Adipoendocrinology and adipoparacrinology: emerging fiels of study in 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. ìAdipoendocrinologyî 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.