AMPK/PPARα/SCAD信号途径对心肌肥大的调控研究

Regulation of AMPK /PPARα/SCAD signal pathway on cardiac hypertrophy

目的:研究短链酰基辅酶A脱氢酶(short-chain acyl-coenzyme A dehydrogenase,SCAD)在心肌细胞肥大中的作用及腺苷酸活化蛋白激酶(adenosine monophosphate-activated protein kinase,AMPK)/过氧化物酶体增殖剂活化受体α(peroxisome proliferator-activated receptorα,PPARα)信号途径对SCAD的调控作用。方法:使用Western blotting和RT-PCR筛选干扰SCAD的最优序列,并使用非诺贝特(10μmol/L)提前干预24 h后给予干扰序列,观察SCAD的mRNA、蛋白表达和酶活性以及脂质代谢和心肌细胞表面积的改变。采用RT-PCR检测心肌细胞内肥大标志物心房利钠因子(atrial natriuretic factor,ANF)和脑利钠肽(brain natriuretic peptide,BNP)mRNA水平,以明确心肌细胞是否发生肥大。分别用10μmol/L非诺贝特和0.5 mmol/L 5-氨基咪唑-4-甲酰胺核糖核苷酸(5-aminoimidazole-4-carboxamide ribonucleotide,AICAR)预处理心肌细胞30 min,用20μmol/L苯肾上腺素(phenylephrine,PE)刺激24 h,观察心肌细胞表面积和游离脂肪酸含量的变化,并采用Western blotting和RT-PCR检测p-AMPKα、PPARα和SCAD在蛋白和mRNA水平的变化。结果:筛选出的最优干扰序列siRNA-1186和PE诱导的心肌细胞肥大趋势一致,与对照组比较,敲低SCAD表达组的心肌细胞ANF和BNP水平显著升高,心肌细胞表面积明显增大,心肌细胞游离脂肪酸含量明显增加。非诺贝特预处理可显著上调PPARα和SCAD的表达,增加SCAD的酶活性,降低心肌细胞的游离脂肪酸含量,预防敲低SCAD引起的心肌细胞肥大。与对照组比较,PE处理组中p-AMPKα(T172)、PPARα和SCAD的蛋白及mRNA水平均明显下调,SCAD的酶活性下降;与PE组相比,用非诺贝特或AICAR预处理30 min组的心肌细胞表面积明显减少,心肌细胞游离脂肪酸含量明显降低,p-AMPKα、PPARα和SCAD蛋白及mRNA水平均明显上调,SCAD的酶活性增加。结论:SCAD表达下调与心肌细胞肥大及其能量代谢密切相关;AMPK/PPARα/SCAD信号途径对心肌肥大可能具有直接的调控作用。

AIM ： To study the effect of short-chain acyl-coenzyme A dehydrogenase （SCAD） on cardiac hypertrophy and to explore the role of adenosine monophosphate-activated protein kinase （AMPK）/peroxisome proliferator-activated receptor α （PPARα） signal pathway in the regulation of SCAD during the development of cardiac hypertrophy. METHODS： The optimal sequence of SCAD interference was chosen by Western blotting and real-time PCR. The cardiomyocytes were treated with fenofibrate （ 10 μmol/L） for 24 h and subsequently stimulated with the optimal sequence of SCAD interference. The changes of SCAD expression at mRNA and protein levels, the enzyme activity of SCAD, the cardiomyocyte surface area and free fatty acids were determined. Using real-time PCR for analyzing the markers of cardiac hy-pertrophy, the mRNA expression of atrial natriuretic factor （ANF） and brain natriuretic peptide （BNP） was detected to judge the development of cardiac hypertrophy. The cardiomyocytes were treated with fenofibrate （ 10 μmol/L） or AMPK activator 5-aminoimidazole-4-carboxamide ribonucleotide （AICAR, 0.5 mmol/L） for 30 min and subsequently stimulated with phenylephrine （ PE, 20μmol/L） for 24 h. The changes of cardiomyocyte surface area, free fatty acids, and the expression of SCAD, PPARμ and p-AMPKα （T172） at mRNA and protein levels were observed. RESULTS： The effect of optimal sequence siRNA-1186 and PE on the cardiomyocytes was the same. Compared with control group, the expression of ANF and BNP at mRNA level, the cardiomyocyte surface area and free fatty acids were increased obviously in siRNA-1186 group. After pretreated with fenofibrate （ 10 μmol/L）, the expression of PPARα and SCAD, and the enzyme activity of SCAD were significantly increased, while the free fatty acids were decreased, indicating that fenofibrate prevented the development of cardiac hypertrophy induced by knockdown of SCAD. Compared with control group, the expression of SCAD, PPARα and p-AMPKα（T172） at mRNA and protein levels was significantly down-regulated, and the enzyme activity of SCAD was obviously decreased in PE group. Compared with PE group, the expression of SCAD, PPARα and p-AMPKα（ T172 ） was significantly up-regulated, and the cardiomyocyte surface area and the content of free fatty acids were obviously decreased in the cardiomyocytes pretreated with fenofibrate or AICAR for 30 min. CONCLUSION： Down-regulation of SCAD is related to the cardiac hypertrophy and energy metabolism. AMPK/PPARα/SCAD signaling pathway may regulate cardiac hypertrophy directly.