One in eight is genetically protected against jaundice

Almost all newborn babies have jaundice in their very first few days of life. The babies will develop a yellowish tinge to their skin and the whites of their eyes. The yellow tint is caused by bilirubin, which is a residual product of the baby's breakdown of excess red blood cells.

Usually, jaundice goes away on its own within a week, but some children need special treatment. Jaundice can affect energy and appetite. If the condition is prolonged, high levels of bilirubin can cause brain damage.

Almost full protection

The study, published in the journal Nature Communications, is the result of an international research collaboration, led by the University of Gothenburg. The research is based on blood samples from almost 30,000 newborn babies and their parents in a research database in Norway. About 2,000 of the babies had jaundice. One of the millions of genetic variants analyzed was found to almost completely protect infants from developing jaundice. The gene variant is found in around 12% of babies born in Europe and the United States.

"The gene variant codes for an enzyme that has not previously been linked to the metabolism of bilirubin. Although the enzyme itself does not protect against jaundice, the discovery has led us further down an exciting research path, opening new avenues for individualized medicine," says Pol Solé Navais, a researcher at Sahlgrenska Academy at the University of Gothenburg, who is the lead author of the study.

Activity in the intestines

The research team was able to identify that the gene variant can be linked to an increase in another enzyme, UGT1A1, that is important for the body's metabolism of bilirubin.

"This enzyme converts bilirubin into a variant that is water-soluble, allowing the body to get rid of the bilirubin. We are surprised that we only see this effect in the intestines of the babies, but not in the liver, as it is the liver that is responsible for the metabolism of bilirubin in adults," says Professor Bo Jacobsson, who leads the research group.

The study provides an opportunity to further study the UGT1A1 enzyme and its activity in the intestines of newborns, with the aim of preventing or treating neonatal jaundice.