PYY1-36

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.

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.

(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.

We present (d-Arg³⁵)-sea lamprey PYY (1-36) as the first-in-class N- and C-terminally stable PYY (1-36) peptide analogue.

Enzymatically stable, long-acting PYY (1-36) peptides highlight the therapeutic benefits of sustained activation of NPYR1's in diabetes.

Recent studies have identified a beneficial role for peptide tyrosine tyrosine (PYY) on pancreatic beta-cell function and survival. These effects are linked to the activation of neuropeptide Y1 receptors (NPYR1s) by PYY(1-36). However, PYY(1-36) is subject to rapid degradation by dipeptidyl peptidase-4 (DPP-4), resulting is the loss of NPYR1 activity. Therefore, the aim of this study was to develop 2 enzymatically stable PYY(1-36) analogues, namely, (P3L31P34)PYY(1-36) and PYY(1-36)(Lys12PAL), with further structural modifications to enhance NPYR1 specificity. As expected, (P3L31P34)PYY(1-36) was fully resistant to DPP-4-mediated degradation in vitro, whereas PYY(1-36) and PYY(1-36)(Lys12PAL) were both liable to DPP-4 breakdown. PYY(1-36) and (P3L31P34)PYY(1-36) induced significant reductions in glucose-stimulated insulin secretion (GSIS) from BRIN BD11 cells, but only PYY(1-36) diminished alanine-stimulated insulin secretion. In contrast, PYY(1-36)(Lys12PAL) had no impact on GSIS or alanine-induced insulin release. All 3 PYY peptides significantly enhanced proliferation in BRIN BD11 and 1.1B4 beta-cell lines, albeit only at the highest concentration examined, 10-6 M, for (P3L31P34)PYY(1-36) and PYY(1-36)(Lys12PAL) in BRIN BD11 cells. Regarding the protection of beta-cells against cytokine-induced apoptosis, PYY(1-36) induced clear protective effects. Both (P3L31P34)PYY(1-36) and PYY(1-36)(Lys12PAL) offered some protection against apoptosis in BRIN BD11 cells, but were significantly less efficacious than PYY(1-36). Similarly, in 1.1B4 cells, both PYY analogues (10-6 M) protected against cytokine-induced apoptosis, but (P3L31P34)PYY(1-36) was significantly less effective than PYY(1-36). All 3 PYY peptides had no impact on refeeding in overnight fasted mice. These data underline the beta-cell benefits of PYY(1-36) and highlight the challenges of synthesising stable, bioactive, NPYR1-specific, PYY(1-36) analogues.