Incretin therapies: highlighting common features and differences in the modes of action of glucagon-like peptide-1 receptor agonists and dipeptidyl peptidase-4 inhibitors

Cardiovascular outcome studies with incretin-based therapies: Comparison between DPP-4 inhibitors and GLP-1 receptor agonists

Dipeptidyl peptidase-4 inhibitors (DPP-4is) and glucagon-like peptide-1 receptor agonists (GLP-1RAs) represent two distinct classes of incretin-based therapies used for the treatment of type 2 diabetes. Non-inferiority versus placebo was shown in large prospective cardiovascular outcome trials in patients with high cardiovascular risk: SAVOR-TIMI 53 (saxagliptin), EXAMINE (alogliptin), and TECOS (sitagliptin); ELIXA (lixisenatide), LEADER (liraglutide) and SUSTAIN 6 (semaglutide). The promises raised by meta-analyses of phase 2-3 trials with DPP-4is were non confirmed as no cardiovascular protection could be evidenced. However, LEADER showed a significant reduction in major cardiovascular events, myocardial infarction, cardiovascular and all-cause mortality in patients treated by liraglutide compared to placebo. These positive results contrasted with the non-inferiority results with lixisenatide in ELIXA. They were partially confirmed with semaglutide in SUSTAIN 6 despite the absence of reduction in cardiovascular mortality. Hospitalisation for heart failure was not increased except with saxagliptin in SAVOR-TIMI 53. The reasons for different outcomes between trials remain largely unknown as well as the precise underlying mechanisms explaining the cardiovascular protection by liraglutide. The clinical relevance of results with DPP-4is and GLP-1RAs is discussed. Ongoing trials with linagliptin and several once-weekly GLP-1RAs should provide new insights into remaining fundamental questions.

Efficacy and safety of once-weekly semaglutide versus once-daily sitagliptin as an add-on to metformin, thiazolidinediones, or both, in patients with type 2 diabetes (SUSTAIN 2): a 56-week, double-blind, phase 3a, randomised trial

BACKGROUND

Semaglutide is a novel glucagon-like peptide-1 (GLP-1) analogue, suitable for once-weekly subcutaneous administration, in development for treatment of type 2 diabetes. We assessed the efficacy and safety of semaglutide versus the dipeptidyl peptidase-4 (DPP-4) inhibitor sitagliptin in patients with type 2 diabetes inadequately controlled on metformin, thiazolidinediones, or both.

METHODS

We did a 56-week, phase 3a, randomised, double-blind, double-dummy, active-controlled, parallel-group, multinational, multicentre trial (SUSTAIN 2) at 128 sites in 18 countries. Eligible patients were aged at least 18 years (or at least 20 years in Japan) and diagnosed with type 2 diabetes, with insufficient glycaemic control (HbA_1c 7·0-10·5% [53·0-91·0 mmol/mol]) despite stable treatment with metformin, thiazolidinediones, or both. We randomly assigned participants (2:2:1:1) using an interactive voice or web response system to 56 weeks of treatment with subcutaneous semaglutide 0·5 mg once weekly plus oral sitagliptin placebo once daily, subcutaneous semaglutide 1·0 mg once weekly plus oral sitagliptin placebo once daily, oral sitagliptin 100 mg once daily plus subcutaneous semaglutide placebo 0·5 mg once weekly, or oral sitagliptin 100 mg once daily plus subcutaneous semaglutide placebo 1·0 mg once weekly. The two oral sitagliptin 100 mg groups (with semaglutide placebo 0·5 mg and 1·0 mg) were pooled for the analyses. The primary endpoint was change in HbA_1c from baseline to week 56, assessed in the modified intention-to-treat population (all randomly assigned participants who received at least one dose of study drug); change in bodyweight from baseline to week 56 was the confirmatory secondary endpoint. Safety endpoints included adverse events and hypoglycaemic episodes. This trial is registered with ClinicalTrials.gov, number NCT01930188.

FINDINGS

Between Dec 2, 2013, and Aug 5, 2015, we randomly assigned 1231 participants; of the 1225 included in the modified intention-to-treat analysis, 409 received semaglutide 0·5 mg, 409 received semaglutide 1·0 mg, and 407 received sitagliptin 100 mg. Mean baseline HbA_1c was 8·1% (SD 0·93); at week 56, HbA_1c was reduced by 1·3% in the semaglutide 0·5 mg group, 1·6% in the semaglutide 1·0 mg group, and 0·5% with sitagliptin (estimated treatment difference vs sitagliptin -0·77% [95% CI -0·92 to -0·62] with semaglutide 0·5 mg and -1·06% [-1·21 to -0·91] with semaglutide 1·0 mg; p<0·0001 for non-inferiority and for superiority, for both semaglutide doses vs sitagliptin). Mean baseline bodyweight was 89·5 kg (SD 20·3); at week 56, bodyweight reduced by 4·3 kg with semaglutide 0·5 mg, 6·1 kg with semaglutide 1·0 mg, and 1·9 kg with sitagliptin (estimated treatment difference vs sitagliptin -2·35 kg [95% CI -3·06 to -1·63] with semaglutide 0·5 mg and -4·20 kg [-4·91 to -3·49] with semaglutide 1·0 mg; p<0·0001 for superiority, for both semaglutide doses vs sitagliptin). The proportion of patients who discontinued treatment because of adverse events was 33 (8%) for semaglutide 0·5 mg, 39 (10%) for semaglutide 1·0 mg, and 12 (3%) for sitagliptin. The most frequently reported adverse events in both semaglutide groups were gastrointestinal in nature: nausea was reported in 73 (18%) who received semaglutide 0·5 mg, 72 (18%) who received semaglutide 1·0 mg, and 30 (7%) who received placebo, and diarrhoea was reported in 54 (13%) who received semaglutide 0·5 mg, 53 (13%) who received semaglutide 1·0 mg, and 29 (7%) who received placebo. Seven (2%) patients in the semaglutide 0·5 mg group, two (<1%) in the semaglutide 1·0 mg group, and five (1%) in the sitagliptin group had blood-glucose confirmed hypoglycaemia. There were six fatal events (two in the semaglutide 0·5 mg group, one in the semaglutide 1·0 mg group, and three in the sitagliptin group); none were considered likely to be related to the trial drugs.

INTERPRETATION

Once-weekly semaglutide was superior to sitagliptin at improving glycaemic control and reducing bodyweight in participants with type 2 diabetes on metformin, thiazolidinediones, or both, and had a similar safety profile to that of other GLP-1 receptor agonists. Semaglutide seems to be an effective add-on treatment option for this patient population.

FUNDING

Novo Nordisk A/S.

Oxyntomodulin analog and exendin-4 derivative lower plasma glucose in cattle

The present study was undertaken with the aim of examining whether and how exendin-4 (1-3) fragment, ie, Ex-4 (1-3) fragment, contributes to the regulation of glucose. An analog of oxyntomodulin (OXM) ([Gly², Glu³]-OXM), a glucagon analog ([Gly², Glu³]-glucagon), and two derivatives of Ex-4 (glucandin and [Gly², Glu³]-glucandin) were synthesized by substituting with Gly², Glu³ at the N-terminuses of OXM and glucagon and/or by attaching Ex-4 (30-39) amide at the C-terminus of glucagon. Effects of these peptides on plasma insulin and glucose concentrations were investigated in cattle by conducting 3 in vivo experiments. In all 3 experiments, 0.1% BSA saline was injected as a control. In experiment 1, glucandin (amino acid sequence was glucagon [1-29]-Ex-4 [30-39] amide) and [Gly², Glu³]-glucandin were injected at the dose rates of 5 μg/kg BW in 4-mo-old Holstein steers. Results showed that glucoregulatory effects of glucandin were similar to those of glucagon. [Gly², Glu³]-glucandin stimulated insulin secretion at 2 to 10 min and lowered glucose concentrations at 15 to 75 min. Experiment 2 was carried out to better understand the glucose-lowering potency of [Gly², Glu³]-glucandin, in comparison with Ex-4 and glucagon-like peptide-1 (GLP-1), using 4.5-mo-old Holstein steers. [Gly², Glu³]-glucandin was injected at dose rates of 0.3 μg/kg BW, 1.0 μg/kg BW, 3.2 μg/kg BW, and 6.4 μg/kg BW. Ex-4 and GLP-1 were injected at dose rates of 0.3 μg/kg BW. Results showed that the insulinotropic and glucose-lowering effects of [Gly², Glu³]-glucandin were not as potent as for Ex-4 and GLP-1, and the minimum effective dose of [Gly², Glu³]-glucandin to regulate plasma glucose concentrations was 3.2 μg/kg BW. In experiment 3, [Gly², Glu³]-OXM and [Gly², Glu³]-glucagon were injected at dose rates of 5 μg/kg BW in 5-mo-old Holstein steers. Both [Gly², Glu³]-OXM and [Gly², Glu³]-glucagon increased insulin concentration. [Gly², Glu³]-OXM potently lowered plasma glucose, but [Gly², Glu³]-glucagon did not change it. In summary, our findings clearly demonstrate that Ex-4 (1-3) fragment contributes to the regulation of glucose. [Gly², Glu³]-OXM and [Gly², Glu³]-glucandin are insulinotropic and glucose-lowering peptides. It was of interest that the substitution of the first 3 amino acids of OXM with Ex-4 (1-3) could reverse the upregulation of glucose by OXM into downregulation of glucose. In lowering glycemia, [Gly², Glu³]-OXM seemed almost as effective as Ex-4, and [Gly², Glu³]-glucandin was less profound than Ex-4. These findings contributed new insights into the hormonal regulation of glucose in ruminants. The action of [Gly², Glu³]-OXM and [Gly², Glu³]-glucandin might provide an advantage in glycemic control of insulin resistance in cattle and humans.

Reduction of visceral fat by liraglutide is associated with ameliorations of hepatic steatosis, albuminuria, and micro-inflammation in type 2 diabetic patients with insulin treatment: a randomized control trial

Liraglutide, an analogue of human glucagon-like peptide 1, reduces cardiovascular events in patients with type 2 diabetes; however, it has still been unknown by which mechanisms liraglutide could reduce cardiovascular events. Type 2 diabetic patients with insulin treatment were enrolled in this randomized, open-label, comparative study. Participants were randomly assigned to liraglutide plus insulin (liraglutide group) and insulin treatment (control group) at 1:1 allocation. Primary endpoint was the change in viscera fat are (VFA, cm²) at 24 weeks. Liver attenuation index (LAI) measured by abdominal computed tomography, urinary albumin-to-creatinine ratio (ACR, mg/g), and C-reactive protein (CRP) levels, skeletal muscle index (SMI), and quality of life (QOL) related to diabetes treatment were also determined. Seventeen patients (8; liraglutide group, 9; control group, mean age 59 ± 13 years; 53% female) completed this study. Liraglutide treatment significantly reduced VFA at 24 weeks; whereas, SFA was unchanged. ACR, LAI, and CRP levels were significantly reduced by liraglutide at 24 weeks and there was no difference in SMI between the two groups. Changes in VFA from baseline to 24 weeks were significantly associated with those in LAI, albuminuria, and HbA1c. Liraglutide treatment significantly improved QOL scores associated with anxiety and dissatisfaction with treatment and satisfaction with treatment. No severe adverse events were observed in both groups. Our data suggest that liraglutide could reduce visceral adiposity in parallel with attenuation of hepatic fat accumulation, albuminuria and micro-inflammation and improve QOL related to diabetes care in insulin-treated patients with type 2 diabetes.

The anti-diabetic drug exenatide, a glucagon-like peptide-1 receptor agonist, counteracts hepatocarcinogenesis through cAMP-PKA-EGFR-STAT3 axis

Epidemiological studies have demonstrated a close association of type 2 diabetes and hepatocellular carcinoma (HCC). Exenatide (Ex-4), a potent diabetes drug targeting glucagon-like peptide-1 receptor (GLP-1R), is protective against non-alcoholic fatty liver disease (NAFLD). However, the Ex-4 function and GLP-1R status have yet been explored in HCC. Herein we investigated the effect of Ex-4 in diethylnitrosamine (DEN)-treated mice consuming control or high-fat high-carbohydrate diet. Administration of Ex-4 significantly improved obesity-induced hyperglycemia and hyperlipidemia and reduced HCC multiplicity in obese DEN-treated mice, in which suppressed proliferation and induced apoptosis were confined to tumor cells. The tumor suppression effects of Ex-4 were associated with high expression of GLP-1R and activation of cyclic AMP (cAMP) and protein kinase A (PKA). Importantly, Ex-4 also downregulated epidermal growth factor receptor (EGFR) and signal transducer and activator of transcription 3 (STAT3), which lie downstream of cAMP-PKA signaling, resulting in suppression of multiple STAT3-targeted genes including c-Myc, cyclin D1, survivin, Bcl-2 and Bcl-xl. The growth inhibitory effects of Ex-4 were consistent in GLP-1R-abundant hepatoma cell lines and xenograft mouse model, wherein both PKA and EGFR had obligatory roles in mediating Ex-4 functions. In addition, Ex-4 also effectively suppressed inflammatory and fibrotic phenotypes in mice fed with methionine-choline-deficient (MCD) diet and choline-deficient ethionine-supplemented (CDE) diet, respectively. In summary, Ex-4 elicits protective functions against NAFLD and obesity-associated HCC through cAMP-PKA-EGFR-STAT3 signaling, suggesting its administration as a novel approach to reduce HCC risk in diabetic patients.

Incretin-based agents in type 2 diabetic patients at cardiovascular risk: compare the effect of GLP-1 agonists and DPP-4 inhibitors on cardiovascular and pancreatic outcomes

Background

Incretin-based agents, including dipeptidyl peptidase-4 inhibitors (DPP-4Is) and glucagon-like peptide-1 agonists (GLP-1As), work via GLP-1 receptor for hyperglycemic control directly or indirectly, but have different effect on cardiovascular (CV) outcomes. The present study is to evaluate and compare effects of incretin-based agents on CV and pancreatic outcomes in patients with type 2 diabetes mellitus (T2DM) and high CV risk.

Methods

Six prospective randomized controlled trials (EXMAINE, SAVOR-TIMI53, TECOS, ELIXA, LEADER and SUSTAIN-6), which included three trials for DPP-4Is and three trials for GLP-1As, with 55,248 participants were selected to assess the effect of different categories of incretin-based agents on death, CV outcomes (CV mortality, major adverse CV events, nonfatal myocardial infarction, nonfatal stroke, heart failure hospitalization), pancreatic events (acute pancreatitis and pancreatic cancer) as well as on hypoglycemia.

Results

When we evaluated the combined effect of six trials, the results suggested that incretin-based treatment had no significant effect on overall risks of CV and pancreatic outcomes compared with placebo. However, GLP-1As reduced all-cause death (RR = 0.90, 95% CI 0.82–0.98) and CV mortality (RR = 0.84, 95% CI 0.73–0.97), whereas DPP-4Is had no significant effect on CV outcomes but elevated the risk for acute pancreatitis (OR = 1.76, 95% CI 1.14–2.72) and hypoglycemia (both any and severe hypoglycemia), while GLP-1As lowered the risk of severe hypoglycemia.

Conclusions

GLP-1As decreased risks of all-cause and CV mortality and severe hypoglycemia, whereas DPP-4Is had no effect on CV outcomes but increased risks in acute pancreatitis and hypoglycemia.

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-017-0512-z) contains supplementary material, which is available to authorized users.

Occurrence of nausea, vomiting and diarrhoea reported as adverse events in clinical trials studying glucagon-like peptide-1 receptor agonists: A systematic analysis of published clinical trials

AIM

GLP-1 receptor agonists (RAs) may cause nausea, vomiting or diarrhoea. The aim of this study was to assess the risk of adverse events (AEs) with GLP-1 RAs and their relation to dose, background medication and duration of action.

RESEARCH DESIGN AND METHODS

The PubMed database was searched and 32 clinical trials with GLP-1 RAs (phase 3) were selected. We performed a systematic analysis and compared the proportion of patients reporting nausea, vomiting or diarrhoea, for different doses and glucose-lowering background medications, and relative to a reference compound within the subclasses of short- (exenatide b.i.d.) and long-acting (liraglutide) GLP-1 RAs, calculating the relative risks ± 95% confidence intervals.

RESULTS

The risk of nausea was dose-dependent for long-acting (P = .0063) and across all GLP-1 RAs (P = .0017), and a similar trend was observed for vomiting (P = .23). Diarrhoea was dose-dependent (P = .031). Background treatment with metformin was associated with more nausea (P = .04) and vomiting (P = .0009). Compared to exenatide b.i.d., there was less nausea and diarrhoea with lixisenatide. Compared to liraglutide, there was a similar risk associated with dulaglutide, and less with exenatide q.w. and albiglutide. Long-acting GLP-1 RAs were associated with less nausea and vomiting, but with more diarrhoea than short-acting agents.

CONCLUSIONS

GLP-1 RAs are associated with gastrointestinal AEs that are related to dose and background medications (especially metformin) and may vary in a compound-specific manner. Long-acting agents are associated with less nausea and vomiting but with more diarrhoea.

Pharmacotherapy of 'treatment resistant' type 2 diabetes

INTRODUCTION

Despite type 2 diabetes (T2D) management offers a variety of pharmacological interventions targeting different defects, numerous patients remain with persistent hyperglycaemia responsible for severe complications. Unlike resistant hypertension, treatment resistant T2D is not a classical concept although it is a rather common observation in clinical practice. Areas covered: This article proposes a definition for 'treatment resistant diabetes', analyses the causes of poor glucose control despite standard therapy, briefly considers the alternative approaches to glucose-lowering pharmacotherapy and finally describes how to overcome poor glycaemic control, using innovative oral or injectable combination therapies. Expert opinion: Before considering intensifying the pharmacotherapy of a patient with poorly controlled T2D, it is important to verify treatment adherence, target obesity and consider various non pharmacological improvement quality interventions. If treatment resistant diabetes is defined as not achieving glycated haemoglobin target despite oral triple therapy with a third glucose-lowering agent added to metformin-sulfonylurea dual treatment, the combination of a dipeptidyl peptidase-4 (DPP-4) inhibitor and a sodium glucose cotransporter type 2 (SGLT2) inhibitor may offer new opportunities before considering injectable therapies. Insulin basal therapy (± metformin) may be optimized by the addition of a SGLT2 inhibitor or a glucagon-like peptide-1 (GLP-1) receptor agonist.

Resistant maltodextrin or fructooligosaccharides promotes GLP-1 production in male rats fed a high-fat and high-sucrose diet, and partially reduces energy intake and adiposity

PURPOSE

Increasing secretion and production of glucagon-like peptide-1 (GLP-1) by continuous ingestion of certain food components has been expected to prevent glucose intolerance and obesity. In this study, we examined whether a physiological dose (5% weight in diet) of digestion-resistant maltodextrin (RMD) has a GLP-1-promoting effect in rats fed a high-fat and high-sucrose (HFS) diet.

METHODS

Rats were fed a control diet or the HFS (30% fat, 40% sucrose wt/wt) diet supplemented with 5% RMD or fructooligosaccharides (FOS) for 8 weeks or for 8 days in separated experiments. Glucose tolerance, energy intake, plasma and tissue GLP-1 concentrations, and cecal short-chain fatty acids concentrations were assessed.

RESULTS

After 4 weeks of feeding, HFS-fed rats had significantly higher glycemic response to oral glucose than control rats, but rats fed HFS + RMD/FOS did not (approx. 50% reduction vs HFS rats). HFS + RMD/FOS-fed rats had higher GLP-1 responses (~twofold) to oral glucose, than control rats. After 8 weeks, visceral adipose tissue weight was significantly higher in HFS-fed rats than control rats, while HFS + RMD/FOS rats had a trend of reduced gain (~50%) of the tissue weight. GLP-1 contents and luminal propionate concentrations in the large intestine increased (>twofold) by adding RMD/FOS to HFS. Eight days feeding of RMD/FOS-supplemented diets reduced energy intake (~10%) and enhanced cecal GLP-1 production (~twofold), compared to HFS diet.

CONCLUSIONS

The physiological dose of a prebiotic fiber promptly (within 8 days) promotes GLP-1 production in rats fed an obesogenic diet, which would help to prevent excess energy intake and fat accumulation.

Real-world effectiveness and safety of dapagliflozin therapy added to a GLP1 receptor agonist in patients with type 2 diabetes

BACKGROUND AND AIM

To evaluate the effectiveness and safety of a sodium-glucose cotransporter-2 (SGLT-2) inhibitor, dapagliflozin, in patients with type 2 diabetes mellitus (T2DM) and background glucagon-like peptide-1 receptor agonist (GLP1-RA) therapy.

METHODS AND RESULTS

This is a 12-month, real-world observational study, which assessed the effectiveness and safety of dapagliflozin in patients with T2DM and background GLP1-RA therapy. The main outcome measures were changes in A1C and weight at 6 and 12 months from baseline. Secondary outcomes were differences in A1C and weight reduction between this cohort and another group of patients with T2DM treated with dapagliflozin but without background GLP1-RA therapy. In total, 109 patients with GLP1-RA and 104 patients without GLP1-RA were included. Baseline mean A1C and weight in the GLP1-RA and non-GLP1-RA groups were 7.4% vs. 7.3% and 96.2 kg vs. 95.1 kg, respectively. A significant reduction in A1C was seen with dapagliflozin in both cohorts at 6 and 12 months (GLP1-RA: -0.51% and -0.34%, non-GLP1-RA: -0.69% and -0.62%, respectively, p < 0.0001 in all analyses). Weight was significantly reduced in both groups at 6 and 12 months (GLP1-RA: -2.3 kg and -2.4 kg, non-GLP1-RA: -3.9 kg and -4.8 kg, respectively, p < 0.0001 in all analyses). A1C reduction and weight loss were significantly lower in patients with GLP1-RA than in patients without GLP1-RAs. Drug discontinuation rates were similar in both cohorts.

CONCLUSIONS

Dapagliflozin, when added in real life to patients with T2DM treated with GLP1-RAs, induced a further significant, albeit modest improvement in A1C and a further weight loss.

A meta-analysis comparing clinical effects of short- or long-acting GLP-1 receptor agonists versus insulin treatment from head-to-head studies in type 2 diabetic patients

AIMS

To study differences in clinical outcomes between initiating glucagon-like peptide-1 receptor agonist (GLP-1 RAs) vs insulin treatment in patients with type 2 diabetes treated with oral glucose-lowering medications (OGLM).

METHODS

Prospective, randomized trials comparing GLP-1 RA and insulin treatment head-to-head as add-on to OGLM were identified (PubMed). Differences from baseline values were compared for HbA1c, fasting plasma glucose, bodyweight, blood pressure, heartrate and lipoproteins. Proportions of patients reporting hypoglycaemic episodes were compared.

RESULTS

Of 712 publications identified, 23 describing 19 clinical trials were included in the meta-analysis. Compared to insulin, GLP-1 RAs reduced HbA1c more effectively (Δ -.12%, P < .0001). Basal insulin was more effective in reducing fasting plasma glucose (Δ -1.8 mmol/L, P < .0001). GLP-1 RAs reduced bodyweight more effectively (Δ -3.71 kg; P < .0001). The proportion of patients experiencing hypoglycaemic episodes was 34% lower with GLP-1 RAs ( P < .0001), with a similar trend for severe hypoglycaemia. Systolic blood pressure was lower and heartrate was higher with GLP-1 RAs ( P < .0001). Triglycerides and LDL cholesterol were significantly lower with GLP-1 RAs. Long-acting GLP-1 RAs were better than short-acting GLP-1 RAs in reducing HbA1c and fasting glucose, but were similar regarding bodyweight.

CONCLUSIONS

Slightly better glycaemic control can be achieved by adding GLP-1 RAs to OGLM as compared to insulin treatment, with added benefits regarding bodyweight, hypoglycaemia, blood pressure and lipoproteins. These differences are in contrast to the fact that insulin is prescribed far more often than GLP-1 RAs.

Efficacy and safety of switching from sitagliptin to liraglutide in subjects with type 2 diabetes (LIRA-SWITCH): a randomized, double-blind, double-dummy, active-controlled 26-week trial

AIMS

To confirm superiority on glycaemic control by switching from sitagliptin to liraglutide 1.8 mg/d versus continued sitagliptin.

MATERIALS AND METHODS

A randomized, multicentre, double-blind, double-dummy, active-controlled trial across 86 office- or hospital-based sites in North America, Europe and Asia. Subjects with type 2 diabetes who had inadequate glycaemic control (glycated haemoglobin [HbA1c] 7.5-9.5% on sitagliptin (100 mg/d) and metformin (≥1500 mg daily) for ≥90 days were randomized to either switch to liraglutide (n = 203) or continue sitagliptin (n = 204), both with metformin. The primary endpoint was change in HbA1c from baseline to week 26. Change in body weight was a confirmatory secondary endpoint.

RESULTS

Greater reduction in mean HbA1c was achieved with liraglutide than with continued sitagliptin [-1.14% vs. -0.54%; estimated mean treatment difference (ETD): -0.61% (95% CI -0.82 to -0.40; p < 0.0001)], confirming superiority of switching to liraglutide. Body weight was reduced more with liraglutide [-3.31 kg vs. -1.64 kg; ETD: -1.67 kg (95% CI -2.34 to -0.99; p < 0.0001)]. Nausea was more common with liraglutide [44 subjects (21.8%)] than with continued sitagliptin [16 (7.8%)]. Three subjects (1.5%) taking sitagliptin reported a confirmed hypoglycaemic episode.

CONCLUSIONS

Subjects insufficiently controlled with sitagliptin who switch to liraglutide can obtain clinically relevant reductions in glycaemia and body weight, without compromising safety. A switch from sitagliptin to liraglutide provides an option for improved management of type 2 diabetes while still allowing patients to remain on dual therapy.

Anagliptin increases insulin-induced skeletal muscle glucose uptake via an NO-dependent mechanism in mice

AIMS/HYPOTHESIS

Recently, incretin-related agents have been reported to attenuate insulin resistance in animal models, although the underlying mechanisms remain unclear. In this study, we investigated whether anagliptin, the dipeptidyl peptidase 4 (DPP-4) inhibitor, attenuates skeletal muscle insulin resistance through endothelial nitric oxide synthase (eNOS) activation in the endothelial cells. We used endothelium-specific Irs2-knockout (ETIrs2KO) mice, which show skeletal muscle insulin resistance resulting from a reduction of insulin-induced skeletal muscle capillary recruitment as a consequence of impaired eNOS activation.

METHODS

In vivo, 8-week-old male ETIrs2KO mice were fed regular chow with or without 0.3% (wt/wt) DPP-4 inhibitor for 8 weeks to assess capillary recruitment and glucose uptake by the skeletal muscle. In vitro, human coronary arterial endothelial cells (HCAECs) were used to explore the effect of glucagon-like peptide 1 (GLP-1) on eNOS activity.

RESULTS

Treatment with anagliptin ameliorated the impaired insulin-induced increase in capillary blood volume, interstitial insulin concentration and skeletal muscle glucose uptake in ETIrs2KO mice. This improvement in insulin-induced glucose uptake was almost completely abrogated by the GLP-1 receptor (GLP-1R) antagonist exendin-(9-39). Moreover, the increase in capillary blood volume with anagliptin treatment was also completely inhibited by the NOS inhibitor. GLP-1 augmented eNOS phosphorylation in HCAECs, with the effect completely disappearing after exposure to the protein kinase A (PKA) inhibitor H89. These data suggest that anagliptin treatment enhances insulin-induced capillary recruitment and interstitial insulin concentrations, resulting in improved skeletal muscle glucose uptake by directly acting on the endothelial cells via NO- and GLP-1-dependent mechanisms in vivo.

CONCLUSIONS/INTERPRETATION

Anagliptin may be a promising agent to ameliorate skeletal muscle insulin resistance in obese patients with type 2 diabetes.

Feedback suppression of meal-induced glucagon-like peptide-1 (GLP-1) secretion mediated through elevations in intact GLP-1 caused by dipeptidyl peptidase-4 inhibition: a randomized, prospective comparison of sitagliptin and vildagliptin treatment

AIM

To compare directly the clinical effects of vildagliptin and sitagliptin in patients with type 2 diabetes, with a special emphasis on incretin hormones and L-cell feedback inhibition induced by dipeptidyl peptidase (DPP-4) inhibition.

METHODS

A total of 24 patients (12 on a diet/exercise regimen, 12 on metformin) were treated, in randomized order, for 7-9 days, with either vildagliptin (50 mg twice daily = 100 mg/d), sitagliptin (100 mg once daily in those on diet, 50 mg twice daily in those on metformin treatment = 100 mg/d) or placebo (twice daily). A mixed-meal test was performed.

RESULTS

Intact glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide concentrations were doubled by both DPP-4 inhibitors. Meal-related total GLP-1 responses were reduced by vildagliptin and sitagliptin treatment alike in the majority of patients (vildagliptin: p = 0.0005; sitagliptin: p = 0.019), but with substantial inter-individual variation. L-cell feedback appeared to be more pronounced in those whose intact GLP-1 relative to total GLP-1 increased more, and who had greater reductions in fasting plasma glucose after DPP-4 inhibition. K-cell feedback inhibition overall was not significant. There were no differences in any of the clinical variables (glycaemia, insulin and glucagon secretory responses) between vildagliptin and sitagliptin treatment.

CONCLUSIONS

Vildagliptin and sitagliptin affected incretin hormones, glucose concentrations, insulin and glucagon secretion in a similar manner. Inter-individual variations in L-cell feedback inhibition may indicate heterogeneity in the clinical response to DPP-4 inhibition.

Intra-islet glucagon-like peptide 1

PURPOSE

Glucagon-like peptide-1 (GLP-1) is originally identified in the gut as an incretin hormone, and it is potent in stimulating insulin secretion in the pancreas. However, increasing evidence suggests that GLP-1 is also produced locally within pancreatic islets. This review focuses on the past and current discoveries regarding intra-islet GLP-1 production and its functions.

MAIN FINDINGS

There has been a long-standing debate with regard to whether GLP-1 is produced in the pancreatic α cells. Early controversies lead to the widely accepted conclusion that the vast majority of proglucagon is processed to form glucagon in the pancreas, whereas an insignificant amount is cleaved to produce GLP-1. With technological advancements, recent studies have shown that bioactive GLP-1 is produced locally in the pancreas, and the expression and secretion of GLP-1 within islets are regulated by various factors such as cytokines, hyperglycemia, and β cell injury.

CONCLUSIONS

GLP-1 is produced by the pancreatic α cells, and it is fully functional as an incretin. Therefore, intra-islet GLP-1 may exert insulinotropic and glucagonostatic effects locally via paracrine and/or autocrine actions, under both normal and diabetic conditions.

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

AIMS

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Efficacy and safety of liraglutide versus sitagliptin, both in combination with metformin, in Chinese patients with type 2 diabetes: a 26-week, open-label, randomized, active comparator clinical trial

AIMS

To compare the efficacy and safety of liraglutide versus sitagliptin as add-on to metformin after 26 weeks of treatment in Chinese patients with type 2 diabetes mellitus (T2DM).

METHODS

This 26-week open-label, active comparator trial (NCT02008682) randomized patients (aged 18-80 years) with T2DM inadequately controlled with metformin [glycated haemoglobin (HbA1c) 7.0-10.0% (53-86 mmol/mol)] 1 : 1 to once-daily subcutaneously administered liraglutide 1.8 mg (n = 184) or once-daily oral sitagliptin 100 mg (n = 184), both as add-on to metformin. The primary endpoint was change in HbA1c from baseline to week 26.

RESULTS

Liraglutide was superior to sitagliptin in reducing HbA1c from baseline [8.1% (65 mmol/mol)] to 26 weeks, as evidenced by estimated mean HbA1c change of -1.65% (-18.07 mmol/mol) versus -0.98% (-10.72 mmol/mol), respectively [estimated treatment difference for liraglutide vs sitagliptin of -0.67% (95% CI -0.86, -0.48) or -7.35 mmol/mol (95% CI -9.43; -5.26); p < 0.0001]. More patients receiving liraglutide (76.5%) than sitagliptin (52.6%) achieved the HbA1c target of <7.0% (53 mmol/mol) at week 26 [odds ratio 3.65 (95% CI 2.18, 6.12); p < 0.0001]. Reductions in fasting plasma glucose, 7-point self-measured plasma glucose and body weight were greater with liraglutide than with sitagliptin (p < 0.0001 for all). More patients experienced nausea (14.8% vs 0.5%), diarrhoea (8.2% vs 2.2%) and decreased appetite (10.9% vs 0.5%) with liraglutide than sitagliptin. Two hypoglycaemic episodes were confirmed for liraglutide and one for sitagliptin; none were severe or nocturnal.

CONCLUSIONS

Liraglutide provided better glycaemic control and greater body weight reduction than sitagliptin when administered as add-on to metformin. More patients had nausea, diarrhoea and decreased appetite with liraglutide versus sitagliptin.

A review of glycemic efficacy of liraglutide once daily in achieving glycated hemoglobin targets compared with exenatide twice daily, or sitagliptin once daily in the treatment of type 2 diabetes

Incretin-based therapies such as glucagon-like peptide-1 (GLP-1) receptor agonists (RA) and dipeptidyl peptidase-4 (DPP-4) inhibitors have gained prominence in recent years for the treatment of type 2 diabetes (T2D). Such therapies offer the potential to stimulate endogenous insulin activity in proportion to circulating glucose levels; thereby, lowering the risk of hypoglycemic episodes. The synthetic GLP-1 RA exenatide, the human GLP-1 RA liraglutide, and the DPP-4 inhibitor sitagliptin are the first agents in their respective classes to be approved for the treatment of T2D and their efficacy and safety has been studied extensively in clinical trials. This article reviewed the efficacy of liraglutide once daily in achieving clinical guidelines-recommended glycated hemoglobin A1c levels in patients with T2D compared with exenatide twice daily, or sitagliptin once daily, based on published literature, with an aim to elucidate the preferred choice of incretin-related therapy in treating uncontrolled T2D.

Liraglutide and Cardiovascular Outcomes in Type 2 Diabetes

BACKGROUND

The cardiovascular effect of liraglutide, a glucagon-like peptide 1 analogue, when added to standard care in patients with type 2 diabetes, remains unknown.

METHODS

In this double-blind trial, we randomly assigned patients with type 2 diabetes and high cardiovascular risk to receive liraglutide or placebo. The primary composite outcome in the time-to-event analysis was the first occurrence of death from cardiovascular causes, nonfatal myocardial infarction, or nonfatal stroke. The primary hypothesis was that liraglutide would be noninferior to placebo with regard to the primary outcome, with a margin of 1.30 for the upper boundary of the 95% confidence interval of the hazard ratio. No adjustments for multiplicity were performed for the prespecified exploratory outcomes.

RESULTS

A total of 9340 patients underwent randomization. The median follow-up was 3.8 years. The primary outcome occurred in significantly fewer patients in the liraglutide group (608 of 4668 patients [13.0%]) than in the placebo group (694 of 4672 [14.9%]) (hazard ratio, 0.87; 95% confidence interval [CI], 0.78 to 0.97; P<0.001 for noninferiority; P=0.01 for superiority). Fewer patients died from cardiovascular causes in the liraglutide group (219 patients [4.7%]) than in the placebo group (278 [6.0%]) (hazard ratio, 0.78; 95% CI, 0.66 to 0.93; P=0.007). The rate of death from any cause was lower in the liraglutide group (381 patients [8.2%]) than in the placebo group (447 [9.6%]) (hazard ratio, 0.85; 95% CI, 0.74 to 0.97; P=0.02). The rates of nonfatal myocardial infarction, nonfatal stroke, and hospitalization for heart failure were nonsignificantly lower in the liraglutide group than in the placebo group. The most common adverse events leading to the discontinuation of liraglutide were gastrointestinal events. The incidence of pancreatitis was nonsignificantly lower in the liraglutide group than in the placebo group.

CONCLUSIONS

In the time-to-event analysis, the rate of the first occurrence of death from cardiovascular causes, nonfatal myocardial infarction, or nonfatal stroke among patients with type 2 diabetes mellitus was lower with liraglutide than with placebo. (Funded by Novo Nordisk and the National Institutes of Health; LEADER ClinicalTrials.gov number, NCT01179048.).

Endoplasmic reticulum stress and the unfolded protein response in pancreatic islet inflammation

Insulin-secreting pancreatic β-cells are extremely dependent on their endoplasmic reticulum (ER) to cope with the oscillatory requirement of secreted insulin to maintain normoglycemia. Insulin translation and folding rely greatly on the unfolded protein response (UPR), an array of three main signaling pathways designed to maintain ER homeostasis and limit ER stress. However, prolonged or excessive UPR activation triggers alternative molecular pathways that can lead to β-cell dysfunction and apoptosis. An increasing number of studies suggest a role of these pro-apoptotic UPR pathways in the downfall of β-cells observed in diabetic patients. Particularly, the past few years highlighted a cross talk between the UPR and inflammation in the context of both type 1 (T1D) and type 2 diabetes (T2D). In this article, we describe the recent advances in research regarding the interplay between ER stress, the UPR, and inflammation in the context of β-cell apoptosis leading to diabetes.

Liraglutide and Cardiovascular Outcomes in Type 2 Diabetes

BACKGROUND

The cardiovascular effect of liraglutide, a glucagon-like peptide 1 analogue, when added to standard care in patients with type 2 diabetes, remains unknown.

METHODS

In this double-blind trial, we randomly assigned patients with type 2 diabetes and high cardiovascular risk to receive liraglutide or placebo. The primary composite outcome in the time-to-event analysis was the first occurrence of death from cardiovascular causes, nonfatal myocardial infarction, or nonfatal stroke. The primary hypothesis was that liraglutide would be noninferior to placebo with regard to the primary outcome, with a margin of 1.30 for the upper boundary of the 95% confidence interval of the hazard ratio. No adjustments for multiplicity were performed for the prespecified exploratory outcomes.

RESULTS

A total of 9340 patients underwent randomization. The median follow-up was 3.8 years. The primary outcome occurred in significantly fewer patients in the liraglutide group (608 of 4668 patients [13.0%]) than in the placebo group (694 of 4672 [14.9%]) (hazard ratio, 0.87; 95% confidence interval [CI], 0.78 to 0.97; P<0.001 for noninferiority; P=0.01 for superiority). Fewer patients died from cardiovascular causes in the liraglutide group (219 patients [4.7%]) than in the placebo group (278 [6.0%]) (hazard ratio, 0.78; 95% CI, 0.66 to 0.93; P=0.007). The rate of death from any cause was lower in the liraglutide group (381 patients [8.2%]) than in the placebo group (447 [9.6%]) (hazard ratio, 0.85; 95% CI, 0.74 to 0.97; P=0.02). The rates of nonfatal myocardial infarction, nonfatal stroke, and hospitalization for heart failure were nonsignificantly lower in the liraglutide group than in the placebo group. The most common adverse events leading to the discontinuation of liraglutide were gastrointestinal events. The incidence of pancreatitis was nonsignificantly lower in the liraglutide group than in the placebo group.

CONCLUSIONS

In the time-to-event analysis, the rate of the first occurrence of death from cardiovascular causes, nonfatal myocardial infarction, or nonfatal stroke among patients with type 2 diabetes mellitus was lower with liraglutide than with placebo. (Funded by Novo Nordisk and the National Institutes of Health; LEADER ClinicalTrials.gov number, NCT01179048.).

Clinical Effectiveness of Liraglutide vs Sitagliptin on Glycemic Control and Body Weight in Patients with Type 2 Diabetes: A Retrospective Assessment in Sweden

INTRODUCTION

The aim of the present study was to use real-world data from Swedish primary-care and national registries to understand clinical outcomes in patients with Type 2 diabetes (T2D) treated with liraglutide in clinical practice, and to compare with data from those treated with sitagliptin.

METHODS

This was a non-interventional, retrospective study conducted between February 2014 and September 2014 using T2D patient data from Swedish primary-care centers and national healthcare registries. The primary objective was to assess the effectiveness of liraglutide in control of glycemia and body weight in clinical practice (stage 1). The secondary objective was to compare the clinical effectiveness of liraglutide with sitagliptin on glycemic control and body weight in clinical practice in a propensity-score-matched population (stage 2).

RESULTS

In stage 1 (n = 402), 39.4% of patients treated with liraglutide achieved ≥1.0% (10.9 mmol/mol) reduction in glycated hemoglobin (HbA1c) after 180 days of treatment and 54.9% achieved the target HbA1c of <7.0% (53.0 mmol/mol). Moreover, compared with baseline, 22.5% of patients treated with liraglutide achieved both ≥1.0% reduction in HbA1c and ≥3.0% reduction in body weight. In stage 2, a significantly greater proportion of patients receiving liraglutide (n = 180) than sitagliptin (n = 208) achieved ≥1.0% reduction in HbA1c [52.9% vs 33.5%, respectively (P = 0.0002)]. Mean body-weight loss was also significantly greater in patients receiving liraglutide vs sitagliptin [-3.5 vs -1.3 kg, respectively (P < 0.0001)].

CONCLUSION

This study provides real-world evidence from Sweden corroborating previous clinical trials that demonstrate greater efficacy of liraglutide over sitagliptin on glycemic control and body-weight reduction in patients with T2D.

FUNDING

Novo Nordisk A/S.

TRIAL REGISTRATION

ClinicalTrials.gov identifier NCT02077946.

Anti-Inflammatory Effects of GLP-1-Based Therapies beyond Glucose Control

Glucagon-like peptide-1 (GLP-1) is an incretin hormone mainly secreted from intestinal L cells in response to nutrient ingestion. GLP-1 has beneficial effects for glucose homeostasis by stimulating insulin secretion from pancreatic beta-cells, delaying gastric emptying, decreasing plasma glucagon, reducing food intake, and stimulating glucose disposal. Therefore, GLP-1-based therapies such as GLP-1 receptor agonists and inhibitors of dipeptidyl peptidase-4, which is a GLP-1 inactivating enzyme, have been developed for treatment of type 2 diabetes. In addition to glucose-lowering effects, emerging data suggests that GLP-1-based therapies also show anti-inflammatory effects in chronic inflammatory diseases including type 1 and 2 diabetes, atherosclerosis, neurodegenerative disorders, nonalcoholic steatohepatitis, diabetic nephropathy, asthma, and psoriasis. This review outlines the anti-inflammatory actions of GLP-1-based therapies on diseases associated with chronic inflammation in vivo and in vitro, and their molecular mechanisms of anti-inflammatory action.

Growth Hormone-Releasing Hormone in Diabetes

Growth hormone-releasing hormone (GHRH) is produced by the hypothalamus and stimulates growth hormone synthesis and release in the anterior pituitary gland. In addition, GHRH is an important regulator of cellular functions in many cells and organs. Expression of GHRH G-Protein Coupled Receptor (GHRHR) has been demonstrated in different peripheral tissues and cell types, including pancreatic islets. Among the peripheral activities, recent studies demonstrate a novel ability of GHRH analogs to increase and preserve insulin secretion by beta-cells in isolated pancreatic islets, which makes them potentially useful for diabetes treatment. This review considers the role of GHRHR in the beta-cell and addresses the unique engineered GHRH agonists and antagonists for treatment of type 2 diabetes mellitus. We discuss the similarity of signaling pathways activated by GHRHR in pituitary somatotrophs and in pancreatic beta-cells and possible ways as to how the GHRHR pathway can interact with glucose and other secretagogues to stimulate insulin secretion. We also consider the hypothesis that novel GHRHR agonists can improve glucose metabolism in Type 2 diabetes by preserving the function and survival of pancreatic beta-cells. Wound healing and cardioprotective action with new GHRH agonists suggest that they may prove useful in ameliorating certain diabetic complications. These findings highlight the future potential therapeutic effectiveness of modulators of GHRHR activity for the development of new therapeutic approaches in diabetes and its complications.