The holy grail of metabolic disease: Brown adipose tissue

PURPOSE OF REVIEW: The finding that brown adipose tissue (BAT) is present in adults brought BAT physiology into the focus of many researchers interested in energy metabolism. Here, we review recent insight into how BAT develops, functions and might help to treat metabolic disorders in humans. RECENT FINDINGS: BAT is under control of the nervous system, and several pathways have been identified that allow direct manipulation of BAT biology. In addition, some brown adipocytes arise from a distinct subset of white adipocyte precursors and studies were performed that characterize the development of these 'brite' adipocytes. Importantly, progress has been made in understanding how BAT takes up and dissipates nutrients that in metabolic disorders are present in excess. Finally, as it seems that BAT activity declines with age and obesity, we review findings that might shed light on how humans could sustain or increase BAT activity, thus preventing or treating obesity, hyperlipidemia and type 2 diabetes. SUMMARY: BAT is a powerful organ that controls the development of metabolic disease. These powers are boosted by mechanisms that turn white into brown fat and enhance lipid flux into BAT. However, in humans, it remains unclear what was the first: metabolic disease or decreased BAT activity.