Brown vs white adipose tissue roles of pericardial fat
Brown vs white adipose tissue roles of pericardial fat: In healthy persons, epicardial fat behaves like brown adipose tissue and utilises fatty acids, preventing local proinflammatory action and providing nutrition to adjacent tissue. on the other hand, in obesity it functions like white adipose tissue which causes lipolysis and release of fatty acids which are proinflammatory . In mouse models, it has been shown that thoracic perivascular adipose tissue is resistant to diet induced macrophage infiltration and may protect the vascular bed from inflammatory stress .
In addition, epicardium is an important source of mesenchymal stem cells which may contribute to cardiac regeneration. When the oxidative stress is low, epicardial adipocytes secrete adiponectin which minimizes cardiomyocyte hypertrophy and inflammation and fibrosis in coronary arteries and myocardium, reducing the chance of adverse events .
Local and systemic concentrations of adiponectin has been inversely correlated to the presence of coronary artery disease . This suggests and anti atherogenic effect for adiponectin. This study was conducted using serum and adipose tissue samples collected from pericoronary depots in patients undergoing coronary artery bypass grafting and patients without coronary artery disease undergoing aortic valve replacement .
Adipokine synthesis pattern of epicardial also changes in obesity and dyslipidemia. Adiponectin synthesis comes down and proinflammatory adipokines like leptin, tumour necrosis factor alpha, interleukin 1 beta, interleukin 6 and resistin gets synthesised. These are proinflammatory, causing macrophage infiltration, destruction of microvasculature and increase in fibrosis . In one study, abdominal and epicardial fat tissue samples were obtained from those with coronary artery disease undergoing coronary artery bypass grafting and from those without coronary artery disease undergoing other types of open heart surgery. Tissue levels of tumor necrosis factor-alpha, interleukin-6 and leptin were significantly higher in those with coronary artery disease .
Packer M. Epicardial Adipose Tissue May Mediate Deleterious Effects of Obesity and Inflammation on the Myocardium. J Am Coll Cardiol. 2018 May 22;71(20):2360-2372.