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The glucagon-like peptide-1 receptor (GLP-1R) is an important regulator of glucose homeostasis and has been successfully targeted for the treatment of type 2 diabetes. Recently described biased GLP-1R agonists with selective reductions in beta-arrestin versus G protein coupling show improved metabolic actions in vivo. However, two prototypical G protein-favouring GLP-1R agonists, P5 and exendin-F1, are reported to show divergent effects on insulin secretion. In this study we aimed to resolve this discrepancy by performing a side-by-side characterisation of these two ligands across a variety of in vitro and in vivo assays. Exendin-F1 showed reduced acute efficacy versus P5 for several readouts, including recruitment of mini-G proteins, G protein-coupled receptor kinases (GRKs) and beta-arrestin-2. Maximal responses were also lower for both GLP-1R internalisation and the presence of active GLP-1R-mini-Gs complexes in early endosomes with exendin-F1 treatment. In contrast, prolonged insulin secretion in vitro and sustained anti-hyperglycaemic efficacy in mice were both greater with exendin-F1 than with P5. We conclude that the particularly low acute efficacy of exendin-F1 and associated reductions in GLP-1R downregulation appear to be more important than preservation of endosomal signalling to allow sustained insulin secretion responses. This has implications for the ongoing development of affinity- versus efficacy-driven biased GLP-1R agonists as treatments for metabolic disease.

Original publication

DOI

10.1016/j.bcp.2021.114656

Type

Journal article

Journal

Biochem Pharmacol

Publication Date

2021

Volume

190

Keywords

Animals Cell Line Exenatide/*pharmacology Gene Expression Regulation/*drug effects Glucagon-Like Peptide-1 Receptor/*agonists/genetics/*metabolism Humans Insulin-Secreting Cells Male Mice Mice, Inbred C57BL Pyridines/*pharmacology beta-Arrestin 2/genetics/metabolism *Biased agonism *Endocytosis *Exendin-4 *glp-1r *beta-arrestin