Word: leptin
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Dates: during 1995-1995
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...early to predict, however, whether this rare elixir (called leptin, after the Greek leptos, meaning slender) will be a stunning pharmaceutical success or just another "miracle" cure that never pans out. Even if all goes well, it could be five to 10 years before leptin is approved for human use. Researchers must first demonstrate that leptin benefits people as well as rodents and that it causes no serious side effects...
...search for leptin began in the 1960s, when Douglas Coleman, a researcher at the Jackson Laboratory in Bar Harbor, Maine, began studying a strain of obese laboratory mice. In a series of ingenious experiments, Coleman surgically joined the blood vessels of an obese mouse to those of a normal-size mouse, creating a sort of artificial Siamese twin. What happened then was astonishing: the fat animal immediately began to lose weight. This suggested that the blood of nonobese mice carried a potent biochemical messenger, one that played a vital role in regulating appetite and metabolism. But the mysterious agent...
...obese, gene. Sure enough, late last year, after eight years of effort, Friedman and his colleagues pinpointed the ob gene in both average-weight and obese mice. They then inserted the normal gene into bacterial cells, providing at long last detectable quantities of the protein they called leptin...
...injecting leptin into obese mice, three separate teams of researchers, including Friedman's, have confirmed that this protein is indeed the blood factor that makes fat mice thin. But they are still trying to puzzle out just how it works. Friedman, for one, believes leptin is almost certainly a hormone that travels through the bloodstream to act on the brain. In fact, it appears leptin may act in a feedback loop like the temperature sensor in a thermostat--or in this case a "fatstat"--to tell the body whether to turn metabolism and appetite up or down. Thus when leptin...
...Because leptin is produced in fat tissue, the fatter an animal is, the more leptin its cells should make. Normal mice then respond to weight gain by turning out more leptin. As a result, their appetites slacken and their energy consumption speeds up. But the obese mice cannot produce leptin, so their brains never receive this vital message. "These animals," marvels Friedman, "get fat because they think they're starving, and then when we give them the protein, they get thin because they think they...