1. What are the dangers of atherosclerosis? Atherosclerosis (sometimes called arteriosclerosis) is the process by which excess cholesterol is deposited in the walls of arteries within the circulatory system, gradually forming lipid deposits called plaques. More and more cholesterol collects in the plaque, causing the lumen of the arteries to narrow, resulting in an impaired blood supply to the organs. In the heart, this atherosclerosis is called coronary artery disease and can cause symptoms of chest pain called angina. If the plaque continues to grow in size, or if the plaque has localized blood flow disturbances, the plaque covered with lipid contents may become fragile disease may rupture. When this happens, the contents of the plaque are exposed to the blood and can form a blood clot (generally called a thrombus). If a clot forms in any of the blood vessels supplying the heart, it can cause an obstruction that blocks the blood supply to the distal heart muscle, called myocardial ischemia. This condition can cause damage to the heart muscle cells, or myocardial infarction, ending with the heart’s inability to pump blood efficiently. Myocardial necrosis also leads to severe electrical disturbances or arrhythmias in the heart, which can sometimes be fatal. Atherosclerosis also has some other possible bad outcomes. Atherosclerosis in the lower legs can lead to peripheral artery disease (PAD), which causes pain when walking (called intermittent claudication). If not recognized and treated early, this condition can eventually evolve into gangrene and require amputation. If the blood vessel supplying the brain is blocked, patients can experience transient neurological symptoms (called transient ischemic attack). If left undiagnosed and untreated, this usually leads to a stroke. Related nomenclature: Angina: Deep, hard-to-locate chest or arm pain that occurs when the heart does not receive a localized supply of oxygen (blood). Plaque rupture: Impairment of plaque integrity or partial detachment of the plaque surface, exposing the lipid component underneath, which can lead to localized blood clotting and blockage of the artery containing the plaque. Blood clot (thrombus): aggregation of blood components within a blood vessel, stopping bleeding, or blocking arterial blood flow and venous return. Ischemia: A decrease in blood flow to a part of the body due to narrowing or blockage of blood vessels. Myocardial infarction: necrosis of heart muscle cells. In severe cases, it can lead to sudden death. Intermittent claudication: Inadequate blood supply to the lower extremities due to peripheral arterial disease, causing leg or foot pain. Transient ischemic attack (TIA): Inadequate blood supply to the cerebral arteries leading to transient, reversible neurological symptoms. Stroke: Also known as a stroke, partial loss of cerebral blood flow resulting in the death of some brain tissue, causing loss of one or more functions, including limb weakness, paresthesia, loss of sensation or coordination, speech function or visual impairment. 2. How do lipoproteins cause or prevent atherosclerosis? We all know that oil (or fat) and water do not mix. The organism is mainly composed of water. Therefore, essential fats, especially cholesterol, must be “wrapped” with proteins and transported to where the body needs them. The lipoproteins that transport cholesterol and triglycerides in the body are one or more protein particles (called apolipoproteins) located on the surface of the “package”. Lipoproteins are important in transporting triglycerides to adipose tissue for energy production, transporting cholesterol to tissue to form cell membranes and produce hormones, and removing cholesterol from the arterial wall to reduce the risk of heart disease and stroke. The main lipoproteins that deposit cholesterol in the cells of the arterial wall and form atherosclerosis over time are low density lipoproteins (LDL), very low density lipoproteins (VLDL), and intermediate density lipoproteins (IDL). As cholesterol-containing LDL, VLDL and IDL increase, the risk of heart disease and stroke also increases. High-density lipoprotein (HDL) is a lipoprotein that helps remove cholesterol from peripheral tissues; therefore, as HDL levels increase, the risk of heart disease and stroke decreases. All lipoproteins have a unique protein on their surface, collectively called apolipoproteins or descofactorins. More than 10 different apolipoproteins have been identified, the most clinically important being apolipoproteins A and B. Apolipoprotein A (apo A) is associated with HDL, a lipoprotein that helps protect against heart disease and stroke. There are several types of apo A, but the main component of HDL, apo A, is named apolipoprotein A-I (apo A-I). apo A-I is the strongest at removing cholesterol from the artery wall (this is the reverse cholesterol transport). Most health centers measure HDL, but some experts have recently suggested that measuring apo A-I helps with more accurate risk stratification. As with HDL, the higher the apo A-I level, the lower the risk of heart disease and stroke. Apolipoprotein B (apo B) is found on the surface of all lipoproteins except HDL and is associated with lipoproteins that promote atherosclerosis. As with apo A-I, some experts believe that measuring apo B is more accurate and predictive of health risk than measuring LCL or non-HDL cholesterol. As apo B levels increase, the risk of heart disease and stroke increases. Related terminology: Lipoproteins: Protein-covered fat particles that help transport cholesterol and triglycerides. Very low density lipoprotein: A lipoprotein produced by the liver that contains most triglycerides and some cholesterol. Apolipoprotein: The protein part of the surface of a lipoprotein. Apolipoprotein A-I (Apo A-I): the protein fraction on the surface of HDL. Apolipoprotein B: Apolipoprotein associated with LDL cholesterol and other atherosclerosis-related proteins.