Furuichi Yasuro, Goto-Inoue Naoko, Manabe Yasuko, Setou Mitsutoshi, Masuda Kazumi, Fujii Nobuharu L
Department of Health Promotion Sciences, Graduate School of Human Health Sciences, Tokyo Metropolitan University, Tokyo, Japan.
Department of Health Promotion Sciences, Graduate School of Human Health Sciences, Tokyo Metropolitan University, Tokyo, Japan; Department of Cell Biology and Anatomy, Hamamatsu University School of Medicine, Hamamatsu, Japan.
Biochim Biophys Acta. 2014 Oct;1837(10):1699-706. doi: 10.1016/j.bbabio.2014.05.356. Epub 2014 May 29.
Carnitine is well recognized as a key regulator of long-chain fatty acyl group translocation into the mitochondria. In addition, carnitine, as acetylcarnitine, acts as an acceptor of excess acetyl-CoA, a potent inhibitor of pyruvate dehydrogenase. Here, we provide a new methodology for accurate quantification of acetylcarnitine content and determination of its localization in skeletal muscles. We used matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS) to visualize acetylcarnitine distribution in rat skeletal muscles. MALDI-IMS and immunohistochemistry of serial cross-sections showed that acetylcarnitine was enriched in the slow-type muscle fibers. The concentration of ATP was lower in muscle regions with abundant acetylcarnitine, suggesting a relationship between acetylcarnitine and metabolic activity. Using our novel method, we detected an increase in acetylcarnitine content after muscle contraction. Importantly, this increase was not detected using traditional biochemical assays of homogenized muscles. We also demonstrated that acetylation of carnitine during muscle contraction was concomitant with glycogen depletion. Our methodology would be useful for the quantification of acetylcarnitine and its contraction-induced kinetics in skeletal muscles.
肉碱作为长链脂肪酰基转运进入线粒体的关键调节因子已广为人知。此外,肉碱以乙酰肉碱的形式,作为过量乙酰辅酶A的受体,而乙酰辅酶A是丙酮酸脱氢酶的强效抑制剂。在此,我们提供了一种准确量化乙酰肉碱含量并确定其在骨骼肌中定位的新方法。我们使用基质辅助激光解吸/电离成像质谱(MALDI-IMS)来可视化大鼠骨骼肌中乙酰肉碱的分布。MALDI-IMS和连续横断面的免疫组织化学显示,乙酰肉碱在慢肌纤维中富集。在乙酰肉碱丰富的肌肉区域,ATP浓度较低,这表明乙酰肉碱与代谢活性之间存在关联。使用我们的新方法,我们检测到肌肉收缩后乙酰肉碱含量增加。重要的是,使用传统的匀浆肌肉生化检测方法未检测到这种增加。我们还证明,肌肉收缩过程中肉碱的乙酰化与糖原消耗同时发生。我们的方法将有助于量化骨骼肌中乙酰肉碱及其收缩诱导的动力学。