Restoring Autophagy by Exercise Ameliorates Insulin Resistance Partly via Calcineurin-Driven TFEB Nuclear Translocation

Abstract

Exercise activates autophagy and lysosome system in skeletal muscle, which are known to play an important role in metabolic adaptation. However, the mechanism of exercise-activated autophagy and lysosome system in obese insulin resistance remains covert. In this study, we investigated the role of exercise-induced activation of autophagy and lysosome system in improving glucose metabolism of skeletal muscle. Male C57BL/6 mice were randomly divided into five groups: the chow diet (CD) group, the high-fat diet (HFD) group, the high-fat diet plus exercise (HFD-E) group and the HFD-E treated with calcineurin inhibitor FK506 (HFD-E-F) or saline (HFD-E-S) groups. The mice in exercise groups (HFD-E, HFD-E-F and HFD-E-S) were subjected to aerobic treadmill exercise (speed at 12 m/min for 1 h per session, 0° slope, 5 days per week for 12 weeks). Mice of HFD-E-F group were intraperitoneally administered FK506 (1 mg/kg), once each day for 2 weeks before the end of exercise. Expressions pTFEB, T-TFEB and autophagy–lysosome markers, including Beclin1, LC3, ULK1, SQSTM1, LAMP1, CTSD and CTSL proteins in gastrocnemius muscle were analysed. We demonstrated that HFD induced insulin resistance and decreased autophagy-lysosomal proteins and the exercise significantly increased transcription factor EB (TFEB) translocation from the cytoplasm to the nucleus, restored the impaired autophagy-lysosomal-related protein expressions, and improved glucose metabolism. The increase in TFEB nuclear translocation was partly blocked by the calcineurin inhibitor FK506. Our results suggest that exercise promotes autophagy and lysosome restoration by regulating calcineurin-mediated TFEB nuclear translocation, ultimately alleviating HFD-induced insulin resistance in mice skeletal muscle.