GLUCOCORTICOID REGULATION OF INSULIN-RECEPTOR AND SUBSTRATE IRS-1 TYROSINE PHOSPHORYLATION IN RAT SKELETAL-MUSCLE INVIVO
GLUCOCORTICOID REGULATION OF INSULIN-RECEPTOR AND SUBSTRATE IRS-1 TYROSINE PHOSPHORYLATION IN RAT SKELETAL-MUSCLE INVIVO
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DOI：
10.1172/jci116424
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发表时间：
1993-05-01
影响因子：
15.9
通讯作者：
SMITH, RJ
中科院分区：
文献类型：
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作者：
GIORGINO, F;ALMAHFOUZ, A;SMITH, RJ
为了验证糖皮质激素诱导的胰岛素抵抗可能源于胰岛素受体信号异常的假设，我们研究了糖皮质激素对大鼠骨骼肌中胰岛素受体酪氨酸磷酸化和胰岛素受体底物IRS-1的影响。雄性Sprague-Dawley大鼠给予可的松（100 mg/kg，连续5 d）治疗，并与成对喂养的对照组进行比较。可的松治疗大鼠可引起高血糖和高胰岛素血症。麻醉动物经心脏穿刺注射10 U/kg胰岛素，2 min后取出后肢肌肉，快速冷冻，SDS匀浆。用磷酸酪氨酸抗体免疫印迹法研究蛋白酪氨酸磷酸化。用特异性抗体对胰岛素受体和底物IRS-1进行鉴定和定量。可的松治疗组胰岛素受体蛋白含量升高36%，受体酪氨酸磷酸化总水平降低（为对照组的69+/-4%，P < 0.05）。受体磷酸化水平降低的原因是含有磷酸化酪氨酸残基的受体数量减少（64.6+/-5%，P< 0.05）。糖皮质激素过量使骨骼肌IRS-1含量降低50%，但对IRS-1酪氨酸磷酸化总水平无显著影响。IRS-1的表观M(r)降低了约10 kD。蛋白磷酸酶- 2a治疗降低了对照组的IRS-1 M(r)，但糖皮质激素治疗的肌肉中没有，这表明较低的M(r)可能是由于较低的磷酸丝氨酸和/或磷苏氨酸含量。为了研究高胰岛素血症在糖皮质激素反应中的作用，用链脲佐菌素（100 mg / kg, ig）治疗胰岛素缺乏大鼠。随后用可的松治疗5 d，对胰岛素水平、胰岛素受体或IRS-1的酪氨酸磷酸化或IRS-1的M(r)没有影响。总之，糖皮质激素治疗的骨骼肌的特点是：(a)由于酪氨酸磷酸化的受体减少，胰岛素受体的总酪氨酸磷酸化减少；(b)降低IRS-1含量，降低IRS-1的丝氨酸和/或苏氨酸磷酸化。糖皮质激素诱导的高胰岛素血症似乎对这些改变的发展至关重要。
To test the hypothesis that glucocorticoid-induced insulin resistance might originate from abnormalities in insulin receptor signaling, we investigated the effects of glucocorticoids on in vivo tyrosine phosphorylation of the insulin receptor and the insulin receptor substrate IRS-1 in rat skeletal muscle. Male Sprague-Dawley rats were treated with cortisone (100 mg/kg for 5 d) and compared to pair-fed controls. Cortisone treatment of rats resulted in both hyperglycemia and hyperinsulinemia. Anesthetized animals were injected with 10 U/kg insulin via cardiac puncture and, after 2 min, hindlimb muscles were removed, snap-frozen, and homogenized in SDS. Protein tyrosine phosphorylation was studied by immunoblotting with phosphotyrosine antibody. Insulin receptors and substrate IRS-1 were identified and quantified with specific antibodies. Cortisone treatment increased the amount of insulin receptor protein by 36%, but decreased the total level of receptor tyrosine phosphorylation (69+/-4% of control, P < 0.05). The decreased level of receptor phosphorylation was explained by a reduced number of receptors containing phosphorylated tyrosine residues (64.6+/-5% of control, P< 0.05). Glucocorticoid excess decreased skeletal muscle IRS-1 content by 50%, but did not significantly alter the total level of IRS-1 tyrosine phosphorylation. The apparent M(r) of IRS-1 was reduced by approximately 10 kD. Treatment with protein phosphatase-2A reduced IRS-1 M(r) in control but not in glucocorticoid-treated muscle indicating that the lower M(r) likely results from lower phosphoserine and/or phosphothreonine content. To investigate the role of hyperinsulinemia in the glucocorticoid response, rats were made insulin-deficient with streptozotocin (100 mg / kg, i.p.). Subsequent treatment with cortisone for 5 d had no effects on insulin levels, tyrosine phosphorylation of insulin receptors or IRS-1, or the M(r) of IRS-1. In conclusion, glucocorticoid-treated skeletal muscle is characterized by: (a) decreased total tyrosine phosphorylation of insulin receptors as a result of a reduction in the pool of receptors undergoing tyrosine phosphorylation; (b) decreased IRS-1 content and reduced serine and/or threonine phosphorylation of IRS-1. Glucocorticoid-induced hyperinsulinemia appears to be essential for the development of these alterations.