Arsenic metabolism is influenced by polymorphisms in genes involved in one-carbon metabolism and reduction reactions.

OBJECTIVES: The susceptibility to arsenic (As)-induced diseases differs greatly between individuals, probably to a large extent due to genetic differences in arsenic metabolism. The aim for this study was to identify genetic variants affecting arsenic metabolism. METHODS: We evaluated the association between urinary metabolite pattern and polymorphisms in three gene-groups related to arsenic metabolism: (1) methyltransferases, (2) other genes involved in one-carbon metabolism and (3) genes involved in reduction reactions. Forty-nine polymorphisms were successfully genotyped in indigenous women (N=104) from northern Argentina, exposed to approximately 200 microg/L of arsenic in drinking water, with a unique metabolism with low percent monomethylated arsenic (%MMA) and high percent dimethylated As (%DMA). RESULTS: Genetic factors affecting arsenic metabolite pattern included two polymorphisms in arsenic (+III) methyltransferase (AS3MT) (rs3740400, rs7085104), where carriers had lower %MMA and higher %DMA. These single nucleotide polymorphisms (SNPs) were in strong linkage disequilibrium (LD) with three intronic AS3MT SNPs, previously reported to be associated with arsenic metabolism, indicating the existence of a strongly methylating, population-specific haplotype. The CYP17A1 rs743572, 27kilobasepairs (kbs) upstream of AS3MT, was in strong LD with the AS3MT SNPs and thus had similar effects on the metabolite profile. Smaller effects were also seen for one-carbon metabolism genes choline dehydrogenase (CHDH) (rs9001, rs7626693) and 5-methyltetrahydrofolate-homocysteine methyltransferase reductase (MTRR) (rs1801394) and genes involved in reduction reactions, glutaredoxin (GLRX) (rs3822751) and peroxiredoxin 2 (PRDX2) (rs10427027, rs12151144). Genotypes associated with more beneficial arsenic metabolite profile (low %MMA and/or high %DMA in urine) were more common in this population, which has been exposed to arsenic in drinking water for thousands of years. CONCLUSIONS: Polymorphisms in AS3MT and in genes involved in one-carbon metabolism and reduction reactions affects arsenic metabolism.