ABSTRACT
The aqueous environment of plasma dictates that hydrophobic lipids are transported in complex macromolecules referred to as lipoproteins. All lipoproteins are comprised of a core of hydrophobic lipids, predominantly esterified cholesterol and triglyceride, encompassed by a monolayer of amphiphylic lipids including unesterified cholesterol and phospholipids. A series of proteins containing lipid binding domains (referred to as apolipoproteins) bind to the lipoprotein complex and essentially dictate the catabolism of the particle by acting as co-factors for enzymes, or ligands for cell membrane binding sites (Mahley et al., 1984). The simplistic definition of lipoproteins suggests homogeneity, however, of the spectrum of plasma lipoproteins, chylomicrons are perhaps uniquely heterogeneic, because unlike other lipoproteins they are the vehicle by which dietary hydrophobic substances are transported into circulation. In addition to ingested fats, chylomicrons mediate the transport of fat soluble vitamins, hydrophobic antioxidants such as atocopherol and beta carotene (Traber et al., 1990) and lipophylic chemicals including therapeutic compounds (Cheema et al., 1987; Mamo et al., 1993; Roth et al., 1993). In fact chylomicrons might even be a vehicle for delivery of microbial lipopolysaccharides (Read et al., 1993). Chylomicron size and lipid composition will also vary widely depending on the nature of lipids ingested (Redgrave, 1983). Therefore, it would seem reasonable to suggest that the putative atherogenicity of chylomicrons may to some extent be dependent on the compliment of lipophylic substances which could influence their catabolism.
