Kidney Energetics and Cyst Burden in Autosomal Dominant Polycystic Kidney Disease: A Pilot Study

RATIONALE & OBJECTIVE

In this pilot study, we hypothesized that autosomal dominant polycystic kidney disease (ADPKD) is characterized by impaired kidney oxidative metabolism that associates with kidney size and cyst burden.

STUDY DESIGN

Cross-sectional study.

SETTING & PARTICIPANTS

Twenty adults with ADPKD (31±6 years of age, 65% women, BMI: 26.8 [22.7, 30.4] kg/m2, eGFR (2021 CKD-EPI Creatinine): 103±18 ml/min/1.73m2, height-adjusted total kidney volume [HtTKV]: 731±370 ml/m, Mayo Classifications: 1B [5%], 1C [42%], 1D [21%], 1E [32%]) and 11 controls in normal weight category (NWC; 25±3 years of age, 45% women, BMI: 22.5 [21.7, 24.2] kg/m2, eGFR: 113±15 ml/min/1.73m2, HtTKV: 159±31 ml/m) at the University of Colorado Anschutz Medical Campus.

PREDICTORS

ADPKD status (yes/no) and severity (Mayo Classifications).

OUTCOMES

HtTKV and cyst burden by MRI, kidney oxidative metabolism and perfusion by 11C-acetate PET/CT, insulin sensitivity by hyperinsulinemic-euglycemic clamps (presented as ratio of M-value of steady state insulin concentration [M/I]).

ANALYTICAL APPROACH

Chi-square/Fisher's exact tests used for categorical variables and t-tests/ Mann-Whitney U tests for continuous variables. Pearson correlation used to estimate the relationships between variables.

RESULTS

Compared to NWC, participants with ADPKD exhibited lower mean±SD M/I ratio (0.586±0.205 vs. 0.424±0.171 (mg/kg lean/min) / (μIU/mL), p=0.04), lower median [p25, p75] cortical perfusion (1.93 [1.80, 2.09 vs. 0.68 [0.47, 1.04] mL/min/g, p<0.001) and lower median [p25, p75] total kidney oxidative metabolism (0.17 [0.16,0.19] vs. 0.14 [0.12, 0.15] min-1, p=0.001) in voxel-wise models excluding cysts. HtTKV correlated inversely with cortical perfusion (r:-0.83, p<0.001), total kidney oxidative metabolism (r:-0.61, p<0.001) and M/I (r:-0.41, p=0.03).

LIMITATIONS

Small sample size and cross-sectional design.

CONCLUSION

Adults with ADPKD and preserved kidney function exhibited impaired renal perfusion and kidney oxidative metabolism across a wide range of cysts and kidney enlargements.

Polycystic Kidney Disease Diet: What is Known and What is Safe

Autosomal dominant polycystic kidney disease (ADPKD) is a genetic disorder characterized by kidney cyst formation and progressive kidney function loss. Dietary interventions such as caloric restriction, intermittent fasting, and ketogenic diet have recently emerged as potential strategies to induce metabolic reprogramming and slow ADPKD progression. We review the available evidence supporting the efficacy and safety of these interventions in ADPKD. Dietary interventions show promise in managing ADPKD by improving metabolic health and reducing oxidative stress. However, while preclinical studies have shown favorable outcomes, limited clinical evidence supports their effectiveness. In addition, the long-term consequences of these dietary interventions, including their effect on adverse events in patients with ADPKD, remain uncertain. To optimize ADPKD management, patients are advised to follow a dietary regimen that aims to achieve or maintain an ideal body weight and includes high fluid intake, low sodium, and limited concentrated sweets. Caloric restriction seems particularly beneficial for patients with overweight or obesity because it promotes weight loss and improves metabolic parameters. Supplementation with curcumin, ginkgolide B, saponins, vitamin E, niacinamide, or triptolide has demonstrated uncertain clinical benefit in patients with ADPKD. Notably, β -hydroxybutyrate supplements have shown promise in animal models; however, their safety and efficacy in ADPKD require further evaluation through well-designed clinical trials. Therefore, the use of these supplements is not currently recommended for patients with ADPKD. In summary, dietary interventions such as caloric restriction, intermittent fasting, and ketogenic diet hold promise in ADPKD management by enhancing metabolic health. However, extensive clinical research is necessary to establish their effectiveness and long-term effects. Adhering to personalized dietary guidelines, including weight management and specific nutritional restrictions, can contribute to optimal ADPKD management. Future research should prioritize well-designed clinical trials to determine the benefits and safety of dietary interventions and supplementation in ADPKD.

Immune checkpoint activity regulates polycystic kidney disease progression

Innate and adaptive immune cells modulate the severity of autosomal dominant polycystic kidney disease (ADPKD), a common kidney disease with inadequate treatment options. ADPKD has parallels with cancer, in which immune checkpoint inhibitors have been shown to reactivate CD8+ T cells and slow tumor growth. We have previously shown that in PKD, CD8+ T cell loss worsens disease. This study used orthologous early-onset and adult-onset ADPKD models (Pkd1 p.R3277C) to evaluate the role of immune checkpoints in PKD. Flow cytometry of kidney cells showed increased levels of programmed cell death protein 1 (PD-1)/cytotoxic T lymphocyte associated protein 4 (CTLA-4) on T cells and programmed cell death ligand 1 (PD-L1)/CD80 on macrophages and epithelial cells in Pkd1RC/RC mice versus WT, paralleling disease severity. PD-L1/CD80 was also upregulated in ADPKD human cells and patient kidney tissue versus controls. Genetic PD-L1 loss or treatment with an anti-PD-1 antibody did not impact PKD severity in early-onset or adult-onset ADPKD models. However, treatment with anti-PD-1 plus anti-CTLA-4, blocking 2 immune checkpoints, improved PKD outcomes in adult-onset ADPKD mice; neither monotherapy altered PKD severity. Combination therapy resulted in increased kidney CD8+ T cell numbers/activation and decreased kidney regulatory T cell numbers correlative with PKD severity. Together, our data suggest that immune checkpoint activation is an important feature of and potential novel therapeutic target in ADPKD.

The tryptophan-metabolizing enzyme indoleamine 2,3-dioxygenase 1 regulates polycystic kidney disease progression

Autosomal dominant polycystic kidney disease (ADPKD), the most common monogenic nephropathy, is characterized by phenotypic variability that exceeds genic effects. Dysregulated metabolism and immune cell function are key disease modifiers. The tryptophan metabolites, kynurenines, produced through indoleamine 2,3-dioxygenase 1 (IDO1), are known immunomodulators. Here, we study the role of tryptophan metabolism in PKD using an orthologous disease model (C57BL/6J Pkd1RC/RC). We found elevated kynurenine and IDO1 levels in Pkd1RC/RC kidneys versus wild type. Further, IDO1 levels were increased in ADPKD cell lines. Genetic Ido1 loss in Pkd1RC/RC animals resulted in reduced PKD severity, as measured by cystic index and percentage kidney weight normalized to body weight. Consistent with an immunomodulatory role of kynurenines, Pkd1RC/RC;Ido1-/- mice presented with significant changes in the cystic immune microenvironment (CME) versus controls. Kidney macrophage numbers decreased and CD8+ T cell numbers increased, both known PKD modulators. Also, pharmacological IDO1 inhibition in Pkd1RC/RC mice and kidney-specific Pkd2-knockout mice with rapidly progressive PKD resulted in less severe PKD versus controls, with changes in the CME similar to those in the genetic model. Our data suggest that tryptophan metabolism is dysregulated in ADPKD and that its inhibition results in changes to the CME and slows disease progression, making IDO1 a therapeutic target for ADPKD.

The Impact of Suboptimal 25-Hydroxyvitamin D Levels and Cholecalciferol Replacement on the Pharmacokinetics of Oral Midazolam in Control Subjects and Patients With Chronic Kidney Disease

The aim of this study was to investigate the impact of suboptimal 25-hydroxyvitamin D (25-VitD) and cholecalciferol (VitD3 ) supplementation on the pharmacokinetics of oral midazolam (MDZ) in control subjects and subjects with chronic kidney disease (CKD). Subjects with CKD (n = 14) and controls (n = 5) with suboptimal 25-VitD levels (<30 ng/mL) were enrolled in a 2-phase study. In phase 1 (suboptimal), subjects were administered a single oral dose of VitD3 (5000 IU) and MDZ (2 mg). In phase 2 (replete) subjects who achieved 25-VitD repletion after receiving up to 16 weeks of daily cholecalciferol were given the identical single oral doses of VitD3 and MDZ as in phase 1. Concentrations of MDZ and metabolites, 1'-hydroxymidazolam (1'-OHMDZ), and 1'-OHMDZ glucuronide (1'-OHMDZ-G) were measured by liquid chromatography-tandem mass spectrometry and pharmacokinetic analysis was performed. Under suboptimal 25-VitD, reductions in MDZ clearance and renal clearance of 47% and 87%, respectively, and a 72% reduction in renal clearance of 1'-OHMDZ-G were observed in CKD vs controls. In phase 1 versus phase 2, MDZ clearance increased in all control subjects, with a median (interquartile range) increase of 10.5 (0.62-16.7) L/h. No changes in MDZ pharmacokinetics were observed in subjects with CKD between phases 1 and 2. The effects of 25-VitD repletion on MDZ disposition was largely observed in subjects without kidney disease. Impaired MDZ metabolism and/or excretion alterations due to CKD in a suboptimal 25-VitD state may not be reversed by cholecalciferol therapy. Suboptimal 25-VitD may augment the reductions in MDZ and 1'-OHMDZ-G clearance values observed in patients with CKD.

Overweight and Obesity and Progression of ADPKD

BACKGROUND AND OBJECTIVES

On the basis of earlier observations, we evaluated the association between overweight and obesity and rapid progression of autosomal dominant polycystic kidney disease in participants in the Tolvaptan Efficacy and Safety in Management of Autosomal Dominant Polycystic Kidney Disease and Its Outcomes (TEMPO) 3:4 trial. More importantly, we also determined whether efficacy of tolvaptan was attenuated in individuals with baseline overweight or obesity.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A total of 1312 study participants with relatively early-stage autosomal dominant polycystic kidney disease (mean eGFR 78±22 ml/min per 1.73 m²) who were at high risk of rapid progression were categorized by body mass index (BMI; calculated using nonkidney weight) as normal weight (18.5-24.9 kg/m²; n=670), overweight (25.0-29.9 kg/m²; n=429), or obese (≥30 kg/m²; n=213). Linear and multinomial logistic regression models were used to determine the association of baseline overweight and obesity with change in total kidney volume (TKV) over the 3-year study period.

RESULTS

In fully adjusted models, higher BMI was associated with greater annual percent change in TKV (difference of 1.20 [95% confidence interval (95% CI), 0.85 to 1.55] per five-unit higher BMI). Overweight and obesity were associated with higher odds of annual percent change in TKV of ≥7% versus <5% (overweight: odds ratio, 2.04 [95% CI, 1.45 to 2.87]; obese: odds ratio, 4.31 [95% CI, 2.83 to 6.57] versus normal weight). eGFR decline did not differ according to BMI (fully adjusted difference in decline of -0.95 [95% CI, -2.32 to 0.40] ml/min per 1.73 m² per year per five-unit higher BMI). The three-way interaction (treatment×time×BMI group) was not statistically significant in linear mixed models with an outcome of TKV (log-transformed estimated coefficient comparing the treatment effect for overweight versus normal weight: 0.56% [95% CI, -0.70% to 1.84%] per year; P=0.38; obese versus normal weight: 0.07% [95% CI, -1.47% to 1.63%] per year; P=0.93) or eGFR (estimated coefficient comparing overweight versus normal weight: -0.07 [95% CI, -0.95 to 0.82] ml/min per 1.73 m² per year; P=0.88; obese versus normal weight: 0.22 [95% CI, -0.93 to 1.36] ml/min per 1.73 m² per year; P=0.71).

CONCLUSIONS

Overweight and particularly obesity are strongly and independently associated with kidney growth, but not eGFR slope, in the TEMPO 3:4 trial, and tolvaptan efficacy is irrespective of BMI categorization.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

Tolvaptan Efficacy and Safety in Management of Autosomal Dominant Polycystic Kidney Disease and Its Outcomes (TEMPO) 3:4, NCT00428948.

Kidney Functional Magnetic Resonance Imaging and Change in eGFR in Individuals with CKD

BACKGROUND AND OBJECTIVES

Kidney functional magnetic resonance imaging (MRI) requires further investigation to enhance the noninvasive identification of patients at high risk of CKD progression.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In this exploratory study, we obtained baseline diffusion-weighted and blood oxygen level-dependent MRI in 122 participants of the CKD Optimal Management with Binders and Nicotinamide trial, which was a multicenter, randomized, double-blinded, 12-month, four-group parallel trial of nicotinamide and lanthanum carbonate versus placebo conducted in individuals with eGFR 20-45 ml/min per 1.73 m². Lower values of apparent diffusion coefficient (ADC) on diffusion-weighted MRI may indicate increased fibrosis, and higher values of relaxation rate (R2*) on blood oxygen level-dependent MRI may represent decreased oxygenation. Because there was no effect of active treatment on eGFR over 12 months, we tested whether baseline kidney functional MRI biomarkers were associated with eGFR decline in all 122 participants. In a subset of 87 participants with 12-month follow-up MRI data, we evaluated whether kidney functional MRI biomarkers change over time.

RESULTS

Mean baseline eGFR was 32±9 ml/min per 1.73 m², and mean annual eGFR slope was -2.3 (95% confidence interval [95% CI], -3.4 to -1.1) ml/min per 1.73 m² per year. After adjustment for baseline covariates, baseline ADC was associated with change in eGFR over time (difference in annual eGFR slope per 1 SD increase in ADC: 1.3 [95% CI, 0.1 to 2.5] ml/min per 1.73 m² per year, ADC×time interaction P=0.04). This association was no longer significant after further adjustment for albuminuria (difference in annual eGFR slope per 1 SD increase in ADC: 1.0 (95% CI, -0.1 to 2.2) ml/min per 1.73 m² per year, ADC×time interaction P=0.08). There was no significant association between baseline R2* and change in eGFR over time. In 87 participants with follow-up functional MRI, ADC and R2* values remained stable over 12 months (intraclass correlation: 0.71 and 0.68, respectively).

CONCLUSIONS

Baseline cortical ADC was associated with change in eGFR over time, but this association was not independent of albuminuria. Kidney functional MRI biomarkers remained stable over 1 year.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

CKD Optimal Management with Binders and Nicotinamide (COMBINE), NCT02258074.

PTH, FGF23, and Intensive Blood Pressure Lowering in Chronic Kidney Disease Participants in SPRINT

BACKGROUND AND OBJECTIVES

The Systolic Blood Pressure Intervention Trial (SPRINT) demonstrated that intensive BP lowering reduced the risk of cardiovascular disease, but increased eGFR decline. Serum parathyroid hormone (PTH) and fibroblast growth factor-23 (FGF23) concentrations are elevated in CKD and are associated with cardiovascular disease. We evaluated whether intact PTH or intact FGF23 concentrations modify the effects of intensive BP control on cardiovascular events, heart failure, and all-cause mortality in SPRINT participants with CKD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We measured PTH and FGF23 in 2486 SPRINT participants with eGFR<60 ml/min per 1.73 m2 at baseline. Cox models were used to evaluate whether serum PTH and FGF23 concentrations were associated with cardiovascular events, heart failure, and all-cause mortality, and whether PTH and FGF23 modified the effects of intensive BP control.

RESULTS

The mean age of this subcohort was 73 years, 60% were men, and mean eGFR was 46±11 ml/min per 1.73 m2. Median PTH was 48 (interquartile range [IQR], 35-67) pg/ml and FGF23 was 66 (IQR, 52-88) pg/ml. There were 261 composite cardiovascular events, 102 heart failure events, and 179 deaths within the subcohort. The adjusted hazard ratio (HR) per doubling of PTH concentration for cardiovascular events, heart failure, and all-cause mortality were 1.29 (95% confidence interval [95% CI], 1.06 to 1.57), 1.32 (95% CI, 0.96 to 1.83), and 1.04 (95% CI, 0.82 to 1.31), respectively. There were significant interactions between PTH and BP arm for both the cardiovascular (P-interaction=0.01) and heart failure (P-interaction=0.004) end points. Participants with a PTH above the median experienced attenuated benefits of intensive BP control on cardiovascular events (adjusted HR, 1.02; 95% CI, 0.72 to 1.42) compared with participants with a PTH below the median (adjusted HR, 0.67; 95% CI, 0.45 to 1.00). FGF23 was not independently associated with any outcome and did not modify the effects of the intervention.

CONCLUSIONS

SPRINT participants with CKD and a high serum PTH received less cardiovascular protection from intensive BP therapy than participants with a lower serum PTH.

Effects of L-Carnitine on Mineral Metabolism in the Multicentre, Randomized, Double Blind, Placebo-Controlled CARNIDIAL Trial

BACKGROUND

The use of L-carnitine has been proposed in haemodialysis (HD) when deficiency is present to improve anaemia resistant to erythropoietin stimulating agent, intradialytic hypotension or cardiac failure. We tested the effects of L-carnitine supplementation on parameters of chronic kidney disease-mineral bone disorder.

METHODS

CARNIDIAL was a randomized, double-blinded trial having included 92 incident HD subjects for a 1-year period to receive L-carnitine versus placebo. Determinant factors of C-terminal fibroblast growth factor 23 (cFGF23) and intact FGF23 were studied including Klotho level. The L-carnitine effect on mineral metabolism was analyzed between groups by mixed linear models for repeated measurements.

RESULTS

Klotho was below the lower limit of quantification (LLOQ) in 55% of the 163 samples. In multivariate analysis, cFGF23 was positively correlated with calcium and phosphate and was higher in subjects having Klotho > LLOQ. No correlation existed between Klotho and phosphate and phosphate was even higher in subjects having Klotho > LLOQ (p < 0.001). Both forms of FGF23 were not related to iron markers nor to IV iron dose. No L-carnitine effect was detected on parathyroid hormone (PTH) or FGF23 during the study period where PTH slightly decreased over time, whereas FGF23 increased. But calcium and phosphate increased more in the L-carnitine group.

CONCLUSION

L-carnitine supplementation increased calcium and phosphate plasma concentrations with no detected downregulation effect on PTH and FGF23. (Clinical Trial 00322322, May 5, 2006).

CD8+ T cells modulate autosomal dominant polycystic kidney disease progression

Autosomal dominant polycystic kidney disease (ADPKD) is the most prevalent inherited nephropathy. To date, therapies alleviating the disease have largely focused on targeting abnormalities in renal epithelial cell signaling. ADPKD has many hallmarks of cancer, where targeting T cells has brought novel therapeutic interventions. However, little is known about the role and therapeutic potential of T cells in ADPKD. Here, we used an orthologous ADPKD model, Pkd1 p.R3277C (RC), to begin to define the role of T cells in disease progression. Using flow cytometry, we found progressive increases in renal CD8⁺ and CD4⁺ T cells, correlative with disease severity, but with selective activation of CD8⁺ T cells. By immunofluorescence, T cells specifically localized to cystic lesions and increased levels of T-cell recruiting chemokines (CXCL9/CXCL10) were detected by qPCR/in situ hybridization in the kidneys of mice, patients, and ADPKD epithelial cell lines. Importantly, immunodepletion of CD8⁺ T cells from one to three months in C57Bl/6 Pkd1^RC/RC mice resulted in worsening of ADPKD pathology, decreased apoptosis, and increased proliferation compared to IgG-control, consistent with a reno-protective role of CD8⁺ T cells. Thus, our studies suggest a functional role for T cells, specifically CD8⁺ T cells, in ADPKD progression. Hence, targeting this pathway using immune-oncology agents may represent a novel therapeutic approach for ADPKD.

Curcumin supplementation and motor-cognitive function in healthy middle-aged and older adults

BACKGROUND:

Recent studies suggest curcumin is a promising nutraceutical for improving important clinical and physiological markers of healthy aging, including motor and cognitive function.

OBJECTIVE:

To determine if curcumin supplementation improves motor and cognitive function in healthy middle-aged and older adults.

METHODS:

39 healthy men and postmenopausal women (45–74 yrs) were randomized to 12 weeks of placebo (n = 19) or curcumin supplementation (2000 mg/day Longvida^®; n = 20) with motor and cognitive function assessed at week 0 and 12.

RESULTS:

Using measures of the NIH Toolbox and other standardized tests, there were no changes in muscle strength and rate of torque development, dexterity, fatigability, mobility, endurance, and balance between the placebo and curcumin groups after 12 weeks (all P > 0.05). Additionally, there were no changes after 12 weeks of placebo and curcumin supplementation in measures of fluid cognitive ability, a cognitive domain that declines with age, including processing speed, executive function, working memory, and episodic memory (all P > 0.3). There were marginal changes in language, a measure of crystallized cognitive ability that is stable with age, following the intervention, wherein reading decoding increased 3% in the curcumin group (post: 2428±35 vs. pre: 2357±34, P = 0.003), but was unchanged in the placebo group (post: 2334±39 vs. pre: 2364±40, P = 0.07).

CONCLUSIONS:

Overall, 12 weeks of curcumin supplementation does not improve motor and cognitive functions in healthy middle-aged and older adults. It is possible that curcumin may enhance these functions in groups with greater baseline impairments than those studied here, including adults greater than 75 years of age and/or patients with clinical disorders.

Serum Bicarbonate Concentration and Cognitive Function in Hypertensive Adults

BACKGROUND AND OBJECTIVES

Cognitive function worsens as kidney function declines, but mechanisms contributing to this association are not completely understood. Metabolic acidosis, a common complication of CKD, leads to neural networks overexcitation and is involved in cerebral autoregulation. We aimed to evaluate the association between serum bicarbonate concentration as a measure of metabolic acidosis, and cognitive function in hypertensive adults with and without CKD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Five cognitive summary scores were measured (global cognitive function, executive function, memory, attention/concentration, and language) in 2853 participants in the Systolic BP Intervention Trial (SPRINT). Multivariable linear regression models adjusted for demographics, comorbidities, systolic BP, medications, eGFR and albuminuria evaluated the cross-sectional association between bicarbonate and cognition at SPRINT baseline. In a subset (n=681) who underwent brain magnetic resonance imaging, the models were adjusted for white matter hyperintensity volume, vascular reactivity, and cerebral blood flow.

RESULTS

The mean age (SD) was 68 (8.5) years. Global cognitive and executive functions were positively associated with serum bicarbonate (estimate [SEM]: 0.014 [0.006]; P=0.01, and 0.018 [0.006]; P=0.003, respectively). Each 1 mEq/L lower bicarbonate level had a similar association with global cognitive and executive function as being 4.3 and 5.4 months older, respectively. The association with global cognition persisted after magnetic resonance imaging findings adjustment (estimate [SEM]: 0.03 [0.01]; P=0.01). There was no association between serum bicarbonate level and memory, attention/concentration, and language.

CONCLUSIONS

In a large cohort of hypertensive adults, higher serum bicarbonate levels were independently associated with better global cognitive and executive performance. (ClinicalTrials.gov: NCT01206062).

Hyperuricemia, Acute and Chronic Kidney Disease, Hypertension, and Cardiovascular Disease: Report of a Scientific Workshop Organized by the National Kidney Foundation

Urate is a cause of gout, kidney stones, and acute kidney injury from tumor lysis syndrome, but its relationship to kidney disease, cardiovascular disease, and diabetes remains controversial. A scientific workshop organized by the National Kidney Foundation was held in September 2016 to review current evidence. Cell culture studies and animal models suggest that elevated serum urate concentrations can contribute to kidney disease, hypertension, and metabolic syndrome. Epidemiologic evidence also supports elevated serum urate concentrations as a risk factor for the development of kidney disease, hypertension, and diabetes, but differences in methodologies and inpacts on serum urate concentrations by even subtle changes in kidney function render conclusions uncertain. Mendelian randomization studies generally do not support a causal role of serum urate in kidney disease, hypertension, or diabetes, although interpretation is complicated by nonhomogeneous populations, a failure to consider environmental interactions, and a lack of understanding of how the genetic polymorphisms affect biological mechanisms related to urate. Although several small clinical trials suggest benefits of urate-lowering therapies on kidney function, blood pressure, and insulin resistance, others have been negative, with many trials having design limitations and insufficient power. Thus, whether uric acid has a causal role in kidney and cardiovascular diseases requires further study.

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

Introduction

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

Methods

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

Results

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

Discussion

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

Curcumin supplementation improves vascular endothelial function in healthy middle-aged and older adults by increasing nitric oxide bioavailability and reducing oxidative stress

We hypothesized that curcumin would improve resistance and conduit artery endothelial function and large elastic artery stiffness in healthy middle-aged and older adults. Thirty-nine healthy men and postmenopausal women (45-74 yrs) were randomized to 12 weeks of curcumin (2000 mg/day Longvida®; n=20) or placebo (n=19) supplementation. Forearm blood flow response to acetylcholine infusions (FBF_ACh; resistance artery endothelial function) increased 37% following curcumin supplementation (107±13 vs. 84±11 AUC at baseline, P=0.03), but not placebo (P=0.2). Curcumin treatment augmented the acute reduction in FBF_ACh induced by the nitric oxide synthase inhibitor NG monomethyl-L-arginine (L-NMMA; P=0.03), and reduced the acute increase in FBF_ACh to the antioxidant vitamin C (P=0.02), whereas placebo had no effect (both P>0.6). Similarly, brachial artery flow-mediated dilation (conduit artery endothelial function) increased 36% in the curcumin group (5.7±0.4 vs. 4.4±0.4% at baseline, P=0.001), with no change in placebo (P=0.1). Neither curcumin nor placebo influenced large elastic artery stiffness (aortic pulse wave velocity or carotid artery compliance) or circulating biomarkers of oxidative stress and inflammation (all P>0.1). In healthy middle-aged and older adults, 12 weeks of curcumin supplementation improves resistance artery endothelial function by increasing vascular nitric oxide bioavailability and reducing oxidative stress, while also improving conduit artery endothelial function.

Serum Bicarbonate Is Associated with Heart Failure in the Multi-Ethnic Study of Atherosclerosis

BACKGROUND

Low serum bicarbonate concentrations are associated with mortality and kidney disease progression. Data regarding associations between bicarbonate and cardiovascular disease (CVD) are scarce.

METHODS

We performed a cohort study of 6,229 adult participants from the Multi-Ethnic Study of Atherosclerosis, a community-based cohort free of CVD at baseline. Serum bicarbonate was measured at baseline. Cardiovascular outcomes were defined as: (1) subclinical CVD (left ventricular mass [LVM] and aortic pulse pressure [PP] measured at baseline), (2) incident atherosclerotic cardiovascular events (CVE; composite of myocardial infarction, resuscitated cardiac arrest, stroke, coronary heart disease death, and stroke death), and (3) incident heart failure.

RESULTS

During a median (interquartile range) follow-up of 8.5 (7.7-8.6) years, 331 (5.3%) participants had an incident CVE and 174 (2.8%) developed incident heart failure. We stratified analyses by use of diuretics because we observed a significant interaction between diuretic use and bicarbonate with study outcomes. Among diuretic nonusers, with adjustment, bicarbonate ≥25 mEq/L was associated with an estimated 3.0 g greater LVM (95% CI 0.5-5.0) and 1.0 mm Hg higher aortic PP (95% CI 0.4-2.0) compared to bicarbonate 23-24 mEq/L. Each 1 mEq/L of bicarbonate increase was associated with a 13% higher risk of incident heart failure (hazards ratio 1.13, 95% CI 1.01-2.11). Among diuretic users, higher bicarbonate was not associated with CVD. Bicarbonate was not associated with incident atherosclerotic CVE irrespective of diuretic use.

CONCLUSION

Among nonusers of diuretics in a large community-based study, higher serum bicarbonate concentrations are associated with subclinical CVD and new heart failure.

Improved motor and cognitive performance with sodium nitrite supplementation is related to small metabolite signatures: a pilot trial in middle-aged and older adults

Advancing age is associated with reductions in nitric oxide bioavailability and changes in metabolic activity, which are implicated in declines in motor and cognitive function. In preclinical models, sodium nitrite supplementation (SN) increases plasma nitrite and improves motor function, whereas other nitric oxide-boosting agents improve cognitive function. This pilot study was designed to translate these findings to middle-aged and older (MA/O) humans to provide proof-of-concept support for larger trials. SN (10 weeks, 80 or 160 mg/day capsules, TheraVasc, Inc.) acutely and chronically increased plasma nitrite and improved performance on measures of motor and cognitive outcomes (all p<0.05 or better) in healthy MA/O adults (62 ± 7 years). Untargeted metabolomics analysis revealed that SN significantly altered 33 (160 mg/day) to 45 (80 mg/day) different metabolites, 13 of which were related to changes in functional outcomes; baseline concentrations of 99 different metabolites predicted functional improvements with SN. This pilot study provides the first evidence that SN improves aspects of motor and cognitive function in healthy MA/O adults, and that these improvements are associated with, and predicted by, the plasma metabolome. Our findings provide the necessary support for larger clinical trials on this promising pharmacological strategy for preserving physiological function with aging.

Long-Term Outcomes in Patients with Very-Early Onset Autosomal Dominant Polycystic Kidney Disease

BACKGROUND

Long-term clinical outcomes in children with very-early onset (VEO; diagnosis in utero or within the first 18 months of life) autosomal dominant polycystic kidney disease (ADPKD) are currently not well understood. We conducted a longitudinal retrospective cohort study to assess the association between VEO status and adverse clinical outcomes.

METHODS

Seventy patients with VEO-ADPKD matched (by year of birth, sex and race/ethnicity) to 70 patients with non-VEO-ADPKD who participated in research at the University of Colorado were studied. Kaplan-Meier survival analysis was performed. The predictor was VEO status, and outcomes were progression to end-stage renal disease (ESRD), development of hypertension, progression to estimated glomerular filtration rate (eGFR <90 ml/min/1.73 m2), glomerular hyperfiltration (eGFR ≥140 ml/min/1.73 m2) and height-adjusted total kidney volume (htTKV) measured by MRI ≥600 ml/m.

RESULTS

Median follow-up was until 16.0 years of age. There were only 4 ESRD events during the follow-up period, all in the VEO group (p < 0.05). VEO patients were more likely to develop hypertension (hazard ratio, HR 3.15, 95% CI 1.86-5.34; p < 0.0001) and to progress to eGFR <90 ml/min/1.73 m2 (HR 1.97, 95% CI 1.01-3.84; p < 0.05) than non-VEO patients. There was no difference between groups in the development of glomerular hyperfiltration (HR 0.89, 95% CI 0.56-1.42; p = 0.62). There were only 7 patients who progressed to htTKV ≥600 ml/m, 4 in the VEO group and 3 in the non-VEO group (p < 0.01).

CONCLUSIONS

Several clinical outcomes are worse in patients with VEO-ADPKD compared to non-VEO ADPKD. Children with VEO-ADPKD represent a particularly high-risk group of ADPKD patients.

Mineral Metabolites, Angiotensin II Inhibition and Outcomes in Advanced Chronic Kidney Disease

BACKGROUND

Evidence suggests that the renin-angiotensin-aldosterone system (RAAS) interacts with the vitamin D-fibroblast growth factor 23-Klotho axis. We investigated whether circulating mineral metabolism markers modify outcomes in response to RAAS inhibition in subjects with advanced chronic kidney disease (CKD).

METHODS

In this retrospective cohort study, we analyzed the association of angiotensin-converting enzyme inhibitor (ACEI) and angiotensin receptor blocker (ARB) use with all-cause mortality and dialysis initiation among 1,753 subjects (1,099 CKD, estimated glomerular filtration rate 18 ± 6 ml/min/1.73 m(2) and 654 end-stage renal disease [ESRD]) from the Homocysteine in Kidney and End Stage Renal Disease (HOST) study. A propensity score analysis accounted for indication bias and Cox regression models adjusted for mineral metabolism markers.

RESULTS

Mean follow-up was 3.2 years; 714 (41%) subjects died and 615 (56%) initiated dialysis. In adjusted analyses, all subjects treated with ACEI/ARB had a significantly lower hazard of death (hazards ratio (HR) 0.81, 95% CI 0.70-0.95, p = 0.007). Those with CKD not on dialysis and treated with ACEI/ARB trended toward a lower hazard of dialysis initiation (HR 0.86, 95% CI 0.73-1.01, p = 0.06). The association with mortality did not differ by level of mineral metabolism marker (p for interaction >0.16); however, the relationship with dialysis initiation differed according to the median serum phosphorus level (p for interaction <0.001).

CONCLUSIONS

RAAS inhibition was associated with decreased all-cause mortality independent of disordered mineral metabolism among mostly male HOST subjects with advanced CKD and ESRD. However, among those with CKD not requiring dialysis, the renoprotection associated with RAAS inhibition was attenuated by higher serum phosphorus levels. Further studies are needed to confirm this association.

Effects of sodium nitrite supplementation on vascular function and related small metabolite signatures in middle-aged and older adults

Insufficient nitric oxide (NO) bioavailability plays an important role in endothelial dysfunction and arterial stiffening with aging. Supplementation with sodium nitrite, a precursor of NO, ameliorates age-related vascular endothelial dysfunction and arterial stiffness in mice, but effects on humans, including the metabolic pathways altered, are unknown. The purpose of this study was to determine the safety, feasibility, and efficacy of oral sodium nitrite supplementation for improving vascular function in middle-aged and older adults and to identify related circulating metabolites. Ten weeks of sodium nitrite (80 or 160 mg/day, capsules, TheraVasc; randomized, placebo control, double blind) increased plasma nitrite acutely (5- to 15-fold, P < 0.001 vs. placebo) and chronically (P < 0.10) and was well tolerated without symptomatic hypotension or clinically relevant elevations in blood methemoglobin. Endothelial function, measured by brachial artery flow-mediated dilation, increased 45-60% vs. baseline (P < 0.10) without changes in body mass or blood lipids. Measures of carotid artery elasticity (ultrasound and applanation tonometry) improved (decreased β-stiffness index, increased cross-sectional compliance, P < 0.05) without changes in brachial or carotid artery blood pressure. Aortic pulse wave velocity was unchanged. Nitrite-induced changes in vascular measures were significantly related to 11 plasma metabolites identified by untargeted analysis. Baseline abundance of multiple metabolites, including glycerophospholipids and fatty acyls, predicted vascular changes with nitrite. This study provides evidence that sodium nitrite supplementation is well tolerated, increases plasma nitrite concentrations, improves endothelial function, and lessens carotid artery stiffening in middle-aged and older adults, perhaps by altering multiple metabolic pathways, thereby warranting a larger clinical trial.

CKD and nonalcoholic fatty liver disease

The possible link between nonalcoholic fatty liver disease and chronic kidney disease (CKD) recently has attracted considerable scientific interest. Accumulating clinical evidence indicates that the presence and severity of nonalcoholic fatty liver disease is associated significantly with CKD (defined as decreased estimated glomerular filtration rate and/or proteinuria) and that nonalcoholic fatty liver disease predicts the development and progression of CKD, independently of traditional cardiorenal risk factors. Experimental evidence also suggests that nonalcoholic fatty liver disease itself may exacerbate systemic and hepatic insulin resistance, cause atherogenic dyslipidemia, and release a variety of proinflammatory, procoagulant, pro-oxidant, and profibrogenic mediators that play important roles in the development and progression of CKD. However, despite the growing evidence linking nonalcoholic fatty liver disease with CKD, it has not been definitively established whether a causal association exists. The clinical implication for these findings is that patients with nonalcoholic fatty liver disease may benefit from more intensive surveillance or early treatment interventions to decrease the risk of CKD. In this review, we discuss the evidence linking nonalcoholic fatty liver disease with CKD and the putative mechanisms by which nonalcoholic fatty liver disease contributes to kidney damage. We also briefly discuss current treatment options for this increasingly prevalent disease that is likely to have an important future impact on the global burden of disease.

Serum uric acid and insulin sensitivity in adolescents and adults with and without type 1 diabetes

HYPOTHESIS

Decreased insulin sensitivity (IS) exists in type 1 diabetes. Serum uric acid (SUA), whose concentration is related to renal clearance, predicts vascular complications in type 1 diabetes. SUA is also inversely associated with IS in non-diabetics, but has not been examined in type 1 diabetes. We hypothesized SUA would be associated with reduced IS in adolescents and adults with type 1 diabetes.

METHODS

The cross-sectional and longitudinal associations of SUA with IS were investigated in 254 adolescents with type 1 diabetes and 70 without in the Determinants of Macrovascular Disease in Adolescents with Type 1 Diabetes Study, and in 471 adults with type 1 diabetes and 571 without in the Coronary Artery Calcification in Type 1 diabetes (CACTI) study.

RESULTS

SUA was lower in subjects with type 1 diabetes (p<0.0001), but still remained inversely associated with IS after multivariable adjustments in adolescents (β±SE: -1.99±0.62, p=0.001, R2 =2%) and adults (β±SE: -0.91±0.33, p=0.006, R2 = 6%) with type 1 diabetes, though less strongly than in non-diabetic controls (adolescents: β±SE: -2.70±1.19, p=0.03, R2 = 15%, adults: β±SE: -5.99±0.75, p<0.0001, R2 =39%).

CONCLUSION

We demonstrated a significantly weaker relationship between SUA and reduced IS in subjects with type 1 diabetes than non-diabetic controls.

Serum uric acid and hypertension in adults: a paradoxical relationship in type 1 diabetes

Adults with type 1 diabetes have lower serum uric acid levels compared with nondiabetic adults. Little is known about the relationship between serum uric acid and blood pressure in type 1 diabetes and whether it differs from the positive relationship found in nondiabetic adults. The authors assessed the cross-sectional and longitudinal relationships over 6 years between serum uric acid and blood pressure in adults with (35±9 years [n=393]) and without (38±9 years [n=685]) type 1 diabetes in the Coronary Artery Calcification in Type 1 Diabetes study. In nondiabetic adults, serum uric acid was associated with systolic blood pressure in multivariable models adjusted for cardiovascular risk factors. In adults with type 1 diabetes, a negative association was observed between serum uric acid and systolic blood pressure after multivariable adjustments. A positive association was observed between serum uric acid and systolic blood pressure in nondiabetic adults. In contrast, an inverse relationship was demonstrated after multivariable adjustments in type 1 diabetes.

Fibroblast growth factor 23, the ankle-brachial index, and incident peripheral artery disease in the Cardiovascular Health Study

BACKGROUND

Fibroblast growth factor 23 (FGF23) has emerged as a novel risk factor for mortality and cardiovascular events. Its association with the ankle-brachial index (ABI) and clinical peripheral artery disease (PAD) is less known.

METHODS

Using data (N = 3143) from the Cardiovascular Health Study (CHS), a cohort of community dwelling adults >65 years of age, we analyzed the cross-sectional association of FGF23 with ABI and its association with incident clinical PAD events during 9.8 years of follow up using multinomial logistic regression and Cox proportional hazards models respectively.

RESULTS

The prevalence of cardiovascular disease (CVD) and traditional risk factors like diabetes, coronary artery disease, and heart failure increased across higher quartiles of FGF23. Compared to those with ABI of 1.1-1.4, FGF23 per doubling at baseline was associated with prevalent PAD (ABI < 0.9) although this association was attenuated after adjusting for CVD risk factors, and kidney function (OR 0.91, 95% CI 0.76-1.08). FGF23 was not associated with high ABI (>1.4) (OR 1.06, 95% CI 0.75-1.51). Higher FGF23 was associated with incidence of PAD events in unadjusted, demographic adjusted, and CVD risk factor adjusted models (HR 2.26, 95% CI 1.28-3.98; highest versus lowest quartile). The addition of estimated glomerular filtration and urine albumin to creatinine ratio to the model however, attenuated these findings (HR 1.46, 95% CI, 0.79-2.70).

CONCLUSIONS

In community dwelling older adults, FGF23 was not associated with baseline low or high ABI or incident PAD events after adjusting for confounding variables. These results suggest that FGF23 may primarily be associated with adverse cardiovascular outcomes through non atherosclerotic mechanisms.

Early diabetic nephropathy: a complication of reduced insulin sensitivity in type 1 diabetes

OBJECTIVE

Diabetic nephropathy (DN) is a major cause of mortality in type 1 diabetes. Reduced insulin sensitivity is a well-documented component of type 1 diabetes. We hypothesized that baseline insulin sensitivity would predict development of DN over 6 years.

RESEARCH DESIGN AND METHODS

We assessed the relationship between insulin sensitivity at baseline and development of early phenotypes of DN-microalbuminuria (albumin-creatinine ratio [ACR] ≥30 mg/g) and rapid renal function decline (glomerular filtration rate [GFR] loss >3 mL/min/1.73 m2 per year)-with three Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations over 6 years. Subjects with diabetes (n = 449) and without diabetes (n = 565) in the Coronary Artery Calcification in Type 1 Diabetes study had an estimated insulin sensitivity index (ISI) at baseline and 6-year follow-up.

RESULTS

The ISI was lower in subjects with diabetes than in those without diabetes (P < 0.0001). A higher ISI at baseline predicted a lower odds of developing an ACR ≥30 mg/g (odds ratio 0.65 [95% CI 0.49-0.85], P = 0.003) univariately and after adjusting for HbA1c (0.69 [0.51-0.93], P = 0.01). A higher ISI at baseline conferred protection from a rapid decline of GFR as assessed by CKD-EPI cystatin C (0.77 [0.64-0.92], P = 0.004) and remained significant after adjusting for HbA1c and age (0.80 [0.67-0.97], P = 0.02). We found no relation between ISI and rapid GFR decline estimated by CKD-EPI creatinine (P = 0.38) or CKD-EPI combined cystatin C and creatinine (P = 0.50).

CONCLUSIONS

Over 6 years, a higher ISI independently predicts a lower odds of developing microalbuminuria and rapid GFR decline as estimated with cystatin C, suggesting a relationship between insulin sensitivity and early phenotypes of DN.

Calcification of the abdominal aorta as an independent predictor of cardiovascular events: a meta-analysis

CONTEXT

Abdominal aortic calcification (AAC) is a common finding in patients with atherosclerosis.

OBJECTIVE

The aim of this study was to demonstrate the incremental value of AAC in predicting long term cardiovascular (CV) outcome by conducting a meta-analysis of observational studies.

DATA SOURCES

MEDLINE and Cochrane databases.

STUDY SELECTION

Longitudinal studies with at least 2 years of follow-up, reporting the influence of AAC on CV outcome of general population patients.

DATA EXTRACTION

Four separate end points-coronary events, cerebrovascular events, all CV events and CV related death-were tested for their relationship with AAC at baseline, using weighted random effects meta-analysis. Heterogeneity was calculated using Q and I(2) statistic tests. Publication bias was assessed by funnel plot symmetry and trim and fill methods. The importance of calcium quantification was also explored (sensitivity analysis).

RESULTS

10 studies were included. An increased relative risk (RR) was found for all end points: for coronary events (five studies, n=11250) 1.81 (95% CI 1.54 to 2.14); for cerebrovascular events (four studies, n=9736) 1.37 (1.22 to 3.54); for all CV events (four studies, n=4960) 1.64 (1.24 to 2.17); and for CV death (three studies, n=4986) 1.72 (1.03 to 2.86). Analysis of studies presenting results in categories (no/minimal, moderate and severe calcification) revealed a stepwise increase in the RR for all end points. Significant heterogeneity was found in the included studies. Sources of heterogeneity were identified in the publication date, duration of follow-up, and mean age and gender differences in the included patient cohorts.

CONCLUSION

Existing data suggest that AAC is a strong predictor of CV related events or death in the general population. The predictive impact is greater in more calcified aortas. The generalisability of the meta-analysis is limited by heterogeneity in the coronary events, all CV events and CV death end points.

Insulin resistance, cystatin C, and mortality among older adults

OBJECTIVE

Insulin resistance is a risk factor for cardiovascular and noncardiovascular diseases. Impaired kidney function is linked with insulin resistance and may affect relationships of insulin resistance with health outcomes.

RESEARCH DESIGN AND METHODS

We performed a cohort study of 3,138 Cardiovascular Health Study participants (age ≥ 65 years) without diabetes. Insulin sensitivity index (ISI) was calculated from fasting and 2-h postload insulin and glucose concentrations. Associations of ISI and fasting insulin concentration with all-cause mortality were tested using Cox proportional hazards models, adjusting for demographic variables, prevalent cardiovascular disease, lifestyle variables, waist circumference, and LDL cholesterol. Subsequent models were additionally adjusted for or stratified by glomerular filtration rate estimated using serum cystatin C (eGFR).

RESULTS

A total of 1,810 participants died during the 14.7-year median follow-up. Compared with the highest quartile of ISI, the lowest quartile (most insulin resistant) was associated with 21% (95% CI 6-41) and 11% (-3 to 29) higher risks of death without and with adjustment for eGFR, respectively. Compared with the lowest quartile of fasting insulin concentration, the highest quartile was associated with 22% (4-43) and 4% (-12 to 22) higher risks of death without and with adjustment for eGFR, respectively. Similar attenuation by eGFR was observed when blood pressure, triglycerides, HDL cholesterol, and C-reactive protein were included in models.

CONCLUSIONS

Insulin resistance measured as ISI or fasting insulin concentration is associated with increased risk of death among older adults, adjusting for conventional confounding characteristics. Impaired kidney function may mediate or confound this relationship.

High dietary fiber intake is associated with decreased inflammation and all-cause mortality in patients with chronic kidney disease

Chronic kidney disease is considered an inflammatory state and a high fiber intake is associated with decreased inflammation in the general population. Here, we determined whether fiber intake is associated with decreased inflammation and mortality in chronic kidney disease, and whether kidney disease modifies the associations of fiber intake with inflammation and mortality. To do this, we analyzed data from 14,543 participants in the National Health and Nutrition Examination Survey III. The prevalence of chronic kidney disease (estimated glomerular filtration rate less than 60 ml/min per 1.73 m(2)) was 5.8%. For each 10-g/day increase in total fiber intake, the odds of elevated serum C-reactive protein levels were decreased by 11% and 38% in those without and with kidney disease, respectively. Dietary total fiber intake was not significantly associated with mortality in those without but was inversely related to mortality in those with kidney disease. The relationship of total fiber with inflammation and mortality differed significantly in those with and without kidney disease. Thus, high dietary total fiber intake is associated with lower risk of inflammation and mortality in kidney disease and these associations are stronger in magnitude in those with kidney disease. Interventional trials are needed to establish the effects of fiber intake on inflammation and mortality in kidney disease.

Nontraditional risk factors for cardiovascular disease in patients with chronic kidney disease

Patients with chronic kidney disease (CKD) have a reduced lifespan, and a substantial proportion of these individuals die from cardiovascular disease. Although a large percentage of patients with CKD have traditional cardiac risk factors such as diabetes, hypertension and abnormalities in cholesterol, interventions to address these factors--which have significantly decreased cardiovascular mortality in the general population--have not shown such benefit in the CKD population. In addition, the severity and extent of cardiovascular complications in patients with CKD is disproportionate to the number and severity of traditional risk factors. This realization has focused attention on nontraditional cardiac risk factors that are particularly relevant to patients with CKD, including decreased hemoglobin levels, microalbuminuria, increased inflammation and oxidative stress, and abnormalities in bone and mineral metabolism. However, large prospective trials in patients with advanced CKD or in those requiring chronic dialysis have not shown that normalization of these nontraditional risk factors improves survival. Moreover, the mechanisms by which these nontraditional risk factors contribute to cardiovascular disease are unknown. Therefore, although current treatment of patients with CKD includes management of traditional and nontraditional risk factors, the value of modifying some nontraditional risk factors remains unclear.

Long-term outcomes after coronary artery bypass grafting: Preoperative kidney function is prognostic

OBJECTIVE

End-stage renal disease is an independent predictor of mortality after coronary artery bypass grafting. Limited information exists, however, regarding the impact of chronic kidney disease on long-term outcome after bypass grafting. The purpose of this study was to assess the impact of kidney function on long-term outcomes in patients undergoing coronary artery bypass grafting.

METHODS

We studied 931 consecutive patients undergoing coronary artery bypass grafting in a single center. Demographic and clinical data were collected preoperatively. Chronic kidney disease was defined preoperatively according to the Modification of Diet in Renal Disease equation as an estimated glomerular filtration rate less than 60 mL x min(-1) x 1.73 m(-2). Multivariate Cox proportional hazard analyses were performed to determine the independent prognostic factors after bypass grafting. The primary outcome was a composite, combining death, acute coronary syndrome, stroke or transient ischemic attack, and coronary or peripheral revascularization during follow-up. Secondary outcomes were overall causes of death and cardiovascular death, acute coronary syndrome, and stroke or transient ischemic attack.

RESULTS

One hundred fourteen (12.2%) patients had preoperative chronic kidney disease (estimated glomerular filtration rate range, 20.5-59.8 mL x min(-1) x 1.73 m(-2)). After a mean follow-up of 3.1 +/- 1.4 years (median, 3.3 years), chronic kidney disease was found to be an independent predictor of the composite outcome (hazard ratio and 95% confidence interval, 1.46 [1.01-2.11]; P = .0467) and overall death (hazard ratio and 95% confidence interval, 1.89 [1.16-3.07]; P = .0106).

CONCLUSIONS

Beyond the perioperative period, preoperative moderate-to-severe chronic kidney disease is an independent long-term predictor of cardiovascular events and total mortality after coronary artery bypass grafting. Chronic kidney disease status should be incorporated into prediction models and clinical risk assessments.