Does the smoking of a father affect his baby? New study shows changes in sperm

IIn the United States, FDA warnings on tobacco products target either the general population or women only. There is no warning specifically aimed at men. The risks of smoking or using tobacco for pregnant women and their children have been clear for a long time, but no one had really considered whether smoking in a father's home could affect his children. For too long, we have assumed that fathers were safe because they did not bear children.

But a study published Wednesday in Biology of Plos shows that some effects of nicotine consumption by the father can be passed on to his children – and to some extent to his grandchildren. Pradeep Bhide, Ph.D., director of the Center for Brain Repair at Florida State University's College of Medicine, led a team of scientists who showed that the cognitive effects of nicotine use persisted for three generations. male mice.

In the current FDA tobacco warnings, Bhide says reversethere is "nothing that prevents men from smoking at any given time". His article suggests that it is time for this to change.

Nicotine derails generations of brains

The link between nicotine use by a mother and cognitive problems such as ADHD in her children is well established, and some previous analyzes of existing data suggested that smoking in a father's home could cause the same problems to his parents. children, said Bhide. The new study, however, is the first to show that the link is a robust phenomenon.

During the experiments, the Bhide team administered nicotine to 12 male mice during the period when they produced sperm, and mated these mice with females that had not been exposed to nicotine. The children all had features such as hyperactivity, attention deficit disorder and cognitive rigidity, tested with the help of delicate mouse tasks called the Maze Barnes and the Y-Maze. .

Using females from this generation of mice, the team induced mating with males from a separate group, devoid of nicotine. Once the babies of this generation grew up, it was clear that the cognitive effects had persisted, but to a lesser extent.

"We did not know much about the effects of paternal smoking on their children and grandchildren," says Bhide. "Our study shows that paternal exposure to nicotine can be detrimental to offspring of several generations." But what he wanted to know, it was: How.

epigenetics

Obviously, the nicotine-induced changes in the DNA of the "grandfather's" origin were passed down from generation to generation, meaning that these changes had to be present in the DNA of the his sperm. When the team examined the sperm of the original men, she found that several genes carried "epigenetic modifications", namely impermanent physical changes in the DNA making some genes more or less usable. The scientists called them "ornaments on a Christmas tree".

The dopamine D2 gene, involved in the development and learning of the brain, is one of the genes affected by epigenetic modifications.

The team's hypothesis is that these epigenetic changes, induced by exposure to nicotine, were transmitted by the sperm of the initial generation to the children of the next generation. The changes persisted in the DNA of these children. It is therefore possible that some decorations are removed from the DNA Christmas tree. That's why cognitive problems were not as robust in the last generation.

Epigenetics is a relatively new field that is not completely understood. "We do not know the answers to all these questions," says Bhide.

The threat to humans

According to Bhide, some critics have argued that the findings of his study on mice can not be applied to humans. "It's a shame, because at least [they could] give it a chance, "he says. "There is nothing to lose saying," It could happen, so be careful. "

It is true that no human trial has shown that the effects of nicotine are transmitted from generation to generation to men. Unfortunately, says Bhide, these studies would be "virtually impossible to do, at least in the current population of potential subjects, because smoking and ADHD go hand in hand." because their father was smoking if we did not know if he had any nicotine-induced sperm changes or if he was previously carrying other genes related to ADHD.

That said, there is less direct evidence, essentially retrospective questioning of existing data, showing that paternal exposure to nicotine increases the risk of ADHD for children. "The results in humans and animal models agree fairly with respect to maternal exposure to nicotine," says Bhide. "I see no reason why the same thing does not apply to studies of paternal exposure to nicotine."

And now?

In addition to considering the usual warnings about smoking causing cancer, Bhide says it's time that men consider that nicotine could affect their effectiveness. germ cells – their sperm – and pass lasting changes to their children. They should also keep in mind that the findings probably apply to all types of nicotine consumption: cigarettes, electronic cigarettes, vapes, juul and even chewing tobacco.

It is not known how long the epigenetic effects of smoking affect a man's sperm. It is therefore probably more prudent for future fathers to act with caution. "Our study raises concern on another level," says Bhide, "the father's smoking status before and at the time of conception!"