Altered flies live twice as long

Drosophila melanogaster is used to model human health

Scientists have learnt how to double the lifespan of flies in a study that could have implications for human health.

We are still many steps away from understanding how caloric restriction may affect human lifespan

Dr David Finkelstein

The fruit flies lived for between 69 and 71 days - the animals would normally die after about 37 days - because of an error introduced into a single gene associated with the way their bodies stored and used energy.

Some flies in the study even lived for 110 days.

The gene complex has been named Indy, which stands for "I'm not dead yet" - a reference to a comic sequence in the famous film Monty Python and the Holy Grail. The line is uttered by a supposed plague victim as he is hauled off for burial while still alive.

Drug target

Joking apart, the experiments will help scientists understand the ageing process in humans since we possess a similar DNA sequence.

Dr Stephen Helfand, of the University of Connecticut Health Center, US, said it offered "a target for future drug therapies aimed at extending life".

The gene mutation appears to work by restricting energy absorption on a cellular level - in effect, putting the cells on a diet. This raises the possibility, Dr Helfand said, of one day developing a pill that would both extend life and control weight.

"From what we know about this gene, that makes perfect sense,'' he said.

Courtship ritual

Dr Helfand said a key finding of the study, which is published in the journal Science, is that not only did the fruit flies live longer but they also seemed to maintain a high quality of life.

"It is not an empty or hollow increase in lifespan. It prolongs active adult life, and I think, delays the onset of ageing,'' he said.

Blanka Rogina, a co-author of the study, said female flies with the mutated genes were able to reproduce throughout life. They had the energy for the fruit flies' complex courtship ritual and could lay up to 2,000 eggs in their lifetime, compared with about 1,300 eggs normally, she said.

Indy is the second single gene found to prolong life in fruit flies. The first, named Methuselah, extended lifespan by 35%. However, unlike in the case of Indy, scientists have no idea how Methuselah works.

'Many steps'

Studies of higher animals have already shown that restricting calorie intake can lengthen lifespan. Altering metabolism genetically may have the same effect, scientists speculate.

"What is interesting about this line of research is the recurrence of the link between metabolism, caloric restriction and longevity. This study points to the possibility that if you genetically alter metabolism, you can alter lifespan," said Dr David Finkelstein, research director for metabolic regulation research at the National Institute on Aging.

"While there is an 80% homology between the fruit fly and human genomes, we are still many steps away from understanding how caloric restriction may affect human lifespan," Dr Finkelstein said.

The research was supported in part by the US National Institute on Aging, part of the US National Institutes of Health.