Association of vitamin D status and vitamin D receptor polymorphism in diabetic foot ulcer patients: A prospective observational study in a South-Indian tertiary healthcare facility

Objective of the study was to find the association of vitamin D receptor (VDR) polymorphisms (Fokl, Taql and Apal) with vitamin D levels in diabetic foot ulcer (DFU) patients in South India. In this case–control study, plasma vitamin D levels and VDR genotype frequencies of 70 cases (DFU patients) were compared with 70 diabetic (diabetes mellitus [DM] [non-DFU]) patients and 70 apparently healthy controls (HC) from South India. Plasma vitamin D levels were measured using the ELISA technique, and genotyping of VDR polymorphisms was carried out using real-time polymerase chain reaction. Logistic regression was used to find the association between DFU versus HC and DFU versus DM traits. Association analysis was performed based on additive, dominant and recessive models with age and gender as covariates. A 45.7% of DFU patients have sufficient vitamin D levels than 48.6% and 40% of DM patients and HC, respectively. Linkage disequilibrium analysis for DFU versus HC and DFU versus DM traits shows that single nucleotide polymorphisms (SNPs) Taq1 (rs731236) and Apal (rs7975232) are in strong linkage disequilibrium in DFU patients. The alleles and genotype frequencies were similar in all three groups. Although the additive model does not show statistical significance, age and sex correlate with the three SNPs (Fokl, Taql and Apal). No association was found between VDR gene polymorphisms and vitamin D levels in DFU patients in Southern India. On the other hand, age and sex correlate with the three SNPs.