Kahn B B, Simpson I A, Cushman S W
Experimental Diabetes Section, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland 20892.
J Clin Invest. 1988 Aug;82(2):691-9. doi: 10.1172/JCI113649.
The effects of fasting and refeeding on the glucose transport response to insulin in isolated rat adipose cells have been examined using 3-O-methylglucose transport in intact cells and cytochalasin B binding and Western blotting in subcellular membrane fractions. After a 72-h fast, basal glucose transport activity decreases slightly and insulin-stimulated activity decreases greater than 85%. Following 48 h of fasting, insulin-stimulated glucose transport activity is diminished from 3.9 +/- 0.5 to 1.3 +/- 0.3 fmol/cell per min (mean +/- SEM). Similarly, the concentrations of glucose transporters are reduced with fasting in both the plasma membranes from insulin-stimulated cells from 38 +/- 5 to 18 +/- 3 pmol/mg of membrane protein and the low density microsomes from basal cells from 68 +/- 8 to 34 +/- 9 pmol/mg of membrane protein. Ad lib. refeeding for 6 d after a 48-h fast results in up to twofold greater maximally insulin-stimulated glucose transport activity compared with the control level (7.1 +/- 0.4 vs. 4.5 +/- 0.2 fmol/cell per min), before returning to baseline at 10 d. However, the corresponding concentration of glucose transporters in the plasma membranes is restored only to the control level (45 +/- 5 vs. 50 +/- 5 pmol/mg of membrane protein). Although the concentration of glucose transporters in the low density microsomes of basal cells remains decreased, the total number is restored to the control level due to an increase in low density microsomal protein. Thus, the insulin-resistant glucose transport in adipose cells from fasted rats can be explained by a decreased translocation of glucose transporters to the plasma membrane due to a depleted intracellular pool. In contrast, the insulin hyperresponsive glucose transport observed with refeeding appears to result from (a) a restored translocation of glucose transporters to the plasma membrane from a repleted intracellular pool and (b) enhanced plasma membrane glucose transporter intrinsic activity.
利用完整细胞中的3-O-甲基葡萄糖转运以及亚细胞膜组分中的细胞松弛素B结合和蛋白质免疫印迹法，研究了禁食和再喂养对分离的大鼠脂肪细胞中葡萄糖转运对胰岛素反应的影响。禁食72小时后，基础葡萄糖转运活性略有下降，胰岛素刺激的活性下降超过85%。禁食48小时后，胰岛素刺激的葡萄糖转运活性从3.9±0.5降至1.3±0.3 fmol/细胞每分钟（平均值±标准误）。同样，禁食时，胰岛素刺激细胞的质膜中葡萄糖转运体的浓度从38±5降至18±3 pmol/mg膜蛋白，基础细胞的低密度微粒体中葡萄糖转运体的浓度从68±8降至34±9 pmol/mg膜蛋白。禁食48小时后自由采食6天，与对照水平相比，最大胰岛素刺激的葡萄糖转运活性提高了两倍（分别为7.1±0.4和4.5±0.2 fmol/细胞每分钟），然后在第10天恢复到基线水平。然而，质膜中相应的葡萄糖转运体浓度仅恢复到对照水平（分别为45±5和50±5 pmol/mg膜蛋白）。虽然基础细胞低密度微粒体中葡萄糖转运体的浓度仍然降低，但由于低密度微粒体蛋白增加，其总数恢复到对照水平。因此，禁食大鼠脂肪细胞中胰岛素抵抗性葡萄糖转运可解释为由于细胞内池耗尽导致葡萄糖转运体向质膜的转位减少。相反，再喂养时观察到的胰岛素高反应性葡萄糖转运似乎是由于：（a）细胞内池充盈后葡萄糖转运体向质膜的转位恢复；（b）质膜葡萄糖转运体内在活性增强。
