β-Hydroxybutyrate maintains energetically demanding neural functions during glucose deprivation

Ketone bodies are a major source of cerebral energy during fasting and the ketogenic diet, but whether they can independently sustain brain tissue metabolism when glucose is absent remains uncertain. This question is difficult to resolve in vivo because circulating glucose is maintained, even during starvation, through endogenous production. We therefore used an ex vivo brain preparation to examine the metabolic capacity of tissue supplied with {beta}-hydroxybutyrate (BHB) as the only exogenous fuel, isolating brain tissue from the primary endogenous glucose sources. Mitochondrial function was monitored following prolonged exposure to glucose-free, BHB-rich artificial cerebrospinal fluid, and tissue resilience was tested by inducing spreading depolarization, a severe energetic challenge that requires rapid restoration of ionic and metabolic homeostasis. Following acute reliance on BHB, mitochondria appeared to dynamically regulate electron transfer system function, utilizing lower O2 flux, while maintaining sufficient energetic reserves to preserve tissue ability to generate and recover from repeated spreading depolarizations. These findings demonstrate that BHB can independently maintain essential metabolic and functional properties of brain tissue in the absence of exogenous glucose. The results broaden our understanding of cerebral fuel flexibility and provide additional support for the use of ketogenic strategies in neurological disorders where tissue excitability, energy metabolism, or glucose availability may be altered. O_FIG O_LINKSMALLFIG WIDTH=182 HEIGHT=200 SRC="FIGDIR/small/730699v2_ufig1.gif" ALT="Figure 1"> View larger version (42K): org.highwire.dtl.DTLVardef@82e0a1org.highwire.dtl.DTLVardef@698703org.highwire.dtl.DTLVardef@1ee27aorg.highwire.dtl.DTLVardef@1a6d45e_HPS_FORMAT_FIGEXP M_FIG C_FIG Cerebral fuel flexibility: glucose and ketones{beta}-Hydroxybutyrate (BHB) supports continual mitochondrial oxygen flux, along with induction of and recovery from repeated spreading depolarizations in mouse brain tissue in the absence of glucose. These findings demonstrate that ketone-supported metabolism can sustain energetically demanding neural function through a distinct bioenergetic strategy. Created in BioRender. Parrish, R. (2026) https://BioRender.com/k92j91u.