Importance of fiber type characteristics of the skeletal muscle as a determining factor for the degree of obesity

为了阐明骨骼肌纤维类型特征在确定肥胖程度中的作用，我们进行了三个实验。第一个实验比较具有肥胖遗传易感性的模型动物Zucker肥胖大鼠与非肥胖对照大鼠骨骼肌纤维类型特征。结果表明，Zucker大鼠骨骼肌的氧化能力整体较低，这是由于骨骼肌质量较低。第二个实验检测了喂食高脂肪饮食和正常饮食的大鼠骨骼肌代谢能力和腹部脂肪沉积之间的关系。在正常饮食的大鼠中，骨骼肌氧化能力与腹部脂肪量呈显著负相关。高脂肪饮食诱导肥胖，尽管骨骼肌的氧化能力增强。第三个实验考察了采用自主轮跑的体能训练是否会引起静息代谢率和呼吸交换率R的变化，这种训练可以增加骨骼肌的氧化能力，抑制腹部脂肪的沉积。结果表明，尽管MDH活性显著增加，腹部脂肪重量显著减少，但训练对静息代谢率和R没有显著影响。

Three experiments were conducted in order to elucidate the role of fiber type characteristics of the skeletal muscle in determining the degree of obesity. In the first experiment, fiber type characteristics of the skeletal muscles of Zucker obese rat , the model animal with genetic predisposition for obesity, were compared with those of non-obese control rat. The results indicated that oxidative capacity of the skeletal muscle as a whole was lower in the Zucker rat, which was attributable to lower skeletal muscle mass. The second experiment examined the relationship between metabolic capacity of the skeletal muscle and abdominal fat deposition in the rat fed either high-fat diet or normal diet. In the rats fed normal diet, significant negative relationship existed between oxidative capacity of the skeletal muscle and abdominal fat weight. High-fat diet induced obesity despite the augmentation of the oxidative capacity of the skeletal muscle. The third experiment examined whether or not physical training employing voluntary wheel running, which is known to increase the oxidative capacity of the skeletal muscle and to suppress the deposition of abdominal fat, induced the change in resting metabolism or respiratory exchange ratio R. The results showed that the training induced no significant change in resting metabolic rate and R, despite a significant increase in MDH activity and a significant decrease in abdominal fat weight.