DR. BILL'S SCIENCE INFORMATION SITE.

CLASSES OF LIPOPROTEINS- FUNCTIONS AND IMPORTANCE

LIPOPROTEINS  are proteins that carry lipids (fats) around the body. Those lipoproteins with highest fat content have the lowest density. The five major types of lipoproteins are: - chylomicrons - very low density lipoprotein (VLDL) - intermediate density lipoprotein (IDL) - low density lipoprotein - high density lipoprotein The functions of each of these lipoproteins are very important. CHYLOMICRONS primarily carry triglycerides and other lipids from intestinal wall to the liver. Thus, these lipoproteins will function after we eat lipids, digest them, and absorb them into the intestinal wall. Triglycerides produced in the body are carried from liver to cells by: VLDL, IDL, and LDL. Each of these lipoproteins contain some amount of triglyceride - VLDL carries the greatest amount of triglyceride from liver to some site in the body. In terms of cholesterol, one should remember it is an important chemical that is found in ALL cell membranes and is the backbone of the steroid hormones: -  produced in testes (testosterone) -  produced in ovaries (estrogens) -  produced in the adrenal glands (cortisol, aldosterone, androstenedione). Cholesterol is used to make bile - which is stored in the gall bladder LDL transports cholesterol from the liver to cells, glands, and where cell repair is necessary; HDL transports cholesterol from cells to the liver (for destruction).

One should also note that lipoproteins are composed of lipids and proteins. The protein part of lipoproteins are referred to as APOPROTEINS. Apoproteins are genetically determined components and influence the structure, receptor binding, and metabolism of the lipoproteins. Apoproteins are labeled as A,B,C,D,and E classes. In turn, each class consists of subtypes. For example, A-I,  A-II, A-III, A-IV, B-48, B-100, C-I, C-II, C-III.

Hence, the role of lipoproteins in identifying persons at risk for developing coronary heart disease and atherosclerosis, must include not only the lipids - triglycerides and cholesterol , but apoprotein synthesis, receptor activities , and enzyme deficiencies as well. Stay tuned for future developments.

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