Scientists: Obesity-Chemical Exposure Link Is Both “Plausible and Provocative”

A common pesticide used to kill pests on food crops, boats, wood and textiles could be causing diabetes, according to new research by Japanese scientists published in Bioscience.

The pesticide in question, tributyltin, had already been known to cause chemical burns and other skin irritation, dizziness, difficulty breathing and flulike symptoms to workers exposed to contaminated dust. It had already been known that tributyltin suppresses the immune system, as well as reproductive problems and increased rates of infant mortality and deformities in lab rats. Lab studies have also shown that tributyltin can disrupt the endocrine system of mammals, upsetting hormone levels in the pituitary, gonad and thyroid glands, and causing disruptions to reproductive, immune and nervous systems and the liver.

That’s to say nothing of its effect on marine organisms, which are also well documented. It is highly toxic to mollusks, causes female snails to develop male characteristics, and it builds up in the food chain, affecting predators that consume prey exposed to the chemical.

Now, new research implicates it in the obesity epidemic.

According to the American Institute of Biological Sciences:

“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.

“The 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 tributyltin 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.”

Earlier this year, a National Institutes of Health study fund that a different pesticide, trichlorfon, commonly used on golf courses, was associated with an 85% increase in risk of diabetes for even infrequent users, and a 250% increase in risk for workers who had applied it more than 10 times. The same pesticide has been used to kill cockroaches, crickets, bedbugs, fleas, flies and ticks, but its main current use is on turf, such as at golf courses.

It was the most extreme connection researchers found between pesticide applicators and diabetes, but not the only one. Use of any of the pesticides studied for more than 100 days in a lifetime increased diabetes risk 17%. The other pesticides studied were aldrin, chlordane, heptachlor, dichlorvos, alachlor and cynazine, all of which are chlorinated pesticides.

Diabetes affects nearly 21 million Americans, and rates of disease have been increasing dramatically in recent years, particularly among children.

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