The glucose-dependent insulinotropic polypeptide (GIP) regulates body weight and food intake via CNS-GIPR signaling

Review Article: GLP-1 Receptor Agonists and Glucagon/GIP/GLP-1 Receptor Dual or Triple Agonists-Mechanism of Action and Emerging Therapeutic Landscape in MASLD

BACKGROUND

Metabolic dysfunction-associated steatotic liver disease (MASLD) is primarily managed through diet and lifestyle modifications. However, these behavioural interventions alone may not achieve disease regression or remission, and maintaining long-term adherence is challenging. Incretin mimetics and other gastrointestinal hormones targeting the pleiotropic pathophysiological pathways underlying MASLD have now emerged as promising disease-modifying therapies.

AIMS

This is a comprehensive review summarising the role of glucagon-like peptide-1 (GLP-1) receptor agonists and glucagon/glucose-dependent insulinotropic polypeptide (GIP)/GLP-1 receptor dual or triple agonists in the treatment of metabolic dysfunction-associated steatohepatitis (MASH).

METHODS

Only clinical trials with endpoints assessed by liver histology were included for a robust evaluation of therapeutic efficacy.

RESULTS

Recent evidence from phase 2 clinical trials for MASH demonstrated that pharmacological agents based on GLP-1 receptor agonism are effective in improving disease activity. Additionally, tirzepatide and survodutide showed potential clinical benefits in reducing fibrosis. Other cardiometabolic benefits observed include weight loss and improvements in glycaemic control and lipid profile. Adherence to treatment may be limited by gastrointestinal side effects, though they were found to be generally mild to moderate in severity. An interim analysis of the semaglutide phase 3 trial confirmed its efficacy in improving steatohepatitis and demonstrated its potential to improve fibrosis.

CONCLUSIONS

GLP-1 receptor agonists, alone or in combination with GIP and/or glucagon receptor agonists, represent promising, effective pharmacotherapies for the treatment of MASLD/MASH. Larger and longer-duration clinical trials are needed to further evaluate the efficacy and safety of GIP receptor and glucagon receptor agonism.

Neuroprotective effect of niacin in a rat model of obesity induced by high-fat-rich diet

This study investigates the impact of a high-fat-rich diet (HFRD) on behavioral, biochemical, neurochemical, and histopathological studies using the hypothalamus of rats following niacin (NCN) administration. The rats were divided into HFRD and normal diet (ND)-fed groups and administered selected doses of NCN, i.e., 25 mg/mL/kg (low dose) and 50 mg/mL/kg (high dose), for 8 weeks. The grouping of male rats (n = 8) was as follows: (i) Vehicle (Veh) + ND; (ii) ND + NCN (low dose); (iii) ND + NCN (high dose); (iv) Veh + HFRD; (v) HFRD + NCN (low dose); and (vi) HFRD + NCN (high dose). Behavioral tests assessed depression-like symptoms and spatial memory; after that, the hypothalamus was isolated for various analyses of sacrificed animals. NCN at both doses decreased food intake and growth rate in both diet groups and demonstrated antidepressant and memory-enhancing effects. HFRD-induced oxido-neuroinflammation decreased with both doses of NCN. HFRD-induced decreases in serotonergic neurotransmission, 5-HT1A receptor expression, and morphological alterations in the rat's hypothalamus were normalized by both doses of NCN. In conclusion, NCN, as a potential antioxidant and neuromodulator, can normalize feeding behavior and produce antidepressant and memory-improving effects in a rat model of obesity following HFRD intake.

Imo-induced changes in gut hormones and glucose metabolism: A key to improving insulin sensitivity in type 2 diabetes

Isomalto-oligosaccharides (IMO) are prebiotic oligosaccharides that have shown promise in improving insulin sensitivity and glucose metabolism, making them potential therapeutic agents for Type 2 Diabetes (T2D). IMO selectively stimulates beneficial gut microbiota, particularly Bifidobacterium and Lactobacillus, leading to the production of short-chain fatty acids (SCFAs) like acetate, propionate, and butyrate. These SCFAs play a pivotal role in enhancing the release of gut hormones such as GLP-1 (Glucagon-like peptide-1) and PYY (Peptide YY), which improve insulin secretion and promote satiety, thus improving glucose homeostasis. Clinical studies have reported that IMO supplementation can lower HbA1c by 0.5% and reduce postprandial glucose spikes, demonstrating its efficacy in glycemic control. Additionally, IMO promotes insulin sensitivity by reducing inflammation and enhancing adiponectin levels. Although the current findings are promising, further research is needed to determine optimal dosing, long-term safety, and the role of individual gut microbiomes in tailoring IMO interventions. Future studies focusing on personalized nutrition strategies and the synergistic effects of IMO with other lifestyle interventions could enhance its applicability as a key component in T2D management.

The Premise of the Paradox: Examining the Evidence That Motivated GIPR Agonist and Antagonist Drug Development Programs

Emerging clinical data support the paradoxical notion that glucose-dependent insulinotropic polypeptide (GIP) receptor (GIPR) agonism and antagonism can provide additive weight loss when combined with a glucagon-like peptide 1 (GLP-1) receptor (GLP-1R) agonist. In this review, we examine data that motivated the initiation of these seemingly contradictory drug discovery programs. We focus on the physiologic role of GIP in humans, human genetics evidence, rodent genetic models, and preclinical rodent and non-human primate pharmacology studies. Furthermore, we highlight where early preclinical findings translated into relevant clinical efficacy in the development of tirzepatide and maridebart cafraglutide (MariTide).

Animal models for development of anti-obesity drugs in the age of GLP-1 agents

INTRODUCTION

Obesity is a major health crisis globally, with prevalence escalating significantly in recent decades. Obesity is not merely excessive weight but is associated with myriad health complications. Ensuring the translational effectiveness of pre-clinical obesity models is paramount, and the success of GLP-1 therapies has highlighted important benchmarks for guiding drug development.

AREAS COVERED

The authors discuss the status of various animal models used for the development of anti-obesity drugs, with particular emphasis on rodent models and their validity of preclinical-to-clinical translation. They also highlight innovative animal model integration opportunities between obesity and other associated pathology. The article is based on literature searches using PubMed for content (up until February 2025).

EXPERT OPINION

The effectiveness of GLP-1 therapies in treating type 2 diabetes and obesity presents an opportunity to evaluate the translational relevance of animal models of obesity. Due to their compelling safety profiles, GLP-1(s) are being tested in a wide range of obesity-associated diseases. Optimization of the mechanistic qualities in this drug class requires the incorporation of new endpoints beyond body weight, including lean mass preservation, cardiovascular health, and anti-inflammatory activities. Finally, we are compelled by the intersection of non-obesity disease models into an obesogenic framework to understand the combinatorial effects of obesity on these other disease indications, including heart failure, neurodegenerative diseases, and cancer.

Tirzepatide as Compared with Semaglutide for the Treatment of Obesity

BACKGROUND

Tirzepatide and semaglutide are highly effective medications for obesity management. The efficacy and safety of tirzepatide as compared with semaglutide in adults with obesity but without type 2 diabetes is unknown.

METHODS

In this phase 3b, open-label, controlled trial, adult participants with obesity but without type 2 diabetes were randomly assigned in a 1:1 ratio to receive the maximum tolerated dose of tirzepatide (10 mg or 15 mg) or the maximum tolerated dose of semaglutide (1.7 mg or 2.4 mg) subcutaneously once weekly for 72 weeks. The primary end point was the percent change in weight from baseline to week 72. Key secondary end points included weight reductions of at least 10%, 15%, 20%, and 25% and a change in waist circumference from baseline to week 72.

RESULTS

A total of 751 participants underwent randomization. The least-squares mean percent change in weight at week 72 was -20.2% (95% confidence interval [CI], -21.4 to -19.1) with tirzepatide and -13.7% (95% CI, -14.9 to -12.6) with semaglutide (P<0.001). The least-squares mean change in waist circumference was -18.4 cm (95% CI, -19.6 to -17.2) with tirzepatide and -13.0 cm (95% CI, -14.3 to -11.7) with semaglutide (P<0.001). Participants in the tirzepatide group were more likely than those in the semaglutide group to have weight reductions of at least 10%, 15%, 20%, and 25%. The most common adverse events in both treatment groups were gastrointestinal, and most were mild to moderate in severity and occurred primarily during dose escalation.

CONCLUSIONS

Among participants with obesity but without diabetes, treatment with tirzepatide was superior to treatment with semaglutide with respect to reduction in body weight and waist circumference at week 72. (Funded by Eli Lilly; SURMOUNT-5 ClinicalTrials.gov number, NCT05822830.).

Exploration of immune-related diagnostic biomarkers in unexplained infertility by bioinformatics analysis and machine learning

OBJECTIVE

We aimed to discover the biomarkers associated with UI and their correlation with immune cell infiltration.

MATERIALS AND METHODS

The GSE165004 data set was extracted from the Gene Expression Omnibus and IRGs were obtained from Immport and InnateDB databases. Differential expression analysis, WGCNA, and three machine learning algorithms (LASSO, SVM, and random forest) were used to determine the immune-related hub biomarkers for UI. The diagnostic performance of these markers was evaluated in GSE165004 and validation set (GSE16532). Furthermore, single-sample GSEA was employed to analyze the infiltration level of immune cells and Spearman analysis was conducted to assess the correlation between biomarker and immune cells. The functional enrichment and potential drugs for each biomarker were explored. The biomarker genes were validated in clinical samples by real time PCR assay.

RESULTS

Six shared genes (ANXA2, CD300E, IL27RA, SEMA3F, GIPR, and WFDC2) were identified as diagnostic biomarkers by integration analysis. ROC analysis revealed that these markers had diagnostic value for UI both in training and validation sets. Moreover, these biomarkers are closely associated with immune cells, such as natural killer T cells and effector memory CD8 T cells. GSEA analysis showed that these genes were mainly involved in chromosome and mitochondria-related biological functions. Drug prediction indicated that all genes targeted Benzo(a)pyrene. All the biomarker genes, expect for GIPR were differentially expressed in endometrium tissues of UI patients, compared with controls.

CONCLUSION

This study identified immune-related diagnostic biomarkers in UI, providing new insights into understanding the molecular mechanisms and therapeutic targets of UI.

Specific loss of GIPR signaling in GABAergic neurons enhances GLP-1R agonist-induced body weight loss

OBJECTIVES

Dual incretin agonists are among the most effective pharmaceutical treatments for obesity and type 2 diabetes to date. Such therapeutics can target two receptors, such as the glucagon-like peptide-1 (GLP-1) receptor and the glucose-dependent insulinotropic polypeptide (GIP) receptor in the case of tirzepatide, to improve glycemia and reduce body weight. Regarding body weight effects, GIPR signaling is thought to involve at least two relevant mechanisms: the enhancement of food intake reduction and the attenuation of aversive effects caused by GLP-1R agonists. Although it is known that dual GLP-1R-GIPR agonism produces greater weight loss than GLP-1R agonism alone, the precise mechanism is unknown.

METHODS

To address this question, we used mice lacking GIPR in the whole body, GABAergic neurons, or glutamatergic neurons. These mice were given various combinations of GLP-1R and GIPR agonist drugs with subsequent food intake and conditioned taste aversion measurements.

RESULTS

A GIPR knockout in either the whole body or selectively in inhibitory GABAergic neurons protects against diet-induced obesity, whereas a knockout in excitatory glutamatergic neurons had a negligible effect. Furthermore, we found that GIPR in GABAergic neurons is essential for the enhanced weight loss efficacy of dual incretin agonism, yet, surprisingly, its removal enhances the effect of GLP-1R agonism alone. Finally, GIPR knockout in GABAergic neurons prevents the anti-aversive effects of GIPR agonism.

CONCLUSIONS

Our findings are consistent with GIPR research at large in that both enhancement and removal of GIPR signaling are metabolically beneficial. Notably, however, our findings suggest that future obesity therapies designed to modulate GIPR signaling, whether by agonism or antagonism, would be best targeted towards GABAergic neurons.

Glucose-dependent insulinotropic polypeptide (GIP)

BACKGROUND

Glucose-dependent insulinotropic polypeptide (GIP) was the first incretin identified and plays an essential role in the maintenance of glucose tolerance in healthy humans. Until recently GIP had not been developed as a therapeutic and thus has been overshadowed by the other incretin, glucagon-like peptide 1 (GLP-1), which is the basis for several successful drugs to treat diabetes and obesity. However, there has been a rekindling of interest in GIP biology in recent years, in great part due to pharmacology demonstrating that both GIPR agonism and antagonism may be beneficial in treating obesity and diabetes. This apparent paradox has reinvigorated the field, led to new lines of investigation, and deeper understanding of GIP.

SCOPE OF REVIEW

In this review, we provide a detailed overview on the multifaceted nature of GIP biology and discuss the therapeutic implications of GIPR signal modification on various diseases.

MAJOR CONCLUSIONS

Following its classification as an incretin hormone, GIP has emerged as a pleiotropic hormone with a variety of metabolic effects outside the endocrine pancreas. The numerous beneficial effects of GIPR signal modification render the peptide an interesting candidate for the development of pharmacotherapies to treat obesity, diabetes, drug-induced nausea and both bone and neurodegenerative disorders.

Tirzepatide reduces body weight by increasing fat utilization via the central nervous system-adipose tissue axis in male mice

AIMS

Tirzepatide, a dual glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) receptor agonist, demonstrates promise as a potent medication for obesity. However, the extent to which its weight-reducing effects go beyond suppressing appetite remains unclear. This study aimed to elucidate this by establishing a pair-fed control group, effectively eliminating the influence of reduced caloric intake.

MATERIALS AND METHODS

Mice fed on a chow diet or a high-fat diet received single or long-term intracerebroventricular (i.c.v.) injections of tirzepatide or vehicle. The vehicle-treated mice were pair-fed to the tirzepatide-treated group to avoid the impact induced by different caloric intakes. Body weight and food intake were monitored daily. Respiratory exchange ratio (RER) was determined in metabolic cages. Fat utilization was calculated based on RER. Parameters of lipid metabolism were evaluated.

RESULTS

Mice receiving i.c.v. administration of tirzepatide exhibited significant reductions in body weight and fat content compared with pair-fed controls. These effects were mediated by increased lipolytic capacity in white adipose tissue and enhanced thermogenesis in brown and beige adipose tissues, leading to decreased RER and increased lipid utilization. Mechanistic investigations revealed that these effects were primarily mediated by sympathetic nervous system innervation of adipose tissues. This innervation, in turn, might be associated with the neuronal activity changes in the dorsomedial hypothalamus and the nucleus of the solitary tract within the hindbrain.

CONCLUSIONS

These findings establish a critical role for tirzepatide in shifting the substrate preference to fat utilization through the central nervous system-adipose tissue axis, promoting weight loss independent of food intake.

GIPR agonism and antagonism decrease body weight and food intake via different mechanisms in male mice

Agonists and antagonists of the glucose-dependent insulinotropic polypeptide receptor (GIPR) enhance body weight loss induced by glucagon-like peptide-1 receptor (GLP-1R) agonism. However, while GIPR agonism decreases body weight and food intake in a GLP-1R-independent manner via GABAergic GIPR+ neurons, it remains unclear whether GIPR antagonism affects energy metabolism via a similar mechanism. Here we show that the body weight and food intake effects of GIPR antagonism are eliminated in mice with global loss of either Gipr or Glp-1r but are preserved in mice with loss of Gipr in either GABAergic neurons of the central nervous system or peripherin-expressing neurons of the peripheral nervous system. Single-nucleus RNA-sequencing shows opposing effects of GIPR agonism and antagonism in the dorsal vagal complex, with antagonism, but not agonism, closely resembling GLP-1R signalling. Additionally, GIPR antagonism and GLP-1R agonism both regulate genes implicated in synaptic plasticity. Collectively, we show that GIPR agonism and antagonism decrease body weight via different mechanisms, with GIPR antagonism, unlike agonism, depending on functional GLP-1R signalling.

GIPR-Ab/GLP-1 peptide-antibody conjugate requires brain GIPR and GLP-1R for additive weight loss in obese mice

Glucose-dependent insulinotropic polypeptide receptor (GIPR) and glucagon-like peptide 1 receptor (GLP-1R) are expressed in the central nervous system (CNS) and regulate food intake. Here, we demonstrate that a peptide-antibody conjugate that blocks GIPR while simultaneously activating GLP-1R (GIPR-Ab/GLP-1) requires both CNS GIPR and CNS GLP-1R for maximal weight loss in obese, primarily male, mice. Moreover, dulaglutide produces greater weight loss in CNS GIPR knockout (KO) mice, and the weight loss achieved with dulaglutide + GIPR-Ab is attenuated in CNS GIPR KO mice. Wild-type mice treated with GIPR-Ab/GLP-1 and CNS GIPR KO mice exhibit similar changes in gene expression related to tissue remodelling, lipid metabolism and inflammation in white adipose tissue and liver. Moreover, GIPR-Ab/GLP-1 is detected in circumventricular organs in the brain and activates c-FOS in downstream neural substrates involved in appetite regulation. Hence, both CNS GIPR and GLP-1R signalling are required for the full weight loss effect of a GIPR-Ab/GLP-1 peptide-antibody conjugate.

GLP-1-based therapies for diabetes, obesity and beyond

Glucagon-like peptide 1 (GLP-1)-based therapies, such as semaglutide and tirzepatide, represent highly effective treatment options for people with type 2 diabetes and obesity, enabling effective control of glucose and weight loss, while reducing cardiovascular and renal morbidity and mortality. The success of these medicines has spurred development of next-generation GLP-1-based drugs, promising greater weight loss, improved tolerability and additional options for the route and frequency of dosing. This Review profiles established and emerging GLP-1-based medicines, discussing optimization of pharmacokinetics and tolerability, engagement of new therapeutically useful pathways and safety aspects. Structurally unique GLP-1-based medicines that achieve substantially greater and rapid weight loss may impact musculoskeletal health, providing a rationale for therapeutics that more selectively target adipose tissue loss while preserving muscle mass and strength. Ongoing clinical trials in peripheral vascular disease, neuropsychiatric and substance use disorders, metabolic liver disease, arthritis, hypertension and neurodegenerative disorders may broaden indications for GLP-1-based therapeutics.

Multi-ancestry sequencing-based genome-wide association study of C-reactive protein in 513,273 genomes

C-reactive protein (CRP) serves as a pivotal marker of systemic inflammation, yet its genetic architecture has predominantly been explored within European populations. Our multi-ancestry sequencing-based genome-wide association study (seqGWAS) meta-analysis encompasses 447,369 Europeans, 10,389 Africans, 9685 Asians, and 9200 Hispanics in the discovery set, and 23,521 Europeans, 7160 Africans, 771 Asians, and 5178 Hispanics in the replication set. We identify 113 independent association signals (Pdiscovery ≤ 5 × 10-9 and Preplication ≤ 0.05), including 21 loci that passed the conditional analysis, among which 3 are European-specific. Cross ancestry fine-mapping pinpoints 19 of 113 independent signals within the 95% credible set. Functional annotation reveals significant enrichment in blood tissue, H3K27me3 histone marks, and exonic regions. Leveraging the Polygenic Priority Score (PoPS) and gene-based analyses, we implicate 151 genes as potential regulators of CRP levels, 55 of which have not been previously reported. Among these, 17 genes and four proteins show causal evidence or strong colocalization with CRP-related pathologies.

Glucagon-like peptide-1 receptor agonists: a review from a cardiovascular perspective

Introduction

Glucagon-like peptide-1 receptor agonists (GLP-1 RA) are novel agents with proven cardiovascular (CV) benefits. GLP-1 RAs have been used for diabetes and found to improve CV outcomes in diabetic and nondiabetic patients. They are authorized for treating obesity. Our narrative review discussed the CV benefits of GLP-1 RAs in terms of controlling CV risk factors and improving CV outcomes in diabetic and nondiabetic patients regardless of their CV history, and the CV perspectives related to their use in clinical practice.

Areas covered

Literature was searched with no limits on date or language, using various combinations of keywords. Data on the CV benefits of GLP-1 RAs and their use in clinical practice were summarized.

Results

Several studies have discussed the CV beneficial effects of GLP-1 RAs in terms of reducing blood pressure, lipid levels, body weight, risk for arrhythmias, reducing the risk of major adverse CV events, and hospital admission for heart failure.

Conclusion

The cardioprotective effects and low risk of hypoglycemia of GLP-1 RAs make them preferred agents in any multidisciplinary approach aiming to reduce CV disease burden and improve prognosis. Cardiologists are encouraged to strongly consider the CV benefits of GLP-1 RAs in their risk-reduction strategies.

Dual and Triple Gut Peptide Agonists on the Horizon for the Treatment of Type 2 Diabetes and Obesity. An Overview of Preclinical and Clinical Data

PURPOSE OF REVIEW

The development of long-acting incretin receptor agonists represents a significant advance in the fight against the concurrent epidemics of type 2 diabetes mellitus (T2DM) and obesity. The aim of the present review is to examine the cellular processes underlying the actions of these new, highly significant classes of peptide receptor agonists. We further explore the potential actions of multi-agonist drugs as well as the mechanisms through which gut-brain communication can be used to achieve long-term weight loss without negative side effects.

RECENT FINDINGS

Several unimolecular dual-receptor agonists have shown promising clinical efficacy studies when used alone or in conjunction with approved glucose-lowering medications. We also describe the development of incretin-based pharmacotherapy, starting with exendin- 4 and ending with the identification of multi-incretin hormone receptor agonists, which appear to be the next major step in the fight against T2DM and obesity. We discuss the multi-agonists currently in clinical trials and how each new generation of these drugs improves their effectiveness. Since most glucose-dependent insulinotropic polypeptide (GIP) receptor: glucagon-like peptide- 1 receptor (GLP- 1) receptor: glucagon receptor triagonists compete in efficacy with bariatric surgery, the success of these agents in preclinical models and clinical trials suggests a bright future for multi-agonists in the treatment of metabolic diseases. To fully understand how these treatments affect body weight, further research is needed.

The neurobiology of overeating

Food intake serves to maintain energy homeostasis; however, overeating can result in obesity, which is associated with serious health complications. In this review, we explore the intricate relationship between overeating, obesity, and the underlying neurobiological mechanisms. We review the homeostatic and hedonic feeding systems, highlighting the role of the hypothalamus and reward systems in controlling food intake and energy balance. Dysregulation in both these systems leads to overeating, as seen in genetic syndromes and environmental models affecting appetite regulation when consuming highly palatable food. The concept of "food addiction" is examined, drawing parallels to drug addiction. We discuss the cellular substrate for addiction-related behavior and current pharmacological obesity treatments-in particular, GLP-1 receptor agonists-showcasing synaptic plasticity in the context of overeating and palatable food exposure. A comprehensive model integrating insights from addiction research is proposed to guide effective interventions for maladaptive feeding behaviors. Ultimately, unraveling the neurobiological basis of overeating holds promise for addressing the pressing public health issue of obesity.

The unexpected role of GIP in transforming obesity treatment

Despite sharing incretin activity with glucagon-like peptide 1 (GLP-1), the development of gastric inhibitory polypeptide (GIP)-based drugs has been hindered by the minor effects of native GIP on appetite and body weight and genetic studies associating loss-of-function with reduced obesity. Yet, pharmacologically optimized GIP-based molecules have demonstrated profound weight lowering benefits of GIPR agonism when combined with GLP-1-based therapies, which has re-energized deeper exploration of the molecular mechanisms and downstream signaling of GIPR. Interestingly, both GIPR agonism and antagonism offer metabolic benefits, leading to differing viewpoints on how to target GIPR therapeutically. Here we summarize the emerging evidence about the tissue-specific mechanisms that positions GIP-based therapies as important targets for the next generation of anti-obesity and metabolic therapies.

Targeting central pathway of Glucose-Dependent Insulinotropic Polypeptide, Glucagon and Glucagon-like Peptide-1 for metabolic regulation in obesity and type 2 diabetes

Obesity and type 2 diabetes are significant public health challenges that greatly impact global well-being. The development of effective therapeutic strategies has become more and more concentrated on the central nervous system and metabolic regulation. The primary pharmaceutical interventions for the treatment of obesity and uncontrolled hyperglycemia are now generally considered to be incretin-based anti-diabetic treatments, particularly glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide receptor agonists. This is a result of their substantial influence on the central nervous system and the consequent effects on energy balance and glucose regulation. It is increasingly crucial to understand the neural pathways of these pharmaceuticals. The purpose of this review is to compile and present the most recent central pathways regarding glucagon-like peptide-1, glucose-dependent insulinotropic polypeptide and glucagon receptors, with a particular emphasis on central metabolic regulation.

The role of GIPR in food intake control

Glucose-dependent insulinotropic polypeptide (GIP) is one of two incretin hormones playing key roles in the control of food intake, nutrient assimilation, insulin secretion and whole-body metabolism. Recent pharmacological advances and clinical trials show that unimolecular co-agonists that target the receptors for the incretins - GIP and glucagon-like peptide 1 (GLP-1) - offer more effective treatment strategies for obesity and type 2 diabetes mellitus (T2D) compared with GLP-1 receptor (GLP1R) agonists alone, suggesting previously underappreciated roles of GIP in regulating food intake and body weight. The mechanisms by which GIP regulates energy balance remain controversial as both agonism and antagonism of the GIP receptor (GIPR) produce weight loss and improve metabolic outcomes in preclinical models. Recent studies have shown that GIPR signalling in the central nervous system (CNS), especially in regions of the brain that regulate energy balance, is essential for its action on appetite regulation. This finding has sparked interest in understanding the mechanisms by which GIP engages brain circuits to reduce food intake and body weight. In this review, we present key knowledge around the actions of GIP on food intake regulation and the potential mechanisms by which GIPR and GIPR/GLP1R agonists may regulate energy balance.

Weight Reduction with GLP-1 Agonists and Paths for Discontinuation While Maintaining Weight Loss

Worldwide, nearly 40% of adults are overweight and 13% are obese. Health consequences of excess weight include cardiovascular diseases, type 2 diabetes, dyslipidemia, and increased mortality. Treating obesity is challenging and calorie restriction often leads to rebound weight gain. Treatments such as bariatric surgery create hesitancy among patients due to their invasiveness. GLP-1 medications have revolutionized weight loss and can reduce body weight in obese patients by between 15% and 25% on average after about 1 year. Their mode of action is to mimic the endogenous GLP-1, an intestinal hormone that regulates glucose metabolism and satiety. However, GLP-1 drugs carry known risks and, since their use for weight loss is recent, may carry unforeseen risks as well. They carry a boxed warning for people with a personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia syndrome type 2. Gastrointestinal adverse events (nausea, vomiting, diarrhea) are fairly common while pancreatitis and intestinal obstruction are rarer. There may be a loss of lean body mass as well as premature facial aging. A significant disadvantage of using these medications is the high rate of weight regain when they are discontinued. Achieving success with pharmacologic treatment and then weaning to avoid future negative effects would be ideal.

Why does GLP-1 agonist combined with GIP and/or GCG agonist have greater weight loss effect than GLP-1 agonist alone in obese adults without type 2 diabetes?

Obesity is a chronic condition demanding effective treatment strategies, among which pharmacotherapy plays a critical role. As glucagon-like peptide-1 (GLP-1) agonist approved by the Food and Drug Administration (FDA) for long-term weight management in adults with obesity, liraglutide and semaglutide have great weight loss effect through reducing food intake and delaying gastric emptying. The emergence of unimolecular polypharmacology, which utilizes single molecules to simultaneously target multiple receptors or pathways, marked a revolutionary improvement in GLP-1-based obesity pharmacotherapy. The dual agonist tirzepatide activates both GLP-1 and glucose-dependent insulinotropic polypeptide (GIP) receptors and has shown enhanced potency for weight loss compared to conventional GLP-1 mono agonist. Furthermore, emerging data suggests that unimolecular GLP-1/glucagon (GCG) dual agonist, as well as GLP-1/GIP/GCG triple agonist, may offer superior weight loss efficacy over GLP-1 agonist. This review summarizes the comprehensive mechanisms underlying the pronounced advantages of GLP-1/GIP dual agonist, GLP-1/GCG dual agonist and GLP-1/GIP/GCG triple agonist over GLP-1 mono agonist in weight reduction in obese adults without type 2 diabetes. A deeper understanding of these unimolecular multitargeting GLP-1-based agonists will provide insights for their clinical application and guide the development of new drugs for obesity treatment.

What is the pipeline for future medications for obesity?

Obesity is a chronic disease associated with increased risk of obesity-related complications and mortality. Our better understanding of the weight regulation mechanisms and the role of gut-brain axis on appetite has led to the development of safe and effective entero-pancreatic hormone-based treatments for obesity such as glucagon-like peptide-1 (GLP-1) receptor agonists (RA). Semaglutide 2.4 mg once weekly, a subcutaneously administered GLP-1 RA approved for obesity treatment in 2021, results in 15-17% mean weight loss (WL) with evidence of cardioprotection. Oral GLP-1 RA are also under development and early data shows similar WL efficacy to semaglutide 2.4 mg. Looking to the next generation of obesity treatments, combinations of GLP-1 with other entero-pancreatic hormones with complementary actions and/or synergistic potential (such as glucose-dependent insulinotropic polypeptide (GIP), glucagon, and amylin) are under investigation to enhance the WL and cardiometabolic benefits of GLP-1 RA. Tirzepatide, a dual GLP-1/GIP receptor agonist has been approved for glycaemic control in type 2 diabetes as well as for obesity management leading in up to 22.5% WL in phase 3 obesity trials. Other combinations of entero-pancreatic hormones including cagrisema (GLP-1/amylin RA) and the triple agonist retatrutide (GLP-1/GIP/glucagon RA) have also progressed to phase 3 trials as obesity treatments and early data suggests that may lead to even greater WL than tirzepatide. Additionally, agents with different mechanisms of action to entero-pancreatic hormones (e.g. bimagrumab) may improve the body composition during WL and are in early phase clinical trials. We are in a new era for obesity pharmacotherapy where combinations of entero-pancreatic hormones approach the WL achieved with bariatric surgery. In this review, we present the efficacy and safety data for the pipeline of obesity pharmacotherapies with a focus on entero-pancreatic hormone-based treatments and we consider the clinical implications and challenges that the new era in obesity management may bring.

Advances in Oral Biomacromolecule Therapies for Metabolic Diseases

Metabolic diseases like obesity and diabetes are on the rise, and therapies with biomacromolecules (such as proteins, peptides, antibodies, and oligonucleotides) play a crucial role in their treatment. However, these drugs are traditionally injected. For patients with chronic diseases (e.g., metabolic diseases), long-term injections are accompanied by inconvenience and low compliance. Oral administration is preferred, but the delivery of biomacromolecules is challenging due to gastrointestinal barriers. In this article, we introduce the available biomacromolecule drugs for the treatment of metabolic diseases. The gastrointestinal barriers to oral drug delivery and strategies to overcome these barriers are also explored. We then discuss strategies for alleviating metabolic defects, including glucose metabolism, lipid metabolism, and energy metabolism, with oral biomacromolecules such as insulin, glucagon-like peptide-1 receptor agonists, proprotein convertase subtilisin/kexin type 9 inhibitors, fibroblast growth factor 21 analogues, and peptide YY analogues.

Otolaryngologic Side Effects of GLP-1 Receptor Agonists

OBJECTIVES

With the increasing use of GLP-1 receptor agonist (GLP-1 RA) drugs for weight loss and diabetes management, concerns have been raised regarding their potential side effects. We aim to assess the frequency of otolaryngologic adverse events (AEs).

STUDY DESIGN

Retrospective analysis of national registry.

METHODS

The Food and Drug Administration's Adverse Event Reporting System (FAERS) database was queried for events related to the GLP-1 RA: exenatide, liraglutide, dulaglutide, semaglutide, and tirzepatide from 1 year after their approval until the end of 2023. AEs were collected and sub-stratified according to anatomic site. Reporting odds ratios (ROR) and proportional reporting ratios (PRR) were determined for all AEs.

RESULTS

The number of AEs reported from all drugs within this study totaled 9,746. Significant signal ratios were defined as a PRR≥2 and a lower CI ROR >1. Medullary thyroid carcinoma (MTC) and papillary thyroid carcinoma (PTC) had the highest signals and were significant in virtually all medications. This was followed by GERD which also had very high signal ratios and was significant in all drugs assessed. Semaglutide also had significant signals in anosmia, dry mouth, dysgeusia, and Bell's palsy. Liraglutide had significance in both signals in dysphonia, dysgeusia, tinnitus, and Bell's palsy. This was followed by exenatide which also included dysgeusia and hearing disability.

CONCLUSIONS

GLP-1 RA were associated with various otolaryngologic AEs, with significant signals observed for semaglutide and liraglutide. GERD, MTC, and PTC were of significance in all GLP-1 RA in this study. Monitoring these AEs is recommended.

LEVEL OF EVIDENCE

4 Laryngoscope, 2025.

Hormonal regulation of human adipose tissue lipolysis: impact of adipose GIP system in overweight and obesity

OBJECTIVE

Given the promising effects of GLP-1/GIP/glucagon receptor triagonists on weight loss in animals and humans, improved understanding of underlying mechanism is required. We investigated a direct lipolytic effect of a specific GLP-1/GIP/glucagon receptor triagonist on human adipose tissue to disentangle central and peripheral effects as potential drivers of weight loss.

DESIGN AND METHODS

Isolated primary adipocytes from subcutaneous adipose tissue biopsies of 22 non-diabetic subjects [63.0 (57.0-69.5) years] were incubated with increasing concentrations of isoprenaline, GLP-1, GIP, glucagon, or a GLP-1/GIP/glucagon receptor triagonist. Glycerol concentration was measured following stimulation to assess lipolysis. mRNA expression of adipose tissue receptors was analyzed in parallel.

RESULTS

Glycerol concentration only increased by isoprenaline, GIP (+13%), and GLP-1/GIP/glucagon receptor triagonist (+28%) but not by GLP-1 or glucagon. This effect was not related to age or body mass index (BMI). Higher adipose tissue GIP receptor mRNA expression was related to elevated glycerol release after GIP and GLP-1/GIP/glucagon receptor triagonist stimulation.

CONCLUSIONS

Direct lipolytic effects of GIP seem to exist in human subcutaneous adipose tissue. This might be targetable by multiple receptor agonists, especially with a high GIP receptor affinity. Such a mechanism can potentiate the beneficial effect on weight loss and will therefore represent a promising target of future research.

CLINICAL TRIAL REGISTRATION NUMBER

The trial was registered at German Clinical Trials Register (drks.de) as DRKS00010049.

Chronic GIPR agonism results in pancreatic islet GIPR functional desensitisation

OBJECTIVES

There is renewed interest in targeting the glucose-dependent insulinotropic polypeptide receptor (GIPR) for treatment of obesity and type 2 diabetes. G-protein coupled receptor desensitisation is suggested to reduce the long-term efficacy of glucagon-like-peptide 1 receptor (GLP-1R) agonists and may similarly affect the efficacy of GIPR agonists. We explored the extent of pancreatic GIPR functional desensitisation with sustained agonist exposure.

METHODS

A long-acting GIPR agonist, GIP108, was used to probe the effect of sustained agonist exposure on cAMP responses in dispersed pancreatic islets using live cell imaging, with rechallenge cAMP responses after prior agonist treatment used to quantify functional desensitisation. Receptor internalisation and β-arrestin-2 activation were investigated in vitro using imaging-based assays. Pancreatic mouse GIPR desensitisation was assessed in vivo via intraperitoneal glucose tolerance testing.

RESULTS

GIP108 treatment led to weight loss and improved glucose homeostasis in mice. Prolonged exposure to GIPR agonists produced homologous functional GIPR desensitisation in isolated islets. GIP108 pre-treatment in vivo also reduced the subsequent anti-hyperglycaemic response to GIP re-challenge. GIPR showed minimal agonist-induced internalisation or β-arrestin-2 activation.

CONCLUSIONS

Although GIP108 chronic treatment improved glucose tolerance, it also resulted in partial desensitisation of the pancreatic islet GIPR. This suggests that ligands with reduced desensitisation tendency might lead to improved in vivo efficacy. Understanding whether pancreatic GIPR desensitisation affects the long-term benefits of GIPR agonists in humans is vital to design effective metabolic pharmacotherapies.

Differences in GIP Receptor Expression by Feeding Status in the Mouse Brain

Gastric inhibitory polypeptide (GIP) contributes to energy metabolism regulation. We investigated differences in GIP receptor expression in the brain by feeding status among lean and obese mice and the effect of acute central GIP administration on the expression of appetite-regulating hypothalamic neuropeptides. We divided the mice into four groups: fed/lean, fasted/lean, fed/obese, and fasted/obese. The arcuate nucleus (ARC), paraventricular nucleus of the hypothalamus, and nucleus of the solitary tract in the brainstem were harvested. GIP (6 nmol) or saline was injected for the acute intracerebroventricular administration test, followed by the collection of hypothalamic tissue after 2 h. Fed/obese mice had higher ARC GIP receptor mRNA levels than fasted/obese and lean mice. This difference was not observed among lean mice by feeding status. Obese mice had higher blood GIP levels than lean mice. Fed/obese mice had higher blood GIP levels than fasted/obese mice. This difference was not observed among lean mice by feeding status. GIP administration significantly increased proopiomelano-cortin (Pomc) mRNA levels (GIP: 7.59 ± 0.14; saline: 3.44 ± 1.38 arbitrary units; p = 0.030). Increased GIP receptor expression in the ARC in obese mice indicates its central nervous system involvement in energy balance regulation. GIP potentially regulates POMC-mediated appetite regulation in the hypothalamus. It is possible that POMC neurons are targets of GIP action in the brain.

Exploring the molecular mechanisms of tirzepatide in alleviating metabolic dysfunction-associated fatty liver in mice through integration of metabolomics, lipidomics, and proteomics

Clinical studies have suggested that tirzepatide may also possess hepatoprotective effects; however, the molecular mechanisms underlying this association remain unclear. In our study, we performed biochemical analyses of serum and histopathological examinations of liver tissue in mice. To preliminarily explore the molecular mechanisms of tirzepatide on metabolic dysfunction-associated fatty liver disease (MAFLD), liquid chromatography-mass spectrometry (LC-MS) was employed for comprehensive metabolomic, lipidomic, and proteomic analyses in MAFLD mice fed a high-fat diet (HFD). The results demonstrated that tirzepatide significantly reduced serum levels of alanine transaminase (ALT) and aspartate transaminase (AST), as well as hepatic triglycerides (TG) and total cholesterol (TC), indicating its efficacy in treating MAFLD. Further findings revealed that tirzepatide reduced fatty acid uptake by downregulating Cd36 and Fabp2/4, as well as enhance the mitochondrial-lysosomal function by upregulating Lamp1/2. In addition, tirzepatide promoted cholesterol efflux and reduced cholesterol reabsorption by upregulating the expression of Hnf4a, Abcg5, and Abcg8. These results suggest that tirzepatide exerts its therapeutic effects on MAFLD by reducing fatty acid uptake, promoting cholesterol excretion, and enhancing mitochondrial-lysosomal function, providing a theoretical basis for a comprehensive understanding of tirzepatide.

The GIP receptor activates futile calcium cycling in white adipose tissue to increase energy expenditure and drive weight loss in mice

Obesity is a chronic disease that contributes to the development of insulin resistance, type 2 diabetes (T2D), and cardiovascular risk. Glucose-dependent insulinotropic polypeptide (GIP) receptor (GIPR) and glucagon-like peptide-1 (GLP-1) receptor (GLP-1R) co-agonism provide an improved therapeutic profile in individuals with T2D and obesity when compared with selective GLP-1R agonism. Although the metabolic benefits of GLP-1R agonism are established, whether GIPR activation impacts weight loss through peripheral mechanisms is yet to be fully defined. Here, we generated a mouse model of GIPR induction exclusively in the adipocyte. We show that GIPR induction in the fat cell protects mice from diet-induced obesity and triggers profound weight loss (∼35%) in an obese setting. Adipose GIPR further increases lipid oxidation, thermogenesis, and energy expenditure. Mechanistically, we demonstrate that GIPR induction activates SERCA-mediated futile calcium cycling in the adipocyte. GIPR activation further triggers a metabolic memory effect, which maintains weight loss after the transgene has been switched off, highlighting a unique aspect in adipocyte biology. Collectively, we present a mechanism of peripheral GIPR action in adipose tissue, which exerts beneficial metabolic effects on body weight and energy balance.

Incretin-based therapies for the management of cardiometabolic disease in the clinic: Past, present, and future

Among newer classes of drugs for type 2 diabetes mellitus (T2DM), glucagon-like peptide 1 receptor agonists (GLP-1 RAs) are incretin-based agents that lower both blood sugar levels and promote weight loss. They do so by activating pancreatic GLP-1 receptors (GLP-1R) to promote glucose-dependent insulin release and inhibit glucagon secretion. They also act on receptors in the brain and gastrointestinal tract to suppress appetite, slow gastric emptying, and delay glucose absorption. Phase 3 clinical trials have shown that GLP-1 RAs improve cardiovascular outcomes in the setting of T2DM or overweight/obesity in people who have, or are at high risk of having atherosclerotic cardiovascular disease. This is largely driven by reductions in ischemic events, although emerging evidence also supports benefits in other cardiovascular conditions, such as heart failure with preserved ejection fraction. The success of GLP-1 RAs has also seen the evolution of other incretin therapies. Tirzepatide has emerged as a dual glucose-dependent insulinotropic polypeptide (GIP)/GLP-1 RA, with more striking effects on glycemic control and weight reduction than those achieved by isolated GLP-1R agonism alone. This consists of lowering glycated hemoglobin levels by more than 2% and weight loss exceeding 15% from baseline. Here, we review the pharmacological properties of GLP-1 RAs and tirzepatide and discuss their clinical effectiveness for T2DM and overweight/obesity, including their ability to reduce adverse cardiovascular outcomes. We also delve into the mechanistic basis for these cardioprotective effects and consider the next steps in implementing existing and future incretin-based therapies for the broader management of cardiometabolic disease.

The power of three: Retatrutide's role in modern obesity and diabetes therapy

The increasing prevalence of obesity and type 2 diabetes mellitus has resulted in a significant challenge to public health throughout the globe. It required the development of novel therapeutic approaches. Retatrutide is a groundbreaking triple agonist that targets glucagon receptors, gastric inhibitory polypeptide, and glucagon-like peptide-1. Retatrutide's complex mechanism of action involves a synergistic interaction among these receptors, resulting in increased insulin secretion, improved glucose homeostasis, and refined appetite modulation. Clinical trials in phases 1 to 3 have demonstrated significant efficacy, highlighted by significant reductions in body weight and favorable glycemic control outcomes. Additionally, retatrutide shows promise in mitigating cardiovascular risk factors and addressing metabolic dysfunction-associated steatotic liver disease. However, careful attention is required to delineate its long-term safety profile, explore its potential in special populations, unravel its adjunctive therapeutic roles, and elucidate its mechanisms in pediatric cohorts. As a transformative therapeutic modality, retatrutide represents a beacon of hope, signifying transformative changes in the management landscape of obesity and type 2 diabetes mellitus (T2DM), and warranting continued exploration and refinement in clinical practice. This narrative review examines the therapeutic potential of retatrutide in the management of obesity and T2DM.

Recent achievements and future directions of anti-obesity medications

Pharmacological management of obesity long suffered from a reputation of a 'Mission Impossible,' with inefficient weight loss and/or unacceptable tolerability. However, the tide has turned with recent progress in biochemical engineering and the development of long-acting agonists at the receptor for glucagon-like peptide-1 (GLP-1), and with unimolecular peptides that simultaneously possess activity at the receptors for GLP-1, the glucose-dependent insulinotropic polypeptide (GIP) and glucagon. Some of these novel therapeutics not only improve body weight and glycemic control in individuals with obesity and type 2 diabetes with hitherto unmet efficacy and tolerable safety, but also exhibit potential therapeutic value in diverse areas such as neurodegenerative diseases, fatty liver disease, dyslipidemia, atherosclerosis, and cardiovascular diseases. In this review, we highlight recent advances in incretin-based therapies and discuss their pharmacological potential within and beyond the treatment of obesity and diabetes, as well as their limitations in use, side effects, and underlying molecular mechanisms.

Effects of the switch from dulaglutide to tirzepatide on glycemic control, body weight, and fatty liver: a retrospective study

Objectives

Tirzepatide belongs to a new class of anti-diabetic agents that stimulate both glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide receptors, resulting in a greater blood glucose-lowering effect and body weight reduction than glucagon-like peptide-1 analogs. However, data on the effects of switching from glucagon-like peptide-1 analogs to tirzepatide on the blood glucose level, body weight, and liver functions are unavailable.

Methods

Data from 40 patients with type 2 diabetes who received a prescription change from dulaglutide to tirzepatide were retrospectively analyzed at the 3 and 6 months after the switch. The analyzed data included glycosylated hemoglobin, body weight, aspartate aminotransferase, alanine aminotransferase, γ-glutamyl transpeptidase levels, and fibrosis-4 index.

Results

Six months after the treatment switch, average reductions of 1.2% and 3.6 kg were observed in the glycosylated hemoglobin and body weight, respectively. The change in glycosylated hemoglobin level was negatively correlated with the baseline glycosylated hemoglobin level. However, body weight reduction was observed regardless of the baseline characteristics. Moreover, the aspartate aminotransferase, alanine aminotransferase, and γ-glutamyl transpeptidase levels decreased 6 months after the switch. Reductions in alanine aminotransferase levels was greater in patients with higher baseline aspartate aminotransferase, alanine aminotransferase, and γ-glutamyl transpeptidase levels. Although the fibrosis-4 index did not improve during the study period, a trend toward a decrease was observed in patients with a higher baseline fibrosis-4 index.

Conclusions

Switching from dulaglutide to tirzepatide has a beneficial effect on the blood glucose level, body weight, and liver function in patients with type 2 diabetes.

GLP-1 and GIP agonism has no direct actions in human hepatocytes or hepatic stellate cells

The use of incretin agonists for managing metabolic dysfunction-associated steatohepatitis (MASH) is currently experiencing considerable interest. However, whether these compounds have a direct action on MASH is still under debate. This study aims to investigate whether GLP-1R/GIPR agonists act directly in hepatocytes and hepatic stellate cells (HSCs). For this, human hepatocyte and HSCs lines, as well as primary human hepatocytes and HSCs treated with Liraglutide, Acyl-GIP or the GLP-1/GIP dual agonist (MAR709) were used. We show that the concentrations of each compound, which were effective in insulin release, did not induce discernible alterations in either hepatocytes or HSCs. In hepatocytes displaying elevated fatty acid content after the treatment with oleic acid and palmitic acid, none of the three compounds reduced lipid concentration. Similarly, in HSCs activated with transforming growth factor-β (TGFb), Liraglutide, Acyl-GIP and MAR709 failed to ameliorate the elevated expression of fibrotic markers. The three compounds were also ineffective in phosphorylating CREB, which mediates insulinotropic actions, in both hepatocytes and HSCs. These findings indicate that incretin agonists have no direct actions in human hepatocytes or hepatic stellate cells, suggesting that their beneficial effects in patients with MASH are likely mediated indirectly, potentially through improvements in body weight, insulin resistance and glycemic control.

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.

Unraveling the impaired incretin effect in obesity and type 2 diabetes: Key role of hyperglycemia-induced unscheduled glycolysis and glycolytic overload

Glucagon-like peptide-1 (GLP-1) agonists and GLP-1 and glucose-dependent insulinotropic polypeptide (GIP) co-agonists are major treatment options for subjects with obesity and patients with type 2 diabetes mellitus (T2DM). They counter without addressing the mechanistic cause of the impaired incretin effect associated with obesity and T2DM. Incretin effect impairment is characterized by decreased secretion of incretins from enteroendocrine cells and incretin resistance of pancreatic β-cells. It is linked to hyperglycemia. We present evidence that subversion of the gating of glucose entry into glycolysis, mainly by glucokinase (hexokinase-4), during persistent hyperglycemia in enteroendocrine cells, pancreatic β- and α-cells and appetite-regulating neurons contributes to the biochemical mechanism of the impaired incretin effect. Unscheduled glycolysis and glycolytic overload thereby produced decreases cell signalling of incretin secretion to glucose and other secretion stimuli and incretin receptor responses. This mechanism provides a guide for development of alternative therapies targeting recovery of the impaired incretin effect.

Efficacy and Safety of GLP-1 Medicines for Type 2 Diabetes and Obesity

The development of glucagon-like peptide 1 receptor agonists (GLP-1RA) for type 2 diabetes and obesity was followed by data establishing the cardiorenal benefits of GLP-1RA in select patient populations. In ongoing trials investigators are interrogating the efficacy of these agents for new indications, including metabolic liver disease, peripheral artery disease, Parkinson disease, and Alzheimer disease. The success of GLP-1-based medicines has spurred the development of new molecular entities and combinations with unique pharmacokinetic and pharmacodynamic profiles, exemplified by tirzepatide, a GIP-GLP-1 receptor coagonist. Simultaneously, investigational molecules such as maritide block the GIP and activate the GLP-1 receptor, whereas retatrutide and survodutide enable simultaneous activation of the glucagon and GLP-1 receptors. Here I highlight evidence establishing the efficacy of GLP-1-based medicines, while discussing data that inform safety, focusing on muscle strength, bone density and fractures, exercise capacity, gastrointestinal motility, retained gastric contents and anesthesia, pancreatic and biliary tract disorders, and the risk of cancer. Rapid progress in development of highly efficacious GLP-1 medicines, and anticipated differentiation of newer agents in subsets of metabolic disorders, will provide greater opportunities for use of personalized medicine approaches to improve the health of people living with cardiometabolic disorders.

NK2R control of energy expenditure and feeding to treat metabolic diseases

The combination of decreasing food intake and increasing energy expenditure represents a powerful strategy for counteracting cardiometabolic diseases such as obesity and type 2 diabetes1. Yet current pharmacological approaches require conjugation of multiple receptor agonists to achieve both effects2-4, and so far, no safe energy-expending option has reached the clinic. Here we show that activation of neurokinin 2 receptor (NK2R) is sufficient to suppress appetite centrally and increase energy expenditure peripherally. We focused on NK2R after revealing its genetic links to obesity and glucose control. However, therapeutically exploiting NK2R signalling has previously been unattainable because its endogenous ligand, neurokinin A, is short-lived and lacks receptor specificity5,6. Therefore, we developed selective, long-acting NK2R agonists with potential for once-weekly administration in humans. In mice, these agonists elicit weight loss by inducing energy expenditure and non-aversive appetite suppression that circumvents canonical leptin signalling. Additionally, a hyperinsulinaemic-euglycaemic clamp reveals that NK2R agonism acutely enhances insulin sensitization. In diabetic, obese macaques, NK2R activation significantly decreases body weight, blood glucose, triglycerides and cholesterol, and ameliorates insulin resistance. These findings identify a single receptor target that leverages both energy-expending and appetite-suppressing programmes to improve energy homeostasis and reverse cardiometabolic dysfunction across species.

Research Progress on Peptide Drugs for Type 2 Diabetes and the Possibility of Oral Administration

Diabetes is a global disease that can lead to a range of complications. Currently, the treatment of type 2 diabetes focuses on oral hypoglycemic drugs and insulin analogues. Studies have shown that drugs such as oral metformin are useful in the treatment of diabetes but can limit the liver's ability to release sugar. The development of glucose-lowering peptides has provided new options for the treatment of type 2 diabetes. Peptide drugs have low oral utilization due to their easy degradation, short half-life, and difficulty passing through the intestinal mucosa. Therefore, improving the oral utilization of peptide drugs remains an urgent problem. This paper reviews the research progress of peptide drugs in the treatment of diabetes mellitus and proposes that different types of nano-formulation carriers, such as liposomes, self-emulsifying drug delivery systems, and polymer particles, should be combined with peptide drugs for oral administration to improve their absorption in the gastrointestinal tract.

Growth hormone promotes the reconstruction of injured axons in the hypothalamo-neurohypophyseal system

JOURNAL/nrgr/04.03/01300535-202410000-00026/figure1/v/2024-02-06T055622Z/r/image-tiff Previous studies have shown that growth hormone can regulate hypothalamic energy metabolism, stress, and hormone release. Therefore, growth hormone has great potential for treating hypothalamic injury. In this study, we established a specific hypothalamic axon injury model by inducing hypothalamic pituitary stalk electric lesions in male mice. We then treated mice by intraperitoneal administration of growth hormone. Our results showed that growth hormone increased the expression of insulin-like growth factor 1 and its receptors, and promoted the survival of hypothalamic neurons, axonal regeneration, and vascular reconstruction from the median eminence through the posterior pituitary. Altogether, this alleviated hypothalamic injury-caused central diabetes insipidus and anxiety. These results suggest that growth hormone can promote axonal reconstruction after hypothalamic injury by regulating the growth hormone-insulin-like growth factor 1 axis.

The role of incretin receptor agonists in the treatment of obesity

INTRODRODUCTION

Obesity and its associated metabolic conditions have become a significant global health problem in recent years, with many people living with obesity fulfilling criteria for pharmacological treatment. The development of the glucagon-like peptide-1 receptor agonists for chronic weight management has triggered new interest in the incretins and other hormones as targets for obesity, and investigations into dual and triple co-agonists.

METHODS

The objective of this narrative review was to summarize the available data on approved and emerging incretin-based agents for the treatment of obesity.

RESULTS

In clinical trials of currently available agents in people with overweight or obesity, weight loss of between 6% and 21% of baseline body weight has been observed, with between 23% and 94% of participants achieving 10% or higher weight loss, depending on the study and the agent used. Favourable outcomes have also been seen with regard to cardiovascular risk and outcomes, diabetes prevention, metabolic dysfunction-associated steatotic liver disease/steatohepatitis and prevention of weight regain after metabolic surgery. Limitations associated with these agents include high costs, the potential for weight regain once treatment is stopped, the potential loss of lean body mass and gastrointestinal adverse events; potential issues with respect to gallbladder and biliary diseases require further investigation.

CONCLUSIONS

Many dual and triple co-agonists are still in development, and more data are needed to assess the efficacy, safety and tolerability of these emerging therapies versus the established incretin-based therapies; however, data are promising, and further results are eagerly awaited.

Safflower yellow and its main component hydroxysafflor yellow A alleviate hyperleptinemia in diet-induced obesity mice through a dual inhibition of the GIP-GIPR signaling axis

Glucose-dependent insulinotropic polypeptide (GIP) is a gastrointestinal hormone secreted by K cells in the small intestine and is considered an obesity-promoting factor. In this study, we systematically investigated the anti-obesity effects of intragastric safflower yellow (SY)/hydroxysafflor yellow A (HSYA) and the underlying mechanism for the first time. Our results showed that intragastric SY/HSYA, rather than an intraperitoneal injection, notably decreased serum GIP levels and GIP staining in the small intestine in diet-induced obese (DIO) mice. Moreover, intragastric SY/HSYA was also first found to significantly suppress GIP receptor (GIPR) signaling in both the hypothalamus and subcutaneous White adipose tissue. Our study is the first to show that intragastric SY/HSYA obviously reduced food intake and body weight gain in leptin sensitivity experiments and decreased serum leptin levels in DIO mice. Further experiments demonstrated that SY treatment also significantly reduced leptin levels, whereas the inhibitory effect of SY on leptin levels was reversed by activating GIPR in 3 T3-L1 adipocytes. In addition, intragastric SY/HSYA had already significantly reduced serum GIP levels and GIPR expression before the serum leptin levels were notably changed in high-fat-diet-fed mice. These findings suggested that intragastric SY/HSYA may alleviate diet-induced obesity in mice by ameliorating hyperleptinemia via dual inhibition of the GIP-GIPR axis.

The Impact of Gastrointestinal Hormones on Human Adipose Tissue Function

BACKGROUND

Obesity is a global issue, the development of which depends on many interacting factors. Among these, hormones secreted in the gastrointestinal tract play an important role. The aim of this review was to assess the impact of these hormones on the functions of adipose tissue.

METHODS

The analysis was based on the latest research concerning both adipose tissue and gastrointestinal hormones.

RESULTS

It was found that these hormones can significantly affect adipose tissue, both directly and indirectly. Some hormones, when secreted in excess, can stimulate adipose tissue formation processes, while others can inhibit them. The impact of hormones depends on the location and type of adipose tissue as well as the physiological state of the body. It should also be noted that no hormone acts in isolation but in close cooperation with other factors.

CONCLUSIONS

The relationship between gastrointestinal hormones and adipose tissue, and their role in obesity, is a complex and evolving field of study. Further research is necessary, particularly into the interactions between hormones and other factors, as well as their mutual interactions.

Yoyo Dieting, Post-Obesity Weight Loss, and Their Relationship with Gut Health

Excessive body weight is associated with many chronic metabolic diseases and weight loss, so far, remains the gold standard treatment. However, despite tremendous efforts exploring optimal treatments for obesity, many individuals find losing weight and maintaining a healthy body weight difficult. Weight loss is often not sustainable resulting in weight regain and subsequent efforts to lose weight. This cyclic pattern of weight loss and regain is termed "yoyo dieting" and predisposes individuals to obesity and metabolic comorbidities. How yoyo dieting might worsen obesity complications during the weight recurrence phase remains unclear. In particular, there is limited data on the role of the gut microbiome in yoyo dieting. Gut health distress, especially gut inflammation and microbiome perturbation, is strongly associated with metabolic dysfunction and disturbance of energy homeostasis in obesity. In this review, we summarise current evidence of the crosstalk between the gastrointestinal system and energy balance, and the effects of yoyo dieting on gut inflammation and gut microbiota reshaping. Finally, we focus on the potential effects of post-dieting weight loss in improving gut health and identify current knowledge gaps within the field, including gut-derived peptide hormones and their potential suitability as targets to combat weight regain, and how yoyo dieting and associated changes in the microbiome affect the gut barrier and the enteric nervous system, which largely remain to be determined.

Approved and Emerging Hormone-Based Anti-Obesity Medications: A Review Article

Obesity is a heterogeneous, complex, and chronic disease that has a detrimental impact on disability-adjusted life years across the globe. Recent advancements in our understanding of gut-brain communication at the molecular level have driven the development of next-generation anti-obesity medications (AOMs). Glucagon-like peptide-1 receptor agonists (GLP1RAs) remain the front-runners in this rapidly evolving landscape of hormone-based AOMs. Two GLP1RAs, namely Liraglutide and Semaglutide, have been approved by the Food and Drug Administration (FDA) and European Medicine Agency (EMA) for use in clinical practice for weight loss. Three oral GLP1RAs, namely Semaglutide, Danuglipron, and Orforglipron, are undergoing advanced clinical trials in individuals with obesity. Amylin receptor agonist (AMYRA) Cagrilintide, when used alone or in combination with Semaglutide, has demonstrated substantial weight reduction in clinical trials. Tirzepatide, a dual agonist for the glucose-dependent insulinotropic polypeptide (GIP) and GLP-1 receptors, has been observed to be associated with a significant placebo-subtracted weight reduction of 17.8% in a 72-week randomized controlled trial. Novel approaches targeting glucagon signalling have also yielded promising preliminary results. Three long-acting GLP1R/glucagon receptor (GCGR) dual agonists, namely Survodutide, Mazdutide, and Pemvidutide, exhibited significant weight loss in clinical trials. Retatrutide, a GLP1R/GCGR/GIPR tri-agonist, has been associated with a placebo-subtracted weight reduction of -22.1% in a 48-week phase-II trial. As a note of caution, long-term data on such medications' safety and cardiovascular benefits is yet to be ascertained. Our review provides a comprehensive overview of the approved and emerging hormone-based AOMs, highlighting the diversity of options that might become available in the near future.

Experimental colonization with H. hepaticus, S. aureus and R. pneumotropicus does not influence the metabolic response to high-fat diet or incretin-analogues in wildtype SOPF mice

OBJECTIVES

We here assessed whether typical pathogens of laboratory mice affect the development of diet-induced obesity and glucose intolerance, and whether colonization affects the efficacy of the GLP-1R agonist liraglutide and of the GLP-1/GIP co-agonist MAR709 to treat obesity and diabetes.

METHODS

Male C57BL/6J mice were experimentally infected with Helicobacter hepaticus, Rodentibacter pneumotropicus and Staphylococcus aureus and compared to a group of uninfected specific and opportunistic pathogen free (SOPF) mice. The development of diet-induced obesity and glucose intolerance was monitored over a period of 26 weeks. To study the influence of pathogens on drug treatment, mice were then subjected for 6 days daily treatment with either the GLP-1 receptor agonist liraglutide or the GLP-1/GIP co-agonist MAR709.

RESULTS

Colonized mice did not differ from SOPF controls regarding HFD-induced body weight gain, food intake, body composition, glycemic control, or responsiveness to treatment with liraglutide or the GLP-1/GIP co-agonist MAR709.

CONCLUSIONS

We conclude that the occurrence of H. hepaticus, R. pneumotropicus and S. aureus does neither affect the development of diet-induced obesity or type 2 diabetes, nor the efficacy of GLP-1-based drugs to decrease body weight and to improve glucose control in mice.

Tanycytic transcytosis inhibition disrupts energy balance, glucose homeostasis and cognitive function in male mice

OBJECTIVES

In Western society, high-caloric diets rich in fats and sugars have fueled the obesity epidemic and its related disorders. Disruption of the body-brain communication, crucial for maintaining glucose and energy homeostasis, arises from both obesogenic and genetic factors, leading to metabolic disorders. Here, we investigate the role of hypothalamic tanycyte shuttles between the pituitary portal blood and the third ventricle cerebrospinal fluid in regulating energy balance.

METHODS

We inhibited vesicle-associated membrane proteins (VAMP1-3)-mediated release in tanycytes by expressing the botulinum neurotoxin type B light chain (BoNT/B) in a Cre-dependent manner in tanycytes. This was achieved by injecting either TAT-Cre in the third ventricle or an AAV1/2 expressing Cre under the control of the tanycyte-specific promoter iodothyronine deiodinase 2 into the lateral ventricle of adult male mice.

RESULTS

In male mice fed a standard diet, targeted expression of BoNT/B in adult tanycytes blocks leptin transport into the mediobasal hypothalamus and results in normal-weight central obesity, including increased food intake, abdominal fat deposition, and elevated leptin levels but no marked change in body weight. Furthermore, BoNT/B expression in adult tanycytes promotes fatty acid storage, leading to glucose intolerance and insulin resistance. Notably, these metabolic disturbances occur despite a compensatory increase in insulin secretion, observed both in response to exogenous glucose boluses in vivo and in isolated pancreatic islets. Intriguingly, these metabolic alterations are associated with impaired spatial memory in BoNT/B-expressing mice.

CONCLUSIONS

These findings underscore the central role of tanycytes in brain-periphery communication and highlight their potential implication in the age-related development of type 2 diabetes and cognitive decline. Our tanycytic BoNT/B mouse model provides a robust platform for studying how these conditions progress over time, from prediabetic states to full-blown metabolic and cognitive disorders, and the mechanistic contribution of tanycytes to their development. The recognition of the impact of tanycytic transcytosis on hormone transport opens new avenues for developing targeted therapies that could address both metabolic disorders and their associated cognitive comorbidities, which often emerge or worsen with advancing age.