Hibernating bears could hold a clue to treating diabetes
Scientists have discovered eight key proteins–also found in people–that help keep grizzly bears diabetes free.
Published September 27, 2022
6 min read
If a human ate tens of thousands of calories a day, ballooned in size, then barely moved for months, the health outcomes would be catastrophic. Scientists have long been puzzled why this same behavior doesn’t lead to diabetes in grizzly bears–until now.
By feeding honey water to hibernating bears, researchers at Washington State University have discovered genetic clues to how these bruins can control their insulin. Their results–published in iScience–might lead to better diabetes treatments for people.
Insulin is a hormone found in most mammals that regulates the body’s blood sugar levels, for instance by telling the liver, muscle, and fat cells to absorb blood sugar, a source of energy. If there is too much sugar in the bloodstream, the cells will become resistant to insulin. This is a leading cause of Type 2 diabetes, a disease that can lead to heart attacks, strokes, and blindness. About 1 in 10 Americans, or about 37 million people, have Type 2 diabetes. Bears, however, can control their insulin resistance like a switch, which is something that humans cannot do.
To find out how, researchers drew blood serum from six captive grizzly bears–aged between five and 13 years–at the WSU Bear Center, a research facility in Pullman, Washington. They also collected fat tissue from bears to use in growing cell cultures in the lab. “It gives us a way to test things that we couldn’t do in a fully grown bear,” says study co-author Blair Perry, a postdoctoral researcher at the university. (Read how bottlenose dolphins can turn diabetes on and off. )
This experiment helped the team narrow down the bears’ secret to controlling their insulin: Eight key proteins that seem to have a unique role in bear biology, working either independently or together to regulate insulin during hibernation.
Because humans share most of our genes with bears, understanding the role of these eight proteins could teach scientists more about human insulin resistance, Perry says.
Bear seasons
Grizzly bears–found in parts of the western U.S., Canada, and Alaska–experience three stages in a year: Active, hyperphagia, and hibernation. The massive mammals spend the spring and summer foraging, mating, caring for their young, and then transition into hyperphagia. Perry states that the animals then go into hyperphagia in the fall when they “pretty much all of their energy is devoted towards eating as much as they can.” (Read about the fascinating ways animals prepare for fall. )
During this time, bears consume up to 20,000 daily calories and gain up to eight pounds each day to prepare for the upcoming winter.
When the bears begin hibernating in early winter, they rely on their fat deposits to sustain them through the cold months. Perry says hibernation is more than a deep sleep. “Lots physiological changes allow bears survive these long winters, without food.” Their metabolic rate and heart rate decreases, and they become insulin-resistant.
Hibernating bears experience periods of wakefulness, during which they move around but don’t eat. The team fed the bears honey water, a favorite treat, when they awoke. They then collected their blood for two weeks. The team had already taken blood samples from the bears in the spring and summer.
Next, in the lab, the researchers combined various blood serums with cell cultures of various types–for instance, they mixed a cell culture from fat tissue taken from hibernating bears with blood serum taken from active bears. This allowed the team see what genetic changes would take place within the cells.
Of all the combinations studied, the serum taken from the honey-fed hibernating bears helped the most in narrowing down those eight key proteins involved in regulating insulin sensitivity and resistance. (Learn more how bears’ bodies change during hibernation. )
For Mike Sawaya, a bear biologist at Sinopah Wildlife Research Associates who was not involved in the study, the big take home of this “fascinating study” is how many implications bear hibernation can have for human health.
“Identifying those eight proteins is an important step,” he says, as is identifying “exactly what is being turned on and off” when bears change their insulin resistance, he says.
One step closer to diabetes prevention?
While insulin resistance and its consequences are well understood, there is much to learn about its genetics. Perry says that scientists have a unique opportunity to study how insulin resistance occurs in bears each year. (Learn about a link between COVID-19 and developing diabetes. )
For instance, figuring out how to manipulate those eight proteins in people could potentially “reverse a human out of insulin resistance,” Perry says. He says that although such medications or interventions are still far away, “we’re getting closer.”
Sawaya agrees that this is “definitely one more piece of the puzzle” and hopes that unravelling the mysteries of bear physiology could lead to diabetes prevention.
In future studies, the team hopes to investigate exactly how these specific proteins turn off insulin resistance in bears.
The author of 5 books, 3 of which are New York Times bestsellers. I’ve been published in more than 100 newspapers and magazines and am a frequent commentator on NPR.