The Gut microbiota and Alzheimer's disease

Alzheimer's disease (AD) is a chronic neurodegenerative disease that affects memory and learning processes. Its complex multifactorial origin hinders an effective drug development. Recent studies uncovered an essential contribution of gut microbiota (GM) in the pathogenesis of AD, as gut dysbiosis is observed in AD and mild cognitive impairment (MCI) patients. GM analysis implicates several variables that impede the understanding of its contribution in a disease. Here, we aim to critically evaluate the role of GM in AD, with a special emphasis on subject selection, country of origin, and methods of analysis. Despite the large differences among studies, gut dysbiosis characterizes AD and MCI patients. Moreover, transgenic (Tg) mouse models of AD also develop GM dysbiosis and its modulation evades the development of the neuropathological features. Therefore, we confirm that GM dysbiosis is a risk factor to develop dementia, and we conclude that Tg mice are suitable models to study the bacteria-gut-brain axis.