The study will be an important step towards understanding how to control aging
Why do women live longer than men? The cells from which sperm and eggs develop may provide an answer to this question. Japanese scientists have discovered that blocking the production of germ cells in fish reduces the difference in life expectancy between men and women.
The enduring mystery of why women often outlive men may have something to do with the body's smallest and largest cells: sperm and eggs, which play a central role in human reproduction, writes The Guardian.
Japanese scientists have shown for the first time in vertebrates, that the cells that develop into eggs in females and sperm in males determine sex differences in lifespan, and that removing the cells causes the animals' lifespan to remain the same.
The experiments were conducted on small turquoise killifish, a freshwater species that reach sexual maturity in two weeks and live only a few months, but the researchers suspect that a similar biological mechanism may be responsible for the difference in lifespan between humans and other species.
“The aging process in killifish is similar to the aging process in humans, so I don’t think humans are necessarily more complex,” said Professor Toru Ishitani, senior author of the study from Osaka University. – I think this study will be an important step towards understanding how to control aging in humans.
On average, women live about 5% longer than men around the world, notes The Guardian. These inequalities are exacerbated by many factors: young men are more likely to die from accidents and suicide, while women often lead healthier lifestyles. But this disparity is also observed in other species: female primates and Old World monkeys tend to live longer than their male counterparts.
When it comes to people, the size of the life expectancy gap varies greatly across countries. Life expectancy for people born in the UK between 2020 and 2022 is 78.6 years for men and 82.6 years for women. Meanwhile, in Russia, men tend to die about 13 years earlier than women, partly due to excessive drinking and smoking, according to The Guardian.
Professor Ishitani says the presence of sperm or eggs is one of the most obvious differences between men and women, so it makes sense to investigate whether they affect lifespan. In a series of experiments, his team showed that stopping the production of germ cells, which develop into sperm or eggs, causes men to live longer and women to die earlier than usual, significantly narrowing the gap in life expectancy.
“We expected that removing germ cells would extend the lifespan of both men and women, but it only extends the lifespan of men and shortens the lifespan of women,“ Ishitani continues. – It was unexpected, but we realized that this discovery could shed light on sex differences in life expectancy.
In a paper published in the journal Science Advances, the researchers describe how blocking sperm and egg production had negative effects on fish. Hormonal changes in females stimulated growth by maintaining tissue health, while decreased estrogen levels increased the risk of cardiovascular disease. Men produced more vitamin D in their livers, which may explain improvements in bone, muscle, and skin health.
The team then tested whether taking vitamin D increased the lifespan of the fish, and found an increase of 21% in males and 7% in females. Although no side effects were found, Ishitani said it is important to use «an appropriate amount.» In the UK, health authorities recommend taking 10 mcg or 400 IU of vitamin D daily in autumn and winter. Taking more than 100 mcg or 4,000 IU of vitamin D daily may be harmful.
It's unclear whether sperm reduces men's lifespan, but Ishitani said there is some evidence to support the idea. A 2012 study of 81 Korean eunuchs found that they lived 14 to 19 years longer than uncastrated men of similar socioeconomic status. But the evidence dates back to the 16th to 19th centuries and it is difficult to rule out other factors.
Dr David Clancy, who is researching ways to extend healthy life at Lancaster University, said that in studies of other animals, blocking reproductive capacity increased lifespan. especially in females, suggesting a trade-off between growth and reproduction versus maintenance and longevity.
“In this case, removal of sperm or egg progenitor cells shortened the lifespan of females, but increased lifespan in males as and the increase is likely due to a mechanism related to increased vitamin D activity,” he said. “It is clear that the signals transmitted by these cells that regulate lifespan differ between sexes in these fish and, quite likely, in other animals too.“
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