One more role for the gut: microbiota and blood brain barrier

The gut microbiota is composed of trillions of microbes that perform several tasks which are essential to our physiology. Recent emerging evidences have suggested the important contribution of gut microbiota in several biological functions of mamals, such as the regulation of the immune system, metabolism, intestinal development or brain physiology (1-4). In fact, recent work, mainly performed in experimental model of Multiple Sclerosis (MS), have demonstrated that resident commensal microbiota can modulate central nervous system (CNS) autoimmunity (5-8). The microbiota is now known to shift the balance between protective and pathogenic immune responses, in the CNS, but also in other organs. A growing body of evidence in animal support also the concept that the gut microbiota influences emotional behavior (9,10) and that its products and metabolites may promote metabolic effects such as reduced body weight, reduced adiposity, and improved glucose control (11). As regards, CNS physiology, the gut microbiota influence synaptogenesis, regulate neurotransmitters and neurotrophic factors release and function (4).