Pronounced reduction of postprandial glucagon by lixisenatide: a meta-analysis of randomized clinical trials

The postprandial actions of GLP-1 receptor agonists: The missing link for cardiovascular and kidney protection in type 2 diabetes

Recent clinical trials in people with type 2 diabetes have demonstrated beneficial actions on heart and kidney outcomes following treatment with GLP-1RAs. In part, these actions are consistent with improved glucose control and significant weight loss. But GLP-1RAs may also have additive benefits by improving postprandial dysmetabolism. In diabetes, dysregulated postprandial nutrient excursions trigger inflammation, oxidative stress, endothelial dysfunction, thrombogenicity, and endotoxemia; alter hormone levels; and modulate cardiac output and regional blood and lymphatic flow. In this perspective, we explore the actions of GLP-1RAs on the postprandial state and their potential role in end-organ benefits observed in recent trials.

Effects of sequential treatment with lixisenatide, insulin glargine, or their combination on meal-related glycaemic excursions, insulin and glucagon secretion, and gastric emptying in patients with type 2 diabetes

AIM

To examine the glucose-lowering mechanisms of the glucagon-like peptide-1 receptor agonist lixisenatide after two subsequent meals and in combination with basal insulin.

MATERIALS AND METHODS

Twenty-eight metformin-treated patients with type 2 diabetes were randomly assigned to treatment sequences with either lixisenatide or insulin glargine alone for 4 weeks, and a combination of both treatments for 4 weeks. Metabolic examinations were performed before and after each treatment period following breakfast and a late lunch 8 hours later.

RESULTS

Lixisenatide mainly reduced postprandial glycaemia, while insulin glargine mainly reduced fasting glucose after breakfast (P < 0.05). This was partially preserved after a late lunch (P < 0.05). After breakfast, lixisenatide reduced insulin secretion and glucagon levels significantly. These effects were lost after a late lunch. Insulin glargine did not significantly reduce glucagon or insulin secretion. Gastric emptying was slowed by lixisenatide, but not by insulin glargine after breakfast. After the late lunch, lixisenatide slightly accelerated gastric emptying.

CONCLUSIONS

Lixisenatide decelerates gastric emptying after breakfast, thereby reducing glycaemic excursions, insulin secretion and glucagon levels. The glycaemic reduction persists until after a late lunch, despite accelerated gastric emptying. The combination with insulin glargine enhances the glucose-lowering effect because of complementary modes of action.

Lixisenatide Reduces Chylomicron Triacylglycerol by Increased Clearance

CONTEXT

Glucagon-like peptide-1 (GLP-1) agonists control postprandial glucose and lipid excursion in type 2 diabetes; however, the mechanisms are unclear.

OBJECTIVE

To determine the mechanisms of postprandial lipid and glucose control with lixisenatide (GLP-1 analog) in type 2 diabetes.

DESIGN

Randomized, double-blind, cross-over study.

SETTING

Centre for Diabetes, Endocrinology, and Research, Royal Surrey County Hospital, Guildford, United Kingdom.

PATIENTS

Eight obese men with type 2 diabetes [age, 57.3 ± 1.9 years; body mass index, 30.3 ± 1.0 kg/m2; glycosylated hemoglobin, 66.5 ± 2.6 mmol/mol (8.2% ± 0.3%)].

INTERVENTIONS

Two metabolic studies, 4 weeks after lixisenatide or placebo, with cross-over and repetition of studies.

MAIN OUTCOME MEASURES

Study one: very-low-density lipoprotein (VLDL) and chylomicron (CM) triacylglycerol (TAG) kinetics were measured with an IV bolus of [2H5]glycerol in a 12-hour study, with hourly feeding. Oral [13C]triolein, in a single meal, labeled enterally derived TAG. Study two: glucose kinetics were measured with [U-13C]glucose in a mixed-meal (plus acetaminophen to measure gastric emptying) and variable IV [6,6-2H2]glucose infusion.

RESULTS

Study one: CM-TAG (but not VLDL-TAG) pool-size was lower with lixisenatide (P = 0.046). Lixisenatide reduced CM [13C]oleate area under the curve (AUC)60-480min concentration (P = 0.048) and increased CM-TAG clearance, with no effect on CM-TAG production rate. Study two: postprandial glucose and insulin AUC0-240min were reduced with lixisenatide (P = 0.0051; P < 0.05). Total glucose production (P = 0.015), rate of glucose appearance from the meal (P = 0.0098), and acetaminophen AUC0-360min (P = 0.006) were lower with lixisenatide than with placebo.

CONCLUSIONS

Lixisenatide reduced [13C]oleate concentrations, derived from a single meal in CM-TAG and glucose rate of appearance from the meal through delayed gastric emptying. However, day-long CM production, measured with repeated meal feeding, was not reduced by lixisenatide and decreased CM-TAG concentration resulted from increased CM-TAG clearance.

Consistent findings in glycaemic control, body weight and hypoglycaemia with iGlarLixi (insulin glargine/lixisenatide titratable fixed-ratio combination) vs insulin glargine across baseline HbA1c, BMI and diabetes duration categories in the LixiLan-L trial

AIMS

To assess the impact of baseline characteristics on clinical outcomes in the LixiLan-L trial, a randomized open-label trial designed to evaluate the efficacy and safety of iGlarLixi, a novel fixed-ratio combination of insulin glargine 100 U (iGlar) plus lixisenatide, in comparison with iGlar over 30 weeks in a population of patients with type 2 diabetes mellitus (T2DM) inadequately controlled on a previous regimen of basal insulin alone or in combination with 1 or 2 oral glucose-lowering drugs.

MATERIALS AND METHODS

In this exploratory analysis of LixiLan-L (N = 736), efficacy outcomes were assessed within population subgroups derived from the following baseline characteristics: glycated haemoglobin [HbA1c; <8%, ≥8% (<64, ≥64 mmol/mol)]; duration of T2DM (<10, ≥10 years); body mass index (<30, ≥30 kg/m2 ). Furthermore, the incidence of symptomatic hypoglycaemia with plasma glucose ≤3.9 mmol/L (≤70 mg/dL) was also analysed according to the same subgroups.

RESULTS

Compared with the iGlar treatment group, patients treated with iGlarLixi showed consistently greater reductions in HbA1c during the treatment period, with higher percentages of patients achieving the HbA1c target level of <7% (<53 mmol/mol) in all of the subpopulations tested (P < .0001 for all), having consistent mitigation of body weight gain and with no major differences in the incidence of hypoglycaemia.

CONCLUSIONS

iGlarLixi consistently improved glycaemic control compared with iGlar in all baseline characteristic subgroups of patients with T2DM inadequately controlled with insulin, including difficult-to-treat subgroups of patients with long duration of diabetes, obesity and high HbA1c. Clinical trial number: NCT02058160 (clinicaltrials.gov).

Lixisenatide, a Once-Daily Prandial Glucagon-Like Peptide-1 Receptor Agonist for the Treatment of Adults with Type 2 Diabetes

Lixisenatide, a short-acting glucagon-like peptide-1 receptor agonist (GLP-1 RA), has been available in Europe since 2013 and was recently approved in the United States for the treatment of type 2 diabetes (T2D) as an adjunct to diet and exercise. The objective of this systematic review is to describe the pharmacology, pharmacokinetics, safety, and efficacy of lixisenatide in patients with T2D. We conducted a search of the EMBASE database, limited to human studies with abstracts available in English. Published conference abstracts, limited to the American Diabetes Association (ADA) and the European Association for the Study of Diabetes meetings in 2015, as well as abstracts presented at the ADA meeting in 2016, were also screened. The abstracts retrieved were assessed for relevance; review articles and meta-analyses focusing on GLP-1 RAs as a class were excluded. Lixisenatide induced mean reductions of 0.46-0.99% in glycated hemoglobin A_1c (Hb_A1c ), 55.86-143.43 mg/dl in 2-hour postprandial glucose (PPG) levels, and 56.58-127.75 mg/dl in mealtime glucose level variations. Changes in fasting plasma glucose (FPG) levels and weight ranged from -21.98 to +5.41 mg/dl and from -2.96 to +0.3 kg, respectively, in patients with T2D enrolled in the GetGoal clinical program (a program of clinical trials that established the efficacy and safety profile of lixisenatide 20 μg once/day across patients with T2D with differing background therapies). Lixisenatide was well tolerated, demonstrating rates of symptomatic hypoglycemia of 0.8-42.9% and a very low rate of severe hypoglycemia (< 1.5%) as well as no increased risk of cardiovascular events. The most common adverse events were gastrointestinal in nature, mainly transient nausea and vomiting of mild-to-moderate severity. Lixisenatide effectively lowers Hb_A1c levels in patients with T2D through a mechanism of action complementary to that of agents that mainly target FPG, with the additional benefit of weight loss. Its once-daily administration schedule and effect on PPG levels make it an attractive option as add-on treatment to basal insulin therapy or oral antidiabetic agents.

What next after basal insulin? Treatment intensification with lixisenatide in Asian patients with type 2 diabetes mellitus

There is increasing evidence that the pathophysiology of type 2 diabetes mellitus (T2DM) in Asian patients differs from that in Western patients, with early phase insulin deficiencies, increased postprandial glucose excursions, and increased sensitivity to insulin. Asian patients may also experience higher rates of gastrointestinal adverse events associated with glucagon-like peptide-1 receptor agonists (GLP-1RAs), such as nausea and vomiting, compared with their Western counterparts. These factors should be taken into consideration when selecting therapy for basal insulin treatment intensification in Asian patients. However, the majority of studies to establish various agents for treatment intensification in T2DM have been conducted in predominantly Western populations, and the levels of evidence available in Chinese or Asian patients are limited. This review discusses the different mechanisms of action of short-acting, prandial, and long-acting GLP-1RAs in addressing hyperglycemia, and describes the rationale and available clinical data for basal insulin in combination with the short-acting prandial GLP-1RA lixisenatide, with a focus on treatment of Asian patients with T2DM.

A global study of the unmet need for glycemic control and predictor factors among patients with type 2 diabetes mellitus who have achieved optimal fasting plasma glucose control on basal insulin

BACKGROUND

This study used data from different sources to identify the extent of the unmet need for postprandial glycemic control in patients with type 2 diabetes mellitus (T2DM) after the initiation of basal insulin therapy in Europe, Asia Pacific, the United States, and Latin America.

METHODS

Different levels of evidence were used as available for each country/region, with data extracted from seven randomized controlled trials (RCTs), three clinical trial registries (CTRs), and three electronic medical record (EMR) databases. Glycemic status was categorized as "well controlled" (glycated hemoglobin [HbA1c ] at target [<7%]), "residual hyperglycemia" (fasting plasma glucose [FPG] but not HbA1c at target [FPG <7.2/7.8 mmol/L, <130/140 mg/dL, depending on country-specific recommendations]), or "uncontrolled" (both FPG and HbA1c above target). Predictor factors were identified from the RCT data set using logistic regression analysis.

RESULTS

RCT data showed that 16.9% to 28.0%, 42.7% to 54.4%, and 16.9% to 38.1% of patients with T2DM had well-controlled glycemia, residual hyperglycemia, and uncontrolled hyperglycemia, respectively. In CTRs, respective ranges were 21.8% to 33.6%, 31.5% to 35.6%, and 30.7% to 46.8%, and in EMR databases were 4.4% to 21.0%, 23.9% to 31.8%, and 53.6% to 63.8%. Significant predictor factors of residual hyperglycemia identified from RCT data included high baseline HbA1c (all countries/regions except Brazil), high baseline FPG (United Kingdom/Japan), longer duration of diabetes (Brazil), and female sex (Europe/Latin America).

CONCLUSIONS

Irrespective of intrinsic differences between data sources, 24% to 54% of patients with T2DM globally had residual hyperglycemia with HbA1c not at target, despite achieving FPG control, indicating a significant unmet need for postprandial glycemic control.

Rationale for treatment options for mealtime glucose control in patients with type 2 diabetes

While glycemic control is routinely assessed using HbA1c and fasting glucose measures, postprandial glucose (PPG) is also an important contributor of overall glycemia. Furthermore, PPG excursions have been linked to complications of diabetes. This review examines the effects of glucose-lowering therapies (including treatments administered at mealtime) on postprandial hyperglycemia in patients with type 2 diabetes. A PubMed search was conducted to identify clinical studies of treatments for mealtime glucose control in type 2 diabetes. Different treatments may have comparable effects on HbA1c but varying effects on PPG control and glucose fluctuations. Older classes of oral glucose-lowering treatments administered at mealtime to lower PPG include meglitinides and α-glucosidase inhibitors. Injectable therapies, including prandial insulin analogs, glucagon-like peptide-1 receptor agonists (GLP-1RAs), and the amylin analog pramlintide, all effectively target postprandial hyperglycemia. Compared with longer-acting GLP-1RAs, short-acting GLP-1RAs, such as exenatide twice daily and lixisenatide once daily, have a greater effect on PPG control, which is primarily mediated by a more pronounced effect on delayed gastric emptying. Dipeptidyl peptidase-4 inhibitors and sodium-glucose cotransporter 2 inhibitors also reduce postprandial hyperglycemia. To achieve more physiologically normal glycemic control, choice of therapy should ideally aim to address daily glucose fluctuations, including hyperglycemic peaks and hypoglycemic troughs, and long-term glycemic control.

Predictors of outcomes in patients with type 2 diabetes in the lixisenatide GetGoal clinical trials

AIMS

To explore the treatment outcomes in adult patients with type 2 diabetes (T2D) enrolled in the GetGoal trials of lixisenatide (LIXI), and the predictive effects of baseline characteristics on outcomes.

METHODS

This study was a pooled analysis of patient-level data from the LIXI GetGoal studies comparing LIXI and placebo. Patients were divided into baseline therapy groups: those receiving oral antidiabetes drugs (OADs) at baseline (n = 2760) or those receiving basal insulin at baseline (n = 1198).

RESULTS

Compared with placebo, LIXI treatment led to significantly greater reductions in glycated haemoglobin (HbA1c), and greater achievement of the composite endpoint of HbA1c <7.0% (53 mmol/mol) with no symptomatic hypoglycaemia and no weight gain in either the OAD (34% vs 18%; P < .0001) or the basal insulin groups (19% vs 10%; P < .0001). Treatment with LIXI was associated with a greater percentage of patients experiencing a symptomatic hypoglycaemic event compared with placebo in both the OAD (5% vs 3%; P = .0098) and basal insulin groups (27% vs 17%; P < .0001). In assessing baseline factors that were predictors of treatment outcomes, only baseline HbA1c and LIXI treatment were strong predictors of outcomes in both the OAD and basal insulin groups. No other baseline characteristic had such a large or consistent clinically relevant predictive effect across treatment outcomes.

CONCLUSIONS

The results from this study show that irrespective of baseline characteristics, LIXI treatment, as an add-on to OAD or basal insulin therapy, is effective in reducing HbA1c and achieving composite endpoints.

A Plethora of GLP-1 Agonists: Decisions About What to Use and When

Incretin-based therapies are important addition to our armamentarium for the treatment of type 2 diabetes (T2DM). There are six Glucagon-like peptide-1 receptor agonists (GLP-1RAs) which have received regulatory approval for clinical use. The short-acting GLP-1RAs include exenatide twice daily, liraglutide once daily, and lixisenatide once daily. The approved long-acting GLP-1RAs are administered weekly and are exenatide, albiglutide, and dulaglutide. Although all of these therapies lower hemoglobin A1C (HbA1C), there also are unique features of GLP-1RAs that have been made manifest from clinical trial data with regard to weight-loss efficacy, fasting and post-prandial glucose control, cardiovascular safety and protection, and gastrointestinal and injection adverse effects. It is imperative to consider these features when tailoring the choice of a GLP-1RA to patient specific characteristics.

Pharmacology and therapeutic implications of current drugs for type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a global epidemic that poses a major challenge to health-care systems. Improving metabolic control to approach normal glycaemia (where practical) greatly benefits long-term prognoses and justifies early, effective, sustained and safety-conscious intervention. Improvements in the understanding of the complex pathogenesis of T2DM have underpinned the development of glucose-lowering therapies with complementary mechanisms of action, which have expanded treatment options and facilitated individualized management strategies. Over the past decade, several new classes of glucose-lowering agents have been licensed, including glucagon-like peptide 1 receptor (GLP-1R) agonists, dipeptidyl peptidase 4 (DPP-4) inhibitors and sodium/glucose cotransporter 2 (SGLT2) inhibitors. These agents can be used individually or in combination with well-established treatments such as biguanides, sulfonylureas and thiazolidinediones. Although novel agents have potential advantages including low risk of hypoglycaemia and help with weight control, long-term safety has yet to be established. In this Review, we assess the pharmacokinetics, pharmacodynamics and safety profiles, including cardiovascular safety, of currently available therapies for management of hyperglycaemia in patients with T2DM within the context of disease pathogenesis and natural history. In addition, we briefly describe treatment algorithms for patients with T2DM and lessons from present therapies to inform the development of future therapies.

Postprandial Glucagon Reductions Correlate to Reductions in Postprandial Glucose and Glycated Hemoglobin with Lixisenatide Treatment in Type 2 Diabetes Mellitus: A Post Hoc Analysis

INTRODUCTION

The extent to which postprandial glucagon reductions contribute to lowering of postprandial glucose in patients with type 2 diabetes mellitus (T2DM) is currently unknown. The aim of this analysis was to determine whether a reduction in postprandial glucagon following treatment with the glucagon-like peptide-1 receptor agonist lixisenatide correlates with a reduction in postprandial glucose and glycated hemoglobin (HbA1c) in patients with T2DM.

METHODS

A post hoc analysis was performed on pooled data from the modified intent-to-treat populations of two lixisenatide Phase 3 trials: GetGoal-M (lixisenatide versus placebo as add-on to metformin) and GetGoal-S (lixisenatide versus placebo as add-on to sulfonylurea [SU] ± metformin). Glucagon levels were assessed 2 h after a standardized meal test performed at baseline and Week 24 and were examined for correlation with changes in 2-h postprandial glucose and HbA1c.

RESULTS

Lixisenatide reduced 2-h postprandial glucagon at Week 24 compared with placebo (P < 0.00001). The mean change in postprandial glucagon significantly correlated with reductions in postprandial glucose (P < 0.00001) and HbA1c (P < 0.00001).

CONCLUSION

A reduction in postprandial glucagon following lixisenatide administration correlated with a decrease in postprandial glucose and HbA1c in patients with T2DM insufficiently controlled on metformin and/or SU. This suggests that lowering of postprandial glucagon contributes to the overall glycemic improvement observed with lixisenatide.

FUNDING

Sanofi.

CLINICAL TRIAL NUMBERS

NCT00712673 (GetGoal-M) and NCT00713830 (GetGoal-S).

Prandial Options to Advance Basal Insulin Glargine Therapy: Testing Lixisenatide Plus Basal Insulin Versus Insulin Glulisine Either as Basal-Plus or Basal-Bolus in Type 2 Diabetes: The GetGoal Duo-2 Trial

OBJECTIVE

To provide evidence-based options on how to intensify basal insulin, we explored head-to-head prandial interventions in overweight patients with type 2 diabetes inadequately controlled on basal insulin glargine with or without 1-3 oral antidiabetic agents (OADs).

RESEARCH DESIGN AND METHODS

Patients were randomized to lixisenatide once daily or insulin glulisine given once or thrice daily, added to glargine, with or without metformin, if HbA1c remained ≥7 to ≤9% (≥53 to ≤75 mmol/mol) after 12 weeks of glargine optimization with OADs other than metformin stopped at the start of optimization. Coprimary end points at 26 weeks were 1) noninferiority (95% CI upper bound <0.4% [<4.4 mmol/mol]) in HbA1c reduction with lixisenatide versus glulisine once daily, and either 2a) noninferiority in HbA1c reduction for lixisenatide versus glulisine thrice daily or 2b) superiority in body weight change for lixisenatide versus glulisine thrice daily. Fasting and postprandial plasma glucose, composite efficacy/safety end points, and adverse events were also assessed.

RESULTS

Baseline characteristics were similar between arms (n = 298, diabetes and basal insulin duration of 12.2 and 3.2 years, respectively; BMI 32.2 kg/m(2)). HbA1c improved from 8.5% to 7.9% (69 to 63 mmol/mol) with glargine optimization and further to 7.2%, 7.2%, and 7.0% (55, 55, and 53 mmol/mol) with lixisenatide and glulisine once daily and thrice daily, respectively; all coprimary end points were met. Symptomatic hypoglycemia and body weight were lower in lixisenatide versus glulisine patients. More gastrointestinal events occurred with lixisenatide.

CONCLUSIONS

Short-acting glucagon-like peptide-1 receptor agonists as add-on to basal insulin may become a preferred treatment intensification option, attaining meaningful glycemic targets with fewer hypoglycemic events without weight gain versus basal-plus or basal-bolus in uncontrolled basal insulin-treated type 2 diabetes.

Effect of the GLP-1 Receptor Agonist Lixisenatide on Counterregulatory Responses to Hypoglycemia in Subjects With Insulin-Treated Type 2 Diabetes

OBJECTIVE

Counterregulatory responses are critical to prevent hypoglycemia in subjects with type 2 diabetes. This is particularly important in insulin-treated patients. This study explored the effect of the glucagon-like peptide 1 receptor agonist lixisenatide on the hormonal counterregulatory responses to insulin-induced hypoglycemia when added to basal insulin therapy in subjects with type 2 diabetes.

RESEARCH DESIGN AND METHODS

The study was a single-center, double-blind, randomized, placebo-controlled crossover study involving 18 subjects with type 2 diabetes (11 males) with a mean age of 55 years, diabetes duration of 12 years, HbA1c level of 7.7%, fasting blood glucose (FBG) concentration of 9.7 mmol/L, and a BMI of 33 kg/m(2), who were treated with basal insulin (mean duration 7 years, daily dose 39 units/day) and metformin (mean daily dose 2.1 g). Subjects received treatment with lixisenatide or placebo for 6 weeks in random order, with a 4-week washout period in between. After 6 weeks of treatment, subjects underwent a two-step hyperinsulinemic hypoglycemic clamp at 3.5 and 2.8 mmol/L.

RESULTS

After 6 weeks of treatment, HbA1c and FBG levels were lower after lixisenatide therapy than after placebo therapy. At the hypoglycemic level of 3.5 mmol/L, glucagon and epinephrine levels were significantly lower during lixisenatide treatment than during placebo treatment, whereas at 2.8 mmol/L glucagon and epinephrine levels did not differ between the subjects. Cortisol, pancreatic polypeptide, and norepinephrine levels did not differ significantly between the treatments.

CONCLUSIONS

Glucagon and epinephrine levels are reduced by lixisenatide at a concentration of 3.5 mmol/L, but their counterregulatory responses to deep hypoglycemia at a concentration of 2.8 mmol/L are sustained during treatment with lixisenatide in combination with basal insulin.

Glucagon-like polypeptide agonists in type 2 diabetes mellitus: efficacy and tolerability, a balance

Glucagon-like polypeptide (GLP-1) receptor agonist treatment has multiple effects on glucose metabolism, supports the β cell, and promotes weight loss. There are now five GLP-1 agonists in clinical use with more in development. GLP-1 treatment typically can induce a lowering of hemoglobin A1c (HbA1c) of 0.5-1.5% over time with weight loss of 2-5%. In some individuals, a progressive loss of weight occurs. There is evidence that GLP-1 therapy opposes the loss of β cells which is a feature of type 2 diabetes. The chief downside of GLP-1 treatment is the gastrointestinal motility disturbance which is one of the modes of action of the hormone; significant nausea, vomiting, and diarrhea may lead to discontinuation of treatment. Although daily injection of GLP-1 agents is successful, the development of extended release preparations allows for injection once weekly, and perhaps much longer in the future. The indication for GLP-1 use is diabetes, but now, liraglutide has been approved for primary treatment of obesity. When oral agents fail to control glucose levels in type 2 diabetes, there is a choice between long-acting insulin and GLP-1 agonists as additional treatments. The lowering of HbA1c by either modality is equivalent in most studies. Patients lose weight with GLP-1 treatment and gain weight on insulin. There is a lower incidence of hypoglycemia with GLP-1 therapy but a much higher incidence of gastrointestinal complaints. Insulin dosing is flexible while GLP-1 agents have historically been administered at fixed dosages. Now, the use of combined long-acting insulin and GLP-1 agonists is promising a major therapeutic change. Combined therapy takes advantage of the benefits of both insulin and GLP-1 agents. Furthermore, direct admixture of both in the same syringe will permit flexible dosing, improvement of glucose levels, and reduction of both hypoglycemia and gastrointestinal side effects.

Glucagon--Early breakthroughs and recent discoveries

Glucagon was discovered in 1922 as a hyperglycemic factor in the pancreas. During its early history up to 1970, glucagon was shown to increase circulating glucose through stimulating glycogenolysis in the liver. It was also shown to be a constituent of islet non-β cells and to signal through G protein coupled receptors and cyclic AMP. Furthermore, its chemical characteristics, including amino acid sequence, and its processing from the preproglucagon gene had been established. During the modern research during the last 40 years, glucagon has been established as a key hormone in the regulation of glucose homeostasis, including a key role for the glucose counterregulation to hypoglycemia and for development of type 2 diabetes, and today glucagon is a potential target for treatment of the disease. Glucagon has also been shown to be a key factor beyond glucose control and involved in many processes. For the coming, future research, studies will be focused on α-cell biology beyond glucagon, hyperglucagonemia in other conditions than diabetes, its involvement in the regulation of body weight and energy expenditure and the potential of glucagon as a target for other diseases than type 2 diabetes, such as type 1 diabetes and obesity. This review summarizes the more than 90 years history of this important hormone as well as discusses potential future research regarding glucagon.

Lixisenatide accelerates restoration of normoglycemia and improves human beta-cell function and survival in diabetic immunodeficient NOD-scid IL-2rg(null) RIP-DTR mice engrafted with human islets

OBJECTIVE

Glucagon-like peptide-1 induces glucose-dependent insulin secretion and, in rodents, increases proliferation and survival of pancreatic beta cells. To investigate the effects on human beta cells, we used immunodeficient mice transplanted with human islets. The goal was to determine whether lixisenatide, a glucagon-like peptide-1 receptor agonist, improves human islet function and survival in vivo.

METHODS

Five independent transplant studies were conducted with human islets from five individual donors. Diabetic human islet-engrafted immunodeficient mice were treated with lixisenatide (50, 150, and 500 µg/kg) or vehicle. Islet function was determined by blood glucose, plasma human insulin/C-peptide, and glucose tolerance tests. Grafts were analyzed for total beta- and alpha-cell number, percent proliferation, and levels of apoptosis.

RESULTS

Diabetic mice transplanted with marginal human islet mass and treated with lixisenatide were restored to euglycemia more rapidly than vehicle-treated mice. Glucose tolerance tests, human plasma insulin, and glucose-stimulation indices of lixisenatide-treated mice were significantly improved compared to vehicle-treated mice. The percentages of proliferating or apoptotic beta cells at graft recovery were not different between lixisenatide-treated and vehicle-treated mice. Nevertheless, in one experiment we found a significant twofold to threefold increase in human beta-cell numbers in lixisenatide-treated compared to vehicle-treated mice.

CONCLUSION

Diabetic human islet-engrafted immunodeficient mice treated with lixisenatide show improved restoration of normoglycemia, human plasma insulin, and glucose tolerance compared to vehicle-treated mice engrafted with the same donor islets. Because the proliferative capacity of human beta cells is limited, improved beta-cell survival coupled with enhanced beta-cell function following lixisenatide treatment may provide the greatest benefit for diabetic patients with reduced functional islet mass.

Basal insulin combined incretin mimetic therapy with glucagon-like protein 1 receptor agonists as an upcoming option in the treatment of type 2 diabetes: a practical guide to decision making

The combination of basal insulin and glucagon-like protein 1 receptor agonists (GLP-1 RAs) is a new intriguing therapeutic option for patients with type 2 diabetes. In our daily practice we abbreviate this therapeutic concept with the term BIT (basal insulin combined incretin mimetic therapy) in a certain analogy to BOT (basal insulin supported oral therapy). In most cases BIT is indeed an extension of BOT, if fasting, prandial or postprandial blood glucose values have not reached the target range. In our paper we discuss special features of combinations of short- or prandial-acting and long- or continuous-acting GLP-1 RAs like exenatide, lixisenatide and liraglutide with basal insulin in relation to different glycemic targets. Overall it seems appropriate to use a short-acting GLP-1 RA if, after the near normalization of fasting blood glucose with BOT, the prandial or postprandial values are elevated. A long-acting GLP-1 RA might well be given, if fasting blood glucose values are the problem. Based on pathophysiological findings, recent clinical studies and our experience with BIT and BOT as well as BOTplus we developed chart-supported algorithms for decision making, including features and conditions of patients. The development of these practical tools was guided by the need for a more individualized antidiabetic therapy and the availability of the new BIT principle.