chylomicron
American Heritage Dictionary:
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chy·lo·mi·cron
(kī'lō-mī'krŏn') 
n.
One of the microscopic particles of emulsified fat found in the blood and lymph and formed during the digestion of fats.
n.
One of the microscopic particles of emulsified fat found in the blood and lymph and formed during the digestion of fats.
[CHYL(E) + Greek mīkron, small thing, from neuter of mīkros, small.]
Oxford Food & Nutrition Dictionary:
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chylomicrons
Oxford Dictionary of Sports Science & Medicine:
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chylomicron
A lipoprotein formed from emulsified droplets of lipid that enter the lymph system from the intestine and transport fat-soluble vitamins A, D, E, and K to the liver. A chylomicron is about 100 nm in diameter, and consists of a lipid core enveloped by protein, cholesterol, and phospholipid.
Oxford Dictionary of Biochemistry:
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chylomicron
a large lipoprotein particle, of molecular mass up to 107 kDa, measuring up to 100 nm in diameter, and of density < 1.006. Chylomicrons appear in plasma during absorption of a fat-containing meal and normally disappear by 12 — 15 hours. Their approximate composition (% by weight) is 2% cholesterol, unesterified; 5% cholesterol, esterified; 7% phospholipid; 84% triacylglycerol; 2% protein. Their apolipoprotein composition (% by weight total apolipoprotein) is 7.4% A-I; 4.2% A-II; 22.5% B-48; 66% C-I + C-II + C-III. Chylomicrons are formed in the mucosa of the small intestine, and contain mostly triacylglycerols re-esterified in the mucosal cells from dietary long-chain fatty acids associated with apolipoproteins. They then enter the lymphatic capillaries (lacteals) of the intestinal villi, and thence the bloodstream. Binding to lipoprotein lipase on the capillary endothelial surface deprives them of triglycerides, and converts them into chylomicron remnants. They are the vehicle by which fat and fat-soluble vitamins are absorbed. Hyperchylomicronemia results from deficiency of lipoprotein lipase. Chylomicron retention disease is a defect in secretion of chylomicrons characterized by fat malabsorption, absence of chylomicrons in plasma after ingestion of fat, and sometimes acanthocytosis and neurological abnormalities. There is accumulation in enterocytes of chylomicron-like particles that are rich in ApoB-48 (see apolipoprotein B).
| chyle, chrysotherapy, chronobiochemistry | |
| chylomicron remnant, chymase, chyme |
Saunders Veterinary Dictionary:
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chylomicron
A stable droplet containing principally triglyceride fat, but also cholesterol, phospholipids and protein; found in intestinal lymphatics (lacteals) and blood during and after meals.
- c. test — in chilled serum, chylomicrons rise to form a creamy top layer and the serum clears; very low-density lipoproteins remain dispersed and the serum is turbid. Called also the refrigeration test.
Mosby's Dental Dictionary:
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chylomicrons
(kīlōmīkronz)
n.pl
n.pl
Tiny lipoproteins of approximately 2% protein that convey dietary fat throughout the body.
Wikipedia on Answers.com:
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Chylomicron
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This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (December 2009) |
ApoA, ApoB, ApoC, ApoE (apolipoproteins); T (triacylglycerol); C (cholesterol); green (phospholipids)
Chylomicrons are lipoprotein particles that consist of triglycerides (85-92%), phospholipids (6-12%), cholesterol (1-3%) and proteins (1-2%).[1] They transport dietary lipids from the intestines to other locations in the body. Chylomicrons are one of the five major groups of lipoproteins (chylomicrons, VLDL, IDL, LDL, HDL) that enable fats and cholesterol to move within the water-based solution of the bloodstream.
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Contents
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Function
Chylomicrons transport exogenous lipids to liver, adipose, cardiac, and skeletal muscle tissue, where their triglyceride components are unloaded by the activity of lipoprotein lipase. As a consequence, chylomicron remnants are left over and are taken up by the liver.
Origin
Chylomicrons are a type of lipoprotein produced in absorptive cells of small intestines, specifically, the epithelial cells within the villi of the duodenum.
Stages
There are three stages in the chylomicron's "life cycle":
- Nascent chylomicron
- Mature chylomicron
- Chylomicron remnant
Nascent chylomicrons
Chylomicrons are created by the absorptive cells of the small intestine, known as enterocytes. They are relatively large, having a diameter of 75 to 1,200 nm. These nascent chylomicrons are released by exocytosis from enterocytes into lacteals, lymphatic vessels originating in the villi of the small intestine, and are then secreted into the bloodstream at the thoracic duct's connection with the left subclavian vein.
Nascent chylomicrons are primarily composed of triglycerides (85%) and contain some cholesterol and cholesteryl esters. The main apolipoprotein component is apolipoprotein B-48 (APOB48).
Mature chylomicron
While circulating in lymph and blood, chylomicrons exchange components with high-density lipoproteins (HDL). The HDL donates apolipoprotein C-II (APOC2) and apolipoprotein E (APOE) to the nascent chylomicron and thus converts it to a mature chylomicron (often referred to simply as "chylomicron"). APOC2 is the cofactor for lipoprotein lipase (LPL) activity.
Chylomicron remnant
Once triglyceride stores are distributed, the chylomicron returns APOC2 to the HDL (but keeps APOE), and, thus, becomes a chylomicron remnant, now only 30–50 nm. APOB48 and APOE are important to identify the chylomicron remnant in the liver for endocytosis and breakdown.
References
- ^ M Mahmood Hussain: "Review Article: A proposed model for the assembly of chylomicrons"; Arterosclerosis; Vol. 148; 2000; pages 1-15;
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American Heritage Dictionary
The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.
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Oxford Food & Nutrition Dictionary
A Dictionary of Food and Nutrition. Copyright © 1995, 2003, 2005 by A. E. Bender and D. A. Bender. All rights reserved.
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Oxford Dictionary of Sports Science & Medicine
The Oxford Dictionary of Sports Science & Medicine. Copyright © Michael Kent 1998, 2006, 2007. All rights reserved.
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Oxford Dictionary of Biochemistry
Oxford University Press. Oxford Dictionary of Biochemistry and Molecular Biology © 1997, 2000, 2006 All rights reserved.
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Saunders Veterinary Dictionary
Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved.
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Mosby's Dental Dictionary
Mosby's Dental Dictionary. Copyright © 2004 by Elsevier, Inc. All rights reserved.
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