Uncoupling protein-1 and related messenger ribonucleic acids in human epicardial and other adipose tissues: epicardial fat functioning as brown fat

Epicardial Adipose Tissue and Heart Failure, Friend or Foe?

Heart failure (HF) management guidelines recommend individualized assessments based on HF phenotypes. Adiposity is a known risk factor for HF. Recently, there has been an increased interest in organ-specific adiposity, specifically the role of the epicardial adipose tissue (EAT), in HF risk. EAT is easily assessable through various imaging modalities and is anatomically and functionally connected to the myocardium. In pathological conditions, EAT secretes inflammatory cytokines, releases excessive fatty acids, and increases mechanical load on the myocardium, resulting in myocardial remodeling. EAT plays a pathophysiological role in characterizing both HF with reduced ejection fraction (HFrEF) and HF with preserved ejection fraction (HFpEF). In HFrEF, EAT volume is reduced, reflecting an impaired metabolic reservoir, whereas in HFpEF, the amount of EAT is associated with worse biomarker and hemodynamic profiles, indicating increased EAT activity. Studies have examined the possibility of therapeutically targeting EAT, and recent studies using sodium glucose cotransporter 2 inhibitors have shown potential in reducing EAT volume. However, further research is required to determine the clinical implications of reducing EAT activity in patients with HF.

Exploring the role of epicardial adipose-tissue-derived extracellular vesicles in cardiovascular diseases

Epicardial adipose tissue (EAT) is a fat depot located between the myocardium and the visceral layer of the epicardium, which, owing to its location, can influence surrounding tissues and can act as a local transducer of systemic inflammation. The mechanisms upon which such influence depends on are however unclear. Given the role EAT undoubtedly has in the scheme of cardiovascular diseases (CVDs), understanding the impact of its cellular components is of upmost importance. Extracellular vesicles (EVs) constitute promising candidates to fill the gap in the knowledge concerning the unexplored mechanisms through which EAT promotes onset and progression of CVDs. Owing to their ability of transporting active biomolecules, EAT-derived EVs have been reported to be actively involved in the pathogenesis of ischemia/reperfusion injury, coronary atherosclerosis, heart failure, and atrial fibrillation. Exploring the precise functions EVs exert in this context may aid in connecting the dots between EAT and CVDs.

Epicardial Adipose Tissue: a Potential Therapeutic Target for Cardiovascular Diseases

With increased ageing of the population, cardiovascular disease (CVD) has become the most important factor endangering human health worldwide. Although the treatment of CVD has become increasingly advanced, there are still a considerable number of patients with conditions that have not improved. According to the latest clinical guidelines of the European Cardiovascular Association, obesity has become an independent risk factor for CVD. Adipose tissue includes visceral adipose tissue and subcutaneous adipose tissue. Many previous studies have focused on subcutaneous adipose tissue, but visceral adipose tissue has been rarely studied. However, as a type of visceral adipose tissue, epicardial adipose tissue (EAT) has attracted the attention of researchers because of its unique anatomical and physiological characteristics. This review will systematically describe the physiological characteristics and evaluation methods of EAT and emphasize the important role and treatment measures of EAT in CVD.

The zebrafish heart harbors a thermogenic beige fat depot analog of human epicardial adipose tissue

Epicardial adipose tissue (eAT) is a metabolically active fat depot that has been associated with a wide array of cardiac homeostatic functions and cardiometabolic diseases. A full understanding of its diverse physiological and pathological roles is hindered by the dearth of animal models. Here, we show, in the heart of an ectothermic teleost, the zebrafish, the existence of a fat depot localized underneath the epicardium, originating from the epicardium and exhibiting the molecular signature of beige adipocytes. Moreover, a subset of adipocytes within this cardiac fat tissue exhibits primitive thermogenic potential. Transcriptomic profiling and cross-species analysis revealed elevated glycolytic and cardiac homeostatic gene expression with downregulated obesity and inflammatory hallmarks in the teleost eAT compared to that of lean aged humans. Our findings unveil epicardium-derived beige fat in the heart of an ectotherm considered to possess solely white adipocytes for energy storage and identify pathways that may underlie age-driven remodeling of human eAT.

Role of epicardial adipose tissue in diabetic cardiomyopathy through the lens of cardiovascular magnetic resonance imaging - a narrative review

Accumulating evidence suggests that ectopic/visceral adiposity may play a key role in the pathogenesis of nonischaemic cardiovascular diseases associated with type 2 diabetes. Epicardial adipose tissue (EAT) is a complex visceral fat depot, covering 80% of the cardiac surface with anatomical and functional contiguity to the myocardium and coronary arteries. EAT interacts with the biology of the underlying myocardium by secreting a wide range of adipokines. Magnetic resonance imaging (MRI) is the reference modality for structural and functional imaging of the heart. The technique is now also emerging as the reference imaging modality for EAT quantification. With this narrative review, we (a) surveyed contemporary clinical studies that utilized cardiovascular MRI to characterize EAT (studies published 2010-2023); (b) listed the clinical trials monitoring the response to treatment in EAT size as well as myocardial functional and structural parameters and (c) discussed the potential pathophysiological role of EAT in the development of diabetic cardiomyopathy. We concluded that increased EAT quantity and its inflammatory phenotype correlate with early signs of left ventricle dysfunction and may have a role in the pathogenesis of cardiac disease in diabetes with and without coronary artery disease.

Association of epicardial adipose tissue with metabolic risk factors on cardiovascular outcomes: serial coronary computed tomography angiography study

BACKGROUND/AIMS

Epicardial adipose tissue (EAT) shares pathophysiological properties with other visceral fats and potentially triggers local inflammation. However, the association of EAT with cardiovascular disease (CVD) is still debatable. The study aimed to observe the changes and associations in EAT and risk factors over time, as well as to investigate whether EAT was associated with CVD.

METHODS

A total of 762 participants from Seoul National University Hospital (SNUH) and SNUH Gangnam Center were included in this study. EAT was measured using coronary computed tomography angiography.

RESULTS

Baseline EAT level was positively associated with body mass index (BMI), calcium score, atherosclerotic cardiovascular disease (ASCVD) 10-year risk score, glucose, triglycerides (TG)/high-density lipoprotein (HDL), but not with total cholesterol, low-density lipoprotein (LDL). At follow-up, EAT levels increased in all groups, with low EAT groups demonstrating a significant increase in EAT per year. Change in EAT was associated with a change in BMI, TG/HDL, and glucose, while changes in LDL, calcium score, and ASCVD 10-year risk score were not associated. Although calcium score and ASCVD 10-year risk score were associated with CVD events, baseline information of EAT, baseline EAT/body surface area, or EAT change was not available.

CONCLUSION

Metabolic risks, e.g., BMI, TG/HDL, and glucose, were associated with EAT change per year, whereas classical CVD risks, e.g., LDL, calcium score, and ASCVD 10-year risk score, were not. The actual CVD event was not associated with EAT volume, warranting future studies combining qualitative assessments with quantitative ones.

Epicardial and pericoronary adipose tissue and coronary plaque burden in patients with Cushing's syndrome: a propensity score-matched study

PURPOSE

To assess coronary inflammation by measuring the volume and density of the epicardial adipose tissue (EAT), perivascular fat attenuation index (FAI) and coronary plaque burden in patients with Cushing's syndrome (CS) based on coronary computed tomography angiography (CCTA).

METHODS

This study included 29 patients with CS and 58 matched patients without CS who underwent CCTA. The EAT volume, EAT density, FAI and coronary plaque burden were measured. The high-risk plaque (HRP) was also evaluated. CS duration from diagnosis, 24-h urinary free cortisol (UFC), and abdominal visceral adipose tissue volume (VAT) of CS patients were recorded.

RESULTS

The CS group had higher EAT volume (146.9 [115.4, 184.2] vs. 119.6 [69.0, 147.1] mL, P = 0.006), lower EAT density (- 78.79 ± 5.89 vs. - 75.98 ± 6.03 HU, P = 0.042), lower FAI (- 84.0 ± 8.92 vs. - 79.40 ± 10.04 HU, P = 0.038), higher total plaque volume (88.81 [36.26, 522.5] vs. 44.45 [0, 198.16] mL, P = 0.010) and more HRP plaques (7.3% vs. 1.8%, P = 0.026) than the controls. The multivariate analysis suggested that CS itself (β [95% CI], 29.233 [10.436, 48.03], P = 0.014), CS duration (β [95% CI], 0.176 [0.185, 4.242], P = 0.033), and UFC (β [95% CI], 0.197 [1.803, 19.719], P = 0.019) were strongly associated with EAT volume but not EAT density, and EAT volume (β [95% CI] - 0.037[- 0.058, - 0.016], P = 0.001) not CS was strongly associated with EAT density. EAT volume, FAI and plaque burden increased (all P < 0.05) in 6 CS patients with follow-up CCTA. The EAT volume had a moderate correlation with abdominal VAT volume (r = 0.526, P = 0.008) in CS patients.

CONCLUSIONS

Patients with CS have higher EAT volume and coronary plaque burden but less inflammation as detected by EAT density and FAI. The EAT density is associated with EAT volume but not CS itself.

Epicardial adipose tissue, metabolic disorders, and cardiovascular diseases: recent advances classified by research methodologies

Epicardial adipose tissue (EAT) is located between the myocardium and visceral pericardium. The unique anatomy and physiology of the EAT determines its great potential in locally influencing adjacent tissues such as the myocardium and coronary arteries. Classified by research methodologies, this study reviews the latest research progress on the role of EAT in cardiovascular diseases (CVDs), particularly in patients with metabolic disorders. Studies based on imaging techniques demonstrated that increased EAT amount in patients with metabolic disorders is associated with higher risk of CVDs and increased mortality. Then, in-depth profiling studies indicate that remodeled EAT may serve as a local mediator of the deleterious effects of cardiometabolic conditions and plays a crucial role in CVDs. Further, in vitro coculture studies provided preliminary evidence that the paracrine effect of remodeled EAT on adjacent cardiomyocytes can promote the occurrence and progression of CVDs. Considering the important role of EAT in CVDs, targeting EAT might be a potential strategy to reduce cardiovascular risks. Several interventions have been proved effective in reducing EAT amount. Our review provides valuable insights of the relationship between EAT, metabolic disorders, and CVDs, as well as an overview of the methodological constructs of EAT-related studies.

MicroRNAs in extracellular vesicles released from epicardial adipose tissue promote arrhythmogenic conduction slowing

Background

Patients with excess epicardial adipose tissue (EAT) are at increased risk of developing cardiac arrhythmias. EAT promotes arrhythmias by depolarizing the resting membrane of cardiomyocytes, which slows down conduction and facilitates re-entrant arrhythmias. We hypothesized that EAT slows conduction by secreting extracellular vesicles (EVs) and their microRNA (miRNA) cargo.

Objective

We aimed to determine the role of EAT-derived EVs and their miRNA cargo in conduction slowing.

Methods

EAT and subcutaneous adipose tissue (SAT) were collected from patients with atrial fibrillation. Adipose tissue explants were incubated in culture medium and secretome was collected. The numbers of EVs in the EAT and SAT secretome were measured by calibrated flow cytometry. EVs in the EAT secretome were isolated by size exclusion chromatography and miRNAs were sequenced. Pathway analysis was performed to predict candidates involved in cardiac electrophysiology. The candidates were validated in the EAT and SAT by quantitative real-time polymerase chain reaction. Finally, miRNA candidates were overexpressed in neonatal rat ventricular myocytes.

Results

The EV concentration was higher in the EAT secretome than in the SAT and control secretomes. miRNA sequencing of EAT-derived EVs detected a total of 824 miRNAs. Pathway analysis led to the identification of 7 miRNAs potentially involved in regulation of cardiac resting membrane potential. Validation of those miRNA candidates showed that they were all expressed in EAT, and that miR-1-3p and miR-133a-3p were upregulated in EAT in comparison with SAT. Overexpression of miR-1-3p and miR-133a-3p in neonatal rat ventricular myocytes led to conduction slowing and reduced Kcnj2 and Kcnj12 expression.

Conclusion

miR-1-3p and miR-133a-3p are potential mediators of EAT arrhythmogenicity.

Association Between Epicardial Adipose Tissue and Left Atrial and Ventricular Function in Patients With Heart Failure: A Systematic Review and Meta-Analysis

Existing evidence suggested that the role of epicardial adipose tissue (EAT) in heart failure with reduced and preserved ejection fraction (HFrEF/HFpEF) might be divergent. Here, we conducted a systematic review and meta-analysis to evaluate the association between EAT and HF. Several databases were searched from their inception to January 20, 2023. We calculated the standard mean difference (SMD) in EAT between the HF and control groups, as well as the correlation coefficient between EAT and left atrial (LA) and left ventricular (LV) function. This meta-analysis included 23 studies, involving 1563 HFrEF and 1351 HFpEF patients. Our findings indicated that EAT was significantly higher in HFpEF patients (SMD: 0.61, 95% CI: 0.27-0.94), but not in total HF or HFrEF patients compared to controls. In HFrEF, EAT was positively correlated with LVEF, LV end-diastolic volume index (LVEDVI), LA global longitudinal strain (LAGLS), and negatively correlated with N-terminal pro-B-type natriuretic peptide (NT-ProBNP). However, no significant relationship existed between EAT and LV mass index (LVMI) or LVGLS. For HFpEF, EAT correlated positively with LVMI, LVEDVI, LV end-systolic volume index (LVESVI), LA volume index (LAVI), cardiac troponin T, and extracellular volume (ECV), but negatively with LVGLS and LAGLS. EAT was shown to be higher in HFpEF, but not in HFrEF. Less EAT was linked with worse LA function but not worse LV function in HFrEF, while more EAT was associated with worse LA/LV function in HFpEF.

The role of perivascular adipose tissue-secreted adipocytokines in cardiovascular disease

Perivascular adipose tissue and the vessel wall are connected through intricate bidirectional paracrine and vascular secretory signaling pathways. The secretion of inflammatory factors and oxidative products by the vessel wall in the diseased segment has the ability to influence the phenotype of perivascular adipocytes. Additionally, the secretion of adipokines by perivascular adipose tissue exacerbates the inflammatory response in the diseased vessel wall. Therefore, quantitative and qualitative studies of perivascular adipose tissue are of great value in the context of vascular inflammation and may provide a reference for the assessment of cardiovascular ischemic disease.

Epicardial adipose tissue and cardiac lipotoxicity: A review

Epicardial adipose tissue (EAT) has morphological and physiological contiguity with the myocardium and coronary arteries, making it a visceral fat deposit with some unique properties. Under normal circumstances, EAT exhibits biochemical, mechanical, and thermogenic cardioprotective characteristics. Under clinical processes, epicardial fat can directly impact the heart and coronary arteries by secreting proinflammatory cytokines via vasocrine or paracrine mechanisms. It is still not apparent what factors affect this equilibrium. Returning epicardial fat to its physiological purpose may be possible by enhanced local vascularization, weight loss, and focused pharmacological therapies. This review centers on EAT's developing physiological and pathophysiological dimensions and its various and pioneering clinical utilities.

Amino acids contribute to adaptive thermogenesis. New insights into the mechanisms of action of recent drugs for metabolic disorders are emerging

Adaptive thermogenesis is the heat production by muscle contractions (shivering thermogenesis) or brown adipose tissue (BAT) and beige fat (non-shivering thermogenesis) in response to external stimuli, including cold exposure. BAT and beige fat communicate with peripheral organs and the brain through a variegate secretory and absorption processes - controlling adipokines, microRNAs, extracellular vesicles, and metabolites - and have received much attention as potential therapeutic targets for managing obesity-related disorders. The sympathetic nervous system and norepinephrine-releasing adipose tissue macrophages (ATM) activate uncoupling protein 1 (UCP1), expressed explicitly in brown and beige adipocytes, dissolving the electrochemical gradient and uncoupling tricarboxylic acid cycle and the electron transport chain from ATP production. Mounting evidence has attracted attention to the multiple effects of dietary and endogenously synthesised amino acids in BAT thermogenesis and metabolic phenotype in animals and humans. However, the mechanisms implicated in these processes have yet to be conclusively characterized. In the present review article, we aim to define the principal investigation areas in this context, including intestinal microbiota constitution, adipose autophagy modulation, and secretome and metabolic fluxes control, which lead to increased brown/beige thermogenesis. Finally, also based on our recent epicardial adipose tissue results, we summarise the evidence supporting the notion that the new dual and triple agonists of glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), and glucagon (GCG) receptor - with never before seen weight loss and insulin-sensitizing efficacy - promote thermogenic-like amino acid profiles in BAT with robust heat production and likely trigger sympathetic activation and adaptive thermogenesis by controlling amino acid metabolism and ATM expansion in BAT and beige fat.

Epicardial Adipose Tissue and Development of Atrial Fibrillation (AFIB) and Heart Failure With Preserved Ejection Fraction (HFpEF)

Epicardial adipose tissue (EAT) has been associated with the development of many cardiovascular abnormalities, of which the development of atrial fibrillation (AFIB) in this group of patients is not an uncommon finding. Several mechanisms have been proposed to explain the role of EAT in the development of AFIB. It involves cardiac remodeling owing to the underlying fatty infiltration and the subsequent inflammation and fibrosis. This leads to the formation of ectopic foci that can lead to AFIB. Some studies propose that structural and valvular heart disease and increased hemodynamic stress further augment the development of AFIB in patients with underlying EAT. The degree of development of AFIB is also related to EAT thickness and volume. Therefore, EAT quantification can be used as an imaging technique to predict cardiovascular outcomes in these patients. Obesity also plays an important role in the development of AFIB both as an independent factor and by leading to adipose tissue deposition on the epicardial tissue. Understanding the pathophysiology of EAT is important as it can lead to the development of therapies that can target obesity as a risk factor for preventing AFIB. Some promising therapies have already been investigated for decreasing the risk of AFIB in patients with EAT. Dietary changes and weight loss have been shown to reduce the deposition of fat on epicardial tissue. Antidiabetic drugs and statin therapy have also shown promising results. Bariatric surgery has been shown to decrease EAT volume on echocardiography in obese patients.

Role of Epicardial Adipose Tissue Secretome on Cardiovascular Diseases

Obesity and insulin resistance are associated with the inflamed and defective adipose tissue (AT) phenotype, and are established risk factors for cardiovascular diseases (CVDs). Extracellular vesicles (EVs) are a heterogeneous group of cell-derived lipid membrane vesicles involved in the onset and development of many pathologies, including insulin resistance, diabetes, and CVDs. The inflammation associated with overweight and obesity triggers the transition of the AT secretome from healthy to pathological, with a consequent increased expression of pro-inflammatory mediators. Epicardial adipose tissue (EAT) is a specialized fat depot that surrounds the heart, in direct contact with the myocardium. Recently, the role of EAT in regulating the physiopathology of many heart diseases has been increasingly explored. In particular, the EAT phenotype and derived EVs have been associated with the onset and exacerbation of CVDs. In this review, we will focus on the role of the AT secretome in the case of CVDs, and will discuss the beneficial effects of EVs released by AT as promising therapeutic candidates.

The role of epicardial adipose tissue dysfunction in cardiovascular diseases: an overview of pathophysiology, evaluation, and management

In recent decades, the epicardial adipose tissue (EAT) has been at the forefront of scientific research because of its diverse role in the pathogenesis of cardiovascular diseases (CVDs). EAT lies between the myocardium and the visceral pericardium. The same microcirculation exists both in the epicardial fat and the myocardium. Under physiological circumstances, EAT serves as cushion and protects coronary arteries and myocardium from violent distortion and impact. In addition, EAT acts as an energy lipid source, thermoregulator, and endocrine organ. Under pathological conditions, EAT dysfunction promotes various CVDs progression in several ways. It seems that various secretions of the epicardial fat are responsible for myocardial metabolic disturbances and, finally, leads to CVDs. Therefore, EAT might be an early predictor of CVDs. Furthermore, different non-invasive imaging techniques have been proposed to identify and assess EAT as an important parameter to stratify the CVD risk. We also present the potential therapeutic possibilities aiming at modifying the function of EAT. This paper aims to provide overview of the potential role of EAT in CVDs, discuss different imaging techniques to assess EAT, and provide potential therapeutic options for EAT. Hence, EAT may represent as a potential predictor and a novel therapeutic target for management of CVDs in the future.

Epicardial and thoracic subcutaneous fat texture analysis in patients undergoing cardiac CT

Introduction

The aim of our study was to evaluate the feasibility of texture analysis of epicardial fat (EF) and thoracic subcutaneous fat (TSF) in patients undergoing cardiac CT (CCT).

Materials and methods

We compared a consecutive population of 30 patients with BMI ≤25 kg/m² (Group A, 60.6 ± 13.7 years) with a control population of 30 patients with BMI >25 kg/m² (Group B, 63.3 ± 11 years). A dedicated computer application for quantification of EF and a texture analysis application for the study of EF and TSF were employed.

Results

The volume of EF was higher in group B (mean 116.1 cm³ vs. 86.3 cm³, p = 0.014), despite no differences were found neither in terms of mean density (-69.5 ± 5 HU vs. -68 ± 5 HU, p = 0.28), nor in terms of quartiles distribution (Q1, p = 0.83; Q2, p = 0.22, Q3, p = 0.83, Q4, p = 0.34). The discriminating parameters of the histogram class were mean (p = 0.02), 0,1st (p = 0.001), 10_th (p = 0.002), and 50_th percentiles (p = 0.02). DifVarnc was the discriminating parameter of the co-occurrence matrix class (p = 0.007).The TSF thickness was 15 ± 6 mm in group A and 19.5 ± 5 mm in group B (p = 0.003). The TSF had a mean density of -97 ± 19 HU in group A and -95.8 ± 19 HU in group B (p = 0.75). The discriminating parameters of texture analysis were 10_th (p = 0.03), 50_th (p = 0.01), 90_th percentiles (p = 0.04), S(0,1)SumAverg (p = 0.02), S(1,-1)SumOfSqs (p = 0.02), S(3,0)Contrast (p = 0.03), S(3,0)SumAverg (p = 0.02), S(4,0)SumAverg (p = 0.04), Horzl_RLNonUni (p = 0.02), and Vertl_LngREmph (p = 0.0005).

Conclusions

Texture analysis provides distinctive radiomic parameters of EF and TSF. EF and TSF had different radiomic features as the BMI varies.

Epicardial fat links obesity to cardiovascular diseases

Patients with obesity have been historically associated with higher risk to develop cardiovascular diseases (CVD). However, regional, visceral, organ specific adiposity seems to play a stronger role in the development of those cardiovascular diseases than obesity by itself. Epicardial adipose tissue is the visceral fat depot of the heart with peculiar anatomy, regional differences, genetic profile and functions. Due to its unobstructed contiguity with heart and intense pro inflammatory and pro arrhythmogenic activities, epicardial fat is directly involved in major obesity-related CVD complications, such as coronary artery disease (CAD), atrial fibrillation (AF) and heart failure (HF). Current and developing imaging techniques can measure epicardial fat thickness, volume, density and inflammatory status for the prediction and stratification of the cardiovascular risk in both symptomatic and asymptomatic obese individuals. Pharmacological modulation of the epicardial fat with glucagon like peptide-1 receptor (GLP1R) analogs, sodium glucose transporter-2 inhibitors, and potentially dual (glucose-dependent insulinotropic polypeptide -GLP1R) agonists, can reduce epicardial fat mass, resume its original cardio-protective functions and therefore reduce the cardiovascular risk. Epicardial fat assessment is poised to change the traditional paradigm that links obesity to the heart.

The Different Pathways of Epicardial Adipose Tissue across the Heart Failure Phenotypes: From Pathophysiology to Therapeutic Target

Epicardial adipose tissue (EAT) is an endocrine and paracrine organ constituted by a layer of adipose tissue directly located between the myocardium and visceral pericardium. Under physiological conditions, EAT exerts protective effects of brown-like fat characteristics, metabolizing excess fatty acids, and secreting anti-inflammatory and anti-fibrotic cytokines. In certain pathological conditions, EAT acquires a proatherogenic transcriptional profile resulting in increased synthesis of biologically active adipocytokines with proinflammatory properties, promoting oxidative stress, and finally causing endothelial damage. The role of EAT in heart failure (HF) has been mainly limited to HF with preserved ejection fraction (HFpEF) and related to the HFpEF obese phenotype. In HFpEF, EAT seems to acquire a proinflammatory profile and higher EAT values have been related to worse outcomes. Less data are available about the role of EAT in HF with reduced ejection fraction (HFrEF). Conversely, in HFrEF, EAT seems to play a nutritive role and lower values may correspond to the expression of a catabolic, adverse phenotype. As of now, there is evidence that the beneficial systemic cardiovascular effects of sodium-glucose cotransporter-2 receptors-inhibitors (SGLT2-i) might be partially mediated by inducing favorable modifications on EAT. As such, EAT may represent a promising target organ for the development of new drugs to improve cardiovascular prognosis. Thus, an approach based on detailed phenotyping of cardiac structural alterations and distinctive biomolecular pathways may change the current scenario, leading towards a precision medicine model with specific therapeutic targets considering different individual profiles. The aim of this review is to summarize the current knowledge about the biomolecular pathway of EAT in HF across the whole spectrum of ejection fraction, and to describe the potential of EAT as a therapeutic target in HF.

The Role of Epicardial Adipose Tissue-Derived MicroRNAs in the Regulation of Cardiovascular Disease: A Narrative Review

Cardiovascular diseases have been leading cause of death worldwide for many decades, and obesity has been acknowledged as a risk factor for cardiovascular diseases. In the present review, human epicardial adipose tissue-derived miRNAs reported to be differentially expressed under pathologic conditions are discussed and summarized. The results of the literature review indicate that some of the epicardial adipose tissue-derived miRNAs are believed to be cardioprotective, while some others show quite the opposite effects depending on the underlying pathologic conditions. Furthermore, they suggest that that the epicardial adipose tissue-derived miRNAs have great potential as both a diagnostic and therapeutic modality. Nevertheless, mainly due to highly limited availability of human samples, it is very difficult to make any generalized claims on a given miRNA in terms of its overall impact on the cardiovascular system. Therefore, further functional investigation of a given miRNA including, but not limited to, the study of its dose effect, off-target effects, and potential toxicity is required. We hope that this review can provide novel insights to transform our current knowledge on epicardial adipose tissue-derived miRNAs into clinically viable therapeutic strategies for preventing and treating cardiovascular diseases.

Treatment Resulting Changes in Volumes of High-18F-FDG-Uptake Adipose Tissues over Orbit and Epicardium Correlate with Treatment Response for Non-Hodgkin's Lymphoma

BACKGROUND

A regimen of rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) is the standard treatment for non-Hodgkin's lymphoma. Brown adipose tissue possesses anti-cancer potential. This study aimed to explore practical biomarkers for non-Hodgkin's lymphoma by analyzing the metabolic activity of adipose tissue.

METHODS

Twenty patients who received R-CHOP for non-Hodgkin's lymphoma were reviewed. Positron emission tomography/computed tomography (PET/CT) images, lactate dehydrogenase (LDH) levels, and body mass index (BMI) before and after treatment were collected. Regions with a high standardized uptake value (SUV) in epicardial and orbital adipose tissue were selected and analyzed by a PET/CT viewer. The initial measurements and changes in the high SUV of epicardial and orbital adipose tissues, LDH levels, and BMI of treatment responders and non-responders, and complete and partial responders, were compared.

RESULTS

The volumes of high-SUV epicardial and orbital adipose tissues significantly increased in responders after R-CHOP (p = 0.03 and 0.002, respectively). There were significant differences between changes in the high-SUV volumes of epicardial and orbital adipose tissues (p = 0.03 and 0.001, respectively) and LDH levels (p = 0.03) between responders and non-responders. The changes in high-SUV epicardial adipose tissue volumes were greater among complete responders than partial responders (p = 0.04). Poorer treatment responses were observed in patients with lower high-SUV epicardial adipose tissue volumes and higher LDH levels after R-CHOP (p = 0.03 and 0.03, respectively).

CONCLUSIONS

The preliminary results of greater changes in high-SUV epicardial and orbital adipose tissue volumes among responders indicate that brown adipose tissue could be considered a favorable prognostic biomarker.

Sodium-glucose co-transporter-2 inhibitors and epicardial adiposity

Epicardial adipose tissue is a layer of adipocytes that physiologically surround the myocardium and play some physiologic roles in normal heart function. However, in pathologic conditions, the epicardial adipose tissue can present a potent cardiac risk factor that is capable of impairing heart function through several pathways, increasing the risk of dysrhythmia and creating an inflammatory milieu around the heart tissues. Sodium-glucose cotransporter 2 inhibitors (SGLT2is) are a relatively newly introduced class of antidiabetes drugs which effectively normalize blood glucose via overt glycosuria. Some recent reports suggest that these drugs are able to modulate epicardial adiposity and decrease the risk of cardiac complications in diabetic patients who are at higher risk of epicardial adiposity-dependent cardiac disorders. If proven to be true, these antidiabetic drugs can provide dual benefits as both hypoglycemic agents and as epicardial adiposity normalizing agents, thus providing cardiac benefits. In this study, we discuss the physiological and pathophysiological importance of epicardial adiposity and the potential positive effects of SGLT2is in the diabetic milieu.

Epicardial Adipose Tissue and Diabetic Cardiomyopathy

Diabetes is a long-term chronic disease, and cardiovascular disease is the leading cause of death. Diabetic cardiomyopathy (DCM), one of the cardiovascular complications of diabetes, has many uncertain factors. Epicardial fat, as the heart fat bank, functions as fatty tissue and is the heart's endocrine organ. The existence of diabetes affects the distribution of heart fat and promotes the secretion of adipokine. In different pathological conditions, it can promote the secretion of pro-inflammatory adipokine, reactive oxygen species, oxidative stress, and even autophagy, thus affecting cardiac function. In this paper, we will elaborate on the mechanism of epicardial fat in the pathogenesis of diabetic cardiomyopathy.

Benefits of GLP-1 Mimetics on Epicardial Adiposity

The epicardial adipose tissue, which is referred to as fats surrounding the myocardium, is an active organ able to induce cardiovascular problems in pathophysiologic conditions through several pathways, such as inflammation, fibrosis, fat infiltration, and electrophysiologic problems. So, control of its volume and thickness, especially in patients with diabetes, is highly important. Incretin-based pharmacologic agents are newly developed antidiabetics that could provide further cardiovascular benefits through control and modulating epicardial adiposity. They can reduce cardiovascular risks by rapidly reducing epicardial adipose tissues, improving cardiac efficiency. We are at the first steps of a long way, but current evidence demonstrates the sum of possible mechanisms. In this study, we evaluate epicardial adiposity in physiologic and pathologic states and the impact of incretin-based drugs.

The Influence of the Differentiation of Genes Encoding Peroxisome Proliferator-Activated Receptors and Their Coactivators on Nutrient and Energy Metabolism

Genetic components may play an important role in the regulation of nutrient and energy metabolism. In the presence of specific genetic variants, metabolic dysregulation may occur, especially in relation to the processes of digestion, assimilation, and the physiological utilization of nutrients supplied to the body, as well as the regulation of various metabolic pathways and the balance of metabolic changes, which may consequently affect the effectiveness of applied reduction diets and weight loss after training. There are many well-documented studies showing that the presence of certain polymorphic variants in some genes can be associated with specific changes in nutrient and energy metabolism, and consequently, with more or less desirable effects of applied caloric reduction and/or exercise intervention. This systematic review focused on the role of genes encoding peroxisome proliferator-activated receptors (PPARs) and their coactivators in nutrient and energy metabolism. The literature review prepared showed that there is a link between the presence of specific alleles described at different polymorphic points in PPAR genes and various human body characteristics that are crucial for the efficacy of nutritional and/or exercise interventions. Genetic analysis can be a valuable element that complements the work of a dietitian or trainer, allowing for the planning of a personalized diet or training that makes the best use of the innate metabolic characteristics of the person who is the subject of their interventions.

Connecting epicardial adipose tissue and heart failure with preserved ejection fraction: mechanisms, management and modern perspectives

Obesity is very common in patients with heart failure with preserved ejection fraction (HFpEF) and it has been suggested that obesity plays an important role in the pathophysiology of this disease. While body mass index defines the presence of obesity, this measure provides limited information on visceral adiposity, which is probably more relevant in the pathophysiology of HFpEF. Epicardial adipose tissue is the visceral fat situated directly adjacent to the heart and recent data demonstrate that accumulation of epicardial adipose tissue is associated with the onset, symptomatology and outcome of HFpEF. However, the mechanisms by which epicardial adipose tissue may be involved in HFpEF remain unclear. It is also questioned whether epicardial adipose tissue may be a specific target for therapy for this disease. In the present review, we describe the physiology of epicardial adipose tissue and the pathophysiological transformation of epicardial adipose tissue in response to chronic inflammatory diseases, and we postulate conceptual mechanisms on how epicardial adipose tissue may be involved in HFpEF pathophysiology. Lastly, we outline potential treatment strategies, knowledge gaps and directions for further research.

Depot-specific adipose tissue modulation by SGLT2 inhibitors and GLP1 agonists mediates their cardioprotective effects in metabolic disease

Sodium-glucose transporter-2 inhibitors (SGLT-2i) and glucagon-like peptide 1 (GLP-1) receptor agonists are newer antidiabetic drug classes, which were recently shown to decrease cardiovascular (CV) morbidity and mortality in diabetic patients. CV benefits of these drugs could not be directly attributed to their blood glucose lowering capacity possibly implicating a pleotropic effect as a mediator of their impact on cardiovascular disease (CVD). Particularly, preclinical and clinical studies indicate that SGLT-2i(s) and GLP-1 receptor agonists are capable of differentially modulating distinct adipose pools reducing the accumulation of fat in some depots, promoting the healthy expansion of others, and/or enhancing their browning, leading to the suppression of the metabolically induced inflammatory processes. These changes are accompanied with improvements in markers of cardiac structure and injury, coronary and vascular endothelial healing and function, vascular remodeling, as well as reduction of atherogenesis. Here, through a summary of the available evidence, we bring forth our view that the observed CV benefit in response to SGLT-2i or GLP-1 agonists therapy might be driven by their ameliorative impact on adipose tissue inflammation.

Impact of Dysfunctional Adipose Tissue Depots on the Cardiovascular System

Obesity with its associated complications represents a social, economic and health problem of utmost importance worldwide. Specifically, obese patients carry a significantly higher risk of developing cardiovascular disease compared to nonobese individuals. Multiple molecular mechanisms contribute to the impaired biological activity of the distinct adipose tissue depots in obesity, including secretion of proinflammatory mediators and reactive oxygen species, ultimately leading to an unfavorable impact on the cardiovascular system. This review summarizes data relating to the contribution of the main adipose tissue depots, including both remote (i.e., intra-abdominal, hepatic, skeletal, pancreatic, renal, and mesenteric adipose fat), and cardiac (i.e., the epicardial fat) adipose locations, on the cardiovascular system. Finally, we discuss both pharmacological and non-pharmacological strategies aimed at reducing cardiovascular risk through acting on adipose tissues, with particular attention to the epicardial fat.

Crosstalk Between Adipose Tissue and the Heart: An Update

It is important to understand how different human organs coordinate and interact with each other. Since obesity and cardiac disease frequently coincide, the crosstalk between adipose tissues and heart has drawn attention. We appreciate that specific peptides/proteins, lipids, nucleic acids, and even organelles shuttle between the adipose tissues and heart. These bioactive components can profoundly affect the metabolism of cells in distal organs, including heart. Importantly, this process can be dysregulated under pathophysiological conditions. This also opens the door to efforts targeting these mediators as potential therapeutic strategies to treat patients who manifest diabetes and cardiovascular disease. Here, we summarize the recent progress toward a better understanding of how the adipose tissues and heart interact with each other.

CHCHD10 Modulates Thermogenesis of Adipocytes by Regulating Lipolysis

Brown and beige adipocytes dissipate energy in a nonshivering thermogenesis manner, exerting beneficial effects on metabolic homeostasis. CHCHD10 is a nuclear-encoded mitochondrial protein involved in cristae organization; however, its role in thermogenic adipocytes remains unknown. We identify CHCHD10 as a novel regulator for adipocyte thermogenesis. CHCHD10 is dramatically upregulated during thermogenic adipocyte activation by PPARγ-PGC1α and positively correlated with UCP1 expression in adipose tissues from humans and mice. We generated adipocyte-specific Chchd10 knockout mice (Chchd10-AKO) and found that depleting CHCHD10 leads to impaired UCP1-dependent thermogenesis and energy expenditure in the fasting state, with no effect in the fed state. Lipolysis in adipocytes is disrupted by CHCHD10 deficiency, while augmented lipolysis through ATGL overexpression recovers adipocyte thermogenesis in Chchd10-AKO mice. Consistently, overexpression of Chchd10 activates thermogenic adipocytes. Mechanistically, CHCHD10 deficiency results in the disorganization of mitochondrial cristae, leading to impairment of oxidative phosphorylation complex assembly in mitochondria, which in turn inhibits ATP generation. Decreased ATP results in downregulation of lipolysis by reducing nascent protein synthesis of ATGL, thereby suppressing adipocyte thermogenesis. As a result, Chchd10-AKO mice are prone to develop high-fat diet-induced metabolic disorders. Together, our findings reveal an essential role of CHCHD10 in regulating lipolysis and the thermogenic program in adipocytes.

Epicardial Adipose Tissue as an Independent Cardiometabolic Risk Factor for Coronary Artery Disease

During the last decades, visceral adiposity has been at the forefront of scientific research because of its complex role in the pathogenesis of cardiovascular diseases. Epicardial adipose tissue (EAT) is the visceral lipid compartment between the myocardium and the visceral pericardium. Due to their unobstructed anatomic vicinity, epicardial fat and myocardium are nourished by the same microcirculation. It is widely known that EAT serves as an energy lipid source and thermoregulator for the human heart. In addition to this, epicardial fat exerts highly protective effects since it releases a great variety of anti-inflammatory molecules to the adjacent cardiac muscle. Taking into account the unique properties of human EAT, it is undoubtedly a key factor in cardiac physiology since it facilitates complex heart functions. Under pathological circumstances, however, epicardial fat promotes coronary atherosclerosis in a variety of ways. Therefore, the accurate estimation of epicardial fat thickness and volume could be utilized as an early detecting method and future medication target for coronary artery disease (CAD) elimination. Throughout the years, several therapeutic approaches for dysfunctional human EAT have been proposed. A balanced healthy diet, aerobic and anaerobic physical activity, bariatric surgery, and pharmacological treatment with either traditional or novel antidiabetic and antilipidemic drugs are some of the established medical approaches. In the present article, we review the current knowledge regarding the anatomic and physiological characteristics of epicardial fat. In addition to this, we describe the pathogenic mechanisms which refer to the crosstalk between epicardial fat alteration and coronary arterial atherosclerosis development. Lastly, we present both lifestyle and pharmacological methods as possible treatment options for EAT dysfunction. 

Quantification of epicardial adipose tissue in obese patients using an open-bore MR scanner

Background

Our aim was to evaluate the reproducibility of epicardial adipose tissue (EAT) volume, measured on scans performed using an open-bore magnetic resonance scanner.

Methods

Consecutive patients referred for bariatric surgery, aged between 18 and 65 years who agreed to undergo cardiac imaging (MRI), were prospectively enrolled. All those with cardiac pathology or contraindications to MRI were excluded. MRI was performed on a 1.0-T open-bore scanner, and EAT was segmented on all scans at both systolic and diastolic phase by two independent readers (R1 with four years of experience and R2 with one year). Data were reported as median and interquartile range; agreement and differences were appraised with Bland-Altman analyses and Wilcoxon tests, respectively.

Results

Fourteen patients, 11 females (79%) aged 44 (41–50) years, underwent cardiac MRI. For the first and second readings, respectively, EAT volume was 86 (78–95) cm³ and 85 (79–91) cm³ at systole and 82 (74–95) cm³ and 81 (75–94) cm³ at diastole for R1, and 89 (79–99) cm³ and 93 (84–98) cm³ at systole and 92 (85–103) cm³ and 93 (82–94) cm³ at diastole for R2. R1 had the best reproducibility at diastole (bias 0.3 cm³, standard deviation of the differences (SD) 3.3 cm³). R2 had the worst reproducibility at diastole (bias 3.9 cm³, SD 12.1 cm³). The only significant difference between systole and diastole was at the first reading by R1 (p = 0.016). The greatest bias was that of inter-reader reproducibility at diastole (-9.4 cm³).

Conclusions

Reproducibility was within clinically acceptable limits in most instances.

Profiling of Non-Coding Regulators and Their Targets in Epicardial Fat from Patients with Coronary Artery Disease

Epicardial fat is a continuously growing target of investigation in cardiovascular diseases due to both its anatomical proximity to the heart and coronary circulation and its unique physiology among adipose depots. Previous reports have demonstrated that epicardial fat plays key roles in coronary artery disease, but the non-coding RNA and transcriptomic alterations of epicardial fat in coronary artery disease have not been investigated thoroughly. Micro- and lncRNA microarrays followed by GO-KEGG functional enrichment analysis demonstrated sex-dependent unique mi/lncRNAs altered in human epicardial fat in comparison to subcutaneous fat in both patients with and without coronary artery disease (IRB approved). Among the 14 differentially expressed microRNAs in epicardial fat between patients with and without coronary artery disease, the hsa-miR-320 family was the most highly represented. IPW lncRNA interacted with three of these differentially expressed miRNAs. Next-generation sequencing and pathway enrichment analysis identified six unique mRNAs–miRNA pairs. Pathway enrichment identified inflammation, adipogenesis, and cardiomyocyte apoptosis as the most represented functions altered by the mi/lncRNAs and atherosclerosis and myocardial infarction among the highest cardiovascular pathologies associated with them. Overall, the epicardial fat in patients with coronary artery disease has a unique mi/lncRNA profile which is sex-dependent and has potential implications for regulating cardiac function.

A preliminary coronary computed tomography angiography-based study of perivascular fat attenuation index: relation with epicardial adipose tissue and its distribution over the entire coronary vasculature

OBJECTIVES

To investigate the perivascular fat attenuation index (FAI) in association with epicardial adipose tissue (EAT) parameters and its distribution over the entire coronary vasculature in patients with known or suspected coronary artery disease (CAD).

METHODS

Patients with known or suspected CAD who underwent coronary computed tomography angiography from January 1, 2019, to June 1, 2019, were retrospectively included. The perivascular FAI was quantified on four main epicardial coronary arteries and seven coronary segments. Moreover, EAT density and volume were measured.

RESULTS

We included 192 consecutive patients (55 without coronary plaque [mean age 46.4 ± 13.2 years, 69.1% male] and 137 with coronary plaque [mean age 57.9 ± 13.0 years, 84.7% male]). EAT density was lower than perivascular FAI in both groups, but they exhibited substantial correlation (- 83.33 ± 4.54 vs. - 78.22 ± 6.52 HU, p < 0.001; r = 0.667 in plaque- patients and - 83.11 ± 4.48 vs. - 77.81 ± 5.63 HU, p < 0.001; r = 0.778 in plaque+ patients). The left main coronary artery had the highest perivascular FAI, followed by the left circumflex artery. The perivascular FAI in proximal segments was significantly higher compared to that in distal segments (all p < 0.05). Furthermore, the presence of plaque did not alter perivascular FAI on the patient or segmental level.

CONCLUSION

The perivascular FAI was significantly higher than EAT density and correlated substantially with EAT density. The perivascular FAI distribution over the entire coronary tree varied and prompted for vessel-specific or segment-specific thresholds to determine abnormal perivascular FAI in practice.

KEY POINTS

• The perivascular FAI correlated well with EAT density and had higher values than EAT density. • The distributions of perivascular FAI differ between coronary vessels or segments; considering segment and vessel confounding factors while conducting a perivascular FAI study is necessary. • No significant difference of perivascular FAI was observed between patients without and with coronary plaque, nor between coronary segments without plaque and those with plaque.

Epicardial adipose tissue in contemporary cardiology

Interest in epicardial adipose tissue (EAT) is growing rapidly, and research in this area appeals to a broad, multidisciplinary audience. EAT is unique in its anatomy and unobstructed proximity to the heart and has a transcriptome and secretome very different from that of other fat depots. EAT has physiological and pathological properties that vary depending on its location. It can be highly protective for the adjacent myocardium through dynamic brown fat-like thermogenic function and harmful via paracrine or vasocrine secretion of pro-inflammatory and profibrotic cytokines. EAT is a modifiable risk factor that can be assessed with traditional and novel imaging techniques. Coronary and left atrial EAT are involved in the pathogenesis of coronary artery disease and atrial fibrillation, respectively, and it also contributes to the development and progression of heart failure. In addition, EAT might have a role in coronavirus disease 2019 (COVID-19)-related cardiac syndrome. EAT is a reliable potential therapeutic target for drugs with cardiovascular benefits such as glucagon-like peptide 1 receptor agonists and sodium–glucose co-transporter 2 inhibitors. This Review provides a comprehensive and up-to-date overview of the role of EAT in cardiovascular disease and highlights the translational nature of EAT research and its applications in contemporary cardiology.

In this Review, Iacobellis provides a comprehensive overview of the role of epicardial adipose tissue (EAT) in cardiovascular disease, including coronary artery disease, heart failure and atrial fibrillation, discusses imaging techniques for EAT assessment and highlights the therapeutic potential of targeting EAT in cardiovascular disease.

Epicardial adipose tissue (EAT) has anatomical and functional interactions with the heart owing to the shared circulation and the absence of muscle fascia separating the two organs.

EAT can be clinically measured with cardiac imaging techniques that can help to predict and stratify cardiovascular risk.

Regional distribution of EAT is important because pericoronary EAT and left atrial EAT differently affect the risk of coronary artery diseases and atrial fibrillation, respectively.

EAT has a role in the development of several cardiovascular diseases through complex mechanisms, including gene expression profile, pro-inflammatory and profibrotic proteome, neuromodulation, and glucose and lipid metabolism.

EAT could be a potential therapeutic target for novel cardiometabolic medications that modulate adipose tissue such as glucagon-like peptide 1 receptor agonists and sodium–glucose co-transporter 2 inhibitors.

EAT might be a reservoir of severe acute respiratory syndrome coronavirus 2 and an amplifier of coronavirus disease 2019 (COVID-19)-related cardiac syndrome.

Browning Epicardial Adipose Tissue: Friend or Foe?

The epicardial adipose tissue (EAT) is the visceral fat depot of the heart which is highly plastic and in direct contact with myocardium and coronary arteries. Because of its singular proximity with the myocardium, the adipokines and pro-inflammatory molecules secreted by this tissue may directly affect the metabolism of the heart and coronary arteries. Its accumulation, measured by recent new non-invasive imaging modalities, has been prospectively associated with the onset and progression of coronary artery disease (CAD) and atrial fibrillation in humans. Recent studies have shown that EAT exhibits beige fat-like features, and express uncoupling protein 1 (UCP-1) at both mRNA and protein levels. However, this thermogenic potential could be lost with age, obesity and CAD. Here we provide an overview of the physiological and pathophysiological relevance of EAT and further discuss whether its thermogenic properties may serve as a target for obesity therapeutic management with a specific focus on the role of immune cells in this beiging phenomenon.

Epicardial adipose tissue in obesity-related cardiac dysfunction

Obesity is associated with the development of heart failure and is a major risk factor for heart failure with preserved ejection fraction (HFpEF). Epicardial adipose tissue (EAT) is a unique visceral fat in close proximity to the heart and is of particular interest to the study of cardiac disease. Small poorly differentiated adipocytes with altered lipid:water content are associated with a proinflammatory secretome and may contribute to the pathophysiology observed in HFpEF. Multimodality imaging approaches can be used to quantify EAT volume and characterise EAT composition. Current research studies remain unclear as to the magnitude of effect that EAT plays on myocardial dysfunction and further work using multimodality imaging techniques is ongoing. Pharmacological interventions, including glucagon-like peptide 1 receptor agonists and sodium-dependent glucose linked transporter 2 inhibitors have shown promise in attenuating the deleterious metabolic and inflammatory changes seen in EAT. Clinical studies are ongoing to explore whether these therapies exert their beneficial effects by modifying this unique adipose deposit.

Cardiovascular risk reduction throughout GLP-1 receptor agonist and SGLT2 inhibitor modulation of epicardial fat

Epicardial adipose tissue is a novel cardiovascular risk factor. It plays a role in the progression of coronary artery disease, heart failure and atrial fibrillation. Given its rapid metabolism, clinical measurability, and modifiability, epicardial fat works well as therapeutic target of drugs modulating the adipose tissue. Epicardial fat responds to glucagon-like peptide 1 receptor agonists (GLP1A) and sodium glucose co-transporter 2 inhibitors (SGLT2i). GLP-1A and SGLT2i provide weight loss and cardiovascular protective effects beyond diabetes control, as recently demonstrated. The potential of modulating the epicardial fat morphology and genetic profile with targeted pharmacological agents can open new avenues in the pharmacotherapy of diabetes and obesity, with particular focus on cardiovascular risk reduction.

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.

Functions and origins of cardiac fat

Triglyceride droplets can be stored within cardiac adipocytes (CAs) and cardiomyocytes in the heart. Cardiac adipocytes reside in three distinct regions: pericardial, epicardial, and intramyocardial adipose tissues. In healthy individuals, cardiac adipose tissues modulate cardiovascular functions and energy partitioning, which are, thus, protective. However, ectopic deposition of cardiac adipose tissues turns them into adverse lipotoxic, prothrombotic, and pro-inflammatory tissues with local and systemic contribution to the development of cardiovascular disorders. Accumulation of triglyceride droplets in cardiomyocytes may lead to lipotoxic injury of cardiomyocytes and contribute to the development of cardiac hypertrophy and dysfunction. Here, we summarize the roles of CAs and myocardial triglyceride droplets under physiological and pathological conditions and review the cellular sources of CAs in heart development and diseases. Understanding the functions and cellular origins of cardiac fat will provide clues for future studies on pathophysiological processes and treatment of cardiovascular diseases.

Epicardial adipose tissue as a mediator of cardiac arrhythmias

Obesity is associated with higher risks of cardiac arrhythmias. Although this may be partly explained by concurrent cardiometabolic ill-health, growing evidence suggests that increasing adiposity independently confers risk for arrhythmias. Among fat depots, epicardial adipose tissue (EAT) exhibits a proinflammatory secretome and, given the lack of fascial separation, has been implicated as a transducer of inflammation to the underlying myocardium. The present review explores the mechanisms underpinning adverse electrophysiological remodeling as a consequence of EAT accumulation and the consequent inflammation. We first describe the physiological and pathophysiological function of EAT and its unique secretome and subsequently discuss the evidence for ionic channel and connexin expression modulation as well as fibrotic remodeling induced by cytokines and free fatty acids that are secreted by EAT. Finally, we highlight how weight reduction and regression of EAT volume may cause reverse remodeling to ameliorate arrhythmic risk.

Dysregulated Epicardial Adipose Tissue as a Risk Factor and Potential Therapeutic Target of Heart Failure with Preserved Ejection Fraction in Diabetes

Cardiovascular (CV) disease and heart failure (HF) are the leading cause of mortality in type 2 diabetes (T2DM), a metabolic disease which represents a fast-growing health challenge worldwide. Specifically, T2DM induces a cluster of systemic metabolic and non-metabolic signaling which may promote myocardium derangements such as inflammation, fibrosis, and myocyte stiffness, which represent the hallmarks of heart failure with preserved ejection fraction (HFpEF). On the other hand, several observational studies have reported that patients with T2DM have an abnormally enlarged and biologically transformed epicardial adipose tissue (EAT) compared with non-diabetic controls. This expanded EAT not only causes a mechanical constriction of the diastolic filling but is also a source of pro-inflammatory mediators capable of causing inflammation, microcirculatory dysfunction and fibrosis of the underlying myocardium, thus impairing the relaxability of the left ventricle and increasing its filling pressure. In addition to representing a potential CV risk factor, emerging evidence shows that EAT may guide the therapeutic decision in diabetic patients as drugs such as metformin, glucagon-like peptide‑1 (GLP-1) receptor agonists and sodium-glucose cotransporter 2 inhibitors (SGLT2-Is), have been associated with attenuation of EAT enlargement.

Microvascular Inflammation and Cardiovascular Prevention: The Role of Microcirculation as Earlier Determinant of Cardiovascular Risk

Healthcare systems encumbered by cardiovascular diseases demand adequate cardiovascular prevention. Indeed, even with the most novel therapies, the residual cardiovascular risk still fuels morbidity and mortality. Addressing inflammation as a putative mediator of this risk has brought along promising in vitro results, though large clinical trials have only in part confirmed them. To fully exploit the therapeutic potential between the inflammatory hypothesis, a change of viewpoint is required. Focus on microcirculation, whose dysfunction is the primary driver of cardiometabolic disease, is mandatory. Several factors play a pivotal role in the capacity of microvascular inflammation to promote a health-to-disease transition: the adipose tissue (in particular, perivascular and epicardial), the mitochondria function, the hyperglycemic damage and their epigenetic signature. Indeed, the low-grade inflammatory response, which is now an acknowledged hallmark of cardiometabolic disease, is promoted by these mediators and leaves a permanent epigenetic scar on the microvasculature. Even if a more profound knowledge about the mechanisms of metabolic memory has been brought to light by recent evidence, we still have to fully understand its mechanisms and clinical potential. Addressing the detrimental role of inflammation by targeting the microvascular phenotype and leveraging epigenetics is the road down which we must go to achieve satisfactory cardiovascular prevention, ultimately leading to disease-free ageing.

Adipose-related microRNAs as modulators of the cardiovascular system: the role of epicardial adipose tissue

Adipose tissue expansion and subsequent metabolic dysfunction has been considered one of the major risk factors for development of cardiometabolic disease. Epicardial adipose tissue (EAT) in particular is a unique subtype of visceral adipose tissue located on the surface of the heart, around the coronary arteries. Due to its proximity, EAT can modulate the local metabolic and immune function of cardiomyocytes and coronary arteries. Several microRNAs have been described as key players in both cardiac and vascular function that when dysregulated will contribute to dysfunction. Here we review the influence of obesity in the crosstalk between specific adipose tissue types, in particular the EAT-secreted microRNAs, as key modulators of cardiac disease progression, not only as early biomarkers but also as therapeutic targets for cardiometabolic disease.

Impact of epicardial adipose tissue on cardiovascular haemodynamics, metabolic profile, and prognosis in heart failure

AIMS

We evaluated the impact of echocardiographic epicardial adipose tissue (EAT) on cardiovascular haemodynamics, metabolic profile and prognosis in heart failure (HF) using combined cardiopulmonary-echocardiography exercise stress.

METHODS AND RESULTS

We analysed EAT thickness of HF patients with reduced (HFrEF, n = 205) and preserved (HFpEF, n = 188) ejection fraction, including 44 controls. HFpEF patients displayed the highest EAT, while HFrEF patients had lower values than controls. EAT showed an inverse correlation with natriuretic peptides, troponin T and C-reactive protein in HFrEF, while having a direct association with troponin T and C-reactive protein in HFpEF. EAT was independently associated with peak oxygen consumption (VO₂ ) and peripheral extraction (AVO₂ diff), regardless of body mass index. EAT was inversely correlated with peak VO₂ and AVO₂ diff in HFpEF, while a direct association was observed in HFrEF, where lower EAT values were associated with worse left ventricular systolic dysfunction. In HFpEF, increased EAT was related to right ventriculo-arterial (tricuspid annular plane systolic excursion/systolic pulmonary artery pressure) uncoupling. After 21 months of follow-up, 146 HF hospitalizations and 34 cardiovascular deaths were recorded in the HF population. Cox multivariable analysis supported an independent differential role of EAT in HF cohorts (interaction P = 0.01): higher risk of adverse events for increasing EAT in HFpEF [hazard ratio (HR) 1.12, 95% confidence interval (CI) 1.04-1.37] and for decreasing EAT in HFrEF (HR 0.75, 95% CI 0.54-0.91).

CONCLUSION

In HFpEF, EAT accumulation is associated with worse haemodynamic and metabolic profile, also affecting survival. Conversely, lower EAT values imply higher left ventricular dysfunction, global functional impairment and adverse prognosis in HFrEF.

Thoracic Visceral Adipose Tissue Area and Pulmonary Hypertension in Lung Transplant Candidates. The Lung Transplant Body Composition Study

Rationale: Obesity is associated with an increased risk of pulmonary hypertension (PH); however, regional adipose tissue deposition is heterogeneous with distinct cardiovascular phenotypes.Objectives: To determine the association of body mass index (BMI) and thoracic visceral and subcutaneous adipose tissue areas (VAT and SAT, respectively) with PH in patients with advanced lung disease referred for lung transplantation.Methods: We studied patients undergoing evaluation for lung transplantation at three centers from the Lung Transplant Body Composition Study. PH was defined as mean pulmonary artery pressure >20 mm Hg and pulmonary vascular resistance ≥3 Wood units. VAT and SAT were measured on chest computed tomography and normalized to height squared.Results: One hundred thirty-seven (34%) of 399 patients included in our study had PH. Doubling of thoracic VAT was associated with significantly lower pulmonary vascular resistance (β, -0.24; 95% confidence interval [95% CI], -0.46 to -0.02; P = 0.04), higher pulmonary arterial wedge pressure (β, 0.79; 95% CI, 0.32 to 1.26; P = 0.001), and decreased risk of PH (relative risk, 0.86; 95% CI, 0.74 to 0.99; P = 0.04) after multivariate adjustment. Vaspin levels were higher in patients without PH (median, 101.8 vs. 92.0 pg/ml; P < 0.001) but did not mediate the association between VAT and the risk of PH. SAT and BMI were not independently associated with risk of PH.Conclusions: Lower thoracic VAT was associated with a higher risk of PH in patients with advanced lung disease undergoing evaluation for lung transplantation. The role of adipokines in the pulmonary vascular disease remains to be evaluated.

Epicardial fat thickness in infants of diabetic mothers

BACKGROUND

Epicardial fat thickness (EFT) in adults and children has been related to the metabolic syndrome and other cardiovascular risk factors; however, scarce studies have evaluated it in infants of diabetic mothers (IDM) in whom, alterations in the thickness of the interventricular septum have been reported. This study compares the EFT in IDM versus infants of non-diabetic mothers (INDM) and its association with others echocardiographic parameters.

METHODS

We performed a cross sectional study in 93 infants (64 IDM and 29 INDM). To evaluate EFT dimensions, an echocardiogram was performed within the first 24h of extrauterine life in both groups. In diabetic mothers, HbA1c was also determined.

RESULTS

There was no significant difference in birth weight between the groups although gestational age was lower in IDM. The EFT (3.6 vs. 2.5 mm, p <  0.0001), the interventricular septum thickness (IVST) (6.2 vs. 5.2 mm, p <  0.0001) and the IVST / left ventricle posterior wall (1.3 vs. 1.1, p = 0.001) were higher in the IDM; while the left ventricular expulsion fraction [LVFE] (71.1 vs. 77.8; p <  0.0001) was lower than in the INDM, respectively. We found a positive correlation between EFT with IVST (r = 0.577; p = 0.0001), LVPW (r = 0.262; p = 0.011), IVST/LVPW index (r = 0.353; p = 0.001), and mitral integral early velocity (r = 0.313; p = 0.002), while a negative correlation with LVFE was observed (r = -0.376; p = 0.0001).

CONCLUSIONS

The EFT is higher in IDM than in INDM. It was positively related with echocardiographic parameters of left ventricular thickness and negatively with left ventricular ejection function.