Proteomic analysis of exercise-induced hypertrophy reveals sex-related mitochondrial differences mediated by AMPK

Background

Regular physical activity results in characteristic structural and functional changes in the heart, which are collectively referred to as the athlete's heart. However, the extent of exercise-induced left ventricular (LV) hypertrophy and functional changes show significant differences between men and women, the molecular background of which is not fully elucidated.

Objective

The aim of this study was to provide a proteomic characterization of long-term, intense exercise-induced LV myocardial hypertrophy in a rat model, with a focus on sex-related differences.

Methods

Our rats were divided into trained (FEx) and control female (FCo) as well as trained (MEx) and control male (MCo) groups. In the trained groups, athlete's heart was induced by a 12-week swimming protocol. Myocardial hypertrophy was confirmed by echocardiography and functional adaptation by pressure-volume analysis. Proteomic measurements based on liquid chromatograph-coupled mass spectrometry were performed on proteins isolated from our LV myocardial samples.

Results

Echocardiography and post-mortem myocardial mass showed significant LV hypertrophy in both sexes, which was more pronounced in female animals (tibial length normalized LV muscle mass: + 17.4% MEx vs. MCo, + 31.0% FEx vs. FCo). LV contractility increased to the same extent in both sexes. Relative expression of 3074 proteins were determined by proteomics. There was a significant change in expression of 229 proteins in males and 599 in females compared to the level of same-sex controls. Based on our gene ontological analysis, physiological LV remodeling in females is characterized by increased expression of proteins in mitochondrial function (cellular respiration and fatty acid oxidation) and biogenesis, whereas in males, proteins that bind to the actin cytoskeleton is primarily increased. Further investigation revealed that the quantity of AMP-activated protein kinase (AMPK) and sirtuin 3 (SIRT3) was increased only in female animals.

Conclusions

Our data suggests that physiological LV hypertrophy resulting from regular, balanced exercise is associated with sex-specific changes in the myocardial proteome. The main differences might be associated with different regulation of mitochondrial function and biogenesis, related to AMPK pathway. Our results contribute to the understanding of the development of physiological myocardial hypertrophy.

Funding Acknowledgement

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Bolyai János Research Scholarship (BO/00837/21) to OANational Research, Development and Innovation Office (NKFIH) K135076 to B.M.

Pressure overload and volume overload-induced chronic heart failure are associated with characteristic left ventricular myocardial proteomic alterations

Introduction

Hemodynamic overload induces pathological remodeling of the left ventricle (LV) and eventually heart failure (HF). The two types of chronic hemodynamic stress, namely pressure overload (PO) and volume overload (VO) evoke characteristically different functional and structural alterations in the myocardium. Nevertheless, whether PO- and VO-induced HF are also associated with distinct LV proteomic alterations has not been investigated yet.

Aim

Hence, we thought to perform a proteomic analysis on LV myocardial samples from rat models of PO- and VO-induced HF.

Methods

PO–induced HF was evoked by transverse aortic constriction (TAC). VO–induced HF was established by creating an aortocaval fistula (ACF). Age-matched sham-operated animals served as controls for TAC (ShamT) and ACF (ShamA), respectively. Pressure-volume (P-V) analysis, echocardiography, histology and quantitative real-time PCR were carried out to provide a detailed characterization of the two HF models. Peptides obtained via the digestion of myocardial proteins with trypsin and LysC were labeled with isobaric tags (TMT16) and measured with LC-MS/MS in a bottom-up explorative proteomic approach. Differential expression and gene ontology enrichment analysis (GO:BP) was carried out on summarized protein reporter ion intensities.

Results

In both the TAC and ACF groups, presence of typical signs and symptoms of HF (dyspnea at rest, fatigue, ascites) increased lung-to-tibial length ratio and elevated LV natriuretic peptide mRNA expression levels confirmed the development of advanced HF. Furthermore, the TAC model was associated with massive wall thickening, concentric LV hypertrophy (LVH), marked interstitial fibrosis and substantially impaired active relaxation and passive filling (slope of end-diastolic P-V relationship: 0.103±0.015 vs. 0.023±0.003mmHg/μl, TAC vs. ShamT, P<0.001). In contrast, the ACF model was predominantly characterized by LV dilatation, eccentric LVH, moderate fibrosis and severely reduced LV contractility (slope of end-systolic P-V relationship: 0.5±0.1 vs. 2.3±0.3mmHg/μl, ACF vs. ShamA, P<0.001). Proteomic analysis revealed that out of the 4691 identified and quantified proteins, 1404 and 913 have shown upregulation, while 1359 and 886 downregulation in the TAC and ACF groups respectively compared to their corresponding sham groups. GO:BP analysis has indicated that the downregulation of mitochondrion organization, ATP metabolic processes and oxidative phosphorylation and the upregulation of actin cytoskeleton organization were the most profound alterations in the TAC model. In contrast, the ACF model was associated with robust downregulation of fatty acid oxidation and upregulation of endocytosis, defense and immune response on the proteomic level.

Conclusions

PO and VO-induced advanced HF are not only associated with characteristically different functional and structural remodeling but also with distinct LV proteomic alterations.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): National Research, Development and Innovation Office (NKFIH) of Hungary

Pharmacological selectivity of SGLT2 inhibitors and cardiovascular outcomes in patients with type 2 diabetes: a meta-analysis

Background

Sodium-glucose cotransporter 2 (SGLT2) inhibitors reduce major adverse cardiovascular events (MACE) in patients with type 2 diabetes mellitus. However, SGLT2 inhibitors show great variance in pharmacological selectivity to SGLT2 over SGLT1. Reduced functional capacity of SGLT1 is associated with lower risk of heart failure development and mortality in humans. Yet, the clinical relevance of additional pharmacological SGLT1 inhibition is unclear.

Purpose

To assess whether additional pharmacological SGLT1 blockade adds further benefits to SGLT2 inhibition.

Methods

In this preregistered meta-analysis, we included randomized placebo-controlled cardiovascular outcome trials (CVOTs) of SGLT2 inhibitors assessing MACE (composite of cardiovascular death, nonfatal myocardial infarction, and nonfatal stroke) in patients with type 2 diabetes. Hazard ratios (HRs) and 95% confidence intervals (CIs) of prespecified clinical endpoints were pooled using a random-effects model. Interactions were assessed according to low versus high pharmacological SGLT2 selectivity of the given medication. Mixed-effects meta-regression analysis was performed to quantify correlation between pharmacological SGLT2:SGLT1 selectivity ratio and clinical outcomes.

Results

A total of 6 independent CVOTs comprising 57553 type 2 diabetic patients (mean age 64.6±7.9 years; 36769 [63.9%] men) were included. Overall, SGLT2 inhibitors significantly reduced risk of adverse cardiovascular and renal outcomes, but had no significant impact on the risk of fatal and nonfatal stroke compared with placebo (HR, 0.92; 95% CI, 0.77–1.10; p=0.36; I2=63%). Agents with clinically relevant SGLT1 inhibitory effect (sotagliflozin, canagliflozin) significantly reduced the risk of stroke (HR, 0.78; 95% CI, 0.64–0.94) compared with placebo, whereas those with high SGLT2 selectivity did not (HR, 1.06; 95% CI, 0.92–1.22), yielding a significant interaction (p=0.018). The difference was also significant in patients with estimated glomerular filtration rate (eGFR) lower than 60 mL/min/1.73 m2 (p=0.047). Meta-regression indicated that lower SGLT2:SGLT1 pharmacological selectivity ratio was associated with lower risk of stroke (pseudo-R2=78%; p=0.011), which was evident even after adjusting for baseline eGFR values (p=0.047). Pharmacological selectivity of SGLT2 inhibitors had no significant impact on any other assessed clinical outcomes, including hospitalization for heart failure and all-cause death.

Conclusion

These hypothesis-generating results indicate that targeting SGLT1 in addition to SGLT2 inhibition might constitute a new avenue for stroke risk reduction in patients with type 2 diabetes. Further confirmatory studies are needed.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): This project was supported by grants from the National Research, Development and Innovation Office (NKFIH) of Hungary (K134939 to T.R.), and by the New National Excellence Program of the Ministry of Human Capacities of Hungary (ÚNKP-21-3-II-SE-45 to A.A.S.).

Sex-related proteomic differences of the athlete's heart

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Bolyai János Research Scholarship - BO/00837/21 to O.A., National Research, Development and Innovation Office (NKFIH) of Hungary - K135076 to B.M.

Introduction

Regular physical activity results in characteristic structural and functional changes in the heart, which are collectively referred to as the athlete’s heart. However, the extent of exercise-induced left ventricular (LV) hypertrophy and functional changes show significant differences between men and women, the molecular background of which is not fully elucidated.

Purpose

The aim of this study was to provide a proteomic characterization of long-term, intense exercise-induced LV myocardial hypertrophy in a rat model, with a focus on sex-related differences.

Methods

Our rats were divided into trained (FEx) and control female (FCo) as well as trained (MEx) and control male (MCo) groups. In the trained groups, athlete’s heart was induced by a 12-week swimming protocol. Myocardial hypertrophy was confirmed by echocardiography and functional adaptation by pressure-volume analysis. Proteomic measurements based on liquid chromatograph-coupled mass spectrometry were performed on proteins isolated from our LV myocardial samples.

Results

Echocardiography and post-mortem myocardial mass showed significant LV hypertrophy in both sexes, which was more pronounced in female animals (tibial length normalized LV muscle mass: + 17.4% MEx vs. MCo, + 31.0% FEx vs. FCo). LV contractility increased to the same extent in both sexes. Relative expression of 3074 proteins were determined by proteomics. There was a significant change in expression of 229 proteins in males and 599 in females compared to the level of same-sex controls. Based on our gene ontological analysis, physiological LV remodeling in females is characterized by increased expression of proteins in cellular respiration and fatty acid oxidation, whereas in males, proteins that bind to the actin cytoskeleton is primarily increased.

Conclusions

Our data suggests that physiological LV hypertrophy resulting from regular, balanced exercise is associated with sex-specific changes in the myocardial proteome. Our results contribute to the understanding of the development of physiological myocardial hypertrophy.

Exercise-induced right ventricular alterations in a rodent model of athletes heart

Funding Acknowledgements

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): János Bolyai Research Scholarship of the Hungarian Academy of Sciences (BO/00837/21) to AO

National Research, Development and Innovation Office (NKFIH) of Hungary (K120277 and K135076 to BM)

Background

Intense sports activity leads to the adaptation of cardiac structure and function, the so-called athlete’s heart. Research over the last years has focused on exercise-induced adaptation of the right ventricle (RV), because the disproportionate load on the RV - when compared with left ventricle - might lead to pathological consequences, such as interstital fibrosis or chamber dilation.

Purpose

We aimed at investigating right ventricular alterations induced by regular aerobic exercise training in a rat model of athlete's heart.

Methods

Young, adult rats were divided into control (Co) and exercised (Ex) groups. Trained rats swam 200 min/day for 12 weeks. In vivo electrophysiological study and in vitro force measurements on isolated permeabilized cardiomyocytes were carried out to investigate electrical and functional alterations, respectively. Molecular biological (qRT-PCR, Western-blot) and histological investigations were applied to reveal underlying mechanisms.

Results

Exercise training was associated with increased RV cardiomyocyte width (12.5±0.1µm Co vs. 13.8±0.2µm Ex, p<0.05) and corresponding hyperphosphorylation of protein kinase B (Akt). RV myofilaments from exercised animals showed increased maximal force development and improved calcium sensitivity. Sarcomere protein investigations revealed marked overall and site-specific hypophosphorylation of troponin I.  We found prolonged QT interval and right ventricular effective refracter period (RVERP: 44.0±1.6ms Co vs. 52.8±2.1ms Ex, p<0.05) along with decreased gene expression of potassium channels. Picrosirius staining did not reveal fibrosis, that was underlied by unchanged protein expression of connective tissue growth factor (CTGF) and gene expression of profibrotic markers. Gene expression of apoptotic markers and fetal gene program did not differ between the groups.

Conclusions

According to our data, regular swim training induced RV hypertrophy, that was associated with functional improvement adn hypophosphorilation of troponin I. Prolonged repolarization without pathological alterations in RV myocardial tissue suggest physiological remodeling after balanced training.

Left ventricular SGLT1 expression is upregulated in heart failure in humans and rat model

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): National Research, Development and Innovation Fund of Hungary;

Ministry of Human Capacities of Hungary

Introduction

Myocardial sodium-glucose cotransporter 1 (SGLT1) has been shown to contribute to cardiac pathological processes, whereas humans with functionally limited SGLT1 are at lower risk of developing heart failure (HF). The novel HF medications, SGLT2 inhibitors, non-selectively inhibit SGLT1 to different extent, therefore, characterization of its expression in disease conditions is relevant.

Purpose

To investigate left ventricular (LV) SGLT1 expression in humans with end-stage HF, and in a rat model of HF.

Methods

Myocardial LV samples were harvested from control subjects (Controls, n=9) undergoing valve surgery, and from patients with end-stage dilated cardiomyopathy (DCM, n=12) undergoing heart transplantation. The rat model of aorto-caval fistula (ACF, n=12) was used to induce HF with predominant LV dilation in rats during a course of 24 weeks; sham-operated animals served as controls (Sham-A, n=12). Echocardiography was used to assess LV structure and function prior to surgery in humans, as well as in rats at the end of the follow-up period. Western blotting was performed to characterize LV SGLT1 protein expression and to investigate the activity of the master regulators AMPK and ERK1/2. The extent of LV nitro-oxidative stress was quantified by immunohistochemistry (3-nitrotyrosine) in rats with HF.

Results

Both humans with DCM and rats with ACF-induced HF presented with severely dilated LVs compared to respective controls, whereas LV SGLT1 protein expression was significantly upregulated similarly by ~1.7-fold in both cases (both P<0.01). These increases in SGLT1 expressions were accompanied by significant reductions in ERK1/2 activating phosphorylation (both P<0.05), whereas AMPK activity was unaffected. In rats with HF, LV SGLT1 expression correlated significantly with the extent of myocardial nitro-oxidative stress (r=0.762, P=0.037).

Conclusions

LV SGLT1 expression is upregulated in HF in both humans and small animals, and ERK1/2 shows a concomitantly reduced activity. LV SGLT1 expression correlates with the extent of nitro-oxidative stress, suggesting a possible pathological role in HF. Whether SGLT2 inhibitors exert direct cardiac actions via inhibition of myocardial SGLT1 needs to be elucidated.

The development of systolic heart failure in case of pressure overload-induced left ventricular myocardial hypertrophy is associated with a unique microRNA expression profile in a rat model

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): New National Excellence Program of the Ministry of Human Capacities

Introduction

Growing body of evidence suggests that distinct alterations in myocardial microRNA (miRNA) expression contribute to pressure overload (PO)-induced pathological cardiac remodeling. Nevertheless, it is still under intense investigation whether the changes in miRNA expression patterns are also associated with the decompensation of LV systolic function in case of PO-evoked LV hypertrophy (LVH). Hence, we aimed to characterize miRNA expression in PO-induced LVH with and without systolic heart failure (HF).

Methods

PO was evoked by abdominal aortic banding (AB) in male Sprague-Dawley rats. Age-matched, sham-operated animals served as controls. Functional and morphological alterations were assessed by echocardiography and histology. At the end of the experimental period, rats in the AB group were subcategorized based on ejection fraction [EF] into ABLVH (EF>40%) and ABHF groups (EF<40%). Global miRNA expression profiling was performed using next generation sequencing. Bioinformatics analysis was carried out to predict miRNA-target interactions. Expression of selected target genes was measured by qRT-PCR.

Results

Increased heart weight-to-tibial length, LV mass and fibrosis confirmed the development of pathological LVH in both the ABLVH and ABHF groups. Nevertheless, increased lung weight-to-tibial length, chamber dilatation and severely reduced EF was noted only in the ABHF and not in the ABLVH, when compared to the sham group. 50 miRNA showed different expression in the ABHF compared to the ABLVH group. Based on the altered gene expression profile, in silico bioinformatics analysis predicted several target genes. Among them, reduced mRNA expression level of Fmr1 (FMRP translational regulator 1), Zfpm2 (zinc finger protein, multitype 2), Wasl (WASP like actin nucleation promoting factor), Ets1 (ETS proto-oncogene 1) and Atg16l1 (Autophagy Related 16 Like 1) was confirmed in ABHF compared to ABLVH.

Conclusions

Decompensation of systolic function in PO-induced LVH is associated with unique miRNA profile leading to specific regulation of gene expression.

Left ventricular SGLT1 expression correlates with the extent of myocardial nitro-oxidative stress in rat models of heart failure

Introduction

Recently, selective sodium glucose cotransporter 2 (SGLT2) inhibitors have been shown to reduce hospitalization for heart failure (HF) in patients with HF, irrespective of type 2 diabetes mellitus (T2DM). The mechanism of action is currently unclear as SGLT2 is not expressed in the heart. Unlike selective SGLT2 inhibitors, the dual SGLT1/2 inhibitor sotagliflozin not only reduced hospitalization for HF, but also decreased the risk of myocardial infarction, suggesting cytoprotective action. Even though SGLT1 it highly expressed in the sarcolemma of cardiomyocytes, its pathophysiological role is unclear. Previous studies have postulated that SGLT1 propagates nitro-oxidative stress in cardiomyocytes through NADPH oxidases.

Purpose

We aimed to assess myocardial left ventricular (LV) SGLT1 protein expression in two rat models of chronic heart failure and assess possible downstream effectors.

Methods

We evoked chronic HF in male rats by pressure overload using transverse aortic constriction (TAC, n=7) or by volume overload using aorto-caval fistula (ACF, n=7). Respective sham operated animals (Sham-T or Sham-A, both n=7) served as controls. At the end of the protocol, LV function was assessed using echocardiography and invasive pressure-volume analysis. Myocardial protein expression analysis was performed by western blotting, whereas nitro-oxidative stress was quantified by immunohistochemical staining for 3-nitrotyrosine (3-NT).

Results

In both TAC and ACF, systolic and diastolic dysfunction was evident, whereas LV mass was significantly increased compared with respective controls. The LV protein expression of SGLT1 was significantly upregulated in both HF models (∼1.5-fold increase, both P<0.01). Whereas the phosphorylation of ERK1/2 was decreased only in ACF, AMPKα activity was significantly reduced in both types of HF. The protein expression of the Nox4 NADPH isoform was substantially upregulated in both TAC and ACF (both P<0.01). The expression of SGLT1 and Nox4 showed a strong positive correlation in the Sham-T plus TAC (r=0.855, P<0.001) and Sham-A plus ACF (r=0.798, P=0.001) cohorts, respectively. Furthermore, SGLT1 expression positively correlated with the extent of myocardial nitro-oxidative stress as assessed by 3-NT staining (Sham-T plus TAC: r=0.833, P=0.015; Sham-A plus ACF: r=0.762, P=0.037).

Conclusions

LV SGLT1 protein expression was upregulated in both pressure and volume overload-induced HF, irrespective of aetiology, and correlated significantly with Nox4 expression and with the extent of myocardial nitro-oxidative stress. These suggest that SGLT1 might play an important role in the pathophysiology of HF. Future studies should elucidate the possible link between the upregulation of SGLT1 in HF and the increase of myocardial nitro-oxidative stress, so that the salutary effects of the dual SGLT1/2 inhibitor sotagliflozin could be partially explained.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): National Research, Development and Innovation Fund of Hungary (NVKP_16-1-2016-0017)Ministry for Innovation and Technology in Hungary (2020-4.1.1.-TKP2020)National Research, Development and Innovation Office (NKFIH) of Hungary (K134939 to TR)

Exercise training induces benign right ventricular hypertrophy along with functional improvement and without pathological processes or arrhythmogenicity in a rodent model of athletes heart

Introduction

Regular sport activity leads to the adaptation of cardiac structure and function, the so-called athlete's heart. Research projects over the last years have focused on exercise-induced adaptation of the right ventricle (RV), because the disproportionate load on the RV - when compared with the left ventricle - might lead to pathological consequences, such as myocardial interstital fibrosis or chamber dilation.

Purpose

We aimed at investigating comprehensively RV alterations induced by regular aerobic exercise training in a rat model of athlete's heart.

Methods

Young, adult rats were divided into control (Co) and exercised (Ex) groups (n=12–12). Exercised rats underwent a 12-week-long swim training program. In vivo electrophysiological study and in vitro cellular force assessments on isolated cardiomyocytes were carried out to investigate electrical and functional RV alterations, respectively. Molecular biological (qRT-PCR, Western-blot) and histological investigations were applied to reveal underlying mechanisms.

Results

Exercise training was associated with increased RV cardiomyocyte diameter (12.5±0.1 μm Co vs. 13.8±0.2 μm Ex, p<0.05), that was associated with hyperphosphorylation of protein kinase B (Akt). RV cardiomyocytes from exercised animals showed improved calcium sensitivity and increased maximal force development, that was associated with hypophosphorylation of troponin I. We found increased length of repolarization as reflected by prolonged QT interval and ventricular effective refracter period (VERP: 44.0±1.6 ms Co vs. 52.8±2.1 ms Ex, p<0.05) along with decreased gene expression of potassium channels (Kcnd2, Kcnj2). We could not induce ventricular arrhythmia by programmed stimulation. Picrosirius staining did not reveal fibrosis, that was associated with unchanged protein expression of connective tissue growth factor (CTGF) and gene expression of profibrotic markers (such as TGF-β). Gene expression of apoptotic markers (Bax, Bcl-2) and fetal gene program (such as β-MHC) did not differ between groups.

Conclusions

According to our data, regular swim training induced RV hypertrophy, that was associated with functional improvement (improved calcium sensitivity and maximal force), hypophosphorylation of troponin I and prolonged repolarization without characteristic pathological alterations or arrhythmogenicity of RV myocardial tissue.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): National Research, Development and Innovation Office of Hungary

Different myocardial microRNA expression patterns are observed in pressure overload- and volume overload-induced chronic heart failure

Introduction

MicroRNAs (miRNA) are short, single-stranded non-coding RNA molecules that regulate gene expression on the post-transcriptional level. Dysregulation of distinct miRNAs has been found to contribute to the development of chronic heart failure (CHF). However, whether distinct types of CHF are associated with different miRNA expression patterns is debated.

Aim

To characterize left ventricular (LV) miRNA expression in rat models of pressure overload (PO) versus volume overload (VO)-induced CHF.

Methods

Transverse aortic constriction (TAC) was performed to evoke PO-induced CHF. Aortocaval fistula (ACF) was created to establish VO-induced CHF. Age-matched sham-operated rats served as controls for TAC (ShamT) and ACF (ShamA), respectively. Pressure-volume analysis, echocardiography, histology and quantitative real-time PCR were carried out to assess alterations of the LV. Global miRNA expression profiling was performed using Nanostring technology. Bioinformatics analysis of differentially expressed miRNAs was also carried out to predict relevant miRNA-target interactions.

Results

Reduced LV systolic function (ejection fraction: 38±5 vs. 65±2% TAC vs. ShamT, 55±3 vs. 67±3%, ACF vs. ShamA, P<0.01) as well as elevated myocardial B-type natriuretic peptide and increased β-to-α myosin heavy chain gene expression confirmed the development of pathological remodeling and CHF in both models. Nevertheless, characteristic differences could be observed in LV morphology and ultrastructure. Accordingly, the TAC model was associated with robustly increased wall thickness, concentric LV hypertrophy and marked fibrotic remodeling. On the contrary, LV dilatation, eccentric LV hypertrophy and moderate fibrosis were the main morphometric findings in the ACF model. A group of miRNA (rno-miR-130a, 132, 199a-5p, 21, 210, 27b, 326) showed similar alterations in both phenotypes of CHF. However, other miRNAs demonstrated unique (specific to TAC: rno-miR-148b-3p, 150, 199a-3p, 203, 23b, 27b, let-7e; specific to ACF: rno-miR-140, 142-3p, 17-5p, 195, 20a, 204, 214, 27a, 29b, 322, 365, 425, 450a, let-7i) LV expressional changes in distinct phenotypes of CHF. In silico bioinformatics analysis revealed that the altered miRNA expression pattern predominantly controls the cardiac neural crest cell development, the inositol-phosphate pathway and the expression of microtubules-binding proteins. In contrast, alterations in the expression of genes responsible for redox state and epithelial-mesenchymal transition were modified only in the ACF group. Despite of the different signaling cascades, expression of Arhgap12 (Rho GTPase activating protein 12) was predicted to be strongly inhibited in both CHF models.

Conclusions

PO and VO-induced CHF are associated with unique miRNA expression patterns, which drive different signaling pathways. miRNA-controlled downregulation of Arhgap12 might represent a common feature in both phenotypes of CHF.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): ÚNKP-20-4-II-SE-20/New National Excellence Program of the Ministry of Human CapacitiesNVKP_16-1–2016-0017 (“National Heart Program”) National Research, Development and Innovation Fund of Hungary

Functional and proteomic investigation of potential role of steroid hormones in regulating early cardiac recovery in a rat model of isoproterenol induced intermittent myocardial ischemia

Introduction

Women benefit from higher levels of protection from cardiovascular diseases until menopause, after which they gradually lose their privileged status. Pivotal role of sex hormones, primarily estrogens were the focus of interest in explaining this clinical observation. Estradiol (E2) was a prime target of these investigations showing promising results. Nonetheless the potential influence of other estrogens and numerous estrogen metabolites have so far been neglected.

Purpose

The aim of our study was to investigate the influence of circulating steroid hormones on early functional and proteomic changes following repeated ischemic periods in female rats by applying the highly unbiased methods of in vivo pressure-volume analysis and mass spectrometry based proteomics.

Methods

Diffuse subendocardial ischemia was induced in female (F-Isch) Wistar rats with sc. injection of isoproterenol (ISO, 85mg/kg) daily for two consecutive days, while the control group (F-Co) received an equivalent volume of sc. saline solution. 48 hours after the first injection pressure-volume analysis (P-V) was carried out to assess left ventricular function. FFPE tissue slides were scanned and analyzed digitally, while peptides from the snap frozen left ventricular myocardium were measured by liquid chromatography-tandem mass spectrometry using isobaric labeling (TMT11plex). Serum and plasma samples were taken to measure circulating steroid hormone levels with mass spectrometry.

Results

Two day induction of ischemia resulted in 17% mortality in F-Isch. ISO treatment resulted in significant myocardial tissue damage compared to controls as assessed by histology. Ischemia led to a prominent impairment of diastolic aspects (active relaxation and myocardial stiffness) of left ventricular function (Tau: 11.1±0.7 vs. 16.1±1.1 F-Co vs. F-Isch; EDPVR: 0.05±0.005 vs. 0.131±0.016 F-Co vs. F-Isch.). Unsupervised hierarchical clustering performed on P-V parameters identified two distinct subgroups of F-Isch with severe or mild functional impairment. Supervised PLS-DA analysis of P-V and hormone datasets found three estrogens that might play a role in determining functional outcomes (2-Hydroxyestrone: 2-OHE1, 4-Hydroxyestrone: 4-OHE1, 4-Methoxyestrone: 4-MeE2). PLS analysis followed by gene ontology enrichment associated E2 and 2-OHE1 concentrations with mitochondrial protein expressions, while 4-OHE1 seemed to influence the reassembly of contractile structures after ischemia.

Conclusions

Our study has highlighted 2-OHE1 and 4-OHE1 as well as E2 as potentially influential estrogens on early post-ischemic recovery both on functional and on proteomic level.

Funding Acknowledgement

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): New National Excellence Program of the Ministry of Human Capacities of Hungary (ÚNKP-20-3-I-SE-1 to BA. B.) National Research, Development and Innovation Office (NKFIH) of Hungary (K134939 to T. R.)

Pursuing the non-invasive assessment of cardiac contractility: the added value of pressure-area-strain loop analysis in volume overload-induced heart failure

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): This work was supported by the New National Excellence Programme (ÚNKP-19-3-I) of the Ministry for Innovation and Technology in Hungary, and the Artificial Intelligence Research Field Excellence Programme of the National Research, Development and Innovation Office of the Ministry of Innovation and Technology in Hungary.

Background

Global longitudinal strain (GLS) by speckle-tracking echocardiography (STE) is a sensitive parameter of left ventricular (LV) systolic function. Nevertheless, GLS is dependent on loading conditions. Through the analysis of pressure-strain loops, myocardial work was recently introduced and tested in different clinical scenarios. Myocardial work incorporates afterload, but still, it neglects changes in preload and LV geometry.

Purpose

Accordingly, our aim was to test our hypothesis that adding instantaneous LV size to myocardial work calculation can further mitigate the load-dependency of GLS, and therefore, a better correlation with intrinsic myocardial contractility can be achieved.

Methods

Volume overload-induced heart failure was established by an aortocaval fistula (ACF) in male Wistar rats (n = 12). Age-matched sham-operated animals served as controls (n = 12). STE was performed to assess GLS, which was immediately followed by invasive pressure-volume (P-V) analysis to assess LV pressure and to compute a gold-standard index of cardiac contractility (preload recruitable stroke work [PRSW]). Global myocardial work index (GMWI) was calculated from GLS and the invasively measured LV pressure. To compute GMWI indexed to LV area (GMWIA), the instantaneous power (calculated by multiplying the strain rate and the instantaneous LV pressure) was divided by the instantaneous LV area, and then it was integrated from mitral valve closure until mitral valve opening.

Results

LV ejection fraction did not differ significantly (ACF vs. controls: 59 ± 4 vs. 65 ± 9%, p = NS), whereas GLS (Figure 1A - representative animals) was slightly decreased in the ACF group (-13.2 ± 2.3 vs. -15.4 ± 1.9%, p < 0.05). In contrast, PRSW, GMWI (Figure 1B - representative animals) and GMWIA (Figure 1C - representative animals) were considerably reduced in ACF compared to controls (57 ± 13 vs. 111 ± 38mmHg, 1383 ± 382 vs. 1928 ± 281mmHg%, 11.6 ± 3.7 vs. 47.9 ± 22.8mmHg%/mm2, all p < 0.01). GLS showed moderate correlation with PRSW (r=-0.550, p < 0.01), whereas GMWI correlated more significantly, but still moderately with the invasively measured LV contractility (r = 0.681, p < 0.001). Correlation between the pressure-area-strain loop-derived GMWIA and P-V analysis-derived PRSW (Figure 1D) was found to be very strong (r = 0.924, p < 0.001).

Conclusions

In the case of LV volume overload-induced heart failure, our pressure-area-strain loop-derived metric reflected LV contractility better than GLS and even GMWI. Therefore, the incorporation of instantaneous LV size into myocardial work calculation represents a promising clinical tool to assess and monitor intrinsic myocardial function independently of loading conditions.

Abstract Figure 1

Myocardial work index better reflects contractility than longitudinal strain in rat models of pressure- and volume overload-induced heart failure

Funding Acknowledgements

Type of funding sources: None.

Speckle-tracking echocardiography (STE)-derived global longitudinal strain (GLS) is considered to be a sensitive marker of left ventricular (LV) function in a wide variety of cardiovascular diseases. Still, evidence suggests that GLS is significantly influenced by loading conditions. Myocardial work index (MWI) evaluates myocardial deformation in the context of afterload through the interpretation of strain in relation to instantaneous LV pressure. MWI may potentially overcome the limitations of mere strain calculation, and may better reflect cardiac contractility in hemodynamic overload states.

Accordingly, our aim was to examine the relationship of GLS and MWI with load-independent markers of LV contractility in rat models of pressure- and volume overload-induced heart failure.

Male Wistar rats underwent transverse aortic constriction (TAC; n = 12) to generate LV pressure overload, or aortocaval fistula (ACF; n = 12) was established to induce severe LV volume overload. In case of the control groups, sham procedures were performed (n = 12/12). Echocardiography loops were obtained to determine STE-derived GLS and global MWI. Pressure-volume analysis with transient occlusion of the inferior vena cava was carried out to calculate preload recruitable stroke work (PRSW), as a load-independent „gold-standard" parameter of LV contractility.

GLS was mildly reduced in the ACF group (-13.2 ± 2.4 vs. -15.4 ± 2.0%, p < 0.05), while it was significantly lower in TAC group compared to controls (-7.0 ± 2.8 vs. -14.5 ± 2.5%; p < 0.001). In contrast with these findings, PRSW and also MWI were significantly reduced in ACF (58 ± 14 vs. 111 ± 40 mmHg; 1328 ± 411 vs. 1934 ± 308 mmHg%, both p < 0.01), however, they were comparable between TAC and the corresponding sham group (110 ± 26 vs. 116 ± 68 mmHg; 1687 ± 275 Hgmm% vs. 1537 ± 662 Hgmm%; both p = NS). In the pooled population, GLS did not show relationship with PRSW (r=-0.23; p = 0.12), while MWI showed significant correlation with it (r = 0.70; p < 0.001).

GLS is significantly influenced by loading conditions, therefore, in case of severe pressure- or volume overload it may not be a reliable marker of LV contractility. In our rat model of pressure overload induced heart failure, contractility was maintained despite decreased GLS, while in the model of volume overload induced heart failure, GLS was maintained despite decreased contractility. MWI reflects contractility in hemodynamic overload states, therefore, it may be a more suitable marker of systolic function.

Abstract Figure. Pressure-strain loops of the groups

P4424Detailed characterization of atrial remodeling induced by exercise training in a rodent model of exercise-induced cardiac hypertrophy

Introduction

Atrial fibrillation and heart failure share common risk factors and frequently coexist as atrial fibrillation leads to impaired myocardial function. Although regular exercise training is associated with cardiovascular benefits, the increased risk of atrial arrhythmias has been observed, with differences regarding prevalence between genders. While multiple mechanisms are likely, the atrial alterations induced by long-term physical exercise still need to be elucidated.

Purpose

We aimed at investigating exercise-induced atrial remodeling in a rat model of athlete's heart and determining sex-specific differences.

Methods

Age-matched young adult rats were divided into female exercised (FEx), female control (FCo), male exercised (MEx) and male control (MCo) groups. After exercised animals completed a 12-week-long swim training protocol, echocardiography was used to describe atrial alterations. In vivo electrophysiologic investigation was performed by programmed stimulation with an octapolar catheter inserted into the right atrium and atrial gene expression analysis was carried out.

Results

Post-mortem atrial weight data revealed marked atrial hypertrophy (atrial weight to tibial length: 18.6±2.7g/cm FEx, 10.3±1.0g/cm FCo, 23.7±2.2g/cm MEx, 15.8±1.9g/cm MCo pex<0.01), while echocardiography data showed slight atrial dilatation and improved contraction in both exercised groups. Exercise training was associated with bradycardia, P-wave enlargement and prolonged right atrial effective refractory period (RAERP: 45.7±4.3ms FEx, 40.2±5.9ms, FCo, 49.8±4.2ms MEx, 43.1±4.6ms MCo pex<0.01). Sinus node recovery time (SNRT) did not differ between groups and we could not induce significant number of arrhytmias by programmed stimulation (double extrastimulation, burst pacing) in any groups. We found increased atrial gene expression of antioxidant enzymes (e.g. NADPH oxidase 2, superoxide dismutase 2) in both genders. Despite the marked atrial hypertrophy, no gene expression alteration was found regarding markers that describe pathological remodeling (atrial natriuretic factor), proinflammatoric (tumor necrosis factor-α) and profibrotic [e.g. transforming growth factor-β (TGF-β), matrix metalloproteinase-2 (MMP-2)] processes. While exercise training did not affect on the expression of profibrotic markers, female gender was associated with lower TGF-β and MMP-2 expression. We found altered expression of ion channels participating in atrial depolarization and repolarization.

Conclusions

Our data suggests that long-term exercise-induced atrial hypertrophy is not associated with harmful electrical remodeling and no inflammatory or profibrotic response was observed in the atrium of exercised rats.

Acknowledgement/Funding

NKFIH (K 120277), ÚNKP-17-4 (to A.O.), STIA-KF-17 (to A.O.)

P3454Myocardial reverse remodeling occurs to a comparable extent in male and female aortic-banded rats following pressure unloading

Background

Sex differences have been intensely investigated during the development of pressure overload (PO; e.g. aortic stenosis, arterial hypertension)-induced left ventricular (LV) myocardial hypertrophy (LVH). However, it is less clear whether sex-related differences also affect the regression of pathological LVH after pressure unloading.

Purpose

Therefore, we investigated the potential influential effect of sex on myocardial reverse remodeling in a relevant rat model of banding and debanding of the abdominal aorta.

Methods

PO of the left ventricle was induced in male (M) and female (F) rats by abdominal aortic banding (AB) for 6 or 12 weeks. Sham operated animals served as controls. Pressure unloading was evoked by removing the aortic constriction at week 6 (debanded). Serial echocardiography was performed to detect temporal alterations in LV morphology and geometry. Furthermore, distinct aspects of LV systolic and diastolic function were assessed by pressure-volume analysis. Structural changes, such as cardiomyocyte hypertrophy and interstitial fibrosis were measured on histological sections. Fetal gene expression (a molecular marker of pathological LVH) was analyzed by quantitative real-time PCR.

Results

In both male and female AB rats, PO induced the development of marked LVH as confirmed by increased LV mass, heart weight-to-tibial length ratio (HW/TL [g/cm]: 0.47±0.01 AB-M vs. 0.36±0.01 Sham-M, p<0.05; 0.36±0.02 AB-F vs. 0.26±0.01 Sham-F, p<0.05) and cardiomyocyte diameter. Similarly, reactivation of fetal gene expression (indicated by increased atrial natriuretic peptide [ANP]) and enhanced interstitial collagen accumulation was also observed in male and female AB groups as well. The extent of myocardial hypertrophy was greater among female AB animals, while fibrosis was more severe in male AB rats. In both genders, LVH was associated with prolonged ventricular relaxation (active relaxation time constant, Tau [ms]: 19.6±0.8 AB-M vs. 13.1±0.4 Sham-M, p<0.05; 15.2±1.3 AB-F vs. 12.2±0.3 Sham-F, p<0.05). However, systolic function was impaired only in males (ejection fraction, [%]: 44.4±2.3 AB-M vs. 57.5±2.1 Sham-M, p<0.05; 49.7±2.2 AB-F vs. 53.4±1.7 Sham-F, n.s.). Contrary to the sex-dependent differences during the development of LVH, removing the aortic constriction resulted in a comparable degree of reverse remodeling on the morphological (decreased LV mass, HW/TL), histological (decreased CD and interstitial fibrosis), molecular (reduced ANP expression) and functional (recovered ejection fraction and Tau) levels in both male and female rats.

Conclusion

Pressure unloading at a relatively early time point leads to myocardial reverse remodeling to a comparable degree in male and female rats.

Acknowledgement/Funding

NVKP-16-1-2016-0017; ÚNKP-18-3-I-SE-9

Isolation of Brucella abortus from a Dog and a Cat Confirms their Biological Role in Re-emergence and Dissemination of Bovine Brucellosis on Dairy Farms

Brucellosis is highly contagious bacterial zoonoses affecting a wide range of domesticated and wild animals. In this study, Brucella (B.) abortus bv 1 was identified in uterine discharge of apparently healthy bitch and queen with open pyometra housed on a cattle farm. This study highlights the role of dogs and cats as symptomatic carriers and reservoirs for Brucella. To the best of our knowledge, this study represents the first report of feline infection with B. abortus bv 1 globally. These pet animals may contaminate the environment and infect both livestock and humans. Surveillance and control programmes of brucellosis have to include eradication of the disease in dogs, cats and companion animals.