Airway FABP4 is Decreased in COPD Patients with Airway Bacterial Infection

Introduction: Airway infection worsens outcomes in COPD. Fatty-acid binding protein 4 (FABP4) is an adipokine released by alveolar macrophages and epithelial cells that may play a role in immunity against airway infection. The aim of the study was to determine the relationship between pulmonary FABP4 levels and airway infection in stable COPD patients. Methods: 52 adult patients with clinically stable COPD (mean age 65.27.9, mean FEV1 59.015.8 % of predicted) and 29 controls were prospectively enrolled at 5 university centers in Barcelona (Spain). Bronchoalveolar lavage (BAL) and induced sputum were obtained. Bacterial infection was defined by the presence of pathogenic bacteria at ≥103 cfu/ml in BAL. FABP4 levels were measured in BAL and sputum by ELISA. BAL total protein was determined using Qubit fluorometer and BAL FABP4 levels were adjusted by the total protein content. Results: Airway infection was detected in 10 COPD patients (19%), being Haemophilus spp (n=8, 80%) the most common one. COPD patients presented lower FABP4 levels in BAL than controls (0.0003 ± 0.0002 vs 0.0004 ± 0.0004, p=0.03). Infected patients presented lower sputum FABP4 levels than non-infected patients (4.5 ± 6.5 vs 18.9 ± 16.5, p=0.0075). A correlation between sputum and BAL FABP4 was observed (r=0.33, p=0.02). In addition, BAL and sputum FABP4 were positively correlated with FEV1 (r=0.28, p=0.04 and r=0.33, p=0.02). Conclusions: Airway FABP4 is decreased in COPD patients with airway infection. This finding suggested that FABP4 may be important in the pathogenesis of airway infection. *Supported by FIS PI15/02042, FIS PI15/00167 and Fundació Ramon Pla I Armengol