Word: leptin
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...have a weight problem, you have more than your diet or your gym to thank. You also owe a nod to your leptin gene. And while you're at it, tip a hat to your MC4 receptors and your PC1 enzymes and your POMC peptides. Hard to figure out the role this alphabet soup of stuff plays in helping keep you thin? Don't feel bad. It's all new to scientists...
...discovery of leptin in 1994 that got the genetic study of obesity rolling, and it was Friedman's research team that was responsible. Studying the genome of a rare strain of hugely obese mice, the investigators found that all of them shared a defect in a gene that coded for a previously unknown hormone released by body fat. When a normal animal gains too much weight, the hormone signals the brain to turn down the appetite rheostat. When fat stores drop, the hormone is shut off, causing appetite to rebound. In the gene-damaged mice, there was no leptin...
...spite of anecdotal reports. Your article seemed to emphasize the vague possibility that a host of chemicals, those found in the environment or in foods, could initiate early puberty. But the only scientifically documented cause is the increase in childhood obesity, and the demonstrated involvement of fat cell-derived leptin in initiating pubertal events. Next time, I hope you will do your readers a favor by presenting such stories in a more realistic context, rather than alarming them on the basis of weak scientific evidence. RUTH KAVA, DIRECTOR OF NUTRITION American Council on Science and Health New York City
Exactly why obesity and early development should be linked is not 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...
...blame the agro-food industry quickly argued that pesticides in food might have a hormone-like effect on children's bodies. Many pediatric endocrinologists, however, believe the suspected change has more to do with the extraordinary increase in childhood obesity over the past two decades. Fat cells produce leptin, a protein known to help trigger puberty. With more fat cells churning out leptin, earlier puberty would seem highly likely...