Hydrolysis of emulsions with different triglycerides and droplet sizes by gastric lipase in vitro. Effect on pancreatic lipase activity

Abstract

Digestion of dietary fat first takes place in the stomach in numerous species including humans. Thus, we have studied in vitro the gastric lipase-catalyzed hydrolysis of four emulsions devoted to tube feeding. The emulsions contained phospholipids, sugar-esters, and triglycerides in the form of either medium-chain triglycerides (MCT) or long-chain triglycerides (LCT) or a 1 4 (wt/wt) mixture of both (MCT/LCT). The mean droplet sizes were 0.19 μm (MCT), 0.43 μm (LCT), and 0.46 μm or 3.18 μm (MCT/LCT). Gastric lipase activity was greater on the fine mixed emulsion than on the coarse one, but enzyme affinities and bindings onto droplets were comparable. The affinity of gastric lipase was higher for LCT emulsion. Free fatty acid concentration played a key role in the progressive inhibition of lipolysis, the extent of which was dependent on the emulsion surface area. Prehydrolyzing emulsions by gastric lipase helped pancreatic lipase binding to the fine droplets and enhanced the subsequent activity of pancreatic enzyme. Relevant implications of nutritional importance can be drawn concerning lipolysis in the stomach, such as (1) suitability of mixed emulsions, (2) key role of the nature of triglycerides, (3) apparent advantage of small droplet size (0.4 versus 3 μm), and (4) potential detrimental effect of free fatty acids present in emulsions to be tube fed in the stomach, especially in patients with reduced pancreas capacity. ( J. Nutr. Biochem. 5:124–133, 1994.)