title: Cardiorespiratory fitness modifies the association between the UCP3-55C>T (rs1800849) polymorphism and plasma homocysteine in Swedish youth.
abstract: OBJECTIVE
  Whether the polymorphisms in the UCP3 gene have an influence on plasma homocysteine levels during youth is not known, and to elucidate the putative modifying role of fitness is also of clinical interest. We analysed the association between polymorphisms in the UCP3 gene and plasma homocysteine in youth and to examine whether fitness modifies this association.
  
  
  METHODS
  The study population comprised 267 Swedish children (8-10 years) and 305 adolescents (14-16 years). Fasting total plasma homocysteine was the outcome variable. We genotyped five UCP3 polymorphisms (rs1800849, rs1800006, rs2075577, rs647126, and rs591758) and one MTHFR 677C>T (rs1801133) polymorphism. Cardiorespiratory fitness was measured with a maximal ergometer bike test.
  
  
  RESULTS
  Youth homozygous or heterozygous for the T allele of the rs1800849 polymorphism had significantly higher levels of homocysteine than those carrying the CC genotype (8.56+/-4.72 micromol/L vs. 7.72+/-2.73 micromol/L, respectively, P=0.011) after adjusting for gender, age, pubertal status, folate and vitamin B(12) intake and MTHFR 677C>T polymorphism, whereas no association was observed for the other analysed polymorphisms. There was a significant interaction effect of fitnessxrs1800849 polymorphism (P=0.042). The effect of the rs1800849 polymorphism on homocysteine levels persisted in youth with low fitness, whereas it was abolished in those with moderate or high cardiorespiratory fitness (P>0.1).
  
  
  CONCLUSIONS
  Cardiorespiratory fitness modifies the association between the rs1800849 polymorphism and homocysteine so that the negative effect of the T allele does not persist in youth with moderate to high levels of fitness.
authors.affiliation: Department of Nutrition and Food Science, University of the Basque Country, 01006 Vitoria, Spain.
authors.forename: Idoia
authors.initials: I
authors.lastname: Labayen
authors.forename: Lovisa A
authors.initials: LA
authors.lastname: Olsson
authors.forename: Francisco B
authors.initials: FB
authors.lastname: Ortega
authors.forename: Torbjörn K
authors.initials: TK
authors.lastname: Nilsson
authors.forename: Michael
authors.initials: M
authors.lastname: Sjöström
authors.forename: Alejandro
authors.initials: A
authors.lastname: Lucia
authors.forename: Jonatan R
authors.initials: JR
authors.lastname: Ruiz
mesh_terms: D000293:Adolescent; D002320:Cardiovascular Physiological Phenomena / Q000235:genetics*; D002648:Child; D016552:Ergometry; D006710:Homocysteine / Q000097:blood*; D006801:Humans; D010809:Physical Fitness / Q000502:physiology*; D020641:Polymorphism, Single Nucleotide
chemical_list: D006710:Homocysteine