Palmitoyl ceramide promotes milk sphingomyelin gel phase domains formation and affects the mechanical properties of the fluid phase in milk-SM/DOPC supported membranes
Résumé
Ceramides are minor structural components of membranes involved in biological functions. In the milk fat
globule membrane (MFGM), ceramides are susceptible to affect the lateral packing of polar lipids, especially the
milk sphingomyelin (MSM). To investigate this, palmitoylceramide (PCer) was added to MSM/DOPC (dioleoylphosphatidylcholine)
in order to form hydrated lipid bilayers. Differential scanning calorimetry evidenced
interactions of PCer with the MSM in the solid-ordered phase to form MSM/PCer structures with a higher
thermostability than MSM. Atomic force microscopy revealed that PCer modified lipid packing in both the
liquid-disordered DOPC phase where it increased thickness and mechanical stability, and the solid-ordered MSM
phase where it recruited MSM molecules yet initially in the liquid phase at 26 °C and then increased the area of
the MSM/PCer domains. The effect of PCer on the mechanical properties of the MSM-rich domains remains to be
elucidated. These results bring new insights on the role of ceramides in the control of biophysical and biological
properties of the MFGM. They also open perspectives for the design of emulsions and liposomes, using milk polar
lipids as food-grade ingredients.