• J. Steroid Biochem. Mol. Biol. · Jan 2015

    JNK and IKKβ phosphorylation is reduced by glucocorticoids in adipose tissue from insulin-resistant rats.

    • Katia Motta, Amanda Marreiro Barbosa, Franciane Bobinski, Antonio Carlos Boschero, and Alex Rafacho.
    • Multicenter Graduate Program in Physiological Sciences, Center of Biological Sciences, Federal University of Santa Catarina (UFSC), Florianópolis, Brazil.
    • J. Steroid Biochem. Mol. Biol. 2015 Jan 1; 145: 1-12.

    ObjectivesPeripheral insulin resistance (IR) is one of the main side effects caused by glucocorticoid (GC)-based therapies, and the molecular mechanisms of GC-induced IR are not yet fully elucidated. Thus, we aimed to investigate the effects of dexamethasone treatment on the main components of insulin and inflammatory signaling in the adipose tissue of rats.Materials/MethodsMale Wistar rats received daily injections of dexamethasone (1mg/kg body weight (b.w.), intraperitoneally (i.p.)) for 5 days (DEX), whereas control rats received saline (CTL). The metabolic status was investigated, and the epididymal fat fragments were collected for lipolysis and western blot analyses.ResultsThe DEX rats became hyperglycemic, hyperinsulinemic, insulin resistant and glucose intolerant, compared with the CTL rats (P<0.05). The basal glycerol release in the fat fragments was 1.5-fold higher in the DEX rats (P<0.05). The phosphorylation of protein kinase B (PKB) at ser(473) decreased by 44%, whereas, the phosphorylation of insulin receptor substrate (IRS)-1 at ser(307) increased by 93% in the adipose tissue of the DEX rats after an oral bolus of glucose (P<0.05). The basal phosphorylation of c-jun-N-terminal kinase (JNK) and inhibitor of nuclear factor kappa-B (IKKβ) proteins was reduced by 46% and 58%, respectively, in the adipose tissue of the DEX rats (P<0.05). This was paralleled with a significant reduction (47%) in the glucocorticoid receptor (GR) protein content in the adipose tissue of the DEX rats (P<0.05).ConclusionThe insulin-resistant status of rats induced by dexamethasone administration have PKB and IRS-1 activity attenuated in epididymal fat without increases in the phosphorylation of the proinflammatory signals JNK and IKKβ.Copyright © 2014 Elsevier Ltd. All rights reserved.

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