Amgen Inc.'s experimental weight-loss hormone leptin appears to work by decreasing the pleasure of eating, according to new research conducted in mice. The study, to be published next week in the journal Science, may give insight into the way the drug lowers weight. Unlike Roche Holding's new diet drug Xenical, which works by blocking the body's ability to process fat, leptin appears to work by changing behavior. Researchers at Concordia University in Montreal compared mice who had been placed on a restricted-calorie diet with mice who coupled the low-calorie diet with leptin injections.
Those mice were then hooked up to a device that pleasurably stimulated specific regions of the brain when certain levers were pushed. Low-calorie diets enhanced pleasure in one of those brain regions, the researchers said, and hungry mice were likely to press the corresponding lever more frequently. Mice injected with leptin, however, pressed that lever less often than those who didn't receive the hormone, which the researchers said was an indication that leptin dulls the neurological "reward" of eating.
At the same time, mice injected with leptin were more likely than other hungry mice to press levers that stimulated parts of the brain that have nothing to do with hunger. Amgen has begun human testing of the drug, which must be injected, for use in seriously overweight patients. Shares of Thousand Oaks-based Amgen gained $3.13 to close at $64.88 on Nasdaq.