Component
Human fibroblast growth factor 21 / FGF21
Context-specific entity; species, compartment and exposure are stated on each claim.
3 recorded relationships. Experimental role, claim status and evidence remain attached to each record.
How nutrients influence it
Every nutrient with a recorded effect on this component, credited to the nutrient that acted rather than the chapter that recorded it. Open a nutrient to see the findings and the conditions they were measured under.
Other things that act on it
Enzymes, hormones, genes, and other components with a recorded effect. These are not nutrients, so they do not count toward the arrows above. Each finding names the chapter that recorded it.
How nutrients reach it in more than one step
Chains of two or more recorded steps that end here, grouped by the nutrient they start from. Each step is a separate finding, so a chain is a route a mechanism could take, not proof that it does.
Tracing routes…
What it does
Every recorded relationship this component is part of, grouped by its role. Plain wording comes first; the technical statement follows.
What it acts on
FGF21 induction was associated with decreased thermogenesis and adiponectin.
Experimental context and source evidence
- evidence_access
- Primary abstract; protocol checked in PMC4665770
- experimental_model
- Eleven volunteers; ten-day fast with daily multivitamin, 20 mEq potassium chloride and 200 mg allopurinol.
- limitations
- Association does not prove FGF21 caused either decrease.
- nutrient_topic
- Fasting physiological-state collection; human protocols, cellular deprivation and refeeding are distinguished. · Fasting / abstention from energy intake
- plain_language
- Late starvation signaling accompanied energy conservation.
- primary_references
- FGF21 and the late adaptive response to starvation in humans. · 2015 · https://pubmed.ncbi.nlm.nih.gov/26529252/ · DOI 10.1172/JCI83349
Fasting: fuel switching, nutrient sensing, ketone signaling, nutrient dependencies and refeeding (2026-09-18) · lines 288–294
AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Eleven volunteers; ten-day fast with daily multivitamin, 20 mEq potassium chloride and 200 mg allopurinol. · source_derived_draft · unverified_draft
## fast-human-fgf-heat Late starvation signaling accompanied energy conservation. FGF21 induction was associated with decreased thermogenesis and adiponectin. Model: Eleven volunteers; ten-day fast with daily multivitamin, 20 mEq potassium chloride and 200 mg allopurinol. Limitations: Association does not prove FGF21 caused either decrease. Evidence access: Primary abstract; protocol checked in PMC4665770 FGF21 and the late adaptive response to starvation in humans. · 2015 · https://pubmed.ncbi.nlm.nih.gov/26529252/ · DOI 10.1172/JCI83349
Complete structured claim and evidence
What acts on it
FGF21 rose notably on days 7–10, after ketone concentrations had already increased.
Experimental context and source evidence
- evidence_access
- Primary abstract; protocol checked in PMC4665770
- experimental_model
- Eleven volunteers; ten-day fast with daily multivitamin, 20 mEq potassium chloride and 200 mg allopurinol.
- limitations
- Small supported protocol; timing does not exclude every possible FGF21 contribution.
- nutrient_topic
- Fasting physiological-state collection; human protocols, cellular deprivation and refeeding are distinguished. · Fasting / abstention from energy intake
- plain_language
- This hormone did not precede initial human ketogenesis.
- primary_references
- FGF21 and the late adaptive response to starvation in humans. · 2015 · https://pubmed.ncbi.nlm.nih.gov/26529252/ · DOI 10.1172/JCI83349
Fasting: fuel switching, nutrient sensing, ketone signaling, nutrient dependencies and refeeding (2026-09-18) · lines 280–286
AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Eleven volunteers; ten-day fast with daily multivitamin, 20 mEq potassium chloride and 200 mg allopurinol. · source_derived_draft · unverified_draft
## fast-human-fgf-delay This hormone did not precede initial human ketogenesis. FGF21 rose notably on days 7–10, after ketone concentrations had already increased. Model: Eleven volunteers; ten-day fast with daily multivitamin, 20 mEq potassium chloride and 200 mg allopurinol. Limitations: Small supported protocol; timing does not exclude every possible FGF21 contribution. Evidence access: Primary abstract; protocol checked in PMC4665770 FGF21 and the late adaptive response to starvation in humans. · 2015 · https://pubmed.ncbi.nlm.nih.gov/26529252/ · DOI 10.1172/JCI83349
Complete structured claim and evidence
Where it participates (unsigned role)
FNDC5 and FGF21 treatment upregulated human adipocyte brown-fat gene and protein expression and thermogenesis in a depot-specific manner, suggesting a thermogenic cold-activated endocrine axis between muscle and fat.
Experimental context and source evidence
- evidence_span
- {"source_cache": "artifacts/cold-research/24506871.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "980c2630ed13bf2a55f813a6df483edb68a1d6370c0f1afdfcbc7df7817eb610", "start_char": 0, "end_char": 1149, "text_sha256": "980c2630ed13bf2a55f813a6df483edb68a1d6370c0f1afdfcbc7df7817eb610"}
- experimental_model
- Human cold exposure with circulating myokine measurement and human adipocyte treatment
- exposure
- Cold exposure sufficient to induce shivering; FNDC5 and FGF21 treatment of human adipocytes
- limitations
- The proportionality to shivering intensity is the mechanistic link. Depot-specific adipocyte responses mean this is not a uniform browning effect.
- nutrient_topic
- Cold water immersion research collection; topical membership is not evidence of a direct clinical effect, and a therapeutic exposure is not a dietary intake. · Cold water immersion
- organism
- Human
- plain_language
- The messenger from shivering muscle tells fat to start making heat.
- primary_references
- [cold-p24506871] Irisin and FGF21 are cold-induced endocrine activators of brown fat function in humans. (2014). https://pubmed.ncbi.nlm.nih.gov/24506871/ DOI: 10.1016/j.cmet.2013.12.017
- tissue_or_cell_type
- Skeletal muscle and adipose tissue
Cold water immersion: cold sensing, heat production, the catecholamine axis and what repeated exposure changes (2026-09-19) · lines 494–505
AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Human cold exposure with circulating myokine measurement and human adipocyte treatment · source_derived_draft · unverified_draft
### cold-irisin-browning FNDC5 and FGF21 treatment upregulated human adipocyte brown-fat gene and protein expression and thermogenesis in a depot-specific manner, suggesting a thermogenic cold-activated endocrine axis between muscle and fat. Condition category: normal nutrient_topic: Cold water immersion research collection; topical membership is not evidence of a direct clinical effect, and a therapeutic exposure is not a dietary intake. plain_language: The messenger from shivering muscle tells fat to start making heat. organism: Human tissue_or_cell_type: Skeletal muscle and adipose tissue experimental_model: Human cold exposure with circulating myokine measurement and human adipocyte treatment limitations: The proportionality to shivering intensity is the mechanistic link. Depot-specific adipocyte responses mean this is not a uniform browning effect. exposure: Cold exposure sufficient to induce shivering; FNDC5 and FGF21 treatment of human adipocytes evidence_span: {"source_cache": "artifacts/cold-research/24506871.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "980c2630ed13bf2a55f813a6df483edb68a1d6370c0f1afdfcbc7df7817eb610", "start_char": 0, "end_char": 1149, "text_sha256": "980c2630ed13bf2a55f813a6df483edb68a1d6370c0f1afdfcbc7df7817eb610"} [cold-p24506871] Irisin and FGF21 are cold-induced endocrine activators of brown fat function in humans. (2014). https://pubmed.ncbi.nlm.nih.gov/24506871/ DOI: 10.1016/j.cmet.2013.12.017
Complete structured claim and evidence
The events it takes part in
A mechanism often involves more than two components. These are the full events, with every participant and its role.
Situations it appears in
Low-supply and faulty-machinery situations recorded in the chapters where this component plays a part.
In the sources
Preserved passages that mention this component, quoted exactly. Open one to read it in context.
Open hypotheses
Proposed ideas that involve this component. They are labeled as hypotheses and do not change any recorded statement.
This is a research prototype built from draft material. It is not medical advice, and its statements still await verification against the original studies.