Causal inference regarding the relationship between the gut microbiota metabolite Phenylacetylglutamine, the upstream gut microbiota Lachnospiraceae, and downstream related genes CXCL8, EGFR, and IL6 with COPD revealed a positive causal relationship between Phenylacetylglutamine and COPD. Here, IL6 is linked to chronic obstructive pulmonary disease.