Endocrine Abstracts

Brown adipose tissue (BAT), in addition to its role in adaptive thermogenesis, secretes regulatory factors (brown adipokines or ‘batokines’) that have autocrine, paracrine, and endocrine actions. Local secretion of brown adipokines by brown adipocytes target distinct cell types in the tissue (e.g. vascular cells, sympathetic nerve endings, immune cells) and promote the remodeling of BAT in response to distinct physiological conditions requiring adaptive thermogenesis. Evidence from BAT transplantation in rodents led to hypothesize that brown adipokines may have endocrine actions which may be involved in the systemic healthy effects (mainly prevention of insulin resistance and obesity) of active brown fat. There is evidence that such healthy effects occur also for the human brown adipocyte secretome. Brown adipokines identified to date are polypeptides, lipid molecules or microRNAs. However, a comprehensive knowledge of the secretome from BAT fat is still lacking. The identification and characterization of brown adipokines may help to identify novel tools for treatment of metabolic diseases, due to the expected healthy properties of signaling molecules released by BAT. Moreover, circulating biomarkers of BAT activity are not available at present, and research on brown adipokines may contribute to the identification of such systemic biomarkers that will be particularly useful in clinical research. Recently, a distinct type of adipose tissue has been identified, the so-called ‘beige’ adipose tissue which contain thermogenic ‘beige’ adipocytes resembling brown adipocytes. Several experimental data suggest that the extent of induction of ‘beige’ adipose tissue in response to thermogenic challenges is associated with protection against obesity and hyperglycemia. To date, the secretome of ‘beige’ adipocytes appears to resemble that from brown adipocytes, but research for potential differential secretion beige-versus-brown adipokines is ongoing.