高脂饮食对老年大鼠骨骼肌脂肪酸含量及乙酰辅酶A羧化酶表达和活性的影响

目的 探讨增龄和高脂饮食对大鼠骨骼肌脂肪酸含量及乙酰辅酶A羧化酶(acetyl-coenzyme A carboxylase,ACC)表达和活性的影响.方法 将22～24月龄雄性Wistar大鼠随机分为老年对照组和高脂组;4～5月龄大鼠作为青年对照组.老年对照组和青年对照组给基础饲料,高脂组给予高脂饲料,喂养8周.用高胰岛素-正葡萄糖钳夹实验评价各组大鼠胰岛素敏感性,用全自动生化分析仪测定骨骼肌三酰甘油,用荧光分光光度计测定骨骼肌总的长链脂酰辅酶A含量,用Western-blot方法测定骨骼肌ACC、和磷酸化ACC(P-ACC)蛋白表达.结果 (1)老年对照组空腹血糖、胰岛索和游离脂肪酸高于青年对照组,高脂组上述几项指标进一步升高,并且出现血清三酰甘油和总胆固醇水平增高;(2)老年对照组葡萄糖输注率(glucose infusion rates,GIR)低于青年对照组,高脂组GIR低于老年对照组,高脂组GIR在8周末低于4周末;(3)老年对照组骨骼肌三酰甘油及长链脂酰辅酶A含量高于青年对照组,高脂组与老年对照组比较进一步升高;(4)老年对照组与青年对照组之间、高脂组与老年对照组之间骨骼肌ACC蛋白表达均无明显变化(P>0.05);骨骼肌P-ACC蛋白水平在老年对照组低于青年对照组,高脂组与老年对照组比较进一步降低(P<0.05或P<0.01).结论 与青年大鼠比较,老年大鼠更易出现脂肪酸代谢异常及胰岛素抵抗;高脂饮食导致老年大鼠骨骼肌脂质积聚更加严重,ACC活性的改变可能在骨骼肌脂质堆积和胰岛素抵抗发生中起了一定作用.

Effects of high-fat diet on fatty acid metabolism, expression and activity of acetyl-coenzyme A carboxylase in skeletal muscle in aged rats

Objective To investigate the effects of high-fat diet on fatty acid metabolism, expression and activity of acetyl coenzyme A carboxylase (ACC) in skeletal muscle in rats. Methods Male Wistar rats aged 22-24 months were randomly divided into old control (OC) group and high-fat diet (HF) group. Male Wistar rats aged 4-5 months were selected as young control (YC) group. The rats in OC and YC groups were fed with basic diet, and the rats in HF group received high-fat diet. Insulin sensitivity was evaluated by hyperinsulinemic-euglycemic clamp technique. Skeletal muscle triglyceride was extracted and measured by an automated biochemistry analyzer. Long-chain acetyl coenzyme A (LCACoAs) were extracted from muscle and measured by a fluorospectrophotometer. Protein expressions of ACC and P-ACC were measured using SDS-PAGE and Western blot techniques. Results (1)Fasting blood glucose (FBG), fasting insulin (FINS) and free fatty acid were higher in OC group than in YC group and they increased significantly in HF group. Triglyceride (TG) and total cholesterol (TO levels were also elevated after high-fat feeding. (2)Glucose infusion rates (GIR) were reduced in OC group than in YC group, and decreased significantly after high-fat feeding. GIR was lower at the end of the 8th week than at the end of the 4th week in HF group. (3) Compared with YC group, skeletal muscle triglyceride and LCACoAs increased in OC group and increased significantly in HF group. (4)No alterations of protein levels of ACC in skeletal muscle were detected among three groups (P>0.05). The protein levels of P-ACC in skeletal muscle were lower in OC group, and much lower in HF group than in YC group (P<0.05 or P<0.01). Conclusions Compared with young rats, abnormal fatty acid metabolism and insulin resistance always exist in aged rats. High-fat feeding results in a significant increase in lipid content in skeletal muscle. Alterations of ACC activity may contribute to fat accumulation in skeletal muscle and insulin resistance.