CR, Ageing Rate, in Fruit Flies.

[Guest guest]

Hi folks:

Although CR fruit flies live much longer than those ad lib, this is

NOT because of a slowdown in the RATE of ageing:

" Dietary restriction, mortality trajectories, risk and damage.

Partridge L, Pletcher SD, Mair W.

Department of Biology, University College London, Darwin Building,

Gower Street, London WC1E 6BT, UK. l.partridge@...

Restriction of food intake extends lifespan in evolutionarily diverse

organisms, including mammals. Dietary restriction (DR) also delays

the appearance of ageing-related damage and pathology and keeps

organisms in a youthful state for longer. DR has hence been suggested

to lower the rate of ageing. Analysis of mortality rates can be used

to test this idea. During ageing, mortality rates in general

increase, approximately exponentially. Lifespan can be extended

either by a reduction in the rate of increase in mortality rate with

age or a lowering of the initial rate of mortality. A reduction in

the slope of a mortality trajectory has generally been taken to

indicate that the rate of ageing has been lowered. Data on the

effects of temperature on mortality in Drosophila are in accordance

with this idea. Lowered temperature extends lifespan solely by

lowering the slope of the mortality trajectory and flies with a

hotter thermal history have permanently elevated death rates. In

contrast, lowering of the initial rate of mortality has been taken to

leave the rate of ageing unaffected. In Drosophila and in mice, but

not in rats, DR extends lifespan by lowering the initial mortality

rate. In Drosophila, the effect of DR is acute, and mortality rate

switches rapidly between DR and control values with the corresponding

changes in nutritional regime. DR in Drosophila therefore has no

impact upon the rate of ageing. Possible mechanisms by which DR can

both delay damage and pathology and yet act acutely to determine

mortality rates are discussed. In rodents, some phenotypes associated

with DR, including microarray profiles, show rapid switching with

changed nutritional regime, pointing to potentially acute effects of

DR in mammals.

PMID: 15610760 [PubMed - in process] "

Rodney.

[Guest guest]

Full text here:

http://biology.plosjournals.org/perlserv/?request=get-document & doi=10.1371/journ\

al.pbio.0030223

The response of Drosophila life span to nutrition is not governed by

calories, but rather by specific nutritional components of the food.

This finding represents a departure from the generally accepted model

in rodents, where it has been suggested that the level of calorie

intake per se, not the source of calories, is critical for life-span

extension [1]. The apparent disparity between the factors in the diet

that affect life span in fruit flies and rodents leads to two possible

conclusions. First, the mechanisms by which these organisms respond to

food shortage could be different. Second, the long-held view that

calorie intake is the critical variable in the response of mammalian

life span to DR may require further evaluation.

Our results suggest that it may be possible to obtain the full

extension of life span by DR by reducing critical nutrients in the

food without any reduction in overall calorie intake.

> Hi folks:

>

> Although CR fruit flies live much longer than those ad lib, this is

> NOT because of a slowdown in the RATE of ageing:

>

> " Dietary restriction, mortality trajectories, risk and damage.

>

> Partridge L, Pletcher SD, Mair W.

>

> Department of Biology, University College London, Darwin Building,

> Gower Street, London WC1E 6BT, UK. l.partridge@u...

>

> Restriction of food intake extends lifespan in evolutionarily diverse

> organisms, including mammals. Dietary restriction (DR) also delays

> the appearance of ageing-related damage and pathology and keeps

> organisms in a youthful state for longer. DR has hence been suggested

> to lower the rate of ageing. Analysis of mortality rates can be used

> to test this idea. During ageing, mortality rates in general

> increase, approximately exponentially. Lifespan can be extended

> either by a reduction in the rate of increase in mortality rate with

> age or a lowering of the initial rate of mortality. A reduction in

> the slope of a mortality trajectory has generally been taken to

> indicate that the rate of ageing has been lowered. Data on the

> effects of temperature on mortality in Drosophila are in accordance

> with this idea. Lowered temperature extends lifespan solely by

> lowering the slope of the mortality trajectory and flies with a

> hotter thermal history have permanently elevated death rates. In

> contrast, lowering of the initial rate of mortality has been taken to

> leave the rate of ageing unaffected. In Drosophila and in mice, but

> not in rats, DR extends lifespan by lowering the initial mortality

> rate. In Drosophila, the effect of DR is acute, and mortality rate

> switches rapidly between DR and control values with the corresponding

> changes in nutritional regime. DR in Drosophila therefore has no

> impact upon the rate of ageing. Possible mechanisms by which DR can

> both delay damage and pathology and yet act acutely to determine

> mortality rates are discussed. In rodents, some phenotypes associated

> with DR, including microarray profiles, show rapid switching with

> changed nutritional regime, pointing to potentially acute effects of

> DR in mammals.

>

> PMID: 15610760 [PubMed - in process] "

>

> Rodney.