Patterns of metabolic activity during aging of the wild type and longevity mutants of Caenorhabditis elegans |
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Authors: | Bart P Braeckman K Houthoofd Dr Jacques R Vanfleteren |
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Institution: | (1) Department of Biology, University of Gent, Ledeganckstraat 35, B-9000 Gent, Belgium |
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Abstract: | At least three mechanisms determine life span in Caenorhabditis elegans. An insulin-like signaling pathway regulates dauer diapause, reproduction and longevity. Reduction-or loss-of-function mutations
in this pathway can extend longevity substantially, suggesting that the wild-type alleles shorten life span. The mutations
extend life span by activating components of a dauer longevity assurance program in adult life, resulting in altered metabolism
and enhanced stress resistance. The Clock (Clk) genes regulate many temporal processes, including life span. Mutation in the
Clk genes clk-1 and gro-1 mildly affect energy production, but repress energy consumption dramatically, thereby reducing the rate of anabolic metabolism
and lengthening life span. Dietary restriction, either imposed by mutation or by the culture medium increases longevity and
uncovers a third mechanism of life span determination. Dietary restriction likely elicits the longevity assurance program.
There is still uncertainty as to whether these pathways converge on daf-16 to activate downstream longevity effector genes such as ctl-1 and sod-3.
There is overwhelming evidence that the interplay between reactive oxygen species (ROS) and the capacity to resist oxidative
stress controls the aging process and longevity. It is as yet not clear whether metabolic homeostasis collapses with age as
a direct result of ROS-derived damage or is selectively repressed by longevity-determining genes. The dramatic decline of
protein turnover during senescence results in the accumulation of altered enzymes and in a gradual decline of metabolic performance
eventually followed by fatal failure of the system. |
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