Epicardial adipose tissue is associated with cardiorespiratory fitness and hemodynamics among Japanese individuals of various ages and of both sexes

Epicardial adipose tissue may affect hemodynamics and cardiorespiratory fitness as it is a metabolically active visceral adipose tissue and a source of inflammatory bioactive substances that can substantially modulate cardiovascular morphology and function. However, the associations between epicardial adipose tissue and hemodynamics and cardiorespiratory fitness remain unclear. This cross-sectional study aimed to examine the association between epicardial adipose tissue volume and hemodynamics, and cardiorespiratory fitness among Japanese individuals of various ages and of both sexes. Epicardial adipose tissue volume was measured in 120 participants (age, 21-85 years) by cardiac magnetic resonance imaging. To evaluate cardiorespiratory fitness, peak oxygen uptake was measured by cardiopulmonary exercise testing. Peak cardiac output and arteriovenous oxygen difference were calculated by impedance cardiography. The epicardial adipose tissue volume was significantly increased in middle-aged and older women. The epicardial adipose tissue volume was significantly and negatively correlated to peak cardiac output and peak oxygen uptake, regardless of age and sex; furthermore, epicardial adipose tissue showed a strong negative correlation with peak heart rate. Epicardial adipose tissue and peak cardiac output were significantly associated (β = -0.359, 95% confidence interval, -0.119 to -0.049, p < 0.001), even after multivariate adjustment (R2 = 0.778). However, in the multiple regression analysis with peak oxygen uptake as a dependent variable, the epicardial adipose tissue volume was not an independent predictor. These data suggest that increased epicardial adipose tissue volume may be correlated with decreased peak oxygen uptake, which might have mediated the abnormal hemodynamics among Japanese people of various ages and of both sexes. Interventions targeting epicardial adipose tissue could potentially improve hemodynamics and cardiorespiratory fitness.

Role of Epicardial Adipose Tissue in Health and Disease: A Matter of Fat?

Epicardial adipose tissue (EAT) is a small but very biologically active ectopic fat depot that surrounds the heart. Given its rapid metabolism, thermogenic capacity, unique transcriptome, secretory profile, and simply measurability, epicardial fat has drawn increasing attention among researchers attempting to elucidate its putative role in health and cardiovascular diseases. The cellular crosstalk between epicardial adipocytes and cells of the vascular wall or myocytes is high and suggests a local role for this tissue. The balance between protective and proinflammatory/profibrotic cytokines, chemokines, and adipokines released by EAT seem to be a key element in atherogenesis and could represent a future therapeutic target. EAT amount has been found to predict clinical coronary outcomes. EAT can also modulate cardiac structure and function. Its amount has been associated with atrial fibrillation, coronary artery disease, and sleep apnea syndrome. Conversely, a beiging fat profile of EAT has been identified. In this review, we describe the current state of knowledge regarding the anatomy, physiology and pathophysiological role of EAT, and the factors more globally leading to ectopic fat development. We will also highlight the most recent findings on the origin of this ectopic tissue, and its association with cardiac diseases. © 2017 American Physiological Society. Compr Physiol 7:1051-1082, 2017.

Impact of obesity and epicardial fat on early left atrial dysfunction assessed by cardiac MRI strain analysis

BACKGROUND

Diastolic dysfunction is a major cause of morbidity in obese individuals. We aimed to assess the ability of magnetic resonance imaging (MRI) derived left atrial (LA) strain to detect early diastolic dysfunction in individuals with obesity and type 2 diabetes, and to explore the association between cardiac adipose tissue and LA function.

METHODS

Twenty patients with obesity and T2D (55 ± 8 years) and nineteen healthy controls (48 ± 13 years) were imaged using cine steady state free precession and 2-point Dixon cardiovascular magnetic resonance. LA function was quantified using a feature tracking technique with definition of phasic longitudinal strain and strain rates, as well as radial motion fraction and radial velocities.

RESULTS

Systolic left ventricular size and function were similar between the obesity and type 2 diabetes and control groups by MRI. All patients except four had normal diastolic assessment by echocardiography. In contrast, measures of LA function using magnetic resonance feature tracking were uniformly altered in the obesity and type 2 diabetes group only. Although there was no significant difference in intra-myocardial fat fraction, Dixon 3D epicardial fat volume(EFV) was significantly elevated in the obesity and type 2 diabetes versus control group (135 ± 31 vs. 90 ± 30 mL/m², p < 0.001). There were significant correlations between LA functional indices and both BMI and EFV (p ≤ 0.007).

CONCLUSIONS

LA MRI-strain may be a sensitive tool for the detection of early diastolic dysfunction in individuals with obesity and type 2 diabetes and correlated with BMI and epicardial fat supporting a possible association between adiposity and LA strain. Trials Registration Australian New Zealand Clinical Trials Registry No. ACTRN12613001069741.

Left Ventricular Hypertrophy and Asymptomatic Cardiac Function Impairment in Chinese Patients with Simple Obesity using Echocardiography

BACKGROUND

Simple obesity in China is rising rapidly and causing increasing concern. The objectives of our study are to investigate cardiac structure and function in individuals with simple obesity and to analyze the effect of BMI on left ventricular structure and function.

METHODS

Between January 2012 and July 2014, echocardiography was performed in 361 consecutive patients visiting the outpatient echocardiography center for a health examination or cardiac evaluation before a weight loss operation in our hospital. Echocardiographic indices, waist-to-hip ratios, BMI, and metabolic markers were evaluated. We analyzed these data using Student's t test (normally distributed) or a nonparametric test (not normally distributed) for continuous variables and chi-square test for categorical variables. Multivariate correlation and regression analysis were conducted for comparisons.

RESULTS

The study sample was divided into three groups: a normal/overweight group (BMI < 28.0 kg/m(2)), a mildly/moderately obese group (BMI 28-39.9 kg/m(2)), and a severely obese group (BMI ≥ 40 kg/m(2)). There were no significant differences in clinical and laboratory characteristics among the groups, except for BMI and waist-to-hip ratio. The severely obese group had a higher left ventricular end diastolic diameter (LVEDD; p < 0.01) and lower left ventricular ejection fraction (LVEF; p < 0.01) than the mildly/moderately obese group, which had a higher LVEDD and LV mass index (LVMI) than the normal/overweight group. BMI correlated well with LVEDD, left ventricular posterior wall thickness at end-diastole (LVPW), LV mass, LVMI, and E/e'. In addition, age was significantly associated with some echocardiographic parameters, including left atrial dimension (r = 0.366, p < 0.01), LVPW (r = 0.347, p < 0.01), interventricular septal thickness at end- diastole (r = 0.351, p< 0.01), and E/A (r = -0.47, p < 0.01).

CONCLUSIONS

Simple obesity caused cardiac structural changes, including LV hypertrophy and LV enlargement, and severe obesity resulted in asymptomatic LV systolic and diastolic function impairment.

The relationship between epicardial fat and indices of obesity and the metabolic syndrome: a systematic review and meta-analysis

Epicardial fat (epicardial adipose tissue, EAT) has been implicated in the pathogenesis of coronary artery disease (CAD). The objective of this study was to examine the relationship between EAT and generalized obesity, central or visceral adipose tissue (VAT), and the components of the metabolic syndrome--systolic blood pressure (SBP), triglycerides (TGs), high-density lipoprotein cholesterol (HDL-C), and fasting blood glucose (FBG)--that are linked to CAD. A systematic review of the literature, following meta-analysis guidelines, was conducted until May, 2013, using the search strategy "Obesity" OR "abdominal obesity" OR "metabolic syndrome" OR "metabolic syndrome X" AND "epicardial fat". Thirty-eight studies fulfilled the criteria. There was a highly significant (P<0.00001) correlation between EAT and body mass index (BMI), waist circumference (WC), or VAT. The correlation between EAT and VAT was significantly (P<0.0001) greater than the correlation between EAT and WC, which in turn was significantly greater than the correlation between EAT and BMI. Overall, EAT was 7.5 ± 0.1 mm in thickness in the metabolic syndrome (n=427) compared to 4.0 ± 0.1 mm in controls (n=301). EAT correlated significantly (P<0.0001) with SBP, TGs, HDL, and FBG, but the strength of the association was less than one-half of the relationship of EAT to indices of obesity. The results of multivariate analysis were less consistent but show a relationship between EAT and metabolic syndrome independent of BMI. In summary, the very strong correlation between EAT and VAT suggests a relationship between these two adipose tissue depots. Measurement of EAT can be useful to indicate VAT. Whereas EAT correlates significantly with each of the components of the metabolic syndrome- SBP, TGs, HDL, or FBG-the magnitude of the relationship is considerably and significantly less than the relationship of EAT to BMI. These data show the strong relationship between EAT and BMI but especially with WC and VAT. They also demonstrate the smaller magnitude of the association of EAT with standard coronary risk factors, related to the metabolic syndrome, and suggest that the unique features of this adipose tissue warrant detailed investigation.