Development and characterisation of a peptidergic N-and C-terminally stabilised mammalian NPY1R agonist which protects against diabetes induction.

BACKGROUND: PYY (1-36) peptides from phylogenetically ancient fish, such as sea lamprey, have previously been shown to function as specific neuropeptide Y1 receptor (NPYR1) agonists. Although, sea lamprey PYY (1-36) is N-terminally stable, we reveal in this study that the peptide is subject to endopeptidase mediated C-terminal dipeptide degradation. In an attempt to prevent this, (d-Arg35)-sea lamprey PYY (1-36) was developed.
METHODS: In vitro bioassays assessed enzymatic stability, insulinostatic activity as well as beta-cell anti-apoptotic actions of (d-Arg35)-sea lamprey PYY (1-36). Follow-up studies examined the impact of twice daily administration of sea lamprey PYY (1-36) or (d-Arg35)-sea lamprey PYY (1-36) in multiple low dose STZ-induced diabetic mice.
RESULTS: (d-Arg35)-sea lamprey PYY (1-36) was fully resistant to plasma enzymatic degradation. The peptide possessed similar significant insulinostatic, as well as positive anti-apoptotic biological actions, as the parent peptide. Sea lamprey PYY (1-36) and (d-Arg35)-sea lamprey PYY (1-36) delayed diabetes progression in STZ mice. Both treatment interventions induced a significant decrease in body weight, food and fluid intake as well as glucose and glucagon concentrations. In addition, glucose tolerance, plasma and pancreatic insulin were partially normalised. (d-Arg35)-sea lamprey PYY (1-36) was significantly more effective than sea lamprey PYY (1-36) in terms of enhancing glucose-stimulate insulin release. Both treatments improved pancreatic islet morphology, linked to decreased apoptosis of beta-cells.
CONCLUSION: We present (d-Arg35)-sea lamprey PYY (1-36) as the first-in-class N- and C-terminally stable PYY (1-36) peptide analogue. GENERAL SIGNIFICANCE: Enzymatically stable, long-acting PYY (1-36) peptides highlight the therapeutic benefits of sustained activation of NPYR1's in diabetes.