Background: The endocrine role of white adipose tissue (WAT), as a site of release of the so-called adipokines, has been recognized for long. Brown adipose tissue (BAT) is the main site of adaptive thermogenesis in mammals, especially relevant in neonates and early infancy. The amount and activity of BAT are associated with a healthy metabolic profile and protection against obesity, type II diabetes and hyperlipidemia. This biological role of BAT is traditionally attributed to its capacity of oxidation of metabolic substrates to fuel thermogenesis. However, recent findings suggest that BAT activity could result in systemic effects due to the secretion of endocrine factors, distinct from white adipokines, the so-called BAT adipokines or batokines.
Objective and hypotheses: Which are the current evidences for an endocrine role for BAT?
Method: Summarizing currently available literature highlights two main sources of evidence for an endocrine role of BAT: i) the identification of endocrine factors preferentially released by BAT versus WAT, which expression and release is enhanced when BAT is activated and ii) the evidence for beneficial effects of BAT transplantation that cannot be attribute to the intrinsic thermogenic activity of the transplated tissue.
Results: Recently reported endocrine factors released by BAT, specially under therogenic activation of the tissue, include FGF21, an anti-diabetic hormone, BMP8b and neuregulin-4. These factors usually combine autocrine action with endocrine effects, acting on tissues such as liver or WAT. Interleukin 6 and IGF1 are also proposed to be released by BAT and to account for the beneficial effects of BAT transplantation on glucose homeostasis and protection against diabetes.
Conclusion: Although the endocrine role of BAT is an emerging concept, we are still far from a comprehensive identification of the endocrine BAT secretome. Identification of BAT adipokines will expand the current availability of potential therapeutic tools for obesity and associated metabolic diseases.
01 Oct 2015 - 03 Oct 2015