An overview of new GLP-1 receptor agonists for type 2 diabetes

A web-based scoping review assessing the influence of smoking and smoking cessation on antidiabetic drug meabolism: implications for medication efficacy

Currently 1.3 billion individuals globally engage in smoking, leading to significant morbidity and mortality, particularly among diabetic patients. There is urgent need for a better understanding of how smoking influences antidiabetic treatment efficacy. The review underscores the role of cigarette smoke, particularly polycyclic aromatic hydrocarbons (PAHs), in modulating the metabolic pathways of antidiabetic drugs, primarily through the induction of cytochrome P450 (CYP450) enzymes and uridine diphosphate (UDP)-glucuronosyltransferases (UGTs), thus impacting drug pharmacokinetics and therapeutic outcomes. Furthermore, the review addresses the relatively uncharted territory of how smoking cessation influences diabetes treatment, noting that cessation can lead to significant changes in drug metabolism, necessitating dosage adjustments. Special attention is given to the interaction between smoking cessation aids and antidiabetic medications, a critical area for patient safety and effective diabetes management. This scoping review aims to provide healthcare professionals with the knowledge to better support diabetic patients who smoke or are attempting to quit, ensuring tailored and effective treatment strategies. It also identifies gaps in current research, advocating for more studies to fill these voids, thereby enhancing patient care and treatment outcomes for this at-risk population.

Comparative effects of glucagon-like peptide-1 receptors agonists, 4-dipeptidyl peptidase inhibitors, and metformin on metabolic syndrome

AIMS

To assess the comparative effects of glucagon-like peptide-1 receptor agonists (GLP-1RA), 4-dipeptidyl peptidase inhibitors (DPP-4I), and metformin treatment during one year on metabolic syndrome (MetS) components and severity in MetS patients.

METHODS

Prospective study (n = 6165 adults) within the frame of PREDIMED-Plus trial. The major end-point was changes on MetS components and severity after one- year treatment of GLP-1RA, DPP-4I, and metformin. Anthropometric measurements (weight, height and waist circumference), body mass index (BM), and blood pressure were registered. Blood samples were collected after overnight fasting. Plasma glucose, glycosylated hemoglobin (HbA1c), plasma triglycerides and cholesterol were measured. Dietary intakes as well as physical activity were assessed through validated questionnaires.

RESULTS

MetS parameters improved through time. The treated groups improved glycaemia compared with untreated (glycaemia ∆ untreated: -1.7 mg/dL(± 13.5); ∆ metformin: - 2.5(± 23.9) mg/dL; ∆ DPP-4I: - 4.5(± 42.6); mg/dL ∆ GLP-1RA: - 4.3(± 50.9) mg/dL; and HbA1c: ∆ untreated: 0.0(± 0.3) %; ∆ metformin: - 0.1(± 0.7) %; ∆ DPP-4I: - 0.1(± 1.0) %; ∆ GLP-1RA: - 0.2(± 1.2) %. Participants decreased BMI and waist circumference. GLP-1RA and DPP-4I participants registered the lowest decrease in BMI (∆ untreated: -0.8(± 1.6) kg/m²; ∆ metformin: - 0.8(± 1.5) kg/m²; ∆ DPP-4I: - 0.6(± 1.3) kg/m²; ∆ GLP-1RA: - 0.5(± 1.2) kg/m². and their waist circumference (∆ untreated: -2.8(± 5.2) cm; ∆ metformin: - 2.6(± 15.2) cm; ∆ DPP-4I: - 2.1(± 4.8) cm; ∆ GLP-1RA: - 2.4(± 4.1) cm.

CONCLUSION

In patients with MetS and healthy lifestyle intervention, those treated with GLP-1RA and DPP-4I obtained better glycemic profile. Anthropometric improvements were modest.

Discovery of a novel anti-obesity meroterpenoid agent targeted subcutaneous adipose tissue

BACKGROUND

Meroterpenoid furanasperterpene A (T2-3) with a novel 6/6/6/6/5 pentacyclic skeleton was isolated from the Aspergillus terreus GZU-31-1. Previously, we showed that T2-3 possessed significant lipid-lowering effects in 3T3-L1 adipocytes at 5 μM concentration. However, its therapeutic effect in metabolic disease and the underlying mechanisms of action remain unclear.

METHODS

High fat diet-induced obesity (DIO) mouse model and 3T3-L1 cell model were used to assess the anti-obesity effects of T2-3. Lipids in the adipocytes were examined by Oil Red O staining. β-catenin expression was examined by immunofluorescence and Western blotting, its activity was assessed by TOPflash/FOPflash assay.

RESULTS

T2-3 possessed potent anti-obesity effects in DIO mice, it significantly reduced body weight and subcutaneous adipose tissue (SAT) mass. Mechanistic studies showed that T2-3 significantly inhibited 3T3-L1 preadipocyte differentiation as indicated by the reduced number of mature adipocytes. The treatments also reduced the expressions of critical adipogenic transcription factors CEBP-α and PPAR-γ in both 3T3-L1 adipocytes and SAT in DIO mice. Interestingly, T2-3 increased the cytoplasmic and nuclear expressions of β-catenin and the transcriptional activity of β-catenin in 3T3-L1 adipocytes; the elevated β-catenin expression was also observed in SAT of the T2-3-treated DIO mice. Indeed, upregulation of β-catenin activity suppressed adipogenesis, while β-catenin inhibitor JW67 reversed the anti-adipogenic effect of T2-3. Taken together, our data suggest that T2-3 inhibits adipogenesis by upregulating β-catenin activity.

CONCLUSIONS

Our study is the first report demonstrating meroterpenoid furanasperterpene A as a novel 6/6/6/6/5 pentacyclic skeleton (T2-3) that possesses potent anti-adipogenic effect by targeting β-catenin signaling pathway. Our findings drive new anti-obesity drug discovery and provide drug leads for chemists and pharmacologists.

Semaglutide for the treatment of type 2 Diabetes Mellitus: A systematic review and network meta-analysis of safety and efficacy outcomes

BACKGROUND AND AIMS

To assess the safety and efficacy of semaglutide compared with placebo and other anti-hyperglycaemic agents in type 2 diabetes (T2DM).

METHODS

We searched PubMed, Scopus, Web of Science, and Cochrane library for relevant randomized controlled trials (RCTs). A network meta-analysis was conducted to compare different doses, durations, and interventions in T2DM. We presented results as mean difference (MD) or relative risk (RR) and 95% confidence interval (CI).

RESULTS

Twenty-six included RCTs studied different doses of subcutaneous (SC) and oral semaglutide, tirzepatide, liraglutide, sitagliptin, canagliflozin, and empagliflozin compared with placebo. Tirzepatide showed the highest efficacy, however, it was comparable to semaglutide. SC semaglutide 1 mg once-weekly showed higher reduction in HbA_1c (MD = -1.72, 95% CI [-2.32; -1.12]), and fasting blood glucose (MD = -1.93, 95% CI [-2.81; -1.04]) versus placebo at 30 weeks and other timepoints. Adverse events (ADs) were comparable to placebo with oral and SC semaglutide, oral sitagliptin, SC liraglutide, and oral empagliflozin at most timepoints. However, SC semaglutide 0.8 mg and tirzepatide 10 mg groups had the highest gastrointestinal adverse events.

CONCLUSION

Tirzepatide, oral and SC semaglutide has a favourable efficacy in treating T2DM. The adverse events were comparable to placebo; however, gastrointestinal adverse events were highly recorded in tirzepatide, oral and SC semaglutide groups.

Anti-ADAMTS13 autoantibody profiling in patients with immune-mediated thrombotic thrombocytopenic purpura

Anti-A Disintegrin and Metalloproteinase with a ThromboSpondin type 1 motif, member 13 (ADAMTS13) autoantibodies cause a severe ADAMTS13 deficiency in immune-mediated thrombotic thrombocytopenic purpura (iTTP). ADAMTS13 consists of a metalloprotease (M), a disintegrin-like (D) domain, 8 thrombospondin type 1 repeats (T1-T8), a cysteine-rich (C), a spacer (S), and 2 CUB domains (CUB1-2). We recently developed a high-throughput epitope mapping assay based on small, nonoverlapping ADAMTS13 fragments (M, DT, CS, T2-T5, T6-T8, CUB1-2). With this assay, we performed a comprehensive epitope mapping using 131 acute-phase samples and for the first time a large group of remission samples (n = 50). Next, samples were stratified according to their immunoprofiles, a field that is largely unexplored in iTTP. Three dominant immunoprofiles were found in acute-phase samples: profile 1: only anti-CS autoantibodies (26.7%); profile 2: both anti-CS and anti-CUB1-2 autoantibodies (12.2%); and profile 3: anti-DT, anti-CS, anti-T2-T5, anti-T6-T8, and anti-CUB1-2 autoantibodies (8.4%). Interestingly, profile 1 was the only dominant immunoprofile in remission samples (52.0%). Clinical data were available for a relatively small number of patients with acute iTTP (>68), and no correlation was found between immunoprofiles and disease severity. Nevertheless, profile 1 was linked with younger and anti-T2-T5 autoantibodies with older age and the absence of anti-CUB1-2 autoantibodies with cerebral involvement. In conclusion, identifying acute phase and remission immunoprofiles in iTTP revealed that anti-CS autoantibodies seem to persist or reappear during remission providing further support for the clinical development of a targeted anti-CS autoantibody therapy. A large cohort study with acute iTTP samples will validate possible links between immunoprofiles or anti-domain autoantibodies and clinical data.

Design, synthesis and biological evaluation of double fatty chain-modified glucagon-like peptide-1 conjugates

Twelve double fatty chains and Aib⁸-Arg³⁴-GLP-1 (7-37) were designed and obtained by microwave-assisted solid-phase synthesis. Then, twelve conjugates of Aib⁸-Arg³⁴-GLP-1 (7-37) were synthesized in 1% triethylamine aqueous solution. Conjugates 2, 3, 6, 7, 10 and 11 showed better GLP-1 receptor activation potency than semaglutide. However, conjugates 2, 6 and 10 showed slightly worse glucose-lowering effects in vivo than semaglutide but better effects than conjugates 3, 7 and 11. The CD spectra of conjugates 2, 6 and 10 indicated that they had the same secondary structure as liraglutide and semaglutide. The receptor affinity results for conjugates 2, 6 and 10 measured by SPR (surface plasmon resonance) showed that conjugate 2 had higher receptor affinity than conjugates 6 and 10. In addition, albumin binding assays indicated that double fatty acid chains had obvious synergistic effects compared with single fatty acid chains. In conclusion, the structure-activity relationship of different side chains was summarized and one candidate, conjugate 2, was screened.

Relationship Between Oral Semaglutide Tablet Erosion and Pharmacokinetics: A Pharmacoscintigraphic Study

Semaglutide, a glucagon‐like peptide‐1 (GLP‐1) analogue, has been coformulated in a tablet with the absorption enhancer, sodium N‐(8‐[2‐hydroxybenzoyl] amino) caprylate (SNAC). We investigated tablet erosion and the pharmacokinetics of oral semaglutide administered with 2 different water volumes and evaluated the relationships between these parameters. In a randomized, single‐center (Quotient Sciences, UK), open‐label, 2‐period crossover trial, 26 healthy men received single doses of 10 mg oral semaglutide with 50 or 240 mL water while fasting. Tablet erosion and gastrointestinal transit were assessed by gamma scintigraphy. Semaglutide and SNAC plasma concentrations were measured until 24 and 6 hours, respectively, after administration. Complete tablet erosion (CTE) occurred in the stomach irrespective of water volume administered with the tablet (primary end point). Mean time to CTE was 85 versus 57 minutes with 50 versus 240 mL water (ratio 50/240 mL, 1.51; 95% confidence interval, 0.96‐2.37; P = .072). Area under the semaglutide concentration‐time curve from 0 to 24 hours (AUC_{0‐24h,semaglutide}) and maximum semaglutide concentration (C_{max,semaglutide}) were ∼70% higher with 50 versus 240 mL water (P = .056 and P = .048, respectively). Median time to maximum semaglutide concentration (t_{max,semaglutide}) was 1.5 hours independent of water volume with dosing. Higher AUC_{0‐24h,semaglutide} and C_{max,semaglutide} and longer t_{max,semaglutide} were significantly correlated with longer time to CTE and later gastric emptying of tablet and water (all P < .05). The safety profile was as expected for the GLP‐1 receptor agonist drug class. In conclusion, the oral semaglutide tablet erodes in the stomach irrespective of water volume with dosing. Slower tablet erosion in the stomach results in higher semaglutide plasma exposure.

Oral GLP1 Analog: Where Does the Tide Go?

T2D is a potentially preventable disease that has been ranked the seventh leading cause of mortality in the United States. There is strong evidence demonstrating that preventing type 2 diabetes is, in many cases, attainable through lifestyle intervention. Unfortunately, prediabetes is mostly overlooked and awareness with diabetes prevention tools is lacking among primary care physicians. Nationally, efforts were not successful in reversing this epidemic even with an array of diabetes medications. Among the most effective medications for T2D are glucagon-like peptide-1 receptor agonists (GLP-1 RAs), which have been shown to reduce both A1C and body weight. Dulaglutide, liraglutide and injectable semaglutide also reduced cardiovascular events and cardiovascular mortality in patients with established cardiovascular disease or multiple cardiovascular risk factors. In this review, we will examine the first FDA approved oral GLP-1 RA; semaglutide. Moreover, this review will discuss the potential impact oral semaglutide may have on glycemic control, weight loss and cardiovascular comorbidities. It also examines the factors that may impact patient compliance, including cost, side effects and clinical issues. Finally, it deliberates the optimism surrounding the development of oral semaglutide in the treatment of diabetes as well as related conditions, such as obesity and non-alcoholic fatty liver disease (NAFLD).

The evolution of polymer conjugation and drug targeting for the delivery of proteins and bioactive molecules

Polymer conjugation can be considered one of the leading approaches within the vast field of nanotechnology-based drug delivery systems. In fact, such technology can be exploited for delivering an active molecule, such as a small drug, a protein, or genetic material, or it can be applied to other drug delivery systems as a strategy to improve their in vivo behavior or pharmacokinetic activities such as prolonging the half-life of a drug, conferring stealth properties, providing external stimuli responsiveness, and so on. If on the one hand, polymer conjugation with biotech drug is considered the linchpin of the protein delivery field boasting several products in clinical use, on the other, despite dedicated research, conjugation with low molecular weight drugs has not yet achieved the milestone of the first clinical approval. Some of the primary reasons for this debacle are the difficulties connected to achieving selective targeting to diseased tissue, organs, or cells, which is the main goal not only of polymer conjugation but of all delivery systems of small drugs. In light of the need to achieve better drug targeting, researchers are striving to identify more sophisticated, biocompatible delivery approaches and to open new horizons for drug targeting methodologies leading to successful clinical applications. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Toxicology and Regulatory Issues in Nanomedicine > Regulatory and Policy Issues in Nanomedicine.

Cyclic tailor-made amino acids in the design of modern pharmaceuticals

Tailor-made AAs are indispensable components of modern medicinal chemistry and are becoming increasingly prominent in new drugs. In fact, about 30% of small-molecule pharmaceuticals contain residues of tailor-made AAs or structurally related diamines and amino-alcohols. Cyclic tailor-made AAs present a particular value to rational structural design by virtue of their local conformational constraints and are widely used in lead optimization programs. The present review article highlights 34 compounds, all of which are derived from cyclic AAs, representing recently-approved, small-molecule pharmaceuticals as well as promising drug candidates currently in various phases of clinical study. For each compound, the discussion includes the discovery, therapeutic profile and optimized synthesis, with a focus on the preparation of cyclic tailor-made AA as the principal structural feature. The present review article is intended to serve as a reference source for organic, medicinal and process chemists along with other professionals working in the fields of drug design and pharmaceutical discovery.

Postprandial hyperlipidemia as a risk factor in patients with type 2 diabetes

Introduction: Postprandial hyperlipidemia is a common feature of the atherogenic dyslipidemia in patients with type 2 diabetes. Quantification of this with oral fat tolerance tests is not used routinely in clinical practice and abnormal postprandial lipids are usually inferred from non-fasting plasma triglyceride levels. Identifying excessive postprandial hyperlipidemia may help to refine cardiovascular risk assessment but there are no treatments currently available which selectively target postprandial lipids and no large cardiovascular outcome trials using this as the entry criterion.Areas covered: In this review of relevant published material, we summarize the findings from the most important publications in this area.Expert opinion: Postprandial hyperlipidemia appears to contribute to the cardiovascular risk in patients with diabetes. Non-fasting triglyceride levels provide a surrogate marker of postprandial hyperlipidemia but more specific markers such as apoB48 levels may prove to be more reliable. Omega-3 fatty acids, fibrates and ezetimibe can reduce postprandial lipids but may not correct them completely. Several novel treatments have been developed to target hypertriglyceridemia and some of these may be particularly effective in improving postprandial levels. Further clinical trials are needed to establish the role of postprandial lipids in assessment of cardiovascular risk and to identify the most effective treatments.

Structural Modeling and in Silico Screening of Potential Small-Molecule Allosteric Agonists of a Glucagon-like Peptide 1 Receptor

The glucagon-like peptide 1 receptor (GLP-1R) belongs to the pharmaceutically important class B family of G-protein-coupled receptors (GPCRs), and its incretin peptide ligand GLP-1 analogs are adopted drugs for the treatment of type 2 diabetes. Despite remarkable antidiabetic effects, GLP-1 peptide-based drugs are limited by the need of injection. On the other hand, developing nonpeptidic small-molecule drugs targeting GLP-1R remains elusive. Here, we first constructed a three-dimensional structure model of the transmembrane (TM) domain of human GLP-1R using homology modeling and conformational sampling techniques. Next, a potential allosteric binding site on the TM domain was predicted computationally. In silico screening of druglike compounds against this predicted allosteric site has identified nine compounds as potential GLP-1R agonists. The independent agonistic activity of two compounds was subsequently confirmed using a cAMP response element-based luciferase reporting system. One compound was also shown to stimulate insulin secretion through in vitro assay. In addition, this compound synergized with GLP-1 to activate human GLP-1R. These results demonstrated that allosteric regulation potentially exists in GLP-1R and can be exploited for developing small-molecule agonists. The success of this work will help pave the way for small-molecule drug discovery targeting other class B GPCRs through allosteric regulations.

Liraglutide Treatment Reduces Endothelial Endoplasmic Reticulum Stress and Insulin Resistance in Patients With Diabetes Mellitus

Background Prior studies have shown that nutrient excess induces endoplasmic reticulum ( ER ) stress in nonvascular tissues from patients with diabetes mellitus ( DM ). ER stress and the subsequent unfolded protein response may be protective, but sustained activation may drive vascular injury. Whether ER stress contributes to endothelial dysfunction in patients with DM remains unknown. Methods and Results To characterize vascular ER stress, we isolated endothelial cells from 42 patients with DM and 37 subjects without DM. Endothelial cells from patients with DM displayed higher levels of ER stress markers compared with controls without DM. Both the early adaptive response, evidenced by higher phosphorylated protein kinase-like ER eukaryotic initiation factor-2a kinase and inositol-requiring ER-to-nucleus signaling protein 1 ( P=0.02, P=0.007, respectively), and the chronic ER stress response evidenced by higher C/ EBP α-homologous protein ( P=0.02), were activated in patients with DM . Higher inositol-requiring ER-to-nucleus signaling protein 1 activation was associated with lower flow-mediated dilation, consistent with endothelial dysfunction ( r=0.53, P=0.02). Acute treatment with liraglutide, a glucagon-like peptide 1 receptor agonist, reduced p-inositol-requiring ER-to-nucleus signaling protein 1 ( P=0.01), and the activation of its downstream target c-jun N-terminal kinase ( P=0.025) in endothelial cells from patients with DM . Furthermore, liraglutide restored insulin-stimulated endothelial nitric oxide synthase activation in patients with DM ( P=0.019). Conclusions In summary, our data suggest that ER stress contributes to vascular insulin resistance and endothelial dysfunction in patients with DM . Further, we have demonstrated that liraglutide ameliorates ER stress, decreases c-jun N-terminal kinase activation and restores insulin-mediated endothelial nitric oxide synthase activation in endothelial cells from patients with DM .

Complement 1q-like-3 protein inhibits insulin secretion from pancreatic β-cells via the cell adhesion G protein-coupled receptor BAI3

Secreted proteins are important metabolic regulators in both healthy and disease states. Here, we sought to investigate the mechanism by which the secreted protein complement 1q-like-3 (C1ql3) regulates insulin secretion from pancreatic β-cells, a key process affecting whole-body glucose metabolism. We found that C1ql3 predominantly inhibits exendin-4- and cAMP-stimulated insulin secretion from mouse and human islets. However, to a lesser extent, C1ql3 also reduced insulin secretion in response to KCl, the potassium channel blocker tolbutamide, and high glucose. Strikingly, C1ql3 did not affect insulin secretion stimulated by fatty acids, amino acids, or mitochondrial metabolites, either at low or submaximal glucose concentrations. Additionally, C1ql3 inhibited glucose-stimulated cAMP levels, and insulin secretion stimulated by exchange protein directly activated by cAMP-2 and protein kinase A. These results suggest that C1ql3 inhibits insulin secretion primarily by regulating cAMP signaling. The cell adhesion G protein-coupled receptor, brain angiogenesis inhibitor-3 (BAI3), is a C1ql3 receptor and is expressed in β-cells and in mouse and human islets, but its function in β-cells remained unknown. We found that siRNA-mediated Bai3 knockdown in INS1(832/13) cells increased glucose-stimulated insulin secretion. Furthermore, incubating the soluble C1ql3-binding fragment of the BAI3 protein completely blocked the inhibitory effects of C1ql3 on insulin secretion in response to cAMP. This suggests that BAI3 mediates the inhibitory effects of C1ql3 on insulin secretion from pancreatic β-cells. These findings demonstrate a novel regulatory mechanism by which C1ql3/BAI3 signaling causes an impairment of insulin secretion from β-cells, possibly contributing to the progression of type 2 diabetes in obesity.

α-Helix or β-Turn? An Investigation into N-Terminally Constrained Analogues of Glucagon-like Peptide 1 (GLP-1) and Exendin-4

Peptide agonists acting on the glucagon-like peptide 1 receptor (GLP-1R) promote glucose-dependent insulin release and therefore represent important therapeutic agents for type 2 diabetes (T2D). Previous data indicated that an N-terminal type II β-turn motif might be an important feature for agonists acting on the GLP-1R. In contrast, recent publications reporting the structure of the full-length GLP-1R have shown the N-terminus of receptor-bound agonists in an α-helical conformation. To reconcile these conflicting results, we prepared N-terminally constrained analogues of glucagon-like peptide 1 (GLP-1) and exendin-4 and evaluated their receptor affinity and functionality in vitro; we then examined their crystal structures in complex with the extracellular domain of the GLP-1R and used molecular modeling and molecular dynamics simulations for further investigations. We report that the peptides' N-termini in all determined crystal structures adopted a type II β-turn conformation, but in vitro potency varied several thousand-fold across the series. Potency correlated better with α-helicity in our computational model, although we have found that the energy barrier between the two mentioned conformations is low in our most potent analogues and the flexibility of the N-terminus is highlighted by the dynamics simulations.

Glucagon-Like Peptide-1 (GLP-1)-Based Therapeutics: Current Status and Future Opportunities beyond Type 2 Diabetes

Glucagon-like peptide-1 (GLP-1) is secreted by intestinal L-cells following food intake, and plays an important role in glucose homeostasis due to its stimulation of glucose-dependent insulin secretion. Further, GLP-1 is also associated with protective effects on pancreatic β-cells and the cardiovascular system, decreased appetite, and weight loss, making GLP-1 derivatives an exciting treatment for type 2 diabetes and obesity. Despite these benefits, wild-type GLP-1 exhibits a short circulation time due to its poor metabolic stability and rapid renal clearance, and must be administered by injection, making it a poor therapeutic agent. Many strategies have been used to improve the circulation time of GLP-1 (e.g., mutations, unnatural amino acids, depot formulations, use of exendin-4 sequences, and fusions with high-molecular-weight proteins or polymers), with its therapeutic utility further improved by adding agonist activity for gastric inhibitory peptide and glucagon receptors. This minireview focuses on strategies that have been used to improve the pharmacokinetics of GLP-1 and provides an overview of GLP-1-based therapeutics in the pipeline.

A novel GLP-1/xenin hybrid peptide improves glucose homeostasis, circulating lipids and restores GIP sensitivity in high fat fed mice

Combined modulation of peptide hormone receptors including, glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP) and xenin, have established benefits for the treatment of diabetes. The present study has assessed the biological actions and therapeutic efficacy of a novel exendin-4/xenin-8-Gln hybrid peptide, both alone and in combination with the GIP receptor agonist (DAla²)GIP. Exendin-4/xenin-8-Gln was enzymatically stable and exhibited enhanced insulin secretory actions when compared to its parent peptides. Exendin-4/xenin-8-Gln also possessed ability to potentiate the in vitro actions of GIP. Acute administration of exendin-4/xenin-8-Gln in mice induced appetite suppressive effects, as well as significant and protracted glucose-lowering and insulin secretory actions. Twice daily administration of exendin-4/xenin-8-Gln, alone or in combination with (DAla²)GIP, for 21-days significantly reduced non-fasting glucose and increased circulating insulin levels in high fat fed mice. In addition, all exendin-4/xenin-8-Gln treated mice displayed improved glucose tolerance, insulin sensitivity and metabolic responses to GIP. Combination therapy with (DAla²)GIP did not result in any obvious further benefits. Metabolic improvements in all treatment groups were accompanied by reduced pancreatic beta-cell area and insulin content, suggesting reduced insulin demand. Interestingly, body weight, food intake, circulating glucagon, metabolic rate and amylase activity were unaltered by the treatment regimens. However, all treatment groups, barring (DAla²)GIP alone, exhibited marked reductions in total- and LDL-cholesterol. Furthermore, exendin-4 therapy also reduced circulating triacylglycerol. This study highlights the positive antidiabetic effects of exendin-4/xenin-8-Gln, and suggests that combined modulation of GLP-1 and xenin related signalling pathways represents an exciting treatment option for type 2 diabetes.

Xenopus-derived glucagon-like peptide-1 and polyethylene-glycosylated glucagon-like peptide-1 receptor agonists: long-acting hypoglycaemic and insulinotropic activities with potential therapeutic utilities

BACKGROUND AND PURPOSE

Incretin-based therapies based on glucagon-like peptide-1 (GLP-1) receptor agonists are effective treatments of type 2 diabetes. Abundant research has focused on the development of long-acting GLP-1 receptor agonists. However, all GLP-1 receptor agonists in clinical use or development are based on human or Gila GLP-1. We have identified a potent GLP-1 receptor agonist, xGLP-1B, based on Xenopus GLP-1.

EXPERIMENTAL APPROACH

To further modify the structure of xGLP-1B, alanine scanning was performed to study the structure -activity relationship of xGLP-1B. Two strategies were then employed to improve bioactivity. First, the C-terminal tail of lixisenatide was appended to cysteine-altered xGLP-1B analogues. Second, polyethylene glycol (PEG) chains with different molecular weights were conjugated with the peptides, giving a series of PEGylated conjugates. Comprehensive bioactivity studies of these conjugates were performed in vitro and in vivo.

RESULTS

From the in vitro receptor activation potency and in vivo acute hypoglycaemic activities of conjugates 25 -36, 33 was identified as the best candidate for further biological assessments. Conjugate 33 exhibited prominent hypoglycaemic and insulinotropic activities, as well as improved pharmacokinetic profiles in vivo. The prolonged antidiabetic duration of 33 was further confirmed by pre-oral glucose tolerance tests (OGTT) and multiple OGTT. Furthermore, chronic treatment of db/db mice with 33 ameliorated non-fasting blood glucose and insulin levels, reduced HbA1c values and normalized their impaired glucose tolerance. Importantly, no in vivo toxicity was observed in mice treated with 33.

CONCLUSIONS AND IMPLICATIONS

Peptide 33 is a promising long-acting type 2 diabetes therapeutic deserving further investigation.

Pharmacokinetic drug evaluation of exenatide for the treatment of type 2 diabetes

INTRODUCTION

Glucagon-like peptide-1 (GLP-1) receptor analogs are a group of therapeutic agents which mimic endogenous GLP-1, exerting their effect by the stimulation of the GLP-1 receptor with a wide distribution. Its activation increases insulin releasing dependent on blood glucose levels, suppression of glucagon secretion and a reduction of hepatic glucose output. It delays gastric emptying and increases satiety. Exenatide is the synthetic version of exendin-4, a natural peptide with similar properties to human GLP-1. There are two pharmaceutical forms, for subcutaneous injection: twice daily and once weekly. Clinical practice guidelines recommend them because of a high efficacy reducing hyperglycemia, low risk of hypoglycemia and a significative weight loss effect. Gastrointestinal adverse events are the most common beside injection site-related. Their cost is the main limitation to use. Areas covered: We review the recent literature investigating the pharmacokinetics and pharmacodynamics and efficacy-safety studies of exenatide twice daily and once weekly in type 2 diabetes Expert opinion: GLP-1 receptor analogs are now positioned as an effective and safe drug for the treatment of type 2 diabetes. Exenatide significally reduces HbA1c and fasting plasma glucose. Additionally, it produces moderate weight loss and decreases blood pressure. One weekly formulation may improve compliance while cost is still a limitation. EXSCEL trial has shown that, despite cardiovascular safety, exenatide do not exhibits cardiovascular benefits.

Antiobesity and emetic effects of a short-length peptide YY analog and its PEGylated and alkylated derivatives

Neuropeptide Y2 receptor (Y2R) agonism is an important anorectic signal and a target of antiobesity drug discovery. Recently, we synthesized a short-length Y2R agonist, PYY-1119 (4-imidazolecarbonyl-[d-Hyp²⁴,Iva²⁵,Pya(4)²⁶,Cha^27,36,γMeLeu²⁸,Lys³⁰,Aib³¹]PYY(23-36), 1) as an antiobesity drug candidate. Compound 1 induced marked body weight loss in diet-induced obese (DIO) mice; however, 1 also induced severe vomiting in dogs at a lower dose than the minimum effective dose administered to DIO mice. The rapid absorption of 1 after subcutaneous administration caused the severe vomiting. Polyethylene glycol (PEG)- and alkyl-modified derivatives of 1 were synthesized to develop Y2R agonists with improved pharmacokinetic profiles, i.e., lower maximum plasma concentration (C_max) and longer time at maximum concentration (T_max). Compounds 5 and 10, modified with 20 kDa PEG at the N-terminus and eicosanedioic acid at the Lys³⁰ side chain of 1, respectively, showed high Y2R binding affinity and induced significant body weight reduction upon once-daily administration to DIO mice. Compounds 5 and 10, with their relatively low C_max and long T_max, partially attenuated emesis in dogs compared with 1. These results indicate that optimization of pharmacokinetic properties of Y2R agonists is an effective strategy to alleviate emesis induced by Y2R agonism.

Recent Advances in GLP-1 Receptor Agonists for Use in Diabetes Mellitus

Preclinical Research Mimetics of Glucagon-like peptide 1 (GLP-1) represent a useful alternative or complementary treatment choice to insulin in the treatment of diabetes mellitus. The lack of hypoglycemia as a side effect when GLP-1 receptor agonists are used along with the tendency of these therapeutic agents to prevent or even reduce weight gain makes them valuable targets in therapy development. However, native GLP-1 and many of its early analogues have very short half-lives, requiring repeated treatment to maintain therapeutic levels. As all current treatments are injected subcutaneously, a large focus has been made on trying to extend the half-lives of GLP-1 analogues while retaining bioactivity. Most success in this regard has been achieved with the use of peptide-protein fusions, which are not as well suited for oral administration. However, recent work focused on the development of non-fusion peptides with increased half-lives that may be more appropriate for oral administration. This minireview discusses the structural characteristics of past and present analogues as well as the recent work conducted toward developing novel GLP-1 receptor agonists. Drug Dev Res 78 : 292-299, 2017. © 2017 Wiley Periodicals, Inc.

Improving drug-like properties of insulin and GLP-1 via molecule design and formulation and improving diabetes management with device & drug delivery

There is an increased incidence of diabetes worldwide. The discovery of insulin revolutionized the management of diabetes, the revelation of glucagon-like peptide-1 (GLP-1) and introduction of GLP-1 receptor agonists to clinical practice was another breakthrough. Continued translational research resulted in better understanding of diabetes, which, in combination with cutting-edge biology, chemistry, and pharmaceutical tools, have allowed for the development of safer, more effective and convenient insulins and GLP-1. Advances in self-administration of insulin and GLP-1 receptor agonist therapies with use of drug-device combination products have further improved the outcomes of diabetes management and quality of life for diabetic patients. The synergies of insulin and GLP-1 receptor agonist actions have led to development of devices that can deliver both molecules simultaneously. New chimeric GLP-1-incretins and insulin-GLP-1-incretin molecules are also being developed. The objective of this review is to summarize molecular designs to improve the drug-like properties of insulin and GLP-1 and to highlight the continued advancement of drug-device combination products to improve diabetes management.

ZB-16, a Novel GPR119 Agonist, Relieves the Severity of Streptozotocin-Nicotinamide-Induced Diabetes in Rats

GPR119 is involved in the regulation of incretin and insulin secretion, so the GPR119 agonists have been suggested as novel antidiabetic medications. The purpose of this work was to assess the influence of novel GPR119 agonist ZB-16 on the glucose utilization, insulin, and glucagon-like peptide-1 (GLP-1) secretion and the morphology of pancreas in rats with streptozotocin-nicotinamide-induced diabetes. 45 male Wistar rats were used in the study. The criteria of streptozotocin-nicotinamide-induced diabetes were blood glucose levels of 9-14 mmol/l measured in fasting conditions on the third day since administration of streptozotocin (65 mg/kg) and nicotinamide (230 mg/kg). Animals failed to reach the criteria were excluded from the experiment. The substances were administered per os once per day for 28 days. Measurements included blood glucose monitoring (every 7 days), glucose tolerance test (every 14 days), the assessment of insulin and GLP-1 levels in blood plasma (28 days after beginning), and the results of immunohistochemical staining of pancreas. It was found that ZB-16 (1 mg/kg per os, once a day) decreases the blood glucose levels under fasting conditions and improves the glucose utilization. These changes were associated with the increase in stimulated secretion of GLP-1 and insulin, accompanied by the growth of insulin-positive cells in pancreas. Thus, ZB-16 could be a promising antidiabetic drug for oral administration.

Evaluation of the pharmacokinetics, pharmacodynamics and clinical efficacy of empagliflozin for the treatment of type 2 diabetes

INTRODUCTION

Sodium-glucose co-transporter 2 (SGLT2) inhibitors are the latest class of drugs to be introduced for the treatment of type 2 diabetes mellitus. These drugs improve glycemic control by increasing urinary glucose excretion and exert additional benefits of weight loss and blood pressure reductions. Areas covered: This review outlines the background to SGLT2 inhibitors and provides details on the pharmacokinetics, pharmacodynamics and clinical efficacy of empagliflozin and discusses the cardiovascular outcome trial. Expert opinion: Empagliflozin was the first from a new group of antidiabetic drugs to show benefits in a cardiovascular outcome trial. There were significant reductions in cardiovascular and all-cause mortality and empagliflozin treatment reduced hospitalizations for heart failure and reduced the progression of diabetic nephropathy. These benefits, which occurred at a very early stage during the study, may be related to a reduction in circulating volume or changes in metabolic fuel utilization in the heart and kidneys. Whether these effects are shared by other SGLT2 inhibitors is not yet known, but there may be differences between drugs related to selectivity for inhibition of SGLT2 compared to SGLT1 or other pharmacological effects. Currently the outcome evidence is only available to support the use of empagliflozin in this drug class.

Peptide-based GLP-1/glucagon co-agonists: A double-edged sword to combat diabesity

Diabesity is a new term for obesity-dependent diabetes, which is also associated with cardiovascular and other comorbidities with rising epidemic. Traditional treatments (sulfonylureas and thiazolidinediones) of diabetes are associated with weight gain, except metformin. Newer agents such as glucagon-like peptide-1 receptor agonists (GLP-1 RAs) and Sodium glucose co-transporter 2 inhibitors (SGLT2i) are causing a modest weight reduction, whereas dipeptidyl peptidase-4 inhibitors (DPP-4i) are weight neutral. Oxyntomodulin, a native GLP-1/glucagon receptor agonist produced a superior weight loss and antihyperglycemic effects in obese mice and humans. Recent findings with synthetic dual GLP-1/glucagon receptor agonists have shown a good weight loss and antihyperglycemic profile in diet-induced obese (DIO) mice. Targeting combinations of GLP-1 receptor and glucagon receptor simultaneously with a single peptide may be the better strategy to achieve marked weight loss and considerable glycemic control in diabesity. Cardiovascular safety is very important with new antidiabetic agents due to rosiglitazone controversy. Current on-going clinical trials will clarify the cardiovascular effects of incretin-based therapies in near future. Based on current knowledge and rapid progress in the field, there is a strong possibility that the GLP-1/glucagon receptor co-agonists will likely be the new therapeutic treatment for diabesity for decades to come.

Investigational glucagon-like peptide-1 agonists for the treatment of obesity

INTRODUCTION

Obesity is a worldwide problem predisposing to type 2 diabetes mellitus (T2DM), hypertension, cardiovascular disease, cancer and other comorbidities. Lifestyle modification is the first line intervention but adjunctive pharmacotherapy is often required. The GLP-1 receptor agonists (GLP-1RAs) were developed primarily for T2DM and they also reduce body weight. Liraglutide was approved for the treatment of obesity and other GLP-1RAs are likely to be suitable for this indication.

AREAS COVERED

This review describes the GLP-1RAs that have been approved for the treatment of T2DM as potential candidates for the treatment of obesity and the new agents currently under development which may have advantages in patient adherence.

EXPERT OPINION

The GLP-1RAs offer a welcome addition to obesity pharmacotherapy. They appear to be free of serious adverse effects although uncertainty remains about possible risks of pancreatitis and neoplasms. However, they have frequent gastrointestinal side effects, particularly nausea, which limits their tolerability. Cardiovascular outcome studies in T2DM support their use and this is likely to increase in both T2DM and obesity. Other GLP-1RAs which can be given by subcutaneous injection once weekly or less frequently or by oral administration would have advantages especially if nausea is less frequent than with liraglutide.

Allostery and Biased Agonism at Class B G Protein-Coupled Receptors

Class B G protein-coupled receptors (GPCRs) respond to paracrine or endocrine peptide hormones involved in control of bone homeostasis, glucose regulation, satiety, and gastro-intestinal function, as well as pain transmission. These receptors are targets for existing drugs that treat osteoporosis, hypercalcaemia, Paget's disease, type II diabetes, and obesity and are being actively pursued as targets for numerous other diseases. Exploitation of class B receptors has been limited by difficulties with small molecule drug discovery and development and an under appreciation of factors governing optimal therapeutic efficacy. Recently, there has been increasing awareness of novel attributes of GPCR function that offer new opportunity for drug development. These include the presence of allosteric binding sites on the receptor that can be exploited as drug binding pockets and the ability of individual drugs to enrich subpopulations of receptor conformations to selectively control signaling, a phenomenon termed biased agonism. In this review, current knowledge of biased signaling and small molecule allostery within class B GPCRs is discussed, highlighting areas that have progressed significantly over the past decade, in addition to those that remain largely unexplored with respect to these phenomena.