Abstract
BackgroundThe frequency of vitamin D-associated gene variants appear to reflect changes in long-term ultraviolet B radiation (UVB) environment, indicating interactions exist between the primary determinant of vitamin D status, UVB exposure and genetic disposition. Such interactions could have health implications, where UVB could modulate the impact of vitamin D genetic variants identified as disease risk factors. However, the current understanding of how vitamin D variants differ between populations from disparate UVB environments is limited, with previous work examining a small pool of variants and restricted populations only.MethodsGenotypic data for 46 variants within multiple vitamin D-related loci (DHCR7/NADSYN1, GC, CYP2R1, CYP11A1, CYP27A1, CYP24A1, VDR, RXRα and RXRγ) was collated from 60 sample sets (2633 subjects) with European, East Asian and Sub-Saharan African origin via the NCBI 1000 Genomes Browser and ALFRED (Allele Frequency Database), with the aim to examine for patterns in the distribution of vitamin D-associated variants across these geographic areas.ResultsThe frequency of all examined genetic variants differed between populations of European, East Asian and Sub-Saharan African ancestry. Changes in the distribution of variants in CYP2R1, CYP11A1, CYP24A1, RXRα and RXRγ genes between these populations are novel findings which have not been previously reported. The distribution of several variants reflected changes in the UVB environment of the population’s ancestry. However, multiple variants displayed population-specific patterns in frequency that appears not to relate to UVB changes.ConclusionsThe reported population differences in vitamin D-related variants provides insight into the extent by which activity of the vitamin D system can differ between cohorts due to genetic variance, with potential consequences for future dietary recommendations and disease outcomes.
Highlights
Ultraviolet B radiation (UVB; 290–320 nm) exposure is the primary factor influencing vitamin D status in humans, with environmental ultraviolet B radiation (UVB) levels varying considerably by latitude and season
Validation of European, East Asian and Sub-Saharan African groups with skin pigmentation single nucleotide polymorphisms (SNPs) The mean allelic frequencies of SLC24A5 rs1426654, SLC45A2 rs16891982 and OCA2 rs1800414 in derived geographic groups did not deviate from previously reported frequencies in populations of European (EUR), East Asian (EAS) and Sub-Saharan African (AFR) ancestry [20, 21]. rs1426654 and rs16891982 frequency were the highest in EUR (0.99 and 0.91, respectively)
Annual UVB levels in European, East Asian and SubSaharan African sample set areas Global mean annual UVB levels and sample set locations are shown in Fig. 1, with the highest mean annual UVB levels found in AFR locations followed by EAS and EUR sample set locations as expected (82.2 vs. 48.1 vs. 18.4 Mw/m2/nm respectively)
Summary
Ultraviolet B radiation (UVB; 290–320 nm) exposure is the primary factor influencing vitamin D status in humans, with environmental UVB levels varying considerably by latitude and season. The frequency of vitamin D-associated gene variants appear to reflect changes in long-term ultraviolet B radiation (UVB) environment, indicating interactions exist between the primary determinant of vitamin D status, UVB exposure and genetic disposition. Such interactions could have health implications, where UVB could modulate the impact of vitamin D genetic variants identified as disease risk factors. The current understanding of how vitamin D variants differ between populations from disparate UVB environments is limited, with previous work examining a small pool of variants and restricted populations only
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