Association of Vitamin D Receptor Gene Polymorphisms with Serum Vitamin D Levels in a Greek Rural Population (Velestino Study)

Background/Aim: An alarming increase in vitamin D deficiency even in sunny regions highlights the need for a better understanding of the genetic background of the vitamin D endocrine system and the molecular mechanisms of gene polymorphisms of the vitamin D receptor (VDR). In this study, the serum levels of 25(OH)D-3 were correlated with common VDR polymorphisms (ApaI, BsmI, FokI, and TaqI) in 98 subjects of a Greek homogeneous rural population. Methods: 25(OH)D-3 concentration was measured by ultra-HPLC, and the VDR gene polymorphisms were identified by quantitative real-time PCR followed by amplicon high-resolution melting analysis. Results: Subjects carrying either the B BsmI (OR: 0.52, 95% CI: 0.27-0.99) or t TaqI (OR: 2.06, 95%: 1.06-3.99) allele presented twice the risk for developing vitamin D deficiency compared to the reference allele. Moreover, subjects carrying 1, 2, or all 3 of these genotypes (BB/Bb, Tt/tt, and FF) demonstrated 2-fold (OR: 2.04, 95% CI: 0.42-9.92), 3.6-fold (OR: 3.62, 95% CI: 1.07-12.2), and 7-fold (OR: 6.92, 95% CI: 1.68-28.5) increased risk for low 25(OH)D-3 levels, respectively. Conclusions: Our findings reveal a cumulative effect of specific VDR gene polymorphisms that may regulate vitamin D concentrations explaining, in part, the paradox of vitamin D deficiency in sunny regions, with important implications for precision medicine.