Effects of long-term voluntary running exercise and caloric restriction during development on intracellular signaling in female rat skeletal muscles

Abstract

In this study, we aimed to investigate the effects of long-term voluntary running exercise and caloric restriction during development on the skeletal muscle mass and intracellular signaling in female rats. Four-week-old female Wistar rats (n = 23) were randomly divided into the sedentary (SED) and voluntary running exercise (EX) groups, and then acclimated to a new environment. At 5 weeks of age, the rats in both groups were further divided into the ad libitum (AD+SED or AD+EX, n = 6) and calorie-restricted (CR+SED or CR+EX, n = 5-6) groups. EX group underwent 12 weeks of voluntary running exercise. CR group was only fed 70% of the food fed to the AD + SED group. After 12 weeks of intervention, soleus and plantaris muscles were removed, and the levels of intracellular signal transduction proteins involved in protein synthesis and degradation were measured by Western blotting. Significant diet × condition interactions were observed in the body, soleus muscle, and plantaris muscle weights. Specifically, plantaris muscle weight in the CR + EX group was significantly lower than that in the other groups; however, their soleus muscle weight was similar to that in the CR + SED group. In the plantaris muscles, significant diet × condition interactions were observed in the phosphorylation levels of 4E-binding protein 1, UNC-51-like autophagy-activating kinase-1, and light chain 3-II/I. Moreover, these factors were significantly altered in the CR + EX group than in the other groups. Notably, no significant interactions were observed in the soleus muscles. Our data suggest that long-term voluntary running exercise and caloric restriction exacerbate skeletal muscle loss, possibly mediated by muscle type-specific intracellular signaling mechanisms involved in protein synthesis and degradation.