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Management of protein-energy wasting in non-dialysis-dependent chronic kidney disease: reconciling low protein intake with nutritional therapy.

ABSTRACT: Protein-energy wasting (PEW), characterized by a decline in body protein mass and energy reserves, including muscle and fat wasting and visceral protein pool contraction, is an underappreciated condition in early to moderate stages of chronic kidney disease (CKD) and a strong predictor of adverse outcomes. The prevalence of PEW in early to moderate CKD is ?20-25% and increases as CKD progresses, in part because of activation of proinflammatory cytokines combined with superimposed hypercatabolic states and declines in appetite. This anorexia leads to inadequate protein and energy intake, which may be reinforced by prescribed dietary restrictions and inadequate monitoring of the patient's nutritional status. Worsening uremia also renders CKD patients vulnerable to potentially deleterious effects of uncontrolled diets, including higher phosphorus and potassium burden. Uremic metabolites, some of which are anorexigenic and many of which are products of protein metabolism, can exert harmful effects, ranging from oxidative stress to endothelial dysfunction, nitric oxide disarrays, renal interstitial fibrosis, sarcopenia, and worsening proteinuria and kidney function. Given such complex pathways, nutritional interventions in CKD, when applied in concert with nonnutritional therapeutic approaches, encompass an array of strategies (such as dietary restrictions and supplementations) aimed at optimizing both patients' biochemical variables and their clinical outcomes. The applicability of many nutritional interventions and their effects on outcomes in patients with CKD with PEW has not been well studied. This article reviews the definitions and pathophysiology of PEW in patients with non-dialysis-dependent CKD, examines the current indications for various dietary modification strategies in patients with CKD (eg, manufactured protein-based supplements, amino acids and their keto acid or hydroxyacid analogues), discusses the rationale behind their potential use in patients with PEW, and highlights areas in need of further research.

SUBMITTER: Kovesdy CP

PROVIDER: S-EPMC3652918 | biostudies-literature | 2013 Jun

REPOSITORIES: biostudies-literature

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Management of protein-energy wasting in non-dialysis-dependent chronic kidney disease: reconciling low protein intake with nutritional therapy.

Kovesdy Csaba P CP Kopple Joel D JD Kalantar-Zadeh Kamyar K

The American journal of clinical nutrition 20130501 6

Protein-energy wasting (PEW), characterized by a decline in body protein mass and energy reserves, including muscle and fat wasting and visceral protein pool contraction, is an underappreciated condition in early to moderate stages of chronic kidney disease (CKD) and a strong predictor of adverse outcomes. The prevalence of PEW in early to moderate CKD is ≥20-25% and increases as CKD progresses, in part because of activation of proinflammatory cytokines combined with superimposed hypercatabolic ...[more]

PMID: 23636234

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Project description:Introduction:Depression comorbid with chronic disease may be mediated by inflammation. We sought to characterize relationships between inflammatory biomarkers and depressive symptoms in patients with chronic kidney disease and end-stage kidney disease. Methods:A systematic literature search was conducted by 2 authors up to March 19, 2019, for studies of patients with chronic kidney disease or end-stage kidney disease evaluating circulating inflammatory biomarkers associated with depression of chronic disease: albumin, C-reactive protein (CRP), high-sensitivity CRP, interleukin-6 (IL-6), tumor necrosis factor-?, and interleukin-1. Standardized mean differences in biomarkers between individuals with and without depression were computed and analyzed using mixed effects models. Correlations between biomarkers and the severity of depressive symptoms were computed. Results:Thirty-four studies (5652 participants) compared biomarkers between depressed and nondepressed individuals. Individuals with depression had lower albumin levels (standardized mean difference, -0.37; 95% confidence interval [CI], -0.61 to -0.13), higher CRP levels (standardized mean difference, 0.76; 95% CI, 0.16-1.37), and higher IL-6 levels (standardized mean difference, 0.42; 95% CI, 0.21-0.63). Studies were heterogeneous for albumin, CRP, high-sensitivity CRP, and tumor necrosis factor-?. Twenty-three studies (3047 participants) investigated correlations between biomarkers and depressive symptoms. The severity of depressive symptoms correlated with albumin (Z = -0.25; 95% CI, -0.36 to -0.14), high-sensitivity CRP (Z = 0.28; 95% CI, 0.13-0.43), and IL-6 (Z = 0.34; 95% CI, 0.18-0.49). There was heterogeneity across studies of IL-6. Only 6 studies (321 participants) investigated the effect of antidepressant treatment on inflammatory biomarkers, which was insufficient to combine in meta-analysis. Conclusion:Lower albumin and higher IL-6 were associated with both the presence and severity of depression, CRP with the presence of depression, and high-sensitivity CRP with the severity of depressive symptoms. The effect of interventions to lower inflammation in patients with kidney disease and depression deserves investigation.

Project description:BackgroundFour models are commonly used to adjust for energy intake when estimating the causal effect of a dietary component on an outcome: 1) the "standard model" adjusts for total energy intake, 2) the "energy partition model" adjusts for remaining energy intake, 3) the "nutrient density model" rescales the exposure as a proportion of total energy, and 4) the "residual model" indirectly adjusts for total energy by using a residual. It remains underappreciated that each approach evaluates a different estimand and only partially accounts for confounding by common dietary causes.ObjectivesWe aimed to clarify the implied causal estimand and interpretation of each model and evaluate their performance in reducing dietary confounding.MethodsSemiparametric directed acyclic graphs and Monte Carlo simulations were used to identify the estimands and interpretations implied by each model and explore their performance in the absence or presence of dietary confounding.ResultsThe "standard model" and the mathematically identical "residual model" estimate the average relative causal effect (i.e., a "substitution" effect) but provide biased estimates even in the absence of confounding. The "energy partition model" estimates the total causal effect but only provides unbiased estimates in the absence of confounding or when all other nutrients have equal effects on the outcome. The "nutrient density model" has an obscure interpretation but attempts to estimate the average relative causal effect rescaled as a proportion of total energy. Accurate estimates of both the total and average relative causal effects may instead be derived by simultaneously adjusting for all dietary components, an approach we term the "all-components model."ConclusionsLack of awareness of the estimand differences and accuracy of the 4 modeling approaches may explain some of the apparent heterogeneity among existing nutritional studies. This raises serious questions regarding the validity of meta-analyses where different estimands have been inappropriately pooled.

Dataset Information

Management of protein-energy wasting in non-dialysis-dependent chronic kidney disease: reconciling low protein intake with nutritional therapy.

Publications

Management of protein-energy wasting in non-dialysis-dependent chronic kidney disease: reconciling low protein intake with nutritional therapy.

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