目的：探讨膳食补充亮氨酸对增龄所致骨骼肌萎缩的影响及可能机制。方法：13月龄雄性ICR小鼠根据体重随机分为补充亮氨酸（Leu ）、补充丙氨酸（Ala ）以及空白对照组（NC ），Leu和 Ala组分别在饲料中添加5％比例亮氨酸和3．4％比例丙氨酸8周，NC组饲喂普通饲料。末次给食后禁食17 h处死小鼠，便携式血糖仪检测血糖；ELISA法检测血清胰岛素、IG F‐1；分光光度法检测血尿素氮；氨基酸分析仪检测血浆游离氨基酸谱；H E染色观察肌纤维适应性及病理性改变；BCA 法定量蛋白后，Western Blotting 法检测 Ub、Atrogin‐1、MuRF‐1及M HCⅡ的蛋白表达。结果：与NC组和Ala组小鼠相比，添加5％亮氨酸（Leu组）未显著影响小鼠体重、采食量，血糖、胰岛素水平与IG F‐1无显著变化，血尿素氮水平显著下降；血浆游离亮氨酸含量升高而丙氨酸、甘氨酸和谷氨酸含量下降；腓肠白肌湿重／体重比值、肌纤维横截面积及直径均表现出增长的趋势，但增幅并不显著；骨骼肌纤维圆形化、核中心化病变显著减少；腓肠白肌总蛋白含量、M HCⅡ蛋白表达显著增加，而 Ub、Atrogin‐1及MuRF‐1的蛋白表达均显著下降。Ala组与 NC组小鼠相比各指标差异均无统计学意义。结论：亮氨酸能够削弱老年前期小鼠骨骼肌萎缩，其机制可能与亮氨酸对泛素‐蛋白酶体系统的抑制有关。%Objective :To investigate the effect of leucine supplementation on muscle atrophy in‐duced by ageing and preliminarily analyzes the possible mechanism .Methods :Thirteen‐month‐old male ICR mice were randomly divided into dietary leucine supplementation (Leu) ,alanine supplementation (Ala) and normal control group (NC) by body weight .Mice in leucine (Leu) and alanine (Ala ) supplementation group were treated with normal chow diet supplemented with 5% leucine and 3 .4% alanine respectively for 8 weeks ,while normal control group were fed with normal diet .Seventeen hours of fasting after the last feeding ,mice were sacrificed . The blood glucose was determined with a portable blood glucose meter .The level of BUN was detected by using spectrophotometry .The profile of plasma free amino acids was detected with an amino acids analyzer .The serum insulin and IGF‐1 concentration were determined by ELISA .The skeletal muscle morphology was observed by using hematoxylin and eosin stai‐ning .The protein expression of Ub ,Atrogin‐1 ,MuRF‐1 as well as MHC Ⅱ was detected by the method of Western blotting after BCA protein assay .Results :Compared with both NC and Ala group ,the results showed that ,leucine supplementation (Leu) did not change the level of body weight ,food intake ,blood glucose ,serum insulin and IGF‐1 ,while the level of BUN was significantly elevated ;The content of plasma leucine was increased ,content of alanine ,glutamic acid and glycine were all depressed significantly .Although the wet ratio of wet white gastroc‐nemius muscle to body weight ,cross‐sectional area and diameter of fibers were not influenced significantly by leucine supplementation ,still showed a tendency to increase .The incidence of rounded and central nucleus fibers was reduced .Moreover ,total protein content ,the protein ex‐pression of MHCⅡ were both elevated ,while the expression of Ub ,Atrogin‐1 and MuRF‐1 in white gastrocnemius muscle were significantly depressed .There weren’t statistically significant differences of all parameters between mice in NC and Ala group .Conclusion :Leucine supple‐mentation significantly attenuates skeletal muscle atrophy in pre‐senile mice ,which may be cor‐related with inhibiting the activity of ubiquitin‐proteasome system .
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