Abstract
BACKGROUND: Chronic obstructive pulmonary disease (COPD) is a disease with high morbidity and mortality. Functional abdominal bloating/distension (FABD), a functional gastrointestinal disorder characterized by recurrent sensations of abdominal fullness and/or visible abdominal distension without identifiable organic causes. FABD mainly impairs gastrointestinal functions-particularly intestinal transit and gas handling-rather than pulmonary function. This study characterized fecal microbiota in COPD patients with FABD to identify precision medicine biomarkers. METHODS: Fecal samples from 20 COPD & FABD, 20 COPD, and 10 healthy controls (HC) were analyzed via metagenomic analysis. Gut microbiota diversity/composition were compared, and immune parameters (serum IgG, CD4+/CD8+ T cells) were assessed. RESULTS: COPD/COPD & FABD patients showed significantly higher fecal microbiota α-diversity (COPD vs. HC: Chao1, P = 0.12; ACE, P = 0.14; Shannon, P = 0.0016; Simpson, P = 0.0013; COPD & FABD vs. HC: Chao1, P = 0.031; ACE, P = 0.031; Shannon, P = 0.00032; Simpson, P = 0.0005) vs. HC. β-Diversity analyses (PCA/PCoA) revealed distinct clustering between patients and HC (PCA, P = 0.014; PCoA, P = 0.013), but no separation between COPD and COPD & FABD (P > 0.05). Linear discriminant analysis (LEfSe) identified 50 discriminative biomarkers: 41 enriched in HC (Bacteroides uniformis), five in COPD & FABD (Bacilli, Enterococcus faecium), and four in COPD (Streptococcus parasanguinis). Notably, Enterococcus faecium was highly abundant in patients (22.04-26.92%) but absent in HC, suggesting a potential association with the COPD-FABD condition. Random forest models showed moderate diagnostic accuracy for all microbes (AUC = 0.632) and strong performance for fungal biomarkers (Clostridium fessum, Clostridioides difficile; AUC = 0.856). CONCLUSION: Gut microbiota signatures, particularly Enterococcus faecium and fungal taxa, may serve as non-invasive biomarkers for COPD progression and FABD diagnosis, warranting clinical validation.