Cinchonain Ia inhibits uric acid reabsorption by binding to the TRP-459 residue of the GLUT9 protein.

BACKGROUND: Hyperuricemia, a chronic metabolic disorder resulting from purine metabolism abnormalities, imposes a substantial burden on patients, their families, and society. Consequently, discovering more efficient prevention strategies and treatment drugs is of crucial importance. Polygonum capitatum (Buch.-Ham. ex D. Don) H. Gross is a plant belonging to the Polygonaceae family and Polygonum genus. Polygonum capitatum can reduce uric acid levels and alleviate gouty arthritis; However, whether its aqueous extract contains other uric acid-lowering active components besides quercetin and gallic acid still requires further research.

PURPOSE: This study aims to investigate the protective effects and potential mechanisms of Polygonum capitatum aqueous extract on liver and kidney function, while also identifying new potential pharmacologically active components for hyperuricemia within the extract.

METHODS: This study established a hyperuricemia rat and mice model and a uric acid-induced renal injury cell model. Liquid chromatography-tandem mass spectrometry was employed to analyze the active components of Polygonum capitatum aqueous extract. The target was analyzed by proteomics. Metagenomics and spatial metabolome were used to analyze gut microbes and metabolites associated with liver and kidney injury. Finally, SPR, DARTS, and CETSA were used to assess the binding potential of active components to targets. Additionally, mutant plasmids were constructed to analyze the binding sites between pharmacologically active components and their targets.

RESULTS: The aqueous extract of Polygonum capitatum significantly reduced serum uric acid levels and alleviated renal injury in the hyperuricemia rat model, with no apparent damage on liver tissue morphology or hepatic function indicators. Metagenomic and spatial metabolomics analyses demonstrated that the extract increased the relative abundance of beneficial gut microbiota and decreased that of harmful bacteria. It also modulated the levels and distribution of renal metabolites such as l-arginine and N-acetylglucosamine, reduced lipid oxidation in the kidney. Proteomics analysis suggests that renal GLUT9 may be one of the action targets of this extract. LC-MS/MS analysis indicated that the chemical composition of the extract underwent significant changes after entering rat blood and undergoing renal metabolism. Specifically, serves as a new active component in Polygonum capitatum aqueous extract, Cinchonain Ia was found to bind to the TRP-459 residue of GLUT9, inhibiting its expression and thereby reducing uric acid reabsorption in vivo and in vitro, and alleviated oxidative stress, inflammation, and tissue damage. However, overexpression of GLUT9 markedly reversed the inhibitory effects of Cinchonain Ia on inflammation and injury.

CONCLUSIONS: The aqueous extract of Polygonum capitatum prevents liver damage and alleviates kidney injury by regulating gut microbiota and renal metabolites. Furthermore, Cinchonain Ia, as one of its active components, can bind to the TRP-459 residue of the GLUT9 protein and inhibit its expression, thereby suppressing uric acid reabsorption and lowering serum uric acid levels.