Genetic impact of methylenetetrahydrofolate reductase (MTHFR) polymorphism on the susceptibility to colorectal polyps: a meta-analysis

BACKGROUND: There are several studies with inconsistent conclusions regarding the association between the rs1801133 and rs1801131 polymorphisms within the MTHFR (methylenetetrahydrofolate reductase) gene and colorectal polyp risk. This discrepancy led us to assess the genetic impact of the two polymorphisms on the susceptibility to colorectal polyps. METHODS: A meta-analysis was carried out for quantitative synthesis. According to the inclusion/exclusion criteria, we retrieved, screened and selected all published articles related to colorectal polyps and the MTHFR rs1801133 and rs1801131 polymorphisms. The P value of association test, RRs (risk ratios) and 95% CIs (confidence intervals) were mainly produced. RESULTS: A total of twenty-three case-control studies were included from twenty-two eligible articles. Pooling the results of both rs1801133 and rs1801131 polymorphisms in the overall population suggested a nonsignificant association between colorectal polyp cases and controls, in that all P values in the test of association were larger than 0.05. Nevertheless, pooling results in the “UK” subgroup of rs1801131, comprising five studies (1257 cases/1407 controls), indicated an elevated risk in colorectal polyp cases in comparison with controls, under the genetic models of CC vs. AA (P = 0.032, RR = 1.27, 95% CIs = 1.02, 1.57) and CC vs. AA+AC (P = 0.036, RR = 1.27, 95% CIs = 1.02, 1.60). CONCLUSION: The C/C genotype of MTHFR rs1801131 is more likely to be a genetic risk factor for colorectal polyps in the UK region, although this finding should be verified with a larger sample size. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12881-019-0822-y) contains supplementary material, which is available to authorized users.