Malnutrition: a frequent misdiagnosis for hemodialysis patients

The Neutrophil-to-Albumin Ratio as a New Predictor of All-Cause Mortality in Patients with Heart Failure

Background

Methods

Results

Conclusion

Ameliorating Chronic Kidney Disease Using a Whole Food Plant-Based Diet

Novel approaches to ameliorating chronic kidney disease (CKD) are warranted as most patients are undiagnosed until they begin displaying symptoms of kidney failure. There is increasing evidence that a whole food plant-based (WFPB) diet may offer benefits that slow the progression of CKD, decrease the incidence cardiovascular disease, decrease rates of diabetes and obesity, and reduce inflammation and cholesterol, which in turn can delay kidney failure and the initiation of dialysis. While animal-based protein ingestion promotes an acidic environment, inflammation and renal hyperfiltration, study authors report plant-based protein can be alkaline-producing and anti-inflammatory and can contain renoprotective properties. Although there may be benefits to adopting a WFPB diet, macronutrient and micronutrient content should be carefully considered and adjusted to avoid malnutrition in CKD patients. Further research needs to be done in order to establish the biological plausibility and feasibility of a WFPB in individuals with diagnosed CKD.

Nutritional treatment of advanced CKD: twenty consensus statements

The Italian nephrology has a long tradition and experience in the field of dietetic-nutritional therapy (DNT), which is an important component in the conservative management of the patient suffering from a chronic kidney disease, which precedes and integrates the pharmacological therapies. The objectives of DNT include the maintenance of an optimal nutritional status, the prevention and/or correction of signs, symptoms and complications of chronic renal failure and, possibly, the delay in starting of dialysis. The DNT includes modulation of protein intake, adequacy of caloric intake, control of sodium and potassium intake, and reduction of phosphorus intake. For all dietary-nutritional therapies, and in particular those aimed at the patient with chronic renal failure, the problem of patient adherence to the dietetic-nutritional scheme is a key element for the success and safety of the DNT and it can be favored by an interdisciplinary and multi-professional approach of information, education, dietary prescription and follow-up. This consensus document, which defines twenty essential points of the nutritional approach to patients with advanced chronic renal failure, has been written, discussed and shared by the Italian nephrologists together with representatives of dietitians (ANDID) and patients (ANED).

Effects of aging and comorbidities on nutritional status and muscle dysfunction in patients with COPD

Chronic obstructive pulmonary disease (COPD) is a prevalent, complex and debilitating disease which imposes a formidable burden on patients and the healthcare system. The recognition that COPD is a multifaceted disease is not new, and increasing evidence have outlined the importance of its extra-pulmonary manifestations and its relation to other comorbid conditions in the clinical course of the disease and its societal cost. The relationship between aging, COPD and its comorbidities on skeletal muscle function and nutritional status is complex, multidirectional and incompletely understood. Despite this, the current body of knowledge allows the identification of various, seemingly partially independent factors related both to the normal aging process and to the independent deleterious effects of chronic diseases on muscle function and body composition. There is a dire need of studies evaluating the relative contribution of each of these factors, and their potential synergistic effects in patients with COPD and advanced age/comorbid conditions, in order to delineate the best course of therapeutic action in this increasingly prevalent population.

Muscle wasting in chronic kidney disease

Loss of lean body mass is a relevant component of the cachexia, or protein energy wasting (PEW), syndrome. Reduced muscle mass seems to be the most solid criterion for the presence of cachexia/PEW in patients with chronic kidney disease (CKD), and those with greater muscle mass loss have a higher risk of death. Children with CKD have many risk factors for lean mass and muscle wasting, including poor appetite, inflammation, growth hormone resistance, and metabolic acidosis. Mortality risks in patients with CKD increases as body mass index (BMI) and weight decreases. However, data regarding cachexia/PEW and muscle wasting in children with CKD is scarce due to lack of consensus in diagnostic criteria and an appropriate investigative methodology. Further research is urgently needed to address this important complication in the pediatric CKD setting, which may have fundamental impact on clinical outcomes.

Effects of Low-Protein, and Supplemented Very Low-Protein Diets, on Muscle Protein Turnover in Patients With CKD

Introduction

Early studies have shown that patients with chronic kidney disease (CKD) are able to maintain nitrogen balance despite significantly lower protein intake, but how and to what extent muscle protein metabolism adapts to a low-protein diet (LPD) or to a supplemented very LPD (sVLPD) is still unexplored.

Methods

We studied muscle protein turnover by the forearm perfusion method associated with the kinetics of ²H-phenylalanine in patients with CKD: (i) in a parallel study in subjects randomized to usual diet (1.1 g protein/kg, n = 5) or LPD (0.55 g protein/kg, n = 6) (Protocol 1); (ii) in a crossover, self-controlled study in subjects on a 0.55 g/kg LPD followed by a sVLPD (0.45 g/kg + amino/ketoacids 0.1 g/kg, n = 6) (Protocol 2).

Results

As compared with a 1.1 g/kg containing diet, a 0.55 g/kg LPD induced the following: (i) a 17% to 40% decrease in muscle protein degradation and net protein balance, respectively, (ii) no change in muscle protein synthesis, (iii) a slight (by approximately 7%, P < 0.06) decrease in whole-body protein degradation, and (iv) an increase in the efficiency of muscle protein turnover. As compared with an LPD, an sVLPD induced the following: (i) no change in muscle protein degradation, and (ii) an approximately 50% decrease in the negative net protein balance, and an increase in the efficiency of muscle protein turnover.

Conclusion

The results of these studies indicate that in patients with CKD the adaptation of muscle protein metabolism to restrained protein intake can be obtained via combined responses of protein degradation and the efficiency of recycling of amino acids deriving from protein breakdown.

Associations of Dietary Protein and Energy Intakes With Protein-Energy Wasting Syndrome in Hemodialysis Patients

Introduction

The associations of dietary protein and/or energy intakes with protein or energy wasting in patients on maintenance hemodialysis are controversial. We examined these in the Hemodialysis (HEMO) Study.

Methods

In 1487 participants in the HEMO Study, baseline dietary protein intake (grams per kilogram per day) and dietary energy intake (kilocalories per kilograms per day) were related to the presence of the protein-energy wasting (PEW) syndrome at month 12 (defined as the presence of at least 1 criteria in 2 of the 3 categories of low serum chemistry, low body mass, and low muscle mass) in logistic regression models. In additional separate models, protein intake estimated from equilibrated normalized protein catabolic rate (enPCR) was also related to the PEW syndrome.

Results

Compared with the lowest quartile, the highest quartile of baseline dietary protein intake was paradoxically associated with increased risk of the PEW syndrome at month 12 (odds ratio [OR]: 4.11; 95% confidence interval [CI]: 2.79-6.05). This relationship was completely attenuated (OR: 1.35; 95% CI: 0.88-2.06) with adjustment for baseline body weight, which suggested mathematical coupling. Results were similar for dietary energy intake. Compared with the lowest quartile of baseline enPCR, the highest quartile was not associated with the PEW syndrome at 12 months (OR: 0.78; 95% CI: 0.54-1.12).

Discussion

These data do not support the use of dietary protein intake or dietary energy intake criteria in the definition of the PEW syndrome in patients on maintenance hemodialysis.

High Serum Alkaline Phosphatase, Hypercalcaemia, Race, and Mortality in South African Maintenance Haemodialysis Patients

Objective. To determine the association between serum total alkaline phosphatase (TAP) and mortality in African maintenance haemodialysis patients (MHD). Patients and Methods. The study enrolled a total of 213 patients on MHD from two dialysis centers in Johannesburg between January 2009 and March 2016. Patients were categorized into a low TAP group (≤112 U/L) versus a high TAP group (>112 U/L) based on a median TAP of 112 U/L. Results. During the follow-up period of 7 years, there were 55 (25.8%) deaths. After adjusting for cofounders such as age, other markers of bone disorder, and comorbidity (diabetes mellitus), patients in the high TAP group had significantly higher risk of death compared to patients in the low TAP group (hazard ratio, 2.50; 95% CI 1.24-5.01, P = 0.01). Similarly, serum calcium >2.75 mmol/L was associated with increased risk of death compared to patients within levels of 2.10-2.37 mmol/L (HR 6.34, 95% CI 1.40-28.76; P = 0.02). The HR for death in white patients compared to black patients was 6.88; 95% CI 1.82-25.88; P = 0.004. Conclusion. High levels of serum alkaline phosphatase, hypercalcaemia, and white race are associated with increased risk of death in MHD patients.

Myostatin Activates the Ubiquitin-Proteasome and Autophagy-Lysosome Systems Contributing to Muscle Wasting in Chronic Kidney Disease

Our evidence demonstrated that CKD upregulated the expression of myostatin, TNF-α, and p-IkBa and downregulated the phosphorylation of PI3K, Akt, and FoxO3a, which were also associated with protein degradation and muscle atrophy. The autophagosome formation and protein expression of autophagy-related genes were increased in muscle of CKD rats. The mRNA level and protein expression of MAFbx and MuRF-1 were also upregulated in CKD rats, as well as proteasome activity of 26S. Moreover, activation of myostatin elicited by TNF-α induces C2C12 myotube atrophy via upregulating the expression of autophagy-related genes, including MAFbx and MuRF1 and proteasome subunits. Inactivation of FoxO3a triggered by PI3K inhibitor LY294002 prevented the myostatin-induced increase of expression of MuRF1, MAFbx, and LC3-II protein in C2C12 myotubes. The findings were further consolidated by using siRNA interference and overexpression of myostatin. Additionally, expression of myostatin was activated by TNF-α via a NF-κB dependent pathway in C2C12 myotubes, while inhibition of NF-κB activity suppressed myostatin and improved myotube atrophy. Collectively, myostatin mediated CKD-induced muscle catabolism via coordinate activation of the autophagy and the ubiquitin-proteasome systems.

Nutritional Markers and Body Composition in Hemodialysis Patients

The aims of this study were to analyse body composition, to detect the presence of undernutrition, and to establish a relationship between undernutrition and the biological markers routinely used as indicators of nutritional status in hemodialysis (HD) patients (pts). We used a body composition monitor (BCM) that expresses body weight in terms of lean tissue mass (LTM) and fat tissue mass (FTM) independent of hydration status. From nine HD units, 934 pts were included. Undernutrition was defined as having a lean tissue index (LTI = LTM/height²) below the 10th percentile of a reference population. Biochemical markers and parameters delivered by BCM were used to compare low LTI and normal LTI groups. Undernutrition prevalence was 58.8% of the population studied. Low LTI pts were older, were significantly more frequently overhydrated, and had been on HD for a longer period of time than the normal LTI group. FTI (FTI = FTM/ height²) was significantly higher in low LTI pts and increased according to BMI. LTI was not influenced by different BMI levels. Albumin and C-reactive protein correlated inversely (r = −0.28). However neither of them was statistically different when considering undernourished and normal LTI pts. Our BCM study was able to show a high prevalence of undernutrition, as expressed by low LTI. In our study, BMI and other common markers, such as albumin, failed to predict malnutrition as determined by BCM.

Early-stage chronic kidney disease, insulin resistance, and osteoporosis as risk factors of sarcopenia in aged population: the fourth Korea National Health and Nutrition Examination Survey (KNHANES IV), 2008-2009

Sarcopenia means the progressive loss of skeletal muscle mass and strength with aging. In this study, we found that insulin resistance, chronic kidney disease stage 3, and osteoporosis at the femur neck were closely associated with sarcopenia in elderly men. These conditions modified to slow down the progression of sarcopenia.

INTRODUCTION

Sarcopenia is known to have multiple contributing factors; however, its modifiable risk factors have not yet been determined. The aim of this study was to identify the most influential and modifiable risk factors for sarcopenia in elderly.

METHODS

This was a population-based, cross-sectional study using data from the Fourth Korea National Health and Nutrition Examination Survey (KNHANES IV), 2008-2009. This study included 940 men and 1,324 women aged 65 years and older who completed a body composition analysis using dual-energy X-ray absorptiometry. Sarcopenia was defined as an appendicular skeletal muscle mass divided by height(2) of less than 1 standard deviation below the sex-specific mean for a younger reference group.

RESULTS

Using univariate analysis, age, body mass index (BMI), homeostasis model assessment for insulin resistance (HOMA-IR), limitations in daily activities, regular exercise, high-risk drinking, family income, osteoporosis, daily energy, and protein intake were associated with sarcopenia in men; age, BMI, limitations in daily activities, regular exercise, occupation, osteoporosis at the total hip, and daily energy intake were associated with sarcopenia in women. In the multivariate logistic regression analysis, HOMA-IR ≥2.5 (odds ratio [OR] for sarcopenia, 2.27; 95 % confidence interval [CI], 1.21-4.25), chronic kidney disease stage 3 (OR, 3.13; 95 % CI, 1.14-8.61), and osteoporosis at the femur neck (OR, 6.83; 95 % CI, 1.08-43.41) were identified as risk factors for sarcopenia in men.

CONCLUSIONS

Insulin resistance, chronic kidney disease, and osteoporosis at the femur neck should be modified to prevent the acceleration of skeletal muscle loss in elderly men.

Mechanisms of muscle wasting in chronic kidney disease

In patients with chronic kidney disease (CKD), loss of cellular proteins increases the risks of morbidity and mortality. Persistence of muscle protein catabolism in CKD results in striking losses of muscle proteins as whole-body protein turnover is great; even small but persistent imbalances between protein synthesis and degradation cause substantial protein loss. No reliable methods to prevent CKD-induced muscle wasting currently exist, but mechanisms that control cellular protein turnover have been identified, suggesting that therapeutic strategies will be developed to suppress or block protein loss. Catabolic pathways that cause protein wasting include activation of the ubiquitin-proteasome system (UPS), caspase-3, lysosomes and myostatin (a negative regulator of skeletal muscle growth). These pathways can be initiated by complications associated with CKD, such as metabolic acidosis, defective insulin signalling, inflammation, increased angiotensin II levels, abnormal appetite regulation and impaired microRNA responses. Inflammation stimulates cellular signalling pathways that activate myostatin, which accelerates UPS-mediated catabolism. Blocking this pathway can prevent loss of muscle proteins. Myostatin inhibition could yield new therapeutic directions for blocking muscle protein wasting in CKD or disorders associated with its complications.

Muscle wasting in hemodialysis patients: new therapeutic strategies for resolving an old problem

Muscle wasting has long been recognized as a major clinical problem in hemodialysis (HD) patients. In addition to its impact on quality of life, muscle wasting has been proven to be associated with increased mortality rates. Identification of the molecular mechanisms underlying muscle wasting in HD patients provides opportunities to resolve this clinical problem. Several signaling pathways and humeral factors have been reported to be involved in the pathogenic mechanisms of muscle wasting in HD patients, including ubiquitin-proteasome system, caspase-3, insulin/insulin-like growth factor-1 (IGF-1) signaling, endogenous glucocorticoids, metabolic acidosis, inflammation, and sex hormones. Targeting the aforementioned crucial signaling and molecules to suppress protein degradation and augment muscle strength has been extensively investigated in HD patients. In addition to exercise training, administration of megestrol acetate has been proven to be effective in improving anorexia and muscle wasting in HD patients. Correction of metabolic acidosis through sodium bicarbonate supplements can decrease muscle protein degradation and hormone therapy with nandrolone decanoate has been reported to increase muscle mass. Although thiazolidinedione has been shown to improve insulin sensitivity, its role in the treatment of muscle wasting remains unclear. This review paper focuses on the molecular pathways and potential new therapeutic approaches to muscle wasting in HD patients.

Obesity paradox in end-stage kidney disease patients

In the general population, obesity is associated with increased cardiovascular risk and decreased survival. In patients with end-stage renal disease (ESRD), however, an "obesity paradox" or "reverse epidemiology" (to include lipid and hypertension paradoxes) has been consistently reported, i.e. a higher body mass index (BMI) is paradoxically associated with better survival. This survival advantage of large body size is relatively consistent for hemodialysis patients across racial and regional differences, although published results are mixed for peritoneal dialysis patients. Recent data indicate that both higher skeletal muscle mass and increased total body fat are protective, although there are mixed data on visceral (intra-abdominal) fat. The obesity paradox in ESRD is unlikely to be due to residual confounding alone and has biologic plausibility. Possible causes of the obesity paradox include protein-energy wasting and inflammation, time discrepancy among competitive risk factors (undernutrition versus overnutrition), hemodynamic stability, alteration of circulatory cytokines, sequestration of uremic toxin in adipose tissue, and endotoxin-lipoprotein interaction. The obesity paradox may have significant clinical implications in the management of ESRD patients especially if obese dialysis patients are forced to lose weight upon transplant wait-listing. Well-designed studies exploring the causes and consequences of the reverse epidemiology of cardiovascular risk factors, including the obesity paradox, among ESRD patients could provide more information on mechanisms. These could include controlled trials of nutritional and pharmacologic interventions to examine whether gain in lean body mass or even body fat can improve survival and quality of life in these patients.

Association of genetic variants of ghrelin, leptin and UCP2 with malnutrition inflammation syndrome and survival in end-stage renal disease patients

Malnutrition inflammation syndrome (MIS) is common among ESRD patients. In the present study, we have investigated the association of genetic markers associated with appetite and energy regulation with malnutrition inflammation syndrome among end-stage renal disease (ESRD) patients. Two hundred and fifty-seven patients on maintenance hemodialysis and 200 normal healthy controls were included in the study. Nutritional assessment was done by subjective global assessment scores (SGA). Genotyping of leptin-2548 G/A (rs7799039), ghrelin Leu72Met (rs696217-408 C/A), Arg51Gln (rs34911341-346 G/A) and uncoupling protein 2 (UCP2) 45 bp insertion deletion was done using PCR-RFLP. Levels of leptin and acyl ghrelin were assessed using ELISA. Leptin-2548 AA genotype was associated with twofold higher risk of disease susceptibility while UCP2 insertion-deletion heterozygotes showed protective effect. Ghrelin Gln51Gln and Met72Met genotype were associated with 3.4- and 2.5-fold higher disease susceptibility. The Met72 and Gln51 allele showed 3.3- and 2.1-fold higher susceptibility to malnutrition in severe SGA group. Further, the levels of acyl ghrelin were significantly less in severe category of malnutrition and in poor appetite group. On combined analysis, the group 2 (presence of 3-4 risk alleles) showed 1.5- and twofold higher susceptibility to disease and malnutrition, respectively. On docking analysis, it was observed that higher receptor binding energy was associated with the mutant form of ghrelin (Gln51). Moderate and severe SGA were associated with 2.2- and 4.1-fold higher death hazard. Our study suggests that ghrelin may be major marker contributing to susceptibility to MIS among ESRD patients.

Muscle wasting from kidney failure-a model for catabolic conditions

PURPOSE

Muscle atrophy is a frequent complication of chronic kidney disease (CKD) and is associated with increased morbidity and mortality. The processes causing loss of muscle mass are also present in several catabolic conditions. Understanding the pathogenesis of CKD-induced muscle loss could lead to therapeutic interventions that prevent muscle wasting in CKD and potentially, other catabolic conditions.

MAJOR FINDINGS

Insulin or IGF-1 resistance caused by CKD, acidosis, inflammation, glucocorticoids or cancer causes defects in insulin-stimulated intracellular signaling that suppresses IRS-1 activity leading to decreased phosphorylation of Akt (p-Akt). A low p-Akt activates caspase-3 which provides muscle proteins substrates of the ubiquitin-proteasome system (UPS). A low p-Akt also leads to decreased phosphorylation of forkhead transcription factors which enter the nucleus to stimulate the expression of atrogin-1/MAFbx and MuRF1, E3 ubiquitin ligases that can be associated with proteolysis of muscle cells by the UPS. Caspase-3 also stimulates proteasome-dependent proteolysis in muscle.

SUMMARY

In CKD, diabetes, inflammatory conditions or in response to acidosis or excess glucocorticoids, insulin resistance develops, initiating reduced IRS-1/PI3K/Akt signaling. In CKD, this reduces p-Akt which stimulates muscle proteolysis by activating caspase-3 and the UPS. Second, caspase-3 cleaves actomyosin yielding substrates for the UPS and increased proteasome-mediated proteolysis. Third, p-Akt down-regulation suppresses myogenesis in CKD. Fourth, exercise in CKD stimulates insulin/IGF-1 signaling to reduce muscle atrophy. Lastly, there is evidence that microRNAs influence insulin signaling providing a potential opportunity to design therapeutic interventions. This article is part of a Directed Issue entitled: Molecular basis of muscle wasting.

Ghrelin and cachexia in chronic kidney disease

Ghrelin is a growth hormone (GH) secretagogue and a potent orexigenic factor that stimulates feeding by interacting with hypothalamic feeding-regulatory nuclei. Its multifaceted effects are potentially beneficial as a treatment in human disease states. In both adult and pediatric chronic kidney disease (CKD) patients, decreased appetite plays a major role in wasting, which in turn is linked to morbidity and mortality; wasting has also been linked to high levels of leptin and proinflammatory cytokines. The beneficial effects of ghrelin treatment in CKD are potentially mediated by multiple concurrent actions, including the stimulation of appetite-regulating centers, anti-inflammatory effects, and direct kidney effects. Further evaluation of this appetite-regulating hormone in CKD is needed to confirm previous findings and to determine the underlying mechanisms.

Mechanisms stimulating muscle wasting in chronic kidney disease: the roles of the ubiquitin-proteasome system and myostatin

Catabolic conditions including chronic kidney disease (CKD), cancer, and diabetes cause muscle atrophy. The loss of muscle mass worsens the burden of disease because it is associated with increased morbidity and mortality. To avoid these problems or to develop treatment strategies, the mechanisms leading to muscle wasting must be identified. Specific mechanisms uncovered in CKD generally occur in other catabolic conditions. These include stimulation of protein degradation in muscle arising from activation of caspase-3 and the ubiquitin-proteasome system (UPS). These proteases act in a coordinated fashion with caspase-3 initially cleaving the complex structure of proteins in muscle, yielding fragments that are substrates that are degraded by the UPS. Fortunately, the UPS exhibits remarkable specificity for proteins to be degraded because it is the major intracellular proteolytic system. Without a high level of specificity cellular functions would be disrupted. The specificity is accomplished by complex reactions that depend on recognition of a protein substrate by specific E3 ubiquitin ligases. In muscle, the specific ligases are Atrogin-1 and MuRF-1, and their expression has characteristics of a biomarker of accelerated muscle proteolysis. Specific complications of CKD (metabolic acidosis, insulin resistance, inflammation, and angiotensin II) activate caspase-3 and the UPS through mechanisms that include glucocorticoids and impaired insulin or IGF-1 signaling. Mediators activate myostatin, which functions as a negative growth factor in muscle. In models of cancer or CKD, strategies that block myostatin prevent muscle wasting, suggesting that therapies that block myostatin could prevent muscle wasting in catabolic conditions.

Targeting the myostatin signaling pathway to treat muscle wasting diseases

PURPOSE OF REVIEW

To understand the mechanisms of muscle wasting and how inhibiting myostatin signaling affects them.

RECENT FINDINGS

Myostatin signaling is critical for the understanding of the pathogenesis of muscle wasting as blocking signaling mitigates muscle losses in rodent models of catabolic diseases including cancer, chronic kidney, or heart failure.

SUMMARY

Muscle wasting increases the risks of morbidity and mortality. But, the reliability of estimates of the degree of muscle wasting is controversial as are definitions of terms like cachexia. Much information has been learnt about the pathophysiology of muscle wasting, including the major role of the ubiquitin-proteasome system (UPS) which along with other proteases degrades protein and limits protein synthesis. In contrast, few successful strategies for reversing muscle loss have been tested. Several catabolic conditions are characterized by inflammation, increased glucocorticoid production, and impaired intracellular signaling in response to insulin and IGF-1. These characteristics lead to activation of the UPS and other proteases producing muscle wasting. Another potential initiator of muscle wasting is myostatin and its expression is increased in muscles of animal models and patients with certain catabolic conditions. Myostatin is a member of the TGF-β family; it suppresses muscle growth and its absence stimulates muscle growth substantially. Recently, pharmacologic suppression of myostatin was found to counteract inflammation, increased glucocorticoids and impaired insulin/IGF-1 signaling and most importantly, prevents muscle wasting in rodent models of cancer and kidney failure. Myostatin antagonism as a therapy for patients with muscle wasting should become a topic of clinical investigation.

Cachexia and protein-energy wasting in children with chronic kidney disease

Children with chronic kidney disease (CKD) are at risk for "cachexia" or "protein-energy wasting" (PEW). These terms describe a pathophysiologic process resulting in the loss of muscle, with or without loss of fat, and involving maladaptive responses, including anorexia and elevated metabolic rate. PEW has been defined specifically in relation to CKD. We review the diagnostic criteria for cachexia and PEW in CKD and consider the limitations and applicability of these criteria to children with CKD. In addition, we present an overview of the manifestations and mechanisms of cachexia and PEW. A host of pathogenetic factors are considered, including systemic inflammation, endocrine perturbations, and abnormal neuropeptide signaling, as well as poor nutritional intake. Mortality risk, which is 100- to 200-fold higher in patients with end-stage renal disease than in the general population, is strongly correlated with the components of cachexia/PEW. Further research into the causes and consequences of wasting and growth retardation is needed in order to improve the survival and quality of life for children with CKD.

Protein-energy wasting and mortality in chronic kidney disease

Protein-energy wasting (PEW) is common in patients with chronic kidney disease (CKD) and is associated with an increased death risk from cardiovascular diseases. However, while even minor renal dysfunction is an independent predictor of adverse cardiovascular prognosis, PEW becomes clinically manifest at an advanced stage, early before or during the dialytic stage. Mechanisms causing loss of muscle protein and fat are complex and not always associated with anorexia, but are linked to several abnormalities that stimulate protein degradation and/or decrease protein synthesis. In addition, data from experimental CKD indicate that uremia specifically blunts the regenerative potential in skeletal muscle, by acting on muscle stem cells. In this discussion recent findings regarding the mechanisms responsible for malnutrition and the increase in cardiovascular risk in CKD patients are discussed. During the course of CKD, the loss of kidney excretory and metabolic functions proceed together with the activation of pathways of endothelial damage, inflammation, acidosis, alterations in insulin signaling and anorexia which are likely to orchestrate net protein catabolism and the PEW syndrome.

Wasting in chronic kidney disease

Wasting/cachexia is prevalent among patients with chronic kidney disease (CKD). It is to be distinguished from malnutrition, which is defined as the consequence of insufficient food intake or an improper diet. Malnutrition is characterized by hunger, which is an adaptive response, whereas anorexia is prevalent in patients with wasting/cachexia. Energy expenditure decreases as a protective mechanism in malnutrition whereas it remains inappropriately high in cachexia/wasting. In malnutrition, fat mass is preferentially lost and lean body mass and muscle mass is preserved. In cachexia/wasting, muscle is wasted and fat is relatively underutilized. Restoring adequate food intake or altering the composition of the diet reverses malnutrition. Nutrition supplementation does not totally reverse cachexia/wasting. The diagnostic criteria of cachexia/protein-energy wasting in CKD are considered. The association of wasting surrogates, such as serum albumin and prealbumin, with mortality is strong making them robust outcome predictors. At the patient level, longevity has consistently been observed in patients with CKD who have more muscle and/or fat, who report better appetite and who eat more. Although inadequate nutritional intake may contribute to wasting or cachexia, recent evidence indicates that other factors, including systemic inflammation, perturbations of appetite-controlling hormones from reduced renal clearance, aberrant neuropeptide signaling, insulin and insulin-like growth factor resistance, and metabolic acidosis, may be important in the pathogenesis of CKD-associated wasting. A number of novel therapeutic approaches, such as ghrelin agonists and melanocortin receptor antagonists are currently at the experimental level and await confirmation by randomized controlled clinical trials in patients with CKD-associated cachexia/wasting syndrome.

Association of serum bicarbonate levels with gait speed and quadriceps strength in older adults

BACKGROUND

Metabolic acidosis is associated with skeletal muscle proteolysis, and alkali supplementation has shown improvements in lean body mass and urinary nitrogen wasting in several studies. However, the association of acidosis with functional outcomes has not been examined on a population-based level.

STUDY DESIGN

Cross-sectional study.

SETTING & PARTICIPANTS

2,675 nationally representative adults 50 years or older in the National Health and Nutrition Examination Survey 1999-2002.

FACTOR

Serum bicarbonate level.

OUTCOMES

Low gait speed and low peak torque were defined as being in the lowest sex-specific quartile of gait speed and peak torque, respectively.

MEASUREMENTS

Serum bicarbonate was measured in all participants. Gait speed was determined from a 20-foot timed walk. Peak torque was calculated using peak isokinetic knee extensor force.

RESULTS

Serum bicarbonate level <23 mEq/L was present in 22.7% of the cohort. Compared with participants with bicarbonate levels ≥23 mEq/L, those with bicarbonate levels <23 mEq/L had higher body mass index and serum albumin levels; were more likely to have low socioeconomic status, a diagnosis of diabetes mellitus, or glomerular filtration rate <60 mL/min/1.73 m(2); and were less likely to use diuretics. Serum bicarbonate level <23 mEq/L compared with ≥23 mEq/L was associated with low gait speed (OR, 1.43; 95% CI, 1.04-1.95) and low peak torque (OR, 1.36; 95% CI, 1.07-1.74) after multivariable adjustment. The association with low peak torque was modified by race/ethnicity in women, but not men (ORs, 1.52 [95% CI, 1.08-2.13] for men, 2.33 [95% CI, 1.23-4.44] for nonwhite women, and 0.93 [95% CI, 0.47-1.82] for white women).

LIMITATIONS

Cross-sectional study using a single bicarbonate measurement.

CONCLUSIONS

Lower serum bicarbonate levels are associated with slower gait speed and decreased quadriceps strength in older adults. Further studies should examine the effect of alkali therapy on functional outcomes.

Animal models of anorexia and cachexia

BACKGROUND: Cachexia is a devastating syndrome of body wasting that worsens quality of life and survival for patients suffering from diseases such as cancer, chronic kidney disease and chronic heart failure. Successful treatments have been elusive in humans, leaving a clear need for the development of new treatment compounds. Animal models of cachexia are able to recapitulate the clinical findings from human disease and have provided a much-needed means of testing the efficacy of prospective therapies. OBJECTIVE: This review focuses on animal models of cachexia caused by cancer, chronic heart failure and chronic kidney disease, including the features of these models, their implementation, and commonly-followed outcome measures. CONCLUSION: Given a dire clinical need for effective treatments of cachexia, animal models will continue a vital role in assessing the efficacy and safety of potential treatments prior to testing in humans. Also important in the future will be the use of animal models to assess the durability of effect from anti-cachexia treatments and their effect on prognosis of the underlying disease states.

Exercise ameliorates chronic kidney disease-induced defects in muscle protein metabolism and progenitor cell function

Chronic kidney disease (CKD) impairs muscle protein metabolism leading to muscle atrophy, and exercise can counteract this muscle wasting. Here we evaluated how resistance exercise (muscle overload) and endurance training (treadmill running) affect CKD-induced abnormalities in muscle protein metabolism and progenitor cell function using mouse plantaris muscle. Both exercise models blunted the increase in disease-induced muscle proteolysis and improved phosphorylation of Akt and the forkhead transcription factor FoxO1. Muscle overloading, but not treadmill running, corrected protein synthesis and levels of mediators of protein synthesis such as phosphorylated mTOR and p70S6K in the muscles of mice with CKD. In these mice, muscle overload, but not treadmill, running, increased muscle progenitor cell number and activity as measured by the amounts of MyoD, myogenin, and eMyHC mRNAs. Muscle overload not only increased plantaris weight and reduced muscle proteolysis but also corrected intracellular signals regulating protein and progenitor cell function in mice with CKD. Treadmill running corrects muscle proteolysis but not protein synthesis or progenitor cell function. Our results provide a basis for evaluating different types of exercise on muscle atrophy in patients with chronic kidney disease.

Serum bicarbonate levels and the progression of kidney disease: a cohort study

BACKGROUND

Animal models of kidney disease have linked metabolic acidosis with renal damage. The role of low serum bicarbonate levels in kidney disease progression in humans has not been studied.

STUDY DESIGN

Retrospective cohort study.

SETTING & PARTICIPANTS

Adults visiting a medical clinic in the Bronx, NY, from January 1, 2001, to December 31, 2003, were included in the study (n = 5,422) and followed up until June 30, 2007.

PREDICTOR

Serum bicarbonate level.

OUTCOMES

Kidney disease progression was defined as either a decrease in estimated glomerular filtration rate (eGFR) by 50% or reaching an eGFR less than 15 mL/min/1.73 m(2) (n = 337).

MEASUREMENTS

Patients' baseline demographics, comorbid conditions, laboratory data, and socioeconomic status were recorded. Serial outpatient serum creatinine levels were collected (median, 5 measurements/person).

RESULTS

Mean age was 52 years, 69% were women, 45% were African American, 31% were Hispanic, 21% had diabetes mellitus, 41% had hypertension, and 9% had a baseline eGFR less than 60 mL/min/1.73 m(2). Kidney disease progressed as defined in 337 patients (6.2%). Compared with the reference group (bicarbonate level, 25 to 26 mEq/L), hazard ratios for progression after adjustment for potential confounders were 1.54 (95% confidence interval [CI], 1.13 to 2.09) for bicarbonate levels of 22 mEq/L or less, 0.97 (95% CI, 0.70 to 1.35) for 23 to 24 mEq/L, and 1.14 (95% CI, 0.84 to 1.55) for 27 mEq/L or greater (global P for inclusion of serum bicarbonate level in the model = 0.01). These results were similar using different definitions of the outcome (eGFR decrease of 30%, 1,288 outcomes [24%]; or doubling of serum creatinine level, 268 outcomes [4.9%]).

LIMITATIONS

Data used in the study were collected for clinical, not research, purposes.

CONCLUSIONS

Low serum bicarbonate level is associated with progression of kidney disease independent of baseline eGFR and other clinical, demographic, and socioeconomic factors. Prospective studies are needed to confirm this relationship and evaluate the efficacy of alkali supplements for slowing progression.

Ubiquitin, proteasomes and proteolytic mechanisms activated by kidney disease

The ubiquitin-proteasome system (UPS) includes 3 enzymes that conjugate ubiquitin to intracellular proteins that are then recognized and degraded in the proteasome. The process participates in the regulation of cell metabolism. In the kidney, the UPS regulates the turnover of transporters and signaling proteins and its activity is down regulated in acidosis-induced proximal tubular cell hypertrophy. In chronic kidney disease (CKD), muscle wasting occurs because complications of CKD including acidosis, insulin resistance, inflammation, and increased angiotensin II levels stimulate the UPS to degrade muscle proteins. This response also includes caspase-3 and calpains which act to cleave muscle proteins to provide substrates for the UPS. For example, caspase-3 degrades actomyosin, leaving a 14 kDa fragment of actin in muscle. The 14 kDa actin fragment is increased in muscle of patient with kidney disease, burn injury and surgery. In addition, acidosis, insulin resistance, inflammation and angiotensin II stimulate glucocorticoid production. Glucocorticoids are also required for the muscle wasting that occurs in CKD. Thus, the UPS is involved in regulating kidney function and participates in highly organized responses that degrade muscle protein in response to loss of kidney function.

Ghrelin treatment of chronic kidney disease: improvements in lean body mass and cytokine profile

Chronic kidney disease (CKD) is associated with an increase in inflammatory cytokines and can result in cachexia with loss of muscle and fat stores. We previously demonstrated the efficacy of treating a model of cancer cachexia with ghrelin and a ghrelin receptor agonist. Currently, we examine a surgical model of CKD in rats, resulting in uremia and decreased accrual of lean body mass. Treatment with ghrelin and two ghrelin receptor agonists (BIM-28125 and BIM-28131) resulted in increased food intake and an improvement in lean body mass accrual that was related in part to a decrease in muscle protein degradation as assessed by muscle levels of the 14-kDa actin fragment resulting from cleaved actomyosin. Additionally, there was a decrease in circulating inflammatory cytokines in nephrectomized animals treated with ghrelin relative to saline treatment. Ghrelin-treated animals also had a decrease in the expression of IL-1 receptor in the brainstem and a decrease in expression of prohormone convertase-2, an enzyme involved in the processing of proopiomelanocortin to the anorexigenic peptide alpha-MSH. We conclude that ghrelin treatment in uremia results in improved lean mass accrual in part due to suppressed muscle proteolysis and possibly related to antiinflammatory effects.

Muscle wasting in chronic kidney disease: the role of the ubiquitin proteasome system and its clinical impact

Muscle wasting in chronic kidney disease (CKD) and other catabolic diseases (e.g. sepsis, diabetes, cancer) can occur despite adequate nutritional intake. It is now known that complications of these various disorders, including acidosis, insulin resistance, inflammation, and increased glucocorticoid and angiotensin II production, all activate the ubiquitin-proteasome system (UPS) to degrade muscle proteins. The initial step in this process is activation of caspase-3 to cleave the myofibril into its components (actin, myosin, troponin, and tropomyosin). Caspase-3 is required because the UPS minimally degrades the myofibril but rapidly degrades its component proteins. Caspase-3 activity is easily detected because it leaves a characteristic 14kD actin fragment in muscle samples. Preliminary evidence from several experimental models of catabolic diseases, as well as from studies in patients, indicates that this fragment could be a useful biomarker because it correlates well with the degree of muscle degradation in dialysis patients and in other catabolic conditions.

Hypoalbuminaemia--a marker of cardiovascular disease in patients with chronic kidney disease stages II-IV

Cardiovascular disease (CVD) is a major cause of morbidity and mortality in patients with chronic kidney disease (CKD) patients. Serum albumin, a negative acute-phase reactant and marker for underlying inflammation and/or malnutrition, is an independent predictor of CVD and mortality in CKD VI patients. Such an association in patients with less severe CKD is not well established. We conducted a cross sectional study of all CKD II-IV patients attending the nephrology clinic (N=376; mean age: 57+/-17 years; GFR: 47+/-20 mL/min/1.73 m(2); females 48%; blacks 15%; diabetics 27%; hypertensive 79%). Laboratory and clinical data including risk factors and evidence of CVD were obtained at the point of the most recent visit. The association between risk factors and CVD was evaluated by logistic regression. In the simple logistic regression model, age (p<0.0001), sex (P= 0.02), hypertension (P<0.0001), diabetes (P<.0001), dyslipidemia (p=.01), and serum albumin (p<.0001) were found to be statistically significant. Serum albumin was found to be an independent predictor (p=0.04) of CVD by multiple logistic regression analysis using the above risk factor variables.

IN CONCLUSION

a) hypoalbuminaemia is an independent predictor of CVD in early CKD stages; b) hypoalbuminaemia may be used to identify the population at higher risk for CVD.

Inflammation and inverse associations of body mass index and serum creatinine with mortality in hemodialysis patients

OBJECTIVE

Protein-energy wasting and inflammation are common and associated with an increased risk of mortality in hemodialysis (HD) patients. We examined the extent to which they mediate the associations of each other with death in this population.

STUDY DESIGN

Retrospective analysis of the Hemodialysis (HEMO) Study data.

SETTING

Prevalent HD patients.

PARTICIPANTS

One-thousand HEMO study participants with data available on C-reactive protein (CRP), body mass index (BMI), and serum creatinine.

INTERVENTION

None.

MAIN OUTCOME MEASURE

The associations of CRP, BMI, and serum creatinine with time to all-cause mortality separately and together in multivariate Cox models.

RESULTS

In 1,437 patient-years of follow-up, there were 265 (26.5%) all-cause deaths. Compared with the lowest CRP quartile, the highest quartile was associated with a hazard ratio (HR) of 2.02 (95% confidence interval [CI], 1.31-3.10) for all-cause mortality. This association of highest CRP quartile with mortality was not attenuated with further adjustment for BMI and serum creatinine (HR, 2.13; 95% CI, 1.38-3.30). When serum albumin was added to the model, the hazard of death associated with highest CRP quartile was modestly attenuated (HR, 1.88; 95% CI, 1.21-2.92). In contrast, both BMI (for each kg/m2 increase; HR, 0.94; 95% CI, 0.91-0.96 for all-cause mortality) and serum creatinine (for each mg/dL increase; HR, 0.85; 95% CI, 0.79-0.90 for all-cause mortality) had strong, independent protective effects. Further adjustment with CRP had a negligible effect on these associations.

CONCLUSION

The associations of markers of nutrition and inflammation with mortality are largely independent of each other in HD patients.

The malnutrition and inflammation axis in pediatric patients with chronic kidney disease

Malnutrition and inflammation are closely linked in adult chronic kidney disease (CKD) patients and are both related to poor outcome, but data on pediatric patients are lacking. To describe the prevalence of inflammation, evaluate nutritional status, their correlation to each other, and their possible determinants in pediatric patients with CKD in predialysis, on hemodialysis (HD), and peritoneal dialysis (PD) who were submitted to demographic, nutritional, and inflammatory evaluations. Patients' nutritional status was evaluated according to anthropometric parameters and body composition assessed by measurements of skinfold thickness and bioelectrical impedance. Inflammation was assessed by measurement of highly sensitive C-reactive protein (CRP), ferritin, and albumin. Patients with CRP > 1 mg/l were considered inflamed. Sixty-four pediatric patients (mean age 9 +/- 4 years-, 40% on HD, 22% on PD, and 38% predialysis) were studied. Mean CRP concentration was 3.4 +/- 6.5 mg/l (median 0.78 mg/l, range 0.78-33.4 mg/l), and 41% presented CRP levels above 1 mg/l. Mean ferritin was 148 +/- 197 mg/dl and was above the normal reference values in 28% of patients. On the other hand, mean albumin was 3.9 +/- 0.5 mg/dl, below reference value in only 13% of patients. A larger proportion of HD patients (52%) were inflamed compared with those on PD (31%; p < 0.05). Malnutrition prevalence varied from 5% to 65% according to the method used. While inflamed patients presented lower serum bicarbonate and were on HD for a longer time, there were no consistent associations between malnutrition and inflammation. Inflammation is highly prevalent in the pediatric CKD population and was not consistently related to malnutrition. Other risk factors linked to high mortality and morbidity (acidosis and longer time on dialysis) were associated with inflammation. Prospective studies will need to analyze the predictive value of inflammation and malnutrition markers in the pediatric CKD population.

Proteolytic mechanisms, not malnutrition, cause loss of muscle mass in kidney failure

Hypoalbuminemia and muscle atrophy are frequently found in patients with chronic kidney disease (CKD) and patients being treated by dialysis. These abnormalities are usually attributed to malnutrition, meaning that they are caused by an inadequate diet. However, the evidence indicates that malnutrition is rarely the mechanism causing loss of protein stores. Instead, low values of serum albumin are closely related to the presence of inflammation and loss of muscle mass is attributable to activation of specific proteases. In uremic rodents and patients, the initial step in the loss of muscle protein is an activation of caspase-3. This cleaves the complex structure of muscle, and its action can be detected by the presence of a characteristic 14-kDa actin fragment in the insoluble fraction of muscle. The second step in uremia-induced loss of muscle protein is an activation of the ubiquitin-proteasome system, which rapidly degrades proteins released by caspase-3 cleavage of muscle proteins. Activation of both caspase-3 and the ubiquitin-proteasome system occur when there is suppression of the cellular signaling pathway activated by insulin/insulinlike growth factor 1, the phosphatidylinositol 3-kinase/Akt pathway. A potential therapeutic target for preventing loss of muscle protein is to stimulate activity of this signaling pathway.

Menu Suggestion: An Effective Way to Improve Dietary Compliance in Peritoneal Dialysis Patients

OBJECTIVE

Poor compliance with the dietary prescriptions is quite common in dialysis patients. We believe that most of the noncompliance is caused by the patient's poor understanding of the dietary prescription. Therefore, in the present study, we tried to investigate the role of menu suggestion in improving the patient's compliance with the dietary prescription.

DESIGN AND SETTING

A longitudinal cohort study conducted at an outpatient dialysis clinic.

PATIENTS

Seventy clinically stable patients on peritoneal dialysis were included in this prospective study during April 1, 2004, to November 31, 2004, in a single center. Patients who had significant cognitive impairment and thus did not understand the food contents during the training course were not eligible for enrollment.

INTERVENTION

All the patients were randomly assigned to 1 of 2 groups. Group 1 patients received the traditional patient education method. Group 2 patients additionally received individualized menu suggestions based on their food preferences and education on how to exchange the foods at equivalent amounts according to the exchange list.

MAIN OUTCOME MEASURES

At present, there are no clear optimal dietary protein intake levels for peritoneal dialysis patients. Our experience is that a dietary protein intake level of 0.8 to 1.2 g/kg/d can maintain our patients in a good nutritional status. Thereafter, in this study we prescribed the dietary protein intake level at 0.8 to 1.2 g/kg/d and defined compliance as meeting this target protein intake level.

RESULTS

There were 35 patients in each group. The compliance was 22.9% in group 1 and 57.1% in group 2 (P < .05).

CONCLUSIONS

Our study suggests that menu suggestion may be an effective way of improving the compliance with the diet in peritoneal dialysis patients. It improves the patient's understanding of the dietary prescription.

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.

The future of pediatric nephrology

The delineation of renal disease in children dates to the 1880s with descriptions of Henoch's purpura, bladder exstrophy, renal rickets and nephritis. The discipline of pediatric nephrology mainly emerged during the 20th century in response to problems in fluid and electrolyte balance, characterization of the nephrotic syndrome, use of renal biopsy, antibiotic therapy of urinary tract infections, dialysis and transplantation in children, growth problems associated with chronic renal failure, detection and therapy of hypertension, and the creation of both national and international pediatric nephrology societies and a journal now in its 18th year. The development of molecular and cell biology, genetic and genomic techniques and bioinformatics methods underlie many future directions. We should anticipate further elucidation of single gene disorders, of complex trait analysis of disorders, such as diabetic nephropathy and hypertension, the interplay of developmental genes and gene products and interactions within the podocyte. Specific therapies directed against inflammation, vascular damage, cyst development, the ravages of proteinuria and graft rejection (or induction leading to tolerance) will be developed. Stem cell therapies may replace lost renal mass, even of specific nephron sites. Novel therapies will also modulate the cell cycle, tyrosine kinase signaling and apoptosis. In addition, drugs will be specifically tested in children for many renal conditions. Larger and more specialized registries will be developed; epidemiologic studies and exploration of large data sets will lead to clinical guidelines that are evidenced-based. There is a need for more careful measurement of glomerular filtration rate (GFR), proteinuria and cytokines, and a fuller appreciation of the nutritional and hormonal role of the kidney. Finally, the antecedents of adult renal disease and the need to intervene in a proactive fashion will be realized. Despite these impressive advances in care, the greatest challenges will be in providing children with renal disease access to well-trained pediatric nephrologists, especially in Asia (1 billion children), Africa, Central and South America, and in immigrant and refugee populations. Included in this challenge is the capacity to have affordable access to use of contemporary techniques, and effective medications and prevention strategies. The International Pediatric Nephrology Association (IPNA), its journal, and pediatric advocates will need to use their energies to take on these challenges.

Strong Association Between Volume Status and Nutritional Status in Peritoneal Dialysis Patients

BACKGROUND

Malnutrition is a strong predictor of mortality in maintenance peritoneal dialysis (PD) patients. Various factors have been identified to contribute to the development of malnutrition. The present study tried to investigate the possible role of fluid overload in the development of malnutrition.

METHODS

Twenty-eight PD patients were included in this study. Fluid status was evaluated by means of repeated bioimpedance analysis, and nutritional status was assessed by means of handgrip strength and subjective global assessment. All patients were followed up closely for 9 months. Based on changes in bioimpedance analysis data, patients were divided into group A (with continuous and steadily improved fluid status; n = 18) and group B (with consistent fluid overload; n = 10).

RESULTS

There were no differences in sex, age, and height between the 2 groups. In group A, patients' extracellular water (ECW) volume decreased significantly during follow-up, whereas intracellular water (ICW) volume increased significantly (both P < 0.001). In group B, ECW volume increased significantly, whereas ICW volume increased at an early stage and then decreased. The ratio of ECW to total-body water decreased significantly in group A, but increased significantly in group B. Along with the improvement in fluid status, nutritional status in group A also improved significantly (the prevalence of malnutrition decreased from 66.7% to 11.1%; P < 0.01). However, in group B, nutritional status deteriorated significantly (handgrip strength decreased from 238.33 +/- 88.93 to 216.1 +/- 86.19 N; P < 0.05; and the prevalence of malnutrition increased from 40% to 50%).

CONCLUSION

Our data suggest there is a strong association between fluid status and nutritional status. Improved fluid status is associated with improvement in nutritional status, whereas deterioration in fluid status is associated with the development of malnutrition.

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.

Nutritional status and dietary manipulation in predialysis chronic renal failure patients

OBJECTIVE

A properly implemented dietary treatment for patients with chronic renal failure (CRF) can correct several metabolic and endocrine disturbances and delay initiation of dialysis, but concerns exist about the risk of malnutrition and protein depletion. The goal of this study is to evaluate nutritional status and its relation to the dietary treatment in patients with advanced CRF.

DESIGN

Cross-sectional survey.

SETTING

Predialysis outpatient clinic.

PATIENTS

Seventy patients (43 males, 27 females, 50 +/- 12 years) with severe CRF (glomerular filtration rate [GFR] <15 mL/min) being treated with a low-protein (0.6 g/kg/day) diet (LPD) or a very-low-protein (0.3 g/kg/day) diet supplemented with essential amino acids and ketoacids (KAD). Fifty-two healthy subjects with comparable age and sex served as controls.

MAIN OUTCOME MEASURES

In all patients and controls, we performed biochemistry, anthropometry, bioelectrical impedance vector analysis (BIVA), and subjective global assessment (SGA), and the patients' outcomes were also assessed.

RESULTS

Values of anthropometry and BIVA were similar in patients and controls. SGA scores showed a normal nutritional status (SGA-0) in 50 patients (71.4%) and mild to moderate SGA abnormalities (SGA-1) in 20 patients (28.6%); none had severe malnutrition. The SGA-1 patients differed from the SGA-0 patients by having higher serum urea, lower bicarbonate, and lower renal function (87% of SGA-1 patients had GFR <10 mL/min.). At the same GFR values (6.6 +/- 2.3 versus 6.6 +/- 2.3 mL/min) SGA-1 patients had lower bicarbonate (21.9 +/- 4.3 versus 25.3 +/- 2.7 mM, P <.01) and higher serum urea (115 +/- 29 versus 82 +/- 38 mg/dL, P =.01) and protein intake than SGA-0 patients; SGA-1 score was more prevalent with LPD compared with KAD treatment (45% versus 27%, P <.05). BIVA and anthropometry, serum levels of albumin, prealbumin, insulin-like growth factor-1, hematocrit, and lymphocyte count did not differ between SGA-1 and SGA-0 patients, but the number entering dialysis was higher in the group scoring as SGA-1 compared with SGA-0 (82% versus 47%, P <.05).

CONCLUSIONS

With a planned dietary regimen, severe or overt malnutrition does not occur in predialysis CRF without other serious illnesses. However, some mild to moderate SGA abnormalities were detected in association with a more severe renal insufficiency, a lower serum bicarbonate, a higher serum urea and dietary protein levels and were predictive of poor renal outcome. This study emphasizes the role of proper dietary implementation, correction of metabolic acidosis, and clinical monitoring including SGA in the predialysis conservative care of CRF patients.

Nutritional effects of delivered bicarbonate dose in maintenance hemodialysis patients

OBJECTIVE

Metabolic acidosis is common in patients with end-stage renal disease (ESRD). Studies suggest that correction of acidosis may improve nutritional status and patient outcomes. The purpose of this study was to examine the effects of increasing delivered bicarbonate dose from 35 mmol/L to 39 mmol/L with respect to nutrition-related outcomes in maintenance hemodialysis patients (MHD).

DESIGN AND SETTING

This was a longitudinal, observational study conducted at 4 dialysis centers in western Massachusetts. Patients were followed for 6 months after change in bicarbonate dose protocol.

PATIENTS

The study sample consisted of 248 patients who had been on MHD for at least 1 year on the standard bicarbonate dialysate of 35 mmol/L without oral bicarbonate supplements.

MAIN OUTCOME MEASURES

Measures of interest included predialysis serum bicarbonate, albumin, hemoglobin, potassium, phosphorus, calcium, and parathyroid hormone (iPTH), as well as protein catabolic rate (nPCR). A subset of patients (n = 35) was examined for changes via Subjective Global Assessment (SGA).

RESULTS

Serum bicarbonate improved significantly from baseline (21.7 +/- 2.8 mmol/L; mean +/- SD) at 3 months (23.3 +/- 3.3) and 6 months (23.1 +/- 3.3) (P <.0001). Phosphorus decreased from 6.0 +/- 2.0 mmol/L at baseline to 5.7 +/- 1.7 mmol/L (P =.02) at 6 months, although calcium, iPTH, and potassium remained relatively stable. Serum bicarbonate was inversely and significantly correlated with nPCR at baseline (r = -0.23; P <.05) and 3 months (r = -0.22; P <.05). The nPCR decreased significantly (P =.001) from baseline (0.99 +/- 0.26) at 6 months (0.93 +/- 0.23), whereas the serum albumin and SGA scores did not differ.

CONCLUSION

Increasing delivered bicarbonate dose improves serum bicarbonate and may decrease catabolism. Further study is needed to confirm the potential nutritional benefits.