Our results suggest that early milk exposure could have lasting, systemic impacts on gut resilience,
said Robert Tukey, PhD, a Distinguished Professor of Pharmacology at the UC San Diego School of Medicine.
University of California San Diego researchers have identified a specific sugar in human breast milk that may support intestinal maturation and help infants process bilirubin, a metabolic waste product. The study, published in the journal Cellular and Molecular Gastroenterology and Hepatology, identifies the sugar 3’-sialyllactose (3’SL) as a factor in preventing jaundice.
Jaundice, or neonatal hyperbilirubinemia, occurs when bilirubin—a byproduct of the breakdown of red blood cells—builds up in the blood and yellows the skin and eyes. This condition affects 80% of preterm infants and 60% of term infants. While most cases are mild, high or persistent bilirubin levels can cross the blood-brain barrier and lead to neurological consequences.
Sugar Influences Bilirubin Metabolism
Researchers worked with scientists at UC San Diego’s Human Milk Institute to study mouse models of neonatal hyperbilirubinemia to see how milk composition influences bilirubin metabolism. The team discovered that 3’SL is vital for development and waste processing.
Mouse pups raised on milk lacking 3’SL exhibited lower survival rates and poorer growth. These pups also had shorter intestines and more severe jaundice. Researchers found markedly reduced intestinal levels of the enzyme UGT1A1, which clears bilirubin.
The study noted disrupted cellular signaling and different patterns of gene expression in these pups, specifically reduced markers of cellular maturation. The loss of the St3gal4 gene, which is linked to the availability of 3’SL, was associated with the abnormal activation of pancreatic genes in the pups.
These effects may extend into adulthood. Mice with a persistent St3gal4 deficiency were more vulnerable to colon injury induced by chemicals, showing greater weight loss and lower survival rates.
Nutritional Strategies May Prevent Jaundice
The research offers insight into why some infants experience more severe jaundice than others. Breastfed infants can develop breast milk jaundice, often attributed to milk composition and slower milk intake during the first days of life, but this study points to specific bioactive components in bilirubin metabolism.
Our research also suggests that natural differences in milk sugar composition could help explain why some infants develop more severe jaundice than others,
Tukey said.
Tukey noted these findings offer the possibility of developing nutritional strategies to support intestinal maturation and prevent the onset of jaundice. The study was led by Tukey and received funding in part from the Human Milk Institute at UC San Diego and U.S. Public Health Service Grants.