lipoprotein

lip·o·pro·tein

L0192300 (lĭp′ō-prō′tēn′, -tē-ĭn, lī′pō-)n. 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.

lipoprotein

(ˌlɪpəʊˈprəʊtiːn; ˌlaɪ-) n (Biochemistry) any of a group of proteins to which a lipid molecule is attached, important in the transport of lipids in the bloodstream. They exist in two main forms: high-density lipoproteins and low-density lipoproteins. See also low-density lipoprotein

lip•o•pro•tein

(ˌlɪp əˈproʊ tin, -ti ɪn, ˌlaɪ pə-)

n. any of the class of proteins that contain a lipid combined with a simple protein. [1905–10]

lip•o•pro•tein(a)

(ˌlɪp əˌproʊ tinˈæ, -ti ɪnˈeɪ, ˌlaɪ pə-)
n. a plasma lipoprotein containing protein and cholesterol, high levels of which are associated with atherosclerosis.

Thesaurus

Noun

lipoprotein - a conjugated protein having a lipid component; the principal means for transporting lipids in the bloodcompound protein, conjugated protein - a protein complex combining amino acids with other substancesalpha-lipoprotein, HDL, high-density lipoprotein - a lipoprotein that transports cholesterol in the blood; composed of a high proportion of protein and relatively little cholesterol; high levels are thought to be associated with decreased risk of coronary heart disease and atherosclerosisbeta-lipoprotein, LDL, low-density lipoprotein - a lipoprotein that transports cholesterol in the blood; composed of moderate amount of protein and a large amount of cholesterol; high levels are thought to be associated with increased risk of coronary heart disease and atherosclerosisvery low density lipoprotein, VLDL - large lipoproteins rich in triglycerides; VLDLs circulate through the blood giving up their triglycerides to fat and muscle tissue until the VLDL remnants are modified and converted into LDL

Translations

lipoprotein

(lĭp'əprō`tēn), any organic compound that is composed of both proteinprotein,
any of the group of highly complex organic compounds found in all living cells and comprising the most abundant class of all biological molecules. Protein comprises approximately 50% of cellular dry weight.
..... Click the link for more information. and the various fatty substances classed as lipidslipids,
a broad class of organic products found in living systems. Most are insoluble in water but soluble in nonpolar solvents. The definition excludes the mineral oils and other petroleum products obtained from fossil material.
..... Click the link for more information. , including fatty acidsfatty acid,
any of the organic carboxylic acids present in fats and oils as esters of glycerol. Molecular weights of fatty acids vary over a wide range. The carbon skeleton of any fatty acid is unbranched. Some fatty acids are saturated, i.e.
..... Click the link for more information. and steroidssteroids,
class of lipids having a particular molecular ring structure called the cyclopentanoperhydro-phenanthrene ring system. Steroids differ from one another in the structure of various side chains and additional rings. Steroids are common in both plants and animals.
..... Click the link for more information. such as cholesterolcholesterol
, fatty lipid found in the body tissues and blood plasma of vertebrates; it is only sparingly soluble in water, but much more soluble in some organic solvents. A steroid, cholesterol can be found in large concentrations in the brain, spinal cord, and liver.
..... Click the link for more information. . The lipoprotein complex of proteins and steroids is usually provided by a weak, noncovalent interaction; proteins complexed with some other lipids do so by the information of covalent chemical bonds. There are several types of lipoproteins present in human blood, including low-density lipoproteins (LDLs)—molecules with a larger molecular weight and a relatively low percentage of protein—and high-density lipoproteins (HDLs)—molecules with a smaller molecular weight and a relatively high percentage of protein. LDLs are the main transport for cholesterol through the body. HDLs appear to carry excess cholesterol to the liver for processing. Studies have found that high levels of HDLs, which seem to retard or even reverse the formation of cholesterol plaque in the arteries (see arteriosclerosisarteriosclerosis
, general term for a condition characterized by thickening, hardening, and loss of elasticity of the walls of the blood vessels. These changes are frequently accompanied by accumulations inside the vessel walls of lipids, e.g.
..... Click the link for more information. ), reduce the risk of cardiovascular disease. Cell membranes are essentially lipoprotein in nature; the membrane is a continuous sheet of lipid molecules, largely phospholipidsphospholipid
, lipid that in its simplest form is composed of glycerol bonded to two fatty acids and a phosphate group. The resulting compound called phosphatidic acid contains a region (the fatty acid component) that is fat-soluble along with a region (the charged phosphate
..... Click the link for more information. , in close association with proteins that either face one side of the membrane or penetrate all the way through the membrane.

Lipoprotein

Classes of conjugated proteins consisting of a protein combined with a lipid. The normal functioning of higher organisms requires movement of insoluble lipids, such as cholesterol, steroid hormones, bile, and triglycerides, between tissues. To accomplish this movement, lipids are incorporated into macromolecular complexes called lipoproteins.

All major types of lipoproteins share a general structure. The core of these spherical particles contains primarily cholesteryl ester and triglyceride. These insoluble molecules are surrounded by a coating of proteins and phospholipids that are amphipathic; that is, they have both polar and nonpolar regions. Lipoproteins vary by size and density. The largest lipoproteins, chylomicrons, are up to 500 nanometers in diameter, and since they contain primarily triglyceride they are so buoyant that they float in plasma. Very low density lipoproteins (VLDL) also primarily transport triglyceride. Low-density lipoproteins (LDL) and the smallest, most dense lipoproteins, high-density lipoproteins (HDL), transport cholesterol. The interactions of these particles with cell surface receptors and with metabolic enzymes are mediated by the protein components of the particles, termed apolipoproteins. See Cholesterol, Triglyceride

Chylomicrons contain triglyceride (fat) from the diet. In addition, they carry fat-soluble vitamins, such as vitamin A and E, into the circulation. Chylomicrons are produced in the intestine, enter the body via the lymphatic system, and then enter the bloodstream.

Very low density lipoproteins are made in the liver and contain triglyceride that is synthesized either from excess carbohydrate sources of calories or from fatty acids that enter the liver and are reassembled into triglyceride. Lipoprotein lipase (LpL) is an enzyme found on the surface of blood vessels that is responsible for the breakdown of triglyceride in lipoproteins. The partially degraded lipoproteins are termed remnants. They are ultimately removed from the circulation by the liver.

Low-density lipoproteins result after triglyceride is removed from very low density lipoproteins. This leaves a smaller, denser particle that primarily contains cholesteryl ester as its core lipid and a single protein called apoB. Cells throughout the body contain an LDL receptor that recognizes apoB. This allows the uptake of low-density lipoproteins into cells, supplying them with cholesterol. When sufficient low-density lipoproteins and cholesterol are available, cells use them in preference to synthesizing new cholesterol from precursors. In contrast, high-density lipoproteins both deliver and remove cholesterol from tissues.

Blood levels of lipoproteins are major factors regulating risk for development of coronary artery atherosclerosis. Via unknown mechanisms, low-density lipoproteins and remnant lipoproteins infiltrate and then become attached to extracellular matrix molecules within the artery. Some of the lipoproteins are internalized by macrophages and smooth muscle cells. This might first require chemical modification such as oxidation of the lipids. The resulting pathological findings are deposition of cholesterol in cells and matrix within the vessel wall, leading to a decrease in the diameter of the artery.

In contrast, high-density lipoproteins appear to prevent atherosclerosis formation. The reasons are not entirely understood. Most likely, high-density lipoproteins remove excess cholesterol that accumulates in the artery, or prevent the oxidation of low-density lipoproteins. See Arteriosclerosis

lipoprotein

[‚lip·ə′prō‚tēn] (biochemistry) Any of a class of conjugated proteins consisting of a protein combined with a lipid.

lipoprotein

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

(lĭp′ō-prō′tēn′, -tē-ĭn, lī′pō-)n. 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.

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

lip·o·pro·tein

(lip'ō-prō'tēn) 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.

Lipoprotein

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.Mentioned in: Cholesterol Test, Hypolipoproteinemia

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

lipoprotein

Related to lipoprotein: lipoprotein lipase, Low density lipoprotein

noun

Words related to lipoprotein

noun a conjugated protein having a lipid component

Related Words

compound protein
conjugated protein
alpha-lipoprotein
HDL
high-density lipoprotein
beta-lipoprotein
LDL
low-density lipoprotein
very low density lipoprotein
VLDL