Exercise and the microbiota-gut-brain axis: implications for stress-related disorders

The microbiota-gut-brain axis is heavily implicated in the regulation of brain function and behaviour and the role of intestinal barrier function is a fundamental aspect of this bidirectional communication. Alterations in gut barrier function can impact the central nervous system via gut-brain axis signaling pathways. Evidence from clinical studies of an association between stress-related psychiatric disorders including depression, gut microbiota composition and increased intestinal permeability levels is accumulating. Exercise has shown some potential as an adjunct to the standard treatment options employed in the management of major depression. However, the mechanism underpinning this effect is poorly understood, a limiting factor in the uptake of this appealing option. Research also highlights that exercise can alter the composition and function of the gut microbiota and potentially exert its benefits via recruitment of the biological pathways of the gut-brain axis. One way by which exercise can impact the gut-brain axis is by having hormetic effects on gastrointestinal permeability, acting initially as an acute stressor that subsequently stimulates positive adaptation to support good mental health. This study aims to assess the impact of exercise training intensity (light, moderate or high) on gastrointestinal permeability, hypothalamus-pituitary-adrenal axis reactivity and stress levels in sedentary healthy controls, both acutely and chronically over a 12-week duration.