Atherosclerosis and Lipoproteins |
From the Department of Human Genetics (K.W.v.D., M.P.J.d.W., A.v.d.Z., M.H.H.) and the Departments of Cardiology and Internal Medicine (L.M.H.), Leiden University Medical Center, and TNO Prevention and Health, Gaubius Laboratory (B.J.M.v.V., B.v.t.H., H.v.d.B., L.M.H.), Leiden, The Netherlands.
Correspondence to Dr K. Willems van Dijk, Department of Human Genetics, Leiden University Medical Center, PO Box 9503, 2300 RA Leiden, The Netherlands. E-mail ko{at}ruly46.medfac.leidenuniv.nl
AbstractTo investigate the relative roles of the LDL receptor and nonLDL receptormediated pathways in the clearance of apolipoprotein E (apoE) variants in vivo, we have generated apoE2(Arg158-Cys) (apoE2) and apoE3-Leiden transgenic mice deficient for the endogenous mouse Apoe and Ldl receptor genes (Apoe-/-.Ldlr-/- mice). Unexpectedly, on the Apoe-/-.Ldlr-/- background, expression of neither apoE2 nor apoE3-Leiden results in a decrease of the hyperlipidemia. In contrast, serum cholesterol levels are increased by the introduction of apoE2 and apoE3-Leiden in Apoe-/-.Ldlr-/- mice (to 39.1±7.1 and 37.6±7.6 mmol/L, respectively, from 25.9±6.5 mmol/L). In addition, in these transgenic mice, the serum triglyceride levels are substantially increased (to 9.6±7.0 and 5.8±2.8 mmol/L, respectively, from 0.7±0.5 mmol/L), which is associated with a decreased efficiency of in vitro LPL-mediated lipolysis of circulating VLDL. The VLDL-triglyceride secretion rate is not affected by the expression of apoE2 or apoE3-Leiden on the Apoe-/-.Ldlr-/- background. These results indicate that in the absence of the LDL receptor, clearance of triglyceride-rich apoE2 and apoE3-Leidencontaining lipoproteins via alternative hepatic receptors, such as the LDL receptorrelated protein (LRP) is inefficient. Although apoE2 and apoE3-Leiden are disturbed in binding to the LDL receptor in vitro, expression of 1 or 2 mouse Ldlr alleles in an apoE2.Apoe-/- or apoE3-Leiden.Apoe-/- background results in a gene dosedependent decrease of the hyperlipidemia. Furthermore, overexpression of the LDL receptor via adenovirus-mediated gene transfer rescues the hyperlipidemia associated with apoE2 and apoE3-Leiden expression. These data indicate that in apoE2 and apoE3-Leiden transgenic mice, the LDL receptor constitutes the predominant route for clearance of VLDL remnants, carrying even poorly binding apoE variants, and that this pathway is functional despite an apoE-mediated disturbance in VLDL triglyceride lipolysis.
Key Words: apolipoprotein E LDL receptor LDL receptorrelated protein hypertriglyceridemia VLDL triglyceride lipolysis
This article has been cited by other articles:
![]() |
M. Altenburg, J. Arbones-Mainar, L. Johnson, J. Wilder, and N. Maeda Human LDL Receptor Enhances Sequestration of ApoE4 and VLDL Remnants on the Surface of Hepatocytes but Not Their Internalization in Mice Arterioscler Thromb Vasc Biol, June 1, 2008; 28(6): 1104 - 1110. [Abstract] [Full Text] [PDF] |
||||
![]() |
S.-J. Lee, I. Grosskopf, S. Y. Choi, and A. D. Cooper Chylomicron remnant uptake in the livers of mice expressing human apolipoproteins E3, E2 (Arg158->Cys), and E3-Leiden J. Lipid Res., December 1, 2004; 45(12): 2199 - 2210. [Abstract] [Full Text] [PDF] |
||||
![]() |
X. Li, H.-Y. Kan, S. Lavrentiadou, M. Krieger, and V. Zannis Reconstituted Discoidal ApoE-Phospholipid Particles Are Ligands for the Scavenger Receptor BI. THE AMINO-TERMINAL 1-165 DOMAIN OF ApoE SUFFICES FOR RECEPTOR BINDING J. Biol. Chem., June 7, 2002; 277(24): 21149 - 21157. [Abstract] [Full Text] [PDF] |
||||
![]() |
B. Teusink, A. R. Mensenkamp, H. van der Boom, F. Kuipers, K. W. van Dijk, and L. M. Havekes Stimulation of the in Vivo Production of Very Low Density Lipoproteins by Apolipoprotein E Is Independent of the Presence of the Low Density Lipoprotein Receptor J. Biol. Chem., October 26, 2001; 276(44): 40693 - 40697. [Abstract] [Full Text] [PDF] |
||||
|
ATVB Home | Subscriptions | Archives | Feedback | Authors | Help | AHA Journals Home | Search Copyright © 1999 American Heart Association, Inc. All rights reserved. Unauthorized use prohibited. |