Low-Intensity Exercise Improves Aerobic Exercise Capacity in Rats After Myocardial Infarction and the Possible Role of Skeletal Muscle Autophagy

Abstract

Abstract Background To investigate the effects of low-intensity exercise on aerobic exercise capacity and autophagy of skeletal muscle in rats after myocardial infarction (MI) and its possible mechanisms. Methods Thirty male Sprague Dawley rats, weighing 180–200 g, were randomly divided into sham, MI, and MI with exercise training (MI + Ex) groups. MI was induced by ligation of the left anterior descending artery. One week after surgery, low-intensity exercise training was carried out on a treadmill 5 days per week for 4 weeks. Results Infarct size of MI and MI + Ex groups was 30.8 ± 5.5% and 27.6 ± 5.0% of left ventricle, respectively (P > 0.05). Heart weight and heart to body weight ratio in the MI group were significantly higher than those in the sham group (P < 0.01), and were lowered by exercise training (P < 0.01). The maximal exercise distance and duration in the MI group were lower than those in the sham group (P < 0.01), but were significantly increased by exercise training (P < 0.05). Autophagosome of the gastrocnemius was not detectable in the sham group, scattered in the MI group but clustered in the MI + Ex group. Microtubule-associated protein light chain 3 (LC3-I/II) and Beclin-1 protein levels in the gastrocnemius were similar between MI and sham groups, but were significantly higher in the MI + Ex group (P < 0.05). Conclusions Low-intensity exercise improves exercise capacity in rats after MI. The effect is associated with enhanced autophagy of the skeletal muscle.