Chylomicron
ApoA, ApoB, ApoC, ApoE ( apolipoproteins ); T ( triacylglycerol ); C ( cholesterol ); green ( phospholipids )
Chylomicrons are lipoprotein particles with a diameter of 0.5 to 1.0 µm and a density of less than 1,000 g / ml, which are secreted from the small intestine via the lymph into the bloodstream . Their lipid core mainly contains triacylglycerides and a comparatively small amount of cholesterol esters . Apolipoprotein B-48 is embedded in the cholesterol- containing phospholipid shell as an apolipoprotein structure. Other apolipoproteins, some of which are transferred to chylomicrons at a later point in time, are apolipoprotein E (ApoE) , the apolipoprotein C family and apolipoprotein A-IV. Chylomicrons are a factor in the development and symptoms of food allergies .
The chylomicrons transport the dietary fats absorbed in the intestine , bypassing the liver, via the lymphatic system into the large bloodstream and have roughly the following composition:
- 1% protein
- 4% cholesterol and cholesterol esters
- 5% phospholipids
- 90% triglycerides
Chylomicrons enter the bloodstream via the lymphatic vessels and the breast duct ( thoracic duct ). In the capillaries of fat and muscle tissue, lipoprotein lipase breaks down a large part of the triglycerides contained in the chylomicrons. The released fatty acids are then absorbed by the surrounding fat and muscle cells and stored or used up. The particles remaining in the bloodstream, which now have a greatly increased relative cholesterol content, are referred to as chylomicron remnants . The apolipoprotein C2 attaches to them, which ultimately mediates the receptor-mediated uptake of the chylomicron remnants in the liver (in particular via the membrane receptor LRP1 , and to a lesser extent also via the LDL receptor ). If no food is consumed for around ten hours, chylomicrons can no longer be detected.
Chylomicrons and food allergies
In a study on mice it could be shown for the first time that the intake of the dietary protein that is not digested occurs mainly via the chylomicron transport, especially if the food contains a lot of triglycerides . This is the case with peanuts , eggs and milk , and there is also the fact that corresponding protein antigens have emulsifying properties, which means that they have a high affinity for chylomicrons.
Verification procedure
literature
- Albert L. Lehninger, David L. Nelson, Michael M. Cox: Principles of Biochemistry . 2nd Edition. Spektrum Akademischer Verlag, Heidelberg, Berlin, Oxford 1994, ISBN 3-86025-106-6 , pp. 562, 774-776 .
Individual evidence
- ↑ Wang Y., Ghoshal S., Ward M., de Villiers W., Woodward J., Eckhardt E .: Chylomicrons promote intestinal absorption and systemic dissemination of dietary antigen (ovalbumin) in mice . In: PLoS ONE . 4, No. 12, 2009, p. E8442. doi : 10.1371 / journal.pone.0008442 . PMID 20041190 . PMC 2793525 (free full text).