Glucocorticoids cause insulin resistance in skeletal muscle. The aims of the present study were to investigate the effects of contraction on glucose uptake, insulin signaling, and regulation of glycogen synthesis in skeletal muscles from rats treated with the glucocorticoid analog dexamethasone (1 ip for 12 days). Insulin resistance in dexamethasone-treated rats was confirmed by reduced insulin-stimulated glucose uptake (similar to 35%), glycogen synthesis (similar to 70%), glycogensynthase activation (similar to 80%), and PKB Ser(473) phosphorylation (similar to 40%). Chronic dexamethasone treatment did not impair glucose uptake during contraction in soleus or epitrochlearis muscles. In epitrochlearis (but not in soleus), the presence of insulin during contraction enhanced glucose uptake to similar levels in control and dexamethasone-treated rats. Contraction also increased glycogen synthase fractional activity and dephosphorylated glycogen synthase at Ser(645), Ser(649), Ser(653), and Ser(657) normally in muscles from dexamethasone-treated rats. After contraction, insulin-stimulated glycogen synthesis was completely restored in epitrochlearis and improved in soleus from dexamethasone-treated rats. Contraction did not increase insulin-stimulated PKB Ser(473) or glycogen synthase kinase-3 (GSK-3) phosphorylation. Instead, contraction increased GSK-3 beta Ser(9) phosphorylation in epitrochlearis (but notin soleus) in muscles from control and dexamethasone-treated rats. In conclusion, contraction stimulates glucose uptake normally in dexamethasone-induced insulin resistant...

Ruzzin, Jérôme; Jensen, Jørgen
American Journal of Physiology. Endocrinology and Metabolism HighWire Press, American Journal of Physiology. Endocrinology and Metabolism 289(2): 241–250
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