| We inherit our DNA - the
genetic blueprint that determines our make-up - from our parents: 50% of
our DNA from our mothers and 50% from our fathers. Apart from the
occasional mutation, deletion or duplication of information, this DNA
remains unchanged between generations.
The environment, for example our diet, whether we
smoke, and the toxins that we encounter in our daily life, can cause
changes in how our genes are expressed - in other words, how they
function - and these changes can be inherited, even when the DNA
sequence itself does not change. These so-called "epigenetic" effects
can occur through a process known as DNA methylation, where methyl caps
bind to our DNA and act like dimmer switches on our genes.
Now, Dr Branwen Hennig and colleagues from the Medical
Research Council (MRC) International Nutrition Group based at the London
School of Hygiene and Tropical Medicine have been awarded £360,000 from
the Wellcome Trust to look at whether a mother's diet during pregnancy
can influence these epigenetic effects.
The study will be conducted at the MRC Laboratories in
Keneba, The Gambia, where the seasonal variability of food provides the
ideal environment to conduct an "experiment of nature".
"During the 'hungry season' people eat mainly what
they have in store, such as cereals and dried food," explains Ms Paula
Dominguez-Salas, who will conduct the fieldwork in The Gambia. "They are
working in the fields and have a very high energy expenditure, but their
intake is very low. The 'harvest season' is the other way round and
food, including fresh foods, is in relatively plentiful supply."
The researchers will measure the diets of women in
early pregnancy for nutrients which affect methylation, such as folate
and choline, and some B vitamins which are essential co-factors in
methylation. They will compare these to levels of the nutrients in the
women's blood and once the children have been born, the researchers will
measure methylation patterns of the babies' DNA. This will help the
researchers assess whether there is a correlation between the mother's
diet and her nutritional status, and whether there are differences in
methylation patterns in babies conceived during the harvest or hungry
seasons.
If a mother's diet does affect her offspring's
methylation patterns, this could prove very important as epigenetic
changes mediated by DNA methylation are likely to have long term effects
on the health and physical characteristics of offspring. Animal studies
have shown that supplementing the diet of pregnant mice can lead to very
marked differences in their offspring with mice fed a folate-depleted
diet producing litter with different coat colour or "kinked" tails
compared to those fed a diet rich in folate.
"Alterations in DNA methylation are thought to
increase the risk of a child developing chronic conditions later in
life, such as cardiovascular disease, cancers and type II diabetes,"
says Dr Hennig. "We think these epigenetic changes are established very
early on in the womb."
This will be the first time that the effects of a
mother's diet on epigenetic alterations of her children will be studied
so extensively. A study published recently in the Proceedings of the
National Academy of Sciences looked at the effect of wartime blockades
in the Netherlands on the nutritional intake of mothers and whether this
affected their children's expression of the IGF2 gene, which is involved
in growth, as adults. It found that the IGF2 gene had 5 per cent fewer
methyl caps in "famine babies" than in their siblings born outside this
period. However, the study by Dr Hennig and colleagues will enable the
researchers to accurately measure maternal nutritional intake and
compare this to methylation patterns in their children.
The study has been welcomed by Dr Alan Schafer, Head
of Molecular and Physiological Sciences at the Wellcome Trust.
"This is a very interesting and exciting area of
research," says Dr Schafer. "Finding a link between these women's diet
and epigenetic changes could ultimately have important implications for
our understanding of long term health effects and advice on healthy
eating."
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