Association of Vitamin D levels and Vitamin D receptor gene polymorphism with obesity in Bangladeshi school-going children: A case-control study

Abstract

Background: Childhood obesity and vitamin D deficiency (VDD) are recent health concerns associated with several clinical, psychosocial, and genetic manifestations like cardiovascular diseases, diabetes, depression, and cancer. This study aimed to investigate the association between lifestyle variables and vitamin D levels and VDR gene polymorphism with obesity among Bangladeshi school-going children. Methods: Epidemiological data and blood samples were collected from a total of 164 participants aged 6-13. Serum vit-D level was measured using electrochemiluminescence immunoassay (ECLIA) and four single nucleotide polymorphisms (SNPs) of the VDR gene such as TaqI, BsmI, ApaI, and FokI were genotyped by polymerase chain reaction-restriction fragment length polymorphism assay (PCR-RFLP). Results: The vit-D level was significantly lower in obese children (37.54 ± 14.39 ng/mL) compared to the underweight, normal, and overweight groups (44 .08 ± 15.57 to 50.46 ± 19.25 ng/mL) (p=0.013). Among the lifestyle variables, sunlight exposure during the daytime had a significant effect on the vit-D level of the participants regardless of their BMI status (p=0.003). The SNPs of the VDR gene study demonstrated that the Bb allele of the BsmI gene in obese children (58.62%) was significantly different from the control groups (73.33%) (p=0.02). 24.14% of obese children were of BB genotype, 58.62% of Bb genotype, and 17.24% of bb genotype, while in controls, BB, Bb, and bb genotypes were 20%, 73.33%, and 6.67%, respectively. Importantly, 66.67% of children with vit-D deficiency were BsmI-bb genotype carriers whereas only 5% of children were BsmI-bb genotype carriers who had sufficient vit-D concentrations. Conclusion: A significant association of reduced vitamin D levels and Bb alleles of the BsmI with childhood obesity has been identified. Hence, reduced vitamin D levels and VDR-BsmI polymorphism are risk factors for childhood obesity and suggest further study with a larger number of participants and lifestyle as well as therapeutic interventions in obese children.