WASHINGTON - 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 its good to exercise
and not eat too much, said Dr. Morris White, a Howard Hughes
Medical Institute investigator at Childrens 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 Whites 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 bodys use of insulin.
Whites team engineered mice that had no working copies of one of
the genes involved in this pathway, called insulin receptor
substrate 2, or Irs2.
Best use of insulin
Mice with no copies of Irs2 had defective brains and diabetes. But
mice with one working copy lived 18 percent longer than normal
mice.
Whats more, the animals lived longer even though they had
characteristics that should shorten their lives such as being
overweight and having higher insulin levels in the blood, White
said in a statement.
They were also more active than normal mice, and after eating,
their brains had higher levels of a compound called superoxide
dismutase, an antioxidant that protects cells from damage.
Diet, exercise and lower weight keep your peripheral tissues
sensitive to insulin, White said. That means the body needs to
make less insulin.
Since insulin turns on Irs2 in the brain, that means lower Irs2
activity, which weve linked to longer life span in the mouse, he
said.
One obvious question is whether drugs can mimic the effects of
having less Irs2, perhaps by interfering with its action. The
researchers note that people who live to be 100 or more often have
reduced insulin levels and their cells show better insulin
sensitivity.
New diabetes drugs that increase insulin sensitivity may help, too,
White said. But, he added: The easiest way to keep insulin levels
low in the brain is old-fashioned diet and exercise.
http://www.msnbc.msn.com/id/19870167/