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

Glycaemic management in diabetes: old and new approaches

HbA_1c is the most used parameter to assess glycaemic control. However, evidence suggests that the concept of hyperglycaemia has profoundly changed and that different facets of hyperglycaemia must be considered. A modern approach to glycaemic control should focus not only on reaching and maintaining optimal HbA_1c concentrations as early as possible, but to also do so by reducing postprandial hyperglycaemia, glycaemic variability, and to extend as much as possible the time in range in near-normoglycaemia. These goals should be achieved while avoiding hypoglycaemia, which, should it occur, should be reverted to normoglycaemia. Modern technology, such as intermittently scanned glucose monitoring and continuous glucose monitoring, together with new drug therapies (eg, ultra-fast insulins, SGLT2 inhibitors, and GLP-1 receptor agonists), could help to change the landscape of glycaemia management based on HbA_1c in favour of a more holistic approach that considers all the different aspects of this commonly oversimplified pathophysiological feature of diabetes.

Liraglutide as Adjunct to Insulin Treatment in Patients with Type 1 Diabetes: A Systematic Review and Meta-analysis

BACKGROUND

A few Randomized Controlled Trials (RCTs) have evaluated the use of liraglutide in Type 1 Diabetes (T1D). Through the present systematic review and meta-analysis, we aim at critically appraising and summarizing those RCTs, providing precise effect estimates.

METHODS

We searched major databases and grey literature from their inception to October 2018, for RCTs with a duration ≥ 12 weeks, comparing liraglutide with placebo or any other comparator as adjunct to insulin in patients with T1D, investigating major efficacy and safety endpoints. This review is reported in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) statement.

RESULTS

We included 5 trials with 2,445 randomized participants. Liraglutide provided modest reductions in HbA1c, with liraglutide 1.8 mg producing the greatest decrease (MD = -0.24%, 95% CI -0.32 to -0.16, I2=0%). Significant weight reduction, up to 4.87 kg with liraglutide 1.8 mg was also observed (95% CI -5.31 to -4.43, I2=0%). Decrease in total daily insulin dose, primarily driven by a decrease in bolus insulin requirements, was demonstrated. Liraglutide decreased non-significantly the odds for severe hypoglycemia (OR=0.80, 95% CI 0.57-1.14, I2=0%), while it increased significantly the odds for gastrointestinal adverse events (for nausea, OR=4.70, 95% CI 3.68-6.00, I2=37%, and for vomiting, OR=2.50, 95% CI 1.54-4.72, I2=27%). A significant increase in heart rate was also demonstrated. No association with diabetic ketoacidosis or malignancies was identified.

CONCLUSION

In patients with T1D, liraglutide might prove be an adjunct to insulin, improving glycemic control, inducing body weight loss and decreasing exogenous insulin requirements and severe hypoglycemia.

Andrographolide promotes pancreatic duct cells differentiation into insulin-producing cells by targeting PDX-1

Regeneration of β-cells by differentiation of pancreatic progenitor cells has the potential to fundamentally solve the problems of the loss of β-cell function and mass during disease progression in both type 1 or 2 diabetes. Therefore, discovery of novel differentiation inducers to promote islet regeneration is of great significance. Pancreatic and duodenal homeobox1 (PDX-1) is a key transcription factor that promotes the development and maturation of pancreatic β-cells. To screen potential novel small molecules for enhancing differentiation of PNAC-1 cells, a human pancreatic ductal cell lines into insulin-producing cells (IPCs), we developed a high-throughput screening method through fusing the PDX-1 promoter region with a luciferase reporter gene. We screened and identified that andrographolide named C1037 stimulates PDX-1 expression in both mRNA and protein level and significantly promotes PANC-1 cells differentiation into IPCs as compared with that of control cells. The therapeutic effect of C037 in Streptozotocin induced diabetic mouse model through differentiation of pancreatic ductal cells into insulin positive islets was also observed. Our study provides a novel method to screen compounds regulating the differentiation of pancreatic progenitor cells having the potential of enhancing islet regeneration for diabetes therapy.

Do glucagon-like peptide-1 receptor (GLP-1R) agonists have potential as adjuncts in the treatment of type 1 diabetes?

INTRODUCTION

Glucagon-like peptide-1 (GLP-1) is produced by the gut, stimulates insulin secretion from the pancreatic β-cells, and inhibits glucagon secretion from the α-cells. The GLP-1 receptor (GLP-1R) agonists are used in the treatment of type 2 diabetes (T2DM).

AREAS COVERED

This review covers the clinical trials of the GLP-1R agonists (exenatide and liraglutide) and their potential as adjunct treatment in type 1 diabetes mellitus (T1DM).

EXPERT OPINION

GLP-1R agonists are unable to increase insulin secretion, in subjects with T1DM, who are C-peptide negative. Also, the GLP-1R agonists either have no effect or cause a small inhibition of glucagon secretion in subjects with T1DM. There is no evidence that the GLP-1R agonists cause a major reduction in HbA1c, or have a major effect on hypo- or hyperglycemia in subjects with TD1M. The main beneficial effect of the GLP-1R agonists is probably the modest weight loss, which may underlie the reduction in dose of insulin used. Given that the GLP-1R agonists cause gastrointestinal adverse effects, and with reduced insulin doses, increase the risk of ketosis, it seems to me that the risk with these agents may outweigh any benefit in T1DM, and that they have little potential as adjuncts in the treatment of T1DM.

Short-acting glucagon-like peptide-1 receptor agonists as add-on to insulin therapy in type 1 diabetes: A review

A large proportion of patients with type 1 diabetes do not reach their glycaemic target of glycated hemoglobin (HbA1c) <7.0% (53 mmol/mol) and, furthermore, an increasing number of patients with type 1 diabetes are overweight and obese. Treatment of type 1 diabetes is based on insulin therapy, which is associated with well-described and unfortunate adverse effects such as hypoglycaemia and increased body weight. Glucagon-like peptide-1 (GLP-1) receptor agonists (RAs) are the focus of increasing interest as a possible adjunctive treatment to insulin in type 1 diabetes because of their glucagonostatic and extrapancreatic effects. So far, the focus has mainly been on the long-acting GLP-1RAs, but the risk-benefit ratio emerging from studies evaluating the effect of long-acting GLP-1RAs as adjunctive therapy to insulin therapy in patients with type 1 diabetes has been disappointing. This might be attributable to a lack of glucagonostatic effect of these long-acting GLP-1RAs in type 1 diabetes, alongside development of tachyphylaxis to GLP-1-induced retardation of gastric emptying. In contrast, the short-acting GLP-1RAs seem to have a preserved and sustained effect on glucagon secretion and gastric emptying in patients with type 1 diabetes, which could translate into effective lowering of postprandial glucose excursions; however, these observations regarding short-acting GLP-1RAs are all derived from small open-label trials and should thus be interpreted with caution. In the present paper we review the potential role of GLP-1RAs, in particular short-acting GLP-1RAs, as add-on to insulin in the treatment of type 1 diabetes.

Differentiation of Diabetes by Pathophysiology, Natural History, and Prognosis

The American Diabetes Association, JDRF, the European Association for the Study of Diabetes, and the American Association of Clinical Endocrinologists convened a research symposium, "The Differentiation of Diabetes by Pathophysiology, Natural History and Prognosis" on 10-12 October 2015. International experts in genetics, immunology, metabolism, endocrinology, and systems biology discussed genetic and environmental determinants of type 1 and type 2 diabetes risk and progression, as well as complications. The participants debated how to determine appropriate therapeutic approaches based on disease pathophysiology and stage and defined remaining research gaps hindering a personalized medical approach for diabetes to drive the field to address these gaps. The authors recommend a structure for data stratification to define the phenotypes and genotypes of subtypes of diabetes that will facilitate individualized treatment.

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 Insulin Treatment in Type 1 Diabetes: The ADJUNCT ONE Treat-To-Target Randomized Trial

OBJECTIVE

To investigate whether liraglutide added to treat-to-target insulin improves glycemic control and reduces insulin requirements and body weight in subjects with type 1 diabetes.

RESEARCH DESIGN AND METHODS

A 52-week, double-blind, treat-to-target trial involving 1,398 adults randomized 3:1 to receive once-daily subcutaneous injections of liraglutide (1.8, 1.2, or 0.6 mg) or placebo added to insulin.

RESULTS

HbA1c level was reduced 0.34-0.54% (3.7-5.9 mmol/mol) from a mean baseline of 8.2% (66 mmol/mol), and significantly more for liraglutide 1.8 and 1.2 mg compared with placebo (estimated treatment differences [ETDs]: 1.8 mg liraglutide -0.20% [95% CI -0.32; -0.07]; 1.2 mg liraglutide -0.15% [95% CI -0.27; -0.03]; 0.6 mg liraglutide -0.09% [95% CI -0.21; 0.03]). Insulin doses were reduced by the addition of liraglutide 1.8 and 1.2 mg versus placebo (estimated treatment ratios: 1.8 mg liraglutide 0.92 [95% CI 0.88; 0.96]; 1.2 mg liraglutide 0.95 [95% CI 0.91; 0.99]; 0.6 mg liraglutide 1.00 [95% CI 0.96; 1.04]). Mean body weight was significantly reduced in all liraglutide groups compared with placebo ETDs (1.8 mg liraglutide -4.9 kg [95% CI -5.7; -4.2]; 1.2 mg liraglutide -3.6 kg [95% CI -4.3; -2.8]; 0.6 mg liraglutide -2.2 kg [95% CI -2.9; -1.5]). The rate of symptomatic hypoglycemia increased in all liraglutide groups (estimated rate ratios: 1.8 mg liraglutide 1.31 [95% CI 1.07; 1.59]; 1.2 mg liraglutide 1.27 [95% CI 1.03; 1.55]; 0.6 mg liraglutide 1.17 [95% CI 0.97; 1.43]), and hyperglycemia with ketosis increased significantly for liraglutide 1.8 mg only (event rate ratio 2.22 [95% CI 1.13; 4.34]).

CONCLUSIONS

Liraglutide added to insulin therapy reduced HbA1c levels, total insulin dose, and body weight in a population that was generally representative of subjects with type 1 diabetes, accompanied by increased rates of symptomatic hypoglycemia and hyperglycemia with ketosis, thereby limiting clinical use in this group.

The GLP-1 receptor agonists exenatide and liraglutide activate Glucose transport by an AMPK-dependent mechanism

Aims/hypothesis

Potentiation of glucose-induced insulin secretion is the main mechanism of exenatide (EXE) antidiabetic action, however, increased glucose utilization by peripheral tissues has been also reported. We here studied the effect of EXE on glucose uptake by skeletal muscle cells.

Methods

2-deoxy-glucose (2DG) uptake and intracellular signal pathways were measured in rat L6 skeletal muscle myotubes exposed to 100 nmol/l EXE for up to 48 h. Mechanisms of EXE action were explored by inhibiting AMPK activity with compound C (CC, 40 μmol/l) or siRNAs (2 μmol/l).

Results

Time course experiments show that EXE increases glucose uptake up to 48 h achieving its maximal effect, similar to that induced by insulin, after 20 min (2- vs 2.5-fold-increase, respectively). Differently from insulin, EXE does not stimulate: (i) IR β-subunit- and IRS1 tyrosine phosphorylation and binding to p85 regulatory subunit of PI-3kinase; (ii) AKT activation; and (iii) ERK1/2 and JNK1/2 phosphorylation. Conversely, EXE increases phosphorylation of α-subunit of AMPK at Thr172 by 2.5-fold (p < 0.01). Co-incubation of EXE and insulin does not induce additive effects on 2DG-uptake. Inhibition of AMPK with CC, and reduction of AMPK protein expression by siRNA, completely abolish EXE-induced 2DG-uptake. Liraglutide, another GLP-1 receptor agonist, also stimulates AMPK phosphorylation and 2DG-uptake. Moreover, EXE stimulates 2DG-uptake also by L6 myotubes rendered insulin-resistant with methylglyoxal. Finally, EXE also induces glucose transporter Glut-4 translocation to the plasma membrane.

Conclusions/interpretation

In L6 myotubes, EXE and liraglutide increase glucose uptake in an insulin-independent manner by activating AMPK.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-0985-7) contains supplementary material, which is available to authorized users.

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.