Studies of baby pigs address breathing problems

University research on baby pigs may soon help doctors improve the way they care for premature infants.

Nutritional scientists Barb Mickelson and Norlin J. Benevenga from the College of Agricultural and Life Sciences examined the growth-suppressing side effects of dexamethasone, a medication commonly used to help premature infants breathe.

After establishing that baby pigs and human babies respond similarly to the drug, the researchers investigated how dexamethasone changes protein metabolism. What they found out might lead to clues about how to counteract the side effects.

Frank Greer, a pediatrician at Meriter Hospital and a Medical School professor, is working with Mickelson and Benevenga and hopes to apply the results of their research to his tiny patients at Meriter.

Pediatricians use dexamethasone as an effective and inexpensive treatment for respiratory distress syndrome, a potentially life-threatening condition for premature infants. However, the steroid-type drug is known to cause growth problems in human infants. Mickelson says the new research shows piglets build less muscle and lung tissue, and gain weight more slowly while on the drug.

Earlier work by other researchers found that weight gain and linear growth declined by 40 percent and 60 percent respectively after two weeks of dexamethasone treatment. Mickelson says two-week old piglets treated with the drug for up to four days gained 15 percent to 30 percent less weight than untreated piglets, depending on how much drug they received.

As for the drug’s other side effects, Mickelson says, “We saw a 15-percent to 25-percent decrease in the rate of protein synthesis in skeletal muscle and lung. Dexamethasone interfered with the ability of certain tissues to synthesize protein and thus grow.”

Human infants commonly receive dexamethasone treatment lasting from three days to three weeks and suffer similar growth setbacks, medical experts say.

Mickelson’s study says dexamethasone could compromise an infant’s health because it changes how the body uses amino acids, the building blocks of body proteins. During dexamethasone treatment, amino acids are not used to build protein. Instead the body uses them for energy or to make fat. These negative effects begin within 24 to 48 hours of the first dose, and subside within 24 to 48 hours after the last dose.

“We have a better idea of the mechanism thanks to Barb’s study,” says Greer. The study was partially funded by the Meriter Foundation.

Wisconsin has about 5 percent fewer premature infants born each year compared with other states. Nevertheless, Greer estimates that 1 to 2 percent of the premature infants at Meriter require dexamethasone treatment each year.