STRESS DURING PREGNANCY CAN BE PASSED DOWN THROUGH GENERATIONS
To better understand problems
during pregnancies today, we should look to the experiences of our ancestors,
research published in the open access journal BMC Medicine suggests. Scientists investigating pregnancies in four generations of
rats show that inherited epigenetic effects of stress could affect pregnancies
for generations.
Researchers from the
University of Lethbridge in Canada wanted to investigate how preterm births are
influenced by stress. Preterm birth is one of the leading causes of neonatal
death and can lead to health problems later in life. They examined the length of
pregnancies in rats because in general there is very little variation between
them.
A first generation of
rats were subjected to stress late in pregnancy. The following two generations
were then split into two groups that were either stressed or not stressed. The
daughters of stressed rats had shorter pregnancies than the daughters of those
who had not been. Remarkably, the grand-daughters of stressed rats had shorter
pregnancies, even if their mothers had not been stressed.
As well as shorter
pregnancies, the rats whose grandmothers and mothers experienced stress
displayed higher glucose levels than the control group. In addition, rats whose
grandmothers or mothers who were stressed weighed less.
Gerlinde Metz, senior
author of the article, says: "We show that stress across generations
becomes powerful enough to shorten pregnancy length in rats and induce hallmark
features of human preterm birth. A surprising finding was that mild to moderate
stress during pregnancy had a compounding effect across generations. Thus, the
effects of stress grew larger with each generation."
The researchers believe
that these changes are due to epigenetics -- the arrangement and expression of
our genes. In most cases this refers to DNA methylation of the nucleotide base
pairs. In this study the researchers believe the epigenetic changes are due to
microRNA (miRNA) -- non-coding RNA molecules that play a role in regulating
gene expression.
Gerlinde Metz says:
"Previous epigenetic studies have mainly focused on inheritance of DNA
methylation signatures. What we didn't know was whether microRNAs, which are
important biomarkers of human disease, can be generated by experiences and
inherited across generations. We have now shown that maternal stress can
generate miRNA modifications with effects across several generations. I think
this is an interesting feature of our manuscript."
Further work needs to
be done to understand the mechanisms that generate these epigenetic signatures
and how they are passed down from generation to generation. With more knowledge
of these mechanisms it may be possible to predict and prevent preterm pregnancy
but also other diseases.
Gerlinde Metz says:
"Preterm births can be caused by many factors, 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. The findings
have implications outside of pregnancy, in that they suggest that the causes of
many complex diseases could be rooted in the experiences of our ancestors. When
we better understand the mechanisms of inherited epigenetic signatures, we can
predict disease risk and potentially reduce the future risk of illness."
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