The type 2 diabetes drug liraglutide reduces chronic inflammation induced by irradiation in the mouse brain

A novel dual CCK/ GLP-1 receptor agonist ameliorates cognitive impairment in 5 × FAD mice by modulating mitophagy via the PINK1/Parkin pathway

To date, no therapeutic drugs available on the market can effectively reverse the progression of Alzheimer's disease (AD). Although Glucagon-like peptide-1 (GLP-1) receptor agonists (RAs) and Cholecystokinin (CCK) RAs have shown some promise in AD research, little is known about the neuroprotective effects of a novel dual CCK/GLP-1 RA in AD. This study sought to examine the effects of the novel dual CCK/GLP-1 RA on cognitive performance in an AD mouse model and to explore the associated mechanisms. Our findings indicate that dual CCK/GLP-1 RA improved cognitive deficits, reduced amyloid-beta (Aβ) accumulation, and alleviated mitochondrial damage in 5 × FAD mice by inducing mitophagy. In an in vitro model of AD cells induced by Aβ, CCK/GLP-1 RA could exert neuroprotective effects by regulating PINK1/Parkin-mediated mitophagy. These data reveal for the first time that the new CCK/GLP-1 RA modulates mitophagy via PINK1/Parkin pathway and enhances cognitive function in the 5 × FAD animal model. Moreover, the performance of the CCK/GLP-1 RA in certain indicators was superior to that of GLP-1 analogue liraglutide, suggesting that it may represent a more promising therapeutic option for AD.

Targeting Diabetic Atherosclerosis: The Role of GLP-1 Receptor Agonists, SGLT2 Inhibitors, and Nonsteroidal Mineralocorticoid Receptor Antagonists in Vascular Protection and Disease Modulation

Atherosclerosis is a closely related complication of diabetes mellitus (DM), driven by endothelial dysfunction, inflammation, and oxidative stress. The progression of atherosclerosis is accelerated by hyperglycemia, insulin resistance, and hyperlipidemia. Novel antidiabetic agents, SGLT2 inhibitors, and GLP-1 agonists improve glycemic control and offer cardiovascular protection, reducing the risk of major adverse cardiovascular events (MACEs) and heart failure hospitalization. These agents, along with nonsteroidal mineralocorticoid receptor antagonists (nsMRAs), promise to mitigate metabolic disorders and their impact on endothelial function, oxidative stress, and inflammation. This review explores the potential molecular mechanisms through which these drugs may prevent the development of atherosclerosis and cardiovascular disease (CVD), supported by a summary of preclinical and clinical evidence.

Exploring the Analgesic Effect of Acupuncture on Knee Osteoarthritis Based on MLT/cAMP/PKA/CREB Signaling Pathway

Background

Acupuncture is an effective treatment for knee osteoarthritis (KOA), reducing pain and improving function. While melatonin (MLT) has notable pain relief benefits, the analgesic mechanism of acupuncture in KOA and its relationship with melatonin are still unknown. This study aims to explore this mechanism.

Methods

In this work, the KOA rabbit model was constructed using the traditional Hulth method, and the therapeutic effect was assessed by the Lequesne MG score and Pain assessment by hot plate test. The pathological alterations of cartilage tissue were observed using hematoxylin and eosin (H&E) staining, Safranin O-fast green and MASSON staining to observe the pathological changes in cartilage tissue, and the efficacy was evaluated according to the principles of Mankin score and Osteoarthritis Research Society International (OARSI) score. Meanwhile, MLT in serum, cyclic adenosine monophosphate (cAMP) in cartilage, and matrix metalloproteinase-3 (MMP-3) in joint fluid were detected by enzyme-linked immunosorbent assay. In addition, the expression of aromatic L-amino acid N-acetyltransferase (AANAT), melatonin receptor 1 (MT1) and 2 (MT2) mRNAs in cartilage was determined by real-time quantitative reverse transcription-polymerase chain reaction, and the levels of proteins related to PKA/CREB signaling pathway were detected by Western blotting.

Results

Based on the results of Lequesne MG score and Pain assessment by hot plate test experimental data, the treatment group presented significant improvements in knee pain and overall function relative to OA (Osteoarthritis) group. Besides, according to results of histologic staining, Mankin and OARSI scores, articular cartilage degeneration of treatment group remarkably improved. In addition, acupuncture significantly reduced the expression of the inflammatory factor MMP-3 in knee joint fluid and significantly increased the levels of MLT, AANAT, MT1, MT2, cAMP, PKA and CREB.

Conclusion

By regulating sympathetic excitability, acupuncture may activate the MLT/cAMP/PKA/CREB signaling pathway, decrease inflammatory factor expression and slow down degradation of articular cartilage, resulting in the relief of knee pain.

Semaglutide promotes the transition of microglia from M1 to M2 type to reduce brain inflammation in APP/PS1/tau mice

A growing number of studies show that the diabetes drug Semaglutide is neuroprotective in Alzheimer's disease (AD) animal models, but its mode of action is not fully understood. In order to explore the mechanism of Semaglutide, 7-month-old APP/PS1/tau transgenic (3xTg) mice and wild-type (WT) mice were randomly divided into four groups: control group (WT + PBS), AD model group (3xTg + PBS), Semaglutide control group (WT + Semaglutide) and Semaglutide treatment group (3xTg + Semaglutide). Semaglutide (25 nmol/kg) or PBS was administered intraperitoneally once every two days for 30 days, followed by behavioral and molecular experiments. The results show that Semaglutide can improve working memory and spatial reference memory of 3xTg-AD mice, promote the release of anti-inflammatory factors and inhibit the production of pro-inflammatory factors in the cortex and hippocampus, and reduce Aβ deposition in the hippocampal CA1 region of 3xTg mice. Semaglutide can inhibit the apoptosis of BV2 cells induced by Aβ1-42 in a dose-dependent manner and promote the transformation of microglia from M1 to M2, thereby exerting anti-inflammatory and neuroprotective effects. Therefore, we speculate that Semaglutide shows an anti-inflammatory effect by promoting the transformation of microglia from M1 to M2 type in the brain of 3xTg mice, and thus exerts a neuroprotective effect.

Liraglutide and resveratrol alleviated cyclosporin A induced nephrotoxicity in rats through improving antioxidant status, apoptosis and pro-inflammatory markers

The recent study delves into the role of both liraglutide and/or resveratrol on the nephropathic affection in rats treated with cyclosporine A (CsA). Rats were intoxicated with CsA (25 mg/kg) orally for 21 days and were supplemented with liraglutide (30 μg/kg) s/c daily and 20 mg/kg of resveratrol (20 mg/kg) orally. At the end of the experiment, serum samples and renal tissues were collected to determine renal damage markers, apoptotic markers, proinflammatory markers, and antioxidant status markers. Kidney function tests and antioxidant activity notably improved in the treated rats (CsA + Lir/CsA + Res/CsA + Lir + Res). Moreover, both Lir and/or Res enhanced Bcl-2 levels while down-regulating the Bax levels in rats treated with CsA. Interestingly, the immune-staining for tumor necrosis factor (TNF-α) was tested negative and mild positive in renal tissue of rats given Lir and/or Res while being treated with Cs A which indicated their anti-inflammatory effect that reduced the renal damage. The findings of this investigation revealed the ameliorative anti-inflammatory in addition to the antioxidant role of both liraglutide and resveratrol against the kidney damage caused due to CsA administration.

Unlocking longevity with GLP-1: A key to turn back the clock?

Traditionally known for managing blood sugar, GLP-1, a gut hormone, is emerging as a potential key to both lengthening lifespan and combating age-related ailments. While widely recognized for its role in blood sugar control, GLP-1 is increasingly recognized for its diverse effects on various biological pathways beyond glucose metabolism. Research across organisms and humans suggests that activating GLP-1 receptors significantly impacts cellular processes linked to aging. Its ability to boost mitochondrial function, enhance cellular stress resistance, and quell inflammation hints at its wider influence on aging mechanisms. This intricate interplay between GLP-1 and longevity appears to act through multiple pathways. One key effect is its ability to modulate insulin sensitivity, potentially curbing age-related metabolic issues like type 2 diabetes. Its neuroprotective properties also make it a promising candidate for addressing age-related cognitive decline and neurodegenerative diseases. Furthermore, preclinical studies using GLP-1 analogs or agonists have shown promising results in extending lifespan and improving healthspan in various model organisms. These findings provide a compelling rationale for exploring GLP-1-based interventions in humans to extend healthy aging. However, despite the exciting therapeutic prospects of GLP-1 in promoting longevity, challenges remain. Determining optimal dosages, establishing long-term safety profiles, and investigating potential adverse effects require comprehensive clinical investigations before we can confidently translate these findings to humans. This article emphasises the wide applicability of GLP-1.

Glucagon-like peptide-1 class drugs show clear protective effects in Parkinson's and Alzheimer's disease clinical trials: A revolution in the making?

Parkinson's disease (PD) is a complex syndrome for which there is no disease-modifying treatment on the market. However, a group of drugs from the Glucagon-like peptide-1 (GLP-1) class have shown impressive improvements in clinical phase II trials. Exendin-4 (Bydureon), Liraglutide (Victoza, Saxenda) and Lixisenatide (Adlyxin), drugs that are on the market as treatments for diabetes, have shown clear effects in improving motor activity in patients with PD in phase II clinical trials. In addition, Liraglutide has shown improvement in cognition and brain shrinkage in a phase II trial in patients with Alzheimer disease (AD). Two phase III trials testing the GLP-1 drug semaglutide (Wegovy, Ozempic, Rybelsus) are ongoing. This perspective article will summarize the clinical results obtained so far in this novel research area. We are at a crossroads where GLP-1 class drugs are emerging as a new treatment strategy for PD and for AD. Newer drugs that have been designed to enter the brain easier are being developed already show improved effects in preclinical studies compared with the older GLP-1 class drugs that had been developed to treat diabetes. The future looks bright for new treatments for AD and PD.

From diabetes to diverse domains: the multifaceted roles of GLP-1 receptor agonists

Glucagon-like Peptide-1 (GLP-1) receptor agonists (GLP-1RAs) emerged as a primary treatment for type-2 diabetes mellitus (T2DM), however, their multifaceted effects on various target organs beyond glycemic control opened a new era of treatment. We conducted a comprehensive literature search using databases including Scopus, Google Scholar, PubMed, and the Cochrane Library to identify clinical, in-vivo, and in-vitro studies focusing on the diverse effects of GLP-1 receptor agonists. Eligible studies were selected based on their relevance to the varied roles of GLP-1RAs in T2DM management and their impact on other physiological functions. Numerous studies have reported the efficacy of GLP-1RAs in improving outcomes in T2DM, with demonstrated benefits including glucose-dependent insulinotropic actions, modulation of insulin signaling pathways, and reductions in glycemic excursions. Additionally, GLP-1 receptors are expressed in various tissues and organs, suggesting their widespread physiological functions beyond glycemic control potentially include neuroprotective, anti-inflammatory, cardioprotective, and metabolic benefits. However, further scientific studies are still underway to maximize the benefits of GLP-1RAs and to discover additional roles in improving health benefits. This article sought to review not only the actions of GLP1RAs in the treatment of T2DM but also explore its effects on potential targets in other disorders.

Glucagon-like peptide-1 receptor agonists and sodium-glucose cotransporter 2 inhibitors, anti-diabetic drugs in heart failure and cognitive impairment: potential mechanisms of the protective effects

Heart failure and cognitive impairment emerge as public health problems that need to be addressed due to the aging global population. The conditions that often coexist are strongly related to advancing age and multimorbidity. Epidemiological evidence indicates that cardiovascular disease and neurodegenerative processes shares similar aspects, in term of prevalence, age distribution, and mortality. Type 2 diabetes increasingly represents a risk factor associated not only to cardiometabolic pathologies but also to neurological conditions. The pathophysiological features of type 2 diabetes and its metabolic complications (hyperglycemia, hyperinsulinemia, and insulin resistance) play a crucial role in the development and progression of both heart failure and cognitive dysfunction. This connection has opened to a potential new strategy, in which new classes of anti-diabetic medications, such as glucagon-like peptide-1 receptor (GLP-1R) agonists and sodium-glucose cotransporter 2 (SGLT2) inhibitors, are able to reduce the overall risk of cardiovascular events and neuronal damage, showing additional protective effects beyond glycemic control. The pleiotropic effects of GLP-1R agonists and SGLT2 inhibitors have been extensively investigated. They exert direct and indirect cardioprotective and neuroprotective actions, by reducing inflammation, oxidative stress, ions overload, and restoring insulin signaling. Nonetheless, the specificity of pathways and their contribution has not been fully elucidated, and this underlines the urgency for more comprehensive research.

GLP-1 receptor agonists and atherosclerosis protection: the vascular endothelium takes center stage

Atherosclerotic cardiovascular disease is a chronic condition that often copresents with type 2 diabetes and obesity. Glucagon-like peptide-1 receptor agonists (GLP-1RAs) are incretin mimetics endorsed by major professional societies for improving glycemic status and reducing atherosclerotic risk in people living with type 2 diabetes. Although the cardioprotective efficacy of GLP-1RAs and their relationship with traditional risk factors are well established, there is a paucity of publications that have summarized the potentially direct mechanisms through which GLP-1RAs mitigate atherosclerosis. This review aims to narrow this gap by providing comprehensive and in-depth mechanistic insight into the antiatherosclerotic properties of GLP-1RAs demonstrated across large outcome trials. Herein, we describe the landmark cardiovascular outcome trials that triggered widespread excitement around GLP-1RAs as a modern class of cardioprotective agents, followed by a summary of the origins of GLP-1RAs and their mechanisms of action. The effects of GLP-1RAs at each major pathophysiological milestone of atherosclerosis, as observed across clinical trials, animal models, and cell culture studies, are described in detail. Specifically, this review provides recent preclinical and clinical evidence that suggest GLP-1RAs preserve vessel health in part by preventing endothelial dysfunction, achieved primarily through the promotion of angiogenesis and inhibition of oxidative stress. These protective effects are in addition to the broad range of atherosclerotic processes GLP-1RAs target downstream of endothelial dysfunction, which include systemic inflammation, monocyte recruitment, proinflammatory macrophage and foam cell formation, vascular smooth muscle cell proliferation, and plaque development.

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.

GLP-1 Analogs, SGLT-2, and DPP-4 Inhibitors: A Triad of Hope for Alzheimer's Disease Therapy

Alzheimer's is a prevalent, progressive neurodegenerative disease marked by cognitive decline and memory loss. The disease's development involves various pathomechanisms, including amyloid-beta accumulation, neurofibrillary tangles, oxidative stress, inflammation, and mitochondrial dysfunction. Recent research suggests that antidiabetic drugs may enhance neuronal survival and cognitive function in diabetes. Given the well-documented correlation between diabetes and Alzheimer's disease and the potential shared mechanisms, this review aimed to comprehensively assess the potential of new-generation anti-diabetic drugs, such as GLP-1 analogs, SGLT-2 inhibitors, and DPP-4 inhibitors, as promising therapeutic approaches for Alzheimer's disease. This review aims to comprehensively assess the potential therapeutic applications of novel-generation antidiabetic drugs, including GLP-1 analogs, SGLT-2 inhibitors, and DPP-4 inhibitors, in the context of Alzheimer's disease. In our considered opinion, antidiabetic drugs offer a promising avenue for groundbreaking developments and have the potential to revolutionize the landscape of Alzheimer's disease treatment.

Dopamine in the Regulation of Glucose Homeostasis, Pathogenesis of Type 2 Diabetes, and Chronic Conditions of Impaired Dopamine Activity/Metabolism: Implication for Pathophysiological and Therapeutic Purposes

Dopamine regulates several functions, such as voluntary movements, spatial memory, motivation, sleep, arousal, feeding, immune function, maternal behaviors, and lactation. Less clear is the role of dopamine in the pathophysiology of type 2 diabetes mellitus (T2D) and chronic complications and conditions frequently associated with it. This review summarizes recent evidence on the role of dopamine in regulating insular metabolism and activity, the pathophysiology of traditional chronic complications associated with T2D, the pathophysiological interconnection between T2D and chronic neurological and psychiatric disorders characterized by impaired dopamine activity/metabolism, and therapeutic implications. Reinforcing dopamine signaling is therapeutic in T2D, especially in patients with dopamine-related disorders, such as Parkinson's and Huntington's diseases, addictions, and attention-deficit/hyperactivity disorder. On the other hand, although specific trials are probably needed, certain medications approved for T2D (e.g., metformin, pioglitazone, incretin-based therapy, and gliflozins) may have a therapeutic role in such dopamine-related disorders due to anti-inflammatory and anti-oxidative effects, improvement in insulin signaling, neuroinflammation, mitochondrial dysfunction, autophagy, and apoptosis, restoration of striatal dopamine synthesis, and modulation of dopamine signaling associated with reward and hedonic eating. Last, targeting dopamine metabolism could have the potential for diagnostic and therapeutic purposes in chronic diabetes-related complications, such as diabetic retinopathy.

Augmentation Therapies as Treatments for Coexisting Somatic Problems in Schizophrenia-A Systematic Review

The aim of this review is to appraise the data from available randomized clinical trials (RCT) regarding the possible combinations of neuroleptic and non-antipsychotic treatment which could enhance antipsychotic therapy efficacy whilst simultaneously addressing somatic symptoms in individuals with schizophrenia. A systematic search of the PubMed database up to February 2022 was conducted. Inclusion criteria: randomized controlled trials using augmentation therapy in chronic schizophrenia in adults, written in English, and only studies with psychometric assessments of schizophrenia were incorporated. Exclusion criteria: non-clinical, first episode of schizophrenia, patients on medication other than antipsychotics augmented, and not adjunctive therapy. Overall, 37 studies of 1931 patients with schizophrenia who received a combination of antipsychotic medication with other drugs were selected. A statistically significant reduction of negative and positive symptoms of schizophrenia, measured with the PANSS scale, when using a combination of antipsychotic treatment along with aspirin, simvastatin, N-acetylcysteine, or pioglitazone was found. A combination of antipsychotic medication with aspirin, simvastatin, N-acetylcysteine, or pioglitazone seems to be effective in the reduction of symptoms of schizophrenia in adults, but long-term studies are required to confirm this effect.

Glucagon-like peptide-1: a multi-faceted anti-inflammatory agent

Inflammation contributes to many chronic conditions. It is often associated with circulating pro-inflammatory cytokines and immune cells. GLP-1 levels correlate with disease severity. They are often elevated and can serve as markers of inflammation. Previous studies have shown that oxytocin, hCG, ghrelin, alpha-MSH and ACTH have receptor-mediated anti-inflammatory properties that can rescue cells from damage and death. These peptides have been studied well in the past century. In contrast, GLP-1 and its anti-inflammatory properties have been recognized only recently. GLP-1 has been proven to be a useful adjuvant therapy in type-2 diabetes mellitus, metabolic syndrome, and hyperglycemia. It also lowers HbA1C and protects cells of the cardiovascular and nervous systems by reducing inflammation and apoptosis. In this review we have explored the link between GLP-1, inflammation, and sepsis.

The GLP-1 receptor agonist exenatide ameliorates neuroinflammation, locomotor activity, and anxiety-like behavior in mice with diet-induced obesity through the modulation of microglial M2 polarization and downregulation of SR-A4

Obesity is associated with multiple comorbidities, such as metabolic abnormalities and cognitive dysfunction. Moreover, accumulating evidence indicates that neurodegenerative disorders are associated with chronic neuroinflammation. GLP-1 receptor agonists (RAs) have been extensively studied as a treatment for type 2 diabetes. Emerging evidence has demonstrated a protective effect of GLP-1 RAs on neurodegenerative disease, which is independent of its glucose-lowering effects. In this study, we aimed to examine the effects of a long-acting GLP-1 RA, exenatide, on high-fat diet (HFD)-induced neuroinflammation and related brain function impairment. First, mice treated with exenatide exhibited significantly reduced HFD-increased body weight and blood glucose. In an open field test, exenatide treatment ameliorated the reduction in local motor activity and anxiety in HFD-fed mice. Moreover, HFD induced astrogliosis, microgliosis, and upregulation of IL-1β, IL-6 and TNF-α in hippocampus and cortex. Exenatide treatment reduced HFD-induced astrogliosis and IL-1β and TNF-α expressions. Moreover, exenatide increased phosphor-ERK and M2-type microglia marker arginase-1 expression in the hippocampus and cortex. In addition, we found that scavenger receptor-A4 protein expression was induced by HFD and was subsequently inhibited by exenatide. SR-A4 knockout reversed the locomotor activity impairment but not the anxiety behavior caused by HFD consumption. SR-A4 knockout also reduced HFD-induced neuroinflammation, as shown by the reduced expression of GFAP and IBA-1 compared with that in wild-type control mice. These results demonstrate that exenatide decreases HFD-increased neuroinflammation and promotes anti-inflammatory M2 differentiation. The inhibition of SR-A4 by exenatide exerts anti-inflammatory activity.

The Impact of Various Methods of Obesity Treatment on the Quality of Life and Mental Health-A Narrative Review

Obesity, defined as body mass index (BMI) ≥ 30 kg/m², is one of the most important public health problems. Over one billion people are obese, including 650 million adults, which is 13% of the worldwide population, according to the World Health Organization (WHO). Similar to obesity, mental disorders such as depression and anxiety are huge social problems with serious health implications. There are numerous studies proving a strong link between the prevalence of obesity and depressive disorders, and being overweight is also associated with decreased health-related quality of life (HRQoL). Due to the broad negative impact of obesity on a patient's health, proper treatment is crucial. Currently, the literature describes many methods of treatment such as dietary treatment, pharmacotherapy using glucagon-like peptide-1 (GLP-1) analogs, orlistat, naltrexone/bupropion (NB), or finally bariatric surgery. The most commonly used methods of obesity treatment significantly improve the patient's quality of life and reduce the symptoms of depression and anxiety. The aim of our study was to summarize the knowledge about the impact of known and commonly used methods of obesity treatment (e.g., dietary treatment, bariatric surgery, and pharmacological treatment) on mental health and quality of life. For this purpose, we will try to review the current scientific data, originating from international reports.

Effects of treatment of non-alcoholic fatty liver disease on heart failure with preserved ejection fraction

In the past few decades, non-alcoholic fatty liver disease (NAFLD) and heart failure with preserved ejection fraction (HFpEF) have become the most common chronic liver disease and the main form of heart failure (HF), respectively. NAFLD is closely associated with HFpEF by sharing common risk factors and/or by boosting systemic inflammation, releasing other secretory factors, and having an expansion of epicardial adipose tissue (EAT). Therefore, the treatments of NAFLD may also affect the development and prognosis of HFpEF. However, no specific drugs for NAFLD have been approved by the Food and Drug Administration (FDA) and some non-specific treatments for NAFLD are applied in the clinic. Currently, the treatments of NAFLD can be divided into non-pharmacological and pharmacological treatments. Non-pharmacological treatments mainly include dietary intervention, weight loss by exercise, caloric restriction, and bariatric surgery. Pharmacological treatments mainly include administering statins, thiazolidinediones, glucagon-like peptide-1 receptor agonists, sodium-glucose cotransporter 2 inhibitors, and metformin. This review will mainly focus on analyzing how these treatments may affect the development and prognosis of HFpEF.

Hypoglycemic medicines in the treatment of Alzheimer's disease: Pathophysiological links between AD and glucose metabolism

Alzheimer's Disease (AD) is a global chronic disease in adults with beta-amyloid (Aβ) deposits and hyperphosphorylated tau protein as the pathologic characteristics. Although the exact etiology of AD is still not fully elucidated, aberrant metabolism including insulin signaling and mitochondria dysfunction plays an important role in the development of AD. Binding to insulin receptor substrates, insulin can transport through the blood-brain barrier (BBB), thus mediating insulin signaling pathways to regulate physiological functions. Impaired insulin signaling pathways, including PI3K/Akt/GSK3β and MAPK pathways, could cause damage to the brain in the pathogenesis of AD. Mitochondrial dysfunction and overexpression of TXNIP could also be causative links between AD and DM. Some antidiabetic medicines may have benefits in the treatment of AD. Metformin can be beneficial for cognition improvement in AD patients, although results from clinical trials were inconsistent. Exendin-4 may affect AD in animal models but there is a lack of clinical trials. Liraglutide and dulaglutide could also benefit AD patients in adequate clinical studies but not semaglutide. Dipeptidyl peptidase IV inhibitors (DPP4is) such as saxagliptin, vildagliptin, linagliptin, and sitagliptin could boost cognitive function in animal models. And SGLT2 inhibitors such as empagliflozin and dapagliflozin were also considerably protective against new-onset dementia in T2DM patients. Insulin therapy is a promising therapy but some studies indicated that it may increase the risk of AD. Herbal medicines are helpful for cognitive function and neuroprotection in the brain. For example, polyphenols, alkaloids, glycosides, and flavonoids have protective benefits in cognition function and glucose metabolism. Focusing on glucose metabolism, we summarized the pharmacological mechanism of hypoglycemic drugs and herbal medicines. New treatment approaches including antidiabetic synthesized drugs and herbal medicines would be provided to patients with AD. More clinical trials are needed to produce definite evidence for the effectiveness of hypoglycemic medications.

Protection against stroke with glucagon-like peptide-1 receptor agonists: a comprehensive review of potential mechanisms

Several randomized controlled trials have demonstrated the benefits of glucagon-like peptide-1 receptor agonists (GLP-1RAs) on ischemic stroke in patients with diabetes. In this review, we summarize and discuss the potential mechanisms of stroke protection by GLP-1RAs. GLP-1RAs exert multiple anti-atherosclerotic effects contributing to stroke prevention such as enhanced plaque stability, reduced vascular smooth muscle proliferation, increased nitric oxide, and improved endothelial function. GLP-1RAs also lower the risk of stroke by reducing traditional stroke risk factors including hyperglycemia, hypertension, and dyslipidemia. Independently of these peripheral actions, GLP-1RAs show direct cerebral effects in animal stroke models, such as reduction of infarct volume, apoptosis, oxidative stress, neuroinflammation, excitotoxicity, blood-brain barrier permeability, and increased neurogenesis, neuroplasticity, angiogenesis, and brain perfusion. Despite these encouraging findings, further research is still needed to understand more thoroughly the mechanisms by which GLP-1RAs may mediate stroke protection specifically in the human diabetic brain.

The neuroprotective effects of glucagon-like peptide 1 in Alzheimer's and Parkinson's disease: An in-depth review

Currently, there is no disease-modifying treatment available for Alzheimer's and Parkinson's disease (AD and PD) and that includes the highly controversial approval of the Aβ-targeting antibody aducanumab for the treatment of AD. Hence, there is still an unmet need for a neuroprotective drug treatment in both AD and PD. Type 2 diabetes is a risk factor for both AD and PD. Glucagon-like peptide 1 (GLP-1) is a peptide hormone and growth factor that has shown neuroprotective effects in preclinical studies, and the success of GLP-1 mimetics in phase II clinical trials in AD and PD has raised new hope. GLP-1 mimetics are currently on the market as treatments for type 2 diabetes. GLP-1 analogs are safe, well tolerated, resistant to desensitization and well characterized in the clinic. Herein, we review the existing evidence and illustrate the neuroprotective pathways that are induced following GLP-1R activation in neurons, microglia and astrocytes. The latter include synaptic protection, improvements in cognition, learning and motor function, amyloid pathology-ameliorating properties (Aβ, Tau, and α-synuclein), the suppression of Ca2+ deregulation and ER stress, potent anti-inflammatory effects, the blockage of oxidative stress, mitochondrial dysfunction and apoptosis pathways, enhancements in the neuronal insulin sensitivity and energy metabolism, functional improvements in autophagy and mitophagy, elevated BDNF and glial cell line-derived neurotrophic factor (GDNF) synthesis as well as neurogenesis. The many beneficial features of GLP-1R and GLP-1/GIPR dual agonists encourage the development of novel drug treatments for AD and PD.

Inside the diabetic brain: Insulin resistance and molecular mechanism associated with cognitive impairment and its possible therapeutic strategies

Type 2 diabetes mellitus (T2DM) the most prevalent metabolic disease that has evolved into a major public health issue. Concerning about its secondary complications, a growing body of evidence links T2DM to cognitive impairment and neurodegenerative disorders. The underlying pathology behind this secondary complication disease is yet to be fully known. Nonetheless, they are likely to be associated with poor insulin signaling as a result of insulin resistance. We have combed through a rising body of literature on insulin signaling in the normal and diabetic brains along with various factors like insulin resistance, hyperglycemia, obesity, oxidative stress, neuroinflammation and Aβ plaques which can act independently or synergistically to link T2DM with cognitive impairments. Finally, we explored several pharmacological and non-pharmacological methods in the hopes of accelerating the rational development of medications for cognitive impairment in T2DM by better understanding these shared pathways.

Cross-translational models of late-onset cognitive sequelae and their treatment in pediatric brain tumor survivors

Pediatric brain tumor treatments have a high success rate, but survivors are at risk of cognitive sequelae that impact long-term quality of life. We summarize recent clinical and animal model research addressing pathogenesis or evaluating candidate interventions for treatment-induced cognitive sequelae. Assayed interventions encompass a broad range of approaches, including modifications to radiotherapy, modulation of immune response, prevention of treatment-induced cell loss or promotion of cell renewal, manipulation of neuronal signaling, and lifestyle/environmental adjustments. We further emphasize the potential of neuroimaging as a key component of cross-translation to contextualize laboratory research within broader clinical findings. This cross-translational approach has the potential to accelerate discovery to improve pediatric cancer survivors' long-term quality of life.

The Role of Glucagon-Like Peptide-1 Receptor Agonists (GLP-1 RA) in Diabetes-Related Neurodegenerative Diseases

Recent clinical guidelines have emphasized the importance of screening for cognitive impairment in older adults with diabetes, however, there is still a lack of understanding about the drug therapy. Glucagon-like peptide 1 receptor agonists (GLP-1 RAs) are widely used in the treatment of type 2 diabetes and potential applications may include the treatment of obesity as well as the adjunctive treatment of type 1 diabetes mellitus in combination with insulin. Growing evidence suggests that GLP-1 RA has the potential to treat neurodegenerative diseases, particularly in diabetes-related Alzheimer’s disease (AD) and Parkinson’s disease (PD). Here, we review the molecular mechanisms of the neuroprotective effects of GLP-1 RA in diabetes-related degenerative diseases, including AD and PD, and their potential effects.

Effects of Glucagon-like peptide 1 (GLP-1) analogs in the hippocampus

The glucagon-like peptide-1 (GLP-1) is a pleiotropic hormone very well known for its incretin effect in the glucose-dependent stimulation of insulin secretion. However, GLP-1 is also produced in the brain, and it displays critical roles in neuroprotection by activating the GLP-1 receptor signaling pathways. GLP-1 enhances learning and memory in the hippocampus, promotes neurogenesis, decreases inflammation and apoptosis, modulates reward behavior, and reduces food intake. Its pharmacokinetics have been improved to enhance the peptide's half-life, enhancing exposure and time of action. The GLP-1 agonists are successfully in clinical use for the treatment of type-2 diabetes, obesity, and clinical evaluation for the treatment of neurodegenerative diseases.

Protective properties of GLP-1 and associated peptide hormones in neurodegenerative disorders

Type 2 diabetes mellitus and the associated desensitisation of insulin signalling has been identified as a risk factor for progressive neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease and others. Glucagon-like peptide 1 (GLP-1) is a hormone that has growth factor-like and neuroprotective properties. Several clinical trials have been conducted, testing GLP-1 receptor agonists in patients with Alzheimer's disease, Parkinson's disease or diabetes-induced memory impairments. The trials showed clear improvements in Alzheimer's disease, Parkinson's disease and diabetic patients. Glucose-dependent insulinotropic polypeptide/gastric inhibitory peptide (GIP) is the 'sister' incretin hormone of GLP-1. GIP analogues have shown neuroprotective effects in animal models of disease and can improve on the effects of GLP-1. Novel dual GLP-1/GIP receptor agonists have been developed that can enter the brain at an enhanced rate. The improved neuroprotective effects of these drugs suggest that they are superior to single GLP-1 receptor agonists and could provide disease-modifying care for Alzheimer's disease and Parkinson's disease patients. LINKED ARTICLES: This article is part of a themed issue on GLP1 receptor ligands (BJP 75th Anniversary). To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v179.4/issuetoc.

Liraglutide, a glucagon-like peptide 1 receptor agonist, exerts analgesic, anti-inflammatory and anti-degradative actions in osteoarthritis

Osteoarthritis (OA) is a common disabling disease worldwide, with no effective and safe disease-modifying drugs (DMOAD) in the market. However, studies suggest that drugs, such as liraglutide, which possess strong potential in decreasing low-grade systemic inflammation may be effective in treating OA. Therefore, the aim of this study was to examine the anti-inflammatory, analgesic, and anti-degradative effects in OA using in vitro and in vivo experiments. The results showed that intra-articular injection of liraglutide alleviated pain-related behavior in in vivo sodium monoiodoacetate OA mouse model, which was probably driven by the GLP-1R-mediated anti-inflammatory activity of liraglutide. Moreover, liraglutide treatment significantly decreased IL-6, PGE2 and nitric oxide secretion, and the expression of inflammatory genes in vitro in chondrocytes and macrophages in a dose-dependent manner. Additionally, liraglutide shifted polarized macrophage phenotype in vitro from the pro-inflammatory M1 phenotype to the M2 anti-inflammatory phenotype. Furthermore, liraglutide exerted anti-catabolic activity by significantly decreasing the activities of metalloproteinases and aggrecanases, a family of catabolic enzymes involved in cartilage breakdown in vitro. Overall, the findings of this study showed that liraglutide ameliorated OA-associated pain, possess anti-inflammatory and analgesic properties, and could constitute a novel therapeutic candidate for OA treatment.

The Role of Gut Microbiota in the Progression of Parkinson's Disease and the Mechanism of Intervention by Traditional Chinese Medicine

Parkinson's disease (PD) is a common degenerative disease of the nervous system that seriously affects the quality of life of the patients. The pathogenesis of PD is not yet fully clear. Previous studies have confirmed that patients with PD exhibit obvious gut microbiota imbalance, while intervention of PD by regulating the gut microbiota has become an important approach to the prevention and treatment of this disease. Traditional Chinese medicine (TCM) has been shown to be safe and effective in treating PD. It has the advantages of affecting multiple targets. Studies have shown TCM can regulate gut microbiota. However, the specific mechanism of action is still unclear. Therefore, this article will mainly discuss the association of the alteration of the gut microbiota and the incidence of PD, the advantages of TCM in treating PD, and the mechanism of regulating gut microbiota by TCM to treat PD. It will clarify the target and mechanism of TCM treating PD by acting gut microbiota and provided a novel methodology for the prevention and treatment of PD.

The mechanism and efficacy of GLP-1 receptor agonists in the treatment of Alzheimer's disease

Since type 2 diabetes mellitus (T2DM) is a risk factor for Alzheimer's disease (AD) and both have the same pathogenesis (e.g., insulin resistance), drugs used to treat T2DM have been gradually found to reduce the progression of AD in AD models. Of these drugs, glucagon-like peptide 1 receptor (GLP-1R) agonists are more effective and have fewer side effects. GLP-1R agonists have reducing neuroinflammation and oxidative stress, neurotrophic effects, decreasing Aβ deposition and tau hyperphosphorylation in AD models, which may be a potential drug for the treatment of AD. However, this needs to be verified by further clinical trials. This study aims to summarize the current information on the mechanisms and effects of GLP-1R agonists in AD.

Targeting the GLP-1/GLP-1R axis to treat osteoarthritis: A new opportunity?

Osteoarthritis (OA) is a degenerative joint disease affecting millions of people worldwide. In OA, chondrocytes, synovial cells and other joint cells become activated when exposed to an abnormal environment, including mechanical stress, inflammatory cytokines or disorganization of matrix proteins. Several analogues of the hormones called incretins have been developed and are used notably for treating type 2 diabetes mellitus. Data has accumulated to suggest that incretinomimetics, which bind to the glucagon-like peptide-1 receptor (GLP-1R), have beneficial pleiotropic effects such as immunomodulation, anti-inflammation and neuronal protection. Thus, because of their anti-inflammatory properties, GLP-1-based therapies could benefit OA patients. This review focuses on the GLP-1R pathway, molecular mechanisms and phenotypes related to OA pathogenesis.

The translational potential of this article

The search for new therapeutic targets to treat people suffering from OA remains urgent as there is currently no disease-modifyingtherapy available for this disease. This review discusses how GLP-1 analogues could be potential DMOADs for treating OA thanks to their anti-inflammatory, immunoregulatory and differentiation properties.

The role of incretins and incretin-based drugs in autoimmune diseases

Incretin hormones, including glucagon-like peptide (GLP)-1, GLP-2 and glucose-dependent insulinotropic polypeptide (GIP), are gastrointestinal peptides secreted from enteroendocrine cells. These hormones play significant roles in many physiological processes via binding to G-protein coupled receptors (GPCRs) on different organs and tissues; one of them is the immunomodulatory effect on the immune system and its molecular components such as cytokines and chemokines. Anti-inflammatory effects of incretins and dependent molecules involving long-acting analogs and DPP4 inhibitors through regulation of T and B cell activation may attenuate autoimmune diseases caused by immune system disorders in mistakenly recognizing self as the foreign agent. In this review, we investigate incretin effects on the immune system response and the potential benefits of incretin-based therapy for treating autoimmune diseases.

The Novel Dual GLP-1/GIP Receptor Agonist DA-CH5 Is Superior to Single GLP-1 Receptor Agonists in the MPTP Model of Parkinson's Disease

BACKGROUND

Parkinson's disease (PD) is a progressive neurodegenerative disease for which there is no cure. In a clinical trial, the glucagon-like peptide-1 (GLP-1) receptor agonist exendin-4 has shown good protective effects in PD patients. The hormone glucose-dependent insulinotropic polypeptide (GIP) has also shown protective effects in animal models of PD.

OBJECTIVE

We tested DA-CH5, a novel dual GLP-1/GIP receptor agonist.

METHODS

DA-CH5 activity was tested on cells expressing GLP-1, GLP-2, GIP or glucagon receptors. The ability to cross the blood-brain barrier (BBB) of DA-CH5, exendin-4, liraglutide or other dual receptor agonists was tested with fluorescein-labelled peptides. DA-CH5, exendin-4 and liraglutide were tested in the MPTP mouse model of PD.

RESULTS

Analysing the receptor activating properties showed a balanced activation of GLP-1 and GIP receptors while not activating GLP-2 or glucagon receptors. DA-CH5 crossed the BBB better than other single or other dual receptor agonists. In a dose-response comparison, DA-CH5 was more effective than the GLP-1 receptor agonist exendin-4. When comparing the neuroprotective effect of DA-CH5 with Liraglutide, a GLP-1 analogue, both DA-CH5 and Liraglutide improved MPTP-induced motor impairments. In addition, the drugs reversed the decrease of the number of neurons expressing tyrosine hydroxylase (TH) in the SN, alleviated chronic inflammation, reduced lipid peroxidation, inhibited the apoptosis pathway (TUNEL assay) and increased autophagy -related proteins expression in the substantia nigra (SN) and striatum. Importantly, we found DA-CH5 was superior to Liraglutide in reducing microglia and astrocyte activation, improving mitochondrial activity by reducing the Bax/Bcl-2 ratio and normalising autophagy as found in abnormal expression of LC3 and p62.

CONCLUSION

The results demonstrate that the DA-CH5 is superior to liraglutide and could be a therapeutic treatment for PD.

Towards Better Drug Repositioning: Targeted Immunoinflammatory Therapy for Diabetic Nephropathy

Diabetic nephropathy (DN) is one of the most common and important microvascular complications of diabetes mellitus (DM). The main clinical features of DN are proteinuria and a progressive decline in renal function, which are associated with structural and functional changes in the kidney. The pathogenesis of DN is multifactorial, including genetic, metabolic, and haemodynamic factors, which can trigger a sequence of events. Controlling metabolic risks such as hyperglycaemia, hypertension, and dyslipidaemia is not enough to slow the progression of DN. Recent studies emphasized immunoinflammation as a critical pathogenic factor in the progression of DN. Therefore, targeting inflammation is considered a potential and novel treatment strategy for DN. In this review, we will briefly introduce the inflammatory process of DN and discuss the anti-inflammatory effects of antidiabetic drugs when treating DN.

Protective effect of liraglutide on experimental testicular ischaemia reperfusion in rats

This study was performed to evaluate the effect of liraglutide on experimental testicular ischaemia reperfusion in rats in terms of biochemistry, histopathology and immunohistochemistry. A total of 28 male Wistar-Albino rats were divided randomly into 4 groups: control (7), sham (7), ischaemia-reperfusion (7) and ischaemia-reperfusion + liraglutide (7). Biochemically, Nitric Oxide, Malondialdehyde, Superoxide dismutase, Glutathione peroxidase and Catalase levels were measured in the testis. Apoptosis protease activating factor-1 and inducible nitric oxide synthase activity were evaluated immunohistochemically as well. Statistical analyses were made via the Kruskal-Wallis and Mann-Whitney U tests. In the reperfusion group, CAT and SOD values were increased (p > .05), NO and MDA values were decreased (p < .05) after administration of liraglutide. In addition, GPx values were significantly increased in ischaemia reperfusion + liraglutide administered group compared to reperfusion group (p < .05). Apaf-1 and iNOS activity were significantly decreased with the addition of liraglutide treatment to the ischaemia-reperfusion group (p < .05). First of all, we would like to say that liraglutide treatment is moderately preventive against I/R injury in testicular torsion. The anti-inflammatory, antioxidant and antiapoptotic properties of liraglutide are create a moderately protective effect as we show in this study.

Liraglutide Has Anti-Inflammatory and Anti-Amyloid Properties in Streptozotocin-Induced and 5xFAD Mouse Models of Alzheimer's Disease

Recent clinical and epidemiological studies support the contention that diabetes mellitus (DM) is a strong risk factor for the development of Alzheimer’s disease (AD). The use of insulin cell toxin, streptozotocin (STZ), when injected into the lateral ventricles, develops an insulin resistant brain state (IRBS) and represents a non-transgenic, or sporadic AD model (SAD), with several AD-like neuropathological features. The present study explored the effects of an anti-diabetic drug, liraglutide (LIR), in reversing major pathological hallmarks in the prodromal disease stage of both the 5xFAD transgenic and SAD mouse models of AD. Three-month-old 5xFAD and age-matched wild type mice were given a single intracerebroventricular (i.c.v) injection of STZ or vehicle (saline) and were subsequently treated with LIR, intraperitoneally (IP), once a day for 30 days. The extent of neurodegeneration, Aβ plaque load, and key proteins associated with the insulin signaling pathways were measured using Western blot and neuroinflammation (via immunohistological assays) in the cortical and hippocampal regions of the brain were assessed following a series of behavioral tests used to measure cognitive function after LIR or vehicle treatments. Our results indicated that STZ significantly increased neuroinflammation, Aβ plaque deposition and disrupted insulin signaling pathway, while 25 nmol/kg LIR, when injected IP, significantly decreased neuroinflammatory responses in both SAD and 5xFAD mice before significant cognitive changes were observed, suggesting LIR can reduce early neuropathology markers prior to the emergence of overt memory deficits. Our results indicate that LIR has neuroprotective effects and has the potential to serve as an anti-inflammatory and anti-amyloid prophylactic therapy in the prodromal stages of AD.

Dulaglutide exerts beneficial anti atherosclerotic effects in ApoE knockout mice with diabetes: the earlier, the better

There has been no report about the mechanism for anti-atherosclerotic effects of dulaglutide (Dula) and/or about the difference of its effectiveness between in an early and a late phase of diabetes. To address such questions, streptozotocin (STZ) was intraperitoneally injected to ApoE knockout mice at 8 weeks of age. Either Dula or vehicle was administered to STZ-induced diabetic ApoE knockout mice from 10 to 18 weeks of age as an early intervention group and from 18 to 26 weeks as a late intervention group. Next, non-diabetic ApoE knockout mice without STZ injection were subcutaneously injected with either Dula or vehicle. In an early intervention group, atherosclerotic lesion in aortic arch and Mac-2 and CD68-positive areas in aortic root were significantly smaller in Dula group. In abdominal aorta, expression levels of some villain factors were lower in Dula group. In a late intervention group, there were no immunohistological differences in aortic root and expression levels of various factors between two groups. Furthermore, even in non-diabetic ApoE knockout mice, expression levels of inflammatory and macrophage markers were reduced by treatment with Dula. Taken together, Dula exerts more beneficial anti-atherosclerotic effects in an early phase of diabetes rather than in a late phase.

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.

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.

Liraglutide Protects Against Brain Amyloid-β1-42 Accumulation in Female Mice with Early Alzheimer's Disease-Like Pathology by Partially Rescuing Oxidative/Nitrosative Stress and Inflammation

Alzheimer’s disease (AD) is the most common form of dementia worldwide, being characterized by the deposition of senile plaques, neurofibrillary tangles (enriched in the amyloid beta (Aβ) peptide and hyperphosphorylated tau (p-tau), respectively) and memory loss. Aging, type 2 diabetes (T2D) and female sex (especially after menopause) are risk factors for AD, but their crosslinking mechanisms remain unclear. Most clinical trials targeting AD neuropathology failed and it remains incurable. However, evidence suggests that effective anti-T2D drugs, such as the GLP-1 mimetic and neuroprotector liraglutide, can be also efficient against AD. Thus, we aimed to study the benefits of a peripheral liraglutide treatment in AD female mice. We used blood and brain cortical lysates from 10-month-old 3xTg-AD female mice, treated for 28 days with liraglutide (0.2 mg/kg, once/day) to evaluate parameters affected in AD (e.g., Aβ and p-tau, motor and cognitive function, glucose metabolism, inflammation and oxidative/nitrosative stress). Despite the limited signs of cognitive changes in mature female mice, liraglutide only reduced their cortical Aβ_1–42 levels. Liraglutide partially attenuated brain estradiol and GLP-1 and activated PKA levels, oxidative/nitrosative stress and inflammation in these AD female mice. Our results support the earlier use of liraglutide as a potential preventive/therapeutic agent against the accumulation of the first neuropathological features of AD in females.

Neuromodulatory effects of anti-diabetes medications: A mechanistic review

Diabetes mellitus is a potent upstream event in the molecular pathophysiology which gives rise to various diabetes-related complications. There are several classes of anti-diabetic medications that have been developed to normalize blood glucose concentrations through a variety of molecular mechanisms. Beyond glucose-lowering effects, these agents may also provide further therapeutic potential. For instance, there is a high incidence of diabetes-induced neuronal disorders among patients with diabetes, who may also develop neurodegenerative and psychological complications. If anti-diabetic agents can modify the molecular mechanisms involved in the pathophysiology of neuronal comorbidities, this could potentially be translated to reducing the risk of other neurological conditions such as Alzheimer's disease, Parkinson's disease, depression, memory deficits and cognition impairments among patients with diabetes. This review aimed to shed light on some of the potentially beneficial aspects of anti-diabetic agents in lowering the risk or treating neuronal disorders by reviewing the molecular mechanisms by which these agents can potentially modulate neuronal behaviors.

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

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

The investigation of therapeutic potential of oxytocin and liraglutide on vincristine-induced neuropathy in rats

The aim of this study was to assess the therapeutic potential of oxytocin and liraglutide (LIR), a GLP-1 analogue, in a rat model of vincristine-induced neuropathy. Rats were injected with vincristine (VCR) at a dose of 4 mg/kg twice a week for 5 weeks. The VCR-administered rats were divided into three groups and received saline, oxytocin, or liraglutide simultaneously with VCR. After the treatment period, electrophysiological, biochemical, histological, and immunohistochemical investigations were performed. Electromyography (EMG) recordings demonstrated significant alterations in the VCR + saline group (p < .001). Also, motor performance was decreased in the VCR + saline group (p < .05). Histologically, the axonal diameter was decreased in all groups. VCR + saline group showed significantly increased lipid peroxidation and decreased nerve growth factor (NGF) expression. However, the administration of oxytocin and liraglutide significantly prevented the EMG alterations, lipid peroxidation, and reduction in neuronal NGF expression. On the basis of these findings, oxytocin and liraglutide may be considered as potential agents for the prevention of VCR-induced neuropathy.

Liraglutide improves insulin sensitivity in high fat diet induced diabetic mice through multiple pathways

Glucagon like peptide-1 (GLP-1) promotes postprandial insulin secretion. Liraglutide, a full agonist of the GLP-1 receptor, reduces body weight, improve insulin sensitivity, and alleviate Non Alcoholic Fatty Liver Disease (NAFLD). However, the underlying mechanisms remain unclear. This study aims to explore the underlying mechanisms and cell signaling pathways involved in the anti-obesity and anti-inflammatory effects of liraglutide. Mice were fed a high fat high sucrose diet to induce diabetes, diabetic mice were divided into two groups and injected with liraglutide or vehicle for 14 days. Liraglutide treatment improved insulin sensitivity, accompanied with reduced expression of the phosphorylated Acetyl-CoA carboxylase-2 (ACC2) and upregulation of long chain acyl CoA dehydrogenase (LCAD) in insulin sensitive tissues. Furthermore, liraglutide induced adenosine monophosphate-activated protein kinase-α (AMPK-α) and Sirtuin-1(Sirt-1) protein expression in liver and perigonadal fat. Liraglutide induced elevation of fatty acid oxidation in these tissues may be mediated through the AMPK-Sirt-1 cell signaling pathway. In addition, liraglutide induced brown adipocyte differentiation in skeletal muscle, including induction of uncoupling protein-1 (UCP-1) and PR-domain-containing-16 (PRDM-16) protein in association with induction of SIRT-1. Importantly, liraglutide displayed anti-inflammation effect. Specifically, liraglutide led to a significant reduction in circulating interleukin-1 β (IL-1 β) and interleukin-6 (IL-6) as well as hepatic IL-1 β and IL-6 content. The expression of inducible nitric oxide synthase (iNOS-1) and cyclooxygenase-2 (COX-2) in insulin sensitive tissues was also reduced following liraglutide treatment. In conclusion, liraglutide improves insulin sensitivity through multiple pathways resulting in reduction of inflammation, elevation of fatty acid oxidation, and induction of adaptive thermogenesis.

Exendin-4 regulates Wnt and NF-κB signaling in lipopolysaccharide-induced human periodontal ligament stem cells to promote osteogenic differentiation

A major feature of chronic periodontitis (CP) is the damage and destruction of alveolar bone. Periodontal ligament stem cells (PDLSCs) can differentiate into bone and improve CP. Exendin-4 (Ex-4) has been shown to have anti-inflammatory mechanisms and can promote bone regeneration. However, the effects of Ex-4 on the osteogenic differentiation of PDLSCs in the inflammatory microenvironment remains uncharacterized. In this study, we assessed the effects of Ex-4 on PDLSCs stimulated with lipopolysaccharide (LPS) to mimic the inflammatory environment. PDLSCs proliferation was assessed through CCK-8 assays and osteogenic differentiation was measured using Alizarin Red staining. The anti-inflammatory and osteogenic mechanisms of Ex-4 were assessed by western blot, RT-PCR, ELISA and immunofluorescence. We found that LPS treatment promoted the proliferative capacity of PDLSCs and inhibited their osteogenic differentiation. However, Ex-4 reversed these effects through suppressing PDLSCs proliferation and promoting osteogenic differentiation. Ex-4 increased Runx2, ALP, and Osx levels and decreased TNF-α and IL-6 expression. Ex-4 also reduced the expression of IκBα and p-IκBα, and inhibited the nuclear translocation of NF-κB/p65. The expression of β-catenin decreased in nucleus after co-treatment of Ex-4 with LPS. Taken together, these data demonstrate that Ex-4 promotes PDLSCs osteogenic differentiation in the inflammatory microenvironment through regulating NF-κB and Wnt signaling.

The GLP-1 agonist, liraglutide, ameliorates inflammation through the activation of the PKA/CREB pathway in a rat model of knee osteoarthritis

Background

Inflammation is a common pathological phenomenon of osteoarthritis (OA). Accumulated evidence indicates that ameliorating or suppressing inflammation might be a promising and effective therapeutic strategy for the treatment of OA. Notably, glucagon-like peptide-1 (GLP-1)-based drugs are being successfully used to control glucose levels in patients with diabetes mellitus. In addition, recent findings have indicated that GLP-1 agonists, such as liraglutide have therapeutic potential in preventing inflammation-related disorders through the regulation of protein kinase A (PKA)/ cyclic adenosine monophosphate (cAMP) response element-binding protein (CREB) signals. Intra-articular injection of monoiodoacetate (MIA) has been widely used to induce OA. Thus, the present study aimed to investigate whether liraglutide has anti-inflammatory effects on MIA-induced OA rats and uncover its underlying molecular mechanisms.

Methods

Intra-articular injection of MIA was used to induce knee OA in a rat model. Subcutaneous injection of liraglutide was used to upregulate the expression of GLP-1 receptor (GLP-1R). Western blot analysis was utilized to measure the expression of GLP-1R, PKA/CREB pathway components and inflammation-related proteins, such as tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), and IL-6. Immunoprecipitation techniques were used to detect the interactions between GLP-1R and the PKA/CREB pathway.

Results

The levels of GLP-1R decreased significantly in the knees of OA rats, accompanied by the downregulation of PKA /CREB signals and upregulation of inflammation-related proteins. We also found that GLP-1R interacted with the PKA/CREB pathway and that liraglutide could activate PKA/CREB signals, thereby inhibiting the expression of inflammation-related proteins.

Conclusions

Together our results suggest that liraglutide exhibits anti-inflammatory activity through the activation of the PKA/CREB pathway in an OA rat model.

GLP-1's role in neuroprotection: a systematic review

Glucagon-like peptide 1 (GLP-1) is a target for treatment of diabetes; however, its function in the brain is not well studied. In this systematic review, we aimed to analyze the neuroprotective role of GLP-1 and its defined mechanisms. Methods: We searched 'Web of Science' and 'Pubmed' to identify relevant studies using GLP-1 as the keyword. Two hundred and eighty-nine clinical and preclinical studies have been included. Data have been presented by grouping neurodegenerative, neurovascular and specific cell culture models. Results: Recent literature shows that GLP-1 and its agonists, DPP-4 inhibitors and combined GLP-1/GIP molecules are effective in partially or fully reversing the effects of neurotoxic compounds, neurovascular complications of diabetes, neuropathological changes related with Alzheimer's disease, Parkinson's disease or vascular occlusion. Possible mechanisms that provide neuroprotection are enhancing the viability of the neurons and restoring neurite outgrowth by increased neurotrophic factors, increasing subventricular zone progenitor cells, decreasing apoptosis, decreasing the level of pro-inflammatory factors, and strengthening blood-brain barrier. Conclusion: Based on the preclinical studies, GLP-1 modifying agents are promising targets for neuroprotection. On the other hand, the number of clinical studies that investigate GLP-1 as a treatment is low and further clinical trials are needed for a benchside to bedside translation of recent findings.

The GLP-1 analog, liraglutide prevents the increase of proinflammatory mediators in the hippocampus of male rat pups submitted to maternal perinatal food restriction

Background

Perinatal maternal malnutrition is related to altered growth of tissues and organs. The nervous system development is very sensitive to environmental insults, being the hippocampus a vulnerable structure, in which altered number of neurons and granular cells has been observed. Moreover, glial cells are also affected, and increased expression of proinflammatory mediators has been observed. We studied the effect of Glucagon-like peptide-1 receptor (GLP-1R) agonists, liraglutide, which have very potent metabolic and neuroprotective effects, in order to ameliorate/prevent the glial alterations present in the hippocampus of the pups from mothers with food restriction during pregnancy and lactation (maternal perinatal food restriction—MPFR).

Methods

Pregnant Sprague-Dawley rats were randomly assigned to 50% food restriction (FR; n = 12) or ad libitum controls (CT, n = 12) groups at day of pregnancy 12 (GD12). From GD14 to parturition, pregnant FR and CT rats were treated with liraglutide (100 μg/kg) or vehicle. At postnatal day 21 and before weaning, 48 males and 45 females (CT and MPFR) were sacrificed. mRNA expression levels of interleukin-1β (IL1β), interleukin-6 (IL-6), nuclear factor-κβ, major histocompatibility complex-II (MHCII), interleukin 10 (IL10), arginase 1 (Arg1), and transforming growth factor (TGFβ) were assessed in the hippocampus by quantitative real-time polymerase chain reaction. Iba1 and GFAP-immunoreactivity were assessed by immunocytochemistry.

Results

The mRNA expression IL1β, IL6, NF-κB, and MHCII increased in the hippocampus of male but not in female pups from MPFR. In addition, there was an increase in the percentage of GFAP and Iba1-immupositive cells in the dentate gyrus compared to controls, indicating an inflammatory response in the brain. On the other hand, liraglutide treatment prevented the neuroinflammatory process, promoting the production of anti-inflammatory molecules such as IL10, TGFβ, and arginase 1, and decreasing the number and reactivity of microglial cells and astrocytes in the hippocampus of male pups.

Conclusion

Therefore, the GLP-1 analog, liraglutide, emerges as neuroprotective drug that minimizes the harmful effects of maternal food restriction, decreasing neuroinflammation in the hippocampus in a very early stage.