| Summary: | Objective To investigate how insulin affects the metabolism of amyloid precursor protein (APP) in a cell model of Alzheimer's disease (AD). Methods Human neuroblastoma SH-SY5Y cells and the nonneural cell lines HEK293 and 2EB2 were treated with different concentrations of insulin for 48 h, and the changes in cell viability were evaluated with CCK-8 assay. The expression levels of APP, C-terminal fragment of APP (CTF), β-site APP cleaving enzyme 1 (BACE1), the α-secretase ADAM10 (a disintegrin and metalloproteinase 10) and γ-secretase presenilin 1 (PS1) in the cells were detected using Western blotting. ELISA was used to determine the cellular expression levels of Aβ40 and Aβ42. The key signaling pathways mediated by insulin were screened using a protein chip. The effect of insulin on protein phosphorylation levels of AKT and GSK3β pathways was examined by detecting p-AKT and p-GSK3β expression in the cells with Western blotting. Results Treatment with insulin below 10 μmol/L did not obviously affect the viability of the cells (P>0.05). Western blotting showed that treatment with 1.00 and 10.00 μmol/L insulin significantly increased the protein expression of APP and CTF (P < 0.05) and also the expression of BACE1, a key enzyme for APP metabolism (P < 0.05). The results of ELISA demonstrated that the expression level of Aβ42 increased significantly in the cells following treatment with 1.00 and 10.00 μmol/L insulin (P < 0.05). The protein microarray data identified GSK3β as a potential target of insulin. Western blot analysis showed that the expression of p-AKT and p-GSK3β proteins was down-regulated following insulin treatment, but the differences were not statistically significant (P>0.05). Conclusion Insulin promotes the metabolism of APP into CTF and Aβ42, which play certain rolesin pathogenesis of AD.
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