Abnormal regulation of LDL receptor activity and abnormal cellular metabolism of hypertriglyceridaemic low density lipoprotein: normalization with bezafibrate therapy

1987 ◽  
Vol 17 (6) ◽  
pp. 538-543 ◽  
Author(s):  
Y. KLEINMAN ◽  
Y. OSCHRY ◽  
S. EISENBERG
Keyword(s):  
Low Density Lipoprotein ◽  
Ldl Receptor ◽  
Density Lipoprotein ◽  
Cellular Metabolism ◽  
Receptor Activity ◽  
Low Density

scholarly journals A study of the chylomicron metabolism in WHHL rabbits after fat loading. Discrepancy between results based on measurement of apoprotein B-48 or retinyl palmitate

1992 ◽  
Vol 285 (2) ◽  
pp. 641-646 ◽  
Author(s):  
P N M Demacker ◽  
P J van Heijst ◽  
A F H Stalenhoef
Keyword(s):  
New Zealand ◽  
Strong Correlation ◽  
Low Density Lipoprotein ◽  
Ldl Receptor ◽  
Density Lipoprotein ◽  
Retinyl Palmitate ◽  
Receptor Activity ◽  
Low Density ◽  
Apoprotein B ◽  
Chylomicron Metabolism

We studied the metabolism of chylomicrons in homozygous Watanabe heritable hyperlipidaemic (WHHL) rabbits and in cholesterol-fed or normally fed New Zealand White (NZW) rabbits by measuring the concentrations of apoprotein B-48 and of retinyl palmitate in their serum after feeding fat plus this vitamin according to two different protocols. Compared with NZW controls, retinyl palmitate accumulated in both hyperlipidaemic groups under study, not only in the d less than 1.019 fraction but also in the low-density lipoprotein (LDL) fraction. A strong correlation was found between the retinyl palmitate concentration in either the d less than 1.019 fraction or the LDL fraction of the WHHL rabbits and the concentrations of cholesterol and triacylglycerols in these fractions. This suggests that retinyl palmitate is exchanged rapidly between exogenous and endogenous lipoproteins. This is supported by the lack of a correlation between the retinyl palmitate concentrations and the intensity of the apoprotein B-48 band in the respective d less than 1.019 fractions or LDL fractions; in most fractions, in which large amounts of retinyl palmitate were present, the intensity of the apoprotein B-48 band was not increased compared with the fasting concentrations. Assuming that retinyl palmitate is a marker for the transfer of exogenous lipids, the results of our experiments indicate that the removal of exogenous lipids is delayed by complexing to endogenously synthesized lipoproteins. However, the clearance of apoprotein B-48 is normal and thus independent of the LDL-receptor activity.

scholarly journals Addition of a mannose-6-phosphate-containing oligosaccharide alters cellular processing of low density lipoprotein by parental and LDL-receptor-defective Chinese hamster ovary cells

1984 ◽  
Vol 68 (1) ◽  
pp. 183-194
Author(s):  
A.M. Leichtner ◽  
M. Krieger
Keyword(s):  
Chinese Hamster Ovary ◽  
Cho Cells ◽  
Low Density Lipoprotein ◽  
Chinese Hamster ◽  
Ldl Receptor ◽  
Density Lipoprotein ◽  
Receptor Activity ◽  
Low Density ◽  
Cellular Processing ◽  
Mannose 6 Phosphate

Low density lipoprotein (LDL) was chemically modified by the addition of omega-(6-phospho)-tetra(alpha 1–3)mannosyl-(alpha 1–2)mannose (M56P), a phosphorylated oligosaccharide containing a terminal mannose 6-phosphate residue. Uptake and degradation of this modified LDL (M56P-LDL) by Chinese hamster ovary (CHO) cells occurred via the lysosomal enzyme (mannose 6-phosphate) receptor pathway. Cellular processing of M56P-LDL was saturable, specific for the mannose 6-phosphate marker, and occurred with approximately threefold higher affinity than that of native LDL by the LDL receptor pathway. Mannose 6-phosphate receptor activity, as measured by degradation of M56P-LDL, was ninefold lower than the LDL receptor activity. Degradation of M56P-LDL was more sensitive to inhibition by the lysosomotropic agent chloroquine than was degradation of LDL, suggesting differences in the intracellular processing of mannose 6-phosphate-bearing ligands and LDL. Previously isolated CHO cell lines defective in LDL receptor activity resembled parental CHO cells in their ability to process M56P-LDL. The potential use of M56P-LDL in the isolation of cells with pleiotropic mutations affecting receptor-mediated endocytosis is discussed.

Heritability of the Low Density Lipoprotein Receptor Activity of Human Blood Mononuclear Cells: Studies in Normolipidaemic Adult Male Twins

1982 ◽  
Vol 62 (4) ◽  
pp. 397-401 ◽  
Author(s):  
M. Weight ◽  
C. Cortese ◽  
U. Sule N. E. Miller ◽  
B. Lewis
Keyword(s):  
Adult Male ◽  
Mononuclear Cells ◽  
Low Density Lipoprotein ◽  
Ldl Receptor ◽  
Monozygotic Twins ◽  
Density Lipoprotein ◽  
Correlation Coefficients ◽  
Receptor Activity ◽  
Low Density ◽  
Blood Mononuclear Cells

1. The concordance of low density lipoprotein (LDL) receptor activity of blood mononuclear cells was examined in 26 pairs of monozygotic and 17 pairs of dizygotic normolipidaemic young adult male twins. 2. Receptor activity was quantified as the degradation of 125I-labelled LDL during a 6 h incubation, after derepression of the cells for 72 h in lipoprotein-deficient medium. 3. The total variance of receptor activity was similar in the two groups of twins. In contrast, within-pair variance was five times greater in dizygotic twins than in monozygotic twins (P < 0.001). 4. Estimates of heritability, mostly based on the intra-class correlation coefficients (monozygotic, r = 0.83; dizygotic, r = 0.39), ranged from 0.72 to 1.05. 5. These results suggest that the maximal LDL receptor activity of peripheral cells in normolipidaemic subjects is largely genetically determined.

Lack of Correlation between the Maximum Low-Density Lipoprotein (Ldl) Receptor Activity of Blood Lymphocytes and Plasma LDL Concentration in Normal Men

1983 ◽  
Vol 65 (1) ◽  
pp. 95-98 ◽  
Author(s):  
C. Cortese ◽  
P. R. Turner ◽  
C. B. Marenah ◽  
U. Sule ◽  
S. Price ◽  
...  
Keyword(s):  
Ldl Cholesterol ◽  
Low Density Lipoprotein ◽  
Ldl Receptor ◽  
Density Lipoprotein ◽  
Receptor Activity ◽  
Cholesterol Concentration ◽  
Low Density ◽  
Blood Lymphocytes ◽  
Wide Range

1. Measurements were made of the maximal low-density lipoprotein (LDL) receptor activities of blood lymphocytes from 81 healthy men with a wide range of plasma LDL cholesterol concentrations (1.45-7.55 mmol/l). 2. Receptor activity was quantified by measuring the degradation of 125I-labelled LDL (10 μg of protein/ml) to trichloroacetic acid-soluble material during a 6 h incubation, after derepression of the lymphocytes for 72 h in lipoprotein-deficient medium. 3. No significant correlation existed between LDL receptor activity in vitro and plasma LDL cholesterol concentration in vivo (r = −0.08).

scholarly journals Cholesterol esterification plays a major role in determining low-density-lipoprotein receptor activity in primary monolayer cultures of rat hepatocytes

1989 ◽  
Vol 263 (1) ◽  
pp. 255-260 ◽  
Author(s):  
A M Salter ◽  
N Ekins ◽  
M al-Seeni ◽  
D N Brindley ◽  
B Middleton
Keyword(s):  
Specific Binding ◽  
Low Density Lipoprotein ◽  
Ldl Receptor ◽  
Density Lipoprotein ◽  
Rat Hepatocytes ◽  
Receptor Activity ◽  
Cholesterol Esterification ◽  
Low Density ◽  
Density Lipoprotein Receptor ◽  
Ldl Binding

1. We have previously shown that the capacity for specific binding of human 125I-labelled low-density lipoprotein (LDL) to rat hepatocytes increases with time in culture [Salter, Bugaut, Saxton, Fisher & Brindley (1987) Biochem. J. 247, 79-84]. 2. In the present study we show that this up-regulation is accompanied by a rise in the cholesterol ester content of the cells. 3. Inhibition of cholesterol esterification with the drug 58-035 (Sandoz) significantly decreases the time-dependent ‘up-regulation’ of LDL receptors. 4. Incubation of hepatocytes with LDL itself has little effect on subsequent LDL binding. However, when cholesterol esterification is inhibited, incubation with LDL decreases binding below that attained with the drug alone. 5. Inhibition of cholesterol synthesis with Lovastatin significantly increases LDL binding and antagonizes the effect of 58-035. 6. We conclude that in hepatocytes the rate of cellular cholesterol esterification can become the major determinant of LDL-receptor activity.

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