficiency. · 1984 · https://pubmed.ncbi.nlm.nih.gov/6723070/ · DOI 10.1016/0009-8981(84)90187-6

trigger_kind

nutrient_deficiency Imported condition classification; unverified.

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 258–264

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Two PA and two MMA cases; plasma, urine and selected muscle measurements. · source_derived_draft · unverified_draft

## l-carnitine-organic-acid-loss A metabolic block can tie up carnitine and lead to its loss in urine. Four patients with propionic or methylmalonic aciduria had low plasma free carnitine and elevated short-chain acylcarnitine excretion; muscle carnitine was low in two biopsied patients. Model: Two PA and two MMA cases; plasma, urine and selected muscle measurements. Limitations: Export-driven tissue depletion is the authors' mechanism; these inherited conditions are not synonymous with dietary B12 deficiency. Evidence access: Primary abstract Propionylcarnitine excretion in propionic and methylmalonic acidurias: a cause of carnitine deficiency. · 1984 · https://pubmed.ncbi.nlm.nih.gov/6723070/ · DOI 10.1016/0009-8981(84)90187-6

availability_state

nutrient_deficiency Imported condition classification; unverified.

evidence_access

Primary abstract

experimental_model

Six healthy men; 1200 mg/day.

limitations

A small provocation study, not a universal drug effect size.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

A drug-associated shortfall can differ between blood and muscle.

primary_references

Impaired ketogenesis in carnitine depletion caused by short-term administration of pivalic acid prodrug. · 1994 · https://pubmed.ncbi.nlm.nih.gov/7917463/ · DOI 10.1006/bmmb.1994.1028

trigger_kind

nutrient_deficiency Imported condition classification; unverified.

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 266–272

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Six healthy men; 1200 mg/day. · source_derived_draft · unverified_draft

## l-carnitine-pivalate-depletion A drug-associated shortfall can differ between blood and muscle. Twelve days of pivmecillinam reduced mean serum free carnitine from 42.8 to 11.6 micromolar, while measured muscle carnitine was unchanged. Model: Six healthy men; 1200 mg/day. Limitations: A small provocation study, not a universal drug effect size. Evidence access: Primary abstract Impaired ketogenesis in carnitine depletion caused by short-term administration of pivalic acid prodrug. · 1994 · https://pubmed.ncbi.nlm.nih.gov/7917463/ · DOI 10.1006/bmmb.1994.1028

availability_state

nutrient_deficiency Imported condition classification; unverified.

evidence_access

Primary abstract

experimental_model

Human before-and-after fasting challenge.

limitations

Only a subset was affected; no universal plasma cutoff or dietary diagnosis was established.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

Low carnitine can limit the switch to fat-derived fasting fuel.

primary_references

Impaired ketogenesis in carnitine depletion caused by short-term administration of pivalic acid prodrug. · 1994 · https://pubmed.ncbi.nlm.nih.gov/7917463/ · DOI 10.1006/bmmb.1994.1028

trigger_kind

nutrient_deficiency Imported condition classification; unverified.

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 274–280

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Human before-and-after fasting challenge. · source_derived_draft · unverified_draft

## l-carnitine-pivalate-ketones Low carnitine can limit the switch to fat-derived fasting fuel. After pivmecillinam-associated carnitine depletion, two of six subjects showed impaired ketone production during a 36-hour fast. Model: Human before-and-after fasting challenge. Limitations: Only a subset was affected; no universal plasma cutoff or dietary diagnosis was established. Evidence access: Primary abstract Impaired ketogenesis in carnitine depletion caused by short-term administration of pivalic acid prodrug. · 1994 · https://pubmed.ncbi.nlm.nih.gov/7917463/ · DOI 10.1006/bmmb.1994.1028

evidence_access

Primary abstract and full-text mouse genetic methods

experimental_model

Mouse T-cell conditional knockout and differentiation/infection experiments.

limitations

Does not exclude other tissue or immune contexts.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

Genetic tests limit broad claims about carnitine-shuttle dependence of immunity.

primary_references

Etomoxir Actions on Regulatory and Memory T Cells Are Independent of Cpt1a-Mediated Fatty Acid Oxidation. · 2018 · https://pubmed.ncbi.nlm.nih.gov/30043753/ · DOI 10.1016/j.cmet.2018.06.002

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 458–464

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Mouse T-cell conditional knockout and differentiation/infection experiments. · source_derived_draft · unverified_draft

## l-carnitine-tcell-cpt-loss Genetic tests limit broad claims about carnitine-shuttle dependence of immunity. T-cell-specific Cpt1a deletion showed that the ACC2/Cpt1a pathway was largely dispensable for memory and regulatory T-cell formation in the tested models. Model: Mouse T-cell conditional knockout and differentiation/infection experiments. Limitations: Does not exclude other tissue or immune contexts. Evidence access: Primary abstract and full-text mouse genetic methods Etomoxir Actions on Regulatory and Memory T Cells Are Independent of Cpt1a-Mediated Fatty Acid Oxidation. · 2018 · https://pubmed.ncbi.nlm.nih.gov/30043753/ · DOI 10.1016/j.cmet.2018.06.002

evidence_access

Primary abstract

experimental_model

Human tissue homogenate enzyme assays.

limitations

Detection limits, developmental stage and sampled tissues constrain the result; not an absolute modern atlas.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

Some tissues rely on importing the finished molecule.

primary_references

Tissue distribution of carnitine biosynthetic enzymes in man. · 1980 · https://pubmed.ncbi.nlm.nih.gov/6770910/ · DOI 10.1016/0304-4165(80)90133-6

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 26–32

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Human tissue homogenate enzyme assays. · source_derived_draft · unverified_draft

## l-carnitine-tissue-synthesis Some tissues rely on importing the finished molecule. Human tissue assays detected gamma-butyrobetaine-to-carnitine activity in liver, kidney and brain, but not heart or skeletal muscle; the earlier steps were detected in all five tissues. Model: Human tissue homogenate enzyme assays. Limitations: Detection limits, developmental stage and sampled tissues constrain the result; not an absolute modern atlas. Evidence access: Primary abstract Tissue distribution of carnitine biosynthetic enzymes in man. · 1980 · https://pubmed.ncbi.nlm.nih.gov/6770910/ · DOI 10.1016/0304-4165(80)90133-6

evidence_access

Primary abstract

experimental_model

Human urine/plasma measurements and OCTN2 assays.

limitations

The authors found that excreted valproylcarnitine did not impair renal handling of free carnitine in vivo.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

The drug-linked ester is handled differently from free carnitine.

primary_references

Effect of short- and long-term treatment with valproate on carnitine homeostasis in humans. · 2012 · https://pubmed.ncbi.nlm.nih.gov/22743351/ · DOI 10.1097/FTD.0b013e3182608e2f

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 290–296

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Human urine/plasma measurements and OCTN2 assays. · source_derived_draft · unverified_draft

## l-carnitine-valproate-clearance The drug-linked ester is handled differently from free carnitine. Valproylcarnitine fractional renal excretion approached 100%, unlike the strongly reabsorbed free carnitine pool; transporter assays showed low OCTN2 affinity. Model: Human urine/plasma measurements and OCTN2 assays. Limitations: The authors found that excreted valproylcarnitine did not impair renal handling of free carnitine in vivo. Evidence access: Primary abstract Effect of short- and long-term treatment with valproate on carnitine homeostasis in humans. · 2012 · https://pubmed.ncbi.nlm.nih.gov/22743351/ · DOI 10.1097/FTD.0b013e3182608e2f

evidence_access

Primary abstract

experimental_model

One longitudinal initiation case plus ten long-term patients.

limitations

Suppressed synthesis and increased OCTN2 expression were proposed explanations, not directly measured human mechanisms.

nutrient_topic

L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit. · L-Carnitine

plain_language

Drug-associated carnitine changes can evolve over time.

primary_references

Effect of short- and long-term treatment with valproate on carnitine homeostasis in humans. · 2012 · https://pubmed.ncbi.nlm.nih.gov/22743351/ · DOI 10.1097/FTD.0b013e3182608e2f

L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19) · lines 282–288

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · One longitudinal initiation case plus ten long-term patients. · source_derived_draft · unverified_draft

## l-carnitine-valproate-timecourse Drug-associated carnitine changes can evolve over time. In the patient observed when starting valproate, plasma carnitine fell during weeks 1-3 and recovered by weeks 3-5. Model: One longitudinal initiation case plus ten long-term patients. Limitations: Suppressed synthesis and increased OCTN2 expression were proposed explanations, not directly measured human mechanisms. Evidence access: Primary abstract Effect of short- and long-term treatment with valproate on carnitine homeostasis in humans. · 2012 · https://pubmed.ncbi.nlm.nih.gov/22743351/ · DOI 10.1097/FTD.0b013e3182608e2f

evidence_access

Primary abstract

experimental_model

ICR mice and treadmill exercise; protein modification and localization measurements.

limitations

CPT I isoform was not resolved in the accessed abstract; astaxanthin is not a demonstrated CPT cofactor.

nutrient_topic

Astaxanthin collection; molecular form, preparation, species, exposure and manipulation remain explicit. · Astaxanthin

plain_language

A fat-transport pathway was less oxidatively modified during exercise.

primary_references

Astaxanthin improves muscle lipid metabolism in exercise via inhibitory effect of oxidative CPT I modification. · 2008 · https://pubmed.ncbi.nlm.nih.gov/18082622/ · DOI 10.1016/j.bbrc.2007.12.019

Astaxanthin: transport, membrane chemistry, signaling and nutrient interactions (2026-09-19) · lines 342–348

AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · ICR mice and treadmill exercise; protein modification and localization measurements. · source_derived_draft · unverified_draft

## astaxanthin-cpt1-oxidation A fat-transport pathway was less oxidatively modified during exercise. Four weeks of astaxanthin feeding reduced exercise-associated oxidative modification of CPT I and increased FAT/CD36-CPT I colocalization in mice. Model: ICR mice and treadmill exercise; protein modification and localization measurements. Limitations: CPT I isoform was not resolved in the accessed abstract; astaxanthin is not a demonstrated CPT cofactor. Evidence access: Primary abstract Astaxanthin improves muscle lipid metabolism in exercise via inhibitory effect of oxidative CPT I modification. · 2008 · https://pubmed.ncbi.nlm.nih.gov/18082622/ · DOI 10.1016/j.bbrc.2007.12.019

availability_state

nutrient_deficiency Imported condition classification; unverified.

cross_nutrient

Vitamin C chemistry in collagen, modified-lysine/carnitine metabolism or copper-dependent peptide/catecholamine processing.

experimental_model

Guinea-pig dietary deficiency with pair feeding and precursor loading

exposure

Vitamin C deficient diet for 28 days; oral trimethyllysine or gamma-butyrobetaine 0.5 mmol/kg/day on days 19–28, with replete and pair-fed controls.

limitations

Estimate is derived from excretion during a large precursor load, not isotope-resolved basal flux; does not show all tissues are vitamin-C-independent.

nutrient_topic

Vitamin C research collection; topical membership is not evidence of a direct dietary effect. · Vitamin C

organism

Cavia porcellus

plain_language

Even vitamin-C-deficient animals could make substantial carnitine when given this precursor.

primary_references

[carnitine1995] The ability of guinea pigs to synthesize carnitine at a normal rate from epsilon-N-trimethyllysine or gamma-butyrobetaine in vivo is not compromised by experimental vitamin C deficiency. (1995). https://pubmed.ncbi.nlm.nih.gov/7752911/ DOI: 10.1016/0026-0495(95)90120-5

tissue_or_cell_type

Whole animal; urine-based synthesis estimate

trigger_kind

nutrient_deficiency Imported condition classification; unverified.

Vitamin C: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 767–778

AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Guinea-pig dietary deficiency with pair feeding and precursor loading · source_derived_draft · unverified_draft

### vc-enzyme-deficient-bb-response Oral gamma-butyrobetaine increased urine-based estimated carnitine synthesis by 41–50 micromol/kg/day across ascorbate-replete, deficient and pair-fed guinea-pig groups; vitamin C deficiency did not abolish the precursor response. Condition category: nutrient_deficiency nutrient_topic: Vitamin C research collection; topical membership is not evidence of a direct dietary effect. plain_language: Even vitamin-C-deficient animals could make substantial carnitine when given this precursor. organism: Cavia porcellus tissue_or_cell_type: Whole animal; urine-based synthesis estimate experimental_model: Guinea-pig dietary deficiency with pair feeding and precursor loading limitations: Estimate is derived from excretion during a large precursor load, not isotope-resolved basal flux; does not show all tissues are vitamin-C-independent. cross_nutrient: Vitamin C chemistry in collagen, modified-lysine/carnitine metabolism or copper-dependent peptide/catecholamine processing. exposure: Vitamin C deficient diet for 28 days; oral trimethyllysine or gamma-butyrobetaine 0.5 mmol/kg/day on days 19–28, with replete and pair-fed controls. [carnitine1995] The ability of guinea pigs to synthesize carnitine at a normal rate from epsilon-N-trimethyllysine or gamma-butyrobetaine in vivo is not compromised by experimental vitamin C deficiency. (1995). https://pubmed.ncbi.nlm.nih.gov/7752911/ DOI: 10.1016/0026-0495(95)90120-5

availability_state

nutrient_deficiency Imported condition classification; unverified.

cross_nutrient

Vitamin C chemistry in collagen, modified-lysine/carnitine metabolism or copper-dependent peptide/catecholamine processing.

experimental_model

Guinea-pig dietary deficiency with pair feeding and precursor loading

exposure

Vitamin C deficient diet for 28 days; oral trimethyllysine or gamma-butyrobetaine 0.5 mmol/kg/day on days 19–28, with replete and pair-fed controls.

limitations

Authors favored excessive excretion as an explanation for depletion; this does not isolate a renal transporter or quantify its contribution in human deficiency.

nutrient_topic

Vitamin C research collection; topical membership is not evidence of a direct dietary effect. · Vitamin C

organism

Cavia porcellus

plain_language

Greater loss in urine can contribute to low carnitine during vitamin C deficiency.

primary_references

[carnitine1995] The ability of guinea pigs to synthesize carnitine at a normal rate from epsilon-N-trimethyllysine or gamma-butyrobetaine in vivo is not compromised by experimental vitamin C deficiency. (1995). https://pubmed.ncbi.nlm.nih.gov/7752911/ DOI: 10.1016/0026-0495(95)90120-5

tissue_or_cell_type

Whole animal; urine-based synthesis estimate

trigger_kind

nutrient_deficiency Imported condition classification; unverified.

Vitamin C: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 780–791

AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Guinea-pig dietary deficiency with pair feeding and precursor loading · source_derived_draft · unverified_draft

### vc-enzyme-deficient-carnitine-excretion Without carnitine-precursor supplements, vitamin-C-deficient guinea pigs excreted approximately three times as much free and total carnitine as replete animals on days 19–28; pair feeding alone did not produce that pattern. Condition category: nutrient_deficiency nutrient_topic: Vitamin C research collection; topical membership is not evidence of a direct dietary effect. plain_language: Greater loss in urine can contribute to low carnitine during vitamin C deficiency. organism: Cavia porcellus tissue_or_cell_type: Whole animal; urine-based synthesis estimate experimental_model: Guinea-pig dietary deficiency with pair feeding and precursor loading limitations: Authors favored excessive excretion as an explanation for depletion; this does not isolate a renal transporter or quantify its contribution in human deficiency. cross_nutrient: Vitamin C chemistry in collagen, modified-lysine/carnitine metabolism or copper-dependent peptide/catecholamine processing. exposure: Vitamin C deficient diet for 28 days; oral trimethyllysine or gamma-butyrobetaine 0.5 mmol/kg/day on days 19–28, with replete and pair-fed controls. [carnitine1995] The ability of guinea pigs to synthesize carnitine at a normal rate from epsilon-N-trimethyllysine or gamma-butyrobetaine in vivo is not compromised by experimental vitamin C deficiency. (1995). https://pubmed.ncbi.nlm.nih.gov/7752911/ DOI: 10.1016/0026-0495(95)90120-5

availability_state

nutrient_deficiency Imported condition classification; unverified.

cross_nutrient

Vitamin C chemistry in collagen, modified-lysine/carnitine metabolism or copper-dependent peptide/catecholamine processing.

experimental_model

Guinea-pig vitamin C deficiency and pair-fed comparison

exposure

Vitamin C deficient, control and underfed pair-fed groups; duration not verified in abstract.

limitations

Do not infer that every between-group comparison was statistically significant from these means; biosynthesis was not directly measured.

nutrient_topic

Vitamin C research collection; topical membership is not evidence of a direct dietary effect. · Vitamin C

organism

Cavia porcellus

plain_language

Both vitamin C shortage and reduced food intake affected liver carnitine in this experiment.

primary_references

[carnitine1983] Combined effect of ascorbic acid deficiency and underfeeding on the hepatic carnitine level in guinea-pigs. (1983). https://pubmed.ncbi.nlm.nih.gov/6852178/ DOI: 10.1007/bf01965181

tissue_or_cell_type

Liver

trigger_kind

nutrient_deficiency Imported condition classification; unverified.

Vitamin C: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 741–752

AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Guinea-pig vitamin C deficiency and pair-fed comparison · source_derived_draft · unverified_draft

### vc-enzyme-deficient-liver-carnitine Hepatic carnitine was 148 +/- 9.8 nmol/g in vitamin-C-deficient guinea pigs versus 249 +/- 16.1 in controls; pair-fed animals measured 181 +/- 14.1 nmol/g (means +/- SEM). Condition category: nutrient_deficiency nutrient_topic: Vitamin C research collection; topical membership is not evidence of a direct dietary effect. plain_language: Both vitamin C shortage and reduced food intake affected liver carnitine in this experiment. organism: Cavia porcellus tissue_or_cell_type: Liver experimental_model: Guinea-pig vitamin C deficiency and pair-fed comparison limitations: Do not infer that every between-group comparison was statistically significant from these means; biosynthesis was not directly measured. cross_nutrient: Vitamin C chemistry in collagen, modified-lysine/carnitine metabolism or copper-dependent peptide/catecholamine processing. exposure: Vitamin C deficient, control and underfed pair-fed groups; duration not verified in abstract. [carnitine1983] Combined effect of ascorbic acid deficiency and underfeeding on the hepatic carnitine level in guinea-pigs. (1983). https://pubmed.ncbi.nlm.nih.gov/6852178/ DOI: 10.1007/bf01965181

availability_state

nutrient_deficiency Imported condition classification; unverified.

cross_nutrient

Vitamin C chemistry in collagen, modified-lysine/carnitine metabolism or copper-dependent peptide/catecholamine processing.

experimental_model

Guinea-pig dietary deficiency with pair feeding and precursor loading

exposure

Vitamin C deficient diet for 28 days; oral trimethyllysine or gamma-butyrobetaine 0.5 mmol/kg/day on days 19–28, with replete and pair-fed controls.

limitations

Estimate is derived from excretion during a large precursor load, not isotope-resolved basal flux; does not show all tissues are vitamin-C-independent.

nutrient_topic

Vitamin C research collection; topical membership is not evidence of a direct dietary effect. · Vitamin C

organism

Cavia porcellus

plain_language

Even vitamin-C-deficient animals could make substantial carnitine when given this precursor.

primary_references

[carnitine1995] The ability of guinea pigs to synthesize carnitine at a normal rate from epsilon-N-trimethyllysine or gamma-butyrobetaine in vivo is not compromised by experimental vitamin C deficiency. (1995). https://pubmed.ncbi.nlm.nih.gov/7752911/ DOI: 10.1016/0026-0495(95)90120-5

tissue_or_cell_type

Whole animal; urine-based synthesis estimate

trigger_kind

nutrient_deficiency Imported condition classification; unverified.

Vitamin C: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 754–765

AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Guinea-pig dietary deficiency with pair feeding and precursor loading · source_derived_draft · unverified_draft

### vc-enzyme-deficient-tml-response Oral trimethyllysine increased urine-based estimated carnitine synthesis by 32–40 micromol/kg/day across ascorbate-replete, deficient and pair-fed guinea-pig groups; vitamin C deficiency did not abolish the precursor response. Condition category: nutrient_deficiency nutrient_topic: Vitamin C research collection; topical membership is not evidence of a direct dietary effect. plain_language: Even vitamin-C-deficient animals could make substantial carnitine when given this precursor. organism: Cavia porcellus tissue_or_cell_type: Whole animal; urine-based synthesis estimate experimental_model: Guinea-pig dietary deficiency with pair feeding and precursor loading limitations: Estimate is derived from excretion during a large precursor load, not isotope-resolved basal flux; does not show all tissues are vitamin-C-independent. cross_nutrient: Vitamin C chemistry in collagen, modified-lysine/carnitine metabolism or copper-dependent peptide/catecholamine processing. exposure: Vitamin C deficient diet for 28 days; oral trimethyllysine or gamma-butyrobetaine 0.5 mmol/kg/day on days 19–28, with replete and pair-fed controls. [carnitine1995] The ability of guinea pigs to synthesize carnitine at a normal rate from epsilon-N-trimethyllysine or gamma-butyrobetaine in vivo is not compromised by experimental vitamin C deficiency. (1995). https://pubmed.ncbi.nlm.nih.gov/7752911/ DOI: 10.1016/0026-0495(95)90120-5

cross_nutrient

Vitamin C chemistry in collagen, modified-lysine/carnitine metabolism or copper-dependent peptide/catecholamine processing.

experimental_model

Primary cultured male guinea-pig hepatocyte monolayers

exposure

Ascorbate preloading followed by 4-hour gamma-butyrobetaine incubation; precursor range includes 0.05–1.0 mM and 5 mM.

limitations

Species-specific cell exposure; accumulation reflects production and other handling, not directly a human dietary dose-response.

nutrient_topic

Vitamin C research collection; topical membership is not evidence of a direct dietary effect. · Vitamin C

organism

Cavia porcellus

plain_language

Vitamin C helped isolated liver cells convert a supplied precursor into carnitine.

primary_references

[hepatocytes1991] The regulatory effect of ascorbate on the carnitine synthesis in primary cultured guinea pig hepatocytes. (1991). https://pubmed.ncbi.nlm.nih.gov/1765841/ DOI: 10.3177/jnsv.37.371

tissue_or_cell_type

Hepatocytes

Vitamin C: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 702–713

AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Primary cultured male guinea-pig hepatocyte monolayers · source_derived_draft · unverified_draft

### vc-enzyme-hepatocyte-carnitine Increasing ascorbate supplementation increased carnitine accumulation from gamma-butyrobetaine in primary guinea-pig hepatocytes after four hours. Condition category: normal nutrient_topic: Vitamin C research collection; topical membership is not evidence of a direct dietary effect. plain_language: Vitamin C helped isolated liver cells convert a supplied precursor into carnitine. organism: Cavia porcellus tissue_or_cell_type: Hepatocytes experimental_model: Primary cultured male guinea-pig hepatocyte monolayers limitations: Species-specific cell exposure; accumulation reflects production and other handling, not directly a human dietary dose-response. cross_nutrient: Vitamin C chemistry in collagen, modified-lysine/carnitine metabolism or copper-dependent peptide/catecholamine processing. exposure: Ascorbate preloading followed by 4-hour gamma-butyrobetaine incubation; precursor range includes 0.05–1.0 mM and 5 mM. [hepatocytes1991] The regulatory effect of ascorbate on the carnitine synthesis in primary cultured guinea pig hepatocytes. (1991). https://pubmed.ncbi.nlm.nih.gov/1765841/ DOI: 10.3177/jnsv.37.371

availability_state

nutrient_deficiency Imported condition classification; unverified.

cross_nutrient

Vitamin C chemistry in collagen, modified-lysine/carnitine metabolism or copper-dependent peptide/catecholamine processing.

experimental_model

Guinea pigs with graded dietary vitamin C supply

exposure

Dietary regimens produced tissue vitamin C approximately 12% versus 100% saturation; regimen duration/dose not verified in abstract.

limitations

No direct synthesis-rate measurement; suggested explanation for human fatigue was not tested.

nutrient_topic

Vitamin C research collection; topical membership is not evidence of a direct dietary effect. · Vitamin C

organism

Cavia porcellus

plain_language

Low vitamin C coincided with lower muscle carnitine before obvious scurvy signs in these animals.

primary_references

[carnitine1980] Dietary ascorbic acid and muscle carnitine (beta-OH-gamma-(trimethylamino) butyric acid) in guinea-pigs. (1980). https://pubmed.ncbi.nlm.nih.gov/7378344/ DOI: 10.1079/bjn19800102

tissue_or_cell_type

Skeletal muscle

trigger_kind

nutrient_deficiency Imported condition classification; unverified.

Vitamin C: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 728–739

AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Guinea pigs with graded dietary vitamin C supply · source_derived_draft · unverified_draft

### vc-enzyme-low-c-muscle-carnitine Guinea pigs with tissue vitamin C around 12% saturation had significantly lower muscle carnitine than animals near 100% saturation, without the customary overt hypovitaminosis-C signs in this experiment. Condition category: nutrient_deficiency nutrient_topic: Vitamin C research collection; topical membership is not evidence of a direct dietary effect. plain_language: Low vitamin C coincided with lower muscle carnitine before obvious scurvy signs in these animals. organism: Cavia porcellus tissue_or_cell_type: Skeletal muscle experimental_model: Guinea pigs with graded dietary vitamin C supply limitations: No direct synthesis-rate measurement; suggested explanation for human fatigue was not tested. cross_nutrient: Vitamin C chemistry in collagen, modified-lysine/carnitine metabolism or copper-dependent peptide/catecholamine processing. exposure: Dietary regimens produced tissue vitamin C approximately 12% versus 100% saturation; regimen duration/dose not verified in abstract. [carnitine1980] Dietary ascorbic acid and muscle carnitine (beta-OH-gamma-(trimethylamino) butyric acid) in guinea-pigs. (1980). https://pubmed.ncbi.nlm.nih.gov/7378344/ DOI: 10.1079/bjn19800102

cross_nutrient

Vitamin C chemistry in collagen, modified-lysine/carnitine metabolism or copper-dependent peptide/catecholamine processing.

experimental_model

Primary cultured male guinea-pig hepatocyte monolayers

exposure

Ascorbate preloading followed by 4-hour gamma-butyrobetaine incubation; precursor range includes 0.05–1.0 mM and 5 mM.

limitations

Pool decrease alone does not establish exact ascorbate stoichiometry or identify all oxidation, export and degradation pathways.

nutrient_topic

Vitamin C research collection; topical membership is not evidence of a direct dietary effect. · Vitamin C

organism

Cavia porcellus

plain_language

Supplying the carnitine precursor lowered the cells’ measured vitamin C pools.

primary_references

[hepatocytes1991] The regulatory effect of ascorbate on the carnitine synthesis in primary cultured guinea pig hepatocytes. (1991). https://pubmed.ncbi.nlm.nih.gov/1765841/ DOI: 10.3177/jnsv.37.371

tissue_or_cell_type

Hepatocytes

Vitamin C: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 715–726

AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Primary cultured male guinea-pig hepatocyte monolayers · source_derived_draft · unverified_draft

### vc-enzyme-precursor-lowers-cell-ascorbate Gamma-butyrobetaine supplementation lowered both reduced and total cellular vitamin C content during the guinea-pig hepatocyte carnitine-synthesis experiment. Condition category: normal nutrient_topic: Vitamin C research collection; topical membership is not evidence of a direct dietary effect. plain_language: Supplying the carnitine precursor lowered the cells’ measured vitamin C pools. organism: Cavia porcellus tissue_or_cell_type: Hepatocytes experimental_model: Primary cultured male guinea-pig hepatocyte monolayers limitations: Pool decrease alone does not establish exact ascorbate stoichiometry or identify all oxidation, export and degradation pathways. cross_nutrient: Vitamin C chemistry in collagen, modified-lysine/carnitine metabolism or copper-dependent peptide/catecholamine processing. exposure: Ascorbate preloading followed by 4-hour gamma-butyrobetaine incubation; precursor range includes 0.05–1.0 mM and 5 mM. [hepatocytes1991] The regulatory effect of ascorbate on the carnitine synthesis in primary cultured guinea pig hepatocytes. (1991). https://pubmed.ncbi.nlm.nih.gov/1765841/ DOI: 10.3177/jnsv.37.371