Indoleamine 2,3 dioxygenase (IDO) level as a marker for significant coronary artery disease

Abstract Background Indoleamine 2,3 dioxygenase (IDO), the rate-limiting enzyme in the kynurenine (Kyn) pathway of tryptophan (Trp) degradation, is modulated by inflammation, and is regarded as a key molecule driving immunotolerance and immunosuppressive mechanisms. Little is known about IDO activity in patients with active coronary artery disease (CAD). Methods We prospectively enrolled patients who were scheduled to undergo coronary angiography. Measurement of IDO, high-sensitivity troponin T (hs-TnT), and high-sensitivity C-reactive protein (hs-CRP) levels was performed at baseline, and IDO activity was monitored at the 6-month follow-up. Results Three hundred and five patients were enrolled. Ninety-eight patients (32.1%) presented with recent acute coronary syndrome (ACS). Significant difference in IDO, kynurenine, and hs-TnT between patients with and without significant CAD was observed. Baseline IDO activity, kynurenine level, and hs-TnT level were all significantly higher in significant CAD patients with 3-vessel, 2-vessel, and 1-vessel involvement than in those with insignificant CAD [(0.17, 0.13, and 0.16 vs. 0.03, respectively; p = 0.003), (5.89, 4.58, and 5.24 vs. 2.74 µM/g, respectively; p = 0.011), and (18.27, 12.22, and 12.86 vs. 10.89 mg/dL, respectively; p