Effect of exercise type on Autophagy mechanism in aging rat skeletal muscle

This study aimed to investigate the effects of exercise type (uphill vs. downhill) and muscle fiber type (fast-twitch vs. slow-twitch) on the expression of autophagy-related proteins (ATG-5, Beclin-1, LC3-I/II, p62) in aged skeletal muscles of rats. Male Sprague–Dawley rats were divided into four groups: young control (YC, n=10, 8weeks), old control (OC, n=10, 60weeks), old-uphill exercise (Ex2, n=10), and old-downhill exercise (Ex1, n=10). The exercise groups performed treadmill endurance training for eight weeks. After the training, the extensor digitorum longus (EDL) and soleus (SOL) muscles were extracted, and protein expression was analyzed using western blotting. The OC group showed a significant decrease in ATG-5, Beclin-1, and LC3-II expression and an increase in p62 compared with YC (p<.05), indicating reduced autophagic activity. Both exercise groups demonstrated significant recovery of these indices, with the uphill group (Ex2) showing greater improvements than the downhill group (Ex1) (p<.05). Furthermore, the recovery was more pronounced in the slow-twitch dominant SOL than in the fast-twitch dominant EDL. These findings suggest that regular endurance exercise can restore impaired autophagy in aged skeletal muscles, and that uphill (concentric) exercise is particularly effective in improving autophagic function associated with aging.