Platypus venom may hold diabetes key

An evolutionary twist for monotremes could lead to new treatments for diabetes

Platypus venom could be the key to new type 2 diabetes medications, with researchers surprised to find the animal has weaponised its insulin regulation hormone.

Since our common ancestors parted ways 180 million years ago, monotremes such as the platypus and the echidna have evolved different mechanisms to use the glucagon-like peptide-1 (GLP-1) hormone.

“The new function in venom has basically led to the more stable and more potent GLP-1, but because monotremes also produce the same GLP-1 in their gut, it has the normal function to trigger insulin release,” lead researcher Professor Frank Grutzner, from the department of Genetics and Evolution at the University of Adelaide, said.

It was a fascinating evolutionary twist, he said.

In humans, GLP-1 secreted from the gut is short-lived, with the gut enzymes degrading the hormone within minutes. But the platypus has evolved a long-lasting form of GLP-1, probably because of its novel function in venom, meaning the hormone doesn’t degrade as quickly. This opens up an avenue for the development of a human insulin-releasing medication.

Platypus venom, which is extremely painful to humans, is injected by males from a spur located above the heel of each hind foot.

While it was still an open question, the most likely use for the venom was in competition between males for female mates during the breeding season, Professor Grutzner said.

Venom is usually a complex cocktail of peptides that enhance the effectiveness of the venom. So injecting it into the blood stream or tissue of a human would prompt a number of reactions, including pain.

“But one of the reactions would be to trigger insulin release, which could cause a dramatic drop in blood sugar,” Professor Grutzner said.

“That means the platypus is exposed to its own venom when the males are fighting, but it is also using GLP-1 as its own way to regulate blood glucose,” he said.

“We can see evolutionary traces of this tug of war, between these two functions on the single gene.”

People might see evolutionary medicine as an abstract and theoretical discipline, but discoveries like this were exciting and held great potential for drug development, Professor Grutzner said.

In recent years, researchers have uncovered medical uses in a several strange areas of the animal world. Venom from the Gila monster (a venomous lizard) now underpins a leading drug for type 2 diabetes.

“There is a lot of evolutionary pressure to optimise the function of molecules in venom, because it can be a very important tool for animals either to defend themselves or to fight their prey,” Professor Grutzner said.

Sci Rep 2016; online 29 November