Fig. 4: Kyn mediates metabolic disorder and insulin resistance in adipocytes via the AhR/STAT3/IL-6 axis.

a 3T3-L1-derived mature adipocytes were stimulated with gradient concentrations of Kyn (0, 25, 50, 100 μg mL⁻¹), representatively. Oil Red staining of lipid droplets within the adipocytes was recorded. The experiments were repeated independently three times. Scale bar, 100 µm. b Transcriptional levels of lipogenesis associated genes (C/ebpα, PPARγ, Fabp4) in the above adipocytes (n = 3). c After the treatment of Kyn (0, 25, 50, 100 μg mL⁻¹) and palmitate (0.25 mmol L⁻¹, PA, Sigma), 100 nM insulin was added into the medium for 15 min before collecting the adipocytes. Western blot was conducted to detect p-ACC^Ser79/ACC, p-HSL^Ser660/HSL, p-AKT^Ser473/AKT in the adipocytes. The experiments were performed independently three times, and the quantitative analysis was shown as a bar graph in the bottom panel (n = 3). d AhR, p-STAT3^Tyr705 and STAT3 expression levels in above adipocytes were determined by Western blot. β-Actin or Lamin b was used as internal controls. The quantitative analysis was shown as a bar graph in the bottom panel (n = 3 independent experiments). e The predicted AhR binding site within the Stat3 promoter. f ChIP results for the analysis of AhR binding activity to the Stat3 promoter. gDNA: guide DNA. g, h Relative luciferase activity in 3T3-L1. MU: mutant. The experiments were repeated independently three times (n = 3). i ELISA analysis of IL-6 in the culture supernatants of adipocytes following Kyn (100 μg mL⁻¹) exposure for 48 h (n = 7). j Western blot analysis of p-AKT^Ser473/AKT, p-STAT3^Tyr705/STAT3 and AhR in mature adipocytes treated with SR1 or Stattic (n = 3 independent experiments). k ELISA analysis of IL-6 in the culture supernatants of adipocytes treated with SR1 or Stattic. The experiments were repeated independently four times (n = 4). Data were represented as mean ± SEM. Statistical significance was assessed by one-way ANCOVA (b–d, j and k), two-sided Student’s t test (i), two-way ANCOVA (h) and significant differences were indicated with p values. Source data are provided in the Source Data file.