Construction of a Synthetic Colostrum Substitute and Its Protection of Intestinal Cells against Inflammation in an In Vitro Model of Necrotizing Enterocolitis.

Colostrum provides bioactive components that are essential for the colonization of microbiota in the infant gut, while preventing infectious diseases such as necrotizing enterocolitis. As colostrum is not always available from the mother, particularly for premature infants, effective and safe substitutes are keenly sought after by neonatologists. The benefits of bioactive factors in colostrum are recognized; however, there have been no accounts of human colostrum being studied during digestion of the lipid components or their self-assembly in gastrointestinal environments. Due to the weaker bile pool in infants than adults, evaluating the lipid composition of human colostrum and linking it to structural self-assembly behavior is important in these settings and thus enabling the formulation of substitutes for colostrum. This study is aimed at the rational design of an appropriate lipid component for a colostrum substitute and determining the ability of this formulation to reduce inflammation in intestinal cells. Gas chromatography was utilized to map lipid composition. The self-assembly of lipid components occurring during digestion of colostrum was monitored using small-angle X-ray scattering for comparison with substitute mixtures containing pure triglyceride lipids based on their abundance in colostrum. The digestion profiles of human colostrum and the substitute mixtures were similar. Subtle differences in lipid self-assembly were evident, with the substitute mixtures exhibiting additional non-lamellar phases, which were not seen for human colostrum. The difference is attributable to the distribution of free fatty acids released during digestion. The biological markers of necrotizing enterocolitis were modulated in cells that were treated with bifidobacteria cultured on colostrum substitute mixtures, compared to those treated with infant formula. These findings provide an insight into a colostrum substitute mixture that resembles human colostrum in terms of composition and structural behavior during digestion and potentially reduces some of the characteristics associated with necrotizing enterocolitis.

Cholesterol stabilization of phospholipid vesicles against bile-induced solubilization.

Sphingomyelin (SM) and cholesterol complex to form functional liquid-ordered (Lo) domains. It has been suggested that the detergent resistance of these domains plays a key role during gastrointestinal digestion of the milk fat globule membrane (MFGM), which is rich in both SM and cholesterol. Small-angle X-ray scattering was employed to determine the structural alterations that occur when milk sphingomyelin (MSM)/cholesterol, egg sphingomyelin (ESM)/cholesterol, soy phosphatidylcholine (SPC)/cholesterol, and milk fat globule membrane (MFGM) phospholipid/cholesterol model bilayer systems were incubated with bovine bile under physiological conditions. The persistence of diffraction peaks was indicative of multilamellar vesicles of MSM with cholesterol concentrations > 20 % mol, and also for ESM with or without cholesterol. The complexation of ESM with cholesterol is therefore capable of inhibiting the resulting vesicles from disruption by bile at lower cholesterol concentrations than MSM/cholesterol. After subtraction of background scattering by large aggregates in the bile, a Guinier fitting was used to determine changes in the radii of gyration (Rgs) over time for the biliary mixed micelles after mixing the vesicle dispersions with bile. Swelling of the micelles by phospholipid solubilization from vesicles was a function of cholesterol concentration, with less swelling of the micelles occurring as the cholesterol concentration was increased. With 40% mol cholesterol, the Rgs of the bile micelles mixed with MSM/cholesterol, ESM/cholesterol, and MFGM phospholipid/cholesterol were equal to the control (PIPES buffer + bovine bile), indicating negligible swelling of the biliary mixed micelles.

Emulsions containing optimum cow milk fat and canola oil mixtures replicate the lipid self-assembly of human breast milk during digestion.

HYPOTHESIS: The digestion of different milks and milk substitutes leads to the formation of a variety of self-assembled lipid structures, with the structuring of human milk being paramount for infant nutrition. It was hypothesised that mixing cow milk fat rich in medium/long-chain lipids with canola oil rich in long-chain unsaturated lipids would replicate the structuring of human milk by balancing lipid chain lengths and saturation levels. EXPERIMENTS: Emulsions of cow milk fat/canola oil mixtures were prepared in two ways - by pre-mixing ghee and canola oil before dispersing them and by dispersing canola oil directly into commercial cow milk. Small angle X-ray scattering combined with titration of the fatty acids produced during digestion allowed for the correlation of dynamic lipid self-assembly with the extent of lipid digestion. Laser light scattering was used to show that the particle sizes in the digesting mixtures were similar and coherent anti-Stokes Raman spectroscopy (CARS) microscopy was used to confirm the mixing of canola oil into cow milk fat globules. FINDINGS: As the amount of long-chain unsaturated canola oil lipids in the mixtures increased, the lipid self-assembly tended towards colloidal structures of greater interfacial curvature. When the ratio of cow milk fat to canola oil lipids was 1:1 (w/w), the digesting lipids assembled themselves into the same liquid crystalline structures as human breast milk. This observation was independent of the method used to mix the lipids, with CARS microscopy indicating uniform mixing of the canola oil into cow milk upon ultrasonication.