lip·o·pro·tein (lip'ō-prō'tēn, lī'pō-),
Any complex or compound containing both lipid and protein. Lipoproteins are important constituents of biologic membranes and of myelin. Conjugation with protein facilitates transport of lipids, which are hydrophobic, in the aqueous medium of the plasma. Plasma lipoproteins can be separated by ultracentrifugation, electrophoresis, or immunoelectrophoresis. They migrate electrophoretically with α- and β-globulins, but are usually classified according to their densities (flotation constants). The principal classes by density are chylomicrons, which transport dietary cholesterol and triglycerides from the intestine to the liver and other tissues; very low density lipoproteins (VLDL), which transport triglycerides from the intestine and liver to muscle and adipose tissue; low density lipoproteins (LDL), which transport cholesterol to tissues other than the liver; and high density lipoproteins (HDL), which transport cholesterol to the liver for excretion in bile. The properties of these and other plasma lipoproteins are set forth in the accompanying table (see this page). The protein moiety of a lipoprotein is called an apolipoprotein (or apoprotein). Besides rendering lipids soluble in an aqueous solution, some apolipoproteins perform biochemical functions such as enzyme activation. The apolipoproteins of plasma lipoproteins are synthesized by the liver and intestinal mucosal cells and vary in molecular weight from 7,000 to 500,000. Protein makes up more than 50% of some HDLs but only 1% of chylomicrons. As the proportion of lipid in a lipoprotein increases, its density decreases. A plasma lipoprotein particle is typically spheric, with a hydrophobic core of triacylglycerol, cholesteryl esters, and apolar amino acid residues surrounded by hydrophilic protein structures and phospholipids.
The concentrations of certain serum lipoproteins correlate closely with the risk of atherosclerosis. Although dietary factors are important in some people with hyperlipidemia, basal levels of lipoprotein, cholesterol, and triglycerides depend chiefly on heredity. Several phenotypes of familial hyperlipoproteinemia associated with risk of premature cardiovascular disease and death have been identified. see hyperlipoproteinemia. An HDL cholesterol level below 35 mg/dL (0.90 mmol/L), an LDL cholesterol level above 160 mg/dL (4.15 mmol/L), and a fasting triglyceride level above 250 mg/dL (2.83 mmol/L) are all independent risk factors for coronary artery disease. Medical management of patients with coronary artery disease (myocardial infarction, angina pectoris, history of coronary artery bypass graft or coronary angioplasty) and other atherosclerotic disorders (peripheral arterial disease, abdominal aortic aneurysm, carotid artery disease) includes detection and correction of hypercholesterolemia and hyperlipoproteinemia. Reducing elevated LDL cholesterol diminishes the risk of coronary artery disease. The currently recommended target serum levels for treatment of disorders of lipid metabolism are LDL cholesterol less than 100 mg/dL (2.6 mmol/L), HDL cholesterol more than 40 mg/dL (1 mmol/L), and triglyceride less than 150 mg/dL (1.7 mmol/L). Dietary recommendations for patients with hyperlipidemia include a total fat intake providing less than 35% of all calories (saturated fat less than 7%, polyunsaturated fat less than 10%, and monounsaturated fat less than 20%), carbohydrate (mostly complex carbohydrates from fruits and vegetables) 50-60% of total calories, fiber 20-30 g/day, and cholesterol less than 200 mg/day. Dietary saturated fat raises LDL cholesterol more than any other dietary component, cholesterol itself not excepted. Of people with elevated LDL cholesterol, 75% can achieve normal levels with diet, weight reduction, and exercise; the others need drug treatment. Factors besides familial hyperlipoproteinemias that can elevate LDL cholesterol include diabetes mellitus, hypothyroidism, nephrotic syndrome, obstructive liver disease, and drugs (progestogens, anabolic steroids, corticosteroids, thiazide diuretics).
lipoprotein /lipo·pro·tein/ (-prō´tēn) a complex of lipids and apolipoproteins, the form in which lipids are transported in the blood.
α-lipoprotein , alpha lipoprotein one with electrophoretic mobility equivalent to that of the α1-globulins, e.g., high-density lipoprotein.
β-lipoprotein , beta lipoprotein one with electrophoretic mobility equivalent to that of the β-globulins, e.g., low-density lipoprotein.
high-density lipoprotein (HDL) a class of plasma lipoproteins that promote transport of cholesterol from extrahepatic tissue to the liver for excretion in the bile; serum levels have been negatively correlated with premature coronary heart disease.
intermediate-density lipoprotein (IDL) a class of lipoproteins formed in the degradation of very-low-density lipoproteins; some are cleared rapidly into the liver and some are degraded to low-density lipoproteins.
low-density lipoprotein (LDL) a class of plasma lipoproteins that transport cholesterol to extrahepatic tissues; high serum levels have been correlated with premature coronary heart disease.
Lp(a) lipoprotein a lipoprotein particle containing apolipoprotein B-100 as well as an antigenically unique apolipoprotein; its occurrence at high levels in plasma has been correlated with increased risk of heart disease.
very-high-density lipoprotein (VHDL) a class of lipoproteins composed predominantly of proteins and also containing a high concentration of free fatty acids.
very-low-density lipoprotein (VLDL) a class of lipoproteins that transport triglycerides from the intestine and liver to adipose and muscle tissues; they contain primarily triglycerides with some cholesteryl esters.
lipoprotein (lĭp′ō-prō′tēn′, -tē-ĭn, lī′pō-)
Any of a group of conjugated proteins in which at least one of the components is a lipid. Lipoproteins, classified according to their densities and chemical qualities, are the principal means by which lipids are transported in the blood.
Etymology: Gk, lipos + proteios, first rank
a conjugated protein in which lipids form an integral part of the molecule. They are synthesized primarily in the liver; contain varying amounts of triglycerides, cholesterol, phospholipids, fat-soluble vitamins, and protein; and are classified according to their composition and density. Practically all of the plasma lipids are present as lipoprotein complexes. The elevation of low-density lipoproteins (LDLs) in plasma is associated with an increased risk of atherosclerosis. Normal adult levels of lipoproteins include high-density lipoproteins, greater than 35 mg/dl; LDLs, 60 to 180 mg/dl; and very low-density lipoproteins, 25% to 50%. Kinds of lipoproteins are chylomicrons
, high-density lipoproteins
, low-density lipoproteins
, and very low-density lipoproteins
lipoprotein(a) Lp(a) Physiology A lipoprotein with a range of serum levels, a lipid content similar to LDL, which binds to the LDL receptor with lesser affinity than LDL; Lp(a)'s role in ASHD is controversial; it is ↑ in Pts at risk for CAD Ref range 0-30 mg/dL
Complexes or compounds containing lipid and protein. Almost all the lipids in plasma are present as lipoproteins and are therefore transported as such. Plasma lipoproteins are characterized by their flotation constants as chylomicra, very low density (VLDL), intermediate density (IDL), low density (LDL), high density (HDL), and very high density (VHDL). They range in molecular weight from 175,000 to 1 × 109. Gauging lipoprotein levels is important in assessing the risk of cardiovascular disease.
lipoprotein a water-soluble molecule made up of a protein containing a lipid group. It is found, for example, in protoplasm where it is involved in transport of lipids in a soluble form.
A complex molecule that consists of a protein membrane surrounding a core of lipids. Lipoproteins carry cholesterol and other lipids from the digestive tract to the liver and other body tissues. There are five major types of lipoproteins.
lipoprotein a complex of lipids and proteins. Lipoproteins transport triacylglycerols ( syn triglycerides, TG) and cholesterol around the body in the blood. Classified into four main groups by increasing density (related inversely to the % TG content): (1) chylomicrons the most rich in TG, formed in intestinal cells from the absorbed breakdown products of dietary fat, carried in lymphatic vessels to reach the liver and the general circulation; (2) very low-density lipoproteins (VLDL) synthesized in and released into the blood from the liver, rich in endogenously produced TG; (3) low-density lipoproteins (LDL), formed mainly from VLDL after they have lost TG in the tissues. LDL have the highest cholesterol content, carrying this to all tissues. High plasma LDL is associated with increased risk of coronary heart disease, as some cells (particularly macrophages in the arterial wall) may become cholesterol-laden; (4) high-density lipoproteins (HDL), formed in liver and intestinal cells, take up cholesterol from the tissues and transport it to the liver for excretion in the bile. High plasma HDL is associated with reduced risk of coronary heart disease.
any of the macromolecular complexes that are the form in which lipids are transported in the blood. They consist of a core of hydrophobic lipids covered by a layer of phospholipids and apoproteins, which make the complex water-soluble. There are four main classes of lipoproteins: chylomicrons, in which lipids are transported after a meal from the intestine to tissues, where they are stored or used; very low density lipoproteins (VLDL); low density lipoproteins (LDL); and high density lipoproteins (HDL). VLDL and HDL are produced by both the liver and the intestine; LDL is produced by the metabolism of VLDL.
high density lipoproteins which migrate in the alpha position in paper chromatography. Inherited deficiency of these proteins is described in humans but there is no known animal model of the disease.
lipoprotein factor Xa inhibitor
a blood coagulation inhibitor present in the low density lipoprotein fraction of plasma.
high density lipoprotein (HDL)
a fraction of lipoproteins separable by ultracentrifugation.
intermediate density lipoprotein (IDL)
intermediate in density between LDL and VLDL; migrate in electrophoresis with β-globulins.
specific lipase hydrolyzing lipoproteins.
lipoprotein lipase deficiency
Patient discussion about lipoprotein
Q. what are the sources for high density lipoprotein? I have heard that high density lipoprotein is good for heart. What differences does it make in heart’s health and what are the sources for high density lipoprotein?
A. Hi Liam, it is very important that we have high density lipoprotein (HDL) in our body. The fact is that the HDL is formed inside the body. They are known as good cholesterol as they are famous for their protection for heart against the heart diseases. It has been found that Vitamin B3 or Niacin consumption increases the count of HDL. It’s good to cut on the diet having more of saturated fats and oils, which increases the chances of heart attack.More discussions about lipoprotein