Supplements with spermidine, a molecule that the human body produces naturally, rejuvenate eggs and increase fertility at older ages, according to research in mice presented today in Nature Aging. If the same results are confirmed in people, as the research authors hope, spermidine could increase the expectations of having children of women who want to become mothers at an age when their fertility has declined.
“Our next goal is to collaborate with a reproductive medicine center in a hospital to test the effects of spermidine on human eggs and fertility,” says Bo Xiong, director of the research, from the University of Agriculture in an email. Nanjing (China). “We hope to help women trying to conceive at older ages.”
To study why female fertility reduces with age, researchers have compared the ovaries of young and older female mice – 7 and 54 weeks old. They have thus discovered that the amount of spermidine in the ovaries is drastically reduced as females get older.
Although spermidine was originally isolated from semen – hence its name – it is found in all organs and tissues of the human body, as well as in other species of animals, plants and fungi. It is well known among scientists who study aging, since it regulates some of the processes associated with the deterioration of organisms such as – among others – oxidative stress, inflammation or the destruction of cells that must be removed. There is even a clinical trial underway in the UK to study whether spermidine can improve immunity in older people and another in Germany to see if it can help people with heart failure.
Bo Xiong’s team has decided to extend spermidine studies to female fertility. In experiments with mice, it has been shown that giving spermidine supplements to older females restores the function of the ovaries, which recover spermidine levels typical of younger ages.
Spermidine supplements increase the number of eggs produced by the ovaries and also increase their quality, which is comparable to that of the eggs of young females. In short, they promote fertility: older females treated with spermidine have twice as many offspring per litter as those who do not receive supplements.
As researchers at Nanjing Agricultural University have shown, the rejuvenating effect of spermidine on the ovaries is due to its action on mitochondria, one of the components of cells. Specifically, spermidine has turned out to be key so that mitochondria that do not function correctly are eliminated in a process called mitophagy.
Researchers have proven that this phenomenon occurs not only in mice but also in pig eggs. As they write in Nature Aging, “we have shown that the mechanism of action of spermidine in the development of oocytes (…) is highly conserved” between mammalian species, so it probably acts in a similar way in human ovaries.
Some of the research mice have received spermidine injected and others as an oral supplement. “We have seen that the effects are similar,” Bo Xiong tells La Vanguardia. “For use in people, I think the oral route would be more convenient than injections, but more research is needed to determine its effectiveness and doses.”
“With the increasing number of people attending fertility clinics (…), clinical trials to explore the potential of spermidine supplements seem justified,” assess Andreas Zimmermann and Frank Madeo, from the University of Graz (Austria), in an analysis article in Nature Aging.
Since spermidine is found in the cells of animals, plants and fungi, almost all foods contain it in greater or lesser amounts. Legumes, potatoes, soy, broccoli, corn and aged cheese are some of the products that have the most, according to a study by the Karolinska Institute in Stockholm. It is also sold as a parapharmacy product.
But the authors of the research warn that “an excess of spermidine is not necessarily beneficial for female reproduction.” In their experiments, egg maturation has been better in mice treated with 50 milligrams of spermidine per kilo of weight than in those that have received double the dose. While waiting to establish what the appropriate dose would be in people, researchers do not advocate self-medication with spermidine to preserve fertility.
