Karolinska Institute. Sweden: Studies conducted at the Karolinska Institutet and Uppsala University in Sweden show that some indigenous groups in the Andes of northern Argentina have increased resistance to arsenic. The researchers also identified the gene that underlies the altered metabolism and protects against exposure to arsenic. This study is the first to show that some humans have genetically adapted to a polluted environment.
Arsenic occurs naturally in the bedrock in many places in the
world and is one of the most potent carcinogens in our environment.
People are exposed mainly through drinking water and food, especially
rice and various rice products. People living in the Argentinean Andes
have likely been exposed to high levels of arsenic in drinking water for
thousands of years. The present study shows that residents who live in
this region today have a clearly higher frequency of gene variants that
enable the body to efficiently handle arsenic by methylating and
excreting a less-toxic arsenic metabolite. By contrast, people who lack
the protective gene variant produce a more-toxic arsenic metabolite if
they are exposed to arsenic. Other communities in neighboring areas
without the same historical arsenic exposure have significantly lower
frequencies of the protective gene variant.
These researchers have identified changes in the main gene for
arsenic metabolism, AS3MT, as the cause of the altered metabolism. Their
results suggest that people have adapted to arsenic via an increase in
the frequency of protective variants of AS3MT. This study is a striking
example of how humans have been able to adapt to local, sometimes
harmful, environmental conditions. Those who survived the exposure to
arsenic lived longer and had more children; thus, the protective gene
variants are very common in some regions of the Andes today. Only a few
such examples have previously been described in man.
Karin Broberg, researcher at the Institute of Environmental Medicine (IMM) at Karolinska Institutet says:
“Our study shows that there are not only
extra-susceptible individuals, but also individuals who are particularly
tolerant to environmental toxicants. This phenomenon is probably not
unique to arsenic, but also applies to other toxicants in food and the
environment, to which humans have been exposed for a long time. The
results also highlight the necessity to be observant and not base health
risk assessments for chemicals on data from people who may have strong
genetic tolerance to the particular chemical.”
Carina Schlebusch, researcher at the Department of Ecology and Genetics at Uppsala University says:
“Only few other studies have found evidence of local
adaptation in humans; for instance adaptation to high altitude
conditions and the malaria parasite. This study adds another example of
how humans have adapted, in
a relatively short time, to tolerate an environmental stressor that they encountered when they settled in a new area.”
The researchers will now study whether other populations with
historical arsenic exposure show an equivalent adaptation, and examine
if other toxic substances in the environment can result in increased
frequency of genetic variants that provide resistance in humans. This
study was supported bySwedish Council for
Working Life and Social Research, the Erik Philip
Sörensen’s Foundation, EU’s Sixth Framework Programme, the Wenner-Gren
Foundations, the Swedish Research Council Formas, and the Swedish
Research Council for Science.
Genotyping was performed by the SNP&SEQ Technology
Platform in Uppsala, Sweden, which is a part of the national research
facility Science for Life Laboratory.
Read more about arsenic at IMM’s Risk Web
Publication:
‘
Human adaptation to arsenic-rich environments
', Carina M Schlebusch, Lucie M Gattepaille, Karin Engström, Marie Vahter, Mattias Jakobsson, Karin Broberg,
Molecular Biology & Evolution
, online 3 March 2015, doi:
doi:
10.1093/molbev/msv046
.