scholarly journals Chylomicron-remnant uptake by freshly isolated hepatocytes. Effect of heparin and of hepatic triacylglycerol lipase

1989 ◽  
Vol 258 (2) ◽  
pp. 587-594 ◽  
Author(s):  
F Sultan ◽  
D Lagrange ◽  
X Le Liepvre ◽  
S Griglio
Keyword(s):  
Cholesteryl Ester ◽  
Hepatic Lipase ◽  
Isolated Hepatocytes ◽  
Chylomicron Remnant ◽  
Triacylglycerol Lipase ◽  
Cell Pellet ◽  
Chylomicron Remnants ◽  
Dose Response Study ◽  
Cholesteryl Ester Accumulation

Chylomicron remnants labelled biologically with [3H]cholesterol were efficiently taken up by freshly isolated hepatocytes during a 3 h incubation in Krebs bicarbonate medium. Their [3H]cholesteryl ester was hydrolysed (74% net hydrolysis), and 0.1 mM-chloroquine could partially inhibit this hydrolysis, provided that hepatocytes were first preincubated for 2 h 30 min at 37 degrees C. This hydrolysis was also measured in preincubated cells with remnants double-labelled (3H and 14C) on their free cholesterol moiety; [3H]cholesterol arising from [3H]cholesteryl ester hydrolysis was recovered in the free [3H]cholesterol pool. A dose-response study showed saturation of remnant uptake at 180 micrograms of remnant protein/10(7) cells. Heparin (10 units/ml) increased remnant uptake by 63% (P less than 0.01), [3H]cholesteryl ester accumulation in the cell pellet by 110% (P less than 0.025) and hepatic lipase activity secreted in the medium by 2.4-fold (P less than 0.01) and by 3.3-fold (P less than 0.01) at the end of the preincubation and incubation periods respectively. Addition of 100 munits of semi-purified hepatic lipase preparation/flask stimulated remnant uptake by 44-69%, and [3H]cholesteryl ester accumulation in the presence of chloroquine by 2.1-fold (P less than 0.025). When hepatic lipase was incubated solely with the remnants, it decreased their triacylglycerol and phospholipid contents by 24% and 26% respectively. Thus freshly isolated hepatocytes may be used to study chylomicron-remnant uptake. Hepatic lipase, which seems to underly the stimulating effect of heparin, facilitates remnant uptake in vitro, and this could be mediated by at least one (or both) of its hydrolytic properties.

Comparison of the lipolysis of chylomicron remnants derived from corn oil or olive oil by hepatic lipase in vitro

1995 ◽  
Vol 23 (2) ◽  
pp. 284S-284S ◽  
Author(s):  
KATHLEEN M. BOTHAM ◽  
PETER A. MAYES ◽  
MICHAEL AVELLA ◽  
ALFREDO CANTAFORA ◽  
ELENA BRAVO
Keyword(s):  
Olive Oil ◽  
Corn Oil ◽  
Hepatic Lipase ◽  
Chylomicron Remnants

Lipid synthesis in macrophages derived from the human cell line THP-1: modulation of the effects of native and oxidized chylomicron-remnant-like particles by oestrogen

2001 ◽  
Vol 101 (4) ◽  
pp. 403-413 ◽  
Author(s):  
Mariarosaria NAPOLITANO ◽  
Kelly V. BATT ◽  
Michael AVELLA ◽  
Elena BRAVO ◽  
Kathleen M. BOTHAM
Keyword(s):  
Cholesteryl Ester ◽  
Cell Line ◽  
Lipid Synthesis ◽  
Thiobarbituric Acid ◽  
Human Monocyte ◽  
Cholesterol Esterification ◽  
Chylomicron Remnant ◽  
Triacylglycerol Synthesis ◽  
Ester Formation ◽  
Chylomicron Remnants

The effects of native and oxidized chylomicron remnants on the synthesis of cholesteryl ester and triacylglycerol in macrophages, and the way that this is influenced by exposure of the cells to oestrogen, was investigated using the human monocyte cell line THP-1 and chylomicron-remnant-like particles containing human apolipoprotein E (CRLPs). Synthesis of the lipids was measured by the incorporation of [3H]oleate into cholesteryl ester and triacylglycerol. CRLPs (5-40μg of cholesterol/ml) containing either trilinolein or triolein as the triacylglycerol component caused a dose-dependent decrease in cholesteryl ester formation, while triacylglycerol production was unchanged. After oxidation of the CRLPs, the level of thiobarbituric acid-reactive substances was increased by 6.3-fold and 2.2-fold in particles containing trilinolein and triolein respectively. Furthermore, CRLPs containing oxidized trilinolein lost their ability to down-regulate cholesterol esterification, while CRLPs containing oxidized triolein did not. Both types of oxidized CRLPs decreased triacylglycerol synthesis. Treatment of the macrophages with 17β-oestradiol caused increases of approx. 94% and 34% in the synthesis of cholesteryl ester and triacylglycerol respectively in the absence of CRLPs. The differences between control and oestrogen-treated cells were abolished, however, when CRLPs (40μg of cholesterol/ml) were added to the incubations. In addition, in contrast with their lack of effect in control cells, CRLPs containing oxidized trilinolein decreased cholesterol esterification in oestrogen-treated cells by approx. 48%. These findings with CRLPs suggest that chylomicron remnants have significant effects on cholesteryl ester and triacylglycerol synthesis in macrophages, which may be modulated both by the oxidation state of the particles and by oestrogen.

scholarly journals Phospholipase A2 Mediates Apolipoprotein-Independent Uptake of Chylomicron Remnant-Like Particles by Human Macrophages

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Mariarosaria Napolitano ◽  
Howard S. Kruth ◽  
Elena Bravo
Keyword(s):  
Phospholipase A2 ◽  
Cholesteryl Ester ◽  
Apolipoprotein E ◽  
Lipoprotein Lipase ◽  
Human Monocyte ◽  
Cholesteryl Ester Hydrolase ◽  
Chylomicron Remnant ◽  
Ester Hydrolase ◽  
Chylomicron Remnants ◽  
Cytosolic Pla2

Apolipoprotein E-receptor-mediated pathways are the main routes by which macrophages take up chylomicron remnants, but uptake may also be mediated by receptor-independent routes. To investigate these mechanisms, triacylglycerol (TG) accumulation induced by apolipoprotein-free chylomicron remnant-like particles (CRLPw/o) in human monocyte-derived macrophages was evaluated. Macrophage TG content increased about 5-fold after incubation with CRLPw/o, and this effect was not reduced by the inhibition of phagocytosis, macropinocytosis, apolipoprotein E function, or proteoglycan bridging. The role of lipases, including lipoprotein lipase, cholesteryl ester hydrolase, and secretory (sPLA2) and cytosolic phospholipase A2, was studied using [3H]TG-labelled CRLPw/o. Total cell radioactivity after incubation with [3H]TG CRLPw/o was reduced by 15–30% by inhibitors of lipoprotein lipase and cholesteryl ester hydrolase and by about 45% by inhibitors of sPLA2 and cytosolic PLA2. These results suggest that macrophage lipolytic enzymes mediate the internalization of postprandial TG-rich lipoproteins and that sPLA2and cytosolic PLA2, play a more important role than extracellular lipoprotein lipase-mediated TG hydrolysis.

scholarly journals Binding, interiorization and degradation of cholesterol ester-labelled chylomicron-remnant particles by rat hepatocyte monolayers

1977 ◽  
Vol 168 (3) ◽  
pp. 483-494 ◽  
Author(s):  
Claes-Henrik Florén ◽  
Åke Nilsson
Keyword(s):  
Cell Surface ◽  
Cholesteryl Ester ◽  
Time Course ◽  
Inhibitory Effect ◽  
Metabolic Inhibitors ◽  
High Density Lipoproteins ◽  
Chylomicron Remnant ◽  
Very Low Density Lipoproteins ◽  
Chylomicron Remnants ◽  
Hydrolysis Of

1. The cholesteryl ester of isolated chylomicron-remnant particles was efficiently degraded by hepatocyte monolayers. The degradation was sensitive to metabolic inhibitors. 2. With increasing amounts of remnant cholesteryl ester the rate of uptake approached saturation and conformed to a linear double-reciprocal plot. The Vmax. was determined as 80ng of cholesteryl ester/h per mg of protein and the apparent Km as 1.4μg of cholesteryl ester per mg of protein. The time course for the uptake and hydrolysis suggested that binding of particles to the cell surface preceded the degradation. 3. Cholesteryl esters of native chylomicrons were degraded to a much smaller extent and their presence had only a small inhibitory effect on the degradation of chylomicron remnants. Intestinal very-low-density lipoproteins were degraded somewhat faster than chylomicrons, and caused more inhibition of remnant degradation. Rat high-density lipoproteins inhibited the hydrolysis of remnant cholesteryl ester by up to 50%, but had less influence on the amount of cholesteryl ester that was bound to the cells. Serum decreased both the uptake and hydrolysis, whereas d=1.21 infranatant had no effect. 4. The cholesteryl ester hydrolysis after the uptake by the cells was inhibited by chloroquine and by colchicine. Only 28–36% of the unhydrolysed cholesteryl ester could be released from these cells by trypsin treatment, indicating that the major portion was truly intracellular. The particles that could be released from the cell surface by trypsin and those remaining in the medium had the same triacylglycerol/cholesteryl ester ratio as the added remnant particles. Significant amounts of denser particles were thus not formed during contact with the cell surface. 5. The presence of heparin, as well as preincubation of the cells with heparin, increased the uptake of chylomicron remnants. This effect was most marked in the presence of serum. A much smaller proportion of the other serum lipoproteins was taken up, and this proportion was not increased by heparin.

scholarly journals Chylomicron-remnant clearance in homozygote and heterozygote Watanabe-heritable-hyperlipidaemic rabbits is defective. Lack of evidence for an independent chylomicron-remnant receptor

1991 ◽  
Vol 276 (2) ◽  
pp. 381-386 ◽  
Author(s):  
A Bowler ◽  
T G Redgrave ◽  
J C L Mamo
Keyword(s):  
Cholesteryl Ester ◽  
Plasma Cholesterol ◽  
Low Density Lipoproteins ◽  
Low Density ◽  
Lipid Emulsions ◽  
Chylomicron Remnant ◽  
Unesterified Cholesterol ◽  
Apolipoprotein B100 ◽  
Plasma Triacylglycerol ◽  
Chylomicron Remnants

Lymph chylomicrons radiolabelled in triacylglycerol and cholesteryl ester were injected into control and Watanabe heritable-hyperlipidaemic (WHHL) rabbits. Clearance of chylomicrons was slower in heterozygote and homozygote WHHL rabbits. Slower remnant clearance in WHHL rabbits was confirmed by monitoring the clearance from plasma of preformed chylomicron remnants. Use of chylomicron-like lipid emulsions injected into control and WHHL rabbits also confirmed the defect in remnant clearance in heterozygote WHHL and homozygote WHHL groups. Clearance from plasma of emulsion triolein was delayed in both WHHL groups compared with controls, owing to slower remnant clearance. The clearance from plasma of radioiodinated rabbit low-density lipoproteins (LDL) in heterozygote WHHL rabbits was the same as control rabbits. Defective chylomicron-remnant removal but normal LDL clearance in the heterozygote WHHL corresponded to elevated concentrations of plasma triacylglycerol and normal concentrations of plasma cholesterol. Receptor versus non-receptor clearances of chylomicron remnants were studied by comparing the clearance of emulsions with and without unesterified cholesterol respectively. Unlike control rabbits, there were no significant differences in the clearances of the two emulsion types in either the homozygote or heterozygote WHHL rabbits, indicating that the apolipoprotein-B100/E receptor is the primary route for clearance of chylomicron remnants from plasma.

Glucagon and insulin regulate lipolysis in trout liver by altering phosphorylation of triacylglycerol lipase

1993 ◽  
Vol 265 (1) ◽  
pp. R255-R260 ◽  
Author(s):  
J. S. Harmon ◽  
L. M. Rieniets ◽  
M. A. Sheridan
Keyword(s):  
Hormonal Regulation ◽  
Hepatic Lipase ◽  
Isolated Hepatocytes ◽  
Triacylglycerol Lipase ◽  
Complete Inactivation ◽  
Lipase Enzyme ◽  
Hormonal Modulation ◽  
Monopotassium Phosphate ◽  
Glucagon And Insulin ◽  
Hepatic Triacylglycerol

Rainbow trout were used to investigate the hormonal regulation by glucagon and insulin of hepatic triacylglycerol (TG) lipase activation. Two purified preparations of the trout hepatic TG lipase enzyme, the 110,000-g preparation and the resuspended ammonium sulfate fraction (ASF), were activated up to 58% with (in mM) 0.5 ATP, 0.01 cAMP, 5 MgCl2, and exogenous protein kinase over control levels. ATP or cAMP alone had no effect on activation. Activation of the trout hepatic lipase was reversible; complete inactivation of the ASF was obtained within 3 h in the presence of exogenous phosphorylase phosphatase. Adenosine 3',5'-cyclic monophosphate (cAMP)/ATP-dependent 32P-phosphorylation of trout hepatic lipase was observed within 5 min of incubation with the cAMP/ATP-Mg2+ activation system and 25 microCi [32P]ATP. Hormonal modulation of trout hepatic lipase phosphorylation was studied in isolated hepatocytes. Hepatocytes were incubated with [32P]-monopotassium phosphate for 3 h, then exposed to mammalian glucagon (GLU). Within 5 min, increased lipolysis was accompanied by a 95% increase in phosphorylation of the enzyme. Mammalian insulin (INS) depressed GLU-stimulated phosphorylation by 56% and inhibited GLU-stimulated lipolysis. These results indicate that GLU and INS modulate lipolysis in trout liver by altering phosphorylation of the TG lipase enzyme.

scholarly journals Cell density can affect cholesteryl ester accumulation in the human THP-1 macrophage.

1994 ◽  
Vol 35 (11) ◽  
pp. 1909-1917
Author(s):  
A Rodriguez ◽  
S D Kafonek ◽  
A Georgopoulos ◽  
P S Bachorik
Keyword(s):  
Cholesteryl Ester ◽  
Cell Density ◽  
Cholesteryl Ester Accumulation
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