Osteoporosis: On the Cutting Edge of Bone Health
Advances in research are changing the way osteoporosis experts think about this widespread disease.
Understanding Bone Remodeling continued...
Now that they understand the importance of bone remodeling, osteoporosis
experts are trying to use that knowledge to help predict osteoporosis risk
factors. They're developing tools known as biomarkers, which are chemical
measures of the rate of bone remodeling that can be found in secretions from
blood or urine. There are already biomarkers for the rate of bone remodeling
that work very well in large population studies, says Heaney, but they do not
yet have markers that work well in the doctor's office, on an individual
patient level. Once more accurate biomarkers are developed, these and advanced
imaging techniques may enormously improve our understanding of who is at
greatest risk from osteoporosis.
"This allows us to focus on where the problem really lies: the excess
remodeling that's making bone fragile," Heaney says.
New Osteoporosis Treatments
A few years ago, Heaney saw an 18-year-old girl who'd been in a serious car
accident. She'd escaped with only a few bruises, and X-rays revealed that she
had unusually high bone density. It turned out that her mother, too, had bone
density well above the average. Heaney and his colleagues at Creighton began
studying the entire family -- over 150 people -- and eventually identified what
they call the "high bone mass gene."
A particular mutation in this gene causes the body to make abnormally high
amounts of a protein called LRP5 (low density lipoprotein receptor-related
protein 5). LRP5 influences how much bone is formed and maintained. "None of
the people with the high bone mass gene had ever broken anything, even if
they'd fallen off the barn roof," says Heaney.
The identification of the high bone mass gene and the chemical signaling
pathway it involves has opened up a wide range of new possibilities for
osteoporosis treatment. "The prospect here is to build an osteoporosis drug or
drugs that cause the body to act as if it has that mutation, building up more
bone," says Heaney. He believes that drugs aimed at this pathway are already in
human testing, but it may take some time before they can come to market.
"Because this pathway acts on other areas of the body besides bone, you have to
be sure that your drug isn't producing unintended results elsewhere."