Humans have always linked diabetes with obesity, but grizzlies are shedding some new light on this relationship. Researchers studying grizzly bears, which are clearly obese animals, have discovered a natural state of diabetes that serves a real biological purpose and is also reversible, according to a new study.
The research team hopes that this natural biology can teach how animals naturally cope with conditions that would cause disease in humans.
As described in the journal Cell Metabolism, 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.
During summertime, grizzly bears, or brown bears, use their massive paws to snatch spawning salmon out from rivers, stocking up for hibernation during winter. These brown bears can weigh as much as 800 pounds, according to National Geographic.
While this type of indulgence may seem a recipe for diabetes, it's not. For 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. But when researchers looked at grizzlies they found that, unlike in humans, insulin levels in the animals' blood do not change. Instead, certain cells turn on and off their ability to communicate with and respond to insulin.
Even more surprising, It's when these bears are most obese that that they are also the most insulin sensitive, or least diabetic. They developed this ability by shutting down the activity of a protein called PTEN in fat cells.
"This is in contrast to the common notion that obesity leads to diabetes in humans," lead investigator Dr. Kevin Corbit said in a press release.
In addition, the research team also found that grizzlies somehow store all of the fuel they need during hibernation in fat tissue, not in liver and muscle, which are common places for fat to accumulate in other animals with obesity - likely the result of evolutionary experimentation.
"Our results clearly and convincingly add to an emerging paradigm where diabetes and obesity - in contrast to the prevailing notion that the two always go hand-in-hand - may exist naturally on opposite ends of the metabolic spectrum," Corbit added.
These findings, he says, could lead to the development of therapies targeting similar mechanisms in humans, and could also yield a more holistic approach to diabetes treatment.