QandAs: Health

What Is LDL Cholesterol?

Answer:
LDL cholesterol, or Low Density Lipoprotein cholesterol, is a type of lipoprotein which moves cholesterol and triglycerides from the liver to the outlying tissues on the body.

LDL is one of the five major groups of lipoproteins (chylomicrons, very low density lipoproteins, intermediate density lipoproteins, low density lipoproteins, and high density lipoproteins).

Just like all other lipoproteins, LDL allows fats and cholesterol to move in the blood stream. LDL also regulates the cholesterol synthesis. It is measured during a cholesterol blood test, because high levels of LDL cholesterol can indicate other medical problems such as heart disease. LDL cholesterol is sometimes referred to as bad cholesterol.

Each LDL particle contains a single apolipoprotein B-100 molecule which circulates the fatty acids, which keeps them soluble in the environment. LDL also has a highly hydrophobic core which contains a polyunsaturated fatty acid known as linoleate and roughly 1500 esterified cholesterol molecules. This core is surrounded by a shell of phospholipids and unesterified cholesterol, as well as a single B-100 large protein. LDL particles are roughly 22nm in diameter.

Because LDLs move cholesterol to the arteries and can be held there by arterial proteoglycans which start plaque formation, increased levels have become associated with atherosclerosis. Which can lead to heart attack, stroke, and peripheral vascular disease. Because of this, LDL cholesterol; is often called bad cholesterol. However, the cholesterol itself is not bad, but it is how and where the cholesterol is being transported, and in what amounts, which causes the bad effects.

Studies have shown that the size and concentration of the FDL particles relates more directly to the degree of atherosclerosis progression than the concentration of cholesterol that is in the LDL particles. Although this is rare, the healthiest condition is to have small numbers of large LDL particles and no small particles. Small LDL particles are unhealthy, and high amounts of small LDL particles correlates to a much faster growth of atheroma, progression of atherosclerosis, and more severe cardiovascular disease and death. This is the case even if the cholesterol numbers are the same.

The largest risk for cardiovascular disease is when LDL invades the endothelium and becomes oxidized, because the oxidized form of LDL is retained easier by the proteoglycans. A group of biochemical reactions controls the oxidation of LDL, and this is stimulated by free radicals in the endothelium. Nitric oxide slows this process.

Both medication and diet are sometimes used to try to lower cholesterol.