Etiology of the Protein-Energy Wasting Syndrome in Chronic Kidney Disease: A Consensus Statement From the International Society of Renal Nutrition and Metabolism (ISRNM)

Effect of continuous progressive resistance training during hemodialysis on body composition, physical function and quality of life in end-stage renal disease patients: a randomized controlled trial

Objective:

This study aimed to investigate the effect of continuous progressive resistance training on body composition, functional capacity and self-reported quality of life in end-stage renal disease patients.

Design:

A randomized controlled trial.

Subjects:

The study included 52 hemodialysis patients (aged 55.7 ± 14.03 years) randomized into exercise (progressive resistance training (PRT), n = 28) or control (CON, n = 24) groups.

Intervention:

Patients randomized into the PRT group received prescribed strength exercises in two sets of 15–20 repetitions, in a repetition maximum training zone regime, thrice a week for 12 weeks, during hemodialysis. Patients randomized into the CON group received a sham-exercise with active mobilization of the arms and legs without load and progression.

Main outcome measure:

Body composition using dual-energy X-ray absorptiometry (DXA), strength using handgrip dynamometry (HGS), repeated sit-to-stand test (STT), 6-minute walk test, flexibility and the SF-36 questionnaire (quality of life (QoL)) were assessed at baseline and at 12 weeks.

Results:

Leg lean mass ( P = 0.04, effect size (ES) of 0.56), bone mineral content ( P = 0.02, ES of 0.65), leg strength in STT repetitions ( P = 0.01, ES of 0.66) and flexibility ( P < 0.01, ES of 1.03) were significantly improved in the PRT group compared to the CON group. Walking capacity, HGS and QoL were not different between the groups.

Conclusion:

12 weeks of PRT with a repetition maximum training zone regime provided significant load to increase leg lean mass and STT performance as well as bone mineral content, compared to the CON, which continued to deteriorate. There was lack of efficacy on walking test, HGS and QoL.

Modeling a Predictive Energy Equation Specific for Maintenance Hemodialysis

BACKGROUND

Hypermetabolism is theorized in patients diagnosed with chronic kidney disease who are receiving maintenance hemodialysis (MHD). We aimed to distinguish key disease-specific determinants of resting energy expenditure to create a predictive energy equation that more precisely establishes energy needs with the intent of preventing protein-energy wasting.

MATERIALS AND METHODS

For this 3-year multisite cross-sectional study (N = 116), eligible participants were diagnosed with chronic kidney disease and were receiving MHD for at least 3 months. Predictors for the model included weight, sex, age, C-reactive protein (CRP), glycosylated hemoglobin, and serum creatinine. The outcome variable was measured resting energy expenditure (mREE). Regression modeling was used to generate predictive formulas and Bland-Altman analyses to evaluate accuracy.

RESULTS

The majority were male (60.3%), black (81.0%), and non-Hispanic (76.7%), and 23% were ≥65 years old. After screening for multicollinearity, the best predictive model of mREE (R2 = 0.67) included weight, age, sex, and CRP. Two alternative models with acceptable predictability (R2 = 0.66) were derived with glycosylated hemoglobin or serum creatinine. Based on Bland-Altman analyses, the maintenance hemodialysis equation that included CRP had the best precision, with the highest proportion of participants' predicted energy expenditure classified as accurate (61.2%) and with the lowest number of individuals with underestimation or overestimation.

CONCLUSIONS

This study confirms disease-specific factors as key determinants of mREE in patients on MHD and provides a preliminary predictive energy equation. Further prospective research is necessary to test the reliability and validity of this equation across diverse populations of patients who are receiving MHD.

Phosphate stimulates myotube atrophy through autophagy activation: evidence of hyperphosphatemia contributing to skeletal muscle wasting in chronic kidney disease

Background

Accelerated muscle atrophy is associated with a three-fold increase in mortality in chronic kidney disease (CKD) patients. It is suggested that hyperphosphatemia might contribute to muscle wasting, but the underlying mechanisms remain unclear. Although evidence indicates that autophagy is involved in the maintenance of muscle homeostasis, it is not known if high phosphate levels can result in activation of autophagy, leading to muscle protein loss.

Methods

Immortalized rat L6 myotubes were exposed to a high concentration of phosphate, with or without autophagy inhibition. Myotube atrophy was examined by phase contrast microscopy. Autophagic activity was assessed by measuring the expression of microtubule-associated protein 1 light chain 3 (LC3) and p62 using quantitative real-time polymerase chain reaction and western blot.

Results

Phosphate induced cell atrophy in L6 myotubes in a dose- and time-dependent manner, and these responses were not associated with calcification or osteogenesis. Phosphate also dose- and time-dependently increased the LC3-II/LC3-I ratio. Inhibition of autophagy with wortmannin or knockdown of Atg5 significantly suppressed myotube atrophy caused by high phosphate concentration.

Conclusions

High phosphate concentration induces muscle cell atrophy through the activation of autophagy. Targeting autophagy could be a therapeutic strategy for preventing muscle wasting caused by hyperphosphatemia.

Prevalence and Risk of Protein-Energy Wasting Assessed by Subjective Global Assessment in Older Adults With Advanced Chronic Kidney Disease: Results From the EQUAL Study

OBJECTIVES

Prevalence and risk factors for protein-energy wasting (PEW) are poorly studied in the nondialysis, older population with advanced chronic kidney disease (CKD). Our aim was to evaluate the prevalence of PEW in advanced stage CKD patients aged greater than 65 years. Furthermore, we aimed to describe risk factors for PEW in the overall study population and among obese individuals.

DESIGN

Prospective observational cohort study.

METHODS

The EQUAL study, a European Quality Study on treatment in advanced chronic kidney disease, is a multicenter prospective observational cohort study in six European countries. We included patients aged ≥65 years with incident glomerular filtration rate <20mL/min/1.73m² not on dialysis attending nephrology care. PEW was assessed by 7-point Subjective Global Assessment (7-p SGA).

RESULTS

In general, the study cohort (n = 1,334) was overweight (mean body mass index [BMI] 28.4 kg/m²). The majority of the patients had a normal nutritional status (SGA 6-7), 26% had moderate PEW (SGA 3-5), and less than 1% had severe PEW (SGA 1-2). Muscle wasting and loss of fat tissue were the most frequent alterations according to the SGA subscales, especially in those aged >80 years. The prevalence of PEW was higher among women, increased with age, and was higher in those with depression/dementia. PEW was the most common in those with underweight (BMI <22 kg/m²), 55% or normal weight (BMI 22-25 kg/m²), 40%. In obese individuals (BMI >30 kg/m²), 25% were diagnosed with protein wasting. Risk factors for SGA ≤5 in obese people were similar to those for the overall study population.

CONCLUSION

This European multicenter study shows that the prevalence of PEW is high in patients with advanced CKD aged >65 years. The risk of PEW increases substantially with age and is commonly characterized by muscle wasting. Our study suggests that focus on nutrition should start early in the follow-up of older adults with CKD.

Body Mass Index Change and Hospitalization Risk in Elderly Hemodialysis Patients: Results from Japanese Dialysis Outcomes and Practice Patterns Study

BACKGROUND

Short-term weight gains and losses are associated with a lower and higher mortality risk, respectively, in patients undergoing hemodialysis (HD). However, little is known about their association with the risk of subsequent hospitalization.

METHODS

In a prospective cohort of 1,804 HD patients aged ≥65 years enrolled in the Japanese Dialysis Outcomes and Practice Patterns Study phases 3 (2005-2008) and 4 (2009-2011), we examined the associations between changes in body mass index (BMI) over a 4-month baseline period (<-3%, -3 to <-1%, -1 to <1% [reference], 1 to <3%, and ≥3%) and subsequent risk of all-cause, cardiovascular, and noncardiovascular hospitalization using Cox models with adjustment for potential confounders.

RESULTS

During a median follow-up of 1.2 years, we noted 1,028 incident hospitalizations for any cause, including 275 and 753 hospitalizations for cardiovascular and noncardiovascular causes, respectively. An L-shaped association was observed between BMI change and all-cause hospitalization. The multivariable-adjusted hazard ratios (HRs; 95% CI) of all-cause hospitalization associated with BMI changes of <-3%, -3 to <-1%, 1 to <3%, and ≥3% (vs. -1 to <1%) were 1.29 (1.01-1.65), 1.22 (0.98-1.51), 1.04 (0.83-1.29), and 1.10 (0.83-1.45), respectively. Qualitatively similar associations were present for cardiovascular-related hospitalization (corresponding HRs [95% CI]: 1.58 [1.06-2.37], 1.09 [0.75-1.58], 0.99 [0.72-1.36], and 0.91 [0.51-1.64], respectively) but not for noncardiovascular-related hospitalization (corresponding HRs [95% CI]: 1.19 [0.90-1.57], 1.26 [0.99-1.59], 1.06 [0.84-1.35], and 1.18 [0.86-1.63], respectively).

CONCLUSIONS

Decreases in BMI over a relatively short-term period were independently associated with higher risk of subsequent hospitalization, particularly cardiovascular-related hospitalization, among elderly HD patients.

Prognostic impact of nutritional risk assessment in patients with chronic schizophrenia

Protein-energy wasting is associated with poor outcome in various clinical settings. However, the prevalence of malnutrition and the prognostic impact of nutritional status are poorly understood in institutionalized patients with chronic schizophrenia. This study aimed to assess the predictive ability of the Geriatric Nutritional Risk Index and Onodera's Prognostic Nutritional Index for long-term outcomes in patients with chronic schizophrenia. All measurements, including nutritional scores, were performed at baseline after the enrollment of 542 (64.6% men, mean age 53.8±9.7years) patients with chronic schizophrenia. The median follow-up period was 408days. The endpoints were falls and infection-related hospitalizations. At study completion, 34 patients suffered falls and 40 patients were admitted to hospitals due to infection. Both indices showed significant association with infectious complications, whereas only the Onodera's Prognostic Nutritional Index was significantly associated with falls. The adjusted hazard ratios (95% confidence intervals) of low Onodera's Prognostic Nutritional Index were 2.38 (1.16-4.86) for falls and 1.99 (1.05-3.76) for infectious complications. The Onodera's Prognostic Nutritional Index is more appropriate than the Geriatric Nutritional Risk Index in identifying patients with chronic schizophrenia who are at risk for malnutrition and nutrition-related morbidity. Further studies are needed to explore whether early detection of patients with schizophrenia who are at risk for malnutrition could lead to the reduction of morbidity and mortality with the aid of appropriate interventions.

Protein Carbamylation: Chemistry, Pathophysiological Involvement, and Biomarkers

Protein carbamylation refers to a nonenzymatic modification, which consists in the binding of isocyanic acid on protein functional groups. This reaction is responsible for the alteration in structural and functional properties of proteins, which participate in their molecular aging. Protein molecular aging is now considered a molecular substratum for the development of chronic and inflammatory diseases, including atherosclerosis, chronic kidney disease, or rheumatoid arthritis. As a consequence, carbamylation-derived products have been proposed as interesting biomarkers in various pathological contexts and appropriate analytical methods have been developed for their quantification in biological fluids. The purpose of this review is (i) to describe the biochemical bases of the carbamylation reaction, (ii) to explain how it contributes to protein molecular aging, (iii) to provide evidence of its involvement in aging and chronic diseases, and (iv) to list the available biomarkers of carbamylation process and the related analytical methods.

Muscle Atrophy in Chronic Kidney Disease

The renal damage and loss of kidney function that characterize chronic kidney disease (CKD) cause several complex systemic alterations that affect muscular homeostasis, leading to loss of muscle mass and, ultimately, to muscle atrophy. CKD-induced muscle atrophy is highly prevalent and, in association with common CKD comorbidities, is responsible for the reduction of physical capacity, functional independence, and an increase in the number of hospitalizations and mortality rates. Thus, this chapter summarizes current knowledge about the complex interactions between CKD factors and the pathophysiological mechanisms that induce muscle atrophy that, despite growing interest, are not yet fully understood. The current treatments of CKD-induced muscle atrophy are multidisciplinary, including correction of metabolic acidosis, nutritional supplementation, reducing insulin resistance, administration of androgenic steroids, resisted and aerobic exercise, neuromuscular electrical stimulation, and inspiratory muscle training. However, further studies are still needed to strengthen the comprehension of CKD-induced muscle atrophy and the better treatment strategies.

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.

Irisin and Volume Overload are Associated with Protein Energy Wasting in Peritoneal Dialysis Patients

BACKGROUND/AIMS

Protein energy wasting (PEW) is a common medical phenomenon that is observed in maintenance dialysis patients. PEW also increases morbidity and mortality of these patients. Its pathogenesis is unclear. We hypothesize that serum irisin levels and volume overload may induce PEW in peritoneal dialysis (PD) patients. The aim of this study is to measure serum irisin levels, evaluate volume status of PD patients, and study their correlations with PEW in PD patients.

METHODS

This study is a cross-sectional study with 160 PD patients from the PD center of Peking University Third Hospital and 35 healthy control subjects. PD patients were divided into PEW group and non-PEW group according to PEW diagnosis criteria. Serum irisin concentrations were measured by ELISA. Volume overload status (volume overload is defined as overhydration value ≥2 liters) of PD patients was analyzed by bioelectrical impedance.

RESULTS

The serum irisin levels were significantly lower in PD patients compared with those of the controls (113.2±11.8 ng/ml vs. 464.2±37.4 ng/ml, P<0.01). The serum irisin levels were lower in PD patients with PEW than those of the patients without PEW (106.5±15.2 ng/ml vs. 117.4±17.6 ng/ml, P<0.01). PEW is more prevalent in patients with volume overload than patients without volume overload (62.5% vs. 43.1%, x2=5.756, P=0.016); however, no direct relationship was found between irisin levels and volume overload status. The independent influencing factors of PEW were serum irisin, serum albumin, and volume overload.

CONCLUSION

Our results are the first to provide clinical evidence of the association between serum irisin, volume overload, and PEW in PD patients. PEW may inhibit the release or synthesis of irisin from skeletal muscles, and volume overload may aggravate PEW in PD patients.

Effects of Oral Nutritional Supplements on Mortality, Missed Dialysis Treatments, and Nutritional Markers in Hemodialysis Patients

OBJECTIVE

Protein-energy wasting is common in end-stage renal disease patients undergoing dialysis and is strongly associated with mortality and adverse outcomes. Intradialytic oral nutritional supplements (ONS) reduce risk of mortality in these patients. Large studies characterizing the impact of ONS on other outcomes are lacking. We assessed the associations between administration of ONS and clinical and nutritional outcomes.

DESIGN

Retrospective evaluation of a pilot program providing ONS to patients at a large dialysis organization in the United States. The pilot program provided ONS to in-center hemodialysis patients with serum albumin ≤3.5 g/dL at 408 facilities.

SUBJECTS

ONS patients were compared to matched controls with serum albumin ≤3.5 g/dL, identified from facilities not participating in the ONS program (n = 3,374 per group).

INTERVENTION

Receipt of ONS.

MAIN OUTCOME MEASURES

Death, missed dialysis treatments, hospitalizations, serum albumin, normalized protein catabolic rate, and postdialysis body weight were abstracted from large dialysis organization electronic medical records.

RESULTS

There was a 69% reduction in deaths (hazard ratio = 0.31; 95% confidence interval = 0.25-0.39), and 33% fewer missed dialysis treatments (incidence rate ratio = 0.77; 95% confidence interval = 0.73-0.82) among ONS patients compared to controls (P < .001 for both). The effects of ONS on nutritional indices were mixed: serum albumin was lower, whereas normalized protein catabolic rate values, a surrogate for dietary protein intake, and postdialysis body weights were higher for ONS patients compared to controls during follow-up.

CONCLUSIONS

Our evaluation confirmed the beneficial effects of ONS in reducing mortality and improving some indices of nutritional status for hypoalbuminemic hemodialysis patients. We also report the novel finding that ONS can reduce the number of missed dialysis treatments. These results support the use of intradialytic ONS as an effective intervention to improve the outcomes in hemodialysis patients with low serum albumin.

Metabolomics and Gene Expression Analysis Reveal Down-regulation of the Citric Acid (TCA) Cycle in Non-diabetic CKD Patients

Chronic kidney disease (CKD) is a public health problem with very high prevalence and mortality. Yet, there is a paucity of effective treatment options, partly due to insufficient knowledge of underlying pathophysiology. We combined metabolomics (GCMS) with kidney gene expression studies to identify metabolic pathways that are altered in adults with non-diabetic stage 3-4 CKD versus healthy adults. Urinary excretion rate of 27 metabolites and plasma concentration of 33 metabolites differed significantly in CKD patients versus controls (estimate range-68% to +113%). Pathway analysis revealed that the citric acid cycle was the most significantly affected, with urinary excretion of citrate, cis-aconitate, isocitrate, 2-oxoglutarate and succinate reduced by 40-68%. Reduction of the citric acid cycle metabolites in urine was replicated in an independent cohort. Expression of genes regulating aconitate, isocitrate, 2-oxoglutarate and succinate were significantly reduced in kidney biopsies. We observed increased urine citrate excretion (+74%, p=0.00009) and plasma 2-oxoglutarate concentrations (+12%, p=0.002) in CKD patients during treatment with a vitamin-D receptor agonist in a randomized trial. In conclusion, urinary excretion of citric acid cycle metabolites and renal expression of genes regulating these metabolites were reduced in non-diabetic CKD. This supports the emerging view of CKD as a state of mitochondrial dysfunction.

Removal of uremic retention products by hemodialysis is coupled with indiscriminate loss of vital metabolites

BACKGROUND

Although dialysis ameliorates uremia and fluid and electrolytes disorders, annual mortality rate remains high in dialysis population reflecting its shortcoming in replacing renal function. Unlike the normal kidney, dialysis causes dramatic shifts in volume and composition of body fluids and indiscriminate removal of vital solutes. Present study was undertaken to determine the impact of hemodialysis on plasma metabolites in end-stage renal disease (ESRD) patients.

METHODS

80 hemodialysis patients and 80 age/gender-matched healthy controls were enrolled in the study. Using ultra performance liquid chromatography-high-definition mass spectrometry, we measured plasma metabolites before, during, and after hemodialysis procedure and in blood entering and leaving the dialysis filter.

RESULTS

Principal component analysis revealed significant difference in concentration of 214 metabolites between healthy control and ESRD patients' pre-dialysis plasma (126 increased and 88 reduced in ESRD group). Comparison of post-dialysis with pre-dialysis data revealed significant changes in the 362 metabolites. Among ESI+ metabolites 195 decreased and 55 increased and among ESI- metabolites 82 decreased and 30 increased following hemodialysis. Single blood passage through the dialyzer caused significant changes in 323 metabolites. Comparison of ESRD patients' post-hemodialysis with healthy subjects' data revealed marked differences in metabolic profiles. We identified 55 of the 362 differential metabolites including well known uremic toxins, waste products and vital biological compounds.

CONCLUSION

In addition to uremic toxins and waste products hemodialysis removes large number of identified and as-yet un-identified metabolites. Depletion of vital biological compounds by dialysis may contribute to the high morbidity and annual mortality rate in this population.

Chronic kidney disease

Chronic kidney disease (CKD) is defined by persistent urine abnormalities, structural abnormalities or impaired excretory renal function suggestive of a loss of functional nephrons. The majority of patients with CKD are at risk of accelerated cardiovascular disease and death. For those who progress to end-stage renal disease, the limited accessibility to renal replacement therapy is a problem in many parts of the world. Risk factors for the development and progression of CKD include low nephron number at birth, nephron loss due to increasing age and acute or chronic kidney injuries caused by toxic exposures or diseases (for example, obesity and type 2 diabetes mellitus). The management of patients with CKD is focused on early detection or prevention, treatment of the underlying cause (if possible) to curb progression and attention to secondary processes that contribute to ongoing nephron loss. Blood pressure control, inhibition of the renin-angiotensin system and disease-specific interventions are the cornerstones of therapy. CKD complications such as anaemia, metabolic acidosis and secondary hyperparathyroidism affect cardiovascular health and quality of life, and require diagnosis and treatment.

Systemic inflammation is associated with exaggerated skeletal muscle protein catabolism in maintenance hemodialysis patients

BACKGROUND

Systemic inflammation and muscle wasting are highly prevalent and coexist in patients on maintenance hemodialysis (MHD). We aimed to determine the effects of systemic inflammation on skeletal muscle protein metabolism in MHD patients.

METHODS

Whole body and skeletal muscle protein turnover were assessed by stable isotope kinetic studies. We incorporated expressions of E1, E214K, E3αI, E3αII, MuRF-1, and atrogin-1 in skeletal muscle tissue from integrin β1 gene KO CKD mice models.

RESULTS

Among 129 patients with mean (± SD) age 47 ± 12 years, 74% were African American, 73% were male, and 22% had diabetes mellitus. Median high-sensitivity C-reactive protein (hs-CRP) concentration was 13 (interquartile range 0.8, 33) mg/l. There were statistically significant associations between hs-CRP and forearm skeletal muscle protein synthesis, degradation, and net forearm skeletal muscle protein balance (P < 0.001 for all). The associations remained statistically significant after adjustment for clinical and demographic confounders, as well as in sensitivity analysis, excluding patients with diabetes mellitus. In attempting to identify potential mechanisms involved in this correlation, we show increased expressions of E1, E214K, E3αI, E3αII, MuRF-1, and atrogin-1 in skeletal muscle tissue obtained from an animal model of chronic kidney disease.

CONCLUSION

These data suggest that systemic inflammation is a strong and independent determinant of skeletal muscle protein homeostasis in MHD patients, providing rationale for further studies using anticytokine therapies in patients with underlying systemic inflammation.

FUNDING

This study was in part supported by NIH grants R01 DK45604 and 1K24 DK62849, the Clinical Translational Science Award UL1-TR000445 from the National Center for Advancing Translational Sciences, the Veterans Administration Merit Award I01 CX000414, the SatelliteHealth Normon Coplon Extramural Grant Program, and the FDA grant 000943.

How to Prevent Renal Cachexia? A Clinical Randomized Pilot Study Testing Oral Supplemental Nutrition in Hemodialysis Patients With and Without Human Immunodeficiency Virus Infection

OBJECTIVE

End-stage renal disease associates with catabolism and sarcopenia. Hypothetically, peroral supplemental nutrition over 6 months prevents catabolism in hemodialysis patients.

DESIGN

Prospective randomized pilot study (ClinicalTrials.gov Identifier: NCT00687050).

SUBJECTS

Twenty-three hemodialysis patients (15 males and 7 females) with or without human immunodeficiency virus (HIV) infection of 2 ambulatory hemodialysis centers.

INTERVENTION

HIV-positive hemodialysis patients (n = 7, Group 1) were started on supplemental nutrition drinks (250 kcal/day), HIV-negative hemodialysis patients (n = 16, Group 2) were randomized to supplemental nutrition drinks (250 kcal/day) or received none.

MAIN OUTCOME MEASURES

Body impedance analysis, anthropometric measures, magnetic resonance imaging results for mid-iliopsoas muscle cross-sectional area and laboratory parameters including albumin, cytokines at baseline, and at 6 months follow-up.

RESULTS

Seven patients in Group 1 (mean age: 50.6 ± 9.6 years) and 16 patients in Group 2 (mean age: 54.0 ± 13.3 years) were recruited. Serum creatinine (Group 1: 6.4 ± 3.0 mg/dL; Group 2: 10.7 ± 2.5 mg/dL; P < .01), Body impedance analysis-derived phase angle alpha (Group 1: 5.1 ± 1.2; Group 2: 6.9 ± 1.6; P < .01), mid-arm circumference (Group 1: 26.1 ± 1.3 cm; Group 2: 29.6 ± 2.4 cm; P < .01) were less in Group 1 versus Group 2 patients at baseline suggesting that HIV-positive hemodialysis patients had a poorer nutritional status at baseline. At 6-month follow-up, mortality was higher in Group 1 patients (29%) than in Group 2 patients (6%). There was no significant treatment effect on nutritional status in survivors of Group 1 or in the supplemental nutrition arm of Group 2 when compared with baseline or to untreated controls.

CONCLUSIONS

A new oral supplemental nutrition over 6 months had no treatment effect in surviving HIV-positive hemodialysis patients or in maintenance hemodialysis patients without HIV infection. The limitations of this study were small study size and unexpected high mortality among HIV-positive hemodialysis patients.

Vitamin D, a modulator of musculoskeletal health in chronic kidney disease

The spectrum of activity of vitamin D goes beyond calcium and bone homeostasis, and growing evidence suggests that vitamin D contributes to maintain musculoskeletal health in healthy subjects as well as in patients with chronic kidney disease (CKD), who display the combination of bone metabolism disorder, muscle wasting, and weakness. Here, we review how vitamin D represents a pathway in which bone and muscle may interact. In vitro studies have confirmed that the vitamin D receptor is present on muscle, describing the mechanisms whereby vitamin D directly affects skeletal muscle. These include genomic and non-genomic (rapid) effects, regulating cellular differentiation and proliferation. Observational studies have shown that circulating 25-hydroxyvitamin D levels correlate with the clinical symptoms and muscle morphological changes observed in CKD patients. Vitamin D deficiency has been linked to low bone formation rate and bone mineral density, with an increased risk of skeletal fractures. The impact of low vitamin D status on skeletal muscle may also affect muscle metabolic pathways, including its sensitivity to insulin. Although some interventional studies have shown that vitamin D may improve physical performance and protect against the development of histological and radiological signs of hyperparathyroidism, evidence is still insufficient to draw definitive conclusions.

Comparison of a Handheld Indirect Calorimetry Device and Predictive Energy Equations Among Individuals on Maintenance Hemodialysis

OBJECTIVES

Practical methods for determining resting energy expenditure (REE) among individuals on maintenance hemodialysis (MHD) are needed because of the limitations of indirect calorimetry. Two disease-specific predictive energy equations (PEEs) have been developed for this metabolically complex population. The aim of this study was to compare estimated REE (eREE) by PEEs to measured REE (mREE) with a handheld indirect calorimetry device (HICD).

METHODS

A prospective pilot study of adults on MHD (N = 40) was conducted at 2 dialysis clinics in Houston and Texas City, Texas. mREE by an HICD was compared with eREE determined by 6 PEEs using Bland-Altman analysis with a band of acceptable agreement of ±10% of the group mean mREE. Paired t-test and the intraclass correlation coefficient were also used to compare the alternate methods of measuring REE. A priori alpha was set at P < .05.

RESULTS

The mean (±standard deviation) age was 56.7 ± 12.9 years, 52.5% (n = 21) were female, and 85% (n = 34) were African American. Body mass index (BMI) ranged from 18.1 to 47.1 kg/m², 67.5% were overweight (BMI ≥25 kg/m²) and 50% were obese (BMI ≥30 kg/m²). The Maintenance Hemodialysis Equation-Creatinine version (MHCD-CR) was the most accurate PEE with 52.5% of values within the band of acceptable agreement, followed by the Mifflin-St. Jeor Equation and the Vilar et al. Equation at 45.0% and 42.5%, respectively.

CONCLUSION

When compared with mREE by the HICD, the MHDE-CR was more accurate and precise than other PEEs evaluated; however, this must be interpreted with caution as mREE was consistently lower than eREE from all PEEs. Further research is needed to validate the MHDE-CR and other practical methods for determining REE among individuals on MHD.

Red meat intake in chronic kidney disease patients: Two sides of the coin

Red meat is an important dietary source of high biological value protein and micronutrients such as vitamins, iron, and zinc that exert many beneficial functions. However, high consumption of animal protein sources, especially red meat, results in an increased intake of saturated fat, cholesterol, iron, and salt, as well as an excessive acid load. Red meat intake may lead to an elevated production of uremic toxins by the gut microbiota, such as trimethylamine n-oxide (TMAO), indoxyl sulfate, and p-cresyl sulfate. These uremic toxins are associated with increased risk for cardiovascular (CV) mortality. Limiting the intake of red meat in patients with chronic kidney disease (CKD) thus may be a good strategy to reduce CV risk, and may slow the progression of kidney disease. In the present review, we discuss the role of red meat in the diet of patients with CKD. Additionally, we report on a pilot study that focused on the effect of a low-protein diet on TMAO plasma levels in nondialysis CKD patients.

Protein-energy wasting syndrome in advanced chronic kidney disease: prevalence and specific clinical characteristics

INTRODUCTION

Protein-energy wasting (PEW) is associated with increased mortality and differs depending on the chronic kidney disease (CKD) stage and the dialysis technique. The prevalence in non-dialysis patients is understudied and ranges from 0 to 40.8%.

OBJECTIVE

To evaluate the nutritional status of a group of Spanish advanced CKD patients by PEW criteria and subjective global assessment (SGA).

PATIENTS AND METHODS

Cross-sectional study of 186 patients (101 men) with a mean age of 66.1±16 years. The nutritional assessment consisted of: SGA, PEW criteria, 3-day dietary records, anthropometric parameters and bioelectrical impedance vector analysis.

RESULTS

The prevalence of PEW was 30.1%, with significant differences between men and women (22.8 vs. 33.8%, p < 0.005), while 27.9% of SGA values were within the range of malnutrition. No differences were found between the 2methods. Men had higher proteinuria, percentage of muscle mass and nutrient intake. Women had higher levels of total cholesterol, HDL and a higher body fat percentage. The characteristics of patients with PEW were low albumin levels and a low total lymphocyte count, high proteinuria, low fat and muscle mass and a high Na/K ratio. The multivariate analysis found PEW to be associated with: proteinuria (OR: 1.257; 95% CI: 1.084-1.457, p=0.002), percentage of fat intake (OR: 0.903; 95% CI: 0.893-0.983, p=0.008), total lymphocyte count (OR: 0.999; 95% CI: 0.998-0.999, p=0.001) and cell mass index (OR: 0.995; 95% CI: 0.992-0.998).

CONCLUSION

Malnutrition was identified in Spanish advanced CKD patients measured by different tools. We consider it appropriate to adapt new diagnostic elements to PEW criteria.

Urea, a true uremic toxin: the empire strikes back

Blood levels of urea rise with progressive decline in kidney function. Older studies examining acute urea infusion suggested that urea was well-tolerated at levels 8-10× above normal values. More recent in vitro and in vivo work argue the opposite and demonstrate both direct and indirect toxicities of urea, which probably promote the premature aging phenotype that is pervasive in chronic kidney disease (CKD). Elevated urea at concentrations typically encountered in uremic patients induces disintegration of the gut epithelial barrier, leading to translocation of bacterial toxins into the bloodstream and systemic inflammation. Urea induces apoptosis of vascular smooth muscle cells as well as endothelial dysfunction, thus directly promoting cardiovascular disease. Further, urea stimulates oxidative stress and dysfunction in adipocytes, leading to insulin resistance. Finally, there are widespread indirect effects of elevated urea as a result of the carbamylation reaction, where isocyanic acid (a product of urea catabolism) alters the structure and function of proteins in the body. Carbamylation has been linked with renal fibrosis, atherosclerosis and anaemia. In summary, urea is a re-emerging Dark Force in CKD pathophysiology. Trials examining low protein diet to minimize accumulation of urea and other toxins suggest a clinical benefit in terms of slowing progression of CKD.

Development and validation of a Fall Risk Assessment Index for dialysis patients

BACKGROUND

Dialysis patients often have low physical performance due to uremic sarcopenia, protein energy wasting (PEW), and incidence intradialytic hypotension (IDH), which are indicated as risk factors for falling. The objective of this study was to develop a symptom-encompassing evaluation form to predict falls with high sensitivity for dialysis patients.

METHODS

A total of 251 patients who had been receiving maintenance hemodialysis therapy three times a week were enrolled in the study. Demographics, malnutrition and inflammatory status, dialytic therapeutic management situation, physical function and performance, and inquiries about falling were recorded. The Cox proportional hazards analysis evaluated the impact of falls. Calculated hazard ratios were converted to weighted scores, using approximate multiples of 0.5 and an evaluation form was created, which we called the Dialysis Fall Risk Index (DFRI). Kaplan-Meier survival analyses with the log-rank test and the Cox proportional hazard analysis were performed to evaluate the validity of the DFRI.

RESULTS

The DFRI consisted of seven items and a total of 12 points. The predictive validity of DFRI included hazard ratios for quartile 3 and 4 of 2.65 and 3.84, respectively, compared with quartile 1 as a reference point. The cut-off point of the DFRI showed the highest sensitivity and specificity among other screening indices.

DISCUSSION

The present study included the development of a new evaluation form that encompasses symptoms of end-stage kidney disease to predict falls in dialysis patients.

[Common therapeutic approaches of sarcopenia in the elderly and uremic myopathy]

The gradual loss of weight and function of muscle in patients with chronic kidney disease as in the elderly impacts the quality of life. Early management should help slow the functional limitation. Physical activity is the first therapy to propose that ensures stability of muscle mass and improved function. Resistance training programs have proven effective but are not yet widely available in nephrology units. The nutritional management should not be forgotten because there is a resistance to anabolism and protein intake should be involved in physical activity program. Associated treatments should not be neglected: vitamin D, anti-inflammatory, androgens. Some are still under evaluation. Therapeutic option, tomorrow, could be anti-myostatin antibodies and glitazones.

Comparison of Subjective Global Assessment and Protein Energy Wasting Score to Nutrition Evaluations Conducted by Registered Dietitian Nutritionists in Identifying Protein Energy Wasting Risk in Maintenance Hemodialysis Patients

OBJECTIVE

To compare the 7-point subjective global assessment (SGA) and the protein energy wasting (PEW) score with nutrition evaluations conducted by registered dietitian nutritionists in identifying PEW risk in stage 5 chronic kidney disease patients on maintenance hemodialysis.

DESIGN AND METHODS

This study is a secondary analysis of a cross-sectional study entitled "Development and Validation of a Predictive energy Equation in Hemodialysis". PEW risk identified by the 7-point SGA and the PEW score was compared against the nutrition evaluations conducted by registered dietitian nutritionists through data examination from the original study (reference standard).

SUBJECTS

A total of 133 patients were included for the analysis.

MAIN OUTCOME MEASURES

The sensitivity, specificity, positive and negative predictive value (PPV and NPV), positive and negative likelihood ratio (PLR and NLR) of both scoring tools were calculated when compared against the reference standard.

RESULTS

The patients were predominately African American (n = 112, 84.2%), non-Hispanic (n = 101, 75.9%), and male (n = 80, 60.2%). Both the 7-point SGA (sensitivity = 78.6%, specificity = 59.1%, PPV = 33.9%, NPV = 91.2%, PLR = 1.9, and NLR = 0.4) and the PEW score (sensitivity = 100%, specificity = 28.6%, PPV = 27.2%, NPV = 100%, PLR = 1.4, and NLR = 0) were more sensitive than specific in identifying PEW risk. The 7-point SGA may miss 21.4% patients having PEW and falsely identify 40.9% of patients who do not have PEW. The PEW score can identify PEW risk in all patients, but 71.4% of patients identified may not have PEW risk.

CONCLUSIONS

Both the 7-point SGA and the PEW score could identify PEW risk. The 7-point SGA was more specific, and the PEW score was more sensitive. Both scoring tools were found to be clinically confident in identifying patients who were actually not at PEW risk.

Tissue sodium accumulation and peripheral insulin sensitivity in maintenance hemodialysis patients

BACKGROUND

Recent data suggest that sodium (Na⁺ ) is stored in the muscle and skin without commensurate water retention in maintenance hemodialysis (MHD) patients. In this study, we hypothesized that excessive Na⁺ accumulation would be associated with abnormalities in peripheral insulin action.

METHODS

Eleven MHD patients and eight controls underwent hyperinsulinemic-euglycemic-euaminoacidemic clamp studies to measure glucose (GDR) and leucine disposal rates (LDR), as well as lower left leg ²³ Na magnetic resonance imaging to measure Na⁺ concentration in the muscle and skin tissue.

RESULTS

The median GDR and LDR levels were lower, and the median muscle Na⁺ concentration was higher in MHD patients compared with controls. No significant difference was found regarding skin Na⁺ concentration between group comparisons. Linear regression revealed inverse relationships between muscle Na⁺ concentration and GDR and LDR in MHD patients, whereas no relationship was observed in controls. There was no association between skin Na⁺ content and GDR or LDR in either MHD patients or controls.

CONCLUSIONS

These data suggest that excessive muscle Na⁺ content might be a determinant of IR in MHD patients, although the causality and mechanisms remain to be proven.

Physical activity, immune function and inflammation in kidney patients (the PINK study): a feasibility trial protocol

INTRODUCTION

Patients with chronic kidney disease (CKD) display increased infection-related mortality and elevated cardiovascular risk only partly attributed to traditional risk factors. Patients with CKD also exhibit a pro-inflammatory environment and impaired immune function. Aerobic exercise has the potential to positively impact these detriments, but is under-researched in this patient population. This feasibility study will investigate the effects of acute aerobic exercise on inflammation and immune function in patients with CKD to inform the design of larger studies intended to ultimately influence current exercise recommendations.

METHODS AND ANALYSIS

Patients with CKD, including renal transplant recipients, will visit the laboratory on two occasions, both preceded by appropriate exercise, alcohol and caffeine restrictions. On visit 1, baseline assessments will be completed, comprising anthropometrics, body composition, cardiovascular function and fatigue and leisure time exercise questionnaires. Participants will then undertake an incremental shuttle walk test to estimate predicted peak O2 consumption (VO2peak). On visit 2, participants will complete a 20 min shuttle walk at a constant speed to achieve 85% estimated VO2peak. Blood and saliva samples will be taken before, immediately after and 1 hour after this exercise bout. Muscle O2 saturation will be monitored throughout exercise and recovery. Age and sex-matched non-CKD 'healthy control' participants will complete an identical protocol. Blood and saliva samples will be analysed for markers of inflammation and immune function, using cytometric bead array and flow cytometry techniques. Appropriate statistical tests will be used to analyse the data.

ETHICS AND DISSEMINATION

A favourable opinion was granted by the East Midlands-Derby Research Ethics Committee on 18 September 2015 (ref 15/EM/0391), and the study was approved and sponsored by University Hospitals of Leicester Research and Innovation (ref 11444). The study was registered with ISRCTN (ref 38935454). The results will be presented at relevant conferences, and it is anticipated that the reports will be published in appropriate journals in 2018.

The Effect of Diet on the Survival of Patients with Chronic Kidney Disease

The prevalence of chronic kidney disease (CKD) is high and it is gradually increasing. Individuals with CKD should introduce appropriate measures to hamper the progression of kidney function deterioration as well as prevent the development or progression of CKD-related diseases. A kidney-friendly diet may help to protect kidneys from further damage. Patients with kidney damage should limit the intake of certain foods to reduce the accumulation of unexcreted metabolic products and also to protect against hypertension, proteinuria and other heart and bone health problems. Despite the fact that the influence of certain types of nutrients has been widely studied in relation to kidney function and overall health in CKD patients, there are few studies on the impact of a specific diet on their survival. Animal studies demonstrated prolonged survival of rats with CKD fed with protein-restricted diets. In humans, the results of studies are conflicting. Some of them indicate slowing down of the progression of kidney disease and reduction in proteinuria, but other underline significant worsening of patients' nutritional state, which can be dangerous. A recent systemic study revealed that a healthy diet comprising many fruits and vegetables, fish, legumes, whole grains, and fibers and also the cutting down on red meat, sodium, and refined sugar intake was associated with lower mortality in people with kidney disease. The aim of this paper is to review the results of studies concerning the impact of diet on the survival of CKD patients.

Body mass index mortality paradox in chronic kidney disease patients with suspected cardiac chest pain

Background: Chronic kidney disease (CKD) is a silent clinical condition associated with adverse comorbidity and high cardiovascular disease (CVD) risk. An inverse relationship with body mass index (BMI) and mortality has been demonstrated in hemodialysis patients. However, it is unclear if this risk-factor paradox is evident in non-dialysis CKD patients. The aims of this study were to explore the relationship between, nutritional status, markers of inflammation, autonomic and cardiac function with BMI. Longitudinal follow-up explored the relationship between BMI and all-cause mortality. Methods: 211-consecutive CKD patients referred for dobutamine stress echocardiography to detect or exclude myocardial ischemia were recruited. BMI, albumin, C-reactive protein (CRP) and haemoglobin (Hb) were recorded as markers of nutritional and inflammatory status. Left ventricular ejection fraction (LVEF) and heart rate variability (HRV) as an indicator of cardiac function was recorded. All subjects were followed prospectively until November 2014 and study end-point was all-cause mortality. Results: BMI was inversely associated with CKD status. After covariate adjustment, this association remained. During a mean follow-up period of 3.3±0.9 years there were 35 deaths (17%). BMI was inversely associated with all-cause mortality (HR 0.81, 95% CI 0.71-0.9). Other important independent predictors of mortality were heart rate variability (HR 0.98, 95% CI 0.97-0.99), myocardial ischemia (HR 1.37, 95% CI 1.17-1.81), and albumin (HR 0.86, 95% CI 0.81-0.92). Conclusions: The presence of a body mass index paradox exists in non-dialysis CKD patients. This risk-factor paradox was an independent predictor of all-cause mortality and may have significant clinical implications relevant to screening, assessment and treatment and requires further study.

Factors Associated with Decreased Lean Tissue Index in Patients with Chronic Kidney Disease

Muscle wasting is common and is associated with increased morbidity and mortality in patients with chronic kidney disease (CKD). However, factors associated with decreased muscle mass in CKD patients are seldom reported. We performed a cross-sectional study of 326 patients (age 65.8 ± 13.3 years) with stage 3–5 CKD who were not yet on dialysis. Muscle mass was determined using the Body Composition Monitor (BCM), a multifrequency bioimpedance spectroscopy device, and was expressed as the lean tissue index (LTI, lean tissue mass/height²). An LTI of less than 10% of the normal value (low LTI) indicates muscle wasting. Patients with low LTI (n = 40) tended to be diabetic, had significantly higher fat tissue index, urine protein creatinine ratio, and interleukin-6 and tumor necrosis factor-α levels, but had significantly lower serum albumin and hemoglobin levels compared with those with normal LTI. In multivariate linear regression analysis, age, sex, cardiovascular disease, and interleukin-6 were independently associated with LTI. Additionally, diabetes mellitus remained an independent predictor of muscle wasting according to low LTI by multivariate logistic regression analysis. We conclude that LTI has important clinical correlations. Determination of LTI may aid in clinical assessment by helping to identify muscle wasting among patients with stage 3–5 CKD.

Nutritional Status Predicts 10-Year Mortality in Patients with End-Stage Renal Disease on Hemodialysis

Protein-energy wasting (PEW) is associated with mortality in patients with end-stage renal disease (ESRD) on maintenance hemodialysis. The correct diagnosis of PEW is extremely important in order to predict clinical outcomes. However, it is unclear which parameters should be used to diagnose PEW. Therefore, this retrospective observational study investigated the relationship between mortality and nutritional parameters in ESRD patients on maintenance hemodialysis. A total of 144 patients were enrolled. Nutritional parameters, including body mass index, serum albumin, dietary intake, normalized protein catabolic rate (nPCR), and malnutrition inflammation score (MIS), were measured at baseline. Fifty-three patients died during the study. Survivors had significantly higher nPCR (1.10 ± 0.24 g/kg/day vs. 1.01 ± 0.21 g/kg/day; p = 0.048), energy intake (26.7 ± 5.8 kcal/kg vs. 24.3 ± 4.2 kcal/kg; p = 0.009) and protein intake (0.91 ± 0.21 g/kg vs. 0.82 ± 0.24 g/kg; p = 0.020), and lower MIS (5.2 ± 2.3 vs. 6.1 ± 2.1, p = 0.039). In multivariable analysis, energy intake <25 kcal/kg (HR 1.860, 95% CI 1.018–3.399; p = 0.044) and MIS > 5 (HR 2.146, 95% CI 1.173–3.928; p = 0.013) were independent variables associated with all-cause mortality. These results suggest that higher MIS and lower energy intake are harmful to ESRD patients on maintenance hemodialysis. Optimal energy intake could reduce mortality in these patients.

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.

Resveratrol attenuates skeletal muscle atrophy induced by chronic kidney disease via MuRF1 signaling pathway

Skeletal muscle atrophy is an important clinical characteristic of chronic kidney disease (CKD); however, at present, the therapeutic approaches to muscle atrophy induced by CKD are still at an early stage of development. Resveratrol is used to attenuate muscle atrophy in other experimental models, but the effects on a CKD model are largely unknown. Here, we showed that resveratrol prevented an increase in MuRF1 expression and attenuated muscle atrophy in vivo model of CKD. We also found that phosphorylation of NF-κB was inhibited at the same time. Dexamethasone-induced MuRF1 upregulation was significantly attenuated in C2C12 myotubes by resveratrol in vitro, but this effect on C2C12 myotubes was abrogated by a knockdown of NF-κB, suggesting that the beneficial effect of resveratrol was NF-κB dependent. Our findings provide novel information about the ability of resveratrol to prevent or treat muscle atrophy induced by CKD.

Visceral Adipose Tissue and Leptin Hyperproduction Are Associated With Hypogonadism in Men With Chronic Kidney Disease

OBJECTIVE

Hypogonadism is a common endocrine disorder in men with chronic kidney disease (CKD), but its pathophysiology is poorly understood. We here explore the plausible contribution of abdominal adiposity and leptin hyperproduction to testosterone deficiency in this patient population.

DESIGN

Cross-sectional analysis with all men included the Malnutrition, Inflammation and Vascular Calcification cohort, which enrolled consecutive nondialyzed patients with CKD stages 3-5.

SUBJECTS

A total of 172 men with CKD stages 3-5 nondialysis (median age 61 [45-75] years, median glomerular filtration rate 24 [9-45] mL/min/1.73 m²). In them, serum levels of total testosterone, estrogen, sex hormone binding globulin, and leptin were quantified, together with visceral adipose tissue (VAT) by thoracic and abdominal CT scan.

INTERVENTION

None, observational study.

MAIN OUTCOME MEASURE

Total testosterone, hypogonadism.

RESULTS

The median level of total testosterone was 11.7 (7.3-18.4) nmol/L, with hypogonadism (<10 nmol/L) present in 52 (30%) patients. Testosterone-deficient patients presented with significantly higher body mass index, waist circumference, and VAT. An inverse correlation between testosterone and VAT (rho = -0.25, P = .001) or waist circumference (rho = -0.20, P = .008) was found, also after multivariate adjustment including sex hormone binding globulin and estrogen. Total testosterone was inversely correlated with serum leptin (rho = -0.22, P = .003), and the ratio of leptin/VAT, an index of leptin hyperproduction, was strongly and independently associated with the prevalence of hypogonadism in multivariable regression analyses.

CONCLUSION

Visceral adiposity independently associated with lower testosterone levels among men with CKD stage 3-5 nondialysis. The observed link between hyperleptinemia and hypogonadism is in line with previous evidence on direct effects of leptin on testosterone production.

Predicting clinical outcomes using phase angle as assessed by bioelectrical impedance analysis in maintenance hemodialysis patients

OBJECTIVE

Protein-energy wasting is common in patients on hemodialysis and is an independent risk factor for adverse events. The aim of this study was to retrospectively investigate whether phase angle (PA), known as a nutritional marker, can predict various clinical outcomes in patients with end-stage renal disease (ESRD) who are receiving hemodialysis.

METHODS

Using bioelectrical impedance analysis (BIA), PA was obtained every 6 mo, and patients were divided into two groups according to baseline PA: group A included patients with PA ≥4.5°, and group B included patients with PA <4.5°.

RESULTS

We followed 142 patients for a median of 29 mo (12-42 mo). We found that a decrease in PA was associated with an increased risk for death that persisted after adjusting for age, sex, and comorbidities (hazard ratio [HR], 0.56; 95% confidence interval [CI], 0.33-0.97). Cardiovascular events were not associated with PA (P = 0.685). We found that PA predicted the occurrence of infection, independent of age, sex, and comorbidities (HR, 0.65; 95% CI, 0.45-0.94). Although levels of hemoglobin did not differ between groups during the study period, patients in group B received higher doses of erythropoiesis-stimulating agents and intravenous iron than those in group A (P = 0.004 and 0.044, respectively). In longitudinal analyses, we did not find increases in PA over time in patients who had a mean dialysis adequacy ≥1.4, daily protein catabolic rate ≥1.2 g/kg, or total carbon dioxide level ≥22 mmol/L.

CONCLUSIONS

PA assessed in a simple manner using BIA provides practical information to predict clinical outcomes in ESRD patients on maintenance hemodialysis.

Sarcopenia and its individual criteria are associated, in part, with mortality among patients on hemodialysis

The relative importance of sarcopenia and its individual components as independent predictors of mortality in the dialysis population has not been determined. We estimated whole-body muscle mass using pre-dialysis bioimpedance spectroscopy measurements in 645 ACTIVE/ADIPOSE-enrolled prevalent hemodialysis patients from San Francisco and Atlanta. Low muscle mass was defined as two standard deviations below sex-specific means for young adults from NHANES and indexed to height², body weight, body surface area, or body mass index. We evaluated the association of sarcopenia (low muscle mass) by four indexing methods, weak hand grip strength, and slow gait speed with mortality. Seventy-eight deaths were observed during a mean follow-up of 1.9 years. Sarcopenia was not significantly associated with mortality after adjusting for covariates. No muscle mass criteria were associated with death, regardless of indexing metrics. In contrast, having weak grip strength or slow walking speed was associated with mortality in the adjusted model. Only gait slowness significantly improved the predictive accuracy for death with an increase in C-statistic from 0.63 to 0.68. However, both gait slowness and hand grip weakness significantly improved the net reclassification index compared to models without performance measures (50.5% for slowness and 33.7% for weakness), whereas models with muscle size did not. Neither sarcopenia nor low muscle mass by itself was a better predictor of mortality than functional limitation alone in patients receiving hemodialysis. Thus, physical performance measures, including slow gait speed and weak hand grip strength, were associated with mortality even after adjustment for muscle size and other confounders.

Stirring the Pot: Can Dietary Modification Alleviate the Burden of CKD?

Diet is one of the largest modifiable risk factors for chronic kidney disease (CKD)-related death and disability. CKD is largely a progressive disease; however, it is increasingly appreciated that hallmarks of chronic kidney disease such as albuminuria can regress over time. The factors driving albuminuria resolution remain elusive. Since albuminuria is a strong risk factor for GFR loss, modifiable lifestyle factors that lead to an improvement in albuminuria would likely reduce the burden of CKD in high-risk individuals, such as patients with diabetes. Dietary therapy such as protein and sodium restriction has historically been used in the management of CKD. Evidence is emerging to indicate that other nutrients may influence kidney health, either through metabolic or haemodynamic pathways or via the modification of gut homeostasis. This review focuses on the role of diet in the pathogenesis and progression of CKD and discusses the latest findings related to the mechanisms of diet-induced kidney disease. It is possible that optimizing diet quality or restricting dietary intake could be harnessed as an adjunct therapy for CKD prevention or progression in susceptible individuals, thereby reducing the burden of CKD.

Intestinal Microbiota in Type 2 Diabetes and Chronic Kidney Disease

PURPOSE OF THE REVIEW

Diabetes mellitus is a major cause of kidney disease [chronic kidney disease (CKD) and end-stage renal disease (ESRD)] and are both characterized by an increased risk of cardiovascular events. Diabetes and kidney disease are also commonly associated with a chronic inflammatory state, which is now considered a non-traditional risk factor for atherosclerosis. In the case of type 2 diabetes mellitus (T2DM), inflammation is mainly a consequence of visceral obesity, while in the case of CKD or ESRD patients on dialysis, inflammation is caused by multiple factors, classically grouped as dialysis-related and non-dialysis-related. More recently, a key role has been credited to the intestinal microbiota in the pathogenesis of chronic inflammation present in both disease states. While many recent data on the intestinal microbiota and its relationship to chronic inflammation are available for CKD patients, very little is known regarding T2DM and patients with diabetic nephropathy. The aim of this review is to summarize and discuss the main pathophysiological issues of intestinal microbiota in patients with T2DM and CKD/ESRD.

RECENT FINDINGS

The presence of intestinal dysbiosis, along with increased intestinal permeability and high circulating levels of lipopolysaccharides, a condition known as "endotoxemia," characterize T2DM, CKD, and ESRD on dialysis. The hallmark of intestinal dysbiosis is a reduction of saccharolytic microbes mainly producing short-chain fatty acids (SCFA) and, in the case of CKD/ESRD, an increase in proteolytic microbes that produce different substances possibly related to uremic toxicity. Dysbiosis is associated with endotoxemia and chronic inflammation, with disruption of the intestinal barrier and depletion of beneficial bacteria producing SCFAs. T2DM and CKD/ESRD, whose coexistence is increasingly found in clinical practice, share similar negative effects on both intestinal microbiota and function. More studies are needed to characterize specific alterations of the intestinal microbiota in diabetic nephropathy and to assess possible effects of probiotic and prebiotic treatments in this setting.

Effect of administration of high-protein diet in rats submitted to resistance training

PURPOSE

Although there is limited evidence regarding the pathophysiological effects of a high-protein diet (HD), it is believed that this type of diet could overload the body and cause damage to the organs directly involved with protein metabolism and excretion. The aim of this study was to verify the effects of HD on biochemical and morphological parameters of rats that completed a resistance training protocol (RT; aquatic jump) for 8 weeks.

METHODS

Thirty-two adult male Wistar rats were divided into four groups (n = 8 for each group): sedentary normal protein diet (SN-14%), sedentary high-protein diet (SH-35%), trained normal protein diet (TN-14%), and trained high-protein diet (TH-35%). Biochemical, tissue, and morphological measurements were made.

RESULTS

Kidney (1.91 ± 0.34) and liver weights (12.88 ± 1.42) were higher in the SH. Soleus muscle weight was higher in the SH (0.22 ± 0.03) when compared to all groups. Blood glucose (123.2 ± 1.8), triglycerides (128.5 ± 44.0), and HDL cholesterol levels (65.7 ± 20.9) were also higher in the SH compared with the other experimental groups. Exercise reduced urea levels in the trained groups TN and TH (31.0 ± 4.1 and 36.8 ± 6.6), respectively. Creatinine levels were lower in TH and SH groups (0.68 ± 0.12; 0.54 ± 0.19), respectively. HD negatively altered renal morphology in SH, but when associated with RT, the apparent damage was partially reversed. In addition, the aquatic jump protocol reversed the damage to the gastrocnemius muscle caused by the HD.

CONCLUSIONS

A high-protein diet promoted negative metabolic and morphological changes, while RT was effective in reversing these deleterious effects.

Nutritional Status in Adults with Predialysis Chronic Kidney Disease: KNOW-CKD Study

Adverse changes in nutrition are prevalent and are strong indicators of adverse outcomes in patients with chronic kidney disease (CKD). The International Society of Renal Nutrition and Metabolism (ISRNM) proposed a common nomenclature and diagnostic criteria to identify protein-energy wasting (PEW) in CKD patients. We examined the nutritional status in 1,834 adults with predialysis CKD enrolled in the KoreaN cohort study for Outcome in patients With Chronic Kidney Disease (KNOW-CKD) study. As there was a need for further understanding of nutritional status and associated factors in CKD, we evaluated the prevalence and associated factors of PEW in adults with predialysis CKD. The prevalence of PEW was about 9.0% according to ISRNM criteria and tended to increase with advanced stage in predialysis CKD. Those who concurrently had PEW, inflammation, and CVD were a small proportion (0.4%). In multivariate logistic regression model, PEW was independently associated with estimated glomerular filtration rate (eGFR) (odds ratio [OR], 0.98; 95% confidence interval [CI], 0.96-0.99), total CO₂ (OR, 0.93; 95% CI, 0.87-0.99), physical activity (OR, 0.43; 95% CI, 0.26-0.69), comorbid diabetes (OR, 1.68; 95% CI, 1.09-2.59), and high sensitivity C-reactive protein (hs-CRP) (OR, 1.03; 95% CI, 1.01-1.06). Our study suggests that PEW increases with advanced CKD stage. PEW is independently associated with renal function, low total CO₂, low physical activity, comorbid diabetes, and increased hs-CRP in adults with predialysis CKD.

Associations of Protein-Energy Wasting Syndrome Criteria With Body Composition and Mortality in the General and Moderate Chronic Kidney Disease Populations in the United States

Introduction

It is unknown whether the criteria used to define protein−energy wasting (PEW) syndrome in dialysis patients reflect protein or energy wasting in the general and moderate CKD populations.

Methods

In 11,834 participants in the 1999 to 2004 National Health and Nutrition Examination Survey, individual PEW syndrome criteria and the number of PEW syndrome categories were related to lean body and fat masses (measured by dual-energy absorptiometry) using linear regression in the entire cohort and CKD subpopulation.

Results

Serum chemistry, body mass, and muscle mass PEW criteria tended to be associated with lower lean body and fat masses, but the low dietary protein and energy intake criteria were associated with significantly higher protein and energy stores. When the number of PEW syndrome categories was defined by nondietary categories alone, there was a monotonic inverse relationship with lean body and fat masses and a strong positive relationship with mortality. In contrast, when dietary category alone was present, mean body mass index was in the obesity range; the additional presence of 2 nondietary categories was associated with lower body mass index and lower lean body and fat masses. Thus, the association of a dietary category plus 2 additional nondietary categories with lower protein or energy stores was driven by the presence of the 2 nondietary categories. Results were similar in CKD subgroup.

Discussion

Hence, a definition of PEW syndrome without dietary variables has face validity and reflects protein or energy wasting.

Sex Differences in Muscle Wasting

With aging and other muscle wasting diseases, men and women undergo similar pathological changes in skeletal muscle: increased inflammation, enhanced oxidative stress, mitochondrial dysfunction, satellite cell senescence, elevated apoptosis and proteasome activity, and suppressed protein synthesis and myocyte regeneration. Decreased food intake and physical activity also indirectly contribute to muscle wasting. Sex hormones also play important roles in maintaining skeletal muscle homeostasis. Testosterone is a potent anabolic factor promoting muscle protein synthesis and muscular regeneration. Estrogens have a protective effect on skeletal muscle by attenuating inflammation; however, the mechanisms of estrogen action in skeletal muscle are less well characterized than those of testosterone. Age- and/or disease-induced alterations in sex hormones are major contributors to muscle wasting. Hence, men and women may respond differently to catabolic conditions because of their hormonal profiles. Here we review the similarities and differences between men and women with common wasting conditions including sarcopenia and cachexia due to cancer, end-stage renal disease/chronic kidney disease, liver disease, chronic heart failure, and chronic obstructive pulmonary disease based on the literature in clinical studies. In addition, the responses in men and women to the commonly used therapeutic agents and their efficacy to improve muscle mass and function are also reviewed.

Correlation of Residual Diuresis with MIS Score and Nutritional Status in Peritoneal Dialysis Patients: A Croatian Nationwide Study

Introduction. Residual diuresis (RD) is an important predictor of mortality and cardiovascular (CV) deaths in peritoneal dialysis (PD) patients, and contributes more to overall survival compared to PD clearance. In this study we investigated the correlation between RD and CV outcomes in PD patients.

Methods. A total of 190 PD patients from 13 dialysis centers, a national representation, were included in this analysis. Biomarkers of anemia, nutritional status [malnutrition inflammation score (MIS), subjective global assessment (SGA), serum albumin, anthropometric measurements including body mass index (BMI)], dialysis dose (Kt/V) and laboratory measurements were determined. RD was estimated using the volume of daily urine.

Results. There were 78(41.05 %) females and 112 (58.95 %) males; aged 57.35±14.41 years, on PD for 24.96±24.43 months. Fifty-six patients had diabetes type II (44 as primary kidney disease). The mean RD was 1170±673.6 ml (range 0-3000 mL). Statistically significant correlations between RD and BMI, hip circumference, time on PD, Kt/V, MIS, SGA, erythrocytes (E), Hemoglobin (Hb), PTH, and serum albumin were observed.

Conclusions. We demonstrated a significant correlation between RD and MIS score, SGA, anthropometry and albumin. Every effort should be invested to maintain RD for as long as possible to achieve optimal treatment results and to decrease CV mortality in PD population.