Men may pass on obesity through sperm, according to a new study.
Obesity is a metabolic disorder resulting from behavioral and heritable causes. Children of obese fathers more frequently develop metabolic diseases later in life, regardless of the mother's body weight.
This suggests that obesity and related conditions could stem from the father, supporting the findings of previous rodent studies.
Senior author Romain Barrès, an associate professor at the University of Copenhagen in Denmark, was inspired by a previous study in which the availability of food to people during a famine correlated with the risk of their grandchildren developing cardiometabolic diseases.
That study indicated that the nutritional stress of the grandparents was probably passed down through epigenetic marks.
These can be chemical additions on protein that wrap up DNA, methyl groups that change the structure of DNA once attached or molecules called small RNAs.
Different marks in lean and obese men
Epigenetic marks can control how genes are expressed, and they have been seen to affect the health of offspring in insects and rodents.
Barrès and colleagues compared specific epigenetic marks in the ejaculate of 13 lean and 10 obese men.
Sperm cells of lean and obese men were found to possess different epigenetic marks, especially in regions associated with appetite control.
While no differences were seen in the proteins that wrap up DNA, there were variations between the participants' small RNAs, as well as methylation of genes associated with brain development and appetite. The function of the RNAs is not yet determined.
Does weight make a difference?
To find out whether these differences were byproducts of obesity, the researchers looked at the effect of bariatric surgery on sperm epigenetics. They tracked six men undergoing weight-loss surgery to study the impact on their sperm.
An average of 5,000 structural changes to sperm cell DNA were observed before the surgery, directly after and 1 year later, indicating that weight is the main factor.
The findings suggest that sperm carries information about a man's health, but more research is needed to establish the meaning of these differences and their effects on offspring.
"Our research could lead to changing behavior, particularly pre-conception behavior of the father. It is common knowledge that when a woman is pregnant she should take care of herself, not drink alcohol, stay away from pollutants, and so on; but if the implication of our study holds true, then recommendations should be directed towards men, too."
Medical News Today recently reported on a link between obesity, testosterone and type 2 diabetes in men.