Although in this review we specifically focused on tryptophan metabolism throughthe KP, it is important to acknowledge that KP alterations may also dysregulatethe serotonin and melatonin pathways by changing tryptophan availability andaryl hydrocarbon receptor activation by kynurenine, and consequently affectmitochondrial function.79,80 Indeed, melatonin and serotonin were suggested to havea role in the pathogenesis of depression during pregnancy, GDM, PE, and FGR aswell.19, , , , -24. This evidence concerns the gene NPPA and depressive disorder.