The physiological role of HDL centers around the reverse cholesterol transport system.  Nascent HDL secreted into the plasma by the liver or intestine pick up free cholesterol from peripheral tissues and the arterial wall, an action mediated mainly by the ATP-binding cassette A1 (ABCA1).  The enzyme lecithin-cholesteryl acetyltransferase (LCAT) catalyzes the esterification of the free cholesterol, and also converts the nascent HDL into the mature form.  The esterified cholesterol is transported to the liver where cholesterylester transfer protein (CETP), an enzyme produced in the liver, acts on it transferring the cholesterol to other apo B containing lipoproteins.   The cholesterol-deplete HDL gets broken down by triglyceride lipases releasing apo A-I which either takes up free cholesterol to continue the cycle, or gets eliminated in the kidneys.  In addition to its atheroprotective against cardiovascular diseases, HDL also exhibits anti-oxidant, anti-inflammatory, anti-apoptotic, anti-coagulant, vasodilatory, and metabolic properties.
High density lipoprotein physiology
Very low density lipoprotein physiology
Low density lipoprotein physiology
High density lipoprotein epidemiology and demographics
Low density lipoprotein epidemiology and demographics
High density lipoprotein pathophysiology
Low density lipoprotein pathophysiology
Hyperlipoproteinemia epidemiology and demographics