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article imageStudying how bears resist diabetes holds clues for humans

By Tim Sandle     Aug 9, 2014 in Science
Seattle - Bears do not seem to develop diabetes. A new study suggests that a genetic switch in hibernating bears keeps the animals from becoming insulin-resistant.
Bears consume great quantities of food (up to twice their weight) before hibernating. Being obese and sedentary could potentially lead to insulin resistance and, eventually, type 2 diabetes. Certainly such an effect would probably occur in most humans. However, grizzly bears avoid the disease. A new research report has offered a theory as to why bears remain diabetes-free.
The research, NPR summarizes, shows that the bears’ insulin sensitivity is reversed during hibernation. To show this, researchers studied weight fluctuations in six captive grizzly bears over the course of a year to understand how the animals adapted. The scientists discovered that, unlike humans, the bears remained highly sensitive to insulin even at their heaviest: a tiny dose that a person might take proved nearly lethal to the 700-pound bears.
According to Science News, molecular studies subsequently revealed that this insulin sensitivity was controlled by a protein called PTEN. In the fall, PTEN signaling was switched “off” in bear fat cells, which kept the animals responsive to insulin, allowing them to bulk up. Well into the hibernation process, the bears became insulin-resistant. This process was reversed in the springtime, when the animals emerged from hibernation with normal insulin sensitivity.
Lynne Nelson of Washington State University in Pullman and her colleagues, who were behind the study, hope that further studies may help reveal molecular switches relevant to human diabetes.
The findings have been published in the journal Cell Metabolism, in a paper titled "Grizzly Bears Exhibit Augmented Insulin Sensitivity while Obese Prior to a Reversible Insulin Resistance during Hibernation."
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