Jake Port
Jake Port contributes to the Cosmos explainer series.
Platypuses aren’t entirely the cuddly creatures they appear to be. They boast spurs loaded with excruciating venom – but these painful compounds could be good news for people with diabetes.
Researchers in Australia found a hormone in platypus venom called GLP-1 is also produced in their gut to regulate blood glucose levels. And while the human form of the hormone degrades within minutes, the platypus version lasts hours – which could form the basis of long-lasting diabetes treatment.
The work was published in Scientific Reports.
In animals such as humans and platypuses (Ornithorhynchus anatinus), GLP-1, or glucagon-like peptide-1, stimulates production of insulin, a hormone that signals cells to scoop sugar from the bloodstream.
But patients with type 2 diabetes – a condition that will develop in at least one in three Americans (PDF download) – are unable to use insulin properly. And the short period that GLP-1 stimulates insulin before breaking apart isn’t long enough to regulate sugar levels.
It turns out a longer lasting form of GLP-1 is found in monotremes – a group of egg-laying mammals comprising platypuses and echidnas (family Tachyglossidae).
(Like platypuses, echidnas wield spurs on their hind legs, but unlike platypuses, they aren’t venomous, so echidna GLP-1 is found only in the gut.)
Normally, GLP-1 is degraded by a protein called dipeptidyl peptidase-4. But to the surprise of the University of Adelaide’s Enkhjargal Tsend-Ayush, Chuan He and their colleagues, monotreme GLP-1 resisted dipeptidyl peptidase-4 degradation, surviving at least four hours.
The team believes that this dual-purpose form of GLP-1 may have evolved from a biological arms race within the species.
During mating season, males fight off competitors using their spurs, around 1.5 centimetres long, that inject poison produced in a gland in their thigh.
If a platypus cops a dose of venom, its blood sugar levels drop – not a great thing to happen in a fight.
To counteract this, monotreme GLP-1 is 50 times less potent than human GLP-1 so they don’t die of hypoglycaemia.
“The lack of a spur on echidnas remains an evolutionary mystery, but the fact that both platypus and echidnas have evolved the same long-lasting form of the hormone GLP-1 is in itself a very exciting finding,” says study senior author Frank Grutzner, also from the University of Adelaide.
By better understanding the differences between monotreme and human GLP-1, it’s hoped that a long-lasting form of the hormone could be developed for use in type 2 diabetes medication.
