IDO2, one of the isoforms of IDO (Indoleamine 2, 3-dioxygenase) which forms part of the tryptophan metabolism and catalyzes the conversion of tryptophan to kynurenine, is upregulated in T2D patients with baseline tryptophan being associated with higher risk of incident T2D [56].Variants of PBRM1 have been reported to be associated with BMI-related traits and diabetes pathways [57, 58]. Here, IDO1 is linked to diabetes mellitus.