Serum angiopoietin-like 4 is over-expressed in COPD patients: association with pulmonary function and inflammation.

Chronic obstructive pulmonary disease (COPD) is both a pulmonary and systematic disease, which will cause abnormal expression of some circulating factors. Angiopoietin-like protein 4 (ANGPTL4) has been reported to play important role in inflammatory responses and several diseases. However, whether it contributes to COPD is an open question. The aim of this study is to explore the potential relationship between ANGPTL4 and COPD.In this study, circulating levels of ANGPTL4, C-reactive protein (CRP), adiponectin, tumor necrosis factor (TNF)-α, matrix metalloproteinase (MMP)-9 and monocyte chemotactic protein (MCP)-1 in 73 COPD patients and 40 healthy volunteers were investigated using multiplex enzyme-linked immunosorbent assay Kits. Then, we analyzed the correlations between ANGPTL4 with other inflammatory mediators and pulmonary function.Serum ANGPTL4 levels were significantly elevated in COPD patients compared with healthy controls (122.86 ± 38.59 ng/mL versus 99.03 ± 31.84 ng/mL, p = 0.001). Besides, serum ANGTPL4 levels were much higher in ever-smokers with COPD than in never-smokers with COPD (131.71 ± 32.92 ng/mL versus 113.25 ± 42.34 ng/mL, p = 0.03). More importantly, the concentrations of circulating ANGPLT4 correlated inversely with forced expiratory volume in 1 second (FEV1) % predicted, an index of lung function in COPD (r = -0.450, p < 0.001) and in all participants (r = -0.369, p < 0.001), while correlated positively with CRP (r = 0.312, p = 0.007 for COPD; r = 0.404, p < 0.001 for total subjects), adiponectin (r = 0.266, p = 0.004 for total subjects), and MMP-9 (r = 0.254, p = 0.03 for COPD).Our results suggest that circulating ANGPTL4 levels are up-regulated in COPD patients, and have correlations with pulmonary function and systematic inflammation in COPD, which provides a novel idea to further dig the pathogenic mechanisms of COPD, and justifies more studies to determine how ANGPTL4 contributes to COPD.