[Show abstract][Hide abstract] ABSTRACT: Stem cell therapy for myocardial infarction (MI) has been shown to improve cardiac function and reduce infarct size. Exercise training, in the form of cardiac rehabilitation, is an essential part of patient care post-MI. Hence, we tested the effects of acute and chronic aerobic exercise on stem cell retention and cardiac remodeling post-MI. Small epicardial MI's were induced in 12-month-old C57BL/6 mice via cryoinjury. Two weeks post-MI, vehicle infusion (N = 4) or GFP(+) bone marrow-derived cells (BMC) were injected (tail vein I.V.) immediately after acute exercise (N = 14) or sedentary conditions (N = 14). A subset of mice continued a 5-week intervention of chronic treadmill exercise (10-13 m/min; 45 min/day; 4 days/week; N = 7) or remained sedentary (N = 6). Exercise tolerance was assessed using a graded exercise test, and cardiac function was assessed with echocardiography. Acute exercise increased GFP(+) BMC retention in the infarcted zone of the heart by 30% versus sedentary (P < 0.05). This was not associated with alterations in myocardial function or gene expression of key cell adhesion molecules. Animals treated with chronic exercise increased exercise capacity (P < 0.05) and cardiac mass (P < 0.05) without change in left ventricular ejection fraction (LVEF), infarct size, or regional wall thickness (P = NS) compared with sedentary. While BMC's alone did not affect exercise capacity, they increased LVEF (P < 0.05) and Ki67(+) nuclei number in the border zone of the heart (P < 0.05), which was potentiated with chronic exercise training (P < 0.05). We conclude that acute exercise increases BMC retention in infarcted hearts and chronic training increases exogenous BMC-mediated effects on stimulating the cardiomyocyte cell cycle. These preclinical results suggest that exercise may help to optimize stem cell therapeutics following MI.
[Show abstract][Hide abstract] ABSTRACT: The standard expression quantitative trait loci (eQTL) detects polymorphisms associated with gene expression without revealing causality. We introduce a coupled Bayesian regression approach-eQTeL, which leverages epigenetic data to estimate regulatory and gene interaction potential, and identifies combination of regulatory single-nucleotide polymorphisms (SNPs) that explain the gene expression variance. On human heart data, eQTeL not only explains a significantly greater proportion of expression variance but also predicts gene expression more accurately than other methods. Based on realistic simulated data, we demonstrate that eQTeL accurately detects causal regulatory SNPs, including those with small effect sizes. Using various functional data, we show that SNPs detected by eQTeL are enriched for allele-specific protein binding and histone modifications, which potentially disrupt binding of core cardiac transcription factors and are spatially proximal to their target. eQTeL SNPs capture a substantial proportion of genetic determinants of expression variance and we estimate that 58% of these SNPs are putatively causal.
[Show abstract][Hide abstract] 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).
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
[Show abstract][Hide abstract] 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 https://github.com/jiach/MetaDiff.
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.
[Show abstract][Hide abstract] 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
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] 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: http://www.clinicaltrials.gov. Unique identifier: NCT00094302.
[Show abstract][Hide abstract] 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 Information-www.clinicaltrials.gov.Identifier: NCT01919177.
[Show abstract][Hide abstract] 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.