Acetyl-CoA is the source of all carbon atoms in Cholesterol. Cholesterol formation from Lanosterol takes place in the ER membranes. Methyl groups are removed from it to form 14-Desmethyl Lanosterol and then to form Zymosterol. Then double bonds are removed sequentially to form Cholestadienol then Desmosterol [24-dehydro Cholesterol] and the double bond of the side chain is removed forming Cholesterol.
Approx 1g of Cholesterol is eliminated from the body in a day and almost half of it is given off as Coprostanol formed in the fecal matter by bacterial decomposition in the lower intestine.
Atherosclerosis
It is a disorder caused by deposition of cholesterol and cholesteryl ester from the plasma lipoproteins into the arterial walls due to elevated levels of VLDL, LDL or chylomicron remnants in the blood causing disorders such as lipid nephrosis, diabetes mellitus, hypothyroidism, etc.
Role of PUFA, MUFA in reducing serum cholesterol
Vegetable oils like corn oil, sunflower oil, safflower oil have a high proportion of polyunsaturated fatty acid (PUFA) and olive oil contains MUFA. These fatty acids cause increased catabolic rate of LDL (main atherogenic lipoprotein) and help in lowering serum cholesterol levels.
Hypolipidemic drugs
These drugs reduce Cholesterol and Triacylglycerol from blood. Sitosterol is a hypocholestrolemic agent by blocking the absorption of Cholesterol from the GI TRACT.
Fibrates such as Fenofibrate, clofibrate, gemfibrozil, etc. act mainly to lower plasma Triacylglycerol by increasing natural enzymes that break down fats in the body. They decrease risk of pancreatitis and also decrease secretion of Cholesterol-containing VLDL by the liver.
Statins such as Rosuvastatin, Atorvastatin, Simvastatin and Pravastatin inhibit HMG-CoA (3- hydroxy-3- methylglutaryl- CoA) reductase. These drugs work by slowing the production of Cholesterol that may build up on the walls of the arteries and block blood flow to the heart, brain and other parts of the body.
Probucol increases LDL catabolism via receptor- independent pathways and has a fantastic Antioxidant property.
Coffee raises Cholesterol
Coffee doesn’t contain Cholesterol but the diterpenes present in Coffee suppress the production of substances involved in Cholesterol breakdown causing increased levels of LDL and total Cholesterol.
