The Induction of MicroRNA Targeting IRS-1 Is Involved in the Development of Insulin Resistance under Conditions of Mitochondrial Dysfunction in Hepatocytes

Abstract

BackgroundMitochondrial dysfunction induces insulin resistance in myocytes via a reduction of insulin receptor substrate-1 (IRS-1) expression. However, the effect of mitochondrial dysfunction on insulin sensitivity is not understood well in hepatocytes. Although research has implicated the translational repression of target genes by endogenous non-coding microRNAs (miRNA) in the pathogenesis of various diseases, the identity and role of the miRNAs that are involved in the development of insulin resistance also remain largely unknown.MethodologyTo determine whether mitochondrial dysfunction induced by genetic or metabolic inhibition causes insulin resistance in hepatocytes, we analyzed the expression and insulin-stimulated phosphorylation of insulin signaling intermediates in SK-Hep1 hepatocytes. We used qRT-PCR to measure cellular levels of selected miRNAs that are thought to target IRS-1 3′ untranslated regions (3′UTR). Using overexpression of miR-126, we determined whether IRS-1-targeting miRNA causes insulin resistance in hepatocytes.Principal FindingsMitochondrial dysfunction resulting from genetic (mitochondrial DNA depletion) or metabolic inhibition (Rotenone or Antimycin A) induced insulin resistance in hepatocytes via a reduction in the expression of IRS-1 protein. In addition, we observed a significant up-regulation of several miRNAs presumed to target IRS-1 3′UTR in hepatocytes with mitochondrial dysfunction. Using reporter gene assay we confirmed that miR-126 directly targeted to IRS-1 3′UTR. Furthermore, the overexpression of miR-126 in hepatocytes caused a substantial reduction in IRS-1 protein expression, and a consequent impairment in insulin signaling.Conclusions/SignificanceWe demonstrated that miR-126 was actively involved in the development of insulin resistance induced by mitochondrial dysfunction. These data provide novel insights into the molecular basis of insulin resistance, and implicate miRNA in the development of metabolic disease.

MicroRNA-126 inhibits cell viability and invasion in a diabetic retinopathy model via targeting IRS-1

“…Expression of miR-126 is decreased in multiple types of cancer cell, and has previously been regarded as a cell growth suppressor that acts on IRS-1 (16) or as a metabolic regulator in hepatocytes (31). The loss of miR-126 has been reported in the plasma of patients with diabetes mellitus (DM).…”

Application of microRNAs in diabetes mellitus

“…miR-96 and miR-126 directly target the insulin receptor substrate 1 (IRS1) 3 0 UTR. The reduction in IRS1 is involved in insulin resistance under conditions of mitochondrial dysfunction in hepatocytes (Ryu et al 2011, Jeong et al 2013. Protein tyrosine phosphatase 1B (PTP1B), a target of miR-122, inhibits hepatic insulin signaling by dephosphorylating tyrosine residues in the insulin receptor (IR) and IRS.…”

miRNAs link metabolic reprogramming to oncogenesis

“…The inhibition of insulin receptor substrate-1 (IRS1) by miR-126 also promotes insulin resistance [64], while miR-33a and miR-33b affect insulin signaling and glucose regulation by targeting IRS2, SIRT6 and AMPKα1 [65]. Additionally, miR-33a may regulate Pim-1, a kinase that possesses overlapping functions with Akt [66].…”