Vitamin D binding protein gene polymorphism and its association with free serum bioavailability among tuberculosis patients and household contacts

Genetic variants influence the distribution of vitamin D in circulation leading to vitamin D deficiency. This study aimed to determine the association between the DBP gene polymorphism with vitamin D bioavailability among active tuberculosis patients, latent Tuberculosis and with no Tuberculosis infection individuals. This was a cross-sectional study of 52 active tuberculosis patients, 23 latent tuberculosis individuals, and 27 with no tuberculosis infection. Sanger sequencing was performed and single nucleotide polymorphisms were identified using the BioEdit tool. Logistic regression was used to determine associations. Frequencies of 97% Gc1F, 2% Gc2 and 1% Gc1S genotypes were reported. The median (IQR) vitamin D levels of the predominant genotype, Gc1F were 3.8 (1.1-10.5) ng/ml, Gc1S individual, 2.2 ng/ml, and Gc2 individuals were 1.9 ng/ml. No significant association was found between vitamin D binding protein gene and free and bioavailable vitamin D levels, p=value 0.05. Spearman’s correlation revealed a negative association (r-0.0404) between the two. The Gc1F genotype was predominantly found in the study population with the minor alleles associated with active and latent TB states. However, the non-significant association observed between the vitamin D Binding Protein gene and the free and bioavailable vitamin D levels may be a consequence of the homogenous population.