Exercise, the Gut Microbiome and Gastrointestinal Diseases: Therapeutic Impact and Molecular Mechanisms

The benefits of regular physical activity (PA) on disease prevention and treatment outcomes have been recognized for centuries. However, only recently has interorgan communication triggered by the release of "myokines" from contracting skeletal muscles emerged as a putative mechanism by which exercise confers protection against numerous disease states. Cross-talk between active skeletal muscles and the gut microbiota reveal how regular PA boosts host immunity, facilitates a more diverse gut microbiome and functional metabolome, and plays a positive role in energy homeostasis and metabolic regulation. In contrast, and despite the large interindividual variation in the human gut microbiome, reduced microbial diversity has been implicated in several diseases of the gastrointestinal (GI) tract, systemic immune diseases, and cancers. Although prolonged, intense, weight-bearing exercise conducted in extreme conditions can increase intestinal permeability, compromising gut-barrier function and resulting in both upper and lower GI symptoms, these are transient and benign. Accordingly, the gut microbiome has become an attractive target for modulating many of the positive effects of regular PA on GI health and disease, although the precise dose of exercise required to induce favourable changes in the microbiome and enhance host immunity is currently unknown. Future efforts should concentrate on gaining a deeper understanding of the factors involved in exercise-gut interactions through the generation of functional 'omics readouts (ie, metatranscriptomics, metaproteomics, and metabolomics) that have the potential to identify functional traits of the microbiome that are linked to host health and disease states, and validating these interactions in experimental and preclinical systems. A greater understanding of how PA interacts with the GI tract and the microbiome may enable targeted therapeutic strategies to be developed for individuals and populations at risk for a variety of GI diseases.