Adipoparacrinology – vascular periadventitial adipose tissue (tunica adiposa) as an example

Abstract

Human adipose tissue is partitioned into two large depots (subcutaneous and visceral), and many small depots associated with internal organs, e.g. heart, blood vessels, major lymph nodes, pancreas, prostate gland and ovaries. Since the adipose 'Big Bang' led to the discovery of leptin (Zhang, Proenca, Maffei, Barone, Leopold and Friedman, Nature 1994;372:425-32), adipose tissue has been seen not merely as a lipid store, but as a secretory - endocrine and paracrine - organ, particularly in the pathogenesis of a number of diseases. Accordingly, two major sub-fields of adipobiology have emerged, viz. adipoendocrinology and adipoparacrinology, the latter herein being illustrated by PAAT (periadventitial adipose tissue) in vascular walls. A long-standing paradigm holds that the vascular wall consists of three coats, tunica intima, tunica media and tunica adventitia. It is now imperative that 'to further elucidate vascular function, we should no longer, as hitherto, separate adventitia and PAAT from the vascular wall, but keep them attached and in place, and subject to thorough examination' (Chaldakov, Fiore, Ghenev, Stankulov and Aloe, Int Med J 2000;7:43-9; Chaldakov, Stankulov and Aloe, Atherosclerosis 2001;154:237-8; Chaldakov GN, Stankulov IS, Fiore M, Ghenev PI and Aloe L, Atherosclerosis 2001;159:57-66). From the available data, we propose that it is time to rethink about vascular wall composition, and suggest that the PAAT may be considered the fourth and outermost vascular coat, hence, tunica adiposa (regarding the proximal segment of coronary artery, it is the innermost part of the EAT (epicardial adipose tissue) situated around the coronary adventitia). Its significance in the pathogenesis and therapy of CMDs (cardiometabolic diseases), particularly atherosclerosis and hypertension, requires further basic, translational and clinical studies.

Human Periprostatic Adipose Tissue: its Influence on Prostate Cancer Cells

“…We believe that both studying the adipoparacrinology [28] and "mapping" of the fat will provide a step forward in the understanding of prostate diseases.…”

Relationship between epicardial adipose tissue, coronary artery disease and adiponectin in a Mexican population

“…Previous studies have shown that adipose tissue, particularly visceral fat, express numerous genes related to adipokine production, which have important roles in the development of atherosclerosis in obese patients [7,24]. Epicardial fat located near to the coronary tree could facilitate the paracrine effects of epicardial adipokines, as part of the pathogenesis of CAD [11,25]. …”

Lack of Association Between Epicardial Fat Volume and Extent of Coronary Artery Calcification, Severity of Coronary Artery Disease, or Presence of Myocardial Perfusion Abnormalities in a Diverse, Symptomatic Patient Population

“…17 The mechanisms underlying these associations have not been elucidated but current hypotheses implicate the release of free fatty acids and triglycerides from epicardial fat as a source of inflammatory cytokines. 1819 Specifically, the vasa vasorum in the peripheral arterial wall arising from smaller circular and parallel branches of the epicardial coronary arteries provides a ready source of cytokines which may stimulate inflammation and recruitment of macrophages and B-lymphocytes. 19,20,21 These inflammatory processes are connected to the development of atherosclerosis and adverse clinical events.…”

“…1819 Specifically, the vasa vasorum in the peripheral arterial wall arising from smaller circular and parallel branches of the epicardial coronary arteries provides a ready source of cytokines which may stimulate inflammation and recruitment of macrophages and B-lymphocytes. 19,20,21 These inflammatory processes are connected to the development of atherosclerosis and adverse clinical events. 19,22 …”