Apelin-13 alleviates diabetic nephropathy by enhancing nitric oxide production and suppressing kidney tissue fibrosis

Diabetes is a serious metabolic disease, and the kidney damage induced by diabetes also seriously affects the survival of patients. Apelin is a molecule that plays a crucial role in lipid metabolism, and recent studies have revealed that apelin-13, a subtype of apelin, plays an important role in regulating blood glucose levels. However, the role of apelin-13 in diabetic nephropathy remains unclear. In the present study, a rat model of diabetic nephropathy was constructed by the injection of streptozocin (STZ). During this process, these rats were injected with apelin-13. The blood glucose, urine protein and insulin levels were determined weekly. Next, the expression of angiotensin domain type 1 receptor-associated protein (APJ), endothelial nitric oxide synthase (eNOS), E-cadherin and alpha-smooth muscle actin (alpha-SMA) in the kidney tissues was determined with western blotting. Then, the endothelial cells of glomerular vessels were cultured with high glucose medium. These cells were treated with apelin-13 for 24 h. Finally, cell viability of these cells and the expression of APJ, eNOS, E-cadherin and alpha-SMA in these cells were determined with western blotting. As a result, treatment of apelin-13 induced the lower levels of blood glucose and urine protein. In addition, application of apelin-13 promoted the production of insulin and alleviated the insulin resistance. Treatment with apelin-13 promoted the expression of APJ, eNOS and E-cadherin while it suppressed the expression of alpha-SMA in kidney tissues of rats and endothelial cells of glomerular vessels. Furthermore, application of apelin-13 also promoted the cell viability of these cells. In conclusion, apelin-13 relieved diabetic nephropathy by promoting the production of nitric oxide (NO) and alleviating the fibrosis of kidney tissues.