Adiponectin improves diabetic nephropathy by inhibiting necrotic apoptosis

Abstract

Introduction: This study aimed to investigate the effect of adiponectin (Apn) on necrotic apoptosis (Nec) in vitro and in vivo to clarify the possible role of Apn in the pathogenesis of diabetic nephropathy (DN).

Material and methods: Rat glomerular endothelial (RGE) cells were treated with high glucose (HG, 30 mmol/l) for 24 h and the effects of Apn on cell viability, RIP1 and RIP3 expression and p-p38MAPK activation were assayed by CCK-8, immunofluorescence and western blot. Then a streptozotocin (STZ)-induced DN rat model was established. The body weight, left kidney weight, left kidney weight/body weight (KW/BW), creatinine clearance rate (Ccr), 24 h urine protein and blood glucose were recorded. The expression of RIP1, RIP3 and p-p38MAPK in renal tissues was examined by immunohistochemistry and western blot.

Results: Treatment of RGE cells with HG induced significant cytotoxicity and increased expression levels of RIP1, RIP3 and p-p38MAPK, which were abrogated by Apn in a concentration-dependent manner. In vivo, compared with the control group, the Ccr, 24 h urine protein and the blood glucose level of the rats in the model group were significantly increased, effects which were abrogated by Apn intervention. Moreover, the expression levels of RIP1, PIP3 and p-p38MAPK were also significantly increased in the model group, effects which were canceled by Apn intervention.

Conclusions: Apn can alleviate the inflammatory response and damage of DN by inhibiting Nec via p-p38MAPK signaling.

Keywords: diabetic nephropathy; necroptosis; p38MAPK; rat glomerular endothelial cells.

Figure 1

Apn protects HG-induced Nec. A – Cell viability was assayed by CCK-8 assay. Treatment of RGE cells with HG (30 mmol/l) for 24 h can cause significant cytotoxicity. Cell viability was promoted by co-treatment of the cells with 1, 5 or 25 μg/ml Apn. B – The expression of RIP1 and RIP3 in cells were examined by immunofluorescence. C – The expression of RIP1, RIP3 and p-p38MAPK were assayed by western blot. The expression levels of RIP1, RIP3 and p-p38MAPK in HG-treated cells were significantly increased. Co-treatment of cells with 1, 5 or 25 μg/ml Apn could reduce the expression of RIP1, RIP3 and p-p38MAPK *p < 0.05 and **p < 0.01 vs. Control; #p < 0.05 and ##p < 0.01 vs. HG.

Figure 2

Apn improves DN animal models (n = 8). Compared with the rats in the control group, the body weights of the rats in the model group were significantly reduced from the 4^th week, and were increased from the 6^th week after Apn intervention. The left kidney weight and KW/BW of the rats in the model group were significantly increased and KW/BW significantly decreased after Apn intervention. Ccr, 24 h urine protein and blood glucose from the rats in the model group increased significantly from the 4^th week, and significantly decreased from the 4^th week after Apn intervention *p < 0.05 and **p < 0.01 vs. Control; #p < 0.05 and ##p < 0.01 vs. Model.

Figure 3

Apn reduced the expression of RIP1, RIP3 and p-p38MAPK (n = 8). A – HE staining. The glomerular diameter was significantly increased in the model group, and was decreased after Apn intervention. B – Immunohistochemistry of RIP1 and PIP3 in renal tissues. C – Western blot assay. The expression levels of RIP1, PIP3 and p-p38MAPK for the rats in the model group were significantly increased, while they were significantly decreased after Apn intervention **p < 0.01 vs. Control; #p < 0.05 and ##p < 0.01 vs. Model.