Scientists experimenting with stressed out lab rats discovered that they passed genetic changes on to their offspring — and their offspring's offspring. Those changes caused an increased rate of preterm births.
"Preterm births can be caused by many factors," said Gerlinde Metz, senior author of a new study, in a statement. "In our study we provide new insights into how stress in our mothers, grandmothers and beyond could influence our risk for pregnancy and childbirth complications." They showed that grandchildren of stressed grandmothers suffered effects of stress — even if their mothers were not stressed.
The study, which appears in the open-access journal BMC Medicine, builds on other work demonstrating curious links between the effects of parental stress on their offspring. Typically, scientists have focused on the effects of stress during pregnancy. (Indeed, the new rat study looked at stress during pregnancy.) But there are plenty of reports about mothers and fathers passing bad news onto their children. Famous studies have even examined post-traumatic stress disorder in the children and grandchildren of Holocaust survivors.
There's a greater mystery all this research hopes to address. Stress is our body's reaction to something troubling in the environment — a roller coaster or a deadline. It prepares us to fight or flee, raising our blood pressure and releasing hormones into our muscles. Stress is not encoded in our genes and doesn't seem like something that could passed to offspring. But, somehow, science has proven its effects can be inherited.
To solve the puzzle, scientists are examining the role of molecules that aren't part of DNA strands but help regulate gene expression. Some molecules, called microRNA, have the power to shut off or turn on genes responsible for certain of our attributes. The study of this non-DNA, inherited stuff is called epigenetics.
"We have now shown that maternal stress can generate microRNA modifications with effects across several generations," Metz says. Metz and colleagues at the University of Lethbridge in Canada dealt specifically with inherited information that contributed to a greater risk of giving birth prematurely, a leading cause of neonatal death and health problems later in life. "A surprising finding was that mild to moderate stress during pregnancy had a compounding effect across generations," Metz said. "Thus, the effects of stress grew larger with each generation."
The findings may have implications for other diseases and offer clues about how non-genetic information can be transfered. According to the journal, "further work needs to be done" to figure out how the transfer actually works, the processes involved. "With more knowledge of these mechanisms it may be possible to predict and prevent preterm pregnancy but also other diseases."
Source: G.A.S. Metz, et al. Exposure to Stress Epigenetically Programs Preterm Birth Risk and Adverse Maternal and Newborn Outcomes. BMC Medicine. 2014.