10 Minute Walking Workout For Weight Loss Full Body Fat Burn Monicasokhan Weightloss

However, in rats, GLP-1 elevation of BP is preserved upon pretreatment with reserpine, propanolol or phentolamine, thus indicating that the hypertensive effect of GLP-1 does not exclusively depend on catecholamine signaling . Both central and peripheral administration of GLP-1R agonists increase HR and BP in rodents , , , with induction of c-Fos expression in adrenal medullary catecholamine neurons and activation of tyrosine hydroxylase, the key enzyme involved in production of norepinephrine, in the brainstem . In rats, intravenous infusion of GLP-1 (7-37amide) or exendin-4 acutely increases HR as well as systolic, diastolic, and mean arterial BP (Figure 7) 634,635. Whether the low endogenous concentration and the restricted pharmacokinetic action profile of endogenous GLP-1 metabolites are sufficient to elicit such effects under physiological circumstances remains questionable. Administration of GLP-1 at high physiological doses stimulates vagal afferents, and this is blocked by pretreatment with exendin (9–39) . Or i.p., exendin-4 and liraglutide induced acute neuronal activation (measured by activation of cFos) in PVN, AP, and NTS 686,690. Injected liraglutide and exendin-4 , and bilateral neurochemical lesions of the lateral parabrachial nucleus (IPBN) with ibotenic acid blunted the anorexigenic effect of peripherally administered exendin-4 . Preclinical proof of concept of enhanced body weight lowering relative to GLP-1 mono-therapy without impaired glycemic control was first demonstrated by two independent research efforts. This strategy has refined the toolbox of weight loss pharmacology, and several molecules with agonism at key metabolic receptors are, as reviewed below, currently in clinical evaluation. Preclinical studies have evaluated the therapeutic potential of GLP-1 based polypharmacology for the treatment of obesity and diabetes. One study in type-2 diabetic patients reported improved glycemic control when exenatide was added to ongoing treatment with sitagliptin as compared to switching from sitagliptin to exenatide monotherapy . Underlining the role of cAMP in the insulinotropic effect of GLP-1, enhanced cAMP hydrolysis through overexpression of the cyclic nucleotide phosphodiesterase 3B (PDE3B) diminishes GLP-1-induced insulin secretion . While both GLP-1 (1–37) and GLP-1 (7–37) stimulate insulin secretion, GLP-1 (7–37) is efficacious at a lower dose. While GLP-1 enhances proinsulin expression 82,372,373,463,464, there are no differences in pancreatic insulin expression in GLP-1R KO mice . When chronically fed a high-fat diet (HFD), GLP-1R KO mice are paradoxically leaner than their wild-type controls yet are more glucose intolerant . These studies suggest that recruitment of β-arrestin following ligand-induced activation of GLP-1R is important for the insulinotropic effect of GLP-1. The cellular mechanisms underlying glucose-stimulation of GLP-1 secretion from L-cells are, at least in part, similar to the stimulation of insulin secretion in the islets. Consistent with this, glucagon-stimulation of insulin secretion is decreased in islets isolated from β-cell-specific GLP-1R KO mice . Further, glucagon receptor KO mice also have compensatory increases in α-cell GLP-1, and GLP-1 receptor (GLP-1R) signaling has been reported to contribute to the preserved glucose responses after streptozotocin administration 166,167. Consistent with this, adenoviral overexpression of PCSK1 in α-cells increases islet GLP-1 production and secretion, ultimately leading to enhanced glucose-stimulation of insulin secretion and improved survival of the islets . When administered s.c., liraglutide fails to inhibit eating in mice possessing a CNS-specific deletion of GLP-1R . Peripheral administration of GLP-1 analogs decreases body weight via suppression of food intake , , ,665,685. The anorexigenic effect of GLP-1R agonism has been demonstrated in numerous clinical studies and fMRI analysis support that GLP-1 inhibition of food intake is centrally mediated in healthy individuals and patients with type-2 diabetes , , , , , . In a recent meta-analysis of 60 clinical studies, GLP-1R agonists were demonstrated to reduce diastolic BP with a range of −1.84 to −4.60 mmHg and to slightly increase heart rate by 2–3.35 beats/min . In summary, there is substantial evidence indicating that cAMP is an important second messenger driving the acute insulinotropic effect of GLP-1. The residence time of the ligand interaction with the receptor is commonly hypothesized to affect the duration an internalized receptor can continue to signal . The exact mechanisms underlying continuation of receptor signaling after sequestration of the ligand–receptor complex seemingly involve preserved association of the receptor with the Gαs subunit. Consistent with this, continuous cAMP formation has been demonstrated upon internalization of the receptors for parathyroid hormone , thyroid-stimulating hormone , and sphingosine 1-phosphate . In summary, accumulating evidence indicates that ligand-induced GLP-1R signaling is partially preserved after endocytosis of the receptor. Notably, induction of proinsulin expression by either GLP-1 or forskolin can be blocked by galanin, suggesting that GLP-1 stimulation of insulin expression is cAMP dependent . Membrane depolarization by GLP-1 was mimicked by the PKC activator phorbol myristate acetate (PMA) and was not affected by treatment with either the PKA inhibitor myr-PKI, the KATP channel blocker tolbutamide, or the L-type Ca2+ channel inhibitor isradipine . The dissociated Epac2 then dimerizes with Rim2 and Piccolo in a Ca2+-dependent manner followed by induction of exocytosis of the insulin granules through binding of the Epac2/Rim2/Piccolo complex to Rab3 which is located at the membrane of the insulin granules (Figure 6) 508,511. Apart from binding SUR1, Epac2 also binds to a series of molecules that potentially participate in transport, priming and fusion of the insulin vesicles, including Rab3, Rim2, and the Ca2+ sensor Piccolo 493,512,513. Additionally, GIP directly stimulates lipogenesis, while GLP-1 indirectly promotes lipolysis, collectively maintaining healthy adipocytes, reducing ectopic fat distribution, and increasing the production and secretion of adiponectin from adipocytes. Thus, increased circulating GLP-1 is invariably reported after bariatric surgery , , , , , and after surgical repositioning of the distal gut (so-called ileal interposition), both of which rapidly expose the L-cells to incoming incompletely digested nutrients . In line with this notion, blockade of GLP-1R with exendin-9 has been demonstrated to normalize post-bariatric hyperinsulinemia and alleviate resulting hypoglycemia after RYGB or gastrectomy . The commonly observed increase in GLP-1 after bariatric surgery , , , , , is considered a causal factor leading to increased circulating levels of insulin after the surgery. Although there is some species variation, the density of L-cells is relatively low in the proximal small bowel and increases distally along the gut, with greatest density in the ileum and colon , , , , . Statistically significant differences were assessed by one-way ANOVA followed by Tukey’s multiple comparison tests to analyze the effects of compound intervention vs. vehicle administration in PWA mice. In order to assess integral glucose levels in the glucose tolerance test, the area under the curve (AUC) was calculated using the trapezoidal rule. Moreover, no effects were observed in ovarian cyclicity and histology following pharmacological treatment in any of the experimental groups (Suppl. Fig. S3G). However, the triagonist caused a substantial reduction in ovarian weight and a significant drop in serum LH levels (Suppl. Fig. S3D, F). Chronic administration of GLP1/E significantly improved also glucose handling, as compared with the vehicle-treated PWA group, whereas no glucoregulatory actions were detected in mice treated with the dual or triple agonist (Fig. 1E-upper panel). Activation of GLP-1R stimulates formation of cAMP via Gs signaling, increases intracellular Ca2+ via the Gq/11 pathway, and promotes ERK1/2 signaling via recruitment of β-arrestin , , , , , . Similar conclusions have been reached by analysis of the GLP-1 bound receptor conformation using cryo-electron microscopy and by analyzing the crystal structure of GLP-1R bound to truncated peptide agonist . A positive allosteric modulator binds and activates GLP-1R through binding between helix V and VI, thereby creating an intercellular binding site for the G protein . While norepinephrine seemingly inhibits GLP-1 secretion via its action on α-adrenergic receptors, its secretion is stimulated by isoproterenol, and this effect can be blocked by co-infusion of the β-adrenergic receptor antagonist propanolol . Direct infusion of glucose into the duodenum at a rate that ensured ∼ total absorption close to the infusion site (2 kcal/min) triggered robust GIP, but not GLP-1 secretion, whereas both hormones were released when glucose was directly delivered into the ileum . In humans, GLP-1 secretion in response to duodenal glucose delivery does not become robustly stimulated until the delivery rate overcomes the absorptive capacity of the duodenum, i.e. until such time as non-absorbed glucose reaches the jejunum and beyond. In rats, induction of gut glucagon-like immunoreactivity induced by either lipids or by physiological concentrations of GIP can be blocked by subdiaphragmatic vagotomy, suggesting that in rats GIP regulation of GLP-1 secretion requires either afferent or efferent signal transmission via the vagus . Because the L-cells co-secrete the PGDPs, factors stimulating GLP-2 or oxyntomodulin are also natural secretagogues of GLP-1.

Identification of GIP and GLP-1 as gastrointestinal insulinotropic hormones

Pancreatic β-cell mass is significantly reduced by more than 50% in patients with T2DM, with lesser reductions already occurring in the prediabetes state (124). Preclinical data indicated that tirzepatide exhibited an affinity for GIPR equivalent to GIP binding, while its affinity for GLP-1R was approximately five times weaker compared to GLP-1 (63). Higher doses of oral semaglutide (up to 50 mg/day) are under development for the treatment of both T2DM (104) and obesity (105), with effectiveness on par with 2.4 mg/week subcutaneous semaglutide approved for weight management. In addition, liraglutide combined with insulin degludec (IDegLira®) is a once-daily, fixed dual combination product approved for T2DM. Both liraglutide and semaglutide have received FDA approval for the treatment of T2DM, obesity, and cardiovascular risk reduction Table 2. Interestingly, disruption of the intrapancreatic infusion of Zn2+ but not of Zn2+ free insulin accelerates glucagon secretion in rats made diabetic by STZ, indicating that Zn2+ but not insulin is the main stimulus underlying the Zn2+-insulin inhibition of glucagon secretion . Insulin is co-crystalized with Zn2+ in the secretory granules of the β-cells 590,591 and Zn2+ is co-secreted with insulin under conditions of hyperglycemia 592,593. Accordingly, treatment of isolated murine islets with low concentrations of forskolin (1–10 nM) suppresses glucagon secretion by up to 60%, while high concentrations of forskolin (0.1–10 μM) stimulate glucagon release . Consistent with the conclusion that GLP-1 suppression of glucagon secretion does not fully depend on somatostatin, GLP-1 effects on glucagon secretion can be mimicked by forskolin-induced changes in cAMP. In the isolated perfused rat pancreas, co-infusion of GLP-1 with a specific somatostatin receptor 2 (SSTR2) antagonist (PRL-2903) abolishes the GLP-1-induced suppression of glucagon secretion . Although these studies convincingly demonstrate the importance of the GLP-1R ECD for ligand binding, this interaction seems less important for ligand-induced activation of the receptor . This signal peptide is of crucial importance for translocation of the receptor across the ER as well as for trafficking of the receptor to the cell surface 359,, , , . Low expression of GLP-1R occurred in parietal cells and smooth muscle cells of the stomach and in myenteric plexus neurons of the gut with no expression in the liver and thyroid gland . Autoradiography studies identified binding of 125IGLP-1 and 125ITyr39exendin-4 in the rat lateral septum, subfornical regions, thalamus, hypothalamus, interpenduncular nucleus, posterodorsal tegmental nucleus, area postrema, inferior olive, and NTS . In the pancreas, glucagon has physiologically relevant cross-reactivity with GLP-1R, with an EC50 of 36.4 ± 0.22 nM, but there is no affinity of GLP-1 to the glucagon receptor . Weekly insulins, compared to GLP-1/GIP agonists, showed a more tolerable profile and were beneficial for certain patient demographics emphasizing weight stability. To determine the effects of multi-agonists treatment on thermogenesis, infrared pictures were taken with a handheld infrared thermal camera (FLIR Systems E54; Oregon, USA). For calculation, 5-h fasting blood samples were collected from the tail, and glucose and insulin levels were determined using a digital glucometer (Roche) and a commercial ultrasensitive insulin ELISA kit (ALPCO; NH, USA), respectively. Liraglutide was approved for obesity treatment in 2014, and semaglutide, the first oral GLP-1 receptor agonist, was approved in 2019 6, 7. Glucagon-like peptide-1 (GLP-1) is a hormone secreted by intestinal L-cells in the distal ileum and colon. GLP-1 agonists have shown recent benefits in Obstructive Sleep Apnea, and the treatment of neurodegenerative diseases such as Alzheimer’s and Parkinson’s, as well as reducing the risk of stroke. Liu QK (2024) Mechanisms of action and therapeutic applications of GLP-1 and dual GIP/GLP-1 receptor agonists. Brain GLP-1Rs, rather than peripheral GLP-1Rs, appear crucial for the weight-reducing effects of GLP-1RAs. In type-1 diabetic models, although liraglutide is less effective than GIP analogues in promoting osteoblast differentiation, it improves tissue material biomechanics by reducing collagen degradation . Double incretin receptor knock-out (DIRKO) animals revealed that the GLP-1/GLP-1R pathway was important for the integrity of cortical but not trabecular bone . In rodents, but not in humans, activation of thyroid GLP-1R leads to C-cell stimulation in the thyroid 855,856, and involvement of calcitonin in GLP-1-mediated osteoclast activation has been suspected . The first understanding of GLP-1 actions in skeletal physiology arose from GLP-1R KO mice, which exhibit a reduction in trabecular bone mass due to a higher osteoclast activity . In humans, the presence of GLP-1R has primarily been demonstrated in the endothelium, the coronary arteries and the smooth muscle cells 381,612. This occurs in part by a paracrine stimulatory effect on the islets to secrete somatostatin, and perhaps insulin, Zn2+, GABA, and amylin, at elevated glucose concentrations. Amylin dose-dependently suppresses arginine-mediated glucagon secretion in rats whereas pharmacological inhibition of amylin signaling enhances glucagon secretion . Notably, the PKA inhibitor 8-Br-Rp-cAMPS attenuates the inhibitory effect of GLP-1 on glucagon secretion, suggesting that GLP-1 suppression of glucagon secretion is PKA-dependent . Somatostatin inhibits glucagon secretion via paracrine mechanisms and, when blocked, stimulates glucagon release in isolated rat islets 585,586. Stimulation of β-cell proliferation secondary to stimulating GLP-1R is usually only observed in young animals (during periods characterized by preserved proliferative capacity), and not in older rodents . GLP-1R regulation of β-cell proliferation and apoptosis seems to engage mechanisms that include signaling via Pdx1. Collectively, these observations suggest that age-related changes in β-cell neogenesis and replication might be causally linked to the development of type 2 diabetes 525,532,538. GLP-1 induced activation of PKA increases Pdx1 expression and translocation of Pdx1 to the nucleus, where Pdx1 binds to the insulin promoter to initiate insulin expression and synthesis (Figure 5) 490,524. GLP-1-induced stimulation of insulin synthesis is initiated by Pdx1, a transcription factor implicated in development of the pancreas and in MODY type-4 diabetes 522,523. Treatment of primary neonatal mouse cardiomyocytes with liraglutide increases cAMP formation and reduces apoptosis, as indicated by inhibition of TNFa induction of caspase 3 activity . The cardioprotective effect of GLP-1R agonism seems to be, at least in part, independent of GLP-1-induced weight loss, dependent on the canonical GLP-1R, and accompanied by enhanced expression of cardioprotective genes in the heart, including Akt, GSK3β, PPARΔ, NRF-2, and HO-1 . In dogs with acute myocardial infarction, infusion of GLP-1 improves cardiac performance by increasing myocardial glucose uptake and by enhancing left ventricular function . In rats, GLP-1 (7-36amide) and, perhaps paradoxically, the GLP-1R antagonist exendin (9–39), dose-dependently cause relaxation of the aorta, potentially via elevation of cAMP formation and activation of KATP channels . GLP-1 improvement of endothelial function, assessed by flow-mediated vasodilation, was also demonstrated during a hyperglycemic clamp in patients with T2DM and normoglycemic controls . Treatment of mice with GPR40 agonists 296,297 has been reported to decrease body weight and food intake in DIO mice, effects notably absent in mice deficient for either GPR40 or GLP-1R . The type of G protein responsible for the effect on hormone secretion has not been determined for all the receptors; for those where it has not been described, we have indicated the most likely coupling, based on data from other cell studies. In isolated murine and human L-cell cultures, glucose, and the artificial sweetener sucralose, each stimulates GLP-1 secretion with diminished glucose stimulation of GLP-1 secretion in mice lacking α-gustducin, an integral sweet-taste receptor element . Underlining the role of the KATP channels in mediating this process, glucose-stimulated Ca2+ entry and GLP-1 secretion are mimicked upon treatment of GLUTag cells with the KATP channel inhibitor tolbutamide .

Pharmacological effects of GIP, GLP-1 and their mimetics

In murine and human islets, GLP-1, via phospholipase C (PLC), leads to an activation of PKC, followed by membrane depolarization and stimulation of insulin secretion. Epac2 interaction with Rim2 and Piccolo is crucial for cAMP-induced Ca2+-dependent insulin secretion and is not blocked by inhibition of PKA 493,512,513. Consistent with this, clinical studies demonstrate that GLP-1R agonism improves glycemic control in patients with type 2 diabetes but with little risk of hypoglycemia when GLP-1 is used without accompanying sulfonylurea therapy , , , , , , . Given the natural fluctuations in hormone levels and the intricate rhythms of human physiology throughout the day and over a person’s lifetime, there is concern about the uncertain health ramifications of sustained elevation of incretin activity over decades of treatment. For all their promise, GLP-1 and dual GIP/GLP-1 receptor agonists have raised more questions, particularly regarding their long-term safety implications. The FLOW trial also highlights the renal protective effects of GLP-1RAs, suggesting a close link between renal and cardiovascular benefits, which warrants further mechanistic studies (256). Clinical trials of GLP-1RAs have primarily focused on patients with obesity or overweight, yet the effectiveness in the cardiovascular protection appears independent of baseline BMI range (265). Following the withdrawal of albiglutide from the market in 2018 by the manufacturer for financial reasons (257), liraglutide, injectable semaglutide, and dulaglutide should currently be the preferred choices within this class for reducing cardiovascular events until further data are available (248). Transgenic mice overexpressing PDE3B under control of the rat insulin 2 promoter are glucose intolerant and have impaired insulin secretion following an intravenous glucose challenge . In summary, the most obvious metabolic phenotype of the global germline GLP-1R KO mice is diminished insulin secretion in response to oral glucose, and a paradoxical protection from diet-induced obesity despite impaired glycemic control. The molecular mechanism underlying the diminished insulinotropic response of the GLP-1R KO mice to orally administered glucose likely reflects loss of GLP-1R-dependent augmentation of insulin secretion. In contrast to these findings, siRNA mediated knockdown of β-arrestin in INS-1 cells attenuates GLP-1-induced phosphorylation of CREB, ERK1/2, and IRS-2 and diminishes the insulinotropic effect of GLP-1 in conditions of low (2.5 mM) and high glucose (25 mM) .

• While both GLP-1 (1–37) and GLP-1 (7–37) stimulate insulin secretion, GLP-1 (7–37) is efficacious at a lower dose.
• The subsequent phase 3 trial of tirzepatide demonstrated more effective reductions in the glycated hemoglobin levels and body weight, along with greater overall improvements in the lipid profile compared to semaglutide in patients with T2DM, elevating incretin therapeutic agents to a new level (112).
• We pooled data from 25 studies encompassing 18,257 patients.
• These agents not only improve glycemic control by increasing insulin secretion and reducing glucagon levels but also promote significant weight loss, enhance cardiovascular and renal health, and offer potential neuroprotective benefits.
• This suggests a potential niche for weekly insulins in personalized diabetes management, particularly for patients where weight stability is preferred or where GLP-1/GIP receptor agonists’ effects on weight are contraindicated.
• Hyperglycemia plays a pivotal role in triggering DKD, precipitating a cascade of cellular alterations that disrupt glucose metabolism, fatty acid, and amino acid ratios, mitochondrial function, and the coupling of respiratory chain proteins.
• GLP-1/gastrin fusions hold potential to re-granulate diseased islets and improve islet cell health in rodents genetically prone to develop diabetes .

In the phase 2 study of type-2 diabetic patients, Tirzepatide produced a profound reduction in body weight and improved HbA1c levels, both of which were superior relative to effects of Dulaglutide in the active comparator arm , thus demonstrating the translation of the preclinical observations. The first reported GLP-1/GIP co-agonists, which had prolonged half-lives due to the use of fatty acylation or PEGylation, yielded synergistic effects, lowering body weight in obese rodents relative to the individual mono-agonist comparators and having a greater insulinotropic effect in non-human primates. Chronic co-administration of selective mono-agonists to obese non-human primates resulted in significantly more body weight loss when compared to the individual treatments, thus demonstrating the translation of these acute effects observed in humans and the chronic effects observed in primates . In patients with T2DM, exenatide decreases fasting and post-prandial levels of blood glucose , , , , slows gastric emptying , reduces cardiovascular risk factors and decreases body weight accompanied by suppression of food intake , , . GLP-1/FGF21 fusions have been reported to dose-dependently lower body weight in obese mice, and co-administration of the respective mono-agonists results in synergistic body weight loss in obese mice (abstracts). Indeed, a monomeric peptide with potent and balanced triple agonism of GLP-1R, GIPR, and GcgR induced greater body weight loss than the respective co-agonists and mono-agonists in obese mice . Two unique compounds have been evaluated in Phase 2 trials (SAR and MEDI0382), and although dual-agonism has produced promising results on body weight and glycemic control in diabetic patients 926,927, it is not apparent that these co-agonists are superior to selective GLP-1R agonists. The prospect emerged of using GLP-1 to buffer the hyperglycemic effect of glucagon while providing complementary mechanisms to lower body weight, most notably the effects of GLP-1 to suppress appetite to coincide with the energy expenditure effect of glucagon. Treatment of type-2 diabetic patients with a combination of the DPP-4 inhibitor sitagliptin and liraglutide showed no greater efficacy on glucose control relative to treatment with liraglutide alone, potentially because of GLP-1R saturation by the liraglutide monotherapy . Nonetheless, GLP-1 and liraglutide induce adipocyte formation in vitro and in vivo, and adipogenesis is decreased in preadipocytes lacking GLP-1R . Cloning of the human pancreatic GLP-1R cDNA was also used to demonstrate comparable binding affinity of exendin-4 and exendin (9–39) to human GLP-1R , and consolidated the work of Jean-Pierre Raufman and John Eng that identified exendin-4 as a GLP-1 paralog and exendin (9–39) as a GLP-1R antagonist . Each receptor of this family is concisely named based on its single and unique endogenous ligand (GLP-1R, GLP-2R, GCGR, GIPR, SCTR, and GHRHR). Of note, the hindbrain GCG + neurons lack the GLP-1 receptor such that they cannot be directly activated by peripherally-derived GLP-1 . Generation of mice that express eYFP under control of the Gcg promoter has enabled the isolation and characterization of NTS GCG + neurons in ex vivo tissue slices .

• Additionally, 63.2% of patients in the liraglutide group lost at least 5% of their body weight, versus 27.1% in the placebo group.
• These effects include neurotrophic, neurogenic, neuroprotective, anti-inflammatory, and insulin sensitizing actions, a field currently under intensive investigation and not yet fully understood.
• A subsequent analysis of the trial data showed that lixisenatide reduced albuminuria in patients with macroalbuminuria by 39.18% over a median follow-up period of 108 weeks.
• In addition, liraglutide combined with insulin degludec (IDegLira®) is a once-daily, fixed dual combination product approved for T2DM.
• For reference purposes, control non-androgenized mice are included (black bars and dashed lines).
• Counteraction of GLP-1 effect on gastric emptying by co-infusion with prokinetic drug erythromycin during a liquid test meal diminished GLP-1’s ability to decrease postprandial hyperglycemia in patients with T2DM (153).
• These effects were blunted in CNS-specific GIPR knockout mice, suggesting a key role of CNS GIPR in the control of energy metabolism (138) (Figure 1 – Section C).

The long-term steady-state BP is affected by the intravascular volume, which is influenced by the vascular tone and the extracellular fluid volume (ECFV); the ECFV is in turn determined by the sodium balance. Relative to placebo, the reduction of diastolic BP only reached significance for the treatment of exenatide 10 μg/twice daily (−1.08 mmHg) . Most human studies report a moderate stimulatory effect of GLP-1 on HR with unchanged or with reduced BP only in hypertensive individuals 620,622,640,, , , , , . Not all rodent studies report elevated BP in response to GLP-1R agonism, but dose could be a discriminatory factor. In initial validation analyses, we documented that consumption of a high-fat diet (HFD) overtly exacerbated the metabolic profile of PWA animals (Suppl. Fig. S2A, C), while in PNA mice, the impact of HFD was of similar magnitude in control and prenatally-androgenized animals (Suppl. Fig. S2B). We explored metabolic, hormonal, and gonadal responses to different GLP1-based multi-agonists in two experimental (mouse) models of PCOS, namely PWA (postweaning androgenization) and PNA (prenatal androgenization); see Suppl. Here, we document the efficacy of such unimolecular GLP1 multi-agonists, and particularly the superiority of the GLP1/E conjugate, in managing the metabolic complications of PCOS in two mouse models of the disease, with evidence also for improvement of reproductive traits in an ovulatory model of PCOS. In addition, estrogen signaling has been reported to potentiate the suppressive effects of GLP1-RA on food reward55. While the metabolic efficacy of GLP1-RA has been extensively explored, the metabolic actions of estrogen have received less attention due to the undesirable oncogenic and reproductive effects linked to estrogen therapy. Notably, considerable metabolic improvement was achieved at relatively low doses of GLP1/E, thus increasing the safety margin of this compound, which did not cause uterotrophic effects per se. Safety outcomes encompassed the incidence of hypoglycemia, treatment-emergent adverse events (TEAE), and rates of treatment discontinuation due to adverse events. We excluded non-randomized studies, observational studies, extension studies, exploratory analyses, post hoc analyses, and animal studies. We conducted a comprehensive search in the databases Scopus, PubMed, Cochrane, and Web of Science from inception to 5 April 2024 (search strategy detailed in Supplement S1). The modified peptide contains 2 Aib substitutions at positions 2 and 20 with a molecular weight of 4.5 kDa. After absorption, the pharmacokinetic properties and effects of semaglutide are similar, irrespective of the route of administration (103). In another study, semaglutide exhibited greater potency in activating GLP-1R compared to GLP-1, with an EC50 of 6.2 pM for semaglutide vs 16.2 pM for GLP-1 (95) (The variability in EC50 values among different studies for GLP-1 was not uncommon attributable to varying assay conditions).

4. GIP and GLP-1 effects on lipid and glucose metabolism in adipose tissue and liver

Studies in humans with resection of different parts of the small intestine demonstrated that the incretin effect and the GIP response to oral glucose did not correlate – the incretin effect was better correlated with preservation of the ileum . In 1965, Ellis Samols and colleagues had already hypothesized that the intestinal glucagon-like material might somehow be related to the incretin effect . Once the first insulin radioimmunoassays (RIA) became available in the 1960's 58,59, the insulinotropic action of intestinal mucosa extracts was confirmed in healthy humans and was demonstrated to be absent in individuals with type-1 diabetes . GIP has a glucagonotropic effect in pancreatic α-cells during hypoglycemia but no effect during hyperglycemia. Most intestinal K cells secrete a biologically active form of GIP consisting of 42 amino acids, GIP (1–42), which is derived from a 153 amino acid preprohormone precursor distinct from preproglucagon (14). In normal subjects, both fat and carbohydrate stimulate GIP secretion from enteroendocrine K cells, which are dispersed in the upper portion of the gastrointestinal tract (duodenum and jejunum). In the early 1970s, Dupre et al. (11) discovered that infusion of GIP purified from porcine duodenojejunal mucosa, when combined with glucose, led to enhanced insulin secretion and improved glucose intolerance in humans. Consequently, researchers have devoted decades to studying incretins, postulating that incretin-based therapies could potentially reverse this diminished incretin effect and restore insulin secretion in patients with T2DM. The source data supporting the findings of this article are included in this article and its supplementary information files. This method strikes a balance by reducing the impact of large-fold changes while preserving the inherent variability of the data. A Comprehensive data management procedure encompassing three key steps was carried out to ensure the robustness and comparability of our dataset. These data agree with reports demonstrating a crucial role of the GLP-1R ECD for recognition by GLP-1 405,, , , . Several studies have aimed to identify the functional GLP-1 motifs orchestrating its interaction with GLP-1R , , . Underlining the importance of the signal peptide in receptor trafficking, blocking the signal peptide through site-directed mutagenesis causes retention of the receptor within the ER . No changes in lean mass were observed after chronic treatment with the lower doses of any of the poly-agonists (Fig. 3D). As in previous experiments, intervention with an effective dose of metformin had minimal effects on the metabolic profile (Fig. 3A–G), except for marginal improvement of insulin resistance, denoted by a modest reduction of HOMA-IR (Fig. 3H). Statistically significant differences were assessed by one-way ANOVA followed by Tukey’s multiple comparison tests to analyze the effects of compound intervention vs. vehicle administration in PNA mice. In contrast, the triagonist induced a significant decrease in ovarian and uterus weight vs. vehicle-treated PNA mice (Suppl. Fig. S4A, B). Research has shown that intracerebral administration of exendin-4 provides neuroprotection and improves locomotor activity after a stroke in rats, with these effects confirmed in GLP-1R knockout mice, indicating the involvement of GLP-1R . Metabolic improvements, such as better glycemic control and enhanced insulin-stimulated glucose uptake, were observed alongside improved cell architecture. Overexpression of mutant HTT disrupts insulin signaling and promotes neuronal apoptosis in human neuronal cells. While GIP reduces food intake and body weight in rodents, these effects have not been demonstrated in humans. Tirzepatide was significantly more effective in reducing HbA1c and body weight than the selective GLP-1 RA semaglutide (1.0 mg per week), and titrated basal insulin. Tirzepatide is an acylated peptide engineered to activate the GIP and GLP-1 receptors, key mediators of insulin secretion that are also expressed in regions of the brain that regulate food intake. GLP-1 agonists have proven highly effective in managing type 2 diabetes and related metabolic disorders, offering benefits such as improved glycemic control, weight loss, enhanced cardiovascular and renal health, and potential neuroprotective effects. Since tolerability varies between individuals and specific GLP1 receptor agonists, it is important to ensure proper patient education about potential side effects and their typically transient nature to improve tolerability and adherence 78, 79. Additional factors such as increased release of adiponectin from adipose tissue, amelioration of insulin resistance in liver and peripheral tissues, and improved circulatory lipid profile all contribute to the reduced risk of ASCVD (267). Although the pathophysiological processes underlying the cardiovascular disease may improve with weight loss, weight loss alone is insufficient to fully account for the observed cardiovascular improvements. These benefits are independent of baseline glycemia and duration of diabetes and only minimally related to their glucose-lowering efficacy (254). The different GLP1-based multi-agonists employed in the study, including GLP1/E, GLP1/GIP dual agonist, and GLP1/GIP/glucagon triagonist, as well as the GLP1 mono-agonist, were synthesized, purified and characterized as extensively reported elsewhere33,34,35,74. In addition, in order to compare the pharmacological efficacy of the multi-agonists with the standard treatment, subgroups of animals were orally treated with a daily dose of metformin (300 mg/kg); a dose adjusted to that employed in humans by means of the application of the body surface area normalization method71, frequently used in rodent models72,73. Interestingly, despite the lack of consistent actions of metformin in terms of metabolic profiles, treatment with the insulin sensitizer caused a complete normalization of ovarian cyclicity, pointing to a discernible reproductive effect of metformin in some PCOS conditions, in line with clinical literature68, although conflictive results have been reported also69. Notably, these effects were not mimicked by E alone, which failed to rescue cycle perturbations and had a discernible uterotrophic action, but were replicated, in terms of reversal of irregularities of the ovarian cycle, by GLP1 alone, which nonetheless did not elevate LH levels. Anyhow, according to our preclinical data, GLP1/E may be superior in terms of metabolic handling in women with PCOS and obesity not actively seeking pregnancy, as reflected by our results in the metabolically-compromised PWA mice36.

Promising drugs for PCOS: targeting metabolic and endocrine dysfunctions

Furthermore, both guidelines suggest that non-steroidal mineralocorticoid receptor antagonists (such as finerenone) may be an effective option for patients with CKD who are at high risk of cardiovascular events, CKD progression, or cannot tolerate SGLT2is 30, 31. Thus having an oral antidiabetic that tackles both diabetes and obesity significantly reduces the risk of obstructive sleep apnea occurring and serves therapeutic effects in patients with the disease, as weight loss is one of the mainstays of management of Obstructive Sleep Apnea . A systematic review and meta-analysis by Liu Y et al., which included 41 trials, explored the weight-loss effects of GLP-1 agonists in non-diabetic individuals with obesity or overweight.

• The crystal structures of un-acylated liraglutide and semaglutide are almost identical to GLP-1 (7–37).
• In addition, Jelsing et al. report that food intake inhibition by liraglutide is observed in the absence of reduced gastric emptying effects that some have linked to visceral malaise .
• The anabolic effects of GIP may play a physiologically permissive role for adipose tissue synthesis, and GIP antagonist antibodies have been developed as pharmacological agents for obesity treatment (68, 74) (Figure 1 – Section E).
• However, vagal afferents and vagal afferent GLP-1 receptors are presumably less important for the effects of peripheral GLP-1 on body mass.
• Readouts from the first clinical trials with triagonists will determine if such triple agonism has the curative potential that the preclinical data suggest.
• In cultured α-cell lines or isolated islets, high-media glucose concentrations increase PCSK1 expression and cellular GLP-1 content 161,162.

3. Interaction of GIP and GLP-1 in the incretin effect

Substantial evidence supports that peptide-mediated GLP-1 secretion is a Ca2+ sensitive process and involves L-cell signaling via the Ca2+ sensing receptor (CaSR) and the peptide transporter 1 (PEPT1) . The low molecular fraction of wheat protein hydrolysate (LWP) increases GLP-1 secretion in both GLUTag cells and when directly administered in rats . The corn protein zein stimulates GLP-1 secretion in GLUTag cells and in the small intestine of anesthetized rats , and it stimulates GLP-1 secretion when administered either orally or directly into the ileum . Long-term use of GLP-1 agonists such as semaglutide and liraglutide has been shown to reduce blood pressure via increased natriuresis and inhibition of the renin-angiotensin-aldosterone system . In patients with heart failure, semaglutide has been shown to cause reduced levels of N-terminal pro B-type natriuretic peptide (NT-proBNP) and C-reactive protein, thus leading to improved exercise function and quality of life . The STEP (Semaglutide Treatment Effect in People with obesity) trials showed weight loss of up to 17% of body weight with the use of semaglutide for a period of 68 weeks . Through these mechanisms, GLP-1 agonists effectively promote weight loss and are used in the management of overweight and obese individuals. The findings provided conclusive evidence that GLP-1 agonists cause weight loss in a nonlinear dose-response manner in individuals who are overweight or obese without diabetes. Effects of tirzepatide on adjudicated… Efficacy of tirzepatide in phase 2 (GPGB; ) and phase 3 (SURPASS-1 to… Efficacy of tirzepatide in phase… Binding affinity of GIP, GLP-1, and the dual (GIP and GLP-1 receptor) co-agonist… He is member of a data monitoring and safety board for Inventiva. These data suggest that hindbrain GLP-1R activation suppresses food intake via PKA/MAPK-induced inhibition of AMPK. Hindbrain GLP-1R activation enhances phosphorylation of PKA and MAPK while decreasing the activity of AMPK in the NTS, and inhibition of PKA/MAPK activity by administration of Rp-cAMP or UO126 attenuates food intake inhibition of exendin-4 administered into the 4th ventricle . Consistent with this, delivery of exendin (9–39) to these sites increases meal size and food intake , , , , . Chronic blockade of GLP-1R with intra 3rd ventricular infusion of exendin (9–39) increases food intake and fat mass . The left heatmap compares PWA + Vehicle (control) against PWA + GLP1/E (treatment), and the right heatmap compares PNA + Vehicle (control) against PNA + GLP1/E (treatment). Volcano plots further highlighted the differential protein profiles induced by GLP1/E treatment. Similarly, in the PNA group, a marked difference in expression patterns was observed between PNA + Vehicle and PNA + GLP1/E conditions, with a noticeable reduction in protein expression in GLP1/E-treated mice (Fig. 10A—right panel). In PWA groups, heatmaps displayed a clear separation between PWA + Vehicle and PWA + GLP1/E, indicating substantial alterations in proteomic profiles upon treatment, with both increased and decreased proteins being observed in the treated group (Fig. 10A—left panel). GLP1/E significantly ameliorated also insulin sensitivity, as denoted by ITT and HOMA-IR, regardless of the dose, and reduced basal insulin levels (Fig. 5E, G, H); yet, the latter was significant only in mice treated with the highest dose. In addition, mice treated with any of the three low doses of GLP1/E displayed improved glucose handling and basal glucose levels, with higher responses in mice treated with 10 and 25 nmol/kg doses (Fig. 5E, F). Finally, none of the multi-agonists at lower doses, nor metformin, had a beneficial effect on ovarian cyclicity or any other gonadal parameter, such as ovarian and uterus weights and circulating LH levels (Suppl. Fig. S5D–F). In contrast, no effects on ovarian function were observed after treatment with high doses of the different multi-agonists in this PCOS model (Suppl. Fig. S4D). As in PWA mice, such body weight loss was accompanied by a significant decrease in food intake and fat mass (Fig. 2C, D), while only mice treated with the triagonist displayed a significant reduction in lean mass (Fig. 2D).

• Receptors for acetylcholine, including the muscarinic receptors M1, M2, and M3, are expressed in rat L-cells and human NCI-H716 cells .
• In enteroendocrine GLUTag cells, glucose, and fructose dose-dependently increase GLP-1 secretion through closure of ATP-sensitive KATP channels and subsequent membrane depolarization (Figure 3) 247,249,265.
• To this end, we applied indirect calorimetry and infrared thermography systems in PWA mice, treated with equimolar doses (10 nmol/kg) of GLP1/E, GLP1/GIP, and GLP1/GIP/Glucagon, during the first 3 days of treatment; a period when body weight loss was particularly marked.
• In contrast, weekly insulin analogs like icodec showed modest HbA1c reductions but showed lower efficacy in controlling body weight, sometimes even leading to weight gain.
• The glucose concentration after a meal may exceed the absorptive capacity in the proximal intestine so that the ingested glucose rapidly reaches the more distally located L-cells.
• At the plasma membrane, GLP-1R recruitment of arrestin is observed as early as 1 min after stimulation with exendin-4 .
• Glucagon-stimulation of insulin secretion is preserved in islets isolated from β-cell-specific GCGR KO mice but is attenuated upon treatment of these islets with exendin (9–39) .
• In mice, 7-d infusion of exendin-4 into the lateral ventricle was sufficient to protect from MPTP-induced damage of the dopaminergic system and from the development of locomotor deficits that typically arise from dopamine deficiency .

These novel agents offer intriguing alternatives to traditional therapies, potentially revolutionizing the treatment paradigm. However, the proliferation of these agents has created a complex decision-making landscape for healthcare providers, necessitating evidence-based strategies for personalized treatment plans . There are remarkable advancements in the practice of diabetes, particularly in the realm of once-weekly agents designed to enhance treatment adherence and simplify patient management 3,4. This comprehensive comparison aids in refining personalized treatment strategies for T2DM management. And M.T.S. should be considered as joint senior authors, with shared leading roles in terms of conceptualization of the project, study design, supervision of experiments, data interpretation and discussion, and writing of the manuscript, to whom correspondence should be addressed. GLP-1 inhibition of glucagon secretion has been demonstrated in vivo in numerous species including mice , dogs , and humans 516,517,573,, , , , , as well as in the isolated perfused pancreas of rats 473,474,582, dogs , and pigs and in isolated intact murine islets . In this model, human β-cells were grafted under the renal capsule of lean diabetic immunodeficient NOD scid gamma mice. In mouse pancreatic βTC-6 cells, liraglutide enhances β-cell survival via stimulation of anti-apoptotic signaling mechanisms that include stimulation of PI3 kinase-dependent phosphorylation of AKT, leading to inactivation of the pro-apoptotic protein BAD and silencing of FoxO1 . STZ-induced β-cell apoptosis is reduced upon administration of exendin-4 or GLP-1 (7–36 amide) and treatment with exendin-4 diminishes hyperglycemia induced by STZ . Nonetheless, the use of these improved GLP-1R monoagonists to treat obesity is still limited, perhaps related to the level of body weight-lowering efficacy achieved with GLP-1R agonism alone. After 82 wk of treatment of T2DM patients with exenatide, the placebo-subtracted weight loss from baseline is approximately 5% . In contrast, liraglutide was capable of enhancing bone formation in obese weight-reducing women while having no effects on bone resorption . Human studies report less compelling data on the effects of GLP-1 or its analogues in bone remodeling markers or fracture. In a double blind placebo controlled study, 12 week treatment with liraglutide in patients at risk for AD did not show cognitive differences between the study cohorts . Moreover, it remains to be shown that GIPR agonism can improve insulin secretion in type 2 diabetic patients who have been noted in previous studies to be unresponsive to GIP. Long-acting GLP-1 receptor agonists (GLP-1RAs) like liraglutide tend to have more pronounced and persistent gastrointestinal effects compared to short-acting ones like exenatide. Although research on the effects of GLP-1 in HD is limited, a study using a mouse model demonstrated that peripherally administered exendin-4 improved motor coordination and general activity levels in HD mice, extending their survival compared to controls . Treatment with liraglutide improves insulin sensitivity and cell viability by reducing neuronal glucotoxicity, oxidative stress, and mutant HTT levels . The cAMP/PKA signaling pathway plays a key role in exendin-4's protective effects against Aβ-induced memory impairments, highlighting the therapeutic potential of GLP-1R agonists in AD treatment . Furthermore, a preclinical study conducted by Finan et al. (44) reported that both GIPR agonist (GIPRA) and dual GIP/GLP-1 receptor agonist similarly improved glucose tolerance in GLP-1R knockout mice, but not in dual incretin receptor knockout mice. When exposed to a hyperglycemic milieu, the GIPR was found to downregulate in a study of pancreatic islet cells (59) and the patients with T2DM might express a small amount of GIPR or defective GIPR (60, 61). Notably, while both carbohydrate and fat ingestions induce considerable increase in GIP secretion, plasma GLP-1 levels primarily surge after glucose-rich meals (56) Figure 1 – Section A. Despite extensive research into the molecular mechanisms of GLP-1 and GIP actions in pancreatic β-cells, their effects in other cell types remain relatively unexplored. Considering that obesity and/or insulin resistance are predominant among patients with PCOS, lifestyle interventions aimed at lessening the metabolic burden of the syndrome are often at the first-line approach45. Our data delineate the therapeutic superiority of the di-agonist, GLP1/E, in the management of the metabolic alterations of PCOS, with beneficial effects also on ovarian function in our PCOS model of preserved ovulatory function. To further exacerbate the metabolic compromise, the effects of the GLP1 multi-agonists were tested in androgenized animals fed on HFD. We report herein a series of pharmacological and molecular studies in two validated mouse models of PCOS, generated by gestational (PNA) or postweaning (PWA) androgenization, addressing the effects of GLP1-based multi-agonist therapies on metabolic and reproductive traits of PCOS. For each protein, normalized expression levels are compared between Vehicle (green) and GLP1/E treatment (red) groups. Other well-described central nervous system (CNS) actions include reduction of gastric acid secretion, increased satiety, reduction in food craving, and lower preference for energy-dense foods 65, 66. In pyridoxine-induced peripheral neuropathy in non-diabetic rodents, GLP-1 and subcutaneous exendin-4 were observed to partially protect against several pyridoxine-induced functional and morphological damages and to promote normalization of axonal size . Exendin-4 was also shown to increase survival and levels of tyrosine hydroxylase, the key enzyme in dopamine production . Central administration of GLP-1 in rats and mice stimulates the HPA axis and increases secretion of corticosterone, and this is accompanied by increased cFOS immunoreactivity in CRH-positive neurons in the PVN 668,698,814. These data are consistent with the failure of GLP-1 to inhibit gastric acid secretion in vagotomized human subjects as well as the failure of GLP-1 to inhibit vagally-induced motility in the isolated perfused pig antrum . Vagal afferent GLP-1 receptor knockdown accelerates gastric emptying and vagal afferent denervation or peripheral administration of exendin (9–39) 794,795 blocks the effect of centrally or peripherally administered GLP-1 on gastric emptying. Caudal brainstem delivery of Cocaine- and amphetamine-regulated transcript (CART) induces hypothermia, and this effect is blocked by pretreatment with exendin (9–39) . Taken together, these studies suggest that pharmacological activation of brain GLP-1R signaling increases energy expenditure in mice. A pharmaceutically-optimized GLP-1/anti-PCSK9 antibody was reported to have potent weight lowering efficacy in obese rodents and to have potent effects to lower cholesterol in cynomolgous monkeys . The combination of GLP-1 and anti-PCSK9 antibodies, like the GLP-1/FGF21 combinations, has great promise in diabetic patients at risk of cardiovascular disease due to effects on hypercholesterolemia. An optimized GLP-1/CCK fusion had enhanced efficacy to lower body weight in obese rodents relative to mono-agonist controls and their co-administration 946,947. GLP-1/amylin fusions have potential in obese diabetic patients by capitalizing on two independent pharmacological functions to reduce food intake and lower blood glucose. Isl1 also interacts with the enhancer region of the genes encoding for insulin and somatostatin , stimulating their transcription. The cell-specific expression of Gcg is orchestrated by a series of homeodomain proteins that bind to specific cis-acting elements in the Gcg promoter and/or enhancer region to either stimulate or inhibit Gcg promoter activity 94,, , . Diphtheria toxin-induced ablation of preproglucagon-positive neurons in the NTS demonstrated that this small population of neurons is the primary source of endogenous GLP-1 in the brain . Relative to wildtype controls, lean chow-fed GLP-1R KO mice do not have alterations in energy expenditure, neither when kept at a standard room temperature nor when challenged with moderate cold exposure . A role of endogenous GLP-1R signaling in the control of energy expenditure was inferred from studying mice with congenital GLP-1R deficiency. Consistent with this, GLP-1, exendin-4, and the DPP-4 inhibitor sitagliptin reduced proximal tubular sodium reabsorption in rats 660,761,769,770 and humans . In rodents, the ∼1.3 kb 5′-flanking sequence is sufficient to direct transgene expression to Gcg + cells in the brain and the pancreas but extension of this region to include ∼2.5 kb is required to target Gcg + cells in the intestine , including evolutionarily preserved sequences in the first intron . In 1973, John Dupré demonstrated in healthy human volunteers that GIP, when given intravenously at near-physiological doses together with glucose, potentiates immunoreactive insulin and improves glucose tolerance, thus identifying GIP as a contributor to the incretin effect . In 1902, Ernest Bayliss and William Starling identified a substance that is produced in and secreted from the epithelial cells of the duodenum in response to the contact of these cells with acidic chyme . Immunoprecipitation analysis of rat pancreatic islets identified this precursor as an 18,000 molecular weight (MW) protein, now classified as proglucagon . However, data obtained in KO animals generally have to be regarded with caution since compensatory mechanisms, which limit interpretations and affect study outcomes, might develop. Nevertheless, in rats, activation of hindbrain GLP-1R via i.c.v. administration of exendin-4 into the 4th ventricle reduces food intake via reduction of meal frequency; i.e., via increased satiety . Diphtheria toxin-induced ablation of GLP-1 producing neurons in the NTS had no effect on either ad libitum food intake or glucose metabolism . Incretin action may also be reduced during hyperglycemia and in some individuals with diabetes, prediabetes and insulin resistance . The association between WFS1 variants and impaired incretin action may result from alterations of endoplasmic reticulum homeostasis and, consequently, β-cell dysfunction . However, in juvenile but not adult human islets, exendin-4 stimulated calcineurin/NFAT signaling and enhanced expression of proliferation-promoting factors such as NFATC1, FOXM1, and CCNA1 . An innovative approach to assess human β-cell replication in vivo was recently established by the group of Alvin Powers . Prior to initiation of treatments, mice were randomized and distributed into groups allowing similar mean values of body weight and fat mass. Intriguingly, in our studies, hypothalamic CAMK2 expression was upregulated by GLP1/E; an effect that may be due to compensatory mechanisms in response to the marked reduction of body weight after chronic treatment with GLP1/E. GLP1/E therapy also elicited specific changes in the hypothalamic proteomic profile in PNA mice, upregulating proteins involved in the metabolism of non-coding RNA, signaling of nuclear receptor and estrogen-dependent gene expression and downregulating pathways involved in apoptosis, signaling by insulin receptor and cellular responses to starvation. Our data were congruent with those findings, suggesting that GLP1/E retains its powerful body weight-lowering effects in female models of persistent androgenization and PCOS. In addition, our data unambiguously documented that the effects of this and other multi-functional analogs on body weight and food intake are not merely due to food aversion or malaise linked to gastrointestinal distress, regarded as one of the main side-effects of GLP1-based therapy in humans49.

The glucagon receptor family

In human NCI-H716 cells, stimulation of GLP-1 secretion was also demonstrated for leucine, isoleucine, valine, skimmed milk, casein, and whey . A receptor-independent stimulation of GLP-1 release from GLUTag cells has been reported for oleic acid, which stimulates GLP-1 release by uncoupling oxidative phosphorylation and, hence, indirectly stimulating glycolysis with the resulting activation of the mechanism alluded to above . GPR40, the other long chain FFA receptor, is also highly expressed and the most enriched GPCR in L-cells 266,293. However, The GLP-1 response to oleic acid is unaltered in GPR120-deficient mice, and synthetic GPR120 agonists do not stimulate GLP-1 from primary cell cultures . The FFA-induced rise in intracellular Ca2+ is substantially reduced when cells are cultured in a Ca2+ free medium, and is abolished upon treatment of cells with the Ca2+ channel inhibitor nicardipine or when using BSA (which binds fatty acids) . Studies using a stabilized radiolabeled (Ser8)GLP-1 revealed rapid uptake into the brain after intravenous (i.v.) administration without self-inhibition when challenged with increased doses of unlabeled (Ser8)GLP-1 or upon inhibition of brain GLP-1 influx upon pretreatment with exendin (9–39). In addition, Jelsing et al. report that food intake inhibition by liraglutide is observed in the absence of reduced gastric emptying effects that some have linked to visceral malaise . Accordingly, pharmacological activation of AMPK in the VMH blunts food intake suppression by i.c.v. exendin-4 714,715 and attenuates central GLP-1 effects on brown and inguinal white adipose tissue . Consistent with this, i.c.v. administration of exendin (9–39) is sufficient to attenuate the anorexigenic effect of peripherally administered liraglutide and exendin-4 . Intra 4th-ventricular administration of exendin (9–39) or lesions of the AP also block food intake inhibition by GLP-1 infused into the hepatic portal vein (HPV) , suggesting that high levels of circulating GLP-1 inhibit eating at least in part by acting on the hindbrain. Wilding JPH et al. demonstrated the efficacy of Semaglutide (a GLP-1 agonist) in weight loss, with 86.4% of participants achieving a 5% reduction in body weight compared to 31.5% in the placebo group. At week 104, the exenatide plus dapagliflozin group showed greater reductions in HbA1C, weight, fasting plasma glucose, and 2-hour postprandial glucose, highlighting the dual benefits of exenatide (a GLP-1 agonist) in glycemic control and weight loss . Results showed an average weight loss of 8.4 ±7.3 kg in the liraglutide group, compared to 2.8±6.5 kg in the placebo group. In mice, liraglutide blunts hypertension induced by angiotensin II (Ang-II), an effect that is absent in GLP-1R KO mice, and is also attenuated upon pretreatment of WT mice with exendin (9–39) . Notably, while GLP-1 can potentially affect glucagon secretion via its stimulatory effect on the β-cells in normal physiological conditions, GLP-1 also inhibits glucagon release in type 1 diabetes, thus demonstrating that GLP-1 inhibition of glucagon secretion does not fully depend on the β-cell secretome . Pramlintide, a synthetic amylin receptor agonist, improves glycemic control in diabetic patients via inhibition of postprandial glucagon secretion and inhibition of gastric emptying 599,600. In summary, there is credible evidence indicating that Zn2+ that is co-secreted with insulin from the β-cells plays a prominent role in inhibiting release of glucagon , , . As demonstrated in isolated rat α-cells, intact islets and the perfused rat pancreas, Zn2+ inhibits pyruvate-induced glucagon secretion via opening of KATP channels and inhibition of α-cell electrical activity . Studies have shown that GLP-1R agonists, such as exendin-4, liraglutide, and lixisenatide, can rescue spatial memory impairments induced by Aβ in rats . However, subsequent studies have not confirmed these findings, and animal studies have shown that GLP-1 receptor agonists may actually protect against AKI . Post-marketing reports have linked GLP-1 receptor agonists, including liraglutide, to acute kidney failure and worsening chronic kidney disease, sometimes requiring dialysis. Differences among treatment groups were considered statistically significant when P Further information on research design is available in the Nature Portfolio Reporting Summary linked to this article. Overall, the combination of these approaches (i.e., univariate analysis and Random Forest) leverages the strengths of both univariate and multivariate analyses, leading to a more robust and comprehensive understanding of the data. This method strikes a balance by reducing the impact of large-fold changes while preserving the inherent variability of the data.In terms of statistical analysis, we followed two main approaches. Collectively, these data suggest that FFAs increase intracellular Ca2+ by stimulating the influx of Ca2+ via the cell-surface (most likely L-type) Ca2+ channels . Treatment of STC-1, GLUTag, or NCI-H716 cells with long-chain fatty acids potently increases intracellular Ca2+ 253,292. Green or red color background color indicates stimulation (green) or inhibition (red) of hormone secretion upon receptor activation. Schematic on the GPCR Repertoire Involved in Control of Hormone Secretion from Gastric cells expressing either ghrelin or GLP-1. In PNA mice, GLP1/E therapy caused upregulation of pathways involved in the metabolism of non-coding RNA, estrogen-dependent gene expression, autophagy, vesicle-mediated transport, and signaling by nuclear receptors, whereas proteins related to inflammation (ROS and RNS production in phagocytes), cellular response to starvation, signaling by insulin receptor, apoptosis, and immune system were downregulated. As in the PWA model, the improvement caused by GLP1/E therapy in PNA mice in terms of body weight, fat mass, food intake, and insulin sensitivity largely exceeded that of GLP1 or E monotherapies (Fig. 8A–H). Chronic administration of GLP1 decreased body weight, fat mass, and food intake, whereas no glucoregulatory or insulin-sensitizing actions were detected (Fig. 8A–H), while treatment with a similar dose of E improved only insulin sensitivity (Fig. 8A–H). Epac2 binds to the nucleotide binding domain-1 of the SUR1 subunit of the KATP channel and this interaction is aborted when levels of cAMP increase (Figure 6) . CAMP enhances insulin exocytosis by promoting maturation of the granules and thus by increasing the pool of release-competent (RRP/IRP) granules , , . As reviewed previously , the insulin granules are organized in distinct pools that vary in their release competence. This consequently increases the sensitization of the KATP channels to ATP, leading to closure of the KATP channels, depolarization of the cell membrane, and opening of VDC channels (Figure 5).

5. Statistical Analysis

The study will provide a more comprehensive assessment of the cardiovascular outcomes of this dual GIP/GLP-1 receptor agonist. A meta-analysis of seven SURPASS clinical trials in participants with T2DM showed the hazard ratios comparing tirzepatide versus controls of 0.80 (95% CI, 0.57 – 1.11) for 4-MACE, 0.90 (95% CI, 0.50 – 1.61) for cardiovascular death, and 0.80 (95% CI, 0.51 – 1.25) for all-cause mortality (264). However, the benefit in reducing stroke events was not seen in the outcome studies of SGLT-2 inhibitors (260). Moreover, in addition to the direct action of GIP in adipose tissue to reduce serum triglyceride levels, GLP-1 may abolish the postprandial rise in triglyceride and free fatty acid concentrations by reducing intestinal absorption of dietary lipid, stemmed from the delayed gastric emptying (197, 198). The secretion of adiponectin from adipose tissue enhanced by both incretins elicits a signal akin to a fasting state in hepatocytes through the cAMP/pAMPK pathway. Elevated adiponectin concentrations have been noted in major clinical trials with GLP-1RAs (123, 188) and, more robustly, with tirzepatide (189). The sympathetic nerves release norepinephrine, which activates receptors on adipocytes, leading to the mobilization of stored triglycerides. In a study utilizing a cultured mouse embryo preadipocyte cell line, GIP was shown to enhance the synthesis and release of lipoprotein lipase (LPL) into the medium, thereby facilitating the uptake of triglycerides into the adipocytes (171). Our analysis focused on the impact of GLP-1/GIP receptor agonists and weekly insulin analogs on fasting plasma glucose (FPG) levels, using daily insulin as the baseline for comparison. In this case, 5-h-fasted mice were intraperitoneally administered with 0.75 U of insulin (Sigma-Aldrich, MO, USA) per kg body weight, and blood glucose concentrations were determined before (0) and at 15, 30, 60, and 120 min after insulin injection. Thus, integration of both hormones into a single molecule may not only maximize the metabolic efficacy of the individual signals, but allow also specific delivery of estrogen into GLP1 receptor-expressing cells, avoiding potential undesired effects of estrogen on reproductive tissues, as shown also in our studies. Notwithstanding, previous studies have documented beneficial effects of the activation of estrogen receptors in diet-induced obese females, by reducing body weight and fat accumulation and improving leptin resistance at central level53,54. Here, we provide a concise overview of the core physiology of GLP-1 secretion and action, and the role of the peptide in human health, disease and therapeutics. GLP-1 forms the basis for a variety of current drugs for the treatment of type 2 diabetes and obesity, as well as new agents currently being developed. Effects of tirzepatide on adjudicated cardiovascular events in SURPASS-4 ( A ),… Research in rats has shown that administering GLP-1 receptor (GLP-1R) agonists to the hippocampus can prevent spatial learning and memory impairments caused by amyloid β (Aβ), a protein implicated in AD . The hippocampus is a part of the brain involved in spatial learning and memory and the expression of GLP-1 receptors has been found in the hippocampus of rats and mice, thereby improving different aspects of learning and memory . Rare cases of acute kidney injury (AKI) and interstitial nephritis have been reported after taking GLP-1 receptor agonists. Another possible explanation is that GLP-1 receptor agonists alter blood flow to the kidneys 30, 40. However, a recent analysis found no evidence of worsening kidney function in patients with heart failure who took liraglutide 30, 40. The next generation of regimens may involve combining GLP-1 or dual GIP/GLP-1 receptor agonists with other nutrient-based hormone receptor agonists or antagonists that offer equal or greater effectiveness with fewer gastrointestinal adverse effects. Like virtually all medications, incretin mimetics come with side-effects, leading some patients to abandon treatment. Nevertheless, it is crucial to consider the potential adverse effects of weight fluctuation after discontinuing these medications, particularly the increased risk of cardiovascular and all-cause mortality in patients with obesity or overweight. Furthermore, the cardiovascular benefits emerged early in treatment, preceding significant weight loss, suggesting that the cardiovascular effects may be mediated, at least partially, by other salutary processes in atherosclerotic protection. Conversely, in another study with 10 healthy adults where glucose levels were maintained between 70 – 80 mg/dL, fat ingestion elicited a fivefold to sixfold rise in GIP levels without concomitant insulin secretion (119). Previous physiological studies have shown that both GIP (113–116) and GLP-1 (117) act in concert with glucose to enhance insulin gene transcription, mRNA stability, insulin biosynthesis, and insulin secretion. Conversely, in another phase 2b study involving patients with T2DM, tirzepatide showed significantly better efficacy in glucose control and weight loss compared to both placebo and dulaglutide, with an acceptable safety and tolerability profile (111). Notably, treatments with the multi-agonists or GLP1 did not cause signs of nausea/malaise at any time-point tested (2–72 h), since pica behavior (i.e., kaolin intake) was similar, or even lower, in mice treated with GLP1/E, GLP1/GIP, GLP1/GIP/Glucagon, or GLP1 vs. the control PWA group (Suppl. Fig. S8C). Treatments with any of the multi-agonists significantly reduced body weight from 24- to 72-h relative to control PWA animals, while GLP1 decreased body weight only from 24- to 48-h; the magnitude of such effect was much lower than of multi-agonists (Suppl. Fig. S8A). As in previous experiments in PWA mice, no effects on the gonadal profiles were found after treatments with GLP1/E, independently of the dose (Suppl. Fig. S7D–F). Based on these findings, it is hypothesized that the heightened insulin resistance might render patients more resistant to the weight-reducing effects of GLP-1RAs and tirzepatide. A mechanism of action phase 1 study showed that the glycemic efficacy of tirzepatide in T2DM results from concurrent improvements in key components of diabetes pathophysiology, including β-cell function, insulin sensitivity, and glucagon secretion (135). It has been demonstrated that the insulinotropic effect on β-cells and glucagonostatic effect on α-cells each contribute to about half of GLP-1’s blood glucose-lowering activity (134). The dose-dependent effect of GLP-1 on decelerating gastric emptying plays a substantial role in improving postprandial glycemic concentrations to the extent that postprandial insulin secretion may no longer be stimulated or could even be reduced (154, 155) (Figure 1 – Section D). These effects include neurotrophic, neurogenic, neuroprotective, anti-inflammatory, and insulin sensitizing actions, a field currently under intensive investigation and not yet fully understood. Importantly, preclinical studies have demonstrated that co-administration of GIP and GLP-1 intracerebroventricularly results in an additive enhancement in weight-lowering efficacy (138). The ability of peripherally circulating GLP-1 and GLP-1RAs to breach the blood-brain barrier remains uncertain; they may potentially do so via the relatively permeable CVO or through endocytosis and transcytosis of vascular endothelial cells to reach the deep brain (143–145). These effects were blunted in CNS-specific GIPR knockout mice, suggesting a key role of CNS GIPR in the control of energy metabolism (138) (Figure 1 – Section C). Similar neuroprotective effects have been reported in various PD rodent models treated with GLP-1R agonists , , , , , . In mice, 7-d infusion of exendin-4 into the lateral ventricle was sufficient to protect from MPTP-induced damage of the dopaminergic system and from the development of locomotor deficits that typically arise from dopamine deficiency . In a rat model of neurodegeneration, GLP-1 and exendin-4 ameliorated neurodegeneration by reducing ibotenic acid-induced depletion of cholinergic cell bodies, as demonstrated by preservation of choline acetyltransferase immunoreactivity in basal forebrain cholinergic neurons .

• Central administration of GLP-1 in rats and mice stimulates the HPA axis and increases secretion of corticosterone, and this is accompanied by increased cFOS immunoreactivity in CRH-positive neurons in the PVN 668,698,814.
• In order to assess the effects of the different pharmacotherapies on glucose tolerance, animals were subjected to an intraperitoneal glucose tolerance test (GTT) during the third week of treatment, 24 h after the last drug administration.
• Although glucocorticoids are potent anti-inflammatory molecules, chronic treatment oftentimes results in compromised metabolic control, notably due to hepatic action to increase glucose production.
• Intriguingly, emerging data involving gain or loss of function from those cells in mice argue against such a contribution.
• Intraluminal administration of peptones stimulate GLP-1 secretion in the isolated perfused rat ileum but not upon ileal perfusion in healthy human volunteers .
• While the importance of KATP channel activity in mediating GLP-1 release has been confirmed in vitro, its relevance for GLP-1 secretion in vivo is less clear.
• The role of CVO is crucial for sensing peripheral GLP-1 levels and relaying this information to the hypothalamus and other deep brain regions.

Several studies in mice 465,467,685,774 and humans , , , , have failed to detect changes in energy expenditure following chronic or acute peripheral treatment with different GLP-1R agonists. Consistent with these data, central administration of the GLP-1R agonists liraglutide and exendin-4 increases energy expenditure and BAT thermogenesis through mechanisms that include AMPK signaling in the mediobasal hypothalamus . Intriguingly, emerging data involving gain or loss of function from those cells in mice argue against such a contribution. Selective ablation of NTS PPG neurons prevents stress-induced hyperphagia in mice but has no effect on long-term ad libitum food intake, body weight, or glucose tolerance . Agonists of the GLP-1 receptor improve glycemic control via both their acute insulinotropic action and, under certain circumstances, also by chronic action to preserve β-cell mass through stimulation of β-cell proliferation and inhibition of apoptosis (Figure 7) , , , , , . These data led to the hypothesis that the increased insulin mRNA levels occurring upon GLP-1 exposure might be due to stabilization of the mRNA, whereas the elevated expression of GLUT1 and hexokinase are due to direct transcriptional stimulation by GLP-1 . Treatment with the transcription inhibitor actinomycin D blocks GLP-1 stimulation of GLUT1 and hexokinase1 expression in these cells without affecting GLP-1 induction of insulin expression . In addition to the ability of GLP-1 to stimulate insulin secretion via signaling through PKA and Epac2, GLP-1R agonism also increases glucose metabolism by promoting insulin synthesis (Figure 5). These data are consistent with a recent report showing that GLP-1 stimulation of insulin secretion requires GLP-1R and neuronal nitric oxide synthase in the enteric nervous system . Unlike treatment with GLP-1RAs, which generally leads to body weight and fat mass reduction, pioglitazone dose-dependently increases body weight and fat mass. The first seven trials involved patients with T2DM and baseline glycated hemoglobin levels ranging from 7.3 to 8.7, whereas the most recent SELECT trial focused on nondiabetic patients with overweight or obesity and preexisting cardiovascular disease. Moreover, in studies involving patients with T2DM, the magnitude of body-weight loss with GLP-1RAs diminished as baseline hyperglycemia worsened (235, 236). In isolated rat β-cells, treatment with exendin-4 reduces the apoptotic effect induced by treatment with pro-apoptotic cytokines, such as IL1b, TNFa, and interferon gamma . Irs2 is a substrate of the IGF1 and insulin receptor tyrosine kinases that promote growth, function and survival of the β-cells . Post-prandial levels of portal blood glucose are elevated and insulin levels decreased in rats with knockdown of GLP-1R in vagal afferent neurons, suggesting that GLP-1 also regulates blood glucose via activation of vagal afferent GLP-1 receptors .

• Collectively, these observations suggest that age-related changes in β-cell neogenesis and replication might be causally linked to the development of type 2 diabetes 525,532,538.
• GLP-1 forms the basis for a variety of current drugs for the treatment of type 2 diabetes and obesity, as well as new agents currently being developed.
• Studies in GLP-1R KO mice documented that obese mice exhibit comparable weight loss and improved glucose metabolism to wildtype controls following VSG .
• Intriguingly, in the two PCOS models tested, metformin was only marginally effective in improving the metabolic profile, despite the high dose used and its consideration as gold standard for the treatment of insulin resistance in women suffering PCOS.
• Most studies report the absence , , or very restricted expression of the GLP-1 receptor in a small subset (10%) of α-cells , and treatment of isolated rat α-cells with GLP-1 enhances rather than inhibits the release of glucagon , , .
• Therefore, the expression and cleavage of proglucagon and secretion of the various PGDPs must be precisely controlled in a cell-specific process.
• (C) treatment discontinuation due to adverse events compared with daily insulin.

Although 16 of the 30 amino acids in its N-terminus are identical to human GLP-1 (7–36) amide, exendin-4 is not the lizard homolog of GLP-1. Tirzepatide, the only FDA-approved dual GIP/GLP-1 receptor agonist, is a peptide with potent and imbalanced co-agonism at both GIPR and GLP-1R. Its half maximal inhibitory concentration (IC50) for GIPR is 42.4 nM, and its EC50 for GLP-1R is 24.4 pM in a human cell-based functional assays (74). Additionally, intraperitoneal administration of GLP-1 at supraphysiological doses elicited an anti-adipogenic effect in rats (72), making GLP-1 a potential target for obesity treatment. Surface re-expression of GLP-1R after ligand-induced GLP-1R endocytosis appears with a half-time of 15 min with no GLP-1R endocytosis upon treatment of cells with exendin (9–39) . In vitro studies using 125I-labeled GLP-1 (7-36amide) in rat insulinoma cells indicate that internalization of the ligand-GLP-1R complex is saturable and time- and temperature-dependent . In INS-1 cells, knockdown of β-arrestin attenuates GLP-1-stimulation of insulin secretion and decreases activation of ERK1/2 and CREB . These recent studies include the finding of the receptor in differentiating mouse 3T3-L1 pre-adipocytes , , , adipocytes formed from human bone marrow-derived mesenchymal stem cells , human epicardial fat , and in human visceral white adipose tissue .

• In wildtype but not GLP-1R KO mice, liraglutide stimulates the secretion of natriuretic peptide (ANP) from the atrial cardiomyocytes and liraglutide fails to affect natriuresis and vasorelaxation in mice deficient for ANP .
• Underlining the importance of the signal peptide in receptor trafficking, blocking the signal peptide through site-directed mutagenesis causes retention of the receptor within the ER .
• In non-diabetic patients, they have also been shown to reduce the risk of cardiovascular events and mortality.
• Pharmacological inhibition of GLP-1R endocytosis by dynasor attenuates cAMP formation in BRIN BD11 pancreatic β-cells and lowers PKA substrate phosphorylation, resulting in a lesser magnitude of glucose-stimulated insulin secretion .
• In rats, combined administration of dexamethasone and exendin-4 leads to a greater anorexigenic effect and greater weight loss relative to treatment with exendin-4 alone .
• Assuming a preferential central action of GLP1/E, we conducted label-free, quantitative proteomic analyses in the hypothalamus of the two models of PCOS, after chronic treatment with the di-agonist, as a means to disclose putative pathways for the metabolic actions of the di-agonist, and the basis for the partially differential responses between the two models of PCOS, which diverge also in terms of phenotypic presentation.

Pharmacological inhibition or genetic reduction of DPP-4 activity preserves much higher circulating levels of intact GLP-1 191,192, and this was demonstrated to potentiate the insulinotropic effect of GLP-1 in anesthetized pigs (eventually leading to the development of DPP-4 inhibitors for clinical use) . While GLP-1 (7-36amide) and GLP-1 (7–37) are equally potent to stimulate the secretion of insulin and c-peptide , GLP-1 (1–37) has a much lower insulinotropic efficacy , , . Further work is needed to understand the pathological and physiological role for GLP-1 vs. glucagon and paracrine signaling in islet cell development. Multiple lines of evidence are accumulating that challenge current dogma and imply that pancreatic GLP-1 production also has a role, under some circumstances, in regulating insulin secretion via paracrine action , , . In cultured α-cell lines or isolated islets, high-media glucose concentrations increase PCSK1 expression and cellular GLP-1 content 161,162. Regarding long-term tolerability, the rate of discontinuation of GLP1 agonists due to adverse events is generally low (around 10%) and comparable to or slightly higher than other diabetes medications 75, 77. Thus, as a precaution for elective procedures, it is suggested that GLP-1 agonists be discontinued temporarily. In these cases, it's often recommended to reduce the dose of insulin or sulfonylurea to mitigate the risk of hypoglycemic episodes 73, 74. Similarly, injection site reactions are more prevalent with once-weekly exenatide or dulaglutide than with once-daily liraglutide. On the other hand, while the triagonist, GLP1/GIP/Glucagon, was very effective in terms of body weight lowering, in keeping with previous references42, treatment of PWA mice led to a massive, likely detrimental weight loss, also at the expense of lean mass, that was not bound to clear amelioration of glucose intolerance in androgenized female mice. GLP1 alone significantly reduced body weight and fat mass, and improved glucose handling, as well as serum glucose and insulin concentrations, and insulin sensitivity in this PCOS model (Fig. 7A–H), together with a decrease in circulating leptin levels (Suppl. Fig. S9A). Treatment with the multi-agonists caused a very significant reduction in body weight during the 72-h treatment period, which was more pronounced in mice treated with GLP1/GIP/Glucagon (Fig. 6A). PWA mice were administered with equimolar doses of GLP1, E, or GLP1/E (10 nmol/kg), and results were compared with those of vehicle- or metformin-treated (300 mg/kg) PWA mice. Daily treatment with these doses of GLP1/E also reduced food intake; an effect that reached statistical significance with the 10 and 25 nmol/kg doses (Fig. 5C). To this end, we performed a dose-finding study in PWA mice, as model with more severe metabolic alterations, testing the doses of 5, 10, and 25 nmol/kg of GLP1/E. No significant alterations were detected either in circulating FGF21 or adiponectin levels (Suppl. Fig. S5B, C). However, although it may not be relevant for receptor inactivation, receptor internalization is nevertheless important for receptor resensitization. While such ligand-induced receptor internalization has been demonstrated for many GPCRs (including GLP-1R), its importance for receptor deactivation is controversial and is potentially receptor specific. Desensitization of GPCRs is generally achieved by two families of serine/threonine kinases, the second-messenger-dependent protein kinases and the receptor-specific G protein-coupled receptor kinases (GRKs) 436,437. At some point, the ligand-induced receptor activation has to be terminated, and the sensitivity of the receptor to be activated by its ligand has to be restored. Surprisingly, in one recent study, robust expression of the GLP-1 receptor mRNA was also reported in human cardiac ventricles, but the exact localization of the GLP-1R protein could not be determined . Nevertheless, there is little concordance between the available localization data from immunohistochemistry vs. detection of GLP-1R mRNA in situ hybridization. Expression was subsequently confirmed at the protein level 201,610 and histologically using mice that express GFP under control of the GLP1-R promoter. Yet, while GLP1/E and GLP1/GIP reduced body weight by 10% at the end of the treatment, the triagonist caused a 22% reduction (Fig. 2B). Moreover, none of the treatments altered circulating adiponectin levels, and only mice treated with triagonist showed a significant elevation in serum levels of FGF21 (Suppl. Fig. S3B, C). In PWA mice, metformin therapy caused very modest metabolic effects (Fig. 1A–G), denoted only by a moderate reduction in HOMA-IR (Fig. 1H), despite the dose employed was much higher (300 mg/kg) than the doses of multi-agonists. In addition, GLP1/E and GLP1/GIP/Glucagon significantly improved insulin sensitivity, as denoted by ITT and HOMA-IR index, and decreased insulin levels; effects that were not observed in GLP1/GIP-treated animals (Fig. 1E-lower panel, G, H). Administration of exendin-4 and this effect was attenuated when GLP-1R was knocked down on vagal afferent neurons . Administered GLP-1 inhibits eating via activation of hindbrain GLP-1 receptors 261,694 and suggests a similar mechanism for i.v. In mice, acute central (i.c.v.) but not peripheral administration of GLP-1 increased brown adipose tissue (BAT) temperature and increased the activity of sympathetic fibers that innervate the inguinal BAT . The DMH is part of the neuronal network involved in the control of BAT thermogenesis and receives innervation from pre-proglucagon-expressing neurons of the hindbrain . However, relative to wildtype controls, diet-induced obese GLP-1R KO mice exhibit reduced energy expenditure at standard ambient room temperature but not at temperatures favoring thermoneutrality . Yet, animals administered with GLP1/GIP or GLP1/E displayed reduced basal glucose levels at the end of treatment (Fig. 1F). In contrast, GLP1/GIP therapy was unable to consistently reduce body weight, food intake, or fat mass in PWA mice over the study period (Fig. 1A–D). In the PWA model, with overt metabolic and gonadal perturbations, chronic intervention with GLP1/E or the triagonist markedly reduced body weight, food intake, and circulating leptin levels (Fig. 1A–C and Suppl. Fig. S3A). Of note, since we aimed to test the effects of compounds against the most unfavorable metabolic conditions, we assessed the potential therapeutic utility of GLP1 multi-agonists in androgenized animals fed on HFD (Suppl. Fig. S1), which phenocopy a predominant subset of women suffering PCOS, who display overweight or obesity and may be exposed to unhealthy Western diets39,40. Insulin stimulation of intestinal Gcg promoter activity and of GLP-1 secretion is noteworthy because insulin inhibits glucagon production and secretion in isolated rat islets and in hamster islet InR1-G9 cells . Among the numerous metabolic effects of GLP-1 are the glucose-dependent stimulation of insulin secretion, decrease of gastric emptying, inhibition of food intake, increase of natriuresis and diuresis, and modulation of rodent β-cell proliferation. Other GLP-1 receptor agonists, such as liraglutide and lixisenatide, have exhibited superior neuroprotective effects compared to exendin-4 in the MPTP mouse model of PD. The glucagon component would presumably confer energy expenditure benefits that are noticeably absent from GLP-1 and GIP pharmacology 465,932,938, and thus permit greater body weight lowering potency and efficacy. Based on the encouraging efficacy of GLP-1/glucagon and GLP-1/GIP co-agonists, it was rationalized that a single molecule with triple agonism at all three of these receptors might provide even greater efficacy than the respective co-agonists. Tirzepatide (LY ), a once-weekly GLP-1/GIP co-agonist, was superior to a GLP-1R agonist (dulaglutide) in preclinical studies in terms of body weight loss and glycemic control improvement . Since these initial reports, other medicinal chemistry strategies have been employed to design unique GLP-1/glucagon co-agonists, including the use of exendin-4 derived sequences , resulting in a rich pipeline of candidates that are advancing through clinical trials . Both of these GLP-1/glucagon co-agonists, one based on a glucagon-derived backbone and the other based on an oxyntomodulin-derived sequence , had superior weight loss in obese rodents relative to matched analogs that were selective in activity towards GLP-1R. Subsequent studies then confirmed the presence of GLP-1R in these and other insulinoma cell lines , , , , , , , as well as in somatostatin-secreting cells 370,375 and in islets isolated from rats and humans . In mice, peripheral administration of ghrelin further enhances glucose-stimulated GLP-1 secretion and improves glucose tolerance, an effect that is blocked by pre-administration of the ghrelin receptor antagonist D-Lys GHRP6 and that is absent in GLP-1R KO mice . Other factors influencing GLP-1 secretion include activation of the olfactory receptor OR51E1 using nonanoic acid, which stimulates secretion of GLP-1 and PYY in human and rodent enteroendocrine L-cells . Upon ligand binding, GPCRs located on the cell surface transduce the extracellular signal to the interior of the cell. Based on this model, the ligand-specific response of the receptor is mediated by a unique receptor conformation/stabilization that results from the specific and individual contact of the ligand with the receptor . Relative to GLP-1 and exendin-4, the biased GLP-1R agonist exendin P5 favors G protein coupled signaling over recruitment of β-arrestin . By assessing cAMP formation, Ca2+ accumulation and ERK1/2 phosphorylation, biased agonism was demonstrated for exendin-4 and oxyntomodulin, which, relative to GLP-1, have a bias for β-arrestin signaling 427,431,432. Downstream of glucose-mediated membrane depolarization, vesicular exocytosis of GLP-1 is orchestrated in a Ca2+ dependent manner involving a cellular machinery like that in β-cells 277,278. Low concentrations of glucose or methyl-α-glucopyranoside stimulate L-cell electrical activity and promote GLP-1 secretion via sodium-glucose cotransporter (SGLT1)-dependent induction of small inward currents (Figure 3) . While sulphonylureas potently promote insulin secretion in type-2 diabetic patients via inhibition of KATP channel activity , , , , there is no clear evidence that sulphonylureas affect GLP-1 secretion in humans (as reviewed in ). There is controversy as to whether glucose-induced GLP-1 secretion is disturbed in patients with type-2 diabetes. In anesthetized pigs, baseline levels of total GLP-1 in the portal vein are in the range of ∼30 pmol/l and increase up to 150 pmol/l upon treatment with neuromedin C, which is a known stimulator of GLP-1 secretion . This is primarily due to their prolonged action and continuous activation of GLP-1 receptors . In a more recent study, taspoglutide had the maximum probability of causing vomiting and nausea, whereas lixisenatide had the maximum probability of causing the development of diarrhea versus other treatments . These diseases represent pathological processes like immune cell infiltration, epithelial cell damage, and chronic inflammation. Hence, Type 2 diabetes patients on GLP-1 therapy are less hungry due to a decrease in gastric emptying and inhibition of feeding by a CNS mechanism. Interestingly, individuals with low levels of GIP may also have low levels of GLP-1 and vice versa (49). Shortly after food intake, these incretins are released into body circulation and bind to their receptors. This section collects any data citations, data availability statements, or supplementary materials included in this article. In order to calculate integral glucose levels in the glucose tolerance test, the area under the curve (AUC) was calculated using the trapezoidal rule. None of the compounds caused changes in testosterone levels, except for a modest but significant increase in GLP1-treated PWA mice (Fig. 7I). As internal control, in PWA mice, generated by chronic exposure to exogenous DHT, circulating levels of this androgen were consistently elevated, without differences among the different experimental groups (Suppl. Table S1, upper panel). After 26 wk of once-weekly treatment of T2DM patients, dulaglutide at 1.5 mg reduces body weight by nearly 3% from baseline and lowered HbA1c by 1.4% . Once-weekly injections of semaglutide dose-dependently induces body weight loss of up to 7% and reduces HbA1c by 1.8% after 40 wk of treatment in T2DM patients . The weight loss induced by liraglutide at 3 mg is typically in the range of ∼5–10% after 52 wk of treatment of non-diabetic obese patients . Data are more controversial in type-2 diabetes and although first reports did not find evidence of protective effects of the GLP-1 receptor agonist on bone fracture 872,873, more recent data suggest that liraglutide and lixisenatide, but not exenatide, contribute to reduce fractures in the diabetic population . These pills, which enjoyed great popularity in the 1940's and 1950's, comprised a series of weight lowering substances such as thyroid hormone, amphetamines, and laxatives. Historic examples of such a co-administration therapy for the treatment of obesity include the famous rainbow pills . However, adverse gastrointestinal effects generally preclude the use of higher doses, even with adjusted uptitration dosing algorithms 734,877. Chemical modification of native GLP-1 has been essential to advance the pharmacological value of GLP-1R agonism for the treatment of type 2 diabetes and obesity. Consistent with this, treatment of RYGB patients with exendin (9–39) increases the fMRI response to images of food in the caudate nucleus, and in the insula in the human brain in response to consuming palatable food . However, sleeve gastrectomy differs markedly from gastric bypass with faster systemic appearance of ingested glucose and higher secretion of insulin, GLP-1, PYY, CCK, and ghrelin after RGYB . Studies in GLP-1R KO mice documented that obese mice exhibit comparable weight loss and improved glucose metabolism to wildtype controls following VSG . Nonetheless, the ability of L-cells to secrete GLP-1 in direct response to luminal nutrients certainly plays an additional role, and may be the main mechanism of GLP-1 secretion. The serendipitous discovery of exendin-4 led to the development of exenatide immediate-release (exenatide IR, Byetta®), a synthetic version of exendin-4 with C-terminal amidation to enhance its stability Figure 2, Table 1, which became the first FDA-approved GLP-1RA in 2005 for the treatment of T2DM in adults Table 2. However, in murine models, exendin-4 demonstrates about 5,500-fold greater potency in improving glucose control, evidenced by the percentage fall in plasma glucose at 1 hour (87). In cellular assays, exendin-4 exhibits similar potency as human GLP-1 in binding to and activating GLP-1R (86). Exenatide and lixisenatide are exendin 4-based agents, while albiglutide, dulaglutide, liraglutide, and semaglutide are GLP-1-based agents. Unimolecular peptides with dual GIP/GLP-1 receptor agonism have been developed to improve metabolic efficacy and therapeutic index beyond what incretin mono-agonists can achieve (44, 63). However, pharmacological inhibition of active, sodium-coupled glucose transport impaired glucose-stimulated GLP-1 secretion in vitro, whereas inhibition of facilitative GLUT-mediated glucose transport was without effect . Monosaccharides demonstrated to stimulate GLP-1 secretion include glucose, galactose, and fructose 239,247. In summary, while L-cell depolarization is crucial for GLP-1 secretion, the role of the Kir6.2/SUR1 channel complex of the KATP channels for mediating this process in vivo warrants clarification. Overexpression of mutant HTT impairs insulin signaling and stimulates neuronal apoptosis in human SK-N-MC neuronal cells . In PC12 cells, GLP-1 stimulation of neurite outgrowth is only partially silenced by treatment with the PKA inhibitor H89, indicating that cAMP-mediated activation of PI3K and ERK following GLP-1R agonism does not fully depend on PKA signaling, at least in these cells 825,827. Pharmacological inhibition of either PI3-Kinase or ERK blocks the stimulatory effect GLP-1 and exendin-4 on neurite outgrowth in PC12 cells . Studies in mice suggest that GIP may potentiate the GLP-1-induced reduction of food intake and body weight by enhancing POMC expression and neuronal activation within distinct neuron populations in the hypothalamus (149). Emerging evidence suggests that GLP-1RAs may reduce food intake and body weight through diffuse brain effects rather than targeting a specific localized population of GLP-1Rs (145). However, semaglutide exerted broader effects, extending laterally and more deeply into the posterior ARH compared to liraglutide, potentially explaining its greater effectiveness in weight reduction (147). Salameh et al. (146) observed significant blood-to-brain influx for non-acylated GLP-1 mimetics like exendin-4 and lixisenatide, whereas acylated GLP-1 analogues such as liraglutide and semaglutide showed minimal blood-brain barrier penetration in mice. The anti-apoptotic effect of GLP-1R agonism has been demonstrated in vivo in mice 543,550,551 and rats 552,553 as well as in several rodent 550,551 and human 554,555 cell lines, purified rat β-cells , and humans . Solid clinical proof of slowed diabetes progression or enhanced β-cell mass has not been provided in type-2 diabetic patients treated with any GLP-1 receptor agonist . Chronic administration of exendin-4 is unable to prevent β-cell loss in mice that are lacking Irs2 , demonstrating the requirement of Irs2 to GLP-1-mediated β-cell plasticity. GLP-1R agonism also promotes β-cell growth and survival by stimulating the expression of the insulin receptor substrate 2 (Irs2) via mechanisms that include activation of CREB . While substantial evidence supports a role of Pdx1 in the negative regulation of Gcg expression, Pdx1 immunoreactivity has also been demonstrated in some Gcg expressing L-cells . In STC-1 cells, disruption of the CRE element in the Gcg enhancer only partially blunts PKA-stimulation of Gcg expression 130,131. In both α-cells and intestinal L-cells, Gcg expression is controlled by certain homeodomain proteins 94,98,100 and by cAMP-activation of protein kinase A (PKA), as demonstrated in primary rat intestinal cultures , isolated pancreatic cell lines 127,128 and enteroendocrine GLUTag and STC-1 cell lines 129,130. Research has found that all GLP-1 RA regimens significantly increased the incidence of side effects on the gastrointestinal system, compared with placebo or other anti-diabetic treatments commonly used 64, 70. These side effects are induced by various mechanisms majorly activation of central and peripheral GLP-1 receptors . Hunt JE et al reviewed data investigating GLP-1 as a novel treatment for intestinal diseases, such as inflammatory bowel diseases, short-bowel syndrome, intestinal mucositis, and coeliac disease . Beyond glucose maintenance, there is accumulating evidence to support the beneficial role of GLP-1 agonists in the gastrointestinal tract. Indeed, there is evidence that truncated GLP-1 (9-36amide) has no effect on glucose clearance or insulin secretion in healthy humans . However, one report of an experiment in obese humans suggested that GLP-1 (9-36amide) is a weak insulin secretagogue , and administration of GLP-1 (9-36amide) improves glucose handling without affecting insulin secretion in anesthetized pigs and in humans 199,200. Lastly, upon streptozotocin-induced destruction of the β-cells, there is an acute increase in islet PCSK1 and Gcg expression and increased processing of proglucagon to GLP-1 . The hypoglycemia and α-cell hyperplasia seem to directly result from glucagon deficiency because continuous intraperitoneal glucagon supplementation is sufficient to correct the hypoglycemia and the α-cell hyperplasia of Pcsk2−/− mice . In contrast, PC2 (a.k.a. PCSK2) is highly expressed in the pancreas , and its expression in α-cells results in cleavage of Gcg into “pancreatic type” glucagon, GRPP, MPGF, and a small intervening peptide (IP1). When their respective postprandial concentrations were increased through exogenous infusion, GLP-1 elicited a more robust insulin response, suggesting its superior potency compared to GIP as an incretin (28, 55). However, a study by Nauck et al. (48) did not support the existence of this proximal-distal incretin loop in humans as intravenous injection of GIP into humans did not enhance GLP-1 secretion, pointing to the fact that the animal models may differ from humans in essential physiology. GIPR was first cloned in rats, identifying a 455-amino acid glycoprotein with a predicted molecular weight of approximately 59 kDa (41). Under physiological conditions, postprandial GIP levels are approximately 3 – 4 times higher in molar concentration compared to GLP-1, irrespective of diabetic status (28, 39). Nonetheless, the presumed loop (if it exists) would likely be important for the early postprandial phase at a time when the L-cells of the distal gut are not yet in direct contact with luminal nutrients. Importantly, the GLP-1 response to dietary fat is vastly reduced not only in GPR40 KO animals but also in GPR119 KO mice, and agonists for the Gq-coupled GPR40 act in synergy with the Gs-coupled GPR119 to robustly stimulate GLP-1 286,300. Importantly, synthetic GPR40 agonists are efficacious GLP-1 secretagogues both in vitro in primary cultures, in perfused intestines and in vivo when studied in mice 252,294,295. In summary, compelling evidence indicates that FFA increase GLP-1 secretion by stimulating extracellular Ca2+ influx via cell-surface Ca2+ channels. Common adverse effects include nausea and vomiting, as well as increased hazards of gastroparesis and small bowel obstruction. Clinical trials have provided limited insight into the long-term effects, as the longest trials spanned less than six years in adults and about one year in adolescents. Recent findings indicate that the anti-inflammatory effects of GLP-1RAs, mediated through GLP-1R in CNS neurons (268) and intrahepatic lymphocytes (269), play an important role in their antiatherogenic actions. Comparison-adjusted funnel plots indicated no publication bias for HbA1c, hypoglycemia, FPG, and body weight, but there was some indication of publication bias for the incidence of adverse events. The characteristics of studies and patients’ baseline features are presented in Supplement S2. SUCRA provides a hierarchical ranking of treatments facilitating comparison across studies . In summary, there are several mechanisms that may contribute to the rapid increase in GLP-1 secretion following nutrient intake. In rats, infusion of GRP stimulates the secretion of GLP-1 while administration of the GRP antagonist BW10 blocks GLP-1 secretion when fat is directly administered into the duodenum . Interestingly, in rat ileum preparations, administration of atropine was not able to block GIP-induced GLP-1 secretion . Albeit with notable physiological challenges (atropine powerfully inhibits GI motility), infusion of atropine also blunts nutrient induced GLP-1 secretion in healthy human volunteers . Acetylcholine also stimulates GLP-1 secretion in the perfused porcine ileum, and this effect can be blocked by co-infusion of atropine . Insulin has also been suggested to play a significant role as a paracrine regulator of glucagon secretion (the intra-islet hypothesis), although the mechanism by which this inhibition occurs is not well elucidated (133). On the contrary, GLP-1 suppresses glucagon secretion in both healthy individuals and those with T2DM under normoglycemia and hyperglycemia (58) but not during hypoglycemia (131), thereby reducing the potential for developing severe hyperglycemia or hypoglycemia. The safeguard against reactive hypoglycemia is evolutionally crucial, as central nervous tissue relies on stable blood glucose levels (Figure 1 – Section B). Based on collective human data, a glycemic threshold of 99 – 108 mg/dL may exist, below which GIP primarily exerts glucagonotropic actions (35). Furthermore, exendin-4 has been found to stimulate β-cell mass expansion and pancreas regeneration in a partial pancreatectomy rat model of T2DM (129). In contrast to GLP-2 administration, subcutaneous injection of GLP-1 in healthy individuals had no effects on bone formation or resorption markers . As such, a stable GIP agonist has been demonstrated to improve bone quality in rats , whereas DPP-4 inhibition positively modified bone composition but not bone microstructure in high fat fed mice . However, it is not clear whether these ameliorations in bone strength result from activation of skeletal GLP-1 receptors or whether it requires extra-skeletal receptors as observed for the GIP/GIPR pathway . While these data point to a prominent role of somatostatin in mediating GLP-1 suppression of glucagon secretion, treatment of isolated murine islets with the SSTR2 antagonist CYN does not fully inhibit GLP-1's ability to suppress glucagon secretion . Diminished insulin secretion in response to treatment with GLP-1 has been replicated in other studies , , . Notably, the age-dependent decline in the exendin-4 induced β-cell proliferation was not related to changes of GLP-1R expression, as also indicated by preservation of exendin-4-induced insulin secretion in the adult islets . Actively participated in the provision of basic reagents, the study design and interpretation of data, and critically reviewed the manuscript. Participated in the study design, discussion of data, and conducted histological analyses. Conducted the proteomic analysis by LC-MS/MS and participated in data analysis, with in-depth proteomic data analysis and interpretation being conducted by M.M.-O. B.Y., J.D.D., B.F., and R.D.D. participated in the development and synthesis of the different multi-agonists and GLP1-RA and interpretation and discussion of results. Any other information regarding the data is available from corresponding authors, upon request. A–H Effects on body weight (A), body weight change (B), food intake (C), body composition (fat and lean mass change) (D), glucose (upper panel) and insulin tolerance (E), fasting glucose (F), serum insulin levels (G), and HOMA-IR index (H) in PWA female mice daily administered with vehicle (saline) or GLP1/E (5, 10, and 25 nmol/kg) during 28 days. A–H Effects on body weight (A), body weight change (B), food intake (C), body composition (fat and lean mass change) (D), glucose (upper panel) and insulin tolerance (E), fasting glucose (F), serum insulin levels (G), and HOMA-IR index (H) in PNA female mice daily administered with vehicle (saline), GLP1/E (50 nmol/kg), GLP1/GIP (3 nmol/kg), GLP1/GIP/Glucagon triagonist (3 nmol/kg) or metformin (300 mg/kg) during 28 days. A–H Effects on body weight (A), body weight change (B), food intake (C), body composition (fat and lean mass change) (D), glucose (upper panel) and insulin tolerance (E), fasting glucose (F), serum insulin levels (G), and HOMA-IR index (H) in PWA female mice daily administered with vehicle (saline), GLP1/E (50 nmol/kg), GLP1/GIP (3 nmol/kg), GLP1/GIP/Glucagon triagonist (3 nmol/kg) or metformin (300 mg/kg) during 28 days. Emerging preclinical data suggest that a GLP-1/estrogen conjugate enhances the anorectic, body weight lowering, insulinotropic, and islet preservation effects in mice relative to the GLP-1 analog or estrogen alone 467,952,953. In cases where the original studies reported data as medians and ranges, we converted these to means and standard deviations to ensure uniformity in our analysis . We selected data for analysis that represented the longest follow-up periods and included comparisons with daily basal insulin since there is no direct comparison between GLP-1/GIP and weekly insulin. Additionally, we excluded studies involving individuals without type 2 diabetes mellitus, pediatric populations, studies that did not have daily insulin as a comparator, and studies not reporting relevant outcomes related to efficacy and safety. We included randomized controlled trials (RCTs) involving individuals diagnosed with type 2 diabetes mellitus that evaluated weekly GLP-1/GIP agonists and weekly insulin in comparison to daily insulin. By elucidating the relative merits of once-weekly GLP-1/GIP agonists and insulin formulations, our analysis aims to inform clinical decision-making, guide guideline development, and inform healthcare policies. In summary, GLP-1R agonism improves BP through stimulation of natriuresis via Epac2-dependent stimulation of cardiac ANP secretion . However, in humans there is no consistent effect of GLP-1 on ANP secretion whereas angiotensin II is generally lowered 657,, , . Liraglutide stimulation of cardiac ANP secretion is PKA independent but mediated by Epac2 in a cAMP and PLC-dependent manner . GLP-1R agonists acutely stimulate natriuresis in rodents and may also do so in humans, lowering BP, potentially also via reduction of the ECFV 641,642,660,661. Placebo-subtracted weight loss achieved by Qsymia is typically in the range of 5–10% after up to 56 wk of treatment 904,905. Dulaglutide at 0.75 and 1.5 mg (Trulicity®, Eli Lilly & Co) has been approved for the treatment of T2DM patients. Semaglutide at a higher dose is being explored clinically for the treatment of non-diabetic obese patients, and an alternative oral formulation of semaglutide has completed Phase 3 clinical trials for type 2 diabetes. Furthermore, cell bodies that are immunoreactive to GLP-1 antisera are detected in the NTS, and GLP-1 immunoreactive nerve fibers are widely distributed throughout the brain with highest density in the hypothalamus, thalamus and septal regions whereas the lowest density is in the cortex and hindbrain 86,698. In one study GLP-1 infused into the vena cava or hepatic portal vein of rats had similar effects on food intake , whereas in another study in rats GLP-1 infusions into the jugular vein inhibited food intake more potently than infusions into the hepatic portal vein . In rats, on the other hand, lesions of the AP or administration of exendin (9–39) into the 4th ventricle blocked the food intake inhibition by GLP-1 infused into the hepatic portal vein , suggesting that high concentrations of circulating GLP-1 act on the hindbrain to reduce food intake. GLP-1 infusion on food intake was lost after truncal vagotomy , indicating that vagal afferents are involved in mediating the effects of circulating native GLP-1 on appetite. While these data collectively emphasize the importance of neuronal GLP-1R for the food intake inhibition by long-acting GLP-1 analogs, it is unclear whether and to what extend this accounts for physiological doses of intestinal-derived native GLP-1. Similar findings are reported in humans upon intragastric infusion of glucose and fructose at doses that are matched for sweetness . When given orally, fructose is a far less potent GLP-1 secretagogue relative to an isocaloric load of glucose . While the importance of KATP channel activity in mediating GLP-1 release has been confirmed in vitro, its relevance for GLP-1 secretion in vivo is less clear. Glucose-induced membrane depolarization entails opening of voltage-dependent Ca2+ (VDC) channels, and the resulting Ca2+ influx then triggers vesicular exocytosis and secretion of GLP-1 into the circulation (Figure 3) . The loss of GLP-1 effect on stimulating insulin secretion at basal plasma glucose concentrations limits the hypoglycemic risk even at high pharmacological concentrations of GLP-1 (28, 58). In a study involving 10 healthy male subjects, GIP infusion more than doubled the insulin secretion rate compared to the placebo group when the glucose was maintained at 216 mg/dL (35). In another study, dulaglutide demonstrated full receptor activity in vitro and elicited insulinotropic effects in islets similar to GLP-1 (94). Binding studies in CHO-K1 cells expressing GLP-1R showed that lixisenatide is a potent and selective GLP-1RA, with a binding affinity to GLP-1R approximately four times greater than that of GLP-1 (88). Additionally, GLP-1RAs or dual GIP/GLP-1 receptor agonists have been combined with other nutrient-based hormone (e.g., glucagon and amylin) receptor agonists (77–82), a detailed discussion of which is beyond the scope of this review. AD is frequently reported to be accompanied by decreased glucose transport across the BBB and 6 month treatment of AD patients with liraglutide improved BBB glucose transfer relative to placebo controls . Treatment of SK-N-MC cells with liraglutide improves insulin sensitivity and enhances cell viability, potentially by mechanisms that include amelioration of neuronal glucotoxicity, improvement of oxidative stress and less aggregation of the mutant HTT through stimulation of AMPK-mediated autophagy . GLP-1's improvement of learning and memory can be blocked by pretreatment with exendin (9–39), and is absent in mice deficient for the GLP-1 receptor . Inhibition of gastric motility and gastric acid secretion following treatment with GLP-1R agonists has been demonstrated in mice , rats , , , dogs , , , pigs 799,800, and humans 573,, , ,799,, , , , . In addition to its direct and vagally mediated insulinotropic action on β-cells, GLP-1 also improves postprandial glucose handling by inhibition of gastric emptying, decelerating the rate at which glucose is absorbed into the circulation (Figure 7) 573,, , . A common feature of the GLP-1 analogs is the dose-dependent appearance of gastrointestinal adverse effects, most commonly nausea, vomiting, and diarrhea. Albiglutide at 50 mg (Tanzeum®, GlaskoSmithKline) is approved for the treatment of type 2 diabetes but is no longer marketed. In each of the two GLP-1 motifs, certain exendin-4 residues are introduced to replace the native GLP-1 residues. In patients with type 2 diabetes, semaglutide also reduces the risk for an adverse cardiovascular event, with decreased rates of MACE (Major Adverse Cardiovascular Events, comprising cardiovascular death, nonfatal myocardial infarction and stroke) . The range of placebo-corrected weight loss varied from 0.83 kg (95%CI, -1.06 to -0.60) with albiglutide (50 mg/week) at 16 months in the Harmony Outcomes trial (228) to 11.6 kg with tirzepatide (15 mg/week) in the 72-week SURMOUNT-2 trial (229) in patients with T2DM. In trials comparing the addition of injectable agents in individuals requiring further glucose lowering, glycemic efficacy of GLP-1RAs and tirzepatide was found to be similar or greater than that of basal insulin (224–226). Originally developed for the treatment of T2DM, GLP-1RAs and tirzepatide have shown promise in promoting weight loss and attenuating the risk of cardiovascular diseases. On the other hand, chronically elevating GIP levels in a transgenic mouse model exhibited reduced diet-induced obesity (69). By facilitating GIP function at its full metabolic capacity alongside GLP-1, this interaction could effectively harness the full potential of incretin effect to enhance insulinotropic physiology and maintain euglycemia. These findings may explain the reduced responsiveness to GIP observed in individuals with T2DM who may have normal or even increased secretion of GIP. In β-cells, binding of GLP-1 to its receptor leads to activation of adenylate cyclase (AC) and subsequently to an increase in cAMP (Figure 5) . Although the incretin effect is diminished in GLP-1R KO mice, these mice have normal body weight and food intake on regular chow diets , , . The insulinotropic efficacy of these biased-signaling molecules was inversely correlated to the receptor internalization; i.e. insulin release was greatest using molecules that retain GLP-1R at the cell surface . These distinct proteomic responses in PWA vs. PNA mice may provide the basis for the differential efficiency of GLP1/E in these two PCOS models. Molecular hypothalamic profiling revealed common and distinct proteins and pathways being affected by GLP1/E in the two PCOS models, with a consistently higher number of individual proteins being differentially expressed (DE), either up- or down-regulated, in the hypothalamus of PWA mice treated with GLP1/E vs. PNA animals. Assuming a preferential central action of GLP1/E, we conducted label-free, quantitative proteomic analyses in the hypothalamus of the two models of PCOS, after chronic treatment with the di-agonist, as a means to disclose putative pathways for the metabolic actions of the di-agonist, and the basis for the partially differential responses between the two models of PCOS, which diverge also in terms of phenotypic presentation. NMA enables the integration of data from diverse randomized controlled trials (RCTs), offering a robust framework for assessing the comparative efficacy and safety of different treatment modalities. Nonetheless, the challenge lies in personalizing therapy in order to optimize treatment outcomes while minimizing adverse effects and the risk of polypharmacy. Tirzepatide significantly outperformed other treatments in reducing HbA1c and promoting weight loss. In conclusion, this network meta-analysis provides comprehensive insights into the comparative efficacy and safety of GLP-1/GIP receptor agonists and weekly insulin analogs. Combining lower doses of GLP-1/GIP agonists with weekly insulin may enhance patient adherence and satisfaction by reducing the frequency of injections and side effects while maintaining efficacy. However, for patients where weight loss is not necessary or desired, weekly insulins offer an effective alternative that maintains weight stability while still providing good glycemic control. However, these insulins could be a viable option for individuals in low to moderate weight categories where significant weight loss is not a primary treatment goal. Exendin-4 also prevents Aβ-induced apoptosis by maintaining Bcl-2 levels and inhibiting caspase-3 activation, crucial factors in AD pathogenesis . Similarly, GLP-1 in the brain acts as a growth factor, enhancing cell growth, repair, and neuroprotection . Insulin not only regulates blood glucose but also promotes neuronal growth, repair, and cognitive functions. The kidney function of patients taking these medications should be monitored closely and their doses adjusted carefully if necessary. Perhaps analogously, rodent experiments have found that GLP-1R signaling is not required for the weight-reducing effect of Roux-en-Y Gastric Bypass (RYGB) . In some studies, depending on subject characteristics and nutrient load, GLP-1 responses were augmented by acarbose or voglibose (α-glucosidase inhibitors) 217,218. Similar effects are elicited by α-glucosidase inhibitors, which prevent digestion of starch and oligosaccharides, thus moving the unprocessed nutrients to more distal parts of the gut. Consistent with this, plasma levels of GLP-1 rapidly increase in healthy humans upon direct administration of carbohydrates or lipids into the ileum . The apical surface of the L-cell faces the gut lumen, where it has direct contact with luminal nutrients (Figure 3) . Primary outcomes included changes in HbA1c, body weight, and tolerability. This analytical procedure allowed accurate determination of testosterone, dihydrotestosterone, androstenedione, progesterone, 17-alpha hydroxyprogesterone, and estradiol levels in serum samples from PNA and PWA mice. Home-cage locomotor activity was measured also along the treatments by means of an extensiometric weight transducer integrated below each cage. Exendin-4 stimulates β-cell proliferation and inhibits β-cell apoptosis in wildtype mice but not in mice with β-cell specific inactivation of Pdx1 . While inconsistent results have been reported, the treatment duration, age of the animal, and species under investigation as well as diet-composition might affect the ability of GLP-1R agonism to improve β-cell replication . The replication rate of human β-cells is greatest in young childhood and puberty but declines with increasing age 526,531,533,536. In summary, GLP-1 stimulates both the synthesis and secretion of insulin via multiple cAMP-dependent pathways. Another recent report suggests that incretin-stimulation of insulin secretion requires incorporation of glutamate in the insulin granules. The analysis pooled results from multiple studies that reported level 1 (≤70 mg/dL) and level 2 (≤55 mg/dL) hypoglycemia. Treatments are presented according to their effect estimate compared with daily insulin. (A) Network meta-analysis results for change from baseline in FPG compared with daily insulin. The surface under the cumulative ranking (SUCRA) plot displays the ranking probabilities of treatments in reducing hemoglobin A1c (HbA1c). All data from certainty analysis are included in (Supplement S6). Interestingly, the metabolic effects of GLP1/E in PWA mice were greater than those of GLP1 or E alone, documenting the potent enhancement of the actions of the individual compounds when integrated in a single, stable molecule with dual agonist activity, also in the context of PCOS. Interestingly, a comparison of acute metabolic responses with the chronic profiles at the end of the treatment period strongly suggests that while the different GLP1-based agonists may share primary mechanisms of action, the durability and efficiency of their long-term metabolic responses differ, with clear superiority for the GLP1/E compound. Investigation of the mechanisms underlying the beneficial metabolic effects of multi-agonist therapies, conducted in PWA mice, as a genuine model for the metabolic alterations of PCOS36, revealed a predominant action in terms of suppression of food intake, with negligible effects in terms of energy expenditure, thermogenic function or locomotor activity. Interestingly, clinical trials reported to date on the effects of tirzepatide did include obese men and women, but results were not segregated by gender47, thus making it difficult to anticipate whether a sex dimorphism exist in GLP1/GIP responses. Yet, the efficiency of such interventions is, in many cases, limited, and additional, second-line treatments are frequently implemented, that mainly involve the use of metformin, as insulin-sensitizer, with variable efficacy in terms of improvement of reproductive and metabolic alterations.Activlife Keto Acv Gummies Phone Number Customer Service 61231072
How To Stop Emotional Eating And Lose Weight In A Healthier Way
Losing Weight On Metformin Type 2 Tudiabetes Forum
Kelly Clarkson Keto Acv Gummies On Amazon What You Need To Check First
How To Consume Mangoes For Weight Loss
Lowcarb Diet Can It Help You Lose Weight
Positive Weight Loss Quotes
How To Make Ginger Shots At Home For Weight Loss
Activlife Ketoacv Gummies 10111832
Enhanced Weight Management Support