运动训练通过诱导自噬、抑制凋亡改善老龄大鼠心脏功能

 目的：观察梯度运动对老龄大鼠心肌细胞自噬及凋亡的影响,探讨运动训练提高老龄大鼠心脏功能的机制。方法：实验分为3组，青年组(young)、老年组(old)和老年运动组（old+Ex）。超声心动图记录大鼠心脏功能,透射电镜观察心肌细胞超微结构变化、自噬体的形成以及线粒体形态学的改变,Westernblotting检测心肌组织自噬相关蛋白5（Atg5）、自噬相关蛋白Beclin 1、微管相关蛋白1轻链3(LC3)及心肌线粒体细胞色素C(Cyt C)蛋白的表达,TUNEL方法检测心肌细胞凋亡,分光光度法检测钙诱导的线粒体通透性转换孔(mPTP)开放。结果: （1）与young组比较,透射电镜下可见old组大鼠心肌肌原纤维排列不整齐,线粒体基质疏松,线粒体膜有破裂,肌丝间有大量脂褐素颗粒沉积；心肌组织中Beclin 1与Atg5蛋白表达降低,LC3Ⅱ/Ⅰ比值降低,线粒体Cyt C表达下降,细胞凋亡指数增加，mPTP开放数目增加，左心室收缩末期与舒张末期直径明显增大，左心室射血分数与缩短分数降低(P＜0.05或P＜0.01)。（2）与old组比较,old+Ex组大鼠心肌超微结构观察可见肌节结构清晰,线粒体基质致密,数目增多,自噬体形成增多，脂褐素颗粒沉积明显减少；并且心肌组织Beclin 1与Atg5蛋白表达增加,LC3 I向LC3 II转换增加,细胞凋亡指数减少,mPTP开放数目减少,心肌线粒体Cyt C表达上调,左室功能有明显改善（P＜0.05或P＜0.01）。结论：运动训练通过上调老龄大鼠心肌细胞自噬，抑制细胞凋亡，改善老龄大鼠心脏功能。

Exercise training improves heart function through inducing autophagy and inhibitingapoptosis in aged rats

AIM：To study the mechanism of exercise training in improving old  rat cardiac functions, and the effect of gradient exercise training on autophagy and apoptosis in aged rats. METHODS：The rats were randomly divided into 3 groups: young, old  and old+exercise (old+Ex). Ultrasonic cardiogram was employed to determine the cardiac functions in the rats. Transmission electron microscope was applied to observe the changes of cardiomyocyte ultrastructure, autophagosome formation and mitochondrial morphology. Western blotting was used to observe the protein expression of Atg5, Beclin 1, microtubule-associated protein 1 light chain 3 (LC3) in cardiac tissues and cytochrome C (Cyt C) in the myocardial mitochondria. TUNEL was adopted to test the apoptosis and spectrophotometry was used to detect the opening of calcium-induced mitochondrial permeability transition pore (mPTP). RESULTS：(1) Compared with young group, the observation in old  hearts under transmission electronic microscope found irregular arrangement in myofibrils, loose mitochondria matrix, rupture in mitochondrial membrane and mass deposition of lipofuscin granular in myofilament. In old  group, the protein expression of Atg5 and Beclin 1 in the cardiac tissues decreased, the ratio of LC3Ⅱ to LC3Ⅰdropped, mitochondrial Cyt C expression declined, apoptotic index rose, and mitochondrial mPTP opening increased. Noticeable increases were found in left ventricular end-systolic diameter and left ventricular end-diastolic diameter, but left ventricular ejection fraction and left ventricular fractional shortening were decreased. (2) The ultra-structure of the hearts in old +Ex group showed clear sacromere structure, dense matrix and increased number of mitochondria, more autophagosomes and distinct decrease in lipofuscin granular deposition. In addition, the protein expression of Beclin 1 and Atg5 rose, conversion from LC3 I to LC3 II increased, apoptotic index decreased, mPTP opened less, the expression of mitochondrial Cyt C up-regulated, and a significant improvement was observed in left ventricle functions in old+Ex group as compared with old  group. CONCLUSION：Exercise training may improve the heart functions in aged rat by upgrading cardiomyocyte autophagy and inhibiting cell apoptosis.