title: N-terminal His(7)-modification of glucagon-like peptide-1(7-36) amide generates dipeptidyl peptidase IV-stable analogues with potent antihyperglycaemic activity.
abstract: Glucagon-like peptide-1(7-36)amide (GLP-1) possesses several unique and beneficial effects for the potential treatment of type 2 diabetes. However, the rapid inactivation of GLP-1 by dipeptidyl peptidase IV (DPP IV) results in a short half-life in vivo (less than 2 min) hindering therapeutic development. In the present study, a novel His(7)-modified analogue of GLP-1, N-pyroglutamyl-GLP-1, as well as N-acetyl-GLP-1 were synthesised and tested for DPP IV stability and biological activity. Incubation of GLP-1 with either DPP IV or human plasma resulted in rapid degradation of native GLP-1 to GLP-1(9-36)amide, while N-acetyl-GLP-1 and N-pyroglutamyl-GLP-1 were completely resistant to degradation. N-acetyl-GLP-1 and N-pyroglutamyl-GLP-1 bound to the GLP-1 receptor but had reduced affinities (IC(50) values 32.9 and 6.7 nM, respectively) compared with native GLP-1 (IC(50) 0.37 nM). Similarly, both analogues stimulated cAMP production with EC(50) values of 16.3 and 27 nM respectively compared with GLP-1 (EC(50) 4.7 nM). However, N-acetyl-GLP-1 and N-pyroglutamyl-GLP-1 exhibited potent insulinotropic activity in vitro at 5.6 mM glucose (P<0.05 to P<0.001) similar to native GLP-1. Both analogues (25 nM/kg body weight) lowered plasma glucose and increased plasma insulin levels when administered in conjunction with glucose (18 nM/kg body weight) to adult obese diabetic (ob/ob) mice. N-pyroglutamyl-GLP-1 was substantially better at lowering plasma glucose compared with the native peptide, while N-acetyl-GLP-1 was significantly more potent at stimulating insulin secretion. These studies indicate that N-terminal modification of GLP-1 results in DPP IV-resistant and biologically potent forms of GLP-1. The particularly powerful antihyperglycaemic action of N-pyroglutamyl-GLP-1 shows potential for the treatment of type 2 diabetes.
authors.affiliation: School of Biomedical Sciences, University of Ulster, Coleraine BT52 1SA, N. Ireland, UK. b.green@ulster.ac.uk
authors.forename: B D
authors.initials: BD
authors.lastname: Green
authors.forename: M H
authors.initials: MH
authors.lastname: Mooney
authors.forename: V A
authors.initials: VA
authors.lastname: Gault
authors.forename: N
authors.initials: N
authors.lastname: Irwin
authors.forename: C J
authors.initials: CJ
authors.lastname: Bailey
authors.forename: P
authors.initials: P
authors.lastname: Harriott
authors.forename: B
authors.initials: B
authors.lastname: Greer
authors.forename: F P M
authors.initials: FP
authors.lastname: O'Harte
authors.forename: P R
authors.initials: PR
authors.lastname: Flatt
mesh_terms: D000818:Animals; D002461:Cell Line, Transformed; D006224:Cricetinae; D000242:Cyclic AMP / Q000378:metabolism; D003920:Diabetes Mellitus / Q000188:drug therapy / Q000378:metabolism; D018819:Dipeptidyl Peptidase 4 / Q000378:metabolism; D005934:Glucagon / Q000031:analogs & derivatives / Q000138:chemical synthesis / Q000378:metabolism / Q000627:therapeutic use; D052216:Glucagon-Like Peptide 1 / Q000031:analogs & derivatives; D004763:Glucagon-Like Peptides; D007004:Hypoglycemic Agents / Q000032:analysis / Q000138:chemical synthesis* / Q000627:therapeutic use; D007328:Insulin / Q000378:metabolism; D008647:Mesocricetus; D051379:Mice; D008820:Mice, Obese; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000378:metabolism* / Q000627:therapeutic use; D011498:Protein Precursors / Q000378:metabolism; D011761:Pyrrolidonecarboxylic Acid / Q000031:analogs & derivatives
chemical_list: D007004:Hypoglycemic Agents; D007328:Insulin; D010446:Peptide Fragments; D011498:Protein Precursors; C485578:glucagon-like peptide-1 (7-36)amide, N-acetyl-; C485579:glucagon-like peptide-1 (7-36)amide, N-pyroglutamyl-; C055453:glucagon-like peptide 1 (7-36)amide; D004763:Glucagon-Like Peptides; D052216:Glucagon-Like Peptide 1; D005934:Glucagon; D000242:Cyclic AMP; D018819:Dipeptidyl Peptidase 4; D011761:Pyrrolidonecarboxylic Acid