VLDL lipolysis products increase VLDL fluidity and convert apolipoprotein E4 into a more expanded conformation

Our previous work indicated that apolipoprotein (apo) E4 assumes a more expanded conformation in the postprandial period. The postprandial state is characterized by increased VLDL lipolysis. In this article, we tested the hypothesis that VLDL lipolysis products increase VLDL particle fluidity, which mediates expansion of apoE4 on the VLDL particle. Plasma from healthy subjects was collected before and after a moderately high-fat meal and incubated with nitroxyl-spin labeled apoE. ApoE conformation was examined by electron paramagnetic resonance spectroscopy using targeted spin probes on cysteines introduced in the N-terminal (S76C) and C-terminal (A241C) domains. Further, we synthesized a novel nitroxyl spin-labeled cholesterol analog, which gave insight into lipoprotein particle fluidity. Our data revealed that the order of lipoprotein fluidity was HDL∼LDL<VLDL<VLDL+lipoprotein lipase. Moreover, the conformation of apoE4 depended on the lipoprotein fraction: VLDL-associated apoE4 had a more linear conformation than apoE4 associated with LDL or HDL. Further, by changing VLDL fluidity, VLDL lipolysis products significantly altered apoE4 into a more expanded conformation. Our studies indicate that after every meal, VLDL fluidity is increased causing apoE4 associated with VLDL to assume a more expanded conformation, potentially enhancing the pathogenicity of apoE4 in vascular tissue. Our previous work indicated that apolipoprotein (apo) E4 assumes a more expanded conformation in the postprandial period. The postprandial state is characterized by increased VLDL lipolysis. In this article, we tested the hypothesis that VLDL lipolysis products increase VLDL particle fluidity, which mediates expansion of apoE4 on the VLDL particle. Plasma from healthy subjects was collected before and after a moderately high-fat meal and incubated with nitroxyl-spin labeled apoE. ApoE conformation was examined by electron paramagnetic resonance spectroscopy using targeted spin probes on cysteines introduced in the N-terminal (S76C) and C-terminal (A241C) domains. Further, we synthesized a novel nitroxyl spin-labeled cholesterol analog, which gave insight into lipoprotein particle fluidity. Our data revealed that the order of lipoprotein fluidity was HDL∼LDL<VLDL<VLDL+lipoprotein lipase. Moreover, the conformation of apoE4 depended on the lipoprotein fraction: VLDL-associated apoE4 had a more linear conformation than apoE4 associated with LDL or HDL. Further, by changing VLDL fluidity, VLDL lipolysis products significantly altered apoE4 into a more expanded conformation. Our studies indicate that after every meal, VLDL fluidity is increased causing apoE4 associated with VLDL to assume a more expanded conformation, potentially enhancing the pathogenicity of apoE4 in vascular tissue. apolipoprotein dimyristoylphosphatidylcholine doxyl stearic acid electron paramagnetic resonance lipoprotein lipase triglyceride Apolipoprotein E (apoE), a 34 kDa protein that is important in lipid metabolism and cholesterol transport, has three common alleles (ε2, ε3, and ε4). ApoE polymorphisms influence the risk of atherosclerotic cardiovascular disease and neurodegenerative disorders (1Davignon J. Apolipoprotein E and atherosclerosis: beyond lipid effect.Arterioscler. Thromb. Vasc. Biol. 2005; 25: 267-269Crossref PubMed Scopus (81) Google Scholar). ApoE3 binds preferentially to HDL and apoE4 to VLDL (2Weisgraber K.H. Apolipoprotein E distribution among human plasma lipoproteins: role of the cysteine-arginine interchange at residue 112.J. Lipid Res. 1990; 31: 1503-1511Abstract Full Text PDF PubMed Google Scholar). ApoE contains a 22 kDa N-terminal domain (residues 1–191) and a 10 kDa C-terminal domain (residues 222–299) separated by a protease-sensitive loop (3Wetterau J.R. Aggerbeck L.P. Rall Jr., S.C. Weisgraber K.H. Human apolipoprotein E3 in aqueous solution. I. Evidence for two structural domains.J. Biol. Chem. 1988; 263: 6240-6248Abstract Full Text PDF PubMed Google Scholar). ApoE4 shows a more pronounced domain interaction or closed conformation than the other apoE isoforms because it has Arg-112, which enables Arg-61 in the N-terminal domain to interact with Glu-255 in the C-terminal domain, a feature responsible for the preferential association of apoE4 with VLDL (4Dong L.M. Weisgraber K.H. Human apolipoprotein E4 domain interaction. Arginine 61 and glutamic acid 255 interact to direct the preference for very low density lipoproteins.J. Biol. Chem. 1996; 271: 19053-19057Abstract Full Text Full Text PDF PubMed Scopus (262) Google Scholar, 5Saito H. Dhanasekaran P. Baldwin F. Weisgraber K.H. Phillips M.C. Lund-Katz S. Effects of polymorphism on the lipid interaction of human apolipoprotein E.J. Biol. Chem. 2003; 278: 40723-40729Abstract Full Text Full Text PDF PubMed Scopus (79) Google Scholar). Upon binding to lipid, apolipoproteins undergo conformational rearrangements (6Saito H. Lund-Katz S. Phillips M.C. Contributions of domain structure and lipid interaction to the functionality of exchangeable human apolipoproteins.Prog. Lipid Res. 2004; 43: 350-380Crossref PubMed Scopus (188) Google Scholar, 7Oda M.N. Forte T.M. Ryan R.O. Voss J.C. The C-terminal domain of apolipoprotein A-I contains a lipid-sensitive conformational trigger.Nat. Struct. Biol. 2003; 10: 455-460Crossref PubMed Scopus (114) Google Scholar) that affect their function. The association of apoE isoform–dependant postprandial lipoprotein metabolism with vascular disease is not well understood. Previously, we reported that lipolytic products of VLDL reduce the intermolecular interaction of apoE4, i.e., the self-association of apoE4 via its C terminus (8Tetali S.D. Budamagunta M.S. Voss J.C. Rutledge J.C. C-terminal interactions of apolipoprotein E4 respond to the postprandial state.J. Lipid Res. 2006; 47: 1358-1365Abstract Full Text Full Text PDF PubMed Scopus (12) Google Scholar); however, the mechanism for such effect was unknown. In this study, we used electron paramagnetic resonance (EPR) spectroscopy to investigate intramolecular interaction, i.e., domain interaction in apoE4 affected by VLDL lipolysis products. Our findings show that the conformation of apoE4 is modulated postprandially and is mediated by VLDL particle fluidity. These conformational changes may be important in lipoprotein-vascular cell binding and possibly in vascular injury. Materials for this work are as follows: streptokinase, ICN Pharmaceuticals (Costa Mesa, CA); vacutainers and venipuncture supplies, Fisher Scientific International (Hampton, NH); glass capillaries, VitroCom (Mountain Lakes, NJ); flat cell (catalog no. ES-LC11), JEOL (Tokyo, Japan); lipoprotein lipase, 5-doxy and 16-doxylstearic acid spin probes, and guanidine thiocyanate, Sigma-Aldrich (St. Louis, MO); (1-oxyl-2,2,5,5-tetramethyl-3-pyrroline-3-methyl) methanethiosulfonate and 12-doxylstearic acid, Toronto Research Chemicals (Toronto, Canada); titan gel electrophoresis supplies, Helena Laboratories (Beaumont, TX); dimyristoylphosphatidylcholine (DMPC), egg yolk phosphatidylcholine, extruder were from Avanti Polar Lipids (Alabaster, AL); and trioelin, cholesteryl oleate, cholesterol, and free fatty acids were from Nu-Chek-Prep (Elysian, MN). α-Thrombin was from Hematologic Technologies (Essex Junction, VT), and Slide-A-Lyzer dialysis cassettes (MWCO 10,000) were from Pierce (Rockford, IL). Recombinant plasmids containing thioredoxin-his tagged apoE sequences in pET32a-NT were expressed in BL21 (DE3) Escherichi coli cells as described previously but with modifications (9Morrow J.A. Arnold K.S. Weisgraber K.H. Functional characterization of apolipoprotein E isoforms overexpressed in Escherichia coli.Protein Expr. Purif. 1999; 16: 224-230Crossref PubMed Scopus (91) Google Scholar, 10Hatters Budamagunta M.S. Voss J.C. Weisgraber K.H. of apolipoprotein E structure by domain in and Biol. Chem. 2005; Full Text Full Text PDF PubMed Scopus Google Scholar). The protein was with a with and The thioredoxin-his was from apoE with human The was in of and at for at to the The protein was in guanidine and by a to the N-terminal labeled with a methanethiosulfonate spin and for protein as described Budamagunta M.S. Voss J.C. Weisgraber K.H. of apolipoprotein E structure by domain in and Biol. Chem. 2005; Full Text Full Text PDF PubMed Scopus Google Scholar). The and of the protein was tested by The apoE used for this were apoE4 with two at acid and and protein human subjects were from the of The was by the Human Research of the of was from The were a moderately high-fat meal from and was by venipuncture into containing or before and and after of the meal (8Tetali S.D. Budamagunta M.S. Voss J.C. Rutledge J.C. C-terminal interactions of apolipoprotein E4 respond to the postprandial state.J. Lipid Res. 2006; 47: 1358-1365Abstract Full Text Full Text PDF PubMed Scopus (12) Google Scholar). were at for 10 at to plasma from were by with modifications S.D. E.J. of very low density and low density lipoprotein apolipoprotein and density lipoprotein A-I in human subjects using of and 1990; PubMed Scopus Google Scholar). Plasma was into and was as a Plasma was in and and at for at to The plasma was at for at to The density of the plasma was to to LDL and to to HDL and at for at for lipoprotein Lipid were at Plasma and lipid were at and used after lipoprotein containing and VLDL were by the plasma at for at were by with lipoprotein lipase at for and for fatty LDL cholesterol, HDL cholesterol, cholesterol, and fatty acids were with of spin-labeled apoE4 or protein were incubated with postprandial or postprandial VLDL at for and to the association of apoE with lipoprotein lipoprotein on the gel were by and (8Tetali S.D. Budamagunta M.S. Voss J.C. Rutledge J.C. C-terminal interactions of apolipoprotein E4 respond to the postprandial state.J. Lipid Res. 2006; 47: 1358-1365Abstract Full Text Full Text PDF PubMed Scopus (12) Google Scholar). and VLDL were from the in guanidine at and by and the of spin-labeled apoE associated with the VLDL was (8Tetali S.D. Budamagunta M.S. Voss J.C. Rutledge J.C. C-terminal interactions of apolipoprotein E4 respond to the postprandial state.J. Lipid Res. 2006; 47: 1358-1365Abstract Full Text Full Text PDF PubMed Scopus (12) Google Scholar). The and stearic acid spin probes in were to and by to of the with the The of the and probes in the lipoprotein was cholesterol were the at The of is described as a of in and were The was at for with and with The was with and The residue was by with to the a of in was at The was to to at the was with the was and the aqueous was with The was and by to the The was and for C C and the spin-labeled of was in and into the lipoprotein to a of in a glass with at for before the In this the spin-labeled cholesterol was the spin-labeled cholesterol is The of the in the not and was the The were as previously described of in of the lipoprotein lipase 2003; PubMed Scopus Google Scholar). of egg yolk phosphatidylcholine, cholesteryl oleate, and of cholesterol were and a of The were in a of 10 containing and and in a at for or the was the were using extruder to by to of the were for their triglyceride and cholesterol Further, the were used for apoE binding on the of of apoE4 were with a JEOL with a (8Tetali S.D. Budamagunta M.S. Voss J.C. Rutledge J.C. C-terminal interactions of apolipoprotein E4 respond to the postprandial state.J. Lipid Res. 2006; 47: 1358-1365Abstract Full Text Full Text PDF PubMed Scopus (12) Google Scholar). apoE in and to a of protein was to plasma or lipoprotein or VLDL as described in S.D. Budamagunta M.S. Voss J.C. Rutledge J.C. C-terminal interactions of apolipoprotein E4 respond to the postprandial state.J. Lipid Res. 2006; 47: 1358-1365Abstract Full Text Full Text PDF PubMed Scopus (12) Google Scholar, with of fatty acids or and the fatty acid and cholesterol of lipoprotein was at The were into glass capillaries, incubated at for and by the were The were by of three at a of and a of at or at the in gel a flat cell was and the from the were for the of containing spin-labeled were as described of fluidity and in the Res. 1988; PubMed Scopus Google Scholar). containing the the order was as C the in the and was from were using as by with using the data are reported as was reported for as studies J. human apolipoprotein E 2004; 43: PubMed Scopus Google Scholar, S. human apolipoprotein PubMed Scopus Google Scholar) that apoE via a the C-terminal domain intermolecular is apoE4 binds as by the interaction of spin at (8Tetali S.D. Budamagunta M.S. Voss J.C. Rutledge J.C. C-terminal interactions of apolipoprotein E4 respond to the postprandial state.J. Lipid Res. 2006; 47: 1358-1365Abstract Full Text Full Text PDF PubMed Scopus (12) Google Scholar, 10Hatters Budamagunta M.S. Voss J.C. Weisgraber K.H. of apolipoprotein E structure by domain in and Biol. Chem. 2005; Full Text Full Text PDF PubMed Scopus Google Scholar, Voss J.C. Budamagunta M.S. Weisgraber K.H. on the of apolipoprotein E from electron paramagnetic resonance Biol. PubMed Scopus Google Scholar). The intermolecular interaction as by spin-labeled to be a for apoE4 binding to plasma collected and postprandially (8Tetali S.D. Budamagunta M.S. Voss J.C. Rutledge J.C. C-terminal interactions of apolipoprotein E4 respond to the postprandial state.J. Lipid Res. 2006; 47: 1358-1365Abstract Full Text Full Text PDF PubMed Scopus (12) Google Scholar). the influence of lipolysis on the conformation and distribution of apoE4, we used a previously intramolecular domain interaction to conformational and apoE4 that are to be important in their Budamagunta M.S. Voss J.C. Weisgraber K.H. of apolipoprotein E structure by domain in and Biol. Chem. 2005; Full Text Full Text PDF PubMed Scopus Google Scholar). In lipid and spin of intermolecular spin interaction from of is from or Budamagunta M.S. Voss J.C. Weisgraber K.H. of apolipoprotein E structure by domain in and Biol. Chem. 2005; Full Text Full Text PDF PubMed Scopus Google Scholar, Voss J.C. Budamagunta M.S. Weisgraber K.H. on the of apolipoprotein E from electron paramagnetic resonance Biol. PubMed Scopus Google Scholar). In the apoE4 is by domain interaction the N-terminal and the C-terminal which is responsible for its binding preference for VLDL Budamagunta M.S. Voss J.C. Weisgraber K.H. of apolipoprotein E structure by domain in and Biol. Chem. 2005; Full Text Full Text PDF PubMed Scopus Google Scholar, Voss J.C. Budamagunta M.S. Weisgraber K.H. on the of apolipoprotein E from electron paramagnetic resonance Biol. 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Weisgraber K.H. on the of apolipoprotein E from electron paramagnetic resonance Biol. PubMed Scopus Google Scholar). the is for domain interaction in the protein and for a or conformation in the The which cysteines at acids and the in the the two of apoE are with spin and by spectroscopy Budamagunta M.S. Voss J.C. Weisgraber K.H. of apolipoprotein E structure by domain in and Biol. Chem. 2005; Full Text Full Text PDF PubMed Scopus Google Scholar). has that with a spin we used with Budamagunta M.S. Voss J.C. Weisgraber K.H. of apolipoprotein E structure by domain in and Biol. Chem. 2005; Full Text Full Text PDF PubMed Scopus Google Scholar). and because the domain interaction L.M. Weisgraber K.H. Human apolipoprotein of 61 in the lipoprotein of the E3 and E4 Biol. Chem. Full Text PDF PubMed Google Scholar). of apoE4 has is by the with apoE4 containing the and on the of interaction in the in apoE4 containing two spin-labeled the the and C-terminal is has we used protein to the of to lipolysis (4Dong L.M. Weisgraber K.H. Human apolipoprotein E4 domain interaction. Arginine 61 and glutamic acid 255 interact to direct the preference for very low density lipoproteins.J. Biol. Chem. 1996; 271: 19053-19057Abstract Full Text Full Text PDF PubMed Scopus (262) Google Scholar, 10Hatters Budamagunta M.S. Voss J.C. Weisgraber K.H. of apolipoprotein E structure by domain in and Biol. Chem. 2005; Full Text Full Text PDF PubMed Scopus Google Scholar). The interaction the spin at two be by the of we examined the apoE4 and after in postprandial plasma The in are that the of The increased the the in the in as previously Budamagunta M.S. Voss J.C. Weisgraber K.H. of apolipoprotein E structure by domain in and Biol. Chem. 2005; Full Text Full Text PDF PubMed Scopus Google Scholar). plasma the of The effect was at but the was than that in the that this of apoE4 of the conformational of its state in In the protein a more conformation in the state and in a of apoE in the postprandial and postprandial lipid of of the healthy in this are in of healthy human for the and were for the the data from are of two The data from and are from a direct of direct of in a and were for the the data from are of two The data from and are from a direct of direct of the and apoE4 binding to of the we incubated plasma from healthy with spin-labeled protein or apoE4 for at The were separated by gel The of binding and distribution of protein or apoE4 with plasma lipoprotein or was by the of spin-labeled by spectroscopy (8Tetali S.D. Budamagunta M.S. Voss J.C. Rutledge J.C. C-terminal interactions of apolipoprotein E4 respond to the postprandial state.J. Lipid Res. 2006; 47: 1358-1365Abstract Full Text Full Text PDF PubMed Scopus (12) Google Scholar). the protein preferentially to HDL to LDL and to and apoE4 to VLDL to HDL and to the conformation of apoE on lipoprotein spin-labeled apoE4 and protein were incubated with or HDL at for before of protein with HDL or VLDL in in with In HDL of the apoE4 that the conformation of the protein is in HDL. VLDL a in than the not lipolysis for in the of from we the in the for apoE4 and the with or HDL from the the lipoprotein increase of the for apoE4, the increase in the was for apoE4 to VLDL than for apoE4 to HDL or LDL The of the spin in the two in apoE4 was to that of on apoE4 These data that the conformation of apoE4 is more affected on VLDL than on HDL or Budamagunta M.S. Voss J.C. Weisgraber K.H. of apolipoprotein E structure by domain in and Biol. Chem. 2005; Full Text Full Text PDF PubMed Scopus Google Scholar) apoE4 conformational this is the to show the in apoE4 conformation on that the in apoE spin interaction after to postprandial plasma be to the VLDL-associated we incubated apoE4 and with lipoprotein from plasma or postprandial plasma at or plasma as to ApoE4 the of the and probes to a on HDL In with the effect with the of in plasma postprandial HDL not influence the conformation of apoE4, as by the of the labeled protein the conformation of the protein was not altered by with HDL from the or postprandial and spin-labeled apoE4 and the after to VLDL increased lipolytic is associated with the postprandial we examined the effect of VLDL lipolysis on apoE conformation. of spin-labeled protein or apoE4 were incubated with or postprandial VLDL for at before with apoE4 in apoE4 incubated with postprandial VLDL a which increased to apoE4 was incubated with VLDL protein a increase in with VLDL and a increase with VLDL has for apoE4, we used gel electrophoresis to apoE4 that had incubated with VLDL or The VLDL on the were by and the gel were in guanidine by at for the from the to the of protein associated with VLDL or not significantly the association of VLDL with apoE4 or in association of apoE4 with VLDL or VLDL were the in the changes in apoE4 conformation, not the of apoE4 to the we used probes to investigate in lipoprotein particle fluidity influence the structure of apoE. particle fluidity, we or to or VLDL and the to The spin in with LDL or HDL but free with VLDL of the spin indicated by a and be by a in the order These show that VLDL is more than LDL and for spin-labeled fatty acids in plasma lipid in a the role of in the increased fluidity of postprandial The effect of on the lipid order VLDL and was examined using spin-labeled fatty acids the and probes of the and order with lipolysis and increased of a more had effect on the that the is affected by lipolysis. investigate the of lipolysis on fluidity, we used fatty acid spin probes stearic and a cholesterol spin to lipid fluidity incubated or with with the spin-labeled spin and spectroscopy to the of domains. increased the fluidity and The influence of fluidity was by of cholesterol which is to reduce lipid fluidity at in apoE4 a of domain interaction incubated with containing the cholesterol was for the In the data with lipid probes indicate that lipolysis the fluidity of and to the previous that the of in apoE of domain interaction a of lipolysis and lipoprotein fluidity. the lipoprotein fluidity and on the conformation of apoE4, we VLDL with fatty acids of with of and fatty acids and were more than stearic and fatty acids and in domain interaction of apoE4 not to the changes in VLDL after we the free fatty acid of postprandial VLDL in the of of VLDL increased the of by to in and postprandial VLDL were not significantly lipolysis VLDL increased to lipolysis of postprandial VLDL a to increase in in not be by which be because the and is the for in is free fatty acid in human plasma be as as and on postprandial effect of and on plasma cholesterol, and fatty acid metabolism in J. 2006; PubMed Scopus Google Scholar). may important role in fluidity and apoE conformation. In this study, we used spectroscopy to investigate conformational changes of apoE4 by VLDL lipolysis products. Our findings show that the conformation of apoE4 is modulated postprandially and is mediated by VLDL particle fluidity. ApoE4 was more to lipid fluidity than and lipid fluidity was to the of in the and C-terminal of VLDL was more than LDL and and VLDL-associated apoE4 had a more conformation than associated with LDL or HDL. Our findings a for apoE association with lipid These conformational changes may be important in lipoprotein-vascular cell binding and possibly in vascular injury. Lipid association structural rearrangements in apoE. The conformation of apoE4 on it is to or Budamagunta M.S. Voss J.C. Weisgraber K.H. of apolipoprotein E structure by domain in and Biol. Chem. 2005; Full Text Full Text PDF PubMed Scopus Google Scholar). Plasma are in and and apoE4 and for plasma for on apoE conformation. ApoE4 on VLDL HDL and a more effect on VLDL with HDL or ApoE3 conformation was by association with lipoprotein The for the apoE4 structural conformational is not with that of and the of and apolipoproteins are important of the binding and of of apolipoproteins and of association with and 1988; PubMed Scopus Google Scholar, of and with containing cholesterol of and PubMed Scopus Google Scholar, J.A. Lund-Katz S. Phillips M.C. of and lipoprotein and apolipoprotein A-I PubMed Scopus Google Scholar, J. The lipid of binding and Biol. PubMed Google Scholar). lipid fluidity increased in the order HDL LDL VLDL and with their of human plasma and lipoprotein J. Full Text Full Text PDF PubMed Scopus Google Scholar). used the of apoE and protein to conformational the apoE spin-labeled apoE4 preferentially associated with VLDL and protein with HDL after a moderately high-fat the in not affect their structural or their preference for plasma Our findings are with work by and of human plasma and lipoprotein J. Full Text Full Text PDF PubMed Scopus Google used probes to a fluidity for HDL and LDL but a more for a fluidity of lipoprotein with of and in the of low and density after lipolysis with 1996; PubMed Scopus Google Scholar) that order at the by is with the in VLDL fluidity by the the density may be the more P. of lipoprotein fluidity by fatty acids to affect cholesteryl protein electron spin resonance J. 1996; PubMed Scopus Google Scholar) that more than Previously, we that to VLDL C-terminal interaction and the of apoE4 from a state to a state (8Tetali S.D. Budamagunta M.S. Voss J.C. Rutledge J.C. C-terminal interactions of apolipoprotein E4 respond to the postprandial state.J. Lipid Res. 2006; 47: 1358-1365Abstract Full Text Full Text PDF PubMed Scopus (12) Google Scholar). the lipoprotein fluidity and conformational changes in of apoE4, we tested the effect of fatty acids with of and fatty acids a effect than stearic and fatty acids in the of the and C-terminal of Our previous (8Tetali S.D. Budamagunta M.S. Voss J.C. Rutledge J.C. C-terminal interactions of apolipoprotein E4 respond to the postprandial state.J. Lipid Res. 2006; 47: 1358-1365Abstract Full Text Full Text PDF PubMed Scopus (12) Google Scholar) a in apoE4 conformation after with apoE4 conformation in healthy Our was to the mechanism of this in apoE4 conformation in the postprandial that VLDL lipolysis products this the postprandial state is a of we to the postprandial state by postprandial VLDL with lipoprotein lipase. Our studies the findings in the postprandial state and that VLDL lipolysis products the in particle fluidity that apoE4 conformational changes in the postprandial fatty acids at the lipoprotein because the of fatty acid is than lipolysis F. F. J.A. of and very fatty acids from 1996; PubMed Scopus Google Scholar, of lipid and protein J. Full Text PDF PubMed Scopus Google Scholar). of fatty acids on the lipoprotein changes in lipoprotein fluidity. we changes in the fluidity of the particle and its association with structural conformation of apoE. ApoE4 is and associated with increased risk of and however, the are not with Our studies indicate that the postprandial state significantly the structural conformation of is to postprandial conformational changes in apoE4 affect its interactions with cells and to and postprandial and Rutledge J.C. and cardiovascular 2003; PubMed Google Scholar, Plasma the postprandial a in vascular J. 2005; PubMed Scopus Google Scholar). postprandial has in the of via to the Rutledge J.C. products from increase and and J. PubMed Scopus Google the role of the apoE isoforms and their conformation in may be very important in Our direct that apoE assumes on its association with lipoprotein ApoE4 preferentially binds to but the for its preference are not that apoE4 assumes a more linear conformation on VLDL The increase in free fatty acid in VLDL to lipolysis is by increase in lipid fluidity, which apoE4 conformation we that the conformation of apoE4 is by lipoprotein and lipid fluidity. may the of apoE in apoE4 structure to changes in lipoprotein fluidity, postprandial may lipoprotein binding and by studies are to the lipoprotein particle fluidity and its to cardiovascular and Our shows structural conformation of apoE4 to VLDL LDL and HDL. lipolysis products of VLDL significantly affect the conformation of apoE4 the postprandial state by VLDL fluidity. studies the in structural conformation of apoE4 has on its binding and of apoE4 by studies increase of the of apoE4 structural changes in the postprandial state to and to vascular and atherosclerotic cardiovascular