Thermogenic brown adipocytes as new targets for the treatment of obesity in humans

In rodents, brown adipose tissue, owing to its unique thermogenic uncoupling protein-1, is the main effector of adaptative thermogenesis. In humans, it was generally accepted that brown adipose tissue was present only in newborns. White adipose tissue, on the other hand, is devoted to the storage of lipids. Despite their two diametrically opposed functions, brown and white adipose tissues were considered close relatives. Since 2007, the brown adipose tissue research field has been in turmoil. First, developmental studies have shown that brown adipocytes share a common origin, not with white adipocytes, but with myocytes. Second, metabolically active brown adipose tissue depots have been identified by PET in adult humans. Third, cells sorted from the human muscle, expressing the CD34 surface protein, were found to differentiate into typical brown adipocytes in vitro. These findings altogether suggest new possibilities to fight human obesity by stimulating energy dissipation via activation of the recently discovered brown fat depots or of the muscle CD34 progenitor cells.