WEDNESDAY, May 23, 2018 -- Preliminary research suggests that abuse or neglect in childhood might have an effect on the quality of a man's sperm.
The study was small and can't prove cause and effect. But researchers at Tufts University School of Medicine in Boston say it points to a way in which stress early in a man's life might be passed on to his children.
The finding is based on a survey of 28 men who completed questionnaires that assessed the degree to which they had been exposed to physical, verbal or sexual abuse and/or physical or emotional neglect.
In turn, investigators analyzed each man's ejaculate to assess the status of two key gene regulators found in sperm. Such regulators are known as "miRNAs" -- bits of genetic code that control how specific DNA is or is not activated.
The new research was led by Larry Feig, a professor of developmental, molecular and chemical biology at Tufts. His team found that levels of the miRNAs in question were 300 times lower among men who experienced the most early life abuse, compared with those men who had experienced the least amount of abuse.
In mice, the miRNAs in question are known to be connected to levels of anxiety and "sociability defects" in the female offspring of affected males. Studies in mice have also connected the miRNAs to embryonic development and brain development, the researchers said.
This finding of lower levels of miRNAs was subsequently reconfirmed in work with male mice, whose sperm was tested after they'd been exposed to varying degrees of stress and anxiety.
"This is the first study to show that stress is associated with altered levels of sperm miRNAs in humans," study co-author David Dickson noted in a Tufts news release.
"We are currently setting up a new, larger study in men," he said, "and additional experiments in mice that could yield further support for the idea that changes in these sperm miRNAs do, in fact, contribute to an elevation of stress-related disorders across generations.
"Looking to the future, we may be able to figure out a way to restore the low miRNA levels found in men exposed to extreme trauma," added Dickson, who is a doctoral student at Tufts.
Dr. Tomer Singer directs reproductive endocrinology and infertility at Lenox Hill Hospital in New York City. He stressed that the study population was just too small to be sure of the findings.
"A larger population will need to be studied, especially in humans, in order to support and validate the data, but it is a step in the right direction," said Singer, who wasn't involved in the new research.
But fertility specialists have long noticed a steady decline in sperm quality in men over the past 20 years, "leading to rising infertility rates," he said.
"Part of the explanation could be stressful life events as early as in childhood -- as this study suggests -- coupled with the modern lifestyle, which includes stressful work environment, use of electronic devices, unhealthy diets, reduced physical activity, alcohol and drug usage and pollution," Singer said.
The new study was published Wednesday in Translational Psychiatry.
There's more information on epigenetics at U.S. National Institutes of Health.
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