Incident heart failure in chronic kidney disease: proteomics informs biology and risk stratification.

BACKGROUND AND AIMS: Incident heart failure (HF) among individuals with chronic kidney disease (CKD) incurs hospitalizations that burden patients and health care systems. There are few preventative therapies, and the Pooled Cohort equations to Prevent Heart Failure (PCP-HF) perform poorly in the setting of CKD. New drug targets and better risk stratification are urgently needed. METHODS: In this analysis of incident HF, SomaScan V4.0 (4638 proteins) was analysed in 2906 participants of the Chronic Renal Insufficiency Cohort (CRIC) with validation in the Atherosclerosis Risk in Communities (ARIC) study. The primary outcome was 14-year incident HF (390 events); secondary outcomes included 4-year HF (183 events), HF with reduced ejection fraction (137 events), and HF with preserved ejection fraction (165 events). Mendelian randomization and Gene Ontology were applied to examine causality and pathways. The performance of novel multi-protein risk models was compared to the PCP-HF risk score. RESULTS: Over 200 proteins were associated with incident HF after adjustment for estimated glomerular filtration rate at P < 1 × 10-5. After adjustment for covariates including N-terminal pro-B-type natriuretic peptide, 17 proteins remained associated at P < 1 × 10-5. Mendelian randomization associations were found for six proteins, of which four are druggable targets: FCG2B, IGFBP3, CAH6, and ASGR1. For the primary outcome, the C-statistic (95% confidence interval [CI]) for the 48-protein model in CRIC was 0.790 (0.735, 0.844) vs. 0.703 (0.644, 0.762) for the PCP-HF model (P = .001). C-statistic (95% CI) for the protein model in ARIC was 0.747 (0.707, 0.787). CONCLUSIONS: Large-scale proteomics reveal novel circulating protein biomarkers and potential mediators of HF in CKD. Proteomic risk models improve upon the PCP-HF risk score in this population.

Evaluation of a large-scale aptamer proteomics platform among patients with kidney failure on dialysis.

BACKGROUND: Patients with kidney failure suffer high mortality, and we currently lack markers for risk stratification for these patients. We carried out a quality control study of a modified aptamer assay (SomaScan v.4.0) that measures ~ 5000 proteins, in preparation for a larger study using this platform in cohorts with kidney failure. METHODS: Forty participants from the Cardiac, Endothelial Function and Arterial Stiffness in End-Stage Renal Disease (CERES study) were selected to analyze technical and short-term biological variability, orthogonal correlations and differential protein expression in plasma from patients who died during 2.5 year follow-up. Long-term (one year) variability was studied in 421 participants in the Chronic Renal Insufficiency Cohort. We evaluated 4849 aptamers (4607 unique proteins) using data formats including raw data and data formatted using Adaptive Normalization by Maximum Likelihood (ANML), an algorithm developed for SomaScan data in individuals with normal kidney function. RESULTS: In ANML format, median[IQR] intra-assay coefficient of variation (CV) was 2.38%[1.76, 3.40] and inter-assay CV was 7.38%[4.61, 13.12]. Short-term within-subject CV was 5.76% [3.35, 9.72]; long-term CV was 8.71%[5.91, 13.37]. Spearman correlations between aptamer and traditional assays for PTH, NT-proBNP, FGF-23 and CRP were all > 0.7. Fold-change (FC) in protein levels among non-survivors, significant after Bonferroni correction, included SVEP1 (FC[95% CI] 2.14 [1.62, 2.82]), keratocan (1.74 [1.40, 2.15]) and LanC-like protein 1 (0.56 [0.45, 0.70]). Compared to raw aptamer data, technical and short-term biological variability in paired samples was lower in ANML-formatted data. ANML formatting had minimal impact on orthogonal correlations with traditional assays or the associations of proteins with the phenotype of mortality. CONCLUSIONS: SomaScan had excellent technical variability and low within-subject short-term variability. ANML formatting could facilitate comparison of biomarker results with other studies that utilize this format. We expect SomaScan to provide novel and reproducible information in patients with kidney failure on dialysis.

Proteomics of CKD progression in the chronic renal insufficiency cohort.

Progression of chronic kidney disease (CKD) portends myriad complications, including kidney failure. In this study, we analyze associations of 4638 plasma proteins among 3235 participants of the Chronic Renal Insufficiency Cohort Study with the primary outcome of 50% decline in estimated glomerular filtration rate or kidney failure over 10 years. We validate key findings in the Atherosclerosis Risk in the Communities study. We identify 100 circulating proteins that are associated with the primary outcome after multivariable adjustment, using a Bonferroni statistical threshold of significance. Individual protein associations and biological pathway analyses highlight the roles of bone morphogenetic proteins, ephrin signaling, and prothrombin activation. A 65-protein risk model for the primary outcome has excellent discrimination (C-statistic[95%CI] 0.862 [0.835, 0.889]), and 14/65 proteins are druggable targets. Potentially causal associations for five proteins, to our knowledge not previously reported, are supported by Mendelian randomization: EGFL9, LRP-11, MXRA7, IL-1 sRII and ILT-2. Modifiable protein risk markers can guide therapeutic drug development aimed at slowing CKD progression.

Proteomic cardiovascular risk assessment in chronic kidney disease.

AIMS: Chronic kidney disease (CKD) is widely prevalent and independently increases cardiovascular risk. Cardiovascular risk prediction tools derived in the general population perform poorly in CKD. Through large-scale proteomics discovery, this study aimed to create more accurate cardiovascular risk models. METHODS AND RESULTS: Elastic net regression was used to derive a proteomic risk model for incident cardiovascular risk in 2182 participants from the Chronic Renal Insufficiency Cohort. The model was then validated in 485 participants from the Atherosclerosis Risk in Communities cohort. All participants had CKD and no history of cardiovascular disease at study baseline when ∼5000 proteins were measured. The proteomic risk model, which consisted of 32 proteins, was superior to both the 2013 ACC/AHA Pooled Cohort Equation and a modified Pooled Cohort Equation that included estimated glomerular filtrate rate. The Chronic Renal Insufficiency Cohort internal validation set demonstrated annualized receiver operating characteristic area under the curve values from 1 to 10 years ranging between 0.84 and 0.89 for the protein and 0.70 and 0.73 for the clinical models. Similar findings were observed in the Atherosclerosis Risk in Communities validation cohort. For nearly half of the individual proteins independently associated with cardiovascular risk, Mendelian randomization suggested a causal link to cardiovascular events or risk factors. Pathway analyses revealed enrichment of proteins involved in immunologic function, vascular and neuronal development, and hepatic fibrosis. CONCLUSION: In two sizeable populations with CKD, a proteomic risk model for incident cardiovascular disease surpassed clinical risk models recommended in clinical practice, even after including estimated glomerular filtration rate. New biological insights may prioritize the development of therapeutic strategies for cardiovascular risk reduction in the CKD population.

Alterations in the Circulating Proteome Associated with Albuminuria.

SIGNIFICANCE STATEMENT: We describe circulating proteins associated with albuminuria in a population of African American Study of Kidney Disease and Hypertension with CKD (AASK) using the largest proteomic platform to date: nearly 7000 circulating proteins, representing approximately 2000 new targets. Findings were replicated in a subset of a general population cohort with kidney disease (ARIC) and a population with CKD Chronic Renal Insufficiency Cohort (CRIC). In cross-sectional analysis, 104 proteins were significantly associated with albuminuria in the Black group, of which 67 of 77 available proteins were replicated in ARIC and 68 of 71 available proteins in CRIC. LMAN2, TNFSFR1B, and members of the ephrin superfamily had the strongest associations. Pathway analysis also demonstrated enrichment of ephrin family proteins. BACKGROUND: Proteomic techniques have facilitated understanding of pathways that mediate decline in GFR. Albuminuria is a key component of CKD diagnosis, staging, and prognosis but has been less studied than GFR. We sought to investigate circulating proteins associated with higher albuminuria. METHODS: We evaluated the cross-sectional associations of the blood proteome with albuminuria and longitudinally with doubling of albuminuria in the African American Study of Kidney Disease and Hypertension (AASK; 38% female; mean GFR 46; median urine protein-to-creatinine ratio 81 mg/g; n =703) and replicated in two external cohorts: a subset of the Atherosclerosis Risk in Communities (ARIC) study with CKD and the Chronic Renal Insufficiency Cohort (CRIC). RESULTS: In cross-sectional analysis, 104 proteins were significantly associated with albuminuria in AASK, of which 67 of 77 available proteins were replicated in ARIC and 68 of 71 available proteins in CRIC. Proteins with the strongest associations included LMAN2, TNFSFR1B, and members of the ephrin superfamily. Pathway analysis also demonstrated enrichment of ephrin family proteins. Five proteins were significantly associated with worsening albuminuria in AASK, including LMAN2 and EFNA4, which were replicated in ARIC and CRIC. CONCLUSIONS: Among individuals with CKD, large-scale proteomic analysis identified known and novel proteins associated with albuminuria and suggested a role for ephrin signaling in albuminuria progression.

Analytical and Biological Variability of a Commercial Modified Aptamer Assay in Plasma Samples of Patients with Chronic Kidney Disease.

BACKGROUND: We carried out a study of the aptamer proteomic assay, SomaScan V4, to evaluate the analytical and biological variability of the assay in plasma samples of patients with moderate to severe chronic kidney disease (CKD). METHODS: Plasma samples were selected from 2 sources: (a) 24 participants from the Chronic Renal Insufficiency Cohort (CRIC) and (b) 49 patients from the Brigham and Women's Hospital-Kidney/Renal Clinic. We calculated intra-assay variability from both sources and examined short-term biological variability in samples from the Brigham clinic. We also measured correlations of aptamer measurements with traditional biomarker assays. RESULTS: A total of 4656 unique proteins (4849 total aptamer measures) were analyzed in all samples. Median (interquartile range [IQR] intra-assay CV) was 3.7% (2.8-5.3) in CRIC and 5.0% (3.8-7.0) in Brigham samples. Median (IQR) biological CV among Brigham samples drawn from one individual on 2 occasions separated by median (IQR) 7 (4-14) days was 8.7% (6.2-14). CVs were independent of CKD stage, diabetes, or albuminuria but were higher in patients with systemic lupus erythematosus. Rho correlations between aptamer and traditional assays for biomarkers of interest were cystatin C = 0.942, kidney injury model-1 = 0.905, fibroblast growth factor-23 = 0.541, tumor necrosis factor receptors 1 = 0.781 and 2 = 0.843, P < 10-100 for all. CONCLUSIONS: Intra-assay and within-subject variability for SomaScan in the CKD setting was low and similar to assay variability reported from individuals without CKD. Intra-assay precision was excellent whether samples were collected in an optimal research protocol, as were CRIC samples, or in the clinical setting, as were the Brigham samples.

Testican-2 Is Associated with Reduced Risk of Incident ESKD.

BACKGROUND: Testican-2 was recently identified as a podocyte-derived protein that is released into circulation by the kidneys and is positively correlated with eGFR and eGFR slope. However, whether higher testican-2 levels are associated with lower risk of ESKD is unknown. METHODS: Aptamer-based proteomics assessed blood testican-2 levels among participants in the African American Study of Kidney Disease and Hypertension (AASK, n =703), the Chronic Renal Insufficiency Cohort (CRIC) study ( n =3196), and the Atherosclerosis Risk in Communities (ARIC) study ( n =4378). We compared baseline characteristics by testican-2 tertile and used Cox proportional hazards models to study the association of testican-2 with incident ESKD. RESULTS: Higher testican-2 levels were associated with higher measured GFR (mGFR) in AASK, higher eGFR in the CRIC and ARIC studies, and lower albuminuria in all cohorts. Baseline testican-2 levels were significantly associated with incident ESKD in Cox proportional hazards models adjusted for age, sex, and race (model 1) and model 1+mGFR or eGFR+comorbidities (model 2). In model 3 (model 2+proteinuria), the associations between testican-2 (per SD increase) and incident ESKD were AASK (hazard ratio [HR]=0.84 [0.72 to 0.98], P =0.023), CRIC (HR=0.95 [0.89 to 1.02], P =0.14), ARIC (HR=0.54 [0.36 to 0.83], P =0.0044), and meta-analysis (HR=0.92 [0.86 to 0.98], P =0.0073). CONCLUSIONS: Across three cohorts spanning >8000 individuals, testican-2 is associated with kidney health and prognosis, with higher levels associated with reduced risk of ESKD.

Left atrial strain is associated with adverse cardiovascular events in patients with end-stage renal disease: Findings from the Cardiac, Endothelial Function and Arterial Stiffness in ESRD (CERES) study.

INTRODUCTION: We lack cardiovascular (CV) markers for patients with end-stage renal disease (ESRD), and left atrial (LA) strain has not been studied definitively in this population. We examined associations of LA reservoir, conduit, and booster strain with major adverse cardiovascular events (MACE) among stable patients with ESRD on dialysis. METHODS: One hundred and ninety patients in the Cardiac, Endothelial and Arterial Stiffness in ESRD study underwent echocardiography, including strain imaging. The primary outcome was 2-year composite non-fatal MACE or CV death. We performed Cox proportional hazards regression for LA strain measures, adjusting for demographics, comorbidities, left ventricular global longitudinal strain (LV GLS), E/e' and LA volume index. FINDINGS: Mean ± SD LA reservoir strain was 24.1 ± 7.0%, and LA conduit strain 11.9 ± 5.1%. In age-adjusted analyses, lower LA reservoir strain and LA conduit strain were associated with the primary outcome (HR per 1-SD worsening LA strain parameter = 1.57 [95% CI 1.2-2.1], p = 0.003 and 1.68 [95% CI 1.2-2.3], p = 0.002, respectively). After adjusting for comorbidities, LA reservoir strain remained associated with the primary outcome and with deaths alone, and LA conduit strain with the primary outcome and hospitalizations alone (p < 0.05 for all). Associations of LA conduit strain were independent of LV GLS. Associations were stronger in participants with serum albumin <3.6 mg/dl (p for interaction 0.008). DISCUSSION: Left atrial reservoir strain and conduit strain were independently associated with MACE among patients with ESRD. Our study provides unique ascertainment of CV hospitalizations not attributed to missed dialysis, and LA conduit strain was a strong marker for this outcome.

Identification of Novel Biomarkers and Pathways for Coronary Artery Calcification in Nondiabetic Patients on Hemodialysis Using Metabolomic Profiling.

BACKGROUND: A better understanding of the pathophysiology involving coronary artery calcification (CAC) in patients on hemodialysis (HD) will help to develop new therapies. We sought to identify the differences in metabolomics profiles between patients on HD with and without CAC. METHODS: In this case-control study, nested within a cohort of 568 incident patients on HD, the cases were patients without diabetes with a CAC score >100 (n=51), and controls were patients without diabetes with a CAC score of zero (n=48). We measured 452 serum metabolites in each participant. Metabolites and pathway scores were compared using Mann-Whitney U tests, partial least squares-discriminant analyses, and pathway enrichment analyses. RESULTS: Compared with controls, cases were older (64±13 versus 42±12 years) and were less likely to be Black (51% versus 94%). We identified three metabolites in bile-acid synthesis (chenodeoxycholic, deoxycholic, and glycolithocholic acids) and one pathway (arginine/proline metabolism). After adjusting for demographics, higher levels of chenodeoxycholic, deoxycholic, and glycolithocholic acids were associated with higher odds of having CAC; comparing the third with the first tertile of each bile acid, the OR was 6.34 (95% CI, 1.12 to 36.06), 6.73 (95% CI, 1.20 to 37.82), and 8.53 (95% CI, 1.50 to 48.49), respectively. These associations were no longer significant after further adjustment for coronary artery disease and medication use. Per 1 unit higher in the first principal component score, arginine/proline metabolism was associated with CAC after adjusting for demographics (OR, 1.83; 95% CI, 1.06 to 3.15), and the association remained significant with additional adjustments for statin use (OR, 1.84; 95% CI, 1.04 to 3.27). CONCLUSIONS: Among patients on HD without diabetes mellitus, chenodeoxycholic, deoxycholic, and glycolithocholic acids may be potential biomarkers for CAC, and arginine/proline metabolism is a plausible mechanism to study for CAC. These findings need to be confirmed in future studies.

Proteins Associated with Risk of Kidney Function Decline in the General Population.

BACKGROUND: Proteomic profiling may allow identification of plasma proteins that associate with subsequent changesin kidney function, elucidating biologic processes underlying the development and progression of CKD. METHODS: We quantified the association between 4877 plasma proteins and a composite outcome of ESKD or decline in eGFR by ≥50% among 9406 participants in the Atherosclerosis Risk in Communities (ARIC) Study (visit 3; mean age, 60 years) who were followed for a median of 14.4 years. We performed separate analyses for these proteins in a subset of 4378 participants (visit 5), who were followed at a later time point, for a median of 4.4 years. For validation, we evaluated proteins with significant associations (false discovery rate <5%) in both time periods in 3249 participants in the Chronic Renal Insufficiency Cohort (CRIC) and 703 participants in the African American Study of Kidney Disease and Hypertension (AASK). We also compared the genetic determinants of protein levels with those from a meta-analysis genome-wide association study of eGFR. RESULTS: In models adjusted for multiple covariates, including baseline eGFR and albuminuria, we identified 13 distinct proteins that were significantly associated with the composite end point in both time periods, including TNF receptor superfamily members 1A and 1B, trefoil factor 3, and ß-trace protein. Of these proteins, 12 were also significantly associated in CRIC, and nine were significantly associated in AASK. Higher levels of each protein associated with higher risk of 50% eGFR decline or ESKD. We found genetic evidence for a causal role for one protein, lectin mannose-binding 2 protein (LMAN2). CONCLUSIONS: Large-scale proteomic analysis identified both known and novel proteomic risk factors for eGFR decline.

FGF23 and Cause-Specific Mortality in Community-Living Individuals-The Health, Aging, and Body Composition Study.

OBJECTIVES: Fibroblast growth factor (FGF)-23 is a key regulator of mineral metabolism and has been linked with left ventricular hypertrophy in animal models. Most existing epidemiologic studies evaluated a C-terminal FGF23 assay which measures both the intact (active) hormone and inactive fragments. The relationship of intact FGF23 with cause-specific mortality is unknown. DESIGN: Prospective analyses of data from Health, Aging, & Body Composition (HABC) study. SETTING: Community-living adults aged 70 to 79 years with longitudinal follow up.

Renal Dysfunction in Heart Failure With Preserved Ejection Fraction: Insights From the RELAX Trial.

BACKGROUND: Patients with heart failure with preserved ejection fraction (HFpEF) and chronic kidney disease (CKD) represent a high-risk phenotype. The Phosphodiesterase-5 Inhibition to Improve Clinical Status and Exercise Capacity in Heart Failure with Preserved Ejection Fraction (RELAX) trial enrolled a high proportion of CKD participants, allowing investigation into differences in HFpEF by CKD status. METHODS AND RESULTS: Among 212 participants, we investigated the associations of CKD with biomarkers, cardiac structure, and exercise capacity, and identified predictors of change in estimated glomerular filtration rate (eGFR) over trial follow-up. CKD participants (eGFR ≤60 mL/min/1.73m2) were older, had more comorbidities, and had worse diastolic function. Lower eGFR was associated with higher levels of endothelin-1, N-terminal pro-B-type natriuretic peptide, aldosterone, uric acid, and biomarkers of fibrosis (P < .05 for all). Whereas lower eGFR was associated with worse peak oxygen consumption (VO2) after adjustment for demographics, clinical comorbidities, exercise modality, ejection fraction, and chronotropic index (ß coefficient per 1 SD decrease in eGFR: -0.61, 95% CI: -1.01, -0.22, P = .002), this association was attenuated after further adjustment for hemoglobin (ß coefficient: -0.26, 95% CI: -0.68, 0.16, P = .22). Hemoglobin mediated 35% of the association between eGFR and peak VO2. Sildenafil therapy was independently associated with worsening eGFR over the trial (ß coefficient: -2.79, 95% CI: -5.34, -0.24, P = .03). CONCLUSION: Renal dysfunction in HFpEF is characterized by echocardiographic and biomarker profiles indicative of more advanced disease, and reduced hemoglobin is a strong mediator of the association between renal dysfunction and low exercise capacity. Sildenafil therapy was associated with worsening of renal function in RELAX.

Proteomics and Metabolomics in Kidney Disease, including Insights into Etiology, Treatment, and Prevention.

In this review of the application of proteomics and metabolomics to kidney disease research, we review key concepts, highlight illustrative examples, and outline future directions. The proteome and metabolome reflect the influence of environmental exposures in addition to genetic coding. Circulating levels of proteins and metabolites are dynamic and modifiable, and thus amenable to therapeutic targeting. Design and analytic considerations in proteomics and metabolomics studies should be tailored to the investigator's goals. For the identification of clinical biomarkers, adjustment for all potential confounding variables, particularly GFR, and strict significance thresholds are warranted. However, this approach has the potential to obscure biologic signals and can be overly conservative given the high degree of intercorrelation within the proteome and metabolome. Mass spectrometry, often coupled to up-front chromatographic separation techniques, is a major workhorse in both proteomics and metabolomics. High-throughput antibody- and aptamer-based proteomic platforms have emerged as additional, powerful approaches to assay the proteome. As the breadth of coverage for these methodologies continues to expand, machine learning tools and pathway analyses can help select the molecules of greatest interest and categorize them in distinct biologic themes. Studies to date have already made a substantial effect, for example elucidating target antigens in membranous nephropathy, identifying a signature of urinary peptides that adds prognostic information to urinary albumin in CKD, implicating circulating inflammatory proteins as potential mediators of diabetic nephropathy, demonstrating the key role of the microbiome in the uremic milieu, and highlighting kidney bioenergetics as a modifiable factor in AKI. Additional studies are required to replicate and expand on these findings in independent cohorts. Further, more work is needed to understand the longitudinal trajectory of select protein and metabolite markers, perform transomics analyses within merged datasets, and incorporate more kidney tissue-based investigation.

Associations of microvascular dysfunction with cardiovascular outcomes: The cardiac, endothelial function and arterial stiffness in ESRD (CERES) cohort.

INTRODUCTION: Patients with end-stage renal disease (ESRD) have reduced endothelial function, but whether macro- and microvascular endothelial function correlate with baseline risk factors and cardiovascular outcomes in this population is not well understood. METHODS: Among 146 participants of the Cardiac, Endothelial Function and Arterial Stiffness in ESRD (CERES) study, we evaluated macro- and microvascular endothelial dysfunction as flow-mediated dilation (FMD) and velocity time integral (VTI), respectively. We examined cross-sectional correlations of baseline characteristics, inflammatory and cardiac markers with FMD and VTI. We followed participants for the composite outcome of cardiovascular hospitalization or all-cause death over fourteen months. Cox survival analyses were adjusted for demographics, comorbidities, medications, systolic blood pressure, inflammation, high-sensitivity troponin T (hs-TnT), and N-terminal pro B-type natriuretic peptide (NT-proBNP). FINDINGS: Impaired VTI was associated with older age and Black race (P < 0.05), as well as female gender, atherosclerosis, and hemodialysis (as opposed to peritoneal dialysis) (P < 0.2). Myocardial injury, measured as hs-TnT, inflammatory markers and NT-proBNP correlated with impaired VTI. In unadjusted analyses, VTI was significantly associated with the composite outcome (HR per SD VTI 0.65 [95%CI 0.45, 0.95]), but FMD was not (HR per SD FMD 0.97 [95%CI 0.69, 1.4]). When VTI was calculated as the ratio of (hyperemic VTI-baseline VTI)/baseline VTI, its association with the outcome persisted after multivariable adjustment. DISCUSSION: Microvascular function was associated with higher rates of cardiovascular hospitalizations and all-cause mortality among individuals with ESRD on dialysis. Further research is needed to learn whether novel therapies that target microvascular endothelial function could improve outcomes in this high-risk population.

Proteomic analysis of heart failure hospitalization among patients with chronic kidney disease: The Heart and Soul Study.

BACKGROUND: Patients with chronic kidney disease (CKD) are at increased risk for heart failure (HF). We aimed to investigate differences in proteins associated with HF hospitalizations among patients with and without CKD in the Heart and Soul Study. METHODS AND RESULTS: We measured 1068 unique plasma proteins from baseline samples of 974 participants in The Heart and Soul Study who were followed for HF hospitalization over a median of 7 years. We sequentially applied forest regression and Cox survival analyses to select prognostic proteins. Among participants with CKD, four proteins were associated with HF at Bonferroni-level significance (p<2.5x10(-4)): Angiopoietin-2 (HR[95%CI] 1.45[1.33, 1.59]), Spondin-1 (HR[95%CI] 1.13 [1.06, 1.20]), tartrate-resistant acid phosphatase type 5 (HR[95%CI] 0.65[0.53, 0.78]) and neurogenis locus notch homolog protein 1 (NOTCH1) (HR[95%CI] 0.67[0.55, 0.80]). These associations persisted at p<0.01 after adjustment for age, estimated glomerular filtration and history of HF. CKD was a significant interaction term in the associations of NOTCH1 and Spondin-1 with HF. Pathway analysis showed a trend for higher representation of the Cardiac Hypertrophy and Complement/Coagulation pathways among proteins prognostic of HF in the CKD sub-group. CONCLUSIONS: These results suggest that markers of heart failure differ between patients with and without CKD. Further research is needed to validate novel markers in cohorts of patients with CKD and adjudicated HF events.

Urinary Tubular Injury Biomarkers Are Associated With ESRD and Death in the REGARDS Study.

INTRODUCTION: Urinary neutrophil gelatinase-associated lipocalin (uNGAL) and urinary kidney injury molecule-1 (uKIM-1) are established markers of subclinical acute kidney injury. In persons with reduced estimated glomerular filtration rate (eGFR) and albuminuria who are at high risk for end-stage renal disease (ESRD) and death, the associations of these urinary markers with incident ESRD or death is an area of active investigation. METHODS: Among 1472 black and white participants from the REasons for Geographic and Racial Differences in Stroke (REGARDS) study with eGFR ≤60 ml/min per 1.73 m2 (Chronic Kidney Disease Epidemiology Collaboration [CKD-EPI] cystatin, 2012) and albumin-to-creatinine ratio (ACR) ≥30 mg/g, we evaluated the associations of baseline uNGAL and uKIM-1 with progression to ESRD and all-cause death. Cox models were sequentially adjusted for urinary creatinine, traditional risk factors, C-reactive protein, ACR, and eGFR. RESULTS: There were 257 ESRD events and 819 deaths over a median follow-up of 5.7 and 6.5 years, respectively. In demographic adjusted models, higher levels of uNGAL were associated with increased risk of ESRD and death, but these associations were attenuated in fully adjusted models including baseline eGFR for both ESRD (hazard ratio [HR] = 1.06 per doubling, 95% confidence interval [CI] 0.98-1.14) and death (HR = 1.04, 95% CI = 1.00-1.08). Higher levels of uKIM-1 were associated with increased risk of ESRD and death in demographic-adjusted models, and although attenuated in fully adjusted models, remained statistically significant for both ESRD (HR = 1.24 per doubling, 95% CI = 1.08-1.42) and death (HR = 1.10, 95% CI =1.03-1.19). CONCLUSION: In this cohort of high-risk patients with baseline eGFR ≤60 ml/min per 1.73 m2 and albuminuria, renal tubular injury is associated with higher mortality and progression to ESRD. Further studies are necessary to investigate the mechanism underlying this increased risk.

Application of echocardiographic data in patients with chronic kidney disease.

PURPOSE OF REVIEW: Patients with chronic kidney disease (CKD) are at a high risk for cardiovascular events and mortality, particularly heart failure. Echocardiography is the most commonly used diagnostic imaging modality for heart failure. The purpose of this review is to summarize recent literature that demonstrates how echocardiography may be used to define cardiac structure and function in the CKD population and to identify echocardiographic abnormalities that have utility in predicting clinical outcomes in this population. RECENT FINDINGS: Recent studies have highlighted the high prevalence of echocardiographic abnormalities in this population, and the challenge of identifying specific echocardiographic criteria for heart failure. There have been advances in application of strain echocardiography for evaluating systolic function in patients with normal ejection fraction, understanding pulmonary hypertension and identifying echocardiographic correlates of albuminuria. Additional studies have focused on diastolic dysfunction, left ventricular hypertrophy and echocardiographic findings in children with CKD. SUMMARY: Recent studies demonstrate the utility of echocardiography in characterizing heart structure and function and in providing potential tools for risk stratification in the high-risk CKD population.

Sex differences in vascular dysfunction and cardiovascular outcomes: The cardiac, endothelial function, and arterial stiffness in ESRD (CERES) study.

INTRODUCTION: Recent studies suggest that women with end-stage renal disease (ESRD) may have higher rates of mortality than men, but it is unknown whether sex differences in vascular function explain this disparity. The cardiac, endothelial function, and arterial stiffness in ESRD (CERES) study is an ongoing, prospective observational study designed to investigate vascular function, myocardial injury, and cardiovascular outcomes in ESRD. METHODS: Among 200 CERES participants (34% women), we evaluated arterial wave reflections as augmentation index normalized to a heart rate of 75 (AIx75), arterial stiffness as pulse wave velocity, and macro- and microvascular endothelial dysfunction as flow-mediated dilation and velocity time integral (VTI). Over a median of 14 months, participants were followed for the composite outcome of cardiovascular hospitalization or all-cause death. FINDINGS: Women had higher arterial wave reflection (Mean, SD AIx75 30% ± 9% for women vs. 21% ± 10% for men; P < 0.001) and worse microvascular function (VTI 55 ± 30 cm for women vs. 70 ± 27 cm for men; P = 0.007). After multivariable adjustment, female sex remained associated with a 0.5-SD higher AIx75 (95% CI [0.01, 0.9]) and 0.3-SD lower VTI (95%CI [0.1, 0.7]). Women experienced higher adjusted rates of the composite outcome (HR 2.5; 95%CI [1.1, 5.6]; P = 0.03), and further adjustment for arterial wave reflection attenuated this risk. DISCUSSION: Vascular dysfunction may partly explain the association of female sex with higher cardiovascular risk and mortality in patients with ESRD. Further studies are needed to explore whether sex differences in vascular function predict long-term outcomes, and whether hormonal or inflammatory factors explain these associations.

Associations of Conventional Echocardiographic Measures with Incident Heart Failure and Mortality: The Chronic Renal Insufficiency Cohort.

BACKGROUND AND OBJECTIVES: Heart failure is the most frequent cardiac complication of CKD. Left ventricular hypertrophy is common and develops early in CKD, but studies have not adequately evaluated the association of left ventricular mass index with heart failure incidence among men and women with CKD. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: We evaluated echocardiograms of 2567 participants without self-reported heart failure enrolled in the Chronic Renal Insufficiency Cohort Study. Two-dimensional echocardiograms were performed at the year 1 study visit and interpreted at a central core laboratory. Left ventricular mass index was calculated using the linear method, indexed to height2.7, and analyzed using sex-specific quartiles. The primary outcomes of incident heart failure and all-cause mortality were adjudicated over a median of 6.6 (interquartile range, 5.7-7.6) years. RESULTS: Among 2567 participants, 45% were women, and 54% were nonwhite race; mean (SD) age was 59±11 years old, and mean eGFR was 44±17 ml/min per 1.73 m2. During a median follow-up period of 6.6 years, 262 participants developed heart failure, and 470 participants died. Compared with participants in the first quartile of left ventricular mass index, those in the highest quartile had higher rates of incident heart failure (hazard ratio, 3.96; 95% confidence interval, 1.96 to 8.02) and mortality (hazard ratio, 1.86; 95% confidence interval, 1.22 to 2.85), even after adjustment for B-type natriuretic peptide, troponin T, mineral metabolism markers, and other cardiovascular disease risk factors. Those in the lowest quartile of ejection fraction had higher rates of incident heart failure (hazard ratio, 3.01; 95% confidence interval, 1.94 to 4.67) but similar mortality rates (hazard ratio, 1.18; 95% confidence interval, 0.89 to 1.57) compared with those in the highest quartile. Diastolic dysfunction was not significantly associated with heart failure or death. CONCLUSIONS: Among persons with CKD and without history of cardiovascular disease, left ventricular mass index is strongly associated with incident heart failure, even after adjustment for major cardiovascular risk factors and biomarkers.