IL-26 in the induced sputum is associated with the level of systemic inflammation, lung functions and body weight in COPD patients

BACKGROUND: Chronic inflammatory process is the main link in COPD pathogenesis, which causes structural changes in the respiratory tract and lungs. In overweight patients, an adipose tissue could contribute to activation of the inflammatory process. Therefore, it is highly important to identify potential biomarkers of inflammation for patients with COPD and obesity. The aim of this study was to investigate the role of interleukin-26 (IL-26) and evaluate the relationship between the level of systemic inflammation, lung function, and body mass index (BMI) in patients with COPD. PATIENTS AND METHODS: Eighty-three patients with COPD in the stable condition (stage 2 according to the 2016 Global Initiative for Chronic Obstructive Lung Disease recommendations), aged 40–70 years, were included in the study. All patients were divided into 2 groups: obese (n=53) (BMI – 30.0–39.9 kg/m(2)) and non-obese (n=30) (BMI – 18.5–24.9 kg/m(2)). We conducted patients’ examination, spirometry, induced the sputum, determined the level of C-reactive protein (CRP), leptin in serum and IL-26 in sputum. RESULTS: Obese and non-obese COPD patients had a significant increase in IL-26 compared with healthy subjects by 2.3 and 2.6 (P=0.0003). We also observed a higher level of CRP by 1.38 times (P=0.0008), compared with the rate in non-obese COPD patients, and by 1.8 times (P=0.015) higher concentration level of leptin compared with healthy subjects. The sputum IL-26 level had positive correlation with BMI, CRP, and leptin, and a negative – with forced expiratory volume in 1 second (FEV(1)) and FEV(1)/forced vital capacity. Leptin level had positive correlation with BMI and CRP, and negative with FEV(1), FEV(1)/forced vital capacity. CONCLUSION: Obese COPD patients had a higher level of persistent systemic inflammation than non-obese ones, which is confirmed by a significant increase of CRP and leptin in serum. The data confirm that IL-26 can be considered as a perspective marker to detect the inflammation level in lung tissue of COPD patients.