Early exposure to diesel exhaust linked to heart failure in mice

Exposure to diesel exhaust in the womb or as a newborn may raise the risk of heart failure in adulthood, according to a new study of mice.

While diesel exhaust already has been linked to heart attacks in adults, this is the first study suggesting that fetal and early life exposure may make adults more susceptible to heart disease.

In the study, lab mice breathed either diesel exhaust or filtered air for three weeks before pregnancy, during pregnancy, and three weeks after giving birth.

Their 54 baby mice then had eight weeks of exposure to either diesel exhaust or filtered air, then underwent surgery at 12 weeks to induce more pressure on the heart.

The mice exposed in the womb and during early development were more susceptible to cardiac hypertrophy, systolic failure, myocardial fibrosis, and pulmonary congestion compared with mice exposed to filtered air or those exposed only as an adult, the study found.

The mice were exposed to levels--300 micrograms per cubic metre of air--that people regularly breathe in highly polluted cities, according to the study published in the journal Particle and Fibre Toxicology.

Mice exposed to diesel in the womb had a fivefold increase in fibrosis, or thickening of the heart valves, which can lead to heart failure, said Chad Weldy, lead author and senior fellow at the University of Washington school of medicine.

All of the mice went into some level of heart failure because of the surgery, but mice that were exposed to diesel exhaust in the womb or during early development responded most poorly, Weldy said.

The eight weeks of diesel exposure did not affect the heart health of the adult mice, which confirms findings of previous studies, Weldy said.

The study “implies that adult cardiovascular disease may have more origins in developmental exposure to air pollution than is currently appreciated,” the authors wrote.

Previous studies have determined that development in the womb and during early life is a critical time in determining susceptibility to heart disease later in life.

Also recent animal research found that diesel exposure during pregnancy led to fetal inflammation, which makes babies more susceptible to obesity and pulmonary problems later in life.

It is not clear how early diesel-exhaust exposure may spur heart problems later in life, but the researchers speculated that it alters how the placenta functions.

“The placenta plays an important role in regulating fetal development--blood flow, nutrient flow, oxygen transfer,” Weldy said. “All of these are necessary for fetal growth, so it ends up growing in a malnourished environment, which can predispose to heart disease.”