Chylomicrons

Chylomicrons are lipoprotein particles that are necessary for the transport of triglycerides, phospholipids and cholesterol from the small intestine to the liver. Chylomicrons have a diameter of 0.5 to 1.0 µm and a density of <1.000 g/ml.

In the intestine, triacylglycerides are split into diacylglycerides, monoacylglycerides and free fatty acids. These diffuse together with phospholipids and cholesterol into the intestinal mucosa cells. There they are synthesized again in the smooth endoplasmic reticulum to triacylglycerides and packed together with the other lipids, apolipoprotein A and apolipoprotein B-48, to form a lipoprotein called chylomicron.

The chylomicrons are then released into the lymph. By completely bypassing the liver circulation, the chylomicrons are transported via the lymphatic system into the thoracic duct and finally into the blood. In the blood, the chylomicrons release their ApoA to the HDL, receiving ApoC and ApoE from the "high density lipoproteins". The ApoC serves to activate the lipoprotein lipase, which is located in the endothelium of the heart capillaries, the muscle capillaries and the capillaries in fatty tissue.

The lipoprotein lipase cleaves the triacylglycerides to free fatty acids, which can be used by the above-mentioned tissues as an energy supplier or stored as triacylglycerides. The chylomicrons then reach the liver as so-called remnants, where they are bound to LDL receptors, then absorbed into the liver cells via endocytosis and finally degraded. The remaining triacylglycerides are packaged into VLDL.