Interleukin-1{szligbeta}-Induced Insulin Resistance in Adipocytes through Down-Regulation of Insulin Receptor Substrate-1 Expression

• Published in: Endocrinology (Philadelphia) 2007-01, Vol.148 (1), p.241-251
• Main Authors: Jager, Jennifer, Gremeaux, Thierry, Cormont, Mireille, Le Marchand-Brustel, Yannick, Tanti, Jean-Francois
• Format: Article
• Language: English
• ISSN: 0013-7227

Inflammation is associated with obesity and insulin resistance. Proinflammatory cytokines produced by adipose tissue in obesity could alter insulin signaling and action. Recent studies have shown a relationship between IL-1{szligbeta} level and metabolic syndrome or type 2 diabetes. However, the ability of IL-1{szligbeta} to alter insulin signaling and action remains to be explored. We demonstrated that IL-1{szligbeta} slightly increased Glut 1 translocation and basal glucose uptake in 3T3-L1 adipocytes. Importantly, we found that prolonged IL-1{szligbeta} treatment reduced the insulin-induced glucose uptake, whereas an acute treatment had no effect. Chronic treatment with IL-1{szligbeta} slightly decreased the expression of Glut 4 and markedly inhibited its translocation to the plasma membrane in response to insulin. This inhibitory effect was due to a decrease in the amount of insulin receptor substrate (IRS)-1 but not IRS-2 expression in both 3T3-L1 and human adipocytes. The decrease in IRS-1 amount resulted in a reduction in its tyrosine phosphorylation and the alteration of insulin-induced protein kinase B activation and AS160 phosphorylation. Pharmacological inhibition of ERK totally inhibited IL-1{szligbeta}-induced down-regulation of IRS-1 mRNA. Moreover, IRS-1 protein expression and insulin-induced protein kinase B activation, AS160 phosphorylation, and Glut 4 translocation were partially recovered after treatment with the ERK inhibitor. These results demonstrate that IL-1{szligbeta} reduces IRS-1 expression at a transcriptional level through a mechanism that is ERK dependent and at a posttranscriptional level independently of ERK activation. By targeting IRS-1, IL-1{szligbeta} is capable of impairing insulin signaling and action, and could thus participate in concert with other cytokines, in the development of insulin resistance in adipocytes.