Gut microbiota should be considered as a whole instead of focusing on some species to study the cause of AD; (iii) the rats receiving the microbiota transplantation from AD patients showed some behavioral alterations associated with alcohol dependence, including increased anxiety- and depression-like behaviors, reduced exploratory and recognition memory, and higher alcohol preference; and (iv) the gut microbiota dysbiosis induced by alcohol may involve the development of alcohol addiction through regulating the endogenous CCK and related receptors. The gene discussed is CCK; the disease is Alzheimer disease.