Are sperm and eggs responsible for the gender gap in life expectancy?

Women, with an average global life expectancy of 73.8 years, tend to live 5 years longer than men on average.

This trend isn’t unique to humans and males of many animal species have shorter lifespans.

In a new study in Science Advances researchers have shown for the first time that germ cells, which develop into eggs in females and sperm in males, drive sex-dependent lifespan differences in the turquoise killifish (Nothobranchius furzeri).

These small, freshwater fish are native to Zimbabwe and Mozambique. They are fast-growing, only living for 1-5 months in the wild, and females typically live longer than males.

By removing the killifish’s germ cells the researchers discovered that they effect the fish’s longevity in opposite ways.

“After removing the germ cells, male killifish lived longer than usual and female lifespans became shorter,” says lead author Kota Abe of Osaka University in Japan.

“We wanted to understand how germ cells could affect males and females so differently. Our next step was to investigate the factors responsible.”

They found that germ cell-lacking female killifish had less estrogen signalling, and more growth factor signalling, than females with germ cells. This made them larger, while also suppressing signals within the body important for maintaining health and slowing aging.

Male killifish without germ cells had improved muscle, skin, and bone health, compared to those with germ cells. They also had increased amounts of a substance that activates vitamin D, as well as evidence of vitamin D signalling, in their muscles and skin.

“When we administered active vitamin D, we found that the lifespans of both males and females were significantly extended, suggesting that vitamin D signalling provides health benefits throughout the body,” says senior author Tohru Ishitani of Osaka University.

“Our work suggests that vitamin D signalling could influence the longevity of other vertebrates, [backboned animals], including humans.”

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