An American study lifts the veil on one of the mysteries of our humanity: why do women generally live longer than men? According to the results, the response is genetic, but also hormonal.
According to the latest data of the National Institute of Demographic Studies (INED), life expectancy in France is 79 years for men, and 85 years for women. A difference that is sometimes explained by the way of life: food, consumption of alcohol or tobacco. However, this tendency is also the same in animals. Researchers from the University of California, San Francisco (USA), tried to find out if there was a scientific explanation. Their study, published in the journal Aging Cells, explains that the answer lies in our chromosomes.
It is better to have XX chromosomes
To carry out this study, the researchers genetically modified mice, divided into four groups. In the first, they had XX chromosomes, the female chromosomes, with developed ovaries. In the second, they had XY chromosomes, the male chromosomes, and testicles. Finally in the last two groups, the rodents had either XX chromosomes and testes, or XY chromosomes and ovaries.
In the Y chromosomes is a gene that determines male traits. This is the “SRY” gene. It is by moving this gene that they managed to grow testicles on mice that nevertheless had XX chromosomes. They found that all mice with XX chromosomes tended to live longer than others, whether they had ovaries or testicles.
Hormones play a role
However, life expectancy was really longer when mice had XX chromosomes and ovaries, like women. “This suggests that hormones produced by the ovaries increase the lifespan of mice with two X chromosomes, either by influencing the development of the mouse or by activating certain biological pathways during its lifetime,” explains Dr. Dena Dubal, lead author of the study.
It remains to be seen now how having two X chromosomes increases life expectancy. What role does this second chromosome play? Previously, other studies have shown that in women, there is an X chromosome in each cell that is randomly deactivated. Thus, if the active chromosome is damaged, the other can reactivate and take over. Women therefore seem to be the winners of this genetic chance.
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