Elevated interleukin-6 predicts progressive carotid artery atherosclerosis in dialysis patients: association with Chlamydia pneumoniae seropositivity

Chlamydial infection and progression of carotid atherosclerosis in patients on regular haemodialysis

BACKGROUND

Recent findings have suggested a possible contribution of chlamydial infection to the pathogenesis of atherosclerosis in the general population. However, the role that chlamydial antibody status plays in atherosclerosis generation in haemodialysis (HD) patients remains uncertain.

METHODS

We measured carotid artery intima medial thickness (IMT) over 4 years in 100 HD subjects (age: 58+/-10 years; time on HD: 13+/-7 years; male/female: 67/33) and examined potential associations between Chlamydia pneumoniae (Cp) antibody seropositivity and changes in carotid artery IMT.

RESULTS

During 4 years, carotid artery IMT increased significantly from 0.62+/-0.13 to 0.73+/-0.12 mm (P< 0.01). IMT progression was significantly and positively correlated with age (r = 0.37, P<0.01), log-transformed C-reactive protein (CRP; r = 0.33, P<0.01) and log-transformed interleukin-6 (IL-6; r = 0.22, P<0.04), but inversely correlated with blood creatinine (r = -0.36, P<0.01) and albumin (r = -0.24, P<0.02). IMT increases were more prominent in patients positive for IgA antibodies (0.039+/- 0.022 mm/year, n = 52) compared with those without IgA antibodies (0.025+/-0.032 mm/year, n = 48) (P<0.01). IgA seropositivity did not accelerate IMT progression in patients with increased CRP (>0.11 mg/dl, n = 53), but significantly increased IMT to a greater extent in IgA-positive subjects than in IgA-negative subjects having lower CRP (</=0.11 mg/dl, n = 47) (0.017+/-0.024 vs 0.034+/- 0.021 mm/year; P = 0.01). Multivariate regression analysis revealed that serum creatinine, log-transformed CRP and IgA Cp seropositivity were independent risk factors for IMT progression (P<0.01). In contrast, IgG Cp antibody did not affect IMT progression or carotid plaque formation.

CONCLUSIONS

IMT progression is associated with inflammation and malnutrition. In addition, persistent chlamydial infection may be associated with IMT progression, but only in HD patients having low blood CRP.

Vascular biology in uremia: insights into novel mechanisms of vascular injury

Cardiovascular disease is the leading cause of death in patients with end-stage renal disease. Although the prevalence of traditional atherosclerotic risk factors is increased in patients with chronic kidney disease, these traditional risk factors alone do not seem to account for the increased cardiovascular mortality. It has been proposed that additional risk factors may play a role in vascular injury. Among nontraditional risk factors, chronic inflammation, oxidative stress, and vascular calcification have been implicated in the accelerated athersclerosis of chronic kidney disease. Uremia is a proinflammatory state. Elevated levels of the proinflammatory cytokine interleukin-6 and suppressed levels of the anti-inflammatory cytokine interleukin-10 are present in chronic kidney disease and have been implicated in accelerated atherosclerosis. Uremia also results in increased oxidative stress. Asymmetric dimethyl arginine and myeloperoxidase may be critical mediators of the endothelial damage that results from oxidative stress. Finally, the uremic milieu seems to promote vascular calcification. The abundance of proinflammatory cytokines, the possible deficiency in calcification inhibitory proteins and the high phosphorus that are often present in uremia contribute to vascular calcification. Smooth muscle cells in calcifying lesions undergo phenotypic changes and molecular reprogramming that are reminiscent of endochondral bone formation during embryogenesis.

Influence of initiation of maintenance hemodialysis on biomarkers of inflammation and oxidative stress

BACKGROUND

Chronic inflammation and oxidative stress are highly prevalent in patients with chronic kidney disease and end-stage renal disease (ESRD). These conditions contribute to high mortality rates associated with cardiovascular disease, the leading cause of death in this patient population. To our knowledge, no prospective studies have examined how initiation of maintenance hemodialysis (MHD) affects biomarkers of inflammation and oxidative stress status.

METHODS

This was a prospective cohort study evaluating time-dependent changes in C-reactive protein (CRP), interleukin-6 (IL-6), interleukin-10 (IL-10), and protein carbonyl content before and after initiation of MHD over a 12-month period. Fifty incident hemodialysis patients [57.6 +/- 17.2 years, 60% male, 38% Caucasians, 32% insulin-dependent diabetes mellitus (IDDM) were studied, with 50 healthy subjects for comparison. The study variables were assessed before the initial outpatient hemodialysis treatment, and every 3 months thereafter for 12 months.

RESULTS

At baseline, CRP, IL-6, and carbonyl content levels were significantly higher in MHD patients compared with healthy subjects (P < 0.001 for each). After initiation of MHD, there were no significant changes in any of the study variables. Patients who initiated MHD with the highest levels of all the study variables had a significant decrease over the next year, but the variables were still higher than normal at the end of the 12-month study period.

CONCLUSION

Our data show that initiation of MHD does not have significant influence on plasma concentrations of CRP, IL-6, and IL-10, as well as plasma protein carbonyl content. These findings suggest that MHD is ineffective in controlling inflammation and oxidative stress in uremia.

Impact of medical comorbid disease on antidepressant treatment of major depressive disorder

A major factor in evaluating and treating depression is the presence of comorbid medical problems. In this paper, the authors will first evaluate studies showing that medical illness is a risk factor for depression. The authors will review a series of randomized, controlled studies of antidepressant treatment in subjects with major depressive disorder (MDD) and comorbid medical illnesses (myocardial infarction, stroke, diabetes, cancer, and rheumatoid arthritis). Most of these studies report an advantage for an active antidepressant over placebo in improvement of depressive symptoms. The authors also will review a series of studies in which the outcome of antidepressant treatment is compared between subjects with MDD with and without comorbid medical illness. In these studies, subjects with medical illness tend to have lower improvement of depressive symptoms and higher rates of depressive relapse with antidepressant treatment compared with MDD subjects with no medical comorbidity. In addition, the authors will review hypotheses on the mechanism of the interaction between medical illness and clinical response in MDD. The paper will conclude that medical comorbidity is a predictor of treatment resistance in MDD.

SEROLOGIC EVIDENCE OF CHLAMYDIA PNEUMONIAE INFECTION AS A LONG-TERM PREDICTOR OF CARDIOVASCULAR DEATH IN RENAL TRANSPLANT RECIPIENTS

BACKGROUND

Cardiovascular disease is the main cause of death with a functioning graft in renal transplant recipients. Elevated levels of C-reactive protein (CRP) and evidence of chronic Chlamydia pneumoniae infection have been linked to cardiovascular disease and survival in patients with normal renal function and patients with end-stage renal disease on dialysis. So far, no such data have been available in renal transplant recipients.

METHODS

CRP, immunoglobulin (Ig)G and IgA antibodies to C. pneumoniae, and classic risk factors were compiled in 143 patients who underwent renal transplantation between January 1989 and April 1991. Samples were collected at transplantation, 1 year later, and at study end. Cardiovascular disease, death, and graft loss were documented during follow-up.

RESULTS

A total of 44 patients died during a mean follow-up of 10 years. Cardiac events were responsible for 37% of deaths. Age, gender, number of antihypertensive drugs, and seropositivity for IgG and IgA antibodies to C. pneumoniae, but not CRP levels, were significantly associated with cardiac death. C. pneumoniae serology and CRP levels, however, did not influence graft survival. Age, presence of diabetes, calcium phosphorus ion product, number of antihypertensive drugs, serum creatinine at 1 year, and presence of chronic rejection were all negatively correlated with graft survival.

CONCLUSIONS

Serologic evidence of chronic C. pneumoniae infection is associated with mortality as the result of cardiovascular disease in renal transplant recipients. CRP serum levels do not predict cardiac death in renal transplant recipients, in contrast with patients with normal renal function and patients on dialysis.

Malnutrition-inflammation complex syndrome in dialysis patients: causes and consequences

Protein-energy malnutrition (PEM) and inflammation are common and usually concurrent in maintenance dialysis patients. Many factors that appear to lead to these 2 conditions overlap, as do assessment tools and such criteria for detecting them as hypoalbuminemia. Both these conditions are related to poor dialysis outcome. Low appetite and a hypercatabolic state are among common features. PEM in dialysis patients has been suggested to be secondary to inflammation; however, the evidence is not conclusive, and an equicausal status or even opposite causal direction is possible. Hence, malnutrition-inflammation complex syndrome (MICS) is an appropriate term. Possible causes of MICS include comorbid illnesses, oxidative and carbonyl stress, nutrient loss through dialysis, anorexia and low nutrient intake, uremic toxins, decreased clearance of inflammatory cytokines, volume overload, and dialysis-related factors. MICS is believed to be the main cause of erythropoietin hyporesponsiveness, high rate of cardiovascular atherosclerotic disease, decreased quality of life, and increased mortality and hospitalization in dialysis patients. Because MICS leads to a low body mass index, hypocholesterolemia, hypocreatininemia, and hypohomocysteinemia, a "reverse epidemiology" of cardiovascular risks can occur in dialysis patients. Therefore, obesity, hypercholesterolemia, and increased blood levels of creatinine and homocysteine appear to be protective and paradoxically associated with a better outcome. There is no consensus about how to determine the degree of severity of MICS or how to manage it. Several diagnostic tools and treatment modalities are discussed. Successful management of MICS may ameliorate the cardiovascular epidemic and poor outcome in dialysis patients. Clinical trials focusing on MICS and its possible causes and consequences are urgently required to improve poor clinical outcome in dialysis patients.

Characteristics and effects of inflammation in end-stage renal disease

Malnutrition and cardiovascular disease are associated with end-stage renal disease (ESRD) and both are closely associated with one another, both in cross-sectional analysis and when the courses of individual patients are followed over time. Inflammation, by suppressing synthesis of albumin, transferrin, and other negative acute-phase proteins and increasing their catabolic rates, either combines with modest malnutrition or mimics malnutrition, resulting in decreased levels of these proteins in dialysis patients. Inflammation also leads to reduced muscle mass by increasing muscle protein catabolism and blocking synthesis of muscle protein. More importantly, inflammation alters plasma protein composition and endothelial structure and function so as to promote vascular disease. Markers of inflammation, C-reactive protein (CRP), and interleukin (IL)-6 powerfully predict death from all causes and from cardiovascular disease in dialysis patients as well as progression of vascular injury. The causes of inflammation are likely multifactorial, including oxidative modification of plasma proteins, interaction of blood with nonbiocompatible membranes and lipopolysaccharides in dialysate, subclinical infection of vascular access materials, oxidative catabolism of endothelium-derived nitric oxide, and other infectious processes. Treatment should be focused on identifying potential causes of inflammation, if obvious, and reduction of other risk factor for cardiovascular disease.

Comparing outcome predictability of markers of malnutrition-inflammation complex syndrome in haemodialysis patients

BACKGROUND

Markers of malnutrition-inflammation complex syndrome (MICS) are reported to predict mortality and hospitalization in maintenance haemodialysis (MHD) patients. However, it is not clear which one is a more sensitive and stronger predictor of outcome.

METHODS

We examined the utility of 10 markers of MICS as predictors of prospective mortality and hospitalization, which included malnutrition-inflammation score (MIS), a fully quantitative score adopted from subjective global assessment, and serum levels of C-reactive protein (CRP), interleukin-6 (IL-6), tumour necrosis factor-alpha (TNF-alpha), albumin, pre-albumin, total iron binding capacity, creatinine, total cholesterol and normalized protein nitrogen appearance. A cohort of 378 MHD patients, who were randomly selected from eight DaVita dialysis facilities in the South Bay Los Angeles area, was studied.

RESULTS

Patients, aged 54.5+/-14.7 years, included 53% men, 47% Hispanics, 30% African-Americans and 55% diabetics, who had undergone MHD for 37+/-34 months. Over a 12-month follow-up, 39 patients died and 208 were hospitalized at least once. Multivariate Cox and Poisson models that included 11 covariates [gender, age, race, ethnicity, diabetes, dialysis vintage, Charlson co-morbidity index (CCI), insurance status, Kt/V, body mass index and history of cardiovascular disease] were explored for the highest quartiles of inflammatory markers or the lowest quartiles of nutritional markers. The magnitude of relative risk of death and hospitalization was greatest for MIS, CRP and IL-6. In extended multivariate models that included all 10 MICS markers and 11 additional covariates simultaneously, CRP, MIS and CCI were the only consistent predictors of mortality and hospitalization, and their outcome predictabilities were superior to serum albumin.

CONCLUSIONS

The MIS appears to be a useful, short-term tool to risk-stratify MHD patients and may circumvent the need for measuring inflammatory markers such as CRP or IL-6.

Resistance training to reduce the malnutrition-inflammation complex syndrome of chronic kidney disease

BACKGROUND

Systemic inflammation and protein-energy malnutrition may be associated with poor outcomes in kidney disease.

METHODS

We studied 26 adults (age, 65 +/- 10 [SD] years) with chronic kidney disease, not on dialysis therapy. Subjects were randomly assigned to resistance training (n = 14) or a control group (n = 12) for 12 weeks, while counseled to consume a low-protein diet (protein, approximately 0.6 g/kg/d). We determined whether resistance training reduces levels of inflammatory mediators (serum C-reactive protein [CRP] and interleukin-6 [IL-6]), in addition to previously reported improvements in nutritional and functional status in this same subject population.

RESULTS

Serum CRP levels were reduced in subjects undergoing resistance training (-1.7 mg/L) compared with controls (1.5 mg/L; P = 0.05). Similarly, IL-6 levels were reduced in the resistance-exercise group versus controls (-4.2 versus 2.3 pg/mL; P = 0.01). Resistance training lead to skeletal muscle hypertrophy, shown by increases in type I (24% +/- 31%) and type II (22% +/- 41%) muscle fiber cross-sectional areas, compared with control subjects (-14% +/- 34% and -13% +/- 18%, respectively; P < 0.05). Muscle strength also improved with resistance training (28% +/- 14%) compared with controls (-13% +/- 22%; P = 0.001).

CONCLUSION

Resistance training reduced inflammation and improved nutritional status in individuals with moderate chronic kidney disease consuming a low-protein diet. These results need to be investigated further in larger cohorts of patients with varying stages of kidney disease to determine whether resistance training can improve disease outcomes long term.

Beta-2 microglobulin in ESRD: an in-depth review

Beta-2 microglobulin is the most widely studied low-molecular-weight protein in end-stage renal disease. It is known to cause dialysis-related amyloidosis (DRA), by virtue of its retention when renal function fails, its deposition in tissues, its aggregation into fibrils, and its ability to become glycosylated. The onset of DRA may be protracted by the use of noncellulosic membranes, especially when high-volume hemodiafiltration is used in the treatment of renal failure. Adsorptive methods have been developed to improve the removal of beta-2 microglobulin. There seems to be a relative risk reduction in mortality when patients are treated with dialysis membranes that have a higher clearance of beta-2 microglobulin.

Effect of malnutrition-inflammation complex syndrome on EPO hyporesponsiveness in maintenance hemodialysis patients

BACKGROUND

Elements of malnutrition-inflammation complex syndrome (MICS) may blunt the responsiveness of anemia of end-stage renal disease (ESRD) to recombinant human erythropoietin (EPO).

METHODS

The authors examined cross-sectional associations between the required dose of EPO within a 13-week interval as prescribed by practicing nephrologists who were blind to the study and several laboratory values known to be related to nutrition and/or inflammation, as well as the malnutrition-inflammation score (MIS), which is a fully quantitative assessment tool based on the subjective global assessment of nutrition.

RESULTS

A total of 339 maintenance hemodialysis (MHD) outpatients, including 181 men, who were aged 54.7 +/- 14.5 years (mean +/- SD), who had undergone dialysis for 36.3 +/- 33.2 months, were selected randomly from 7 DaVita dialysis units in Los Angeles South/East Bay area. The average weekly dose of administered recombinant human EPO within a 13-week interval was 217 +/- 187 U/kg. Patients were receiving intravenous iron supplementation (iron gluconate or dextran) averaging 39.5 +/- 47.5 mg/wk. The MIS and serum concentrations of high-sensitivity C-reactive protein, interleukin 6 (IL-6), tumor necrosis factor-alpha, and lactate dehydrogenase had positive correlation with required EPO dose and EPO responsiveness index (EPO divided by hemoglobin), whereas serum total iron binding capacity (TIBC), prealbumin and total cholesterol, as well as blood lymphocyte count had statistically significant but negative correlations with indices of refractory anemia. Most correlations remained significant even after multivariate adjustment for case-mix and anemia factors and other relevant covariates. Similar associations were noticed across EPO per body weight tertiles via analysis of variance and after estimating odds ratio for higher versus lower tertile via logistic regression after same case-mix adjustment.

CONCLUSION

The existence of elements of MICS as indicated by a high MIS and increased levels of proinflammatory cytokines such as IL-6 as well as decreased nutritional values such as low serum concentrations of total cholesterol, prealbumin, and TIBC correlates with EPO hyporesponsiveness in MHD patients.

Middle molecules and small-molecular-weight proteins in ESRD: properties and strategies for their removal

Molecular weight has traditionally been the parameter most commonly used to classify uremic toxins, with a value of approximately 500 Da frequently used as a demarcation point below which the molecular weights of small nitrogenous waste products fall. This toxin group, the most extensively studied from a clinical perspective, is characterized by a high degree of water solubility and the absence of protein binding. However, uremia is mediated by the retention of a plethora of other compounds having characteristics that differ significantly from those of the previously mentioned group. As opposed to the relative homogeneity of the nitrogenous metabolite class, other uremic toxins collectively are a very heterogeneous group, not only with respect to molecular weight but also other characteristics, such as protein binding and hydrophobicity. A recently proposed classification scheme by the European Uraemic Toxin Work Group subdivides the remainder of molecules into 2 categories: protein-bound solutes and middle molecules. For the latter group, the Work Group proposes a molecular weight range (500-60,000 Da) that incorporates many toxins identified since the original middle molecule hypothesis, for which the upper molecular weight limit was approximately 2,000 Da. In fact, low-molecular-weight peptides and proteins (LMWPs) comprise nearly the entire middle molecule category in the new scheme. The purpose of this article is to provide an overview of the middle molecule class of uremic toxins, with the focus on LMWPs. A brief review of LMWP metabolism under conditions of normal (and in a few cases, abnormal) renal function will be presented. The physical characteristics of several LMWPs will also be presented, including molecular weight, conformation, and charge. Specific LMWPs to be covered will include beta 2-microglobulin, complement proteins (C3a and Factor D), leptin, and proinflammatory cytokines. The article will also include a discussion of the treatment-related factors influencing dialytic removal of middle molecules. Once these factors, which include membrane characteristics, protein-membrane interactions, and solute removal mechanisms, are discussed, an overview of the different therapeutic strategies used to enhance clearance of these compounds is provided.

Association of interleukin-6 -174G/C promoter polymorphism with hypertension and left ventricular hypertrophy in dialysis patients

BACKGROUND

Gene polymorphisms of proinflammatory cytokines, such as interleukin-6 (IL-6) and the chemokine receptor CX3CR1, have been found in association with cardiovascular disease in the general population. In dialysis patients, in whom the prevalence of cardiovascular comorbidity is strikingly high, these polymorphisms have not been investigated.

METHODS

The -174G/C polymorphism of the IL-6 gene and the chemokine receptor CX3CR1 polymorphisms 249V/I and 280T/M were examined for their association with cardiovascular abnormalities in a cohort of 161 patients with end-stage renal disease (ESRD) treated by hemodialysis. Arterial blood pressure, electrocardiogram (ECG) ischemic changes, and left ventricular mass index (LVMI) were the parameters examined for the association study. The control group was made up of 169 healthy subjects.

RESULTS

We found that for both IL-6 and chemokine receptor, genotype frequency and allelic distribution in both ESRD patients and controls were comparable. The genetic association study showed that in the whole group of dialysis patients, individuals with GC + CC genotype for the -174G/C polymorphism had a higher diastolic blood pressure (P = 0.008) and LVMI (P = 0.026) than GG homozygotes. The prevalence of left ventricular hypertrophy (LVH) in the former group was 58.6% vs. 39.2% in the latter (P = 0.02). The same analysis limited to diabetic patients in dialysis, showed that the prevalence of LVH in those with CG + CC genotype was 87.5% vs. 36.3% in those with GG genotype (P = 0.02). In diabetic patients, lower levels of serum albumin was found in the GC + CC genotypic group than in GG subjects; 34.63 +/- 5.18 g/L vs. 41.75 +/- 4.79 g/L (P = 0.003).

CONCLUSION

These data demonstrate an association between the IL-6 promoter polymorphism -174G/C and high blood pressure and LVH in hemodialysis patients, especially those with diabetes. The results strengthen the hypothesis that chronic inflammation is a mechanism of cardiovascular damage in dialysis patients and the role played by the IL-6 system in this mechanism.

Risk factors for aortic atherosclerosis determined by transesophageal echocardiography in patients with CRF

BACKGROUND

The significance of various risk factors for cardiovascular disease (CVD) in the pathogenesis of atherosclerosis in patients with chronic renal failure (CRF) is, to a great deal, unresolved. The high risk for CVD in patients with CRF may be caused by the high prevalence of recognized risk factors for CVD or by factors characteristic of CRF in these patients. In this prospective cross-sectional study, we examined risk factors for thoracic aortic atherosclerosis in a population of patients with CRF consisting of predialysis and dialysis patients, as well as renal transplant recipients.

METHODS

Of 118 patients, 52 patients had moderate to severe predialysis CRF, 32 patients were on dialysis treatment, and 34 patients were renal transplant recipients. Mean age was 52 +/- 12 years, and 35 patients (30%) had diabetes. Multiplane transesophageal echocardiography (TEE) was performed using local anesthesia.

RESULTS

Large aortic plaques (LAPs; > or = 3.0 mm in diameter) were found in 39 patients (33%). In univariate analysis, age, duration of hypertension, pulse pressure, low diastolic blood pressure, elevated fibrinogen level, C-reactive protein level, total cholesterol level, low-density lipoprotein cholesterol level, and duration of dialysis or a functioning renal transplant were significantly associated (P < 0.05) with LAP. In multivariate analysis, age, duration of hypertension, and total cholesterol level were associated with LAP.

CONCLUSION

Results of the present TEE study suggest that in addition to duration of hypertension and renal disease, hypercholesterolemia has a role in the pathogenesis of atherosclerosis in patients with CRF.

Linkage of hypoalbuminemia, inflammation, and oxidative stress in patients receiving maintenance hemodialysis therapy

BACKGROUND

Hypoalbuminemia is a powerful predictor of cardiovascular mortality in maintenance hemodialysis patients. Increased biomarkers of acute-phase inflammation and oxidative stress are highly prevalent and also correlate with cardiovascular morbidity and mortality. The extent to which hypoalbuminemia, biomarkers of inflammation, and biomarkers of oxidative stress are linked in this patient population is unknown. We hypothesized that a high proportion of hypoalbuminemic hemodialysis patients also would manifest increased levels of biomarkers of inflammation and oxidative stress.

METHODS

We surveyed 600 maintenance hemodialysis patients and identified 18 severely hypoalbuminemic patients (serum albumin level < 3.2 g/dL [32 g/L]) without recent infection or hospitalization. We then identified 18 age-, race-, sex-, and diabetes-matched normoalbuminemic hemodialysis patients, as well as 18 age-, race-, sex-, and diabetes-matched healthy subjects, for cohort comparison. Measurements of plasma interleukin-6 (IL-6) levels, plasma protein reduced thiol content, plasma protein carbonyl content, and plasma free F2-isoprostane levels, as well as serum concentrations of C-reactive protein (CRP) and prealbumin, were performed for study purposes.

RESULTS

Levels of serum CRP, IL-6, plasma protein thiol oxidation, and protein carbonyl formation were significantly elevated in both hypoalbuminemic and normoalbuminemic hemodialysis patients compared with healthy subjects and also were significantly different in hypoalbuminemic maintenance dialysis patients compared with normoalbuminemic hemodialysis patients. Prealbumin levels were significantly lower in hypoalbuminemic hemodialysis patients than in other groups.

CONCLUSION

There is a high prevalence of inflammation and oxidative stress in the maintenance hemodialysis population. Levels of inflammatory and oxidative stress biomarkers are increased further in hypoalbuminemic compared with normoalbuminemic dialysis patients. Hypoalbuminemia, acute-phase inflammation, and oxidative stress may act synergistically to increase cardiovascular morbidity and mortality risk in maintenance hemodialysis patients.

Chlamydia pneumoniae, overall and cardiovascular mortality in end-stage renal disease (ESRD)

BACKGROUND

Cross-sectional and retrospective studies suggest that Chlamydia pneumoniae infection may contribute importantly to the high cardiovascular risk of patients with end-stage renal disease (ESRD).

METHODS

We investigated the relationship between C. pneumoniae serology and survival and incident fatal cardiovascular events in a cohort of 227 ESRD patients (follow-up of 39 +/- 20 months).

RESULTS

On univariate Cox regression analysis patients with anti-C. pneumoniae immunogloblulin A (IgA) titer > or = 1:16 had a significantly higher risk of all-cause and cardiovascular mortality when compared to patients without IgA antibodies. However, after data adjustment for age and smoking, the hazard ratio (HR) decreased substantially and became largely nonsignificant. Adjustments for traditional and nontraditional risk factors further decreased the independent association of IgA anti-C. pneumoniae and these outcomes (all-cause mortality HR, 1.08; 95% CI, 0.68 to 1.72; P = 0.74; cardiovascular mortality HR, 1.07; 95% CI, 0.60 to 1.89; P = 0.83). A similar loss of prognostic power was observed for IgG anti-C. pneumoniae so that in fully adjusted models the HRs were very close to those observed for IgA anti-C. pneumoniae (all-cause mortality HR, 1.13; 95% CI, 0.68 to 1.86, P = 0.64; cardiovascular mortality HR, 1.10; 95% CI, 0.60 to 2.00; P = 0.77).

CONCLUSION

C. pneumoniae seropositivity is associated to shorter survival and incident fatal cardiovascular events in patients with ESRD but these associations are in large part attributable to the link between C. pneumoniae and well-established, traditional risk factors. It is highly unlikely that C. pneumoniae infection is a major risk factor in patients with ESRD.

White blood cells as a novel mortality predictor in haemodialysis patients

BACKGROUND

Many conventional cardiovascular risk factors in the general population are not as predictive in end-stage renal disease (ESRD). As absolute neutrophil count and total white blood cell (WBC) count are associated with adverse cardiovascular outcomes and all-cause mortality, this analysis was undertaken to explore the associations of WBC variables with mortality risk in ESRD.

METHODS

Of a total study population of 44 114 ESRD patients receiving haemodialysis during 1998 at facilities operated by Fresenius Medical Care, North America, 25 661 patients who underwent differential white cell count and had complete follow-up were included. Information on case mix (age, gender, race), clinical (diabetes, body mass index), and laboratory variables (haematocrit, albumin, creatinine, potassium, calcium, phosphorus, bicarbonate, ferritin, transferrin saturation and differential WBC count) was obtained. Associations between lymphocyte count, neutrophil count and demographic and clinical variables were examined using linear regression. Associations between WBC variables and survival were estimated using Cox proportional hazard regression.

RESULTS

A higher lymphocyte count was associated with higher serum albumin and creatinine, lower age and black race. High neutrophil count was associated with lower serum albumin and creatinine, younger age and white race (all Ps <0.0001). Cox proportional hazard regression showed an increased lymphocyte count was associated with reduced mortality risk [HR 0.86 (0.83-0.89) per 500/ml increase in lymphocyte count] and an increased neutrophil count was associated with increased mortality risk [HR 1.08 (1.06-1.09) per 1000/ml increase in neutrophil count].

CONCLUSIONS

An increased neutrophil count is strongly associated with, and reduced lymphocyte count associated less strongly with, many surrogates of both malnutrition and inflammation. An increased neutrophil count and reduced lymphocyte count are independent predictors of increased mortality risk in haemodialysis patients.

Uremic malnutrition: new insights into an old problem

Uremic malnutrition is highly prevalent and is associated with poor clinical outcomes in end-stage renal disease (ESRD) patients. Inadequate diet and a state of persistent catabolism play major roles in predisposing these patients to uremic malnutrition and appear to have an additive effect on overall outcome. Recent studies highlight the existence of a complex syndrome involving chronic inflammation, metabolic abnormalities, and hormonal derangements contributing to the increased morbidity and mortality observed in ESRD patients. Novel strategies such as appetite stimulants, anti-inflammatory drugs, and anabolic hormones along with conventional nutritional supplementation may provide potential interventions to improve clinical outcome in ESRD patients.

Adipose tissue as a source of inflammatory cytokines in health and disease: focus on end-stage renal disease

Adipose tissue is a necessary survival characteristic of species that do not have constant access to food. TNF-alpha is a very fundamental "internal regulator" (intra-system) of adipose tissue metabolism, and IL-6 and IL-1 beta are relevant control factors, as well. Leptin and IL-6, but not TNF-alpha, appear to be the major signals linking adipose tissue to the systemic immunologic response. In ESRD, it has been coherently observed that acute-phase reactants like CRP and serum amyloid A are independently associated to atherosclerosis, death, and cardiovascular complications. Leptin is inversely related with plasma creatinine, suggesting that reduced renal clearance is a primary factor responsible for hyperleptinemia in ESRD. On the other hand, this adipose tissue hormone behaves as an inverse acute-phase reactant (i.e., it decreases during spontaneous episodes of the acute-phase response). Dialysis patients with hyperleptinemia have more severe degrees of insulin resistance but further studies are required to see whether leptin plays a role in insulin resistance in these patients. The most abundant protein synthesized in the adipose tissue, adiponectin, is inversely related to metabolic risk factors like glucose, triglycerides, insulin, and HDL cholesterol in uremic patients, suggesting that this cytokine is a protective factor for the cardiovascular system. Accordingly, plasma adiponectin is an independent, inverse predictor of incident cardiovascular events in dialysis patients.

Inflammation in ESRD: causes and potential consequences

Malnutrition in end-stage renal disease (ESRD) is characterized by hypoalbuminemia, decreased serum creatinine and prealbumin, and decreased subjective global assessment (SGA) scores. Markers of malnutrition predict mortality and correlate closely with inflammatory markers, including serum cytokines and acute phase proteins. After multiple regression analysis, markers of inflammation become stronger predictors of mortality than nutritional markers, suggesting that malnutrition is a result of inflammation. The etiology of inflammation is variable and includes vascular access infection, bioincompatible dialyzers, back filtration of nonsterile dialysate, periodontal disease, urinary tract infections, and other pyogenic infections. Renal failure also may serve to promote inflammation through protein carbonylation. Differences in care patterns of ESRD patients and genetics may contribute to inflammation as evidenced by lower levels of C-reactive protein (CRP) in Asian populations. Inflammation results in loss of muscle mass and hypoalbuminemia as a consequence of its decreased synthesis and increased catabolism. Vascular disease occurs partly because of changes in lipoprotein structure and function, including oxidation of low-density lipoprotein (LDL) and modification of high-density lipoprotein (HDL) by serum amyloid A (SAA) and loss of apolipoprotein A-I. Leukocyte adhesion is promoted by changes in endothelial structure and function, whereas plasma proteins associated with cardiovascular disease (fibrinogen, lipoprotein[a]; SAA) are increased. Consequences of inflammation in ESRD patients include muscle wasting, erythropoetin resistance, and vascular disease. Whereas improvements in nutrition can increase serum albumin and creatinine levels, identification and removal of the underlying cause of inflammation should be one treatment goal.

Interactions between inflammation, oxidative stress, and endothelial dysfunction in end-stage renal disease

Despite a rapid improvement in dialysis technology during the last 20 years, the mortality rate is still very high in patients with end-stage renal disease (ESRD), and the death rate is comparable with that of many cancer patients with metastases. The main cause of mortality in ESRD is cardiovascular disease (CVD), and cardiac mortality for dialysis patients aged 45 years or younger is more than 100-fold greater than in the general population. The high cardiovascular mortality rate suggests that ESRD patients are subjected to a process of accelerated atherogenesis. Because factors proven to contribute to atherosclerosis in the general population, such as dyslipidemia, smoking, diabetes mellitus, and hypertension are highly prevalent in ESRD patients, it is reasonable to assume that such risk factors also apply to these patients. However, as it has been shown that the high cardiovascular risk in ESRD is incompletely accounted for by traditional risk factors, it may be speculated that nontraditional risk factors, seemingly more difficult to reconcile, also contribute. Among several putative nontraditional risk factors, chronic inflammation has attracted a lot of interest recently because it seems to be associated to both increased vascular oxidative stress and endothelial dysfunction, both of which are important predictors of cardiovascular events in nonrenal patient groups.

C-reactive protein and procalcitonin as markers of mortality in hemodialysis patients: a 2-year prospective study

OBJECTIVE

We have previously shown in a transversal study that PCT combined to CRP is associated to an altered nutritional status in hemodialysis patients. In a 2-year prospective study, we have assessed the relationship between markers of inflammation or nutrition and mortality.

DESIGN

Two-year prospective study, in 61 patients dialyzed in our unit (29 M/32 F, age 63 +/- 15 years, on dialysis for 76 +/- 94 months, 12 hrs/wk, on high-flux (HF) membrane for 25 patients and low-flux (LF) for 36 patients, without reuse). Kt/V was 1.53 +/- 0.30.

SETTING

Hospital-based dialysis unit.

MAIN OUTCOME MEASURE

CRP, PCT, ferritin, albumin, and prealbumin, were measured in 04/99 (T0) and every 6 months thereafter. Interleukin-6 (IL6) and fibrinogen were measured at the start of study. The outcome and the causes of death of patients were noted in 58 patients, 3 patients were lost of follow-up.

RESULTS

The mortality (24 deaths) was 42% at 2 years in this hospital based unit. The main causes of mortality were cardiovascular diseases (71%) and infection (17%). Patients were classified according to their CRP (CRP+ if CRP > or = 5 mg/L; n = 40), and PCT values (PCT + if PCT > or = 0.5 ng/mL; n = 25). IL6 level was > or = 10 pg/mL for 95% of the patients. Mortality was higher in the CRP+ group (Kaplan-Meier test P < .01) but not in the PCT or IL6 positive patients. All patients of the CRP+ group at T0 remained CRP+. Only 56% of patients of PCT+ remained positive at 6 months. When patients were grouped according to CRP quartile the difference on survival remained significant (P = .03), patients who were classified in the third and fourth quartile (upper than 9.9 mg/L), exhibited a higher rate of mortality than the lower quartile. The concomitant presence of a high level of PCT and CRP was associated with a worsened nutritional status at T0 but PCT level had no influence on 2-year mortality.

CONCLUSION

In this 2-year prospective study in a hospital-based cohort of high-risk hemodialysis patients, elevated CRP, but not raised PCT, was associated with increased mortality. Inflammation remained present throughout a 2-year follow-up in patients with an initial CRP higher than 5 mg/L. An upper value of CRP above 9.9 mg/L is independly predictive of mortality, mainly from cardiovascular causes. The association of high PCT and CRP was no more predictive of mortality than high CRP.

Interleukins in atherosclerosis: molecular pathways and therapeutic potential

Interleukins are considered to be key players in the chronic vascular inflammatory response that is typical of atherosclerosis. Thus, the expression of proinflammatory interleukins and their receptors has been demonstrated in atheromatous tissue, and the serum levels of several of these cytokines have been found to be positively correlated with (coronary) arterial disease and its sequelae. In vitro studies have confirmed the involvement of various interleukins in pro-atherogenic processes, such as the up-regulation of adhesion molecules on endothelial cells, the activation of macrophages, and smooth muscle cell proliferation. Furthermore, studies in mice deficient or transgenic for specific interleukins have demonstrated that, whereas some interleukins are indeed intrinsically pro-atherogenic, others may have anti-atherogenic qualities. As the roles of individual interleukins in atherosclerosis are being uncovered, novel anti-atherogenic therapies, aimed at the modulation of interleukin function, are being explored. Several approaches have produced promising results in this respect, including the transfer of anti-inflammatory interleukins and the administration of decoys and antibodies directed against proinflammatory interleukins. The chronic nature of the disease and the generally pleiotropic effects of interleukins, however, will demand high specificity of action and/or effective targeting to prevent the emergence of adverse side effects with such treatments. This may prove to be the real challenge for the development of interleukin-based anti-atherosclerotic therapies, once the mediators and their targets have been delineated.

Reverse epidemiology of cardiovascular risk factors in maintenance dialysis patients

Conventional risk factors of cardiovascular disease and mortality in the general population such as body mass, serum cholesterol, and blood pressure are also found to relate to outcome in maintenance dialysis patients, but often in an opposite direction. Obesity, hypercholesterolemia, and hypertension appear to be protective features that are associated with a greater survival among dialysis patients. A similar protective role has been described for high serum creatinine and possibly homocysteine levels in end-stage renal disease (ESRD) patients. These findings are in contrast to the well-known association between over-nutrition and poor outcome in the general population. The association between under-nutrition and adverse cardiovascular outcome in dialysis patients, which stands in contrast to that seen in non-ESRD individuals, has been referred to as "reverse epidemiology." Publication bias may have handicapped or delayed additional reports with such paradoxical findings in ESRD patients. The etiology of this inverse association between conventional risk factors and clinical outcome in dialysis patients is not clear. Several possible causes are hypothesized. First, survival bias may play a role since only a small number of patients with chronic kidney disease (CKD) survive long enough to reach ESRD. Hence, the dialysis patients are probably a distinctively selected population out of CKD patients and may not represent the risk factor constellations of their CKD predecessors. Second, the time discrepancy between competitive risk factors may play a role. For example, the survival disadvantages of under-nutrition, which is frequently present in dialysis patients, may have a major impact on mortality in a shorter period of time, and this overwhelms the long-term negative effects of over-nutrition on survival. Third, the presence of the "malnutrition-inflammation complex syndrome" (MICS) in dialysis patients may also explain the existence of reverse epidemiology in dialysis patients. Both protein-energy malnutrition and inflammation or the combination of the two are much more common in dialysis patients than in the general population and many elements of MICS, such as low weight-for-height, hypocholesterolemia, or hypocreatininemia, are known risk factors of poor outcome in dialysis patients. The existence of reverse epidemiology may have a bearing on the management of dialysis patients. It is possible that new standards or goals for such traditional risk factors as body mass, serum cholesterol, and blood pressure should be considered for these individuals.

Comorbidity and cardiovascular risk factors in patients with chronic kidney disease

The mortality rate among dialysis patients is high. Although guidelines have been in place to improve outcomes in dialysis patients, new emphasis is being placed on better management of patients who are pre-end-stage renal disease (pre-ESRD)-patients with chronic kidney disease (CKD). Spearheaded by the National Kidney Foundation, the National Institute of Health, and the nephrology community at large, an effort is underway to improve the care of patients with kidney disease. We hope that improvement in health and outcomes of patients with kidney disease will be optimized through attention to care before the development of advanced renal disease. Cardiovascular disease (CVD) is an important comorbidity of chronic kidney disease, and reducing cardiovascular events in this population is an important goal for the people who care for chronic kidney disease patients. In this article, we review the available literature regarding certain risk factors for cardiovascular disease: proteinuria, hyperglycemia, hypertension, homocysteine, hyperlipidemia, and inflammation. When possible, recommendations for treatment are provided based on the information reviewed.

Inflammation in end-stage renal disease: sources, consequences, and therapy

Cardiovascular disease (CVD) remains the main cause of morbidity and mortality in patients with end-stage renal disease (ESRD). Although traditional risk factors are common in ESRD patients, they alone may not be sufficient to account for the high prevalence of CVD in this condition. Recent evidence demonstrates that chronic inflammation, a nontraditional risk factor which is commonly observed in ESRD patients, may cause malnutrition and progressive atherosclerotic CVD by several pathogenetic mechanisms. The causes of inflammation in ESRD are multifactorial and, while it may reflect underlying CVD, an acute-phase reaction may also be a direct cause of vascular injury by several pathogenetic mechanisms. Available data suggest that proinflammatory cytokines play a central role in the genesis of both malnutrition and CVD in ESRD. Thus it could be speculated that suppression of the vicious cycle of malnutrition, inflammation, and atherosclerosis (MIA syndrome) would improve survival in dialysis patients. Recent evidence has demonstrated strong associations between inflammation and both increased oxidative stress and endothelial dysfunction in ESRD patients. As there is not yet any recognized, or even proposed, treatment for ESRD patients with chronic inflammation, it would be of obvious interest to study the long-term effect of various anti-inflammatory treatment strategies on the nutritional and cardiovascular status as well as outcome in these patients.