title: TCF7L2 variant genotypes and type 2 diabetes risk in Brazil: significant association, but not a significant tool for risk stratification in the general population.
abstract: BACKGROUND
  Genetic polymorphisms of the TCF7L2 gene are strongly associated with large increments in type 2 diabetes risk in different populations worldwide. In this study, we aimed to confirm the effect of the TCF7L2 polymorphism rs7903146 on diabetes risk in a Brazilian population and to assess the use of this genetic marker in improving diabetes risk prediction in the general population.
  
  
  METHODS
  We genotyped the single nucleotide polymorphisms (SNP) rs7903146 of the TCF7L2 gene in 560 patients with known coronary disease enrolled in the MASS II (Medicine, Angioplasty, or Surgery Study) Trial and in 1,449 residents of Vitoria, in Southeast Brazil. The associations of this gene variant to diabetes risk and metabolic characteristics in these two different populations were analyzed. To access the potential benefit of using this marker for diabetes risk prediction in the general population we analyzed the impact of this genetic variant on a validated diabetes risk prediction tool based on clinical characteristics developed for the Brazilian general population.
  
  
  RESULTS
  SNP rs7903146 of the TCF7L2 gene was significantly associated with type 2 diabetes in the MASS-II population (OR = 1.57 per T allele, p = 0.0032), confirming, in the Brazilian population, previous reports of the literature. Addition of this polymorphism to an established clinical risk prediction score did not increased model accuracy (both area under ROC curve equal to 0.776).
  
  
  CONCLUSIONS
  TCF7L2 rs7903146 T allele is associated with a 1.57 increased risk for type 2 diabetes in a Brazilian cohort of patients with known coronary heart disease. However, the inclusion of this polymorphism in a risk prediction tool developed for the general population resulted in no improvement of performance. This is the first study, to our knowledge, that has confirmed this recent association in a South American population and adds to the great consistency of this finding in studies around the world. Finally, confirming the biological association of a genetic marker does not guarantee improvement on already established screening tools based solely on demographic variables.
authors.affiliation: Heart Institute, University of São Paulo Medical School, Sao Paulo, Brazil. g.marq2@gmail.com
authors.forename: G F
authors.initials: GF
authors.lastname: Marquezine
authors.forename: A C
authors.initials: AC
authors.lastname: Pereira
authors.forename: A G P
authors.initials: AG
authors.lastname: Sousa
authors.forename: J G
authors.initials: JG
authors.lastname: Mill
authors.forename: W A
authors.initials: WA
authors.lastname: Hueb
authors.forename: J E
authors.initials: JE
authors.lastname: Krieger
mesh_terms: D000368:Aged; D001938:Brazil / Q000453:epidemiology; D015331:Cohort Studies; D003324:Coronary Artery Disease / Q000150:complications / Q000453:epidemiology / Q000235:genetics; D003430:Cross-Sectional Studies; D003924:Diabetes Mellitus, Type 2 / Q000150:complications / Q000453:epidemiology / Q000235:genetics*; D005260:Female; D020022:Genetic Predisposition to Disease; D055106:Genome-Wide Association Study; D005838:Genotype; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D020641:Polymorphism, Single Nucleotide; D012372:ROC Curve; D018570:Risk Assessment; D051820:TCF Transcription Factors / Q000235:genetics*; D058118:Transcription Factor 7-Like 2 Protein
chemical_list: D051820:TCF Transcription Factors; C544894:TCF7L2 protein, human; D058118:Transcription Factor 7-Like 2 Protein