1945-P: The Mitochondrial Protein DRP1 Is Required for Endogenous Fatty Acid Oxidation

Introduction: Mitochondria are organelles that routinely undergo fission and fusion in a process known as mitochondrial dynamics. Increased mitochondrial fission is implicated in the pathogenesis of obesity, type 2 diabetes, and metabolic disease. DRP1 has been identified as a key regulator of mitochondrial fission. We and others have demonstrated that loss of DRP1 is associated with improvements in glucose homeostasis, however, the role of DRP1 in mitochondrial fatty acid oxidation is unknown. The purpose of this study was to measure endogenous fatty acid oxidation in DRP1-deficient skeletal muscle cells. Methods: C2C12 myoblasts were stably transfected with DRP1 shRNA (KO) or a scrambled control (CT). Myoblasts were then cultured in a substrate-limited DMEM (0.5mM glucose, 0.5mM carnitine, 1mM glutamine, and 1% FBS) overnight. 15 minutes prior to assay, etomoxir was added to inhibit endogenous fatty acid oxidation (FAO). Cells were then challenged with either bovine serum albumin (BSA) or palmitate (PA) and assessed for mitochondrial function using whole cell respirometry (Agilent XFe24). Additionally, cells were treated with 14 C-labeled PA in the absence and presence of increasing glucose concentrations to assess metabolic flexibility and fatty acid oxidation. Results: Basal whole cell (P Conclusion: Here, we show that DRP1 is required for FAO. After inhibition of FAO with etomoxir, basal and ATP-linked respiration were ablated in DRP1-deficient cells. These findings suggest that loss of DRP1 ablates the ability of cells to use endogenous fatty acids as substrate when carbohydrate is not available. These data suggest that impaired lipid metabolism, rather than inhibition of mitochondrial fission, may explain improvements in glucose homeostasis with the loss of DRP1. Disclosure W.T. King: None. C.L. Axelrod: None. G. Davuluri: None. R.C. Noland: None. J.P. Kirwan: None. Funding National Institutes of Health (R01DK108089, U54GM104940, R01DK103860)