We also measured the mRNA expression of three downstream metabolic enzymes of KP involved in QUIN and PIC production and/or catabolism: 3-hydroxyanthranilic acid oxidase (3HAAO), α-amino-α-carboxymuconate-semialdehyde decarboxylase (ACMSD), and quinolinate phosphoribosyltransferase (QPRT) in 3xTg AD mouse brains at various ages (Fig. 7). Here, QPRT is linked to Alzheimer disease.