米非司酮对胰岛素抵抗大鼠心肌损伤的保护作用及其机制

目的：考察米非司酮对高脂饮食所致胰岛素抵抗大鼠心肌功能和结构变化的影响，并从细胞水平研究其作用机制。方法：1）将40只SD大鼠随机分为正常对照组、模型组、吡格列酮组及米非司酮高、低剂量组，每组8只。除正常对照组给予普通饲料外，其余各组均给予高脂饲料。正常对照组和模型组每日灌胃给予0．5％CMC-Na溶液（0．1mL·kg^-1），给药组分别给予吡格列酮（3mg·kg^-1·d^-1）及米非司酮（40，20mg·kg^-1·d^-1）。8周后，测定各组大鼠空腹血糖、空腹胰岛素水平，计算HOMA-胰岛素抵抗指数，模型组该指数显著高于正常对照组时，视为造模成功；采用套尾法测定各组大鼠血压，并做心脏病理切片观察心肌功能和结构的变化。2）将原代培养2—3天的心肌细胞随机分为正常对照组、地塞米松（6×10^-6mol·L^-1）组、地塞米松（6×10^-6mol·L^-1）＋吡格列酮（2×1^-4mol·L^-1）／米非司酮（高、中、低剂量）（2×10^-4，2×10^-5，2×10^-6mol·L^-1）组、胰岛素（5×10^-6mol·L^-1）组、胰岛素（5×10^-4mol·L^-1）＋吡格列酮（2×10^-4mol·L^-1）／米非司酮（高、中、低剂量）（2×10^-4，2×10^-5，2×10^-6mol·L^-1）组。分组给药、连续培养48小时后，测定各组原代心肌细胞葡萄糖消耗量、细胞活力及游离脂肪酸和乳酸脱氢酶的含量，考察心肌细胞功能状态变化。结果：1）高脂饮食饲养8周后，大鼠出现胰岛素抵抗并伴有脂质代谢紊乱，血清皮质酮含量升高，病理切片结果显示模型组大鼠心肌受损，米非司酮组上述状况明显改善（P〈0．01）。2）胰岛素和地塞米松均能造成原代心肌细胞胰岛素抵抗模型，并造成细胞代谢紊乱，而米非司酮可改善地塞米松造成的心肌功能状态异常（P〈0．05，P〈0．01），但对胰岛素诱导的异常无效（P〉0．05）。结论：米非司酮可降低高脂饮食所致的胰岛素抵抗大鼠心肌受损程度，推测其通过拮抗糖皮质激素而发挥作用。

Effect and Mechanism of Mifepristone on Myocardial Injuries of Insulin-resistant Rats

Objective： To observe the effect of mifepristone on the changes of myocardial functions and structures of insulin-resistant （IR） rats induced by high-fat diet, and to investigate the mechanism at the cell level. Methods： 1） Forty SD rats were randomly divided into five groups： including normal group, model group, pioglitazone group and two mifepristone groups in high and low dosage. The rats in normal group were given normal feed and the rats in other groups were given high fat feed. Meanwhile, 0.5% CMC-Na （0. 1 mL.kg^-1） were administered once daily by gavage in normal and model groups. Pioglitazone （3 mg.kg^-1.d-1） or mifepristone （40, 20 mg.kg-1 .d^-1） was administered by gavage in pioglitazone group and mifepristone groups, respectively. Eight weeks later, fasting blood glucose and insulin were assayed to calculate HOMA-IR index. The IR model was considered successful when HOMA-IR index in model group increased significantly compared with normal group. Blood pressure was measured by tail-cuff method and pathological changes of myocardium were observed to evaluate the function and structure of the heart. 2） The myocardial cells were primarily cultured for 2-3 days and randomly divided into normal group, dexamethasone （ 6 × 10 ^-6 mol- L^-1） group, dexamethasone （ 6 × 10^ -6 mol. L^-1 ） ＋ pioglitazone （2 × 10^-4 mol · L^-1 ）/ mifepristone （2 × 10^-4, 2 × 10^-5, 2 × 10^-6 mol ·L^-1） groups, insulin （5 × 10^-6mol-L^-1） group, insulin （5 ×10^-6 mol.L^-1） ＋ pioglitazone （2 × 10^-4 mol.L^-1）/mifepristone （2 × 10^-4, 2 × 10^-5, 2 ×10^-6 mol. L^-1） groups. After these drugs were administered respectively, the cardiomycytes were cultured again for 48 hours, and the glucose consumption, viability, FFA and LDH levels of primary myocardial cells were assayed to investigate the changes of the cells. Results： 1） Administration of high-fat diet for eight weeks resulted in IR, accompanied with lipid metabolism disorder, corticosteron increasing and myocardial injury, while mifepristone could attenuate these changes （P 〈0. 01）. 2） IR of cell model can be established and metabolism disorder of the cells can be caused by using dexa- methasone and insulin. Mifepristone can improve the dysfunction of the cells induced by dexamethasone （P 〈0.05, P 〈0. 01） , but it has no effect on that induced by insulin （P 〉0. 05）. Conclusion： Myocardial injuries in IR rats induced by high-fat diet may be attenuated by mifepristone. It might be related to the biological effect of antagonism of mifepristone on glucocorticoid