Xin Li

Inefficient arsenic methylation capacity has been associated with various health hazards induced by arsenic. In this study, we aimed to explore the interaction effect of lower arsenic methylation capacity with demographic characteristics on hypertension risk. A total of 512 adult participants (126 hypertension subjects and 386 non-hypertension subjects) residing in an arsenic-endemic area in Inner Mongolia, China were included. Urinary levels of inorganic arsenic (iAs), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) were measured for all subjects. The percentage of urinary arsenic metabolites (iAs%, MMA%, and DMA%), primary methylation index (PMI) and secondary methylation index (SMI) were calculated to assess arsenic methylation capacity of individuals. Results showed that participants carrying a lower methylation capacity, which is characterized by lower DMA% and SMI, have a higher risk of hypertension compared to their corresponding references after adjusting for multiple confounders. A potential synergy between poor arsenic methylation capacity (higher MMA%, lower DMA% and SMI) and older age or higher BMI were detected. The joint effects of higher MMA% and lower SMI with cigarette smoking also suggest some evidence of synergism. The findings of present study indicated that inefficient arsenic methylation capacity was associated with hypertension and the effect might be enhanced by certain demographic factors.

Background: Although some studies mainly from Taiwan, Bangladesh and the United States, have suggested a consistent dose–response increase in the prevalence of hypertension with increasing arsenic exposure, the association between chronic environmental arsenic exposure and the risk of hypertension is still inconclusive. Most of the studies discussed the association from the point of view of arsenic concentration in drinking water or cumulative arsenic exposure (CAE), few involved arsenic speciation into the discussion. In this cross-sectional study, we evaluated the potential association between environmental arsenic exposure through drinking water and the prevalence of hypertension by analyzing not only CAE but also urinary arsenic speciation, and provided data on arsenic exposure and hypertension from mainland of China. Methods: A cross-sectional study was conducted in one of the arsenic contaminated areas in the northwest of China. Among a total of 1005 residents who voluntarily participated in the study, 604 of eligible subjects were confirmed and interviewed door to door. Standing height, body weight, and blood pressure were measured. First void urine was collected and measured for the concentration of urinary arsenic speciation. CAE was calculated in a subpopulation of 360 subjects with detailed water consumption history. The association between urinary arsenic speciation, CAE and the risk of hypertension were analyzed by multiple logistic regressions. Results: We found that the levels of urinary arsenic species of inorganic arsenic (iAs), monomethylated arsenic (MMA), dimethylated arsenic (DMA) and total arsenic (tAs) were significantly correlated with systolic or pulse blood pressure. A positive relationship was found between the highest tertile of CAE and hypertension in a dose-dependent manner. Subjects with higher concentration of urinary MMA or lower percentage of DMA tended to be liable to suffer from hypertension. A significant increasing trend of the risk of hypertension with increasing tertiles of MMA concentration was also observed in the logistic regression models both before and after adjustment for confounders. Conclusions: Our findings suggested that arsenic exposure, especially high level of CAE, was positively associated with the prevalence of hypertension, and that higher concentration of urinary MMA might be related to the increased susceptibility to hypertension.

To observe the effects of arsenic exposure through drinking water on methylation in persons. The levels of inorganic arsenic (iAs), monomethylated arsenic (MMA), dimethylated arsenic (DMA) in blood and urine were detected by atomic absorption spectrophotometer with an arsenic speciation pretreatment system. Total arsenic (tAs), the first methylation index (PMI) and the second methylation index (SMI) were calculated as iAs+ MMA + DMA, (MMA+ DMA)/tAs and DMA/(MMA + DMA), respectively. iAs, MMA, DMA, tAs and PMI in blood of exposed persons were more higher than those of control, while SMI was more lower than that of control. Significant positive correlations were found between urinary MMA and blood PMI (r = 0.419, P < 0.01), while significant negative correlations were found between urinary MMA and blood SMI (r = -0.326, P < 0.05). No significant differences were found in methylation capacity between men and women. The arsenic methylation capacity of the persons exposed to arsenic was different from that of person non-exposed to arsenic, indicating an increase of PMI and decrease of SMI. There were no differences between sex in methylation capacity.