Solubilization of free β-sitosterol in milk sphingomyelin and polar lipid vesicles as carriers: Structural characterization of the membranes and sphingosome morphology

Christelle Lopez; Elisabeth David-Briand; Virginie Lollier; Cristelle Mériadec; Thomas Bizien; Javier Pérez; Franck Artzner

doi:10.1016/j.foodres.2023.112496

Solubilization of free β-sitosterol in milk sphingomyelin and polar lipid vesicles as carriers: Structural characterization of the membranes and sphingosome morphology

Food Res Int. 2023 Mar:165:112496. doi: 10.1016/j.foodres.2023.112496. Epub 2023 Feb 2.

Authors

Christelle Lopez¹, Elisabeth David-Briand², Virginie Lollier³, Cristelle Mériadec⁴, Thomas Bizien⁵, Javier Pérez⁵, Franck Artzner⁴

Affiliations

¹ INRAE, BIA, F-44316 Nantes, France; INRAE, STLO, F-35000 Rennes, France. Electronic address: christelle.lopez@inrae.fr.
² INRAE, BIA, F-44316 Nantes, France.
³ INRAE, BIA, F-44316 Nantes, France; INRAE, PROBE Research Infrastructure, BIBS Facility, F-44316 Nantes, France.
⁴ IPR, UMR 6251, CNRS, University of Rennes 1, F-35042 Rennes, France.
⁵ Synchrotron Soleil, L'Orme des Merisiers, Saint-Aubin BP48, F-91192 Gif-sur-Yvette, France.

PMID: 36869506
DOI: 10.1016/j.foodres.2023.112496

Abstract

High consumption of plant sterols reduces the risk of cardiovascular diseases in humans and provides health benefits. Increasing the amount of plant sterols in the diet is therefore necessary to reach the recommended daily dietary intake. However, food supplementation with free plant sterols is challenging because of their low solubility in fats and water. The objectives of this study were to investigate the capacity of milk-sphingomyelin (milk-SM) and milk polar lipids to solubilise β-sitosterol molecules in bilayer membranes organised as vesicles called sphingosomes. The thermal and structural properties of milk-SM containing bilayers composed of various amounts of β-sitosterol were examined by differential scanning calorimetry (DSC) and temperature-controlled X-ray diffraction (XRD), the molecular interactions were studied using the Langmuir film technique, the morphologies of sphingosomes and β-sitosterol crystals were observed by microscopy. We showed that the milk-SM bilayers devoid of β-sitosterol exhibited a gel to fluid L_α phase transition for T_m = 34.5 °C and formed facetted spherical sphingosomes below T_m. The solubilisation of β-sitosterol within milk-SM bilayers induced a liquid-ordered L_o phaseabove 25 %mol (1.7 %wt) β-sitosterol and a softening of the membranes leading to the formation of elongated sphingosomes. Attractive molecular interactions revealed a condensing effect of β-sitosterol on milk-SM Langmuir monolayers. Above 40 %mol (25.7 %wt) β-sitosterol, partitioning occured with the formation of β-sitosterol microcrystals in the aqueous phase. Similar results were obtained with the solubilization of β-sitosterol within milk polar lipid vesicles. For the first time, this study highlighted the efficient solubilization of free β-sitosterol within milk-SM based vesicles, which opens new market opportunities for the formulation of functional foods enriched in non-crystalline free plant sterols.

Keywords: Encapsulation; Functional food; Liposome; Membrane bilayer; Milk polar lipid; Phytosterol; Plant sterol; Sphingolipid.

MeSH terms

Animals
Humans
Milk*
Phytosterols*
Sitosterols
Sphingomyelins

Substances

gamma-sitosterol
Sphingomyelins
Sitosterols
Phytosterols