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The Journal of Clinical Endocrinology & Metabolism Vol. 82, No. 11 3734-3740
Copyright © 1997 by The Endocrine Society

From the Clinical Research Centers

Abnormalities of Apolipoprotein E in the Acquired Immunodeficiency Syndrome1

Carl Grunfeld, William Doerrler, Miyin Pang, Peter Jensen, Karl H. Weisgraber and Kenneth R. Feingold

Departments of Medicine and Pathology and the Cardiovascular Research Institute, University of California, San Francisco, the Gladstone Institute of Cardiovascular Disease and the Metabolism and Infectious Diseases Sections, Department of Veterans Affairs Medical Center, San Francisco, California 94121

Address all correspondence and requests for reprints to: Carl Grunfeld, M.D., Ph.D., Metabolism Section (111F), Department of Veterans Affairs Medical Center, 4150 Clement Street, San Francisco, California 94121.


   Abstract
Top
 Abstract
Introduction
 Subjects and Methods
 Results
 Discussion
 References
 
Given the important role of apolipoprotein E (apoE) in triglyceride metabolism, we analyzed plasma levels and degree of sialylation of apoE in subjects with the acquired immunodeficiency syndrome (AIDS), a disorder accompanied by hypertriglyceridemia. Levels of apoE were significantly increased (1.84-fold) and correlated with plasma triglycerides (r = .663, P < .001) in AIDS. Subjects with AIDS and the apoE3/E2 phenotype showed the most prominent increases in both plasma triglyceride and apoE levels (3.4 and 2.2-fold over controls). Additionally, apoE from subjects with AIDS showed an increased amount of sialylation, compared with controls (34% increase in apoE3/E3 subjects). Increased sialylation correlated with the increase in apoE levels. In contrast, there was no increase in sialylation of apo C-III in AIDS. Thus, triglyceride levels in AIDS are influenced by apoE subtype and subjects with AIDS show changes in apoE structure.


   Introduction
Top
 Abstract
 Introduction
Subjects and Methods
 Results
 Discussion
 References
 
HUMAN apolipoprotein E (apoE) is a polypeptide of 299 amino acids with a calculated molecular mass of 34,000 Da (1). The protein is polymorphic, as the consequence of three major alleles, resulting in three major isoforms (apoE4, apoE3, and apoE2) that differ in their arginine and cysteine content (2, 3). In addition, minor, more acid isoforms arise as a product of posttranslational modification, i.e. varying degrees of sialylation of the major isoforms (2). apoE associates with very-low-density lipoprotein (VLDL), chylomicrons remnants, and one subspecies of high-density apoprotein (4). Lipoproteins containing apoE can bind to the low-density lipoprotein (LDL) receptor or the LDL receptor-related protein that may be important for clearance of remnant particles (5, 6, 7, 8, 9); receptor-related protein also is the receptor for {alpha}-2 macroglobulin, an acute-phase response protein (10).

Type III hyperlipidemia, or dysbetalipoproteinemia, a disorder characterized by accumulation of remnant particles, with resulting elevations of both plasma cholesterol and triglycerides, occurs in subjects homozygous for apoE2; which has defective receptor binding caused by the presence of a cysteine at residue 158 (1, 4, 8). However, the frequency of subjects homozygous for apoE2 in the general population is much higher (approximately 1 in 100) than the frequency of Type III hyperlipoproteinemia, suggesting that environmental influences (or other genetic factors) contribute to the appearance of dysbetalipoproteinemia (4).

In contrast to dysbetalipoproteinemia, other disorders associated with increased plasma triglycerides do not always show marked elevations of apoE levels (11, 12). For example, treatment with contraceptive drugs or estrogens raises plasma triglycerides but lowers apoE levels (12). In contrast, in diabetes mellitus with hypertriglyceridemia, apoE levels are increased, compared with controls, and even with nondiabetic hypertriglyceridemic patients (13, 14, 15). Genetic apoE polymorphism contributes to the hypertriglyceridemia of uncontrolled diabetes (14, 15, 16, 17, 18, 19, 20, 21). Hypertriglyceridemia is more common in diabetic individuals with the apoE3/E2 phenotype (14, 18). In nondiabetics, the presence of apoE2 is associated with delayed triglyceride clearance (22, 23, 24).

In contrast, the physiological effects of posttranslational modifications of apoE, such as sialylation, are not yet understood. Several reports have found that an increase in more heavily sialylated forms may occur in diabetes and/or renal failure but not in nondiabetic hypertriglyceridemic patients with normal renal function (15, 16, 17, 18, 25). It is of note that diabetes is accompanied by increased circulating levels of cytokines and acute-phase response proteins, such as {alpha}-2 macroglobulin (26, 27, 28, 29, 30, 31).

The acquired immunodeficiency syndrome (AIDS) is characterized by hypertriglyceridemia and decreases in plasma cholesterol levels (32, 33, 34). The increase in plasma triglyceride levels occurs late in the course of infection with the human immunodeficiency virus (HIV), at the time that AIDS develops (32, 34). The increased triglycerides are accounted for by increases in VLDL of normal composition (32, 34). AIDS is accompanied by increased levels of cytokines and acute-phase response proteins. Indeed, the increase in plasma triglycerides is thought to be caused by increased circulating levels of interferon {alpha} (33, 34), a cytokine that has been shown to modulate triglyceride metabolism in vitro and in vivo (35, 36). In the present study, we determined whether, in AIDS, apoE subtype also influences the degree of hypertriglyceridemia; whether apoE levels are increased in parallel to the increase in plasma triglyceride; and whether the amount of sialylated forms of apoE is increased.


   Subjects and Methods
Top
 Abstract
 Introduction
 Subjects and Methods
Results
 Discussion
 References
 
Patients

This study was approved by the Committee on Human Research, University of California, San Francisco. Eighteen subjects with AIDS, as defined by the revised Centers for Disease Control Criteria (37), and 16 controls who had no evidence of HIV infection, as determined by the absence of antibodies against HIV, were studied. Plasma samples for measurements were drawn after a 14-h overnight fast, observed during an in-patient admission to a metabolic ward at the San Francisco Veterans Affairs Medical Center. Many of these subjects have had details of other aspects of their lipid and lipoprotein levels published previously (34).

Analytical methods

Triglycerides were analyzed enzymatically with reagents from WAKO Pure Chemical Industries, Ltd. (Richmond, VA). Cholesterol was measured by the cholesterol oxidase technique with reagents from Sigma Chemical Co. (St. Louis, MO). Interferon {alpha} levels were measured as previously described (33, 34).

ApoE levels were measured by modification of an RIA that has been previously described in detail (38). In brief, purified apoE (10 ng/200 µL) was incubated in Immulon Removawell polystyrene 96-well plates (Dynatech Labs Inc., Chantilly, VA) overnight at 4 C. Nonspecific binding was then blocked with 10% FBS in PBS for 4 h at 4 C. A 1:1 mixture of diluted plasma samples or apoE standards and rabbit antihuman apoE (1:10,000 final dilution) was then added to each well, and the plates were incubated overnight at 4 C. The wells were washed with PBS containing 0.025% Tween-20, then incubated with (200,000 cpm/200 µL) 125I goat antirabbit IgG (NEN, Boston, MA) for 4 h at 4 C. Plates were then washed in PBS with Tween. Given variations in the absolute levels of apoE measured by this, all samples were run simultaneously in the same assay and normalized to a standard plasma sample.

Gel electrophoresis of apolipoproteins

Plasma (10 µl) was lyophylized and delipidated with chloroform methanol (2:1). The protein pellet was centrifuged and dried, then dissolved in 6 M urea containing 20% sucrose, 2% ß-mercaptoethanol, 1% decyl sulfate, and 0.1 M Tris HCl at pH 10.

For removal of sialic acid, 10-µL samples were treated twice sequentially with 40 µL 0.1 N ammonium acetate (pH 6.0), containing 0.2 U neuraminidase (Sigma), for 2 h at 37°, which was adequate to eliminate all of the minor isoforms that are a result of sialylation. Samples were then treated as above.

Isoelectric focusing was performed on 5% polyacrylamide gels containing 8 M urea and 2% ampholines, pH 4–6 (LKB-Pharmacia, Piscataway, NJ), as previously described (39). For two-dimensional (2-D) gel analysis, each subject’s lane was excised from the isoelectric focusing gel and run on a 10–20% denaturing polyacrylamide gel system (39).

Immunoblotting was performed on either 1-D isoelectric focusing gels or 2-D gels. Proteins were transferred from those gels to nitrocellulose (Schleicher and Schuell, Keene, NH) by electrophoresis (40). After blocking remaining binding sites with 5% nonfat dry milk, the nitrocellulose was blotted with an IgG fraction of a rabbit polyclonal antibody to human apoE or apo C III. The blot was developed using 125I-labeled goat antirabbit IgG from New England Nuclear (Boston, MA) and exposed using Kodak XAR x-ray film (Eastman Kodak, Rochester, NY). For quantitative analysis, 1-D gel bands were cut from the nitrocellulose and counted in a {gamma} counter.

Statistics

Values are presented as mean ± SE. Means for control and AIDS were compared using the Student’s t test. Comparisons among apoE phenotypes were done using ANOVA. Correlations were performed by linear regression analysis.


   Results
Top
 Abstract
 Introduction
 Subjects and Methods
 Results
Discussion
 References
 
The distribution of apoE phenotype was similar in AIDS and controls (Table 1Go). As found previously (32, 34), plasma triglyceride levels were nearly doubled (1.86-fold increased) in subjects with AIDS, compared with controls, whereas plasma cholesterol was decreased in AIDS (Table 1Go). In addition, we found an elevation of plasma apoE levels of a similar magnitude (1.84-fold) to the increase in triglycerides (Table 1Go).


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  		Table 1. Plasma APO E and triglyceride levels in AIDS and controls

 
Although the numbers within some phenotypes are too small for complete statistical analysis, certain trends appear. The increase in triglycerides is greater in the subjects with AIDS and the apoE3/E2 phenotype, compared with the appropriate genotypic controls, than in AIDS subjects with the apoE3/3 or 4/3 phenotypes (3.4-fold for apoE3/E2, 1.6-fold for apoE3/E3, 1.4-fold for apoE4/E3, for AIDS vs. controls). apoE levels also tend to be increased most in AIDS subjects with the apoE3/E2 phenotype (2.2-, 1.8-, and 1.4-fold, respectively). In controls, cholesterol levels were lower in the apoE3/E2 phenotype than in the other phenotypes, as expected. In contrast, cholesterol levels were higher in subjects with AIDS and the apoE3/E2 phenotype, because the increase in VLDL significantly contributes to plasma cholesterol in AIDS (34).

There was a highly significant correlation (r = .663, P < .001) between apoE levels and triglyceride levels (Fig. 1Go). When the values for subjects with AIDS were analyzed separately, the r-value was .624 (P < .01). There was no correlation between apoE levels and triglycerides within controls [r = .225, not significant (n.s.)]. The increase in triglycerides in AIDS is thought to be caused by increased circulating levels of interferon {alpha}, a cytokine that has been shown to regulate lipid metabolism in vitro and in vivo (33, 34, 35, 36). The correlation between apoE and interferon {alpha} was weaker (r = .333, n.s., data not shown) than that between apoE and triglycerides. There also was no correlation between apoE levels and plasma cholesterol in AIDS (r = .306, n.s.) or controls (r = .203, n.s.).



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  		Figure 1. Correlation between plasma levels of apoE and triglycerides. apo E was determined by specific RIA, and triglycerides by enzymatic analysis, as described under Subjects and Methods. {square}, controls; {circ}, AIDS. Linear regression analysis for all samples gave r = .663, P < .001. For AIDS alone, r = .624, P < .01. For controls alone, r = .225, n.s.

 
Plasma from controls and subjects with AIDS and the apoE3/E3 genotype were analyzed by Western blots of isoelectric focusing gels. As shown in Fig. 2Go (lower panel), after neuraminidase treatment, all of these controls and subjects with AIDS had a single band migrating in the E3 location (band 3 in figure). When apoE from control subjects with the apoE3/E3 phenotype is analyzed without neuraminidase treatment, band 32 is the most prominent band with the sialylated forms (bands 2 and 1) being less prominent (Fig. 2Go, upper panel, left). In contrast, in the subjects with AIDS, the sialylated forms are much more prominent (Fig. 2Go, upper panel, right); in fact the E2 band was so prominent that these subjects could be mistaken as having the apoE3/E2 phenotype when examined without neuraminidase treatment.



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  		Figure 2. Western blot of 1-D isoelectric focusing for apoE. Plasma samples were extracted and subjected to 1-D electrophoresis, followed by electrophoretic transfer and immunoblotting, as described under Subjects and Methods (upper panel). The samples represent three different controls (C) and subjects with AIDS (A). In the lower panel, the same samples were subjected to neuraminidase treatment before extraction and electrophoresis. Band 3 = apoE3 of the consensus nomenclature (28). Band 2 = apoE3S1 (or apoE2 in those subjects with apoE2), band 1 = apoE3S2 (28). S1 and S2 represent sialylation.

 
The increase in sialylation in AIDS was confirmed by 2-D gel electrophoresis. The increase in sialylated forms in apoE3/E3 can be seen when apoE from two subjects with AIDS (Fig. 3Go, b and c) are compared with control (Fig. 3aGo). The sialylated forms in AIDS are completely eliminated by neuraminidase treatment (compare Fig. 3dGo with Fig. 3Go, b and c).



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  		Figure 3. 2-D analysis of apoE3/3 isoforms. Serum samples were extracted and subjected to SDS PAGE in the first dimension and isoelectric focusing in the second dimension. The proteins were then electrophoretically transferred and analyzed by immunoblotting. a, Control; b, AIDS; c, AIDS; d, sample from a patient with AIDS (c) treated with neuraminidase before extraction and electrophoresis. Band 3 = apoE3, band 2 = apoE3S1, and band 1 = apoE3S2 of the consensus nomenclature (28)

 
Western blots of 1-D isoelectric focusing gels of 8 controls and 8 subjects with AIDS who had the apoE3/E3 phenotype were quantitated by {gamma} counting. A significant 34% increase in total sialylated forms of apoE3/E3 was seen in patients with AIDS, with a corresponding decrease in the unsialylated form. There was a significant correlation (r = .650, P < .01) between the level of apoE and percentage of sialylation in subjects with the apoE3/E3 phenotype (Fig. 4Go). For subjects with AIDS alone, the correlation was not as significant (r = .652, P < .1); there was no significant correlation within the controls (r = .197, n.s.).



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  		Figure 4. Correlation between percent sialylation and apoE levels in subjects with apo E3/3 genotype. Percent sialylation was determined from immunoblots of 1-D isoelectric focusing; and apo E levels, by specific RIA. {square}, Control; {circ}, AIDS. Linear regression analysis of all samples gave an r = .650, P < .01. For AIDS alone, r = .652, P < .1. For controls, r = .197, n.s.

 
A similar increase in sialylation was found in AIDS subjects with the apoE3/E2 genotype when analyzed by 2D gel electrophoresis and immunoblotting. In these subjects, neuraminidase treatment yields two bands (one consistent with apoE3 and another consistent with apoE2; Fig. 5cGo). Increased sialylated forms can be seen in a patient with AIDS (Fig. 5bGo) vs. a control (Fig. 5aGo). Because apoE2 has a pI that is identical to the monosialylated form of apoE3 on isoelectric focusing, it was not possible to quantify percent sialylation in subjects with the apoE3/E2 phenotype, as was done for those with apoE3/E3. Likewise, it was not possible to quantify sialylation in subjects with the apoE4/E3 phenotype.



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  		Figure 5. 2-D gel electrophoresis of samples from subjects with the apoE3/E2 genotypes. Samples were prepared as for Fig. 3Go. A, Control; B, AIDS without neuraminidase treatment; C, AIDS with neuraminidase treatment before electrophoresis. E3 and E2 identify the unsialylated forms of apoE3 and apoE2. apoE3S1 also runs with apoE3.

 
An increase in sialylation was not found for apolipoprotein C III, which also circulates in mono- and disialylated forms. A typical variable pattern in sialylation was seen in apo C-III, with no distinct increase or decrease in AIDS vs. controls (Fig. 6Go).



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  		Figure 6. Analysis of apo CIII. Plasma samples were treated with neuraminidase where indicated (+), extracted, and subjected to a 1-D isoelectric focussing, followed by immunoblotting for apo CIII. C, Control; A, AIDS. neuraminidase treatment (+) gives a single unsialylated band. Without neuraminidase (-), mono- and disialylated forms occur with no differences between AIDS and controls.

 

   Discussion
Top
 Abstract
 Introduction
 Subjects and Methods
 Results
 Discussion
References
 
We have previously reported that during the course of HIV infection, triglycerides begin to rise at the time of transition to AIDS, when the body responds to increasing viral burden from HIV with increased circulating interferon {alpha} (33, 34). Studies in animals and in vitro models suggest that interferon {alpha} can modulate triglyceride metabolism at multiple steps (35, 36).

We have now shown that the most marked elevations in triglycerides were found in patients with AIDS and the apoE3/E2 phenotype. These data are similar to those in patients with diabetes mellitus, where the presence of the apoE2 isoform is more likely to lead to hypertriglyceridemia (14, 18).

Additionally, we have demonstrated that levels of apoE were significantly elevated in proportion to levels of plasma triglycerides in AIDS. In parallel, an increase in sialylation of apoE was seen. In AIDS, the elevation in triglycerides is caused by VLDL of normal composition (32, 34). In diabetes with hypertriglyceridemia, apoE levels also are elevated (14, 18); in contrast, other forms of hypertriglyceridemia (nondiabetic, not infection related) are not inevitably accompanied by increases in apoE levels (11, 12).

An increase in levels of the sialylated forms of apoE was found in AIDS. Increases in the more acidic sialylated forms of apoE have been found in diabetes and renal failure (15, 16, 17, 18, 25). Increased acidic isoforms of apoE are not found in other forms of hypertriglyceridemia (14, 18, 25). The increased sialylation of apoE in AIDS is specific; we did not find an increase in sialylation of apo C-III. In contrast, excessively sialylated apo C-III is seen in other forms of severe hypertriglyceridemia and in chronic renal failure (25, 41). The extent of sialylation of apo C-III correlates with the residence time of nascent VLDL in the Golgi body (42).

The origin of the increased sialylation of apoE in AIDS is not yet understood. In animals, cholesterol feeding can cause increased secretion of highly sialylated apoE from perfused liver (43). Recent studies of patients undergoing liver transplantation indicate that greater than 90% of apoE in the circulation of humans is derived from the liver (44, 45), as the apoE isoform reflects that of the donor liver. However, examination of the small amounts of circulating apoE that retain the phenotype of the recipient (and therefore, are produced by extra hepatic tissues) revealed much more intense sialylation. Thus, it is possible that the increase in sialylated apoE in AIDS is caused by extra hepatic apoE. Of note, macrophages are known to produce apoE (46, 47), and macrophages are infected by HIV (48). Macrophage activation also may occur in diabetes mellitus, caused by the presence of advanced glycosylation end products (49).

Another possible explanation is that the increase in both apoE and sialylation of apoE in AIDS originates in the liver. The body’s response to infection includes changes in the hepatic production of proteins that have been termed the acute-phase response and are mediated by cytokines (50, 51, 52, 53, 54). Certain acute-phase response proteins show increased glycosylation in addition to increased circulating levels; in vitro treatment of cultured hepatocytes with cytokines can directly increase the glycosylation of those proteins (55, 56, 57). Increased circulating cytokines and activation of the acute-phase response have been reported in both AIDS (32, 34) and diabetes (26, 27, 28, 29, 30, 31).

Lastly, cultured fetal hepatocytes and hepatoma cells secrete apoE in a more highly sialylated form than is seen circulating in plasma (58, 59). If peripheral desialylation occurs, it is possible that defects in this processing occur in AIDS. However, when labeled purified sialylated apoE is infused into humans, no apparent desialylation occurs (60).

There is, at this time, no evidence that sialylation affects the function or kinetics of apoE. Excess sialylation of other plasma proteins does alter their functional properties. Changes in sialylation of T4-binding globulin, fibrinogen, or TSH affect their clearance and/or biological activity (61, 62, 63). Decreases in the glycosylation of TSH are induced by cytokines (64). Such studies raise the possibility that changes in sialylation of apoE may affect its function and thus contribute to the disturbances in lipid metabolism seen in AIDS. One early study suggested that particles containing acidic forms of apoE were metabolized less effectively (65), but this work preceded the recognition of the complexity of the genetic variations and posttranslational modifications of apoE. More recent work suggests that sialylation has no effect on apoE kinetics (61) or receptor binding (66).

Finally, it should be pointed out that the role of increased circulating triglycerides in AIDS and other infections is not yet understood. Rather than being deliterious, the elevation in circulating lipoproteins may represent, like the rest of the acute-phase response, part of host defense. Lipoproteins have been shown to prevent endotoxin-induced toxicity in vivo (67, 68, 69), as well as neutralize a variety of viruses (70, 71, 72, 73). Thus, it is important to understand how lipoproteins and apolipoproteins are modulated during pathological states, such as infection. The data reported here indicate that in at least one infection, AIDS, abnormalities are found in both the quantity and structure of apoE.


   Acknowledgments
 
We thank Lynne H. Shinto for technical advice and Pamela Herranz for editorial assistance.


   Footnotes
 
1 This work was supported by grants from the National Institutes of Health (DK-40990, DK-49448, and HL-41633); the AIDS Clinical Research Center of the University of California, San Francisco; and the Department of Veterans Affairs. Back

2 Band 3 = apoE3 of the consensus nomenclature (28 ). If apoE4 were present, band 3 also would contain apoE4S1. Likewise, band 2 represents either apoE2 or apoE3S1, whereas band 1 represents either apoE3S2 or apoE2S1 (28 ). Back

Received March 26, 1997.

Revised July 3, 1997.

Accepted July 11, 1997.


   References
Top
 Abstract
 Introduction
 Subjects and Methods
 Results
 Discussion
 References
 

  1. Rall Jr SC, Weisgraber KH, Mahley RW. 1982 Human apolipoprotein E: the complete amino acid sequence. J Biol Chem. 257:4171–4178.[Free Full Text]
  2. Zannis VI, Breslow JL. 1981 Human very low density lipoprotein apolipoprotein E isoprotein polymorphism is explained by genetic variation and posttranslational modification. Biochemistry. 20:1033–1041.[CrossRef][Medline]
  3. Weisgraber KH. 1994 Apolipoprotein E: structure-function relationships. Adv Protein Chem. 45:249–302.[Medline]
  4. Rall Jr SC, Mahley RW. 1989 Type III Hyperlipoproteinemia (Dysbetalipoproteinemia): the role of apolipoprotein E in normal and abnormal lipoprotein metabolism. In: Scriver CR, Beaudet AL, Sly WS, Vale D, eds. Metabolic basis of inherited disease. 6th ed. New York: McGraw Hill; 1195–1213.
  5. Herz J, Hamann U, Rogne S, Myklebost O, Gausepohl H, Stanley KK. 1988 Surface location and high affinity for calcium of a 500-kd liver membrane protein closely related to the LDL-receptor suggest a physiological role as lipoprotein receptor. EMBO J. 7:4119–4127.[Medline]
  6. Kowal RC, Herz J, Goldstein JL, Esser V, Brown M. 1989 Low density lipoprotein receptor-related protein mediates uptake of cholesteryl esters derived from apoprotein E-enriched lipoproteins. Proc Natl Acad Sci USA. 86:5810–5814.[Abstract/Free Full Text]
  7. Lund H, Takahashi K, Hamilton RL, Havel RJ. 1989 Lipoprotein binding and endosomal itinerary of the low density lipoprotein receptor-related protein in rat liver. Proc Natl Acad Sci USA. 86:9318–9322.[Abstract/Free Full Text]
  8. Weisgraber KH, Innerarity TL, Mahley RW. 1982 Abnormal lipoprotein receptor-binding activity of human E apoprotein due to cysteine-arginine interchange at a single site. J Biol Chem. 257:2518–2521.[Free Full Text]
  9. Hussain MM, Maxfield FR, Mas-Olivas J, et al. 1991 Clearance of chylomicron remnants by the low density lipoprotein receptor-related protein/a2-macroglobulin receptor. J Biol Chem. 266:13936–13940.[Abstract/Free Full Text]
  10. Strickland DK, Ashcom JD, Williams S, Burgess WH, Migliorini M, Argraves WS. 1990 Sequence identity between the alpha 2-macroglobulin receptor and low density lipoprotein receptor-related protein suggests that this molecule is a multifunctional receptor. J Biol Chem. 265:17401–17404.[Abstract/Free Full Text]
  11. Evans AJ, Huff MW, Wolfe BM. 1989 Accumulation of an apoE-poor subfraction of very low density lipoprotein in hypertriglyceridemic men. J Lipid Res. 30:1691–1701.[Abstract]
  12. Phillips NR, Havel RJ, Kane JP. 1983 Sex-related differences in the concentrations of apolipoprotein E in human blood plasma and plasma lipoproteins. J Lipid Res. 24:1525–1531.[Abstract]
  13. Weisweiler P, Drosner M, Schwandt P. 1982 Dietary effects on very low-density lipoproteins in Type 2 (non-insulin-dependent) diabetes mellitus. Diabetologia. 23:101–103.[CrossRef][Medline]
  14. Eto M, Watanabe K, Sata T, Makino I. 1989 Apolipoprotein-E2 and hyperlipoproteinemia in noninsulin-dependent diabetes mellitus. J Clin Endocrinol Metab. 69:1207–1212.[Abstract]
  15. Black SC, Hewett S, Kotubi Y, Brunt RV, Reckless JPD. 1990 Isoform patterns of apolipoprotein E in diabetes mellitus. Diabet Med. 7:532–539.[Medline]
  16. Weisweiler P, Jungst D, Schwandt P. 1983 Quantitation of apolipoprotein E-isoforms in diabetes mellitus. Horm Metabol Res. 15:201–201.[Medline]
  17. Sano R, Abe R, Oikawa S-I, Fujii Y, Toyota T. 1985 apoE-2/E-3 ratio of very low density lipoprotein in diabetes mellitus. Tohoku J Exp Med. 146:131–136.[Medline]
  18. Eto M, Watanabe K, Iwashima Y, et al. 1986 Apolipoprotein E polymorphism and hyperlipemia in Type II diabetics. Diabetes. 35:1374–1382.[Abstract]
  19. Winocour PH, Tetlow L, Durrington PN, Ishola M, Hillier V, Anderson DC. 1989 Apolipoprotein E polymorphism and lipoproteins in insulin-treated diabetes mellitus. Atherosclerosis. 75:167–173.[CrossRef][Medline]
  20. Eto M, Watanabe K, Makino I. 1991 Relationship of metabolic control and body weight to hypercholesterolemia in NIDDM patients with apolipoprotein E4. Diabetes Care. 14:127–129.[Abstract]
  21. Shriver MD, Boerwinkle E, Hewett-Emmett D, Hanis CL. 1991 Frequency and effects of apolipoprotein E polymorphism in Mexican-American NIDDM subjects. Diabetes. 40:334–337.[Abstract]
  22. Cortner JA, Coates PM, Ngoc-Anh L, et al. 1987 Kinetics of chylomicron remnant clearance in normal and in hyperlipoproteinemic subjects. J Lipid Res. 28:195–206.[Abstract]
  23. Renninkmeijer BJ, Stuyt PMJ, Demacker PNM, Stalenhoef AFH, van’t Laar A. 1987 Catabolism of chylomicron remnants in normolipidemic subjects in relation to the apoprotein E phenotype. J Lipid Res. 28:361–370.[Abstract]
  24. Weintraub MS, Eisenberg S, Breslow JL. 1987 Dietary fat clearance in normal subjects is regulated by genetic variation in apolipoprotein E. J Clin Invest. 80:1571–1577.
  25. Cassader M, Ruiu G, Gambino R, Alemanno N, Triolo G, Pagano G. 1989 Apolipoprotein C and E isoforms in diabetic uraemic patients. Diabetes Nutr Metab. 2:33–37.
  26. Hussein MJ, Peakman M, Leslie RDG, Viberti GC, Watkins PJ, Vergani D. 1991 Circulating levels of interleukin-1 alpha, tumor necrosis factor alpha and interferon gamma are high in newly diagnosed Type I diabetes. Diabetes. [Suppl 1]40:147A.
  27. Dasgupta B, Messent J, Corrigall V, Panaji G, Keen H. 1991 Interleukin-6 in insulin dependent diabetes mellitus. Diabetes. [Suppl 1]40:264A.
  28. Ganrot PO, Gydelli K, Ekelund H. 1967 Serum concentration of alpha 2-macroglobulin, haptoglobulin and alpha-1 antitrypsin in diabetes mellitus. Acta Endocrinol. 55:537–544.
  29. Johnsson A, Wales JK. 1976 Blood glycoprotein levels in diabetes mellitus. Diabetologia. 12:245–250.[CrossRef][Medline]
  30. McMillan DE. 1989 Increased levels of acute-phase serum proteins in diabetes. Metabolism. 38:1042–1046.[CrossRef][Medline]
  31. Ganda OM, Arkin CF. 1992 Hyperfibrinogenemia: an important risk factor for vascular complications in diabetes. Diabetes Care. 15:1245–1250.[Abstract]
  32. Grunfeld C, Kotler DP, Hamadeh R, Tierney A, Wang J, Pierson Jr RN. 1989 Hypertriglyceridemia in the acquired immunodeficiency syndrome. Am J Med. 86:27–31.[Medline]
  33. Grunfeld C, Kotler DP, Shigenaga JK, et al. 1991 Circulating interferon alpha levels and hypertriglyceridemia in the acquired immunodeficiency syndrome. Am J Med. 90:154–162.[Medline]
  34. Grunfeld C, Pang M, Doerrler W, Shigenaga JK, Jensen P, Feingold KR. 1992 Lipids, lipoproteins, triglyceride clearance and cytokines in human immunodeficiency virus infection and the acquired immunodeficiency syndrome. J Clin Endorinol Metab. 74:1045–1052.[Abstract]
  35. Patton JS, Shepard HM, Wilking H, et al. 1986 Interferons and tumor necrosis factors have similar catabolic effect on 3T3–L1 cells. Proc Natl Acad Sci USA. 83:8313–8317.[Abstract/Free Full Text]
  36. Feingold KR, Soued M, Serio MK, Moser AH, Dinarello CA, Grunfeld C. 1989 Multiple cytokines stimulate hepatic lipid synthesis in vivo. Endocrinology. 125:267–274.[Abstract]
  37. Centers for Disease Control. 1987 Revision of the CDC surveillance case definition for acquired immunodeficiency syndrome. MMWR Morb Mortal Wkly Rep. [Suppl 2S]36:3S–14S.
  38. Innerarity TL, Bersot TP, Arnold KS, et al. 1984 Receptor binding activity of high-density lipoproteins containing apoprotein E from abetalipoproteinemic and normal neonate plasma. Metabolism. 33:186–195.[CrossRef][Medline]
  39. Wardell MR, Rall Jr SC, Brennan SO, et al. 1990 Apolipoprotein E2-Dunedin (228 Arg->Cys): an apolipoprotein E2 variant with normal receptor-binding activity. J Lipid Res. 31:535–543.[Abstract]
  40. Towbin H, Staehelin T, Gordon J. 1979 Electrophoretic transfer of proteins from polyacrylamide gels to nitrocellulose sheets: procedure and some applications. Proc Natl Acad Sci USA. 76:4350–4354.[Abstract/Free Full Text]
  41. Holdsworth G, Stocks J, Dodson P, Galton DJ. 1982 An abnormal triglyceride-rich lipoprotein containing excess sialylated apolipoprotein C-III. J Clin Invest. 69:932–939.
  42. Nestruck AC, Rubinstein D. 1976 The synthesis of apoproteins of very low density lipoproteins isolated from the Golgi apparatus of rat liver. Can J Biochem. 54:617–628.[CrossRef][Medline]
  43. Guo LSS, Hamilton RL, Kane JP, Fielding CJ, Chen GC. 1982 Characterization and quantitation of apolipoproteins A-1 and E of normal and cholesterol-fed guinea pigs. J Lipid Res. 23:531–542.[Abstract]
  44. Kraft HG, Menzel HJ, Hoppichler F, Voge W, Utermann G. 1989 Changes of genetic apolipoprotein phenotypes caused by liver transplantation. Implications for apolipoprotein synthesis. J Clin Invest. 83:137–142.
  45. Linton MF, Gish R, Hubl ST, et al. 1991 Phenotypes of apolipoprotein B and apolipoprotein E after liver transplantation. J Clin Invest. 88:270–281.
  46. Basu SK, Brown MS, Ho YK, Havel RJ, Goldstein JL. 1981 Mouse macrophages synthesize and secrete a protein resembling apolipoprotein E. Proc Natl Acad Sci USA. 78:7545–7549.[Abstract/Free Full Text]
  47. Wang-Ivenson P, Gibson JC, Brown WV. 1985 Plasma apolipoprotein secretion by human monocyte-derived macrophages. Biochem Biophys Acta. 834:256–262.[Medline]
  48. Bowen DL, Lane HC, Fauci AS. 1985 Immunopathogenesis of the acquired immunodeficiency syndrome. Ann Intern Med. 102:704–709.
  49. Vlassara H, Brownlee M, Manogue KR, Dinarello CA, Pasagian A. 1988 Cachectin/TNF and IL-1 induced by glucose-modified proteins: role in normal tissue remodeling. Science. 240:1546–1548.[Abstract/Free Full Text]
  50. Kushner I. 1982 The phenomenon of the acute phase response. Ann NY Acad Sci. 389:39–48.[Medline]
  51. Perlmutter DH, Dinarello CA, Punsal PI, Colten HR. 1986 Cachectin/tumor necrosis factor regulates hepatic acute-phase gene expression. J Clin Invest. 78:1349–1354.
  52. Darlington GJ, Wilson DR, Lachman LB. 1987 Monocyte conditioned medium, interleukin-1 and tumor necrosis factor stimulate the acute phase response in human hepatoma cells in vitro. J Cell Biol. 103:787–793.[Abstract/Free Full Text]
  53. Castell JV, Gomez-Lechon MJ, David M, et al. 1989 Interleukin-6 is the major regulator of acute phase protein synthesis in adult human hepatocytes. FEBS Lett. 242:237–239.[CrossRef][Medline]
  54. Marinkovic S, Jahreis GP, Wong GG, Baumann H. 1989 IL-6 modulates the synthesis of a specific set of acute phase plasma proteins in vivo. J Immunol. 142:808–812.[Abstract]
  55. Mackiewicz A, Ganapathi MK, Schultz D, Kushner I. 1987 Monokines regulate glycosylation of acute phase proteins. J Exp Med. 166:253–258.[Abstract/Free Full Text]
  56. Mackiewicz A, Schultz D, Mathison J, Ganapathi MK, Kushner I. 1989 Effect of cytokines on glycosylation of acute phase proteins in human hepatoma cell lines. Clin Exp Immunol. 75:70–75.[Medline]
  57. Mackiewicz A, Kushner I. 1989 Interferon B2/BSF-2/IL-6 affects glycosylation of acute phase proteins in human hepatoma cell lines. Scand J Immunol. 29:265–271.[CrossRef][Medline]
  58. Zannis VI, Kurnit DM, Breslow JL. 1982 Hepatic apo-A-I and apo-E and intestinal apo-A-I are synthesized in precursor isoprotein forms by organ cultures of human fetal tissues. J Biol Chem. 257:536–544.[Free Full Text]
  59. Zannis VI, McPherson J, Goldberg G, Karathanasis SK, Breslow JL. 1984 Synthesis, intracellular processing, and signal peptide of human apolipoprotein E. J Biol Chem. 259:5495–5499.[Abstract/Free Full Text]
  60. Ghiselli G, Beigel Y, Soma M, Gotto Jr AM. 1986 Plasma catabolism of human apolipoprotein E isoproteins: lack of conversion of the doubly sialylated form to the asialo form in plasma. Metabolism. 35:399–403.[CrossRef][Medline]
  61. Ain KB, Mori Y, Refetoff S. 1987 Reduced clearance rate of thyroxine-binding globulin (TBG) with increased sialylation: a mechanism for estrogen-induced elevation of serum TBG concentration. J Clin Endocrinol Metab. 65:689–696.[Abstract]
  62. Refetoff S, Fang VS, Marshall JS. 1975 Studies on human thyroxine-binding globulin (TBG). J Clin Invest. 56:177–187.
  63. Martinez J, Palascak JE, Kwasmak D. 1978 Abnormal sialic content of the dysfibrinogenemia associated with liver disease. J Clin Invest. 61:535–538.
  64. Pang X-P, Hershman JM, Mirell CJ, Pekary AE. 1989 Impairment of hypothalamic-pituitary-thyroid function in rats treated with human recombinant tumor necrosis factor-alpha (cachectin). Endocrinology. 125:76–84.[Abstract]
  65. Havel RJ, Chao Y-S, Windler EE, Kotite L, Guo LSS. 1980 Isoprotein specificity in the hepatic uptake of apolipoprotein E and the pathogenesis of familial dysbetalipoproteinemia. Proc Natl Acad Sci USA. 66:4349–4353.
  66. Rall SC, Weisgraber KH, Innerarity TL, Mahley RW. 1985 The carbohydrate moiety of human plasma apolipoprotein E. Circulation. 72:111–143 (Abstract).
  67. Ulevitch RJ, Johnston AR, Weinstein DB. 1979 New function for high density lipoproteins. Their participation in intravascular reactions of bacterial lipopolysaccharides. J Clin Invest. 64:1516–1524.
  68. Harris HW, Grunfeld C, Feingold KR, Rapp JH. 1990 Human VLDL and chylomicrons can protect against endotoxin-induced death in mice. J Clin Invest. 86:696–792.
  69. Harris HW, Grunfeld C, Feingold KR, et al. 1993 Chylomicrons alter the fate of endotoxin, decreasing tumo rnecrosis factor release and preventing death. J Clin Invest. 91:1028–1034.
  70. Sernatinger J, Hoffman A, Harman D, Kane JP, Levy JA. 1988 Neutralization of mouse xenotropic virus by lipoproteins involves binding to the virions. J Gen Virol. 69:2651–2661.
  71. Chisari FV, Curtiss LK, Jensen FC. 1981 Physiologic concentrations of normal human plasma lipoproteins inhibit the immortalization of peripheral B lymphocytes by the Epstein-Barr virus. J Clin Invest. 68:329–336.
  72. Shortridge KF, Ho WK, Oya A, Kobayashi M. 1975 Studies on the inhibitory activities of human serum lipoproteins for Japanese encephalitis virus. Southeast Asian J Trop Med Pub Health. 6:461–466.[Medline]
  73. Seganti L, Grass M, Mastromarino P, Pan’a A, Superti F, Orsi N. 1983 Activity of human serum lipoproteins on the infectivity of rhabdoviruses. Microbiology. 6:91–99.



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