Effects Of Aerobic And Resistance Exercise On Cardiac Function And Protein Expression Of P-AMPK?, PGC-1? And FNDC5 In Tail-suspended Rats

Objective: lack of physical activity is one of the important risk factors of cardiovascular disease.Exercise can improve the level of cardiac function and prevent and treat cardiovascular disease.Moreover,exercise can promote the expression of PGC-1? and its related proteins in the heart,which may be an important target for exercise to improve cardiac function in people with insufficient physical activity.Therefore,in this study,the tail suspension rat model was used to simulate people with insufficient physical activity,to observe the effects of tail suspension and different exercise intervention methods(aerobic exercise and resistance exercise)on myocardial morphology,ultrastructure,cardiac function and the expression of PGC-1? related protein in rats,and to explore the possible mechanism of myocardial injury caused by tail suspension and exercise intervention to promote myocardial recovery in rats.Methods: thirty-six SPF-grade 8-week-old male SD rats were randomly divided into control group(group C,n=12)and tail suspension group(group TS,n=24)after one week of adaptive feeding.The rats in group C were fed normally,and the rats in group TS were suspended for 4 weeks.Four weeks later,group C was randomly divided into two groups: blank control group 1(group C1,n=6)and blank control group 2(group C2,n=6).They were randomly divided into tail suspension group 1(group TS1,n=6),aerobic exercise group(group A,n=6),resistance exercise group(group R,n=6)and recovery group(group RE,n=6).Group A,group R continued to receive aerobic exercise and resistance exercise for 4 weeks,while group RE and group C2 were fed normally.After 4 weeks of tail suspension,the body weight and the wet weight of soleus muscle in C1 and TS1 groups were measured,and the myocardial samples were taken to observe the changes of corresponding indexes.After 4 weeks of exercise training,myocardial samples were taken from groups A,R,RE and C2,and the changes of corresponding indexes were observed.Echocardiography was used to detect the changes of cardiac function,HE staining was used to observe the changes of myocardial morphology,transmission electron microscope was used to observe the changes of myocardial ultrastructure,and Western blot method was used to detect the expression of p-AMPK ?,PGC-1 ? and FNDC5 protein in myocardial tissue of rats in each group.Results:(1)After 4 weeks of tail suspension,compared with C1 group,the body weight of TS1 group had no significant change(P>0.05),but the ratio of soleus muscle to body weight decreased significantly(P<0.01).(2)After 4 weeks of tail suspension,compared with C1 group,myocardial morphology and integrity were significantly damaged,myocardial mitochondria were damaged,cardiac HR was significantly increased(P<0.05),SV and CO were significantly decreased(P<0.01),FS were significantly decreased too(P<0.05),and the expression of p-AMPK?,PGC-1 ? and FNDC5 protein in TS1 group was significantly lower than that in C1group(P<0.01).(3)After 4 weeks of natural recovery,there was no significant difference in myocardial morphology,cardiac function,p-AMPK ?,PGC-1 ? and FNDC5 protein expression between RE group and C2 group(P>0.05,only the structure of myocardial mitochondria has not been fully recovered..(4)After 4 weeks of exercise intervention,the myocardial morphology and mitochondrial structure of group A and R were similar to those of group C2.The cardiac FS,SV and CO in R group were significantly higher than those in RE group(P<0.01).The EF in R group was also significantly higher than that in RE group(P<0.05),and HR were decrease(P<0.05).Compared with C2 group,SV and CO were significantly increased,while FS was significantly increased(P<0.05).Compared with RE group,SV,CO and FS in group A increased significantly(P<0.01),EF also increased significantly(P<0.05),and HR were decrease(P<0.05).SV and CO in group A were significantly higher than those in group C2(P<0.01).The expressions of p-AMPK?,PGC-1? and FNDC5 protein in myocardium of group A and R were significantly higher than those of group RE and group C2(P<0.01).(5)Except that the expression of myocardial PGC-1 ? in group R was significantly higher than that in group A(P<0.01),there was no significant difference in other indexes.Conclusion:(1)The cardiac function decreased significantly and the myocardial structure was damaged in tail-suspended rats for 4 weeks,which may be related to the decreased expression of p-AMPK?,PGC-1? and FNDC5 protein in myocardium.(2)After 4 weeks of natural recovery,the cardiac function,myocardial structure,p-AMPK?,PGC-1? and FNDC5 protein expression of tail suspended rats returned to nearly normal levels.(3)4-week exercise intervention can significantly improve the injury of myocardial mitochondria and the decrease of cardiac function induced by tail suspension in rats,and the effect is more significant than that of natural recovery.The mechanism may be that exercise induces the expression of p-AMPK?,PGC-1?and FNDC5 protein in myocardium.(4)Compared with aerobic exercise,resistance exercise induced the expression of PGC-1 ? protein more significantly.