PULLMAN, Wash. - Grizzly bears love pastries, can be 50 percent body fat and spend nearly half the year sleeping.
Yet the hibernating bears don't suffer heart attacks, have no hardening of the arteries, no fatty deposits and no circulation issues, said Charles Robbins, director of the Washington State University bear research center.
Robbins, who founded the center in 1986, and other WSU scientists are seeking to learn how bear hearts stay so healthy, and whether the answers can be applied to humans.
"The changes in the heart that occur in hibernation are things you and I couldn't survive," said Lynne Nelson, a veterinary cardiologist who has spent seven years studying the bears. "Yet bear hearts are very healthy."
Scientists have found that grizzly hearts drop from more than 80 beats per minute when bears are awake to less than 20 beats, and sometimes into single digits, when bears are hibernating. Nelson said echocardiograms show blood starting to pool in the heart, but the bears do not suffer clots.
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So far, Nelson and Robbins have only theories to explain how the bears, which share 95 percent of human DNA, maintain healthy hearts. They have published papers saying that protein changes make bear hearts stiffer during hibernation, allowing them to maintain their shape and perhaps avoid the formation of clots. Bears also shut down two of the four heart chambers without suffering damage.
The scientists are also studying beta receptors and beta blockers in bears, which control heart rate.
Washington State's Bear Center is the only university facility in the nation that has adult grizzly bears, Nelson said. Grizzlies are listed as a threatened species, although numbers have rebounded since the 1970s.
Learning how bears cope with being asleep for so long could have implications for long manned space flights, and for humans who are bedridden, scientists say.
Harry Reynolds, a past president of the International Association for Bear Research and Management, said bears make excellent stand-ins for humans in medical research because they share many biological similarities.
"If there is any model species for human medicine and health studies, it's got to be bears," said Reynolds, retired from the Alaska Department of Fish and Game, but still actively involved in bear field studies in Mongolia.
Christopher Servheen, U.S. Fish and Wildlife Service grizzly recovery coordinator, said the studies are important for bears, too. "All the work that comes out of there brings added information about the physiology and food habits and survival of bears."
