In vivo activation of ROCK1 by insulin is impaired in skeletal muscle of humans with type 2 diabetes

Abstract

To determine whether serine/threonine ROCK1 is activated by insulin in vivo in humans and whether impaired activation of ROCK1 could play a role in the pathogenesis of insulin resistance, we measured the activity of ROCK1 and the protein content of the Rho family in vastus lateralis muscle of lean, obese nondiabetic, and obese type 2 diabetic subjects. Biopsies were taken after an overnight fast and after a 3-h hyperinsulinemic euglycemic clamp. Insulin-stimulated GDR was reduced 38% in obese nondiabetic subjects compared with lean, 62% in obese diabetic subjects compared with lean, and 39% in obese diabetic compared with obese nondiabetic subjects (all comparisons P < 0.001). Insulin-stimulated IRS-1 tyrosine phosphorylation is impaired 41-48% in diabetic subjects compared with lean or obese subjects. Basal activity of ROCK1 was similar in all groups. Insulin increased ROCK1 activity 2.1-fold in lean and 1.7-fold in obese nondiabetic subjects in muscle. However, ROCK1 activity did not increase in response to insulin in muscle of obese type 2 diabetic subjects without change in ROCK1 protein levels. Importantly, insulin-stimulated ROCK1 activity was positively correlated with insulin-mediated GDR in lean subjects (P < 0.01) but not in obese or type 2 diabetic subjects. Moreover, RhoE GTPase that inhibits the catalytic activity of ROCK1 by binding to the kinase domain of the enzyme is notably increased in obese type 2 diabetic subjects, accounting for defective ROCK1 activity. Thus, these data suggest that ROCK1 may play an important role in the pathogenesis of resistance to insulin action on glucose disposal in muscle of obese type 2 diabetic subjects.

ROCK1 isoform-specific deletion reveals a role for diet-induced insulin resistance

“…Supporting this, in vitro studies with muscle cells also revealed that the ability of insulin to increase glucose transport was decreased when endogenous ROCK1 expression was inhibited (7). Furthermore, insulin stimulation of ROCK1 activity in skeletal muscle was significantly reduced in human subjects with obesity and type 2 diabetes, suggesting that impaired ROCK1 activation could contribute to the pathogenesis of insulin resistance in humans (8). However, experimental evidence from vasculature-related cell lines, including vascular smooth muscle cells, endothelial cells, and mammary epithelial cells, indicates that suppression of ROCK isoform activity with ROCK inhibitors fasudil or Y-27632 enhances insulin signaling by affecting IRS-1 tyrosine phosphorylation or PTEN (2,32,44,45).…”

Pathophysiological Functions of Rnd 3/ RhoE

“…Differing from previous studies, Chun et al indicated that RND3 can also bind to the kinase domain of ROCK1 and inhibit the catalytic activity of ROCK1. The effect of inhibition was notably increased in obese type 2 diabetic patients, accounting for defective ROCK1 activity (27). …”

Excessive secretion of IL-8 by skeletal muscle in type 2 diabetes impairs tube growth: potential role of PI3K and the Tie2 receptor

“…For chronic exposure experiments, HUVEC were treated with rIL-8 or CM from myotubes for 24 -72 h with or without anti IL-8-neutralizing antibodies (R & D Systems) or the phosphatidylinositol 3-kinase (PI3K) inhibitor LY-294002 (Sigma, St. Louis, MO) and then lysed in extraction buffer (7,38). Frozen muscle tissue was homogenized with a Polytron at half speed and lysed in extraction buffer, as described previously (6).…”