Circulation, Volume 146, Issue Suppl_1, Page A15165-A15165, November 8, 2022. Introduction:Guidelines recommend the use of Dobutamine stress echocardiography (DSE) in case of low flow low gradient aortic stenosis (LFLG AS) when left ventricular ejection fraction (LVEF)
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Abstract 12919: Stress Induced Cardiomyopathy After the Covid-19 Vaccine
Circulation, Volume 146, Issue Suppl_1, Page A12919-A12919, November 8, 2022. Introduction:The SARS-CoV-2 virus has potential to cause acute and long-term cardiac effects. The vaccines were developed to prevent severe illness, but there are concerns about vaccine related side effects. Specific to the heart there have been case reports of mRNA vaccine related cardiomyopathies, particularly myocarditis. We present a case of a patient with presumptive stress induced cardiomyopathy in the setting of recent Covid-19 mRNA vaccination.Case Presentation:A 93-year-old female with a past medical history of hypertension presented with worsening shortness of breath and bilateral lower extremity edema. She received her second dose of the Covid-19 mRNA vaccine five days prior to presentation. She had no history of heart disease, was a nonsmoker, and denied alcohol or drug use. In the ED she was noted to be fluid-overloaded, and her CT chest showed minimal coronary calcification and bilateral pleural effusions. She was admitted for heart failure exacerbation and started on IV furosemide. Her transthoracic echocardiogram showed an ejection fraction of 40-45%. The pattern of left ventricular dysfunction was consistent with stress induced cardiomyopathy with apical akinesis and basal sparing of the left ventricular wall segments. Cardiology was consulted and recommended management with diuretics and beta blocker. She had a diuresis of 5 liters during her hospitalization. At clinic follow-up, dyspnea had improved, and her peripheral edema had resolved. Repeat echocardiogram showed recovery of left ventricular ejection fraction to 61% by Simpsons biplane technique with no regional wall motion abnormalities. Further cardiac assessment to evaluate for obstructive coronary artery disease and myocarditis was discussed and offered to the patient but was declined due to her positive response to conservative management.Discussion:The precise etiology of stress induced cardiomyopathy is unknown, but it is thought to be secondary to the sudden release of stress hormones. There are isolated reports of stress induced cardiomyopathy associated with Covid-19 vaccination, but the potential mechanism is unclear. An improved understanding of the potential effects of mRNA vaccines may help guide decisions regarding future booster vaccinations.
Abstract 10038: Combined Low Endothelial Shear Stress and High Plaque Structural Stress Heterogeneity Predicts Non-Culprit Major Adverse Cardiovascular Events; Insights From the PROSPECT Study
Circulation, Volume 146, Issue Suppl_1, Page A10038-A10038, November 8, 2022. Introduction:Low endothelial shear stress (ESS) is a pro-atherogenic stimulus associated with coronary plaque development, while high plaque structural stress (PSS) and its heterogeneity is associated with plaque destabilization. Previous studies showed that combining ESS and PSS additively predicts plaque progression, but no studies have determined their ability to predict major adverse cardiovascular events (MACE). We examined whether combining ESS and PSS improves MACE prediction in patients with acute coronary syndrome.Methods:We examined baseline ESS, ESS gradient, PSS, and PSS heterogeneity index (HI) in 22 non-culprit lesions (NCL) leading to future MACE, and 64 randomly selected control NCLs without MACE from the PROSPECT (Providing Regional Observations to Study Predictors of Events in the Coronary Tree) study. ESS was calculated by computational fluid dynamics and PSS by finite element analysis on co-registered lesions.Results:86 lesions (55 thin-cap and 31 thick-cap fibroatheromas) were analyzed from 67 patients. Lesions that caused future MACE showed baseline higher PSS HI (0.32 vs. 0.24, p
Abstract 13208: Pathways Linking Posttraumatic Stress Disorder to Ischemic Heart Disease in Women Veterans
Circulation, Volume 146, Issue Suppl_1, Page A13208-A13208, November 8, 2022. Introduction:Posttraumatic stress disorder (PTSD) is associated with increased risk of ischemic heart disease (IHD). It is unclear if this excess risk is entirely mediated through traditional IHD risk factors (hyperlipidemia, hypertension, diabetes, and smoking). We examined 13 potential mediators of the PTSD-IHD association in a large cohort of women veterans: traditional risk factors, other conditions (obesity, chronic kidney disease, neuroendocrine disorders), women-specific risk factors (e.g., gestational diabetes and hypertension, pre-eclampsia), and psychiatric disorders (depression, anxiety, psychotic disorders, alcohol dependence, and drug dependence).Methods:The study cohort included women veterans ≥18 years of age who were enrolled in Veterans Health Administration care between 1/1/2000 to12/31/2017. Diagnosis of each risk factor and disorder was based on administrative billing codes (International Classification of Disease versions 9 and 10). The final study cohorts included 1:2 propensity-score matched group of patients with and without PTSD respectively. The cohorts were matched for age, number of prior visits, and presence of the above risk factors. Cox regression examined associations of PTSD with time to development of the above 13 risk factors. Cox regression with time-varying covariates was used to model time to development of IHD as a function of PTSD and each of above 13 risk factors as time-varying predictors in separate models.Results:The cohorts included 132,293 patients with, and 265,846 patients without PTSD. PTSD was positively associated with each of the 13 risk factors. Results are tabulated in the table below.Conclusion: Traditional risk factors cumulatively accounted for just one third of the risk of IHD posed by PTSD, and all examined risk factors accounted for less than half of the increased risk associated with PTSD. More research is needed to identify pathways by which PTSD accelerates cardiovascular risk.
Abstract 12676: Psychological Stress Stimulates Vascular Inflammatory Responses and Destabilizes Atherosclerotic Plaques as Assessed by High-Speed, High-Resolution Intravital Imaging
Circulation, Volume 146, Issue Suppl_1, Page A12676-A12676, November 8, 2022. Backgrounds:Psychological stress increases leukocyte accumulation within atherosclerotic lesions and exacerbates plaque vulnerability. However, the stress-induced real-time behavior of immune cells in the atheroma has been poorly definedin vivo. Here, we aim to investigate whether stress stimulates the inflammatory leukocyte dynamics in the atherosclerotic plaques and destabilizes the lesions using customizedin vivocell tracking strategies.Methods and Results:We developed a system and motion reconstruction algorithm that can probe and compensate for respiratory and pulsatile movements. Individual leukocytes near the atherosclerotic plaques were imaged in real-time by adapting a custom-built high-speed intravital microscopy system with multiple fluorescence channels. Stress was achieved by immobilization procedures and/or stereotaxic application of stress stimulus onto the brain amygdala. The high spatial and temporal resolution of our real-time cell tracking system allowed clear identification of rhodamine 6G-positive leukocytesin vivo. In the common femoral artery bifurcation of apolipoprotein E knockout mice, white blood cells firmly adhered to the inner layer of the vessel walls while some slowly flowed along the endothelium (Figure). We further demonstrate that the stress increased the rolling and adhesion of inflammatory leukocyte subsets near the atherosclerotic lesions, and enhanced the plaque macrophage activity as assessed byin vivoimaging. Confocal laser scanning microscopy and immunostaining analyses corroborated thein vivofindings that the stress induced the destabilization of the atherosclerotic plaques.Conclusion:Our data show that stress stimulated the dynamics of inflammatory leukocyte subsets in atherosclerotic environments and increased the plaque vulnerability as assessed by the customized high-resolution motion-compensatedin vivoimaging strategy.
Abstract 13610: Imbalance Between GCN5L1 Mediated CypD Acetylation and Sirt3 Deacetylase Promotes Mitochondrial Oxidative Stress, Endothelial Dysfunction and Hypertension
Circulation, Volume 146, Issue Suppl_1, Page A13610-A13610, November 8, 2022. Nearly half of adult population has hypertension which is a main risk factor for cardiovascular disease. Mitochondrial dysfunction contributes to hypertension and targeting mitochondria can potentially improve treatment of hypertension. We found hyperacetylation of mitochondrial Cyclophilin D (CypD) in essential hypertension and proposed that CypD acetylation can promote endothelial dysfunction and hypertension. CypD acetylation is mediated by general control of amino acid synthesis 5 like 1 (GCN5L1) protein which is counteracted by deacetylase Sirt3. We tested potential role GCN5L1 and Sirt3 in endothelial dysfunction and hypertension. Western blot of aortic mitochondria showed an increased GCN5L1 level in hypertensive mice coupled with the reduction of Sirt3 deacetylase resulting in 250% increase in GCN5L1/Sirt3 ratio promoting CypD acetylation. We reported pathogenic role of lipid oxidation products isolevuglandins (isoLGs) and scavenging isoLGs by mitochondria-targeted mito2HOBA reduces mitochondrial acetylation. We tested if mitochondrial isoLGs contributes to acetylase/deacetylase imbalance driving CypD acetylation. Treatment with mito2HOBA improves Sirt3 expression and reduces GCN5L1 level resulting in normalization of GCN5L1/Sirt3 ratio and reduced CypD acetylation. To define the pathophysiological role of GCN5L1 in endothelial cells we tested if GCN5L1 depletion prevents cytokine-induced of mitochondrial oxidative stress. Indeed, treatment of human aortic endothelial cells with AngII+TNFα induces mitochondrial O2.-, however, GCN5L1 depletion using siRNA completely abrogated the cytokine-induced mitochondrial oxidative stress. To define the role GNC5L1 in pathogenesis of endothelial dysfunction we developed new tamoxifen-inducible endothelial specific GNC5L1 knockout mice (EcGNC5L1KO). Depletion of endothelial GCN5L1 reduces vascular mitochondrial O2.-, prevents inactivation of endothelial nitric oxide and preserves endothelial dependent relaxation in angiotensin II-infused EcGNC5L1KOmice compared with wild-type littermates. These data support the pathogenic role of GNC5L1 in CypD acetylation and endothelial dysfunction and targeting GNC5L1 can be beneficial in cardiovascular disease.
Abstract 11237: Dose Response and Long QT Genotype During Exercise Stress Testing in Children
Circulation, Volume 146, Issue Suppl_1, Page A11237-A11237, November 8, 2022. Introduction:Beta-blockers (BB) are first-line therapy for long QT syndrome (LQTS). Many physicians rely on repeated exercise stress tests (ESTs) to establish the optimal dose in each patient.Hypothesis:Increased BB dose is associated with a decrease in maximum heart rate, influenced by precision-medicine factors including genotype.Methods:Retrospective chart review of treadmill ESTs with the outcome variable “% predicted heart rate (HR)” = (maximum HR achieved/(220-age))*100. Genotype positive patients had pathogenic or likely pathogenic variants, re-adjudicated in 2022. Doses of BB other than nadolol were converted to nadolol equivalents using an established methodology.Results:We evaluated 345 ESTs in 132 LQTS patients (58% genotype positive) from 2003-21. The mean age at first EST was 12.5 years (standard deviation 4.0 years). Most patients were prescribed nadolol (59%) or atenolol (28%). When controlled for person-level fixed effects, we observed an inverse relationship between BB dose and % predicted HR. The dose-response slope was steeper in genotype positive patients than genotype negative patients (-4.8 vs. -3.3,Figure, p
Abstract 15616: Single Cell Transcriptomic Profiling Identifies Ferroptosis and Oxidative Stress as Potential Drivers of Muscle Dysfunction in Pad
Circulation, Volume 146, Issue Suppl_1, Page A15616-A15616, November 8, 2022. Introduction:Peripheral artery disease (PAD) affects >8 million people nationwide and is disabling. PAD-associated myopathy causes weakness yet is understudied. Unbiased transcriptomic profiling of muscle satellite cells (MuSC) which drive recovery may elucidate the etiology of ischemic myopathic change.Hypothesis:MuSC in PAD differentially express injury associated pathways that may be novel targets for intervention to reduce ischemic myopathy.Methods:Muscle tissue biopsies were obtained during lower extremity amputation or bypass in PAD/ischemic (N=4; ABI
Abstract 14174: Abnormal Exercise Electrocardiography With Normal Stress Echocardiography is Associated With Increased Subclinical Coronary Atherosclerosis: Insights From the Project Baseline Health Study
Circulation, Volume 146, Issue Suppl_1, Page A14174-A14174, November 8, 2022. IntroductionPatients with an abnormal (positive) exercise electrocardiography (ECG), but normal stress echocardiography (+ECG/-Echo) have more adverse cardiac events than patients with a negative ECG and normal stress Echo (-ECG/-Echo). However, it is unclear if ECG/Echo discordance is associated with a greater burden of concurrent subclinical coronary atherosclerosis.MethodsIn the Project Baseline Health Study (PBHS), participants underwent stress Echo and a coronary artery calcium (CAC) scan. For this PBHS substudy, participants with no known coronary artery disease (CAD) were analyzed by stress result: -ECG/-Echo, +ECG/-Echo, or +Echo (with or without +ECG). Patients with a submaximal stress test, uninterpretable ECG, resting wall motion abnormality, and/or baseline ejection fraction
Abstract 11938: Novel Approach for Optimal Assessment of Cardiovascular Risk of Blood Pressure in Asymptomatic Subjects Utilizing Mild Exercise Stress Test Protocol
Circulation, Volume 146, Issue Suppl_1, Page A11938-A11938, November 8, 2022. Background:BP risk class assessment has been relying on resting BP (rBP) measurements by healthcare providers. Often, this measurement does not correlate with 24-hour ambulatory BP monitoring nor with at-home measurements.Purpose:To assess whether abnormal rise in BP post-mild exercise protocol (PMEP), which resembles most of the activities subjects are under all day, will be more physiologic and informative for risk stratification, beyond the rBP measurements.Methods:We screened 2,924 subjects, ages 20-79, for CVD risk using the Early Cardiovascular Disease Risk Scoring System, also known as the Rasmussen Risk Score, which consists of 10 tests: 7 vascular and 3 cardiac (published previously). The vascular tests include rBP, BP PMEP (2.4 mi/hr and 7% elevation for 3 minutes), small (C2) artery stiffness, and CIMT. Out of the total subjects, 1094 (37%) were asymptomatic and on no medications. These were divided into four BP classes according to the current ACC/AHA guidelines.Results:In the table, normotension with an abnormal rise in BP PMEP has significant cardiovascular structural and functional abnormalities (CVSFA) than those without. Also noted, the higher the BP class, the higher the CVSFA with and without an abnormal rise in BP PMEP.Conclusions:Abnormal rise in BP PMEP in normotensive subjects is associated with significant CVSFA. This may represent a “masked hypertension” cohort. These findings mandate early diagnosis, follow-up, and optimal treatment. Additionally, an abnormal rise in BP PMEP in other classes is more pronounced with stepwise increases in BP class. Hence, we advocate for PMEP for BP classification and treatment. Early detect to protect.
Abstract 14940: Neonatal Cardiac Mesenchymal Stem Cells Target ERK/MAPK Signaling Pathway to Ameliorate Oxidative Stress and Inflammation in Acute Kidney Injury
Circulation, Volume 146, Issue Suppl_1, Page A14940-A14940, November 8, 2022. Introduction:Failure of multidrug therapy and the multifactorial nature of kidney injury has paved the path way regenerative medicine with over 45 clinical trials using stem cells-based therapy underway. Neonatal cardiac mesenchymal stem cells (nMSC) are one of the most potent stem cells due to their secretome. HYPOTHESIS: SOD2 and anti-inflammatory miRNAs (miR-214 & 95p) in paracrine secretions (secretome) of nMSC provides renoprotection in a rodent model of glycerol-induced AKI.Methods:nMSC were generated from neonatal myocardium using enzymatic digestion and antibodies-based selection. Secretome was collected by conditioning nMSCs for 72 hours in serum free basal medium. Human kidney cells (HKC) were used forin vitroanti-oxidation assays using cisplatin. THP-1 cells were used for anti-inflammatory assessment. CD1 mice were used for glycerol-induced AKI model. Mice were subjected to AKI via IM glycerol (9mg/kg). nMSC-derived secretome was intravenously administered immediately after, or 4 hours post-glycerol. Blood urea nitrogen (BUN) and creatinine were analyzed in serum. Cell survival/KIM1 was assessed by immunohistology/FACS. Other experiments utilized cisplatin toxicity in HKC.Results:Administration of nMSC secretome (5 or 10mg/kg) at the same time or 4-hours post-glycerol administration significantly reduced serum creatinine and BUN in a glycerol induced AKI animal model. Caspase-9 and KIM1 expression was significantly decreased in tubular cells as compared to placebo at a dose of 10mg/kg. KIM-1 was significantly downregulated as compared to placebo following nMSC-secretome administration. Western blot analysis of HKC treated with cisplatin in presence of nMSC-secretome showed significant reduction in NFkb and pERK expression (p
Abstract 11065: Stress T1 Mapping Demonstrates Coronary Microcirculatory Dysfunction in Both Nonhypertrophied and Hypertrophied Myocardium of Hypertrophic Cardiomyopathy
Circulation, Volume 146, Issue Suppl_1, Page A11065-A11065, November 8, 2022. Introduction:Coronary microcirculatory dysfunction (CMD) in hypertrophic cardiomyopathy (HCM) is associated with clinical deterioration. We have shown that stress T1 mapping could detect CMD of hypertrophied interventricular septum (IVS). However, CMD in nonhypertrophied left ventricular free wall (LVFW) has not been fully elucidated.Hypothesis:We assessed the hypothesis that regional CMD in LVFW of HCM can be detected using stress T1 mapping.Methods:We evaluated 36 consecutive subjects (26 HCM patients and 10 control subjects, mean age: 61±3 years) who underwent CMR at 3T. Cine imaging, rest and adenosine stress T1 mapping, late gadolinium enhancement (LGE) and phase-contrast imaging of coronary sinus flow were performed. The T1 values at rest and after adenosine stress were measured as an averaged T values of 3 short-axis slices of LV myocardium and T1 reactivity (ΔT1) was calculated as follows: ΔT1 (%) = (T1stress – T1rest)/T1rest х 100. Coronary flow reserve (CFR) was measured coronary sinus blood flow during adenosine stress divided by that at rest.Results:The T1 values at rest were significantly higher in HCM than control (1245±9ms vs. 1196±11ms, p=0.0027), and the T1 values after adenosine stress significantly increased in both groups (HCM: 1285±10ms, p=0.0018 vs. rest, control: 1244±9ms, p=0.0128 vs. rest, Figure 1). Both IVS and LVFW demonstrated significantly lower ΔT1 in HCM than control (IVS: 3.95±0.35% vs. 5.68±0.41%, p=0.0163, LVFW: 4.80±0.39% vs. 6.75±0.65%, p=0.0163, Figure 2). CFR in HCM significantly decreased than that in control (2.48±0.40 % vs. 5.97±1.31 %, p=0.0051). Multiple regression analysis revealed that ΔT1 of both IVS and LVFW was correlated with CFR (β=0.527, p=0.0026, β=0.445, p=0.0325).Conclusions:T1 reactivity significantly decreased in both nonhypertrophied and hypertrophied myocardium of HCM compared to control. Stress T1 mapping have the advantage of being able to estimate regional CMD in addition to global CMD.
Abstract 14359: Impact of Marital Stress on 12-month Health Outcomes Among Young Adults With Acute Myocardial Infarction
Circulation, Volume 146, Issue Suppl_1, Page A14359-A14359, November 8, 2022. Background:Psychosocial stress is associated with worse cardiac outcomes, but little is known about the prognostic impact of marital stress in young adults (≤55 years) with acute myocardial infarction (AMI). We investigated the association between marital stress and 1-year health outcomes in young AMI survivors.Methods:We used data from the VIRGO study (Variation in Recovery: Role of Gender on Outcomes of Young AMI Patients), which enrolled people aged 18-55 years with AMI (2008-2012). Marital stress was assessed among married/partnered participants at 1 month post-AMI using the Stockholm Marital Stress Scale, categorized as absent/mild, moderate, and severe. Main outcomes were physical/mental health status, generic/disease-specific quality of life, angina, depressive symptoms, and all-cause readmission at 1 year post-AMI. Linear and logistic regression models were sequentially adjusted for baseline health status, demographics, and socioeconomic factors (including education level, income level, employment status, and insurance status).Results:Among the 1593 married/partnered participants in our study, more women reported severe marital stress than men (39.4% vs 30.4%, p=0.001). Having severe marital stress was associated with worse physical and mental health, lower generic and cardiovascular-specific quality of life, more angina and depressive symptoms, and 1.48 times higher all-cause readmission at 1 year post-AMI. These associations remained significant after adjusting for baseline health score and patient demographics (Table Model 1), but they attenuated and became non-significant when further adjusting for socioeconomic factors (Model 2).Conclusion:Marital stress was associated with worse health outcomes in young AMI patients, which can be partially mediated by socioeconomic factors. Further research is needed to understand this complex relationship and potential causal pathway associated with these findings.
Abstract 14263: Asessment of Pulmonary Vascular Reserve Using Pharmacologic Stress Testing in Patients With Fontan Physiology
Circulation, Volume 146, Issue Suppl_1, Page A14263-A14263, November 8, 2022. Introduction:The presence of pulmonary vascular disease (PVD) may be under-recognized during standard hemodynamic evaluation in patients with Fontan physiology. Assessment of pulmonary vascular reserve (VR) (Δ pulmonary artery pressure/Δ cardiac index) utilizing pharmacologic stress testing could be a better way of identifying PVD in pediatric patients. The objective of this study is to diagnose Fontan patients with PVD utilizing pharmacologic stress testing.Hypothesis:Pharmacologic stress testing will unmask Fontan patients as having PVD.Methods:Single center record review of cardiac catheterizations with dobutamine administration in Fontan patients from January 2021 to June 2022. Following acquisition of baseline data on room air, a dobutamine infusion was started at 5 mcg/kg/min with dose escalation as needed until an appropriate heart rate response was achieved. Hemodynamics were reassessed at each dose interval, but data are reported at the highest cardiac index (CI). Abnormal VR was defined as > 3 mmHg/l.Results:Eighteen Fontan patients (87% male) were included. Median age at the time of catheterization was 14 (IQR 11, 16) years with mean duration of Fontan circulation of 9.9 ± 3.9 years. The primary indication for catheterization was exercise intolerance (65%). Dobutamine administration did not result in a significant change in indexed pulmonary vascular resistance (PVRi) (2.1 ± 0.8 v 2.4 ± 1.31 iWU, p = 0.21) or Fontan pressure (12 [IQR 11, 14] v 14 (IQR 12, 15), p=1.0]. Eight patients had a PVRi ≥ 2.0 iWu at baseline; while 4 (22% of the cohort) had a PVRi < 2.0 iWU at baseline but had an abnormal VR.Conclusions:PVD is common in Fontan patients but may be missed in some patients without pharmacologic stress testing. Accurate diagnosis of PVD will allow for optimization of Fontan circulation with pulmonary vasodilators.
Abstract 11298: Bioenergetics-Independent Stress Response to Mitochondrial Protein Import Clogging in the Heart
Circulation, Volume 146, Issue Suppl_1, Page A11298-A11298, November 8, 2022. Mitochondria are double-membraned organelles indispensable in metabolically active organs such as the heart. Much of the mitochondrial proteome is encoded by the nuclear genome and requires import into mitochondria via channels present on the outer and inner mitochondrial membranes. If protein import goes awry at any step, it can cause unimported mitochondrial proteins to accumulate in the cytosol, leading to mitochondrial Precursor Overaccumulation Stress (mPOS). Defects in mitochondrial protein import have been linked to many forms of heart disease such as Senger’s syndrome, cardiac arrhythmia, and chronic atrial fibrillation. The A123D mutation in adenine nucleotide translocase 1 (Ant1), an ATP/ADP antiporter present on the mitochondrial inner membrane, has been shown to cause hypertrophic cardiomyopathy, while other mutations inAnt1(A114P, A90D, V289M, L98P) have been shown to cause Autosomal Dominant Progressive External Ophthalmoplegia. Our studies suggested that the mutant ANT1 can cause mitochondrial protein import clogging. To characterize the pathophysiology induced by mitochondrial protein import clogging, we developed a mouse model (the “clogger mouse”) expressing two clinically relevant mutations inAnt1, namelyA114PandA123D. While prior work on this model revealed a low-penetrant neurodegenerative and mild myopathic phenotype, the impact of this mutation on the heart has not been studied. In the current study, we show that expression of Ant1A114P, A123Dhas little effect on mitochondrial respiration and heart function. This is consistent with the rapid degradation of Ant1A114P, A123Din the heart. Interestingly, transcriptomic analysis revealed an altered expression of circadian regulator and output genes such asClock,Ciart, Per1-3, CebpbandHlfin the clogger mouse relative to wild type. These data suggest that mitochondrial protein import clogging can induce a stress response independent of bioenergetics. It also led us to hypothesize that the circadian pathway plays a role in adapting to mitochondria-induced proteostatic stress in the heart. Our current experiments focused on testing this hypothesis are anticipated to help us understand how the heart can uniquely adapt to mitochondrial protein import clogging.
Abstract 10461: Single-Cell Transcriptional Analysis of Altered Cardiomyocyte Pdk4 as Indicator of Ischemic Stress Vulnerability in Aging
Circulation, Volume 146, Issue Suppl_1, Page A10461-A10461, November 8, 2022. Introduction:The mechanisms by which aging increases vulnerability to ischemic insult are not well understood. Single-Cell RNA sequencing (scRNA seq) was employed to characterize transcriptional differences in various cell types between aged and young mice which may contribute to aged-related vulnerability to ischemic insult. Pyruvate Dehydrogenase Kinase 4 (Pdk4) has been shown to impact capacity for fatty-acid oxidation (FAO) and consequently adaption to metabolic alterations of ischemic insult.Hypothesis:Alteration of Pdk4 expression levels is an adaptive response transcriptionally under pathological stress to maintain metabolic homeostasis during ischemia and reperfusion (I/R).Methods:Young (3-5 months) and aged (24-26 months) C57BL/6J mice were subjected toin vivoregional 45 min of ischemia and 24 hr of reperfusion (I/R) or sham operations. Bioinformatic analysis was done using Seurat integration vignettes allowing for cell type identification and differential expression testing. Observing genetic expression profiles by cell types. Substrate metabolism was determined with working heart system and Seahorse XF Analyzer.Results:Pdk4 was profoundly found in cardiomyocytes versus fibroblasts, endothelial cells and macrophages of both young and aged hearts. Interestingly, I/R stress triggered Pdk4 mRNA expression of young but not aged cardiomyocytes. Moreover, there is a relative higher Pdk4 level in aged versus young cardiomyocytes under sham operations, indicating Pdk4 mRNA respond to pathological stress. Theex vivoworking heart perfusion data showed that young versus aged hearts exhibited higher FAO in response to I/R. Moreover, Seahorse XF Analyzer showed a higher glycolysis rate in young versus aged cardiomyocytes during I/R. It suggests that an impaired cardiomyocyte Pdk4 mRNA response occurred in aging under I/R stress conditions, this could result in cardiac maladaptive metabolic alterations in aging during pathological stress.Conclusions:Alterations in Pdk4 levels of cardiomyocytes regulates cardiac adaptive metabolism in response to pathological stress. This adaptive regulation of cardiomyocyte Pdk4 is impaired in aging that leads to more vulnerability of aged versus young hearts to ischemic insult.