Native Oxyntomodulin Has Significant Glucoregulatory Effects Independent of Weight Loss in Obese Humans With and Without Type 2 Diabetes

Quantification of glucagon and oxyntomodulin by protein precipitation-immunoaffinity enrichment-LC-MS/MS

Introduction

Glucagon and oxyntomodulin are peptide hormones differentially released from proglucagon that function in regulating blood glucose. Their overlapping amino acid sequences make the development of specific immunoassays difficult, but the specificity of liquid chromatography-tandem mass spectrometry can be used to distinguish the peptides. We aimed to develop a sensitive and specific mass spectrometric assay that uses non-proprietary reagents and normal-flow liquid chromatography in the simultaneous quantification of both analytes.

Methods

Bulk plasma proteins were precipitated in ethanol/ammonium hydroxide. Analytes were enriched using monoclonal antibodies generated in-house and analyzed using liquid chromatography-tandem mass spectrometry. A glucagon calibration material was sourced commercially and characterized for purity and concentration by high-performance liquid chromatography-ultraviolet detection and amino acid analysis. Single-point calibration was used to minimize between-day variability.

Results

The novel antibodies performed acceptably (peptide recovery 45-59 %). The assay was precise (<13 %CV) and linear over the range of 1.3-14.7 pM and 1.1-13.7 pM for glucagon and oxyntomodulin, respectively. The glucagon calibration material concentration was determined to be 1.596 mg/g. Tube-type studies supported the use of protease inhibitor tubes at the time of blood draw. Patients with type 1 diabetes had lower concentrations of glucagon when maintained on an insulin pump, but not with injectable insulin.

Conclusion

We have validated a method with a highly detailed standard operating procedure. We have characterized calibration materials to help maintain accuracy and achieve between-day and between-laboratory harmonization. The assay will be beneficial in better understanding α-cell health and glycemic control in diabetes and other diseases.

The role of gut-islet axis in pancreatic islet function and glucose homeostasis

The gastrointestinal tract plays a vital role in the occurrence and treatment of metabolic diseases. Recent studies have convincingly demonstrated a bidirectional axis of communication between the gut and islets, enabling the gut to influence glucose metabolism and energy homeostasis in animals strongly. The 'gut-islet axis' is an essential endocrine signal axis that regulates islet function through the dialogue between intestinal microecology and endocrine metabolism. The discovery of glucagon-like peptide-1 (GLP-1), gastric inhibitory peptide (GIP) and other gut hormones has initially set up a bridge between gut and islet cells. However, the influence of other factors remains largely unknown, such as the homeostasis of the gut microbiota and the integrity of the gut barrier. Although gut microbiota primarily resides and affect intestinal function, they also affect extra-intestinal organs by absorbing and transferring metabolites derived from microorganisms. As a result of this transfer, islets may be continuously exposed to gut-derived metabolites and components. Changes in the composition of gut microbiota can damage the intestinal barrier function to varying degrees, resulting in increased intestinal permeability to bacteria and their derivatives. All these changes contribute to the severe disturbance of critical metabolic pathways in peripheral tissues and organs. In this review, we have outlined the different gut-islet axis signalling mechanisms associated with metabolism and summarized the latest progress in the complex signalling molecules of the gut and gut microbiota. In addition, we will discuss the impact of the gut renin-angiotensin system (RAS) on the various components of the gut-islet axis that regulate energy and glucose homeostasis. This work also indicates that therapeutic approaches aiming to restore gut microbial homeostasis, such as probiotics and faecal microbiota transplantation (FMT), have shown great potential in improving treatment outcomes, enhancing patient prognosis and slowing down disease progression. Future research should further uncover the molecular links between the gut-islet axis and the gut microbiota and explore individualized microbial treatment strategies, which will provide an innovative perspective and approach for the diagnosis and treatment of metabolic diseases.

GLP-1-based therapies for type 2 diabetes: from single, dual and triple agonists to endogenous GLP-1 production and L-cell differentiation

Glucagon-like peptide-1 (GLP-1) is an incretin peptide hormone mainly secreted by enteroendocrine intestinal L-cells. GLP-1 is also secreted by α-cells of the pancreas and the central nervous system (CNS). GLP-1 secretion is stimulated by nutrient intake and exerts its effects on glucose homeostasis by stimulating insulin secretion, gastric emptying confiding the food intake, and β-cell proliferation. The insulinotropic effects of GLP-1, and the reduction of its effects in type 2 diabetes mellitus (T2DM), have made GLP-1 an attractive option for the treatment of T2DM. Furthermore, GLP-1-based medications such as GLP-1 receptor agonists and dipeptidyl peptidase-4 inhibitors, have been shown to improve diabetes control in preclinical and clinical trials with human subjects. Importantly, increasing the endogenous production of GLP-1 by different mechanisms or by increasing the number of intestinal L-cells that tend to produce this hormone may be another effective therapeutic approach to managing T2DM. Herein, we briefly describe therapeutic agents/compounds that enhance GLP-1 function. Then, we will discuss the approaches that can increase the endogenous production of GLP-1 through various stimuli. Finally, we introduce the potential of L-cell differentiation as an attractive future therapeutic approach to increase GLP-1 production as an attractive therapeutic alternative for T2DM.

Incretin hormones and obesity

The incretin hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) play critical roles in co-ordinating postprandial metabolism, including modulation of insulin secretion and food intake. They are secreted from enteroendocrine cells in the intestinal epithelium following food ingestion, and act at multiple target sites including pancreatic islets and the brain. With the recent development of agonists targeting GLP-1 and GIP receptors for the treatment of type 2 diabetes and obesity, and the ongoing development of new incretin-based drugs with improved efficacy, there is great interest in understanding the physiology and pharmacology of these hormones.

Principles and Biomedical Applications of Self-Assembled Peptides: Potential Treatment of Type 2 Diabetes Mellitus

Type 2 diabetes mellitus (T2DM) is the most prevalent metabolic disorder worldwide. There have been tremendous efforts to find a safe and prolonged effective therapy for its treatment. Peptide hormones, from certain organisms in the human body, as the pharmaceutical agents, have shown outstanding profiles of efficacy and safety in plasma glucose regulation. Their therapeutic promises have undergone intensive investigations via examining their physicochemical and pharmacokinetic properties. Their major drawback is their short half-life in vivo. To address this challenge, researchers have recently started to apply the state-of-the-art molecular self-assembly on peptide hormones to form nanofibrillar structures, as a smart nanotherapeutic drug delivery technique, to tremendously enhance their prolonged bioactivity in vivo. This revolutionary therapeutic approach would significantly improve patient compliance. First, this review provides a comprehensive summary on the pathophysiology of T2DM, various efforts to treat this chronic disorder, and the limitations and drawbacks of these treatment approaches. Next, this review lays out detailed insights on various aspects of peptide self-assembly: adverse effects, potential applications in nanobiotechnology, thermodynamics and kinetics of the process, as well as the molecular structures of the self-assembled configurations. Furthermore, this review elucidates the recent efforts on applying reversible human-derived peptide self-assembly to generate highly organized smart nanostructured drug formulations known as nanofibrils to regulate and prolong the bioactivity of the human gut hormone peptides in vivo to treat T2DM. Finally, this review highlights the future research directions to advance the knowledge on the state-of-the-art peptide self-assembly process to apply the revolutionary smart nanotherapeutics for treatment of chronic disorders such as T2DM with highly improved patient compliance.

Incretin and glucagon receptor polypharmacology in chronic kidney disease

Chronic kidney disease is a debilitating condition associated with significant morbidity and mortality. In recent years, the kidney effects of incretin-based therapies, particularly glucagon-like peptide-1 receptor agonists (GLP-1RAs), have garnered substantial interest in the management of type 2 diabetes and obesity. This review delves into the intricate interactions between the kidney, GLP-1RAs, and glucagon, shedding light on their mechanisms of action and potential kidney benefits. Both GLP-1 and glucagon, known for their opposing roles in regulating glucose homeostasis, improve systemic risk factors affecting the kidney, including adiposity, inflammation, oxidative stress, and endothelial function. Additionally, these hormones and their pharmaceutical mimetics may have a direct impact on the kidney. Clinical studies have provided evidence that incretins, including those incorporating glucagon receptor agonism, are likely to exhibit improved kidney outcomes. Although further research is necessary, receptor polypharmacology holds promise for preserving kidney function through eliciting vasodilatory effects, influencing volume and electrolyte handling, and improving systemic risk factors.

OXM-104, a potential candidate for the treatment of obesity, NASH and type 2 diabetes

OBJECTIVE

Dual glucagon-like peptide-1 (GLP-1) and glucagon receptor agonists are therapeutic agents with an interesting liver-specific mode of action suitable for metabolic complications. In this study, dual GLP-1 and glucagon receptor agonist OXM-104 is compared head-to-head with the once-daily dual GLP-1 and glucagon receptor agonist cotadutide and GLP-1 receptor agonist semaglutide to explore the metabolic efficacy of OXM-104.

METHODS

The in vitro potencies of OXM-104, cotadutide and semaglutide were assessed using reporter assays. In addition, in vivo efficacy was investigated using mouse models of diet-induced obesity (DIO mice), diabetes (db/db mice) and diet-induced NASH mice (MS-NASH).

RESULTS

OXM-104 was found to only activate the GLP-1 and glucagon with no cross-reactivity at the (GIP) receptor. Cotadutide was also found to activate the GLP-1 and glucagon receptors, whereas semaglutide only showed activity at the GLP-1 receptor. OXM-104, cotadutide, and semaglutide elicited marked reductions in body weight and improved glucose control. In contrast, hepatoprotective effects, i.e., reductions in steatosis and fibrosis, as well as liver fibrotic biomarkers, were more prominent with OXM-104 and cotadutide than those seen with semaglutide, demonstrated by an improved NAFLD activity score (NAS) by OXM-104 and cotadutide, underlining the importance of the glucagon receptor.

CONCLUSION

These results show that dual GLP-1 and glucagon receptor agonism is superior to GLP-1 alone. OXM-104 was found to be a promising therapeutic candidate for the treatment of metabolic complications such as obesity, type 2 diabetes and NASH.

Self-assembled GLP-1/glucagon peptide nanofibrils prolong inhibition of food intake

Introduction

Oxyntomodulin (Oxm) hormone peptide has a number of beneficial effects on nutrition and metabolism including increased energy expenditure and reduced body weight gain. Despite its many advantages as a potential therapeutic agent, Oxm is subjected to rapid renal clearance and protease degradation limiting its clinical application. Previously, we have shown that subcutaneous administration of a fibrillar Oxm formulation can significantly prolong its bioactivity in vivo from a few hours to a few days.

Methods

We used a protease resistant analogue of Oxm, Aib2-Oxm, to form nanfibrils depot and improve serum stability of released peptide. The nanofibrils and monomeric peptide in solution were characterized by spectroscopic, microscopic techniques, potency assay, QCM-D and in vivo studies.

Results

We show that in comparison to Oxm, Aib2-Oxm fibrils display a slower elongation rate requiring higher ionic strength solutions, and a higher propensity to dissociate. Upon subcutaneous administration of fibrillar Aib2-Oxm in rodents, a 5-fold increase in bioactivity relative to fibrillar Oxm and a significantly longer bioactivity than free Aib2-Oxm were characterized. Importantly, a decrease in food intake was observed up to 72-hour post-administration, which was not seen for free Aib2-Oxm.

Conclusion

Our findings provides compelling evidence for the development of long-lasting peptide fibrillar formulations that yield extended plasma exposure and enhanced in vivo pharmacological response.

Diabetes of the Exocrine Pancreas: Implications for Pharmacological Management

Post-pancreatitis diabetes mellitus, pancreatic cancer-related diabetes, and cystic fibrosis-related diabetes are often underappreciated. As a result, a substantial proportion of people with these sub-types of diabetes receive antidiabetic medications that may be suboptimal, if not harmful, in the context of their underlying disease of the exocrine pancreas. The present article delineates both classical (biguanides, insulin, sulfonylureas, α-glucosidase inhibitors, thiazolidinediones, and meglitinides) and newer (glucagon-like peptide-1 receptor agonists, amylin analogs, dipeptidyl peptidase-4 inhibitors, sodium-glucose co-transporter-2 inhibitors, D2 receptor agonists, bile acid sequestrants, and dual glucagon-like peptide-1 receptor and glucose-dependent insulinotropic polypeptide receptor co-agonists) therapies and provides recommendations for managing people with diabetes of the exocrine pancreas based on the most up-to-date clinical evidence. Also, several emerging directions (lipid-enriched pathways, Y4 receptor agonism, glucagon-like peptide-1 and glucagon receptor co-agonism) are presented with a view to informing the process of new drug discovery and development.

State of art on the mechanisms of laparoscopic sleeve gastrectomy in treating type 2 diabetes mellitus

Obesity and type-2 diabetes mellitus (T2DM) are metabolic disorders. Obesity increases the risk of T2DM, and as obesity is becoming increasingly common, more individuals suffer from T2DM, which poses a considerable burden on health systems. Traditionally, pharmaceutical therapy together with lifestyle changes is used to treat obesity and T2DM to decrease the incidence of comorbidities and all-cause mortality and to increase life expectancy. Bariatric surgery is increasingly replacing other forms of treatment of morbid obesity, especially in patients with refractory obesity, owing to its many benefits including good long-term outcomes and almost no weight regain. The bariatric surgery options have markedly changed recently, and laparoscopic sleeve gastrectomy (LSG) is gradually gaining popularity. LSG has become an effective and safe treatment for type-2 diabetes and morbid obesity, with a high cost-benefit ratio. Here, we review the me-chanism associated with LSG treatment of T2DM, and we discuss clinical studies and animal experiments with regard to gastrointestinal hormones, gut microbiota, bile acids, and adipokines to clarify current treatment modalities for patients with obesity and T2DM.

Metabolic effects of truncal vagotomy when combined with bariatric-metabolic surgery

Bariatric-metabolic surgery (BMS) in patients with obesity frequently leads to remission of concurrent type 2 diabetes mellitus (T2DM), even before body weight loss takes place. This is probably based on the correction of a dysmetabolic cycle in the gastrointestinal physiology of T2DM that includes increased vagus-dependent exocrine pancreatic secretion (EPS) and, hence, amplified digestion and nutrient absorption. The resultant chronic exposure of tissues to high plasma levels of glucose, fatty acids and amino acids causes tissue resistance to the actions of insulin and, at a later stage, β-cell dysfunction and reduction of insulin release. We hypothesize that the addition of a surgical truncal vagotomy (TV) may improve and solidify the beneficial results of BMS on T2DM by stably decreasing EPS, - hence reducing the digestion and absorption of nutrients -, and increasing incretin secretion as a result of increased delivery of unabsorbed nutrients to the distal intestine. This hypothesis is supported by surgical data from gastrointestinal malignancies and peptic ulcer operations that include TV, as well as by vagal blockade studies. We suggest that TV may result in a stable reduction of EPS, and that its combination with the appropriate type of BΜS, may enhance and sustain the salutary effects of the latter on T2DM.

Targeted therapeutics and novel signaling pathways in non-alcohol-associated fatty liver/steatohepatitis (NAFL/NASH)

Non-alcohol-associated fatty liver/steatohepatitis (NAFL/NASH) has become the leading cause of liver disease worldwide. NASH, an advanced form of NAFL, can be progressive and more susceptible to developing cirrhosis and hepatocellular carcinoma. Currently, lifestyle interventions are the most essential and effective strategies for preventing and controlling NAFL without the development of fibrosis. While there are still limited appropriate drugs specifically to treat NAFL/NASH, growing progress is being seen in elucidating the pathogenesis and identifying therapeutic targets. In this review, we discussed recent developments in etiology and prospective therapeutic targets, as well as pharmacological candidates in pre/clinical trials and patents, with a focus on diabetes, hepatic lipid metabolism, inflammation, and fibrosis. Importantly, growing evidence elucidates that the disruption of the gut-liver axis and microbe-derived metabolites drive the pathogenesis of NAFL/NASH. Extracellular vesicles (EVs) act as a signaling mediator, resulting in lipid accumulation, macrophage and hepatic stellate cell activation, further promoting inflammation and liver fibrosis progression during the development of NAFL/NASH. Targeting gut microbiota or EVs may serve as new strategies for the treatment of NAFL/NASH. Finally, other mechanisms, such as cell therapy and genetic approaches, also have enormous therapeutic potential. Incorporating drugs with different mechanisms and personalized medicine may improve the efficacy to better benefit patients with NAFL/NASH.

The Enteroendocrine System in Obesity

The enteroendocrine system coordinates the physiological response to food intake by regulating rates of digestion, nutrient absorption, insulin secretion, satiation and satiety. Gut hormones with important anorexigenic and/or insulinotropic roles include glucagon-like peptide 1 (GLP-1), peptide YY (PYY_3-36), cholecystokinin (CCK) and glucose-dependent insulinotropic peptide (GIP). High BMI or obesogenic diets do not markedly disrupt this enteroendocrine system, which represents a critical target for inducing weight loss and treating co-morbidities in individuals with obesity.

Obesity-An Update on the Basic Pathophysiology and Review of Recent Therapeutic Advances

Obesity represents a major public health problem with a prevalence increasing at an alarming rate worldwide. Continuous intensive efforts to elucidate the complex pathophysiology and improve clinical management have led to a better understanding of biomolecules like gut hormones, antagonists of orexigenic signals, stimulants of fat utilization, and/or inhibitors of fat absorption. In this article, we will review the pathophysiology and pharmacotherapy of obesity including intersection points to the new generation of antidiabetic drugs. We provide insight into the effectiveness of currently approved anti-obesity drugs and other therapeutic avenues that can be explored.

Oral Semaglutide, the First Ingestible Glucagon-Like Peptide-1 Receptor Agonist: Could It Be a Magic Bullet for Type 2 Diabetes?

The gastrointestinal tract secretes gut hormones in response to food consumption, and some of these stimulate insulin secretion. Glucagon-like peptide-1 (GLP-1) is an incretin peptide hormone released from the lower digestive tract that stimulates insulin secretion, suppresses glucagon secretion, and decreases hunger. GLP-1 receptor agonist (GLP-1RA) mimics the action of endogenous GLP-1, consequently reversing hyperglycemia and causing weight reduction, demonstrating its efficacy as an antidiabetic and antiobesity agent. Previously restricted to injection only, the invention of the absorption enhancer sodium N-(8-[2-hydroxybenzoyl]amino) caprylate resulted in the development of oral semaglutide, the first ingestible GLP-1RA. Oral semaglutide demonstrated its efficacy in glycemic management and body weight loss with a low risk of hypoglycemia as a monotherapy and in combination with other hypoglycemic medications in its clinical trial programs named Peptide Innovation for Early Diabetes Treatment. Consistent with other injectable GLP-1RAs, gastrointestinal side effects were often reported. Additionally, cardiovascular safety was established by demonstrating that oral semaglutide was not inferior to a placebo in terms of cardiovascular outcomes. Thus, oral semaglutide represents a novel treatment option that is particularly well-suited for patients with type 2 diabetes and/or obesity.

New Incretin Combination Treatments under Investigation in Obesity and Metabolism: A Systematic Review

The worldwide upward trend in obesity in adults and the increased incidence of overweight children suggests that the future risk of obesity-related illnesses will be increased. The existing anti-obesity drugs act either in the central nervous system (CNS) or in the peripheral tissues, controlling the appetite and metabolism. However, weight regain is a common homeostatic response; current anti-obesity medications show limited effectiveness in achieving long-term weight loss maintenance; in addition to being linked to various side effects. Combined anti-obesity medications (per os or injectable) target more than one of the molecular pathways involved in weight regulation, as well as structures in the CNS. In this systematic review, we conducted a search of PubMed and The ClinicalTrials.gov up to February 2021. We summarized the Food and Drug Administration (FDA)-approved medications, and we focused on the combined pharmacological treatments, related to the incretin hormones, currently in a clinical trial phase. We also assessed the mechanism of action and therapeutic utility of these novel hybrid peptides and potential interactions with other regulatory hormones that may have beneficial effects on obesity. As we improve our understanding of the pathophysiology of obesity, we hope to identify more novel treatment strategies.

Conjugation of a peptide to an antibody engineered with free cysteines dramatically improves half-life and activity

The long circulating half-life and inherently bivalent architecture of IgGs provide an ideal vehicle for presenting otherwise short-lived G-protein-coupled receptor agonists in a format that enables avidity-driven enhancement of potency. Here, we describe the site-specific conjugation of a dual agonist peptide (an oxyntomodulin variant engineered for potency and in vivo stability) to the complementarity-determining regions (CDRs) of an immunologically silent IgG4. A cysteine-containing heavy chain CDR3 variant was identified that provided clean conjugation to a bromoacetylated peptide without interference from any of the endogenous mAb cysteine residues. The resulting mAb-peptide homodimer has high potency at both target receptors (glucagon receptor, GCGR, and glucagon-like peptide 1 receptor, GLP-1R) driven by an increase in receptor avidity provided by the spatially defined presentation of the peptides. Interestingly, the avidity effects are different at the two target receptors. A single dose of the long-acting peptide conjugate robustly inhibited food intake and decreased body weight in insulin resistant diet-induced obese mice, in addition to ameliorating glucose intolerance. Inhibition of food intake and decrease in body weight was also seen in overweight cynomolgus monkeys. The weight loss resulting from dosing with the bivalently conjugated dual agonist was significantly greater than for the monomeric analog, clearly demonstrating translation of the measured in vitro avidity to in vivo pharmacology.

New Aspects of Diabetes Research and Therapeutic Development

Both type 1 and type 2 diabetes mellitus are advancing at exponential rates, placing significant burdens on health care networks worldwide. Although traditional pharmacologic therapies such as insulin and oral antidiabetic stalwarts like metformin and the sulfonylureas continue to be used, newer drugs are now on the market targeting novel blood glucose-lowering pathways. Furthermore, exciting new developments in the understanding of beta cell and islet biology are driving the potential for treatments targeting incretin action, islet transplantation with new methods for immunologic protection, and the generation of functional beta cells from stem cells. Here we discuss the mechanistic details underlying past, present, and future diabetes therapies and evaluate their potential to treat and possibly reverse type 1 and 2 diabetes in humans. SIGNIFICANCE STATEMENT: Diabetes mellitus has reached epidemic proportions in the developed and developing world alike. As the last several years have seen many new developments in the field, a new and up to date review of these advances and their careful evaluation will help both clinical and research diabetologists to better understand where the field is currently heading.

Novel therapies with precision mechanisms for type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is one of the greatest health crises of our time and its prevalence is projected to increase by >50% globally by 2045. Currently, 10 classes of drugs are approved by the US Food and Drug Administration for the treatment of T2DM. Drugs in development for T2DM must show meaningful reductions in glycaemic parameters as well as cardiovascular safety. Results from an increasing number of cardiovascular outcome trials using modern T2DM therapeutics have shown a reduced risk of atherosclerotic cardiovascular disease, congestive heart failure and chronic kidney disease. Hence, guidelines have become increasingly evidence based and more patient centred, focusing on reaching individualized glycaemic goals while optimizing safety, non-glycaemic benefits and the prevention of complications. The bar has been raised for novel therapies under development for T2DM as they are now expected to achieve these aims and possibly even treat concurrent comorbidities. Indeed, the pharmaceutical pipeline for T2DM is fertile. Drugs that augment insulin sensitivity, stimulate insulin secretion or the incretin axis, or suppress hepatic glucose production are active in more than 7,000 global trials using new mechanisms of action. Our collective goal of being able to truly personalize medicine for T2DM has never been closer at hand.

Post-pancreatitis diabetes mellitus: investigational drugs in preclinical and clinical development and therapeutic implications

Introduction: Post-pancreatitis diabetes mellitus is one of the most common types of secondary diabetes. The pharmaceutical armamentarium in the field of diabetology can be broadened if the design of novel drugs is informed by pathogenetic insights from studies on post-pancreatitis diabetes mellitus.Areas covered: The article provides an overview of preclinical and clinical studies of compounds selectively antagonizing the gastric inhibitory peptide receptor, simultaneously stimulating both the glucagon-like peptide-1 and glucagon receptors, and activating ketogenesis.Expert opinion: The current pharmacotherapy for post-pancreatitis diabetes mellitus is relatively ineffective. This type of diabetes represents a unique platform for rigorous, efficient, and practical search for glucose-lowering therapeutic candidates. Various methods of gastric inhibitory peptide receptor (expressed in the pancreas) antagonism have undergone extensive preclinical testing in diabetes, with promising compounds being trialed in man. Molecular mimicry with oxyntomodulin ─ an extra-pancreatic hormone homologous with pancreatic hormone glucagon and involved in the regulation of exocrine pancreatic function ─ could be harnessed. The emerging findings of a salutary effect of ketosis mimetics in people with prediabetes set the stage for a novel approach to preventing diabetes.

Oxyntomodulin May Distinguish New-Onset Diabetes After Acute Pancreatitis From Type 2 Diabetes

OBJECTIVE

New-onset diabetes is an important sequela of acute pancreatitis, but there are no biomarkers to differentiate it from the much more common type 2 diabetes. The objective was to investigate whether postprandial circulating levels of gut hormones can serve this purpose.

METHODS

This was a case-control study nested into a prospective longitudinal cohort study that included 42 insulin-naive cases with new-onset prediabetes/diabetes after acute pancreatitis (NODAP) and prediabetes/diabetes followed by acute pancreatitis (T2D-AP), sex matched with 21 healthy controls. All individuals underwent a standardized mixed-meal test, and blood samples were assayed for gut hormones (glucose-dependent insulinotropic peptide, glucagon-like peptide-1, oxyntomodulin, and peptide YY). Analysis of variance and linear regression analysis were conducted in unadjusted and adjusted models (accounting for age, homeostatic model assessment of β-cell function, and magnetic resonance imaging-derived body fat composition).

RESULTS

Oxyntomodulin levels were significantly lower in NODAP compared with T2D-AP and healthy controls (P = 0.027 and P = 0.001, respectively, in the most adjusted model). Glucagon-like peptide-1 and peptide YY were significantly lower in NODAP compared with T2D-AP (P = 0.001 and P = 0.014, respectively, in the most adjusted model) but not compared with healthy controls (P = 1.000 and P = 0.265, respectively, in the most adjusted model). Glucose-dependent insulinotropic peptide levels were not significantly different between NODAP and T2D-AP.

DISCUSSION

Oxyntomodulin is a promising biomarker to guide the differential diagnosis of new-onset diabetes after acute pancreatitis. However, external validation studies are warranted before it can be recommended for routine use in clinical practice.

Thermo-Responsive self-assembly of a dual glucagon-like peptide and glucagon receptor agonist

The human peptide hormone Oxyntomodulin (Oxm) is known to induce satiety, increase energy expenditure, and control blood glucose in humans, making it a promising candidate for treatment of obesity and/or type 2 diabetes mellitus. However, a pharmaceutical exploitation has thus far been impeded by fast in vivo clearance and the molecule's sensitivity to half-life extending structural modifications. We recently showed that Oxm self-assembles into amyloid-like nanofibrils that continuously release active, soluble Oxm in a peptide-deprived environment. S.c. injected Oxm nanofibrils extended plasma exposure from a few hours to five days in rodents, compared to s.c. applied soluble Oxm. Here we show that Oxm fibril elongation kinetics and thermodynamics display a uniquely low temperature optimum compared to previously reported amyloid-like peptide and protein assemblies. Elongation rate is optimal at room temperature, with association rates 2-3 times higher at 25 °C than at ≥37 °C or ≤20 °C. We deduce from a combination of Cryo electron microscopy and spectroscopic methods that Oxm fibrils have a double-layered, triangular cross-section composed of arch-shaped monomers. We suggest a thermodynamic model that links the necessary molecular rearrangements during fibrillation and peptide release to the unique temperature effects in Oxm self-assembly and disassembly.

Neuroendocrine Peptides of the Gut and Their Role in the Regulation of Food Intake

The regulation of food intake encompasses complex interplays between the gut and the brain. Among them, the gastrointestinal tract releases different peptides that communicate the metabolic state to specific nuclei in the hindbrain and the hypothalamus. The present overview gives emphasis on seven peptides that are produced by and secreted from specialized enteroendocrine cells along the gastrointestinal tract in relation with the nutritional status. These established modulators of feeding are ghrelin and nesfatin-1 secreted from gastric X/A-like cells, cholecystokinin (CCK) secreted from duodenal I-cells, glucagon-like peptide 1 (GLP-1), oxyntomodulin, and peptide YY (PYY) secreted from intestinal L-cells and uroguanylin (UGN) released from enterochromaffin (EC) cells. © 2021 American Physiological Society. Compr Physiol 11:1679-1730, 2021.

Role of Enteroendocrine Hormones in Appetite and Glycemia

Enteroendocrine cells (EECs) are specialized cells that are widely distributed throughout the gastrointestinal tract. EECs sense luminal content and release hormones, such as: ghrelin, cholecystokinin, glucagon like peptide 1, peptide YY, insulin like peptide 5, and oxyntomodulin. These hormones can enter the circulation to act on distant targets or act locally on neighboring cells and neuronal pathways to modulate food digestion, food intake, energy balance and body weight. Obesity, insulin resistance and diabetes are associated with alterations in the levels of enteroendocrine hormones. Evidence also suggests that modified regulation and release of gut hormones are the result of compensatory mechanisms in states of excess adipose tissue and hyperglycemia. This review collects the evidence available detailing pathophysiological alterations in enteroendocrine hormones and their association with appetite, obesity and glycemic control.

Anti-diabetic effects of bioactive peptides: recent advances and clinical implications

Diabetes mellitus, particularly type 2 diabetes, is a major global health issue, the prevalence of which seems to be on the rise worldwide. Interventions such as healthy diet, physical activity, maintaining a healthy weight, and medication (for those with a diagnosis of diabetes) are among the most effective strategies to prevent and control diabetes. Three-quarters of patients diagnosed with diabetes are in countries with poor financial infrastructure, nutritional awareness and health care systems. Concomitantly, the cost involved in managing diabetes through the intake of antidiabetic drugs makes it prohibitive for majority of patients. Food protein-derived bioactive peptides have the potential of being formulated as nutraceuticals and drugs in combating the pathogenesis and pathophysiology of metabolic disorders with little or "no known" complications in humans. Coupled with lifestyle modifications, the potential of bioactive peptides to maintain normoglycemic range is actualized by influencing the activities of incretins, DPP-IV, α-amylase, and α-glucosidase enzymes. This article discusses the biofunctionality and clinical implications of anti-diabetic bioactive peptides in controlling the global burden of diabetes.

Amino acids are sensitive glucagon receptor-specific biomarkers for glucagon-like peptide-1 receptor/glucagon receptor dual agonists

AIM

The aim of this study was to evaluate amino acids as glucagon receptor (GCGR)-specific biomarkers in rodents and cynomolgus monkeys in the presence of agonism of both glucagon-like peptide-1 receptor (GLP1R) and GCGR with a variety of dual agonist compounds.

MATERIALS AND METHODS

Primary hepatocytes, rodents (normal, diet-induced obese and GLP1R knockout) and cynomolgus monkeys were treated with insulin (hepatocytes only), glucagon (hepatocytes and cynomolgus monkeys), the GLP1R agonist, dulaglutide, or a variety of dual agonists with varying GCGR potencies.

RESULTS

A long-acting dual agonist, Compound 2, significantly decreased amino acids in both wild-type and GLP1R knockout mice in the absence of changes in food intake, body weight, glucose or insulin, and increased expression of hepatic amino acid transporters. Dulaglutide, or a variant of Compound 2 lacking GCGR agonism, had no effect on amino acids. A third variant with ~31-fold less GCGR potency than Compound 2 significantly decreased amino acids, albeit to a significantly lesser extent than Compound 2. Dulaglutide (with saline infusion) had no effect on amino acids, but an infusion of glucagon dose-dependently decreased amino acids on the background of GLP1R engagement (dulaglutide) in cynomolgus monkeys, as did Compound 2.

CONCLUSIONS

These results show that amino acids are sensitive and translatable GCGR-specific biomarkers.

The GLP1R Agonist Liraglutide Reduces Hyperglucagonemia Induced by the SGLT2 Inhibitor Dapagliflozin via Somatostatin Release

The newest classes of anti-diabetic agents include sodium-glucose cotransporter 2 (SGLT2) inhibitors and glucagon-like peptide 1 receptor (GLP1R) agonists. The SGLT2 inhibitor dapagliflozin reduces glucotoxicity by glycosuria but elevates glucagon secretion. The GLP1R agonist liraglutide inhibits glucagon; therefore, we hypothesize that the cotreatment of dapagliflozin with liraglutide could reduce hyperglucagonemia and hyperglycemia. Here we use five complementary models: human islet cultures, healthy mice, db/db mice, diet-induced obese (DIO) mice, and somatostatin receptor-2 (SSTR2) KO mice. A single administration of liraglutide and dapagliflozin in combination improves glycemia and reduces dapagliflozin-induced glucagon secretion in diabetic mice. Chronic treatment with liraglutide and dapagliflozin produces a sustainable reduction of glycemia compared with each drug alone. Moreover, liraglutide reduces dapagliflozin-induced glucagon secretion by enhancing somatostatin release, as demonstrated by SSTR2 inhibition in human islets and in mice. Collectively, these data provide mechanistic insights into how intra-islet GLP1R activation is critical for the regulation of glucose homeostasis.

A novel long-acting oxyntomodulin analogue eliminates diabetes and obesity in mice

Oxyntomodulin (OXM) was identified as a glucagon (GCG) receptor (GCGR) and glucagon-like peptide 1 (GLP-1) receptor (GLP-1R) dual agonist to suppress appetite, increase energy expenditure, and induce body weight loss in obese humans. However, the activities of native OXM to activate GCGR and GLP-1R in vitro were much weaker than the natural ligands. To address this gap, structural modifications were adopted and novel OXM analogues were obtained through chimeric peptide sequence design. One specific analogue with enhanced and balanced GCGR/GLP-1R activations was chemically conjugated with polyethylene glycol (PEG) to achieve sustained release in vivo. This PEGylated analogue was further explored pharmacologically in db/db and diet-induced obese (DIO) mice models. Chronic weekly administration significantly induced hypoglycemic effects and body weight loss with dose dependency, along with normalized adiposity, lipid metabolism, and liver steatosis. Based on its profiles in vitro and in vivo, the analogue has the great potential to develop as a novel anti-diabetic and/or anti-obese candidate. As observed more insulin stimulation and improved insulin resistance, it may be also explored for the treatment of nonalcoholic steatohepatitis (NASH) in the future.

Drug Therapy in Obesity: A Review of Current and Emerging Treatments

Whilst the prevalence of obesity continues to increase at an alarming rate worldwide, the personal and economic burden of obesity-related complications becomes ever more important. Whilst dietary and lifestyle measures remain the fundamental focus of the patient to counter obesity, more frequently pharmacological and/or surgical interventions are required. Nevertheless, these therapies are often limited by weight loss efficacy, side effects, surgical risks and frequently obesity relapse. Currently, only five drug therapies are approved for the specific treatment of obesity. However, our understanding of the pathophysiology of obesity and of gut hormones has developed precipitously over the last 20-30 years. As a result, there has been a recent movement to create and use analogues that manipulate these gut hormones to support weight loss. In this article we review the efficacy of the currently approved drug therapies and discuss future potential drug mechanisms and early clinical trial results exploring these budding avenues. We discuss the use of glucagon-like peptide-1 (GLP-1) analogues as monotherapy and unimolecular dual or triple agonists that exploit the GLP-1 receptor and/or the gastric inhibitory peptide (GIP) receptor and/or the glucagon receptor. We also explore the use of sodium-glucose co-transporter-2 (SGLT-2) inhibitors, amylin mimetics, leptin analogues, ghrelin antagonists and centrally acting agents to suppress appetite [neuropeptide Y (NPY) antagonists, melanocortin-4 receptor (MC4R) agonists and cannabinoid-1 receptor antagonists]. Whilst further evidence is required to support their clinical use, preclinical and early clinical trial results are encouraging.

Gastrointestinal Peptides as Therapeutic Targets to Mitigate Obesity and Metabolic Syndrome

PURPOSE OF REVIEW

Obesity affects over than 600 million adults worldwide resulting in multi-organ complications and major socioeconomic impact. The purpose of this review is to summarise the physiological effects as well as the therapeutic implications of the gut hormones glucagon-like peptide-1 (GLP-1), oxyntomodulin, peptide YY (PYY), and glucose-dependent insulinotropic peptide (GIP) in the treatment of obesity and type 2 diabetes.

RECENT FINDINGS

Clinical trials have proven that the widely used GLP-1 analogues have pleotropic effects beyond those on weight and glucose metabolism and appear to confer favourable cardiovascular and renal outcomes. However, GLP-1 analogues alone do not deliver sufficient efficacy for the treatment of obesity, being limited by their dose-dependent gastrointestinal side effects. Novel dual agonists for GLP-1/glucagon and GLP-1/GIP are being developed by the pharmaceutical industry and have demonstrated some promising results for weight loss and improvement in glycaemia over and above GLP-1 analogues. Triagonists (for example GLP-1/GIP/glucagon) are currently in pre-clinical or early clinical development. Gastrointestinal hormones possess complementary effects on appetite, energy expenditure, and glucose metabolism. We highlight the idea that combinations of these hormones may represent the way forward in obesity and diabetes therapeutics.

Leveraging the Gut to Treat Metabolic Disease

25 years ago, the future of treating obesity and diabetes focused on end organs known to be involved in energy balance and glucose regulation, including the brain, muscle, adipose tissue, and pancreas. Today, the most effective therapies are focused around the gut. This includes surgical options, such as vertical sleeve gastrectomy and Roux-en-Y gastric bypass, that can produce sustained weight loss and diabetes remission but also extends to pharmacological treatments that simulate or amplify various signals that come from the gut. The purpose of this Review is to discuss the wealth of approaches currently under development that seek to further leverage the gut as a source of novel therapeutic opportunities with the hope that we can achieve the effects of surgical interventions with less invasive and more scalable solutions.

Efficacy, Safety, and Mechanistic Insights of Cotadutide, a Dual Receptor Glucagon-Like Peptide-1 and Glucagon Agonist

CONTEXT

Cotadutide is a dual receptor agonist with balanced glucagon-like peptide-1 and glucagon activity.

OBJECTIVE

To evaluate different doses of cotadutide and investigate underlying mechanisms for its glucose-lowering effects.

DESIGN/SETTING

Randomized, double-blind, phase 2a study conducted in 2 cohorts at 5 clinical trial sites.

PATIENTS

Participants were 65 adult overweight/obese patients with type 2 diabetes mellitus; 63 completed the study; 2 were withdrawn due to AEs.

INTERVENTION

Once-daily subcutaneous cotadutide or placebo for 49 days. Doses (50-300 µg) were uptitrated weekly (cohort 1) or biweekly (cohort 2).

MAIN OUTCOME MEASURES

Co-primary end points (cohort 1) were percentage changes from baseline to end of treatment in glucose (area under the curve from 0 to 4 hours [AUC0-4h]) post-mixed-meal tolerance test (MMTT) and weight. Exploratory measures included postprandial insulin and gastric emptying time (GET; cohort 2).

RESULTS

Patients received cotadutide (cohort 1, n = 26; cohort 2, n = 20) or placebo (cohort 1, n = 13; cohort 2, n = 6). Significant reductions were observed with cotadutide vs placebo in glucose AUC0-4h post MMTT (least squares mean [90% CI], -21.52% [-25.68, -17.37] vs 6.32% [0.45, 12.20]; P < 0.001) and body weight (-3.41% [-4.37, -2.44] vs -0.08% [-1.45, 1.28]; P = 0.002). A significant increase in insulin AUC0-4h post MMTT was observed with cotadutide (19.3 mU.h/L [5.9, 32.6]; P = 0.008) and GET was prolonged on day 43 with cotadutide vs placebo (t½: 117.2 minutes vs -42.9 minutes; P = 0.0392).

CONCLUSION

These results suggest that the glucose-lowering effects of cotadutide are mediated by enhanced insulin secretion and delayed gastric emptying.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03244800.

A dual GLP-1 and Gcg receptor agonist rescues spatial memory and synaptic plasticity in APP/PS1 transgenic mice

Alzheimer's disease (AD) is a neurodegenerative disease that severely affects the health and lifespan of the elderly worldwide. Recently, the correlation between AD and type 2 diabetes mellitus (T2DM) has received intensive attention, and a promising new anti-AD strategy is the use of anti-diabetic drugs. Oxyntomodulin (Oxm) is a peptide hormone and growth factor that acts on neurons in the hypothalamus. OXM activates glucagon-like peptide 1 (GLP-1) and glucagon (Gcg) receptors, facilitates insulin signaling and has neuroprotective effects against Aβ_1-42-induced cytotoxicity in primary hippocampal neurons. Here, we tested the effects of the protease-resistant analogue (D-Ser2)Oxm on spatial memory and synaptic plasticity and the underlying molecular mechanisms in the APP/PS1 transgenic mouse model of AD. The results showed that (D-Ser2)Oxm not only alleviated the impairments of working memory and long-term spatial memory, but also reduced the number of Aβ plaques in the hippocampus, and reversed the suppression of hippocampal synaptic long-term potentiation (LTP). Moreover, (D-Ser2)Oxm administration significantly increased p-PI3K/p-AKT1 expression and decreased p-GSK3β levels in the hippocampus. These results are the first to show an in vivo neuroprotective role of (D-Ser2)Oxm in APP/PS1 mice, and this role involves the improvement of synaptic plasticity, clearance of Aβ and normalization of PI3K/AKT/GSK3β cell signaling in the hippocampus. This study suggests that (D-Ser2)Oxm holds promise for the prevention and treatment of AD.

Circulating levels of gastrointestinal hormones in response to the most common types of bariatric surgery and predictive value for weight loss over one year: Evidence from two independent trials

AIMS

Bariatric surgery leads to profound and sustainable weight loss. Gastrointestinal hormones are involved in energy and glucose homeostasis, thus postoperative changes of their circulating levels may be mediating future weight loss. To investigate how the circulating concentrations of gastrointestinal hormones change in response to the most common types of bariatric operation and whether these changes can predict future weight loss.

MATERIALS AND METHODS

We measured circulating GLP-1, GLP-2, oxyntomodulin, glicentin, glucagon, major proglucagon fragment (MPGF), ghrelin, GIP, PYY after overnight fasting and/or after a mixed meal test (MMT) in: a) 14 subjects that have undergone either an adjustable gastric banding [AGB] (n = 9) or a Roux-en-Y bypass (RYGB) (n = 5) (Pilot study 1), b) 28 subjects that have undergone either a vertical sleeve gastrectomy (n = 17) or a RYGB (n = 11) before and three, six and twelve months after surgery.

RESULTS

In addition to the expected associations with GLP-1, the most robust increases were observed in postprandial levels of oxyntomodulin and glicentin three months after VSG or RYGB (but not after AGB) and are associated with degree of weight loss. Oxyntomodulin and glicentin levels at the third and sixth month postoperative visit are positively associated with feeling of satiety which may be underlying the observed associations with future weight loss.

CONCLUSION

Beyond GLP-1, early postprandial changes in circulating oxyntomodulin and glicentin are predictors of weight loss after bariatric surgery, possibly through regulation of satiety. Further studies should focus on underlying mechanisms, and their potential as attractive therapeutic tools against obesity and related comorbidities.

Will medications that mimic gut hormones or target their receptors eventually replace bariatric surgery?

Bariatric surgery is currently the most effective therapeutic modality through which sustained beneficial effects on weight loss and metabolic improvement are achieved. During recent years, indications for bariatric surgery have been expanded to include cases of poorly controlled type 2 (T2DM) diabetes mellitus in lesser extremes of body weight. A spectrum of the beneficial effects of surgery is attributed to robust changes of postprandial gut peptide responses that are observed post operatively. Consolidated knowledge regarding gut peptide physiology as well as emerging new evidence shedding light on the mode of action of previously overlooked gut hormones provide appealing potential obesity and T2DM therapeutic perspectives. The accumulation of evidence from the effect of exogenous administration of native gut peptides alone or in combinations to humans as well as the development of mimetic agents exerting agonistic effects on combinations of gut hormone receptors pave the way for future integrated gut peptide-based treatments, which may mimic the effects of bariatric surgery.

New Insights into Beta-Cell GLP-1 Receptor and cAMP Signaling

Harnessing the translational potential of the GLP-1/GLP-1R system in pancreatic beta cells has led to the development of established GLP-1R-based therapies for the long-term preservation of beta cell function. In this review, we discuss recent advances in the current research on the GLP-1/GLP-1R system in beta cells, including the regulation of signaling by endocytic trafficking as well as the application of concepts such as signal bias, allosteric modulation, dual agonism, polymorphic receptor variants, spatial compartmentalization of cAMP signaling and new downstream signaling targets involved in the control of beta cell function.

No Guts, No Loss: Toward the Ideal Treatment for Obesity in the Twenty-First Century

Over the last century, our knowledge of the processes which control appetite and weight regulation has developed significantly. The understanding of where gut hormones fit into the control of energy homeostasis in addition to the rapid advancement of pharmacotherapeutics has paved the way for the development of novel gut hormone analogs to target weight loss. Currently, bariatric surgery remains the most efficacious treatment for obesity. The emergence of gut hormone analogs may provide a useful non-surgical addition to the armamentarium in treating obesity. Simply targeting single gut hormone pathways may be insufficiently efficacious, and combination/multiple-agonist approaches may be necessary to obtain the results required for clear clinical impact.

The Regulation of Peripheral Metabolism by Gut-Derived Hormones

Enteroendocrine cells lining the gut epithelium constitute the largest endocrine organ in the body and secrete over 20 different hormones in response to cues from ingested foods and changes in nutritional status. Not only do these hormones convey signals from the gut to the brain via the gut-brain axis, they also act directly on metabolically important peripheral targets in a highly concerted fashion to maintain energy balance and glucose homeostasis. Gut-derived hormones released during fasting tend to be orexigenic and have hyperglycaemic potential. Conversely, gut hormones secreted postprandially generally promote satiety and facilitate glucose clearance. Although some of the metabolic benefits conferred by bariatric surgeries have been ascribed to changes in the secretory profiles of various gut hormones, the therapeutic potential of the enteroendocrine system as a viable target against metabolic diseases remain largely underexploited, except for incretin-mimetics. This review provides a brief overview of the physiological importance and highlights the therapeutic potential of the following gut hormones: serotonin, glucose-dependent insulinotropic peptide, glucagon-like peptide 1, oxyntomodulin, peptide YY, insulin-like peptide 5, and ghrelin.