Indole metabolites can alleviate colitis; for example, supplementation with indole metabolites such as indole-3-carbinol (I3C), inhibition of kynurenine monooxygenase (KMO), and selective stimulation or inhibition of specific serotonin receptors can mitigate colitis (Tashita et al., 2020). Here, KMO is linked to colitis.