Tongmai Hypoglycemic Capsule Attenuates Myocardial Oxidative Stress and Fibrosis in the Development of Diabetic Cardiomyopathy in Rats

Objective: To investigate the effect of Tongmai Hypoglycemic Capsule(THC) on myocardium injury in diabetic cardiomyopathy(DCM) rats. Methods: A total of 24 Sprague Dawley rats were fed for 4 weeks with highfat and high-sugar food and then injected with streptozotocin intraperitoneally for the establishment of the DCM model. In addition, 6 rats with normal diets were used as the control group. After modeling, 24 DCM rats were randomly divided into the model, L-THC, M-THC, and H-THC groups by computer generated random numbers,and 0, 0.16, 0.32, 0.64 g/kg of THC were adopted respectively by gavage, with 6 rats in each group. After 12 weeks of THC administration, echocardiography, histopathological staining, biochemical analysis, and Western blot were used to detect the changes in myocardial structure, oxidative stress(OS), biochemical indexes, protein expressions of myocardial fibrosis, and nuclear factor erythroid 2-related faactor 2(Nrf2) element, respectively. Results:Treatment with THC significantly decreased cardiac markers such as creatine kinase, lactate dehydrogenase,and creatine kinase-MB, etc.(P<0.01); enhanced cardiac function indicators including heart rate, ejection fraction,cardiac output, interventricular septal thickness at diastole, and others(P<0.05 or P<0.01); decreased levels of biochemical indicators such as fasting blood glucose, total cholesterol, triglycerides, low-density lipoprotein cholesterol, aspartate transaminase,(P<0.05 or P<0.01); and decreased the levels of myocardial fibrosis markers α-smooth muscle actin(α-SMA), and collagen Ⅰ(Col-1) protein(P<0.01), improved myocardial morphology and the status of myocardial interstitial fibrosis. THC significantly reduced malondialdehyde levels in model rats(P<0.01),increased levels of catalase, superoxide dismutase, and glutathione(P<0.01), and significantly increased the expression of Nrf2, NAD(P)H:quinone oxidoreductase 1, heme oxygenase-1, and superoxide dismutase 2 proteins in the left ventricle of rats(P<0.01). Conclusion: THC activates the Nrf2 signaling pathway and plays a protective role in reducing OS injury and cardiac fibrosis in DCM rats.