Targeted Disruption of ROCK1 Causes Insulin Resistance in Vivo

Dae Ho Lee,Jianjian Shi,Nam Ho Jeoung,Min Seon Kim,Janice M Zabolotny,Sam W Lee,Morris F White,Lei Wei,Young-Bum Kim

doi:10.1074/jbc.c900014200

Abstract

Insulin signaling is essential for normal glucose homeostasis. Rho-kinase (ROCK) isoforms have been shown to participate in insulin signaling and glucose metabolism in cultured cell lines. To investigate the physiological role of ROCK1 in the regulation of whole body glucose homeostasis and insulin sensitivity in vivo, we studied mice with global disruption of ROCK1. Here we show that, at 16-18 weeks of age, ROCK1-deficient mice exhibited insulin resistance, as revealed by the failure of blood glucose levels to decrease after insulin injection. However, glucose tolerance was normal in the absence of ROCK1. These effects were independent of changes in adiposity. Interestingly, ROCK1 gene ablation caused a significant increase in glucose-induced insulin secretion, leading to hyperinsulinemia. To determine the mechanism(s) by which deletion of ROCK1 causes insulin resistance, we measured the ability of insulin to activate phosphatidylinositol 3-kinase and multiple distal pathways in skeletal muscle. Insulin-stimulated phosphatidylinositol 3-kinase activity associated with IRS-1 or phospho-tyrosine was also reduced approximately 40% without any alteration in tyrosine phosphorylation of insulin receptor in skeletal muscle. Concurrently, serine phosphorylation of IRS-1 at serine 632/635, which is phosphorylated by ROCK in vitro, was also impaired in these mice. Insulin-induced phosphorylation of Akt, AS160, S6K, and S6 was also decreased in skeletal muscle. These data suggest that ROCK1 deficiency causes systemic insulin resistance by impairing insulin signaling in skeletal muscle. Thus, our results identify ROCK1 as a novel regulator of glucose homeostasis and insulin sensitivity in vivo, which could lead to new treatment approaches for obesity and type 2 diabetes.

Highlights

Insulin signaling is essential for normal glucose homeostasis
Our previous work demonstrated that dominant negative ROCK overexpression or chemical ROCK inhibition decreases insulinstimulated glucose transport in L6 muscle cells and isolated skeletal muscle ex vivo via impairing insulin receptor substrates (IRSs)-1associated phosphatidylinositol 3-kinase (PI3K) activity [22]
Consistent with these in vitro data, we report here that ROCK1 deficiency in mice results in whole body insulin ulation of Akt and AS160 phosphorylation in skeletal muscle resistance and impaired skeletal muscle insulin signaling. was decreased in ROCK1Ϫ/Ϫ mice as compared with wild type (WT)

Summary

Introduction

Insulin signaling is essential for normal glucose homeostasis. Rho-kinase (ROCK) isoforms have been shown to participate in insulin signaling and glucose metabolism in cultured cell lines. Rylation of Akt, AS160, S6K, and S6 was decreased in skeletal muscle These data suggest that ROCK1 deficiency causes systemic insulin resistance by impairing insulin signaling in skeletal muscle. Our results identify ROCK1 as a novel regulator of glucose homeostasis and insulin sensitivity in vivo, which could lead to new treatment approaches for obesity and type 2 diabetes. The ability of insulin to acutely stimulate glucose uptake and metabolism in peripheral tissues such as skeletal muscle and adipose tissue is critical for the regulation of normal glucose homeostasis [1]. In normal mice, we found that acute treatment with ROCK inhibitor Y-27632 causes insulin resistance in vivo by reducing insulin-mediated glucose uptake in skeletal muscle. The fact that ROCK inhibitors target both ROCK isoforms and that their specificities may not be absolute further complicates interpretation of these studies [23]

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Conclusion