Low levels of leptin encourage bone development?

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Leptin, the chemical which has something to do with appetite and fat formation, has been increasingly interesting to researchers.  It has been discovered, for example, that when the body goes into famine -survival mode (and that happens when people 'diet' with a very low calorie intake, as well), it stops producing leptin and this causes the individual to be very hungry and also to form more fat when food is eaten (in case there is food, to store it up).  Leptin levels continue to be low for as long as two months after a famine or a very low calorie diet and this may explain, in part why dieters coming off a diet are so ravenously hungry, why they have an affinity to overeat ('diet related binge-ing') and why they gain weight back so quickly after a diet.  There are doctors treating underweight by having the individual go on a diet as dieting is also a very good way to gain weight.

But researchers have recently discovered something else interesting about Leptin - it seems to influence the formation of bone.  So in 2000 when Dr. Gerard Karsenty from the Baylor College of Medicine examined the bone density of rats bred with low levels of leptin, he expected them to have less bone density than normal rats but in fact, discovered the rats with lower levels of leptin had 3 times the normal bone density.

>>>"By tracking bone formation with radioisotopes, the researchers traced the bone buildup to overtime work of cells called osteoblasts. Further, leptin infusions into the rodents' brains whittled away the excess bone. But leptin did not appear to be acting directly on the osteoblasts--rather, leptin appears to act on its receptor in the hypothalamus and then relay some secondary signal to the body."<<<

Note: osteoblasts are the cells which produce new bone growth.

Low levels of leptin may also contribute to obesity.

The researchers were amazed that it was the 'obese' rats who had dense bones.  Actually osteoporosis is in lower incidence among obese human beings also.

Karsenty was hopeful that this might led to a cure for osteoporosis, a malady which affects 28 million individuals, mostly female.

However as of 2011, no such cure had been found.
 
Source: NIH bulletin see also Science News Magazine Jan 2000