The fate of fat.

Adipose tissue is not merely a storage depot for fat. Both brown and white adipose tissues are finely regulated endocrine organs that modulate energy balance and temperature homeostasis. In a recent issue of Gerontology, Saely and Drexel dissected the different morphology and the prime functions of brown and white adipose tissue. They impressively showed that adipose tissues are not inert deposits, but instead highly plastic tissues in close interface with guts, liver, and brain. Brown and white adipose tissues are essentially complementary organs that serve different teleological purposes. The molecular understanding of their physiological pathways opens the door to the development of a rational pharmacotherapy of obesity and associated disorders. Thus, the targeting of energy expenditure in brown adipose tissue may be an attractive alternative strategy to combat obesity. However, every intervention in cellular bioenergetics to treat obesity or cachexia will have to face principal safety considerations, as the thermodynamic implications of such interventions are largely unknown and potentially dangerous.