Metabolic Rate not Responsible for CR Life Extension in Fruit Flies

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" Metabolic rate is not reduced by dietary-restriction or by lowered

insulin/IGF-1 signalling and is not correlated with individual

lifespan in Drosophila melanogaster.

Hulbert AJ, Clancy DJ, Mair W, Braeckman BP, Gems D, Partridge L.

Metabolic Research Centre and School of Biological Sciences,

University of Wollongong, Wollongong, NSW 2522, Australia.

hulbert@...

The link between resting metabolic rate and aging, measured as adult

lifespan, was investigated in Drosophila melanogaster by (i)

comparing lifespan and metabolic rate of individual flies, (ii)

examining the effect of dietary-restriction on the metabolic rate of

adult flies, and (iii) comparing the metabolic rate of wild-type and

insulin/IGF-1 signalling mutant chico1 flies. The resting oxygen

consumption of 65 individually housed and fully fed Drosophila was

measured weekly throughout their lifetime. There was no significant

difference in the mass-specific rate of oxygen consumption between

cohorts that differed in lifespan. Nor was there any statistical

correlation between mass-specific oxygen consumption and lifespan of

individual Drosophila. The average mass-specific rate of oxygen

consumption at 25 degrees C was 3.52+/-0.07 microl O2 mg(-1) h(-1).

Variation in mass-specific metabolic rate explained only 4% of

variation in individual life span in these flies. Contrary to

predictions from the 'rate of living' theory of aging lifetime oxygen

consumption was not constant and the lifespan of individual flies

accounted for 91% of their lifetime oxygen consumption. An average

Drosophila consumes about 3 ml O2 during its adult life. Dietary-

restriction had no effect on mass-specific resting metabolic rate

both when measured as oxygen consumption by respirometry and when

measured as heat production by microcalorimetry. The mass-specific

resting heat production of fully fed adult flies at 25 degrees C

averaged 17.3+/-0.3 microW mg(-1). Similarly there was no difference

in mass-specific metabolic rate of wild-type flies and longliving

chico1 insulin/IGF-1 signalling mutant flies, either when measured as

oxygen consumption or heat production. Thus, individual variation in

lifespan in wild-type flies, and life extension by dietary-

restriction and reduced insulin/IGF-1 signalling is not attributable

to differences in metabolic rate.

PMID: 15288688 [PubMed - indexed for MEDLINE] "

Rodney.