It's in their genes

The health effects of a bad diet can carry over to offspring through eggs and sperm cells without DNA mutations, researchers have found.

A mouse study, published in Nature Genetics, provides some of the strongest evidence yet for the nongenetic inheritance of traits acquired during an organism’s lifetime. And although previous work has suggested that sperm cells can carry “epigenetic” factors, this is the first time that such an effect has been observed with egg cells.

Endocrinologist Peter Huypens at the German Research Centre for Environmental Health in Neuherberg, Germany, and his colleagues gave genetically identical mice one of three diets — high-fat, low-fat or standard laboratory chow — for six weeks. As expected, those fed the high-fat diet became obese and had impaired tolerance to glucose, an early sign of Type 2 diabetes.

The team then took eggs and sperm cells from each of the three groups and performed in vitro fertilisation, implanting the resulting embryos into healthy surrogate mothers. The idea was that if a physical trait or behaviour was observed in the offspring, it could only have been transmitted through the egg or sperm cells.

“Their design means that previous possible confounders like maternal bonding, feeding and the microbiome are ruled out,” says Tim Spector, a genetic epidemiologist at King’s College London, who was not involved in the study.

When the adult offspring were subsequently fed a high-fat diet, those with obese parents seemed more prone to gaining weight and developing glucose intolerance, particularly if both parents were obese. Curiously, daughters seemed more prone to gaining weight if their parents had been obese, whereas sons were only more prone to developing glucose intolerance. The mother’s diet also seemed to have a greater influence on the offspring’s metabolism than the father’s did.