Glucagon-like peptide-1 receptor agonist exendin 4 ameliorates diabetes-associated vascular calcification by regulating mitophagy through the AMPK signaling pathway.

BACKGROUND: Vascular calcification (VC) is a complication in diabetes mellitus (DM) patients. Osteogenic phenotype switching of vascular smooth muscle cells (VSMCs) plays a critical role in diabetes-related VC. Mitophagy can inhibit phenotype switching in VSMCs. This study aimed to investigate the role of the glucagon-like peptide-1 receptor (GLP-1R) agonist exendin 4 (EX4) in mitophagy-induced phenotype switching. MATERIALS AND METHODS: The status of VC in T2DM mice was monitored using Von Kossa and Alizarin Red S (ARS) staining in mouse aortic tissue. Human aortic smooth muscle cells were cultured in high glucose (HG) and ß-glycerophosphate (ß-GP) conditioned medium. Accumulation of LC3B and p62 was detected in the mitochondrial fraction. The effect of EX4 in vitro and in vivo was investigated by knocking down AMPKα1. RESULTS: In diabetic VC mice, EX4 decreased the percentage of von Kossa/ARS positive area. EX4 inhibited osteogenic differentiation of HG/ß-GP-induced VSMCs. In HG/ß-GP-induced VSMCs, the number of mitophagosomes was increased, whereas the addition of EX4 restored mitochondrial function, increased the number of mitophagosome-lysosome fusions, and reduced p62 in mitochondrial frictions. EX4 increased the phosphorylation of AMPKα (Thr172) and ULK1 (Ser555) in HG/ß-GP-induced VSMCs. After knockdown of AMPKα1, ULK1 could not be activated by EX4. The accumulation of LC3B and p62 could not be reduced after AMPKα1 knockdown. Knockdown of AMPKα1 negated the therapeutic effects of EX4 on VC of diabetic mice. CONCLUSION: EX4 could promote mitophagy by activating the AMPK signaling pathway, attenuate insufficient mitophagy, and thus inhibit the osteogenic phenotype switching of VSMCs.

Dietary salt promotes cognition impairment through GLP-1R/mTOR/p70S6K signaling pathway.

Dietary salt has been associated with cognitive impairment in mice, possibly related to damaged synapses and tau hyperphosphorylation. However, the mechanism underlying how dietary salt causes cognitive dysfunction remains unclear. In our study, either a high-salt (8%) or normal diet (0.5%) was used to feed C57BL/6 mice for three months, and N2a cells were cultured in normal medium, NaCl medium (80 mM), or NaCl (80 mM) + Liraglutide (200 nM) medium for 48 h. Cognitive function in mice was assessed using the Morris water maze and shuttle box test, while anxiety was evaluated by the open field test (OPT). Western blotting (WB), immunofluorescence, and immunohistochemistry were utilized to assess the level of Glucagon-like Peptide-1 receptor (GLP-1R) and mTOR/p70S6K pathway. Electron microscope and western blotting were used to evaluate synapse function and tau phosphorylation. Our findings revealed that a high salt diet (HSD) reduced the level of synaptophysin (SYP) and postsynaptic density 95 (PSD95), resulting in significant synaptic damage. Additionally, hyperphosphorylation of tau at different sites was detected. The C57BL/6 mice showed significant impairment in learning and memory function compared to the control group, but HSD did not cause anxiety in the mice. In addition, the level of GLP-1R and autophagy flux decreased in the HSD group, while the level of mTOR/p70S6K was upregulated. Furthermore, liraglutide reversed the autophagy inhibition of N2a treated with NaCl. In summary, our study demonstrates that dietary salt inhibits the GLP-1R/mTOR/p70S6K pathway to inhibit autophagy and induces synaptic dysfunction and tau hyperphosphorylation, eventually impairing cognitive dysfunction.

GLP-1 modulated the firing activity of nigral dopaminergic neurons in both normal and parkinsonian mice.

The spontaneous firing activity of nigral dopaminergic neurons is associated with some important roles including modulation of dopamine release, expression of tyrosine hydroxylase (TH), as well as neuronal survival. The decreased neuroactivity of nigral dopaminergic neurons has been revealed in Parkinson's disease. Central glucagon-like peptide-1 (GLP-1) functions as a neurotransmitter or neuromodulator to exert multiple brain functions. Although morphological studies revealed the expression of GLP-1 receptors (GLP-1Rs) in the substantia nigra pars compacta, the possible modulation of GLP-1 on spontaneous firing activity of nigral dopaminergic neurons is unknown. The present extracellular in vivo single unit recordings revealed that GLP-1R agonist exendin-4 significantly increased the spontaneous firing rate and decreased the firing regularity of partial nigral dopaminergic neurons of adult male C57BL/6 mice. Blockade of GLP-1Rs by exendin (9-39) decreased the firing rate of nigral dopaminergic neurons suggesting the involvement of endogenous GLP-1 in the modulation of firing activity. Furthermore, the PKA and the transient receptor potential canonical (TRPC) 4/5 channels are involved in activation of GLP-1Rs-induced excitatory effects of nigral dopaminergic neurons. Under parkinsonian state, both the exogenous and endogenous GLP-1 could still induce excitatory effects on the surviving nigral dopaminergic neurons. As the mild excitatory stimuli exert neuroprotective effects on nigral dopaminergic neurons, the present GLP-1-induced excitatory effects may partially contribute to its antiparkinsonian effects.

The dual GCGR/GLP-1R agonist survodutide: Biomarkers and pharmacological profiling for clinical candidate selection.

AIM: To describe the biomarker strategy that was applied to select survodutide (BI 456906), BI 456908 and BI 456897 from 19 dual glucagon receptor (GCGR)/ glucagon-like peptide-1 receptor (GLP-1R) agonists for in-depth pharmacological profiling, which led to the qualification of survodutide as the clinical development candidate. MATERIALS AND METHODS: Potencies to increase cyclic adenosine monophosphate (cAMP) were determined in Chinese hamster ovary (CHO)-K1 cells stably expressing human GCGR and GLP-1R. Agonism for endogenously expressed receptors was investigated in insulinoma cells (MIN6) for mouse GLP-1R, and in rat primary hepatocytes for the GCGR. In vivo potencies to engage the GLP-1R or GCGR were determined, measuring improvement in oral glucose tolerance (30 nmol/kg) and increase in plasma fibroblast growth factor-21 (FGF21) and liver nicotinamide N-methyltransferase (NNMT) mRNA expression (100 nmol/kg), respectively. Body weight- and glucose-lowering efficacies were investigated in diet-induced obese (DIO) mice and diabetic db/db mice, respectively. RESULTS: Upon acute dosing in lean mice, target engagement biomarkers for the GCGR and GLP-1R demonstrated a significant correlation (Spearman correlation coefficient with p < 0.05) to the in vitro GCGR and GLP-1R potencies for the 19 dual agonists investigated. Survodutide, BI 456908 and BI 456897 were selected for in-depth pharmacological profiling based on the significant improvement in acute oral glucose tolerance achieved (area under the curve [AUC] of 54%, 57% and 60% vs. vehicle) that was comparable to semaglutide (AUC of 45% vs. vehicle), while showing different degrees of in vivo GCGR engagement, as determined by hepatic NNMT mRNA expression (increased by 15- to 17-fold vs. vehicle) and plasma FGF21 concentrations (increased by up to sevenfold vs. vehicle). In DIO mice, survodutide (30 nmol/kg/once daily), BI 456908 (30 nmol/kg/once daily) and BI 456897 (10 nmol/kg/once daily) achieved a body weight-lowering efficacy from baseline of 25%, 27% and 26%, respectively. In db/db mice, survodutide and BI 456908 (10 and 20 nmol/kg/once daily) significantly lowered glycated haemoglobin (0.4%-0.6%); no significant effect was observed for BI 456897 (3 and 7 nmol/kg/once daily). CONCLUSIONS: Survodutide was selected as the clinical candidate based on its balanced dual GCGR/GLP-1R pharmacology, engaging the GCGR for robust body weight-lowering efficacy exceeding that of selective GLP-1R agonists, while achieving antidiabetic efficacy that was comparable to selective GLP-1R agonism. Survodutide is currently being investigated in Phase 3 clinical trials in people living with obesity.

Glucagon-based therapy for people with diabetes and obesity: What is the sweet spot?

People with obesity and type 2 diabetes have a high prevalence of metabolic-associated steatotic liver disease, hyperlipidemia and cardiovascular disease. Glucagon increases hepatic glucose production; it also decreases hepatic fat accumulation, improves lipidemia and increases energy expenditure. Pharmaceutical strategies to antagonize the glucagon receptor improve glycemic outcomes in people with diabetes and obesity, but they increase hepatic steatosis and worsen dyslipidemia. Co-agonism of the glucagon and glucagon-like peptide-1 (GLP-1) receptors has emerged as a promising strategy to improve glycemia in people with diabetes and obesity. Addition of glucagon receptor agonism enhances weight loss, reduces liver fat and ameliorates dyslipidemia. Prior to clinical use, however, further studies are needed to investigate the safety and efficacy of glucagon and GLP-1 receptor co-agonists in people with diabetes and obesity and related conditions, with specific concerns regarding a higher prevalence of gastrointestinal side effects, loss of muscle mass and increases in heart rate. Furthermore, co-agonists with differing ratios of glucagon:GLP-1 receptor activity vary in their clinical effect; the optimum balance is yet to be identified.

Differential effect of endogenous glucagon-like peptide-1 on prandial glucose counterregulatory response to hypoglycaemia in humans with and without bariatric surgery.

AIM: To determine the effect of endogenous glucagon-like peptide 1 (GLP-1) on prandial counterregulatory response to hypoglycaemia after gastric bypass (GB). MATERIALS AND METHODS: Glucose fluxes, and islet-cell and gut hormone responses before and after mixed-meal ingestion, were compared during a hyperinsulinaemic-hypoglycaemic (~3.2 mmol/L) clamp with and without a GLP-1 receptor (GLP-1R) antagonist exendin-(9-39) infusion in non-diabetic patients who had previously undergone GB compared to matched participants who had previously undergone sleeve gastrectomy (SG) and non-surgical controls. RESULTS: Exendin-(9-39) infusion raised prandial endogenous glucose production (EGP) response to insulin-induced hypoglycaemia in the GB group but had no consistent effect on EGP response among the SG group or non-surgical controls (p < 0.05 for interaction). The rates of systemic appearance of ingested glucose or prandial glucose utilization did not differ among the three groups or between studies with and without exendin-(9-39) infusion. Blockade of GLP-1R had no effect on insulin secretion or insulin action but enhanced prandial glucagon in all three groups. CONCLUSIONS: These results indicate that impaired post-meal glucose counterregulatory response to hypoglycaemia after GB is partly mediated by endogenous GLP-1, highlighting a novel pathogenic mechanism of GLP-1 in developing hypoglycaemia in this population.

New Mechanisms to Prevent Heart Failure with Preserved Ejection Fraction Using Glucagon-like Peptide-1 Receptor Agonism (GLP-1 RA) in Metabolic Syndrome and in Type 2 Diabetes: A Review.

This review examines the impact of obesity on the pathophysiology of heart failure with preserved ejection fraction (HFpEF) and focuses on novel mechanisms for HFpEF prevention using a glucagon-like peptide-1 receptor agonism (GLP-1 RA). Obesity can lead to HFpEF through various mechanisms, including low-grade systemic inflammation, adipocyte dysfunction, accumulation of visceral adipose tissue, and increased pericardial/epicardial adipose tissue (contributing to an increase in myocardial fat content and interstitial fibrosis). Glucagon-like peptide 1 (GLP-1) is an incretin hormone that is released from the enteroendocrine L-cells in the gut. GLP-1 reduces blood glucose levels by stimulating insulin synthesis, suppressing islet α-cell function, and promoting the proliferation and differentiation of ß-cells. GLP-1 regulates gastric emptying and appetite, and GLP-1 RA is currently indicated for treating type 2 diabetes (T2D), obesity, and metabolic syndrome (MS). Recent evidence indicates that GLP-1 RA may play a significant role in preventing HFpEF in patients with obesity, MS, or obese T2D. This effect may be due to activating cardioprotective mechanisms (the endogenous counter-regulatory renin angiotensin system and the AMPK/mTOR pathway) and by inhibiting deleterious remodeling mechanisms (the PKA/RhoA/ROCK pathway, aldosterone levels, and microinflammation). However, there is still a need for further research to validate the impact of these mechanisms on humans.

GLP-1 receptor agonists and atherosclerosis protection: the vascular endothelium takes center stage.

Atherosclerotic cardiovascular disease is a chronic condition that often copresents with type 2 diabetes and obesity. Glucagon-like peptide-1 receptor agonists (GLP-1RAs) are incretin mimetics endorsed by major professional societies for improving glycemic status and reducing atherosclerotic risk in people living with type 2 diabetes. Although the cardioprotective efficacy of GLP-1RAs and their relationship with traditional risk factors are well established, there is a paucity of publications that have summarized the potentially direct mechanisms through which GLP-1RAs mitigate atherosclerosis. This review aims to narrow this gap by providing comprehensive and in-depth mechanistic insight into the antiatherosclerotic properties of GLP-1RAs demonstrated across large outcome trials. Herein, we describe the landmark cardiovascular outcome trials that triggered widespread excitement around GLP-1RAs as a modern class of cardioprotective agents, followed by a summary of the origins of GLP-1RAs and their mechanisms of action. The effects of GLP-1RAs at each major pathophysiological milestone of atherosclerosis, as observed across clinical trials, animal models, and cell culture studies, are described in detail. Specifically, this review provides recent preclinical and clinical evidence that suggest GLP-1RAs preserve vessel health in part by preventing endothelial dysfunction, achieved primarily through the promotion of angiogenesis and inhibition of oxidative stress. These protective effects are in addition to the broad range of atherosclerotic processes GLP-1RAs target downstream of endothelial dysfunction, which include systemic inflammation, monocyte recruitment, proinflammatory macrophage and foam cell formation, vascular smooth muscle cell proliferation, and plaque development.

The role of G protein-coupled receptor kinases in GLP-1R ß-arrestin recruitment and internalisation.

The glucagon-like peptide 1 receptor (GLP-1R) is a validated clinical target for the treatment of type 2 diabetes and obesity. Unlike most G protein-coupled receptors (GPCRs), the GLP-1R undergoes an atypical mode of internalisation that does not require ß-arrestins. While differences in GLP-1R trafficking and ß-arrestin recruitment have been observed between clinically used GLP-1R agonists, the role of G protein-coupled receptor kinases (GRKs) in affecting these pathways has not been comprehensively assessed. In this study, we quantified the contribution of GRKs to agonist-mediated GLP-1R internalisation and ß-arrestin recruitment profiles using cells where endogenous ß-arrestins, or non-visual GRKs were knocked out using CRISPR/Cas9 genome editing. Our results confirm the previously established atypical ß-arrestin-independent mode of GLP-1R internalisation and revealed that GLP-1R internalisation is dependent on the expression of GRKs. Interestingly, agonist-mediated GLP-1R ß-arrestin 1 and ß-arrestin 2 recruitment were differentially affected by endogenous GRK knockout with ß-arrestin 1 recruitment more sensitive to GRK knockout than ß-arrestin 2 recruitment. Moreover, individual overexpression of GRK2, GRK3, GRK5 or GRK6 in a newly generated GRK2/3/4/5/6 HEK293 cells, rescued agonist-mediated ß-arrestin 1 recruitment and internalisation profiles to similar levels, suggesting that there is no specific GRK isoform that drives these pathways. This study advances mechanistic understanding of agonist-mediated GLP-1R internalisation and provides novel insights into how GRKs may fine-tune GLP-1R signalling.

Protecting cardiomyocytes from hypoxia-reoxygenation injury, empaglifozin and liraglutide alone or in combination?

OBJECTIVES: Empagliflozin, a sodium-dependent glucose co-transporter 2 (SGLT2) inhibitor, and liraglutide, a GLP-1 receptor (GLP-1R) agonist, are commonly recognized for their cardiovascular benefits in individuals with type 2 diabetes (T2D). In prior studies, we have demonstrated that both drugs, alone or in combination, were able to protect cardiomyocytes from injury induced by diabetes. Mechanistic investigations also suggested that the cardioprotective effect may be independent of diabetes In this study, we utilized a hypoxia-reoxygenation (H/R) model to investigate the cardiovascular benefits of SGLT2 inhibitor empagliflozin and GLP-1 receptor (GLP-1R) agonist liraglutide, both alone and in combination, in the absence of T2D. Our hypothesis was that empagliflozin and liraglutide, either individually or in combination, would demonstrate cardioprotective properties against H/R-induced injury, with an additive and/or synergistic effect anticipated from combination therapy. METHODS: In this study, the cardiac muscle cell line, HL-1 cells, were treated with vehicle, empagliflozin, liraglutide, or a combination of the two drugs. The cells were then subjected to a hypoxia-reoxygenation (H/R) protocol, consisting of 1 h of hypoxia followed by 24 h of reoxygenation. The effects of the treatments on cytotoxicity, oxidative stress, endothelial nitric oxide synthase (eNOS) activity, phospho-protein kinase C (PKC) beta and phospho-eNOS (Thr495) expression were subsequently evaluated at the end of the treatments. RESULTS: We found that H/R increased cytotoxicity and reduces eNOS activity, empagliflozin, liraglutide or combination treatment attenuated some or all of these effects with the combination therapy showing the greatest improvement. CONCLUSIONS: Empagliflozin, liraglutide or combination of these two have cardioprotective effect regardless of diabetes. Cardioprotective effects of SGLT2 inhibitor and GLP-1R agonist is additive and synergistic.

The role of glucagon-like peptide-1 receptor agonists in metabolic dysfunction-associated steatohepatitis.

Despite its considerable and growing burden, there are currently no Food and Drug Administration-approved treatments for metabolic dysfunction-associated steatotic liver disease or its progressive form, metabolic dysfunction-associated steatohepatitis (MASH). Several glucagon-like peptide-1 receptor agonists (GLP-1RAs) and other agents are in various phases of clinical development for use in MASH; an ideal therapy should reduce liver fat content, improve chronic liver disease, help mitigate metabolic comorbidities and decrease all-cause mortality. Because of interconnected disease mechanisms, metabolic dysfunction-associated steatotic liver disease/MASH often coexists with type 2 diabetes (T2D), obesity and cardiovascular disease. Various GLP-1RAs are Food and Drug Administration-approved for use in T2D, and two, liraglutide and semaglutide, are approved for overweight and obesity. GLP-1RAs decrease glucose levels and body weight and improve cardiovascular outcomes in people with T2D who are at high risk of cardiovascular disease. In addition, GLP-1RAs have been reported to reduce liver fat content and liver enzymes, reduce oxidative stress and improve hepatic de novo lipogenesis and the histopathology of MASH. Weight loss may contribute to these effects; however, the exact mechanisms are unknown. Adverse events that are commonly associated with GLP-1RAs include vomiting, nausea and diarrhoea. There is a lack of evidence from meta-analyses regarding the increased risk of acute pancreatitis and various forms of cancer with GLP-1RAs. Large-scale, phase 3 trials, which will provide definitive data on GLP-1RAs and other potential therapies in MASH, are ongoing. Given the spectrum of modalities under investigation, it is hoped that these trials will support the identification of pharmacotherapies that provide clinical benefit for patients with MASH.

Loss of GIPR in LEPR cells impairs glucose control by GIP and GIP:GLP-1 co-agonism without affecting body weight and food intake in mice.

OBJECTIVE: The glucose-dependent insulinotropic polypeptide (GIP) decreases body weight via central GIP receptor (GIPR) signaling, but the underlying mechanisms remain largely unknown. Here, we assessed whether GIP regulates body weight and glucose control via GIPR signaling in cells that express the leptin receptor (Lepr). METHODS: Hypothalamic, hindbrain, and pancreatic co-expression of Gipr and Lepr was assessed using single cell RNAseq analysis. Mice with deletion of Gipr in Lepr cells were generated and metabolically characterized for alterations in diet-induced obesity (DIO), glucose control and leptin sensitivity. Long-acting single- and dual-agonists at GIPR and GLP-1R were further used to assess drug effects on energy and glucose metabolism in DIO wildtype (WT) and Lepr-Gipr knock-out (KO) mice. RESULTS: Gipr and Lepr show strong co-expression in the pancreas, but not in the hypothalamus and hindbrain. DIO Lepr-Gipr KO mice are indistinguishable from WT controls related to body weight, food intake and diet-induced leptin resistance. Acyl-GIP and the GIPR:GLP-1R co-agonist MAR709 remain fully efficacious to decrease body weight and food intake in DIO Lepr-Gipr KO mice. Consistent with the demonstration that Gipr and Lepr highly co-localize in the endocrine pancreas, including the ß-cells, we find the superior glycemic effect of GIPR:GLP-1R co-agonism over single GLP-1R agonism to vanish in Lepr-Gipr KO mice. CONCLUSIONS: GIPR signaling in cells/neurons that express the leptin receptor is not implicated in the control of body weight or food intake, but is of crucial importance for the superior glycemic effects of GIPR:GLP-1R co-agonism relative to single GLP-1R agonism.

GLP-1R signaling modulates colonic energy metabolism, goblet cell number and survival in the absence of gut microbiota.

OBJECTIVES: Gut microbiota increases energy availability through fermentation of dietary fibers to short-chain fatty acids in conventionally raised mice. Energy deficiency in germ-free (GF) mice increases glucagon-like peptide-1 (GLP-1) levels, which slows intestinal transit. To further analyze the role of GLP-1-mediated signaling in this model of energy deficiency, we re-derived mice lacking GLP-1 receptor (GLP-1R KO) as GF. METHODS: GLP-1R KO mice were rederived as GF through hysterectomy and monitored for 30 weeks. Mice were subjected to rescue experiments either through feeding an energy-rich diet or colonization with a normal cecal microbiota. Histology and intestinal function were assessed at different ages. Intestinal organoids were assessed to investigate stemness. RESULTS: Unexpectedly, 25% of GF GLP-1R KO mice died before 20 weeks of age, associated with enlarged ceca, increased cecal water content, increased colonic expression of apical ion transporters, reduced number of goblet cells and loss of colonic epithelial integrity. Colonocytes from GLP-1R KO mice were energy-deprived and exhibited increased ER-stress; mitochondrial fragmentation, increased oxygen levels and loss of stemness. Restoring colonic energy levels either by feeding a Western-style diet or colonization with a normal gut microbiota normalized gut phenotypes and prevented lethality. CONCLUSIONS: Our findings reveal a heretofore unrecognized role for GLP-1R signaling in the maintenance of colonic physiology and survival during energy deprivation.

The effects of Fc fusion protein glucagon-like peptide-1 and glucagon dual receptor agonist with different receptor selectivity in vivo studies.

BACKGROUND: Glucagon-like peptide-1 (GLP-1)/glucagon (GCG) dual receptor agonists with different receptor selectivity are under investigation and have shown significant improvement in both weight loss and glycemic control, but the optimal potency ratio between the two receptors to balance efficacy and safety remains unclear. EXPERIMENTAL APPROACH: We designed and constructed several dual receptor agonists with different receptor potency ratios using Fc fusion protein technology. The long-term effects of the candidates on body weight and metabolic dysfunction-associated steatotic liver disease (MASLD) were evaluated in diet-induced obese (DIO) model mice, high-fat diet (HFD)-ob/ob mice and AMLN diet-induced MASLD mice. Repeat dose toxicity assays were performed to investigate the safety profile of the candidate (HEC-C070) in Sprague Dawley (SD) rats. KEY RESULTS: The high GCG receptor (GCGR) selectivity of HEC-C046 makes it more prominent than other compounds for weight loss and most MASLD parameters but may lead to safety concerns. The weight change of HEC-C052 with the lowest GCG agonism was inferior to that of selective GLP-1 receptor agonist (GLP-1RA) semaglutide in DIO model mice. The GLP-1R selectivity of HEC-C070 with moderate GCG agonism has a significant effect on weight loss and liver function in obese mice, and its lowest observed adverse effect level (LOAEL) was 30 nmol/kg in the repeat dose toxicity study. CONCLUSION: We compared the potential of the Fc fusion protein GLP-1/GCG dual receptor agonists with different receptor selectivity to provide the setting for future GLP-1/GCG dual receptor agonists to treat obesity and MASLD.

The role of nanosystems in the delivery of glucose-lowering drugs for the preemption and treatment of diabetes-associated atherosclerosis.

Diabetes is one of the most prevalent diseases worldwide. In recent decades, type-2 diabetes has become increasingly common, particularly in younger individuals. Diabetes leads to many vascular complications, including atherosclerosis. Atherosclerosis is a cardiovascular disease characterized by lipid-rich plaques within the vasculature. Plaques develop over time, restricting blood flow, and can, therefore, be the underlying cause of major adverse cardiovascular events, including myocardial infarction and stroke. Diabetes and atherosclerosis are intrinsically linked. Diabetes is a metabolic syndrome that accelerates atherosclerosis and increases the risk of developing other comorbidities, such as diabetes-associated atherosclerosis (DAA). Gold standard antidiabetic medications focus on attenuating hyperglycemia. Though recent evidence suggests that glucose-lowering drugs may have broader applications, beyond diabetes management. This review mainly evaluates the role of glucagon-like peptide-1 receptor agonists (GLP-1 RAs), such as liraglutide and semaglutide in DAA. These drugs mimic gut hormones (incretins), which inhibit glucagon secretion while stimulating insulin secretion, thus improving insulin sensitivity. This facilitates delayed gastric emptying and increased patient satiety; hence, they are also indicated for the treatment of obesity. GLP-1 RAs have significant cardioprotective effects, including decreasing low-density lipoprotein (LDL) cholesterol and triglycerides levels. Liraglutide and semaglutide have specifically been shown to decrease cardiovascular risk. Liraglutide has displayed a myriad of antiatherosclerotic properties, with the potential to induce plaque regression. This review aims to address how glucose-lowering medications can be applied to treat diseases other than diabetes. We specifically focus on how nanomedicines can be used for the site-specific delivery of antidiabetic medicines for the treatment of diabetes-associated atherosclerosis.

Regulation of energy metabolism through central GIPR signaling.

In recent years, significant progress has been made to pharmacologically combat the obesity pandemic, particularly with regard to biochemically tailored drugs that simultaneously target the receptors for glucagon-like peptide-1 (GLP-1) and the glucose-dependent insulinotropic polypeptide (GIP). But while the pharmacological benefits of GLP-1 receptor (GLP-1R) agonism are widely acknowledged, the role of the GIP system in regulating systems metabolism remains controversial. When given in adjunct to GLP-1R agonism, both agonism and antagonism of the GIP receptor (GIPR) improves metabolic outcome in preclinical and clinical studies, and despite persistent concerns about its potential obesogenic nature, there is accumulating evidence indicating that GIP has beneficial metabolic effects via central GIPR agonism. Nonetheless, despite growing recognition of the GIP system as a valuable pharmacological target, there remains great uncertainty as to where and how GIP acts in the brain to regulate metabolism, and how GIPR agonism may differ from GIPR antagonism in control of energy metabolism. In this review we highlight current knowledge on the central action of GIP, and discuss open questions related to its multifaceted biology in the brain and the periphery.

Immunomodulation and inflammation: Role of GLP-1R and GIPR expressing cells within the gut.

Glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are peptide hormones produced by enteroendocrine cells in the small intestine. Despite being produced in the gut, the leveraging of their role in potentiating glucose-stimulated insulin secretion, also known as the incretin effect, has distracted from discernment of direct intestinal signaling circuits. Both preclinical and clinical evidence have highlighted a role for the incretins in inflammation. In this review, we highlight the discoveries of GLP-1 receptor (GLP-1R)+ natural (TCRαß and TCRγδ) and induced (TCRαß+CD4+ cells and TCRαß+CD8αß+) intraepithelial lymphocytes. Both endogenous signaling and pharmacological activation of GLP-1R impact local and systemic inflammation, the gut microbiota, whole-body metabolism, as well as the control of GLP-1 bioavailability. While GIPR signaling has been documented to impact hematopoiesis, the impact of these bone marrow-derived cells in gut immunology is not well understood. We uncover gaps in the literature of the evaluation of the impact of sex in these GLP-1R and GIP receptor (GIPR) signaling circuits and provide speculations of the maintenance roles these hormones play within the gut in the fasting-refeeding cycles. GLP-1R agonists and GLP-1R/GIPR agonists are widely used as treatments for diabetes and weight loss, respectively; however, their impact on gut homeostasis has not been fully explored. Advancing our understanding of the roles of GLP-1R and GIPR signaling within the gut at homeostasis as well as metabolic and inflammatory diseases may provide targets to improve disease management.

Engineering of a Biologically Active Glycosylated Glucagon-Like Peptide-1 Analogue.

Glucagon-like peptide receptor (GLP-1R) agonists (e.g., semaglutide, liraglutide, etc.) are efficient treatment options for people with type 2 diabetes and obesity. The manufacturing method to produce semaglutide, a blockbuster GLP-1 drug on the market, involves multistep synthesis. The large peptide has a hydrophobic fatty acid side chain that makes it sparingly soluble, and its handling, purification, and large-scale production difficult. The growing demand for semaglutide that the manufacturer is not capable of addressing immediately triggered a worldwide shortage. Thus, we have developed a potential alternative analogue to semaglutide by replacing the hydrophobic fatty acid with a hydrophilic human complex-type biantennary oligosaccharide. Our novel glycoGLP-1 analogue was isolated in an ∼10-fold higher yield compared with semaglutide. Importantly, our glycoGLP-1 analogue possessed a similar GLP-1R activation potency to semaglutide and was biologically active in vivo in reducing glucose levels to a similar degree as semaglutide.

Computational modelling of dynamic cAMP responses to GPCR agonists for exploration of GLP-1R ligand effects in pancreatic ß-cells and neurons.

The glucagon-like peptide-1 receptor (GLP-1R) is a class B G protein-coupled receptor (GPCR) which plays important physiological roles in insulin release and promoting fullness. GLP-1R agonists initiate cellular responses by cyclic AMP (cAMP) pathway signal transduction. Understanding of the potential of GLP-1R agonists in the treatment of type 2 diabetes may be advanced by considering the cAMP dynamics for agonists at GLP-1R in both pancreatic ß-cells (important in insulin release) and neurons (important in appetite regulation). Receptor desensitisation in the cAMP pathway is known to be an important regulatory mechanism, with different ligands differentially promoting G protein activation and desensitisation. Here, we use mathematical modelling to quantify and understand experimentally obtained cAMP timecourses for two GLP-1R agonists, exendin-F1 (ExF1) and exendin-D3 (ExD3), which give markedly different signals in ß-cells and neurons. We formulate an ordinary differential equation (ODE) model for the dynamics of cAMP signalling in response to G protein-coupled receptor (GPCR) ligands, encompassing ligand binding, receptor activation, G protein activation, desensitisation and second messenger generation. We validate our model initially by fitting to timecourse data for HEK293 cells, then proceed to parameterise the model for ß-cells and neurons. Through numerical simulation and sensitivity studies, our analysis adds support to the hypothesis that ExF1 offers more potential glucose regulation benefit than ExD3 over long timescales via signalling in pancreatic ß-cells, but that there is little difference between the two ligands in the potential appetite suppression effects offered via long-time signalling in neurons on the same timescales.

A review of an investigational drug retatrutide, a novel triple agonist agent for the treatment of obesity.

BACKGROUND: Obesity is one of the critical public health problems in our society. It leads to various health conditions, such as type 2 diabetes mellitus, cardiovascular disease, hypertension, dyslipidaemia, and non-alcoholic fatty liver disease. With the rising incidence of obesity, there is a growing demand for new therapies which can effectively manage body weight and improve health. CURRENT EVIDENCE: Currently under development, multi-receptor agonist drugs may offer a promising solution to meet this unmet medical need. Retatrutide is a novel triple receptor agonist peptide that targets the glucagon receptor (GCGR), glucose-dependent insulinotropic polypeptide receptor (GIPR), and glucagon-like peptide-1 receptor (GLP-1R). This novel drug has the potential to treat metabolic abnormalities associated with obesity as well as diseases resulting from it due to its distinct mechanism of action. The Phase III trial of this pipeline drug for treating type 2 diabetes mellitus, non-alcoholic fatty liver disease, and obesity started on August 28, 2023. The results of a Phase II clinical trial have demonstrated significant weight reduction in overweight and obese adults. Specifically, the trial reported an average weight loss of 17.5% and 24.4% at 24 and 48 weeks, respectively. CONCLUSIONS: These findings hold promise for the development of effective weight loss interventions in this population group. There is a need for more phase III studies to provide sufficient clinical evidence for the effectiveness of retatrutide, as current evidence is limited to phase II studies and has yet to prove its worth in a larger population. Here, we aimed to provide an overview of retatrutide's safety and effectiveness in treating obesity.