Among the 17 fecal metabolites and 12 microbial genes associated with tryptophan metabolism detected in our cohort, only skatole and its upstream enzyme aldehyde dehydrogenase (ALDH, K00128) showed consistent positive associations with both CAD status and the abundance of O. scatoligenes, whereas other tryptophan-related metabolites, such as 2-aminophenol and 2-aminobenzoic acid, displayed discordant associations (Fig. S5). The gene discussed is LDHA; the disease is coronary artery disorder.