Unlocking Hormone Secrets in Bruins May Aid Humans
Do bears hold the secret to preventing osteoporosis? How is it that black bears can hibernate, shut down their systems and not exercise for five or six months over winter, and yet do not develop a bone-loss condition?
At Michigan Technological University in Houghton researcher Seth Donahue is trying to unlock the hormonal secrets that protect bears against the bone disease. It’s hoped that the work eventually will lead to approval of a new drug to fight osteoporosis.
Osteoporosis is a common degenerative bone disease that gradually weakens the bones and may lead to serious fractures later in life. About one in five American women older than 50 develop the disease.
The New York Times says osteoporosis “occurs when the body fails to form enough new bone, when too much old bone is reabsorbed by the body, or both.” The leading causes are a drop in estrogen in women during menopause, and for men, a drop in testosterone. There are different ways to treat osteoporosis, including lifestyle changes – get regular exercise, stop smoking, limit alcohol use and develop a diet that delivers sufficient calcium and vitamin D. It’s often treated with drugs known as bisphosphonates.
Seth, a professor of biomedical engineering, has been studying bears and questions about their resilience to the disease for more than a decade.
He and his colleagues are working to determine whether parathyroid hormone in bears holds the key to protection, as Seth believes. They are focusing on mice with osteoporosis and on a related study that involves human bone-making cells.
“We’re not taking hormone from bears,” Seth says, emphasizing that the research team makes synthetic bear parathyroid hormone in the lab. (There have been times when bones donated by local bear hunters were tested as part of Seth’s research.)
Hibernation reduces energy expenditure; it also slows bone metabolism. One important discovery is that bears, during hibernation, recycle calcium so it’s reabsorbed into the skeleton, Seth explains. Humans, in contrast, excrete calcium in their waste during periods of inactivity, which can lead to loss of bone.
A couple of years ago in Fairbanks, Alaska, Seth gave a seminar on using bears as a model for preventing osteoporosis. There, he told how hibernating bears don’t lose bone mass, but apparently they build stronger bones during the winter shutdown, according to an article by Ned Rozell for Alaska Science Forum.
“Bisphosphonates slow it down, but we need bone-building drugs,” Seth told the symposium.
Seth heads an advisory board for Aursos, a pharmaceutical company seeking approval from the U.S. Food and Drug Administration to use bear parathyroid hormone as a treatment for osteoporosis. That approval may be years down the road, he says, “but if the studies go well, it could be used in humans.”
Michigan Technological University, Houghton, Michigan. 906-487-1885, mtu.edu/research.