Incubation of lipid emulsions with plasma lipoproteins modifies the fluidity of each particle

Lipid emulsions (LE) contain triglyceride (TG)-rich particles (TGRP) and ph ospholipid-rich particles (PLRP). Various lipid and protein exchanges take place during in vitro incubations of LE with lipoproteins. These compositio n changes affect physical properties of particles. The aim of this study wa s to determine the role of different LE particles and the effect of TG comp osition on physical modifications. Low density lipoproteins (LDL: 1.025 < d < 1.040 g/mL) or high density lipoproteins (HDL: 1.085 < d < 1.150 g/mL) w ere incubated with the following four LE or their TGRP or PLRP, which were manufactured with the same phospholipid emulsifier: long-chain triglyceride s (LCT): 100% soybean oil; medium-chain triglycerides (MCT)/LCT (MCT/LCT, 5 :5, w/w); FO (100% fish oil); and MLF541 (MCT/LCT/FO, 5:4:1, by wt). After incubation, modified LE particles and lipoproteins were analyzed by fluores cence polarization. Observed physical modifications were significant in emu lsion particles (ordering effect) but not in lipoproteins and also were sig nificant for TG composition effect. Since intact emulsion contained a large excess of TGRP over PLRP, it is not surprising that intact emulsion had th e same behavior as TGRP alone, and that PLRP had the same physical characte ristics as lipoproteins. TG loss and cholesterol and protein acquisitions b y emulsion particles rigidify their envelope. The two emulsions containing FO were less ordered after incubation. In conclusion, incubation of LE with lipoproteins changes physical properties of each kind of particle, and TG composition of the emulsion affects emulsion particle changes but has no ef fect on LDL and HDL. These order modifications induce more effective exchan ges between LE particles and lipoproteins and modify their metabolism; HDL changes may increase the reverse cholesterol transport.