Altered expression of miR-181a-5p and miR-23a-3p is associated with obesity and TNFα-induced insulin resistance.

Context: The proinflammatory cytokine TNFa is a key player in insulin resistance (IR). The role of miRNAs in inflammation associated with IR is poorly understood. Objective: To investigate miR-181a-5p and miR-23a-3p expression profiles in obesity and to study their role in TNF alpha-induced IR in adipocytes. Design: Two separate cohorts were used. Cohort 1 was used in adipose tissue (AT) expression studies and included 28 subjects with body mass index (BMI), <30 kg/m(2) and 30 with BMI >= 30 kg/m(2). Cohort 2 was used in circulating serum miRNA studies and included 101 subjects with 4 years of follow-up (48 case subjects and 53 control subjects). miR-181a-5p and miR-23a-3p expression was assessed in subcutaneous and visceral AT. Functional analysis was performed in adipocytes, using miRNA mimics and inhibitors. Key molecules of the insulin pathway, AKT, PTEN, AS160, and S6K, were analyzed. Results: Expression of miR-181a-5p and miR-23a-3p was reduced in adipose tissue from obese and diabetic subjects and was inversely correlated to adiposity and homeostasis model assessment of IR index. Overexpression of miR-181a-5p and miR-23a-3p in adipocytes upregulated insulin-stimulated AKT activation and reduced TNFa-induced IR, regulating PTEN and S6K expression. Serum levels of miR-181a-5p were reduced in case vs control subjects at baseline, suggesting a prognostic value. Variable importance in projection scores revealed miR-181a-5p had more effect on the model than insulin or glucose at 120 minutes. Conclusion: miR-181a-5p and miR-23a-3p may prevent TNFa-induced IR in adipocytes through modulation of PTEN and S6K expression.