Associations between obesity and vitamin D availability depending on the rs2228570 polymorphism of the VDR gene and rs9939609 polymorphism of the FTO gene in the midland and the Extreme North of Russia

Abstract

Background: It has been shown that vitamin  D availability depends on the body mass index (BMI). Genetic polymorphisms contribute to the development of vitamin  D deficiency.Aim: To study the availability of vitamin D in the population of various regions of the Russian Federation, depending on the BMI values and the rs2228570 polymorphisms of the VDR gene and rs9939609 of the FTO gene.Materials and methods: The rs2228570 polymorphisms of the VDR gene and rs9939609 of the FTO gene were identified in 311 subjects (136, from the midland of Russia, and 175 from the Far North). Serum 25-hydroxyvitamin  D [25(OH)D] levels were measured by an immunoenzyme assay in the autumn and winter seasons. Genotyping was performed with the allele-specific amplification and real-time detection of results using TaqMan probes complementary to the polymorphic DNA segments and the CFX96 Real Time System amplifier (Bio-Rad, USA). We studied associations of the rs9939609 polymorphism of the fat mass and obesity-associated (FTO) gene located at 16q12.2, as well as the rs2228570 polymorphism of the vitamin D receptor gene (VDR) located at 12q13.11.Results: Frank vitamin D deficiency (serum 25 (OH) D level<20 ng/ml) was observed in 39.7% (54/136) of the sample from the midland, in 40% (14/35) of the migrants and in 30.7% (43/140) of the indigenous inhabitants of the Far North (Nenets). Obese residents of the midland Russia had significantly lower serum 25(OH)D levels, and the indigenous population of the Far North had significantly higher levels than those with BMI<30 (р<0.05). In the indigenous population of the Northern Region, there was a  significant association between vitamin  D deficiency and C allele of the rs2228570 polymorphism of the VDR gene (odds ratio [OR] 2.5, 95% confidence interval [CI] 1.46–4.27, p=0.0006) and the AA genotype of the rs9939609 polymorphism of the FTO gene (OR 8.83, 95% CI 0.94–82.5, p=0.02).Conclusion: The association between obesity and vitamin  D availability in the individuals with the rs2228570 polymorphism of the VDR gene and the rs9939609 polymorphism of the FTO gene depends on their ethnicity.