Effects And Mechanisms Of Endurance And Resistance Training On Cardiac Structure And Function In Diabetic Rats

Objective: To observe the different effects of aerobic training and resistance training on the blood glucose and lipid levels in diabetic rats,and to compare the different effects of aerobic training and resistance training on the cardiac structure and function in early diabetes mellitus,then to explore the mechanisms of different exercise intervention on the cardiac diastolic dysfunction in diabetes mellitus.Methods: After using the method of "7 weeks of feeding high fat and high sugar diet combined with small-dose streptozotocin" to bulid type 2 diabetes mellitus model,male SD rats were randomly divided into six groups: Control(C),Control + Aerobic training treatment(CA),Control + Resistance training group(CR),Diabetes mellitus model group(D),Diabetes + Endurance training treatment group(DA),and Diabetes+ Resistance training treatment group(DR).Treadmill was used for aerobic training,and ladder was used for resistance training.The training last 8 weeks.To test the levels of fasting blood glucose(FBG),fasting insulin(FINS),glucose tolerance test(GTT),triglyceride(TG),cholesterol(CHOL),high density lipoprotein(HDL),low density lipoprotein(LDL),and very low density lipoprotein(VLDL);Myocardail histological structure was observed by Hematoxylin-Eosin(HE)staining and transmission electron microscope.Indexes of cardiac function,such as left ventricular end-systolic internal diameter(LVIDs),left ventricular end-diastolic internal diameter(LVIDd),end-systolic volume(ESV),end-diastolic volume(EDV),ejection fraction(EF),fractional shortening(FS),were tested by echocardiogram.Hemodynamic indexes,such as left ventricular systolic pressure(LVSP),left ventricular diastolic pressure(LVDP),left ventricular end diastolic pressure(LVEDP),maximum rate of left ventricular pressure development(dp/dtmax),minimum rate of left ventricular pressure decay(dp/dtmin),and Tau,were tested by powerlab after left ventricle intubated.the protein expressions of HSP27,phosphorylated HSP27,collagen I,collagen ? and TGF?1 were detected by Western blot,and the amount of co-localization of titin and HSP27 were measured by immunofluorescence double labeling technique.The collagen volume fraction was measured by Masson staining.Results:(1)The levels of FBG,AUC,TG,CHOL,LDL,and VLDL were significantly increased,and the levels of FINS was significantly decreased in early diabetic rats;Aerobic training intervention improved glycometablism of diabetic myocardium,more than resistance training,but resistance training intervention improved lipid metabolism of diabetic myocardium,more than aerobic training.(2)The histological light microscopic structure had no change in early diabetes mellitus,and the pathological changes of ultrastructure included: myocardial fibers dissolved partially,steatosis,and so on.Meanwhile,8-week diabetic rats have normal systolic function,and diastolic dysfunction.Aerobic training mitigated or prevented the pathological changes,but resistance training aggravated cardiac ultrastructural damage and dysfunction.(3)The protein expression of titin was decreased significantly,and the expression of collagen ?,TGF?1 were increased slightly,the ratio of type ? and ? collagen was raised in 8-week diabetic rats.Aerobic training intervention increased the protein expression of titin and HSP27,and the amount of co-localization of titin and HSP27 elevated,the protein expression of collagen ?,TGF?1 were decreased,and the ratio of type I and type ? got close to normal.On the contrary,resistance training further decreased the expression of titin,collagen ?,and TGF?1,collagen volume fraction(CVF)was increased significantly,and the ratio of type I and ? collagen was disturbed,but the co-localization of titin and HSP27 elevated slightly.Conclusion:(1)About improving metabolism of blood glucose and lipid,aerobic and resistance training have their own different advantages.(2)Aerobic training could ameliorate or prevent cardiac diastolic dysfunction via increasing titin repaired by HSP27.(3)Resistance training could aggravate the cardiac diastolic dysfunction in early diabetes mellitus via worsening the damage of titin even further,promoting myocardial interstitial fibrosis.