Re: Smelling food increases aging, at least in flies

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The pdf is availed for the below paper, All,

PHYSIOLOGY: Odor of Food Hastens Dieting Flies' Deaths

Mitch

Science 2 February 2007: 584.

Put a fruit fly on a near-starvation diet, and it is

likely to live much longer than its well-fed cousins.

But if it smells food odors, some of the

life-stretching effects of the diet disappear,

researchers report in a study published online by

Science this week

(www.sciencemag.org/cgi/content/abstract/1136610). The

finding adds to a growing body of evidence that an

organism's perceptions of its environment can have a

big impact on its longevity.

Molecular geneticist Kenyon of the University

of California, San Francisco, and her colleagues first

sniffed out the link between life span and perception.

In 2004, for example, Kenyon and postdoc Joy Alcedo

reported that frying nematodes' olfactory neurons with

a laser prolongs the worms' lives. Zapping certain

taste neurons also promotes longevity, but destroying

another one cuts survival.

Unhealthy glow. An inserted gene, marked by

fluorescence (green) and expressed in antennae,

restored this fly's ability to smell and shortened its

life.

CREDIT: S. LIBERT ET AL., SCIENCE

To further probe the link between smell and life span,

geneticist Pletcher of Baylor College of

Medicine in Houston, Texas, and colleagues placed

fruit flies on an ascetic diet known as calorie

restriction, which slashes food intake and can extend

an animal's life by up to 50%. The researchers then

planted tantalizing (at least to Drosophila) yeast

paste in a screened-off end of the insects' home

tubes; the bugs could smell and see the goodies but

not eat them. Although the calorie-restricted flies

lived longer than normal, they died sooner than

similarly hungry insects not exposed to the yeast

scent. The aroma had no impact on survival in well-fed

Drosophila.

Further support that the sense of smell affects life

span came when the researchers measured survival in

flies harboring a mutant form of the protein Or83b.

The molecule helps direct odor receptors into position

in the fly's olfactory organs, which are part of the

antennae, and a faulty Or83b dulls the sense of smell.

It also stretches fly longevity by up to 56%, the

researchers found. Like many long-lived organisms,

flies with mutant Or83b showed increased resistance to

stresses such as starvation and a pure oxygen

atmosphere. Restoring functional Or83b returned fly

longevity to normal.

Many animals with extended life spans dial down

insulin signaling (Science, 6 April 2001, p. 41).

However, levels of fly insulinlike proteins didn't

differ between the normal and Or83b-mutant insects,

suggesting that odor exerts some of its longevity

effects through another pathway.

The results " point out a central role for

environmental perception in mediating life-history

decisions, " says Pletcher. The smell of food might cue

animals to live for the moment because times appear to

be good. But if nutrients are scarce, animals hunker

down to await better conditions, boosting their

resistance to stress and aging more slowly.

" It's incredibly exciting that the group has been able

to show a link between the olfactory system and life

span, " says molecular geneticist Helfand of

Brown University. The work reveals that " your brain

has control over your life span. "

The findings might also help clarify whether reduced

food intake or another stimulus spurs calorie

restriction's physiological changes. This study

establishes that " some component of the response to

caloric restriction is olfactory, " says Kenyon.

So far, no evidence indicates that scent regulates

vertebrate life span. However, says Kenyon, that the

effect occurs in animals as distantly related as

nematodes and flies indicates it could. Another

unknown is whether other smells shorten longevity. And

Pletcher notes that the presence of life-extending and

life-shortening sensory neurons in nematodes " suggests

that we could find odors that increase life span. "

--- brucegalbreath <bruce.galbreath@...> wrote:

> http://www.the-scientist.com/news/home/45885/

>

> Incredible results, but from a very solid source,

> Baylor University.

> Seems to show that decreased time experiencing the

> smell of food is at

> least part of what makes CR work.

-- Al Pater, PhD; email: Alpater@...

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