Constitutive expression of suppressor of cytokine signalling-3 in skeletal muscle leads to reduced mobility and overweight in mice (original) (raw)
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Regulation of Insulin and Leptin Signaling by Muscle Suppressor of Cytokine Signaling 3 (SOCS3)
PLoS ONE, 2012
Skeletal muscle resistance to the key metabolic hormones, leptin and insulin, is an early defect in obesity. Suppressor of cytokine signaling 3 (SOCS3) is a major negative regulator of both leptin and insulin signaling, thereby implicating SOCS3 in the pathogenesis of obesity and associated metabolic abnormalities. Here, we demonstrate that SOCS3 mRNA expression is increased in murine skeletal muscle in the setting of diet-induced and genetic obesity, inflammation, and hyperlipidemia. To further evaluate the contribution of muscle SOCS3 to leptin and insulin resistance in obesity, we generated transgenic mice with muscle-specific overexpression of SOCS3 (MCK/SOCS3 mice). Despite similar body weight, MCK/SOCS3 mice develop impaired systemic and muscle-specific glucose homeostasis and insulin action based on glucose and insulin tolerance tests, hyperinsulinemic-euglycemic clamps, and insulin signaling studies. With regards to leptin action, MCK/SOCS3 mice exhibit suppressed basal and leptin-stimulated activity and phosphorylation of alpha2 AMP-activated protein kinase (a2AMPK) and its downstream target, acetyl-CoA carboxylase (ACC). Muscle SOCS3 overexpression also suppresses leptin-regulated genes involved in fatty acid oxidation and mitochondrial function. These studies demonstrate that SOC3 within skeletal muscle is a critical regulator of leptin and insulin action and that increased SOCS may mediate insulin and leptin resistance in obesity.
Deletion of Skeletal Muscle SOCS3 Prevents Insulin Resistance in Obesity
Diabetes, 2013
Obesity is associated with chronic low-grade inflammation that contributes to defects in energy metabolism and insulin resistance. Suppressor of cytokine signaling (SOCS)-3 expression is increased in skeletal muscle of obese humans. SOCS3 inhibits leptin signaling in the hypothalamus and insulin signal transduction in adipose tissue and the liver. Skeletal muscle is an important tissue for controlling energy expenditure and wholebody insulin sensitivity; however, the physiological importance of SOCS3 in this tissue has not been examined. Therefore, we generated mice that had SOCS3 specifically deleted in skeletal muscle (SOCS MKO). The SOCS3 MKO mice had normal muscle development, body mass, adiposity, appetite, and energy expenditure compared with wild-type (WT) littermates. Despite similar degrees of obesity when fed a high-fat diet, SOCS3 MKO mice were protected against the development of hyperinsulinemia and insulin resistance because of enhanced skeletal muscle insulin receptor substrate 1 (IRS1) and Akt phosphorylation that resulted in increased skeletal muscle glucose uptake. These data indicate that skeletal muscle SOCS3 does not play a critical role in regulating muscle development or energy expenditure, but it is an important contributing factor for inhibiting insulin sensitivity in obesity. Therapies aimed at inhibiting SOCS3 in skeletal muscle may be effective in reversing obesity-related glucose intolerance and insulin resistance. Diabetes 62: [56][57][58][59][60][61][62][63][64] 2013 O besity is associated with a chronic low-grade inflammatory response that induces defects in energy balance, insulin sensitivity, and lipid metabolism (1). The suppressor of cytokine signaling (SOCS) family of proteins (SOCS1-7), which bind via their SH2 domains to tyrosine phosphorylation sites on cytokine receptors, inhibit inflammatory signal transduction. In obesity, consistent with increases in inflammation, SOCS3 is upregulated in the hypothalamus (2), adipose tissue , and liver (4,5). SOCS3 expression is also increased in human and rodent skeletal muscle with obesity (6,7).
Diabetes, 2004
Using a cDNA microarray, we found that suppressor of cytokine signaling 3 (SOCS3) is highly expressed in anaplastic lymphoma kinase (ALK) + anaplastic large cell lymphoma (ALCL) cell lines. As SOCS3 is induced by activated signal transducer and activator of transcription 3 (STAT3), and ALK activates STAT3, we hypothesized that SOCS3 may play a role in ALK + ALCL pathogenesis via the Janus kinase 3 (JAK3)-STAT3 pathway. Using ALCL cell lines, we show by coimmunoprecipitation experiments that SOCS3 physically binds with JAK3 in vitro, and that JAK3 inhibition by WHI-P154 downregulates SOCS3 expression. Western blot analysis confirmed expression of SOCS3 and also showed coexpression of phosphorylated (activated) STAT3 (pSTAT3). Direct sequencing of the SOCS3 gene showed no mutations or alternative splicing. In ALCL tumors that were assessed by immunohistochemistry, nine of 12 (75%) ALK + tumors were SOCS3 positive and eight (67%) coexpressed pSTAT3. In comparison, 18 of 25 (72%) ALKtumors were SOCS3 positive and seven (28%) coexpressed pSTAT3. These results show that SOCS3 is overexpressed in ALCL, attributable to JAK3-STAT3 activation and likely related to ALK in ALK + tumors. However, SOCS3 is also expressed in tumors that lack STAT3 and ALK suggesting alternative mechanisms of upregulation.
Journal of Biological Chemistry, 2001
Insulin resistance contributes to a number of metabolic disorders, including type II diabetes, hypertension, and atherosclerosis. Cytokines, such as tumor necrosis factor-␣, interleukin-1, and interleukin-6, and hormones, such as growth hormone, are known to cause insulin resistance, but the mechanisms by which they inhibit the cellular response to insulin have not been elucidated. One mechanism by which these agents could cause insulin resistance is by inducing the expression of cellular proteins that inhibit insulin receptor (IR) signaling. Suppressors of cytokine signaling (SOCS) proteins are negative regulators of cytokine signaling pathways, the expression of which is regulated by certain cytokines. SOCS proteins are therefore attractive candidates as mediators of cytokine-induced insulin resistance. We have found that SOCS-1 and SOCS-6 interact with the IR when expressed in human hepatoma cells (HepG2) or in rat hepatoma cells overexpressing the human IR. In SOCS-1-expressing cells, insulin treatment increases the extent of interaction with the IR, whereas in SOCS-6-expressing cells the association with the IR appears to require insulin treatment. SOCS-1 and SOCS-6 do not inhibit insulin-dependent IR autophosphorylation, but both proteins inhibit insulin-dependent activation of ERK1/2 and protein kinase B in vivo and IR-directed phosphorylation of IRS-1 in vitro. These results suggest that SOCS proteins may be inhibitors of IR signaling and could mediate cytokine-induced insulin resistance and contribute to the pathogenesis of type II diabetes. Insulin resistance contributes to a number of important metabolic disorders, including type II diabetes, hypertension, and atherosclerosis (reviewed in Refs. 1 and 2). At the cellular level, insulin resistance has been shown to be associated with decreased insulin receptor (IR) 1 tyrosine kinase activity and de
SOCS2 modulates adipose tissue inflammation and expansion in mice
The Journal of Nutritional Biochemistry, 2020
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Aerobic training reverses high-fat diet-induced pro-inflammatory signalling in rat skeletal muscle
European Journal of Applied Physiology, 2010
High-fat feeding activates components of the pro-inflammatory pathway and increases coimmunoprecipitation of suppressor of cytokine signalling (SOCS)-3 with both the insulin receptor (IR)-β subunit and IRS-1, which together contribute to keeping PI-3 kinase from being fully activated. However, whether aerobic training reverses these impairments is unknown. Sprague-Dawley rats were fed a chow (CON, n = 8) or saturated high-fat (n = 16) diets for 4 weeks. Highfat-fed rats were then allocated (n = 8/group) to either sedentary (HF) or aerobic exercise training (HFX) for an additional 4 weeks after which all animals underwent hind limb perfusions. Insulinstimulated red quadriceps 3-O-methylglucose transport rates and PI-3 kinase activity were greater (p < 0.05) in CON and HFX compared to HF. IRS-1 tyrosine phosphorylation was increased (p < 0.05) and IRS-1 serine 307 phosphorylation was decreased (p < 0.05) in HFX compared to HF. IRβ subunit co-immunoprecipitation with IRS-1 was increased in HFX compared to HF. SOCS-3 coimmunoprecipitation with both the IR-β subunit and IRS-1 was decreased (p < 0.05) in HFX compared to HF. IKKα/β serine phosphorylation, and IκBα serine phosphorylation were decreased (p < 0.05) while IκBα protein concentration was increased in HFX compared to HF. By decreasing the association of SOCS-3 with both the IR-β subunit and IRS-1 the interaction between IRS-1 and the IR-β subunit was normalized in the HFX, and may have contributed to skeletal muscle PI-3 kinase being fully activated by insulin. Additionally, the reduction in IKKα/β
The FASEB Journal, 2012
Hepatic steatosis is a prominent feature in patients with growth hormone (GH) deficiency. The ubiquitin ligase SOCS2 attenuates hepatic GH signaling by inhibiting the Janus kinase 2 (JAK2)-signal transducer and activator of transcription 5b (STAT5b) axis. Here, we investigated the role of SOCS2 in the development of diet-induced hepatic steatosis and insulin resistance. SOCS2-knockout (SOCS2 ؊/؊ ) mice and wild-type littermates were fed for 4 mo with control or high-fat diet, followed by assessment of insulin sensitivity, hepatic lipid content, and expression of inflammatory cytokines. SOCS2 ؊/؊ mice exhibited increased hepatic TG secretion by 77.6% (P<0.001) as compared with wild-type control mice and were protected from high-fat-diet (HFD)-induced hepatic steatosis, showing 49.3% (P<0.01) reduction in liver TG levels compared to HFD-fed wild-type littermates. In contrast, we found that HFD-triggered attenuation of systemic insulin sensitivity was more marked in SOCS2 ؊/؊ mice. Livers from the HFD-fed SOCS2 ؊/؊ mice showed increased NF-B activity as well as elevated expression of genes for the inflammatory cytokines IFN-␥ and IL-6. An inhibitory role of SOCS2 on Toll-like receptor 4 signaling was demonstrated in macrophages obtained from the SOCS2 ؊/؊ and wild-type mice. This study identified SOCS2 as an important regulator of hepatic homeostasis under conditions of high-fat dietary stress.-Zadjali, F., Santana-Farre, R., Vesterlund, M., Carow, B., Mirecki-Garrido, M., Hernandez-Hernandez, I., Flodström-Tullberg, M., Parini, P., Rottenberg, M., Norstedt, G., Fernandez-Perez, L., Flores-Morales, A. SOCS2 deletion protects against hepatic steatosis but worsens insulin resistance in high-fat-diet-fed mice. FASEB J. 26, 000 -000 (2012). www.fasebj.org
Molecular and cellular biology, 2002
SOCS-6 is a member of the suppressor of cytokine signaling (SOCS) family of proteins (SOCS-1 to SOCS-7 and CIS) which each contain a central SH2 domain and a carboxyl-terminal SOCS box. SOCS-1, SOCS-2, SOCS-3, and CIS act to negatively regulate cytokine-induced signaling pathways; however, the actions of SOCS-4, SOCS-5, SOCS-6, and SOCS-7 remain less clear. Here we have used both biochemical and genetic approaches to examine the action of SOCS-6. We found that SOCS-6 and SOCS-7 are expressed ubiquitously in murine tissues. Like other SOCS family members, SOCS-6 binds to elongins B and C through its SOCS box, suggesting that it might act as an E3 ubiquitin ligase that targets proteins bound to its SH2 domain for ubiquitination and proteasomal degradation. We investigated the binding specificity of the SOCS-6 and SOCS-7 SH2 domains and found that they preferentially bound to phosphopeptides containing a valine in the phosphotyrosine (pY) +1 position and a hydrophobic residue in the pY...
Cytokine
Excessive inflammation reduces skeletal muscle protein synthesis leading to wasting and weakness. The janus kinase/signal transducers and activators of transcription-3 (JAK/STAT3) pathway is important for the regulation of inflammatory signaling. As such, suppressor of cytokine signaling-3 (SOCS3), the negative regulator of JAK/STAT signaling, is thought to be important in the control of muscle homeostasis. We hypothesized that muscle-specific deletion of SOCS3 would impair the anabolic response to leucine during an inflammatory insult. Twelve week old (n=8 per group) SOCS3 muscle-specific knockout mice (SOCS3-MKO) and littermate controls (WT) were injected with lipopolysaccharide (LPS, 1 mg/kg) or saline and were studied during fasted conditions or after receiving 0.5 g/kg leucine 3 h after the injection of LPS. Markers of inflammation, anabolic signaling, and protein synthesis were measured 4 h after LPS injection. LPS injection robustly increased mRNA expression of inflammatory molecules (Socs3, Socs1, Il-6, Ccl2, Tnfα and Cd68). In muscles from SOCS3-MKO mice, the Socs3 mRNA response to LPS was significantly blunted (~6-fold) while STAT3 Tyr705 phosphorylation was exacerbated (18-fold). Leucine administration increased protein synthesis in both WT (~1.6-fold) and SOCS3-MKO mice (~1.5-fold) compared to basal levels. LPS administration blunted this effect, but there were no differences between WT and SOCS3-MKO mice. Muscle-specific SOCS3 deletion did not alter the response of AKT, mTOR, S6 or 4EBP1 under any treatment conditions. Therefore, SOCS3 does not appear to mediate the early inflammatory or leucine-induced changes in protein synthesis in skeletal muscle. Highlights SOCS3 deletion in skeletal muscle does not alter LPS-induced inflammation. SOCS3 does not mediate the anabolic response to leucine in skeletal muscle. Leucine augments the LPS-induced expression of IL-6 and STAT3 phosphorylation.