石斛合剂对高脂高糖糖尿病大鼠心肌细胞Ca^2+代谢的影响

目的以糖尿病心肌病大鼠为研究对象,探讨石斛合剂对糖尿病心肌病心肌细胞Ca^2+代谢的影响。方法 Wistar大鼠24只,取5只作为正常组,余19只采用高脂高糖饮食联合链脲佐菌素腹腔注射进行糖尿病心肌病造模。成模后,随机分为模型组、二甲双胍组、石斛合剂组。二甲双胍组、石斛合剂组分别予二甲双胍、石斛合剂灌胃,正常组、模型组予生理盐水灌胃。4周后,测空腹血糖,取左心室心肌组织进行组织病理学观察和心肌细胞内游离钙(MyoCa^2+)浓度测定,Western blot法检测肌浆网Ca^2+-ATP酶(SERCA2a)、L型钙通道α1C亚单位蛋白(CACNA1C)蛋白表达,RT-PCR法测定SERCA2a mRNA表达。结果石斛合剂组心肌纤维较模型组、二甲双胍组排列整齐,断裂较少。与正常组比较,模型组血糖、心肌细胞MyoCa^2+含量和CACNA1C蛋白表达明显升高(P<0.01,P<0.05),SERCA2a mRNA和蛋白表达明显降低(P<0.01)。与模型组比较,石斛合剂组血糖、心肌细胞MyoCa^2+含量和CACNA1C蛋白表达明显降低(P<0.01,P<0.05),SERCA2a mRNA和蛋白表达明显升高(P<0.01,P<0.05);二甲双胍组血糖明显降低(P<0.01)。与二甲双胍组比较,石斛合剂组心肌细胞MyoCa^2+含量明显降低(P<0.01,P<0.05),血糖、SERCA2a mRNA和蛋白表达明显升高(P<0.05)。结论石斛合剂通过提高SERCA2a mRNA和蛋白表达,加快摄取Ca^2+的速率,降低细胞质Ca^2+负荷,缓解钙超载,最终达到维持糖尿病心肌病钙稳态的作用,有效维持心肌细胞的正常收缩舒张功能;其降糖作用不是预防糖尿病心肌病的主要机理,而在于抑制CACNA1C蛋白表达,抑制钙诱导钙释放过程。

Effect of Dendrobium Compound on Ca^2+ Metabolism of Cardiac Myocytes in High-Glucose and High-Fat Diet Induced Diabetic Rats

Objective:To investigate the effect of Dendrobium Compound(DC) on Ca^2+ metabolism in cardiomyocytes of rats with diabetic cardiomyopathy and its possible mechanism.Methods:Among a total of 20 wistar rats,five were selected as the normal group,the remaining were treated by a high-suger and high-fat diet combined with intraperitoneal injection of streptozotocin to induce diabetic cardiomyopathy.After modeling,they were randomly divided into the model group,the metformin group,and the DC group,and water,metformin and DC were intragastrically administered to these groups respectively for consecutive 4 weeks.The levels of fasting blood glucose were measured.The left ventricle myocardial tissue was collected for the histopathological observation and the measurement of calcium in myocardium(MyoCa^2+).Western blot and RT-PCR were used to detect the expression of CACNA1 C and SERCA2 a.Results:The Cardiac fibroblasts of the DC group were more aligned and less broken than the model group and the metformin group.Compared with the normal group,the levels of blood glucose,MyoCa^2+ concentration and the CACNA1 C protein were significantly increased,while the mRNA and protein of SERCA2 a were both reduced in the model group(P<0.01).Compared to the model group,the levels of blood glucose,calcium concentration,and the CACNA1 C protein were decreased,while the mRNA and protein of SERCA2 a were significantly increased in the DC group,and the levels of blood glucose was decreased in the metformin group.Compared to the metformin group,MyoCa^2+concentration was significantly reduced,while the levels of blood glucose and the mRNA and protein expression of SERCA2 a were significantly increased in DC group(P<0.05).Conclusion:DC could increase the expression of SERCA2 a gene,accelerate calcium uptake,reduce cytoplasmic calcium load,alleviate calcium overload,and maintain calcium homeostasis finally to keep the normal diastolic and systolic function of myocardial cells.Furthermore,the protective effect of DC to diabetic cardiomyopathy should be mainly attributed to the inhibition of CACNA1 C protein expression and reduction of calcium-induced calcium releasing,not hypoglycemic effect.