Glucose-dependent Insulinotropic Polypeptide Receptor Research Articles

The Efficacy of GLP-1 Agonists in Treating Substance Use Disorder in Patients: A Scoping Review.

Substance use disorder (SUD) continues to be a leading cause of morbidity and mortality with limited treatments. There is interest in expanding the use of GLP-1 agonists in treating SUD. However, evidence for safety and efficacy in humans is limited. This review aims to bridge the existing knowledge gap by establishing a baseline of literature in this area to inform future trials and clinical practice. Our inclusion criteria were English peer-reviewed manuscripts reporting on use of GLP-1, GIP, and/or glucagon receptor agonists in treatment of SUDs, excluding case studies. The literature search was performed in accordance to PRISMA guidelines. Five studies were included in this review examining the use of this medication in tobacco use disorder, alcohol use disorder, and cocaine use disorder. No studies regarding substance withdrawal syndrome were identified. The included studies varied widely in terms of patient selection, dose/formulation of GLP-1 agonists, and follow-up. The results of this scoping review are mixed, with 3 studies demonstrating positive results and 2 studies finding no efficacy of this medication on SUD outcomes. It is premature to prescribe this medication off-label to patients. Further research is needed to determine the efficacy of GLP-1 agonists in treating SUD.

Molecular Mechanisms behind Obesity and Their Potential Exploitation in Current and Future Therapy.

Obesity is a chronic disease caused primarily by the imbalance between the amount of calories supplied to the body and energy expenditure. Not only does it deteriorate the quality of life, but most importantly it increases the risk of cardiovascular diseases and the development of type 2 diabetes mellitus, leading to reduced life expectancy. In this review, we would like to present the molecular pathomechanisms underlying obesity, which constitute the target points for the action of anti-obesity medications. These include the central nervous system, brain-gut-microbiome axis, gastrointestinal motility, and energy expenditure. A significant part of this article is dedicated to incretin-based drugs such as GLP-1 receptor agonists (e.g., liraglutide and semaglutide), as well as the brand new dual GLP-1 and GIP receptor agonist tirzepatide, all of which have become "block-buster" drugs due to their effectiveness in reducing body weight and beneficial effects on the patient's metabolic profile. Finally, this review article highlights newly designed molecules with the potential for future obesity management that are the subject of ongoing clinical trials.

From the First Case Reports to KDM1A Identification: 35 Years of Food (GIP)-Dependent Cushing's Syndrome.

Food-dependent Cushing's syndrome (FDCS) is a rare presentation of hypercortisolism from adrenal origin, mostly observed in primary bilateral macronodular adrenal hyperplasia (PBMAH) but also in some cases of unilateral adrenocortical adenoma. FDCS is mediated by the aberrant expression of glucose-dependent insulinotropic peptide (GIP) receptor (GIPR) in adrenocortical cells. GIP, secreted by duodenal K cells after food intake, binds to its ectopic adrenal receptor, and stimulates cortisol synthesis following meals. FDCS was first described more than 35 years ago, and its genetic cause in PBMAH has been recently elucidated: KDM1A inactivation by germline heterozygous pathogenic variants is constantly associated with a loss-of-heterozygosity of the short arm of chromosome 1, containing the KDM1A locus. This causes biallelic inactivation of KDM1A, resulting in the GIPR overexpression in the adrenal cortex. These new insights allow us to propose the KDM1A genetic screening to all PBMAH patients with signs of FDCS (low fasting cortisol that increases after a mixed meal or oral glucose load) and to all first-degree relatives of KDM1A variant carriers. Given that KDM1A is a tumor suppressor gene that has also been associated with monoclonal gammopathy of uncertain significance and multiple myeloma, the investigation of FDCS in the diagnostic management of patients with PBMAH and further genetic testing and screening for malignancies should be encouraged.

Incretin-Based Multi-Agonist Peptides Are Neuroprotective and Anti-Inflammatory in Cellular Models of Neurodegeneration.

Glucagon-like peptide-1 (GLP-1)-based drugs have been approved by the United States Food and Drug Administration (FDA) and are widely used to treat type 2 diabetes mellitus (T2DM) and obesity. More recent developments of unimolecular peptides targeting multiple incretin-related receptors ("multi-agonists"), including the glucose-dependent insulinotropic polypeptide (GIP) receptor (GIPR) and the glucagon (Gcg) receptor (GcgR), have emerged with the aim of enhancing drug benefits. In this study, we utilized human and mouse microglial cell lines, HMC3 and IMG, respectively, together with the human neuroblastoma SH-SY5Y cell line as cellular models of neurodegeneration. Using these cell lines, we studied the neuroprotective and anti-inflammatory capacity of several multi-agonists in comparison with a single GLP-1 receptor (GLP-1R) agonist, exendin-4. Our data demonstrate that the two selected GLP-1R/GIPR dual agonists and a GLP-1R/GIPR/GcgR triple agonist not only have neurotrophic and neuroprotective effects but also have anti-neuroinflammatory properties, as indicated by the decreased microglial cyclooxygenase 2 (COX2) expression, nitrite production, and pro-inflammatory cytokine release. In addition, our results indicate that these multi-agonists have the potential to outperform commercially available single GLP-1R agonists in neurodegenerative disease treatment.

Molecular dynamics-guided optimization of BGM0504 enhances dual-target agonism for combating diabetes and obesity

The dual activation of glucagon-like peptide-1 receptor (GLP-1R) and glucose-dependent insulinotropic polypeptide receptor (GIPR) has emerged as a promising therapeutic strategy for managing type 2 diabetes and obesity. Tirzepatide, a dual agonist peptide, has exhibited superior clinical efficacy in glycemic and weight control compared to selective GLP-1R agonists. Nevertheless, the structural basis of Tirzepatide's extended half-life, attributed to an acylation side chain on the parent peptide, raises questions regarding its partial agonistic activity. Employing molecular dynamics simulations, we explored the dynamic processes of peptide-receptor interactions. We uncovered a crucial salt bridge between parent peptide and GLP-1R/GIPR at K20, a feature not discernible in cryo-electron microscopy structures. Building upon these insights, we developed an optimization strategy based on the parent peptide which involved repositioning the acylation side chain. The results of both in vitro and in vivo experiments demonstrated that the optimized peptide has twofold to threefold increase in agonistic activity compared to Tirzepatide while maintaining its extended half-life in plasma. This led to the design of BGM0504, which proved to be more effective than its predecessor, Tirzepatide, in both laboratory and animal studies.

Incretin-mediated control of cardiac energy metabolism.

Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like-peptide-1 (GLP-1) are incretin hormones that stimulate insulin secretion and improve glycemic control in individuals with type 2 diabetes (T2D). Data from several cardiovascular outcome trials for GLP-1 receptor (GLP-1R) agonists have demonstrated significant reductions in the occurrence of major adverse cardiovascular events in individuals with T2D. Although the cardiovascular actions attributed to GLP-1R agonism have been extensively studied, little is known regarding the cardiovascular consequences attributed to GIP receptor (GIPR) agonism. As there is now an increasing focus on the development of incretin-based co-agonist therapies that activate both the GLP-1R and GIPR, it is imperative that we understand the mechanism(s) through which these incretins impact cardiovascular function. This is especially important considering that cardiovascular disease represents the leading cause of death in individuals with T2D. With increasing evidence that perturbations in cardiac energy metabolism are a major contributor to the pathology of diabetes-related cardiovascular disease, this may represent a key component through which GLP-1R and GIPR agonism influence cardiovascular outcomes. Not only do GIP and GLP-1 increase the secretion of insulin, they may also modify glucagon secretion, both of which have potent actions on cardiac substrate utilization. Herein we will discuss the potential direct and indirect actions through which GLP-1R and GIPR agonism impact cardiac energy metabolism while interrogating the evidence to support whether such actions may account for incretin-mediated cardioprotection in T2D.

Tirzepatide shows neuroprotective effects via regulating brain glucose metabolism in APP/PS1 mice

Tirzepatide (LY3298176), a GLP-1 and GIP receptor agonist, is fatty-acid-modified and 39-amino acid linear peptide, which ameliorates learning and memory impairment in diabetic rats. However, the specific molecular mechanism remains unknown. In the present study, we investigated the role of tirzepatide in the neuroprotective effects in Alzheimer's disease (AD) model mice. Tirzepatide was administrated intraperitoneal (i.p.) APP/PS1 mice for 8 weeks with at 10 nmol/kg once-weekly, it significantly decreased the levels of GLP-1R, and GFAP protein expression and amyloid plaques in the cortex, it also lowered neuronal apoptosis induced by amyloid-β (Aβ), but did not affect the anxiety and cognitive function in APP/PS1 mice. Moreover, tirzepatide reduced the blood glucose levels and increased the mRNA expression of GLP-1R, SACF1, ATF4, Glu2A, and Glu2B in the hypothalamus of APP/PS1 mice. Tirzepatide increased the mRNA expression of glucose transporter 1, hexokinase, glucose-6-phosphate dehydrogenase, and phosphofructokinase in the cortex. Lastly, tirzepatide improved the energetic metabolism by regulated reactive oxygen species production and mitochondrial membrane potential caused by Aβ, thereby decreasing mitochondrial function and ATP levels in astrocytes through GLP-1R. These results provide valuable insights into the mechanism of brain glucose metabolism and mitochondrial function of tirzepatide, presenting potential strategies for AD treatment.

Class B1 GPCRs: insights into multireceptor pharmacology for the treatment of metabolic disease.

The secretin-like, class B1 subfamily of seven transmembrane-spanning G protein-coupled receptors (GPCRs) consists of 15 members that coordinate important physiological processes. These receptors bind peptide ligands and use a distinct mechanism of activation that is driven by evolutionarily conserved structural features. For the class B1 receptors, the C-terminus of the cognate ligand is initially recognized by the receptor via an N-terminal extracellular domain that forms a hydrophobic ligand-binding groove. This binding enables the N-terminus of the ligand to engage deep into a large volume, open transmembrane pocket of the receptor. Importantly, the phylogenetic basis of this ligand-receptor activation mechanism has provided opportunities to engineer analogs of several class B1 ligands for therapeutic use. Among the most accepted of these are drugs targeting the glucagon-like peptide-1 (GLP-1) receptor for the treatment of type 2 diabetes and obesity. Recently, multifunctional agonists possessing activity at the GLP-1 receptor and the glucose-dependent insulinotropic polypeptide (GIP) receptor, such as tirzepatide, and others that also contain glucagon receptor activity, have been developed. In this article, we review members of the class B1 GPCR family with focus on receptors for GLP-1, GIP, and glucagon, including their signal transduction and receptor trafficking characteristics. The metabolic importance of these receptors is also highlighted, along with the benefit of polypharmacologic ligands. Furthermore, key structural features and comparative analyses of high-resolution cryogenic electron microscopy structures for these receptors in active-state complexes with either native ligands or multifunctional agonists are provided, supporting the pharmacological basis of such therapeutic agents.

Altered desensitization and internalization patterns of rodent versus human glucose-dependent insulinotropic polypeptide (GIP) receptors. An important drug discovery challenge.

The gut hormone glucose-dependent insulinotropic polypeptide (GIP) signals via the GIP receptor (GIPR), resulting in postprandial potentiation of glucose-stimulated insulin secretion. The translation of results from rodent studies to human studies has been challenged by the unexpected effects of GIPR-targeting compounds. We, therefore, investigated the variation between species, focusing on GIPR desensitization and the role of the receptor C-terminus. The GIPR from humans, mice, rats, pigs, dogs and cats was studied in vitro for cognate ligand affinity, G protein activation (cAMP accumulation), recruitment of beta-arrestin and internalization. Variants of the mouse, rat and human GIPRs with swapped C-terminal tails were studied in parallel. The human GIPR is more prone to internalization than rodent GIPRs. Despite similar agonist affinities and potencies for Gαs activation, especially, the mouse GIPR shows reduced receptor desensitization, internalization and beta-arrestin recruitment. Using an enzyme-stabilized, long-acting GIP analogue, the species differences were even more pronounced. 'Tail-swapped' human, rat and mouse GIPRs were all fully functional in their Gαs coupling, and the mouse GIPR regained internalization and beta-arrestin 2 recruitment properties with the human tail. The human GIPR lost the ability to recruit beta-arrestin 2 when its own C-terminus was replaced by the rat or mouse tail. Desensitization of the human GIPR is dependent on the C-terminal tail. The species-dependent functionality of the C-terminal tail and the different species-dependent internalization patterns, especially between human and mouse GIPRs, are important factors influencing the preclinical evaluation of GIPR-targeting therapeutic compounds.

Changes in lean body mass with glucagon-like peptide-1-based therapies and mitigation strategies.

Weight loss induced by glucagon-like peptide-1 receptor agonists (GLP-1RAs) and dual glucagon-like peptide-1 receptor (GLP-1R)/glucose-dependent insulinotropic polypeptide receptor agonists is coming closer to the magnitudes achieved with surgery. However, with greater weight loss there is concern about potential side effects on muscle quantity (mass), health and function. There is heterogeneity in the reported effects of GLP-1-based therapies on lean mass changes in clinical trials: in some studies, reductions in lean mass range between 40% and 60% as a proportion of total weight lost, while other studies show lean mass reductions of approximately 15% or less of total weight lost. There are several potential reasons underlying this heterogeneity, including population, drug-specific/molecular, and comorbidity effects. Furthermore, changes in lean mass may not always reflect changes in muscle mass as the former measure includes not only muscle but also organs, bone, fluids, and water in fat tissue. Based on contemporary evidence with the addition of magnetic resonance imaging-based studies, skeletal muscle changes with GLP-1RA treatments appear to be adaptive: reductions in muscle volume seem to be commensurate with what is expected given ageing, disease status, and weight loss achieved, and the improvement in insulin sensitivity and muscle fat infiltration likely contributes to an adaptive process with improved muscle quality, lowering the probability for loss in strength and function. Nevertheless, factors such as older age and severity of disease may influence the selection of appropriate candidates for these therapies due to risk of sarcopenia. To further improve muscle health during weight loss, several pharmacological treatments to maintain or improve muscle mass designed in combination with GLP-1-based therapies are under development. Future research on GLP-1-based and other therapies designed for weight loss should focus on more accurate and meaningful assessments of muscle mass, composition, as well as function, mobility or strength, to better define their impact on muscle health for the substantial number of patients who will likely be taking these medications well into the future.

Gut hormone multi-agonists for the treatment of type 2 diabetes and obesity: advances and challenges.

The rapidly rising incidence of obesity, coupled with type 2 diabetes mellitus (T2DM), is a growing concern. Glucagon-like peptide 1 (GLP-1), an endogenous peptide secreted by enteroendocrine L-cells, demonstrates exceptional pharmacological potential for the treatment of T2DM and obesity, primarily through its pivotal roles in regulating glucose homeostasis, stimulating glucose-dependent insulin secretion, and promoting satiety. Considering its proven efficacy in glucoregulation and weight loss, GLP-1 receptor agonists (GLP-1RAs) have emerged as a revolutionary breakthrough in the arena of diabetes management and weight control. Additional gastrointestinal hormones, such as glucose-dependent insulinotropic peptide (GIP) and glucagon, exhibit structural similarities to GLP-1 and work synergistically to lower blood glucose levels or aid in weight loss. Today, various classes of gut hormone receptor multiple agonists are steadily progressing through development and clinical trials, including dual GLP-1/glucagon receptor agonists (first discovered in 2009), dual GLP-1/GIP receptor agonists (first described in 2013), and triple GLP-1/GIP/glucagon receptor agonists (initially designed in 2015). The GLP-1/GIP receptor co-agonist, tirzepatide, was approved by the U.S. Food and Drug Administration (FDA) for the treatment of T2DM, outperforming basal insulin or selective GLP-1RAs by providing superior HbA1c reductions. Remarkably, tirzepatide also facilitated unprecedented weight loss of up to 22.5% in non-diabetic individuals living with obesity. This result is comparable to those achieved with certain types of bariatric surgery. Therefore, the advent of gut hormone multi-agonists signifies the dawn of an exciting new era in peptide-based therapy for obesity and T2DM. This review offers a comprehensive summary of the various types of gut hormone multiple agonists, including their discovery, development, action of mechanisms, and clinical effectiveness. We further delve into potential hurdles, limitations, and prospective advancements in the field.

Comparative efficacy and safety of weekly tirzepatide versus weekly insulin in type 2 diabetes: A network meta-analysis of randomized clinical trials.

To compare the efficacy and safety profiles of recent innovations in type 2 diabetes mellitus (T2DM), which include once-weekly formulations such as tirzepatide, a dual glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide receptor agonist, and once-weekly insulin options such as icodec and basal insulin Fc. A systematic search of the PubMed, Scopus, Cochrane, and Web of Science databases was conducted. The network meta-analysis protocol was registered at OSF registries (https://osf.io/gd67x). The primary outcome of interest was change in glycated haemoglobin (HbA1c), with change in fasting plasma glucose (FPG), body weight, incidence of hypoglycaemia, and treatment discontinuation as secondary outcomes. Tirzepatide exhibited superior efficacy in reducing HbA1c levels compared with insulin therapies, with the 15-mg dose showing the most significant reduction (mean difference [MD] -1.27, 95% confidence interval [CI] -1.49; -1.0). In terms of FPG reduction, tirzepatide 15 mg ranked highest (MD -0.70, 95% CI -1.05; -0.34), followed by tirzepatide 10 mg and 5 mg. Additionally, tirzepatide led to substantial weight loss, with the 15-mg dose exhibiting the most pronounced effect (MD -12.13, 95% CI -13.98; -10.27). However, a higher incidence of adverse events (AEs) and treatment discontinuation were associated with tirzepatide, particularly at higher doses. Tirzepatide, particularly at higher doses, demonstrates superior efficacy in lowering HbA1c and reducing hypoglycaemia risk compared with weekly insulin. However, its use is also associated with a higher incidence of AEs and treatment discontinuation.

Tirzepatide against obesity and insulin-resistance: pathophysiological aspects and clinical evidence.

Obesity is a chronic, multifactorial disease in which accumulated excess body fat has a negative impact on health. Obesity continues to rise among the general population, resulting in an epidemic that shows no significant signs of decline. It is directly involved in development of cardiometabolic diseases, ischemic coronary heart disease peripheral arterial disease, heart failure, and arterial hypertension, producing global morbidity and mortality. Mainly, abdominal obesity represents a crucial factor for cardiovascular illness and also the most frequent component of metabolic syndrome. Recent evidence showed that Tirzepatide (TZP), a new drug including both Glucagon Like Peptide 1 (GLP-1) and Glucose-dependent Insulinotropic Polypeptide (GIP) receptor agonism, is effective in subjects with type 2 diabetes (T2D), lowering body weight, fat mass and glycated hemoglobin (HbA1c) also in obese or overweight adults without T2D. This review discusses the pathophysiological mechanisms and clinical aspects of TZP in treating obesity.

1861-LB: Efficacy and Safety of HRS9531, a Novel Dual GLP-1/GIP Receptor Agonist, in Obese Adults—A Phase 2 Trial

1861-LB: Efficacy and Safety of HRS9531, a Novel Dual GLP-1/GIP Receptor Agonist, in Obese Adults—A Phase 2 Trial

Bilateral Adrenocortical Nodular Disease and Cushing's Syndrome.

Primary pigmented nodular adrenocortical disease (PPNAD) and bilateral macronodular adrenocortical disease (BMAD) are 2 forms of adrenocortical nodular diseases causing Cushing's syndrome but are 2 very distinct conditions. PPNAD, affecting mostly young patients with an almost constant severe Cushing's syndrome, is characterized by pigmented micronodules, usually less than 1 cm, not always visible on imaging. On the contrary, BMAD is predominantly diagnosed in the fifth and sixth decades, with highly variable degrees of cortisol excess, from mild autonomous cortisol secretion to overt Cushing's syndrome. BMAD presents as large bilateral adrenal macronodules, easily observed on imaging. Both diseases are often genetically determined: frequently PPNAD is observed in a multiple neoplasia syndrome, Carney complex, and a germline genetic defect is identified in around 80% of index cases, always affecting key actors of the cAMP/protein kinase A (PKA) pathway: mostly PRKAR1A, encoding the PKA 1-alpha regulatory subunit. On the other hand, BMAD appears mostly isolated, and 2 predisposing genes are known at present: ARMC5, accounting for around 20% of index cases, and the recently identified KDM1A, causing the rare presentation with food-dependent Cushing's syndrome, mediated by the ectopic expression of the glucose-dependent insulinotropic polypeptide receptor (GIPR) in adrenal nodules. GIPR was the first demonstrated receptor to illegitimately regulate cortisol secretion in nodular adrenocortical diseases, and a myriad of other receptors and paracrine signals were discovered afterward. The last 30 years were pivotal in the understanding of the genetics and pathophysiology of bilateral adrenocortical nodular diseases, leading to a personalized approach of these fascinating conditions.

Tirzepatide modulates the regulation of adipocyte nutrient metabolism through long-acting activation of the GIP receptor

Tirzepatide, a glucose-dependent insulinotropic polypeptide/glucagon-like peptide 1 receptor (GIPR/GLP-1R) agonist, has, in clinical trials, demonstrated greater reductions in glucose, body weight, and triglyceride levels compared with selective GLP-1R agonists in people with type 2 diabetes (T2D). However, cellular mechanisms by which GIPR agonism may contribute to these improved efficacy outcomes have not been fully defined. Using human adipocyte and mouse models, we investigated how long-acting GIPR agonists regulate fasted and fed adipocyte functions. In functional assays, GIPR agonism enhanced insulin signaling, augmented glucose uptake, and increased the conversion of glucose to glycerol in a cooperative manner with insulin; however, in the absence of insulin, GIPR agonists increased lipolysis. In diet-induced obese mice treated with a long-acting GIPR agonist, circulating triglyceride levels were reduced during oral lipid challenge, and lipoprotein-derived fatty acid uptake into adipose tissue was increased. Our findings support a model for long-acting GIPR agonists to modulate both fasted and fed adipose tissue function differentially by cooperating with insulin to augment glucose and lipid clearance in the fed state while enhancing lipid release when insulin levels are reduced in the fasted state.

Characterization of genetic variants of GIPR reveals a contribution of β-arrestin to metabolic phenotypes

Incretin-based therapies are highly successful in combatting obesity and type 2 diabetes1. Yet both activation and inhibition of the glucose-dependent insulinotropic polypeptide (GIP) receptor (GIPR) in combination with glucagon-like peptide-1 (GLP-1) receptor (GLP-1R) activation have resulted in similar clinical outcomes, as demonstrated by the GIPR–GLP-1R co-agonist tirzepatide2 and AMG-133 (ref. 3) combining GIPR antagonism with GLP-1R agonism. This underlines the importance of a better understanding of the GIP system. Here we show the necessity of β-arrestin recruitment for GIPR function, by combining in vitro pharmacological characterization of 47 GIPR variants with burden testing of clinical phenotypes and in vivo studies. Burden testing of variants with distinct ligand-binding capacity, Gs activation (cyclic adenosine monophosphate production) and β-arrestin 2 recruitment and internalization shows that unlike variants solely impaired in Gs signalling, variants impaired in both Gs and β-arrestin 2 recruitment contribute to lower adiposity-related traits. Endosomal Gs-mediated signalling of the variants shows a β-arrestin dependency and genetic ablation of β-arrestin 2 impairs cyclic adenosine monophosphate production and decreases GIP efficacy on glucose control in male mice. This study highlights a crucial impact of β-arrestins in regulating GIPR signalling and overall preservation of biological activity that may facilitate new developments in therapeutic targeting of the GIPR system.

New Developments in Pharmacological Treatment of Obesity and Type 2 Diabetes-Beyond and within GLP-1 Receptor Agonists.

Guidelines for the management of obesity and type 2 diabetes (T2DM) emphasize the importance of lifestyle changes, including a reduced-calorie diet and increased physical activity. However, for many people, these changes can be difficult to maintain over the long term. Medication options are already available to treat obesity, which can help reduce appetite and/or reduce caloric intake. Incretin-based peptides exert their effect through G-protein-coupled receptors, the receptors for glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), and glucagon peptide hormones are important regulators of insulin secretion and energy metabolism. Understanding the role of intercellular signaling pathways and inflammatory processes is essential for the development of effective pharmacological agents in obesity. GLP-1 receptor agonists have been successfully used, but it is assumed that their effectiveness may be limited by desensitization and downregulation of the target receptor. A growing number of new agents acting on incretin hormones are becoming available for everyday clinical practice, including oral GLP-1 receptor agonists, the dual GLP-1/GIP receptor agonist tirzepatide, and other dual and triple GLP-1/GIP/glucagon receptor agonists, which may show further significant therapeutic potential. This narrative review summarizes the therapeutic effects of different incretin hormones and presents future prospects in the treatment of T2DM and obesity.

Does glucose-dependent insulinotropic polypeptide receptor blockade as well as agonism have a role to play in management of obesity and diabetes?

Recent approval of the dual glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonist, tirzepatide, for the management of type 2 diabetes mellitus (T2DM) has reinvigorated interest in exploitation of GIP receptor (GIPR) pathways as a means of metabolic disease management. However, debate has long surrounded the use of the GIPR as a therapeutic target and whether agonism or antagonism is of most benefit in management of obesity/diabetes. This controversy appears to be partly resolved by the success of tirzepatide. However, emerging studies indicate that prolonged GIPR agonism may desensitise the GIPR to essentially induce receptor antagonism, with this phenomenon suggested to be more pronounced in the human than rodent setting. Thus, deliberation continues to rage in relation to benefits of GIPR agonism vs antagonism. That said, as with GIPR agonism, it is clear that the metabolic advantages of sustained GIPR antagonism in obesity and obesity-driven forms of diabetes can be enhanced by concurrent GLP-1 receptor (GLP-1R) activation. This narrative review discusses various approaches of pharmacological GIPR antagonism including small molecule, peptide, monoclonal antibody and peptide-antibody conjugates, indicating stage of development and significance to the field. Taken together, there is little doubt that interesting times lie ahead for GIPR agonism and antagonism, either alone or when combined with GLP-1R agonists, as a therapeutic intervention for the management of obesity and associated metabolic disease.

Tirzepatide for Metabolic Dysfunction–Associated Steatohepatitis with Liver Fibrosis

BackgroundMetabolic dysfunction–associated steatohepatitis (MASH) is a progressive liver disease associated with liver-related complications and death. The efficacy and safety of tirzepatide, an agonist of the glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1 receptors, in patients with MASH and moderate or severe fibrosis is unclear.MethodsWe conducted a phase 2, dose-finding, multicenter, double-blind, randomized, placebo-controlled trial involving participants with biopsy-confirmed MASH and stage F2 or F3 (moderate or severe) fibrosis. Participants were randomly assigned to receive once-weekly subcutaneous tirzepatide (5 mg, 10 mg, or 15 mg) or placebo for 52 weeks. The primary end point was resolution of MASH without worsening of fibrosis at 52 weeks. A key secondary end point was an improvement (decrease) of at least one fibrosis stage without worsening of MASH.ResultsAmong 190 participants who had undergone randomization, 157 had liver-biopsy results at week 52 that could be evaluated, with missing values imputed under the assumption that they would follow the pattern of results in the placebo group. The percentage of participants who met the criteria for resolution of MASH without worsening of fibrosis was 10% in the placebo group, 44% in the 5-mg tirzepatide group (difference vs. placebo, 34 percentage points; 95% confidence interval [CI], 17 to 50), 56% in the 10-mg tirzepatide group (difference, 46 percentage points; 95% CI, 29 to 62), and 62% in the 15-mg tirzepatide group (difference, 53 percentage points; 95% CI, 37 to 69) (P<0.001 for all three comparisons). The percentage of participants who had an improvement of at least one fibrosis stage without worsening of MASH was 30% in the placebo group, 55% in the 5-mg tirzepatide group (difference vs. placebo, 25 percentage points; 95% CI, 5 to 46), 51% in the 10-mg tirzepatide group (difference, 22 percentage points; 95% CI, 1 to 42), and 51% in the 15-mg tirzepatide group (difference, 21 percentage points; 95% CI, 1 to 42). The most common adverse events in the tirzepatide groups were gastrointestinal events, and most were mild or moderate in severity.ConclusionsIn this phase 2 trial involving participants with MASH and moderate or severe fibrosis, treatment with tirzepatide for 52 weeks was more effective than placebo with respect to resolution of MASH without worsening of fibrosis. Larger and longer trials are needed to further assess the efficacy and safety of tirzepatide for the treatment of MASH. (Funded by Eli Lilly; SYNERGY-NASH ClinicalTrials.gov number, NCT04166773.)