Compound shown to affect gene activity at extremely low concentrations
a ubiquitous pollutant that has a potent effect on gene activity, could
be promoting obesity, according to an article in the December issue of
The chemical is used in antifouling paints for boats, as a wood and
textile preservative, and as a pesticide on high-value food crops,
among many other applications.
Tributyltin affects sensitive receptors in the cells of animals,
from water fleas to humans, at very low concentrations—a thousand times
lower than pollutants that are known to interfere with sexual
development of wildlife species. Tributyltin and its relatives are
highly toxic to mollusks, causing female snails to develop male sexual
characteristics, and it bioaccumulates in fish and shellfish.
The harmful effects of the chemical on the liver and the nervous and
immune systems in mammals are well known, but its powerful effects on
the cellular components known as retinoid X receptors (RXRs) in a range
of species are a recent discovery. When activated, RXRs can migrate
into the nuclei of cells and switch on genes that cause the growth of
fat storage cells and regulate whole body metabolism; compounds that
affect a related receptor often associated with RXRs are now used to
treat diabetes. RXRs are normally activated by signaling molecules
found throughout the body.
BioScience article, by Taisen Iguchi and Yoshinao Katsu,
of the Graduate University for Advanced Studies in Japan, describes how
RXRs and related receptors are also strongly activated by tributyltin
and similar chemicals. Tributyltin impairs reproduction in water fleas
through its effects on a receptor similar to the RXR. In addition,
tributyltin causes the growth of excess fatty tissue in newborn mice
exposed to it in utero. The effects of tributytin on RXR-like nuclear
receptors might therefore be widespread throughout the animal kingdom.
The rise in obesity in humans over the past 40 years parallels the
increased use of industrial chemicals over the same period. Iguchi and
Katsu maintain that it is "plausible and provocative" to associate the
obesity epidemic to chemical triggers present in the modern
environment. Several other ubiquitous pollutants with strong biological
effects, including environmental estrogens such as bisphenol A and
nonylphenol, have been shown to stimulate the growth of fat storage
cells in mice. The role that tributyltin and similar persistent
pollutants may play in the obesity epidemic is now under scrutiny.
noon EST on 1 December and for the remainder of the month, the full
text of the article will be available for free download through the
copy of this Press Release available at http://www.aibs.org/bioscience-press-releases/.
Contact: Jennifer Williams
American Institute of Biological Sciences
BioScience, published 11 times per year, is the journal of the American Institute of Biological Sciences (AIBS).
publishes commentary and peer-reviewed articles covering a wide range
of biological fields, with a focus on "Organisms from Molecules to the
Environment." The journal has been published since 1964. AIBS is an
umbrella organization for professional scientific societies and
organizations that are involved with biology. It represents some 200
member societies and organizations with a combined membership of about