scholarly journals Selective uptake of cholesteryl esters from apolipoprotein-E-free high-density lipoproteins by rat parenchymal cells in vivo is efficiently coupled to bile acid synthesis

1991 ◽  
Vol 280 (2) ◽  
pp. 359-365 ◽  
Author(s):  
M N Pieters ◽  
D Schouten ◽  
H F Bakkeren ◽  
B Esbach ◽  
A Brouwer ◽  
...  
Keyword(s):  
Bile Acid ◽  
Cholesteryl Ester ◽  
Bile Acids ◽  
Density Lipoprotein ◽  
Cholesteryl Oleate ◽  
Cholesteryl Esters ◽  
Liver Uptake ◽  
Selective Uptake ◽  
Parenchymal Cells ◽  
Kinetics Of

[3H]Cholesteryl ester-labelled human high-density lipoprotein (HDL) was injected into rats and its decay, intrahepatic cellular distribution and the kinetics of biliary secretion were determined. At 10 min after injection the hepatic uptake of cholesteryl esters from HDL was 3-fold higher as compared with the apolipoprotein. Selective uptake was exerted only by parenchymal cells (5.6-fold more cholesteryl esters than apolipoprotein) and not by liver endothelial or Kupffer cells. The kinetics of biliary secretion of processed cholesteryl esters initially associated with HDL or low-density lipoprotein (LDL) were compared in unrestrained rats, equipped with permanent catheters in bile duct, duodenum and heart. At 72 h after injection of [3H]cholesteryl oleate-labelled HDL, 51.0 +/- 2.5% of the injected dose was recovered as bile acids, which is about twice as high as the secretion of biliary radioactivity after injection of [3H]cholesteryl oleate-labelled LDL. Oestradiol treatment stimulated only liver uptake of LDL cholesteryl esters, and resulted in a 2-fold higher liver uptake than with HDL. However, the rate of radioactive bile acid formation from [3H]cholesteryl oleate-labelled HDL was still more rapid than for LDL. It is concluded that the selective uptake pathway for cholesteryl esters from HDL in parenchymal cells is more efficiently coupled to the formation of bile acids than is the cholesteryl ester uptake from LDL. This efficient coupling may facilitate the role of HDL in reverse cholesterol transport.

scholarly journals Increased selective uptake in vivo and in vitro of oxidized cholesteryl esters from high-density lipoprotein by rat liver parenchymal cells

1996 ◽  
Vol 319 (2) ◽  
pp. 471-476 ◽  
Author(s):  
Kees FLUITER ◽  
Helene VIETSCH ◽  
Eric A. L. BIESSEN ◽  
Gert M. KOSTNER ◽  
Theo J. C. van BERKEL ◽  
...  
Keyword(s):  
High Density Lipoprotein ◽  
Cholesteryl Ester ◽  
Density Lipoprotein ◽  
High Density ◽  
Biliary Secretion ◽  
Liver Uptake ◽  
Selective Uptake ◽  
Parenchymal Cells

Oxidation of low-density lipoprotein (LDL) leads initially to the formation of LDL-associated cholesteryl ester hydroperoxides (CEOOH). LDL-associated CEOOH can be transferred to high-density lipoprotein (HDL), and HDL-associated CEOOH are rapidly reduced to the corresponding hydroxides (CEOH) by an intrinsic peroxidase-like activity. We have now performed in vivo experiments to quantify the clearance rates and to identify the uptake sites of HDL-associated [3H]Ch18:2-OH in rats. Upon injection into rats, HDL-associated [3H]Ch18:2-OH is removed more rapidly from the circulation than HDL-associated [3H]Ch18:2. Two minutes after administration of [3H]Ch18:2-OH-HDL, 19.6±2.6% (S.E.M.; n = 4) of the label was taken up by the liver as compared with 2.4±0.25% (S.E.M.; n = 4) for [3H]Ch18:2-HDL. Organ distribution studies indicated that only the liver and adrenals exhibited preferential uptake of [3H]Ch18:2-OH as compared with [3H]Ch18:2, with the liver as the major site of uptake. A cell-separation procedure, employed 10 min after injection of [3H]Ch18:2-OH-HDL or [3H]Ch18:2-HDL, demonstrated that within the liver only parenchymal cells take up HDL-CE by the selective uptake pathway. Selective uptake by parenchymal cells of [3H]Ch18:2-OH was 3-fold higher than that of [3H]Ch18:2, while Kupffer and endothelial cell uptake of the lipid tracers reflected HDL holoparticle uptake (as analysed with iodinated versus cholesteryl ester-labelled HDL). The efficient uptake of [3H]Ch18:2-OH by parenchymal cells was coupled to a 3-fold increase in rate of radioactive bile acid secretion from [3H]Ch18:2-OH-HDL as compared with [3H]Ch18:2-HDL. In vitro studies with freshly isolated parenchymal cells showed that the association of [3H]Ch18:2-OH-HDL at 37 °C exceeded [3H]Ch18:2-HDL uptake almost 4-fold. Our results indicate that HDL-associated CEOH are efficiently and selectively removed from the blood circulation by the liver in vivo. The selective liver uptake is specifically exerted by parenchymal cells and coupled to a rapid biliary secretion pathway. The liver uptake and biliary secretion route may allow HDL to function as an efficient protection system against potentially atherogenic CEOOH.

Cholesteryl ester transfer protein (CETP) increases postprandial triglyceridaemia and delays triacylglycerol plasma clearance in transgenic mice

2009 ◽  
Vol 419 (3) ◽  
pp. 629-634 ◽  
Author(s):  
Alessandro G. Salerno ◽  
Patrícia R. Patrício ◽  
Jairo A. Berti ◽  
Helena C. F. Oliveira
Keyword(s):  
Cholesteryl Ester ◽  
Cholesteryl Ester Transfer Protein ◽  
Plasma Clearance ◽  
Low Density Lipoprotein ◽  
Lipoprotein Metabolism ◽  
Density Lipoprotein ◽  
Kinetic Studies ◽  
Cholesteryl Oleate ◽  
Liver Uptake ◽  
Transfer Protein

The CETP (cholesteryl ester transfer protein) is a plasma protein synthesized in several tissues, mainly in the liver; CETP reduces plasma HDL (high-density lipoprotein) cholesterol and increases the risk of atherosclerosis. The effect of CETP levels on postprandial intravascular metabolism of TAGs (triacylglycerols) is an often-overlooked aspect of the relationship between CETP and lipoprotein metabolism. Here, we tested the hypothesis that CETP delays the plasma clearance of TAG-rich lipoprotein by comparing human CETP expressing Tg (transgenic) and non-Tg mice. After an oral fat load, the postprandial triglyceridaemia curve was markedly increased in CETP-Tg compared with non-Tg mice (280±30 versus 190±20 mg/dl per 6 h respectively, P<0.02). No differences in intestinal fat absorption and VLDL (very-low-density lipoprotein) secretion rates were observed. Kinetic studies of double-labelled chylomicron-like EMs (emulsions) showed that both [3H]triolein and [14C]cholesteryl oleate FCRs (fractional clearance rates) were significantly reduced (∼20%) in CETP-Tg mice. Furthermore, TAG from lipid EM pre-incubated with CETP-Tg plasma had plasma clearance and liver uptake significantly lower than the non-Tg plasma-treated lipid EM. In addition, reductions in post-heparin plasma LPL (lipoprotein lipase) activity (50%) and adipose tissue mRNA abundance (39%) were verified in CETP-Tg mice. Therefore we conclude that CETP expression in Tg mice delays plasma clearance and liver uptake of TAG-rich lipoproteins by two mechanisms: (i) transferring TAG to HDLs and increasing CE content of the remnant particles and (ii) by diminishing LPL expression. These findings show that the level of CETP expression can influence the responsiveness to dietary fat and may lead to fat intolerance.

scholarly journals Scavenger receptor B1 (SR-B1) substrates inhibit the selective uptake of high-density-lipoprotein cholesteryl esters by rat parenchymal liver cells

1997 ◽  
Vol 326 (2) ◽  
pp. 515-519 ◽  
Author(s):  
Kees FLUITER ◽  
Theo J. C. van BERKEL
Keyword(s):  
High Density Lipoprotein ◽  
Rat Liver ◽  
Oxidized Ldl ◽  
Scavenger Receptor ◽  
Density Lipoprotein ◽  
High Density ◽  
Cholesteryl Esters ◽  
Selective Uptake ◽  
Liver Parenchymal ◽  
Parenchymal Cells

High-density lipoprotein cholesteryl esters (HDL-CE) are selectively taken up by liver parenchymal cells without parallel apolipoprotein uptake, and this selective uptake route forms an important step in reverse cholesterol transport. Recent data from Acton, Rigotti, Landschulz, Xu, Hobbs and Krieger [(1996) Science 271, 518–520] provide evidence that scavenger receptor B (SR-B1) can mediate selective uptake of HDL-CE. In order to identify if selective uptake of HDL-CE by rat liver parenchymal cells can be mediated by a protein with scavenger receptor properties we performed competition experiments in vivo with substrates for scavenger receptors. Addition of either low-density lipoprotein (LDL), acetylated LDL (AcLDL) or oxidized LDL (OxLDL) only marginally (< 10%) decreased the association of HDL particles to parenchymal cells as measured by 125I-labelled HDL. HDL-CE association was inhibited by AcLDL by 35%, while addition of OxLDL did inhibit HDL-CE association by 80%, thereby completely blocking the selective uptake of HDL-CE. Studies with HDL labelled with a fluorescent cholesteryl-ester analogue confirmed that OxLDL mediated complete inhibition of HDL-CE selective uptake by rat liver parenchymal cells. The inhibition of HDL-CE selective uptake by OxLDL was insensitive to the additional presence of polyinosinic acid (poly I), indicating that the inhibitory effect did not involve a poly I-sensitive site. Anionic phospholipid liposomes inhibited HDL-CE association by 40%, while neutral liposomes were ineffective. The inhibition of the selective uptake of HDL-CE in liver parenchymal cells by modified LDL, in particular OxLDL and anionic phospholipids suggests that, in liver, the SR-B1 is responsible for the efficient uptake of HDL-CE.

scholarly journals Morphological characterization of the cholesteryl ester cycle in cultured mouse macrophage foam cells.

1983 ◽  
Vol 97 (4) ◽  
pp. 1156-1168 ◽  
Author(s):  
D J McGookey ◽  
R G Anderson
Keyword(s):  
Cholesteryl Ester ◽  
Lipase Activity ◽  
Lipid Droplets ◽  
Free Cholesterol ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
The Body ◽  
Cyclic Process ◽  
Low Density ◽  
Cholesteryl Esters

Mouse peritoneal macrophages can be induced to accumulate cholesteryl esters by incubating them in the presence of acetylated low density lipoprotein. The cholesteryl esters are sequestered in neutral lipid droplets that remain in the cell even when the acetylated low density lipoprotein is removed from the culture media. Previous biochemical studies have determined that the cholesterol component of cholesteryl ester droplets constantly turns over with a half time of 24 h by a cyclic process of de-esterification and re-esterification. We have used morphologic techniques to determine the spatial relationship of cholesteryl ester, free cholesterol, and lipase activity during normal turnover and when turnover is disrupted. Lipid droplets were surrounded by numerous 7.5-10.0-nm filaments; moreover, at focal sites on the margin of each droplet there were whorles of concentrically arranged membrane that penetrated the matrix. Histochemically detectable lipase activity was associated with these stacks of membrane. Using filipin as a light and electron microscopic probe for free cholesterol, we determined that a pool of free cholesterol was associated with each lipid droplet. Following incubation in the presence of the exogenous cholesterol acceptor, high density lipoprotein, the cholesteryl ester droplets disappeared and were replaced with lipid droplets of a different lipid composition. Inhibition of cholesterol esterification caused cholesteryl ester droplets to disappear and free cholesterol to accumulate in numerous myelin-like structures in the body of the cell.

Sign in / Sign up

Export Citation Format

Share Document