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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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