Association of Glutathione S-Transferase M1 null genotype with inflammatory bowel diseases: A systematic review and meta-analysis

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Background: Ulcerative colitis (UC) and Crohn disease (CD) are the 2 main types of inflammatory bowel diseases (IBDs). Several studies have been conducted to investigate the association of Glutathione S-Transferase M1 (GSTM1) null genotype with UC and CD, but the results are inconsistent. Here, we performed a meta-analysis to clarify this controversy based on relative large sample size. Methods: A systematic article searching was conducted in the PubMed, EMBASE, SCOPUS, WOS, ProQuest, Chinese National Knowledge Infrastructure (CNKI), and Chinese Wanfang databases up to August 31, 2019. Meta-analysis results were synthesized by using crude odds ratio (OR) with its 95% confidence interval (CI). Heterogeneity, sensitivity analysis, subgroup analysis, and publication bias were assessed by using STATA 11.0 software. Results: A total of 15 relevant studies including 4353 IBDs patients (1848 CD cases, 2505 UC cases) and 5413 controls were included in this meta-analysis. Totally, we found a significant association between GSTM1 null genotype and risk to IBDs in the overall populations (OR = 1.37, 95%CI = 1.13−1.65, P = .001). Stratified by ethnicity, we found a significant association between GSTM1 null genotype and risk to IBDs in the Asian population (OR = 2.54, 95%CI = 2.15−3.00, P = .001), but not in the Caucasian population. Stratified by disease type, we found a significant association between GSTM1 null genotype with CD in the Asian population (OR = 2.37, 95%CI = 1.11−5.06, P = .026), and with UC in the Asian (OR = 2.48, 95%CI = 1.93−3.20, P = .001) population. In addition, funnel plot and Egger linear regression test suggests no publication bias in all genetic models. Conclusion: GSTM1 null genotype is associated with susceptibility to IBD, UC, and CD in the Asian population. Further well-designed studies are still needed to confirm these findings.