chylomicrons

Last reviewed 07/2021

Chylomicrons transport dietary fat from gut to adipose tissue, liver and muscle cells. They have the heaviest mass of any lipid-containing particle and are the richest in triglyceride. In general, fat absorption is complete within a few hours of ingesting food, and the chylomicron concentration fluctuates during this period. In fit, healthy people chylomicrons account for a modest postprandial rise in triglycerides. However in individuals where the clearance of chylomicrons from the circulation is delayed there may be a marked rise in triglycerides following food ingestion.

Chylomicrons are initially secreted into the lacteals of the villi and join the lymphatic circulation to ender the blood via the thoracic duct in the chest.

They consist of approximately:

• 80% triglyceride
• 9% phospholipids
• 6% cholesterol and cholesterol-esters
• small proportion of protein:
• apolipoprotein B from small intestine
• apolipoprotein C from HDL

Lipoprotein lipase, an enzyme located on the surface of endothelial capillaries, works in the presence of apolipoprotein C to degrade triglyceride within the chylomicron to free fatty acids and glycerol. These products may be taken up and either respired or resynthesized into triglycerides for storage.

Thus, the chylomicron is reduced in size by the removal of lipid. The resulting particle is a chylomicron remnant which is phagocytosed in hepatocytes via receptors that recognize apolipoprotein E (apo E).