Kuntai capsule ameliorates PCOS by reversing tryptophan metabolic shift and aberrant nuclear AHR activation: a multi-omics investigation

BACKGROUND: Polycystic ovary syndrome (PCOS) represents a multifaceted reproductive endocrine disorder with growing evidence linking its pathogenesis to metabolic alterations. In particular, dysregulation of the tryptophan-kynurenine metabolism has emerged as a key contributor, though the precise mechanisms involved remain poorly defined. Kuntai Capsule (KT) has shown potential in managing obese PCOS, yet its role in modulating tryptophan metabolism warrants further investigation. PURPOSE: To define the contribution of tryptophan metabolic shift to PCOS and to evaluate the therapeutic potential of KT. METHODS: An obese PCOS rat model was developed with testosterone propionate and high-fat diet. The efficacy of KT was assessed by tracking changes in weight, glycolipid metabolism, estrous cycle, ovarian morphology, and serum sex hormone levels. Additionally, multi-omics analyses and WB were integrated to investigate alterations in the tryptophan-kynurenine metabolism in serum and multiple target organs. The distribution of the kynurenine ligand, the AHR in the cytoplasm and nucleus, as well as changes in its downstream molecules, were investigated to elucidate the role of tryptophan metabolism-kynurenine pathway-AHR signaling axis in the mechanism underlying the metabolic and reproductive comorbidities of PCOS and the effect of KT. An in vitro model was established by treating KGN cells with L-kynurenine. The expression levels of AHR, CYP1B1, and CX43 in KGN cells were analyzed. Finally, confirmatory studies were performed using AHR agonist and antagonist. RESULTS: KT effectively attenuated the disturbed glycolipid metabolism, disrupted estrous cycle, altered sex hormone levels, and aberrant ovarian morphology in PCOS rats. Mechanistically, the model rats exhibited overactivated IDO1 and TDO2 and disrupted gut microbiota homeostasis, inducing a marked shift in tryptophan metabolism toward the kynurenine pathway. It resulted in the accumulation of kynurenine in the circulation and tissues. This kynurenine accumulation further drove aberrant nuclear AHR accumulation, which was associated with upregulation of CYP1B1 and CD36 expression in the liver, and upregulation of CYP1B1 accompanied by downregulation of the CX43 along with enhanced phosphorylation of CX43 in the ovaries. These key molecular alterations were effectively reversed by KT intervention. In vitro experiment further confirmed that KT directly antagonized kynurenine-induced excessive nuclear accumulation of AHR and elevated expression of CYP1B1. CONCLUSIONS: Overactivated IDO1 and TDO2, together with disrupted gut microbiota homeostasis, induced tryptophan metabolism shift, which overactivated nuclear AHR accumulation. It was linked to hepatic steatosis and insulin resistance via CYP1B1 and CD36 upregulation, and was also associated with disrupted ovarian function through altered CYP1B1 and CX43 expression. KT restored tryptophan metabolism and curtailed the exorbitant expression of nuclear AHR, ameliorating both metabolic and reproductive disorders in PCOS.