Effects of PYY and PP on endocrine pancreas

Abstract

Novel intestinal polypeptide YY (PYY) and pancreatic polypeptide (PP) were infused in fed anaesthetized rats. The peptides (10 and 100 pmol/kg X min) were administered during 30 min, alone, together with glucose or together with arginine. Plasma concentrations of glucose, insulin and glucagon were measured. At the dose of 10 pmol/kg X min the peptides had no effect. PP at the dose of 100 pmol/kg X min slightly augmented basal, but had no effect on stimulated insulin and glucagon release. PYY at the dose of 100 pmol/kg X min was without effect on basal insulin and glucagon levels and on glucose-induced insulin release, but exerted an inhibitory effect on arginine-induced secretion of both insulin and glucagon. It is unlikely that PYY and PP can affect secretion of insulin and glucagon via blood circulation. The potential capability of high doses of PP to affect insulin and glucagon secretion suggests that this peptide may exert direct (paracrine) effects on the pancreatic A- and B-cells.

Mechanisms underlying the insulinostatic effect of peptide YY in mouse pancreatic islets

“…Previous studies have shown that PYY inhibits insulin release both in vivo [8][9][10][11], and in vitro [12]. The present study provides further evidence for a direct islet action of this peptide, since a clear-cut inhibition of insulin secretion was observed in perifused mouse islets.…”

“…Recently, PYY has been localized to the alpha cells in both the mouse and the rat pancreas [6,7], where it is co-stored with glucagon in the secretory granules [8]. The peptide has previously been demonstrated to inhibit stimulated insulin secretion under in vivo conditions in the rat [9], dog [10,11] and mouse [8], and in vitro in the perfused isolated rat pancreas and in isolatedrat islets [12]. This suggests that PYY participates in the regulation of insulin secretion.…”

Low serum PYY is linked to insulin resistance in first-degree relatives of subjects with type 2 diabetes

“…These islet isolation performed in 13 week old chow-fed PYY k mals that were lean, showing that changes tion does not arise as a secondary eVec Indeed, a role for PYY in inhibiting gluco insulin secretion has been demonstrated in vitro in animals. Intravenously administe no eVect on basal plasma insulin levels, but cose-stimulated insulin secretion in mice (B 1989;Szecowka et al, 1983). In vitro studi that PYY dose-dependently inhibits gluco but not basal insulin secretion (Karlsson 1996;Nieuwenhuizen et al, 1994).…”

A porcine gut polypeptide identical to the pancreatic hormone PP (pancreatic polypeptide)

“…For porcine PP, data have appeared conflicting since this peptide suppressed insulin secretion in dogs [33] but not in rats [34]. It is possible, however, that this previously apparent difference was accounted for by the administration of larger, pharmacological, amounts of PP in most studies, showing an effect on the insulin release, while smaller amounts of PP were infused in the second study [34]. In this context, it is of interest that the gut PP, as now shown, exerts a direct insulin-suppressive effect on the isolated pancreatic islet.…”