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Biochim Biophys Acta. 2014 Oct;1837(10):1699-706. doi: 10.1016/j.bbabio.2014.05.356. Epub 2014 May 29.

Imaging mass spectrometry reveals fiber-specific distribution of acetylcarnitine and contraction-induced carnitine dynamics in rat skeletal muscles.

Author information

1
Department of Health Promotion Sciences, Graduate School of Human Health Sciences, Tokyo Metropolitan University, Tokyo, Japan.
2
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. Electronic address: naokog@tmu.ac.jp.
3
Department of Cell Biology and Anatomy, Hamamatsu University School of Medicine, Hamamatsu, Japan.
4
Faculty of Human Sciences, Kanazawa University, Kanazawa, Japan.
5
Department of Health Promotion Sciences, Graduate School of Human Health Sciences, Tokyo Metropolitan University, Tokyo, Japan. Electronic address: fujiin@tmu.ac.jp.

Abstract

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.

KEYWORDS:

Carnitine; Fiber type; Muscle contraction

PMID:
24882639
DOI:
10.1016/j.bbabio.2014.05.356
[Indexed for MEDLINE]
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