title: Folate, Cobalamin, Cysteine, Homocysteine, and Arsenic Metabolism among Children in Bangladesh.
abstract: BACKGROUND
  Approximately 35 million people in Bangladesh are chronically exposed to inorganic arsenic (InAs) in drinking water. Methylation of InAs to monomethylarsonic (MMA) and dimethylarsinic acids (DMA) relies on folate-dependent one-carbon metabolism and facilitates urinary arsenic (uAs) elimination.
  
  
  OBJECTIVE
  We examined the relationships between folate, cobalamin, cysteine, total homocysteine (tHcys), and uAs metabolites in a sample of 6-year-old Bangladeshi children (n = 165).
  
  
  METHODS
  Children provided blood samples for measurement of tHcys, folate, cobalamin, and cysteine, and urine specimens for the measurement of total uAs and As metabolites.
  
  
  RESULTS
  Consistent with our studies in adults, mean tHcys concentrations (7.9 micromol/L) were higher than those reported among children of similar ages in other populations. Nineteen percent of the children had plasma folate concentrations < 9.0 nmol/L. The proportion of total uAs excreted as InAs (%InAs) was inversely correlated with folate (r = -0.20, p = 0.01) and cysteine (r = -0.23, p = 0.003), whereas the correlations between %DMA and both folate (r = 0.12, p = 0.14) and cysteine (r = 0.11, p = 0.15) were positive. Homocysteine was inversely correlated (r = -0.27, p = 0.009) with %MMA in males, and the correlation with %DMA was positive (r = 0.13, p = 0.10).
  
  
  CONCLUSIONS
  These findings suggest that, similar to adults, folate and cysteine facilitate As methylation in children. However, the inverse correlation between tHcys and %MMA, and positive correlation with %DMA, are both opposite to our previous findings in adults. We propose that upregulation of one-carbon metabolism, presumably necessary to meet the considerable demands for DNA and protein biosynthesis during periods of rapid growth, results in both increased tHcys biosynthesis and increased As methylation.
authors.affiliation: Department of Epidemiology, Columbia University, New York, New York 10032, USA.
authors.forename: Megan N
authors.initials: MN
authors.lastname: Hall
authors.forename: Xinhua
authors.initials: X
authors.lastname: Liu
authors.forename: Vesna
authors.initials: V
authors.lastname: Slavkovich
authors.forename: Vesna
authors.initials: V
authors.lastname: Ilievski
authors.forename: J Richard
authors.initials: JR
authors.lastname: Pilsner
authors.forename: Shafiul
authors.initials: S
authors.lastname: Alam
authors.forename: Pam
authors.initials: P
authors.lastname: Factor-Litvak
authors.forename: Joseph H
authors.initials: JH
authors.lastname: Graziano
authors.forename: Mary V
authors.initials: MV
authors.lastname: Gamble
mesh_terms: D001151:Arsenic / Q000378:metabolism / Q000652:urine*; D002648:Child; D003545:Cysteine / Q000097:blood*; D004781:Environmental Exposure; D005260:Female; D005492:Folic Acid / Q000097:blood*; D006710:Homocysteine / Q000097:blood*; D006801:Humans; D016014:Linear Models; D008297:Male; D012737:Sex Factors; D014805:Vitamin B 12 / Q000097:blood*; D014875:Water Pollutants, Radioactive / Q000097:blood* / Q000378:metabolism
chemical_list: D014875:Water Pollutants, Radioactive; D006710:Homocysteine; D005492:Folic Acid; D003545:Cysteine; D001151:Arsenic; D014805:Vitamin B 12