Cross-sectional Analysis of VDBP Polymorphisms rs7041 and rs4588 and their Impact on Vitamin D Levels in Ivoran Hemodialysis Patients (Subsaharian Africa)

Abstract

Introduction: Hypovitaminosis D is a real public health problem. Populations in sub-Saharan Africa, despite favorable sun exposure, are not immune to this scourge. Among the reasons mentioned are the inhibitory action of melanin on the cutaneous synthesis of vitamin D but also the involvement of genetic variants of the vitamin D binding protein. In a pathology such as chronic kidney disease already characterized by a deficit in the activation of vitamin D, knowing the polymorphisms of this binding protein is important because it could influence not only the status of vitamin D in the serum but also its bioavailability and the response to vitamin D supplementation. This study aimed to determine the genetic variants rs7041 and rs4588 of the vitamin D transporter protein and to correlate them with the vitamin D status of hemodialysis patients from Sub-Saharan Africa systematically supplemented orally with vitamin D. Methods: This cross-sectional study involved 48 patients who gave their written consent. The genetic variants of the transporter protein were determined by PCR-RFLP and the dosage of 25(OH)D was done by ELFA technique. SNPStats software was used to estimate allele, genotype, and haplotype frequencies. Fisher's exact test was used to establish correlations between vitamin D concentrations and polymorphisms. Results: The results showed a predominance of the Gc1f variant (rs7041-T and rs4588-C). Despite vitamin D supplementation, 40% of patients had hypovitaminosis D. We did not find a direct association between vitamin D transporter protein variants and vitamin D concentrations. As found in other Black populations, the Gc1f variant remains predominant. Conclusion: Conducting this study on a larger population would allow us to better assess its association with 25(OH)D.