IGF1 and Alzheimer disease: Earlier onset and increased incidence of neurological deficits were observed in IGF-1-deficient mice induced by liver-specific knockdown of IGF-1 [30], while boosting brain expression of IGF-1 through adenovirus-mediated transduction has been proved to protect hippocampal neurons from the toxicity of amyloid-β oligomers and prevent memory loss in an AD mouse model [31].