title: Peroxisome proliferator-activated receptor-gamma2 Pro12Ala polymorphism, cod liver oil and risk of type 1 diabetes.
abstract: OBJECTIVE
  We have previously described an association between use of cod liver oil (a dietary n-3 fatty acid supplement) and reduced risk of type 1 diabetes. n-3 fatty acids are ligands for the peroxisome proliferator-activated receptor-gamma (PPARG), which has recently been implicated in the control of inflammation and possibly autoimmunity. We aimed to estimate the association between the common Pro12Ala polymorphism of PPARG2 and risk of type 1 diabetes, and to test whether there is gene-environment interaction with use of cod liver oil in the first year of life or gene-gene interaction with the established insulin gene (INS) and human leukocyte antigen DQ (HLA-DQ) genetic susceptibility loci.
  
  
  METHODS
  We designed a population-based case-control study of childhood-onset type 1 diabetes in Norway with information on use of cod liver oil in the first year of life from questionnaires and PPARG2 genotype data for 483 cases and 1520 control subjects. We used logistic regression for analysis.
  
  
  RESULTS
  The odds ratio for the PPARG2 Ala/Ala or Pro/Ala vs. Pro/Pro genotype and type 1 diabetes was 0.89 (95% CI: 0.69-1.13, p = 0.33). There was no significant interaction with cod liver oil in the first year of life [P (interaction) = 0.35] or with the INS polymorphism [P(interaction) = 0.42].
  
  
  CONCLUSIONS
  Although the association between PPARG2 and type 1 diabetes was not significant, the observed odds ratio was almost identical to that observed in two previous studies and can contribute to meta-analysis indicating a weak but significant association. Our hypothesized interaction between cod liver oil and PPARG2 in reducing type 1 diabetes risk was not supported.
authors.affiliation: Department of Chronic Diseases, Norwegian Institute of Public Health, Oslo,Norway. lars.christian.stene@fhi.no
authors.forename: Lars C
authors.initials: LC
authors.lastname: Stene
authors.forename: Per M
authors.initials: PM
authors.lastname: Thorsby
authors.forename: Jens P
authors.initials: JP
authors.lastname: Berg
authors.forename: Kjersti S
authors.initials: KS
authors.lastname: Rønningen
authors.forename: Geir
authors.initials: G
authors.lastname: Joner
mesh_terms: D000409:Alanine; D019943:Amino Acid Substitution; D016022:Case-Control Studies; D002648:Child; D003060:Cod Liver Oil / Q000627:therapeutic use*; D003922:Diabetes Mellitus, Type 1 / Q000453:epidemiology* / Q000235:genetics*; D015525:Fatty Acids, Omega-3 / Q000627:therapeutic use*; D006801:Humans; D009664:Norway / Q000453:epidemiology; D047495:PPAR gamma / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide; D011392:Proline; D012042:Registries; D012307:Risk Factors
chemical_list: D015525:Fatty Acids, Omega-3; D047495:PPAR gamma; D003060:Cod Liver Oil; D011392:Proline; D000409:Alanine