Yoshida K, Hirokawa J, Tagami S, Kawakami Y, Urata Y, Kondo T
First Department of Medicine, Hokkaido University School of Medicine, Sapporo, Japan.
Diabetologia. 1995 Feb;38(2):201-10. doi: 10.1007/BF00400095.
Glutathione functions to scavenge oxidants or xenobiotics by covalently binding them and transporting the resulting metabolites through an adenosine 5'-triphosphate-dependent transport system. It has been reported that the intracellular concentration of glutathione decreases in diabetes mellitus. In order to elucidate the physiological significance and the regulation of anti-oxidants in diabetic patients, changes in the activity of the glutathione-synthesizing enzyme, gamma-glutamylcysteine synthetase, and transport of thiol [S-(2,4-dinitrophenyl)glutathione] were studied in erythrocytes from patients with non-insulin-dependent diabetes and K562 cells cultured with 27 mmol/l glucose for 7 days. The activity of gamma-glutamylcysteine synthetase, the concentration of glutathione, and the thiol transport were 77%, 77% and 69%, respectively in erythrocytes from diabetic patients compared to normal control subjects. Treatment of patients with an antidiabetic agent for 6 months resulted in the restoration of gamma-glutamylcysteine synthetase activity, the concentration of glutathione, and the thiol transport. A similar impairment of glutathione metabolism was observed in K562 cells with high glucose levels. The cytotoxicity by a xenobiotic (1-chloro-2,4-dinitrobenzene) was higher in K562 cells with high glucose than in control subjects (50% of inhibitory concentration 300 +/- 24 mumol/l vs 840 +/- 29 mumol/l, p < 0.01). Expression of gamma-glutamylcysteine synthetase protein was augmented in K562 cells with high glucose, while enzymatic activity and expression of mRNA were lower than those in the control subjects. These results suggest that inactivation of glutathione synthesis and thiol transport in diabetic patients increases the sensitivity of the cells to oxidative stresses, and these changes may lead to the development of some complications in diabetes mellitus.
谷胱甘肽通过与氧化剂或外源性物质共价结合，并通过依赖三磷酸腺苷的转运系统运输生成的代谢产物，发挥清除这些物质的作用。据报道，糖尿病患者细胞内谷胱甘肽浓度会降低。为了阐明糖尿病患者体内抗氧化剂的生理意义及其调节机制，我们研究了非胰岛素依赖型糖尿病患者红细胞中谷胱甘肽合成酶γ-谷氨酰半胱氨酸合成酶的活性变化以及硫醇[S-(2,4-二硝基苯基)谷胱甘肽]的转运情况，并对K562细胞进行了为期7天的27 mmol/l葡萄糖培养。与正常对照受试者相比，糖尿病患者红细胞中γ-谷氨酰半胱氨酸合成酶的活性、谷胱甘肽浓度和硫醇转运分别为77%、77%和69%。用抗糖尿病药物治疗患者6个月后，γ-谷氨酰半胱氨酸合成酶活性、谷胱甘肽浓度和硫醇转运得以恢复。在高糖水平的K562细胞中也观察到了类似的谷胱甘肽代谢受损情况。外源性物质（1-氯-2,4-二硝基苯）对高糖K562细胞的细胞毒性高于对照受试者（半数抑制浓度分别为300±24 μmol/l和840±29 μmol/l，p<0.01）。高糖K562细胞中γ-谷氨酰半胱氨酸合成酶蛋白表达增加，而酶活性和mRNA表达低于对照受试者。这些结果表明，糖尿病患者谷胱甘肽合成和硫醇转运失活会增加细胞对氧化应激的敏感性，这些变化可能导致糖尿病某些并发症的发生。
