Association between X-ray repair cross-complementing group 1(XRCC1) Arg399Gln polymorphism and endometriosis: A systematic review and meta-analysis.

OBJECTIVE(S): X-ray repair cross-complementing group 1(XRCC1) gene is one of the DNA repair pathway genes playing a vital role in endometriosis risk. Various studies have explored the association between them, however, the results remained inconsistent. So to confirm the association between XRCC1 Arg399Gln polymorphism and the risk of endometriosis, a meta-analysis was conducted. STUDY DESIGN: PubMed, Web of Science, Science Director, Cochrane Library, Google Scholar, China National Knowledge Infrastructure (CNKI) and Wanfang Data databases were searched to identify the all relevant studies before Sep. 30, 2016 focusing on the association between XRCC1 Arg399Gln polymorphism and the risk of endometriosis. Summary odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated and analyzed by Review Manager 5.2 and Stata 12 to assess the strength of the association. Meanwhile, Begg's test was used to check the publication bias. RESULTS: The present meta-analysis identified 6 studies with 646 cases and 616 controls. The overall analysis revealed that the AA genotype exhibited a significant association with a decreased risk for endometriosis compared with GG (OR=0.43, 95%CI=0.20-0.94, P=0.03), GA (OR=0.57, 95%CI=0.35-0.95, P=0.03) and GG+GA (OR=0.54, 95%CI=0.31-0.96, P=0.04) respectively. In addition, subgroup analyses based on varied regions indicated that a total comparisons of allelic and various genetic models had statistical significances among Asians (A allele vs. G allele: OR=0.62, 95%CI=0.48-0.81, P=0.0004; AA vs. GG: OR=0.22, 95%CI=0.11-0.46, P<0.0001; AA vs. GA: OR=0.32, 95%CI=0.16-0.63, P=0.001; AA vs. GG+GA: OR=0.28, 95%CI=0.14-0.54, P=0.0002; AA+GA vs. GG: OR=0.28, 95%CI=0.14-0.54, P=0.008) but not among Middle Eastern. The Begg's test did not reveal any obvious publication bias in the present study. CONCLUSION(S): Our meta-analysis suggested that Arg399Gln in XRCC1 was associated with endometriosis risk. And especially in Asians, the A allele might be a preventive factor for this disease. Further well-designed researches with larger sample size and various regions are required to validate our conclusion.

Associations of C677T polymorphism in methylenetetrahydrofolate reductase (MTHFR) gene with male infertility risk: A meta-analysis.

PURPOSE: Methylenetetrahydrofolate reductase is one of the key enzymes in folate metabolism. But the association between polymorphism and the risk of male infertility is still controversial. Therefore, this study used a meta-analysis on the collection of data to analyze MTHFR gene C677T polymorphism (known as c.665 C>T, rs1801133, p.Ala222Val). METHODS: PubMed, EMBASE, China National Knowledge Infrastructure (CNKI), and Wan fang. Data were searched to identify eligible studies. We sifted the data collection by Hardy-Weinberg equilibrium calculator and used odds ratios (ORs) and 95% confidence intervals (95% CIs) to conduct data through RevMan5.0 and StataSE12.0 software. RESULTS: A total of 15 studies have 3853 patients with infertility and 3613 healthy controls in this meta-analysis. Our results showed that T variant of MTHFR C677T gene polymorphism was significantly associated with an increased risk of male infertility (forT vs. C: OR=1.38, 95% CI=1.18-1.63; for TT vs. CC: OR=1.86, 95% CI=1.36-2.54; for CT vs. CC: OR=1.34, 95% CI=1.03-1.74; for TT vs. CT: OR=1.52, 95% CI=1.26-1.84; for TT vs. CT+CC: OR=1.42, 95% CI=1.19-1.70; for TT+CT versus CC: OR=1.46, 95%CI=1.05-2.04). In addition, the results indicated that T allele had the positive association which was driven by East-asian populations (random: OR=1.44, 95% CI=1.2-1.74; fixed: OR=1.39, 95% CI=1.20-1.61), Middle-eastern populations (random: OR=1.30, 95% CI=1.05-1.63; fixed: OR=1.30, 95% CI=1.05-1.63) and Mixed-race (random: OR=1.96, 95% CI=1.35-2.85; fixed: OR=1.31, 95% CI=1.20-1.43). CONCLUSION: This meta-analysis suggests that MTHFR C677T polymorphism is associated with male infertility.