The impact of GPX1 on the association of groundwater selenium and depression: a project FRONTIER study

We used a cross-sectional design to analyze data from 585 participants (183 men and 402 women) from Project FRONTIER, a study of rural health in West Texas. Residential selenium concentrations were estimated using Geospatial Information System (GIS) analyses. Linear regression models were created using Geriatric Depression Scale (GDS-30) total and subfactor scores as outcome variables and selenium concentrations as predictor variables. Analyses were re-run after stratification of the sample on GPX1 Pro198Leu genotype (rs1050454).Selenium levels were significantly and negatively related to all GDS and subfactor scores accounting for up to 17% of the variance beyond covariates. Selenium was most strongly protective against depression among homozygous carriers of the C allele at the Pro198Leu polymorphism of the GPX1 gene. Analyses also point towards a gene-environmental interaction between selenium exposure and GPX1 polymorphism.Our results support the link between groundwater selenium levels and decreased depression symptoms. These findings also highlight the need to consider the genetics of the glutathione peroxidase system when examining this relationship, as variation in the GPX1 gene is related to depression risk and significantly influences the protective impact of selenium, which is indicative of a gene-environment interaction.Depression is the most frequently occurring psychiatric disorder [1] with 1 in 10 adults reporting depression [2]. Depression has been shown to have a wide variety of adverse health outcomes including poorer physical and social functioning, and decreased quality of life [3-5] as well as an increase in morbidity and mortality [6-8]. Understanding the link between depression and environmental factors that may influence its occurrence, symptom presentation, and severity, may have a significant impact on our understanding of the biological mechanisms underlying depression and its treatment. Past research has shown relationships between depres