Adipose tissue hormones

It is now widely accepted that white adipose tissue (WAT) secretes a number of peptide hormones, including leptin, several cytokines, adipsin and acylation-stimulating protein (ASP), angiotensinogen, plasminogen activator inhibitor-1 (PAI-1), adiponectin, resistin etc., and also produces steroids hormones. This newly discovered secretory function has shifted our view of WAT, which is no longer considered only an energy storage tissue but a major endocrine organ, at the heart of a complex network influencing energy homeostasis, glucose and lipid metabolism, vascular homeostasis, immune response and even reproduction. Virtually all known adipose secreted proteins are dysregulated when the WAT mass is markedly altered, either increased in the obese state or decreased in lipoatrophy. This strongly implicates adipose-secreted products in the ethiopathology and/or complications of both obesity and cachexia. This review discusses the physiological relevance of adipose secretion by focusing on protein and steroid hormones. Regulation of WAT secretion by the major regulatory factors impinging on the adipocytes, i.e. insulin, glucocorticoids, catecholamines and thiazolidinediones (TZD) will be addressed. The rationale for therapeutic strategies aimed at compensating adverse effects resulting from overproduction or lack of a specific adipose secretory product will be discussed.