2519-P: Altered Palmitoylation Dynamics Impairs Exercise Performance and Muscle Contraction Force in Mice by Downregulating Mitochondrial Respiration

Introduction and Objective: Diabetes is associated with decreased exercise tolerance in part related to reduced fat oxidative capacity. Emerging evidence suggests a role for differential palmitoylation in cellular signaling and the evolution diabetes. To test the hypothesis that palmitoylation dynamics impacts exercise, we evaluated the effects of inactivating major enzymes that mediate the reversal of protein palmitoylation in skeletal muscle, acyl-protein thioesterase-1 (APT1) and acyl-protein thioesterase-2 (APT2). Methods: Skeletal muscle APT1 knockout (ACTA1-APT1), APT2 knockout (ACTA1-APT2) and double knockout (ACTA1-APTD) mice were generated and characterized. Results: Treadmill exercise performance showed that running distance was significantly decreased in ACTA1-APT mice as compared to controls, without compromising muscle fiber morphology. There was no effect on body weight or body composition. Physiological testing of isolated skeletal muscle contraction indicated that the peak tetanic tension of EDL in knockouts was decreased in mice fed HFD. Despite these differences, there was no effect on forelimb strength tested by grip meter. Loss of skeletal muscle APT2 led to glucose intolerance in female mice. In high-resolution respirometry assays, oxygen consumption rate (OCR) was not significantly different between genotypes in permeabilized skeletal muscle. However, OCR was diminished by APT knockdown in C2C12 myotubes, suggesting that restricted mitochondrial function may be responsible for phenotypes. Palmitoylation proteomic analyses revealed the possible involvement of two palmitoylated proteins, CKMT2 (creatine kinase S-type, mitochondrial) and VDAC2 (voltage-gated ion channel 2), in APT1-mediated mitochondria function. Conclusion: Since diabetes impairs APT function, these findings are consistent with the possibility that disrupted palmitoylation dynamics contributes to dysfunctional skeletal muscle mitochondria in diabetes. R. Xu: None. G. Dong: None. W. Zhang: None. S. Adak: None. G. Kashgari: None. G. Meyer: None. J.L. Ferey: None. X. Wei: None. C.F. Semenkovich: Stock/Shareholder; Current; AirSeal Cardiovascular Inc.