title: Has toll-like receptor 4 been prematurely dismissed as an inflammatory bowel disease gene? Association study combined with meta-analysis shows strong evidence for association.
abstract: OBJECTIVE
  Published association studies of the TLR4 Asp299Gly polymorphism and inflammatory bowel disease (IBD) in caucasian populations have inconsistent results. We tested two TLR4 variants for association with IBD in the New Zealand caucasian population and assessed the cumulative evidence for association of TLR4 Asp299Gly and IBD.
  
  
  METHODS
  The TLR4 Asp299Gly and Thr399Ile polymorphisms were genotyped and tested for case-control frequency differences in a New Zealand white cohort of 389 Crohn's disease (CD) patients, 405 ulcerative colitis (UC) patients, and 416 population controls. Meta-analysis using a random effects model was performed to test whether 299Gly carriage was associated with UC, CD, or phenotypes of CD patients.
  
  
  RESULTS
  There were no significant allele or genotype frequency differences between cases and controls or between CD phenotypes in our New Zealand data. Meta-analysis did not identify any significant associations between CD phenotypes and 299Gly carriage. However, meta-analysis demonstrated significantly higher 299Gly carrier frequencies in CD patients (odds ratio 1.45, 95% CI 1.11-1.90) and in IBD patients (odds ratio 1.36, 95% CI 1.01-1.84) compared to controls.
  
  
  CONCLUSIONS
  The meta-analysis provides evidence that Asp299Gly is associated with CD and IBD in whites. Only the Asp299Gly polymorphism has been consistently genotyped in previous TLR4 studies with IBD patients, therefore other TLR4 variants with stronger associations with IBD may exist. Additional well-powered studies of Asp299Gly and other TLR4 variants are urgently needed.
authors.affiliation: Discipline of Nutrition, The University of Auckland, Auckland, New Zealand.
authors.forename: Brian L
authors.initials: BL
authors.lastname: Browning
authors.forename: Claudia
authors.initials: C
authors.lastname: Huebner
authors.forename: Ivonne
authors.initials: I
authors.lastname: Petermann
authors.forename: Richard B
authors.initials: RB
authors.lastname: Gearry
authors.forename: Murray L
authors.initials: ML
authors.lastname: Barclay
authors.forename: Andrew N
authors.initials: AN
authors.lastname: Shelling
authors.forename: Lynnette R
authors.initials: LR
authors.lastname: Ferguson
mesh_terms: D000293:Adolescent; D000328:Adult; D016009:Chi-Square Distribution; D005260:Female; D005787:Gene Frequency; D020022:Genetic Predisposition to Disease; D005838:Genotype; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000208:ethnology / Q000235:genetics*; D016015:Logistic Models; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics; D009520:New Zealand; D010641:Phenotype; D011110:Polymorphism, Genetic / Q000235:genetics; D051197:Toll-Like Receptor 4 / Q000235:genetics*; D044465:White People
chemical_list: D008562:Membrane Glycoproteins; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4