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Human and mouse muscle transcriptomic analyses identify insulin receptor mRNA downregulation in hyperinsulinemia-associated insulin resistance

ABSTRACT: Hyperinsulinemia is often viewed as compensatory to insulin resistance, but studies have shown that high levels of insulin may contribute to insulin resistance. The precise mechanisms by which hyperinsulinemia contributes to insulin resistance remain poorly defined. To understand direct effects of prolonged exposure to excess insulin in muscle cells, we incubated differentiated C2C12 myotubes with elevated insulin for 16 hours, followed by 6 hours serum starvation, before examining key insulin signaling nodes. Using this model, we found that prolonged high insulin treatment significantly increased the phosphorylation of insulin receptor (INSR) and AKT, but not ERK. After starvation, acute AKT and ERK signaling stimulated by 0.2 - 20 nM insulin was attenuated. INSR protein was significantly downregulated by hyperinsulinemia in a insulin-dose-dependent manner. Surface INSR was reduced proportionally to total INSR levels. Mechanistically, we found that hyperinsulinemia strongly downregulated Insr mRNA, which was correlated with increased threonine 24 phosphorylation of FOXO1. Interestingly, 6h starvation reversed the effects of high insulin on basal phosphorylation of INSR, AKT and FOXO1, and Insr transcription. Using RNAseq, bioinformatics, and follow-up RNAi studies, we identified SIN3A as a negative regulator of Insr mRNA levels and JUND, MAX and MXI as positive regulators of Irs2 mRNA. We validated our in vitro results by determining that INSR levels in mouse skeletal muscle were negatively correlated with circulating insulin in vivo. Together, our findings shed new light on the mechanisms underlying hyperinsulinemia-induced insulin resistance in muscle cells, which are likely to be relevant in the pathogenesis of type 2 diabetes.

ORGANISM(S): Mus musculus

PROVIDER: GSE147422 | GEO | 2020/12/31

REPOSITORIES: GEO

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Human and mouse muscle transcriptomic analyses identify insulin receptor mRNA downregulation in hyperinsulinemia-associated insulin resistance

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