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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 study the changes of cognitive function and the activity of choline acetyltransferase (ChAT) in brain tissue of rats with insulin resistance (IR). The effects of β-amyloid (Aβ42), P-Tau (ser396), amyloid precursor protein APP), β-secretase (BACE1) and presenilin (PS1), and explore the possible mechanism of insulin resistance in Alzheimer’s disease (AD). Methods Twenty-five Wistar male rats were randomly selected as normal control group (NC) and fed with normal standard feed and tap water. The remaining 15 rabbits were fed with normal standard diet supplemented with 10% fructose fructose for 12 weeks Thirteen rabbits were randomly divided into control group and control group. Thirteen IR rats were selected. Morris water maze test was used to measure the change of cognitive function of rats in each group. Plasma insulin level was measured by radioimmunoassay, plasma glucose level by glucose oxidase method, and ChAT activity , APP, Aβ42 were detected by immunohistochemistry. The protein expression of BACE1, PS1 and P-Tau (ser396) were detected by Western blotting. Results The escape latency in IR group was significantly longer than that in NC group (P <0.01). The levels of plasma glucose, insulin and HOMA-IR in IR group were significantly higher than those in NC group (P <0.01) (P <0.01). Compared with NC group, the average optical density of APP and Aβ42 in IR group was significantly increased (P <0.01) The protein expression of BACE1, PS1 and P-tau (ser396) in the tissue was significantly higher than that in NC group (P <0.01). CONCLUSION: Cognitive function is impaired in insulin-resistant rats, which is related to the activity of ChAT. Insulin resistance may increase the production of Aβ and increase the expression of P-Tau by up-regulating the activity of BACE1 and PS1, which may be involved in the development of AD-like lesions .