胰岛素抵抗大鼠血脑屏障上P-糖蛋白表达和转运功能的研究

Studies on expression and transport function of P-glycoprotein at the blood-brain barrier in insulin resistance rats

目的:建立胰岛素抵抗大鼠模型,观察胰岛素抵抗大鼠血脑屏障(BBB)上P-糖蛋白(P-gp)的表达和转运功能。方法:采用高脂饲料喂养制备胰岛素抵抗大鼠模型,用口服葡萄糖耐量、胰岛素耐量和胰岛素敏感性指数评价大鼠胰岛素抵抗。用伊文思蓝检测BBB通透性,用透射电镜观察BBB的完整性,用Westernblot测定BBB上P-gp的蛋白水平,用RT-PCR技术检测BBB上mdr1a/mdr1b的mRNA水平,用Rh123累积实验测定BBB上P-gp的转运功能。结果:用高脂饲料喂养大鼠6周后,葡萄糖耐量和胰岛素耐量明显异常,空腹胰岛素含量显著升高,胰岛素敏感性显著下降。胰岛素抵抗大鼠BBB上P-gp表达水平和转运功能显著下降,但BBB通透性和完整性未发生明显改变。结论:胰岛素抵抗下调BBB上P-gp表达和转运功能。

AIM:To investigate the expression and transport function of P-glycoprotein(P-gp)at the blood-brain barrier(BBB)in insulin resistance(IR)rats.METHODS:The rats were fed with high-fat diet to induce insulin resistance.At 6 weeks after the induction,the oral glucose tolerance test(OGTT)and insulin tolerance test(ITT)were carried out,and the insulin sensitivity index(ISI)was determined,all of which were used to evaluate IR.The rats were sacrificed for observing the integrity of the BBB by electron microscopy,and Evans blue was used to examine the permeability of the BBB.The levels of P-gp protein were determined by Western blot,the mRNA levels of mdr1a/mdr1b were examined by RT-PCR,and Rhodamine 123(Rh123)accumulation tests were used to evaluate the transport function of P-gp at the BBB in the rats.RESULTS:The rats fed with high-fat diet displayed overweigh,abnormal glucose tolerance,significant increase in their fasting serum insulin(FINS)and significant decrease in insulin sensitivity,compared with those of control rats,at 6 weeks after the induction.The data of Evans blue test and electron microscopy showed that no significant changes of the permeability and integrity of BBB were found in IR rats.The data of Rh123 accumulation test suggested that the transport function of P-gp at the BBB was impaired in the IR rats.The data of Western blot and RT-PCR showed that the levels of P-gp protein and mRNA levels of mdr1a were decreased significantly at the BBB in the IR rats.CONCLUSION:IR impairs the transport function of P-gp,which that results from the down-regulation of its expression at the BBB.