Abstract
Icariin, a major prenylated flavonoid found in Epimedium spp., is a bioactive constituent of Herba Epimedii and has been shown to exert neuroprotective effects in experimental models of Alzheimer's disease. In this study, we investigated the neuroprotective mechanism of icariin in an APP/PS1/Tau triple-transgenic mouse model of Alzheimer's disease. We performed behavioral tests, pathological examination, and western blot assay, and found that memory deficits of the model mice were obviously improved, neuronal and synaptic damage in the cerebral cortex was substantially mitigated, and amyloid-β accumulation and tau hyperphosphorylation were considerably reduced after 5 months of intragastric administration of icariin at a dose of 60 mg/kg body weight per day. Furthermore, deficits of proteins in the insulin signaling pathway and their phosphorylation levels were significantly reversed, including the insulin receptor, insulin receptor substrate 1, phosphatidylinositol-3-kinase, protein kinase B, and glycogen synthase kinase 3β, and the levels of glucose transporter 1 and 3 were markedly increased. These findings suggest that icariin can improve learning and memory impairments in the mouse model of Alzheimer's disease by regulating brain insulin signaling and glucose transporters, which lays the foundation for potential clinical application of icariin in the prevention and treatment of Alzheimer's disease.