The inhibition of SGK1 suppresses epithelial-mesenchymal transition and promotes renal tubular epithelial cell autophagy in diabetic nephropathy.

Diabetic nephropathy (DN) is a common complication of diabetes that is the dominant cause of end-stage renal disease. However, the pathological mechanism of DN is yet to be elucidated. Serum and glucocorticoid induced kinase (SGK) 1, a ubiquitously expressed kinase, was employed in the current study to assess its effect on DN in vivo and in vitro. Male BALB/C mice and a human tubular epithelial cell line (HK-2) were utilized for experimentation. Male BALB/C mice and a human tubular epithelial cell line (HK-2) were utilized for experimentation. Pathological changes were measured via HE and staining and immunohistochemistry was performed to measure the expression of SGK 1. An SGK1 inhibitor, GSK650394, was applied to analyze the role of SGK1 in HK-2 cell epithelial-mesenchymal transition (EMT). Associated protein expressions were assessed via western blotting. In addition, migration was measured using a scratch wound healing assay. 3-methyladenine (3-MA), an autophagy inhibitor, was used to determine the variation of autophagy following SGK1 inhibition. The expression of autophagy proteins were analyzed. Furthermore, the expression of PI3K, AKT, mTOR and their levels of phosphorylation were measured. The results revealed that the ultrastructure of renal tissue suffered damage and that the expression of SGK1 was markedly increased. After SGK1 inhibition, HK-2 cell EMT was suppressed and cell migration was attenuated. Furthermore, the autophagy of HK-2 cells was promoted, an increased expression of Beclin-1 and LC3 II was detected, and a decreased expression of p62 was observed. Additionally, the phosphorylation of PI3K, AKT and mTOR were markedly upregulated. The results indicated that blocking autophagy signaling via 3-MA muted SGK1-protected against HG-evoked cell injury. Our study demonstrated that SGK1 inhibition promoted autophagy and suppressed renal tubular epithelial cell EMT in DN, indicating that SGK1 may serve as a potential therapeutic target of DN.