224-LB: Role of the Mitochondrial Calcium Uniporter in the Regulation of Hepatic Mitochondrial Metabolism and Gluconeogenesis

Abstract

The mitochondrial calcium uniporter (MCU) is a key regulator of mitochondrial calcium, however, the role of MCU in mediating hepatic mitochondrial metabolism and gluconeogenesis has received limited attention. In order to address these questions, we examined rates of mitochondrial oxidation in both liver slices and in awake liver-specific MCU knockout (MCU KO) mice. We found that deletion of MCU significantly increases glucagon-induced intrahepatic lipolysis (p<0.04) and glucose production (p<0.04) in ex vivo liver slices. We also observed significantly reduced liver triglyceride accumulation (p<0.05) and increased hepatic long chain acyl-CoA (p<0.02) and acetyl-CoA (p=0.05) content in MCU KO mice, consistent with increased intrahepatic lipolysis and fat oxidation. This effect was not due to changes in white adipose tissue lipolysis. Deletion of MCU also impaired glucose tolerance in chow-fed mice, indicating dysregulated hepatic glucose production in these mice. These metabolic alterations could be attributed to reduced mitochondrial buffering of cytoplasmic calcium, leading to a 77% increase in cytoplasmic calcium (p<0.0001). This led to activation of CAMKII (p<0.04) and subsequent increase in ATGL phosphorylation (p<0.04) in hepatocytes lacking MCU. In conclusion, these results demonstrate a critical role for MCU in mediating hepatic mitochondrial oxidation and hepatic gluconeogenesis. Disclosure T.E. LaMoia: None. J. Lee: None. M. Guerra: None. R. Goodman: None. G.I. Shulman: Advisory Panel; Self; AstraZeneca, Janssen Research & Development, LLC, Merck & Co., Inc. Advisory Panel; Spouse/Partner; Merck & Co., Inc. Consultant; Self; Novo Nordisk A/S. Consultant; Spouse/Partner; Novo Nordisk A/S. Other Relationship; Self; Gilead Sciences, Inc., iMetabolic Biopharma Corporation. Other Relationship; Spouse/Partner; iMetabolic Biopharma Corporation. Other Relationship; Self; Maze Therapeutics. Funding National Institutes of Health (T32GM0007324)