Page Banner

United States Department of Agriculture

Agricultural Research Service

Research Project: LIPOPROTEINS AND NUTRITION

Location: Human Nutrition Research Center on Aging

Title: Dysfunctional HDL containing L159R apoA-I leads to exacerbation of atherosclerosis in hyperlipidemic mice

Authors
item Sorci-Thomas, Mary G. -
item Zabalawi, Manal -
item Bharadwaj, Manish S. -
item Wilhelm, Ashley J. -
item Owen, John S. -
item Asztalos, Bela F. -
item Bhat, Shaila -
item Thomas, Michael J. -

Submitted to: Biochimica et Biophysica Acta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 31, 2011
Publication Date: March 1, 2012
Citation: Sorci-Thomas, M., Zabalawi, M., Bharadwaj, M., Wilhelm, A., Owen, J., Asztalos, B., Bhat, S., Thomas, M. 2012. Dysfunctional HDL containing L159R apoA-I leads to exacerbation of atherosclerosis in hyperlipidemic mice. Biochimica et Biophysica Acta. 1821(3):502-512.

Interpretive Summary: The mutation L159R apoA-I or apoA-IL159R (FIN) is associated with a dominant negative phenotype, displaying low levels of high-density lipoprotein cholesterol and an increased risk of hardening of the arteries in humans. Mice lacking both mouse apoA-I and LDL receptor (LDL -/-, apoA-I-/-) (double knockout or DKO) were crossed with mice transgenic for human FIN to obtain L159R apoA-I, LDLr -/-, ApoA-I -/- (FIN-DKO) mice. A similar cross was also performed with human wild-type (WT) apoA-I (WT-DKO). In addition, FIN-DKO and WT-DKO were crossed to obtain WT/FIN-DKO mice. To determine the effects of the apoA-I mutations on hardening of the arteries, groups of each geno-type were fed either a regular diet or a diet that accelerated hardening of the arteries for 12 weeks. Interestingly, the production of dysfunctional HDL-like particles occurred in DKO and FIN-DKO mice. These particles were distinct with respect to size, and their enrichment in apoE and cholesterol esters. The particles found in the blood of FIN-DKO mice migrated as large alpha 3-HDL. Analysis of the hardening of their arteries showed that FIN-DKO mice developed the greatest extent of cholesterol accumulation in the aorta compared to all other genotypes, including DKO mice which lack any apoA-I. Taken together these data suggest that the presence of large apoE enriched HDL particles containing apoA-I L159R lack the normal cholesterol expulsion promoting properties of HDL, rendering them dysfunctional and contributors to artery hardening. In conclusion, large HDL-like particles containing apoE and apoA-IL159R contribute rather than protect against atherosclerosis, possibly through defective expulsion properties and their potential for accumulation at their site of interaction in the aorta.

Technical Abstract: In this study, the effect of the mutation L159R apoA-I or apoA-IL159R (FIN) was assessed. apoA-IL159R (FIN) is associated with a dominant negative phenotype, displaying hypoalphaproteinemia and an increased risk for atherosclerosis in humans. Transgenic mice lines were created through strategic mating. Mice lacking both mouse apoA-I and LDL receptor (LDL -/-, apoA-I-/-) (double knockout or DKO) were crossed N 9 generations with mice transgenic for human FIN to obtain L159R apoA-I, LDLr -/-, ApoA-I -/- (FIN-DKO) mice. A similar cross was also performed with human wild-type (WT) apoA-I (WT-DKO). In addition, FIN-DKO and WT-DKO were crossed to obtain WT/FIN-DKO mice. Each geno- type were fed either chow or an atherogenic diet for 12 weeks. Plasma from both chow- and diet-fed mice was analyzed for total plasma cholesterol and triglycerides by enzymatic assay. To isolate the total lipoprotein fraction, plasma was subjected to density-gradient ultracentrifugation. To separate into lipoprotein classes, the d b 1.225 fraction was applied to 2 Superose-6 columns connected in tandem and eluted at 0.5 mL/min with 0.9% NaCl, 2.6 micrometres EDTA and 1.5 micrometres sodium azide. Total cholesterol was determined in each fraction by enzymatic assay. Classes of lipoproteins for chow and diet plasma were pooled using the cholesterol distribution pro'le. To assess plasma lipoprotein particle size after FPLC 10 micrograms of protein from pooled fractions were run on 4-30% nondenaturing gradient gel electrophoresis. The production of dysfunctional HDL-like particles occurred in DKO and FIN-DKO mice. These particles were distinct with respect to size, and their enrichment in apoE and cholesterol esters. The particles found in the plasma of FIN-DKO mice migrated as large alpha 3-HDL. Atherosclerosis analysis showed that FIN-DKO mice developed the greatest extent of aortic cholesterol accumulation compared to all other genotypes, including DKO mice which lack any apoA-I.

Last Modified: 4/19/2014
Footer Content Back to Top of Page