Evaluation of Vitamin D binding protein (DBP) gene polymorphism in Vitamin D deficient patients attending a tertiary care hospital–a pilot study

Abstract

Polymorphism in Vitamin D binding protein (DBP) has been implicated as one of the causes for Vitamin D deficiency. However there is paucity of data regarding the effect of genetic polymorphism in DBP in Vitamin D deficient patients in our population. This pilot study was undertaken to analyze the common genetic polymorphism in vitamin DBP in these population and its effect on vitamin D supplementation. 80 vitamin D deficient subjects were selected by convenient sampling. Genetic analysis for DBP (GC) gene polymorphism (rs7041 + rs4588) was carried out in all these individuals after informed consent and correlated with the vitamin D levels post supplementation. Six combinations of genotype were obtained (rs7041 + rs4588): TT+CA, TG+CC, TT+CA, TT+CC, TT+AA, GG+CC. A third of all individuals (33%) were found to have the TG+CA genotype, followed by about 26 % of individuals having the GG+CC genotype. TT+CA group was found to have 13% individuals and a tenth of all individuals belonged to each of the groups with TG+CC and TT+AA genotypes. Least proportion of individuals was found to have the TT+CA genotype (6%). There was no significant difference in the vitamin D levels with individual polymorphism (p value <0.01). However the combined genotype had an effect, with homozygotes for both such as TT-CC, TT-AA showing least response and heterozygotes such TG-CA and CG-CC showing better response: In this study, the individual SNP (rs7041 and rs4588) did not seem to significantly influence the response to vitamin D supplementation. However the combined genotype seem ed to influence the proportion of patients showing improvement after supplementation. The homozygotes for both such as TT-CC, TT-AA showing least response and heterozygotes such TG-CA and CG-CC showing better response.