Inflammatory profile in subcutaneous and epicardial adipose tissue in men with and without diabetes

Association of epicardial adipose tissue with early structural and functional cardiac changes in Type 2 diabetes

BACKGROUND

Dysregulated epicardial adipose tissue (EAT) may contribute to the development of heart failure in Type 2 diabetes (T2D). This study aimed to evaluate the associations between EAT volume and composition with imaging markers of subclinical cardiac dysfunction in people with T2D and no prevalent cardiovascular disease.

METHODS

Prospective case-control study enrolling participants with and without T2D and no known cardiovascular disease. Two hundred and fifteen people with T2D (median age 63 years, 60 % male) and thirty-nine non-diabetics (median age 59 years, 62 % male) were included. Using computed tomography (CT), total EAT volume and mean CT attenuation, as well as, low attenuation (Hounsfield unit range -190 to -90) EAT volume were quantified by a deep learning method and volumes indexed to body surface area. Associations with cardiac magnetic resonance-derived left ventricular (LV) volumes and strain indices were assessed using linear regression.

RESULTS

T2D participants had higher LV mass/volume ratio (median 0.89 g/mL [0.82-0.99] vs 0.79 g/mL [0.75-0.89]) and lower global longitudinal strain (GLS; 16.1 ± 2.3 % vs 17.2 ± 2.2 %). Total indexed EAT volume correlated inversely with mean CT attenuation. Low attenuation indexed EAT volume was 2-fold higher (18.8 cm3/m2 vs. 9.4 cm3/m2, p < 0.001) in T2D and independently associated with LV mass/volume ratio (ß = 0.002, p = 0.01) and GLS (ß = -0.03, p = 0.03).

CONCLUSIONS

Higher EAT volumes seen in T2D are associated with a lower mean CT attenuation. Low attenuation indexed EAT volume is independently, but only weakly, associated with markers of subclinical cardiac dysfunction in T2D.

Epicardial fat and ventricular arrhythmias

The arrhythmogenic role of epicardial adipose tissue (EAT) in atrial arrhythmias is well established, but its effect on ventricular arrhythmias has been significantly less investigated. Since ventricular arrhythmias are thought to cause 75%-80% of cases of sudden cardiac death, this is not a trivial issue. We provide an overview of clinical data as well as experimental and molecular data linking EAT to ventricular arrhythmias, attempting to dissect possible mechanisms and indicate future directions of research and possible clinical implications. However, despite a wealth of data indicating the role of epicardial and intramyocardial fat in the induction and propagation of ventricular arrhythmias, unfortunately there is currently no direct evidence that indeed EAT triggers arrhythmia or can be a target for antiarrhythmic strategies.

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.

Pre-diabetes is associated with attenuation rather than volume of epicardial adipose tissue on computed tomography

The volume of epicardial adipose tissue (EATV) is increased in type-2 diabetes (T2D), while its attenuation (EATA) appears to be decreased. Similar patterns have been suggested in pre-diabetes, but data is scarce. In both pre-diabetes and T2D, any independent role of EATV and EATA in disease development remains to be proven, a task complicated by their substantial co-variation with other anthropometrics, e.g. BMI, waist circumference, and abdominal visceral adipose tissue (VAT). EATV and EATA was quantified in computed tomography (CT) images in a population study (n = 1948) using an automatic technique. Data was available on BMI, waist circumference, abdominal visceral adipose tissue (VAT) area, insulin resistance (IR) and glucose tolerance, the latter ranging from normal (NGT), over pre-diabetes (impaired fasting glucose [IFG, n = 414] impaired glucose tolerance [IGT, n = 321] and their combination [CGI, n = 128]), to T2D. EATV was increased in pre-diabetes, T2D and IR in univariable analyses and when adjusting for BMI, however not when adjusting for waist or VAT. EATA was reduced in pre-diabetes, T2D and IR in univariable analyses and when adjusting for BMI and waist, however not when adjusting for VAT. Adjustment for other co-variates had little influence on the results. In conclusion, EATV is increased and EATA reduced in pre-diabetes, T2D and IR, however, significant co-variation with other anthropometrics, especially VAT, obscures their function in disease development. The current results do not exclude a pathophysiological role of epicardial fat, but future studies need to adjust for anthropometrics, or focus on the microenvironment within the pericardial sac.

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.

Impact of Type 2 Diabetes Mellitus on Epicardial Adipose Tissue and Myocardial Microcirculation by MRI in Postmenopausal Women

BACKGROUND

Type 2 diabetes mellitus (T2DM) often occurs conjunctly with the menopausal transition in female patients. In addition, epicardial adipose tissue (EAT) has an unfavorable impact on the myocardium and coronary arteries under the influence of metabolic disorders.

PURPOSE

To investigate the impact of T2DM on EAT and myocardial microvascular function in postmenopausal women.

STUDY TYPE

Retrospective.

POPULATION

One-hundred sixty-one postmenopausal women divided into three groups: newly diagnosed (≤5 years) T2DM (n = 56, 58.6 ± 7.7 years), long-term (>5 years) T2DM (n = 57, 61.9 ± 7.9 years), and healthy controls (n = 48, 59.4 ± 7.4 years).

FIELD STRENGTH/SEQUENCE

3.0 T; balanced steady-state free precession and inversion recovery prepared echo-planar sequences.

ASSESSMENT

EAT volume was quantified by delineating the epicardial border and the visceral layer of pericardium on the short-axis cine stacks. Perfusion parameters including upslope, maximum signal intensity (MaxSI) and time to maximum signal intensity (TTM) were derived from the first-pass perfusion signal intensity-time curves.

STATISTICAL TESTS

One-way analysis of variance, Pearson's and Spearman correlation, and multivariable linear regression. Two-sided P < 0.05 was considered statistically significant.

RESULTS

EAT volume was significantly increased in diabetic postmenopausal women compared to the controls (48.4 ± 13.4 mL/m² [newly diagnosed T2DM] vs. 58.4 ± 17.3 mL/m² [long-term T2DM] vs. 35.8 ± 12.3 mL/m² [controls]). Regarding perfusion parameters, upslope and MaxSI were significantly reduced (2.6 ± 1.0 [newly diagnosed T2DM] vs. 2.1 ± 0.8 [long-term T2DM] vs. 3.6 ± 1.3 [controls]; and 21.4 ± 6.9 [newly diagnosed T2DM] vs. 18.7 ± 6.4 [long-term T2DM] vs. 28.4 ± 8.6 [controls]), whereas TTM was significantly increased in the T2DM groups compared to the control group (23.6 ± 8.7 [newly diagnosed T2DM] vs. 27.1 ± 9.4 [long-term T2DM] vs. 21.4 ± 6.0 [controls]). Multivariable analysis (adjusted coefficient of determination [R² ] = 0.489) showed that EAT volume (β = -0.610) and menopausal age (β = 0.433) were independently correlated with decreased perfusion upslope.

DATA CONCLUSION

Diabetic postmenopausal women had significantly higher EAT volume and more impaired microcirculation compared to the controls. Increased EAT volume and earlier menopausal age were independently associated with microvascular dysfunction in these patients.

LEVEL OF EVIDENCE

3 TECHNICAL EFFICACY STAGE: 3.

Epicardial Adipose Tissue and Cardiac Arrhythmias: Focus on Atrial Fibrillation

Atrial Fibrillation (AF) is the most frequent cardiac arrhythmia and its prevalence increases with age. AF is strongly associated with an increased risk of stroke, heart failure and cardiovascular mortality. Among the risk factors associated with AF onset and severity, obesity and inflammation play a prominent role. Numerous recent evidence suggested a role of epicardial adipose tissue (EAT), the visceral fat depot of the heart, in the development of AF. Several potential arrhythmogenic mechanisms have been attributed to EAT, including myocardial inflammation, fibrosis, oxidative stress, and fat infiltration. EAT is a local source of inflammatory mediators which potentially contribute to atrial collagen deposition and fibrosis, the anatomical substrate for AF. Moreover, the close proximity between EAT and myocardium allows the EAT to penetrate and generate atrial myocardium fat infiltrates that can alter atrial electrophysiological properties. These observations support the hypothesis of a strong implication of EAT in structural and electrical atrial remodeling, which underlies AF onset and burden. The measure of EAT, through different imaging methods, such as echocardiography, computed tomography and cardiac magnetic resonance, has been proposed as a useful prognostic tool to predict the presence, severity and recurrence of AF. Furthermore, EAT is increasingly emerging as a promising potential therapeutic target. This review aims to summarize the recent evidence exploring the potential role of EAT in the pathogenesis of AF, the main mechanisms by which EAT can promote structural and electrical atrial remodeling and the potential therapeutic strategies targeting the cardiac visceral fat.

Accelerated fatty acid composition MRI of epicardial adipose tissue: Development and application to eplerenone treatment in a mouse model of obesity-induced coronary microvascular disease

Purpose

To develop an accelerated MRI method to quantify the epicardial adipose tissue (EAT) fatty acid composition (FAC) and test the hypothesis that eplerenone (EPL) shifts the EAT FAC toward unsaturation in obese mice.

Methods

Undersampled multi‐echo gradient echo imaging employing a dictionary‐based compressed‐sensing reconstruction and iterative decomposition with echo asymmetry and least‐squares–based mapping (IDEAL) was developed, validated, and used to study EAT in obese mice scanned at 7T. Fully sampled and rate 2, 2.5, 3, and 3.5 undersampled image data were acquired, reconstructed, and assessed using RMSE and structural similarity (SSIM). Two groups of mice were studied: untreated (control, n = 10) and EPL‐treated (n = 10) mice fed a high‐fat high‐sucrose diet. MRI included imaging of EAT FAC, EAT volume, and myocardial perfusion reserve.

Results

Rate 3 acceleration provided RMSE <5% and structural similarity >0.85 for FAC MRI. After 6 weeks of diet, EPL‐treated compared to untreated mice had a reduced EAT saturated fatty acid fraction (0.27 ± 0.09 vs. 0.39 ± 0.07, P < 0.05) and increased EAT unsaturation degree (4.37 ± 0.32 vs. 3.69 ± 0.58, P < 0.05). Also, EAT volume in EPL‐treated compared to untreated mice was reduced (8.1 ± 0.6 mg vs. 11.4 ± 0.7 mg, P < 0.01), and myocardial perfusion reserve was improved (1.83 ± 0.15 vs. 1.61 ± 0.17, P < 0.05).

Conclusion

Rate 3 accelerated FAC MRI enabled accurate quantification of EAT FAC in mice. EPL treatment shifted the EAT FAC toward increased unsaturation and was associated with improvement of coronary microvascular function.

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Cardiovascular risk stratification by coronary computed tomography angiography imaging: current state-of-the-art

Current cardiovascular risk stratification by use of clinical risk score systems or plasma biomarkers is good but less than satisfactory in identifying patients at residual risk for coronary events. Recent clinical evidence puts now further emphasis on the role of coronary anatomy assessment by coronary computed tomography angiography (CCTA) for the management of patients with stable ischaemic heart disease. Available computed tomography (CT) technology allows the quantification of plaque burden, identification of high-risk plaques, or the functional assessment of coronary lesions for ischaemia detection and revascularization for refractory angina symptoms. The current CT armamentum is also further enhanced by perivascular Fat Attenuation Index (FAI), a non-invasive metric of coronary inflammation, which allows for the first time the direct quantification of the residual vascular inflammatory burden. Machine learning and radiomic features' extraction and spectral CT for tissue characterization are also expected to maximize the diagnostic and prognostic yield of CCTA. The combination of anatomical, functional, and biological information on coronary circulation by CCTA offers a unique toolkit for the risk stratification of patients, and patient selection for targeted aggressive prevention strategies. We hereby provide a review of the current state-of-the art in the field and discuss how integrating the full capacities of CCTA into clinical care pathways opens new opportunities for the tailored management of coronary artery disease.

Surgically Metabolic Resection of Pericardial Fat to Ameliorate Myocardial Mitochondrial Dysfunction in Acute Myocardial Infarction Obese Rats

BACKGROUND

Pericardial fat (PF) is highly associated with cardiovascular disease but the effectiveness of surgical resection of PF is still unknown for myocardial mitochondrial structure and function in acute myocardial infarction (AMI) with obesity. The aim of this study was to demonstrate the difference in myocardial mitochondrial structure and function between obese AMI with additionally resected PF and those without resected PF.

METHODS

Obese rats with 12-week high fat diet (45 kcal% fat, n = 21) were randomly assigned into 3 groups: obese control, obese AMI and obese AMI with additionally resected PF. One week after developing AMI and additional resection of PF, echocardiogram, myocardial mitochondrial histomorphology, oxidative phosphorylation system (OXPHOS), anti-oxidative enzyme and sarcoplasmic reticulum Ca²⁺ ATPase 2 (SERCA2) in the non-infarcted area were assessed between these groups.

RESULTS

There was significant improvement of systolic function in AMI with PF resection compared with the AMI group in the echocardiogram. Even though the electron microscopic morphology for the mitochondria seems to be similar between the AMI with PF resection and AMI groups, there was an improved expression of PGC-1α and responsive OXPHOS including NDUFB3, NDUFB5 and SDHB are associated with the ATP levels in the AMI with PF resection compared with those in the AMI group. In addition, the expression levels of antioxidant enzymes (MnSOD) and SERCA2 were improved in the AMI with PF resection compared with those in the AMI group.

CONCLUSION

Surgical resection of PF might ameliorate myocardial mitochondria dysfunction in obese AMI.

The Relationship of Epicardial Adipose Tissue and Cardiovascular Disease in Chronic Kidney Disease and Hemodialysis Patients

Cardiovascular diseases remain the most common cause of morbidity and mortality in chronic kidney disease patients undergoing hemodialysis. Epicardial adipose tissue (EAT), visceral fat depot of the heart, was found to be associated with coronary artery disease in cardiac and non-cardiac patients. Additionally, EAT has been proposed as a novel cardiovascular risk in the general population and in end-stage renal disease patients. It has also been shown that EAT, more than other subcutaneous adipose tissue deposits, acts as a highly active organ producing several bioactive adipokines, and proinflammatory and proatherogenic cytokines. Therefore, increased visceral adiposity is associated with proinflammatory activity, impaired insulin sensitivity, increased risk of atherosclerosis, and high morbidity and mortality in hemodialysis patients. In the present review, we aimed to demonstrate the role of EAT in the pathophysiological mechanisms of increased cardiovascular morbidity and mortality in hemodialysis patients.

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.

Magnetic Resonance Imaging Quantification of Accumulation of Epicardial Adipose Tissue Adds Independent Risks for Diastolic Dysfunction among Dialysis Patients

BACKGROUND

Diastolic dysfunction (DD) frequently occurs in dialysis patients; however, the risk factors of DD remain to be further explored in such a population. Epicardial adipose tissue (EAT) volume has proven to be an independent clinical risk factor for multiple cardiac disorders.

PURPOSE

To assess whether EAT volume is an independent risk factor for DD in dialysis patients.

STUDY TYPE

Case-control study.

POPULATION

A total of 113 patients (mean age: 54.5 ± 14.4 years; 41 women) who had underwent dialysis for at least 3 months due to uremia.

FIELD STRENGTH

A 3 T, steady-state free precession (SSFP) sequence for cine imaging, modified Look-Locker imaging (MOLLI) for T1 mapping and gradient-recalled-echo for T2*.

ASSESSMENT

All participants were performed cardiac magnetic resonance imaging (MRI) and echocardiogram. For MRI images analysis, borders of the EAT were manually delineated, as well as, pericardial adipose tissue (PeAT) and paracardial adipose tissue (PaAT), T1 mapping, T2* mapping, global longitudinal strain (GLS), and left atrial strain. For echocardiogram assessments, the thickness of PaAT, e' velocity, E velocity, E/e ratio, A velocity, and deceleration time were measured.

STATISTICAL TESTS

Univariate and multivariate logistic regressions were performed to explore the independent risk factors for DD. P value less than 0.05 was considered as significant.

RESULTS

Compared with the DD(-) group, the DD(+) group had significantly more epicardial tissue fat (18.5 ± 1.3 vs. 30.9 ± 2.3) In addition, EAT volumes increased significantly with the grades of DD (grade 1 vs. grade 2 and 3: 27.9 ± 15.9 vs. 35.4 ± 13.1). Moreover, EAT had significant correlations with T1 mapping, T2* mapping, GLS, left atrial strain, e' velocity, and E/e ratio. EAT accumulation added an independent risk for DD (Odds Ratio = 1.03) over conventional clinical risk factors including age, diabetes mellitus, and hemodialysis.

DATA CONCLUSION

EAT was associated with diastolic function, and its accumulation may be an independent risk factor for DD among dialysis patients.

EVIDENCE LEVEL

2 TECHNICAL EFFICACY: Stage 2.

Adipokine gene expression in adipocytes isolated from different fat depots of coronary artery disease patients

To compare DPP4, LCN2, NAMPT, ITLN1, APLN mRNA levels in adipocytes isolated from the biopsies of subcutaneous, epicardial and perivascular fat obtained from 25 patients with coronary artery disease. Gene expression signature was determined by RT-qPCR with hydrolysis probes. We found DPP4 and APLN mRNA was higher expressed only in adipocytes isolated from epicardial adipose tissue compared to the subcutaneous fat. The ITLN1 gene was overexpressed in epicardial adipose tissue compared to both subcutaneous and perivascular tissues. APLN mRNA expression was positively correlated with total and LDL cholesterol plasma level, and DPP4 mRNA expression - with VLDL cholesterol concentration. Thus, adipocytes isolated from different adipose depots are characterised by differential gene expression of adipokines. Epicardial adipose tissue is of particular interest in the context of its function, molecular and genetic mechanisms of regulation of the cardiovascular system and as a therapeutic target for correction of adipose tissue-induced effects on health.

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.

Relationship between Epicardial and Coronary Adipose Tissue and the Expression of Adiponectin, Leptin, and Interleukin 6 in Patients with Coronary Artery Disease

Adipose tissue (AT) is an endocrine and paracrine organ that synthesizes biologically active adipocytokines, which affect inflammation, fibrosis, and atherogenesis. Epicardial and perivascular fat depots are of great interest to researchers, owing to their potential effects on the myocardium and blood vessels. The aim of the study was to assess the expression and secretion of adipocytokine genes in the AT of patients with coronary artery disease (CAD) and patients with aortic or mitral valve replacement. This study included 84 patients with CAD and 50 patients with aortic or mitral valve replacement. Adipocytes were isolated from subcutaneous, epicardial (EAT), and perivascular AT (PVAT), and were cultured for 24 h. EAT exhibited the lowest level of adiponectin gene expression and secretion, regardless of nosology, and high expression levels of the leptin gene and interleukin-6 (IL-6). However, EAT adipocytes in patients with CAD were characterized by more pronounced changes in comparison with the group with heart defects. High leptin and IL-6 levels resulted in increased pro-inflammatory activity, as observed in both EAT and PVAT adipocytes, especially in individuals with CAD. Therefore, our results revealed the pathogenetic significance of alterations in the adipokine and cytokine status of adipocytes of EAT and PVAT in patients with CAD.

Fat Cell Size: Measurement Methods, Pathophysiological Origins, and Relationships With Metabolic Dysregulations

The obesity pandemic increasingly causes morbidity and mortality from type 2 diabetes, cardiovascular diseases and many other chronic diseases. Fat cell size (FCS) predicts numerous obesity-related complications such as lipid dysmetabolism, ectopic fat accumulation, insulin resistance, and cardiovascular disorders. Nevertheless, the scarcity of systematic literature reviews on this subject is compounded by the use of different methods by which FCS measurements are determined and reported. In this paper, we provide a systematic review of the current literature on the relationship between adipocyte hypertrophy and obesity-related glucose and lipid dysmetabolism, ectopic fat accumulation, and cardiovascular disorders. We also review the numerous mechanistic origins of adipocyte hypertrophy and its relationship with metabolic dysregulation, including changes in adipogenesis, cell senescence, collagen deposition, systemic inflammation, adipokine secretion, and energy balance. To quantify the effect of different FCS measurement methods, we performed statistical analyses across published data while controlling for body mass index, age, and sex.

Potential role of epicardial adipose tissue in coronary artery endothelial cell dysfunction in type 2 diabetes

Cardiovascular disease is the most prevalent cause of morbidity and mortality in diabetes. Epicardial adipose tissue (EAT) lies in direct contact with the myocardium and coronary arteries and can influence cardiac (patho) physiology through paracrine signaling pathways. This study hypothesized that the proteins released from EAT represent a critical molecular link between the diabetic state and coronary artery endothelial cell dysfunction. To simulate type 2 diabetes-associated metabolic and inflammatory status in an ex vivo tissue culture model, human EAT samples were treated with a cocktail composed of high glucose, high palmitate, and lipopolysaccharide (gplEAT) and were compared with control EAT (conEAT). Compared to conEAT, gplEAT showed a markedly increased gene expression profile of proinflammatory cytokines, corroborating EAT inflammation, a hallmark feature observed in patients with type 2 diabetes. Luminex assay of EAT-secretome identified increased release of various proinflammatory cytokines, including tumor necrosis factor-alpha (TNF-alpha), interferon-alpha 2 (IFNA2), interleukin 1 beta (IL1B), interleukin 5 (IL5), interleukin 13 (IL13), and CCL5, among others, in response to high glucose, high palmitate, and lipopolysaccharide. Conditioned culture media was used to collect the concentrated proteins (CPs). In response to gplEAT-CPs, human coronary artery endothelial cells (HCAECs) exhibited an inflammatory endothelial cell phenotype, featuring a significantly increased gene expression of proinflammatory cytokines and cell surface expression of VCAM-1. Moreover, gplEAT-CPs severely decreased Akt-eNOS signaling, nitric oxide production, and angiogenic potential of HCAECs, when compared with conEAT-CPs. These findings indicate that EAT inflammation may play a key role in coronary artery endothelial cell dysfunction in type 2 diabetes.

Obesity and diabetes are major risk factors for epicardial adipose tissue inflammation

BACKGROUND

Epicardial adipose tissue (EAT) directly overlies the myocardium, with changes in its morphology and volume associated with myriad cardiovascular and metabolic diseases. However, EAT’s immune structure and cellular characterization remain incompletely described. We aimed to define the immune phenotype of EAT in humans and compare such profiles across lean, obese, and diabetic patients.

METHODS

We recruited 152 patients undergoing open-chest coronary artery bypass grafting (CABG), valve repair/replacement (VR) surgery, or combined CABG/VR. Patients’ clinical and biochemical data and EAT, subcutaneous adipose tissue (SAT), and preoperative blood samples were collected. Immune cell profiling was evaluated by flow cytometry and complemented by gene expression studies of immune mediators. Bulk RNA-Seq was performed in EAT across metabolic profiles to assess whole-transcriptome changes observed in lean, obese, and diabetic groups.

RESULTS

Flow cytometry analysis demonstrated EAT was highly enriched in adaptive immune (T and B) cells. Although overweight/obese and diabetic patients had similar EAT cellular profiles to lean control patients, the EAT exhibited significantly (P ≤ 0.01) raised expression of immune mediators, including IL-1, IL-6, TNF-α, and IFN-γ. These changes were not observed in SAT or blood. Neither underlying coronary artery disease nor the presence of hypertension significantly altered the immune profiles observed. Bulk RNA-Seq demonstrated significant alterations in metabolic and inflammatory pathways in the EAT of overweight/obese patients compared with lean controls.

CONCLUSION

Adaptive immune cells are the predominant immune cell constituent in human EAT and SAT. The presence of underlying cardiometabolic conditions, specifically obesity and diabetes, rather than cardiac disease phenotype appears to alter the inflammatory profile of EAT. Obese states markedly alter EAT metabolic and inflammatory signaling genes, underlining the impact of obesity on the EAT transcriptome profile.

FUNDING

Barts Charity MGU0413, Abbott, Medical Research Council MR/T008059/1, and British Heart Foundation FS/13/49/30421 and PG/16/79/32419.

Differential Pathophysiological Mechanisms in Heart Failure With a Reduced or Preserved Ejection Fraction in Diabetes

Diabetes promotes the development of both heart failure with a reduced ejection fraction and heart failure with a preserved ejection fraction through diverse mechanisms, which are likely mediated through hyperinsulinemia rather than hyperglycemia. Diabetes promotes nutrient surplus signaling (through Akt and mammalian target of rapamycin complex 1) and inhibits nutrient deprivation signaling (through sirtuin-1 and its downstream effectors); this suppresses autophagy and promotes endoplasmic reticulum and oxidative stress and mitochondrial dysfunction, thereby undermining the health of diabetic cardiomyocytes. The hyperinsulinemia of diabetes may also activate sodium-hydrogen exchangers in cardiomyocytes (leading to injury and loss) and in the proximal renal tubules (leading to sodium retention). Diabetes may cause epicardial adipose tissue expansion, and the resulting secretion of proinflammatory adipocytokines onto the adjoining myocardium can lead to coronary microcirculatory dysfunction and myocardial inflammation and fibrosis. Interestingly, sodium-glucose cotransporter 2 (SGLT2) inhibitors-the only class of antidiabetic medication that reduces serious heart failure events-may act to mitigate each of these mechanisms. SGLT2 inhibitors up-regulate sirtuin-1 and its downstream effectors and autophagic flux, thus explaining the actions of these drugs to reduce oxidative stress, normalize mitochondrial structure and function, and mute proinflammatory pathways in the stressed myocardium. Inhibition of SGLT2 may also lead to a reduction in the activity of sodium-hydrogen exchangers in the kidney (leading to diuresis) and in the heart (attenuating the development of cardiac hypertrophy and systolic dysfunction). Finally, SGLT2 inhibitors reduce the mass and mute the adverse biology of epicardial adipose tissue (and reduce the secretion of leptin), thus explaining the capacity of these drugs to mitigate myocardial inflammation, microcirculatory dysfunction, and fibrosis, and improve ventricular filling dynamics. The pathophysiological mechanisms by which SGLT2 inhibitors may benefit heart failure likely differ depending on ejection fraction, but each represents interference with distinct pathways by which hyperinsulinemia may adversely affect cardiac structure and function.

Adipose Tissue Macrophage Polarization in Healthy and Unhealthy Obesity

Over 650 million adults are obese (body mass index ≥ 30 kg/m²) worldwide. Obesity is commonly associated with several comorbidities, including cardiovascular disease and type II diabetes. However, compiled estimates suggest that from 5 to 40% of obese individuals do not experience metabolic or cardiovascular complications. The existence of the metabolically unhealthy obese (MUO) and the metabolically healthy obese (MHO) phenotypes suggests that underlying differences exist in both tissues and overall systemic function. Macrophage accumulation in white adipose tissue (AT) in obesity is typically associated with insulin resistance. However, as plastic cells, macrophages respond to stimuli in their microenvironments, altering their polarization between pro- and anti-inflammatory phenotypes, depending on the state of their surroundings. The dichotomous nature of MHO and MUO clinical phenotypes suggests that differences in white AT function dictate local inflammatory responses by driving changes in macrophage subtypes. As obesity requires extensive AT expansion, we posit that remodeling capacity with adipose expansion potentiates favorable macrophage profiles in MHO as compared with MUO individuals. In this review, we discuss how differences in adipogenesis, AT extracellular matrix deposition and breakdown, and AT angiogenesis perpetuate altered AT macrophage profiles in MUO compared with MHO. We discuss how non-autonomous effects of remote organ systems, including the liver, gastrointestinal tract, and cardiovascular system, interact with white adipose favorably in MHO. Preferential AT macrophage profiles in MHO stem from sustained AT function and improved overall fitness and systemic health.

The pivotal role of heme Oxygenase-1 in reversing the pathophysiology and systemic complications of NAFLD

The pathogenesis and molecular pathways involved in non-alcoholic fatty liver disease (NAFLD) are reviewed, as well as what is known about mitochondrial dysfunction that leads to heart disease and the progression to steatohepatitis and hepatic fibrosis. We focused our discussion on the role of the antioxidant gene heme oxygenase-1 (HO-1) and its nuclear coactivator, peroxisome proliferator-activated receptor-gamma coactivator (PGC1-α) in the regulation of mitochondrial biogenesis and function and potential therapeutic benefit for cardiac disease, NAFLD as well as the pharmacological effect they have on the chronic inflammatory state of obesity. The result is increased mitochondrial function and the conversion of white adipocyte tissue to beige adipose tissue ("browning of white adipose tissue") that leads to an improvement in signaling pathways and overall liver function. Improved mitochondrial biogenesis and function is essential to preventing the progression of hepatic steatosis to NASH and cirrhosis as well as preventing cardiovascular complications.

Characterization of the inflammatory-metabolic phenotype of heart failure with a preserved ejection fraction: a hypothesis to explain influence of sex on the evolution and potential treatment of the disease

Accumulating evidence points to the existence of an inflammatory-metabolic phenotype of heart failure with a preserved ejection fraction (HFpEF), which is characterized by biomarkers of inflammation, an expanded epicardial adipose tissue mass, microvascular endothelial dysfunction, normal-to-mildly increased left ventricular volumes and systolic blood pressures, and possibly, altered activity of adipocyte-associated inflammatory mediators. A broad range of adipogenic metabolic and systemic inflammatory disorders - e.g. obesity, diabetes and metabolic syndrome as well as rheumatoid arthritis and psoriasis - can cause this phenotype, independent of the presence of large vessel coronary artery disease. Interestingly, when compared with men, women are both at greater risk of and may suffer greater cardiac consequences from these systemic inflammatory and metabolic disorders. Women show disproportionate increases in left ventricular filling pressures following increases in central blood volume and have greater arterial stiffness than men. Additionally, they are particularly predisposed to epicardial and intramyocardial fat expansion and imbalances in adipocyte-associated proinflammatory mediators. The hormonal interrelationships seen in inflammatory-metabolic phenotype may explain why mineralocorticoid receptor antagonists and neprilysin inhibitors may be more effective in women than in men with HFpEF. Recognition of the inflammatory-metabolic phenotype may improve an understanding of the pathogenesis of HFpEF and enhance the ability to design clinical trials of interventions in this heterogeneous syndrome.

[Epicardial and subcutenious adipose tissue adiponectin gene expression in coronary artery disease patients]

Aim To determine the expression of adiponectin gene (ADIPOQ) and the content of high-molecular-weight adiponectin (HMWA) in epicardial (EAT) and subcutaneous adipose tissue (SCAT) in patients with ischemic heart disease (IHD).Material and methods Paired samples of EAT and SCAT and blood serum were withdrawn from patients with IHD after bypass surgery and 16 subjects without IHD (comparison group). Matrix RNA (mRNA) level was measured using real-time polymerase chain reaction. HMWA levels in EAT and SCAT were evaluated by Western blotting. Serum adiponectin concentration was measured immunoenzymatically. For all patients, echocardiography was performed to measure the EAT thickness; coronarography was performed to determine severity of coronary atherosclerosis.Results Serum adiponectin concentration was lower in IHD patients than in the comparison group (p&lt;0.001). Levels of ADIPOO gene mRNA and HMWA in SCAT were lower in IHD patients than in the comparison group (р=0.020 and p=0.003, respectively). The HMWA level in EAT was lower with the EAT thickness of 8 mm compared to the HMWA level in IHD patients with EAT ≤8 mm (p=0.034).Conclusion The decreased serum concentration of antiatherogenic adiponectin and the reduced expression of ADIPOQ gene in SCAT (mRNA, HMWA) are associated with IHD.

The Role of Secretory Activity Molecules of Visceral Adipocytes in Abdominal Obesity in the Development of Cardiovascular Disease: A Review

Adipose tissue is considered one of the endocrine organs in the body because of its ability to synthesize and release a large number of hormones, cytokines, and growth and vasoactive factors that influence a variety of physiological and pathophysiological processes, such as vascular tone, inflammation, vascular smooth muscle cell migration, endothelial function, and vascular redox state. Moreover, genetic factors substantially contribute to the risk of obesity. Research into the biochemical effects of molecules secreted by visceral adipocytes as well as their molecular genetic characteristics is actively conducted around the world mostly in relation to pathologies of the cardiovascular system, metabolic syndrome, and diabetes mellitus. Adipokines could be developed into biomarkers for diagnosis, prognosis, and therapeutic targets in different diseases. This review describes the relevance of secretory activity molecules of visceral adipocytes in cardiovascular disease associated abdominal obesity.

Diabetic cardiomyopathy

The relationship between diabetes and heart failure is complex and bidirectional. Nevertheless, the existence of a cardiomyopathy attributable exclusively to diabetes has been and is still the subject of controversy, due, among other reasons, to a lack of a consensus definition. There is also no unanimous agreement in terms of the physiopathogenic findings that need to be present in the definition of diabetic cardiomyopathy or on its classification, which, added to the lack of diagnostic methods and treatments specific for this disease, limits its general understanding. Studies conducted on diabetic cardiomyopathy, however, suggest a unique physiopathogenesis different from that of other diseases. Similarly, new treatments have been shown to play a potential role in this disease. The following review provides an update on diabetic cardiomyopathy.

Epicardial adipose tissue: an emerging biomarker of cardiovascular complications in type 2 diabetes?

Type 2 diabetes (T2D) is associated with an increased risk of cardiovascular disease and heart failure, which highlights the need for improved understanding of factors contributing to the pathophysiology of these complications as they are the leading cause of mortality in T2D. Patients with T2D have high levels of epicardial adipose tissue (EAT). EAT is known to secrete inflammatory factors, lipid metabolites, and has been proposed to apply mechanical stress on the cardiac muscle that may accelerate atherosclerosis, cardiac remodeling, and heart failure. High levels of EAT in patients with T2D have been associated with atherosclerosis, diastolic dysfunction, and incident cardiovascular events, and this fat depot has been suggested as an important link coupling diabetes, obesity, and cardiovascular disease. Despite this, the predictive potential of EAT in general, and in patients with diabetes, is yet to be established, and, up until now, the clinical relevance of EAT is therefore limited. Should this link be established, importantly, studies show that this fat depot can be modified both by pharmacological and lifestyle interventions. In this review, we first introduce the role of adipose tissue in T2D and present mechanisms involved in the pathophysiology of EAT and pericardial adipose tissue (PAT) in general, and in patients with T2D. Next, we summarize the evidence that these fat depots are elevated in patients with T2D, and discuss whether they might drive the high cardiometabolic risk in patients with T2D. Finally, we discuss the clinical potential of cardiac adipose tissues, address means to target this depot, and briefly touch upon underlying mechanisms and future research questions.

Plasma concentration and expression of adipokines in epicardial and subcutaneous adipose tissue are associated with impaired left ventricular filling pattern

Background

Adipokines in serum derive mainly from subcutaneous and visceral adipose tissues. Epicardial adipose tissue (EAT), being a relatively small but unique fat depot, probably does not make an important contribution to systemic concentrations of adipokines. However, proximity of EAT to cardiac muscle and coronary arteries allows cells and proteins to penetrate between tissues. It is hypothesized that overexpression of proinflammatory cytokines in EAT plays an important role in pathophysiology of the heart. The aim of the study was to analyze the relationship between echocardiographic heart parameters and adipokines in plasma, epicardial, and subcutaneous fat in patients with obesity and type 2 diabetes mellitus (T2DM). Additionally, we evaluate proinflammatory properties of EAT by comparing that depot with subcutaneous adipose tissue.

Methods

The study included 55 male individuals diagnosed with coronary artery disease (CAD) who underwent planned coronary artery bypass graft. Plasma concentrations of leptin, adiponectin, resistin, visfatin, apelin, IL-6, and TNF-α, as well as their mRNA and protein expressions in EAT and subcutaneous adipose tissue (SAT) were determined.

Results

Obesity and diabetes were associated with increased leptin and decreased adiponectin plasma levels, higher protein expression of leptin and IL-6 in SAT, and higher visfatin protein expression in EAT. Impaired left ventricular (LV) diastolic function was associated with increased plasma concentrations of leptin, resistin, IL-6, and adiponectin, as well as with increased expressions of resistin, apelin, and adiponectin in SAT, and leptin in EAT.

Conclusions

Obesity and T2DM in individuals with CAD have a limited effect on adipokines. Expression of adipokines in EAT and SAT is linked to certain heart parameters, however diastolic dysfunction of the LV is strongly associated with circulating adipokines.

Overexpression of scavenger receptor and infiltration of macrophage in epicardial adipose tissue of patients with ischemic heart disease and diabetes

Background

Oxidized low-density lipoproteins and scavenger receptors (SRs) play an important role in the formation and development of atherosclerotic plaques. However, little is known about their presence in epicardial adipose tissue (EAT). The objective of the study was to evaluate the mRNA expression of different SRs in EAT of patients with ischemic heart disease (IHD), stratifying by diabetes status and its association with clinical and biochemical variables.

Methods

We analyzed the mRNA expression of SRs (LOX-1, MSR1, CXCL16, CD36 and CL-P1) and macrophage markers (CD68, CD11c and CD206) in EAT from 45 patients with IHD (23 with type 2 diabetes mellitus (T2DM) and 22 without T2DM) and 23 controls without IHD or T2DM.

Results

LOX-1, CL-P1, CD68 and CD11c mRNA expression were significantly higher in diabetic patients with IHD when compared with those without T2DM and control patients. MSR1, CXCL16, CD36 and CD206 showed no significant differences. In IHD patients, LOX-1 (OR 2.9; 95% CI 1.6–6.7; P = 0.019) and CD68 mRNA expression (OR 1.7; 95% CI 0.98–4.5; P = 0.049) were identified as independent risk factors associated with T2DM. Glucose and glycated hemoglobin were also shown to be risk factors.

Conclusions

SRs mRNA expression is found in EAT. LOX-1 and CD68 and were higher in IHD patients with T2DM and were identified as a cardiovascular risk factor of T2DM. This study suggests the importance of EAT in coronary atherosclerosis among patients with T2DM.

Linking Arrhythmias and Adipocytes: Insights, Mechanisms, and Future Directions

Obesity and atrial fibrillation have risen to epidemic levels worldwide and may continue to grow over the next decades. Emerging evidence suggests that obesity promotes atrial and ventricular arrhythmias. This has led to trials employing various strategies with the ultimate goal of decreasing the atrial arrhythmic burden in obese patients. The effectiveness of these interventions remains to be determined. Obesity is defined by the expansion of adipose mass, making adipocytes a prime candidate to mediate the pro-arrhythmogenic effects of obesity. The molecular mechanisms linking obesity and adipocytes to increased arrhythmogenicity in both the atria and ventricles remain poorly understood. In this focused review, we highlight areas of potential molecular interplay between adipocytes and cardiomyocytes. The effects of adipocytes may be direct, local or remote. Direct effect refers to adipocyte or fatty infiltration of the atrial and ventricular myocardium itself, possibly causing increased dispersion of normal myocardial electrical signals and fibrotic substrate of adipocytes that promote reentry or adipocytes serving as a direct source of aberrant signals. Local effects may originate from nearby adipose depots, specifically epicardial adipose tissue (EAT) and pericardial adipose tissue, which may play a role in the secretion of adipokines and chemokines that can incite inflammation given the direct contact and disrupt the conduction system. Adipocytes can also have a remote effect on the myocardium arising from their systemic secretion of adipokines, cytokines and metabolites. These factors may lead to mitochondrial dysfunction, oxidative stress, autophagy, mitophagy, autonomic dysfunction, and cardiomyocyte death to ultimately produce a pro-arrhythmogenic state. By better understanding the molecular mechanisms connecting dysfunctional adipocytes and arrhythmias, novel therapies may be developed to sever the link between obesity and arrhythmias.

The interplay between adipose tissue and the cardiovascular system: is fat always bad?

Obesity is a risk factor for cardiovascular disease (CVD). However, clinical research has revealed a paradoxically protective role for obesity in patients with chronic diseases including CVD, suggesting that the biological 'quality' of adipose tissue (AT) may be more important than overall AT mass or body weight. Importantly, AT is recognised as a dynamic organ secreting a wide range of biologically active adipokines, microRNAs, gaseous messengers, and other metabolites that affect the cardiovascular system in both endocrine and paracrine ways. Despite being able to mediate normal cardiovascular function under physiological conditions, AT undergoes a phenotypic shift characterised by acquisition of pro-oxidant and pro-inflammatory properties in cases of CVD. Crucially, recent evidence suggests that AT depots such as perivascular AT and epicardial AT are able to modify their phenotype in response to local signals of vascular and myocardial origin, respectively. Utilisation of this unique property of certain AT depots to dynamically track cardiovascular biology may reveal novel diagnostic and prognostic tools against CVD. Better understanding of the mechanisms controlling the 'quality' of AT secretome, as well as the communication links between AT and the cardiovascular system, is required for the efficient management of CVD.

Epicardial Adipose Tissue May Mediate Deleterious Effects of Obesity and Inflammation on the Myocardium

Epicardial adipose tissue has unique properties that distinguish it from other depots of visceral fat. Rather than having distinct boundaries, the epicardium shares an unobstructed microcirculation with the underlying myocardium, and in healthy conditions, produces cytokines that nourish the heart. However, in chronic inflammatory disorders (especially those leading to heart failure with preserved ejection fraction), the epicardium becomes a site of deranged adipogenesis, leading to the secretion of proinflammatory adipokines that can cause atrial and ventricular fibrosis. Accordingly, in patients at risk of heart failure with preserved ejection fraction, drugs that promote the accumulation or inflammation of epicardial adipocytes may lead to heart failure, whereas treatments that ameliorate the proinflammatory characteristics of epicardial fat may reduce the risk of heart failure. These observations suggest that epicardial adipose tissue is a transducer of the adverse effects of systemic inflammation and metabolic disorders on the heart, and thus, represents an important target for therapeutic interventions.

Detecting human coronary inflammation by imaging perivascular fat

Early detection of vascular inflammation would allow deployment of targeted strategies for the prevention or treatment of multiple disease states. Because vascular inflammation is not detectable with commonly used imaging modalities, we hypothesized that phenotypic changes in perivascular adipose tissue (PVAT) induced by vascular inflammation could be quantified using a new computerized tomography (CT) angiography methodology. We show that inflamed human vessels release cytokines that prevent lipid accumulation in PVAT-derived preadipocytes in vitro, ex vivo, and in vivo. We developed a three-dimensional PVAT analysis method and studied CT images of human adipose tissue explants from 453 patients undergoing cardiac surgery, relating the ex vivo images with in vivo CT scan information on the biology of the explants. We developed an imaging metric, the CT fat attenuation index (FAI), that describes adipocyte lipid content and size. The FAI has excellent sensitivity and specificity for detecting tissue inflammation as assessed by tissue uptake of 18F-fluorodeoxyglucose in positron emission tomography. In a validation cohort of 273 subjects, the FAI gradient around human coronary arteries identified early subclinical coronary artery disease in vivo, as well as detected dynamic changes of PVAT in response to variations of vascular inflammation, and inflamed, vulnerable atherosclerotic plaques during acute coronary syndromes. Our study revealed that human vessels exert paracrine effects on the surrounding PVAT, affecting local intracellular lipid accumulation in preadipocytes, which can be monitored using a CT imaging approach. This methodology can be implemented in clinical practice to noninvasively detect plaque instability in the human coronary vasculature.

Sleep-disordered breathing and epicardial adipose tissue in patients with heart failure

BACKGROUND AND AIMS

Sleep-disordered breathing (SDB) is common in patients with heart failure (HF), contributes to the progression of cardiac disease, and is associated with adverse prognosis. Previous evidence indicates that epicardial adipose tissue (EAT) is independently associated with sleep apnea in obese individuals. We explored the relationship between SDB and EAT in HF patients.

METHODS AND RESULTS

EAT thickness was assessed by echocardiography in 66 patients with systolic HF undergoing nocturnal cardiorespiratory monitoring. A significantly higher EAT thickness was found in patients with SDB than in those without SDB (10.7 ± 2.8 mm vs. 8.3 ± 1.8 mm; p = 0.001). Among SDB patients, higher EAT thickness was found in both those with prevalent obstructive sleep apnea (OSA) and those with prevalent central sleep apnea (CSA). Of interest, EAT thickness was significantly higher in CSA than in OSA patients (11.9 ± 2.9 vs. 10.1 ± 2.5 p = 0.022). Circulating plasma norepinephrine levels were higher in CSA than in OSA patients (2.19 ± 1.25 vs. 1.22 ± 0.92 ng/ml, p = 0.019). According to the apnea-hypopnea index (AHI), patients were then stratified in three groups of SDB severity: Group 1, mild SDB; Group 2, moderate SDB; Group 3, severe SDB. EAT thickness progressively and significantly increased from Group 1 to Group 3 (ANOVA p < 0.001). At univariate analysis, only left ventricular ejection fraction and AHI significantly correlated with EAT (p = 0.019 and p < 0.0001, respectively). At multivariate analysis, AHI was the only independent predictor of EAT (β = 0.552, p < 0.001).

CONCLUSIONS

Our results suggest an association between the presence and severity of sleep apneas and cardiac visceral adiposity in HF patients.

Association between histological features of epicardial adipose tissue and coronary plaque characteristics on computed tomography angiography

The means by which epicardial adipose tissue (EAT) could influence coronary plaque progression biologically remain unclear. We investigated the association between the histological findings of EAT and coronary plaque characteristics assessed by coronary computed tomography angiography (CCTA). We enrolled 34 patients in whom one or more coronary plaques containing non-calcified components were detected on CCTA before cardiac surgery [coronary artery bypass graft (CABG) or non-CABG]. We evaluated visceral adipose tissue (VAT) area, EAT volume, and coronary plaque characteristics including minimum computed tomography density (CTD) and vascular Remodeling Index (RI). Lower CTD and higher RI were considered as high-risk characteristics, and coronary plaque with both CTD < 39 Hounsfield units and RI > 1.05 was defined as two-characteristic plaque (2-CP). The numbers of CD68⁺ macrophages and CD31⁺ microvessels were assessed in six random high-power fields (400×) of EAT samples obtained during cardiac surgery. The entire cohort showed a wide range of EAT volume, which were similar between patients with 2-CP and those without. Patients with 2-CP had more amounts of EAT macrophages (85 ± 38 versus 45 ± 22, p = 0.0005) and vascularity (62 ± 33 versus 37 ± 19, p = 0.013) than those without. On multivariate analyses adjusted for age, sex, coronary risk factors, statin use, type of surgery, VAT area, EAT volume, and coronary calcium score, the presence of 2-CP showed significant correlation with increased EAT macrophages (β = 0.65, p = 0.014) and vascularity (β = 0.74, p = 0.0053). Our findings support the hypothesis that EAT biologic activities are associated with coronary plaque vulnerability.

Association Between Airway Parameters and Abdominal Fat Measured via Computed Tomography in Asthmatic Patients

Purpose

We aimed to investigate whether airway parameters, assessed via computed tomography (CT), are associated with abdominal fat areas and to compare the clinical characteristics of asthmatic patients with and without elevated visceral to subcutaneous fat area ratio (EV).

Methods

Asthmatic patients (aged ≥40 years) were prospectively recruited. Chest (airway) and fat areas were assessed via CT. Airway parameters, including bronchial wall thickness (WT), lumen diameter (LD), lumen area (LA), wall area (WA), total area (TA), as well as WA/TA percentage (wall area %) were measured at the apical segmental bronchus in the right upper lobe. Visceral (VFA), subcutaneous (SFA) and total (TFA) fat areas (cm²) were also measured. The correlations between abdominal fat areas and airway parameters were assessed. EV was defined as VFA/SFA ≥ 0.4.

Results

Fifty asthmatic patients were included (mean age 62.9 years; 52% female); 38% had severe asthma. Significant correlations were found between VFA and both LD and LA (r = −0.35, P = 0.01; r = −0.34, P = 0.02, respectively), and SFA and both WA and TA (r = 0.38, P = 0.007; r = 0.34, P = 0.02, respectively). Exacerbations, requiring corticosteroid therapy or ER visitation, were significantly more frequent in subjects without EV (83% vs. 34%, P = 0.05).

Conclusions

Abdominal fat is associated with asthma, according to the location of fat accumulation. In asthmatic subjects, visceral fat seems to be attributable to the bronchial luminal narrowing, while subcutaneous fat may be related to thickening of bronchial wall.

The effect of fluvastatin on cardiac fibrosis and angiotensin-converting enzyme-2 expression in glucose-controlled diabetic rat hearts

Independently of the lipid-lowering effects, statin has been reported to attenuate the development of diabetic cardiomyopathy. However, the effect of statin in glucose-controlled diabetic condition has not been demonstrated. We evaluated the effect of fluvastatin on cardiac function, fibrosis, and angiotensin-converting enzyme-2 (ACE2) expression in glucose-controlled diabetic rats. Male Wistar rats were randomly divided into four groups: control (Group C), diabetes (Group D), diabetes with insulin (Group I), and diabetes with insulin and fluvastatin (Group I+F). Diabetes was induced by a single injection of streptozotocin (65 mg/kg). After 8 weeks, the hearts were extracted following echocardiographic evaluation. Cardiac fibrosis was analyzed using Masson's trichrome stain. Collagens I and III and ACE2 expressions were evaluated by immunohistochemistry and western blot. Group D showed reduced cardiac systolic function compared to the other groups (all P < 0.05). However, diastolic function estimated by E/A ratio was significantly decreased in groups D and I (median: 0.88 and 1.45, respectively) compared to groups C and I+F (2.97 and 2.15) (all P < 0.05). Cardiac fibrosis was more severe in groups D and I than in groups C and I+F (all P < 0.05) on Masson's trichrome stain. On immunohistochemistry, ACE2 expression was significantly decreased only in group D (all P < 0.05). However, collagen I and III showed higher expressions in group D compared to groups C and I+F while no significant difference was observed compared with group I (all P < 0.05). On western blot, collagen I and ACE2 expressions in group D (median: 1.78 and 0.35, respectively) were significantly different from groups C (references: 1) and I+F (0.76 and 1.21) (all P < 0.05), but not from group I (1.19 and 0.92). Our study suggested a combination of fluvastatin and insulin would be more effective than insulin alone in diabetic hearts. However, the exact mechanism remains to be elucidated.

Effects of lifestyle intervention on left ventricular regional myocardial function in metabolic syndrome patients from the RESOLVE randomized trial

AIMS

The purpose of our study was to determine the effect of lifestyle intervention on left ventricular (LV) regional myocardial function in patients with metabolic syndrome (MetS) and investigate the relationships of the changes in myocardial function to changes in epicardial adipose tissue (EAT), inflammatory profile and MetS components.

METHODS

Eighty-seven MetS patients were enrolled in a 6month lifestyle intervention program based on dietary management and increased physical activity, and compared with 44 aged and sex-matched healthy controls. MetS individuals were allocated to different groups randomized (computer-generated randomization) on exercise modalities (high-intensity dominant resistance or aerobic training, and moderate-intensity of both modes). EAT was measured by transthoracic echocardiography and LV longitudinal strains and strain rates were obtained using vector velocity imaging. Blood chemistry allowed assessments of adipocytokines (TNF-α: tumor necrosis factor α, PAI active: active plasminogen activator inhibitor-1 and adiponectin) and glucose tolerance markers.

RESULTS

Regardless of exercise training modalities, lifestyle intervention improved significantly LV strains and strain rates (p<0.001) as well as metabolic and inflammatory profiles. Stepwise multiple regression analyses revealed EAT (β=0.73, p<0.01), log adiponectin (β=-0.13, p<0.05) and log TNF-α (β=0.15, p<0.05) as independent predictors of LV longitudinal strain (R(2)=0.74, p<0.001) while myocardial function improvement consecutive to lifestyle intervention was explained by EAT changes only (R(2)=0.54, p<0.001).

CONCLUSION

The mechanisms through which regional myocardial function is impaired in MetS and improved consecutive to intervention involved EAT, possibly via paracrine effects of adipocytokines. EAT should be considered as a future therapeutic target of interest in the treatment of metabolic-related cardiac diseases.

Glucose uptake and lipid metabolism are impaired in epicardial adipose tissue from heart failure patients with or without diabetes

Type 2 diabetes mellitus is a complex metabolic disease, and cardiovascular disease is a leading complication of diabetes. Epicardial adipose tissue surrounding the heart displays biochemical, thermogenic, and cardioprotective properties. However, the metabolic cross-talk between epicardial fat and the myocardium is largely unknown. This study sought to understand epicardial adipose tissue metabolism from heart failure patients with or without diabetes. We aimed to unravel possible differences in glucose and lipid metabolism between human epicardial and subcutaneous adipocytes and elucidate the potential underlying mechanisms involved in heart failure. Insulin-stimulated [(14)C]glucose uptake and isoproterenol-stimulated lipolysis were measured in isolated epicardial and subcutaneous adipocytes. The expression of genes involved in glucose and lipid metabolism was analyzed by reverse transcription-polymerase chain reaction in adipocytes. In addition, epicardial and subcutaneous fatty acid composition was analyzed by high-resolution proton nuclear magnetic resonance spectroscopy. The difference between basal and insulin conditions in glucose uptake was significantly decreased (P= 0.006) in epicardial compared with subcutaneous adipocytes. Moreover, a significant (P< 0.001) decrease in the isoproterenol-stimulated lipolysis was also observed when the two fat depots were compared, and it was strongly correlated with lipolysis, lipid storage, and inflammation-related gene expression. Moreover, the fatty acid composition of these tissues was significantly altered by diabetes. These results emphasize potential metabolic differences between both fat depots in the presence of heart failure and highlight epicardial fat as a possible therapeutic target in situ in the cardiac microenvironment.

Measurement of epicardial fat thickness by transthoracic echocardiography for predicting high-risk coronary artery plaques

Epicardial adipose tissue (EAT) volume is reported to be associated with coronary plaques. We evaluated whether non-invasive measurement of EAT thickness by echocardiography can predict high-risk coronary plaque characteristics determined independently by coronary computed tomography (CT) angiography. We enrolled 406 patients (mean age 63 years, 57 % male) referred for 64-slice CT. EAT was measured on the right ventricle free wall from a parasternal long-axis view at the end of systole. High-risk coronary plaques were defined as low-density plaques (<30 Hounsfield units) with positive remodeling (remodeling index >1.05). Patients were divided into thin or thick EAT groups using a cutoff value derived from receiver operator characteristic curve analysis for discriminating high-risk plaques. The receiver operator characteristic cutoff value was 5.8 mm with a sensitivity of 83 % and specificity of 64 % (area under the curve 0.77, 95 % confidence interval 0.70-0.83, p < 0.01). Compared with the thin EAT group, the thick EAT group had a high prevalence of low-density plaques (4 vs. 24 %, p < 0.01), positive remodeling (39 vs. 60 %, p < 0.01), and high-risk plaques (3 vs. 17 %, p < 0.01). Multiple logistic analysis revealed that thick EAT was a significant predictor of high-risk plaques (odds ratio 7.98, 95 % confidence interval 2.77-22.98, p < 0.01) after adjustment for covariates, including conventional risk factors, visceral adipose tissue area, and medications. The measurement of EAT thickness by echocardiography may provide a non-invasive option for predicting high-risk coronary plaques.

Transcriptome and Molecular Endocrinology Aspects of Epicardial Adipose Tissue in Cardiovascular Diseases: A Systematic Review and Meta-Analysis of Observational Studies

The objective of this study was to perform a systematic review of published literature on differentially expressed genes (DEGs) in human epicardial adipose tissue (EAT) to identify molecules associated with CVDs. A systematic literature search was conducted in PubMed, SCOPUS, and ISI Web of Science literature databases for papers published before October 2014 that addressed EAT genes and cardiovascular diseases (CVDs). We included original papers that had performed gene expressions in EAT of patients undergoing open-heart surgery. The Reporting Recommendations for Tumor Marker Prognostic Studies (PRIMARK) assessment tool was also used for methodological quality assessment. From the 180 papers identified by our initial search strategy, 40 studies met the inclusion criteria and presented DEGs in EAT samples from patients with and without CVDs. The included studies reported 42 DEGs identified through comparison of EAT-specific gene expression in patients with and without CVDs. Among the 42 DEGs, genes involved in regulating apoptosis had higher enrichment scores. Notably, interleukin-6 (IL-6) and tumor protein p53 (TP53) were the main hub genes in the network. The results suggest that regulation of apoptosis in EAT is critical for CVD development. Moreover, IL-6 and TP53 as hub genes could serve as biomarkers and therapeutic targets for CVDs.

Increased Epicardial Adipose Tissue Thickness in Type 2 Diabetes Mellitus and Obesity

BACKGROUND

Epicardial adipose tissue (EAT) is suggested to play an important role in the progression of metabolic syndrome. We aimed to establish a simple method to measure EAT and examine the differences in EAT thickness according to the presence of type 2 diabetes mellitus or obesity.

METHODS

A total of 94 patients (42.6% type 2 diabetes mellitus, 53.2% obese, mean age 61±13) who underwent multidetector computed tomography were enrolled. Thickness of EAT was measured on the parasternal short and horizontal long axis view. Epicardial fat area (EFA) was measured at the level of left main coronary artery (LMCA).

RESULTS

All EAT thicknesses were correlated with EFA at the LMCA level (r=0.235 to 0.613, all Ps<0.05), and EAT thickness in the left atrioventricular groove (LAVG) had the highest correlation coefficient (r=0.613). EFA, and EAT thicknesses in the LAVG and the left ventricular apex were higher in the group with type 2 diabetes mellitus than in the group without type 2 diabetes mellitus when adjusted only for body mass index. When adjusted only for type 2 diabetes mellitus, EFA, and EAT thicknesses in the LAVG and the right atrioventricular groove were higher in obese group than in nonobese group.

CONCLUSION

In conclusion, EAT thickness can be easily measured and represent EFA. EAT thickness, especially in LAVG, was higher in groups with type 2 diabetes mellitus and obesity independently. These findings implicate that EAT thickness may be a useful indicator for type 2 diabetes mellitus and obesity.