Decline In Diastolic Function Research Articles

Abstract Or108: The role of SARM1 in regulation of immune response in heart failure with preserved ejection fraction

Heart failure with preserved ejection fraction (HFpEF) is an unmet medical need. Recent studies have shown that HFpEF is associated with immune dysregulation and decline in nicotinamide adenine dinucleotide (NAD + ) levels. However, the molecular mechanisms linking these factors in HFpEF are not completely understood. Sterile alpha and TIR motif-containing 1 (SARM1) is a NAD + consuming enzyme that may regulate immune response and NAD + metabolism. Here, we investigated the role of SARM1 in HFpEF pathophysiology. We utilized a two-hit diet model to induce HFpEF in mice (HFpEF diet: high-fat diet and L-NAME). Wild-type (WT) mice on HFpEF diet showed progressive decline in diastolic function (e.g. decreased E’/A’, increased relaxation time, IVRT) at 5- and 15-week, associated with unchanged systolic function and increased cardiac hypertrophy. Despite decline in NAD + levels as previously reported in HFpEF hearts, qPCR analysis showed no significant differences in the expression of enzymes involved in NAD + biosynthesis including the salvage, Preiss-Handler and de novo pathways. We employed RNA-sequencing to identify cardiac gene signatures that are associated with HFpEF. Gene ontology analysis showed activation of various immune pathways in HFpEF hearts. Using flow cytometry analysis, we observed around 66% increase in total leukocytes (CD45+) number, along with infiltration of both T cells (CD3+ CD4+/CD8+) and myeloid cell populations (CD11b+) in HFpEF hearts. To understand the role of SARM1 in HFpEF pathogenesis, we subjected global SARM1 knock out (KO) mice to HFpEF diet. SARM1 KO hearts had improved diastolic function and reduced hypertrophy after 15-week HFpEF diet. RNA-sequencing of SARM1 KO-HFpEF hearts showed downregulations of transcripts in immune activation pathways, compared to WT-HFpEF hearts. In summary, our findings suggest that SARM1 may regulate immune activation pathways and promote HFpEF pathogenesis. We plan to determine the intricate relationships between immune dysregulation, metabolic stress, and cardiac dysfunction in HFpEF pathogenesis. The future direction may identify potential avenues for targeted therapeutic interventions aimed at modulating immune responses for HFpEF.

Survivors of Pediatric Hematopoietic Stem Cell Transplantation Exhibit Progressive Diastolic Dysfunction Over Years of Follow-Up

Patients who have undergone hematopoietic stem cell transplantation (HSCT) in childhood have a higher risk of diastolic heart failure (HF). The rate of progression of diastolic dysfunction in aging pediatric patients is unknown and is more difficult to assess in young patients secondary to changes in diastolic indices as they grow. HSCT recipients at our center were previously found to have decline in diastolic function indices at 1 year after HSCT. This study provides follow-up of this cohort, using age-normalized z-scores to assess whether the decline in diastolic function noted at 1-year post-HSCT persists, worsens, or improves over time. Patients age <21 years who underwent HSCT at Boston Children's Hospital/Dana-Farber Cancer Center between 2005 and 2008 with ≥3 surveillance echocardiograms, including 1 performed pre-HSCT, were included. Diastolic measures included mitral inflow (E/A ratio) and Doppler tissue imaging of left ventricular lateral wall (LV lateral e'), LV septal wall (septal e') and right ventricular free wall (RV e'). Systolic function was measured by LV ejection fraction (LVEF). Normalization by age was done using z-scores, and >±2 SD was defined as abnormal in linear modeling of diastolic dysfunction and systolic dysfunction over time. In a subset of patients with adequate post-HSCT images of the entire left atrium (LA), LA volume and LA strain analyses also were performed. The study cohort comprised 61 patients (41% female; median age at HSCT, 10.7 years; median follow-up, 7.4 years). Diastolic index z-scores declined by -.045/year for LV lateral e', -.06/year for LV septal e', and -.14/year for RV e' (P < .01). The E/A ratio z-score increased by .034/year (P=.028). Linear modeling demonstrated that LV lateral e' and LV septal e' would become abnormal at 25 and 20 years post-HSCT, respectively, whereas RV e' would become abnormal sooner, at 12.6 years. LVEF z-score declined by -.04/year (P < .01) and was estimated to become abnormal at 40 years post-HSCT. Exposure to total body irradiation (TBI) was associated with worsening diastolic indices, lower LVEF (P ≤ .002), and decreased LA reservoir strain (42.0% versus 45.0%; P=.016) and conduit strain (-31.5% versus -35.1%; P=.029), although there was significant overlap between TBI and anthracycline exposure. Treatment with anthracyclines even at low doses (median, 150 mg/m2) was associated with declining LVEF but not with changes in diastolic indices. Long-term survivors of childhood HSCT exhibit declines in both LV and RV diastolic function indices. These results inform the rate of progression of LV and RV diastolic dysfunction indices over time in long-term survivors of pediatric HSCT. A significant association was observed between TBI and diastolic dysfunction and a decline in LVEF. Treatment with anthracyclines even at low doses was associated with a mild decline in LVEF. Our results can inform a lifespan perspective on disease management in this population, encourage clinicians and patients to be vigilant in following guideline-directed surveillance echocardiography, and inform anticipatory responses by clinicians as patients transition from pediatric care to adult care.

Phasic left atrial strain to predict worsening of diastolic function: Results from the prospective Berlin Female Risk Evaluation follow-up trial.

The predictive value of maximum left atrial volume index (LAVI), phasic left atrial strain (LAS) and other standard echocardiographic parameters assessing left ventricular (LV) diastolic function to discriminate a future worsening of diastolic function (DD) in patients at risk is unclear. We aimed to prospectively assess and compare the clinical impact of these parameters in a randomly selected study sample of the general urban female population. A comprehensive clinical and echocardiographic evaluation was performed in 256 participants of the Berlin Female Risk Evaluation (BEFRI) trial after a mean follow up time of 6.8 years. After an assessment of participants' current DD status, the predictive impact of an impaired LAS on the course of DD was assessed and compared with LAVI and other DD parameters using receiver operating characteristic (ROC) curve and multivariate logistic regression analyses. Subjects with no DD (DD0) who showed a decline of diastolic function by the time of follow-up showed a reduced LA reservoir (LASr) and conduit strain (LAScd) compared to subjects who remained in the healthy range (LASr 28.0% ± 7.0 vs. 41.9% ± 8.5; LAScd -13.2% ± 5.1 vs. -25.4% ± 9.1; p < 0.001). With an area under the curve (AUC) of 0.88 (95%CI 0.82-0.94) and 0.84 (95%CI 0.79-0.89), LASr and LAScd exhibited the highest discriminative value in predicting worsening of diastolic function, whereas LAVI was only of limited prognostic value [AUC 0.63 (95%CI 0.54-0.73)]. In logistic regression analyses, LAS remained a significant predictor for a decline of diastolic function after controlling for clinical and standard echocardiographic DD parameters, indicating its incremental predictive value. The analysis of phasic LAS may be useful to predict worsening of LV diastolic function in DD0 patients at risk for a future DD development.GRAPHICAL ABSTRACT.

SARM1 NAD Hydrolase Deficiency Normalizes Fibrosis and Ameliorates Cardiac Dysfunction in Diabetic Hearts

Decline in cellular NAD levels emerges as a hallmark of diseases such as diabetes and heart failure. Strategies to activate NAD synthesis pathways and replenish NAD levels have shown promises to treat heart disease. However, how NAD consumption mechanisms lead to NAD depletion and disease pathogeneses are less understood. SARM1 is an intracellular NAD hydrolase, and its role in heart disease has never been investigated. We therefore hypothesized that SARM1 deficiency may protect hearts against diabetic cardiomyopathy. Male C57BL/6 wild‐type (WT) and SARM1‐KO mice were challenged with 16‐week diabetic stress initiated by streptozotocin injections (STZ). Longitudinal cardiac function was measured by echocardiography after 8 or 16 weeks of diabetes, and tissue and plasma samples were harvested for biochemical and molecular analyses. Chronic diabetic stress lowered cardiac NAD levels and led to progressive decline in systolic function of WT mice. Diabetic SARM1‐KO mice showed improved systolic function and increased cardiac NAD levels, compared to diabetic WT mice. Progressive decline in diastolic function induced by chronic diabetes was also improved by SARM1 deficiency. Heart weights and hyperglycemia were similar in diabetic WT or diabetic SARM1‐KO mice. Metabolomic analyses of plasma showed significant changes in 58 out of ~300 aqueous metabolites assessed when comparing non‐diabetic WT to diabetic WT plasma, including increased levels of glucose and branched‐chain amino acids. However, the 58 metabolites showed no changes in levels when comparing diabetic WT to diabetic SARM1‐KO plasma. Similarly, we found that 26 out of 85 lipid species showed significant changes when comparing non‐diabetic WT to diabetic WT plasma, and only one of these 26 lipid metabolites showed a significant change between diabetic WT and diabetic SARM1‐KO plasma. The data suggest that cardioprotection in SARM1‐KO mice was likely due to the reversal of cardiac pathogenic mechanisms but not improved systemic metabolic state.To determine how SARM1 deficiency affects cardiac NAD metabolism, expression of genes in NAD metabolic pathways were assessed. Levels of Bst1 and Cd38 did not change in SARM1‐KO hearts, suggesting that SARM1 deficiency did not induce compensatory changes in expression of the other NAD hydrolases. SARM1‐KO hearts showed lower expressions in some of the NAD consuming genes (e.g. Sirtuins) and NAD synthesis genes (e.g. Nmnats). Cardiac dysfunction marker, Nppb expression, was induced in diabetic WT hearts, and was reversed by SARM1 deficiency. Cardiac fibrosis and pro‐fibrotic genes (e.g. ctgf) were induced in diabetic WT hearts and were suppressed by SARM1 deficiency. Using the total SARM1 KO mice, our data support that SARM1 deficiency normalizes decline in NAD levels and pro‐fibrotic pathways to ameliorate diabetic cardiomyopathy. Further experiments are warranted to dissect the cell‐type specific roles of SARM1 in diabetic hearts.

Regulation of NAD Metabolism in Diastolic Dysfunction Induced by Metabolic Stress

Patients of heart failure with preserved ejection fraction (HFpEF) have diastolic dysfunction. Intervention targeting mechanisms of diastolic dysfunction is lacking, leading to a growing population of patients with HFpEF. Diabetes and obesity are key risk factors of HFpEF. NAD depletion is associated with heart failure, diabetes and obesity, and is due to NAD redox imbalance, suppressed synthesis and/or activated consumption pathways. Here, we used mouse models manipulating NAD redox balance and hydrolysis to determine their roles in metabolic cardiomyopathy. Cardiac Ndufs4‐KO mice (cKO) have lowered cardiac NAD/NADH ratio, normal baseline function, geometry and energetics. Chronic diabetic stress induced by streptozotocin (STZ) or diet‐induced obesity (DIO) in wild type (WT) mice promoted diastolic dysfunction, which was further exacerbated in cKO mice with latent cardiac NAD redox imbalance. Elevated oxidative stress by SOD2 acetylation and increased TnI‐S150 phosphorylation by energetic deficiency in diabetic cKO hearts led to exacerbated diastolic dysfunction. Elevation of cardiac NAD levels normalized NAD/NADH ratio, ameliorated these pathogenic mechanisms and diastolic dysfunction in metabolically stressed mice. These results supported the causal role of NAD redox imbalance in metabolic cardiomyopathy.Next, we tested whether deficiency of SARM1, an intracellular NAD hydrolase, will ameliorate diastolic dysfunction induced by metabolic stresses. WT and total SARM1‐KO mice were challenged with diabetic stress or DIO. These metabolic stresses led to a decline in diastolic function, which was improved in SARM1‐KO mice. DIO also promoted cardiac hypertrophy that was ameliorated by SARM1 deficiency. To determine that the improvement of diastolic function by SARM1 deficiency was not due to a reversal of systemic metabolic state, a comprehensive plasma metabolomic analyses was performed. Hyperglycemia was similar in diabetic WT and SARM1‐KO plasma. Metabolomic analyses showed significant changes in 58 out of 298 aqueous metabolites and in 26 out of 85 lipid species measured, when comparing non‐diabetic WT to diabetic WT plasma. When comparing the 84 metabolites with diabetic changes from diabetic WT and diabetic SARM1‐KO plasma, only one of the lipid metabolites (PC 16:0/16:0) showed a mild further decrease in SARM1‐KO plasma. The metabolomic data suggest that WT and SARM1‐KO hearts experienced similar metabolic stress, and that the improvement of diastolic dysfunction by SARM1 deficiency was due to the reversal of cardiac pathogenic mechanisms.To determine how SARM1 deficiency affected cardiac NAD metabolism, transcript levels of genes in NAD metabolic pathways were assessed. Expressions of Bst1 and Cd38 NAD hydrolases did not change in SARM1‐KO hearts, suggesting that SARM1 deficiency did not induce compensatory changes in expression of the other NAD hydrolases. SARM1‐KO hearts showed lower expressions in several other NAD consuming genes (e.g. Sirtuins) and NAD synthesis genes (e.g. Nmnats). Cardiac fibrosis, pro‐fibrotic genes (e.g. ctgf) and Nppb expression were induced in diabetic WT hearts and were suppressed by SARM1 deficiency. In summary, our data support the critical roles of NAD redox imbalance and SARM1 in diastolic dysfunction induced by metabolic stress.

Abstract 13316: Cardiomyopathy Induced by Metabolic and Hypertensive Stresses is Alleviated by SARM1 Deficiency

Introduction: NAD depletion emerges as a hallmark of diseases. Strategies to replenish NAD levels have shown promise to treat heart disease, including heart failure with preserved ejection fraction (HFpEF). However, how NAD consumption mechanisms lead to NAD depletion are less understood. SARM1 is a novel intracellular NAD hydrolase that promotes axonal degeneration after axon injury, and its role in cardiomyopathy has not been tested. Hypothesis: We hypothesized that SARM1 deficiency will protect hearts against cardiomyopathy induced by metabolic and hypertensive stresses. Methods and Results: Aged-matched male C57BL/6 wild type (WT) and whole-body SARM1-KO mice were challenged with 16-week diabetic stress initiated by streptozotocin (STZ). SARM1 mRNA or protein levels were suppressed in KO hearts. STZ induced similar hyperglycemia (~600 mg/dL) in both WT and KO mice after 16 weeks. Chronic diabetic stress led to progressive decline in systolic function (FS: 50% vs 35%; P&lt;0.05; n=5) in WT mice, which was ameliorated in KO mice (48%; P&lt;0.05; n=5). Progressive decline in diastolic function by chronic diabetes (E’/A’: 1.53 vs 1.12; n=5) was also improved in diabetic KO mice (1.5; P&lt;0.05; n=5). Up-regulated Nppb in diabetic WT hearts was suppressed by SARM1 deficiency. No compensatory changes in expressions of other NAD hydrolases were observed in diabetic KO hearts. Cardiac fibrosis was induced in diabetic WT hearts and were suppressed in diabetic KO hearts after 16-week diabetic stress. WT and KO mice were challenged with high fat diet feeding (HFD) or HFD with L-NAME (a HFpEF regimen) for 16 weeks. Systolic function was unchanged in mice after HFD or HFpEF regimen, with or without SARM1 deficiency. However, SARM1 deficiency ameliorated diastolic dysfunction of male mice induced by HFD (WT vs KO E’/A’ = 1.07 vs 1.37, n=5) or HFpEF regimen (WT vs KO E’/A’ = 0.96 vs 1.31, n=6). Unlike diabetic cardiomyopathy induced by STZ, cardiac hypertrophy in WT mice was induced by HFD or HFpEF regimen, and KO mice showed decreases in hypertrophy induced by the two stressors. Conclusion: Our data support a protective role of SARM1 deficiency in cardiomyopathy. Pathogenic mechanisms of SARM1 in cardiomyopathy induced by metabolic or hypertensive stresses remain to be determined.

Abstract 9505: Myocardial Energetic Impairment is the Basis for Reduced Cardiac Reserve and Exercise-Induced Pulmonary Congestion in Heart Failure With Preserved Ejection Fraction: Insights From Novel Cardiopulmonary Magnetic Resonance Imaging

Introduction: Abnormal cardiac mitochondrial function and energetics may be a unifying feature in the pathogenesis of heart failure with preserved ejection fraction (HFpEF), while transient pulmonary congestion during exercise is an important determinant of reduced exercise capacity and symptoms. Hypothesis: We hypothesized that a gradient of myocardial energetic impairment exists across the spectrum of HFpEF and limits cardiac reserve during exercise, leading to transient pulmonary congestion. Methods: 43 patients across the spectrum of diastolic dysfunction and HFpEF (age-matched controls n=11; type 2 diabetes (T2DM) n=9; HFpEF n=14; severe diastolic dysfunction due to cardiac amyloid n=9) underwent assessment of cardiac energetics (myocardial phosphocreatine to ATP ratio, PCr/ATP) and function using CMR, and lung water using a novel MR proton density mapping sequence. Studies were performed at rest and during exercise (20 W for 6 minutes). Results: Paralleling the stepwise decline in diastolic function across the groups (E/e’ ratio p&lt;0.001) was an increase in NT-pro BNP (p&lt;0.001) and a reduction in PCr/ATP (p&lt;0.001). During exercise, lower left ventricular (LV) diastolic filling rates (r 0.58, p&lt;0.001), left atrial (LA) dilatation (r -0.52, p&lt;0.001), lower right ventricular (RV) contractile reserve (ΔRVEF; r 0.57, p&lt;0.001), and right atrial (RA) dilatation (r -0.71, p&lt;0.001) were strongly linked with impaired energetics. The pulmonary proton density sequence provided images that scaled linearly with water content, validated using a water-doped sponge phantom (r 0.98, p&lt;0.0001), and revealed transient pulmonary congestion in patients with HFpEF (+4.4% [0.5, 6.4], p=0.002) and amyloid (+6.4% [3.3, 10.0], p=0.004), which was not seen in controls (-0.1% [-1.9, 2.1], p=0.89) or T2DM (+0.8% [-1.7, 1.9], p=0.82). Exercise-induced pulmonary congestion was associated with reduced LV diastolic filling (r -0.33, p=0.03), RVEF augmentation (r-0.50, p&lt;0.001), RA dilatation (r 0.44, p=0.004), and impaired myocardial energetics (r -0.43, p=0.004). Conclusion: A gradient of myocardial energetic deficit exists across the spectrum of HFpEF, leading to impaired cardiac functional reserve and transient exercise-induced pulmonary congestion.

Energetic Basis for Exercise-Induced Pulmonary Congestion in Heart Failure With Preserved Ejection Fraction.

Transient pulmonary congestion during exercise is emerging as an important determinant of reduced exercise capacity in heart failure with preserved ejection fraction (HFpEF). We sought to determine whether an abnormal cardiac energetic state underpins this process. We recruited patients across the spectrum of diastolic dysfunction and HFpEF (controls, n=11; type 2 diabetes, n=9; HFpEF, n=14; and severe diastolic dysfunction attributable to cardiac amyloidosis, n=9). Cardiac energetics were measured using phosphorus spectroscopy to define the myocardial phosphocreatine to ATP ratio. Cardiac function was assessed by cardiovascular magnetic resonance cine imaging and echocardiography and lung water using magnetic resonance proton density mapping. Studies were performed at rest and during submaximal exercise using a magnetic resonance imaging ergometer. Paralleling the stepwise decline in diastolic function across the groups (E/e' ratio; P<0.001) was an increase in NT-proBNP (N-terminal pro-brain natriuretic peptide; P<0.001) and a reduction in phosphocreatine/ATP ratio (control, 2.15 [2.09, 2.29]; type 2 diabetes, 1.71 [1.61, 1.91]; HFpEF, 1.66 [1.44, 1.89]; cardiac amyloidosis, 1.30 [1.16, 1.53]; P<0.001). During 20-W exercise, lower left ventricular diastolic filling rates (r=0.58; P<0.001), lower left ventricular diastolic reserve (r=0.55; P<0.001), left atrial dilatation (r=-0.52; P<0.001), lower right ventricular contractile reserve (right ventricular ejection fraction change, r=0.57; P<0.001), and right atrial dilation (r=-0.71; P<0.001) were all linked to lower phosphocreatine/ATP ratio. Along with these changes, pulmonary proton density mapping revealed transient pulmonary congestion in patients with HFpEF (+4.4% [0.5, 6.4]; P=0.002) and cardiac amyloidosis (+6.4% [3.3, 10.0]; P=0.004), which was not seen in healthy controls (-0.1% [-1.9, 2.1]; P=0.89) or type 2 diabetes without HFpEF (+0.8% [-1.7, 1.9]; P=0.82). The development of exercise-induced pulmonary congestion was associated with lower phosphocreatine/ATP ratio (r=-0.43; P=0.004). A gradient of myocardial energetic deficit exists across the spectrum of HFpEF. Even at low workload, this energetic deficit is related to markedly abnormal exercise responses in all 4 cardiac chambers, which is associated with detectable pulmonary congestion. The findings support an energetic basis for transient pulmonary congestion in HFpEF.

Impaired myocardial energetics limits cardiac functional reserve and leads to exercise-induced pulmonary congestion in heart failure with preserved ejection fraction

Abstract Background Abnormal cardiac mitochondrial function and energetics may be a unifying feature in the pathogenesis of heart failure with preserved ejection fraction (HFpEF). Transient pulmonary congestion during exercise is emerging as an important determinant of reduced exercise capacity and symptoms in patients with HFpEF. Purpose We sought to determine if impaired myocardial energetics limits cardiac exercise reserve and leads to exercise-induced pulmonary congestion in HFpEF. Methods 42 patients across the spectrum of diastolic dysfunction and HFpEF (controls n=10; type 2 diabetes (T2DM) n=9; HFpEF n=14; severe diastolic dysfunction due to cardiac amyloid n=9) (Fig. 1a) underwent assessment of cardiac energetics (myocardial phosphocreatine to adenosine triphosphate ratio, PCr/ATP) and function using cardiovascular magnetic resonance (CMR) imaging and echocardiography, and lung-water using a novel pulmonary proton-density MR sequence. Studies were performed at rest and during exercise (20W for 6 minutes) using a CMR-ergometer. Results Paralleling the stepwise decline in diastolic function across the groups (E/e' ratio, p&amp;lt;0.0001) was an increase in NT-pro BNP (p&amp;lt;0.0001, Fig. 1b) and reduction in PCr/ATP (control 2.00 [1.86,2.15], T2DM 1.71 [1.61,1.91], HFpEF 1.66 [1.44,1.89], amyloid 1.30 [1.16,1.53], p&amp;lt;0.0001, Fig. 1c). During exercise, there was progressive blunting of left ventricular (LV) diastolic filling (p&amp;lt;0.0001) (Fig. 2a-b), left atrial (LA) dilatation (p&amp;lt;0.0001), failure of RVEF augmentation (p=0.003), RV-PA uncoupling (RV stroke volume to end-systolic volume (SV/ESV) ratio, p=0.0002), and right atrial (RA) dilatation (p&amp;lt;0.0001) across the groups (Fig. 2b). LV diastolic filling (r 0.41, p=0.008), LA dilatation (r −0.35, p=0.03), RVEF augmentation (r 0.46, p=0.003), RV-PA uncoupling (r 0.36, p=0.02), and RA dilatation (r −0.68, p&amp;lt;0.001) during exercise were strongly linked with impaired myocardial energetics (Fig. 2b). The novel pulmonary proton-density sequence provided images that scaled linearly with water content (validated using a water-doped sponge phantom; r 0.98, p&amp;lt;0.0001), and revealed a progressive increase in lung water signal/pulmonary congestion (Fig. 2c) post-exercise (p&amp;lt;0.0001) across the groups (controls: +0.25% [−1.8, 3.1], p=0.82; T2DM: +0.8% [−1.7, 1.9], p=0.82; HFpEF: +4.4% [0.5, 6.4], p=0.002; amyloid: +6.4% [3.3, 10.0], p=0.004). Pulmonary congestion was associated with impaired LV diastolic filling (r −0.32, p=0.04), RV-PA uncoupling (r −0.39, p=0.01) and RA dilatation (r 0.4, p=0.01) during exercise, and impaired myocardial energetics (r −0.36, p=0.02). Conclusion A gradient of myocardial energetic deficit exists across the spectrum of HFpEF. This energetic deficit is related to markedly abnormal cardiac exercise responses, which leads to transient pulmonary congestion. The findings support an energetic basis for impaired cardiac reserve and exercise-induced pulmonary congestion in HFpEF. Funding Acknowledgement Type of funding sources: Foundation. Main funding source(s): British Heart Foundation Baseline clinical and CMR parametersExercise cardiopulmonary parameters

Abstract P319: SARM1 NAD Hydrolase Deficiency Protects Hearts Against Diabetic Cardiomyopathy

NAD depletion is associated with the pathogenesis of diseases such as heart failure. Strategies to replenish cellular NAD levels by activating NAD synthesis pathways have shown promises to treat heart disease. However, how NAD consumption mechanisms lead to NAD depletion are less understood. SARM1 is a novel intracellular NAD hydrolase that degrades NAD and promotes axonal degeneration in neurons. We recently showed that NAD redox imbalance and depletion promote the progression of diabetic cardiomyopathy. Therefore, we hypothesized that SARM1 deficiency might protect hearts against diabetic cardiomyopathy. 16-week diabetic stress initiated by streptozotocin (STZ) injections was applied to wild-type C57BL/6 (WT) and whole-body SARM1-KO mice. Cardiac function was measured after 8-week or 16-week of diabetic stress, and cardiac tissue and plasma samples from these mice were harvested after 16 weeks of diabetes. SARM1 mRNA or protein levels were suppressed in SARM1-KO hearts. STZ induced similar hyperglycemia (~600 mg/dL) in both WT and SARM1-KO male mice after 16 weeks. Chronic diabetic stress led to progressive decline in systolic function (Baseline fractional shortening: 50%; 16-week diabetes: 35%; P&lt;0.05; n=5) in WT male mice, which was ameliorated in SARM1-KO male mice (16-week diabetes: 48%; P&lt;0.05; n=5). Progressive decline in diastolic function induced by chronic diabetes (Baseline WT E’/A’: 1.53; WT 16-week diabetes: 1.12; n=5) was also improved in diabetic SARM1-KO mice (KO E’/A’ ratio at 16-week diabetes: 1.5; P&lt;0.05; n=5). Heart weights were similar in diabetic WT or diabetic SARM1-KO hearts. A similar study is on-going in a female cohort. Despite loss of SARM1 expression, no compensatory changes in expressions of other NAD hydrolases (i.e. Cd38 or Bst1) were observed in diabetic SARM1-KO hearts, while expression levels of genes related to NAD consumption and synthesis pathways were mostly unchanged except Qprt and Haao. Cardiac fibrosis was induced in diabetic WT hearts and were suppressed in diabetic SARM1-KO hearts after 16-week diabetic stress, but these changes were not observed in tissues harvested after 8-week diabetic stress. The results suggest fibrosis is a later event in the progression of diabetic cardiomyopathy. WT and SARM1-KO mice have also been challenged with high fat diet feeding (HFD) for 16 weeks, and increased fasting glucose levels and body weights were similarly observed in HFD-WT and HFD-SARM1-KO mice. Longitudinal cardiac function analyses are on-going. Our data thus far support the protective role of SARM1 deficiency in metabolic stress-induced cardiomyopathy, while pathogenic mechanisms of SARM1 in diabetic hearts remain to be determined.

SS-31 and NMN: Two paths to improve metabolism and function in aged hearts.

The effects of two different mitochondrial‐targeted drugs, SS‐31 and NMN, were tested on Old mouse hearts. After treatment with the drugs, individually or Combined, heart function was examined by echocardiography. SS‐31 partially reversed an age‐related decline in diastolic function while NMN fully reversed an age‐related deficiency in systolic function at a higher workload. Metabolomic analysis revealed that both NMN and the Combined treatment increased nicotinamide and 1‐methylnicotinamide levels, indicating greater NAD+ turnover, but only the Combined treatment resulted in significantly greater steady‐state NAD(H) levels. A novel magnetic resonance spectroscopy approach was used to assess how metabolite levels responded to changing cardiac workload. PCr/ATP decreased in response to increased workload in Old Control, but not Young, hearts, indicating an age‐related decline in energetic capacity. Both drugs were able to normalize the PCr/ATP dynamics. SS‐31 and NMN treatment also increased mitochondrial NAD(P)H production under the higher workload, while only NMN increased NAD+ in response to increased work. These measures did not shift in hearts given the Combined treatment, which may be owed to the enhanced NAD(H) levels in the resting state after this treatment. Overall, these results indicate that both drugs are effective at restoring different aspects of mitochondrial and heart health and that combining them results in a synergistic effect that rejuvenates Old hearts and best recapitulates the Young state.

335 Effects of Healthy Aging on Left Atrial Phasic Function Using Strain Analysis

Left atrial size and function are increasingly recognised as functional and prognostic biomarkers. Age related changes in phasic LA volumes and function are associated with age related diastolic dysfunction. We hypothesised that there is an age-related decline in diastolic function with compensatory changes in LA strain, with alterations in phasic LA function. 102 healthy volunteers had a TTE and phasic LA volumes and 2D LA strain measurements performed. LAmax volumes were similar across all ages (p=1.0). LAmin volume was significantly higher in group ‘c’ vs groups ‘a’ and ‘b’ (p<0.001 and p=0.042, respectively). LAPreP volume was significantly increased between each age bracket (p<0.01 for all). LA reservoir strain was significantly reduced in group ‘c’ vs groups ‘a’ and ‘b’ (p=0.003 and p=0.018, respectively). LA conduit strain progressively declined between each age bracket (p<0.015), with LA contractile strain increasing in groups ‘b’ and ‘c’ vs group ‘a’ (p=0.006 and p<0.001, respectively). LA conduit strain is altered early with a compensatory increase in LA contractile strain, whilst LA reservoir strain shows progressive reduction with increasing age. These phasic functional changes are reflected by an early increase in LAPreP volume and subsequent increase in LAmin.Tabled 1Age (yrs)LAmax (ml/m2)LAmin (ml/m2)LAPreP (ml/m2)LA reservoir strain (%)LA conduit strain (%)LA contractile strain (%)18-30(a)25.2±7.310.3±3.2113.5±3.61,236.8±5.8123.4±5.71,213.4±2.71,231-50(b)26.9±4.711.7±2.6316.6±3.7335.5±6.2319.4±5.5316.1±3.751+(c)27.3±6.513.6±419.3±4.631.7±6.614.6±5.116.9±3.41(a) vs (c) p<0.05; 2(a) vs (b) p<0.05; 3(b) vs (c) p<0.05 Open table in a new tab

Rapamycin persistently improves cardiac function in aged, male and female mice, even following cessation of treatment.

Even in healthy aging, cardiac morbidity and mortality increase with age in both mice and humans. These effects include a decline in diastolic function, left ventricular hypertrophy, metabolic substrate shifts, and alterations in the cardiac proteome. Previous work from our laboratory indicated that short‐term (10‐week) treatment with rapamycin, an mTORC1 inhibitor, improved measures of these age‐related changes. In this report, we demonstrate that the rapamycin‐dependent improvement of diastolic function is highly persistent, while decreases in both cardiac hypertrophy and passive stiffness are substantially persistent 8 weeks after cessation of an 8‐week treatment of rapamycin in both male and female 22‐ to 24‐month‐old C57BL/6NIA mice. The proteomic and metabolomic abundance changes that occur after 8 weeks of rapamycin treatment have varying persistence after 8 further weeks without the drug. However, rapamycin did lead to a persistent increase in abundance of electron transport chain (ETC) complex components, most of which belonged to Complex I. Although ETC protein abundance and Complex I activity were each differentially affected in males and females, the ratio of Complex I activity to Complex I protein abundance was equally and persistently reduced after rapamycin treatment in both sexes. Thus, rapamycin treatment in the aged mice persistently improved diastolic function and myocardial stiffness, persistently altered the cardiac proteome in the absence of persistent metabolic changes, and led to persistent alterations in mitochondrial respiratory chain activity. These observations suggest that an optimal translational regimen for rapamycin therapy that promotes enhancement of healthspan may involve intermittent short‐term treatments.

P899Long-term evolution of Fabry cardiomyopathy under enzyme replacement therapy in the Swiss Fabry cohort. An echocardiographic study

Abstract Introduction Fabry cardiomyopathy may present with left ventricular hypertrophy (LVH) and enzyme replacement therapy (ERT) aims to slow its progression in affected patients. LVH progression may be observed despite ERT and the aim of this study was to identify predictors of adverse LV remodeling under treatment. Methods This multicentric study included consecutive Fabry patients receiving ERT and for whom a clinical follow-up (FU) with echocardiography (TTE) of at least 5 years was available. The first TTE was performed at the time of ERT start and disease progression was defined as an increase in LV mass index between the first and the last available FU TTE. Results Sixty-one patients (median age 35 years [23–48] and 40 (66%) men) were included with a median FU of 10.5 years [7.2–12.2]. Progression was seen in 33 (54%) patients with an annual increase in LV mass index of 1.8 g/m2/year [0.7–3.2] (vs −0.8 g/m2/year [−1.6 to 0.4] in the non-progression group). Presence of LVH (&gt;95 g/m2 in women or &gt;115 g/m2 in men) at the start of ERT was the only morphological baseline parameter significantly associated with progression after adjustment for age, gender and baseline arterial hypertension (OR 22.5, 95% CI 2.7–188.3, p=0.004). Over the FU duration, patients with baseline LVH (n=22) had higher increase in LV diastolic diameter (2.3±4.9 mm vs 0.9±4.1, p=0.009), a lower increase in relative wall thickness (−1.7±14.1% vs 4.6±9.8%, p=0.04), and a higher increase in LV mass index (22±22 g/m2 vs 0±17 g/m2, p=0.001), as compared with patients with no baseline LVH. While no difference was seen in the evolution of the LV ejection fraction, a faster decline in diastolic function was observed in patients with baseline LVH, with a higher increase in E/e' ratio (5.9±7.4 vs 1.1±2.8, p=0.001) and in left atrial diameter (4.7±5.4 mm vs 1.8±5.2 mm). Baseline characteristics All (n=61) No LVH (n=39) LVH (n=22) p Age (years) 35 [23–48] 17 [21–36] 50 [44–54] &lt;0.001 Male gender 40 (66%) 22 (56%) 18 (82%) 0.79 Arterial hypertension 10 (17%) 3 (8%) 7 (31%) 0.03 LV mass index (g/m2) 105±43 79±18 150±38 &lt;0.001 Mitral E/e' ratio 7.8±5.0 6.7±2.0 9.9±7.8 0.02 Conclusion Over a median FU of over 10 years, LV wall thickness, LV mass and LV diastolic function remained stable under ERT, providing the treatment was started, early, i.e. before development of LVH. If LVH is already present at baseline, ERT appears to be less effective, with significant progression in LV mass and significantly faster decrease in diastolic function.

Abstract 903: Rapamycin Treatment Reduces Myocardial Stiffness and Promotes Cardiomyocyte Relaxation to Restore Diastolic Function in Old Murine Hearts

Aging is associated with a decline in diastolic function and is a strong risk factor for heart failure with preserved ejection fraction (HFpEF), which has no effective treatment. We previously showed that late-life rapamycin treatment can reverse age-related cardiac dysfunction in mice. However, the mechanisms of the reversal of diastolic dysfunction have not been established. The objective of this study is to determine the mechanisms by which rapamycin reverses age-related diastolic dysfunction. To study the effects of rapamycin on myocardial stiffness, we assessed the passive length-tension relationship of demembranated trabecular muscle from young, old control and old rapamycin-treated mice. We observed a substantial increase in the slope of the length-tension curve with aging, indicating an age-related increase in myocardial stiffness. The age-related increase in myocardial stiffness was significantly reduced by rapamycin treatment, by a mechanism independent of titin isoform shift. We measured the force-calcium relationship of the demembranated trabeculae and revealed an age-related increase in Ca 2+ sensitivity, as indicated by a left-shift of the force-pCa curve, which was partially restored after rapamycin treatment (pCa50: 5.59±0.04 for young controls; 5.76±0.04 for old controls; and 5.65±0.04 for old rapamycin-treated group). To investigate the changes at myofibril level, we assessed kinetic properties of control and rapamycin-treated myofibrils following maximal (pCa 4.0) and submaximal (pCa 5.6) Ca 2+ activation. Myofibrils from rapamycin-treated mice displayed increased rate of the fast phase of relaxation (kREL, fast) compared to old control at both maximal and submaximal Ca 2+ levels, potentially due to reduced myofibril Ca 2+ sensitivity. Studies have detected age-related reductions in expression and activity of SERCA2, which is responsible for SR calcium reuptake during diastole. In this study, we showed that rapamycin increased SERCA2 expression, which may improve cardiomyocyte relaxation. In summary, our results suggest that rapamycin normalizes age-related increases in myocardial stiffness and Ca 2+ sensitivity and improves myofibril relaxation kinetics, therefore, improving diastolic function.

Left atrial strain associated with alterations in cardiac diastolic function in patients with end-stage renal disease

The purpose of this study was to investigate the correlation between left atrial (LA) strain and alterations in cardiac diastolic function in patients with end-stage renal disease. 59 patients with stage 5 chronic kidney disease(CKD5) and 30 healthy controls were enrolled in this study. Patients with CKD5 were divided into three groups, from normal to Grade II diastolic dysfunction. LA longitudinal strain was evaluated using two-dimensional speckle tracking echocardiography. The peak LA longitudinal strain values (PALS) and LA stiffness index were recorded as the main parameters. Comparing with control group, index of LA volume (LAVI, 14.57 ± 6.92 vs. 20.15 ± 6.21 vs. 30.49 ± 10.66 vs. 42.99 ± 18.77) and index of left ventricular mass (LVMI, 77.64 ± 12.60 vs. 103.83 ± 15.90 vs. 155.01 ± 36.92 vs. 178.34 ± 44.47) significantly increased in CKD5 patients, along with the decline of diastolic function (p < 0.001). An incremental reduction in PALS (51.75 ± 5.82 vs. 40.23 ± 12.72 vs. 36.37 ± 8.59 vs. 33.33 ± 9.30, p < 0.001) as well as increase in LA stiffness index (0.11 ± 0.02 vs. 0.25 ± 0.10 vs. 0.38 ± 0.21 vs. 0.61 ± 0.51, p = 0.003) in apical 4 chamber (A4C) view and global value were observed in CKD5 patients, and higher LA stiffness index were shown in patients with Grade II diastolic dysfunction. What's more, estimated glomerular filtration rate was independently correlated with PALS-A4C (B = 0.084, 95% CI 0.002-0.166, p = 0.046), and LAVI adversely correlated with PALS-A4C (B=-0.191, 95% CI -0.379 to -0.002), p = 0.047) and correlated with LA stiffness index in A4C (B = 0.011, 95% CI 0.006 -0.017, p < 0.001). In conclusion, LA longitudinal strain, combined with LAVI and LVMI, were independently associated with the decline in diastolic function in CKD5 patients, which might provide novel cardiovascular events predictors in these patients.

Sex-differences in diastolic dysfunction in hypertrophic cardiomyopathy

Background: One of the first clinically detectable alterations in heart function in hypertrophic cardiomyopathy (HCM) is a decline in diastolic function. Diastolic dysfunction is caused by changes in intrinsic properties of cardiomyocytes and/or an increase in fibrosis. We investigated if clinical and cellular parameters of diastolic function are sex-dependent in HCM.

Sex Differences at the Time of Myectomy in Hypertrophic Cardiomyopathy.

One of the first clinically detectable alterations in heart function in hypertrophic cardiomyopathy (HCM) is a decline in diastolic function. Diastolic dysfunction is caused by changes in intrinsic properties of cardiomyocytes or an increase in fibrosis. We investigated whether clinical and cellular parameters of diastolic function are different between male and female patients with HCM at the time of myectomy. Cardiac tissue from the interventricular septum of patients with HCM (27 women and 44 men) was obtained during myectomy preceded by echocardiography. At myectomy, female patients were 7 years older than male patients and showed more advanced diastolic dysfunction than men evident from significantly higher values for E/e' ratio, left ventricular filling pattern, tricuspid regurgitation velocity, and left atrial diameter indexed for body surface. Whereas most male patients (56%) showed mild (grade I) diastolic dysfunction, 50% of female patients showed grade III diastolic dysfunction. Passive tension in HCM cardiomyocytes was comparable with controls, and myofilament calcium sensitivity was higher in HCM compared with controls, but no sex differences were observed in myofilament function. In female patients with HCM, titin was more compliant, and more fibrosis was present compared with men. Differences between female and male patients with HCM remained significant after correction for age. Female patients with HCM are older at the time of myectomy and show greater impairment of diastolic function. Furthermore, left ventricular and left atrial remodeling is increased in women when corrected for body surface area. At a cellular level, HCM women showed increased compliant titin and a larger degree of interstitial fibrosis.

Rapamycin Treatment Promotes Myofibril Relaxation Kinetics and Reduces Myocardial Stiffness to Improve Diastolic Function in Old Murine Hearts

At least half of heart failure patients have normal systolic function (heart failure with preserved ejection fraction, HFpEF) and there is no current approved therapy that improves mortality in this patient population. Aging is associated with a decline in diastolic function and is a very strong risk factor for HFpEF, which is especially prevalent in aged women. We previously showed that late‐life 10‐week rapamycin treatment can reverse established cardiac aging, including a reversal of diastolic dysfunction, in old mice. Rapamycin induces mitochondrial remodeling within first 2 weeks of treatment to rejuvenate energy metabolism in old hearts, but the time course of improved diastolic function is much slower. This indicates that additional undefined mechanisms are responsible for the reversal of diastolic dysfunction induced by rapamycin. The objective of this study is to determine the mechanisms of rapamycin‐induced reversal of diastolic dysfunction in old mice.Proteomic analysis revealed that 10‐week rapamycin treatment can partially rescue the age‐related changes in abundance of proteins in actin cytoskeleton and calcium handling pathways. The effects of rapamycin on protein expression of these key pathways regulating contraction and relaxation kinetics suggest that rapamycin may promote relaxation kinetics of the aged myocardium. To determine the effects of aging and rapamycin treatment on biomechanical properties of the myocardium, we measured contractile and relaxation properties of multicellular ventricular trabeculae preparations and isolated myofibrils. Analysis of the passive length‐tension relationship of demembranated trabeculae showed a substantial increase in the slope of the length‐tension curve with aging, indicating an age‐related increase in myocardial stiffness. This age‐related increase in myocardial stiffness is significantly reduced by rapamycin treatment. Trichrome staining revealed similar myocardial collagen contents in old control and rapamycin‐treated mice, suggesting the reduced stiffness is not due to reduced fibrosis. Old myocardial tissues also exhibit increased Ca2+ sensitivity, as denoted by a left‐shift of the isometric force‐pCa curve, which is partially restored by rapamycin treatment. In particular, the Ca2+ concentration required to elicit half maximum force (pCa50) decreased from pCa 5.59±0.08 for young controls to 5.75±0.14 for old controls, and rapamycin treatment restored it to 5.65±0.14. For myofibril relaxation kinetics, myofibrils from rapamycin treated mice displayed increased rate of the fast phase of relaxation (kREL, fast) compared to old control at both maximal (pCa 4.0) and submaximal (pCa 5.6) Ca2+ levels.In summary, these results suggest that rapamycin treatment alters the kinetics of myofibril relaxation and reverses the age‐related increase in myocardial stiffness and Ca2+ sensitivity. These biomechanical changes likely contribute to the reversal of diastolic dysfunction in old murine hearts.Support or Funding InformationNIH K99 AG051735 and Glenn/AFAR Postdoctoral Fellowship for Translational Research on Aging to Y.A.C., NIH K08HL128826 to F.M‐H., and NIH R01 AG038550 to P.S.R.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

P2523Regular physical exercise to prevent age-related decline of diastolic function

P2523Regular physical exercise to prevent age-related decline of diastolic function