Fig. 1: IDO1-catalyzed Kyn exacerbates insulin resistance in subjects with obesity.

a Correlation analysis between body mass index (BMI) and plasma Kyn levels in human samples (n = 735). Plasma Kyn levels (b) and KTR (c) in lean subjects (18 ≤ BMI < 24, n = 354), subjects with overweight (24 ≤ BMI < 28, n = 268) and subjects with obesity (BMI ≥ 28, n = 113). d Plasma Kyn levels and e KTR in WT mice fed with NCD (n = 12) or HFD (n = 16). f Body weights of Kyn-treated and PBS-treated WT mice. Glucose tolerance test (GTT) (g) and insulin tolerance test (ITT) (h) in Kyn-treated and PBS-treated WT mice (n = 6). i Plasma insulin levels of Kyn-treated and PBS-treated WT mice (n = 6). j Body weights of WT and Ido^−/− mice fed with HFD for 12 weeks (n = 8). GTT (k) and ITT (l) in WT and Ido^−/− mice fed with HFD for 12 weeks (n = 8). m Plasma insulin levels of WT and Ido^−/− mice fed with HFD for 12 weeks (n = 8). Data were represented as mean ± SEM. Statistical significance was assessed by two-sided Spearman’s correlation (a), One-way ANOVA (b, c), two-sided Student’s t test (d, e, i and m) or two-way ANOVA followed with Bonferroni’s multiple comparisons test (f–h, j–l) and significant differences were indicated with p values. Source data are provided in the Source Data file.