[The correlation of vitamin D level and vitamin D-binding protein gene polymorphism in chronic obstructive pulmonary disease]

Abstract

Objective: To assess the correlation of serum 25-hydroxyvitamin D (25-OHD) levels with vitamin D-binding protein (the group-specific component, GC) gene polymorphism in chronic obstructive pulmonary disease (COPD).

Methods: In a cross-sectional case-control study, 250 participants, including 116 COPD patients with smoking history and 134 healthy smokers, were investigated. A questionnaire about smoking history, vitamin D intake and comorbidities was collected. General pulmonary function was done by routine. Serum 25-OHD levels were detected by ELISA. The genetic variants (rs4588 and rs7041) were genotyped by real time fluorescence polymerase chain reaction (RT-PCR) with TaqMan probe technology.

Results: The COPD patients had lower serum vitamin D level than the smoker subjects (36.58 nmol/L vs 43.80 nmol/L, P < 0.001). In the COPD patients, vitamin D level was 39.43 nmol/L in those with percentage of predicted forced expiratory volume in 1 second (FEV1%pred) greater than or equal to 80%.In other groups with FEV1%pred 50%-80%, 30%-50% and lower than 30%, vitamin D levels were 35.32 nmol/L, 32.21 nmol/L, 26.25 nmol/L respectively (P < 0.01). Moreover, there was a significant relevance of 25-OHD levels with FEV1%pred in both COPD patients and healthy smokers (r(2) = 1.911; P < 0.000 1). The mean 25-OHD concentration had a negative correlation with Global Initiative for Obstructive Lung Disease (GOLD) stages. Homozygous carriers of vitamin D-binding protein gene rs7041 T allele were independently related to 25-OHD levels and susceptibility of COPD (P < 0.01; OR = 2.140, 95%CI 1.157-3.959, P = 0.015 respectively).

Conclusions: Patients with COPD are at high risk of vitamin D deficiency and the severity of COPD is inversely correlated with vitamin D levels. Furthermore, homozygous carrier of rs7041 T allele influences 25-OHD serum levels and is related to susceptibility of COPD, which may be a potential candidate gene for screening COPD.