Surprising Insights into Diabetes-Obesity Link in Grizzly Research

A natural state of diabetes that serves a real biological purpose, has been discovered by researchers studying grizzly bears, and this state could be reversible. Investigators reporting in the August 5 issue of the Cell Press journal Cell Metabolism note that grizzly bears are obese but not diabetic in the fall, become diabetic only weeks later in hibernation, and then somehow become "cured" of diabetes when they wake up in the spring. The research reveals how natural biology, through evolutionary experimentation, can teach us new things about how animals naturally cope with conditions that would cause disease in humans.

In humans with type 2 diabetes, cells lose the ability to respond to insulin, a hormone that helps regulate the level of sugar in the body. When investigators looked at grizzly bears, they found that, unlike in humans, insulin levels in the animals' blood do not change. Instead, the cells that insulin communicates with turn on and off their ability to respond to insulin. The team also made the surprising discovery that when grizzlies are most obese, they are also the most insulin sensitive (or least diabetic), and they become this way by shutting down the activity of a protein called PTEN in fat cells.