Entry of exendin-4 into brain is rapid but may be limited at high doses

Brain energy failure in dementia syndromes: Opportunities and challenges for glucagon-like peptide-1 receptor agonists

Medications for type 2 diabetes (T2DM) offer a promising path for discovery and development of effective interventions for dementia syndromes. A common feature of dementia syndromes is an energy failure due to reduced energy supply to neurons and is associated with synaptic loss and results in cognitive decline and behavioral changes. Among diabetes medications, glucagon‐like peptide‐1 (GLP‐1) receptor agonists (RAs) promote protective effects on vascular, microglial, and neuronal functions. In this review, we present evidence from animal models, imaging studies, and clinical trials that support developing GLP‐1 RAs for dementia syndromes. The review examines how changes in brain energy metabolism differ in conditions of insulin resistance and T2DM from dementia and underscores the challenges that arise from the heterogeneity of dementia syndromes. The development of GLP‐1 RAs as dementia therapies requires a deeper understanding of the regional changes in brain energy homeostasis guided by novel imaging biomarkers.

Exendin-4 increases absence-like seizures and anxiety-depression-like behaviors in WAG/Rij rats

AIM

Epilepsy is a neurological condition affecting millions of people worldwide. Glucagon-like peptide-1 (GLP-1) is a gut hormone, and its neuroprotective effect was investigated in previous studies. In this study, the effects of exendin-4, a GLP-1 receptor agonist, were studied in genetic absence epileptic Wistar Albino Glaxo/Rijswijk rats (WAG/Rij). WAG/Rij rat is a genetic model of the absence epilepsy and depression-like comorbidity.

METHOD

We examined the effects of exendin-4 (10, 50 and 100 µg/kg) on the absence seizures (Electrocorticography [ECoG] recordings), anxiety level (open-field test [OF]), and depression-like levels (forced swimming test [FST]) in the WAG/Rij rats. Basal ECoG recording was performed for all rats. Then, exendin-4 (10, 50 or 100 µg/kg) was administered intraperitoneally and ECoG recording was made for 180 min. After ECoG recording, forced swimming test and open-field test were applied.

RESULTS

Administration of 10, 50, or 100 µg/kg exendin-4 increased the duration and number of spike-wave discharges (SWDs) considerably without changing the amplitude. The 100 µg/kg dose of exendin-4 was the most effective in increasing the total duration of SWDs. Additionally, all exendin-4 doses increased anxiety level in OF and depression-like level in FST.

CONCLUSION

Our results showed that exendin-4 increased SWD incidence and anxiety- and depression-like behaviors in the WAG/Rij rats. Besides, it was also found that high doses caused the most proabsence effect.

Exendin-4 Pretreatment Attenuates Kainic Acid-Induced Hippocampal Neuronal Death

Exendin-4 (Ex-4) is a glucagon-like peptide-1 receptor (GLP-1R) agonist that protects against brain injury. However, little is known about the effect of Ex-4 on kainic acid (KA)-induced seizures and hippocampal cell death. Therefore, this study evaluated the neuroprotective effects of Ex-4 pretreatment in a mouse model of KA-induced seizures. Three days before KA treatment, mice were intraperitoneally injected with Ex-4. We found that Ex-4 pretreatment reversed KA-induced reduction of GLP-1R expression in the hippocampus and attenuated KA-induced seizure score, hippocampal neuronal death, and neuroinflammation. Ex-4 pretreatment also dramatically reduced hippocampal lipocalin-2 protein in KA-treated mice. Furthermore, immunohistochemical studies showed that Ex-4 pretreatment significantly alleviated blood–brain barrier leakage. Finally, Ex-4 pretreatment stimulated hippocampal expression of phosphorylated cyclic adenosine monophosphate (cAMP) response element-binding protein (p-CREB), a known target of GLP-1/GLP-1R signaling. These findings indicate that Ex-4 pretreatment may protect against KA-induced neuronal damage by regulating GLP-1R/CREB-mediated signaling pathways.

GLP-1 in diabetes care: Can glycemic control be achieved without nausea and vomiting?

Introduced less than two decades ago, glucagon-like peptide-1 receptor agonists (GLP-1RAs) rapidly re-shaped the field of type 2 diabetes (T2DM) care by providing glycemic control in tandem with weight loss. However, FDA-approved GLP-1RAs are often accompanied by nausea and emesis, and in some lean T2DM patients, by undesired anorexia. Importantly, the hypophagic and emetic effects of GLP-1RAs are caused by central GLP-1R activation. This review summarizes two different approaches to mitigate the incidence/severity of nausea and emesis related to GLP-1RAs: conjugation with vitamin B12, or related corrin-ring containing compounds ("corrination"), and development of dual-agonists of the GLP-1R with glucose dependent-insulinotropic polypeptide (GIP). Such approaches could lead to the generation of GLP-1RAs with improved therapeutic efficacy thus, decreasing treatment attrition, increasing patient compliance, and extending treatment to a broader population of T2DM patients. The data reviewed show that it is possible to pharmacologically separate emetic effects of GLP-1RAs from glucoregulatory action.

Glucagon-like peptide-1 attenuated carboxymethyl lysine induced neuronal apoptosis via peroxisome proliferation activated receptor-γ

Backgrounds and aims: The role of peroxisome proliferator activated receptor-γ (PPAR-γ) in neuronal apoptosis remains unclear. We aim to investigate the role of PPAR-γ in glucagon-like peptide-1 (GLP-1) alleviated neuronal apoptosis induced by carboxymethyl-lysine (CML).

Materials and Methods: In vitro, PC12 cells were treated by CML/GLP-1. Moreover. the function of PPAR-γ was blocked by GW9662. In vivo, streptozotocin (STZ) was used to induce diabetic rats with neuronal apoptosis. The cognitive function of rats was observed by Morris water maze. Apoptosis was detected by TUNEL assay. Bcl2, Bax, PPAR-γ and receptor of GLP-1 (GLP-1R) were measured by western blotting or immunofluorescence.

Results: In vitro experiment, CML triggered apoptosis, down-regulated GLP-1R and PPAR-γ. Moreover, GLP-1 not only alleviated the apoptosis, but also increased levels of PPAR-γ. GW9662 abolished the neuroprotective effect of GLP-1 on PC12 cells from apoptosis. Furthermore, GLP-1R promoter sequences were detected in the PPAR-γ antibody pulled mixture. GPL-1 levels decreased, while CML levels increased in diabetic rats, compared with control rats. Additionally, we observed elevated bax, decreased bcl2, GLP-1R and PPAR-γ in diabetic rats.

Conclusions: GLP-1 could attenuate neuronal apoptosis induced by CML. Additionally, PPAR-γ involves in this process.

Insights into a possible role of glucagon-like peptide-1 receptor agonists in the treatment of depression

Depression is a highly prevalent mood disorder and one of the major health concerns in modern society. Moreover, it is characterized by a high prevalence of coexistence with many other diseases including metabolic disorders such as type 2 diabetes mellitus (T2DM) and obesity. Currently used antidepressant drugs, which mostly target brain monoaminergic neurotransmission, have limited clinical efficacy. Although the etiology of depression has not been fully elucidated, current scientific data emphasize the role of neurotrophic factors deficiencies, disturbed homeostasis between the nervous system and the immune and endocrine systems, as well as disturbances in brain energy metabolism and dysfunctions in the gut-brain axis as important factors in the pathogenesis of this neuropsychiatric disorder. Therefore, therapeutic options that could work in a way other than classic antidepressants are being sought to increase the effectiveness of the treatment. Interestingly, glucagon-like peptide-1 receptor agonists (GLP-1RAs), used in the treatment of T2DM and obesity, are known to show pro-cognitive and neuroprotective properties, and exert modulatory effects on immune, endocrine and metabolic processes in the central nervous system. This review article discusses the potential antidepressant effects of GLP-1RAs, especially in the context of their action on the processes related to neuroprotection, inflammation, stress response, energy metabolism, gut-brain crosstalk and the stability of the gut microbiota.

Normalisation of glucose metabolism by exendin-4 in the chronic phase after stroke promotes functional recovery in male diabetic mice

BACKGROUND AND PURPOSE

Glucagon-like peptide-1 (GLP-1) receptor activation decreases stroke risk in people with Type 2 diabetes (T2D), while animal studies have shown the efficacy of this strategy to counteract stroke-induced acute brain damage. However, whether GLP-1 receptor activation also improves recovery in the chronic phase after stroke is unknown. We investigated whether post-acute, chronic administration of the GLP-1 receptor agonist, exendin-4, improves post-stroke recovery and examined possible underlying mechanisms in T2D and non-T2D mice.

EXPERIMENTAL APPROACH

We induced stroke via transient middle cerebral artery occlusion (tMCAO) in T2D/obese mice (8 months of high-fat diet) and age-matched controls. Exendin-4 was administered for 8 weeks from Day 3 post-tMCAO. We assessed functional recovery by weekly upper-limb grip strength tests. Insulin sensitivity and glycaemia were evaluated at 4 and 8 weeks post-tMCAO. Neuronal survival, stroke-induced neurogenesis, neuroinflammation, atrophy of GABAergic parvalbumin+ interneurons, post-stroke vascular remodelling and fibrotic scar formation were investigated by immunohistochemistry.

KEY RESULTS

Exendin-4 normalised T2D-induced impairment of forepaw grip strength recovery in correlation with normalised glycaemia and insulin sensitivity. Moreover, exendin-4 counteracted T2D-induced atrophy of parvalbumin+ interneurons and decreased microglia activation. Finally, exendin-4 normalised density and pericyte coverage of micro-vessels and restored fibrotic scar formation in T2D mice. In non-T2D mice, the exendin-4-mediated recovery was minor.

CONCLUSION AND IMPLICATIONS

Chronic GLP-1 receptor activation mediates post-stroke functional recovery in T2D mice by normalising glucose metabolism and improving neuroplasticity and vascular remodelling in the recovery phase. The results warrant clinical trial of GLP-1 receptor agonists for rehabilitation after stroke in T2D.

Activation of glucagon-like peptide-1 receptors and skilled reach foraging

Glucagon‐like peptide‐1 receptor (GLP‐1R) agonists, such as exendin‐4 (Ex4), liraglutide and dulaglutide, regulate glucose homeostasis and are thus used to treat diabetes type II. GLP‐1 also contributes towards a variety of additional physiological functions, including suppression of reward and improvement of learning. Acute activation of GLP‐1R in the nucleus accumbens (NAc) shell, an area essential for motivation, reduces the motivation to consume sucrose or alcohol when assessed in a simple motor task. However, the effects of repeated administration of the different GLP‐1R agonists on behaviours in a more complex motor task are unknown. The aim was therefore to investigate the effects of repeated Ex4, liraglutide or dulaglutide on the motivation and learning of a complex motor tasks such as skilled reach foraging in the Montoya staircase test. To explore the neurophysiological correlates of the different GLP‐1R agonists on motivation, ex vivo electrophysiological recordings were conducted. In rats with an acquired skilled reach performance, Ex4 or liraglutide but not dulaglutide reduced the motivation of skilled reach foraging. In trained rats, Ex4 infusion into NAc shell decreased this motivated behaviour, and both Ex4 and liraglutide supressed the evoked field potentials in NAc shell. In rats without prior Montoya experience, dulaglutide but not Ex4 or liraglutide enhanced the learning of skilled reach foraging. Taken together, these findings indicate that the tested GLP‐1R agonists have different behavioural outcomes depending on the context.

The Future of Incretin-Based Approaches for Neurodegenerative Diseases in Older Adults: Which to Choose? A Review of their Potential Efficacy and Suitability

The current treatment options for neurodegenerative diseases in older adults rely mainly on providing symptomatic relief. Yet, it remains imperative to identify agents that slow or halt disease progression to avoid the most disabling features often associated with advanced disease stages. A potential overlap between the pathological processes involved in diabetes and neurodegeneration has been established, raising the question of whether incretin-based therapies for diabetes may also be useful in treating neurodegenerative diseases in older adults. Here, we review the different agents that belong to this class of drugs (GLP-1 receptor agonists, dual/triple receptor agonists, DPP-4 inhibitors) and describe the data supporting their potential role in treating neurodegenerative conditions including Parkinson's disease and Alzheimer's disease. We further discuss whether there are any distinctive properties among them, particularly in the context of safety or tolerability and CNS penetration, that might facilitate their successful repurposing as disease-modifying drugs. Proof-of-efficacy data will obviously be of the greatest importance, and this is most likely to be demonstrable in agents that reach the central nervous system and impact on neuronal GLP-1 receptors. Additionally, however, the long-term safety and tolerability (including gastrointestinal side effects and unwanted weight loss) as well as the route of administration of this class of agents may also ultimately determine success and these aspects should be considered in prioritising which approaches to subject to formal clinical trial evaluations.

Drug Repurposing for Parkinson's Disease: The International Linked Clinical Trials experience

The international Linked Clinical Trials (iLCT) program for Parkinson's to date represents one of the most comprehensive drug repurposing programs focused on one disease. Since initial planning in 2010, it has rapidly grown - giving rise to seven completed, and 15 ongoing, clinical trials of 16 agents each aimed at delivering disease modification in Parkinson's disease (PD). In this review, we will provide an overview of the history, structure, process, and progress of the program. We will also present some examples of agents that have been selected and prioritized by the program and subsequently evaluated in clinical trials. Our goal with this review is to provide a template that can be considered across other therapeutic areas.

Sustained Release GLP-1 Agonist PT320 Delays Disease Progression in a Mouse Model of Parkinson's Disease

GLP-1 agonists have become increasingly interesting as a new Parkinson's disease (PD) clinical treatment strategy. Additional preclinical studies are important to validate this approach and define the disease stage when they are most effective. We hence characterized the efficacy of PT320, a sustained release formulation of the long acting GLP-1 agonist, exenatide, in a progressive PD (MitoPark) mouse model. A clinically translatable biweekly PT320 dose was administered starting at 5 weeks of age and longitudinally evaluated to 24 weeks, and multiple behavioral/cellular parameters were measured. PT320 significantly improved spontaneous locomotor activity and rearing in MitoPark PD mice. "Motivated" behavior also improved, evaluated by accelerating rotarod performance. Behavioral improvement was correlated with enhanced cellular and molecular indices of dopamine (DA) midbrain function. Fast scan cyclic voltammetry demonstrated protection of striatal and nucleus accumbens DA release and reuptake in PT320 treated MitoPark mice. Positron emission tomography showed protection of striatal DA fibers and tyrosine hydroxylase protein expression was augmented by PT320 administration. Early PT320 treatment may hence provide an important neuroprotective therapeutic strategy in PD.

Irisin and Incretin Hormones: Similarities, Differences, and Implications in Type 2 Diabetes and Obesity

Incretins are gut hormones that potentiate glucose-stimulated insulin secretion (GSIS) after meals. Glucagon-like peptide-1 (GLP-1) is the most investigated incretin hormone, synthesized mainly by L cells in the lower gut tract. GLP-1 promotes β-cell function and survival and exerts beneficial effects in different organs and tissues. Irisin, a myokine released in response to a high-fat diet and exercise, enhances GSIS. Similar to GLP-1, irisin augments insulin biosynthesis and promotes accrual of β-cell functional mass. In addition, irisin and GLP-1 share comparable pleiotropic effects and activate similar intracellular pathways. The insulinotropic and extra-pancreatic effects of GLP-1 are reduced in type 2 diabetes (T2D) patients but preserved at pharmacological doses. GLP-1 receptor agonists (GLP-1RAs) are therefore among the most widely used antidiabetes drugs, also considered for their cardiovascular benefits and ability to promote weight loss. Irisin levels are lower in T2D patients, and in diabetic and/or obese animal models irisin administration improves glycemic control and promotes weight loss. Interestingly, recent evidence suggests that both GLP-1 and irisin are also synthesized within the pancreatic islets, in α- and β-cells, respectively. This review aims to describe the similarities between GLP-1 and irisin and to propose a new potential axis-involving the gut, muscle, and endocrine pancreas that controls energy homeostasis.

Association between exenatide use and incidence of Alzheimer's disease

INTRODUCTION

Recent developments suggest that insulin-sensitizing agents used to treat type II diabetes (T2DM) may also prove useful in reducing the risk of Alzheimer's disease (AD). The objective of this study is to analyze the association between exenatide use among Medicare beneficiaries with T2DM and the incidence of AD.

METHODS

We performed a retrospective cohort analysis on claims data from a 20% random sample of Medicare beneficiaries with T2DM from 2007 to 2013 (n = 342,608). We compared rates of incident AD between 2009 and 2013 according to exenatide use in 2007-2008, measured by the number of 30-day-equivalent fills. We adjusted for demographics, comorbidities, and use of other drugs. Unmeasured confounding was assessed with an instrumental variables approach.

RESULTS

The sample was mostly female (65%), White (76%), and 74 years old on average. Exenatide users were more likely to be male (38% vs. 35%), White (87% vs. 76%), and younger (by 4.2 years) than non-users. Each additional 30-day-equivalent claim was associated with a 2.4% relative reduction in incidence (odds ratio 0.976; 95% confidence interval 0.963-0.989; P < .001). There was no evidence of unmeasured confounding.

DISCUSSION

Exenatide use is associated with a reduced incidence of AD among Medicare beneficiaries aged 65 years or older with T2DM. The association shown in this study warrants consideration by clinicians prescribing insulin sensitizing agents to patients.

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.

Potential Role of Hypothalamic and Plasma Ghrelin in the Feeding Behavior of Obese Type 2 Diabetic Rats with Intraventricular Glucagon-Like Peptide-1 Receptor Agonist Intervention

OBJECTIVE

To investigate the relationship of central and peripheral ghrelin during an exendin-4 (Ex-4) intervention to feeding in obese type 2 diabetic rodents.

METHODS

Animal models of diet-induced obesity (DIO) and type 2 diabetes were developed using male Sprague-Dawley rats fed with a high-fat diet and induced into DIO-streptozotocin diabetic rats. Ex-4 or the glucagon-like peptide-1 (GLP-1) receptor agonist exendin fragment-[9-39] (Ex-9) was intracerebroventricularly (ICV) administered. Multivariate linear regression analysis was performed to investigate potential predictors of food intake after Ex-4 administration.

RESULTS

ICV administration of Ex-4 significantly inhibited feeding and decreased weight, plasma active ghrelin, hypothalamic ghrelin, and gastric ghrelin levels. The changes in hypothalamic ghrelin and plasma ghrelin could predict the amount of 8-h average food intake. Central preadministration of Ex-9 followed by treatment with Ex-4 could inhibit the decrease in feeding at 0.5, 2, and 8 h. It could also inhibit the decrease in hypothalamic ghrelin at 0.5, 2, and 8 h, as well as in plasma and gastric ghrelin at 2 and 8 h.

CONCLUSIONS

In a GLP-1 receptor-dependent manner, central and peripheral ghrelin play a vital role in the inhibition of feeding by Ex-4 administration. Hypothalamic ghrelin, but not plasma ghrelin, may be involved in central Ex-4 inhibition of feeding in the very early feeding period.

Long-Acting Glucagon-Like Peptide-1 Receptor Agonists Suppress Voluntary Alcohol Intake in Male Wistar Rats

Alcohol use disorder (AUD) is a chronic relapsing condition characterized by compulsive alcohol-seeking behaviors, with serious detrimental health consequences. Despite high prevalence and societal burden, available approved medications to treat AUD are limited in number and efficacy, highlighting a critical need for more and novel pharmacotherapies. Glucagon-like peptide-1 (GLP-1) is a gut hormone and neuropeptide involved in the regulation of food intake and glucose metabolism via GLP-1 receptors (GLP-1Rs). GLP-1 analogs are approved for clinical use for diabetes and obesity. Recently, the GLP-1 system has been shown to play a role in the neurobiology of addictive behaviors, including alcohol seeking and consumption. Here we investigated the effects of different pharmacological manipulations of the GLP-1 system on escalated alcohol intake and preference in male Wistar rats exposed to intermittent access 2-bottle choice of 10% ethanol or water. Administration of AR231453 and APD668, two different agonists of G-protein receptor 119, whose activation increases GLP-1 release from intestinal L-cells, did not affect voluntary ethanol intake. By contrast, injections of either liraglutide or semaglutide, two long-acting GLP-1 analogs, potently decreased ethanol intake. These effects, however, were transient, lasting no longer than 48 h. Semaglutide, but not liraglutide, also reduced ethanol preference on the day of injection. As expected, both analogs induced a reduction in body weight. Co-administration of exendin 9-39, a GLP-1R antagonist, did not prevent liraglutide- or semaglutide-induced effects in this study. Injection of exendin 9-39 alone, or blockade of dipeptidyl peptidase-4, an enzyme responsible for GLP-1 degradation, via injection of sitagliptin, did not affect ethanol intake or preference. Our findings suggest that among medications targeting the GLP-1 system, GLP-1 analogs may represent novel and promising pharmacological tools for AUD treatment.

Estrogen and gut satiety hormones in vagus-hindbrain axis

Estrogens modulate different physiological functions, including reproduction, inflammation, bone formation, energy expenditure, and food intake. In this review, we highlight the effect of estrogens on food intake regulation and the latest literature on intracellular estrogen signaling. In addition, gut satiety hormones, such as cholecystokinin, glucagon-like peptide 1 and leptin are essential to regulate ingestive behaviors in the postprandial period. These peripheral signals are sensed by vagal afferent terminals in the gut wall and transmitted to the hindbrain axis. Here we 1. review the role of the vagus-hindbrain axis in response to gut satiety signals and 2. consider the potential synergistic effects of estrogens on gut satiety signals at the level of vagal afferent neurons and nuclei located in the hindbrain. Understanding the action of estrogens in gut-brain axis provides a potential strategy to develop estrogen-based therapies for metabolic diseases and emphasizes the importance of sex difference in the treatment of obesity.

Neurotrophic, anti-neuroinflammatory, and redox balance mechanisms of chalcones

The passage of time that evoke aging; the tilted redox balance that contribute oxidative entropy; the polarization of microglia cells that produce inflammatory phenotype; all represent the intricacies of CNS-dependent disease progression. Neurological diseases that result from CNS injury raise social concerns and the available therapeutic strategies are frustrated by low efficacy, high toxicity, and multiple side effects. However, emergent studies have shown the neuroprotective role of natural compounds - including chalcones - with high efficacy in the protection of CNS structures. These compounds reportedly demonstrate neurotrophic mechanism through the upregulation of neurotrophic factors, anti-apoptotic Bcl-2, and downregulation of Bax protein; anti-neuroinflammatory mechanism via the inhibition of neuroinflammatory pathways, attenuated secretion of pro-inflammatory cytokines, prevention of blood brain barrier (BBB) disruption, and protection against nerve senescence; antioxidant mechanism through the upregulation of Nrf2 activities, inhibition of Keap1, synthesis of antioxidant enzymes, and maintenance of high antioxidant/oxidant ratio. All these mechanisms represent chalcones' neuroprotective mechanisms. In this review, we highlight different pathways involved in CNS-related diseases and elucidate various mechanisms by which chalcones can perturb these shunts as a potential therapeutic modality.

Brain uptake pharmacokinetics of incretin receptor agonists showing promise as Alzheimer's and Parkinson's disease therapeutics

Among the more promising treatments proposed for Alzheimer's disease (AD) and Parkinson's disease (PD) are those reducing brain insulin resistance. The antidiabetics in the class of incretin receptor agonists (IRAs) reduce symptoms and brain pathology in animal models of AD and PD, as well as glucose utilization in AD cases and clinical symptoms in PD cases after their systemic administration. At least 9 different IRAs are showing promise as AD and PD therapeutics, but we still lack quantitative data on their relative ability to cross the blood-brain barrier (BBB) reaching the brain parenchyma. We consequently compared brain uptake pharmacokinetics of intravenous 125I-labeled IRAs in adult CD-1 mice over the course of 60 min. We tested single IRAs (exendin-4, liraglutide, lixisenatide, and semaglutide), which bind receptors for one incretin (glucagon-like peptide-1 [GLP-1]), and dual IRAs, which bind receptors for two incretins (GLP-1 and glucose-dependent insulinotropic polypeptide [GIP]), including unbranched, acylated, PEGylated, or C-terminally modified forms (Finan/Ma Peptides 17, 18, and 20 and Hölscher peptides DA3-CH and DA-JC4). The non-acylated and non-PEGylated IRAs (exendin-4, lixisenatide, Peptide 17, DA3-CH and DA-JC4) had significant rates of blood-to-brain influx (Ki), but the acylated IRAs (liraglutide, semaglutide, and Peptide 18) did not measurably cross the BBB. The brain influx of the non-acylated, non-PEGylated IRAs were not saturable up to 1 μg of these drugs and was most likely mediated by adsorptive transcytosis across brain endothelial cells, as observed for exendin-4. Of the non-acylated, non-PEGylated IRAs tested, exendin-4 and DA-JC4 were best able to cross the BBB based on their rate of brain influx, percentage reaching the brain that accumulated in brain parenchyma, and percentage of the systemic dose taken up per gram of brain tissue. Exendin-4 and DA-JC4 thus merit special attention as IRAs well-suited to enter the central nervous system (CNS), thus reaching areas pathologic in AD and PD.

Pharmacologically reversible zonation-dependent endothelial cell transcriptomic changes with neurodegenerative disease associations in the aged brain

The molecular signatures of cells in the brain have been revealed in unprecedented detail, yet the ageing-associated genome-wide expression changes that may contribute to neurovascular dysfunction in neurodegenerative diseases remain elusive. Here, we report zonation-dependent transcriptomic changes in aged mouse brain endothelial cells (ECs), which prominently implicate altered immune/cytokine signaling in ECs of all vascular segments, and functional changes impacting the blood–brain barrier (BBB) and glucose/energy metabolism especially in capillary ECs (capECs). An overrepresentation of Alzheimer disease (AD) GWAS genes is evident among the human orthologs of the differentially expressed genes of aged capECs, while comparative analysis revealed a subset of concordantly downregulated, functionally important genes in human AD brains. Treatment with exenatide, a glucagon-like peptide-1 receptor agonist, strongly reverses aged mouse brain EC transcriptomic changes and BBB leakage, with associated attenuation of microglial priming. We thus revealed transcriptomic alterations underlying brain EC ageing that are complex yet pharmacologically reversible.

Blood–brain barrier dysfunction occurs in ageing and in neurodegenerative diseases. Here, the authors use scRNA-seq to identify transcriptomic changes in endothelial cell subtypes in the aged mouse brain, some of which may generalize to human and can be reversed by treatment with a GLP-1R agonist.

Alleviation of Depression by Glucagon-Like Peptide 1 Through the Regulation of Neuroinflammation, Neurotransmitters, Neurogenesis, and Synaptic Function

Depression has emerged as a major cause of mortality globally. Many studies have reported risk factors and mechanisms associated with depression, but it is as yet unclear how these findings can be applied to the treatment and prevention of this disorder. The onset and recurrence of depression have been linked to diverse metabolic factors, including hyperglycemia, dyslipidemia, and insulin resistance. Recent studies have suggested that depression is accompanied by memory loss as well as depressive mood. Thus, many researchers have highlighted the relationship between depressive behavior and metabolic alterations from various perspectives. Glucagon-like peptide-1 (GLP-1), which is secreted from gut cells and hindbrain areas, has been studied in metabolic diseases such as obesity and diabetes, and was shown to control glucose metabolism and insulin resistance. Recently, GLP-1 was highlighted as a regulator of diverse pathways, but its potential as the therapeutic target of depressive disorder was not described comprehensively. Therefore, in this review, we focused on the potential of GLP-1 modulation in depression.

Evidence for pathophysiological commonalities between metabolic and neurodegenerative diseases

Diabetes mellitus is a risk factor for developing neurodegenerative diseases, such as Alzheimer's and Parkinson's diseases. This relationship seems counter-intuitive as these pathological syndromes appear to be very different. However, they share underlying mechanisms such as desensitization of insulin signaling. Insulin not only regulates blood glucose levels, but also acts as a growth factor that is important for neuronal activity and repair. Insulin signaling desensitization has been found in the brains of people with progressive neurodegenerative diseases, which is most likely driven by chronic inflammation. Based on this, insulin has been tested in patients with Alzheimer's disease, and it was found that memory formation was improved and brain pathology reduced. Glucagon-like peptide-1 (GLP-1) is an incretin hormone, and numerous drugs that mimic this peptide are on the market to treat type 2 diabetes mellitus. Preclinical studies have provided robust evidence that some of these drugs, such as liraglutide or lixisenatide can enter the brain and improve key pathological parameters, such as memory loss, impairment of motor activity, synapse loss, reduced energy utilization by neurons and chronic inflammation in the brain. First clinical trials with a GLP-1 mimetic show good effects in patients with Parkinson's disease, improving motor control and insulin signaling in the brain. This is a proof of concept that this approach is viable and that drug treatment affects the main drivers of the disease and does not just modify the symptoms. It demonstrates that this new research area is a promising and fertile space for the development of novel treatments for neurodegenerative diseases.

Genetic engineering of novel super long-acting Exendin-4 chimeric protein for effective treatment of metabolic and cognitive complications of obesity

A common bottleneck challenge for many therapeutic proteins lies in their short plasma half-lives, which often makes the treatment far less compliant or even disables achieving sufficient therapeutic efficacy. To address this problem, we introduce a novel drug delivery strategy based on the genetic fusion of an albumin binding domain (ABD) and an anti-neonatal Fc receptor (FcRn) affibody (AFF) to therapeutic proteins. This ABD-AFF fusion strategy can provide a synergistic effect on extending the plasma residence time by, on one hand, preventing the rapid glomerular filtration via ABD-mediated albumin binding and, on the other hand, increasing the efficiency of FcRn-mediated recycling by AFF-mediated high-affinity binding to the FcRn. In this research, we explored the feasibility of applying the ABD-AFF fusion strategy to exendin-4 (EX), a clinically available anti-diabetic peptide possessing a short plasma half-life. The EX-ABD-AFF produced from the E. coli displayed a remarkably (241-fold) longer plasma half-life than the SUMO tagged-EX (SUMO-EX) (0.7 h) in mice. Furthermore, in high-fat diet (HFD)-fed obese mice model, the EX-ABD-AFF could provide significant hypoglycemic effects for over 12 days, accompanied by a reduction of body weight. In the long-term study, the EX-ABD-AFF could significantly reverse the obesity-related metabolic complications (hyperglycemia, hyperlipidemia, and hepatic steatosis) and, moreover, improve cognitive deficits. Overall, this study demonstrated that the ABD-AFF fusion could be an effective strategy to greatly increase the plasma half-lives of therapeutic proteins and thus markedly improve their druggability.

Reduction of hippocampal IL-6 levels in LPS-injected rats following acute exendin-4 treatment

Preclinical evidence on the role of glucagon-like peptide-1 receptor (GLP-1r) agonists in the brain led to an increased interest in repurposing these compounds as a therapy for central nervous system (CNS) disorders and associated comorbidities. We aimed to investigate the neuroprotective effects of acute treatment with exendin (EX)-4, a GLP-1r agonist, in an animal model of inflammation. We evaluated the effect of different doses of EX-4 on inflammatory, neurotrophic, and oxidative stress parameters in the hippocampus and serum of lipopolysaccharide (LPS)-injected animals. Male Wistar rats were injected with LPS (0.25 mg/kg i.p.) and treated with different doses of EX-4 (0.1, 0.3, or 0.5 μg/kg i.p.). Sickness behavior was assessed by locomotor activity and body weight, and depressive-like behavior was also evaluated using forced swim test (FST). Brain-derived neurotrophic factor (BDNF), thiobarbituric acid reactive species (TBARS), and interleukin (IL)-6 were quantified in the serum and hippocampus. Glycemia was also analyzed pre- and post-EX-4 treatment. LPS groups exhibited decreased frequency of crossing and reduced body weight (p < 0.001), while alterations on FST were not observed. The higher dose of EX-4 reduced IL-6 in the hippocampus of LPS-injected animals (p = 0.018), and EX-4 per se reduced TBARS serum levels with a modest antioxidant effect in the LPS groups (p ≤ 0.005). BDNF hippocampal levels seemed to be increased in the LPS+EX-4 0.5 group compared with LPS+Saline (p > 0.05). Our study provides evidence on acute anti-inflammatory effects of EX-4 in the hippocampus of rats injected with LPS, contributing to future studies on repurposing compounds with potential neuroprotective properties.

The treament of hyperglycemia in acute ischemic stroke with incretin-based drugs

Stroke is a major cause of mortality and morbidity worldwide. Considerable experimental and clinical evidence suggests that both diabetes mellitus (DM) and post-stroke hyperglycemia are associated with increased mortality rate and worsened clinical conditions in acute ischemic stroke (AIS) patients. Insulin treatment does not seem to provide convincing benefits for these patients, therefore prompting a change of strategy. The selective agonists of Glucagon-Like Peptide-1 Receptors (GLP-1Ras) and the Inhibitors of Dipeptidyl Peptidase-IV (DPP-IVIs, gliptins) are two newer classes of glucose-lowering drugs used for the treatment of DM. This review examines in detail the rationale for their development and the physicochemical, pharmacokinetic and pharmacodynamic properties and clinical activities. Emphasis will be placed on their neuroprotective effects at cellular and molecular levels in experimental models of acute cerebral ischemia. In perspective, an adequate basis does exist for a novel therapeutic approach to hyperglycemia in AIS patients through the additive treatment with GLP-1Ras plus DPP-IVIs.

Brain Endothelial Cells Regulate Glucagon-Like Peptide 1 Entry Into the Brain via a Receptor-Mediated Process

Glucagon-like peptide 1 (GLP-1) in addition to regulating glucose-dependent insulin and glucagon secretion exerts anorexic and neuroprotective effects. While brain-derived GLP-1 may participate in these central actions, evidence suggests that peripherally derived GLP-1 plays an important role and GLP-1 analogs are known to cross the blood brain barrier. To define the role of brain microvascular endothelial cells in GLP-1 entry into the brain, we infused labeled GLP-1 or exendin-4 into rats intravenously and examined their appearance and protein kinase A activities in various brain regions. We also studied the role of endothelial cell GLP-1 receptor and its signaling in endothelial cell uptake and transport of GLP-1. Systemically infused labeled GLP-1 or exendin-4 appeared rapidly in various brain regions and this was associated with increased protein kinase A activity in these brain regions. Pretreatment with GLP-1 receptor antagonist reduced labeled GLP-1 or exendin-4 enrichment in the brain. Sub-diaphragmatic vagus nerve resection did not alter GLP-1-mediated increases in protein kinase A activity in the brain. Rat brain microvascular endothelial cells rapidly took up labeled GLP-1 and this was blunted by either GLP-1 receptor antagonism or protein kinase A inhibition but enhanced through adenylyl cyclase activation. Using an artificially assembled blood brain barrier consisting of endothelial and astrocyte layers, we found that labeled GLP-1 time-dependently crossed the barrier and the presence of GLP-1 receptor antagonist blunted this transit. We conclude that GLP-1 crosses the blood brain barrier through active trans-endothelial transport which requires GLP-1 receptor binding and activation.

Glucagon-like peptide-1 receptor regulation of basal dopamine transporter activity is species-dependent

INTRODUCTION

A solid body of preclinical evidence shows that glucagon-like peptide-1 receptor (GLP-1R) agonists attenuate the effects of substance use disorder related behaviors. The mechanisms underlying these effects remain elusive. In the present study, we hypothesized that GLP-1R activation modulates dopaminetransporter (DAT) and thus dopamine (DA) homeostasis in striatum. This was evaluated in three different experiments: two preclinical and one clinical.

METHODS

Rat striatal DA uptake, DA clearance and DAT cell surface expression was assessed following GLP-1 (7-36)-amide exposure in vitro. DA uptake in mice was assesed ex vivo following systemic treatment with the GLP-1R agonist exenatide. In addition, DA uptake was measured in GLP-1R knockout mice and compared with DA-uptake in wild type mice. In healthy humans, changes in DAT availability was assessed during infusion of exenatide measured by single-photon emission computed tomography imaging.

RESULTS

In rats, GLP-1 (7-36)-amide increased DA uptake, DA clearance and DAT cell surface expression in striatum. In mice, exenatide did not change striatal DA uptake. In GLP-1R knockout mice, DA uptake was similar to what was measured in wildtype mice. In humans, systemic infusion of exenatide did not result in acute changes in striatal DAT availability.

CONCLUSIONS

The GLP-1R agonist-induced modulation of striatal DAT activity in vitro in rats could not be replicated ex vivo in mice and in vivo in humans. Therefore, the underlying mechanisms of action for the GLP-1R agonists-induced efficacy in varios addiction-like behavioural models still remain.

Liraglutide Up-regulation Thioredoxin Attenuated Müller Cells Apoptosis in High Glucose by Regulating Oxidative Stress and Endoplasmic Reticulum Stress

Purpose: Diabetic retinopathy (DR) has become one of the most important complications of diabetes which is the leading cause of vision impairment and blindness all over the world. Increasing evidence shows that reactive gliosis are basic pathological features of early DR. The study was aimed to explore the protective effect and mechanism of Liraglutide (LIRA) which has similar properties to Glucagon-like peptide-1 (GLP-1) on Müller cell damage induced by diabetes. Materials and methods: In vitro, the Müller cell was cultured in high glucose (HG) to establish the model of diabetic retinopathy. The apoptosis was detected using flow cytometry. Western blot and immunofluorescence were used to detect the expression of related proteins. DCFH-DA probe was used to detect the ROS generation. Results: The data showed that the apoptosis and the expression of GFAP were increased significantly with HG treatment. However, the apoptosis percentage and the expression of GFAP were decreased after LIRA treatment. Moreover, the expression of p-Erk/Nrf2/Trx-signaling pathway proteins was also up-regulated and the generation of ROS was decreased after LIRA treatment which was inhibited after treatment with U0126 (Erk inhibitor). Besides, endoplasmic reticulum stress (ER stress) related proteins were up-regulated after Trx down-regulation by transfection with sh-RNA. Conclusions: LIRA could protect Müller cells from HG-induced damage via activating p-Erk pathway through increasing Trx expression which attenuated oxidative stress and ER stress. Trx could play a key role in the process.

Brain insulin resistance: role in neurodegenerative disease and potential for targeting

Introduction: This review evaluates the novel strategy of treating Alzheimer's and Parkinson's disease (AD and PD) withdrugs that initially have been developed to treat type 2 diabetes. As insulin signalling has been found to be de-sensitized in the brains of patients, drugs that can re-sensitize insulin signalling have been tested to evaluate if this strategy can alter disease progression.Areas covered: The review will give an overview of preclinical and clinical tests in AD and PD of drugs activating insulin receptors, glucagon-like peptide -1 (GLP-1) receptors, and glucose-dependent insulinotropic polypeptide (GIP) receptors.Expert opinion: Insulin, GLP-1 and GIP receptor agonists have shown good effects in preclinical studies. First clinical trials in MCI/AD patients have shown that insulin can improve on key pathological symptoms of AD such as memory impairment, brain activity, neuronal energy utilization, and inflammation markers. A GLP-1 receptor agonist has shown disease-modifying effects in PD patients, and first pilot studies have shown encouraging effects of a GLP-1 receptor agonist in AD patients. Novel dual GLP-1/GIP receptor agonists that cross the blood brain barrier show superior neuroprotective effects compared to single GLP-1 or GIP receptor agonists, and show great promise as novel treatments of AD and PD.

Blood-brain barrier transport kinetics of NOTA-modified proteins: the somatropin case

BACKGROUND

Chemical modifications such as PEG, polyamine and radiolabeling on proteins can alter their pharmacokinetic behavior and their blood-brain barrier (BBB) transport characteristics. NOTA, i.e. 1,4,7-triazacyclononane-1,4,7-triacetic acid, is a bifunctional chelating agent that has attracted the interest of the scientific community for its high complexation constant with metals like gallium. Until now, the comparative BBB transport characteristics of NOTA-modified proteins versus unmodified proteins are not yet described.

METHODS

Somatropin (i.e. recombinant human growth hormone), NOTA-conjugated somatropin and gallium-labelled NOTA-conjugated somatropin were investigated for their brain penetration characteristics (multiple time regression and capillary depletion [CD]) in an in vivo mice model to determine the blood-brain transfer properties.

RESULTS

The three compounds showed comparable initial brain influx, with Kin=0.38±0.14 µL/(g×min), 0.36±0.16 µL/(g×min) and 0.28±0.18 µL/(g×min), respectively. CD indicated that more than 80% of the influxed compounds reached the brain parenchyma. All three compounds were in vivo stable in serum and brain during the time frame of the experiments.

CONCLUSIONS

Our results show that modification of NOTA as well as gallium chelation onto proteins, in casu somatropin, does not lead to a significantly changed pharmacokinetic profile at the blood-brain barrier.

The novel GLP-1/GIP analogue DA5-CH reduces tau phosphorylation and normalizes theta rhythm in the icv. STZ rat model of AD

INTRODUCTION

Alzheimer's disease (AD) is the most common progressive neurodegenerative disease for which there is no cure. Recent studies have shown a close link between type 2 diabetes and AD, which suggested that drugs for type 2 diabetes may be effective for AD. GLP-1 and GIP are incretin hormones that can ameliorate diabetes.

METHODS

In the present study, we tested the novel dual GLP-1/GIP receptor agonist DA5-CH in the icv. streptozotocin (STZ)-induced insulin desensitization model of AD in rats to explore the protective effects of DA5-CH.

RESULTS

The results show that DA5-CH could reverse the STZ-induced working memory impairments in a Y-maze tests, and spatial memory impairments in the water maze task, and decrease the levels of phosphorylated tauS396 protein in the hippocampus. In EEG recordings, STZ treatment diminished the power of the theta band frequency. DA5-CH was able to increase the energy of theta band activity in the hippocampal CA1 region. The drug also increased the expression of synapse-related proteins in the hippocampus. After DA5-CH treatment, mitochondrial stress was alleviated as shown by the improved ratio of Bax/Bcl-2 in the hippocampus. Growth factor signaling was also normalized as shown by the increased level of the transcription factor P-CREBS133 . In addition, we were able to show that DA5-CH can cross the blood-brain barrier at an increased rate compared with other dual GLP-1/GIP or single GLP-1 receptor agonists.

CONCLUSION

Therefore, our results demonstrate that DA5-CH has neuroprotective effects in the STZ-induced animal model and that DA5-CH has potential to treat neurodegenerative disorders such as AD.

Exenatide induces frataxin expression and improves mitochondrial function in Friedreich ataxia

Friedreich ataxia is an autosomal recessive neurodegenerative disease associated with a high diabetes prevalence. No treatment is available to prevent or delay disease progression. Friedreich ataxia is caused by intronic GAA trinucleotide repeat expansions in the frataxin-encoding FXN gene that reduce frataxin expression, impair iron-sulfur cluster biogenesis, cause oxidative stress, and result in mitochondrial dysfunction and apoptosis. Here we examined the metabolic, neuroprotective, and frataxin-inducing effects of glucagon-like peptide-1 (GLP-1) analogs in in vivo and in vitro models and in patients with Friedreich ataxia. The GLP-1 analog exenatide improved glucose homeostasis of frataxin-deficient mice through enhanced insulin content and secretion in pancreatic β cells. Exenatide induced frataxin and iron-sulfur cluster-containing proteins in β cells and brain and was protective to sensory neurons in dorsal root ganglia. GLP-1 analogs also induced frataxin expression, reduced oxidative stress, and improved mitochondrial function in Friedreich ataxia patients' induced pluripotent stem cell-derived β cells and sensory neurons. The frataxin-inducing effect of exenatide was confirmed in a pilot trial in Friedreich ataxia patients, showing modest frataxin induction in platelets over a 5-week treatment course. Taken together, GLP-1 analogs improve mitochondrial function in frataxin-deficient cells and induce frataxin expression. Our findings identify incretin receptors as a therapeutic target in Friedreich ataxia.

Antidiabetic Drugs for the Risk of Alzheimer Disease in Patients With Type 2 DM Using FAERS

Alzheimer disease (AD) may develop after the onset of type 2 diabetes mellitus (T2DM), and the risk of AD may depend on the antidiabetic drug administered. We compared the risk of AD among 66 085 patients (≥ 65 years) with T2DM (1250 having concomitant AD) who had been administered antidiabetic drug monotherapy for T2DM who had voluntarily reported themselves in the Food and Drug Administration Adverse Event Reporting System. The risk of AD from the use of different antidiabetic drug monotherapies compared to that of metformin monotherapy was assessed by logistic regression. Rosiglitazone (adjusted reporting odds ratio [aROR] = 0.11; 95% confidence interval [CI]: 0.07-0.17; P < .001), exenatide (aROR = 0.22; 95% CI: 0.11-0.37; P < .001), liraglutide (aROR = 0.36; 95% CI: 0.19-0.62; P < .001), dulaglutide (aROR = 0.39; 95% CI: 0.17-0.77; P = .014), and sitagliptin (aROR = 0.75; 95% CI: 0.60-0.93; P = .011) were found to have a significantly lower associated risk of AD than that of metformin. Therefore, the administration of glucagon-like peptide 1 receptor agonists and rosiglitazone may reduce the risk of AD in patients with T2DM.

Glucagon-like peptide 1 (GLP-1)

BACKGROUND

The glucagon-like peptide-1 (GLP-1) is a multifaceted hormone with broad pharmacological potential. Among the numerous metabolic effects of GLP-1 are the glucose-dependent stimulation of insulin secretion, decrease of gastric emptying, inhibition of food intake, increase of natriuresis and diuresis, and modulation of rodent β-cell proliferation. GLP-1 also has cardio- and neuroprotective effects, decreases inflammation and apoptosis, and has implications for learning and memory, reward behavior, and palatability. Biochemically modified for enhanced potency and sustained action, GLP-1 receptor agonists are successfully in clinical use for the treatment of type-2 diabetes, and several GLP-1-based pharmacotherapies are in clinical evaluation for the treatment of obesity.

SCOPE OF REVIEW

In this review, we provide a detailed overview on the multifaceted nature of GLP-1 and its pharmacology and discuss its therapeutic implications on various diseases.

MAJOR CONCLUSIONS

Since its discovery, GLP-1 has emerged as a pleiotropic hormone with a myriad of metabolic functions that go well beyond its classical identification as an incretin hormone. The numerous beneficial effects of GLP-1 render this hormone an interesting candidate for the development of pharmacotherapies to treat obesity, diabetes, and neurodegenerative disorders.

Association between use of oral hypoglycemic agents in Japanese patients with type 2 diabetes mellitus and risk of depression: A retrospective cohort study

Type 2 diabetes mellitus (T2DM) is a risk factor for depression. Since brain insulin resistance plays a potential role in depression, the future risk of depression in patients with T2DM may be altered depending on the class of oral hypoglycemic agent (OHA) used for T2DM therapy. The aim of the present study was to determine if specific classes of OHAs are associated with a risk for comorbid depression in T2DM. Japanese adult patients with T2DM (n = 40 214) were divided into a case group (with depression; n = 1979) and control group (without depression; n = 38 235). After adjustment for age [adjusted odds ratio (AOR) for 10 years: 1.03; 95% confidence interval (CI): 0.99-1.07; P = .1211], sex [AOR for female: 1.39; 95% CI: 1.26-1.53; P < .0001], hemoglobin A1c [AOR for 1.0%: 1.18; 95% CI: 1.11-1.26; P < .0001], duration of T2DM [AOR for 1 year: 1.00; 95% CI: 0.99-1.01; P = .4089], and history of seven medical conditions, the odds ratios for the development of depression was significantly lower for dipeptidyl peptidase-4 (DPP-4) inhibitors [AOR: 0.31; 95% CI: 0.24-0.42; P < .0001]. However, there was no significant association for the other classes of OHAs. Therefore, this study finds that there is less risk of depression associated with the use of DPP-4 inhibitors for the treatment of T2DM.

The use of GLP-1 receptor agonists in hospitalised patients: An untapped potential

In the outpatient setting, glucagon-like peptide-1 (GLP-1) receptor agonists have proved to be highly efficacious drugs that provide glycaemic control with a low risk of hypoglycaemia. These characteristics make GLP-1 receptor agonists attractive agents to treat dysglycaemia in perioperative or high-dependency hospital settings, where glycaemic variability and hyperglycaemia are associated with poor prognosis. GLP-1 also has a direct action on the myocardium and vasculature-which may be advantageous in the immediate aftermath of a vascular insult. This is a narrative review of the work in this area. The aim was to determine the populations of hospitalised patients being evaluated and the clinical and mechanistic end-points tested, with the institution of GLP-1 therapy in hospital. We searched the PubMed, Embase, and Google scholar databases, combining the term "glucagon-like peptide 1" OR "GLP-1" OR "incretin" OR "liraglutide" OR "exenatide" OR "lixisenatide" OR "dulaglutide" OR "albiglutide" AND "inpatient" OR "hospital" OR "perioperative" OR "postoperative" OR "surgery" OR "myocardial infarction" OR "stroke" OR "cerebrovascular disease" OR "transient ischaemic attack" OR "ICU" OR "critical care" OR "critical illness" OR "CCU" OR "coronary care unit." Pilot studies were reported in the fields of acute stroke, cardiac resuscitation, coronary care, and perioperative care that showed advantages for GLP-1 therapy, with normalisation of glucose, lower glucose variability, and lower risk of hypoglycaemia. Animal and human studies have reported improvements in myocardial performance when given acutely after vascular insult or surgery, but these have yet to be translated into randomised clinical trials.

GLP-1 secretion in acute ischemic stroke: association with functional outcome and comparison with healthy individuals

BACKGROUND

Glucagon-like peptide-1 (GLP-1) treatment has been shown to reduce stroke incidence in diabetes and also to be neuroprotective in experimental stroke models. The prognostic value of endogenous levels of GLP-1 in the recovery phase after stroke remains to be elucidated. The aim of the study was to investigate the potential association between GLP-1 levels and functional outcome after stroke and to determine whether GLP-1 is altered in the acute phase of stroke compared to 3 months post stroke and to healthy controls.

METHODS

Fasting GLP-1 was measured on hospital day 2-4 in patients without previously known diabetes (n = 59) that received recombinant tissue plasminogen activator (rtPA) for ischemic stroke. Fasting GLP-1 was measured again after 3 months and neurologic outcome was measured as modified Rankin Scale (mRS). mRS ≥ 2 was considered as unfavorable outcome. A control group of healthy individuals (n = 27) was recruited and their fasting GLP-1 was measured.

RESULTS

Fasting GLP-1 was higher in the patients that suffered a stroke compared to healthy controls (25.1 vs. 18.0 pmol/L; p = 0.004). The GLP-1 levels did not change significantly at the 3-month follow up OGTT (25.8 vs. 25.6; p = 0.80). There was no significant association between GLP-1 levels and unfavorable mRS (OR 1.03, 95% CI 0.95-1.12, p = 0.50).

CONCLUSIONS

Endogenous GLP-1 levels in patients that recently suffered an ischemic stroke are higher than in healthy controls and remained unchanged at the 3 months follow-up, possibly indicating an elevation of the levels of GLP-1 already pre-stroke. However, no association between endogenous GLP-1 and functional outcome of stroke 3 months post stroke was found.

Effects of glucagon-like peptide 1 receptor agonists on comorbidities in older patients with diabetes mellitus

Elderly patients with diabetes are at high risk of polypharmacy because of multiple coexisting diseases and syndromes. Polypharmacy increases the risk of drug–drug and drug–disease interactions in these patients, who may already have age-related sensory and cognitive deficits; such deficits may delay timely communication of early symptoms of adverse drug events. Several glucagon-like peptide-1 receptor agonists (GLP-1 RAs) have been approved for diabetes: liraglutide, exenatide, lixisenatide, dulagluatide, semaglutide, and albiglutide. Some are also approved for treatment of obesity. The current review of literature along with clinical case discussion provides evidence supporting GLP-1 RAs as diabetes medications for polypharmacy reduction in older diabetes patients because of their multiple pleiotropic effects on comorbidities (e.g. hyperlipidemia, hypertension, and fatty liver) and syndromes (e.g. osteoporosis and sleep apnea) that commonly co-occur with diabetes. Using one medication (in this case, GLP-1 RAs) to address multiple conditions may help reduce costs, medication burden, adverse drug events, and medication nonadherence.

Interleukin-6 in the central amygdala is bioactive and co-localised with glucagon-like peptide-1 receptor

Neuronal circuits involving the central amygdala (CeA) are gaining prominence as important centres for regulation of metabolic functions. As a part of the subcortical food motivation circuitry, CeA is associated with food motivation and hunger. We have previously shown that interleukin (IL)-6 can act as a downstream mediator of the metabolic effects of glucagon-like peptide-1 (GLP-1) receptor (R) stimulation in the brain, although the sites of these effects are largely unknown. In the present study, we used the newly generated and validated RedIL6 reporter mouse strain to investigate the presence of IL-6 in the CeA, as well as possible interactions between IL-6 and GLP-1 in this nucleus. IL-6 was present in the CeA, mostly in cells in the medial and lateral parts of this structure, and a majority of IL-6-containing cells also co-expressed GLP-1R. Triple staining showed GLP-1 containing fibres co-staining with synaptophysin close to or overlapping with IL-6 containing cells. GLP-1R stimulation enhanced IL-6 mRNA levels. IL-6 receptor-alpha (IL-6Rα) was found to a large part in neuronal CeA cells. Using electrophysiology, we determined that cells with neuronal properties in the CeA could be rapidly stimulated by IL-6 administration in vitro. Moreover, microinjections of IL-6 into the CeA could slightly reduce food intake in vivo in overnight fasted rats. In conclusion, IL-6 containing cells in the CeA express GLP-1R, are close to GLP-1-containing synapses, and demonstrate increased IL-6 mRNA in response to GLP-1R agonist treatment. IL-6, in turn, exerts biological effects in the CeA, possibly via IL-6Rα present in this nucleus.

Regulation of Memory Function by Feeding-Relevant Biological Systems: Following the Breadcrumbs to the Hippocampus

The hippocampus (HPC) controls fundamental learning and memory processes, including memory for visuospatial navigation (spatial memory) and flexible memory for facts and autobiographical events (declarative memory). Emerging evidence reveals that hippocampal-dependent memory function is regulated by various peripheral biological systems that are traditionally known for their roles in appetite and body weight regulation. Here, we argue that these effects are consistent with a framework that it is evolutionarily advantageous to encode and recall critical features surrounding feeding behavior, including the spatial location of a food source, social factors, post-absorptive processing, and other episodic elements of a meal. We review evidence that gut-to-brain communication from the vagus nerve and from feeding-relevant endocrine systems, including ghrelin, insulin, leptin, and glucagon-like peptide-1 (GLP-1), promote hippocampal-dependent spatial and declarative memory via neurotrophic and neurogenic mechanisms. The collective literature reviewed herein supports a model in which various stages of feeding behavior and hippocampal-dependent memory function are closely linked.

Pharmacokinetics and efficacy of PT302, a sustained-release Exenatide formulation, in a murine model of mild traumatic brain injury

Traumatic brain injury (TBI) is a neurodegenerative disorder for which no effective pharmacological treatment is available. Glucagon-like peptide 1 (GLP-1) analogues such as Exenatide have previously demonstrated neurotrophic and neuroprotective effects in cellular and animal models of TBI. However, chronic or repeated administration was needed for efficacy. In this study, the pharmacokinetics and efficacy of PT302, a clinically available sustained-release Exenatide formulation (SR-Exenatide) were evaluated in a concussive mild (m)TBI mouse model. A single subcutaneous (s.c.) injection of PT302 (0.6, 0.12, and 0.024 mg/kg) was administered and plasma Exenatide concentrations were time-dependently measured over 3 weeks. An initial rapid regulated release of Exenatide in plasma was followed by a secondary phase of sustained-release in a dose-dependent manner. Short- and longer-term (7 and 30 day) cognitive impairments (visual and spatial deficits) induced by weight drop mTBI were mitigated by a single post-injury treatment with Exenatide delivered by s.c. injection of PT302 in clinically translatable doses. Immunohistochemical evaluation of neuronal cell death and inflammatory markers, likewise, cross-validated the neurotrophic and neuroprotective effects of SR-Exenatide in this mouse mTBI model. Exenatide central nervous system concentrations were 1.5% to 2.0% of concomitant plasma levels under steady-state conditions. These data demonstrate a positive beneficial action of PT302 in mTBI. This convenient single, sustained-release dosing regimen also has application for other neurological disorders, such as Alzheimer's disease, Parkinson's disease, multiple system atrophy and multiple sclerosis where prior preclinical studies, likewise, have demonstrated positive Exenatide actions.

Neuroprotective Actions of Glucagon-Like Peptide-1 (GLP-1) Analogues in Alzheimer's and Parkinson's Diseases

The current absence of effective treatments for Alzheimer's disease (AD) and Parkinson's disease (PD) reflects an incomplete knowledge of the underlying disease processes. Considerable efforts have been made to investigate the central pathological features of these diseases, giving rise to numerous attempts to develop compounds that interfere with such features. However, further characterization of the molecular targets within the interconnected AD and PD pathways is still required. Impaired brain insulin signaling has emerged as a feature that contributes to neuronal dysfunction in both AD and PD, leading to strategies aiming at restoring this pathway in the brain. Long-acting glucagon-like peptide-1 (GLP-1) analogues marketed for treatment of type 2 diabetes mellitus have been tested and have shown encouraging protective actions in experimental models of AD and PD as well as in initial clinical trials. We review studies revealing the neuroprotective actions of GLP-1 analogues in pre-clinical models of AD and PD and promising results from recent clinical trials.

PYY(3-36) and exendin-4 reduce food intake and activate neuronal circuits in a synergistic manner in mice

Peptide YY(3-36) ((PYY(3-36)) and glucagon like peptide 1 (GLP-1) in combination reduce food intake and body weight in an additive or synergistic manner in animal models and in humans. Nevertheless, the mechanisms behind are not completely understood. The present study aims to investigate the effect of combining PYY(3-36) and the GLP-1 receptor agonist exendin-4 (Ex4) by examining acute food intake and global neuronal activation as measured by c-fos in C57BL/6 J mice. An additive reduction in food intake was found 1.5 h after s.c dosing with the combination of PYY(3-36) (200 μg/kg) and Ex4 (2.5 μg/kg). This was associated with a synergistic enhancement of c-fos reactivity in central amygdalar nucleus (CeA), rostral part of the mediobasal arcuate nucleus (ARH), supratrigeminal nucleus (SUT), lateral parabrachial nucleus (PB), area postrema (AP) and nucleus tractus solitarius (NTS) compared to vehicle, PYY(3-36) and Ex4 individually dosed mice. The regions activated by Ex4 individually and PYY(3-36) and Ex4 in combination resembled each other, but the combination group had a significantly stronger c-fos response. Twenty-five brain areas were activated by PYY(3-36) and Ex4 in combination compared to vehicle versus nine brain areas by Ex4 individually. No significant increase in c-fos reactivity was found by PYY(3-36) compared to vehicle dosed mice. The neuronal activation of ARH and the AP/NTS to PB to CeA pathway is important for appetite regulation while SUT has not previously been reported in the regulation of energy balance. As PYY(3-36) and Ex4 act on different neurons leading to recruitment of different signalling pathways within and to the brain, an interaction of these pathways may contribute to their additive/synergistic action. Thus, PYY(3-36) boosts the effect of Ex4 possibly by inducing less inhibition of neuronal activity leading to an enhanced neuronal activity induced by Ex4.

Effects of glucagon-like peptide 1 analogs on alcohol intake in alcohol-preferring vervet monkeys

BACKGROUND

Preclinical studies in rodents have demonstrated inhibitory effects of glucagon-like peptide-1 (GLP-1) receptor stimulation on alcohol consumption. The effects of GLP-1 receptor stimulation on alcohol intake in primates have not been investigated.

METHODS

We performed placebo-controlled studies on the effects of the GLP-1 receptor agonists exenatide and liraglutide on alcohol consumption in alcohol-preferring male African vervet monkeys. Monkeys selected for voluntary alcohol drinking were observed for at least 10 days of baseline drinking and allocated to drug or vehicle (n = 11-12 per group) balanced with respect to alcohol intake. Monkeys had access to alcohol 4 h/day. In a first study, monkeys were treated with exenatide 0.04 mg/kg or vehicle once weekly for 5 weeks to obtain steady-state plasma levels. In a second study, monkeys were treated daily with liraglutide (increasing dosing, 10 to 50 μg/kg/day) or vehicle over 2 weeks. In both studies, access to alcohol was suspended during drug up-titration. Then, alcohol was again made available 4 h/day and treatment was continued for 2 weeks, during which alcohol intake was recorded. Observation of alcohol intake was continued for a week of drug washout.

RESULTS

Liraglutide and to a lesser extent exenatide significantly reduced alcohol consumption without causing any signs of emesis and with no effect on water intake as compared to vehicle.

CONCLUSIONS

The present study demonstrates for the first time that GLP-1 receptor agonists can reduce voluntary alcohol drinking in non-human primates. The data substantiate the potential usefulness of GLP-1 receptor agonists in the treatment of alcohol use disorder.

GLP-1RAs in type 2 diabetes: mechanisms that underlie cardiovascular effects and overview of cardiovascular outcome data

Patients with type 2 diabetes (T2DM) have a substantial risk of developing cardiovascular disease. The strong connection between the severity of hyperglycaemia, metabolic changes secondary to T2DM and vascular damage increases the risk of macrovascular complications. There is a challenging demand for the development of drugs that control hyperglycaemia and influence other metabolic risk factors to improve cardiovascular outcomes such as cardiovascular death, nonfatal myocardial infarction, nonfatal stroke, hospitalization for unstable angina and heart failure (major adverse cardiovascular events). In recent years, introduction of the new drug class of glucagon-like peptide-1 receptor agonists (GLP-1RAs) has changed the treatment landscape as GLP-1RAs have become well-established therapies in T2DM. The benefits of GLP-1RAs are derived from their pleiotropic effects, which include appetite control, glucose-dependent secretion of insulin and inhibition of glucagon secretion. Importantly, their beneficial effects extend to the cardiovascular system. Large clinical trials have evaluated the cardiovascular effects of GLP-1RAs in patients with T2DM and elevated risk of cardiovascular disease and the results are very promising. However, important aspects still require elucidation, such as the specific mechanisms involved in the cardioprotective effects of these drugs. Careful interpretation is necessary because of the heterogeneity across the trials concerning the definition of cardiovascular risk or cardiovascular disease, baseline characteristics, routine care and event rates. The aim of this review is to describe the main clinical aspects of the GLP-1RAs, compare them using data from both the mechanistic and randomized controlled trials and discuss potential reasons for improved cardiovascular outcomes observed in these trials. This review may help clinicians to decide which treatment is most appropriate in reducing cardiovascular risk in patients with T2DM.

Structural Changes Observed in the Piriform Cortex in a Rat Model of Pre-motor Parkinson's Disease

Early diagnosis of Parkinson’s disease (PD) offers perhaps, the most promising route to a successful clinical intervention, and the use of an animal model exhibiting symptoms comparable to those observed in PD patients in the early stage of the disease, may facilitate screening of novel therapies for delaying the onset of more debilitating motor and behavioral abnormalities. In this study, a rat model of pre-motor PD was used to study the etiology of hyposmia, a non-motor symptom linked to the early stage of the disease when the motor symptoms have yet to be experienced. The study focussed on determining the effect of a partial reduction of both dopamine and noradrenaline levels on the olfactory cortex. Neuroinflammation and striking structural changes were observed in the model. These changes were prevented by treatment with a neuroprotective drug, a glucagon-like peptide-1 (GLP1) receptor agonist, exendin-4 (EX-4).

Gut-brain axis and addictive disorders: A review with focus on alcohol and drugs of abuse

Due to the limited efficacy of existing medications for addictive disorders including alcohol use disorder (AUD), the need for additional medications is substantial. Potential new medications for addiction can be identified through investigation of the neurochemical substrates mediating the ability of drugs of abuse such as alcohol to activate the mesolimbic dopamine system. Interestingly, recent studies implicate neuropeptides of the gut-brain axis as modulators of reward and addiction processes. The present review therefore summarizes the current studies investigating the ability of the gut-brain peptides ghrelin, glucagon-like peptide-1 (GLP-1), amylin and neuromedin U (NMU) to modulate alcohol- and drug-related behaviors in rodents and humans. Extensive literature demonstrates that ghrelin, the only known orexigenic neuropeptide to date, enhances reward as well as the intake of alcohol, and other drugs of abuse, while ghrelin receptor antagonism has the opposite effects. On the other hand, the anorexigenic peptides GLP-1, amylin and NMU independently inhibits reward from alcohol and drugs of abuse in rodents. Collectively, these rodent and human studies imply that central ghrelin, GLP-1, amylin and NMU signaling may contribute to addiction processes. Therefore, the need for randomized clinical trials investigating the effects of agents targeting these aforementioned systems on drug/alcohol use is substantial.