How is "Selenium" encoded by the genome?
Selenium (Se) is a mineral found in the soil. Natural foods such as nuts, tuna, and grains are good sources of Se. Se plays a crucial role in human metabolism. Still, its role in certain health conditions, particularly among Se sufficient populations, is controversial, warranting further research on dietary or supplemental Se intake for optimal health.
Biomarkers of Se exposure such as blood and nail Se concentrations vary substantially and are influenced by diet, geographical region, supplements, and smoking status. Characterizing genetic variation in response to Se exposure may be especially useful in identifying individuals most susceptible to the adverse effects of Se, who might be advised to avoid Se supplementation. A recent genome-wide association study (GWAS) of blood Se concentrations reported a GW-significant locus at 5q14, harboring the betaine homocysteine S-methyltransferase (BHMT) gene, BHMT2, and dimethylglycine dehydrogenase (DMGDH) gene. Although blood and toenail Se concentrations are validated biomarkers of Se exposure, the latter may reflect a longer average duration of exposure and perhaps a more stable trait amendable to GWAS.
Researchers thus aimed to perform the first GWAS of toenail Se concentrations and compare their findings with those reported for blood Se, enabling insight into the genetic architecture underlying similar traits. In this study, data from a total of 4162 men and women sourced from four independent population-based studies: Coronary Artery Risk Development in Young Adults (CARDIA), Johnston County Osteoarthritis Project (JoCo), Nurses’ Health Study (NHS), and the Health Professionals Follow-up Study (HPFS). The toenail Se was measured using neutron activation analysis. Three SNPs showed significant relationships with toenail Se, which include rs248381 and rs17823744 in the DMGDH gene, and rs7700970 in the BHMT gene. These SNPs are located in the same locus identified in the published GWAS of blood Se based on independent cohorts. Proteins encoded by DMGDH and BHMT play an important role in homocysteine (Hcy) metabolism, which is composed of two pathways. The perturbations of these pathways are usually discussed with reference to their impact on Hcy levels and modification by vitamin B status.
Strengths of the current study include the four independent studies of similar techniques, showing similar data. Future dietary or supplemental Se studies might account for genetic variation in Se response and monitor changes in Se function and Hcy metabolism. Read more about the study here:
https://pubmed.ncbi.nlm.nih.gov/25343990/
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