Unidad de Investigación Médica en Bioquímica, Centro Médico Nacional Siglo XXI, México DF, México.
Pharmacology. 2010;85(2):121-30. doi: 10.1159/000279329. Epub 2010 Feb 3.
Glucosamine (GlcN)-induced insulin resistance is associated with an increase in O-linked-N-acetylglucosaminylated modified proteins (O-GlcNAcylated proteins). The role played by O-GlcNAc-selective-N-acetyl-beta-D-glucosaminidase (O-GlcNAcase), which removes O-N-acetyl-glucosamine residues from O-GlcNAcylated proteins, has not yet been demonstrated. We investigated whether GlcN-induced whole-body insulin resistance is related to tissue O-GlcNAcase activity and mRNA expression. GlcN (30 mumol/kg/min) or physiological saline (control) was intravenously infused into Sprague-Dawley rats for 2 h. After GlcN treatment, rats were subjected to the following: intravenous glucose tolerance test, insulin tolerance test or removal of the liver, muscle and pancreas. GlcN was found to provoke hyperglycemia compared to control (8.6 +/- 0.41 vs. 4.82 +/- 0.17 mM, p < 0.001). The insulin resistance index (HOMA-IR) increased (15.76 +/- 1.47 vs. 10.14 +/- 1.41, p < 0.001) and the beta-cell function index (HOMA-beta) diminished (182.69 +/- 22.37 vs. 592.01 +/- 103, p < 0.001). Liver glucose concentration was higher in the GlcN group than in the control group (0.37 +/- 0.04 vs. 0.24 +/- 0.038 mmol/g dry weight, p < 0.001). Insulin release index (insulin/glucose) was less in the GlcN group than in the control (2.2 +/- 0.1 vs. 8 +/- 0.8 at 120 min, p < 0.001). In the GlcN group, muscle O-GlcNAcase activity diminished (0.28 +/- 0.019 vs. 0.36 +/- 0.018 nmol of p-nitrophenyl/mg protein/min, p < 0.001), and K(m) increased (1.51 +/- 0.11 vs. 1.12 +/- 0.1 mM, p < 0.001) compared to the control. In the GlcN group, O-GlcNAcase activity/mRNA expression was altered (0.6 +/- 0.07 vs. 1 +/- 0.09 of control, p < 0.05). In conclusion, O-GlcNAcase activity is posttranslationally inhibited during GlcN-induced insulin resistance.
氨基葡萄糖（GlcN）诱导的胰岛素抵抗与 O-连接-N-乙酰氨基葡萄糖修饰蛋白（O-GlcNAcylated 蛋白）的增加有关。O-GlcNAc 选择性-N-乙酰-β-D-氨基葡萄糖苷酶（O-GlcNAcase）的作用尚未得到证实，O-GlcNAcase 可从 O-GlcNAcylated 蛋白上去除 O-N-乙酰葡萄糖胺残基。我们研究了 GlcN 诱导的全身胰岛素抵抗是否与组织 O-GlcNAcase 活性和 mRNA 表达有关。将 GlcN（30 µmOl/kg/min）或生理盐水（对照）静脉输注到 Sprague-Dawley 大鼠体内 2 小时。在 GlcN 处理后，对大鼠进行以下处理：静脉葡萄糖耐量试验、胰岛素耐量试验或肝脏、肌肉和胰腺的切除。与对照组相比，GlcN 引起高血糖（8.6 ± 0.41 与 4.82 ± 0.17 mM，p < 0.001）。胰岛素抵抗指数（HOMA-IR）增加（15.76 ± 1.47 与 10.14 ± 1.41，p < 0.001），β细胞功能指数（HOMA-β）降低（182.69 ± 22.37 与 592.01 ± 103，p < 0.001）。GlcN 组大鼠肝葡萄糖浓度高于对照组（0.37 ± 0.04 与 0.24 ± 0.038 mmol/g 干重，p < 0.001）。GlcN 组大鼠胰岛素释放指数（胰岛素/葡萄糖）低于对照组（120 分钟时为 2.2 ± 0.1 与 8 ± 0.8，p < 0.001）。GlcN 组大鼠肌肉 O-GlcNAcase 活性降低（0.28 ± 0.019 与 0.36 ± 0.018 nmol 对硝基苯基/mg 蛋白/min，p < 0.001），Km 值增加（1.51 ± 0.11 与 1.12 ± 0.1 mM，p < 0.001），与对照组相比。GlcN 组大鼠 O-GlcNAcase 活性/基因表达改变（0.6 ± 0.07 与 1 ± 0.09 为对照组，p < 0.05）。总之，在 GlcN 诱导的胰岛素抵抗期间，O-GlcNAcase 活性被翻译后抑制。
