Humanin protein plays a role in breaking down carbohydrates and delivering nutrients to other organs, including muscle.
The UCLA scientists suspect that levels of humanin rise to protect the fetus during placenta failure.
Up to 10 percent of pregnancies are affected by intrauterine growth restriction, in which a newborn weighs less than 5 ― pounds at full-term delivery. The condition heightens the risk for a wide range of serious health problems.
The cause remains poorly understood, but most physicians blame a malfunction in the placenta that prevents the mother's bloodstream from delivering oxygen and nutrients to her fetus.
In studying the human placenta, researchers looked at gene expression: the process by which a gene's DNA sequence is converted into cellular proteins. They compared the placentas of women who gave birth to healthy babies to the placentas of women who delivered low-birthweight infants
The team found significantly higher levels of humanin in the latter group. This protein protects the body against oxidative stress, which hampers the body's ability to defend itself against toxic free radicals (a type of particle linked to disease).
The finding may help researchers unravel the reasons why low birthweight babies face a higher risk of obesity, high blood pressure, diabetes and heart disease as adults.