[Lipoprotein (a)--link between lipid metabolism and coagulation system?].

Lipoprotein(a) is a dimer consisting of one low density lipoprotein molecule joined by a disulfide bridge to apolipoprotein(a). Apo(a) shows a considerable structural homology to plasminogen, the zymogen of the proteolytic enzyme plasmin, which dissolves fibrin clots. Apo(a) may compete with plasminogen in several manners, but itself displays no proteolytic activity. It therefore may potentially interfere with fibrinolysis. On the other hand it may also be atherogenic, as indicated by its presence in atherosclerotic plaques. Although lipoprotein(a) consists of one molecule of LDL it does not appear to be regulated by the same mechanism as LDL. Likewise, cholesterol feeding does not appear to increase levels of Lp(a), although it does increase levels of LDL cholesterol. In addition, most lipid regulating drugs that do have an effect on lowering LDL cholesterol levels have little effect on Lp(a) thus also indicating regulation under different metabolic control. Lp(a) seems to constitute a genetic risk factor for coronary atherosclerosis which is independent of all other parameters and of exogenous factors.