FFAR1 and Insulin resistance: Although an initial report of systemic GPR40 knockout (KO) mice and beta cell-specific GPR40 transgenic (Tg) mice using the PDX-1/IPF1 promoter suggested possible involvement of GPR40 in insulin resistance in the liver and beta cell failure (14), later reports using GPR40 KO mice found no link between GPR40 and beta cell dysfunction (15, 16).