Fasting and sexual dimorphism
Scientists have uncovered an unusual link between sex, calories and longevity
Scientists have uncovered an unusual example of the influence of sex on the longevity of living creatures – male worms do not begin to live longer with a chronic lack of food, but have sex more often, which is not typical for their hermaphrodite relatives, according to an article published in the journal Cell Reports (Honjoh et al., The Sexual Dimorphism of Dietary Restriction Responsibility in Caenorhabditis elegans).
"We hope that our research will help us understand how aging develops and what determines life expectancy. For example, in most animal species, representatives of both sexes are necessary for the prolongation of the genus, and a strict diet approximately equally prolongs their life. Male nematodes are not required for procreation, and this technique does not work on them," says Sakiko Honjoh from Kyoto University (in a press release Dietary restriction and life span in male and hermaphrodite worms – VM).
Experiments conducted on worms, mice and a number of other animals back in the 60s of the last century showed that reducing the number of calories in the diet significantly prolongs the life of animals. Over the following decades, biologists have identified dozens of genes and hormones potentially involved in this phenomenon, but none of them have been able to learn how to use to prolong the life of humans or these same animals.
Honjo and her colleagues found a possible cause of all these failures by observing how calorie restriction affected the vital activity of two varieties of ordinary laboratory worms-nematodes (Caenorhabditis elegans) – hermaphrodites and males unable to continue the genus on their own.
As a rule, hermaphrodites dominate most populations of these worms – only one individual out of a thousand is a male. For this reason, most experiments, including life extension experiments, are carried out on hermaphrodites. The authors of the article corrected this flaw, and received extremely unexpected results.
When scientists limited the number of calories in the diet of worms, hermaphrodites behaved in the expected way – they stopped reproducing, and their life expectancy increased by an average of several weeks compared to individuals who ate normal food. This, however, did not happen with the males.
The lack of food affected them in a strange way – they actively sought partners for procreation and multiplied more often than hermaphrodites did in a similar situation. As a result, their life expectancy did not increase, but remained about the same.
The lifespan of nematodes under different maintenance regimes
(from an article in Cell Reports – VM).
Interestingly, the behavior of males and their life span can be changed by blocking the work of just one gene, DAF-12, responsible for reading the "male" hormones of nematodes. Males with blocked DAF-12 lived as long as hermaphrodites, but at the same time remained same-sex creatures and did not change their behavior.
Similar unusual connections between aging, sex and diet, according to Japanese biologists, may exist among other species of multicellular animals. Their study and disclosure will help us understand why calorie restriction affects the life expectancy of humans, other mammals and other living beings in different ways.
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