Lipoprotein (a) and heart disease

Lipoprotein (a), or Lp(a), is nearly identical in structure to an LDL particle.  Its distinguishing feature is the presence of an additional apolipoprotein molecule, apo(a), which is covalently linked at a single site to apo B-100.

Circulating levels of Lp(a) are determined primarily by genetics. However, factors such as diet may play some role, as trans FA have been reported to increase it. The physiologic function of Lp(a) is unknown. When present in large quantities in the plasma, Lp(a) is associated with an increased risk of coronary heart disease. [Note: Apo(a) is structurally homologous to plasminogen, the precursor of a blood protease whose target is fibrin, the main protein component of blood clots. It is hypothesized that elevated Lp(a) slows the breakdown of blood clots that trigger heart attacks because it competes with plasminogen for binding to fibrin.] Niacin reduces Lp(a), as well as LDL-C and TAG, and raises HDLC.