Urine microRNA-7977/G6PD level in DKD patients and its association with dysfunction of albumin-induced autophagy in proximal epithelial tubular cells

Abstract

Studies have shown that decreased expression of glucose-6-phosphate dehydrogenase (G6PD) play an important role in DKD. However, the upstream and downstream pathways of G6PD downregulation leading to DKD have not been elucidated.We conducted a series of studies including clinical study, animal studies, and in vitro studies to explore this. Firstly, a total of 90 subjects were evaluated. The urinary G6PD activity and its association with the clinical markers were analyzed. Then, urine differentially microRNAs that can bind and degrade G6PD were screened and verified in DKD patients. After that, high glucose (HG)-cultured Human kidney cells (HK-2) and Zucker diabetic fatty (ZDF) rats were used to test the roles of miR-7977/G6PD/albumin-induced autophagy in DKD. The plasma and urinary G6PD activity were decreased significantly in patients with DKD, accompanied by increased urinary mir-7977 level. The fasting plasma glucose (FPG), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), and urinary albumin excretion were independent predictors of urinary G6PD activity by multiple linear regression analysis.The increased expression of miR-7977 and decreased expression of G6PD were also found in the kidney of ZDF rats with early renal tubular damage.In HK-2 cells cultured with normal situation, low level of albumin could induce autophagy along with the stimulation of G6PD although this was impaired under high glucose. Overexpression of G6PD reversed albumin-induced autophagy in HK2 cells under high glucose.Inhibition mir-7977 expression led to significantly increased expression of G6PD and reversed the effects of high glucose on albumin induced autophagy.Our study supports a new mechanism of G6PD downregulation in DKD.