The gut microbiome in neurodegenerative disorders

A bi-directional channel of communication, referred to as the gut-brain axis, has been recognized for decades based, first, on the many parallels in morphology and function that exist between the central and enteric nervous systems and, second, on the extensive interconnections that exist between them. Now another dimension is added to this axis: the gut microbiome. Facilitated by ever-advancing techniques that permit the enumeration of the microbial populations that normally inhabit the gastrointestinal tract and their various functions, the critical role of gut microbiota in health has now been amply demonstrated. Evidence indicates a critical role for gut microbes in brain development and function; findings that have spurred a plethora of studies into relationships between gut microbiota profiles and neurodegenerative disorders such as Alzheimer’s and Parkinson’s disease. While findings in animal models, as well as some data from human studies, suggest that a disturbed gut microbiome might contribute to the pathophysiology of these and other neurological disorders, a causative relationship has yet to be defined and effective therapeutic strategies based on the modulation of the microbiota-gut-brain axis have not, as yet, emerged.