AsianScientist (Jan. 8, 2018) – A research group in Kyoto University, Japan, has demonstrated that dietary restriction prolongs the lifespan of hermaphrodite worms but not male worms. Their work is published in the journal Cell Reports.
An organism’s lifespan is known to be affected by its sex and diet, but where these two factors overlap biologically is not well understood. Caloric restriction, or the limitation of food intake, is known to extend lifespan, but how it affects each sex remains unclear.
In this study, a team of scientists in Japan looked for clues in worms—C. elegans—that have two sexes; they are either hermaphrodite or male. They found that hermaphrodite worms can live for two weeks longer when put on various forms of dietary restriction, whereas male worms showed no change in lifespan.
Behaviorally, the hermaphrodites and the males reacted in opposite ways when faced with the same dietary restriction conditions. The hermaphrodites would immediately stop mating and saw an increase in their lifespan, whereas the males continued in their reproductive behaviors and lived for the same amount of time. The researchers posit that the hermaphrodites have evolved to stop their reproductive activities until their environment is favorable again.
One of the key differences between male worms and hermaphrodite worms is a pathway related to sex determination, specifically, a steroid hormone receptor called DAF-12. The researchers found that DAF-12 was not helping the hermaphrodites live longer, but was instead suppressing longevity in males. To test this further, the researchers studied males with a mutated DAF-12 pathway and observed that they lived 20 days longer, just like the hermaphrodites.
“We hope that this study will help answer our fundamental questions of how ageing evolves and how lifespans are determined,” said first author Dr. Sakiko Honjoh, who conducted the work in the lab of Professor Eisuke Nishida at Kyoto University.
“In most species, both sexes are needed for the succession of the species and both show longevity responses during diet restriction. The C. elegans male is a rare case where they are not required for the short-term succession,” she added.
The article can be found at: Honjoh et al. (2017) The Sexual Dimorphism of Dietary Restriction Responsiveness in Caenorhabditis elegans.
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Source: Cell Press; Photo: Nishida Lab.
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