Stable isotope-labeled carnitine reveals its rapid transport into muscle cells and acetylation during contraction
Stable isotope-labeled carnitine reveals its rapid transport into muscle cells and acetylation during contraction
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稳定同位素标记的肉碱揭示了其在收缩过程中快速转运至肌肉细胞和乙酰化
DOI：
10.1016/j.heliyon.2023.e15281
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发表时间：
2023
期刊：
影响因子：
4
通讯作者：
Fujii Nobuharu L.
中科院分区：
文献类型：
--
作者：
Furuichi Yasuro;Goto-Inoue Naoko;Uchida Saki;Masuda Shun;Manabe Yasuko;Fujii Nobuharu L.
肉毒碱在骨骼肌代谢中起着多种作用，包括脂肪酸转运和缓冲线粒体中过量的乙酰辅酶A。骨骼肌不能合成肉毒碱;因此，肉毒碱必须从血液中进入细胞质。肉毒碱的代谢，其吸收到细胞中，以及肉毒碱的后续反应通过肌肉收缩加速。同位素示踪能够标记靶分子并监测组织分布。在这项研究中，稳定同位素标记的肉毒碱示踪结合基质辅助激光解吸/电离质谱（MALDI-MS）成像，以确定肉毒碱在小鼠骨骼肌组织中的分布。将氘标记的肉毒碱（d3-肉毒碱）静脉注射到小鼠体内，并扩散到骨骼肌中30和60分钟。为了检查肌肉收缩是否改变肉毒碱及其衍生物的分布，进行单侧原位肌肉收缩; 60分钟肌肉收缩显示肌肉中d3-肉毒碱及其衍生物d3-乙酰肉毒碱增加，表明细胞中的肉毒碱摄取迅速转化为乙酰肉毒碱，因此缓冲积累的乙酰辅酶A。而内源性肉毒碱是本地化的慢型纤维，而不是快型，收缩诱导的分布d3-肉毒碱和乙酰肉毒碱不一定与肌纤维类型。结论：同位素示踪和MALDI-MS成像的结合可以揭示肌肉收缩过程中肉毒碱的流动，并显示肉毒碱在骨骼肌中的意义。
Carnitine plays multiple roles in skeletal muscle metabolism, including fatty acid transport and buffering of excess acetyl-CoA in the mitochondria. The skeletal muscle cannot synthesize carnitine; therefore, carnitine must be taken up from the blood into the cytoplasm. Carnitine metabolism, its uptake into cells, and the subsequent reactions of carnitine are accelerated by muscle contraction. Isotope tracing enables the marking of target molecules and monitoring of tissue distribution. In this study, stable isotope-labeled carnitine tracing was combined with matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) imaging to determine carnitine distribution in mouse skeletal muscle tissues. Deuterium-labeled carnitine (d3-carnitine) was intravenously injected into the mice and diffused to the skeletal muscles for 30 and 60 min. To examine whether muscle contraction changes the distribution of carnitine and its derivatives, unilateral in situ muscle contraction was performed; 60 min muscle contraction showed increased d3-carnitine and its derivative d3-acetylcarnitine in the muscle, indicating that carnitine uptake in cells is promptly converted to acetylcarnitine, consequently, buffering accumulated acetyl-CoA. While the endogenous carnitine was localized in the slow type fibers rather than fast type, the contraction-induced distributions of d3-carnitine and acetylcarnitine were not necessarily associated with muscle fiber type. In conclusion, the combination of isotope tracing and MALDI-MS imaging can reveal carnitine flux during muscle contraction and show the significance of carnitine in skeletal muscles.