Lipoproteins What Are They ?
Cholesterol travels in the blood in packages called lipoproteins. Just like oil and water, cholesterol (which is fatty) and blood (which is watery) do not mix. In order to be able to travel in the bloodstream, the cholesterol made in the liver is combined with protein, making a lipoprotein. This lipoprotein then carries the cholesterol through the bloodstream. Lipoproteins are protein spheres that transport cholesterol, triglyceride, or other lipid molecules through the bloodstream. Most of the information about the effects of cholesterol and triglyceride actually concerns lipoproteins. |
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Types of Lipoprotein
Lipoproteins are categorized into six types according to size and density. They can be further defined by whether they carry cholesterol (the two smaller lipoproteins) or triglycerides (the three largest lipoproteins).
- Low density lipoproteins(LDL). (Often called the bad cholesterol.)
- High-density lipoproteins(HDL), the smallest and most dense. (Referred to as the good cholesterol)
- Triglyceride-Carrying
- Intermediate density(IDL). They tend to carry triglycerides.
- Very low density (VLDL). These tend to carry triglycerides.
- Chylomicrons (largest in size and lowest in density).
Lipoproteins - What Are They Made Of?
The lipoprotein particle is composed of an outer shell of phospholipid, which renders the particle soluble in water; a core of fats called lipid, including cholesterol and a surface apoprotein molecule that allows tissues to recognize and take up the particle. These are characterized by their density: high density (HDL), low density (LDL), very low density (VLDL).
How Can Lipoproteins Be Harmful
The first stages of cholesterol build up in the blood vessels (atherosclerosis) occur when LDL particles circulating in the blood penetrate through the inner lining of blood vessels and become trapped in the artery wall. Eventual build up of LDL, fat-filled cells, cells of inflammation, and blood clotting can block the normal blood flow in the coronary arteries. This is a catastrophic event that stops the flow of nutrients and oxygen to the heart muscle, leading to heart attack (myocardial infarction).
The above links will send you to a page with more detailed information on those topics. Below are some general guidelines.
Low Density Lipoproteins (LDL)
The bad cholesterol. LDL carry most of the cholesterol in the blood, and the cholesterol from LDL is the main source of damaging buildup and blockage in the arteries. Thus, the more LDL-cholesterol you have in your blood, the greater your risk of heart disease. If you have heart disease or are at high risk for developing it and your LDL is 100 mg/dLor higher, your cholesterol may well be too high for you.
High Density Lipoproteins (HDL)
The good cholesterol. HDL carry cholesterol in the blood from other parts of the body back to the liver, which leads to its removal from the body. So HDL help keep cholesterol from building up in the walls of the arteries. If your level of HDL-cholesterol is below 40 mg/dL, you are at substantially higher risk for heart disease. The higher your HDL-cholesterol, the better. The average HDL-cholesterol for men is about 45 mg/dL, and for women it is about 55 mg/dL.
Triglycerides |
microscopic view of