Lp(a) lipoprotein is formed from LDL and the (a) protein, linked by a disulfide bridge. The (a) protein is highly homologous with plasminogen but is not activated by tissue plasminogen activator. It occurs in a number of isoforms of different molecular weights. Levels of Lp(a) vary from nil to over 2000 nM/L and are determined chiefly by genetic factors. Lp(a) is found in atherosclerotic plaques and contributes to coronary disease by inhibiting thrombolysis. It is also associated with aortic stenosis. Levels are elevated in certain inflammatory states. The risk of coronary disease is strongly related to the level of Lp(a). A common variant (I4399M) in the coding region is associated with elevated levels.
E. High-Density Lipoproteins
The apoproteins of HDL are secreted largely by the liver and intestine. Much of the lipid comes from the surface monolayers of endothelium Lipoprotein lipase FFA HDL VLDL remnant B-100 ApoC VLDL ApoE HDL LDL Peripheral cell Cholesterol Cholesteryl estersLysosome Acetyl-CoA HMG-CoA reductase Lysosome Cholesterol Mevalonic acid ApoB, ApoE, ApoC RER Golgi vesicle LDL receptor * * Cholesterol biosynthetic pathway