TDO2 and cardiovascular disorder: Host-derived indoleamine-2,3-dioxygenase (IDO) and tryptophan-2,3-dioxygenase (TDO) transform TRP into kynurenine metabolites that have anti-inflammatory properties and can modulate cardiovascular disease pathology by activating the immune system, inducing inflammation, and exacerbating oxidative stress [19,20,21,22,23].