Association of Differing Qatari Genotypes with Vitamin D Metabolites

Association of Differing Qatari Genotypes with Vitamin D Metabolites:



Objective. Genetic studies have identified four Qatari genotypes: Q1 Arab, Bedouin; Q2 Asian/Persian; Q3 African; and a fourth admixed group not fitting into the previous 3 groups. This study was undertaken to determine if there was an increased risk of deficiency of vitamin D and its metabolites associated with differing genotypes, perhaps due to genetic differences in skin pigmentation. Methods. 398 Qatari subjects (220 type 2 diabetes and 178 controls) had their genotype determined by Affymetrix 500 k SNP arrays. Total values of 1,25-dihydroxyvitamin D (1,25(OH)2D), 25-hydroxyvitamin D (25(OH)D), 24,25-dihydroxyvitamin D (24,25(OH)2D), and 25-hydroxy-3epi-vitamin D (3epi-25(OH)D) concentrations were measured by the LC-MS/MS analysis. Results. The distribution was as follows: 164 (41.2%) genotyped Q1, 149 (37.4%) genotyped Q2, 31 (7.8%) genotyped Q3, and 54 (13.6%) genotyped “admixed.” Median levels of 25(OH)D and 3epi-25(OH)D did not differ across Q1, Q2, Q3, and “admixed” genotypes, respectively. 1,25(OH)2D levels were lower () between Q2 and the admixed groups, and 24,25(OH)2D levels were lower () between Q1 and the admixed groups. Vitamin D metabolite levels were lower in females for 25(OH)D, 1,25(OH)2D (), and 24,25(OH)2D (), but 3epi-25(OH)D did not differ (). Diabetes prevalence was not different between genotypes. Total 1,25(OH)2D (), total 24,25(OH)2D (), and total 3epi-25(OH)D () were all significantly lower in diabetes patients compared to controls whilst the total 25(OH)D was higher in diabetes than controls ().Conclusion. Whilst 25(OH)D levels did not differ between genotype groups, 1,25(OH)2D and 24,25(OH)2D were lower in the admixed group, suggesting that there are genetic differences in vitamin D metabolism that may be of importance in a population that may allow a more targeted approach to vitamin D replacement. This may be of specific importance in vitamin D replacement strategies with the Q2 genotype requiring less, and the other genotypes requiring more to increase 1,25(OH)2D. Whilst overall the group was vitamin D deficient, total 25(OH)D was higher in diabetes, but 1,25(OH)2D, 24,25(OH)2D, and 3epi-25(OH)D were lower in diabetes that did not affect the relationship to genotype.