Dysregulated indoleamine 2,3-dioxygenase contributes to metabolic syndrome

Dysregulation of tryptophan (Trp) metabolism, specifically changes in Kynurenine (Kyn) and indoleamine 2,3-dioxygenase (IDO) activity, has been associated with the initiation of chronic inflammation, oxidative stress, insulin resistance, and metabolic syndrome (MetS). This study aimed to evaluate the connection between the IDO activity, lipid profile, and oxidative stress with the risk of MetS.

This study was conducted on 140 women, including subjects with MetS (n = 40) and controls (n = 100). The levels of Kyn and Trp were measured using the HPLC method. The fasting plasma glucose (FPG), insulin, ischemic modified albumin (IMA), uric acid, and lipid profile of serum specimens were also measured. The levels of the homeostasis model for the assessment of insulin resistance (HOMA-IR) were calculated.

The levels of FPG, triglycerides, uric acid, insulin, HOMA-IR, Kyn, IDO activity, and IMA were significantly higher in the MetS group compared to non-MetS subjects. Multiple regression analyses showed that uric acid (r = 0.315; P < 0.001) was an independent predictor of IDO activity in all subjects. Additionally, TG/HDL-C ratio and IDO activity independently predicted MetS. In ROC curve analysis, TG/HDL-C demonstrated high (AUC = 0.886) and IDO activity moderate (AUC = 0.646) performance in predicting Mtes.

The findings demonstrate that IDO activity increases in MetS participants. Additionally, due to the high specificity and sensitivity of IDO activity and TG/HDL-C, they can serve as prognostic biomarkers for MetS.