ABSTRACT
The purpose of this study was to examine the effects of combination of a heat stress and astaxanthin supplementation, known as a potent anti-oxidative nutrient, on muscle protein degradation and disuse muscle atrophy. Fifty-two male Wistar rats (261.7±1.17 g) were divided into five groups: control (Cont, n=10), suspension (Sus, n=11), heat stress and suspension (Heat, n=10), astaxanthin and suspension (Ax, n=10), and heat stress, astaxanthin and suspension (H+A, n=11). There were no significant differences in Cu,Zn-SOD, cathepsin L and caspase-3 levels among the Heat, Ax and H+A groups in the soleus and plantaris muscles. Although levels of calpain 2 and ubiquitinated protein in the myofibrillar fraction in the soleus muscle were not significantly different among the Heat, Ax and H+A groups, levels in the H+A group were significantly (p<0.05) lower than Sus. Concerning atrophied plantaris muscles, the H+A group significantly (p<0.05) suppressed the expression of calpain 1 in the myofibrillar fraction, but there were no marked changes of proteolytic indexes. These data indicate that the combination of the heat stress and astaxanthin supplementation could be effective in inhibiting muscle protein degradation in disuse atrophy of the soleus.
ABSTRACT
In the present study, we investigated the effect of heat stress on disuse atrophy from changes in the muscle protein levels of desmin and calpain. Wistar strain female rats (6-8 months old) were randomly assigned to two experimental groups: control (C) and heat stress (H). One hindlimb of all animals was immobilized in plantar flexion with plaster. Before immobilization, animals in H group were placed in a heat chamber (42°C for 60 min). Following 6 days of immobilization, the soleus muscles were removed and analyzed. Although immobilization resulted in significant muscle atrophy in all experimental animals, the soleus weight-to-body weight ratio in immobilized limbs of H group was significantly higher compared to that of C group. Expression of desmin and HSP72 in the atrophied soleus muscle from C group was significantly lower compared with the contralateral muscle; but this was not the case in H group. Further, in C group, the ratio of autolyzed calpains I increased significantly in the atrophied muscle compared to the contralateral muscle. These results show that the effect of heat stress on disuse skeletal muscle atrophy is attributed to the decreasing degradation of desmin by suppressing the activation of calpain.