title: 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 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.
authors.affiliation: Division of Endocrinology, Diabetes and Metabolism, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA.
authors.forename: Dae Ho
authors.initials: DH
authors.lastname: Lee
authors.forename: Jianjian
authors.initials: J
authors.lastname: Shi
authors.forename: Nam Ho
authors.initials: NH
authors.lastname: Jeoung
authors.forename: Min Seon
authors.initials: MS
authors.lastname: Kim
authors.forename: Janice M
authors.initials: JM
authors.lastname: Zabolotny
authors.forename: Sam W
authors.initials: SW
authors.lastname: Lee
authors.forename: Morris F
authors.initials: MF
authors.lastname: White
authors.forename: Lei
authors.initials: L
authors.lastname: Wei
authors.forename: Young-Bum
authors.initials: YB
authors.lastname: Kim
mesh_terms: D050154:Adiposity / Q000235:genetics; D000818:Animals; D003924:Diabetes Mellitus, Type 2 / Q000235:genetics / Q000378:metabolism / Q000628:therapy; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism; D005947:Glucose / Q000235:genetics / Q000378:metabolism*; D007328:Insulin / Q000235:genetics / Q000378:metabolism*; D055504:Insulin Receptor Substrate Proteins / Q000235:genetics / Q000378:metabolism; D007333:Insulin Resistance; D051379:Mice; D018345:Mice, Knockout; D009765:Obesity / Q000235:genetics / Q000378:metabolism / Q000628:therapy; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000235:genetics; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D019893:Ribosomal Protein S6 Kinases / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D054460:rho-Associated Kinases
chemical_list: D020690:GTPase-Activating Proteins; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; C526295:Irs1 protein, mouse; C505647:Tbc1d4 protein, mouse; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D019893:Ribosomal Protein S6 Kinases; C515854:Rock1 protein, mouse; D054460:rho-Associated Kinases; D005947:Glucose