Lithocarpus litseifolius leaf extract alleviate hyperuricemia-induced renal injury by regulating uric acid metabolism and inhibiting the AKT/S6K pathway.

Abstract

ETHNOPHARMACOLOGICAL RELEVANCE: Lithocarpus litseifolius (Hance) Chun is a tall evergreen tree belonging to the genus Lithocarpus in the family Fagaceae. According to the Chinese Materia Medica, its roots, stems, leaves, and fruits can all be used medicinally. Documented functions include clearing heat, detoxification, dispelling wind, lowering blood pressure, promoting blood circulation to alleviate pain, tonifying the liver and kidney, harmonizing the stomach, and directing rebellious qi downward. AIM OF THE STUDY: This study aimed to elucidate the active constituents and mechanisms of action underlying the hypouricemic and renoprotective effects of L. litseifolius. MATERIALS AND METHODS: The chemical constituents of L. litseifolius extract (LLE) were identified by UPLC-Q-TOF-MS/MS. The hypouricemic effect of LLE was first confirmed in a hyperuricemia (HUA) mouse model induced by potassium oxonate and yeast extract. Mechanistic studies were then conducted using renal untargeted metabolomics and Western blot analysis. To identify the key active component, we employed a multi-method approach: identifying blood-absorbed constituents in rats, performing in vitro XOD inhibition and HK-2 cell UA reabsorption assays, and finally verifying efficacy in the HUA mouse model. RESULTS: A total of 42 compounds were identified from the LLE, predominantly flavonoids, of which 10 were identified as prototype blood-absorbed components. In vivo and in vitro experiments results demonstrated that the LLE and its major active component, trilobatin (TR), dose-dependently reduced serum levels of UA, creatinine, and blood urea nitrogen in HUA mice. These effects were accompanied by downregulating URAT1 and upregulating OAT1 expression in kidney, as well as inhibiting both the activity and expression of XOD in liver. Untargeted metabolomics and Western blot analysis confirmed that the LLE and TR effectively inhibited the expression of p-AKT and p-S6K. In vitro assays revealed that TR not only exhibited XOD inhibitory activity but also suppressed UA uptake in HK-2 cells. Furthermore, results from both cellular thermal shift assay (CETSA) and drug affinity responsive target stability (DARTS) assay experiments indicated that TR shows direct interaction potential with URAT1. CONCLUSION: LLE and its active component TR reduced serum UA in HUA mice through a dual mechanism: decreasing hepatic UA production (inhibiting XOD) and promoting renal UA excretion (downregulating URAT1 and upregulating OAT1). Simultaneously, they ameliorated renal injury, which was associated with the suppression of AKT/S6K signaling pathway overexpression.