Added the following:
In 2007 scientists at New York's Mount Sinai Hospital discovered that the intestine has receptors for sugar identical to those found on the tongue and that these receptors regulate secretion of glucagon-like peptide-1 (GLP-1). GLP-1 is the peptide that is mimicked by the diabetes drug Byetta and which is kept elevated by Januvia and Onglyza. You can read about that finding in this Science Daily report:
Science Daily: Your Gut Has Taste Receptors
In November 2009, these same scientists reported that a very common herbicide 2,4 D blocked this taste receptor, effectively turning off its ability to stimulate the production GLP-1. The fibrate drugs used to lower cholesterol were also found to block the receptor.
Science Daily: Common Herbicides and Fibrates Block Nutrient-Sensing Receptor Found in Gut and Pancreas
What was even more of concern was the discovery that the ability of these compounds to block this gut receptor "did not generalize across species to the rodent form of the receptor." The lead researcher was quoted as saying,
...most safety tests were done using animals, which have T1R3 receptors that are insensitive to these compounds,This takes on additional meaning when you realize that most compounds released into the environment are tested only on animals, not humans. It may help explain why so many supposedly "safe" chemicals are damaging human glucose metabolisms.