Abstract
BackgroundThe associations between toll-like receptor 2 (TLR2) and toll-like receptor 4(TLR4) polymorphisms and inflammatory bowel disease (IBD) susceptibility remain controversial. A meta-analysis was performed to assess these associations.MethodsA systematic search was performed to identify all relevant studies relating TLR2 and TLR4 polymorphisms and IBD susceptibility. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated. Subgroup analyses were performed by ethnicity and publication quality.ResultsThirty-eight eligible studies, assessing 10970 cases and 7061 controls were included. No TLR2 Arg677Trp polymorphism was found. No significant association was observed between TLR2 Arg753Gln polymorphism and Crohn’s disease (CD) or ulcerative colitis (UC) in all genetic models. Interestingly, TLR4 Asp299Gly polymorphism was significantly associated with increased risk of CD and UC in all genetic models, except for the additive one in CD. In addition, a statistically significant association between TLR4 Asp299Gly polymorphism and IBD was observed among high quality studies evaluating Caucasians, but not Asians. Associations between TLR4 Thr399Ile polymorphisms and CD risk were found only in the allele and dominant models. The TLR4 Thr399Ile polymorphism was associated with UC risk in pooled results as well as subgroup analysis of high quality publications assessing Caucasians, in allele and dominant models.ConclusionsThe meta-analysis provides evidence that TLR2 Arg753Gln is not associated with CD and UC susceptibility in Asians; TLR4 Asp299Gly is associated with CD and UC susceptibility in Caucasians, but not Asians. TLR4 Thr399Ile may be associated with IBD susceptibility in Caucasians only. Additional well-powered studies of Asp299Gly and other TLR4 variants are warranted.
Highlights
Inflammatory bowel disease (IBD), which mainly consists of ulcerative colitis (UC) and Crohn's disease (CD), is a group of chronic non-specific gastrointestinal inflammatory conditions
No significant association was observed between toll-like receptor 2 (TLR2) Arg753Gln polymorphism and Crohn’s disease (CD) or ulcerative colitis (UC) in all genetic models
TLR4 Asp299Gly polymorphism was significantly associated with increased risk of CD and UC in all genetic models, except for the additive one in CD
Summary
Inflammatory bowel disease (IBD), which mainly consists of ulcerative colitis (UC) and Crohn's disease (CD), is a group of chronic non-specific gastrointestinal inflammatory conditions. IBD is an autoimmune disease that results from an aberrant immune response to intestinal bacteria or other foreign substances as well as genetic factors[2]. Previous studies have demonstrated that genetic polymorphisms contribute to individual variations in the genetic susceptibility to IBD[3]. TLRs play an important role in the digestive system They can recognize invading microbes in the intestinal barrier and activate the immune response. At least 13 TLR family members recognizing different pathogens independently or together in various internal organs have been described, of which TLR2 and TLR4 are most commonly studied for their association with risk of IBD[6]. The associations between toll-like receptor 2 (TLR2) and toll-like receptor 4(TLR4) polymorphisms and inflammatory bowel disease (IBD) susceptibility remain controversial.
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