The adipose organ

In mammals, the adipose tissues are contained in a multi-depot organ: the adipose organ. It consists of several subcutaneous and visceral depots. Some areas of these depots are brown and correspond to brown adipose tissue, while many are white and correspond to white adipose tissue. The organ is rich of vessels and parenchymal nerve fibers, but their density is higher in the brown areas. White areas contain a variable amount of brown adipocytes and their number varies with age, strain and environmental conditions. All adipocytes of the adipose organ express a specific adrenoceptor: beta 3AR. Recent data have stressed the plasticity of the adipose organ in adult animals, and in parallel with the cytological variations there are also vascular as well as neural variations. Of note, treatment of genetically and diet induced obese rats with beta 3 adrenoceptor agonists ameliorate their pathological condition and this is accompanied by the appearance of brown adipocytes in white areas of the adipose organ. This drug-induced modification of the anatomy of the organ is also obtained by the treatment with PPAR gamma agonists in rats and dogs. We have previously shown that the transformation of white adipose tissue into brown adipose tissue in rats treated with 133 adrenoceptor agonists is due to a direct transformation of differentiated unilocular adipocytes (transdifferentiation). We recently also showed that the absence of beta 3 adrenoceptors strongly depress this type of plasticity in the adipose organ. All together these experiments strongly suggest the possibility to modulate the plasticity of the adipose organ with therapeutic implications for obesity and related disorders. (c) 2005 Elsevier Ltd. All rights reserved.