Medtronic officials think unlocking the secrets of hibernation could provide insights to better treat heart disease.
|The black bear, or Ursus americanus (Photo courtesy of the Minnesota Department of Natural Resources)|
Suspended animation might still be the stuff of sci-fi for humans, but for bears, it happens every year.
In northwestern Minnesota, the University of Minnesota and Medtronic have spent the past seven years studying how black bears survive hibernation, in hopes of benefiting humans who are bedridden or have heart disease.
Bedridden humans suffer muscle atrophy--including atrophy of the heart--after a short time, but bears can emerge from four to six months of hibernation fully alert and moving, according to a report on the research in the Grand Forks Herald. Until its recent purchase of Ireland-based Covidien, Medtronic was officially headquartered in Minnesota, and it is still operationally run out of Fridley, MN.
"They're in this state of starvation--no exercise, really nothing to drink, so you presume they're dehydrated as well--yet they remain awake," Tim Laske, vice president of research at Medtronic and an adjunct professor at the U of M, told the Herald. "We joke around you can't sneak up on a hibernating bear because they may be staying still in the den, but they're aware of your presence."
That's one bit of knowledge that U of M surgery professor Paul Iaizzo said he has found in 18 years of studying hibernating bears. The university asked Laske to get involved when it wanted to expand its research to the heart, Iaizzo told Qmed on Tuesday.
For the last two years, the researchers have implanted Medtronic Reveal LINQ cardiac monitors beneath the bears' skin. The Reveal is one-third the size of a AAA battery, making it more than 80% smaller than other ICMs.
The Medtronic and U of M researchers accompany staff from by the Minnesota Department of Natural Resources (DNR), which tracks the bears' movements using GPS collars. Medtronic donates equipment for the study and all three partners provide funding and research expertise, according to Laske.
The heart monitors have shown that hibernating bears' hearts slow to five to 10 beats per minute, pausing for 20 to 30 seconds after each exhale, said Iaizzo, also the Medtronic professor of visible heart research. The bears continue to breathe, and their body temperatures drop very little, he added.
The U of M researchers are trying to determine if hormones known as delta opioid agonists (which humans and bears have) and ursodeoxycholic acid (which only bears have) can help protect human organs that have been deprived of oxygen, according to Iaizzo.
"We are routinely giving such agents as pretreatments to animal organs that we recover and try to reanimate in the laboratories," he said. "We're seeing good results."
Brian Barnes at the Institute of Arctic Biology discovered that the Alaskan ground squirrel does not hibernate because it's cold.
"It hibernates because he turns himself off. We don't know what the signal is that turns him on and off," explained Richard Satava, a self-described "technology harvester," a.k.a. a senior science advisor at the U.S. Army Medical Research and Material Command. It is possible to turn small animals on and off in the laboratory, Satava said last year during the LinkedIn Medical Devices Group's conference in the Twin Cities. The trick is how to do it with larger animals, including people.
Researchers the University of Pittsburgh Medical Center are already working on the problem, according to a New York Times story. In a study begun last year, Pitt ER doctors began replacing blood with cold saltwater in trauma victims who come to the emergency room close to death. The idea is to slow metabolism by inducing hypothermia, giving surgeons time to operate and save the patient's life.
The Department of Defense is funding the study, in which patients who survive surgery gradually have their warmed blood returned by a heart-lung machine, the Times story said. Other researchers have performed the technique, known as emergency preservation and resuscitation, on hundreds of dogs and pigs, most without cognitive impairment, the story added.
The human study was to last a couple of years.
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Nancy Crotti is a contributor to Qmed and MPMN.
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