Word: insulin
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Dates: during 2000-2000
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...well understood. But Kaplowitz suspects early breast development may be encouraged by a protein called leptin. "We know that fat cells produce leptin," he says. "And leptin is necessary for the progression of puberty." Another clue, according to Duke's Freemark, is that overweight girls have more insulin circulating in their blood. Says Freemark: "Those higher levels of insulin appear to stimulate the production of sex hormones from the ovary and the adrenal gland...
...years we've known about insulin signaling and we've always though that it works by engaging receptors on muscles and fat," he said. "It was always assumed that the tissue where you see the aging is where it would be functioning...
...idea that the brain may control aging is attractive from an evolutionary perspective too. Closely related species sometimes age at very different rates. Perhaps small changes in brain insulin systems allow for these changes...
Ruvkun believes that the interaction between insulin and "free radicals" may explain its powerful effect on aging. Too many of these dangerous by-products of cellular metabolism can be lethal for an animal, but insulin can cause cells to stop producing enzymes which scavenge free radicals. If this process is turned off, he speculates, animals may live longer because they continue to eliminate free radicals...
...role insulin plays in aging in mice is not yet known, but when mice are placed on a restricted diet, which lowers their insulin levels, they live longer...