For more than 60 years, scientists have gathered information about how abnormalities in lipid levels, such as high cholesterol, can affect your health. One of the longest-running trials, the Framingham Heart Study, has demonstrated that high total cholesterol, high low-density lipoprotein cholesterol, high triglycerides or low high-density lipoprotein cholesterol can increase your risk for heart attack and stroke. Armed with this information, scientists and pharmaceutical companies have designed drugs, known as statins, to treat these abnormalities.
Cholesterol Synthesis
Every cell in your body makes cholesterol, which is used as a structural component in cell membranes and as the precursor for other molecules, such as steroid hormones. The complex metabolic pathway that leads to cholesterol synthesis is initiated by the joining of fatty acid molecules to form a larger molecule called hydroxymethylglutaryl-coenzyme A. Through a series of chemical reactions, HMG-CoA is converted to cholesterol, with a critical enzyme called HMG-CoA reductase controlling the rate of cholesterol production.
Cholesterol Packaging
Cholesterol does not mix with water, so it must be carried through your bloodstream by special transport molecules called lipoproteins. These lipoproteins are classified according to their density. Generally, the more cholesterol a lipoprotein carries, the less dense it is. LDL is the major carrier of cholesterol in your blood, and it is largely responsible for triggering the process that leads to atherosclerosis, or hardening of the arteries. For this reason, LDL is often called the "bad" cholesterol.
Inhibiting Cholesterol Production
Researchers discovered that inhibition of HMG-CoA reductase, the key enzyme in the cholesterol synthetic pathway, reduced cholesterol levels in animals and humans. Statin drugs, which are also called HMG-CoA reductase inhibitors, interfere with the action of HMG-CoA reductase. If you take a statin medication, such as lovastatin, pravastatin or simvastatin, it reduces the amount of cholesterol your cells can make. This lowers your total cholesterol level. Because of the relative amounts of cholesterol that are packaged in different lipoproteins and the complex mechanisms that control the production and transport of cholesterol, your LDL may fall proportionally more than your total cholesterol.
Considerations
Like many enzymes, HMG-CoA reductase is instrumental in more than one metabolic pathway. This enzyme not only drives the synthesis of cholesterol but also participates in the production coenzyme Q10, which is needed for energy metabolism. Statins effectively lower your cholesterol by inhibiting HMG-CoA reductase, but they also limit the production of CoQ10. A 2005 report in "Cardiology in Review" acknowledges that statins reduce the synthesis of CoQ10 in your body but questions the need for CoQ10 supplementation in people who take statins. If you take a statin for your cholesterol, check with your doctor to see whether you should also take a CoQ10 supplement.
