IDO1 and atherosclerosis: High concentrations of KA in atheromatous plaques were associated with an unstable plaque phenotype in human atherosclerotic lesions, whereas there were no detectable or low levels of KA in stable fibrous plaques.18 Elevation of 3-HAA levels by IDO1 activation inhibited vascular inflammation and subsequent atherosclerosis in LDLR−/− or ApoE−/− mice.