Additionally, steatosis was observed in the control mice as validated by the massive lipid depositions (Supplementary Fig. 6b), while the Ido1-aKO mice were featured by the increased lipolysis (p-HSLSer660) and decreased lipogenesis (p-ACCSer79) (Supplementary Fig. 6d) coupled with relieved adipocyte hypertrophy in the WAT (Supplementary Fig. 6c). Here, IDO1 is linked to steatosis.