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: Aisling M Lynch, Nupur Pathak, Yasmin E Flatt, Victor A Gault, Finbarr P M O'Harte, Nigel Irwin, Peter R Flatt
• Journal: European journal of pharmacology (Eur J Pharmacol) Vol. 743 Pg. 69-78 (Nov 15 2014) ISSN: 1879-0712 [Electronic] Netherlands
• PMID: 25246014 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2014 Elsevier B.V. All rights reserved.

Chemical References

• Blood Glucose
• Glp1r protein, mouse
• Glucagon-Like Peptide-1 Receptor
• Hypoglycemic Agents
• Insulin
• Oxyntomodulin
• Peptides
• Receptors, Glucagon
• Glucagon-Like Peptide 1
• Glucagon
• Cyclic AMP
• Dipeptidyl Peptidase 4
• Glucose

Topics

• Animals
• Appetite (drug effects)
• Blood Glucose (drug effects)
• Cyclic AMP (metabolism)
• Dipeptidyl Peptidase 4 (metabolism)
• Glucagon (metabolism)
• Glucagon-Like Peptide 1 (metabolism)
• Glucagon-Like Peptide-1 Receptor
• Glucose (metabolism)
• Half-Life
• Hypoglycemic Agents (pharmacology)
• Insulin (metabolism)
• Male
• Mice
• Mice, Inbred C57BL
• Oxyntomodulin (pharmacology)
• Peptides (pharmacology)
• Receptors, Glucagon (metabolism)