Autophagic response to a single bout of moderate exercise in murine skeletal muscle

Abstract

The effect of a single bout of exercise on autopahgy in murine gastrocnemius muscle was investigated. Autophagy is a process for the degradation system of cytoplasmic components, which may help maintain intracellular quality control of cell survival and turnover under normal conditions. The present study investigated the changes of autophagy-related proteins including microtubule-associated protein 1b light chain 3 (LC3), Beclin-1, Atg7 (autophagy-related gene 7), conjugation form of Atg12 to Atg5, lysosome-associated membrane protein (LAMP2a), and muscle-specific RING finger protein-1 (MURF-1) protein level in gastrocnemius muscle after a single bout of treadmill exercise. Mice exercised on a treadmill for 50 min at a speed of 12.3 m/min with a slope of 5°. The animals were sacrificed by cervical dislocation 0, 3, 6, or 12 h after exercise, and muscle samples were collected immediately. Western blot analysis demonstrated that the autophagy marker LC3-II was significantly decreased during the recovery period (3, 6, and 12 h) whereas there was no decrease immediately after exercise (0 h). To identify factors related to this decrease, autophagosome component proteins were examined in murine gastrocnemius muscle. A decrease in Beclin-1, Atg7, and LAMP2a during recovery period was concomitant with the decreased level of LC3-II. Additionally, MuRF-1 expression was significantly increased after a single bout of exercise. This study is the first to demonstrate autophasic related protein expression after a single bout of treadmill exercise and our results suggest that a single bout of treadmill exercise attenuates the autophagic response in murine skeletal muscle.