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

有几篇报道称肌纤维成分与体脂肪积累和胰岛素刺激的葡萄糖摄取有关。人们认为快速收缩II型纤维比例较高是肥胖和胰岛素抵抗综合征的决定因素之一，但肌纤维组成与胰岛素抵抗综合征之间的因果关系尚不清楚。我们先用高百分比的快肌纤维选育获得的快肌纤维优势大鼠（FFDR）和随机育种获得的对照大鼠（CR），利用FFDR和CR检测肌纤维组成的遗传差异是否影响高脂肪饮食的饮食肥胖倾向，并通过高胰岛素正糖钳技术检测胰岛素对FFDR和CR中葡萄糖摄取的刺激是否存在差异。此外，我们还测定了FFDR组的自主轮跑活动水平，并与CR组进行了比较，结果表明，FFDR组比CR组表现出更强的抗肥胖能力和更高的肌肉氧化酶活性，而且FFDR组的胰岛素反应性也比CR组高，此外，FFDR组的身体活动水平也比CR组高。我们认为肌肉代谢特征而不是肌纤维组成可能是肥胖和胰岛素抵抗综合征的决定因素，而且，这种动物群体可能是胰岛素敏感性和肌肉特征之间关系的良好模型。

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.