Myocardial, perivascular, and epicardial fat

The roles of epicardial adipose tissue in heart failure

Heart failure is a growing health problem resulting in the decreased life expectancy of patients and severely increased the healthcare burden. Penetrating research on the pathogenesis and regulation mechanism of heart failure is important for treatment of heart failure. Epicardial adipose tissue (EAT) has been demonstrated as not only a dynamic organ with biological functions but also an inert lipid store with regulating systemic metabolism. EAT mediates physiological and pathophysiological processes of heart failure by regulating adipogenesis, cardiac remodeling, insulin resistance, cardiac output, and renin angiotensin aldosterone system (RAAS). Moreover, EAT secretes a wide range of adipokines, adrenomedullin, adiponectin, and miRNAs through paracrine, endocrine, and vasocrine pathways, which involve in various extracellular and intracellular mechanism of cardiac-related cells in the progress of cardiovascular disease especially in heart failure. Nevertheless, mechanisms and roles of EAT on heart failure are barely summarized. Understanding the regulating mechanisms of EAT on heart failure may give rise to novel therapeutic targets and will open up innovative strategies to myocardial injury as well as in heart failure.

Unique Genetic and Histological Signatures of Mouse Pericardial Adipose Tissue

Obesity is a major risk factor for a plethora of metabolic disturbances including diabetes and cardiovascular disease. Accumulating evidence is showing that there is an adipose tissue depot-dependent relationship with obesity-induced metabolic dysfunction. While some adipose depots, such as subcutaneous fat, are generally metabolically innocuous, others such as visceral fat, are directly deleterious. A lesser known visceral adipose depot is the pericardial adipose tissue depot. We therefore set out to examine its transcriptional and morphological signature under chow and high-fat fed conditions, in comparison with other adipose depots, using a mouse model. Our results revealed that under chow conditions pericardial adipose tissue has uncoupling-protein 1 gene expression levels which are significantly higher than classical subcutaneous and visceral adipose depots. We also observed that under high-fat diet conditions, the pericardial adipose depot exhibits greatly upregulated transcript levels of inflammatory cytokines. Our results collectively indicate, for the first time, that the pericardial adipose tissue possesses a unique transcriptional and histological signature which has features of both a beige (brown fat-like) but also pro-inflammatory depot, such as visceral fat. This unique profile may be involved in metabolic dysfunction associated with obesity.

Heart Failure among People with HIV: Evolving Risks, Mechanisms, and Preventive Considerations

PURPOSE

People with HIV (PHIV) with access to modern antiretroviral therapy (ART) face a two-fold increased risk of heart failure as compared with non-HIV-infected individuals. The purpose of this review is to consider evolving risks, mechanisms, and preventive considerations pertaining to heart failure among PHIV.

RECENT FINDINGS

While unchecked HIV/AIDS has been documented to precipitate heart failure characterized by overtly reduced cardiac contractile function, ART-treated HIV may be associated with either heart failure with reduced ejection fraction (HFrEF) or with heart failure with preserved ejection fraction (HFpEF). In HFpEF, a "stiff" left ventricle cannot adequately relax in diastole-a condition known as diastolic dysfunction. Diastolic dysfunction, in turn, may result from processes including myocardial fibrosis (triggered by hypertension and/or immune activation/inflammation) and/or myocardial steatosis (triggered by metabolic dysregulation). Notably, hypertension, systemic immune activation, and metabolic dysregulation are all common conditions among even those PHIV who are well-treated with ART. Of clinical consequence, HFpEF is uniquely intransigent to conventional medical therapies and portends high morbidity and mortality. However, diastolic dysfunction is reversible-as are contributing processes of myocardial fibrosis and myocardial steatosis. Our challenges in preserving myocardial health among PHIV are two-fold. First, we must continue working to realize UNAIDS 90-90-90 goals. This achievement will reduce AIDS-related mortality, including cardiovascular deaths from AIDS-associated heart failure. Second, we must work to elucidate the detailed mechanisms continuing to predispose ART-treated PHIV to heart failure and particularly HFpEF. Such efforts will enable the development and implementation of targeted preventive strategies.

21st Century Advances in Multimodality Imaging of Obesity for Care of the Cardiovascular Patient

Although obesity is typically defined by body mass index criteria, this does not differentiate true body fatness, as this includes both body fat and muscle. Therefore, other fat depots may better define cardiometabolic and cardiovascular disease (CVD) risk imposed by obesity. Data from translational, epidemiological, and clinical studies over the past 3 decades have clearly demonstrated that accumulation of adiposity in the abdominal viscera and within tissue depots lacking physiological adipose tissue storage capacity (termed "ectopic fat") is strongly associated with the development of a clinical syndrome characterized by atherogenic dyslipidemia, hyperinsulinemia/glucose intolerance/type 2 diabetes mellitus, hypertension, atherosclerosis, and abnormal cardiac remodeling and heart failure. This state-of-the-art paper discusses the impact of various body fat depots on cardiometabolic parameters and CVD risk. Specifically, it reviews novel and emerging imaging techniques to evaluate adiposity and the risk of cardiometabolic diseases and CVD.

Echocardiographic measurement of epicardial adipose tissue thickness in patients with microvascular angina

Introduction

Impaired coronary microcirculation, inflammation, and endothelial dysfunction were reported etiological factors for microvascular angina (MVA). Recently, increased epicardial adipose tissue (EAT) thickness has been associated with hypertension, metabolic syndrome, and coronary artery disease in general population. In this study, we aimed to evaluate the EAT thickness in patients with MVA.

Methods

This study enrolled 200 patients (83 males; mean age: 55.4 ± 8.2 years) who have been diagnosed with MVA and 200 controls (89 males; mean age: 54.4 ± 8.5 years). All patients underwent transthoracic echocardiography, and EAT thickness was measured from a parasternal long-axis view as the hypoechoic space on the right ventricular free wall.

Results

The mean EAT thickness was significantly higher in MVA patients than the controls (5.5 ± 1.1 vs. 4.9 ± 0.7 mm; p < 0.001). Multiple logistic regression analysis showed that increased EAT thickness was an independent predictor of MVA (OR = 1.183, 95% CI = 1.063-1.489; p = 0.023). In receiver operating characteristic curve analyses, EAT thickness above 5.3 mm predicted MVA with a sentivity of 68% and a specificity of 63% (AUC = 0.711, 95% CI = 0.659-0.762; p < 0.001).

Conclusions

The EAT thickness was observed significantly higher in MVA patients as compared to controls. Increased EAT thickness may be associated with mechanisms that play a major role in the pathogenesis of MVA.

Adipose Tissue Distribution, Inflammation and Its Metabolic Consequences, Including Diabetes and Cardiovascular Disease

Adipose tissue plays essential roles in maintaining lipid and glucose homeostasis. To date several types of adipose tissue have been identified, namely white, brown, and beige, that reside in various specific anatomical locations throughout the body. The cellular composition, secretome, and location of these adipose depots define their function in health and metabolic disease. In obesity, adipose tissue becomes dysfunctional, promoting a pro-inflammatory, hyperlipidemic and insulin resistant environment that contributes to type 2 diabetes mellitus (T2DM). Concurrently, similar features that result from adipose tissue dysfunction also promote cardiovascular disease (CVD) by mechanisms that can be augmented by T2DM. The mechanisms by which dysfunctional adipose tissue simultaneously promote T2DM and CVD, focusing on adipose tissue depot-specific adipokines, inflammatory profiles, and metabolism, will be the focus of this review. The impact that various T2DM and CVD treatment strategies have on adipose tissue function and body weight also will be discussed.

Novel Invasive and Noninvasive Cardiac-Specific Biomarkers in Obesity and Cardiovascular Diseases

Cardiovascular disease (CVD) is the leading cause of fatality and disability worldwide regardless of gender. Obesity has reached epidemic proportions in population across different regions. According to epidemiological studies, CVD risk markers in childhood obesity are one of the significant risk factors for adulthood CVD, but have received disproportionally little attention. This review has examined the evidence for the presence of traditional cardiac biomarkers (nonspecific; lactate dehydrogenase, alanine aminotransferase, aspartate aminotransferase, creatine kinase, myoglobulin, glycogen phosphorylase isoenzyme BB, myosin light chains, ST2, and ischemia-modified albumin) and novel emerging cardiac-specific biomarkers (cardiac troponins, natriuretic peptides, heart-type fatty acid-binding protein, and miRNAs). Besides, noninvasive anatomical and electrophysiological markers (carotid intima-media thickness, coronary artery calcification, and heart rate variability) in CVDs and obesity are also discussed. Modifiable and nonmodifiable risk factors associated with metabolic syndrome in the progression of CVD, such as obesity, diabetes, hypertension, dyslipidemia, oxidative stress, inflammation, and adipocytokines are also outlined. These underlying prognostic risk factors predict the onset of future microvascular and macrovascular complications. The understanding of invasive and noninvasive cardiac-specific biomarkers and the risk factors may yield valuable insights into the pathophysiology and prevention of CVD in a high-risk obese population at an early stage.

The Gene and Protein Expression of the Main Components of the Lipolytic System in Human Myocardium and Heart Perivascular Adipose Tissue. Effect of Coronary Atherosclerosis

The aim of our study was to examine the regulation of triacylglycerols (TG) metabolism in myocardium and heart perivascular adipose tissue in coronary atherosclerosis. Adipose triglyceride lipase (ATGL) is the major TG-hydrolase. The enzyme is activated by a protein called comparative gene identification 58 (CGI-58) and inhibited by a protein called G0/G1 switch protein 2 (G0S2). Samples of the right atrial appendage and perivascular adipose tissue were obtained from two groups of patients: 1—with multivessel coronary artery disease qualified for coronary artery bypass grafting (CAD), 2—patients with no atherosclerosis qualified for a valve replacement (NCAD). The mRNA and protein analysis of ATGL, HSL, CGI-58, G0S2, FABP4, FAT/CD36, LPL, β-HAD, CS, COX4/1, FAS, SREBP-1c, GPAT1, COX-2, 15-LO, and NFκβ were determined by using real-time PCR and Western Blot. The level of lipids (i.e., TG, diacylglycerol (DG), and FFA) was examined by GLC. We demonstrated that in myocardium coronary atherosclerosis increases only the transcript level of G0S2 and FABP4. Most importantly, ATGL, β-HAD, and COX4/1 protein expression was reduced and it was accompanied by over double the elevation in TG content in the CAD group. The fatty acid synthesis and their cellular uptake were stable in the myocardium of patients with CAD. Additionally, the expression of proteins contributing to inflammation was increased in the myocardium of patients with coronary stenosis. Finally, in the perivascular adipose tissue, the mRNA of G0S2 was elevated, whereas the protein content of FABP-4 was increased and for COX4/1 diminished. These data suggest that a reduction in ATGL protein expression leads to myocardial steatosis in patients with CAD.

Pericoronary fat inflammation and Major Adverse Cardiac Events (MACE) in prediabetic patients with acute myocardial infarction: effects of metformin

BACKGROUND/OBJECTIVES

Pericoronary adipose tissue inflammation might lead to the development and destabilization of coronary plaques in prediabetic patients. Here, we evaluated inflammation and leptin to adiponectin ratio in pericoronary fat from patients subjected to coronary artery bypass grafting (CABG) for acute myocardial infarction (AMI). Furthermore, we compared the 12-month prognosis of prediabetic patients compared to normoglycemic patients (NG). Finally, the effect of metformin therapy on pericoronary fat inflammation and 12-months prognosis in AMI-prediabetic patients was also evaluated.

METHODS

An observational prospective study was conducted on patients with first AMI referred for CABG. Participants were divided in prediabetic and NG-patients. Prediabetic patients were divided in two groups; never-metformin-users and current-metformin-users receiving metformin therapy for almost 6 months before CABG. During the by-pass procedure on epicardial coronary portion, the pericoronary fat was removed from the surrounding stenosis area. The primary endpoints were the assessments of Major-Adverse-Cardiac-Events (MACE) at 12-month follow-up. Moreover, inflammatory tone was evaluated by measuring pericoronary fat levels of tumor necrosis factor-α (TNF-α), sirtuin 6 (SIRT6), and leptin to adiponectin ratio. Finally, inflammatory tone was correlated to the MACE during the 12-months follow-up.

RESULTS

The MACE was 9.1% in all prediabetic patients and 3% in NG-patients. In prediabetic patients, current-metformin-users presented a significantly lower rate of MACE compared to prediabetic patients never-metformin-users. In addition, prediabetic patients showed higher inflammatory tone and leptin to adiponectin ratio in pericoronary fat compared to NG-patients (P < 0.001). Prediabetic never-metformin-users showed higher inflammatory tone and leptin to adiponectin ratio in pericoronary fat compared to current-metformin-users (P < 0.001). Remarkably, inflammatory tone and leptin to adiponectin ratio was significantly related to the MACE during the 12-months follow-up.

CONCLUSION

Prediabetes increase inflammatory burden in pericoronary adipose tissue. Metformin by reducing inflammatory tone and leptin to adiponectin ratio in pericoronary fat may improve prognosis in prediabetic patients with AMI. Trial registration Clinical Trial NCT03360981, Retrospectively Registered 7 January 2018.

Cardiac expression of the microsomal triglyceride transport protein protects the heart function during ischemia

AIMS

The microsomal triglyceride transport protein (MTTP) is critical for assembly and secretion of apolipoprotein B (apoB)-containing lipoproteins and is most abundant in the liver and intestine. Surprisingly, MTTP is also expressed in the heart. Here we tested the functional relevance of cardiac MTTP expression.

MATERIALS AND METHODS

We combined clinical studies, advanced expression analysis of human heart biopsies and analyses in genetically modified mice lacking cardiac expression of the MTTP-A isoform of MTTP.

RESULTS

Our results indicate that lower cardiac MTTP expression in humans is associated with structural and perfusion abnormalities in patients with ischemic heart disease. MTTP-A deficiency in mice heart does not affect total MTTP expression, activity or lipid concentration in the heart. Despite this, MTTP-A deficient mice displayed impaired cardiac function after a myocardial infarction. Expression analysis of MTTP indicates that MTTP expression is linked to cardiac function and responses in the heart.

CONCLUSIONS

Our results indicate that MTTP may play an important role for the heart function in conjunction to ischemic events.

Sphingolipid Synthesis Inhibition by Myriocin Administration Enhances Lipid Consumption and Ameliorates Lipid Response to Myocardial Ischemia Reperfusion Injury

Myocardial infarct requires prompt thrombolytic therapy or primary percutaneous coronary intervention to limit the extent of necrosis, but reperfusion creates additional damage. Along with reperfusion, a maladaptive remodeling phase might occur and it is often associated with inflammation, oxidative stress, as well as a reduced ability to recover metabolism homeostasis. Infarcted individuals can exhibit reduced lipid turnover and their accumulation in cardiomyocytes, which is linked to a deregulation of peroxisome proliferator activated receptors (PPARs), controlling fatty acids metabolism, energy production, and the anti-inflammatory response. We previously demonstrated that Myriocin can be effectively used as post-conditioning therapeutic to limit ischemia/reperfusion-induced inflammation, oxidative stress, and infarct size, in a murine model. In this follow-up study, we demonstrate that Myriocin has a critical regulatory role in cardiac remodeling and energy production, by up-regulating the transcriptional factor EB, PPARs nuclear receptors and genes involved in fatty acids metabolism, such as VLDL receptor, Fatp1, CD36, Fabp3, Cpts, and mitochondrial FA dehydrogenases. The overall effects are represented by an increased β–oxidation, together with an improved electron transport chain and energy production. The potent immunomodulatory and metabolism regulatory effects of Myriocin elicit the molecule as a promising pharmacological tool for post-conditioning therapy of myocardial ischemia/reperfusion injury.

Epicardial adipose tissue is a predictor of decreased kidney function and coronary artery calcification in youth- and early adult onset type 2 diabetes mellitus

PURPOSE

To examine the association of epicardial and pericardial fat volume (EFV, PFV) with cardiovascular risk factors and kidney function in Native Americans of southwestern heritage with youth and early adult onset type 2 diabetes mellitus (T2DM) versus healthy controls.

METHODS

Using computed tomography, we quantified EFV and PFV in 149 Native Americans (92 women, 57 men), 95 of which had T2DM (38 diagnosed prior to age 20 years). Duration of T2DM, mean carotid arterial mass (AM), coronary artery calcification (CAC), IL-6, and estimated glomerular filtration rate eGFR_cr(CKD-EPI) were measured.

RESULTS

EFV and PFV were associated with BMI (r = 0.37, p < 0.0001; r = 0.26, p = 0.001) and did not differ between onset age-groups and controls (p > 0.05). EFV was associated with AM only in controls (r = 0.51, p < 0.0001). After adjustment for BMI, T2DM duration, HbA1C, age, and sex, EFV was a predictor of CAC and IL-6 concentrations in early adult onset T2DM (β = 0.05 ± 0.02 cm³, p = 0.03; β = 0.05 ± 0.01 pg/ml/cm³, p = 0.002). EFV and PFV were independent predictors of reduced eGFR_cr(CKD-EPI) in the youth onset T2DM group (β = -0.3 ± 0.08 ml/min/cm³, p = 0.001; β = -0.25 ± 0.05 ml/min/cm³, p < 0.0001).

CONCLUSIONS

Epicardial fat volume may be a risk factor for heart disease in individuals with early adult onset T2DM and a predictor of decreased kidney function in individuals with youth onset T2DM.

Dysfunctional EAT thickness may promote maladaptive heart remodeling in CVD patients through the ST2-IL33 system, directly related to EPAC protein expression

Dysfunctional epicardial adipose tissue (EAT) secretome can influence the heart’s stretch response. However, the molecular mechanisms are still poorly understood. The aim of this study was to clarify how dysfunctional EAT promotes maladaptive heart remodeling in cardiovascular disease (CVD) through ST2 production associated with exchange protein directly activated by cAMP (EPAC) proteins. A series of 55 CVD males were enrolled and their EAT thickness, LV mass and volumes were measured by echocardiography. Blood, plasma and EAT biopsies were collected for molecular and proteomic assays. Taking EAT thickness as a continuous variable there was a direct correlation between the ST2 cardiac stretch mediator and EAT thickness (r = 0.54, p < 0.01) and an inverse relation between the ST2 gene and IL-33 expression (r −0.50, p < 0.01). In the CVD population EPAC2 expression directly correlated with the ST2 gene (r = 0.74, p < 0.0001) causing an ST2/IL-33 system local (p < 0.001) and systemic (sST2 = 57.33 ± 3.22 and IL-33 = 0.53 ± 017 pg/mL; p < 0.0001) protein imbalance associated with maladaptive remodeling. This indicated that dysfunctional EAT is a source of both EPAC and ST2 protein and an EPAC2 isoform seems involved in ST2 production in adipose tissue. Both EPAC2 and ST2 expression were directly related to maladaptive heart remodeling indices, suggesting EAT measurements could be useful in the early assessment of CVD complications.

Presence of fragmented QRS is associated with increased epicardial adipose tissue thickness in hypertensive patients

BACKGROUND

Epicardial adipose tissue (EAT) is a cardiometabolic risk factor, and its possible relationship with hypertension has been reported previously. Fragmented QRS (fQRS) detected on electrocardiography (ECG) has been demonstrated to be a marker of myocardial fibrosis. In this study, we aimed to investigate the relationship between the thickness of EAT, and presence of fQRS in hypertensive patients.

METHODS

Consecutive patients who were diagnosed with hypertension were included in the study. ECG and transthoracic echocardiography (TTE) were performed to all patients. fQRS was defined as additional R' wave or notching/splitting of S wave in two contiguous ECG leads. Thickness of EAT was measured by TTE.

RESULTS

This study enrolled 69 hypertensive patients with fQRS on ECG and 45 hypertensive patients without fQRS as the control group. Age (P = .869), and gender distribution (P = .751) were similar in both groups. Left atrial diameter (P = .012), interventricular septal thickness (P < .001), posterior wall thickness (P < .001), left ventricular ejection fraction (P = .009), left ventricular mass (P = .006), left ventricular mass ındex (P = .014), left ventricular hypertrophy (P = .003), and EAT thickness (P < .001) were found to be significantly increased in patients with fQRS. In multivariate analysis, among these variables only EAT was observed to be an independent predictor of fQRS (odds ratio:3.306 [95% confidence interval, 0.030-0.118], P = .001).

CONCLUSION

A significant association exists between the presence of fQRS and EAT thickness in hypertensive patients. The presence of fQRS, just as EAT thickness, may be used as a cardiometabolic risk factor in hypertensive patients.

Adipose Tissue Dysfunction as Determinant of Obesity-Associated Metabolic Complications

Obesity is a critical risk factor for the development of type 2 diabetes (T2D), and its prevalence is rising worldwide. White adipose tissue (WAT) has a crucial role in regulating systemic energy homeostasis. Adipose tissue expands by a combination of an increase in adipocyte size (hypertrophy) and number (hyperplasia). The recruitment and differentiation of adipose precursor cells in the subcutaneous adipose tissue (SAT), rather than merely inflating the cells, would be protective from the obesity-associated metabolic complications. In metabolically unhealthy obesity, the storage capacity of SAT, the largest WAT depot, is limited, and further caloric overload leads to the fat accumulation in ectopic tissues (e.g., liver, skeletal muscle, and heart) and in the visceral adipose depots, an event commonly defined as “lipotoxicity.” Excessive ectopic lipid accumulation leads to local inflammation and insulin resistance (IR). Indeed, overnutrition triggers uncontrolled inflammatory responses in WAT, leading to chronic low-grade inflammation, therefore fostering the progression of IR. This review summarizes the current knowledge on WAT dysfunction in obesity and its associated metabolic abnormalities, such as IR. A better understanding of the mechanisms regulating adipose tissue expansion in obesity is required for the development of future therapeutic approaches in obesity-associated metabolic complications.

In New-Onset Diabetes Mellitus, Metformin Reduces Fat Accumulation in the Liver, But Not in the Pancreas or Pericardium

Background: Nonalcoholic fatty pancreas and liver disease (NAFPD and NAFLD) and pericardial adipose tissue (PAT) are often associated with type 2 diabetes mellitus (T2DM). Our aim was to evaluate the incidence rate of NAFLD and NAFPD, PAT size, and the effect of metformin treatment on NAFLD, NAFPD, and PAT in new-onset T2DM (NODM). Methods: Seventeen patients with NODM and 10 subjects used as a control group were involved in the study. Computed tomography (CT) and laboratory tests were performed before the beginning of metformin therapy and 4 months afterward. PAT and the amount of fat in the pancreas and liver were determined by X-ray attenuation during unenhanced CT examination and compared with the values for the control subjects. Results: Metabolic parameters improved significantly after metformin therapy. NAFLD was diagnosed in 64.7% of the patients with NODM and in 10% of the control subjects. The radiation absorption of the liver was significantly lower in the patients with NODM compared with the control group and significantly higher after metformin therapy compared with the baseline values. Only six patients (35.3%) had NAFLD after metformin therapy. NAFPD was diagnosed in 82.3% of the patients with NODM and in 20% of the control subjects. The radiation absorption of the pancreas was significantly lower in the patients with NODM compared with the control group but did not change significantly after treatment. PAT size was significantly larger in the patients with NODM and did not change significantly after metformin treatment. Conclusions: NAFLD, NAFPD, and increased PAT were detected in the majority of patients with NODM. Metformin therapy decreased the amount of fat in the liver in parallel with an improvement in the metabolic parameters and may, thus, be beneficial for preventing the late consequences of NAFLD.

Epicardial Adipose Tissue and Cardiovascular Disease

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

Adipose-derived stromal/stem cells from different adipose depots in obesity development

The increasing prevalence of obesity is alarming because it is a risk factor for cardiovascular and metabolic diseases (such as type 2 diabetes). The occurrence of these comorbidities in obese patients can arise from white adipose tissue (WAT) dysfunctions, which affect metabolism, insulin sensitivity and promote local and systemic inflammation. In mammals, WAT depots at different anatomical locations (subcutaneous, preperitoneal and visceral) are highly heterogeneous in their morpho-phenotypic profiles and contribute differently to homeostasis and obesity development, depending on their ability to trigger and modulate WAT inflammation. This heterogeneity is likely due to the differential behavior of cells from each depot. Numerous studies suggest that adipose-derived stem/stromal cells (ASC; referred to as adipose progenitor cells, in vivo) with depot-specific gene expression profiles and adipogenic and immunomodulatory potentials are keys for the establishment of the morpho-functional heterogeneity between WAT depots, as well as for the development of depot-specific responses to metabolic challenges. In this review, we discuss depot-specific ASC properties and how they can contribute to the pathophysiology of obesity and metabolic disorders, to provide guidance for researchers and clinicians in the development of ASC-based therapeutic approaches.

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.

Obesity and cardiovascular disease: revisiting an old relationship

A wealth of clinical and epidemiological evidence has linked obesity to a broad spectrum of cardiovascular diseases (CVD) including coronary heart disease, heart failure, hypertension, stroke, atrial fibrillation and sudden cardiac death. Obesity can increase CVD morbidity and mortality directly and indirectly. Direct effects are mediated by obesity-induced structural and functional adaptations of the cardiovascular system to accommodate excess body weight, as well as by adipokine effects on inflammation and vascular homeostasis. Indirect effects are mediated by co-existing CVD risk factors such as insulin resistance, hyperglycemia, hypertension and dyslipidemia. Adipose tissue (AT) quality and functionality are more relevant aspects for cardiometabolic risk than its total amount. The consequences of maladaptive AT expansion in obesity are local and systemic: the local include inflammation, hypoxia, dysregulated adipokine secretion and impaired mitochondrial function; the systemic comprise insulin resistance, abnormal glucose/lipid metabolism, hypertension, a pro-inflammatory and pro-thrombotic state and endothelial dysfunction, all of which provide linking mechanisms for the association between obesity and CVD. The present narrative review summarizes the major pathophysiological links between obesity and CVD (traditional and novel concepts), analyses the heterogeneity of obesity-related cardiometabolic consequences, and provides an overview of the cardiovascular impact of weight loss interventions.

Epicardial fat thickness correlates with coronary in-stent restenosis in patients with acute myocardial infarction

OBJECTIVE

To determine the relation between epicardial fat thickness and coronary in-stent restenosis in patients with acute myocardial infarction and percutaneous coronary intervention.

METHODS

A prospective study was conducted, which included 129 patients (67.3% male, mean age 62.9±10 years) with ST segment elevation acute myocardial infarction undergoing primary percutaneous coronary intervention with bare metal stent. Patients were divided in two groups according to the presence (n=21) or not (n=108) of in-stent restenosis during one year follow-up.

RESULTS

Epicardial fat was significantly thicker in patients with coronary in-stent restenosis (5.51±1.6 vs 4.14±2.0mm, p=0.006). A proportionally and significantly thicker epicardial fat was found according to the increase in coronary disease severity (3.3±0.9mm vs 4.3±1.8mm vs 4.7±2.3mm vs 6.7±2.2mm, for type A, B1, B2 and C lesions, respectively, p=0.001) and number of vessels (3.07±1.2mm vs 4.92±1.8mm vs 5.43±2.2mm, for one, two and three vessels disease, respectively, p<0.0001). Epicardial fat thickness ≥4.7mm had 75.0% sensibility and 69.0% specificity for predicting restenosis (AUC=0.737).

CONCLUSIONS

Echocardiographic evaluation of epicardial fat thickness could identify those patients with acute myocardial infarction with greater probabilities of in-stent restenosis after percutaneous coronary intervention.

Cardiac Obesity and Cardiac Cachexia: Is There a Pathophysiological Link?

Obesity is a risk factor for cardiometabolic and vascular diseases like arterial hypertension, diabetes mellitus type 2, dyslipidaemia, and atherosclerosis. A special role in obesity-related syndromes is played by cardiac visceral obesity, which includes epicardial adipose tissue and intramyocardial fat, leading to cardiac steatosis; hypertensive heart disease; atherosclerosis of epicardial coronary artery disease; and ischemic cardiomyopathy, cardiac microcirculatory dysfunction, diabetic cardiomyopathy, and atrial fibrillation. Cardiac expression of these changes in any given patient is unique and multimodal, varying in clinical settings and level of expressed changes, with heart failure development depending on pathophysiological mechanisms with preserved, midrange, or reduced ejection fraction. Progressive heart failure with misbalanced metabolic and catabolic processes will change muscle, bone, and fat mass and function, with possible changes in the cardiac fat state from excessive accumulation to reduction and cardiac cachexia with a worse prognosis. The question we address is whether cardiac obesity or cardiac cachexia is to be more feared.

A different effect of obesity on ECG in premenopausal and postmenopausal women

Both obesity and menopause are significant cardiovascular risk factors. In postmenopausal women the protective effect of estrogens is reduced and menopause is frequently associated with occurrence of other significant cardiovascular factors including obesity. This study was focused on evaluating the effect of obesity on the QRS complex in pre- and postmenopausal women. We present results of analysis of 199 electrocardiograms of pre- and postmenopausal women analyzed in relation to the body mass index within normal limits (BMI 20 to 24.9 kg/m²) and obesity (BMI > 30 kg/m²), respectively. Obesity in premenopausal women and menopause significantly affected both the electrical axis (EA) and maximum QRS spatial vector magnitude (QRSmax). The highest QRSmax and electrical axis values were observed in premenopausal lean women, and they were significantly higher as than in the premenopausal obese women, postmenopausal lean and obese women (QRSmax: 1.66 ± 0.4 mV, 1.17 ± 0.35 mV, 1.4 ± 0.46 mV, and 1.35 ± 0.39 mV, resp.). (EA: 56.4 ± 18.0°, 38.22 ± 18.38°, 45.82 ± 18.63°, and 36.75 ± 17.51°). The differences between obese premenopausal women, lean and obese postmenopausal women were not statistically significant. These differences were reflected in 12-lead ECG amplitude. The presence of additional cardiovascular risk factors did not affect the ECG parameters. Obesity significantly affected QRS complex in premenopausal women. This effect was comparable with the effect of menopause. Because all QRS complex changes were within normal limits, these results suggest that ECG evaluation in women should go beyond traditional diagnostic categories and consider the relationship between ECG changes and two cardiovascular risk factors - obesity and menopause.

Arrhythmogenic Substrates for Atrial Fibrillation in Obesity

Global obesity rates have nearly tripled since 1975. This obesity rate increase is mirrored by increases in atrial fibrillation (AF) that now impacts nearly 10% of Americans over the age of 65. Numerous epidemiologic studies have linked incidence of AF and obesity and other obesity-related diseases, including hypertension and diabetes. Due to the wealth of epidemiologic data linking AF with obesity-related disease, mechanisms of AF pathogenesis in the context of obesity are an area of ongoing investigation. However, progress has been somewhat slowed by the complex phenotype of obesity; separating the effects of obesity from those of related sequelae is problematic. While the initiation of pathogenic pathways leading to AF varies with disease (including increased glycosylation in diabetes, increased renin angiotensin aldosterone system activation in hypertension, atrial ischemia in coronary artery disease, and sleep apnea) the pathogenesis of AF is united by shared mediators of altered conduction in the atria. We suggest focusing on these downstream mediators of AF in obesity is likely to yield more broadly applicable data. In the context of obesity, AF is driven by the interrelated processes of inflammation, atrial remodeling, and oxidative stress. Obesity is characterized by a constant low-grade inflammation that leads to increased expression of pro-inflammatory cytokines. These cytokines contribute to changes in cardiomyocyte excitability. Atrial structural remodeling, including fibrosis, enlargement, and fatty infiltration is a prominent feature of AF and contributes to the altered conduction. Finally, obesity impacts oxidative stress. Within the cardiomyocyte, oxidative stress is increased through both increased production of reactive oxygen species and by downregulation of scavenging enzymes. This increased oxidative stress modulates of cardiomyocyte excitability, increasing susceptibility to AF. Although the initiating insults vary, inflammation, atrial remodeling, and oxidative stress are conserved mechanisms in the pathophysiology of AF in the obese patients. In this review, we highlight mechanisms that have been shown to be relevant in the pathogenesis of AF across obesity-related disease.

Obesity, Visceral Fat, and Hypertension-Related Complications

Background: Hypertension and obesity are very common and complex cardiovascular (CV) risk factors. Our aim was to provide a comprehensive assessment of associations between visceral fat depots and vascular or cardiac complications of hypertension. Methods: All the consecutive patients (age: 45-80 years old) scheduled for elective coronary angiography in the Department of Cardiology were screened, and 400 patients were included into the study group. All the patients had a comprehensive clinical assessment focused on hypertension and obesity, risk factors, fat depots, and several hypertension-related vascular or cardiac complications. Results: The study group (n = 400; F/M: 140/260; age: 61 ± 7 years) included patients with hypertension (n = 354; 88.5%) and normal blood pressure (n = 46; 11.5%) and individuals with obesity (n = 192; 48%), diabetes (n = 139; 35%), metabolic syndrome (n = 240; 60%), and coronary artery disease (n = 286; 71%). Patients with higher degrees of hypertension (grade 3 vs. 2 vs. 1) showed increased body mass index (BMI) and waist circumference and ultrasound indexes of perivascular, epicardial, and abdominal visceral fat with no differences in age, waist-hip ratio, and subcutaneous fat. Both visceral fat depots: perivascular fat (carotid extra-media thickness) and abdominal visceral fat (intra-abdominal thickness) assessed as single measures and ratios were significantly increased in hypertensive patients with high versus low global CV risk in a hypertension-focused risk model (differences more pronounced in patients ≤60 years old). Visceral fat parameters were not independent, but rather additive to general obesity (BMI), except for visceral abdominal fat depot. Conclusions: Visceral abdominal and perivascular fat depots assessed as ultrasound indexes are associated with complications of hypertension and CV risk indicators, especially in patients with a mild-to-moderate hypertension and in younger patients.

Epicardial adipose tissue thickness and type 2 diabetes risk according to the FINDRISC modified for Latin America

BACKGROUND

The Finnish Diabetes Risk Score (FINDRISC) is a tool to predict 10-year risk of type 2 diabetes mellitus (T2DM), and visceral adiposity is associated with higher cardio-metabolic risk. The objective of the study was to assess the relationship of epicardial adipose tissue (EAT) thickness with T2DM risk according to the FINDRISC tool.

METHODS

The study was conducted in Ciudad Bolívar, Venezuela, and included 55 subjects of whom 37 (67.3%) were women and 18 (32.7%) men with ages between 18 and 75 years. A record was made of weight, height, body mass index (BMI), waist circumference (WC), fasting glucose, baseline insulin, plasma lipids, Homeostasis Model Assessment-Insulin Resistance (HOMA-IR), and EAT thickness. The FINDRISC tool, with WC cut-off points modified for Latin America (LA-FINDRISC) was used.

RESULTS

BMI, WC, plasma insulin concentration, HOMA-IR index, and EAT thickness were higher (P<0.0001) in the high-risk group compared to subjects in the low-moderate risk group according to the LA-FINDRISC. LA-FINDRISC was positively correlated with BMI (r=0.513; P=0.0001), WC (r=0.524; P=0.0001), fasting blood glucose (r=0.396; P=0.003); baseline plasma insulin (r=0.483; P=0.0001); HOMA-IR index (r=0.545; P=.0.0001); and EAT thickness (r=0.702; P=0.0001). The multivariate regression analysis showed that fasting blood glucose (P=0.023) and EAT thickness (P=0.007) remained independently associated with high T2DM risk.

CONCLUSIONS

LA-FINDRISC was associated with EAT thickness and insulin resistance markers. Both were independently and directly associated with high risk for diabetes in the LA-FINDRISC category.

High Density of Periaortic Adipose Tissue in Abdominal Aortic Aneurysm

OBJECTIVES

Perivascular adipose tissue (PVAT) is currently seen as a paracrine organ that produces vasoactive substances, including inflammatory agents, which may have an impact on the vasculature. In this study PVAT density was quantified in patients with an aortic aneurysm and compared with those with a non-dilated aorta. Since chronic inflammation, as the pathway to medial thinning, is a hallmark of abdominal aortic aneurysms (AAAs), it was hypothesised that PVAT density is higher in AAA patients.

METHODS

In this multicentre retrospective case control study, three groups of patients were included: non-treated asymptomatic AAA (n = 140), aortoiliac occlusive disease (AIOD) (n = 104), and individuals without aortic pathology (n = 97). A Hounsfield units based analysis was performed by computed tomography (CT). As a proxy for PVAT, the density of adipose tissue 10 mm circumferential to the infrarenal aorta was analysed in each consecutive CT slice. Intra-individual PVAT differences were reported as the difference in PVAT density between the region of the maximum AAA diameter (or the mid-aortic region in patients with AIOD or controls) and the two uppermost slices of infrarenal non-dilated aorta just below the renal arteries. Furthermore, subcutaneous (SAT) and visceral (VAT) adipose tissue measurements were performed. Linear models were fitted to assess the association between the study groups, different adipose tissue compartments, and between adipose tissue compartments and aortic dimensions.

RESULTS

AAA patients presented higher intra-individual PVAT differences, with higher PVAT density around the aneurysm sac than the healthy neck. This association persisted after adjustment for cardiovascular risk factors and diseases and other fat compartments (β = 13.175, SE 4.732, p = .006). Furthermore, intra-individual PVAT differences presented the highest correlation with aortic volume that persisted after adjustment for other fat compartments, body mass index, sex, and age (β = 0.566, 0.200, p = .005).

CONCLUSION

The results suggest a relation between the deposition of PVAT and AAA pathophysiology. Further research should explore the exact underlying processes.

Epicardial adipose tissue feeding and overfeeding the heart

Epicardial adipose tissue is a particular visceral fat depot with unique anatomic, biomolecular, and genetic features. Epicardial fat displays both physiological and pathological properties. Epicardial fat expresses genes and secretes cytokines actively involved in the thermogenesis and regulation of lipid and glucose metabolism of the adjacent myocardium. A disequilibrium between epicardial fat feeding and overfeeding the myocardium with free fatty acids leads to intramyocardial fat infiltration causing organ damage and clinical consequences. The upregulation of epicardial fat proinflammatory and lipogenic genes contributes to the fat build up in the proximal coronary arteries. Epicardial fat is a measurable and modifiable risk factor that can serve as a novel and additional tool for cardiovascular risk stratification. Pharmacologically targeting epicardial fat with drugs such as glucagon peptide-like 1 analogs or sodium glucose transport 2 inhibitors reduces the epicardial fat burden and induces beneficial cardiometabolic effects. Assessment and manipulation of epicardial fat transcriptome might open new avenues in the prevention of cardiometabolic diseases.

Epicardial adipose tissue as a metabolic transducer: role in heart failure and coronary artery disease

Obesity and diabetes are strongly associated with metabolic and cardiovascular disorders including dyslipidemia, coronary artery disease, hypertension, and heart failure. Adipose tissue is identified as a complex endocrine organ, which by exerting a wide array of regulatory functions at the cellular, tissue and systemic levels can have profound effects on the cardiovascular system. Different terms including "epicardial," "pericardial," and "paracardial" have been used to describe adipose tissue deposits surrounding the heart. Epicardial adipose tissue (EAT) is a unique and multifaceted fat depot with local and systemic effects. The functional and anatomic proximity of EAT to the myocardium enables endocrine, paracrine, and vasocrine effects on the heart. EAT displays a large secretosome, which regulates physiological and pathophysiological processes in the heart. Perivascular adipose tissue (PVAT) secretes adipose-derived relaxing factor, which is a "cocktail" of cytokines, adipokines, microRNAs, and cellular mediators, with a potent effect on paracrine regulation of vascular tone, vascular smooth muscle cell proliferation, migration, atherosclerosis-susceptibility, and restenosis. Although there are various physiological functions of the EAT and PVAT, a phenotypic transformation can lead to a major pathogenic role in various cardiovascular diseases. The equilibrium between the physiological and pathophysiological properties of EAT is very delicate and susceptible to the influences of intrinsic and extrinsic factors. Various adipokines secreted from EAT and PVAT have a profound effect on the myocardium and coronary arteries; targeting these adipokines could be an important therapeutic approach to counteract cardiovascular disease.

Obesity, ectopic fat and cardiac metabolism

INTRODUCTION

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

AREAS COVERED

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

EXPERT COMMENTARY

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

Overview of Epidemiology and Contribution of Obesity and Body Fat Distribution to Cardiovascular Disease: An Update

Obesity is recognized as a heterogeneous condition in which individuals with similar body mass index may have distinct metabolic and cardiovascular risk profiles. Susceptibility to obesity-related cardiometabolic complications is not solely mediated by overall body fat mass, but is largely dependent upon individual differences in regional body fat distribution and ability of subcutaneous adipose tissue to expand. The present review will discuss to what extent the individual variation in body fat distribution is one of the clinical key variables explaining the metabolic heterogeneity of obesity and its related cardiovascular risk. We will present the evidence for the complex nature of the relationship between obesity and cardiovascular disease, outline our current understanding of the mechanisms involved, and identify future direction of research pertinent to this interaction.

Interplay between epicardial adipose tissue, metabolic and cardiovascular diseases

Cardiovascular disease is the primary cause of death in obese and diabetic patients. In these groups of patients, the alterations of epicardial adipose tissue (EAT) contribute to both vascular and myocardial dysfunction. Therefore, it is of clinical interest to determine the mechanisms by which EAT influences cardiovascular disease. Two key factors contribute to the tight intercommunication among EAT, coronary arteries and myocardium. One is the close anatomical proximity between these tissues. The other is the capacity of EAT to secrete cytokines and other molecules with paracrine and vasocrine effects on the cardiovascular system. Epidemiological studies have demonstrated that EAT thickness is associated with not only metabolic syndrome but also atherosclerosis and heart failure. The evaluation of EAT using imaging modalities, although effective, presents several disadvantages including radiation exposure, limited availability and elevated costs. Therefore, there is a clinical interest in EAT as a source of new biomarkers of cardiovascular and endocrine alterations. In this review, we revise the mechanisms involved in the protective and pathological role of EAT and present the molecules released by EAT with greater potential to become biomarkers of cardiometabolic alterations.

Diagnostic imaging in the management of patients with metabolic syndrome

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

Perivascular Adipose Tissue as a Relevant Fat Depot for Cardiovascular Risk in Obesity

Obesity is associated with increased risk of premature death, morbidity, and mortality from several cardiovascular diseases (CVDs), including stroke, coronary heart disease (CHD), myocardial infarction, and congestive heart failure. However, this is not a straightforward relationship. Although several studies have substantiated that obesity confers an independent and additive risk of all-cause and cardiovascular death, there is significant variability in these associations, with some lean individuals developing diseases and others remaining healthy despite severe obesity, the so-called metabolically healthy obese. Part of this variability has been attributed to the heterogeneity in both the distribution of body fat and the intrinsic properties of adipose tissue depots, including developmental origin, adipogenic and proliferative capacity, glucose and lipid metabolism, hormonal control, thermogenic ability, and vascularization. In obesity, these depot-specific differences translate into specific fat distribution patterns, which are closely associated with differential cardiometabolic risks. The adventitial fat layer, also known as perivascular adipose tissue (PVAT), is of major importance. Similar to the visceral adipose tissue, PVAT has a pathophysiological role in CVDs. PVAT influences vascular homeostasis by releasing numerous vasoactive factors, cytokines, and adipokines, which can readily target the underlying smooth muscle cell layers, regulating the vascular tone, distribution of blood flow, as well as angiogenesis, inflammatory processes, and redox status. In this review, we summarize the current knowledge and discuss the role of PVAT within the scope of adipose tissue as a major contributing factor to obesity-associated cardiovascular risk. Relevant clinical studies documenting the relationship between PVAT dysfunction and CVD with a focus on potential mechanisms by which PVAT contributes to obesity-related CVDs are pointed out.

Presence of Intramyocardial Fat Tissue in the Right Atrium and Right Ventricle - Postmortem Human Analysis

Histologic and radiologic studies describe intramyocardial fat tissue as a normal finding or as part of cardiac pathology. The role of fat cells within the myocardium is not fully understood. The aim of this study was to assess fat tissue distribution in the myocardium of right atrium (RA) and right ventricle (RV) and age differences in subjects free from cardiac disease. The study included 10 males without cardiac disease divided into two groups according to age (below/above 50 years). Three cross sections were performed (RV free wall and apex and RA free wall) with histomorphological analysis on digital photographs. The shares of total myocardial fat (TMF), peri-vascular fat (PVF) and non-perivascular (nPVF) fat were calculated. Samples from the older group had larger amounts of fat in the epicardium and myocardium, without statistically significant differ-ence (TMF p=0.847, PVF p=0.4 and nPVF p=0.4). The largest quantities of fat tissue were found in the RV apex samples (14.9%), followed by RV free wall (7.5%) and RA (4.5%), where total apical RV fat share was significantly larger than in RA sample (p=0.044). Intramyocardial fat cells were present within the non-diseased RA and RV in all samples, mostly in the apex. Further investigations on age difference, effect of visceral obesity and sex differences are needed.

Fatty Infiltration of the Myocardium and Arrhythmogenesis: Potential Cellular and Molecular Mechanisms

Anatomical evidence in several species shows highly heterogeneous fat distribution in the atrial and ventricular myocardium. Atrial appendages have fat deposits, and more so on the posterior left atrium. Although such fat distributions are considered normal, fatty infiltration is regarded arrhythmogenic, and various cardiac pathophysiological conditions show excess myocardial fat deposits, especially in the epicardium. Hypotheses have been presented for the physiological and pathophysiological roles of epicardial fat, however this issue is poorly understood. Therefore, this mini-review will focus on epicardial fat distribution and the (patho)-physiological implications of this distribution. Potential molecular mechanisms that may drive structural and electrical myocardial remodeling attendant to fatty infiltration of the heart are also reviewed.

Communication Is Key: Mechanisms of Intercellular Signaling in Vasodilation

Thirty years ago, Robert F. Furchgott concluded that nitric oxide, a compound traditionally known to be a toxic component of fuel exhaust, is in fact released from the endothelium, and in a paracrine fashion, induces relaxation of underlying vascular smooth muscle resulting in vasodilation. This discovery has helped pave the way for a more thorough understanding of vascular intercellular and intracellular communication that supports the process of regulating regional perfusion to match the local tissue oxygen demand. Vasoregulation is controlled not only by endothelial release of a diverse class of vasoactive compounds such as nitric oxide, arachidonic acid metabolites, and reactive oxygen species, but also by physical forces on the vascular wall and through electrotonic conduction through gap junctions. Although the endothelium is a critical source of vasoactive compounds, paracrine mediators can also be released from surrounding parenchyma such as perivascular fat, myocardium, and cells in the arterial adventitia to exert either local or remote vasomotor effects. The focus of this review will highlight the various means by which intercellular communication contributes to mechanisms of vasodilation. Paracrine signaling and parenchymal influences will be reviewed as well as regional vessel communication through gap junctions, connexons, and myoendothelial feedback. More recent modes of communication such as vesicular and microRNA signaling will also be discussed.

Inverse Association of Circulating SIRT1 and Adiposity: A Study on Underweight, Normal Weight, and Obese Patients

Context: Sirtuins (SIRTs) are NAD+-dependent deacetylases, cellular sensors to detect energy availability, and modulate metabolic processes. SIRT1, the most studied family member, influences a number of tissues including adipose tissue. Expression and activity of SIRT1 reduce with weight gain and increase in conditions of starvation. Objective: To focus on SIRT1 plasma concentrations in different conditions of adiposity and to correlate SIRT1 with fat content and distribution, energy homeostasis and inflammation in under-weight, normal-weight, and obese individuals. Materials and Methods: 21 patients with anorexia nervosa, 26 normal-weight and 75 patients with obesity were evaluated. Body fat composition by dual-energy X-ray absorptiometry, ultrasound liver adiposity, echocardiographic epicardial fat thickness (EFT), inflammatory (ESR, CRP, and fibrinogen), and metabolic (FPG, insulin, LDL- and HDL-cholesterol, triglycerides) parameters, calculated basal metabolic rate (BMR) and plasma SIRT1 (ELISA) were measured. Results: SIRT1 was significantly higher in anorexic patients compared to normal-weight and obese patients (3.27 ± 2.98, 2.27 ± 1.13, and 1.36 ± 1.31 ng/ml, respectively). Linear regression models for each predictor variable adjusted for age and sex showed that SIRT1 concentration was inversely and significantly correlated with EFT, fat mass %, liver fat content, BMR, weight, BMI, WC, LDL-cholesterol, insulin, ESR. Stepwise multiple regression analysis revealed that age and EFT were the best independent correlates of SIRT1 (β = -0.026 ± 0.011, p = 0.025, and β = -0.516 ± 0.083, p < 0.001, respectively). Conclusions: Plasma SIRT1 shows a continuous pattern that inversely follows the whole spectrum of adiposity. SIRT1 significantly associates with EFT, a strong index of visceral fat phenotype, better than other indexes of adiposity studied here.

Adipokines at the crossroad between obesity and cardiovascular disease

Obesity, and especially excessive visceral adipose tissue accumulation, is considered as a low-grade inflammatory state that is responsible for adipocyte dysfunction and associated metabolic disorders. Adipose tissue displays endocrine functions by releasing pro- or antiinflammatory bioactive molecules named adipokines. An altered expression of these molecules, provoked by obesity or adipocyte dysregulation, contributes to major metabolic diseases such as insulin resistance and type 2 diabetes mellitus that are important risk factors for cardiovascular disease. However, obesity is also characterised by the expansion of perivascular adipose tissue that acts locally via diffusion of adipokines into the vascular wall. Local inflammation within blood vessels induced by adipokines contributes to the onset of endothelial dysfunction, atherosclerosis and thrombosis, but also to vascular remodelling and hypertension. A fast expansion of obesity is expected in the near future, which will rapidly increase the incidence of these cardiovascular diseases. The focus of this review is to summarise the link between metabolic and cardiovascular disease and discuss current treatment approaches, limitations and future perspectives for more targeted therapies.

Functional characterization of the Ucp1-associated oxidative phenotype of human epicardial adipose tissue

Brown fat presence and metabolic activity has been associated with lower body mass index, higher insulin sensitivity and better cardiometabolic profile in humans. We, and others, have previously reported the presence of Ucp1, a marker of brown adipocytes, in human epicardial adipose tissue (eAT). Characterization of the metabolic activity and associated physiological relevance of Ucp1 within eAT, however, is still awaited. Here, we validate the presence of Ucp1 within human eAT and its ‘beige’ nature. Using in-vitro analytical approaches, we further characterize its thermogenic potential and demonstrate that human eAT is capable of undergoing enhanced uncoupling respiration upon stimulation. Direct biopsy gene expression analysis reveals a negative association between thermogenic markers and oxidative stress-related genes in this depot. Consistently, isoproterenol (Iso) stimulation of eAT leads to a downregulation of secreted proteins included in the GO terms ‘cell redox homeostasis’ and ‘protein folding’. In addition, cardiac endothelial cells exhibit a downregulation in the expression of adhesion markers upon treatment with Iso-stimulated eAT derived conditioned media. Overall, these observations suggest that Ucp1- associated metabolic activity plays a significant role in local tissue homeostasis within eAT and can plausibly alter its communication with neighboring cells of the cardiovascular system.

Investigating interactions between epicardial adipose tissue and cardiac myocytes: what can we learn from different approaches?

Heart disease is a major cause of morbidity and mortality throughout the world. Some cardiovascular conditions can be modulated by lifestyle factors such as increased exercise or a healthier diet, but many require surgical or pharmacological interventions for their management. More targeted and less invasive therapies would be beneficial. Recently, it has become apparent that epicardial adipose tissue plays an important role in normal and pathological cardiac function, and it is now the focus of considerable research. Epicardial adipose tissue can be studied by imaging of various kinds, and these approaches have yielded much useful information. However, at a molecular level, it is more difficult to study as it is relatively scarce in animal models and, for practical and ethical reasons, not always available in sufficient quantities from patients. What is needed is a robust model system in which the interactions between epicardial adipocytes and cardiac myocytes can be studied, and physiologically relevant manipulations performed. There are drawbacks to conventional culture methods, not least the difficulty of culturing both cardiac myocytes and adipocytes, each of which has special requirements. We discuss the benefits of a three-dimensional co-culture model in which in vivo interactions can be replicated.

LINKED ARTICLES

This article is part of a themed section on Molecular Mechanisms Regulating Perivascular Adipose Tissue - Potential Pharmacological Targets? To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.20/issuetoc.

Evolutional change in epicardial fat and its correlation with myocardial diffuse fibrosis in heart failure patients

OBJECTIVES

The aim of this study was to characterize the characteristics of epicardial fat (EAT) in different stage heart failure (HF) patients and its relationship between cardiac fibrosis.

BACKGROUND

EAT is visceral adipose tissue that possesses inflammatory properties. Inflammation and obesity are associated with cardiac fibrosis, but the relationship between cardiac fibrosis and EAT is unknown.

METHODS

EAT volume was measured using cardiac magnetic resonance imaging (CMR) in 180 subjects: 58 patients with systolic HF, 63 patients with HF and preserved ejection fraction, and 59 patients without HF. CMR derived myocardial extracellular volume (ECV) was used for fibrosis quantification.

RESULTS

Patients with systolic HF had significantly more EAT compared with patients with HF and preserved ejection fraction or the control group (patients without HF) (indexed EAT volume [mL/m²], 27.0 [22.7-31.6] vs 25.6 [21.4-31.2] and 24.2 [21.0-27.6], P < .05). The adjusted EAT amount was associated with ECV completely independent of age, hypertension, diabetes, etiology of HF, left ventricular ejection fraction, CMR-late gadolinium enhancement (LGE), left ventricular mass index, and left ventricular end-diastolic volume index (correlation coefficient: 0.49; 95% confidence interval: 0.12-0.86, P < .01). Increased CMR ECV was more associated with EAT in those with advanced age, male sex, LGE on magnetic resonance imaging-LGE images, and less left ventricular end-diastolic volume index.

CONCLUSIONS

EAT volume is highly associated with CMR ECV independent of traditional risk factors and left ventricular mass or volume. Whether EAT plays a role in the long-term prognosis of HF requires future investigation.

Intrathoracic Fat Measurements Using Multidetector Computed Tomography (MDCT): Feasibility and Reproducibility

Intrathoracic fat volume, more specifically, epicardial fat volume, is an emerging imaging biomarker of adverse cardiovascular events. The purpose of this work is to show the feasibility and reproducibility of intrathoracic fat volume measurement applied to contrast-enhanced multidetector computed tomography images. A retrospective cohort study of 62 subjects free of cardiovascular disease (55% females, age = 49 ± 11 years) conducted from 2008 to 2011 formed the study group. Intrathoracic fat volume was defined as all fat voxels measuring −50 to −250 Hounsfield Unit within the intrathoracic cavity from the level of the pulmonary artery bifurcation to the heart apex. The intrathoracic fat was separated into epicardial and extrapericardial fat by tracing the pericardium. The measurements were obtained by 2 readers and compared for interrater reproducibility. The fat volume measurements for the study group were 141 ± 72 cm³ for intrathoracic fat, 58 ± 27 cm³ for epicardial fat, and 84 ± 50 cm³ for extrapericardial fat. There was no statistically significant difference in intrathoracic fat volume measurements between the 2 readers, with correlation coefficients of 0.88 (P = .55) for intrathoracic fat volume and −0.12 (P = .33) for epicardial fat volume. Voxel-based measurement of intrathoracic fat, including the separation into epicardial and extrapericardial fat, is feasible and highly reproducible from multidetector computed tomography scans.

Novel atherogenic pathways from the differential transcriptome analysis of diabetic epicardial adipose tissue

BACKGROUND AND AIM

To evaluate the epicardial adipose tissue (EAT) transcriptome in comparison to subcutaneous fat (SAT) in coronary artery disease (CAD) and type 2 diabetes (T2DM).

METHODS AND RESULTS

SAT and EAT samples were obtained from subjects with T2DM and CAD (n = 5) and those without CAD with or without T2DM (=3) undergoing elective cardiac surgery. RNA-sequencing analysis was performed in both EAT and SAT. Gene enrichment analysis was conducted to identify pathways affected by the differentially expressed genes. Changes of top genes were verified by quantitative RT-PCR (qRT-PCR), western blot, and immunofluorescence. A total of 592 genes were differentially expressed in diabetic EAT, whereas there was no obvious changes in SAT transcriptome between diabetics and non-diabetics. Diabetic EAT was mainly enriched in inflammatory genes, such as Colony Stimulating Factor 3 (CSF3), Interleukin-1b (IL-1b), IL-6. KEGG pathway analysis confirmed that upregulated genes were involved in inflammatory pathways, such as Tumor Necrosis Factor (TNF), Nuclear Factor-κB (NF-κB) and advanced glycation end-products-receptor advanced glycation end products (AGE-RAGE). The overexpression of inflammatory genes in diabetic EAT was largely correlated with upregulated transcription factors such as NF-κB and FOS.

CONCLUSIONS

Diabetic EAT transcriptome is significantly different when compared to diabetic SAT and highly enriched with genes involved in innate immune response and endothelium, like Pentraxin3 (PTX3) and Endothelial lipase G (LIPG). EAT inflammatory genes expression could be induced by upregulated transcription factors, mainly NF-kB and FOSL, primarily activated by the overexpressed AGE-RAGE signaling. This suggests a unique and novel atherogenic pathway in diabetes.

Maximal pericoronary adipose tissue thickness is associated with hypertension in nonobese patients with acute or chronic illness

BACKGROUND/AIMS

Recent studies have shown an association of epicardial fat thickness with diabetes and hypertension (HTN) in asymptomatic populations. However, there is lack of information as to whether there is similar association between pericoronary adipose tissue (PAT) and HTN in the patients who have acute or chronic illness.

METHODS

This study included 214 nonobese patients hospitalized with acute or chronic noncardiogenic illness. PAT thicknesses were measured from fat tissues surrounding left and right coronary arteries in enhanced, chest computed tomography scans, yielding the maximal PAT value from left and right coronary arteries was used for analysis. Baseline data from hypertensive (n = 81) and normotensive (n = 133) patients were collected and compared.

RESULTS

PAT is positively correlated with age (r = 0.377, p <0.001), body mass index (BMI; r = 0.305, p < 0.001), systolic blood pressure (r = 0.216, p = 0.001), and total cholesterol (r = 0.200, p = 0.006). The hypertensive group was older (69.58 ± 11.69 years vs. 60.29 ± 14.98 years), and had higher PAT content (16.30 ± 5.37 mm vs. 13.06 ± 5.58 mm) and BMI (23.14 ± 3.32 kg/m² vs. 20.96 ± 3.28 kg/m) than the normotensive group (all p < 0.001). Multivariate analysis showed that age (odds ratio [OR], 2.193; p = 0.016), PAT thickness (OR, 1.065; p = 0.041), and BMI (25 ≤ BMI < 30 kg/m² ; OR, 6.077; p = 0.001) were independent risk factors for HTN.

CONCLUSIONS

In nonobese patients with noncardiogenic acute or chronic illness, PAT thickness is independently correlated with HTN, age, and BMI.

The ratio of pericardial to subcutaneous adipose tissues is associated with insulin resistance

OBJECTIVE

To examine the association between pericardial adipose tissue (PAT) and the ratio of PAT to subcutaneous adipose tissue (SAT) with insulin resistance in adults with and without type 1 diabetes (T1D).

METHODS

Data for this report came from a substudy of the Coronary Artery Calcification in Type 1 Diabetes cohort (n = 83; 38 with T1D, 45 without T1D). Insulin resistance was measured by hyperinsulinemic-euglycemic clamp. Abdominal computed tomography (CT) was used to measure visceral adipose tissue (VAT) and SAT. PAT was measured from CT scans of the heart.

RESULTS

PAT and the ratio of PAT to SAT was higher in males compared to females. After adjustment for demographics, diabetes, blood pressure and lipid factors, BMI, VAT, and log PAT/SAT ratio, log PAT was positively associated with the glucose infusion rate (GIR) in females only (β = 3.36 ± 1.96, P = 0.097, P for sex interaction = 0.055). Conversely, the log PAT/SAT ratio was significantly associated with decreased GIR in both males and females (β = -2.08 ± 1.03, P = 0.047, P for sex interaction = 0.768).

CONCLUSIONS

A significant association between the PAT/SAT ratio and insulin resistance was found, independent of BMI, VAT, and PAT. These results highlight the importance of considering fat distribution independent of volume.