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1.
1. We compared binding characteristics of 125I-labeled high density lipoprotein (HDL) subclasses to porcine liver, adrenal and skeletal muscle plasma membranes. 2. HDL subclasses were discriminated by their buoyant densities (HDL2 and HDL3) or by their apolipoprotein (apo) content (Lp-AI (particles containing apoA-I but no apoA-II) and LpA-I/A-II (particles containing both apoA-I and apoA-II)). 3. HDL2 and HDL3 showed saturable binding to the three types of membrane preparations. 4. No differences were found in the Kds within one HDL subclass. 5. Kds and maximal binding of HDL2 were lower than these of HDL3. Unlabeled HDL2 and HDL3, but not LDL, effectively displaced 125I-HDL2 and 125I-HDL3. 6. Binding of HDL was independent of the concentration of NaCl and did not require calcium. 7. These results suggest a process mediated by a single specific receptor in porcine liver, adrenal and skeletal muscle plasma membranes. 8. We also studied binding characteristics of HDL subclasses Lp-AI and LpA-I/A-II to porcine liver membranes. LpA-I showed the highest Kd and maximal binding. 9. All types of HDL subclasses studied (i.e. HDL2, HDL3, LpA-I and LpA-I/A-II) effectively competed for binding of both Lp-AI and LpA-I/A-II, suggesting that the HDL subclasses studied bind to the same receptor by their apoA-I moiety.  相似文献   

2.
描述了一种微流控芯片电泳快速分离血清高密度脂蛋白(high density lipoprotein,HDL)亚类的方法.利用自制的微流控芯片,结合激光诱导荧光检测系统,40mmol/L Tricine、50mmol/L甲基葡胺(MEG)、0.2mmol/LSDS(pH8.5)为样品缓冲液,40mmol/L Tricine、50mmol/LMEG、0.01mmol/L SDS(pH8.5)为分离缓冲液,4min内HDL3和HDL2两种亚类得到基线分离.该法操作过程简单,重复性较佳,测试费用低廉,在临床HDL亚类的检测中具有较好的应用前景.  相似文献   

3.
Copper deficiency in rats produces a hypercholesterolemia with a marked increase in HDL fraction. This study investigated changes in the plasma distribution and composition of HDL subclasses as affected by copper deficiency. Plasma HDL were separated into the following three subclasses by heparin-affinity chromatography: HDL containing no apo E but high in apo A-I (HDL-E0); HDL with an intermediate level of apo E (HDL-E1); and HDL highly enriched in apo E but low in apo A-I (HDL-E2). The compositional analysis showed that the hypercholesterolemia observed in copper-deficient rats was due specifically to an increase in plasma cholesterol carried by HDL-E0. Copper deficiency did not alter the percent distribution of apo A-I in HDL-E0, but lowered the apo A-I content in HDL-E1 and HDL-E2, with an increase in apo E in these subclasses. The total plasma concentration of apo A-I was, however, significantly elevated in Cu-deficient rats, which was attributable to an increase in the total number of circulating HDL particles. No difference was noted between Cu-deficient and control groups in the distribution of free cholesterol or the ratio of free cholesterol to esterified cholesterol in any of the HDL subclasses. The present results and earlier observations suggest that copper deficiency may produce a defect in the plasma clearance or tissue uptake of the HDL subclass high in apo A-I but devoid of apo E (HDL-E0), which may be mediated by the specific apo A-I receptor or non-endocytotic transfer of HDL-E0 cholesterol to the liver. Such metabolic defects may partly explain the simultaneous increases in both plasma HDL cholesterol and apo A-I and altered cholesterol homeostasis observed in copper deficiency.  相似文献   

4.
There is relatively little information on the role of high density lipoprotein (HDL) oxidation in atherogenesis although there are indications that oxidation might affect atheroprotective activities of HDL. Recently we reported the study on LDL oxidation initiated and sustained by traces of the transition metal ions under conditions, which favor slow oxidation. Here we report the results of the analogous study on the oxidation of the two HDL subclasses. The oxidation process was monitored by measuring the time dependence of oxygen consumption and concentration of the spin-trapped free radicals using EPR spectroscopy. In both HDL2 and HDL3 subclasses, the dependence of the oxidation process on the copper/lipoprotein molar ratio is different from that in LDL dispersions. Comparison of the kinetic profiles of HDL2 and HDL3 oxidation revealed that under all studied experimental conditions HDL2 was more susceptible to copper-induced oxidation than HDL3.  相似文献   

5.
In order to obtain information on the determinants of the lipid dynamics in the high density lipoproteins (HDL), we have compared the structural properties of human HDL subclasses with porcine HDL artificially subdivided into density subfractions corresponding to those of human HDL. Four different positional isomers of spin labeled fatty acids and spin labeled androstanol experienced more restricted motion in porcine HDL than in the human HDL2 and HDL3 subclasses. The differences in the spin label motion could not be accounted for on the basis of the differences in the chemical composition of the lipoproteins examined. They are, however, most probably due to the specific properties of the interactions between lipids and proteins that differ among the lipoproteins.  相似文献   

6.
The major apoproteins of human high density lipoproteins (HDL) labeled with 125I have been shown to exchange between the two major HDL subclasses HDL2 and HDL3 in vitro. This bidirectional exchange process is inhibited by cross-linking with bifunctional reagents and is apparently dependent upon the formation of collision complexes. This exchange has been demonstrated both when the subclasses of HDL are free in solution and also when one of them is covalently bound to Sepharose. Using system involving Sepharose-bound HDL, it could be shown that not only free apoprotein molecules but subunits consisting of lipid-apoprotein combinations were exchanged between HDL2 and HDL3. The rate of exchange in these processes is significant in the lifetime of the protein particles in vivo equalling approximately 2.5% per h for apoprotein exchange. These experiments suggest that there is a dynamic relationship between HDL2 and HDL3 even though each of them exists alone in vitro as stable separate entities; when they are placed together in solution significant interaction occurs between the particles. Apoprotein exchange occurs between HDL2:HDL2 and HDL3:HDL3 as well as between HDL2 and HDL3 molecules. These data also suggest that the interconversion of HDL2 and HDL3 may be affected by the availability of lipids.  相似文献   

7.
We describe a rapid and reliable three-step precipitation procedure for the isolation of large amounts of the two major components of high density lipoproteins (HDL) in human serum. Precipitation was accomplished by means of dextran sulfate (DS) of mol. wt. 500,000 and MgCl2. First, all apoB-associated lipoproteins of any density were selectively precipitated with critical concentrations of reagents. Secondly, a subfraction of HDL was differentially precipitated from the apoB-depleted serum by increasing the concentration of both reagents. Eventually, the bulk of the remainder of HDL was precipitated by lowering the pH to 5.4. According to the precipitation patterns and the density profiles, the DS-Mg procedure provides a clear differentiation between the two HDL components. According to the compositional criteria and the ultracentrifugal characteristics, the two polyanion-precipitated subclasses are very similar to, if not identical with, the two density subclasses, the lighter HDL2 and the heavier HDL3, isolated by preparative ultracentrifugation after apoB-containing lipoproteins had been removed.  相似文献   

8.
HDL subclasses detection, in cardiovascular risk, has been limited due to the time-consuming nature of current techniques. We have developed a time-saving and reliable separation of the principal HDL subclasses employing iodixanol density gradient ultracentrifugation (IxDGUC) combined with digital photography. HDL subclasses were separated in 2.5 h from prestained plasma on a three-step iodixanol gradient. HDL subclass profiles were generated by digital photography and gel scan software. Plasma samples (n = 46) were used to optimize the gradient for the resolution of HDL heterogeneity and to compare profiles generated by IxDGUC with gradient gel electrophoresis (GGE); further characterization from participants (n = 548) with a range of lipid profiles was also performed. HDL subclass profiles generated by IxDGUC were comparable to those separated by GGE as indicated by a significant association between areas under the curve for both HDL2 and HDL3 (HDL2, r = 0.896, P < 0.01; HDL3, r = 0.894, P < 0.01). The method was highly reproducible, with intra- and interassay coefficient of variation percentage < 5 for percentage area under the curve HDL2 and HDL3, and < 1% for peak Rf and peak density. The method provides time-saving and cost-effective detection and preparation of the principal HDL subclasses.  相似文献   

9.
High-density lipoproteins (HDLs) are complexes of proteins (mainly apoA-I and apoA-II) and lipids that remove cholesterol and prevent atherosclerosis. Understanding the distinct properties of the heterogeneous HDL population may aid the development of new diagnostic tools and therapies for atherosclerosis. Mature human HDLs form two major subclasses differing in particle diameter and metabolic properties, HDL2 (large) and HDL3 (small). These subclasses are comprised of HDL(A-I) containing only apoA-I, and HDL(A-I/A-II) containing apoA-I and apoA-II. ApoA-I is strongly cardioprotective, but the function of the smaller, more hydrophobic apoA-II is unclear. ApoA-II is thought to counteract the cardioprotective action of apoA-I by stabilizing HDL particles and inhibiting their remodeling. To test this notion, we performed the first kinetic stability study of human HDL subclasses. The results revealed that the stability of plasma spherical HDL decreases with increasing particle diameter; which may facilitate preferential cholesterol ester uptake from large lipid-loaded HDL2. Surprisingly, size-matched plasma HDL(A-I/A-II) showed comparable or slightly lower stability than HDL(A-I); this is consistent with the destabilization of model discoidal HDL observed upon increasing the A-II to A-I ratio. These results clarify the roles of the particle size and protein composition in HDL remodeling, and help reconcile conflicting reports regarding the role of apoA-II in this remodeling.  相似文献   

10.
The delivery of cholesterol to canine serum or plasma altered the distribution of cholesterol and apoproteins in subclasses of high density lipoproteins (HDL). In these experiments, two in vitro systems were employed. The first system used cholesterol-celite particles to deliver cholesterol to canine plasma during 4-h incubations. When the cholesterol distribution in the lipoproteins was analyzed by Geon-Pevikon electrophoresis, an increase in cholesterol content was found in the slower migrating subclasses of HDL (HDL1 and HDLc). A large increase in apoprotein E (apo-E) was also observed in the lipoproteins. Densitometric analysis of lipid-stained, 4 to 30% gradient acrylamide gels of canine plasma after incubation with cholesterol-celite revealed that the concentration of the major high density lipoproteins (HDL3) decreased, and the concentration of subclasses of HDL-with apo-E (HDL1 and HDLc) increased 2- to 5-fold. In the second system, cholesterol-loaded mouse peritoneal macrophages released cholesterol to HDL in an incubation medium containing 10 to 20% canine serum. The HDL1 and HDLc, which demonstrated slower electrophoretic mobility as determined by Geon-Pevikon block electrophoresis, became enriched in cholesterol and cholesteryl esters. Gradient gel electrophoresis showed substantial increases in these subclasses of HDL-with apo-E. The cholesterol-loaded mouse peritoneal macrophages synthesized and secreted apo-E into the medium. When L-[35S]methionine was used as a precursor, 65 to 90% of the 35S-labeled protein associated with the lipoproteins in the 1.02 to 1.09 density range was immunoprecipitated with antibody directed against rat apo-E. Gradient gel electrophoresis of density fractions demonstrated the presence of HDL1 and HDLc as the major lipoproteins. In addition, when canine 125I-HDL3 (primarily apo-A-I-containing HDL) were added to canine serum and incubated with cholesterol-loaded macrophages, the appearance of HDL1 and HDLc was associated with a marked increase in the 125I label in these newly formed, cholesteryl ester-rich lipoproteins. There was a corresponding marked reduction in the 125I-HDL3 in the serum. Similar results were observed using human HDL3 and human serum.  相似文献   

11.
Forms of human serum high density lipoprotein protein   总被引:19,自引:0,他引:19  
Delipidation by ethanol-diethyl ether at -10 degrees C of human serum high-density lipoprotein (HDL, d 1.063-1.21) or of its subclasses HDL(2) (d 1.063-1.120) and HDL(3) (d 1.120-1.21), yielded proteins-alphaP, alphaP(2), and alphaP(3)-containing 3% phospholipid (largely lecithin) and 3.3% carbohydrate (glucosamine:L-fucose:D-galactose, D-mannose:sialic acid, 1.00:41 : 0.56:0.31). Solubility data and analytical ultracentrifugal analyses indicated that, upon lipid removal, HDL protein aggregates readily; the aggregation is dependent upon pH and ionic strength of the solvent medium. Subunits of 21,000 mol wt were obtained by acetylation or addition of sodium dodecyl sulfate (SDS). HDL and alphaP elicited in the rabbit a similar immunological response. By agar gel immunoelectrophoresis both anti-HDL and anti-alphaP sera detected a major and two minor antigenic determinants in HDL, HDL(3), alphaP, alphaP(2), and alphaP(3). HDL(2), antigenically homogeneous, gave an immunoelectrophoretic pattern of HDL(3) upon mixing with alphaP. alphaP, alphaP(2), and alphaP(3) exhibited a single antigenic determinant after treatment with SDS (0.5 M) or upon acetylation. Native or delipidated forms of HDL, HDL(2), and HDL(3) were separated by vertical starch gel electrophoresis into several components, which showed identical reactions against anti-HDL or anti-alphaP sera. The data suggest that (a) the proteins of HDL, HDL(2), and HDL(3) are made of subunits, probably identical, of an average molecular weight of 21,000; (b) the difference in antigenic behavior between HDL(2) and HDL(3) is due to the presence in the latter of a lipid-poor protein; (c) antigenic polymorphism of alphaP is probably related to the presence in solution of monomeric and polymeric forms having different reactivity against anti-HDL and anti-alphaP sera.  相似文献   

12.
A new apolipoprotein, termed apolipoprotein J (apoJ), was purified from human plasma by immunoaffinity chromatography. ApoJ is a glycoprotein consisting of disulfide-linked subunits of 34-36 and 36-39 kDa. Each subunit is glycosylated and has a pI range of 4.9-5.4. ApoJ exists in the plasma associated with high density lipoproteins (HDL) and specifically with subclasses of HDL which also contain apoAI and cholesteryl ester transfer protein activity. Immunoaffinity purified apoJ-HDL subclasses have apparent molecular masses of 80, 160, 240, 340, and 520 kDa, as determined by gradient gel electrophoresis. By negative staining electron microscopy, apoJ-HDL range in diameter from 5 to 16 nm. Fractionation of plasma by vertical gradient density centrifugation revealed apoJ-HDL in HDL2 (d 1.063-1.125 g/ml) with the majority overlapping HDL3 (d 1.125-1.21 g/ml) and very high density lipoprotein (d 1.21-1.25 g/ml). The bimodal density distribution of apoJ-HDL suggests that these subclasses have a unique metabolic relationship and may play a role in the transport of cholesterol from peripheral tissues to the liver.  相似文献   

13.
High-density lipoprotein (HDL) subclasses 2 and 3 prepared by density gradient ultracentrifugation have been further fractionated by immunoaffinity chromatography using antibody affinity gels targetting the major HDL apolipoproteins, A-I and A-II. Fractions containing A-I without A-II (AI w/o AII) and A-I with A-II (AI w AII) were isolated from both density ranges. Whereas there were similar concentrations of the major subfraction (HDL3(AI w AII] in both males and females, the remaining subfractions were present in higher concentrations in females as compared to males, in the order HDL3 (AI w/o AII) less than HDL2(AI w AII) less than HDL2(AI w/o AII). The difference was most marked for HDL2 (AI w/o AII), where plasma concentrations in females were almost 3-fold greater than in males. Compositional analyses indicated that the plasma concentrations of the fractions, rather than their compositions, were the major determinants of male-female differences in HDL levels. In contrast, fractions defined by similar apolipoprotein criteria and isolated from different density subclasses (i.e., HDL2(AI w/o AII) vs. HDL3(AI w/o AII) and HDL2(AI w AII) vs. HDL3(AI w AII] showed major compositional differences. This is suggestive of distinct lipoprotein particles.  相似文献   

14.
In order to study the impact of high-density lipoproteins (HDL) subclasses on the ability of HDL to act as substrate for lecithin: cholesterol acyltransferase (LCAT), we isolated HDL from nine normolipidemic male subjects. The HDL particle size distribution was analysed by gradient gel electrophoresis and the esterification rate of the isolated homologous HDL was compared with a pool of HDL where all the nine subjects took part. It was found that the strongest determinant for HDL cholesterol esterification rate was the inhibitory action of HDL subclass 2B.  相似文献   

15.
The relative susceptibility of the apoprotein components of human lipoproteins [high-density lipoprotein (HDL) and low-density lipoprotein (LDL)] and their subclasses to oxidation by the myeloperoxidase/H2O2/Cl- system in vitro was studied by measuring the decrease in rate of tryptophan fluorescence. Whereas the lipoprotein-modification rate showed a saturation type of dependence on the concentration of myeloperoxidase, a biphasic dependence on the concentration of the lipoproteins was found. High concentrations of H2O2 were also found to inhibit tryptophan oxidation in LDL but to a lesser extent in HDL. The optimal rate of LDL and HDL modification was observed at pH 6.0. HDL was modified much more rapidly than LDL, which may be due to differences in size and different relative contents of protein and lipids per particle. No differences in rates of modification of LDL subclasses were observed, when the assays were standardized to equal LDL protein concentrations, but, when standardized to equal particle mass, an optimum at subclass 8 was found, which is probably due to differences in apolipoprotein B-100 conformation. It was concluded that HDL may have a beneficial effect in retarding LDL modification in inflammatory processes.  相似文献   

16.
In order to further investigate the behaviour of high density lipoproteins in diabetes mellitus, we studied HDL subclasses, HDL2 and HDL3, in 10 patients with newly detected, untreated insulin-deficient diabetes before starting insulin treatment and after getting a good metabolic control. We used the extractive method of Abell to determine HDL-cholesterol after LDL and VLDL precipitation with polyanions and HDL3-cholesterol after HDL2 precipitation with dextransulphate 15,000 m.w. After insulin therapy, we observed a significant increase in HDL-cholesterol and a decrease in serum triglycerides. Only HDL2-cholesterol, but not HDL3-cholesterol, raised; moreover, we found a significant inverse relationship between HDL-cholesterol (and also HDL2-cholesterol) and triglycerides. So, we think that an increase of lipoprotein lipase activity, owing to insulin treatment, could account for our results.  相似文献   

17.
Cavigiolio G  Shao B  Geier EG  Ren G  Heinecke JW  Oda MN 《Biochemistry》2008,47(16):4770-4779
High-density lipoprotein (HDL) mediates reverse cholesterol transport (RCT), wherein excess cholesterol is conveyed from peripheral tissues to the liver and steroidogenic organs. During this process HDL continually transitions between subclass sizes, each with unique biological activities. For instance, RCT is initiated by the interaction of lipid-free/lipid-poor apolipoprotein A-I (apoA-I) with ABCA1, a membrane-associated lipid transporter, to form nascent HDL. Because nearly all circulating apoA-I is lipid-bound, the source of lipid-free/lipid-poor apoA-I is unclear. Lecithin:cholesterol acyltransferase (LCAT) then drives the conversion of nascent HDL to spherical HDL by catalyzing cholesterol esterification, an essential step in RCT. To investigate the relationship between HDL particle size and events critical to RCT such as LCAT activation and lipid-free apoA-I production for ABCA1 interaction, we reconstituted five subclasses of HDL particles (rHDL of 7.8, 8.4, 9.6, 12.2, and 17.0 nm in diameter, respectively) using various molar ratios of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, free cholesterol, and apoA-I. Kinetic analyses of this comprehensive array of rHDL particles suggest that apoA-I stoichiometry in rHDL is a critical factor governing LCAT activation. Electron microscopy revealed specific morphological differences in the HDL subclasses that may affect functionality. Furthermore, stability measurements demonstrated that the previously uncharacterized 8.4 nm rHDL particles rapidly convert to 7.8 nm particles, concomitant with the dissociation of lipid-free/lipid-poor apoA-I. Thus, lipid-free/lipid-poor apoA-I generated by the remodeling of HDL may be an essential intermediate in RCT and HDL's in vivo maturation.  相似文献   

18.
We have previously shown that hepatic lipase (HL) is inactive when bound to purified heparan sulfate proteoglycans and can be liberated by HDL and apolipoprotein A-I (apoA-I), but not by LDL or VLDL. In this study, we show that HDL is also able to displace HL directly from the surface of the hepatoma cell line, HepG2, and Chinese hamster ovary cells stably overexpressing human HL. ApoA-I is more efficient at displacing cell surface HL than is HDL, and different HDL classes vary in their ability to displace HL from the cell surface. HDL2s have a greater capacity to remove HL from the cell surface and intracellular compartments, as compared with the smaller HDL particles. The different HDL subclasses also uniquely affect the activity of the enzyme. HDL2 stimulates HL-mediated hydrolysis of VLDL-triacylglycerol, while HDL3 is inhibitory. Inhibition of VLDL hydrolysis appears to result from a decreased interlipoprotein shuttling of HL between VLDL and the smaller, more dense HDL particles. This study suggests that high HDL2 levels are positively related to efficient triacylglycerol hydrolysis by their ability to enhance the liberation of HL into the plasma compartment and by a direct stimulation of VLDL-triacylglycerol hydrolysis.  相似文献   

19.
High density lipoproteins (HDL, d 1.063-1.21 g/ml) are reported to stimulate, to have no effect on, or to inhibit agonist-induced platelet aggregation. We have hypothesized that these conflicting reports might be explained by opposing effects of individual HDL subclasses on platelet aggregability. Physiologic concentrations of HDL3 had little effect on ADP-induced aggregation of washed platelet suspensions, although higher levels were stimulatory. Normal concentrations of HDL2 (0.2-0.4 mg of protein/ml) inhibited aggregation; further fractionation by heparin-Sepharose chromatography identified the particles rich in apolipoprotein E, termed HDL-E, as the major anti-aggregatory subclass. Washed platelets bound radioiodinated HDL-E to a uniform class of saturable sites; they numbered 4,200 per platelet and the KD was 7.9 x 10(-7) M. Binding of HDL-E by platelets, and its anti-aggregatory action, showed a similar rapidity and both occurred within the physiologic concentration range. Moreover, the two processes were independent of the presence of divalent ions and were impaired by chemical modification of the apolipoprotein constituents of HDL-E. We conclude that occupation of cell-surface receptors by HDL-E particles impairs platelet responsiveness to exogenous agonists and that platelet aggregability in the presence of whole HDL may reflect the relative concentrations of the individual subclasses in the particular sample.  相似文献   

20.
Concentrations in serum were determined for 18 fatty acids (FAs) and 21 lipoprotein main and subclasses by chromatographic analyses and the average size was calculated for very low density (VLDL), low density (LDL) and high density (HDL) particles. 283 ethnic Norwegian children and adults from the rural Fjord region of Western Norway were compared with the objectives to reveal patterns and gender differences during the development from prepuberty to adulthood and during aging in adults. Both genders showed a large increase in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from child to adult. Males, but not females, show a significant increase in most C16–C18 FAs from prepuberty to adulthood. These changes in males correlate to a pattern of increased concentrations of triglycerides, VLDL and LDL particles, especially the atherogenic subclasses of small and very small LDL particles. Furthermore, concentrations of medium, large and very large HDL particles decrease, while concentration of very small HDL particles increase leading to reduced average size of HDL particles. Females only showed significant increase in concentrations of small and very small LDL particles, very small HDL particles and apolipoprotein B. While EPA and DHA continued to increase during aging in women, no validated model for connecting age to FA profile was obtained for men. Women showed significant increase in concentrations of all subclasses of LDL particles during aging, while men exhibited a more complex pattern with increase also in apolipoprotein A1 and HDL particles.  相似文献   

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