Occurrence of spontaneous pancreatic lesions in normal and diabetic rats: a potential confounding factor in the nonclinical assessment of GLP-1-based therapies

Incretin based therapy and pancreatic cancer: Realising the reality

Incretin-based therapies like glucagon-like peptide-1 receptor agonists and dipeptidyl peptidase-4 inhibitors help maintain the glycaemic control in patients with type 2 diabetes mellitus with additional systemic benefits and little risk of hypoglycaemia. These medications are associated with low-grade chronic pancreatitis in animal models inconsistently. The incidence of acute pancreatitis was also reported in some human studies. This inflammation provides fertile ground for developing pancreatic carcinoma (PC). Although the data from clinical trials and population-based studies have established safety regarding PC, the pathophysiological possibility that low-grade chronic pancreatitis leads to PC remains. We review the existing literature and describe the relationship between incretin-based therapies and PC.

Research-Relevant Conditions and Pathology of Laboratory Mice, Rats, Gerbils, Guinea Pigs, Hamsters, Naked Mole Rats, and Rabbits

Animals are valuable resources in biomedical research in investigations of biological processes, disease pathogenesis, therapeutic interventions, safety, toxicity, and carcinogenicity. Interpretation of data from animals requires knowledge not only of the processes or diseases (pathophysiology) under study but also recognition of spontaneous conditions and background lesions (pathology) that can influence or confound the study results. Species, strain/stock, sex, age, anatomy, physiology, spontaneous diseases (noninfectious and infectious), and neoplasia impact experimental results and interpretation as well as animal welfare. This review and the references selected aim to provide a pathology resource for researchers, pathologists, and veterinary personnel who strive to achieve research rigor and validity and must understand the spectrum of "normal" and expected conditions to accurately identify research-relevant experimental phenotypes as well as unusual illness, pathology, or other conditions that can compromise studies involving laboratory mice, rats, gerbils, guinea pigs, hamsters, naked mole rats, and rabbits.

Liraglutide Therapy in a Prediabetic State: Rethinking the Evidence

BACKGROUND

Prediabetes is defined as a state of glucose metabolism between normal glucose tolerance and type 2 diabetes. Continuous β-cell failure and death are the reasons for the evolution from normal glucose tolerance to prediabetes and finally type 2 diabetes.

INTRODUCTION

The necessity of new therapeutic approaches in order to prevent or delay the development of type 2 diabetes is obligatory. Liraglutide, a long-acting GLP-1 receptor agonist, has 97% homology for native GLP-1. Identification of the trophic and antiapoptotic properties of liraglutide in preclinical studies, together with evidence of sustained β-cell function longevity during its administration in type 2 diabetes individuals, indicated its earliest possible administration during this disease, or even before its development, so as to postpone or delay its onset.

METHODS

Pubmed and Google databases have been thoroughly searched and relevant studies were selected.

RESULTS

This paper explores the current evidence of liraglutide administration both in humans and animal models with prediabetes. Also, it investigates the safety profile of liraglutide treatment and its future role to postpone or delay the evolution of type 2 diabetes.

CONCLUSION

Liralgutide remains a valuable tool in our therapeutic armamentarium for individuals who are overweight or obese and have prediabetes. Future well designed studies will give valuable information that will help clinicians to stratify individuals who will derive the most benefit from this agent, achieving targeted therapeutic strategies.

Pancreatitis Incidence in the Exenatide BID, Exenatide QW, and Exenatide QW Suspension Development Programs: Pooled Analysis of 35 Clinical Trials

INTRODUCTION

Glucagon-like peptide-1 receptor agonists (GLP-1RAs) are widely used for treatment of type 2 diabetes mellitus; however, there have been concerns that GLP-1RA treatment may be associated with an increased incidence of pancreatitis. This study aimed to evaluate the incidence of pancreatitis in a pooled population of type 2 diabetes trials from the clinical development program of the GLP-1RA exenatide as well as to describe patient-level data for all reported cases.

METHODS

The primary analysis examined pooled data among patients with type 2 diabetes from the controlled arms of 35 trials (ranging from 4 to 234 weeks' duration) in the integrated clinical databases for exenatide twice daily, once weekly, and once-weekly suspension, excluding comparator arms with other incretin-based therapies. The exposure-adjusted incidence rate (EAIR) of pancreatitis was calculated for exenatide and non-exenatide (non-incretin-based therapy or placebo) treatment groups. Patient-level data were described for all pancreatitis incidences.

RESULTS

The primary analysis included 5596 patients who received exenatide and 4462 in the non-exenatide group. The mean duration of study medication exposure for the exenatide and non-exenatide treatment groups was 57.0 and 47.9 weeks, respectively. Pancreatitis was diagnosed in 14 patients (exenatide, n = 8; non-exenatide, n = 6), of whom 13 recovered with or without sequelae. The pancreatitis EAIR was 0.1195 events per 100 patient-years [95% confidence interval (CI), 0.0516-0.2154] in the exenatide group versus 0.1276 events per 100 patient-years (95% CI 0.0468-0.2482) in the non-exenatide treatment group. The EAIR ratio for the exenatide versus non-exenatide treatment group was 0.761 (95% CI 0.231-2.510).

CONCLUSION

In this pooled analysis of 10,058 patients among studies comparing exenatide with other glucose-lowering medications or placebo, pancreatitis was rare. The EAIRs of pancreatitis were low and similar between exenatide and non-exenatide treatment groups. No evidence of an association between exenatide and pancreatitis was observed.

FUNDING

Bristol-Myers Squibb and AstraZeneca. Plain language summary available for this article.

Toxicologic Pathology Forum: Current Status on the Use of Animal Models of Human Disease in the Pharmaceutical Industry in Japan in Nonclinical Safety Assessment-Opinion Paper

In nonclinical safety studies for new drug development, healthy animals have been commonly used. However, in some cases, the use of animal models of human disease is considered to be more favorable in evaluating risks in patients. To elucidate the current status of the use of animal models for nonclinical safety assessment, an internal questionnaire from the Japan Pharmaceutical Manufacturers Association and surveys (questionnaire period: August 27 to September 30, 2015) of both common technical documents and review reports of approved drugs (approval period: May 1999 to May 2017) disclosed by the Pharmaceutical and Medical Devices Agency were conducted. Although there were some concerns and limitations raised, the survey results revealed that animal models have been used in nonclinical safety assessment on a case-by-case basis and that nonclinical safety studies using animal models were included in the data packages of several approved drugs in Japan. The survey results also revealed that nonclinical safety studies using animal models have become more frequent in the past few years. In almost all cases, useful information, such as signs of toxicity under disease conditions and mechanisms of toxic change, was obtained from the results of nonclinical studies using animal models. Note: This is an opinion article submitted to the Toxicologic Pathology Forum. It represents the views of the author(s). It does not constitute an official position of the Society of Toxicologic Pathology, British Society of Toxicological Pathology, or European Society of Toxicologic Pathology, and the views expressed might not reflect the best practices recommended by these Societies. This article should not be construed to represent the policies, positions, or opinions of their respective organizations, employers, or regulatory agencies.

The Ascending GLP-1 Road From Clinical Safety to Reduction of Cardiovascular Complications

Glucagon-like peptide 1 (GLP-1) was originally identified as a gut-derived incretin hormone that lowered glycemia through potentiation of glucose-dependent insulin secretion. Subsequent studies expanded the actions of GLP-1 to include inhibition of glucagon secretion, gastric emptying, and appetite, collectively useful attributes for a glucose-lowering agent. The introduction of GLP-1 receptor (GLP-1R) agonists for the treatment of diabetes was associated with questions surrounding their safety, principally with regard to medullary thyroid cancer, pancreatitis, and pancreatic cancer, yet cardiovascular outcome trials subsequently revealed reductions in rates of stroke, myocardial infarction, and cardiovascular death with a paucity of major safety signals. We discuss the controversies, unanswered questions, and established use of GLP-1R agonists from a mechanistic and clinical perspective. We highlight methods for detection and cellular sites of GLP-1R expression, key uncertainties, recent insights, and experimental caveats surrounding the use of GLP-1R agonists for the treatment of diabetes and the reduction of diabetes-related complications.

Pancreatic Effects of a Bruton's Tyrosine Kinase Small-molecule Inhibitor in Rats Are Strain-dependent

Inhibitors of Bruton's tyrosine kinase (BTK) are under development as potential therapies for various autoimmune diseases. In repeat-dose toxicity studies, small-molecule BTK inhibitors (BTKi) have been reported to cause a constellation of histologic effects at the pancreatic endocrine-exocrine interface in male rats; however, similar findings were not reported in other species. Since the BTKi-induced pancreatic effect is morphologically similar to well-documented spontaneous changes (predominantly characterized by insular/peri-insular hemorrhage, pigment deposition, chronic inflammation, and fibrosis) that are known to vary by rat strain, we investigated potential strain-dependent differences in the pancreatic effects of a small-molecule BTKi, LY3337641. Following 13 weeks of LY3337641 treatment, Crl:CD(SD) rats were most sensitive, Crl:WI(Han) rats were of intermediate sensitivity, and Hsd:SD rats were least sensitive. These strain differences appear to be related to differences in rate of weight gain across strains and sexes; however, a definitive mechanism was not determined. This study demonstrated that BTKi-induced pancreatic effects were highly dependent on rat strain and correlated with differences in the incidence and severity of the spontaneous background change. When considered with the lack of pancreas effects in nonrat species, these changes in rats are unlikely predictive of similar changes in humans administered a BTK inhibitor.

Mechanisms of Action and Therapeutic Application of Glucagon-like Peptide-1

Glucagon-like peptide-1 (GLP-1) released from gut enteroendocrine cells controls meal-related glycemic excursions through augmentation of insulin and inhibition of glucagon secretion. GLP-1 also inhibits gastric emptying and food intake, actions maximizing nutrient absorption while limiting weight gain. Here I review the circuits engaged by endogenous versus pharmacological GLP-1 action, highlighting key GLP-1 receptor (GLP-1R)-positive cell types and pathways transducing metabolic and non-glycemic GLP-1 signals. The role(s) of GLP-1 in the benefits and side effects associated with bariatric surgery are discussed and actions of GLP-1 controlling islet function, appetite, inflammation, and cardiovascular pathophysiology are highlighted. Refinement of the risk-versus-benefit profile of GLP-1-based therapies for the treatment of diabetes and obesity has stimulated development of orally bioavailable agonists, allosteric modulators, and unimolecular multi-agonists, all targeting the GLP-1R. This review highlights established and emerging concepts, unanswered questions, and future challenges for development and optimization of GLP-1R agonists in the treatment of metabolic disease.

Incretin Therapies Do Not Expand β-Cell Mass or Alter Pancreatic Histology in Young Male Mice

The impact of incretins upon pancreatic β-cell expansion remains extremely controversial. Multiple studies indicate that incretin-based therapies can increase β-cell proliferation, and incretins have been hypothesized to expand β-cell mass. However, disagreement exists on whether incretins increase β-cell mass. Moreover, some reports indicate that incretins may cause metaplastic changes in pancreatic histology. To resolve these questions, we treated a large cohort of mice with incretin-based therapies and carried out a rigorous analysis of β-cell turnover and pancreatic histology using high-throughput imaging. Young mice received exenatide via osmotic pump, des-fluoro-sitagliptin, or glipizide compounded in diet for 2 weeks (short-term) on a low-fat diet (LFD) or 4.5 months (long-term) on a LFD or high-fat diet (HFD). Pancreata were quantified for β-cell turnover and mass. Slides were examined for gross anatomical and microscopic changes to exocrine pancreas. Short-term des-fluoro-sitagliptin increased serum insulin and induced modest β-cell proliferation but no change in β-cell mass. Long-term incretin therapy in HFD-fed mice resulted in reduced weight gain, improved glucose homeostasis, and abrogated β-cell mass expansion. No evidence for rapidly dividing progenitor cells was found in islets or pancreatic parenchyma, indicating that incretins do not induce islet neogenesis or pancreatic metaplasia. Contrasting prior reports, we found no evidence of β-cell mass expansion after acute or chronic incretin therapy. Chronic incretin administration was not associated with histological abnormalities in pancreatic parenchyma; mice did not develop tumors, pancreatitis, or ductal hyperplasia. We conclude that incretin therapies do not generate β-cells or alter pancreatic histology in young mice.

Regulatory Forum Opinion Piece*: Use and Utility of Animal Models of Disease for Nonclinical Safety Assessment: A Pharmaceutical Industry Survey

An Innovation and Quality (IQ) Consortium focus group conducted a cross-company survey to evaluate current practices and perceptions around the use of animal models of disease (AMDs) in nonclinical safety assessment of molecules in clinical development. The IQ Consortium group is an organization of pharmaceutical and biotechnology companies with the mission of advancing science and technology. The survey queried the utilization of AMDs during drug discovery in which drug candidates are evaluated in efficacy models and limited short-duration non-Good Laboratory Practices (GLP) toxicology testing and during drug development in which drug candidates are evaluated in GLP toxicology studies. The survey determined that the majority of companies used AMDs during drug discovery primarily as a means for proactively assessing potential nonclinical safety issues prior to the conduct of toxicology studies, followed closely by the use of AMDs to better understand toxicities associated with exaggerated pharmacology in traditional toxicology models or to derisk issues when the target is only expressed in the disease state. In contrast, the survey results indicated that the use of AMDs in development is infrequent, being used primarily to investigate nonclinical safety issues associated with targets expressed only in disease states and/or in response to requests from global regulatory authorities.

Pancreatic Safety of Sitagliptin in the TECOS Study

OBJECTIVE

We evaluated the incidence of acute pancreatitis and pancreatic cancer in patients with type 2 diabetes and cardiovascular disease who were treated with sitagliptin, a dipeptidyl peptidase-4 inhibitor (DPP-4i).

RESEARCH DESIGN AND METHODS

In the Trial Evaluating Cardiovascular Outcomes with Sitagliptin (TECOS) study, a cardiovascular safety study of sitagliptin, all suspected cases of acute pancreatitis and pancreatic cancer were collected prospectively for 14,671 participants during a median follow-up time of 3 years, and were adjudicated blindly.

RESULTS

Baseline differences were minimal between participants confirmed to have no pancreatic events, acute pancreatitis, or pancreatic cancer. Among those participants randomized to receive sitagliptin, 23 (0.3%) (vs. 12 randomized to receive placebo [0.2%]) had pancreatitis (hazard ratio 1.93 [95% CI 0.96-3.88], P = 0.065; 0.107 vs. 0.056/100 patient-years), with 25 versus 17 events, respectively. Severe pancreatitis (two fatal) occurred in four individuals allocated to receive sitagliptin. Cases of pancreatic cancer were numerically fewer with sitagliptin (9 [0.1%]) versus placebo (14 [0.2%]) (hazard ratio 0.66 [95% CI 0.28-1.51], P = 0.32; 0.042 vs. 0.066 events/100 patient-years). Meta-analysis with two other DPP-4i cardiovascular outcome studies showed an increased risk for acute pancreatitis (risk ratio 1.78 [95% CI 1.13-2.81], P = 0.01) and no significant effect for pancreatic cancer (risk ratio 0.54 [95% CI 0.28-1.04], P = 0.07).

CONCLUSIONS

Pancreatitis and pancreatic cancer were uncommon events with rates that were not statistically significantly different between the sitagliptin and placebo groups, although numerically more sitagliptin participants developed pancreatitis and fewer developed pancreatic cancer. Meta-analysis suggests a small absolute increased risk for pancreatitis with DPP-4i therapy.

Impact of the Genetics and Source of Preclinical Safety Animal Models on Study Design, Results, and Interpretation

It has been long established that not only the species but also the strain and supplier of rodents used in preclinical safety studies can have a significant impact on the outcome of studies due to variability in their genetic background and thus spontaneous pathologic findings. In addition, local husbandry, housing, and other environmental conditions may have effects on the development and expression of comorbidities, particularly in longer-term or chronic studies. More recently, similar effects related to the source, including genetic and environmental variability, have been recognized in cynomolgus macaques ( Macaca fascicularis). The increased use of cynomolgus macaques from various sources of captive-bred animals (including nonnative, U.S./European Union-based breeding facilities or colonies) can affect study design and study results and outcome. It is important to acknowledge and understand the impact of this variability on the results and interpretation of research studies. This review includes recent examples where variability of preclinical animal models (rats and monkeys) affected the postmortem observations highlighting its relevance to study design or interpretation in safety studies.

The anti-hyperglycemic efficacy of a lipid-lowering drug Daming capsule and the underlying signaling mechanisms in a rat model of diabetes mellitus

Diabetes mellitus (DM) is a metabolic disorder manifested by hyperglycemia. Daming Capsule (DMC), a combination of traditional Chinese herbs, is used clinically as a lipid-lowering drug. This study was designed to evaluate if DMC possesses an anti-hyperglycemic effect and to elucidate the underlying mechanisms. Compared to diabetic rats, the rats received DMC (200 mg/kg/d) had significantly lower blood lipid and glucose levels. DMC markedly restored the decreased secretion of GLP-1 and GIP as well as the coding gene GCG and GIP in ileum. Moreover, DMC normalized depressed GCG and GIP transcription by significantly enhancing the GSK-3β/β-catenin signaling pathway and expression of TCF7L2, a transactivator of GCG and GIP in diabetic rats. DMC possesses an anti-hyperglycemic property characterized by preservation/stimulation of GLP-1 and GIP secretion in DM rats. Here, we proposed DMC → GSK-3β/β-catenin↑ → TCF7L2↑ → GLP-1, GIP secretion↑ → blood glucose↓ as a regulatory pathway of blood glucose homeostasis. Our findings suggest DMC as a promising therapeutic drug in the clinical treatment of diabetes.

The Cardiovascular Biology of Glucagon-like Peptide-1

Glucagon-like peptide-1, produced predominantly in enteroendocrine cells, controls glucose metabolism and energy homeostasis through regulation of islet hormone secretion, gastrointestinal motility, and food intake, enabling development of GLP-1 receptor (GLP-1R) agonists for the treatment of diabetes and obesity. GLP-1 also acts on the immune system to suppress inflammation, and GLP-1R signaling in multiple tissues impacts cardiovascular function in health and disease. Here we review how GLP-1 and clinically approved GLP-1R agonists engage mechanisms that influence the risk of developing cardiovascular disease. We discuss how GLP-1R agonists modify inflammation, cardiovascular physiology, and pathophysiology in normal and diabetic animals through direct and indirect mechanisms and review human studies illustrating mechanisms linking GLP-1R signaling to modification of the cardiovascular complications of diabetes. The risks and benefits of GLP-1R agonists are updated in light of recent data suggesting that GLP-1R agonists favorably modify outcomes in diabetic subjects at high risk for cardiovascular events.

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.

Activation of GLP-1 and gastrin signalling induces in vivo reprogramming of pancreatic exocrine cells into beta cells in mice

AIMS/HYPOTHESIS

Lineage conversion of non-beta cells into insulin-producing cells has been proposed as a therapy for the cure of diabetes. Glucagon-like peptide-1 (GLP-1) and its derivatives can induce beta cell neogenesis in vitro and beta cell mass expansion in vivo, but GLP-1 signalling has not been shown to regulate cell fate decisions in vivo. We therefore tested the impact of GLP-1 receptor (GLP1R) expression on beta cell differentiation in vivo.

METHODS

Mice overexpressing GLP1R in pancreatic exocrine cells were generated by Cre-mediated recombination in sex-determining region Y-box 9 (SOX9)-expressing cells and then treated with exendin-4 and/or gastrin. Histological analysis was performed to detect cellular reprogramming from the exocrine lineage into insulin-producing cells.

RESULTS

Whereas no newly generated beta cells were detected in the mice treated with exendin-4 alone, treatment with gastrin only induced the conversion of exocrine cells into insulin-producing cells. Furthermore, the overexpression of GLP1R, together with gastrin and exendin-4, synergistically promoted beta cell neogenesis accompanied by the formation of islet-like clusters. These newly generated beta cells expressed beta cell specific transcription factors, such as pancreatic and duodenal homeobox 1 (PDX1), NK6 homeobox 1 (NKX6.1) and musculoaponeurotic fibrosarcoma oncogene family A (MafA). These mice showed no histological evidence of pancreatitis or pancreatic dysplasia in their acini and had normal plasma amylase levels.

CONCLUSIONS/INTERPRETATION

Activation of GLP-1 and gastrin signalling induces beta cell neogenesis in the exocrine lineage without any deleterious pancreatic changes, which may lead to a potential therapy to cure diabetes by generating surrogate beta cells.

An Investigative Study of Pancreatic Exocrine Biomarkers, Histology, and Histomorphometry in Male Zucker Diabetic Fatty (ZDF) Rats Given Dulaglutide by Subcutaneous Injection Twice Weekly for 13 Weeks

Glucagon-like peptide-1 (GLP-1) receptor agonist therapy has been implicated as a possible risk factor for acute pancreatitis in patients with type 2 diabetes. Dulaglutide is a long-acting GLP-1 receptor agonist in development for treatment of type 2 diabetes. The effects of dulaglutide were evaluated in male Zucker diabetic fatty (ZDF) rats to examine whether dulaglutide may induce or modulate pancreatitis. Rats were randomized to dose groups receiving twice-weekly subcutaneously administered dulaglutide 0.5, 1.5, and 5.0 mg/kg/dose (corresponding human plasma exposures following twice-weekly dosing are 3-, 8-, and 30-fold, respectively) for 13 weeks or to vehicle control. Following termination, serially trimmed sections of pancreases were stained with hematoxylin and eosin or co-stained with an epithelial marker and a marker of either proliferation or apoptosis. Efficacious reductions in glucose and hemoglobin A1c occurred at all dulaglutide doses. Lipase activity was unaffected, and there were modest increases in total and pancreatic amylase activities at all doses without individual microscopic inflammatory correlates. Microscopic dulaglutide-related pancreatic changes included increased interlobular ductal epithelium without ductal cell proliferation (≥0.5 mg/kg), increased acinar atrophy with/without inflammation (≥1.5 mg/kg), and increased incidence/severity of neutrophilic acinar pancreatic inflammation (5.0 mg/kg). In summary, dulaglutide treatment was associated with mild alterations in ductal epithelium and modest exacerbation of spontaneous lesions of the exocrine pancreas typically found in the ZDF rat model.

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.

Synergistic metabolic benefits of an exenatide analogue and cholecystokinin in diet-induced obese and leptin-deficient rodents

AIM

To test the impact of cholecystokinin (CCK) plus either amylin or a glucagon-like peptide-1 receptor (GLP-1R) agonist on metabolic variables in diet-induced obese (DIO) rodents.

METHODS

A stabilized acetylated version of CCK-8 (Ac-Y*-CCK-8), selective CCK1 receptor (CCK1R) or CCK2 receptor (CCK2R) agonists, amylin or the GLP-1R agonist and exenatide analogue AC3174 were administered in select combinations via continuous subcutaneous infusion to DIO rats for 14 days, or Lep(ob) /Lep(ob) mice for 28 days, and metabolic variables were assessed.

RESULTS

Combined administration of Ac-Y*-CCK-8 with either amylin or AC3174 induced greater than additive weight loss in DIO rats, with the overall magnitude of effect being greater with AC3174 + Ac-Y*-CCK-8 treatment. Co-infusion of AC3174 with a specific CCK1R agonist, but not a CCK2R agonist, recapitulated the weight loss mediated by AC3174 + Ac-Y*-CCK-8 in DIO rats, suggesting that synergy is mediated by CCK1R activation. In a 4 × 4 full-factorial response surface methodology study in DIO rats, a synergistic interaction between AC3174 and the CCK1R-selective agonist on body weight and food intake was noted. Co-administration of AC3174 and the CCK1R-selective agonist to obese diabetic Lep(ob) /Lep(ob) mice elicited a significantly greater reduction in percentage of glycated haemoglobin and food intake relative to the sum effects of monotherapy groups.

CONCLUSIONS

The anti-obesity and antidiabetic potential of combined GLP-1R and CCK1R agonism is an approach that warrants further investigation.

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.

Adverse drug reactions associated with the use of liraglutide in patients with type 2 diabetes--focus on pancreatitis and pancreas cancer

INTRODUCTION

The glucagon-like peptide-1 (GLP-1) receptor agonist, liraglutide , is a widely used drug for the treatment of type 2 diabetes. Liraglutide is one of several incretin-based agents that have been suggested to be associated with pancreatitis and pancreas cancer. The suspicion accelerated after publication of an autopsy study claiming increased incidences of several pathological changes in pancreata from patients with diabetes treated with incretin-based drugs.

AREAS COVERED

The aim of the present review is to give an overview of the pharmacology of liraglutide and provide a review of adverse reactions associated with liraglutide with a focus on the risk of pancreatitis and pancreas cancer.

EXPERT OPINION

When comprehensively reviewing the available literature, no clear and significant associations between liraglutide and pancreatitis and/or pancreas cancer seem evident. However, a recently published analysis suggests a trend toward a slightly elevated risk of pancreatitis with GLP-1 receptor agonists (including liraglutide), which may become statistical significant as more data become available. Well-established side effects are of gastrointestinal origin, typical mild-to-moderate and of transient character. The risk of hypoglycemia associated with liraglutide treatment is low.

Divergent effects of liraglutide, exendin-4, and sitagliptin on beta-cell mass and indicators of pancreatitis in a mouse model of hyperglycaemia

AIMS

Glucagon-like peptide-1 (GLP-1) receptor agonists and dipeptidyl peptidase-4 (DPP4) inhibitors improve glucose tolerance by still incompletely understood mechanisms. Each class of antihyperglycemic drugs has also been proposed to increase pancreatitis risk. Here, we compare systematically the effects of two widely-used GLP-1 analogues, liraglutide and exendin-4, and the DPP4 inhibitor, sitagliptin, in the mouse.

METHODS

C57BL6 mice were maintained for 131 days on a normal diet (ND) or a diet comprising 60% fat (HFD) before measurements of fasting blood glucose and insulin, and intraperitoneal glucose tolerance. Beta- and alpha- cell volume, and Reg3b immunoreactivity, were measured by immunohistochemical analysis of pancreatic slices.

RESULTS

Whereas liraglutide (200 µg/kg) and exendin-4 (10 µg/kg) treatment reduced body weight and/or improved glucose tolerance, sitagliptin (10 mg/kg) was without effect on either parameter. Liraglutide caused a sharp reduction in beta-cell mass in both ND and HFD mice, whereas exendin-4 exerted no effect. By contrast, sitagliptin unmasked an action of high fat diet to increase beta-cell mass. Reg3B positive area was augmented by all three agents in normal chow-fed mice, whilst sitagliptin and exendin-4, but not liraglutide, affected this parameter in HFD animals. Correspondingly sitagliptin, but not the GLP-1 analogues, increased circulating amylase levels in ND and HFD mice.

CONCLUSIONS

Liraglutide improves glucose tolerance in the mouse whilst exerting relatively modest effects on pancreatitis risk. Conversely, exendin-4 and sitagliptin, at doses which exert, respectively, minor or no effects on metabolic parameters, lead to signs of pancreatitis.