Bruneau C, Hubert P, Waksman A, Beck J P, Staedel-Flaig C
Biochim Biophys Acta. 1987 May 18;928(3):297-304. doi: 10.1016/0167-4889(87)90189-3.
We altered the cellular lipid composition of an insulin sensitive rat hepatoma cell line through supplementation of the culture medium with linoleic acid (18:2) or 25-hydroxycholesterol, and we studied the effects on insulin stimulation of aminoacid transport system A and glycogen synthesis. The basal rate of sodium-dependent aminoisobutyric acid uptake was slightly reduced in hydroxysterol-treated cells and increased in 18:2-enriched cells. Maximal insulin stimulation of transport was decreased by about 40% in both 18:2 and 25-hydroxycholesterol modified cells, as compared to control cells. In addition to reduced responsiveness, the hydroxysterol-treated cells also showed a diminished sensitivity to insulin, as revealed by a right-shift of the dose-response curve leading to a ED50 of 1.2 X 10(-8) M (P less than 0.02), as compared to 2.45 X 10(-9) M in control cells and 2.13 X 10(-9) M in 18:2 enriched cells. Concerning glycogen synthesis, the basal rate was unaffected by 25-hydroxycholesterol supplementation and slightly reduced in cells enriched in 18:2. Maximal insulin stimulation of glycogen synthesis was reduced by about 40% in both types of lipid modified cells. 25-Hydroxycholesterol again provoked a decrease in sensitivity to insulin: the ED50 was enhanced to 4.9 X 10(-9) M (P less than 0.05), as compared to 1.25 X 10(-9) M in control cells and 1.57 X 10(-9) M in 18:2-supplemented cells. Taken together with the previously reported changes of insulin binding to lipid modified hepatoma cells (Bruneau et al. (1987) Biochim. Biophys. Acta 928, 287-296) our results demonstrate an influence of alterations of the cellular lipid composition on both binding and biological actions of insulin, leading to an insulin-resistant state. Divergences between insulin binding and action were obtained and it was suggested that post-binding events may be responsible for the observed changes. Our findings may be relevant to experimental and clinical states of insulin resistance.
我们通过在培养基中添加亚油酸（18:2）或25-羟基胆固醇来改变胰岛素敏感大鼠肝癌细胞系的细胞脂质组成，并研究其对胰岛素刺激氨基酸转运系统A和糖原合成的影响。在经羟基甾醇处理的细胞中，钠依赖性氨基异丁酸摄取的基础速率略有降低，而在富含18:2的细胞中则有所增加。与对照细胞相比，在18:2和25-羟基胆固醇修饰的细胞中，胰岛素对转运的最大刺激均降低了约40%。除了反应性降低外，经羟基甾醇处理的细胞对胰岛素的敏感性也降低，剂量反应曲线右移导致ED50为1.2×10（-8）M（P<0.02），而对照细胞中为2.45×10（-9）M，富含18:2的细胞中为2.13×10（-9）M。关于糖原合成，基础速率不受添加25-羟基胆固醇的影响，而在富含18:2的细胞中略有降低。在两种脂质修饰的细胞中，胰岛素对糖原合成的最大刺激均降低了约40%。25-羟基胆固醇再次导致对胰岛素的敏感性降低：ED50提高到4.9×10（-9）M（P<0.05），而对照细胞中为1.25×10（-9）M，添加18:2的细胞中为1.57×10（-9）M。结合先前报道的胰岛素与脂质修饰肝癌细胞结合的变化（Bruneau等人（1987年），《生物化学与生物物理学报》928，287-296），我们的结果表明细胞脂质组成的改变对胰岛素的结合和生物学作用均有影响，导致胰岛素抵抗状态。胰岛素结合与作用之间存在差异，提示结合后事件可能是观察到的变化的原因。我们的发现可能与胰岛素抵抗的实验和临床状态相关。
