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首页> 外文期刊>Journal of cellular biochemistry. >Phosphatase activity in rat adipocytes: effects of insulin and insulin resistance.
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Phosphatase activity in rat adipocytes: effects of insulin and insulin resistance.

机译：大鼠脂肪细胞中的磷酸酶活性：胰岛素和胰岛素抵抗的影响。

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Insulin regulates the activity of both protein kinases and phosphatases. Little is known concerning the subcellular effects of insulin on phosphatase activity and how it is affected by insulin resistance. The purpose of this study was to determine insulin-stimulated subcellular changes in phosphatase activity and how they are affected by insulin resistance. We used an in vitro fatty acid (palmitate) induced insulin resistance model, differential centrifugation to fractionate rat adipocytes, and a malachite green phosphatase assay using peptide substrates to measure enzyme activity. Overall, insulin alone had no effect on adipocyte tyrosine phosphatase activity; however, subcellularly, insulin increased plasma membrane adipocyte tyrosine phosphatase activity 78 +/- 26% (n = 4, P < 0.007), and decreased high-density microsome adipocyte tyrosine phosphatase activity 42 +/- 13% (n = 4, P < 0.005). Although insulin resistance induced specific changes in basal tyrosine phosphatase activity, insulin-stimulated changes were not significantly altered by insulin resistance. Insulin-stimulated overall serine/threonine phosphatase activity by 16 +/- 5% (n = 4, P < 0.005), which was blocked in insulin resistance. Subcellularly, insulin increased plasma membrane and crude nuclear fraction serine/threonine phosphatase activities by 59 +/- 19% (n = 4, P < 0. 005) and 21 +/- 7% (n = 4, P < 0.007), respectively. This increase in plasma membrane fractions was inhibited 23 +/- 7% (n = 4, P < 0. 05) by palmitate. Furthermore, insulin increased cytosolic protein phosphatase-1 (PP-1) activity 160 +/- 50% (n = 3, P < 0.015), and palmitate did not significantly reduce this activity. However, palmitate did reduce insulin-treated low-density microsome protein phosphatase-1 activity by 28 +/- 6% (n = 3, P < 0.04). Insulin completely inhibited protein phosphatase-2A activity in the cytosol and increased crude nuclear fraction protein phosphatase-2A activity 70 +/- 29% (n = 3, P < 0.038). Thus, the major effects of insulin on phosphatase activity in adipocytes are to increase plasma membrane tyrosine and serine/threonine phosphatase, crude nuclear fraction protein phosphatase-2A, and cytosolic protein phosphatase-1 activities, while inhibiting cytosolic protein phosphatase-2A. Insulin resistance was characterized by reduced insulin-stimulated serine/threonine phosphatase activity in the plasma membrane and low-density microsomes. Specific changes in phosphatase activity may be related to the development of insulin resistance. Copyright 2000 Wiley-Liss, Inc.
机译：胰岛素调节蛋白激酶和磷酸酶的活性。关于胰岛素对磷酸酶活性的亚细胞作用及其受胰岛素抵抗的影响知之甚少。这项研究的目的是确定胰岛素刺激的磷酸酶活性亚细胞变化以及它们如何受到胰岛素抵抗的影响。我们使用了体外脂肪酸（棕榈酸酯）诱导的胰岛素抵抗模型，差异离心分离大鼠脂肪细胞，以及使用肽底物测量酶活性的孔雀石绿磷酸酶测定法。总体而言，仅胰岛素对脂肪细胞酪氨酸磷酸酶活性没有影响。然而，在亚细胞中，胰岛素使质膜脂肪细胞酪氨酸磷酸酶活性增加了78 +/- 26％（n = 4，P <0.007），而高密度微粒体脂肪细胞酪氨酸磷酸酶活性降低了42 +/- 13％（n = 4，P <0.005）。尽管胰岛素抵抗引起基础酪氨酸磷酸酶活性的特定变化，但胰岛素抵抗并未明显改变胰岛素刺激的变化。胰岛素刺激的总丝氨酸/苏氨酸磷酸酶活性为16 +/- 5％（n = 4，P <0.005），这被胰岛素抵抗所阻断。在亚细胞中，胰岛素使质膜和粗核组分丝氨酸/苏氨酸磷酸酶活性增加59 +/- 19％（n = 4，P <0.005）和21 +/- 7％（n = 4，P <0.007），分别。棕榈酸酯抑制了质膜分数的这种增加23 +/- 7％（n = 4，P <0. 05）。此外，胰岛素将胞质蛋白磷酸酶-1（PP-1）活性提高了160 +/- 50％（n = 3，P <0.015），而棕榈酸酯并没有显着降低这种活性。然而，棕榈酸酯确实使胰岛素治疗的低密度微粒体蛋白磷酸酶-1活性降低了28 +/- 6％（n = 3，P <0.04）。胰岛素完全抑制了细胞溶质中的蛋白磷酸酶2A活性，并使粗核级分蛋白磷酸酶2A活性增加了70 +/- 29％（n = 3，P <0.038）。因此，胰岛素对脂肪细胞中磷酸酶活性的主要影响是增加细胞膜酪氨酸和丝氨酸/苏氨酸磷酸酶，粗核级分蛋白磷酸酶2A和胞质蛋白磷酸酶1的活性，同时抑制胞质蛋白磷酸酶2A。胰岛素抵抗的特征在于质膜和低密度微粒体中胰岛素刺激的丝氨酸/苏氨酸磷酸酶活性降低。磷酸酶活性的特定变化可能与胰岛素抵抗的发展有关。版权所有2000 Wiley-Liss，Inc.

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