Angoroside C: a potent AMPK activator in the aqueous extract of Scrophularia ningpoensis, alleviates metabolic syndrome in db/db mice

Background Scrophularia ningpoensis Hemsl. (SN) is a traditional herbal medicine used for treating diabetes mellitus (DM). Previous studies indicated that the aqueous extract of SN (AESN) improves type 2 DM (T2DM) by activating AMPK, but the active components were unclear. Purpose This study aimed to identify the compound in AESN responsible for AMPK activation and to verify its therapeutic effects on T2DM. Methods Rats were administered AESN intragastrically. The absorbed compounds in serum samples were analyzed using LC-MS/MS and subjected to molecular docking with AMPK. The compound with the highest docking score was further verified using SPR, CETSA, and TR-FRET to confirm its effects on AMPK activation. Primary mouse hepatocytes were used to examine the effects of ANC on AMPK activity, Akt/GSK3β signaling, NLRP3 inflammasome activation, and lipid accumulation. An AMPK inhibitor was used to determine whether the effects were AMPK-dependent. In type 2 diabetic db/db mice, various dosages of ANC were administered intragastrically to observe its therapeutic effects. Results Among the 17 absorbed prototype compounds, ANC exhibited the strongest binding ability to AMPK. SPR, CETSA, and TR-FRET assays confirmed that ANC binds to and activates AMPK. In hepatocytes, ANC activated the Akt/GSK3β signaling, suppressed NLRP3 inflammasome activation, and inhibited lipid accumulation in an AMPK-dependent manner. In db/db mice, ANC intervention improved glucose and lipid metabolic disorders, insulin resistance, and histopathological abnormalities in a dose-dependent manner, while activating AMPK and alleviating lipid metabolic disorders and metabolic inflammatory responses. Conclusion ANC can treat T2DM by directly binding to and activating AMPK.