Carotid atherosclerosis is associated with inflammation, malnutrition and intercellular adhesion molecule-1 in patients on continuous ambulatory peritoneal dialysis
Aikaterini Papagianni1,
Elisavet Kokolina1,
Michalis Kalovoulos2,
Andreas Vainas1,
Chrisostomos Dimitriadis1 and
Dimitrios Memmos1
1University Department of Nephrology and 2Department of Radiology, Hippokration General Hospital,
Thessaloniki, Greece
Correspondence and offprint requests to: Aikaterini Papagianni, MD, University Department of Nephrology, Hippokration General Hospital, 50 Papanastasiou Str, 54642 Thessaloniki, Greece. Email: aikpapag{at}otenet.gr
 |
Abstract
|
---|
Background. Recent evidence suggests that endothelial cell adhesion molecules may participate in the initiation and progression of atherosclerotic vascular damage. The aim of the present report was to investigate serum intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and E-selectin concentrations and their probable association with atherosclerotic disease in patients on continuous ambulatory peritoneal dialysis (CAPD).
Methods. Sixty-three CAPD patients and 40 age- and sex-matched apparently healthy normotensive controls participated in the study. Atherosclerotic disease in both groups was assessed by measuring the intima-media thickness (IMT) and plaque score of the common carotid arteries using an ultrasound scanner.
Results. Compared with controls, CAPD patients had significantly increased IMT and plaque score values (P<0.001 and P<0.0001, respectively), as well as serum ICAM-1, VCAM-1 and E-selectin concentrations (P<0.0001, P<0.0001 and P<0.05, respectively). In univariate analyses, IMT values were significantly correlated with age, systolic blood pressure (BP), logCRP, fibrinogen, albumin and ICAM-1 levels (P = 0.001, P = 0.04, P = 0.01, P = 0.04, P = 0.02 and P = 0.002, respectively). Multivariate analysis showed that ICAM-1 levels were a strong independent correlate of IMT (P = 0.005). Serum albumin also remained independently associated with IMT values (P = 0.03). Plaque score values were significantly correlated with age, systolic BP and fibrinogen (P = 0.002, P = 0.04 and P = 0.01, respectively). Multivariate analysis showed that fibrinogen concentrations were a significant independent contributor to plaque score values (P = 0.002). Adhesion molecule concentrations did not show any relation with plaque score either on univariate or multivariate analyses.
Conclusions. In CAPD patients, carotid atherosclerosis is associated with markers of inflammation, malnutrition and circulating levels of adhesion molecule ICAM-1. Hypoalbuminaemia and ICAM-1 appear independently related with atherogenesis but the mechanisms supporting these associations remain to be identified.
Keywords: adhesion molecules; atherosclerosis; continuous ambulatory peritoneal dialysis; inflammation; intima-media thickness; malnutrition
 |
Introduction
|
---|
The morbidity and mortality from atherosclerotic cardiovascular disease (AVD) is greatly increased in patients with end-stage renal disease (ESRD) undergoing renal replacement therapy [13]. The higher prevalence of several traditional and uraemia-related risk factors for atherogenesis, such as hypertension, hyperlipidaemia, diabetes mellitus, haemodynamic overload, anaemia and increased oxidative stress cannot fully explain this increased burden of AVD, indicating that other factors, yet to be defined, are also likely to be triggered in this patient population [1,2]. Several recent studies have reported a particularly strong association between atherosclerosis and chronic inflammation, as defined by elevated C-reactive protein (CRP) and other acute phase proteins, in ESRD patients [46]. In addition, emerging evidence suggests an important role for endothelial cell adhesion molecules in the initiation and progression of atherosclerosis through their effects on leukocyte activation, cell migration and smooth muscle cell proliferation. Adhesion molecules intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and E-selectin, expressed on the surface of vascular endothelial cells in response to proinflammatory cytokines, have been detected by immunohistochemistry in human atherosclerotic lesions, and their expression was found to be correlated with intimal infiltration by T lymphocytes and monocytes/macrophages [7]. Moreover, there are some reports indicating that circulating levels of adhesion molecules may serve as indirect markers for atherosclerotic vascular damage [8]. We have previously demonstrated that endothelial adhesion molecules are increased in chronic haemodialysis (HD) patients and are associated with markers of inflammation and carotid atherosclerosis [6]. Since studies in the restricted population of ESRD patients on continuous ambulatory peritoneal dialysis (CAPD) are limited, we undertook an investigation of circulating endothelial adhesion molecule levels in stable CAPD patients and their probable association with atherosclerotic disease as assessed by high-resolution ultrasonography of the common carotid arteries.
 |
Subjects and methods
|
---|
Subjects
Between March and April 2002, 63 adult patients on CAPD (27 male, mean age 67 years, range 1986 years) from the Peritoneal Dialysis Unit of the University Department of Nephrology at Hippokration General Hospital consecutively entered the study. All patients had been on CAPD for more than 3 months (mean CAPD duration 42 months, range 6147 months) and were clinically stable and free of active infection. Chronic renal failure was attributed to diabetic nephropathy in 19 cases, glomerulonephritis in 16 cases, tubulointerstitial nephritis in 12 cases, polycystic kidney disease in four cases, renovascular hypertension in four cases and was undetermined in eight cases. Patients with liver disease, autoimmune diseases or malignancies were excluded, in order to avoid the possible effects of these comorbid conditions on cytokine production. None of the patients was receiving antibiotics, corticosteroids or cytotoxic drugs at the time of the study. All patients were on a four to five exchanges per day schedule with standard dialysis bags. Forty-seven patients (74.6%) were receiving one or more antihypertensive drugs (calcium channel blockers, angiotensin-converting enzyme inhibitors, angiotensin II receptor antagonists, oral nitrates or beta-blockers) at the time of the study. Forty-nine patients (77.8%) were on recombinant human erythropoietin therapy and the mean dosage was 52±27 IU/kg body weight/week. Thirty-three patients (52.4%) had a past history of cardiovascular events (CVE). Of the 33 patients, 19 had a history of myocardial infarction, coronary artery bypass or angina with abnormal coronarography or myocardial scintigraphy, five had suffered from stroke and nine had abdominal aortic or lower extremity arterial disease. The control group consisted of 40 age- and sex-matched apparently healthy subjects (17 male, mean age 65 years, range 2285 years) who were recruited from hospital staff members and their relatives. These control subjects did not have any history of hypertension, diabetes mellitus and renal or vascular disease, and were receiving no drugs at the time of the study. The study protocol conformed to the ethical guidelines of our institution and an informed consent was obtained from each participant.
Blood pressure measurements
In CAPD patients, the average blood pressure (BP) was calculated on the basis of a series of 1020 measurements taken at home during the month preceding the study. Average home BP was reported to be closely related to 24 h ambulatory arterial pressure and satisfactory reflect the pressor burden of the cardiovascular system in these patients [9]. In control subjects, BP was measured after 15 min of recumbency and five measurements 2 min apart were averaged.
Laboratory methods
Blood samples from CAPD patients and control subjects were taken from a peripheral vein under fasting conditions. Serum samples were separated from clotted blood by immediate centrifugation (1500 g for 10 min), aliquoted and stored at 70°C until assay. Serum levels of the circulating adhesion molecules ICAM-1, VCAM-1 and E-selectin were measured by an enzyme-linked immunosorbent assay using commercially available standard kits (Quantikine human sICAM-1, sVCAM-1 and sE-selectin; Research and Diagnostic Systems Europe Ltd, Abington, UK) as previously described [6]. Haemoglobulin, fibrinogen, serum albumin, total cholesterol, triglycerides and HDL-cholesterol measurements were carried out by using standard methods in the routine clinical laboratory. For CAPD patients, monthly serum albumin concentration was averaged for the 6 months preceding the study start date. The mean value for serum albumin was then obtained for each patient and was considered for statistical assessment. LDL-cholesterol was calculated using the Friedewald formula. Serum CRP levels were evaluated by high sensitivity nephelometry and exact CRP values were obtained in all patients.
Carotid ultrasonography
Ultrasonographic studies were performed with a Aloka Sonos SSD-1700 (Aloka, Tokyo, Japan) instrument using a 7.5 MHz high-resolution probe. Each subject was examined in the supine position in a semi-dark room. The ultrasonographic study was performed within 1 week after blood sampling and on an empty abdomen in CAPD patients. The carotid artery was investigated bilaterally by the same expert radiologist (M.K.) who was unaware of clinical and laboratory data. Intima-media thickness (IMT) was defined as a low-level echo grey band that does not project into the arterial lumen and was measured at the diastolic phase as the distance between the leading edge of the first and second echogenic line. IMT was measured on the longitudinal views of the far wall of the distal segment of common carotid artery, the carotid bifurcation, and the initial tract of the internal carotid artery on both sides. Measurements were performed 0.5, 1 and 2 cm below and above the bifurcation (six measurements on each side) in a plaque-free arterial segment. The average measurement of the obtained values was taken as IMT and it was considered abnormal when it exceeded 0.82 mm [10]. Carotid plaques were defined (and counted) either as faint grey echoes (soft plaques) or bright white echoes (calcified plaques) protruding into the arterial lumen. Plaque thickness was measured in a suitable longitudinal or transverse view. Plaque score was computed by summing maximum thickness in millimetres of plaques in each segment on both sides.
Statistical analysis
Data are expressed as means±SD. The significance of differences in means between the two groups was assessed by Student's t-test or the MannWhitney test as appropriate. Differences in proportions were tested with the use of the chi-square statistic. Correlations were tested by regression analysis. Not-normally distributed variables were log- transformed before entering regression analysis. Multiple regression analysis with a forward elimination procedure was used to assess the combined influence of variables on IMT and plaque score values. The following variables were used: age, sex, smoking, CAPD duration, history of CVE, diabetes mellitus, systolic and diastolic BP, serum albumin, cholesterol, triglycerides, HDL, LDL, fibrinogen, logCRP, ICAM-1, VCAM-1 and E-selectin levels. The calculations were performed using Statview v. 4.5 statistical software (Abacus Concept Inc., Berkeley, CA, USA). A two-tailed P-value of <0.05 was considered to be statistically significant.
 |
Results
|
---|
The somatometric, haemodynamic and biochemical characteristics as well as the risk factors for atherosclerosis of controls and CAPD patients are shown in Table 1. Triglycerides were significantly increased and HDL-cholesterol was significantly decreased in CAPD patients compared with control subjects. In addition, systolic BP was elevated in CAPD patients whereas diastolic BP did not differ significantly between the two groups (Table 1).
View this table:
[in this window]
[in a new window]
|
Table 1. Somatometric, haemodynamic and biochemical characteristics and risk factors for atherosclerosis of 40 control subjects and 63 CAPD patients
|
|
CAPD patients had a significantly increased IMT and plaque score compared with control subjects (0.89±0.13 vs 0.71±0.08 mm, P<0.001 and 9.30± 5.43 vs 0.54±0.83 mm, P<0.0001, respectively). IMT was increased (>0.82 mm) in 41 (65.1%) of the CAPD patients. Atherosclerotic plaques were detected in 60 (95.2%) of the CAPD patients and in 11 (27.5%) of the controls. The difference in plaque occurrence between the two groups was significant (P<0.001).
Ultrasonographic findings and risk factors for atherosclerosis
IMT and plaque score were significantly correlated with age both in control subjects (r = 0.52, P = 0.0005 and r = 0.46, P = 0.003, respectively) and CAPD patients (r = 0.41, P = 0.001 and r = 0.39, P = 0.002, respectively). In addition, IMT showed a significant correlation with systolic BP in both groups (r = 0.38, P = 0.02 and r = 0.25, P = 0.04, respectively). In CAPD patients, plaque score was also significantly correlated with systolic BP (r = 0.26, P = 0.04). Ultrasonographic parameters did not show any significant correlation with other classic cardiovascular risk factors in both groups, such as gender, smoking status, total cholesterol, triglycerides, HDL- and LDL-cholesterol or CAPD duration, diabetes mellitus and history of CVE in CAPD patients.
Ultrasonographic findings, inflammation and malnutrition
Compared with controls, CAPD patients had significantly increased CRP and fibrinogen values (3.8±0.8 vs 12.9±13.9 mg/l, P<0.0001 and 2.68±0.70 vs 5.44±1.14 g/l, P<0.0001, respectively) (Table 1). Thirty-nine CAPD patients (61.9%) had abnormal CRP (normal <5 mg/l) and 60 patients (95.2%) had increased fibrinogen levels (normal range 24 g/l). Fibrinogen values were significantly correlated with logCRP (r = 0.38, P = 0.002). In univariate analyses, IMT, but not plaque score, values were significantly correlated with log-transformed CRP (r = 0.32, P = 0.01 and r = 0.14, P = NS, respectively). Fibrinogen levels were significantly correlated with both IMT and plaque score values (r = 0.26, P = 0.04 and r = 0.34, P = 0.01, respectively) (Figure 1). Multivariate analysis showed that fibrinogen values were a strong independent correlate of plaque score (r = 39, P = 0.002) (Table 2).

View larger version (18K):
[in this window]
[in a new window]
|
Fig. 1. Correlation between fibrinogen concentrations and IMT (top) and plaque score values (bottom) in 63 CAPD patients.
|
|
Mean 6 month serum albumin concentration was significantly decreased in CAPD patients compared with control subjects (3.63±0.43 vs 4.78±0.55 g/dl, P<0.0001) (Table 1). In univariate analyses, IMT, but not plaque score, values had a significant inverse correlation with albumin concentrations (r = 0.28, P = 0.02) (Figure 2, top). Multivariate analysis showed that serum albumin was an independent contributor to IMT values (Table 3). In addition, compared with patients with normal IMT, patients with increased IMT values (>0.82 mm) had significantly lower serum albumin (3.79±0.46 vs 3.55±0.46 g/dl, P<0.05).

View larger version (19K):
[in this window]
[in a new window]
|
Fig. 2. Correlation between IMT values and serum albumin (top) and ICAM-1 levels (bottom) in 63 CAPD patients.
|
|
Ultrasonographic findings and endothelial adhesion molecules
Compared with control subjects, CAPD patients had significantly increased ICAM-1, VCAM-1 and E-selectin levels (234±73 vs 599±273 ng/ml, P<0.0001, 941±149 vs 2024±780 ng/ml, P<0.0001 and 62±32 vs 81±43 ng/ml, P<0.05, respectively). No significant differences were observed in adhesion molecule levels between diabetic and non-diabetic patients. In addition, adhesion molecule levels did not show any relation with age, gender or CAPD duration. However, ICAM-1 and VCAM-1, but not E-selectin, levels were significantly correlated with logCRP values (r = 0.31, P = 0.01 and r = 0.27, P = 0.03, respectively).
Serum levels of ICAM-1, but not VCAM-1 or E-selectin, were significantly correlated with IMT (r = 0.39, P = 0.002) (Figure 2, bottom). Moreover, compared with patients with normal IMT, patients with increased IMT values (>0.82 mm) had significantly elevated ICAM-1 (494±208 vs 655±289 ng/ml, P<0.05). Multivariate analysis showed that serum ICAM-1 levels were a strong independent correlate of IMT (r = 0.36, P = 0.005) (Table 3). When ICAM-1 was excluded from the model, the independent variables linked to IMT values were age, serum albumin and fibrinogen (r = 0.39, P = 0.001, r = 0.33, P = 0.01 and r = 0.26, P = 0.04, respectively). Adhesion molecule concentrations failed to be significant contributors to the plaque score either on univariate or multivariate analyses.
 |
Discussion
|
---|
Recently, atherosclerotic disease has been regarded as an inflammatory disorder and several studies have reported a strong association between chronic inflammation, as defined by increased CRP levels and atherosclerosis in ESRD patients both on conservative treatment and on maintenance HD [46]. However, the value of CRP as a marker of atherosclerotic vascular damage is less well known in the restricted population of ESRD patients on CAPD. In the present study, a significant association was observed between CRP and IMT values but the former failed to be an independent correlate of carotid atherosclerotic changes in multivariate analysis.
Fibrinogen is a principal coagulation protein as well as an acute phase reactant and is recently considered to be atherogenic. Fibrinogen levels have been reported to be increased and associated with vascular disease and an increased risk of death in ESRD patients [1113]. In univariate analysis, IMT values were significantly correlated with fibrinogen concentrations, whereas in multivariate analysis the latter was independently associated with IMT if serum ICAM-1 was not included in the model. Moreover, fibrinogen levels were significantly associated with plaque score values both on univariate and multivariate analyses. Overall, the above findings, which have not been previously reported, indicate that, at least in CAPD patients, fibrinogen concentrations are a valuable surrogate marker for atherosclerotic vascular damage. In addition, based on these results it could be speculated that the hypercoagulable state produced by high fibrinogen levels has an important role in the advanced stages of atherosclerosis characterized by the development of plaques and obstructive lesions.
In recent years, several studies in ESRD patients have shown an association between signs of malnutrition and particularly low serum albumin and increased morbidity and mortality [1417]. However, some reports in HD patients have demonstrated that the activity of the acute phase response is an important predictor of low serum albumin, suggesting that malnutrition and atherosclerosis could be interlinked by inflammation [18,19]. The present study showed a significant and inverse correlation of IMT values with serum albumin levels both on univariate and multivariate analyses. Furthermore, this relationship appeared minimally influenced by other covariates including inflammatory markers. The above results support the concept that hypoalbuminaemia per se may also accelerate atherosclerosis, although the biological basis of this association remains to be elucidated.
Compared with controls, CAPD patients had significantly increased serum ICAM-1, VCAM-1 and E-selectin levels and these results concur with a previous report in a small number of patients [20]. Moreover, significant correlations were observed between CRP and adhesion molecule ICAM-1 and VCAM-1 levels suggesting that inflammation may be a major cause of elevated serum levels of these proteins in CAPD patients. Interestingly, and in accordance with our previous report in HD patients [6], a highly significant association was observed between carotid IMT, but not plaque score values, and serum ICAM-1 levels. Multivariate analysis showed that ICAM-1 levels were a strong independent correlate of IMT, whereas serum albumin and fibrinogen became significant correlates of IMT values only when ICAM-1 levels were excluded from the analysis. Furthermore, this association appeared relatively independent from a number of traditional or uraemia-related risk factors for atheroscerosis. The above data indicate that ICAM-1 is a valuable molecular marker of early atherosclerotic changes, integrating information otherwise present in a number of other less strongly related variables, including other markers of inflammation. Moreover, based on the above results, it is tempting to speculate that this correlation implies a pathogenic role for ICAM-1 on the early events of the atherosclerotic process leading to diffuse intimal thickening. However, clearly, additional studies are necessary to confirm the above intriguing hypothesis.
In conclusion, in CAPD patients, carotid atherosclerosis is associated with markers of inflammation and malnutrition and circulating levels of adhesion molecule ICAM-1. Hypoalbuminaemia and serum ICAM-1 appeared independently correlated with atherogenesis, although the mechanisms supporting these associations remain to be identified. Larger additional studies are needed to investigate the potential value of ICAM-1 levels for cardiovascular risk stratification in chronic renal failure patients.
 |
Acknowledgments
|
---|
Preliminary results from this study were presented at the World Congress of Nephrology, June 2003, Berlin, Germany, and were published in abstract form.
Conflict of interest statement. None declared.
 |
References
|
---|
- Cheung AK, Sarnak MJ, Yan G et al. Atherosclerotic cardiovascular disease risks in chronic hemodialysis patients. Kidney Int 2000; 58: 353362[CrossRef][ISI][Medline]
- Lameire N, Bernaert P, Lambert M-C, Vijt D. Cardiovascular risk factors and their management in patients on continuous ambulatory peritoneal dialysis. Kidney Int 1994; 46 [Suppl 48]: S31S38
- Locatelli F, Bommer J, London GM et al. Cardiovascular disease determinants in chronic renal failure: clinical approach and treatment. Nephrol Dial Transplant 2001; 16: 459468[Abstract/Free Full Text]
- Stenvinkel P, Heimbürger O, Paultre F et al. Strong association between malnutrition, inflammation, and atherosclerosis in chronic renal failure. Kidney Int 1999; 55: 18991911[CrossRef][ISI][Medline]
- Zoccali C, Benedetto FA, Mallamaci F et al. Inflammation is associated with carotid atherosclerosis in dialysis patients. J Hypertens 2000; 18: 12071213[CrossRef][ISI][Medline]
- Papagianni A, Kalovoulos M, Kirmizis D et al. Carotid atherosclerosis is associated with inflammation and endohelial cell adhesion molecules in chronic haemodialysis patients. Nephrol Dial Transplant 2003; 18: 113119[Abstract/Free Full Text]
- OBrien KD, McDonald TO, Chait A, Allen MD, Alpers CE. Neovascular expression of E-selectin, intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 in human atherosclerosis and their relation to intimal leukocyte content. Circulation 1996; 93: 672682[Abstract/Free Full Text]
- Rohde LE, Lee RT, Rivero J et al. Circulating cell adhesion molecules are correlated with ultrasound-based assessment of carotid atherosclerosis. Arterioscler Thromb Vasc Biol 1998; 18: 17651770[Abstract/Free Full Text]
- Benedetto FA, Mallamaci F, Tripepi G, Zoccali C. Prognostic value of ultrasonographic measurement of carotid intima media thickness in dialysis patients. J Am Soc Nephrol 2001; 12: 24582464[Abstract/Free Full Text]
- Aminbakhsh A, Mancini GB. Carotid intima media thickness measurements. What defines an abnormality? A systematic review. Clin Invest Med 1999; 22: 149157[ISI][Medline]
- Wanner C, Zimmermann J, Quaschning T, Galle J. Inflammation, dyslipidemia and vascular risk factors in hemodialysis patients. Kidney Int 1997; 52 [Suppl 62]: S53S55
- Koch M, Kutkuhn B, Trenkwalder E et al. Apolipoprotein B, fibrinogen, HDL cholesterol, and apolipoprotein (a) phenotypes predict coronary artery disease in hemodialysis patients. J Am Soc Nephrol 1997; 8: 18891898[Abstract]
- Bartens W, Nauck M, Schollmeyer P, Wanner C. Elevated lipoprotein (a) and fibrinogen levels increase the cardiovascular risk in continuous ambulatory peritoneal dialysis patients. Perit Dial Int 1996; 16: 2733[ISI][Medline]
- Goldwasser P, Mittma N, Antignani A et al. Predictors of mortality in hemodialysis patients. J Am Soc Nephrol 1993; 3: 16131622[Abstract]
- Iseki K, Kawasoe N, Fukiyama K. Serum albumin is a strong predictor of death in chronic dialysis patients. Kidney Int 1993; 44: 115119[ISI][Medline]
- Folwey RN, Parfrey PS, Harnett JD, Kent GM, Murray DC, Barre PE. Hypoalbuminemia, cardiac morbidity, and mortality in end-stage renal disease. J Am Soc Nephrol 1996; 7: 728736[Abstract]
- Avram MM, Fein PA, Bonomini L et al. Predictors of survival in continuous ambulatory peritoneal dialysis patients: a five-year prospective study. Perit Dial Int 1996; 16 [Suppl 1]: S190S194[Medline]
- Kaysen GA, Stevenson FT, Depner TA. Determinants of albumin concentration in hemodialysis patients. Am J Kidney Dis 1997; 29: 659668
- Qureshi AR, Alvestrand A, Danielson A et al. Factors predicting malnutrition in hemodialysis patients: a cross-sectional study. Kidney Int 1998; 53: 773782[CrossRef][ISI][Medline]
- Bonomini M, Reale M, Santarelli P, Stuard S, Settefrati N, Albertazzi A. Serum levels of soluble adhesion molecules in chronic renal failure and dialysis patients. Nephron 1998; 79: 399407[CrossRef][ISI][Medline]
Received for publication: 10. 7.03
Accepted in revised form: 28.11.03