Next generation GLP-1/GIP/glucagon triple agonists normalize body weight in obese mice

Advancing Cardiovascular, Kidney, and Metabolic Medicine: A Narrative Review of Insights and Innovations for the Future

Cardiovascular, kidney and metabolic (CKM) conditions are interrelated, significantly contributing to morbidity, mortality and healthcare burden. Despite therapeutic advances, traditional disease-specific approaches often fail to address their complex interplay. Key therapeutic agents-including glucagon-like peptide-1 receptor agonists (GLP-1 RAs), dual GLP-1/glucose-dependent insulinotropic polypeptide RAs, sodium glucose co-transporter inhibitors and the nonsteroidal mineralocorticoid receptor antagonist (MRA) finerenone-offer multi-organ benefits. Emerging therapies, such as triple receptor agonists and second-generation MRAs, target new pathways further expanding treatment options for CKM conditions. A holistic CKM management approach must address and recognise that conditions such as metabolic dysfunction-associated steatotic liver disease, metabolic dysfunction-associated steatohepatitis, obstructive sleep apnoea and obesity are part of the CKM spectrum. Frailty assessment is also important alongside CKM conditions, warranting comprehensive geriatric assessment and deprescribing when appropriate. Multidisciplinary care-including lifestyle interventions, pathway redesign, pharmacological advances and novel technologies-is essential for improving outcomes. As the CKM landscape evolves, future strategies should prioritise early intervention, personalised treatment and addressing unmet needs in high-risk populations. This review advocates for an integrated CKM framework, exploring treatment strategies, emerging therapies and technological innovations. It also examines the role of artificial intelligence and digital health tools in risk stratification, early diagnosis and long-term condition management, alongside ethical and regulatory considerations.

Unlocking the multifaceted roles of GLP-1: Physiological functions and therapeutic potential

Glucagon (GCG) like peptide 1 (GLP-1) has emerged as a powerful player in regulating metabolism and a promising therapeutic target for various chronic diseases. This review delves into the physiological roles of GLP-1, exploring its impact on glucose homeostasis, insulin secretion, and satiety. We examine the compelling evidence supporting GLP-1 receptor agonists (GLP-1RAs) in managing type 2 diabetes (T2D), obesity, and other diseases. The intricate molecular mechanisms underlying GLP-1RAs are explored, including their interactions with pathways like extracellular signal-regulated kinase 1/2 (ERK1/2), activated protein kinase (AMPK), cyclic adenine monophosphate (cAMP), mitogen-activated protein kinase (MAPK), and protein kinase C (PKC). Expanding our understanding, the review investigates the potential role of GLP-1 in cancers. Also, microribonucleic acid (RNA) (miRNAs), critical regulators of gene expression, are introduced as potential modulators of GLP-1 signaling. We delve into the link between miRNAs and T2D obesity and explore specific miRNA examples influencing GLP-1R function. Finally, the review explores the rationale for seeking alternatives to GLP-1RAs and highlights natural products with promising GLP-1 modulatory effects.

A once-daily GLP-1/GIP/glucagon receptor tri-agonist (NN1706) lowers body weight in rodents, monkeys and humans

Single molecules that combine complementary modes of action with glucagon-like peptide-1 receptor (GLP-1R) agonism are best-in-class therapeutics for obesity treatment. NN1706 (MAR423, RO6883746) is a fatty-acylated tri-agonist designed for balanced activity at GLP-1R and glucose-dependent insulinotropic peptide receptor (GIPR) with lower relative potency at the glucagon receptor (GcgR). Obese mice, rats and non-human primates dosed with NN1706 showed significant body weight reductions and improved glycemic control. In human participants with overweight or obesity, daily subcutaneous NN1706 treatment resulted in substantial body weight loss in a dose-dependent manner without impairing glycemic control (NCT03095807, NCT03661879). However, increased heart rate was observed across NN1706 treatment cohorts, which challenges further clinical development of NN1706.

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.

A Comprehensive Review on the Pharmacokinetics and Drug-Drug Interactions of Approved GLP-1 Receptor Agonists and a Dual GLP-1/GIP Receptor Agonist

Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) are peptide-derived analogs that were initially investigated to treat type 2 diabetes. Recently, a drug targeting the receptors of both GLP-1 and glucose-dependent insulinotropic polypeptide (GIP) (tirzepatide) has been introduced to the market, and its indications have expanded to include treating obesity. Here, we review the pharmacokinetics, pharmacokinetic drug-drug interactions (DDIs), and pharmacokinetic modeling approaches of four currently available GLP-1 RAs (exenatide, liraglutide, dulaglutide, and semaglutide) and tirzepatide. To address the extremely short half-life (2 min) of native human GLP-1, structural modifications have been applied to GLP-1 RAs and a dual GLP-1/GIP RA. These include amino acid sequence substitutions, fatty acid conjugation using a linker, and fusion with albumin or the IgG fragment crystallizable (Fc) region, resulting in minimal metabolism and renal excretion. Due to their diverse structures, the pharmacokinetic profiles vary, and a prolonged half-life may be associated with an increased risk of adverse events. Clinically significant drug-metabolizing enzyme- and transporter-mediated DDIs are yet to be reported. Mechanism-of-action-mediated DDIs are currently limited to those involving delayed gastric emptying, and most studies have found them to be clinically insignificant. However, significant changes in exposure were observed for oral contraceptives and levothyroxine following the administration of tirzepatide and oral semaglutide, respectively, indicating the need for close monitoring in these instances. Thirty models have been developed to predict pharmacokinetics and physiologically based pharmacokinetic modeling can be useful for assessing mechanism-of-action-mediated DDIs. Alterations in the volume of distribution and clearance resulting from other mechanisms of action (eg, reduced fat mass, changes in cytochrome P450 activity, and glomerular filtration rate) are key factors in determining pharmacokinetics. However, the DDIs mediated by these factors remain poorly understood and require further investigation to ensure that GLP-1 RAs can be safely used with concomitant medications.

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.

Rational design of dual-agonist peptides targeting GLP-1 and NPY2 receptors for regulating glucose homeostasis and body weight with minimal nausea and emesis

There is an urgent need for effective treatments targeting comorbidities of type 2 diabetes (T2DM) and obesity. Developing dual agonists of glucagon-like peptide 1 receptor (GLP-1R) and neuropeptide Y receptor type 2 (NPY2R) with combined PYY3-36 and GLP-1 bioactivity is promising. However, designing such dual agonists that effectively control glycemia and reduce weight while minimizing gastrointestinal side effects is challenging. In this study, we systematically evaluated the side effects induced by co-administering various GLP-1R agonists and PYY3-36 analogue. Our findings revealed that different GLP-1R agonist-PYY analogue combinations elicited gastrointestinal side effects of varying intensities. Among these, the co-administration of bullfrog GLP-1 analogue (bGLP-1) with PYY3-36 analogue resulted in lower gastrointestinal side effects. Thus, bGLP-1 was selected as the preferred candidate for designing dual GLP-1R/NPY2R agonists. Through stepwise structural design, optimization of linker arms, and durability enhancements, coupled with in vitro receptor screening, the novel peptide bGLP/PYY-19 emerged as the lead candidate. Notably, experimental results in mice and rats showed a significant reduction in emesis with bGLP/PYY-19 compared to semaglutide and bGLP-1 long-acting analogue (LAbGLP-1). Furthermore, bGLP/PYY-19 significantly outperformed semaglutide and LAbGLP-1 in reducing body weight in diet-induced obese (DIO) mice, without inducing nausea-associated behavior. These findings underscore the potential of dual-targeting single peptide conjugates as a promising strategy for developing glucoregulatory treatments that offer superior weight loss benefits and are better tolerated compared to treatments targeting GLP-1R alone.

Estimation of Glucose Absorption, Insulin Sensitivity, and Glucose Effectiveness From the Oral Glucose Tolerance Test

CONTEXT

Glucose tolerance during an oral glucose tolerance test (OGTT) is affected by variations in glucose effectiveness (GE) and glucose absorption and thus affects minimal model calculations of insulin sensitivity (SI). The widely used OGTT SI by Dalla Man et al does not account for variances in GE and glucose absorption.

OBJECTIVE

To develop a novel model that concurrently assesses SI, GE, and glucose absorption.

METHODS

In this cross-sectional study conducted at an academic medical center, 17 subjects without abnormalities on OGTT (controls) and 88 subjects with diabetes underwent a 75-gram 120-minute 6-timepoint OGTT. The SI from the Dalla Man model was validated with the novel model SI using Bland-Altman limits of agreement methodology. Comparisons of SI, GE, and gastrointestinal glucose half-life (GIGt1/2), a surrogate measure for glucose absorption, were made between subjects with diabetes and controls.

RESULTS

In controls and diabetes, the novel model SI was higher than the current OGTT model. The SI from both controls (ƿ=0.90, P < .001) and diabetes (ƿ=0.77, P < .001) has high agreement between models. GE was higher in diabetes (median: 0.021 1/min, interquartile range [IQR]: 0.020-0.022) compared to controls (median: 0.016 1/min, IQR: 0.015-0.017), P = .02. GIGt1/2 was shorter in diabetes (median: 48.404 min, IQR: 54.424-39.426) than in controls (median: 55.086 min, IQR: 61.368-48.502) without statistical difference.

CONCLUSION

Our novel model SI has a good correlation with SI from the widely used Dalla Man's model while concurrently calculating GE and GIGt1/2. Thus, besides estimating SI, our novel model can quantify differences in insulin-independent glucose disposal mechanisms important for diabetes pathophysiology.

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.

An oral liraglutide nanomicelle formulation conferring reduced insulin-resistance and long-term hypoglycemic and lipid metabolic benefits

Type 2 diabetes is a chronic disease characterized by insulin resistance and often worsened by obesity. Effective management involves the use of glucagon-like peptide-1 receptor agonists (GLP-1 RAs) to assist with glycemic control and weight management. However, these drugs must be administered subcutaneously due to their low oral bioavailability. We developed an oral liraglutide (LRG) formulation by electrostatic complexation of GLP-1 RA with bile acid derivatives and nanomicelle (NM) formation, with non-ionic surfactant n-dodecyl-β-d-maltoside (DDM). The optimized formulation, LDD[1:2:4]-NM, had a mean particle size of 75.9 ± 5.60 nm and a permeability 1347 % higher than that of unformulated LRG when tested in Caco-2/HT29-MTX-E12 cell monolayers. In rats, oral bioavailability was 4.63-fold higher than that of unformulated LRG (1.11 ± 0.20 % vs. 5.14 ± 0.63 %). The absorption mechanism included clathrin-mediated endocytosis, macropinocytosis, and an ASBT-mediated pathway. A 12-week oral treatment consisting of a daily dose of 20 mg LDD[1:2:4]-NM/kg significantly reduced glycohemoglobin levels, a marker of diabetic control, and the HOMA-IR index, a marker of insulin resistance. The weight of epididymal and inguinal white adipose tissue and brown adipose tissue (BAT) was also reduced. Moreover, LDD[1:2:4]-NM had a greater impact on BAT activation, pro-inflammatory gene expression, and lipid metabolism than subcutaneous LRG. This study showed that an oral NM formulation can efficiently deliver LRG. Long-term treatment led to improved hyperglycemic effects, insulin resistance, and modulated lipid metabolism. LDD[1:2:4]-NM is thus a promising oral therapeutic option for the management of type 2 diabetes, potentially transforming treatment paradigms based on the availability of a more convenient administration route.

Tirzepatide alleviates oxidative stress and inflammation in diabetic nephropathy via IL-17 signaling pathway

Oxidative stress (OS) and inflammation play essential roles in the development of diabetic nephropathy (DN). Tirzepatide (TZP) has a protective effect in diabetes. However, its underlying mechanism in DN remains unclear. DN model mice were induced by intraperitoneal injection of streptozotocin (STZ; 60 mg/kg), followed by administration of different doses of TZP (3 and 10 nmol/kg) via intraperitoneal injection for 8 weeks. The effects of TZP on DN were evaluated by detecting DN-related biochemical indicators, kidney histopathology, apoptosis, OS, and inflammation levels. Additionally, to further reveal the potential mechanism, we investigated the role of TZP in modulating the IL-17 pathway. TZP reduced serum creatinine (sCR), blood urea nitrogen (BUN), and advanced glycosylation end products (AGEs) levels, while simultaneously promoting insulin secretion in diabetic mice. Additionally, TZP attenuated tubular and glomerular injury and reduced renal apoptosis levels. Further studies found that TZP increased the levels of SOD and CAT, and decreased MDA. Meanwhile, TZP also reduced the expression of pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6) in both mouse serum and kidney homogenates. TZP effectively inhibited the IL-17 pathway, and subsequent intervention with an IL-17 pathway agonist (IL-17A) reversed the suppressive effects of TZP on OS and inflammation. TZP can improve DN by inhibiting OS and inflammation through the suppression of the IL-17 pathway.

Mechanisms of GLP-1 Receptor Agonist-Induced Weight Loss: A Review of Central and Peripheral Pathways in Appetite and Energy Regulation

Glucagon-like peptide-1 (GLP-1) receptor agonists (RAs) have become central in managing obesity and type 2 diabetes, primarily through appetite suppression and metabolic regulation. This review explores the mechanisms underlying GLP-1 RA-induced weight loss, focusing on central and peripheral pathways. Centrally, GLP-1 RAs modulate brain regions controlling appetite, influencing neurotransmitter and peptide release to regulate hunger and energy expenditure. Peripherally, GLP-1 RAs improve glycemic control by enhancing insulin secretion, reducing glucagon release, delaying gastric emptying, and regulating gut hormones. They also reduce triglycerides and low-density lipoprotein cholesterol, mitigate adipose tissue inflammation, and minimize ectopic fat deposition, promoting overall metabolic health. Emerging dual and triple co-agonists, targeting GLP-1 alongside glucose-dependent insulinotropic polypeptide, and glucagon pathways, may enhance weight loss and metabolic flexibility. Understanding these mechanisms is crucial as the therapeutic landscape evolves, offering clinicians and researchers insights to optimize the efficacy of current and future obesity treatments.

GLP-1/GIP dual agonist tirzepatide normalizes diabetic nephropathy via PI3K/AKT mediated suppression of oxidative stress

BACKGROUND

Effective therapeutic approaches for the treatment of diabetic nephropathy (DN) with irreversible deterioration of renal function are currently lacking. In this study, we aimed to investigate the ability of the glucagon-likepeptide-1 (GLP-1)/ gastric inhibitory polypeptide (GIP) dual agonist, tirzepatide to alleviate DN in mice and its underlying mechanisms.

METHODS

We investigated the reno-protective effect of semaglutide and tirzepatide in a mouse model of DN, an insulin-treated positive control group was also included. Indicators of diabetic kidney injury and oxidative stress biomarkers were also assessed. RNA-seq analysis of renal tissue was conducted to explore the potential mechanism of action of tirzepatide and in vitro cell experiments were performed to validate its pathway.

RESULTS

In DN mice, one-third the dose of tirzepatide was consistent with that of semaglutide in lowering glucose, body weight, and urine albumin-to-creatine ratio (UACR) and in improving antioxidative stress activities, while insulin treatment could not effectively restore the UACR. RNA-seq analysis revealed that the PI3K-AKT signaling pathway was significantly enriched after tirzepatide treatment compared with that in the DN model. Confirmatory experiments demonstrated that tirzepatide regulated oxidative stress and the PI3K-AKT pathway in mouse podocyte cell-5 cells exposed to high glucose. Further mechanistic validation suggested that the antioxidative activity of tirzepatide was reversed by PI3K inhibitor.

CONCLUSION

These findings expand the potential effects and mechanics of tirzepatide in the treatment of DN, which may provide a novel therapeutic approach and therapeutic target for DN treatment.

Weight Loss Blockbuster Development: A Role for Unimolecular Polypharmacology

Obesity and type 2 diabetes mellitus (T2DM) impact more than 2.5 billion adults worldwide, necessitating innovative therapeutic approaches. Unimolecular polypharmacology, which involves designing single molecules to target multiple receptors or pathways simultaneously, has revolutionized treatment strategies. Blockbuster drugs such as tirzepatide and retatrutide have shown unprecedented success in managing obesity and T2DM, demonstrating superior efficacy compared to conventional single agonists. Tirzepatide, in particular, has garnered tremendous attention for its remarkable effectiveness in promoting weight loss and improving glycemic control, while offering additional cardiovascular and renal benefits. Despite their promises, such therapeutic agents also face challenges that include gastrointestinal side effects, patient compliance issues, and body weight rebound after cessation of the treatment. Nonetheless, the development of these therapies marks a significant leap forward, underscoring the transformative potential of unimolecular polypharmacology in addressing metabolic diseases and paving the way for future innovations in personalized medicine.

Effects of once-weekly subcutaneous retatrutide on weight and metabolic markers: A systematic review and meta-analysis of randomized controlled trials

Aim

To assess the effects of once-weekly subcutaneous retatrutide on weight and metabolic markers and the occurrence of side effects in patients with overweight, obesity and/or type 2 diabetes (T2D).

Methods

PubMed, Embase, Cochrane Library, and ClinicalTrials.gov databases were systematically searched for placebo-controlled, randomized clinical trials (RCTs) published up until February 23, 2024. Weighted mean differences (WMDs) for continuous outcomes and risk ratios (RRs) for binary endpoints were computed, with 95 % confidence intervals (CIs).

Results

A total of three studies were included, comprising 640 patients, of whom 510 were prescribed retatrutide. Compared with placebo, retatrutide significantly reduced body weight (WMD -10.66 kg; 95 % CI -17.63, -3.69), body mass index (WMD -4.53 kg/m2; 95 % CI -7.51, -1.55), and waist circumference (WMD -6.61 cm; 95 % CI -13.17, -0.05). In addition, retatrutide significantly increased the proportion of patients who achieved a weight reduction of ≥5 % (RR 2.92; 95 % CI 2.17-3.93), ≥10 % (RR 9.32; 95 % CI 4.56-19.06), ≥15 % (RR 18.40; 95 % CI 6.00-56.42), and ≥20 % (RR 16.61; 95 % CI 4.17-66.12).

Conclusions

In this meta-analysis, the use of once-weekly subcutaneous retatrutide was associated with a significant reduction in body weight and improvement of metabolic markers in patients with overweight, obesity and/or T2D, compared with placebo, with an increase in non-severe gastrointestinal and hypersensitivity adverse events. Phase 3 RCTs are expected to shed further light on the efficacy and safety of once-weekly subcutaneous retatrutide over the long term.

A Case of Severe Cholestatic Hepatitis Induced by a Novel Dual Agonist of Glucagon-like Peptide-1 and Glucose-dependent Insulinotropic Polypeptide Receptors

Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) receptor agonists are increasingly used in the management of type 2 diabetes mellitus and obesity due to their ability to stimulate insulin secretion, delay gastric emptying, and suppress appetite. The combination of GLP-1 and GIP agonists improves glycemic control and promotes weight loss. However, the introduction of these novel therapies has raised safety concerns, including the risk of cholestatic hepatitis. We report a case of a patient with obesity who was prescribed a GLP-1/GIP dual-receptor agonist as part of his treatment regimen. Importantly, both before the initiation of this therapy and during the course of treatment, the patient was not taking any other medications. Shortly after receiving four doses of the therapy, the patient developed symptoms of severe cholestatic hepatitis, including jaundice and elevated liver enzyme levels. During hospitalization, no alternative causes for the condition were identified, and a liver biopsy confirmed the diagnosis of drug-induced cholestatic hepatitis. This is the first recorded case of cholestatic hepatitis induced by a GLP-1/GIP dual agonist, and it aimed to raise global awareness of this potential side effect.

The dual GLP-1/glucagon receptor agonist G49 mimics bariatric surgery effects by inducing metabolic rewiring and inter-organ crosstalk

Bariatric surgery is effective for the treatment and remission of obesity and type 2 diabetes, but pharmacological approaches which exert similar metabolic adaptations are needed to avoid post-surgical complications. Here we show how G49, an oxyntomodulin (OXM) analog and dual glucagon/glucagon-like peptide-1 receptor (GCGR/GLP-1R) agonist, triggers an inter-organ crosstalk between adipose tissue, pancreas, and liver which is initiated by a rapid release of free fatty acids (FFAs) by white adipose tissue (WAT) in a GCGR-dependent manner. This interactome leads to elevations in adiponectin and fibroblast growth factor 21 (FGF21), causing WAT beiging, brown adipose tissue (BAT) activation, increased energy expenditure (EE) and weight loss. Elevation of OXM, under basal and postprandial conditions, and similar metabolic adaptations after G49 treatment were found in plasma from patients with obesity early after metabolic bariatric surgery. These results identify G49 as a potential pharmacological alternative sharing with bariatric surgery hormonal and metabolic pathways.

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.

Isoquinoline small molecule ligands are agonists and probe-dependent allosteric modulators of the glucagon subfamily of GPCRs

Class B1 G protein-coupled receptors (GPCRs) are peptide hormone receptors and well validated therapeutic targets, however development of non-peptide drugs targeting this class of receptors is challenging. Recently, a series of isoquinoline-based derivates were reported in the patent literature as allosteric ligands for the glucagon receptor subfamily, and two compounds, LSN3451217 and LSN3556672, were used to facilitate structural studies with the glucagon-like peptide-1 receptor (GLP-1R) and glucose dependent insulinotropic peptide receptor (GIPR) bound to orthosteric agonists. Here we pharmacologically characterized stereoisomers of LSN3451217 and LSN3556672, across the class B1 GPCR family. This revealed LSN3556672 isomers are agonists for the glucagon receptor (GCGR), GLP-1R, GIPR and the calcitonin receptor (CTR), albeit the degree of agonism varied at each receptor. In contrast, LSN3451217 isomers were more selective agonists at the GLP-1R, with lower potency at the GCGR and CTR and no activity at the GIPR. All compounds also modulated peptide-mediated cyclic adenosine monophosphate (cAMP) signaling at the GIPR, and to a lesser extent the GLP-1R, in a probe-dependent manner, with modest positive allosteric modulation observed for some peptides, and negligible effects observed with other peptides. In contrast neutral or weak negative/positive allosteric modulation was observed with peptides assessed at the GCGR and CTR. This study expands our knowledge on class B1 GPCR allosteric modulation and may have implications for future structural and drug discovery efforts targeting the class B1 GPCR subfamily.

Efficacy and safety of GLP-1 analog ecnoglutide in adults with type 2 diabetes: a randomized, double-blind, placebo-controlled phase 2 trial

Glucagon-like peptide-1 (GLP-1) analogs are important therapeutics for type 2 diabetes and obesity. Ecnoglutide (XW003) is a novel, long-acting GLP-1 analog. We conducted a Phase 2, randomized, double-blind, placebo-controlled study enrolling 145 adults with T2DM. Participants were randomized to 0.4, 0.8, or 1.2 mg ecnoglutide or placebo as once-weekly injections for 20 weeks. The primary objective was to evaluate the efficacy of ecnoglutide, as measured by HbA1c change from baseline at Week 20. Secondary endpoints included body weight, glucose and lipid parameters, as well as safety. We show that, at end of treatment, the 0.4, 0.8, and 1.2 mg groups had statistically significant HbA1c reductions from baseline of -1.81%, -1.90%, and -2.39%, respectively, compared to -0.55% for placebo (P < 0.0001). At end of treatment, 71.9% of the 1.2 mg group had HbA1c ≤ 6.5% versus 9.1% on placebo, and 33.3% had body weight reductions ≥5% versus 3.0% for placebo. Ecnoglutide was generally safe and well tolerated. China Drug Trials Registry CTR20211014.

Glucagon-like peptide-1 receptor: mechanisms and advances in therapy

The glucagon-like peptide-1 (GLP-1) receptor, known as GLP-1R, is a vital component of the G protein-coupled receptor (GPCR) family and is found primarily on the surfaces of various cell types within the human body. This receptor specifically interacts with GLP-1, a key hormone that plays an integral role in regulating blood glucose levels, lipid metabolism, and several other crucial biological functions. In recent years, GLP-1 medications have become a focal point in the medical community due to their innovative treatment mechanisms, significant therapeutic efficacy, and broad development prospects. This article thoroughly traces the developmental milestones of GLP-1 drugs, from their initial discovery to their clinical application, detailing the evolution of diverse GLP-1 medications along with their distinct pharmacological properties. Additionally, this paper explores the potential applications of GLP-1 receptor agonists (GLP-1RAs) in fields such as neuroprotection, anti-infection measures, the reduction of various types of inflammation, and the enhancement of cardiovascular function. It provides an in-depth assessment of the effectiveness of GLP-1RAs across multiple body systems-including the nervous, cardiovascular, musculoskeletal, and digestive systems. This includes integrating the latest clinical trial data and delving into potential signaling pathways and pharmacological mechanisms. The primary goal of this article is to emphasize the extensive benefits of using GLP-1RAs in treating a broad spectrum of diseases, such as obesity, cardiovascular diseases, non-alcoholic fatty liver disease (NAFLD), neurodegenerative diseases, musculoskeletal inflammation, and various forms of cancer. The ongoing development of new indications for GLP-1 drugs offers promising prospects for further expanding therapeutic interventions, showcasing their significant potential in the medical field.

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.

Tirzepatide protects against doxorubicin-induced cardiotoxicity by inhibiting oxidative stress and inflammation via PI3K/Akt signaling

BACKGROUND

Doxorubicin (DOX) is a highly effective and widely used cytotoxic agent with application for various malignancies, but it's clinically limited due to its cardiotoxicity Oxidative stress and inflammation were reported to take part in DOX-induced cardiotoxicity. Tirzepatide, a dual glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) receptor agonist has been approved to treat type 2 diabetes. However, its role in DOX-induced cardiotoxicity and the underlying mechanisms has not been explored.

METHODS

The cardioprotective properties of Tirzepatide against DOX-induced cardiotoxicity are examined in this work both in vivo and in vitro. For four weeks, an intraperitoneal injection of 4 mg/kg DOX was used to cause cardiotoxicity in C57BL/6 mice. To ascertain the cardioprotective function and underlying mechanisms of Tirzepatide against DOX-induced cardiotoxicity, mice and H9c2 cells were treated with and without Tirzepatide.

RESULTS

Tirzepatide treatment significantly inhibited DOX-induced oxidative stress, inflammation and cardiac injury. Mechanistically, PI3K/Akt signaling pathway contributes to the protective effect of Tirzepatide against DOX-induced cardiotoxicity and inhibited PI3K/Akt signaling pathway with LY294002 almost blocked its therapeutic effect.

CONCLUSIONS

Collectively, Tirzepatide could alleviate DOX-induced oxidative stress, inflammation and cardiac injury via activating PI3K/Akt signaling pathway and Tirzepatide may be a novel therapeutic target for DOX-induced cardiotoxicity.

Transforming obesity: The advancement of multi-receptor drugs

For more than a century, physicians have searched for ways to pharmacologically reduce excess body fat. The tide has finally turned with recent advances in biochemically engineered agonists for the receptor of glucagon-like peptide-1 (GLP-1) and their use in GLP-1-based polyagonists. These polyagonists reduce body weight through complementary pharmacology by incorporating the receptors for glucagon and/or the glucose-dependent insulinotropic polypeptide (GIP). In their most advanced forms, gut-hormone polyagonists achieve an unprecedented weight reduction of up to ∼20%-30%, offering a pharmacological alternative to bariatric surgery. Along with favorable effects on glycemia, fatty liver, and kidney disease, they also offer beneficial effects on the cardiovascular system and adipose tissue. These new interventions, therefore, hold great promise for the future of anti-obesity medications.

Bridging the gap between GLP1-receptor agonists and cardiovascular outcomes: evidence for the role of tirzepatide

Tirzepatide is a new drug targeting glucagon-like peptide 1(GLP1) and gastric inhibitory polypeptide (GIP) receptors. This drug has demonstrated great potential in improving the clinical outcomes of patients with type 2 diabetes. It can lead to weight loss, better glycemic control, and reduced cardiometabolic risk factors. GLP1 receptor agonists have been proven effective antidiabetic medications with possible cardiovascular benefits. Even though they have been proven to reduce the risk of major adverse cardiovascular events, their effectiveness in treating heart failure is unknown. Unlike traditional GLP1 receptor agonists, tirzepatide is more selective for the GIP receptor, resulting in a more balanced activation of these receptors. This review article discusses the possible mechanisms tirzepatide may use to improve cardiovascular health. That includes the anti-inflammatory effect, the ability to reduce cell death and promote autophagy, and also its indirect effects through blood pressure, obesity, and glucose/lipid metabolism. Additionally, tirzepatide may benefit atherosclerosis and lower the risk of major adverse cardiac events. Currently, clinical trials are underway to evaluate the safety and efficacy of tirzepatide in patients with heart failure. Overall, tirzepatide's dual agonism of GLP1 and GIP receptors appears to provide encouraging cardiovascular benefits beyond glycemic control, offering a potential new therapeutic option for treating cardiovascular diseases and heart failure.

The emerging role of glucagon-like peptide 1 in binge eating

Binge eating is a central component of two clinical eating disorders: binge eating disorder and bulimia nervosa. However, the large treatment gap highlights the need to identify other strategies to decrease binge eating. Novel pharmacotherapies may be one such approach. Glucagon-like peptide-1 (GLP-1) is an intestinal and brain-derived neuroendocrine signal with a critical role in promoting glycemic control through its incretin effect. Additionally, the energy balance effects of GLP-1 are well-established; activation of the GLP-1 receptor (GLP-1R) reduces food intake and body weight. Aligned with these beneficial metabolic effects, there are GLP-1R agonists that are currently used for the treatment of diabetes and obesity. A growing body of literature suggests that GLP-1 may also play an important role in binge eating. Dysregulation of the endogenous GLP-1 system is associated with binge eating in non-human animal models, and GLP-1R agonists may be a promising approach to suppress the overconsumption that occurs during binge eating. Here, we briefly discuss the role of GLP-1 in normal energy intake and reward and then review the emerging evidence suggesting that disruptions to GLP-1 signaling are associated with binge eating. We also consider the potential utility of GLP-1-based pharmacotherapies for reducing binge eating behavior.

Identification and utility exploration of a highly potent and long-acting bullfrog GLP-1 analogue in GLP-1 and amylin combination therapy

This study assesses the efficacy of an innovative therapeutic approach that combines GLP-1 and amylin analogues for weight reduction. Focusing on GLP-1 analogues from bullfrog (Rana catesbeiana), we designed ten bGLP-1 analogues with various modifications. Among them, bGLP-10 showed high potency in binding and activating GLP-1 receptors, with superior albumin affinity. In diet-induced obesity (DIO) mice fed a high-fat diet, bGLP-10 demonstrated significant superiority over semaglutide in reducing blood sugar and food intake at a dose of 10 nmol/kg (P < 0.001). Notably, in a chronic study involving DIO mice, the combination of bGLP-10 with the amylin analogue cagrilintide led to a more substantial weight loss (-38.4%, P < 0.001) compared to either the semaglutide-cagrilintide combination (-23.0%) or cagrilintide (-5.7%), bGLP-10 (-16.1%), and semaglutide (-10.9%) alone. Furthermore, the bGLP-10 and cagrilintide combination exhibited superior glucose control and liver lipid management compared to the semaglutide-cagrilintide combination (P < 0.001). These results highlight bGLP-10's potential in GLP-1 and amylin-based therapies and suggest exploring more GLP-1 analogues from natural sources for anti-obesity and anti-diabetic treatments.

Intra-islet α-cell Gs signaling promotes glucagon release

Glucagon, a hormone released from pancreatic α-cells, is critical for maintaining euglycemia and plays a key role in the pathophysiology of diabetes. To stimulate the development of new classes of therapeutic agents targeting glucagon release, key α-cell signaling pathways that regulate glucagon secretion need to be identified. Here, we focused on the potential importance of α-cell Gs signaling on modulating α-cell function. Studies with α-cell-specific mouse models showed that activation of α-cell Gs signaling causes a marked increase in glucagon secretion. We also found that intra-islet adenosine plays an unexpected autocrine/paracrine role in promoting glucagon release via activation of α-cell Gs-coupled A2A adenosine receptors. Studies with α-cell-specific Gαs knockout mice showed that α-cell Gs also plays an essential role in stimulating the activity of the Gcg gene, thus ensuring proper islet glucagon content. Our data suggest that α-cell enriched Gs-coupled receptors represent potential targets for modulating α-cell function for therapeutic purposes.

Glucagon-like peptide-1 receptor agonists and sodium-glucose cotransporter 2 inhibitors, anti-diabetic drugs in heart failure and cognitive impairment: potential mechanisms of the protective effects

Heart failure and cognitive impairment emerge as public health problems that need to be addressed due to the aging global population. The conditions that often coexist are strongly related to advancing age and multimorbidity. Epidemiological evidence indicates that cardiovascular disease and neurodegenerative processes shares similar aspects, in term of prevalence, age distribution, and mortality. Type 2 diabetes increasingly represents a risk factor associated not only to cardiometabolic pathologies but also to neurological conditions. The pathophysiological features of type 2 diabetes and its metabolic complications (hyperglycemia, hyperinsulinemia, and insulin resistance) play a crucial role in the development and progression of both heart failure and cognitive dysfunction. This connection has opened to a potential new strategy, in which new classes of anti-diabetic medications, such as glucagon-like peptide-1 receptor (GLP-1R) agonists and sodium-glucose cotransporter 2 (SGLT2) inhibitors, are able to reduce the overall risk of cardiovascular events and neuronal damage, showing additional protective effects beyond glycemic control. The pleiotropic effects of GLP-1R agonists and SGLT2 inhibitors have been extensively investigated. They exert direct and indirect cardioprotective and neuroprotective actions, by reducing inflammation, oxidative stress, ions overload, and restoring insulin signaling. Nonetheless, the specificity of pathways and their contribution has not been fully elucidated, and this underlines the urgency for more comprehensive research.

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.

Futile cycles: Emerging utility from apparent futility

Futile cycles are biological phenomena where two opposing biochemical reactions run simultaneously, resulting in a net energy loss without appreciable productivity. Such a state was presumed to be a biological aberration and thus deemed an energy-wasting "futile" cycle. However, multiple pieces of evidence suggest that biological utilities emerge from futile cycles. A few established functions of futile cycles are to control metabolic sensitivity, modulate energy homeostasis, and drive adaptive thermogenesis. Yet, the physiological regulation, implication, and pathological relevance of most futile cycles remain poorly studied. In this review, we highlight the abundance and versatility of futile cycles and propose a classification scheme. We further discuss the energetic implications of various futile cycles and their impact on basal metabolic rate, their bona fide and tentative pathophysiological implications, and putative drug interactions.

Do anti-obesity medical treatments have a direct effect on adipose tissue?

During the past years, several drugs have been developed for the treatment of obesity. Some are already used in clinical practice: orlistat, GLP-1 receptor agonists (RA), GLP-1/GIP biagonists and the melanocortin 4 receptor (MC4R) agonist, setmelanotide. Some should be available in the future: GLP-1/glucagon biagonists, GLP-1/GIP/glucagon triagonists. These drugs act mainly by reducing food intake or fat absorption. However, many of them show specific effects on the adipose tissue. All these drugs show significant reduction of fat mass and, more particularly of visceral fat. If most of the drugs, except orlistat, have been shown to increase energy expenditure in rodents with enhanced thermogenesis, this has not yet been clearly demonstrated in humans. However, biagonists or triagonist stimulating glucagon seem to a have a more potent effect to increase thermogenesis in the adipose tissue and, thus, energy expenditure. Most of these drugs have been shown to increase the production of adiponectin and to reduce the production of pro-inflammatory cytokines by the adipose tissue. GLP-1RAs reduce the size of adipocytes and promote their differentiation. GLP-1RAS and GLP-1/GIP biagonists reduce, in the adipose tissue, the expression of several genes involved in lipogenesis. Further studies are still needed to clarify the precise roles, on the adipose tissue, of these drugs dedicated for the treatment of obesity.

Glucagon-Like Peptide Receptor-1 Agonists Used for Medically-Supervised Weight Loss in Patients With Hip and Knee Osteoarthritis: Critical Considerations for the Arthroplasty Surgeon

Patients with morbid obesity and concomitant hip or knee osteoarthritis represent a challenging patient demographic to treat as these patients often present earlier in life, have more severe symptoms, and have worse surgical outcomes following total hip and total knee arthroplasty. Previously, bariatric and metabolic surgeries represented one of the few weight loss interventions that morbidly obese patients could undergo prior to total joint arthroplasty. However, data regarding the reduction in complications with preoperative bariatric surgery remain mixed. Glucagon-like peptide receptor-1 (GLP-1) agonists have emerged as an effective treatment option for obesity in patients with and without diabetes mellitus. Furthermore, recent data suggest these medications may serve as potential anti-inflammatory and disease-modifying agents for numerous chronic conditions, including osteoarthritis. This review will discuss the GLP-1 agonists and GLP-1/glucose-dependent insulinotropic polypeptide dual agonists currently available, along with GLP-1/glucose-dependent insulinotropic polypeptide/glucagon triple agonists presently being developed to address the obesity epidemic. Furthermore, this review will address the potential problem of GLP-1-related delayed gastric emptying and its impact on the timing of elective total joint arthroplasty. The review aims to provide arthroplasty surgeons with a primer for implementing this class of medication in their current and future practice, including perioperative instructions and perioperative safety considerations when treating patients taking these medications.

The interplay of glucose-dependent insulinotropic polypeptide in adipose tissue

Adipose tissue was once known as a reservoir for energy storage but is now considered a crucial organ for hormone and energy flux with important effects on health and disease. Glucose-dependent insulinotropic polypeptide (GIP) is an incretin hormone secreted from the small intestinal K cells, responsible for augmenting insulin release, and has gained attention for its independent and amicable effects with glucagon-like peptide 1 (GLP-1), another incretin hormone secreted from the small intestinal L cells. The GIP receptor (GIPR) is found in whole adipose tissue, whereas the GLP-1 receptor (GLP-1R) is not, and some studies suggest that GIPR action lowers body weight and plays a role in lipolysis, glucose/lipid uptake/disposal, adipose tissue blood flow, lipid oxidation, and free-fatty acid (FFA) re-esterification, which may or may not be influenced by other hormones such as insulin. This review summarizes the research on the effects of GIP in adipose tissue (distinct depots of white and brown) using cellular, rodent, and human models. In doing so, we explore the mechanisms of GIPR-based medications for treating metabolic disorders, such as type 2 diabetes and obesity, and how GIPR agonism and antagonism contribute to improvements in metabolic health outcomes, potentially through actions in adipose tissues.

Ultra-stable insulin-glucagon fusion protein exploits an endogenous hepatic switch to mitigate hypoglycemic risk

The risk of hypoglycemia and its serious medical sequelae restrict insulin replacement therapy for diabetes mellitus. Such adverse clinical impact has motivated development of diverse glucose-responsive technologies, including algorithm-controlled insulin pumps linked to continuous glucose monitors ("closed-loop systems") and glucose-sensing ("smart") insulins. These technologies seek to optimize glycemic control while minimizing hypoglycemic risk. Here, we describe an alternative approach that exploits an endogenous glucose-dependent switch in hepatic physiology: preferential insulin signaling (under hyperglycemic conditions) versus preferential counter-regulatory glucagon signaling (during hypoglycemia). Motivated by prior reports of glucagon-insulin co-infusion, we designed and tested an ultra-stable glucagon-insulin fusion protein whose relative hormonal activities were calibrated by respective modifications; physical stability was concurrently augmented to facilitate formulation, enhance shelf life and expand access. An N-terminal glucagon moiety was stabilized by an α-helix-compatible Lys 13 -Glu 17 lactam bridge; A C-terminal insulin moiety was stabilized as a single chain with foreshortened C domain. Studies in vitro demonstrated (a) resistance to fibrillation on prolonged agitation at 37 °C and (b) dual hormonal signaling activities with appropriate balance. Glucodynamic responses were monitored in rats relative to control fusion proteins lacking one or the other hormonal activity, and continuous intravenous infusion emulated basal subcutaneous therapy. Whereas efficacy in mitigating hyperglycemia was unaffected by the glucagon moiety, the fusion protein enhanced endogenous glucose production under hypoglycemic conditions. Together, these findings provide proof of principle toward a basal glucose-responsive insulin biotechnology of striking simplicity. The fusion protein's augmented stability promises to circumvent the costly cold chain presently constraining global insulin access.

Significance Statement

The therapeutic goal of insulin replacement therapy in diabetes is normalization of blood-glucose concentration, which prevents or delays long-term complications. A critical barrier is posed by recurrent hypoglycemic events that results in short- and long-term morbidities. An innovative approach envisions co-injection of glucagon (a counter-regulatory hormone) to exploit a glycemia-dependent hepatic switch in relative hormone responsiveness. To provide an enabling technology, we describe an ultra-stable fusion protein containing insulin- and glucagon moieties. Proof of principle was obtained in rats. A single-chain insulin moiety provides glycemic control whereas a lactam-stabilized glucagon extension mitigates hypoglycemia. This dual-hormone fusion protein promises to provide a basal formulation with reduced risk of hypoglycemia. Resistance to fibrillation may circumvent the cold chain required for global access.

Molecular design of peptide therapeutics via N-terminal modification

Glucagon-like peptide-1, glucose-dependent insulinotropic polypeptide, and glucagon are three naturally occurring peptide hormones that mediate glucoregulation. Several agonists representing appropriately modified native ligands have been developed to maximize metabolic benefits with reduced side-effects and many have entered the clinic as type 2 diabetes and obesity therapeutics. In this work, we describe strategies for improving the stability of the peptide ligands by making them refractory to dipeptidyl peptidase-4 catalyzed hydrolysis and inactivation. We describe a series of alkylations with variations in size, shape, charge, polarity, and stereochemistry that are able to engender full activity at the receptor(s) while simultaneously resisting enzyme-mediated degradation. Utilizing this strategy, we offer a novel method of modulating receptor activity and fine-tuning pharmacology without a change in peptide sequence.

Semaglutide alleviates gut microbiota dysbiosis induced by a high-fat diet

This study investigated the effects of semaglutide (Sema) on the gut microbiota of obese mice induced with high-fat diet (HFD). Male C57BL/6 J mice aged 6 weeks were enrolled and randomly distributed to four groups, which were provided with a normal control diet (NCD,NCD + Sema) and a 60% proportion of a high-fat diet (HFD,HFD + Sema), respectively. HFD was given for 10 weeks to develop an obesity model and the intervention was lasted for 18 days. The results showed semaglutide significantly reduced body weight gain, areas under the curve (AUC) of glucose tolerance test and insulin resistance test, as well as adipose tissue weight in mice. Semaglutide effectively reduced lipid deposition and lipid droplet formation in the liver of obese mice, and regulated the expression of genes related to abnormal blood glucose regulation. Additionally, semaglutide influenced the composition of gut microbiota, mitigating the microbial dysbiosis induced by a high-fat diet by impacting the diversity of the gut microbiota. After the high-fat diet intervention, certain strains such as Akkermansia, Faecalibaculum, and Allobaculum were significantly decreased, while Lachnospiraceae and Bacteroides were significantly increased. However, the application of semaglutide restored the lost flora and suppressed excessive bacterial abundance. Moreover, semaglutide increased the content of tight junction proteins and repaired the damage to intestinal barrier function caused by the high-fat diet intervention. Furthermore, correlation analysis revealed inverse relationship among Akkermansia levels and weight gain, blood glucose levels, and various obesity indicators. Correlation analysis also showed that Akkermansia level was negatively correlated with weight gain, blood glucose levels and a range of obesity indicators. This phenomenon may explain the anti-obesity effect of semaglutide, which is linked to alterations in gut microbiota, specifically an increase in the abundance of Akkermansia. In summary, our findings indicate that semaglutide has the potential to alleviate gut microbiota dysbiosis, and the gut microbiota may contribute to the obesity-related effects of this drug.

Duodenal enteroendocrine cells and GIP as treatment targets for obesity and type 2 diabetes

The duodenum is an important source of endocrine and paracrine signals controlling digestion and nutrient disposition, notably including the main incretin hormone glucose-dependent insulinotropic polypeptide (GIP). Bariatric procedures that prevent nutrients from contact with the duodenal mucosa are particularly effective interventions to reduce body weight and improve glycaemic control in obesity and type 2 diabetes. These procedures take advantage of increased nutrient delivery to more distal regions of the intestine which enhances secretion of the other incretin hormone glucagon-like peptide-1 (GLP-1). Preclinical experiments have shown that either an increase or a decrease in the secretion or action of GIP can decrease body weight and blood glucose in obesity and non-insulin dependent hyperglycaemia, but clinical studies involving administration of GIP have been inconclusive. However, a synthetic dual agonist peptide (tirzepatide) that exerts agonism at receptors for GIP and GLP-1 has produced marked weight-lowering and glucose-lowering effects in people with obesity and type 2 diabetes. This appears to result from chronic biased agonism in which the novel conformation of the peptide triggers enhanced signalling by the GLP-1 receptor through reduced internalisation while reducing signalling by the GIP receptor directly or via functional antagonism through increased internalisation and degradation.

A Robust Platform for the Molecular Design of Potent, Protease-Stable, Long-Acting GIP Analogues

Glucose-dependent insulinotropic peptide (GIP) is a 42-amino acid peptide hormone that regulates postprandial glucose levels. GIP binds to its cognate receptor, GIPR, and mediates metabolic physiology by improved insulin sensitivity, β-cell proliferation, increased energy consumption, and stimulated glucagon secretion. Dipeptidyl peptidase-4 (DPP4) catalyzes the rapid inactivation of GIP within 6 min in vivo. Here, we report a molecular platform for the design of GIP analogues that are refractory to DPP4 action and exhibit differential activation of the receptor, thus offering potentially hundreds of GIP-based compounds to fine-tune pharmacology. The lead compound from our studies, which harbored a combination of N-terminal alkylation and side-chain lipidation, was equipotent and retained full efficacy at GIPR as the native peptide, while being completely refractory toward DPP4, and was resistant to trypsin. The GIP analogue identified from these studies was further evaluated in vivo and is one of the longest-acting GIPR agonists to date.

Mechanisms of body fat distribution and gluteal-femoral fat protection against metabolic disorders

Obesity is a major health problem that affects millions of individuals, and it is associated with metabolic diseases including insulin resistance (IR), type 2 diabetes (T2D), and cardiovascular diseases (CVDs). However, Body fat distribution (BFD) rather than crude obesity is now considered as a more accurate factor associated with these diseases. The factors affecting BFD vary, from genetic background, epigenetic factors, ethnicity, aging, hormonal changes, to lifestyle and medication consumptions. The main goal of controlling BFD comes from the fact that fat accumulation in different depots has a different effect on the overall health and metabolic health of individuals. It is well established that fat storage in the abdominal visceral depot is associated with metabolic disorder occurrence, while gluteal-femoral subcutaneous fat depot seems to be protective against these diseases. In this paper, we will summarize the factors affecting fat distribution. Then, we will present evidence connecting gluteal-femoral fat depot with protection against metabolic disorders including IR, T2D, and CVDs. Finally, we will list the suggested mechanisms that lead to this protective effect. The abstract is visualized in Graphical Abstract.

Management of type 2 diabetes, obesity, or nonalcoholic steatohepatitis with high-dose GLP-1 receptor agonists and GLP-1 receptor-based co-agonists

Type 2 diabetes (T2D), obesity, and nonalcoholic fatty liver disease/nonalacoholic steatohepatitis (NAFLD/NASH) share mutual causalities. Medications that may offer clinical benefits to all three conditions are being developed. Glucagon-like peptide-1 receptor agonists (GLP-1RAs) are approved for the management of T2D and obesity and there is great interest in evaluating higher doses of available GLP-1RAs and developing novel GLP-1RA-based co-agonists to provide greater reductions in glycated hemoglobin (HbA1c) and body weight as well as modifying NAFLD/NASH complications in clinically meaningful ways. High-dose GLP-1RAs and multi-hormonal strategies including GLP-1R agonism have either already been approved or are in development for managing T2D, obesity, or NASH. We provide a mechanistic outline with a detailed summary of the available clinical data and ongoing trials that are adjudicating the impact of high-dose GLP-1RAs, unimolecular, and multimolecular GLP-1R-based co-agonists in populations living with T2D, obesity, or NASH. The available trial findings are aligned with preclinical observations, showing clinical efficacy and safety thus providing optimism for the expansion of GLP-1R-based drug classes for managing the triad of T2D, obesity and NASH. Development, access, and wide-spread utilization of these new therapeutic approaches will offer important opportunities to markedly improve the collective global burden of T2D, obesity, and NASH.

Physiological functions of glucose transporter-2: From cell physiology to links with diabetes mellitus

Glucose is a sugar crucial for human health since it participates in many biochemical reactions. It produces adenosine 5'-triphosphate (ATP) and nucleosides through glucose metabolic and pentose phosphate pathways. These processes require many transporter proteins to assist in transferring glucose across cells, and the most notable ones are glucose transporter-2 (GLUT-2) and sodium/glucose cotransporter 1 (SGLT1). Glucose enters small intestinal epithelial cells from the intestinal lumen by crossing the brush boundary membrane via the SGLT1 cotransporter. It exits the cells by traversing the basolateral membrane through the activity of the GLUT-2 transporter, supplying energy throughout the body. Dysregulation of these glucose transporters is involved in the pathogenesis of several metabolic diseases, such as diabetes. Natural loss of GLUT-2 or its downregulation causes abnormal blood glucose concentrations in the body, such as fasting hypoglycemia and glucose tolerance. Therefore, understanding GLUT-2 physiology is necessary for exploring the mechanisms of diabetes and targeted treatment development. This article reviews how the apical GLUT-2 transporter maintains normal physiological functions of the human body and the adaptive changes this transporter produces under pathological conditions such as diabetes.

Poly-Agonist Pharmacotherapies for Metabolic Diseases: Hopes and New Challenges

The use of glucagon-like peptide-1 (GLP-1) receptor-based multi-agonists in the treatment of type 2 diabetes and obesity holds great promise for improving glycaemic control and weight management. Unimolecular dual and triple agonists targeting multiple gut hormone-related pathways are currently in clinical trials, with recent evidence supporting their efficacy. However, significant knowledge gaps remain regarding the biological mechanisms and potential adverse effects associated with these multi-target agents. The mechanisms underlying the therapeutic efficacy of GLP-1 receptor-based multi-agonists remain somewhat mysterious, and hidden threats may be associated with the use of gut hormone-based polyagonists. In this review, we provide a critical analysis of the benefits and risks associated with the use of these new drugs in the management of obesity and diabetes, while also exploring new potential applications of GLP-1-based pharmacology beyond the field of metabolic disease.

The Road towards Triple Agonists: Glucagon-Like Peptide 1, Glucose-Dependent Insulinotropic Polypeptide and Glucagon Receptor - An Update

Obesity is the fifth leading risk factor for global deaths with numbers continuing to increase worldwide. In the last 20 years, the emergence of pharmacological treatments for obesity based on gastrointestinal hormones has transformed the therapeutic landscape. The successful development of glucagon-like peptide-1 (GLP-1) receptor agonists, followed by the synergistic combined effect of glucose-dependent insulinotropic polypeptide (GIP)/GLP-1 receptor agonists achieved remarkable weight loss and glycemic control in those with the diseases of obesity and type 2 diabetes. The multiple cardiometabolic benefits include improving glycemic control, lipid profiles, blood pressure, inflammation, and hepatic steatosis. The 2023 phase 2 double-blind, randomized controlled trial evaluating a GLP-1/GIP/glucagon receptor triagonist (retatrutide) in patients with the disease of obesity reported 24.2% weight loss at 48 weeks with 12 mg retatrutide. This review evaluates the current available evidence for GLP-1 receptor agonists, dual GLP-1/GIP receptor co-agonists with a focus on GLP-1/GIP/glucagon receptor triagonists and discusses the potential future benefits and research directions.

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

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

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Introduction of a fatty acid chain modification to prolong circulatory half-life of a radioligand towards glucose-dependent insulinotropic polypeptide receptor

BACKGROUND

The beneficial role of glucose-dependent insulinotropic polypeptide receptor (GIPR) in weight control and maintaining glucose levels has led to the development of several multi-agonistic peptide drug candidates, targeting GIPR and glucagon like peptide 1 receptor (GLP1R) and/or the glucagon receptor (GCGR). The in vivo quantification of target occupancy by these drugs would accelerate the development of new drug candidates. The aim of this study was to evaluate a novel peptide (GIP1234), based on previously reported ligand DOTA-GIP-C803, modified with a fatty acid moiety to prolong its blood circulation. It would allow higher target tissue exposure and consequently improved peptide uptake as well as in vivo PET imaging and quantification of GIPR occupancy by novel drugs of interest.

METHOD

A 40 amino acid residue peptide (GIP1234) was synthesized based on DOTA-GIP-C803, in turn based on the sequences of endogenous GIP and Exendin-4 with specific amino acid modifications to obtain GIPR selectivity. A palmitoyl fatty acid chain was furthermore added at Lys14 via a glutamic acid linker to prolong its blood circulation time by the interaction with albumin. GIP1234 was conjugated with a DOTA chelator at the C-terminal cysteine residue to achieve 68Ga radiolabeling. The resulting PET probe, [68Ga]Ga-DOTA-GIP1234 was evaluated for receptor binding specificity and selectivity using HEK293 cells transfected with human GIPR, GLP1R, or GCGR. Blocking experiments with tirzepatide (2 μM) were conducted using huGIPR HEK293 cells to investigate binding specificity. Ex vivo and in vivo organ distribution of [68Ga]Ga-DOTA-GIP1234 was studied in rats and a pig in comparison to [68Ga]Ga-DOTA-C803-GIP. Binding of [68Ga]Ga-DOTA-GIP1234 to albumin was assessed in situ using polyacrylamide gel electrophoresis (PAGE). The stability was tested in formulation buffer and rat blood plasma.

RESULTS

[68Ga]Ga-DOTA-GIP1234 was synthesized with non-decay corrected radiochemical yield of 88 ± 3.7 % and radiochemical purity of 97.8 ± 0.8 %. The molar activity for the radiotracer was 8.1 ± 1.1 MBq/nmol. [68Ga]Ga-DOTA-GIP1234 was stable and maintained affinity to huGIPR HEK293 cells (dissociation constant (Kd) = 40 ± 12.5 nM). The binding of [68Ga]Ga-DOTA-GIP1234 to huGCGR and huGLP1R cells was insignificant. Pre-incubation of huGIPR HEK293 cell sections with tirzepatide resulted in the decrease of [68Ga]Ga-DOTA-GIP1234 binding by close to 90 %. [68Ga]Ga-DOTA-GIP1234 displayed slow blood clearance in pigs with SUV = 3.5 after 60 min. Blood retention of the tracer in rat was 2-fold higher than that of [68Ga]Ga-DOTA-C803-GIP. [68Ga]Ga-DOTA-GIP1234 also demonstrated strong liver uptake in both pig and rat combined with decreased renal excretion. The concentration dependent binding of [68Ga]Ga-DOTA-GIP1234 to albumin was confirmed in situ by PAGE.

CONCLUSION

[68Ga]Ga-DOTA-GIP1234 demonstrated nanomolar affinity and selectivity for huGIPR in vitro. Addition of a fatty acid moiety prolonged blood circulation time and tissue exposure in both rat and pig in vivo. However, the liver uptake was also increased which may make PET imaging of abdominal tissues such as pancreas challenging. The investigation of the influence of fatty acid moiety on the biological performance of the peptide ligand paved the way for further rational design of GIPR ligand analogues with improved characteristics.

Recent clinical and pharmacological advancements of incretin-based therapy and the effects of incretin on physiology

A novel therapeutic target for diabetes mellitus is incretin-based therapies, glucagon-like peptide-1, and glucose-dependent insulinotropic polypeptides are released from the gastrointestinal (GI) tract and act on beta cells of pancreatic islets by increasing the secretion of insulin. The management and prevention of diabetes require habitual and pharmacological therapies along with quality and healthy lifestyle. This includes maintaining the body weight, blood glucose level, cardiovascular risk, complexity, and co-morbidities. The utilization of glucagon-like peptide-1 (GLP-1) agonists is an object of research with favorable hemoglobin A1C levels and weight loss in type 1 diabetic patients. However, cost-effectiveness and tolerability, remain significant barriers for patients to using these medications. The risk of suicidal tendencies and thoughts of self-harm have been increased in patients receiving GLP-1 receptor agonists. Tirzepatide treatment showed a potent glucose-lowering effect and promoted weight loss with minimum GI adverse effects in animal studies as well as phase I and II human trials, in comparison with established GLP-1 receptor agonists. The glucose-dependent insulinotropic polypeptide receptor (GIPR) peptide-antagonist effectively blocks the action of gastric-inhibitory-polypeptide (GIP) in vitro and ex vivo in human pancreas and in vivo in rodent models. However, incretin-based therapies have received enormous attention in the last few decades for the treatment of diabetes, obesity, and other repurposing including central nervous system disorders. Therefore, in this article, we demonstrate the overview, physiological, and pharmacological advances of incretin-based pharmacotherapies and their physiological roles. Furthermore, the recent updates of glucagon-like peptide-1 receptor agonist, Glucagon-like peptide-2 receptor agonist, GLP-1/GIP co-agonists, GIP/GLP-1/glucagon triple agonist and GIP-antagonist are also discussed.

G protein-coupled receptors and obesity

G protein-coupled receptors (GPCRs) have emerged as important drug targets for various chronic diseases, including obesity and diabetes. Obesity is a complex chronic disease that requires long term management predisposing to type 2 diabetes, heart disease, and some cancers. The therapeutic landscape for GPCR as targets of anti-obesity medications has undergone significant changes with the approval of semaglutide, the first peptide glucagon like peptide 1 receptor agonist (GLP-1RA) achieving double digit weight loss (≥10%) and cardiovascular benefits. The enhanced weight loss, with the expected beneficial effect on obesity-related complications and reduction of major adverse cardiovascular events (MACE), has propelled the commercial opportunity for the obesity market leading to new players entering the space. Significant progress has been made on approaches targeting GPCRs such as single peptides that simultaneously activate GIP and/or GCGR in addition to GLP1, oral tablet formulation of GLP-1, small molecules nonpeptidic oral GLP1R and fixed-dose combination as well as add-on therapy for patients already treated with a GLP-1 agonist.