Martin M S, Pohl S L
J Biol Chem. 1979 Oct 25;254(20):9976-8.
Cultured fibroblasts derived from skin biopsies were used to develop a system for studying insulin resistance in human tissue in vitro. Uptake of alpha-aminoisobutyric acid by cultured human skin fibroblasts was found to occur by a combination of saturable and nonsaturable processes. Insulin stimulated uptake by decreasing the Km of the saturable transport system from 0.58 mM to 0.26 mM. The maximal velocity of saturable uptake was 16.6 nmol/10(7) cells/min in both the presence and absence of insulin. Uptake of alpha-aminoisobutyric acid at 0.2 mM was studied in human skin fibroblasts with and without chronic exposure to insulin for 4 days at an initial concentration of 10 micrograms/ml. Unstimulated uptake was increased from 17 to 20 nmol/10(8) cells/min, and the increase in uptake due to maximal stimulation by insulin was unchanged at 16 nmol/10(8) cells/min in the cells exposed chronically to insulin. The apparent Km for insulin was increased from 80 microunits/ml to 2400 microunits/ml in the insulin-exposed cells. Thus, chronic exposure to insulin induces resistance of alpha-aminoisobutyric acid uptake by decreasing the apparent affinity for insulin.
取自皮肤活检的培养成纤维细胞被用于建立一个体外研究人体组织胰岛素抵抗的系统。发现培养的人皮肤成纤维细胞对α-氨基异丁酸的摄取是由可饱和和不饱和过程共同作用的结果。胰岛素通过将可饱和转运系统的Km值从0.58 mM降至0.26 mM来刺激摄取。在有胰岛素和无胰岛素的情况下，可饱和摄取的最大速度均为16.6 nmol/10(7)个细胞/分钟。在初始浓度为10微克/毫升的条件下，对有或无胰岛素慢性暴露4天的人皮肤成纤维细胞，研究其在0.2 mM时对α-氨基异丁酸的摄取。未受刺激的摄取从17 nmol/10(8)个细胞/分钟增加到20 nmol/10(8)个细胞/分钟，在慢性暴露于胰岛素的细胞中，胰岛素最大刺激引起的摄取增加保持不变，为16 nmol/10(8)个细胞/分钟。在暴露于胰岛素的细胞中，胰岛素的表观Km值从80微单位/毫升增加到2400微单位/毫升。因此，慢性暴露于胰岛素会通过降低对胰岛素的表观亲和力来诱导对α-氨基异丁酸摄取的抵抗。
