胰岛素抵抗大鼠认知功能的变化及其脑组织Alzheimer样病变

The change of cognition function in insulin resistance rats and its brain tissues with Alzheimer-Like disease

目的研究胰岛素抵抗大鼠(IR)认知功能的变化及其脑组织胆碱乙酰转移酶(ChAT)的活性、β-淀粉样(Aβ42)、P-Tau(ser396)、淀粉样前体蛋白(APP),β-分泌酶(BACE1)及早老素(PS1)的表达,探讨胰岛素抵抗在阿尔茨海默病(AD)中可能的作用机制。方法从25只Wistar雄性大鼠中随机选取10只作为正常对照组(NC),以普通标准饲料+自来水喂养;余15只为模型组以普通标准饲料+10%果糖水连续喂养12周后筛选出IR大鼠13只;12周末用Morris水迷宫试验测定各组大鼠认知功能行为学改变,放免法检测血浆胰岛素水平,葡萄糖氧化酶法检测血浆葡萄糖水平,化学比色法测定ChAT的活性,免疫组化法检测APP、Aβ42,蛋白印迹法检测BACE1,PS1及P-Tau(ser396)蛋白表达水平。结果 IR组大鼠逃避潜伏期较NC组明显延长(P<0.01);IR组血浆血糖、胰岛素水平及运用HOMA-IR计算的胰岛素抵抗指数均显著高于NC组(P<0.01);IR组ChAT的活性较NC组明显降低(P<0.01);与NC组相比,IR组APP、Aβ42平均光密度值明显升高,组间差异有统计学意义(P<0.01);IR组大鼠脑组织中BACE1,PS1及P-tau(ser396)蛋白表达水平较NC组显著增高(P<0.01)。结论胰岛素抵抗大鼠认知功能受损,其程度与ChAT的活性相关;胰岛素抵抗通过上调BACE1,PS1的活性,使Aβ生成增加,同时P-Tau蛋白表达增加,从而可能参与类AD病变的发生。

Objective To investigate the change of cognition function in insulin resistance rats,the activity of choline acetyltransterase or the expressions of Aβ42,P-Tau（ser396）,APP or its metabolism-related enzymes,and to explore the possible mechanism of Alzheimer＇s disease in insulin resistance rats.Methods The 10 rats were randomly chosen from the twenty-five Wistar male rats as control group（NC group）,others were given with 10% fructose to develop insulin resistance（IR） mold for 12 weeks,and 13 IR rats were screened out.The cognition function of rats was assayed with Morris water maze test,the activity of choline acetyhltsterase was detected by chemical coloration.Plasma insulin was detected by radioimmunoassay,and blood Sugar level measured by gluose oxidase method.Immunohistochemistry and western blotting were employed to examine the levels ofAPP,Aβ42 and the changes of BACE1,PS1 and P-tau（ser396） in brain tissues of rats.Results Morris water maze test showed that the escape latency was longer in IR group.The levels of Blood sugar,IRI（Homeostasis Model assessment of insulin resistance-HMOA）and insulin in IR group were higher.Immunohistochemistry result indicated that optical densities of APP,Aβ42 in IR group were significantly higher than that of control group.Western blotting showed that P-Tau（ser396）,APP,BACE1 and PS1 levels in the rat brain were significantly elevated in the IR group compared with normal controls（P0.01）.Conclusions The level of cognition function impairment in insulin resistance rats was related to the activities of choline acetyltransterase.Insulin resistance made Aβ42 increase by up-regulating the activities of BACE1,PS-1,and the Level of P-Tau increased.So,insulin resistance was involved in pathogenesis of Alzheimer-Like disease.