Increasing evidence have implied that microbiota from airway and gut might be involved in the pathogenesis of chronic obstructive pulmonary disease (COPD). However, the cross-talk between respiratory and gastrointestinal microbiome in COPD is still undetermined. The study is aimed to investigate the interaction between lung and gut flora, and their role in the process of COPD.

Despite the high prevalence of chronic obstructive pulmonary disease (COPD), there continues to be a large gap in our understanding of disease pathogenesis and mechanisms accounting for large variability in disease phenotype. Cigarette smoking is the principal cause of COPD, but only approximately 15% of adults with substantial tobacco exposure develop clinical COPD. Besides, bacterial colonization or infection is also considered as an important factor in COPD. There are very limited data from microbiome studies that suggest that respiratory and gastrointestinal microbiota may be involved in the pathogenesis of COPD. However, the cross-talk between between lung and gut microbiome, and their relationship with various clinical phenotypes of COPD. Here, we conducted 16S rRNA-based pyrosequencing to evaluate the link between the lung-gut axis and the clinical phenotypes of COPD, such as lung function, emphysema, symptoms, exacerbations, inflammation levels and metabolic features.

Inclusion Criteria:

1. males aged 40-80;
2. diagnosed with COPD according to the GOLD guidelines;
3. clinically stable patients without medication changes or exacerbation in two months;
4. smoking history of more than 10 pack years

Exclusion Criteria:

1. diagnosed with unstable cardiovascular diseases, significant renal or hepatic dysfunction or mental incompetence;
2. diagnosed with asthma, active pulmonary tuberculosis, diffuse panbronchiolitis, cystic fibrosis, clinically significant bronchiectasis, exacerbation of COPD or pneumonia in two months;
3. prescribed immunosuppressive medications.

Clinically stable patients with COPD and controls without COPD are enrolled.