Serum Vitamin D Binding Protein in Asthma-Chronic Obstructive Pulmonary Disease Overlap and the Individual Diseases

Abstract

Vitamin D binding protein (VDBP) has been shown to influence asthma and chronic obstructive pulmonary disease (COPD), but its specific effects are unclear. Moreover, serum VDBP has not been investigated in asthma-COPD overlap (ACO). In this study, we compared serum concentrations of VDBP among 252 participants (63 patients with ACO, 70 with bronchial asthma, 69 with COPD, and 50 healthy donors). We also analyzed correlations of blood VDBP concentration with smoking, serum immunoglobin E, peripheral blood eosinophil and neutrophil counts, serum calcium, serum 25-hydroxyvitamin D₃, respiratory function (FEV1: forced expiratory volume in 1 s), and fractional exhaled nitric oxide in ACO, bronchial asthma, and COPD. Serum VDBP concentrations were significantly lower in the healthy donors compared with the ACO, bronchial asthma, and COPD groups (all p < 0.05), but did not differ significantly among ACO, bronchial asthma, and COPD. Analysis of correlations of various parameters with serum VDBP concentration showed a negative correlation with smoking history (pack-years) (r = −0.266, p = 0.037) and a positive correlation with FEV1 (r = 0.267, p = 0.036) for ACO, but no correlation between serum VDBP and smoking history or FEV1 for bronchial asthma or COPD. A positive correlation between serum VDBP and peripheral blood eosinophil count was found for COPD alone (r = 0.279, p = 0.039). These results suggest that VDBP influences smoking-related respiratory dysfunction in ACO and peripheral blood eosinophil count in COPD.