The microbial populations of the gut influence and are influenced by the state of the immune system. They also have effects on tissue function throughout the body via secreted compounds such as butyrate, mediating some of the effects of diet on long-term health. These microbes change with age, losing beneficial populations and gaining harmful populations that contribute to chronic inflammation. These changes are far from fully explored at the present time, but may have effects on health that rival those resulting from regular exercise. In this open access review, researchers discuss the influence of gut microbes on chronic inflammation of the brain, and the development of neurodegenerative conditions such as Alzheimer's disease.
Alzheimer's disease (AD) is a complex, multi-factorial disease affecting various brain systems. This complexity implies that successful therapies must be directed against several core neuropathological targets rather than single ones. The scientific community has made great efforts to identify the right AD targets beside the historic amyloid-β. Neuroinflammation is re-emerging as determinant in the neuropathological process of AD. A new theory, still in its infancy, highlights the role of gut microbiota in the control of brain development, but also in the onset and progression of neurodegenerative diseases.
Bidirectional communication between the central and the enteric nervous systems, called gut-brain axes, is largely influenced by gut microbiota and the immune system is a potential key mediator of this interaction. Growing evidence points to the role of gut microbiota in the maturation and activation of host microglia and peripheral immune cells. Several recent studies have found abnormalities in gut microbiota (dysbiosis) in AD populations. These observations raise the intriguing question whether and how gut microbiota dysbiosis could contribute to AD development through action on the immune system and whether, in a therapeutic prospective, the development of strategies preserving a healthy gut microbiota might become a valuable approach to prevent AD.