Lipoprotein(a) in vascular disease, cancer and longevity.

Lipoprotein(a) [Lp(a)] is a unique lipoprotein with controversial functions. Lp(a) contains apolipoprotein(a) [apo(a)] covalently attached to apolipoprotein B on the low-density lipoprotein (LDL) particle. The distribution of blood Lp(a) concentrations in several populations have been found to be skewed with Lp(a) being mostly present at low level (0-200 mg/L). A high Lp(a) concentration (greater than 200 mg/L) in blood increases the risk of various vascular diseases including chronic heart disease, acute myocardial infarction and cerebral thrombosis. With Lp(a) potentially having such deleterious effects, there is a need to ask what are the evolutionary benefit(s) of Lp(a) to humans and other mammals that have it. Lp(a) has been reported to offer a number of benefits such as providing protection from LDL cholesterol and providing a source of cholesterol in wound tissue. Furthermore, some evidence is emerging that Lp(a) has anti-tumor properties. Other surveys have indicated that Lp(a) is advantageous because it promotes longevity. Lp(a) is only found in humans, old world monkeys and hedgehogs. Individuals who do not express Lp(a) do not show any disease symptoms, which indicates that Lp(a) is not essential for human life. It still remains unclear why mysterious Lp(a) has evolved and is present in humans.