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Encyclopedia > Apolipoprotein B

Apolipoprotein B (APOB) is the primary apolipoprotein of low density lipoproteins (LDL or "bad cholesterol"), and is responsible for carrying cholesterol to tissues. While it is unclear exactly what functional role APOB plays in LDL, it is the primary component and is absolutely required for its formation. Through a mechanism that is not fully understood, high levels of APOB can lead to plaques that cause heart disease (atherosclerosis). It is considered by many to be a better indicator of heart disease risk than total cholesterol or LDL. To meet Wikipedias quality standards, this article or section may require cleanup. ... Low-density lipoprotein (LDL) refers to a class and range of lipoprotein particles, varying somewhat in their size and contents, which carry cholesterol in the blood and around the body, for use by various cells. ... Cholesterol is a sterol (a combination steroid and alcohol) and a lipid found in the cell membranes of all body tissues, and transported in the blood plasma of all animals. ... Look up Tissue on Wiktionary, the free dictionary The word tissue has several meanings: Aerial tissu is an acrobatic art form, and is one of the circus arts. ... The word plaque or placque may mean: Wiktionary has related dictionary definitions, such as: plaque, placque Dental plaque, a yellowish film that builds up on the teeth Atheromatous plaque, a buildup of fatty deposits within the wall of a blood vessel Mucoid plaque, a supposed thick coating of plaque in... Heart disease is one of a number of different diseases which afflict the heart. ... The heart and lungs, from an older edition of Grays Anatomy. ...

Contents

Genetic disorders

High levels of APOB are related to heart disease. While there does appear to be a genetic component, the environmental component (what you eat) is a significant factor that should not be ignored.


Hypobetalipoproteinemia is a genetic disorder that can be caused by a mutation in the APOB gene, APOB, although it is usually caused by a mutation in the MTP gene, MTP. A genetic disorder, or genetic disease is a disease caused by abnormal expression of one or more genes in a person causing a clinical phenotype. ...


Mouse studies

Most relevant information regarding mouse APOB homologue, mApoB, has come from mouse studies. Mice overexpressing mApoB have increased levels of LDL "bad cholesterol" and decreased levels of HDL "good cholesterol" [1]. Mice containing only one functional copy of the mApoB gene show the opposite effect, being resistant to hypercholesterolemia. Mice containing no functional copies of the gene are not viable [2]. Feral mouse A mouse (Plural mice) is a mammal that belongs to one of numerous species of small rodents. ... Low-density lipoprotein (LDL) refers to a class and range of lipoprotein particles, varying somewhat in their size and contents, which carry cholesterol in the blood and around the body, for use by various cells. ... HDL is an initialism that may refer to any of the following: High density lipoprotein Hardware description language german: Hab Dich Lieb This page concerning a three-letter acronym or abbreviation is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... Hypercholesterolemia (literally: high blood cholesterol) is the presence of high levels of cholesterol in the blood. ...


Molecular biology

The protein occurs in the plasma in 2 main isoforms, APOB48 and APOB100. The first is synthesized exclusively by the small intestine, the second by the liver. Both isoforms are coded by APOB and by a single mRNA transcript larger than 16 kb. APOB48 is generated when a stop codon (UAA) at residue 2153 is created by RNA editing. There appears to be a trans-acting tissue-specific splicing gene that determines which isoform is ultimately produced. Alternatively, there is some evidence that a cis-acting element several thousand bp upstream determines which isoform is produced. A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Blood plasma is the liquid component of blood, in which the blood cells are suspended. ... Diagram showing the small intestine In biology the small intestine is the part of the gastrointestinal tract (gut) between the stomach and the large intestine. ... The liver is the largest internal organ of the human body. ... The interaction of mRNA in a eukaryote cell. ... RNA codons. ... // Introduction The term RNA editing describes those molecular processes in which the information content is altered in a RNA molecule through a chemical change in the base makeup. ... In molecular biology, two nucleotides on opposite complementary DNA or RNA strands that are connected via hydrogen bonds are called a base pair (often abbreviated bp). ...


As a result of the RNA editing, APOB48 and APOB100 share a common N-terminal sequence, but APOB48 lacks APOB100's C-terminal LDL-receptor binding region.


References

  1. a  Image:Free_text.png Transgenic mice that overexpress mouse apolipoprotein B. Evidence that the DNA sequences controlling intestinal expression of the apolipoprotein B gene are distant from the structural gene. J Biol Chem. 1996 May 17; 271(20): 11963-70; PubMed Free text
  2. a  Image:Free_text.png Knockout of the Mouse Apolipoprotein B Gene Results in Embryonic Lethality in Homozygotes and Protection Against Diet-Induced Hypercholesterolemia in Heterozygotes. Proc Natl Acad Sci USA. 1995 Feb 28; 92(5): 1774-8; PubMed Free text


Image File history File links Free_text. ... Image File history File links Free_text. ...

Lipoproteins edit 
Chylomicron | HDL | IDL | LDL | VLDL

APOA1 | APOA2 | APOB | APOC1 | APOC2 | APOC3 | APOC4 | APOD | APOE | APOH A lipoprotein is a biochemical assembly that contains both proteins and lipids and may be structural or catalytic in function. ... Chylomicrons are large lipoprotein particles (having a diameter of 75 to 1,200nm) that are created by the absorptive cells of the small intestine. ... High density lipoproteins (HDL) form a class of lipoproteins, varying somewhat in their size (8-11 nm in diameter) and contents, that carry cholesterol from the bodys tissues to the liver. ... Intermediate density lipoproteins are a class of lipoproteins formed from the degradation of very low density lipoproteins, constituted essentially of triacylglycerols and cholesterol esters. ... Low-density lipoprotein (LDL) refers to a class and range of lipoprotein particles, varying in their size and contents, which carry cholesterol in the blood and around the body, for use by cells. ... Very Low Density Lipoprotein (VLDL) is a lipoprotein subclass. ... Apolipoprotein E (APOE), a main apoprotein of the chylomicron, binds to a specific receptor on liver cells and peripheral cells. ...


  Results from FactBites:
 
NEJM -- Increased concentrations of cholestanol and apolipoprotein B in the cerebrospinal fluid of patients with ... (461 words)
NEJM -- Increased concentrations of cholestanol and apolipoprotein B in the cerebrospinal fluid of patients with cerebrotendinous xanthomatosis.
Increased concentrations of cholestanol and apolipoprotein B in the cerebrospinal fluid of patients with cerebrotendinous xanthomatosis.
Apolipoprotein AIV and apolipoprotein E concentrations were comparable to those in controls, and apolipoprotein AII was considerably decreased.
Apolipoprotein Assessment (857 words)
When apo A-1, apo B, lipids, and lipoprotein cholesterol were measured in school-aged children (mean age of 10 years), apo A-1 and apo B levels were associated with a history of myocardial infarction in their parents.
Maciejko has suggested apo B levels are helpful in differentiating primary causes of hypertriglyceridemia, provided that secondary causes (diabetes, alcohol ingestion, uremia, acromegaly, emotional stress or stress from acute illness, and certain drugs such as estrogen or beta blockers) have been ruled out.
Apo B measurements will also provide laboratory evidence of hyperapobetalipoproteinemia with excess apo B, whereas apo B deficiency states are found in abetalipoproteinemia, hypobetalipoproteinemia, familial hypobetalipoproteinemia with chylomicronemia, and abetalipoproteinemia with normotriglyceridemia.
  More results at FactBites »

 
 

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