Key to a long life -- less insulin in the brain

By Maggie Fox, Health and Science Editor

WASHINGTON (Reuters) - Good, old-fashioned diet and exercise might keep you young by reducing the action of insulin in the brain, researchers reported on Thursday.

They created mutant mice that over-ate, got fat and even had symptoms of diabetes, and yet lived 18 percent longer than normal lab mice. The secret: they lacked a certain key gene that affects insulin, the hormone that regulates glucose.

The genetic engineering mimicked the effects of eating less and exercising, the researchers report in the journal Science.

"This study provides a new explanation of why it's good to exercise and not eat too much," said Dr. Morris White, a Howard Hughes Medical Institute investigator at Children's Hospital in Boston who led the study.

The findings also raise questions about how desirable it is to use insulin to treat type 2 diabetes, said the researchers.

Doctors know that people who exercise regularly live longer on average. Researchers have also learned that putting animals on a strict diet makes them live longer, although this has not yet been shown to work in people.

So White's team sought to see if the two effects were linked. They looked at insulin, because both fasting and exercise make cells more insulin-sensitive, meaning they respond more efficiently to the effects of insulin.

They looked at the entire insulin pathway -- a series of actions in the cell that control the body's use of insulin.  Continued...