Low-density lipoprotein

Low-density lipoprotein (LDL) is one of the five major groups of lipoprotein that transport all fat molecules around the body in extracellular water. These groups, from least dense to most dense, are chylomicrons (aka ULDL by the overall density naming convention), very low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), low-density lipoprotein (LDL) and high-density lipoprotein (HDL). LDL delivers fat molecules to cells.

Lipoproteins transfer lipids (fats) around the body in the extracellular fluid, making fats available to body cells for receptor-mediated endocytosis. Lipoproteins are complex particles composed of multiple proteins, typically 80–100 proteins per particle (organized by a single apolipoprotein B for LDL and the larger particles). A single LDL particle is about 22–27.5 nanometers in diameter, typically transporting 3,000 to 6,000 fat molecules per particle and varying in size according to the number and mix of fat molecules contained within. The lipids carried include all fat molecules with cholesterol, phospholipids, and triglycerides dominant; amounts of each vary considerably.

Elevated LDL is an established causal factor for the development of atherosclerotic cardiovascular disease. A normal non-atherogenic LDL-C level is 20–40 mg/dl. Guidelines recommend maintaining LDL-C under 2.6 mmol/L (100 mg/dl) and under 1.8 mmol/L (70 mg/dL) for those at high risk.