A group of researchers from the United States discovered what is behind female life expectancy. Apparently, the X chromosome, which affects women to live longer than men, is important for survival.
The study conducted at the University of California San Francisco (UCSF) says that in the second X chromosome, the cause of life expectancy and other benefits are believed.
"The X chromosome contains many genes related to the brain, and it is vital for survival. Without at least one X, an animal can not live. The Y chromosome, which is found only in men, contains very few genes other than those who create secondary sexual characteristics, such as male genitals and facial hair, and are not necessary for survival, explained a press release from this university.
In a laboratory, the researchers gave mice (women and men) four combinations of chromosomes and gonades, the two natural (XX with ovaries and XY with testicles) and two created (XX in testicles and XY in the ovaries).
The animals were identical and lived in the same environment, besides the sex chromosomes.
The mice that lived longer were those with XX chromosomes in the ovaries.
"We have long wondered what causes female longevity," says Dena Dubal, senior author of the study published in Aging Cell.
"One can imagine that nature has led women to develop in this way. When you live longer, you can really assure the welfare of your offspring, and perhaps even your offspring," he says.
The study lasted several years, they observed the mice for 30 months to see if they died or not.
They discovered that female chromosomes and female gonads prolonged the life of mice from 12 to 30 months, "equivalent of mice from middle ages to old age".
The major part of the effect was on the chromosomes, as the XX mice lived longer than XY, whether they had ovaries or testicles. The longest living mice, however, were those with ovaries with XX chromosomes.
"This indicates that the hormones produced by female gonads increase the lifespan of mice with two X chromosomes, either by affecting how the mouse develops or activates some biological pathways during their lives," Dubal said.
They compared two different types of genetic female mice (with ovaries and testicles) and found that by having "two X's and ovaries, the mouse had to live longer, starting at 21 months, which is towards the end of a normal lifetime. "
For mice that were "genetically female but hormonal masculine, the other X chromosome only protected them from dying before."
According to Iryna Lobach, a professor and part of the study, to live longer than expected, the mice needed ovaries and the two XX chromosomes, but to live a normal life, it did not matter if they had ovaries or testicles.
"While they had XX, they died early in the aging process," he said.
Dubal concludes by saying that "when things go wrong in aging, it may be very beneficial to have more of the X chromosome along with its diversity of expressions."