Male mice that work out spawn healthier offspring than their lethargic counterparts, according to a new study. Whether the results hold true for humans remains uncertain, but they support the notion that some of the benefits of exercise are somehow passed on to the next generation.
“The science is solid, and it’s pretty exciting,” says epigeneticist Sarah Kimmins of McGill University in Montreal, Canada, who wasn’t connected to the work.
Scientists already know that a parent’s bad exercise or dietary habits can affect their offspring. Mothers who are obese during pregnancy, for example, give birth to children who are more likely to be obese as adults and develop metabolic illnesses such as cardiovascular disease. Another study found that male rats that snarfed high-fat chow fathered offspring that didn’t respond normally to glucose, a hallmark of type 2 diabetes.
To determine whether the opposite is true, molecular exercise physiologist Kristin Stanford of The Ohio State University College of Medicine in Columbus and colleagues fed male mice a fat-rich diet for 3 weeks. One group of animals had access to running wheels, scampering nearly 6 kilometers per night on average, but the rest were couch potatoes. After dissecting some of the rodents to obtain samples of their sperm, the researchers allowed the remaining mice to mate.
Stanford and her colleagues tracked the resulting offspring until they were a year old, about middle age for a mouse. Even though the offspring of exercising and nonexercising dads all ate a high-fat diet their entire lives and didn’t get any physical activity, the offspring of healthy fathers seemed to inherit their dads’ metabolism. The progeny of the runners showed a better response to increases in blood glucose and had lower insulin levels—both hallmarks of a sound metabolism—the researchers report today in Diabetes. “Exercise was completely negating the effect of a high-fat diet” on the offspring, Stanford says.
The researchers suspect the offspring might inherit their dads’ metabolic condition through small RNA molecules in sperm. Previous studies have linked these molecules to changes in metabolism in the next generation. And indeed, the sperm of the lazy dads were loaded with fragments of transfer RNA. These molecules, when whole, are essential for synthesizing proteins, but how the fragments function is a mystery—they may modify protein production. The sperm of the exercisers, in contrast, had relatively few such fragments. Stanford and her colleagues still don’t know how the RNA shards affect an offspring’s metabolism, but they speculate that the pieces alter the growth or development of the young early in pregnancy.
“It’s a well-executed paper,” says reproductive biologist Michelle Lane of the University of Adelaide in Australia, who wasn’t connected to the study. Previous research has only gauged the immediate effects of paternal exercise on young offspring, she says, but the fact that the researchers followed the mice for a year shows that “the possible impacts are maintained throughout life.”
Lane cautions that researchers don’t know whether exercise provides the same benefits in people, so it may be too early for would-be fathers to start training for marathons. Nevertheless, Kimmins says, the study “provides hope that if men would exercise, they would have healthier children.”