Antidiabetic actions of endogenous and exogenous GLP-1 in type 1 diabetic patients with and without residual β-cell function

Critical role for GLP-1 in symptomatic post-bariatric hypoglycaemia

AIMS/HYPOTHESIS

Post-bariatric hypoglycaemia (PBH) is a rare, but severe, metabolic disorder arising months to years after bariatric surgery. It is characterised by symptomatic postprandial hypoglycaemia, with inappropriately elevated insulin concentrations. The relative contribution of exaggerated incretin hormone signalling to dysregulated insulin secretion and symptomatic hypoglycaemia is a subject of ongoing inquiry. This study was designed to test the hypothesis that PBH and associated symptoms are primarily mediated by glucagon-like peptide-1 (GLP-1).

METHODS

We conducted a double-blinded crossover study wherein eight participants with confirmed PBH were assigned in random order to intravenous infusion of the GLP-1 receptor (GLP-1r) antagonist. Exendin (9-39) (Ex-9), or placebo during an OGTT on two separate days at the Stanford University Clinical and Translational Research Unit. Metabolic, symptomatic and pharmacokinetic variables were evaluated. Results were compared with a cohort of BMI- and glucose-matched non-surgical controls (NSCs).

RESULTS

Infusion of Ex-9 decreased the time to peak glucose and rate of glucose decline during OGTT, and raised the postprandial nadir by over 70%, normalising it relative to NSCs and preventing hypoglycaemia in all PBH participants. Insulin AUC and secretion rate decreased by 57% and 71% respectively, and peak postprandial insulin was normalised relative to NSCs. Autonomic and neuroglycopenic symptoms were significantly reduced during Ex-9 infusion.

CONCLUSIONS/INTERPRETATION

GLP-1r blockade prevented hypoglycaemia in 100% of individuals, normalised beta cell function and reversed neuroglycopenic symptoms, supporting the conclusion that GLP-1 plays a primary role in mediating hyperinsulinaemic hypoglycaemia in PBH. Competitive antagonism at the GLP-1r merits consideration as a therapeutic strategy.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02550145.

Effect of GLP-1 receptor agonist treatment on body weight in obese antipsychotic-treated patients with schizophrenia: a randomized, placebo-controlled trial

AIMS

Schizophrenia is associated with cardiovascular co-morbidity and a reduced life-expectancy of up to 20 years. Antipsychotics are dopamine D₂ receptor antagonists and are the standard of medical care in schizophrenia, but the drugs are associated with severe metabolic side effects such as obesity and diabetes. Glucagon-like peptide-1 receptor agonists (GLP-1RAs) are registered for treatment of both obesity and type 2 diabetes. We investigated metabolic effects of the GLP-1RA, exenatide once-weekly, in non-diabetic, antipsychotic-treated, obese patients with schizophrenia.

MATERIAL AND METHODS

Antipsychotic-treated, obese, non-diabetic, schizophrenia spectrum patients were randomized to double-blinded adjunctive treatment with once-weekly subcutaneous exenatide (n = 23) or placebo (n = 22) injections for 3 months. The primary outcome was loss of body weight after treatment and repeated measures analysis of variance was used as statistical analysis.

RESULTS

Between March 2013 and June 2015, 40 patients completed the trial. At baseline, mean body weight was 118.3 ± 16.0 kg in the exenatide group and 111.7 ± 18.0 kg in the placebo group, with no group differences ( P = .23). The exenatide and placebo groups experienced significant ( P = .004), however similar ( P = .98), weight losses of 2.24 ± 3.3 and 2.23 ± 4.4 kg, respectively, after 3 months of treatment.

CONCLUSIONS

Treatment with exenatide once-weekly did not promote weight loss in obese, antipsychotic-treated patients with schizophrenia compared to placebo. Our results could suggest that the body weight-lowering effect of GLP-1RAs involves dopaminergic signaling, but blockade of other receptor systems may also play a role. Nevertheless, anti-obesity regimens effective in the general population may not be readily implemented in antipsychotic-treated patients with schizophrenia.

Addressing Unmet Medical Needs in Type 1 Diabetes: A Review of Drugs Under Development

INTRODUCTION

The incidence of type 1 diabetes (T1D) is increasing worldwide and there is a very large need for effective therapies. Essentially no therapies other than insulin are currently approved for the treatment of T1D. Drugs already in use for type 2 diabetes and many new drugs are under clinical development for T1D, including compounds with both established and new mechanisms of action. Content of the Review: Most of the new compounds in clinical development are currently in Phase 1 and 2. Drug classes discussed in this review include new insulins, SGLT inhibitors, GLP-1 agonists, immunomodulatory drugs including autoantigens and anti-cytokines, agents that regenerate β-cells and others. Regulatory Considerations: In addition, considerations are provided with regard to the regulatory environment for the clinical development of drugs for T1D, with a focus on the United States Food and Drug Administration and the European Medicines Agency. Future opportunities, such as combination treatments of immunomodulatory and beta-cell regenerating therapies, are also discussed.

Insulin resistance, role of metformin and other non-insulin therapies in pediatric type 1 diabetes

Type 1 diabetes mellitus (T1DM) in youth is a challenging chronic medical condition. Its management should address not only the glycemic control but also insulin resistance and cardiovascular disease risk factors which are increasingly recognized to be present in youth with TID. Current knowledge on the mechanisms of insulin resistance in T1DM is reviewed. The use of adjunctive therapies that are beneficial to achieve adequate glycemic control while mitigating the effects of insulin resistance are discussed with a focus on metformin therapy and an overview of other new pharmacologic agents.

Liraglutide for treating type 1 diabetes

INTRODUCTION

Many persons with type 1 diabetes do not achieve glycemic targets, why new treatments, complementary to insulin, are of interest. Liraglutide, a long-acting glucagon-like peptide-1 receptor agonist could be a potential pharmacological supplement to insulin. This review discusses the mechanism of actions, efficacy and safety of liraglutide as add-on to insulin in persons with type 1 diabetes.

AREAS COVERED

Physiological and clinical data on liraglutide in type 1 diabetes were reviewed. We searched the Cochrane library, MEDLINE and EMBASE, with the final search performed February 16, 2016.

EXPERT OPINION

Liraglutide as adjunct to insulin treatment reduced body weight and daily dose of insulin compared with insulin alone. The effect on HbA1c was inconsistent with mostly uncontrolled, small-scale studies reporting improvements in glycemic control. In placebo-controlled studies there was no clinically relevant effect on HbA1c. Adverse events were mostly transient gastrointestinal side effects, primarily nausea. Based on the available data, liraglutide cannot be recommended as add-on therapy to insulin in persons with type 1 diabetes with the aim to improve glycemic control. Ongoing trials in newly diagnosed patients with type 1 diabetes and in insulin pump-treated patients will help define the future role of liraglutide therapy in type 1 diabetes.

Efficacy and Safety of Liraglutide Added to Capped Insulin Treatment in Subjects With Type 1 Diabetes: The ADJUNCT TWO Randomized Trial

OBJECTIVE

To investigate the efficacy and safety of liraglutide added to capped insulin doses in subjects with type 1 diabetes.

RESEARCH DESIGN AND METHODS

A 26-week, placebo-controlled, double-blind, parallel-group trial enrolling 835 subjects randomized 3:1 receiving once-daily subcutaneous liraglutide (1.8, 1.2, and 0.6 mg) or placebo added to an individually capped total daily dose of insulin.

RESULTS

Mean baseline glycated hemoglobin (HbA1c) (8.1% [65.0 mmol/mol]) was significantly decreased with liraglutide versus placebo at week 26 (1.8 mg: -0.33% [3.6 mmol/mol]; 1.2 mg: -0.22% [2.4 mmol/mol]; 0.6 mg: -0.23% [2.5 mmol/mol]; placebo: 0.01% [0.1 mmol/mol]). Liraglutide significantly reduced mean body weight (-5.1, -4.0, and -2.5 kg for 1.8, 1.2, and 0.6 mg, respectively) versus placebo (-0.2 kg). Significant reductions in daily insulin dose and increases in quality of life were seen with liraglutide versus placebo. There were higher rates of symptomatic hypoglycemia (21.3 vs. 16.6 events/patient/year; P = 0.03) with liraglutide 1.2 mg vs. placebo and of hyperglycemia with ketosis >1.5 mmol/L with liraglutide 1.8 mg vs. placebo (0.5 vs. 0.1 events/patient/year; P = 0.01).

CONCLUSIONS

In a broad population of subjects with long-standing type 1 diabetes, liraglutide added to capped insulin reduced HbA1c, body weight, and insulin requirements but with higher rates of hypoglycemia for liraglutide 1.2 mg and hyperglycemia with ketosis for liraglutide 1.8 mg.

Non-insulin drugs to treat hyperglycaemia in type 1 diabetes mellitus

Insulin treatment of individuals with type 1 diabetes has shortcomings and many patients do not achieve glycaemic and metabolic targets. Consequently, the focus is on novel non-insulin therapeutic approaches that reduce hyperglycaemia and improve metabolic variables without increasing the risk of hypoglycaemia or other adverse events. Several therapies given in conjunction with insulin have been investigated in clinical trials, including pramlintide, glucagon-like peptide-1 receptor agonists, dipeptidyl peptidase-4 inhibitors, sodium-glucose co-transporter inhibitors, metformin, sulfonylureas, and thiazolidinediones. These drugs have pleiotropic effects on glucose metabolism and different actions complementary to those of insulin-this Review reports the effects of these drugs on glycaemic control, glucose variability, hypoglycaemia, insulin requirements, and bodyweight. Existing studies are of short duration with few participants; evidence for the efficacy of concomitant treatments is scarce and largely clinically insignificant. A subgroup of patients with type 1 diabetes for whom non-insulin antidiabetic drugs could significantly benefit glycaemic control cannot yet be defined, but we suggest that obese patients prone to hypoglycaemia and patients with residual β-cell function are populations of interest for future trials.

Short-term administration of the GLP-1 analog liraglutide decreases circulating leptin and increases GIP levels and these changes are associated with alterations in CNS responses to food cues: A randomized, placebo-controlled, crossover study

BACKGROUND

GLP-1 agonists, including liraglutide, have emerged as effective therapies for type 2 diabetes (DM) and obesity. Here, we attempted to delineate how liraglutide, at doses approved for DM, may impact circulating hormones influencing energy homeostasis in diabetics.

BASIC PROCEDURES

Using a randomized, placebo-controlled, double-blind, cross-over trial of 20 patients with type 2 diabetes, we examined the effects of liraglutide as compared to placebo on fasting levels of circulating hormones important to energy homeostasis, including leptin, ghrelin, PYY, and GIP. After 17days (0.6mg for 7days, 1.2mg for 7days and 1.8mg for 3days) of treatment, we also studied changes in fMRI responses to food cues.

MAIN FINDINGS

By design, to avoid any confounding by weight changes, subjects were studied for 17days, i.e. before body weight changed. Participants on liraglutide had significantly increased GLP-1 levels (p<0.001), decreased percent change in leptin levels (p<0.01) and increased GIP levels (p<0.03) in comparison to placebo treated subjects. Whole brain regressions of functional activity in response to food cues reveal that increased GIP levels were associated with deactivation of the attention- and reward-related insula. Decreases in leptin levels were associated with activations in the reward-related midbrain, precuneus, and dorsolateral prefrontal cortex (DLPFC), and sensorimotor-related motor cortex and with deactivations in the attention-related parietal cortex and the cognitive control-related thalamus and pre-SMA.

PRINCIPAL CONCLUSIONS

We demonstrate herein short-term changes to circulating levels of GIP and leptin in response to GLP-1 agonist liraglutide therapy. These findings suggest that liraglutide may alter the circulating levels of hormones important in energy homeostasis that, in turn, influence CNS perception of food cues. This could possibly lead to compensatory changes in energy homeostasis that could over time limit the efficacy of liraglutide to decrease body weight. These novel findings, which, pointing to the potential advantages of combination therapies, may have therapeutic implications, will need to be confirmed by larger and longer-term trials.

GLP-1 Agonists in Type 1 Diabetes Mellitus

OBJECTIVE

To review the use of GLP-1 agonists in patients with type 1 diabetes mellitus (T1DM).

DATA SOURCES

A search using the MEDLINE database, EMBASE, and Cochrane Database was performed through March 2016 using the search terms glucagon-like peptide 1 (GLP-1) agonists, incretin, liraglutide, exenatide, albiglutide, dulaglutide, type 1 diabetes mellitus

STUDY SELECTION AND DATA EXTRACTION

All English-language trials that examined glycemic end points using GLP-1 agonists in humans with T1DM were included.

DATA SYNTHESIS

A total of 9 clinical trials examining the use of GLP-1 agonists in T1DM were identified. On average, hemoglobin A1C (A1C) was lower than baseline, with a maximal lowering of 0.6%. This effect was not significant when tested against a control group, with a relative decrease in A1C of 0.1% to 0.2%. In all trials examined, reported hypoglycemia was low, demonstrating no difference when compared with insulin monotherapy. Weight loss was seen in all trials, with a maximum weight loss of 6.4 kg over 24 weeks. Gastrointestinal adverse effects are potentially limiting, with a significant number of patients in trials reporting nausea.

CONCLUSION

The use of GLP-1 agonists should be considered in T1DM patients who are overweight or obese and not at glycemic goals despite aggressive insulin therapy; however, tolerability of these agents is a potential concern. Liraglutide has the strongest evidence for use and would be the agent of choice for use in overweight or obese adult patients with uncontrolled T1DM.

Incretins role in Latent autoimmune diabetes of adults pathogenesis, the possibility of therapy with combination of glucagon-like peptide-1 agonist (GLP-1) and insulin

Recently, the bihormonal theory of the autoimmune diabetes development is discussed in the world literature. The abnormal suppression of glucagon and reduced incretin response are considered in the development and progression of type 1 diabetes mellitus in addition to insulin deficiency. Animal studies demonstrate a GLP-1 – role in beta cell-proliferation and decrease in apoptosis. The information concerning the functioning of the incretin system in patients with type 1 diabetes and LADA is systematized in the present review. We also discuss the studies of the use of GLP-1 agonists in patients with autoimmune diabetes.

Effects of endogenous GLP-1 and GIP on glucose tolerance after Roux-en-Y gastric bypass surgery

Exaggerated secretion of glucagon-like peptide 1 (GLP-1) is important for postprandial glucose tolerance after Roux-en-Y gastric bypass (RYGB), whereas the role of glucose-dependent insulinotropic polypeptide (GIP) remains to be resolved. We aimed to explore the relative importance of endogenously secreted GLP-1 and GIP on glucose tolerance and β-cell function after RYGB. We used DPP-4 inhibition to enhance concentrations of intact GIP and GLP-1 and the GLP-1 receptor antagonist exendin-(9-39) (Ex-9) for specific blockage of GLP-1 actions. Twelve glucose-tolerant patients were studied after RYGB in a randomized, placebo-controlled, 4-day crossover study with standard mixed-meal tests and concurrent administration of placebo, oral sitagliptin, Ex-9 infusion, or combined Ex-9-sitagliptin. GLP-1 receptor antagonism increased glucose excursions, clearly attenuated β-cell function, and aggravated postprandial hyperglucagonemia compared with placebo, whereas sitagliptin had no effect despite two- to threefold increased concentrations of intact GLP-1 and GIP. Similarly, sitagliptin did not affect glucose tolerance or β-cell function during GLP-1R blockage. This study confirms the importance of GLP-1 for glucose tolerance after RYGB via increased insulin and attenuated glucagon secretion in the postprandial state, whereas amplification of the GIP signal (or other DPP-4-sensitive glucose-lowering mechanisms) did not appear to contribute to the improved glucose tolerance seen after RYGB.

Efficacy and safety of liraglutide for overweight adult patients with type 1 diabetes and insufficient glycaemic control (Lira-1): a randomised, double-blind, placebo-controlled trial

BACKGROUND

The combination of insulin and glucagon-like peptide-1 (GLP-1) receptor agonist therapy improves glycaemic control, induces weight loss, and reduces insulin dose needed in type 2 diabetes. We assessed the efficacy and safety of the GLP-1 receptor agonist liraglutide as an add-on therapy to insulin for overweight adult patients with type 1 diabetes.

METHODS

We did a randomised, double-blind, placebo-controlled trial at Steno Diabetes Center (Gentofte, Denmark). Patients aged 18 years or older with type 1 diabetes, insufficient glycaemic control (HbA1c >8% [64 mmol/mol]), and overweight (BMI >25 kg/m(2)) were randomly assigned (1:1) to receive insulin treatment plus either liraglutide or placebo (saline solution) by subcutaneous injection once per day. Randomisation was done in blocks of four. Treatment assignment was masked to investigators and patients. Treatment lasted 24 weeks and liraglutide was started at a dose of 0·6 mg per day, escalated to 1·2 mg per day after 1 week, and then again to 1·8 mg per day after another week. Intervals between dose increments could be extended at the discretion of the investigator. The primary endpoint was change in HbA1c from baseline to week 24. Secondary endpoints were changes in hypoglycaemic events, glycaemic variability, glycaemic excursions, insulin dose, bodyweight, postprandial plasma concentrations of glucagon and GLP-1, gastric emptying, blood pressure, heart rate, patient-reported outcome measures, time spent in hypoglycaemia, near-normoglycaemia, and hyperglycaemia, plasma fasting glucose, mean glucose, and cholesterol. Efficacy analyses were calculated by use of a mixed model, whereby a patient's data are used as long as the patient is in the study. The safety analyses were done in the intention-to-treat population, which consisted of all patients who received at least one dose of their randomly assigned study drug. This study is registered with ClinicalTrials.gov, number NCT01612468.

FINDINGS

Between July 10, 2012, and May 30, 2014, we enrolled 100 patients with type 1 diabetes, with 50 patients allocated liraglutide and 50 to placebo. Four patients from the liraglutide group and six patients from the placebo group discontinued treatment before 24 weeks. At the end of treatment, change in HbA1c from baseline did not differ between groups (-0·5%, 95% CI -0·8 to -0·4 [-6·0 mmol/mol, 95% CI -8·7 to -4·4] with liraglutide vs -0·3%, -0·6 to -0·2 [-4·0 mmol/mol, -6·6 to -2·3] with placebo; between-group difference -0·2% [-0·5 to 0·1; 2·2 mmol/mol, -5·5 to 1·1], p=0·1833). The number of hypoglycaemic events was reduced with liraglutide, with an incident rate ratio of 0·82 (95% CI 0·74 to 0·90). However, we detected no changes in glycaemic variability (continuous overall net glycaemic action per 60 min from 10·3 [95% CI 9·8 to 10·8] to 9·9 [9·2 to 10·6] in the liraglutide treated patients vs 10·2 [9·7 to 10·7] to 9·7 [9·1 to 10·3] in the placebo treated patients). Both bolus insulin (difference -5·8 IU, 95% CI -10·7 to -0·8, p=0·0227) and bodyweight (difference -6·8 kg, 95% CI -12·2 to -1·4, p=0·0145) decreased with liraglutide treatment compared with placebo. Heart rate increased with liraglutide, with a difference between groups of 7·5 bpm (95% CI 2·8-12·2, p=0·0019). Postprandial plasma glucagon and GLP-1 concentrations did not differ between groups (difference between groups at end of treatment: -408 mmol/L per 240 min [95% CI -941 to 125, p=0·1309] for glucagon and -266 mmol/L per 240 min [-1034 to 501, p=0·4899] for GLP-1). Gastric emptying was delayed after 3 weeks of treatment with liraglutide (19·9 min, 95% CI 0·8 to 39·0, p=0·0412), but we detected no difference after 24 weeks of treatment (-1·5 min, -20·5 to 17·6, p=0·8793). Patient-reported outcome measures differed between groups only with respect to perceived frequency of hypoglycaemia, which was higher with placebo, with a difference between groups of -0·6 (95% CI -1·1 to -0·07, p=0·0257). Liraglutide was associated with more frequent nausea (29 [58%] patients with liraglutide vs five [10%] with placebo), dyspepsia (11 [22%] patients with liraglutide vs one [2%] with placebo), diarrhoea (ten [20%] patients with liraglutide vs one [2%] with placebo), decreased appetite (seven patients [14%] with liraglutide vs none with placebo), and vomiting (seven [14%] patients with liraglutide vs one [2%] with placebo).

INTERPRETATION

In patients with type 1 diabetes, overweight, and insufficient glycaemic control, the reduction in HbA1c did not differ between insulin plus placebo and insulin plus liraglutide treatment. Liraglutide was associated with reductions in hypoglycaemic events, bolus and total insulin dose, and bodyweight, and increased heart rate.

FUNDING

Novo Nordisk.

Gastrointestinal actions of glucagon-like peptide-1-based therapies: glycaemic control beyond the pancreas

The gastrointestinal hormone glucagon-like peptide-1 (GLP-1) lowers postprandial glucose concentrations by regulating pancreatic islet-cell function, with stimulation of glucose-dependent insulin and suppression of glucagon secretion. In addition to endocrine pancreatic effects, mounting evidence suggests that several gastrointestinal actions of GLP-1 are at least as important for glucose-lowering. GLP-1 reduces gastric emptying rate and small bowel motility, thereby delaying glucose absorption and decreasing postprandial glucose excursions. Furthermore, it has been suggested that GLP-1 directly stimulates hepatic glucose uptake, and suppresses hepatic glucose production, thereby adding to reduction of fasting and postprandial glucose levels. GLP-1 receptor agonists, which mimic the effects of GLP-1, have been developed for the treatment of type 2 diabetes. Based on their pharmacokinetic profile, GLP-1 receptor agonists can be broadly categorized as short- or long-acting, with each having unique islet-cell and gastrointestinal effects that lower glucose levels. Short-acting agonists predominantly lower postprandial glucose excursions, by inhibiting gastric emptying and intestinal glucose uptake, with little effect on insulin secretion. By contrast, long-acting agonists mainly reduce fasting glucose levels, predominantly by increased insulin and reduced glucagon secretion, with potential additional direct inhibitory effects on hepatic glucose production. Understanding these pharmacokinetic and pharmacodynamic differences may allow personalized antihyperglycaemic therapy in type 2 diabetes. In addition, it may provide the rationale to explore treatment in patients with no or little residual β-cell function.

Markers of β-Cell Failure Predict Poor Glycemic Response to GLP-1 Receptor Agonist Therapy in Type 2 Diabetes

OBJECTIVE

To assess whether clinical characteristics and simple biomarkers of β-cell failure are associated with individual variation in glycemic response to GLP-1 receptor agonist (GLP-1RA) therapy in patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

We prospectively studied 620 participants with type 2 diabetes and HbA1c ≥58 mmol/mol (7.5%) commencing GLP-1RA therapy as part of their usual diabetes care and assessed response to therapy over 6 months. We assessed the association between baseline clinical measurements associated with β-cell failure and glycemic response (primary outcome HbA1c change 0-6 months) with change in weight (0-6 months) as a secondary outcome using linear regression and ANOVA with adjustment for baseline HbA1c and cotreatment change.

RESULTS

Reduced glycemic response to GLP-1RAs was associated with longer duration of diabetes, insulin cotreatment, lower fasting C-peptide, lower postmeal urine C-peptide-to-creatinine ratio, and positive GAD or IA2 islet autoantibodies (P ≤ 0.01 for all). Participants with positive autoantibodies or severe insulin deficiency (fasting C-peptide ≤0.25 nmol/L) had markedly reduced glycemic response to GLP-1RA therapy (autoantibodies, mean HbA1c change -5.2 vs. -15.2 mmol/mol [-0.5 vs. -1.4%], P = 0.005; C-peptide <0.25 nmol/L, mean change -2.1 vs. -15.3 mmol/mol [-0.2 vs. -1.4%], P = 0.002). These markers were predominantly present in insulin-treated participants and were not associated with weight change.

CONCLUSIONS

Clinical markers of low β-cell function are associated with reduced glycemic response to GLP-1RA therapy. C-peptide and islet autoantibodies represent potential biomarkers for the stratification of GLP-1RA therapy in insulin-treated diabetes.

Increasing GLP-1 Circulating Levels by Bariatric Surgery or by GLP-1 Receptor Agonists Therapy: Why Are the Clinical Consequences so Different?

The "incretin effect" is used to describe the observation that more insulin is secreted after the oral administration of glucose compared to that after the intravenous administration of the same amount of glucose. During the absorption of meals, the gut is thought to regulate insulin secretion by secreting a specific factor that targets pancreatic beta cells. Additional research confirmed this hypothesis with the discovery of two hormones called incretins: gastric inhibitory peptide (GIP) and glucagon-like peptide 1 (GLP-1). During meals, specific cells in the gut (L and K enteroendocrine cells) secrete incretins, causing an increase in the blood concentrations of, respectively, GLP-1 and GIP. Bariatric surgery is now proposed during the therapeutic management of type 2 diabetes in obese or overweight populations. It has been hypothesized that restoration of endogenous GLP-1 secretion after the surgery may contribute to the postsurgical resolution of diabetes. In 2005, the commercialization of GLP-1 receptor agonists gave the possibility to test this hypothesis. A few years later, it is now accepted that GLP-1 receptor agonists and bariatric surgery differently improve type 2 diabetes. These differences between endogenous and exogenous GLP-1 on glucose homeostasis emphasized the dual properties of GLP-1 as a peptide hormone and as a neurotransmitter.

GLP-1 receptor agonists in type 1 diabetes: a proof-of-concept approach

AIMS

To test potential efficacy of liraglutide, a GLP-1 receptor agonist, in subjects with type 1 diabetes (T1DM).

METHODS

We have recruited nine T1DM patients (age 40.1 ± 6.4 years, duration of diabetes 19.2 ± 8.8 years, BMI 24.3 ± 3.5 kg/m(2), HbA1c 8.2 ± 1.0 %-66 ± 11 mmol/mol, daily insulin dose: 0.6 ± 0.1 IU/kg) on continuous subcutaneous insulin therapy with undetectable C-peptide. In addition to existing treatment was administered in single-blind (a) therapy subcutaneously with 0.1 ml of saline solution for 3 days and (b) 0.1 ml of liraglutide (0.6 mg/day) for a further 3 days with daily glucose excursions recorded by continuous glucose monitoring.

RESULTS

Adding liraglutide resulted in a significant reduction in mean blood glucose (138 ± 29 vs. 163 ± 29 mg/dl, p < 0.0001) and standard deviation (42 ± 9 vs. 60 ± 15 mg/dl, p < 0.0001). The area under the curve (AUC) for blood glucose >140 mg/dl was also significantly reduced (22.2 ± 16.4 vs. 41.1 ± 19.7 mg/dl h, p < 0.05) with no difference in AUC for blood glucose <70 mg/dl (liraglutide 0.7 ± 0.9 mg/dl h; placebo: 0.8 ± 1.4 mg/dl h, p = NS). Finally, adding liraglutide reduced daily insulin requirement (37.5 ± 17.2 vs. 42.9 ± 22.4 UI/day, p < 0.01).

CONCLUSIONS

Short-term treatment with liraglutide, in T1DM, reduces average blood glucose, blood glucose variability and daily insulin requirement without increasing risk of hypoglycemia.

Twelve-Week Treatment With Liraglutide as Add-on to Insulin in Normal-Weight Patients With Poorly Controlled Type 1 Diabetes: A Randomized, Placebo-Controlled, Double-Blind Parallel Study

OBJECTIVE

This study investigated the efficacy and safety of once-daily liraglutide 1.2 mg versus placebo as add-on to insulin treatment in normal-weight patients with poorly controlled type 1 diabetes.

RESEARCH DESIGN AND METHODS

In a randomized (1:1), double-blind, placebo-controlled design, 40 patients with type 1 diabetes (HbA1c ≥8% [64 mmol/mol]) received once-daily liraglutide 1.2 mg or placebo for 12 weeks. Continuous glucose monitoring was performed before and at the end of treatment. The primary end point was change in HbA1c. Secondary end points included change in insulin dose, weight, glycemic excursions, heart rate, and blood pressure.

RESULTS

Baseline HbA1c was similar in the liraglutide and placebo group (8.8 ± 0.2 and 8.7 ± 0.1% [72.5 ± 2.2 and 71.8 ± 1.5 mmol/mol]). Change in HbA1c from baseline was -0.6 ± 0.2% (-6.22 ± 1.71 mmol/mol) with liraglutide and -0.5 ± 0.2% (-5.56 ± 1.67 mmol/mol) with placebo (P = 0.62). Variation in glycemic excursions did not change in either group. Change in body weight was -3.13 ± 0.58 and +1.12 ± 0.42 kg (P < 0.0001) with liraglutide and placebo, respectively. The bolus insulin dose decreased in liraglutide-treated patients and did not change with placebo treatment (4.0 ± 1.3 vs. 0.0 ± 1.0 IU, P = 0.02). Heart rate increased within the liraglutide group (P = 0.04) but not compared with placebo, whereas mean systolic blood pressure decreased compared with placebo (between-group difference 3.21 mmHg [95% CI -8.31 to 1.90], P = 0.04). Liraglutide was more frequently associated with gastrointestinal adverse effects. The incidence of hypoglycemia did not differ between groups.

CONCLUSIONS

Liraglutide significantly reduces body weight and insulin requirements but has no additional effect on HbA1c in normal-weight patients with type 1 diabetes inadequately controlled on insulin alone.

The role for gut permeability in the pathogenesis of type 1 diabetes--a solid or leaky concept?

Increasing evidence, both functional and morphological, supports the concept of increased intestinal permeability as an intrinsic characteristic of type 1 diabetes (T1D) in both humans and animal models of the disease. Often referred to as a 'leaky gut', its mechanistic impact on the pathogenesis of T1D remains unclear. Hypotheses that this defect influences immune responses against antigens (both self and non-self) predominate, yet others argue hyperglycemia and insulitis may contribute to increased gut permeability in T1D. To address these complicated issues, we herein review the many conceptual role(s) for a leaky gut in the pathogenesis of T1D and suggest ways that if true, therapeutic interventions aimed at the gut-pancreas axis may prove promising for future therapeutic interventions.

Sustained treatment with a stable long-acting oxyntomodulin analogue improves metabolic control and islet morphology in an experimental model of type 1 diabetes

AIM

To assess the therapeutic benefits of regulatory peptides other than insulin, which have to date received limited consideration in the context of type 1 diabetes.

METHODS

We assessed the effects of subchronic administration of the stable, oxyntomodulin (Oxm) analogue, (d-Ser(2) )Oxm[Lys(38) -γ-glu-PAL], for 28 days in streptozotocin (STZ)-induced insulin-deficient diabetic mice.

RESULTS

Twice-daily injection with (d-Ser(2) )Oxm[Lys(38) -γ-glu-PAL] significantly countered the excessive food and fluid intake in STZ-induced diabetic mice, and maintained normal body weight. Lean body mass was normalized, whilst fat mass was significantly increased compared with control STZ-induced diabetic mice. In addition, circulating glucose was significantly reduced by the Oxm analogue, whilst plasma and pancreatic insulin concentrations were increased and glucagon decreased by day 28. Plasma lipid profile was normalized by (d-Ser(2) )Oxm[Lys(38) -γ-glu-PAL] administration and circulating amylase was not significantly altered by induction of diabetes or Oxm analogue therapy. This was associated with significantly improved glucose tolerance and insulin secretion. Peripheral insulin sensitivity was also significantly improved by Oxm analogue treatment. Histological examination of pancreata showed beneficial elevations of total islet and β-cell area, associated with an increase in the number of smaller-sized islets. Further analysis revealed enhanced islet cell proliferation relative to apoptosis in Oxm analogue-treated mice.

CONCLUSION

These studies emphasize the potential of stable Oxm-based peptides, such as (d-Ser(2) )Oxm[Lys(38) -γ-glu-PAL], as therapeutic agents for insulin-deficient type 1 diabetes.

Counter-regulatory hormone responses to hypoglycaemia in people with type 1 diabetes after 4 weeks of treatment with liraglutide adjunct to insulin: a randomized, placebo-controlled, double-blind, crossover trial

AIMS

To investigate the effect of glucagon-like peptide 1 receptor agonist liraglutide on the counter-regulatory hormone response to hypoglycaemia in type 1 diabetes.

METHODS

We conducted a randomized, double-blind, placebo-controlled, single-centre trial, in which a total of 45 adults with type 1 diabetes [mean ± standard deviation age 34.5 ± 11.2 years, BMI 23.9 ± 2.4 kg/m(2) , glycated haemoglobin (HbA1c) 7.6 ± 0.8%, diabetes duration 16.6 ± 9.4 years] underwent a hypoglycaemic clamp after 4 weeks' crossover treatment with once-daily liraglutide/placebo added to insulin in one of three liraglutide dose groups: 0.6 mg (n = 15); 1.2 mg (n = 14); and 1.8 mg (n = 16). The main outcome measure was glucagon concentration at nadir plasma glucose (2.5 mmol/l). Clinical outcomes were also evaluated. Five participants were withdrawn from the trial; three because of adverse events. All participants were included in the analysis.

RESULTS

Glucagon concentration at nadir plasma glucose was modest, trending towards lower concentrations at increasing liraglutide dose versus placebo: 34.7 versus 38.1 pg/ml, p = 0.555 (0.6 mg); 28.8 versus 37.2 pg/ml, p = 0.126 (1.2 mg); and 28.4 versus 37.5 pg/ml, p = 0.092 (1.8 mg). There was no difference, however, between liraglutide and placebo in incremental change in glucagon during hypoglycaemia. Other counter-regulatory hormone levels increased during hypoglycaemia with no systematic differences between groups. Glucose infusion rates were significantly lower with liraglutide versus placebo during the clamp. After 4 weeks' treatment, HbA1c remained unchanged in the liraglutide and placebo groups. Greater reductions in insulin dose and body weight were seen with liraglutide versus placebo.

CONCLUSIONS

Liraglutide did not compromise hypoglycaemic responses in type 1 diabetes after 4 weeks' treatment.

Complementary glucagonostatic and insulinotropic effects of DPP-4 inhibitors in the glucose-lowering action in Japanese patients with type 2 diabetes

The dipeptidyl peptidase-4 (DPP-4) inhibitors have a low risk of causing hypoglycemia as monotherapy. However, insulin administration is frequently required, particularly in patients with type 2 diabetes and with reduced insulin secretory capacity. The effects of adding DPP-4 inhibitors were evaluated using continuous glucose monitoring (CGM) in Japanese patients with type 2 diabetes who were insufficiently controlled by basal insulin with biguanide. The effects of adding DPP-4 inhibitors on blood glucose and plasma insulin and glucagon levels were evaluated. Δ glucagon showed a significant association with post-prandial glucose increase in the group with diminished insulin secretory capacity, C-peptide index (CPI) <0.8 (p = 0.016), while Δ C-peptide reached significant association in the group with relatively intact insulin secretory capacity, CPI ≥0.8 (p = 0.017). The mean plasma glucose levels and M values were similarly improved in patients treated with the three DPP-4 inhibitors. Hypoglycemia did not occur in any of the DPP-4 inhibitor groups. In conclusion, complementary glucagonostatic and insulinotropic effects of adding DPP-4 inhibitors are involved in the glucose-lowering action of Japanese patients with type 2 diabetes according to their insulin secretory capacity. Such combination therapy may well be a superior therapeutic option for the treatment of diabetes in Japanese patients who often exhibit reduced insulin secretory capacity.

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.

Efficacy and safety of the glucagon-like peptide-1 receptor agonist liraglutide added to insulin therapy in poorly regulated patients with type 1 diabetes--a protocol for a randomised, double-blind, placebo-controlled study: the Lira-1 study

INTRODUCTION

Intensive insulin therapy is recommended for the treatment of type 1 diabetes (T1D). Hypoglycaemia and weight gain are the common side effects of insulin treatment and may reduce compliance. In patients with insulin-treated type 2 diabetes, the addition of glucagon-like peptide-1 receptor agonist (GLP-1RA) therapy has proven effective in reducing weight gain and insulin dose. The present publication describes a protocol for a study evaluating the efficacy and safety of adding a GLP-1RA to insulin treatment in overweight patients with T1D in a randomised, double-blinded, controlled design.

METHODS AND ANALYSIS

In total, 100 patients with type 1 diabetes, poor glycaemic control (glycated haemoglobin (HbA1c) >8%) and overweight (body mass index >25 kg/m(2)) will be randomised to either liraglutide 1.8 mg once daily or placebo as an add-on to intensive insulin therapy in this investigator initiated, double-blinded, placebo-controlled parallel study. The primary end point is glycaemic control as measured by changes in HbA1c. Secondary end points include changes in the insulin dose, hypoglyacemic events, body weight, lean body mass, fat mass, food preferences and adverse events. Glycaemic excursions, postprandial glucagon levels and gastric emptying rate during a standardised liquid meal test will also be studied.

ETHICS AND DISSEMINATION

The study is approved by the Danish Medicines Authority, the Regional Scientific-Ethical Committee of the Capital Region of Denmark and the Data Protection Agency. The study will be carried out under the surveillance and guidance of the good clinical practice (GCP) unit at Copenhagen University Hospital Bispebjerg in accordance with the ICH-GCP guidelines and the Helsinki Declaration.

TRIAL REGISTRATION NUMBER

NCT01612468.

The influence of glucagon on postprandial hyperglycaemia in children 5 years after onset of type 1 diabetes

AIMS/HYPOTHESIS

The influence of glucagon on glycaemic control in type 1 diabetes is debated. We investigated the relationship between postprandial glucagon levels and HbA1c during a period up to 60 months after diagnosis of childhood type 1 diabetes.

METHODS

The Danish remission phase cohort comprised 129 children (66 boys) with type 1 diabetes whose mean (SD) age at onset was 10.0 (3.9) years. Liquid mixed-meal tests were performed prospectively at 1, 3, 6 and 12 months and a subset of 40 patients completed follow-up at 60 months. Postprandial (90 min) plasma levels of glucagon, glucose (PG), C-peptide, total glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP) and HbA1c were analysed. Multivariate regression (repeated measurements with all five visits included) was applied and results expressed as relative change (95% CI).

RESULTS

Postprandial glucagon levels increased 160% from 1 to 60 months after diagnosis (p < 0.0001). A doubling in postprandial PG corresponded to a 21% increase in postprandial glucagon levels (p = 0.0079), whereas a doubling in total GLP-1 levels corresponded to a 33% increase in glucagon levels (p < 0.0001). Postprandial glucagon associated negatively with postprandial C-peptide (p = 0.017). A doubling in postprandial glucagon corresponded to a 3% relative increase in HbA1c levels (p = 0.0045).

CONCLUSIONS/INTERPRETATION

Postprandial glucagon levels were associated with deterioration of glycaemic control and declining beta cell function in the first 5 years after diagnosis of type 1 diabetes. The positive association of glucagon with total GLP-1 and PG suggests that physiological regulation of alpha cell secretion in type 1 diabetes is seriously disturbed.

Chronic hyperglycemia downregulates GLP-1 receptor signaling in pancreatic β-cells via protein kinase A

Objective

Glucagon-like peptide 1 (GLP-1) enhances insulin secretion and protects β-cell mass. Diabetes therapies targeting the GLP-1 receptor (GLP-1R), expressed in numerous tissues, have diminished dose-response in patients with type 2 diabetes compared with healthy human controls. The aim of this study was to determine the mechanistic causes underlying the reduced efficacy of GLP-1R ligands.

Methods

Using primary mouse islets and the β-cell line MIN6, outcomes downstream of the GLP-1R were analyzed: Insulin secretion; phosphorylation of the cAMP-response element binding protein (CREB); cAMP responses. Signaling systems were studied by immunoblotting and qRT-PCR, and PKA activity was assayed. Cell surface localization of the GLP-1R was studied by confocal microscopy using a fluorescein-tagged exendin-4 and GFP-tagged GLP-1R.

Results

Rodent β-cells chronically exposed to high glucose had diminished responses to GLP-1R agonists including: diminished insulin secretory response; reduced phosphorylation of (CREB); impaired cAMP response, attributable to chronically increased cAMP levels. GLP-1R signaling systems were affected by hyperglycemia with increased expression of mRNAs encoding the inducible cAMP early repressor (ICER) and adenylyl cyclase 8, reduced PKA activity due to increased expression of the PKA-RIα subunit, reduced GLP-1R mRNA expression and loss of GLP-1R from the cell surface. To specifically examine the loss of GLP-1R from the plasma membrane a GLP-1R-GFP fusion protein was employed to visualize subcellular localization. Under low glucose conditions or when PKA activity was inhibited, GLP-1R-GFP was found at the plasma membrane. Conversely high glucose, expression of a constitutively active PKA subunit, or exposure to exendin-4 or forskolin led to GLP-1R-GFP internalization. Mutation of serine residue 301 of the GLP-1R abolished the glucose-dependent loss of the receptor from the plasma membrane. This was associated with a loss of an interaction between the receptor and the small ubiquitin-related modifier (SUMO), an interaction that was found to be necessary for internalization of the receptor.

Conclusions

These data show that glucose acting, at least in part, via PKA leads to the loss of the GLP-1R from the cell surface and an impairment of GLP-1R signaling, which may underlie the reduced clinical efficacy of GLP-1R based therapies in individuals with poorly controlled hyperglycemia.

Responses of GLP1-secreting L-cells to cytotoxicity resemble pancreatic β-cells but not α-cells

Little is known about responses of intestinal L-cells to chemical or cytokine-mediated attack and how these compare with pancreatic β- or α-cells. Administration of streptozotocin to mice induced severe diabetes, islet lymphocytic infiltration, increased α-cell proliferation and decreased numbers of β- and L-cells. In vitro, streptozotocin and cytokines reduced cell viability with higher lethal dose 50 values for α-TC1 cells. mRNA expression of Glut2 was lower and Cat was greater in GLUTag and α-TC1 cells compared with MIN6 cells. Cytotoxins affected the transcription of genes involved in secretion in GLUTag and MIN6 cells. They are also involved in upregulation of antioxidant defence enzymes, transcription of NfκB and Nos2, and production of nitrite in all cell types. Cytotoxin-induced DNA damage and apoptosis were apparent in all cells, but α-TC1 cells were less severely affected. Thus, responses of GLP1-secreting L-cells to cytotoxicity resemble β-cells, whereas α-cells are resistant due to differences in the expression of genes involved in cytotoxicity or antioxidant defence.

Nutrient induced type 2 and chemical induced type 1 experimental diabetes differently modulate gastric GLP-1 receptor expression

T2DM patients demonstrate reduced GLP-1 receptor (GLP-1R) expression in their gastric glands. Whether induced T2DM and T1DM differently affect the gastric GLP-1R expression is not known. This study assessed extrapancreatic GLP-1R system in glandular stomach of rodents with different types of experimental diabetes. T2DM and T1DM were induced in Psammomys obesus (PO) by high-energy (HE) diet and by streptozotocin (STZ) in Sprague Dawly (SD) rats, respectively. GLP-1R expression was determined in glandular stomach by RT PCR and immunohistomorphological analysis. The mRNA expression and cellular association of the GLP-1R in principal glands were similar in control PO and SD rats. However, nutrient and chemical induced diabetes resulted in opposite alterations of glandular GLP-1R expression. Diabetic PO demonstrated increased GLP-1R mRNA expression, intensity of cellular GLP-1R immunostaining, and frequency of GLP-1R positive cells in the neck area of principal glands compared with controls. In contrast, SD diabetic rats demonstrated decreased GLP-1 mRNA, cellular GLP-1R immunoreactivity, and frequency of GLP-1R immunoreactive cells in the neck area compared with controls. In conclusion, nutrient and chemical induced experimental diabetes result in distinct opposite alterations of GLP-1R expression in glandular stomach. These results suggest that induced T1DM and T2DM may differently modulate GLP-1R system in enteropancreatic axis.

Glucose-dependent insulinotropic polypeptide augments glucagon responses to hypoglycemia in type 1 diabetes

Glucose-dependent insulinotropic polypeptide (GIP) is glucagonotropic, and glucagon-like peptide-1 (GLP-1) is glucagonostatic. We studied the effects of GIP and GLP-1 on glucagon responses to insulin-induced hypoglycemia in patients with type 1 diabetes mellitus (T1DM). Ten male subjects with T1DM (C-peptide negative, age [mean ± SEM] 26 ± 1 years, BMI 24 ± 0.5 kg/m(2), HbA1c 7.3 ± 0.2%) were studied in a randomized, double-blinded, crossover study, with 2-h intravenous administration of saline, GIP, or GLP-1. The first hour, plasma glucose was lowered by insulin infusion, and the second hour constituted a "recovery phase." During the recovery phase, GIP infusions elicited larger glucagon responses (164 ± 50 [GIP] vs. 23 ± 25 [GLP-1] vs. 17 ± 46 [saline] min ⋅ pmol/L, P < 0.03) and endogenous glucose production was higher with GIP and lower with GLP-1 compared with saline (P < 0.02). On the GIP days, significantly less exogenous glucose was needed to keep plasma glucose above 2 mmol/L (155 ± 36 [GIP] vs. 232 ± 40 [GLP-1] vs. 212 ± 56 [saline] mg ⋅ kg(-1), P < 0.05). Levels of insulin, cortisol, growth hormone, and noradrenaline, as well as hypoglycemic symptoms and cognitive function, were similar on all days. Our results suggest that during hypoglycemia in patients with T1DM, exogenous GIP increases glucagon responses during the recovery phase after hypoglycemia and reduces the need for glucose administration.

Glucagon and type 2 diabetes: the return of the alpha cell

In normal physiology, glucagon from pancreatic alpha cells plays an important role in maintaining glucose homeostasis via its regulatory effect on hepatic glucose production. Patients with type 2 diabetes suffer from fasting and postprandial hyperglucagonemia, which stimulate hepatic glucose production and, thus, contribute to the hyperglycemia characterizing these patients. Although this has been known for years, research focusing on alpha cell (patho)physiology has historically been dwarfed by research on beta cells and insulin. Today the mechanisms behind type 2 diabetic hyperglucagonemia are still poorly understood. Preclinical and clinical studies have shown that the gastrointestinal hormone glucose-dependent insulinotropic polypeptide (GIP) might play an important role in this pathophysiological phenomenon. Furthermore, it has become apparent that suppression of glucagon secretion or antagonization of the glucagon receptor constitutes potentially effective treatment strategies for patients with type 2 diabetes. In this review, we focus on the regulation of glucagon secretion by the incretin hormones glucagon-like peptide-1 (GLP-1) and GIP. Furthermore, potential advantages and limitations of suppressing glucagon secretion or antagonizing the glucagon receptor, respectively, in the treatment of patients with type 2 diabetes will be discussed.

Alternative Agents in Type 1 Diabetes in Addition to Insulin Therapy: Metformin, Alpha-Glucosidase Inhibitors, Pioglitazone, GLP-1 Agonists, DPP-IV Inhibitors, and SGLT-2 Inhibitors

Insulin is the mainstay of current treatment for patients with type 1 diabetes mellitus (T1DM). Due to increasing insulin resistance, insulin doses are often continually increased, which may result in weight gain for patients. Medications currently approved for the treatment of type 2 diabetes offer varying mechanisms of action that can help to reduce insulin resistance and prevent or deter weight gain. A MEDLINE search was conducted to review literature evaluating the use of metformin, alpha-glucosidase inhibitors, pioglitazone, glucagon-like peptide 1 agonists, dipeptidyl peptidase, and sodium-dependent glucose transporter 2 inhibitors, in patients with T1DM. Varying results were found with some benefits including reductions in hemoglobin A1c, decreased insulin doses, and favorable effects on weight. Of significance, a common fear of utilizing multiple therapies for diabetes treatment is the risk of hypoglycemia, and this review displayed limited evidence of hypoglycemia with multiple agents.

Role of glucagon-like peptide-1 analogue versus amylin as an adjuvant therapy in type 1 diabetes in a closed loop setting with ePID algorithm

Postprandial hyperglycemia due to paradoxical hyperglucagonemia is a major challenge of diabetes treatment despite the use of the artificial pancreas. We postulated that adjunctive therapy with pramlintide or exenatide would attenuate hyperglycemia in the postprandial phase through glucagon suppression, thereby optimizing the functioning of the closed-loop (CL) system. Subjects with type 1 diabetes (T1DM) on insulin pump therapy were recruited to participate in a 27-hour hospitalized admission on 3 occasions (2-4 weeks apart) and placed on the insulin delivery via CL system in random order to receive (1) insulin alone (control), (2) exenatide 2.5 µg + insulin, (3) pramlintide 30 µg + insulin. Medications were given prior to lunch and dinner, which was a standardized meal of 60 grams of carbohydrates. Insulin delivery was as per the ePID algorithm via the Medtronic CL system and continuous subcutaneous glucose monitoring via Medtronic Sof-sensors. Ten subjects age 23 ± 1 years with a HbA1c of 7.29 ± 0.3% (56 ± 1 mmol/mol) and duration of T1DM 10.6 ± 2.0 years participated in the 3-part study. Exenatide was found to be significantly better in attenuating postprandial hyperglycemia as compared to insulin monotherapy (P < .03) and pramlintide (P > .05). Glucagon suppression was statistically significant with exenatide (P < .03) as compared to pramlintide. Insulin requirements were lower with adjunctive therapy, but statistically insignificant. Insulin monotherapy results in postprandial hyperglycemia in T1DM in the CL setting and adjunctive therapy with exenatide reduces postprandial hyperglycemia effectively and should be considered as adjunctive therapy in T1DM.

Difference in glucagon-like peptide-1 concentrations between C-peptide negative type 1 diabetes mellitus patients and healthy controls

Background

The role of glucagon-like peptide-1 (GLP-1) has become a new scientific interest in the field of pathophysiology of type 1 diabetes mellitus (T1DM), but the results of the published studies were contradictory. The aim of our study was therefore to measure fasting and postprandial GLP-1 concentrations in T1DM patients and in healthy controls and to examine the difference in those concentrations between the two groups of subjects.

Methods

The cross-sectional study included 30 C-peptide negative T1DM patients, median age 37 years (20–59), with disease duration 22 years (3–45), and 10 healthy controls, median age 30 years (27–47). Fasting and postprandial total and active GLP-1 concentrations were measured by ELISA (ALPCO, USA). The data were statistically analysed by SPSS, and significance level was accepted at P < 0.05.

Results

Both fasting total and active GLP-1 concentrations were significantly lower in T1DM patients (total 0.4 pmol/L, 0–6.4 and active 0.2 pmol/L, 0–1.9) compared with healthy controls (total 3.23 pmol/L, 0.2–5.5 and active 0.8 pmol/L, 0.2–3.6), P = 0.008 for total GLP-1 and P = 0.001 for active GLP-1. After adjustment for age, sex and body mass index, binary logistic regression showed that both fasting total and active GLP-1 remained significantly independently lower in T1DM patients (total GLP-1: OR 2.43, 95% CI 1.203–4.909 and active GLP-1: OR 8.73, 95% CI 1.472–51.787).

Conclusions

T1DM patients had independently lower total and active GLP-1 fasting concentrations in comparison with healthy people, which supports the potential therapeutic role of incretin therapy, along with insulin therapy, in T1DM patients.

Combination of monoclonal antibodies and DPP-IV inhibitors in the treatment of type 1 diabetes: a plausible treatment modality?

Regulatory T cells (Tregs) are crucial for the maintenance of immunological tolerance. Type 1 diabetes (T1D) occurs when the immune-regulatory mechanism fails. In fact, T1D is reversed by islet transplantation but is associated with hostile effects of persistent immune suppression. T1D is believed to be dependent on the activation of type-1 helper T (Th1) cells. Immune tolerance is liable for the activation of the Th1 cells. The important role of Th1 cells in pathology of T1D entails the depletion of CD4(+) T cells, which initiated the use of monoclonal antibodies (mAbs) against CD4(+) T cells to interfere with induction of T1D. Prevention of autoimmunity is not only a step forward for the treatment of T1D, but could also restore the β-cell mass. Glucagon-like peptide (GLP)-1 stimulates β-cell proliferation and also has anti-apoptotic effects on them. However, the potential use of GLP-1 as a possible method to restore pancreatic β-cells is limited due to rapid degradation by dipeptidyl peptidase (DPP)-IV. We hypothesize that treatment with combination of CD4 mAbs and DPP-IV inhibitors could prevent/reverse T1D. CD4 mAbs have the ability to induce immune tolerance, thereby arresting further progression of T1D; DPP-IV inhibitors have the capability to regenerate the β-cell mass. Consequently, the combination of CD4 mAbs and DPP-IV inhibitor could avoid or at least minimize the constraints of intensive subcutaneous insulin therapy. We presume that if this hypothesis proves correct, it may become one of the plausible therapeutic options for T1D.

Defining the role of GLP-1 in the enteroinsulinar axis in type 2 diabetes using DPP-4 inhibition and GLP-1 receptor blockade

Understanding the incretin pathway has led to significant advancements in the treatment of type 2 diabetes (T2D). Still, the exact mechanisms are not fully understood. In a randomized, placebo-controlled, four-period, crossover study in 24 patients with T2D, dipeptidyl peptidase-4 (DPP-4) inhibition and its glucose-lowering actions were tested after an oral glucose tolerance test (OGTT). The contribution of GLP-1 was examined by infusion of the GLP-1 receptor (GLP-1r) antagonist exendin-9. DPP-4 inhibition reduced glycemia and enhanced insulin levels and the incretin effect (IE). Glucagon was suppressed, and gastric emptying (GE) was decelerated. Exendin-9 increased glucose levels and glucagon secretion, attenuated insulinemia and the IE, and accelerated GE. With the GLP-1r antagonist, the glucose-lowering effects of DPP-4 inhibition were reduced by ∼ 50%. However, a significant effect on insulin secretion remained during GLP-1r blockade, whereas the inhibitory effects of DPP-4 inhibition on glucagon and GE were abolished. Thus, in this cohort of T2D patients with a substantial IE, GLP-1 contributed ∼ 50% to the insulin excursion after an OGTT with and without DPP-4 inhibition. Thus, a significant DPP-4-sensitive glucose-lowering mechanism contributes to glycemic control in T2D patients that may be not mediated by circulating GLP-1.

Type 1 diabetes

Over the past decade, knowledge of the pathogenesis and natural history of type 1 diabetes has grown substantially, particularly with regard to disease prediction and heterogeneity, pancreatic pathology, and epidemiology. Technological improvements in insulin pumps and continuous glucose monitors help patients with type 1 diabetes manage the challenge of lifelong insulin administration. Agents that show promise for averting debilitating disease-associated complications have also been identified. However, despite broad organisational, intellectual, and fiscal investments, no means for preventing or curing type 1 diabetes exists, and, globally, the quality of diabetes management remains uneven. This Seminar discusses current progress in epidemiology, pathology, diagnosis, and treatment of type 1 diabetes, and prospects for an improved future for individuals with this disease.

Evaluation of long-term treatment effect in a type 1 diabetes intervention trial: differences after stimulation with glucagon or a mixed meal

OBJECTIVE

Endogenous insulin secretion, measured by C-peptide area under the curve (AUC), can be tested using both the glucagon stimulation test (GST) and the mixed-meal tolerance test (MMTT). This study compares these two stimulation methods using long-term data from patients newly diagnosed with type 1 diabetes or with latent autoimmune diabetes.

RESEARCH DESIGN AND METHODS

A recently completed phase 3 intervention study with DiaPep277 demonstrated improved glycemic control and a significant treatment effect of glucagon-stimulated C-peptide secretion. Unexpectedly, MMTT failed to detect differences between the treated and control groups. Data from 343 patients in two balanced-randomized, double-blind, placebo-controlled, parallel-group trials of DiaPep277 were used to compare and correlate between GST- and MMTT-derived C-peptide AUC. Pearson's correlations were calculated for absolute C-peptide AUC at baseline and 12 and 24 months and for long-term changes in AUC (AUC).

RESULTS

The absolute AUC values obtained at any single time point by the two tests were well correlated in both data sets (r = 0.74-0.9). However, the correlations between the AUC were much weaker (r = 0.39-0.58). GST-stimulated C-peptide secretion was stable over the fasting glucose range permitted for the test (4-11.1 mmol/L), but MMTT-stimulated C-peptide secretion decreased over the same range, implying differences in sensitivity to glucose.

CONCLUSIONS

Measurement of long-term changes in stimulated C-peptide, reflecting endogenous insulin secretion, during the course of intervention trials may be affected by the method of stimulation, possibly reflecting different sensitivities to the physiological status of the tested subject.

Acute metabolic effects of exenatide in patients with type 1 diabetes with and without residual insulin to oral and intravenous glucose challenges

OBJECTIVE Glucagon-like peptide 1 (GLP-1) is an incretin hormone that is released from the gastrointestinal tract. Treatment with GLP-1 analogs has proven to be of clinical use for patients with type 2 diabetes. Patients with type 1 diabetes, particularly those with residual β-cell function, may also respond to treatment, but the acute metabolic effects of GLP-1 analogs on these patients in reaction to both oral and intravenous glucose challenges are not well understood. RESEARCH DESIGN AND METHODS Seventeen patients with type 1 diabetes, half of whom had residual insulin production, underwent two mixed-meal tolerance tests (MMTTs) and two intravenous glucose tolerance tests (IVGTTs), with and without pretreatment with exenatide. No exogenous bolus insulin was administered for the studies. Glucose excursions, insulin secretion rates (ISRs), and levels of glucagon, endogenous GLP-1, and gastric inhibitory polypeptide were measured after the meal or glucose loads. RESULTS During the MMTT, glucose levels were suppressed with exenatide in patients with or without residual insulin production (P = 0.0003). Exenatide treatment did not change the absolute ISR, but the ISR to glucose levels were increased (P = 0.0078). Gastric emptying was delayed (P = 0.0017), and glucagon was suppressed (P = 0.0015). None of these hormonal or glucose changes were detected during the IVGTT with exenatide administration. CONCLUSIONS Exenatide showed a significant antidiabetogenic effect prior to an oral meal in patients with type 1 diabetes involving glucagon suppression and gastric emptying, while preserving increased insulin secretion. GLP-1 analogs may be useful as an adjunctive treatment in type 1 diabetes.

Glucagon-like peptide-1 as a treatment for chemotherapy-induced mucositis

BACKGROUND

Glucagon-like peptide-2 (GLP-2) has been suggested for the treatment of mucositis, but the peptide has also been shown to accentuate colonic dysplasia in carcinogen-treated mice. Recently, an effect on intestinal growth was discovered for glucagon-like peptide-1 (GLP-1), OBJECTIVE: To determine whether endogenous GLP-1 contributes to the healing processes and if exogenous GLP-1 has a potential role in treating mucositis.

METHODS

Mice were injected with 5-fluorouracil (5-FU) or saline to induce mucositis and were then treated with GLP-1, GLP-2, GLP-2 (3-33), exendin (9-39) or vehicle. The mice were sacrificed 48 or 96 h after the 5-FU injections. The end points were intestinal weight, villus height, proliferation and histological scoring of mucositis severity. Rats were injected with 5-FU or saline, and after 48 h, blood was drawn and analysed for GLP-1 and GLP-2 concentration.

RESULTS

GLP-1 and GLP-2 significantly prevented the loss of mucosal mass and villus height and significantly decreased the mucositis severity score in the duodenum and jejunum 48 h after chemotherapy. The effect was equivalent. Exendin (9-39) reduced the intestinal weight 96 h after chemotherapy. The GLP-1 levels in blood were increased more than 10-fold, and GLP-2 levels were increased sevenfold.

CONCLUSIONS

GLP-1 and GLP-2 were secreted after intestinal injury, and recovery was delayed after treatment with exendin (9-39), indicating an important role for the peptides in the protection of the intestine from injury. GLP-1 treatment ameliorated mucositis, which suggests that mucositis and other acute intestinal disorders might benefit from treatment with GLP-1 analogues.

Complications of diabetes therapy

Current strategies for the treatment of type 2 diabetes mellitus promote individualized plans to achieve target glucose levels on a patient-by-patient basis while minimizing treatment related risks. Maintaining glycemic control over time is a significant challenge because of the progressive nature of diabetes as a result of declining β-cell function. This article identifies complications of non-insulin treatments for diabetes. The major classes of medications are reviewed with special focus on target population, mechanism of action, effect on weight, cardiovascular outcomes and additional class-specific side effects including effects on bone. Effects on β-cell function are also highlighted.

Rationale use of GLP-1 receptor agonists in patients with type 1 diabetes

Clinicians and patients are rapidly adapting GLP-1 receptor agonists as efficacious and safe therapeutic options for managing type 2 diabetes (T2DM). GLP-1 receptor agonists stimulate insulin production and secretion from the pancreatic β cells in a glucose-dependent manner, improve gastric emptying, favor weight reduction, and reduce postabsorptive glucagon secretion from pancreatic α cells. GLP-1 receptor activity is impaired in patients with T2DM. GLP-1 secretion and subsequent physiologic actions in patients with type 1 diabetes (T1DM) is ill-defined. Some researchers have suggested that the use of GLP-1 receptor agonists in T1DM may reduce excessive postprandial glucagon secretion allowing patients to reduce their total daily dose of exogenous insulin. Hypoglycemia risk may also be minimized in T1DM as glucagon counter-regulation can be preserved to some degree via the glucose-dependent action of the GLP-1 receptor agonists. This paper will consider the physiologic and pharmacologic benefits of adding GLP-1 receptor agonists to therapeutic regimens of patients with T1DM.

Exaggerated glucagon-like peptide 1 response is important for improved β-cell function and glucose tolerance after Roux-en-Y gastric bypass in patients with type 2 diabetes

β-Cell function improves in patients with type 2 diabetes in response to an oral glucose stimulus after Roux-en-Y gastric bypass (RYGB) surgery. This has been linked to the exaggerated secretion of glucagon-like peptide 1 (GLP-1), but causality has not been established. The aim of this study was to investigate the role of GLP-1 in improving β-cell function and glucose tolerance and regulating glucagon release after RYGB using exendin(9-39) (Ex-9), a GLP-1 receptor (GLP-1R)-specific antagonist. Nine patients with type 2 diabetes were examined before and 1 week and 3 months after surgery. Each visit consisted of two experimental days, allowing a meal test with randomized infusion of saline or Ex-9. After RYGB, glucose tolerance improved, β-cell glucose sensitivity (β-GS) doubled, the GLP-1 response greatly increased, and glucagon secretion was augmented. GLP-1R blockade did not affect β-cell function or meal-induced glucagon release before the operation but did impair glucose tolerance. After RYGB, β-GS decreased to preoperative levels, glucagon secretion increased, and glucose tolerance was impaired by Ex-9 infusion. Thus, the exaggerated effect of GLP-1 after RYGB is of major importance for the improvement in β-cell function, control of glucagon release, and glucose tolerance in patients with type 2 diabetes.

Role of pancreatic β-cell death and inflammation in diabetes

Apoptosis of pancreatic β-cells is the final step in the development of type 1 diabetes (T1D), leading to critically diminished β-cell mass and contributing to the onset of hyperglycaemia. The spontaneous apoptosis of pancreatic β-cells during pancreas ontogeny also induces cell death-associated inflammation, stimulates antigen-presenting cells and sensitizes naïve diabetogenic T cells. The role of pancreatic β-cell death in type 2 diabetes (T2D) is less clear. In the preclinical period of T2D, hyperinsulinaemia and β-cell hyperplasia develop to compensate for insulin resistance, which is clearly seen in animal models of T2D. For the development of overt T2D, relative insulin deficiency is critical in addition to insulin resistance. Insulin deficiency could be due to β-cell dysfunction and/or decreased β-cell mass. Pancreatic β-cell apoptosis due to lipid injury (lipoapoptosis), endoplasmic reticulum (ER) stress or JNK activation could contribute to the decreased β-cell mass in T2D. Activation of inflammasomes by lipid injury, ER stress, human islet amyloid polypeptide, hyperglycaemia or autophagy insufficiency could also lead to β-cell death or dysfunction. Thus, β-cell death and cell death-associated inflammation through innate immune receptors could be important in both T1D and T2D.