Effects of recombinant human gastric lipase and pancreatin during in vitro pediatric gastro-intestinal digestion.

The aim of the study was to implement a gastric digestion step using recombinant human gastric lipase (rHGL) in an in vitro pediatric gastro-intestinal digestion model to achieve a physiologically relevant gastric contribution to total gastro-intestinal lipid digestion. A commercial infant formula (NAN Comfort stage 1 (NAN1)) with 3.4% lipid and an in-lab prepared oil-in-water emulsion, emulsified with soy phosphatidylcholine (SPCemul), with 3.5% lipid (oil-blend containing Akonino NS, MEG-3 and ARASCO oils) were subjected to in vitro gastro-intestinal digestion. To achieve a physiologically relevant level of gastric digestion, 50 min of in vitro gastric digestion, using either 0, 3.75 or 7.5 TBU mL-1 rHGL, was followed by 90 min of in vitro intestinal digestion, using either 0 or 26.5 TBU mL-1 pancreatic triglyceride lipase (PTL) from porcine pancreatin. The digestion of the substrates was assessed using titration-based quantification supported by HPLC-ELSD analysis. In vitro gastric digestion of NAN1 and SPCemul with either 3.75 or 7.5 TBU mL-1 rHGL contributed with 10-27% of the total gastro-intestinal digestion, corresponding to the reported contribution in human infants. At the end of the gastro-intestinal digestion (t = 140 min), the combined lipolytic effect of rHGL and PTL was additive during digestion of SPCemul, but not for the digestion of NAN1, as all lipase activity combinations resulted in a similar degree of NAN1 digestion. The effect of gastric digestion with rHGL on total digestion therefore appeared to be substrate dependent. To conclude, a gastric digestion step using rHGL resulting in physiologically relevant gastric contribution to the observed gastro-intestinal digestion was successfully implemented into an in vitro pediatric gastro-intestinal digestion model.

Bovine Milk-Derived Emulsifiers Increase Triglyceride Absorption in Newborn Formula-Fed Pigs.

Efficient lipid digestion in formula-fed infants is required to ensure the availability of fatty acids for normal organ development. Previous studies suggest that the efficiency of lipid digestion may depend on whether lipids are emulsified with soy lecithin or fractions derived from bovine milk. This study, therefore, aimed to determine whether emulsification with bovine milk-derived emulsifiers or soy lecithin (SL) influenced lipid digestion in vitro and in vivo. Lipid digestibility was determined in vitro in oil-in-water emulsions using four different milk-derived emulsifiers or SL, and the ultrastructural appearance of the emulsions was assessed using electron microscopy. Subsequently, selected emulsions were added to a base diet and fed to preterm neonatal piglets. Initially, preterm pigs equipped with an ileostomy were fed experimental formulas for seven days and stoma output was collected quantitatively. Next, lipid absorption kinetics was studied in preterm pigs given pure emulsions. Finally, complete formulas with different emulsions were fed for four days, and the post-bolus plasma triglyceride level was determined. Milk-derived emulsifiers (containing protein and phospholipids from milk fat globule membranes and extracellular vesicles) showed increased effects on fat digestion compared to SL in an in vitro digestion model. Further, milk-derived emulsifiers significantly increased the digestion of triglyceride in the preterm piglet model compared with SL. Ultra-structural images indicated a more regular and smooth surface of fat droplets emulsified with milk-derived emulsifiers relative to SL. We conclude that, relative to SL, milk-derived emulsifiers lead to a different surface ultrastructure on the lipid droplets, and increase lipid digestion.

Lipid hydrolysis products affect the composition of infant gut microbial communities in vitro.

Some lipid hydrolysis products such as medium-chained NEFA (MC-NEFA), sphingosine and monoacylglycerols (MAG) possess antibacterial activity, while others, including oleic acid, are essential for the optimal growth of Lactobacillus species. Thus, changes in the concentrations of NEFA and MAG in the distal ileum and colon can potentially selectively modulate the composition of the gut microbiota, especially in early life when lipid absorption efficacy is reduced. As medium-chained fatty acids are enriched in mothers' milk, such effects may be highly relevant during gut colonisation. In the present study, we examined the effect of selected NEFA, MAG and sphingosine on the composition of faecal microbial communities derived from infants aged 2-5 months during a 24 h anaerobic in vitro fermentation. We tested lipid mixtures in the concentration range of 0-200 µm, either based on MC-NEFA (10 : 0 to 14 : 0 and MAG 12 : 0) or long-chained NEFA (LC-NEFA; 16 : 0 to 18 : 1 and MAG 16 : 0) with and without sphingosine, representing lipid hydrolysis products characteristic for intestinal hydrolysis of breast milk lipids. Ion Torrent sequencing of the bacterial 16S ribosomal RNA gene revealed that the relative abundance of lactic acid-producing genera, including Lactobacillus and Bifidobacterium, was generally increased in the presence of 50 µm or higher concentrations of MC-NEFA. For Bifidobacterium, the same effect was also observed in the presence of a mixture containing LC-NEFA with sphingosine. On the contrary, the relative abundance of Enterobacteriaceae was significantly decreased in the presence of both lipid mixtures. Our findings suggest that the high concentration of medium-chained fatty acids in breast milk might have functional effects on the establishment of the gut microbiota in early life.