Prophylactic liraglutide treatment prevents amyloid plaque deposition, chronic inflammation and memory impairment in APP/PS1 mice

Type 2 diabetes is a risk factor for Alzheimer's disease (AD). Previously, we have shown that the diabetes drug liraglutide is protective in middle aged and in old APP/PS1 mice. Here, we show that liraglutide has prophylactic properties. When injecting liraglutide once-daily ip. in two months old mice for 8 months, the main hallmarks of AD were much reduced. Memory formation in object recognition and Morris water maze were normalised and synapse loss and the loss of synaptic plasticity was prevented. In addition, amyloid plaque load, including dense core congophilic plaques, was much reduced. Chronic inflammation (activated microglia) was also reduced in the cortex, and neurogenesis was enhanced in the dentate gyrus. The results demonstrate that liraglutide may protect from progressive neurodegeneration that develops in AD. The drug is currently in clinical trials in patients with 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

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

Neuroprotective effects of lixisenatide and liraglutide in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine mouse model of Parkinson's disease

Glucagon-like peptide 1 (GLP-1) is a growth factor. GLP-1 mimetics are on the market as treatments for type 2 diabetes and are well tolerated. These drugs have shown neuroprotective properties in animal models of neurodegenerative disorders. In addition, the GLP-1 mimetic exendin-4 has shown protective effects in animal models of Parkinson's disease (PD), and a clinical trial in PD patients showed promising first results. Liraglutide and lixisenatide are two newer GLP-1 mimetics which have a longer biological half-life than exendin-4. We previously showed that these drugs have neuroprotective properties in an animal model of Alzheimer's disease. Here we demonstrate the neuroprotective effects in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD. MPTP was injected once-daily (20mg/kg i.p.) for 7days, and drugs were injected once-daily for 14days i.p. When comparing exendin-4 (10nmol/kg), liraglutide (25nmol/kg) and lixisenatide (10nmol/kg), it was found that exendin-4 showed no protective effects at the dose chosen. Both liraglutide and lixisenatide showed effects in preventing the MPTP-induced motor impairment (Rotarod, open-field locomotion, catalepsy test), reduction in tyrosine hydroxylase (TH) levels (dopamine synthesis) in the substantia nigra and basal ganglia, a reduction of the pro-apoptotic signaling molecule BAX and an increase in the anti-apoptotic signaling molecule B-cell lymphoma-2. The results demonstrate that in this study, both liraglutide and lixisenatide are superior to exendin-4, and both drugs show promise as a novel treatment of PD

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

Neuroprotective effects of an oxyntomodulin analogue in the MPTP mouse model of Parkinson's disease

Oxyntomodulin is a hormone and a growth factor. It activates two receptors, the Glucagon-like peptide 1 (GLP-1) and the glucagon receptor. GLP-1 mimetics are on the market as treatments for type 2 diabetes and are well tolerated. These drugs have shown neuroprotective properties in animal models of neurodegenerative disorders. In addition, the GLP-1 mimetic exendin-4 has shown protective effects in animal models of Parkinson's disease (PD), and a clinical trial in PD patients showed promising first positive results. d-Ser2-oxyntomodulin (Oxy) is a protease resistant oxyntomodulin analogue that has been developed to treat diabetes. Here we demonstrate for the first time that such analogues have neuroprotective effects. The drug showed protective effects in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD. MPTP was injected daily (20mg/kg i.p.) for 7 days, and Oxy injected once-daily for 14 days i.p. Oxy treatment prevented or reversed the MPTP- induced motor impairment (Rotarod, spontaneous locomotion, swim activity, muscle strength test), the MPTP-induced reduction in Tyrosine Hydroxylase (TH) levels (dopamine synthesis) in the substantia nigra and basal ganglia, the reduction of the synaptic marker synapstophysin, the inactivation of the growth factor kinase Akt/PKB and of the anti-apoptotic signaling molecule Bcl-2, and the increase of levels of the pro-inflammatory cytokine TNF-α. The results demonstrate that oxyntomodulin analogues show promise as a novel treatment of PD

Neural circuit responses to change in connection strength from Ox to GABAergic neurons (LHA).

<p>Steady-state firing frequencies of the neural populations as functions of the connection strength (in pA/Hz). Label as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088003#pone-0088003-g011" target="_blank">Figure 11</a>.</p

Representative z-stack_max (30 µm thickness) confocal images.

<p>Colocalization of Orexin A with (A) 5HT_1AR, (B) 5HT_3AR, 63× magnification. White arrows indicate orexin neuron expressing the respective 5HT receptor and white boxes indicate orexin neuron not expressing the receptor.</p

LHA-DRN system can exhibit oscillations with weak excitatory from 5-HT to GABAergic (LHA) neurons.

<p>Steady-state values of the firing rate activity of 5-HT neurons are plotted as a function of the connection strength J_{5-HT-to-GABA(LHA)} (in pA/Hz). Oscillatory region (left of dashed) is bounded by the values of J_{5-HT-to-GABA(LHA)} below 0.804 pA/Hz. Max (Min): maximum (minimum) firing rates during oscillation. Label as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088003#pone-0088003-g011" target="_blank">Figure 11</a>.</p

Neural circuit responses to change in connection strength from 5-HT to GABAergic neurons (LHA).

<p>Change in the steady-state values of the neural firing frequencies of the neuronal groups with varying connection strength factor J_{5-HT-to-GABA(LHA)} (in pA/Hz) from 5-HT neurons to the GABAergic neurons (LHA) for excitatory connection. Steady states are obtained after simulating for a sufficiently long time. f_5-HT, f_Ox, g_GABA(LHA), and g_GABA(DRN): population firing frequencies of 5-HT, Ox, LHA’s GABAergic and DRN’s GABAergic neurons, respectively.</p