严重烧伤脓毒症患者骨骼肌蛋白分解代谢的临床研究

目的分析严重烧伤脓毒症患者骨骼肌蛋白降解变化及其生物学机制。方法收集同期收治的20例严重烧伤脓毒症患者(烧伤脓毒症组)和12例整形患者(对照组)的血、24h尿和股四头肌标本,通过放免法测定血浆皮质醇和肿瘤坏死因子(TNF)-α含量,高效液相-色谱分析法检测股四头肌内3-甲基组氨酸(3-MH)含量以及尿中3-MH排出量,核糖核酸印迹法检测股四头肌内编码泛素、E2-14k和蛋白酶体C2亚基的mRNA表达变化。蛋白免疫印迹法检测股四头肌内蛋白酶体C2亚基的蛋白表达变化。结果烧伤脓毒症组血浆内皮质醇含量(478±56)μg/L和TNF-α含量(22·4±3·8)μg/L均显著高于对照组血内皮质醇含量(72±12)μg/L和TNF-α含量(0·5±0·1)μg/L(均P<0·01)。烧伤脓毒症组股四头肌内3-MH含量(4·3±0·6)μmol/g及24h尿内3-MH排出量(456±25)μmol均显著高于对照组股四头肌内3-MH含量(2·5±0·4)μmol/g和24h尿内3-MH排出量(202±29)μmol(均P<0·01)。烧伤脓毒症组股四头肌泛素mRNA2·4kb条带和1·2kb条带的表达分别较对照组增强51%和32%,差异有统计学意义(P<0·01);E2-14k mRNA1·2kb条带的表达较对照组增强75%,差异有统计学意义(P<0·01);蛋白酶体C2亚基mRNA和蛋白表达分别较对照组增强39%和130%,差异有统计学意义(P<0·01)。结论重症烧伤脓毒症时骨胳肌蛋白降解显著增强,体内糖皮质激素及TNF-α含量增加,从基因水平激活细胞内蛋白降解途径-泛素系统是重症烧伤脓毒症患者骨胳肌蛋白降解增强的原因之一。

Clinical study of skeletal muscle proteolysis in severely burned patients with sepsis

OBJECTIVE: To study the changes of skeletal muscle proteolysis in severely burned patients with sepsis and analyze its possible mechanism. METHODS: Blood samples were collected from 20 burned patients with sepsis, aged 42 +/- 10 (burn sepsis group), and 12 patients undergoing plastic operation after burn, aged 43 +/- 8 (control group) to determine the plasma concentrations of cortisol and tumor necrosis factor (TNF-alpha) by radioimmunoassay. 24 h urine was retained to determine the level of 3-methylhistidine (3-MH) by high performance liquid chromatography. An appropriate amount of quadriceps femoris muscle sample was collected during operation to determine the concentration of 3-methylhistidine with high performance liquid chromatography, the expression of ubiquitin mRNA, E(2)-14k mRNA and C(2) subunit mRNA by Northern blot analysis, and the protein expression of C(2) subunit by Western blot analysis. RESULTS: The plasma concentrations of cortisol and TNF-alpha in the burn sepsis group were 478 +/- 56 microg/L and 22.4 +/- 3.8 microg/L respectively, both significantly higher than the those in the normal control group, 72 +/- 12 microg/L and 0.5 +/- 0.1 microg/L respectively (both P < 0.01). The amount of 3-MH in the quadriceps femoris muscle of the burn sepsis group was 4.3 +/- 0.6 micromol/g, significantly higher than that of the control group (2.5 +/- 0.4 micromol/g, P < 0.01). The 24 h urinary output of 3-MH of the burn sepsis group was 456 +/- 25 micromol, significantly higher than that of the control group (202 +/- 29 micromol, P < 0.091). The expressions of ubiquitin mRNA 2.4 Kilobase pair (kb) and 1.2 kb, E(2)-14k mRNA 1.2 kb and C(2) subunit mRNA in quadriceps femoris muscles of the burn sepsis group were increased with 51%, 32%, 75%, and 39% respectively, as compared with those of the control group (all P < 0.01). The protein expression of C(2) subunit in quadriceps femoris muscles of the burn sepsis group was increased with 130% than that of the control group (P < 0.01). CONCLUSION: The proteolytic rate in skeletal muscle is increased during sepsis after severe burn and the mechanism is related to the enhanced function of the ubiquitin system at both gene and protein levels with the hypersecretion of glucocorticoid and TNF-alpha.