PROJECT SUMMARY Dietary regimens that promote ketone production are gaining popularity due to their ability to facilitate weight loss and improve metabolic health. Ketones (e.g. acetoacetate and 3-hydroxybutyrate (3OHB)) are produced by the liver and oxidized by the brain and peripheral tissues when glucose is low. Whereas the field has largely focused on the positive effects of ketones on the brain and heart, the role of ketone oxidation in skeletal muscle has been largely overlooked and under investigated. Data from our laboratory suggests that the skeletal muscle is a major site of 3OHB clearance, therefore we postulate that skeletal muscle 3OHB oxidation is necessary for optimal metabolic benefits of ‘ketogenic’ dietary weight loss regimens. To this end, this application links the enzyme that catalyzes the first step of 3OHB oxidation, D-ꞵ-hydroxybutyrate dehydrogenase (BDH1), to improved whole-body glucose metabolism and energy homeostasis due to post-obesity weight loss. The central objective of this proposal is to determine if skeletal muscle BDH1 plays a key role in mediating the health benefits of dietary regimens that promote ketogenesis and weight loss. BDH1 catalyzes a near-equilibrium reaction that couples ketone oxidation to the mitochondrial NAD(H) redox state. Herein, we propose a novel conceptual model that positions BDH1 as a mitochondrial redox buffer that promotes optimal skeletal muscle health during fasting and refeeding. Our conceptual model and central objective will be rigorously tested by the following studies. First, we use a novel mouse model with an inducible skeletal muscle-specific deletion of BDH1 to determine the impact of BDH1 on skeletal muscle mitochondrial bioenergetics and glucose metabolism in response to fasting and refeeding. Second, we will test the hypothesis that muscle BDH1 is required for the metabolic benefits of calorie-restricted feeding of a typical Western diet. Third, we will apply genetic engineering in primary human skeletal muscle cells test the hypothesis that ketone-induced shifts in the myocellular redox state impact glucose uptake and downstream metabolism. Results from these studies will expand our understanding of the functional relevance of skeletal muscle BDH1 and ketone oxidation with the long term goal of identifying new therapeutic targets for the prevention of obesity-induced metabolic disease. Importantly, this project will provide advanced training and mentoring in ketone metabolism, cellular genetic engineering, 13C stable isotope tracing, and computational 13C metabolic flux analysis. The career development plan will be implemented via a team of outstanding mentors including Dr. Muoio (Duke Molecular Physiology Institute, DMPI) as the primary mentor, Dr. Newgard (DMPI) as the co-mentor, and Drs. Zhang (DMPI) and Crawford (UMN) as members of the advisory committee. The DMPI is an ideal environment for training as it contains a diverse team of researchers with expertise in nutri...