Pathways In Heart Research Articles

Proteomic analysis reveals activation of platelet- and fibrosis-related pathways in hearts of ApoE−/− mice exposed to diesel exhaust particles

Air pollution is an environmental risk factor linked to multiple human diseases including cardiovascular diseases (CVDs). While particulate matter (PM) emitted by diesel exhaust damages multiple organ systems, heart disease is one of the most severe pathologies affected by PM. However, the in vivo effects of diesel exhaust particles (DEP) on the heart and the molecular mechanisms of DEP-induced heart dysfunction have not been investigated. In the current study, we attempted to identify the proteomic signatures of heart fibrosis caused by diesel exhaust particles (DEP) in CVDs-prone apolipoprotein E knockout (ApoE−/−) mice model using tandem mass tag (TMT)-based quantitative proteomic analysis. DEP exposure induced mild heart fibrosis in ApoE−/− mice compared with severe heart fibrosis in ApoE−/− mice that were treated with CVDs-inducing peptide, angiotensin II. TMT-based quantitative proteomic analysis of heart tissues between PBS- and DEP-treated ApoE−/− mice revealed significant upregulation of proteins associated with platelet activation and TGFβ-dependent pathways. Our data suggest that DEP exposure could induce heart fibrosis, potentially via platelet-related pathways and TGFβ induction, causing cardiac fibrosis and dysfunction.

Influence of organism stimulation with bacterial lipopolysaccharide on nitric oxide production and metabolism in rat heart on the background of metabolic syndrome

Aim. The aim of the study was to establish the changes in nitric oxide production and metabolism in rat heart during combined influence of organism stimulation with bacterial lipopolysaccharide (LPS) and modeling of metabolic syndrome (MetS).
 Materials and methods. The study was conducted on 24 mature male Wistar rats weighing 200–260 g. Experiment lasted 60 days. The animals were divided into 4 groups of 6 animals each: control group, MetS group, LPS stimulation group, LPS + MetS group. MetS was reproduced by using a 20 % fructose solution as the only source of drinking water. LPS of Salmonella typhi was administered at a dose of 0.4 μg/kg intraperitoneally. Animals from LPS + MetS group received a 20 % fructose solution as the only source of drinking water and were administered LPS. In 10 % tissue homogenate of rat heart we studied: total activity of NO-synthases (NOS), activity of constitutive (cNOS) and inducible (iNOS) isoforms, activity of nitrate (NaR) and nitrite (NiR) reductases, concentration of peroxynitrites (ONOO-), nitrites, nitrosothiols and hydrogen sulfide.
 Results. Combination of MetS and stimulation of organism with LPS led to increase in total NOS activity by 32.72 % compared to control group. Activity of cNOS did not change compared to control group. Activity of iNOS increased by 33.76 %. Arginase activity decreased by 23.53 %. NaR activity and NiR activity were increased by 86.67 % and by 149.29 %, respectively. Combination of MetS and stimulation of organism with LPS led to decrease in nitrite and nitrosothiols concentration by 38.73 % and by 54.79 %, respectively. Under these conditions concentration of ONOOelevated by 398.0 % compared to control group. Concentration of H S decreased by 27.56 %.
 Conclusions. Combination of metabolic syndrome and stimulation of organism with bacterial lipopolysaccharide leads to prevalence of peroxynitrite formation during increased nitric oxide production NO-synthase-dependent and nitrate-nitrite-NO pathways in rat heart.

Effect of Choline and Vitamin E Co-Treatment on Hedgehog Pathway and Histopathological Changes in Heart and Kidney Associated with Obese Rats with Non-Alcoholic Fatty Liver Disease

Effect of Choline and Vitamin E Co-Treatment on Hedgehog Pathway and Histopathological Changes in Heart and Kidney Associated with Obese Rats with Non-Alcoholic Fatty Liver Disease

Common and specific proteins and pathways in heart and cerebral ischemia

ObjectiveTo understand the similarities and differences between acute ischemic stroke and acute myocardial infarction (AMI) to help in the development of specific or common treatment strategies. MethodsUsing an aptamer-based proteomic array, we measured and compared 1310 circulating proteins in the blood of 40 patients with AIS, 9 patients with AMI, and 31 healthy controls. Pathway enrichment analysis was performed using GSEA and g:profiler. ResultsNinety-four proteins were differentially expressed in AIS, and 284 were differentially expressed in AMI. Of these, 8 were specific to cerebral ischemia, and 197 were specific to myocardial infarction. Forty-two proteins were altered in both ischemia processes. Most altered pathways in AIS could be classified as immune response, cell cycle processing, molecular transport, or signaling. Pathways altered in AMI were mostly related to lipid metabolism and transport, highlighting cholesterol metabolic processes and estrogen signaling. In both types of ischemia, we found pathways related to metabolism, specifically purine metabolism, and signaling processes, such as TNF signaling or MAPK1/3. ConclusionsThe present study revealed proteins and pathways that were specifically altered in cerebral ischemia, in cardiac ischemia, or in both diseases, providing information on the similarities and differences of ischemic conditions. The role of common and specific proteins and pathways should be explored in detail to find possible therapeutic targets.

Abstract 16613: Study of Modified HEART Score and HEART Pathway as Predictor of Major Adverse Cardiac Events (MACE) in Patients Presenting With Non ST Elevation- Acute Coronary Syndrome (NST-ACS)

Introduction: Among the various scores studied in literature, the modified HEART score and HEART pathway were found to have high discriminatory power of predicting major adverse cardiac events (MACE) in Non ST elevation acute coronary syndrome (NSTEACS) patients in various international studies. This warrants need for evaluation of these scores for better management of patients in hectic emergency departments of Indian healthcare system. Methods: This prospective observational study was conducted between January 2021 and May 2022 in a tertiary care hospital of New Delhi, India. Modified HEART score was calculated based on history, ECG, age, risk factors and highly sensitive troponin I (hsTrop I) values for 60 patients. Collected serum samples of hsTrop I at 0 and 3 hours were measured using ELISA kits. As per the score, patients in low risk group were discharged safely and intermediate and high risk groups were assessed with the help of stress testing and coronary angiography and managed accordingly. The occurrence of MACE was assessed at 30 days from presentation to healthcare facility. Results: The study showed that proportion of patients with MACE was significantly higher in high risk group (82.14%) as compared to low (0%) and intermediate risk group (20.83%) (p value <0.001). Modified HEART score was the best predictor of MACE at cut off point of >6 with 88.1% chances of correctly predicting MACE. Negative predictive value of HEART pathway was found to be 100% which enabled safe disposition of low risk group patients. Conclusions: Hence, when modified HEART score and HEART pathway were used together, it allowed efficient use of resources and prediction of MACE in NSTEACS. This was the first study done on Indian population where modified HEART score and HEART pathway were used simultaneously to predict the occurence of MACE.

Abstract 18698: PCBP1 Regulates Alternative Splicing of Aars2 in Congenital Cardiomyopathy

Rationale: Alanyl-transfer RNA synthetase 2 (AARS2) is a nuclear encoded mitochondrial tRNA synthetase that is responsible for charging of tRNA-Ala with alanine during mitochondrial translation. Homozygous or compound heterozygous mutations in the Aars2 gene, including those affecting its alternative splicing, are linked to congenital cardiomyopathy in humans. However, the underlying molecular mechanism of how Aars2 regulates heart development remains unknown. Hypothesis: The alternative splicing of Aars2 and its function is essential for cardiac development. Methods and Results: We found that alternative splicing of the Aars2 transcript is mediated by poly(rC) binding protein 1 (PCBP1), an RNA binding protein, through direct interaction. Cardiomyocyte-specific deletion of Pcbp1 in mice resulted in defects in heart development that are reminiscent of human congenital cardiac defects, including noncompaction cardiomyopathy and a disruption of the cardiomyocyte maturation trajectory. Loss of Pcbp1 led to an aberrant alternative splicing and a premature termination of Aars2 in cardiomyocytes. Therefore, Pcbp1 is critical for the expression and function of Aars2. Additionally, Aars2 mutant mice with exon-16 skipping recapitulated heart developmental defects observed in Pcbp1 mutant mice. Mechanistically, we found dysregulated gene and protein expression of the oxidative phosphorylation pathway in both Pcbp1 and Aars2 mutant hearts; these data provide further evidence that the infantile hypertrophic cardiomyopathy associated with the disorder oxidative phosphorylation defect type 8 (COXPD8) is mediated by Aars2. Conclusion: Our study therefore identifies Pcbp1 and Aars2 as critical regulators of heart development and provides important molecular insights into the role of disruptions in metabolism on congenital heart defects.

Receptor interacting protein kinase-3 mediates both myopathy and cardiomyopathy in preclinical animal models of Duchenne muscular dystrophy.

Duchenne muscular dystrophy (DMD) is a progressive muscle degenerative disorder, culminating in a complete loss of ambulation, hypertrophic cardiomyopathy and a fatal cardiorespiratory failure. Necroptosis is the form of necrosis that is dependent upon the receptor-interacting protein kinase (RIPK) 3; it is involved in several inflammatory and neurodegenerative conditions. We previously identified RIPK3 as a key player in the acute myonecrosis affecting the hindlimb muscles of the mdx dystrophic mouse model. Whether necroptosis also mediates respiratory and heart disorders in DMD is currently unknown. Evidence of activation of the necroptotic axis was examined in dystrophic tissues from Golden retriever muscular dystrophy (GRMD) dogs and R-DMDdel52 rats. A functional assessment of the involvement of necroptosis in dystrophic animals was performed on mdx mice that were genetically depleted for RIPK3. Dystrophic mice aged from 12 to 18months were analysed by histology and molecular biology to compare the phenotype of muscles from mdxRipk3+/+ and mdxRipk3-/- mice. Heart function was also examined by echocardiography in 40-week-old mice. RIPK3 expression in sartorius and biceps femoris muscles from GRMD dogs positively correlated to myonecrosis levels (r=0.81; P=0.0076). RIPK3 was also found elevated in the diaphragm (P≤0.05). In the slow-progressing heart phenotype of GRMD dogs, the phosphorylated form of RIPK1 at the Serine 161 site was dramatically increased in cardiomyocytes. A similar p-RIPK1 upregulation characterized the cardiomyocytes of the severe DMDdel52 rat model, associated with a marked overexpression of Ripk1 (P=0.007) and Ripk3 (P=0.008), indicating primed activation of the necroptotic pathway in the dystrophic heart. MdxRipk3-/- mice displayed decreased compensatory hypertrophy of the heart (P=0.014), and echocardiography showed a 19% increase in the relative wall thickness (P<0.05) and 29% reduction in the left ventricle mass (P=0.0144). Besides, mdxRipk3-/- mice presented no evidence of a regenerative default or sarcopenia in skeletal muscles, moreover around 50% less affected by fibrosis (P<0.05). Our data highlight molecular and histological evidence that the necroptotic pathway is activated in degenerative tissues from dystrophic animal models, including the diaphragm and the heart. We also provide the genetic proof of concept that selective inhibition of necroptosis in dystrophic condition improves both histological features of muscles and cardiac function, suggesting that prevention of necroptosis is susceptible to providing multiorgan beneficial effects for DMD.

Formaldehyde induced the cardiac damage by regulating the NO/cGMP signaling pathway and L-Ca2+ channels.

Formaldehyde (FA) is a common environmental pollutant that has been found to cause negative cardiovascular effects, however, the toxicological mechanism is not well understood. In this study, we investigated the molecular effects of the Nitric Oxide (NO)/cyclic Guanosine Monophosphate (cGMP) signaling pathway and L-type calcium (L-Ca2+) channels in rat hearts. We designed the short-term FA exposure on the rat heart in different concentrations (0, 0.5, 3, 18 mg/m3). After 7 days of exposure, the rats were sacrificed and the rat tissues were removed for various experiments. Our experimental data showed that FA resulted in the upregulation NO and cGMP, especially at 18 mg/m3. Further, when exposed to high concentrations of FA, Cav1.2 and Cav1.3 expression decreased. We conclude that the NO/cGMP signaling pathway and downstream related channels can be regulated by increasing the production of NO in the low concentration group of FA. High concentration FA directly regulates L-Ca22+ channels. This study suggests that FA damages the function of the cardiovascular system by regulating the NO/cGMP signaling pathway and L-Ca2+ channels.

Comprehensive validation of early diagnostic algorithms for myocardial infarction in the emergency department.

To comprehensively evaluate diagnostic algorithms for myocardial infarction using a high-sensitivity cardiac troponin I (hs-cTnI) assay. We prospectively enrolled patients with suspected myocardial infarction without ST-segment elevation from nine emergency departments in Japan. The diagnostic algorithms evaluated: (i) based on hs-cTnI alone, such as the European Society of Cardiology (ESC) 0/1-h or 0/2-h and High-STEACS pathways; or (ii) used medical history and physical findings, such as the ADAPT, EDACS, HEART, and GRACE pathways. We evaluated the negative predictive value (NPV), sensitivity as safety measures, and proportion of patients classified as low or high-risk as an efficiency measure for a primary outcome of type 1 myocardial infarction or cardiac death within 30 days. We included 437 patients, and the hs-cTnI was collected at 0 and 1 hours in 407 patients and at 0 and 2 hours in 394. The primary outcome occurred in 8.1% (33/407) and 6.9% (27/394) of patients, respectively. All the algorithms classified low-risk patients without missing those with the primary outcome, except for the GRACE pathway. The hs-cTnI-based algorithms classified more patients as low-risk: the ESC 0/1-h 45.7%; the ESC 0/2-h 50.5%; the High-STEACS pathway 68.5%, than those using history and physical findings (15-30%). The High-STEACS pathway ruled out more patients (20.5%) by hs-cTnI measurement at 0 hours than the ESC 0/1-h and 0/2-h algorithms (7.4%). The hs-cTnI algorithms, especially the High-STEACS pathway, had excellent safety performance for the early diagnosis of myocardial infarction and offered the greatest improvement in efficiency.

Ferroptosis inhibitor improves cardiac function more effectively than inhibitors of apoptosis and necroptosis through cardiac mitochondrial protection in rats with iron-overloaded cardiomyopathy

Iron overload cardiomyopathy (IOC) is the leading cause of death in cases of iron overload in patients. Previous studies demonstrated that iron overload led to cardiomyocyte dysfunction and death through multiple pathways including apoptosis, necroptosis and ferroptosis. However, the dominant cell death pathway in the iron-overloaded heart needs clarification. We tested the hypothesis that ferroptosis, an iron-dependent cell death, plays a dominant role in IOC, and ferroptosis inhibitor exerts greater efficacy than inhibitors of apoptosis and necroptosis on improving cardiac function in iron-overloaded rats. Iron dextran was injected intraperitoneally into male Wistar rats for four weeks to induce iron overload. Then, the rats were divided into 5 groups: treated with vehicle, apoptosis inhibitor (z-VAD-FMK), necroptosis inhibitor (Necrostatin-1), ferroptosis inhibitor (Ferrostatin-1) or iron chelator (deferoxamine) for 2 weeks. Cardiac function, mitochondrial function, apoptosis, necroptosis and ferroptosis were determined. The increased expression of apoptosis-, necroptosis- and ferroptosis-related proteins, were associated with impaired cardiac and mitochondrial function in iron-overloaded rats. All cell death inhibitors attenuated cardiac apoptosis, necroptosis and ferroptosis in iron-overloaded rats. Ferrostatin-1 was more effective than the other drugs in diminishing mitochondrial dysfunction and Bax/Bcl-2 ratio. Moreover, both Ferrostatin-1 and deferoxamine reversed iron overload-induced cardiac dysfunction as indicated by restored left ventricular ejection fraction and E/A ratio, whereas z-VAD-FMK and Necrostatin-1 only partially improved this parameter. These results indicated that ferroptosis could be the predominant form of cardiomyocyte death in IOC, and that inhibiting ferroptosis might be a potential novel treatment for IOC.

Role of ventrolateral part of ventromedial hypothalamus in post-myocardial infarction cardiac dysfunction induced by sympathetic nervous system

Psychological stress has been recognized as a contributing factor to worsened prognosis in patients with cardiac failure following myocardial infarction (MI). Although the ventrolateral part of the ventromedial hypothalamus (VMHVL) has been implicated in emotional distress, its involvement in post-MI cardiac dysfunction remains largely unexplored. This study was designed to investigate the effect of the VMHVL activation in the MI rat model and its underlying mechanisms. Our findings demonstrate that activation of VMHVL neurons enhances the activity of the cardiac sympathetic nervous system through the paraventricular nucleus (PVN) and superior cervical ganglion (SCG). This activation leads to an elevation in catecholamine levels, which subsequently modulates myosin function and triggers the release of anti-inflammatory factors, to exacerbate the post-MI cardiac prognosis. The denervation of the superior cervical ganglion (SGN) effectively blocked the cardiac sympathetic effects induced by the VMHVL activation, and ameliorated the cardia fibrosis and dysfunction. Therefore, our study identified the role of the “VMHVL-PVN-SCG” sympathetic pathway in the post-MI heart, and proposed SGN as a promising strategy in mitigating cardiac prognosis in stressful rats.

Protein concentrations and activities of fatty acid desaturase and elongase enzymes in liver, brain, testicle, and kidney from mice: Substrate dependency.

The synthesis rates of n-3 and n-6 polyunsaturated fatty acids (PUFAs) in rodents and humans are not agreed upon and depend on substrate availability independently of the capacity for synthesis. Therefore, we aimed to assess the activities of the enzymes for n-3 and n-6 PUFA synthesis pathways in liver, brain, testicle, kidney, heart, and lung, in relation to their protein concentration levels. Eight-week-old Balb/c mice (n = 8) were fed a standard chow diet (6.2% fat, 18.6% protein, and 44.2% carbohydrates) until 14 weeks of age, anesthetized with isoflurane and tissue samples were collected (previously perfused) and stored at -80°C. The protein concentration of the enzymes (Δ-6D, Δ-5D, Elovl2, and Elovl5) were assessed by ELISA kits; their activities were assayed using specific PUFA precursors and measuring the respective PUFA products as fatty acid methyl esters by gas chromatographic analysis. The liver had the highest capacity for PUFA biosynthesis, with limited activity in the brain, testicles, and kidney, while we failed to detect activity in the heart and lung. The protein concentration and activity of the enzymes were significantly correlated. Furthermore, Δ-6D, Δ-5D, and Elovl2 have a higher affinity for n-3 PUFA precursors compared to n-6 PUFA. The capacity for PUFA synthesis in mice mainly resides in the liver, with enzymes having preference for n-3 PUFAs.

Cytosolic DNA sensing protein pathway is activated in human hearts with dilated cardiomyopathy.

The genome is constantly exposed to numerous stressors, which induce DNA lesions, including double-stranded DNA breaks (DSBs). DSBs are the most dangerous, as they induce genomic instability. In response to DNA damage, the cell activates nuclear DNA damage response (DDR) and the cytosolic DNA sensing protein (CDSP) pathways, the latter upon release of the DSBs to the cytosol. The CDSP pathway activates NFκB and IRF3, which induce the expression of the pro-inflammatory genes. There is scant data on the activation of the CDSP pathway in human hearts with dilated cardiomyopathy (DCM). We aimed to determine expression levels of selected components of the CDSP pathway in human hearts with DCM. The DNA strand breaks were detected by the single-cell gel electrophoresis or the comet assay and expression of selected proteins by immunoblotting. Transcript levels were quantified in the RNA-Seq data. Single-cell gel electrophoresis showed an approximately 2-fold increase in the number of COMET cells in the DCM hearts. Immunoblotting showed increased levels of cyclic GMP-AMP synthase (CGAS), the canonical CDSP; TANK-binding kinase 1 (TBK1), an intermediary kinase in the pathway; and RELB, P52, and P50 components of the NFκB pathway in human heart samples from patients with DCM. Likewise, transcript levels of over 2 dozen genes involved in inflammatory responses were increased. The findings provide the first set of evidence for the activation of the CDSP pathway in human hearts with DCM. The data in conjunction with the previous evidence of activation of the DDR pathway implicate the DSBs in the pathogenesis of human DCM.

1632-P: Effects of MTOR Signaling in Muscle-Specific Irs1/2 Knockout Mice

Disruption of Irs1 and Irs2 expression in skeletal and cardiac muscle (MDKO mice) caused death from dilated cardiomyopathy within the first 30 days of life. MDKO showed muscle atrophy but were not glucose intolerant, despite impaired muscle glucose uptake. Beiging of white adipose fat increased glucose uptake into white adipose tissue of MDKO mice, and glucose uptake into brown adipose was also increased. Knockout of atrophy-driving genes FoxO1 and FoxO3a in MDKO mice (MQKO mice) extended life span to 70 days, when MQKO mice died with cardiomyopathy. High fat diet feeding increased life span in both MDKO and MQKO mice; however, genetic activation of the MTOR pathway in muscle of MDKO mice by Tsc1 knockout (MTKO mice) increased life span to 220 days. Regardless, MTKO mice developed cardiac hypertrophy with reduced ejection fraction by 24 weeks. Cardiac glucose uptake in MTKO mice was impaired during non-insulin as well as during insulin-stimulated conditions. Moreover, fat mass of MTKO mice decreased over time, implying a shift in consumption by MTKO hearts from glucose to fatty acids as source for cardiac energy. Tracing of radiolabeled palmitic acid did not support increased cardiac fatty acid uptake in MTKO mice; however, expression of lactate transporters was significantly elevated in MTKO hearts and circulating lactate generated by skeletal muscle was significantly reduced, indicating a potential use of lactate in MTKO hearts. These results show more robust effects of activating the MTOR pathway in insulin resistant hearts of MDKO mice rather than manipulating atrophy-related genes FoxO1/3a to counter early death from cardiomyopathy. Furthermore, activated MTOR signaling potentiated a metabolic switch in MDKO hearts. Disclosure O.Stoehr: None. K.D.Copps: None. R.Tao: None. M.F.White: Board Member; Housey Pharma.

Sirtuin 3 controls cardiac energetics and protects against oxidative stress in electromagnetic radiation-induced cardiomyopathy

Electromagnetic radiation can cause injuries to both the structures and functions of the heart. No therapy is currently available to inhibit these untoward effects. Mitochondrial energetic damage and oxidative stress are drivers of electromagnetic radiation-induced cardiomyopathy (eRIC); however, the pathways that mediate these events are poorly defined. Sirtuin 3 (SIRT3) has been emerged as a key target for maintaining mitochondrial redox potential and metabolism, but its role in eRIC remains unknown. Here, Sirt3-KO mice and cardiac-specific SIRT3 transgenic mice were subjected to the investigation of eRIC. We found that Sirt3 protein expression level was down-regulated in eRIC mice model. Sirt3-KO markedly exaggerated decreases in cardiac energetics and increases in oxidative stress in microwave irradiation (MWI)-stressed mice. Conversely, cardiac-specific SIRT3 overexpression protected the hearts from these effects and rescued cardiac malfunction. Mechanistically, Sirt3 maintained AMP-activated protein kinase (AMPK) signaling pathway in MWI-stressed hearts in vivo. In conclusion, electromagnetic radiation repressed SIRT3 expression and disturbed cardiac energetics and redox homeostasis. The increased SIRT3 expression and AMPK activation in vivo prevented eRIC, indicating that SIRT3 will be a potential therapeutic target for curative interventions in eRIC.

105 Burning Heart - An Animal Model of Chronic Heart Failure Following Severe Burn Injury

Abstract Introduction Our clinical research unveiled chronic heart failure with preserved ejection fraction (HFpEF) as a long-term sequel in survivors of severe pediatric burn injury due to a yet unknown molecular pathomechanism. Applying a standardized rat model, we systematically determined the pathophysiological impact of burn injury on long-term cardiac performance to uncover systemic and molecular pathomechanisms that may cause post-burn HFpEF development. Methods Male adolescent SD-rats were subjected to a 60 % total body surface area (TBSA) full-thickness burn- or sham-trauma and subsequently characterized after burn-injury by serial transthoracic echocardiography, bulk myocardial next-generation sequencing and proteomics as well as RT-PCR, immuno-blotting (IB), histology and plasma proteomics for cardiac performance and molecular alterations, respectively, at 3, 7, 30 and 90days. Results In comparison to the sham-group (SG), animals from the burn-group (BG) recapitulated typical post-burn clinical traits, such as significant loss in body weight (BG 27 % less than SG at 30d, p&amp;lt; 0.05) or skeletal muscle wasting (27 % less at 30d, p&amp;lt; 0.05) in accord with elevated molecular atrophy markers. We show post-burn cardiac muscle wasting (BG 22 % less at 30d, p&amp;lt; 0.05) and persistent markers of cardiac dysfunction in accord with significant histological cardiomyocyte hypotrophy (BG -8 % at 30d, p&amp;lt; 0.05) and significantly diminished left ventricular (LV) global longitudinal strain and isovolumic relaxation time in BGs, while LV-EF remained unchanged. Weighted gene network correlation analysis from bulk myocardial NGS and clinical traits related activation of immunological and pro-fibrotic pathways in post-burn injury hearts to cardiac dysfunction in BGs. Subsequent RT-PCR and histology confirmed significant myocardial accumulation of cardio-depressive damage associated molecular patterns (i.e., S100A8 and A9) and infiltration by granulocytes and monocytes as well as significant LV fibrosis. Serial plasma proteomic analysis indicated elevated plasma levels of S100A8 and A9 and other heart failure markers that mirrored similar changes in human post-burn plasma samples. Conclusions Here we report the development of HFpEF as a novel systemic consequence of severe burn injury in a rodent model, which warrants further mechanistic and translational studies. Cardiac inflammation and fibrosis are known to negatively impact cardiac performance and may be mechanistic key findings that will guide further therapeutic studies and subsequent validation of post-burn heart failure biomarkers Applicability of Research to Practice This model is part of a translational and interdisciplinary experimental and clinical effort to inform pathophysiology and mechanistics of long-term heart failure in burn patients. Echocardiographic data and parameters from this model are currently being used to evaluate adult survivors of severe burn injury for signs of HFpEF.

PO-03-159 TRANSSEPTAL VERSUS RETROGRADE AORTIC ABLATION OF LEFT-SIDED ACCESSORY PATHWAYS IN PEDIATRIC PATIENTS IN THE MODERN ERA

In the modern era of widespread use of three-dimensional electroanatomical mapping and minimal fluoroscopy, a comparison of the advantages and disadvantages of transseptal (TS) and retrograde aortic (RA) approaches to left-sided accessory pathway ablation in pediatrics has not been performed. The purpose of this study is to evaluate procedural safety and outcomes of catheter ablation via TS versus RA catheterization in pediatric patients with structurally normal heart and left-sided accessory pathways. This is a retrospective single-center chart review of pediatric patients from 2012-2021 at a free-standing children's hospital. This study was approved by our Institution Review Board. Inclusion criteria include age 0-21 years with a structurally normal heart. Exclusion criteria include significant structural heart disease and patients in whom ablation was not attempted. Outcomes assessed include procedural success, complications, recurrence, fluoroscopy exposure, and total ablation time. A total of 161 patients across 160 procedures met inclusion criteria. The median age was 13.5 years ([IQR] 9 - 16) and 40.4% (n=65) were female with median weight of 53.1kg (28.5-66.0). TS was performed in 58.1% (n=93) of procedures, while RA catheterization was performed in the other 41.9% (n=67). There were no significant differences in age, gender, weight, body surface area, or indication for ablation between either approach. Ablation success was achieved in 100.0% (n=67) of TS patients compared to 96.8% (n=90) of RA patients. There were no complications in the TS group and 4 (4.3%) complications in the RA group, with no major complications or mortality for either group. Overall, fluoroless ablation was achieved 79 procedures (50.6%), with zero fluoroscopy achieved in significantly more RA cases compared to TS (70.8% vs 23.9% p<0.001). For patients where follow-up clinic visit data was available (n=98), the median follow-up time was 31.2 (7-83) months. Recurrence was observed in 8 (11.9%) TS patients versus 14 (15.1%) RA patients (p=0.55). In the modern era with three-dimensional mapping and low fluoroscopy, both transseptal and retrograde aortic approaches to left-sided AP ablation in pediatric patients remain equivocally safe and efficacious. Although zero fluoroscopy was achieved in significantly more RA cases, nonsignificant increases in complications and recurrence were also observed in the RA approach compared to TS.

Epigenetic modifier alpha-ketoglutarate modulates aberrant gene body methylation and hydroxymethylation marks in diabetic heart

BackgroundDiabetic cardiomyopathy (DCM) is a leading cause of death in diabetic patients. Hyperglycemic myocardial microenvironment significantly alters chromatin architecture and the transcriptome, resulting in aberrant activation of signaling pathways in a diabetic heart. Epigenetic marks play vital roles in transcriptional reprogramming during the development of DCM. The current study is aimed to profile genome-wide DNA (hydroxy)methylation patterns in the hearts of control and streptozotocin (STZ)-induced diabetic rats and decipher the effect of modulation of DNA methylation by alpha-ketoglutarate (AKG), a TET enzyme cofactor, on the progression of DCM.MethodsDiabetes was induced in male adult Wistar rats with an intraperitoneal injection of STZ. Diabetic and vehicle control animals were randomly divided into groups with/without AKG treatment. Cardiac function was monitored by performing cardiac catheterization. Global methylation (5mC) and hydroxymethylation (5hmC) patterns were mapped in the Left ventricular tissue of control and diabetic rats with the help of an enrichment-based (h)MEDIP-sequencing technique by using antibodies specific for 5mC and 5hmC. Sequencing data were validated by performing (h)MEDIP-qPCR analysis at the gene-specific level, and gene expression was analyzed by qPCR. The mRNA and protein expression of enzymes involved in the DNA methylation and demethylation cycle were analyzed by qPCR and western blotting. Global 5mC and 5hmC levels were also assessed in high glucose-treated DNMT3B knockdown H9c2 cells.ResultsWe found the increased expression of DNMT3B, MBD2, and MeCP2 with a concomitant accumulation of 5mC and 5hmC, specifically in gene body regions of diabetic rat hearts compared to the control. Calcium signaling was the most significantly affected pathway by cytosine modifications in the diabetic heart. Additionally, hypermethylated gene body regions were associated with Rap1, apelin, and phosphatidyl inositol signaling, while metabolic pathways were most affected by hyperhydroxymethylation. AKG supplementation in diabetic rats reversed aberrant methylation patterns and restored cardiac function. Hyperglycemia also increased 5mC and 5hmC levels in H9c2 cells, which was normalized by DNMT3B knockdown or AKG supplementation.ConclusionThis study demonstrates that reverting hyperglycemic damage to cardiac tissue might be possible by erasing adverse epigenetic signatures by supplementing epigenetic modulators such as AKG along with an existing antidiabetic treatment regimen.

Role of Klotho and AGE/RAGE-Wnt/β-Catenin Signalling Pathway on the Development of Cardiac and Renal Fibrosis in Diabetes.

Fibrosis plays an important role in the pathogenesis of long-term diabetic complications and contributes to the development of cardiac and renal dysfunction. The aim of this experimental study, performed in a long-term rat model, which resembles type 1 diabetes mellitus, was to investigate the role of soluble Klotho (sKlotho), advanced glycation end products (AGEs)/receptor for AGEs (RAGE), fibrotic Wnt/β-catenin pathway, and pro-fibrotic pathways in kidney and heart. Diabetes was induced by streptozotocin. Glycaemia was maintained by insulin administration for 24 weeks. Serum and urine sKlotho, AGEs, soluble RAGE (sRAGE) and biochemical markers were studied. The levels of Klotho, RAGEs, ADAM10, markers of fibrosis (collagen deposition, fibronectin, TGF-β1, and Wnt/β-catenin pathway), hypertrophy of the kidney and/or heart were analysed. At the end of study, diabetic rats showed higher levels of urinary sKlotho, AGEs and sRAGE and lower serum sKlotho compared with controls without differences in the renal Klotho expression. A significant positive correlation was found between urinary sKlotho and AGEs and urinary albumin/creatinine ratio (uACR). Fibrosis and RAGE levels were significantly higher in the heart without differences in the kidney of diabetic rats compared to controls. The results also suggest the increase in sKlotho and sRAGE excretion may be due to polyuria in the diabetic rats.

Nicotinamide riboside kinase-2 regulates metabolic adaptation in the ischemic heart.

Ischemia-induced metabolic remodeling plays a critical role in the pathogenesis of adverse cardiac remodeling and heart failure however, the underlying molecular mechanism is largely unknown. Here, we assess the potential roles of nicotinamide riboside kinase-2 (NRK-2), a muscle-specific protein, in ischemia-induced metabolic switch and heart failure through employing transcriptomic and metabolomic approaches in ischemic NRK-2 knockout mice. The investigations revealed NRK-2 as a novel regulator of several metabolic processes in the ischemic heart. Cardiac metabolism and mitochondrial function and fibrosis were identified as top dysregulated cellular processes in the KO hearts post-MI. Several genes linked to mitochondrial function, metabolism, and cardiomyocyte structural proteins were severely downregulated in the ischemic NRK-2 KO hearts. Analysis revealed significantly upregulated ECM-related pathways which was accompanied by the upregulation of several key cell signaling pathways including SMAD, MAPK, cGMP, integrin, and Akt in the KO heart post-MI. Metabolomic studies identified profound upregulation of metabolites mevalonic acid, 3,4-dihydroxyphenylglycol, 2-penylbutyric acid, and uridine. However, other metabolites stearic acid, 8,11,14-eicosatrienoic acid, and 2-pyrrolidinone were significantly downregulated in the ischemic KO hearts. Taken together, these findings suggest that NRK-2 promotes metabolic adaptation in the ischemic heart. The aberrant metabolism in the ischemic NRK-2 KO heart is largely driven by dysregulated cGMP and Akt and mitochondrial pathways. KEY MESSAGES: Post-myocardial infarction metabolic switch critically regulates the pathogenesis of adverse cardiac remodeling and heart failure. Here, we report NRK-2 as a novel regulator of several cellular processes including metabolism and mitochondrial function post-MI. NRK-2 deficiency leads to downregulation of genes important for mitochondrial pathway, metabolism, and cardiomyocyte structural proteins in the ischemic heart. It was accompanied by upregulation of several key cell signaling pathways including SMAD, MAPK, cGMP, integrin, and Akt and dysregulation of numerous metabolites essential for cardiac bioenergetics. Taken together, these findings suggest that NRK-2 is critical for metabolic adaptation of the ischemic heart.