High-density lipoprotein plasma composition

The fate of injected liposomes is drastically altered by administration route, dose and size, lipid composition, surface modification, and encapsulated drugs. Liposomes encapsulating drugs are often administered iv, therefore, the stability of liposomes in plasma is important. When liposomes composed of PC with unsaturated fatty acyl chains are incubated in the presence of serum, an efflux of internal solute from the liposomes is observed. This increase in permeability is caused by the transfer of phospholipids to high density lipoprotein (HDL) in serum (55). To reduce the efflux of liposomal contents, cholesterol is added as a liposomal component... 

Alterations in the composition of the plasma lipids caused by estrogens are characterized by an increase in the high-density lipoproteins (HDL), a slight reduction in the low-density lipoproteins (LDL), and a reduction in total plasma cholesterol levels. Plasma triglyceride levels are increased. Estrogens decrease hepatic oxidation of adipose tissue lipid to ketones and increase synthesis of triglycerides. 

The plasma lipoproteins are spherical macromolecular complexes of lipids and specific proteins (apolipoproteins or apoproteins). The lipoprotein particles include chylomicrons, very-low-density lipoproteins (VLDL), low-density lipoproteins (LDL), and high-density lipoproteins (HDL). They differ in lipid and protein composition, size, and density (Figure 18.13). Lipoproteins function both to keep their component lipids soluble as they transport them in the plasma, and also to provide an efficient mechanism for transporting their lipid contents to (and from) the tissues. In humans, the transport system is less perfect than in other animals and, as a result, humans experience a yradual deposition of lipid—especially cholesterol—in tissues. This is a potentially life-threat-en ng occurrence when the lipid deposition contributes to plaque formation, causing the narrowing of blood vessels (atherosclerosis). 

The typical sunflower oil composition is 66-72% linoleic acid, 12% saturated acids (palmitic and stearic), 16-20% oleic acid, and less than 1% a-linolenic acid. An increase in low-density lipoprotein cholesterol (LDL-C) and a decrease of high-density lipoprotein cholesterol (HDL-C) are believed risk factors of coronary heart disease (CHD). Diets rich in saturated fat increase plasma total and LDL-C. Traditional high-linoleic sunflower oil has always been regarded as healthy because of its high content of polyunsaturated fatty acids (PUFA) and relatively low content in saturated fatty acids. 

The TAG show higher proportions of palmitoleic and oleic acids. The FA composition of TAG in the high-density lipoprotein (HDL) fraction in the granules and the low-density lipoprotein (LDL) fraction of the yolk plasma show similar composition (Tables 14.8 and 14.9). 

The lipoproteins present in plasma may be operationally defined according to their density, as low or very low density lipoproteins and high density lipoproteins, but other, more functional definitions may be more appropriate in connection with in vivo metabolism. Examples are the hpoprotein classes chylomicrons and chylomicron remnants. Alaupovic has suggested a classification based on the apolipoprotein composition [1]. As apolipoproteins often determine the metabolic fate of lipoprotein particles this is a logical approach. Lipoprotein particles with specific apolipoprotein compositions exist in all density fractions of human plasma, as well as plasma from a variety of animal species. 

Shepherd, J., Packard, C.J., Patsch, J.R., Gotto, A.M., and Taunton, O.D., 1979. Effects of nicotinic acid therapy on plasma high density lipoprotein subfraction distribution and composition and on apoUpoprotein A metabolism. Journal of Clinical Investigation. 63 858-867. 

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