Abstract:

Objective To investigate the promotion effect of velvet antler polypeptide （VAP） on myocardial injury in the diabetic cardiomyopathy （DCM） mice， and to clarify its mechanism. Methods The DCM model was established by feeding a high-sugar and high-fat diet combined with intraperitoneal injection of streptozotocin （STZ）. Fifty successfully modeled C57BL/6J mice were randomly divided into model group， metformin （Met） group （administered 250 mg·kg^-1 Met）， low dose of VAP group （administered 100 mg·kg^-1 VAP）， medium dose of VAP group （administered 200 mg·kg^-1 VAP）， and high dose of VAP group （administered 300 mg·kg^-1 VAP）， with once daily administration for 4 weeks； another 10 C57BL/6J mice were used as control group （fed a standard diet）. The body weights and fasting blood glucose （FBG） levels of the mice in various groups were monitored； cardiac ultrasound was used to detect the cardiac function of the mice； HE staining was used to observe the pathomorphology of myocardium tissue of the mice； Masson staining was used to observe the degree of myocardial fibrosis of the mice； Oil Red O staining was used to observe the lipid distribution in myocardium tissue of the mice； kits were used to detect the activities of superoxide dismutase （SOD）， catalase （CAT）， and glutathione peroxidase （GSH-Px） and the level of malondialdehyde （MDA） in myocardium tissue of the mice； immunohistochemistry staining was used to observe the expression of Kelch-like ECH-associated protein 1 （Keap1） in myocardium tissue of the mice； immunofluorescence staining was used to observe the expression of nuclear factor erythroid 2-related factor 2 （Nrf2） and heme oxygenase 1 （HO-1） in myocardium tissue of the mice； Western blotting method was used to detect the expression levels of Keap1， Nrf2， HO-1， and cysteinyl aspartate-specific proteinase 3 （Caspase-3） proteins in myocardium tissue of the mice. Results Compared with control group， the myocardial injury of the mice in model group was severe， with enlarged myocardial cell gaps， increased collagen fibers， and increased lipid distribution； the body weight， left ventricular posterior wall thickness at end-systole （LVPWs）， and ejection fraction （EF） of the mice were significantly decreased （P<0.05 or P<0.01）； FBG， left ventricular end-diastolic diameter （LVIDd）， and end-systolic diameter （LVIDs） were significantly increased （P<0.05 or P<0.01）； the activities of SOD， CAT， and GSH-Px in myocardium tissue were significantly decreased （P<0.01）， and the MDA level was significantly increased （P<0.01）； the expression levels of Nrf2 and HO-1 proteins in myocardium tissue were significantly decreased （P<0.01）， while the expression levels of Keap1 and Caspase-3 proteins were significantly increased （P<0.01）. Compared with model group， the pathomorphology， myocardial fibrosis， and lipid distribution of myocardium tissue of the mice in Met group， medium dose of VAP group， and high dose of VAP group were improved to varying degrees； the body weight， LVPWs， and EF were significantly increased （P<0.05 or P<0.01）； FBG， LVIDd， and LVIDs were significantly decreased （P<0.05 or P<0.01）； the activities of SOD， CAT， and GSH-Px in myocardium tissue were significantly increased （P<0.05 or P<0.01）， and the MDA level was significantly decreased （P<0.05 or P<0.01）； the expression levels of Nrf2 and HO-1 proteins in myocardium tissue were significantly increased （P<0.01）， and the expression levels of Keap1 and caspase-3 proteins were significantly decreased （P<0.01）. Compared with model group， the body weight of the mice in low dose of VAP group was significantly increased （P<0.05） and FBG was significantly decreased （P<0.05）， but there were no significant differences in LVPWs， EF， LVIDd， LVIDs， activities of SOD， CAT， and GSH-Px， level of MDA， expression level of Keap1， Nrf2， HO-1， and Caspase-3 proteins （P>0.05）. Conclusion VAP can improve myocardial injury and cardiac function in the DCM mice in a dose-dependent manner， and its mechanism may be related to regulating the Keap1/Nrf2/HO-1 signaling pathway and reducing oxidative stress and apoptosis.

Key words: Velvet antler polypeptide, Diabetic cardiomyopathy, Myocardial injury, Oxidative stress, Apoptosis