Scientists from the University of Alabama and China’s Zhejiang University have revealed the biology behind the bone-loss experienced by millions as they age.  Writing in the journal ‘PNAS’ they explain how the rate of growth for new bone is determined by a protein called Cbf-beta.

For bone growth, young cells, called progenitor cells, are given instructions by genes on how to mature- basically, on what they will grow up to be. Bone marrow could become bone, cartilage or fat cells, for example. When the team looked at what was determining the path of those young cells, they found that Cbf-beta was the determining factor. The Cbf-beta protein was the key between a cell becoming a bone cell or a fat cell.



Cbf-beta cells were deleted at different stages in the growth of progenitor cells in 3 groups of mice. In each group, fat cells were found in the bone marrow, also in the progenitor cells. This was similar to the pattern found in Osteoporosis in humans. The mice were all suffering from severe osteoporosis. It was further determined that the Cbf-beta protein acted as a switch to turn-off production of the expression of a gene which directed progenitor cells to become fat cells.



Osteoporosis is caused when too little new bone is produced.  This results in an imbalance and old bone is re-absorbed at a greater pace than the new bone replaces it.  This, again, results in a loss of density as the bones become more porous and sponge-like.  They will become very fragile and liable to fracture. After 35 years of age, bone mass naturally decreases as the body ages.  This decrease in bone density is more marked in women than in men, particularly after menopause- hence the greater incidence of Osteoporosis in women than men.

Genetics can be a key risk factor for Osteoporosis, but smoking, alcohol consumption, lack of exercise, deficiency in vitamin D and calcium, rheumatoid arthritis and family history can all play their part. Those with slim or small frames are also particularly susceptible. Though any skeletal bone is open to the increased risk of fracture, the hips, wrists, ribs and spine tend to be the most vulnerable.



It is estimated that 1 in 3 women over 50 and 1 in 5 men over 50 endure fractured bones due to osteoporosis. 1 in 2 experiencing a hip fracture will die within 12 months of incurring that fracture.  In the west, over 50% of the population, of that same age, are thought to suffer from bone density problems that are severe enough to fall in to the category of osteoporosis.



Hitherto, treatment has focused on lifestyle changes- giving up smoking and drinking while exercising more. This has been supplemented with medications to promote bone formation. 

The new study offers the hope of a more effective, early treatment directed at the root cause of the problem.