脂肪磷酸烯丙醇羧激酶与胰岛素抵抗的发生和逆转的关系

目的研究脂肪组织磷酸烯丙醇羧激酶（PEPCK）与高脂饲养大鼠的胰岛素抵抗的关系及罗格列酮对其的影响。方法将8周龄雄性SD大鼠,分为两组：短期组（8周,33只）和长期组（28周,30只）。每组各包括正常饲养组（正常组,11只、10只）,高脂组（11只、10只）和罗格列酮组（11只、10只）。饲养至实验终点时取宅腹血测血游离脂肪酸（FFA）和甘油三酯。采用正常血糖高胰岛素钳方法及组织对。H-2-脱氧葡萄糖（2-DG）的摄取能力测定各组的胰岛素敏感性,用逆转录-聚合酶链反应（RT—PCR）方法分析脂肪PEPCK mRNA表达的变化。结果与正常组比较,长期高脂饲养使甘油三酯增加32％（P〈0．05）。短期高脂饲养组葡萄糖输注速率（GIR）下降51％（P〈0．01）;长期高脂饲养组肝脏、肌肉和脂肪组织2-DG摄取率分别下降了42％、36％和48％（P〈0．01）,短期及长期高脂饲养组脂肪组织PEPCK mRNA含量没有改变.与高脂组比较,罗格列酮干预短期组和长期组的FFA分别低125％和49％（P〈0．05）;甘油三酯分别下降54．0％和23％（P〈0．01）;短期干预组GIR增加了150％（P〈0．01）;而长期干预组肝脏、肌肉和脂肪组织2-DG摄取率分别高39％、66％和66％（均P〈0．01）;同时短期及长期罗格列酮干预使大鼠脂肪组织PEPCK mRNA含量分别增加165％和43％（P〈0．05）。结论噻唑烷二酮类药物通过诱导脂肪组织PEPCK表达,增加脂肪酸再酯化．降低循环FFA,可能与改善胰岛素敏感性有关。

Relationship between adipose phosphoenolpyruvate carboxykinase and occurrence and reversion of insulin resistance

OBJECTIVE: To investigate the relationship between the expression of phosphoenolpyruvate carboxykinase (PEPCK) gene and insulin resistance induced by high-fat diet and the effect of rosiglitazone, a thiazolidinedione drug. METHODS: Sixty-three normal 8-week-old male SD rats were randomly divided into 2 groups: short-term group, n = 33, to be fed for 8 weeks and re-divide into 3 equal subgroups: standard chow diet subgroup (NC subgroup fed with standard chow diet), high-fat diet subgroup (HF subgroup, to be fed with lard), and high-fat diet with rosiglitazone subgroup (HF + rosiglitazone subgroup); and long-term group, n = 30, to be fed for 28 weeks, and re-divided into 3 corresponding 3 subgroups: By the end of experiment, serum samples were collected to examine the blood glucose (BG), triglyceride (TG) and free fatty acid (FFA). At the end of the experiment the rats were killed and the visceral adipose tissue was taken out to be weighed, and the liver, muscle, and epididymis were isolated. Glucose infusion rate (GIR) methods and tissue uptake of (3)H-2-deoxyglucose were used to short-and long-term groups evaluate the insulin sensitivity. PEPCK gene expression was investigated to detect the expression of PEPCK mRNA by using semi-quantitative RT-PCR method. RESULTS: In the short-term group, the serum FFA and TG of the HF + rosiglitazone subgroup were lower by 24.5% and 54.0% respectively compared with those the HF subgroup (both P < 0.01). In the long-term group, the serum TG of the HF subgroup was higher by 32.4% in comparison with that of the NC subgroup (P < 0.05), and the serum FFA and TG of the HF + rosiglitazone subgroup were lower by 49.5% and 23.0% respectively compared with those of the HF subgroup (both P < 0.0). In the short-term group the GIR of the HF subgroup was lower by 51.25% in comparison with that of the NC subgroup (P < 0.01). And the GIR of the HF + rosiglitazone subgroup was higher by 149.6% than that of the HF group (P < 0.01). In the long-term group, the rate of uptake of (3)H-2-deoxyglucose in liver, muscle and adipose tissue of the HF subgroup were lower by 42.0%, 36.7%, and 48.1% respectively than those of the HF subgroup (all P < 0.01), and the rate of uptake of 3H-2-deoxyglucose in liver, muscle and adipose tissue of the HF + rosiglitazone subgroup were higher by 39.6%, 66.3%, and 66.7% respectively than those of the HF subgroup (all P < 0.01). In the short-term group the adipose PEPCK mRNA expression of the HF subgroup was 89% +/- 13% that of the NC subgroup; and the adipose PEPCK mRNA expression of the HF + rosiglitazone subgroup was 154% +/- 28% that of the NC subgroup, and was higher by 65.4% than that the HF subgroup (P < 0.05). In the long-term group, the adipose PEPCK mRNA expression of the HF + rosiglitazone subgroup was 144% +/- 17% that of the NC subgroup (P < 0.05), and was higher by 43.3% than that of the HF subgroup (P < 0.05). CONCLUSION: Thiazolidinedione drug increases the re-esterification of fatty acids and reduces circulating FFA, and induces the expression of adipose PEPCK which is accompanied by reduction of FFA, thus improving insulin resistance.