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Thursday, 5 April, 2001, 18:18 GMT 19:18 UK
Hormone key to long life?
Ageing patient and nurse BBC
Hormones may hold the key to ageing, research shows
By BBC News Online's Ivan Noble

Hormones are blamed for many things and now the list is being extended to include growing older.

Insulin vial and syringe BBC
Insulin-like hormones play a vital role
Scientists already know that ageing in a tiny worm called C. elegans is linked to hormones, but new research shows that the same is true of fruit flies and yeast.

If the mechanism works in such widely different creatures, it may well apply to humans as well.

The key, as Marc Tatar, of Brown University, Rhode Island, US, explains, seems to be linked to the hormone insulin.

"We think that in flies and worms, and probably in humans, insulin-like compounds mediate ageing," he said.

Long-life flies

Under normal conditions, insulin causes a receptor in the brain of a fruit fly to release something called juvenile hormone.

This second hormone triggers rapid ageing and reproduction.

When Dr Tatar and his colleagues bred fruit flies with faulty receptors, the flies lived much longer.

"This is the first evidence of the way this ageing mechanism works. It appears that ageing is hormonally regulated," Dr Tatar said.

Side effects

The discovery might not be an immediate answer to those wanting to add a few years to their lifespan, however.

Fruit fly under the microscope BBC
Fruit flies are common subjects for biologists as they breed quickly
There are side effects. Many of the flies with the faulty receptor remained very small.

The females lived 85% longer than normal but remained at dwarf size, while many males died in their first 20 days. Dr Tatar said the findings could lead to more studies on species like mice.

"We'd also like to study how juvenile hormone regulates body ageing. What does it do to tissues and cells, for example?

"Does it increase a fly's resistance to stress or change a fly's immune resistance?" he asked.

More evidence

A team at University College London, UK, has also been trying to find out if the effects of hormones in C. elegans extend to other species, or even humans.

David J Clancy and colleagues found that mutating an insulin-linked gene in fruit flies made them live up to 48% longer. But, as might possibly be expected from a process linked not only to ageing but also to reproduction, some of the flies were much less fertile.

A third study, by Paolo Fabrizzio of the University of Southern California and colleagues, found that mutations in another insulin-linked gene made yeast cells live up to three times longer than normal.

They, too, found side effects. The yeast cells with the mutated gene grew more slowly than their unmutated relations.

Human link

The link between ageing processes in such divergent species shows that the genes at work are what scientists describe as "highly conserved".

Such genes are thought to have developed early on in the process of evolution, before the ancestors of worms, flies and humans went their separate ways.

Many of them are responsible for basic processes of life and, as such, make up a large percentage of the human genome, too.

It is likely but unproven therefore that what is true of worms and flies is also true of humans.

The only catch is that humans have two hormones at work where the worms and flies have one.

In humans, says Dr David Gems at UCL, it is a cousin of insulin called IGF-I which is likely to be responsible for ageing.

The three studies are published in the journal Science.

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