Influence of Vitamin D Receptor Gene Fok1 Polymorphism on Bone Mass Accrual Post Calcium and Vitamin D Supplementation

Objective To examine the association of vitamin D receptor (VDR) gene polymorphisms of the Fok1 locus on bone mass accrual in Indian girls used to a low calcium intake. Methods An intervention trial was undertaken in 102 girls aged 8-16 y, attending a state run school in Pune city, India. All girls received 500 mg calcium daily and 30,000 IU of vitamin D3 quarterly for one year. Dietary calcium intake was evaluated. Bone mineral content (BMC), bone area (BA) and bone mineral density (BMD) were measured at total body using Dual Energy X-ray Absorptiometry (Lunar DPX-PRO). Polymorphisms of the Fok1 locus of the vitamin D Receptor (VDR) gene were detected using SYBR Green quantitative polymerase chain reaction. Results The prevalence of Fok1 polymorphism was 43.1 %(Ff), 9.8 %(ff) and 47.1 %(FF). At baseline, FF genotype had significantly lower BMD as compared to ff and Ff genotype (p<0.05). At baseline, majority of girls (82.4 %) were hypocalcemic with low calcium intake. Post-supplementation, FF genotype had significantly lower bone mass as compared to ff and Ff genotype. Significant increase in BMC [Ff (17.9 %); ff(18.1 %); FF (17.4 %)], and BMD [Ff (5.4 %); ff (6.3 %); FF (4.8 %)] was observed post supplementation (p value<0.05), though percentage increase in BMC and BMD was similar for three Fok1 polymorphisms (p>0.1). Conclusions VDR gene polymorphism, as defined by Fok1 genotype had no positive influence on bone mass accrual in response to calcium supplementation.