title: The effect of hydrogen peroxide-induced oxidative stress on leukocytes depends on age and physical training in healthy human subjects carrying the same genotypes of antioxidant enzymes' gene polymorphisms.
abstract: OBJECTIVE
  Reactive oxygen species account for the background levels of oxidatively damaged DNA in normal tissues. Physical exercise increases oxygen consumption and can cause oxidative stress. This stress can also involve deficient antioxidant defenses, which can be influenced by certain genetic polymorphisms. Because regular exercise is a known inducer of antioxidant enzymes, the objective of this study was to compare, by comet assay, differences in the DNA damage between apparently healthy individuals and trained aerobic sportsmen carrying the same single nucleotide polymorphisms of manganese superoxide dismutase (Val9Ala), catalase (-21A/T), glutathione peroxidase 1 (Pro198Leu), before and after exposing leukocytes from peripheral blood to hydrogen peroxide (H₂O₂).
  
  
  METHODS
  Athletes were compared with nonathletes after a situation that promotes reactive oxygen species increase (a race). Blood samples were submitted to genotyping and comet assay, and the athletes and nonathletes were paired according to their gender, age, and MnSOD, CAT, and GPx-1 genotypes.
  
  
  RESULTS
  For nonathletes, there was a positive correlation between H₂O₂ concentrations and DNA damage levels. For athletes, these correlations showed differences between sexes, indicating that running may impose higher oxidative stress on the DNA of women than of men. Significant differences appeared for nonathletes in the comparisons between younger and older age groups after treatment with H₂O₂ at 250 μM.
  
  
  CONCLUSIONS
  This suggests that, for individuals carrying the same genotypes of antioxidant enzymes' genes, the effect of H₂O₂-induced oxidative stress depends mainly on age and physical training. It also suggests that aerobic physical training can reduce oxidative damages to DNA, preventing related diseases in older people.
authors.affiliation: Departamento de Genética e Morfologia, Laboratório de Genética, Instituto de Ciências Biológicas, Universidade de Brasília, Campus Universitário Darcy Ribeiro, Brasília/DF, Brazil. mirandavilela@unb.br
authors.forename: Ana Luisa
authors.initials: AL
authors.lastname: Miranda-Vilela
authors.forename: Penha Cristina Z
authors.initials: PC
authors.lastname: Alves
authors.forename: Arthur K
authors.initials: AK
authors.lastname: Akimoto
authors.forename: Luiz Carlos S
authors.initials: LC
authors.lastname: Pereira
authors.forename: Maria de
authors.initials: Md
authors.lastname: Nazaré Klautau-Guimarães
authors.forename: Cesar K
authors.initials: CK
authors.lastname: Grisolia
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D056352:Athletes; D002374:Catalase / Q000235:genetics; D004249:DNA Damage; D015444:Exercise / Q000502:physiology*; D005260:Female; D005838:Genotype; D005979:Glutathione Peroxidase / Q000235:genetics; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D007962:Leukocytes / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D018384:Oxidative Stress; D010809:Physical Fitness / Q000502:physiology*; D020641:Polymorphism, Single Nucleotide; D012737:Sex Factors; D013482:Superoxide Dismutase / Q000235:genetics; D000094765:Glutathione Peroxidase GPX1
chemical_list: D006861:Hydrogen Peroxide; D002374:Catalase; D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase; D000094765:Glutathione Peroxidase GPX1; C000722067:GPX1 protein, human