This Article Abstract Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Chappey, B. Articles by Moatti, N. Search for Related Content PubMed PubMed Citation Articles by Chappey, B. Articles by Moatti, N.

(Arteriosclerosis, Thrombosis, and Vascular Biology. 1995;15:334-339.)
© 1995 American Heart Association, Inc.

Articles

Evaluation of the Sialic Acid Content of LDL as a Marker of Coronary Calcification and Extracoronary Atherosclerosis in Asymptomatic Hypercholesterolemic Subjects

B. Chappey; I. Myara; P. Giral; G. Kerharo; M.C. Plainfosse; J. Levenson; A. Simon; N. Moatti; and the PCVMETRA Group

From the Laboratoire de Biochimie, Faculté des Sciences Pharmaceutiques et Biologiques, Chatenay-Malabry (B.C., I.M., N.M.); and the Départements de Biochimie (B.C., I.M., G.K., N.M.) and Radiologie (M.C.P) and the Centre de Medecine Préventive Cardiovasculaire et INSERM U 28 (P.G., J.L., A.S.), Hôpital Broussais, Paris, France.

Correspondence to Dr Isaac Myara, Laboratoire de Biochimie, Appliquée (tour D4, 2ème étage), Faculté des Sciences Pharmaceutiques et Biologiques, 5 Rue JB Clément, 92296 Chatenay-Malabry, France.

	Abstract

Top Abstract Introduction Methods Results Discussion Appendix 1 References

 
Abstract Recent studies have shown that the sialic acid content of LDL isolated from patients with angiographically demonstrated advanced coronary atherosclerosis is lower than that of LDL isolated from healthy subjects. These observations raise the question as to whether LDL sialic acid content could be used as an early marker of atherosclerosis. We screened for carotid, aortic, and femoral plaques by ultrasonography and for coronary calcifications by ultrafast computed tomography in 160 hypercholesterolemic subjects free of cardiovascular disease to investigate the relation between LDL sialic acid content and the prevalence of these early atherosclerotic lesions. LDL sialic acid values varied from 19.6 to 46.6 nmol/mg LDL protein (33.9±4.4, mean±SD) in the whole population, but the distribution was very similar: (1) in subjects with no plaque (34.1±4.9) relative to those with one or several plaques at one (34.2±4.4), two (33.0±3.6), or three (34.8±3.4) different arterial sites; (2) in subjects with (33.9±3.7) and without (34.1±4.8) coronary calcification; and (3) in subjects with both extracoronary and coronary lesions (33.8±3.9) relative to those with no arterial lesions (34.2±4.5). LDL sialic acid content was not related to sex, age, body mass index, smoking, blood pressure, or serum total cholesterol and lipoprotein(a) levels but correlated negatively with serum triglyceride levels (P<.001). These results suggest that LDL sialic acid content is not a discriminant marker of early atherosclerosis in asymptomatic hypercholesterolemic subjects.

Key Words: low-density lipoproteins • sialic acid • atherosclerosis • B-mode ultrasonography • ultrafast computed tomography

	Introduction

Top Abstract Introduction Methods Results Discussion Appendix 1 References

 
Reliable markers of atherosclerosis are necessary for effective cardiovascular disease prevention. A recent study proposed the sialic acid content of serum as a predictor of cardiovascular mortality.¹ However, numerous noncardiovascular diseases^{2 3} such as cancer, inflammatory diseases, chronic liver and kidney diseases, and bacterial infections also increase serum sialic acid concentrations, and the strong positive correlation with serum 1-antitrypsin, orosomucoid, and haptoglobin^{1 2 3} suggests that serum sialic acid reflects only an acute-phase protein response with limited specificity. Other investigators examined the sialic acid content of LDL,^{4 5 6 7 8} which is the main cholesterol-carrying lipoprotein in plasma and is considered atherogenic.^{9 10} Recently, Orekhov et al^{4 5} and Ruelland et al⁶ reported that the sialic acid content of total LDL isolated from patients with angiographically assessed advanced coronary atherosclerosis was lower than that of healthy subjects. These observations raise the question as to whether LDL sialic acid content can be used as an early marker of atherosclerosis. Currently, subclinical atherosclerosis can be assessed in asymptomatic subjects: high-resolution B-mode ultrasonography is a noninvasive method for detecting medium-sized atherosclerotic plaques at the different arterial locations most frequently involved such as the extracranial carotid arteries, abdominal aorta, and upper femoral arteries.^{11 12 13 14 15 16} Ultrafast computed tomography was proposed recently for noninvasive quantification of coronary calcifications,^{17 18 19 20 21} and the use of this method to detect early coronary atherosclerosis has been validated by angiographic and necropsy studies.^{21 22 23 24} We previously described associations of arterial^{13 14 25 26} and coronary²⁰ lesions with other traditional risk factors and associations of arterial lesions with coronary calcifications.²⁰ The purpose of this study was to examine LDL sialic acid concentrations in hypercholesterolemic subjects free of previous or current clinical symptoms of cardiovascular disease to investigate the possible relation between LDL sialic acid content and the presence of early extracoronary and/or coronary atherosclerosis.

	Methods

Top Abstract Introduction Methods Results Discussion Appendix 1 References

 
Study Subjects
The 160 hypercholesterolemic subjects included in the study were selected from an ongoing cholesterol screening program in occupational medicine conducted within the Paris area.^{13 14 20 26} All the subjects were nondiabetic, had blood total cholesterol above 6.2 mmol/L and triglycerides below 4.5 mmol/L, and had never been treated with lipid-lowering drugs. In each case, the presence of any history or symptom of cardiovascular disease, checked by a complete clinical examination and careful questioning, resulted in exclusion from the study. None of the subjects had ever undergone coronary investigations. Nonlipid risk factor evaluation was made as follows. Systemic blood pressure was determined as previously described.²⁵ Hypertension was defined by a systolic blood pressure of 160 mm Hg or more (Korotkoff phase V) and/or a diastolic pressure of 95 mm Hg or more (Korotkoff phase V).²⁷ The body mass index (weight per height squared) was used to evaluate overweight.^{13 14} Lifelong smoking dose (pack-years)¹⁴ was assessed by questioning of the subject.

Analytical Methods
Venous blood was collected after the subjects had fasted for 14 hours, and serum was immediately separated by low-speed centrifugation for 20 minutes at 15°C. LDL (d, 1.019 to 1.063 g/mL) was isolated by sequential ultracentrifugation in a Beckman L90 ultracentrifuge (Beckman Instruments Inc). Serum (8 mL) was adjusted to a density of 1.019 g/mL with solid KBr and centrifuged at 90 000 rpm for 2 hours at 4°C in a Beckman NVT 90 rotor. The top fraction and the intermediate clear region were removed, and the infranatant was adjusted to a density of 1.063 g/mL with solid KBr and then centrifuged in the same conditions. The supernatant LDL was collected and dialyzed for 24 hours at 4°C against four changes of 100 volumes of 10 mmol/L Tris-HCl buffer, pH 7.4, containing 1 mmol/L EDTA. LDL was stored at 4°C in the dark. The purity of LDL preparations was checked by agarose gel electrophoresis.

Total LDL sialic acid content was determined on 250 µg LDL protein in 500 µL. Before the assay, bound sialic acid was released from sialoglycoconjugates by mild hydrolysis (15 minutes at 80°C in 0.05 mol/L H₂SO₄). In these hydrolysis conditions, all sialic acid was released and less than 5% of sialic acid was destroyed. Warren's periodate-thiobarbituric acid (TBA) assay²⁸ was used. A standard curve was constructed using N-acetylneuraminic acid (Ref A2388, Sigma Chemical Co) treated in the same conditions. The assay was linear from 0 to 150 µmol/L. Values are means of duplicate assays, and the within-assay coefficient of variation was below 5%. The potential interference of malondialdehyde (MDA) was examined, and only a slight interference (<5%) was observed with MDA concentrations below 2 nmol/mg LDL protein. In our experimental conditions, MDA concentrations in LDL were below 1 nmol/mg protein. After colorimetric reaction with TBA, the LDL spectrum was very close to that of the sialic acid standard. LDL sialic acid content was also determined according to a recently described chromatographic method that used fluorometric detection.²⁹ Results obtained by the two methods correlated strongly (r=.85). Total LDL protein was measured with the method of Peterson et al³⁰ with bovine serum albumin as the standard.

Lipoprotein(a) [Lp(a)] concentrations were determined in serum and LDL preparations by a noncompetitive enzyme-linked immunosorbent assay with a Biomeck 1000 analyzer (Beckman). Monoclonal antibodies used for antigen capture and conjugated monoclonal antibodies for antigen detection were from Biosys. Serum lipids (total cholesterol, triglycerides, HDL cholesterol, and LDL cholesterol) were routinely determined as previously described.^{13 14 20 26}

Detection of Extracoronary Plaques and Coronary Artery Calcifications
Arterial investigations were performed with real-time B-mode ultrasonography (Ultramark 4, Advanced Technology) with a 3.75-MHz probe for the abdominal aorta and a 7.5-MHz probe for the extracranial carotid and femoral arteries according to a careful procedure previously described in detail.^{13 14 20} The minimal defining thickness of a plaque was 2 mm. At each of the three sites, data were classified into two categories: absence of any atherosclerotic plaque or presence of one or more arterial plaques, regardless of the precise location and number.

Coronary calcifications were detected as previously described²⁰ by use of an ultrafast computed tomography scanner (Imatron) with a 100-millisecond scan time, a 3-mm slice thickness, and electrocardiogram triggering. The threshold for a calcific lesion was set at a computed tomographic density of 130 Hounsfield units^{18 31} with an area of 1 mm² or more.¹⁸ The maximal computed tomographic density of each lesion was transformed into four classes in the following manner: 1, 130 to 199; 2, 200 to 299; 3, 300 to 399; and 4, 400 Hounsfield units or more.¹⁸ The total calcium score was defined as the sum of the lesion scores, calculated by multiplying the density number by the area of the lesions.¹⁸

Statistical Analysis
The statistical analysis was carried out on a computer (Apple Macintosh) with JMP (SAS Institute) and STAT VIEW II (Abacus Concepts, Inc) software. Pearson's correlation coefficients were used to describe relations between LDL sialic acid content and quantitative normal variables, and Spearman's correlation coefficients were used for nonnormal quantitative variables. Univariate comparisons of LDL sialic acid content were performed with a t test according to the presence or absence of plaque or coronary calcifications and with ANOVA according to the number of diseased sites. Qualitative variables were compared by the ² test. Spearman's correlation coefficients were used for the total calcium score because of the skewed distribution of the scores. Probability values <.05 were considered significant.

	Results

Top Abstract Introduction Methods Results Discussion Appendix 1 References

 
Table 1 details the characteristics of the 134 men and 26 women, 30 to 65 years of age.

View this table: [in this window] [in a new window]   Table 1. Characteristics of the Study Population

Table 2 shows the prevalence of coronary calcifications and arterial plaques in the study population: 43% had no coronary calcification (total calcium score, 0) and 41% had no extracoronary plaque. In addition, 22% of the study population had neither coronary calcification nor arterial plaque, whereas 40% had both coronary and extracoronary lesions.

View this table: [in this window] [in a new window]   Table 2. Coronary Calcifications and Extracoronary Plaques in the Study Population

Fig 1 shows the frequency distribution of LDL sialic acid content in the study group. The distribution was bell-shaped, ranging from 19.6 to 46.6 nmol/mg LDL protein, with a mean value of 33.9±4.4 nmol/mg LDL protein.

View larger version (16K): [in this window] [in a new window]   Figure 1. Bar graph shows frequency distribution of LDL sialic acid content among subjects in the study group.

Fig 2 compares LDL sialic acid content according to the absence or presence of extracoronary plaque at one, two, or three different arterial sites. No significant difference was found among these subgroups. No difference was found when each site (carotid, abdominal aortic, and femoral) was considered separately. In addition, the percentage of subjects with at least one arterial plaque associated with the highest quintile of LDL sialic acid content was not statistically different from that associated with the lowest quintile.

View larger version (18K): [in this window] [in a new window]   Figure 2. Graphs show individual values of LDL sialic acid content in subjects according to the distribution of arterial atherosclerotic plaques: 0 indicates no diseased site; 1, one diseased site; 2, two diseased sites; and 3, three diseased sites. At each site investigated (carotid, femoral, and aortic), arterial plaque was characterized as a dichotomous variable: absence (0) or presence (1) and comparisons among subgroups of subjects were performed by use of ANOVA as described in "Methods."

Fig 3 compares LDL sialic acid content according to the absence or presence of coronary calcification. No statistical difference was found between these two groups of subjects. Moreover, no correlation was found between LDL sialic acid content and the total calcium score with Spearman's rank test.

View larger version (16K): [in this window] [in a new window]   Figure 3. Graphs show individual values of LDL sialic acid content in subjects according to the absence (A) or presence (P) of coronary calcification. The presence of calcification was characterized by a total calcium score above zero. Comparisons among subgroups of subjects were performed by use of a t test as described in "Methods."

Table 3 compares mean LDL sialic acid content in four groups of subjects defined by the combined results of clinical investigations: coronary calcification (absence or presence) with or without extracoronary plaque. No statistical difference was found even between subjects with and without both coronary and extracoronary lesions.

View this table: [in this window] [in a new window]   Table 3. Comparison of LDL Sialic Acid Content of Subjects With and Without Extracoronary Plaque in Groups With and Without Coronary Calcification

As regards other variables, LDL sialic acid content was not related to sex, age, body mass index, blood pressure, smoking status, or blood total cholesterol. Among the lipid parameters, only the serum triglyceride level (Fig 4) correlated (negatively) with LDL sialic acid content (=-.36, P<.001, Spearman's rank test). This correlation disappeared when triglyceridemia was below 1.5 mmol/L. Lp(a), which is highly sialylated and has a density range overlapping that of LDL,³² was determined in LDL preparations to evaluate its possible interference with the LDL sialic acid level. A strong positive correlation was observed between serum Lp(a) and the percentage of Lp(a) present in LDL preparations (=.54, P=.0001, Spearman's rank test). However, LDL sialic acid content did not correlate with serum Lp(a) on the one hand or Lp(a) content of LDL preparations on the other hand.

View larger version (18K): [in this window] [in a new window]   Figure 4. Scatterplot shows LDL sialic acid values versus serum triglycerides. The coefficient of correlation ( =-.36) and the probability value (P<.001) were determined by use of Spearman's rank test.

	Discussion

Top Abstract Introduction Methods Results Discussion Appendix 1 References

 
Hypercholesterolemia is an important risk factor for atherosclerosis.^{9 10} However, the silent phase of disease development before the onset of clinical symptoms is difficult to identify, and the detection of early arterial lesions may be important for cardiovascular prevention. High-resolution B-mode ultrasonography and ultrafast computed tomography were used to assess clinical presymptomatic stages of extracoronary and coronary atherosclerosis, respectively, in hypercholesterolemic subjects exempt of clinical symptoms, history, and physical signs of cardiovascular disease. Ultrasound detection of atherosclerotic plaque in the carotid, abdominal aortic, and femoral arteries showed that a majority (60%) of the study population had extracoronary plaque, with a higher prevalence of femoral lesions. These observations are in keeping with our previous reports^{14 20} and may be related to the fact that femoral plaques are influenced by most risk factors, ie, age, blood pressure, lifelong smoking, and lipid levels.^{14 24 33} In addition, the low prevalence of carotid plaques may be related to the inclusion of women, in whom the carotid site is less frequently diseased than other arterial sites.³⁴ A relatively high prevalence (57%) of coronary calcifications was found in our population, and this also agrees with our previous observations.²⁰ As regards the number of extracoronary diseased sites, the low prevalence of three-site disease indicates that only a minority of subjects had extensive extracoronary atherosclerosis. By contrast, 40% of the population had both coronary and extracoronary lesions, whereas only 22% had neither coronary calcification nor arterial plaque. These results confirm recent observations by our group that show a close association between coronary calcifications and extracoronary plaques.²⁰

The main objective of this study was to examine in asymptomatic subjects LDL sialic acid content, which was recently described as a cardiovascular risk factor in symptomatic subjects.^{4 5 6} Sialic acid is a component of both protein and lipid moieties of LDL.^{5 7 8} Although the function of LDL carbohydrates remains unknown, several investigators observed that LDL sialic acid content may modulate receptor-mediated uptake of LDL.^{4 5 35 36} LDL sialic acid content also correlated negatively with the avidity of LDL for negatively charged arterial proteoglycans.³⁷ Binding of LDL to proteoglycans gives rise to soluble³⁸ or insoluble³⁷ complexes. LDL released from soluble complexes is structurally modified,³⁸ more susceptible to oxidation,³⁹ and efficiently taken up by macrophages.^{39 40} Insoluble complexes induce cholesterol accumulation in mouse macrophages.⁴¹ As regards clinical studies, Camejo et al⁴² showed that LDL with high reactivity for arterial proteoglycans was more frequently found in subjects with apparent ischemic heart disease. Recently, Orekhov et al^{4 5} showed that total LDL isolated from plasma of patients with angiographically assessed coronary artery disease (CAD) induced lipid accumulation in cells and had a sialic acid content 40% to 75% lower than that isolated from healthy donors. This was explained by a greater proportion of desialylated LDL in patients with CAD. More recently, Ruelland et al⁶ also found a difference in LDL sialic acid content between patients with CAD and healthy subjects but to a lesser extent (20% to 30%) than that reported by Orekhov's group. These last observations raise the question as to whether LDL sialic acid content could be used as an early marker of atherosclerosis. To the best of our knowledge, there is no information on LDL sialic acid content in subjects with subclinical atherosclerosis. In our study, the distribution of LDL sialic acid values was very similar in subjects with no plaque and in subjects with one or several plaques at one, two, or three different arterial sites. Because ultrasound peripheral plaques are probably early atherosclerotic lesions rather than coronary calcifications,²⁰ we also examined LDL sialic acid content in subjects with early coronary atherosclerosis. No difference was found between subjects with and without coronary calcification detected by ultrafast computed tomography. Moreover, even subjects with both extracoronary and coronary lesions had an LDL sialic acid content within the range of values in subjects with no arterial lesions. These results clearly indicate a lack of relation between LDL sialic acid content and the prevalence of peripheral plaques and/or coronary calcifications in our population. It is noteworthy that the decrease in LDL sialic acid content has been described only in patients with advanced coronary disease, ie, 50% stenosis or more in a main coronary artery.^{4 5 6} However, the very large difference observed by Orekov et al^{4 5} between the ranges of sialic acid values of healthy donors and patients with CAD predicted a lower LDL sialic acid content in subjects with coronary calcifications, at least to a lesser extent. Such a difference was all the more likely because several angiographic studies showed the predictive power of ultrafast computed tomography screening.^{17 21 24} Indeed, while the negative predictive value of the absence of coronary calcification remains to be confirmed, the presence of calcification has been described as invariably associated with coronary atherosclerotic lesions.^{19 23 24} The fact that we used the same method (Warren's TBA assay) as other groups to determine LDL sialic acid content and that the results of this colorimetric method correlate (r=.85) with those of a chromatographic method (data not shown) rule out a methodological explanation for the apparent discordance with the above-mentioned studies. In contrast, this disagreement may be due to differences between our study group and other populations. The first such difference is the cholesterol level: our population was hypercholesterolemic while that of Orekhov et al^{4 5} was normocholesterolemic. The second concerns clinical status: our population consisted of asymptomatic subjects with no history, symptoms, or clinical sign of cardiovascular disease. According to these criteria, they were comparable with the healthy subjects selected by Orekhov et al.^{4 5} The fact that we found a similar range of sialic acid values to that reported for healthy subjects (20 to 40 nmol/mg of LDL protein) by Orekhov et al⁵ supports the idea that LDL sialic acid content does not depend on the cholesterol level but rather is related to clinical status. Such observations suggest that LDL sialic acid content is not a sensitive marker of early atherosclerotic lesions in asymptomatic subjects.

Another objective was to examine the relation between LDL sialic acid content and clinical and biological parameters. LDL sialic acid content was not related to traditional risk factors such as sex, age, body mass index, blood pressure, smoking status, and blood total cholesterol. We paid particular attention to Lp(a) because it is highly sialylated and has a density range that overlaps that of LDL.³² No interference of Lp(a) with the determination of LDL sialic acid content was observed, a hypothesis that had to be verified because our group previously described associations between serum Lp(a) and the prevalence of arterial plaques.²⁶ In contrast, LDL sialic acid content correlated negatively with serum triglyceride levels. This association was reported by La Belle and Krauss,⁷ who provided evidence of heterogeneous LDL carbohydrate content. They found that total LDL sialic acid content was not related to apoB glycosylation but was directly related to the total lipid content of LDL. Because LDL is an end product of the metabolism of triglyceride-rich lipoproteins, these authors suggested that differences in the intravascular processing of these LDL precursors between individuals may contribute to the formation of various LDL subspecies that differ in their sialic acid content. Our data confirm this heterogeneity because LDL sialic acid values varied from 19.6 to 46.6 nmol/mg of LDL protein in our population. In addition, the fact that the correlation with serum triglyceride levels did not persist when triglyceridemia was below 1.5 mmol/L is in keeping with the findings of La Belle and Krauss. The important remaining question is whether these differences in LDL sialic acid content have implications for the development of atherosclerosis. The present study shows the absence of a relation between the heterogeneity of LDL sialic acid content and the presence of peripheral arterial plaque and/or coronary calcification in a symptom-free, high-risk population of hypercholesterolemic subjects. This is in keeping with the recent report of Tertov et al,⁸ who found heterogeneity in LDL sialic acid content both within (sialic acid–rich and sialic acid–poor LDL) and between individuals, even in healthy subjects. Because these investigators observed much greater heterogeneity in LDL sialic acid content in patients with CAD, it may be that desialylation of LDL occurs much later in atherosclerotic processing. Accordingly, a longitudinal population-based study would be of interest to elucidate the events that lead to such a phenomenon.

	Acknowledgments

 
We thank Banque Nationale de Paris, l'Oréal, Paris, MATRA SA, and Procter & Gamble France for sponsoring the PCVMETRA Group. We also thank N. Poulain, I. Souletie, S. Goiny, V. Atger, and M. Cambillau for their helpful contribution.

	Appendix 1

Top Abstract Introduction Methods Results Discussion Appendix 1 References

 
The PCVMETRA Group included the following individuals: P. Segond (chairman), D. Badet, C. Baylac-Lebot, P. Bonneau, A. de Bonnières, A. Borie, M.F. Bourillon, J. Boursier, S. Bressler, M. Bru, M. Chenet, P. Corteel, C. Coulange, C. Delmotte-Devocelle, B. Demure, M.J. Douguet, M. Dubost, T. Drumare, D. Estève, M. Fragny, O. Galamand, A.M. Giard, R. Gitel, C. Guilbert, H. Hage, F. Kiesgen, E. Lamothe, C. Lanoiselée, M.L. Leblanc, N. Le Chevanton, I. Leprince, A. Marty, D. Miara, B. Millet, J. Oziel, A. Parini, M.C. Pasteau, M. Picard, M.M. Pupponi, C. Quinio, F. Raulet, M.L. Rocca, F. Szabason, P. Taine, M.C. Tardieu, C. Tarin, A. Touati-Lumbroso, and L. Troulet.

Received August 31, 1994; accepted January 1, 1995.

	References

Top Abstract Introduction Methods Results Discussion Appendix 1 References

 
1. Lindberg G, Eklund GA, Gullberg B, Rastam L. Serum sialic acid concentration and cardiovascular mortality. Br Med J. 1991;302:143-146.

2. Waters PJ, Lewry E, Pennock CA. Measurement of sialic acid in serum and urine: clinical applications and limitations. Ann Clin Biochem. 1992;29:625-637.

3. Crook M. The determination of plasma or serum sialic acid. Clin Biochem. 1993;26:31-38. [Medline] [Order article via Infotrieve]

4. Orekhov AN, Tertov VV, Mukhin DN. Desialylated low density lipoprotein: naturally occurring modified lipoprotein with atherogenic potency. Atherosclerosis. 1991;86:153-161. [Medline] [Order article via Infotrieve]

5. Orekhov AN, Tertov VV, Sobenin IA, Smirnov VN, Via DP, Guevara J Jr, Gotto AM, Morrisset JD. Sialic acid content of human low density lipoproteins affects their interaction with cell receptors and intracellular lipid accumulation. J Lipid Res. 1992;33:805-817. [Abstract]

6. Ruelland A, Gallou G, Legras B, Paillard F, Cloarec L. LDL sialic acid content in patients with coronary artery disease. Clin Chim Acta. 1993;221:127-133. [Medline] [Order article via Infotrieve]

7. La Belle M, Krauss RM. Differences in carbohydrate content of low density lipoproteins associated with low density lipoprotein subclass patterns. J Lipid Res. 1990;31:1577-1588. [Abstract]

8. Tertov VV, Orekhov AN, Sobenin IA, Morrisset JD, Gotto AM, Guevara J Jr. Carbohydrate composition of protein and lipid components in sialic acid-rich and -poor low density lipoproteins from subjects with and without coronary artery disease. J Lipid Res. 1993;34:365-375. [Abstract]

9. Kannel WB, Castelli WP, Gordon T, McNamara PM. Serum cholesterol, lipoproteins, and the risk of coronary heart disease: the Framingham Study. Ann Intern Med. 1971;74:1-12.

10. Stamler J, Wentworth D, Neaton JD. Is relationship between serum cholesterol and risk of premature death from coronary heart disease continuous and graded? JAMA. 1986;256:334-339.

11. Blankenhorn DH, Rooney JA, Curry JP. Noninvasive assessment of atherosclerosis. Prog Cardiovasc Dis. 1984;26:295-307. [Medline] [Order article via Infotrieve]

12. Pignoli P, Tremoli E, Poli A, Oreste P, Paoletti R. Intimal plus medial thickness of the arterial wall: a direct measurement with ultrasound imaging. Circulation. 1986;74:1399-1406. [Abstract/Free Full Text]

13. Giral P, Filitti V, Levenson J, Pithois-Merli I, Plainfosse MC, Mainardi C, Gold A, Simon A, and the PCVMETRA Group. Relation of risk factors for cardiovascular disease to early atherosclerosis detected by ultrasonography in middle-aged normotensive hypercholesterolemic men. Atherosclerosis. 1990;85:151-159. [Medline] [Order article via Infotrieve]

14. Giral P, Pithois-Merli I, Filitti V, Levenson J, Plainfosse MC, Mainardi C, Simon A, and the PCVMETRA Group. Risk factors and early extracoronary atherosclerotic plaques detected by three-site ultrasound imaging in hypercholesterolemic men. Arch Intern Med. 1991;151:950-956. [Abstract/Free Full Text]

15. Salonen JT, Salonen R. Ultrasound B-mode imaging in observational studies of atherosclerotic progression. Circulation. 1993;87(suppl II):II-56-II-65.

16. Wendelhag I, Wiklund O, Wikstrand J. Atherosclerotic changes in the femoral and carotid arteries in familial hypercholesterolemia: ultrasonographic assessment of intima-media thickness and plaque occurrence. Arterioscler Thromb. 1993;13:1404-1411. [Abstract/Free Full Text]

17. Tanenbaum SR, Dondos GT, Veselik KE, Prendergast MR, Brundage BH, Chomka EV. Detection of calcific deposits in coronary arteries by ultrafast computed tomography and correlation with angiography. Am J Cardiol. 1989;63:870-872. [Medline] [Order article via Infotrieve]

18. Agatston AS, Janowitz WR, Hildner FJ, Zusmer NR, Viamonte M, Detrano R. Quantification of coronary artery calcium using ultrafast computed tomography. J Am Coll Cardiol. 1990;15: 827-832.

19. Ultrafast CT for coronary calcification. Lancet. 1991;337:1449-1450. Editorial.

20. Megnien JL, Sene V, Jeannin S, Hernigou A, Plainfosse MC, Merli I, Atger V, Moatti N, Levenson J, Simon A, and the PCVMETRA Group. Coronary calcification and its relation to extracoronary atherosclerosis in asymptomatic hypercholesterolemic men. Circulation. 1992;85:1799-1807. [Abstract/Free Full Text]

21. Hoeg JM, Feuerstein IM, Tucker EE. Detection and quantification of calcific atherosclerosis by ultrafast computed tomography in children and young adults with homozygous familial hypercholesterolemia. Arterioscler Thromb. 1994;14:1066-1074. [Abstract/Free Full Text]

22. Frink RJ, Achor RWP, Brown AL, Kincaid OW, Brandenburg RO. Significance of calcification of the coronary arteries. Am J Cardiol. 1970;26:241-247. [Medline] [Order article via Infotrieve]

23. Simons DB, Schwartz RS, Shredy PF, Breen JF, Edwards WD, Rumberger JA. Coronary artery calcification by ultrafast CT predicts stenosis size: a necropsy study. Circulation. 1990;82(suppl III):A-234.

24. Breen JF, Sheedy PF, Stanson AW, Rumberger J, Schwartz RS. Coronary Calcification Detected With Ultrafast CT as a Marker of Coronary Artery Disease. Chicago, Ill: Radiological Society of North America; 1990:1-224.

25. Simon A, Levenson J, Bouthier J, Safar M, Avolio P. Evidence of early degenerative changes in large arteries in human essential hypertension. Hypertension. 1985;7:675-680. [Abstract/Free Full Text]

26. Cambillau M, Simon A, Amar J, Giral P, Atger V, Segond P, Levenson J, Merli I, Megnien JL, Plainfosse MC, Moatti N, and the PCVMETRA Group. Serum Lp(a) as a discriminant marker of early atherosclerotic plaque at three extracoronary sites in hypercholesterolemic men. Arterioscler Thromb. 1992;12:1346-1352. [Abstract/Free Full Text]

27. 1989 Guidelines for the management of mild hypertension: memorandum from a WHO/ISH meeting. J Hypertens. 1989;7:689-693. [Medline] [Order article via Infotrieve]

28. Warren L. The thiobarbituric acid assay of sialic acids. J Biol Chem. 1959;234:1971-1975. [Free Full Text]

29. Li K. Determination of sialic acids in human serum by reversed-phase liquid chromatography with fluorimetric detection. J Chromatogr Sci. 1992;579:209-213.

30. Peterson GL. A simplification of the protein assay method of Lowry et al. which is more generally applicable. Anal Biochem. 1977;83:346-356. [Medline] [Order article via Infotrieve]

31. Janowitz WR, Agatson AS, Viamonte M. Comparison of serial quantitative evaluation of calcified coronary artery plaque by ultrafast computed tomography in persons with and without obstructive coronary artery disease. Am J Cardiol. 1991;68:1-6. [Medline] [Order article via Infotrieve]

32. Sattler W, Kostner GM, Waeg G, Esterbauer H. Oxidation of lipoprotein Lp(a): a comparison with low-density lipoproteins. Biochim Biophys Acta. 1991;1081:65-74. [Medline] [Order article via Infotrieve]

33. McGill HC. The cardiovascular pathology of smoking. Am Heart J. 1988;115:250-257. [Medline] [Order article via Infotrieve]

34. Pelourdeau T, Filitti V, Assad N, Pithois-Merli I, Levenson J, Giral P, Cambillau M, Moatti N, Plainfosse MC, Simon A, and the PCVMETRA group. Risk factors and early extracoronary atherosclerotic plaques detected by two-site ultrasound imaging in hypercholesterolemic women. Cardiovasc Risk Factors. 1991;1:498-504.

35. Filipovic I, Schwarzmann G, Mraz W, Wiegandt H, Buddecke E. Sialic acid content of low-density lipoproteins controls their binding and uptake by cultured cells. Eur J Biochem. 1979;93:51-55. [Medline] [Order article via Infotrieve]

36. Orekhov AN, Tertov VV, Mukhin DN, Mikhailenko IA. Modification of low density lipoprotein by desialylation causes lipid accumulation in cultured cells: discovery of desialylated lipoprotein with altered cellular metabolism in the blood of atherosclerotic patients. Biochem Biophys Res Commun. 1989;162:206-211. [Medline] [Order article via Infotrieve]

37. Camejo G, Lopez A, Lopez F, Quinones J. Interaction of low density lipoproteins with arterial proteoglycans: the role of charge and sialic acid content. Atherosclerosis. 1985;55:93-105. [Medline] [Order article via Infotrieve]

38. Camejo G, Hurt E, Wiklund O, Rosengren B, Lopez F, Bondjers G. Modification of low density lipoprotein induced by arterial proteoglycans and chondroitin-6-sulfate. Biochim Biophys Acta. 1991;1096:253-261. [Medline] [Order article via Infotrieve]

39. Hurt-Camejo E, Camejo G, Rosengren B, Lopez F, Ahlstrom C, Fager G, Bondjers G. Effect of arterial proteoglycans and glycosaminoglycans on low density lipoprotein oxidation and its uptake by human macrophages and arterial smooth muscle cells. Arterioscler Thromb. 1992;12:569-583. [Abstract/Free Full Text]

40. Hurt E, Bondjers G, Camejo G. Interaction of LDL with human arterial proteoglycans stimulates its uptake by human monocyte-derived macrophages. J Lipid Res. 1990;31:443-454. [Abstract]

41. Basu SK, Brown MS, Ho YK, Goldstein JL. Degradation of low density lipoprotein-dextran sulfate complexes associated with deposition of cholesteryl esters in mouse macrophages. J Biol Chem. 1979;254:7141-7146.[Free Full Text]

42. Camejo G, Acquatella H, Lalaguna F. The interactions of low density lipoproteins with arterial proteoglycans: an additional risk factor? Atherosclerosis. 1980;36:55-65. [Medline] [Order article via Infotrieve]

This article has been cited by other articles:

				B. Garner, D. J. Harvey, L. Royle, M. Frischmann, F. Nigon, M. J. Chapman, and P. M. Rudd Characterization of human apolipoprotein B100 oligosaccharides in LDL subfractions derived from normal and hyperlipidemic plasma: deficiency of {alpha}-N-acetylneuraminyllactosyl-ceramide in light and small dense LDL particles Glycobiology, October 1, 2001; 11(10): 791 - 802. [Abstract] [Full Text] [PDF]

				N. Lindbohm, H. Gylling, and T. A. Miettinen Sialic acid content of low density lipoprotein and its relation to lipid concentrations and metabolism of low density lipoprotein and cholesterol J. Lipid Res., July 1, 2000; 41(7): 1110 - 1117. [Abstract] [Full Text]

				B. Vedie, X. Jeunemaitre, J. L. Megnien, I. Myara, H. Trebeden, A. Simon, and N. Moatti Charge Heterogeneity of LDL in Asymptomatic Hypercholesterolemic Men Is Related to Lipid Parameters and Variations in the ApoB and CIII Genes Arterioscler Thromb Vasc Biol, November 1, 1998; 18(11): 1780 - 1789. [Abstract] [Full Text] [PDF]

				B. Chappey, B. Beyssen, E. Foos, F. Ledru, J. L. Guermonprez, J. C. Gaux, and I. Myara Sialic Acid Content of LDL in Coronary Artery Disease: No Evidence of Desialylation in Subjects With Coronary Stenosis and Increased Levels in Subjects With Extensive Atherosclerosis and Acute Myocardial Infarction : Relation Between Desialylation and In Vitro Peroxidation Arterioscler Thromb Vasc Biol, June 1, 1998; 18(6): 876 - 883. [Abstract] [Full Text] [PDF]

				K. Demuth, I. Myara, B. Chappey, B. Vedie, M. A. Pech-Amsellem, M. E. Haberland, and N. Moatti A Cytotoxic Electronegative LDL Subfraction Is Present in Human Plasma Arterioscler Thromb Vasc Biol, June 1, 1996; 16(6): 773 - 783. [Abstract] [Full Text]

This Article Abstract Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Chappey, B. Articles by Moatti, N. Search for Related Content PubMed PubMed Citation Articles by Chappey, B. Articles by Moatti, N.