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

Leptin Levels and Appetite Score in Patients on Hemodialysis Using High Flux or Medium Cutoff Membranes

OBJECTIVES

Chronic kidney disease (CKD) patients on hemodialysis may have a modified appetite due to several factors including a lack of uremic toxins elimination. The use of medium cutoff (MCO) dialysis membranes has been suggested as an alternative to improve the removal of toxins, especially those of medium and high molecular weight. This study aimed to compare the effect of hemodialysis using MCO and high-flux membranes on the appetite and leptin levels of CKD patients.

DESIGN AND METHODS

This is a predefined exploratory analysis of a randomized, open study, with a crossover design of 28 weeks of follow-up, which compared the effects of MCO and high-flux membranes in 32 CKD patients on hemodialysis. Appetite assessments were performed using the Appetite and Food Satisfaction Questionnaire.

RESULTS

The MCO group had an appetite score of 3.00 (1.00-5.50) and 3.00 (1.00-5.00) at the beginning and at the end of the treatment period, respectively, while the high-flux group had 1.00 (0.25-6.00) and 2.00 (0.75-3.25). There were no effects of treatment (P = .573), time (P = .376), and interaction (P = .770) between the MCO and high-flux groups. Leptin levels, at the beginning and at the end of the treatment period, were 2,342.30 (1,156.50-4,091.50) and 2,571.50 (1,619.40-4,036.47) pg/mL in the MCO group, respectively, and 2,183.15 (1,550.67-3,656.50) and 2,685.65 (1,458.20-3,981.08) pg/mL in the high-flux group. There was a time effect (P = .014), showing an increase in leptin levels in both groups, while treatment (P = .771) or interaction (P = .218) effects were not observed.

CONCLUSIONS

There is no difference between the effects of MCO or high-flux membranes on leptin levels or appetite of CKD patients on hemodialysis.

Evolving Concepts on Inflammatory Biomarkers and Malnutrition in Chronic Kidney Disease

While patient care, kidney replacement therapy, and transplantation techniques for chronic kidney disease (CKD) have continued to progress, the incidence of malnutrition disorders in CKD appears to have remained unchanged over time. However, there is now a better understanding of the underlying pathophysiology according to the disease background, disease stage, and the treatment received. In CKD patients, the increased production of proinflammatory cytokines and oxidative stress lead to a proinflammatory milieu that is at least partially responsible for the increased morbidity and mortality in this patient population. New insights into the pathogenic role of innate immunity and the proinflammatory cytokine profile, characterized, for instance, by higher levels of IL-6 and TNF-α, explain some of the clinical and laboratory abnormalities observed in these patients. In this article, we will explore currently available nutritional-inflammatory biomarkers in distinct CKD populations (hemodialysis, peritoneal dialysis, transplantation) with a view to evaluating their efficacy as predictors of malnutrition and their involvement in the common proinflammatory process. Although there is a direct relationship between inflammatory-nutritional status, signs and symptoms [e.g., protein-energy wasting (PEW), anorexia], and comorbidities (e.g., atheromatosis, atherosclerosis), we are in need of clearly standardized markers for nutritional-inflammatory assessment to improve their performance and design appropriate bidirectional interventions.

Characteris Tics and Causes of Immune Dysfunction Related to Uremia and Dialysis

From the immunologic viewpoint, chronic kidney disease (CKD) is characterized by disorders of both the innate and adaptive systems, generating a complex and still not fully understood immune dysfunction. Markers of a chronically activated immune system are closely linked to several complications of CKD and represent powerful predictors for mortality in the CKD population. On the other hand, CKD patients respond poorly to vaccination and to challenges such as bacterial infection. Interestingly, the main causes of death in patients with CKD are cardiovascular and infectious diseases, both being pathologic processes closely linked to immune function. Therefore, accelerated tissue degeneration (as a consequence of chronic inflammation) and increased rate of sepsis (because of a poorly orchestrated immune response) represent the most important targets for interventions aiming to reduce mortality in CKD patients. Understanding the mechanisms behind the immune dysfunction that is peculiar to CKD generates a perspective to improve outcomes in this group of patients.

Plasma Ghrelin Levels in Children with Chronic Renal Failure on Peritoneal Dialysis

Objectives

Malnutrition and loss of appetite represent a serious problem in children with chronic renal failure. Ghrelin is a newly described hormone involved in control of growth hormone secretion, stimulation of food intake, and regulation of energy balance.

Methods

Plasma ghrelin levels were compared between 12 children on automated peritoneal dialysis (APD) and 9 children on conservative treatment of chronic renal failure. Eight healthy children matched for age and body mass index (BMI) served as a control group.

Results

Plasma ghrelin levels were similar in children on APD (698.3 ± 59.7 pg/mL) and children on conservative treatment (675.4 ± 41.9 pg/mL) compared to healthy controls (700.1 ± 24.7 pg/mL). There was no difference in plasma ghrelin levels in children with chronic renal failure regardless of the method of treatment (peritoneal dialysis vs conservative treatment). The plasma ghrelin index was similar in all three investigated groups: APD 40.2 ± 8.7 vs conservative treatment 39.1 ± 5.6 vs controls 41.0 ± 7.8 (pg/mL)/BMI (kg/m2). Plasma ghrelin levels did not correlate with age, duration of dialysis treatment, height, weight, BMI, creatinine and urea levels, adequacy parameters, or nightly glucose load.

Conclusion

Plasma ghrelin levels in children on APD were not different from levels in children on conservative treatment or healthy controls with comparable BMI. The persistent state of toxic influence of uremic end-products could be responsible for such a lack of correlation with anthropometrical parameters. Further studies on a larger group of children on APD are needed to clarify the effect of ghrelin on nutritional status in children with chronic renal failure.

Prevalence and associated factors of protein- energy wasting among patients with chronic kidney disease at Mulago hospital, Kampala-Uganda: a cross-sectional study

Background

Chronic kidney disease (CKD) is global health concern and priority. It is the 12th leading cause of death worldwide. Protein Energy Wasting occurs in 20–25% of patients with chronic kidney disease and can lead to a high morbidity and mortality rate. We determined the prevalence of protein energy wasting and factors associated among patients with chronic kidney disease at Mulago National Referral Hospital, Kampala, Uganda.

Methods

We conducted a cross-sectional study recruiting 182 (89 non-CKD patients and 93 CKD patients) consecutively from the outpatient clinic and wards on New Mulago Hospital complex. We took anthropometric measurements including heights, weights, Triceps skin fold (TSF), Mid- Upper Arm circumference (MUAC), Body Mass Index (BMI) and Mid-arm muscle circumference (MAMC). Serum albumin levels and lipid profile levels were also obtained. Following consent of study participants, Data was collected using questionnaires and analyzed using STATA 14.1. Percentages, frequencies, means, medians, standard deviation and interquartile range were used to summarise data. Crude and adjusted binary logistic regression was performed to assess unadjusted and adjusted effect measures of protein energy wasting due to several factors. Stratification by CKD status was performed during the analysis to minimize confounding.

Results

The median age for CKD patients was 39 years compared to 27 years for non-CKD participants (p < 0.001). The prevalence of protein energy wasting (PEW) was 68.6% in this study with 47.3 and 21.3% among CKD and non-CKD participants respectively. Factors which were associated with PEW included CKD age between 18 and 24, being single, catholic religion, CKD stage 4, Hb < 11.5 g/dl and LDL > 160 mg/dl.

Conclusion

Protein energy Wasting is prevalent among patients with chronic kidney disease and clinicians should routinely screen for it during patient care.

Electronic supplementary material

The online version of this article (10.1186/s12882-018-0920-7) contains supplementary material, which is available to authorized users.

Malnutrition in Chronic Kidney Disease

Patients with chronic kidney disease are at substantial risk for malnutrition, characterized by protein energy wasting and micronutrient deficiency. Studies show a high prevalence rate of malnutrition in both children and adults with chronic kidney disease. Apart from abnormalities in growth hormone-insulin like growth factor axis, malnutrition also plays a role in the development of stunted growth, commonly observed in children with chronic kidney disease. The pathogenic mechanisms of malnutrition in chronic kidney disease are complex and involve an interplay of multiple pathophysiologic alterations including decreased appetite and nutrient intake, hormonal derangements, metabolic imbalances, inflammation, increased catabolism, and dialysis related abnormalities. Malnutrition increases the risk of morbidity, mortality and overall disease burden in these patients. The simple provision of adequate calorie and protein intake does not effectively treat malnutrition in patients with chronic kidney disease owing to the intricate and multifaceted derangements affecting nutritional status in these patients. A clear understanding of the pathophysiologic mechanisms involved in the development of malnutrition in chronic kidney disease is necessary for developing strategies and interventions that are effective, and capable of restoring normal development and mitigating negative clinical outcomes. In this article, a review of the pathophysiologic mechanisms of malnutrition in chronic kidney disease is presented.

Association of plasma des-acyl ghrelin levels with CKD

BACKGROUND AND OBJECTIVES

There are no effective therapies for malnutrition in CKD/ESRD patients. This study hypothesized that ghrelin, an endogenous orexigenic hormone, would correlate with renal function and might suggest therapeutic interventions for CKD/ESRD malnutrition.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Fifty-one CKD and 15 hemodialysis patients were enrolled. Acyl ghrelin (AG) and des-acyl ghrelin (DG) were determined using separate two-site-specific assays. Leptin, insulin, growth hormone, insulin-link growth factor-1, C-reactive protein, TNF-α, and IL-6 were also measured.

RESULTS

Univariate correlation analyses showed that CKD stage was highly, positively correlated with the levels of preprandial and postprandial DG and positively correlated with TNF-α, IL-6, leptin, and age. Multivariate partial-correlation analyses showed that CKD was independently associated with the proportion of preprandial and postprandial DG, whereas TNF-α, IL-6, leptin, insulin, and age were not independently associated with either. Geometric mean (GM) preprandial and postprandial AG were comparable between CKD stages ≤2 and >2, whereas GM preprandial DG and postprandial DG were 1.95-fold and 2.17-fold greater, respectively, for CKD stage >2 versus stage ≤2. DG was the dominant form of ghrelin preprandially and postprandially for both CKD stages ≤2 and >2. Dialysis had no effect on AG, but reduced DG by 73% to levels even lower (GM 48.7 pg/ml) than those seen postprandially in CKD stage ≤2 patients (GM 77.0 pg/ml).

CONCLUSIONS

This study shows a strong and independent correlation of DG with CKD stage. Postprandial suppression of ghrelin is impaired with reduced renal function. Hemodialysis selectively removes DG but not AG.

Endothelial dysfunction and insulin resistance

In this article, we review several mechanisms by which insulin resistance is related to endothelial dysfunction. The mechanisms we discuss may explain the high prevalence of cardiovascular disease found in people with the metabolic syndrome and diabetes mellitus.

Leptin as a link between the immune system and kidney-related diseases: leading actor or just a coadjuvant?

Food intake and nutritional status modify the physiological responses of the immune system to illness and infection and regulate the development of chronic inflammatory processes, such as kidney disease. Adipose tissue secretes immune-related proteins called adipokines that have pleiotropic effects on both the immune and neuroendocrine systems, linking metabolism and immune physiology. Leptin, an adipose tissue-derived adipokine, displays a variety of immune and physiological functions, and participates in several immune responses. Here, we review the current literature on the role of leptin in kidney diseases, linking adipose tissue and the immune system with kidney-related disorders. The modulation of this adipose hormone may have a major impact on the treatment of several immune- and metabolic-related kidney diseases.

Impact of the duration of posttransplant renal replacement therapy on bacterial infections in liver transplant recipients

Whether the duration of renal replacement therapy (RRT) after liver transplantation influences the rate and types of bacterial infections is not known. In this study, 47 of 299 consecutive liver transplant recipients (16%) required posttransplant RRT. The incidence of bacterial infections was higher in the RRT group versus the non-RRT group (8.84 versus 1.38 per 1000 patient days, P < 0.001). In the RRT group, 49% of the patients (23/47) required long-term RRT (≥30 days), and 51% (24/47) required short-term RRT (<30 days). Long-term RRT (hazard ratio = 2.27, 95% confidence interval = 1.16-4.47, P = 0.017) was a significant predictor of infections. Bacteremia and intra-abdominal infections were the most common sources of infections, and Enterobacteriaceae and enterococci were the predominant pathogens in both groups. The mortality rate for patients requiring RRT was higher than the rate for patients not requiring RRT (P < 0.001), but the mortality rates of the short-term RRT group and the long-term RRT group did not significantly differ (P = 0.654). In conclusion, although both short-term RRT and long-term RRT confer a higher risk of bacterial infections, only long-term RRT is a statistically significant predictor of these infections.

Combination of maintenance hemodialysis with hemoperfusion: a safe and effective model of artificial kidney

OBJECTIVE

To investigate whether the combination of maintenance hemodialysis (MHD) with hemoperfusion (HP) could improve the clearance rate of middle and large molecule uremic toxins so as to improve the quality of life of MHD patients and reduce their mortality rate.

METHODS

This study was a prospective, randomized, controlled clinical trial. 100 MHD patients were selected and then randomly divided into two groups after four weeks of run-in period. Group 1 received HD alone 2 times a week and the combined treatment of HD with HP (HD+HP) once a week, whereas Group 2 was given HD alone 3 times a week. This study was followed up for a mean of 2 years. The primary outcome was the death of patients. Secondary end points included normal clinical data, leptin, high sensitive C-reactive protein (hsCRP), interleukin-6 (IL-6), ß(2) microglobulin (ß(2)-MG), immunoreactive parathyroid hormone (iPTH), tumor necrosis factor-α (TNF-α) and the index of dimensions of Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36 Chinese Edition ).

RESULTS

At the end of the two-year observation, the serum concentration of leptin, hsCRP, iPTH, IL-6, ß(2)-MG and TNF-α, systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR), cardiothoracic ratio, left ventricular mass index (LVMI), the EPO doses and the types of antihypertensive drugs used were lower with Group 1 than with Group 2 (p<0.05); Group 1 had higher hemoglobin (Hb), ejection fraction (EF), and body mass index (BMI) (p<0.05). No statistical difference between the two groups was observed in terms of serum albumin, serum iron (SI), total iron binding capacity (TIBC), cardiac output (CO), Kt/V, early/atrial mitral inflow velocities (E/A) (p>0.05). Besides, the SF-36 indicated that the total score of overall dimentions of Group 1 was higher than Group 2 (p<0.05) and the quality of life of Group 1 was evidently better than Group 2. The Kaplan-Meier Survival Curves for the 2-year observation period showed that patients in Group 1 had obvious survival advantage while Log-rank test results showed p<0.05. No serious adverse incidents occurred during the HD+HP treatment.

CONCLUSIONS

HD+HP was superior to HD in regularly eliminating middle and large molecule uremic toxins accumulated in the body. These findings suggest a potential role for HD+HP in the treatment to improve the quality of life and survival rate of MHD patients.

Adipokines, endothelial dysfunction and nutritional status in peritoneal dialysis patients

OBJECTIVE

Adipokines such as leptin and adiponectin are adipocyte-specific secretory proteins that play important roles in the metabolic regulation of body weight, insulin resistance and cardiovascular complications. The relationship between the malnutrition-inflammation complex syndrome and high levels of some adipokines in peritoneal dialysis (PD) patients is still unclear. An association between high body mass index (BMI) and improved survival in PD patients has also been proposed. The purpose of this study was to investigate the levels of plasma adipokines and inflammation and oxidative stress markers in overweight and normal weight PD patients.

MATERIAL AND METHODS

Thirty PD patients (12 M, 18 F; mean age 57.3 ± 16.6 years) were examined and 23 healthy volunteers were included as a control group. The levels of high-sensitivity C-reactive protein (hsCRP), tumour necrosis factor-α, interleukin-6, leptin, the leptin receptor, adiponectin, malondialdehyde/4-hydroxynonenal, oxidized low-density lipoprotein, carbonyl groups and asymmetric dimethylarginine (ADMA) were measured in both groups. The nutritional status of each patient was determined by albumin levels, BMI, percentage of body fat (%F), lean body mass (LBM) and the Subjective Global Assessment (SGA) score. The adequacy of dialysis was estimated by weekly Kt/V measurements.

RESULTS

According to the seven-point SGA scores and the albumin levels, the nutrition status of 15 patients was good (6-7 points), while 15 patients were mildly malnourished (3-5 points). The concentrations of hsCRP, leptin and adiponectin were statistically higher in the PD group than in the control group (p < 0.05). Markers of oxidative stress and inflammation were also higher in the PD group. The adiponectin level was inversely correlated with %F and BMI (Spearman's R = -0.3, p ≤ 0.05) and positively correlated with hsCRP level (R = -0.4). The level of leptin was positively correlated with %F, BMI and LBM (R = 0.4, p ≤ 0.05). Patients with normal BMI values had lower leptin concentrations (50.2 vs 242.8 μg/l) and higher adiponectin levels (30.0 vs 20.3 μg/ml) than overweight patients. The statistical analysis indicated that there were no differences in oxidative stress, inflammation and ADMA concentration between the lean and overweight PD patients.

CONCLUSION

The nutritional status of lean and overweight patients was comparable. Signs of malnutrition were detected in both groups. The severity of chronic inflammation and oxidative stress were not related to BMI in PD patients.

Low serum acylated ghrelin levels are associated with the development of cardiovascular disease in hemodialysis patients

BACKGROUND

Ghrelin has a protective effect on endothelial cells. Endothelial cell dysfunction is associated with cardiovascular disease (CVD) and CVD remains the leading cause of morbidity in hemodialysis (HD) patients. Acylated ghrelin (A-Ghr) is the functional form of ghrelin, so we hypothesized that A-Ghr is associated with the occurrence of CVD in HD patients.

METHODS

We conducted a prospective cohort study in 412 HD patients. The cohort was sub-grouped into low and high A-Ghr groups according to the median A-Ghr level of 4.88 pg/mL. The association between the low/high A-Ghr groups and the incidence of CVD were analyzed.

RESULTS

The HD patients in a low A-Ghr group had a greater risk of incidental CVD than those in a high A-Ghr ghrelin. This association remained significant after the adjustment for possible confounding factors, including age, gender, HD duration, BMI, diabetes, albumin, nPCR and Charlson's comorbidity index score.

CONCLUSION

It appears that a low serum A-Ghr level is associated with the development of CVD in HD patients.

Bicarbonate-Based Peritoneal Dialysis Solution has Less Effect on Ingestive Behavior than Lactate-Based Peritoneal Dialysis Solution

Objective

The anorexia seen in peritoneal dialysis (PD) patients may be due partially to factors of dialysis solutions, such as pH and buffering agent. We tested the effects of different PD solutions in an experimental rat model for appetite.

Design

The intraoral intake of a sucrose solution from an implanted intraoral cannula in freely moving male Wistar rats was used to evaluate appetite at 30 minutes and 120 minutes after intraperitoneal (IP) infusion of bicarbonate (25 mmol/L)/lactate (15 mmol/L)-based PD solution (P) and conventional lactate (40 mmol/L)-based PD solution (D) with different concentrations of glucose. We also tested different buffer solutions containing lactate and bicarbonate with different pH but with no glucose.

Results

The IP infusion as such and the 30 mL volume did not inhibit appetite; however, appetite was significantly less inhibited by P than by D in the 1.36%, 2.27%, and 3.86% solutions ( p < 0.05). Furthermore, intraoral intake was significantly higher in rats receiving IP solution with bicarbonate buffer (pH 7.4) than with lactate buffer ( p < 0.05), whereas there was no significant difference in intraoral intake for lactate with pH 5.5, pH 6.6, or pH 7.4.

Conclusions

The bicarbonate/lactate solution inhibited appetite less than the lactate solution; this was due partially to the use of bicarbonate. The results show possible benefit on appetite of reducing the lactate concentration in PD solutions.

Identification of patients with eating disorders: clinical and biochemical signs of appetite loss in dialysis patients

Patients with chronic kidney disease (CKD) frequently experience loss of appetite (anorexia), which increases in severity during the disease progression. The optimal medical assessment of an anorectic patient depends on an appropriate knowledge of the associated signs and symptoms. Some of these signs are diagnostic of anorexia in CKD. The aim of the present review is to provide a general understanding of the consequences of anorexia in the CKD patient, while describing simple assessment methods of appetite loss easy to implement in the clinical setting. Early clinical and physical diagnostic signs associated with appetite loss, as well as the expected reflections in several blood biomarkers, are discussed. Finally, the potential role of sex hormones in modulating the severity of these symptoms is introduced as a platform toward the understanding of sex hormone action in regulating/treating uremic anorexia.

Nutrition assessment and hormonal influences on body composition in children with chronic kidney disease

Malnutrition is a serious complication of chronic kidney disease (CKD) in the pediatric population. Management of the nutritional status of children presents the challenge of ensuring sufficient energy to promote linear growth, development of brain and organs, and maintenance of appropriate fat and muscle stores, while preventing excess protein intake and controlling electrolytes. Aggressive nutrition intervention in the early stages of CKD may be critical in the prevention of more serious complications further in the disease process. Nutrition assessment involves analysis of dietary intake, anthropometric parameters, and laboratory data. Currently, no guidelines are available for nutritional management of pediatric patients with CKD before the onset of dialysis. The content and algorithms in this article are intended to serve as a guide in the management of the nutritional status of children with CKD. Although adequate calorie and protein intake is critical in prevention of malnutrition, it is only part of a complex mechanism in the development of cachexia in CKD. Research suggests that the effects of inflammatory cytokines and hormones such as leptin and ghrelin play a role in the development of malnutrition in CKD. As a more thorough understanding of this mechanism emerges, new treatments aimed at inhibiting cachexia can be developed.

Leptin and resistin levels and their relationships with glucose metabolism in children with chronic renal insufficiency and undergoing dialysis

AIM

The aim of the present study is: (i) to evaluate the serum concentrations of leptin and resistin in the paediatric patients with chronic renal impairment (CRI), on haemodialysis (HD) and on peritoneal dialysis (PD) treatment; (ii) to examine the relationship between these hormones; and (iii) to investigate the possible influence of these hormones on the insulin resistance and sensitivity indexes as well as on serum insulin-like growth factor-1 (IGF-1) and insulin-like growth factor binding protein-3 (IGFBP-3) levels.

METHODS

In total, 52 patients (15 patients with CRI, 24 PD patients and 13 HD patients) and 23 healthy age- and sex-matched control subjects were included in the present study.

RESULTS

Homeostasis model assessment of insulin resistance (HOMA-IR) was higher than 2.5 in 47.1% of the patients. IGF-1 levels of patients with CRI, PD and HD patients were significantly lower than those in the controls (P < 0.001, P < 0.001, P < 0.001, respectively). The leptin levels of patients with CRI and on PD and HD treatment were significantly higher than the control group (P = 0.038, P = 0.002, P = 0.006, respectively). Similarly, serum resistin levels of patients with CRI and those of PD and HD patients were higher when compared with healthy controls (P = 0.037, P < 0.001, P = 0.005, respectively).

CONCLUSION

Leptin and resistin levels were increased in the children with CRF; however, this elevation was not found to be associated with hyperinsulinism. Further studies to explain the mechanisms and consequences of the accumulation of these hormones in CRF may provide the therapeutical approach aiming to normalize their circulating levels.

Preproghrelin Leu72Met polymorphism is not associated with type 2 diabetes mellitus

Ghrelin is a novel gut-brain peptide, which exerts somatotropic, orexigenic, and adipogenic effects. Genetic variants of ghrelin have been associated with both obesity and insulin metabolism. In this study, we determined a role of preproghrelin Leu72Met polymorphism on type 2 diabetes mellitus and its relationship to variables studied. Genotypes were assessed by polymerase chain reaction. Frequencies of the Leu72Met polymorphism were found to be 35.4% in the type 2 diabetic patients and 32.5% in the normal controls. The Leu72Met polymorphism was not associated with hypertension, macroangiopathy, retinopathy, serum cholesterol, triglyceride, blood urea nitrogen, HbA(1c), lipoprotein (a), fasting insulin, or 24-hour urinary protein levels in the type 2 diabetic group. However, the Leu72Met polymorphism was clearly associated with serum creatinine levels in the diabetic group, as the Met72 carriers exhibited lower serum creatinine levels than the Met72 noncarriers. Our data indicate that the preproghrelin Leu72Met polymorphism is not associated with type 2 diabetes mellitus. However, the Leu72Met polymorphism is associated with serum creatinine levels. These data suggest that Met72 carrier status may be a predictable marker for diabetic nephropathy or renal impairment in type 2 diabetes mellitus.

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.

Ghrelin is produced by the human erythroleukemic HEL cell line and involved in an autocrine pathway leading to cell proliferation

Ghrelin, a ligand of the GH secretagogue receptor (GHS-R 1a), is a 28-amino acid peptide with an unusual octanoyl group on Ser3, crucial for its biological activity. For the first time, ghrelin and GHS-R 1b, a truncated variant of the receptor resulting from alternative splicing, but not GHS-R 1a, mRNAs were detected in the human erythroleukemic cell line HEL. Two antibodies, used for RIA, were directed against octanoylated and total (octanoylated and desoctanoylated) ghrelin, and the recognized epitopes were characterized. Using reverse phase HPLC analysis followed by RIA, we demonstrated that octanoylated and desoctanoylated ghrelins were present in HEL cells and their culture medium, of which more than 90% was octanoylated. The ghrelin levels were not affected after 24 h treatment with sodium butyrate, phorbol 12-myristate 13-acetate, or forskolin, but a significant 3-fold increase in desoctanoylated ghrelin was detected in the culture medium after 48 h treatment with sodium butyrate. The antighrelin SB801 and SB969 antisera inhibited HEL cell proliferation by 24% and 39%, respectively, after 72 h. Taken together, these data suggested that endogenous ghrelin stimulated HEL cell proliferation by an autocrine pathway involving an unidentified receptor, distinct from GHS-R1a, and that the HEL cell line represents a unique model to study the octanoylation of ghrelin.

Orexigenic and anorexigenic mechanisms in the control of nutrition in chronic kidney disease

Malnutrition is defined as abnormalities caused by an inadequate diet, but this term is often used inappropriately to describe the syndrome of loss of body weight with muscle mass being replaced by fatty tissue and declining serum proteins present in adults and children with chronic kidney disease (CKD). This syndrome is more accurately described as cachexia, and manifests as growth failure in children with CKD. Cachexia is common and is an important risk factor for poor quality of life and increased mortality and morbidity in both adults and children with CKD. Anorexia, acidosis and inflammation are important causes of cachexia, but the underlying molecular mechanism is not well understood. Dietary intake is often poor and resting metabolic rate is increased in CKD. The energy cost of growth is increased in experimental CKD. Circulating concentrations of cytokines, such as leptin, tumor necrosis factor-alpha and interleukins 1 and 6 are increased in patients with CKD and correlate with the degree of cachexia in these individuals. We hypothesize that cytokines signal through orexigenic neuropetides such as agouti-related peptide and neuropeptide Y (NPY), and anorexigenic neuropetides such as proopiomelanocortin and alpha-melanocyte-stimulating hormone in the arcuate nucleus in the hypothalamus. This signaling system also involves the NPY receptor and the melanocortin receptors and controls appetite and metabolic rate in health and disease. Furthermore, the first order neurons of this system are located outside the blood-brain barrier and can therefore sense the circulating levels of cytokines, as well as long-term satiety hormones such as leptin and insulin and short-term satiety hormones such as ghrelin and peptide (P) YY. There is experimental evidence that this hypothalamic neuropeptide signaling system may have an important role in the pathogenesis of cachexia in CKD. Understanding the molecular mechanism of cachexia in CKD may lead to novel therapeutic strategies.

Adipose tissue and its relation to inflammation: The role of adipokines

An activated inflammatory response is a common feature of end-stage renal disease (ESRD) patients and predicts outcome. Although various factors related to the dialysis procedure may contribute to inflammation in ESRD, a number of nondialysis-related factors also are of importance. Adipose tissue is a complex organ with functions far beyond the mere storage of energy and secretes a number of proinflammatory adipokines, such as leptin, resistin, tumor necrosis factor-alpha and interleukin-6, as well as one anti-inflammatory adipokine, adiponectin. It has been proposed that adipose tissue may be a significant contributor to increased systemic inflammation in nonrenal patients. In this review, we put forward the hypothesis that a reduction of renal mass will contribute to retention of proinflammatory adipokines, thus generating adipokine imbalance. Such an imbalance may, via effects on the central nervous system and the vasculature, contribute to wasting, atherosclerosis, and insulin resistance--all common features of ESRD.