Heat stress-induced protection against skeletal muscle atrophy via suppression of the apoptotic and proteolytic systems

Abstract

Heat stress has been shown to attenuate reduction in soleus muscle mass and fiber size in various animal models, and it appears likely that heat shock protein 72 (HSP72) plays a key role in heat stress-induced suppression of muscle atrophy. However, there is no evidence that repeated heat stress attenuates the acceleration of apoptotic and proteolytic systems in atrophied rat skeletal muscle. We recently examined the effects of repeated heat stress on muscle atrophy and in terms of apoptosis and proteolysis in unloaded rat skeletal muscle induced by hindlimb unloading. Our results revealed that repeated bouts of heat stress elicited protective effects against disuse atrophy in both soleus and plantaris muscles. Interestingly, this heat stress-induced protection against muscular atrophy may be partially attributed to the suppression of apoptotic activation in slow- and fast-twitch muscles, and decreased ubiquitination in only the soleus muscle. Thus, we have established that repeated heat stress attenuates skeletal muscle atrophy via both upregulation of HSP72 and suppression of apoptotic and proteolytic systems.