The adipose tissue as a third brain

Although a concept of adipocyte plasticity has emerged recently, histologically and functionally, two types of adi- pose tissue can be distinguished: white and brown adipose tissue (WAT and BAT, respectively). Today the adipose tissue is viewed as a dynamic system, consisting of adipocytes and non-adipocyte cellular elements, including stromal, vascu- lar, nerve and immune cells. By sending and receiving dif- ferent types of protein and non-protein signals, adipose tis- sue communicates with many organs in the body (Fig. 1). In effect, the adipose-brain, like the gut-brain (1), axis stays at the heart of food intake and energy balance regulation (2). It is increasingly recognized that WAT expresses not only metabolic, but also secretory phenotype, producing more than 100 signaling proteins collectively designated adipokines. These may contribute to feeding behavior, en- ergy homeostasis, inflammation, immunity, vascular tone, and insulin resistance as well as play a pivotal role in the pathogenesis of cardiometabolic and other diseases (2-4).