The basic function of these two hormones is to control the availability and delivery of energy to all cells of the body. When levels of cholesterol are high, the level of expression of the HMG-CoA gene is reduced. Conversely, reduced levels of cholesterol activate expression of the gene. When cholesterol is abundant, the rate of HMG-CoA reductase degradation increases. The Utilization of Cholesterol Cholesterol is transported in the plasma predominantly as cholesteryl esters associated with lipoproteins .
Dietary cholesterol is transported from the small intestine to the liver within chylomicrons.
Cholesterol synthesized by the liver, as well as any dietary cholesterol in the liver that exceeds hepatic needs, is transported in the serum within LDLs. The liver synthesizes VLDLs and these are converted to LDLs through the action of endothelial cell-associated lipoprotein lipase. Reverse cholesterol transport allows peripheral cholesterol to be returned to the liver in LDLs. Ultimately, cholesterol is excreted in the bile as free cholesterol or as bile salts following conversion to bile acids in the liver. The end products of cholesterol utilization are the bile acids, synthesized in the liver.