Improved glucose control and reduced body weight in rodents with dual mechanism of action peptide hybrids

Amylin receptor agonism enhances the effects of liraglutide in protecting against the acute metabolic side effects of olanzapine

Olanzapine is a second-generation antipsychotic (AP) used in the management of schizophrenia. Although effective at reducing psychoses, APs cause rapid hyperglycemia, insulin resistance, and dyslipidemia, an effect mediated in part by glucagon. We tested if amylin, a hormone that reduces glucagon, or the amylin receptor agonist pramlintide would protect against acute olanzapine-induced impairments in glucose and lipid homeostasis alone or in combination with other glucose-lowering agents such as liraglutide. We demonstrated that pramlintide lowered olanzapine-induced increases in glucagon:insulin ratio with a trend to protect against excursions in blood glucose. There was an additive effect of pramlintide and liraglutide in protecting against olanzapine-induced hyperglycemia, which was mirrored by reductions in glucagon and attenuated markers of dyslipidemia. Our findings provide evidence that pramlintide, although moderately protective against some aspects of olanzapine-induced metabolic dysfunction, can be used to enhance the protective effects of other interventions against acute olanzapine-induced metabolic dysfunction.

Polyagonists in Type 2 Diabetes Management

PURPOSE OF THE REVIEW

This review summarizes the new developments in polyagonist pharmacotherapy for type 2 diabetes.

RECENT FINDINGS

Several dual- and triple-agonists targeting different pathogenic pathways of type 2 diabetes have entered clinical trials and have led to significant improvements in glycaemia, body weight, fatty liver, and cardio-renal risk factors, with variable adverse event profiles but no new serious safety concerns. Combining agents with complementary and synergistic mechanisms of action have enhanced efficacy and safety. Targeting multiple pathogenic pathways simultaneously has led to enhanced benefits which potentially match those of bariatric surgery. Tirzepatide, cotadutide, BI456906, ritatrutide, and CagriSema have entered phase 3 clinical trials. Outcomes from published clinical studies are reviewed. Efficacy-safety profiles are heterogeneous between agents, suggesting the potential application of precision medicine and need for personalized approach in pharmacological management of type 2 diabetes and obesity. Polyagonism has become a key strategy to address the complex pathogenesis of type 2 diabetes and co-morbidities and increasing number of agents are moving through clinical trials. Heterogeneity in efficacy-safety profiles calls for application of precision medicine and need for judicious personalization of care.

Novel Noninvasive Approaches to the Treatment of Obesity: From Pharmacotherapy to Gene Therapy

Recent insights into the pathophysiologic underlying mechanisms of obesity have led to the discovery of several promising drug targets and novel therapeutic strategies to address the global obesity epidemic and its comorbidities. Current pharmacologic options for obesity management are largely limited in number and of modest efficacy/safety profile. Therefore, the need for safe and more efficacious new agents is urgent. Drugs that are currently under investigation modulate targets across a broad range of systems and tissues, including the central nervous system, gastrointestinal hormones, adipose tissue, kidney, liver, and skeletal muscle. Beyond pharmacotherapeutics, other potential antiobesity strategies are being explored, including novel drug delivery systems, vaccines, modulation of the gut microbiome, and gene therapy. The present review summarizes the pathophysiology of energy homeostasis and highlights pathways being explored in the effort to develop novel antiobesity medications and interventions but does not cover devices and bariatric methods. Emerging pharmacologic agents and alternative approaches targeting these pathways and relevant research in both animals and humans are presented in detail. Special emphasis is given to treatment options at the end of the development pipeline and closer to the clinic (ie, compounds that have a higher chance to be added to our therapeutic armamentarium in the near future). Ultimately, advancements in our understanding of the pathophysiology and interindividual variation of obesity may lead to multimodal and personalized approaches to obesity treatment that will result in safe, effective, and sustainable weight loss until the root causes of the problem are identified and addressed.

GLP-1 receptor agonists in diabetic kidney disease: current evidence and future directions

With the emergence of various classes of blood glucose-lowering agents, choosing the appropriate drug for each patient is emphasized in diabetes management. Among incretin-based drugs, glucagon-like peptide 1 (GLP-1) receptor agonists are a promising therapeutic option for patients with diabetic kidney disease (DKD). Several cardiovascular outcome trials have demonstrated that GLP-1 receptor agonists have beneficial effects on cardiorenal outcomes beyond their blood glucose-lowering effects in patients with type 2 diabetes mellitus (T2DM). The renal protective effects of GLP-1 receptor agonists likely result from their direct actions on the kidney, in addition to their indirect actions that improve conventional risk factors for DKD, such as reducing blood glucose levels, blood pressure, and body weight. Inhibition of oxidative stress and inflammation and induction of natriuresis are major renoprotective mechanisms of GLP-1 analogues. Early evidence from the development of dual and triple combination agents suggests that GLP-1 receptor agonists will probably become popular treatment options for patients with T2DM.

Multiagonist Unimolecular Peptides for Obesity and Type 2 Diabetes: Current Advances and Future Directions

The ever-increasing prevalence of obesity and Type 2 diabetes has necessitated the development of newer and more effective approaches for achieving efficient glycemic control and weight loss. Conventional treatment methods often result in weight gain, further deteriorating the already impaired metabolic control in people with obesity/Type 2 diabetes. Alleviation of obesity and diabetes achieved after bariatric surgeries highlight the therapeutic importance of gut-brain axis and entails development of more patient-friendly approaches replicating the positive metabolic effects of bariatric surgery. Given the potential involvement of several gut hormones in the success of bariatric surgery, the therapeutic importance of synergistic interaction between these hormones for improved metabolism cannot be ignored. Many unimolecular multiagonist peptides are in preclinical and clinical trials as they maximize the combinatorial metabolic efficacy by concurrent activation of multiple gut hormone receptors. This review summarizes the ongoing developments of multiagonist peptides as novel therapeutic approaches against obesity-diabetes.

Glucagon-like peptide 1 (GLP-1)

BACKGROUND

The glucagon-like peptide-1 (GLP-1) is a multifaceted hormone with broad pharmacological potential. 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. GLP-1 also has cardio- and neuroprotective effects, decreases inflammation and apoptosis, and has implications for learning and memory, reward behavior, and palatability. Biochemically modified for enhanced potency and sustained action, GLP-1 receptor agonists are successfully in clinical use for the treatment of type-2 diabetes, and several GLP-1-based pharmacotherapies are in clinical evaluation for the treatment of obesity.

SCOPE OF REVIEW

In this review, we provide a detailed overview on the multifaceted nature of GLP-1 and its pharmacology and discuss its therapeutic implications on various diseases.

MAJOR CONCLUSIONS

Since its discovery, GLP-1 has emerged as a pleiotropic hormone with a myriad of metabolic functions that go well beyond its classical identification as an incretin hormone. The numerous beneficial effects of GLP-1 render this hormone an interesting candidate for the development of pharmacotherapies to treat obesity, diabetes, and neurodegenerative disorders.

CNS-targeting pharmacological interventions for the metabolic syndrome

The metabolic syndrome (MetS) encompasses medical conditions such as obesity, hyperglycemia, high blood pressure, and dyslipidemia that are major drivers for the ever-increasing prevalence of type 2 diabetes, cardiovascular diseases, and certain types of cancer. At the core of clinical strategies against the MetS is weight loss, induced by bariatric surgery, lifestyle changes based on calorie reduction and exercise, or pharmacology. This Review summarizes the past, current, and future efforts of targeting the MetS by pharmacological agents. Major emphasis is given to drugs that target the CNS as a key denominator for obesity and its comorbid sequelae.

Glucagon, GLP-1 and Thermogenesis

Brown adipose tissue (BAT) thermogenesis is a conserved mechanism to maintain body temperature in mammals. However, since BAT contribution to energy expenditure can represent a relevant modulator of metabolic homeostasis, many studies have focused on the nervous system and endocrine factors that control the activity of this tissue. There is long-established evidence that the counter-regulatory hormone glucagon negatively influences energy balance, enhances satiety, and increases energy expenditure. Despite compelling evidence showing that glucagon has direct action on BAT thermogenesis, recent findings are questioning this conventional attribute of glucagon action. Glucagon like peptide-1 (GLP-1) is an incretin secreted by the intestinal tract which strongly decreases feeding, and, furthermore, improves metabolic parameters associated with obesity and diabetes. Therefore, GLP-1 receptors (GLP-1-R) have emerged as a promising target in the treatment of metabolic disorders. In this short review, we will summarize the latest evidence in this regard, as well as the current therapeutic glucagon- and GLP-1-based approaches to treating obesity.

Combined Amylin/GLP-1 pharmacotherapy to promote and sustain long-lasting weight loss

A growing appreciation of the overlapping neuroendocrine mechanisms controlling energy balance has highlighted combination therapies as a promising strategy to enhance sustained weight loss. Here, we investigated whether amylin- and glucagon-like-peptide-1 (GLP-1)-based combination therapies produce greater food intake- and body weight-suppressive effects compared to monotherapies in both lean and diet-induced obese (DIO) rats. In chow-maintained rats, systemic amylin and GLP-1 combine to reduce meal size. Furthermore, the amylin and GLP-1 analogs salmon calcitonin (sCT) and liraglutide produce synergistic-like reductions in 24 hours energy intake and body weight. The administration of sCT with liraglutide also led to a significant enhancement in cFos-activation in the dorsal-vagal-complex (DVC) compared to mono-therapy, suggesting an activation of distinct, yet overlapping neural substrates in this critical energy balance hub. In DIO animals, long-term daily administration of this combination therapy, specifically in a stepwise manner, results in reduced energy intake and greater body weight loss over time when compared to chronic mono- and combined-treated groups, without affecting GLP-1 receptor, preproglucagon or amylin-receptor gene expression in the DVC.

Long-Acting Neurotensin Synergizes With Liraglutide to Reverse Obesity Through a Melanocortin-Dependent Pathway

Neurotensin (NT), a gut hormone and neuropeptide, increases in circulation after bariatric surgery in rodents and humans and inhibits food intake in mice. However, its potential to treat obesity and the subsequent metabolic dysfunctions have been difficult to assess owing to its short half-life in vivo. Here, we demonstrate that a long-acting, pegylated analog of the NT peptide (P-NT) reduces food intake, body weight, and adiposity in diet-induced obese mice when administered once daily for 6 days. Strikingly, when P-NT was combined with the glucagon-like peptide 1 mimetic liraglutide, the two peptides synergized to reduce food intake and body weight relative to each monotherapy, without inducing a taste aversion. Further, P-NT and liraglutide coadministration improved glycemia and reduced steatohepatitis. Finally, we show that the melanocortin pathway is central for P-NT-induced anorexia and necessary for the full synergistic effect of P-NT and liraglutide combination therapy. Overall, our data suggest that P-NT and liraglutide combination therapy could be an enhanced treatment for obesity with improved tolerability compared with liraglutide monotherapy.

Emerging hormonal-based combination pharmacotherapies for the treatment of metabolic diseases

Obesity and its comorbidities, such as type 2 diabetes mellitus and cardiovascular disease, constitute growing challenges for public health and economies globally. The available treatment options for these metabolic disorders cannot reverse the disease in most individuals and have not substantially reduced disease prevalence, which underscores the unmet need for more efficacious interventions. Neurobiological resilience to energy homeostatic perturbations, combined with the heterogeneous pathophysiology of human metabolic disorders, has limited the sustainability and efficacy of current pharmacological options. Emerging insights into the molecular origins of eating behaviour, energy expenditure, dyslipidaemia and insulin resistance suggest that coordinated targeting of multiple signalling pathways is probably necessary for sizeable improvements to reverse the progression of these diseases. Accordingly, a broad set of combinatorial approaches targeting feeding circuits, energy expenditure and glucose metabolism in concert are currently being explored and developed. Notably, several classes of peptide-based multi-agonists and peptide-small molecule conjugates with superior preclinical efficacy have emerged and are currently undergoing clinical evaluation. Here, we summarize advances over the past decade in combination pharmacotherapy for the management of obesity and type 2 diabetes mellitus, exclusively focusing on large-molecule formats (notably enteroendocrine peptides and proteins) and discuss the associated therapeutic opportunities and challenges.

Anti-Obesity Therapy: from Rainbow Pills to Polyagonists

With their ever-growing prevalence, obesity and diabetes represent major health threats of our society. Based on estimations by the World Health Organization, approximately 300 million people will be obese in 2035. In 2015 alone there were more than 1.6 million fatalities attributable to hyperglycemia and diabetes. In addition, treatment of these diseases places an enormous burden on our health care system. As a result, the development of pharmacotherapies to tackle this life-threatening pandemic is of utmost importance. Since the beginning of the 19th century, a variety of drugs have been evaluated for their ability to decrease body weight and/or to improve deranged glycemic control. The list of evaluated drugs includes, among many others, sheep-derived thyroid extracts, mitochondrial uncouplers, amphetamines, serotonergics, lipase inhibitors, and a variety of hormones produced and secreted by the gastrointestinal tract or adipose tissue. Unfortunately, when used as a single hormone therapy, most of these drugs are underwhelming in their efficacy or safety, and placebo-subtracted weight loss attributed to such therapy is typically not more than 10%. In 2009, the generation of a single molecule with agonism at the receptors for glucagon and the glucagon-like peptide 1 broke new ground in obesity pharmacology. This molecule combined the beneficial anorectic and glycemic effects of glucagon-like peptide 1 with the thermogenic effect of glucagon into a single molecule with enhanced potency and sustained action. Several other unimolecular dual agonists have subsequently been developed, and, based on their preclinical success, these molecules illuminate the path to a new and more fruitful era in obesity pharmacology. In this review, we focus on the historical pharmacological approaches to treat obesity and glucose intolerance and describe how the knowledge obtained by these studies led to the discovery of unimolecular polypharmacology.

Peptide-based multi-agonists: a new paradigm in metabolic pharmacology

Obesity and its comorbidities, such as type 2 diabetes, are pressing worldwide health concerns. Available anti-obesity treatments include weight loss pharmacotherapies and bariatric surgery. Whilst surgical interventions typically result in significant and sustained weight loss, available pharmacotherapies are far less effective, typically decreasing body weight by no more than 5-10%. An emerging class of multi-agonist drugs may eventually bridge this gap. This new class of specially tailored drugs hybridizes the amino acid sequences of key metabolic hormones into one single entity with enhanced potency and sustained action. Successful examples of this strategy include multi-agonist drugs targeting the receptors for glucagon-like peptide-1 (GLP-1), glucagon and the glucose-dependent insulinotropic polypeptide (GIP). Due to the simultaneous activity at several metabolically relevant receptors, these multi-agonists offer improved body weight loss and glucose tolerance relative to their constituent monotherapies. Further advancing this concept, chimeras were generated that covalently link nuclear acting hormones such as oestrogen, thyroid hormone (T₃ ) or dexamethasone to peptide hormones such as GLP-1 or glucagon. The benefit of this strategy is to restrict the nuclear hormone action exclusively to cells expressing the peptide hormone receptor, thereby maximizing combinatorial metabolic efficacy of both drug constituents in the target cells whilst preventing the nuclear hormone cargo from entering and acting on cells devoid of the peptide hormone receptor, in which the nuclear hormone might have unwanted effects. Many of these multi-agonists are in preclinical and clinical development and may represent new and effective tools in the fight against obesity and its comorbidities.

Recent updates on GLP-1 agonists: Current advancements & challenges

Glucagon-like peptide (GLP)-1 is an incretin hormone exhibiting several pharmacological actions such as neuroprotection, increased cognitive function, cardio-protection, decreased hypertension, suppression of acid secretion, increase in lyposis, and protection from inflammation. The most potent actions are glucose-dependent insulinotropic and glucagonostatic actions, stimulation of β-cell proliferation, enhanced insulin secretion and reduced weight gain in patients with type-2 diabetes pertaining to blood glucose control. Despite all these actions, its short half-life (around 2∼min) and degradation by a dipeptidyl peptidase-4 enzyme (DPP-4) limits the therapeutic utility of GLP1. In this review, we have discussed DPP IV-resistant analogs of GLP-1 currently present in clinical trials such as Exenatide, Liraglutide, Semaglutide, Efpeglenatide, Exenatide ER, Ittca 650 (Intarcia), Dulaglutide, Albiglutide, and Lixisenatide. Moreover, we have also discussed in detail the pharmacology, signaling mechanisms, and pharmacokinetic properties (Cmax, Tmax, T_1/2, Vd, and Bioavailability) of DPP IV-resistant analogs of (GLP-1). Interestingly, GLP-1 agonist drugs have shown better potential to treat type-2 diabetes mellitus (T2DM) as compared to currently used drugs in clinics without causing the side effects of hypoglycemia and weight gain.

Molecular Signature for Receptor Engagement in the Metabolic Peptide Hormone Amylin

The pancreatic peptide hormone, amylin, plays a critical role in the control of appetite, and synergizes with other key metabolic hormones such as glucagon-like peptide 1 (GLP-1). There is opportunity to develop potent and long-acting analogues of amylin or hybrids between these and GLP-1 mimetics for treating obesity. To achieve this, interrogation of how the 37 amino acid amylin peptide engages with its complex receptor system is required. We synthesized an extensive library of peptides to profile the human amylin sequence, determining the role of its disulfide loop, amidated C-terminus and receptor "capture" and "activation" regions in receptor signaling. We profiled four signaling pathways with different ligands at multiple receptor subtypes, in addition to exploring selectivity determinants between related receptors. Distinct roles for peptide subregions in receptor binding and activation were identified, resulting in peptides with greater activity than the native sequence. Enhanced peptide activity was preserved in the brainstem, the major biological target for amylin. Interpretation of our data using full-length active receptor models supported by molecular dynamics, metadynamics, and supervised molecular dynamics simulations guided the synthesis of a potent dual agonist of GLP-1 and amylin receptors. The data offer new insights into the function of peptide amidation, how allostery drives peptide-receptor interactions, and provide a valuable resource for the development of novel amylin agonists for treating diabetes and obesity.

Guanylin and uroguanylin mRNA expression is increased following Roux-en-Y gastric bypass, but guanylins do not play a significant role in body weight regulation and glycemic control

AIM

To determine whether intestinal expression of guanylate cyclase activator 2A (GUCA2A) and guanylate cyclase activator 2B (GUCA2B) genes is regulated in obese humans following Roux-en-Y gastric bypass (RYGB), and to evaluate the corresponding guanylin (GN) and uroguanylin (UGN) peptides for potentially contributing to the beneficial metabolic effects of RYGB.

METHODS

Enteroendocrine cells were harvested peri- and post-RYGB, and GUCA2A/GUCA2B mRNA expression was compared. GN, UGN and their prohormones (proGN, proUGN) were administered subcutaneously in normal-weight mice to evaluate effects on food intake and glucose regulation. The effect of pro-UGN or UGN overexpression, using adeno-associated virus (AAV) vectors, was assessed in diet-induced obese (DIO) mice. Intracerebroventricular administration of GN and UGN was performed in rats for assessment of putative centrally mediated effects on food intake. GN and UGN, as well as their prohormones, were evaluated for effects on glucose-stimulated insulin secretion (GSIS) in rat pancreatic islets and perfused rat pancreas.

RESULTS

GUCA2A and GUCA2B mRNA expression was significantly upregulated in enteroendocrine cells after RYGB. Peripheral administration of guanylins or prohormones did not influence food intake, oral glucose tolerance, and GSIS. Central administration of GN and UGN did not affect food intake in rats. Chronic AVV-mediated overexpression of UGN and proUGN had no effect on body weight or glucose homeostasis in DIO mice.

CONCLUSION

GN and UGN, as well as their prohormones, do not seem to play a significant role in body weight regulation and glycemic control, suggesting that guanylin-family peptides do not show promise as targets for the treatment of obesity or diabetes.

Chimeric peptide EP45 as a dual agonist at GLP-1 and NPY2R receptors

We report the design and target validation of chimeric peptide EP45, a novel 45 amino acid monomeric dual agonist peptide that contains amino acid sequence motifs present within the blood glucose-lowering agent exendin-4 (Ex-4) and the appetite-suppressing agent PYY(3-36). In a new high-throughput FRET assay that provides real-time kinetic information concerning levels of cAMP in living cells, EP45 recapitulates the action of Ex-4 to stimulate cAMP production via the glucagon-like peptide-1 receptor (GLP-1R), while also recapitulating the action of PYY(3-36) to inhibit cAMP production via the neuropeptide Y2 receptor (NPY2R). EP45 fails to activate glucagon or GIP receptors, whereas for cells that co-express NPY2R and adenosine A2B receptors, EP45 acts in an NPY2R-mediated manner to suppress stimulatory effects of adenosine on cAMP production. Collectively, such findings are remarkable in that they suggest a new strategy in which the co-existing metabolic disorders of type 2 diabetes and obesity will be treatable using a single peptide such as EP45 that lowers levels of blood glucose by virtue of its GLP-1R-mediated effect, while simultaneously suppressing appetite by virtue of its NPY2R-mediated effect.

Optimization of tolerability and efficacy of the novel dual amylin and calcitonin receptor agonist KBP-089 through dose escalation and combination with a GLP-1 analog

Amylin and GLP-1 agonism induce a well-known anorexic effect at dose initiation, which is managed by dose escalation. In this study we investigated how to optimize tolerability while maintaining efficacy of a novel, highly potent dual amylin and calcitonin receptor agonist (DACRA), KBP-089. Furthermore, we tested the GLP-1 add-on potential of KBP-089 in high-fat diet (HFD)-fed rats. KBP-089 potently activated both the amylin and calcitonin receptors in vitro and demonstrated a prolonged receptor activation as well as a potent reduction of acute food intake. HFD rats dosed every day or every second day obtained equal weight loss at study end, albeit with an uneven reduction in both food intake and body weight in rats dosed every second day. In a 4-fold dose escalation, KBP-089 induced a transient reduction in food intake at every escalation step, with reducing magnitude over time, and the following treatment with 2.5, 10, and 40 µg/kg resulted in an ~15% vehicle-corrected weight loss, a corresponding reduction in adipose tissue (AT), and, in all treatment groups, improved oral glucose tolerance (P < 0.01). Twofold and linear escalations suppressed body weight evenly with no significant reduction in food intake at either escalation step. KBP-089 (1.25 µg/kg) and liraglutide (50 µg/kg) reduced 24-h food intake by 29% and 37% compared with vehicle, respectively; however, when they were combined, 24-h food intake was reduced by 87%. Chronically, KBP-089 (1.25 µg/kg) and liraglutide (50 µg/kg) lowered body weight 8% and 2% in HFD rats, respectively, whereas the combination resulted in a 12% body weight reduction. Moreover, the combination improved glucose tolerance (P < 0.05). In conclusion, DACRAs act complementarily with GLP-1 on food intake and body weight. Furthermore, on escalation, KBP-089 was well tolerated and induced and sustained a significant weight loss and a reduction in AT in lean and HFD rats, underscoring the potential of KBP-089 as an anti-obesity agent.

Gut check on diabesity: leveraging gut mechanisms for the treatment of type 2 diabetes and obesity

Gut hormones have long been understood to regulate food intake and metabolism. Bariatric surgery significantly elevates circulating gut hormone levels and is proven to affect acute remission of type 2 diabetes before any weight loss is observed. Subsequent weight loss is accrued over weeks to months but is sustained into the long term. Hence, there exists great enthusiasm to recapitulate these changes in gut hormones in the form of novel combination drugs for type 2 diabetes and obesity.

Dogfish glucagon analogues counter hyperglycaemia and enhance both insulin secretion and action in diet-induced obese diabetic mice

AIMS

To investigate the antidiabetic actions of three dogfish glucagon peptide analogues [known glucagon-like peptide-1 and glucagon receptor co-agonists] after chronic administration in diet-induced high-fat-diet-fed diabetic mice.

MATERIALS AND METHODS

National Institutes of Health Swiss mice were pre-conditioned to a high-fat diet (45% fat) for 100 days, and control mice were fed a normal diet (10% fat). Normal diet control and high-fat-fed control mice received twice-daily intraperitoneal (i.p.) saline injections, while the high-fat-fed treatment groups (n = 8) received twice-daily injections of exendin-4(1-39), [S2a]dogfish glucagon, [S2a]dogfish glucagon exendin-4(31-39) or [S2a]dogfish glucagon-Lys(30) -γ-glutamyl-PAL (25 nmol/kg body weight) for 51 days.

RESULTS

After dogfish glucagon analogue treatment, there was a rapid and sustained decrease in non-fasting blood glucose and an associated insulinotropic effect (analysis of variance, p < .05 to <.001) compared with saline-treated high-fat-fed controls. All peptide treatments significantly improved i.p. and oral glucose tolerance with concomitant increased insulin secretion compared with saline-treated high-fat-fed controls (p <.05 to <.001). After chronic treatment, no receptor desensitization was observed but insulin sensitivity was enhanced for all peptide-treated groups (p < .01 to <.001) except [S2a]dogfish glucagon. Both exendin-4 and [S2a]dogfish glucagon exendin-4(31-39) significantly reduced plasma triglyceride concentrations compared with those found in lean controls (p = .0105 and p = .0048, respectively). Pancreatic insulin content was not affected by peptide treatments but [S2a]dogfish glucagon and [S2a]dogfish glucagon exendin-4(31-39) decreased pancreatic glucagon by 28%-34% (p = .0221 and p = .0075, respectively). The percentage of β-cell area within islets was increased by exendin-4 and peptide analogue treatment groups compared with high-fat-fed controls and the β-cell area decreased (p < .05 to <.01).

CONCLUSIONS

Overall, dogfish glucagon co-agonist analogues had several beneficial metabolic effects, showing therapeutic potential for type 2 diabetes.

Novel dual agonist peptide analogues derived from dogfish glucagon show promising in vitro insulin releasing actions and antihyperglycaemic activity in mice

The antidiabetic potential of thirteen novel dogfish glucagon derived analogues were assessed in vitro and in acute in vivo studies. Stable peptide analogues enhanced insulin secretion from BRIN-BD11 β-cells (p < 0.001) and reduced acute glycaemic responses following intraperitoneal glucose (25 nmol/kg) in healthy NIH Swiss mice (p < 0.05-p<0.001). The in vitro insulinotropic actions of [S2a]dogfish glucagon, [S2a]dogfish glucagon-exendin-4(31-39) and [S2a]dogfish glucagon-Lys(30)-γ-glutamyl-PAL, were blocked (p < 0.05-p<0.001) by the specific GLP-1 and glucagon receptor antagonists, exendin-4(9-39) and (desHis(1)Pro(4)Glu(9))glucagon amide but not by (Pro(3))GIP, indicating lack of GIP receptor involvement. These analogues dose-dependently stimulated cAMP production in GLP-1 and glucagon (p < 0.05-p<0.001) but not GIP-receptor transfected cells. They improved acute glycaemic and insulinotropic responses in high-fat fed diabetic mice and in wild-type C57BL/6J and GIPR-KO mice (p < 0.05-p<0.001), but not GLP-1R-KO mice, confirming action on GLP-1 but not GIP receptors. Overall, dogfish glucagon analogues have potential for diabetes therapy, exerting beneficial metabolic effects via GLP-1 and glucagon receptors.

Amylin structure-function relationships and receptor pharmacology: implications for amylin mimetic drug development

Amylin is an important, but poorly understood, 37 amino acid glucoregulatory hormone with great potential to target metabolic diseases. A working example that the amylin system is one worth developing is the FDA-approved drug used in insulin-requiring diabetic patients, pramlintide. However, certain characteristics of pramlintide pharmacokinetics and formulation leave considerable room for further development of amylin-mimetic compounds. Given that amylin-mimetic drug design and development is an active area of research, surprisingly little is known about the structure/function relationships of amylin. This is largely due to the unfavourable aggregative and solubility properties of the native peptide sequence, which are further complicated by the composition of amylin receptors. These are complexes of the calcitonin receptor with receptor activity-modifying proteins. This review explores what is known of the structure-function relationships of amylin and provides insights that can be drawn from the closely related peptide, CGRP. We also describe how this information is aiding the development of more potent and stable amylin mimetics, including peptide hybrids.

GLP-1 and Amylin in the Treatment of Obesity

For decades, extensive research has aimed to clarify the role of pancreas and gut-derived peptide hormones in the regulation of glucose homeostasis and feeding behavior. Among these are the beta-cell hormone amylin and the intestinal L cell hormone glucagon-like peptide-1 (GLP-1). They exhibit distinct and yet several similar physiological actions including suppression of food intake, postprandial glucagon secretion, and gastric emptying-altogether lowering plasma glucose and body weight. These actions have been clinically exploited by the development of amylin and GLP-1 hormone analogs now used for treatment of diabetes and obesity. This review will outline the physiology and pharmacological potential of amylin and GLP-1, respectively, and focus on innovative peptide drug development leading to drugs acting on two or more distinct receptors, such as an amylin and GLP-1 peptide hybrid, potentially producing a more effective treatment strategy to combat the rapidly increasing global obesity.

Emerging opportunities for the treatment of metabolic diseases: Glucagon-like peptide-1 based multi-agonists

Obesity is a pathogenic gateway to the metabolic syndrome and the complications thereof, thus interventions aimed at preventing or reversing the metabolic derangements underlying obesity hold great therapeutic promise. However, the complexity of energy balance regulation, combined with the heterologous pathophysiology of human obesity, renders effective medicinal intervention very difficult. Indeed, the search for the silver bullet in anti-obesity medicines has been laden with drugs of underwhelming efficacy and unacceptable side effects. This can partly be the consequence that many of these drug interventions have been historically directed at single molecular targets. New multi-molecular combination therapies have shown promising clinical outcomes in terms of weight loss, yet multi-functional single molecules may offer even more advantages than adjunctive co-treatments. Single molecules with integrated activities derived from multiple hormones involved in the physiological control of metabolism have emerged as one of the more promising candidates for reversing obesity. The inclusion of glucagon-like peptide-1 (GLP-1) as one of the constituents is a unifying factor amongst the majority of these unimolecular multi-agonists. The scope of this review is to summarize the current preclinical and clinical landscape of GLP-1-based therapies, focusing on combinatorial therapies with a particular emphasis on single molecule compounds displaying multi-agonist properties.

New perspectives on the development of antiobesity drugs

After many years of research, obesity is still a disease with an unmet medical need. Very few compounds have been approved, acting mainly on neuromediators; researches, in recent years, pointed toward compounds potentially safer than first-generation antiobesity drugs, able to interact with one or more (multitarget therapy) receptors for substances produced by the gut, adipose tissue and other targets outside CNS. Other holistic approaches, such as those involving gut microbiota and plant extracts, appeared recently in the literature, and undoubtedly will contribute to the discovery of a valuable therapy for this disease. This review deals with the positive results and the pitfalls obtained following these approaches, with a view on their clinical trial studies.

Glucagon-like peptide-1 (GLP-1) analogs: recent advances, new possibilities, and therapeutic implications

Glucagon-like peptide-1 (GLP-1) is an incretin that plays important physiological roles in glucose homeostasis. Produced from intestine upon food intake, it stimulates insulin secretion and keeps pancreatic β-cells healthy and proliferating. Because of these beneficial effects, it has attracted a great deal of attention in the past decade, and an entirely new line of diabetic therapeutics has emerged based on the peptide. In addition to the therapeutic applications, GLP-1 analogs have demonstrated a potential in molecular imaging of pancreatic β-cells; this may be useful in early detection of the disease and evaluation of therapeutic interventions, including islet transplantation. In this Perspective, we focus on GLP-1 analogs for their studies on improvement of biological activities, enhancement of metabolic stability, investigation of receptor interaction, and visualization of the pancreatic islets.