基于肠道菌群-短链脂肪酸调控Aβ积累的芝麻酚改善AD小鼠认知障碍机制研究

Alzheimer’s disease (AD) is a neurodegenerative disease characterized by symptoms of cognitive impairment and memory loss, and there is no effective medical treatment for AD now. Accumulation of beta-amyloid peptides is one of essential pathological characteristics of AD. Numerous of reports found that short-chain fatty acids (SCFAs) generated by intestinal microbiota possess anti-neuroinflammatory bioactivity and inhibitory effects on Aβ accumulation. Some nutritional/functional food components could regulate the generation of SCFAs. Sesamol, a lignan from sesame, has excellent neuroprotective effects on several animal models. Our previous study has also indicated that sesamol could regulate the balance of intestinal microbiota and the generation of SCFAs. Therefore, we propose a hypothesis that sesamol might have beneficial effects on AD-related cognitive impairments via regulating SCFAs-gut-brain axis. The current program will determine the effects of sesamol on Aβ deposition and cognitive defects in APP/PS1 mouse model of AD by behavioral tests and electrophysiology technique. Besides, the effects of sesamol on balancing of intestinal microbiota, generation of SCFAs, and preserving intestinal barrier function will be detected by experiments such as 16S rDNA sequencing, GC/MS, and Ussing chamber. Moreover, the molecular mechanisms of intestinal microbiota-SCFAs involved in sesamol attenuating AD-related cognitive defects will be explored. The preventive roles of SCFAs on Aβ aggregation and protofibril formation will be detected with assays including thioflavin T spectroscopic assay and electron microscopy examination. The inhibitory effects and mechanisms of microbiota-SCFAs on amyloidogenesis and Aβ deposition in vivo will be investigated by oral administration of sesamol-treated mice feces or SCFAs in germ-free AD mice. This research is expected to provide new clues for nutritional studies of prevention and treatment of neurodegenerative diseases with function food components.

阿尔兹海默病（AD）是以认知障碍为主要表现的神经退行性疾病，尚缺乏有效治疗手段。β淀粉样蛋白（Aβ）沉积是AD的主要病理特征之一。研究表明，肠道菌群代谢物短链脂肪酸（SCFAs）具有抑制Aβ聚集等活性。申请者前期研究发现，芝麻中的重要活性成分芝麻酚具有潜在的神经保护作用，并可调控肠道菌群平衡及SCFAs的生成。据此推测，芝麻酚可能经SCFAs-肠-脑轴途径改善AD认知障碍。本项目拟利用APP/PS1转基因AD小鼠，通过行为学、电生理学等手段，明确芝麻酚对脑内Aβ沉积、突触可塑性损伤及认知障碍的改善作用；利用高通量测序、GC/MS、尤斯室等技术研究芝麻酚对AD小鼠肠道菌群-SCFAs及肠屏障功能的调控作用；通过研究SCFAs对Aβ单体互作/纤维化及无菌AD小鼠脑内Aβ积累的影响，揭示其在芝麻酚改善AD认知障碍中的介导机制。本项目将为利用食物活性成分干预神经退行性疾病的营养学研究提供新线索。

伴随社会老龄化程度不断加深，阿尔兹海默症（AD）等与衰老相关的神经退行性疾病已成为严重的公共卫生问题。AD主要表现为认知障碍，并伴有β淀粉样蛋白（Aβ）沉积、胆碱能系统紊乱、神经元退化等特征，尚缺乏有效治疗手段。申请者前期研究发现，芝麻中的重要活性成分芝麻酚具有潜在的神经保护作用，并可调控肠道菌群平衡及短链脂肪酸（SCFAs）的生成。基于以上背景，本项目拟利用多种认知障碍模型，通过行为学、多组学分析、GC/MS等技术等手段，明确芝麻酚对脑内Aβ沉积、突触可塑性损伤及认知障碍的改善作用，揭示肠道菌群-SCFAs及肠屏障功能在芝麻酚改善认知障碍中的介导机制。项目研究结果发现：（1）芝麻酚可抑制氧化应激和神经炎症，改善与年龄有关的认知障碍、Aβ沉积、神经元损伤和突触功能障碍，此外芝麻酚可保护肠道屏障完整性，提高肠道微生物多样性，通过肠-脑轴改善全身炎症；（2）芝麻酚能够保护AD小鼠脑部海马区突触超微结构和神经元损伤，减少Aβ积累，减轻AD相关的认知功能障碍和神经炎症反应，并且芝麻酚可重塑肠道菌群，改善肠道屏障，提高SCFAs水平，通过微生物群-肠道-大脑轴来预防AD的发生发展；（3）芝麻酚能够激活ApoE相关脂质代谢信号通路，以ApoE依赖的方式改善了突触的超微结构、抑制Aβ的积累，此外芝麻酚可预防饮食引起的肠道屏障损伤，抑制全身炎症，通过肠道菌群/代谢产物的有益作用延缓神经退行性疾病的发生发展；（4）芝麻酚可抑制脑部氧化应激损伤，改善神经元损伤及突触功能障碍，并通过抑制乙酰胆碱酯酶活性，提高乙酰胆碱转移酶活性，增加胆碱能受体M1的mRNA表达，恢复胆碱能系统平衡，从而改善东莨菪碱诱导的认知损伤。综上，芝麻酚可能通过肠道菌群-SCFAs-脑轴抑制Aβ积累，改善胆碱能系统紊乱，抑制氧化应激及神经炎症，改善衰老及AD小鼠的和认知障碍。本项目将为利用芝麻酚等食物功能成分干预神经退行性疾病的营养学研究提供新线索。