KEY POINTS:
United States research showing it may be possible to boost bone formation by controlling the body chemical serotonin may have negative implications for New Zealand dairy sales campaigns built on fighting osteoporosis.
Existing treatments for osteoporosis largely rely on slowing bone density losses with drugs, or by persuading people to consume calcium supplements in milk or other foods, boosting their load-bearing exercise while young, and manufacturing sufficient vitamin D.
Dairy exporter Fonterra has relied heavily on promoting premium products such as Anlene for their potential to fend off effects of osteoporosis.
It has rolled out free ultrasound bone scans, initially in nine Asian countries, and has predicted that they are likely to be extended to Australia and New Zealand.
Osteoporosis involves bone density loss, and its hallmark is fragile bones that break easily, with most treatments slowing further bone loss rather than increasing bone formation.
Gerard Karsenty, chairman of the department of genetics and development at Columbia University, has just reported in the international scientific journal Cell his discovery of an unexpected system that appears to control bone formation.
At its heart is serotonin made by the gut. Though 95 per cent of the body's serotonin is made by the gut, it cannot enter the brain because it is barred by the blood-brain barrier.
But Dr Karsenty reported that gut serotonin released into the bloodstream can directly control bone formation: the more serotonin that reaches bone, the more bone is lost. Conversely, the less serotonin, the denser and stronger bones become.
Dr Karsenty was able to even prevent menopause-induced osteoporosis in mice engineered to have human genes by slowing serotonin production, stunning other osteoporosis researchers. Christopher Gallagher, an osteoporosis specialist and professor of medicine at Creighton University, said it was a "ground-breaking paper", and Dr Ronald Margolis, senior adviser for molecular endocrinology at the National Institute of Diabetes and Digestive and Kidney
Diseases, said he was "astonished" .
Dr Karsenty discovered that a gene called LRP5 acts on serotonin-producing cells in the gut. It blocks an enzyme that converts the amino acid tryptophan to serotonin. The more LRP5, the more the enzyme is blocked, and the less serotonin is made.
He was able to control bone formation in laboratory mice by giving them a diet deficient in tryptophan, the precursor of serotonin. Without much tryptophan, the mice could not make much serotonin. And their bones grew denser.
Osteoporosis patients tend to have normal serotonin levels, and Dr Karsenty said their disease resulted not from impaired bone formation but from accelerated bone loss.
His hope was to find a new drug that depresses the gut's serotonin synthesis and stimulates bone growth in these patients.
- NZPA
