The Cardiac Function Of Rats With Myocardial Infarction Was Improved By The Sirt3 Pathway After 8 Weeks Of Different Exercise Modes

Objective:Myocardial infarction（MI）is one of the main causes of death and physical disability.It has become an urgent public health concern to help people with MI to return to society and work.The benefits of cardiac rehabilitation（CR）with exercise training on patients with MI are well known,but the most effective exercise method,intensity and duration are still controversial.The purpose of this study was to conduct 8-week sedentary（SED）,moderate-intensity continuous training（MCT）and high-intensity interval training（HIIT）on MI rats,by observing the effect of different exercise modes on the heart function of rats with MI,exploring the effect of different exercise modes on the improvement of heart function after MI and its possible molecular mechanism,to provide guidance and theoretical foundation for CR of clinical center patients with MI.Methods:Twenty-four male SD rats were randomly assigned to sham operation group（SHAM）,MI plus SED group（MI-SED）,MI plus MCT group（MI-MCT）,MI plus HIIT group（MI-HIIT）,respectively.The left anterior descending branch ligation model and sham operation model were established for rats in each group.After successful modeling,all rats rest for one week,and the rats in the MI-MCT group and MI-HIIT group for 8 weeks were intervened with different exercise patterns by animal experimental treadmill.The MI-SED group and the SHAM group were normally reared in cages.Before the start of the intervention and after the end of the8-week intervention,the exercise capacity was measured.After the intervention,put to death in the rat,take out the heart,measure the relative weight of heart（heart weight/body weight）,myocardial infarction area ratio.Before and after the intervention,,the left ventricular end-diastolic diameter（LVEDD）,left ventricular end-systolic diameter（LVESD）,left ventricular ejection fraction（LVEF）and left ventricular fraction shortening（LVFS）were measured.Detecting the expression of myocardial Sirtuin3（Sirt3）,while detecting the mitochondria marker cytochrome C oxidase subunit IV（Cox IV）to observe the mitochondrial oxidative phosphorylation of protein expression levels.Results:After 8 weeks of intervention,（1）compared with MI-SED group,exercise capacity of MI-MCT group and MI-HIIT group were significantly increased(P_MI-MCT=0.000,P_MI-HIIT=0.000);There was no statistically significant difference between the MI-MCT group and the MI-HIIT group（P=0.615）.（2）Compared with the SHAM group,only the MI-HIIT group’s relative heart weight increased significantly（P=0.044）.（3）Compared with the MI-SED group,the ratio of infarct area in the MI-MCT group and the MI-HIIT group decreased significantly(P_MI-MCT=0.000,P_MI-HIIT=0.000);MI-MCT compared with the MI-HIIT group The infarct size decreased slightly,but there was no significant difference（P=0.087）.（4）Compared with the MI-SED group,the LVEDD of MI-MCT group rats decreased significantly（P=0.034）,while the LVEDD,LVESD,LVEF,and LVFS of MI-HIIT group rats showed no significant changes;compared with MI-MCT group,LVEDD（P=0.001）and LVESD（P=0.000）significantly increased in MI-HIIT group,while LVEF（P=0.021）and LVFS（P=0.030）decreased significantly.（5）Compared with MI-SED group,the Sirt3 protein in MI-MCT group was significantly increased（P=0.005）,while Sirt3 protein in MI-HIIT group increased slightly without significant difference（P=0.082）;Sirt3 protein in MI-HIIT group and MI-MCT group have not statistically different（P=0.206）.（6）Compared with MI-SED group,the expression of Cox IV protein in MI-MCT group and MI-HIIT group were significantly increased(P_MI-MCT=0.001,P_MI-HIIT=0.004).The expression of Cox IV protein between MI-MCT group and MI-HIIT group has not changed significantly（P=0.545）.Conclusion:8 weeks of MCT and HIIT intervention can improve the myocardial mitochondrial oxidative phosphorylation level,reduce myocardial fibrosis level,improve exercise tolerance,and protect cardiac function by activating Sirt3 pathway in MI rats.But HIIT can cause myocardial hypertrophy and decreased ejection fraction,and MCT can inhibit the pathological remodeling process.When performing CR for patients with MI,we should pay attention to choose appropriate exercise mode.