Fatty acids generated by gastric lipase promote human milk triacylglycerol digestion by pancreatic colipase-dependent lipase

Abstract

The concerted action of purified bovine gastric lipase and human pancreatic colipase-dependent lipase and colipase, or crude human pancreatic juice, in the digestion of human milk triacylglycerols was explored in vitro. Gastric lipase hydrolyzed milk triacylglycerol with an initially high rate but became severely inhibited already at low concentration of released fatty acid. In contrast, colipase-dependent lipase could not, by itself, hydrolyze milk triacylglycerol. However, a short preincubation of milk with gastric lipase, resulting in a limited lipolysis, made the milk fat triacylglycerol available for an immediate and rapid hydrolysis by pancreatic juice, and also for purified colipase-dependent lipase, provided colipase and bile salts were present. The same effect was obtained when incubation with gastric lipase was replaced by addition of long-chain fatty acid. Long-chain fatty acid increased the binding of colipase-dependent lipase to the milk fat globule. Binding was efficient only in the presence of both fatty acid and colipase. We conclude that a limited gastric lipolysis of human milk triacylglycerol, resulting in a release of a low concentration of long-chain fatty acids, is of major importance for the subsequent hydrolysis by colipase-dependent lipase in the duodenum.