Neurobiology of adipose tissue

Adipose tissue's secretory phenotype paradigm shift has been upregulating since December 1, 1994, the birthday of leptin, an endocrine signaling protein (adipokine), which triggered the development of adipoendocrinology. Today, more than hundred adipokines are identified. Here an update of adipose-derived neurotrophic factors and neuropeptides and their receptors is presented, raising a hypothesis of neuroendocrine potential of this dynamic tissue.Biomedical Reviews 2008; 19: 45-48

State-of-the-artery: periadventitial adipose tissue (tunica adiposa)

Traditional view considers that the arterial wall is composed of three concentric tissue coats (tunicae): intima, media, and adventitia. However, large- and medium-sized arteries, where usually atherosclerosis develops, are consistently surrounded by periadventitial adipose tissue (PAAT). Here we update growing information about PAAT, and  conceptualize it as the fourth coat of arterial wall, that is, tunica adiposa (in brief, adiposa, like intima, media, adventitia). Recent evidence has revealed that adipose tissue expresses not only metabolic, but also secretory (endo- and paracrine) phenotype, producing/releasing a large number of signaling proteins collectively termed adipokines. Through paracrine ("vasocrine") way, adiposa-derived mediators may contribute to various arterial functions such as contraction-relaxation, smooth muscle cell growth, inflammation, hemostasis, and innervation, hence to "outside-in" signaling pathway of atherogenesis.Biomedical Reviews 2009; 20: 41-44

Adipobiology of stem cell-based therapy: secretome insight

Stem from the promise of stem cells therapeutic potential for a number of diseases, the regenerative medicine is reaching enthusiastic proportions nowadays. Current therapies include drug treatment, lifestyle modification, organ transplantation, RNA interference "breakthrough technology", and stem cell-based therapy. Research on stem cells is a multiplex challenge provoking both the attention and the confusion of biologists, biotechnologists, medical specialists, and politicians. By integrating various approaches of transcriptomics, proteomics and metabolomics, current adipobiology has identified more than 100 secretory proteins that are produced by the adipose tissue. These proteins designated adipokines include growth factors, cytokines, chemokines, neuropeptides and hypothalamic hormones/releasing factors. In addition, the adipose tissue`s secretome contains steroid hormones, free fatty acids, prostaglandins, and endocannabinoinds. Moreover, adipose tissue is the source of adipose-derived stem cells (ADSC). Current interest in the ADSC stems from their multilineage differentiation potential, and ease of derivation in larger quantities using less invasive methods, compared with other stem cell types. The possible benefits of ADSC-based therapy may be mediated via cell proliferation/differentiation and/or paracrine mechanisms. The present review, focusing on adipose tissue secretory activity, also highlights the possible implication of ADSC in the therapy of various disorders, particularly neurodegenerative diseases, myocardial infarction and stroke, along with gut and liver diseases.Biomedical Reviews 2010; 21: 57-63

Adipose-derived stem cells as a remedy

Adipobiology of stem cells is reaching enthusiastic proportions in today's regenerative medicine. Current interest in the adipose-derived stem cells (ADSC) stems from their multilineage differentiation potential, and ease of derivation in larger quantities using less invasive methods, compared with other stem cell types. The possible benefits of ADSC-based therapy may be mediated by both cell proliferation/differentiation and paracrine secretion. Adipose tissue's secretome includes adipokines (growth factors, cytokines, chemokines, neuropeptides, hypothalamic hormones/releasing factors), steroid hormones, free fatty acids, prostaglandins, and endocannabinoids. The present review, focusing on adipose tissue secretory activity, also highlights the possible implication of ADSC in the therapy of various disorders, particularly neurodegenerative diseases, myocardial infarction and stroke as well as gut, liver and skin diseases.Adipobiology 2010; 2: 51-56

In the heart of adipobiology: cardiometabolic disease

Published on 1 December 1994 issue of Nature, the Jeffrey Friedman's discovery "gave leptin in the beginning" of the endocrine saga of adipose tissue. Onwards, studies on this tissue have enjoyed an explosive growth that conceptualized a novel field of research, adipobiology. Arguably, in the heart of adipobiology and adipopharmacology are studies focusing on the pathogenesis, prevention and therapy of cardiometabolic diseases (CMD) including atherosclerosis, hypertension, obesity, type 2 diabetes, metabolic syndrome (global cardiometabolic risk), and lipodystrophies.Biomedical Reviews 2009; 20: 1-5

SOS for Homo sapiens obesus

Published on 1 December 1994 issue of Nature, the Jeffrey Friedman's discovery "gave leptin in the beginning" of the endocrine saga of adipose tissue. Onwards, studies on this tissue have enjoyed an explosive growth that conceptualized a novel field of research, adipobiology. Arguably, in the heart of adipobiology and adipopharmacology are studies focusing on the pathogenesis, prevention and therapy of cardiometabolic diseases (CMD) including atherosclerosis, hypertension, obesity, type 2 diabetes, metabolic syndrome (global cardiometabolic risk), and lipodystrophies.Adipobiology 2010; 2: 5-8

The adipose tissue: a new member of the diffuse neuroendocrine system?

Adipose tissue is a sophisticated module, consisting of adipocytes and non-adipocyte cellular elements including stromal, vascular, nerve and immune cells. There is at present evidence that sharing of ligands and their receptors constitutes a molecular language of the human's body, which is also the case for adipose tissue and hypothalamus-pituitary gland. Historically, Nikolai Kulchitsky's identification of the enterochromaffin cell in 1897 formed the basis for the subsequent delineation of the diffuse neuroendocrine system (DNES) by Friedrich Feyrter in 1938. In DNES paradigm, the secretion of hormones, neuropeptides and neurotrophic factors is executed by cells disseminated throughout the body, for example, Kulchitsky (enterochromaffin) cells, testicular Leydig cells, and hepatic stellate cells. Here we propose that the adipose tissue might be a new member of DNES. Today (dnes, in Bulgarian), adipose tissue is "getting nervous" indeed: (i) synthesizes neuropeptides, neurotrophic factors, neurotransmitters, hypothalamic hormones/releasing factors and their receptors, (ii) like brain expresses endocannabinoids and amyloid precursor protein and, for steroidogenesis, the enzyme aromatase (P450arom), (iii) adipocytes may originate from the neural crest cells, and (iv) adipose-derived stem cells may differentiate into neuronal cells. Further molecular profiling of adipose tissue may provide new biological insights on its neuroendocrine potential. Overall this may frame a novel field of study, neuroadipobiology; its development and clinical application may contribute to the improvement of human's health.Adipobiology 2009; 1: 87-93

Adipoendocrinology and adipoparacrinology: emerging fields of study on the adipose tissue

Adipose tissue was conceived originally as merely passive, space-filling, fat storage tissue. However, in the last 10 years, investigations aimed at studying the endocrine secretion by adipose tissue have enjoyed explosive growth. The major secretory compartment of adipose tissue consists of adipocytes and stromal fibroblasts (adipofibroblasts). These cells secrete multiple bioactive molecules, conceptualized as adipokines or adipocytokines. Overall, this intellectual grown process framed an emerging field of study, adipoendocrinology. "Adipoendocrinology" connotes the study of the cellular and molecular biology of the endocrine function of adipose tissue in normal and diseased conditions. In humans, white adipose tissue is partitioned into a few large depots, including visceral and subcutaneous location, and many small depots, associated with heart, large blood vessels, major lymph nodes and other organs. The possibility that the endocrine secretory activity of large adipose depots may directly contribute to the elevated plasma levels of disease-associated adipokines has recently gained considerable attention. However, the paracrine secretory activity of organ-associated adipose tissue (the small adipose depots) has until now attracted little attention in the adipobiology of disease. Here we attempt to emphasize that studies aimed at evaluation of the paracrine secretion of organ-associated adipose tissue are becoming mandatory, since identification of the secreted molecules, particularly, adipokines, may yield clues to a possible transmission of pathogenic and/or protective stimuli, from the associated adipose tissue towards the interior of the associating organ. In this review we summarize most of the current information about adipoendocrinology and adipoparacrinology of various diseases.Biomedical Reviews 2001; 12: 31-39