Reverse cholesterol transport
Cholesterol from non-hepatic peripheral tissues is transferred to HDL by the ABCA1 (ATP-binding cassette transporter). Apolipoprotein A1 (ApoA-1), the major protein component of HDL, acts as an acceptor, and the phospholipid component of HDL acts as a sink for the mobilised cholesterol. The cholesterol is converted to cholesteryl esters by the enzyme LCAT (lecithin-cholesterol acyltransferase). The cholesteryl esters can be transferred, with the help of CETP (cholesterylester transfer protein) in exchange for triglycerides, to other lipoproteins (such as LDL and VLDL), and these lipoproteins can be taken up by secreting unesterified cholesterol into the bile or by converting cholesterol to bile acids.
Uptake of HDL2 is mediated by hepatic lipase, a special form of lipoprotein lipase found only in the liver. Hepatic lipase activity is increased by androgens and decreased by estrogens, which may account for higher concentrations of HDL2 in women.
- Tall, AR (February 1998). "An overview of reverse cholesterol transport.". Eur. Heart J. 19 Suppl A: A31–5. doi:10.1093/eurheartj/19.Abstract_Supplement.1. PMID 9519340.
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