Association of group component genetic variations in COPD and COPD exacerbation in a Japanese population.

BACKGROUND AND OBJECTIVE: Vitamin D supplementation can decrease the vulnerability to pulmonary infections. Therefore, it is speculated that the genes related to vitamin D metabolism are associated with an exacerbation-prone phenotype in chronic obstructive pulmonary disease (COPD). Because genetic variations of group component (GC) affect immunological capacity and serum vitamin D concentration, they could also affect the susceptibility to COPD exacerbation and the disease progression. We investigated the association between GC genetic variations and COPD and its exacerbation frequency in a Japanese population. METHODS: We performed genotype analysis of 361 COPD patients and 219 controls to identify two coding single nucleotide polymorphisms of GC, rs4588 and rs7041. We examined whether these polymorphisms were associated with the frequency of COPD exacerbation and analysed the correlation between the genotypes, COPD, emphysema severity and COPD progression, namely, the annual decline in airflow obstruction and diffusing capacity. RESULTS: Subjects with a C allele at rs4588 exhibited a higher frequency of exacerbations (P = 0.0048), greater susceptibility to chronic obstructive pulmonary disease (P = 0.0003), and emphysema (P = 0.0029), and a tendency for rapid decline of airflow obstruction (P = 0.0927). CONCLUSIONS: GC variations may affect exacerbation susceptibility, possibly leading to COPD worsening and its progression.