Sex-based differences in short- and longer-term diet-induced metabolic heart disease

Sex-based differences in the development of obesity-induced cardiometabolic dysfunction are well documented, however, the specific mechanisms are not completely understood. Obesity has been linked to dysregulation of the epitranscriptome, but the role of N6-methyladenosine (m6A) RNA methylation has not been investigated in relation to the sex differences during obesity-induced cardiac dysfunction. In the current study, male and female C57BL/6J mice were subjected to short- and long-term high-fat/high-sucrose (HFHS) diet to induce obesogenic stress. Cardiac echocardiography showed males developed systolic and diastolic dysfunction after 4 mo of diet, but females maintained normal cardiac function despite both sexes being metabolically dysfunctional. Cardiac m6A machinery gene expression was differentially regulated by duration of HFHS diet in male, but not female mice, and left ventricular ejection fraction correlated with RNA machinery gene levels in a sex- and age-dependent manner. RNA-sequencing of cardiac transcriptome revealed that females, but not males may undergo protective cardiac remodeling early in the course of obesogenic stress. Taken together, our study demonstrates for the first time that cardiac RNA methylation machinery genes are regulated early during obesogenic stress in a sex-dependent manner and may play a role in the sex differences observed in cardiometabolic dysfunction.NEW & NOTEWORTHY Sex differences in obesity-associated cardiomyopathy are well documented but incompletely understood. We show for the first time that RNA methylation machinery genes may be regulated in response to obesogenic diet in a sex- and age-dependent manner and levels may correspond to cardiac systolic function. Our cardiac RNA-seq analysis suggests female, but not male mice may be protected from cardiac dysfunction by a protective cardiac remodeling response early during obesogenic stress.

Landscape fire smoke airway exposure impairs respiratory and cardiac function and worsens experimental asthma

BACKGROUND

Millions of people are exposed to landscape fire smoke (LFS) globally, and inhalation of LFS particulate matter (PM) is associated with poor respiratory and cardiovascular outcomes. However, how LFS affects respiratory and cardiovascular function is less well understood.

OBJECTIVE

We aimed to characterize the pathophysiologic effects of representative LFS airway exposure on respiratory and cardiac function and on asthma outcomes.

METHODS

LFS was generated using a customized combustion chamber. In 8-week-old female BALB/c mice, low (25 μg/m3, 24-hour equivalent) or moderate (100 μg/m3, 24-hour equivalent) concentrations of LFS PM (10 μm and below [PM10]) were administered daily for 3 (short-term) and 14 (long-term) days in the presence and absence of experimental asthma. Lung inflammation, gene expression, structural changes, and lung function were assessed. In 8-week-old male C57BL/6 mice, low concentrations of LFS PM10 were administered for 3 days. Cardiac function and gene expression were assessed.

RESULTS

Short- and long-term LFS PM10 airway exposure increased airway hyperresponsiveness and induced steroid insensitivity in experimental asthma, independent of significant changes in airway inflammation. Long-term LFS PM10 airway exposure also decreased gas diffusion. Short-term LFS PM10 airway exposure decreased cardiac function and expression of gene changes relating to oxidative stress and cardiovascular pathologies.

CONCLUSIONS

We characterized significant detrimental effects of physiologically relevant concentrations and durations of LFS PM10 airway exposure on lung and heart function. Our study provides a platform for assessment of mechanisms that underpin LFS PM10 airway exposure on respiratory and cardiovascular disease outcomes.

Cancer Therapies and Cardiomyocyte Viability: Which Drugs are Directly Cardiotoxic?

BACKGROUND

Increased cancer survivorship represents a remarkable achievement for modern medicine. Unfortunately, cancer treatments have inadvertently contributed to cardiovascular (CV) damage, significantly threatening the health and quality of life of patients living with, through and beyond cancer. Without understanding the mechanisms, including whether the cardiotoxicity is due to the direct or indirect effects on cardiomyocytes, prevention and management of cardiotoxicity can pose challenges in many patients. To date, the cardiotoxicity profiles of most of the chemotherapy drugs are still poorly understood.

AIM

To conduct a pilot study to investigate the direct effects of a range of cancer therapies on cardiomyocyte viability.

METHODS

Primary human cardiomyocytes (HCM) were cultured and seeded into 96-well culture plates. A total of 35 different Food and Drug Administration-approved anti-cancer drugs were added to the HCM cells with a concentration of 1uM for 72 hours. The viability of HCMs was determined using CellTitre-Glo. The experiments were repeated at least three times for each drug with HCMs of different passages.

RESULTS

We identified 15 anti-cancer agents that significantly reduced HCM viability. These drugs were: (1) anthracyclines (daunorubicin [HCM viability, mean %±standard error, 13.7±3.2%], epirubicin [47.6±5.3%]), (2) antimetabolite (azacitidine [67.1±2.4%]), (3) taxanes (paclitaxel [60.2±3.0%]), (4) protein kinase inhibitors (lapatinib [49.8±7.0%], ponatinib [42.4±9.0%], pemigatinib [68.1±2.3%], sorafenib [52.9±10.6%], nilotinib [64.4±4.5%], dasatinib [38.5±3.6%]), (5) proteasome inhibitors (ixazomib citrate [65.4±7.2%]), (6) non-selective histone-deacetylase inhibitor (panobinostat [19.1±4.1%]), poly adenosine diphosphate-ribose polymerase inhibitor (olaparib [68.2±1.7%]) and (7) vinca alkaloids (vincristine [44.6±7.4%], vinblastine [31.2±3.9%]).

CONCLUSIONS

In total, 15 of the 35 commercially available anti-cancer drugs have direct cardiotoxic effects on HCM. Some of those, have not been associated with clinical cardiotoxicity, while others, known to be cardiotoxic do not appear to mediate it via direct effects on cardiomyocytes. More detailed investigations of the effects of cancer therapies on various cardiovascular cells should be performed to comprehensively determine the mechanisms of cardiotoxicity.

Integrating CardioOncology Across the Research Pipeline, Policy, and Practice in Australia-An Australian Cardiovascular Alliance Perspective

Over 18 million people worldwide were diagnosed with cancer in 2020, including over 150,000 people in Australia. Although improved early detection and treatment have increased the survival rates, cardiotoxic treatment and inadequate management of cardiovascular risk factors have resulted in cardiovascular disease (CVD) being one of the leading causes of non-cancer-related death and disability among cancer survivors. International guidelines outline the standards of care for CVD risk surveillance and management. However, Australian cardio-oncology policies and clinical guidelines are limited. There is increasing growth of cardio-oncology research in Australia and support from leading Australian professional bodies and advocacy and research networks, including the Cardiac Society of Australia and New Zealand, the Clinical Oncology Society of Australia, the National Heart Foundation of Australia, and the Australian Cardiovascular Alliance (ACvA). Thus, opportunities to drive multidisciplinary cardio-oncology initiatives are growing, including grant funding, position statements, and novel research to inform new policies. The ACvA has a unique flagship structure that spans the translational research pipeline from drug discovery to implementation science. This article aims to highlight how multidisciplinary cardio-oncology innovations could intersect with the seven ACvA flagships, and to showcase Australian achievements in cardio-oncology thus far. We summarise eight key priority areas for future cardio-oncology research that emerged. These strategies will strengthen cardio-oncology research and care in Australia, and drive new guidelines, policies, and government initiatives to ensure equity in health outcomes for all cardio-oncology patients.

Women's cardiovascular health - the cardio-oncologic jigsaw

Improvements in cancer care have led to an exponential increase in cancer survival. This is particularly the case for breast cancer, where 5-year survival in Australia exceeds 90%. Cardiovascular disease (CVD) has emerged as one of the competing causes of morbidity and mortality among cancer survivors, both as a complication of cancer therapies and because the risk factors for cancer are shared with those for CVD. In this review we cover the key aspects of cardiovascular care for women throughout their cancer journey: the need for baseline cardiovascular risk assessment and management, a crucial component of the cardiovascular care; the importance of long-term surveillance for ongoing maintenance of cardiovascular health; and strong evidence for the beneficial effects of physical exercise to improve both cancer and cardiovascular outcomes. There is general disparity in cardiovascular outcomes for women, which is further exacerbated when both CVD and cancer co-exist. Collaboration between oncology and cardiac services, with an emergence of the whole field of cardio-oncology, allows for expedited investigation and treatment for these patients. This collaboration as well as a holistic approach to patient care and key role of patients' general practitioners are essential to ensure long-term health of people living with, during and beyond cancer.

Association of Circulating Plasma Secreted Frizzled-Related Protein 5 (Sfrp5) Levels with Cardiac Function

Secreted frizzled-related protein 5 (SFRP5) is a novel anti-inflammatory adipokine that may play a role in cardiovascular development and disease. However, there is yet to be a comprehensive investigation into whether circulating SFRP5 can be a biomarker for cardiac function. Plasma SFRP5 levels were measured via ELISA in 262 patients admitted to a cardiology unit. Plasma SFRP5 levels were significantly lower in patients with a history of heart failure (HF), coronary artery disease (CAD), and atrial fibrillation (AF; p = 0.001). In univariate analyses, SFRP5 levels were also significantly positively correlated with left ventricular ejection fraction (LVEF) (r = 0.52, p < 0.001) and negatively correlated with E/E' (r = -0.30, p < 0.001). Patients with HF, CAD, low LVEF, low triglycerides, high CRP, and high eGFR were associated with lower SFRP5 levels independent of age, BMI, or diabetes after multivariate analysis (overall model r = 0.729, SE = 0.638). Our results show that low plasma SFRP5 levels are independently associated with the presence of HF, CAD, and, importantly, impaired LV function. These results suggest a potential role of SFRP5 as a biomarker, as well as a mediator of cardiac dysfunction independent of obesity and metabolic regulation.

Overexpression of Mitochondrial Catalase within Adipose Tissue Does Not Confer Systemic Metabolic Protection against Diet-Induced Obesity

Obesity is associated with significant metabolic co-morbidities, such as diabetes, hypertension, and dyslipidaemia, as well as a range of cardiovascular diseases, all of which lead to increased hospitalisations, morbidity, and mortality. Adipose tissue dysfunction caused by chronic nutrient stress can result in oxidative stress, mitochondrial dysfunction, inflammation, hypoxia, and insulin resistance. Thus, we hypothesised that reducing adipose tissue oxidative stress via adipose tissue-targeted overexpression of the antioxidant mitochondrial catalase (mCAT) may improve systemic metabolic function. We crossed mCAT (floxed) and Adipoq-Cre mice to generate mice overexpressing catalase with a mitochondrial targeting sequence predominantly in adipose tissue, designated AdipoQ-mCAT. Under normal diet conditions, the AdipoQ-mCAT transgenic mice demonstrated increased weight gain, adipocyte remodelling, and metabolic dysfunction compared to the wild-type mice. Under obesogenic dietary conditions (16 weeks of high fat/high sucrose feeding), the AdipoQ-mCAT mice did not result in incremental impairment of adipose structure and function but in fact, were protected from further metabolic impairment compared to the obese wild-type mice. While AdipoQ-mCAT overexpression was unable to improve systemic metabolic function per se, our results highlight the critical role of physiological H₂O₂ signalling in metabolism and adipose tissue function.

Cardiovascular outcomes of cancer patients in rural Australia

Background

Cancer and heart disease are the two most common health conditions in the world, associated with high morbidity and mortality, with even worse outcomes in regional areas. Cardiovascular disease is the leading cause of death in cancer survivors. We aimed to evaluate the cardiovascular outcomes of patients receiving cancer treatment (CT) in a regional hospital.

Methods

This was an observational retrospective cohort study in a single rural hospital over a ten-year period (17th February 2010 to 19th March 2019). Outcomes of all patients receiving CT during this period were compared to those who were admitted to the hospital without a cancer diagnosis.

Results

268 patients received CT during the study period. High rates of cardiovascular risk factors: hypertension (52.2%), smoking (54.9%), and dyslipidaemia (38.4%) were observed in the CT group. Patients who had CT were more likely to be readmitted with ACS (5.9% vs. 2.8% p = 0.005) and AF (8.2% vs. 4.5% p = 0.006) when compared to the general admission cohort. There was a statistically significant difference observed for all cause cardiac readmission, with a higher rate observed in the CT group (17.1% vs. 13.2% p = 0.042). Patients undergoing CT had a higher rate of mortality (49.5% vs. 10.2%, p ≤ 0.001) and shorter time (days) from first admission to death (401.06 vs. 994.91, p ≤ 0.001) when compared to the general admission cohort, acknowledging this reduction in survival may be driven at least in part by the cancer itself.

Conclusion

There is an increased incidence of adverse cardiovascular outcomes, including higher readmission rate, higher mortality rate and shorter survival in people undergoing cancer treatment in rural environments. Rural cancer patients demonstrated a high burden of cardiovascular risk factors.

Elevated Soluble Suppressor of Tumorigenicity 2 Predict Hospital Admissions Due to Major Adverse Cardiovascular Events (MACE)

The role of soluble suppression of tumorigenicity (sST2) as a biomarker in predicting clinical outcomes in patients with cardiovascular diseases (CVD) has not been fully elucidated. In this study, we sought to determine the relationship between sST2 levels and any unplanned hospital readmissions due to a major adverse cardiovascular event (MACE) within 1 year of first admission. Patients (n = 250) admitted to the cardiology unit at John Hunter Hospital were recruited. Occurrences of MACE, defined as the composite of total death, myocardial infarction (MI), stroke, readmissions for heart failure (HF), or coronary revascularization, were recorded after 30, 90, 180, and 365 days of first admission. On univariate analysis, patients with atrial fibrillation (AF) and HF had significantly higher sST2 levels vs. those who did not. Increasing levels of sST2 by quartiles were significantly associated with AF, HF, older age, low hemoglobin, low eGFR, and high CRP levels. On multivariate analysis: high sST2 levels and diabetes remained as risk predictors of any MACE occurrence; an sST2 level in the highest quartile (Q4: >28.4 ng/mL) was independently associated with older age, use of beta-blockers, and number of MACE events within a 1 year period. In this patient cohort, elevated sST2 levels are associated with unplanned hospital admission due to MACE within 1 year, independent of the nature of the index cardiovascular admission.

Mind The Gap, Aboriginal and Torres Strait Islander Cardiovascular Health: A Narrative Review

Australia's First Nations Peoples, Aboriginal and Torres Strait Islanders, have reduced life expectancy compared to the wider community. Cardiovascular diseases, mainly driven by ischaemic heart disease, are the leading contributors to this disparity. Despite over a third of First Nations Peoples living in New South Wales, the bulk of the peer-reviewed literature is from Central Australia and Far North Queensland. Regardless of the site of publication, First Nations Peoples are significantly younger at disease onset and have higher rates of comorbidities, in turn driving adverse health events. On top of this, very few First Nations Peoples specific cardiovascular interventions or programs have been shown to improve outcomes. The traditional biomedical model of care is less efficacious and non-traditional models of communication such as clinical yarning may benefit both clinicians and patients. The key purpose of this review is to highlight the deficiencies of our knowledge of cardiovascular burden of disease for First Nations Peoples; and to serve as a catalyst for more dedicated research. We need to have relationships with communities and concentrate on community improvement and partnerships. By involving First Nations Peoples researchers in collaboration with local communities in all levels of health care design and intervention will improve outcomes.

Heart failure is associated with low circulating levels of secreted frizzled receptor protein 5 (Sfrp5)

Background/Introduction

Obesity and metabolic dysregulation are closely associated with the pathophysiology of multiple cardiovascular diseases (CVD). To date, the pathophysiological mechanism(s) of obesity and its link with cardiovascular systems remain largely unknown. Adipose tissue inflammation as a result of excessive fat expansion in obesity, leading to increased systemic production of growth factors and recruitment of inflammatory cells have been postulated to be a major factor. Secreted frizzled-related protein 5 (SFRP5) is an anti-inflammatory adipokine that is linked with obesity and metabolic regulation and has been indicated to affect cardiovascular functions. Currently, the role of circulating SFRP5 levels as a biomarker for cardiovascular diseases are poorly understood, with studies yielding discordant results.

Purpose

This study aims to evaluate the relationship between circulating SFRP5 and cardiovascular functions in a cohort of patients with established CVD.

Methods

Patients (n=262, 148 male (56.5%), age (68±11 yrs)) presenting to the cardiology unit for cardiovascular investigations were recruited into the study. Plasma SFRP5 levels were measured via enzyme-linked immunosorbent assay (ELISA). Associations between plasma SFRP5 levels, cardiovascular functions, and patients' co-morbidities were analysed using univariate and multivariate analyses.

Results

Plasma SFRP5 levels were significantly lower in patients presenting with: heart failure (HF) vs non-HF (median; (10.7 vs 31.0; p&lt;0.001); coronary artery disease (CAD) vs non-CAD; (11.0 vs 33.8; p&lt;0.001); and atrial fibrillation (AF) vs non-AF; (11.2 vs 23.2; p=0.001). On univariate analyses, SFRP5 levels also significantly positively correlated with left ventricular ejection fraction (LVEF) (r=0.52, p&lt;0.001), estimated glomerular filtration rate (eGFR) (r=0.16, p=0.02), total cholesterol levels and triglycerides (r=0.29, p&lt;0.001; r=0.17, p&lt;0.01 respectively). Low SFRP5 levels were correlated with high C-reactive protein (CRP) and E/E' (r=−0.29, p&lt;0.001, r=−0.30, p&lt;0.001, respectively). Patients with HF, CAD, statin use, low LVEF, low triglycerides, high CRP and high eGFR were associated with lower SFRP5 levels independent of age, BMI or diabetes on multivariate analysis (overall model r=0.729, SE=0.638).

Conclusion

Our results show that low plasma SFRP5 levels are independently associated with HF, CAD, and impaired systolic and diastolic functions. These results suggest that SFRP5 may regulate cardiovascular functions independent of obesity and metabolic regulations.

Funding Acknowledgement

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Heart Foundation of Australia Future Leader FellowshipsNSW Ministry of Health EMC FellowshipHeart Foundation of Australia Future Leader Fellowship

Mechanism(s) for age-related sex differences in diet-induced cardiomyopathy: role of RNA methylation

Background/Introduction

Age and sexual dimorphism contribute to the differential cardiometabolic dysfunctions associated with diet-induced obesity. However, the underlying mechanisms remain elusive. RNA modifications via RNA m6A methylation, is an emerging mediator of RNA stability, translation and localization responsible for regulation of multiple biological functions. RNA m6A modifications are regulated by “writers”, “erasers” and “readers”. The role of RNA methylation machinery genes in the heart is largely unexplored, and may provide insight into the influence of age and sex on cardiometabolic dysfunction.

Purpose

We aim to determine differential RNA methylation changes within the heart in a diet-induced cardiomyopathy mouse model, stratified according to age and sex.

Methods

Male and female C57BL/6 mice (6–8wk-old) were fed normal chow (NC) or high-fat/high-sucrose (HFHS) diet for 1 or 4 months. Echocardiographic measurements were performed at 1 and 4 months according to the American Society of Echocardiography and European Association of Cardiovascular Imaging guidelines. At study endpoint, glucose and insulin tolerance testing was conducted by injecting mice intraperitoneally with 2g/kg glucose or 0.6U/kg insulin, and monitoring blood glucose levels over a 2 hour period. RNA from heart tissue was subjected to quantitative PCR for RNA methylation machinery genes (FTO, ALKBH5, METTL3, METTL4, METTL14, YTHDF1 and YTHDF2). PPIA was used to normalise qPCR data.

Results

Both male and female mice showed evidence of age- and diet-induced metabolic dysfunction, however, males and females showed markedly different metabolic impairments. For example, glucose tolerance was exacerbated by 4 months of HFHS diet in males but not females; and only females showed impaired insulin tolerance. Echocardiography showed that males had systolic (stoke volume, cardiac output) and diastolic (E/A ratio) dysfunction after 4 months of HFHS diet, while females were unperturbed. We identified that METTL3 and METTL14, the “writers” of m6A methylation, were consistently increased in male mouse hearts at 1 vs 4 months of age but were unchanged or decreased in females, irrespective of diet. Conversely, YTHDF1, a “reader”, was unchanged in male mouse hearts at 1 vs. 4 months of age but was significantly increased in female hearts.

Conclusion

Our study confirms that markedly different cardiometabolic impairments occur in male versus female mice in response to long-term HFHS diet. Despite significant metabolic impairment in both sexes, cardiac dysfunction was only evident in males. RNA methylation machinery genes were differentially expressed in mouse hearts according to age and sex, suggesting that RNA methylation may be involved in age-related sexual dimorphism in cardiometabolic impairments.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): Heart Foundation

Early access to a cardio-oncology clinic in an Australian context: a qualitative exploration of patient experiences

Background

Dedicated cardio-oncology services are emerging rapidly around the world in order to provide cardiovascular care (CV) for cancer patients. The perspectives of patients regarding their experience of cardiac surveillance during their cancer journey has not been qualitatively evaluated.

Methods

An interpretative qualitative study. Fifteen, in-depth qualitative interviews were conducted with a diverse range of community dwelling patients who attended a newly established cardio-oncology clinic in a large regional city in Australia. Data were analysed using an inductive thematic approach.

Results

Key themes were identified: (1) Access to a cardio-oncology clinic promotes information and understanding, (2) The experience of early CV intervention, (3) Factors promoting integrated care, (4) Balancing cancer treatment and CV symptoms and (5) Managing past and emerging CV risk factors.

Conclusion

As cardio oncology clinics continue to emerge, this study confirms the benefit of early access to a cardiologist for management of existing or emerging CV risk factors and diseases in the context of cancer treatment. Participants valued the opportunity for regular monitoring and management of CV issues that enabled them to continue cancer treatment. However, we identified gaps in education and support towards making positive lifestyle changes that reduce the risk of CV diseases in cancer patients.

Patient characteristics, short-term and long-term outcomes after incident heart failure admissions in a regional Australian setting

AIMS

This study aims to (1) define the characteristics of patients with a first admission for heart failure (HF), stratified by type (reduced (HFrEF) vs preserved (HFpEF) ejection fraction) in a regional Australian setting; (2) compare the outcomes in terms of mortality and rehospitalisation and (3) assess adherence to the treatment guidelines.

METHODS

We identified all index hospitalisations with HF to John Hunter Hospital and Tamworth Rural Referral Hospital in the Hunter New England Local Health District over a 12 months. We used the recent Australian HF guidelines to classify HFrEF and HFpEF and assess adherence to guideline-directed therapy. The primary outcome of the study was to compare short-term (1 year) and long-term all-cause mortality and the composite of all-cause hospitalisation or all-cause mortality of patients with HFrEF and HFpEF.

RESULTS

There were 664 patients who had an index HF admission to John Hunter and Tamworth hospitals in 2014. The median age was 80 years, 47% were female and 22 (3%) were Aboriginal. In terms of HF type, 29% had HFrEF, 37% had HFpEF, while the remainder (34%) did not have an echocardiogram within 1 year of admission and could not be classified. The median follow-up was 3.3 years. HFrEF patients were predominantly male (64%) and in 48% the aetiology was ischaemic heart disease. The 1-year all-cause mortality was 23% in HFpEF subgroup and 29% in HFrEF subgroup (p=0.15). Five-year mortality was 61% in HFpEF and HFrEF patients. Of the HFrEF patients, only 61% were on renin-angiotensin-aldosterone blockers, 74% were on β-blockers and 39% were on aldosterone antagonist.

CONCLUSION

HF patients are elderly and about evenly split between HFrEF and HFpEF. In this regional cohort, both HF types are associated with similar 1-year and 5-year mortality following incident HF hospitalisation. Echocardiography and guideline-directed therapies were underused.

Mitochondrial Dynamin-Related Protein Drp1: a New Player in Cardio-oncology

PURPOSE OF REVIEW

This study is aimed at reviewing the recent progress in Drp1 inhibition as a novel approach for reducing doxorubicin-induced cardiotoxicity and for improving cancer treatment.

RECENT FINDINGS

Anthracyclines (e.g. doxorubicin) are one of the most common and effective chemotherapeutic agents to treat a variety of cancers. However, the clinical usage of doxorubicin has been hampered by its severe cardiotoxic side effects leading to heart failure. Mitochondrial dysfunction is one of the major aetiologies of doxorubicin-induced cardiotoxicity. The morphology of mitochondria is highly dynamic, governed by two opposing processes known as fusion and fission, collectively known as mitochondrial dynamics. An imbalance in mitochondrial dynamics is often reported in tumourigenesis which can lead to adaptive and acquired resistance to chemotherapy. Drp1 is a key mitochondrial fission regulator, and emerging evidence has demonstrated that Drp1-mediated mitochondrial fission is upregulated in both cancer cells to their survival advantage and injured heart tissue in the setting of doxorubicin-induced cardiotoxicity. Effective treatment to prevent and mitigate doxorubicin-induced cardiotoxicity is currently not available. Recent advances in cardio-oncology have highlighted that Drp1 inhibition holds great potential as a targeted mitochondrial therapy for doxorubicin-induced cardiotoxicity.

Heart Failure in Breast Cancer Survivors: Focus on Early Detection and Novel Biomarkers

PURPOSE OF REVIEW

Breast cancer survival rate has greatly improved in the last two decades due to the emergence of next-generation anti-cancer agents. However, cardiotoxicity remains a significant adverse effect arising from traditional and emerging chemotherapies as well as targeted therapies for breast cancer patients. In this review, we will discuss cardiotoxicities of both traditional and emerging therapies for breast cancer. We will discuss current practices to detect cardiotoxicity of these therapies with the focus on new and emerging biomarkers. We will then focus on 'omics approaches, especially the use of epigenetics to discover novel biomarkers and therapeutics to mitigate cardiotoxicity.

RECENT FINDINGS

Significant cardiotoxicities of conventional chemotherapies remain and new and unpredictable new forms of cardiac and/or vascular toxicity emerge with the surge in novel and targeted therapies. Yet, there is no clear guidance on detection of cardiotoxicity, except for significant left ventricular systolic dysfunction, and even then, there is no uniform definition of what constitutes cardiotoxicity. The gold standard for detection of cardiotoxicity involves a serial echocardiography in conjunction with blood-based biomarkers to detect early subclinical cardiac dysfunction. However, the ability of these tests to detect early disease remains limited and not all forms of toxicity are detectable with these modalities. There is an unprecedented need to discover novel biomarkers that are sensitive and specific for early detection of subclinical cardiotoxicity. In that space, novel echocardiographic techniques, such as strain, are becoming more common-place and new biomarkers, discovered by epigenetic approaches, seem to become promising alternatives or adjuncts to conventional non-specific cardiac biomarkers.

The Importance of Primary Care in Cardio-Oncology

OPINION STATEMENT

There is significant interplay between cancer and cardiovascular disease involving shared risk factors, cross disease communication where cardiovascular events can influence cancer recurrence, and mortality rates and cardiotoxicity from cancer treatments with resultant increased cardiovascular mortality and morbidity in cancer patients. This is a major cause of death in many long-term cancer survivors. As a result, cardio-oncology, which involves the prevention, early detection, and optimal treatment of cardiovascular disease in patients treated for cancer, is expanding globally. However, there is still limited awareness of its importance and limited application of the lessons already learnt. Primary care physicians, and their clinical teams, especially nursing colleagues, have a foundation role in the management of all patients, and this paper outlines areas where they can lead in the cardio-oncology management of cancer patients. Although there is currently a lack of an adequate clinical framework or shared care plan, primary care physicians have a role to play in the various phases of cancer treatment: pre-therapy, during therapy, and survivorship.

Adipose-targeted overexpression of mitochondrial-targeted catalase does not improve cardio-metabolic parameters in mice with diet-induced obesity

Background

Obesity is associated with significant cardio-metabolic complications. Adipokines, and cytokines released from adipose tissue (AT) stimulate excessive mitochondrial production of reactive oxygen species (ROS). ROS-mediated oxidative modifications is associated with development of insulin resistance and impaired cardiac function. We hypothesised that adipose-targeted overexpression of mitochondrial-targeted catalase (AT-mCAT) could lead to improvement in diet-induced cardio-metabolic dysfunction.

Methods/Results

mCAT (floxed) and AdipoQ-Cre mice were crossed to generate mice overexpressing catalase with a mitochondrial-targeting sequence predominantly in AT (AT-mCAT). Wild-type (WT) and AT-mCAT male mice were fed normal chow (NC) or high-fat/high-sucrose (HFHS) diet (36%fat/34%sucrose) for 4 months. At endpoint, echocardiography showed reduced cardiac output in all groups v WT NC (p&lt;0.05); reduced IVSd in AT-mCAT NC and HFHS groups v WT NC (p&lt;0.01); reduced left ventricular ejection fraction in AT-mCAT HFHS v WT NC (p&lt;0.05) and no differences in fractional shortening or E/A ratio between groups. Glucose tolerance tests (2g/kg) showed impairment in WT HFHS and AT-mCAT HFHS v WT NC (p&lt;0.01, p&lt;0.05 respectively). Triglyceride levels were increased in WT HFHS and AT-mCAT HFHS v WT NC (p&lt;0.05). Analysis of hypertrophic signalling in cardiac tissues by ELISA showed p-AKT/total Akt levels were decreased in AT-mCAT hearts regardless of diet (WT NC v AT-mCAT NC p&lt;0.01; WT HFHS v AT-mCAT HFHS p&lt;0.05).

Conclusion

Our results confirm previous findings that diet-induced obesity is a systemic condition. Targeting adipose tissue with mitochondrial catalase may not be adequate to prevent development of cardio-metabolic dysfunction. More systemic approaches may be required to combat obesity-induced cardio-metabolic impairment.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): National Heart Foundation of Australia

Cardiotoxicity of Radiation Therapy: Mechanisms, Management, and Mitigation

OPINION STATEMENT

Radiation therapy is a key component of modern-day cancer therapy and can reduce the rates of recurrence and death from cancer. However, it can increase risk of cardiovascular (CV) events, and our understanding of the timeline associated with that risk is shorter than previously thought. Risk mitigation strategies, such as different positioning techniques, and breath hold acquisitions as well as baseline cardiovascular risk stratification that can be undertaken at the time of radiotherapy planning should be implemented, particularly for patients receiving chest radiation therapy. Primary and secondary prevention of cardiovascular disease (CVD), as appropriate, should be used before, during, and after radiation treatment in order to minimize the risks. Opportunistic screening for subclinical coronary disease provides an attractive possibility for primary/secondary CVD prevention and thus mitigation of long-term CV risk. More data on long-term clinical usefulness of this strategy and development of appropriate management pathways would further strengthen the evidence for the implementation of such screening. Clear guidelines in initial cardiovascular screening and cardiac aftercare following radiotherapy need to be formulated in order to integrate these measures into everyday clinical practice and policy and subsequently improve post-treatment morbidity and mortality for these patients.

Heart failure outcomes in Aboriginal and Torres Strait Islander peoples in the Hunter New England region of New South Wales

Background Aboriginal and Torres Strait Islander suffer poor health outcomes, driven predominately by cardiovascular disease. Previous work has focused on remote communities although majority of Aboriginal and Torres Strait Islander patients live in urban New South Wales. We describe the heart failure characteristics and outcomes of the Aboriginal and Torres Strait Islander patients in Hunter New England Health, New South Wales, Australia. Methods A large retrospective, multi-centre cohort study from 2007 till 2016 in a geographically diverse Local Health District. The primary outcomes were all-cause mortality and all-cause readmission. The Aboriginal and Torres Strait Islander cohort was described by demographics, locality, and outcomes relative to the non-Indigenous patients from the same time period. Findings During the study period there were 20,480 index admissions, of which 3.1% identified as Aboriginal and/or Torres Strait Islander. Aboriginal and Torres Strait Islander people admitted were younger by an average of 15 years (81 vs 66 years, p < 0.001), were more likely to live in a non-metropolitan locality (80 vs 61%, p < 0.001). Once adjustments were made for age, there was no significant difference in all-cause mortality. Indigenous status was a strong predictor of readmission on multivariate analysis, hazard ratio of 1.31 (p < 0.001). Interpretation Aboriginal and Torres Strait Islander patients, compared to non-Indigenous patients, who are admitted with heart failure are younger, more commonly live in rural localities and suffer from a higher burden of comorbidities. Once adjustments are made for age and co-morbidities, indigenous status does not portend a worse outcome.

Factors Associated with Adverse Cardiovascular Events in Cancer Patients Treated with Bevacizumab

Background: Bevacizumab, a vascular endothelial growth factor (VEGF) monoclonal antibody commonly used for the treatment of various cancers, is often associated with adverse cardiovascular effects such as hypertension, cardiac and cerebral ischemia, thrombosis, and bleeding events. Factors associated with increased risks of adverse cardiovascular effects with bevacizumab have not been intensively studied. In this study, we determined factors associated with hospital admissions due to cardiovascular complications in patients who received bevacizumab for cancer treatment. Methods and Results: We retrospectively collected data for all patients treated with bevacizumab between the 1st January 2016 and the 31st December 2017 at the Hunter New England Local Health District. Patients' characteristics and their medical history were obtained from hospital electronic medical records. Outcome data were sourced from the Institutional Cardiac and Stroke Outcomes Unit database. A total of n = 230 patients (mean age 65, males n = 124 (53.9%)) were treated with bevacizumab during the study period. N = 28 patients were admitted to hospital for a major cardiovascular-related event. Higher total treatment dose (p < 0.05), concomitant hypertension (p = 0.005), diabetes (p = 0.04), atrial fibrillation (p = 0.03), and lack of use of statin therapy (p = 0.03) were key contributors to hospital admission. Conclusions: Results of our study highlight the fact that patients with concomitant baseline cardiovascular disease/risk factors are at an increased risk of cardiovascular hospitalization related to bevacizumab treatment. Careful baseline cardiovascular assessment may be an essential step to minimize cardiovascular complications.

Ibrutinib-related atrial fibrillation: A single center Australian experience

BACKGROUND

Ibrutinib increases the risk of atrial fibrillation (AF) and is associated with bleeding tendencies. Reported rates of arrhythmia are variable in different studies. The aim of the current analysis was to evaluate the incidence of AF in a single-center cohort of patients.

METHODS

This analysis was conducted at Hunter New England Local Health District, Australia between April 1, 2015 and June 30, 2017. We included all consecutive patients commenced on ibrutinib for hematological malignancies. Patients with a history of paroxysmal AF were excluded. The primary end point was incidence of AF. Time to diagnosis and management were secondary outcomes of interest.

RESULTS

A total of 24 patients (age 73 ± 9 years, males n = 16 [67%]) were commenced on ibrutinib treatment during the study period with chronic lymphocytic leukemia (n = 21, 88%) as the main indication. During a median follow-up of 12 months, four (17%) patients were diagnosed with AF with increasing age, duration of ibrutinib treatment as associations. The median time to AF diagnosis was 9 (interquartile range [IQR]: 7-18) months. All patients were managed with a rate control strategy with beta blockers as the preferred agents. Three (75%) patients were commenced on anticoagulation for stroke prevention. During a follow-up of 18 (IQR: 17-23) months following AF onset, one patient required hospitalization for AF. There were no bleeding complications reported.

CONCLUSIONS

In conclusion, this series noted a higher incidence of AF than previously reported. Oncologists and cardiologists need to be aware of the increased risk of AF in patients receiving ibrutinib.

Oxidative modifications of mitochondrial complex II are associated with insulin resistance of visceral fat in obesity

Obesity, particularly visceral adiposity, has been linked to mitochondrial dysfunction and increased oxidative stress, which have been suggested as mechanisms of insulin resistance. The mechanism(s) behind this remains incompletely understood. In this study, we hypothesized that mitochondrial complex II dysfunction plays a role in impaired insulin sensitivity in visceral adipose tissue of subjects with obesity. We obtained subcutaneous and visceral adipose tissue biopsies from 43 subjects with obesity (body mass index ≥ 30 kg/m²) during planned bariatric surgery. Compared with subcutaneous adipose tissue, visceral adipose tissue exhibited decreased complex II activity, which was restored with the reducing agent dithiothreitol (5 mM) ( P < 0.01). A biotin switch assay identified that cysteine oxidative posttranslational modifications (OPTM) in complex II subunit A (succinate dehydrogenase A) were increased in visceral vs. subcutaneous fat ( P < 0.05). Insulin treatment (100 nM) stimulated complex II activity in subcutaneous fat ( P < 0.05). In contrast, insulin treatment of visceral fat led to a decrease in complex II activity ( P < 0.01), which was restored with addition of the mitochondria-specific oxidant scavenger mito-TEMPO (10 µM). In a cohort of 10 subjects with severe obesity, surgical weight loss decreased OPTM and restored complex II activity, exclusively in the visceral depot. Mitochondrial complex II may be an unrecognized and novel mediator of insulin resistance associated with visceral adiposity. The activity of complex II is improved by weight loss, which may contribute to metabolic improvements associated with bariatric surgery.

WNT5A regulates adipose tissue angiogenesis via antiangiogenic VEGF-A165b in obese humans

Experimental studies have suggested that Wingless-related integration site 5A (WNT5A) is a proinflammatory secreted protein that is associated with metabolic dysfunction in obesity. Impaired angiogenesis in fat depots has been implicated in the development of adipose tissue capillary rarefaction, hypoxia, inflammation, and metabolic dysfunction. We have recently demonstrated that impaired adipose tissue angiogenesis is associated with overexpression of antiangiogenic factor VEGF-A165b in human fat and the systemic circulation. In the present study, we postulated that upregulation of WNT5A is associated with angiogenic dysfunction and examined its role in regulating VEGF-A165b expression in human obesity. We biopsied subcutaneous and visceral adipose tissue from 38 obese individuals (body mass index: 44 ± 7 kg/m2, age: 37 ± 11 yr) during planned bariatric surgery and characterized depot-specific protein expression of VEGF-A165b and WNT5A using Western blot analysis. In both subcutaneous and visceral fat, VEGF-A165b expression correlated strongly with WNT5A protein (r = 0.9, P < 0.001). In subcutaneous adipose tissue where angiogenic capacity is greater than in the visceral depot, exogenous human recombinant WNT5A increased VEGF-A165b expression in both whole adipose tissue and isolated vascular endothelial cell fractions (P < 0.01 and P < 0.05, respectively). This was associated with markedly blunted angiogenic capillary sprout formation in human fat pad explants. Moreover, recombinant WNT5A increased secretion of soluble fms-like tyrosine kinase-1, a negative regulator of angiogenesis, in the sprout media (P < 0.01). Both VEGF-A165b-neutralizing antibody and secreted frizzled-related protein 5, which acts as a decoy receptor for WNT5A, significantly improved capillary sprout formation and reduced soluble fms-like tyrosine kinase-1 production (P < 0.05). We demonstrated a significant regulatory nexus between WNT5A and antiangiogenic VEGF-A165b in the adipose tissue of obese subjects that was linked to angiogenic dysfunction. Elevated WNT5A expression in obesity may function as a negative regulator of angiogenesis.NEW & NOTEWORTHY Wingless-related integration site 5a (WNT5A) negatively regulates adipose tissue angiogenesis via VEGF-A165b in human obesity.

Biology and therapeutic implications of VEGF-A splice isoforms and single-nucleotide polymorphisms in colorectal cancer

Tumor growth, dissemination and metastasis are dependent on angiogenesis. The predominant vascular endothelial growth factor (VEGF) isoform that plays a major role in angiogenesis is VEGF-A. Indeed, VEGF-A is implicated in promoting angiogenesis of numerous solid malignancies, including colorectal cancer (CRC). A large body of preclinical and clinical evidence indicates that the expression of specific VEGF-A isoforms represents a predominant pro-angiogenic factor, which is associated with formation of metastases and poor prognosis in CRC patients. Different isoforms of human VEGF-A have been identified, all of which arise from alternative splicing of the primary transcript of a single gene. Notably, it has been recently demonstrated that expression of type 3 isoform pattern is significantly correlated with venous involvement in CRC as well as in progression to metastatic colorectal cancer (mCRC), although it remains unclear what proportion of CRC tumors express these isoforms. This review highlights the importance of investigating the genetic and the epigenetic variations in VEGF-A pathways in CRC, the functions of different VEGF-A isoforms and their potential application as prognostic markers and/or therapeutic targets. Better understanding of the mechanisms controlling angiogenesis in liver metastases is necessary to address the limitations of current anti-angiogenic therapies.

B-Type natriuretic peptide suppression of neutrophil superoxide generation: mechanistic studies in normal subjects

Many acute cardiovascular disease states are associated with neutrophil infiltration of myocardium and subsequent release of superoxide (O2 (-) ) and myeloperoxidase (MPO), which contribute to inflammatory reactions. B-Type natriuretic peptide (BNP) is known to exert anti-inflammatory and antifibrotic effects, but it is not known whether these may include interactions with neutrophils. In neutrophils isolated from 20 healthy subjects, we assessed the effect of BNP on the 'neutrophil burst' (O2 (-) production and MPO release) stimulated by phorbol myristate acetate (PMA) and N-formyl-methionyl-leucyl-phenylalanine (fMLP), respectively. Effects of BNP on cGMP accumulation, and the effects of the cell-permeable cGMP analogue 8-(4-chlorophenylthio) guanosine-cGMP (8-p-CPT-cGMP) and protein kinase G (PKG) inhibition with KT5823 on the neutrophil-BNP interaction were also evaluated. B-Type natriuretic peptide suppressed O2 (-) release from neutrophils by 23 ± 6% (P < 0.001) and 24 ± 8% (P < 0.05) following PMA and fMLP stimulation, respectively. Although BNP did not significantly increase cGMP formation, 8-p-CPT-cGMP suppressed both PMA- and fMLP-induced neutrophil O2 (-) release by 16% and 28%, respectively (P < 0.05). The PKG inhibitor KT5823 attenuated the effects of BNP on both fMLP- and PMA-associated O2 (-) production. Neither BNP nor 8-p-CPT-cGMP significantly affected MPO release from neutrophils. Suppression of O2 (-) release from neutrophils by BNP may contribute to its anti-inflammatory and antifibrotic actions.

Forkhead box O-1 modulation improves endothelial insulin resistance in human obesity

OBJECTIVE

Increased visceral adiposity has been closely linked to insulin resistance, endothelial dysfunction, and cardiometabolic disease in obesity, but pathophysiological mechanisms are poorly understood. We sought to investigate mechanisms of vascular insulin resistance by characterizing depot-specific insulin responses and gain evidence that altered functionality of transcription factor forkhead box O-1 (FOXO-1) may play an important role in obesity-related endothelial dysfunction.

APPROACH AND RESULTS

We intraoperatively collected paired subcutaneous and visceral adipose tissue samples from 56 severely obese (body mass index, 43 ± 7 kg/m(2)) and 14 nonobese subjects during planned surgical operations, and characterized depot-specific insulin-mediated responses using Western blot and quantitative immunofluorescence techniques. Insulin signaling via phosphorylation of FOXO-1 and consequent endothelial nitric oxide synthase stimulation was selectively impaired in the visceral compared with subcutaneous adipose tissue and endothelial cells of obese subjects. In contrast, tissue actions of insulin were preserved in nonobese individuals. Pharmacological antagonism with AS1842856 and biological silencing using small interfering RNA-mediated FOXO-1 knockdown reversed insulin resistance and restored endothelial nitric oxide synthase activation in the obese.

CONCLUSIONS

We observed profound endothelial insulin resistance in the visceral adipose tissue of obese humans which improved with FOXO-1 inhibition. FOXO-1 modulation may represent a novel therapeutic target to diminish vascular insulin resistance. In addition, characterization of endothelial insulin resistance in the adipose microenvironment may provide clues to mechanisms of systemic disease in human obesity.

Suppression of neutrophil superoxide generation by BNP is attenuated in acute heart failure: a case for 'BNP resistance'

AIMS

The release of the B-type natriuretic peptide (BNP) is increased in heart failure (HF), a condition associated with oxidative stress. BNP is known to exert anti-inflammatory effects including suppression of neutrophil superoxide (O2(-)) release. However, BNP-based restoration of homeostasis in HF is inadequate, and the equivocal clinical benefit of a recombinant BNP, nesiritide, raises the possibility of attenuated response to BNP. We therefore tested the hypothesis that BNP-induced suppression of neutrophil O2(-) generation is impaired in patients with acute HF.

METHODS AND RESULTS

We have recently characterized suppression of neutrophil O2(-) generation (PMA- or fMLP-stimulated neutrophil burst) by BNP as a measure of its physiological activity. In the present study, BNP response was compared in neutrophils of healthy subjects (n = 29) and HF patients (n = 45). Effects of BNP on fMLP-induced phosphorylation of the NAD(P)H oxidase subunit p47phox were also evaluated. In acute HF patients, the suppressing effect of BNP (1 µmol/L) on O2(-) generation was attenuated relative to that in healthy subjects (P < 0.05 for both PMA and fMLP). Analogously, BNP inhibited p47phox phosphorylation in healthy subjects but not in HF patients (P < 0.05). However, O2(-)-suppressing effects of the cell-permeable cGMP analogue (8-pCPT-cGMP) were preserved in acute HF. Conventional HF treatment for 5 weeks partially restored neutrophil BNP responsiveness (n = 25, P < 0.05), despite no significant decrease in plasma NT-proBNP levels.

CONCLUSIONS

BNP inhibits neutrophil O2(-) generation by suppressing NAD(P)H oxidase assembly. This effect is impaired in acute HF patients, with partial recovery during treatment.

Impaired platelet nitric oxide response in patients with new onset atrial fibrillation

BACKGROUND

Clinical factors associated with thromboembolic risk in AF patients are well characterized and include new onset AF. Biochemically, AF is associated with inflammatory activation and impairment of nitric oxide (NO) signalling, which may also predispose to thromboembolism: the bases for variability in these anomalies have not been identified. We therefore sought to identify correlates of impaired platelet NO signalling in patients hospitalized with atrial fibrillation (AF), and to evaluate the impact of acuity of AF.

METHODS

87 patients hospitalized with AF were evaluated. Platelet aggregation, and its inhibition by the NO donor sodium nitroprusside, was evaluated using whole blood impedance aggregometry. Correlates of impaired NO response were examined and repeated in a "validation" cohort of acute cardiac illnesses.

RESULTS

Whilst clinical risk scores were not significantly correlated with integrity of NO signalling, new onset AF was associated with impaired NO response (6 ± 5% inhibition versus 25 ± 4% inhibition for chronic AF, p<0.01). New onset AF was a multivariate correlate (p<0.01) of impaired NO signalling, along with platelet ADP response (p<0.001), whereas the associated tachycardia was not. Platelet ADP response was predicted by elevation of plasma thrombospondin-1 concentrations (p<0.01). Validation cohort evaluations confirmed that acute AF was associated with significant (p<0.05) impairment of platelet NO response, and that neither acute heart failure nor acute coronary syndromes were associated with similar impairment.

CONCLUSION

Recent onset of AF is associated with marked impairment of platelet NO response. These findings may contribute to thromboembolic risk in such patients.

Aging of the nitric oxide system: are we as old as our NO?

Background

Impaired generation and signaling of nitric oxide (NO) contribute substantially to cardiovascular (CV) risk (CVR) associated with hypertension, hyperlipidemia, and diabetes mellitus. In our rapidly aging society, advanced age is, in itself, a consistent and independent CVR factor. Many processes involved in aging are modulated by NO. We therefore postulated that aging might be independently associated with impaired NO signaling.

Methods and Results

In a prospective cohort study of 204 subjects (mean age 63±6 at study entry), we evaluated the effects of 4 years of aging on parameters of NO generation and effect, including platelet aggregability and responsiveness to NO, and plasma concentrations of the NO synthase inhibitor, asymmetric dimethylarginine (ADMA). Clinical history, lipid profile, high‐sensitivity C‐reactive protein, routine biochemistry, and 25‐hydroxyvitamin D levels were obtained at study entry and after 4 years of follow‐up. Aging was associated with marked deterioration of responsiveness of platelets to NO (P<0.0001) and increases in plasma ADMA concentrations (P<0.0001). There was a significant correlation between changes in these parameters over time (r=0.2; P=0.013). On multivariable analyses, the independent correlates of deterioration of responsiveness of platelets to NO were female gender (β=0.17; P=0.034) and low vitamin D concentrations (β=0.16; P=0.04), whereas increases in ADMA were associated with presence of diabetes (β=0.16; P=0.03) and impaired renal function (β=0.2; P=0.004).

Conclusions

Aging is associated with marked impairment of determinants of NO generation and effect, to an extent which is commensurate with adverse impact on CV outcomes. This deterioration represents a potential target for therapeutic interventions.

Antiangiogenic actions of vascular endothelial growth factor-A165b, an inhibitory isoform of vascular endothelial growth factor-A, in human obesity

BACKGROUND

Experimental studies suggest that visceral adiposity and adipose tissue dysfunction play a central role in obesity-related cardiometabolic complications. Impaired angiogenesis in fat has been implicated in the development of adipose tissue hypoxia, capillary rarefaction, inflammation, and metabolic dysregulation, but pathophysiological mechanisms remain unknown. In this study, we examined the role of a novel antiangiogenic isoform of vascular endothelial growth factor-A (VEGF-A), VEGF-A165b, in human obesity.

METHODS AND RESULTS

We biopsied paired subcutaneous and visceral adipose tissue in 40 obese subjects (body mass index, 45±8 kg/m(2); age, 45±11 years) during bariatric surgery and characterized depot-specific adipose tissue angiogenic capacity using an established ex vivo assay. Visceral adipose tissue exhibited significantly blunted angiogenic growth compared with subcutaneous fat (P<0.001) that was associated with marked tissue upregulation of VEGF-A165b (P=0.004). The extent of VEGF-A165b expression correlated negatively with angiogenic growth (r=-0.6, P=0.006). Although recombinant VEGF-A165b significantly impaired angiogenesis, targeted inhibition of VEGF-A165b with neutralizing antibody stimulated fat pad neovascularization and restored VEGF receptor activation. Blood levels of VEGF-A165b were significantly higher in obese subjects compared with lean control subjects (P=0.02), and surgical weight loss induced a marked decline in serumVEGF-A165b (P=0.003).

CONCLUSIONS

We demonstrate that impaired adipose tissue angiogenesis is associated with overexpression of a novel antiangiogenic factor, VEGF-A165b, that may play a pathogenic role in human adiposopathy. Moreover, systemic upregulation of VEGF-A165b in circulating blood may have wider-ranging implications beyond the adipose milieu. VEGF-A165b may represent a novel area of investigation to gain further understanding of mechanisms that modulate the cardiometabolic consequences of obesity.

The nitric oxide redox sibling nitroxyl partially circumvents impairment of platelet nitric oxide responsiveness

Impaired platelet responsiveness to nitric oxide (NO resistance) is a common characteristic of many cardiovascular disease states and represents an independent risk factor for cardiac events and mortality. NO resistance reflects both scavenging of NO by superoxide (O2(-)), and impairment of the NO receptor, soluble guanylate cyclase (sGC). There is thus an urgent need for circumvention of NO resistance in order to improve clinical outcomes. Nitroxyl (HNO), like NO, produces vasodilator and anti-aggregatory effects, largely via sGC activation, but is not inactivated by O2(-). We tested the hypothesis that HNO circumvents NO resistance in human platelets. In 57 subjects with or without ischemic heart disease, platelet responses to the HNO donor isopropylamine NONOate (IPA/NO) and the NO donor sodium nitroprusside (SNP) were compared. While SNP (10μM) induced 29±3% (p<0.001) inhibition of platelet aggregation, IPA/NO (10μM) caused 75±4% inhibition (p<0.001). In NO-resistant subjects (n=28), the IPA/NO:SNP response ratio was markedly increased (p<0.01), consistent with partial circumvention of NO resistance. Similarly, cGMP accumulation in platelets was greater (p<0.001) with IPA/NO than with SNP stimulation. The NO scavenger carboxy-PTIO (CPTIO, 200μM) inhibited SNP and IPA/NO responses by 92±7% and 17±4% respectively (p<0.001 for differential inhibition), suggesting that effects of IPA/NO are only partially NO-mediated. ODQ (10μM) inhibited IPA/NO responses by 36±8% (p<0.001), consistent with a contribution of sGC/haem to IPA/NO inhibition of aggregation. There was no significant relationship between whole blood ROS content and IPA/NO responses. Thus the HNO donor IPA/NO substantially circumvents platelet NO resistance while acting, at least partially, as a haem-mediated sGC activator.

Reciprocal regulation of NO signaling and TXNIP expression in humans: impact of aging and ramipril therapy

BACKGROUND

Impaired tissue responsiveness to nitric oxide (NO) occurs in many cardiovascular diseases as well as with advanced age and is a correlate of poor outcomes. This phenomenon results from oxidative stress, with NO "scavenging" and dysfunction of soluble guanylate cyclase (sGC). Thioredoxin-interacting protein (TXNIP) is a major intracellular regulator of inflammatory activation and redox stress, but its interactions with NO/sGC are poorly understood. We have now evaluated the relationship between platelet TXNIP expression and function of the NO/sGC axis in subjects of varying age and during therapy with ramipril.

METHODS & RESULTS

Young (n=42) and aging (n=49) subjects underwent evaluation of platelet TXNIP content. Aging subjects additionally had measurements of platelet NO responsiveness and routine biochemistry. Platelet TXNIP content was greater (376±33 units) in the aging compared to younger subjects (289±13 units; p<0.05). In the aging subjects there was a significant negative correlation (r=-0.50, p<0.001) between platelet TXNIP content and NO responsiveness. In a separate cohort of 15 subjects two week treatment with ramipril, which reversed platelet NO resistance and potentiated sGC activity, also decreased platelet TXNIP content by 40% (p=0.011).

CONCLUSIONS

Platelet TXNIP content increases with aging, varies inversely with responsiveness to NO, and diminishes rapidly following treatment with ramipril. These data suggest that TXNIP-induced oxidative stress may be a critical modulator of tissue resistance to NO, a fundamental basis for cardiovascular disease. Analogously suppression of TXNIP expression can potentially be utilized as an index of restoration of cardiovascular homeostasis.

Vitamin D(2) supplementation induces the development of aortic stenosis in rabbits: interactions with endothelial function and thioredoxin-interacting protein

Understanding of the pathophysiology of aortic valve stenosis (AVS) and finding potentially effective treatments are impeded by the lack of suitable AVS animal models. A previous study demonstrated the development of AVS in rabbits with vitamin D(2) and cholesterol supplementation without any hemodynamic changes in the cholesterol supplemented group alone. The current study aimed to determine whether AVS develops in an animal model with vitamin D(2) supplementation alone, and to explore pathophysiological mechanisms underlying this process. The effects of 8 weeks' treatment with vitamin D(2) alone (n=8) at 25,000 IU/4 days weekly on aortic valve structure and function were examined in male New Zealand white rabbits. Echocardiographic aortic valve backscatter (AV(BS)), transvalvular velocity, and transvalvular pressure gradient were utilized to quantitate changes in valve structure and function. Valvular histology/immunochemistry and function were examined after 8 weeks. Changes in valves were compared with those in endothelial function and in valvular measurement of thioredoxin-interacting protein (TXNIP), a marker/mediator of reactive oxygen species-induced oxidative stress. Vitamin D(2) treated rabbits developed AVS with increased AV(BS) (17.6+/-1.4 dB vs 6.7+/-0.8 dB, P<0.0001), increased transvalvular velocity and transvalvular pressure gradient (both P<0.01 via 2-way ANOVA) compared to the control group. There was associated valve calcification, lipid deposition and macrophage infiltration. Endothelial function was markedly impaired, and intravalvular TXNIP concentration increased. In this model, vitamin D(2) induces the development of AVS with histological features similar to those of early AVS in humans and associated endothelial dysfunction/redox stress. AVS development may result from the loss of nitric oxide suppression of TXNIP expression.

Aortic stenosis is associated with elevated plasma levels of asymmetric dimethylarginine (ADMA)

OBJECTIVES

We tested the hypothesis that the presence of aortic stenosis (AS) is associated with elevation of plasma levels of asymmetric dimethylarginine (ADMA), a physiological inhibitor of nitric oxide synthase, a mediator and marker of endothelial dysfunction and an indicator of incremental cardiovascular risk.

BACKGROUND

The presence of aortic sclerosis (ASC), the precursor of AS is independently associated both with endothelial dysfunction, and with incremental coronary event risk. It remains uncertain whether elevations of ADMA levels might mediate endothelial dysfunction in these conditions.

METHODS

Forty two consecutive patients referred for echocardiography for evaluation of AS, who had calculated aortic valve areas of <1.4 cm(2) (AS group) were evaluated together with 42 consecutive age-matched referred patients (non-AS group). Plasma ADMA levels were measured by high-performance liquid chromatography (HPLC). Determinants of elevation of plasma ADMA levels were identified via stepwise multiple linear regression analysis.

RESULTS

Plasma ADMA levels were not statistically different between the AS and non-AS group (median 0.59 vs 0.54 micromol/L, p=0.13, Mann-Whitney test) on univariate analysis. However, in backward stepwise multiple linear regression, the presence of AS was a significant predictor of elevated ADMA levels (p=0.04, 95% CI=0.001, 0.072). In addition, elevated plasma ADMA levels were also associated with history of atrial fibrillation (p=0.009, 95% CI=0.015, 0.100), and negatively associated with creatinine clearance (p=0.01, 95% CI=-0.002, 0.000), and the use of statin therapy (p=0.01, 95% CI=-0.081, -0.011).

CONCLUSIONS

AS is independently associated with elevation of ADMA levels, beyond that implied by "conventional" risk factors for endothelial dysfunction. The clinical status of AS as an incremental marker of cardiovascular risk may reflect ADMA-mediated endothelial dysfunction.

Quantitative assessment of aortic sclerosis using ultrasonic backscatter

BACKGROUND

The development of therapeutic interventions to prevent progressive valve damage is more likely to limit the progression of structural damage to the aortic valve with normal function (aortic sclerosis [ASC]) than clinically apparent aortic stenosis. Currently, the ability to appreciate the progression of ASC is compromised by the subjective and qualitative evaluation of sclerosis severity.

METHODS

We sought to reveal whether the intensity of ultrasonic backscatter could be used to quantify sclerosis severity in 26 patients with ASC and 23 healthy young adults. Images of the aortic valve were obtained in the parasternal long-axis view and saved in raw data format. Six square-shaped 11 x 11 pixel regions of interest were placed on the anterior and posterior leaflets, and calibrated backscatter values were obtained by subtracting the regions of interest in the blood pool from the averaged backscatter values obtained from the leaflets.

RESULTS

Mean ultrasonic backscatter values for sclerotic valves exceeded the results in normal valve tissue (16.3 +/- 4.4 dB vs 9.8 +/- 3.3 dB, P < .0001). Backscatter values were greater (22.0 +/- 3.5 dB) in a group of 6 patients with aortic stenosis. Within the sclerosis group, the magnitude of backscatter was directly correlated (P < .05) with a subjective sclerosis score, and with transvalvular pressure gradient. Mean reproducibility was 2.4 +/- 1.8 dB (SD) between observers, and 2.3 +/- 1.7 dB (SD) between examinations.

CONCLUSION

Measurement of backscatter from the valve leaflets of patients with ASC may be a feasible means of following the progression and treatment response of aortic sclerosis.