Modulation of adipose tissue lipolysis and body weight by high-density lipoproteins in mice

The interaction between high density lipoproteins (HDL) and adipose tissue is an important pathway for cholesterol and cholesteryl ester flux. In intact fat cells, a disproportionately greater net uptake of cholesteryl ester occurs subsequent to lipoprotein binding than would have been predicted from a consideration of holoparticle uptake alone. To characterize the early events in this process, cholesteryl hexadecyl ether, a nonmetabolizable, accumulative marker of cholesteryl ester, was incorporated into canine HDL2, and its uptake by omental adipocyte plasma membranes was measured in relation to the binding of HDL2, which in this animal species is enriched in apolipoprotein A-I and free of apolipoprotein E. The dose–response profile for HDL2 binding was consistent with a single lipoprotein binding site at all concentrations of HDL2, whereas uptake of cholesteryl ester from HDL2 was biphasic, suggesting a high affinity site at low HDL2 concentrations and a low affinity site at high lipoprotein concentrations. Pronase treatment stimulated binding twofold and this was accompanied by a parallel twofold stimulation of cholesteryl ester uptake. EDTA, on the other hand, reduced binding and uptake of cholesteryl ester by 20%, indicating partial dependence upon divalent cations. The proportion of HDL2 cholesteryl ester accumulated by plasma membranes relative to HDL2 protein bound was not altered by either pronase or EDTA, despite the fact that these agents had opposite effects upon binding. In dissociation studies, a portion of membrane-associated HDL2 did not equilibrate with exogenous HDL2 and a greater proportion of the cholesteryl ester failed to dissociate. A stepwise mechanism for cholesteryl ester uptake, involving (i) saturable, high affinity HDL2 binding to cell surface sites, (ii) vectoral, HDL2 concentration-dependent delivery of cholesteryl ester to the membrane, and (iii) cholesteryl ester sequestration into a nonexchangeable membrane compartment, appears to be independent of metabolic energy or cell processing.Key words: cholesteryl ester transport, high density lipoprotein receptor, cholesterol storage.

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Characterization of high-density lipoprotein binding to rat adipocytes and adipocyte plasma membranes

Biochemistry and Cell Biology ◽

10.1139/o88-113 ◽

1988 ◽

Vol 66 (9) ◽

pp. 986-997 ◽

Cited By ~ 4

Author(s):

Eva Zsigmond ◽

Bessie Fong ◽

Aubie Angel

Keyword(s):

Adipose Tissue ◽

Plasma Membranes ◽

Density Lipoprotein ◽

Membrane System ◽

Rat Plasma ◽

High Density ◽

High Density Lipoproteins ◽

Binding Characteristics ◽

Isolated Adipocytes ◽

Adipocyte Plasma Membranes

The interaction of high-density lipoproteins (HDL) with adipocytes is important in the regulation of cellular cholesterol flux. To study the mechanisms of HDL binding and cellular processing, we incubated adipocytes isolated from epididymal and perirenal adipose tissue of male Wistar rats (300 g) with HDL1 (1.07–1.10 g/mL) and HDL2 (1.10–1.14 g/mL) fractions separated from rat plasma by gradient ultracentrifugation. Freshly isolated adipocytes were incubated with 125I-labeled HDL for 2 h at 37 °C to determine cell-associated uptake and degradation. Adipocytes from both fat regions showed significant cell-associated HDL1 and HDL2 uptake and very high medium degradation (2- to 6-fold higher than uptake). To assess 125I-labeled HDL binding independent of cellular metabolism, we purified adipocyte plasma membranes from isolated adipocytes and used them in binding assays. Binding of HDL1 and HDL2 in the membrane system was 85–95% specific, sensitive to high NaCl concentrations, and abolished by pronase treatment. In contrast to HDL2 binding, the maximum HDL1 binding to perirenal plasma membranes was significantly higher than its binding to epididymal membranes (7.2 ± 1.3 vs. 4.4 ± 0.2 μg/mg, n = 6, p < 0.05). This increment in HDL1 binding to perirenal membranes represented an EDTA- sensitive, calcium-dependent component. These results indicate that HDL binding to adipocyte plasma membranes depends on both adipose tissue region and HDL subtype. The membrane binding characteristics, taken together with the cellular uptake results, suggest that adipocytes bind and metabolize HDL and that this interaction may involve a protein receptor.

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Metabolism of apolipoprotein A-I of chylomicrons in rats and humans

Canadian Journal of Biochemistry ◽

10.1139/o81-085 ◽

1981 ◽

Vol 59 (8) ◽

pp. 613-618 ◽

Cited By ~ 21

Author(s):

Jean-Louis Vigne ◽

Richard J. Havel

Keyword(s):

Body Weight ◽

Elevated Level ◽

High Density ◽

High Density Lipoproteins ◽

Rat Serum ◽

Apolipoprotein A ◽

Apo E ◽

High Concentrations ◽

Chylomicron Remnants ◽

Intact Rats

After intravenous injection of a large amount of small chylomicrons into intact rats, the concentration of apolipoprotein (apo) A-I was increased by about 40% and remained at this elevated level as most of the chylomicron triglycerides were removed from plasma during the ensuing hour. This apo A-I rapidly left the chylomicrons and was transferred to lipoproteins of higher density. Such transfer of apo A-I did not occur when chylomicrons were incubated at comparably high concentrations with rat serum. In normolipidemic humans, the concentration of apo A-I and apo A-II, as well as phospholipids, increased in the light subfraction of high density lipoproteins (HDL2) 4 to 7 h after ingestion of a meal containing 1.5 g cream fat per kilogram body weight. The concentration of these components increased in the heavy subfraction of high density lipoproteins (HDL3) after 12 to 24 h. The concentration of apo E in plasma was unaffected by fat ingestion, but the concentration of this protein increased in lipoproteins of density less than 1.006 g∙mL−1 and fell in lipoproteins of higher density. It is concluded that apo A-I in rat chylomicrons is transferred quantitatively to HDL as chylomicron remnants are formed. Chylomicron apo A-I and apo A-II appear to be transferred similarly to HDL in humans, whereas apo E is transferred from HDL to chylomicrons after chylomicrons enter the blood.

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Zur Körperzusammensetzung von neugeborenen Ferkeln der Deutschen Landrasse und des Deutschen Sattelschweines (Kurzmitteilung)

Archives Animal Breeding ◽

10.5194/aab-44-47-2001 ◽

2001 ◽

Vol 44 (1) ◽

pp. 47-52

Author(s):

G. Kuhn ◽

H. Falkenberg ◽

M. Langhammer ◽

M. Härtung ◽

J. Wegner ◽

...

Keyword(s):

Body Composition ◽

Body Weight ◽

Lipid Metabolism ◽

Blood Plasma ◽

Short Communication ◽

Hdl Cholesterol ◽

High Density ◽

The Body ◽

High Density Lipoproteins

Abstract. Title of the paper: Body composition in newbom piglets of the breeds German Landrace and German Saddleback (short communication) Newbom piglets from 15 litters of German Landrace sows (DL) and 19 litters of German Saddleback sows (DS) were used to determine the body weight, body composition, and characteristics of lipid metabolism in the blood. At the date of birth no differences in body weight and body composition of the piglets were found between the two breeds. The piglets of the DS-sows showed in comparison to the piglets of the DL-sows a significant higher content in high density lipoproteins (HDL)-cholesterol in the blood plasma.

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