High-density lipoprotein characteristics

Other classes sometimes included are intermediate density lipoprotein ODL) and very-high-density lipoproteins (VHDL) (Schjeide SAjeide, 1981 Hermier et al, 1984 1985). There is some variation in the protocol for fractionation used by different research groups and ako in the density range used for classification. All three main fractions contain characteristic proteins and have been assigned particular functions. 

An inherited lack of, or deficiency in, cell surface receptors for low density lipoproteins results in a condition, familial hypercholesterolaemia, in which blood cholesterol concentrations are rather high. This condition, if untreated, leads to severe vascular disease and death from ischaemic heart disease. Lipids are involved in several ways. First, one of the characteristics of developing atherosclerotic plaques is an accumulation of lipids, particularly cholesteryl esters, which are derived from plasma lipoproteins secondly, lipids are involved (because of their role as precursors of eicosanoids) in the formation of thrombi which may block arteries and cause ischaemia. Another risk factor for ischaemic heart disease that involves lipid metabolism is obesity, characterized by an excessive accumulation of adipose tissue. In particular, upper body obesity is also associated with Type II diabetes and hyperinsulinaemia. Hyperlipoproteinaemia is secondary to obesity and diabetes mellitus and if these conditions are treated, blood lipid concentrations return to normal. 

The carbohydrate-dependent hyperglyceridemia occurs only after high carbohydrate intake. The fat particles appear to be carried by lipoproteins which, according to the observations by Ahrens et al. (l957), Kuo and Carson (1959), Brown and Page (1960), and Bierman (1963), float at densities characteristic for the VLDL class. In these patients plasma lipolytic activity is normal (Fredrickson et al., 1963). It would thus appear that the hyperlipoproteinemia is due to hepatic overproduc-... 

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