Echocardiographic determination of epicardial adipose tissue in healthy bonnet macaques

Background: Nonhuman primates have served as models for human cardiovascular (CV) and metabolic diseases. Recently, echocardiographic measurement of epicardial adipose tissue (EAT) thickness has been shown to be a reliable marker of visceral adiposity, and greater EAT is associated with increased CV risk, left ventricular (LV) hypertrophy, and metabolic syndrome. The objective of the present study was to determine EAT thickness in apparently healthy bonnet macaques and assess its relations with anthropometric and CV variables. Methods: Echocardiography was performed on 61 monkeys (41 females and 20 males, mean age 13.0 ± 4.7 years). EAT was measured on the right ventricular free wall in parasternal windows. Applanation tonometry was performed in 25 unselected monkeys using a SphygmoCor pulse wave system. Results: The mean EAT thickness was 2.4 ± 0.6 mm. EAT thickness was directly correlated with age (r = 0.26, P = 0.04), male gender (r = 0.47, P < 0.01), weight (r = 0.42, P < 0.01), crown-rump length (r = 0.45, P < 0.01), BMI (r = 0.38, P < 0.01), diastolic BP (r = 0.46, P = 0.01), and HR (r = -0.49, P < 0.01). EAT thickness also correlated with augmentation index (r = 0.42, P = 0.04), LV mass (r = 0.48, P < 0.01), and left atrial (LA) diameter (r = 0.26, P = 0.04). Intra- and interobserver coefficients of variation between measurements of EAT were 1.4% and 3.7%. On multivariate analysis adjusting for age, gender, weight, and CRL, EAT was independently related to age and weight (r² = 0.47, P < 0.01). Conclusion: This study found echocardiography to be a feasible and practical method to evaluate EAT in nonhuman primates. In bonnet macaques, EAT thickness correlates with LV and LA dimensions and augmentation index, and is independently related to age and weight.