Bookmarkers beware: Bookmarks to pages other than the home page may not work after we change our server in April Editor's Choice | This Week in BMJ | Press releases BMJ No 7132 Volume 316 News Saturday 28 February 1998 New obesity mediator is discovered Scientists at the University of Texas have uncovered a new hormonal cascade that is concerned with the regulation of feeding behaviour. The discovery may eventually lead to new drug treatment for obesity, diabetes, and cachexia. The researchers identified centrally acting neuropeptides and their associated receptors, which they named orexin A and B and OX-1R and OX-2R respectively (Cell1998; 92:573-83). The orexins are produced in the lateral hypothalamus, an area of the brain known to be concerned with the sensation of hunger. Rats which received orexin injections consumed 10 times more food than usual within two hours. There is a lucrative market for anti-obesity drugs Photo: TONY STONE/GETTY IMAGES Moreover, orexin production was affected by nutritional state. Starved rats produced high of orexin concentrations - 2.4 times those of well fed control rats that had not been subjected to a 48 hour fast. These results suggest that orexins play a central part in regulating appetite. The drug company SmithKline Beecham is already designing orexin based compounds to both block and activate the hormone receptors. Such drugs would be useful for dieters as well as people struggling to gain weight - for example, patients with cancer, AIDS, or anorexia nervosa. Orexins are the latest hormones to emerge in obesity research. Last year, a neuropeptide, glucacon-like peptide-1, or GLP-1, was found to act on the hypothalamus as a potent appetite suppressant. Starved rats injected with GLP-1 behaved as if they were sated, and this satiety was reversed by a GLP-1 antagonist which caused the rats to eat. In 1995 scientists discovered leptin, a hormone produced by fat cells which signals the fed state. In rats, leptin influenced appetite reliably. Researchers and drug companies had hoped that leptin would lead to the development of a "magic bullet" for weight control. So far, however, leptin is proving to be more complicated. Although it decreases the appetites of some people, researchers estimate that only 20% of the population respond to high concentrations of leptin with a decrease in food intake. Obese people produce higher concentrations of leptin than normal weight controls, yet do not respond to it and continue to overeat. Researchers are racing to unravel the mechanism of appetite regulation, and pharmaceutical companies are eager to develop and unveil the next drug to help people to lose weight. An estimated 33% of Americans are clinically obese, and a pill leading to successful weight loss would capture a lucrative market. Deborah Josefson San Francisco Home | Current issue | Past issues | Classified ads | Career Focus | Feedback Collections | About this site | About the BMJ | BMA | Medline