Exenatide upregulates gene expression of glucagon-like peptide-1 receptor and nerve growth factor in streptozotocin/nicotinamide-induced diabetic mice

Quercetin and Kaempferol as Multi-Targeting Antidiabetic Agents against Mouse Model of Chemically Induced Type 2 Diabetes

Diabetes, a multifactorial metabolic disorder, demands the discovery of multi-targeting drugs with minimal side effects. This study investigated the multi-targeting antidiabetic potential of quercetin and kaempferol. The druggability and binding affinities of both compounds towards multiple antidiabetic targets were explored using pharmacokinetic and docking software (AutoDock Vina 1.1.2). Our findings showed that quercetin and kaempferol obey Lipinski's rule of five and exhibit desirable ADMET (absorption, distribution, metabolism excretion, and toxicity) profiles. Both compounds showed higher binding affinities towards C-reactive protein (CRP), interleukin-1 (IL-1), dipeptidyl peptidase-4 (DPP-IV), peroxisome proliferator-activated receptor gamma (PPARG), protein tyrosine phosphatase (PTP), and sodium-glucose co-transporter-1 (SGLT-1) compared to metformin (the positive control). Both quercetin and kaempferol inhibited α-amylase activity (in vitro) up to 20.30 ± 0.49 and 37.43 ± 0.42%, respectively. Their oral supplementation significantly reduced blood glucose levels (p < 0.001), improved lipid profile (p < 0.001), and enhanced total antioxidant status (p < 0.01) in streptozotocin-nicotinamide (STZ-NA)-induced diabetic mice. Additionally, both compounds significantly inhibited the proliferation of Huh-7 and HepG2 (cancer cells) (p < 0.0001) with no effect on the viability of Vero cell line (non-cancer). In conclusion, quercetin and kaempferol demonstrated higher binding affinities towards multiple targets than metformin. In vitro and in vivo antidiabetic potential along with the anticancer activities of both compounds suggest promise for further development in diabetes management. The combination of both drugs did not show a synergistic effect, possibly due to their same target on the receptors.

Glucagon-like peptide-1 receptor agonists for the management of diabetic peripheral neuropathy

Diabetes mellitus is a prevalent chronic disease characterized by hyperglycemia. Diabetic peripheral neuropathy (DPN) is one of the complications of diabetes mellitus and is caused by neuron injury induced by hyperglycemic circumstances. The incidence of DPN varies among different countries and regions, ranging from nearly 20% to over 70%. Patients with DPN may encounter symmetric pain or discomfort of the extremes, leading to reduced quality of life and even amputation. The pharmacological management for painful DPN mainly includes antidepressants due to their analgesic effects. Nevertheless, effective therapies to impact the pathogenesis and progression of DPN are lacking. Glucagon-like peptide-1 receptor (GLP-1R) agonists show efficacy in controlling blood glucose and serve as a treatment modality for diabetes mellitus. In recent years, evidence has been proposed that GLP-1R agonists exert neuroprotective effects through modulating inflammation, oxidative stress, and mitochondrial dysfunction. On the other hand, clinical evidence on the potential of GLP-1R agonists for treating DPN is still controversial and limited. This narrative review summarizes the preclinical and clinical studies investigating the capacity of GLP-1R agonists as therapeutic agents for DPN.

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.

Antidiabetic Activity of Dihydropyrimidine Scaffolds and Structural Insight by Single Crystal X-ray Studies

BACKGROUND

This research project is designed to identify the anti-diabetic effects of the newly synthesized compounds to conclude the perspective of consuming one or more of these new synthetic compounds for diabetes management.

INTRODUCTION

A series of dihydropyrimidine (DHPM) derivative bearing electron releasing and electron-withdrawing substituent's on phenyl ring (a-j) were synthesized and screened for antihyperglycemic( anti-diabetic) activity on streptozotocin (STZ) induced diabetic rat model. The newly synthesized compounds were characterized by using FT-IR, melting point, 1H and 13C NMR analysis. The crystal structure and supramolecular features were analyzed through single-crystal X-ray study. Anti-diabetic activity testing of newly prepared DHPM scaffolds was mainly based on their relative substituent on the phenyl ring along with urea and thiourea. Among the synthesized DHPM scaffold, the test compound c having chlorine group on phenyl ring at the ortho position to the hydropyrimidine ring with urea and methyl acetoacetate derivative shows moderate lowering of glucose level. However, the title compounds methyl 4-(4-hydroxy-3-methoxyphenyl)- 6-methyl-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate(g) and ethyl 4-(3-ethoxy-4- hydroxyphenyl)-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate(h) having methoxy and ethoxy substituents on phenyl ring show significant hypoglycemic activity compared to the remaining compounds from the Scheme 1.

METHODS

The experimental rat models for the study were divided into 13 groups (n = 10); group 1 animals were treated with 0.5% CMC (0.5mL) (vehicle); group 2 were considered the streptozotocin (STZ)/nicotinamide diabetic control group (DC) and untreated, group 3 diabetic animals were administered with gliclazide 50 mg/kg and act as a reference drug group. The remaining groups of the diabetic animals were administered with the newly synthesized dihydropyrimidine compounds in a single dose of 50 mg/kg orally using the oral gavage, daily for 7 days continuously. The blood glucose level was measured before and 72 hrs after nicotinamide-STZ injection, for confirmation of hyperglycemia and type 2 diabetes development.

RESULTS

Blood glucose levels were significantly (p<0.05) reduced after treatment with these derivatives. The mean percentage reduction for gliclazide was 50%, while that of synthesized compounds were approximately 36%.

CONCLUSION

Our result suggests that the synthesized new DHPM derivative containing alkoxy group on the phenyl ring shows a significant lowering of glucose level compared to other derivatives.

Deciphering the Neuroprotective Role of Glucagon-like Peptide-1 Agonists in Diabetic Neuropathy: Current Perspective and Future Directions

Diabetic neuropathy is referred to as a subsequential and debilitating complication belonging to type 1 and type 2 diabetes mellitus. It is a heterogeneous group of disorders with a particularly complex pathophysiology and also includes multiple forms, ranging from normal discomfort to death. The evaluation of diabetic neuropathy is associated with hyperglycemic responses, resulting in an alteration in various metabolic pathways, including protein kinase C pathway, polyol pathway and hexosamine pathway in Schwann and glial cells of neurons. The essential source of neuronal destruction is analogous to these respective metabolic pathways, thus identified as potential therapeutic targets. These pathways regulating therapeutic medications may be used for diabetic neuropathy, however, only target specific drugs could have partial therapeutic activity. Various antidiabetic medications have been approved and marketed, which possess the therapeutic ability to control hyperglycemia and ameliorate the prevalence of diabetic neuropathy. Among all antidiabetic medications, incretin therapy, including Glucagon-like peptide-1 receptor agonists and dipeptidyl peptidase-4 inhibitors, are the most favorable medications for the management of diabetes mellitus and associated peripheral neuropathic complications. Besides enhancing glucose-evoked insulin release from pancreatic β-cells, these therapeutic agents also play a vital role to facilitate neurite outgrowth and nerve conduction velocity in dorsal root ganglion. Furthermore, incretin therapy also activates cAMP and ERK signalling pathways, resulting in nerve regeneration and repairing. These effects are evidently supported by a series of preclinical data and investigations associated with these medications. However, the literature lacks adequate clinical trial outcomes related to these novel antidiabetic medications. The manuscript emphasizes the pathogenesis, current pharmacological approaches and vivid description of preclinical and clinical data for the effective management of diabetic neuropathy.

The Neurotrophic Function of Glucagon-Like Peptide-1 Promotes Human Neuroblastoma Differentiation via the PI3K-AKT Axis

Simple Summary

The study demonstrated that the treatment with GLP-1 of SH-SY5Y human neuroblastoma cells increased the expression of AMPA receptors, NMDA receptors, dopamine receptors, synaptic proteins-synapsin 1, synaptophysin, and postsynaptic density protein 95, but not muscular and nicotinic acetylcholine receptors. In addition, the biomarker of dividing neuronal cells, vimentin, was decreased after treatment with GLP-1. Tuj1 immunostaining images showed that GLP-1 induced neurite processes and the development of neuronal morphologies. The GLP-1-differentiated neurons were able to be induced to generate action potentials by single cell patch-clamp. Our results also suggested that the PI3K-AKT axis is the dominant signaling pathway promoting the differentiation of SH-SY5Y cells into mature and functional neurons in response to GLP-1 receptor activation. The sequential treatment of retinoic acid and GLP-1 within a serum-free medium is able to trigger the differentiation of SH-SY5Y cells into morphologically and physiologically mature glutamatergic and dopaminergic neurons.

Abstract

Background: Neurons are terminally-differentiated cells that generally develop from neuronal stem cells stimulated by various neurotrophic factors such as NGF, BDNF, NT3, and NT-4. Neurotrophic factors have multiple functions for neurons, including enabling neuronal development, growth, and protection. Glucagon-like peptide-1 (GLP-1) is an intestinal-secreted incretin that enhances cellular glucose up-take to decrease blood sugar levels. However, many studies suggest that the function of GLP-1 is not limited to the regulation of blood sugar levels. Instead, it may also act as a neurotrophic factor with a role in ensuring neuronal survival and neurite outgrowth, as well as protecting synaptic plasticity and memory formation. Methods: The SH-SY5Y cells were differentiated by sequential treatments of retinoic acid and GLP-1 treatment within polyethylenimine-coated dishes under serum-free Neurobasal medium. PI3K inhibitor (LY294002) and MEK inhibitor (U0126) were used to determine the signaling pathway in regulation of neuronal differentiation. Neuronal marker (TUJ1) and synaptic markers (synapsin 1, synaptophysin, and PSD95) as well as single cell patch-clamp were applied to determine maturity of neurons. Antibodies of AMPA receptor, NMDA receptor subunit 2A, dopamine receptor D1, muscarinic acetylcholine receptor 2, and nicotinic acetylcholine receptor α4 were used to examine the types of differentiated neurons. Results: Our study’s results demonstrated that the treatment with GLP-1 of SH-SY5Y human neuroblastoma cells increased the expression of AMPA receptors, NMDA receptors, dopamine receptors, synaptic proteins-synapsin 1, synaptophysin, and postsynaptic density protein 95, but not muscular and nicotinic acetylcholine receptors. In addition, the biomarker of dividing neuronal cells, vimentin, was decreased after treatment with GLP-1. Tuj1 immunostaining images showed that GLP-1 induced neurite processes and the development of neuronal morphologies. The GLP-1-differentiated neurons were able to be induced to generate action potentials by single cell patch-clamp. Our study also suggested that the PI3K-AKT axis is the dominant signaling pathway promoting the differentiation of SH-SY5Y cells into mature and functional neurons in response to GLP-1 receptor activation. Conclusions: The sequential treatment of retinoic acid and GLP-1 within a serum-free medium is able to trigger the differentiation of SH-SY5Y cells into morphologically and physiologically mature glutamatergic and dopaminergic neurons.

SIS3, a good candidate for the reverse of type 2 diabetes mellitus in mice

TGF-β signaling plays an extremely important role in the occurrence and development of type 2 diabetes mellitus (T2DM), and the blockade of TGF-β/Smad3 pathway protests against the high-fat diet-induced obesity and diabetes. As a specific small molecule inhibitor of Smad3 protein, the biological activities of compound SIS3 were evaluated by high-fat diet-induced T2DM model mice. In vivo results indicated that SIS3 can not only significantly reduce the body weight, fat mass, and fasting blood glucose in high-fat diet-induced T2DM model mice, but also improve insulin sensitivity and oral glucose tolerance of high-fat diet-induced T2DM model mice after the injection of SIS3 with 5 mg/kg for 45 days.

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.

Exenatide promotes cardiac lncRNAs HOX transcript antisense RNA (HOTAIR) in Wistar rats with liver cirrhosis; a novel role of GLP-1 receptor agonists in cirrhotic cardiomyopathy

Long acting non-coding RNAs lncRNAs HOX Transcript Antisense RNA (HOTAIR) is cardioprotective and mediates its effect through sirtulin 1 (SIRT1). The decrease in HOTAIR expression predisposes to various types of cardiomyopathy. We aimed to investigate whether decrease HOTAIR expression is involved in cirrhotic cardiomyopathy or not and the role of glucagon like peptide 1 receptor (GLP-1 receptor) in facilitating its effect through studying the effect of a exenatide (EXA), on cardiac function as well as the expression of some relevant bio-molecules. Rats were used and divided into: naïve, EXA, Thioacetamide (TAA) and TAA + EXA groups. ECG, dobutamine stress test (DST) were done. AST, ALT, fasting blood glucose, troponin I were measured. Cardiac HOTAIR & SIRT1, hepatic and cardiac GLP-1 receptor expression levels were investigated in addition to histological studies. Our results showed that EXA administration in control rats produced no significant changes. TAA induced cirrhosis with insulin resistance and significant changes in cardiac functions. GLP-1 receptor, HOTAIR and SIRT1 expression in cardiac tissue were significantly decreased with a significant increase in troponin I. EXA + TAA group showed a restoration of the hepatic architecture and function. EXA treatment produced significant improvement in cardiac parameters and was associated with increasing the expression of cardiac GLP-1 receptor, HOTAIR. The cardiac muscle showed an apparent decrease in collagen fibers. So we can conclude that EXA promotes the protective effect of HOTAIR on cardiac structure and function in rat model of cirrhosis which may introduce a new therapeutic strategy in cirrhotic cardiomyopathy.

Dulaglutide ameliorates STZ induced AD-like impairment of learning and memory ability by modulating hyperphosphorylation of tau and NFs through GSK3β

Dulaglutide, a novel long-acting glucagon-like peptide 1 (GLP-1) receptor agonist, is an incretin mimetic approved for type 2 diabetes mellitus (T2DM) treatment. Alzheimer's disease (AD) is called type 3 diabetes. The aim of this study is to explore the effects of dulaglutide on the learning and memory impairment in AD mice induced by injection of streptozocin (STZ) via intracerebroventricularly (i.c.v.). 32 male C57/BL6 mice were randomly divided into four groups: control group (CON); AD model group (STZ); dulaglutide treated (Dul); dulaglutide and exendin(9-39) (Ex). Western blotting was used to detect the levels of phosphorylated tau, neurofilament (NFs) proteins and phosphorylated PI3K/AKT/GSK3β signaling pathway. Morris water maze (MWM) test was used to assess the spatial learning and memory ability. The results displayed that the hyperphosphorylation of tau and NFs were increased in the STZ and Ex groups compared to the control and Dul groups. Dulaglutide also significantly shortened the escape latency and increased the number of hidden platform crossings in MWM test. The effects of dulaglutide on decreasing the hyperphosphorylation of tau and NFs proteins through improving the PI3K/AKT/GSK3β signaling pathway may be related to its protective effects on impairment of AD-like learning and memory.

The effect of body mass index on glucagon-like peptide receptor gene expression in the post mortem brain from individuals with mood and psychotic disorders

There is an increasing interest in the putative role of glucagon-like peptide 1 receptor (GLP-1R) agonists as novel therapeutic agents for mental disorders. Herein, we investigated the expressions of GLP-1R and GLP-2R genes, and its relationship with body mass index (BMI), in the post-mortem brain tissue of patients with mood (MD) and psychotic disorders. Brain samples were localized to the dorsolateral prefrontal cortex (dlPFC) (n = 459) and hippocampus (n = 378). After adjustment for age, sex, ethnicity, post-mortem interval (PMI) and BMI, we observed significant differences, between healthy controls and MD subjects, in GLP-1R and GLP-2R gene expression in the dlPFC (β = 1.504, p = 0.004; and β = 1.305, p = 0.011, respectively); whereas in the hippocampus, only GLP-1R expression was significantly associated with MD (β = -1.28, p = 0.029). No significant differences were found in relation to schizophrenia. In addition, we observed a moderating effect of MD diagnosis on the associations between BMI, GLP-1R and GLP-2R expression values in the dlPFC (β = -0.05, p = 0.003; and β = -0.04, p = 0.004, respectively). There was a similar moderating effect for GLP-1R in the hippocampus (β = 0.043, 95% CI 0.003; 0.08 p = 0.03), but in an opposite direction than observed in the dlPFC. This is the first evidence of abnormal gene expression of GLP-1R and GLP-2R in postmortem brain of individuals with MD, providing a rationale for further inquiry and proof of principle interventional studies.