ASSOCIATION OF A VARIANT LIPASE IN HUMAN MILK WITH PROLONGED NEONATAL JAUNDICE

Abstract

Human milk samples that inhibit billrubin-UDP-glucuronyl transferase activity in vitro have been associated with prolonged unconjugated hyperbilirubinemia in newborn infants. 1/178 milk samples collected at random inhibited the enzyme as compared to 7/15 suspected samples. The non-esterified fatty acid (NEFA) content of five inhibitory milks (27.6 ± 4.9 mM) differed from control samples (12.3 ± 5.5 mM, p<0.05). This is in agreement with Bevan and Holton (Clin Chlm Acta, 1972). The concentration of each fatty acid measured by GLC was higher in inhibitory milks. The lipase activity of 124 milk samples collected from volunteers on day 3 or 4 of lactation (control group) was compared with that of 8 samples from mothers of infants with prolonged unconjugated hyperbilirubinemia (jaundiced group). The lipase assays were performed in duplicate using tributyrin as substrate with and without sodium taurocholate (TC) in the incubation mixture. Results as follows: Agarose gel electrophoresis of milk proteins showed a difference in mobility between lipases from normal and abnormal milk. Thus, a lipase with abnormally high activity and variant electrophoretic mobility appears to be the cause of increased concentrations of NEFA in the abnormal breast milks.