Chylomicron Catabolism and Uptake by the Liver

Chylomicrons carry lipids of intestinal origin to peripheral tissues and the liver. The lipids are of two sources. First, there are the endogenous lipids of desquamated intestinal epithelial cells and the bile. Secondly, exogenous lipids of dietary origin are absorbed. This latter source is the most important for triglycerides, while much of the cholesterol and phospholipids follow the conservative cycle of endogenous lipids being reabsorbed. As the quantity of triglycerides determines the size of chylomicron particles, postprandially their diameter rises up to 2000 A or more. That is why chylomicrons are postprandially easily recognized in the blood stream, although they are continuously secreted. The particles produced in the fasting state are much smaller with a diameter in the range of 500 A, which is similar to that of very low density lipoproteins (VLDL) of hepatic origin. For this reason these “small chylomicrons” are also referred to as “intestinal VLDL”, which gives rise to confusion as the catabolic pathways of chylomicrons and VLDL differ considerably [1].