Deregulated profiles of urinary microRNAs may explain podocyte injury and proximal tubule dysfunction in normoalbuminuric patients with type 2 diabetes mellitus

MicroRNAs (miRNAs) are short non-coding RNA species that are important post-transcriptional regulators of gene expression. The aim of the study was to establish a potential explanation of podocyte damage and proximal tubule (PT) dysfunction induced by deregulated miRNAs expression in the course of type 2 diabetes mellitus (DM). A total of 68 patients with type 2DM and 11 healthy subjects were enrolled in a cross-sectional study and assessed concerning urinary albumin:creatinine ratio (UACR), urinary N-acetyl--D-glucosamininidase (NAG), urinary kidney injury molecule-1, urinary nephrin, podocalyxin, synaptopodin, estimated glomerular filtration rate (eGFR), urinary miRNA21, miRNA124, and miRNA192. In univariable regression analysis, miRNA21, miRNA124, and miRNA192 correlated with urinary nephrin, synaptopodin, podocalyxin, NAG, KIM-1, UACR, and eGFR. Multivariable regression analysis yielded models in which miRNA192 correlated with synaptopodin, uNAG, and eGFR (R-2=0.902; P<0.0001), miRNA124 correlated with synaptopodin, uNAG, UACR, and eGFR (R-2=0.881; P<0.0001), whereas miRNA21 correlated with podocalyxin, uNAG, UACR, and eGFR (R-2=0.882; P<0.0001). Urinary miRNA192 expression was downregulated, while urinary miRNA21 and miRNA124 expressions were upregulated. In patients with type 2DM, there is an association between podocyte injury and PT dysfunction, and miRNA excretion, even in the normoalbuminuria stage. This observation documents a potential role of the urinary profiles of miRNA21, miRNA124, and miRNA192 in early DN. Despite their variability across the segments of the nephron, urinary miRNAs may be considered as a reliable tool for the identification of novel biomarkers in order to characterize the genetic pattern of podocyte damage and PT dysfunction in early DN of type 2DM.