Exercise influence on the microbiome-gut-brain axis

Abstract

The microbiome in the gut is a diverse environment, housing the majority of our bacterial microbes. This microecosystem has a symbiotic relationship with the surrounding multicellular organism, and a balance and diversity of specific phyla of bacteria support general health. When gut bacteria diversity diminishes, there are systemic consequences, such as gastrointestinal and psychological distress. This pathway of communication is known as the microbiome-gut-brain axis. Interventions such as probiotic supplementation that influence microbiome also improve both gut and brain disorders. Recent evidence suggests that aerobic exercise improves the diversity and abundance of genera from the Firmcutes phylum, which may be the link between the positive effects of exercise on the gut and brain. The purpose of this review is to explain the complex communication pathway of the microbiome-gut-brain axis and further examine the role of exercise on influencing this communication highway.

Keywords: Exercise; brain; gut; microbiome–gut–brain axis; probiotics.

Figure 1.

The role of exercise in the microbiome–gut–brain axis. Exercise and the gut microbiome have been independently shown to improve symptoms of IBS and stabilize the TJ barrier and have also been linked to decrease psychological disorders (e.g. depression, anxiety), promote neurogenesis (through BDNF), and improve HPA axis control. It has been demonstrated that aerobic exercise caused greater diversity in the microbiome along with increasing genera of the Firmicutes phylum, which produce short-chain fatty acids. In addition, athletes have demonstrated higher levels of the Akkermansia genus, which has been linked to metabolic and neural diseases. The extent to which the effect of exercise on the gut and brain is mediated through alterations in the microbiome is unknown. The dotted line represents a proposed mechanism. Solid lines represent known mechanisms. BDNF – brain-derived neurotropic factor, SCFA – short-chain fatty acids, ZO-1 – zona occluden-1 protein, HPA axis – hypothalamic–pituitary–adrenal axis, TJ – tight junction.