Effect Of 12 Weeks Exercise With Different Intensity On Cardiorespiratory Fitness And PGC-1α Signal Pathway In Rats

Objective:To investigate the effectiveness of 12 weeks aerobic exercise with different intensities on cardiorespiratory fitness(CRF), as well as the changing characteristics of PGC-la signal pathway in heart and skeletal muscle. Moreover, the possible mechanisms for the increased CRF were also investigated.Methods:40 male Wistar rats(4 weeks) were randomly divided into four groups, i.e., low intensity group (50%VO2max), moderate intensity group (65%VO2max), high intensity group (80%VO2max) and sedentary group. All rats were measured the VO2max after three days adaptive training, then they repeated the VO2max test per two weeks on a non-training day and the load of the next two weeks was adjusted according to the test result. The treadmill speed was controlled to maintain the specific exercise intensity of each group in the training period. The rats in the exercise group were trained 5 days per week and 60 min per day. After 12 weeks of exercise training intervention, the ultrasonic cardiogram tests were conducted. Abdominal aortic blood, myocardium and right side of soleus were collected at the end of 48 hours after the last exercise training. The PGC-la, AMPK, SIRT1,NRF1, NRF2 and ERRa mRNA expression were analyzed by RT-qPCR. The protein expression of PGC-la, AMPK, phosphorylation AMPK and SIRT1 were examined by western blotting analysis.Results:1) After 12 weeks of aerobic exercise, the rats’body weight of high intensity group was the lowest compared with the other three groups. The VO2max of all three exercise group were significantly higher than that of sedentary group. Different from other 2 exercise groups, the VO2max of low intensity group was similar with the sedentary group at the beginning of exercise training. But the VO2max was increased to a high level as the moderate and high intensity group, and it was significantly greater than the sedentary group.2) Blood lipid were well controlled in all three exercise groups, but there is no differences between different intensity groups. Only 80%VO2max exercise can significantly improve the cardiac function.3) PGC-la mRNA was increased in exercise groups,but the protein expression of soleus PGC-la was significantly increased only in the moderate intensity group.4) The AMPK protein expression of myocardium and soleus was not different among the exercise groups, but the pAMPK and SIRT1 protein expression were increased with the increase of exercise intensity.5) Myocardium NRF1 mRNA expression was increased in moderate and high intensity group, soleus NRF1 mRNA of all three exercise groups were lower than sedentary group, and so was the mRNA expression of NRF2.6) The moderate and high intensity exercise induced myocardial ERRa mRNA expression, but it was decreased in the low intensity group. The change of soleus ERRa was different with the myocardial, the high intensity group was the lowest.Conclusions:l) 12 weeks of exercise intervention can significantly improve the CRF. The promotion effects of cardiorespiratory fitness in moderate and high intensity group are faster, and peak value appear in the sixth and eighth week respectively. But the low intensity group improved significantly from the tenth week, and the peak value appears in the twelfth week.2) 12 weeks of exercise intervention can reduce the range of the rats weight gain significantly. High intensity exercise gain greater effect of weight control and heart function.2) The molecular mechanism of exercise improved CRF was mainly by increasing the expression of skeletal muscle PGC-1α, but not myocardium. AMPK activation and the expression of SIRT1 were increased in moderate and high intensity group, especially in moderate group.4) AMPK, SIRT1, PGC-1α mRNA expression in exercise groups can’t reflect the respective levels of protein expression, possiblely the transcription regulation plays an important role.