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

Longitudinal strain reflects the interaction of myocardial contractility to afterload in rat models of hemodynamic overload-induced heart failure

Background

Two-dimensional (2D) speckle tracking echocardiography (STE)-derived myocardial strain parameters are sensitive markers of left ventricular (LV) systolic function. Novel findings suggest that the contractile state of the myocardium, afterload and preload are major determinants of STE measurements. However, the hypothesis that longitudinal strain expresses the interaction between contractility and loading conditions rather than contractility alone in hemodynamic overload-induced heart failure (HF) has not been tested.

Purpose

This study aimed to explore the connection between longitudinal strain and contractility, afterload and preload in rat models of pressure overload (PO)- and volume overload (VO)-induced heart failure (HF).

Methods

Pressure overload (PO)-induced HF was evoked by transverse aortic constriction ([TAC], n=14). Volume overload (VO)-induced HF was established by an aortocaval fistula ([ACF], n=12). Age-matched sham operated animals served as controls. Pressure-volume analysis was carried out to compute cardiac contractility (slope of end-systolic pressure-volume relationship [ESPVR]), afterload (arterial elastance [Ea]) and ventriculo-arterial coupling ([VAC] = Ea/ESPVR). Preload was evaluated by meridional end-diastolic wall stress (σend-diastolic). STE was performed to assess global longitudinal strain (GLS).

Results

GLS was impaired in both PO-induced HF (−5.9±0.6 vs. −12.9±0.5%, TAC vs Sham, P<0.001) and VO-evoked HF (−11.7±0.7 vs. −13.5±0.4%, ACF vs Sham, P=0.048). Hemodynamic measurements indicated that the TAC group presented with maintained ESPVR, increased Ea and enhanced σend-diastolic. In contrast, the ACF group was characterized by reduced ESPVR, decreased Ea and enhanced σend-diastolic. Ordinary least squares non-linear regression revealed that GLS was predominantly determined by afterload (Ea) in the TAC model and by contractility (ESPVR) in the ACF model. In accordance, GLS showed a strong correlation with Ea in case of PO-induced HF (R= 0.848, P<0.001) and with ESPVR in case of VO-evoked HF (R=−0.526; P=0.008), respectively. Furthermore, GLS also demonstrated strong correlation with VAC in both the TAC and the ACF models. Of particular interest, a robust correlation between VAC and GLS could also be detected in the entire study population (R= 0.654, P<0.001).

Conclusion

Both afterload and contractility define GLS. Hence, under conditions when both factors become altered, GLS reflects VAC.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): NVKP_16-1-2016-0017

Characterization of myocardial sodium-glucose cotransporter 1 expression in humans with heart failure and reduced ejection fraction

Introduction

In diabetic patients, multiple cardiovascular outcome trials consistently showed the robust cardioprotective effects of the novel antidiabetic agents, sodium glucose cotransporter 2 (SGLT2) inhibitors. However, the DAPA-HF study using the SGLT2 inhibitor dapagliflozin have extended these observations onto non-diabetic patients with heart failure (HF), urging previous hypotheses regarding the cardioprotective effects of SGLT2 inhibitors to be revised. This is further complicated by the fact that SGLT2 is not expressed in the human myocardium neither under normal nor diseased states. Hence, it has been postulated that SGLT2 inhibitors might exert direct cardioprotection via non-specific inhibition of SGLT1, which is in turn highly expressed in the myocardium.

Purpose

Because literature data is scarce regarding the expression profile of myocardial SGLT1, we aimed to characterize left ventricular SGLT1 expression in humans with end-stage HF accordingly to HF aetiology and to investigate whether cardiac resynchronization therapy (CRT) affects SGLT1 expression.

Methods

From patients undergoing mitral valve replacement with otherwise no myocardial disease and preserved LV function, we collected control papillary muscles (Control, n=9). From patients with end-stage HF undergoing heart transplantation (n=72), we obtained LV anterior wall samples according to the following HF aetiology groups: hypertrophic cardiomyopathy (HCM, n=7); idiopathic dilated cardiomyopathy (DCM, n=12); ischaemic heart disease (IHD, n=14), IHD with type 2 diabetes mellitus (IHD+T2DM, n=11); and patients with CRT (CRT-DCM, n=9; CRT-IHD, n=9; CRT-IHD+T2DM, n=10). We measured LV SGLT1 expression on the gene and protein expression levels using qRT-PCR and western blotting, respectively. Echocardiography-derived LV end-diastolic diameter (LVEDD) and LV ejection fraction (LVEF) were registered prior to surgery.

Results

Compared to controls, LV SGLT1 mRNA and protein expressions were significantly upregulated in patients with DCM, IHD and IHD+T2DM (all P<0.05), but not in HCM. In these patient groups, LV SGLT1 mRNA expression showed a significant positive correlation with LVEDD (r=0.493; P<0.001) and significant negative correlation with LVEF (r=−0.477; P<0.001). On the protein expression level, CRT was associated with significant reduction in LV SGLT1 only in patients with DCM and IHD, but not in IHD+T2DM.

Conclusions

Myocardial SGLT1 is upregulated in patients with HF (except HCM), and correlated strongly with parameters (LVEDD, LVEF) related to adverse LV remodelling. CRT was associated with reduced SGLT1 expression in DCM and IHD patients, but not in those with IHD+T2DM. Our results suggest that SGLT1 is upregulated in HF and might be implicated in adverse myocardial remodelling. Accordingly, whether SGLT2 inhibitors exert direct cardioprotection in HFrEF via non-specific inhibition of SGLT1 needs to be further elucidated.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): National Research, Development and Innovation Fund of Hungary, Higher Education Institutional Excellence Programme of the Ministry of Human Capacities of Hungary

Cardiac functional consequences of stroke induced by transient middle cerebral artery occlusion in a rodent model

Background

The cardiac functional consequences of ischaemic stroke are still need to be elucidated, while according to ethical issues only non-inasive measurents were carried out in patients underwent transient cerebral ischaemia.

Purpose

We aimed at investigating left ventricular function using non-invasive and invasive modalities in a rat model of transient focal ischaemia.

Methods

Age-matched, young adult rats were used for this study. Serial left ventricular echocardiographic measurements and speckle-tracking analysis were performed in rats (n=9) underwent transient middle cerebral artery occlusion (MCAO) before, during and immediately after the induction of stroke, with a follow-up at 24, 48, 72 hours; 7, 11 and 14 days. In another experimental setting, 48 hours after stroke induction (MCAO group, n=9) we characterized left ventricular function by pressure-volume analysis, that was compared to sham-operated controls (Co group, n=9).

Results

Serial echocardiographic measurements showed impaired systolic function, that was most severe 48 hours after MCAO (global circumferential strain, GCS: −14.8±2.6% 48 hours after MCAO vs. −19.3±2.4% baseline, p<0.05). A complete recovery of systolic functional deterioration was observed after 14 days (GCS: −19.2±2.5% 14 days after MCAO vs. −19.3±2.4% baseline, n.s.). Heart weight (normalized to tibial weight) did not differ between MCAO and Co animals. Pressure-volume analysis revealed unaltered diastolic function and showed unchanged load-independent contractility index values (slope of end-systolic pressure-volume relationship, ESPVR: 2.56±0.29mmHg/μl MCAO vs. 2.55±0.59 mmHg/μl Co, n.s.) after MCAO. There was a tendency towards increased systolic pressure and deteriorated ventriculo-arterial coupling in animals underwent stroke.

Conclusions

Our data suggests that MCAO is associated with reversible impairment of systolic function during echocardiographic measurements, however without alteration of intrinsic myocardial contractility. The tendency towards increased afterload might explain the observed alterations in rats underwent stroke.

Funding Acknowledgement

Type of funding source: None

Sex-related differences in cardiac and myofilament function in rats with pressure-overload induced left ventricular hypertrophy

Introduction

Recent findings indicate that sex is a major determinant of left ventricular (LV) structure in pressure overload (PO)-induced LV myocardial hypertrophy (LVH). However, data are scare regarding sex-related differences in LV function in case of PO-evoked LVH.

Aim

Hence, in the present study we aimed at comprehensively investigating sex-related functional differences on the global cardiac level and also on the myofilament level in PO-induced LVH.

Method

Abdominal aortic banding (AB) was carried out to induce chronic PO for 6 or 12 weeks in male and female rats. Age- and sex-matched sham-operated animals served as controls. The development of LVH was followed by serial echocardiography. The extent of cardiomyocyte hypertrophy and myocardial fibrosis were evaluated by histology. Cardiac function was assessed by pressure-volume analysis. Force measurement was carried out in permeabilized cardiomyocytes to compute myofilament function.

Results

At week 6, robust myocardial hypertrophy, concentric LV geometry and moderate interstitial fibrosis were detected in both male and female AB rats. This early stage of PO-induced LVH was associated with increased LV contractility (slope of end-systolic pressure-volume relationship [ESPVR, mmHg/μl]: 3.09±0.18 Male-AB-wk6 vs. 1.79±0.22 Male-Sham-wk6 P<0.05; 3.68±0.77 Female-AB-wk6 vs. 1.87±0.21 Female-Sham-wk6 P<0.05) and enhanced myofilament Ca2+ sensitivity in both sexes (pCa50: 5.86±0.01 Male-AB-wk6 vs. 5.73±0.02 Male-Sham-wk6 P<0.05; 5.94±0.03 Female-AB-wk6 vs. 5.73±0.01 Female-Sham-wk6 P<0.05). At week 6, the augmented LV contractility effectively counterbalanced the increased afterload in both male and female AB groups. Hence, ventricular-arterial coupling (VAC) was maintained and LV systolic function was preserved in the AB groups in both sexes. In contrast, at week 12, marked sex differences could be observed. At this later stage, LVH was characterized by eccentric remodeling and intensified collagen accumulation in male AB rats. The initial LV contractility augmentation (slope of ESPVR, mmHg/μl: 1.74±0.13 Male-AB-wk12 vs. 1.31±0.17 Male-Sham-wk12 n.s.) as well as the enhanced myofilament Ca2+ sensitivity (pCa50: 5.78±0.02 Male-AB-wk12 vs. 5.75±0.01 Male-Sham-wk12 n.s.) diminished, leading to impaired VAC and reduced LV systolic function. On the contrary, in female AB rats, cardiac contractility (ESPVR, mmHg/ μl: 3.97±0.50 Female-AB-wk12 vs. 2.08±0.17 Female-Sham-wk12 P<0.05) and myofilament Ca2+ sensitivity (pCa50:5.85±0.02 Female-AB-wk12 vs. 5.78±0.01 Female-Sham-wk12 P<0.05) remained increased, resulting in adequate VAC and preserved LV systolic function at late-stage of PO-induced LVH as well.

Conclusion

The initially augmented LV contractility and enhanced myofilament Ca2+ sensitivity declines in male but not in female AB rats at later time points. Hence, characteristically different alterations occur in LV systolic function between the two sexes in late-stage of PO-evoked LVH.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): NVKP_16-1-2016-0017.

Evaluation of cardiac titin expression after long-term exercise in a rat model

Introduction

The main role of the giant elastic protein titin is to provide passive stiffness to striated (i.e. cardiac and skeletal) muscles. The adult cardiac muscle contains two titin isoforms: the more compliant N2BA and the stiffer N2B isoforms. Titin reduces passive stiffness in cardiac muscle by increased expression of the more compliant N2BA isoform (elevated N2BA:N2B ratio). Moreover, decreased passive stiffness is associated with increased exercise tolerance. Long-term exercise induces physiological adaptation of the heart, termed athlete's heart. Currently, there is limited data of titin's role in the athlete's heart.

Aims

Our aim is to evaluate exercise-induced morphological and functional changes of the heart. Furthermore, to determine the N2BA:N2B ratio in the rat model of athlete's heart.

Methods

Rats were divided into exercised (n=12) and control (n=12) groups. Athlete's heart was induced by a 12-week-long swim training (200min/day). The control group swam 5 min/day. Following the training period cardiac changes were assessed by echocardiography. In vivo cardiac function was examined by left ventricular (LV) pressure-volume (P-V) analysis. Titin isoform expressions were detected by sodium-dodecyl-sulfate (SDS)-agarose gel electrophoresis.

Results

Echocardiography and post-mortem measured cardiomyocyte diameters confirmed athlete's heart and LV hypertrophy in exercised rats. P-V analysis showed improved contractility, active relaxation and mechanoenergetics in the exercised group. The N2BA:N2B titin ratio was significantly increased in exercised rats compared to controls (0.28 vs. 0.21, p<0.05).

Conclusions

Our results confirm the morphological and functional changes of the athlete's heart. The increased ratio of N2BA:N2B titin corresponds to a more compliant heart in the exercised rats.

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): National Research, Development and Innovation Office of Hungary (K 120277) and the ÚNKP-19-3-I New National Excellence Program of The Ministry For Innovation and Technology.

Effect of cardiac resynchronization therapy on left ventricular fibrosis-related mRNA expression profile in patients with end-stage heart failure

Background

When indicated, cardiac resynchronization therapy (biventricular pacing, CRT) decreases mortality in patients with heart failure (HF) and reduced ejection fraction, especially in those with non-ischemic cardiomyopathy. This is reflected by relatively rapid improvement of left ventricular (LV) end-diastolic diameter (LVEDD) and LV ejection fraction (LVEF) indicating reverse remodelling. These LV structural and functional improvements are accompanied by characteristic changes in LV gene expression profile. However, whether beneficial gene expression alterations related to biventricular pacing are sustained independently of structural and functional reverse remodelling is unclear.

Purpose

We aimed to compare LV fibrosis-related mRNA expression profile in end-stage HF patients with idiopathic dilated cardiomyopathy (DCM) who were not on CRT versus to those on CRT.

Methods

Left ventricular myocardial samples were harvested from end-stage HF patients undergoing heart transplantation (HTX). Inclusion criteria were negative family history of DCM, negative coronarography (i.e. non-ischemic), no relevant comorbidity (e.g. diabetes, hypertension) and no history of myocarditis. Accordingly, the following patient groups were included: 1.) DCM (n=12, 17% female, mean age [±standard deviation] 46.8±11.8 years) without CRT and 2.) CRT-DCM (n=12, 42% female, mean age 47.8±12.3 years) which comprised DCM patients on active CRT for mean 3.2±2.4 years until HTX. LV RNA was extracted and subjected to a commercially available mRNA expression panel interrogating 760 genes related to the development and regulation of fibrosis. Normalization to 10 housekeeping genes and batch corrections were conducted as per protocol. LV mRNA expression of atrial-natriuretic peptide (ANP) was quantified using qRT-PCR.

Results

Markers of reverse remodelling including LVEDD (73.4±8.3 mm vs 75.4±9.9 mm), LVEF (21.9±3.7% vs 18.5±6.8%) and LV ANP mRNA expression (arbitrary units: 1.05±1.80 vs 1.04±0.88) were comparable between DCM and CRT-DCM patients (all P>0.05), respectively. High-throughput mRNA expression screening revealed significant (all P<0.001) downregulation of 3 genes proven to be implicated in adverse LV remodelling: alpha catalytic subunit of protein phosphatase 2 (PPP2CA), interleukin 20 receptor subunit beta (IL20RB) and lipoprotein lipase (LPL). According to pathway analysis using directed significance scores, CRT was associated with collective upregulation of genes modifying complement activation (SERPING1, C1S, CFH) and collective downregulation of genes promoting cell proliferation (PPP2CA, ANAPC7, HSP90AA1, CSNK2B).

Conclusions

Independently of structural and functional reverse remodelling, CRT might be associated with slightly favourable LV expression profile of genes related to the regulation and development of fibrosis. This suggests that biventricular pacing might be beneficial on the molecular level beyond improvement of LV structure and function.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): National Research, Development and Innovation Fund of Hungary, Higher Education Institutional Excellence Programme of the Ministry of Human Capacities of Hungary

Age-Related Changes in Serum Guanidinoacetic Acid in Women

Guanidinoacetic acid (GAA) is a fundamental intermediate in cellular bioenergetics, with circulating levels of GAA often reflects disturbances in its conversion due to many intrinsic and extrinsic factors, including gender or age. Here, we evaluated serum GAA in 172 healthy women aged 18 to 65 years, with age found to significantly predict serum GAA concentrations (r=0.29; P=0.03). This perhaps nominates serum GAA as a novel gender-specific proxy of impaired bioenergetics with aging.

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

Examination of the interaction of different lighting conditions and chronic mild stress in animal model

We examined the effects of different shift work schedules and chronic mild stress (CMS) on mood using animal model. The most common international shift work schedules in nursing were applied by three groups of Wistar-rats and a control group with normal light-dark cycle. One subgroup from each group was subjected to CMS. Levels of anxiety and emotional life were evaluated in light-dark box. Differences between the groups according to independent and dependent variables were examined with one- and two-way analysis of variance, with a significance level defined at p < 0.05. Interaction of lighting regimen and CMS was proved to be significant according to time spent in the light compartment and the average number of changes between the light and dark compartments. Results of our examination confirm that the changes of lighting conditions evocate anxiety more prominently than CMS. No significant differences were found between the results of the low rotating group and the control group, supposing that this schedule is the least harmful to health. Our results on the association between the use of lighting regimens and the level of CMS provide evidence that the fast rotating shift work schedule puts the heaviest load on the organism of animals.

Ampullary cancer ESPAC-3 (v2) trial: A multicenter, international, open-label, randomized controlled phase III trial of adjuvant chemotherapy versus observation in patients with adenocarcinoma of the ampulla of vater

LBA4006

Background: The effect of adjuvant treatment on overall survival (OS) of resected ampullary adenocarcinoma is not known. The aim was to compare the survival effect of adjuvant chemotherapy compared to observation (OBS) after resection and within the chemotherapy group to compare 5-fluorouracil/folinic acid (5-FU/FA) against gemcitabine (GEM). Methods: Patients were stratified by R0/R1 margins, randomised into three arms: (1) 5-FU/FA (FA, 20 mg/m2 iv bolus then 5-FU, 425 mg/m2, iv bolus, 1-5d every 28 days); (2) GEM (100mg/m2 iv infusion 1d, 8d and 15d every 4 weeks); (3) observation. The primary outcome measure was OS of chemotherapy versus no chemotherapy. 300 patients (200 chemotherapy and 100 observation) would provide 80% power to detect a 15% 5y survival difference, p<0.05. Results: 304 patients were randomised (July 2000 to April 2008), 199 to chemotherapy (101 5FU, 98 GEM) and 105 to observation. Median (range) age was 62 (35 – 81) years; 187 (61.5%) were men. Median (IQR) maximum tumour diameter was 20.0 (15.0 – 28.0) mm, 186 (63%) were moderately differentiated tumours, 174 (57%) had involved lymph nodes and 276 (91%) were R0 resections. Independent prognostic factors were tumour diameter and grade, lymph node status and R0/R1 status. Median (95% CI) OS for chemotherapy [57.1 (41.7 – 73.8) months] versus no chemotherapy [43.0 (27.6 - ) months] gave an HR (95% CI) of 0.85 (0.61 – 1.18), p=0.323. For R0 patients median (95% CI) OS for chemotherapy [58.4 (45.4 – 84.0) months] versus no chemotherapy [45.1 (26.7 - ) months] gave an HR (95% CI) of 0.78 (0.55 – 1.11), p=0.173. Cox proportional hazards modelling for all 304 patients p=0.161 and for 276 R0 patients p=0.057. Conclusions: This is the only large adjuvant trial ever conducted for ampullary adenocarcinoma. The results suggest a benefit for adjuvant monochemotherapy in patients with clear resection margins.

Stress, geomagnetic disturbance, infradian and circadian sampling for circulating corticosterone and models of human depression?

While certain circadian hormonal changes are prominent, their predictable assessment requires a standardization of conditions of sampling. The 24-hour rhythm in circulating corticosterone of rodents, known since the 1950s, was studied as a presumed proxy for stress on 108 rats divided into 9 groups of 6 male and 9 groups of 6 female animals sampled every 4 hours for 24 hours. In a first stress study, the "no-rhythm" (zero-amplitude) assumption failed to be rejected at the 5% probability level in the two control groups and in 16 out of the 18 groups considered. A circadian rhythm could be detected with statistical significance, however, in three separate follow-up studies in the same laboratory, each on 168 rats kept on two antiphasic lighting regimens, with 4-hourly sampling for 7 or 14 days. In the first stress study, pooling of certain groups helped the detection and assessment of the circadian corticosterone rhythm. Without extrapolating to hormones other than corticosterone, which may shift more slowly or adjust differently and in response to different synchronizers, the three follow-up studies yielded uncertainty measures (95% confidence intervals) for the point estimate of its circadian period, of possible use in any future study as a reference standard. The happenstance of a magnetic disturbance at the start of two follow-up studies was associated with the detection of a circasemiseptan component, raising the question whether a geomagnetic disturbance could be considered as a "load". Far beyond the limitations of sample size, the methodological requirements for standardization in the experimental laboratory concerning designs of studies are considered in the context of models of depression. Lessons from nature's unforeseen geomagnetic contribution and from human studies are noted, all to support the advocacy, in the study of loads, of sampling schedules covering more than 24 hours.

THE INCIDENCE OF SUDDEN CARDIAC DEATH IN AUSTRIA

The aim of the study was to assess the time structure (chronome) of sudden cardiac death (SCD) in Austria. The daily incidence of SCD (ICD-10 I46.1) in Austria was obtained for the 4-year span from Jan 2002 to Dec 2005. Data were available separately for men and women. This data series was analyzed by linear-nonlinear rhythmometry. The major feature is the detection of a cis-half-year that is validated nonlinearly, the estimated period of the cis-half-year is 0.408 year (95% CI: 0.389, 0.426). It is concluded that the chronobiological analysis of sudden cardiac death in Austria showed the variability of total incidence with the period of a cis-half-year.

Circadian and extracircadian exploration during daytime hours of circulating corticosterone and other endocrine chronomes

During 7 consecutive days, blood and several tissues were collected during daytime working hours only, three times per day at 4-h intervals from inbred Wistar rats, which had been previously standardized for 1 month in two rooms on a regimen of 12 h of light (L) alternating with 12 h of darkness (LD12:12). In one room, lights were on from 09:00 to 21:00 and in the other room, lights were on from 21:00 to 09:00 (DL12:12; reversed lighting regimen). This setup provides a convenient design to study circadian and extracircadian variations over long (e.g., 7-day) spans. Prior checking of certain circadian rhythms in animals reared in the room on reversed lighting (DL) as compared with animals in the usual (LD) regimen provided evidence that the 180 degrees phase-shift had occurred. These measurements were limited to the circadian (and not extended to infradian) variation. As marker rhythm, the core temperature of a subsample of rats was measured every 4 h around the clock (by night as well as by day) before the start of the 7-day sampling. An antiphase of the circadian rhythm in core temperature was thus demonstrated between rats in the LD vs. DL rooms. A sex difference in core temperature was also found in each room. A reversed rhythm in animals kept in DL and an antiphase between rats kept in DL vs. LD was again shown for the circulating corticosterone rhythm documented in subsamples of 8 animals of each sex sampled around the clock during the first approximately 1.5 day of the 7-day sampling. The findings were in keeping with the proposition that sampling rats at three timepoints 4 h apart during daytime from two rooms on opposite lighting regimens allows the assessment of circadian changes, the daytime samples from animals kept on the reversed lighting regimen accounting for the samples that would have to be obtained by night from animals kept in the room with the usual lighting regimen. During the 7-day-long follow-up, circadian and extracircadian spectral components were mapped for serum corticosterone, taking into account the large day-to-day variability. A third check on the synchronization of the animals to their respective lighting regimen was a comparison (and a good agreement) between studies carried out earlier on the same variables and the circadian results obtained on core temperature and serum corticosterone in this study as a whole. The present study happened to start on the day of the second extremum of a moderate double magnetic storm. The study of any associations of corticosterone with the storm is beyond our scope herein, as are the results on circulating prolactin, characterized by a greater variability and a larger sex difference than corticosterone. Sex differences and extracircadian aspects of prolactin and endothelin determined in the same samples are reported elsewhere, as are results on melatonin. Prior studies on melatonin were confirmed insofar as a circadian profile is concerned by sampling on two antiphasic lighting regimens, as also reported elsewhere. Accordingly, a circadian map for the rat will eventually be extended by the result of this study and aligned with other maps with the qualification of the unassessed contribution in this study of a magnetic storm.

Chronomics, neuroendocrine feedsidewards and the recording and consulting of nowcasts--forecasts of geomagnetics

A multi-center four-hourly sampling of many tissues for 7 days (00:00 on April 5-20:00 to April 11, 2004), on rats standardized for 1 month in two rooms on antiphasic lighting regimens happened to start on the day after the second extremum of a moderate double magnetic storm gauged by the planetary geomagnetic Kp index (which at each extremum reached 6.3 international [arbitrary] units) and by an equatorial index Dst falling to -112 and -81 nT, respectively, the latter on the first day of the sampling. Neuroendocrine chronomes (specifically circadian time structures) differed during magnetically affected and quiet days. The circadian melatonin rhythm had a lower MESOR and lower circadian amplitude and tended to advance in acrophase, while the MESOR and amplitude of the hypothalamic circadian melatonin rhythm were higher during the days with the storm. The circadian parameters of circulating corticosterone were more labile during the days including the storm than during the last three quiet days. Feedsidewards within the pineal-hypothalamic-adrenocortical network constitute a mechanism underlying physiological and probably also pathological associations of the brain and heart with magnetic storms. Investigators in many fields can gain from at least recording calendar dates in any publication so that freely available information on geomagnetic, solar and other physical environmental activity can be looked up. In planning studies and before starting, one may gain from consulting forecasts and the highly reliable nowcasts, respectively.

Influence of surgical resection and post-operative complications on survival following adjuvant treatment for pancreatic cancer in the ESPAC-1 randomized controlled trial

BACKGROUND/AIMS

The influence of type of surgery and occurrence of post-operative complications on survival following adjuvant therapy for pancreatic cancer are uncertain.

METHODS

Cox proportional hazard modelling was used to investigate the influence of type of surgery and the presence of complications on survival in conjunction with clinico-pathological variables in the 550 patients of the ESPAC-1 adjuvant randomized controlled trial.

RESULTS

Standard Kausch-Whipple (KW) was performed in 282 (54%) patients, 186 (35%) had a pylorus-preserving (PP) KW, 39 (7%) had a distal pancreatectomy and 21 (4%) had a total pancreatectomy. Post-operative complications were reported in 140 (27%) patients. PP-KW patients survived longer with a median (95% CI) survival of 19.9 (17.3, 23.1) months compared to 14.8 (13.0, 16.7) for KW patients (chi(2)(LR) = 15.1, p < 0.001). KW patients were more likely however to have R1 margins (67 (24%) vs. 29 (16%), chi(2) = 4.59, p = 0.032), poorly differentiated tumours (70 (26%) vs. 19 (10%), chi(2) = 18.65, p < 0.001) and positive lymph nodes (165 (60%) vs. 81 (44%), chi(2) = 11.32, p < 0.001). Post-operative complications did not significantly affect survival. Independent prognostic factors were tumour grade, nodal status and tumour size but not type of surgery or post-operative complications. There was a survival benefit for chemotherapy irrespective of the type of surgery or post-operative complications.

CONCLUSIONS

The KW and PP-KW procedures did not significantly influence the hazard of death in the presence of tumour staging, demonstrating that ESPAC-1 surgeons showed good judgement in their choice of operation. Post-operative complications did not adversely affect the survival benefit from adjuvant chemotherapy.

Chronomics reveal and quantify circadian rhythmic melatonin in duodenum of rats

A circadian rhythm is documented in duodenal melatonin in rats, peaking 16.8 hours after light onset. This component is more readily detected after log10-transformation of the data. It differs between male and female rats, females having a larger circadian amplitude and an earlier acrophase. The circadian rhythm in duodenal melatonin is also found to lead that of pineal melatonin. The results are qualified by the presence at the start of mapping of the second extremum of a double magnetic storm.

Chronomics: circadian lead of extrapineal vs. pineal melatonin rhythms with an infradian hypothalamic exploration

A circadian rhythm is documented for plasma, pineal, and hypothalamic melatonin of male and female rats kept on staggered lighting regimens. Log[_10]-transformation of the data usually normalizes, when need be, the distribution of residuals from the 24-hour cosine curve fits. A tentative circadian acrophase chart is presented that shows a lead in circadian acrophase of duodenal over pineal melatonin. The use of antiphasic lighting regimens facilitates circadian studies that can be carried out for several days, thereby allowing the assessment of infradian components such as a circasemiseptan variation in hypothalamic melatonin documented herein. The results are qualified by the presence of a second extremum of a double magnetic storm at the start of mapping.

Quantitative reduction of methyl tetrazolium by fresh vein homograft biopsies in vitro is an index of viability

OBJECTIVE

The color density of the methyl tetrazolium (MTT) test is proportional to mitochondrial enzyme activity thus reflecting cellular viability. The aim was to evaluate the MTT test as a viability assay for vein homograft studies.

MATERIALS AND METHODS

Fresh intact vein samples were harvested during multi-organ procurement. The reliability of the MTT assay was tested by a fluorescent dye combination (1 microg/ml propidium iodide PI and 4 microM/ml SYTO-16 stains). The enzyme kinetics of the reaction was also investigated. The optimal reagent concentration, biopsy size and incubation period were established.

RESULTS

There was a linear relationship between the vein homograft's weight and the pigment production activity. A nonspecific reaction (8.6%) was observed in negative controls. The MTT cleavage up to 0.1% (w/v) follows the Michaelis kinetics. The Michaelis constant (2,805 +/- 130 microM), the maximal velocity (196 +/- 2.2 x 10(-5 )microM s(-1)) and the velocity constant (6.98 +/- 0.2 x 10(-7) s(-1)) was calculated. The viability assessed by fluorescent dyes simultaneously visualized the live/dead cell ratio, which can be calculated by image analysis software.

CONCLUSION

The use of MTT in colorimetric assays offers high sensitivity. The assay is simple, inexpensive, and reproducible in vein homograft studies.

Preservation of Vein Allograft Viability during Long-Term Storage

BACKGROUND

The aim of this study was to compare the vein allograft viability following cryopreservation with that remaining after prolonged refrigerated storage.

MATERIALS AND METHODS

Great saphenous vein biopsies had been cryopreserved, and the samples were divided into two matched groups and stored in tissue culture medium for 42 days at +4 degrees C, either with or without regular medium replacement. Each vein allograft was biopsied and assayed for viability every third day by the methyltetrazolium reduction assay. Viability indexes of vein allografts harvested from brain-dead multi-organ donors and from cadavers whose warm ischemic periods were maximally 24 h were also compared.

RESULTS

Vein allografts stored for 42 days at +4 degrees C showed a similar viability (58.9 +/- 1.2%) to that of cryopreserved veins (59.7 +/- 2.3%). This was true even when cryopreserved and thawed allografts were subjected to 3 days of post-thaw incubation under presumably favorable conditions (58.7 +/- 1.6%). There was no viability index difference between the samples with medium replaced and not replaced and the specimens harvested from two different donor groups.

CONCLUSIONS

Long-term storage of vein allografts at +4 degrees C is a valuable option for regular banking practice. Sufficient amounts can be procured from cadavers similar to tissue donors.