Lipoprotein involved in reverse cholesterol transpo?
The HDL paicles are referred to as scavengers because their primary role is to remove free (unesterified) cholesterol from the extrahepatic tissues. HDL paicles transpo cholesterol from extrahepatic tissues to liver (i.e. reverse cholesterol transpo) which is then excreted through bile. Reverse cholesterol transpo All nucleated cells in different tissues synthesize cholesterol, but the excretion of cholesterol is mainly by liver in the bile or by enterocytes in gut lumen. So, cholesterol must be transpoed from peripheral tissue to liver for excretion. This is facilitated by HDL and is called reverse cholesterol transpo because it transpos the cholesterol in reverse direction to that is transpoed from liver to peripheral tissues through VLDL - LDL cycle. Process HDL is synthesized in liver and small intestine. Nascent HDL contain phospholipids and unesterified cholesterol and Apo-A, C, E. This nascent HDL is secreted into circulation where it acquires additional unesterified cholesterol from peripheral tissues. Within the HDL paicle, the cholesterol is esterified by lecithin - cholesterol acetyltransferase (LCAT) to form cholesteryl ester and additional lipid are transpoed to HDL from VLDL and chylomicrons. Apo-A1 activates LCAT.
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