It’s not unusual to hear about herbicides having suspected toxic effects or prescription drugs producing side effects. But a new National Institutes of Health (NIH) funded study just published in the Journal of Medicinal Chemistry has found another negative and surprising way common herbicides and fibrate drugs (which are used to lower elevated blood lipids) impact the human body: they block a nutrient-sensing taste receptor on the tongue called T1R3.
So what’s the big deal about this? It turns out there’s emerging evidence these taste receptors are also found in hormone-producing cells in the intestine and pancreas. When working properly, these internal taste receptors in the gut trigger the release of hormones involved in the regulation of normal homeostasis (the ability of the body to maintain internal physiological stability) of glucose as well as energy metabolism. Simply put, screwing up the ability of T1R3 to sense certain nutrients could possibly wreak havoc on the human body in a variety of ways — from playing a role in unhealthy blood sugar levels to causing people to gain weight .
“Compounds that either activate or block T1R3 receptors could have significant metabolic effects, potentially influencing diseases such as obesity, type II diabetes and metabolic syndrome,” said Monell geneticist and study leader Bedrich Mosinger, MD, PhD, in a statement to the media.
For their study, Dr. Mosinger and his research team tested the ability of two classes of chemical compounds to block the T1R3 taste receptor. These compounds were selected because they have strong structural similarities to lactisole, a sweet taste inhibitor that is known to block T1R3. Specifically, the researchers investigated fibrates (a class of drugs often used to lower blood cholesterol, especially triglycerides), and phenoxy herbicides.
Fibrate drugs are sold in the U.S. under several names including gemibrozil (brand name Lopid) and fenobribrate (brand name Tricor). Phenoxy herbicides are chemicals widely used in agricultural fields, on golf courses, rights-of-way and lawns to control broad-leaf weeds. The best known, called 2,4-D, is one of the most extensively used herbicides in the world. According to the Oregon State University Extension Service web site, popular brands of phenoxy herbicides include MCPA, Crossbow, Banvel, Garlon, Weed-B-Gone, and Brush Killer. They are also incorporated into a host of “weed and feed” and brush control products for use on grass.
In laboratory experiments, the researchers found that both classes of compounds were very potent in blocking activation of the human sweet taste receptors. Additional tests showed that this ability of both fibrates and phenoxy herbicides to block T1R3 is specific to humans.
“The metabolic consequences of short and long-term exposures of humans to phenoxy herbicides are unknown. This is because most safety tests were done using animals, which have T1R3 receptors that are insensitive to these compounds,” Dr. Mosinger said in the press statement. “Given the number of compounds used in agriculture, medicine and the food industry that may affect human T1R3 and related receptors, more work is needed to identify the health-related effects of exposure to these compounds.”
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