[Apolipoproteins: analytical methods, chemical composition, metabolism and diagnostic relevance]

The estimation of apoprotein profiles makes an essential contribution to the study of the lipid metabolism, particularly of the normal and deranged lipid transport. For the clinician patterns of apoproteins might open new possibilities of the differential diagnosis of dyslipoproteinaemias. Four fundamental apoprotein profiles are presented by Alaupovic et al. (2): 1. Significantly reduced serum levels of the apolipoproteins AI, AII and B (essentially corresponding to HLP type I) 2. Increased values of apo-B (types IIa, IIb) 3. Increased concentration of apo-C-III reduction of the CI/CII-quotient (types IIb, IV) 4. Increased levels of the apolipoproteins C and E (types III, V). The authors suppose that these four basic patterns of apolipoproteins reflect the fundamental biochemical defects of the lipoprotein transport. The biochemical characterization of certain, genetically determined disturbances of the lipid transport with the help of apoprotein profiles is the best example for the essential role of these proteins in the lipid metabolism with regard to the clinical diagnostics it is at present not yet possible to get additional informations with the help of the estimation of apoproteins as they would not be got by far simpler methods. As was already mentioned, in these cases the rare genetically determined disturbances of the lipid metabolism and the diagnostics of the HLP type III form an exception. Only few authors try to prove that the proportion of proteins in lipoproteins seems to be somewhat better suited for the differentiation of persons endangered by arteriosclerosis than the proportion of lipids. Especially the increase of concentration of the apo-B is to be regarded as significant factor of risk of a chronic ischaemic heart disease. This is unequivocally confirmed, but the essentially simpler estimation of the LDL-cholesterol yields well comparable results with regard to the characterization of persons, endangered by chronic ischaemic heart disease.