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Glucagon-like-peptide-1 is an incretin hormone that also has neuroprotective properties. Here we analyse where glucagon-like-peptide-1 receptors are expressed in the brain. The receptor is found only on neurons, not on glia cells. The pyramidal cell layer of the CA region and the granule cell layer of the dentate gyrus in the hippocampus show intense staining. In the neocortex, larger pyramidal neurons express the receptor. In the cerebellum, only Purkinje neurons express the receptor. Dendrites of larger neurons were stained; in particular, pyramidal cells in area CA and dendrites of Purkinje cells. The fact that the receptor is located on neurons and dendrites suggests that the neuroprotective action is caused by the modulation of neuronal excitation.

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One of the symptoms of diabetes is the progressive development of neuropathies. One mechanism to replace neurons in the CNS is through the activation of stem cells and neuronal progenitor cells. We have tested the effects of the novel GLP-1 mimetics exenatide (exendin-4; Byetta) and liraglutide (NN2211; Victoza), which are already on the market as treatments for type 2 diabetes, on the proliferation rate of progenitor cells and differentiation into neurons in the dentate gyrus of brains of mouse models of diabetes. GLP-1 analogues were injected subcutaneously for 4, 6, or 10 weeks once daily in three mouse models of diabetes: ob/ob mice, db/db mice, or high-fat-diet-fed mice. Twenty-four hours before perfusion, animals were injected with 5'-bromo-2'-deoxyuridine (BrdU) to mark dividing progenitor cells. By using immunohistochemistry and stereological methods, the number of progenitor cells or doublecortin-positive young neurons in the dentate gyrus was estimated. We found that, in all three mouse models, progenitor cell division was enhanced compared with nondiabetic controls after chronic i.p. injection of either liraglutide or exendin-4 by 100-150% (P < 0.001). We also found an increase in young neurons in the DG of high-fat-diet-fed mice after drug treatment (P < 0.001). The GLP-1 receptor antagonist exendin(9-36) reduced progenitor cell proliferation in these mice. The results demonstrate that GLP-1 mimetics show promise as a treatment for neurodegenerative diseases such as Alzheimer's disease, because these novel drugs cross the blood-brain barrier and increase neuroneogenesis.

BackgroundAlzheimer 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 β−amyloid-associated pathologies and learning impairments.Methodology/Principal FindingsWe 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.ConclusionsOur 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.

Beta-amyloid (Aβ) oligomers contribute to the pathophysiology of Alzheimer disease (AD), and metabotropic glutamate receptor 5 (mGluR5) has been shown to act as a receptor for both Aβ oligomers and cellular prion proteins. Furthermore, the genetic deletion of mGluR5 in an APPswe/PS1ΔE9 mouse model of AD improves cognitive function and reduces Aβ plaques and Aβ oligomer concentrations. Here, we show that chronic administration of the orally bioavailable mGluR5-selective negative allosteric modulator CTEP, which is similar in structure, potency, and selectivity to Basimglurant (RO4917523), which is currently in phase II clinical development for major depressive disorder and fragile X syndrome, reverses cognitive decline in APPswe/PS1ΔE9 mice and reduces Aβ plaque deposition and soluble Aβ oligomer concentrations in both APPswe/PS1ΔE9 and 3xTg-AD male mice. These findings suggest that CTEP or its analogue Basimglutant might potentially be an effective therapeutic for the treatment of AD patients.

BackgroundAlzheimer’s disease (AD) pathology occurs in part as the result of excessive production of β-amyloid (Aβ). Metabotropic glutamate receptor 5 (mGluR5) is now considered a receptor for Aβ and consequently contributes to pathogenic Aβ signaling in AD.ResultsGenetic deletion of mGluR5 rescues the spatial learning deficits observed in APPswe/PS1ΔE9 AD mice. Moreover, both Aβ oligomer formation and Aβ plaque number are reduced in APPswe/PS1ΔE9 mice lacking mGluR5 expression. In addition to the observed increase in Aβ oligomers and plaques in APPswe/PS1ΔE9 mice, we found that both mTOR phosphorylation and fragile X mental retardation protein (FMRP) expression were increased in these mice. Genetic deletion of mGluR5 reduced Aβ oligomers, plaques, mTOR phosphorylation and FMRP expression in APPswe/PS1ΔE9 mice.ConclusionsThus, we propose that Aβ activation of mGluR5 appears to initiate a positive feedback loop resulting in increased Aβ formation and AD pathology in APPswe/PS1ΔE9 mice via mechanism that is regulated by FMRP.

Mixed methods research—i.e., research that draws on both qualitative and qualitative methods in varying configurations—is well suited to address the increasing complexity of public health problems and their solutions. This review focuses specifically on innovations in mixed methods evaluations of intervention, program or policy (i.e., practice) effectiveness and implementation. The article begins with an overview of the structure, function and process of different mixed methods designs and then provides illustrations of their use in effectiveness studies, implementation studies, and combined effectiveness-implementation hybrid studies. The article then examines four specific innovations: procedures for transforming (or “quantitizing”) qualitative data, applying rapid assessment and analysis procedures in the context of mixed methods studies, development of measures to assess implementation outcomes, and strategies for conducting both random and purposive sampling particularly in implementation-focused evaluation research. The article concludes with an assessment of challenges to integrating qualitative and quantitative data in evaluation research.