Amazon frog turns prince for diabetics

Secretions isolated from the skin of a frog from the River Amazon have the potential to deliver completely new treatments for type II diabetes.

A South American tree frog is in the unlikely position of possibly providing a new treatment for people with Type II diabetes. A secretion from the frog's skin stimulates the production of insulin, the essential sugar-regulating hormone that is deficient in those with diabetes.

The Amazonian "paradoxical frog", Pseudis paradoxa, is the hero of the story, along with the group at the University of Ulster who discovered the secretion's effect on insulin-producing beta cells.

The university has a substantial team of researchers including academics, post-doctoral fellows and PhD students looking for naturally occurring substances in plants and frogs that may have an impact on diabetes, explains team leader, Dr Yasser Abdel-Wahab.

"We are looking for bioactive molecules or any compound which stimulates insulin production or reduces blood sugar levels," he explains. It is part of the worldwide effort to find natural substances that have medicinal effects.

In this case the target is for antidiabetic drugs, an important search given the alarming rise in the numbers affected by the disease. There are up to 200,000 diabetics in the Republic according to the Diabetic Federation of Ireland.

At lest 90 per cent of them have Type II, where the body either produces too little insulin or is unable to make use of what insulin is available. Originally considered a disease of middle age, an increasing number of young people are beginning to present with diabetes, making the discovery of new treatments ever more pressing.

"When frogs get attacked by predators they start secreting substances from their skin. It is used as a method of protection," Dr Abdel-Wahab explains. "Once we get the secretion then we start to purify it using analytical chemistry and identify bioactive compounds and peptides."

These can then be tested in vitroto see what effects they have and their mechanism of action is analysed in detail. They are tested for toxicity and the team keeps refining the substance until they isolate the pure active molecule.

Plants and frogs have long served as a novel source of these substances. "It is known that most of the peptides are bioactive," he says. The majority have antimicrobial properties and one discovered some years ago at UU, pseudin-2, was known to have this activity.

His group began studying pseudin-2 to gauge its value in diabetes, going through the rigorous analytical studies to find and isolate the active compound and test its activity. "We have to do all of these studies in parallel."

They quickly discovered that when tested on cultured beta cells pseudin-2 stimulated the cells to increase insulin output. Understanding the mode of action of the molecule encouraged them to modify the substance to make it more bioactive, something that proved quite successful.

"We are at an exciting stage with this research," Dr Abdel-Wahab said. "We have tested a synthetic version of the pseudin-2 peptide and have found that it has the potential for development into a compound for the treatment of Type II diabetes."

They presented their findings, which involved a collaboration with scientists at the United Arab Emirates University, at the Diabetes UK Annual Professional conference earlier this month in Glasgow.

The green and pink paradoxical frog is so named because of the paradox presented by its unusual growth pattern. It starts life as a tadpole 27cm long, but reduces in size as it ages, eventually shrinking to 4cm as an adult.

The substance Pseudis paradoxaproduces could go on to become an important new treatment for diabetes, as has another diabetes drug derived from an unusual source - the saliva of the Gila Monster, a venomous lizard found in the southwest US.