Effects of DPP-4 inhibitor linagliptin and GLP-1 receptor agonist liraglutide on physiological response to hypoglycaemia in Japanese subjects with type 2 diabetes: A randomized, open-label, 2-arm parallel comparative, exploratory trial

Revisiting the role of glucagon in health, diabetes mellitus and other metabolic diseases

Insulin and glucagon exert opposing effects on glucose metabolism and, consequently, pancreatic islet β-cells and α-cells are considered functional antagonists. The intra-islet hypothesis has previously dominated the understanding of glucagon secretion, stating that insulin acts to inhibit the release of glucagon. By contrast, glucagon is a potent stimulator of insulin secretion and has been used to test β-cell function. Over the past decade, α-cells have received increasing attention due to their ability to stimulate insulin secretion from neighbouring β-cells, and α-cell-β-cell crosstalk has proven central for glucose homeostasis in vivo. Glucagon is not only the counter-regulatory hormone to insulin in glucose metabolism but also glucagon secretion is more susceptible to changes in the plasma concentration of certain amino acids than to changes in plasma concentrations of glucose. Thus, the actions of glucagon also include a central role in amino acid turnover and hepatic fat oxidation. This Review provides insights into glucagon secretion, with a focus on the local paracrine actions on glucagon and the importance of α-cell-β-cell crosstalk. We focus on dysregulated glucagon secretion in obesity, non-alcoholic fatty liver disease and type 2 diabetes mellitus. Lastly, the future potential of targeting hyperglucagonaemia and applying dual and triple receptor agonists with glucagon receptor-activating properties in combination with incretin hormone receptor agonism is discussed.

Dipeptidyl peptidase 4 inhibitor improves insulin resistance in Japanese patients with type 2 diabetes: a single-arm study, a brief report

BACKGROUND

Dipeptidyl peptidase 4 inhibitor (DPP4i) is an effective medicine for type 2 diabetes mellitus (T2DM). Some articles reported DPP4i improves insulin secretion and insulin resistance. However, these effects are not well established by glucose clamp test and test meal in Japanese. We investigated the effect of DPP4i on insulin resistance and insulin secretion by using the glucose clamp test and meal tolerance test (MTT).

METHODS

We performed a MTT, and the hyperinsulinemic-euglycemic clamp in 8 Japanese patients with T2DM. This study was a single-arm study. We measured fasting and postprandial glucose, insulin, incretins, and glucagon levels. We also measured serum adiponectin levels.

RESULTS

HbA1c was significantly decreased after 3 months. The fasting and postprandial glucose levels were significantly decreased. Fasting and postprandial insulin levels were not changed. The insulin resistance derived from the glucose clamp test was significantly improved. HOMA-IR was not significantly changed. GLP-1 and GIP were significantly increased but glucagon did not change. Adiponectin was not significantly changed.

CONCLUSIONS

Although the number of patients was very small, these results suggested that DPP4i treatment might improve insulin resistance without changing insulin secretion.

The sodium-glucose cotransporter 2 inhibitor ipragliflozin improves liver function and insulin resistance in Japanese patients with type 2 diabetes

Sodium-glucose cotransporter 2 inhibitor (SGLT2i) treatment is a therapeutic approach for type 2 diabetes mellitus (T2DM). Some reports have shown that SGLT2i treatment improves insulin resistance; however, few studies have evaluated insulin resistance by the glucose clamp method. Hepatic insulin clearance (HIC) is a new pathophysiological mechanism of T2DM. The effect of SGLT2i treatment on hepatic insulin clearance and insulin resistance is not well known. We investigated the effect of SGLT2i treatment on insulin resistance, insulin secretion, incretin levels, body composition, and hepatic insulin clearance. We conducted a meal tolerance test (MTT) and a hyperinsulinemic-euglycemic clamp test in 9 T2DM patients. Ipragliflozin (50 mg/day) was administered, and the MTT and clamp test were performed after 4 months. We calculated HIC as the postprandial C-peptide AUC-to-insulin AUC ratio. We also measured GLP-1, GIP, and glucagon levels during the MTT. Body weight and HbA1c were decreased, although not significantly, after 4 months of treatment. Postprandial glucose, fasting insulin and postprandial insulin were significantly decreased. Insulin resistance with the glucose clamp was not changed, but the HOMA-IR and insulin sensitivity indices were significantly improved. Incretin and glucagon levels were not changed. Hepatic insulin clearance was significantly increased, but whole-body insulin clearance was not changed. The FIB-4 index and fatty liver index were significantly reduced. The HOMA-beta and insulinogenic indices were not changed, but the C-peptide index was significantly increased. Although the number of patients was small, these results suggested that SGLT2i treatment improved liver function, decreased hepatic insulin resistance, and increased hepatic insulin clearance, despite the small weight reduction.

Effects of glucagon-like peptide-1 receptor agonists on secretions of insulin and glucagon and gastric emptying in Japanese individuals with type 2 diabetes: A prospective, observational study

AIMS/INTRODUCTION

Differences in the glucose-lowering mechanisms of glucagon-like peptide-1 receptor agonists (GLP-1RAs) have been noted. Clarifying these differences could facilitate the choice of optimal drugs for individuals with type 2 diabetes and requires investigation in a clinical setting.

MATERIALS AND METHODS

A single-arm, prospective, observational study was conducted to evaluate the effects of various GLP-1RAs on postprandial glucose excursion, secretions of insulin and glucagon as well as on the gastric emptying rate. Participants were subjected to meal tolerance tests before and 2 weeks and 12 weeks after GLP-1RA initiation. Effects on postprandial secretions of glucose-dependent insulinotropic polypeptide (GIP) and apolipoprotein B48 were also investigated.

RESULTS

Eighteen subjects with type 2 diabetes received one of three GLP-1RAs, i.e., lixisenatide, n = 7; liraglutide, n = 6; or dulaglutide, n = 5. While 12-week administration of all of the GLP-1RAs significantly reduced HbA1c, only lixisenatide and liraglutide, but not dulaglutide, significantly reduced body weight. Postprandial glucose elevation was improved by all of the GLP-1RAs. Postprandial insulin levels were suppressed by lixisenatide, while insulin levels were enhanced by liraglutide. Postprandial glucagon levels were suppressed by lixisenatide. The gastric emptying rate was significantly delayed by lixisenatide, while liraglutide and dulaglutide had limited effects on gastric emptying. GIP secretion was suppressed by lixisenatide and liraglutide. Apolipoprotein B48 secretion was suppressed by all of the GLP-1RAs.

CONCLUSIONS

All of the GLP-1RAs were found to improve HbA1c in a 12-week prospective observational study in Japanese individuals with type 2 diabetes. However, differences in the mechanisms of the glucose-lowering effects and body weight reduction were observed.

Role of Renal Sympathetic Nerves in GLP-1 (Glucagon-Like Peptide-1) Receptor Agonist Exendin-4-Mediated Diuresis and Natriuresis in Diet-Induced Obese Rats

Background

The gut‐derived hormone GLP‐1 (glucagon‐like peptide‐1) exerts beneficial effects against established risk factors for chronic kidney disease. GLP‐1 influences renal function by stimulating diuresis and natriuresis and thus lowering arterial blood pressure. The role of the sympathetic nervous system has been implicated as an important link between obesity with elevated arterial pressure and chronic kidney disease. The primary aim of this study was to determine the contribution of renal sympathetic nerves on intrapelvic GLP‐1‐mediated diuresis and natriuresis in high‐fat diet (HFD)‐induced obese rats.

Methods and Results

Obesity was induced in rats by HFD for 12 weeks, followed by either surgical bilateral renal denervation or chronic subcutaneous endopeptidase neprilysin inhibition by sacubitril for a week. Diuretic and natriuretic responses to intrapelvic administration of the GLP‐1R (GLP‐1 receptor) agonist exendin‐4 were monitored in anesthetized control and HFD rats. Renal GLP‐1R expression and neprilysin expression and activity were measured. The effects of norepinephrine on the expression of GLP‐1R and neprilysin in kidney epithelial LLC‐PK1 cells were also examined. We found that diuretic and natriuretic responses to exendin‐4 were significantly reduced in the HFD obese rats compared with the control rats (cumulative urine flow at 40 minutes, 387±32 versus 650±65 µL/gkw; cumulative sodium excretion at 40 minutes, 42±5 versus 75±10 µEq/gkw, P<0.05). These responses in the HFD rats were restored after ablation of renal nerves (cumulative urine flow at 40 minutes, 625±62 versus 387±32 µL/gkw; cumulative sodium excretion at 40 minutes, 70±9 versus 42±5 µEq/gkw, P<0.05). Renal denervation induced significant reductions in arterial pressure and heart rate responses to intrapelvic GLP‐1 in the HFD rats. Renal denervation also significantly increased the GLP‐1R expression and reduced neprilysin expression and activity in renal tissues from the HFD rats. Chronic subcutaneous neprilysin inhibition by sacubitril increased GLP‐1–induced diuretic and natriuretic effects in the HFD rats. Finally, exposure of the renal epithelial cells to norepinephrine in vitro led to downregulation of GLP‐1R expression but upregulation of neprilysin expression and activity.

Conclusions

These results suggest that renal sympathetic nerve activation contributes to the blunted diuretic and natriuretic effects of GLP‐1 in HFD obese rats. This study provides significant novel insight into the potential renal nerve–neprilysin–GLP‐1 pathway involved in renal dysfunction during obesity that leads to hypertension.

Glucose-lowering action through targeting islet dysfunction in type 2 diabetes: Focus on dipeptidyl peptidase-4 inhibition

Dipeptidyl peptidase-4 (DPP-4) inhibition is a glucose-lowering medication for type 2 diabetes. It works through stimulation of insulin secretion and inhibition of glucagon secretion in a glucose-dependent manner, resulting in lowered fasting and postprandial glycemia with low risk of hypoglycemia. As impaired insulin secretion and augmented glucagon secretion are key factors underlying hyperglycemia in type 2 diabetes, DPP-4 inhibition represents a therapy that targets the underlying mechanisms of the disease. If insufficient in monotherapy, it can preferably be used in combination with metformin, which targets insulin resistance, and also in combination with sodium-glucose cotransporter 2 inhibition, thiazolidinediones and insulin, which target other mechanisms. In individuals of East Asian origin, islet dysfunction is of particular importance for the development of type 2 diabetes. Consequently, it has been shown in several studies that DPP-4 is efficient in these populations. This mini-review highlights the islet mechanisms of DPP-4 inhibition, islet dysfunction as a key factor for hyperglycemia in type 2 diabetes and that, consequently, DPP-4 is of particular value in populations where islet dysfunction is central, such as in individuals of East Asian origin.

Benefits of the fixed-ratio combination of insulin glargine 100 units/mL and lixisenatide (iGlarLixi) in Japanese people with type 2 diabetes: A subgroup and time-to-control analysis of the LixiLan JP phase 3 trials

AIMS

To explore the impact of baseline characteristics on clinical outcomes in the phase 3 LixiLan JP trials which evaluated the efficacy and safety of iGlarLixi, a titratable fixed-ratio combination of insulin glargine 100 units/mL (iGlar) and GLP-1 RA lixisenatide (Lixi), vs Lixi (JP-O1, NCT02749890) or iGlar (LixiLan JP-O2, NCT02752828; JP-L, NCT02752412) in Japanese people with type 2 diabetes uncontrolled on oral antidiabetes drugs (OADs; JP-O1, JP-O2) or OADs and basal insulin (JP-L).

MATERIALS AND METHODS

Glycated haemoglobin (HbA1c) change from baseline to week 26 was assessed within patient subgroups. Subgroups were defined by dipeptidyl peptidase-4 inhibitor use at screening (JP-O1, JP-O2 only), baseline HbA1c (<8%, ≥8%), baseline BMI (<25, ≥25 kg/m²) and age (<65, ≥65 years). Incidences of hypoglycaemia (baseline HbA1c, BMI and age subgroups) and gastrointestinal disorders (age subgroup) were evaluated over 52 (JP-O1) or 26 weeks (JP-O2, JP-L). Time to control (first HbA1c <7% or fasting plasma glucose [FPG] ≤130 mg/dL; JP-O2 only) was also assessed.

RESULTS

HbA1c reductions were consistently greater with iGlarLixi vs iGlar or Lixi across all subgroups, and iGlarLixi was equally effective in all subgroups. Incidences of documented symptomatic hypoglycaemia (plasma glucose ≤3.9 mmol/L) were higher with iGlarLixi vs Lixi and generally comparable with iGlar. Across age subgroups, incidences of gastrointestinal disorders with iGlarLixi were higher vs iGlar, but lower vs Lixi. Median time to HbA1c or FPG control was shorter with iGlarLixi vs iGlar.

CONCLUSIONS

iGlarLixi was consistently effective across all baseline characteristic subgroups, with more patients achieving glycaemic control vs iGlar early in treatment.

Hepatic insulin clearance is increased in patients with high HbA1c type 2 diabetes: a preliminary report

INTRODUCTION

Hepatic insulin clearance (HIC) is an important pathophysiology of type 2 diabetes. HIC was reported to decrease in patients with type 2 diabetes and metabolic syndrome. However, hyperglycemia was suggested to enhance HIC, and it is not known whether poorly controlled diabetes increases HIC in patients with type 2 diabetes. We investigated whether HIC was increased in patients with poorly controlled diabetes, and whether HIC was associated with insulin resistance and incretins.

RESEARCH DESIGN AND METHODS

We performed a meal tolerance test and the hyperinsulinemic-euglycemic clamp in 21 patients with type 2 diabetes. We calculated the postprandial C-peptide area under the curve (AUC)-to-insulin AUC ratio as the HIC; measured fasting and postprandial glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP) and glucagon levels and analyzed serum adiponectin and zinc transporter-8 (ZnT8) gene polymorphism.

RESULTS

The HIC significantly correlated with glycated hemoglobin (HbA1c) (r_S=0.58, p<0.01). In patients with high HIC above the median of 6.5, the mean HbA1c was significantly higher compared with low HIC below the median. Homeostatic model assessment (HOMA)-beta (r_S=-0.77, p<0.01) and HOMA-IR (r_S=-0.66, p<0.005) were correlated with HIC. The M/I value in the clamp study was correlated with HIC. GLP-1-AUC and GIP-AUC were not correlated with HIC. Glucagon-AUC was negatively correlated with HIC, but there were no significant differences between the high and low HIC groups. Adiponectin was positively correlated with HIC. The ZnT8 gene polymorphism did not affect HIC.

CONCLUSIONS

These results suggest that HIC was increased in patients with high HbA1c type 2 diabetes, low insulin secretion, low insulin resistance and high adiponectin conditions.

A Randomized Pilot Study of the Effect of Trelagliptin and Alogliptin on Glycemic Variability in Patients with Type 2 Diabetes

INTRODUCTION

This open-label, parallel-group, exploratory study examined the effects of two dipeptidyl peptidase 4 (DPP4) inhibitors on glycemic variability (GV) in patients with type 2 diabetes.

METHODS

Randomized patients with glycated hemoglobin A1c of at least 6.5% to less than 8.5% received trelagliptin 100 mg (n = 13) once weekly or alogliptin 25 mg (n = 14) once daily for 29 days. Continuous glucose monitoring was performed before the start of the treatment period (baseline) and from day 21 to 29, inclusive. The primary endpoint was change from baseline in the standard deviation (SD) of 24-h blood glucose values, measured daily for 7 days (day 22-28) of the treatment period. Secondary and additional efficacy endpoints included changes in glycemic parameters and the rate of DPP4 inhibition, respectively. Adverse events (AEs) were monitored to assess safety.

RESULTS

Mean change from baseline in the SD of 24-h blood glucose (95% confidence interval) at day 28 was - 7.35 (- 15.13, 0.44) for trelagliptin and - 11.63 (- 18.67, - 4.59) for alogliptin. In both treatment groups, glycemic parameters improved and the rate of DPP4 inhibition was maintained. Three patients reported AEs; no severe treatment-emergent AEs were reported in either group.

CONCLUSION

Once-weekly trelagliptin and once-daily alogliptin improved glycemic control and reduced GV without inducing hypoglycemia.

TRIAL REGISTRATION

ClinicalTrials.gov (NCT02771093) and JAPIC (JapicCTI-163250).

FUNDING

Takeda Pharmaceutical Company, Ltd.

Incretin-based medications (GLP-1 receptor agonists, DPP-4 inhibitors) as a means to avoid hypoglycaemic episodes

Hypoglycaemia is common in both type 1 and type 2 diabetes and has both acute and long-term consequences. Therefore, a key to proper glucose-lowering therapy in diabetes is to avoid or prevent hypoglycaemia. Incretin therapy (DPP-4 inhibitors and GLP-1 receptor agonists) offers an advantage in this respect, because it reduces glucose with a low risk of hypoglycaemia, both in monotherapy and in combination with other therapies. The reason for this low risk of hypoglycaemia is the glucose dependency of action of incretin therapy and the sustainment of glucose counter-regulatory hormone responses to hypoglycaemia, in particular the glucagon response. Incretin therapy is also associated with a low risk of hypoglycaemia in patient groups which are especially vulnerable and susceptible for hypoglycaemia, e.g., subjects with renal impairment, elderly subjects and subjects with on-going insulin therapy. This review summarizes how incretin therapy may meet the challenges of hypoglycaemia and suggests that incretin therapy is a therapy of choice to avoid hypoglycaemia, both in the general diabetes population and in subjects with increased risk or vulnerability for hypoglycaemia.

Exendin-4 Exacerbates Burn-Induced Morbidity in Mice by Activation of the Sympathetic Nervous System

Background

Although glucagon-like peptide 1- (GLP-1-) based therapy of hyperglycemia in burn injury has shown great potential in clinical trials, its safety is seldom evaluated. We hypothesize that exendin-4, a GLP-1 analogue, might affect the immune response via the activation of the sympathetic nervous system in burn injury.

Methods

Male Balb/c mice were subjected to sham or thermal injury of 15% total body surface area. Exendin-4 on T cell function in vitro was examined in cultured splenocytes in the presence of β-adrenoceptor antagonist propranolol (1 nmol/L) or GLP-1R antagonist exendin (9-39) (1 μmol/L), whereas its in vivo effect was determined by i.p. injection of exendin-4 (2.4 nmol/kg) in mice. To further elucidate the sympathetic mechanism, propranolol (30 mg/kg) or vehicle was applied 30 min prior to injury.

Results

Although the exacerbated burn-induced mortality by exendin-4 was worsened by propranolol pretreatment, the inhibition of T cell proliferation by exendin-4 in vitro could be restored by propranolol instead of exendin (9-39). However, a Th2 switch by exendin-4 in vitro could only be reversed by exendin (9-39). Likewise, the inhibition of splenic T cell function and NFAT activity by exendin-4 in vivo was restored by propranolol. By contrast, the increased splenic NF-κB translocation by exendin-4 in vivo was potentiated by propranolol in sham mice but suppressed in burn mice. Accordingly, propranolol abrogated the heightened inflammatory response in the lung and the accelerated organ injuries by exendin-4 in burn mice. On the contrary, a Th2 switch and higher serum levels of inflammatory mediators by exendin-4 were potentiated by propranolol in burn mice. Lastly, exendin-4 raised serum stress hormones which could be remarkably augmented by propranolol.

Conclusions

Exendin-4 suppresses T cell function and promotes organ inflammation through the activation of the sympathetic nervous system, while elicits Th2 switch via GLP-1R in burn injury.

Effect of once-weekly semaglutide on the counterregulatory response to hypoglycaemia in people with type 2 diabetes: A randomized, placebo-controlled, double-blind, crossover trial

AIMS

To investigate the effects of semaglutide vs placebo on glucagon and other counterregulatory hormones during hypoglycaemia in type 2 diabetes (T2D).

METHODS

In this double-blind, placebo-controlled, single-centre trial, we randomized 38 men and women (treated only with metformin) 1:1 to 2 12-week crossover periods of once-weekly subcutaneous semaglutide or placebo, each followed by a hypoglycaemic clamp procedure. The primary endpoint was change in glucagon concentration from target plasma glucose (PG) level 5.5 mmol/L to nadir (target 2.5 mmol/L).

RESULTS

The mean (range) participant age was 54.2 (41-64) years, body mass index 29.4 (23.3-36.1) kg/m² , glycated haemoglobin 60.8 (44.3-83.6) mmol/mol (7.7 [6.2-9.8]%), and diabetes duration 4.5 (0.3-13.2) years. A total of 35 participants completed the trial and were included in the analyses. During the hypoglycaemic clamp from 5.5 mmol/L PG to nadir, the absolute change in mean glucagon concentration was similar for semaglutide vs placebo: 88.3 vs 83.1 pg/mL (estimated difference 5.2 pg/mL [95% confidence interval -7.7 to 18.1]). Concentrations of other counterregulatory hormones increased with both treatments, with a statistically significantly lower increase for noradrenaline and cortisol with semaglutide vs placebo. The glucose infusion rate to maintain constant clamp levels was similar for each treatment group, suggesting an overall similar counterregulatory response. The mean hypoglycaemic symptom score and proportion of participants recognizing hypoglycaemia during the study were lower for semaglutide vs placebo treatment at nadir, but cognitive function test results were similar. No new safety issues were observed for semaglutide.

CONCLUSIONS

Semaglutide treatment did not compromise the counterregulatory glucagon response during experimental hypoglycaemia in people with T2D.

Effects on the glucagon response to hypoglycaemia during DPP-4 inhibition in elderly subjects with type 2 diabetes: A randomized, placebo-controlled study

AIMS

Maintainance of glucagon response to hypoglycaemia is important as a safeguard against hypoglycaemia during glucose-lowering therapy in type 2 diabetes. During recent years, DPP-4 (dipeptidyl peptidase-4) inhibition has become more commonly used in elderly patients. However, whether DPP-4 inhibition affects the glucagon response to hypoglycaemia in the elderly is not known and was the aim of this study.

METHODS

In a single-centre, double-blind, randomized, placebo-controlled crossover study, 28 subjects with metformin-treated type 2 diabetes (17 male, 11 female; mean age, 74 years [range 65-86]; mean HbA1c, 51.5 mmol/mol [6.9%]) received sitagliptin (100 mg once daily) as add-on therapy or placebo for 4 weeks with a 4-week washout period in between. After each treatment period, the subjects underwent a standard breakfast test, followed by a 2-step hyperinsulinaemic hypoglycaemic clamp (target 3.5 and 3.0 mmol/L), followed by lunch.

RESULTS

Glucagon levels after breakfast and lunch, and the glucagon response at 3.5 mmol/L, were lower after sitagliptin than after placebo. However, the glucagon response to hypoglycaemia at 3.1 mmol/L did not differ significantly between the two. Similarly, the noradrenaline, adrenaline and cortisol responses were lower with sitagliptin than with placebo at 3.5 mmol/L, but not at 3.1 mmol/L glucose. Responses in pancreatic polypeptide did not differ between the two.

CONCLUSIONS

Elderly subjects with metformin-treated type 2 diabetes have lower glucagon levels at 3.5 mmol/L glucose, but maintain the glucagon response to hypoglycaemia at 3.1 mmol/L during DPP-4 inhibition, which safeguards against hypoglycaemia and may contribute to decreasing the risk of hypoglycaemia by DPP-4 inhibition in this age group.

Retrospective analysis of liraglutide and basal insulin combination therapy in Japanese type 2 diabetes patients: The association between remaining β-cell function and the achievement of the glycated hemoglobin target 1 year after initiation

AIMS/INTRODUCTION

The glucose-lowering effects of the glucagon-like peptide-1 receptor agonist, liraglutide, have been shown to rely on remaining β-cell function. However, the possible associations of remaining β-cell function with the glucose-lowering effects of liraglutide in combination with basal insulin remain unknown and warrant investigation.

MATERIALS AND METHODS

This was a single-center, retrospective, observational study carried out in a private hospital in Osaka, Japan. Type 2 diabetes patients who received a prescription change from insulin therapy, both multiple-dose insulin and basal insulin-supported oral therapy, to liraglutide and basal insulin combination and continued the therapy for 54 weeks without additional oral antidiabetic drugs or bolus insulin were retrospectively analyzed.

RESULTS

Among the 72 participants who received a prescription change from multiple-dose insulin and basal insulin-supported oral therapy to liraglutide and basal insulin combination, 57 continued the therapy for 54 weeks. Of those who continued the therapy without receiving additional oral antidiabetic drugs or bolus insulin, seven participants achieved glycated hemoglobin < 7.0% at 54 weeks, but 30 participants did not. The participants who achieved glycated hemoglobin < 7.0% at 54 weeks had a significantly higher C-peptide immunoreactivity index, a β-cell function-related index frequently used in Japanese clinical settings. The receiver operating curve analysis showed that the C-peptide immunoreactivity index cut-off value for the achievement of glycated hemoglobin <7.0% at 54 weeks is 1.103.

CONCLUSIONS

The current findings show that the glucose-lowering effects of liraglutide rely on remaining β-cell function, even when used with basal insulin; and suggest that liraglutide and basal insulin combination might require additional bolus insulin to fully compensate insulin insufficiency in individuals with reduced β-cell function.

Potential approaches to prevent hypoglycemia-associated autonomic failure

Clear health benefits are associated with intensive glucose control in type 1 diabetes mellitus (T1DM). However, maintaining near-normal glycemia remains an elusive goal for many patients, in large part owing to the risk of severe hypoglycemia. In fact, recurrent episodes of hypoglycemia lead to 'hypoglycemia-associated autonomic failure' (HAAF), characterized by defective counter-regulatory responses to hypoglycemia. Extensive studies to understand the mechanisms underlying HAAF have revealed multiple potential etiologies, suggesting various approaches to prevent the development of HAAF. In this review, we present an overview of the literature focused on pharmacological approaches that may prevent the development of HAAF. The purported underlying mechanisms of HAAF include: 1) central mechanisms (opioid receptors, ATP-sensitive K+(KATP) channels, adrenergic receptors, serotonin selective receptor inhibitors, γ-aminobuyric acid receptors, N-methyl D-aspartate receptors); 2) hormones (cortisol, estrogen, dehydroepiandrosterone (DHEA) or DHEA sulfate, glucagon-like peptide-1) and 3) nutrients (fructose, free fatty acids, ketones), all of which have been studied vis-à-vis their ability to impact the development of HAAF. A careful review of the current literature reveals many promising therapeutic approaches to treat or reduce this important limitation to optimal glycemic control.

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.

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.

Tackling dipeptidyl peptidase IV in neurological disorders

Dipeptidyl peptidase IV (DPP-IV) is a serine protease best known for its role in inactivating glucagon-like peptide-1 (GLP-1), pituitary adenylate cyclase-activating polypeptide (PACAP) and glucose-dependent insulinotropic peptide (GIP), three stimulators of pancreatic insulin secretion with beneficial effects on glucose disposal. Owing to the relationship between DPP-IV and these peptides, inhibition of DPP-IV enzyme activity is considered as an attractive treatment option for diabetic patients. Nonetheless, increasing studies support the idea that DPP-IV might also be involved in the development of neurological disorders with a neuroinflammatory component, potentially through its non-incretin activities on immune cells. In this review article, we aim at highlighting recent literature describing the therapeutic value of DPP-IV inhibitors for the treatment of such neurological conditions. Finally, we will illustrate some of the promising results obtained using berberine, a plant extract with potent inhibitory activity on DPP-IV.

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.

Effects of DPP-4 inhibitor linagliptin and GLP-1 receptor agonist liraglutide on physiological response to hypoglycaemia in Japanese subjects with type 2 diabetes: A randomized, open-label, 2-arm parallel comparative, exploratory trial

Dipeptidyl peptidase-4 (DPP-4) inhibitors reduce the risk of hypoglycaemia, possibly through augmentation of glucose-dependent insulinotropic polypeptide (GIP) action, but not that of glucagon-like peptide-1 (GLP-1) on glucagon secretion. To examine this model in Japanese individuals with type 2 diabetes (T2D), the effects of the DPP-4 inhibitor linagliptin on glucagon and other counter-regulatory hormone responses to hypoglycaemia were evaluated and compared with those of the GLP-1 receptor agonist liraglutide in a multi-centre, randomized, open-label, 2-arm parallel comparative, exploratory trial. Three-step hypoglycaemic clamp glucose tests preceded by meal tolerance tests were performed before and after 2-week treatment with the drugs. Glucagon levels were increased during the hypoglycaemic clamp test at 2.5 mmol/L. This increase was similar in the linagliptin and liraglutide groups, both before and after the 2-week treatment. Changes in other counter-regulatory hormones (ie, growth hormone, cortisol, epinephrine and norepinephrine) were also similar between the groups, but were suppressed substantially after 2-week treatment compared to baseline. In conclusion, we confirmed that the glucagon response to hypoglycaemia was not affected by linagliptin or liraglutide treatment in Japanese individuals with T2D.