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Thursday May 24 11:10 PM ET
Mechanism of Obesity Hormone Revealed
By Suzanne Rostler

NEW YORK (Reuters Health) - In the past decade, researchers discovered a hormone that helped explain why some people could put their fork down after eating a plate of pasta, while others could go back for seconds and thirds without ever feeling full.

Subsequent studies added weight to the role of leptin, a hormone stored primarily in fat cells, in decreasing appetite, lowering the body's ability to store fat and boosting the body's ability to burn fat. But exactly how the ``obesity hormone'' worked has remained a mystery.

Now, a study in the May 24th issue of Nature reveals that leptin targets multiple nerve sites and affects the brain in more complex ways than previously believed. The preliminary findings in mice could pave the way for the development of drugs to treat obesity and, on the other end of the weight spectrum, anorexia nervosa, according to lead author Dr. Malcolm J. Low of Oregon Health Sciences University in Portland.

``A better understanding of the fundamental control of appetite and metabolism by neurons in the hypothalamus will lead to more specific and efficacious means to stimulate feeding and improve nutrition in patients with anorexia illness,'' he explained.

Drugs could also be developed to reverse leptin resistance in obese individuals, Low said. In many cases, obesity is associated with a resistance to the effects of leptin in the same way that type 2 diabetes is caused by a resistance to the hormone insulin, he told Reuters Health.

In this study, Low's team found that in mice, leptin activates brain cells called proopiomelanocortin neurons and also binds to receptors on a second type of cell.

``This duel mechanism of leptin action on two interconnected types of neurons was previously unknown,'' Low said in an interview with Reuters Health. This mechanism may be an important part of the brain's ability to maintain a balance among ``long-term body weight, short-term energy demands, appetite, motivation to seek out food supplies, and feeding behavior,'' he added.

SOURCE: Nature 2001;411:480-484.

http://dailynews.yahoo.com/h/nm/200.../obesity_4.html