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Another Way to Control GLP-1

multiple routesThe incretin, glucagon-like peptide-1 (GLP-1), is an intestinal hormone that stimulates production and release of insulin from pancreatic beta cells. Consequently there has been considerable interest in mimicking the activity of GLP-1 for treatment of metabolic disorders such as Type-II diabetes and obesity. There are currently two approved classes of drug that modulate GLP-1 activity: analogues of GLP-1 and inhibitors of dipeptidyl peptidase IV (DPPIV). Analogues of GLP-1, such as the 39-residue synthetic peptide, exenatide, activate the GLP-1 receptor but are resistant to proteolytic cleavage by DPPIV. The gliptins, such as sitagliptin, inhibit DPPIV, extending the half-life of the natural hormone.

Researchers at Ecole Polytechnique Fédérale de Lausanne, in collaboration with the University of Perugia and Intercept Pharmaceuticals, have now published data showing that stimulation of TGR5, a G-protein coupled receptor, leads to release of GLP-1 in obese mice. The same group had previously demonstrated that activation of TGR5 in brown adipose tissue and muscle by endogenous bile acids boosted energy expenditure and reversed diet-induced obesity in mice.

INT-777 structureIn the current work the researchers used a combination of genetic gain- and loss-of-function studies together with the TGR5 agonist, INT-777, to show the link between TGR5 signalling and GLP-1 secretion. In vitro experiments with INT-777 in enteroendocrine L-cells confirmed the induction of GLP-1 secretion and that this was linked to increased intracellular ATP/ADP ratio and a subsequent rise in intracellular calcium mobilization.

The study, published in the September 2nd edition of Cell Metabolism, opens up a potential third route to modulation of GLP-1 activity and treatment of metabolic disorders.


Non-peptide GLP-1 Agonist Shows Efficacy in Mouse Model of Diabetes

Boc5Metabolic syndrome is a combination of medical disorders that increase the risk of developing cardiovascular disease, diabetes and obesity. A 39-residue synthetic peptide, Exenatide, which is approved for the treatment of type 2 diabetes, acts by mimicking the action of endogenous glucagon-like peptide-1 (GLP-1), a regulator of glucose metabolism and insulin secretion.

Researchers have now shown that chronic administration of a non-peptide molecule, Boc5, can induce weight loss and increase insulin sensitivity in a mouse model of diabetes and obesity by binding to the receptor for GLP-1. Boc5 is the only non-peptide molecule reported so far that behaves as a full GLP-1 mimetic in vitro and in vivo. Although Boc5 itself does not have the properties of a ‘drug-like’ molecule, it may represent a starting point for the discovery of orally bioavailable agents with the potential to treat metabolic disorders.