cron-web.org

[A1CR]

The longevity and physiological effects of CR in the worm
have been
described. The CR conditions used were not readily
apparent. CR had large
effects.

Szewczyk NJ, Udranszky IA, Kozak E, Sunga J, Kim SK,
Jacobson LA, Conley CA.
Delayed development and lifespan extension as features of
metabolic
lifestyle alteration in C. elegans under dietary restriction.
J Exp Biol. 2006 Oct 15;209(Pt 20):4129-39.
PMID: 17023606

Studies of the model organism Caenorhabditis elegans
have almost
exclusively utilized growth on a bacterial diet. Such
culturing presents a
challenge to automation of experimentation and introduces
bacterial
metabolism as a secondary concern in drug and environmental
toxicology
studies. Axenic cultivation of C. elegans can avoid these
problems, yet past
work suggests that axenic growth is unhealthy for C.
elegans. Here we employ
a chemically defined liquid medium to culture C. elegans and
find
development slows, fecundity declines, lifespan increases,
lipid and protein
stores decrease, and gene expression changes relative to
that on a bacterial
diet. These changes do not appear to be random pathologies
associated with
malnutrition, as there are no developmental delays
associated with
starvation, such as L1 or dauer diapause. Additionally,
development and
reproductive period are fixed percentages of lifespan
regardless of diet,
suggesting that these alterations are adaptive. We propose
that C. elegans
can exist as a healthy animal with at least two distinct
adult life
histories. One life history maximizes the intrinsic rate of
population
increase, the other maximizes the efficiency of exploitation
of the carrying
capacity of the environment. Microarray analysis reveals
increased
transcript levels of daf-16 and downstream targets and past
experiments
demonstrate that DAF-16 (FOXO) acting on downstream targets
can influence
all of the phenotypes we see altered in maintenance medium.
Thus, life
history alteration in response to diet may be modulated by
DAF-16. Our
observations introduce a powerful system for automation of
experimentation
on healthy C. elegans and for systematic analysis of the
profound impact of
diet on animal physiology.