Symposium on 'new perspectives on adipose tissue function' - The adipose organ: morphological perspectives of adipose tissues

Anatomically, an organ is defined as a series of tissues which jointly perf orm one or more interconnected functions. The adipose organ qualifies for t his definition as it is made up of two tissue types, the white and brown ad ipose tissues, which collaborate in partitioning the energy contained in li pids between thermogenesis and the other metabolic functions. In rats and m ice the adipose organ consists of several subcutaneous and visceral depots. Some areas of these depots are brown and correspond to brown adipose tissu e, while many are white and correspond to white adipose tissue. The number of brown adipocytes found in white areas varies with age, strain of animal and environmental conditions. Brown and white adipocyte precursors are morp hologically dissimilar, Together with a rich vascular supply, brown areas r eceive abundant noradrenergic parenchymal innervation. The gross anatomy an d histology of the organ vary considerably in different physiological (cold acclimation, warm acclimation, fasting) and pathological conditions such a s obesity; many important genes, such as leptin and uncoupling protein-1, a re also expressed very differently in the two cell types. These basic mecha nisms should be taken into account when addressing the physiopathology of o besity and its treatment.