Potent Glucagon-like Peptide-1 Research Articles

7625 Functional and structural neuronal changes of dulaglutide compared to placebo during smoking cessation - a randomized placebo-controlled trial

Abstract Disclosure: C.O. Sailer: None. S. Lengsfeld: None. D. Coynel: None. F. Baur: None. K. Bologna: None. T. Vukajlovic: None. N.A. Jeanloz: None. C. Bathelt: None. D. Zanchi: None. M. Christ-Crain: None. B.F. Winzeler: None. Introduction: Nicotine activates reward-related brain regions and chronic cigarette smoking can lead to functional and structural neuronal changes. Glucagon-like peptide-1 (GLP-1) receptor agonists (RAs), known for their anti-obesity effects, have emerged as potential treatments for addictive disorders. A pilot study of exenatide vs placebo revealed increased short-term smoking abstinence rates and reduce smoking craving. We previously reported the results of a clinical trial (n=255) investigating the effect of dulaglutide vs placebo on smoking cessation. Herein, we report the functional magnetic resonance imaging (fMRI) results of a subset of participants. This substudy aimed to investigate the influence of dulaglutide on smoking craving, functional and structural neuronal changes of smokers aiming to quit smoking. Methods: This single-center, randomized, double-blind, placebo-controlled trial enrolled 71 participants with at least a moderate nicotine dependence, all committed to quitting smoking. Of these, 35 participants received 12 weeks dulaglutide 1.5mg, and 36 participants placebo, alongside varenicline treatment and behavioral counselling. An fMRI session was conducted at baseline and 12 weeks. The primary outcomes included smoking craving assessed on a visual analogue scale (VAS, range 0-7), differences in blood oxygen level dependent (BOLD) signal (whole brain and regions of interests, e.g., nucleus accumbens, amygdala, thalamus) and gray matter changes between sessions and groups when exposed to smoking and neutral video cues. Secondary outcomes assessed the above in quitters vs persistent smokers. Results: In line with the primary study findings, abstinence rates at 12 weeks were comparable in the dulaglutide (54%) and placebo (68%) groups (p=0.27). In a mixed effect model, smoking craving significantly decreased at 12 weeks vs baseline (-2.13 (95% CI -2.46, -1.80), p<0.001) and were lower for neutral vs smoking cues (-2.02 (-2.34, 1.70,), p<0.001). However, no significant inter-group difference was observed (-0.09 (-0.53, 0.33), p=0.65). Persistent smokers exhibited higher smoking craving at 12 weeks vs quitters (0.48 (0.06, 0.90), p=0.028), particularly when exposed to smoking cues (2.02 (1.70, 2.34), p<0.001). No significant differences were found in functional or structural analyses between interventions or smoking status. Conclusions: The smoking cessation intervention led to a significant reduction in smoking craving at 12 weeks without in-between group differences in behavioral, functional, or structural outcomes. Our findings challenge the hypothesis that GLP-1 RAs modulates smoking craving and behavior. It is plausible that a potential GLP-1 effect might have been masked by varenicline treatment and the unexpectedly high abstinence rate in the placebo group. Future studies should explore more potent GLP-1 RAs or dual agonists. Presentation: 6/1/2024

Discovery of a Novel Glucagon-like Peptide-1 (GLP-1) Analogue from Bullfrog and Investigation of Its Potential for Designing GLP-1-Based Multiagonists.

In this study, we aimed to discover novel GLP-1 analogues from natural sources. We investigated GLP-1 analogues from fish and amphibians, and bullfrog GLP-1 (bGLP-1) showed the highest potency. Starting with bGLP-1, we explored the structure-activity relationship and performed optimization and long-acting modifications, resulting in a potent analogue called 2f. Notably, 2f exhibited superior effects on food intake, glycemic control, and body weight compared to semaglutide. Furthermore, we explored the usefulness of bGLP-1 in designing GLP-1-based multiagonists. Using the bGLP-1 sequence, we designed novel dual GLP-1/glucagon receptor agonists and triple GLP-1/GIP/glucagon receptor agonists. The selected dual GLP-1/glucagon receptor agonist 3o and triple GLP-1/GIP/glucagon receptor agonist 4b exhibited significant therapeutic effects on lipid regulation, glycemic control, and body weight. Overall, our study highlights the potential of discovering potent GLP-1 receptor agonists from natural sources. Additionally, utilizing natural GLP-1 analogues for designing multiagonists presents a practical approach for developing antiobesity and antidiabetic agents.

6-Azaspiro[2.5]octanes as small molecule agonists of the human glucagon-like peptide-1 receptor

Activation of the glucagon-like peptide-1 (GLP-1) receptor stimulates insulin release, lowers plasma glucose levels, delays gastric emptying, increases satiety, suppresses food intake, and affords weight loss in humans. These beneficial attributes have made peptide-based agonists valuable tools for the treatment of type 2 diabetes mellitus and obesity. However, efficient, and consistent delivery of peptide agents generally requires subcutaneous injection, which can reduce patient utilization. Traditional orally absorbed small molecules for this target may offer improved patient compliance as well as the opportunity for co-formulation with other oral therapeutics. Herein, we describe an SAR investigation leading to small-molecule GLP-1 receptor agonists that represent a series that parallels the recently reported clinical candidate danuglipron. In the event, identification of a benzyloxypyrimidine lead, using a sensitized high-throughput GLP-1 agonist assay, was followed by optimization of the SAR using substituent modifications analogous to those discovered in the danuglipron series. A new series of 6-azaspiro[2.5]octane molecules was optimized into potent GLP-1 agonists. Information gleaned from cryogenic electron microscope structures was used to rationalize the SAR of the optimized compounds.

Engineering a potent and long-acting GLP-1/Y2 receptor dual agonist as a multi-agonist therapy for diabetes and obesity

Novel dual agonists for the glucagon-like peptide-1 (GLP-1) and Y2 receptor hold the potential for enhanced efficacy over GLP-1 receptor (GLP-1R) agonists in treating obesity and diabetes. In this study, we aimed to improve the stability and increase the drug development success rate of our previously identified GLP-1/Y2 receptor dual agonist, 6q. To achieve this, we first optimized the structure of the linker within 6q. Additionally, we explored various fatty acid albumin binders to further enhance the stability of 6q. These binders were mainly selected from approved or clinically developed GLP-1R agonists or GLP-1-based multi-agonists. Through this process, we were able to identify a lead peptide, xGLP/PYY-6, that exhibited comparable in vitro potency toward the GLP-1 and Y2 receptors as 6q but with significantly improved stability compared to 6q. In Kunming and DIO mice, xGLP/PYY-6 showed a comparable hypoglycemic effect to semaglutide, and a significantly better effect on inhibiting food intake than semaglutide. In a chronic study in DIO mice, xGLP/PYY-6 exhibited significant metabolic benefits, as reflected by regulation of lipid levels, improved glucose tolerance, weight loss, decreased hepatocellular vacuolation, and the reversal of steatosis effects caused by xGLP/PYY-6. These results indicate the potential of developing xGLP/PYY-6 as an antiobesity, lipid regulation, antisteatotic, and antidiabetic agent.

Glucagon-like peptide-1 therapy for youth with type 2 diabetes.

Glucagon-like peptide-1 therapy for youth with type 2 diabetes.

A GLP-1/glucagon (GCG)/CCK2 receptors tri-agonist provides new therapy for obesity and diabetes.

Glucagon-like peptide-1 (GLP-1) and glucagon (GCG) receptor dual agonist have promising therapeutic effects in the treatment of obesity and diabetes. Moreover, GLP-1 and cholecystokinin 2 (CCK2 ) dual agonists have been shown to restore pancreas function and improve glycaemic control in preclinical studies. We describe, for the first time, the beneficial effects of GLP-1/glucagon receptor and GLP-1/CCK2 dual agonists, which can be integrated into one peptide, resulting in significant anti-diabetes and anti-obesity effectiveness. The in vitro potency of this novel peptide Xenopus (x) GLP-1/GCG/CCK2 tri-agonist (xGLP/GCG/gastrin) against GLP-1, GCG, CCK1 and CCK2 receptors was determined on cells expressing the corresponding receptors by cAMP accumulation or ERK1/2 phosphorylation assays. The in vivo anti-diabetes and anti-obesity effects of this tri-agonist xGLP/GCG/gastrin were studied in both db/db and diet induced obesity (DIO) mice. xGLP/GCG/gastrin was a potent and selective GLP-1, GCG and CCK2 tri-agonist. In DIO mice, the metabolic benefits of xGLP-1/GCG/gastrin, such as reduction of body weight and hepatic lipid contents were significantly better than those of the peptide ZP3022 (GLP-1/CCK-2 dual agonist) and liraglutide. In a short-term study in db/db mice, xGLP/GCG/gastrin treatment had considerable effects, increasing islet numbers, islet areas and insulin content. In a long-term treatment study using db/db mice, xGLP-1/GCG/gastrin showed a significantly and sustained improvement in glucose tolerance and glucose control compared with that of liraglutide, ZP3022, cotadutide (GLP-1/GCG dual agonist) and xGLP/GCG-15. These results demonstrate the therapeutic potential of xGLP-1/GCG/gastrin for the treatment of obesity and diabetes.

Norlignans as potent GLP-1 secretagogues from the fruits of Amomum villosum

The dried fruit of Amomum villosum (Amomi Fructus) is an important spices and traditional Chinese medicine. In this study, the EtOH extract of Amomi Fructus was revealed with hypoglycemic effects on db/db mice by increasing plasma insulin levels. After extracted with EtOAc, the EtOAc fraction showed increased activity in stimulating glucagon-like peptide-1 (GLP-1) secretion compared with the EtOH extract. In order to clarify the antidiabetic constituents, four undescribed norlignans, amovillosumins A‒D, were isolated from the EtOAc fraction, and the subsequent chiral resolution yielded three pairs of enantiomers. Their structures were determined by extensive spectroscopic data (1D and 2D NMR, HRESIMS, IR, UV and [α]D) and ECD calculations. Amovillosumins A and B significantly stimulated GLP-1 secretion by 375.1% and 222.7% at 25.0 μM, and 166.9% and 62.7% at 12.5 μM, representing a new type of GLP-1 secretagogues.

201 Effects of GLP-1 on Glucose and Islet-Cell Secretory Responses to Protein Ingestion After Gastric Bypass or Sleeve Gastrectomy

OBJECTIVES/GOALS: In this study we sought to determine the role of glucagon-like peptide-1 (GLP-1), one of the main gut hormones in regulating glucose metabolism, after protein ingestion in patients with a history of Roux-en-Y gastric bypass (GB) and sleeve gastrectomy (SG). METHODS/STUDY POPULATION: We examined the glucose and islet-cell secretory responses to 50 g protein ingestion with and without a potent GLP-1 receptor antagonist, exendin-(9-39) [Ex-9], in 10 GB-treated subjects, 9 SG-treated, and 7 non-operated controls (CN). The groups were matched for age, BMI, fat-free mass, fasting glucose and insulin, and HbA1c. The surgical groups also were matched for weight loss and time post-surgery. No subjects had diabetes. RESULTS/ANTICIPATED RESULTS: Protein ingestion resulted in an early rise in glycemia (AUCGlucose1hr) in GB and SG, whereas CN had minimal change in glucose (p<0.05). Protein ingestion enhanced C-peptide responses in all groups, but to a larger extent in GB and SG when compared to CN (p<0.05). Early glucagon response to protein ingestion (AUCGlucagon1hr) tended to be larger in GB and SG subjects when compared to CN (p=0.07). Ex-9 increased premeal and prandial glycemia in all groups (p<0.05), but increase in early glycemia (AUCGlucose1hr) was most notable in GB (p=0.1, interaction). This glycemic effect of Ex-9 was associated with a ~25% reduction in prandial C-peptide secretion in GB and SG and ~8% increase in CN (p<0.05, interaction). Early prandial glucagon responses were larger during studies with Ex-9 compared to those without (p<0.05). DISCUSSION/SIGNIFICANCE: Our findings indicate that glucose metabolism after protein ingestion is altered after GB and SG. To our knowledge, this is the first report to demonstrate that endogenous GLP-1 contributes to glucose and islet-cell secretory response to protein ingestion, and that GB and SG exaggerate GLP-1 contribution to insulin secretion after protein ingestion.

Semaglutide: Heart of the Matter (SUSTAIN-6 and PIONEER-6)

T2 diabetes has long been recognised as a major and exponentially growing global public health concern. Asia is no exception. Cardiovascular adverse events remain the leading cause of morbidity and mortality in T2 diabetics. There is an urgent need for effective therapies to improve cardiovascular outcomes and glucagon-like peptide-1 receptor agonists. Semaglutide is a potent glucagon-like peptide-1 analogue with the exclusive advantage of being available in both subcutaneous and oral formulations. The cardiovascular safety of each of these formulations was assessed in the SUSTAIN-6 and PIONEER-6 trials and the observed benefits has led to the approval of both the subcutaneous and oral formulations as an adjunct to diet and lifestyle measures in high-risk patients with Type 2 diabetes.

Expression and Characterization of a Potent Long-Acting GLP-1 Receptor Like Agonist, Exendin-4-Fc

Human GLP-1 (glucagon-like peptide-1) can produce a remarkable improvement in glycemic control in patients with type 2 diabetes. However, its clinical benefits are limited by its short half-life, which is less than 2 min because of its small size and rapid enzymatic inactivation by dipeptidyl peptidase IV. We engineered Exendin-4-Fc, a 66-kDa fusion protein by linking an IgG2 Fc to Exendin-4. A stably transfected Chinese hamster ovary cell line was obtained using electroporation. Exendin-4-Fc stimulated insulin secretion in INS-1 cells in a dose- and glucose-dependent manner and increased insulin mRNA expression. The plasma half-life of Exendin-4-Fc in cynomolgus monkeys was approximately 133.92 ± 25.1 h. In the KKAy mouse model of diabetes, one intraperitoneal injection of Exendin-4-Fc (1 mg/kg) reduced blood glucose levels for 5 days. A 4-week repeat-administration study identified sustained effects on blood glucose levels. Oral glucose tolerance tests conducted at the beginning and end of this 4-week period showed that Exendin-4-Fc produced a stable glucose lowering effect. In addition, KKAy mice treated with Exendin-4-Fc showed statistically significant weight loss from day 23. In conclusion, these properties of Exendin-4-Fc demonstrated that it could be a potential long-acting GLP-1 receptor agonist for the treatment of type 2 diabetes.

The Effect of Counterions in Hydrophobic Ion Pairs on Oral Bioavailability of Exenatide.

The aim of this study was to evaluate the potential of n-octadecyl sulfate (SOS) as a counterion for hydrophobic ion pairing (HIP) with exenatide-a potent glucagon-like peptide-1 (GLP-1) analogue in the treatment of diabetes mellitus-to improve its oral bioavailability. Exenatide was ion-paired with SOS and docusate (DOC) serving as the gold standard followed by the incorporation in a self-emulsifying drug delivery system (SEDDS) comprising Capmul MCM EP, Captex 355, Kolliphor RH40, and propylene glycol at a mass ratio of 41:15:40:4. The hydrophobicity of exenatide-SOS and exenatide-DOC was characterized by determining the butanol-water partition coefficient (log Pbutanol/water). Droplet size and zeta potential of the ion pair-loaded SEDDS were characterized followed by intestinal membrane permeability determination on freshly excised rat intestines compared to exenatide solution. Furthermore, the oral bioavailability of exenatide-SOS- and exenatide-DOC-loaded SEDDS was also evaluated in vivo in healthy male Sprague-Dawley rats. Hydrophobic ion pairing increased the log Pbutanol/water of exenatide from -1.9 to 2.0 for exenatide-SOS and to 1.2 for exenatide-DOC. SEDDSs loaded with 0.26% (m/m) exenatide-SOS and 0.17% (m/m) exenatide-DOC had mean droplet size less than 30 nm and negative zeta potential. Ex vivo permeation experiments revealed 3.5-fold and 6.4-fold improvement in membrane permeability of the exenatide-SOS-loaded SEDDS vs. the exenatide-DOC-loaded SEDDS and exenatide solution, respectively. The orally administered exenatide-SOS-loaded SEDDS and exenatide-DOC-loaded SEDDS resulted in relative oral bioavailability vs. subcutaneous injection (SC) of 19.6 and 15.2%, respectively. Within this study, the key role of counterions for oral peptide delivery via HIP could be confirmed, and SOS was identified as a promising surfactant for this purpose.

The role of GIP and pancreatic GLP-1 in the glucoregulatory effect of DPP-4 inhibition in mice.

Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are two peptides that function to promote insulin secretion. Dipeptidyl peptidase-4 (DPP-4) inhibitors increase the bioavailability of both GLP-1 and GIP but the dogma continues to be that it is the increase in GLP-1 that contributes to the improved glucose homeostasis. We have previously demonstrated that pancreatic rather than intestinal GLP-1 is necessary for improvements in glucose homeostasis in mice. Therefore, we hypothesise that a combination of pancreatic GLP-1 and GIP is necessary for the full effect of DPP-4 inhibitors on glucose homeostasis. We have genetically engineered mouse lines in which the preproglucagon gene (Gcg) is absent in the entire body (GcgRAΔNull) or is expressed exclusively in the intestine (GcgRAΔVilCre) or pancreas and duodenum (GcgRAΔPDX1Cre). These mice were used to examine oral glucose tolerance and GLP-1 and GIP responses to a DPP-4 inhibitor alone, or in combination with incretin receptor antagonists. Administration of the DPP-4 inhibitor, linagliptin, improved glucose tolerance in GcgRAΔNull mice and control littermates and in GcgRAΔVilCre and GcgRAΔPDX1Cre mice. The potent GLP-1 receptor antagonist, exendin-[9-39] (Ex9), blunted improvements in glucose tolerance in linagliptin-treated control mice and in GcgRAΔPDX1Cre mice. Ex9 had no effect on glucose tolerance in linagliptin-treated GcgRAΔNull or in GcgRAΔVilCre mice. In addition to GLP-1, linagliptin also increased postprandial plasma levels of GIP to a similar degree in all genotypes. When linagliptin was co-administered with a GIP-antagonising antibody, the impact of linagliptin was partially blunted in wild-type mice and was fully blocked in GcgRAΔNull mice. Taken together, these data suggest that increases in pancreatic GLP-1 and GIP are necessary for the full effect of DPP-4 inhibitors on glucose tolerance.

Exendin-4 enhances proliferation of senescent osteoblasts through activation of the IGF-1/IGF-1R signaling pathway

A growing body of evidence indicates that treatment with glucagon-like peptide-1 (GLP-1) receptor agonists can be beneficial for patients with osteoporosis. However, the underlying mechanism by which GLP-1 receptor agonists improve osteoporosis remains unclear. In this study, we assessed the anti-osteoporosis effects of Exendin-4, a highly potent GLP-1 receptor agonist, using a rat senescent osteoblast model. We found that Exendin-4 improved proliferation of senescent osteoblasts, as indicated by MTT assay and ALP activity detection. RT-qPCR revealed that Exendin-4 up-regulated the expression of bone metabolism genes (OPG, RANKL, BGP) and down-regulated the expression of aging-related genes (p16, p21, p53). Meanwhile, we observed a sustained increase in IGF-1 receptor (IGF-1R) expression, and not GLP-1 receptor (GLP-1R) expression, in senescent osteoblasts treated with Exendin-4. Furthermore, intervention with Exendin-4 in senescent osteoblasts increased IGF-1, p-PI3K, and p-Akt protein levels, as shown by western blot analysis. Finally, downregulation of IGF-1 by RNAi inhibited the anti-osteoporosis effects of Exendin-4, which is associated with the IGF-1/PI3K/Akt signaling pathway. In summary, these results indicate that the GLP-1 receptor agonist Exendin-4 promotes proliferation of senescent osteoblasts by up-regulating IGF-1R expression and activating the IGF-1/PI3K/Akt signaling pathway, thereby preventing senile osteoporosis.

GLP-1 Secretion Is Increased upon Blockade of the Somatostatin Receptor Subtype 2 and 5 Resulting in GLP-1 Receptor-Mediated Lowering of Blood Glucose in Mice

Somatostatin (SS) is a hormone inhibiting the secretion of the incretin hormone, glucagon-like peptide-1 (GLP-1) by binding to 5 SS receptors (SSTr). However, which SSTrs involved is still unclear. We hypothesized that antagonizing the SSTrs on enteroendocrine L-cells may increase secretion of GLP-1 and via GLP-1 receptor mediated mechanism lead to lowering of blood glucose. To investigate the level of the SSTrs we did expression analysis on L-cells isolated from throughout the murine intestine (n=3). We perfused the proximal small intestine from mice (n=6-7) to investigate the impact of SSTr2 and 5 on GLP-1 secretion using intra-arterial administration of specific antagonists. Lastly we performed oral glucose tolerance tests (OGTT) on mice (n=5-8) after giving 1mg/ml SSTr2 or 5 antagonist with and without the GLP-1 receptor antagonist exendin(9-39) to investigate the role of these receptors on the glucose profile and to elucidate if their effect was mediated via GLP-1. The expression levels of the SSTrs showed that SSTr2 and especially 5 had the highest expression on L-cells throughout the intestine. The SSTr2 antagonist resulted in a increase in GLP-1 secretion from the perfused intestine (100nM, 4.96pM±0.56; 1µM, 14.55pM±1.4; 10µM, 16.46pM±1.18pM; all p<0.0001). The same doses of SSTr5 antagonist gave a more potent GLP-1 secretion in this setup (100nM, 5.82pM±0.7 p=0.0004; 1µM, 19.79pM±1.2 p<0.0001; 10µM, 48pM±2.6 p<0.0001). Both SSTr2 and SSTr5 antagonists significantly reduced the blood glucose during an OGTT compared to the control (p=0.00and p=0.0072 respectively). This reduction in blood glucose was significantly increased when adding exendin(9-39) together with either the SSTr2 or 5 antagonist (p<0.0001 for SSTr2, p=0.0036 for SSTr5). Our results demonstrate that inhibiting the SSTr2 and SSTr5 increases GLP-1 secretion which in turn may cause the lowering in blood glucose during an OGTT. Disclosure S.L. Jepsen: None. N.J. Wewer Albrechtsen: Speaker's Bureau; Self; Merck Sharp & Dohme Corp.. Other Relationship; Self; Mercodia, Alpco. J. Pedersen: None. M.S. Engelstoft: None. C.F. Deacon: Other Relationship; Self; Merck & Co., Inc., Eli Lilly and Company. Employee; Spouse/Partner; Merck Sharp & Dohme Corp.. Stock/Shareholder; Spouse/Partner; Merck & Co., Inc. J.J. Holst: Advisory Panel; Self; Novo Nordisk A/S. Board Member; Self; Zealand Pharma A/S. Speaker's Bureau; Self; Merck Sharp & Dohme Corp., AstraZeneca. Research Support; Self; Danish Diabetes Academy, Novo Nordisk Foundation. Other Relationship; Self; Antag Therapeutics. Other Relationship; Spouse/Partner; Antag Therapeutics.

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.

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

Glucagon-like Peptide 1 Conjugated to Recombinant Human Serum Albumin Variants with Modified Neonatal Fc Receptor Binding Properties. Impact on Molecular Structure and Half-Life.

Glucagon-like peptide 1 (GLP-1) is a small incretin hormone stimulated by food intake, resulting in an amplification of the insulin response. Though GLP-1 is interesting as a drug candidate for the treatment of type 2 diabetes mellitus, its short plasma half-life of <3 min limits its clinical use. A strategy for extending the half-life of GLP-1 utilizes the long half-life of human serum albumin (HSA) by combining the two via chemical conjugation or genetic fusion. HSA has a plasma half-life of around 21 days because of its interaction with the neonatal Fc receptor (FcRn) expressed in endothelial cells of blood vessels, which rescues circulating HSA from lysosomal degradation. We have conjugated GLP-1 to C34 of native sequence recombinant HSA (rHSA) and two rHSA variants, one with increased and one with decreased binding affinity for human FcRn. We have investigated the impact of conjugation on FcRn binding affinities, GLP-1 potency, and pharmacokinetics, combined with the solution structure of the rHSA variants and GLP-1-albumin conjugates. The solution structures, determined by small-angle X-ray scattering, show the GLP-1 pointing away from the surface of rHSA. Combining the solution structures with the available structural information about the FcRn and GLP-1 receptor obtained from X-ray crystallography, we can explain the observed in vitro and in vivo behavior. We conclude that the conjugation of GLP-1 to rHSA does not affect the interaction between rHSA and FcRn, while the observed decrease in the potency of GLP-1 can be explained by a steric hindrance of binding of GLP-1 to its receptor.

Design of Novel Exendin-Based Dual Glucagon-like Peptide 1 (GLP-1)/Glucagon Receptor Agonists

Dual activation of the glucagon-like peptide 1 (GLP-1) and glucagon receptor has the potential to lead to a novel therapy principle for the treatment of diabesity. Here, we report a series of novel peptides with dual activity on these receptors that were discovered by rational design. On the basis of sequence analysis and structure-based design, structural elements of glucagon were engineered into the selective GLP-1 receptor agonist exendin-4, resulting in hybrid peptides with potent dual GLP-1/glucagon receptor activity. Detailed structure-activity relationship data are shown. Further modifications with unnatural and modified amino acids resulted in novel metabolically stable peptides that demonstrated a significant dose-dependent decrease in blood glucose in chronic studies in diabetic db/db mice and reduced body weight in diet-induced obese (DIO) mice. Structural analysis by NMR spectroscopy confirmed that the peptides maintain an exendin-4-like structure with its characteristic tryptophan-cage fold motif that is responsible for favorable chemical and physical stability.

Topical Intestinal Aminoimidazole Agonists of G-Protein-Coupled Bile Acid Receptor 1 Promote Glucagon Like Peptide-1 Secretion and Improve Glucose Tolerance.

The role of the G-protein-coupled bile acid receptor TGR5 in various organs, tissues, and cell types, specifically in intestinal endocrine L-cells and brown adipose tissue, has made it a promising therapeutical target in several diseases, especially type-2 diabetes and metabolic syndrome. However, recent studies have shown deleterious on-target effects of systemic TGR5 agonists. To avoid these systemic effects while stimulating glucagon-like peptide-1 (GLP-1) secreting enteroendocrine L-cells, we have designed TGR5 agonists with low intestinal permeability. In this article, we describe their synthesis, characterization, and biological evaluation. Among them, compound 24 is a potent GLP-1 secretagogue, has low effect on gallbladder volume, and improves glucose homeostasis in a preclinical murine model of diet-induced obesity and insulin resistance, making the proof of concept of the potential of topical intestinal TGR5 agonists as therapeutic agents in type-2 diabetes.

Robust GLP-1 secretion by basic L-amino acids does not require the GPRC6A receptor.

The G protein-coupled receptor GPRC6A (GPCR, Class C, group 6, subtype A) has been proposed to be a sensor for basic L-amino acids that are hypothesized to translate ingestive behaviour to endocrine information. However, the contribution of the GPRC6A receptor to L-amino acid-induced glucagon-like peptide 1 (GLP-1) secretion is unclear. Therefore, to discover whether the GPRC6A receptor is indispensible for amino acid-induced secretion of GLP-1, we treated, with oral gavage, GPRC6A knock-out (KO) and wild-type (WT) littermate mice with GPRC6A ligands (L-arginine and L-ornithine) and assessed GLP-1 levels in circulation. We found that oral administration of both L-arginine and L-ornithine significantly increased total plasma GLP-1 levels to a similar level in GPRC6A KO and WT mice 15 minutes after gavage (both amino acids) and accumulated up to 60 minutes after gavage (L-arginine). Conversely, GLP-1 secretion at the 30- and 60-minute time points in the KO mice was attenuated and did not reach statistical significance. In summary, these data confirm that L-arginine is a potent GLP-1 secretagogue and show that the main effect occurs independently of GPRC6A. In addition, this is the first study to show that also L-ornithine powerfully elicits GLP-1 release in vivo.

Expression and Characterization of a Potent Long-Acting GLP-1 Receptor Agonist, GLP-1-IgG2σ-Fc.

Human GLP-1 (glucagon-like peptide-1) can produce a remarkable improvement in glycemic control in patients with type 2 diabetes. However, its clinical benefits are limited by its short half-life, which is less than 2 min because of its small size and rapid enzymatic inactivation by dipeptidyl peptidase IV. We engineered GLP-1-IgG2σ-Fc, a 68-kDa fusion protein linking a variant human GLP-1 (A8G/G26E/R36G) to a human IgG2σ constant heavy-chain. A stably transfected Chinese hamster ovary cell line was obtained using electroporation. Western blotting showed that the expressed protein was immunoreactive to both GLP-1 and IgG antibodies. GLP-1-IgG2σ-Fc stimulated insulin secretion from INS-1 cells in a dose- and glucose-dependent manner and increased insulin mRNA expression. The half-life of GLP-1-IgG2σ-Fc in cynomolgus monkeys was approximately 57.1 ± 4.5 h. In the KKAy mouse model of diabetes, one intraperitoneal injection of GLP-1-IgG2σ-Fc (1 mg/kg) reduced blood glucose levels for 5 days. A 4-week repeat-administration study identified sustained effects on blood glucose levels. Oral glucose tolerance tests conducted at the beginning and end of this 4-week period showed that GLP-1-IgG2σ-Fc produced a stable glucose lowering effect. In addition, KKAy mice treated with GLP-1-IgG2σ-Fc showed statistically significant weight loss from day 23. In conclusion, these properties of GLP-1-IgG2σ-Fc demonstrated that it represented a potential long-acting GLP-1 receptor agonist for the treatment of type 2 diabetes.