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

In order to characterize neuropeptide Y (NPY) receptors present in human adipocytes, 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 absence of Y-2 signals. Binding studies, using selective radioiodinated ligands, detected a high number (B-max = 497 +/- 124 fmol/mg protein) of a high affinity binding site only with [I-125]peptide YY (PYY) and [I-125](Leu(31),Pro(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 selective NPY receptor antagonists, SR120819A and BIBP3226, In (S-35]GTP gamma S binding experiments, PW activation was totally inhibited by SR120819A and BIBP3226, Both compounds antagonized, with similar efficiency, the antilipolytic effect exerted by NPY in isolated adipocytes. Finally, PYY and Y-1 ligands enhanced adipocyte leptin secretion, an effect totally prevented by SR120819A, Thus, highly expressed in human adipocytes, the Y-1 receptor sustains the strong antilipolytic effect of NPY and exerts a positive action on leptin secretion. (C) 2000 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.