For the new study, which was published in the Journal of Applied Physiology in March, scientists from the University of Virginia Medical School and other institutions first gathered a large group of mice. Some of the animals, male and female, were allowed to eat high-fat and high-calorie diets, which led to obesity and metabolic problems, while others stayed at their usual weight on normal food.
Next, the mice teamed up with obese animals of both sexes, which mated with mice of normal weight, so theoretically one parent in each mating could leave the young with unhealthy habits and metabolism. Some normal weight animals without metabolic problems also mated to produce control offspring.
Finally, some mothers, including the obese, jogged on small exercise bikes during the resulting pregnancies, voluntarily walking up to seven miles a week in the early stages of their three-week pregnancy.
The researchers then tracked the metabolic health and underlying genetic activity of the offspring until they reached adulthood. This second generation ate normal food and lived normal lives with laboratory mice.
However, many developed several metabolic problems as adults, including obesity, insulin resistance, and other disorders of their blood sugar control. These conditions were most pronounced in male children of obese mothers and in both male and female children born to obese fathers.
Interestingly, the underlying genetics of their conditions differed according to the gender of the parents. Mice born to obese mothers showed unusual activity in a number of genes known to be involved in inflammation. Those born to obese fathers did not.
In other words, the genetic inheritance of mothers and fathers “works in different biological ways,” says Zhen Yan, professor of medicine and director of the Center for Skeletal Muscle Research at the University of Virginia Medical School, who oversaw the new study.