{"id":"4c3925d1-93b4-5526-9bb1-7ac23a7f44ce","stable_key":"c9aa15a1-8ba2-5913-b2dd-372af304bf87:fast-brain-ketones","predicate":"increases","statement":"Beta-hydroxybutyrate and acetoacetate became predominant cerebral fuels after prolonged starvation.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"context_dependent","is_public":true,"mechanism_event_id":"3912c586-4d42-5ece-b3a5-6b1f33083dd7","mechanism_event_label":"The brain can use ketones while retaining a glucose requirement.","subject":{"id":"2d5df4b9-44d7-56a5-8ecf-7c08c0ae9f4f","slug":"fasting","display_name":"Fasting / abstention from energy intake","entity_type_key":"cellular_process"},"object":{"id":"12fda8a6-4a31-5f37-ba79-276ea9387362","slug":"cerebral-ketone-utilization","display_name":"Cerebral ketone-body utilization","entity_type_key":"cellular_process"},"evidence_count":1,"mechanism_event":{"id":"3912c586-4d42-5ece-b3a5-6b1f33083dd7","stable_key":"c9aa15a1-8ba2-5913-b2dd-372af304bf87:fast-brain-ketones-event","event_type":"observed_relationship","label":"The brain can use ketones while retaining a glucose requirement.","description":"Beta-hydroxybutyrate and acetoacetate became predominant cerebral fuels after prolonged starvation.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"2d5df4b9-44d7-56a5-8ecf-7c08c0ae9f4f","slug":"fasting","display_name":"Fasting / abstention from energy intake","entity_type_key":"cellular_process"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"12fda8a6-4a31-5f37-ba79-276ea9387362","slug":"cerebral-ketone-utilization","display_name":"Cerebral ketone-body utilization","entity_type_key":"cellular_process"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"59496369-eea6-5302-a0a3-2dcfa8f2b71a","slug":"d-beta-hydroxybutyrate","display_name":"D-(R)-beta-hydroxybutyrate","entity_type_key":"small_molecule"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"1b77cb4a-1f79-50e2-b4f0-fd0953cb914e","slug":"acetoacetate","display_name":"Acetoacetate","entity_type_key":"small_molecule"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":3,"notes":""}]},"contexts":[{"dimension":"evidence_access","value_text":"Primary abstract","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Three obese patients; cerebral catheterization after 5–6 weeks of starvation.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"This prolonged, small historical study does not establish a 16-hour switch.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"Fasting physiological-state collection; human protocols, cellular deprivation and refeeding are distinguished.","comparator":null,"unit":null,"notes":"","entity":{"slug":"fasting","display_name":"Fasting / abstention from energy intake","entity_type_key":"cellular_process"}},{"dimension":"plain_language","value_text":"The brain can use ketones while retaining a glucose requirement.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"Brain metabolism during fasting. · 1967 · https://pubmed.ncbi.nlm.nih.gov/6061736/ · DOI 10.1172/JCI105650","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"5b94945d-61e9-55a8-86ad-17ec69e3cc97","evidence_kind":"source_excerpt","locator":"Lines 88-94","start_line":88,"end_line":94,"excerpt":"## fast-brain-ketones\nThe brain can use ketones while retaining a glucose requirement.\nBeta-hydroxybutyrate and acetoacetate became predominant cerebral fuels after prolonged starvation.\nModel: Three obese patients; cerebral catheterization after 5–6 weeks of starvation.\nLimitations: This prolonged, small historical study does not establish a 16-hour switch.\nEvidence access: Primary abstract\nBrain metabolism during fasting. · 1967 · https://pubmed.ncbi.nlm.nih.gov/6061736/ · DOI 10.1172/JCI105650","model_system":"Three obese patients; cerebral catheterization after 5–6 weeks of starvation.","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":"921d1eb5-2c88-52b9-9898-60b2b5bf6029","stable_key":"import-c9aa15a1-8ba2-5913-b2dd-372af304bf87","title":"Fasting: fuel switching, nutrient sensing, ketone signaling, nutrient dependencies and refeeding (2026-09-18)","document_type":"imported_text","citation_label":"AI-assisted research curation; primary-abstract references and experimental limitations individually identified. 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