Genetic influence on circulating vitamin D among Saudi Arabians

OBJECTIVES  To examine the effect of most common studied single nucleotide polymorphisms (SNP) on serum 25-hydroxyvitamin D (25OHD) levels in Saudi Arabian population.  METHOD A cross-sectional observational study was carried out between July 2014 and October 2015, at King Fahd Hospital of the University (KFHU), Al-Khobar, Kingdom of Saudi Arabia. After informed consent, blood samples from 283 subjects living in the Eastern province were collected for 25-OHD measurement and genetic analysis of SNPs in vitamin D receptor (VDR) [rs2228570 and rs1544410], Cytochrome, P450 family 2 (CYP2R1) [rs10741657 and rs1993116], and Group-specific components (GC) [rs2282679 and rs4588].  RESULTS Vitamin D deficiency was found in 87.6% and insufficiency in 7.7%. The percentages of the different alleles of the 6 SNPs tested ranged between 0-62.5%. There was significant difference between the AA, AG, and GG alleles of VDR rs2228570. The carries of GG allele was associated with increased risks of vitamin D insufficiency (p less than 0.002) and deficiency (p less than or equal to 0.005). The CYP2R1 rs10741657 gene showed that AG and GG allele carriers had significant risk of vitamin D deficiency. AG allele (normal versus Insufficiency p less than 0.02 and normal versus deficiency p less than 0.08) and GG allele normal versus deficiency (p less than 0.002) and insufficiency versus deficiency (p less than 0.001). For group-specific components (GC rs4588), there was only significant difference between the normal and deficiency for the AC allele (p less than 0.0001). CONCLUSION The presence of GG allele of the SNP rs2228570 of VDR gene, SNPs rs4588 of GC gene and CYP2R1 rs10741657 gene was associated with vitamin D deficiency.