title: The impact of GPX1 on the association of groundwater selenium and depression: a Project FRONTIER study.
abstract: BACKGROUND
  Prior animal model and human-based studies have linked selenium concentrations to decreased risk for depression; however, this work has not focused on household groundwater levels or specific depressive symptoms. The current study evaluated the link between groundwater selenium levels and depression. We also sought to determine if a functional polymorphism in the glutathione peroxidase 1 (GPX1) gene impacted this link.
  
  
  METHODS
  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).
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Internal Medicine, Institute for Aging & Alzheimer's Disease Research, University of North Texas Health Science Center, Fort Worth, TX 76107, USA. leigh.johnson@unthsc.edu
authors.forename: Leigh A
authors.initials: LA
authors.lastname: Johnson
authors.forename: Jack A
authors.initials: JA
authors.lastname: Phillips
authors.forename: Cortney
authors.initials: C
authors.lastname: Mauer
authors.forename: Melissa
authors.initials: M
authors.lastname: Edwards
authors.forename: Valerie Hobson
authors.initials: VH
authors.lastname: Balldin
authors.forename: James R
authors.initials: JR
authors.lastname: Hall
authors.forename: Robert
authors.initials: R
authors.lastname: Barber
authors.forename: Tori L
authors.initials: TL
authors.lastname: Conger
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Ho
authors.forename: Sid E
authors.initials: SE
authors.lastname: O'Bryant
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000483:Alleles; D003430:Cross-Sectional Studies; D003863:Depression / Q000209:etiology* / Q000235:genetics; D060766:Drinking Water / Q000032:analysis; D005260:Female; D059647:Gene-Environment Interaction; D020022:Genetic Predisposition to Disease / Q000453:epidemiology / Q000235:genetics; D005979:Glutathione Peroxidase / Q000235:genetics*; D060587:Groundwater / Q000032:analysis*; D006720:Homozygote; D006801:Humans; D008297:Male; D008875:Middle Aged; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D012643:Selenium / Q000032:analysis*; D013781:Texas / Q000453:epidemiology; D000094765:Glutathione Peroxidase GPX1
chemical_list: D060766:Drinking Water; D005979:Glutathione Peroxidase; D012643:Selenium; D000094765:Glutathione Peroxidase GPX1; C000722067:GPX1 protein, human