Inside Pediatrics, Neonatology

Helping the Tiniest Babies Grow

Ariel A. Salas, M.D., a neonatologist at Children’s of Alabama and the University of Alabama at Birmingham (UAB), was completing his master’s in public health when he first became interested in growth and nutrition in premature infants. “It’s a growing field,” he said. For years, neonatology was primarily focused on lung disease because most survival was linked to the degree of respiratory disease, he said, but with significant improvement in respiratory care and outcomes, “we’re now trying to optimize outcomes among the surviving infants.”

Premature infants, particularly those born at the limits of viability, typically don’t grow well during their hospital stay and have a higher risk of developing long-term nutritional complications related to extreme prematurity. Yet nutritional issues were traditionally an afterthought.

Now, thanks to a five-year, $777,384 Mentored Patient-Oriented Research Career Development Award (K23), Salas hopes to change that. The award provides him with the mentorship, training, and research experience to become an independent clinician scientist and leader in neonatal nutrition research. As he wrote in his grant application: “My long-term career goal is to reduce the burden of postnatal growth failure through novel translational studies and large scale, multi-center clinical trials of promising dietary interventions that optimize growth, reduce dysbiosis of the gut microbiome, and ultimately improve neurodevelopment.”

The grant will support a study to determine if giving preemies protein-enriched human milk during their first two weeks can promote lean body mass accretion, stimulate maturation of the gastrointestinal tract, and modify the gut microbiome.

One thing that makes this study unique is its focus on lean mass growth versus growth overall, Salas said. “Preemies are born so small they can grow really fast, but that could be because they’re getting too much fat in the diet,” he said, which could lead to later problems, including obesity. “There are a lot of unknowns in the implications of changing fat mass in preemies.” Still, he said, it will take two decades before the full implications of improved lean mass in premature infants is known.

“The advantage of protein is that it’s so important for structural growth.” Indeed, preliminary evidence from another study he participated in found that increased protein did improve the amount of lean mass growth in premature babies, he said. Those babies received the enhanced milk when they were older and their condition more stable; this study will start babies on the milk in the first two weeks.

The study uses a human-based protein fortifier added either to the mother’s breast milk or milk from the milk bank. It also uses a novel approach of measuring biomarkers in urine to see if they can predict the amount of lean mass seen in the body scans.

It’s not clear how lean mass affects development, Salas said, since the field is so new. “It’s only been in the past 10 years that we started measuring lean mass with non-invasive methods in extremely premature infants,” he said. Data over the past decade suggests, however, that overall lean mass is the safest approach to growth, leading to greater length and other outcomes.

The next step in this research, he said, is to see how the additional protein is digested and absorbed in the intestines and how it affects the gut microbiome. “Possibly some of those microbes can facilitate the digestion and absorption of the nutrients and if we can improve both, we may be able to improve growth overall.”

“This is a fascinating area,” said Salas, “and it probably has more serious implications in preterm infants because they have so much potential for growth.”

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