FRIDAY, Feb. 25 (HealthDay News) -- Medical research often
involves a great deal of creativity, finding unique ways to solve
challenging problems. But scientists can face skepticism when using
creative methods to research human diseases, particularly when
those methods involve animals or insects.
Take, for example, the work of one research team, which is
studying fruit flies to help determine the genetic causes of
So how can a person tell if a fruit fly is suffering from memory
loss? And how would that help advance the fight against
A key expert on fruit flies, which are also called
drosophila, said the connection is a fairly simple one: Humans are not that much different genetically from other animals or even insects.
"Anything you can imagine that's alive can be used to study human health and disease," said Laurie Tompkins, chief of the Genetic Mechanisms Branch in the Division of Genetics and Developmental Biology at the U.S. National Institute of General Medical Sciences in Bethesda, Md.
Tompkins, who has studied fruit flies for more than a decade,
noted that animals, insects, plants and even microorganisms have
certain genetic and systemic similarities to humans that can be
exploited by researchers to better understand human illness.
"People have a hard time comprehending that a lot of the processes
that go on in these organisms are similar to those in humans," she
For example, flies share about two-thirds of the same disease
genes found in humans, Tompkins said.
"But to look at a fly, how would you know?" she added. "They look different. They behave differently. How can you tell that what's going on inside is the same?"
As it turns out, one of those genes that exist in both fruit
flies and humans has been linked to the hereditary form of
Alzheimer's disease, which is particularly aggressive in people,
said Thomas A. Jongens, a member of the fruit fly research team and
an associate professor of genetics at the University of
Pennsylvania School of Medicine.
"In familial Alzheimer's, the genetics are pretty well characterized," Jongens said. "The idea is then to go and find what kind of treatments can be done to rescue and prevent this loss of memory and learning."
Jongens' research team decided to use fruit flies to test
treatments that would counter the genetic mutation that causes
Alzheimer's in people.
Studying the disease in flies has several advantages over
studying the disease in humans:
- The flies' life cycle is much shorter, only 60 to 80 days,
Jongens said. A researcher can watch the onset of senility in a fly
over a matter of weeks, whereas studying humans would take years or
- The flies are plentiful and provide much more research
material. For example, the amount of human brain tissue available
for study by Alzheimer's researchers is very limited. "You don't
have available brain samples except for people who have already
died," Tompkins said.
- Researchers can do things to fruit flies that would be
unacceptable on humans, including genetic manipulation to introduce
Jongens' team used a couple of unique methods related to fruit
flies' courtship rituals to study memory and cognition in their
The researchers would place a virgin male fruit fly inside a
chamber with a female fruit fly that had already been mated. The
male fly might try to entice the female into mating, but she would
rebuff him and eventually he would stop showing interest. That
lesson would overlap into the fly's next encounter: Even if he were
next paired with a virgin female ready for mating, his courtship
behavior would be noticeably decreased.
However, male fruit flies with this particular genetic
propensity for Alzheimer's were unable to retain this lesson. They
would keep badgering receptive and unreceptive females alike,
incapable of remembering and learning that some females were not
available for courtship.
The researchers gave their test flies drugs that theoretically
would block the genetic pathways that allow Alzheimer's to take
root. Some of the drugs were experimental; one, lithium, has been
approved by the U.S. Food and Drug Administration for use in
The investigators found that these drugs prevented the onset of
memory and learning loss in the flies, and also allowed them to
recover some of their memory deficits.
"The results suggest there is a window of time when the loss of cognition is reversible through pharmacological treatment," Jongens said. "Maybe there's a window of time in human patients where these pharmacological treatments might have efficacy."
The results cannot automatically be used to recommend treatment
in humans. Jongens believes that testing on mice is the next
logical step. And after that, human clinical trials could be
But the fact that lithium worked as a means of halting this form
of Alzheimer's is a very hopeful finding, he said.
"One might think that would be a drug you would want to start trying immediately in humans, since it is FDA-approved," Jongens said. "It's interesting that it worked in the fly, and it suggests it should be looked at in careful studies."
The Alzheimer's Association has more on
Alzheimer's disease research.