Department of Cardiovascular Medicine, University of Oxford, Henry Wellcome Building of Genomic Medicine, Roosevelt Drive, Oxford OX3 7BN, UK.
J Mol Cell Cardiol. 2010 Apr;48(4):582-90. doi: 10.1016/j.yjmcc.2009.10.033. Epub 2009 Nov 11.
The metabolic phenotype of the failing heart includes a decrease in phosphocreatine and total creatine concentration [Cr], potentially contributing to contractile dysfunction. Surprisingly, in 32- week-old mice over-expressing the myocardial creatine transporter (CrT-OE), we previously demonstrated that elevated [Cr] correlates with left ventricular (LV) hypertrophy and failure. The aim of this study was to determine the temporal relationship between elevated [Cr] and the onset of cardiac dysfunction and to screen for potential molecular mechanisms. CrT-OE mice were compared with wild-type (WT) littermate controls longitudinally using cine-MRI to measure cardiac function and single-voxel (1)H-MRS to measure [Cr] in vivo at 6, 16, 32, and 52 weeks of age. CrT-OE mice had elevated [Cr] at 6 weeks (mean 1.9-fold), which remained constant throughout life. Despite this increased [Cr], LV dysfunction was not apparent until 16 weeks and became more pronounced with age. Additionally, LV tissue from 12 to 14 week old CrT-OE mice was compared to WT using 2D difference in-gel electrophoresis (DIGE). These analyses detected a majority of the heart's metabolic enzymes and identified seven proteins that were differentially expressed between groups. The most pronounced protein changes were related to energy metabolism: alpha- and beta-enolase were selectively decreased (p<0.05), while the remaining enzymes of glycolysis were unchanged. Consistent with a decrease in enolase content, its activity was significantly lower in CrT-OE hearts (in WT, 0.59+/-0.02 micromol ATP produced/microg protein/min; CrT-OE, 0.31+/-0.06; p<0.01). Additionally, anaerobic lactate production was decreased in CrT-OE mice (in WT, 102+/-3 micromol/g wet myocardium; CrT-OE, 78+/-13; p=0.02), consistent with decreased glycolytic capacity. Finally, we found that enolase may be regulated by increased expression of the beta-enolase repressor transcription factor, which was significantly increased in CrT-OE hearts. This study demonstrates that chronically increased myocardial [Cr] in the CrT-OE model leads to the development of progressive hypertrophy and heart failure, which may be mediated by a compromise in glycolytic capacity at the level of enolase.
衰竭心脏的代谢表型包括磷酸肌酸和总肌酸浓度 [Cr] 的降低，这可能导致收缩功能障碍。令人惊讶的是，在过表达心肌肌酸转运蛋白 (CrT-OE) 的 32 周龄小鼠中，我们之前证明升高的 [Cr] 与左心室 (LV) 肥大和衰竭相关。本研究旨在确定升高的 [Cr] 与心脏功能障碍发作之间的时间关系，并筛选潜在的分子机制。使用电影 MRI 纵向比较 CrT-OE 小鼠与野生型 (WT) 同窝对照，以测量心脏功能，并在 6、16、32 和 52 周龄时使用单体素 (1)H-MRS 测量体内 [Cr]。CrT-OE 小鼠在 6 周时 [Cr] 升高（平均升高 1.9 倍），并在整个生命过程中保持不变。尽管 [Cr] 升高，但 LV 功能障碍直到 16 周才明显，并随着年龄的增长而变得更加明显。此外，与 WT 相比，还使用 2D 差异凝胶电泳 (DIGE) 比较了 12 至 14 周龄 CrT-OE 小鼠的 LV 组织。这些分析检测到心脏的大多数代谢酶，并鉴定出两组之间差异表达的七种蛋白质。最明显的蛋白质变化与能量代谢有关：α-和β-烯醇酶选择性降低（p<0.05），而糖酵解的其余酶不变。与烯醇酶含量降低一致，CrT-OE 心脏中的酶活性显著降低（在 WT 中，0.59+/-0.02 微摩尔 ATP/微克蛋白/分钟；CrT-OE，0.31+/-0.06；p<0.01）。此外，CrT-OE 小鼠的无氧乳酸生成减少（在 WT 中，102+/-3 微摩尔/克湿心肌；CrT-OE，78+/-13；p=0.02），这与糖酵解能力降低一致。最后，我们发现烯醇酶可能受β-烯醇酶抑制转录因子表达增加的调节，该因子在 CrT-OE 心脏中显著增加。这项研究表明，CrT-OE 模型中慢性升高的心肌 [Cr] 导致进行性肥大和心力衰竭的发展，这可能是由于烯醇酶水平的糖酵解能力受损所致。
