Assessing genetic and environmental influences on epicardial and abdominal adipose tissue quantities: a classical twin study

The predictive value of epicardial adipose tissue volume assessed by cardiac magnetic resonance for atrial fibrillation in patients with hypertrophic obstructive cardiomyopathy

Atrial fibrillation (AF) is the most common arrhythmia and potentially increase the risk of embolic stroke and aggravate progressive heart failure in patients with hypertrophic cardiomyopathy (HCM). Recent studies demonstrated that epicardial adipose tissue (EAT) was closely associated with AF in general population. However, the relationship between EAT and AF in HCM patients remains unclear. A total of 93 consecutive patients with hypertrophic obstructive cardiomyopathy (HOCM) at Fuwai Hospital were enrolled in our study. There were 18 patients with AF and 75 patients without it. Cardiac magnetic resonance (CMR) imaging was performed in all participants. EAT volume (EATV) and left atrial volume (LAV) were determined by E-3D medical model software. HOCM patients with AF had significantly greater EATV index (EATVI, P < 0.001), LAV index (LAVI, P < 0.001) and left ventricular end-systole volume index (LVESVI, P = 0.039), and lower left ventricular ejection fraction (LVEF, P = 0.002). In multivariable logistic regression analysis, EATVI, LAVI, and LVEF remained independent determinants of AF occurrence (OR = 1.023, 95% CI, 1.003-1.043, P = 0.023, OR = 1.043, 95% CI, 1.012-1.075, P = 0.006, and OR = 0.887, 95% CI, 0.818-0.962, P = 0.004, respectively). Furthermore, receiver operating characteristic (ROC) curve analysis demonstrated that integration of EATVI, LAVI and LVEF provided better discriminatory performance for incident AF in HOCM patients with a high sensitivity of 94.4% and a specificity of 69.3% (AUC = 0.864, 95% CI, 0.771-0.958, P < 0.001). EATVI is an independent predictor of the presence of AF, and integration of EATVI, LVEF and LAVI determined by CMR provide greater discriminatory performance for identifying AF in HOCM patients.

Environmental Factors Slightly Outweigh Genetic Influences in the Development of Pancreatic Lipid Accumulation: A Classical Twin Study

Background: Several studies showed that lipid accumulation in the pancreas (NAFPD: nonalcoholic fatty pancreas disease) may lead to different pancreatic disorders, including beta-cell dysfunction. The role of genetic and environmental factors in pancreatic lipid accumulation is unclear. We evaluated the magnitude of genetic and environmental impact on pancreatic lipid content within a cohort of adult twin pairs. Patients and Methods: We investigated 136 twin subjects [monozygotic (MZ, n = 86) and dizygotic (DZ, n = 50) same-gender twins (age 57.7 ± 9.1 years; body mass index [BMI] 28.0 ± 4.4 kg/m²; females 64.7%)] with a 256-slice computed tomography (CT)-scanner. Using nonenhanced CT images, we calculated the average value of pancreatic attenuation expressed in Hounsfield unit (HU) suggesting pancreatic lipid content. Crude data were adjusted to age, sex, BMI, and hemoglobinA1c values. Intrapair correlations were established, and structural equation models were used for quantifying the contribution of additive genetic (A), common environmental (C), and unique environmental (E) components to the investigated phenotype. Results: The study cohort represented a moderately overweight, middle-aged Caucasian population. Average pancreatic attenuation was 48.9 ± 11.9 HU in MZ and 49.0 ± 13.0 HU in DZ twins (P = 0.934). The intrapair correlation between HU values was stronger in MZ compared to DZ twins (rMZ = 0.536, P < 0.001; rDZ = 0.115, P = 0.580). Using the structural equation model, a greater unique environmental influence [E: 54%, 95% confidence interval (CI) 19%-66%] and a moderate additive genetic dependence (A: 46%, 95% CI 34%-81%) were found. Conclusions: The results of our classical twin study indicate that environmental (lifestyle) influences slightly outweigh genetic effects on the phenotypic appearance of pancreatic lipid accumulation known as NAFPD.

Relationship of para- and perirenal fat and epicardial fat with metabolic parameters in overweight and obese subjects

BACKGROUND

The accumulation of visceral body fat, has been shown to be associated with higher risk of metabolic and cardiovascular disease. This study was addressed to examine whether para- and perirenal fat thickness and epicardial fat thickness were correlated with anthropometric- and cardiometabolic risk factors.

METHODS

A cohort of 102 uncomplicated overweight and obese patients was examined. BMI, waist circumference, blood pressure, fasting insulin, glucose, triglycerides, total cholesterol, HDL-cholesterol, LDL-cholesterol serum levels, and insulin resistance (assessed by HOMA_IR) were measured. Para- and perirenal fat thickness (PUFT) and epicardial fat thickness (EUFT) were measured by ultrasounds.

RESULTS

PUFT was positively correlated with BMI (p < 0.001), waist circumference (p < 0.001), insulin (p < 0.001), HOMA_IR (p < 0.001), triglycerides (p < 0.05), systolic (p < 0.05) and diastolic (p < 0.05) blood pressure, and negatively correlated with HDL-cholesterol (p < 0.01). EUFT was positively associated with age (p < 0.01), BMI (p < 0.001), waist circumference (p < 0.001), systolic (p < 0.01) and diastolic (p < 0.001) blood pressure, and LDL-cholesterol (p < 0.05). A multivariate analysis by multiple linear regression was performed, and the final model showed a direct association of waist circumference with both PUFT and EUFT, a correlation of PUFT with HOMA_IR (positive) and HDL-cholesterol (negative), and a direct association of EUFT (both long axis and short axis) with LDL-cholesterol. All these correlations were independent of other anthropometric, metabolic and hemodynamic parameters.

CONCLUSIONS

This study shows that accumulation of central fat in apparently healthy overweight and obese subjects is associated to a simultaneous increase of pararenal, perirenal and epicardial fat. Moreover, it shows that only para- and perirenal fat is independently associated to insulin resistance and lower HDL-cholesterol, and only epicardial fat is independently associated to higher LDL cholesterol. Level of evidence Level V, cross-sectional descriptive study.

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: new parameter for cardiovascular risk assessment in high risk populations

Epicardial adipose tissue (EAT) is localized between the myocardial surface and visceral layer of the pericardium. It is a metabolically active organ that secretes several cytokines which modulate cardiovascular morphology and function. EAT may interact locally with coronary arteries through paracrine secretion mechanisms. Cytokines from peri-adventitial EAT may pass through the coronary wall by diffusion from the outside to the inside, interacting with cells. An additional potential mechanism by which EAT interacts locally with coronary arteries may be the vasocrine secretion.EAT may play a significant role as a modulator of cardiac functions. In physiologic conditions, EAT has biochemical cardio-protective properties, secreting anti-atherosclerosis substances; in metabolic disease states, EAT secretes bioactive molecules that may play an important role in the pathogenesis of coronary artery disease and cardiac arrhythmias by promoting atherosclerosis. EAT has been evaluated both in the general population and in metabolic disease states that are characterized by inflammation, such as cardiovascular diseases and chronic kidney disease.This review focuses on the current state of knowledge on EAT as a reliable new parameter for cardiovascular risk stratification in high risk populations.