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

Abstract

However, the in vivo function of the ROCK1 isoform in adipose tissue has not been addressed. To determine the specific role of the adipose ROCK1 isoform in the development of insulin resistance and obesity, mice lacking ROCK1 in adipose tissue globally or selectively were studied. Here, we show that insulin's ability to activate IRS-1/PI3K/ Akt signaling was greatly enhanced in adipose tissue of ROCK1 Ϫ/Ϫ mice compared with wild-type mice. These effects resulted from the inhibitory effect of ROCK1 on insulin receptor action, as evidenced by the fact that IR tyrosine phosphorylation was abolished in ROCK1 Ϫ/Ϫ MEF cells when ROCK1 was reexpressed. Consistently, adipose-specific disruption of ROCK1 increased IR tyrosine phosphorylation in adipose tissue and modestly improved sensitivity to insulin in obese mice induced by high-fat feeding. This effect is independent of any changes in adiposity, number or size of adipocytes, and metabolic parameters, including glucose, insulin, leptin, and triglyceride levels, demonstrating a minimal effect of adipose ROCK1 on whole body metabolism. Enzymatic activity of ROCK1 in adipose tissue remained ϳ50%, which likely originated from the fraction of stromal vascular cells, suggesting involvement of these cells for adipose metabolic regulation. Moreover, ROCK isoform activities were increased in adipose tissue of diet-induced or genetically obese mice. These data suggest that adipose ROCK1 isoform plays an inhibtory role for the regulation of insulin sensitivity in diet-induced obesity in vivo.adipocyte; insulin sensitivity; insulin signaling; Rho kinase; ROCK1 THE INCIDENCE OF OBESITY has been increasing at an alarming rate and has become a major public health concern, affecting over 11% of the worldwide adult population (1, 11). Obesity is a significant causal factor for developing type 2 diabetes (9, 49). Type 2 diabetes is a multifactorial metabolic disorder characterized by peripheral insulin resistance in insulin target tissues such as skeletal muscle, adipose, and liver, all of which are key organs involved in the regulation of glucose disposal and production (9, 30). When these tissues fail to respond adequately to circulating insulin, insulin resistance occurs, resulting from an elevation of blood glucose levels (23). However, knowledge of the molecular mechanisms underlying the pathogenesis of insulin resistance is incomplete.Rho kinase (ROCK) is a serine/threonine protein kinase identified as a GTP-Rho-binding protein (35). The two isoforms, ROCK1 (also known as ROK␤) and ROCK2 (also known as ROK␣), are ubiquitously expressed in metabolically active organs (21,33,37). It is now clear that ROCK isoforms have a dual role either to enhance or to diminish insulin signaling in vivo and in vitro (2,7,12,31,32,44,45). Our previous work demonstrated that activation of ROCK1 is required for insulin-mediated glucose metabolism and insulin signaling in skeletal muscle, as indicated by the finding that global ROCK1-deficient mice show whole body insulin resistance by impairing ske...

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

“…This is in contrast to the results of previous studies of ROCK2 regulation of insulin signaling in cultured 3T3-L1 adipocytes and L6 myoblasts, in which ROCK2 siRNA altered the phosphorylation of IRS and/or its downstream target Akt (10). This difference may be an indication of the complex tissue-and cell-specific regulation of insulin signaling by ROCK isoforms that has been noted in previous studies (5,10,23,30). Alternatively, it is possible that the residual ROCK2 protein levels in the ROCK2 ϩ/Ϫ mice were sufficient to maintain normal IRS phosphorylation, whereas levels achieved by ROCK2 siRNA in the cells were not.…”

“…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). On the other hand, ROCK2 has been implicated in reduced insulin signaling in cultured mouse embryonic fibroblasts (30) and vascular cells (5) by promoting insulin-induced phosphorylation of serine residues in IRS-1.…”

Rho Kinases in Health and Disease: From Basic Science to Translational Research

“…Thus, in adipose tissue, ROCK1 negatively controls insulin action in vivo. However, loss of adipose ROCK1 leads to increased insulin receptor signaling, with a minor effect on whole-body metabolism and glucose homeostasis (Lee et al, 2014b). These data also collectively confirm the complex and tissue-or cellspecific role of ROCKs in glucose metabolism and insulin signaling.…”

“…Despite their insulin resistance, Rock1 2/2 mice display an increase in proximal insulin signaling in adipose tissue, and adipose tissue-selective deletion of Rock1 slightly ameliorates insulin sensitivity in the high-fat diet model of insulin resistance (Lee et al, 2014b). Thus, in adipose tissue, ROCK1 negatively controls insulin action in vivo.…”

Rho-associated coiled-coil containing kinases (ROCK)

“…109 Interestingly, it was recently shown that adipose specific ROCK1 deletion in mice resulted in enhanced insulin signaling, suggesting that ROCK1 deletion had a protective effect against insulin resistance in this tissue. 133 These data suggests that there are tissue or cell type specific roles for ROCK1 in regulating glucose metabolism. Further genetic studies are required to determine the contribution of the ROCK2 isoform in insulin signaling and glucose homeostasis.…”