Characterization of NPY receptors controlling lipolysis and leptin secretion in human adipocytes

In order to characterize neuropeptide Y (NPY) receptors present in human ad ipocytes, we used selective ligands together with specific molecular probes able to recognize the different NPY receptor subtypes, RT-PCR experiments revealed the presence of Y-1 receptor transcripts with Y-4 and Y-5 and abse nce of Y-2 signals. Binding studies, using selective radioiodinated ligands , detected a high number (B-max = 497 +/- 124 fmol/mg protein) of a high af finity binding site only with [I-125]peptide YY (PYY) and [I-125](Leu(31),P ro(34))PYY. These sites exhibited a typical Y-1 profile as indicated by the rank order of affinity of SPY analogs and the high affinity of two selecti ve NPY receptor antagonists, SR120819A and BIBP3226, In (S-35]GTP gamma S b inding experiments, PW activation was totally inhibited by SR120819A and BI BP3226, Both compounds antagonized, with similar efficiency, the antilipoly tic effect exerted by NPY in isolated adipocytes. Finally, PYY and Y-1 liga nds enhanced adipocyte leptin secretion, an effect totally prevented by SR1 20819A, Thus, highly expressed in human adipocytes, the Y-1 receptor sustai ns the strong antilipolytic effect of NPY and exerts a positive action on l eptin secretion. (C) 2000 Federation of European Biochemical Societies. Pub lished by Elsevier Science B.V. All rights reserved.