Left Ventricular Pressure Decay Research Articles

Abstract P2072: Chronic Treatment With An Androgen Receptor Antagonist Promotes Maladaptive Structural And Functional Cardiac Remodeling In Aging Male Mice

Testosterone levels decrease with age in men, while the risk for cardiovascular diseases (CVD) increases dramatically. Indeed, low circulating testosterone levels in men are associated with diseases such as heart failure. Testosterone exerts its effects via androgen receptors, which are even present in the heart. In addition, androgen receptor antagonists are used to treat prostate cancer in older men who may also have CVD. We investigated the effects of the androgen receptor antagonist flutamide on cardiac structure and function in aged mice. Twenty-month-old male C57BL/6 mice were treated with flutamide for 90 days (slow-release pellet implant; ~20mg/kg/day). In-vivo heart structure/function was assessed using echocardiography and then hearts were Langendorff-perfused to assess load-independent ventricular function ex-vivo . Androgen receptor blockade via flutamide caused maladaptive ventricular remodeling. In-vivo studies showed that flutamide-treated mouse hearts had smaller left ventricular inner diameters when compared to vehicle-treated mice ( e.g. , diastolic: 4.7 ± 0.1 vs. 4.4 ± 0.1 mm; p=0.01; n=8,7). Flutamide also caused left ventricular (LV) atrophy with thinner posterior walls (0.91 ± 0.07 vs. 0.74 ± 0.04 mm; p=0.05) and reduced LV mass when compared to vehicle controls (140 ± 12 vs. 105 ± 6 mg; p=0.03). Ex-vivo functional assessment showed a marked reduction in LV developed pressure in the flutamide-treated mice (111 ± 11 vs. 71 ± 3 mmHg; p<0.01). These mice also had significantly slower rates of LV pressure rise (+dP/dT=2219 ± 263 vs. 1406 ± 95 mmHg/s; p<0.01) as well as LV pressure decay (-dP/dT=-1975 ± 263 vs. -1327 ± 132 mmHg/s; p=0.04). This indicates that flutamide-treated mice had defects in both systolic and diastolic cardiac function. These results demonstrate that suppressing the effects of testosterone by blocking androgen receptors promotes maladaptive structural remodeling of the left ventricle and promotes systolic and diastolic dysfunction in hearts from aged male mice. This study suggests that chronic treatment with androgen receptor antagonists may induce cardiac dysfunction in older men, which has implications for individuals taking these medications for prostate cancer treatment.

Urocortin 2 Gene Transfer for Systolic and Diastolic Dysfunction Due to Chronically Increased Left Ventricular Pressure.

We used transverse aortic constriction (TAC) in mice to test the hypothesis that urocortin 2 (Ucn2) gene transfer would increase left ventricular (LV) systolic and diastolic function in the pressure-stressed LV. Three groups were studied: (1) control mice (no TAC); (2) mice that received saline 6 weeks after TAC; and (3) mice that received Ucn2 gene transfer 6 weeks after TAC, using adeno-associated virus 8 encoding murine Ucn2 (AAV8.mUcn2; 2 × 1013 genome copies (gc)/kg, i.v. per mouse). Echocardiography was performed 6 and 12 weeks after TAC. In terminal studies 12 weeks after TAC, rates of LV pressure development and decay and Tau were measured, and LV cardiac myocytes (CMs) were isolated and cytosolic Ca2+ transients and sarcomere shortening rates recorded. Reverse transcription polymerase chain reaction and immunoblotting were used to measure key proteins in LV samples. A CM cell line (HL-1) was used to explore mechanisms. Concentric LV hypertrophy was evident on echocardiography 6 weeks after TAC. Twelve weeks after TAC, LV ejection fraction (EF) was higher in mice that received Ucn2 gene transfer (TAC-saline: 65% ± 3%; TAC-Ucn2: 75% ± 2%; p = 0.01), as was LV peak +dP/dt (1.9-fold increase; p = 0.001) and LV peak -dP/dt (1.7-fold increase; p = 0.017). Tau was more rapid (23% reduction, p = 0.02), indicating improved diastolic function. The peak rates of sarcomere shortening (p = 0.002) and lengthening (p = 0.002) were higher in CMs from TAC-Ucn2 mice, and Tau was reduced (p = 0.001). LV (Ser-16) phosphorylation of phospholamban (PLB) was increased in TAC-Ucn2 mice (p = 0.025), and also was increased in HL-1 cells treated with angiotensin II to induce hypertrophy and incubated with Ucn2 peptide (p = 0.001). Ucn2 gene transfer in TAC-induced heart failure with preserved ejection fraction increased cardiac function in the intact LV and provided corresponding benefits in CMs isolated from study animals, including increased myofilament Ca2+ sensitivity during contraction. The mechanism includes enhanced CM Ca2+ handling associated with increased (Ser-16)-PLB.

Prolonged Asynchronous Left Ventricular Isovolumic Relaxation Constant in Ascending Compared to Descending Thoracic Aortic Stenosis for Chronic Early Left Ventricular Afterload and Late Left Ventricular Afterload Increase.

Background: In arterial hypertension, left ventricular relaxation is affected early on in relation to a chronic difference in peak left ventricular afterload with early development of HF. Objective: in ascending compares to descending thoracic aortic stenosis, resulting in chronic late and early LV afterload increase, to assess the left ventricular isovolumic relaxation pressure decay constant through regression analysis, a parameter of left ventricular relaxation on the 4th and 8th week period from invasive left ventricular pressure measurements. Methods: fourteen pigs underwent posterolateral thoracotomy for ascending aortic stenosis, resulting in chronic early left ventricular afterload increase (EL = 6], or descending thoracic aortic stenosis creating chronic late systolic left ventricular load (LL = 8]. Exponential regression with nonzero asymptote for τ assessment, with linear and nonlinear regression were performed on isovolumic relaxation pressure decay from the left ventricular invasive pressure measurements on 4th and 8th week. Two-way repeated measurement ANOVA, post-hoc Tukey test and linear regression were performed for statistical analysis. Results presented are mean ± SEM or median (quartiles], with significance is at p < 0.05. Results: The ascending aortic stenosis associated with prolonged biexponential asynchronous τ, compared to the descending thoracic aorta stenosis, resulted in data that were different at the 8th week in presence of respirations (interaction p < 0.05]. Monoexponential and linear τ were not different in either respiration being preserved or suspended transitionally and in preload reduction. Preload sensitive response of τ was found in ascending compared to descending thoracic aortic banding that reduced in EL and in LL it increased with load reduction (p < 0.05]. These results indicated that τ is not different in and between LV afterloading conditions in a chronic setting, although it indicates that myocardial ischemia is present and that it is greater in ascending aortic banding, compared to descending thoracic aorta banding at the 8th week. Conclusion: In different sequence of the left ventricular afterload, ventricular relaxation is affected early on, having in EL compared to LL prolonged biexponential asynchronous left ventricular relaxation constant, thus indicating the development left ventricular myocardial ischemia and different elastic recoil in an invasive left ventricular hemodynamic assessment.

Effects of oxymatrine and matrine on left ventricular contractility using pressure-volume relationship analysis in anesthetized rats

The purpose of this study was to investigate the effects of oxymatrine and matrine on integrated cardiac function in rats using pressure-volume loop analysis. A pressure-volume loop catheter was advanced into the left ventricle in anesthetized rats. Steady-state hemodynamic and load-independent parameters were recorded before and after oxymatrine or matrine injection. Oxymatrine (200 mg/kg) and matrine (50, 100 mg/kg) significantly increased the preload recruitable stroke work, slope of maximal systolic pressure increase (dP/dtmax) – end-diastolic volume relationship, end-systolic elastance and volume axis intercept (V0), which are load-independent parameters. Furthermore, the observed increased cardiac efficiency, along with the decreased ventricular arterial coupling, pressure volume area and potential energy, reflect improved mechanoenergetics in oxymatrine (200 mg/kg) and matrine (25, 50 or 100 mg/kg) treated rats respectively. In addition, matrine (25, 50 mg/kg) decreased end-systolic volume and end-diastolic volume, and increased ejection fraction; matrine at 100 mg/kg further decreased end-systolic volume, end-diastolic volume, stroke volume and stroke work, shortened the time constant of left ventricular pressure decay, and increased dP/dtmax, and heart rate. These results suggest that both oxymatrine and matrine enhance left ventricular contractility and improve cardiac mechanical function. As the dose of matrine was much lower than that of oxymatrine, the effect of matrine on myocardial contractility was stronger than that of oxymatrine.

High frame rate speckle tracking echocardiography to assess diastolic function

Abstract Background Left ventricular (LV) strain rate (SR) during isovolumic relaxation (SRIVR) and early diastolic filling (SRe) has previously been shown to correlate with the invasive gold standard for LV diastolic function (i.e. the time constant of LV pressure decay tau). However, the translation of these biomarkers to the clinic has been hampered by technical limitations. Indeed, conventional speckle tracking (STE) is limited by its temporal resolution, whereas tissue Doppler imaging (TDI) is angle-dependent, labor-intensive and thus rarely used clinically nowadays. Purpose The aim of this study was to show that these limitations could be overcome by using a recently proposed STE algorithm operating on high frame rate (HFR) imaging data. Methods 37 subjects (age: 64±12, 81% male) were included in the study; 16 had cardiac amyloidosis, 12 were undergoing clinically indicated left and/or right heart cardiac catheterization and 9 were healthy volunteers. Since the sequence of left ventricular activation and thus the repolarization process (i.e. relaxation) starts at mid septum, we measured SRIVR and SRe in the mid septal segment in an apical 4 chamber view using a commercially available clinical system with: (1) TDI (frame rate (FR) ∼142 Hz); (2) STE (FR ∼65 Hz). Moreover, subjects were scanned with HD-PULSE, an experimental high frame ultrasound scanner (FR ∼915 Hz) and then a manually placed contour was tracked during the cardiac cycle by a custom-made 2D HFR STE algorithm, to compute and extract SRIVR and SRe from the mid septum. Since TDI is considered the reference method to assess SR, conventional as well as HFR STE values were correlated against the TDI SR values. Results In 3 subjects, SRIVR could not be reliably assessed with the clinical STE approach, which we attributed to the relatively low temporal resolution of the images; all other measurements could be made in all subjects. For both biomarkers, HFR STE values correlated better with the TDI reference measurements than the clinical STE estimates (Fig.1). The latter estimates showed a systematic underestimation (bias −0.19 1/s (p&amp;lt;0.01) and −0.46 1/s (p&amp;lt;0.01) for SRIVR and SRe respectively) while no significant bias was observed for the HFR STE values. Similarly, the limits of agreement of the HFR STE values were narrower (−0.45 to +0.54 1/s and −0.94 to +0.86 1/s) than those of the clinical STE measurements (−0.85 to +0.48 1/s and −1.32 to +0.41 1/s). Conclusions These results show that HFR STE offers a reliable way to assess novel biomarkers of diastolic function in a user-friendly manner and can therefore facilitate their incorporation to the clinical practice. Funding Acknowledgement Type of funding sources: None.

Correlation Between Longitudinal Strain in the Apical Segments of the Left Ventricle at End-Systole Obtained by 2-Dimensional Speckle-Tracking Echocardiography and Left Ventricular Relaxation

It is well acknowledged that left ventricular (LV) contractile performance affects LV relaxation via LV elastic recoil. Accordingly, we aimed to investigate whether global longitudinal strain (GLS), particularly longitudinal strain at LV apical segments at end-systole (ALS), obtained by 2-dimensional speckle-tracking echocardiography could be used to assess LV relaxation.Methods and Results:We enrolled 121 patients with suspected or definite coronary artery disease in whom echocardiography and diagnostic cardiac catheterization were performed on the same day. We obtained conventional echo-Doppler parameters and GLS, as well as ALS prior to catheterization. LV functional parameters were obtained from the LV pressure recorded using a catheter-tipped micromanometer. In all patients, GLS and ALS were significantly correlated with the time constant τ of LV pressure decay during isovolumetric relaxation (r=0.63 [P<0.001] and r=0.66 [P<0.001], respectively). Receiver operating characteristic curve analysis for identifying impaired LV relaxation (τ ≥48 ms) revealed that ALS greater than -22.3% was an optimal cut-off value, with 81.7% sensitivity and 82.4% specificity. Even in patients with preserved LV ejection fraction, the same ALS cut-off value enabled the identification of impaired LV relaxation with 70% sensitivity and 87.5% specificity. The findings indicate that contractile dysfunction at LV apical segments slows LV relaxation via loss of LV elastic recoil, even in patients with preserved LVEF.

Left-ventricular hypertrophy in 18-month-old donor rat hearts was not associated with graft dysfunction in the early phase of reperfusion after cardiac transplantation\u2013gene expression profiling

The use of hearts with left-ventricular (LV) hypertrophy (LVH) could offer an opportunity to extend the donor pool for cardiac transplantation. We assessed the effects of LVH in 18-month-old spontaneously hypertensive stroke-prone (SHRSP) donor rats and following transplantation. In donors, cardiac function and structural alterations were assessed. Then, the hearts were transplanted into young normotensive-rats. We evaluated LV graft function 1 h after transplantation. The myocardial expression of 92 genes involved in apoptosis, inflammation, and oxidative-stress was profiled using PCR-array. Compared to controls, SHRSP-rats developed LVH, had increased LV systolic performance (slope of the end-diastolic pressure-volume (PV) relationship: 1.6±0.2 vs 0.8±0.1mmHg/μl, p<0.05) accompanied by diastolic dysfunction [prolonged time constant of LV pressure decay (Tau: 15.8±0.6 vs 12.3±0.5ms) and augmented diastolic stiffness (LV end-diastolic PV relationship: 0.103±0.012 vs 0.045±0.006mmHg/ml), p<0.05]. They presented ECG changes, myocardial fibrosis, and increased nitrotyrosine immunoreactivity and plasma troponin-T and creatine kinase-CM levels. After transplantation, even though the graft contractility was better in SHRSP rats compared to controls, the adverse impact of ischemia/reperfusion-injury on contractility was not altered (Ees ratio after versus before transplantation: 32% vs 29%, p>0.05). Whereas nitrotyrosine immunoreactivity was higher, myeloperoxidase-positive cell infiltration was decreased in the SHRSP+transplanted compared to control+transplanted. Among the tested genes, LVH was associated with altered expression of 38 genes in donors, while transplantation of these hearts resulted in the change of four genes. Alterations in 18-month-old donor hearts, as a consequence of hypertension and LVH, were not associated with graft dysfunction in the early phase of reperfusion after transplantation.

P1510 Assessment of left ventricular relaxation time constant by noninvasive left ventricular pressure-strain loop: invasive validation

Abstract Introduction Left ventricular (LV) relaxation time constant, Tau (τ), is one of the best indexes to evaluate left ventricular diastolic function and is usually assessed invasively. Tau is the time constant of the exponential regression Pt =(P0-P∞)e-t/τ+P∞ that expresses left ventricular isovolumic pressure decay, where Pt is LV pressure (LVP) at time t, P0 is LVP at dP/dtmin and P∞ is the asymptotic pressure, to which relaxation would lead if completed without LV filling. Several noninvasive methods were developed to calculate Tau, however, they are time-consuming and complicated. Recently, a simple method regional left ventricular pressure–strain loops and myocardial work was introduced and validated. We hypothesize that left ventricular relaxation time constant can be derived and calculated from the LV pressure–strain loops. Objective To calculate noninvasively Tau using LV pressure–strain loops and compare it to invasive Tau assessment. Methods The study includes patients with preserved LV systolic function without significant valvular disease that were scheduled to elective coronary catheterization. During catheterization, a fluid-filled catheter was placed in the LV to measure pressure. Echocardiography was performed simultaneously with LV pressure recording. Three standard apical views were acquired and subsequently 2D strain analysis was performed using commercially available GE software and LV pressure–strain loops were calculated. Doppler signal was used for timing of valvular events. Tau was calculated by the equation τ =P/(-dP/dt) that is a derivative of the ventricular pressure decline P = P0e-t/τ+PB with respect to time. The pressure between peak negative dP/dt and the lowest LV pressure shortly after mitral valve opening was used for this calculation. The study was approved by the institutional ethics committee. Results Forty patients, (mean age 65.1 ± 10.9 years, 27 male, BSA1.93 ± 0.18 m2) were included in the study. Heart rate and the mean blood pressure at the time of catheterization were 69.9 ± 11.8 min-1 and 85.2 ± 18.8 mmHg, respectively. The mean LV end diastolic diameter was 44 ± 4 mm, the LV mass was 86.7 ± 25.2 g/m2, LVEF 58.4 ± 6.6% and GLS 21.0 ± 3.2%. Tau, calculated noninvasively using derivative method was significantly lower than invasively derived measurement (40.1 ± 13.4 vs 49.8 ± 7.7 msec, p = 0.002). However, a significant positive correlation was observed between the two methods (r =0.67, p &amp;lt;0.001, Figure). Conclusions This preliminary study demonstrates that Tau estimated by a noninvasive method using LV pressure–strain loops has a good correlation with Tau measured invasively. Therefore, Tau can be estimated noninvasively using novel left ventricular pressure–strain loop method. Abstract P1510 Figure.

P121 Pressure overload-induced functional and metabolic impairments in type 2 diabetic hearts are ameliorated by inhibition of xanthine oxidase

Abstract Funding Acknowledgements SANWA KAGAKU KENKYUSHO Co., Ltd. Background We have recently demonstrated that AMP deaminase (AMPD) is upregulated in OLETF, obese type 2 diabetic (T2DM) rats, and that the upregulated AMPD contributes to depletion of myocardial ATP at the time of pressure overload, leading to diastolic dysfunction. On the other hand, AMPD promotes the formation of IMP from AMP, and IMP is in turn further converted to hypoxanthine and xanthine, substrates of xanthine oxidase (XO), which produces uric acid with ROS as a byproduct. Based on these findings, we tested the hypothesis that inhibition of XO ameliorates the pressure overload-induced diastolic dysfunction in T2DM rats. Methods and results Metabolomic analyses of the left ventricular myocardium revealed that levels of myocardial hypoxanthine and xanthine were significantly higher by 30% and 28%, respectively, in OLETF than in LETO, non-diabetic control rats, under the condition of pressure overloading (200-230 mmHg) induced by phenylephrine infusion. Myocardial XO activity in OLETF was 57.9% higher than that in LETO, and the activity was significantly attenuated by oral administration of topiroxostat, an XO inhibitor, at 0.1-0.5 mg/kg/day for 14 days in a dose-dependent manner. Pressure volume loop analyses showed that the pressure overloading induced by phenylephrine infusion resulted in significantly higher LVEDP in OLETF than in LETO (18.3 ± 1.5 vs. 12.2 ± 1.3 mmHg, p &amp;lt; 0.05, n = 7), though LVEDPs at baseline were comparable in OLETF and LETO (5.6 ± 0.4 vs. 4.7 ± 0.7 mmHg). Treatment with topiroxostat significantly suppressed the pressure overload-induced elevation of LVEDP in OLETF (18.3 ± 1.5 vs. 11.3 ± 1.1 mmHg, p &amp;lt; 0.05) but not in LETO. Tau, the time constant of LV pressure decay, was significantly prolonged to 14.7 ± 0.7 ms (p &amp;lt; 0.05) by pressure overloading in OLETF but not in LETO, though baseline Tau values were similar in LETO and OLETF (6.1 ± 0.2 vs. 8.0 ± 0.4 ms). The prolongation of Tau by pressure overloading in OLETF was significantly attenuated by treatment with topiroxostat. Ea/Ees, an index for ventricular-arterial coupling, was higher in OLETF than in LETO (2.3 ± 0.3 vs. 1.6 ± 0.3, p &amp;lt; 0.05) under the condition of pressure overloading, and it was also improved by topiroxostat in OLETF (1.2 ± 0.2, p &amp;lt; 0.05). Myocardial ATP content was lower in OLETF than in LETO under the condition of pressure overloading (2966 ± 400 vs. 1818 ± 171 nmol/g wet tissue, p &amp;lt; 0.05), but treatment with topiroxostat significantly restored the ATP level (2629 ± 307 nmo/g wet tissue). Conclusion: In T2DM hearts, not only XO activity but also XO substrates are upregulated and upregulated AMPD may be involved in the upregulation. Inhibition of XO ameliorates pressure overload-induced diastolic dysfunction and improves ventricular-arterial coupling most likely through augmented ATP preservation.

Indexing peak rapid filling velocity to both relaxation and filling volume to estimate left ventricular filling pressures.

The peak transmitral velocity/peak mitral annular velocity (E/e') ratio has been used as a left ventricular (LV) filling pressure (LVFP) correlate. However, the E/e' and its changes with haemodynamic alterations have not always correlated with changes in LVFP's. We hypothesized that indexing E/e' to a measure of LV filling volume may enhance the correlation with LVFP and LVFP changes. We summarized previously obtained haemodynamic and Doppler echo data in 137 dogs with coronary microsphere embolization induced-chronic LV dysfunction prior to and following haemodynamic induced alterations in LVFP's. E/e' values were obtained as E*tau where tau is the inverse logarithmic LV pressure decay. E*tau was indexed to LV filling volume by dividing by the diastolic time velocity integral (DVI) and correlated with LV mean diastolic pressure (LVmDP). Similarly, the relationship of E/e' and E/e'/DVI to LV pre A wave pressure was evaluated in 84 patients by invasive haemodynamics and Doppler echo. Combining data from all interventions, LVmDP correlated with E*tau (r = 0.408) but more strongly with E*tau/DVI (r = 0.667, z = 3.03, P = 0.0008). The change in LVmDP correlated with the change in E*tau/DVI (r = 0.742) more strongly than E*Tau (r = 0.187, Z = 4.01, P < 0.0001). In the patient cohort, E/e' was modestly correlated with LV pre A wave pressure (r = 0.301) but more strongly correlated with E/e'/DVI (r = 0.636, z = 2.36, P = 0.0161). Indexing E to both LV relaxation and filling volume results in a more robust relation with LVFP's and with LVFP changes.

Pharmacologic Inhibition of FOXO1 Improves Cardiac Function by Enhancing Glucose Metabolism and Attenuating Apoptosis in Type‐1 Diabetic Rats

IntroductionDiabetic cardiomyopathy, which comprises structural and functional abnormalities of the myocardium, is a major etiological factor for death in diabetic patients. Altered cardiac energy metabolism and increased cardiac apoptosis may underlie the pathology of diabetic cardiomyopathy. Forkhead transcriptional factor (FOXO1) is preferably activated in the myocardium of Type2 diabetic mice and mediates excessive lipid metabolism, resulting in diabetic cardiomyopahty. However, the effect of FOXO1 in cardiac glucose oxidation and apoptosis and its contribution to cardiac function in Type 1 diabetes‐induced cardiomyopathy are largely unknown. Thus, the present study aimed to investigate whether or not pharmacological inhibition of FOXO1 by its selective inhibitor AS1842856 can attenuate diabetic cardiomyopathy in Type 1 diabetic rats and the underlying mechanisms.MethodsControl or streptozotocin (STZ, 65 mg/kg)‐induced diabetic Sprague Dawley rats (n=7 per group) received vehicle or AS1842856 (50 mg/kg) by gavage twice daily for one week starting four weeks after STZ injection. On the day of harvest, the left ventricular (LV) functions of the rats were assessed by Pressure‐volume (PV) loop analysis and the heart tissue were collected for immunofluorescence, qPCR, Western blotting, etc. The translocation of FOXO1 from cytoplasm to nucleus was performed by immunofluorescence. The mRNA expression of pyruvate dehydrogenase kinase 4 (PDK4) was measured by qPCR. The protein levels of FOXO1, phosphorylated‐FOXO1(S256), PDK4, phosphorylated pyruvate dehydrogenase (pSer293‐PDH), B‐cell lymphoma 2 (BCl2), Bcl‐2‐like protein 4 (Bax), total and cleaved‐caspase3 were detected by Western blotting analysis. TUNEL assay was performed for detection of apoptosis in the cardiac tissue.ResultsPV loop analysis indicated that heart rate (HR, bpm) was significantly reduced, and time constant of LV pressure decay (TAU, ms), slope of the end‐diastolic pressure‐volume relationship (EdPVR, mmHg/μl) were all significantly increased in Type‐1 diabeticrats as compared to non‐diabetic control rats (all P &lt;0.05), suggesting that Type‐1 diabetic rats indicated cardiac diastolic dysfunction. These changes were associated with remarkably increased FOXO1 activity (decreased P‐FOXO1/FOXO1 ratio, increased FOXO1 nuclear translocation), reduced cardiac glucose oxidation (increased mRNA and protein expression of PDK4 and reduced expression of P‐PDH) and enhanced cardiac apoptosis (reduced Bcl2/Bax ratio, increased cleaved‐caspase3/total caspase 3 ratio and TUNEL positive cells) in Type‐1 diabetic rats (all P &lt;0.05, vs. Control rats). However, administration of FOXO1 inhibitor AS1842856 significantly inhibited FOXO1 activity (increased P‐FOXO1/FOXO1 ratio, decreased FOXO1 nuclear translocation), increased HR, decreased TAU and EDSPVR, and reverted all the above‐mentioned diabetes‐induced biochemical changes, suggesting that pharmacological inhibition of FOXO1 may attenuate cardiomyopathy in Type‐1 diabetic rats via enhanced glucose oxidation and reduced cardiac apoptosis.ConclusionFoxO1 in mediating PDK4 expression and subsequent PDH inactivation in the heart and also activation of cardiac apoptosis may represent major mechanisms whereby inhibition of FOXO1 improves cardiac function in early stage of diabetic cardiomyopathy in Type 1 diabetic rats and may provide a promising therapeutic target to treat the disease.Support or Funding InformationThe authors' work was supported by the General Research Fund (17124614M, Research Grants Council of Hong Kong).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Overexpression of SARAF Ameliorates Pressure Overload–Induced Cardiac Hypertrophy Through Suppressing STIM1-Orai1 in Mice

Background/Aims: Activation of stromal interaction molecule 1 (STIM1) and Orai1 participates in the development of cardiac hypertrophy. Store-operated Ca²⁺ entry-associated regulatory factor (SARAF) is an intrinsic inhibitor of STIM1-Orai1 interaction. Thus, we hypothesized that SARAF could prevent cardiac hypertrophy. Methods: Male C57BL/6 mice, aged 8 weeks, were randomly divided into sham and abdominal aortic constriction surgery groups and were infected with lentiviruses expressing SARAF and GFP (Lenti-SARAF) or GFP alone (Lenti-GFP) via intramyocardial injection. At 4 weeks after aortic constriction, left ventricular structure and function were assessed by echocardiography and hemodynamic assays. The gene and protein expressions of SARAF, STIM1, and Orai1 were measured by quantitative PCR and Western blot, respectively. Results: Gene and protein expressions of SARAF were significantly decreased, while STIM1 and Orai1 were increased in the heart tissue compared with sham group. Overexpression of SARAF in the heart prevented the upregulation of STIM1 and Orai1, and importantly, attenuated aortic constriction-induced decrease in maximal rate of left ventricular pressure decay and increases in thickness of interventricular septum and left ventricular posterior wall, heart weight/body weight ratio, and size of cardiomyocytes. Blood pressure detected through the carotid artery and left ventricular systolic function were not affected by SARAF overexpression. In addition, overexpression of SARAF also attenuated angiotensin II-induced upregulation of STIM1 and Orai1 and hypertrophy of cultured cardiomyocytes. Conclusion: Overexpression of SARAF in the heart prevents cardiac hypertrophy, probably through suppressing the upregulation of STIM1/Orai1.

Estrogen variation during the menstrual cycle does not influence left ventricular diastolic function and untwisting rate in premenopausal women

BackgroundAlthough a cardioprotective effect of estrogen has been suggested by experimental studies, clinical data on the influence of estrogen on left ventricular (LV) diastolic function are sparse. The LV untwisting rate obtained by 2D speckle tracking echocardiography (2D-STE) is correlated with the time constant of LV pressure decay (tau), and this correlation is independent of left atrial pressure. Therefore, we used conventional Doppler echocardiography and 2D-STE to investigate changes in LV diastolic function during a single menstrual cycle in premenopausal women. MethodsTwenty healthy premenopausal woman (mean age, 28.1±2.7 years) were enrolled. Clinical and echocardiographic data were obtained during the follicular phase (F-phase) and luteal phase (L-phase) of a single menstrual cycle. We compared the clinical and echocardiographic data, and estrogen levels between the two phases. ResultsThere were no significant differences in LV diastolic parameters derived from Doppler echocardiography (E/A, p=0.295; E/e′, p=0.449, DcT, p=0.178) or 2D-STE (peak untwisting rate, p=0.892; time-to-peak untwisting, p=0.951) between the two phases of the menstrual cycle. However, there was a significant decrease in estrogen levels between the F- and L-phases (177±119pg/ml vs. 35±12pg/ml, p<0.0001). ConclusionsLV diastolic function in healthy premenopausal women did not significantly change during the menstrual cycle. Estrogen does not appear to have a significant acute effect on LV diastolic function in premenopausal woman.

Chronic plus binge ethanol feeding induces myocardial oxidative stress, mitochondrial and cardiovascular dysfunction, and steatosis.

Alcoholic cardiomyopathy in humans develops in response to chronic excessive alcohol consumption; however, good models of alcohol-induced cardiomyopathy in mice are lacking. Herein we describe mouse models of alcoholic cardiomyopathies induced by chronic and binge ethanol (EtOH) feeding and characterize detailed hemodynamic alterations, mitochondrial function, and redox signaling in these models. Mice were fed a liquid diet containing 5% EtOH for 10, 20, and 40 days (d) combined with single or multiple EtOH binges (5 g/kg body wt). Isocalorically pair-fed mice served as controls. Left ventricular (LV) function and morphology were assessed by invasive pressure-volume conductance approach and by echocardiography. Mitochondrial complex (I, II, IV) activities, 3-nitrotyrosine (3-NT) levels, gene expression of markers of oxidative stress (gp91phox, p47phox), mitochondrial biogenesis (PGC1α, peroxisome proliferator-activated receptor α), and fibrosis were examined. Cardiac steatosis and fibrosis were investigated by histological/immunohistochemical methods. Chronic and binge EtOH feeding (already in 10 days EtOH plus single binge group) was characterized by contractile dysfunction (decreased slope of end-systolic pressure-volume relationship and preload recruitable stroke work), impaired relaxation (decreased time constant of LV pressure decay and maximal slope of systolic pressure decrement), and vascular dysfunction (impaired arterial elastance and lower total peripheral resistance). This was accompanied by enhanced myocardial oxidative/nitrative stress (3-NT; gp91phox; p47phox; angiotensin II receptor, type 1a) and deterioration of mitochondrial complex I, II, IV activities and mitochondrial biogenesis, excessive cardiac steatosis, and higher mortality. Collectively, chronic plus binge EtOH feeding in mice leads to alcohol-induced cardiomyopathies (National Institute on Alcohol Abuse and Alcoholism models) characterized by increased myocardial oxidative/nitrative stress, impaired mitochondrial function and biogenesis, and enhanced cardiac steatosis.

Abstract 12002: Increasing Heart Rate in Left Bundle Branch Block Results in Incomplete Relaxation and Increases Left Ventricular Diastolic Stiffness

Introduction: Left bundle branch block (LBBB) slows LV pressure decay and shortens diastole. At low heart rates (HR) this may not compromise filling as diastolic duration is sufficient for complete relaxation. Purpose: We investigated if further abbreviation of diastole at increased HR could cause incomplete relaxation, particularly in the late activated LV lateral wall; thereby increasing diastolic LV stiffness, which may cause increased filling pressure. Methods: We analyzed data from a study of 10 canines where HR was increased from 120 to 140 by atrial pacing before and after induction of LBBB. Ventricular and pericardial pressures, LV volume and regional segment lengths (SL) were measured. Global diastolic stiffness was calculated from end diastolic (ED) transmural LV pressure-volume (PV) relations and regional stiffness from pressure-SL relations in septum and lateral wall. A mathematical model was used to estimate the increase in filling pressure due to incomplete relaxation at HR 160 and 180. Results: In LBBB, tau was prolonged and diastole abbreviated at both HR 120 and 140, compared to baseline (Fig. 1). Increased HR during LBBB stiffened the ventricle, seen as an upward shift of the ED PV relation by 1.4±1.7 mmHg (±SD), (p=0.03) whereas no shift (-0.9±1.5 mmHg) (NS) was seen at baseline (Fig. 2). Regional ED P-SL relations showed a larger upward shift of the lateral wall (1.1±1.8 mmHg) and hence a more pronounced stiffening compared to the septum (0.6±1.5 mmHg) (p&lt;0.05), indicating more delayed lateral wall relaxation. Mathematical estimation showed an increase in filling pressure of 7 and 16 mmHg due to further diastolic abbreviation at HR 160 and 180, respectively. Conclusions: LV diastolic stiffness is increased at high heart rates in LBBB due to incomplete relaxation, particularly of the late activated LV lateral wall. Diastolic stiffening by increased HR may lead to exercise intolerance and dyspnoea in LBBB patients due to elevated filling pressure.

The soluble guanylate cyclase activator cinaciguat prevents cardiac dysfunction in a rat model of type-1 diabetes mellitus.

BackgroundDiabetes mellitus (DM) leads to the development of diabetic cardiomyopathy, which is associated with altered nitric oxide (NO)—soluble guanylate cyclase (sGC)—cyclic guanosine monophosphate (cGMP) signalling. Cardioprotective effects of elevated intracellular cGMP-levels have been described in different heart diseases. In the current study we aimed at investigating the effects of pharmacological activation of sGC in diabetic cardiomyopathy.MethodsType-1 DM was induced in rats by streptozotocin. Animals were treated either with the sGC activator cinaciguat (10 mg/kg/day) or with placebo orally for 8 weeks. Left ventricular (LV) pressure–volume (P–V) analysis was used to assess cardiac performance. Additionally, gene expression (qRT-PCR) and protein expression analysis (western blot) were performed. Cardiac structure, markers of fibrotic remodelling and DNA damage were examined by histology, immunohistochemistry and TUNEL assay, respectively.ResultsDM was associated with deteriorated cGMP signalling in the myocardium (elevated phosphodiesterase-5 expression, lower cGMP-level and impaired PKG activity). Cardiomyocyte hypertrophy, fibrotic remodelling and DNA fragmentation were present in DM that was associated with impaired LV contractility (preload recruitable stroke work (PRSW): 49.5 ± 3.3 vs. 83.0 ± 5.5 mmHg, P < 0.05) and diastolic function (time constant of LV pressure decay (Tau): 17.3 ± 0.8 vs. 10.3 ± 0.3 ms, P < 0.05). Cinaciguat treatment effectively prevented DM related molecular, histological alterations and significantly improved systolic (PRSW: 66.8 ± 3.6 mmHg) and diastolic (Tau: 14.9 ± 0.6 ms) function.ConclusionsCinaciguat prevented structural, molecular alterations and improved cardiac performance of the diabetic heart. Pharmacological activation of sGC might represent a new therapy approach for diabetic cardiomyopathy.Electronic supplementary materialThe online version of this article (doi:10.1186/s12933-015-0309-x) contains supplementary material, which is available to authorized users.

A dilated cardiomyopathy mutation blunts adrenergic response and induces contractile dysfunction under chronic angiotensin II stress.

We investigated cardiac contractility in the ACTC E361G transgenic mouse model of dilated cardiomyopathy (DCM). No differences in cardiac dimensions or systolic function were observed in young mice, whereas young adult mice exhibited only mild diastolic abnormalities. Dobutamine had an inotropic and lusitropic effect on the mouse heart. In papillary muscle at 37°C, dobutamine increased relaxation rates [∼50% increase of peak rate of force decline normalized to force (dF/dtmin/F), 25% reduction of time to 90% relaxation (t90) in nontransgenic (NTG) mice], but in the ACTC E361G mouse, dF/dtmin/F was increased 20-30%, and t90 was only reduced 10% at 10 Hz. Pressure-volume measurements showed increases in maximum rate of pressure decline and decreases in time constant of left ventricular pressure decay in the ACTC E361G mouse that were 25-30% of the changes in the NTG mouse, consistent with blunting of the lusitropic response. The inotropic effect of dobutamine was also blunted in ACTC E361G mice, and the dobutamine-stimulated increase in cardiac output (CO) was reduced from 2,100 to 900 μl/min. Mice were treated with high doses of ANG II for 4 wk. The chronic stress treatment evoked systolic dysfunction in ACTC E361G mice but not in NTG. There was a significant reduction in rates of pressure increase and decrease, as well as reduced end-systolic pressure and increased volume. Ejection fraction and CO were reduced in the ACTC E361G mouse, indicating DCM. In vitro DCM-causing mutations uncouple the relationship between Ca(2+) sensitivity and troponin I phosphorylation. We conclude that this leads to the observed, reduced response to β1 agonists and reduced cardiac reserve that predisposes the heart to DCM under conditions of chronic stress.

Intravenous AAV8 Encoding Urocortin-2 Increases Function of the Failing Heart in Mice.

Urocortin-2 (UCn2) peptide infusion increases cardiac function in patients with heart failure, but chronic peptide infusion is cumbersome, is costly, and provides only short-term benefits. Gene transfer would circumvent these shortcomings. We previously showed that a single intravenous (IV) injection of AAV8.UCn2 increases plasma UCn2 and left ventricular (LV) systolic and diastolic function for at least 7 months in normal mice. Here we test the hypothesis that IV delivery of AAV8.UCn2 increases function of the failing heart. Myocardial infarction (MI, by coronary ligation) was used to induce heart failure, which was assessed by echocardiography 3 weeks after MI. Mice with LV ejection fraction (EF) <25% received IV delivery of AAV8.UCn2 (5×1011 gc) or saline, and 5 weeks later echocardiography showed increased LV EF in mice that received UCn2 gene transfer (p=0.01). In vivo physiological studies showed a 2-fold increase in peak rate of LV pressure development (LV +dP/dt; p<0.0001) and a 1.6-fold increase in peak rate of LV pressure decay (LV −dP/dt; p=0.0007), indicating increased LV systolic and diastolic function in treated mice. UCn2 gene transfer was associated with increased peak systolic Ca2+ transient amplitude and rate of Ca2+ decline and increased SERCA2a expression. In addition, UCn2 gene transfer reduced Thr286 phosphorylation of Cam kinase II, and increased expression of cardiac myosin light chain kinase, findings that would be anticipated to increase function of the failing heart. We conclude that a single IV injection of AAV8.UCn2 increases function of the failing heart. The simplicity of IV injection of a vector encoding a gene with beneficial paracrine effects to increase cardiac function is an attractive potential clinical strategy.

Intravenous AAV8 encoding Urocortin‐2 provides sustained augmentation of left ventricular function in heart failure mice (699.4)

Urocortin 2 (UCn2) peptide infusion increases cardiac function in patients with heart failure, but chronic peptide infusion is cumbersome, costly, and provides only short-term benefits. Gene transfer would circumvent these shortcomings. Here we ask if a single intravenous injection of adeno-associated virus type 8 encoding murine UCn2 (AAV8.UCn2) might increase left ventricular (LV) function in mice with heart failure (HF). Myocardial infarction (MI, by coronary ligation) was used to induce HF, which was assessed by echocardiography 3w after MI. Mice with fractional area change (FAC) <30% received AAV8.UCn2 (5x 1011 gc, IV) or IV saline, and 5 weeks later echocardiography showed increased FAC in mice that received UCn2 gene transfer (HF: 11±1%, n=10; HF+UCn2: 19±3%, n=10; p=0.025). In vivo physiological studies showed increased rates of LV pressure development (LV +dP/dt) and decay (LV -dP/dt; Figures), indicating increased LV contractile and diastolic function. We conclude that a single IV of AAV8.UCn2 increases function of the failing heart. The simplicity of IV injection of a long-term expression vector encoding a gene with paracrine activity to increase cardiac function is a potentially attractive strategy for the treatment of heart failure.

Marginal donors: can older donor hearts tolerate prolonged cold ischemic storage?

Both advanced donor age and prolonged ischemic time are significant risk factors for the 1-year mortality. However, its functional consequences have not been fully evaluated in the early-phase after transplantation; even early graft dysfunction is the main determinant of long-term outcome following transplantation. We evaluated in vivo left-ventricular (LV) cardiac and coronary vascular function of old-donor grafts after short and prolonged cold ischemic times in rats 1 h after heart transplantation. The hearts were excised from young donor (3-month-old) or old donor (18-month-old) rats, stored in cold preservation solution for either 1 or 8 h, and heterotopically transplanted. After 1 h of ischemic period, in the old-donor group, LV pressure, maximum pressure development (dP/dt max), time constant of LV pressure decay (τ), LV end-diastolic pressure and coronary blood flow did not differ compared with young donors. However, endothelium-dependent vasodilatation to acetylcholine resulted in a significantly lower response of coronary blood flow in the old-donor group (33 ± 4 vs. 51 ± 15 %, p < 0.05). After 8 h preservation, two of the old-donor hearts showed no mechanical activity upon reperfusion. LV pressure (55 ± 6 vs. 72 ± 5 mmHg, p < 0.05), dP/dt max (899 ± 221 vs. 1530 ± 217 mmHg/s, p < 0.05), coronary blood flow and response to acetylcholine were significantly reduced and τ was increased in the old-donor group in comparison to young controls. During the early-phase after transplantation, the ischemic tolerance of older-donor hearts is reduced after prolonged preservation time and the endothelium is more vulnerable to ischemia/reperfusion.