The development of insulin resistance syndrome model rats using fast-twitch fiber dominant rats

有几个报告说，肌肉纤维的组成与体内脂肪积累和胰岛素模拟的葡萄糖摄取有关。较高比例的快抽动II型纤维被认为是肥胖和胰岛素抵抗综合征的决定因素之一，然而，肌肉纤维组成与这些综合征之间的因果关系尚不清楚。我们以前通过选育高比例快抽动II型纤维获得了快抽动纤维优势大鼠(FFDR)和随机饲养获得的对照大鼠(CR)，用FFDR和CR检验了肌肉纤维组成的遗传差异是否影响高脂饮食的肥胖倾向，并用高胰岛素正血糖钳夹技术检验了FFDR中胰岛素模拟葡萄糖摄取是否与CR不同。此外，还测定了FFDR的自愿车轮跑活动水平，并与CR进行了比较。FFDR表现出比CR更强的抗肥胖性和更高的肌肉氧化酶活性，而且FFDR显示出比CR更高的胰岛素反应性。此外，FFDR显示出比CR更高的体力活动水平。基于这些结果，我们认为肌肉代谢特征而不是肌肉纤维组成是肥胖和胰岛素抵抗综合征的可能决定因素，而且这样的动物群体可能是胰岛素敏感性和肌肉特征之间关联的一个很好的模型。

There are several reports that the muscle fiber composition is associated with body fat accumulation and insulin silmulated glucose uptake. It was considered that higher percentage of fast-twitch type II fibers was one of the determinants of obesity and insulin resistance syndrome, However, the causality between muscle fiber composition and such syndrome was still unclear. We previously produced the fast-twitch fibers dominant rats (FFDR) obtained by the selection breeding for high percentage of fast-twitch type II fibers and control rats (CR) obtained by the random breeding, Using FFDR and CR, we examined whether genetically difference of muscle fiber composition affected the dietary obesity proneness by high-fat diet, In addition, we examined whether the insulin silmulated glucose uptake in FFDR differed the CR by hyperinsulinemic euglycemic clamp technique. Furthermore, voluntary wheel-running activity level in FFDR was also determined and compared with the CR. The FFDR showed more obesity-resistant and higher muscle oxidative enzyme activity than CR, Moreover, FFDR indicated higher insulin responsiveness than CR. In addition, the FFDR showed higher physical activity level than CR. Based on these results, we propose that the muscle metabolic characteristic rather than muscle fiber composition is a possible determinant of obesity and insulin resistance syndrome, Furthermore, such animal group might be a good model for the association between insulin sensitivity and muscle characteristics.