By PAUL RECER
AP Science Writer
WASHINGTON
(AP)--Mutation of a gene whimsically named ``I'm not dead yet''
can double the life span of fruit flies, a laboratory discovery
that researchers said may lead to drugs to help people live longer
and, perhaps, even lose weight.
Researchers
at the University of Connecticut Health Center have found that
the life span of fruit flies was extended from an average of 37
days to 70 days when a gene was modified on a single chromosome.
Some flies in the study lived 110 days.
The same long-life
gene exists in humans, said Dr. Stephen L. Helfand, senior author
of the study, and ``offers a target for future drug therapies
aimed at extending life.''
In human terms,
a doubled life span would be about 150 years.
Helfand said
the gene mutation appears to work by restricting calorie absorption
on a cellular level--in effect, putting the cells on a diet. This
raises the possibility, he 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.
Helfand said
a key finding of the study, which was appearing Friday 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 life span. It prolongs active adult
life, and I think, delays the onset of aging,'' he said.
Some life-extension
studies showed that animals tended to trade vigor and energy for
a longer life, he said.
But the mutant
flies ``do well throughout their longer life,'' Helfand said.
``By the time that 80 to 90 percent of normal flies are dead,
these mutants are still doing just fine.''
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.
The long-life
gene was named for a comical line--``I'm not dead yet''--from
a Monty Python movie, Helfand said. The gene's name was suggested
by co-author Robert A. Reenan and has been shortened to ``Indy.''
``In academic
circles,'' explained Helfand, ``sophomoric humor, such as in Monty
Python, is very common.''
There have
been other studies that found long-life genes in fruit flies and
nematodes. There also have been experiments in mice that show
calorie restriction--a severe diet--can extend life by up to 50
percent.
But Huber
Warner, associate director for research into the biology of aging
at the National Institute of Aging, said the Indy gene discovery
is more significant because ``it may be a different way to get
the same effect that caloric restriction achieved in mice and
other organisms.''
He said it
may be possible to develop a drug that inhibits metabolism in
the same way as the mutated Indy gene. Such a drug would have
to be tested extensively in animals to assure that it is safe,
Warner said.
``If you wanted
to slow metabolism in people, this research suggests that this
could be a way to do it,'' he said. ``It is strictly theoretical
right now, but it is a possibility.''
Helfand and
his colleagues discovered the livelong gene by chance. He said
they were screening a strain of fruit flies in another study and
found that flies were living much longer than normal.
They isolated
the Indy gene and then tested it in a number of different laboratory
fruit fly strains. In all cases, it extended life.
But Helfand
said the researchers discovered that if the gene is mutated too
much, it actually shortens life.
The normal
gene is on two chromosomes of the fruit fly. If one of these genes
is altered, thus reducing the strength of the gene, then the flies
enjoyed a long life. If both genes were knocked out altogether,
said Helfand, the flies actually died sooner, perhaps starving
to death.
``If we restrict
(the gene) a little bit there is a big advantage,'' said Helfand.
``But if we make an animal that has only the mutated gene, we
find that the animal lives a shorter than normal.''
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