The human GLP-1 analogs liraglutide and semaglutide: absence of histopathological effects on the pancreas in nonhuman primates

Incretin mimetics and acute pancreatitis: enemy or innocent bystander?

PURPOSE OF REVIEW

The incretin enhancers and mimetics, including dipeptidyl peptidase-4 (DPP-4) inhibitors, GLP-1 receptor agonists (GLP-1RA) and GLP-1/GIP co-agonists, have become mainstays in the treatment of type 2 diabetes (T2D). Recently, the approval of certain GLP-1RA and GLP-1/GIP co-agonists for the treatment of obesity has broadened their popularity and use. In this review, we summarize the evidence for an association of these drugs with acute pancreatitis and other adverse events of special interest to gastroenterologists.

RECENT FINDINGS

In addition to pancreatic islets, GLP-1 receptors are expressed in the exocrine cells of the pancreas. There is inconsistent evidence for an association of DPP-4 inhibitors, GLP-1RA and co-agonists with risk for acute pancreatitis in individual trials. Meta-analyses of long-term randomized controlled trials indicate a small risk of acute pancreatitis associated with DPP-4 inhibitors but not GLP-1RA or co-agonists. Cholecystitis and cholelithiasis may be more common among those treated with GLP-1RA and GLP-1/GIP co-agonists. There is no evidence that any of these drugs are associated with an increased risk of pancreatic cancer.

SUMMARY

While drugs that leverage the incretin system are increasingly being used for patients with T2D and obesity, caution in warranted in those with a history of pancreatitis and gallbladder disease.

Recent Advances in Incretin-Based Pharmacotherapies for the Treatment of Obesity and Diabetes

The incretin hormone glucagon-like peptide-1 (GLP-1) has received enormous attention during the past three decades as a therapeutic target for the treatment of obesity and type 2 diabetes. Continuous improvement of the pharmacokinetic profile of GLP-1R agonists, starting from native hormone with a half-life of ~2-3 min to the development of twice daily, daily and even once-weekly drugs highlight the pharmaceutical evolution of GLP-1-based medicines. In contrast to GLP-1, the incretin hormone glucose-dependent insulinotropic polypeptide (GIP) received little attention as a pharmacological target, because of conflicting observations that argue activation or inhibition of the GIP receptor (GIPR) provides beneficial effects on systemic metabolism. Interest in GIPR agonism for the treatment of obesity and diabetes was recently propelled by the clinical success of unimolecular dual-agonists targeting the receptors for GIP and GLP-1, with reported significantly improved body weight and glucose control in patients with obesity and type II diabetes. Here we review the biology and pharmacology of GLP-1 and GIP and discuss recent advances in incretin-based pharmacotherapies.

Role of Glucagon-Like Peptide-1 (GLP-1) Receptor Agonists in Hypoglycemia

A relatively recent addition to the arsenal of antidiabetic drugs used for the treatment of type 2 diabetes mellitus (T2DM) has been the “incretin mimetics,” a group of drugs that work on the glucagon-like peptide-1 (GLP-1) receptor and enhance insulin secretion from the pancreatic β-cells in a glucose-dependent manner, more potently in hyperglycemic conditions, while suppressing glucagon secretion at the same time. Therefore, it was assumed that this class of drugs would have a lower risk of hypoglycemia than insulin secretagogues like sulphonylureas. However, GLP-1 receptor agonists have been proposed to cause hypoglycemia in healthy normoglycemic subjects implying that their action is not as glucose-dependent as once thought. Other studies concluded that they might not induce hypoglycemia and the risk is dependent on other individual factors. However, the FDA announced that the 12 GLP-1 receptor agonists currently available on the market had potential safety signs and evaluated the need for regulatory action. This review provides an overview of the studies that investigated the possible hypoglycemic effect of GLP-1 receptor agonists. In addition, the current review describes other adverse effects of GLP-1 receptor agonist treatment.

Revisiting Regulators of Human β-cell Mass to Achieve β-cell-centric Approach Toward Type 2 Diabetes

Type 2 diabetes (T2DM) is characterized by insulin resistance and β-cell dysfunction. Because patients with T2DM have inadequate β-cell mass (BCM) and β-cell dysfunction worsens glycemic control and makes treatment difficult, therapeutic strategies to preserve and restore BCM are needed. In rodent models, obesity increases BCM about 3-fold, but the increase in BCM in humans is limited. Besides, obesity-induced changes in BCM may show racial differences between East Asians and Caucasians. Recently, the developmental origins of health and disease hypothesis, which states that the risk of developing noncommunicable diseases including T2DM is influenced by the fetal environment, has been proposed. It is known in rodents that animals with low birthweight have reduced BCM through epigenetic modifications, making them more susceptible to diabetes in the future. Similarly, in humans, we revealed that individuals born with low birthweight have lower BCM in adulthood. Because β-cell replication is more frequently observed in the 5 years after birth, and β cells are found to be more plastic in that period, a history of childhood obesity increases BCM. BCM in patients with T2DM is reduced by 20% to 65% compared with that in individuals without T2DM. However, since BCM starts to decrease from the stage of borderline diabetes, early intervention is essential for β-cell protection. In this review, we summarize the current knowledge on regulatory factors of human BCM in health and diabetes and propose the β-cell–centric concept of diabetes to enhance a more pathophysiology-based treatment approach for T2DM.

Oral semaglutide in the management of type 2 DM: Clinical status and comparative analysis

BACKGROUND

In the incretin system, Glucagon-like peptide-1 (GLP-1) is a hormone that inhibits the release of glucagon and regulates glucose-dependent insulin secretion. In type 2 diabetes, correcting the impaired incretin system using GLP-1 agonist is a well-defined therapeutic strategy.

OBJECTIVES

This review article aims to discuss the mechanism of action, key regulatory events, clinical trials for glycaemic control and comparative analysis of semaglutide with the second-line antidiabetic drugs.

DESCRIPTION

Semaglutide is a glucagon-like peptide 1 (GLP 1) receptor agonist with enhanced glycaemic control in diabetes patients. In 2019, USFDA approved the first oral GLP-1 receptor agonist, semaglutide to be administered as a once-daily tablet. Further, recent studies highlight the ability of semaglutide to improve the glycaemic control in obese patients with a reduction in body weight. Still, in clinical practice, in type 2 DM treatment paradigm the impact of oral semaglutide remains unidentified. This review article discusses the mechanism of action, pharmacodynamics, key regulatory events, and clinical trials regarding glycaemic control.

CONCLUSION

The review highlights the comparative analysis of semaglutide with the existing second-line drugs for the management of type 2 diabetes mellitus by stressing on its benefits and adverse events.

Safety of Semaglutide

The glucagon-like peptide-1 receptor agonist (GLP-1RA) semaglutide is the most recently approved agent of this drug class, and the only GLP-1RA currently available as both subcutaneous and oral formulation. While GLP-1RAs effectively improve glycemic control and cause weight loss, potential safety concerns have arisen over the years. For semaglutide, such concerns have been addressed in the extensive phase 3 registration trials including cardiovascular outcome trials for both subcutaneous (SUSTAIN: Semaglutide Unabated Sustainability in Treatment of Type 2 Diabetes) and oral (PIONEER: Peptide InnOvatioN for the Early diabEtes tReatment) semaglutide and are being studied in further trials and registries, including real world data studies. In the current review we discuss the occurrence of adverse events associated with semaglutide focusing on hypoglycemia, gastrointestinal side effects, pancreatic safety (pancreatitis and pancreatic cancer), thyroid cancer, gallbladder events, cardiovascular aspects, acute kidney injury, diabetic retinopathy (DRP) complications and injection-site and allergic reactions and where available, we highlight potential underlying mechanisms. Furthermore, we discuss whether effects are specific for semaglutide or a class effect. We conclude that semaglutide induces mostly mild-to-moderate and transient gastrointestinal disturbances and increases the risk of biliary disease (cholelithiasis). No unexpected safety issues have arisen to date, and the established safety profile for semaglutide is similar to that of other GLP-1RAs where definitive conclusions for pancreatic and thyroid cancer cannot be drawn at this point due to low incidence of these conditions. Due to its potent glucose-lowering effect, patients at risk for deterioration of existing DRP should be carefully monitored if treated with semaglutide, particularly if also treated with insulin. Given the beneficial metabolic and cardiovascular actions of semaglutide, and the low risk for severe adverse events, semaglutide has an overall favorable risk/benefit profile for patient with type 2 diabetes.

Risk of acute pancreatitis with incretin-based therapy: a systematic review and updated meta-analysis of cardiovascular outcomes trials

BACKGROUND

The link of acute pancreatitis (AP) with Incretin based therapies (IBTs) in type 2 diabetes has existed since United States Food and Drug Administration alert in 2010. This issue still remains unresolved due to conflicting results among studies.

RESEARCH DESIGN AND METHODS

We performed a systematic search of the PubMed, Embase, and Cochrane Library databases until 31 July 2019, and retrieved all cardiovascular outcome trials (CVOTs) of IBTs conducted for ≥12 months that reported the pre-specified and or pre-adjudicated pancreatitis outcomes. Subsequently, we conducted a meta-analysis to study the risk of AP observed with IBT in CVOTs.

RESULTS

A meta-analysis of seven CVOTs of GLP-1 receptor agonists (GLP-1RAs) compared with placebo (N = 55,932) found no significant increase in AP (odds ratio [OR], 1.05; 95% confidence interval [CI], 0.77-1.42; p = 0.77). In contrast, meta-analysis of five CVOTs comparing DPP-4 inhibitors with placebo (N = 47,714) and six CVOTs comparing DPP-4 inhibitors with placebo or active comparator (N = 53,747), found a significant increase (OR, 1.81; 95% CI, 1.21-2.70; p = 0.04 and OR, 1.54; 95% CI, 1.08-2.18; p = 0.02, respectively) in AP without any significant heterogeneity.

CONCLUSIONS

This meta-analysis revealed a significant association between pancreatitis and DPP-4 inhibitors; however, no such association was observed for GLP-1RAs.

Long-Term Liraglutide Administration Induces Pancreas Neogenesis in Adult T2DM Mice

In vivo beta-cell neogenesis may be one way to treat diabetes. We aimed to investigate the effect of glucagon-like peptide-1 (GLP-1) on beta-cell neogenesis in type 2 diabetes mellitus (T2DM). Male C57BL/6J mice, 6 wk old, were randomly divided into three groups: Control, T2DM, and T2DM + Lira. T2DM was induced using high-fat diet and intraperitoneal injection of streptozotocin (40 mg/kg/d for 3 d). At 8 wk after streptozotocin injection, T2DM + Lira group was injected intraperitoneally with GLP-1 analog liraglutide (0.8 mg/kg/d) for 4 wk. Apparently for the first time, we report the appearance of a primitive bud connected to pancreas in all adult mice from each group. The primitive bud was characterized by scattered single monohormonal cells expressing insulin, GLP-1, somatostatin, or pancreatic polypeptide, and four-hormonal cells, but no acinar cells and ductal epithelial cells. Monohormonal cells in it were small, newborn, immature cells that rapidly proliferated and expressed cell markers indicative of immaturity. In parallel, Ngn3+ endocrine progenitors and Nestin+ cells existed in the primitive bud. Liraglutide facilitated neogenesis and rapid growth of acinar cells, pancreatic ducts, and blood vessels in the primitive bud. Meanwhile, scattered hormonal cells aggregated into cell clusters and grew into larger islets; polyhormonal cells differentiated into monohormonal cells. Extensive growth of exocrine and endocrine glands resulted in the neogenesis of immature pancreatic lobes in adult mice of T2DM + Lira group. Contrary to predominant acinar cells in mature pancreatic lobes, there were still a substantial number of mesenchymal cells around acinar cells in immature pancreatic lobes, which resulted in the loose appearance. Our results suggest that adult mice preserve the capacity of pancreatic neogenesis from the primitive bud, which liraglutide facilitates in adult T2DM mice. To our knowledge, this is the first time such a phenomenon has been reported.

Gut Peptide Agonism in the Treatment of Obesity and Diabetes

Obesity is a global healthcare challenge that gives rise to devastating diseases such as the metabolic syndrome, type-2 diabetes (T2D), and a variety of cardiovascular diseases. The escalating prevalence of obesity has led to an increased interest in pharmacological options to counteract excess weight gain. Gastrointestinal hormones such as glucagon, amylin, and glucagon-like peptide-1 (GLP-1) are well recognized for influencing food intake and satiety, but the therapeutic potential of these native peptides is overall limited by a short half-life and an often dose-dependent appearance of unwanted effects. Recent clinical success of chemically optimized GLP-1 mimetics with improved pharmacokinetics and sustained action has propelled pharmacological interest in using bioengineered gut hormones to treat obesity and diabetes. In this article, we summarize the basic biology and signaling mechanisms of selected gut peptides and discuss how they regulate systemic energy and glucose metabolism. Subsequently, we focus on the design and evaluation of unimolecular drugs that combine the beneficial effects of selected gut hormones into a single entity to optimize the beneficial impact on systems metabolism. © 2020 American Physiological Society. Compr Physiol 10:99-124, 2020.

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.

Inventing Liraglutide, a Glucagon-Like Peptide-1 Analogue, for the Treatment of Diabetes and Obesity

Glucagon-like peptide-1 (GLP-1) has been in focus since the early 1980s as a long looked for incretin hormone, released from the gastrointestinal tract and with an important effect on glucose-dependent insulin secretion, providing efficient glucose lowering, with little risk for hypoglycemia. The enzyme dipeptidyl peptidase-4 (DPP-4) degrades GLP-1 very fast, and the remaining metabolite is cleared rapidly by the kidneys. Liraglutide is a fatty acid acylated analogue of GLP-1 that provides efficacy for 24 h/day. The mechanism of action for liraglutide is reviewed in detail with focus on pancreatic efficacy and safety, thyroid safety, and weight loss mechanism. Evolving science hypothesizes that GLP-1 has important effects on atherosclerosis, relevant for the cardiovascular benefit seen in the treatment of diabetes and obesity. Also, GLP-1 may be relevant in neurodegenerative diseases.

Effects of glucagon-like peptide 1 analogs on alcohol intake in alcohol-preferring vervet monkeys

BACKGROUND

Preclinical studies in rodents have demonstrated inhibitory effects of glucagon-like peptide-1 (GLP-1) receptor stimulation on alcohol consumption. The effects of GLP-1 receptor stimulation on alcohol intake in primates have not been investigated.

METHODS

We performed placebo-controlled studies on the effects of the GLP-1 receptor agonists exenatide and liraglutide on alcohol consumption in alcohol-preferring male African vervet monkeys. Monkeys selected for voluntary alcohol drinking were observed for at least 10 days of baseline drinking and allocated to drug or vehicle (n = 11-12 per group) balanced with respect to alcohol intake. Monkeys had access to alcohol 4 h/day. In a first study, monkeys were treated with exenatide 0.04 mg/kg or vehicle once weekly for 5 weeks to obtain steady-state plasma levels. In a second study, monkeys were treated daily with liraglutide (increasing dosing, 10 to 50 μg/kg/day) or vehicle over 2 weeks. In both studies, access to alcohol was suspended during drug up-titration. Then, alcohol was again made available 4 h/day and treatment was continued for 2 weeks, during which alcohol intake was recorded. Observation of alcohol intake was continued for a week of drug washout.

RESULTS

Liraglutide and to a lesser extent exenatide significantly reduced alcohol consumption without causing any signs of emesis and with no effect on water intake as compared to vehicle.

CONCLUSIONS

The present study demonstrates for the first time that GLP-1 receptor agonists can reduce voluntary alcohol drinking in non-human primates. The data substantiate the potential usefulness of GLP-1 receptor agonists in the treatment of alcohol use disorder.

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.

Clinical pharmacology of glucagon-like peptide-1 receptor agonists

Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) are an important asset in the armamentarium for the treatment of type 2 diabetes mellitus (type 2 DM). Incretin failure is a critical etiopathogenetic feature of type 2 DM, which, if reversed, results in improved glycaemic control. GLP-1 RAs are injectable peptides that resemble the structure and function of endogenous incretin GLP-1, but as they are not deactivated by the dipeptidyl peptidase-4 (DPP-4), their half-life is prolonged compared with native GLP-1. Based on their ability to activate GLP-1 receptor, GLP-1 RAs are classified as short-acting (exenatide twice-daily and lixisenatide once-daily), and long-acting (liraglutide once-daily and the once-weekly formulations of exenatide extended-release, dulaglutide, and albiglutide). Semaglutide, another long-acting, once-weekly GLP-1 RA, was recently approved by the FDA and EMA. Although all of these agents potently reduce haemoglobin A1C (HbA1c), there are unique features and fundamental differences among them related to fasting and postprandial hyperglycaemia reduction, weight loss potency, cardiovascular protection efficacy, and adverse events profile. It is imperative that current evidence be integrated and applied in the context of an individualised patient-centred approach. This should include not only glucose management but also targeting as many as possible of the pathophysiologic mechanisms responsible for type 2 DM development and progression.

Squalene-PEG-Exendin as High-Affinity Constructs for Pancreatic Beta-Cells

Novel drug delivery systems targeting native, transplanted, or cancerous beta-cells are of utmost importance. Herein, we present new exendin-4 derivatives with modified unnatural amino acids at strategic positions within the polypeptide sequence. The modified peptides allowed modular orthogonal chemical modifications to attach imaging agents and amphiphilic squalene-PEG groups. The resulting conjugates, SQ-PEG-ExC₁-Cy5 and SQ-PEG-ExC₄₀-Cy5 fluorescence probes, display low nanomolar affinity to GLP-1R in fluorescence-based binding assays with EC₅₀ at 1.1 ± 0.2 and 0.8 ± 0.2 nM, respectively. Naturally expressing GLP-1R MIN6 cells and recombinantly transfected CHL-GLP-1R positive cells were specifically targeted by all of the new beta-cell probes in vitro. Specific islet targeting was observed after i.v. injection of SQ-PEG-ExC₁-Cy5 with SQ-PEG in normoglycemic mice ex vivo. Semiquantitative biodistribution analysis by epifluorescence indicated prolonged blood half-life (3.8 h) for the amphiphilic Ex conjugate. Liver and pancreas were identified as main biodistribution organs for SQ-PEG-ExC₁-Cy5.

Incretin-based therapies and risk of pancreatic cancer in patients with type 2 diabetes: A meta-analysis of randomized controlled trials

AIMS

To perform a meta-analysis of randomized controlled trials (RCTs), including 6 recently published large-scale cardiovascular outcome trials (CVOTs), to evaluate the risk of pancreatic cancer with incretin-based therapies in patients with type 2 diabetes (T2DM).

MATERIALS AND METHODS

For the period January 1, 2007 to May 1, 2017, the PubMed, Embase, Cochrane Central Register and ClininalTrials.gov databases were searched for RCTs in people with T2DM that compared incretin drugs with placebo or other antidiabetic drugs, with treatment and follow-up durations of ≥52 weeks. Two reviewers screened the studies, extracted the data and assessed the risk of bias independently and in duplicate.

RESULTS

A total of 33 studies (n = 79 971), including the 6 CVOTs, with 87 pancreatic cancer events were identified. Overall, the pancreatic cancer risk was not increased in patients administered incretin drugs compared with controls (Peto odds ratio [OR] 0.67, 95% confidence interval [CI] 0.44-1.02). In the 6 CVOTs, 79 pancreatic cancer events were identified in 55 248 participants. Pooled estimates of the 6 CVOTs showed an identical tendency (Peto OR 0.65, 95% CI 0.42-1.01). Notably, in the subgroup of participants who received treatment and follow-up for ≥104 weeks, 84 pancreatic cancer events were identified in 59 919 participants, and a lower risk of pancreatic cancer was associated with incretin-based therapies (Peto OR 0.62, 95% CI 0.41-0.95).

CONCLUSIONS

Treatment with incretin drugs was not associated with an increased risk of pancreatic cancer in people with T2DM. Instead, it might protect against pancreatic malignancy in patients treated for ≥104 weeks.

GLP-1/glucagon receptor co-agonism for treatment of obesity

Over a relatively short period, obesity and type 2 diabetes have come to represent a large medical and economic burden to global societies. The epidemic rise in the prevalence of obesity has metabolic consequences and is paralleled by an increased occurrence of other diseases, such as diabetes, cancer and cardiovascular complications. Together, obesity and type 2 diabetes constitute one of the more preventable causes of premature death and the identification of novel, safe and effective anti-obesity drugs is of utmost importance. Pharmacological attempts to treat obesity have had limited success, with notable adverse effects, rendering bariatric surgery as the only current therapy for substantially improving body weight. Novel unimolecular, multifunctional peptides have emerged as one of the most promising medicinal approaches to enhance metabolic efficacy and restore normal body weight. In this review, we will mainly focus on the discovery and translational relevance of dual agonists that pharmacologically function at the receptors for glucagon and glucagon-like peptide-1. Such peptides have advanced to clinical evaluation and inspired the pursuit of multiple related approaches to achieving polypharmacy within single molecules.

Efficacy and safety of once-weekly semaglutide for the treatment of type 2 diabetes

INTRODUCTION

Type 2 diabetes is a chronic metabolic disease characterized by persistent hyperglycemia resulting from progressive deficient of insulin in patients with a background of insulin resistance. Current treatment algorithms recommended by American Diabetes Association/The European Association for the Study of Diabetes promote a patient-centered approach that takes into account a comprehensive consideration of pharmacological properties of drugs, including glucose-lowering action, effects on body weight, correction on multiple pathophysiologic defects, tolerability, and long-term safety. Glucagon-likepeptide1 (GLP-1) receptor analogues are appealing due to the improved glycemic control in a glucose-dependent manner, modest weight loss and low risk of hypoglycemia. Areas covered: Semaglutide (Novo Nordisk), a once-weekly GLP-1 analogue, is currently in the phase III clinical trial for the treatment of type 2 diabetes. This article aims to review the pharmacological and clinical profiles of semaglutide based on the available clinical data. Expert opinion: Semaglutide achieved greater reduction from baseline in HbA_1c in comparison to placebo. The greater proportion of patients in semaglutide group than that in placebo group achieved target HbA_1c <7.0% and <6.5%, respectively. Semaglutide is the second GLP-1 analogue contributing to the reduced bodyweight and improving obesity related complications. More importantly, semaglutide is beneficial to diabetic patients with high cardiovascular risk according to the recently completed phase III trial. The incidence of gastrointestinal adverse effects increased with semaglutide dose.

Impact of Liraglutide on Amylase, Lipase, and Acute Pancreatitis in Participants With Overweight/Obesity and Normoglycemia, Prediabetes, or Type 2 Diabetes: Secondary Analyses of Pooled Data From the SCALE Clinical Development Program

OBJECTIVE

To describe amylase/lipase activity levels and events of acute pancreatitis (AP) in the SCALE (Satiety and Clinical Adiposity-Liraglutide Evidence in individuals with and without diabetes) weight-management trials.

RESEARCH DESIGN AND METHODS

Secondary analyses were performed on pooled data from four trials (N = 5,358 with BMI ≥30, or 27 to <30 kg/m² with ≥1 comorbidity). Of these, 1,723 had normoglycemia, 2,789 had prediabetes, and 846 had type 2 diabetes. Participants were randomized to liraglutide 3.0 mg (n = 3,302), liraglutide 1.8 mg (n = 211, only type 2 diabetes), or placebo (n = 1,845). Relationships between baseline characteristics and amylase/lipase activity at baseline and during treatment were investigated.

RESULTS

Over 56 weeks, liraglutide 3.0 mg versus placebo was associated with increases in mean levels of 7% (amylase) and 31% (lipase), respectively. Similar changes in amylase/lipase levels were observed with liraglutide 1.8 mg. More participants receiving liraglutide 3.0 mg versus placebo experienced amylase (9.4% vs. 5.9%) and lipase (43.5% vs. 15.1%) elevations greater than or equal to the upper limit of normal (ULN); few had elevations ≥3 × ULN for amylase (<0.1% with liraglutide 3.0 mg or placebo) or lipase (2.9% vs. 1.5%, respectively). After liraglutide discontinuation, enzymes returned to baseline levels. Thirteen participants developed AP: 12 on (n = 9, 0.3%) or after (n = 3, 0.1%) liraglutide 3.0 mg treatment and one (0.1%) with placebo. A total of 6/13 participants with AP (5/12 liraglutide; 1 placebo) had gallstone disease evident at AP onset. Amylase/lipase elevations either 1 × ULN or ≥3 × ULN before AP onset had very low positive predictive value for AP (<1%).

CONCLUSIONS

Liraglutide resulted in dose-independent, reversible increases in amylase/lipase activity, unrelated to baseline characteristics, not predicting AP onset. Gallstones possibly contributed to 50% of AP cases. Data provide no basis for amylase/lipase level monitoring in liraglutide treatment except in suspected AP.

Histological changes in endocrine and exocrine pancreatic tissue from patients exposed to incretin-based therapies

AIMS

Incretin-based therapies have been associated with an increased risk of pancreatitis. Recently, various histological abnormalities have been reported in human pancreatic tissue from brain-dead organ donors who had been exposed to incretin-based drugs. In the present study we examined pancreatic tissue collected at surgery.

METHODS

Human pancreatic tissue from 7 type 2-diabetic patients treated with incretin-based drugs (type 2-I), 6 diabetic patients without incretin treatment (type 2-NI), 11 patients without diabetes (no diabetes group) and 9 brain-dead organ donors (BDOD group) was examined.

RESULTS

Fractional beta-cell area was reduced in the type 2-NI group compared to the group without diabetes (P < .05), but there was no difference compared to the type 2-I patients. Alpha-cell area (P = .30), beta-cell replication (P = .17) and alpha-cell replication (P = .91) were not different. There were also no differences in acinar cell (P = .13) and duct cell replication (P = .099). Insulin-positive duct cells were more frequent in the type 2-I and the BDOD groups (P = .034). No co-expression of insulin and glucagon was detected. Pancreatic intraepithelial neoplasia (PanIN) lesions were very rare, all low-grade (PanIN 1a and 1b) and tended to occur more frequently in the type 2-I group (P = .084).

CONCLUSIONS

The present results did not reveal marked histological abnormalities in the pancreas of incretin-treated patients with type 2 diabetes. Low numbers of specimens available and a large inter-individual variability of the findings warrant caution regarding the interpretation of histological data concerning drug effects on the human pancreas.

Pancreas Volume and Fat Deposition in Diabetes and Normal Physiology: Consideration of the Interplay Between Endocrine and Exocrine Pancreas

The pancreas is comprised of exocrine and endocrine components. Despite the fact that they are derived from a common origin in utero, these two compartments are often studied individually because of the different roles and functions of the exocrine and endocrine pancreas. Recent studies have shown that not only type 1 diabetes (T1D), but also type 2 diabetes (T2D), is characterized by a deficit in beta-cell mass, suggesting that pathological changes in the pancreas are critical events in the natural history of diabetes. In both patients with T1D and those with T2D, pancreas mass and exocrine function have been reported to be reduced. On the other hand, pancreas volume and pancreatic fat increase with obesity. Increased beta-cell mass with increasing obesity has also been observed in humans, and ectopic fat deposits in the pancreas have been reported to cause beta-cell dysfunction. Moreover, neogenesis and transdifferentiation from the exocrine to the endocrine compartment in the postnatal period are regarded as a source of newly formed beta-cells. These findings suggest that there is important interplay between the endocrine and exocrine pancreas throughout life. This review summarizes the current knowledge on physiological and pathological changes in the exocrine and endocrine pancreas (i.e., beta-cell mass), and discusses the potential mechanisms of the interplay between the two compartments in humans to understand the pathophysiology of diabetes better.

Proglucagon-Derived Peptides Do Not Significantly Affect Acute Exocrine Pancreas in Rats

OBJECTIVES

Reports have suggested a link between treatment with glucagon-like peptide 1 (GLP-1) analogs and an increased risk of pancreatitis. Oxyntomodulin, a dual agonist of both GLP-1 and glucagon receptors, is currently being investigated as a potential antiobesity therapy, but little is known about its pancreatic safety. The aim of the study was to investigate the acute effect of oxyntomodulin and other proglucagon-derived peptides on the rat exocrine pancreas.

METHODS

Glucagon-like peptide 1, oxyntomodulin, glucagon, and exendin-4 were infused into anesthetized rats to measure plasma amylase concentration changes. In addition, the effect of each peptide on both amylase release and proliferation in rat pancreatic acinar (AR42J) and primary isolated ductal cells was determined.

RESULTS

Plasma amylase did not increase postpeptide infusion, compared with vehicle and cholecystokinin; however, oxyntomodulin inhibited plasma amylase when coadministered with cholecystokinin. None of the peptides caused a significant increase in proliferation rate or amylase secretion from acinar and ductal cells.

CONCLUSIONS

The investigated peptides do not have an acute effect on the exocrine pancreas with regard to proliferation and plasma amylase, when administered individually. Oxyntomodulin seems to be a potent inhibitor of amylase release, potentially making it a safer antiobesity agent regarding pancreatitis, compared with GLP-1 agonists.

Glucagon-Like Peptide-1 Receptor Expression in Normal and Neoplastic Human Pancreatic Tissues

OBJECTIVES

Studies have proposed pro-oncogenic effects of glucagon-like peptide-1 receptor (GLP-1R) agonists in the pancreas by promoting GLP-1R overactivation in pancreatic cells. However, the expression of GLP-1R in normal and neoplastic pancreatic cells remains poorly defined, and reliable methods for detecting GLP-1R in tissue specimens are needed.

METHODS

We used RNA in situ hybridization to quantify glp-1r RNA in surgically resected human pancreatic specimens, including pancreatic ductal adenocarcinoma (PDAC), preinvasive intraepithelial lesions (pancreatic intraepithelial neoplasia), and non-neoplastic ductal, acinar, and endocrine cells. A mixed-effect linear regression model was used to investigate the relationship between glp-1r signals and all cells, ordered by increasing grade of dysplasia.

RESULTS

All cell types had evidence of glp-1r transcripts, with the highest expression in endocrine cells and lowest in ductal cells. The slope of the fitted line was not significantly different from zero (0.07; 95% confidence interval, -0.0094 to 0.244; P = 0.39), suggesting that progression from normal cells to PDAC is not associated with a parallel increase in glp-1r RNA. A series of pairwise comparisons between all cell types with respect to their glp-1r expression showed no significant difference in glp-1r in cancer, pancreatic intraepithelial neoplasia, and acinar and ductal cells.

CONCLUSIONS

Our study supports the lack of evidence for GLP-1R overexpression in PDAC.

Comparative aspects of rodent and nonrodent animal models for mechanistic and translational diabetes research

The prevalence of diabetes mellitus, which currently affects 387 million people worldwide, is permanently rising in both adults and adolescents. Despite numerous treatment options, diabetes mellitus is a progressive disease with severe comorbidities, such as nephropathy, neuropathy, and retinopathy, as well as cardiovascular disease. Therefore, animal models predictive of the efficacy and safety of novel compounds in humans are of great value to address the unmet need for improved therapeutics. Although rodent models provide important mechanistic insights, their predictive value for therapeutic outcomes in humans is limited. In recent years, the pig has gained importance for biomedical research because of its close similarity to human anatomy, physiology, size, and, in contrast to non-human primates, better ethical acceptance. In this review, anatomic, biochemical, physiological, and morphologic aspects relevant to diabetes research will be compared between different animal species, that is, mouse, rat, rabbit, pig, and non-human primates. The value of the pig as a model organism for diabetes research will be highlighted, and (dis)advantages of the currently available approaches for the generation of pig models exhibiting characteristics of metabolic syndrome or type 2 diabetes mellitus will be discussed.

GLP-1 based therapies: clinical implications for gastroenterologists

The gut-derived incretin hormone, glucagon-like peptide 1 (GLP-1) lowers postprandial blood glucose levels by stimulating insulin and inhibiting glucagon secretion. Two novel antihyperglycaemic drug classes augment these effects; GLP-1 receptor agonists and inhibitors of the GLP-1 degrading enzyme dipeptidyl peptidase 4. These so called GLP-1 based or incretin based drugs are increasingly used to treat type 2 diabetes, because of a low risk of hypoglycaemia and favourable effect on body weight, blood pressure and lipid profiles. Besides glucose control, GLP-1 functions as an enterogastrone, causing a wide range of GI responses. Studies have shown that endogenous GLP-1 and its derived therapies slow down digestion by affecting the stomach, intestines, exocrine pancreas, gallbladder and liver. Understanding the GI actions of GLP-1 based therapies is clinically relevant; because GI side effects are common and need to be recognised, and because these drugs may be used to treat GI disease.

Glucagon-Like Peptide-1 Receptor Agonists for Type 2 Diabetes: A Clinical Update of Safety and Efficacy

INTRODUCTION

Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) are increasingly being used for the treatment of type 2 diabetes mellitus, but consideration of benefits and potential adverse events is required. This review examines the state of glycemic control, weight loss, blood pressure, and tolerability, as well as the current debate about the safety of GLP-1 RAs, including risk of pancreatitis, pancreatic cancer, and thyroid cancer.

METHODS

A MEDLINE search (2010-2015) identified publications that discussed longer-acting GLP-1 RAs. Search terms included GLP-1 receptor agonists, liraglutide, exenatide, lixisenatide, semaglutide, dulaglutide, albiglutide, efficacy, safety, pancreatitis, pancreatic cancer, and thyroid cancer. Abstracts from the American Diabetes Association, European Association for the Study of Diabetes, and American Association of Clinical Endocrinologists from 2010 to 2015 were also searched. Efficacy and safety studies, pooled analyses, and meta-analyses were prioritized.

RESULTS

Research has confirmed that GLP-1 RAs provide robust glycemic control, weight loss, and blood pressure re-duction. Current studies do not prove increased risk of pancreatitis, pancreatic cancer, or thyroid cancer but more trials are needed since publications that indicate safety or suggest increased risk have methodological flaws that prevent firm conclusions to be drawn about these rare, long-term events.

CONCLUSION

GLP-1 RA therapy in the context of individualized, patient-centered care continues to be supported by current literature. GLP-1 RA therapy provides robust glycemic control, blood pressure reduction, and weight loss, but studies are still needed to address concerns about tolerability and safety, including pancreatitis and cancer.

Glucagon-like peptide-1 loaded phospholipid micelles for the treatment of type 2 diabetes: improved pharmacokinetic behaviours and prolonged glucose-lowering effects

GLP-1-SSM, a sterically stabilized GLP-1 in phospholipid micelles, exhibited improved hypoglycemic activity and long-acting antidiabetic ability.

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.

Small lipidated anti-obesity compounds derived from neuromedin U

A small library of truncated/lipid-conjugated neuromedin U (NmU) analogs was synthesized and tested in vitro using an intracellular calcium signaling assay. The selected, most active analogs were then tested in vivo, and showed potent anorexigenic effects in a diet-induced obese (DIO) mouse model. The most promising compound, NM4-C16 was effective in a once-weekly-dose regimen. Collectively, our findings suggest that short, lipidated analogs of NmU are suitable leads for the development of novel anti-obesity therapeutics.

Effects of the GLP-1 Receptor Agonist Dulaglutide on the Structure of the Exocrine Pancreas of Cynomolgus Monkeys

Clinical and nonclinical studies have implicated glucagon-like peptide-1 (GLP-1) receptor agonist therapy as a risk factor for acute pancreatitis in patients with type 2 diabetes. Therefore, it is critical to understand the effect that dulaglutide, an approved GLP-1 receptor agonist, has on the exocrine pancreas. Dulaglutide 8.15 mg/kg (approximately 500 times the maximum recommended human dose based on plasma exposure) was administered twice weekly for 12 months to cynomolgus monkeys. Serum amylase and lipase activities were measured and 6 sections of each pancreas were examined microscopically. Ductal epithelial cell proliferation was estimated using Ki67 labeling. Dulaglutide administration did not alter serum amylase or lipase activities measured at the end of treatment compared to control values. An extensive histologic evaluation of the pancreas revealed no changes in the acinar or endocrine portions and no evidence of pancreatitis, necrosis, or pancreatic intraepithelial neoplasia. An increase in goblet cells noted in 4 of the 19 treated monkeys was considered an effect of dulaglutide but was not associated with dilation, blockage, or accumulation of mucin in the pancreatic duct. There was no difference in cell proliferation in ductal epithelium between control and dulaglutide-treated monkeys. These data reveal that chronic dosing of nondiabetic primates with dulaglutide does not induce inflammatory or preneoplastic changes in exocrine pancreas.

Glucagon-like peptide-1 receptor agonists increase pancreatic mass by induction of protein synthesis

Glucagon-like peptide-1 (GLP-1) controls glucose homeostasis by regulating secretion of insulin and glucagon through a single GLP-1 receptor (GLP-1R). GLP-1R agonists also increase pancreatic weight in some preclinical studies through poorly understood mechanisms. Here we demonstrate that the increase in pancreatic weight following activation of GLP-1R signaling in mice reflects an increase in acinar cell mass, without changes in ductal compartments or β-cell mass. GLP-1R agonists did not increase pancreatic DNA content or the number of Ki67(+) cells in the exocrine compartment; however, pancreatic protein content was increased in mice treated with exendin-4 or liraglutide. The increased pancreatic mass and protein content was independent of cholecystokinin receptors, associated with a rapid increase in S6 phosphorylation, and mediated through the GLP-1R. Rapamycin abrogated the GLP-1R-dependent increase in pancreatic mass but had no effect on the robust induction of Reg3α and Reg3β gene expression. Mass spectrometry analysis identified GLP-1R-dependent upregulation of Reg family members, as well as proteins important for translation and export, including Fam129a, eIF4a1, Wars, and Dmbt1. Hence, pharmacological GLP-1R activation induces protein synthesis, leading to increased pancreatic mass, independent of changes in DNA content or cell proliferation in mice.

Effects of the glucagon-like peptide-1 receptor agonist liraglutide in juvenile transgenic pigs modeling a pre-diabetic condition

Background

The glucagon-like peptide-1 receptor (GLP1R) agonist liraglutide improves glycemic control and reduces body weight of adult type 2 diabetic patients. However, efficacy and safety of liraglutide in adolescents has not been systematically investigated. Furthermore, possible pro-proliferative effects of GLP1R agonists on the endocrine and exocrine pancreas need to be further evaluated. We studied effects of liraglutide in adolescent pigs expressing a dominant-negative glucose-dependent insulinotropic polypeptide receptor (GIPR^dn) in the beta-cells, leading to a pre-diabetic condition including disturbed glucose tolerance, reduced insulin secretion and progressive reduction of functional beta-cell mass.

Methods

Two-month-old GIPR^dn transgenic pigs were treated daily with liraglutide (0.6-1.2 mg per day) or placebo for 90 days. Glucose homeostasis was evaluated prior to and at the end of the treatment period by performing mixed meal and intravenous glucose tolerance tests (MMGTT and IVGTT). Finally animals were subjected to necropsy and quantitative-stereological analyses were performed for evaluation of alpha- and beta-cell mass, beta-cell proliferation as well as acinus-cell proliferation.

Results

MMGTT at the end of the study revealed 23% smaller area under the curve (AUC) for glucose, a 36% smaller AUC insulin, and improved insulin sensitivity, while IVGTT showed a 15% smaller AUC glucose but unchanged AUC insulin in liraglutide- vs. placebo-treated animals. Liraglutide led to marked reductions in body weight gain (-31%) and food intake (-30%) compared to placebo treatment, associated with reduced phosphorylation of insulin receptor beta (INSRB)/insulin-like growth factor-1 receptor beta (IGF1RB) and protein kinase B (AKT) in skeletal muscle. Absolute alpha- and beta-cell mass was reduced in liraglutide-treated animals, but alpha- and beta-cell mass-to-body weight ratios were unchanged. Liraglutide neither stimulated beta-cell proliferation in the endocrine pancreas nor acinus-cell proliferation in the exocrine pancreas, excluding both beneficial and detrimental effects on the pig pancreas.

Conclusions

Although plasma liraglutide levels of adolescent transgenic pigs treated in our study were higher compared to human trials, pro-proliferative effects on the endocrine or exocrine pancreas or other liraglutide-related side-effects were not observed.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-015-0431-2) contains supplementary material, which is available to authorized users.

Adverse Effects of GLP-1 Receptor Agonists

Glucagon-like peptide-1 (GLP-1) receptor agonists are a class of injective anti-diabetic drugs that improve glycemic control and many other atherosclerosis-related parameters in patients with type 2 diabetes (T2D). However, the use of this relatively new class of drugs may be associated with certain adverse effects. Concerns have been expressed regarding the effects of these drugs on pancreatic and thyroid tissue, since animal studies and analyses of drug databases indicate an association of GLP-1 receptor agonists with pancreatitis, pancreatic cancer, and thyroid cancer. However, several meta-analyses failed to confirm a cause-effect relation between GLP-1 receptor agonists and the development of these adverse effects. One benefit of GLP-1 receptor agonists is that they do not cause hypoglycemia when combined with metformin or thiazolidinediones, but the dose of concomitant sulphonylurea or insulin may have to be decreased to reduce the risk of hypoglycemic episodes. On the other hand, several case reports have linked the use of these drugs, mainly exenatide, with the occurrence of acute kidney injury, primarily through hemodynamic derangement due to nausea, vomiting, and diarrhea. The most common symptoms associated with the use of GLP-1 receptor agonists are gastrointestinal symptoms, mainly nausea. Other common adverse effects include injection site reactions, headache, and nasopharyngitis, but these effects do not usually result in discontinuation of the drug. Current evidence shows that GLP-1 receptor agonists have no negative effects on the cardiovascular risk of patients with T2D. Thus, GLP-1 receptor agonists appear to have a favorable safety profile, but ongoing trials will further assess their cardiovascular effects. The aim of this review is to analyze critically the available data regarding adverse events of GLP-1 receptor agonists in different anatomic systems published in Pubmed and Scopus. Whenever possible, certain differences between GLP-1 receptor agonists are described. The review also provides the reader with structured data that compare the rates of the most common adverse effects for each of the various GLP-1 receptor agonists.

Antidiabetic therapy in post kidney transplantation diabetes mellitus

Post-transplantation diabetes mellitus (PTDM) is a common complication after kidney transplantation that affects up to 40% of kidney transplant recipients. By pathogenesis, PTDM is a diabetes form of its own, and may be characterised by a sudden, drug-induced deficiency in insulin secretion rather than worsening of insulin resistance over time. In the context of deteriorating allograft function leading to a re-occurrence of chronic kidney disease after transplantation, pharmacological interventions in PTDM patients deserve special attention. In the present review, we aim at presenting the current evidence regarding efficacy and safety of the modern antidiabetic armamentarium. Specifically, we focus on incretin-based therapies and insulin treatment, besides metformin and glitazones, and discuss their respective advantages and pitfalls. Although recent pilot trials are available in both prediabetes and PTDM, further studies are warranted to elucidate the ideal timing of various antidiabetics as well as its long-term impact on safety, glucose metabolism and cardiovascular outcomes in kidney transplant recipients.

Semaglutide, a once-weekly human GLP-1 analog, does not reduce the bioavailability of the combined oral contraceptive, ethinylestradiol/levonorgestrel

The effect of semaglutide, a once-weekly human glucagon-like peptide-1 (GLP-1) analog in development for type 2 diabetes (T2D), on the bioavailability of a combined oral contraceptive was investigated. Postmenopausal women with T2D (n = 43) on diet/exercise ± metformin received ethinylestradiol (0.03 mg)/levonorgestrel (0.15 mg) once daily for 8 days before (semaglutide-free) and during (steady-state 1.0 mg) semaglutide treatment (subcutaneous once weekly; dose escalation: 0.25 mg 4 weeks; 0.5 mg 4 weeks; 1.0 mg 5 weeks). Bioequivalence of oral contraceptives was established if 90%CI for the ratio of pharmacokinetic parameters during semaglutide steady-state and semaglutide-free periods was within prespecified limits (0.80-1.25). The bioequivalence criterion was met for ethinylestradiol area under the curve (AUC0-24 h ) for semaglutide steady-state/semaglutide-free; 1.11 (1.06-1.15). AUC0-24 h was 20% higher for levonorgestrel at semaglutide steady-state vs. semaglutide-free (1.20 [1.15-1.26]). Cmax was within bioequivalence criterion for both contraceptives. Reductions (mean ± SD) in HbA1c (-1.1 ± 0.6%) and weight (-4.3 ± 3.1 kg) were observed. Semaglutide pharmacokinetics were compatible with once-weekly dosing; the semaglutide dose and dose-escalation regimen were well tolerated. Adverse events, mainly gastrointestinal, were mild to moderate in severity. Asymptomatic increases in mean amylase and lipase were observed. Three subjects had elevated alanine aminotransferase levels ≥3x the upper limit of normal during semaglutide/oral contraceptive coadministration, which were reported as adverse events, but resolved during follow-up. Semaglutide did not reduce the bioavailability of ethinylestradiol and levonorgestrel.

An updated review on cancer risk associated with incretin mimetics and enhancers

Incretin-based therapies, including the use of incretin mimetics of glucagon-like peptide-1 receptor (GLP-1R) agonists and incretin enhancers of dipeptidyl-peptidase 4 (DPP-4) inhibitors, are widely used by clinicians for glucose lowering in patients with type 2 diabetes mellitus. These agents have benefits of a lower risk of hypoglycemia, being neutral for body weight for DPP-4 inhibitors and having a potential for weight reduction with GLP-1R agonists. They may also have a neutral or beneficial cardiovascular effect. Despite these benefits, an increased risk of cancer (especially pancreatic cancer and thyroid cancer) associated with incretin-based therapies has been reported. In this article, we reviewed related literature of experimental animal and observational human studies, clinical trials, and meta-analyses published until December 15, 2014. Current studies suggested a probable role of GLP-1R activation on the development of pancreatic cancer and thyroid cancer in rodents, but such an effect in humans is not remarkable due to the lower or lack of expression of GLP-1R on human pancreatic ductal cells and thyroid tissues. Findings in human studies are controversial and inconclusive. In the analyses of the US Food and Drug Administration adverse events reporting system, a significantly higher risk of pancreatic cancer was observed for GLP-1R agonists and DPP-4 inhibitors, but a significantly higher risk of thyroid cancer was only observed for GLP-1R agonists. Such a higher risk of pancreatic cancer or thyroid cancer could not be similarly demonstrated in other human observational studies or analyses of data from clinical trials. With regards to cancers other than pancreatic cancer and thyroid cancer, available studies supported a neutral association in humans. Some preliminary studies even suggested a potentially beneficial effect on the development of other cancers with the use of incretins. Based on current evidence, continuous monitoring of the cancer issues related to incretin-based therapies is required, even though the benefits may outweigh the potential cancer risk in the general patients with type 2 diabetes mellitus.

Incretin-based therapies in prediabetes: Current evidence and future perspectives

The prevalence of type 2 diabetes (T2D) is evolving globally at an alarming rate. Prediabetes is an intermediate state of glucose metabolism that exists between normal glucose tolerance (NGT) and the clinical entity of T2D. Relentless β-cell decline and failure is responsible for the progression from NGT to prediabetes and eventually T2D. The huge burden resulting from the complications of T2D created the need of therapeutic strategies in an effort to prevent or delay its development. The beneficial effects of incretin-based therapies, dipeptidyl peptidase-4 inhibitors and glucagon-like peptide-1 (GLP-1) receptor agonists, on β-cell function in patients with T2D, together with their strictly glucose-depended mechanism of action, suggested their possible use in individuals with prediabetes when greater β-cell mass and function are preserved and the possibility of β-cell salvage is higher. The present paper summarizes the main molecular intracellular mechanisms through which GLP-1 exerts its activity on β-cells. It also explores the current evidence of incretin based therapies when administered in a prediabetic state, both in animal models and in humans. Finally it discusses the safety of incretin-based therapies as well as their possible role in order to delay or prevent T2D.