1.Factors affecting arsenic methylation in arsenic-exposed humans：a systematic review and Meta-analysis
Hui SHEN ; Shugang LI ; Qiang NIU ; Mengchuan XU ; Dongsheng RUI ; Shangzhi XU ; Gangling FENG ; Yusong DING
Chinese Journal of Endemiology 2016;35(12):869-874
Objective To explore the regulation and effect factors of arsenic expose and arsenic methylation level, then to provide a reference for study the function of arsenic metabolism in a arsenic poisoning process. Methods A meta-analysis was performed by two researchers. Twenty-five papers satisfying our priori eligibility criteria were included by searching Cochrane library, Pubmed, Springer, Embase and China National Knowledge Infrastructure. Based on the results of heterogeneity, a random or fixed effects model was chosen for the meta-analysis. Results The results showed that the following arsenic metabolites increased (all P<0.01) following arsenic exposure: inorganic arsenic [iAs; standardized mean difference (SMD): 1.07; 95% confidence interval (CI):0.61 - 1.53)], monomethyl arsenic (MMA; SMD: 1.10; 95% CI: 0.81 - 1.40), dimethyl arsenic (DMA; SMD: 2.50;95%CI:1.50-3.69), and total arsenic (TAs, SMD:3.10;95%CI:2.13-4.07). Additionally, the percentages of iAs (iAs%; SMD: 1.00; 95% CI: 0.60 - 1.40) and MMA (MMA%; SMD: 0.49; 95% CI: 0.21 - 0.77) also increased, while the percentage of DMA (DMA%; SMD: - 0.55; 95% CI: - 0.80 - - 0.31) decreased (P<0.01). The primary methylation index (PMI; SMD: - 0.57; 95% CI: - 0.94 - - 0.20), and secondary methylation index (SMI;SMD: - 0.27; 95% CI: - 0.46 - - 0.09) decreased (all P< 0.01). Compared to female, male had higher MMA%(SMD:0.44;95%CI:0.35-0.52), lower DMA%(SMD:-0.33;95%CI:-0.38--0.28) and SMI (SMD:-0.36;95%CI:-0.53--0.19). The smoker had higher MMA%(SMD: 0.22; 95%CI: 0.07 - 0.37) and lower DMA%(SMD:-0.16;95%CI: - 0.26 - - 0.05). The drinker had higher MMA% (SMD: 0.17; 95% CI: 0.07 - 0.27) and lower DMA%(SMD:-0.24;95%CI:-0.39--0.10). The older people had higher MMA%(SMD:-0.23;95%CI:-0.40--0.06). In addition, the body mass index may influence the percentages of MMA (SMD: - 0.18; 95% CI: - 0.31 - - 0.04, P < 0.01). Conclusion Arsenic exposure, smoking, drinking, and older age can reduce the capacity of arsenic methylation. Arsenic methylation is more efficient in women than in men.
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