运动通过激活AMPK调节小鼠脑Aβ沉积的机制研究

Alzheimer's disease (AD) is a neurodegenerative disease characterized by progressive cognitive impairment. Deposition of β-amyloid (Aβ) and formation of senile plaque is the hallmark in brains of AD. It is generally agreed that abnormal deposition of Aβ induces neuronal damages which lead to the development of AD. Despite tremendous research efforts, there is lack of effective therapy in treating AD. Therefore, preventing the onset of AD and delaying the progression have become one of the most important goals. Previous studies have suggested that exercise might alter the ratio of AMP/ATP through ATP consumption, which subsequently induces activation of AMPK. There is also evidence that AMPK can regulate deposition of Aβ by regulating α-secretase and β-secretase. Such activity of AMPK on secretases is associated with production of Aβ. At the same time, animal studies reveals that exercise can inhibit deposition of Aβ in the brain of AD mice. However, the mechanisms underlying exercise-triggered Aβ regulation remains undefined. There has been no study about whether exercise can modulate the deposition of Aβ in the brain through regulating AMPK activation. The studies proposed in this application will determine whether treadmill exercise affects AMPK activity and how exercise-induced AMPK signaling regulates Aβ deposition in mouse brain and affects cognition. Three different mice will be used by integrated approach, ranging from molecular, histological and behavioral analysis. These include AMPKα2 knockout mice, SAMP8 mice and APP/PS1 transgenic mice. The purpose of this study is to explore the relationship among exercise, AMPK activity and Aβ deposition, offering mechanisms of exercise for development of strategies in AD prevention and treatment.

阿尔茨海默病（AD）是以进行性脑认知功能障碍为主要临床症状的神经退行性疾病，脑内淀粉样蛋白（Aβ）沉积形成老年斑是AD的最主要病理特征，Aβ的异常沉积诱导神经元的损害可导致AD发病。研究表明，运动能够通过消耗ATP来调节AMP/ATP的比值变化，激活AMPK。另有研究发现，AMPK可通过调节脑内Aβ生成相关的α-分泌酶和β-分泌酶的变化进而抑制脑Aβ的沉积。同时，运动能够抑制AD小鼠脑内Aβ的沉积，但其机制还不明确。目前还未有研究关于运动是否通过调节AMPK的活性进而调节Aβ的沉积。基于此，本项目通过跑台运动对AMPKα2基因敲除小鼠、SAMP8快速老化小鼠和APP/PS1转基因AD小鼠等3种小鼠的干预实验，从行为学、形态学和分子生物学三个层次来验证运动是否通过调节AMPK的活性进而达到抑制小鼠脑Aβ沉积的目的，探讨运动预防AD的分子机制。

阿尔茨海默症（AD）是一种以记忆力丧失、行为改变以及无法进行正常的日常生活为临床特征的神经退行性疾病。目前，AD发病机制尚不明确，以Aβ沉积及其形成的老年斑为主要病理特征。研究发现，合理的体育锻炼可以延缓老年人认知功能的衰退，并以无副作用等优点成为防治AD的非药物干预方式。本课题以转基因AD小鼠为实验对象，探讨了运动对海马AMPK/Sirtl、Wnt/β-catenin信号通路、糖代谢、线粒体自噬和Aβ血脑屏障（Blood-brain barrier, BBB）的外周转运等方面的影响。.本研究选取野生型和转基因AD小鼠，分别随机分为运动组和安静组，运动组给予12周的跑台运动。结果发现12周的跑台运动显著缩短了AD小鼠的Morris水迷宫潜伏期和总路程，说明跑台运动促进了AD小鼠的空间学习和记忆能力；通过对海马AMPK/Sirtl信号通路以及水解APP的分泌酶的检测，发现运动可通过抑制AD小鼠海马BACE1和PS1的表达，减少了Aβ的产生；运动还提高了NEP、IDE等Aβ降解酶的表达水平，增强了Aβ的酶解清除作用。糖代谢作为AMPK/Sirtl信号通路的上游事件对AMPK激活具有重要作用，跑台运动可以促进AD小鼠葡萄糖转运载体GLUT1/3、葡萄糖代谢关键酶HK1和α-KGDH的表达以及线粒体的生物发生，逆转AD小鼠海马出现的葡萄糖代谢紊乱。同时，跑台运动能有效提高AD小鼠外周血清β-OHB含量，降低海马β-OHB含量，改善AD小鼠酮体代谢系统。除此之外，跑台运动还可显著提高Aβ转运蛋白LRP-1的表达，激活AD小鼠海马Wnt/β-catenin信号通路，上调Occludin、clauding-3的水平，改善BBB功能和Aβ外排转运能力，从而降低海马Aβ水平。在线粒体自噬方面，AMPK是其发生的重要介导因子，运动可以通过激活AMPK增强线粒体募集Parkin的能力，上调线粒体自噬启动水平，改善溶酶体功能，继而提高AD小鼠海马线粒体自噬活性，加快Aβ及受损线粒体的降解清除，改善线粒体功能。研究不仅证实了中等强度跑台运动可以有效改善AD病理，还进一步探讨了运动预防AD发病的分子机制，为防治AD提供了科学依据。