Liraglutide improves cognition function in streptozotocin-induced diabetic rats by downregulating β-secretase and γ-secretase and alleviating oxidative stress in HT-22 cells

Diabetes has been regarded as an independent risk factor for Alzheimer's disease (AD). Liraglutide could improve cognition in AD mouse models, but its precise mechanism remains unclear. In this study, we used STZ-induced diabetic rats and HT-22 cells to investigate the effects of liraglutide. The MWM test, MTT assay, ELISA, western blot, and immunofluorescence were used in this research. Diabetic rats induced by STZ displayed a longer escape latency and entered the target zone less frequently (p < 0.05) in the MWM test. Intraperitoneal injection of liraglutide improved the cognition of diabetic rats (p < 0.05) and reduced Aβ42 expression in the hippocampus (p < 0.05). In vivo experiments showed that HT-22 cell viability decreased in the HG group, but liraglutide (100 nmol/L and 1 μmol/L) enhanced HT-22 cell viability (p < 0.05). Oxidative stress markers were upregulated in HT-22 cells in the HG group, while liraglutide treatment significantly reduced these markers (p < 0.05). Western blot and immunofluorescence analyses demonstrated increased levels of Aβ, BACE1, and γ-secretase in HT-22 cells in the HG group (p < 0.05), whereas these levels were reduced in the liraglutide treatment group (p < 0.05). These effects were reversed by the nuclear factor kappa B (NF-κB) and extracellular signal-regulated kinase 1/2 (ERK1/2) inhibitors (p < 0.05). These findings suggest that liraglutide improved the cognition of diabetic rats and might exert its protective effects by reducing oxidative stress, downregulating BACE1 and γ-secretase expression, and decreasing Aβ deposition via the NF-κB and ERK1/2 pathways.