What?Why?How? Cholestrol

Cholesterol and Heart Disease

Cholesterol is probably the best-known steroid because of the widely publicized correlation
between cholesterol levels in the blood and heart disease. Cholesterol is synthesized in the liver
and is present in almost all body tissues. It is also found in many foods, but we do not require
cholesterol in our diet because the body can synthesize all we need. A diet high in cholesterol
can lead to high levels of cholesterol in the bloodstream, and the excess can accumulate on the
walls of arteries, restricting the flow of blood. This disease of the circulatory system is known as
atherosclerosis and is a primary cause of heart disease.
Cholesterol travels through the bloodstream packaged in particles that are classified according
to their density. Low-density lipoprotein (LDL) particles transport cholesterol from the
liver to other tissues. Receptors on the surfaces of cells bind LDL particles, allowing them
to be brought into the cell so it can use the cholesterol. High-density lipoprotein (HDL) is
a cholesterol scavenger, removing cholesterol from the surfaces of membranes and delivering
it back to the liver, where it is converted into bile acids. LDL is the so-called “bad”
cholesterol, whereas HDL is the “good” cholesterol. The more cholesterol we eat, the less
the body synthesizes. But this does not mean that dietary cholesterol has no effect on the
total amount of cholesterol in the bloodstream, because dietary cholesterol inhibits the
synthesis of the LDL receptors. So the more cholesterol we eat, the less the body synthesizes,
but also the less the body can get rid of by transporting it to target cells.

How High Cholesterol Is Treated Clinically

Statins are drugs that reduce serum cholesterol levels by inhibiting the enzyme that catalyzes the formation of a compound needed for

the synthesis of cholesterol. As a consequence of diminished cholesterol synthesis in the liver, the liver forms more LDL receptors—the
receptors that help clear LDL (the so-called “bad” cholesterol) from the bloodstream. Studies show that for every 10% that cholesterol
is reduced, deaths from coronary heart disease are reduced by 15% and total death risk is reduced by 11%.

Lovastatin and simvastatin are natural statins used clinically under the trade names Mevacor and Zocor. Atorvastatin (Lipitor), a
synthetic statin, is the most popular statin. It has greater potency and lasts longer in the body than natural statins because the products of
its breakdown are as active as the parent drug in reducing cholesterol levels. Therefore, smaller doses of the drug may be administered.
In addition, Lipitor is less polar than lovastatin and simvastatin, so it persists longer in liver cells, where it is needed. Lipitor has been
one of the most widely prescribed drugs in the United States for the past several years.