Fulghum, K. L. | bioRxiv Science

bioRxiv2026

Neuronal ketone body utilization couples exercise and time-restricted feeding to cognitive enhancement

Ketogenesis and ketone body metabolism are linked to brain health benefits, including delaying age-related cognitive decline and neurodegeneration. Exercise, particularly when combined with an overnight fast, stimulates ketogenesis and ketone body turnover as well as improves brain metabolism and cognition. Yet, whether ketone metabolism is obligatory for this response is unknown. Here, we use chronic exercise via voluntary wheel running plus time-restricted feeding (VWR+TRF, fasting from ZT10.5-18.5) to explore whether ketone bodies are a potential mediator of exercise-induced brain health benefits in middle-aged mice. To independently distinguish the roles of neuronal ketone body metabolism vs. hepatic ketone body production, we studied middle-age female neuronal-specific SCOT knockout mice and female hepatocyte-specific HMGCS2 knockout mice, respectively. VWR+TRF was compared to sedentary ad-libitum fed (SED+AL) mice to assess the impact on whole-body metabolism (indirect calorimetry), cognition (Barnes Maze and Y-Maze), and molecular adaptations in the hippocampus (proteomics). VWR+TRF robustly upregulated systemic lipid oxidation in all mice, regardless of genotype, during the first 6.5 hours of the dark period. In female SCOT-Neuron-KO mice, we show impaired responses to VWR+TRF in indices of short- and long-term memory. Proteomic analysis of isolated hippocampi revealed that SCOT-Neuron-KO mice failed to globally upregulate key facilitators of synaptic function, including leucine-rich repeated transmembrane proteins, neurexins, and neuroligins. In female HMGCS2-Liver-KO mice, impaired responses to VWR+TRF in indices of short-term memory were paired with an upregulation in ketogenesis machinery in the hippocampal proteome, suggesting potential in vivo evidence of cerebral ketogenesis, a mechanism mitigating an otherwise more pronounced behavioral phenotype. Together, these findings suggest that neuronal ketone body utilization is essential, and hepatic ketone production is contributory, to the full cognitive and synaptic adaptations to exercise plus time-restricted feeding, supporting ketone metabolism as a key mechanistic link between metabolic state and brain health in midlife.

physiology↗

bioRxiv2025

Hepatic ketogenic insufficiency blunts exercise-induced energy expenditure and alters mitochondrial proteins in skeletal muscle.

Ketone body (KB) utilization increases during fasting and exercise due to enhanced hepatic fatty acid oxidation and KB production via the rate-limiting mitochondrial enzyme hydroxymethylglutaryl-CoA synthase (HMGCS2). Since KB metabolism intersects with multiple metabolic pathways, and skeletal muscle KB catabolism rises during exercise, we tested the hypothesis that liver-specific HMGCS2 knockouts (KO) would have reduced energy expenditure (EE) and changes in the mitochondrial proteome of skeletal muscle with chronic exercise through voluntary wheel running (VWR), time-restricted feeding (TRF), or both combined to boost hepatic KB production and utilization. Control (CON) and HMGCS2 knockout (KO) mice (n=6-8 per group) underwent sedentary ad libitum feeding (SED+AL), SED+TRF, VWR+AL, and VWR+TRF for 16 weeks, with whole-body EE measured using indirect calorimetry. In CON mice, VWR increased total EE by 19.5% and non-resting EE by 50% under AL conditions, and total EE by 16% and non-resting EE by 47.9% under TRF conditions. However, the EE increases seen with VWR did not occur in KO mice. Proteomic analysis revealed that the loss of liver HMGCS2 significantly impacted proteins involved in metabolic processes within skeletal muscle, including reduced oxidative phosphorylation (OXPHOS) protein expression in SED KO mice compared to sedentary CON. Notably, VWR restored OXPHOS protein expression in the muscle of the liver HMGCS2 KO but did not alter it in the CON. Furthermore, muscle from liver HMGCS2 KO mice had elevated expression glycolytic pathways in sedentary and VWR conditions. These results indicate that hepatic ketogenic deficiency (HMGCS2 KO) diminishes exercise-induced increases in EE and uniquely impacts baseline and exercise-related adaptations in the metabolic and mitochondrial proteome of skeletal muscle.

physiology↗