Lizard’s poison may be boon for diabetics
Gila Monster chemical helps stimulate insulin output
IT is one of only two venomous lizards in the world, but the Gila Monster could become an unlikely boon for the health of tens of thousands of Scots.
The poison of the large reptile, native to Mexico and the southern United States, has been found to contain a chemical similar to a human hormone that helps regulate the blood sugar level of diabetics.
Two feet long, with a diet comprising small mammals and birds, the lizard is an unlikely source of medicine. This month, a new type 2 diabetes drug, exenatide, based on the chemical from the garish pink and black lizard, Heloderma suspectum, is available in the UK.
In Scotland, around 150,000 people suffer type 2 diabetes while a further 60,000 are estimated to have the disease without being aware of it.
The number of people with the illness is expected to increase by half over the next decade, partly because of rising obesity.
Exenatide is the first in a new class of medicines known as incretin mimetics. It works by stimulating the pancreas to produce more insulin in response to raised blood sugar, and also influences digestion and appetite.
The Gila Monster’s potent poison, produced by glands in the lower jaw, is used to kill its prey – small mammals and birds. However, the pharmaceutical scientists were more interested in the creature’s spit.
The chemical in its saliva, exendin-4, was found to act in a similar way to the human hormone glucagon-like peptide-1 (GLP-1).
In healthy humans, GLP-1 stimulates beta cells in the pancreas to produce insulin when blood sugar levels get too high.
But in type 2 diabetics, the GLP-1 message system can break down. The signal to make more insulin is weak or missing, and serious illness can result.
Working together, scientists from the drug companies Eli Lilly and Amylin Pharmaceuticals developed an artificial version of exendin-4 that can be injected into patients. The product, exenatide, was launched in the UK last week under the brand name Byetta.
Dr Michael Trautmann, from Eli Lilly, said: “The development of exenatide is an excellent example of how greater understanding of the physiology of humans can lead to innovative treatment discoveries.
“The GLP-1 mechanism plays an important role as an incretin in regulating blood glucose, intestinal food absorption, and appetite.
“The Gila Monster only eats three or four times a year, and a compound produced in its salivary glands called exendin4 may help it digest these meals very slowly over time. That is an advantageous quality when translated into controlling diabetes.”
Wild populations of the Gila Monster and its cousin the Beaded Lizard – also poisonous – are declining rapidly because of habitat loss and illegal hunting for the pet trade.
This has led conservationists to set up Project Heloderma in central and north America, where the reptiles live.
In recognition of the Gila Monster’s gift to medicine, Eli Lilly is making a charitable contribution to the project over the next three years.
Richard Gibson, curator of herpetology at the Zoological Society of London, said: “The Gila Monster is an amazing reptile and one without which this valuable discovery would not have been made.
“Worryingly, both the Gila Monster and its close relative, the Beaded Lizard, are under serious threat, a situation that Project Heloderma is trying to address.
“I hope that further awareness of its role in this exciting medication will highlight the importance of preserving the habitat of Gila Monsters and related species.”