Chimonanthus nitens Oliv. leaves total flavonoids ameliorate insulin resistance by gut-muscle axis in high-fat and high-fructose diet-fed mice

CTF alleviated HFFD-induced insulin resistance by regulating the gut-muscle axis in mice. • Antibiotic-mediated microbiota depletion verified that gut microbiota acts as a critical mediator underlying the insulin-sensitizing effects of CTF. • CTF remodeled intestinal flora homeostasis and activated skeletal muscle AMPK/GLUT4/UCP1 signaling to restore glucose metabolic homeostasis. Insulin resistance (IR) drives obesity and type 2 diabetes, with defective skeletal muscle glucose metabolism as the primary trigger of systemic metabolic dysfunction. We previously confirmed the glycolipid-regulating activity of Chimonanthus nitens Oliv. leaves total flavonoids (CTF), yet its gut microbiota-dependent anti-insulin resistance mechanism remains unclear. In this study, five major flavonoid constituents of CTF were identified using ultra-high performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry (UHPLC-Q-TOF MS/MS), namely rutin, isoquercitrin, kaempferol-3-O-rutinoside, astragalin and quercetin. We established a high-fat and high-fructose diet (HFFD)-induced IR mouse model to explore CTF's protective effects and molecular mechanisms through comprehensive detection of physiological parameters, gut microbial profiles, cecal metabolites and skeletal muscle function. Microbiologically, CTF relieved glucose disorders and IR by restoring gut microbial and cecal metabolite homeostasis. Antibiotics-mediated gut microbiota depletion nearly abolished hypoglycemic and muscle-protective capacities of CTF, demonstrating gut microbiota as an indispensable mediator of CTF efficacy. Mechanistically, CTF activated adenosine monophosphate-activated protein kinase (AMPK) signaling, thereby synchronously upregulating glucose transporter 4 (GLUT4) and uncoupling protein 1 (UCP1). Specifically, CTF raised skeletal muscle glycogen accumulation and succinate dehydrogenase (SDH) activity, enhanced GLUT4 expression and its translocation onto the sarcolemma to accelerate muscular glucose uptake. Meanwhile, the upregulated UCP1 promoted thermogenesis of intermuscular fat and further alleviated lipotoxic damage. In conclusion, CTF alleviates HFFD-induced IR predominantly by regulating gut microbiota and cecal metabolism, and recovers skeletal muscle glucose homeostasis through the gut-muscle-axis-dependent AMPK/GLUT4/UCP1 pathway. This research offers a theoretical basis for CTF as natural anti-metabolic disorder dietary supplements. Download: Download high-res image (336KB) Download: Download full-size image