A lizard's saliva may not seem like the most obvious place to look for a new weight loss drug, but, in the case of the Gila monster, it proved to be the right strategy. The only venomous lizard that is endemic to the United States, the Gila monster is found in the Southwest and Mexico. Despite its intimidating appearance, it presents little real threat, mainly because it is so sluggish.
Unlike some of its fellow reptiles, the Gila monster does not directly inject venom into its prey. Instead, salivary glands in its lower jaw slowly release venom as it begins to chew. A neurotoxin, the venom causes edema (collection of fluid) and sudden drop in blood pressure.
Over the past decade, researchers have isolated over a dozen proteins and individual toxins from the lizard's saliva. One of these, exendin-4, was found to be almost 50 percent identical to a hormone found in the human digestive tract that boosts the production of insulin when blood sugar levels spike.
A synthetic version of exendin-4, called exenatide, was approved for use by the FDA in 2005 after a three-year study showed that it helped patients with type 2 diabetes maintain healthy blood sugar levels and lose weight. According to a more recent study, the drug could also help nondiabetic individuals lose weight as well: Subjects who received the drug reported losing three times more weight over a six-month period than those who received a placebo.