title: Comparison of stability, cellular, glucose-lowering and appetite supressing effects of oxyntomodulin analogues modified at the N-terminus.
abstract: Oxyntomodulin (Oxm) possesses beneficial biological actions for the potential treatment of obesity-diabetes. However, rapid inactivation by dipeptidyl peptidase-4 (DPP-4) results in a short half-life, hindering therapeutic applicability. In the present study, six Oxm analogues namely, (Thr(2))Oxm, (Asp(3))Oxm, (Aib(2))Oxm, (d-Ser(2))Oxm, (N-acetyl)Oxm and (d-Ser(2))Oxm-Lys-γ-glutamyl-PAL were synthesised and tested for DPP-4 stability and biological activity. Native Oxm, (Thr(2))Oxm and (Asp(3))Oxm were rapidly degraded by DPP-4, while (Aib(2))Oxm, (d-Ser(2))Oxm, (N-acetyl)Oxm and (d-Ser(2))Oxm-Lys-γ-glutamyl-PAL were resistant to degradation. All peptides stimulated cAMP production (P<0.01 to P<0.001) in GLP-1-R, but not in GIP-R, transfected cells. In glucagon-R transfected cells, all peptides except (N-acetyl)Oxm and (Thr(2))Oxm evoked significant cAMP generation. Similarly, all analogues, except (N-acetyl)Oxm, exhibited prominent (P<0.05 to P<0.001) insulinotropic activity in BRIN BD11 cells. When administered in conjunction with glucose to normal mice only native Oxm, (Aib(2))Oxm and (d-Ser(2))Oxm significantly (P<0.05 to P<0.01) increased overall plasma insulin levels. The corresponding glycaemic excursion was significantly (P<0.05 to P<0.001) lowered by all Oxm peptides, barring (N-acetyl)Oxm. Further investigations revealed persistent glucose-lowering and insulin-releasing actions of (d-Ser(2))Oxm-Lys-γ-glutamyl-PAL. Studies in GIP- and GLP-1-receptor KO mice with (Aib(2))Oxm, (d-Ser(2))Oxm, and (d-Ser(2))Oxm-Lys-γ-glutamyl-PAL highlighted the importance of GLP-1 receptor signalling for the beneficial glucose homoeostatic actions of these analogues. All peptides, except (N-acetyl)Oxm, possessed significant appetite suppressive effects in mice. These data highlight the significant therapeutic promise of enzymatically stable Oxm-based peptides, particularly with position 2 modifications, for the treatment of obesity-diabetes.
authors.affiliation: SAAD Centre for Pharmacy and Diabetes, Biomedical Sciences Research Institute, University of Ulster, Cromore Road, Coleraine BT52 1SA, Northern Ireland, UK.
authors.forename: Aisling M
authors.initials: AM
authors.lastname: Lynch
authors.affiliation: SAAD Centre for Pharmacy and Diabetes, Biomedical Sciences Research Institute, University of Ulster, Cromore Road, Coleraine BT52 1SA, Northern Ireland, UK.
authors.forename: Nupur
authors.initials: N
authors.lastname: Pathak
authors.affiliation: SAAD Centre for Pharmacy and Diabetes, Biomedical Sciences Research Institute, University of Ulster, Cromore Road, Coleraine BT52 1SA, Northern Ireland, UK.
authors.forename: Yasmin E
authors.initials: YE
authors.lastname: Flatt
authors.affiliation: SAAD Centre for Pharmacy and Diabetes, Biomedical Sciences Research Institute, University of Ulster, Cromore Road, Coleraine BT52 1SA, Northern Ireland, UK.
authors.forename: Victor A
authors.initials: VA
authors.lastname: Gault
authors.affiliation: SAAD Centre for Pharmacy and Diabetes, Biomedical Sciences Research Institute, University of Ulster, Cromore Road, Coleraine BT52 1SA, Northern Ireland, UK.
authors.forename: Finbarr P M
authors.initials: FP
authors.lastname: O'Harte
authors.affiliation: SAAD Centre for Pharmacy and Diabetes, Biomedical Sciences Research Institute, University of Ulster, Cromore Road, Coleraine BT52 1SA, Northern Ireland, UK. Electronic address: n.irwin@ulster.ac.uk.
authors.forename: Nigel
authors.initials: N
authors.lastname: Irwin
authors.affiliation: SAAD Centre for Pharmacy and Diabetes, Biomedical Sciences Research Institute, University of Ulster, Cromore Road, Coleraine BT52 1SA, Northern Ireland, UK.
authors.forename: Peter R
authors.initials: PR
authors.lastname: Flatt
mesh_terms: D000818:Animals; D001066:Appetite / Q000187:drug effects*; D001786:Blood Glucose / Q000187:drug effects; D000242:Cyclic AMP / Q000378:metabolism; D018819:Dipeptidyl Peptidase 4 / Q000378:metabolism; D005934:Glucagon / Q000378:metabolism; D052216:Glucagon-Like Peptide 1 / Q000378:metabolism; D000067757:Glucagon-Like Peptide-1 Receptor; D005947:Glucose / Q000378:metabolism*; D006207:Half-Life; D007004:Hypoglycemic Agents / Q000494:pharmacology; D007328:Insulin / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D053772:Oxyntomodulin / Q000494:pharmacology*; D010455:Peptides / Q000494:pharmacology; D018027:Receptors, Glucagon / Q000378:metabolism
chemical_list: D001786:Blood Glucose; C000593834:Glp1r protein, mouse; D000067757:Glucagon-Like Peptide-1 Receptor; D007004:Hypoglycemic Agents; D007328:Insulin; D053772:Oxyntomodulin; D010455:Peptides; D018027:Receptors, Glucagon; D052216:Glucagon-Like Peptide 1; D005934:Glucagon; D000242:Cyclic AMP; D018819:Dipeptidyl Peptidase 4; D005947:Glucose
keywords: Analogue; Food intake; Glucose homoeostasis; Insulin secretion; Oxyntomodulin