Cholesterolabsorptie

Cholesterolabsorptie refers to the process by which cholesterol from the diet and biliary cholesterol is taken up by the enterocytes, the cells lining the small intestine. This is a critical step in the overall regulation of cholesterol homeostasis in the body. Dietary cholesterol, along with cholesterol secreted into the small intestine via bile, is present in the lumen of the intestine. Before absorption, these cholesterol molecules, along with other lipids, are emulsified by bile salts and packaged into small, water-soluble structures called micelles.

Within the micelle, cholesterol is in close proximity to the brush border of the enterocytes. The absorption of cholesterol is an active process, primarily mediated by the Niemann-Pick C1-Like 1 (NPC1L1) protein, which is located on the apical membrane of the enterocytes. NPC1L1 facilitates the transport of cholesterol from the micelle into the enterocyte. Once inside the enterocyte, cholesterol can be re-esterified by the enzyme acyl-CoA:cholesterol acyltransferase 2 (ACAT2) or packaged into chylomicrons for transport into the lymphatic system and subsequently the bloodstream. A portion of absorbed cholesterol can also be effluxed back into the intestinal lumen by the ATP-binding cassette transporter G5/G8 (ABCG5/G8). The efficiency of cholesterol absorption from the diet is typically around 50%, but this can vary depending on factors such as dietary intake, bile acid levels, and the presence of other dietary components. Inhibiting cholesterol absorption, for example with ezetimibe, is a therapeutic strategy to lower blood cholesterol levels.