OC002—Cyp2r1 Genetic Polymorphisms Are Associated With Lower 25-Hydroxy Vitamin D Levels In Lebanese Subjects

Association of rs7041 and rs4588 Polymorphisms of the Vitamin D Binding Protein and the rs10741657 Polymorphism of CYP2R1 with Vitamin D Status Among Jordanian Patients

AIM

Previous studies have shown a high prevalence of vitamin D deficiency among Jordanians despite adequate exposure to sunlight, suggesting the presence of other causes for this deficiency. The aim of this study was to identify the relationship between 25-hydroxyvitamin D [25-(OH) VD] status and the nonsynonymous single-nucleotide polymorphisms (SNPs) (rs7041 and rs4588) of the GC gene, which encodes the vitamin D binding protein, and one SNP (rs10741657) near the CYP2R1 gene.

METHODS

Blood samples from 381 subjects (74 males and 307 females, 18-60 years of age) were obtained from the "National Center for Diabetes, Endocrinology and Genetics" (Amman, Jordan). The subjects were classified as "apparently healthy" if they did not suffer from chronic diseases and as "unhealthy" if they suffered from certain chronic diseases. Subjects' genotypes for GC; rs7041 and rs4588; CYP2R1; rs10741657 were determined by the polymerase chain reaction-restriction fragment length polymorphism assay method.

RESULTS

Apparently, healthy subjects had significantly higher 25-(OH) VD levels than unhealthy patients. In apparently healthy subjects, the rs10743657 genotypes containing the variant allele A (AA, GA) were associated with higher 25-(OH) VD levels than the homozygous wild-type genotype (GG). The genotypes containing the variant allele of rs7041 (TT, TG) and rs4588 (AA, AC) were associated with lower 25-(OH) VD levels than the wild-type genotypes (GG and CC, respectively). Haplotype analysis of rs7041 and rs4588 revealed that the haplotypes GC1S and GC1S/S were associated with 25-(OH) VD sufficiency, whereas haplotypes GC1F/S, GC1F/2, GC1S/2, GC2, and GC2/2 were associated with 25-(OH) VD deficiency. In unhealthy patients, only the homozygous genotype of the variant allele of rs7041 (TT) was associated with higher 25-(OH) VD levels, which is the reverse of what had been observed in apparently healthy subjects.

CONCLUSIONS

The rs70141657G/A of CYP2R1 and rs7041T/G and rs4588C/A of vitamin D binding protein genetic polymorphisms were associated with increased risk of vitamin D deficiency among apparently healthy Jordanians.

Vitamin D3 dose requirement to raise 25-hydroxyvitamin D to desirable levels in adolescents: results from a randomized controlled trial

Several organizations issued recommendations on desirable serum 25-hydroxy vitamin D [25(OH)D] levels and doses of vitamin D needed to achieve them. Trials allowing the formulation of evidence-based recommendations in adolescents are scarce. We investigated the ability of two doses of vitamin D3 in achieving recommended vitamin D levels in this age group. Post hoc analyses on data from a 1-year double-blind trial that randomized 336 Lebanese adolescents, aged 13 ± 2 years, to placebo, vitamin D3 at 200 IU/day (low dose), or 2000 IU/day (high dose). Serum 25(OH)D level and proportions of children achieving levels ≥ 20 ng/mL and 30 ng/mL were determined. At baseline, mean 25(OH)D was 15 ± 7 ng/mL, 16.4 ± 7 ng/mL in boys, and 14 ± 8 ng/mL in girls, p=0.003, with a level ≥ 20 ng/mL in 18% and ≥ 30 ng/mL in 5% of subjects. At 1 year, mean levels were 18.6 ± 6.6 ng/mL in the low-dose group, 17.1 ± 6 ng/mL in girls, and 20.2 ± 7 ng/mL in boys, p=0.01, and 36.3 ± 22.3 ng/mL in the high-dose group, with no sex differences. 25(OH)D increased to ≥ 20 ng/mL in 34% of children in the low-dose and 96% in the high-dose group, being higher in boys in the low-dose arm only; it remained ≥ 30 ng/mL in 4% of children in the low-dose arm but increased to 64% in the high-dose arm. Baseline 25(OH)D level, body mass index (BMI), and vitamin D dose assigned were the most significant predictors for reaching a 25(OH)D level ≥ 20 ng/mL and 30 ng/mL. A daily dose of 2000 IU raised 25(OH)D level ≥ 20 ng/mL in 96% of adolescents (98% boys versus 93% girls). Dose-response studies are needed to determine in a definitive manner the daily allowance of vitamin D for Middle Eastern adolescents with a similar profile.