Down‐regulation of autophagy induced by caveolin‐3 and myosin heavy chain in response to forced exercise in rats

Abstract

Although suppressing myostatin‐mediated signaling by caveolin‐3 (cav‐3) may results in reduction of muscular atrophy, the skeletal muscle phenotypic response following forced exercise is not fully defined. Therefore, we examined whether the changes of caveolins and myosin heavy chain (MHC) gene expression have relevance to autophagic signaling in forced exercised muscle. Male (n=16) and female (n=16) Wistar rats (10–12 weeks age, 280–300 g each) were divided into two groups: control (Con) and exercise (Ex). The rats in the Ex group were subjected to treadmill exercise at 25 m/min for 30 min, three times a day (07:00, 15:00, and 23:00). Stable expression of cav‐3 was detected in all tissues taken from the Ex group. In the gastrocnemius (GCM) muscle of the female rats, the expression of cav‐3 and MHC2a was significantly increased in the Ex group, as compared with the Con group (p<.05). Similarly, significantly greater MHC2x gene expression was detected in the GCM muscle of the male rats in the Ex group, as compared to the Con group (p<.05). Finally, increased cav‐3 gene expression and slightly decreased TGF‐β1 gene expression were noted in the muscles of the rats, suggesting that cav‐3 influences the expression of MHC isoforms and TGF‐β1. Furthermore, the conversion of LC3I to LC3II was significantly decreased in the GCM muscle of the male rats, indicating that protein degradation was reduced by forced exercise.Funding: BioGreen21 Program (Code No. 20070401‐034‐006‐009‐02‐00), Rural Development Administration, Korea