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

Saxagliptin add-on therapy in Chinese patients with type 2 diabetes inadequately controlled by insulin with or without metformin: Results from the SUPER study, a randomized, double-blind, placebo-controlled trial

This prospective, multicentre, phase III study (NCT02104804) evaluated the efficacy and safety of saxagliptin add-on therapy in Chinese patients with type 2 diabetes inadequately controlled by insulin ± metformin. Patients with glycated haemoglobin (HbA1c) 7.5% to 10.5% and fasting plasma glucose (FPG) <15 mmol/L (270 mg/dL) on stable insulin therapy (20-150 U/d) were randomized (1:1) to saxagliptin 5 mg once daily (N = 232) or placebo (N = 230) for 24 weeks, stratified by metformin use. The primary efficacy measure was change in HbA1c. Saxagliptin treatment resulted in a greater adjusted mean change in HbA1c from baseline to week 24 than placebo (-0.58%; P < .001), irrespective of metformin use, and a greater mean change in FPG (0.9 mmol/L [-15.9 mg/dL]; P < .001). More patients achieved HbA1c <7% with saxagliptin (11.4%) than with placebo (3.5%, P = .002). Adverse events and incidence of hypoglycaemia were similar in both groups. Overall, add-on saxagliptin 5 mg once daily significantly improved glycaemic control without increasing hypoglycaemia risk and was well tolerated in Chinese patients with type 2 diabetes inadequately controlled by insulin (± metformin).

Glucagon-like Peptide-1 Receptor Agonists and Cardiovascular Events: Class Effects versus Individual Patterns

Several new glucose-lowering medications have been approved, such as dipeptidyl peptidase-4 inhibitors, glucagon-like peptide-1 receptor agonists (GLP-1RAs), and sodium glucose cotransporter-2 inhibitors. Among GLP-1RAs, lixisenatide, a short-acting drug, did not show cardiovascular (CV) benefits in patients with Type 2 diabetes mellitus (T2D) and acute coronary syndrome. Extended-release exenatide was also not significantly better for CV outcomes. By contrast, once daily liraglutide and once weekly semaglutide, both long-acting GLP-1RAs, decreased the incidence of major adverse CV events and mortality. This Review attempts to explain favorable CV results with some, but not all, GLP-1RAs, to aid in their differential prescription with the aim of further reducing the adverse CV burden of T2D.

Targeting incretin hormones and the ASK-1 pathway as therapeutic options in the treatment of non-alcoholic steatohepatitis

Non-alcoholic fatty liver disease (NAFLD) is currently one of the leading forms of chronic liver disease, and its rising frequency worldwide has reached epidemic proportions. NAFLD, particularly its progressive variant NASH (non-alcoholic steatohepatitis), can lead to advanced fibrosis, cirrhosis, and HCC. The pathophysiologic mechanisms that contribute to the development and progression of NAFLD and NASH are complex, and as such myriad therapies are under investigation targeting different pathophysiological mechanisms. Incretin-based therapies, including GLP-1RAs and DPP-4 inhibitors and the inhibition of ASK1 pathway have provided two such novel mechanisms in the management of this disease, and will remain focus of this review.

Diabetes Drugs and Cardiovascular Event Reduction: A Paradigm Shift

This review article summarizes the recent cardiovascular outcome data for sodium–glucose cotransporter-2 inhibitors and glucagon-like peptide-1 analogues, which have been found to reduce cardiovascular events. We also detail the implications these new medications will have on clinical practice through a review of recent diabetes guidelines and cost-effectiveness data.

The safety of gliptins : updated data in 2018

INTRODUCTION

Dipeptidyl peptidase-4 inhibitors (DPP-4is) are generally considered as glucose-lowering agents with a safe profile in type 2 diabetes.

AREAS COVERED

An updated review of recent safety data from randomised controlled trials, observational studies, meta-analyses, pharmacovigilance reports regarding alogliptin, linagliptin, saxagliptin, sitagliptin, and vildagliptin, with a special focus on risks of hypoglycemia, pancreatitis and pancreatic cancer, major cardiovascular events, hospitalisation for heart failure and other new safety issues, such as bone fractures and arthralgia. The safety of DPP-4i use in special populations, elderly patients, patients with renal impairment, liver disease or heart failure, will also be discussed.

EXPERT OPINION

The good tolerance/safety profile of DPP-4is has been largely confirmed, including in more fragile populations, with no gastrointestinal adverse effects and a minimal risk of hypoglycemia. DPP-4is appear to be associated with a small increased incidence of acute pancreatitis in placebo-controlled trials, although most observational studies are reassuring. Most recent studies with DPP-4is do not confirm the increased risk of hospitalisation for heart failure reported with saxagliptin in SAVOR-TIMI 53, but further post-marketing surveillance is still recommended. New adverse events have been reported such as arthralgia, yet a causal relationship remains unclear.

Development and characterisation of a novel glucagon like peptide-1 receptor antibody

AIMS/HYPOTHESIS

Glucagon like peptide-1 (GLP-1) enhances glucose-dependent insulin secretion by binding to GLP-1 receptors (GLP1Rs) on pancreatic beta cells. GLP-1 mimetics are used in the clinic for the treatment of type 2 diabetes, but despite their therapeutic success, several clinical effects of GLP-1 remain unexplained at a mechanistic level, particularly in extrapancreatic tissues. The aim of this study was to generate and characterise a monoclonal antagonistic antibody for the GLP1R for use in vivo.

METHODS

A naive phage display selection strategy was used to isolate single-chain variable fragments (ScFvs) that bound to GLP1R. The ScFv with the highest affinity, Glp1R0017, was converted into a human IgG1 and characterised further. In vitro antagonistic activity was assessed in a number of assays: a cAMP-based homogenous time-resolved fluorescence assay in GLP1R-overexpressing cell lines, a live cell cAMP imaging assay and an insulin secretion assay in INS-1 832/3 cells. Glp1R0017 was further tested in immunostaining of mouse pancreas, and the ability of Glp1R0017 to block GLP1R in vivo was assessed by both IPGTT and OGTT in C57/Bl6 mice.

RESULTS

Antibodies to GLP1R were selected from naive antibody phage display libraries. The monoclonal antibody Glp1R0017 antagonised mouse, human, rat, cynomolgus monkey and dog GLP1R. This antagonistic activity was specific to GLP1R; no antagonistic activity was found in cells overexpressing the glucose-dependent insulinotropic peptide receptor (GIPR), glucagon like peptide-2 receptor or glucagon receptor. GLP-1-stimulated cAMP and insulin secretion was attenuated in INS-1 832/3 cells by Glp1R0017 incubation. Immunostaining of mouse pancreas tissue with Glp1R0017 showed specific staining in the islets of Langerhans, which was absent in Glp1r knockout tissue. In vivo, Glp1R0017 reversed the glucose-lowering effect of liraglutide during IPGTTs, and reduced glucose tolerance by blocking endogenous GLP-1 action in OGTTs.

CONCLUSIONS/INTERPRETATION

Glp1R0017 is a monoclonal antagonistic antibody to the GLP1R that binds to GLP1R on pancreatic beta cells and blocks the actions of GLP-1 in vivo. This antibody holds the potential to be used in investigating the physiological importance of GLP1R signalling in extrapancreatic tissues where cellular targets and signalling pathways activated by GLP-1 are poorly understood.

Real-world clinical outcomes and predictors of glycaemic and weight response to exenatide once weekly in patients with type 2 diabetes: The CIBELES project

AIMS

To evaluate in a real-world setting the effectiveness of exenatide once-weekly (ExQW) in patients with T2D and to determine predictors of glycaemic and weight response to this drug at 6 months.

METHODS

Observational, retrospective, multicenter study in adult patients with T2D and BMI ≥30 kg/m² from 4 tertiary Spanish hospitals who started ExQW therapy at least 6 months before the inclusion and had not achieved adequate glycaemic control on oral therapies or other GLP-1 receptor agonists. Glycaemic response was defined as an A1C reduction ≥1.0% and weight response as a weight loss ≥3% 6 months after ExQW. The best predictive models of glycaemic and weight response were estimated by binary logistic regression.

RESULTS

One hundred and forty eight patients were included, mean age 58.0 years, A1C 7.7%, weight 105.9 kg and BMI 38.4 kg/m² . A1C (-1.1%), weight (-3.9 kg), systolic blood pressure (-4.0 mm Hg), diastolic blood pressure (-2.9 mm Hg), LDL-cholesterol (-14.2 mg/dL) and triglycerides (-31.0 mg/dL) significantly decreased 6 months after ExQW. 41.5% of patients had an A1C reduction ≥1.0% and 53.1% lost ≥3% of baseline weight. Glycaemic and weight reductions were sustained in patients completing 1 and 2 years of follow-up. The best predictive model of glycaemic response only included higher A1C levels (OR 3.9), whereas higher BMI (OR 1.1) and prior DPP-4i therapy (OR 3.1) were associated to weight response in the multivariate analysis.

CONCLUSIONS

In a real-world setting, ExQW significantly decreased A1C, weight, blood pressure and lipids at 6 months. Our study identified higher baseline A1C as the sole independent predictor of glycaemic response to ExQW and higher BMI and previous DDP4i treatment as predictive factors of meaningful weight response.

Clinical Impact of ITCA 650, a Novel Drug-Device GLP-1 Receptor Agonist, in Uncontrolled Type 2 Diabetes and Very High Baseline HbA1c: The FREEDOM-1 HBL (High Baseline) Study

OBJECTIVE

ITCA 650 is a subdermal osmotic mini-pump that continuously delivers exenatide subcutaneously for 3-6 months. The efficacy, safety, and tolerability of ITCA 650 added to diet and exercise alone or combined with metformin, sulfonylurea, or thiazolidinedione monotherapy or a combination of these drugs was evaluated in poorly controlled patients with type 2 diabetes (T2D) who were ineligible for participation in a placebo-controlled study (FREEDOM-1) because of severe hyperglycemia (HbA_1c >10% [86 mmol/mol]).

RESEARCH DESIGN AND METHODS

This 39-week, open-label, phase 3 trial enrolled patients aged 18-80 years with HbA_1c >10% to ≤12% (86-108 mmol/mol) and BMI 25-45 kg/m². Patients received ITCA 650 20 μg/day for 13 weeks, then 60 μg/day for 26 weeks. The primary end point was change in HbA_1c at week 39.

RESULTS

Sixty patients were enrolled. At baseline, mean HbA_1c was 10.8% (94.7 mmol/mol) and mean (± SD) duration of diabetes was 8.6 (± 5.3) years. At week 39, there was a mean reduction in HbA_1c of -2.8% (-30.3 mmol/mol; P < 0.001 vs. baseline) and in body weight of -1.2 kg (P = 0.105), and 25% of patients achieved HbA_1c <7% (53 mmol/mol). A reduction in HbA_1c of ≥1% (≥10.9 mmol/mol) occurred in 90% of patients. The most common adverse events were nausea, vomiting, diarrhea, and headache. Gastrointestinal adverse events were generally transient and subsided over time; only 4 patients (6.7%) discontinued for gastrointestinal events.

CONCLUSIONS

Treatment with ITCA 650, the first injection-free glucagon-like peptide 1 receptor agonist, resulted in significant improvements in glycemic control in poorly controlled long-standing T2D patients with a high baseline HbA_1c >10%.

Tissue expression of DPP-IV in obesity-diabetes and modulatory effects on peptide regulation of insulin secretion

Dipeptidyl peptidase type 4 (DPP-4) inhibitors represent an important class of glucose-lowering drug for type 2 diabetes. DPP-4 enzyme activity has been observed to be significantly altered in type 2 diabetes. Here, the role of DPP-4 was examined in a high fat fed (HFF) mouse model of insulin resistance. HFF mice had an increased bodyweight (p < .01), were hyperglycaemic (p < .01) and hyperinsulinaemic (p < .05). Compared to normal diet, HFF mice exhibited increased plasma DPP-4 activity (p < .01). Tissue distribution patterns in lean and HFF mice demonstrated highest levels of DPP-4 activity in lung (20-26 μmol/min/mg protein) and small intestine (13-14 μmol/min/mg protein), and lowest activity in the spleen (3.8 μmol/min/mg protein). Modulation of DPP-4 activity by high fat feeding was observed in several tissues with increases in the lung (p < .05), liver (p < .05), kidney (p < .05) and pancreas (p < .05). With a high fat diet, DPP-4 gene expression was upregulated in the liver (p < .001) and downregulated in the pancreas (p < 0.001) and small intestine (p < .001). Immunohistochemical analysis revealed increased DPP-4 immunostaining localised primarily in the pancreatic islets of HFF mice (p < .01) with no change in islet GLP-1 expression. Treatment of HFF mice with metformin for 21-days resulted in inhibition of circulating DPP-4 activity (p < .05), decreased blood glucose (p < .05) and increased GLP-1 gene expression (p < .001). These data indicate that DPP-4 is modulated in a tissue specific manner and is dependent on physiological conditions such as hyperglycaemia and insulin resistance, suggesting a significant role in disorders such as diabetes.

Efficacy of glucagon-like peptide-1 receptor agonists compared to dipeptidyl peptidase-4 inhibitors for the management of type 2 diabetes: A meta-analysis of randomized clinical trials

AIMS

Glucagon-like peptide-1 (GLP-1) agonists and dipeptidyl peptidase-4 (DPP-4) inhibitors are both incretin-based therapies for type 2 diabetes (T2DM) but have distinct efficacy and side effect profiles. We thus performed a systematic review and meta-analysis to compare the effects of GLP-1 agonists to DPP-4 inhibitors on glycaemic control, weight and incidence of adverse events in adults with T2DM. We also sought to determine whether there was any additional effect in switching from DPP-4 inhibitor to GLP-1 agonist.

MATERIALS AND METHODS

We systematically searched PubMed, Embase and ClinicalTrials.gov for (1) randomized controlled trials (RCTs) comparing any GLP-1 agonist to any DPP-4 inhibitor and (2) interventional studies where a DPP-4 inhibitor was switched to a GLP-1 agonist. We assessed pooled data using random-effects model (CRD42017057115).

RESULTS

The pooled analysis of 13 RCTs (n = 4330) showed that, compared to DPP-4 inhibitors, GLP-1 agonists yielded a greater mean reduction in glycated haemoglobin (HbA1c) of -0.41% (95% CI -0.53 to -0.30) and in weight of -2.15 kg (-3.04 to -1.27). GLP-1 agonists were associated with greater likelihood of gastrointestinal side effects with no increased risk of hypoglycaemia. In 5 interventional studies (n = 433), switching from DPP-4 inhibitor to GLP-1 agonist yielded further mean reduction in HbA1c of -0.69% (-1.03 to -0.35) and in weight of -2.25 kg (-3.12 to -1.38).

CONCLUSIONS

GLP-1 agonists yield greater reduction in HbA1c and weight as compared to DPP-4 inhibitors, with increased incidence of gastrointestinal symptoms but not hypoglycaemia. Replacing a DPP-4 inhibitor with GLP-1 agonist provides additional benefits in glycaemic control and weight loss.

Incretin hormones: Their role in health and disease

Incretin hormones are gut peptides that are secreted after nutrient intake and stimulate insulin secretion together with hyperglycaemia. GIP (glucose-dependent insulinotropic polypeptide) und GLP-1 (glucagon-like peptide-1) are the known incretin hormones from the upper (GIP, K cells) and lower (GLP-1, L cells) gut. Together, they are responsible for the incretin effect: a two- to three-fold higher insulin secretory response to oral as compared to intravenous glucose administration. In subjects with type 2 diabetes, this incretin effect is diminished or no longer present. This is the consequence of a substantially reduced effectiveness of GIP on the diabetic endocrine pancreas, and of the negligible physiological role of GLP-1 in mediating the incretin effect even in healthy subjects. However, the insulinotropic and glucagonostatic effects of GLP-1 are preserved in subjects with type 2 diabetes to the degree that pharmacological stimulation of GLP-1 receptors significantly reduces plasma glucose and improves glycaemic control. Thus, it has become a parent compound of incretin-based glucose-lowering medications (GLP-1 receptor agonists and inhibitors of dipeptidyl peptidase-4 or DPP-4). GLP-1, in addition, has multiple effects on various organ systems. Most relevant are a reduction in appetite and food intake, leading to weight loss in the long term. Since GLP-1 secretion from the gut seems to be impaired in obese subjects, this may even indicate a role in the pathophysiology of obesity. Along these lines, an increased secretion of GLP-1 induced by delivering nutrients to lower parts of the small intestines (rich in L cells) may be one factor (among others like peptide YY) explaining weight loss and improvements in glycaemic control after bariatric surgery (e.g., Roux-en-Y gastric bypass). GIP and GLP-1, originally characterized as incretin hormones, have additional effects in adipose cells, bone, and the cardiovascular system. Especially, the latter have received attention based on recent findings that GLP-1 receptor agonists such as liraglutide reduce cardiovascular events and prolong life in high-risk patients with type 2 diabetes. Thus, incretin hormones have an important role physiologically, namely they are involved in the pathophysiology of obesity and type 2 diabetes, and they have therapeutic potential that can be traced to well-characterized physiological effects.

Efficacy and Safety of ITCA 650, a Novel Drug-Device GLP-1 Receptor Agonist, in Type 2 Diabetes Uncontrolled With Oral Antidiabetes Drugs: The FREEDOM-1 Trial

OBJECTIVE

ITCA 650 (exenatide in osmotic mini-pump) continuously delivers exenatide subcutaneously for 3-6 months. Two doses of ITCA 650 were compared with placebo in patients with uncontrolled type 2 diabetes.

RESEARCH DESIGN AND METHODS

This 39-week, phase 3, double-blind, placebo-controlled trial randomized 460 patients aged 18-80 years with glycated hemoglobin (HbA_1c) 7.5-10% [58-86 mmol/mol] 1:1:1 to placebo, ITCA 650 40 μg/day, or ITCA 650 60 μg/day. Primary end point was change in HbA_1c at 39 weeks.

RESULTS

Least squares (LS) mean change from baseline HbA_1c was -1.1% [-12.2 mmol/mol] and -1.2% [-13.2 mmol/mol] for ITCA 650 40 and 60 μg/day, respectively (P < 0.001 vs. placebo -0.1% [-1.3 mmol/mol]). In a prespecified analysis, greater HbA_1c reductions occurred in patients not receiving sulfonylureas (SUs) versus those receiving SUs (-1.7% vs. -1.2% [-18.6 and -13.1 mmol/mol]). At week 39, HbA_1c <7% [53 mmol/mol] was attained in 37%, 44%, and 9% of ITCA 650 40 μg/day, ITCA 650 60 μg/day, and placebo groups, respectively (P < 0.001 each dose vs. placebo). LS mean change from baseline body weight was -2.3 kg and -3.0 kg for ITCA 650 40 and 60 μg/day, respectively (P ≤ 0.015 vs. placebo -1.0 kg). Nausea was the most common adverse event (AE) and subsided over time. Discontinuation for gastrointestinal AEs occurred in 7.2% with ITCA and 1.3% with placebo. Most AEs associated with procedures to place and remove ITCA 650 were mild and transient.

CONCLUSIONS

ITCA 650 significantly reduced HbA_1c and weight compared with placebo and was well tolerated in patients with uncontrolled type 2 diabetes on oral antidiabetes medications.

A review of GLP-1 receptor agonists: Evolution and advancement, through the lens of randomised controlled trials

AIMS

To review the evolution and advancement of GLP-1 receptor agonist (GLP-1RA) therapy, through the lens of randomised controlled trials, from differentiating characteristics, efficacy, safety, tolerability, and cardiovascular outcomes, to evidence gaps and next steps.

METHODS

Clinical review of published phase 3 or later RCT data studying efficacy, safety, and outcomes of approved GLP-1 RA therapies.

RESULTS

Through a wealth of studies, including both placebo-controlled and active-controlled studies, GLP-1 RAs have demonstrated high glycemic efficacy and ability to facilitate weight loss, with minimal risk of hypoglycemia, potential to restore beta cell function, and evidence for improved cardiovascular outcomes in those at risk.

CONCLUSIONS

Over a decade of clinical studies have established the unique contributions of GLP-1 RAs in the treatment of diabetes. Individual differences between the different GLP-1 RAs, in delivery, pharmacokinetic and clinical effects, exist, allowing for tailored approaches to clinical care. The strength of evidence generated through RCTs, both short-term and long-term studies, will continue to evolve and inform our current paradigms in diabetes care.

Cardiovascular outcomes with glucagon-like peptide-1 receptor agonists in patients with type 2 diabetes: a meta-analysis

BACKGROUND

Glucagon-like peptide-1 (GLP-1) receptor agonists are effective glucose-lowering drugs. Findings from cardiovascular outcome trials showed cardiovascular safety of GLP-1 receptor agonists, but results for cardiovascular efficacy were varied. We aimed to examine overall cardiovascular efficacy for lixisenatide, liraglutide, semaglutide, and extended-release exenatide.

METHODS

In this systematic review and meta-analysis, we analysed data from eligible trials that assessed the safety and efficacy of GLP-1 receptor agonists compared with placebo in adult patients (aged 18 years or older) with type 2 diabetes and had a primary outcome including, but not limited to, cardiovascular mortality, non-fatal myocardial infarction, and non-fatal stroke. We searched PubMed and MEDLINE without language restrictions up to Sept 18, 2017, for eligible trials. We did a meta-analysis of available trial data using a random-effects model to calculate overall hazard ratios (HRs) for cardiovascular efficacy outcomes and odds ratios for key safety outcomes.

FINDINGS

Of 12 articles identified in our search and screened for eligibility, four trials of cardiovascular outcomes of GLP-1 receptor agonists were identified: ELIXA (lixisenatide), LEADER (liraglutide), SUSTAIN 6 (semaglutide), and EXSCEL (extended-release exenatide). Compared with placebo, GLP-1 receptor agonist treatment showed a significant 10% relative risk reduction in the three-point major adverse cardiovascular event primary outcome (cardiovascular mortality, non-fatal myocardial infarction, and non-fatal stroke; HR 0·90, 95% CI 0·82-0·99; p=0·033), a 13% RRR in cardiovascular mortality (0·87, 0·79-0·96; p=0·007), and a 12% relative risk reduction in all-cause mortality (0·88, 0·81-0·95; p=0·002), with low-to-moderate between-trial statistical heterogeneity. No significant effect of GLP-1 receptor agonists was identified on fatal and non-fatal myocardial infarction, fatal and non-fatal stroke, hospital admission for unstable angina, or hospital admission for heart failure. Overall, no significant differences were seen in severe hypoglycaemia, pancreatitis, pancreatic cancer, or medullary thyroid cancer reported between GLP-1 receptor agonist treatment and placebo.

INTERPRETATION

Our findings show cardiovascular safety across all GLP-1 receptor agonist cardiovascular outcome trials and suggest that drugs in this class can reduce three-point major adverse cardiovascular events, cardiovascular mortality, and all-cause mortality risk, albeit to varying degrees for individual drugs, without significant safety concerns. GLP-1 receptor agonists have a favourable risk-benefit balance overall, which should allow the choice of drug to be individualised to each patient's needs.

FUNDING

Amylin Pharmaceuticals (AstraZeneca).

Efficacy and safety of teneligliptin added to canagliflozin monotherapy in Japanese patients with type 2 diabetes mellitus: A multicentre, randomized, double-blind, placebo-controlled, parallel-group comparative study

Dipeptidyl peptidase-4 (DPP-4) inhibitors and sodium glucose co-transporter 2 (SGLT2) inhibitors are frequently used in combination for the treatment of type 2 diabetes mellitus (T2DM). We examined the efficacy and safety of teneligliptin (a DPP-4 inhibitor) added to canagliflozin (an SGLT2 inhibitor) monotherapy in Japanese patients with poorly controlled T2DM as part of the development of a fixed-dose combination of teneligliptin and canagliflozin. Japanese patients treated with canagliflozin (100 mg) for ≥12 weeks were randomized to receive add-on teneligliptin (20 mg; C + T group) or placebo (C + P group) for 24 weeks. The primary endpoint was change in glycated haemoglobin (HbA1c) from baseline to Week 24. The between-group differences in reductions from baseline to Week 24 were significantly greater in the C + T group for HbA1c (-0.94%; P < .001). The incidence of adverse events was similar in both groups (55.8% and 49.4% in the C + T and C + P groups, respectively). No episodes of hypoglycaemia were reported. Teneligliptin added to ongoing canagliflozin monotherapy improved glycaemic control and was well tolerated in Japanese patients with inadequately controlled T2DM.

The Role of Glucagon in the Pathophysiology and Treatment of Type 2 Diabetes

Type 2 diabetes is a disease involving both inadequate insulin levels and increased glucagon levels. While glucagon and insulin work together to achieve optimal plasma glucose concentrations in healthy individuals, the usual regulatory balance between these 2 critical pancreatic hormones is awry in patients with diabetes. Although clinical discussion often focuses on the role of insulin, glucagon is equally important in understanding type 2 diabetes. Furthermore, an awareness of the role of glucagon is essential to appreciate differences in the mechanisms of action of various classes of glucose-lowering therapies. Newer drug classes such as dipeptidyl peptidase-4 inhibitors and glucagon-like peptide-1 receptor agonists improve glycemic control, in part, by affecting glucagon levels. This review provides an overview of the effect of glucose-lowering therapies on glucagon on the basis of an extensive PubMed literature search to identify clinical studies of glucose-lowering therapies in type 2 diabetes that included assessment of glucagon. Clinical practice currently benefits from available therapies that impact the glucagon regulatory pathway. As clinicians look to the future, improved treatment strategies are likely to emerge that will either use currently available therapies whose mechanisms of action complement each other or take advantage of new therapies based on an improved understanding of glucagon pathophysiology.

Dipeptidyl peptidase inhibitor therapy in type 2 diabetes: Control of the incretin axis and regulation of postprandial glucose and lipid metabolism

Dipeptidyl peptidase 4 (DPP4) is a widely expressed, serine protease which regulates the bioactivity of many peptides through cleavage and inactivation including the incretin hormones, glucagon like peptide -1 (GLP-1) and glucose dependent insulinotropic polypeptide (GIP). Inhibitors of DPP4 are used therapeutically to treat patients with Type 2 Diabetes Mellitus (T2DM) as they potentiate incretin action to regulate islet hormone secretion and improve glycemia and post-prandial lipid excursions. The widespread clinical use of DPP4 inhibitors has increased interest in the molecular mechanisms by which these drugs mediate their beneficial effects. Traditionally, focus has remained on inhibiting the catalytic activity of DPP4 within the plasma compartment, however evidence is emerging on the importance of inactivation of membrane-bound DPP4 in selective tissue beds to potentiate local hormone gradients. Here we review the recent advances in identifying the cellular sources of both circulating and membrane-bound DPP4 important for cleavage of the incretin hormones and regulation of glucose and lipoprotein metabolism.

The cardiovascular effect of incretin-based therapies among type 2 diabetes: a systematic review and network meta-analysis

OBJECTIVE

To evaluate the comparative cardiovascular safety of incretin-based therapies in patients with type 2 diabetes mellitus (T2DM).

METHODS

Medline, Embase, the Cochrane Library and www.clinicaltrials.gov were searched for randomized controlled trials (RCTs) with duration≥12 weeks. Network meta-analysis was performed, followed by subgroup analysis and meta-regression. The Grading of Recommendations Assessment, Development and Evaluation system was used to assess the quality of evidence. The outcome of interest was a composite of cardiovascular death, myocardial infarction, stroke and heart failure. Odds ratio (OR) with 95% confidence interval (CI) was calculated as the measure of effect size.

RESULTS

281 RCTs (76.9% double-blinded) with 180,000 patients were included, comparing incretin-based therapies with other six classes of anti-diabetic drugs or placebo. A statistically significant reduction in the risk of cardiovascular events was found in favour of GLP-1RAs when compared with placebo (OR 0.89, 95%CI: 0.80-0.99) and sulfonylurea (OR 0.76, 95%CI: 0.59-0.99), whereas DPP-4 inhibitors showed a neutral effect compared with placebo (OR 0.92, 95%CI: 0.83-1.01).

CONCLUSIONS

Incretin-based therapies show similar cardiovascular risk in comparison with metformin, insulin, thiazolidinediones, alpha-glucosidase inhibitor and sodium-glucose co-transporter 2. GLP-1RA could decrease the risk compared with sulfonylurea or placebo, while DPP-4I appears to have neutral effect on cardiovascular risk.

Have dipeptidyl peptidase-4 inhibitors ameliorated the vascular complications of type 2 diabetes in large-scale trials? The potential confounding effect of stem-cell chemokines

Drugs that inhibit dipeptidyl peptidase-4 (DPP-4) are conventionally regarded as incretin-based agents that signal through the glucagon-like peptide-1 (GLP-1) receptor. However, inhibition of DPP-4 also potentiates the stem cell chemokine, stromal cell-derived factor-1 (SDF-1), which can promote inflammation, proliferative responses and neovascularization. In large-scale cardiovascular outcome trials, enhanced GLP-1 signaling has reduced the risk of atherosclerotic ischemic events, potentially because GLP-1 retards the growth and increases the stability of atherosclerotic plaques. However, DPP-4 inhibitors have not reduced the risk of major adverse cardiovascular events, possibly because potentiation of SDF-1 enhances plaque growth and instability, activates deleterious neurohormonal mechanisms, and promotes cardiac inflammation and fibrosis. Similarly, trials with GLP-1 agonists and sodium-glucose cotransporter 2 inhibitors have reported favorable effects on renal function, even after only 3-4 years of treatment. In contrast, no benefits on the rate of decline in glomerular filtration rate have been seen in trials of DPP-4 inhibitors, perhaps because the renal actions of DPP-4 inhibitors are primarily mediated by potentiation of SDF-1, not GLP-1. Experimentally, SDF-1 can promote podocyte injury and glomerulosclerosis. Furthermore, the natriuretic action of SDF-1 occurs primarily in the distal tubules, where it cannot utilize tubuloglomerular feedback to modulate the deleterious effects of glomerular hyperfiltration. Potentiation of SDF-1 in experimental models may also exacerbate both retinopathy and neuropathy. Therefore, although DPP-4 inhibitors have attractive clinical features, the benefits that might be expected from GLP-1 signaling may be undermined by their actions to enhance SDF-1.

Glycaemic outcomes of an Individualized treatMent aPproach for oldER vulnerable patIents: A randomized, controlled stUdy in type 2 diabetes Mellitus (IMPERIUM)

AIMS

To compare the glycaemic outcomes of 2 glucose-lowering treatment strategies in vulnerable (moderately ill and/or frail) patients aged ≥65 years with type 2 diabetes whose individual HbA1c targets were not met with diet/exercise and/or oral anti-hyperglycaemic medications (OAMs).

METHODS

The primary endpoint of this study was a composite of achieving/maintaining individualized HbA1c targets without "clinically significant" hypoglycaemia (severe hypoglycaemia or repeated hypoglycaemia causing interruption of patients' activities or blood glucose <54 mg/dL). Strategy-A comprised glucose-dependent therapies (n = 99) with a non-sulphonylurea OAM and a glucagon-like peptide-1 receptor agonist as the first injectable. Strategy-B comprised non-glucose-dependent therapies (n = 93) with sulphonylurea as the preferred OAM and insulin glargine as the first injectable.

RESULTS

There was no significant difference between Strategy-A and Strategy-B in percentages of patients achieving the primary endpoint (64.5% vs 54.9%; P = .190). Mean incidences (A vs B) of total (10.2% vs 53.8%), documented symptomatic (5.1% vs 36.6%), and asymptomatic (8.2% vs 32.3%) hypoglycaemia were lower for Strategy-A (P < .001 each). Proportions of patients achieving/maintaining HbA1c target (A, 63.3% vs B, 55.9%) were similar.

CONCLUSION

Similar proportions of older, vulnerable aged ≥65 years patients with type 2 diabetes achieved/maintained glycaemic treatment goals without clinically significant hypoglycaemia with Strategies A or B. However, Strategy-A resulted in lower risk of total, documented symptomatic, and asymptomatic hypoglycaemia. These results identify an approach of potential clinical benefit in this age group and will inform future clinical research in older patients with type 2 diabetes.

Pharmacokinetic drug evaluation of exenatide for the treatment of type 2 diabetes

INTRODUCTION

Glucagon-like peptide-1 (GLP-1) receptor analogs are a group of therapeutic agents which mimic endogenous GLP-1, exerting their effect by the stimulation of the GLP-1 receptor with a wide distribution. Its activation increases insulin releasing dependent on blood glucose levels, suppression of glucagon secretion and a reduction of hepatic glucose output. It delays gastric emptying and increases satiety. Exenatide is the synthetic version of exendin-4, a natural peptide with similar properties to human GLP-1. There are two pharmaceutical forms, for subcutaneous injection: twice daily and once weekly. Clinical practice guidelines recommend them because of a high efficacy reducing hyperglycemia, low risk of hypoglycemia and a significative weight loss effect. Gastrointestinal adverse events are the most common beside injection site-related. Their cost is the main limitation to use. Areas covered: We review the recent literature investigating the pharmacokinetics and pharmacodynamics and efficacy-safety studies of exenatide twice daily and once weekly in type 2 diabetes Expert opinion: GLP-1 receptor analogs are now positioned as an effective and safe drug for the treatment of type 2 diabetes. Exenatide significally reduces HbA1c and fasting plasma glucose. Additionally, it produces moderate weight loss and decreases blood pressure. One weekly formulation may improve compliance while cost is still a limitation. EXSCEL trial has shown that, despite cardiovascular safety, exenatide do not exhibits cardiovascular benefits.

The acute glucose lowering effect of specific GPR120 activation in mice is mainly driven by glucagon-like peptide 1

The mechanism behind the glucose lowering effect occurring after specific activation of GPR120 is not completely understood. In this study, a potent and selective GPR120 agonist was developed and its pharmacological properties were compared with the previously described GPR120 agonist Metabolex-36. Effects of both compounds on signaling pathways and GLP-1 secretion were investigated in vitro. The acute glucose lowering effect was studied in lean wild-type and GPR120 null mice following oral or intravenous glucose tolerance tests. In vitro, in GPR120 overexpressing cells, both agonists signaled through Gα_q, Gα_s and the β-arrestin pathway. However, in mouse islets the signaling pathway was different since the agonists reduced cAMP production. The GPR120 agonists stimulated GLP-1 secretion both in vitro in STC-1 cells and in vivo following oral administration. In vivo GPR120 activation induced significant glucose lowering and increased insulin secretion after intravenous glucose administration in lean mice, while the agonists had no effect in GPR120 null mice. Exendin 9–39, a GLP-1 receptor antagonist, abolished the GPR120 induced effects on glucose and insulin following an intravenous glucose challenge. In conclusion, GLP-1 secretion is an important mechanism behind the acute glucose lowering effect following specific GPR120 activation.

A review of glucagon-like peptide-1 receptor agonists and their effects on lowering postprandial plasma glucose and cardiovascular outcomes in the treatment of type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is an independent risk factor for cardiovascular (CV) comorbidities, with CV disease being the most common cause of death in adults with T2DM. Although glucocentric therapies may improve glycaemic control (as determined by glycated haemoglobin levels), evidence suggests that this approach alone has limited beneficial effects on CV outcomes relative to improvements in lipid and blood pressure control. This may be explained in part by the fact that current antidiabetic treatment regimens primarily address overall glycaemia and/or fasting plasma glucose, but not the postprandial plasma glucose (PPG) excursions that have a fundamental causative role in increasing CV risk. This literature review evaluates the relationship between PPG and the risk of CV disease, discusses the treatment of T2DM with glucagon-like peptide-1 receptor agonists (GLP-1 RAs) and examines the associated CV outcomes. The literature analysis suggests that exaggerated PPG excursions are a risk factor for CV disease because of their adverse pathophysiologic effects on the vasculature, resulting in increased all-cause and CV-related mortality. Although GLP-1 RAs are well established in the current T2DM treatment paradigm, a subgroup of these compounds has a particularly pronounced, persistent and short-lived effect on gastric emptying and, hence, lower PPG substantially. However, current long-term data on CV outcomes with GLP-1 RAs are contradictory, with both beneficial and adverse effects having been reported. This review explores the opportunity to direct treatment towards controlling PPG excursions, thereby improving not only overall glycaemic control but also CV outcomes.

Renal outcomes with dipeptidyl peptidase-4 inhibitors

Dipeptidyl peptidase-4 inhibitors (DPP-4is) are increasingly being used in the management of type 2 diabetes (T2D). The present review summarizes the current knowledge of the effects of DPP-4is on renal outcomes by analyzing the experimental preclinical data, the effects of DPP-4is on urinary albumin-creatinine ratios (UACRs) and estimated glomerular filtration rates (eGFRs) from observational studies and clinical trials, and renal events (including kidney failure requiring renal replacement therapy) in recent large prospective cardiovascular outcome trials. Renal protection has been demonstrated in various animal models that have implicated different underlying mechanisms independent of glucose control, whereas prevention of new onset microalbuminuria and/or progression of albuminuria has been reported in some clinical studies, but with no significant effects on eGFR in most of them. The long-term clinical effects of DPP-4is on renal outcomes and the development of end-stage renal disease remain largely unknown and, thus, demand further investigations in prospective trials and long-term observational studies. In conclusion, despite promising results in animal models, data on surrogate biological markers of renal function and clinical renal outcomes remain rather scanty in patients with T2D, and mostly demonstrate the safety rather than true efficacy of DPP-4is.

Treatment Strategies for Nonalcoholic Fatty Liver Disease and Nonalcoholic Steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is recognized as a global health problem and as a common cause of chronic liver disease. Nonalcoholic steatohepatitis (NASH) carries an increased risk for development of advanced liver disease. Lifestyle modifications with diet and exercise have been the initial management recommendation. However, these changes are difficult to achieve and sustain overtime. There are pharmacologic agents being considered for treatment of NASH. Some target insulin resistance and others focus on oxidative stress, inflammation, apoptosis, and fibrosis. There is a great deal of efforts to develop therapeutic regimens for patients with NASH and NASH with significant fibrosis.

Current Therapies That Modify Glucagon Secretion: What Is the Therapeutic Effect of Such Modifications?

PURPOSE OF REVIEW

Hyperglucagonemia contributes significantly to hyperglycemia in type 2 diabetes and suppressed glucagon levels may increase the risk of hypoglycemia. Here, we give a brief overview of glucagon physiology and the role of glucagon in the pathophysiology of type 2 diabetes and provide insights into how antidiabetic drugs influence glucagon secretion as well as a perspective on the future of glucagon-targeting drugs.

RECENT FINDINGS

Several older as well as recent investigations have evaluated the effect of antidiabetic agents on glucagon secretion to understand how glucagon may be involved in the drugs' efficacy and safety profiles. Based on these findings, modulation of glucagon secretion seems to play a hitherto underestimated role in the efficacy and safety of several glucose-lowering drugs. Numerous drugs currently available to diabetologists are capable of altering glucagon secretion: metformin, sulfonylurea compounds, insulin, glucagon-like peptide-1 receptor agonists, dipeptidyl peptidase-4 inhibitors, sodium-glucose cotransporter 2 inhibitors and amylin mimetics. Their diverse effects on glucagon secretion are of importance for their individual efficacy and safety profiles. Understanding how these drugs interact with glucagon secretion may help to optimize treatment.

The Use of Saxagliptin in People with Type 2 Diabetes in France: The Diapazon Epidemiological Study

INTRODUCTION

Saxagliptin is a potent, reversible inhibitor of dipeptidyl peptidase-4 that is indicated for the treatment of type 2 diabetes. The DIAPAZON study was a multicenter observational study intended to document the effectiveness, safety and patterns of saxagliptin use in France, including the saxagliptin retention rate, over 2 years of follow-up.

METHODS

A geographically representative sample of 304 French physicians (general practitioners and specialist endocrinologists or diabetologists) recruited 1131 adults with type 2 diabetes into an ambispective cohort; 1033 fulfilled the inclusion criteria. All had started saxagliptin during the previous 6 months or at study inclusion, and follow-up was for 24 ± 3 months after starting saxagliptin.

RESULTS

The mean age of the study population when starting saxagliptin was 61 years, and the mean HbA1c level was 8.0%; 79% had an HbA1c level ≥7%. Prior to starting saxagliptin treatment, most participants (91%) were receiving treatment with oral glucose-lowering drugs alone. The most commonly prescribed regimen at starting saxagliptin (53% of participants) was a combination of saxagliptin and metformin. The overall saxagliptin retention rate at 2 years was 79%, as estimated by the Kaplan-Meier method. The most common reasons for discontinuation were inadequate glycemic control (52%) and intolerance (22%). During the course of the study, the mean HbA1c level decreased to 7.0%, and the percentage of people with HbA1c <7% increased from 21% to 49%. The mean change in body weight was -1.8 kg. A total of 294 hypoglycemic episodes were reported in 70 participants (6.8%) during the follow-up period. Of these, 143 episodes in 41 participants (4.0%) occurred when saxagliptin was used in combination with agents associated with hypoglycemia, such as insulin, sulfonylureas or glinides.

CONCLUSION

Saxagliptin is efficacious and well tolerated in a real-world practice setting, with almost 80% of participants remaining on treatment after 2 years.

FUNDING

AstraZeneca, France.

Cardiovascular Actions and Clinical Outcomes With Glucagon-Like Peptide-1 Receptor Agonists and Dipeptidyl Peptidase-4 Inhibitors

Potentiation of glucagon-like peptide-1 (GLP-1) action through selective GLP-1 receptor (GLP-1R) agonism or by prevention of enzymatic degradation by inhibition of dipeptidyl peptidase-4 (DPP-4) promotes glycemic reduction for the treatment of type 2 diabetes mellitus by glucose-dependent control of insulin and glucagon secretion. GLP-1R agonists also decelerate gastric emptying, reduce body weight by reduction of food intake and lower circulating lipoproteins, inflammation, and systolic blood pressure. Preclinical studies demonstrate that both GLP-1R agonists and DPP-4 inhibitors exhibit cardioprotective actions in animal models of myocardial ischemia and ventricular dysfunction through incompletely characterized mechanisms. The results of cardiovascular outcome trials in human subjects with type 2 diabetes mellitus and increased cardiovascular risk have demonstrated a cardiovascular benefit (significant reduction in time to first major adverse cardiovascular event) with the GLP-1R agonists liraglutide (LEADER trial [Liraglutide Effect and Action in Diabetes: Evaluation of Cardiovascular Ourcome Results], -13%) and semaglutide (SUSTAIN-6 trial [Trial to Evaluate Cardiovascular and Other Long-term Outcomes with Semaglutide], -24%). In contrast, cardiovascular outcome trials examining the safety of the shorter-acting GLP-1R agonist lixisenatide (ELIXA trial [Evaluation of Lixisenatide in Acute Coronary Syndrom]) and the DPP-4 inhibitors saxagliptin (SAVOR-TIMI 53 trial [Saxagliptin Assessment of Vascular Outcomes Recorded in Patients With Diabetes Mellitus-Thrombolysis in Myocardial Infarction 53]), alogliptin (EXAMINE trial [Examination of Cardiovascular Outcomes With Alogliptin Versus Standard of Care in Patients With Type 2 Diabetes Mellitus and Acute Coronary Syndrome]), and sitagliptin (TECOS [Trial Evaluating Cardiovascular Outcomes With Sitagliptin]) found that these agents neither increased nor decreased cardiovascular events. Here we review the cardiovascular actions of GLP-1R agonists and DPP-4 inhibitors, with a focus on the translation of mechanisms derived from preclinical studies to complementary findings in clinical studies. We highlight areas of uncertainty requiring more careful scrutiny in ongoing basic science and clinical studies. As newer more potent GLP-1R agonists and coagonists are being developed for the treatment of type 2 diabetes mellitus, obesity, and nonalcoholic steatohepatitis, the delineation of the potential mechanisms that underlie the cardiovascular benefit and safety of these agents have immediate relevance for the prevention and treatment of cardiovascular disease.

Oral glucose lowering with linagliptin and metformin compared with linagliptin alone as initial treatment in Asian patients with newly diagnosed type 2 diabetes and marked hyperglycemia: Subgroup analysis of a randomized clinical trial

AIMS/INTRODUCTION

Type 2 diabetes mellitus is an epidemic in Asia, yet clinical trials of glucose-lowering therapies often enroll predominantly Western populations. We explored the initial combination of metformin and linagliptin, a dipeptidyl peptidase-4 inhibitor, in newly diagnosed type 2 diabetes mellitus patients in Asia with marked hyperglycemia.

MATERIALS AND METHODS

This was a post-hoc subgroup analysis of a multinational, parallel-group clinical trial in which 316 newly diagnosed type 2 diabetes mellitus patients with glycated hemoglobin A1c (HbA1c) 8.5-12.0% were randomized to double-blind oral treatment with linagliptin/metformin or linagliptin monotherapy. The primary end-point was the change from baseline in HbA1c at week 24. We evaluated data for the 125 participants from Asian countries.

RESULTS

After 24 weeks, the mean ± standard error reduction from baseline in HbA1c (mean 10.0%) was -2.99 ± 0.18% with linagliptin/metformin and -1.84 ± 0.18% with linagliptin; a treatment difference of -1.15% (95% confidence interval -1.65 to -0.66, P < 0.0001). HbA1c <7.0% was achieved by 60% of participants receiving linagliptin/metformin. The mean bodyweight change after 24 weeks was -0.45 ± 0.41 kg and 1.33 ± 0.45 kg in the linagliptin/metformin and linagliptin groups, respectively (treatment difference -1.78 kg [95% confidence interval -2.99 to -0.57, P = 0.0043]). Drug-related adverse events occurred in 9.7% of participants receiving linagliptin/metformin and 4.8% of those receiving linagliptin. Hypoglycemia occurred in 6.5% and 4.8% of the linagliptin/metformin and linagliptin groups, respectively, with no severe episodes. Gastrointestinal disorders occurred in 12.9% and 12.7% of the linagliptin/metformin and linagliptin groups, respectively, with no associated treatment discontinuations.

CONCLUSIONS

In people from Asia with newly diagnosed type 2 diabetes mellitus and marked hyperglycemia, the initial combination of linagliptin and metformin substantially improved glycemic control without weight gain and with infrequent hypoglycemia. Initial oral combination therapy might be a viable treatment for such individuals.

Glucagon like peptide-1 receptor agonists for the management of obesity and non-alcoholic fatty liver disease: a novel therapeutic option

Obesity is a major risk factor for the development of type 2 diabetes mellitus (T2DM), and is associated with a cluster of metabolic factors that lead to poor cardiovascular outcomes. In non-alcoholic fatty liver disease (NAFLD), liver fat (triglyceride) accumulation closely mirrors adipose tissue dysfunction and insulin resistance in obesity and T2DM. It is now recognized as the most common chronic liver disease in Westernized societies, often progressing to more severe forms of the disease such as nonalcoholic steatohepatitis (NASH), or cirrhosis and hepatocellular carcinoma. However, NAFLD remains largely overlooked by healthcare providers although it affects about two-thirds of patients with obesity and it promotes the development of T2DM. NAFLD mirrors adipose tissue and systemic insulin resistance, the liver being a 'barometer' of metabolic health. Although pioglitazone is emerging as the treatment of choice for NASH in patients with insulin-resistance, or those with T2DM, many other options are being tested. Due to their overall safety and efficacy, glucagon-like peptide-1 receptor agonists (GLP-1 RAs) are becoming one of the cornerstones for the management of both obesity and T2DM, and a novel alternative for the treatment of NAFLD. In this review, we will briefly summarize the status of GLP-1RA for the treatment of obesity and NAFLD.

GLP-1 and the kidney: from physiology to pharmacology and outcomes in diabetes

The gastrointestinal tract - the largest endocrine network in human physiology - orchestrates signals from the external environment to maintain neural and hormonal control of homeostasis. Advances in understanding entero-endocrine cell biology in health and disease have important translational relevance. The gut-derived incretin hormone glucagon-like peptide 1 (GLP-1) is secreted upon meal ingestion and controls glucose metabolism by modulating pancreatic islet cell function, food intake and gastrointestinal motility, amongst other effects. The observation that the insulinotropic actions of GLP-1 are reduced in type 2 diabetes mellitus (T2DM) led to the development of incretin-based therapies - GLP-1 receptor agonists and dipeptidyl peptidase 4 (DPP-4) inhibitors - for the treatment of hyperglycaemia in these patients. Considerable interest exists in identifying effects of these drugs beyond glucose-lowering, possibly resulting in improved macrovascular and microvascular outcomes, including in diabetic kidney disease. As GLP-1 has been implicated as a mediator in the putative gut-renal axis (a rapid-acting feed-forward loop that regulates postprandial fluid and electrolyte homeostasis), direct actions on the kidney have been proposed. Here, we review the role of GLP-1 and the actions of associated therapies on glucose metabolism, the gut-renal axis, classical renal risk factors, and renal end points in randomized controlled trials of GLP-1 receptor agonists and DPP-4 inhibitors in patients with T2DM.

Three-year data from 5 HARMONY phase 3 clinical trials of albiglutide in type 2 diabetes mellitus: Long-term efficacy with or without rescue therapy

AIMS

Diabetes therapies that provide durable glycaemic control for people with type 2 diabetes mellitus (T2DM) are needed. We present efficacy results of albiglutide, a glucagon-like peptide-1 receptor agonist, in people with T2DM over a 3-year period.

METHODS

Five of the 8 HARMONY phase 3 trials, comparing albiglutide with other therapies or placebo across a spectrum of clinical care, lasted for a preplanned 3years. Participants with uncontrolled hyperglycaemia who met predetermined criteria could receive rescue medication. The ability to remain on study medication without needing additional rescue was an efficacy measure. Glycaemic measures and body weight were analysed in 2 populations: those who remained rescue-free and all participants.

RESULTS

Participants (n=3132) were randomised to albiglutide or comparator. A greater proportion of participants who received albiglutide remained rescue-free (55-71%) compared with placebo (35-51%; p<0.001 to p=0.002). The proportion of rescue-free participants with albiglutide did not differ from glimepiride or insulin glargine, was higher than with sitagliptin (p=0.013), and lower than with pioglitazone (p=0.045). At 3years, albiglutide was associated with clinically significant reductions in hyperglycaemia (eg, rescue-free participants: HbA1c -0.52% [SE0.11] to -0.98% [0.12]; -5.7mmol/mol [1.2] to -10.7mmol/mol [1.3] and all participants: HbA1c -0.29% [0.11] to-0.92% [0.13]; -3.2mmol/mol [1.2] to -10.1mmol/mol [1.4]). Albiglutide was also associated with modest reductions in body weight vs pioglitazone, glimepiride, and insulin glargine, which were associated with weight gain.

CONCLUSION

These 3-year efficacy data support long-term use of albiglutide in the management of people with T2DM. ClinicalTrials.gov NCT00849056, NCT00849017, NCT00838903, NCT00838916, NCT00839527.

The SNARE Protein Syntaxin-1a Plays an Essential Role in Biphasic Exocytosis of the Incretin Hormone Glucagon-Like Peptide 1

Exocytosis of the hormone glucagon-like peptide 1 (GLP-1) by the intestinal L cell is essential for the incretin effect after nutrient ingestion and is critical for the actions of dipeptidyl peptidase 4 inhibitors that enhance GLP-1 levels in patients with type 2 diabetes. Two-photon microscopy revealed that exocytosis of GLP-1 is biphasic, with a first peak at 1-6 min and a second peak at 7-12 min after stimulation with forskolin. Approximately 75% of the exocytotic events were represented by compound granule fusion, and the remainder were accounted for by full fusion of single granules under basal and stimulated conditions. The core SNARE protein syntaxin-1a (syn1a) was expressed by murine ileal L cells. At the single L-cell level, first-phase forskolin-induced exocytosis was reduced to basal (P < 0.05) and second-phase exocytosis abolished (P < 0.05) by syn1a knockout. L cells from intestinal-epithelial syn1a-deficient mice demonstrated a 63% reduction in forskolin-induced GLP-1 release in vitro (P < 0.001) and a 23% reduction in oral glucose-stimulated GLP-1 secretion (P < 0.05) in association with impairments in glucose-stimulated insulin release (by 60%; P < 0.01) and glucose tolerance (by 20%; P < 0.01). The findings identify an exquisite mechanism of metered secretory output that precisely regulates release of the incretin hormone GLP-1 and hence insulin secretion after a meal.

Crystal structure of Porphyromonas gingivalis dipeptidyl peptidase 4 and structure-activity relationships based on inhibitor profiling

The Gram-negative anaerobe Porphyromonas gingivalis is associated with chronic periodontitis. Clinical isolates of P. gingivalis strains with high dipeptidyl peptidase 4 (DPP4) expression also had a high capacity for biofilm formation and were more infective. The X-ray crystal structure of P. gingivalis DPP4 was solved at 2.2 Å resolution. Despite a sequence identity of 32%, the overall structure of the dimer was conserved between P. gingivalis DPP4 and mammalian orthologues. The structures of the substrate binding sites were also conserved, except for the region called S2-extensive, which is exploited by specific human DPP4 inhibitors currently used as antidiabetic drugs. Screening of a collection of 450 compounds as inhibitors revealed a structure-activity relationship that mimics in part that of mammalian DPP9. The functional similarity between human and bacterial DPP4 was confirmed using 124 potential peptide substrates.

Insulin receptor signaling and glucagon-like peptide 1 effects on pancreatic beta cells

Glucagon-like peptide-1 (GLP-1) is a potent gluco-incretin hormone, which plays a central role on pancreatic beta cell proliferation, survival and insulin secreting activity and whose analogs are used for treating hyperglycemia in type 2 diabetes mellitus. Notably, abnormal insulin signaling affects all the above-mentioned aspects on pancreatic beta cells. The aim of our study was to investigate whether the protective effects of GLP1-1 on beta cells are affected by altered insulin receptor signaling. To this end, several effects of GLP-1 were studied in INS-1E rat beta cells transfected either with an inhibitor of insulin receptor function (i.e., the Ectonucleotide Pyrophosphatase Phosphodiesterase 1, ENPP1), or with insulin receptor small interfering RNA, as well as in control cells. Crucial experiments were carried out also in a second cell line, namely the βTC-1 mouse beta cells. Our data indicate that in insulin secreting beta cells in which either ENPP1 was up-regulated or insulin receptor was down-regulated, GLP-1 positive effects on several pancreatic beta cell activities, including glucose-induced insulin secretion, cell proliferation and cell survival, were strongly reduced. Further studies are needed to understand whether such a scenario occurs also in humans and, if so, if it plays a role of clinical relevance in diabetic patients with poor responsiveness to GLP-1 related treatments.

A system model of the effects of exercise on plasma Interleukin-6 dynamics in healthy individuals: Role of skeletal muscle and adipose tissue

Interleukin-6 (IL-6) has been recently shown to play a central role in glucose homeostasis, since it stimulates the production and secretion of Glucagon-like Peptide-1 (GLP-1) from intestinal L-cells and pancreas, leading to an enhanced insulin response. In resting conditions, IL-6 is mainly produced by the adipose tissue whereas, during exercise, skeletal muscle contractions stimulate a marked IL-6 secretion as well. Available mathematical models describing the effects of exercise on glucose homeostasis, however, do not account for this IL-6 contribution. This study aimed at developing and validating a system model of exercise’s effects on plasma IL-6 dynamics in healthy humans, combining the contributions of both adipose tissue and skeletal muscle. A two-compartment description was adopted to model plasma IL-6 changes in response to oxygen uptake’s variation during an exercise bout. The free parameters of the model were estimated by means of a cross-validation procedure performed on four different datasets. A low coefficient of variation (<10%) was found for each parameter and the physiologically meaningful parameters were all consistent with literature data. Moreover, plasma IL-6 dynamics during exercise and post-exercise were consistent with literature data from exercise protocols differing in intensity, duration and modality. The model successfully emulated the physiological effects of exercise on plasma IL-6 levels and provided a reliable description of the role of skeletal muscle and adipose tissue on the dynamics of plasma IL-6. The system model here proposed is suitable to simulate IL-6 response to different exercise modalities. Its future integration with existing models of GLP-1-induced insulin secretion might provide a more reliable description of exercise’s effects on glucose homeostasis and hence support the definition of more tailored interventions for the treatment of type 2 diabetes.

[Why is a combination of basal insulin with a GLP-1 receptor agonist useful in many patients with type 2 diabetes?]

BACKGROUND

In 2015, the combination of basal insulin and GLP-1 receptor agonist (RA) was incorporated into the guideline recommendations for type 2 diabetes as an option for the last escalation step. The two antidiabetics to be injected subcutaneously are complementary regarding their respective main effects and limitations. Basal insulin is predominantly active between meals and in the fasting state, whereas the main action of GLP-1 RA consists in preventing an excessive postprandial blood glucose increase. Moreover, GLP-1 RA is characterised by a low intrinsic risk of hypoglycaemia, body weight reduction and a positive impact on cardiovascular risk factors. Unlike GLP-1 RA, no upper dose limits are defined for basal insulin. However, initiation of insulin therapy is associated with disadvantages in terms of hypoglycaemia and weight increase. Therefore, patients achieving their treatment goals with GLP-1 RA alone are better treated without insulin.

METHOD

In a review, study results on combinations of basal insulin and GLP-1-RA versus comparative therapies are presented.

RESULTS

Most of the studies were carried out in patients pre-treated with basal insulin. The add-on of GLP-1 RA was commonly associated with significant reductions of body weight and also resulted in additional HbA_1c reductions compared with an increase of the basal insulin dose. The add-on of a short acting insulin to an existing basal insulin therapy enabled similar HbA_1c reductions to the add-on of a GLP-1 RA, but simultaneously increased the number of episodes of hypoglycaemia and might lead to more unfavourable body weight developments. A fixed combination of insulin degludec and liraglutide (IDegLira) showed an effective and rather steady blood glucose reduction in a 24-hour interval vs. basal insulin or GLP-1 RA alone.

CONCLUSIONS

Combinations of basal insulin and a GLP-1 RA improve glycaemic control in many patients with type 2 diabetes without any significant increase of the risk of hypoglycaemia and without weight gain, especially compared to a dose increase of the basal insulin or add-on of a short-acting insulin.

Incretin based treatments and mortality in patients with type 2 diabetes: systematic review and meta-analysis

Objective To assess the impact of incretin based treatment on all cause mortality in patients with type 2 diabetes.Design Systematic review and meta-analysis of randomised trials.Data sources Medline, Embase, the Cochrane Central Register of Controlled Trials (CENTRAL), and ClinicalTrials.gov.Eligibility criteria Randomised controlled trials that compared glucagon-like peptide-1 (GLP-1) receptor agonists or dipeptidyl peptidase-4 (DPP-4) inhibitors with placebo or active anti-diabetic drugs in patients with type 2 diabetes.Data collection and analysis Paired reviewers independently screened citations, assessed risk of bias of included studies, and extracted data. Peto's method was used as the primary approach to pool effect estimates from trials, sensitivity analyses were carried out with other statistical approaches, and meta-regression was applied for six prespecified hypotheses to explore heterogeneity. The GRADE approach was used to rate the quality of evidence.Results 189 randomised controlled trials (n=155 145) were included, all of which were at low to moderate risk of bias; 77 reported no events of death and 112 reported 3888 deaths among 151 614 patients. Meta-analysis of 189 trials showed no difference in all cause mortality between incretin drugs versus control (1925/84 136 v 1963/67 478; odds ratio 0.96, 95% confidence interval 0.90 to 1.02, I²=0%; risk difference 3 fewer events (95% confidence interval 7 fewer to 1 more) per 1000 patients over five years; moderate quality evidence). Results suggested the possibility of a mortality benefit with GLP-1 agonists but not DPP-4 inhibitors, but the subgroup hypothesis had low credibility. Sensitivity analyses showed no important differences in the estimates of effects.Conclusions Current evidence does not support the suggestion that incretin based treatment increases all cause mortality in patients with type 2 diabetes. Further studies are warranted to examine if the effect differs between GLP-1 agonists versus DPP-4 inhibitors.

GLP-1 receptor independent pathways: emerging beneficial effects of GLP-1 breakdown products

The glucagon-like peptide-1 (GLP-1) axis has emerged as a major therapeutic target for the treatment of type 2 diabetes and, recently, of obesity. The insulinotropic activity of the native incretin hormone GLP-1(7-36)amide, which is mainly exerted through a unique G protein-coupled receptor (GLP-1R), is terminated via enzymatic cleavage by dipeptidyl peptidase-IV that generates a C-terminal GLP-1 metabolite GLP-1(9-36)amide, the major circulating form in plasma. GLP-1(28-36)amide and GLP-1(32-36)amide are further cleavage products derived from GLP-1(7-36)amide and GLP-1(9-36)amide by the action of a neutral endopeptidase known as neprilysin. Until recently, GLP-1-derived metabolites were generally considered metabolically inactive. However, emerging evidence indicates that GLP-1 byproducts have insulinomimetic activities that may contribute to the pleiotropic effects of GLP-1 independently of the canonical GLP-1R. The recent studies reporting the beneficial effects of the administration of these metabolites in vivo and in vitro are the focus of this review. Collectively, these results suggest that GLP-1 metabolites inhibit hepatic glucose production, exert antioxidant cardio- and neuroprotective actions, reduce oxidative stress in vasculature and have both anti-apoptotic and proliferative effects in pancreatic β-cells, putatively by the modulation of mitochondrial functions. These findings have implication in energy homeostasis, obesity and its associated metabolic and cardiovascular complications as well as incretin-based therapies for the treatment of diabetes and obesity.

Autophagy and its link to type II diabetes mellitus

Autophagy, a double-edged sword for cell survival, is the research object on 2016 Nobel Prize in Physiology or Medicine. Autophagy is a molecular mechanism for maintaining cellular physiology and promoting survival. Defects in autophagy lead to the etiology of many diseases, including diabetes mellitus (DM), cancer, neurodegeneration, infection disease and aging. DM is a metabolic and chronic disorder and has a higher prevalence in the world as well as in Taiwan. The character of diabetes mellitus is hyperglycemia resulting from defects in insulin secretion, insulin action, or both. Type 2 diabetes mellitus (T2DM) is characterized by insulin resistance and failure of producing insulin on pancreatic beta cells. In T2DM, autophagy is not only providing nutrients to maintain cellular energy during fasting, but also removes damaged organelles, lipids and miss-folded proteins. In addition, autophagy plays an important role in pancreatic beta cell dysfunction and insulin resistance. In this review, we summarize the roles of autophagy in T2DM.

Integration of recent evidence into management of patients with atherosclerotic cardiovascular disease and type 2 diabetes

Cardiovascular outcome trials of antihyperglycaemic drugs and non-statin LDL-cholesterol-lowering drugs in patients with type 2 diabetes who have, or who are at high risk of, atherosclerotic cardiovascular disease have provided new evidence that has substantially affected the management of cardiovascular risk in these patients. On the basis of proven cardiovascular and renal benefit, the antihyperglycaemic drugs empagliflozin, liraglutide, and semaglutide-the latter being under review for approval by the US Food and Drug Administration and the European Medicines Agency-should be preferentially used as second-line treatments in these patient populations, typically in addition to metformin. Further treatment differentiation among the remainder of the antihyperglycaemic drugs should be made on the basis of evidence regarding cardiovascular safety, which is available for lixisenatide, alogliptin, saxagliptin, sitagliptin, and insulin glargine. The risk of heart failure, stroke, or retinopathy, or prevalent fasting versus postprandial hyperglycaemia, could also be considered in treatment decision making. Finally, emerging evidence of cardiovascular benefit for ezetimibe, alirocumab, and evolocumab positions these drugs as add-ons to maximally tolerated statin therapy or for those with statin intolerance.

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.