Increased plasma osteopontin in frequent exacerbator and acute exacerbation of COPD

Abstract

Introduction: Osteopontin (OPN) is a phosphorylated glycoprotein expressed by diverse tissues including bone, brain, kidney, liver and lung. Limited data exist regarding OPN in chronic obstructive pulmonary disease (COPD) and the exacerbation of this condition. Objectives: The aim of this study was to evaluate plasma OPN levels and investigate the clinical usefulness of plasma OPN measurement in patients with COPD. Methods: Plasma OPN levels were measured and compared in patients with COPD exacerbation (n = 64), patients with stable COPD (n = 68) and healthy controls (n = 30). In patients with COPD exacerbation, plasma OPN levels were measured repeatedly in convalescence. Patients with stable COPD were categorized into frequent and infrequent exacerbators according to their frequency of exacerbation, and plasma OPN levels were compared between these two groups. Plasma OPN levels were determined by enzyme-linked immunosorbent assay. Results: Patients with COPD exacerbation had increased plasma OPN levels compared with those with stable COPD and healthy controls (32.6 +/- 29.6, 17.6 +/- 11.1, 8.4 +/- 6.1 ng/mL, respectively; P < 0.001). In patients with COPD exacerbation, plasma OPN levels were significantly decreased in convalescence (44.8 +/- 43.5 vs 24.6 +/- 13.6 ng/mL; P = 0.034). Frequent exacerbators had higher plasma OPN levels compared with infrequent exacerbators (22.5 +/- 12.0 vs 15.0 +/- 9.8 ng/mL; P = 0.008). Conclusions: Plasma OPN levels were increased in patients with COPD exacerbation and frequent exacerbators, which suggests a possible role for OPN as a biomarker of COPD exacerbation.