Cholesterol stabilization of phospholipid vesicles against bile-induced solubilization

• Published in: Chemistry and physics of lipids 2023-05, Vol.252, p.105289-105289, Article 105289
• Main Authors: Tai, Patrick, Clulow, Andrew J., Boyd, Ben J., Golding, Matt, Singh, Harjinder, Everett, David W.
• Format: Article
• Language: English
• Subjects: Animals; Bile; Bile Acids and Salts; Cattle; Cholesterol - chemistry; Detergent kinetics; in vitro digestion; Lecithins; Micelles; Milk fat globule membrane; Phosphatidylcholines - chemistry; Phospholipid; Phospholipids; Small angle X-ray scattering; Sphingomyelins - chemistry
• ISSN: 0009-3084; 1873-2941
• DOI: 10.1016/j.chemphyslip.2023.105289

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. •Incorporating cholesterol into MFGM phospholipid model bilayers may reduce solubility by bovine bile.•The lamellar structure of 30% mol cholesterol, MSM/cholesterol MLVs persists in the presence of 10 mM bovine bile.•Biliary mixed micelles radius of gyration (Rg) was ∼15 Å.•After incubation with 0% mol cholesterol MFGM vesicles, mixed micelles were ∼ 17 Å.•After incubation with 40% mol cholesterol MFGM vesicles, mixed micelles were ∼ 15 Å.