DOES THE BILE SALT-STIMULATED LIPASE OF HUMAN-MILK HAVE A ROLE IN THEUSE OF THE MILK LONG-CHAIN POLYUNSATURATED FATTY-ACIDS

Long-chain polyunsaturated (LCP) fatty acids derived from linoleic (18 :2 n-6) and alpha-linolenic (18:3 n-3) acids are considered essential nutrients in preterm infants. The efficiency by which such fatty acids are released as absorbable products from triacylglycerol was explored in vitro using rat chylomicron triacylglycerol as substrate. When inc ubated with purified human pancreatic colipase-dependent lipase and co lipase, arachidonic acid (20:4 n-6) was released less efficiently than linoleic acid from such triacylglycerol. This difference was not seen when purified human milk bile salt-stimulated lipase (BSSL) was incub ated with the triacylglycerol substrate, and it was almost abolished w hen colipase-dependent lipase (with colipase) and BSSL acted simultane ously, as they do in breast-fed infants. There was no difference in ar achidonic acid and eicosapentaenoic acid (20:5 n-3) release rates with either colipase-dependent lipase or BSSL, albeit the release was more rapid with the milk enzyme than with colipase-dependent lipase. Again , the most efficient release as absorbable free fatty acids was achiev ed when the two lipases operated together. The relative resistance to hydrolysis of arachidonic acid and eicosapentaenoic acid by colipase-d ependent lipase was best explained by the localization of the first do uble bond to the delta-5 position of the respective fatty acid. The re sults obtained suggest that BSSL is of importance for the efficient us e of human milk LCP fatty acids.