Microglia-Based Sex-Biased Neuropathology in Early-Stage Alzheimer's Disease Model Mice and the Potential Pharmacologic Efficacy of Dioscin

Alzheimer's disease (AD), the most common form of dementia, is characterized by amyloid-beta (A beta) accumulation, microglia-associated neuroinflammation, and synaptic loss. The detailed neuropathologic characteristics in early-stage AD, however, are largely unclear. We evaluated the pathologic brain alterations in young adult App knock-in model App(NL-G-F) mice at 3 and 6 months of age, which corresponds to early-stage AD. At 3 months of age, microglia expression in the cortex and hippocampus was significantly decreased. By the age of 6 months, the number and function of the microglia increased, accompanied by progressive amyloid-beta deposition, synaptic dysfunction, neuroinflammation, and dysregulation of beta-catenin and NF-kappa B signaling pathways. The neuropathologic changes were more severe in female mice than in male mice. Oral administration of dioscin, a natural product, ameliorated the neuropathologic alterations in young App(NL-G-F) mice. Our findings revealed microglia-based sex-differential neuropathologic changes in a mouse model of early-stage AD and therapeutic efficacy of dioscin on the brain lesions. Dioscin may represent a potential treatment for AD.