KYN is converted to kynurenine acid by KAT (kynurenine aminotransferase) in astrocytes, which can cause cognitive deficits, and is transformed to quinolinic acid by KMO (kynurenine 3-monooxygenase) in microglia, which causes neurotoxicity, including oxidative stress and neurodegeneration (Brown et al., 2021). This evidence concerns the gene KMO and Cognitive impairment.