The Dual GLP-1/GIP Receptor Agonist DA4-JC Shows Superior Protective Properties Compared to the GLP-1 Analogue Liraglutide in the APP/PS1 Mouse Model of Alzheimer's Disease.

Alzheimer's disease (AD) is a neurodegenerative disorder for which there is no cure. Here, we test a dual GLP-1/GIP receptor agonist (DA4-JC) that has a cell penetrating sequence added to enhance blood-brain barrier penetration. We show in a receptor activity study that DA4-JC has balanced activity on both GLP-1 and GIP receptors but not on GLP-2 or Glucagon receptors. A dose-response study in the APP/PS1 mouse model of AD showed both a dose-dependent drug effect on the inflammation response and the reduction of amyloid plaques in the brain. When comparing DA4-JC with the GLP-1 analogue liraglutide at equal doses of 10nmol/kg bw ip. once-daily for 8 weeks, DA4-JC was more effective in reversing memory loss, enhancing synaptic plasticity (LTP) in the hippocampus, reducing amyloid plaques and lowering pro-inflammatory cytokine levels in the brain. The results suggest that DA4-JC may be a novel treatment for AD.

Liraglutide and a lipidized analog of prolactin-releasing peptide show neuroprotective effects in a mouse model of ß-amyloid pathology.

Obesity and type 2 diabetes mellitus (T2DM) are important risk factors for Alzheimer's disease (AD). Drugs originally developed for T2DM treatment, e.g., analog of glucagon-like peptide 1 liraglutide, have shown neuroprotective effects in mouse models of AD. We previously examined the neuroprotective properties of palm11-PrRP31, an anorexigenic and glucose-lowering analog of prolactin-releasing peptide, in a mouse model of AD-like Tau pathology, THY-Tau22 mice. Here, we demonstrate the neuroprotective effects of palm11-PrRP31 in double transgenic APP/PS1 mice, a model of AD-like ß-amyloid (Aß) pathology. The 7-8-month-old APP/PS1 male mice were subcutaneously injected with liraglutide or palm11-PrRP31 for 2 months. Both the liraglutide and palm11-PrRP31 treatments reduced the Aß plaque load in the hippocampus. Palm11-PrRP31 also significantly reduced hippocampal microgliosis, consistent with our observations of a reduced Aß plaque load, and reduced cortical astrocytosis, similar to the treatment with liraglutide. Palm11-PrRP31 also tended to increase neurogenesis, as indicated by the number of doublecortin-positive cells in the hippocampus. After the treatment with both anorexigenic compounds, we observed a significant decrease in Tau phosphorylation at Thr231, one of the first epitopes phosphorylated in AD. This effect was probably caused by elevated activity of protein phosphatase 2A subunit C, the main Tau phosphatase. Both liraglutide and palm11-PrRP31 reduced the levels of caspase 3, which has multiple roles in the pathogenesis of AD. Palm11-PrRP31 increased protein levels of the pre-synaptic marker synaptophysin, suggesting that palm11-PrRP31 might help preserve synapses. These results indicate that palm11-PrRP31 has promising potential for the treatment of neurodegenerative diseases.

The Novel DA-CH3 Dual Incretin Restores Endoplasmic Reticulum Stress and Autophagy Impairments to Attenuate Alzheimer-Like Pathology and Cognitive Decrements in the APPSWE/PS1ΔE9 Mouse Model.

Alzheimer's disease (AD) afflicts more than 46.8 million people worldwide, with a newly diagnosed case every 3 seconds and no remission in the disease progression. The discovery of disease-modifying drugs is now on the summit of the neuropharmacological research priorities. The long-lasting derivatives of the insulinotropic incretin hormones-glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP)-have repeatedly been shown to cross the blood-brain barrier and counteract an array of deleterious effects across a range of experimental models of neuronal degeneration. Clinical trials for the efficacy of GLP-1 agonists in Alzheimer's and Parkinson's diseases have revealed beneficial effects of these anti-diabetic agents in halting neuronal degeneration progression. Herein, we examine whether the chronic treatment with the novel dual GLP-1/GIP receptor agonist DA-CH3 can restore the cognitive decline and AD-like cerebral pathology of the APPSWE/PS1ΔE9 mouse model at the age of 10 months old. We report that once-a-daily, eight-week intraperitoneal administration of 25 nmol/kg of the novel DA-CH3 dual-incretin analog rescues the spatial acquisition and memory impairments of this murine model that corresponds to the attenuation of the excessive plaque deposition, gliosis and synaptic damage in the APPSWE/PS1ΔE9 brain. The amelioration of the AD-related pathology reflects the resolution of the endoplasmic-reticulum stress and derailed autophagy that both lay downstream of the rectified Akt signaling. Collectively, our findings endorse the beneficial effects of the incretin-based therapeutic approaches for the neurotrophic support of the AD brain and for the first time associate the incretin-induced neuroprotection with the proteostasis machinery in vivo.

A novel GLP-1/GIP dual receptor agonist protects from 6-OHDA lesion in a rat model of Parkinson's disease.

The incretins glucagon-like peptide 1 (GLP-1) and glucose dependent insulinotropic polypeptide (GIP) are growth factors that have shown neuroprotective effects in animal models of Parkinson's and Alzheimer's disease. In addition, the GLP-1 mimetic exendin-4 has shown protective effects in a clinical trial in Parkinson's disease (PD) patients. GLP-1 analogues are currently on the market as treatments for type II diabetes. We previously showed that the novel dual agonist (DA-JC1) was effective in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD. Here we demonstrate that DA-JC1 is neuroprotective in the 6-OHDA brain lesion rat model of PD. When treating rats for 6 weeks with DA-JC1 at 25 nmol/kg ip once-daily, motor activity as tested in the Rotarod and in the open field was much improved. In the amphetamine and apomorphine circling behaviour tests, the 6-OHDA induced impairments were much reduced by the DA-JC1 treatment. The number of TH positive dopaminergic neurons in the substantia nigra was decreased by 6-OHDA lesion and was increased by DA-JC1 treatment. Dopamine levels in the basal ganglia were reduced by 6-OHDA lesion and increased by DA-JC1. In western blot analysis, levels of the growth factor GDNF and pAkt/CREB cell signaling was enhanced by DA-JC1. The autophagy marker Beclin1 was also activated by the drug. The results demonstrate that dual GLP-1/GIP receptor agonists show promise as a novel treatment for PD.

Val(8)GLP-1 rescues synaptic plasticity and reduces dense core plaques in APP/PS1 mice.

Diabetes is a risk factor for Alzheimer's disease. We tested the effects of Val(8)GLP-1, an enzyme-resistant analogue of the incretin hormone glucagon-like peptide 1 originally developed to treat diabetes in a mouse model of Alzheimer's disease that expresses mutated amyloid precursor protein (APP) and presenilin-1. We tested long term potentiation (LTP) of synaptic plasticity, inflammation response, and plaque formation. Val(8)GLP-1 crosses the blood-brain barrier when administered via intraperitoneal injection. Val(8)GLP-1 protected LTP in 9- and 18-month-old Alzheimer's disease mice when given for 3 weeks at 25 nmol/kg intraperitoneally. LTP was also enhanced in 18-month-old wild type mice, indicating that Val(8)GLP-1 also ameliorates age-related synaptic degenerative processes. Paired-pulse facilitation was also enhanced. The number of beta-amyloid plaques and microglia activation in the cortex increased with age but was not reduced by Val(8)GLP-1. In 18-month-old mice, however, the number of Congo red positive dense-core amyloid plaques was reduced. Treatment with Val(8)GLP-1 might prevent or delay neurodegenerative processes.

Synaptic plasticity in the hippocampus of a APP/PS1 mouse model of Alzheimer's disease is impaired in old but not young mice.

BACKGROUND: Alzheimer disease (AD) is a neurodegenerative disorder for which there is no cure. We have investigated synaptic plasticity in area CA1 in a novel AD mouse model (APPPS1-21) which expresses the Swedish mutation of APP and the L166P mutation of human PS-1. This model shows initial plaque formation at 2 months in the neocortex and 4 months in the hippocampus and displays beta-amyloid-associated pathologies and learning impairments. METHODOLOGY/PRINCIPAL FINDINGS: We tested long-term potentiation (LTP) and short term potentiation (paired-pulse facilitation, PPF) of synaptic transmission in vivo in area CA1 of the hippocampus. There was no difference in LTP or PPF at 4-5 months of age in APPPS1-21 mice compared to littermate controls. At 6 months of age there was also no difference in LTP but APPPS1-21 mice showed slightly increased PPF (p<0.03). In 8 months old mice, LTP was greatly impaired in APPPS-21 animals (p<0.0001) while PPF was not changed. At 15 months of age, APPPS1-21 mice showed again impaired LTP compared to littermate controls (p<0.005), and PPF was also significantly reduced at 80 ms (p<0.005) and 160 ms (p<0.01) interstimulus interval. Immunohistological analysis showed only modest amyloid deposition in the hippocampus at 4 and 6 months with a robust increase up to 15 months of age. CONCLUSIONS: Our results suggest that increased formation and aggregation of beta amyloid with aging is responsible for the impaired LTP with aging in this mouse model, while the transient increase of PPF at 6 months of age is caused by some other mechanism.

Soluble beta-amyloid[25-35] reversibly impairs hippocampal synaptic plasticity and spatial learning.

Beta-amyloid is a peptide that appears to be responsible for cognitive impairments in patients with Alzheimer's disease. Recent research shows that soluble oligomers of beta-amyloid affect synaptic activity and learning, well before any amyloid has aggregated into plaques. Here we show that injection of 3x10 nmol amyloid [25-35] i.c.v. transiently impairs learning of a radial arm maze and the induction of hippocampal long-term potentiation. Furthermore, hippocampal field potentials had been recorded over a period of 21 days and were found to be reduced from day 9 to day 15 (P<0.001), after which the reduction had reversed to baseline. In the spatial 8-arm learning task, animals had to learn which 3 out of 8 arms had been baited. A significant impairment of working and long-term memory was observed at day 12-20 (P<0.001), but not at days 3-11 or 20-28. Long-term potentiation induction in the hippocampus area CA1 was also impaired at day 12-20 (P<0.001), but not at other days. A scrambled peptide sequence version of amyloid did not have any effect. These results emphasise that soluble amyloid fragments already have detrimental effects on brain function well before aggregation occurs. They also show that these effects are reversible, and therefore most likely do not involve neuronal death. The neurodegeneration seen in Alzheimer's disease brains is most likely a downstream effect, linked to processes such as immune response activation and free radical production. These results suggest that treatment at very early stages of Alzheimer's disease could prevent later irreversible neuronal degeneration.

Impairments of hippocampal synaptic plasticity induced by aggregated beta-amyloid (25-35) are dependent on stimulation-protocol and genetic background.

The aggregation of beta-amyloid to plaques in the brain is one of the hallmarks of Alzheimer disease (AD). Numerous studies have tried to elucidate to what degree amyloid peptides play a role in the neurodegenerative developments seen in AD. While most studies report an effect of amyloid on neural activity and cognitive abilities of rodents, there have been many inconsistencies in the results. This study investigated to what degree the different genetic backgrounds affect the outcome of beta-amyloid fragment (25-35) on synaptic plasticity in vivo in the rat hippocampus. Two strains, Wistar and Lister hooded rats, were tested. In addition, the effects of a strong (600 stimuli) and a weak stimulation protocol (100 stimuli) on impairments of LTP were analysed. Furthermore, since the state of amyloid aggregation appears to play a role in the induction of toxic processes, it was tested by dual polarisation interferometry to what degree and at what speed beta-amyloid (25-35) can aggregate in vitro. It was found that 100 nmol beta-amyloid (25-35) injected icv did impair LTP in Wistar rats when using the weak but not the strong stimulation protocol (P < 0.001). One-hundred nano mole of the reverse sequence amyloid (35-25) had no effect. LTP in Lister Hooded rats was not impaired by amyloid at any stimulation protocol. The aggregation studies showed that amyloid (25-35) aggregated within hours, while amyloid (35-25) did not. These results show that the genetic background and the stimulation protocol are important variables that greatly influence the experimental outcome. The fact that amyloid (25-35) aggregated quickly and showed neurophysiological effects, while amyloid (35-25) did not aggregate and did not show any effects indicates that the state of aggregation plays an important role in the physiological effects.

Abeta42-driven cerebral amyloidosis in transgenic mice reveals early and robust pathology.

We have generated a novel transgenic mouse model on a C57BL/6J genetic background that coexpresses KM670/671NL mutated amyloid precursor protein and L166P mutated presenilin 1 under the control of a neuron-specific Thy1 promoter element (APPPS1 mice). Cerebral amyloidosis starts at 6-8 weeks and the ratio of human amyloid (A)beta42 to Abeta40 is 1.5 and 5 in pre-depositing and amyloid-depositing mice, respectively. Consistent with this ratio, extensive congophilic parenchymal amyloid but minimal amyloid angiopathy is observed. Amyloid-associated pathologies include dystrophic synaptic boutons, hyperphosphorylated tau-positive neuritic structures and robust gliosis, with neocortical microglia number increasing threefold from 1 to 8 months of age. Global neocortical neuron loss is not apparent up to 8 months of age, but local neuron loss in the dentate gyrus is observed. Because of the early onset of amyloid lesions, the defined genetic background of the model and the facile breeding characteristics, APPPS1 mice are well suited for studying therapeutic strategies and the pathomechanism of amyloidosis by cross-breeding to other genetically engineered mouse models.

Inactivation of the rat dorsal striatum impairs performance in spatial tasks and alters hippocampal theta in the freely moving rat.

We analysed the interaction between the dorsal striatum (motor coordination and planning) and the hippocampus (sensory information processing and integration) during performance of goal-directed tasks. The performance of rats that had been injected with different doses of the D(2)-antagonist Sulpiride into the dorsal striatum was tested in an egocentric 4-arm maze task that tests striatal functions. Furthermore, hippocampal EEGs were recorded before, during and after inactivation of the dorsal striatum via injections of Sulpiride of rats that were performing a continuous alternation task. Injection of 5 microl of 100 mM Sulpiride increased the number of errors committed in the egocentric 4-arm maze (p < 0.01), indicating that the dorsal striatum is involved in motor control and motor memory recall in such a task. In the recording study, the same dose of Sulpiride injected into the dorsal striatum had powerful effects on the hippocampal EEG. The main activity in the theta range (5-10 Hz) was shifted from higher frequencies in the 8-10 Hz range to lower frequencies in the 5-7 Hz range (p < 0.005). The impairment in the behavioural egocentric task after Sulpiride injection, and the effects of Sulpiride on hippocampal theta shows that there is a functional interaction between the dorsal striatum and the hippocampus. While the dorsal striatum coordinates the execution of complex motor programs, the hippocampus integrates spatial and other sensory information required for the planning and execution of goal-directed movements.