RESUMEN
Objective: To investigate the effects of aerobic versus resistance exercise on soleus muscle contractile properties and the expressions of MuRF1, PGC-1α and FNDC5 in amyotrophic rats after unloading, and the possible molecular biological mechanisms. Methods: Male Wistar rats were randomly divided into recovery group (CT), aerobic exercise group (A), resistance exercise group (R) and control group (C), with 6 rats in each group. The control group did not receive any treatment. The other three groups underwent tail suspension for 2 weeks, and then the recovery group recovered quietly. The aerobic group and the resistance group underwent a 2-week exercise intervention. Exercise plan: the aerobic group rats were treated with treadmill speed corresponding to 65% maximum oxygen uptake (VO2max), 60 min/d, 5 d/w; the rats in the resistance group were allowed to climb the ladder with 65% of the maximum voluntary weight-bearing (MVCC) for 3 times, with a total of 5 sets. Each time had a rest of 1 min, with an interval of 2 min among sets, and 5 d/w. Fasting for 24 hours after the last exercise, the soleus muscle samples were collected to observe the histological changes, test the contractility, and detect MuRF1 and PGC-1α and FNDC5 expressions. Results: compared with the control group, the body weight, soleus muscle wet weight, average cross-sectional area of muscle fibers and muscle contractility of the recovery group were decreased significantly(P<0.01), and the expression of MuRF1 was increased significantly(P<0.01). Compared with the recovery group, the body weight, wet weight of soleus muscle, the average cross-sectional area of muscle fiber and muscle contractility of rats in aerobic group and resistance group were increased (P<0.01), the expression of PGC-1α/FNDC5 was increased (P<0.01) and the expression of MuRF1 was decreased significantly (P<0.01). Compared with the aerobic group, the expression of PGC-1α in soleus muscle of rats in the resistance group was increased (P<0.05), while the expression of MuRF1 was decreased (P<0.05). Conclusion: Aerobic and resistance exercise can significantly improve muscle contractility, upregulate the expression of PGC-1α/FNDC5, and inhibit the expression of MuRF1, indicating that the molecular mechanisms of aerobic and resistance exercise to improve unloaded muscular atrophy may be related to PGC-1α and MuRF1.