title: Non-monotonic relationships between arsenic and selenium excretion and its implication on arsenic methylation pattern in a Bangladeshi population.
abstract: The toxicity of arsenic differs markedly between individuals and populations, which might be related to the metabolism (methylation) of inorganic arsenic (As), as well as the selenium (Se) nutritional status. Urinary excretion of As (u-As) and Se (u-Se) was examined in an adult population (n=128) living in an As-contaminated area in Bangladesh. Although there was a significant negative correlation between u-Se and u-As (median 137; range 49-927 μg/g creatinine), closer examination revealed a non-monotonous relationship between them. A quadratic curve with an axis of As at 155 μg/g Cre gave a better fit, and u-As and u-Se were positively or negatively correlated depending on whether the As concentration was lower or higher than 155 μg As/g Cre, respectively. Likewise, the relationships between the As methylation pattern and glutathione-S-transferase (GST) polymorphism, body mass index (BMI), and u-Se differed depending on the u-As range; i.e., higher or lower than 155 μg/g Cre. Although we did not determine the causal mechanism for these observations, the non-monotonic relationship between As exposure and the variables examined suggested the existence of a threshold at which the handling of As by human body is qualitatively changed. The possible importance of Se nutrition for As toxicity is also discussed.
authors.affiliation: Department of Human Ecology, School of International Health, Graduate School of Medicine, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Nao
authors.initials: N
authors.lastname: Yoshida
authors.affiliation: Department of Human Ecology, Faculty of Agriculture, Saga University, 1 Honjo-machi, Saga 840-8502, Japan.
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Inaoka
authors.affiliation: Department of Human Ecology, School of International Health, Graduate School of Medicine, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Nayar
authors.initials: N
authors.lastname: Sultana
authors.affiliation: Department of Occupational and Environmental Medicine, Bangladesh University of Health Sciences, Mirpur, Dhaka 1216, Bangladesh.
authors.forename: Sk Akhtar
authors.initials: SA
authors.lastname: Ahmad
authors.affiliation: Department of Human Genetics, School of International Health, Graduate School of Medicine, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Mabuchi
authors.affiliation: Department of Human Ecology, School of International Health, Graduate School of Medicine, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Hana
authors.initials: H
authors.lastname: Shimizu
authors.affiliation: Department of Human Ecology, School of International Health, Graduate School of Medicine, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan. Electronic address: chiho@humeco.m.u-tokyo.ac.jp.
authors.forename: Chiho
authors.initials: C
authors.lastname: Watanabe
mesh_terms: D000328:Adult; D001151:Arsenic / Q000652:urine*; D001459:Bangladesh; D015992:Body Mass Index; D005260:Female; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008297:Male; D008745:Methylation; D008875:Middle Aged; D012643:Selenium / Q000652:urine*
chemical_list: D001151:Arsenic; D005982:Glutathione Transferase; D012643:Selenium; C413545:glutathione S-transferase T1
keywords: Arsenic; Genetic polymorphism; Non-monotonic relationship; Selenium; Urinary arsenic speciation