Chapter 9 Microbiota–brain interactions in aging and neurodegeneration

A progressively aging global population demands a renewed focus on identifying and counteracting the risk factors leading to unhealthy aging, cognitive decline, and neurodegeneration. Aging is associated with behavioral changes, altered brain plasticity, dysregulation of the immune system, dysfunction of the hypothalamic–pituitary–adrenal axis, and an increased risk of developing brain disorders. There are many hallmark molecular mechanisms underpinning age-related changes in brain function, to which must now be added changes in the microbiota–gut–brain axis. Research has identified both compositional and functional alterations in the gut microbiota of relevance to healthy aging in the context of maintenance of brain homeostasis and facilitating adequate responses to stress, with signature alterations identified in age-related pathologies such as Parkinson's Disease and Alzheimer's Disease. The gut microbiome can thus be viewed as a contributory factor in aging-related brain disorders, opening up the possibility of new healthcare strategies such as the targeted restoration of microbial functions associated with healthier brain aging.