Hopes grow for shrinking frog cure

Richard Collins on an amphibian that may provide the solution to diabetes.

ACCORDING to the Irish Medical Times, an exotic amphibian may be able to help diabetes sufferers. The ‘enigmatic’ or ‘shrinking’ frog, found in lakes and ponds of the Amazon basin and in Trinidad, is a very unusual creature.

Normally, baby animals are much smaller than their parents but, with the shrinking frog, the reverse is the case. The eggs, like those of all frogs, are laid in water and develop into tadpoles. Then something quite extraordinary happens: the tadpoles grow and grow. Some reach a length of 26cm (10 inches) but the adult frogs into which they change are only 4cm long. The shrinking frog is unusual in another respect; teams at the University of Ulster and the Emirates, have been studying a substance found in its skin. Dr Yasser Abdel-Wahab presented some of their findings at the UK diabetes conference in Glasgow this month.

There are about 200,000 diabetes sufferers in Ireland. Obesity is a risk factor, so the disease is becoming more common. Indeed, some experts think that a virtual epidemic is on the way. One of the oldest known human ailments, diabetes afflicted the ancient Egyptians. Sufferers pass large amounts of urine which is sweet to the taste. ‘Diabetes mellitus’ roughly translates as ‘honey-sweet siphon’; doctors would taste a patient’s urine. If it contained excess sugar, it would be sweet, indicating that the body was not controlling its glucose levels.

The pancreas, a large gland close to the liver, produces substances needed for digestion. Towards the end of the 19th Century, German doctors concluded that a malfunction of the pancreas caused diabetes. Something essential for breaking down glucose was not being produced in sufficient quantities. The big breakthrough came in 1921 when three Canadians discovered that it was a hormone, insulin.

Hormones are chemical messengers, part of the body’s public address system. When released into the bloodstream, they trigger responses in targeted cells. Insulin from the pancreas locks onto cells throughout the body, making them extract glucose from the blood, thus keeping sugar levels under control. It also prevents the cells from breaking down proteins. Without this controlling influence, the body actually attacks its own tissues.

Until the discovery of insulin, there was no help for victims. Their condition deteriorated steadily and they died. Nowadays, the disease can be controlled and diabetics lead normal lives.

Patients with the Type 1 form of the disease must have daily injections of insulin to control their glucose levels. Sufferers from the more common Type 2 form may get by on a restricted diet. However, these control measures don’t constitute a cure. Abdel-Wahab and his team have produced a synthetic form of a substance found on the skin of the shrinking frog. Known as Pseudin, the compound increases the production of insulin in Type 2 sufferers.

But why did the frog develop such a substance in the first place? Unlike reptiles, amphibians don’t have watertight skins. Their eggs are laid in water and adult frogs and toads must remain close to water, or risk dehydration. Frogs produce oils which help to keep their skins moist. Water passing into the body through the skin may bring infection with it, so the oils contain compounds which act as disinfectants.

The enigmatic frog is not the only cold-blooded creature to help diabetes sufferers. The gila monster of North America used to appear in the TV show Sesame Street. It is one of only two lizards in the world which have poisonous bites, painful to humans but seldom fatal. The venom contains juices which begin digesting a victim’s body even before it is eaten. Among the juices, a compound called Exendin, which helps to break down blood glucose, has been isolated. Trials of the ‘monster drug’ are under way.

The liver and pancreas are closely related, being derived from similar stem cells. Accordingly, hopes of a cure for diabetes have centred on the liver. Could this, the body’s heaviest organ, which has more than 500 known functions, be stimulated into producing insulin? It seems a long shot, but one of the extraordinary compounds produced by amphibians and reptiles may just do the trick. These creatures are in trouble everywhere. We should look after them; we may need their services.