糖脂毒性对肥胖大鼠酮体生成及骨骼肌线粒体结构的影响

Effects of glucoxicity and lipotoxicity on ketone production and the skeletal muscle ultrastructure in high-fat-fed obese rats

目的外源性升高循环中葡萄糖和游离脂肪酸(free fat acid,FFA)水平,探讨糖毒性/脂毒性对肥胖大鼠的循环中酮体水平和骨骼肌超微结构的影响。方法将50只Wistar大鼠分为高脂饲料诱导肥胖组(OB组,n=40)和普通饲料喂养的正常对照组(NC组,n=10)。外源性升高OB组大鼠血糖和血FFA水平,采用水平比色法检测血脂和FFA及β-羟丁酸水平,采用透射电子显微镜观察骨骼肌显微结构尤其是线粒体结构的改变。结果 OB组大鼠的体质量和体脂比高于NC组(P<0.05),正常血糖-高胰岛素钳夹技术评估外周胰岛素敏感性显示:OB组大鼠稳态期葡萄糖输注速率较NC组明显降低[OB组为(19.26±1.84)mg/(kg·min),NC组为(28.82±1.69)mg/(kg·min)],差异有统计学意义(P<0.05)。透射电子显微镜下观察到OB组大鼠骨骼肌线粒体变性、肿胀、嵴排列紊乱、脂滴积聚和空泡化形成,以糖脂联合输注组明显。结论通过外源性升高循环中葡萄糖和FFA水平,机体内酮体产物生成增加,高葡萄糖和高FFA作用下骨骼肌线粒体的受损提示线粒体是糖脂毒性的可能的作用靶点。

Objective To analyze the glucolipotoxicity effects of glucose combined with free fatty acid （FFA） on ketone production and ultrastructure of skeletal muscle, by exogenous elevating circulating glucose and FFA concentration. Methods Fifty Wistar rats were divided into high-fat-feed induced obesity group （OB group, n=40） and ordinary feed as normal control group （NC group, n=10）. Circulating glucose and FFA levels were increased by infusion in high-fat-fed obese rats. The levels of serum lipid, plasma FFA and beta-hydroxybutyric acid were detected by the horizontal colorimetry, and the microstructure of skeletal muscle was observed by transmission electron microscopy, especially the changes of the mitochondrial structure. Euglycemic-hyperinsulinemic clamp with tracer infusion was performed to assess peripheral insulin sensitivity. Results The average weight and body fat ratio in the OB group was higher than that in the NC group （P〈0.05）. Insulin clamp test to assess peripheral insulin sensitivity showed that the steady-state glucose Infusion rate in the OB group during clamp test was significantly lower than that in the NC group [OB： （19.26±1.84） mg/（kg·min）vs. NC： （28.82±1.69） mg/（kg·min）, P〈0.05]. The mitochondrial denaturation of skeletal muscle in the OB group of rats was observed, and the swelling and crest permutation, the accumulation of lipid droplets and cavitation were formed, and hypertrophy of mitochondria were also seen after intralipid and glucose infusion, which was obvious in the combined infusion group. Conclusions By exogenous elevating circulating glucose and FFA concentration, the products of ketone body increases. The mitochondrial damage of skeletal muscle suggests that mitochondrial may be the potential target of glucoxicity and lipotocicity.