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肠道菌群（gut microbiota，GM）是指共生于人体消化道中的大量微生物，GM紊乱和多种疾病有关。最近的研究发现，阿尔茨海默病（Alzheimer′s disease，AD）患者和AD模型小鼠的GM是紊乱的，GM可通过多种途径参与AD的发生和发展。某些细菌产生的神经递质或神经毒性物质可通过循环系统进入大脑，影响神经功能。其中的毒性物质包括氨气、蓝细菌产生的β-N-甲氨基-L-丙氨酸、蛤蚌毒素、α类毒素和淀粉样蛋白等。GM异常引起的海马和大脑皮质脑源性神经营养因子（BDNF）的降低和进行性认知功能丧失有关。GM失调产生的内毒素可诱发炎症反应，而炎症反应是肥胖、胰岛素抵抗和2型糖尿病重要的风险因子。AD和2型糖尿病也具有相关性和相似性。益生菌、益生元和中药可调节GM，有实验表明它们可缓解AD患者或模型小鼠的症状。然而，它们对AD的防治效果如何，以及通过GM发挥防治AD作用的机制细节尚待更多的研究。“,”Gut microbiota(GM)consists of a complex community of microorganism species that live in the digestive tracts of animals including humans. Dysbiosis is believed to involve in the development of some diseases. Recently dysbiosis in the patients with Alzheimer′s disease(AD)and AD rat models was reported. GM may influence the pathogenesis and development of AD in several ways. Some neurotoxic substances produced by GM can invade into the brain via circulation and impair the neural functions. These sub?stances include ammonia,cyanobacteria-producedβ-N-methylamino-L-alanine,saxitoxin,anatoxin-αand amyloid. The decrease in brain-derived neurotrophic factor(BDNF)in hippocampus and cerebral cortex induced by dysbiosis contributes to the cognitive dys?function. Dysbiosis related endotoxin can induce inflammation,which is one important risk factor for obesity,insulin resistance(IR) and type 2 diabetes mellitus(TIDM). AD and diabetes have good correlation and similarity. Probiotics,prebiotics and Chinese herbal medicines can rebuild GM and have been reported to ameliorate the memory loss of AD patients or model rats. However ,whether and how their preventative and therapeutic effects on AD mediated by GM are worthy of further investigation.