Leptin is a negative acute phase protein in chronic hemodialysis patients

Serum Interleukin-6 and Weight Loss in Antiretroviral-naïve and Antiretroviral-treated Patients with HIV/AIDS: Relationships and Predictors

BACKGROUND

Cachexia is usually associated with elevated serum interleukin-6 (IL.6) as it stimulates the breakdown of muscle proteins and promotes wasting.

OBJECTIVE

A case-control study to evaluate the relationship between weight loss, facial fat loss, and IL-6 in antiretroviral-naïve and treated participants living with HIV/AIDS.

METHODS

IL-6 was assayed by High performance liquid chromatography (HPLC) in 97 in consecutive newly diagnosed antiretroviral-naive (ART-naïve) people living with HIV/AIDS (age ≥18 years); and 118 consecutive, age-matched participants currently on Highly Active Antiretroviral Therapy (HAART), using age as a criterion. In the treated group, 78 (66.7%) subjects were on zidovudine, lamivudine with nevirapine (Z+L+N); 27(23.1%) on tenofovir, lamivudine with emtricitabine (T+L+E); 5(4.3%) on zidovudine, lamivudine with emtricitabine (Z+L+E); 4(3.4%) on zidovudine, lamivudine with tenofovir (Z+L+T); 2(1.7%) on lamivudine, tenofovir with nevirapine (L+T+N); 1(0.9%) on tenofovir, zidovudine, emtricitabine (Z+T+E).

RESULTS

A total of 215 participants: 97 ART-naive and 118 HAART-treated, age-matched subjects (40.3±9.6 versus 42.7±10.20years, p=0.08). The mean IL-6 was significantly higher in naïve than treated (0.69±0.04 versus 0.66±0.04 pg/ml, p =0.002). In all, 73 subjects experienced weight loss, 56(76.7%) naive, 17(23.3%) treated, p <0.0001, with significantly higher IL-6 in those with weight loss (0.69±0.05 versus 0.67±0.05pg/ml, p= 0.047). Fifty-eight (27.0%) subjects experienced facial fat loss, 49 (84.5%) naïve, and 9 (15.5%) treated, p <0.0001, with significantly higher IL-6 in those with facial fat loss (0.7 ± 0.05 versus 0.67±0.05pg/ml, p= 0.0001). Negative correlation exists between IL-6 and CD4+ count (r=-0.141, p=0.041). In logistic regression, independent predictors of weight loss include: IL-6 (Adjusted Odds Ratio, aOR 1.3, 95%CI 0·1-2·6, p=0.047); HIV duration (aOR 11.6, p <0.0001); AIDS-defining illness (aOR 3.5, p <0.0001); CD4+ count (aOR 3.2, p=0.004); HAART status (aOR 2.7, p<0.0001).

CONCLUSION

HIV infection is associated with elevation of serum interleukin-6, which likely contributes to weight and facial fat loss among the treatment-naïve participants; while HAART is associated with suppressed IL-6 levels, thereby ameliorating weight and facial fat loss. Inverse relationship exists between serum IL-6 and CD4+ count; serum IL-6 could differentiate between mild- to moderate and severe immunosuppressive states.

Uremic Toxicity: Present State of the Art

The uremic syndrome is a complex mixture of organ dysfunctions, which is attributed to the retention of a myriad of compounds that under normal condition are excreted by the healthy kidneys (uremic toxins). In the area of identification and characterization of uremic toxins and in the knowledge of their pathophysiologic importance, major steps forward have been made during recent years. The present article is a review of several of these steps, especially in the area of information about the compounds that could play a role in the development of cardiovascular complications. It is written by those members of the Uremic Toxins Group, which has been created by the European Society for Artificial Organs (ESAO). Each of the 16 authors has written a state of the art in his/her major area of interest.

Study of Serum Levels of Leptin, C-Reactive Protein and Nutritional Status in Hemodialysis Patients

Background:

Leptin is secreted by adipose tissue and decreases appetite. However, the role of leptin in the pathogenesis of hemodialysis (HD)-related malnutrition has not been fully evaluated.

Objectives:

The aim of study was to investigate the association between the serum leptin levels, serum C-reactive protein (CRP) levels, and nutritional status in hemodialysis patients.

Patients and Methods:

This analytical descriptive study included 45 hemodialysis patients and 40 healthy subjects. Biochemical parameters and serum leptin levels were measured. The nutritional status was evaluated using a food frequency questionnaire (FFQ) and the calculation of the body mass index (BMI).

Results:

Serum leptin (P < 0.05) and albumin (P < 0.0001) levels and BMI (P < 0.001) of HD patients were significantly lower, while CRP levels were significantly higher than those of controls (P < 0.0001). HD patients consumed the lower daily servings of the food groups compared to the control subjects (P < 0.0001). A significant positive correlation between serum levels of leptin and albumin and BMI was demonstrated. No significant correlations were identified between leptin level, CRP level, and other variables.

Conclusions:

The findings suggest that low levels of leptin may be a contributory factor for malnutrition in HD patients. Further studies are required to ascertain the significance of leptin levels in relation to nutritional factors in hemodialysis patients.

Effect of hemodiafiltration with endogenous reinfusion on overt idiopathic chronic inflammation in maintenance hemodialysis patients: a multicenter longitudinal study

Chronic inflammation is widely diffuse in maintenance hemodialysis (MHD) patients and is associated with poor survival. Hemodiafiltration with endogenous reinfusion (HFR) is a dialysis technique, highly biocompatible, able to adsorb proinflammatory cytokines and to decrease amino acids and antioxidants loss. These features could be helpful in MHD patients affected by idiopathic chronic inflammation, but this issue remains to be elucidated. We performed a multicenter longitudinal study to assess the effect of the switching from bicarbonate HD to HFR in patients with serum C-reactive Protein (CRP) > 5 mg/L coupled with albumin <4.0 g/dL in the last 6 months. We enrolled 24/176 (14%) patients, of which 20 patients were assessed at 4 months and 18 completed the study. We excluded 11 patients with evident causes of inflammation. At baseline, serum levels of CRP (18.7[7.0-39.4] mg/L) and albumin (3.5[3.3-3.7] g/dL) were significantly correlated (r = -0.49; P = 0.028). The effect on CRP and albumin was almost evident in the first 4 months and remained stable until to eighth month. A strict correlation (R = -0.49; 0.040) between percentage change of CRP (-35%) and albumin (+14%) after 8 months of HFR. These effects were associated with the reduction of IL-6, IL-1β, and TNF-α and the increment of pre-albumin and leptin, whereas the serum levels of Branched Chain Amino Acid (BCAA) remained unchanged. In MHD patients affected by idiopathic chronic inflammation the switching from BHD to HFR is associated with improvement of inflammation. Whether these favorable effects may modify the outcomes of these high-risk patients needs to be confirmed by studies ad hoc.

Proteinuria and its relation to diverse biomarkers and body mass index in chronic hemodialysis

Background

Certain adipokines exert direct effects on proteinuria, a cardiovascular risk factor ignored in hemodialysis. We measured different adipokines according to body mass index (BMI) in relation to proteinuria.

Methods

Patients numbered 57: group A (GA), BMI<25, n = 22; GB, BMI 25–30, n = 15; and GC, BMI > 30, n = 20. There were no statistical differences in age, sex, time on dialysis, cause of renal failure, diabetes, hypertension, C-reactive protein, or nutritional status. Measures were taken of 24-hour diuresis and proteinuria, ultrafltration, albumin, pro-brain natriuretic peptide (Pro-BNP), insulin, adiponectin, leptin, and ghrelin.

Results

Proteinuria was signifcantly higher in GC versus (vs) GA (1.5 g/day, range 0.30–14 vs 0.72 g/day, range 0.1–2.7; P < 0.01) and correlated signifcantly with leptin levels (ρ = 0.47, P < 0.05). In GA, elevated levels of Pro-BNP, adiponectin, and ghrelin were associated with lower degrees of proteinuria. Signifcant correlations were found between adiponectin and leptin (ρ = −0.54, P = 0.03), and adiponectin and Pro-BNP (ρ = 0.59, P = 0.02). Though not signifcant, there were more diabetics in GC (GA four, GB three, GC ten). As BMI increased in GB and GC, Pro-BNP, adiponectin, and ghrelin levels decreased signifcantly, while proteinuria, insulin, and homeostasis model assessment of insulin resistance increased. Leptin levels were signifcantly elevated in GC vs GA and GB. In GC, ghrelin correlated signifcantly with Pro-BNP (ρ = 0.51, P = 0.03), while leptin correlation with Pro-BNP was inverse and signifcant in GA (ρ = −0.74, P < 0.001) and inverse and nonsignifcant in GB and GC.

Conclusion

In patients with BMI < 25, higher adiponectin, ghrelin, and Pro-BNP levels were associated with lower proteinuria and leptinemia. In obesity, hyperleptinemia and hyperinsulinemia associated with higher proteinuria; whether decreased adiponectin–ghrelin–ProBNP and/or elevated leptin–insulin levels aggravate proteinuria remains to be determined.

The role of novel biomarkers of cardiovascular disease in chronic kidney disease: focus on adiponectin and leptin

Cardiovascular disease (CVD) remains a major cause of premature death in patients with chronic kidney disease (CKD), including renal transplant recipients. Both interplay of traditional cardiovascular and renal specific risk factors have been shown to be associated with an increased risk of cardiovascular death in patients with CKD. Recently, there has been great interest in the role of novel biomarkers, in particular adiponectin and leptin, and its association with CVD in the CKD population. Adiponectin is a multifunctional adipocyte-derived protein with anti-inflammatory, antiatherogenic and insulin sensitizing activity. Recent observational studies have shown adiponectin to be a novel risk marker of CVD in patients with stages 1 to 5 CKD. Leptin is an adipocyte-derived hormone that promotes weight loss by decreasing food intake. Similarly, there are observational studies to support an association between leptin and CVD, including patients with CKD. In the CKD population, leptin may be associated with uremic cachexia and subsequent increased mortality. This review aims to summarize the pathophysiological and potential clinical roles of these cardiovascular biomarkers in patients with CKD.

Longitudinal study of leptin levels in chronic hemodialysis patients

Background

The influence of serum leptin levels on nutritional status and survival in chronic hemodialysis patients remained to be elucidated. We conducted a prospective longitudinal study of leptin levels and nutritional parameters to determine whether changes of serum leptin levels modify nutritional status and survival in a cohort of prevalent hemodialysis patients.

Methods

Leptin, dietary energy and protein intake, biochemical markers of nutrition and body composition (anthropometry and bioimpedance analysis) were measured at baseline and at 6, 12, 18 and 24 months following enrollment, in 101 prevalent hemodialysis patients (37% women) with a mean age of 64.6 ± 11.5 years. Observation of this cohort was continued over 2 additional years. Changes in repeated measures were evaluated, with adjustment for baseline differences in demographic and clinical parameters.

Results

Significant reduction of leptin levels with time were observed (linear estimate: -2.5010 ± 0.57 ng/ml/2y; p < 0.001) with a more rapid decline in leptin levels in the highest leptin tertile in both unadjusted (p = 0.007) and fully adjusted (p = 0.047) models. A significant reduction in body composition parameters over time was observed, but was not influenced by leptin (leptin-by-time interactions were not significant). No significant associations were noted between leptin levels and changes in dietary protein or energy intake, or laboratory nutritional markers. Finally, cumulative incidences of survival were unaffected by the baseline serum leptin levels.

Conclusions

Thus leptin levels reflect fat mass depots, rather than independently contributing to uremic anorexia or modifying nutritional status and/or survival in chronic hemodialysis patients. The importance of such information is high if leptin is contemplated as a potential therapeutic target in hemodialysis patients.

Fasting serum leptin level correlates with mid-arm fat area in peritoneal dialysis patients

Leptin correlates with body fat content and plays a pivotal role in inflammatory response. This study aimed to investigate the relationships of fasting serum leptin levels and the anthropometric fat components among peritoneal dialysis (PD) patients. Fasting blood samples were obtained from 40 PD patients. Leptin levels were measured using a commercial enzyme-linked immunosorbent assay kit. Body weight (r=0.424; P=0.006), waist circumference (r=0.352; P=0.026), body mass index (BMI; r=0.483; P=0.002), body fat mass (r=0.352; P=0.026), high sensitivity C-reactive protein (hs-CRP; r=0.494; P=0.001), triceps skinfold thickness (TSF; r=0.505; P=0.001), mid-arm circumference (MAC; r=0.471; P=0.002), and mid-arm fat area (MAFA; r=0.564; P<0.001) were positively correlated, while high density lipoprotein (HDL)-cholesterol (r=-0.345; P=0.028) was negatively correlated with fasting serum leptin levels among the PD patients. Multivariate forward stepwise linear regression analysis showed that MAFA (R(2)=0.318, P=0.011) was the independent predictor of fasting serum leptin levels among the PD patients. In conclusion, fasting leptin level was positively associated with body fat composition (body weight, waist circumference, BMI, body fat mass, TSF, MAC, and MAFA) and hs-CRP among PD patients, and MAFA was the independent predictor of fasting serum leptin levels among the PD patients.

Are ghrelin and leptin involved in food intake and body mass index in maintenance hemodialysis?

OBJECTIVES

Both leptin and ghrelin (in the forms of acyl ghrelin and des-acyl ghrelin) are involved in food intake, and appear to be dysregulated in chronic kidney disease. This study describes plasma leptin, acyl, and des-acyl ghrelin concentrations in relation to protein intake and body mass index (BMI) in hemodialysis (HD) patients.

DESIGN

This was a cross-sectional study.

SETTING

This study was conducted during the baseline phase of the French multicenter Influence of a High-Flux Dialyzer on Long-Term Leptin Levels Study.

PATIENTS

We studied 125 HD patients (aged 72.5+/-11.7 years; 59% males).

MAIN OUTCOME MEASURE

Blood samples were collected during fasting, and before a regular HD session. Plasma ghrelin and leptin were evaluated. The protein equivalents of total nitrogen appearance and BMI were calculated.

RESULTS

Patients demonstrated elevated serum leptin (48.0+/-49.0 ng/mL) and des-acyl ghrelin (646.6+/-489.5 pg/mL) levels, and low acyl ghrelin levels (29.8+/-58.5 pg/mL), according to normal values. Acyl ghrelin was negatively correlated with C-reactive protein (r=-0.34, P < .001). The des-acyl to acyl ghrelin ratio was negatively correlated with protein intake, as estimated by normalized Protein Nitrogen Appearance (r=-0.22, P=.01). Serum leptin exhibited its well-described positive correlation with BMI and waist circumference, but the other hormones did not.

CONCLUSIONS

This study reports high des-acyl ghrelin and leptin levels and low acyl ghrelin levels in HD patients, a finding potentially associated with inflammation and food intake.

Adipocytokines leptin and adiponectin, and measures of malnutrition-inflammation in chronic renal failure: is there a relationship?

BACKGROUND

Serum levels of adipocytokines such as leptin and adiponectin are significantly elevated in patients with chronic renal failure (CRF). The effect of such adipocytokines on malnutrition in the CRF population has been of substantial interest. We sought to determine the relationship between plasma leptin and adiponectin levels and malnutrition-inflammation status in end-stage renal disease patients.

METHODS

Thirty patients (15 women and 15 men; mean [+/-SD] age, 50 +/- 14 years) on hemodialysis, and 30 patients (12 women and 18 men; mean [+/-SD] age, 47 +/- 16) on continuous ambulatory peritoneal dialysis, were enrolled in this study. Adipocytokine levels were measured by enzyme-linked immunosorbent assay. Inflammatory markers, such as high-sensitivity serum C-reactive protein (hs-CRP), ferritin, and a nutritional inflammatory scoring system known as the malnutrition-inflammation score (MIS), were also measured in all patients.

RESULTS

Serum leptin had negative correlations with ferritin (r = -0.33, P = .016) and MIS (r = -0.39, P = .003). Adiponectin had a weak positive correlation with MIS (r = 0.26, P = .050), indicating that an increased level of serum adiponectin was associated with a worse nutritional status. Levels of hs-CRP, serum albumin, cholesterol, and triglycerides did not correlate with nutritional status.

CONCLUSIONS

Serum leptin concentration seems to be a marker of good nutritional status, rather than an appetite-suppressing uremic toxin, in patients with CRF. However, the positive correlation between serum adiponectin and worse nutritional-inflammatory status suggests that elevated adiponectin levels may contribute to the pathogenesis of malnutrition in such patients.

Concentration of adipokines in peritoneal effluent: a new marker of acute peritonitis in peritoneal dialysis patients?

BACKGROUND

An early and reliable diagnostic procedure for acute peritonitis in patients on peritoneal dialysis (PD) without typical clinical symptoms remains an important challenge in modern nephrology. During the first days of peritonitis, establishing the diagnosis based on peritoneal effluent pleocytosis and inflammatory markers [C-reactive protein (CRP) or interleukin-6] is not efficient in all cases. Increased peritoneal membrane permeability is a well-known consequence of peritonitis. Therefore, we evaluated the concentrations of selected circulating adipose tissue-derived proteins in the peritoneal effluent of PD patients with episodes of acute peritonitis.

MATERIAL AND METHODS

Concentrations of adiponectin and leptin, in both plasma and peritoneal effluent, were assessed in 24 adult PD patients with peritonitis episodes confirmed by clinical symptoms and/or microbiological tests, and in 23 PD patients without signs and symptoms of inflammation (control group).

RESULTS

In peritoneal effluent collected from patients with acute peritonitis (also without pleocytosis or increased CRP), both adiponectin and leptin concentrations were markedly elevated: adiponectin 744.1 (344.2 - 1144.1) ng/mL vs 4.8 (3.1 - 6.5) ng/mL; leptin 16.3 (9.4 - 23.1) ng/mL vs 5.1 (0.5 - 9.6) ng/mL. Receiver operating characteristic analyses revealed that peritoneal effluent adiponectin concentration >180 ng/mL has 100% sensitivity and 100% specificity, while peritoneal effluent leptin concentration >11.0 ng/mL has 58.3% sensitivity and 95.5% specificity for the diagnosis of acute peritonitis. The increases in adiponectin and leptin concentrations in peritoneal effluent were not consequences of changes in their plasma levels. A positive correlation between peritoneal effluent and plasma concentrations of adiponectin and leptin in patients with peritonitis was found.

CONCLUSION

Increased concentration of leptin and especially adiponectin in peritoneal effluent seems to be a valuable and new early marker of high peritoneal membrane permeability due to acute peritonitis.

Role of fat mass and adipokines in chronic kidney disease

PURPOSE OF REVIEW

As traditional risk factors cannot alone explain the high prevalence and incidence of cardiovascular disease in chronic kidney disease, the complex of insulin resistance, oxidative stress, and endothelial dysfunction has increasingly been studied as an important non-traditional risk factor. Recent studies show that the adipose tissue is a complex organ with pleiotropic functions far beyond the mere storage of energy. Fat tissue secretes a number of adipokines including leptin and adiponectin, as well as cytokines, such as resistin, visfatin, tumor-necrosis factor-alpha and interleukin-6.

RECENT FINDINGS

Adipokine serum levels are markedly elevated in chronic kidney disease, likely due to a decreased renal excretion. Evidence suggests that these pluripotent signaling molecules may have multiple effects modulating insulin signaling, endothelial health and vascular outcome.

SUMMARY

Fat tissue is a storage depot for energy and a source of circulating signaling molecules. It plays an important role in the catabolic uremic milieu, and has been linked to systemic inflammation and uremic anorexia. Further research is needed to investigate the complex interactions between adipokine signaling networks and its effects on vascular health and outcome in chronic kidney disease.

Role of leptin in reverse epidemiology in chronic kidney disease

Leptin is mainly produced by adipocytes and metabolized in the kidney. Leptin is taken up into the central nervous system by a saturable transport system, and controls appetite in rodents and in healthy subjects. Leptin acts on peripheral tissue and increases the inflammatory response by stimulating the production of tumor necrosis factor alpha, interleukin-6 and interleukin-12. In healthy humans, serum leptin concentration is related to the size of adipose tissue mass in the body. The majority of obese subjects have inappropriately high levels of circulating plasma leptin concentrations, indicating leptin resistance. In healthy subjects increased leptin concentration constitutes a biomarker for increased cardiovascular risk. On the other hand, a recent prospective long-term study in patients with chronic kidney disease stage 5 on hemodialysis therapy showed that reduced serum leptin concentration is an independent risk factor for mortality in these patients.

Obesity in chronic kidney disease: good or bad?

Cardiovascular disease (CVD) remains the major cause of morbidity and mortality in chronic kidney disease (CKD) patients. As traditional risk factors cannot alone explain the high prevalence and incidence of CVD in this high-risk population, the complex of insulin resistance, oxidative stress, and endothelial dysfunction has increasingly been studied as important non-traditional risk factors. Recent studies show that the adipose tissue is a complex organ with functions far beyond the mere storage of energy. Indeed, it has recently been shown that fat tissue secretes a number of adipokines - including leptin, adiponectin and retinol-binding protein, as well as cytokines such as resistin, visfatin, tumor necrosis factor and interleukin-6. Adipokine serum levels are furthermore markedly elevated in CKD, likely due to a decreased renal excretion. Evidence suggests that these pluripotent signaling molecules may have multiple effects modulating insulin signaling, endothelial health and putatively CVD. As fat tissue is also a storage depot for energy, much needed in the catabolic milieu of uremia, further research is still needed to elucidate the likely complex interactions between these signaling networks, vascular health and outcome in this high-risk population.

Low serum leptin predicts mortality in patients with chronic kidney disease stage 5

OBJECTIVE

Leptin, secreted from adipose tissue, regulates food intake, energy expenditure, and immune function. It is unknown whether leptin predicts mortality in patients with chronic kidney disease stage 5 on hemodialysis therapy.

RESEARCH METHODS AND PROCEDURES

We performed a prospective cohort study of 71 patients with chronic kidney disease stage 5 in an outpatient hemodialysis center. Subjects were recruited in June 1998 and followed for 83 months. Survival was compared by the Kaplan-Meier method.

RESULTS

After 83 months of follow-up, 48 patients (68%) had died. Serum leptin concentrations at study entry were lower among all deceased patients compared with those patients who survived (5.2 +/- 9.0 microg/L; n = 48; vs. 7.7 +/- 7.8 microg/L; n = 23; p = 0.005). Baseline serum leptin concentrations were significantly lower in patients who died from cardiovascular diseases (4.7 +/- 9.4 microg/L, n = 32) or infections (4.0 +/- 2.7 microg/L; n = 10; each p < 0.05), but not cancer (9.4 +/- 7.9 microg/L; n = 6), than in survivors (7.7 +/- 7.8 microg/L; n = 23; p = 0.003). The relative risk for mortality in patients with serum leptin concentrations below the median (<2.6 microg/L) compared with patients above the median was 1.96 (95% confidence interval, 1.01 to 3.79; p = 0.04). Survival was shorter in patients with leptin concentrations below the median compared with those whose leptin concentrations were above the median (all-cause mortality, chi(2) = 5.05; p = 0.02).

DISCUSSION

Low serum leptin concentration is an independent predictor of mortality in patients with chronic kidney disease stage 5 on hemodialysis therapy.

Effect of intradialytic parenteral nutrition in patients with malnutrition–inflammation complex syndrome on body weight, inflammation, serum lipids and adipocytokines: results from a pilot study

OBJECTIVE

Evaluation of the influence of intradialytic parenteral nutrition (IDPN) in patients suffering from Malnutrition-Inflammation Complex Syndrome (MICS) on nutritional status, inflammation, adipocytokines and serum lipids.

SUBJECTS

Six patients with MICS were assigned to IDPN, whereas six patients matched for age, sex, body mass index (BMI) and co-morbidity without malnutrition served as controls. Patients were recruited from Outpatient Dialysis Unit, Medical University Innsbruck and from Dialysis Unit, Hospital Feldkirch.

RESULTS

In all patients with IDPN, dry body weight increased during the interventional period whereas body weight remained stable in patients without IDPN. Tumor necrosis factor (TNF)-alpha levels were higher in patients with MICS compared with controls at all time points. Total cholesterol, LDL- and HDL-levels significantly increased during dialysis at all time points in controls but not in patients with MICS. Albumin, C-reactive protein, interleukin-6 (IL-6), soluble interleukin-2 receptor (sIL-2R) and adipocytokines did not differ between patients and controls during the study period.

CONCLUSIONS

IDPN in patients with MICS increases body weight despite not influencing inflammatory status. Furthermore, IDPN does not induce a pro-atherogenic lipid composition enhancing the risk for atherosclerosis. Thus, IDPN is a safe and effective treatment of malnutrition in patients with MICS.

Epidemiology of dialysis patients and heart failure patients

The epidemiology of maintenance dialysis patients and heart failure patients has striking similarities. Both groups have a high prevalence of comorbid conditions, a high hospitalization rate, a low self-reported quality of life, and an excessively high mortality risk, mostly because of cardiovascular causes. Observational studies in both dialysis and heart failure patients have indicated the lack of a significant association between the traditional cardiovascular risk factors and mortality, or the existence of a paradoxic or reverse association, in that obesity, hypercholesterolemia, and hypertension appear to confer survival advantages. The time discrepancy between the 2 sets of risk factors, that is, overnutrition (long-term killer) versus undernutrition (short-term killer) may explain the overwhelming role of malnutrition, inflammation, and cachexia in causing the reverse epidemiology, which may exist in more than 20 million Americans. We have reviewed the opposing views about the concept of reverse epidemiology in dialysis and heart failure patients, the recent Die Deutsche Diabetes Dialyze study findings, and the possible role of racial disparities. Contradictory findings on hyperhomocysteinemia in dialysis patients are reviewed in greater details as a possible example of publication bias. Additional findings related to intravenous iron and serum ferritin, calcium, and leptin levels in dialysis patients may enhance our understanding of the new paradigm. The association between obesity and increased death risk in kidney transplanted patients is reviewed as an example of the reversal of reverse epidemiology. Studying the epidemiology of dialysis patients as the archetypical population with such paradoxic associations may lead to the development of population-specific guidelines and treatment strategies beyond the current Framingham cardiovascular risk factor paradigm.

Positive acute-phase inflammatory markers in different stages of chronic kidney disease

BACKGROUND

An elevated serum level of acute-phase inflammatory markers is associated with an increased risk of cardiovascular disease. We hypothesized that elevated acute-phase inflammatory markers are directly associated with the different stages of chronic kidney disease (CKD).

METHODS

We evaluated the relationship between serum levels of high-sensitivity C-reactive protein (hsCRP) and alpha1-acid glycoprotein (alpha1-AGP), as well as the renal function in 224 adult patients with CKD (mean age 56.6 years, 46% male, and 40% diabetics), stratified according to the glomerular filtration rate (GFR) (based on the National Kidney Foundation/Kidney Dialysis Outcomes Quality Initiatives), and in 94 hemodialysis patients.

RESULTS

The mean hsCRP was 8.2 +/- 12.1 mg/l, and hsCRP levels were >5 mg/l in 44.4% of the patients; alpha1-AGP levels were >125 mg/dl in 33.3% of the patients. Mean hsCRP and alpha1-AGP were significantly higher in more severe stages of CKD. A weak inverse relationship was found between GFR and serum hsCRP (r = -0.2205; p = 0.0006) and between GFR and serum alpha1-AGP (r = -0.3266; p < 0.0001). There was a correlation between hsCRP and alpha1-AGP (r = 0.3417; p < 0.0001). No significant differences were detected between patients with CKD and those undergoing hemodialysis concerning hsCRP (8.2 +/- 12.1 vs. 6.8 +/- 7.4 mg/l; p = 0.2980) and alpha1-AGP (116.3 +/- 42.5 vs. 117.2 +/- 37.9 mg/dl; p = 0.8590). However, the level of hsCRP was significantly reduced in hemodialysis patients compared with patients with stage 5 predialytic disease (12.1 +/- 13.9 to 6.8 +/- 7.4 mg/l; p = 0.005). More patients with stage 5 predialytic CKD had an elevated hsCRP serum level compared with patients on hemodialysis (64.7 vs. 37.9%; chi2 = 6.230, p < 0.01).

CONCLUSIONS

Approximately 50% of patients with CKD--even in the early phase of renal failure--exhibit an activated acute-phase response, which is closely related to the stages of CKD. Hemodialysis may partially correct the inflammatory process present in the immediate predialysis phase of CKD.

Leptin and Renal Disease

Leptin is a mediator of metabolism and disease in a variety of organ systems, most notably as an agent of energy stores. However, its role in renal disease as an inflammatory agent as well as its potential impact on the cachexia of uremia have sparked new interest in the molecule for nephrologists. This review elucidates the complex uremic state, the historical discovery of leptin and its physiology, and the potential interactions leptin has on both the progression of kidney disease as well as the morbidity and mortality of end-stage renal disease.

A cute plasma ghrelin and leptin responses to oral feeding or intraperitoneal hypertonic glucose-based dialysate in patients with chronic renal failure

BACKGROUND

Chronic renal failure (CRF) is associated with increased plasma levels of ghrelin and leptin, but the regulation of the secretion of these hormones has been insufficiently studied, in this setting. The aim of this study was to analyze the acute effects of oral feeding or intraperitoneal 3.86% glucose-based dialysate infusion on plasma ghrelin and leptin levels in patients with CRF undergoing peritoneal dialysis (PD).

METHODS

Following a crossover design, 10 patients and eight healthy controls underwent a standardized oral intake, a 3.86% glucose-based dialysate PD exchange (patients) and placebo oral intake. We scrutinized acute changes in plasma ghrelin, leptin, glucose, insulin, and growth hormone (GH) levels.

RESULTS

In patients, total ghrelin decreased modestly immediately after oral feeding (nadir 90.6% of baseline, range 85.1, 94.5, P= 0.03) or the PD exchange test (92.2%, range 58.7, 101.9, P= 0.05) (median). Response to oral feeding was markedly blunted when compared with healthy individuals (73.8%, range 56.1, 89.1, P= 0.007) (P < 0.005 vs. patients). Plasma acyl-ghrelin had a less marked but more persistent decay after the PD exchange test (nadir 80.4%, range 55.1, 96.3, P= 0.02) than after oral intake (64.4%, range 45.6, 82.3, P= 0.005); again, changes were more intense in normal controls (47.4%, range 32.1, 67.3, P= 0.01) (P < 0.05 vs. patients). Leptin levels decreased slightly (P < 0.05) after the PD exchange in patients, but did not respond acutely to oral feeding in patients or controls.

CONCLUSION

Ghrelin secretion is partially refractory to the acute inhibitory effect of oral feeding in patients with CRF undergoing PD therapy. A 3.86% glucose-based PD exchange results in a significant decrease of plasma ghrelin levels. Plasma leptin levels are not acutely affected by oral feeding in patients with CRF or healthy individuals.

Cachexia in chronic kidney disease: a link to defective central nervous system control of appetite

Anorexia is one of several abnormalities characterizing chronic kidney disease (CKD) that cause cachexia, the loss of muscle and adipose stores. It has been attributed to mechanisms ranging from accumulation of toxic "middle molecules" to psychological problems. In this issue of the JCI, Cheung and coworkers used elegant techniques to demonstrate that CKD-associated anorexia is caused by defective hypothalamic regulation of appetite. They attributed the defect to an alteration in the hypothalamus's response to leptin and inflammation. Since similar hypothalamic defects suppress appetite in inflammatory states and in cancer, it is possible that anorexia in several cachexia-inducing conditions results from a common set of hypothalamic abnormalities. The development of small molecules capable of preventing these regulatory abnormalities holds the promise of eliminating the contribution of anorexia to the development of cachexia.

Megestrol Acetate in a Moderate Dose for the Treatment of Malnutrition-Inflammation Complex in Maintenance Dialysis Patients

BACKGROUND

Malnutrition-inflammation complex syndrome and anorexia, common conditions in maintenance dialysis patients, are strongly associated with higher mortality and hospitalization and lower quality of life (QoL) in this population. Megestrol acetate, 800 mg/day, has been shown to increase appetite and food intake and to mitigate inflammation in cachectic AIDS and cancer patients, leading to weight gain, but it is also associated with side effects at this dose.

METHODS

We evaluated the efficacy of the oral solution of megestrol acetate in half of its conventional dose in improving the nutritional state and inflammation in 10 hypoalbuminemic dialysis patients (albumin < 3.7 g/dL). Six women and 4 men, ages 60.2 years, took 400 mg of megestrol acetate solution daily for 16 weeks. Anthropometry, dual energy x-ray absorptiometry, 24-hour diet recalls, and biochemical measurements of nutrition and inflammation, including serum C-reactive protein and leptin, were performed.

RESULTS

At the end of the 16 weeks of intervention, weight and body mass index increased by 9%, body fat proportion by 31%, and triceps skinfold by 40% (P < .01). Serum albumin increased from 3.0 to 3.3 g/dL and continued to increase significantly to 3.6 g/dL after 3 months postintervention (P = .03). Serum leptin increased from 5.2 to 10.7 ng/mL (P = .09). Daily protein and energy intake increased progressively up to 27% to 42% by the end of the trial (P < or = .01). In 8 patients without acute infection, serum C-reactive protein declined from 1.24 to 0.78 mg/L (P = .06). QoL and appetite were reported to be improved. No major side effects were observed, and all 10 patients completed the 16 weeks of daily intake of megestrol acetate without interruption.

CONCLUSIONS

Megestrol acetate oral solution in half of its conventional dose is safe and improves the nutritional state, inflammation, and anorexia in maintenance dialysis patients. Larger-scale placebo-controlled randomized studies are needed to confirm the beneficial effects of 400 mg/day of megestrol acetate in dialysis patients.

Metabolic acidosis and malnutrition-inflammation complex syndrome in chronic renal failure

Metabolic acidosis, a common condition in patients with renal failure, may be linked to protein-energy malnutrition (PEM) and inflammation, together also known as malnutrition-inflammation complex syndrome (MICS). Methods of serum bicarbonate measurement may misrepresent the true bicarbonate level, since the total serum carbon dioxide measurement usually overestimates the serum bicarbonate concentration. Moreover, the air transportation of blood samples to distant laboratories may lead to erroneous readings. In patients with chronic kidney disease (CKD) or end-stage renal disease (ESRD), a significant number of endocrine, musculoskeletal, and metabolic abnormalities are believed to result from acidemia. Metabolic acidosis may be related to PEM and MICS due to an increased protein catabolism, decreased protein synthesis, endocrine abnormalities including insulin resistance, decreased serum leptin level, and inflammation among individuals with renal failure. Evidence suggests that the catabolic effects of metabolic acidosis may result from an increased activity of the adenosine triphosphate (ATP)-dependent ubiquitin-proteasome and branched-chain keto acid dehydrogenase. In contrast to the metabolic studies, many epidemiologic studies in maintenance dialysis patients have indicated a paradoxically inverse association between mildly decreased serum bicarbonate and improved markers of protein-energy nutritional state. Hence metabolic acidosis may be considered as yet another element of the reverse epidemiology in ESRD patients. Interventional studies have yielded inconsistent results in CKD and ESRD patients, although in peritoneal dialysis patients, mitigating acidemia appears to more consistently improve nutritional status and reduce hospitalizations. Large-scale, prospective randomized interventional studies are needed to ascertain the potential benefits of correcting acidemia in malnourished and/or inflamed CKD and maintenance hemodialysis patients. Until then, all attempts should be made to adhere to the National Kidney Foundation Kidney Disease and Dialysis Outcome Quality Initiative guidelines to maintain a serum bicarbonate level in ESRD patients of at least 22 mEq/L.

Adipose tissue cytokines, insulin sensitivity, inflammation, and cardiovascular outcomes in end-stage renal disease patients

From an evolutionary perspective, Darwinian selection has favored insulin-resistant individuals, ie, those with a trait ensuring brain functioning in situations of extreme fuel deprivation. The ability to mount a powerful inflammatory response to infection was another survival advantage in our ancestors, and we now have solid evidence showing that these 2 traits, insulin resistance and inflammation (as measured by serum C-reactive protein [CRP]), are associated in modern human beings. In an analysis of 192 nondiabetic hemodialysis patients, leptin and adiponectin were related in an opposite fashion with insulin sensitivity in end-stage renal disease (ESRD) and interacted in determining insulin resistance in these patients. The risk of insulin resistance was about 6 times higher in ESRD patients with an unfavorable combination of the 2 adipokines (high leptin and low adiponectin) than in those with a favorable combination (low leptin and high adiponectin). Low adiponectin but not high leptin predicted incident cardiovascular events in this cohort. Neither leptin nor adiponectin were associated with CRP in a cross-sectional analysis, but they were linked in an opposite fashion to CRP in a longitudinal study in 21 patients with acute inflammation secondary to infection. High sympathetic activity predicts adverse cardiovascular outcomes in ESRD. Of note, we found that the risk for cardiovascular events is more than 3 times higher in patients with high sympathetic activity and low adiponectin than in those with high adiponectin and low sympathetic activity. The adipocyte hormones leptin and adiponectin are associated in an opposite fashion to insulin sensitivity and inflammation in ESRD patients. Relatively lower plasma adiponectin levels are associated with a higher rate of incident cardiovascular events. Finally, low adiponectin and high norepinephrine seem to be interacting factors in the dismal cardiovascular outcomes with ESRD.

Role of nutrition for cardiovascular risk reduction in chronic kidney disease patients

Cardiovascular disease (CVD) is the major cause of death in end-stage renal disease (ESRD) patients. Uremic malnutrition and chronic inflammation are important comorbid conditions, closely associated with CVD risk in ESRD patients. A pathophysiologic link between uremic malnutrition, chronic inflammation, and atherosclerosis has been proposed in this patient population. Uremic malnutrition can result from chronic inflammation and can accelerate the progression of cardiovascular disease. Chronic inflammation can also directly predispose ESRD patients to a proatherogenic state. Both uremic malnutrition and chronic inflammation are also associated with increased oxidative stress, a condition proposed as a unifying concept of CVD in uremia. Although a single common etiology has not been identified in this complex process, nutritional, anti-inflammatory, and antioxidant interventions can provide potential treatment options to improve the high mortality and morbidity in ESRD patients.

Enhanced long-term reduction of plasma leptin concentrations by super-flux polysulfone dialysers

BACKGROUND

Hyperleptinaemia in chronic haemodialysis (CHD) patients has been associated with malnutrition, which is an independent predictor of morbidity and mortality in this patient group.

METHODS

To assess the influence of HD on plasma leptin, 10 CHD patients were crossover randomized to low-flux polysulfone (PS: F 6HPS), high-flux PS (F 60S), super-flux PS (F 500S) or super-flux cellulose-tri-acetate (CTA: Tricea 150G) for 12 weeks each. Blood samples were collected at the start of the study and each 12-week period. In addition, the relationship between patient characteristics, inflammation and leptin was analysed.

RESULTS

At baseline, all groups showed similar leptin concentrations (mean 33.6+/-21.7 ng/ml). After a single HD session, a significant (P<0.01) decrease was observed with all three high permeable devices (Tricea 150G -52.7+/-6.4%; F 60S -63.1+/-5.7%; F 500S -68.7+/-8.2%), whereas leptin remained stable with low-flux PS. After 12 weeks, a marked increase was observed with low-flux PS (week 1, 30.4+/-23.0; week 12, 40.5+/-5.4 ng/ml, P = 0.05), no change with super-flux CTA and high-flux PS (Tricea 150G week 1, 29.4+/-23.7; week 12, 32.0+/-27.9 ng/ml, P = ns; F 60S week 1, 36.0+/-31.8; week 12, 33.0+/-31.2 ng/ml, P = ns), and a significant decrease with super-flux PS (week 1, 38.3+/-33.0; week 12, 29.5+/-31.9 ng/ml, P = 0.02). The change in leptin after 12 weeks was significantly different between super-flux PS, and both low-flux PS (P = 0.009) and super-flux CTA (P = 0.01). Besides interleukin-6 (IL-6) at the start of the study (P = 0.006), no correlations were observed between patient characteristics, parameters of inflammation and plasma leptin levels.

CONCLUSIONS

Apart from low-flux PS, plasma leptin decreased considerably with all three high permeable dialysers after a single HD session. In the long run, leptin levels were lower with high-flux PS than with low-flux PS. Moreover, after switching from high-flux PS to super-flux PS (but not super-flux CTA), an additional decrease in leptin was observed. Apart from IL-6 at the start of the study, neither patient characteristics nor inflammatory parameters correlated with plasma leptin levels in this patient group.

Longitudinal and cross-sectional effects of C-reactive protein, equilibrated normalized protein catabolic rate, and serum bicarbonate on creatinine and albumin levels in dialysis patients

BACKGROUND

Loss of muscle mass and hypoalbuminemia each may result in part from either malnutrition, inflammation, or a combination of both. Short-term acidosis increases muscle protein catabolism and inhibits albumin synthesis.

METHODS

We analyzed albumin and creatinine levels as outcome variables and their association with C-reactive protein (CRP) level, equilibrated normalized protein catabolic rate (enPCR), and serum bicarbonate level as independent variables from laboratory data obtained from patients in the Hemodialysis Study. Analyses controlled for race, sex, age, body mass index, and randomized treatment group.

RESULTS

Albumin level correlated with both enPCR and CRP level, but not serum bicarbonate level, in both cross-sectional and longitudinal analyses. Effects of CRP level and enPCR were not linear. Albumin level correlated positively with enPCR for an enPCR less than 1.0 g/kg/d, but not for a greater enPCR, and correlated inversely with CRP level for a CRP level greater than 13 mg/L. Similarly, creatinine level correlated with both enPCR and CRP level. As in the case of albumin level, effects were not linear. Creatinine level correlated positively with enPCR for values less than 1.0 g/kg/d, but not for greater enPCR values. In contrast to albumin level, creatinine level correlated negatively with serum bicarbonate level, even when adjusted for enPCR.

CONCLUSION

Albumin and creatinine levels are independently associated with nutrition (enPCR) and inflammation (CRP level). The cross-sectional relationship with enPCR is apparent only at values less than 1.0 g/kg/d. CRP level is associated with reduced albumin and creatinine values when increased to values greater than 5.6 mg/dL. CRP may be increased to levels associated with increased cardiovascular risk with little or no effect on either serum albumin or creatinine level. Thus, a normal albumin level does not exclude elevated CRP levels.

Serum albumin concentration in dialysis patients: Why does it remain resistant to therapy?

Serum albumin, transferrin, and prealbumin levels decrease as glomerular filtration rate (GFR) declines, even prior to the start of dialysis. The levels of these serum proteins are also associated with creatinine levels and lean body mass. Lean body mass also decreases with advancing renal failure. While all of these measures are regarded as reflections of nutritional status, each are strongly associated with any of several indicators of inflammation: positive acute-phase proteins or the cytokines that regulate their synthesis rate, in both longitudinal and cross-sectional studies. Inflammation in turn is associated with comorbid conditions, cardiovascular disease, chronic infections, age, and vascular access type. Additionally, dialysis patients are subjected to oxidative stress and exposure of blood to foreign antigens in the dialysis process that also potentially contribute to inflammation. In otherwise healthy individuals reduced protein and calorie intake does not cause hypoalbuminemia since albumin fractional catabolic rate (FCR) and resting energy expenditure (REE) normally decrease in response. The simultaneous occurrence of decreased protein intake and inflammation prevent these homeostatic compensations to reduced nitrogen and energy intake from occurring, resulting in decreasing albumin, transferrin, and prealbumin levels and loss of muscle mass. Nutritional intake may also be challenged as a result of renal failure associated with anorexia, gastroparesis, and socioeconomic factors, which may all cause nutritional intake to be sufficiently marginal so that the combined effects of inflammation and decrease protein intake are expressed as decreased visceral and somatic protein stores.

Leptin, ghrelin, and proinflammatory cytokines: compounds with nutritional impact in chronic kidney disease?

Metabolic and nutritional derangements are prominent features of the uremic syndrome. Recent evidence suggest that several large-molecular-weight molecules that often are elevated in uremia, such as leptin, ghrelin, and proinflammatory cytokines, may have nutritional impact in this patient group. On the basis of present knowledge, these compounds could be regarded as suspected but not established uremic toxins. The discovery of the ob gene, its product leptin, and cerebral leptin receptors has undoubtedly widened our understanding of obesity and the underlying molecular and physiologic mechanisms that regulate food intake and body weight. Moreover, the recent discovery of leptin receptor isoforms in several peripheral organs suggests that leptin besides having a central function also has several important peripheral biological functions. Because uremic patients in general have an inappropriate elevation of circulatory leptin, further research is necessary to determine the potential biological effects of elevated leptin levels in end-stage renal disease. Also, because many symptoms and findings prevalent in the uremic syndrome are known to be associated with elevated levels of proinflammatory cytokines, such as interleukin-6, future studies are needed to evaluate the role of specific anti-inflammatory treatment strategies in malnourished uremic patients.

Protein and energy nutrition among adult patients treated with chronic peritoneal dialysis

Protein-energy malnutrition (PEM) in adult patients treated with chronic peritoneal dialysis (CPD), which is highly prevalent and frequently severe in its manifestation, poses a significant therapeutic dilemma. The causes of PEM include inflammation, low nutrient intake, nutrient losses during dialysis, metabolic acidemia, coexisting illnesses, and possibly the endocrine disorders of uremia. Treatment strategies for PEM in CPD patients include the following: attempt to treat the potentially reversible causes of anorexia, increase nutrient intake (by nutritional counseling, oral food supplements, consideration of appetite stimulants and intraperitonial amino acid solutions), and the correction of metabolic acidosis. Coexisting illnesses engendering PEM should be treated. Experimental evidence suggests that such agents as anabolic steroids, human growth hormone, insulin-like growth factor-I, and L-carnitine may engender positive protein balance in these individuals. Finally, the use of anti-inflammatory agents to improve the nutritional status of malnourished CPD patients remains to be defined. There is a need to carry out clinical trials that examine whether an improvement in the nutritional status of CPD patients is associated with an improvement in their mortality, morbidity and/or quality of life.

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.

Advanced glycation end products in hemodialyzed patients with diabetes mellitus correlate with leptin and leptin/body fat ratio

Advanced glycation end products (AGEs) and other carbonyl and oxidative stress compounds are supposed to play a critical role in the pathogenesis of several diseases and their complications, i.e., diabetes mellitus, diabetic retinopathy, atherosclerosis, and chronic renal failure. In the present investigation, we were interested in the relationship of AGEs in plasma to other prominent factors in the patients on chronic hemodialysis treatment-27 patients with diabetes mellitus, 35 patients without diabetes mellitus. AGE-group reactivity was estimated using a spectrofluorometric method (excitation 350 nm, emission 430 nm) and is expressed in arbitrary units (AU). We found significantly higher AGEs levels in diabetics than in non-diabetics on regular hemodialysis treatment both before (2.7 +/- 0.7 x 10(4) AU vs. 2.2 +/- 0.6 x 10(4) AU, p < 0.001) and after the dialysis session (2.3 +/- 0.5 x 10(4) AU vs. 1.8 +/- 0.7 x 10(4) AU, p < 0.005). AGEs were significantly reduced during hemodialysis in both groups of patients--by 15.4% in the diabetic go (p < 0.001) and by 17.3% in non-diabetics (p < 0.005). In the patients with diabetes mellitus, AGEs did not correlate with parameters of the glucose metabolism correction (blood glucose, HbA1c). We observed a significant correlation between AGEs and leptin (r = 0.48, p < 0.05) as well as the leptin/body fat ratio (r = 0.56, p < 0.05) only in hemodialyzed patients with diabetes mellitus. These findings suggest more detailed studies to identify the molecular links between carbonyl stress, i.e., advanced glycation end products, and leptin metabolism, sign of microinflammation and hypertension.

Serum C-reactive protein and leptin as predictors of kidney disease progression in the Modification of Diet in Renal Disease Study

BACKGROUND

In vitro and in vivo data suggest that markers of inflammation and nutritional status may be risk factors for the progression of chronic kidney disease.

METHODS

We investigated whether higher levels of C-reactive protein (CRP) and leptin were risk factors for progression of chronic kidney disease in the Modification of Diet in Renal Disease (MDRD) Study. Frozen samples were assayed for high sensitivity C-reactive protein (CRP) or leptin in 804 patients. CRP and leptin were then evaluated as risk factors for glomerular filtration rate (GFR) decline using univariate and multivariable analyses.

RESULTS

At baseline, the mean (median) CRP in Study A (GFR between 25 and 55 mL/min/1.73 m2) and Study B (GFR between 13 and 24 mL/min/1.73 m2) were 0.48 (0.25) and 0.46 (0.20) mg/dL, respectively, while the mean (median) leptin in Study A and Study B were 15.2 (9.80) and 15.1 (7.80) ng/mL, respectively. Mean follow-up time was 2.2 years. The mean GFR decline was -4.33 and -3.65 mL/min/year in Study A and B, respectively. There was no significant association between the rate of GFR decline with the level of CRP or leptin in multivariable analysis in Study A [0.08 (-0.14, 0.30) mL/min/year slower GFR decline per twofold increase in CRP level; and 0.14 (-0.13, 0.40) mL/min/year slower GFR decline per twofold increase in leptin level], or in multivariable analysis in Study B [-0.05 (-0.28, 0.18) mL/min/year faster GFR decline per twofold increase in CRP level; and -0.12 (-0.42, 0.19) mL/min/year faster GFR decline per twofold increase in leptin level].

CONCLUSIONS

Higher serum levels of CRP and leptin are not independent risk factors for progression of non-diabetic kidney disease.

Soluble leptin receptors and serum leptin in end-stage renal disease: relationship with inflammation and body composition

BACKGROUND

Elevated serum leptin (S-leptin) levels have been reported in patients with end-stage renal disease (ESRD). Apart from the decreased glomerular filtration rate (GFR), body composition and inflammation may affect leptin levels in ESRD. Leptin circulates both free of and bound to soluble leptin receptors (sOB-R), which are the main determinants of leptin activity and have not been described in ESRD until now.

DESIGN

To analyze the association between S-leptin, sOB-R, and inflammation and body composition, we studied 149 (62% males) normal weight (BMI 24.7 +/- 0.4 kg m(-2)) ESRD patients (51 +/- 1 years old) shortly before the start of dialysis (GFR 7.0 +/- 0.2 mL min(-1)). sOB-R and plasma interleukin-6 (IL-6; n= 113) levels were evaluated using ELISA, S-leptin using RIA, and body composition was assessed by X-ray absorptiometry (n = 139). Forty-one healthy subjects age (51 +/- 1 years), BMI (23.6 +/- 0.5 kg m(-2)) and gender-matched (59% males) were used as controls.

RESULTS

Median S-leptin was higher in the ESRD patients (10.0 ng mL(-1)) compared with the controls (3.9 ng mL(-1)) (P < 0.001). The median sOB-R did not differ significantly between the ESRD patients (44 U mL-1) and the controls (37 U mL-1). Thus, the sOB-R/S-leptin ratio was lower in the ESRD patients (9.5 +/- 1.2 vs. 12.3 +/- 1.8; P < 0.01) than the controls. A negative correlation was observed between S-leptin and sOB-R (Rho = -0.42; P < 0.0001) in the ESRD patients, a positive correlation was observed between lean body mass and the sOB-R/S-leptin ratio (Rho = 0.33, P = 0.0001) whereas fat mass was negatively correlated to both sOB-R (Rho = -0.26, P = 0.002), and the sOB-R/S-leptin ratio (Rho = -0.62, P < 0.0001). Positive correlations were observed between IL-6 and S-leptin (Rho = 0.19; P < 0.05) and weak but significant body fat mass (Rho = 0.20; P < 0.05), respectively.

CONCLUSIONS

This study demonstrates that despite markedly elevated S-leptin levels in the ESRD patients, sOB-R did not differ from the controls. In view of the anorexigenic and pro-atherogenic effects of leptin, further elucidation of the consequences of free bioactive leptin in the development of complications such as malnutrition and cardiovascular disease in ESRD patients is required.

Affect of serum leptin on nutritional status in renal disease

Protein-energy malnutrition is a major comorbid condition in persons with renal disease. A variety of interventions have been implemented to supplement protein and energy intake in malnourished patients with renal disease, but the prevalence of protein-energy malnutrition remains high. Leptin, a hormone secreted by adipose tissue, decreases food intake via neuroendocrine systems in the hypothalamus in persons with normal renal function. Serum leptin levels are elevated in patients with chronic renal insufficiency and end-stage renal disease, and experimental evidence suggests a possible role for leptin in the development of protein-energy malnutrition in this population. Release of leptin from adipocytes may be stimulated by cytokines mediating the inflammatory response, which is frequently pronounced in patients with end-stage renal disease receiving hemodialysis and peritoneal dialysis. This article provides an overview of research conducted on serum leptin levels in different stages of renal disease, and the relationship among serum leptin, body composition, biochemical indexes, and markers of inflammation in persons with end-stage renal disease. Effects of intradialytic parenteral nutrition and anabolic factors on leptin levels and nutritional status are briefly reviewed.

Mortality, malnutrition, and atherosclerosis in ESRD: what is the role of interleukin-6?

There is growing evidence that increased plasma concentrations of CRP strongly predict cardiovascular death in both non-renal and renal patient populations. The interleukin-6 (IL-6) system activity, which is the major mediator of the acute phase response, is often markedly up-regulated in uremic patients and has also been shown to predict outcome. This raises the issue of whether or not IL-6 per se may contribute to increased mortality from malnutrition and atherosclerotic cardiovascular disease in uremic patients. The causes of elevated IL-6 levels in the uremic circulation are not fully understood, although a number of factors prevalent in uremic patients, such as hypertension, adiposity, infections, and chronic heart failure may all contribute. However, factors associated with the dialysis procedure, such as bioincompatibility and non-sterile dialysate, may stimulate IL-6 production. Furthermore, available evidence suggests that genetic factors may also have an impact on circulating plasma IL-6 levels. We advance the hypothesis that IL-6 may play a central role in the genesis of inflammatory-driven malnutrition and that it may be regarded as a significant proatherogenic cytokine. This hypothesis may provide a rationale to test if targeted anti-cytokine therapy may be one way to combat the unacceptable high cardiovascular mortality rate among dialysis patients.

Adiponectin, metabolic risk factors, and cardiovascular events among patients with end-stage renal disease

Adiponectin (ADPN), which is a secretory protein of adipose tissue, attenuates endothelial inflammatory responses in vitro. Among human subjects, plasma ADPN concentrations are reduced among patients with atherosclerotic complications but are substantially increased among patients with advanced renal failure. The clinical and biochemical correlates of plasma ADPN levels were investigated and the predictive power of ADPN levels with respect to survival rates and cardiovascular events was prospectively tested in a cohort of 227 hemodialysis patients, who were monitored for 31 +/- 13 mo. Plasma ADPN levels were 2.5 times higher (P < 0.0001) among dialysis patients (15.0 +/- 7.7 microg/ml) than among healthy subjects (6.3 +/- 2.0 microg/ml), were independent of age, and were higher (P = 0.03) among women (15.2 +/- 7.9 microg/ml) than among men (14.0 +/- 7.4 microg/ml). For both genders, plasma ADPN levels were inversely related to body mass index values, plasma leptin levels, insulin levels, serum triglyceride levels, and homeostatic model assessment index values. Furthermore, plasma ADPN levels were directly related to HDL cholesterol levels and inversely related to von Willebrand factor levels. Plasma ADPN levels were lower (P < 0.05) among patients who experienced new cardiovascular events (13.7 +/- 7.3 microg/ml) than among event-free patients (15.8 +/- 7.8 microg/ml). There was a 3% risk reduction for each 1 microg/ml increase in plasma ADPN levels, and the relative risk of adverse cardiovascular events was 1.56 times (95% confidence interval, 1.12 to 1.99 times) higher among patients in the first ADPN tertile, compared with those in the third tertile. Plasma ADPN levels are an inverse predictor of cardiovascular outcomes among patients with end-stage renal disease. Furthermore, ADPN is related to several metabolic risk factors in a manner consistent with the hypothesis that this protein acts as a protective factor for the cardiovascular system.