Gut microbiota dysbiosis and the gut-lung axis in COPD: mechanisms, clinical relevance, and microbiota-targeted interventions.

Chronic obstructive pulmonary disease (COPD), which is characterised by persistent inflammation and airflow limitation, has increasingly been linked to the gut-lung axis. Patients with COPD commonly exhibit reduced diversity of gut microbiota, decreased levels of bacteria that produce short-chain fatty acids (SCFAs), increased levels of opportunistic pathogens, and compromised intestinal barrier function. These alterations are driven by factors such as smoking, hypoxia, oxidative stress, medication use and ageing, and promote bacterial translocation and systemic inflammation, thereby exacerbating lung injury. Gut microbiota metabolites, including SCFAs, bile acids, tryptophan metabolites and trimetlylamine N-oxide (TMAO), further modulate immune responses and metabolic pathways, thereby influencing disease progression. Intervention strategies targeting the microbiome, including dietary fibre, probiotics, prebiotics, faecal microbiota transplantation (FMT) and phage therapy, have demonstrated potential therapeutic value, though clinical evidence remains limited. Elucidating the mechanisms linking gut dysbiosis and COPD will provide novel targets for precision interventions and disease management.