Protective Effects of DAla2-GIP-GLU-PAL against Cognitive Deficits and Amyloid Deposition in APP/PS1 AD Mice Associated with Reduction of Neuroinflammation

Abstract Background Alzhermer’s disease (AD) is a neurodegenerative disease characterized by progressive decline in cognitive function and high-density deposition of amyloid-β (Aβ) plaques in the brain. Type 2 diabetes mellitus (T2DM) is an important risk factor for AD. Glucose-dependent insulinotropic polypeptide (GIP) has been identified to be effective in T2DM treatment and neuroprotection. The present study further investigated the neuroprotective effects of a novel long lasting GIP analogue DAla2GIP-Glu-PAL in 9-month-old APP swe /PS1 dE9 (APP/PS1) AD mice. Methods Multiple behavioral tests including new object recognition, Y maze and Morris water maze were performed to examine the cognitive function of mice. In vivo hippocampal late-phase long-term potentiation (L-LTP) was recorded to reflect synaptic plasticity. Immunohistochemistry and immunofluorescence were used to examine the Aβ plaques and neuroinflammation in the brain. The expression levels of cAMP, S99 p-PKA, S133 p-CREB, S468 NF-κBp65 and IL-1β were detected by western blotting or ELISA. Results DAla2GIP-Glu-PAL effectively improved cognitive behaviors and synaptic plasticity of APP/PS1 mice, with increased new object recognition, spontaneous alternation and target quadrant swimming time, as well as enhanced in vivo hippocampal L-LTP. DAla2GIP-Glu-PAL significantly reduced Aβ deposition and inhibited astrocyte proliferation, IL-1β secretion and NF-κB activation. Besides, . DAla2GIP-Glu-PAL also up-regulated cAMP/PKA/CREB signal transduction in the hippocampus of APP/PS1 mice. Conclusion DAla2GIP-Glu-PAL improves cognitive behaviors, long-term synaptic plasticity and pathological damages in APP/PS1 mice, which are associated with the reduction of neuroinflammation and the up-regulation of cAMP/PKA/CREB signaling in the hippocampus. This study suggests a potential benefit of DAla2GIP-Glu-PAL in the treatment of AD.