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Potential allelic determinants of vitamin D deficiency


The genes associated with 25-hydroxycholecalciferol [25(OH) vitamin D] deficiency in regard to osteoporosis risk are proving elusive. Trummer et al. focused on three genes recently identified by genome-wide association studies, genotyping 342 patients within a cross-sectional study of bone mineral density and fracture risk and 1093 people from a prospective cohort study of patients in nursing homes.

The group-specific component (GC, which codes for a vitamin D binding protein) and cytochrome P450IIR-1 (CYP2R1, which codes for one of the cytochrome P450 proteins that is involved in vitamin D signaling) were not associated with BMD or the incidence of past fractures, although there was a significant association between GC genotypes and lower mean serum 25(OH) vitamin D levels in both groups of patients.

A variant in the gene DHCR7, which codes for 7-dehydrocholesterol reductase, an enzyme important in synthesizing vitamin D in the skin, did show a significant association with prospective fracture risk, with an odds ratio of 0.68 (95% CI 0.51–0.92; P=0.011).

Editor's comment: This work was performed on a modestly sized group of patients, but suggests that further study of GC, CYP2R1, and DHCR7 as potential predictive factors and perhaps even therapeutic targets in osteoporotic patients may be warranted.

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