Sputum Vitamin D binding protein (VDBP) GC1S/1S genotype predicts airway obstruction: a prospective study in smokers with COPD

<b>Background:</b> Vitamin D Binding Protein (VDBP) has been reported to be associated with COPD. Rs7041 and rs4588 are two single nucleotide polymorphisms of VDBP gene (GC), including three common allelic variants (GC1S, GC1F and GC2). <b>Aim:</b> to examine the association of sputum and plasma VDBP and lung function at baseline and 4-year later and its interaction with the genetic polymorphisms. <b>Method:</b> Sputum VDBP, plasma VDBP and plasma 25-OH-Vitamin-D, as well as GC rs4588 and rs7041 genotypes, were assessed in 233 participants of non-smokers, smokers without and with COPD stage I and stage II+ in a Finnish 4-year follow-up cohort. VDBP was studied by proteomics, western blot and ELISA. DNA were genotyped by PCR. <b>Results:</b> The high frequencies of haplotypes in rs7041/rs4588 were homozygous GC1S/1S (42.5%). Only higher levels of sputum VDBP GC1S/1S genotype were observed in COPD stage I and stage II+ compared with non-smokers (p=0.034 and p=0.002, respectively). In the genotype multivariate regression analysis indicated that baseline sputum VDBP, packyears, and the current smoking COPD were independent predictors for FEV1 % predicted at follow-up.(Fig 1) <b>Conclusion:</b> Baseline sputum VDBP levels expression in GC1S/1S genotype was elevated in smokers with COPD and predicted follow-up airway obstruction.