quilomícron

Quilomícron, or chylomicron in English, is a large, low-density lipoprotein–like particle produced by enterocytes in the small intestine. It functions to transport dietary lipids, including triglycerides, cholesterol esters, phospholipids, and fat-soluble vitamins, from the gastrointestinal tract to peripheral tissues. Quilomícrons are the largest lipoproteins and have the highest triglyceride content, with apolipoproteins such as ApoB-48, ApoC-II, and ApoE associated with their surface.

Formation and secretion occur after dietary fat is digested and absorbed. In enterocytes, triglycerides are assembled with apolipoprotein B-48 in the endoplasmic reticulum with the help of microsomal triglyceride transfer protein (MTP). The particles are then processed through the Golgi and secreted into the lymphatic system via intestinal lacteals, bypassing the liver, before entering the bloodstream through the thoracic duct.

Metabolism involves lipoprotein lipase, located on capillary endothelium, which hydrolyzes the triglycerides in quilomícrons into free fatty acids and glycerol for uptake by muscle and adipose tissue. This leaves chylomicron remnants enriched in cholesterol and fat-soluble vitamins. Remnants are cleared from circulation primarily by the liver through receptor-mediated endocytosis, notably via ApoE interactions with hepatic receptors.

Clinical notes: disorders of quilomícron metabolism can cause hyperchylomicronemia (type I hyperlipoproteinemia), characterized by elevated triglycerides and risk of pancreatitis. Abetalipoproteinemia, involving defective ApoB and impaired chylomicron formation, leads to fat malabsorption and fat-soluble vitamin deficiencies. In routine lipid testing, the presence of excess quilomícrons is suggested by a creamy layer in plasma after overnight fasting.