MicroRNA‑26b is upregulated in a double transgenic mouse model of Alzheimer's disease and promotes the expression of amyloid‑β by targeting insulin‑like growth factor 1

Abstract Alzheimer's disease (AD) is the most common form of dementia among the aging population. It is pathologically characterized by synaptic impairment, accumulation of neurofibrillary tangles and amyloid‑β (Aβ) deposition. MicroRNA‑26b (miR‑26b) has been observed to be upregulated in the human temporal cortex in AD, however, the function of miR‑26b has not been verified. Reverse transcription‑quantitative polymerase chain reaction was conducted to investigate the expression levels of miR‑26b in a double transgenic mouse model of AD. Following transfection of miR‑26b or an miR‑26b inhibitor, western blot analysis, enzyme‑linked immunosorbent assay and luciferase assays were performed. The present study demonstrated that the expression levels of miR‑26b were upregulated in a double transgenic mouse model of AD. It was also demonstrated that upregulation of miR‑26b in N2a/APP cells downregulated the insulin‑like growth factor 1 (IGF‑1) protein expression level and promoted Aβ production, whereas inhibition of miR‑26b in N2a/APP cells upregulated the IGF‑1 protein level and suppressed Aβ production. Furthermore, miR‑26b target sites in IGF‑1 were confirmed using a luciferase assay in HEK293 cells. The present study may be useful in the development of effective therapeutic strategies against AD.