The National Kidney Foundation K/DOQI clinical practice guidelines for dietary protein intake for chronic dialysis patients

The treatment of chronic anemia in heart failure: a global approach

Chronic anemia is an independent risk factor for mortality in patients with heart failure (HF). Restoring physiological hemoglobin (Hb) levels is essential to increase oxygen transport capacity to tissues and improve cell metabolism as well as physical and cardiac performance. Nutritional deficits and iron deficiency are the major causes of chronic anemia, but other etiologies include chronic kidney disease, inflammatory processes, and unexplained anemia. Hormonal therapy, including erythropoietin (EPO) and anabolic treatment in chronic anemia HF patients, may contribute to improving Hb levels and clinical outcomes. Although preliminary studies showed a beneficial effect of EPO therapy on cardiac efficiency and in HF, more recent studies have not confirmed this positive impact of EPO, alluding to its side effect profile. Physical exercise significantly increases Hb levels and the response of anemia to treatment. In malnourished patients and chronic inflammatory processes, low levels of anabolic hormones, such as testosterone and insulin-like growth factor-1, contribute to the development of chronic anemia. This paper aims to review the effect of nutrition, EPO, anabolic hormones, standard HF treatments, and exercise as regulatory mechanisms of chronic anemia and their cardiovascular consequences in patients with HF.

Effect of time-dependent dialysate bicarbonate concentrations on acid-base and uremic solute kinetics during hemodialysis treatments

Recent studies have suggested benefits for time-dependent dialysate bicarbonate concentrations (Dbic) during hemodialysis (HD). In this clinical trial, we compared for the first time in the same HD patients the effects of time-dependent changes with constant Dbic on acid-base and uremic solute kinetics. Blood acid-base and uremic solute concentration were measured in twenty chronic HD patients during 4-h treatments with A) constant Dbic of 35 mmol/L; B) Dbic of 35 mmol/L then 30 mmol/L; and C) Dbic of 30 mmol/L then 35 mmol/L (change of Dbic after two hours during Treatments B and C). Arterial blood samples were obtained predialysis, every hour during HD and one hour after HD, during second and third treatments of the week with each Dbic concentration profile. Blood bicarbonate concentration (blood [HCO3]) during Treatment C was lower only during the first three HD hours than in Treatment A. Overall blood [HCO3] was reduced during Treatment B in comparison to Treatment A at each time points. We conclude that a single change Dbic in the middle of HD can alter the rate of change in blood [HCO3] and pH during HD; time-dependent Dbic had no influence on uremic solute kinetics.

Validity of the hydrogen ion mobilisation model during haemodialysis with time-dependent dialysate bicarbonate concentrations

BACKGROUND

The hydrogen ion (H+) mobilisation model has been previously shown to accurately describe blood bicarbonate (HCO3) kinetics during haemodialysis (HD) when the dialysate bicarbonate concentration ([HCO3]) is constant throughout the treatment. This study evaluated the ability of the H+ mobilization model to describe blood HCO3 kinetics during HD treatments with a time-dependent dialysate [HCO3].

METHODS

Data from a recent clinical study where blood [HCO3] was measured at the beginning of and every hour during 4-h treatments in 20 chronic, thrice-weekly HD patients with a constant (Treatment A), decreasing (Treatment B) and increasing (Treatment C) dialysate [HCO3] were evaluated. The H+ mobilization model was used to determine the model parameter (Hm) that provided the best fit of the model to the clinical data using nonlinear regression. A total of 114 HD treatments provided individual estimates of Hm.

RESULTS

Mean ± standard deviation estimates of Hm during Treatments A, B and C were 0.153 ± 0.069, 0.180 ± 0.109 and 0.205 ± 0.141 L/min (medians [interquartile ranges] were 0.145 [0.118,0.191], 0.159 [0.112,0.209], 0.169 [0.115,0.236] L/min), respectively; these estimates were not different from each other (p = 0.26). The sum of squared differences between the measured blood [HCO3] and that predicted by the model were not different during Treatments A, B and C (p = 0.50), suggesting a similar degree of model fit to the data.

CONCLUSIONS

This study supports the validity of the H+ mobilization model to describe intradialysis blood HCO3 kinetics during HD with a constant Hm value when using a time-dependent dialysate [HCO3].

Amino Acid Homeostasis and Fatigue in Chronic Hemodialysis Patients

Patients dependent on chronic hemodialysis treatment are prone to malnutrition, at least in part due to insufficient nutrient intake, metabolic derangements, and chronic inflammation. Losses of amino acids during hemodialysis may be an important additional contributor. In this study, we assessed changes in plasma amino acid concentrations during hemodialysis, quantified intradialytic amino acid losses, and investigated whether plasma amino acid concentrations and amino acid losses by hemodialysis and urinary excretion are associated with fatigue. The study included a total of 59 hemodialysis patients (65 ± 15 years, 63% male) and 33 healthy kidney donors as controls (54 ± 10 years, 45% male). Total plasma essential amino acid concentration before hemodialysis was lower in hemodialysis patients compared with controls (p = 0.006), while total non-essential amino acid concentration did not differ. Daily amino acid losses were 4.0 ± 1.3 g/24 h for hemodialysis patients and 0.6 ± 0.3 g/24 h for controls. Expressed as proportion of protein intake, daily amino acid losses of hemodialysis patients were 6.7 ± 2.4% of the total protein intake, compared to 0.7 ± 0.3% for controls (p < 0.001). Multivariable regression analyses demonstrated that hemodialysis efficacy (Kt/V) was the primary determinant of amino acid losses (Std. β = 0.51; p < 0.001). In logistic regression analyses, higher plasma proline concentrations were associated with higher odds of severe fatigue (OR (95% CI) per SD increment: 3.0 (1.3; 9.3); p = 0.03), while higher taurine concentrations were associated with lower odds of severe fatigue (OR (95% CI) per log2 increment: 0.3 (0.1; 0.7); p = 0.01). Similarly, higher daily taurine losses were also associated with lower odds of severe fatigue (OR (95% CI) per log2 increment: 0.64 (0.42; 0.93); p = 0.03). Lastly, a higher protein intake was associated with lower odds of severe fatigue (OR (95% CI) per SD increment: 0.2 (0.04; 0.5); p = 0.007). Future studies are warranted to investigate the mechanisms underlying these associations and investigate the potential of taurine supplementation.

Rice Endosperm Protein Improves the Anti-Inflammatory Effects of High-Density Lipoprotein and Produces Lower Atherosclerotic Lesion Accelerated by the Renal Mass Reduction than Casein in a Mouse Model

Chronic kidney disease (CKD) impairs the anti-inflammatory effects of high-density lipoprotein (HDL) and increases cardiovascular mortality. Though the potential role of dietary interventions to manage HDL is well studied, the clinical trials aimed to increase HDL levels have failed to reduce cardiovascular risk, rendering HDL function to be explored as a more relevant clinical parameter. This study investigates the effects of rice endosperm protein (REP), a plant-based protein, on the anti-inflammatory properties of HDL and renal injury-driven atherosclerosis in comparison with casein, an animal protein.

Ten-week-old apolipoprotein E-deficient hyperlipidemic mice underwent uninephrectomy. The mice (n = 6 each) were pair-fed a normal casein-based diet or a REP-based diet (both with 20.0% protein content) for seven weeks. Atherosclerotic lesions were detected by en face Sudan IV staining of the aorta.

The number and sizes of the atherosclerotic lesions were significantly lower in the REP-based diet-fed group than the casein-based diet-fed group (p = 0.038). However, the REP-based diet neither elicited an ameliorative effect on kidney function or histology nor impacted the cholesterol profiles. Furthermore, HDL from the REP-based diet-fed mice significantly suppressed the inflammatory cytokine response of human umbilical vein endothelial cells than that from the casein-based diet-fed mice (MCP-1, p = 0.010; IL-6, p = 0.011; IL-1β, p = 0.028).

The REP-based diet has a higher potential to lessen the atherosclerotic lesions accelerated by renal mass reduction than a casein-based diet, which could be associated with the anti-inflammatory effects of HDL.

Boiling for 15 minutes improves nutrient profiles in fishes included in the diets of dialysis patients

INTRODUCTION

Little is known about the effects of boiling on nutrient levels in fishes that have a relatively high phosphorus-to-protein ratio (PPR), which are important sources of omega-3 polyunsaturated fatty acids. We hypothesized that the beneficial effects of boiling for a shorter duration (15 min) on nutrient contents in fishes were similar to those of boiling for a longer duration (30 min), which has been shown to decrease the PPR in meat.

METHODS

The protein, fat, and phosphorus contents and the PPR of three cooked fish species and their corresponding fish broths were chemically analyzed. The effects of boiling on changes in protein, fat, phosphorus, and the PPR was examined by comparing fish that were prepared with usual cooking methods (no boiling), boiled for 15 min, and boiled for 30 min. The nutrients in fish broths that were boiled for 15 min were also compared with those boiled for 30 min.

FINDINGS

There were no significant differences in the changes in phosphorus, PPR, protein, and fat content in fish and fish broths prepared with the two boiling methods. In the fish boiled for 15 min, the phosphorus content was 24% lower (p = 0.001), and the PPR was 20% lower (p = 0.04) than those in nonboiled fish. Additionally, boiling for 30 min reduced the phosphorus content by 31% (p = 0.001), and the PPR by 27% (p = 0.04) compared to nonboiled fish, but the protein and fat contents were unchanged after both 15 and 30 min of boiling.

DISCUSSION

The 15- and 30-min boiling methods resulted in a similar reduction in phosphorus and the PPR in fish, with minimal effects on protein and fat. A shorter duration of boiling is recommended to achieve better nutrient profiles in fishes consumed by dialysis patients.

Longitudinal Causal Effects of Normalized Protein Catabolic Rate on All-Cause Mortality in Patients With End-Stage Renal Disease: Adjusting for Time-Varying Confounders Using the G-Estimation Method

In this study, we aimed to estimate the causal effect of normalized protein catabolic rate (nPCR) on mortality among end-stage renal disease (ESRD) patients in the presence of time-varying confounding affected by prior exposure using g-estimation. Information about 553 ESRD patients was retrospectively collected over an 8-year period (2011-2019) from hemodialysis facilities in Kerman, Iran. nPCR was dichotomized as <1.2 g/kg/day versus ≥1.2 g/kg/day. Then a standard time-varying accelerated failure time (AFT) Weibull model was built, and results were compared with those generated by g-estimation. After appropriate adjustment for time-varying confounders, weighted g-estimation yielded 78% shorter survival time (95% confidence interval (95% CI): -81, -73) among patients with a continuous nPCR <1.2 g/kg/day than among those who had nPCR ≥1.2 g/kg/day during follow-up, though it was 18% (95% CI: -57, 54) in the Weibull model. Moreover, hazard ratio estimates of 4.56 (95% CI: 3.69, 5.37) and 1.20 (95% CI: 0.66, 2.17) were obtained via weighted g-estimation and the Weibull model, respectively. G-estimation indicated that inadequate dietary protein intake characterized by nPCR increases all-cause mortality among ESRD patients, but the Weibull model provided an effect estimate that was substantially biased toward the null.

Dietary Plant Protein and Mortality Among Patients Receiving Maintenance Hemodialysis: A Cohort Study

RATIONALE & OBJECTIVE

Although greater dietary intake of protein has been associated with beneficial health effects among patients receiving maintenance hemodialysis (MHD), the effects of plant protein intake are less certain. We studied the association of the proportion of protein intake derived from plant sources with the risk of mortality among patients receiving MHD and explored factors that may modify these associations.

STUDY DESIGN

Prospective observational cohort study.

SETTING & PARTICIPANTS

1,119 Chinese hemodialysis patients aged over 18 years receiving MHD in 2014-2015.

PREDICTORS

The proportion of plant protein intake to total protein intake.

OUTCOMES

All-cause mortality and cardiovascular disease (CVD) mortality.

ANALYTICAL APPROACH

Segmented regression models were fit to examine the association of plant protein intake proportion with the risk of all-cause mortality and CVD mortality. Multivariable-adjusted Cox proportional and cause-specific hazards models were used to estimate the hazard ratios (HR) and 95% CI for these outcomes.

RESULTS

The means of plant protein intake normalized to ideal body weight and plant protein intake proportion were 0.6±0.2 (SD) g/kg per day and 0.538±0.134, respectively. During a median follow-up period of 28.0 months, 249 deaths occurred, with 146 of these deaths resulting from CVD. Overall, there was a U-shaped association between plant protein intake proportion and the risk of all-cause mortality, with an inflection point at 45%. Among patients with a plant protein intake proportion<45%, there was a 17% lower rate of mortality with each 5% greater plant protein intake proportion (HR, 0.83 [95% CI, 0.73-0.96]). Among patients with plant protein intake proportion≥45%, there was a 9% greater rate of mortality with each 5% greater plant protein intake proportion. A similar U-shaped association was observed for CVD mortality, with an inflection point at 44%.

LIMITATIONS

Observational study, potential unmeasured confounding.

CONCLUSIONS

There was a U-shaped association between plant protein intake proportion and the risk of all-cause and cardiovascular mortality in MHD patients. If confirmed, these findings suggest a potential avenue to improve outcomes in this patient population.

Protein Intake, Fatigue and Quality of Life in Stable Outpatient Kidney Transplant Recipients

Fatigue is a frequent complaint in kidney transplant recipients (KTR), often accompanied by poor quality of life (QoL). The role of nutrition as determinant of fatigue in KTR is largely unexplored. The aims of this study are to examine the association of protein intake with fatigue and QoL in KTR and to identify other determinants of fatigue. This cross-sectional study is part of the TransplantLines Cohort and Biobank Study (NCT03272841). Protein intake was calculated from urinary urea nitrogen (UUN) in 24-h urine samples. Fatigue was assessed by the Checklist Individual Strength (CIS) questionnaire; moderate and severe fatigue were defined as a CIS score of 20–34 and ≥ 35, respectively. QoL was assessed with the RAND-36-Item Health Survey (RAND-36). Associations of protein intake with fatigue and QoL were analyzed using multinomial logistic and linear regression analyses. We included 730 stable outpatient KTR (median age 58 year [IQR 48–65], 57% male) with a mean protein intake of 82.2 ± 21.3 g/d. Moderate and severe fatigue were present in 254 (35%) and 245 (34%) of KTR. Higher protein intake was significantly associated with lower risk of moderate fatigue (OR 0.89 per 10 g/d; 95%CI 0.83–0.98, p = 0.01), severe fatigue (OR 0.85; 95%CI 0.78–0.92, p < 0.001) and was associated with higher physical component summary score of QoL (β 0.74 per 10 g/d; 95%CI 0.39–1.09, p < 0.001). Higher BMI, a history of dialysis, glomerulonephritis as primary kidney disease and a history of combined organ transplantation were also associated with severe fatigue. In conclusion, amongst the potential modifiable factors of fatigue, higher protein intake is independently associated with lower risk of moderate and severe fatigue and with better QoL in KTR. These findings underline the need to incorporate nutritional assessment in the diagnostic work-up of fatigue. Intervention studies are needed to assess the benefits and safety of higher protein intake in KTR.

Management of Hyperphosphatemia in End-Stage Renal Disease: A New Paradigm

Bone and mineral metabolism becomes dysregulated with progression of chronic kidney disease (CKD), and increasing levels of parathyroid hormone serve as an adaptive response to maintain normal phosphorus and calcium levels. In end-stage renal disease, this response becomes maladaptive and high levels of phosphorus may occur. We summarize strategies to control hyperphosphatemia based on a systematic literature review of clinical trial and real-world observational data on phosphorus control in hemodialysis patients with CKD-mineral bone disorder (CKD-MBD). These studies suggest that current management options (diet and lifestyle changes; regular dialysis treatment; and use of phosphate binders, vitamin D, calcimimetics) have their own benefits and limitations with variable clinical outcomes. A more integrated approach to phosphorus control in dialysis patients may be necessary, incorporating measurement of multiple biomarkers of CKD-MBD pathophysiology (calcium, phosphorus, and parathyroid hormone) and correlation between diet adjustments and CKD-MBD drugs, which may facilitate improved patient management.

The low-protein diet for chronic kidney disease: 8 years of clinical experience in a nephrology ward

BACKGROUND

Guidelines indicate that a low-protein diet (LPD) delays dialysis in severe chronic kidney disease (CKD). We assessed the value of these guidelines by performing a retrospective analysis in our renal clinical practice.

METHODS

The analysis was performed from 1 January 2010 to 31 March 2018 in 299 CKD Stage 4 patients followed for 70 months in collaboration with a skilled nutritionist. The patients included 43 patients on a controlled protein diet (CPD) of 0.8 g/kg/day [estimated glomerular filtration rate (eGFR) 20-30 mL/min/1.73 m2 body surface (b.s.)], 171 patients on an LPD of 0.6 g/kg/day and 85 patients on an unrestricted protein diet (UPD) who were not followed by our nutritionist (LPD and UPD, eGFR <20 mL/min/1.73 m2 b.s.).

RESULTS

eGFR was higher in CPD patients than in UPD and LPD patients (21.9 ± 7.4 mL/min/1.73 m2 versus 17.6 ± 8.00 mL/min/1.73 m2 and 17.1 ± 7.5 mL/min/1.73 m2; P = 0.008). The real daily protein intake was higher in UPD patients than in LPD and CDP patients (0.80 ± 0.1 g/kg/day versus 0.6 ± 0.2 and 0.63 ± 0.2 g/kg/day; P = 0.01). Body mass index (BMI) was stable in the LPD and CPD groups but decreased from 28.5 ± 4.52 to 25.4 ± 3.94 kg/m2 in the UPD group (P < 0.001). The renal survival of UPD, LPD and CPD patients was 47.1, 84.3 and 90.7%, respectively, at 30 months (P < 0.001), 42.4, 72.0 and 79.1%, respectively, at 50 months (P < 0.001) and 42.4, 64.1 and 74.4%, respectively, at 70 months (P < 0.001). The LPD patients started dialysis nearly 24 months later than the UPD patients. Diet was an independent predictor of dialysis [-67% of RR reduction (hazard ratio = 0.33; confidence interval 0.22-0.48)] together with a reduction in BMI.

CONCLUSIONS

An LPD recommended by nephrologists in conjunction with skilled dietitians delays dialysis and preserves nutritional status in severe CKD.

Nutritional Requirements and Actual Dietary Intake of Continuous Ambulatory Peritoneal Dialysis Patients

Objective

Nutritional status is related to morbidity and mortality in the continuous ambulatory peritoneal dialysis (CAPD) population. In the present study, we compared the dietary intake of CAPD patients with their requirements for calorie and protein nutrition and with the recommended intakes of potassium and phosphate.

Design

Patients were recruited from the CAPD clinic. Desirable body weight was derived from the height of the individual patients and the desirable body mass index (BMI) for adult Asians. The calorie requirement was calculated by multiplying desirable body weight by 30 kcal. The protein requirement was calculated by multiplying desirable body weight by 1.2 – 1.5, according to serum albumin level. The K requirement was set at 3500 mg daily, and the PO4requirement, at 1000 mg daily. The actual dietary intake of individual patients was estimated from dietary history by a computer software program.

Results

The study included 57 patients who had been on CAPD for 22.1 ± 23.5 months. Of the 57 patients, 8 patients (14.0%) were below the desirable BMI range, 20 (35.1%) were within the range, and 29 (50.9%) were above the range. By subjective global assessment (SGA), 45 patients (78.9%) were mildly-to-moderately malnourished, and 12 (21.1%) well nourished. Serum albumin was 32.1 ± 4.7 g/L. Patients met 98% ± 35.7% (range: 33% – 224%) of their nutritional requirement for calories and 92.1% ± 37.7% (range: 22% – 202%) of their nutritional requirement for protein. Only 23 patients (40.4%) reached the target for calorie intake, and only 22 (38.6%) reached the target for protein intake. Excess K intake was seen in 1 patient (1.8%), and excess PO4intake, in 6 patients (10.5%). Actual dietary intake was not related to BMI or SGA score.

Conclusion

Most CAPD patients had inadequate calorie and protein intakes. Calorie and protein intakes were not related to BMI and SGA scores. Compliance with recommended K and PO4intakes was good.

Frailty and Sarcopenia in Older Patients Receiving Kidney Transplantation

Kidney transplantation is the treatment of choice for most of the patients with end-stage renal disease (ESRD). It improves quality of life, life expectancy, and has a lower financial burden to the healthcare system in comparison to dialysis. Every year more and more older patients are included in the kidney transplant waitlist. Within this patient population, transplanted subjects have better survival and quality of life as compared to those on dialysis. It is therefore crucial to select older patients who may benefit from renal transplantation, as well as those particularly at risk for post-transplant complications. Sarcopenia and frailty are frequently neglected in the evaluation of kidney transplant candidates. Both conditions are interrelated complex geriatric syndromes that are linked to disability, aging, comorbidities, increased mortality, and graft failure post-transplantation. Chronic kidney disease (CKD) and more importantly ESRD are characterized by multiple metabolic complications that contribute for the development of sarcopenia and frailty. In particular, anorexia, metabolic acidosis and chronic low-grade inflammation are the main contributors to the development of sarcopenia, a key component in frail transplant candidates and recipients. Both frailty and sarcopenia are considered to be reversible. Frail patients respond well to multiprofessional interventions that focus on the patients' positive frailty criteria, while physical rehabilitation and oral supplementation may improve sarcopenia. Prospective studies are still needed to evaluate the utility of formally measuring frailty and sarcopenia in the older candidates to renal transplantation as part of the transplant evaluation process.

Dietary Fiber and Gut Microbiota in Renal Diets

Nutrition is crucial for the management of patients affected by chronic kidney disease (CKD) to slow down disease progression and to correct symptoms. The mainstay of the nutritional approach to renal patients is protein restriction coupled with adequate energy supply to prevent malnutrition. However, other aspects of renal diets, including fiber content, can be beneficial. This paper summarizes the latest literature on the role of different types of dietary fiber in CKD, with special attention to gut microbiota and the potential protective role of renal diets. Fibers have been identified based on aqueous solubility, but other features, such as viscosity, fermentability, and bulking effect in the colon should be considered. A proper amount of fiber should be recommended not only in the general population but also in CKD patients, to achieve an adequate composition and metabolism of gut microbiota and to reduce the risks connected with obesity, diabetes, and dyslipidemia.

Creatine is a Conditionally Essential Nutrient in Chronic Kidney Disease: A Hypothesis and Narrative Literature Review

To accommodate the loss of the plethora of functions of the kidneys, patients with chronic kidney disease require many dietary adjustments, including restrictions on the intake of protein, phosphorus, sodium and potassium. Plant-based foods are increasingly recommended as these foods contain smaller amounts of saturated fatty acids, protein and absorbable phosphorus than meat, generate less acid and are rich in fibers, polyunsaturated fatty acids, magnesium and potassium. Unfortunately, these dietary recommendations cannot prevent the occurrence of many symptoms, which typically include fatigue, impaired cognition, myalgia, muscle weakness, and muscle wasting. One threat coming with the recommendation of low-protein diets in patients with non-dialysis-dependent chronic kidney disease (CKD) and with high-protein diets in patients with dialysis-dependent CKD, particularly with current recommendations towards proteins coming from plant-based sources, is that of creatine deficiency. Creatine is an essential contributor in cellular energy homeostasis, yet on a daily basis 1.6–1.7% of the total creatine pool is degraded. As the average omnivorous diet cannot fully compensate for these losses, the endogenous synthesis of creatine is required for continuous replenishment. Endogenous creatine synthesis involves two enzymatic steps, of which the first step is a metabolic function of the kidney facilitated by the enzyme arginine:glycine amidinotransferase (AGAT). Recent findings strongly suggest that the capacity of renal AGAT, and thus endogenous creatine production, progressively decreases with the increasing degree of CKD, to become absent or virtually absent in dialysis patients. We hypothesize that with increasing degree of CKD, creatine coming from meat and dairy in food increasingly becomes an essential nutrient. This phenomenon will likely be present in patients with CKD stages 3, 4 and 5, but will likely be most pronouncedly present in patients with dialysis-dependent CKD, because of the combination of lowest endogenous production of creatine and unopposed losses of creatine into the dialysate. It is likely that these increased demands for dietary creatine are not sufficiently met. The result of which, may be a creatine deficiency with important contributions to the sarcopenia, fatigue, impaired quality of life, impaired cognition, and premature mortality seen in CKD.

Peritoneal dialysis has optimal intradialytic hemodynamics and preserves residual renal function: Why isn't it better than hemodialysis?

Rates of cardiovascular mortality are disproportionately high in patients with end stage kidney disease receiving dialysis. However, it is now generally accepted that patient survival is broadly equivalent between the two most frequently used forms of dialysis, in-center hemodialysis (HD) and peritoneal dialysis (PD). This equivalent patient survival is notable when considering how specific aspects of HD have been shown to contribute to morbidity and mortality. These include more rapid loss of residual renal function (RRF), HD-induced myocardial and cerebral ischemia, and risk factors associated with the intermittent delivery of HD. Potential mechanisms specific to PD that may drive cardiovascular disease include the metabolic consequences of excessive absorption of glucose and glucose degradation products (GDPs), inadequate volume control, and high rates of hypokalemia. The aim of this review is to compare and contrast the different drivers of adverse outcomes between the dialysis modalities, as greater understanding of this may help in patient-centered decision-making when considering options for renal replacement therapy.

Protective Role of Histidine Supplementation Against Oxidative Stress Damage in the Management of Anemia of Chronic Kidney Disease

Anemia is a major health condition associated with chronic kidney disease (CKD). A key underlying cause of this disorder is iron deficiency. Although intravenous iron treatment can be beneficial in correcting CKD-associated anemia, surplus iron can be detrimental and cause complications. Excessive generation of reactive oxygen species (ROS), particularly by mitochondria, leads to tissue oxidation and damage to DNA, proteins, and lipids. Oxidative stress increase in CKD has been further implicated in the pathogenesis of vascular calcification. Iron supplementation leads to the availability of excess free iron that is toxic and generates ROS that is linked, in turn, to inflammation, endothelial dysfunction, and cardiovascular disease. Histidine is indispensable to uremic patients because of the tendency toward negative plasma histidine levels. Histidine-deficient diets predispose healthy subjects to anemia and accentuate anemia in chronic uremic patients. Histidine is essential in globin synthesis and erythropoiesis and has also been implicated in the enhancement of iron absorption from human diets. Studies have found that L-histidine exhibits antioxidant capabilities, such as scavenging free radicals and chelating divalent metal ions, hence the advocacy for its use in improving oxidative stress in CKD. The current review advances and discusses evidence for iron-induced toxicity in CKD and the mechanisms by which histidine exerts cytoprotective functions.

Impact of Nutrition on Cardiovascular Function

The metabolic sources of energy for myocardial contractility include mainly free fatty acids (FFA) for 95%, and in lesser amounts for 5% from glucose and minimal contributions from other substrates such lactate, ketones, and amino acids. However, myocardial efficiency is influenced by metabolic condition, overload, and ischemia. During cardiac stress, cardiomyocytes increase glucose oxidation and reduce FFA oxidation. In patients with ischemic coronary disease and heart failure, the low oxygen availability limits myocardial reliance on FFA and glucose utilization must increase. Although glucose uptake is fundamental to cardiomyocyte function, an excessive intracellular glucose level is detrimental. Insulin plays a fundamental role in maintaining myocardial efficiency and in reducing glycemia and inflammation; this is particularly evident in obese and type-2 diabetic patients. An excess of F availability increase fat deposition within cardiomyocytes and reduces glucose oxidation. In patients with high body mass index, a restricted diet or starvation have positive effects on cardiac metabolism and function while, in patients with low body mass index, restrictive diets, or starvation have a deleterious effect. Thus, weight loss in obese patients has positive impacts on ventricular mass and function, whereas, in underweight heart failure patients, such weight reduction adds to the risk of heart damage, predisposing to cachexia. Nutrition plays an essential role in the evolution of cardiovascular disease and should be taken into account. An energy-restricted diet improves myocardial efficiency but can represent a potential risk of heart damage, particularly in patients affected by cardiovascular disease. Micronutrient integration has a marginal effect on cardiovascular efficiency.

Hemodialysis versus peritoneal dialysis: an observational study in two international centers

INTRODUCTION

Given that it is difficult to randomize end-stage renal disease (ESRD) patients to either hemodialysis (HD) or peritoneal dialysis (PD), differences between these renal replacement therapy (RRT) modalities are of major interest and remain controversial.

METHODS

All data on maintenance dialysis patients during 2009 to 2013 in the Renji Hospital in Shanghai, China and in the San Bortolo Hospital in Vicenza, Italy were selected. Patients who changed their therapy from HD to PD or PD to HD during this study were excluded.

RESULTS

919 maintenance dialysis patients were included in the present study, including 509 patients on HD and 410 on PD. During the 5-year follow-up, mean arterial pressure (MAP) was higher in HD patients. The level of serum HCO3- was significantly better in PD patients than in HD patients. Phosphate was significantly higher in HD patients than in PD patients. With respect to lipid metabolism, triglyceride, total cholesterol and LDL were significantly higher in PD patients. Serum protein and albumin were higher in HD patients than in PD patients. Overall, 236 patients died (25.7%); 150 (16.3%) on HD and 86 (9.4%) on PD. The main cause of death in HD and PD patients was cerebral vascular disease and infection, respectively. After adjusting for dialysis vintage, the Kaplan-Meier patient survival was similar between HD and PD patients.

CONCLUSIONS

Based on 5 years of data, we demonstrate that lipid metabolism and nutritional status were better in HD patients. However, blood pressure control, acid-base balance, phosphate (P) control were better in PD patients. The main cause of death in HD and PD was cerebral vascular disease and infection, respectively. Considering the dialysis vintage, the Kaplan-Meier patient survival was similar between HD and PD patients.

Does whey protein supplementation affect blood pressure in hypoalbuminemic peritoneal dialysis patients?

Objective

Hypertension and hypoalbuminemia are common risk factors for cardiovascular complications in peritoneal dialysis (PD) patients. Data are limited regarding the effects of whey protein consumption on blood pressure in this population. The aim of the present study was to examine if whey protein supplementation for 12 weeks to hypoalbuminemic PD patients affects their blood pressure.

Patients and methods

This prospective randomized study included 36 stable PD patients with serum albumin levels <3.8 g/dL. During 12 weeks, 18 patients were instructed to consume 1.2 g/kg/day of protein and an additional whey protein supplement at a dose of 25% of the instructed daily protein (whey protein group). Eighteen patients were instructed to consume protein in the amount of 1.2 g/kg/day and an additional 25%, without whey protein supplementation (control group).

Results

Compared to the control group, in the whey protein group, serum albumin levels, oncotic pressure, and dialysate ultrafiltration significantly increased (3.55±0.14 to 4.08±0.15 g/dL, P<0.001; 21.81±2.03 to 24.06±1.54 mmHg, P<0.001; 927.8±120.3 to 1,125.0±125.1 mL/day, P<0.001; respectively) and were significantly higher after 12 weeks (4.08±0.15 vs 3.41±0.49 g/dL, P<0.001; 24.06±1.54 vs 22.71±1.77 mmHg, P=0.010; 1,125.0±125.1 vs 930.6±352.8 mL/day, P=0.017; respectively) in the whey protein group compared to the control group. Fluid overload, the extracellular to intracellular ratio and mean arterial pressure (MAP) significantly decreased (2.46±1.08 to 1.52±0.33, P<0.001; 1.080±0.142 to 0.954±0.124, P<0.001; 102.6±3.80 to 99.83±3.85, P=0.018; respectively) and were significantly lower in the whey protein group after 12 weeks (1.52±0.33 vs 2.23±0.73, P<0.001, 0.954±0.124 vs 1.048±0.111, P=0.002; 99.83±3.85 vs 102.8±3.93, P=0.018; respectively).

Conclusion

Whey protein supplementation for 12 weeks decreased MAP in hypoalbuminemic PD patients.

Longitudinal Associations among Renal Urea Clearance-Corrected Normalized Protein Catabolic Rate, Serum Albumin, and Mortality in Patients on Hemodialysis

BACKGROUND AND OBJECTIVES

There are inconsistent reports on the association of dietary protein intake with serum albumin and outcomes among patients on hemodialysis. Using a new normalized protein catabolic rate (nPCR) variable accounting for residual renal urea clearance, we hypothesized that higher baseline nPCR and rise in nPCR would be associated with higher serum albumin and better survival among incident hemodialysis patients.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Among 36,757 incident hemodialysis patients in a large United States dialysis organization, we examined baseline and change in renal urea clearance-corrected nPCR as a protein intake surrogate and modeled their associations with serum albumin and mortality over 5 years (1/2007-12/2011).

RESULTS

Median nPCRs with and without accounting for renal urea clearance at baseline were 0.94 and 0.78 g/kg per day, respectively (median within-patient difference, 0.14 [interquartile range, 0.07-0.23] g/kg per day). During a median follow-up period of 1.4 years, 8481 deaths were observed. Baseline renal urea clearance-corrected nPCR was associated with higher serum albumin and lower mortality in the fully adjusted model (Ptrend<0.001). Among 13,895 patients with available data, greater rise in renal urea clearance-corrected nPCR during the first 6 months was also associated with attaining high serum albumin (≥3.8 g/dl) and lower mortality (Ptrend<0.001); compared with the reference group (a change of 0.1-0.2 g/kg per day), odds and hazard ratios were 0.53 (95% confidence interval, 0.44 to 0.63) and 1.32 (95% confidence interval, 1.14 to 1.54), respectively, among patients with a change of <-0.2 g/kg per day and 1.62 (95% confidence interval, 1.35 to 1.96) and 0.76 (95% confidence interval, 0.64 to 0.90), respectively, among those with a change of ≥0.5 g/kg per day. Within a given category of nPCR without accounting for renal urea clearance, higher levels of renal urea clearance-corrected nPCR consistently showed lower mortality risk.

CONCLUSIONS

Among incident hemodialysis patients, higher dietary protein intake represented by nPCR and its changes over time appear to be associated with increased serum albumin levels and greater survival. nPCR may be underestimated when not accounting for renal urea clearance. Compared with the conventional nPCR, renal urea clearance-corrected nPCR may be a better marker of mortality.

Relationship between microRNA-146a expression and plasma renalase levels in hemodialyzed patients

BACKGROUND

microRNA (miRNA) belongs to the non-coding RNAs family responsible for the regulation of gene expression. Renalase is a protein composed of 342 amino acids, secreted by the kidneys and possibly plays an important role in the regulation of sympathetic tone and blood pressure. The aim of the present study was to investigate plasma renalase concentration, and explore the relationship between miRNA-146a-5p expression and plasma renalase levels in hemodialyzed patients.

METHODS

The study population comprised 55 subjects who succumbed to various cardiac events, 27 women and 28 men, aged 65-70 years. The total RNA including miRNA fraction was isolated using QiagenmiRNEasy Serum/Plasma kit according to the manufacturer's protocol. The isolated miRNAs were analyzed using a quantitative polymerase chain reaction (qRT-PCR) technique. The plasma renalase levels were measured using a commercial ELISA kit.

RESULTS

In the group of patients with high levels of renalase, higher miRNA-146a expression was found, compared with those with low concentration of renalase. Patients with simultaneous low miRNA-146a expression and high level of renalase were confirmed to deliver a significantly longer survival time compared with other patients.

CONCLUSIONS

miRNA-146a and plasma renalase levels were estimated as independent prognostic factors of hemodialyzed patients' survival time. Patients with low miRNA-146a expression demonstrated a significantly longer survival time in contrast to the patients with a high expression level of miRNA-146a. Moreover, a significantly longer survival time was found in patients with high renalase activity compared with patients with low activity of the enzyme.

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.

Indoxyl Sulfate-Review of Toxicity and Therapeutic Strategies

Indoxyl sulfate is an extensively studied uremic solute. It is a small molecule that is more than 90% bound to plasma proteins. Indoxyl sulfate is derived from the breakdown of tryptophan by colon microbes. The kidneys achieve high clearances of indoxyl sulfate by tubular secretion, a function not replicated by hemodialysis. Clearance by hemodialysis is limited by protein binding since only the free, unbound solute can diffuse across the membrane. Since the dialytic clearance is much lower than the kidney clearance, indoxyl sulfate accumulates to relatively high plasma levels in hemodialysis patients. Indoxyl sulfate has been most frequently implicated as a contributor to renal disease progression and vascular disease. Studies have suggested that indoxyl sulfate also has adverse effects on bones and the central nervous system. The majority of studies have assessed toxicity in cultured cells and animal models. The toxicity in humans has not yet been proven, as most data have been from association studies. Such toxicity data, albeit inconclusive, have prompted efforts to lower the plasma levels of indoxyl sulfate through dialytic and non-dialytic means. The largest randomized trial showed no benefit in renal disease progression with AST-120. No trials have yet tested cardiovascular or mortality benefit. Without such trials, the toxicity of indoxyl sulfate cannot be firmly established.

Ratio of C-Reactive Protein to Albumin Predicts Muscle Mass in Adult Patients Undergoing Hemodialysis

Recent studies have indicated that the ratio of C-reactive protein to albumin (CRP–Alb ratio) is associated with clinical outcomes in patients with disease. We examined the predictive value of this ratio in patients undergoing hemodialysis (HD). In this cross-sectional study, 91 eligible adult HD patients were analyzed, and the correlation between the CRP–Alb ratio and skeletal muscle mass normalized for body weight (SMM/wt; estimated using a bioelectrical impedance analyzer) was investigated. The mean age of the study participants was 54.9 ± 6.6 years (ranging from 27 to 64 years); 43 (47.2%) were men. The mean values for the SMM/wt were 39.1% ± 5.4%. The CRP–Alb ratio was found to be negatively correlated with SMM/wt (r = −0.33, P = 0.002) and creatinine (r = −0.20, P = 0.056). All the univariate significant and nonsignificant relevant covariates were selected for multivariable stepwise regression analysis. We determined that the homeostasis model assessment-estimated insulin resistance and CRP–Alb ratio were independent risk determinants for SMM/wt (β_HOMA-IR = −0.18 and β_{CRP–Alb ratio} = −3.84, adjusted R² = 0.32). This study indicated that the CRP–Alb ratio may help clinicians in predicting muscle mass in adult patients undergoing HD.

Low-protein diet supplemented with ketoacids ameliorates proteinuria in 3/4 nephrectomised rats by directly inhibiting the intrarenal renin-angiotensin system

Low-protein diet plus ketoacids (LPD+KA) has been reported to decrease proteinuria in patients with chronic kidney diseases (CKD). However, the mechanisms have not been clarified. As over-activation of intrarenal renin-angiotensin system (RAS) has been shown to play a key role in the progression of CKD, the current study was performed to investigate the direct effects of LPD+KA on intrarenal RAS, independently of renal haemodynamics. In this study, 3/4 subtotal renal ablated rats were fed 18 % normal-protein diet (Nx-NPD), 6 % low-protein diet (Nx-LPD) or 5 % low-protein diet plus 1 % ketoacids (Nx-LPD+KA) for 12 weeks. Sham-operated rats fed NPD served as controls. The level of proteinuria and expression of renin, angiotensin II (AngII) and its type 1 receptors (AT1R) in the renal cortex were markedly higher in Nx-NPD group than in the sham group. LPD+KA significantly decreased the proteinuria and inhibited intrarenal RAS activation. To exclude renal haemodynamic impact on intrarenal RAS, the serum samples derived from the different groups were added to the culture medium of mesangial cells. It showed that the serum from Nx-NPD directly induced higher expression of AngII, AT1R, fibronectin and transforming growth factor-β1 in the mesangial cells than in the control group. Nx-LPD+KA serum significantly inhibited these abnormalities. Then, proteomics and biochemical detection suggested that the mechanisms underlying these beneficial effects of LPD+KA might be amelioration of the nutritional metabolic disorders and oxidative stress. In conclusion, LPD+KA could directly inhibit the intrarenal RAS activation, independently of renal haemodynamics, thus attenuating the proteinuria in CKD rats.

The Effect of BCAA and ISO-WHEY Oral Nutritional Supplements on Dialysis Adequacy

Background

Protein-energy malnutrition is a common problem in hemodialysis patients and has different outcomes such as reduced quality of life, longer hospitalization time, lower dialysis adequacy, and higher mortality rate. Investigation of dialysis adequacy is an important method for assessing hemodialysis patients, and improving the dialysis adequacy is an important healthcare team goal.

Objectives

The present study aims to investigate and compare the effects of BCAA and ISO-WHEY oral nutritional supplements on dialysis adequacy.

Methods

In a clinical trial study, 66 hemodialysis patients were randomly divided into three groups: Group A (n = 22), Group B (n = 22), and Group C or the control group (n = 22). In Groups A and B, as prescribed and controlled by nutritionists and nephrologists, respectively, ISO-WHEY and BCAA protein powder were used for 2 months on a daily basis. For all groups, before intervention and 1 and 2 months after intervention, the dialysis adequacy was measured using URR and Kt/V. Finally, the data were analyzed using IBM SPSS Statistics Base 21.0 software.

Results

Out of 66 patients, 61 (19 in Group A, 20 in Group B, and 22 in Group C) completed the study period, and before intervention, all groups were equal in terms of quality and quantity variables (P > 0.05). After intervention, there was a significant difference between the three groups with regard to the variables of dialysis adequacy based on Kt/V and URR to independent-t test and repeated measures ANOVA (P < 0.05).

Conclusions

Results show that the intake of oral nutritional supplements leads to an improvement in the dialysis adequacy of hemodialysis patients. Therefore, the use of nutritional supplements along with patients' training and regular consultation will be helpful in improving the nutritional status, dialysis adequacy, and eventually the quality of life.

Low prealbumin levels are independently associated with higher mortality in patients on peritoneal dialysis

Background

Prealbumin, a sensitive marker for protein–energy status, is also known as an independent risk factor for mortality in hemodialysis patients. We investigated the impact of prealbumin on survival in incident peritoneal dialysis (PD) patients.

Methods

In total, 136 incident PD patients (mean age, 53.0 ± 15.8 years) between 2002 and 2007 were enrolled in the study. Laboratory data, dialysis adequacy, and nutritional parameters were assessed 3 months after PD initiation. Patients were classified into 2 groups according to prealbumin level: high prealbumin (≥ 40 mg/dL) and low prealbumin (< 40 mg/dL).

Results

The patients in the low-prealbumin group were older and had more comorbidities such as diabetes and cardiovascular diseases compared with the patients in the high-prealbumin group. Mean subjective global assessment scores were lower, and the high-sensitivity C-reactive protein levels were higher in the low-prealbumin group. Serum creatinine, albumin, and transferrin levels; percent lean body mass; and normalized protein catabolic rate were positively associated, whereas subjective global assessment scores and high-sensitivity C-reactive protein levels were negatively associated with prealbumin concentration. During the median follow-up of 49 months, patients in the lower prealbumin group had a higher mortality rate. Multivariate analysis revealed that prealbumin < 40 mg/dL (hazard ratio, 2.30; 95% confidence interval, 1.14–4.64) was an independent risk factor for mortality. In receiver operating characteristic curves, the area under the curve of prealbumin for mortality was the largest among the parameters.

Conclusion

Prealbumin levels were an independent and sensitive predictor for mortality in incident PD patients, showing a good correlation with nutritional and inflammatory markers.

Potential Role of Vegetarianism on Nutritional and Cardiovascular Status in Taiwanese Dialysis Patients: A Case-Control Study

Background & Objectives

Cardiovascular disease remains the most common cause of death for patients on chronic dialysis. End stage renal disease patients undergoing dialysis imposed to reduce phosphorus intake, which likely contributes to development of vegetarian diet behaviors. Vegetarian diets are often lower in protein content, in contradiction to the recommendation that a high protein diet is followed by patients undergoing dialysis. The purpose of the study was to investigate the effects of a vegetarian diet on the nutritional and cardiovascular status of dialysis patients.

Design, Setting, Participants, Measurements

A study of 21 vegetarian dialysis patients and 42 age- and sex-matched non-vegetarian dialysis patients selected as controls was conducted in the Kaohsiung Veterans General Hospital. Brachial-ankle pulse wave velocity and biochemistry data including total homocysteine levels, serum lipid profiles, high-sensitivity C-reactive protein, vitamin D levels, albumin, and normalized protein catabolic rate were measured.

Results

Compared with the non-vegetarian control group, vegetarian subjects had lower body weight, body mass index, serum phosphate, blood urea nitrogen, serum creatinine, vitamin D, uric acid, albumin, and normalized protein catabolic rate (p < 0.05). The vegetarian group showed higher brachial-ankle pulse wave velocity than the non-vegetarian group (1926.95 ± 456.45 and 1684.82 ± 309.55 cm/sec, respectively, p < 0.05). After adjustment for age, albumin, pre-dialysis systolic blood pressure, and duration of dialysis, vegetarian diet remained an independent risk factor for brachial-ankle pulse wave velocity.

Conclusions

The present study revealed that patients on dialysis who follow vegetarian diets may experience subclinical protein malnutrition and vitamin D deficiency that could offset the beneficial cardiovascular effects of vegetarianism.

Ratio of dietary ω-3 and ω-6 fatty acids-independent determinants of muscle mass-in hemodialysis patients with diabetes

OBJECTIVE

ω-3 and ω-6 polyunsaturated fatty acids (PUFAs) are essential nutrients in the human diet and possibly affect muscle mass. We evaluated the association between the dietary ratios of ω-3 and ω-6 PUFAs and muscle mass, indicated as skeletal muscle mass (SMM) and appendicular skeletal muscle mass (ASM), in patients with diabetes undergoing hemodialysis (HD).

METHODS

In this cross-sectional study, data on 69 patients with diabetes who underwent standard HD therapy were analyzed. For estimating muscle mass, anthropometric and bioelectrical impedance analyses were conducted following dialysis. In addition, routine laboratory and 3-d dietary data were obtained. The adequate intake (AI) cut-off for ω-3 PUFAs was 1.6 g/d and 1.1 g/d for male and female patients, respectively.

RESULTS

The average age of the participants was 63.0 ± 10.4 y. The mean ratios of ω-3/ω-6 PUFA intake, ω-6/ω-3 PUFA intake, SMM, and ASM of the patients were 0.13 ± 0.07, 9.4 ± 6.4, 24.6 ± 5.4 kg, and 18.3 ± 4.6 kg, respectively. Patients who had AI of ω-3 PUFAs had significantly higher SMM and ASM than did their counterparts. Linear and stepwise multivariable adjustment analyses revealed that insulin resistance and the ω-6/ω-3 PUFA ratio were the independent deleterious determinants of ASM normalized to height in HD patients.

CONCLUSIONS

Patients with AI of ω-3 PUFAs had total-body SMM and ASM that were more appropriate. A higher dietary ratio of ω-6/ω-3 PUFAs was associated with reduced muscle mass in HD patients.

Role of nutrition on anemia in elderly

Anemia in elderly population have a great incidence and is related to increased mortality risk. The incidence of nutrition in anemia is about one third of the total. Caloric and protein restriction, iron, vitamin B₁₂, folic deficiency are the causes of nutritional anemia. Protein and energy malnutrition stimulate an increased cytokines production with induction of inflammation, immunodeficiency and anemia. Anorexia and obesity can be associated with anemia due to increased cytokines and hepdicin serum level. Macrophages activity is inhibited and a decrease in red blood cells (RBC), hemoglobin (Hb) concentration due to ineffective erythropoiesis is observed. An adequate energy and protein diet is necessary to reduce inflammation and increase iron absorption. A minimum of 1700 kcal/day and 1.7 gr/kg/day of protein intake are necessary to maintain anabolism in chronic patients to prevent and treat anemia. Iron supplementation by intravenous injection is safe and effective to correct severe iron deficiency. The supplementation of vitamins and oligomineral are useful to reduce oxidative stress and improve RBC longevity. Anemia in elderly could be prevented by an adequate nutrition, a simple and not expensive intervention, and associated to physical exercise reduce the incidence of mortality rate.

Urinary Urea Excretion and Long-term Outcome After Renal Transplantation

BACKGROUND

Little is known about optimal protein intake after transplantation. The aim of this study was to prospectively investigate associations of urinary urea excretion, a marker for protein intake, with graft failure and mortality in renal transplant recipients (RTR) and potential effect modification by body mass index (BMI) and estimated glomerular filtration rate (eGFR).

METHODS

Urinary urea excretion was measured in repeated 24-hr urine collections between 6 and 18 months after transplantation.

RESULTS

In total, 940 RTR were included. During 4.4 (2.3-7.8) years of follow-up for graft failure and 4.8 (2.5-8.3) years for all-cause mortality, 78 RTR developed graft failure and 158 RTR died. Urinary urea excretion was not associated with graft failure in the overall population, but was inversely associated with graft failure in RTR with BMI less than 25 kg/m (hazard ratio [HR], 0.64 [0.28-1.50] and 0.27 [0.09-0.83] for the second and third tertiles, respectively, P < 0.001), and in RTR with eGFR of 45 mL per min per 1.73 m or higher (HR, 0.34 [0.15-0.79], P = 0.015 and HR, 0.31 [0.11-0.86], P = 0.025 for the second and third tertiles, respectively), both independent of potential confounders. Compared to the first tertile, RTR in the second and third tertiles of urinary urea excretion were at a lower risk of all-cause mortality (HR, 0.47 [0.32-0.69]; P < 0.001 and HR, 0.42 [0.26-0.68]; P < 0.001, respectively), independent of potential confounders. Body mass index and eGFR did not influence this association.

CONCLUSION

Urinary urea excretion, a marker for protein intake, was inversely related to graft failure in RTR with BMI less than 25 kg/m and in RTR with an eGFR of 45 mL per min per 1.73 m or higher. In addition, urinary urea excretion was inversely related to mortality.

Supervised oral protein supplementation during dialysis in patients with elevated C-reactive protein levels: a two phase, longitudinal, single center, open labeled study

BACKGROUND

Inflammation is considered one of the major causes of protein-energy wasting in maintenance hemodialysis (MHD) patients. It is unclear whether dietary interventions can impact nutritional status and quality of life in MHD patients with elevated C-reactive protein (CRP) levels. Therefore, we examined the hypothesis that supervised intra-dialysis protein supplementation in MHD patients with elevated plasma CRP will improve protein stores and quality of life.

METHODS

A 24 week, two phase, longitudinal, single center, open labeled study of 50 MHD patients with plasma CRP > 3 mg/L was conducted. During the 12-week observation phase dietary advice was provided to increase protein intake to 1.2 g/kg/day. In the 12-week treatment phase 45 g of liquid protein supplement was provided at each dialysis treatment. Protein nitrogen appearance (PNA), mid-arm muscle circumference (MAMC), serum albumin, body mass index (BMI) and quality of life (assessed by Short Form-12 questionnaire) were measured at baseline, 12 and 24 weeks.

RESULTS

Median plasma CRP at baseline was 16.0 (IQR 7.7 to 25.1) mg/L. The mean MAMC was 26.5 ± 3.9 cm, BMI 29.2 ± 6.9 kg/m(2) and plasma albumin 3.8 ± 0.3 g/dl. During the intervention period, mean PNA increased by 0.13 g/kg/d (p = 0.01) under a mixed effects model. However, there were no clinically or statistically significant effects on MAMC (p = 0.87), plasma albumin (p = 0.70), BMI (p = 0.09), physical (p = 0.32) or mental (p = 0.96) composite scores.

CONCLUSIONS

In MHD patients with elevated plasma CRP but otherwise mostly normal nutritional parameters, intra-dialytic oral protein supplement was effective in increasing protein intake but did not provide a detectable impact on nutritional status or quality of life.

Causal path analyses of the association of protein intake with risk of mortality and graft failure in renal transplant recipients

The effect of a low protein intake on survival in renal transplant recipients (RTR) is unknown. A low protein intake may increase risks of malnutrition, low muscle mass, and death. We aimed to study associations of protein intake with mortality and graft failure and to identify potential intermediate factors. Protein intake was estimated from 24-h urinary urea excretion (24-h UUE). Graft failure was defined as return to dialysis or retransplantation. We used Cox regression analyses to analyze associations with outcome and potential intermediate factors in the causal path. In 604 RTR, mean ± SD 24-h UUE was 380 ± 114 mmol/24-h. During median follow-up for 7.0 yr (interquartile range: 6.2-7.5 yr), 133 RTR died and 53 developed graft failure. In univariate analyses, 24-h UUE was associated with lower risk of mortality (HR [95% CI] = 0.80 [0.69-0.94]) and graft failure (HR [95% CI] = 0.72 [0.56-0.92]). These associations were independent of potential confounders. In causal path analyses, the association of 24-h UUE with mortality disappeared after adjustment for muscle mass. Low protein intake is associated with increased risk of mortality and graft failure in RTR. Causal path analyses reveal that the association with mortality is explained by low muscle mass. These findings suggest that protein intake restriction should not be advised to RTR.

Dietary protein and fiber in end stage renal disease

Prior to the availability of hemodialysis, dietary protein restriction played a large part in the treatment of uremia. This therapy was based on observations that uremic symptoms increased with high protein intake. Early investigators thus presumed that "uremic toxins" were derived from the breakdown of dietary protein; its restriction improved uremic symptoms but caused malnutrition. After the availability of hemodialysis, protein restriction was no longer recommended. Studies in healthy subjects have shown that an intake of 0.6-0.8 g/kg/day is adequate to prevent protein malnutrition. Guidelines for hemodialysis patients, however, currently recommend higher protein intakes of 1.2 g/kg/day. A downside to higher intake may be increased production of protein-derived uremic solutes that caused the symptoms observed by early investigators. Some of these solutes are produced by colon microbes acting on protein which escapes digestion in the small intestine. Increasing dietary fiber may reduce the production of colon-derived solutes in hemodialysis patients without adverse effects of protein restriction. Fiber comprises carbohydrates and related substances that are resistant to digestion in the small intestine. Upon delivery to the colon, fiber is broken down to short chain fatty acids, providing energy to both the microbes and the host. With an increased energy supply, the microbes can incorporate dietary protein for growth rather than breaking them down to uremic solutes. Increasing fiber intake in hemodialysis patients has been shown to reduce the plasma levels of selected colon-derived solutes. Further studies are needed to test whether this provides clinical benefit.

Clinical research in a modern Chinese peritoneal dialysis center

A prerequisite for enhancing the quality of peritoneal dialysis is the continuous review and analysis of clinical data from routine clinical care and research. Here, we describe our strategy (Peking University First Hospital, Beijing, China) to achieve that objective.

Elevated levels of hemoglobin A1c are associated with cerebral white matter disease in patients with stroke

BACKGROUND AND PURPOSE

This study was conducted to investigate the association of cerebral white matter disease (WMD) on MRI with vascular risk factors and laboratory findings in consecutive first acute ischemic stroke patients.

METHODS

Acute ischemic stroke patients underwent MRI ≤24 hours after stroke onset and follow-up on day 2. WMD was scored on fluid attenuated inversion recovery MRI according to the Wahlund score. Vascular risk factors and laboratory parameters were assessed during hospital stay. Univariate and multiple logistic regression analyses were performed.

RESULTS

We included 512 patients with first acute ischemic stroke (mean age, 68.5 [SD, 13.2] years; 192 women (37.5%); median National Institutes of Health Stroke Scale on admission, 3 [interquartile range, 1-6]; and median Wahlund score, 4 [interquartile range, 2-9]). WMD was present in 460 (89.8%) patients. In univariate analysis, age, arterial hypertension, reduced estimated glomerular filtration rate, hemoglobin A1c (HbA1c) levels, diabetes mellitus, and female sex were associated with the presence of WMD (P<0.05). In multiple regression analysis, age, arterial hypertension, and elevated levels of HbA1c (P<0.05) remained independently associated with the extent of WMD.

CONCLUSIONS

Among known risk factors, higher levels of HbA1c were associated with cerebral WMD in stroke patients. This may suggest that chronic disturbance of glycemia measured by HbA1c plays a role in the pathophysiology of WMD.

CLINICAL TRIAL REGISTRATION URL

http://www.clinicaltrials.gov. Unique identifier: NCT00715533.

Body mass index and mortality in patients on maintenance hemodialysis: a meta-analysis

PURPOSE

In patients undergoing maintenance hemodialysis (MHD), increasing numbers of studies have reported a reduced mortality in patients with an increased body mass index (BMI). This article provides a meta-analysis on the assessment of the relationship between BMI and mortality in MHD patients.

METHODS

A systemic literature review was conducted to identify studies that examined all-cause mortality, with or without cardiovascular events, on the basis of bodyweight or obesity measures in MHD population published before October 2012.

RESULTS

Eight observational studies with a total of 190,163 patients were included. Compared to the individuals with a normal BMI, overweight patients and obese patients were associated with lower all-cause mortality [relative risk (RR) 0.86, 95% confidence interval (CI) 0.84-0.88; RR 0.77, 95% CI 0.75-0.78, respectively] and cardiovascular mortality (RR 0.86; 95% CI 0.81-0.91; RR 0.78, 95% CI 0.73-0.83, respectively). Underweight patients had relatively higher all-cause and cardiovascular mortality (RR 1.22, 95% CI 1.20-1.25; RR 1.19, 95% CI 1.11-1.28, respectively). In an obesity-stratified analysis, the patients with moderate or severe obesity presented a strongly decreased all-cause mortality risk (RR 0.64, 95% CI 0.61-0.68) and cardiovascular mortality risk (RR 0.63, 95% CI 0.53-0.75) compared to patients with mild obesity (RR 0.74, 95% CI 0.71-0.77; RR 0.81, 95% CI 0.75-0.87, respectively).

CONCLUSIONS

These findings show that overweight and obese patients have lower all-cause and cardiovascular mortality rates in patients undergoing MHD. Body weight management and optimized nutritional and metabolic support should help to reduce the high mortality rates that are prevalent in the hemodialysis population.

Low protein nitrogen appearance as a surrogate of low dietary protein intake is associated with higher all-cause mortality in maintenance hemodialysis patients

To determine the association between all-cause mortality and dietary protein intake in patients with chronic kidney disease, we performed a large-scale, 8-y prospective cohort study in 98,489 maintenance hemodialysis patients from a multicenter dialysis care provider. Compared with the reference level (60 to <70 g/d), low protein nitrogen appearance (PNA) levels [<30 g/d, HR: 1.40 (95% CI: 1.30, 1.50); 30 to <40 g/d, HR: 1.33 (95% CI: 1.28, 1.39)] was associated with higher all-cause mortality, and high PNA levels [≥110 g/d, HR: 0.92 (95% CI: 0.88, 0.97); 100 to <110 g/d, HR: 0.87 (95% CI: 0.82, 0.91)] were associated with lower all-cause mortality in all analyses. This association was also found in subanalyses performed among racial and hypoalbuminemic groups. Hence, using PNA as a surrogate for protein intake, a low daily dietary protein intake is associated with increased risk of death in all hemodialysis patients. Whether the association between dietary protein intake and survival is causal or a consequence of anorexia secondary to protein-energy-wasting/inflammation or other factors should be explored in interventional trials.

Interventions to enhance adherence to dietary advice for preventing and managing chronic diseases in adults

BACKGROUND

It has been recognized that poor adherence can be a serious risk to the health and wellbeing of patients, and greater adherence to dietary advice is a critical component in preventing and managing chronic diseases.

OBJECTIVES

To assess the effects of interventions for enhancing adherence to dietary advice for preventing and managing chronic diseases in adults.

SEARCH METHODS

We searched the following electronic databases up to 29 September 2010: The Cochrane Library (issue 9 2010), PubMed, EMBASE (Embase.com), CINAHL (Ebsco) and PsycINFO (PsycNET) with no language restrictions. We also reviewed: a) recent years of relevant conferences, symposium and colloquium proceedings and abstracts; b) web-based registries of clinical trials; and c) the bibliographies of included studies.

SELECTION CRITERIA

We included randomized controlled trials that evaluated interventions enhancing adherence to dietary advice for preventing and managing chronic diseases in adults. Studies were eligible if the primary outcome was the client's adherence to dietary advice. We defined 'client' as an adult participating in a chronic disease prevention or chronic disease management study involving dietary advice.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the eligibility of the studies. They also assessed the risk of bias and extracted data using a modified version of the Cochrane Consumers and Communication Review Group data extraction template. Any discrepancies in judgement were resolved by discussion and consensus, or with a third review author. Because the studies differed widely with respect to interventions, measures of diet adherence, dietary advice, nature of the chronic diseases and duration of interventions and follow-up, we conducted a qualitative analysis. We classified included studies according to the function of the intervention and present results in a narrative table using vote counting for each category of intervention.

MAIN RESULTS

We included 38 studies involving 9445 participants. Among studies that measured diet adherence outcomes between an intervention group and a control/usual care group, 32 out of 123 diet adherence outcomes favoured the intervention group, 4 favoured the control group whereas 62 had no significant difference between groups (assessment was impossible for 25 diet adherence outcomes since data and/or statistical analyses needed for comparison between groups were not provided). Interventions shown to improve at least one diet adherence outcome are: telephone follow-up, video, contract, feedback, nutritional tools and more complex interventions including multiple interventions. However, these interventions also shown no difference in some diet adherence outcomes compared to a control/usual care group making inconclusive results about the most effective intervention to enhance dietary advice. The majority of studies reporting a diet adherence outcome favouring the intervention group compared to the control/usual care group in the short-term also reported no significant effect at later time points. Studies investigating interventions such as a group session, individual session, reminders, restriction and behaviour change techniques reported no diet adherence outcome showing a statistically significant difference favouring the intervention group. Finally, studies were generally of short duration and low quality, and adherence measures varied widely.

AUTHORS' CONCLUSIONS

There is a need for further, long-term, good-quality studies using more standardized and validated measures of adherence to identify the interventions that should be used in practice to enhance adherence to dietary advice in the context of a variety of chronic diseases.