Celastrol Reverses Palmitic Acid-Induced Insulin Resistance in HepG2 Cells via Restoring the miR-223 and GLUT4 Pathway

Abstract

The natural triterpenoid compound celastrol ameliorates insulin resistance (IR) in animal models, but the underlying molecular mechanism is unclear. In this study, we investigated how celastrol regulates IR. The HepG2 cellular IR model was initially established with palmitic acid (PA). The expression and activity of glucose transporter 4 (GLUT4), insulin receptor substrate-1 (IRS1) and 9 microRNAs (miRNAs) (miR-7, -34a, -96, -113, -126, -145, -150, -223 and -370) were detected before and after celastrol treatment using the PA-induced HepG2 IR model. The results showed that 250 µM PA for ≥2 days was optimal for inducing IR in HepG2 cells; 600 nM celastrol significantly attenuated the PA-induced IR in HepG2 cells. The PA-induced GLUT4 and IRS1 downregulation and Ser307 phosphorylation on IRS1 was reversed by subsequent treatment with 600 nM celastrol for 6 h. We next investigated which IR-related miRNAs were possible upstream regulators of celastrol-mediated reversal of PA-induced HepG2 IR. Two miRNAs, miR-150 and -223, were significantly downregulated by PA and were re-raised by subsequent celastrol treatment; and miR-223 was upstream of miR-150. Moreover, knocking down miR-223 abolished celastrol's anti-IR effects in the PA-induced model. Collectively, our results demonstrated that celastrol reverses PA-induced IR-related alterations, in part via miR-223 in HepG2 cells. Further investigation is warranted for establishing the clinical potential of celastrol in treating IR-related disorders.