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Fruit Fly Pancreas
Points to Possible Diabetes Cures
posted September 22, 2004
Fruit flies have cells that function
like a miniature pancreas, which is good news for researchers hoping to use the tiny insects
to develop cures for diabetes.
Almost two years ago Seung Kim, MD, PhD, assistant professor of developmental biology and
of medicine at the Stanford University School of Medicine, found cells in the fruit fly brain that make insulin. These
cells tell the fly's energy-storing organ, called a fat body, to store sugar and fat after a meal, now find the other crucial half
of the pancreatic equation -- cells producing a glucagonlike hormone.
Kim thinks the two cell types in flies represent a primordial pancreas that
scientists can study to better understand how the insulin- and glucagon-producing cells
develop and function in humans. An immediate application could be testing new
drugs before trying them in more expensive lab animals such as mice.
The flies could also provide insights into how pancreatic islet cells form --
information that could help Kim and his colleagues devise ways of coaxing stem cells
to develop into pancreatic cells. "We can try to find out what regulates the development
of those cells and use that information to help make human islet cells," he said, adding that stem cells could
potentially be used to replace the lost insulin-producing cells in people with diabetes.
Although the insulin- and glucagon-making cells in fruit flies aren't clumped
together in a solid organ such as the human pancreas, they faithfully mimic the
functions of their human counterparts. When Kim and Rulifson destroyed the
insulin-producing cells, causing the equivalent of human diabetes, the fat body no longer received a signal
to store sugar and the fly's blood sugar skyrocketed. Wiping out the
glucagon-producing cells caused the blood sugar to plummet, as in the potentially fatal human condition known as
hypoglycemia.
In addition to producing similar molecules, flies and humans have a comparable
mechanism for regulating blood sugar, the researchers found. A protein on the
insulin-producing and glycogen-producing cells in humans alters its shape when
it detects changes in energy levels within the cell. This change triggers the
cell to release insulin or glucagon as needed to keep blood sugar and energy levels within a normal range.
Kim and Rulifson found found that the protein in flies is so similar to the human protein that it responds
to common drugs used by diabetics called sulfonylureas. These drugs work
by helping Sur change shape and allow islet cells to release insulin. These same drugs act on Sur in flies, but the result
is a release of AKH rather than insulin.
"This innovative research by Drs. Kim and Rulifson raises the exciting
possibility that the fruit fly may serve as a model organism for discovering
drugs that affect glucose regulation and hypoglycemia and for better
understanding beta cell and islet development," said Richard Insel, MD,
executive vice president for research at the Juvenile Diabetes Research
Foundation in New York.
Source: Diabetes In Control.com: Sept.
16, 2004 Issue
of Nature.
September 2004
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