Modulating pancreatic lipase activity with galactolipids: effects of emulsion interfacial composition

It is widely known that the interfacial quality of lipid emulsion droplets influences the rate and extent of lipolysis. The aim of this work was to investigate the effect of two galactolipids, monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), adsorbed at the interface on in vitro digestibility of olive oil by porcine pancreatic lipase. The experiments were performed under simulated duodenal conditions in the presence of phosphatidylcholine (lecithin) and bile salts. It was found that emulsions prepared with DGDG had a longer lag phase prior to lipase activation with a decrease in lipolysis rate. In contrast, no inhibitory effect on lipase kinetics was observed in emulsions prepared with MGDG. We postulated that the larger headgroup and more tightly packed molecular organization of DGDG at the interface gave rise to steric hindrance that retarded colipase and lipase adsorption onto the substrate surfaces and hence delayed and reduced lipolysis. It was noted that the lag phase and lipolysis rate strongly depended on the DGDG/lecithin molar ratio in the systems: the higher the molar ratio, the longer the lag phase followed by a reduced lipolysis rate. The ability of DGDG to inhibit bile salt adsorption/displacement was also investigated. The results showed that bile salts did not completely displace DGDG from the interface, explaining the reason why DGDG still possessed inhibitory activity even in the presence of bile salts at a physiological relevant concentration. The results provide interesting insights into the influence of the galactolipid headgroup and lecithin on the emulsion interfacial quality which in turn regulates the lipolysis. The findings potentially could lead to the production of generic foods and drugs designed for regulating dietary fat absorption in the prevention and treatment of obesity and related disorders.