National Center for Environmental Assessment, Office of Research and Development, U.S. Environmental Protection Agency, Washington, DC 20460, USA.
Connecticut Department of Public Health, Hartford, CT 06134, USA.
Environ Int. 2014 Sep;70:88-94. doi: 10.1016/j.envint.2014.05.010. Epub 2014 Jun 6.
The majority of mercury (Hg) exposure in the US population is from consumption of fish contaminated with methylmercury (MeHg). Since inorganic Hg is the predominant form excreted in the feces and urine, hepatic biotransformation is a critical step in its normal clearance. This study was set to test the hypothesis that compromised liver function is associated with body burden of Hg as indirectly reflected by Hg sampled in blood and urine. From the National Health and Nutrition Examination Survey (NHANES, 2003-2008), 3769 adults aged 20 years and above were selected for analysis. Hepatic function was inferred from the three standard serum liver-related enzyme activities, aspartate aminotransferase (AST), alanine aminotransferase (ALT), and γ-glutamyltransferase (GGT). Multivariate regression models were used to examine the associations of interest. Although urinary Hg was significantly correlated with serum Hg, the blood-urinary Hg relationship was influenced by liver function, which is also a function of demographic and lifestyle factors (e.g., gender). Although the results were only marginally significant for examined enzymes (p=0.06-0.08), urinary Hg tended to be lower among subjects with elevated liver enzymes, as compared to those with normal enzyme measurements. Conversely, MeHg generally represents a higher fraction of the total circulating Hg among those with elevated liver enzyme levels, especially among participants with elevations in all three enzymes (p=0.01). In conclusion, this population-based study identified an association between liver function, serum Hg and urinary Hg. Urinalysis may not be the optimal approach to monitor Hg elimination toxicokinetics or Hg exposure, since the majority of Hg excretion is fecal and the fidelity of urinary excretion may depend on healthy liver function. Future prospective studies are warranted to expand these findings.
美国人群中大多数汞（Hg）暴露是由于食用受甲基汞（MeHg）污染的鱼类所致。由于无机汞是粪便和尿液中主要排泄形式，因此肝生物转化是其正常清除的关键步骤。本研究旨在检验以下假设，即受损的肝功能与体内汞负荷有关，这可间接反映在血液和尿液中采集的汞。从 2003-2008 年的国家健康和营养调查（NHANES）中，选择了 3769 名年龄在 20 岁及以上的成年人进行分析。通过三种标准血清肝相关酶活性（天冬氨酸氨基转移酶（AST）、丙氨酸氨基转移酶（ALT）和γ-谷氨酰转移酶（GGT））推断肝功能。使用多变量回归模型来检验相关关联。尽管尿汞与血清汞显著相关，但血液-尿汞关系受到肝功能的影响，而肝功能也是人口统计学和生活方式因素（如性别）的函数。尽管所检查的酶（p=0.06-0.08）的结果仅略有统计学意义，但与正常酶测量值相比，肝酶升高的受试者尿汞水平往往较低。相反，MeHg 通常代表循环总汞中较高的分数，尤其是在肝酶水平升高的参与者中，尤其是在三种酶均升高的参与者中（p=0.01）。总之，这项基于人群的研究确定了肝功能、血清汞和尿汞之间的关联。尿分析可能不是监测汞消除毒代动力学或汞暴露的最佳方法，因为大部分汞排泄是粪便，而尿排泄的准确性可能取决于健康的肝功能。需要进一步的前瞻性研究来扩展这些发现。
