The evidence is stacking up that DNA is not the only information that can be passed between parents and their children. More and more research is uncovering the role that epigenetics – the idea that environmental factors or stressful events can physically alter how a person’s genes are expressed – also has the potential to be inherited. Adding to this, a new study has found evidence to suggest that a man’s weight could impact these epigenetic factors in his sperm, passing on a predisposition to obesity to his children.
“Our research could lead to changing behavior, particularly pre-conception behavior of the father,” explains Romain Barrès, who led the study that has been published in Cell Metabolism. “It's common knowledge that when a woman is pregnant she should take care of herself – not drink alcohol, stay away from pollutants – but if the implication of our study holds true, then recommendations should be directed towards men, too.”
The notion that environmental factors, such as smoking or stress, can change the expression of our genes has been growing over the last few years. Whilst it has already been shown that activities like smoking can cause our DNA to mutate, which can then lead to cancer, the idea that it could also be altering which genes are turned on and turned off, and to what degree, has been contentious. More controversial is the suggestion that psychological or physical trauma might also be having the same effect, with one study claiming that survivors of the Holocaust could pass the trauma on to their children.
Normally, which genes are activated – and thus which proteins are produced – is controlled by what are known as methyl groups. These chemical tags stick to the region of DNA that the cell wants to express, acting in effect like a dimmer switch, turning up and down the rate the genes are read. It now seems that where these methyl groups attach to the DNA in cells can be influenced by external environmental factors, and not only that, but that these are then passed down from parent to child.
In the first part, this new study compared the DNA in the sperm from 13 lean and 10 obese men, in order to draw up the differences in the epigenetics between the two groups. They found that in the sperm from the obese men, there were markers on parts of the DNA associated with brain development and appetite. The researchers then looked at how these epigenetic differences changed in the sperm for a group of six obese men from before, and after undergoing extensive weight loss surgery. They found that the markers in the obese men had changed after just one week post-surgery, and again one year on.
Whilst the researchers concede that they don’t know exactly how these changes affect the gene, the fact that they are associated with the regions of the DNA linked to appetite suggest, they claim, that they could have a role in predisposing their offspring to weight gain. One of the researchers suggests that it could that the body has evolved so that during times of abundance, these epigenetic changes could encourage children to eat more and grow bigger.