二甲双胍对高脂喂养糖尿病大鼠心肌细胞PGC-1α及PI3K表达的影响

Effects of metformin on the expression of PGC-1αand PI3K in cardiomyocytes of diabetic rats with high fat diet

目的探究二甲双胍对高脂饮食喂养的链脲佐菌素(STZ)诱导的2型糖尿病大鼠心肌细胞的作用及其可能机制。方法雄性SD大鼠36只,随机选取12只作为正常对照组,余24只高脂高糖饮食喂养,12周末注射小剂量(30 mg/kg)链脲佐菌素(STZ)诱发高血糖,建立2型糖尿病大鼠模型。至第15周成模24只,成模大鼠随机抽取12只,为糖尿病组,余12只为干预组。正常对照组及糖尿病组给予等体积生理盐水灌胃,干预组给予盐酸二甲双胍300 mg/(kg·d)灌胃,共干预8周。观察各组大鼠干预后空腹血糖(FBG)、总胆固醇(TC)、甘油三酯(TG)、低密度脂蛋白(LDL-C)、极低密度脂蛋白(VLDL)、高密度脂蛋白(HDL-C)、游离脂肪酸(FFAs)、空腹胰岛素(FINS),计算胰岛素抵抗指数(HOMA-IR)。免疫印迹法检测各组大鼠干预8周后心肌组织中PGC-1α及PI3K p85亚基蛋白表达情况,HE染色观察心肌组织形态学变化。结果与正常对照组比较,糖尿病组FBG、TC、TG、LDL-C、VLDL、FFAs、FINS、HOMA-IR指标均升高(P<0.01),HDL-C指标降低(P<0.01);与糖尿病组比较,干预组FBG、TC、TG、LDL-C、VLDL、FFAs、FINS、HOMA-IR指标均降低(P<0.01),HDL-C指标升高(P<0.01)。HE染色结果显示正常对照组心肌细胞排列整齐、致密,结构清晰,细胞核形态规则;糖尿病组可见心肌细胞排列不整齐,肿胀明显,部分细胞核可见形态不规则,心肌细胞部分融合,边界不清楚;二甲双胍干预组心肌细胞形态排列整齐,致密,核形态规则,未见细胞肿胀。免疫印迹法结果显示干预组大鼠心肌细胞中PGC-1α表达较正常对照组升高(P<0.05),但较糖尿病组表达降低(P<0.05)。干预组大鼠心肌细胞中PI3K p85表达较正常对照组降低(P<0.05),但较糖尿病组表达升高(P<0.05)。结论二甲双胍可能通过抑制PGC-1α表达改善心肌能量代谢,上调PI3K-Akt信号通路中PI3K表达,增强糖尿病心肌细胞的胰岛素敏感性。

Objective To investigate the effect of metformin on cardiomyocytes of type 2 diabetic rats induced by high-fat and streptozotocin(STZ)and its possible mechanism.Methods Thirty-six male SD rats were chosen,of which,12 rats were randomly selected as normal control group,and the remaining 24 rats were fed with a high-fat and high-sugar diet and then injected with a small dose(30 mg/kg)of STZ at the end of 12 weeks to induce hyperglycemia and establish a rat model of type 2 diabetes.At week 15,24 rats were successfully modeled,and then randomized into diabetes group(n=12)and intervention group(n=12).The rats in normal control group and diabetes group were given an equal volume of normal saline by savage,and the rats in intervention group were given metfor-min 300 mg/(kg·d)by savage for 8 weeks.The levels of fasting blood glucose(FBG),total cholesterol(TC),triglycerides(TG),low-density lipoprotein(LDL-C),very low-density lipoprotein(VLDL),and high-density lipoprotein(HDL-C),free fatty acids(FFAs),and fasting insulin(FINS)were detected,and the insulin resistance index(HOMA-IR)was calculated after intervention in each group.Western blotting was used to detect the expression of PGC-1αand PI3K p85 protein in myocardial tissue,and HE staining was used to observe the morphological changes of myocardial tissue after 8 weeks of intervention in each group.Results Compared with normal control group,the levels of FBG,TC,TG,LDL-C,VLDL,FFAs,FINS,and HOMA-IR in diabetes group were increased(P<0.01),while the level of HDL-C was decreased(P<0.01).Compared with diabetic group,the levels of FBG,TC,TG,LDL-C,VLDL,FFAs,FINS,and HOMA-IR in intervention group were increased(P<0.01),while HDL-C was decreased(P<0.01).The results of HE staining showed that the cardiomyocytes in normal control group were neatly and densely arranged,with clear structures and regular nuclei.In diabetic group,the cardiomyocytes were irregularly arranged and swollen obviously,with some cell nuclei showed irregular shapes,and the cardiomyocytes were partially fused and the boundary was not clear.The cardiomyocytes in metformin intervention group were neatly and densely arranged,and the nuclear morphology was regular,without swollen cells.The results of Western blotting showed that the expression of PGC-1αin the cardiomyocytes in intervention group was higher than that in normal control group(P<0.05),but it was lower than that in diabetic group(P<0.05).The expression of PI3K p85 in the cardiomyocytes of rats in intervention group was lower than that in normal control group(P<0.05),but it was higher than that in diabetic group(P<0.05).Conclusion Metformin may improve the myocardial energy metabolism by inhibiting the expression of PGC-1α,up-regulating the expression of PI3K in the PI3K-Akt signaling pathway,and enhancing the insulin sensitivity of diabetic cardiomyocytes.