Nobiletin Ameliorated the Development of Diabetic Kidney Disease via Modulating Ferroptosis and Epithelial–Mesenchymal Transition Involving Gut–Kidney Axis

Diabetic kidney disease (DKD) is one of the most common microvascular complications associated with diabetes mellitus. However, the existing treatment approaches, aimed at delaying the onset of DKD, exhibit limited efficacy. The flavonoid nobiletin has demonstrated substantial lipid-lowering and insulin-sensitizing effects in mice exhibiting metabolic dysfunction, but the therapeutic potential and mechanism of nobiletin in the context of DKD remains to be comprehensively elucidated. In this study, the active components of polymethoxylated flavonoids (PMFs) were identified via UPLC. A DKD rat model was established through a high-fat diet and the administration of streptozotocin via intraperitoneal injection. The effect and mechanism of nobiletin on DKD was evaluated by histological, biochemical, molecular, and multi-omics analysis. We found that treatment with PMFs and nobiletin inhibited ferroptosis and EMT in high glucose and insulin-induced models, protected the glomerular filtration barrier integrity, and concurrently suppressed ROS, Fe[Formula: see text], and MDA while increasing the GSH level. Animal experiments indicated that nobiletin treatment markedly impeded the progression of DKD and alleviated both EMT and endothelial dysfunction. Moreover, nobiletin significantly preserved the integrity of the intestinal barrier and enriched the diversity of gut microbiota. In conclusion, our findings indicate that nobiletin could attenuate DKD and concomitantly limit ferroptosis and EMT, and that the gut-kidney axis played an important role in its effects.