辛伐他汀对慢性心力衰竭兔心肌细胞糖原合成激酶3β活性、蛋白表达及β-连环蛋白表达的影响

目的:观察辛伐他汀对慢性心力衰竭(心衰)兔心肌重构及心功能的影响,对心肌细胞中糖原合成激酶3β(GSK3β)活性、蛋白表达及β-连环蛋白(β-catenin)表达的影响。方法:24只新西兰白兔分为4组,每组6只。假手术组:为健康对照。其余兔行主动脉瓣反流及腹主动脉缩窄术,建立慢性心衰模型后,分为心衰对照组:术后不给药;早干预组:术后第2天给予辛伐他汀5 mg/(d.kg),连续8周;晚干预组:术后第4周给予辛伐他汀5 mg/(d.kg),连续4周。术后8周观察结束时行左心导管检查,记录左心室舒张末压,处死后称体重、心脏重量、左心室重量,计算心脏质量指数(心脏重量/体重)、左心室质量指数(左心室重量/体重)。West-ern-blotting分析心肌细胞浆GSK3β、细胞核β-catenin表达。免疫沉淀分析GSK3β活性。结果:术后8周时,心衰对照组左心室舒张末压、心脏重量、左心室重量、心脏质量指数及左心室质量指数均显著高于假手术组(P均<0.01);术后8周,早干预组心脏重量、左心室重量、心脏质量指数及左心室质量指数均显著低于心衰对照组(P<0.05～0.01);晚干预组心脏重量、左心室重量、心脏质量指数均显著低于心衰对照组(P<0.05～0.01)。术后8周,早干预组及晚干预组左心室舒张末压均显著低于心衰对照组(P均<0.05)。心衰对照组心肌胞浆中GSK3β活性较假手术组显著降低(P<0.01),而心肌细胞核β-catenin表达显著增加(P<0.01),差异均有统计学意义。早干预组及晚干预组GSK3β活性与心衰对照组比较均显著增加(P均<0.01),而心肌细胞核β-catenin表达均显著降低(P均<0.01)。结论:辛伐他汀治疗有效抑制心力衰竭兔心肌重构、改善心功能;其作用与增加GSK3β活性、抑制心肌细胞核β-catenin表达有关。

Regulation of TCF7L2 in cardiac myocytes by diabetic conditions

Backgrounds： TCF7L2 is a member of T cell factor （TCF）/lymphoid enhancer factor （LEF） family transcription- al factors that interact with β-catenin in canonical Wnt signaling. TCF7L2 plays important roles in metabolism and glucose homeostasis. Genetic variations of TCFTL2 are associated with increased risks of Diabetes Mellitus. It is not known if diabetic conditions also modulate TCFTL2 expression in the heart. Methods TCFTL2 and β-catenin ex- pression was investigated by Western blot, RT-PCR and immunofluorescence in HL-1 cells and neonatal rat ventric-ular myocytes （NRVM） treated with 14 mmol · L 1 mannitol （ M）, 25 mmol· L^-1 glucose （ G）, 10 nmol · L insulin （I）, and G plus I （G ＋ I）. In addition, TCF7L2 and β-catenin levels were examined by Western blot in the heart of B6. Cg-m Leprdb/ ＋ ＋/J （db） and C57B1/6J （C57） mice 4 hours after intraperitoneal injections of 1.5 IU · kg^-1 insulin. Blood glucose levels were determined on blood drawn from the tail vein. Result The ex- pression of TCF7L2 and β-catenin was higher in nucleus of db mice hearts than C57 hearts. Insulin treatment de- creased TCF7L2 and β-catenin level in C57 hearts. Paradoxically, TCF7L2 and β-catenin was further increased by insulin in db hearts. In HL-1 cells and NRVMs, TCF7L2 started to decrease at one hour and remained lower up to 24 hours after insulin treatment compared to untreated controls. In contrast, G increased TCF7L2 expression at 1, 6 and 24 hours after treatment relative to M. Insulin could decrease TCF7L2 at 1 and 6 hours, but failed to do so at 24 hours in G ＋ I. At 48 hours, no difference in TCF7L2 expression was observed among different treatment groups. The immunostaining showed β-catenin translocated to the nucleus and colocalized with TCF7L2 in G at 6 hours and 24 hours. Insulin could inhibit the TCF7L2 and β-catenin expression as well as β-catenin translocation at 6 hours but could not do so at 24 hours in G ＋ I. Conclusion Insulin regulation of TCF7L2 is interfered by high glucose in vitro and misregulation of TCF7L2 in the heart of diabetic mice may contribute to the pathogenesis of dia- betic cardiomyopathy.

小鼠心肌细胞核DNA变化与死亡时间的关系

目的监测小鼠死后细胞核DNA降解的情况,探讨死后细胞核DNA降解的一般规律。方法应用单细胞凝胶电泳(SCGE)技术结合荧光显微镜和专业的计算机图像分析技术,测定111只小鼠在死后72h内不同时间点小鼠心肌组织细胞头半径、尾长度、头DNA含量比例、尾DNA含量比例、尾矩、Olive矩、头面积、尾面积八项参数的变化值。结果在个体死亡72h内,测定的八项参数指标均显示细胞核DNA降解速率和程度与死亡时间具有高度的相关性,并获得了更能体现DNA降解趋势的二项式回归方程和多元回归方程,均具有高度的统计学意义。结论应用72h内心肌组织DNA变化与死亡时间之间呈线性关系的各组回归方程,可为法医学推断死后经过时间提供一种新的、客观的、精确的方法和参考依据。