{"id":"8d4a4733-e05d-5c37-9220-6dfe6504e5ab","stable_key":"8c946991-97f0-55ee-8df0-00e67621962f:nad-plus-aging-flux","predicate":"maintains","statement":"Isotope tracing found a median tissue NAD+ decrease of about 30% in aged mice while absolute synthesis was maintained in most tissues through faster turnover of the smaller pool.","claim_class":"observational","status":"source_derived_draft","evidence_grade":"ungraded","direction":"context_dependent","is_public":true,"mechanism_event_id":"a2b55bc9-a766-5394-8a6b-4e71ad4175f9","mechanism_event_label":"A smaller pool does not necessarily mean slower production.","subject":{"id":"1d8c70a3-b88d-5129-ab6a-be243535c08f","slug":"aged-mouse-nad-turnover","display_name":"NAD turnover in aged mice","entity_type_key":"cellular_process"},"object":{"id":"52cea63d-da4a-517b-a5b0-ac5b9cca2b29","slug":"mouse-absolute-nad-biosynthesis","display_name":"Absolute NAD biosynthetic flux in mice","entity_type_key":"cellular_process"},"evidence_count":1,"mechanism_event":{"id":"a2b55bc9-a766-5394-8a6b-4e71ad4175f9","stable_key":"8c946991-97f0-55ee-8df0-00e67621962f:nad-plus-aging-flux-event","event_type":"observed_relationship","label":"A smaller pool does not necessarily mean slower production.","description":"Isotope tracing found a median tissue NAD+ decrease of about 30% in aged mice while absolute synthesis was maintained in most tissues through faster turnover of the smaller pool.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"1d8c70a3-b88d-5129-ab6a-be243535c08f","slug":"aged-mouse-nad-turnover","display_name":"NAD turnover in aged mice","entity_type_key":"cellular_process"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"52cea63d-da4a-517b-a5b0-ac5b9cca2b29","slug":"mouse-absolute-nad-biosynthesis","display_name":"Absolute NAD biosynthetic flux in mice","entity_type_key":"cellular_process"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"283ed24b-06a1-50aa-9281-df3bac6ce37e","slug":"nad-plus","display_name":"NAD+","entity_type_key":"small_molecule"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""}]},"contexts":[{"dimension":"evidence_access","value_text":"Primary full text","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Mouse isotope tracing and mass spectrometry across tissues.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Tissue-specific animal flux; expression of one enzyme or a static human blood test cannot substitute for this measurement.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"NAD+ collection; molecular form, preparation, species, exposure and manipulation remain explicit.","comparator":null,"unit":null,"notes":"","entity":{"slug":"nad-plus","display_name":"NAD+","entity_type_key":"small_molecule"}},{"dimension":"plain_language","value_text":"A smaller pool does not necessarily mean slower production.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"NAD+ flux is maintained in aged mice despite lower tissue concentrations. · 2021 · https://pubmed.ncbi.nlm.nih.gov/34559996/ · DOI 10.1016/j.cels.2021.09.001","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"0f5d0a4d-5733-517d-ae0b-7a06c6468d0c","evidence_kind":"source_excerpt","locator":"Lines 124-130","start_line":124,"end_line":130,"excerpt":"## nad-plus-aging-flux\nA smaller pool does not necessarily mean slower production.\nIsotope tracing found a median tissue NAD+ decrease of about 30% in aged mice while absolute synthesis was maintained in most tissues through faster turnover of the smaller pool.\nModel: Mouse isotope tracing and mass spectrometry across tissues.\nLimitations: Tissue-specific animal flux; expression of one enzyme or a static human blood test cannot substitute for this measurement.\nEvidence access: Primary full text\nNAD+ flux is maintained in aged mice despite lower tissue concentrations. · 2021 · https://pubmed.ncbi.nlm.nih.gov/34559996/ · DOI 10.1016/j.cels.2021.09.001","model_system":"Mouse isotope tracing and mass spectrometry across tissues.","directness":"reported_statement","verification_status":"source_derived_draft","notes":"Original curation paraphrase; evidence access and experimental limitations specified.","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"f59aa302-d463-5462-876f-e21e64861eac","stable_key":"import-8c946991-97f0-55ee-8df0-00e67621962f","title":"NAD+: compartmental supply, consumption and cross-nutrient mechanisms (2026-09-19)","document_type":"imported_text","citation_label":"AI-assisted research curation; primary references, access levels and experimental limitations individually identified. 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