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LIVER AND BILIARY TRACT
Departments of 1Biochemistry and 2Medicine, Marion Bessin Liver Research Center, Albert Einstein College of Medicine, Bronx, New York
Submitted 29 April 2005 ; accepted in final form 8 August 2005
Phosphatidylcholine transfer protein (PC-TP) is a steroidogenic acute regulatory-related transfer domain protein that is enriched in liver cytosol and binds phosphatidylcholines with high specificity. In tissue culture systems, PC-TP promotes ATP-binding cassette protein A1-mediated efflux of cholesterol and phosphatidylcholine molecules as nascent pre-
-high-density lipoprotein (HDL) particles. Here, we explored a role for PC-TP in HDL metabolism in vivo utilizing 8-wk-old male Pctp/ and wild-type littermate C57BL/6J mice that were fed for 7 days with either chow or a high-fat/high-cholesterol diet. In chow-fed mice, neither plasma cholesterol concentrations nor the concentrations and compositions of plasma phospholipids were influenced by PC-TP expression. However, in Pctp/ mice, there was an accumulation of small
-migrating HDL particles. This occurred without changes in hepatic expression of ATP-binding cassette protein A1 or in proteins that regulate the intravascular metabolism and clearance of HDL particles. In Pctp/ mice fed the high-fat/high-cholesterol diet, HDL particle sizes were normalized, whereas plasma cholesterol and phospholipid concentrations were increased compared with wild-type mice. In the absence of upregulation of hepatic ATP-binding cassette protein A1, reduced HDL uptake from plasma into livers of Pctp/ mice contributed to higher plasma lipid concentrations. These data indicate that PC-TP is not essential for the enrichment of HDL with phosphatidylcholines but that it does modulate particle size and rates of hepatic clearance.
steroidogenic acute regulatory-related transfer domain; phospholipid; cholesterol; plasma; liver
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