ABSTRACT
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 substances include ammonia， cyanobacteria-produced β-N-methylamino-L-alanine， saxitoxin，anatoxin-α and amyloid. The decrease in brain-derived neurotrophic factor BDNF in hippocampus and cerebral cortex induced by dysbiosis contributes to the cognitive dysfunction. 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.