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Healthy Weight Link To Longevity
Keeping a healthy weight may help
people live longer by limiting brain exposure to insulin, say
US scientists.
A study in mice found that reducing insulin signals
inside brain cells increased lifespan.
Writing in Science, the researchers said a healthy
lifestyle and weight reduce insulin levels in humans and may have
the same effect.
Experts said, if proven, insulin would be just
one of many factors, such as genes, that influence longevity.
Previous research in fruit flies and roundworms
has suggested that reducing the activity of the hormone insulin,
which regulates blood sugar levels, can increase lifespan.
The latest study looked at the effects of a protein,
IRS2, which carries the insulin signal in the brain.
Mice who had half the amount of the protein lived
18% longer than normal mice.
Despite being overweight and having high levels
of insulin, the mice were more active as they aged, and their
glucose metabolism resembled that of younger mice.
The researchers said the engineered mice were
living longer because the diseases that kill them, such as cancer
and cardiovascular disease, were being postponed due to reduced
insulin signalling in the brain, even though circulating levels
of insulin were high.
They said, in the future, it may be possible
to design drugs to reduce IRS2 activity to reproduce the same
effect, although they would have to be specific to the brain.
Weighty problem
Study leader Dr Morris White, an investigator
at the Howard Hughes Medical Institute, said the simplest way
to encourage longevity was to limit insulin levels by exercising
and eating a healthy diet.
He said: "Our findings put a mechanism behind
what your mother told when you were growing up - eat a good diet
and exercise, and it will keep you healthy.
"Diet, exercise and lower weight keep your peripheral
tissues sensitive to insulin.
"That reduces the amount and duration of insulin
secretion needed to keep your glucose under control when you eat.
"Therefore, the brain is exposed to less insulin."
His team is now planning to look at possible
links between IRS2 signalling and dementia, which research has
shown is associated with obesity and high insulin levels.
Matt Hunt, science information manager at Diabetes
UK, said: "This is an interesting study as the work done on mice
could suggest that insulin is playing a role in the ageing process.
"Nevertheless, we are looking at numerous and
extremely complex gene interactions in the brain and this research
doesn't yet explain how this mechanism might be working."
He said that human longevity had been steadily
increasing, despite rising levels of obesity and diabetes suggesting
that insulin levels in the brain would be only one of many factors
involved.
"We welcome the fact that this study supports
our key message of the importance of leading a healthy lifestyle."
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