Horuk R, Rodbell M, Cushman S W, Wardzala L J
J Biol Chem. 1983 Jun 25;258(12):7425-9.
A marked resistance to the stimulatory action of insulin on glucose metabolism has previously been shown in guinea pig, compared to rat, adipose tissue and isolated adipocytes. The mechanism of insulin resistance in isolated guinea pig adipocytes has, therefore, been examined by measuring 125I-insulin binding, the stimulatory effect of insulin on 3-0-methylglucose transport and on lipogenesis from [3-3H]glucose, the inhibitory effect of insulin on glucagon-stimulated glycerol release, and the translocation of glucose transporters in response to insulin. The translocation of glucose transporters was assessed by measuring the distribution of specific D-glucose-inhibitable [3H]cytochalasin B binding sites among the plasma, and high and low density microsomal membrane fractions prepared by differential centrifugation from basal and insulin-stimulated cells. At a glucose concentration (0.5 mM) where transport is thought to be rate-limiting for metabolism, insulin stimulates lipogenesis from 30 to 80 fmol/cell/90 min in guinea pig cells and from 25 to 380 fmol/cell/90 min in rat cells with half-maximal effects at approximately 100 pM in both cell types. Insulin similarly stimulates 3-O-methylglucose transport from 0.40 to 0.70 fmol/cell/min and from 0.24 to 3.60 fmol/cell/min in guinea pig and rat fat cells, respectively. Nevertheless, guinea pig cells bind more insulin per cell than rat cells, and insulin fully inhibits glucagon-stimulated glycerol release. In addition, the differences between guinea pig and rat cells in the stimulatory effect of insulin on lipogenesis and 3-O-methylglucose transport cannot be explained by the greater cell size of the former compared to the latter (0.18 and 0.09 micrograms of lipid/cell, respectively). However, the number of glucose transporters in the low density microsomal membrane fraction prepared from basal guinea pig cells is markedly reduced compared to that from rat fat cells (12 and 70 pmol/mg of membrane protein, respectively) and the translocation of intracellular glucose transporters to the plasma membrane fraction in response to insulin is correspondingly reduced. These results suggest that guinea pig adipocytes are markedly resistant to the stimulatory action of insulin on glucose transport and that this resistance is the consequence of a relative depletion in the number of intracellular glucose transporters.
与大鼠相比，先前已证明豚鼠的脂肪组织和分离的脂肪细胞对胰岛素刺激葡萄糖代谢的作用具有明显抗性。因此，通过测量¹²⁵I-胰岛素结合、胰岛素对3-O-甲基葡萄糖转运以及对[3-³H]葡萄糖脂肪生成的刺激作用、胰岛素对胰高血糖素刺激的甘油释放的抑制作用以及葡萄糖转运蛋白对胰岛素的转位，来研究分离的豚鼠脂肪细胞中的胰岛素抵抗机制。通过测量在基础细胞和胰岛素刺激的细胞中通过差速离心制备的血浆以及高密度和低密度微粒体膜部分中特异性D-葡萄糖抑制的[³H]细胞松弛素B结合位点的分布，来评估葡萄糖转运蛋白的转位。在认为转运对代谢起限速作用的葡萄糖浓度（0.5 mM）下，胰岛素刺激豚鼠细胞中脂肪生成从30增加到80 fmol/细胞/90分钟，在大鼠细胞中从25增加到380 fmol/细胞/90分钟，两种细胞类型中半最大效应约为100 pM。胰岛素同样分别刺激豚鼠和大鼠脂肪细胞中3-O-甲基葡萄糖转运从0.40增加到0.70 fmol/细胞/分钟和从0.24增加到3.60 fmol/细胞/分钟。然而，豚鼠细胞比大鼠细胞每个细胞结合更多的胰岛素，并且胰岛素完全抑制胰高血糖素刺激的甘油释放。此外，豚鼠和大鼠细胞在胰岛素对脂肪生成和3-O-甲基葡萄糖转运的刺激作用方面的差异不能用前者细胞大小大于后者（分别为0.18和0.09微克脂质/细胞）来解释。但是，与大鼠脂肪细胞相比，从基础豚鼠细胞制备的低密度微粒体膜部分中的葡萄糖转运蛋白数量明显减少（分别为12和70 pmol/毫克膜蛋白），并且细胞内葡萄糖转运蛋白对胰岛素的转位相应减少。这些结果表明，豚鼠脂肪细胞对胰岛素刺激葡萄糖转运的作用具有明显抗性，并且这种抗性是细胞内葡萄糖转运蛋白数量相对减少的结果。
