Polar bears could hold key to osteoporosis cure, study says

RESEARCH CARRIED out by an Irish scientist into polar bears may have “profound implications” for the treatment of osteoporosis, it has been claimed.

The research has found that female polar bears, do not lose any significant bone mass despite hibernating for six months.

From October to March pregnant female polar bears do not eat or drink, yet in the same period they go through pregnancy and birth, and feed their cubs, emerging from hibernation in a state of semi-starvation.

Despite having their calcium levels severely depleted by nursing, they emerge from their dens with normal levels of bone mass.

The findings, by Alanda Lennox, a TCD graduate and zoologist at University College London, and orthopaedic specialist Allen Goodship have been published in the science journal Comparative Biochemistry and Physiology.

Bone packing during long periods of inactivity is the opposite of what happens in other mammals. Even the brown bear are highly susceptible to fractures on emerging from hibernation, while humans, who have been bedridden for a long period , are at risk of fractures and permanent weakening of the bone structure.

A total of 21 pregnant female polar bears were monitored in the Hudson Bay area of northern Canada from early autumn to spring when they usually hibernate. Blood samples from two biochemical markers for bone formation showed that female polar bears build up their bones before entering hibernation.

Having established that polar bears have an extraordinary physiological mechanism for preserving bone structure, Ms Lennox said they intended to publish further research on why this is the case. Explaining why polar bears appear to defy nature while in hibernation could lead to breakthroughs in research for treating osteoporosis in humans either through drugs or dietary intake.

It could also help bone loss in animals subjected to captivity and even astronauts subject to anti-gravity during space light. Bone mass loss in low gravity is seen as one of the main impediments to long-distance space missions.

“It is quite an investment on their part for them [polar bears] to go physiologically through this whole six-month process of starvation and inactivity, predisposing themselves to the potential of fracture on emergence, yet we have just shown that they don’t do that,” said Lennox.

Women are four times more likely to get osteoporosis, mostly as a result of hormonal changes after the menopause. The scientists involved in research on polar bears believe hormonal changes associated with pregnancy are the reasons why the animals are so efficient at maintaining bone mass levels.

“This is at the concept stage. We are hoping to get to the stage where we can say it definitely has implications for use as a natural model to show that osteoporosis can be prevented,” she said.

The theory the scientists are working on is that hormonal changes when polar bears become pregnant causes them to produce an excess of bone mass before they enter the den. So, they can afford to lose bone mass and still show normal levels when they emerge from hibernation.

“If we can figure out the specifics of a physiological mechanism for doing this, then perhaps we could use a similar mechanism as a method of preventing the huge bone loss seen in immobilised humans as a consequence of a stroke or spinal injury,” Lennox said.