Ageing reduces gender differences in brain: Study

Both male and female fruit flies’ brains become desexualized as they age. Both sexes go through age-related changes, although the male brain gets more feminised than the female brain becomes masculine. This was the outcome of a study done by a research team from Linkoping University.

The study was published in Proceedings of the Royal Society of London B. Weaker people simply cannot afford to “invest” in sexual behaviours to the same extent as their healthier counterparts. It is unknown, however, if ageing, which weakens people, also causes a decline in sexual attraction.

Going “all in” on reproduction may appear to be the ideal option for those towards the end of their life who want to pass on their genes before it’s too late. Researchers studied how the expression of particular genes varies with age in young men and females to determine what happens to sex differences in this tissue in fruit flies.

“Our results reveal that gene expression in male and female brains grows more comparable with age, and that both sexes contribute to this pattern,” says Dr. Antonino Malacrin, one of the study’s primary authors and presently employed at the University of Reggio Calabria in Italy.\

The study shows that if a gene’s expression is higher in the brains of young females than in young men, it is lowered in older females and elevated in old males, and vice versa for genes with higher expression in young males.

“The data also reveal that the alterations are more pronounced in males than in females,” says Antonino Malacrin.

Females age more slowly than males because there is apparently a lesser association between investment in sexual features and reproductive success in females.

A female fruit fly merely needs to decide how much energy she has left for reproduction, but a male fruit fly must compete with other males by swiftly identifying females and convincing them to mate through a difficult dance performance. Age indicates that both sexes have fewer resources to invest in reproduction and other activities, but males face higher costs of increasing investment owing to male-to-male rivalry.

Urban Friberg, senior associate professor at Linkoping University’s Department of Physics, Chemistry, and Biology (IFM) and the study’s principal investigator, claims that if you continue to expend as much energy on reproduction as you did when you were younger, you won’t have any left over for survival.

Studies on other species, including humans, that have primarily focused on age-related changes in one sex’s gene expression have shown similar results. This shows that many other creatures may have similar results to fruit flies.

Despite the fact that the two populations of fruit flies analysed differ greatly in terms of the genes involved, Urban Friberg adds that the overall conclusions are the same in both.

The study’s findings are similar to those obtained by the researchers in a previous analysis. Male and female flies with high and poor genetic quality were evaluated for sex differences in gene expression in that study.

The previous study found that when genetic quality declines, gene expression in male and female flies becomes increasingly comparable, similar to how ageing lowers sex differences. Males modified their gene expression more than females once again.

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The study does not specify which biochemical signal associated with ageing is responsible for the reduced sex differences in the brain. If the signalling molecule is shared by other species, more research on the issue might be worth while.

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