In recent years, growing evidence has supported the deep idea that the legacy of childhood trauma can be passed on to offspring, even affecting the mental and physical health of future generations.
The best known and most problematic clue is that studies have shown that the successors of Holocaust survivors are more likely to have severe schizophrenia and other health problems.
Although this is known to be guided by changes in the epigenome – a multitude of biological and chemical factors that affect how genes are expressed – it has never been clear how the signals triggered by traumatic experience in reproductive cells become “printed”.
Trauma is transmitted through the blood
Recently, scientists at the University of Zurich in Switzerland used mice to explain how the impact of early life trauma could be transmitted over generations through changes that occur in the blood.
Their findings confirm the hypothesis that blood provides stress signals to reproductive cells, which thus transmit inheriting the trauma of the next generation.
How did they conduct the study?
The researchers first compared the blood of mice that suffered trauma at the beginning of life with the blood of control mice and observed some significant differences in lipid metabolism. In this regard, the blood of traumatized mice showed much higher levels of certain metabolites of polyunsaturated fatty acids.
Then they noticed that the same changes were found in the offspring of traumatized mice.
To further analyze the evidence, they inserted the serum of traumatized male mice into trauma-free male mice and found that these offspring also had the same metabolic changes, suggesting that the changes in their blood affected their sperm cells and were transmitted to next generation.
What happens to people?
The researchers then looked at 25 children in an orphanage in Pakistan who had lost their father and were separated from their mother. By comparing blood and saliva samples with those taken from other children without such trauma, they found that orphans had higher levels of lipid metabolites, as in the case of traumatized mice.
The researchers also tried to discover the molecular mechanism that guides this process.
They found that PPAR, a cell surface receptor that helps regulate gene expression in many tissues, reaches a high value in the sperm of traumatized men.
By artificially activating this receptor in male mice, it led to a decrease in body weight and changes in glucose metabolism. The effect was also observed in their descendants over two generations.
Overall, the study presents a clear picture of how childhood trauma can be reflected in reproductive cells and, as such, passed on to offspring.
“These findings are extremely important for medicine because it is the first time that a link between early trauma and metabolic disorders in offspring is characterized,” said Isabelle Mansuy, a professor of neuroepigenetics at the Neural Research Institute. at the University of Zurich and the ETH Zurich Institute.
The researchers say they hope their findings will help inform further research into how hard childhoods and adverse life experiences can have a much-neglected effect on people’s health in later life.