Clinical significance of transfer of apolipoproteins between triacylglycerol-rich particles in lipid emulsions and plasma lipoproteins.

Triacylglycerol (TG)-rich particles in parenteral lipid emulsion have been designed to mimic chylomicrons (CMs), which are exogenous dietary TG-rich lipoproteins. Over the past 30 yr, since lipid emulsions were first used for parenteral nutrition, it has been generally accepted that the intravascular metabolism of TG-rich particles in an emulsion is similar to that of CMs. Both the particles in an emulsion and CMs have a TG core that is stabilized by a surface layer of phospholipids. However, there are major differences between the two types of particles regarding their composition of protein moieties. CMs contain and acquire apolipoproteins, which are essential for the regulation of their intravascular metabolism. In contrast, the TG-rich particles in an emulsion do not contain any apolipoprotein. It has been demonstrated that the particles in an emulsion also acquire various kinds of apolipoprotein during their brief intravascular life. Thus, they may be subject to intravascular metabolic processes similar to those of CMs. In this review, we describe the mechanism by which TG-rich particles in an emulsion acquire apolipoproteins from the perspective of parenteral nutrition with lipid emulsions.