葡萄糖转运蛋白4在宫内发育迟缓大鼠骨骼肌中的表达和转位

Expression and translocation of glucose transporter 4 in skeletal muscle of intrauterine growth retardation rats

目的研究宫内发育迟缓(IUGR)大鼠骨骼肌胰岛素刺激下葡萄糖转运蛋白4(GLUT4)表达和转位的变化,探讨IUGR个体发生胰岛素抵抗的分子机制。方法采用孕期全程低蛋白饮食法建立大鼠IUGR模型,检测18月龄IUGR子鼠骨骼肌胰岛素刺激下的2-D-3H葡萄糖的摄取,同时采用实时荧光定量RT-PCR和Western blot方法检测胰岛素受体(IR)、胰岛素受体底物1(IRS-1)及葡萄糖转运蛋白4(GLUT4)的m RNA和蛋白表达;用Western blot方法分别检测胰岛素刺激前后骨骼肌总/膜GLUT4的蛋白表达变化。结果 1与对照组相比,18月龄IUGR组大鼠骨骼肌胰岛素刺激后葡萄糖摄取率显著降低(P=0.035);2IR和IRS-1 m RNA和蛋白表达在两组大鼠骨骼肌中差异无统计学意义(P>0.05),但GLUT4 m RNA表达在IUGR组大鼠骨骼肌中显著下降(P=0.031);3基础状态时,两组大鼠骨骼肌GLUT4总蛋白表达无明显差异(P=0.967);IUGR组GLUT4膜蛋白表达略降低,但未及统计学意义(P=0.072);经胰岛素刺激后,两组大鼠骨骼肌与各自基础状态相比,GLUT4总蛋白变化不明显,GLUT4膜蛋白表达均较各自的基础状态显著增加,但IUGR大鼠骨骼肌GLUT4膜蛋白的上升程度显著低于对照组(P=0.001)。结论 IUGR老龄大鼠骨骼肌中GLUT4 m RNA表达降低以及胰岛素刺激下的GLUT4转位下降,可能降低对胰岛素的反应性,从而减少葡萄糖摄取,促进胰岛素抵抗发生。

【Objective】To determine the expression and translocation of glucose transporter 4（GLUT4） in the skeletal muscle of intrauterine growth retardation（IUGR） rats, which is stimulated by insulin, so as to explore the molecular mechanism of insulin resistance. 【Methods】An IUGR rat model was prepared by protein malnutrition during pregnancy. The skeletal muscle samples of the IUGR rats were obtained at 18 months of age and put in KHB buffer with/without insulin, 2-D-3H glucose uptake was detected. The expressions of insulin receptor（IR）, insulin receptor substrate 1（IRS-1） and GLUT4 m RNA as well as protein levels were ascertained by quantitative real-time RT-PCR and Western blot, respectively. The expression of total and membrane GLUT4 protein which were stimulated by insulin were measured using Western blot.【Results】1 In comparison with the age-matched control rats,IUGR rats exhibited a significant decrease in insulin-stimulated glucose uptake（P = 0.035）. 2 No statistically significant intergroup differences were found for IR or IRS-1 m RNA and protein（P 〉 0.05）. Compared to the age-matched control rats, the IUGR rats exhibited a significant decrease in expression of GLUT4 m RNA（P = 0.031）. 3The basal levels of total GLUT4 protein did not differ between the IUGR and the control rats（P = 0.967）. Although basal level of membrane GLUT4 protein was mildly decreased in the IUGR rats, there was no statistic significance（P = 0.072）. After administration of insulin, compared to the basal state in each group, no statistically significant difference was found for total GLUT4 protein level; whereas the expression of membrane GLUT4 protein increased significantly, but the rising degree of insulin-induced membrane GLUT4 in the IUGR rats was significantly lower than that in the control rats（P = 0.001）.【Conclusions】GLUT4 m RNA expression levels and insulin-stimulated GLUT4 translocation decrease significantly in skeletal muscle of old IUGR rats. This might reduce the response to insulin and reduce glucose uptake, thus induce insulin resistance.