Jaundice is one of the most common worries on a maternity ward. Up to six in ten full-term babies and eight in ten premature ones develop the tell-tale yellow tinge because bilirubin, a pigment produced when old blood cells are recycled, piles up faster than an immature liver and gut can get rid of it. Usually it fades without treatment, but very high or stubborn levels can reach the brain and cause lasting harm.
A team at UC San Diego now thinks part of the answer lies in a single ingredient of mother’s milk. The researchers, led by pharmacology professor Robert Tukey, focused on 3’-sialyllactose, or 3’SL, one of the complex sugars that babies cannot use as food but that shape their developing gut. The study was published in a specialist gastroenterology journal of the American Gastroenterological Association.
To test the idea, the scientists used mice carrying human genes for bilirubin processing, animals that naturally go through newborn jaundice. Pups whose mothers’ milk lacked 3’SL fared badly: fewer survived, they grew more slowly, their intestines were shorter and their jaundice was worse. Their gut lining also produced far less UGT1A1, the enzyme that converts bilirubin into a form the body can excrete, and genes that mark mature intestinal cells were turned down.
The consequences seemed to outlast infancy. Mice missing St3gal4, a gene tied to the availability of this kind of sugar, coped worse with chemically induced colon damage as adults, losing more weight and dying more often. Tukey believes what a baby drinks in its first days may shape how robust its gut remains for life.
The work has so far been done only in animals. Still, the researchers suspect that differences in milk sugars between mothers might account for why one infant turns noticeably yellow while another barely does, and that supplements might one day support vulnerable newborns.
