Different amounts of microRNA are found in the breast milk of mothers with premature babies compared to mothers with babies born at term, according to new research from Pennsylvania State University. The altered altered microRNAs may help premature babies catch up in growth and development.

MicroRNAs are snippets of RNA that affect gene expression and can be passed to the infant. The findings could help better match babies with donated breast milk and give insight into how to develop better infant formula.

“We found that there are differences in these microRNA profiles, and that the majority of the altered microRNAs influence metabolism. If those microRNAs are being transferred to the infant, that could potentially impact how the newborn processes energy and nutrients."

said Molly Carney, medical student in the Penn State College of Medicine.

Preemie Problems

Babies born prematurely are at risk for a range of problems, including neurodevelopmental delays and failure to thrive. They also tend to be born at a lower weight than term infants.

Due to these issues, premature babies have altered nutritional needs compared to babies born at term.

Previous research has established that the macronutrients — fats, sugars and proteins — in the breast milk of mothers with premature babies are customized to meet the unique needs of these infants. But although researchers have suspected that microRNAs in breast milk have a role in infant health and development, no study has specifically looked at whether microRNAs differed between premature and term breast milk.

So researchers collected 36 samples of breast milk from mothers with infants born at term and 31 samples from mothers with infants born prematurely. Then they processed the samples in a lab, extracting the microRNAs and comparing them to the human genome to pinpoint the differences between premature and term breast milk.

After the analysis, the researchers identified nine microRNAs that were significantly different in the premature breast milk. They found that these microRNAs target metabolic processes and may help regulate gastrointestinal function and energy use in premature babies.

Unique microRNA Profiles

According to Steven Hicks, assistant professor of pediatrics in the Penn State College of Medicine, the findings could help explain why premature infants tend to do better when breast-fed by their mothers.

“We know that babies born prematurely have better health outcomes with breast milk than with formula, and our results may explain some of these health benefits associated with breast-feeding,” Hicks said. “The unique microRNA profiles that we found in premature breast milk seem well suited to premature infants, because they target metabolic pathways that could spark catch-up growth."

For example, microRNAs found in premature breast milk block both ADRB3 and NR3C1 gene expression — both of which negatively affect adipogenesis, or fat storage. Blocking these pathways could help boost fat production in premature babies that are having problems gaining weight.

Hicks said the results could have several applications, including matching babies with donated breast milk.

“For a variety of reasons, babies who are born preterm often rely on donated breast milk,” Hicks said. “Oftentimes, that milk comes from a mother who gave birth at term, and has been breast-feeding for months. That milk may not be optimal for a 32-week premature infant who was born two days ago."

Hicks said the findings could also lead to ways to create better baby formula in the future.

“MicroRNAs are an epigenetic material that is made by our bodies and is not present in formula. So even though formula is made to mirror the nutritional components of breast milk—carbohydrates, lipids and proteins—it doesn’t have any of these epigenetic factors,” Hicks said. “It is possible to create microRNAs in a lab and put them in formula. This approach might help bridge the health gap we see between formula- and breast-fed infants."

The study helps underline the fact that breast milk has multiple nutritional benefits, and may be adapted to individual infant’s needs.

Molly C Carney, Andrij Tarasiuk, Susan L DiAngelo, Patricia Silveyra, Abigail Podany, Leann L Birch, Ian M Paul, Shannon Kelleher & Steven D Hicks Metabolism-related microRNAs in maternal breast milk are influenced by premature delivery Pediatric Research (2017) 82, 226–236 doi:10.1038/pr.2017.54

Image: Johnathan D. Anderson/Flickr

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