Sleeping Deeply, Like a Bear

GMD

Blood clots, bedsores, bone loss… there’s a whole host of ailments that bears and other hibernating animals seem to avoid. That’s why doctors and veterinarians are investigating their ability to help humans sleep soundly.

Ole Frøbert, a cardiologist, cozied up to his next patient, gently turning blood-filled tubes and placing the samples into a plastic bag.

But drawing the blood had been more difficult than Frøbert was used to, given the fat, fur and freezing temperatures.

“It’s not easy to puncture a bear vein,” he said.

Normally a doctor who works at Örebro University Hospital in Sweden and Aarhus University in Denmark, Frøbert had snowmobiled and snowshoed into Swedish bear country, eager to answer the question: How exactly do bears survive their long winter snooze without dying?

Bears and other hibernating animals can avoid many health problems, such as blood clots, bed sores, bone loss, and muscle deterioration, during their torpor.

Doctors and veterinarians worldwide are studying hibernators’ deep-sleep ability to develop drugs for treating cardiovascular issues and other conditions in humans.

Frøbert is conducting research on bear blood to gain insight into hibernation. This is part of a wider field of research into hibernating animals.

Thinking of astronauts

Space agencies and militaries are investing in hibernation research to help astronauts in space travel and injured soldiers.

Manuela Thienel, a cardiologist at Ludwig Maximilian University of Munich, said that you can learn a lot from nature. She worked with Frøbert and led a recent study on hibernating bears.

Many medical studies use lab rats and mice to test treatments. This is part of a movement to study other animals and learn how their bodies work. The goal is to develop new medicines for humans.

“I was frustrated with the traditional approach to medical research,” said Frøbert. “With the bear, it’s the other way around,” he said.

The hibernating brown bear is “an animal that doesn’t get disease, but it should,” he said. “This is a living library of biological solutions.”

‘We were onto something’

Brown bears are serious about their sleep. After the furry giants pack on the pounds in the fall, they can hibernate for up to eight months.

Yet no matter how tired, if a person were to try to sleep for that long, it would get ugly: Muscles would atrophy. Bones would weaken. Skin would scab with bed sores.

Hibernation, in fact, isn’t really a form of “sleep” as people experience it. The brown bear’s heart rate can drop to less than 10 beats per minute, which is an extreme level of energy conservation.

Blood was the main focus of Frøbert. For humans, just taking a transatlantic flight boosts the risk of blood clots. But when bears emerge from their dens after their months-long snooze, they are spry and clot-free.

To figure out why, he and Thienel teamed up with bear researchers in Sweden. The team used a helicopter to chase 13 bruins in the summer. In the winter, they stalked the bruins’ dens and collected their blood. Once, a darted bear briefly woke while a capture specialist was moving the bruin from a creek.

Blood cells deteriorate quickly outside the body. They had to transport lab equipment from Germany to a rural house in Sweden to conduct the analysis. Tobias Petzold, another cardiologist on the project, stated that working with blood and platelets requires being very fast.

The key: proteins

The research found that some proteins, like HSP47, were much less present in bear blood during winter compared to summer.

This protein, which appears on the surface of platelets, helps blood cells stick together. When blood clots form after a cut, they stop the body from bleeding and help it heal. But when blood coagulates inside veins and doesn’t dissolve naturally, clots can be deadly.

To see whether the protein had the same effect in humans, the team turned to people with spinal cord injuries. Patients who are similar to hibernating bears do not experience many blood clots. This suggests that their bodies have discovered a method to reduce the amount of protein after an injury.

The team found those patients have far less HSP47 than uninjured people. Pigs that were captive and individuals involved in bed rest experiments have experienced similar circumstances.

Deep sleep

Other animals take hibernation to even greater extremes than bears.

Every autumn, the 13-lined ground squirrel burrows into the dirt, curls into a tiny fuzzball and falls asleep. In contrast to brown bears, the body temperature of these rodents living in the Great Plains drops to just above freezing during hibernation. It shakes its slumber every week or two and then chills again.

Ashley Zehnder, a veterinarian-scientist, wondered what the squirrel does to repair its body repeatedly after almost freezing to death.

Sheand her colleagues at Fauna Bio, a company she co-founded, looked at heart tissue sampled at different times in their hibernation. The team found genes activated in squirrels’ cells to protect and repair the heart when warming back up.

Fauna Bio is testing a compound to mimic the human response as a potential drug to improve heart function after damage, and they aim to start clinical trials soon.

Zehnder said that more people are increasingly examining how data from various species could be used to enhance human health.

Rats and mice are widely used in medical research. They are easy to buy and keep in captivity. Many studies have been conducted using these animals.

‘Crazy projects’

Frøbert initially faced difficulties in securing funding for the brown bear project due to the conservative nature of the medical research community. But ultimately, his team worked with both NASA and the German Aerospace Center.

His team is looking for a chemical to create a new blood thinner with fewer side effects than current drugs. A new drug may be five to 10 years away, the team said.

“We need to have some space for these crazy projects,” Frøbert said.

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The Washington Post

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