The Relationship of FokI Polymorphism in Vitamin D Receptor (VDR) Gene and Obesity

Background: Obesity is one of the biggest public health challenges of the century. Genetic studies show that proteins associated with vitamin D, such as vitamin D receptor (VDR) are effective in the pathogenesis of obesity. This study aimed to investigate the relationship of FokI polymorphism in VDR gene and the body mass index (BMI), as an indicator of obesity, and other risk factors. Methods: In this case-control study, 91 patients with obesity (BMI > 30 kg/m2) and 100 healthy controls (BMI: 18.5-24.9 kg/m2) participated. The levels of fasting blood sugar (FBS), total cholesterol and triglyceride were measured and the BMI was determined. The genomic DNA was extracted from the peripheral blood of participants. VDR gene amplified using polymerase chain reaction (PCR) technique and FokI polymorphism was investigated via the restriction fragment lengths polymorphism (RFLP) method. The odds ratio was used to examine the relationship between the risk factors and the disease; 95% of confidence interval was used for these calculations. Findings: The frequency of F allele of FokI polymorphism was 95.00% and 88.46%, while the frequency of f allele was 5.00% and 11.53% in control and obese groups, respectively. The difference between F and f alleles in the control and obese groups was significant (P = 0.005). In the obese group, there was no significant relationship between the levels of fasting blood sugar, total cholesterol, and triglyceride and the genotypes. In the control group, significant relationship was observed between the level of fasting blood sugar and genotypes (P = 0.010). Conclusion: Our findings showed that protection against the obesity was conferred significantly when F allele existed. For this reason, the individuals with FF genotype in the control group had lower fasting blood sugar levels compared to the other genotypes.