Effects of VDBP rs4588 and rs7041 gene polymorphism on vitamin D status in obese individuals

Vitamin D plays a major role in bone metabolism regulating body phosphorus and calcium metabolism. Vitamin D binding protein (VDBP) binds to vitamin D metabolites and transports them to target tissues. It is hypothesized that polymorphisms in VDBP affect the absorption of vitamin D in the body. However, the relationship between VDBP polymorphisms and vitamin D levels in individuals with obesity has yet to be sufficiently investigated.

This work aimed to identify the relationship between vitamin D [25(OH)D₃] blood levels in obese and non-obese individuals and the rs4588 and rs7041 polymorphisms in VDBP.

The study included a total of 80 participants from the Kaliningrad region. The sample was stratified based on vitamin D status (normal, insufficiency, deficiency, and acute deficiency) and body mass index (BMI). Vitamin D blood levels were determined using enzyme immunoassay. Genomic DNA was extracted from whole blood samples. VDBP polymorphisms were identified using HaeIII and ErhI restriction endonucleases.

No significant differences in vitamin D blood levels between obese and non-obese individuals were revealed. The rs4588 C > A genotypes were associated with no significant differences in vitamin D levels between individuals with different body mass index (CC, p=0.147; CA, p=0.646; AA, insufficient data). However, for the VDBP rs4588 polymorphism, a significant difference was demonstrated in allele frequency between the groups with different vitamin D levels, i.e., normal vitamin D level group vs. insufficiency group (p=0.009) and normal vitamin D level group vs. acute deficiency group (p <0.0001).

The analysis of the individuals with the VDBP rs7041 T > G polymorphism demonstrated that there were no significant differences in the vitamin D levels between the BMI groups with specific genotypes (TG, p=0.502; GG, p=0.283; TT, insufficient data). However, the control and acute deficiency groups differed significantly (p <0.0001) in allele frequencies of individuals with the rs7041 polymorphism.

Vitamin D blood levels in obese patients were comparable to those of non-obese individuals. VDBP rs7041 and rs4588 polymorphisms do not correlate with variations in vitamin D blood levels among individuals with different BMI. However, the VDBP rs4588 A polymorphism is associated with low vitamin D levels, while the VDBP rs4588 G polymorphism is more common among individuals with normal vitamin D blood levels.