Normal Cardiac Function Research Articles

Abstract 4145899: The Danger of Moderator Band Ectopy: A Case of Premature Ventricular Contraction induced Recurrent Ventricular Fibrillation

Introduction: Premature Ventricular Contractions (PVCs) are often a benign arrhythmia. However, those originating from the Purkinje system can result in fatal arrhythmias. One example is PVCs originating from the moderator band (MB) within the right ventricle (RV) of the heart. We present a case of PVCs originating from the MB triggering idiopathic ventricular fibrillation (VF) and electrical storm. Case: A previously healthy 49-year-old woman was admitted following a witnessed VF cardiac arrest. She had recurrent episodes of VF, initially treated with Amiodarone and Procainamide which failed to suppress the recurrent VF. She received 54 external defibrillations before a transvenous pacer (TVP) was placed to override the PVCs at a pacing rate of 110 bpm. Post-resuscitation ECGs revealed frequent PVCs originating from the RV free wall, potentially from the lateral part of MB (Figure 1). Quinidine was added to suppress the PVCs ultimately allowing removal of the TVP. Transthoracic Echocardiogram revealed normal cardiac function and a prominent MB. A cardiac MRI was performed showing no infiltrative disease or any other abnormalities. The patient underwent sympathectomy and defibrillator placement. Despite recurrent cardiac arrest, she had excellent neurologic recovery and was subsequently discharged on Quinidine. Discussion: MB extends from the septal wall to the base of the anterior papillary muscle in the RV, carrying Purkinje fibers(PF) from the right bundle branch as it exits the septum. Purkinje fibers have been shown to initiate arrhythmias by several mechanisms including enhanced automaticity, triggered activity and re-entry. In the genesis of PVCs, triggered activity is the likely mechanism. This can degenerate into VF in a structurally normal heart, hence the term “idiopathic VF”. Familiarity with this entity and ECG features of MB ectopy leads to timely management and may potentially prevent lethal arrhythmias in symptomatic patients with such PVCs. Further studies are required to fully understand the arrhythmogenic mechanisms and the optimal management approach for MB ectopy.

Cardiac corin and atrial natriuretic peptide regulate liver glycogen metabolism and glucose homeostasis

BackgroundCardiovascular function and metabolic homeostasis are closely linked, but the underlying mechanisms are not fully understood. Corin is a protease that activates atrial natriuretic peptide (ANP), an essential hormone for normal blood pressure and cardiac function. The goal of this study is to investigate a potential corin and ANP function in regulating liver glycogen metabolism and glucose homeostasis.MethodsLiver glycogen and blood glucose levels were analyzed in Corin or Nppa (encoding ANP) knockout (KO) mice. ANP signaling was examined in livers from Corin and Nppa KO mice and in cultured human and mouse hepatocytes by western blotting.ResultsWe found that Corin and Nppa KO mice had reduced liver glycogen contents and increased blood glucose levels. By analyzing conditional KO mice lacking either cardiac or renal Corin, we showed that cardiac corin and ANP act in an endocrine manner to enhance cGMP-protein kinase G (PKG)-AKT-GSK3 signaling in hepatocytes. In cultured hepatocytes, ANP treatment stimulated PKG signaling, glucose uptake, and glycogen production, which could be blocked by small molecule PKG and AKT inhibitors.ConclusionsOur results indicate that corin and ANP are important regulators in liver glycogen metabolism and glucose homeostasis, suggesting that defects in the corin and ANP pathway may contribute to both cardiovascular and metabolic diseases.

Association between dyspnea, chest pain, nt-probnp and cardiac impairment in people with cystic fibrosis

Abstract Background Cystic fibrosis (CF) is an autosomal recessive disease affecting multiple organs. Emerging evidence indicates an elevated risk of cardiovascular complications in people with CF (pwCF), with some studies implicating CF-related cardiomyopathy as an underlying mechanism. Whether screening for cardiac symptoms and N-terminal pro B-type natriuretic peptide (NT-proBNP) levels may aid in identifying cardiac impairment in pwCF remains unknown. Purpose To assess prevalence of dyspnea and chest pain in pwCF and investigate whether symptoms and NT-pro-BNP are predictive of cardiac impairment. Methods We interviewed 104 adult pwCF and 104 age- and sex-matched controls from the general population about symptoms of dyspnea and chest pain. All participants were examined with transthoracic echocardiography and NT-proBNP. Cardiac impairment was defined as left ventricular (LV) ejection fraction (LVEF) <50%, LV global longitudinal strain (GLS) < 16% or presence of diastolic dysfunction. Results Chest pain was more frequent in pwCF than in controls: (29% vs. 1%, p<0.001), although primarily characterized as atypical and non-exertional chest pain (27%). PwCF also suffered more from dyspnea than controls (89% vs. 18%, p<0.001) (Figure 1) and more pwCF had abnormal cardiac function compared to controls (44% versus 22%, p<0.001). Median NT-proBNP in pwCF was 50.0 pg/ml (40.7; 100.8) and increasing NT-proBNP level was associated with decreasing FEV1 (L) (estimate: -0.008, p<0.001). NT-proBNP level was not associated with neither dyspnea nor chest pain (p=0.60 and p=0.15, respectively). PwCF with dyspnea did not differ from those without on clinical or echocardiographic parameters. However, pwCF with chest pain had lower absolute GLS compared to pwCF without (17.4% vs.18.5%, p=0.026). Neither dyspnea nor chest pain was more frequent in pwCF with cardiac impairment versus normal cardiac function (54% vs. 39%, p=0.17 and 29% vs. 28%, p=0.91, respectively). Decreasing absolute GLS was associated with increased odds of chest pain (OR 1.25, 95% CI 1.02; 1.53, p=0.030) (Figure 2). Neither dyspnea or chest pain alone, nor in combination with NT-proBNP were able to predict abnormal cardiac function. While dyspnea and chest pain combined showed a slight improvement in sensitivity and positive predictive value for diagnosing cardiac impairment, the combination of symptoms and increased NT-proBNP did not enhance diagnostic accuracy. Conclusions In this cross-sectional study, dyspnea and atypical, non-exertional chest pain were common symptoms in adult pwCF. While abnormal cardiac function was prevalent in pwCF, neither symptoms, NT-proBNP nor a combination of these were associated with increased odds of cardiac impairment. Dyspnea and chest pain, though prevalent, are multifactorial in pwCF and do not seem to serve as sensitive markers of cardiac impairment, even when combined with NT-proBNP level.

Procurement and Preservation of Neonatal Porcine Cardiac Tissue.

The porcine and human heart are remarkably similar in cardiac physiology and biochemistry. Translational research involving the porcine biomedical model is becoming increasingly applicable for the study of human cardiac function in health and disease. Presently, few protocols exist for collecting experimentally viable cardiac tissue from large animal models, particularly during neonatal maturation. To address this deficiency, we have developed a technique to procure and preserve ventricular tissue from neonatal piglets at day 3 (n=4) and day 30 (n=6) post-partum. Piglets were subjected to a strict sedation, anesthesia, and analgesia regimen. During surgery, cardiopulmonary indices of electrocardiogram, heart rate, systolic and diastolic blood pressure, respiration rate, peripheral O2 saturation, and end-tidal CO2 were monitored continuously to ensure normal cardiac function. Prior to cardiectomy, each heart was perfused with an intravenous administration of heparin (10 ml/kg) and ice-cold Custodiol HTK cardioplegia solution (10 ml/kg). After cardiac explantation, myocardial samples (dimensions: 1 x 1 x 1 cm) were dissected from the left and right ventricles and snap-frozen in liquid nitrogen. Analysis via SDS-PAGE and densitometry demonstrated that myofibrillar proteins are stable and undegraded. Western Blots showed full expression of protein. These results suggest that the detailed cardiac tissue procurement technique preserves the experimental viability of the cardiac tissue and prevents the degradation of myofibrillar proteins.

The increased longitudinal basal-to-apical strain ratio in the right ventricular free wall is associated with neonatal pulmonary hypertension.

As a relatively standardized parameter, Ratio bas/api of RVFW was significantly higher in the case of neonatal PH with normal cardiac function and could be regarded as a new indicator for PH. •It has been challenging work to diagnose neonatal pulmonary hypertension (PH), and conventional echocardiography has been widely applied, though it is not sufficient enough. •RV longitudinal strain (RVLS) is primarily used to assess RV systolic function, and its role in diagnosing PH was rarely considered. •The basal-to-apical strain ratio (Ratio bas/api) of RV free wall increased significantly in all infants with PH regardless of causes. •As a relatively standardized parameter, Ratio bas/api could be regarded as a new indicator for diagnosing PH, apart from conventional echocardiographic parameters.

7071 Cushing disease presenting with Dilated Cardiomyopathy

Abstract Disclosure: H. Majeed: None. C. Nguyen: None. R. Galagan: None. D. Lovre: None. Background: Hypercortisolism manifests with numerous ways due to the wide distribution of glucocorticoid receptors. Here we describe a case of Cushing’s disease presenting with reversible non-ischemic cardiomyopathy. Case Presentation: A 30-year-old male presented to ER with palpitations, dyspnea, and atypical chest pain. His exam was notable for a BMI of 30.26 kg/m2, HR 76 bpm and BP of 200/110 mm Hg. His EKG revealed Left ventricular hypertrophy. Echocardiogram (ECHO) showed an EF of 25-30% with diffuse hypokinesis. An angiogram demonstrated normal coronary anatomy. He was started on Lisinopril, Carvedilol, and Spironolactone for non-ischemic cardiomyopathy. He also complained of a 40 lb weight gain, loss of libido, hot flashes and breast tenderness. He was referred to endocrinology. Initial evaluation demonstrated total testosterone (TT) of 171 ng/dl (286-1511 ng/dl), FSH 3.8 IU/L (2-12 IU/L), LH 5.6 IU/L (2-9 IU/L) consistent with secondary hypogonadism. Further pituitary workup revealed AM cortisol level 31.22 mcg/dl (4.3-22.4mcg/dl), ACTH 79 pg/ml (7.2 - 63.3pg/ml), IGF-1 257 ng/mL (88-246 ng/mL), Prolactin 23.7 ng/dl (2.1- 17.7ng/dl), TSH 0.54 mIU/l (0.35-3.74mIU/l) and FT4 0.6 ng/dl (0.76-1.46 ng/dl). A 24hr urine cortisol was 167 ug(0-50ug/24h) and midnight salivary cortisol 0.160 ug/dl (<0.010-0.090 ug/dl). An overnight 1mg dexamethasone suppression test (DST) resulted in AM cortisol of 20.95 mcg/dl (<1.8mcg/dl) and 8mg DST cortisol fell from 34 mcg/dl to 4.16 mcg/dl. A pituitary MRI revealed a left 6 mm x 4 mm microadenoma. He was treated with levothyroxine pre-op for central hypothyroidism. He underwent transsphenoidal resection of the pituitary adenoma. Post-op AM cortisol was 1.1 mcg/dl. His steroid withdrawal syndrome was treated with a prolonged course of tapered hydrocortisone. Two months post-op ECHO showed EF of 55-60%. His BP normalized on carvedilol alone. Eighteen months post-op he no longer required any hormone replacement. Repeat ACTH 24.4 pg/ml, Total Testosterone 584ng/dl, TSH 0.57 mIU/l and FT4 0.93 and 24hr urine cortisol was 24ug/dl, MN salivary cortisol <0.10 ug/dl confirming remission of his cushing's disease and resolution of secondary hypogonadism and hypothyroidism. Conclusion: Prolonged hypercortisolism can cause abnormal cardiac remodeling resulting in cardiomyopathy. Surgical remission of Cushing’s disease reverses hypercortisolism which may restore normal cardiac function. Presentation: 6/2/2024

Surgical repair of “Swiss Cheese” ventricular septal defects with two-patch and right ventricular apex-exclusion technique: mid-term follow-up results

Background"Swiss Cheese" ventricular septal defects represent a serious congenital heart disease with suboptimal clinical outcomes and a lack of consensus regarding its management. This study presents mid-term follow-up results of surgical repairs for "Swiss Cheese" ventricular septal defects, utilizing the two-patch and right ventricle apex-exclusion technique.MethodsA retrospective review was conducted on 13 patients who underwent surgical repair utilizing the two-patch and right ventricle apex-exclusion technique at our institution between May 2014 and October 2021. The procedure involved the closure of defects in the outflow tract ventricular septal and the apex trabecular ventricular septal regions using two patches, with concurrent exclusion of the right ventricular apex from the right ventricular inflow tract.ResultsMedian follow-up was 4.9 ± 2.1 years (range: 2–9 years). All cases were successful without mortality or major complications. Two years post-surgery, cardiac magnetic resonance revealed median values for left ventricular ejection fraction, right ventricular ejection fraction, left ventricular end-diastolic volume and right ventricular end-diastolic volume of 63.9% ± 1.8% (range: 61–67%), 49.2% ± 2.6% (range: 46–55%), 39.15 ± 2.11 ml (range: 36.2–42.7 ml), 44.55 ± 3.33 ml (range: 38.7–48.6 ml), respectively. No thrombosis occurred. The latest echocardiography results confirmed normal cardiac function in all cases.ConclusionsThe surgical repair of "Swiss Cheese" ventricular septal defects utilizing the two-patch and right ventricle apex-exclusion technique is a viable approach with favorable mid-term outcomes. More cases and long-term follow-up results are needed to validate the feasibility and safety of this technique.

Leiomodin 2 neonatal dilated cardiomyopathy mutation results in altered actin gene signatures and cardiomyocyte dysfunction

Neonatal dilated cardiomyopathy (DCM) is a poorly understood muscular disease of the heart. Several homozygous biallelic variants in LMOD2, the gene encoding the actin-binding protein Leiomodin 2, have been identified to result in severe DCM. Collectively, LMOD2-related cardiomyopathies present with cardiac dilation and decreased heart contractility, often resulting in neonatal death. Thus, it is evident that Lmod2 is essential to normal human cardiac muscle function. This study aimed to understand the underlying pathophysiology and signaling pathways related to the first reported LMOD2 variant (c.1193 G > A, p.Trp398*). Using patient-specific human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) and a mouse model harboring the homologous mutation to the patient, we discovered dysregulated actin-thin filament lengths, altered contractility and calcium handling properties, as well as alterations in the serum response factor (SRF)-dependent signaling pathway. These findings reveal that LMOD2 may be regulating SRF activity in an actin-dependent manner and provide a potential new strategy for the development of biologically active molecules to target LMOD2-related cardiomyopathies.

The structural and functional effects of myosin regulatory light chain phosphorylation are amplified by increases in sarcomere length and [Ca2+

Precise regulation of sarcomeric contraction is essential for normal cardiac function. The heart must generate sufficient force to pump blood throughout the body, but either inadequate or excessive force can lead to dysregulation and disease. Myosin regulatory light chain (RLC) is a thick-filament protein that binds to the neck of the myosin heavy chain. Post-translational phosphorylation of RLC (RLC-P) by myosin light chain kinase is known to influence acto-myosin interactions, thereby increasing force production and Ca2+-sensitivity of contraction. Here, we investigated the role of RLC-P on cardiac structure and function as sarcomere length and [Ca2+] were altered. We found that at low, non-activating levels of Ca2+, RLC-P contributed to myosin head disorder, though there were no effects on isometric stress production and viscoelastic stiffness. With increases in sarcomere length and Ca2+-activation, the structural changes due to RLC-P become greater, which translates into greater force production, greater viscoelastic stiffness, slowed myosin detachment rates and altered nucleotide handling. Altogether, these data suggest that RLC-P may alter thick-filament structure by releasing ordered, off-state myosin. These more disordered myosin heads are available to bind actin, which could result in greater force production as Ca2+ levels increase. However, prolonged cross-bridge attachment duration due to slower ADP release could delay relaxation long enough to enable cross-bridge rebinding. Together, this work further elucidates the effects of RLC-P in regulating muscle function, thereby promoting a better understanding of thick-filament regulatory contributions to cardiac function in health and disease. KEY POINTS: Myosin regulatory light chain (RLC) is a thick-filament protein in the cardiac sarcomere that can be phosphorylated (RLC-P), and changes in RLC-P are associated with cardiac dysfunction and disease. This study assesses how RLC-P alters cardiac muscle structure and function at different sarcomere lengths and calcium concentrations. At low, non-activating levels of Ca2+, RLC-P contributed to myofilament disorder, though there were no effects on isometric stress production and viscoelastic stiffness. With increases in sarcomere length and Ca2+-activation, the structural changes due to RLC-P become greater, which translates into greater force production, greater viscoelastic stiffness, slower myosin detachment rate and altered cross-bridge nucleotide handling rates. This work elucidates the role of RLC-P in regulating muscle function and facilitates understanding of thick-filament regulatory protein contributions to cardiac function in health and disease.

The Efficacy of Vitamins in the Prevention and Treatment of Cardiovascular Disease.

Vitamins are known to affect the regulation of several biochemical and metabolic pathways that influence cellular function. Adequate amounts of both hydrophilic and lipophilic vitamins are required for maintaining normal cardiac and vascular function, but their deficiencies can contribute to cardiovascular abnormalities. In this regard, a deficiency in the lipophilic vitamins, such as vitamins A, D, and E, as well as in the hydrophilic vitamins, such as vitamin C and B, has been associated with suboptimal cardiovascular function, whereas additional intakes have been suggested to reduce the risk of atherosclerosis, hypertension, ischemic heart disease, arrhythmias, and heart failure. Here, we have attempted to describe the association between low vitamin status and cardiovascular disease, and to offer a discussion on the efficacy of vitamins. While there are inconsistencies in the impact of a deficiency in vitamins on the development of cardiovascular disease and the benefits associated with supplementation, this review proposes that specific vitamins may contribute to the prevention of cardiovascular disease in individuals at risk rather than serve as an adjunct therapy.

Smaller Left Ventricular Size But Preserved Function in Adolescents and Adults Born Preterm.

Prematurely born adults have increased risk for cardiovascular disease. There are limited cardiac data on US-born preterm individuals. We aimed to determine whether adolescents and adults born prematurely have altered left ventricular (LV) structure and function, and to interrogate diastolic function using isometric handgrip exercise. Adolescents and adults born moderately to extremely preterm (≤32 weeks gestation or <1500 g birth weight) were recruited from the Parkland Health Neonatal Intensive Care Unit Registry. Full-term participants were recruited from the local area. Study procedures included anthropometrics and vitals, handgrip testing, and echocardiography performed at rest and during isometric handgrip exercise. Data were reported as mean±SD. The study enrolled 107 preterm and 48 term participants. Preterm participants (gestational age: 29.5±2.5 weeks) were shorter with higher body mass index (P<0.001) compared with term participants. Preterm participants exhibited smaller LV end-diastolic volume index (50.8±10.1 versus 56.9±10.0 mL/m2, P<0.001), LV stroke volume index (29.6±6.0 versus 34.1±6.5 mL/m2, P<0.001), and LV mass index (67.2±13.1 versus 73.3±14.2 g/m2, P=0.002) compared with term individuals. Preterm participants also had subclinical reductions in LV peak systolic tissue velocity and peak early diastolic tissue velocity lateral at rest. Isometric handgrip exercise promoted a reduction in diastolic function and an increase in hemodynamic measures, but changes during isometric handgrip exercise were similar between groups. Adolescents and adults born preterm exhibit overall normal cardiac function despite smaller cardiac volumes and mass compared with individuals born full term. Effects are most pronounced at the lowest gestational ages.

Revisiting Peripartum Cardiomyopathy: A Case Report and Review

Peripartum cardiomyopathy (PPCM) is a rare and idiopathic disease characterized by left ventricular dilation and systolic dysfunction, that occurs late in pregnancy or during the postpartum period. Diagnosis is typically achieved through transthoracic echocardiography and cardiac magnetic resonance imaging (MRI). Management includes standard heart failure therapies such as beta-blockers, ACE inhibitors, and diuretics, with the addition of bromocriptine to target the prolactin pathway involved in PPCM pathophysiology. This report presents a case of a 31-year-old female with a history of acute lymphoblastic leukemia who, following an uncomplicated pregnancy, presented with acute heart failure symptoms. Initial evaluations suggested pulmonary embolism, but further diagnostic workup, including echocardiography and cardiac MRI, confirmed PPCM. The patient was treated with diuretics, ACE inhibitors, and beta blockers. Significant improvement was observed, with complete resolution and normal cardiac function at the 6-month follow-up.

Gaucher disease type 3c: Expanding the clinical spectrum of an ultra-rare disease.

Gaucher disease (GD) type 3 is an autosomal recessive lysosomal disease caused by deficiency of β-glucocerebrosidase (GCase) and encompasses a spectrum of cardiac, neurological, and ophthalmological abnormalities. Although the clinical presentations can be diverse, a recognized clinical trajectory points to an early onset, predominantly before 18 years. GD type 3c is primarily caused by homozygosity for GBA pathogenic variant c.1342G>C (p.Asp448His; historically referred to as D409H) and includes visceral, hematological, skeletal, and cardiac abnormalities. Notably, GD type 3c is distinct from other GD types because it is primarily characterized by valvular heart disease. Yet, with less than 50 patients with GD type 3c reported to date, the phenotypic spectrum and extent of cardiac involvement remains ill-defined. We present a 20-year-old female with an atypical presentation of GD type 3c consisting of chronic intermediate uveitis as the presenting feature and the presence of extensive polyneuropathy starting in adolescence which has been previously unreported in GD type 3c. Distinctively, she has maintained normal cardiac function. Moreover, we compare our case with those reported in the literature to broaden awareness of the varied initial presentations of this disease. The diverse presentations seen in GD type 3c, underscored by our case and those previously reported, demonstrate the need for standardized evaluation and management protocols.

Abstract Tu126: Unveiling the Role of GRAF1 in Orchestrating Mitophagy and Metabolic Flexibility in Stressed Cardiomyocytes

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 We143: MED12 Dysregulation Disrupts Transcriptional Programs Leading to Dilated Cardiomyopathy

The Mediator complex serves as a bridge to link transcriptional machinery and transcription factors (TFs) to control transcription, but detailed molecular mechanisms of transcriptional regulation by Mediator are not well-understood. Mediator is comprised of the head, middle, and tail submodules that make up the core Mediator, and the transiently associating kinase submodule. The CDK8 kinase submodule acts to regulate Mediator-RNA Polymerase II interaction. MED12 is an essential Mediator component within the kinase submodule and is required for CDK8 kinase activity. In aging models, dysregulated levels of Med12 mRNA are detected in both atria and ventricles by qRT-PCR. MED12 protein levels are also increased in human heart failure biopsies and in the mouse heart after transverse aortic constriction (TAC)-induced heart failure[KB1] . To test the hypothesis that increased levels of MED12 contribute to development of heart failure we generated cardiac-specific Med12 transgenic mice (cTg) by driving increased MED12 expression in cardiomyocytes using the αMHC promoter. Med12 overexpression leads to a progressive decrease in fractional shortening by serial echocardiography. Decreased cardiac function was accompanied by increased cardiac chamber size and dilation, without cardiac fibrosis. RNA sequencing of cardiomyocytes from cTg and control mice revealed that increased levels of MED12 leads to early changes in gene expression programs. Using ingenuity pathway analysis we identified MED12-regulated gene programs including those involved in calcium cycling. MED12 is a transcriptional regulator but does not directly bind DNA. To determine how MED12 regulates gene expression we screened for TFs that interact with MED12. We performed immunoprecipitation of MED12 and by mass spectrometry and determined that MED12 interacts with the TFs MEF2, CREB, and SRF. In follow-up experiments we demonstrated that MED12 interacts with the transcription factor (TF) MEF2 to regulate calcium handling genes. Current studies are focused on determining how MED12 binding coordinates gene expression through multiple TFs in cardiomyocytes. Collectively, our data demonstrate that increased MED12 expression leads to the development of heart failure, in part by dysregulation of gene expression. Therefore, precise regulation of MED12 levels is important to maintain normal cardiac function. [KB1]What about aging?

Cardiac biomarkers for screening and prognostication of cardiac dysfunction in critically ill patients.

This study aimed to assess the use of high-sensitivity troponin T (hsTNT) and N-terminal pro-brain natriuretic peptide (NT-proBNP) in screening for cardiac dysfunction [left ventricular (LV) systolic or diastolic dysfunction or right ventricular (RV) dysfunction] in mixed intensive care unit (ICU) patients and establish whether these biomarkers are independently associated with an increased risk of death. We performed a secondary analysis of a single-centre prospective observational study in which consecutive ICU patients were examined with transthoracic echocardiography (TTE) and cardiac biomarkers. Patients with systolic or diastolic LV dysfunction, RV dysfunction or a combination of these were compared with patients with normal cardiac function. Sensitivity and specificity for different cut-off levels were calculated using receiver operating characteristic curves. Regression models were used to evaluate the associations between cardiac biomarkers, sepsis, renal failure and mortality. A total of 276 patients were included. Most of the patients had cardiac dysfunction on TTE (64%). Combined cardiac dysfunction was most prevalent (71 patients, 26%), followed by isolated diastolic LV dysfunction (40 patients, 15%). Levels of hsTNT and NT-proBNP were higher in all types of cardiac dysfunction versus patients with normal cardiac function. The area under the curve (AUC) for hsTNT to detect any cardiac dysfunction was 0.75. An optimal cut-off at 30.5ng/L rendered a positive predictive value (PPV) of 80% and a negative predictive value (NPV) of 58%. The AUC for NT-proBNP to detect any cardiac dysfunction was 0.788. Using an optimal cut-off at 1145ng/L rendered a PPV of 86% and an NPV of 58%. Using a clinically relevant 90% sensitivity for detecting cardiac dysfunction put the cut-offs at 14.1ng/L for hsTNT and 247ng/L for NT-proBNP, resulting in a specificity of 48% and 46%, respectively. Levels of NT-proBNP were associated with sepsis and renal failure (P<0.001), while levels of hsTNT were associated with renal failure only (P<0.001) after adjustment for cardiac dysfunction. Levels of biomarkers were associated with an increased risk of 90day mortality after adjustments for age, Simplified Acute Physiology Score 3, cardiac dysfunction and factors independently associated with biomarker increase (sepsis and renal failure) (P=0.048 for hsTNT and P<0.006 for NT-proBNP). Cardiac biomarkers, hsTNT and NT-proBNP, are strongly correlated to cardiac dysfunction in ICU patients and have a robust association with increased mortality. However, the relatively low NPV and the low specificity at relevant sensitivity levels of the biomarkers make them unsuitable for use in screening for cardiac dysfunction.

Ulk1 phosphorylation at S555 is not required for endurance training-induced improvements in exercise and metabolic capacity in mice.

Endurance exercise training improves exercise capacity as well as skeletal muscle and whole body metabolism, which are hallmarks of high quality-of-life and healthy aging. However, its mechanisms are not yet fully understood. Exercise-induced mitophagy has emerged as an important step in mitochondrial remodeling. Unc-51-like autophagy-activating kinase 1, ULK1, specifically its activation by phosphorylation at serine 555, was discovered as an autophagy driver and to be important for energetic stress-induced mitophagy in skeletal muscle, making it a potential mediator of the beneficial effects of exercise on mitochondrial remodeling. Here, we used CRISPR/Cas9-mediated gene editing and generated knock-in mice with a serine-to-alanine mutation of Ulk1 on serine 555. We now report that these mice displayed normal endurance capacity and cardiac function at baseline with a mild impairment in energy metabolism as indicated by an accelerated increase of respiratory exchange ratio (RER) during acute exercise stress; however, this was completely corrected by 8 wk of voluntary running. Ulk1-S555A mice also retained the exercise-mediated improvements in exercise capacity and metabolic flux. We conclude that Ulk1 phosphorylation at S555 is not required for exercise-mediated improvements of exercise and metabolic capacity in healthy mice.NEW & NOTEWORTHY We have used CRISPR/Cas9-mediated gene editing to generate Ulk1-S555A knock-in mice to show that loss of phosphorylation of Ulk1 at S555 blunted exercise-induced mitophagy and mildly impairs energy metabolism during exercise in healthy mice. However, the knock-in mice retained exercise training-mediated improvements of endurance capacity and energy metabolism during exercise. These findings suggest that exercise-induced mitophagy through Ulk1 activation is not required for the metabolic adaptation and improved exercise capacity in young, healthy mice.

Nexilin in cardiomyopathy: unveiling its diverse roles with special focus on endocardial fibroelastosis.

Cardiac disorders exhibit considerable heterogeneity, and understanding their genetic foundations is crucial for their diagnosis and treatment. Recent genetic analyses involving a growing number of participants have uncovered novel mutations within both coding and non-coding regions of DNA, contributing to the onset of cardiac conditions. The NEXN gene, encoding the Nexilin protein, an actin filament-binding protein, is integral to normal cardiac function. Mutations in this gene have been linked to cardiomyopathies, cardiovascular disorders, and sudden deaths. Heterozygous or homozygous variants of the NEXN gene are associated with the development of endocardial fibroelastosis (EFE), a rare cardiac condition characterized by excessive collagen and elastin deposition in the left ventricular endocardium predominantly affecting infants and young children. EFE occurs both primary and secondary to other conditions and often leads to unfavorable prognoses and outcomes. This review explores the role of NEXN genetic variants in cardiovascular disorders, particularly EFE, revealing that functional mutations are not clustered in a specific domain of Nexilin based on the cardiac disorder phenotype. Our review underscores the importance of understanding genetic mutations for the diagnosis and treatment of cardiac conditions.

CASE STUDY OF NORMAL ECHOCARDIOGRAPHYIN AN ADULT SIBERIAN HUSKY DOG

Echocardiography is commonly used in veterinary medicine to assess cardiac structure and function in dogs. This case study was aimed to evaluate normal echocardiography of an adult Siberian Husky. Standard techniques, including B-Mode, M-Mode, and Color Flow Doppler, were carried out by using the Acclarix AX3 Vet USG and a micro convex probe 5-9 MHz. Examinations were conducted in the right parasternal and left apical positions. The results indicate that the six-year-old, 32 kg Siberian Husky in this study exhibited a normal heart. When comparing M-Mode echocardiography with the normal range for dogs of similar size, role, and weight, left ventricular internal dimension in diastole (LVIDd) was below the normal range, while left ventricular posterior wall in diastole (LVWPd) and left ventricular posterior wall in systole (LVPWs) were higher. These findings highlight the necessity for breed-specific reference intervals. This case study emphasizes the correlation between the normal echocardiography interpretation and canine cardiac function, as depicted by the value of ejection fraction (EF) 66.04% and fractional shortening (FS) 35.52%. The echocardiography results of the Siberian Husky in the study are comparable to reference interval values of similar breeds that are working dogs, making them valuable as reference values for future studies.

ATP Citrate Lyase Supports Cardiac Function and NAD+/NADH Balance And Is Depressed in Human Heart Failure.

ATP-citrate lyase (ACLY) converts citrate into acetyl-CoA and oxaloacetate in the cytosol. It plays a prominent role in lipogenesis and fat accumulation coupled to excess glucose, and its inhibition is approved for treating hyperlipidemia. In RNAseq analysis of human failing myocardium, we found ACLY gene expression is reduced; however the impact this might have on cardiac function and/or metabolism has not been previously studied. As new ACLY inhibitors are in development for cancer and other disorders, such understanding has added importance. Cardiomyocytes, ex-vivo beating hearts, and in vivo hearts with ACLY inhibited by selective pharmacologic (BMS303141, ACLYi) or genetic suppression, were studied. Regulation of ACLY gene/protein expression, and effects of ACLYi on function, cytotoxicity, tricarboxylic acid (TCA)-cycle metabolism, and redox and NAD+/NADH balance were assessed. Mice with cardiac ACLY knockdown induced by AAV9-acly-shRNA or cardiomyocyte tamoxifen-inducible Acly knockdown were studied. Acly gene expression was reduced more in obese patients with heart failure and preserved EF (HFpEF) than HF with reduced EF. In vivo pressure-overload and in vitro hormonal stress increased ACLY protein expression, whereas it declined upon fatty-acid exposure. Acute ACLYi (1-hr) dose-dependently induced cytotoxicity in adult and neonatal cardiomyocytes, and caused substantial reduction of systolic and diastolic function in myocytes and ex-vivo beating hearts. In the latter, ATP/ADP ratio also fell and lactate increased. U13C-glucose tracing revealed an ACLYdependent TCA-bypass circuit in myocytes, where citrate generated in mitochondria is transported to the cytosol, metabolized by ACLY and then converted to malate to re-enter mitochondria,bypassing several NADH-generating steps. ACLYi lowered NAD+/NADH ratio and restoring this balance ameliorated cardiomyocyte toxicity. Oxidative stress was undetected with ACLYi. Adult hearts following 8-weeks of reduced cardiac and/or cardiomyocyte ACLY downregulation exhibited ventricular dilation and reduced function that was prevented by NAD augmentation. Cardiac dysfunction from ACLY knockdown was worse in hearts subjected to sustained pressureoverload, supporting a role in stress responses. ACLY supports normal cardiac function through maintenance of the NAD+/NADH balance and is upregulated by hemodynamic and hormonal stress, but depressed by lipid excess. ACLY levels are most reduced in human HFpEF with obesity potentially worsening cardio-metabolic reserve.