Add time:07/22/2019         Source:sciencedirect.com

The importance of dipeptidyl peptidase-4 mediated N-terminal metabolism of the enteroendocrine-derived hormone, peptide YY (PYY), for receptor binding and subsequent biological action profile is well established. However, an intact C-terminus may be fundamental also for bioactivity of PYY peptides. The current study has demonstrated C-terminal degradation of the major recognised circulating forms of PYY, PYY(1–36) and PYY(3–36), in plasma, resulting in production of PYY(1–34) and PYY(3–34). Interestingly, the angiotensin-converting-enzyme (ACE) inhibitor, captopril, blocked formation of PYY(3–34) from PYY(3–36) in plasma, but did result in the appearance of PYY(3–35). In addition, we were able to evidence C-terminal truncation of PYY(1–35) and PYY(3–35) to PYY(1–34) and PYY(3–34), respectively. As expected, PYY(1–36) and PYY(3–36) inhibited (P < 0.05–P < 0.001) glucose- and alanine-stimulated insulin secretion from BRIN-BD11 beta-cells. In contrast, PYY(1–34), PYY(3–34), PYY(1–35) and PYY(3–35) were devoid of insulinostatic actions. Both PYY(1–36) and PYY(3–36), but not related PYY metabolites, significantly (P < 0.05–P < 0.001) enhanced proliferation of BRIN BD11 and 1.1B4 beta-cell lines, and protected (P < 0.01–P < 0.001) these cell lines against cytokine-induced apoptosis. As expected, PYY(3–36) induced clear (P < 0.05–P < 0.01) appetite suppressive effects in mice, but this action was eliminated by mono- or di-peptide C-terminal truncation. Interestingly, captopril significantly (P < 0.05) augmented the anorexigenic effects of PYY(3–36) in mice. PYY(1–36), PYY(3–36), PYY(1–34) and PYY(3–34) lacked effects on in vivo glucose tolerance or glucose-induced insulin release. Taken together, these data highlight the unrecognised importance of C-terminal integrity of PYY peptides for biological activity and therapeutic usefulness in obesity-diabetes.

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