chylomicronok

Chylomicrons are lipoprotein particles that are essential for the transport of dietary lipids from the intestines to other tissues in the body. They are the largest and least dense of the lipoproteins. Chylomicrons are assembled in the enterocytes, the cells lining the small intestine, after the absorption of dietary fats. Their primary function is to carry triglycerides and cholesterol absorbed from the diet.

The formation of chylomicrons begins with the digestion of dietary fats into fatty acids and monoglycerides. These are then reassembled into triglycerides within the enterocytes. These triglycerides, along with cholesterol, phospholipids, and apolipoproteins (particularly ApoB-48), are packaged into nascent chylomicrons.

Once formed, nascent chylomicrons are released into the lymphatic system, bypassing the portal vein that transports nutrients directly to the liver. They travel through the lymphatic vessels and eventually enter the bloodstream via the thoracic duct. In the circulation, nascent chylomicrons acquire additional apolipoproteins, such as ApoC-II and ApoE, from other lipoproteins. ApoC-II is crucial for activating lipoprotein lipase (LPL), an enzyme located on the surface of endothelial cells in capillaries.

Lipoprotein lipase hydrolyzes the triglycerides within chylomicrons into fatty acids and glycerol. These fatty acids are then taken up by tissues such as adipose tissue for storage or by muscles for energy. As chylomicrons lose their triglycerides, they become smaller and denser, transforming into chylomicron remnants. These remnants, enriched in cholesterol, are then cleared from circulation by the liver through receptors that recognize ApoE. The liver can then process this cholesterol.