Vitamin D, vitamin D binding protein, lung function and structure in COPD

RATIONALE: Vitamin D and vitamin D binding protein (DBP) have been with COPD and FEV1. There are limited data regarding emphysema and DBP. OBJECTIVE: This is a pilot study of a portion of the subjects in Evaluation of COPD Longitudinally to Identify Predictive Surrogate (ECLIPSE) study designed to examine the relationship between vitamin D DBP, FEV1 and emphysema in COPD patients. METHODS: We measured serum DBP in 498 ECLIPSE subjects. Subjects were distributed amongst smoker non-smoker controls, and GOLD stages 2, 3 and 4. Within each GOLD stage, subjects were equally divided amongst high and low emphysema burden. The associations between 25(OH)D, DBP, and free vitamin D with FEV1, CT- emphysema, biomarkers and clinical data including CT-measured bone were assessed. MEASUREMENTS: 25(OH)D and DBP were measured using tandem spectroscopy and competitive enzyme-linked immunosorbent assay, MAIN RESULT: 25(OH)D was correlated with FEV1 (p = 0.01) and with emphysema (p < 0.01). 25(OH)D was also associated with six-minute walk 0.02), bronchodilator response (p = 0.04), and Clara cell secretory (CC-16) (p = 0.01). 25(OH)D levels were not associated with CT-measured attenuation, however DBP was associated with bone attenuation in emphysema. DBP was not associated with FEV1 or emphysema. 25(OH)D and inversely associated (p = 0.01). CONCLUSION: This is the first study to demonstrate a relationship between emphysema and vitamin D. We also further evidence for a relationship between vitamin D and FEV1