scholarly journals Catalytically inactive lipoprotein lipase expression in muscle of transgenic mice increases very low density lipoprotein uptake: Direct evidence that lipoprotein lipase bridging occurs in vivo

1998 ◽  
Vol 95 (23) ◽  
pp. 13841-13846 ◽  
Author(s):  
M. Merkel ◽  
Y. Kako ◽  
H. Radner ◽  
I. S. Cho ◽  
R. Ramasamy ◽  
...  
Keyword(s):  
Transgenic Mice ◽  
Lipoprotein Lipase ◽  
Direct Evidence ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Very Low Density Lipoprotein ◽  
Low Density ◽  
Lipoprotein Uptake ◽  
Lipase Expression

scholarly journals Nascent very-low-density lipoprotein triacylglycerol hydrolysis by lipoprotein lipase is inhibited by apolipoprotein E in a dose-dependent manner

1997 ◽  
Vol 328 (3) ◽  
pp. 745-750 ◽  
Author(s):  
C. Miek JONG ◽  
E. H. Vivian DAHLMANS ◽  
H. Marten HOFKER ◽  
M. Louis HAVEKES
Keyword(s):  
Lipoprotein Lipase ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Very Low Density Lipoprotein ◽  
Low Density ◽  
Dependent Manner ◽  
Control Value ◽  
Dose Dependent ◽  
Deficient Mice

In the present study it was investigated whether apolipoprotein (apoE) can inhibit the lipoprotein lipase (LPL)-mediated hydrolysis of very-low-density-lipoprotein (VLDL) triacylglycerols (TAGs). Previous studies have suggested such an inhibitory role for apoE by using as a substrate for LPL either plasma VLDL or artificial TAG emulsions. To mimic the in vivo situation more fully, we decided to investigate the effect of apoE on the LPL-mediated TAG hydrolysis by using VLDL from apoE-deficient mice that had been enriched with increasing amounts of apoE. Furthermore, since plasma VLDL isolated from apoE-deficient mice was relatively poor in TAGs and strongly enriched in cholesterol as compared with VLDL from wild-type mice, we used nascent VLDL obtained by liver perfusions. Nascent VLDL (d < 1.006) isolated from the perfusate of the apoE-deficient mouse liver was rich in TAGs. Addition of increasing amounts of apoE to apoE-deficient nascent VLDL effectively decreased TAG lipolysis as compared with that of apoE-deficient nascent VLDL without the addition of apoE (63.1±6.3 and 20.8±1.8% of the control value at 2.7 μg and 29.6 μg of apoE/mg of TAG added respectively). Since, in vivo, LPL is attached to heparan sulphate proteoglycans (HSPG) at the endothelial matrix, we also performed lipolysis assays with LPL bound to HSPG in order to preserve the interaction of the lipoprotein particle with the HSPG-LPL complex. In this lipolysis system a concentration-dependent decrease in the TAG lipolysis was also observed with increasing amounts of apoE on nascent VLDL, although to a lesser extent than with LPL in solution (72.3±3.6% and 56.6±1.7% of control value at 2.7μg and 29.6 μg of apoE/mg TAGs added respectively). In conclusion, the enrichment of the VLDL particle with apoE decreases its suitability as a substrate for LPL in a dose-dependent manner.

scholarly journals The preferential uptake of very-low-density lipoprotein cholesteryl ester by rat liver in vivo

1990 ◽  
Vol 272 (3) ◽  
pp. 735-741 ◽  
Author(s):  
J C Holder ◽  
V A Zammit ◽  
D S Robinson
Keyword(s):  
Fatty Acid ◽  
Cholesteryl Ester ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Very Low Density Lipoprotein ◽  
Low Density ◽  
Apoprotein B ◽  
Preferential Uptake ◽  
Triacylglycerol Fraction

The removal from the blood and the uptake by the liver of injected very-low-density lipoprotein (VLDL) preparations that had been radiolabelled in their apoprotein and cholesteryl ester moieties was studied in lactating rats. Radiolabelled cholesteryl ester was removed from the blood and taken up by the liver more rapidly than sucrose-radiolabelled apoprotein. Near-maximum cholesteryl ester uptake by the liver occurred within 5 min of the injection of the VLDL. At this time, apoprotein B uptake by the liver was only about 25% of the maximum. Maximum uptake of the injected VLDL apoprotein B label was not achieved until at least 15 min after injection, by which time the total uptakes of cholesteryl ester and apoprotein B label were very similar. The results suggest that preferential uptake of the lipoprotein cholesteryl ester by the liver occurred before endocytosis of the entire lipoprotein complex. The fate of the injected VLDL cholesteryl ester after its uptake by the liver was also monitored. Radiolabel associated with the hepatic cholesteryl ester fraction fell steadily from its early maximum level, the rate of fall being faster and more extensive when the fatty acid, rather than the cholesterol, moiety of the ester was labelled. By 30 min after the injection of VLDL containing [3H]cholesteryl ester, over one-third of the injected label was already present as [3H]cholesterol in the liver. When VLDL containing cholesteryl [14C]oleate was injected, a substantial proportion (about 25%) of the injected radiolabelled fatty acid appeared in the hepatic triacylglycerol fraction within 60 min: very little was present in the plasma triacylglycerol fraction at this time.

scholarly journals Heterogeneity of very-low-density lipoprotein remnants bound and taken up by liver of starved rat in vivo

1983 ◽  
Vol 212 (1) ◽  
pp. 173-182
Author(s):  
M M Ittmann ◽  
C Cooper
Keyword(s):  
Cholesteryl Ester ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Water Soluble ◽  
Very Low Density Lipoprotein ◽  
Low Density ◽  
Density Range ◽  
Mean Diameter ◽  
Vldl Remnant

Very-low-density lipoprotein (VLDL), labelled in vivo with [9,10-3H]oleate, was taken up rapidly by liver after injection in vivo. Initially, radioactive lipoprotein remnants in the VLDL density range were present in liver as a bound extracellular pool that could be released by perfusion with polyphosphate or heparin. The bound remnant showed a decrease in mean diameter and an increased proportion of cholesteryl ester as a function of time after injection. When VLDL of different mean diameters was injected, it was found that: (1) total uptake by liver was independent of diameter; (2) small VLDL was not taken up more rapidly than large VLDL; and (3) Large VLDL lost no more triacylglycerol before binding than did small VLDL and larger species of mean diameter greater than 40 nm were bound. It is concluded that there is no unique VLDL remnant taken up by liver in vivo. When livers were perfused after binding radioactive VLDL in vivo, the lipoprotein was metabolized, with the production of water-soluble products, and this metabolism was inhibited by chloroquine.

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