Chylomicron

Chylomicron structure
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.

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

1. ^ M Mahmood Hussain: "Review Article: A proposed model for the assembly of chylomicrons"; Arterosclerosis; Vol. 148; 2000; pages 1-15;

This protein-related article is a stub. You can help Wikipedia by expanding it.v · Categories: Lipoproteins Protein stubs Wikimedia Foundation. 2010. Игры ⚽ Поможем решить контрольную работу Colorado Party (Uruguay) Akimiski Island Look at other dictionaries: chylomicron — [kī΄lō mī′krän΄] n. pl. chylomicra [kī΄lō mī′krə] or chylomicrons [ CHYL(E) + O + MICRON] a micron sized particle that contains mostly triglycerides with some protein, found in the blood and lymph, esp. after fat is eaten …   English World dictionary Chylomicron — A small fat globule composed of protein and lipid (fat). Chylomicrons are found in the blood and lymphatic fluid where they serve to transport fat from its port of entry in the intestine to the liver and to adipose (fat) tissue. After a fatty… …   Medical dictionary Chylomicron retention disease — Classification and external resources OMIM 246700 DiseasesDB 33188 Chylomicron retention disease is a disorder of fat absorption …   Wikipedia chylomicron — noun Etymology: Greek chylos + mikron, neuter of mikros small more at micro Date: 1921 a lipoprotein rich in triglyceride and common in the blood during fat digestion and assimilation …   New Collegiate Dictionary Chylomicron — Les chylomicrons sont des lipoprotéines qui se forment en période de digestion. Elles sont responsables du transport des lipides de l intestin grêle vers les tissus adipeux périphériques où ils sont retraités. Lors de l absorption, les divers… …   Wikipédia en Français chylomicron — Colloidal fat globule found in blood or lymph; used to transport fat from the intestine to the liver or to adipose tissue. Has a very low density, a low protein and high triacylglyceride content …   Dictionary of molecular biology chylomicron — /kuy leuh muy kron/, n. Biochem. a large plasma lipoprotein particle, occurring as a droplet consisting primarily of triglycerides and functioning in the transport of neutral lipids from the intestine to the tissues by way of the lymph. [1920 25; …   Universalium chylomicron — noun A microscopic globule of lipoprotein, found in blood and lymph, that is associated with the digestion of fats …   Wiktionary chylomicron — chy·lo·mi·cron …   English syllables chylomicron — n. a lipoprotein particle present in the blood after digested fat has been absorbed from the small intestine. The lipid portion consists largely of triglycerides, which are released by the action of lipoprotein lipase …   The new mediacal dictionary 18+ © Academic, 2000-2024 Contact us: Technical Support, Advertising Dictionaries export, created on PHP, Joomla, Drupal, WordPress, MODx. Mark and share Search through all dictionaries Translate… Search Internet Share the article and excerpts Direct link … Do a right-click on the link above and select “Copy Link”