Rasal2 deficiency reduces adipogenesis and occurrence of obesity-related disorders

OBJECTIVE: Identification of additional regulatory factors involved in the onset of obesity is important to understand the mechanisms underlying this prevailing disease and its associated metabolic disorders and to develop therapeutic strategies. Through isolation and analysis of a mutant, we aimed to uncover the function of a Ras-GAP gene, Rasal2 (Ras protein activator like 2), in the development of obesity and related metabolic disorders and to obtain valuable insights regarding the mechanism underlying the function. METHODS: An obesity-based genetic screen was performed to identify an insertional mutation that disrupts the expression of Rasal2 (Rasal2(PB/PB) mice). Important metabolic parameters, such as fat mass and glucose tolerance, were measured in Rasal2(PB/PB) mice. The impact of Rasal2 on adipogenesis was evaluated in the mutant mice and in 3T3-L1 preadipocytes treated with Rasal2 siRNA. Ras and ERK activities were then evaluated in Rasal2-deficient preadipocytes or mice, and their functional relationships with Rasal2 on adipogenesis were investigated by employing Ras and MEK inhibitors. RESULTS: Rasal2(PB/PB) mice showed drastic decrease in Rasal2 expression and a lean phenotype. The mutant mice displayed decreased adiposity and resistance to high-fat diet induced metabolic disorders. Further analysis indicated that Rasal2 deficiency leads to impaired adipogenesis in vivo and in vitro. Moreover, while Rasal2 deficiency resulted in increased activity of both Ras and ERK in preadipocytes, reducing Ras, but not ERK, suppressed the impaired adipogenesis. CONCLUSIONS: Rasal2 promotes adipogenesis, which may critically contribute to its role in the development of obesity and related metabolic disorders and may do so by repressing Ras activity in an ERK-independent manner.