Cholecystokinin (CCK): a neuromodulator with therapeutic potential in Alzheimer's and Parkinson's disease.

Cholecystokinin (CCK) is a neuropeptide modulating digestion, glucose levels, neurotransmitters and memory. Recent studies suggest that CCK exhibits neuroprotective effects in Alzheimer's disease (AD) and Parkinson's disease (PD). Thus, we review the physiological function and therapeutic potential of CCK. The neuropeptide facilitates hippocampal glutamate release and gates GABAergic basket cell activity, which improves declarative memory acquisition, but inhibits consolidation. Cortical CCK alters recognition memory and enhances audio-visual processing. By stimulating CCK-1 receptors (CCK-1Rs), sulphated CCK-8 elicits dopamine release in the substantia nigra and striatum. In the mesolimbic pathway, CCK release is triggered by dopamine and terminates reward responses via CCK-2Rs. Importantly, activation of hippocampal and nigral CCK-2Rs is neuroprotective by evoking AMPK activation, expression of mitochondrial fusion modulators and autophagy. Other benefits include vagus nerve/CCK-1R-mediated expression of brain-derived neurotrophic factor, intestinal protection and suppression of inflammation. We also discuss caveats and the therapeutic combination of CCK with other peptide hormones.

Liraglutide Reduces Alcohol Consumption, Anxiety, Memory Impairment, and Synapse Loss in Alcohol Dependent Mice.

Glucagon-like peptide 1 (GLP-1) analogues have been commercialized for the management of type 2 diabetes. Recent studies have underscored GLP-1's role as a modulator of alcohol-related behavior. However, the role of the GLP-1 analogue liraglutide on alcohol-withdrawal responses have not been fully elucidated. Liraglutide binds to the G-protein-coupled receptor and activates an adenylyl cyclase and the associated classic growth factor signaling pathway, which acts growth factor-like and neuroprotective properties. The underlying neurobiological mechanisms of liraglutide on alcohol withdrawal remains unknown. This study endeavored to explore the effects of liraglutide on the emotion and memory ability of alcohol-withdrawal mice, and synaptic morphology in the medial prefrontal cortex (mPFC) and the hippocampus (HP), and thus affects the relapse-like drinking of alcohol-withdrawal mice. The alcohol-withdrawal group was reintroduced to a 20% v/v alcohol and water through the two-bottle choice for four consecutive days, a period referred to as alcohol re-drinking. Male C57BL/6J mice were exposed to a regimen of 20% alcohol and water for a duration of 6 weeks. This regimen established the two-bottle choice model of alcohol exposure. Learning capabilities, memory proficiency, and anxiety-like behavior were evaluated using the Morris water maze, open field, and elevated plus maze paradigms. Furthermore, synaptic morphology and the levels of synaptic transport-related proteins were assessed via Golgi staining and Western Blot analysis after a two-week alcohol deprivation period. Alcohol re-drinking of alcohol-withdrawal mice was also evaluated using a two-bottle choice paradigm. Our findings indicate that liraglutide can substantially decrease alcohol consumption and preference (p < 0.05) in the alcohol group and enhance learning and memory performance (p < 0.01), as well as alleviate anxiety-like behavior (p < 0.01) of alcohol-withdrawal mice. Alcohol consumption led to a reduction in dendritic spine density in the mPFC and HP, which was restored to normal levels by liraglutide (p < 0.001). Furthermore, liraglutide was found to augment the levels of synaptic transport-related proteins in mice subjected to alcohol withdrawal (p < 0.01). The study findings corroborate that liraglutide has the potential to mitigate alcohol consumption and ameliorate the memory impairments and anxiety induced by alcohol withdrawal. The therapeutic efficacy of liraglutide might be attributed to its role in counteracting synapse loss in the mPFC and HP regions and thus prevented relapse-like drinking in alcohol-withdrawal mice.

MCU knockdown in hippocampal neurons improves memory performance of an Alzheimer's disease mouse model.

Alzheimer's disease (AD) is a progressive and degenerative disorder accompanied by cognitive decline, which could be promoted by mitochondrial dysfunction induced by mitochondrial Ca 2+ (mCa 2+) homeostasis Mitochondrial calcium uniporter (MCU), a key channel of mCa 2+ uptake, may be a target for AD treatment. In the present study, we reveal for the first time that MCU knockdown in hippocampal neurons improves the memory performance of APP/PS1/tau mice through radial arm maze task. Western blot analysis, transmission electron microscopy (TEM), Golgi staining, immunohistochemistry (IHC) and ELISA results demonstrate that MCU knockdown in hippocampal neurons upregulates the levels of postsynaptic density protein 95 (PSD95) and synaptophysin (SYP), and increases the numbers of synapses and dendritic spines. Meanwhile, MCU knockdown in hippocampal neurons decreases the neuroinflammatory response induced by astrogliosis and high levels of IL-1ß and TNF-α, and improves the PINK1-Parkin mitophagy signaling pathway and increases the level of Beclin-1 but decreases the level of P62. In addition, MCU knockdown in hippocampal neurons recovers the average volume and number of mitochondria. These data confirm that MCU knockdown in hippocampal neurons improves the memory performance of APP/PS1/tau mice through ameliorating the synapse structure and function, relieving the inflammation response and recovering mitophagy, indicating that MCU inhibition has the potential to be developed as a novel therapy for AD.

The novel GLP-1/GIP dual agonist DA3-CH is more effective than liraglutide in reducing endoplasmic reticulum stress in diabetic rats with cerebral ischemia-reperfusion injury.

BACKGROUND AND AIMS: Diabetes is one of the most important risk factors and comorbidities of ischemic stroke. Endoplasmic reticulum stress (ERS) is considered to be the major injury mechanism of ischemic stroke with diabetes. Studies have found that incretin can inhibit ERS in ischemia-reperfusion injury of the liver and heart. We aimed to explore the effects of GLP-1/GIP double agonist DA3-CH and GLP-1 single agonist liraglutide on ERS and apoptosis in diabetic rats with cerebral ischemia-reperfusion injury. METHODS AND RESULTS: 72 Sprague-Dawley (SD) male rats were randomly divided into 4 groups: ① blank group (Sham group, n = 18); model group (Saline group, n = 18); DA3 treatment group (DA3 group, n = 18); liraglutide treatment group (Lir group, n = 18). The Sham group was not given any treatment and was only raised in the same environment as the other groups. The remaining 3 groups used STZ-induced diabetes models. After the successful membrane formation of diabetes, DA3-CH and liraglutide (10 mmol/kg, once-daily for 14 days) were injected intraperitoneally. Thereafter, rats were subjected to middle cerebral artery occlusion followed by 24-h reperfusion. Animals were evaluated for neurologic deficit score, infarct volume, and biomarker analyses of the brain after ischemia. The DA3-CH-treated and liraglutide-treated groups showed significantly reduced scores of neurological dysfunction and cerebral infarction size, and reduced the expression of ERS markers GRP78, CHOP and Caspase-12, and the expression of apoptosis marker bax. Anti-apoptotic markers bcl-2 and neuronal numbers increased significantly. CONCLUSIONS: DA3-CH and liraglutide have obvious neuroprotective effects in a rat model of cerebral ischemia-reperfusion injury with diabetes, which can reduce the infarct size and the neurological deficit score. Their exert neuroprotective effects in a rat model of cerebral ischemia-reperfusion injury with diabetes by inhibiting endoplasmic reticulum stress and thereby reducing apoptosis. DA3 is better than liraglutide.

Driving GABAergic neurons optogenetically improves learning, reduces amyloid load and enhances autophagy in a mouse model of Alzheimer's disease.

The changes of local field potentials (LFP, mainly gamma rhythm and theta rhythm) in the brain are closely related to learning and memory formation. Reduced gamma rhythm (20-50 Hz) and theta rhythm (4-10 Hz) has been observed in the progression of Alzheimer's disease (AD), but it is not clear whether it is related to cognition in AD. Here, we investigated behaviorally driven gamma rhythm and theta rhythm in APP/PS1 mice, and optogenetically stimulated GABAergic neurons in the brain to better understand the relationship between the changes of LFP, cognition, and cellular pathologies. Optogenetically driving GABAergic neurons rescued memory formation in a water maze task and normalized theta and gamma rhythm in the EEG. Furthermore, the optogenetic stimulation alleviated neuroinflammation and levels of amyloid-ß (Aß)1-42 fragments, and induced autophagy. GABA blockers also reversed the normalization of theta and gamma rhythms in the brain by optogenetic stimulation. The results demonstrate that stimulation of GABAergic interneurons not only rescues LFP rhythms and memory formation, but furthermore activates autophagy and reduces neuroinflammation, which have beneficial additional effects such as clearing amyloid. This is a proof of concept for a novel therapeutic approach to AD treatment.

A dual GLP-1 and Gcg receptor agonist rescues spatial memory and synaptic plasticity in APP/PS1 transgenic mice.

Alzheimer's disease (AD) is a neurodegenerative disease that severely affects the health and lifespan of the elderly worldwide. Recently, the correlation between AD and type 2 diabetes mellitus (T2DM) has received intensive attention, and a promising new anti-AD strategy is the use of anti-diabetic drugs. Oxyntomodulin (Oxm) is a peptide hormone and growth factor that acts on neurons in the hypothalamus. OXM activates glucagon-like peptide 1 (GLP-1) and glucagon (Gcg) receptors, facilitates insulin signaling and has neuroprotective effects against Aß1-42-induced cytotoxicity in primary hippocampal neurons. Here, we tested the effects of the protease-resistant analogue (D-Ser2)Oxm on spatial memory and synaptic plasticity and the underlying molecular mechanisms in the APP/PS1 transgenic mouse model of AD. The results showed that (D-Ser2)Oxm not only alleviated the impairments of working memory and long-term spatial memory, but also reduced the number of Aß plaques in the hippocampus, and reversed the suppression of hippocampal synaptic long-term potentiation (LTP). Moreover, (D-Ser2)Oxm administration significantly increased p-PI3K/p-AKT1 expression and decreased p-GSK3ß levels in the hippocampus. These results are the first to show an in vivo neuroprotective role of (D-Ser2)Oxm in APP/PS1 mice, and this role involves the improvement of synaptic plasticity, clearance of Aß and normalization of PI3K/AKT/GSK3ß cell signaling in the hippocampus. This study suggests that (D-Ser2)Oxm holds promise for the prevention and treatment of AD.

The diabetes drug liraglutide reverses cognitive impairment in mice and attenuates insulin receptor and synaptic pathology in a non-human primate model of Alzheimer's disease.

Alzheimer's disease (AD) is a devastating neurological disorder that still lacks an effective treatment, and this has stimulated an intense pursuit of disease-modifying therapeutics. Given the increasingly recognized link between AD and defective brain insulin signaling, we investigated the actions of liraglutide, a glucagon-like peptide-1 (GLP-1) analog marketed for treatment of type 2 diabetes, in experimental models of AD. Insulin receptor pathology is an important feature of AD brains that impairs the neuroprotective actions of central insulin signaling. Here, we show that liraglutide prevented the loss of brain insulin receptors and synapses, and reversed memory impairment induced by AD-linked amyloid-ß oligomers (AßOs) in mice. Using hippocampal neuronal cultures, we determined that the mechanism of neuroprotection by liraglutide involves activation of the PKA signaling pathway. Infusion of AßOs into the lateral cerebral ventricle of non-human primates (NHPs) led to marked loss of insulin receptors and synapses in brain regions related to memory. Systemic treatment of NHPs with liraglutide provided partial protection, decreasing AD-related insulin receptor, synaptic, and tau pathology in specific brain regions. Synapse damage and elimination are amongst the earliest known pathological changes and the best correlates of memory impairment in AD. The results illuminate mechanisms of neuroprotection by liraglutide, and indicate that GLP-1 receptor activation may be harnessed to protect brain insulin receptors and synapses in AD. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

A novel GLP-1/GIP/Gcg triagonist reduces cognitive deficits and pathology in the 3xTg mouse model of Alzheimer's disease.

Type 2 diabetes mellitus (T2DM) is an important risk factor for Alzheimer's disease (AD). Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) have been identified to be effective in T2DM treatment and neuroprotection. In this study, we further explored the effects of a novel unimolecular GLP-1/GIP/Gcg triagonist on the cognitive behavior and cerebral pathology in the 7-month-old triple transgenic mouse model of AD (3xTg-AD), and investigated its possible electrophysiological and molecular mechanisms. After chronic administration of the GLP-1/GIP/Gcg triagonist (10 nmol/kg bodyweight, once daily, i.p.) for 30 days, open field, Y maze and Morris water maze tests were performed, followed by in vivo electrophysiological recording, immunofluorescence and Western blotting experiments. We found that the chronic treatment with the triagonist could improve long-term spatial memory of 3xTg-AD mice in Morris water maze, as well as the working memory in Y maze task. The triagonist also alleviated the suppression of long-term potentiation (LTP) in the CA1 region of hippocampus. In addition, the triagonist significantly reduced hippocampal pathological damages, including amyloid-ß (Aß) and phosphorylated tau aggregates, and upregulated the expression levels of S133 p-CREB, T286 p-CAMKII and S9 p-GSK3ß in the hippocampus of the 3xTg-AD mice. These results demonstrate for the first time that the novel GLP-1/GIP/Gcg triagonist is efficacious in ameliorating cognitive deficits and pathological damages of 3xTg-AD mice, suggesting that the triagonist might be potentially beneficial in the treatment of AD.

Defects in Peroxisomal 6-Phosphogluconate Dehydrogenase Isoform PGD2 Prevent Gametophytic Interaction in Arabidopsis thaliana.

We studied the localization of 6-phosphogluconate dehydrogenase (PGD) isoforms of Arabidopsis (Arabidopsis thaliana). Similar polypeptide lengths of PGD1, PGD2, and PGD3 obscured which isoform may represent the cytosolic and/or plastidic enzyme plus whether PGD2 with a peroxisomal targeting motif also might target plastids. Reporter-fusion analyses in protoplasts revealed that, with a free N terminus, PGD1 and PGD3 accumulate in the cytosol and chloroplasts, whereas PGD2 remains in the cytosol. Mutagenesis of a conserved second ATG enhanced the plastidic localization of PGD1 and PGD3 but not PGD2. Amino-terminal deletions of PGD2 fusions with a free C terminus resulted in peroxisomal import after dimerization, and PGD2 could be immunodetected in purified peroxisomes. Repeated selfing of pgd2 transfer (T-)DNA alleles yielded no homozygous mutants, although siliques and seeds of heterozygous plants developed normally. Detailed analyses of the C-terminally truncated PGD2-1 protein showed that peroxisomal import and catalytic activity are abolished. Reciprocal backcrosses of pgd2-1 suggested that missing PGD activity in peroxisomes primarily affects the male gametophyte. Tetrad analyses in the quartet1-2 background revealed that pgd2-1 pollen is vital and in vitro germination normal, but pollen tube growth inside stylar tissues appeared less directed. Mutual gametophytic sterility was overcome by complementation with a genomic construct but not with a version lacking the first ATG. These analyses showed that peroxisomal PGD2 activity is required for guided growth of the male gametophytes and pollen tube-ovule interaction. Our report finally demonstrates an essential role of oxidative pentose-phosphate pathway reactions in peroxisomes, likely needed to sustain critical levels of nitric oxide and/or jasmonic acid, whose biosynthesis both depend on NADPH provision.

Pharmacological targeting of CSF1R inhibits microglial proliferation and prevents the progression of Alzheimer's-like pathology.

The proliferation and activation of microglial cells is a hallmark of several neurodegenerative conditions. This mechanism is regulated by the activation of the colony-stimulating factor 1 receptor (CSF1R), thus providing a target that may prevent the progression of conditions such as Alzheimer's disease. However, the study of microglial proliferation in Alzheimer's disease and validation of the efficacy of CSF1R-inhibiting strategies have not yet been reported. In this study we found increased proliferation of microglial cells in human Alzheimer's disease, in line with an increased upregulation of the CSF1R-dependent pro-mitogenic cascade, correlating with disease severity. Using a transgenic model of Alzheimer's-like pathology (APPswe, PSEN1dE9; APP/PS1 mice) we define a CSF1R-dependent progressive increase in microglial proliferation, in the proximity of amyloid-ß plaques. Prolonged inhibition of CSF1R in APP/PS1 mice by an orally available tyrosine kinase inhibitor (GW2580) resulted in the blockade of microglial proliferation and the shifting of the microglial inflammatory profile to an anti-inflammatory phenotype. Pharmacological targeting of CSF1R in APP/PS1 mice resulted in an improved performance in memory and behavioural tasks and a prevention of synaptic degeneration, although these changes were not correlated with a change in the number of amyloid-ß plaques. Our results provide the first proof of the efficacy of CSF1R inhibition in models of Alzheimer's disease, and validate the application of a therapeutic strategy aimed at modifying CSF1R activation as a promising approach to tackle microglial activation and the progression of Alzheimer's disease.

[GLP-1/GIP/Gcg receptor Triagonist improves the cognitive behaviors in triple-transgenic mice of Alzheimer's disease].

Alzheimer's disease (AD) is a progressively neurodegenerative disorder, which seriously affects human health but is still irreversible up to now. Recent studies indicate that type 2 diabetes mellitus (T2DM) is an important risk factor for AD, and the drugs used for treatment of T2DM have shown some neuroprotective effects in the treatment of AD. Glucagon-like peptide-1 (GLP-1)/ glucose-dependent insulinotropic polypeptide (GIP)/glucagon (Gcg) receptor Triagonist is a new monomeric polypeptide equally activating the GLP-1/GIP/Gcg receptors, which is built on the basis of GLP-1/Gcg receptor coagonist core sequence, and incorporated with partial amino acids of GIP. Recently, the Triagonist has been reported to be effective in alleviating diabetic complications in rodent models of obesity. The present study observed for the first time the cognitive improvement effects of the Triagonist in the triple-transgenic AD mice (3xTg-AD) by using multiple behavioral techniques, and explored its probable molecular mechanisms using ELISA and Western blot. The results showed that the chronic treatment with the Triagonist (i.p.) significantly reversed the impairments in working memory of 3xTg-AD mice, with an obvious increase in the percentage of correct spontaneous alternation in the Y maze; the Triagonist treatment also improved long-term spatial memory and re-learning ability of 3xTg-AD mice in classical Morris water maze and reverse water maze tests, with decreased escape latency in under water platform tests and increased swimming time in probe tests. ELISA and Western blot experiments showed that the Triagonist up-regulated the levels of cAMP, PKA and p-CREB in the hippocampus of 3xTg-AD mice. These results indicate that GLP-1/GIP/Gcg receptor Triagonist can improve the cognitive behaviors in 3xTg-AD mice, and the up-regulation of hippocampal cAMP/PKA/CREB signal pathway may mediate the neuroprotection of the Triagonist, suggesting that the GLP-1/GIP/Gcg receptor Triagonist may be a novel therapeutic strategy for the treatment of AD.

Novel incretin analogues improve autophagy and protect from mitochondrial stress induced by rotenone in SH-SY5Y cells.

Currently, there is no viable treatment available for Parkinson's disease (PD) that stops or reverses disease progression. Interestingly, studies testing the glucagon-like-peptide-1 (GLP-1) mimetic Exendin-4 have shown neuroprotective/neurorestorative properties in pre-clinical tests and in a pilot clinical study of PD. Incretin analogues were originally developed to treat type 2 diabetes and several are currently on the market. In this study, we tested novel incretin analogues on the dopaminergic SH-SY5Y neuroblastoma cells against a toxic mitochondrial complex I inhibitor, Rotenone. Here, we investigate for the first time the effects of six different incretin receptor agonists - Liraglutide, D-Ser2-Oxyntomodulin, a GLP-1/GIP Dual receptor agonist, dAla(2)-GIP-GluPal, Val(8)GLP-1-GluPal and exendin-4. Post-treatment with doses of 1, 10 or 100 nM of incretin analogues for 12 h increased the survival of SH-SY5Y cells treated with 1 µM Rotenone for 12 h. Furthermore, we studied the post-treatment effect of 100 nM incretin analogues against 1 µM Rotenone stress on apoptosis, mitochondrial stress and autophagy markers. We found significant protective effects of the analogues against Rotenone stress on cell survival and on mitochondrial and autophagy-associated markers. The novel GLP-1/GIP Dual receptor agonist was superior and effective at a tenfold lower concentration compared to the other analogues. Using the Phosphatidylinositol 3-kinase (PI3K) inhibitor, LY294002, we further show that the neuroprotective effects are partially PI3K-independent. Our data suggest that the neuroprotective properties exhibited by incretin analogues against Rotenone stress involve enhanced autophagy, increased Akt-mediated cell survival and amelioration of mitochondrial dysfunction. These mechanisms can explain the neuroprotective effects of incretin analogues reported in clinical trials. GLP-1, GIP and dual incretin receptor agonists showed protective effects in SH-SY5Y cells treated with the stressor Rotenone. The novel GLP-1/GIP dual receptor agonist was superior and effective at a tenfold lower concentration compared to the other analogues. The drugs protected the cells from rotenone-induced impairment in cell growth and Akt activation, mitochondrial damage, impairments of autophagy and apoptotic cell signalling. See paper for details.

[Neuroprotective effects of a novel antidiabetic drug (D-Ser2)Oxm on amyloid ß protein-induced cytotoxicity].

The accumulation and neurotoxicity of amyloid ß protein (Aß) in the brain is one of major pathological hallmarks of Alzheimer's disease (AD). The effective drugs against Aß have been still deficient up to now. According to a most recent study, (D-Ser2) Oxm, a new antidiabetic drug, not only improves the disorders in plasma glucose and insulin in type 2 diabetes mellitus (T2DM) rats, but also exerts positive effects on hippocampal neurogenesis and synaptogenesis. However, it is still unclear whether (D-Ser2)Oxm can directly protect cultured neurons against Aß1-42-induced cytotoxicity. In the present study, we investigated the neuroprotective effects of (D-Ser2)Oxm on the cultured primary hippocampal neurons by testing the cell viability, neuronal apoptosis, mitochondrial membrane potential and intracellular calcium concentration. The results showed that treatment with (D-Ser2)Oxm effectively reversed Aß1-42-induced decline in cell viability (P < 0.001), and this protective effect could be inhibited by the pretreatment with exendin(9-39), a GLP-1 receptor blocker. (D-Ser2)Oxm treatment also decreased Aß1-42-induced neuronal early apoptosis and down-regulated apoptotic protein caspase3. Meantime, (D-Ser2)Oxm treatment inhibited Aß1-42-induced [Ca(2+)]i elevation, mitochondrial membrane potential depolarization, and glycogen synthase kinase-3ß (GSK3ß) activation. These results suggest that (D-Ser2)Oxm can protect hippocampal neurons against Aß1-42-induced cytotoxicity and this effect may be related to activation of GLP-1 receptors, regulation of intracellular calcium homeostasis and stabilization of mitochondrial membrane potential.

Neuroprotective effects of geniposide on Alzheimer's disease pathology.

A growing body of evidence has linked two of the most common aged-related diseases: type 2 diabetes mellitus (T2DM) and Alzheimer's disease (AD). It has led to the notion that drugs developed for the treatment of T2DM may be beneficial in modifying the pathophysiology of AD. As a receptor agonist of glucagon-like peptide-1 (GLP-1R), which is a newer drug class to treat T2DM, geniposide shows clear effects in inhibiting pathological processes underlying AD, such as promoting neurite outgrowth. In the present article, we review the possible molecular mechanisms of geniposide to protect the brain from pathologic damages underlying AD: reducing amyloid plaques, inhibiting τ phosphorylation, preventing memory impairment and loss of synapses, reducing oxidative stress and the chronic inflammatory response, and promoting neurite outgrowth via the GLP-1R signaling pathway. In summary, the Chinese herb geniposide shows great promise as a novel treatment for AD.

Restoration of cerebral and systemic microvascular architecture in APP/PS1 transgenic mice following treatment with Liraglutide™.

OBJECTIVE: Cerebral microvascular impairments occurring in AD may reduce Aß peptide clearance and impact upon circulatory ultrastructure and function. We hypothesized that microvascular pathologies occur in organs responsible for systemic Aß peptide clearance in a model of AD and that Liraglutide (Victoza(®)) improves vessel architecture. METHODS: Seven-month-old APP/PS1 and age-matched wild-type mice received once-daily intraperitoneal injections of either Liraglutide or saline (n = 4 per group) for eight weeks. Casts of cerebral, splenic, hepatic, and renal microanatomy were analyzed using SEM. RESULTS: Casts from wild-type mice showed regularly spaced microvasculature with smooth lumenal profiles, whereas APP/PS1 mice revealed evidence of microangiopathies including cerebral microanuerysms, intracerebral microvascular leakage, extravasation from renal glomerular microvessels, and significant reductions in both splenic sinus density (p = 0.0286) and intussusceptive microvascular pillars (p = 0.0412). Quantification of hepatic vascular ultrastructure in APP/PS1 mice revealed that vessel parameters (width, length, branching points, intussusceptive pillars and microaneurysms) were not significantly different from wild-type mice. Systemic administration of Liraglutide reduced the incidence of cerebral microanuerysms and leakage, restored renal microvascular architecture and significantly increased both splenic venous sinus number (p = 0.0286) and intussusceptive pillar formation (p = 0.0129). CONCLUSION: Liraglutide restores cerebral, splenic, and renal architecture in APP/PS1 mice.

Neuroprotective and anti-apoptotic effects of liraglutide on SH-SY5Y cells exposed to methylglyoxal stress.

Glucagon-like peptide 1 (GLP-1) is a growth factor that has demonstrated neuroprotective properties in a range of studies. In an APPswe/PS1ΔE9 mouse model of Alzheimer's disease (AD), we previously found protective effects on memory formation, synaptic plasticity, synapse survival and a reduction of amyloid synthesis and plaque load in the brain. Here, we analyse the neuroprotective properties of the GLP-1 analogue liraglutide in human neuroblastoma cell line SH-SY5Y during methyl glyoxal stress. We show for the first time that cell viability was enhanced by liraglutide (XTT assay) in a dose-dependent way, while cytotoxicity (LDH assay) and apoptosis were reduced. Expression of the pro-survival Mcl1 signaling protein was increased, as was activation of cell survival kinases Akt, MEK1/2 and the transcription factor p90RSK. Liraglutide also decreased pro-apoptotic Bax and Bik expression. In addition, the membrane potential and the influx of calcium into the cell were enhanced by liraglutide. GLP-1 receptor expression was also increased by the drug. The results demonstrate a range of growth factor-related cytoprotective processes induced by liraglutide, which is currently on the market as a treatment for type 2 diabetes (Victoza®). It is also tested in clinical trials in patients with Alzheimer disease.

Insulin, incretins and other growth factors as potential novel treatments for Alzheimer's and Parkinson's diseases.

Recently, it has been shown that in patients with AD (Alzheimer's disease) and, to some degree, in patients with PD (Parkinson's disease) insulin signalling is impaired. This finding has initiated a range of research projects that showed remarkable improvements using treatments that initially had been developed to treat diabetes. Pre-clinical studies showed good neuroprotective effects when applying insulin or long-lasting analogues of incretin peptides. In transgenic animal models of AD and PD, analogues of the incretin GLP-1 (glucagon-like peptide 1) prevented neurodegenerative processes and improved neuronal and synaptic functionality in AD and PD. Amyloid plaque load and synaptic loss as well as cognitive impairment had been ameliorated in AD models, and dopaminergic loss of transmission and motor function was reversed in models of PD. On the basis of these promising findings, several clinical trials are being conducted with the first encouraging clinical results being published. In several pilot studies in AD patients, the nasal application of insulin showed encouraging effects on cognition and biomarkers. A pilot study in PD patients testing a GLP-1 receptor agonist that is currently on the market as a treatment for Type 2 diabetes also showed encouraging effects. Several other clinical trials are currently ongoing in AD patients. The present review summarizes the range of neuroprotective effects that these drugs have demonstrated and emphasizes the great promise that this approach has in providing novel treatments that have protective and even restorative properties that no current drug treatment can offer.

First clinical data of the neuroprotective effects of nasal insulin application in patients with Alzheimer's disease.

Previous reviews have outlined the important role of insulin in the brain, and the observation that insulin signaling is desensitized in patients with Alzheimer's disease (AD). Because insulin is used to treat diabetes and insulin desensitization in the periphery, this motivated the design and execution of clinical pilot trials in patients with AD and mild cognitive impairment. Because insulin has powerful effects on blood sugar levels, a new technique was used by which insulin is applied as a spray. This method avoids high levels of insulin in the periphery and makes use of the transport system, via the nasal epithelium, into the brain. First trials in healthy subjects showed improvement in attention and memory tasks, and confirmed the concept that insulin signaling plays an important role in neuronal function and cognition. In a series of small clinical trials in patients with mild cognitive impairment/AD, nasal application of insulin or long-lasting insulin analogs showed improvements in memory tasks, cerebrospinal fluid biomarkers, and in a fluorodeoxyglucose positron emission tomographic study. In a more recent trial, two patient subgroups were identified, in which the insulin-resistant group improved after drug treatment whereas a subgroup that did not show insulin desensitization deteriorated. This highlights the need to conduct additional studies and demonstrates clearly that the hypothesis that insulin signaling plays in important role in cognition and AD has merit, and that this is a worthwhile target that shows great promise for future drug developments that improve insulin signaling. Insulin itself may not be the best choice, and other drugs that have been developed to treat diabetes that do not enhance insulin desensitization may be a better choice.

The incretin hormones glucagonlike peptide 1 and glucose-dependent insulinotropic polypeptide are neuroprotective in mouse models of Alzheimer's disease.

The incretin hormones glucagonlike peptide 1 and glucose-dependent insulinotropic polypeptide (GIP) have been developed to treat type 2 diabetes and also act as growth factors. We have tested several long-acting incretin mimetics in the amyloid precursor protein (APP)(Swe)/presenilin 1 (PS1)(ΔE9) model of Alzheimer's disease (AD). We found that liraglutide, lixisenatide, and D-Ala2-GIP cross the blood-brain barrier and prevent the impairment in memory formation and synaptic plasticity, increase synapse numbers, reduce amyloid plaque load and soluble amyloid-ß levels, reduce oxidative stress and the chronic inflammation response in the brain, enhance the proliferation of neuronal progenitor cells, and increase neurogenesis in the dentate gyrus. In an (18)fluorodeoxyglucoe positron emission tomographic/computed tomographic imaging study in PLB1-triple mice, a mouse model that expresses human mutated APP, PS1, and tau proteins, glucose metabolism was found to be normalized in forebrain areas after liraglutide treatment, demonstrating that neuronal metabolic activity was normalized. A clinical trial testing liraglutide in patients with AD is currently ongoing.

Drugs developed for treatment of diabetes show protective effects in Alzheimer's and Parkinson's diseases.

Type 2 diabetes has been identified as a risk factor for Alzheimer's disease (AD) and Parkinson's disease (PD). In the brains of patients with AD and PD, insulin signaling is impaired. This finding has motivated new research that showed good effects using drugs that initially had been developed to treat diabetes. Preclinical studies showed good neuroprotective effects applying insulin or long lasting analogues of incretin peptides. In transgenic animal models of AD or PD, analogues of the incretin GLP-1 prevented neurodegenerative processes and improved neuronal and synaptic functionality and reduced the symptoms of the diseases. Amyloid plaque load and synaptic loss as well as cognitive impairment had been prevented in transgenic AD mouse models, and dopaminergic loss of transmission and motor function has been reversed in animal models of PD. On the basis of these promising findings, several clinical trials are being conducted with the first encouraging clinical results already published. In several pilot studies in AD patients, the nasal application of insulin showed encouraging effects on cognition and biomarkers. A pilot study in PD patients testing a GLP-1 receptor agonist that is currently on the market as a treatment for type 2 diabetes (exendin-4, Byetta) also showed encouraging effects. Several other clinical trials are currently ongoing in AD patients, testing another GLP-1 analogue that is on the market (liraglutide, Victoza). Recently, a third GLP-1 receptor agonist has been brought to the market in Europe (Lixisenatide, Lyxumia), which also shows very promising neuroprotective effects. This review will summarise the range of these protective effects that those drugs have demonstrated. GLP-1 analogues show promise in providing novel treatments that may be protective or even regenerative in AD and PD, something that no current drug does.