tbuckley/cabot-search huggingface dataset:
Abstract Tu120: Sarm1 promotes diabetic cardiomyopathy by regulating HIF signaling, lipotoxicity and mitochondrial dysfunction
Authors: Keaton Minor, Hina Lateef Nizami, Ignacy Gorecki, Christine Light, Haiwei Gu, Chi Fung Lee
Journal: Circulation Research (2024)

Heart failure occurs at twice the rate in diabetic patients as compared to normal patients, and reduced NAD levels are associated with diabetic cardiomyopathy. Sterile Alpha and Tir Motif Containing 1 (SARM1) is an intracellular NAD hydrolase. We hypothesized that SARM1 promotes NAD decline and diabetic cardiomyopathy. We subjected wild type (WT) and global SARM1 knockout mice to chronic diabetic stress induced by streptozotocin injections. We showed that 16-week diabetic stress promoted progressive decline in systolic and diastolic function, and in NAD levels, which were ameliorated by SARM1 deficiency despite similar plasma glucose and lipid levels. Gene Module Network Analysis of cardiac transcriptomics identified upregulation of genes in fatty acid and glucose metabolic processes, and suppression of genes in mitochondrial processes in diabetic WT hearts. SARM1 deficiency reversed upregulated fatty acid metabolic genes but had no impact on glucose metabolic and mitochondrial gene expressions in diabetic hearts. By transmission electron microscopy and Oil Red O staining, we observed increases in lipid droplet sizes and lipid accumulation in diabetic WT hearts, which were suppressed by SARM1 deficiency. SARM1 deficiency did not reverse mitochondrial gene expression, but it mitigated the reduction in ADP-driven respiration, mitochondrial fragmentation, and abnormal cristae structure in diabetic WT hearts. Diabetic WT hearts had increased phospho-PDH and PDK4 levels as well as activated HIF signaling, exhibiting an increase in expression of HIF-1a target genes (55 genes) , many of which were related to lipid storage. SARM1 deficiency suppressed expression of HIF1-a target genes (53 genes) , and reduced phospho-PDH and PDK4 levels. These data suggest that SARM1 regulates pseudohypoxic HIF-dependent signaling in diabetic hearts. In summary, our current data support the hypothesis that SARM1 regulates HIF-dependent transcription events, particularly those influencing lipid metabolism of diabetic hearts. However, SARM1 promotes mitochondrial dysfunction in diabetic hearts independent of transcription of mitochondrial genes. Further studies will continue to elucidate the role of SARM1 in diabetic cardiomyopathy, and its potential as a novel therapeutic target.
Abstract Mo101: 3-Mercaptopyruvate Sulfurtransferase is a Critical Regulator of Branched-Chain Amino Acid Catabolism in Cardiometabolic HFpEF
Authors: Zhen Li, Jake Doiron, Huijing Xia, Kyle LaPenna, Thomas Sharp, Xiaoman YU, Noriyuki Nagahara, Traci Goodchild, David Lefer
Journal: Circulation Research (2024)

Background: Heart failure with preserved ejection fraction (HFpEF) is among the leading causes of cardiovascular mortality and morbidity. Recent multi-omics data sets underscore severely impaired branched-chain amino acid (BCAA) catabolism in the failing hearts of HFpEF patients. 3-mercaptopyruvate sulfurtransferase (3-MST) is a mitochondrial hydrogen sulfide (H 2 S) synthase that regulates mitochondrial biogenesis, function, and substrate metabolism. Research Questions and Goals: In the current study, we aimed to elucidate the role of 3-MST in myocardial BCAA catabolism in cardiometabolic HFpEF. Methods: 3-MST knockout or wild-type (WT) mice were subjected to control or L-NAME and high fat diet - induced HFpEF. Echocardiographic measurements, invasive hemodynamic assessment, and exercise capacity testing were conducted to determine HFpEF severity. Metabolomic analysis was performed to study BCAA catabolism. Additionally, a H 2 S donor, SG1002 was administered to increase H 2 S bioavailability in the setting of 3-MST deficiency and HFpEF. Results: We observed progressive deterioration in left ventricular (LV) diastolic function and exercise performance from mice subjected to HFpEF. Genetic ablation of 3-MST further-exacerbated HFpEF severity as evidenced by significantly increased E/e’ ratio, elevated LV end-diastolic pressure, and reduced exercise performance. Metabolomic analysis revealed pathological accumulation of intermediate metabolites of BCAA in the HFpEF hearts, suggesting a major derangement in myocardial BCAA catabolism. 3-MST KO hearts exhibited further BCAA catabolic defects as compared to those from WT. Importantly, H 2 S donor treatment significantly attenuated BCAA catabolic defect and alleviated HFpEF severity in both WT and 3-MST KO HFpEF mice. Conclusion: Our results demonstrate that deficiency of 3-MST impairs myocardial BCAA catabolism, which results in exacerbated HFpEF severity in a “two-Hit” mouse model of HFpEF. These data suggest 3-MST is critically involved in physiological substrate metabolism within the mitochondria and exerts beneficial effects in HFpEF. Future experiments are underway to delineate the mechanisms by which 3-MST regulates BCAA catabolism.
Abstract Mo036: DNA Damage and Repair in Patients Undergoing Myocardial Perfusion Single-Photon Emission Computed Tomography
Authors: Andrea Lorenzo, Maria Clara dos Santos Fernandes, Anna Paula Arpini, Leticia Sabioni, Glauber Dias
Journal: Circulation Research (2024)

Background: As medical imaging has continuously grown, patient exposure to ionizing radiation and the risks associated with it are important issues. Myocardial perfusion single-photon emission computed tomography (MP-SPECT) is one of the most frequently performed noninvasive cardiac imaging tests, generating concern about the potentially excessive radiation exposure for patients, including the cumulative doses of lifetime radiation. even though the individual levels of radiation exposure are considered low. Aim: To evaluate DNA damage and DNA repair markers after MP-SPECT. Methods: Thirty-two patients undergoing Tc-99m sestamibi MP-SPECT (mean injected Tc-99m sestamibi dose: 15.1 mCi) were studied. Peripheral blood was collected before radiotracer injection at rest and 60-90 minutes after injection. The comet assay (single-cell gel electrophoresis) was performed with blood lymphocytes to detect DNA strand breaks, which appear as DNA fragmentation (the comet tail; Figure1). Images of fluorescence microscopy were analyzed using the Comet Assay Software Project Lab (CASPLab 1.2.3 beta 2). Three parameters were evaluated: the percentage of DNA in the comet tail, tail length, and tail moment (the measure of migratory DNA and number of fragments). Quantitative PCR (qPCR) was performed to evaluate the expression of five genes related to signaling pathways in response to DNA damage and repair (ATM, ATR, BRCA1, CDKN1A, XPC). Data are expressed as medians, and Wilcoxon or Mann-Whitney tests were employed for statistical analysis. A p-value &lt;0.05 was considered statistically significant. Results: Figure 2 shows pre- and post- radiation exposure comet assay parameters. After radiotracer injection, there was a 10.7% increase of the DNA percentage in the tail (pre-exposure median 2.185 vs post-exposure median 2.418, p&lt;0.0065). Tail length increased 6.7% (15.0 pre-exposure vs 16.0 post-exposure, p&lt;0.0034). Tail moment increased 27.5% (0.3177 pre-exposure vs 0.4050 post-exposure, p&lt;0.0001). qPCR did not reveal increased expression of any gene after radiation exposure. Conclusion: An increase in DNA damage was detected after a single radiotracer injection for MP-SPECT, yet unaccompanied by activation of repair genes. This may suggest that DNA damage is not large enough to trigger intense repair responses and might not result in biologically significant DNA damage.
Abstract Tu135: FYCO1 ameliorates cardiac remodeling in response to ischemia by amplifying autophagic flux
Authors: Frauke Senger, Anca Remes, Christin Tannert, Emelie Haas, Oliver Mueller, Norbert Frey
Journal: Circulation Research (2024)

Background: Dysregulation of autophagy is known to have detrimental effects on cardiac remodeling. FYCO1, a novel regulator of autophagy mediates the transport of autophagosomes, thereby amplifying autophagic flux. Here, we investigate the impact of FYCO1 on myocardial healing via autophagy modulation. Methods: FYCO1-Tg mice crossed with RFP-EGFP-LC3 reporter mice (FYCO1-TGxRGFP) were utilized to analyze autophagic flux via confocal microscopy following permanent ligation of the left anterior descending artery (LAD) to induce myocardial ischemia. Autophagy activity was evaluated via Western blot of p62 and LC3 II. Macrophage infiltration and apoptosis was assessed by immunofluorescence microscopy, while Masson's Trichrome staining detected fibrosis and infarct size. Cardiac function was determined by echocardiography. Results: FYCO1-TGxRGFP mice displayed significantly enhanced autophagic flux post MI, as evidenced by increased p62 (WT LAD: 2,9±0,4; TG LAD:4,0±0,5) and LC3 II (WT LAD: 1,6±0,2; TG LAD:14,0±1,4) protein levels. Confocal microscopy revealed an accumulation of autolysosomes in WT mice 30 days post MI (WT autophagosomes: 1±0,4; WT autolysosomes: 38,6±3,8), contrasting with the sustained ratio of autophagosomes to autolysosomes in FYCO1-TGxRGFP mice (TG autophagosomes:43,3±5,1; TG autolysosomes: 73,5±12,4), implying the preservation of adequate autophagic flux. FYCO1 overexpression reduced macrophage infiltration into the border zone post MI (WT LAD: 132,4 ±14,3; TG LAD: 18,91±3,7 and inhibited apoptosis induction shown by cleaved caspase7 activity (WT LAD: 64,6±10,1; TG LAD: 9,2±2,1). Moreover, FYCO1-TGxRGFP mice exhibited significantly reduced fibrosis (WT:19,6±1,8%; TG:10,6±1,6%) and infarct size (WT:34,5 ±3,9%; TG:5,5±2%) in the left ventricle (LV), accompanied by marked improvements in global heart function post MI (EF WT: 32,7±3,2%; TG: 56,4±3,9%) compared to WT mice. Conclusion: In conclusion, FYCO1 mitigates adverse consequences of ischemic injury via induction of autophagy and a previously unrecognized role in modulating inflammation in response to myocardial infarction.
Abstract Tu083: Oxytocin improves cardiovascular outcomes in a rat model of pressure-overload heart failure
Authors: Bridget Alber, Emily Cheung, Rebekah Russo, David Mendelowitz, Matthew Kay
Journal: Circulation Research (2024)

Oxytocin (OT) is a peptide made in the hypothalamus and released into circulation by the pituitary gland. Known for its role in childbirth and lactation, recent research suggests that OT has significant cardiovascular benefits, reducing the risk of cardiovascular diseases such as hypertension and atherosclerosis. We tested if OT has beneficial effects on cardiovascular function in a rat model of pressure overload heart failure (HF). Neonatal Sprague Dawley rats underwent transaortic constriction (TAC). Pressure overload and cardiac dysfunction progressed as animals matured. Echocardiography at 5 weeks of age confirmed reduced ejection fraction. Animals were then randomly assigned to receive daily IP injections of either OT (treatment) or saline (control) for two weeks. Echocardiography was performed again before hearts were excised for optical mapping studies to test for electrophysiological differences between groups. Hearts were electromechanically uncoupled using blebbistatin and transmembrane potential (RH237) and intracellular Ca2+ (Rhod2am) were simultaneously mapped during a dynamic restitution protocol. Preliminary results indicate that rats in the treatment (OT, n=3) group had improved cardiac function compared to controls (saline, n=3), with higher ejection fraction (66.71 ± 9.44 vs. 25.83 ± 17.93, p=0.0125), higher cardiac output (62.4 ± 11.45 vs. 20.35 ± 6.12, p=0.0025), and greater stroke volume (180.2 ± 18.19 vs. 73.96 ± 37.29, p=0.0057). Preliminary optical mapping results indicate that the hearts of OT-treated rats (n=3) have lower steady state action potential duration (APD) compared to controls (n=2). APD60 decreased from 109.5 ± 10.09 to 75.79 ± 21.94 (p=.0725) and APD80 decreased from 133.1 ± 10.22 to 101.1 ± 24.5 (p=.09595), indicating preservation of repolarizing currents corresponding to healthier electrophysiological function. In summary, our preliminary results suggest exogenous IP OT administration could have a potent cardioprotective effect on chronic and severe pressure overload hearts. Future work will investigate potential mechanisms of OT mediated cardio-protection, including sites of action.
Abstract Tu087: Knockout of TIGAR Rescues Cardiac Dysfunction in SIRT3 Knockout Mice
Authors: Jessie Besanson, Aubrey Cantrell, Quinesha Williams, Heng Zeng, Jian-Xiong Chen
Journal: Circulation Research (2024)

Introduction: Heart failure (HF) is the leading cause of death in the United States, despite advances in treatment, it maintains the highest disease mortality rate in the country. Previously it has been established that Sirtuin 3 (SIRT3), a mitochondrial NAD+- dependent deacetylase, and the Tp53-induced glycolysis and apoptosis regulator (TIGAR) are associated with the development of HF. SIRT3 plays a key role in the maintenance of cardiac function. Decreases in SIRT3 are associated with human aging and diabetes, whereas knockout results in cardiac dysfunction in mice. We have shown: (1) overexpression of SIRT3 downregulates TIGAR and attenuates diabetic cardiomyopathy; (2) knockout of TIGAR enhances myocardial glycolysis and reduces pathological remodeling while maintaining cardiac function in pressure-overload-induced heart failure. To date, the direct interactions between TIGAR and SIRT3 in the development of HF remain unexplored. Aim: By crossing TIGAR knockout mice (TIGARKO) with SIRT3 knockout (SIRT3KO) mice, this study tested if genetic targeting of TIGAR could rescue cardiac dysfunction in SIRT3KO mice. Methods and Results: Echocardiography was performed on SIRT3KO, TIGARKO, TIGARKO/SIRT3KO, and SIRT3 Control mice. Analysis of cardiac function showed that SIRT3KO mice had significant decreases in coronary flow reserve (CFR), ejection fraction (EF) SIRT3KO (41.52 ± 4.50) vs SIRT3 Control (60.91 ± 4.91, p&lt;0.001) and fractional shortening (FS) SIRT3KO (20.11 ± 2.48) vs SIRT3 Control (32.07 ± 3.37, p&lt;0.001). The diastolic E’/A’ ratio was decreased; IVRT and MPI were significantly increased. Knockout of TIGAR in mice maintained systolic function by increasing EF (62.25 ± 9.84) vs (41.52 ± 4.50, p&lt;0.001), FS (33.33 ± 7.12 vs 20.11 ± 2.48, p&lt;0.05), and CFR, as well as improved diastolic function by decreasing IVRT, MPI, and increasing E’/A’ ratio in SIRT3KO mice. SIRT3KO and TIGARKO mice had a significant increase in weight/tibia length ratio (HW/TL). Interestingly, the knockout of TIGAR significantly reduced LV mass and HW/TL in SIRT3KO mice. Conclusions: The knockout of TIGAR can rescue the HF phenotype of SIRT3KO mice, but the underlying mechanisms require further investigation to develop potential treatments for HF.
Abstract Tu126: Unveiling the Role of GRAF1 in Orchestrating Mitophagy and Metabolic Flexibility in Stressed Cardiomyocytes
Authors: Qiang Zhu, Matthew Combs, Christopher MacK, Joan Taylor
Journal: Circulation Research (2024)

Mitochondria are essential for cardiomyocyte contraction by generating ATP and orchestrating metabolic pathways. Understanding how mitophagy—selective removal of damaged mitochondria in lysosome—and metabolic flexibility are coordinated is crucial for cardiac function under physiological and pathological conditions. Our study explores the molecular mechanisms behind this coordination in cardiomyocytes. We identify GRAF1(Arhgap26) as a pivotal mediator in PINK1-Parkin dependent mitophagy, facilitating damaged mitochondria clearance and regulating mitochondrial substrate flexibility. Depletion of GRAF1 in neonatal rat ventricular cardiomyocytes (NRVCMs) compromises mitochondrial function, evidenced by reduced membrane potential, impaired oxidative phosphorylation, and elevated cleaved Caspase 3 levels. Moreover, GRAF1 depletion attenuates LC3II activation and increases mitochondrial mass following toxin-induced stress. Using tamoxifen-inducible cardiomyocyte-restricted GRAF1 knockout mice (GRAF1 CKO ), we observe normal cardiac function under basal conditions. However, upon isoproterenol (ISO) treatment, GRAF1 CKO mice display cardiac dysfunction and reduced mitophagy. Metabolomics analysis reveal distinct metabolic signatures between ISO-treated control and GRAF1 CKO mice, with impaired fuel flexibility observed in GRAF1 CKO mice, as highlighted by impaired glucose utilization relative to control mice. Mechanistically, phosphorylation of specific sites (S668, T670, and S671) within the proline-rich region of GRAF1 by PINK1 or PINK1-dependent kinases regulates its dual functions. This phosphorylation event releases the autoinhibitory state of the SH3 domain, enabling it to interact with ABI2 and WAVE2 complex for actin remodeling necessary for efficient mitochondria clearance. Additionally, phosphorylation enhances GRAF1’s affinity for Malonyl-CoA Decarboxylase (MCD), promoting MCD degradation and subsequent elevation of cellular malonyl-CoA levels. This rise in malonyl-CoA inhibits carnitine pamitoyl transferase-I (CPT-I), thereby suppressing fatty acid oxidation while promoting glucose oxidation in mitochondria, contributing to the mitochondrial metabolic flexibility. In summary, our findings elucidate GRAF1's role in orchestrating mitophagy and metabolic flexibility in stressed cardiomyocytes. GRAF1 phosphorylation serves as a molecular switch, ensuring efficient mitochondrial clearance and substrate utilization to maintain cardiac energetics and function.
Abstract Mo035: Double (Dual) Sequential Defibrillation Versus Standard Defibrillation for Refractory Ventricular Fibrillation: A Systematic Review and Meta-Analysis
Authors: Rola Ali, Basiem Barsoum, Rodrigo Lago
Journal: Circulation Research (2024)

Background: Refractory ventricular fibrillation (RVF) is VF that persists despite 3 or more single defibrillation attempts. Double sequential defibrillation (DSD) is a proposed defibrillation strategy for RVF that employs delivering 2 rapid sequential, transthoracic electric shocks from 2 separate defibrillators. This meta-analysis aims to identify evidence in the literature surrounding the use of DSD and compare its efficacy with standard defibrillation (SD) in patients with RVF. Methods: We conducted our meta-analysis in compliance with the PRISMA guidelines. PubMed, Embase, and Cochrane databases were used to retrieve articles. We included studies that evaluated and compared the utility of DSD versus SD in cardiac arrest adult patients who received 3 or more standard defibrillatory shocks for RVF. Our predefined outcomes of interest were VF termination (VFT), return of spontaneous circulation (ROSC), survival to hospital admission (SHA), and survival to hospital discharge (SHD). Odds ratio (OR) and 95% confidence intervals (CIs) were calculated using the random-effects model. Heterogeneity was assessed by I 2 statistic. Results: A total of 8 studies (2 randomized controlled trials and 6 observational studies) involving 1,579 patients were included in the meta-analysis. No statistically significant difference existed between DSD and SD in terms of VFT (OR, 1.58; 95% CI, 0.84-2.99; p= 0.15; I 2 =0.54), ROSC (OR, 0.91; 95% CI, 0.53-1.55; p= 0.72; I 2 =0.76), SHA (OR, 1.18; 95% CI, 0.54-2.55; p= 0.68; I 2 =0.79), and SHD (OR, 1.03; 95% CI, 0.49-2.17; p= 0.94; I 2 =0.69). Substantial heterogeneity was noticed across the analysed studies. Conclusion: Despite the growing use of DSD for the management of RVF, there remains insufficient evidence to support its widespread implementation. This meta-analysis demonstrated that DSD had no statistically significant advantage over SD. However , due to limited data in the literature further clinical trials with large sample sizes are warranted to assess the efficacy and clinical impact of DSD, and whether it can potentially be integrated into resuscitation protocols.
Abstract Tu129: Collagen Peptide modulates Enzymatic Activity post-Myocardial Infarction
Authors: Ayodeji Olabiyi, Sirin Nazan Cakir, Lisandra de Castro Bras
Journal: Circulation Research (2024)

Matrix metalloproteinases (MMPs) play critical roles post-myocardial infarction (MI) and directly correlate with adverse LV remodeling. Of the MMPs, MMP-9 shows the highest correlation with MI patient mortality. Clinical trials trying to inhibit MMP-9 were unsuccessful or detrimental, mostly because MMP-9 has critical roles post-MI and inhibition results in exacerbation of adverse remodeling. Previously, we reported a collagen peptide – p1159 – to reduce LV dilation and adverse LV remodeling post-MI. Recently, we discovered p1159 acts as an MMP-9 competitive substrate and reduces substrate proteolysis in vitro . Herein, we investigated whether p1159 can act as a competitive substrate in vivo to reduce proteolysis of endogenous substrates post-MI without inhibiting MMP-9 activity. Also, we compared p1159 actions to those of a MMP-9 inhibitor (MMP-9i). We hypothesized that animals that receive p1159 would show reduced inflammation and adverse remodeling compared to those that received MMP-9i. Adult male and female C57Bl/6 mice (n = 6-8/group) were grouped as follows: saline (control); p1159; MMP-9i, and p1159 + MMP-9i. We performed baseline echocardiography followed by surgery to induce a permanent occlusion MI model. Three hours later, mice received a randomized osmotic mini-pump to continuously deliver p1159 (14μg/day/kg body weight) or vehicle (saline, 0.9%) and/or MMP-9i (10mg/kg body weight, JNJ 0966 by gavage). The LV and plasma were harvested on day 3 (D3) and D5 for downstream proteomics analysis following a final echocardiographic assessment. Infarct sizes were similar between groups, indicating same level of initial injury. Compared to control, p1159 did not inhibit activity or levels of MMP-9, while animals treated with MMP-9i showed significantly reduced MMP-9 activity. As expected, p1159 reduced (p &lt; 0.05) substrate cleavage, as seen by analysis of the LV peptidome, particularly at D3. Substrates that displayed a reduction in proteolysis included fibrinogen, MIF, myosin, titin, and tubulin. These data support p1159 as a competitive substrate of MMP-9 that can modulate its activity without inhibition. Moreover, these results may explain the previously reported effect of p1159 at reducing LV dilation and improving systolic function.