Effect Of Long-term Exercise With Medium Intensity On Heart Function Of Mouse And Heat Shock Proteins (HSPs) And Hypoxia-inducible Factor-1α (HIF-1α) Expression In Mouse Myocardium

Study Objective:Epidemiology data demonstrate that regular exercise can reduce the morbidity and mortality of cardiovascular diseases by 40-50%.One of the mechanisms known is exercise induced myocardial protection.However,the exact mechanisms of myocardial protection are not clear yet.In this study,the effects of long-term exercise with medium intensity on cardiac function,as well as the effects on heat shock proteins(HSPs) and hypoxia-inducible factor-1α(HIF-1α) expression in mouse myocardium were explored.Possible mechanisms of exercise induced myocardial protection were discussed.Materials and Methods:Twenty-four wild-type mice were randomly divided into two groups:control group(n=12) and exercise group(n=12).The mice in exercise group were forced to run with medium intensity on a treadmill for one hour a day,five days per week. All the treatment in the control group are the same as those in the exercise group except running exercise involved.After 12 weeks of intervention,①mice cardiac function and heart weight were analyzed by echocardiography;②left ventricle weight and tibia length were measured after the mice were sacrificed;③the upper part of left ventricle were used for HSPs and HIF-1αgene expression analysis by RT-PCR or Real-time PCR. Results:①Compared to control group,interventricular septum (IVS)(1.22±0.13 vs 0.80±0.09 P＜0.01),posterior wall of left ventricle (LVPW)(1.28±0.30 vs 0.79±0.09 P＜0.01) of exercise group were significantly thicker,ejection fraction(EF)(90.0±3.16 vs 81.6±7.26 P＜0.01) and left ventricular shortening fraction(FS)(53.4±3.28 vs 47.2±5.71 P＜0.05) were dramatically elevated;②Both left ventricle weight to body weight ratio(6.3±0.74 vs 5.0±0.61 P＜0.05) and left ventricle weight to tibia length ratio(17.7±1.35 vs 10.2±2.22 P＜0.01) were significantly higher of exercise group than those of control group;③HSP70(0.59±0.24 vs 2.36±0.32 P＜0.01),HSP90(0.65±0.31 vs 2.29±0.47 P＜0.01),HSP27(0.98±.054 vs 2.15±1.22 P＜0.05),αβ-lensprotein (0.84±0.39 vs 2.16±1.45 P＜0.05) mRNA expression in exercise group were significantly higher than those of control group; HIF-1αexpression in exercise group was increased by 2.82-fold compared to control group(P＜0.01).Conclusion:Long-term exercise with medium intensity caused myocardial hypertrophy and better heart function in mice.Inducing HSPs and HIF-1αexpression in myocardium by exercise might be one of the possible mechanisms.