It may be ugly, but it could save lives

THE naked mole rat is not the prettiest of creatures.

It has no hair, apart from a few whiskers, and its little pink body resembles a half-grown embryo. Two yellow teeth protrude like walrus tusks from the upper jaw, penetrating the lower lip. Big eyes are appealing in an animal but its peepers are tiny. The little rodent may be ugly, but it makes up for this in other ways; its abilities go beyond those of much more famous animals. Not only has it developed immunity to killer diseases which plague us humans, it seems to have stumbled on the key to immortality or, at any rate, longevity. In Move over Lab Rat, in the October 23 edition of New Scientist, Kirsten Weir described some research being done on this intriguing species. Here is the gist of what she had to say.

Small creatures live short lives. The pigmy shrew, for example, lasts about a year, while a brown rat is lucky to reach the age of three even in captivity. Naked mole rats, however, can live for three decades, 10 times as long as other animals of their size. They don’t become senile, suffer from heart disease or develop brittle bones. Females remain fertile to the end of their lives. Cancer has never been detected in mole rats, nor do they develop the disease when injected with cancer cells. So what is their secret elixir of life?

About 20 species of mole rat live in semi-desert regions of Africa. They never see the light of day, their entire lives being spent underground in extensive tunnel networks which they dig. Mole rat society is exceedingly odd by mammal standards; it’s more like that of honeybees. Each community has a ‘queen’, the only female to produce young. Two or three ‘kings’ father her offspring. All other members of the community, which may be up to 80 strong, are temporarily sterile. Soldiers defend the colony against enemies and house-keepers forage for root crops which are the staple food. Cleaners tidy up. When a queen or king dies, a palace revolution ensues as rivals jostle for the top job. Unlike normal mammals, mole rats can’t regulate their body heat. If feeling cold, they visit sections of tunnel close to the surface warmed by the sun.

The environment in the colonies is appalling. There’s an acute shortage of oxygen in the dusty stuffy burrows. Normal air has 21% oxygen, but levels may fall to 12% down below. Carbon dioxide volumes can reach 5% compared to 0.05% above ground and there’s a build-up of ammonia.

According to Weir, the animal’s adaptations to this hostile environment are responsible for its longevity and immunity to diseases. Mole rats can tolerate acute oxygen shortages and survive without oxygen at all for up to half an hour. Research on these abilities, it’s hoped, will lead to better treatments for stroke and heart failure in humans.

Ageing is caused by ‘oxydation damage’ to body cells. Ions, known as ‘free radicals’, attach themselves to DNA, ‘like chewing gum sticking to shoes’, in Weir’s memorable phrase. This causes protein deterioration leading to ageing. Researchers examining mole rat DNA found that it too is oxidised by free radicals but, somehow, the proteins are able to retain their shape for longer than in other species.

Cancer growth is halted by a ‘contact inhibition’ process, which stops cells dividing once a certain density has been reached. The mechanism in humans is controlled by a single gene. In mole rats, there are two genes and their defences are much more effective than ours. Research on the rat’s genetics could lead to breakthroughs in fighting this dreaded disease.

The rats seem to be immune to so-called ‘chemical pain’. Normal pain helps the sufferer, it’s a warning system. For example, pain prompts a person with an injury to go easy on the affected limb. Chemical pain, in response to which the sufferer can’t take any action, is useless. Immunity to this helps mole rats cope with the appalling conditions underground. Discovering its basis may help with anaesthetics and surgery.

Solutions to life’s problems turn up in the most unlikely places!