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Perception is longevity

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2:29pm, July 23, 2007
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Mice engineered to have brains less sensitive to insulin live 18 percent longer than normal mice, new research shows.

The finding could help explain the link between low concentrations of insulin in the blood and greater longevity in centenarians and in some lab animals on calorie-restricted diets.

In the new study, mice ate high-calorie diets and so had high blood insulin. However, the researchers tricked some animals' brains into sensing less insulin. The engineered mice had just one copy of a gene called IRS2 in their brain cells instead of the normal two, explains Morris F. White of Harvard Medical School in Boston. The single gene copy produced less of a protein that's critical to the function of insulin receptors.

The engineered mice, unable to properly regulate insulin, were more overweight and developed a worse diabeteslike condition than the normal mice did. However, brains of the altered mice sensed only a fraction of true insulin levels, which somehow enabled the animals to be healthier and live longer than the other overfed mice, the team concludes in the July 20 Science.

"This points to the brain as the place where reduced insulin signaling increases life span," White says. He adds that the next step is to study how the brain responds to a perception of low insulin and why that response increases longevity.

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