X-Message-Number: 28533
Date: Thu, 28 Sep 2006 21:48:08 -0700 (PDT)
From: Doug Skrecky <>
Subject: mild protein restriction increases drosophila lifespan

[ Inconsistent results have been obtained in the past with calorie
restriction in drosophila, with the best controlled experiments finding a
null result on longevity. Tatar offers the best explanation to date for
why these results vary, and at the same time puts to rest any notion
that CR itself slows aging in drosophila.
  I examined the research reports of a number of these experiments, and
found some evidence that although calorie decreases did not offer a
consistent longevity benefit, the evidence did point to reduced survival
with experimental procedures to increase calorie intake. Thus the absence
of a CR effect in drosophila might be due to a threshold effect, where
excess calories reduce longevity only above a (high) threshold.
  Calorie intake is believed to modulate mammal longevity partly by
body temperature reduction to help block cancer, which is obviously not
germane to cold blooded flies. However CR can also increase
macroautophagy to rid cells of debris such as damaged mitochondria,
protein aggregates, and so on. There are number of lines of evidence
pointing to increased macroautophagy improving the health of aged
mammals, including humans. In some circumstances, protein intake is also
known to modulate macromacrophagy. I suspect Tatar may have found the
protein content of fly food that maximizes macroautophagy in drosophila.]

Mech Ageing Dev. 2006 Jul;127(7):643-6. Epub 2006 Apr 17.
Restriction of amino acids extends lifespan in Drosophila
melanogaster.Min KJ, Tatar M.
  Dietary restriction extends adult Drosophila melanogaster life span
when the concentration of dietary yeast is diluted in a media with
abundant carbohydrates. Here we vary the concentration of casein as a
source of amino acids in adult diet to uncover a quality of nutrient
yeast responsible for longevity control. Longevity is maximized upon diet
with intermediary levels of casein. Differences in survival are not
caused by elevated age-independent mortality; the longevity maximum at
intermediate casein does not arise because casein is non-specifically
harmful at higher concentrations. Furthermore, fecundity increases when
the level of dietary casein is elevated. The demographic phenotypes of
adult Drosophila maintained on intermediate levels of casein resemble
their response to limited dietary yeast. Dietary restriction through
dilution of yeast may extend longevity because this limits the intake of
amino acids.

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