Rs12976445 Polymorphism is Associated with Risk of Diabetic Nephropathy Through Modulating Expression of MicroRNA-125 and Interleukin-6R

BACKGROUND Diabetic nephropathy (DN) is one of the most significant long-term complications of diabetes mellitus (DM), and it is a primary risk factor for end-stage renal disease. MicroRNAs (miRNAs) play important roles in regulating the expression of genes, including interleukin-6R (IL-6R), which has been reported to be involved in the development of DNDN. The aim of this study was to identify the dysregulation of miRNA and its target responsible for the development of DN in DM. MATERIAL AND METHODS We collected the kidney tissues from patients with DN (N=36) and control patients (N=28), and performed real-time PCR and Western blot analysis to determine the expression of IL-6R. Computational analysis and luciferase assay were used to identify the miRNA that regulates IL-6R. To explore the association between rs12976445 polymorphism and risk of DN, we enrolled 594 DM patients with (N=282) or without DN (N=312), and studied the association between a variant in miR-125a and risk of DN in DM. RESULTS The expression of IL-6R was barely detected in the control groups, while in the DN group, the IL-6R was clearly detectable. Next, miR-125a was identified as a regulator of IL-6R by using informatics analysis and luciferase assay. A single-nucleotide polymorphism (rs12976445) in pri-miR-125a has been shown to compromise the mature processing of miR-125a, and we showed that the expression levels of miR-125a was comparable between individuals carrying TT and CT, and when combined into 1 group, the miR-125a expression was approximately 3 times lower than in the CC group. We found significant differences regarding rs12976445 genotype distribution between the DN and the control (OR=1.45, 95% C.I.=1.02-2.08, p<0.05) with the possible confounding factors adjusted for by using logistic regression analysis. CONCLUSIONS We identified miR-125a as a direct regulator of IL-6R, and the genotype of rs12976445 might be a novel predictor of the development of DN in DM.