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Identification of High-Affinity Binding Sites for the Insulin Sensitizer Rosiglitazone (BRL-49653) in Rodent and Human Adipocytes Using a Radioiodinated Ligand for Peroxisomal Proliferator-Activated Receptor Î
A radioiodinated ligand, [ 125 I]SB-236636 [( S )-(â)3-[4-[2-[N-(2-benzoxazolyl)-N-methylamino]ethoxy]3-[ 125 I]iodophenyl]2-ethoxy propanoic acid], which is specific for the γ isoform of the peroxisomal proliferator activated receptor (PPARγ), was developed. [ 125 I]SB-236636 binds with high af...
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Published in: | The Journal of pharmacology and experimental therapeutics 1998-02, Vol.284 (2), p.751 |
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Main Authors: | , , , , , , , , , , , , , , , |
Format: | Article |
Language: | English |
Online Access: | Get full text |
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Summary: | A radioiodinated ligand, [ 125 I]SB-236636 [( S )-(â)3-[4-[2-[N-(2-benzoxazolyl)-N-methylamino]ethoxy]3-[ 125 I]iodophenyl]2-ethoxy propanoic acid], which is specific for the γ isoform of the peroxisomal proliferator activated receptor
(PPARγ), was developed. [ 125 I]SB-236636 binds with high affinity to full-length human recombinant PPARγ 1 and to a GST (glutathione S -transferase) fusion protein containing the ligand binding domain of human PPARγ 1 ( K D = 70 nM). Using this ligand, we characterized binding sites in adipose-derived cells from rat, mouse and humans. In competition
experiments, rosiglitazone (BRL-49653), a potent antihyperglycemic agent, binds with high affinity to sites in intact adipocytes
(IC 50 = 12, 4 and 9 nM for rat, 3T3-L1 and human adipocytes, respectively). Binding affinities (IC 50 ) of other thiazolidinediones for the ligand binding domain of PPARγ 1 were comparable with those determined in adipocytes and reflected the rank order of potencies of these agents as stimulants
of glucose transport in 3T3-L1 adipocytes and antihyperglycemic agents in vivo : rosiglitazone > pioglitazone > troglitazone. Competition of [ 125 I]SB-236636 binding was stereoselective in that the IC 50 value of SB-219994, the ( S )-enantiomer of an α-trifluoroethoxy propanoic acid insulin sensitizer, was 770-fold lower than that of SB-219993 [( R )-enantiomer] at recombinant human PPARγ 1 . The higher binding affinity of SB-219994 also was evident in intact adipocytes and reflected its 100-fold greater potency
as an antidiabetic agent. The results strongly suggest that the high-affinity binding site for [ 125 I]SB-236636 in intact adipocytes is PPARγ and that the pharmacology of insulin-sensitizer binding in rodent and human adipocytes
is very similar and, moreover, predictive of antihyperglycemic activity in vivo . |
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ISSN: | 0022-3565 1521-0103 |