Recipient Pericardial Apolipoprotein Levels Might Be an Indicator of Worse Outcomes after Orthotopic Heart Transplantation

BACKGROUND

End-stage heart failure (ESHF) leads to hypoperfusion and edema formation throughout the body and is accompanied by neurohormonal and immunological alterations. Orthotopic heart transplantation (HTX) has been used as a beneficial option for ESHF. Due to the shortage of donor hearts, the ideal matching and timing of donors and recipients has become more important.

PURPOSE

In this study, our aim was to explore the relationship between the clinical outcomes of HTX and the cytokine and apolipoprotein profiles of the recipient pericardial fluid obtained at heart transplantation after opening the pericardial sac.

MATERIALS AND METHODS

The clinical data and the interleukin, adipokine, and lipoprotein levels in the pericardial fluid of twenty HTX recipients were investigated. Outcome variables included primer graft dysfunction (PGD), the need for post-transplantation mechanical cardiac support (MCS), International Society for Heart and Lung Transplantation grade ≥2R rejection, and mortality. Recipient risk scores were also investigated.

RESULTS

Leptin levels were significantly lower in patients with PGD than in those without PGD (median: 6.36 (IQR: 5.55-6.62) versus 7.54 (IQR = 6.71-10.44); p = 0.029). Higher ApoCII levels (median: 14.91 (IQR: 11.55-21.30) versus 10.31 (IQR = 10.02-13.07); p = 0.042) and ApoCIII levels (median: 60.32 (IQR: 43.00-81.66) versus 22.84 (IQR = 15.84-33.39); p = 0.005) were found in patients (n = 5) who died in the first 5 years after HTX. In patients who exhibited rejection (n = 4) in the first month after transplantation, the levels of adiponectin (median: 74.48 (IQR: 35.51-131.70) versus 29.96 (IQR: 19.86-42.28); p = 0.039), ApoCII (median: 20.11 (IQR: 13.06-23.54) versus 10.32 (IQR: 10.02-12.84); p = 0.007), and ApoCIII (median: 70.97 (IQR: 34.72-82.22) versus 26.33 (IQR: 17.18-40.17); p = 0.029) were higher than in the nonrejection group. Moreover, the pericardial thyroxine (T4) levels (median: 3.96 (IQR: 3.49-4.46) versus 4.69 (IQR: 4.23-5.77); p = 0.022) were lower in patients with rejection than in patients who did not develop rejection.

CONCLUSION

Our results indicate that apolipoproteins can facilitate the monitoring of rejection and could be a useful tool in the forecasting of early and late complications.

Effect of pharmacological selectivity of SGLT2 inhibitors on cardiovascular outcomes in patients with type 2 diabetes: a meta-analysis

Sodium-glucose cotransporter 2 (SGLT2) inhibitors reduce major adverse cardiovascular events (MACE) in type 2 diabetic (T2DM) patients. Pharmacological selectivity of these agents to SGLT2 over SGLT1 is highly variant, with unknown clinical relevance. Genetically reduced SGLT1-but not SGLT2-activity correlates with lower risk of heart failure and mortality, therefore additional non-selective SGLT1 inhibition might be beneficial. In this prespecified meta-analysis, we included 6 randomized, placebo-controlled cardiovascular outcome trials of SGLT2 inhibitors assessing MACE in 57,553 patients with T2DM. Mixed-effects meta-regression revealed that pharmacological selectivity of SGLT2 inhibitors (either as continuous or dichotomized variable) had no significant impact on most outcomes. However, lower SGLT2 selectivity correlated with significantly lower risk of stroke (pseudo-R2 = 78%; p = 0.011). Indeed, dual SGLT1/2 inhibitors significantly reduced the risk of stroke (hazard ratio [HR], 0.78; 95% confidence interval [CI], 0.64-0.94), unlike selective agents (p for interaction = 0.018). The risk of diabetic ketoacidosis and genital infections was higher in both pharmacological groups versus placebo. However, hypotension occurred more often with non-selective SGLT2 inhibitors (odds ratio [OR], 1.87; 95% CI, 1.20-2.92) compared with selective agents (p for interaction = 0.044). In conclusion, dual SGLT1/2 inhibition reduces stroke in high-risk T2DM patients but has limited additional effect on other clinical outcomes.

Pressure overload-induced systolic heart failure is associated with characteristic myocardial microRNA expression signature and post-transcriptional gene regulation in male rats

Although systolic function characteristically shows gradual impairment in pressure overload (PO)-evoked left ventricular (LV) hypertrophy (LVH), rapid progression to congestive heart failure (HF) occurs in distinct cases. The molecular mechanisms for the differences in maladaptation are unknown. Here, we examined microRNA (miRNA) expression and miRNA-driven posttranscriptional gene regulation in the two forms of PO-induced LVH (with/without systolic HF). PO was induced by aortic banding (AB) in male Sprague-Dawley rats. Sham-operated animals were controls. The majority of AB animals demonstrated concentric LVH and slightly decreased systolic function (termed as ABLVH). In contrast, in some AB rats severely reduced ejection fraction, LV dilatation and increased lung weight-to-tibial length ratio was noted (referred to as ABHF). Global LV miRNA sequencing revealed fifty differentially regulated miRNAs in ABHF compared to ABLVH. Network theoretical miRNA-target analysis predicted more than three thousand genes with miRNA-driven dysregulation between the two groups. Seventeen genes with high node strength value were selected for target validation, of which five (Fmr1, Zfpm2, Wasl, Ets1, Atg16l1) showed decreased mRNA expression in ABHF by PCR. PO-evoked systolic HF is associated with unique miRNA alterations, which negatively regulate the mRNA expression of Fmr1, Zfmp2, Wasl, Ets1 and Atg16l1.

The serum proteome of VA-ECMO patients changes over time and allows differentiation of survivors and non-survivors: an observational study

BACKGROUND

Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is applied in patients with refractory hemodynamic failure. Exposure of blood components to high shear stress and the large extracorporeal surfaces in the ECMO circuit trigger a complex inflammatory response syndrome and coagulopathy which are believed to worsen the already poor prognosis of these patients. Mass spectrometry-based proteomics allow a detailed characterization of the serum proteome as it provides the identity and concentration of large numbers of individual proteins at the same time. In this study, we aimed to characterize the serum proteome of patients receiving VA-ECMO.

METHODS

Serum samples were collected on day 1 and day 3 after initiation of VA-ECMO. Samples underwent immunoaffinity based depletion for the 14 most abundant serum proteins, in-solution digestion and PreOmics clean-up. A spectral library was built with multiple measurements of a master-mix sample using variable mass windows. Individual samples were measured in data independent acquisition (DIA) mode. Raw files were analyzed by DIA-neural network. Unique proteins were log transformed and quantile normalized. Differential expression analysis was conducted with the LIMMA-R package. ROAST was applied to generate gene ontology enrichment analyses.

RESULTS

Fourteen VA-ECMO patients and six healthy controls were recruited. Seven patients survived. Three hundred and fifty-one unique proteins were identified. One hundred and thirty-seven proteins were differentially expressed between VA-ECMO patients and controls. One hundred and forty-five proteins were differentially expressed on day 3 compared to day 1. Many of the differentially expressed proteins were involved in coagulation and the inflammatory response. The serum proteomes of survivors and non-survivors on day 3 differed from each other according to partial least-squares discriminant analysis (PLS-DA) and 48 proteins were differentially expressed. Many of these proteins have also been ascribed to processes in coagulation and inflammation (e.g., Factor IX, Protein-C, Kallikrein, SERPINA10, SEMA4B, Complement C3, Complement Factor D and MASP-1).

CONCLUSION

The serum proteome of VA-ECMO patients displays major changes compared to controls and changes from day 1 until day 3. Many changes in the serum proteome are related to inflammation and coagulation. Survivors and non-survivors can be differentiated according to their serum proteomes using PLS-DA analysis on day 3. Our results build the basis for future studies using mass-spectrometry based serum proteomics as a tool to identify novel prognostic biomarkers.

TRIAL REGISTRATION

DRKS00011106.

Proteome alterations in human autopsy tissues in relation to time after death

Protein expression is a primary area of interest for routine histological diagnostics and tissue-based research projects, but the limitations of its post-mortem applicability remain largely unclear. On the other hand, tissue specimens obtained during autopsies can provide unique insight into advanced disease states, especially in cancer research. Therefore, we aimed to identify the maximum post-mortem interval (PMI) which is still suitable for characterizing protein expression patterns, to explore organ-specific differences in protein degradation, and to investigate whether certain proteins follow specific degradation kinetics. Therefore, the proteome of human tissue samples obtained during routine autopsies of deceased patients with accurate PMI (6, 12, 18, 24, 48, 72, 96 h) and without specific diseases that significantly affect tissue preservation, from lungs, kidneys and livers, was analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). For the kidney and liver, significant protein degradation became apparent at 48 h. For the lung, the proteome composition was rather static for up to 48 h and substantial protein degradation was detected only at 72 h suggesting that degradation kinetics appear to be organ specific. More detailed analyses suggested that proteins with similar post-mortem kinetics are not primarily shared in their biological functions. The overrepresentation of protein families with analogous structural motifs in the kidney indicates that structural features may be a common factor in determining similar postmortem stability. Our study demonstrates that a longer post-mortem period may have a significant impact on proteome composition, but sampling within 24 h may be appropriate, as degradation is within acceptable limits even in organs with faster autolysis.

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 similarities and differences in the reverse and anti-remodeling effect of pressure unloading therapy in a rat model of aortic banding and debanding

BACKGROUND

Investigating the effect of sex on pressure unloading therapy in a clinical scenario is limited by several non-standardized factors. Hence, we sought to study sex-related similarities and differences under laboratory conditions.

METHODS

Pressure overload was induced in male and female rats by aortic banding (AB) for 6 and 12 weeks. Age-matched sham operated animals served as controls. Pressure unloading was performed by aortic debanding at week 6. Different aspects of myocardial remodeling were characterized by echocardiography, pressure-volume analysis, histology, qRT-PCR and explorative proteomics.

RESULTS

Hypertrophy, increased fetal gene expression, interstitial fibrosis, and prolonged active relaxation were noted in the AB groups at week 6 in both sexes. However, decompensation of systolic function and further deterioration of diastolic function only occurred in male AB rats at week 12. AB induced similar proteomic alterations in both sexes at week 6, while characteristic differences were found at week 12. After debanding, regression of hypertrophy and recovery of diastolic function took place to a similar extent in both sexes. Nevertheless, fibrosis, transcription of β-to-α myosin-heavy chain ratio, and myocardial proteomic alterations were reduced to a greater degree in females compared to males. Debanding exposed anti-remodeling properties in both sexes, and prevented the functional decline in males.

CONCLUSIONS

Female sex is associated with greater reversibility of fibrosis, fetal gene expression, and proteomic alterations. Nevertheless, pressure unloading exposes a more pronounced anti-remodeling effect on the functional level in males, which is attributed to the more progressive functional deterioration in AB animals.

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.

Sex-related differences of early cardiac functional and proteomic alterations in a rat model of myocardial ischemia

BACKGROUND

Reduced cardiovascular risk in premenopausal women has been the focus of research in recent decades. Previous hypothesis-driven experiments have highlighted the role of sex hormones on distinct inflammatory responses, mitochondrial proteins, extracellular remodeling and estrogen-mediated cardioprotective signaling pathways related to post-ischemic recovery, which were associated with better cardiac functional outcomes in females. We aimed to investigate the early, sex-specific functional and proteomic changes following myocardial ischemia in an unbiased approach.

METHODS

Ischemia was induced in male (M-Isch) and female (F-Isch) rats with sc. injection of isoproterenol (85 mg/kg) daily for 2 days, while controls (M-Co, F-Co) received sc. saline solution. At 48 h after the first injection pressure-volume analysis was carried out to assess left ventricular function. FFPE tissue slides were scanned and analyzed digitally, while myocardial proteins were quantified by liquid chromatography-tandem mass spectrometry (LC-MS/MS) using isobaric labeling. Concentrations of circulating steroid hormones were measured with LC-MS/MS. Feature selection (PLS and PLS-DA) was used to examine associations among functional, proteomic and hormonal datasets.

RESULTS

Induction of ischemia resulted in 38% vs 17% mortality in M-Isch and F-Isch respectively. The extent of ischemic damage to surviving rats was comparable between the sexes. Systolic dysfunction was more pronounced in males, while females developed a more severe impairment of diastolic function. 2224 proteins were quantified, with 520 showing sex-specific differential regulation. Our analysis identified transcriptional, cytoskeletal, contractile, and mitochondrial proteins, molecular chaperones and the extracellular matrix as sources of disparity between the sexes. Bioinformatics highlighted possible associations of estrogens and their metabolites with early functional and proteomic alterations.

CONCLUSIONS

Our study has highlighted sex-specific alterations in systolic and diastolic function shortly after ischemia, and provided a comprehensive look at the underlying proteomic changes and the influence of estrogens and their metabolites. According to our bioinformatic analysis, inflammatory, mitochondrial, chaperone, cytoskeletal, extracellular and matricellular proteins are major sources of intersex disparity, and may be promising targets for early sex-specific pharmacologic interventions.

Long-Term PDE-5A Inhibition Improves Myofilament Function in Left and Right Ventricular Cardiomyocytes through Partially Different Mechanisms in Diabetic Rat Hearts

Heart failure with preserved ejection fraction (HFpEF) and right ventricular (RV) dysfunction are frequent complications of diabetic cardiomyopathy. Here we aimed to characterize RV and left ventricular (LV) remodeling and its prevention by vardenafil (a long-acting phosphodiesterase-5A (PDE-5A) inhibitor) administration in a diabetic HFpEF model. Zucker Diabetic Fatty (ZDF) and control, ZDF Lean (Lean) male rats received 10 mg/kg vardenafil (ZDF + Vard; Lean + Vard) per os, on a daily basis for a period of 25 weeks. In vitro force measurements, biochemical and histochemical assays were employed to assess cardiomyocyte function and signaling. Vardenafil treatment increased cyclic guanosine monophosphate (cGMP) levels and decreased 3-nitrotyrosine (3-NT) levels in the left and right ventricles of ZDF animals, but not in Lean animals. Cardiomyocyte passive tension (F_passive) was higher in LV and RV cardiomyocytes of ZDF rats than in those receiving preventive vardenafil treatment. Levels of overall titin phosphorylation did not differ in the four experimental groups. Maximal Ca²⁺-activated force (F_max) of LV and RV cardiomyocytes were preserved in ZDF animals. Ca²⁺-sensitivity of isometric force production (pCa₅₀) was significantly higher in LV (but not in RV) cardiomyocytes of ZDF rats than in their counterparts in the Lean or Lean + Vard groups. In accordance, the phosphorylation levels of cardiac troponin I (cTnI) and myosin binding protein-C (cMyBP-C) were lower in LV (but not in RV) cardiomyocytes of ZDF animals than in their counterparts of the Lean or Lean + Vard groups. Vardenafil treatment normalized pCa₅₀ values in LV cardiomyocytes, and it decreased pCa₅₀ below control levels in RV cardiomyocytes in the ZDF + Vard group. Our data illustrate partially overlapping myofilament protein alterations for LV and RV cardiomyocytes in diabetic rat hearts upon long-term PDE-5A inhibition. While uniform patterns in cGMP, 3-NT and F_passive levels predict identical effects of vardenafil therapy for the diastolic function in both ventricles, the uneven cTnI, cMyBP-C phosphorylation levels and pCa₅₀ values implicate different responses for the systolic function.

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

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.)

Novel insights into the athlete's heart: is myocardial work the new champion of systolic function?

Aims

We sought to investigate the correlation between speckle-tracking echocardiography (STE)-derived myocardial work (MW) and invasively measured contractility in a rat model of athlete's heart. We also assessed MW in elite athletes and explored its association with cardiopulmonary exercise test (CPET)-derived aerobic capacity.

Methods and results

Sixteen rats underwent a 12-week swim training program and were compared to controls (n = 16). STE was performed to assess global longitudinal strain (GLS), which was followed by invasive pressure-volume analysis to measure contractility [slope of end-systolic pressure–volume relationship (ESPVR)]. Global MW index (GMWI) was calculated from GLS curves and left ventricular (LV) pressure recordings. In the human investigations, 20 elite swimmers and 20 healthy sedentary controls were enrolled. GMWI was calculated through the simultaneous evaluation of GLS and non-invasively approximated LV pressure curves at rest. All subjects underwent CPET to determine peak oxygen uptake (VO₂/kg). Exercised rats exhibited higher values of GLS, GMWI, and ESPVR than controls (−20.9 ± 1.7 vs. −17.6 ± 1.9%, 2745 ± 280 vs. 2119 ± 272 mmHg·%, 3.72 ± 0.72 vs. 2.61 ± 0.40 mmHg/μL, all P_Exercise < 0.001). GMWI correlated robustly with ESPVR (r = 0.764, P < 0.001). In humans, regular exercise training was associated with decreased GLS (−17.6 ± 1.5 vs. −18.8 ± 0.9%, P_Exercise = 0.002) but increased values of GMWI at rest (1899 ± 136 vs. 1755 ± 234 mmHg·%, P_Exercise = 0.025). GMWI exhibited a positive correlation with VO₂/kg (r = 0.527, P < 0.001).

Conclusions

GMWI precisely reflected LV contractility in a rat model of exercise-induced LV hypertrophy and captured the supernormal systolic performance in human athletes even at rest. Our findings endorse the utilization of MW analysis in the evaluation of the athlete’s heart.

Left Ventricular SGLT1 Protein Expression Correlates with the Extent of Myocardial Nitro-Oxidative Stress in Rats with Pressure and Volume Overload-Induced Heart Failure

Myocardial sodium-glucose cotransporter 1 (SGLT1) has been shown to be upregulated in humans with heart failure (HF) with or without diabetes. In vitro studies have linked SGLT1 to increased nitro-oxidative stress in cardiomyocytes. We aimed to assess the relation between left ventricular (LV) SGLT1 expression and the extent of nitro-oxidative stress in two non-diabetic rat models of chronic heart failure (HF) evoked by either pressure (TAC, n = 12) or volume overload (ACF, n = 12). Sham-operated animals (Sham-T and Sham-A, both n = 12) served as controls. Both TAC and ACF induced characteristic LV structural and functional remodeling. Western blotting revealed that LV SGLT1 protein expression was significantly upregulated in both HF models (both p < 0.01), whereas the phosphorylation of ERK1/2 was decreased only in ACF; AMPKα activity was significantly reduced in both models. The protein expression of the Nox4 NADPH oxidase isoform was increased in both TAC and ACF compared with respective controls (both p < 0.01), showing a strong positive correlation with SGLT1 expression (r = 0.855, p < 0.001; and r = 0.798, p = 0.001, respectively). Furthermore, SGLT1 protein expression positively correlated with the extent of myocardial nitro-oxidative stress in failing hearts assessed by 3-nitrotyrosin (r = 0.818, p = 0.006) and 4-hydroxy-2-nonenal (r = 0.733, p = 0.020) immunostaining. Therefore, LV SGLT1 protein expression was upregulated irrespective of the nature of chronic hemodynamic overload, and correlated significantly with the expression of Nox4 and with the level of myocardial nitro-oxidative stress, suggesting a pathophysiological role of SGLT1 in HF.

Myocardial work index: a marker of left ventricular contractility in pressure- or volume overload-induced heart failure

Aims

While global longitudinal strain (GLS) is considered to be a sensitive marker of left ventricular (LV) function, it is significantly influenced by loading conditions. We hypothesized that global myocardial work index (GMWI), a novel marker of LV function, may show better correlation with load‐independent markers of LV contractility in rat models of pressure‐induced or volume overload‐induced heart failure.

Methods and results

Male Wistar rats underwent either transverse aortic constriction (TAC; n = 12) or aortocaval fistula creation (ACF; n = 12), inducing LV pressure or volume overload, respectively. Sham procedures were performed to establish control groups (n = 12/12). Echocardiographic loops were obtained to determine GLS and GMWI. Pressure‐volume analysis with transient occlusion of the inferior caval vein was carried out to calculate preload recruitable stroke work (PRSW), a load‐independent ‘gold‐standard’ parameter of LV contractility. Myocardial samples were collected to assess interstitial and perivascular fibrosis area and also myocardial atrial‐type natriuretic peptide (ANP) and brain‐type natriuretic peptide (BNP) relative mRNA expression. Compared with controls, GLS was substantially lower in the TAC group (−7.0 ± 2.8 vs. −14.5 ± 2.5%; P < 0.001) and was only mildly reduced in the ACF group (−13.2 ± 2.4 vs. −15.4 ± 2.0%, P < 0.05). In contrast with these findings, PRSW and GMWI were comparable with sham in TAC (110 ± 26 vs. 116 ± 68 mmHg; 1687 ± 275 mmHg% vs. 1537 ± 662 mmHg%; both P = NS), while it was found to be significantly reduced in ACF (58 ± 14 vs. 111 ± 40 mmHg; 1328 ± 411 vs. 1934 ± 308 mmHg%, both P < 0.01). In the pooled population, GMWI (r = 0.70; P < 0.001) but not GLS (r = −0.23; P = 0.12) showed a strong correlation with PRSW. GLS correlated with interstitial (r = 0.61; P < 0.001) and perivascular fibrosis area (r = 0.54; P < 0.001), and also with myocardial ANP (r = 0.85; P < 0.001) and BNP relative mRNA expression (r = 0.75; P < 0.001), while GMWI demonstrated no or only marginal correlation with these parameters.

Conclusions

Being significantly influenced by loading conditions, GLS may not be a reliable marker of LV contractility in heart failure induced by pressure or volume overload. GMWI better reflects contractility in haemodynamic overload states, making it a more robust marker of systolic function, while GLS should be considered as an integrative marker, incorporating systolic function, haemodynamic loading state, and adverse tissue remodelling of the LV.

Balanced Intense Exercise Training Induces Atrial Oxidative Stress Counterbalanced by the Antioxidant System and Atrial Hypertrophy That Is Not Associated with Pathological Remodeling or Arrhythmogenicity

Although regular exercise training is associated with cardiovascular benefits, the increased risk of atrial arrhythmias has been observed after vigorous exercise and has been related to oxidative stress. We aimed at investigating exercise-induced atrial remodeling in a rat model of an athlete’s heart and determining sex-specific differences. Age-matched young adult rats were divided into female exercised, female control, male exercised, and male control groups. After exercised animals completed a 12-week-long swim training protocol, echocardiography and in vivo cardiac electrophysiologic investigation were performed. Additionally, atrial histological and gene expression analyses were carried out. Post-mortem atrial weight data and histological examination confirmed marked atrial hypertrophy. We found increased atrial gene expression of antioxidant enzymes along with increased nitro-oxidative stress. No gene expression alteration was found regarding markers of pathological remodeling, apoptotic, proinflammatoric, and profibrotic processes. Exercise training was associated with a prolonged right atrial effective refractory period. We could not induce arrhythmias by programmed stimulation in any groups. We found decreased expression of potassium channels. Female gender was associated with lower profibrotic expression and collagen density. Long-term, balanced exercise training-induced atrial hypertrophy is not associated with harmful electrical remodeling, and no inflammatory or profibrotic response was observed in the atrium of exercised rats.

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 &lt; 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 &lt; 0.01). GLS showed moderate correlation with PRSW (r=-0.550, p &lt; 0.01), whereas GMWI correlated more significantly, but still moderately with the invasively measured LV contractility (r = 0.681, p &lt; 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 &lt; 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 &lt; 0.05), while it was significantly lower in TAC group compared to controls (-7.0 ± 2.8 vs. -14.5 ± 2.5%; p &lt; 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 &lt; 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 &lt; 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

Characterization of left ventricular myocardial sodium-glucose cotransporter 1 expression in patients with end-stage heart failure

Background

Whereas selective sodium-glucose cotransporter 2 (SGLT2) inhibitors consistently showed cardiovascular protective effects in large outcome trials independent of the presence of type 2 diabetes mellitus (T2DM), the cardiovascular effects of dual SGLT1/2 inhibitors remain to be elucidated. Despite its clinical relevance, data are scarce regarding left ventricular (LV) SGLT1 expression in distinct heart failure (HF) pathologies. We aimed to characterize LV SGLT1 expression in human patients with end-stage HF, in context of the other two major glucose transporters: GLUT1 and GLUT4.

Methods

Control LV samples (Control, n = 9) were harvested from patients with preserved LV systolic function who went through mitral valve replacement. LV samples from HF patients undergoing heart transplantation (n = 71) were obtained according to the following etiological subgroups: hypertrophic cardiomyopathy (HCM, n = 7); idiopathic dilated cardiomyopathy (DCM, n = 12); ischemic heart disease without T2DM (IHD, n = 14), IHD with T2DM (IHD + T2DM, n = 11); and HF patients with cardiac resynchronization therapy (DCM:CRT, n = 9, IHD:CRT, n = 9 and IHD-T2DM:CRT, n = 9). We measured LV SGLT1, GLUT1 and GLUT4 gene expressions with qRT-PCR. The protein expression of SGLT1, and activating phosphorylation of AMP-activated protein kinase (AMPKα) and extracellular signal-regulated kinase 1/2 (ERK1/2) were quantified by western blotting. Immunohistochemical staining of SGLT1 was performed.

Results

Compared with controls, LV SGLT1 mRNA and protein expressions were significantly and comparably upregulated in HF patients with DCM, IHD and IHD + T2DM (all P < 0.05), but not in HCM. LV SGLT1 mRNA and protein expressions positively correlated with LVEDD and negatively correlated with EF (all P < 0.01). Whereas AMPKα phosphorylation was positively associated with SGLT1 protein expression, ERK1/2 phosphorylation showed a negative correlation (both P < 0.01). Immunohistochemical staining revealed that SGLT1 expression was predominantly confined to cardiomyocytes, and not fibrotic tissue. Overall, CRT was associated with reduction of LV SGLT1 expression, especially in patients with DCM.

Conclusions

Myocardial LV SGLT1 is upregulated in patients with HF (except in those with HCM), correlates significantly with parameters of cardiac remodeling (LVEDD) and systolic function (EF), and is downregulated in DCM patients with CRT. The possible role of SGLT1 in LV remodeling needs to be elucidated.

Long-term exercise results in morphological and biomechanical changes in coronary resistance arterioles in male and female rats

Background

Biomechanical remodeling of coronary resistance arteries in physiological left ventricular hypertrophy has not yet been analyzed, and the possible sex differences are unknown.

Methods

Wistar rats were divided into four groups: male and female sedentary controls (MSe and FSe) and male and female animals undergoing a 12-week intensive swim training program (MEx and FEx). On the last day, the in vitro contractility, endothelium-dependent dilatation, and biomechanical properties of the intramural coronary resistance arteries were investigated by pressure microarteriography. Elastica and collagen remodeling were studied in histological sections.

Results

A similar outer radius and reduced inner radius resulted in an elevated wall to lumen ratio in the MEx and FEx animals compared to that in the sedentary controls. The wall elastic moduli increased in the MEx and FEx rats. Spontaneous and TxA₂ agonist-induced tone was increased in the FEx animals, whereas endothelium-dependent relaxation became more effective in MEx rats. Arteries of FEx rats had stronger contraction, while arteries of MEx animals had improved dilation.

Conclusions

According to our results, the coronary arterioles adapted to an elevated load during long-term exercise, and this adaptation depended on sex. It is important to emphasize that in addition to differences, we also found many similarities between the sexes in the adaptive response to exercise. The observed sport adaptation in the coronary resistance arteries of rats may contribute to a better understanding of the physiological and pathological function of these arteries in active and retired athletes of different sexes.

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

Sex Differences in Morphological and Functional Aspects of Exercise-Induced Cardiac Hypertrophy in a Rat Model

Background: Recent evidences suggest that sex hormones may be involved in the regulation of exercise-induced left ventricular (LV) hypertrophy. However, the sex-specific functional consequences of exercise-induced myocardial hypertrophy is still not investigated in detail. We aimed at understanding the sex-specific functional and morphological alterations in the LV and the underlying molecular changes in a rat model of athlete’s heart.

Methods: We divided our young, adult male and female rats into control and exercised groups. Athlete’s heart was induced by a 12-week long swim training. Following the training period, we assessed LV hypertrophy with echocardiography, while pressure-volume analysis was performed to investigate in vivo LV function. After in vivo experiments, molecular biological studies and histological investigations were performed.

Results: Echocardiography and post-mortem measured heart weight data indicated LV hypertrophy in both genders, nevertheless it was more pronounced in females. Despite the more significant relative hypertrophy in females, characteristic functional parameters did not show notable differences between the genders. LV pressure-volume analysis showed increased stroke volume, improved contractility and stroke work and unaltered LV stiffness in both male and female exercised rats, while active relaxation was ameliorated solely in male animals. The induction of Akt signaling was more significant in females compared to males. There was also a characteristic difference in the mitogen-activated protein kinase pathway as suppressed phosphorylation of p44/42 MAPK (Erk) and mTOR was observed in female exercised rats, but not in male ones. Myosin heavy chain α (MHC)/β-MHC ratio did not differ in males, but increased markedly in females.

Conclusion: Our results confirm that there is a more pronounced exercise-induced LV hypertrophy in females as compared to the males, however, there are only minor differences regarding LV function. There are characteristic molecular differences between male and female animals, that can explain different degrees of LV hypertrophy.

Myofilament Ca2+ sensitivity correlates with left ventricular contractility during the progression of pressure overload-induced left ventricular myocardial hypertrophy in rats

AIM

Here we aimed at investigating the relation between left ventricular (LV) contractility and myofilament function during the development and progression of pressure overload (PO)-induced LV myocardial hypertrophy (LVH).

METHODS

Abdominal aortic banding (AB) was performed to induce PO in rats for 6, 12 and 18 weeks. Sham operated animals served as controls. Structural and molecular alterations were investigated by serial echocardiography, histology, quantitative real-time PCR and western blot. LV function was assessed by pressure-volume analysis. Force measurement was carried out in permeabilized cardiomyocytes.

RESULTS

AB resulted in the development of pathological LVH as indicated by increased heart weight-to-tibial length ratio, LV mass index, cardiomyocyte diameter and fetal gene expression. These alterations were already present at early stage of LVH (AB-week6). Furthermore, at more advanced stages (AB-week12, AB-week18), myocardial fibrosis and chamber dilatation were also observed. From a hemodynamic point of view, the AB-wk6 group was associated with increased LV contractility, maintained ventriculo-arterial coupling (VAC) and preserved systolic function. In the same experimental group, increased myofilament Ca²⁺ sensitivity (pCa₅₀) and hyperphosphorylation of cardiac troponin-I (cTnI) at Threonine-144 was detected. In contrast, in the AB-wk12 and AB-wk18 groups, the initial augmentation of LV contractility, as well as the increased myofilament Ca²⁺ sensitivity and cTnI (Threonine-144) hyperphosphorylation diminished, leading to impaired VAC and reduced systolic performance. Strong correlation was found between LV contractility parameters and myofilament Ca²⁺-sensitivity among the study groups.

CONCLUSION

Changes in myofilament Ca²⁺ sensitivity might underlie the alterations in LV contractility during the development and progression of PO-induced LVH.

Characterization of the dynamic changes in left ventricular morphology and function induced by exercise training and detraining

BACKGROUND

Although exercise-induced cardiac hypertrophy has been intensively investigated, its development and regression dynamics have not been comprehensively described. In the current study, we aimed to characterize the effects of regular exercise training and detraining on left ventricular (LV) morphology and function.

METHODS

Rats were divided into exercised (n = 12) and control (n = 12) groups. Exercised rats swam 200 min/day for 12 weeks. After completion of the training protocol, rats remained sedentary for 8 weeks (detraining period). Echocardiographic follow-up was performed regularly to obtain LV long- and short-axis recordings for speckle-tracking echocardiography analysis. Global longitudinal and circumferential strain and systolic strain rate were measured. LV pressure-volume analysis was performed using additional groups of rats to obtain haemodynamic data.

RESULTS

Echocardiographic examinations showed the development of LV hypertrophy in the exercised group. These differences disappeared during the detraining period. Strain and strain rate values were all increased after the training period, whereas supernormal values rapidly reversed to the control level after training cessation. Load-independent haemodynamic indices, e.g., preload recruitable stroke work, confirmed the exercise-induced systolic improvement and complete regression after detraining.

CONCLUSIONS AND TRANSLATIONAL ASPECT

Our results provide the first comprehensive data to describe the development and regression dynamics of morphological and functional aspects of physiological hypertrophy in detail. Speckle-tracking echocardiography has been proven to be feasible to follow-up changes induced by exercise training and detraining and might provide an early possibility to differentiate between physiological and pathological conditions.

Pressure-volume analysis reveals characteristic sex-related differences in cardiac function in a rat model of aortic banding-induced myocardial hypertrophy

Sex differences in pressure overload (PO)-induced left ventricular (LV) myocardial hypertrophy (LVH) have been intensely investigated. Nevertheless, sex-related disparities of LV hemodynamics in LVH were not examined in detail. Therefore, we aimed to provide a detailed characterization of distinct aspects of LV function in male and female rats during different stages of LVH. Banding of the abdominal aorta (AB) was performed to induce PO for 6 or 12 wk in male and female rats. Control animals underwent sham operation. The development of LVH was followed by serial echocardiography. Cardiac function was assessed by pressure-volume analysis. Cardiomyocyte hypertrophy and fibrosis were evaluated by histology. At week 6, increased LV mass index, heart weight-to-tibial length, cardiomyocyte diameter, concentric LV geometry, and moderate interstitial fibrosis were detected in both male and female AB rats, indicating the development of an early stage of LVH. Functionally, at this time, impaired active relaxation, increased contractility, and preserved ventricular-arterial coupling were observed in the AB groups in both sexes. In contrast, at week 12, progressive deterioration of LVH-associated structural and functional alterations occurred in male but not female animals with sustained PO. Accordingly, at this later stage, LVH was associated with eccentric remodeling, exacerbated fibrosis, and increased chamber stiffness in male AB rats. Furthermore, augmented contractility declined in male but not female AB animals, resulting in contractility-afterload mismatch. Maintained contractility augmentation, preserved ventricular-arterial coupling, and better myocardial compliance in female rats contribute to sex differences in LV function during the progression of PO-induced LVH. NEW & NOTEWORTHY We investigated sex differences in pressure overload-induced left ventricular myocardial hypertrophy for the first time on the functional level by pressure-volume analysis. We found that left ventricular hypertrophy was initially characterized by prolonged active relaxation, increased contractility, and maintained ventricular-arterial coupling in both sexes. However, at a later stage, augmented contractility declined in mate but not female rats, resulting in contractility-afterload mismatch. Furthermore, in male rats, increased myocardial stiffness also contributed to hypertrophy-associated diastolic dysfunction.

Comparison of speckle-tracking echocardiography with invasive hemodynamics for the detection of characteristic cardiac dysfunction in type-1 and type-2 diabetic rat models

Background

Measurement of systolic and diastolic function in animal models is challenging by conventional non-invasive methods. Therefore, we aimed at comparing speckle-tracking echocardiography (STE)-derived parameters to the indices of left ventricular (LV) pressure–volume (PV) analysis to detect cardiac dysfunction in rat models of type-1 (T1DM) and type-2 (T2DM) diabetes mellitus.

Methods

Rat models of T1DM (induced by 60 mg/kg streptozotocin, n = 8) and T2DM (32-week-old Zucker Diabetic Fatty rats, n = 7) and corresponding control animals (n = 5 and n = 8, respectively) were compared. Echocardiography and LV PV analysis were performed. LV short-axis recordings were used for STE analysis. Global circumferential strain, peak strain rate values in systole (SrS), isovolumic relaxation (SrIVR) and early diastole (SrE) were measured. LV contractility, active relaxation and stiffness were measured by PV analysis.

Results

In T1DM, contractility and active relaxation were deteriorated to a greater extent compared to T2DM. In contrast, diastolic stiffness was impaired in T2DM. Correspondingly, STE described more severe systolic dysfunction in T1DM. Among diastolic STE parameters, SrIVR was more decreased in T1DM, however, SrE was more reduced in T2DM. In T1DM, SrS correlated with contractility, SrIVR with active relaxation, while in T2DM SrE was related to cardiac stiffness, cardiomyocyte diameter and fibrosis.

Conclusions

Strain and strain rate parameters can be valuable and feasible measures to describe the dynamic changes in contractility, active relaxation and LV stiffness in animal models of T1DM and T2DM. STE corresponds to PV analysis and also correlates with markers of histological myocardial remodeling.

Electronic supplementary material

The online version of this article (10.1186/s12933-017-0645-0) contains supplementary material, which is available to authorized users.