CREG improves cardiac function by regulating cardiomyocytes' autophagy in diabetic myocardial infarction rats

OBJECTIVE: We aimed to observe the changes of cardiac function, cell morphology, cellular repressor of E1A-stimulated genes (CREG) and LC3-II after myocardial infarction (MI) in non-diabetic and diabetic rats, and to explore the relationship between myocardial damage and CREG and autophagy in diabetic rats. MATERIALS AND METHODS: Diabetic rat models were prepared by intraperitoneal injection of low concentration (50 mg/kg) streptozotocin (STZ). MI models were established in normal rats and diabetic rats. The cardiac function of each group was detected by echocardiography. The pathological results of myocardial tissue in the infarcted area were observed under light microscope. The expression of CREG was detected by quantitative Real Time-Polymerase Chain Reaction (qRT-PCR). Myocardial protein CREG LC3-II expression was measured by Western blot. Autophagy levels were also detected at the cellular level. Construction of CREG overexpressing adenovirus transfected H9c2 cells, and injection of rats with AAV-CREG to achieve the purpose of overexpressing CREG. In vitro and in vivo experiments were conducted to explore the effects of CREG on autophagy and cardiac function in a diabetic MI model. RESULTS: Compared with the non-diabetic sham (NS) group, there were no marked differences in cardiac function and CREG levels in the diabetic sham (DS) group. Compared with the NS group, the cardiac function of the non-diabetic myocardial infarction (NI) group and the diabetic infarction myocardial (DI) group were reduced, and the levels of autophagy were increased. However, the cardiac function of the DI group was worse than that of the NI group, and the autophagy level of the DI group was lower than the NI group. The results at the cellular level were similar to the experiments in vivo. The overexpression of CREG in vivo or in vitro can increase autophagy levels and improve cardiac function. CONCLUSIONS: The exacerbation of myocardial injury after MI in diabetic rats may be related to the inhibition of CREG in myocardial cells of infarcted area by diabetes.