Gregory Chris M, Williams Richard H, Vandenborne Krista, Dudley Gary A
Department of Physical Therapy, University of Florida, Gainesville, FL 32610-0154, USA.
Eur J Appl Physiol. 2005 Oct;95(4):276-82. doi: 10.1007/s00421-005-0003-x. Epub 2005 Oct 27.
Characteristics of skeletal muscle such as fiber type composition and activities of key metabolic enzymes have been purported to affect glycogen utilization. However, the relative importance individual factors may have in predicting glycogen utilization of individual muscle fibers has not been addressed. Thus, we sought to determine the relative importance that metabolic characteristics and phenotypic expression of individual fibers have in predicting fiber specific glycogen utilization during neuromuscular electrical stimulation (NMES) exercise. Biopsies were taken from the m, vastus lateralis (VL) of eight recreationally active males before and immediately after 30 min of non-fatiguing NMES and analyzed for type (I, IIa and IIx), succinate dehydrogenase activity (SDH), glycerol-phosphate dehydrogenase activity (GPDH), quantitative-actomyosin adenosine triphosphatase activity (qATPase), and glycogen content. Our results demonstrate that a ratio of enzyme activities representing pathways for energy supply and energy demand (SDH: qATPase) accounted for more of the variance in glycogen utilization (y=0.2091 e(-0.0329x ), R2=0.622, P< or = 0.0001) than SDH (R2=0.321) or qATPase (R2=0.365) alone. Fiber phenotype was also a significant predictor of glycogen utilization, but to a lesser extent than the other variables studied (R2=0.201). A ratio of the activities of enzymes representing pathways of energy supply and energy demand, represented by SDH:qATPase, is a better predictor of glycogen utilization than either of its components independently while fiber phenotype, although a statistically significant predictor of glycogen utilization, may not be the most appropriate determinate of the functional characteristics of an individual fiber.
骨骼肌的特征，如纤维类型组成和关键代谢酶的活性，据称会影响糖原的利用。然而，个体因素在预测单个肌纤维糖原利用方面的相对重要性尚未得到探讨。因此，我们试图确定代谢特征和单个纤维的表型表达在预测神经肌肉电刺激（NMES）运动期间纤维特异性糖原利用方面的相对重要性。在8名有运动习惯的男性进行30分钟无疲劳NMES之前和之后立即从股外侧肌（VL）取活检样本，并分析其类型（I、IIa和IIx）、琥珀酸脱氢酶活性（SDH）、甘油磷酸脱氢酶活性（GPDH）、定量肌动球蛋白三磷酸腺苷酶活性（qATPase）和糖原含量。我们的结果表明，代表能量供应和能量需求途径的酶活性比率（SDH:qATPase）比单独的SDH（R2 = 0.321）或qATPase（R2 = 0.365）更能解释糖原利用的差异（y = 0.2091 e(-0.0329x)，R2 = 0.622，P≤0.0001）。纤维表型也是糖原利用的一个重要预测指标，但程度低于其他研究变量（R2 = 0.201）。由SDH:qATPase表示的代表能量供应和能量需求途径的酶活性比率比其任何一个单独成分更能预测糖原利用，而纤维表型虽然是糖原利用的一个统计学上显著的预测指标，但可能不是单个纤维功能特征的最合适决定因素。
