Bioactive components from Turnip improve liver and systemic metabolic homeostasis in mice with T2DM

Type 2 diabetes mellitus (T2DM) is characterized by insulin resistance (IR) and dysregulated glucose and lipid metabolism, among which hepatic IR as an early and pivotal pathological event. Conventional anti-diabetic agents frequently accompany undesirable side effects with limited therapeutic efficacy, which drives extensive research on natural and safe bioactive substances possessing glucose- and lipid-regulating capacities. Turnip ( Brassica rapa var. rapa ), a traditional food-medicinal homologous plant, contains bioactive components with potential metabolic regulatory functions; nevertheless, systematic isolation and mechanistic elucidation remain insufficient. In this study, we isolated and structurally characterized bioactive constituents from turnip comprehensively, and found its n-butanol subfraction T-3B exerts robust anti-T2DM activities in db/db diabetic mice. T-3B lowered fasting blood glucose (FBG), promoted glucose uptake in the liver and alleviated dyslipidemia. Such metabolic improvements are associated with the insulin signaling axis (IRβ-IRS1-AKT) governing glucose homeostasis and the AMPK-mediated lipid metabolic pathway. Six monomeric compounds were purified from T-3B, among which compounds C2 and C6 exhibited potent glucose-lowering and lipid-modulating bioactivities. Notably, C2 could effectively alleviate lipid metabolic disorders and ameliorate hepatic injury mediated by oxidative stress. Collectively, this study provides a scientific foundation for the medicinal potential of turnip and highlights T-3B, C2 and C6 as promising candidates for the intervention of T2DM.