The paper, published in Pediatric Research, looked at breast milk of mothers with babies born prematurely (between 28 and 37 weeks gestation) and babies born at term (after 38 weeks).
Researchers found that there were differences between the milks in the microRNA profiles, parts of RNA that affect gene expression and can be passed to the infant.
This new information could help premature babies be better matched with donated breast milk, as well as shedding new light on developing infant formula.
Helping babies with different nutritional needs
Prematurely born infants are at a higher risk of problems including failure to thrive, sepsis and neurodevelopment delays, as well as being lower in weight, which means they have different nutritional needs compared to babies born at term.
Although previous research has already established that the fats, sugars and proteins in the milk of mothers with premature babies are customised to each infant, this is the first study which looked at whether microRNAs differed between premature and term breast milk.
The researchers believe their results are especially important as premature babies are often given donated breast milk.
“For a variety of reasons, babies who are born preterm often rely on donated breast milk,” said Steven Hicks, study lead and assistant professor of paediatrics in the Penn State College of Medicine.
“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.”
The results of the study showed that microRNAs in premature breast milk block both ADRB3 and NR3C1 gene expression, which both negatively affect adipogenesis, or fat storage.
Thus helping promote fat production in premature babies.
Furthermore, the team found nine microRNAs in premature breast milk that are different to term breast milk. These microRNAs target help regulation gastrointestinal function and energy use in babies.
“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,” said Hicks.
“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.”
The research team believe that the findings could also help develop infant formula better suited to the needs of premature babies.
“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,” said Hicks.
“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.”
Using 36 different samples of breast milk from mothers with babies born at term, and 31 samples of breast milk from mothers with premature babies, the research team examined the microRNA profiles in both.
This was done through extraction of microRNAs and comparing them to the human genome to uncover the differences.
Participants were excluded if there were medical complications with delivery and prenatal ultrasound.
Health and demographic information was collected from all participants including maternal age, pre-pregnancy weight, pregnancy weight gain, basic metabolic index at delivery, maternal race/ethnicity, presence or absence of maternal hypertension, delivery method, infant gestational age and infant sex.
No significant difference was found between the premature breast milk and term breast milk for maternal race/ethnicity, maternal age or infant sex.
Breast milk samples were stored at -4°C before collection and were stored at -80°C while awaiting analyses.
The researchers concluded that breast milk has multiple nutritional benefits and may be adapted to individual baby’s needs.
Source: Pediatric Research
“Metabolism-related microRNAs in maternal breast milk are influences by premature delivery”
Published online, August 2017, DOI: 10.1038/pr.2017.54
Authors: Molly C. Carney, Andrij Tarasiuk, Susan L. DiAngelo, Patricia Silveyra, Abigail Podany, Leann L. Birch, Ian M. Paul, Shannon Kelleher and Steven D. Hicks