肿瘤坏死因子-α削弱谷氨酰胺促大鼠骨骼肌蛋白质合成的途径  

Study of the effects of tumor necrosis factor-α in decreasing the protein synthesis of skeletal muscle stimulated by glutamine and its pathway in rats

作　　者：周济宏[1] 洪志坚[1] 胡心宝[1] 解伟光[1] 于攀[1] 李幼生[2] 

机构地区：[1]南京军区南京总医院烧伤整形科,江苏南京210002 [2]南京军区南京总医院解放军普通外科研究所,江苏南京210002

出　　处：《感染．炎症．修复》2015年第3期152-156,共5页Infection Inflammation Repair

摘　　要：目的:研究肿瘤坏死因子-α(TNF-α)对谷氨酰胺促大鼠骨骼肌蛋白质合成及对细胞膜谷氨酰胺载体ASCT2 mRNA和蛋白表达的影响,揭示TNF-α影响谷氨酰胺促蛋白质合成的途径。方法:30只雄性SD大鼠,随机分为3组:对照组,谷氨酰胺组(Gln组)和谷氨酰胺+肿瘤坏死因子组(Gln+TNF-α组)。所有大鼠均行72 h全肠外静脉营养(TPN)。对照组给予普通TPN;Gln组给予添加丙氨酰谷氨酰胺二肽的肠外营养,谷氨酰胺剂量为0.3 g·kg^(-1)·d^(-1);Gln+TNF-α组TPN方法同Gln组,并于实验结束前24 h持续静脉滴注TNF-α(5μg·kg^(-1)·h^(-1))。所有大鼠均于取材前0.5 h一次性静脉注射L^(-1)5N亮氨酸1.0 mmol/kg。TPN后72 h分别取血和下肢骨骼肌,测定血浆TNF-α浓度(双抗体夹心ELISA法)、血浆和骨骼肌Gln浓度(高效液相色谱分析法)、骨骼肌蛋白质分数合成率(质谱仪测定后计算)、载体ASCT2 mRNA(RT-PCR方法)及蛋白(Western Blot法)表达水平。结果:Gln+TNF-α组血浆TNF-α浓度显著高于其他两组;Gln+TNF-α组血浆及骨骼肌中谷氨酰胺浓度最高;Gln组和Gln+TNF-α组骨骼肌中蛋白质合成率均高于对照组,并且Gln组最高,各组间差异显著(P<0.01)。对照组ASCT2 mRNA表达最低(P<0.01),而另两组间差异无显著性(P>0.05)。3组ASCT2蛋白均有表达,Gln组显著高于对照组和Gln+TNF-α组(P<0.01)。结论:TNF-α能够升高大鼠血浆及骨骼肌中谷氨酰胺的浓度,削弱谷氨酰胺的促蛋白质合成作用;其途径是抑制谷氨酰胺载体蛋白的合成,降低了骨骼肌细胞对谷氨酰胺摄入,导致组织蛋白质合成下降。Objective: To study whether and how tumor necrosis factor-α(TNF-α) affects glutamine-enhanced protein synthesis of skeletal muscle, and the effects of TNF-α on the expression of mRNA and protein of ASCT2, a kind of membrane transportor of glutamine. Methods: Thirty male Sprague-Dawley rats were randomly divided into 3 groups: control group, glutamine group(Gln group,), and Gln+TNF-α group. All rats received total parenteral nutrition(TPN) components for 3 days. The animals of the control group were only supplemented with general TPN, while those in the Gln group were given glutamine-enriched(0.3 g·kg^(-1)·d^(-1), glutamine was supplied by alanyl glutamine dipeptide) TPN, and those of the Gln+TNF-α group were supplemented with glutamine-enriched TPN, and then they received intravenous injection of 5 μg·kg^(-1)·h^(-1) of TNF-α in the last 24 hours. In the last 30 minutes of TPN, all rats received intravenous injection of 1.0 mmol/kg of L^(-1)5 N leucine. The blood and skeletal muscles were sampled 72 hours after TPN, the plasma concentrations of TNF-α, the content of glutamine in plasma and skeletal muscles, the fractional synthesis rate of skeletal muscles, the mRNA and protein expression of ASCT2 were assessed. Results: The plasma level of TNF-α in the Gln+TNF-α group was the highest among 3 groups(P <0.01). The concentration of glutamine in plasma and skeletal muscles was more elevated in the Gln+TNF-α group than that in the other two groups(P<0.01). The fractional synthesis rate of skeletal muscles increased more significantly in the Gln+TNF-αand Gln groups than that in the control group, and it was highest in the Gln group(P<0.01). The mRNA expression of ASCT2 in control group was statistically significantly lower than that in the other two groups(P <0.01), but the difference was not significant between Gln+TNF-α and Gln groups(P﹥0.05). The protein expression level of ASCT2 in Gln group was statistically higher than that in the control and Gln+TNF-α groups(P <0.01). Conclusions: TNF-α coul

关 键 词：肿瘤坏死因子-Α 谷氨酰胺 全肠外营养 蛋白质合成率 谷氨酰胺载体 ASCT2 

分 类 号：R587.1[医药卫生—内分泌]