胰岛素强化治疗对烫伤脓毒症兔骨骼肌蛋白高降解的调节及其机制

目的探讨胰岛素强化治疗对烫伤脓毒症骨骼肌蛋白高降解的调节及机制。方法雄性日本大耳白兔30只，按随机数字表法将动物分为烫伤组（S组）、烫伤脓毒症组（SS组）、烫伤治疗组（SI组）、烫伤脓毒症治疗组（SSI组）以及对照组（C组），每组6只动物。S组使用沸水致背部30％总体表面积Ⅲ度烫伤；SS组同样条件致伤后，立即腹腔注射内毒素（2mg／kg）模拟烫伤脓毒症。SI组和SSI组从伤后2h开始经静脉泵入胰岛素，使血糖值始终波动在4．4～6．1mmol／L。通过高效液相-荧光法检测伸趾长肌和尿内三甲基组氨酸（3-MH）的含量；采用核糖核酸印迹法（Northern blot）检测伸趾长肌内泛素基因的表达变化。结果S组和SS组伸趾长肌和尿内3-MH含量较C组均显著升高（P均〈0．01）；SI组和SSI组伸趾长肌和尿内3-MH含量分别较S组和SS组显著降低（P均〈0．01）。S组和SS组伸趾长肌内编码泛素的基因转录水平则较C组显著增强（P均〈0．01）；SI组和SSI组伸趾长肌内编码泛素的基因转录水平分别较S组和SS组显著降低（P均〈0．01）。结论严重烫伤特别是合并内毒紊攻击后早期伸趾长肌细胞内泛素-蛋白酶体途径活性即显著增强，蛋白降解率显著增加。胰岛素强化治疗能通过基因水平抑制细胞内泛素-蛋白酶体途径的活性，有效降低烫伤脓毒症时骨骼肌蛋白高降解。

Effect of insulin intensive treatment on hyperproteolysis of skeletal muscle in scalded rabbit with sepsis

OBJECTIVE: To study the effect of insulin intensive treatment on hyperproteolysis of skeletal muscle in scalded rabbit with sepsis. METHODS: Male white rabbits were randomly divided into scald group (S group), scald sepsis group (SS group), scald with insulin treatment group (SI group), scald sepsis with insulin treatment group (SSI group), and control group (C group), with 6 animals in each group. The extent of scald injury was 30% total body surface area (TBSA) III degree in depth, and the model of scald sepsis was replicated by administration of endotoxin (2 mg/kg) into the peritoneal cavity immediately after scald injury. Insulin intensive treatment was given with injection of insulin to keep the plasma glucose level in physiologic range (4.4-6.1 mmol/L) for SI group and SSI group. The contents of 3-methylhistidine (3-MH) in extensor digitorium longus (EDL) muscles and urine were determined with high performance liquid chromatography. The expressions of upiquitin mRNA in the EDL muscle were assessed with Northern blot analysis. RESULTS: The contents of 3-MH in EDL muscles and urine of S group and SS group were increased significantly as compared with C group (all P<0.01), and that of SI group and SSI group were decreased markedly compared with S group and SS group (all P<0.01), respectively. The mRNA expression of ubiquitin of S group and SS group was enhanced significantly compared with C group (all P<0.01), and that of SI group and SSI group was down-regulated notably compared with S group and SS group (all P<0.01), respectively. CONCLUSION: The activity of ubiquitin system, one of important protein degradation pathways, and the proteolysis in skeletal muscle are enhanced after scald injury, especially so sepsis sets in, and insulin intensive treatment can effectively alleviate hyperproteolysis of skeletal muscle through inhibiting the activity of ubiquitin system at gene level.