Exercise-induced gut microbiota metabolites and the gut-lung axis: implications for chronic obstructive pulmonary disease.

Chronic obstructive pulmonary disease (COPD) is increasingly recognised as a systemic disorder associated with gut dysbiosis and impaired gutlung communication. COPD-associated gut dysbiosis suggests potential bidirectional interactions between the gut and lung, which may be mediated by circulating immune cells, gut microbiota-derived metabolites and systemic inflammatory mediators. Emerging evidence suggests that exercise may improve COPD-related symptoms and quality of life not only through direct cardiopulmonary adaptations but also by reshaping gut microbiota composition and metabolic function. Microbiota-derived metabolites, including short-chain fatty acids (SCFAs), secondary bile acids (SBAs) and indole derivatives, may act as key mediators linking exercise-induced microbial changes to pulmonary immune regulation, inflammatory signalling, oxidative stress and epithelial barrier integrity. However, current evidence remains fragmented, and the mechanisms by which exercise-responsive microbial metabolites influence COPD-related pulmonary inflammation, barrier dysfunction and immune homeostasis have not been fully clarified. This review synthesises evidence from human studies, animal models and mechanistic investigations to clarify the relationship among exercise, gut microbiota and COPD, with a focus on how exercise-responsive microbial metabolites may contribute to improved pulmonary health. By integrating current evidence within an exercise-gut-lung axis framework, this review provides a mechanistic basis for developing microbiota-targeted exercise strategies for COPD prevention and management.