Researchers have known for decades that what a woman eats during her pregnancy can impact her child's weight later in life. Now, a new study shows a possible mechanism for how mom's diet affects baby's weight: Epigenetic changes---changes that can increase or decrease the expression of a particular gene but don't alter the genetic sequence---to a gene involved in fat metabolism can be passed from mother to child during pregnancy. How the Heck:
What's the News:
The researchers asked nearly 80 pregnant women in Britain about their diets during pregnancy (and checked their blood for traces of some foods, to provide a more objective measure of diet).
At the birth of each child, the researchers took a sample of the child's DNA from the umbilical cord. They analyzed the DNA for methylation, a common epigenetic change that occurs when a structure called a methyl group latches onto a particular point in a person's DNA. When the children were nine years old, the researchers measured their body fat.
Children with methylation of a gene called RXRα, which is important in helping fat cells develop normally and in regulating their metabolism, were more likely to be obese than children who didn't have methylation on that gene, the researchers found.
The researchers then repeated the study with another group of women, this time measuring the children's body fat at age six. Again, RXRα methylation predicted how much body fat the children had. Children's body fat percentage increased from 17% to 21% as the proportion of methylated RXRα genes increased from 40% to 80%.
Looking back at what the mothers ate, the researchers found that a link between a low-carbohydrate diet early in pregnancy and higher levels of RXRα methylation.
Methylation of the RXRα gene predicted a quarter of the variation in children's body fat levels---a better predictor of obesity than birth weight. This link persisted whether or not the mothers themselves were thin.
What's the Context:
Researchers first observed the effects of a pregnant woman's diet on the weight of offspring in the 1970s, studying the children of women who endured the Dutch Famine of 1944 while pregnant. These children were more likely to be obese, and to show other symptoms of metabolic syndrome, than children whose mothers had enough to eat during their pregnancies.
Other factors can influence epigenetic changes, too, such as environment after birth, diet, stress level, and smoking.
Not So Fast:
Since methylation of the RXRα gene only predicted a quarter of body fat variation, that leaves room for lots of other factors to play a role. Unsurprisingly, mom's diet early in pregnancy isn't the only---or even the primary---cause of obesity.
Reference: Keith M. Godfrey et al. "Epigenetic Gene Promoter Methylation at Birth Is Associated With Child’s Later Adiposity." Diabetes online ahead of print, April 6, 2011. DOI: 10.2337/db10-0979
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