Effects of 4-week Hypoxic Exercises on the Temporal Changes of Autophagy-related Factors in Skeletal Muscles of Healthy Obese Rats / 中国运动医学杂志

ABSTRACT

Objective To determine the effect of hypoxia conditions on the expression of autophagyrelated genes including P62,LC3 and Beclin-1 in the gastrocnemius muscles of rats with alimentary obesity and the possible mechanism of cellular autophagy induced by hypoxia exercises.Methods The model of rats with alimentary obesity was induced in Sprague-Dawley rats using high-fat diet.Then the obese rats were randomly divided into a control(C) group,a hypoxia-exercises-for-1-week(E1) group,a hypoxia-exercises-for-2-weeks (E2) group,a hypoxia-exercises-for-3-weeks (E3) group and a hypoxia-exercises-for-4-weeks(E4) group,each of 10.The rats were exposed to the environment where the simulated hypoxia was of about 13.6％ oxygen concentration(about the oxygen concentration at an actual altitude of 3,500 m),and underwent treadmill running with the speed at 20 m/min on a slope of 0 gradient every day,five days a week.After the last training,the rats were killed and sampled.The RT-PCR was used to detect the level of P62,LC3 and Beclin-1 mRNA and Western Blotting was conducted to examine the changes of protein P62 and LC3 before and after the intervention.Results Compared with group C,the expression of Beclin-1 mRNA in group E1,E2 and E3 increased significantly(P＜0.05),while the expression of protein Beclin-1 decreased significantly in group E2.The expression of protein Beclin-1 of group E2 and E3 was significantly lower than that of group E4,but there were no significant differences between group E2 and E3.Compared with group C,the relative expression of P62 mRNA in group E1 and E2 increased significantly(P＜0.05,P＜0.01),with that of group E2 significantly higher than group E1 (P＜0.05).Moreover,the relative expression of P62 mRNA in group E3 was significantly lower than that of E2(P＜0.01),and that of group E4 was significantly higher than group C,E1 and E3(P＜0.01).The relative expression of protein P62 in the obese rats in group E3 was significantly higher than that of group E2(P＜0.05).The relative expression of LC3 mRNA in group E2,E3 and E4 was significantly higher than that of group C(P＜0.01).Moreover,there were no significant differences in LC3-Ⅱ/LC3-Ⅰ protein among the five groups.Conclusion Hypoxia exercise can significantly enhance the relative expression of autophagy genes,and promote,to some extent,the autophagy.However,the transcription of autophagy genes does not happen synchronically with the synthesis of autophagy proteins.Moreover,an increase in autophagy in the skeletal muscle can be seen in the first two weeks of hypoxia exercises,followed by a gradual decrease with time prolonged,which may be the result of the gradual adaptation to hypoxia stimulation of the body.