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Arctic Science Journeys
Radio Script
1996

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Losing Weight with Arctic Ground Squirrels
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STORY: Across Alaska, arctic ground squirrels are stumbling out of their burrows after eight months of winter hibernation. Their first meal must be all the more satisfying because they haven't eaten since September. But come summer, ground squirrels turn into eating fanatics in an all-out effort to put on fat to sustain them during the long slumber ahead.

Because arctic ground squirrels can gain a lot of weight in a short time, they make ideal subjects on which to test a recently discovered hormone called leptin. Leptin curbs the desire for food, and is found in lots of mammals, including humans. Scientists want to know how leptin works so they can develop treatments for human obesity. Bert Boyer is an assistant professor of molecular biology at the University of Alaska Fairbanks.

"The overall goal of the study is to understand how leptin works. We think squirrels are a valuable model to do that because they change the level of body fat and food intake seasonally. So we're using that as a tool, a model system to study how leptin works."

To get the leptin into the squirrel, Boyer surgically implants small pill-shaped cylinders filled with leptin just beneath the squirrel's skin. There, capillaries slowly absorb the hormone into the bloodstream. This is the time when the squirrels should be eating like, well, pigs. But leptin dampened the appetites of six squirrels, while six others that didn't receive the hormone ate normally.

"The idea is that by giving squirrels leptin it should suppress their desire for food and in our first study it indeed did that. It decreased their intake of food by about 75 percent compared to controls receiving normal saline."

Scientists don't know precisely how leptin reduces cravings but they believe it may work as a kind of switch to turn hunger on and off. Boyer says fat cells secrete the hormone into the bloodstream where it is carried to special receptors in the brain. When enough leptin reaches the brain, it sends out a message that says essentially, "Stop eating, I'm full!"

The leptin Boyer is testing on Arctic ground squirrels is made artificially from the gene in mice that codes for the hormone. The National Institutes of Health and Amgen, the pharmaceutical company that owns the rights to leptin, are funding Boyer's research. For Arctic Science Journeys, this is Debra Damron.

Arctic Science Journeys is a radio service highlighting science, culture, and the environment of the circumpolar north. Produced by the Alaska Sea Grant College Program and the University of Alaska Fairbanks.

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