Yki-Järvinen H, Virkamäki A, Daniels M C, McClain D, Gottschalk W K
Department of Medicine, University of Texas Health Science Center at San Antonio, USA.
Metabolism. 1998 Apr;47(4):449-55. doi: 10.1016/s0026-0495(98)90058-0.
O-linked N-acetylglucosamine (O-GlcNAc) is an abundant posttranslational modification of serine/threonine residues of nuclear and cytoplasmic proteins. We determined whether insulin or coinfusion of glucosamine (GlcN) with insulin alters O-GlcNAc of skeletal muscle proteins. Three groups of conscious fasted rats received 6-hour infusions of either saline (BAS), insulin 18 mU/kg.min and saline (INS), or insulin and GlcN 30 micromol/kg.min (GLCN) during maintenance of normoglycemia. At 6 hours, the concentrations of muscle UDP-GlcNAc, UDP-N-acetylgalactosamine (UDP-GalNAc), UDP-glucose (UDP-Glc), UDP-galactose (UDP-Gal), glycogen, and N and O-linked GlcNAc (galactosyltransferase labeling followed by beta elimination) were measured in freeze-clamped abdominis muscle. Insulin increased whole-body glucose uptake from 49 +/- 5 to 239 +/- 8 micromol/kg.min (P < .001) and glycogen in abdominis muscle from 138 +/- 11 to 370 +/- 26 mmol/kg dry weight (P < .001). Insulin increased the amount of cytosolic N - and O-linked GlcNAc by 56% from 362 +/- 30 to 564 +/- 45 dpm/microg protein . 100 min (P < .02), and O-GlcNAc from 221 +/- 16 to 339 +/- 27 dpm/microg . 100 min (P < .02). Glycogen content was positively correlated with the amount of total (r = .90, P < .005) and O-linked GlcNAc in insulin-infused animals. Coinfusion of GlcN with insulin increased muscle UDP-GlcNAc about fourfold (100 +/- 6 nmol/g) compared with insulin (27 +/- 1, P < .001) or saline (25 +/- 1, P < .001) infusion. GlcN also decreased glucose uptake over 6 hours by 30% to 168 +/- 8 micromol/kg . min (P < .001 for GLCN v INS) and muscle glycogen to 292 +/- 24 mmol/kg dry weight (P < .05 for GLCN v INS). Both total (635 +/- 60 dpm/microg . 100 min, P < .002) and O-linked GlcNAc (375 +/- 36 dpm/microg . 100 min, P < .002) in the cytosol were significantly higher in GLCN rats (635 +/- 60 dpm/microg) versus BAS rats (P < .002). As in INS rats, muscle glycogen and O-GlcNAc were positively correlated in GLCN rats (r = .54, P < .05). Variation in total and O-linked GlcNAc in GLCN rats was due both to GlcN (P < .02) and to variation in the glycogen content (P < .005).
O-连接的N-乙酰葡糖胺（O-GlcNAc）是一种存在于核蛋白和胞质蛋白丝氨酸/苏氨酸残基上的丰富的翻译后修饰。我们研究了胰岛素或葡糖胺（GlcN）与胰岛素共同输注是否会改变骨骼肌蛋白的O-GlcNAc。三组清醒禁食大鼠在维持血糖正常的过程中接受了6小时的输注，分别为生理盐水（BAS）、胰岛素18 mU/kg·min和生理盐水（INS）、胰岛素和GlcN 30 μmol/kg·min（GLCN）。6小时后，在冷冻钳夹的腹肌中测量肌肉UDP-GlcNAc、UDP-N-乙酰半乳糖胺（UDP-GalNAc）、UDP-葡萄糖（UDP-Glc）、UDP-半乳糖（UDP-Gal）、糖原以及N-连接和O-连接的GlcNAc（半乳糖基转移酶标记后进行β消除）的浓度。胰岛素使全身葡萄糖摄取量从49±5增加到239±8 μmol/kg·min（P<.001），腹肌中的糖原从138±11增加到370±26 mmol/kg干重（P<.001）。胰岛素使胞质中N-连接和O-连接的GlcNAc量从362±30增加到564±45 dpm/μg蛋白·100分钟，增加了56%（P<.02），O-GlcNAc从221±16增加到339±27 dpm/μg·100分钟（P<.02）。在输注胰岛素的动物中，糖原含量与总GlcNAc量（r =.90，P<.005）和O-连接的GlcNAc量呈正相关。与输注胰岛素（27±1，P<.001）或生理盐水（25±1，P<.001）相比，GlcN与胰岛素共同输注使肌肉UDP-GlcNAc增加了约四倍（100±6 nmol/g）。GlcN还使6小时内的葡萄糖摄取量减少了30%，降至168±8 μmol/kg·min（GLCN与INS相比，P<.001），肌肉糖原降至292±24 mmol/kg干重（GLCN与INS相比，P<.05）。与BAS组大鼠相比，GLCN组大鼠胞质中的总GlcNAc（635±60 dpm/μg·100分钟，P<.002）和O-连接的GlcNAc（375±36 dpm/μg·100分钟，P<.002）均显著升高。与INS组大鼠一样，GLCN组大鼠的肌肉糖原和O-GlcNAc呈正相关（r =.54，P<.05）。GLCN组大鼠中总GlcNAc和O-连接的GlcNAc的变化既归因于GlcN（P<.02），也归因于糖原含量的变化（P<.005）。
