Perivascular adipose tissue as a cause of atherosclerosis.

Perivascular adipose tissue surrounds (coronary) arteries and may be involved in local stimulation of atherosclerotic plaque formation. Epicardial adipose tissue, the adipose tissue within the pericardium, is a frequently used measure of coronary perivascular adipose tissue and can be quantified with echocardiography, computed tomography (CT) and magnetic resonance imaging (MRI). The quantity of (coronary) perivascular adipose tissue is correlated with parameters of the metabolic syndrome, such as increased waist circumference, hypertriglyceridemia and hyperglycemia, and with coronary atherosclerosis. Coronary artery segments covered by myocardium are not exposed to coronary perivascular adipose tissue and interestingly, atherosclerosis is absent in these intra-myocardial segments. Pro-inflammatory cytokines and adipokines are expressed and secreted at a higher level in epicardial adipose tissue of patients with coronary artery disease compared to patients without coronary artery disease. Furthermore, in vitro and ex vivo perivascular adipose tissue induces inflammation of the artery wall by secretion of pro-inflammatory proteins. Atherogenesis in the vascular wall is thus stimulated from 'outside to inside'. Based on the results of clinical, ex vivo and in vitro studies, it can be argued that perivascular adipose tissue may be involved in the process of atherosclerosis.