Liraglutide in the treatment of type 2 diabetes mellitus: clinical utility and patient perspectives

A Review of Current Trends with Type 2 Diabetes Epidemiology, Aetiology, Pathogenesis, Treatments and Future Perspectives

Type 2 diabetes (T2D), which has currently become a global pandemic, is a metabolic disease largely characterised by impaired insulin secretion and action. Significant progress has been made in understanding T2D aetiology and pathogenesis, which is discussed in this review. Extrapancreatic pathology is also summarised, which demonstrates the highly multifactorial nature of T2D. Glucagon-like peptide (GLP)-1 is an incretin hormone responsible for augmenting insulin secretion from pancreatic beta-cells during the postprandial period. Given that native GLP-1 has a very short half-life, GLP-1 mimetics with a much longer half-life have been developed, which are currently an effective treatment option for T2D by enhancing insulin secretion in patients. Interestingly, there is continual emerging evidence that these therapies alleviate some of the post-diagnosis complications of T2D. Additionally, these therapies have been shown to induce weight loss in patients, suggesting they could be an alternative to bariatric surgery, a procedure associated with numerous complications. Current GLP-1-based therapies all act as orthosteric agonists for the GLP-1 receptor (GLP-1R). Interestingly, it has emerged that GLP-1R also has allosteric binding sites and agonists have been developed for these sites to test their therapeutic potential. Recent studies have also demonstrated the potential of bi- and tri-agonists, which target multiple hormonal receptors including GLP-1R, to more effectively treat T2D. Improved understanding of T2D aetiology/pathogenesis, coupled with the further elucidation of both GLP-1 activity/targets and GLP-1R mechanisms of activation via different agonists, will likely provide better insight into the therapeutic potential of GLP-1-based therapies to treat T2D.

Intermittent Use of a Short-Course Glucagon-like Peptide-1 Receptor Agonist Therapy Limits Adverse Cardiac Remodeling via Parkin-dependent Mitochondrial Turnover

Given that adverse remodeling is the leading cause of heart failure and death in the USA, there is an urgent unmet need to develop new methods in dealing with this devastating disease. Here we evaluated the efficacy of a short-course glucagon-like peptide-1 receptor agonist therapy-specifically 2-quinoxalinamine, 6,7-dichloro-N-(1,1-dimethylethyl)-3-(methylsulfonyl)-,6,7-dichloro-2-methylsulfonyl-3-N-tert-butylaminoquinoxaline (DMB; aka Compound 2) - in attenuating adverse LV remodeling. We also examined the role, if any, of mitochondrial turnover in this process. Wild-type, Parkin knockout and MitoTimer-expressing mice were subjected to permanent coronary artery ligation, then treated briefly with DMB. LV remodeling and cardiac function were assessed by histology and echocardiography. Autophagy and mitophagy markers were examined by western blot and mitochondrial biogenesis was inferred from MitoTimer protein fluorescence and qPCR. We found that DMB given post-infarction significantly reduced adverse LV remodeling and the decline of cardiac function. This paralleled an increase in autophagy, mitophagy and mitochondrial biogenesis. The salutary effects of the drug were lost in Parkin knockout mice, implicating Parkin-mediated mitophagy as part of its mechanism of action. Our findings suggest that enhancing Parkin-associated mitophagy and mitochondrial biogenesis after infarction is a viable target for therapeutic mitigation of adverse remodeling.

Molecular Characterisation of Small Molecule Agonists Effect on the Human Glucagon Like Peptide-1 Receptor Internalisation

The glucagon-like peptide receptor (GLP-1R), which is a G-protein coupled receptor (GPCR), signals through both Gαs and Gαq coupled pathways and ERK phosphorylation to stimulate insulin secretion. The aim of this study was to determine molecular details of the effect of small molecule agonists, compounds 2 and B, on GLP-1R mediated cAMP production, intracellular Ca2+ accumulation, ERK phosphorylation and its internalisation. In human GLP-1R (hGLP-1R) expressing cells, compounds 2 and B induced cAMP production but caused no intracellular Ca2+ accumulation, ERK phosphorylation or hGLP-1R internalisation. GLP-1 antagonists Ex(9-39) and JANT-4 and the orthosteric binding site mutation (V36A) in hGLP-1R failed to inhibit compounds 2 and B induced cAMP production, confirming that their binding site distinct from the GLP-1 binding site on GLP-1R. However, K334A mutation of hGLP-1R, which affects Gαs coupling, inhibited GLP-1 as well as compounds 2 and B induced cAMP production, indicating that GLP-1, compounds 2 and B binding induce similar conformational changes in the GLP-1R for Gαs coupling. Additionally, compound 2 or B binding to the hGLP-1R had significantly reduced GLP-1 induced intracellular Ca2+ accumulation, ERK phosphorylation and hGLP-1R internalisation. This study illustrates pharmacology of differential activation of GLP-1R by GLP-1 and compounds 2 and B.

Pathogenesis and management of postprandial hyperglycemia: role of incretin-based therapies

Postprandial plasma glucose concentrations are an important contributor to glycemic control. There is evidence suggesting that postprandial hyperglycemia may be an independent risk factor for cardiovascular disease. Glucagon-like peptide-1 (GLP-1) receptor agonists and dipeptidyl peptidase-4 (DPP-4) inhibitors are antidiabetic agents that predominantly reduce postprandial plasma glucose levels. DPP-4 inhibitors are associated with fewer gastrointestinal side effects than GLP-1 receptor agonists and are administered orally, unlike GLP-1 analogs, which are administered as subcutaneous injections. GLP-1 receptor agonists are somewhat more effective than DPP-4 inhibitors in reducing postprandial plasma glucose and are usually associated with significant weight loss. For these reasons, GLP-1 receptor agonists are generally preferred over DPP-4 inhibitors as part of combination treatment regimens in patients with glycated hemoglobin levels above 8.0%. This article reviews the pathogenesis of postprandial hyperglycemia, the mechanisms by which GLP-1 receptor agonists and DPP-4 inhibitors reduce postprandial plasma glucose concentrations, and the results of recent clinical trials (ie, published 2008 to October 2012) that evaluated the effects of these agents on postprandial plasma glucose levels when evaluated as monotherapy compared with placebo or as add-on therapy to metformin, a sulfonylurea, or insulin. Findings from recent clinical studies suggest that both GLP-1 receptor agonists and DPP-4 inhibitors could become valuable treatment options for optimizing glycemic control in patients unable to achieve glycated hemoglobin goals on basal insulin, with the added benefits of weight loss and a low risk of hypoglycemia.

Randomized trial of continuous subcutaneous delivery of exenatide by ITCA 650 versus twice-daily exenatide injections in metformin-treated type 2 diabetes

OBJECTIVE

To evaluate ITCA 650, a continuous subcutaneous miniature osmotic pump delivery system of exenatide versus twice-daily exenatide injections (Ex-BID) in subjects with type 2 diabetes.

RESEARCH DESIGN AND METHODS

We conducted a randomized, two-stage, 24-week, open-label, phase 2 study in type 2 diabetes inadequately controlled with metformin. Stage I: 155 subjects were randomized to 20 or 40 μg/day of ITCA 650 or Ex-BID 5 → 10 μg. Stage II: 131 subjects were rerandomized to 20, 40, 60, or 80 μg/day of ITCA 650. Change from baseline for HbA1c, weight, and fasting plasma glucose were evaluated at weeks 12 and 24.

RESULTS

HbA1c was significantly lower in all groups after 12 and 24 weeks. Stage I: mean change in HbA1c from a mean baseline of 7.9-8.0% was -0.98, -0.95, and -0.72% for the 20 and 40 μg/day ITCA 650 and Ex-BID groups, respectively, with 63, 65, and 50% of subjects achieving HbA1c levels ≤ 7% (P < 0.05). Stage II: significant (P < 0.05) reductions in HbA1c (≈ 1.4% from baseline) were achieved with 60 and 80 μg/day ITCA 650, and 86 and 78% of subjects achieved HbA1c ≤ 7% at 24 weeks; respectively. Weight was reduced by 2.8-3.7 kg (P < 0.05) at 24 weeks in all except the 20 → 20 μg/day group. ITCA 650 was well tolerated; nausea was lower and transient with 20 μg/day relative to Ex-BID; and 60 μg/day had the best profile of tolerability and HbA1c lowering.

CONCLUSIONS

ITCA 650 significantly reduced HbA1c and weight and was well tolerated. The 20 → 60 μg/day regimen was considered the best dose for further examination in phase 3.

The influence of incretin mimetics on cardiovascular risk factors in diabetes

The authors discuss the strategy of use of incretin hormones in type 2 diabetes treatment in the context of cardiovascular complications. The results of the phase III study on human GLP-1 (Glucagon-like peptide-1) analogue-liraglutide have been presented under common acronym LEAD (Liraglutide-Effect and Action In Diabetes). The liraglutide therapy improved glycemic control with low hypoglycemia risk and decreased glycated hemoglobin by an average 1,13%. Decreases in systolic pressure and significant body weight loss were observed. Not only did the index describing beta cells function HOMA-B improve but also did the ratio of insulin to proinsulin. Summing up, incretin hormones beneficially influence blood glucose level, moreover, their use decreases blood pressure and body weight which might indicate their positive influence on cardiovascular system in diabetic patients.

Management of hyperglycemia in geriatric patients with diabetes mellitus: South Asian consensus guidelines

Asia is home to four of the world's five largest diabetic populations, two of them being South Asian nations, namely, India and Pakistan. This problem is compounded by a substantial rise in the elderly population in Asian countries. On the other hand, the heterogeneous health condition and multiple co-morbidities make the care of chronic disease in the elderly a challenging task. The aim of the South Asian Consensus Guidelines is to provide evidence-based recommendations to assist healthcare providers in the rational management of type 2 diabetes mellitus in the elderly population. Current Guidelines used systematic reviews of available evidence to form its key recommendations. No evidence grading was done for the purpose of this manuscript. The clinical questions of the guidelines, the methodology of literature search, and medical writing strategy were finalized by consultations in person and through mail. The South Asian Consensus guideline emphasizes tailoring of glycemic goals for patients based on age, co-morbid conditions especially that of cardiovascular system, risk of hypoglycemia, and life expectancy. It also recommends cautious use of available pharmacotherapy in geriatric patients with diabetes. The primary principle of diabetes therapy should be to achieve euglycemia, without causing hypoglycemia. Appropriate use of modern insulins and oral drugs, including incretin mimetics will help physicians achieve this aim.