Stress levels and smoking: Why your dad's bad habits may have wrecked your genes
01:40 GMT, 1 May 2012
For years, scientists and doctors have blamed illnesses on our parents, showing how conditions such as blindness and deafness can be passed down genetically, and bad lifestyle habits can put babies at risk of heart defects.
But medicine is increasingly pointing the finger specifically at fathers, with studies showing how male genes and even men’s diets and stress levels can create serious health problems for their offspring, including diabetes, depression and obesity.
This latest finding is part of a larger picture where scientists are starting to discover diseases passed from man to boy through the Y chromosome
It seems that the Bible warning holds true for health: the sins of the fathers really do plague their children — and this effect may pass on to their grandchildren, too.
The latest evidence in this newly emerging jigsaw comes from research that shows a common genetic flaw may increase a son’s risk of heart disease by 50 per cent.
Scientists at Leicester University who analysed samples from more than 3,000 men found that those with a common group of genetic traits (called haplogroup I) had a 50 per cent higher risk of coronary artery disease than men in other genetic groups.
This genetic flaw is at the centre of male genetic identity; it’s carried in the Y chromosome, responsible for determining that babies are born as boys (chromosomes are found in all cells and carry our genetic blueprint) — so it’s passed only from fathers to sons.
It is thought that as yet unidentified genetic flaws in men’s immune systems may cause chronic inflammation in their arteries, which can lead to heart disease.
The British Heart Foundation, which funded the study, said the findings could lead to new tests and treatments for coronary problems.
And while men can’t change their genes, they could benefit from learning if they have inherited this danger, says research scientist Lisa Bloomer, one of the study’s authors.
Indeed, while there are no tests for this haplogroup yet, if your father and uncles have had heart troubles, it is sensible to assume there is a strong chance you may be affected.
‘You can reduce your risk if you mitigate the effects of other dangers, such as your weight, blood pressure and cholesterol levels,’ says Ms Bloomer.
This latest finding is part of a larger picture where scientists are starting to discover diseases passed from man to boy through the Y chromosome.
‘It has already been found genes on this chromosome can increase people’s risk of being born with autism and for contracting HIV,’ says Ms Bloomer.
‘We need to do more work to understand how these problems occur.’
Men can pass on addictive behaviours and stress-related depression
Scientists are also learning how the bad effects of men’s lifestyle habits, such as their diet, stress levels, weight and smoking, can be transmitted through the genes in their sperm.
Just as disturbingly, it seems that men can pass on addictive behaviours and stress-related depression.
Here, it is not only sons who are affected but daughters, too, because these problems are passed on through genes that are not on the Y sex chromosome.
Early clues to this have been found by Washington University researchers who studied the sperm of a group of male heroin addicts.
The men’s sperm contained genes that had been changed from normal and would affect the development of any children they had.
These changes are called ‘epigenetic’ — alterations to a person’s genes that are caused by their lifestyle habits.
Significantly, the researchers found epigenetic changes that boosted the activity of OPRM1, a gene that controls how the body responds to its own heroin-like feel-good hormones.
This change is believed to be a factor in making people more liable to develop addictions.
In a similar fashion, men may transmit stress-related diseases across generations.
Scientists at New York’s Mount Sinai School of Medicine say lab experiments on rats have found epigenetic changes in the semen of males who show signs of stress and anxiety after being isolated or threatened.
Their studies show that baby rats sired by these fathers show an increased vulnerability to stress, and become anxious and depressed more quickly than normal. They also have higher levels of stress hormones.
This is despite the fact that their mothers showed no such problems, according to the study published in the journal Biological Psychiatry.
This may offer one explanation as to why depression can run in families.
Even smoking when very young can affect men’s sperm — and surprisingly, this may make their sons prone to becoming overweight.
The discovery was made using survey results from the Avon Longitudinal Study of Parents and Children — an investigation into the health of 14,000 mothers and their children in the Bristol area.
It began in 1991 and is the most comprehensive study of its kind.
Professor Marcus Pembrey, a clinical geneticist at the Institute of Child Health in London, found men who smoked before puberty had sons who were fatter by the age of nine, even when other lifestyle factors were taken into account. There was no similar effect among women.
‘It seems that before puberty, our genes are tuned to suit the environment we are living in. It is these genetic changes that are passed down the male line,’ says Professor Pembrey.
Perhaps the most important factor in determining a man’s legacy to his children comes from his dietary habits.
This takes us into a newly emerging field of science called nutri- epigenomics — the study of how food can alter our genes.
‘Rather than “you are what you eat”, this science shows “you are what your dad ate”,’ says Anne Ferguson-Smith, professor of developmental genetics at Cambridge University.
She points to research that showed fathers who eat high-fat diets and are obese tend to have daughters with a high risk of developing diabetes.
These girls are born with low insulin levels and glucose intolerance — classic signs of the disease.
The research, published in the journal Nature, concluded that the problems seem to be transmitted through the father’s sperm.
Professor Ferguson-Smith warns in the journal Cell Metabolism that these studies show the problem of ill-health being passed from parents to children ‘is not only just maternal territory.
The father’s nutritional and metabolic status merits attention, too, if we are to optimise the health of his children and grandchildren’.
Parents must understand that having healthy offspring is a joint enterprise if their babies are to inherit healthy genes.
This is most starkly illustrated by a study that found obese mothers produced sons at risk of being morbidly overweight.
These boys grew up to father daughters who, in turn, had an inherited tendency to be perilously overweight.
The Biblical prediction turns out to be more complex than anyone thought: the lifestyle sins of both parents can be visited on their children and are passed on in ways we are only beginning to understand.