Diets and enteral supplements for improving outcomes in chronic kidney disease. Nat Rev Nephrol. 2011;7:369-384. [PMID: 21629229 DOI: 10.1038/nrneph.2011.60]

Nutritional predictors of early mortality in incident hemodialysis patients

PURPOSE

Low serum albumin concentration and low dietary protein intake are associated with protein-energy wasting (PEW) and higher mortality in maintenance hemodialysis patients. The role of these nutritional markers is less clear in clinical outcomes of the first several months of dialysis therapy, where mortality is exceptionally high.

METHODS

In a cohort of 17,445 incident hemodialysis patients, we examined variation in serum albumin and the normalized protein catabolic rate (nPCR), a surrogate of dietary intake, and quarterly mortality in the first 2 years of dialysis therapy. Cox proportional hazard models were fitted to estimate the association between mortality and combined albumin/nPCR categories for eight quarters. We investigated the associations between mortality and baseline and subsequent serum albumin levels per cohort quarter as well as changes in albumin and nPCR over time.

RESULTS

Patients were 64 ± 15 years old (mean ± SD) and included 45 % women, 24 % African Americans and 58 % diabetics. Correlations between quarterly serum albumin and nPCR varied from 0.18 to 0.25. Serum albumin <3.5 g/dL was consistently associated with high mortality as was nPCR <1 g/kg/day (except for qtr1). Low serum albumin and nPCR greater than 0.2 g/dLg/dL or g/kg/day, respectively, were associated with increased risk of death. Quarterly rise in nPCR (>+0.2 g/kg/day) showed reverse effect on mortality from the 2nd to the last quarter.

CONCLUSIONS

Low serum albumin and nPCR are associated with mortality. A rapid rise in nPCR by the end of the second year may indicate pre-existing PEW.

Let them eat during dialysis: an overlooked opportunity to improve outcomes in maintenance hemodialysis patients

In individuals with chronic kidney disease, surrogates of protein-energy wasting, including a relatively low serum albumin and fat or muscle wasting, are by far the strongest death risk factor compared with any other condition. There are data to indicate that hypoalbuminemia responds to nutritional interventions, which may save lives in the long run. Monitored, in-center provision of high-protein meals and/or oral nutritional supplements during hemodialysis is a feasible, inexpensive, and patient-friendly strategy despite concerns such as postprandial hypotension, aspiration risk, infection control and hygiene, dialysis staff burden, diabetes and phosphorus control, and financial constraints. Adjunct pharmacologic therapies can be added, including appetite stimulators (megesterol, ghrelin, and mirtazapine), anabolic hormones (testosterone and growth factors), antimyostatin agents, and antioxidative and anti-inflammatory agents (pentoxiphylline and cytokine modulators), to increase efficiency of intradialytic food and oral supplementation, although adequate evidence is still lacking. If more severe hypoalbuminemia (<3.0 g/dL) not amenable to oral interventions prevails, or if a patient is not capable of enteral interventions (e.g., because of swallowing problems), then parenteral interventions such as intradialytic parenteral nutrition can be considered. Given the fact that meals and supplements during hemodialysis would require only a small fraction of the funds currently used for dialysis patients this is also an economically feasible strategy.

Diminished appetite predicts mortality of Chinese peritoneal dialysis patients

BACKGROUND

Many maintenance dialysis patients experience a common cluster of symptoms, including diminished appetite (anorexia). This symptom has been associated with reduced quality of life and increased mortality in this population.

AIM

The aim of this study was to determine whether diminished appetite is a significant predictor of negative clinical outcomes in patients on peritoneal dialysis (PD).

METHOD

A longitudinal prospective study was conducted in 98 patients receiving PD in Beijing, China. Clinical characteristics, nutritional and inflammatory marker levels, and related peritoneal treatment information were collected. The appetite status and serum albumin levels were assessed initially and reevaluated monthly during the first year of follow-up. All patients were followed for nearly 5 years or until death. Data were collected about mortality, hospitalization, and peritonitis.

RESULTS

The mean age of participants was 60.3 ± 14.4, and 22.8% reported diminished appetite. At baseline, female sex, cardiovascular disease, and prealbumin level were the significant predictors of appetite. The average length of follow-up was 39 (range: 2-57) months. The Kaplan-Meier survival curve showed the survival rate was lower in patients reporting diminished appetite than for patients reporting normal appetite. Multivariate analysis indicated that diminished appetite, diabetes, ferritin, and serum albumin levels were independent predictors of mortality.

CONCLUSION

Self-reported appetite was a predictor of clinical characteristics and outcome for patients receiving PD. Conducting appetite evaluation periodically is recommended as a nursing strategy to improve care for these patients.

Effect of hyperinsulinemia during hemodialysis on the insulin-like growth factor system and inflammatory biomarkers: a randomized open-label crossover study

Background

A marked reduction in serum levels of bioactive insulin-like growth factor-I (IGF-I) has been observed in fasting hemodialysis (HD) patients during a 4-h HD session. The aim of the present study was to investigate the beneficial effect of hyperinsulinemia during HD on bioactive IGF-I and inflammatory biomarkers.

Methods

In a randomized cross-over study, 11 non-diabetic HD patients received a standardised HD session with either: 1) no treatment, 2) glucose infusion (10% glucose, 2.5 mL/kg/h), or 3) glucose-insulin infusion (10% glucose added 30 IU NovoRapid® per litre, 2.5 mL/kg/h). Each experiment consisted of three periods: pre-HD (−120 to 0 min), HD (0 to 240 min), and post-HD (240 to 360 min). A meal was served at baseline (−120 min); infusions were administered from baseline to 240 min. The primary outcome was change in bioactive IGF-I during the experiment. Secondary outcomes were changes in high-sensitivity C-reactive protein, interleukin-1β, interleukin-6, and tumor necrosis factor α. Comparisons were performed using mixed-model analysis of variance for repeated measures.

Results

From baseline to the end of study, no significant differences were observed in the changes in either serum bioactive IGF-I or total IGF-I between study days. Overall, serum bioactive IGF-I levels rose above baseline at 120 to 300 min with a maximum increase of 20% at 120 min (95% confidence interval (CI), 9 to 31%; p < 0.001), whereas total IGF-I levels rose above baseline at 180 to 300 min with a maximum increase of 5% at 240 min (95% CI, 2 to 9%; p = 0.004). A significant difference was observed in the changes in serum IGF-binding protein-1 (IGFBP-1) between study days (p = 0.008), but differences were only significant in the post-HD period. From baseline to the end of HD, no significant difference was observed in the changes in serum IGFBP-1 levels between study days, and in this time period overall serum IGFBP-1 levels were below baseline at all time points with a maximum decrease of 51% at 180 min (95% CI, 45 to 57%; p < 0.001). None of the investigated inflammatory biomarkers showed any differences in the changes over time between study days.

Conclusions

Postprandial insulin secretion stimulated the IGF-system during HD with no further effect of adding glucose or glucose-insulin infusion. Hyperinsulinemia during HD had no effect on biomarkers of inflammation.

Trial registration

ClinicalTrials.gov registry: NCT01209403

Nutritional management and growth in children with chronic kidney disease

Despite continuing improvements in our understanding of the causes of poor growth in chronic kidney disease, many unanswered questions remain: why do some patients maintain a good appetite whereas others have profound anorexia at a similar level of renal function? Why do some, but not all, patients respond to increased nutritional intake? Is feed delivery by gastrostomy superior to oral and nasogastric routes? Do children who are no longer in the 'infancy' stage of growth benefit from enteral feeding? Do patients with protein energy wasting benefit from increased nutritional input? How do we prevent obesity, which is becoming so prevalent in the developed world? This review will address these issues.

Optimal nutrition in hemodialysis patients

Protein-energy wasting (PEW) is highly prevalent in patients undergoing maintenance hemodialysis (MHD). It is important to note that there is a robust association between the extent of PEW and the risk of hospitalization and death in these patients, regardless of the nutritional marker used. The multiple etiologies of PEW in advanced kidney disease are still being elucidated. Apart from the multiple mechanisms that might lead to PEW, it appears that the common pathway for all of the derangements is related to exaggerated protein degradation along with decreased protein synthesis. The hemodialysis procedure per se is an important contributor to this process. Metabolic and hormonal derangements such as acidosis, inflammation, and resistance to anabolic properties of insulin resistance and growth hormone are all implicated for the development of PEW in MHD patients. Appropriate management of MHD patients at risk for PEW requires a comprehensive combination of strategies to diminish protein and energy depletion and to institute therapies that will avoid further losses. The mainstay of nutritional treatment in MHD patients is provision of an adequate amount of protein and energy, using oral supplementation as needed. Intradialytic parenteral nutrition should be attempted in patients who cannot efficiently use the gastrointestinal tract. Other anabolic strategies such as exercise, anabolic hormones, anti-inflammatory therapies, and appetite stimulants can be considered as complementary therapies in suitable patients.

Cardiorenal syndrome: pathophysiology and potential targets for clinical management

Combined dysfunction of the heart and the kidneys, which can be associated with haemodynamic impairment, is classically referred to as cardiorenal syndrome (CRS). Cardiac pump failure with resulting volume retention by the kidneys, once thought to be the major pathophysiologic mechanism of CRS, is now considered to be only a part of a much more complicated phenomenon. Multiple body systems may contribute to the development of this pathologic constellation in an interconnected network of events. These events include heart failure (systolic or diastolic), atherosclerosis and endothelial cell dysfunction, uraemia and kidney failure, neurohormonal dysregulation, anaemia and iron disorders, mineral metabolic derangements including fibroblast growth factor 23, phosphorus and vitamin D disorders, and inflammatory pathways that may lead to malnutrition-inflammation-cachexia complex and protein-energy wasting. Hence, a pathophysiologically and clinically relevant classification of CRS based on the above components would be prudent. With the existing medical knowledge, it is almost impossible to identify where the process has started in any given patient. Rather, the events involved are closely interrelated, so that once the process starts at a particular point, other pathways of the network are potentially activated. Current therapies for CRS as well as ongoing studies are mostly focused on haemodynamic adjustments. The timely targeting of different components of this complex network, which may eventually lead to haemodynamic and vascular compromise and cause refractoriness to conventional treatments, seems necessary. Future studies should focus on interventions targeting these components.

Transthyretin predicts cardiovascular outcome in hemodialysis patients with type 2 diabetes

OBJECTIVE

BMI and albumin are commonly accepted parameters to recognize wasting in dialysis patients and are powerful predictors of morbidity and mortality. However, both parameters reveal limitations and may not cover the entire range of patients with wasting. The visceral protein transthyretin (TTR) may be helpful in overcoming the diagnostic and prognostic gap. Therefore, the aim of this study was to assess the association of TTR with morbidity and mortality in hemodialysis patients.

RESEARCH DESIGN AND METHODS

The TTR concentration was determined in plasma samples of 1,177 hemodialysis patients with type 2 diabetes. Cox regression analyses were used to determine hazard ratios (HRs) for the risk of cardiovascular end points (CVEs) and mortality according to quartiles of TTR concentration for the total study cohort and the subgroups BMI ≥23 kg/m(2), albumin concentration ≥3.8 g/dL, and a combination of both.

RESULTS

A low TTR concentration was associated with an increased risk for CVE for the total study cohort (HR 1.65 [95% CI 1.27-2.14]), patients with BMI ≥23 kg/m(2) (1.70 [1.22-2.37]), albumin ≥3.8 g/dL (1.68 [1.17-2.42]), and the combination of both (1.69 [1.13-2.53]). Additionally, a low TTR concentration predicted mortality for the total study cohort (1.79 [1.43-2.24]) and patients with BMI ≥23 kg/m(2) (1.46 [1.09-1.95]).

CONCLUSIONS

The current study demonstrated that TTR is a useful predictor for cardiovascular outcome and mortality in diabetic hemodialysis patients. TTR was particularly useful in patients who were not identified to be at risk by BMI or albumin status.

Vitamin D supplementation in pre-dialysis chronic kidney disease: A systematic review

Vitamin D deficiency is associated with a variety of skeletal, cardiometabolic, and immunologic co-morbidities that are present in chronic kidney disease (CKD). We performed a systematic review to investigate the effects of vitamin D supplementation, in the form of ergocalciferol or cholecalciferol, on various health outcomes in early CKD. Seventeen clinical trials were identified, only two of which were randomized, placebo controlled trials. The majority of studies supplementing with > 2,000 IU/day of cholecalciferol achieved optimal vitamin D status, whereas studies supplementing with ergocalciferol were less consistent. Studies varied widely in their effects on lowering serum parathyroid hormone concentrations. Few studies investigated effects of vitamin D treatment on other clinical health indicators in early CKD. Rigorous studies are necessary to investigate optimal vitamin D dosing strategies in early CKD for the maintenance of adequate vitamin D status, management of secondary hyperparathyroidism and improvement of non-skeletal related clinical outcomes.

The transcription factor network associated with the amino acid response in mammalian cells

Mammals exhibit multiple adaptive mechanisms that sense and respond to fluctuations in dietary nutrients. Consumption of reduced total dietary protein or a protein diet that is deficient in 1 or more of the essential amino acids triggers wide-ranging changes in feeding behavior and gene expression. At the level of individual cells, dietary protein deficiency is manifested as amino acid (AA) deprivation, which activates the AA response (AAR). The AAR is composed of a collection of signal transduction pathways that terminate in specific transcriptional programs designed to catalyze adaptation to the nutrient stress or, ultimately, undergo apoptosis. Independently of the AAR, endoplasmic reticulum stress activates 3 signaling pathways, collectively referred to as the unfolded protein response. The transcription factor activating transcription factor 4 is one of the terminal transcriptional mediators for both the AAR and the unfolded protein response, leading to a significant degree of overlap with regard to the target genes for these stress pathways. Over the past 5 y, research has revealed that the basic leucine zipper superfamily of transcription factors plays the central role in the AAR. Formation of both homo- and heterodimers among the activating transcription factor, CCAAT enhancer-binding protein, and FOS/JUN families of basic leucine zipper proteins forms the nucleus of a highly integrated transcription factor network that determines the initiation, magnitude, and duration of the cellular response to dietary protein or AA limitation.

Relative contributions of inflammation and inadequate protein intake to hypoalbuminemia in patients on maintenance hemodialysis

PURPOSE

Serum albumin is one of the strongest mortality predictors in maintenance hemodialysis (MHD) patients. Yet, the degree to which serum albumin represents dietary protein intake or an inflammatory state, among others, is not clear. We hypothesize that these inadequate protein intake and inflammation contribute somewhat equally to hypoalbuminemia.

METHODS

In a cross-sectional analysis, we examined correlates of low serum albumin, <3.8 g/dL, in 812 MHD patients in whom interleukin-6 (IL-6) and normalized protein nitrogen appearance (nPNA), also known as normalized protein catabolic rate (nPCR), were also measured. Logistic regression estimated odds ratios were employed, and spline models were plotted to examine the likelihood of relatively low serum albumin <3.8 g/dL.

RESULTS

Mean age (±SD) of patients was 54 ± 15 years; 53 % of patients were men, 50 % Hispanic, 31 % African-American, and 55 % diabetic. The mean dialysis vintage was 31 ± 34 months (median: 19, inter-quartile range: 7-44 months). The baseline serum albumin, averaged over a 3-month period (mean ± SD), was 3.88 ± 0.38 g/mL. The unadjusted correlation coefficients of l IL-6 and nPNA with serum albumin were -0.36 and +0.20, respectively (p < 0.001 for each comparison). The likelihood for an albumin <3.8 gr/dL increased linearly with decreasing nPNA and rising serum IL-6. This trend was steeper with increasing serum IL-6 up to a concentration of 30 ng/mL.

CONCLUSIONS

Both low protein intakes and a high state of inflammation are associated with low serum albumin in MHD patients.

Dialysis at a crossroads--Part II: A call for action

A previous commentary pointed out that the renal community has led American healthcare in the development and continuous improvement of quality outcomes. However, survival, hospitalization, and quality of life for US dialysis patients is still not optimal. This follow-up commentary examines the obstacles, gaps, and metrics that characterize this unfortunate state of affairs. It posits that current paradigms are essential contributors to quality outcomes but are no longer sufficient to improve quality. New strategies are needed that arise from a preponderance of evidence, in addition to beyond a reasonable doubt standard. This work offers an action plan that consists of new pathways of care that will lead to improved survival, fewer hospitalizations and rehospitalizations, and better quality of life for patients undergoing dialysis therapy. Nephrologists in collaboration with large and small dialysis organizations and other stakeholders, including the Centers for Medicare and Medicaid Services, can implement these proposed new pathways of care and closely monitor their effectiveness. We suggest that our patients deserve nothing less and must receive even more.

Protein energy wasting in chronic kidney disease: An update with focus on nutritional interventions to improve outcomes

Protein-energy wasting (PEW) is common in patients with chronic kidney disease (CKD). PEW is one of the strongest predictors of mortality in patients with CKD. The International Society of Renal Nutrition and Metabolism (ISRNM) expert panel has defined PEW as a, "state of decreased body stores of protein and energy fuels (body protein and fat masses)". The ISRNM panel has also proposed diagnostic criteria of PEW with four categories. Cachexia is a severe form of PEW. The proposed causes of PEW are multi-factorial and include nutritional and non-nutritional mechanisms. The literature indicates that PEW can be mitigated or corrected with an appropriate diet and enteral nutritional support that targets dietary protein intake. Dietary requirements and enteral nutritional support must also be considered in patients with CKD and diabetes mellitus and in children with CKD, in addition to dialysis patients. Features of ideal dietary supplement have also been discussed. Dietary interventions such as enteral feeding with high-protein meals or supplements might improve the nutritional status and outcomes in dialysis patients.

Timing of dialysis initiation in transplant-naive and failed transplant patients

Over the past two decades, most guidelines have advocated early initiation of dialysis on the basis of studies showing improved survival in patients starting dialysis early. These recommendations led to an increase in the proportion of patients initiating dialysis with an estimated glomerular filtration rate (eGFR) >10 ml/min/1.73 m(2), from 20% in 1996 to 52% in 2008. During this period, the percentage of patients starting dialysis with an eGFR ≥15 ml/min/1.73 m(2) increased from 4% to 17%. However, recent studies have failed to substantiate a benefit of early dialysis initiation and some data have suggested worse outcomes for patients starting dialysis with a higher eGFR. Several reasons for this seemingly paradoxical observation have been suggested, including the fact that patients requiring early dialysis are likely to have more severe symptoms and comorbidities, leading to confounding by indication, as well as biological mechanisms that causally relate early dialysis therapy to adverse outcomes. Patients with a failing renal allograft who reinitiate dialysis encounter similar problems. However, unique factors associated with a failed allograft means that the optimal timing of dialysis initiation in failed transplant patients might differ from that in transplant-naive patients with chronic kidney disease. In this Review, we discuss studies of dialysis initiation and compare risks and benefits of early versus late initiation and reinitiation of dialysis therapy.

Metabolic diversity of progressive kidney disease in 325 patients with type 1 diabetes (the FinnDiane Study)

Type 1 diabetic patients with varying severity of kidney disease were investigated to create multimetabolite models of the disease process. Urinary albumin excretion rate was measured for 3358 patients with type 1 diabetes. Prospective records were available for 1051 patients, of whom 163 showed progression of albuminuria (8.3-year follow-up), and 162 were selected as stable controls. At baseline, serum lipids, lipoprotein subclasses, and low-molecular weight metabolites were quantified by NMR spectroscopy (325 samples). The data were analyzed by the self-organizing map. In cross-sectional analyses, patients with no complications had low serum lipids, less inflammation, and better glycemic control, whereas patients with advanced kidney disease had high serum cystatin-C and sphingomyelin. These phenotype extremes shared low unsaturated fatty acids (UFAs) and phospholipids. Prospectively, progressive albuminuria was associated with high UFAs, phospholipids, and IDL and LDL lipids. Progression at longer duration was associated with high HDL lipids, whereas earlier progression was associated with poor glycemic control, increased saturated fatty acids (SFAs), and inflammation. Diabetic kidney disease consists of diverse metabolic phenotypes: UFAs, phospholipids, IDL, and LDL may be important in the subclinical phase, high SFAs and low HDL suggest accelerated progression, and the sphingolipid pathway in advanced kidney injury deserves further research.

Mineral and bone disorders and survival in hemodialysis patients with and without polycystic kidney disease

BACKGROUND

Maintenance hemodialysis (MHD) patients with polycystic kidney disease (PKD) have better survival than non-PKD patients. Mineral and bone disorders (MBD) are associated with accelerated atherosclerosis and cardiovascular death in MHD patients. It is unknown whether the different MBD mortality association between MHD populations with and without PKD can explain the survival differential.

METHODS

Survival models were examined to assess the association between different laboratory markers of MBD [such as serum phosphorous, parathyroid hormone (PTH), calcium and alkaline phosphatase] and mortality in a 6-year cohort of 60,089 non-PKD and 1501 PKD MHD patients.

RESULTS

PKD and non-PKD patients were 57±13 and 62±15 years old and included 46 and 45% women and 14 and 32% Blacks, respectively. Whereas PKD individuals with PTH 150 to <300 pg/mL (reference) had the lowest risk for mortality, the death risk was higher in patients with PTH<150 [hazard ratio (HR): 2.16 (95% confidence interval 1.53-3.06)], 300 to <600 [HR: 1.30 (0.97-1.74)] and ≥600 pg/mL [HR: 1.46 (1.02-2.08)], respectively. Similar patterns were found in non-PKD patients. Fully adjusted death HRs of time-averaged serum phosphorous increments<3.5, 5.5 to <7.5 and ≥7.5 mg/dL (reference: 3.5 to <5.5 mg/dL) for PKD patients were 2.82 (1.50-5.29), 1.40 (1.12-1.75) and 2.25 (1.57-3.22). The associations of alkaline phosphatase and calcium with mortality were similar in PKD and non-PKD patients.

CONCLUSION

Bone-mineral disorder markers exhibit similar mortality trends between PKD and non-PKD MHD patients, although some differences are observed in particular in low PTH and phosphorus ranges.

Serum albumin as a predictor of mortality in peritoneal dialysis: comparisons with hemodialysis

BACKGROUND

Serum albumin level predicts mortality in dialysis patients and is used to assess their health status and the quality of delivered care. Whether the threshold level of serum albumin at which mortality risk increases in peritoneal dialysis (PD) patients is the same as for hemodialysis (HD) patients has not been studied.

STUDY DESIGN

Observational cohort study of dialysis patients undertaken to determine the survival-predictability of serum albumin level in PD patients and compare it with that in HD patients.

SETTING & PARTICIPANTS

130,052 dialysis patients (PD, 12,171; HD, 117,851) who received treatment in any of the 580 dialysis units owned by DaVita Inc between July 1, 2001, through June 30, 2006, followed up through June 30, 2007.

PREDICTOR

Baseline and time-averaged serum albumin level (assayed using bromcresol green) and change in serum albumin level over 6 months.

OUTCOME MEASURES

All-cause, cardiovascular, and infection-related mortality.

RESULTS

PD patients with baseline serum albumin level <3.0 g/dL had a more than 3-fold higher adjusted risk of all-cause and cardiovascular mortality and 3.4-fold higher risk of infection-related mortality (reference group: serum albumin, 4.00-4.19 g/dL). Adjusted all-cause mortality was significantly lower in PD patients with a ≥0.3-g/dL increase in serum albumin level over 6 months and significantly higher in those for whom it decreased by ≥0.2 g/dL (reference group: serum albumin change, +0.1 to -0.1 g/dL). A significant increase in death risk was evident for HD patients with serum albumin level <4.0 g/dL, but at <3.8 g/dL for PD patients. For each albumin category, overall death risk for PD patients was lower than for HD patients (reference group: HD patients with serum albumin of 4.00-4.19 g/dL).

LIMITATIONS

Study can identify associations only without attribution of causality and residual confounding cannot be excluded.

CONCLUSIONS

Serum albumin predicts all-cause, cardiovascular, and infection-related mortality in both PD and HD patients. However, the threshold at which risk of death increases varies by dialysis modality, and this difference should be considered by agencies or organizations that set quality standards.