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Reducing insulin signaling in brain helps prolong lifespan |
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11:12, July 22, 2007 |
Keep insulin levels low in the brain might help prolong lifespan, a new study shows.
Establishing the right balance in insulin signaling between the brain and the rest of the body is good for a long and healthy life, according to the study conducted by researchers at Children''s Hospital Boston.
Insulin sends a vital signal throughout the body, telling cells to use sugar from the blood. But when cells become less sensitive to insulin, which often happens as people age and gain weight, the body must make more insulin to keep sugar under control and avoid type 2 diabetes.
For a long time, clinicians and scientists thought that "more insulin was a good thing," says Morris White, PhD, who led the new study.
"But the increased insulin also gets into the brain, where it can be detrimental."
Studies in worms and in fruit flies show that reducing insulin signaling lengthens lifespan. But in humans and rodents, reducing insulin signaling often causes diabetes. The view that insulin could reduce lifespan is difficult to reconcile with decades of clinical practice and scientific investigation to treat diabetes.
White suspected that the key to explaining this paradox -- and to maximizing both health and longevity -- is to reduce insulin signaling only in the brain.
To test this idea, White''s team measured longevity and other characteristics in several groups of mice. In one group, they used a genetic trick to cut in half the amount of Irs2, a protein that carries the insulin signal inside the cell, in every cell of the body. Two other groups of mice were genetically engineered to have half, or nearly all, Irs2 removed only from the brain cells. Another group of normal mice served as controls.
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