GLP-1R agonist therapy for diabetes: benefits and potential risks

Glucagon-like peptide-1 receptor: mechanisms and advances in therapy

The glucagon-like peptide-1 (GLP-1) receptor, known as GLP-1R, is a vital component of the G protein-coupled receptor (GPCR) family and is found primarily on the surfaces of various cell types within the human body. This receptor specifically interacts with GLP-1, a key hormone that plays an integral role in regulating blood glucose levels, lipid metabolism, and several other crucial biological functions. In recent years, GLP-1 medications have become a focal point in the medical community due to their innovative treatment mechanisms, significant therapeutic efficacy, and broad development prospects. This article thoroughly traces the developmental milestones of GLP-1 drugs, from their initial discovery to their clinical application, detailing the evolution of diverse GLP-1 medications along with their distinct pharmacological properties. Additionally, this paper explores the potential applications of GLP-1 receptor agonists (GLP-1RAs) in fields such as neuroprotection, anti-infection measures, the reduction of various types of inflammation, and the enhancement of cardiovascular function. It provides an in-depth assessment of the effectiveness of GLP-1RAs across multiple body systems-including the nervous, cardiovascular, musculoskeletal, and digestive systems. This includes integrating the latest clinical trial data and delving into potential signaling pathways and pharmacological mechanisms. The primary goal of this article is to emphasize the extensive benefits of using GLP-1RAs in treating a broad spectrum of diseases, such as obesity, cardiovascular diseases, non-alcoholic fatty liver disease (NAFLD), neurodegenerative diseases, musculoskeletal inflammation, and various forms of cancer. The ongoing development of new indications for GLP-1 drugs offers promising prospects for further expanding therapeutic interventions, showcasing their significant potential in the medical field.

GLP-1R mediates idebenone-reduced blood glucose in mice

GLP-1 receptor agonists (GLP-1RAs) are an innovative class of drugs with significant therapeutic value for type 2 diabetes mellitus (T2DM). The GLP-1RAs currently available on the market are biologic macromolecular peptide agents that are expensive to treat and not easy to take orally. Therefore, the development of small molecule GLP-1RAs is becoming one of the most sought-after research targets for hypoglycemic drugs. In this study, we sought to find a potential oral small molecule GLP-1RA and to evaluate its effect on insulin secretion in rat pancreatic β cells and on blood glucose in mice. We downloaded the mRNA expression profiles of GSE102194 and GSE37936 from the Gene Expression Omnibus database. Subsequently, the small molecule compound idebenone was screened through the connectivity map database. The results of molecular docking, biolayer interferometry, and cellular thermal shift assay indicated that idebenone could bind potently with GLP-1R. Furthermore, ibebenone elevated intracellular cAMP levels. The radioimmunoassay data showed that idebenone enhanced glucose-stimulated insulin secretion via agonism of GLP-1R. Moreover, the results of oral glucose tolerance tests in C57BL/6, Glp-1r-/-, and hGlp-1r mice demonstrated that the glucose-lowering effects of idebenone were mediated by GLP-1R and that there were no species differences in the agonistic effect of idebenone on GLP-1R. In summary, idebenone reduces blood glucose in mice by promoting insulin release through agonism of GLP-1R, suggesting that idebenone is probably a potential GLP-1RA, which is expected to provide a new therapeutic strategy for the prevention and treatment of metabolic diseases such as T2DM.

Drug repositioning in thyroid cancer treatment: the intriguing case of anti-diabetic drugs

Cancer represents the main cause of death worldwide. Thyroid cancer (TC) shows an overall good rate of survival, however there is a percentage of patients that do not respond or are refractory to common therapies. Thus new therapeutics strategies are required. In the past decade, drug repositioning become very important in the field of cancer therapy. This approach shows several advantages including the saving of: i) time, ii) costs, iii) de novo studies regarding the safety (just characterized) of a drug. Regarding TC, few studies considered the potential repositioning of drugs. On the other hand, certain anti-diabetic drugs, were the focus of interesting studies on TC therapy, in view of the fact that they exhibited potential anti-tumor effects. Among these anti-diabetic compounds, not all were judjed as appropriate for repositioning, in view of well documented side effects. However, just to give few examples biguanides, DPP-4-inhibitors and Thiazolidinediones were found to exert strong anti-cancer effects in TC. Indeed, their effects spaced from induction of citotoxicity and inhibition of metastatic spread, to induction of de-differentiation of TC cells and modulation of TC microenvironment. Thus, the multifacial anti-cancer effect of these compounds would make the basis also for combinatory strategies. The present review is aimed at discuss data from studies regarding the anti-cancer effects of several anti-diabetic drugs recently showed in TC in view of their potential repositioning. Specific examples of anti-diabetic repositionable drugs for TC treatment will also be provided.

The GLP-1 receptor agonist exenatide reduces serum TSH by its effect on body weight in people with type 2 diabetes

OBJECTIVE

Glucagon-like peptide-1 receptor agonist (GLP-1 RA) therapy in patients with type 2 diabetes and obesity leads to a significant reduction in serum thyrotropin (TSH) levels but it is unclear whether this is related to weight loss and improvement in sensitivity to thyroid hormones (TH).

DESIGN, PATIENTS AND MEASUREMENTS

We prospectively analysed clinical and biochemical data in patients with type 2 diabetes and obesity who were commenced on the GLP-1 RA exenatide and followed them for 12 months. We assessed the relationship between changes in body weight and serum TSH and resistance to TH indices.

RESULTS

In 112 patients (mean age: 53.5 years, 43.8% female, mean body mass index: 39.8 kg/m2 ), 12 months of exenatide treatment was associated with a mean (95% CI) percent body weight loss of 6.5% (5.0%-8.1%) and change in serum TSH of -0.25 mU/L (-0.43 to -0.06). There was a significant negative and nonlinear relationship between change in serum TSH and percent body weight loss: -0.25 mU/L with 5%, -0.4 mU/L with 10% and -0.5 mU/L with 15%, respectively, whereas a rise in serum TSH of 0.5 mU/L was associated with 5% weight gain. There were no changes observed in serum FT4 levels with weight loss but a significant reduction in resistance to TH indices was noted.

CONCLUSIONS

Exenatide therapy reduces serum TSH levels and improves central sensitivity to TH action over 12 months via its effect on weight loss. The effectiveness of weight loss strategies, rather than TH replacement, should be investigated in individuals with obesity and mildly raised serum TSH levels.

Structural basis of peptidomimetic agonism revealed by small- molecule GLP-1R agonists Boc5 and WB4-24

Glucagon-like peptide-1 receptor (GLP-1R) agonists are efficacious in the treatment of type 2 diabetes and obesity. While most clinically used agents require subcutaneous injection, Boc5, as the first orthosteric nonpeptidic agonist of GLP-1R, suffers from poor oral bioavailability that hinders its therapeutic development. The cryoelectron microscopy structures of Boc5 and its closely related analog WB4-24 presented here reveal a binding pocket located deeper in the transmembrane domain for nonpeptidic GLP-1R agonists. Molecular interaction with this site may facilitate a broad spectrum of in vivo agonistic activities, in addition to that with the upper helical bundles presumably responsible for biased signaling. These findings deepen our understanding of peptidomimetic agonism at GLP-1R and may help design better drug leads against this important target.

Glucagon-like peptide-1 receptor (GLP-1R) agonists are effective in treating type 2 diabetes and obesity with proven cardiovascular benefits. However, most of these agonists are peptides and require subcutaneous injection except for orally available semaglutide. Boc5 was identified as the first orthosteric nonpeptidic agonist of GLP-1R that mimics a broad spectrum of bioactivities of GLP-1 in vitro and in vivo. Here, we report the cryoelectron microscopy structures of Boc5 and its analog WB4-24 in complex with the human GLP-1R and G_s protein. Bound to the extracellular domain, extracellular loop 2, and transmembrane (TM) helices 1, 2, 3, and 7, one arm of both compounds was inserted deeply into the bottom of the orthosteric binding pocket that is usually accessible by peptidic agonists, thereby partially overlapping with the residues A8 to D15 in GLP-1. The other three arms, meanwhile, extended to the TM1-TM7, TM1-TM2, and TM2-TM3 clefts, showing an interaction feature substantially similar to the previously known small-molecule agonist LY3502970. Such a unique binding mode creates a distinct conformation that confers both peptidomimetic agonism and biased signaling induced by nonpeptidic modulators at GLP-1R. Further, the conformational difference between Boc5 and WB4-24, two closed related compounds, provides a structural framework for fine-tuning of pharmacological efficacy in the development of future small-molecule therapeutics targeting GLP-1R.

Design, synthesis, and biological evaluation of a small molecule oral agonist of the glucagon-like-peptide-1 receptor

An absolute or relative deficiency of pancreatic β-cells mass and functionality is a crucial pathological feature common to type 1 diabetes mellitus and type 2 diabetes mellitus. Glucagon-like-peptide-1 receptor (GLP1R) agonists have been the focus of considerable research attention for their ability to protect β-cell mass and augment insulin secretion with no risk of hypoglycemia. Presently commercially available GLP1R agonists are peptides that limit their use due to cost, stability, and mode of administration. To address this drawback, strategically designed distinct sets of small molecules were docked on GLP1R ectodomain and compared with previously known small molecule GLP1R agonists. One of the small molecule PK2 (6-((1-(4-nitrobenzyl)-1H-1,2,3-triazol-4-yl)methyl)-6H-indolo[2,3-b]quinoxaline) displays stable binding with GLP1R ectodomain and induces GLP1R internalization and increasing cAMP levels. PK2 also increases insulin secretion in the INS-1 cells. The oral administration of PK2 protects against diabetes induced by multiple low-dose streptozotocin administration by lowering high blood glucose levels. Similar to GLP1R peptidic agonists, treatment of PK2 induces β-cell replication and attenuate β-cell apoptosis in STZ-treated mice. Mechanistically, this protection was associated with decreased thioredoxin-interacting protein expression, a potent inducer of diabetic β-cell apoptosis and dysfunction. Together, this report describes a small molecule, PK2, as an orally active nonpeptidic GLP1R agonist that has efficacy to preserve or restore functional β-cell mass.

Treating cognitive impairment in schizophrenia with GLP-1RAs: an overview of their therapeutic potential

INTRODUCTION

Schizophrenia is a neuropsychiatric disorder that affects approximately 1% of individuals worldwide. There are no available medications to treat cognitive impairment in this patient population currently. Preclinical evidence suggests that glucagon-like peptide-1 receptor agonists (GLP-1 RAs) improve cognitive function. There is a need to evaluate how GLP-1 RAs alter specific domains of cognition and whether they will be of therapeutic benefit in individuals with schizophrenia.

AREAS COVERED

This paper summarizes the effects of GLP-1 RAs on metabolic processes in the brain and how these mechanisms relate to improved cognitive function. We provide an overview of preclinical studies that demonstrate GLP-1 RAs improve cognition and comment on their potential therapeutic benefit in individuals with schizophrenia.

EXPERT OPINION

To understand the benefits of GLP-1 RAs in individuals with schizophrenia, further preclinical research with rodent models relevant to schizophrenia symptomology are needed. Moreover, preclinical studies must focus on using a wider range of behavioral assays to understand whether important aspects of cognition such as executive function, attention, and goal-directed behavior are improved using GLP-1 RAs. Further research into the specific mechanisms of how GLP-1 RAs affect cognitive function and their interactions with antipsychotic medication commonly prescribed is necessary.

GLP-1 Receptor Agonists: Beyond Their Pancreatic Effects

Glucagon like peptide-1 (GLP-1) is an incretin secretory molecule. GLP-1 receptor agonists (GLP-1RAs) are widely used in the treatment of type 2 diabetes (T2DM) due to their attributes such as body weight loss, protection of islet β cells, promotion of islet β cell proliferation and minimal side effects. Studies have found that GLP-1R is widely distributed on pancreatic and other tissues and has multiple biological effects, such as reducing neuroinflammation, promoting nerve growth, improving heart function, suppressing appetite, delaying gastric emptying, regulating blood lipid metabolism and reducing fat deposition. Moreover, GLP-1RAs have neuroprotective, anti-infectious, cardiovascular protective, and metabolic regulatory effects, exhibiting good application prospects. Growing attention has been paid to the relationship between GLP-1RAs and tumorigenesis, development and prognosis in patient with T2DM. Here, we reviewed the therapeutic effects and possible mechanisms of action of GLP-1RAs in the nervous, cardiovascular, and endocrine systems and their correlation with metabolism, tumours and other diseases.

EXENATIDE TREATMENT REDUCES THYROID GLAND VOLUME, BUT HAS NO EFFECT ON THE SIZE OF THYROID NODULES

Context

Exenatide is a Glucagon-like Peptide-1 receptor agonist, which is widely used for type 2 diabetes mellitus (T2DM). Limited and conflicting results are present about the effect of exenatide on the thyroid gland.

Objective

The aim of this study was to evaluate the effect of exenatide treatment on structural and functional features of the thyroid gland in patients with T2DM.

Design

The study was a prospective study, performed between 2015 and 2017. The laboratory values and thyroid ultrasonography features were compared before and after exenatide treatment.

Subjects and Methods

The study included 39 obese diabetic patients. After inclusion to the study exenatide was started and patients were followed up for 6 months. Total thyroid volume, thyroid function tests, serum carcinoembryonic antigen (CEA) and calcitonin levels, the size and appearance of thyroid nodules were compared between baseline and after 6 months of treatment.

Results

Exenatide at a dose of 5μg bid was started, increased to 10 μg bid after 4 weeks. We found a statistically significant decrease in thyroid volume (p=0.043) and serum thyroid stimulating hormone (TSH) levels (p=0.007), whereas serum ATPO. ATGl, fT4, fT3, CEA and calcitonin levels did no change with 6 months of exenatide treatment. There were no significant differences in the size and appearance of the thyroid nodules with treatment. The thyroid volume decrease was not correlated with TSH, body mass index and HbA1c reduction.

Conclusion

Exenatide treatment for 6 months decreased serum TSH levels and thyroid volume, but had no effect on thyroid nodules and serum CEA and calcitonin levels.

Exenatide Reverts the High-Fat-Diet-Induced Impairment of BDNF Signaling and Inflammatory Response in an Animal Model of Alzheimer's Disease

Alzheimer's disease (AD) is a multifactorial condition in which, along with amyloid-β (Aβ) and tau-related pathology, the synergistic activity of co-morbidity factors promote the onset and progression of the disease. Epidemiological evidence indicates that glucose intolerance, deficits in insulin secretion, or type-2 diabetes mellitus (T2DM) participate in increasing cognitive impairment or dementia risk. Insulin plays a pivotal role in the process as the hormone critically regulates brain functioning. GLP-1, the glucagon-like peptide 1, facilitates insulin signaling, regulates glucose homeostasis, and modulates synaptic plasticity. Exenatide is a synthetic GLP-1 analog employed in T2DM. However, exenatide has also been shown to affect the signaling of the brain-derived neurotrophic factor (BDNF), synaptic plasticity, and cognitive performances in animal models. In this study, we tested whether exenatide exerts neuroprotection in a preclinical AD model set to mimic the clinical complexity of the human disease. We investigated the effects of exenatide treatment in 3xTg-AD mice challenged with a high-fat diet (HFD). Endpoints of the study were variations in systemic metabolism, insulin and neurotrophic signaling, neuroinflammation, Aβ and tau pathology, and cognitive performances. Results of the study indicate that exenatide reverts the adverse changes of BDNF signaling and the neuroinflammation status of 3xTg-AD mice undergoing HFD without affecting systemic metabolism or promoting changes in cognitive performances.

Independent effects of 15 commonly prescribed drugs on all-cause mortality among US elderly patients with type 2 diabetes mellitus

OBJECTIVE

Most patients with type 2 diabetes mellitus (T2DM) also have hypertension and hyperlipidemia. Consequently, they are taking medications for all three conditions concurrently and the effect of one drug could be confounded with that of another. This study aimed to determine the independent effects of 15 commonly prescribed medications for three conditions on the risk of all-cause mortality among elderly patients with T2DM.

RESEARCH DESIGN AND METHODS

A cohort of 360 437 elderly patients with T2DM from 2007 to 2016 US Medicare data was traced along with cumulative uses of 8 diabetes, 6 hypertension and 1 hyperlipidemia drugs. The relative risk of all-cause mortality for each study drug was estimated using an extended Cox regression analysis adjusting for the concurrent use of other study drugs.

RESULTS

Compared with the no use of each study medication, mortality risk declined with use of 3 diabetes drugs, sodium-glucose cotransporter-2 inhibitors (HR=0.73; 95% CI 0.64 to 0.84), glucagon-like peptide-1 receptor agonists (HR=0.75; 95% CI 0.70 to 0.80) and dipeptidyl peptidase-4 inhibitors (HR=0.94; 95% CI 0.91 to 0.98), the use of 3 blood pressure medications, diuretics (HR=0.89; 95% CI 0.87 to 0.92), angiotensin receptor blockers (HR=0.86; 95% CI 0.84 to 0.89), ACE inhibitors (HR=0.98; 95% CI 0.95 to 1.01) as well as statins (HR=0.83; 95% CI 0.80 to 0.85). It increased moderately with insulin (HR=1.55; 95% CI 1.51 to 1.59), sulfonylureas (HR=1.16; 95% CI 1.13 to 1.20), a small inconsistent amount with metformin (HR=1.05), beta-blockers (HR=1.07), dihydropyridine calcium-channel blockers (HR=0.99) and non-dihydropyridine calcium-channel blockers (HR=1.05). The use of thiazolidinedione had no effect.

CONCLUSION

Among older patients with diabetes, mortality risk decreased importantly with three new diabetes drugs, 3 blood pressure drugs and statins. It increased moderately with sulfonylurea and insulin. Studies of aggressive use of new T2DM drugs instead of sulfonylureas and insulin are needed. Our statin results empirically validate two national guidelines for using statins in older patients with diabetes. However, 23% of study patients never took a statin, suggesting missed opportunities for prevention.

Incretins and microRNAs: Interactions and physiological relevance

MicroRNAs (miRNA) are one class of the small regulatory RNAs that can impact the expression of numerous genes including incretin hormones and their G protein-coupled receptors. Incretin peptides, including GLP-1, GLP-2, and GIP, are released from the gastrointestinal tract and have an crucial role in the glucose hemostasis and pancreatic beta-cell function. These hormones and their analogs with a longer half-life, glucagon like peptide-1 receptor agonists (GLP1RA), modify the expression of miRNAs. Dipeptidyl peptidase IV (DPP-4) is an enzyme that degrades the incretin hormones and is inactivated by DPP-4 inhibitors, which are a class of compounds used in the management of type 2 diabetes. DPP-4 inhibitors may also increase or reduce the expression of miRNAs. In this review, we describe the possible interactions between miRNAs and incretin hormones and the relevance of such interactions to physiological processes and diseases.

Past, present and future of latent autoimmune diabetes in adults

Latent autoimmune diabetes in adults (LADA) is the most common form of autoimmune diabetes diagnosed in adults. Similar to type 1 diabetes, the prevalence of LADA is impacted by ethnicity and geography. LADA is characterized by β cell loss due to autoimmunity and insulin resistance and has highly heterogeneous clinical features, autoimmunity, and genetics in a glutamic acid decarboxylase antibody (GADA) titre-dependent manner, suggesting LADA is part of a continuum spectrum between type 1 and type 2 diabetes. Although LADA is the most frequent form of autoimmune diabetes diagnosed in adults, clinical trials involving LADA are scarce. Here we review the recent advancements in LADA epidemiology, clinical features, pathogenesis, and interventions. We also highlight the environmental factors that are thought to play an important role in addition to genetics in the pathogenesis of LADA. In the future, high-throughput molecular profiles might shed light on the nature of LADA among the wide spectrum of diabetes and offer new opportunities to identify novel LADA-specific biomarkers.

The Effect of Exenatide on Thyroid-Stimulating Hormone and Thyroid Volume

OBJECTIVE

Glucagon-like peptide-1 (GLP-1) analogues are now widely used for the treatment of type 2 diabetes mellitus (DM). Many binding sites for GLP-1 have been demonstrated in the specific tissue compartments of organs in-cluding the brain and thyroid. The aim of this study was to investigate the effect of exenatide treatment on thyroid-stimulating hormone (TSH) and thyroid volume in diabetic patients without thyroid disease.

MATERIAL AND METHODS

The study included 46 diabetic patients without thyroid disease who were receiving exenatide treatment. Comparisons were made of total thyroid volume and serum concentrations of TSH at baseline and after 6 months of follow-up.

RESULTS

Of the 46 patients, 13 were excluded from the study, as they were unable to complete the treatment or left the follow-up process. After 6 months of exenatide treatment, the serum TSH concentration decreased significantly (from 2.3 [0.7-5.4] to 1.8 mIU/L [0.3-4.2], p= 0.007). There were no significant differences in thyroid volume (11.6 ± 9.0 vs. 12.1 ± 8.8 cm³, p = 0.19), free thyroxine (fT4), free tri-iodothyronine (fT3), and calcitonin levels before and after treatment. Thyroid volume was not affected by decreased TSH level (p:= 0.141) or a reduction in body mass index (BMI) (p > 0.05), and no correlation was detected between variation in TSH level and change in BMI (p > 0.05).

CONCLUSIONS

Exenatide treatment for 6 months significantly decreased serum TSH concentration but did not affect thyroid volume in diabetic patients without thyroid disease.

[68Ga]Ga-NOTA-MAL-Cys39-exendin-4, a potential GLP-1R targeted PET tracer for the detection of insulinoma

Glucagon-like peptide-1 receptor (GLP-1R) is a kind of G protein coupled receptor which regulates the insulin secretion and serves as potential target in the diagnosis of functional pancreas neuroendocrine tumor. The aim of this study was to evaluate the feasibility of GLP-1R targeted tracer [⁶⁸Ga]Ga-NOTA-MAL-Cys³⁹-exendin-4 in the detection of insulinoma.

METHODS

NOTA-MAL-Cys³⁹-exendin-4 was synthesized and then radiolabeled with gallium-68 in iQS® Ga-68 Fluidic Labeling Module. The in vitro binding affinity and cell uptake studies were evaluated in INS-1 cells. The in vivo micro-PET/CT imaging and biodistribution studies were performed on INS-1 xenograft tumor models.

RESULTS

[⁶⁸Ga]Ga-NOTA-MAL-Cys³⁹-exendin-4 can be efficiently radiolabelled with a yield of about 85% (non-decay corrected) and radiochemical purity of >95% with a favorable stability. The molar activity was at least 145.5 GBq/μmol. The affinity (IC50) for [⁶⁸Ga]Ga-NOTA-MAL-Cys³⁹-exendin-4 was 12.99 ± 0.81 nM. Micro-PET/CT images showed intense tumor uptake with good contrast to background. Biodistribution study showed the predominant uptake was in the kidney, followed by pancreas, and the liver and spleen just showed mild uptake in the blood-pool phase with rapid clearance. At 1 h post- injection, the tumor to blood, muscle and pancreas ratios were 30.64, 40.21 and 6.46, respectively. Blocking studies showed significantly decreased tumor uptake, which further confirmed binding affinity of [⁶⁸Ga]Ga-NOTA-MAL-Cys³⁹-exendin-4 to GLP-1R.

CONCLUSION

[⁶⁸Ga]Ga-NOTA-MAL-Cys³⁹-exendin-4 was easily synthesized with high yield, favorable biodistribution and high affinity to islet tumor cell, making the tracer may have great potential in the detection of GLP-1R positive tumor such as an insulinoma.

Allosteric Modalities for Membrane-Bound Receptors: Insights from Drug Hunting for Brain Diseases

Medicinal chemists are accountable for embedding the appropriate drug target profile into the molecular architecture of a clinical candidate. An accurate characterization of the functional effects following binding of a drug to its biological target is a fundamental step in the discovery of new medicines, informing the translation of preclinical efficacy and safety observations into human trials. Membrane-bound proteins, particularly ion channels and G protein-coupled receptors (GPCRs), are biological targets prone to allosteric modulation. Investigations using allosteric drug candidates and chemical tools suggest that their functional effects may be tailored with a high degree of translational alignment, making them molecular tools to correct pathophysiological functional tone and enable personalized medicine when a causative target-to-disease link is known. We present select examples of functional molecular fine-tuning of allosterism and discuss consequences relevant to drug design.

GLP-1 Receptor in Pancreatic α-Cells Regulates Glucagon Secretion in a Glucose-Dependent Bidirectional Manner

Glucagon-like peptide 1 (GLP-1) is known to suppress glucagon secretion, but the mechanism by which GLP-1 exerts this effect is unclear. In this study, we demonstrated GLP-1 receptor (GLP-1R) expression in α-cells using both antibody-dependent and antibody-independent strategies. A novel α-cell-specific GLP-1R knockout (αGLP-1R^-/-) mouse model was created and used to investigate its effects on glucagon secretion and glucose metabolism. Male and female αGLP-1R^-/- mice both showed higher nonfasting glucagon levels than their wild-type littermates, whereas insulin and GLP-1 levels remained similar. Female αGLP-1R^-/- mice exhibited mild glucose intolerance after an intraperitoneal glucose administration and showed increased glucagon secretion in response to a glucose injection compared with the wild-type animals. Furthermore, using isolated islets, we confirmed that αGLP-1R deletion did not interfere with β-cell function but affected glucagon secretion in a glucose-dependent bidirectional manner: the αGLP-1R^-/- islets failed to inhibit glucagon secretion at high glucose and failed to stimulate glucagon secretion at very low glucose condition. More interestingly, the same phenomenon was recapitulated in vivo under hypoglycemic and postprandial (fed) conditions. Taken together, this study demonstrates that GLP-1 (via GLP-1R in α-cells) plays a bidirectional role, either stimulatory or inhibitory, in glucagon secretion depending on glucose levels.

Exenatide exerts cognitive effects by modulating the BDNF-TrkB neurotrophic axis in adult mice

Modulation of insulin-dependent signaling is emerging as a valuable therapeutic tool to target neurodegeneration. In the brain, the activation of insulin receptors promotes cell growth, neuronal repair, and protection. Altered brain insulin signaling participates in the cognitive decline seen in Alzheimer's disease patients and the aging brain. Glucagon-like peptide-1 (GLP-1) regulates insulin secretion and, along with GLP-1 analogues, enhances neurotrophic signaling and counteracts cognitive deficits in preclinical models of neurodegeneration. Moreover, recent evidence indicates that GLP-1 modulates the activity of the brain-derived neurotrophic factor (BDNF). In this study, in adult wild-type mice, here employed as a model of mid-life brain aging, we evaluated the effects of a 2-month treatment with exenatide, a GLP-1 analogue. We found that exenatide promotes the enhancement of long-term memory performances. Biochemical and imaging analyses show that the drug promotes the activation of the BDNF-TrkB neurotrophic axis and inhibits apoptosis by decreasing p75NTR-mediated signaling. The study provides preclinical evidence for the use of exenatide to delay age-dependent cognitive decline.

Liraglutide Versus Lixisenatide: Long-Term Cost-Effectiveness of GLP-1 Receptor Agonist Therapy for the Treatment of Type 2 Diabetes in Spain

INTRODUCTION

Glucagon-like peptide-1 (GLP-1) receptor agonists are used successfully in the treatment of patients with type 2 diabetes as they are associated with low hypoglycemia rates, weight loss and improved glycemic control. This study compared, in the Spanish setting, the cost-effectiveness of liraglutide 1.8 mg versus lixisenatide 20 μg, both GLP-1 receptor agonists, for patients with type 2 diabetes who had not achieved glycemic control targets on metformin monotherapy.

METHODS

The IMS CORE Diabetes Model was used to project clinical outcomes and costs, expressed in 2015 Euros, over patient lifetimes. Baseline cohort data and treatment effects were taken from the 26-week, open-label LIRA-LIXI™ trial (NCT01973231). Treatment and management costs of diabetes-related complications were retrieved from published sources and databases. Future benefits and costs were discounted by 3% annually. Sensitivity analyses were conducted.

RESULTS

Compared with lixisenatide 20 μg, liraglutide 1.8 mg was associated with higher life expectancy (14.42 vs. 14.29 years), higher quality-adjusted life expectancy [9.40 versus 9.26 quality-adjusted life years (QALYs)] and a reduced incidence of diabetes-related complications. Higher acquisition costs resulted in higher total costs for liraglutide 1.8 mg (EUR 42,689) than for lixisenatide 20 μg (EUR 42,143), but these were partly offset by reduced costs of treating diabetes-related complications (EUR 29,613 vs. EUR 30,636). Projected clinical outcomes and costs resulted in an incremental cost-effectiveness ratio of EUR 4113 per QALY gained for liraglutide 1.8 mg versus lixisenatide 20 μg.

CONCLUSIONS

Long-term projections in the Spanish setting suggest that liraglutide 1.8 mg is likely to be cost-effective compared with lixisenatide 20 μg in type 2 diabetes patients who have not achieved glycemic control targets on metformin monotherapy. Liraglutide 1.8 mg presents a clinically and economically attractive treatment option in the Spanish setting.

Safety and efficacy of a glucagon-like peptide-1 receptor agonist added to basal insulin therapy versus basal insulin with or without a rapid-acting insulin in patients with type 2 diabetes: results of a meta-analysis

OBJECTIVE

To consolidate the evidence from randomized controlled trials evaluating the use of glucagon-like peptide-1 receptor agonists (GLP-1 RAs) as add-on to basal insulin therapy in type 2 diabetes (T2D) patients.

RESEARCH DESIGN AND METHODS

We searched the EMBASE® and NCBI PubMed (Medline) databases and relevant congress abstracts for randomized controlled trials evaluating the efficacy and safety of GLP-1 RAs as add-on to basal insulin compared with basal insulin with or without rapid-acting insulin (RAI) through 23 May 2016. The pooled data were analyzed using a random-effects meta-analysis model. A subanalysis was performed for trials investigating basal insulin plus GLP-1 RAs versus basal insulin plus RAI.

RESULTS

Of the 2617 retrieved records, 19 randomized controlled trials enrolling 7,053 patients with T2D were included. Compared with basal insulin ± RAI, reduction in glycated hemoglobin (HbA1c) from baseline (difference in means: -0.48% [95% confidence interval (CI), -0.67 to -0.30]; p < 0.0001) and weight loss (-2.60 kg [95% CI, -3.32 to -1.89]; p < 0.0001) were significantly greater with basal insulin plus GLP-1 RA. The subanalysis similarly showed significant results for change in HbA1c from baseline and for weight loss, as well as a significantly lower risk of symptomatic hypoglycemia in patients treated with basal insulin plus GLP-1 RA versus basal insulin plus RAI (odds ratio, 0.52 [95% CI, 0.42 to 0.64]; p < 0.0001).

CONCLUSIONS

Addition of GLP-1 RA to basal insulin provided improved glycemic control, led to weight reduction and similar hypoglycemia rates versus an intensified insulin strategy; however, symptomatic hypoglycemia rates were significantly lower when compared with a basal insulin plus RAI.

Prevention of type 2 Diabetes Mellitus: Potential of pharmacological agents

People with impaired glucose tolerance or impaired fasting glucose, or "pre-diabetes", are at high risk for progression to type 2 diabetes, as are those with metabolic syndrome or a history of gestational diabetes. Both glucose-lowering and anti-obesity pharmacotherapies have been studied to determine if the onset of type 2 diabetes can be delayed or prevented. Here we review the available data in the field. The most common theme is the reduction in insulin resistance, such as with weight loss, decreasing demands on the beta cell to improve insulin secretion and prolong its function. Overall, therapies which decrease diabetes incidence in high-risk populations delay the onset of diabetes but do not correct the underlying beta cell defect.

Oxidative and endoplasmic reticulum stress in β-cell dysfunction in diabetes

The inability of pancreatic β-cells to make sufficient insulin to control blood sugar is a central feature of the aetiology of most forms of diabetes. In this review we focus on the deleterious effects of oxidative stress and endoplasmic reticulum (ER) stress on β-cell insulin biosynthesis and secretion and on inflammatory signalling and apoptosis with a particular emphasis on type 2 diabetes (T2D). We argue that oxidative stress and ER stress are closely entwined phenomena fundamentally involved in β-cell dysfunction by direct effects on insulin biosynthesis and due to consequences of the ER stress-induced unfolded protein response. We summarise evidence that, although these phenomenon can be driven by intrinsic β-cell defects in rare forms of diabetes, in T2D β-cell stress is driven by a range of local environmental factors including increased drivers of insulin biosynthesis, glucolipotoxicity and inflammatory cytokines. We describe our recent findings that a range of inflammatory cytokines contribute to β-cell stress in diabetes and our discovery that interleukin 22 protects β-cells from oxidative stress regardless of the environmental triggers and can correct much of diabetes pathophysiology in animal models. Finally we summarise evidence that β-cell dysfunction is reversible in T2D and discuss therapeutic opportunities for relieving oxidative and ER stress and restoring glycaemic control.

GLP-1 Receptor Agonists: Practical Considerations for Clinical Practice

PURPOSE

Type 2 diabetes (T2D) imparts an increased risk of adverse health outcomes in patients unable to achieve glycemic control. Patient education and individualization of treatment are important for effective management of T2D. Glucagon-like peptide-1 receptor agonists (GLP-1RAs) are a class of injectable glucose-lowering agents that lower A1C with added benefits of weight loss and improved cardiovascular risk markers. This review discusses the role of GLP-1RAs currently approved in the United States (exenatide, liraglutide, albiglutide, dulaglutide) for T2D management and characterizes the efficacy and safety profiles of individual GLP-1RAs.

CONCLUSIONS

GLP-1RAs are recommended as a preferred add-on agent to existing metformin monotherapy, as first-line therapy if metformin is contraindicated or poorly tolerated, and for use in combination with other oral glucose-lowering agents or basal insulin. Shorter-acting GLP-1RAs (exenatide and liraglutide) offer improved coverage of postprandial hyperglycemia, while longer-acting GLP-1RA formulations (exenatide extended-release, dulaglutide, and albiglutide) further improve fasting plasma glucose, which can result in additional A1C lowering. Reductions in body weight and blood pressure appear similar among individual agents, and small increases in heart rate are of unknown clinical relevance. Gastrointestinal adverse events abate over time with continued treatment and are less frequent with longer-acting GLP-1RAs. Hypoglycemia incidence is low but increased when GLP-1RAs are used with insulin secretagogues or insulin. GLP-1RAs target multiple pathophysiologic mechanisms in patients with T2D and improve glycemic control, although there are some differences within this drug class that may be relevant in clinical practice. Therefore, selection of the most appropriate treatment for individual patients is important.

Weight management in type 2 diabetes: current and emerging approaches to treatment

Diabetes is a growing global health concern, as is obesity. Diabetes and obesity are intrinsically linked: obesity increases the risk of diabetes and also contributes to disease progression and cardiovascular disease. Although the benefits of weight loss in the prevention of diabetes and as a critical component of managing the condition are well established, weight reduction remains challenging for individuals with type 2 diabetes due to a host of metabolic and psychological factors. For many patients, lifestyle intervention is not enough to achieve weight loss, and alternative options, such as pharmacotherapy, need to be considered. However, many traditional glucose-lowering medications may lead to weight gain. This article focuses on the potential of currently available pharmacological strategies and on emerging approaches in development to support the glycemic and weight-loss goals of individuals with type 2 diabetes. Two pharmacotherapy types are considered: those developed primarily for blood glucose control that have a favorable effect on body weight and those developed primarily to induce weight loss that have a favorable effect on blood glucose control. Finally, the potential of combination therapies for the management of obese patients with type 2 diabetes is discussed.

An updated review on cancer risk associated with incretin mimetics and enhancers

Incretin-based therapies, including the use of incretin mimetics of glucagon-like peptide-1 receptor (GLP-1R) agonists and incretin enhancers of dipeptidyl-peptidase 4 (DPP-4) inhibitors, are widely used by clinicians for glucose lowering in patients with type 2 diabetes mellitus. These agents have benefits of a lower risk of hypoglycemia, being neutral for body weight for DPP-4 inhibitors and having a potential for weight reduction with GLP-1R agonists. They may also have a neutral or beneficial cardiovascular effect. Despite these benefits, an increased risk of cancer (especially pancreatic cancer and thyroid cancer) associated with incretin-based therapies has been reported. In this article, we reviewed related literature of experimental animal and observational human studies, clinical trials, and meta-analyses published until December 15, 2014. Current studies suggested a probable role of GLP-1R activation on the development of pancreatic cancer and thyroid cancer in rodents, but such an effect in humans is not remarkable due to the lower or lack of expression of GLP-1R on human pancreatic ductal cells and thyroid tissues. Findings in human studies are controversial and inconclusive. In the analyses of the US Food and Drug Administration adverse events reporting system, a significantly higher risk of pancreatic cancer was observed for GLP-1R agonists and DPP-4 inhibitors, but a significantly higher risk of thyroid cancer was only observed for GLP-1R agonists. Such a higher risk of pancreatic cancer or thyroid cancer could not be similarly demonstrated in other human observational studies or analyses of data from clinical trials. With regards to cancers other than pancreatic cancer and thyroid cancer, available studies supported a neutral association in humans. Some preliminary studies even suggested a potentially beneficial effect on the development of other cancers with the use of incretins. Based on current evidence, continuous monitoring of the cancer issues related to incretin-based therapies is required, even though the benefits may outweigh the potential cancer risk in the general patients with type 2 diabetes mellitus.

Peripheral actions of GPCRs in energy homeostasis: view from the Chair

The roles of G-protein-coupled receptors (GPCRs) in the control of food intake and energy expenditure are being increasingly recognized, and new drug candidates targeting these receptors are making their entry into the clinic. GPCRs exert their action along the various sites of regulation of energy homeostasis control including the central nervous system, the pancreas, the gut and fat cells. Exciting new data about GPCRs recognizing and mediating the effects of lipid mediators and concerning receptors for which no endogenous ligands have been identified yet open new exciting avenues for the validation of additional drug targets. In addition, recently developed paradigms around the concepts of cross-talk regulation and functional selectivity should lead to the development of drugs with improved therapeutic efficacy and reduced undesirable effects. Some of these promising discoveries are discussed in the present article and accompanying papers.

GLP-1(28-36)amide, the Glucagon-like peptide-1 metabolite: friend, foe, or pharmacological folly?

The glucagon-like peptide-1 (GLP-1) axis has emerged as a major therapeutic target for the treatment of type 2 diabetes. GLP-1 mediates its key insulinotropic effects via a G-protein coupled receptor expressed on β-cells and other pancreatic cell types. The insulinotropic activity of GLP-1 is terminated via enzymatic cleavage by dipeptidyl peptidase-4. Until recently, GLP-1-derived metabolites were generally considered metabolically inactive; however, accumulating evidence indicates some have biological activity that may contribute to the pleiotropic effects of GLP-1 independent of the GLP-1 receptor. Recent reports describing the putative effects of one such metabolite, the GLP-1-derived nonapeptide GLP-1(28-36) amide, are the focus of this review. Administration of the nonapeptide elevates cyclic adenosine monophosphate (cAMP) and activates protein kinase A, β-catenin, and cAMP response-element binding protein in pancreatic β-cells and hepatocytes. In stressed cells, the nonapeptide targets the mitochondria and, via poorly defined mechanisms, helps to maintain mitochondrial membrane potential and cellular adenosine triphosphate levels and to reduce cytotoxicity and apoptosis. In mouse models of diet-induced obesity, treatment with the nonapeptide reduces weight gain and ameliorates associated pathophysiology, including hyperglycemia, hyperinsulinemia, and hepatic steatosis. Nonapeptide administration in a streptozotocin-induced model of type 1 diabetes also improves glucose disposal concomitant with elevated insulin levels and increased β-cell mass and proliferation. Collectively, these results suggest some of the beneficial effects of GLP-1 receptor analogs may be mediated by the nonapeptide. However, the concentrations required to elicit some of these effects are in the micromolar range, leading to reservations about potentially related therapeutic benefits. Moreover, although controversial, concerns have been raised about the potential for incretin-based therapies to promote pancreatitis and pancreatic and thyroid cancers. The effects ascribed to the nonapeptide make it a potential contributor to such outcomes, raising additional questions about its therapeutic suitability. Notwithstanding, the nonapeptide, like other GLP-1 metabolites, appears to be biologically active. Increasing understanding of such noncanonical GLP-1 activities should help to improve future incretin-based therapeutics.

[Cardiovascular safety of non-insulin anti-diabetic drugs. Scientific position statement of SEMERGEN]

Diabetes increases the risk of both microvascular and macrovascular complications. Although reducing plasma glucose levels to recommended targets decreases the risk of microvascular outcomes, the effects of anti-diabetic drugs on macrovascular complications and cardiovascular death are of concern. In fact, it has been suggested that some anti-diabetic agents could even be harmful for cardiovascular outcomes. In this context, several health care regulatory agencies have established the need for performing clinical trials specifically designed to assess the cardiovascular safety of anti-diabetic drugs. The results of 2 clinical trials have recently been published that provide important information on the cardiovascular safety of dipeptidyl peptidase 4 (DPP-4) inhibitors. The aim of this document was to review the available evidence on the cardiovascular safety of non-insulin anti-diabetic drugs and provide practical recommendations on their use in this context.

Advances in managing type 2 diabetes: challenging old paradigms and developing new ones

As is well known, diabetes rates continue to escalate worldwide, adding cost and disease burden to all health-care institutions. Over the last few years, however, a number of diabetes paradigms have been challenged, not least on the best methods to lessen or delay the development of co-morbidities, in particular cardiovascular disease (CVD) (i.e. targeting blood pressure, cholesterol, and smoking will do more than intensive glucose control). In addition, recent research has offered some hope to potentially reverse diabetes in motivated individuals, with resultant larger and longer trials of such interventions about to commence. This brief review summarizes these important recent developments and suggests that, while many new drugs are being added to the diabetes therapeutic armory, more could and should be done to target sustainable weight change in our patients for multiple health benefits.

Insulin-releasing and cytotoxic properties of the frog skin peptide, tigerinin-1R: a structure-activity study

The frog skin host-defense peptide tigerinin-1R (RVCSAIPLPICH.NH2) is insulinotropic both in vitro and in vivo. This study investigates the effects on insulin release and cytotoxicity of changes in cationicity and hydrophobicity produced by selected substitutions of amino acids by l-arginine, l-lysine and l-tryptophan. The [A5W], [L8W] and [I10W] analogs produced a significant (P<0.01) increase in the rate of insulin release from BRIN-BD11 rat clonal β cells at concentration of 0.01 nM compared with 0.1 nM for tigerinin-1R. The increase in the rate of insulin release produced by a 3 μM concentration of the [S4R], [H12K], and [I10W] analogs from both BRIN-BD11 cells and mouse islets was significantly greater (P<0.05) than that produced by tigerinin-1R. No peptide stimulated the release of lactate dehydrogenase at concentrations up to 3 μM indicating that plasma membrane integrity had been preserved. [A5W] tigerinin-1R was the only analog tested that showed cytotoxic activity against human erythrocytes (LC50=265 ± 16 μM) and inhibited growth of Escherichia coli (MIC=500 μM) and Staphylococcus aureus (MIC=250 μM). The circular dichroism spectra of tigerinin-1R and [A5W] tigerinin-1R indicate that the peptides adopt a mixture of β-sheet, random coil and reverse β-turn conformations in 50% trifluoroethanol/water and methanol/water. Administration of [S4R] tigerinin-1R (75 nmol/kg body weight) to high-fat fed mice with insulin resistance significantly (P<0.05) enhanced insulin release and improved glucose tolerance over a 60 min period following an intraperitoneal glucose load. The study supports the claim that tigerinin-1R shows potential for development into novel therapeutic agents for treatment of type 2 diabetes mellitus.

Optimal therapy of type 2 diabetes: a controversial challenge

Type 2 diabetes mellitus (T2DM) is one of the most common chronic disorders in older adults and the number of elderly diabetic subjects is growing worldwide. Nonetheless, the diagnosis of T2DM in elderly population is often missed or delayed until an acute metabolic emergency occurs. Accumulating evidence suggests that both aging and environmental factors contribute to the high prevalence of diabetes in the elderly. Clinical management of T2DM in elderly subjects presents unique challenges because of the multifaceted geriatric scenario. Diabetes significantly lowers the chances of "successful" aging, notably it increases functional limitations and impairs quality of life. In this regard, older diabetic patients have a high burden of comorbidities, diabetes-related complications, physical disability, cognitive impairment and malnutrition, and they are more susceptible to the complications of dysglycemia and polypharmacy. Several national and international organizations have delivered guidelines to implement optimal therapy in older diabetic patients based on individualized treatment goals. This means appreciation of the heterogeneity of the disease as generated by life expectancy, functional reserve, social support, as well as personal preference. This paper will review current treatments for achieving glycemic targets in elderly diabetic patients, and discuss the potential role of emerging treatments in this patient population.

Effects of glucagon-like peptide-1 receptor agonists on renal function

Glucagon-like peptide-1 (GLP-1) receptor agonists result in greater improvements in glycemic control than placebo and promote weight loss with minimal hypoglycemia in patients with type 2 diabetes mellitus. A number of case reports show an association of GLP-1 receptor agonists, mainly exenatide, with the development of acute kidney injury. The present review aims to present the available data regarding the effects of GLP-1 receptor agonists on renal function, their use in subjects with chronic renal failure and their possible association with acute kidney injury. Based on the current evidence, exenatide is eliminated by renal mechanisms and should not be given in patients with severe renal impairment or end stage renal disease. Liraglutide is not eliminated by renal or hepatic mechanisms, but it should be used with caution since there are only limited data in patients with renal or hepatic impairment. There is evidence from animal studies that GLP-1 receptor agonists exert protective role in diabetic nephropathy with mechanisms that seem to be independent of their glucose-lowering effect. Additionally, there is evidence that GLP-1 receptor agonists influence water and electrolyte balance. These effects may represent new ways to improve or even prevent diabetic nephropathy.