title: Estrogen receptor alpha regulates insulin sensitivity through IRS-1 tyrosine phosphorylation in mature 3T3-L1 adipocytes.
abstract: There are many clinical and experimental reports demonstrating that estrogens and insulin interact when affecting their target organs. Estrogen receptors consist of two isoforms, estrogen receptors-alpha (ER-alpha) and -beta (ER-beta), but their roles in insulin-induced glucose uptake in mature adipose tissue have yet to be clarified. To evaluate the roles of ER-alpha, expressed predominantly in adipocytes, we have investigated the effects of estradiol (E2), an ER-alpha selective agonist (PPT), and its selective antagonist (MPP) on glucose uptake and insulin action in 3T3-L1 adipocytes. 3T3-L1 adipocytes were exposed to E2 or PPT and/or MPP at different concentrations. The cells were then subjected to 2-deoxy-D-glucose transport assay, western blot analysis, or RT-PCR analysis. Treatment of these cells with E2 or PPT resulted in biphasic effects on glucose transport, that is high (10(-5) M or 3 x 10(-6) M each) and low (10(-8) M) doses produced inhibition and stimulation, respectively. The favorable effect observed at 10(-8) M of E2 was diminished by treatment with MPP. Western bolt analysis revealed that these effects of E2, PPT and MPP paralleled the level of IRS-1 tyrosine phosphorylation. However, IRS-1 serine phosphorylation, suppressor of cytokine signaling (SOCS)-1,-2,-3 and protein tyrosine phosphatase 1B (PTP1B) expression did not change compared to control subjects. Our data clearly show that ER-alpha contributes to insulin stimulated glucose uptake through regulation of the tyrosine phosphorylation of IRS-1 protein.
authors.affiliation: Division of Endocrinology, Metabolism, Hematological Sciences and Therapeutics, Department of Bio-Signal Analysis, Yamaguchi University Graduate School of Medicine, Ube, Japan.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Muraki
authors.forename: Shigeru
authors.initials: S
authors.lastname: Okuya
authors.forename: Yukio
authors.initials: Y
authors.lastname: Tanizawa
mesh_terms: D041721:3T3-L1 Cells; D000818:Animals; D003847:Deoxyglucose / Q000493:pharmacokinetics; D004958:Estradiol / Q000494:pharmacology; D047628:Estrogen Receptor alpha / Q000819:agonists / Q000037:antagonists & inhibitors / Q000502:physiology*; D047629:Estrogen Receptor beta / Q000378:metabolism; D055504:Insulin Receptor Substrate Proteins; D007333:Insulin Resistance; D051379:Mice; D010636:Phenols; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D000077489:Piperazine; D010879:Piperazines / Q000494:pharmacology; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011720:Pyrazoles / Q000494:pharmacology; D050826:Suppressor of Cytokine Signaling Proteins / Q000378:metabolism
chemical_list: D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D055504:Insulin Receptor Substrate Proteins; C526295:Irs1 protein, mouse; D010636:Phenols; D010750:Phosphoproteins; D010879:Piperazines; D011720:Pyrazoles; D050826:Suppressor of Cytokine Signaling Proteins; C486184:4,4',4''-(4-propyl-((1)H)-pyrazole-1,3,5-triyl) tris-phenol; D000077489:Piperazine; D004958:Estradiol; D003847:Deoxyglucose; D011505:Protein-Tyrosine Kinases; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D017027:Protein Tyrosine Phosphatases; C516609:Ptpn1 protein, mouse