Neuroprotective effects of a triple GLP-1/GIP/glucagon receptor agonist in the APP/PS1 transgenic mouse model of Alzheimer's disease

doi:10.1016/j.brainres.2017.10.012

Brain Research

Volume 1678, 1 January 2018, Pages 64-74

https://doi.org/10.1016/j.brainres.2017.10.012 Get rights and content

Highlights

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A novel triple GLP-1/GIP/glucagon receptor agonist has been developed.
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The drug improves memory formation in a mouse model of Alzheimer’s disease.
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Amyloid plaque load, inflammation and oxidative stress is reduced by the drug.
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Neurogenesis, BDNF expression and synapse numbers are increased in the brain.

Abstract

Type 2 diabetes mellitus (T2DM) is a risk factor for Alzheimer disease (AD). Previous studies have shown that the incretin hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) that have anti-diabetic properties show very promising effects in animal models of AD. Glucagon (Gcg) is a hormone and growth-factor, and the Gcg receptor is expressed in the brain. Here we test the effects of a triple receptor agonist (TA), which activates GIP-1, GIP and glucagon receptors at the same time. In the present study, the effects of the TA were evaluated in the APP/PS1 transgenic mouse model of AD. The TA was injected once-daily (10 nmol/kg i.p.) for two months. The results showed that treatment with TA significantly reversed the memory deficit in the APP/PS1 mice in a spatial water maze test. Moreover, the drug reduced levels of the mitochondrial pro-apoptotic signaling molecule BAX, increased the anti-apoptotic signaling molecule Bcl-2 and enhanced the levels of BDNF, a key growth factor that protects synaptic function. Levels of synaptophysin were enhanced, demonstrating protection from synaptic loss that is observed in AD. Neurogenesis in the dentate gyrus was furthermore enhanced as shown in the increase of doublecortin positive cells. Furthermore, TA treatment reduced the total amount of β-amyloid, reduced neuroinflammation (activated microglia and astrocytes), and oxidative stress in the cortex and hippocampus. Thus, these findings show that novel TAs are a promising lead for the design of future treatment strategies in AD.

Introduction

Alzheimer’s disease (AD), is a progressive neurodegenerative disease, characterized clinically by progressive memory loss, cognitive decline, and aberrant behavior [1]. Currently, there is no treatment can improve this condition. Epidemiological studies have shown that type 2 diabetes mellitus (T2DM) is a risk factor for Alzheimer disease (AD) (Luchsinger et al., 2004, Ohara et al., 2011). The underlying mechanism is most likely that insulin signaling is impaired in the brains of AD patients (Moloney et al., 2010, Talbot et al., 2012). This motivated research in drugs that have shown good effects in treating diabetes to investigate if they could be helpful in treating AD as well. Previous studies have shown that the incretin hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) can play a neuroprotective role in the brain and show very promising effects in animal models of AD (Duffy and Holscher, 2013, Faivre and Holscher, 2013b, Li et al., 2010, McClean et al., 2011, McClean and Holscher, 2014). Glucagon (Gcg) is a hormone and growth-factor, and the Gcg receptor is expressed in the brain (Hoosein and Gurd, 1984, Mayo et al., 2003). Activation of the receptor can activate neuronal activity and cellular Ca²⁺ signaling and may have neuroprotective properties (Ayush et al., 2015). Here we test the effects of a triple receptor agonist (TA), which activates GIP-1, GIP and glucagon receptors at the same time. This novel drug has been developed as a potential treatment for diabetes (Finan et al., 2015). No studies have been published that test the neuroprotective effects of this novel drug. We therefore tested this promising TA in the APP_SWE/PS1_dE9 mouse model of AD. This mouse model recapitulates some of the hallmarks of AD, such as memory loss, synaptic loss, reduction of synaptic plasticity, reduction of neurogenesis in the dentate gyrus, chronic inflammation in the brain, and formation of amyloid plaques in the brain (Duffy and Holscher, 2013, Goto et al., 2008, Hamilton et al., 2011, Hamilton and Holscher, 2012, McClean et al., 2011). We tested the effects of TA in this transgenic mouse model and evaluated the neuroprotective effects. We analyzed memory formation, hippocampal neurogenesis, the expression levels of Brain Derived Neurotrophic Factor (BDNF) (Blurton-Jones et al., 2009), mitochondrial apoptosis signaling proteins, neuroinflammation and oxidative stress levels.

Section snippets

TA-treatment improved the learning and memory impairment of APP/PS1 mice in the water maze

A two-way ANOVA found a significant difference between groups (p < 0.0001) and over time (p < 0.001). In the Morris water test, it was observed that the control mice, APP/PS1 mice and TA-treated APP/PS1 mice had a similar escape latency (P > 0.05). On day 5, the average escape distance in searching for the hidden platform in the APP/PS1 mice was significantly longer than that in the control mice (P < 0.05). Compared to the APP/PS1 group, the TA-treated APP/PS1 group’s average escape distance

Discussion

The results demonstrate for the first time that the novel GLP-1/GIP/Gcg receptor agonist has clear neuroprotective effects in the APP/PS1 mouse model of AD. Memory formation in the spatial water maze task was improved by the drug, and the amyloid plaque load in the cortex and hippocampus was reduced. This result confirms our previous findings that single GLP-1 or GIP analogues can protect from memory loss in this mouse model of AD (Faivre and Holscher, 2013a, Faivre and Holscher, 2013b, McClean

Peptide and chemicals

The triple GLP-1/GIP/Gcg used in this study was synthesized by China Peptides Co, Ltd. (Shanghai, China) to 95% purity. The identity and purity of the peptide was confirmed by reversed-phase HPLC and characterized using matrix assisted laser resorption/ionization time of flight (MALDI–TOF) mass spectrometry. The peptide was stored in dry form and dissolved in double-distilled water containing 0.9% NaCl₂ before experiments. A Bi-cinchoninicacid (BCA) protein assay kit was purchased from Apply

Contributors

JT, WL and YL conducted the experiments, LL and CH conceived the experiment and wrote the manuscript.

Acknowledgements

This work was funded by the Ministry of Human Resources and Social Security, Shanxi Province [(2010)255], by a Shanxi Scholarship Council of China, and supported by a grant from the Alzheimer Society UK. The authors declare no conflict of interest

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Research reportNeuroprotective effects of a triple GLP-1/GIP/glucagon receptor agonist in the APP/PS1 transgenic mouse model of Alzheimer's disease

Highlights

Abstract

Introduction

Section snippets

TA-treatment improved the learning and memory impairment of APP/PS1 mice in the water maze

Discussion

Peptide and chemicals

Contributors

Acknowledgements

Neurobiol. Aging

Pharmacol. Ther.

Biochem. Biophys. Res. Commun.

Cell Metab.

Pharmacol. Ther.

Neuroscience

Eur. J. Pharmacol.

Eur. J. Pharmacol.

Brain Res.

Neuropharmacology

Brain Res.

Chem. Biol. Interact.

J. Biol. Chem.

Neuropharmacology

Neurobiol. Aging

Eur. J. Pharmacol.

Eur. J. Cell Biol.

Exenatide once weekly versus placebo in Parkinson’s disease: a randomised, double-blind, placebo-controlled trial

The Lancet

Exenatide and the treatment of patients with Parkinson’s disease

J. Clin. Invest.

Motor and cognitive advantages persist 12 months after exenatide exposure in Parkinson’s disease

J. Parkinson’s Dis.

Involvement of peroxisome proliferator-activated receptor beta/delta (PPAR beta/delta) in BDNF signaling during aging and in Alzheimer disease: possible role of 4-hydroxynonenal (4-HNE)

Cell Cycle

Neural stem cells improve cognition via BDNF in a transgenic model of Alzheimer disease

Proc. Natl. Acad. Sci. U.S.A.

A novel dual GLP-1 and GIP incretin receptor agonist is neuroprotective in a mouse model of Parkinson’s disease by reducing chronic inflammation in the brain

Neuroreport

Tumor necrosis factor-induced cerebral insulin resistance in Alzheimer's disease links numerous treatment rationales

Pharmacol. Rev.

D-Ala2GIP facilitated synaptic plasticity and reduces plaque load in aged wild type mice and in an Alzheimer's disease mouse model

J. Alzheimers Dis.

Research report
Neuroprotective effects of a triple GLP-1/GIP/glucagon receptor agonist in the APP/PS1 transgenic mouse model of Alzheimer's disease

Motor and cognitive advantages persist 12 months after exenatide exposure in Parkinson’s disease