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

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 type II muscle fibers(P<0.001), and the total amount of mitochondria in type I muscle fibers was more than type II muscle 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 type Ⅰ muscle fibers is more than type Ⅱ muscle fibers. In addition, the mitochondria(IMF and SS mitochondria) distributed in different subcellular areas also shows the mitochondria content in type Ⅰ muscle fibers is higher than that of type Ⅱ. The Z-line width of human muscle fibers is an important indicator to determine the types of muscle fibers(type Ⅰ, 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.