About this Research Topic
Brown adipose tissue (BAT) has long been recognized as a key thermogenic tissue in eutherian mammals. Brown fat cells contain large numbers of highly specialized mitochondria that oxidize fat and carbohydrate to produce heat. This metabolic inefficiency is due to the presence of Ucp1 in the inner mitochondrial membrane of brown fat cells which dissociates the electrochemical gradient from ATP production. BAT presumably evolved to protect animals against hypothermia in response to cold exposure. However, energy expended by BAT has the added benefit of counteracting obesity and associated metabolic disease, at least in rodents. A very large number of studies have consistently shown that mice carrying increased amounts of active brown fat are lean and healthy. Until recently, it was generally believed that the amount of brown fat tissue was negligible in healthy adult humans. However, PET imaging studies have refuted this notion, and revealed the existence of active BAT in most, if not all, adult humans. Notably, there is a very strong inverse correlation between the amount of activated BAT and fatness in humans. Moreover, activated brown fat is lost with ageing, which also correlates with tendency to gain weight. The field must now address whether variation in brown fat activity is a cause or consequence of weight gain. Brown fat cells are localized in discrete depots of BAT and are also found as clusters interspersed in white fat tissues. The prevalence and function of these so-called “brite” (brown in white) cells in humans remains unknown. The development of strategies to increase the amount and/or activity of brown fat may hold exciting prospects for the treatment of obesity and its associated health consequences. In this Research Topics issue, we would propose to examine the following areas related to brown fat biology:
1. Development of brown and “brite” cells (including: historical/evolutionary perspective, transcriptional pathways, developmental origins)
2. Pathways that influence brown fat cell development (BMP7, TZDs, Prostaglandins, FGF21)
3. Activation of brown fat - focus on sympathetic and sensory innervation (signaling by beta-adrenergic receptors, nerve-fat connections
4. Brown fat thermogenesis in response to cold, diet and hibernation
5. Brown fat in humans including: human brown fat precursors, methods for imaging, factors that influence prevalence, relationship between body mass/obesity and amount of brown fat.
6. Brown fat mitochondria including mechanism of uncoupling (Ucp1 history/structure/function, mitochondrial biogenesis)
Important Note: All contributions to this Research Topic must be within the scope of the section and journal to which they are submitted, as defined in their mission statements. Frontiers reserves the right to guide an out-of-scope manuscript to a more suitable section or journal at any stage of peer review.