TNF-α对红细胞胰岛素受体磷酸化的影响

EFFECTS OF TNF-α ON AUTOPHOSPHORYLATION OF INSULIN RECEPTORS ON ERYTHROCYTE MEMBRANES

目的 :用TNF -α培养离体红细胞 ,观察其对胰岛素诱导的 β亚基自身磷酸化的影响 ,探讨TNF -α致胰岛素抵抗的分子机理。方法 :红细胞加或不加TNF -α(5ng/ml)培养 2 0h ,收集培养的红细胞 ,制备膜蛋白 ,并测定胰岛素诱导的受体自身磷酸化程度。结果 :红细胞TNF -α(- )培养 2 0h后 ,正常人红细胞胰岛素受体自身磷酸化程度为 80 .85± 4 3.92△A/mg蛋白 ,Ⅱ型糖尿病患者胰岛素受体的自身磷酸化程度为 2 4 .2 4± 8.0 5△A/m9蛋白 ,二者有显著性差异 (P <0 .0 5 )。 5ng/mlTNF -d培养 2 0h后 ,正常人红细胞胰岛素受体的磷酸化程度下降至 2 2 .95± 14 .93△A/mg蛋白 ,糖尿病组的胰岛素受体磷酸化程度下降至 8.81± 8.31△A/mg蛋白 ,与TNF -α(- )组相比 ,差异有显著性 (P <0 .0 5 )。正常人红细胞TNF -α(+)培养 2 0h后 ,其受体磷酸化程度与糖尿病组TNF -α(- )培养 2 0h后的受体磷酸化程度相比 ,二者差异无显著性。结论 :小剂量TNF-α(5ng/ml)培养红细胞 2 0h后 ,可抑制细胞膜上胰岛素受体的自身磷酸化 ,且正常人红细胞经TNF -α处理后 ,膜上胰岛素受体自身磷酸化程度可降至患者水平 ,这可能是TNF -α引起糖尿病病人对胰岛素抵抗的机制。

Objective:To determine the molecular mechanism of insulin resistance caused by TNF-α.Methods:The erythrocytes were separated from whole blood samples, and incubated with or without TNF-α (5ng/ml) for 20 hours and the soluble erythrocyte membranes were prepared as described by Comi et al. The phosphorylation reaction of insulin receptor induced by insulin was measured.Results:Autophosphorylation of insulin receptors on erythrocyte membranes of normal subjects was 80.85±43.92△A/mg protein after incubation for 20 hours, higher than that in patients with type 2 diabetes (24.24 ±8.05△A/mg protein), P < 0.05. Autophosphorylation of insulin receptors was decreased following TNF-α treatment, showing significant difference with that in TNF-α(-) group. Insulin recepcor autophosphorylation in control group incubating with TNF-α was not significantly different from that in patient group incubating without TNF-α.Conclusion: Low dose of TNF-α can suppress insulin induced βsubunit autophosphorylation and that may be the mechanism of insulin resistance.