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

Similarities in skeletal muscle strength and exercise capacity between renal transplant and hemodialysis patients

Exercise intolerance is common in hemodialysis (HD) and renal transplant (RTx) patients. Aim of the study was to assess to what extent exercise capacity and skeletal muscle strength of RTx patients differ from HD patients and healthy controls and to elucidate potential determinants of exercise capacity in RTx patients. Exercise capacity, muscle strength, lean body mass (LBM) and physical activity level (PAL) were measured by cycle-ergometry, isokinetic dynamometry, DEXA and Baecke Questionnaire, respectively, in 35 RTx, 16 HD and 21 controls. VO2peak and muscle strength of the RTx patients were significantly lower compared to controls (p<0.01), but not different compared to HD patients. In RTx patients, strength (p<0.001), PAL (p=0.001) and age (p=0.045) were significant predictors of VO2peak. Muscle strength was related to LBM (p=0.001) and age (p=0.001), whereas gender (p<0.001) and renal function (p=0.01) turned out to be significant predictors of LBM. No effects of corticosteroids were observed. Exercise capacity and muscle strength seem equally reduced in RTx and HD patients compared to controls. In RTx patients, muscle strength and PAL are highly related to exercise capacity. Renal function appears to be a significant predictor of LBM, and through the LBM, of muscle strength and exercise capacity.

Inflammation contributes to low plasma amino acid concentrations in patients with chronic kidney disease

BACKGROUND

Inflammation and malnutrition are common in chronic kidney disease (CKD) patients, and plasma concentrations of free amino acids (AAs) in these patients are often abnormal. Malnutrition contributes to alterations in AA concentrations.

OBJECTIVE

The objective was to study the effects of inflammation on plasma AA concentrations.

DESIGN

Concentrations of plasma AAs, serum albumin, and several inflammatory markers were analyzed in 200 fasting, nondiabetic CKD patients who were close to the start of renal replacement therapy. The nutritional status of these patients was assessed by a subjective global assessment.

RESULTS

The patients with inflammation [C-reactive protein (CRP) concentrations >10 mg/L] or malnutrition had lower AA concentrations than did the patients with no inflammation or malnutrition. The presence of both inflammation and malnutrition was associated with more marked reductions in AA concentrations than was malnutrition alone. Significant inverse correlations were observed between the plasma concentrations of most of the essential and nonessential AAs and inflammatory markers, whereas serum albumin concentrations were positively correlated with several AA concentrations. A stepwise multivariate regression analysis showed that serum CRP concentrations were independently associated with low concentrations of the sums of both nonessential AAs and all AAs. An analysis of all-cause mortality with a Kaplan-Meier test showed that the patients with higher AA concentrations had significantly better survival than did the patients with lower AA concentrations.

CONCLUSIONS

Plasma AA concentrations are low in CKD patients with inflammation and are inversely correlated with concentrations of inflammatory markers. Although inflammation and malnutrition are closely related, CRP concentrations were independently associated with low concentrations of the sums of both nonessential AAs and all AAs, which suggests an independent role of inflammation as a cause of low plasma AA concentrations in CKD patients.

Inflammation markers, adhesion molecules, and all-cause and cardiovascular mortality in patients with ESRD: searching for the best risk marker by multivariate modeling

Inflammation is a major risk factor for mortality and cardiovascular (CV) complications in patients with ESRD. The predictive value of C-reactive protein (CRP) of the main proinflammatory cytokines (IL-1beta, IL-6, IL-18, and TNF-alpha) and of two adhesion molecules (intercellular adhesion molecule-1 and vascular cell adhesion molecule-1) in 217 dialysis patients was compared. Serum IL-6 and CRP added significant prediction power to the multivariate Cox model of all-cause death, and the gain in the prediction power attributable to IL-6 was approximately two times higher than that of CRP. Patients in the third tertiles of serum IL-6 and CRP had a relative risk of all-cause mortality 2.5 and 1.8 times higher than those in the first corresponding tertiles, and there was no statistical difference between these two relative risks. The gain in prediction power associated with TNF-alpha, IL-beta, IL-18, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1 was of small degree (P = NS). Similarly, serum IL-6 added the highest prediction power to the CV death model, and the IL-6 attributable gain was approximately two times higher than that of serum CRP. However, the risk estimate for CV mortality of patients with high serum IL-6 did not differ significantly from that of patients with high serum CRP. IL-6 adds significantly greater predictive power for all-cause and CV death to statistical models based on traditional and nontraditional risk factors in ESRD patients. However, the risk estimate by CRP being reasonably close to that of IL-6, CRP may be a cheap alternative to IL-6 in clinical practice.

Chronic systemic inflammation in dialysis patients: an update on causes and consequences

Despite marked improvements in dialysis technology during the last 20 years, the age-adjusted mortality rate in end-stage renal disease (ESRD) patients treated by dialysis is still unacceptably high and comparable to that of many cancer patients with metastases. The main cause of the increased mortality in ESRD patients is cardiovascular disease (CVD), which is twice as common and advances at twice the rate already in patients with early stages of chronic kidney disease as compared to the general population. Although traditional risk factors for CVD are common in dialysis patients, they can only in part explain the very high prevalence of CVD in this patient group. Recent evidence demonstrates that chronic inflammation, a non-traditional risk factor which is a commonly observed in dialysis patients, may cause progressive atherosclerotic CVD and malnutrition, itself an important risk factor for the development of CVD, by several pathogenetic mechanisms. The causes of inflammation in dialysis are multifactorial and include both dialysis-related and unrelated factors. While the long-term effects of chronic inflammation may be most important in the pathogenesis of CVD, the acute-phase reaction may also cause vascular damage by several pathogenic mechanisms. Indeed, it seems logical to speculate that suppression of the vicious cycle of malnutrition, inflammation, and atherosclerosis (MIA syndrome) in ESRD would improve survival and decrease co-morbidity in dialysis patients. As there are currently no established guidelines for the treatment of chronic inflammation in ESRD patients, more studies on the long-term effects of various anti-inflammatory treatment strategies on the nutritional and cardiovascular status, as well as outcome in this patient group, are clearly warranted and will be helpful in identifying precisely which pathways are most involved in the pathogenic process.

Potential antiatherogenic and anti-inflammatory properties of sevelamer in maintenance hemodialysis patients

BACKGROUND

Patients affected by end-stage renal disease (ESRD) demonstrate a very high cardiovascular risk mediated by traditional cardiovascular risk factors as well as abnormal mineral metabolism and a state of chronic inflammation. Sevelamer is a nonabsorbable non-calcium-based hydrogel with potential antiatherosclerotic properties.

METHOD AND RESULTS

One hundred eight patients undergoing maintenance hemodialysis were randomized to sevelamer or calcium acetate as treatment for hyperphosphatemia. A coronary artery calcium score, as a measure of plaque burden, was calculated at baseline and 1 year, along with serial measurements of serum lipoproteins, beta2-microglobulin, and high-sensitivity C-reactive protein (hs-CRP). At 1 year, coronary artery calcium score progressed significantly from baseline in calcium acetate-treated subjects ( P < .001) but not in sevelamer-treated patients (P = NS). Total cholesterol (P < .0001), low-density lipoprotein cholesterol (P < .0001), apolipoprotein B (P < .0001), beta2-microglobulin (P = .018), and hs-CRP (P < .002) decreased, and high-density lipoprotein increased significantly (P = .036) from baseline in the sevelamer-treated subjects but not in subjects treated with calcium acetate despite the more frequent use of statins in the latter group (46% vs 22%, P < .05). The changes in total and low-density lipoprotein cholesterol, apolipoprotein B, and hs-CRP were significantly different between treatment groups (all P < .01).

CONCLUSIONS

Sevelamer leads to favorable changes in lipids and inflammatory markers with potentially useful antiatherogenic effects in hemodialysis patients.

The evidence against malnutrition as a prominent problem for chronic dialysis patients

A large number of dialysis patients have been classified as being malnourished because of anthropometric measurements and laboratory values that are similar to those in patients with protein-energy malnutrition. Malnutrition implies that abnormalities can be reversed with better nutrition. However, this approach of providing more nutrients in the diet has been unsuccessful in reversing these changes, suggesting that a diagnosis of malnutrition is generally a misdiagnosis for dialysis patients In this review we discuss mechanisms that cause a loss of protein stores, muscle mass, albumin, and other plasma proteins in dialysis patients. We also review the shortcomings of techniques that are used to measure the nutritional status of these patients.

Advanced glycation end products in kidney transplant patients: a putative role in the development of chronic renal transplant dysfunction

Chronic renal transplant dysfunction is one of the leading causes of graft failure in kidney transplantation. A complex interplay of both alloantigen-related and alloantigen-unrelated risk factors is believed to underlie its development. We propose that advanced glycation end products (AGEs) are involved in the development of chronic renal transplant dysfunction. AGE formation is associated with different alloantigen-unrelated risk factors for chronic renal transplant dysfunction, such as recipient age, diabetes, proteinuria, hypertension, and hyperlipidemia. In vitro studies have shown that AGEs induce the expression of various mediators associated with chronic renal transplant dysfunction. Furthermore, AGE-induced renal damage has been found in multiple experimental studies. This renal damage shows similarity to the damage found in chronic renal transplant dysfunction. Together, several lines of evidence support a role of AGEs in the development of chronic renal transplant dysfunction and suggest that preventive therapy with AGE inhibitors may be helpful in preserving renal function in transplant recipients.

Emerging drugs for renal failure

Renal failure involves a significant impairment of the essential functions of the kidney, which can be either acute with sudden and rapid onset (acute renal failure [ARF]) or chronic with gradual onset (chronic renal failure [CRF]). ARF, if detected early, may be halted or reversed, whereas CRF is generally irreversible. Without treatment or intervention, both forms of renal failure lead to end stage renal failure (ESRF) or end stage renal disease (ESRD), requiring renal replacement therapy (RRT) in the form of dialysis or renal transplantation for survival. However, provision of RRT requires expert teams working in specialised units, making therapy of patients with renal failure expensive; furthermore, RRT is complex, with its own complications. Although pharmacological interventions have shown promise in experimental models, these have not been as successful in the clinical setting (e.g., administration of atrial natriuretic peptide, low-dose dopamine). At present, drugs are administered during CRF to either reduce one of the many risk factors of CRF (e.g., angiotensin-converting enzyme inhibitors, statins) or to deal with the consequences of CRF (e.g., erythropoietin, calcitriol). Recent evidence suggests that some of these interventions may provide further direct beneficial effects via reduction of renal inflammation. Although these interventions have greatly improved the prospects for patients suffering ESRF, the development of novel drugs and therapies with which to reduce the consequences of renal failure and ESRD remain topics of great interest. This article reviews the therapies available for the prevention and management of renal failure in adults and describes, in detail, emerging drugs and novel interventions that may soon become available for the treatment or prevention of ESRF.

Glycoxidation and inflammatory markers in patients on treatment with PMMA-based protein-leaking dialyzers

BACKGROUND

High-molecular-weight solutes such as glycation and oxidation protein products are putative proinflammatory mediators found in the uremic blood. The elimination of these and other large solutes by protein-leaking dialyzers (PLD) might help to correct the inflammatory status of maintenance hemodialysis (HD) patients.

METHODS

Two matched groups of 13 standard 3 times/week HD patients were treated for 6 months with PMMA-based PLD and non-protein-leaking dialyzers (NPLD), respectively. At baseline, 1, 3, and 6 months, we measured the blood levels of the inflammatory cytokines IL-1beta, TNF-alpha, IL-6, the acute-phase protein C-reactive protein (CRP), the adhesion molecules ICAM-1, VCAM-1, and selectine-E, the chemotaxis factors MCP-1, and the glycation and oxidation protein end products pentosidine, protein carbonyls, and AOPP.

RESULTS

In all the patients at baseline, pre-HD levels of glycation and oxidation protein markers, and inflammatory parameters were significantly higher than in healthy control subjects (P < 0.01 or greater). After 6 months, in the group on treatment with PLD, but not in that on NPLD, there was a significant decrease (P < 0.05 or greater) of pre-HD values of total pentosidine (mainly represented by pentosidine in serum albumin; -43%), protein carbonyls (-42%), AOPP (-38%), and the inflammatory cytokines IL-1beta (-49%), IL-6 (-39%), and TNF-alpha (-20%), while IL-10 and INF-gamma increased by 67% and 37%, respectively. Proinflammatory cytokines, and particularly IL-6, showed a positive correlation with the levels of circulating pentosidine. Protidemia was not significantly modified at the end of the study in both the groups.

CONCLUSION

The results in this pilot study show that the removal of large solutes by PLD can improve some indices of chronic inflammation in HD patients. Further studies are required to determine the relevance of the individual solutes removed with PLD as proinflammatory mediators in the uremic environment.

Modulation and Source of Procalcitonin in Reduced Renal Function and Renal Replacement Therapy

Serum procalcitonin (PCT), an accurate marker of severe infection, is moderately increased in chronic kidney disease (CKD), peritoneal dialysis (PD) and haemodialysis (HD). We studied the extent of PCT elevation and factors accounting for elevated PCT in CKD and dialysis, and whether peripheral blood mononuclear cells (PBMC) contribute to increased PCT. In 37 controls, 281 CKD, 31 PD, and 65 HD patients without infection, PCT was measured and correlated with CKD stage, PD, HD, C-reactive protein (CRP), cardiovascular disease (CVD) and other clinical parameters. PCT release by PBMC from controls, advanced CKD, PD and HD patients (12 subjects each) was measured. PCT increased in parallel to the deterioration of CKD. Oliguria, advanced CKD, PD, HD, CVD and elevated CRP were independently associated with PCT elevation. PCT release from PBMC significantly increased in advanced CKD, PD and HD. PCT release from PBMC correlated closely with the corresponding serum PCT values (r=0.76, P <0.001). In the absence of infection, PCT may increase due to reduced renal elimination and increased synthesis, as due to PBMC. Furthermore, serum PCT could serve as a marker of low-grade inflammation and CVD, which substantially increase mortality in CKD and dialysis.

The pattern of inflammation and a potential new clinical meaning and usefulness of C-reactive protein in end-stage renal failure patients

Inflammatory indexes are frequently elevated in end-stage renal failure (ESRF) patients. It seems that the pattern of inflammation is particular in this population. In the presence of a higher than normal microinflammatory background (CRP, C-reactive protein, values between 0.1 and 10-15 mg/l) that varies with time, waves of 'true' inflammation (CRP > 10-15 mg/l), mainly due to infections, are added periodically. To accurately assess the average microinflammation in these patients, multiple CRP measurements are required. As recent experimental studies showed that inflammation and particularly elevated CRP levels may be risk factors and not just a risk index for atherosclerosis, in this case, the characteristic inflammation pattern might be of importance in the evolution of this disease in ESRF patients. The causes of the inflammatory state in ESRF patients are multiple: renal insufficiency per se and its complications, coexisting diseases, established atherosclerosis, the consequences of renal replacement treatment, and frequent infections are potentially the main ones. The fluctuating inflammatory pattern is probably due to destabilization or changes in time of the above-mentioned parameters. Thus, the clinical meaning of the average microinflammation in these patients, as assessed by CRP measurements, seems to be that of an index indicative of the grade of their health aggravation by the multiple factors implicated in the inflammation formation. CRP is a sensitive, but not specific, risk index of the overall morbidity and mortality in these patients. The manipulation of the inflammation in ESRF patients should include follow-up and treatment of all the factors that contribute to this state and probably medications such as the statins. If inflammation and CRP in particular definitely prove to be risk factors for atherosclerosis, intensification of this treatment will be necessary.

Truncal fat mass as a contributor to inflammation in end-stage renal disease

BACKGROUND

An activated inflammatory response is a common feature of end-stage renal disease (ESRD) and predicts outcome. Adipose tissue is an endocrine organ that may contribute to an inflammatory burden by secreting adipocytokines such as interleukin 6 (IL-6).

OBJECTIVE

The objective was to relate plasma concentrations of IL-6 in ESRD patients to body composition, regional fat mass distribution, and blood lipid profiles.

DESIGN

One hundred ninety-seven ESRD patients (123 men; +/- SE age: 52 +/- 1 y) were evaluated shortly before dialysis started. Lean body mass and truncal and nontruncal fat mass were estimated by dual-energy X-ray absorptiometry. Nutritional status was evaluated on the basis of subjective global assessment and handgrip strength. Inflammatory biomarker and blood lipid concentrations were also evaluated.

RESULTS

Median IL-6 (8.5 compared with 4.5 pg/mL; P < 0.001) concentrations were significantly greater in malnourished than in well-nourished patients. Moreover, negative correlations were observed between IL-6 and serum creatinine (rho = -0.19, P < 0.01), handgrip strength (rho = -0.24, P < 0.001), and serum albumin (rho = -0.34, P < 0.001). A significantly higher truncal fat mass (12.8 +/- 0.7 compared with 10.5 +/- 0.4 kg; P < 0.005) was observed in ESRD patients with inflammation (C-reactive protein >/= 10 mg/L). Inverse correlations were observed between plasma IL-6 and HDL cholesterol (rho = -0.16, P < 0.05) and apolipoprotein A (rho = -0.23, P < 0.001).

CONCLUSIONS

Plausible relations exist between inflammatory biomarkers, such as IL-6 and high-sensitivity C-reactive protein, and regional fat distribution in ESRD patients. Moreover, the strong inverse relations between HDL cholesterol and apolipoprotein A and biomarkers of inflammation suggest that the chronic inflammatory response observed in ESRD patients is an important contributor to the atherogenic lipoprotein profile in uremia.

Roles of oxidative stress and antioxidant therapy in chronic kidney disease and hypertension

PURPOSE OF REVIEW

Oxidative stress is frequently associated with, and is partly involved in, the pathogenesis of chronic renal failure, hypertension and their complications. In the past few years, considerable progress has been made in deciphering the impact and the molecular mechanism of oxidative stress in these disorders. This article is intended to provide an overview of oxidative stress in hypertension and chronic renal failure.

RECENT FINDINGS

Recent studies have provided irrefutable evidence that oxidative stress can cause hypertension and hypertension can cause oxidative stress. The upregulation of nicotinamide adenine dinucleotide phosphate (reduced form) oxidase and the tubulointerstitial accumulation of activated T cells, macrophages and superoxide-producing cells are partly responsible for oxidative stress in several models of hypertension. Antioxidant therapy alleviates hypertension, averts nuclear factor kappa B activation, and mitigates tubulointerstitial inflammation in hypertensive animals. Oxidative stress contributes to hypertension, endothelial dysfunction and brain disorders in chronic renal failure animals, and is partly caused by the upregulation of nicotinamide adenine dinucleotide phosphate (reduced form) oxidase and the downregulation of superoxide dismutase.

SUMMARY

Oxidative stress, hypertension and inflammation are closely interrelated and involve a spiralling vicious cycle that can lead to progressive deterioration of hypertension and target organ damage.

Oxidative stress in uremia: Nature, mechanisms, and potential consequences

Oxidative stress has emerged as a constant feature of chronic renal failure (CRF). The presence of oxidative stress in CRF is evidenced by an overabundance of lipid, carbohydrate, and protein oxidation products in the plasma and tissues of uremic patients and animals. We recently have shown that oxidative stress in CRF animals is associated with and, in part, owing to up-regulation of superoxide-producing enzyme, nicotinamide-adenine dinucleotide phosphate (NAD(P)H) oxidase, and down-regulation of superoxide dismutase (SOD). The functional significance of these findings was confirmed by favorable response to administration of the cell-permeable SOD-mimetic agent, tempol, in CRF rats. Oxidative stress in CRF plays an important role in the pathogenesis of the associated hypertension (oxidation of NO and arachidonic acid and vascular remodeling), cardiovascular disease (oxidation of lipoproteins, atherogenesis), neurologic disorders (nitration of brain proteins, oxidation of myelin), anemia (reduction of erythrocyte lifespan), inflammation (nuclear factor kappa B activation), fibrosis, apoptosis, and accelerated aging. The CRF-induced oxidative stress is aggravated by diabetes, uncontrolled hypertension, and autoimmune diseases, which independently increase production of reactive oxygen intermediates, and frequently are associated with CRF. In addition, dialysis treatment (blood interaction with dialyzer membrane and dialysate impurities), acute and chronic infections (blood access infection, hepatitis, and so forth), and excessive parenteral iron administration intensify CRF-associated oxidative stress and its adverse consequences in patients with end-stage renal disease. The problem is compounded by limited intake of fresh fruits and vegetables (K(+) restriction), which contain numerous natural phytochemicals and antioxidant vitamins.

Inflammation and nutrition in renal insufficiency

Protein-energy malnutrition (PEM) and inflammation are common in patients with chronic kidney disease (CKD) and worsen as the CKD progresses toward the end-stage renal disease (ESRD). These conditions are major predictors of poor clinical outcome in kidney failure, as reflected by a strong association between hypoalbuminemia and cardiovascular disease (CVD). It has been suggested that inflammation is the cause of both PEM and CVD and, hence, the main link among these conditions, but these hypotheses are not well established. Increased release or activation of inflammatory cytokines, such as interleukin-6 or tumor necrosis factor alpha, may suppress appetite, cause muscle proteolysis and hypoalbuminemia, and may be involved in atherogenesis. Increasing serum levels of proinflammatory cytokines caused by reduced renal function, volume overload, oxidative or carbonyl stress, decreased levels of antioxidants, increased susceptibility to infection in uremia, and the presence of comorbid conditions may lead to inflammation in CKD patients. In hemodialysis patients, the exposure to dialysis tubing and dialysis membranes, poor quality of dialysis water, back-filtration or back-diffusion of contaminants, and foreign bodies in dialysis access maybe additional causes of inflammation. Similarly, episodes of overt or latent peritonitis, peritoneal dialysis (PD) catheter and its related infections, and constant exposure to PD solution may contribute to inflammation in these patients. The degree to which PEM in dialysis patients is caused by inflammation is not clear. Because both PEM and inflammation are strongly associated with each other and can change many nutritional measures and outcome concurrently in the same direction, the terms malnutrition-inflammation complex syndrome (MICS) and/or malnutrition-inflammation-atherosclerosis (MIA) have been suggested to denote the important contribution of both of these conditions to poor clinical outcome. Maintenance dialysis patients who are underweight or who have low serum levels of cholesterol, creatinine, or homocysteine may be suffering from the MICS/MIA and its subsequent poor outcome. Consequently, obesity and hypercholesterolemia may appear protective, which is known as reverse epidemiology. Although MICS/MIA may have a significant contribution in reversing the traditional CVD risk factors in dialysis patients, it is not clear whether PEM or inflammation and their complications can be effectively managed in CKD and ESRD or whether their management improves clinical outcome.

Plasma ghrelin levels in patients undergoing haemodialysis and peritoneal dialysis

BACKGROUND

Ghrelin has been characterized as a relevant physiologic regulator of appetite and body weight in humans. However, the potential relationships between ghrelin levels, inflammation and malnutrition in dialysis patients have not been adequately studied.

METHODS

We used a cross-sectional design to study 20 haemodialysis (HD) and 21 peritoneal dialysis (PD) patients, and compared their plasma ghrelin (PGhr) levels with that of an age-matched control group. We also explored correlations between ghrelin and selected hormonal, renal adequacy, nutritional and inflammation markers in both groups.

RESULTS

PGhr levels were higher in HD (median 119.8 pg/ml, range 71.1-333.7, P = 0.001) and PD (99.3, range 45.8-578.5, P = 0.045) patients than in healthy controls (78, range 29-158) (HD vs PD, not significant). Ghrelin levels were strongly and inversely correlated with age (r = -0.46, P = 0.02 for patients; r = -0.61, P = 0.001 for controls). Except for a positive correlation between ghrelin and growth hormone (r = 0.48, P = 0.002), univariate analysis failed to detect associations between PGhr and the measured hormonal values, renal adequacy, nutritional indicators and markers of inflammation. However, multivariate analysis revealed significant inverse correlations between PGhr levels and nutritional markers, including subjective global assessment (P = 0.013), albumin (P = 0.001), transferrin (P = 0.01) and protein nitrogen appearance (as an estimate of protein intake) (P = 0.035), after controlling for the confounding effect of age.

CONCLUSIONS

PGhr levels were moderately and similarly increased in patients undergoing HD and PD. Age was a strong determinant of PGhr levels, both in uraemic patients and in healthy controls. Dialysis adequacy, residual renal function and inflammation did not appear to influence ghrelin levels in these patients. The negative correlation between PGhr and nutritional markers suggests that low dietary intake causes increases in ghrelin secretion in dialysis patients.

The effects of iron dextran on the oxidative stress in cardiovascular tissues of rats with chronic renal failure

BACKGROUND

Redox-active iron can promote oxidative stress and tissue injury by catalyzing hydroxyl radical generation and lipid peroxidation. Intravenous iron preparations are routinely administered in conjunction with erythropoietin to treat anemia in patients with chronic renal failure (CRF), a condition that is marked by oxidative stress and inflammation. This treatment frequently elevates iron burden, which can potentially intensify oxidative stress and, thus, cardiovascular disease in this population.

METHODS

We studied renal function and oxidative stress parameters in the cardiovascular tissues of CRF (5/6 nephrectomized) and sham-operated control rats 3 months after a single intravenous infusion of iron dextran (500 mg/kg).

RESULTS

Arterial pressure was equally elevated and creatinine clearance was equally reduced in both iron-treated and -untreated CRF groups. Iron administration significantly raised the blood hemoglobin, serum iron concentration, and transferrin saturation in both CRF and control groups. Iron administration resulted in a significant rise in plasma concentration of lipid peroxidation product, malondialdehyde in the CRF rats, and an insignificant rise in the control group. Plasma oxidized low-density lipoprotein (LDL) concentration was increased in the CRF groups, and was not affected by iron administrations. Iron administration raised nitrotyrosine abundance in the aorta of CRF but not in the control group. Left ventricular tissue abundance of p22(phox) subunit of NAD(P)H oxidase was elevated in CRF group and was not affected, whereas p67(phox) subunit abundance was raised by prior iron administration. Iron administration insignificantly lowered aorta p22(phox), but had no effect on p67(phox) subunit abundance in the treated CRF group. Previous iron administration significantly lowered superoxide dismutase and catalase abundance in the aorta and glutathione peroxidase in the left ventricle of CRF animals, but did not significantly change these parameters in the iron-treated control animals.

CONCLUSION

A single intravenous injection of iron dextran increased oxidative stress in the cardiovascular tissues in the CRF group, but not the control rats, pointing to heightened susceptibility to iron-mediated toxicity in CRF. However, administration of iron dextran did not adversely affect kidney function, and favorably affected hemoglobin concentration in rats with CRF induced by renal mass reduction. Further studies are needed to explore the effects of other parenteral iron preparations, repeated intravenous iron administration, and presence of comorbid conditions such as diabetes.

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.

When Good Water Goes Bad: How It Happens, Clinical Consequences and Possible Solutions

Dialysis fluid produced by state-of-the-art water preparation and distribution is contaminated with gram-negative bacteria and cytokine-inducing substances (CIS) derived from these microorganisms. The presence of a biofilm increases the risk of continuous contamination of dialysis fluid. Depending on the type of dialyzer membrane (cellulosic vs. synthetic) and the mode of dialysis (low flux vs. high flux with backfiltration), CIS may penetrate intact dialyzer membranes, induce cytokine production in the patient's blood and contribute to chronic inflammation associated with long-term hemodialysis therapy. Measures to improve the microbiological quality of dialysis fluid are: (1) the awareness of the problem and regular testing of dialysate samples using adequate methods; (2) disinfection of the entire water preparation and distribution system on a regular basis, replacement of biofilm-containing tubings, and (3) installation of ultrafilters in the dialysate circuit in particular when high-flux hemodialysis modalities are performed.

RENAL RESEARCH INSTITUTE SYMPOSIUM: Efforts to Determine the Role of Oxidant Stress in Dialysis Outcomes

The role of elevated markers of oxidant stress needs to be established in longitudinal studies. Oxidant stress markers such as malonaldehyde (MDA), isoprostanes, and breath hydrocarbons warrant rigorous application to outcomes, if they are to be used as clinical parameters. For example, investigations of C-reactive protein (CRP), parathyroid hormone (PTH), and several other clinical indicators have shown that these markers can be used to predict outcomes such as morbidity and mortality. Long-term followup is needed for intervention studies with antioxidants, since effects with short-term studies may be focused on critically-ill individuals where intervention would not be expected to be effective. Oxidant stress studies in this population especially need a long-term approach to test the hypothesis that antioxidant intervention is beneficial.

Malnutrition and inflammation in peritoneal dialysis patients

BACKGROUND

Malnutrition, cardiovascular disease, and heightened inflammation are highly prevalent in dialysis patients, and major contributors to morbidity and mortality. We have investigated the inter-relationship between malnutrition and inflammation, and their impact on morbidity and mortality in peritoneal dialysis (PD) patients.

METHOD

We enrolled 63 PD patients beginning in November 2000, and measured C-reactive protein (CRP) and various nutritional markers, including prealbumin.

RESULTS

CRP level was elevated in 29% of the PD patients. Diabetics had higher CRP than non-diabetics (24 vs. 9.3 mg/L, P = 0.016). Patients who were hospitalized during the study had higher enrollment CRP (16 vs. 12.5 mg/L, P = 0.05) and lower enrollment albumin (3.5 vs. 3.9 g/dL, P = 0.002), blood urea nitrogen (BUN) (40 vs. 49 mg/dL, P = 0.034), and protein catabolic rate (nPCR) (0.88 vs. 1.0 g/kg/day, P = 0.02) than those who were not hospitalized. Enrollment level of CRP was inversely correlated with nutritional markers prealbumin (r = -0.5, P < 0.0001) and creatinine (r =-0.35, P < 0.01). After adjusting for age, race, gender, diabetes, and CRP level, prealbumin continued to correlate with other nutritional markers. There was a trend toward association of elevated CRP with all-cause mortality in PD patients.

CONCLUSION

It is useful to incorporate prealbumin and CRP in the regular assessment of PD patients, whose survival may be improved by better management of malnutrition and inflammation.

C-reactive protein as a cardiovascular risk factor and its therapeutic implications in end-stage renal disease patients

We observed the association between a persistent elevation of C-reactive protein (CRP) level and the presence of ischemic heart disease in 73 peritoneal dialysis (PD) patients. Twenty-six patients showed an elevation of CRP for more than 6 months. Seventeen (65%) of the 26 patients had positive thallium single photon computed tomography (SPECT). Three of 9 patients who had a persistent elevation of CRP and negative thallium SPECT had a history of cerebral infarction or peripheral vascular disease. Therefore, 77% (20/26) of an elevated CRP level that lasted longer than 6 months can be explained by the presence of atherosclerotic vascular disease. There are as yet no valid recommendations on how chronic inflammation should be handled. We found that aspirin 200 mg daily for 8 weeks induce no significant changes of the CRP levels in PD patients (0.22 vs. 0.18 mg/dL, p > 0.05). However, 62 HD patients were randomly assigned to treatment group (simvastatin 20 mg/day) and control group. After 8 weeks medication, hs-CRP levels significantly reduced from a median of 0.23 mg/dL to 0.12 mg/dL.

Circulating endothelial cells as potential markers of the state of the endothelium in hemodialysis patients

BACKGROUND

Patients with chronic kidney disease (CKD) are at high risk for atherosclerotic cardiovascular disease (ACVD). In addition to the same epidemiological risk factors of the general population, factors unique or secondary to the uremic milieu may contribute to excess cardiovascular morbidity and mortality. Recent studies suggest the endothelium has a key role in the development of atherosclerosis. Circulating endothelial cells (CECs) may be a tool to study the state of the endothelium, with their number markedly increased in conditions associated with a high degree of endothelial cell activation and/or injury. Our hypothesis is that CEC number increases in diseases that commonly progress to stage 5 CKD, as well as in patients on hemodialysis (HD) therapy, reflecting ongoing endothelial cell activation and/or injury.

METHODS

The study population consisted of 22 healthy nonsmoking individuals, 29 individuals undergoing long-term HD treatment, 10 individuals with the diagnosis of diabetes mellitus and stage 1 or 2 CKD, and 7 individuals with hypertension and stage 1 or 2 CKD. The number of CECs was enumerated in all study groups.

RESULTS

We found that CEC number was increased in HD patients, hypertensive patients, and patients with diabetes compared with healthy individuals. In addition, although CEC number did not accurately reflect the presence of ACVD, the number was increased significantly in a group of HD patients with active ACVD, whereas it was decreased significantly in a group of HD patients with stable ACVD.

CONCLUSION

Our results suggest that CEC number may reflect ACVD activity in HD patients, independent of the presence of ACVD.

Slowing the progression of vascular calcification in hemodialysis

Hyperphosphatemia and secondary hyperparathyroidism are common complications of ESRD (chronic kidney disease stage 5) that, when untreated, may result in increased morbidity and mortality. Hyperphosphatemia and hypercalcemia have been associated with increased coronary artery calcification. Achieving control of serum phosphorus without increasing serum calcium is an important goal for patients with ESRD. Although calcium-based phosphate binders effectively reduce serum phosphorus and parathyroid hormone concentrations, these agents can lead to hypercalcemia and have been associated with increased vascular calcification. The phosphorus binder sevelamer was developed to overcome the limitations associated with the usual management of hyperphosphatemia and secondary hyperparathyroidism (i.e., mineral salts). Sevelamer, a nonabsorbable hydrogel, is as efficacious as calcium-based phosphate binders for reducing serum phosphorus but does not cause hypercalcemia or other adverse metabolic effects. Sevelamer also exhibits beneficial effects on lipids, consistently and significantly decreasing LDL cholesterol and increasing HDL cholesterol in most studies. In a head-to-head randomized clinical trial, sevelamer and calcium-based binders achieved similarly excellent phosphorus control, but the use of calcium-based binders led to significantly higher serum calcium concentrations and an increased incidence of hypercalcemia and unintended suppression of parathyroid hormone. Treatment with calcium-based binders also led to the progression of coronary artery and aortic calcification, whereas sevelamer attenuated or arrested progression. Strategies that use oral calcium and vitamin D in patients with ESRD should be reexamined, and the potential advantages of sevelamer should be considered when selecting a primary agent to reduce serum phosphorus in hemodialysis patients.

Mean arterial pressure and pulse pressure are associated with different clinical parameters in chronic haemodialysis patients

The mean arterial pressure (MAP) usually serves as an expression of blood pressure in patients on chronic haemodialysis (PCHD), instead of using solely systolic or diastolic pressure. Pulse pressure (PP) has been recognized as an important correlate of mortality in PCHD. We conducted this study in order to demonstrate clinical and biochemical determinants and variability of predialysis and postdialysis MAP and PP values. A total of 136 single haemodialysis (HD) treatments in 23 subjects (PCHD, 11 male and 12 female patients) were processed during 15 months. MAP before HD was in negative correlation with haemoglobin (P<0.001) and body mass index (BMI) (P<0.001), and in positive correlation with weekly erythropoietin dosage (P=0.017). MAP after HD was in negative correlation with haemoglobin (P<0.001), ultrafiltration per HD (P=0.015), and BMI (P=0.001), and in positive correlation with weekly erythropoietin dosage (P=0.003). PP before HD was in negative correlation with parathyroid hormone (PTH) level (P=0.020), haemoglobin (P<0.001), ultrafiltration per HD (P=0.001), and years on the chronic HD treatment (P=0.001), and in positive correlation with weekly erythropoietin dosage (P<0.001) and age (P<0.001). PP after HD was in significant negative correlation with PTH (P=0.015), haemoglobin (P=0.005), ultrafiltration per HD (P<0.001), BMI (P=0.003), and in positive correlation with weekly erythropoietin dosage (P<0.001) and age (P=0.004). Multiple regression analyses unveiled the strongest and negative correlations between MAP before HD and BMI (beta=-0.37, P=0.01); MAP after HD and haemoglobin (beta=-0.36, P=0.01); PP after HD and ultrafiltration/body weight ratio (beta=-0.41, P<0.001). The strongest and positive correlation was found between PP before HD and erythropoietin dosage per week (beta=0.51, P&<0.001). In conclusion, our findings support the assumption that PP and MAP are associated with different clinical parameters. PP values have advantages as the method of blood pressure expression.

Obesity and survival on dialysis

Several factors associated with greater cardiovascular mortality in the general population may show a paradoxical relationship in patients on dialysis therapy. This dialysis-risk paradox has been reported for high blood pressure, serum lipid levels, and body mass, but the finding is more consistent and persuasive for obesity. This article examines the literature on the association between body mass and dialysis survival and considers the possible mechanistic and clinical implications.

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.