Subject: Arsenic - Not the Same for Everyone
Date: 06-24-05
Authors: Medical News Today
Medical News Today
Environmental Health Perspective
Arsenic - Not the Same for Everyone
Date: 06-24-05
24 Jun 2005
Children with a particular variation in the CYT19 gene metabolize arsenic differently than adults with
the same genetic variant, according to a new research report. The findings have important
implications for the safety of drinking water worldwide and the use of arsenic as a cancer drug.
Arsenic, a heavy metal found around the globe, including the potable water supplies in many parts of
Arizona and the West, has long been known to cause diseases such as circulatory and neurological
disorders and cancer, predominantly of the skin, lung and bladder. In the body, arsenic is converted
into different compounds, some highly toxic, through a series of biochemical reactions. It finally
leaves the body in the urine.
The new research raises the possibility that the risk of developing arsenic-related disease is not the
same for everybody because an individual's genetic makeup determines how the toxic metal is
metabolized.
"Finding genetic determinants of arsenic metabolism may one day enable us to identify a supersusceptible group of people, and conversely, people who may be relatively resistant to the effects of
arsenic," said Walter T. Klimecki, who led the research team. Klimecki is a research assistant
professor of medicine at The University of Arizona's Arizona Respiratory Center and member of UA's
BIO5 Institute.
The study is published in the current edition of Environmental Health Perspectives. Co-authors on the
article are: Maria Mercedes Meza of the Sonora Institute of Technology (Mexico), Lizhi Yu, Yelitza Y.
Rodriguez, Mischa Guild and David Thompson of the UA Arizona Respiratory Center and A. Jay
Gandolfi of the UA department of pharmacology and toxicology.
The research is part of The University of Arizona's Superfund Basic Research Program, which is
funded by the National Institutes of Health's National Institute for Environmental Health Sciences. The
study was also supported by the Sonora Institute of Technology, Mexico.
Studying the distribution of arsenic metabolites in the body is important because they have different
toxic potencies, said Klimecki. "Since we know that people carry different versions of DNA sequence
for any given gene, we ask, 'Do people with one sequence variant metabolize arsenic differently than
people with another sequence variant?'"
Klimecki and his coworkers found that the answer is yes.
The team analyzed arsenic levels in urine samples from 135 individuals from the Yaqui Valley in
Sonora, Mexico, who were exposed to drinking water containing arsenic. The study participants
ranged from 7 to 79 years in age. The researchers then analyzed DNA samples from the same
individuals for variations in three genes known to play roles in arsenic metabolism. When they
matched the arsenic levels in the urine samples to the variations in the genes, the researchers saw
that the distribution of arsenic metabolites was different in urine samples from people with a certain
At that point, Klimecki's team was in for an unexpected discovery. When the team split up the data
into different age groups, it turned out that the association between the particular form of CYT19 and
altered urinary arsenic metabolites could only be found in children. Adults carrying the same variant of
CYT19 do not metabolize arsenic differently. "Apparently the genetic variation affects arsenic
metabolism only during childhood," said Klimecki.
This result could be important for cancer medicine, as arsenic is used as a drug in leukemia therapy.
Individual differences in the way arsenic is metabolized could influence the drug's efficiency. "It
sounds obvious, but researchers often fall into the trap of assuming that children are just miniature
adults," said Klimecki. "Our data really shout out the pitfall in that."
Reference: Developmentally Restricted Genetic Determinants of Human Arsenic Metabolism:
Association between Urinary Methylated Arsenic and CYT19 Polymorphisms in Children. Maria
Mercedes Meza et al., Environmental Health Perspectives, Vol. 113, No. 6, June 2005.
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