Cardiac steatosis and left ventricular function in men with metabolic syndrome

Central Obesity is Associated with Increased Left Ventricular Maximal Wall Thickness and Intrathoracic Adipose Tissue Measured with Cardiac Magnetic Resonance

INTRODUCTION

Central obesity (CO), characterized by an increased waist circumference increases the risk of cardiovascular disease (CVD) and morbidity, yet the underlying mechanisms are not fully understood. CO is often associated with general obesity, hypertension, and abnormal glucose tolerance, confounding the independent contribution of CO to CVD.

AIM

We investigated the relationship of CO (without associated disorders) with left ventricular (LV) characteristics and intrathoracic adipose tissue (IAT) by cardiac magnetic resonance.

METHODS

LV characteristics, epicardial (EAT), and mediastinal adipose tissue (MAT) were measured from 29 normoglycemic, normotensive males with CO but without general obesity (waist circumference >100 cm, body mass index (BMI) <30 kg/m2) and 18 non-obese male controls.

RESULTS

LV maximal wall thickness (LVMWT) and IAT but not LV mass or volumes were increased in CO subjects compared to controls (LVMWT, 12.3±1.2 vs. 10.7±1.5 mm, p < 0.001; EAT, 5.5±3.0 vs. 2.2±2.0 cm2, p = 0.001; MAT, 31.0±12.8 vs. 15.4±10.7 cm2, p < 0.001). The LVMWT was ≥12 mm in 69% of subjects with CO and 22% of controls (p = 0.002). In CO suspects, EAT correlated inversely with LV end-diastolic volume index (r = - 0.403, p = 0.037) and LV stroke volume (SV) (r = - 0.425, p = 0.027). MAT correlated inversely with SV (r = - 0.427, p=0.026) and positively with LVMWT (r = 0.399, p = 0.035). Among CO subjects, the waist-to-hip ratio (WHR) was an independent predictor of LVMWT (B = 22.4, β = 0.617, p < 0.001). The optimal cut-off with Youden's index for LV hypertrophy was identified at WHR 0.98 (sensitivity 85%, specificity 89%).

CONCLUSIONS

CO independent of BMI is associated with LV hypertrophy and intrathoracic adipose tissue contributing to cardiovascular burden.

Myocardial steatosis across the spectrum of human health and disease

Preclinical data strongly suggest that myocardial steatosis leads to adverse cardiac remodelling and left ventricular dysfunction. Using 1 H cardiac magnetic resonance spectroscopy, similar observations have been made across the spectrum of health and disease. The purpose of this brief review is to summarize these recent observations. We provide a brief overview of the determinants of myocardial triglyceride accumulation, summarize the current evidence that myocardial steatosis contributes to cardiac dysfunction, and identify opportunities for further research.

Effect of Metabolic Dysfunction-Associated Fatty Liver Disease on Left Ventricular Deformation and Atrioventricular Coupling in Patients With Metabolic Syndrome Assessed by MRI

BACKGROUND

Metabolic dysfunction-associated fatty liver disease (MAFLD) was recently recognized as an important risk factor for cardiovascular diseases.

PURPOSE

To examine the effect of MAFLD on cardiac function in metabolic syndrome by MRI.

STUDY TYPE

Retrospective.

POPULATION

One hundred seventy-nine patients with metabolic syndrome (MetS), 101 with MAFLD (MAFLD [+]) and 78 without (MAFLD [-]). Eighty-one adults without any of the components of MetS or cardiac abnormalities were included as control group.

FIELD STRENGTH/SEQUENCE

3.0 T; balanced steady-state free precession sequence.

ASSESSMENT

Left atrial (LA) strain was assessed during three phases: reservoir strain (LA-RS), conduit strain (LA-CS), and booster strain (LA-BS). Left ventricular (LV) global longitudinal (LV-GLS) strain was also derived. The left atrioventricular coupling index (LACI) was calculated as the ratio of LA end-diastolic volume (LA-EDV) and LV-EDV.

STATISTICAL TESTS

Student's t test or Mann-Whitney U test; One-way analysis of variance. A P value <0.05 was considered statistically significant.

RESULTS

Among MetS patients, individuals with MAFLD had significantly lower magnitude LV-GLS (-11.6% ± 3.3% vs. -13.8% ± 2.7%) than those without MAFLD. For LA strains, LA-RS (36.9% ± 13.7% vs. 42.9% ± 13.5%) and LA-CS (20.0% ± 10.6% vs. 24.1% ± 9.2%) were also significantly reduced in MAFLD (+) compared to MAFLD (-). The LACIs (17.2% [12.9-21.2] % vs. 15.8% [12.2-19.7] %) were significantly higher in patients with MAFLD compared to those without MAFLD. After adjustment for other clinical factors, MAFLD was found to be independently correlated with LV-GLS (β = -0.270) and LACI (β = 0.260).

DATA CONCLUSION

MAFLD had an unfavorable effect on LV myocardial strain in MetS. Moreover, LA strain and atrioventricular coupling were further impaired in patients with concomitant MAFLD compared to those without MAFLD. Last, MAFLD was independently associated with subclinical LV dysfunction and atrioventricular coupling after adjustment for other clinical factors.

EVIDENCE LEVEL

3 TECHNICAL EFFICACY: 3.

Cardiac lipid metabolism, mitochondrial function, and heart failure

A fine balance between uptake, storage, and the use of high energy fuels, like lipids, is crucial in the homeostasis of different metabolic tissues. Nowhere is this balance more important and more precarious than in the heart. This highly energy-demanding muscle normally oxidizes almost all the available substrates to generate energy, with fatty acids being the preferred source under physiological conditions. In patients with cardiomyopathies and heart failure, changes in the main energetic substrate are observed; these hearts often prefer to utilize glucose rather than oxidizing fatty acids. An imbalance between uptake and oxidation of fatty acid can result in cellular lipid accumulation and cytotoxicity. In this review, we will focus on the sources and uptake pathways used to direct fatty acids to cardiomyocytes. We will then discuss the intracellular machinery used to either store or oxidize these lipids and explain how disruptions in homeostasis can lead to mitochondrial dysfunction and heart failure. Moreover, we will also discuss the role of cholesterol accumulation in cardiomyocytes. Our discussion will attempt to weave in vitro experiments and in vivo data from mice and humans and use several human diseases to illustrate metabolism gone haywire as a cause of or accomplice to cardiac dysfunction.

A Comprehensive Insight and Mechanistic Understanding of the Lipidomic Alterations Associated With DCM

Dilated cardiomyopathy (DCM) is one of the major causes of heart failure characterized by the enlargement of the left ventricular cavity and contractile dysfunction of the myocardium. Lipids are the major sources of energy for the myocardium. Impairment of lipid homeostasis has a potential role in the pathogenesis of DCM. In this review, we have summarized the role of different lipids in the progression of DCM that can be considered as potential biomarkers. Further, we have also explained the mechanistic pathways followed by the lipid molecules in disease progression along with the cardioprotective role of certain lipids. As the global epidemiological status of DCM is alarming, it is high time to define some disease-specific biomarkers with greater prognostic value. We are proposing an adaptation of a system lipidomics-based approach to profile DCM patients in order to achieve a better diagnosis and prognosis of the disease.

Is increased myocardial triglyceride content associated with early changes in left ventricular function? A 1H-MRS and MRI strain study

Background

Type 2 diabetes (T2D) and obesity induce left ventricular (LV) dysfunction. The underlying pathophysiological mechanisms remain unclear, but myocardial triglyceride content (MTGC) could be involved.

Objectives

This study aimed to determine which clinical and biological factors are associated with increased MTGC and to establish whether MTGC is associated with early changes in LV function.

Methods

A retrospective study was conducted using five previous prospective cohorts, leading to 338 subjects studied, including 208 well-phenotyped healthy volunteers and 130 subjects living with T2D and/or obesity. All the subjects underwent proton magnetic resonance spectroscopy and feature tracking cardiac magnetic resonance imaging to measure myocardial strain.

Results

MTGC content increased with age, body mass index (BMI), waist circumference, T2D, obesity, hypertension, and dyslipidemia, but the only independent correlate found in multivariate analysis was BMI (p=0.01; R²=0.20). MTGC was correlated to LV diastolic dysfunction, notably with the global peak early diastolic circumferential strain rate (r=-0.17, p=0.003), the global peak late diastolic circumferential strain rate (r=0.40, p<0.0001) and global peak late diastolic longitudinal strain rate (r=0.24, p<0.0001). MTGC was also correlated to systolic dysfunction via end-systolic volume index (r=-0.34, p<0.0001) and stroke volume index (r=-0.31, p<0.0001), but not with longitudinal strain (r=0.009, p=0.88). Interestingly, the associations between MTGC and strain measures did not persist in multivariate analysis. Furthermore, MTGC was independently associated with LV end-systolic volume index (p=0.01, R²=0.29), LV end-diastolic volume index (p=0.04, R²=0.46), and LV mass (p=0.002, R²=0.58).

Conclusions

Predicting MTGC remains a challenge in routine clinical practice, as only BMI independently correlates with increased MTGC. MTGC may play a role in LV dysfunction but does not appear to be involved in the development of subclinical strain abnormalities.

Fetal 3D cardiovascular cine image acquisition using radial sampling and compressed sensing

PURPOSE

To explore a fetal 3D cardiovascular cine acquisition using a radial image acquisition and compressed-sensing reconstruction and compare image quality and scan time with conventional multislice 2D imaging.

METHODS

Volumetric fetal cardiac data were acquired in 26 volunteers using a radial 3D balanced SSFP pulse sequence. Cardiac gating was performed using a Doppler ultrasound device. Images were reconstructed using a parallel-imaging and compressed-sensing algorithm. Multiplanar reformatting to standard cardiac views was performed before image analysis. Clinical 2D images were used for comparison. Qualitative and quantitative image evaluation were performed by two experienced observers (scale: 1-4). Volumes, mass, and function were assessed.

RESULTS

Average scan time for the 3D imaging was 6 min, including one localizer. A 2D imaging stack covering the entire heart including localizer sequences took at least 6.5 min, depending on planning complexity. The 3D acquisition was successful in 7 of 26 subjects (27%). Overall image contrast and perceived resolution were lower in the 3D images. Nonetheless, the 3D images had, on average, a moderate cardiac diagnostic quality (median [range]: 3 [1-4]). Standard clinical 2D acquisitions had a high cardiac diagnostic quality (median [range]: 4 [3, 4]). Cardiac measurements were not different between 2D and 3D images (all p > 0.16).

CONCLUSION

The presented free-breathing whole-heart fetal 3D radial cine MRI acquisition and reconstruction method enables retrospective visualization of all cardiac views while keeping examination times short. This proof-of-concept work produced images with diagnostic quality, while at the same time reducing the planning complexity to a single localizer.

Gender Differences and Cardiometabolic Risk: The Importance of the Risk Factors

Metabolic syndrome (Mets) is a clinical condition characterized by a cluster of major risk factors for cardiovascular disease (CVD) and type 2 diabetes: proatherogenic dyslipidemia, elevated blood pressure, dysglycemia, and abdominal obesity. Each risk factor has an independent effect, but, when aggregated, they become synergistic, doubling the risk of developing cardiovascular diseases and causing a 1.5-fold increase in all-cause mortality. We will highlight gender differences in the epidemiology, etiology, pathophysiology, and clinical expression of the aforementioned Mets components. Moreover, we will discuss gender differences in new biochemical markers of metabolic syndrome and cardiovascular risk.

Implicazioni cliniche extraglicemiche dell’insulino-resistenza

L’insulino-resistenza si definisce come un’alterazione del processo di trasduzione del segnale dell’insulina, per cui concentrazioni di insulina normali o aumentate producono un effetto biologico attenuato. Ciò spesso determina un’iperinsulinemia compensatoria. Considerati i suoi effetti biologici, l’insulino-resistenza si manifesta con un quadro clinico variabile, noto come Sindrome da insulino-resistenza, che include alterazioni metaboliche, obesità viscerale, danno d’organo e associazione con altre patologie: sindrome dell’ovaio policistico (PCOS), sindrome delle apnee ostruttive del sonno (OSAS), malattie neurodegenerative, patologie neoplastiche.

Association of body mass index with left ventricular diastolic dysfunction among ambulatory individuals with diabetes mellitus in rural Uganda: a cross-sectional study

Background

Left ventricular diastolic dysfunction (LVDD) is a recognized complication of diabetes mellitus that precedes and is a risk factor for heart failure. We aimed to determine the prevalence of LVDD and its association with body mass index in ambulatory adults with diabetes mellitus in rural Uganda.

Methods

We conducted a cross-sectional study, over 5 months, to enroll 195 ambulatory Ugandan adults living with diabetes mellitus for at least five years at Mbarara Regional Referral Hospital. We collected demographic, and clinical data and measured body mass index (BMI). Echocardiography was performed to determine LVDD by assessing the mitral inflow ventricular filling velocities (E/A and E/è ratios), tricuspid regurgitant jet peak velocity, and left atrium maximum volume index. We used logistic regression to estimate the odds ratio for the association of LVDD with BMI and evaluated the variation of associations by age and hypertension status.

Results

Of the 195 participants, 141 (72.31%) were female, the mean age was 62 [standard deviation, 11.50] years, and the median duration of diabetes diagnosis was 10 [interquartile range, 7, 15] years. Eighty-six percent (n = 168) had LVDD with the majority (n = 127, 65.1%) of participants in the grade 1 category of LVDD. In the adjusted model, the odds of LVDD for each 1 kg/m² increase in BMI was 1.11 [95% confidence interval 1.00, 1.25, p = 0.04]. The adjusted odds of LVDD among individuals aged ≥ 50 years with BMI ≥ 25 kg/m² was 13.82 times the odds of LVDD in individuals aged < 50 years with BMI < 25 kg/m².

Conclusion

LVDD is prevalent and positively associated with BMI among ambulatory Ugandan adults living with diabetes mellitus for at least five years. The association was higher for older overweight/obese than younger individuals with normal weight. Future studies should focus on the effect of weight loss on LVDD as a possible target for the prevention of heart failure.

Metabolite-cycled echo-planar spectroscopic imaging of the human heart

Purpose

Spectroscopic imaging could provide insights into regional cardiac triglyceride variations, but is hampered by relatively long scan times. It is proposed to synergistically combine echo‐planar spectroscopic imaging (EPSI) with motion‐adapted gating, weighted acquisition and metabolite cycling to reduce scan times to less than 10 min while preserving spatial‐spectral quality. The method is compared to single‐voxel measurements and to metabolite‐cycled EPSI with conventional acquisition for assessing triglyceride‐to‐water (TG/W) ratios in the human heart.

Methods

Measurements were performed on 10 healthy volunteers using a clinical 1.5T system. EPSI data was acquired both without and with motion‐adapted gating in combination with weighted acquisition to assess TG/W ratios and relative Cramér‐Rao lower bounds (CRLB) of TG. For comparison, single‐voxel (PRESS) spectra were acquired in the interventricular septum.

Results

Bland–Altman analyses did not show a significant bias in TG/W when comparing both metabolite‐cycled EPSI methods to PRESS for any of the cardiac segments. Scan time was 8.05 ± 2.06 min and 17.91 ± 3.93 min for metabolite‐cycled EPSI with and without motion‐adapted gating and weighted acquisition, respectively, while relative CRLB of TG did not differ significantly between the two methods for any of the cardiac segments.

Conclusions

Metabolite‐cycled EPSI with motion‐adapted gating and weighted acquisition allows detecting TG/W ratios in different regions of the in vivo human heart. Scan time is reduced by more than 2‐fold to less than 10 min as compared to conventional acquisition, while keeping the quality of TG fitting constant.

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Lipids and diastolic dysfunction: Recent evidence and findings

AIM

Diastolic dysfunction is the decreased flexibility of the left ventricle due to the impaired ability of the myocardium to relax and plays an important role in the pathogenesis of heart failure. Lipid metabolism is a well-known contributor to cardiac conditions, including ventricular function. In this article, we aimed to review the literature addressing the connections between lipids, their storage, and metabolism with left ventricular diastolic dysfunction.

DATA SYNTHESIS

We searched Google scholar, Pubmed, Embase and Researchgate for our keywords: "Diastolic function", "Fat" and "Lipid profile". Initially, 250 articles were selected by title and 84 of them were chosen as most relevant and directly reviewed.

CONCLUSIONS

Alterations of lipid metabolism in cardiac muscle and cardiac lipid content can occur in many conditions, including consumption of a high-fat diet, obesity, metabolic syndrome, and non-alcoholic fatty liver disease (NAFLD). These conditions induce alterations in myocardial lipid metabolism, increase myocardial fat content and epicardial fat thickness and increase inflammation and oxidative stress which ultimately lead to cardiac lipotoxicity and diastolic dysfunction. The effects of lipids on diastolic function can differ based on gender. Lipid profile and metabolism are as important in the pathogenesis of diastolic dysfunction as they are in other cardiovascular disorders. A more careful look at cardiac lipid metabolism in molecular, histological and gross levels results in more precise understanding of its role in myocardial function and leads to development of potential treatments for diastolic dysfunction.

Longitudinal effect of myocardial fat deposition on left ventricular diastolic function: a retrospective cohort study

There is a known correlation between myocardial steatosis and heart function, but it is unclear how left ventricular diastolic function worsens over time in the myocardial steatosis setting. We sought to investigate whether intramyocardial fat deposition affects diastolic function over time. This was a retrospective analysis of patients who had undergone 1-3 echocardiography assessments between April 2011 and April 2017. Patients were divided into two groups: those with the presence of myocardial fat deposition in the left ventricular myocardium (assessed by having tissue within any 10-mm2 region with computed tomography values between - 190 and - 30 Hounsfield units; + MF), and those with absence of deposition not meeting the threshold (- MF). The rates of change of the standard early diastolic mitral annulus velocity (e') and the transmitral early peak velocity (E)/e' ratio at the second and third echocardiograph assessments were calculated relative to baseline. In total, 125 patients were eligible (+ MF, n = 39; - MF, n = 86) for inclusion. Compared with the - MF group, e' was significantly lower and E/e' was significantly higher in the + MF group at each scan timepoint, even when adjusted for body mass index and sex. A significant average decrease in e' and increase in E/e' was also observed in the + MF group across all scans compared with the - MF group. Myocardial steatosis was associated with an acceleration of decreased left ventricular diastolic function over time.

Role of Epicardial Adipose Tissue in Cardiovascular Diseases: A Review

Simple Summary

Cardiovascular diseases (CVDs) are the leading causes of death worldwide. Epicardial adipose tissue (EAT) is one of the most important risk factors for cardiovascular events and a promising new therapeutic target in CVDs. Here, we summarize the currently available evidence regarding the role of EAT in the development of CVDs, including coronary artery disease, heart failure and atrial fibrillation; compile data regarding the association between EAT’s function and the course of COVID-19; and present new potential therapeutic possibilities, aiming at modifying EAT’s function. The development of novel therapies specifically targeting EAT could revolutionize the prognosis in CVDs.

Abstract

Cardiovascular diseases (CVDs) are the leading causes of death worldwide. Epicardial adipose tissue (EAT) is defined as a fat depot localized between the myocardial surface and the visceral layer of the pericardium and is a type of visceral fat. EAT is one of the most important risk factors for atherosclerosis and cardiovascular events and a promising new therapeutic target in CVDs. In health conditions, EAT has a protective function, including protection against hypothermia or mechanical stress, providing myocardial energy supply from free fatty acid and release of adiponectin. In patients with obesity, metabolic syndrome, or diabetes mellitus, EAT becomes a deleterious tissue promoting the development of CVDs. Previously, we showed an adverse modulation of gene expression in pericoronary adipose tissue in patients with coronary artery disease (CAD). Here, we summarize the currently available evidence regarding the role of EAT in the development of CVDs, including CAD, heart failure, and atrial fibrillation. Due to the rapid development of the COVID-19 pandemic, we also discuss data regarding the association between EAT and the course of COVID-19. Finally, we present the potential therapeutic possibilities aiming at modifying EAT’s function. The development of novel therapies specifically targeting EAT could revolutionize the prognosis in CVDs.

Deep-Learning Segmentation of Epicardial Adipose Tissue Using Four-Chamber Cardiac Magnetic Resonance Imaging

In magnetic resonance imaging (MRI), epicardial adipose tissue (EAT) overload remains often overlooked due to tedious manual contouring in images. Automated four-chamber EAT area quantification was proposed, leveraging deep-learning segmentation using multi-frame fully convolutional networks (FCN). The investigation involved 100 subjects-comprising healthy, obese, and diabetic patients-who underwent 3T cardiac cine MRI, optimized U-Net and FCN (noted FCNB) were trained on three consecutive cine frames for segmentation of central frame using dice loss. Networks were trained using 4-fold cross-validation (n = 80) and evaluated on an independent dataset (n = 20). Segmentation performances were compared to inter-intra observer bias with dice (DSC) and relative surface error (RSE). Both systole and diastole four-chamber area were correlated with total EAT volume (r = 0.77 and 0.74 respectively). Networks' performances were equivalent to inter-observers' bias (EAT: DSCInter = 0.76, DSCU-Net = 0.77, DSCFCNB = 0.76). U-net outperformed (p < 0.0001) FCNB on all metrics. Eventually, proposed multi-frame U-Net provided automated EAT area quantification with a 14.2% precision for the clinically relevant upper three quarters of EAT area range, scaling patients' risk of EAT overload with 70% accuracy. Exploiting multi-frame U-Net in standard cine provided automated EAT quantification over a wide range of EAT quantities. The method is made available to the community through a FSLeyes plugin.

What Is Normal for an Aging Heart?: A Prospective CMR Cohort Study

BACKGROUND

This study aims to investigate normal changes throughout aging of the heart in cardiac magnetic resonance (CMR) imaging in healthy volunteers. While type 2 diabetes mellitus is a frequent finding in the elderly population, also the influence of this circumstance in otherwise healthy persons is part of our study.

METHODS

In this prospective single-center trial, 75 healthy subjects in distinct age groups and 10 otherwise healthy diabetics were enrolled. All subjects underwent functional, flow sensitive, native T2- and T1-mapping in a 1.5T CMR scanner.

RESULTS

No differences in right and left ventricular ejection fractions were observed between aging healthy groups. Bi-ventricular volumes lowered significantly (p<0.001) between the age groups. There was also a significant decrease in myocardial T1 values, aortic distensibility, and left ventricular peak diastolic strain rates. There were no differences in T2 mapping and the other deformation parameters. Patients with type 2 diabetes mellitus had lower end-diastolic volume indexes; all the other measurements were comparable.

CONCLUSIONS

Aging processes in the healthy heart involve a decrease in ventricular volumes, with ejection fractions remaining normal. Stiffening of the myocardium and aorta and a decrease in T1 values are potential indications of age-related remodeling. Type 2 diabetes mellitus seems to have no major influence on aging processes of the heart.

Trial Registration

EudraCT Identifier: EudraCT 2017-000045-42

Crossroads between Estrogen Loss, Obesity, and Heart Failure with Preserved Ejection Fraction

The prevalence of obesity and heart failure with preserved ejection fraction (HFpEF) increases significantly in postmenopausal women. Although obesity is a risk factor for left ventricular diastolic dysfunction (LVDD), the mechanisms that link the cessation of ovarian hormone production, and particularly estrogens, to the development of obesity, LVDD, and HFpEF in aging females are unclear. Clinical, and epidemiologic studies show that postmenopausal women with abdominal obesity (defined by waist circumference) are at greater risk for developing HFpEF than men or women without abdominal obesity. The study presents a review of clinical data that support a mechanistic link between estrogen loss plus obesity and left ventricular remodeling with LVDD. It also seeks to discuss potential cell and molecular mechanisms for estrogen-mediated protection against adverse adipocyte cell types, tissue depots, function, and metabolism that may contribute to LVDD and HFpEF.

The Contribution of Cardiac Fatty Acid Oxidation to Diabetic Cardiomyopathy Severity

Diabetes is a major risk factor for the development of cardiovascular disease via contributing and/or triggering significant cellular signaling and metabolic and structural alterations at the level of the heart and the whole body. The main cause of mortality and morbidity in diabetic patients is cardiovascular disease including diabetic cardiomyopathy. Therefore, understanding how diabetes increases the incidence of diabetic cardiomyopathy and how it mediates the major perturbations in cell signaling and energy metabolism should help in the development of therapeutics to prevent these perturbations. One of the significant metabolic alterations in diabetes is a marked increase in cardiac fatty acid oxidation rates and the domination of fatty acids as the major energy source in the heart. This increased reliance of the heart on fatty acids in the diabetic has a negative impact on cardiac function and structure through a number of mechanisms. It also has a detrimental effect on cardiac efficiency and worsens the energy status in diabetes, mainly through inhibiting cardiac glucose oxidation. Furthermore, accelerated cardiac fatty acid oxidation rates in diabetes also make the heart more vulnerable to ischemic injury. In this review, we discuss how cardiac energy metabolism is altered in diabetic cardiomyopathy and the impact of cardiac insulin resistance on the contribution of glucose and fatty acid to overall cardiac ATP production and cardiac efficiency. Furthermore, how diabetes influences the susceptibility of the myocardium to ischemia/reperfusion injury and the role of the changes in glucose and fatty acid oxidation in mediating these effects are also discussed.

Lipotoxicity: a driver of heart failure with preserved ejection fraction?

Heart failure with preserved ejection fraction (HFpEF) is a growing public health concern, with rising incidence alongside high morbidity and mortality. However, the pathophysiology of HFpEF is not yet fully understood. The association between HFpEF and the metabolic syndrome (MetS) suggests that dysregulated lipid metabolism could drive diastolic dysfunction and subsequent HFpEF. Herein we summarise recent advances regarding the pathogenesis of HFpEF in the context of MetS, with a focus on impaired lipid handling, myocardial lipid accumulation and subsequent lipotoxicity.

Epicardial Fat Expansion in Diabetic and Obese Patients With Heart Failure and Preserved Ejection Fraction-A Specific HFpEF Phenotype

Heart failure with preserved ejection fraction (HFpEF) is a heterogeneous syndrome with diverse etiologies and pathophysiological factors. Obesity and type 2 diabetes mellitus (T2DM), conditions that coexist frequently, induce a cluster of metabolic and non-metabolic signaling derangements which are in favor to induce inflammation, fibrosis, myocyte stiffness, all hallmarks of HFpEF. In contrast to other HFpEF risk factors, obesity and T2DM are often associated with the generation of enlarged epicardial adipose tissue (EAT). EAT acts as an endocrine tissue that may exacerbate myocardial inflammation and fibrosis via various paracrine and vasocrine signals. In addition, an abnormally large EAT poses mechanical stress on the heart via pericardial restrain. HFpEF patients with enlarged EAT may belong to a unique phenotype that can benefit from specific EAT-targeted interventions, including life-style modifications and pharmacologically via statins and fat modifying anti-diabetics drugs; like metformin, sodium-glucose cotransporter 2 inhibitors, or glucagon-like peptide-1 receptor agonists, respectively.

Evidence for human diabetic cardiomyopathy

Growing interest has been accumulated in the definition of worsening effects of diabetes in the cardiovascular system. This is associated with epidemiological data regarding the high incidence of heart failure (HF) in diabetic patients. To investigate the detrimental effects both of hyperglycemia and insulin resistance, a lot of preclinical models were developed. However, the evidence of pathogenic and histological alterations of the so-called diabetic cardiomyopathy (DCM) is still poorly understood in humans. Here, we provide a stringent literature analysis to investigate unique data regarding human DCM. This approach established that lipotoxic-related events might play a central role in the initiation and progression of human DCM. The major limitation in the acquisition of human data is due to the fact of heart specimen availability. Postmortem analysis revealed the end stage of the disease; thus, we need to gain knowledge on the pathogenic events from the early stages until cardiac fibrosis underlying the end-stage HF.

The Association of Lactation Duration with Visceral and Pericardial Fat Volumes in Parous Women: The CARDIA Study

BACKGROUND

Lactation is associated with lower risks for cardiovascular disease in women. Organ-related adiposity, which plays significant roles in the development of cardiometabolic diseases, could help explain this observation. We evaluated the association of lactation duration with visceral (VAT) and pericardial (PAT) fat volumes in women.

METHODS

Data were obtained from 910 women enrolled in the Coronary Artery Risk Development in Young Adults (CARDIA) study (1985-1986) without diabetes prior to pregnancy who had ≥1 birth during 25 years of follow-up and had VAT and PAT measured from computed tomographic scans in 2010-2011. Cumulative lactation duration across all births since baseline was calculated from self-reports collected at periodic exams.

RESULTS

At baseline, the average age of women (48% black, 52% white) was 24 ± 3.7 years. After controlling for baseline age, race, smoking status, body mass index, fasting glucose, family history of diabetes, fat intake, total cholesterol, physical activity, and follow-up covariates (parity, gestational diabetes), the mean fat volumes across categories of lactation [none (n = 221), 1-5 months (n = 306), 6-11 months (n = 210), and ≥12 months (n = 173)] were 122.0, 113.7 105.0, and 110.1 cm3 for VAT and 52.2, 46.7, 44.5, and 43.4 cm3 for PAT, respectively. Changes in body weight from the first post-baseline birth to the end of follow-up mediated 21% and 18% of the associations of lactation with VAT and PAT, respectively.

CONCLUSIONS

In this prospective study, longer cumulative lactation duration was associated with lower VAT and PAT volumes, with weight gain partially mediating these associations.

Cardiac 1H MR spectroscopy: development of the past five decades and future perspectives

Continued advances in laboratory medicine are required to realize the potential of individualized medicine to impact common cardiovascular diseases. Magnetic resonance imaging (MRI) and spectroscopy (MRS) techniques have advanced over recent years and offer unique, powerful insights into cardiac anatomic and metabolic changes, respectively, occurring in both nascent and advanced heart disease. Although numerous MRI-based in vivo diagnostics are already used in routine clinical practice and more are anticipated, MRS has been less incorporated into routine clinical practice. Given the ability of ¹H MRS to identify and quantify specific molecules with high sensitivity and specificity, its potential utility should be successfully transition from "bench-to-bedside" is tantalizing. The present review will highlight the development of ¹H MRS techniques for cardiac applications, observations in seminal studies with ¹H MRS, and the prospects and challenges for widespread application in patients with cardiovascular disease.

Diabesity: the combined burden of obesity and diabetes on heart disease and the role of imaging

Diabesity is a term used to describe the combined adverse health effects of obesity and diabetes mellitus. The worldwide dual epidemic of obesity and type 2 diabetes is an important public health issue. Projections estimate a sixfold increase in the number of adults with obesity in 40 years and an increase in the number of individuals with diabetes to 642 million by 2040. Increased adiposity is the strongest risk factor for developing diabetes. Early detection of the effects of diabesity on the cardiovascular system would enable the optimal implementation of effective therapies that prevent atherosclerosis progression, cardiac remodelling, and the resulting ischaemic heart disease and heart failure. Beyond conventional imaging techniques, such as echocardiography, CT and cardiac magnetic resonance, novel post-processing tools and techniques provide information on the biological processes that underlie metabolic heart disease. In this Review, we summarize the effects of obesity and diabetes on myocardial structure and function and illustrate the use of state-of-the-art multimodality cardiac imaging to elucidate the pathophysiology of myocardial dysfunction, prognosticate long-term clinical outcomes and potentially guide treatment strategies.

Metabolic syndrome and myocardium steatosis in subclinical type 2 diabetes mellitus: a 1H-magnetic resonance spectroscopy study

BACKGROUND

Metabolic syndrome (MetS) is a cluster of metabolic abnormalities that collectively cause an increased risk of type 2 diabetes mellitus (T2DM) and nonatherosclerotic cardiovascular disease. This study aimed to evaluate the role of myocardial steatosis in T2DM patients with or without MetS, as well as the relationship between subclinical left ventricular (LV) myocardial dysfunction and myocardial steatosis.

METHODS AND MATERIALS

We recruited 53 T2DM patients and 20 healthy controls underwent cardiac magnetic resonance examination. All T2DM patients were subdivide into two group: MetS group and non-MetS. LV deformation, perfusion parameters and myocardial triglyceride (TG) content were measured and compared among these three groups. Pearson's and Spearman analysis were performed to investigate the correlation between LV cardiac parameters and myocardial steatosis. The receiver operating characteristic curve (ROC) was performed to illustrate the relationship between myocardial steatosis and LV subclinical myocardial dysfunction.

RESULTS

An increase in myocardial TG content was found in the MetS group compared with that in the other groups (MetS vs. non-MetS: 1.54 ± 0.63% vs. 1.16 ± 0.45%; MetS vs. normal: 1.54 ± 0.63% vs. 0.61 ± 0.22%; all p < 0.001). Furthermore, reduced LV deformation [reduced longitudinal and radial peak strain (PS); all p < 0.017] and microvascular dysfunction [increased time to maximum signal intensity (TTM) and reduced Upslope; all p < 0.017)] was found in the MetS group. Myocardial TG content was positively associated with MetS (r = 0.314, p < 0.001), and it was independently associated with TTM (β = 0.441, p < 0.001) and LV longitudinal PS (β = 0.323, p = 0.021). ROC analysis exhibited that myocardial TG content might predict the risk of decreased LV longitudinal myocardial deformation (AUC = 0.74) and perfusion function (AUC = 0.71).

CONCLUSION

Myocardial TG content increased in T2DM patients with concurrent MetS. Myocardial steatosis was positively associated with decreased myocardial deformation and perfusion dysfunction, which may be an indicator for predicting diabetic cardiomyopathy.

CMR based measurement of aortic stiffness, epicardial fat, left ventricular myocardial strain and fibrosis in hypertensive patients

Introduction

A combined assessment of different parameters of cardiovascular (CV) risk and prognosis can be supportive and performed with cardiac magnetic resonance (CMR). Aortic stiffness, epicardial fat volume (EFV), left ventricular (LV) strain and fibrosis were evaluated within a single CMR examination and results were related to the presence of hypertension (HTN) and diabetes mellitus (DM).

Methods

20 healthy controls (57.2 ± 8.2 years(y); 26.2 ± 3.9 kg/m²), 31 hypertensive patients without DM (59.6 ± 6.7 y; 28.4 ± 4.7 kg/m²) and 12 hypertensive patients with DM (58.8 ± 9.9y; 30.7 ± 6.3 kg/m²) were examined at 1.5Tesla. Aortic stiffness was evaluated by calculation of aortic pulse wave velocity (PWV), EFV by a 3D-Dixon sequence. Longitudinal & circumferential systolic myocardial strain (LS; CS) were analyzed and T1-relaxation times (T1) were determined to detect myocardial fibrosis.

Results

EFV was highest in hypertensive patients with diabetes (78.4 ± 28.0 ml/m²) followed by only hypertensive patients (64.2 ± 27.3 ml/m²) and lowest in controls (50.3 ± 22.7 ml/m²; p < 0.05). PWV was higher in hypertensive patients with diabetes (9.8 ± 3.3 m/s) compared to only hypertensive patients (8.6 ± 1.7 m/s; p < 0.05) and to controls (8.1 ± 1.9 m/s; p < 0.05). LS&CS were worse in hypertensive patients with diabetes (LS:-20.9 ± 5.1% and CS: -24.4 ± 5.7%) compared to both only hypertensive patients (LS: -24.7 ± 4.6%; CS: -27.1 ± 5.0%; p < 0.05) and to controls (LS: -25.5 ± 3.8; CS: -28.3 ± 4.1%; p < 0.05). Both hypertensive groups with and without DM had higher T1́s (994.0 ± 43.2 ms; 991.6 ± 35.5 ms) than controls (964.6 ± 40.3 ms; p < 0.05).

Conclusion

CMR revealed increased aortic stiffness and EFV in hypertensive patients, which were even higher in the presence of DM. Also signs of LV myocardial fibrosis and a reduced strain were revealed. These parameters support the assessment of CV risk and prognosis. They can accurately be measured with CMR within a single examination when normally different techniques are needed.

Role of Leptin in Cardiovascular Diseases

The adipocyte-derived adipokine leptin exerts pleiotropic effects, which are essential for the regulation of energy balance and cell metabolism, for controlling inflammatory and immune responses, and for the maintenance of homeostasis of the cardiovascular system. Leptin resistance in obese or type 2 diabetes mellitus (T2DM) patients is defined as a decrease in tissue response to leptin. In the cardiovascular system, leptin resistance exhibits the adverse effect on the heart's response to stress conditions and promoting cardiac remodeling due to impaired cardiac metabolism, increased fibrosis, vascular dysfunction, and enhanced inflammation. Leptin resistance or leptin signaling deficiency results in the risk increase of cardiac dysfunction and heart failure, which is a leading cause of obesity- and T2DM-related morbidity and mortality. Animal studies using leptin- and leptin receptor- (Lepr) deficient rodents have provided many useful insights into the underlying molecular and pathophysiological mechanisms of obese- and T2DM-associated metabolic and cardiovascular diseases. However, none of the animal models used so far can fully recapitulate the phenotypes of patients with obese or T2DM. Therefore, the role of leptin in the human cardiovascular system, and whether leptin affects cardiac function directly or acts through a leptin-regulated neurohumoral pathway, remain elusive. As the prevalence of obesity and diabetes is continuously increasing, strategies are needed to develop and apply human cell-based models to better understand the precise role of leptin directly in different cardiac cell types and to overcome the existing translational barriers. The purpose of this review is to discuss the mechanisms associated with leptin signaling deficiency or leptin resistance in the development of metabolic and cardiovascular diseases. We analyzed and comprehensively addressed substantial findings in pathophysiological mechanisms in commonly used leptin- or Lepr-deficient rodent models and highlighted the differences between rodents and humans. This may open up new strategies to develop directly and reliably applicable models, which resemble the human pathophysiology in order to advance health care management of obesity- and T2DM-related cardiovascular complications.

Early left atrial dysfunction is associated with suboptimal cardiovascular health

AIMS

Two-dimensional speckle-tracking echocardiography can assess left atrial (LA) function by measuring atrial volumes and deformation parameters (strain, strain rate). This cross-sectional analysis explores the association between ideal CV health (CVH), LA function, and systemic biomarkers in healthy individuals from the Chilean MAUCO Cohort.

METHODS

We enrolled 95 MAUCO participants with different levels of CVH (mean age: 51 ± 8 years). We categorized participants into low or high CVH groups: A: 0-2, or B: 3-6 CVH risk factors. 2D echocardiography, glucose, insulin, total cholesterol, triglycerides, proBNP, hsCRP, insulin resistance index (HOMA), and right and left atrial strain (RASs and LASs, respectively) were determined.

RESULTS

LASs was lower in Group A, while systolic and diastolic blood pressure (BP), body mass index (BMI), insulin, HOMA, total cholesterol, triglycerides, and LV and RV end-diastolic volume were significantly higher in Group A than Group B (P < .01). Change in LASs was inversely correlated with insulin (P = .040), HOMA (P = .013), total cholesterol (P = .039), glycemia (P = .018), and BMI (P = .0.037).

CONCLUSION

LASs during the reservoir phase was diminished in subjects with a lower level of CVH. Higher insulin, HOMA, total cholesterol, glycemia, and BMI values were associated with decreased LA deformation during the reservoir phase. Morphofunctional alterations of the LA were also identified in the group with suboptimal CVH, as well as BP values in the range of hypertension. LA dysfunction in an asymptomatic population, along with metabolic syndrome, could be an early event in the continuum of CV damage.

Exercise as A Potential Therapeutic Target for Diabetic Cardiomyopathy: Insight into the Underlying Mechanisms

Diabetes mellitus is associated with cardiovascular, ophthalmic, and renal comorbidities. Among these, diabetic cardiomyopathy (DCM) causes the most severe symptoms and is considered to be a major health problem worldwide. Exercise is widely known as an effective strategy for the prevention and treatment of many chronic diseases. Importantly, the onset of complications arising due to diabetes can be delayed or even prevented by exercise. Regular exercise is reported to have positive effects on diabetes mellitus and the development of DCM. The protective effects of exercise include prevention of cardiac apoptosis, fibrosis, oxidative stress, and microvascular diseases, as well as improvement in cardiac mitochondrial function and calcium regulation. This review summarizes the recent scientific findings to describe the potential mechanisms by which exercise may prevent DCM and heart failure.

Effect of Empagliflozin on Cardiac Function, Adiposity, and Diffuse Fibrosis in Patients with Type 2 Diabetes Mellitus

Empagliflozin, a sodium-glucose cotransporter 2 (SGLT2) inhibitor, significantly improves cardiovascular outcomes in diabetic patients; however, the mechanism is unclear. We hypothesized that empagliflozin might have beneficial effects on cardiac function, structure, adiposity, and myocardial diffuse fibrosis. This prospective study enrolled 35 patients (48.6% men, age 63.5 ± 9.7 years) with type 2 diabetes mellitus (T2DM) from June 1, 2017, to November 31, 2018. The patients received an SGLT2 inhibitor (empagliflozin 25 or 12.5 mg/d) for 6 months in addition to stable oral hypoglycaemic treatment. All patients underwent cardiac magnetic resonance imaging (CMRI) before and after empagliflozin treatment. Left ventricular (LV) function and structure were quantified using cine CMRI. Cardiac adiposity was defined based on pericardial fat and intracardiac triglyceride contents, whereas myocardial diffuse fibrosis was indicated by extracellular volume (ECV). The statistical significance of parameter changes was assessed using paired t-test and stepwise multiple linear regression. There were no significant differences in LV function and structure changes. Cardiac adiposity and diffuse fibrosis indices were also not different before and after empagliflozin treatment. Concerning clinical parameters, only a significant decrease in systolic blood pressure (by 6.4 mmHg) was observed (p = 0.013). Stepwise multiple linear regression revealed that worse baseline MRI parameters were associated with better improvements. Intracardiac triglyceride content decrease was inversely associated with baseline intracardiac triglyceride content (p < 0.001). Pericardial fat changes were negatively correlated with baseline pericardial fat (p < 0.001) and ECV changes (p = 0.028). ECV changes were inversely associated with baseline ECV (p < 0.001), baseline LV ejection fraction (p < 0.001), and LV mass index changes (p = 0.020). This study demonstrated that 6 months of empagliflozin treatment did not significantly improve the LV function, structure, adiposity, and diffuse fibrosis in patients with T2DM. Further, the beneficial effects of empagliflozin treatment might be more evident in patients with worse baseline LV substrate and structure.

Myocardial adipose deposition and the development of heart failure with preserved ejection fraction

AIMS

It has been proposed that an increase of myocardial adiposity is related to left ventricular (LV) diastolic dysfunction. The specific roles of myocardial steatosis including epicardial fat and intramyocardial fat for diastolic function are unknown in those patients suffering heart failure (HF) with reduced (HFrEF) or preserved ejection fraction (HFpEF). This study aims to determine the complex relationship between myocardial adiposity in patients with HFrEF or HFpEF.

METHODS AND RESULTS

Using cardiac magnetic resonance imaging (CMRI), myocardial steatosis was measured in 305 subjects (34 patients with HFrEF, 163 with HFpEF, and 108 non-HF controls). We also evaluated cardiac structure and diastolic and systolic function by echocardiography and CMRI. Patients with HFpEF had significantly more intramyocardial fat than HFrEF patients or non-HF controls [intramyocardial fat content (%), 1.56 (1.26, 1.89) vs. 0.75 (0.50, 0.87) and 1.0 (0.79, 1.15), P < 0.05]. Intramyocardial fat amount (%) was higher in HFpEF women than in men [1.91% (1.17%, 2.32%) vs. 1.22 (0.87%, 2.02%), P = 0.01]. When estimated by CMRI (left ventricular peak filling rate), echocardiographic E/e' level, or left atrial volume index, intramyocardial fat correlated with LV diastolic dysfunction parameters in HFpEF patients, and this was independent of age, co-morbidities, body mass index, gender, and myocardial fibrosis (standardized coefficient: β = -0.34, P = 0.03; β = 0.29, P = 0.025; and β = 0.25, P = 0.02, respectively).

CONCLUSIONS

Patients with HFpEF had significantly more intramyocardial fat than HFrEF patients or non-HF controls. Independent of risk factors or gender, intramyocardial fat correlated with LV diastolic dysfunction parameters in HFpEF patients.

Plasma microRNA Profiling Reveals Novel Biomarkers of Epicardial Adipose Tissue: A Multidetector Computed Tomography Study

Epicardial adipose tissue (EAT) constitutes a novel parameter for cardiometabolic risk assessment and a target for therapy. Here, we evaluated for the first time the plasma microRNA (miRNA) profile as a source of biomarkers for epicardial fat volume (EFV). miRNAs were profiled in plasma samples from 180 patients whose EFV was quantified using multidetector computed tomography. In the screening study, 54 deregulated miRNAs were identified in patients with high EFV levels (highest tertile) compared with matched patients with low EFV levels (lowest tertile). After filtering, 12 miRNAs were selected for subsequent validation. In the validation study, miR-15b-3p, miR-22-3p, miR-148a-3p miR-148b-3p and miR-590-5p were directly associated with EFV, even after adjustment for confounding factors (p value < 0.05 for all models). The addition of miRNA combinations to a model based on clinical variables improved the discrimination (area under the receiver-operating-characteristic curve (AUC) from 0.721 to 0.787). miRNAs correctly reclassified a significant proportion of patients with an integrated discrimination improvement (IDI) index of 0.101 and a net reclassification improvement (NRI) index of 0.650. Decision tree models used miRNA combinations to improve their classification accuracy. These results were reproduced using two proposed clinical cutoffs for epicardial fat burden. Internal validation corroborated the robustness of the models. In conclusion, plasma miRNAs constitute novel biomarkers of epicardial fat burden.

Metabolic Profiling of the Diabetic Heart: Toward a Richer Picture

The increasing global prevalence of diabetes has been accompanied by a rise in diabetes-related conditions. This includes diabetic cardiomyopathy (DbCM), a progressive form of heart disease that occurs with both insulin-dependent (type-1) and insulin-independent (type-2) diabetes and arises in the absence of hypertension or coronary artery disease. Over time, DbCM can develop into overt heart failure. Like other forms of cardiomyopathy, DbCM is accompanied by alterations in metabolism which could lead to further progression of the pathology, with metabolic derangement postulated to precede functional changes in the diabetic heart. Moreover in the case of type-2 diabetes, underlying insulin resistance is likely to prevent the canonical substrate switch of the failing heart away from fatty acid oxidation toward increased use of glycolysis. Analytical chemistry techniques, collectively known as metabolomics, are useful tools for investigating the condition. In this article, we provide a comprehensive review of those studies that have employed metabolomic techniques, namely chromatography, mass spectrometry and nuclear magnetic resonance spectroscopy, to profile metabolic remodeling in the diabetic heart of human patients and animal models. These studies collectively demonstrate that glycolysis and glucose oxidation are suppressed in the diabetic myocardium and highlight a complex picture regarding lipid metabolism. The diabetic heart typically shows an increased reliance on fatty acid oxidation, yet triacylglycerols and other lipids accumulate in the diabetic myocardium indicating probable lipotoxicity. The application of lipidomic techniques to the diabetic heart has identified specific lipid species that become enriched and which may in turn act as plasma-borne biomarkers for the condition. Metabolomics is proving to be a powerful approach, allowing a much richer analysis of the metabolic alterations that occur in the diabetic heart. Careful physiological interpretation of metabolomic results will now be key in order to establish which aspects of the metabolic derangement are causal to the progression of DbCM and might form the basis for novel therapeutic intervention.

Retrospective phase-based gating for cardiac proton spectroscopy with fixed scan time

BACKGROUND

Respiratory motion is a major limiting factor for spectral quality and duration of in vivo proton MR spectroscopy of the heart. Prospective navigator gating is frequently applied to minimize the effects of respiratory motion, but scan durations are subject-dependent and hence difficult to predict.

PURPOSE

To implement cardiac proton MRS with fixed scan time by employing retrospective phase-based gating and to compare the proposed method to conventional navigator-gated MRS.

STUDY TYPE

Prospective.

SUBJECTS

Eighteen healthy volunteers (29.7 ± 7.8 years).

FIELD STRENGTH/SEQUENCE

1.5, navigator-gated (16 averages without, 96 with water suppression [WS]) data acquisition as reference and navigator-free data acquisition with a fixed scan time (48 without WS, 304 with WS), cardiac-triggered point-resolved spectroscopy (PRESS).

ASSESSMENT

Navigator-free data acquisition with retrospective phase-based gating was compared with prospective navigator-gating. Navigator-free acquisition was repeated in 10 subjects to assess reproducibility. Scan time was assessed for prospective and retrospective gating. Retrospective phase-based gating was performed using a threshold based on the standard deviation (SD) of individual water (W) and triglyceride (TG) phases.

STATISTICAL TESTS

T-tests and Bland-Altman analysis.

RESULTS

The duration of the prospective navigator-gated scans ranged from 6:09 minutes to 21:50 minutes (mean 10:05 ± 3:46 min, gating efficiency 40.4 ± 10.5%), while data acquisition for retrospective phase-based gating had a fixed scan time of 11:44 minutes. Retrospective phase-based gating using a threshold of 1 × SD yielded a gating efficiency of 72.7 ± 4.3% and a coefficient of variation (CoV) of triglyceride-to-water ratios of 9.8% compared with the navigated reference. The intrasubject reproducibility of retrospective gating revealed a CoV of 9.5%.

DATA CONCLUSION

Cardiac proton MRS employing retrospective phase-based gating is feasible and provides reproducible assessment of TG/W in a fixed scan time. Since scan time is independent of respiratory motion, retrospective phase-based gating offers an approach to motion compensation with predictable exam time for proton MRS of the heart.

LEVEL OF EVIDENCE

2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;50:1973-1981.

Epicardial Adipose Tissue and Cardiovascular Disease

PURPOSE OF REVIEW

Epicardial adipose tissue has been associated with the development/progression of cardiovascular disease. We appraise the strength of the association between epicardial adipose tissue and development/progression of cardiovascular diseases like coronary artery disease, atrial fibrillation, and heart failure with preserved ejection fraction.

RECENT FINDINGS

Cross-sectional clinical and translational correlative studies have established an association between epicardial adipose tissue and progression of coronary artery disease. Recent studies question this association and underline the need for longitudinal studies. Epicardial adipose tissue also plays a definite role in the pathobiology of atrial fibrillation and its recurrence after ablation. In contrast to an early paradigm, epicardial adipose tissue does not appear to play a key role in the pathogenesis of heart failure with preserved ejection fraction in obese patients. The association of epicardial adipose tissue with atrial fibrillation is robust. In contrast, the association of epicardial adipose tissue with coronary artery disease and heart failure with preserved ejection fraction is tenuous. Additional research, including longitudinal studies, is needed to confirm or refute these proposed associations.

Soluble Receptor for Advanced Glycation End Products: A Protective Molecule against Intramyocardial Lipid Accumulation in Obese Zucker Rats?

Most of the obesity-related complications are due to ectopic fat accumulation. Recently, the activation of the cell-surface receptor for advanced glycation end products (RAGE) has been associated with lipid accumulation in different organs. Nevertheless, the role of RAGE and sRAGE, the soluble form that prevents ligands to activate RAGE, in intramyocardial lipid accumulation is presently unknown. To this aim, we analyzed whether, in obesity, intramyocardial lipid accumulation and lipid metabolism-related transcriptome are related to RAGE and sRAGE. Heart and serum samples were collected from 10 lean (L) and 10 obese (OB) Zucker rats. Oil red staining was used to detect lipids on frozen heart sections. The lipid metabolism-related transcriptome (84 genes) was analyzed by a specific PCR array. Heart RAGE expression was explored by real-time RT-PCR and Western blot analyses. Serum levels of sRAGE (total and endogenous secretory form (esRAGE)) were quantified by ELISA. Genes promoting fatty acid transport, activation, and oxidation in mitochondria/peroxisomes were upregulated in OB hearts. Intramyocardial lipid content did not differ between OB and L rats, as well as RAGE expression. A slight increase in epicardial adipose tissue was observed in OB hearts. Total sRAGE and esRAGE concentrations were significantly higher in OB rats. sRAGE may protect against obesity-induced intramyocardial lipid accumulation by preventing RAGE hyperexpression, therefore allowing lipids to be metabolized. EAT also played a protective role by working as a buffering system that protects the myocardium against exposure to excessively high levels of fatty acids. These observations reinforce the potential role of RAGE pathway as an interesting therapeutic target for obesity-related complications, at least at the cardiovascular level.

Cardiac- versus diaphragm-based respiratory navigation for proton spectroscopy of the heart

OBJECTIVES

To study inter-individual differences of the relation between diaphragm and heart motion, the objective of the present study was to implement respiratory navigation on the heart and compare it against the established method of navigator gating on the diaphragm for single-voxel cardiac ¹H-MRS.

MATERIALS AND METHODS

¹H-MRS was performed on a 1.5T system in 19 healthy volunteers of mixed age (range 24-75 years). Spectra were recorded in a 6-8 ml voxel in the ventricular septum using a PRESS (point-resolved spectroscopy) sequence and ECG gating. Water-unsuppressed data acquired with pencil beam navigation on the heart were compared to data with navigation on the diaphragm. Water-suppressed data were obtained to assess triglyceride-to-water ratios.

RESULTS

Water phase and amplitude fluctuations for cardiac versus diaphragm navigation did not reveal significant differences. Both navigator positions provided comparable triglyceride-to-water ratios and gating efficiencies (coefficient of variation (CoV) 7.0%). The cardiac navigator showed a good reproducibility (CoV 5.2%).

DISCUSSION

Respiratory navigation on the heart does not convey an advantage over diaphragm-based navigator gating for cardiac ¹H-MRS, but also no disadvantage. Consequently, cardiac and diaphragm respiratory navigation may be used interchangeably.

The Association of Epicardial Adipose Tissue and the Metabolic Syndrome in Community Participants in South Africa

Background:

We sought to determine the association of echocardiographically derived epicardial adipose tissue (EAT) thickness, which is a component of visceral adipose tissue, with the metabolic syndrome (MetS) in a cohort of randomly selected community participants.

Methods:

South African-Asian Indians aged 15–64 years were recruited over a 2-year period after informed consent was obtained. All participants who had complete measurements done for biochemistry and echocardiography (using established criteria), were dichotomized into the MetS or non-MetS groups defined according to the harmonized criteria.

Results:

Of the 953 (232 men and 721 women) participants recruited, 47.1% (448) were classified with the MetS. These participants had larger waist circumference and body mass index (P < 0.001), with larger LA volumes and diameter, thicker ventricular walls, higher left ventricular mass, relative wall thickness, and EAT (P < 0.001). There was a corresponding increase in EAT thickness with increasing number of MetS risk factors at the transition from 0 MetS factors to 1 (95% confidence interval [CI] −0.8; −0.2) and from 2 to 3 MetS factors (95% CI −0.9; −0.4). The AUC of the receiver operator curve was highest for triglycerides (0.845), followed by fasting plasma glucose (0.795) and then EAT (0.789). An EAT value of <3.6 mm predicted the presence of the MetS with a 78% sensitivity and 70% specificity. Using backward stepwise logistic regression, the most significant independent determinants of the MetS after adjusting for age, gender, and type 2 diabetes mellitus, was fasting plasma glucose (odds ratio [OR] = 1.2), triglycerides (OR = 7.1), and EAT (OR = 2.3).

Conclusion:

Although EAT is associated with the MetS, and can identify individuals at increased cardiometabolic risk, it has a limited additional role compared to current risk markers.

Epicardial adipose tissue and cardiovascular diseases

Obesity is a heterogeneous disease with different degrees of cardiovascular (CV) and metabolic manifestations. Certain ectopic fat depots may contribute to obesity-related CV risk and may explain part of the risk differential observed in metabolically healthy obese and the so called "obesity paradox". The growing interest towards the potential impact of epicardial adipose tissue (EAT) in cardiovascular (CV) risk has led to deepen its biological function. Genetic, epigenetic and environmental factors may drive the shift towards a dysfunctional EAT characterized by a pro-inflammatory and pro-fibrotic phenotype. Due to the close anatomic proximity to coronary arteries, a thicker and dysfunctional EAT actively contribute to development and progression of coronary atherosclerosis. Beside classical paracrine transmission, EAT may directly release mediators into the vasa vasorum of the coronary arterial wall, a mechanism referred to as "vasocrine". Similarly, the pro-inflammatory and pro-fibrotic secretome characterizing dysfunctional EAT may impair cardiac structure and function, thus being implicated in the pathogenesis of diastolic heart failure and atrial fibrillation. The development of 3D imaging techniques have paved the way for clarifying the causative role of EAT in CV pathophysiology, the use of EAT volume/thickness in CV risk stratification and potential cardio-protective effects of EAT reduction. The aim of this narrative review is to update current knowledge on the pathophysiological functions of EAT, focusing on basic mechanisms and potential clinical implications.

Characterization of different fat depots in NAFLD using inflammation-associated proteome, lipidome and metabolome

Non-alcoholic fatty liver disease (NAFLD) is recognized as a liver manifestation of metabolic syndrome, accompanied with excessive fat accumulation in the liver and other vital organs. Ectopic fat accumulation was previously associated with negative effects at the systemic and local level in the human body. Thus, we aimed to identify and assess the predictive capability of novel potential metabolic biomarkers for ectopic fat depots in non-diabetic men with NAFLD, using the inflammation-associated proteome, lipidome and metabolome. Myocardial and hepatic triglycerides were measured with magnetic spectroscopy while function of left ventricle, pericardial and epicardial fat, subcutaneous and visceral adipose tissue were measured with magnetic resonance imaging. Measured ectopic fat depots were profiled and predicted using a Random Forest algorithm, and by estimating the Area Under the Receiver Operating Characteristic curves. We have identified distinct metabolic signatures of fat depots in the liver (TAG50:1, glutamate, diSM18:0 and CE20:3), pericardium (N-palmitoyl-sphinganine, HGF, diSM18:0, glutamate, and TNFSF14), epicardium (sphingomyelin, CE20:3, PC38:3 and TNFSF14), and myocardium (CE20:3, LAPTGF-β1, glutamate and glucose). Our analyses highlighted non-invasive biomarkers that accurately predict ectopic fat depots, and reflect their distinct metabolic signatures in subjects with NAFLD.

Association between insulin resistance and the development of cardiovascular disease

For many years, cardiovascular disease (CVD) has been the leading cause of death around the world. Often associated with CVD are comorbidities such as obesity, abnormal lipid profiles and insulin resistance. Insulin is a key hormone that functions as a regulator of cellular metabolism in many tissues in the human body. Insulin resistance is defined as a decrease in tissue response to insulin stimulation thus insulin resistance is characterized by defects in uptake and oxidation of glucose, a decrease in glycogen synthesis, and, to a lesser extent, the ability to suppress lipid oxidation. Literature widely suggests that free fatty acids are the predominant substrate used in the adult myocardium for ATP production, however, the cardiac metabolic network is highly flexible and can use other substrates, such as glucose, lactate or amino acids. During insulin resistance, several metabolic alterations induce the development of cardiovascular disease. For instance, insulin resistance can induce an imbalance in glucose metabolism that generates chronic hyperglycemia, which in turn triggers oxidative stress and causes an inflammatory response that leads to cell damage. Insulin resistance can also alter systemic lipid metabolism which then leads to the development of dyslipidemia and the well-known lipid triad: (1) high levels of plasma triglycerides, (2) low levels of high-density lipoprotein, and (3) the appearance of small dense low-density lipoproteins. This triad, along with endothelial dysfunction, which can also be induced by aberrant insulin signaling, contribute to atherosclerotic plaque formation. Regarding the systemic consequences associated with insulin resistance and the metabolic cardiac alterations, it can be concluded that insulin resistance in the myocardium generates damage by at least three different mechanisms: (1) signal transduction alteration, (2) impaired regulation of substrate metabolism, and (3) altered delivery of substrates to the myocardium. The aim of this review is to discuss the mechanisms associated with insulin resistance and the development of CVD. New therapies focused on decreasing insulin resistance may contribute to a decrease in both CVD and atherosclerotic plaque generation.

Obesity, ectopic fat and cardiac metabolism

INTRODUCTION

Obesity is recognized as a risk factor for cardiovascular disease, expending independent adverse effects on the cardiovascular system. This relationship is complex due to several associations with cardiovascular disease risk factors/markers such as hypertension, dyslipidemia, insulin resistance/dysglycemia, or type 2 diabetes mellitus. Obesity induces a variety of cardiovascular system structural adaptations, from subclinical myocardial dysfunction to severe left ventricular systolic heart failure. Abnormalities in cardiac metabolism and subsequent cardiac energy, have been proposed as major contributors to obesity-related cardiovascular disease. Ectopic fat depots play an important role in several of the hypotheses postulated to explain the association between obesity, cardiac metabolism and cardiac dysfunction.

AREAS COVERED

In this review, we addressed with contemporary studies how obesity-associated metabolic conditions and ectopic cardiac fat accumulation, translate into cardiac energy metabolism disturbances that may lead to adverse effects on the cardiovascular system.

EXPERT COMMENTARY

Obesity and ectopic fat accumulation has long been related to metabolic diseases and adverse cardiovascular outcomes. Recent imaging advances have just started to address the complex interplays between obesity, ectopic fat depots, cardiac metabolism and the risk of obesity-related cardiovascular disease. A better comprehension of these obesity-associated metabolic disturbances will lead to earlier detection of patients at increased risk of cardiovascular disease and to the development of novel therapeutic metabolic targets to treat a wide variety of cardiovascular diseases.

Metabolic syndrome associates with left atrial dysfunction

BACKGROUND AND AIMS

Obesity and metabolic syndrome (MetS) are risk factors of atrial fibrillation (AF), but limited data exist on their effect on left atrial (LA) function. The aim of the study was to evaluate the effects of cardiac, hepatic and intra-abdominal ectopic fat depots and cardiometabolic risk factors on LA function in non-diabetic male subjects.

METHODS AND RESULTS

Myocardial and hepatic triglyceride contents were measured with 1.5T ¹H-magnetic resonance spectroscopy and LA and left ventricular function, visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), epicardial and pericardial fat by magnetic resonance imaging (MRI) in 33 men with MetS and 40 men without MetS. LA volumes were assessed using a novel three-chamber orientation based MRI approach. LA ejection fraction (EF) was lower in MetS patients than in the control group (44 ± 7.7% in MetS vs. 49 ± 8.6% in controls, p = 0.013) without LA enlargement, indicating LA dysfunction. LA EF correlated negatively with waist circumference, body mass index, SAT, VAT, fasting serum insulin, and homeostasis model assessment of insulin resistance index, and positively with fasting serum high-density lipoprotein cholesterol. VAT was the best predictor of reduced LA EF.

CONCLUSIONS

MetS associates with subclinical LA dysfunction. Multiple components of MetS are related to LA dysfunction, notably visceral obesity and insulin resistance. Further studies are needed to elucidate the role of mechanical atrial remodeling in the development of AF.

Diagnostic imaging in the management of patients with metabolic syndrome

Metabolic syndrome (MetS) is the constellation of metabolic risk factors that might foster development of type 2 diabetes and cardiovascular disease. Abdominal obesity and insulin resistance play a prominent role among all metabolic traits of MetS. Because intervention including weight loss can reduce these morbidity and mortality in MetS, early detection of the severity and complications of MetS could be useful. Recent advances in imaging modalities have provided significant insight into the development and progression of abdominal obesity and insulin resistance, as well as target organ injuries. The purpose of this review is to summarize advances in diagnostic imaging modalities in MetS that can be applied for evaluating each components and target organs. This may help in early detection, monitoring target organ injury, and in turn developing novel therapeutic target to alleviate and avert them.

Epicardial adipose tissue is related to arterial stiffness and inflammation in patients with cardiovascular disease and type 2 diabetes

Background

Epicardial adipose tissue (EAT) is an emerging cardio-metabolic risk factor and has been shown to correlate with adverse cardiovascular (CV) outcome; however the underlying pathophysiology of this link is not well understood. The aim of this study was to evaluate the relationship between EAT and a comprehensive panel of cardiovascular risk biomarkers and pulse wave velocity (PWV) and indexed left ventricular mass (LVMI) in a cohort of patients with cardiovascular disease (CVD) and diabetes compared to controls.

Methods

One hundred forty-five participants (mean age 63.9 ± 8.1 years; 61% male) were evaluated. All patients underwent cardiovascular magnetic resonance (CMR) examination and PWV. EAT measurements from CMR were performed on the 4-chamber view. Blood samples were taken and a range of CV biomarkers was evaluated.

Results

EAT measurements were significantly higher in the groups with CVD, with or without T2DM compared to patients without CVD or T2DM (group 1 EAT 15.9 ± 5.5 cm² vs. group 4 EAT 11.8 ± 4.1 cm², p = 0.001; group 3 EAT 15.1 ± 4.3 cm² vs. group 4 EAT 11.8 ± 4.1 cm², p = 0.024). EAT was independently associated with IL-6 (beta 0.2, p = 0.019). When added to clinical variables, both EAT (beta 0.16, p = 0.035) and IL-6 (beta 0.26, p = 0.003) were independently associated with PWV. EAT was significantly associated with LVMI in a univariable analysis but not when added to significant clinical variables.

Conclusions

In patients with cardio-metabolic disease, EAT was independently associated with PWV. EAT may be associated with CVD risk due to an increase in systemic vascular inflammation. Whether targeting EAT may reduce inflammation and/or cardiovascular risk should be evaluated in prospective studies.

Electronic supplementary material

The online version of this article (10.1186/s12872-018-0770-z) contains supplementary material, which is available to authorized users.