title: Sex differences in the reduction of arsenic methylation capacity as a function of urinary total and inorganic arsenic in Mexican children.
abstract: Chronic arsenic (As) exposure decreases adult and children's ability to methylate inorganic As (iAs); however, few studies have examined children's sex differences. We measured urinary concentrations of iAs, monomethylarsonic (MMA), and dimethylarsinic (DMA) acids, and calculated the primary (PMI: MMA/iAs) and secondary (SMI: DMA/MMA) methylation capacity indexes in 591 children 6-8 years in Torreón, Mexico. We determined iAs, MMA, and DMA by hydride generation cryotrapping AAS. Lineal regression models estimated associations between methylation capacity and total As (TAs) or iAs. Interactions with sex were tested at p<0.10. Boys had significantly higher TAs levels, (58.4µg/L) than girls (46.2µg/L). We observed negative associations between TAs and PMI (β=-0.039; p<0.18) and SMI (β=-0.08; p=0.002) with significant sex differences; PMI reduction was significant in boys (β=-0.09; p=0.02) but not in girls (β=0.021; p=0.63), p for interaction=0.06. In contrast, SMI reduction was significantly more pronounced in girls. Furthermore, negative associations PMI (β=-0.19; p<0.001) and SMI (β=-0.35; p<0.001) were a function of urinary iAs levels, independently of TAs; however, the reduction in PMI was more pronounced in boys (β=-0.24; p<0.001; girls β=-0.15; p<0.001), p for interaction=0.04. A significant negative association was observed between SMI and iAs levels without significant sex differences. TAs and iAs associations with metabolite percentages were in good agreement with those observed with methylation indexes. Our results suggest that iAs plays an important role in reducing As methylation ability and that significant sex differences are present in As metabolism. These differences merit further investigation to confirm our findings and their potential implications for arsenic toxicity in children.
authors.affiliation: Instituto Nacional de Salud Pública, Cuernavaca, Morelos, Mexico.
authors.forename: Luisa
authors.initials: L
authors.lastname: Torres-Sánchez
authors.affiliation: Instituto Nacional de Salud Pública, Cuernavaca, Morelos, Mexico.
authors.forename: Lizbeth
authors.initials: L
authors.lastname: López-Carrillo
authors.affiliation: Escuela de Ciencias Naturales, Universidad Autónoma del Estado de Querétaro, Querétaro, Mexico.
authors.forename: Jorge L
authors.initials: JL
authors.lastname: Rosado
authors.affiliation: International Exchange Program for Minority Students, Mount Sinai School of Medicine, New York, NY, USA.
authors.forename: Valentina M
authors.initials: VM
authors.lastname: Rodriguez
authors.affiliation: Departamento de Farmacología, Centro de Investigación y de Estudios Avanzados del IPN, México City, Mexico.
authors.forename: Eunice
authors.initials: E
authors.lastname: Vera-Aguilar
authors.affiliation: School of Social and Community Medicine, University of Bristol, Bristol, UK.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Kordas
authors.affiliation: Facultad de Medicina, Universidad Juárez del Estado de Durango, Gómez Palacio, Durango, Mexico.
authors.forename: Gonzalo G
authors.initials: GG
authors.lastname: García-Vargas
authors.affiliation: Departamento de Toxicología, Centro de Investigación y de Estudios Avanzados del IPN, México City, Mexico. Electronic address: mcebrian@cinvestav.mx.
authors.forename: Mariano E
authors.initials: ME
authors.lastname: Cebrian
mesh_terms: D001151:Arsenic / Q000378:metabolism* / Q000652:urine; D001152:Arsenicals / Q000652:urine*; D002101:Cacodylic Acid / Q000652:urine*; D002648:Child; D004784:Environmental Monitoring; D004785:Environmental Pollutants / Q000378:metabolism* / Q000652:urine; D005260:Female; D006801:Humans; D008297:Male; D008745:Methylation; D008800:Mexico; D012727:Sex Characteristics
chemical_list: D001152:Arsenicals; D004785:Environmental Pollutants; D002101:Cacodylic Acid; C020300:monomethylarsonic acid; D001151:Arsenic
keywords: Arsenic methylation capacity; Children; Methylation indexes; Mexico