Search

Despite the successful development of new therapies for the treatment of type 2 diabetes, such as glucagon-like peptide-1 (GLP-1) receptor agonists and sodium-glucose cotransporter-2 inhibitors, the search for novel treatment options that can provide better glycaemic control and at reduce complications is a continuous effort. The present Review aims to present an overview of novel targets and mechanisms and focuses on glucose-lowering effects guiding this search and developments. We discuss not only novel developments of insulin therapy (eg, so-called smart insulin preparation with a glucose-dependent mode of action), but also a group of drug classes for which extensive research efforts have not been rewarded with obvious clinical impact. We discuss the potential clinical use of the salutary adipokine adiponectin and the hepatokine fibroblast growth factor (FGF) 21, among others. A GLP-1 peptide receptor agonist (semaglutide) is now available for oral absorption, and small molecules activating GLP-1 receptors appear on the horizon. Bariatric surgery and its accompanying changes in the gut hormonal milieu offer a background for unimolecular peptides interacting with two or more receptors (for GLP-1, glucose-dependent insulinotropic polypeptide, glucagon, and peptide YY) and provide more substantial glycaemic control and bodyweight reduction compared with selective GLP-1 receptor agonists. These and additional approaches will help expand the toolbox of effective medications needed for optimising the treatment of well delineated subgroups of type 2 diabetes or help develop personalised approaches for glucose-lowering drugs based on individual characteristics of our patients., Competing Interests: Declaration of interests MAN has been a member on advisory boards or has consulted with AstraZeneca, Boehringer Ingelheim, Eli Lilly, GlaxoSmithKline, Menarini/Berlin Chemie, Merck, Sharp & Dohme, and NovoNordisk. He has received grant support from AstraZeneca, Eli Lilly, Menarini/Berlin-Chemie, Merck, Sharp & Dohme, and NovoNordisk. He has also served on the speakers' bureau of AstraZeneca, Boehringer Ingelheim, Eli Lilly, Menarini/Berlin Chemie, Merck, Sharp & Dohme, and NovoNordisk. JJM has received consulting and speaker honoraria from AstraZeneca, Eli Lilly, Merck, Sharp & Dohme, Novo Nordisk, Sanofi, and Servier. He has received research support from Boehringer Ingelheim, Eli Lilly, Merck, Sharp & Dohme, Novo Nordisk, and Sanofi. JW has declares no competing interests., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The incretin effect describes the phenomenon whereby oral glucose elicits higher insulin secretory responses than does intravenous glucose, despite inducing similar levels of glycaemia, in healthy individuals. This effect, which is uniformly defective in patients with type 2 diabetes, is mediated by the gut-derived incretin hormones glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1). The importance of the incretin effect for the maintenance of glucose homoeostasis is clearly established, and incretin-based therapies are among the most promising new therapies for type 2 diabetes. However, despite the effectiveness of these therapies in many patients, the idea that they restore the incretin effect is a common misconception. In type 2 diabetes, the endocrine pancreas remains responsive to GLP-1 but is no longer responsive to GIP, which is the most likely reason for a reduced or absent incretin effect. Incretin-based drugs, including GLP-1 receptor agonists and dipeptidyl peptidase 4 (DPP-4) inhibitors, stimulate GLP-1 receptors and thus augment insulin secretion in response to both oral and intravenous glucose stimulation, thereby abolishing any potential difference in the responses to these stimuli. These drugs therefore do not restore the defective incretin effect in patients. By contrast, some bariatric surgical procedures enhance GLP-1 responses and also restore the incretin effect in obese individuals with type 2 diabetes. Thus, not all biological actions elicited by the stimulation of GLP-1 receptors lead to quantitative changes to the incretin effect., (Copyright © 2016 Elsevier Ltd. All rights reserved.)