From: Anders Sandberg (asa@nada.kth.se)
Date: Thu Jul 18 2002 - 04:07:45 MDT
An interesting paper in the recent Nature on CR in yeast:
SU-JU LIN, MATT KAEBERLEIN, ALEX A. ANDALIS, LORI A. STURTZ,
PIERRE-ANTOINE DEFOSSEZ, VALERIA C. CULOTTA, GERALD R. FINK &
LEONARD GUARENTE, Calorie restriction extends Saccharomyces
cerevisiae lifespan by increasing respiration,
Nature 418, 344 - 348 (2002); doi:10.1038/nature00829
They show that yeast undergoing CR respires *more* (a factor of
three) than yeast without CR. So the free radical model of ageing
gets into trouble.
Some good comments in the news and views (and a bite at the human
CR movement):
SIU SYLVIA LEE AND GARY RUVKUN, Longevity: Don't hold your breath
Nature 418, 287 - 288 (2002); doi:10.1038/418287a
The main importance might not be the yeast result, but the SIR2
pathway; they end with:
What applies in yeast won't necessarily apply in animals. Notably,
animals do not have the luxury of choosing between respiration and
anaerobic growth. Under CR, mammals shift metabolism towards the
breakdown of fat or glycogen and the biosynthesis of glucose,
rather than glucose respiration. It is not clear whether the
respiration rate changes in CR mammals, but free-radical-induced
cellular damage seems to be reduced9. Interestingly, some of the
gene-expression changes detected in CR mice, including changes in
genes that regulate energy metabolism and stress, are similar to
those observed during the shift from anaerobic to aerobic growth in
yeast12. And SIR2 is known to affect lifespan in the worm
Caenorhabditis elegans as well as in yeast13. There may therefore
be a common gene-regulatory cascade downstream of SIR2 that is
involved in regulating lifespan, even though the upstream
regulatory pathway differs. Further analysis of the SIR2 downstream
pathway in yeast may well illuminate what happens in mammals.
An interesting complement to the article by Lane, Ingram and Roth
in the current Scientific American:
http://www.sciam.com/article.cfm?articleID=000BC08E-5B8C-1D2B-97CA809EC588EEDF&catID=2
-- ----------------------------------------------------------------------- Anders Sandberg Towards Ascension! asa@nada.kth.se http://www.nada.kth.se/~asa/ GCS/M/S/O d++ -p+ c++++ !l u+ e++ m++ s+/+ n--- h+/* f+ g+ w++ t+ r+ !y
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