8周有氧和抗阻运动对糖尿病大鼠心肌钙代谢及左室舒张功能的影响

Effects of 8-week Aerobic and Resistance Exercise on Myocardial Calcium Metabolism and Left Ventricular Diastolic Function of Diabetic Rats

目的:比较抗阻运动和有氧运动对糖尿病大鼠心肌Ca^(2+)代谢及左室舒张功能的影响。方法:44只SD大鼠随机分为空白对照组(C,n=8)和高脂建模组(n=36),C组正常饮食,高脂建模组饲喂高糖高脂饲料7周联合一次性注射小剂量链脲佐菌素(STZ)制备糖尿病模型,共26只大鼠造模成功。建模成功大鼠分组为糖尿病对照组(D,n=8)、糖尿病有氧运动组(DA,n=9)和糖尿病抗阻运动组(DR,n=9)。DA组和DR组分别进行8周跑台和负重爬梯训练(5天/周,60分钟/天)。运动8周后,采用超声心动图与PowerLab数据采集分析系统检测大鼠心脏舒张功能及血流动力学指标;测定空腹血糖(FBG);ELISA法测定大鼠血清胰岛素(FINS)和甘油三酯(TG)、总胆固醇(TC)、高密度脂蛋白胆固醇(HDL-C)、低密度脂蛋白胆固醇(LDL-C)、极低密度脂蛋白胆固醇(VLDL-C)水平并计算胰岛素抵抗指数(HOMA-IRI);透射电镜观察大鼠心肌超微结构变化;荧光探针法检测心肌肌浆网和胞浆Ca^(2+)浓度;Western blot法测定心肌钙泵(SERCA2a)和受磷蛋白(PLB)表达量。结果:(1)与C组大鼠相比,D组大鼠血清FBG、TG和LDL-C水平明显升高(P<0.05),FINS水平显著降低(P<0.01);心肌肌原纤维呈明显的断裂、排列紊乱及线粒体肿胀变性表现;左心室内压最大下降速率(-dp/dtmax)显著下降,左心室松弛时间常数(Tau)明显延长(P<0.05);心肌肌浆网与胞浆Ca^(2+)浓度比值以及SERCA2a和PLB蛋白表达均显著降低(P<0.01或P<0.05)。(2)8周运动干预后,DA和DR组较D组大鼠血清糖、脂代谢指标明显降低(P<0.01或P<0.05),肌浆网与胞浆Ca^(2+)浓度比值显著增加(P<0.05),但HDL-C水平和PLB蛋白表达变化则不显著(P>0.05)。此外,与D组相比,DA组大鼠心肌肌纤维排列较整齐,线粒体肿胀程度明显减轻,-dp/dtmax和SERCA2a蛋白表达显著升高(P<0.05),Tau明显缩短(P<0.05);DR组大鼠心肌细胞纤维排列紊乱,线粒体肿胀明显,-dp/dtmax、Tau和SERCA2a蛋白表达均无明显变化(P>0.05)。(3)8周运动后,DA组大鼠血清TG、TC、LDL-C、FINS水平和Tau均显著低于DR组(P<0.05或P<0.01),而血清FBG水平和-dp/dtmax明显高于DR组(P<0.05或P<0.01)。结论:8周抗阻和有氧运动能有效改善糖尿病所致的糖脂代谢紊乱,其中抗阻运动改善血糖代谢更为明显,有氧运动改善血脂代谢效果更佳;有氧运动能有效改善糖尿病大鼠心肌超微结构紊乱及左室舒张功能障碍,而抗阻运动未见改善表现;两种运动均可上调心肌肌浆网和胞浆Ca^(2+)浓度,有氧运动效果更为显著,这可能与运动上调心肌SERCA2a蛋白和PLB蛋白的表达进而改善心肌的Ca^(2+)回收有关。

Objective To compare the effect of resistance exercise and aerobic exercise on the myocardial Ca^(2+)metabolism and left ventricular diastolic function of diabetic rats.Methods Forty-four Sprague-Dawley rats were randomly divided into a blank control group(C,n=8)and a high-fat modeling group(n=36).The C group was given a normal diet.The high-fat modeling group was on a highsugar and high-fat diet for 7 weeks in addition to an injection of small-dose streptozotocin(STZ)to induce the successful diabetic model in 26 rats,which were further divided into a diabetic control group(D,n=8),a diabetic aerobic exercise group(DA,n=9)and a diabetic resistance exercise group(DR,n=9).The DA and DR groups received daily 60-minute treadmill running and weight-bearing ladder climbing respectively 5 days a week for eight weeks.Then,the cardiac diastolic function and hemodynamic indexes were measured by echocardiography and PowerLab system accordingly.The insulin(FINS),triglyceride(TG),total cholesterol(TC),high density lipoprotein cholesterol(HDL-C),low density lipoprotein cholesterol(LDL-C)and very low density lipoprotein cholesterol(VLDL-C)were detected using the enzyme-linked immunosorbent assay and the insulin resistance index(HOMA-IR)was calculated.The changes in the cardiac ultrastructure were observed through the transmission electron microscope.The concentrations of Ca^(2+)in the myocardial sarcoplasmic reticulum and cytoplasm were detected using the fluorescence probe.Moreover,the expressions of the cardiac calcium pump(SERCA2 a)and phosphoprotein(PLB)were measured using Western blotting.Results(1)Compared with group C,the average level of the serum FBG,TG and LDL-C in group D increased significantly(P<0.05),while that of FINS decreased significantly(P<0.01).Significant rupture,disordered arrangement and mitochondrial swelling and degeneration were observed in the myocardial myofibrils.The maximum declining rate of left ventricular diastolic pressure(-dp/dtmax)decreased significantly but the left ventricular diastolic time constant(Tau)prolonged significantly(P<0.05).Moreover,the ratio of myocardial sarcoplasmic reticulum to the cytoplasmic Ca^(2+)concentration and the expression of SERCA2 a and PLB protein reduced significantly(P<0.01 or P<0.05).After the intervention,compared with group D,the indexes of serum glucose and lipid metabolism of the DA and DR groups decreased significantly(P<0.01 or P<0.05),while the ratio of sarcoplasmic reticulum and cytoplasmic Ca^(2+)concentration increased significantly(P<0.05),without significant differences in the changes of HDL-C level and PLB protein expression(P>0.05).Moreover,compared with group D,the myocardial muscle fibers of the DA group were more neatly arranged,and the swelling of mitochondria reduced significantly;the expressions of-dp/dtmax and SERCA2a protein increased significantly(P<0.05),and Tau shortened significantly(P<0.05).Meanwhile,in the DR group,the arrangement of myocardial fibers was disordered,and the mitochondria were significantly swollen,with no significant changes in-dp/dtmax and Tau,as well as the expression of SERCA2a protein(P>0.05).(3)After 8 weeks of exercise,the average levels of serum TG,TC,LDL-C,FINS and Tau of the DA group were significantly lower than the DR group(P<0.05 or P<0.01),while the average serum FBG levels and-dp/dtmax were significantly higher than the DR group(P<0.05 or P<0.01).Conclusion The 8-week resistance and aerobic exercise can effectively improve the glucose and lipid metabolism disorder caused by diabetes mellitus,with the former improving blood glucose metabolism more obviously and the latter promoting blood lipid metabolism better.Moreover,the latter can relieve the myocardial ultrastructural disorder and left ventricular diastolic dysfunction.Both exercises can up-regulate the ratio of myocardial SR and cytoplasmic Ca^(2+)concentration,and the effect of aerobic exercise is superior to the resistance exercise,which may be related to the recovery of myocardial Ca^(2+)through the up-regulation of the protein expression of myocardial SERCA2a and PLB.