亚细胞特定区域化线粒体含量是否与肌纤维类型、饮食干预有关?

Research on the Relationship between the Subcellular Localization Specific Mitochondrial Contents and Fiber Types or Diet

目的:亚细胞特定区域化线粒体的超微结构与功能表达相关,但亚细胞特定区域下的线粒体含量与肌纤维类型及饮食干预的关系尚不清楚。研究探讨亚细胞特定区域化线粒体(肌原纤维间线粒体、肌膜下线粒体、总线粒体)的含量与不同肌纤维类型的关系,并探究短期饮食干预对肌细胞亚细胞特定区域线粒体含量的影响。方法:招募11名无训练经历的业余锻炼者。在依次接受3种不同的短期饮食(依次为混合饮食、高脂肪+高蛋白质饮食、高碳水化合物饮食)干预后,分别进行75%最大摄氧量强度的功率自行车耐力力竭测试,在运动前、运动中每隔一个小时、运动后即刻对受试者的股外侧肌部位进行肌肉活检,根据受试者在3种不同饮食干预影响下的不同运动表现(112±22 min vs.69±18 min vs.150±30 min),每位受试者在3次测试中分别被采集3条、2条、4条,共9条肌纤维。使用体视学方法分析并计算特定亚细胞定位的线粒体含量。结果:Ⅰ型肌纤维中肌原纤维间(intermyofibrillar,IMF)、肌膜下(subsarcolemmal,SS)线粒体含量显著多于Ⅱ型肌纤维(P<0.001),Ⅰ型肌纤维中总线粒体含量多于Ⅱ型肌纤维(P<0.001)。IMF、SS及总线粒体含量和其对应的z线宽度均具有显著中度正相关(P<0.001,R_(Total)=0.44;P<0.001,R_(IMF)=0.42;P<0.001,R_(SS)=0.37)。此外,高碳水化合物饮食相比于其他两种饮食干预,耐力测试的力竭时间显著更长(P<0.001)。3种不同方式的短期饮食干预下,无论快肌还是慢肌,不同区域的线粒体含量及总含量均不存在显著性差异(P>0.05)。结论:Ⅰ型肌纤维中线粒体总量多于Ⅱ型肌纤维,且在肌细胞微观特性视角下,亚细胞不同区域下分布的线粒体(IMF和SS线粒体),均呈现出在Ⅰ型肌纤维中的分布含量多于Ⅱ型肌纤维的状态;不同肌纤维的总线粒体含量为Z线宽度作为区分快慢肌的判断方法提供了更直接的数据支撑;不同糖原储备的短期饮食干预下,长时间亚极量运动至力竭时间有显著性差异,但运动表现的差异与亚细胞特定区域化线粒体含量无关。

Objective:To explore the relationship between the contents of subcellular localization specific mitochondria(mitochondria between myofibrils,mitochondria under the muscle membrane,total mitochondria)and different muscle fiber types,and the effect of short-term diet intervention on the content of subcellular localization specific mitochondria of muscle cells was investigated as well.Methods:Eleven subjects with exercise habits were reported to lab three times for a bicycle endurance test at 75%VO_(2max)until exhaustion.Each test was performed following either a mixed diet or a Fat+CHO diet or a high CHO diet.Biopsies were taken before exercise,every hour during exercise and immediately after exhaustion.According to the sports performance in the three different diet intervention,nine biopsies(three,two,and four biopsies in three tests,respectively)were obtained from each subject.Results:The content of intermyofibrillar(IMF)and subsarcolemmal(SS)mitochondria in type I muscle fibers was higher than that of typeⅡmuscle fibers(P<0.001),and the total amount of mitochondria in type I muscle fibers was more than typeⅡmuscle fiber(P<0.001).IMF,SS and Total mitochondrial content were positively associated with their corresponding z-line width(P<0.001,R_(Total)=0.44;P<0.001,R_(IMF)=0.42;P<0.001,R_(SS)=0.37).There was no significantly difference in mitochondrial content among the three diets(P>0.05).Conclusions:The total amount of mitochondria in typeⅠmuscle fibers is more than typeⅡmuscle fibers.In addition,the mitochondria(IMF and SS mitochondria)distributed in different subcellular areas also shows the mitochondria content in typeⅠmuscle fibers is higher than that of typeⅡ.The Z-line width of human muscle fibers is an important indicator to determine the types of muscle fibers(typeⅠ,Ⅱ).Significant difference is observed in exhaustion time of the submaximal intensity exercise under the short-term diet intervention of different glycogen reserves,but the difference in exercise performance is not related to the content of subcellular localization specific mitochondria.