Methamphetamine-induced changes in myocardial gene transcription are sex-dependent

Background Prior work demonstrated that female rats (but not their male littermates) exposed to methamphetamine become hypersensitive to myocardial ischemic injury. Importantly, this sex-dependent effect persists following 30 days of subsequent abstinence from the drug, suggesting that it may be mediated by long term changes in gene expression that are not rapidly reversed following discontinuation of methamphetamine use. The goal of the present study was to determine whether methamphetamine induces sex-dependent changes in myocardial gene expression and whether these changes persist following subsequent abstinence from methamphetamine. Results Methamphetamine induced changes in the myocardial transcriptome were significantly greater in female hearts than male hearts both in terms of the number of genes affected and the magnitude of the changes. The largest changes in female hearts involved genes that regulate the circadian clock (Dbp, Per3, Per2, BMal1, and Npas2) which are known to impact myocardial ischemic injury. These genes were unaffected by methamphetamine in male hearts. All changes in gene expression identified at day 11 returned to baseline by day 30. Conclusions These data demonstrate that female rats are more sensitive than males to methamphetamine-induced changes in the myocardial transcriptome and that methamphetamine does not induce changes in myocardial transcription that persist long term after exposure to the drug has been discontinued.

Abstract 16641: The SGLT2 Inhibitor Ertugliflozin Induces Oxidative Phosphorylation Gene Expression and Improves Systolic Function Independent of Diabetes in Mice

Background: Inhibitors of sodium glucose linked transporter 2 (SGLT2i) improve heart failure (HF) outcomes in patients independent of diabetes. While animal studies suggest SGLT2i improve cardiac metabolism, the effect of SGLT2i on mitochondrial function in the heart is not known. Our goal was to assess the effects of SGLT2i on mitochondrial function, high energy phosphates and genes encoding mitochondrial proteins in hearts of mice with and without diet-induced diabetes. Methods & Results: Ertugliflozin (Ertu; 0.5 mg/g) was given for 4 months to mice fed a high fat, high sucrose (HFHS) diet that causes diabetic cardiomyopathy or control diet (CD). Mitochondrial function was measured in isolated cardiac mitochondria. Myocardial energetics were assessed by NMR spectroscopy simultaneously with systolic function in isolated beating hearts. Myocardial gene expression was assessed by RNA seq using gene set analysis. HFHS diet caused myocardial hypertrophy and diastolic dysfunction, mitochondrial dysfunction (decreased ATP production, increased reactive oxygen species release) and an impaired energetic response to increased work demand - all of which were prevented by Ertu. Systolic function, as reflected by the rate x pressure product (RPP), was super-normalized to a value 124% of CD hearts at high work demand. In control mice, Ertu had no effect on isolated mitochondria function or high energy phosphates, but similar to HFHS hearts, caused super-normalization of RPP to 125% of CD hearts. Myocardial gene expression analysis revealed oxidative phosphorylation (OXPHOS) as the top scoring gene set that was both down-regulated by HFHS with a normalized enrichment score (NES) of -2.08, and up-regulated by Ertu in HFHS (NES, +3.32 vs HFHS). OXPHOS was the top scoring gene set up-regulated by Ertu a) across all groups while controlling for diet (NES, +3.71) and b) in CD-fed mice only (NES, +3.34). Conclusion: The super-normalization of systolic function and induction of the OXPHOS gene set by Ertu is independent of diabetic status. Pro-metabolic remodeling of the myocardium by Ertu may support increased systolic function and contribute to the beneficial actions of Ertu in states such as HF that are associated with impaired cardiac mitochondrial function.

Evaluation of Myocardial Gene Expression Profiling for Superior Diagnosis of Idiopathic Giant-Cell Myocarditis and Clinical Feasibility in a Large Cohort of Patients with Acute Cardiac Decompensation

Aims: The diagnostic approach to idiopathic giant-cell myocarditis (IGCM) is based on identifying various patterns of inflammatory cell infiltration and multinucleated giant cells (GCs) in histologic sections taken from endomyocardial biopsies (EMBs). The sampling error for detecting focally located GCs by histopathology is high, however. The aim of this study was to demonstrate the feasibility of gene profiling as a new diagnostic method in clinical practice, namely in a large cohort of patients suffering from acute cardiac decompensation. Methods and Results: In this retrospective multicenter study, EMBs taken from n = 427 patients with clinically acute cardiac decompensation and suspected acute myocarditis were screened (mean age: 47.03 ± 15.69 years). In each patient, the EMBs were analyzed on the basis of histology, immunohistology, molecular virology, and gene-expression profiling. Out of the total of n = 427 patient samples examined, GCs could be detected in 26 cases (6.1%) by histology. An established myocardial gene profile consisting of 27 genes was revealed; this was narrowed down to a specified profile of five genes (CPT1, CCL20, CCR5, CCR6, TLR8) which serve to identify histologically proven IGCM with high specificity in 25 of the 26 patients (96.2%). Once this newly established profiling approach was applied to the remaining patient samples, an additional n = 31 patients (7.3%) could be identified as having IGCM without any histologic proof of myocardial GCs. In a subgroup analysis, patients diagnosed with IGCM using this gene profiling respond in a similar fashion to immunosuppressive therapy as patients diagnosed with IGCM by conventional histology alone. Conclusions: Myocardial gene-expression profiling is a promising new method in clinical practice, one which can predict IGCM even in the absence of any direct histologic proof of GCs in EMB sections. Gene profiling is of great clinical relevance in terms of (a) overcoming the sampling error associated with purely histologic examinations and (b) monitoring the effectiveness of therapy.

2425Evaluation of myocardial gene expression profiling for superior diagnosis of idiopathic giant cell myocarditis in a large cohort of patients with acute cardiac decompensation

Background Idiopathic giant cell myocarditis (IGCM) diagnostics is based on differential patterns of inflammatory cell infiltration, and multinucleated giant cells (GCs) in histological sections of endomyocardial biopsies (EMBs). However, the sampling error is high for the detection of focally GCs by histopathology. We report on a clinical evaluation of a recently published method for improved differential diagnosis of this frequently fatal disease by myocardial gene expression profiling. Objective This is to improve the diagnostics of IGCM by gene expression profiling, and to demonstrate the feasibility of this method in clinical practice in a large cohort of patients. Methods In this multicenter study, EMBs of n=427 patients with clinically acute cardiac decompensation and suspected acute myocarditis were screened (mean age 47.03±15.69 years). In each patient, EMBs were analyzed by histology, immunohistology, molecular virology, and gene expression profiling. Results Out of the total of n=427 patient samples examined, GCs could be detected in 26 cases (6.0%) by histology. An established myocardial gene profile – consisting of 27 genes – was revealed resulting in a specified profile of 5 genes (chemokine receptor 5 (CCR5), chemokine receptor 6 (CCR6); carnitine palmitoyltransferase I (CPT1), toll-like receptor 8 (TLR8), and chemokine (C-C motif) ligand 20 (CCL20)) which identified histologically proven IGCM with high specificity in 25 of the 26 patients (96.2%). Applying this newly established profiling on the remaining patient samples, additional n=31 (7.3%) patients were identified for IGCM without any histological proof of myocardial GCs. Conclusions Myocardial gene expression profiling is a reliable method in clinical practice to predict IGCM even without direct histological proof of GCs in EMB section. The gene profiling is of high clinical relevance to overcome the sampling error of purely histological examination, and to control the effectiveness of the therapy. The data clearly show the importance to take EMB in unexplained acute decompensation to get a diagnosis and improve the prognosis.

Role of catecholamines in the pathogenesis of diabetic cardiomyopathy

Although the sympathetic nervous system plays an important role in the regulation of cardiac function, the overactivation of the sympathetic nervous system under stressful conditions including diabetes has been shown to result in the excessive production of circulating catecholamines as well as an increase in the myocardial concentration of catecholamines. In this brief review, we provide some evidence to suggest that the oxidation products of catecholamines such as aminochrome and oxyradicals, lead to metabolic derangements, Ca2+-handling abnormalities, increase in the availability of intracellular free Ca2+, as well as activation of proteases and changes in myocardial gene expression. These alterations due to elevated levels of circulatory catecholamines are associated with oxidative stress, subcellular remodeling, and the development of cardiac dysfunction in chronic diabetes.