Aurantio-obtusin ameliorates prediabetes in a gut microbiota-dependent manner via regulating LPS-TLR4 axis and Akt/GLUT4 signaling

Ethnopharmacological relevance Cassiae Semen, the dried seeds of Cassia obtusifolia L., has traditionally been used in East Asian medicine to manage metabolic disorders, including hyperglycemia and dyslipidemia. Aurantio-obtusin (AO), a bioactive anthraquinone compound, exhibits diverse pharmacological activities, derived from Cassiae Semen, a traditional herb used for metabolic disorders; however, its protective efficacy against prediabetes remains poorly understood. Aim of the study This study aimed to investigate the effects of AO on prediabetes and to elucidate the underlying mechanisms, with particular emphasis on gut microbiota-mediated regulation of metabolic homeostasis. Materials and methods Mice were subjected to prediabetes by a combination of a high-fat diet and streptozotocin. Metabolic parameters, liver function, oxidative stress, inflammatory responses, insulin signaling, and gut microbiota composition were assessed. Fecal microbiota transfer and models simulating antibiotic-induced germ-free conditions were utilized to investigate the function of gut microbiota. Results AO exhibited a marked improvement in glucose tolerance, lipid profiles, and insulin sensitivity among prediabetic mice. Furthermore, AO demonstrated a protective effect against liver damage, as suggested by the notable reductions in serum levels of alanine aminotransferase and aspartate aminotransferase. Oxidative stress was markedly suppressed, as indicated by decreased malondialdehyde levels, along with enhanced antioxidant defenses, including superoxide dismutase, catalase, and reduced glutathione. Additionally, AO preserved intestinal barrier integrity, reduced endotoxemia, and suppressed Toll-like receptor 4-mediated inflammatory signaling, accompanied by restoration of the PI3K/Akt/GLUT4 pathway. Notably, depletion of gut microbiota completely abolished the metabolic benefits of AO. Conclusion Collectively, this study substantiates the ethnomedical value of Cassiae Semen, demonstrating that AO improves prediabetes through the regulation of intestinal barrier function, oxidative stress, inflammation, and insulin signaling, which is dependent on gut microbiota.