IDO1 and atherosclerosis: In the Tampere Vascular Study, increased IDO1 expression was observed in the macrophage-rich cores of human atherosclerotic plaques.26 In a large cohort study, IDO1 activity was found to have a significant positive correlation in both sexes with carotid artery intima/media thickness, an early marker of atherosclerosis.33 Specifically, IDO1 activity has been reported to positively correlate with a range of atherosclerosis risk factors for the female population, including age, BMI, and LDL cholesterol.34 In contrast, the atheroprotective role of IDO1 has also been documented.