Early results from an ongoing study from the University of Massachusetts Amherst provide a new window into how chemicals in the environment might be affecting men’s sperm. The study suggests that a man’s environment might cause changes in how genes are expressed in his sperm.
These findings are from a larger study being led by UMass professor and environmental health scientist Richard Pilsner in collaboration with Wayne State University.
The study was published Tuesday in the current issue of “Human Reproduction,” a monthly journal of the European Society of Human Reproduction and Embryology published by Oxford Journals.
Research has found that phthalates, compounds found in plastics and personal care products such as shaving cream, might have an effect on couples’ reproductive success. Exposure to phthalates is known to disrupt some hormones and is associated with changes to semen quality and testosterone levels, the university said in a statement.
Phthalates are estimated to be detectable in nearly 100 percent of the United States population.
There are two types of phthalates: those with a high molecular weight and those with a low molecular weight, Pilsner said in an interview. Phthalates with a high molecular weight can be found in many polyvinyl products that contain somewhat flexible plastic, such as vinyl flooring or shower curtains. Phthalates with low molecular weight are used as stabilizers for perfumes in personal care products, so they often appear in perfumes and aftershaves.
What’s unique about this study is people have studied the connection between sperm epigenetics and phthalates, but, Pilsner said, no one has thoroughly examined the mechanism that’s responsible for it.
Pilsner and his team have studied 48 couples so far and hope to eventually work with 250, according to the study. They received urine and semen samples from prospective fathers after they donated sperm during in vitro fertilization appointments at Bay State Medical Center in Springfield.
In a cross-sectional study, they compared the phthalate levels in the urine samples with the DNA methylation of the sperm. Methylation is a chemical change in the DNA that determines whether a gene is activated, or expressed.
“Causation cannot really be applied so we can’t necessarily say phthalates caused or had an effect on sperm methylation,” Pilsner said. “We found an association or correlation between the two.”
For each sample of sperm DNA (the molecules that contain the instructions for growth and development of cells), they measured the methylation levels at about 480,000 gene sites. The researchers ran statistical association tests to find patterns between the different percentages of methylation in the sperm and phthalate levels in the urine. They identified 6,479 possible regions to study.
Of the 6,479 regions examined, 131 were associated with at least one of the phthalates. The researchers said most of the phthalates that were associated with changes to the sperm’s DNA were either known or suspected to be anti-androgenic compounds, which means they can influence hormones.
Pilsner has received two additional grants to conduct similar experiments with mice to potentially replicate the results he’s seen in humans.
The experiments could produce “more of a definitive finding of the true effects” of phthalates, he said.Sophia Eppolito can be reached at firstname.lastname@example.org. Follow her on Twitter @SophiaEppolito.