Kenneth B Margulies

Hospital of the University of Pennsylvania, Filadelfia, Pennsylvania, United States

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Publications (188)1346.12 Total impact

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    ABSTRACT: Intracellular Na(+) concentration ([Na(+)]i) regulates Ca(2+) cycling, contractility, metabolism, and electrical stability of the heart. [Na(+)]i is elevated in heart failure, leading to arrhythmias and oxidative stress. We hypothesized that myocyte [Na(+)]i is also increased in type 2 diabetes (T2D) due to enhanced activity of the Na(+)-glucose cotransporter. To test this hypothesis, we used myocardial tissue from humans with T2D and a rat model of late-onset T2D (HIP rat). Western blot analysis showed increased Na(+)-glucose cotransporter expression in failing hearts from T2D patients compared with nondiabetic persons (by 73±13%) and in HIP rat hearts versus wild-type (WT) littermates (by 61±8%). [Na(+)]i was elevated in HIP rat myocytes both at rest (14.7±0.9 versus 11.4±0.7 mmol/L in WT) and during electrical stimulation (17.3±0.8 versus 15.0±0.7 mmol/L); however, the Na(+)/K(+)-pump function was similar in HIP and WT cells, suggesting that higher [Na(+)]i is due to enhanced Na(+) entry in diabetic hearts. Indeed, Na(+) influx was significantly larger in myocytes from HIP versus WT rats (1.77±0.11 versus 1.29±0.06 mmol/L per minute). Na(+)-glucose cotransporter inhibition with phlorizin or glucose-free solution greatly reduced Na(+) influx in HIP myocytes (to 1.20±0.16 mmol/L per minute), whereas it had no effect in WT cells. Phlorizin also significantly decreased glucose uptake in HIP myocytes (by 33±9%) but not in WT, indicating an increased reliance on the Na(+)-glucose cotransporter for glucose uptake in T2D hearts. Myocyte Na(+)-glucose cotransport is enhanced in T2D, which increases Na(+) influx and causes Na(+) overload. Higher [Na(+)]i may contribute to arrhythmogenesis and oxidative stress in diabetic hearts. © 2015 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.
    Journal of the American Heart Association 08/2015; 4(9). DOI:10.1161/JAHA.115.002183 · 4.31 Impact Factor
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    ABSTRACT: Background: Worsening renal function in heart failure may be related to increased venous congestion, decreased cardiac output, or both. Diuretics are universally used in acute decompensated heart failure, but they may be ineffective and may lead to azotemia. We aimed to compare the decongestive properties of a urine output-guided diuretic adjustment and standard therapy for the management of cardiorenal syndrome in acute decompensated heart failure. Methods and results: Data were pooled from subjects randomized to the stepwise pharmacologic care algorithm (SPCA) in the CARRESS-HF trial and those who developed cardiorenal syndrome (rise in creatinine >0.3 mg/dL) in the DOSE-AHF and ROSE-AHF trials. Patients treated with SPCA (n = 94) were compared with patients treated with standard decongestive therapy (SDT) that included intravenous loop diuretic use (DOSE-AHF and ROSE-AHF; n = 107) at the time of cardiorenal syndrome and followed for net fluid balance, weight loss, and changing renal function. The SPCA group had higher degrees of jugular venous pressure (P < .0001) at the time of cardiorenal syndrome. The group that received SPCA had more weight change (-3.4 ± 5.2 lb) and more net fluid loss (1.705 ± 1.417 L) after 24 hours than the SDT group (-0.8 ± 3.4 lb and 0.892 ± 1.395 L, respectively; P < .001 for both) with a slight improvement in renal function (creatinine change -0.1 ± 0.3 vs 0.0 ± 0.3 mg/dL, respectively; P = .03). Conclusions: Compared with SDT, patients who received an intensification of medication therapy for treating persisting congestion had greater net fluid and weight loss without being associated with renal compromise.
    Journal of cardiac failure 08/2015; DOI:10.1016/j.cardfail.2015.07.007 · 3.05 Impact Factor
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    ABSTRACT: RNA sequencing (RNA-Seq) allows an unbiased survey of the entire transcriptome in a high-throughput manner. A major application of RNA-Seq is to detect differential isoform expression across experimental conditions, which is of great biological interest due to its direct relevance to protein function and disease pathogenesis. Detection of differential isoform expression is challenging because of uncertainty in isoform expression estimation owing to ambiguous reads and variability in precision of the estimates across samples. It is desirable to have a method that can account for these issues and is flexible enough to allow adjustment for covariates. In this paper, we present MetaDiff, a random-effects meta-regression model that naturally fits for the above purposes. Through extensive simulations and analysis of an RNA-Seq dataset on human heart failure, we show that the random-effects meta-regression approach is computationally fast, reliable, and can improve the power of differential expression analysis while controlling for false positives due to the effect of covariates or confounding variables. In contrast, several existing methods either fail to control false discovery rate or have reduced power in the presence of covariates or confounding variables. The source code, compiled JAR package and documentation of MetaDiff are freely available at Our results indicate that random-effects meta-regression offers a flexible framework for differential expression analysis of isoforms, particularly when gene expression is influenced by other variables.
    BMC Bioinformatics 07/2015; 16(1):208. DOI:10.1186/s12859-015-0623-z · 2.58 Impact Factor
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    ABSTRACT: Oxidative stress may contribute to heart failure (HF) progression. Inhibiting xanthine oxidase in hyperuricemic HF patients may improve outcomes. We randomly assigned 253 patients with symptomatic HF, left ventricular ejection fraction ≤40%, and serum uric acid levels ≥9.5 mg/dL to receive allopurinol (target dose, 600 mg daily) or placebo in a double-blind, multicenter trial. The primary composite end point at 24 weeks was based on survival, worsening HF, and patient global assessment. Secondary end points included change in quality of life, submaximal exercise capacity, and left ventricular ejection fraction. Uric acid levels were significantly reduced with allopurinol in comparison with placebo (treatment difference, -4.2 [-4.9, -3.5] mg/dL and -3.5 [-4.2, -2.7] mg/dL at 12 and 24 weeks, respectively, both P<0.0001). At 24 weeks, there was no significant difference in clinical status between the allopurinol- and placebo-treated patients (worsened 45% versus 46%, unchanged 42% versus 34%, improved 13% versus 19%, respectively; P=0.68). At 12 and 24 weeks, there was no significant difference in change in Kansas City Cardiomyopathy Questionnaire scores or 6-minute walk distances between the 2 groups. At 24 weeks, left ventricular ejection fraction did not change in either group or between groups. Rash occurred more frequently with allopurinol (10% versus 2%, P=0.01), but there was no difference in serious adverse event rates between the groups (20% versus 15%, P=0.36). In high-risk HF patients with reduced ejection fraction and elevated uric acid levels, xanthine oxidase inhibition with allopurinol failed to improve clinical status, exercise capacity, quality of life, or left ventricular ejection fraction at 24 weeks. URL: Unique identifier: NCT00987415. © 2015 American Heart Association, Inc.
    Circulation 05/2015; 131(20). DOI:10.1161/CIRCULATIONAHA.114.014536 · 14.43 Impact Factor
  • The Journal of Heart and Lung Transplantation 04/2015; 34(4):S167. DOI:10.1016/j.healun.2015.01.453 · 6.65 Impact Factor
  • The Journal of Heart and Lung Transplantation 04/2015; 34(4):S209. DOI:10.1016/j.healun.2015.01.575 · 6.65 Impact Factor
  • The Journal of Heart and Lung Transplantation 04/2015; 34(4):S89-S90. DOI:10.1016/j.healun.2015.01.239 · 6.65 Impact Factor
  • The Journal of Heart and Lung Transplantation 04/2015; 34(4):S58-S59. DOI:10.1016/j.healun.2015.01.148 · 6.65 Impact Factor
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    ABSTRACT: The cardiac voltage-gated sodium channel, NaV1.5, drives the upstroke of the cardiac action potential and is a critical determinant of myocyte excitability. Recently, Calcium (Ca)/Calmodulin(CaM) dependent protein kinase II (CaMKII) has emerged as a critical regulator of NaV1.5 function through phosphorylation of multiple residues including S516, T594, and S571 and these phosphorylation events may be important for the genesis of acquired arrhythmias, as occur in heart failure. However, phosphorylation of full-length human NaV1.5 has not been systematically analyzed and NaV1.5 phosphorylation in human heart failure is incompletely understood. In the present study, we used label-free mass spectrometry to assess phosphorylation of human NaV1.5 purified from HEK293 cells with full coverage of phosphorylatable sites and identified 23 sites that were phosphorylated by CaMKII in vitro. We confirmed phosphorylation of S516 and S571 by LC-MS/MS and found a decrease in S516 phosphorylation in human heart failure, using a novel phospho-specific antibody. This work furthers our understanding of the phosphorylation of NaV1.5 by CaMKII under normal and disease conditions, provides novel CaMKII target sites for functional validation, and provides the first phospho-proteomic map of full-length human NaV1.5.
    Journal of Proteome Research 03/2015; 14(5). DOI:10.1021/acs.jproteome.5b00107 · 4.25 Impact Factor
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    ABSTRACT: Cyclic guanosine monophosphate (cGMP) is a second messenger molecule that transduces nitric-oxide- and natriuretic-peptide-coupled signalling, stimulating phosphorylation changes by protein kinase G. Enhancing cGMP synthesis or blocking its degradation by phosphodiesterase type 5A (PDE5A) protects against cardiovascular disease. However, cGMP stimulation alone is limited by counter-adaptions including PDE upregulation. Furthermore, although PDE5A regulates nitric-oxide-generated cGMP, nitric oxide signalling is often depressed by heart disease. PDEs controlling natriuretic-peptide-coupled cGMP remain uncertain. Here we show that cGMP-selective PDE9A (refs 7, 8) is expressed in the mammalian heart, including humans, and is upregulated by hypertrophy and cardiac failure. PDE9A regulates natriuretic-peptide- rather than nitric-oxide-stimulated cGMP in heart myocytes and muscle, and its genetic or selective pharmacological inhibition protects against pathological responses to neurohormones, and sustained pressure-overload stress. PDE9A inhibition reverses pre-established heart disease independent of nitric oxide synthase (NOS) activity, whereas PDE5A inhibition requires active NOS. Transcription factor activation and phosphoproteome analyses of myocytes with each PDE selectively inhibited reveals substantial differential targeting, with phosphorylation changes from PDE5A inhibition being more sensitive to NOS activation. Thus, unlike PDE5A, PDE9A can regulate cGMP signalling independent of the nitric oxide pathway, and its role in stress-induced heart disease suggests potential as a therapeutic target.
    Nature 03/2015; 519(7544):472-6. DOI:10.1038/nature14332 · 41.46 Impact Factor
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    ABSTRACT: -Early studies showed beneficial effects of phosphodiesterase 5 inhibitors (PDE5i) on cardiovascular function in heart failure (HF) patients, but the RELAX trial observed no improvement in exercise capacity with sildenafil treatment in subjects with HF and preserved ejection fraction (HFpEF). -A subgroup of participants in the RELAX trial (n=48) underwent comprehensive noninvasive cardiovascular assessment before and after treatment with sildenafil or placebo in a prospective ancillary study. Left ventricular (LV) contractility was assessed by peak power index (PWR/EDV) and stroke work index (SW/EDV). Systemic arterial load was assessed by arterial elastance (Ea) and right ventricular afterload by pulmonary artery systolic pressure (PASP). Endothelial function was assessed by reactive hyperemia index (RHI) following upper arm cuff occlusion. Compared to placebo (n=25), sildenafil (n=23) decreased Ea (-0.29±0.28mmHg/ml vs +0.02±0.29, p=0.008) and tended to improve RHI (+0.30±0.45 vs -0.17±0.30, p=0.054). In contrast, LV contractility was reduced by 11-16% with sildenafil compared to placebo (ΔPWR/EDV -52±70 vs +0±40 mmHg/s, p=0.006; ΔSW/EDV +0.3±5.8 vs -6.0±5.1 mmHg, p=0.04). Sildenafil had no effect on PASP. -In subjects with HFpEF, sildenafil displayed opposing effects on ventricular and vascular function. We speculate that beneficial effects of PDE5i in the systemic vasculature and endothelium were insufficient to improve clinical status, or that the deleterious effects on left ventricular function offset any salutary vascular effects, contributing to the absence of benefit observed with sildenafil in subjects with HFpEF in the RELAX trial. Clinical Trial Registration-URL: Unique identifier: NCT00094302.
    Circulation Heart Failure 03/2015; 8(3). DOI:10.1161/CIRCHEARTFAILURE.114.001915 · 5.89 Impact Factor
  • Journal of the American College of Cardiology 03/2015; 65(10):A893. DOI:10.1016/S0735-1097(15)60893-2 · 16.50 Impact Factor
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    ABSTRACT: Regular exercise is recommended to improve outcomes in patients with heart failure. Exercise is known to decrease inflammation and thought to decrease myocardial stress; however, studies of exercise in heart failure have had mixed results on levels of N-terminal pro-B-type natriuretic peptide (NT-proBNP) and high-sensitivity C-reactive protein (hsCRP). A multi-marker analysis may help identify distinct subgroups of patients who respond to exercise. The primary study objective was to identify common and distinct patterns of change in hsCRP and NT-proBNP and quantify the influence of exercise therapy on the observed patterns of change. NT-proBNP and hsCRP were assessed in a random sample of 320 participants from the biomarker sub-study of HF-ACTION, a randomized clinical trial of exercise training versus usual care in patients with stable and chronic heart failure. Growth mixture modeling was used to identify unique biomarker patterns over 12-months. Three statistically independent and clinically meaningful biomarker patterns of NTproBNP and hsCRP were identified. Two patterns were combined and compared to the "low/stable" pattern, which was characterized by the lowest levels of NT-proBNP and hsCRP over time. Participants who were taking a loop diuretic, had hypertension or ischemic etiology were about two times as likely to be in the "elevated/worsening" biomarker pattern. Participants randomized to the exercise intervention were less likely to be in the elevated/worsening pattern of NT-proBNP and hsCRP (relative risk ratio: 0.56, CI: 0.32-0.98, p=0.04). Exercise therapy was protective for reducing the frequency of membership in the elevated/worsening biomarker pattern, indicating that exercise may be helpful in delaying the progression of heart failure. Copyright © 2015 Elsevier Inc. All rights reserved.
    Journal of Cardiac Failure 02/2015; DOI:10.1016/j.cardfail.2015.02.006 · 3.05 Impact Factor
  • The Journal of Heart and Lung Transplantation 12/2014; 34(4). DOI:10.1016/j.healun.2014.12.007 · 6.65 Impact Factor
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    ABSTRACT: -Inorganic nitrate (NO3 (-)), abundant in certain vegetables, is converted to nitrite by bacteria in the oral cavity. Nitrite can be converted to nitric oxide (NO) in the setting of hypoxia. We tested the hypothesis that NO3 (-) supplementation improves exercise capacity in HFpEF via specific adaptations to exercise. -Seventeen subjects participated in this randomized, double-blind, cross-over study comparing a single-dose of NO3-rich beetroot juice (NO3 (-):12.9 mmoles) versus an identical nitrate-depleted placebo. Subjects performed supine-cycle maximal-effort cardiopulmonary exercise tests, with measurements of cardiac output (CO) and skeletal muscle oxygenation. We also assessed skeletal muscle oxidative function. Study endpoints included exercise efficiency (total work/total oxygen consumed), peak VO2, total work performed, vasodilatory reserve, forearm mitochondrial oxidative function, and augmentation index (a marker of arterial wave reflections, measured via radial arterial tonometry). Supplementation increased plasma NO-metabolites (median 326 μM versus 10 μM; P=0.0003), peak VO2 (12.6±3.7 vs. 11.6±3.1 mL O2/min/kg; P=0.005), and total work performed (55.6±35.3 vs. 49.2±28.9 kJ; P=0.04). However, efficiency was unchanged. NO3 (-) led to greater reductions in SVR (-42.4±16.6 vs. -31.8±20.3%; P=0.03) and increases in CO (121.2±59.9 vs. 88.7±53.3%; P=0.006) with exercise. NO3 (-) reduced aortic augmentation index (132.2±16.7 vs. 141.4±21.9%, P=0.03) and tended to improve mitochondrial oxidative function. -NO3 (-) increased exercise capacity in HFpEF by targeting peripheral abnormalities. Efficiency did not change due to parallel increases in total work and VO2. NO3 (-) increased exercise vasodilatory and cardiac output reserves. NO3 (-) also reduced arterial wave reflections, which are linked to left ventricular diastolic dysfunction and remodeling. Clinical Trial Registration NCT01919177.
    Circulation 12/2014; 131(4). DOI:10.1161/CIRCULATIONAHA.114.012957 · 14.43 Impact Factor
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    ABSTRACT: Heart failure is a complex clinical syndrome and has become the most common reason for adult hospitalization in developed countries. Two subtypes of heart failure, ischemic heart disease (ISCH) and dilated cardiomyopathy (DCM), have been studied using microarray platforms. However, microarray has limited resolution. Here we applied RNA sequencing (RNA-Seq) to identify gene signatures for heart failure from six individuals, including three controls, one ISCH and two DCM patients. Using genes identified from this small RNA-Seq dataset, we were able to accurately classify heart failure status in a much larger set of 313 individuals. The identified genes significantly overlapped with genes identified via genome-wide association studies for cardiometabolic traits and the promoters of those genes were enriched for binding sites for transcriptions factors. Our results indicate that it is possible to use RNA-Seq to classify disease status for complex diseases such as heart failure using an extremely small training dataset. Copyright © 2014. Published by Elsevier Inc.
    Genomics 12/2014; 105(2). DOI:10.1016/j.ygeno.2014.12.002 · 2.28 Impact Factor
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    ABSTRACT: The QT interval, an electrocardiographic measure reflecting myocardial repolarization, is a heritable trait. QT prolongation is a risk factor for ventricular arrhythmias and sudden cardiac death (SCD) and could indicate the presence of the potentially lethal mendelian long-QT syndrome (LQTS). Using a genome-wide association and replication study in up to 100,000 individuals, we identified 35 common variant loci associated with QT interval that collectively explain ∼8-10% of QT-interval variation and highlight the importance of calcium regulation in myocardial repolarization. Rare variant analysis of 6 new QT interval-associated loci in 298 unrelated probands with LQTS identified coding variants not found in controls but of uncertain causality and therefore requiring validation. Several newly identified loci encode proteins that physically interact with other recognized repolarization proteins. Our integration of common variant association, expression and orthogonal protein-protein interaction screens provides new insights into cardiac electrophysiology and identifies new candidate genes for ventricular arrhythmias, LQTS and SCD.
    Nature Genetics 12/2014; DOI:10.1038/ng.3014 · 29.35 Impact Factor
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    ABSTRACT: This study evaluates needleless liquid jet method and compares it with three common experimental methods: (1) intramuscular injection (IM), (2) left ventricular intracavitary infusion (LVIC), and (3) LV intracavitary infusion with aortic and pulmonary occlusion (LVIC-OCCL). Two protocols were executed. First (n = 24 rats), retention of dye was evaluated 10 min after delivery in an acute model. The acute study revealed the following: significantly higher dye retention (expressed as % myocardial cross-section area) in the left ventricle in both the liquid jet [52 ± 4] % and LVIC-OCCL [58 ± 3] % groups p < 0.05 compared with IM [31 ± 8] % and LVIC [35 ± 4] %. In the second (n = 16 rats), each animal received adeno-associated virus encoding green fluorescent protein (AAV.EGFP) at a single dose with terminal 6-week endpoint. In the second phase with AAV.EGFP at 6 weeks post-delivery, a similar trend was found with liquid jet [54 ± 5] % and LVIC-OCCL [60 ± 8] % featuring more LV expression as compared with IM [30 ± 9] % and LVIC [23 ± 9] %. The IM and LVIC-OCCL cross sections revealed myocardial fibrosis. With more detailed development in future model studies, needleless liquid jet delivery offers a promising strategy to improve direct myocardial delivery.
    Journal of Cardiovascular Translational Research 10/2014; 7(8). DOI:10.1007/s12265-014-9593-1 · 3.02 Impact Factor
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    Shaukat Khan · Jennifer Joyce · Kenneth B Margulies · Takeshi Tsuda
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    ABSTRACT: Background: Transforming growth factor (TGF)-β activation is known to play a central role in progressive ventricular remodeling in advanced heart failure in animal models, but there has been no direct evidence of increased TGF-β activity in the myocardium of patients with advanced human heart failure. METHODS AND RESULTS: Using a recently developed bioassay that measures TGF-β bioactivity rather than TGF-β abundance, we measured bioactive TGF-β in human myocardium from control non-failing donors (NF), and patients with ischemic cardiomyopathy (ICM) and dilated cardiomyopathy (DCM). Both free and total soluble TGF-β were significantly increased in ICM and DCM compared with NF. Free TGF-β had an excellent correlation with phosphorylated Smad2 (R(2)=0.55, P<0.0001), a downstream marker of TGF-β signaling. Collagen type I and type III were significantly upregulated in DCM compared with NF, consistent with histological evidence of myocardial fibrosis. Expression of fibulin-2, a positive modulator of TGF-β, was significantly increased in DCM compared with NF, and the free TGF-β level was correlated with fibulin-2 mRNA (R(2)=0.24, P<0.006). Conclusions: Although both free and total soluble TGF-β are significantly increased in ICM and DCM compared with NF, the superior correlation of free TGF-β with downstream signaling suggests that this is the most functionally relevant form. The present findings suggest that sustained TGF-β activation in both ICM and DCM contributes to excess myocardial fibrosis.
    Circulation Journal 10/2014; 78(11). DOI:10.1253/circj.CJ-14-0511 · 3.94 Impact Factor

Publication Stats

5k Citations
1,346.12 Total Impact Points


  • 2014–2015
    • Hospital of the University of Pennsylvania
      • Department of General Internal Medicine
      Filadelfia, Pennsylvania, United States
  • 2006–2015
    • University of Pennsylvania
      • • Department of Surgery
      • • Cardiovascular Institute
      • • Department of Medicine
      Filadelfia, Pennsylvania, United States
  • 2006–2014
    • William Penn University
      Filadelfia, Pennsylvania, United States
  • 2008
    • University of Cincinnati
      Cincinnati, Ohio, United States
  • 2007
    • Cardiovascular Research Foundation
      New York, New York, United States
  • 1997–2007
    • Temple University
      • • Department of Mechanical Engineering
      • • Department of Physiology
      Filadelfia, Pennsylvania, United States
  • 2003
    • University of Pittsburgh
      Pittsburgh, Pennsylvania, United States
    • Allegheny General Hospital
      Pittsburgh, Pennsylvania, United States
  • 1990–1994
    • Mayo Clinic - Rochester
      • Department of Cardiovascular Diseases
      Рочестер, Minnesota, United States