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Journal article: Arsenic metabolism by human gut microbiota upon in vitro digestion of contaminated soils

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  • deborah barrie
    Arsenic metabolism by human gut microbiota upon in vitro digestion of contaminated soils. Van de Wiele, T, CM Gallawa, KM Kubachka, JT Creed, N Basta, EA
    Message 1 of 1 , Jun 30, 2010
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      Arsenic metabolism by human gut microbiota upon in vitro digestion of contaminated soils. Van de Wiele, T, CM Gallawa, KM Kubachka, JT Creed, N Basta, EA Dayton, S Whitacre, GD Laing and K Bradham. 2010.
      Environmental Health Perspectives
      http://dx.doi.org/10.1289/ehp.0901794

      Abstract

      Background: Speciation analysis is essential when evaluating risks from arsenic (As) exposure. In an oral exposure scenario, the importance of presystemic metabolism by gut microorganisms has been evidenced with in vivo animal models and in vitro experiments with animal microbiota. However, it is unclear whether human microbiota display similar As metabolism, especially when present in a contaminated matrix.

      Objectives: We evaluated the metabolic potency of in vitro cultured human colon microbiota toward inorganic As (iAs) and As-contaminated soils.

      Methods: A colon microbial community was cultured in a dynamic model of the human gut. These colon microbiota were incubated with iAs and with As-contaminated urban soils. We determined As speciation analysis using high-performance liquid chromatography coupled with inductively coupled plasma mass spectrometry.

      Results: We found a high degree of methylation for colon digests both of iAs (10 ��g methylarsenical/g biomass/hr) and of As-contaminated soils (up to 28 ��g/g biomass/hr). Besides the formation of monomethylarsonic acid (MMAV), we detected the highly toxic monomethylarsonous acid (MMAIII). Moreover, this is the first description of microbial thiolation leading to monomethylmonothioarsonic acid (MMMTAV). MMMTAV, the toxicokinetic properties of which are not well known, was in many cases a major metabolite.

      Conclusions: Presystemic As metabolism is a significant process in the human body. Toxicokinetic studies aiming to completely elucidate the As metabolic pathway would therefore benefit from incorporating the metabolic potency of human gut microbiota. This will result in more accurate risk characterization associated with As exposures.

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      EHN press release about this research:
      Gut bacteria transforms arsenic, increases its toxicity.
      http://www.environmentalhealthnews.org/ehs/newscience/gut-bacteria-can-increase-toxicity-of-arsenic/. 30 June 2010

      Bacteria living in human intestines can change arsenic's
      chemistry, in some cases producing a more toxic form that is
      linked to cancer. This is the first report of arsenic becoming
      more harmful as it passes through the human digestive track. The
      results parallel those found in animal studies and suggest that
      regulators may need to take into account the way exposures occur
      when determining the health risks associated with arsenic.

      ___________________
      posted by

      Deborah Elaine Barrie
      4 Catherine Street
      Smiths Falls, On
      Canada
      K7A 3Z8
      (613)284-8259
      deborahbarrie@...

      With thanks to Teresa Binstock

      This is something I having been questioning about for years with doctors and scientists. I certainly wonder if it accounts for bloating and inflammation. Arsenic gets into soil through other means as well like road paving, fertilizers, treated wood etc.

      Take care everybody and please keep safe.

      deborah
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