侧脑室注射链脲佐菌素致大鼠脑内胰岛素通路障碍和认知水平降低

 目的：本文旨在研究胰岛素信号通路在阿尔茨海默病（Alzheimer disease，AD）发病中的作用，并探讨其可能的作用机制。方法：于实验第1 d和第3 d侧脑室（intracerebroventricular，ICV）注射链脲佐菌素（streptozotocin，STZ；3 mg/kg）建立大鼠模型。第1次注射后21 d采用Morris水迷宫检测大鼠的学习和记忆水平；采用Western blotting检测胰岛素降解酶（insulin-degrading enzyme，IDE）、糖原合成酶激酶 3β（glycogen synthase kinase 3β，GSK-3β）、磷酸化糖原合成酶激酶 3β（p-GSK-3β）、tau和磷酸化tau（p-tau）的表达；采用免疫组化检测淀粉样β蛋白（Aβ1-40和Aβ1-42)在大脑皮质的沉积；用real-time RT-PCR法检测胰岛素、胰岛素受体、tau、IDE mRNA的表达。结果：Morris水迷宫结果显示ICV-STZ明显降低大鼠的认知能力(P<0.05)；Western blotting结果显示ICV-STZ能降低IDE的表达，增加GSK-3β的活性和tau的磷酸化水平(P<0.05)；免疫组化结果显示ICV-STZ处理的大鼠大脑皮质 Aβ1-40和Aβ1-42均明显增加；PCR结果显示ICV-STZ处理的大鼠大脑胰岛素和胰岛素受体的mRNA水平均降低，IDE mRNA的水平亦下降。结论：ICV-STZ通过影响脑内胰岛素通路导致大鼠出现AD样行为学及病理改变，表明胰岛素信号通路在AD发病中可能起到了一定的重要作用。

Intracerebroventricular injection of streptozotocin induces dysfunction of insulin signaling in brain and cognitive deficits in rats

AIM：To investigate the effect of insulin signaling on the development of Alzheimer disease (AD) and to explore its potential mechanisms. METHODS：The rats were treated with streptozotocin (STZ, 3 mg/kg) intracerebroventricularly (ICV) at the 1st day and  the 3rd day of the experiment to induce dementia model. Twenty-one days after the injection of STZ at the 1st day, spatial learning and memory of the rats were determined by Morris water maze test. The expression levels of insulin-degrading enzyme (IDE), glycogen synthase kinase 3β (GSK-3β), phosphorylated GSK-3β (p-GSK-3β), tau and phosphorylated tau (p-tau) were measured by Western blotting. The levels of amyloid β-proteins (Aβ1-40 and Aβ1-42) in the brain of the rats were detected by the method of immunohistochemistry. The mRNA levels of insulin, insulin receptor, tau and IDE were measured by real-time RT-PCR. RESULTS：ICV-STZ deteriorated the abilities of spatial learning and memory of the rats and reduced the activity of IDE and the mRNA levels of insulin and insulin receptor. STZ treatment enhanced GSK-3β activity and tau phosphorylation. The levels of Aβ1-40 and Aβ1-42 in cerebral cortex were significantly increased in the rats treated with STZ. CONCLUSION：ICV-STZ results in AD-like behaviors and pathological changes via damaging the brain insulin signaling, indicating that insulin signaling may play important roles in the AD pathogenesis.