Physiology and Cardioprotection of the Epicardial Adipose Tissue

Epicardial adipose tissue (EAT) is a peculiar visceral fat depot with both protective and detrimental properties. The physiological role of EAT within the heart is complex and not completely understood. EAT functions can be distinguished in (1) nutritional, (2) metabolic, (3) thermogenic, (4) regulatory, and (5) mechanical. Under normal physiological EAT serves as a buffer, absorbing fatty acids and protecting the heart against high fatty acids levels and as pad protecting abnormal curvature of the coronary arteries. EAT is enriched in genes coding for cardioprotective adipokines such as adiponectin and adrenomedullin, both with potential anti-inflammatory and anti-atherogenic properties. EAT could also function as local energy source at times of high demand, channeling fatty acids to the myocardium and as brown fat to defend the myocardium against hypothermia. EAT expresses genes and secretes cytokines actively involved in the thermogenesis and regulation of lipid and glucose metabolism of the adjacent myocardium. EAT may adapt itself to different metabolic circumstances and function as brown-like or beige fat depot as needed

Epicardial adipose tissue in endocrine and metabolic diseases

Epicardial adipose tissue has recently emerged as new risk factor and active player in metabolic and cardiovascular diseases. Albeit its physiological and pathological roles are not completely understood, a body of evidence indicates that epicardial adipose tissue is a fat depot with peculiar and unique features. Epicardial fat is able to synthesize, produce, and secrete bioactive molecules which are then transported into the adjacent myocardium through vasocrine and/or paracrine pathways. Based on these evidences, epicardial adipose tissue can be considered an endocrine organ. Epicardial fat is also thought to provide direct heating to the myocardium and protect the heart during unfavorable hemodynamic conditions, such as ischemia or hypoxia. Epicardial fat has been suggested to play an independent role in the development and progression of obesity- and diabetes-related cardiac abnormalities. Clinically, the thickness of epicardial fat can be easily and accurately measured. Epicardial fat thickness can serve as marker of visceral adiposity and visceral fat changes during weight loss interventions and treatments with drugs targeting the fat. The potential of modulating the epicardial fat with targeted pharmacological agents can open new avenues in the pharmacotherapy of endocrine and metabolic diseases. This review article will provide Endocrine's reader with a focus on epicardial adipose tissue in endocrinology. Novel, established, but also speculative findings on epicardial fat will be discussed from the unexplored perspective of both clinical and basic Endocrinologist

Local and systemic effects of the multifaceted epicardial adipose tissue depot

Epicardial adipose tissue is a unique and multifaceted fat depot with local and systemic effects. This tissue is distinguished from other visceral fat depots by a number of anatomical and metabolic features, such as increased fatty acid metabolism and a unique transcriptome enriched in genes that are associated with inflammation and endothelial function. Epicardial fat and the heart share an unobstructed microcirculation, which suggests these tissues might interact. Under normal physiological conditions, epicardial fat has metabolic, thermogenic (similar to brown fat) and mechanical (cardioprotective) characteristics. Development of pathological conditions might drive the phenotype of epicardial fat such that it becomes harmful to the myocardium and the coronary arteries. The equilibrium between protective and detrimental effects of this tissue is fragile. Expression of the epicardial-fat-specific transcriptome is downregulated in the presence of severe and advanced coronary artery disease. Improved local vascularization, weight loss and targeted medications can restore the protective physiological functions of epicardial fat. Measurements of epicardial fat have several important applications in the clinical setting: accurate measurement of its thickness or volume is correlated with visceral adiposity, coronary artery disease, the metabolic syndrome, fatty liver disease and cardiac changes. On account of this simple clinical assessment, epicardial fat is a reliable marker of cardiovascular risk and an appealing surrogate for assessing the efficacy of drugs that modulate adipose tissues