Background: This study was undertaken to measure the concentration of adiponectin (APN) in serum and induced sputum in patients with chronic obstructive pulmonary disease (COPD during acute exacerbation (AECOPD) and at stable stage and to determine the role of APN as a marker of inflammation in the pathogenesis of COPD.
Methods: All the patients in this prospective study were enrolled from October 2008 to October 2009, including 30 male AECOPD patients from the emergency department, 30 male stable COPD patients from the department of respiratory diseases, and 30 healthy non-smoking male controls from the department of medical examination. The serum and induced sputum were collected from each patient. All of the patients had normal weight (BMI range 18.5-24.9 kg/m(2)). Patients with severe bronchial asthma, bronchiectasis or autoimmune disease were excluded. Cell count and classification was performed for the induced sputum. The concentrations of APN, IL-8, IL-6 and TNF-α were measured by ELISA. Pulmonary function was tested among the three groups. Comparisons between the groups were conducted by Student's t test, ANOVA analysis or nonparametric test. Correlation analysis was carried out by Pearson's product-moment correlation coefficient test or Spearman's rank-order correlation coefficient test.
Results: The concentrations of APN in the serum or induced sputum in AECOPD patients were significantly higher than those in stable COPD patients or healthy non-smoking controls (P<0.01). The concentration of APN in stable COPD patients was significantly higher than that in healthy non-smoking controls (P<0.01). For the AECOPD patients, APN was positively correlated with IL-8 and TNF-α in the serum and induced sputum (r=0.739, 0.734, 0.852, 0.857 respectively, P<0.05). For the stable COPD patients, APN was also positively correlated with IL-8 and TNF-α in the serum and induced sputum (r=0.751, 0.659, 0.707, 0.867 respectively, P<0.05). In addition, for the AECOPD patients, APN was positively correlated with the percentage of neutrophils in the induced sputum (r=0.439, P<0.05).
Conclusions: APN is involved in the process of systematic and airway inflammation of COPD. This process is related to neutrophils in the airway, IL-8 and TNF-α. APN could be used as a new marker for inflammation of COPD.
Keywords: Adiponectin; Chronic obstructive pulmonary disease; Induced sputum; Interleukin-6; Interleukin-8; Neutrophil; Serum; Tumor necrosis factor-a.