Targeted Disruption of ROCK1 Causes Insulin Resistance in Vivo

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 ϳ40% 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.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). Impairments in insulin secretion and in the response of peripheral tissues to insulin (i.e. insulin resistance) are major pathogenic features of type 2 diabetes and contribute to the morbidity of obesity (1, 2). Insulin action involves a series of signaling cascades initiated by insulin binding to its receptor, eliciting receptor autophosphorylation and activation of the receptor tyrosine kinase, resulting in tyrosine phosphorylation of insulin receptor substrates (IRSs) 4 (3). Phosphorylation of IRSs leads to activation of phosphatidylinositol 3-kinase (PI3K) and subsequently to activation of Akt and its downstream mediator AS160, all of which are important steps for the stimulation of glucose transport induced by insulin (4 -6). Although the mechanism(s) underlying insulin resistance are not completely understood in peripheral tissues such as skeletal muscle, they are thought to result, at least in part, from impaired insulin-stimulated signal transduction (7).Rho-kinase (ROCK) is a Ser/Thr protein kinase identified as a GTP-Rho-binding protein (8). There are two ...

Partial deletion of ROCK2 protects mice from high-fat diet-induced cardiac insulin resistance and contractile dysfunction

“…Studies in cultured cells have suggested that both ROCK isoforms promote Ser 632/635 phosphorylation of IRS, although the consequences on downstream insulin signaling seem to vary in different cell types (14,30). Furthermore, the genetic deletion of ROCK1 resulted in decreased Ser 632/635 phosphorylation of IRS in skeletal muscle, which was associated with reduced Tyr 612 phosphorylation and insulin signaling (21). However, in the present study, the reduced Tyr 612 phosphorylation of IRS was not associated with a change in Ser 632/635 phosphorylation in hearts from HFD-WT mice, despite increases in the activity of ROCK1 and ROCK2.…”

“…For instance, ROCK1 is required for normal insulin sensitivity in mice, since its deletion was associated with reduced tyrosine phosphorylation of IRS and impaired glucose transport in skeletal muscle (21). However, recently, ROCK1 was also shown to negatively regulate insulin signaling in adipose tissue (23).…”

Involvement of RhoA/ROCK in myocardial fibrosis in a rat model of type 2 diabetes

“…Insulin signaling is essential for normal glucose homeostasis. ROCK1 have been demonstrated as a novel regulator of glucose homeostasis and insulin sensitivity in vivo [43] . However, studies of the effects of ROCK inhibitors on glucose metabolism in vivo have yielded conflicting results.…”

Lipid-induced Muscle Insulin Resistance Is Mediated by GGPPS via Modulation of the RhoA/Rho Kinase Signaling Pathway

“…Kim and co-workers (29,30) have reported that inhibition of the Rho kinase isoform Rock1 causes insulin resistance in skeletal muscle via inhibitory phosphorylation of IRS-1 and decreases downstream signaling, whereas Bankar's study (31) finds that heterozygous Rock2 deficiency augments skeletal muscle IRS-1/PI3K/Akt signaling and whole body insulin sen- sitivity. These studies indicate that the role of Rock2 in regulation of insulin sensitivity is opposite to that of Rock1.…”