Statins – The Mainstay Cholesterol Lowering Agents
by MedPlus Team, November 18, 2017
Cholesterol is a word most of us are familiar with these days. Without knowing much about it, everyone seemingly knows high levels of cholesterol are bad for health and cause heart attacks. A large proportion of us takes active measures to reduce it either by watching our diet, exercising or using medications. If you are one among the latter set of people taking medication, you are more than likely taking a statin, which is the most commonly prescribed class of cholesterol-lowering drugs. Please read on to know some interesting facts about cholesterol and statins.
Cholesterol is a type of fat or lipid and is an essential component of all cell membranes. It is an immediate precursor of steroid hormones and bile acids and vital for their production. It is also responsible for the conversion of vitamin D into its useful form in the body when exposed to sunlight. About one-third of it is obtained directly from the diet, and about two-thirds of the body’s cholesterol is synthesized in the liver using fat substrates. Despite its essential nature, an excess of cholesterol in our blood gets deposited inside our blood vessels causing them to narrow and prone to clots, a process known as atherosclerosis. This puts us at an increased risk of heart attacks. Cholesterol is transported in the blood combined with a protein called a lipoprotein. Depending on the density of fat vs protein, lipo-proteins are classified into low-density lipoproteins (LDL), very low-density lipoproteins (VLDL) and high-density lipoproteins (HDL). A higher than normal level of LDL and a lower level of HDL are considered risk factors for heart disease.
Serum cholesterol levels can be reduced by inhibition of hepatic cholesterol biosynthesis. The rate-limiting enzyme in cholesterol synthesis in the liver is HMG-CoA reductase, which catalyzes the conversion of HMG-CoA to mevalonic acid. Inhibitors of HMG-CoA reductase or statins were originally identified as secondary metabolites of fungi. Statins work by reversibly inhibiting HMG-CoA reductase through side chains that bind to the enzyme’s active site and block the substrate-product transition state of the enzyme. The statins are predominantly extracted by the liver and they reduce the total plasma cholesterol levels. There is also a substantial decrease in urinary and plasma levels of mevalonic acid. Statins are also responsible for the reduction of circulating total and LDL cholesterol. The LDL clearance from the blood circulation requires hepatic LDL cholesterol receptors and statins increase the cholesterol clearance from the bloodstream by increasing LDL-C receptors.
Some examples of statins, are simvastatin, pravastatin, lovastatin, mevastatin, fluvastatin, cerivastatin, pitavastatin, rosuvastatin, etc. Statins effectively reduce cholesterol in the blood and are helpful in reducing the progress of atherosclerosis, thereby reducing the risk of cardiovascular diseases like heart attacks and stroke. Risk of serious side effects from statins is extremely low, a few cases in a million, however some complications one should be aware of include:
This is one of the more common complaints in patients taking statins. It is usually a mild discomfort or may be experienced as soreness and muscle weakness. Very rarely, patients may experience muscle damage, known as rhabdomyolysis. This is an emergency and can be life threatening if not identified and treated early.
Enzymes that indicate liver inflammation or damage should be periodically monitored for any evidence of liver damage.
They may increase insulin resistance and consequently blood sugar levels in people with type 2 diabetes.
Not everyone is at an equal risk of side effects from statins. Some factors that increase the risk include being on multiple lipid-lowering medications at the same time, female gender, having kidney or liver disease, a small body frame, older age, and consuming alcohol.