Inhibition of glucose stimulated insulin secretion by neuropeptide Y is mediated via the Y1 receptor and inhibition of adenylyl cyclase in RIN 5AH rat insulinoma cells

Neuropeptide Y (NPY) has been shown to inhibit insulin secretion from the i slets of Langerhans. We show that insulin secretion in the insulinoma cell line RIN 5AH is inhibited by NPY. I-125-Peptide YY (PYY) saturation and com petition-binding studies using NPY fragments and analogues on membranes pre pared from this cell line show the presence of a single class of NPY recept or with a Y1 receptor subtype-like profile. Inhibition of insulin secretion in this cell line by NPY fragments and analogues also shows a Y1 receptor- like profile. Both receptor binding and inhibition of insulin secretion sho wed the same orders of potency with NPY > [Pro(34)] NPY > NPY 3-36 > > NPY 13-36. The Y1 receptor antagonist, BIBP 3226, blocks NPY inhibition of insu lin secretion from, and inhibits I-125-PYY binding to, RIN 5AH cells. North ern blot analysis using a Y1-receptor specific probe shows that NPY Y1 rece ptors are expressed by RIN 5AH cells. Y5 receptors are not expressed in thi s cell line. Neuropeptide Y inhibition of insulin secretion is blocked by i ncubation with pertussis toxin, implying that the effect is via a G-protein (G(i) or G(o)) coupled receptor. Neuropeptide Y inhibits the activation of adenylyl cyclase by isoprenaline in RIN 5AH. cell lysates, and the stimula tion of cAMP by glucagon-like peptide-1 (7-36) amide (GLP-1). It also block s insulin secretion stimulated by GLP-1, but not by dibutyryl cyclic AMP. H ence, we suggest that NPY inhibits insulin secretion from RIN SAH cells via a Y1 receptor linked through G(i) to the inhibition of adenylyl cyclase.