High-density lipoprotein (HDL) is one of the five major groups of lipoproteins. Lipoproteins are complex particles composed of multiple proteins which transport all fat molecules (lipids) around the body within the water outside cells. They are typically composed of 80–100 proteins per particle. HDL particles enlarge while circulating in the blood, aggregating more fat molecules and transporting up to hundreds of fat molecules per particle.
Low-density lipoprotein (LDL) is one of the five major groups of lipoprotein that transport all fat molecules around the body in extracellular water. These groups, from least dense to most dense, are chylomicrons, very low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), low-density lipoprotein (LDL) and high-density lipoprotein (HDL). LDL delivers fat molecules to cells. LDL is involved in atherosclerosis, a process in which it is oxidized within the walls of arteries.
Atherosclerosis is a pattern of the disease arteriosclerosis, characterized by development of abnormalities called lesions in walls of arteries. These lesions may lead to narrowing of the arteries' walls due to buildup of atheromatous plaques. At onset there are usually no symptoms, but if they develop, symptoms generally begin around middle age. In severe cases, it can result in coronary artery disease, stroke, peripheral artery disease, or kidney disorders, depending on which body parts(s) the affected arteries are located in the body.
A lipoprotein is a biochemical assembly whose primary function is to transport hydrophobic lipid molecules in water, as in blood plasma or other extracellular fluids. They consist of a triglyceride and cholesterol center, surrounded by a phospholipid outer shell, with the hydrophilic portions oriented outward toward the surrounding water and lipophilic portions oriented inward toward the lipid center. A special kind of protein, called apolipoprotein, is embedded in the outer shell, both stabilising the complex and giving it a functional identity that determines its role.
Lipid-lowering agents, also sometimes referred to as hypolipidemic agents, cholesterol-lowering drugs, or antihyperlipidemic agents are a diverse group of pharmaceuticals that are used to lower the level of lipids and lipoproteins such as cholesterol, in the blood (hyperlipidemia). The American Heart Association recommends the descriptor 'lipid lowering agent' be used for this class of drugs rather than the term 'hypolipidemic'.
Dyslipidemia is a metabolic disorder characterized by abnormally high or low amounts of any or all lipids or lipoproteins in the blood. Dyslipidemia is a risk factor for the development of atherosclerotic cardiovascular diseases (ASCVD), which include coronary artery disease, cerebrovascular disease, and peripheral artery disease. Although dyslipidemia is a risk factor for ASCVD, abnormal levels don't mean that lipid lowering agents need to be started. Other factors, such as comorbid conditions and lifestyle in addition to dyslipidemia, is considered in a cardiovascular risk assessment. In developed countries, most dyslipidemias are hyperlipidemias; that is, an elevation of lipids in the blood. This is often due to diet and lifestyle. Prolonged elevation of insulin resistance can also lead to dyslipidemia. Likewise, increased levels of O-GlcNAc transferase (OGT) may cause dyslipidemia.
In vascular diseases, endothelial dysfunction is a systemic pathological state of the endothelium. Along with acting as a semi-permeable membrane, the endothelium is responsible for maintaining vascular tone and regulating oxidative stress by releasing mediators, such as nitric oxide, prostacyclin and endothelin, and controlling local angiotensin-II activity.
Hyperlipidemia is abnormally high levels of any or all lipids or lipoproteins in the blood. The term hyperlipidemia refers to the laboratory finding itself and is also used as an umbrella term covering any of various acquired or genetic disorders that result in that finding. Hyperlipidemia represents a subset of dyslipidemia and a superset of hypercholesterolemia. Hyperlipidemia is usually chronic and requires ongoing medication to control blood lipid levels.
Campesterol is a phytosterol whose chemical structure is similar to that of cholesterol, and is one of the ingredients for E number E499.
Mevastatin is a hypolipidemic agent that belongs to the statins class.
A CETP inhibitor is a member of a class of drugs that inhibit cholesterylester transfer protein (CETP). They are intended to reduce the risk of atherosclerosis by improving blood lipid levels. At least three medications within this class have failed to demonstrate a beneficial effect.
Pitavastatin is a member of the blood cholesterol lowering medication class of statins.
Cholesterol absorption inhibitors are a class of compounds that prevent the uptake of cholesterol from the small intestine into the circulatory system. Most of these molecules are monobactams but show no antibiotic activity. An example is ezetimibe Another example is Sch-48461. The "Sch" is for Schering-Plough, where these compounds were developed. Phytosterols are also cholesterol absorption inhibitors.
ATP-binding cassette transporter ABCA1, also known as the cholesterol efflux regulatory protein (CERP) is a protein which in humans is encoded by the ABCA1 gene. This transporter is a major regulator of cellular cholesterol and phospholipid homeostasis.
Proprotein convertase subtilisin/kexin type 9 (PCSK9) is an enzyme encoded by the PCSK9 gene in humans on chromosome 1. It is the 9th member of the proprotein convertase family of proteins that activate other proteins. Similar genes (orthologs) are found across many species. As with many proteins, PCSK9 is inactive when first synthesized, because a section of peptide chains blocks their activity; proprotein convertases remove that section to activate the enzyme. The PCSK9 gene also contains one of 27 loci associated with increased risk of coronary artery disease.
Angiopoietin-like 3, also known as ANGPTL3, is a protein that in humans is encoded by the ANGPTL3 gene.
Hypoalphalipoproteinemia is a high-density lipoprotein deficiency, inherited in an autosomal dominant manner.
Paraoxonases are a family of mammalian enzymes with aryldialkylphosphatase activity. There are three paraoxonase isozymes, which were originally discovered for their involvement in the hydrolysis of organophosphates.
The chronic endothelial injury hypothesis is one of two major mechanisms postulated to explain the underlying cause of atherosclerosis and coronary heart disease (CHD), the other being the lipid hypothesis. Although an ongoing debate involving connection between dietary lipids and CHD sometimes portrays the two hypotheses as being opposed, they are in no way mutually exclusive. Moreover, since the discovery of the role of LDL cholesterol (LDL-C) in the pathogenesis of atherosclerosis, the two hypotheses have become tightly linked by a number of molecular and cellular processes.
Remnant cholesterol, also known as remnant lipoprotein, is a very atherogenic lipoprotein composed primarily of very low-density lipoprotein (VLDL) and intermediate-density lipoprotein (IDL). Stated another way, remnant cholesterol is all plasma cholesterol that is not LDL cholesterol or HDL cholesterol, which are triglyceride-poor lipoproteins. However, remnant cholesterol is primarily chylomicron and VLDL, and each remnant particle contains about 40 times more cholesterol than LDL.
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