The sperm of men who smoke, compared to those who don't, have more damaged DNA, fewer active energy-generating mitochondria and more proteins indicating a revved up immune response, according to a small study.
Past research has found that smokers tend to have more abnormal sperm in terms of number, motility, shape and structures known as acrosomes that help sperm penetrate an egg.
"We knew that smoking leads to decreased sperm DNA integrity, decreased mitochondrial activity and decreased acrosome integrity," said senior author of the new study Dr. Ricardo Pimenta Bertolla of Sao Paulo Federal University in Brazil. "Sperm from these men are thus less capable of achieving fertilization, and, due to high rates of DNA fragmentation, are more likely to lead to early embryo loss and even to consequences in the offspring."
DNA damage in a father's sperm has been tied to a child's risk of childhood cancer, he told Reuters Health by email.
"All these effects were known by previous studies from our group and from other groups as well," but the new study confirms this with new patients, and helps to demonstrate how these alterations happen, Bertolla said.
Smoking cigarettes may change protein manufacture in the sperm, increasing some and decreasing others, which indicates inflammation in the testicles and other glands, he and his coauthors write in BJU International.
"Excessive seminal inflammation, thus, seems to be one of the mechanisms through which smoking alters sperm," Bertolla said.
The researchers tested the functional quality of sperm from 20 nonsmoking men with normal semen quality and from 20 men who said they smoked at least 10 cigarettes per day. They tested semen volume, pH, sperm concentration, motility and shape. They also observed DNA damage and activity in the mitochondria, the so-called powerhouses of the cell.
More mitochondria in the sperm cells of smokers were inactive or only partially active and the cap-like acrosome over the head of the sperm was less often intact, they found.
"Another important point is that fertilization is an orchestrated event, in that sperm undergo alterations at specific points in order to be able to fertilize the oocyte," Bertolla said. "If they trigger these effects too soon, they may lose that capacity."
The acrosome is a membrane filled with enzymes that allow sperm to penetrate the oocyte, and which may be activated prematurely in smokers, he said.
For women, smoking has been tied to earlier menopause, higher risk of miscarriage and ectopic pregnancy and less success with in-vitro fertilization, he said.
"Based on our results, I would recommend men to stop smoking when they wish to achieve fatherhood," Bertolla said. "The whole process of producing a mature sperm takes around three months, so if a man wishes to quit smoking before attempting fatherhood, I would recommend quitting three months ahead of time."
( This article has corrected the journal name in paragraph six and source line.)
SOURCE: http://bit.ly/28RgeKs BJU International, online June 20, 2016.