The journey to understanding incretin systems: Theory, practice and more theory

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

AIMS/INTRODUCTION

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Efficacy and safety of once-weekly semaglutide versus once-daily sitagliptin as add-on to metformin in patients with type 2 diabetes in SUSTAIN China: A 30-week, double-blind, phase 3a, randomized trial

AIM

To evaluate the efficacy and safety of once-weekly subcutaneous semaglutide, a glucagon-like peptide-1 (GLP-1) analogue, versus once-daily sitagliptin as add-on to metformin in patients with type 2 diabetes (T2D) in a multiregional clinical trial.

MATERIALS AND METHODS

In the 30-week, randomized, double-blind, double-dummy, active comparator SUSTAIN China trial, 868 adults with T2D inadequately controlled on metformin (HbA1c 7.0%-10.5%) were randomized to receive once-weekly semaglutide 0.5 mg (n = 288), semaglutide 1.0 mg (n = 290) or once-daily sitagliptin 100 mg (n = 290). The primary and confirmatory secondary endpoints were change from baseline to week 30 in HbA1c and body weight, respectively.

RESULTS

The trial enrolled ~70% (605/868) of the patients in China, and the remaining patients from four other countries, including the Republic of Korea. Both doses of semaglutide were superior to sitagliptin in reducing HbA1c and body weight after 30 weeks of treatment. The odds of achieving target HbA1c  of less than 7.0% (53 mmol/mol), weight loss of 5% or higher, or 10% or higher, and the composite endpoint of HbA1c  less than 7.0% (53 mmol/mol) without severe or blood glucose-confirmed symptomatic hypoglycaemia no weight gain, were all significantly higher with both semaglutide doses compared with sitagliptin. The safety profile for semaglutide was consistent with the known class effects of GLP-1 receptor agonists (RAs). Consistent efficacy and safety findings were seen in the Chinese subpopulation.

CONCLUSIONS

Once-weekly semaglutide was superior to sitagliptin in improving glycaemic control and reducing body weight in patients with T2D inadequately controlled on metformin. The safety and tolerability profiles were consistent with those of semaglutide and other GLP-1 RAs. Semaglutide is an effective once-weekly treatment option for the Chinese population.

Diabetes and Its Complications: Therapies Available, Anticipated and Aspired

Worldwide, diabetes ranks among the ten leading causes of mortality. Prevalence of diabetes is growing rapidly in low and middle income countries. It is a progressive disease leading to serious co-morbidities, which results in increased cost of treatment and over-all health system of the country. Pathophysiological alterations in Type 2 Diabetes (T2D) progressed from a simple disturbance in the functioning of the pancreas to triumvirate to ominous octet to egregious eleven to dirty dozen model. Due to complex interplay of multiple hormones in T2D, there may be multifaceted approach in its management. The 'long-term secondary complications' in uncontrolled diabetes may affect almost every organ of the body, and finally may lead to multi-organ dysfunction. Available therapies are inconsistent in maintaining long term glycemic control and their long term use may be associated with adverse effects. There is need for newer drugs, not only for glycemic control but also for prevention or mitigation of secondary microvascular and macrovascular complications. Increased knowledge of the pathophysiology of diabetes has contributed to the development of novel treatments. Several new agents like Glucagon Like Peptide - 1 (GLP-1) agonists, Dipeptidyl Peptidase IV (DPP-4) inhibitors, amylin analogues, Sodium-Glucose transport -2 (SGLT- 2) inhibitors and dual Peroxisome Proliferator-Activated Receptor (PPAR) agonists are available or will be available soon, thus extending the range of therapy for T2D, thereby preventing its long term complications. The article discusses the pathophysiology of diabetes along with its comorbidities, with a focus on existing and novel upcoming antidiabetic drugs which are under investigation. It also dives deep to deliberate upon the novel therapies that are in various stages of development. Adding new options with new mechanisms of action to the treatment armamentarium of diabetes may eventually help improve outcomes and reduce its economic burden.