Skeletal muscle 1H MRSI before and after prolonged exercise. II. visibility of free carnitine
Article first published online: 27 JAN 2012
Copyright © 2012 Wiley Periodicals, Inc.
Magnetic Resonance in Medicine
Volume 68, Issue 5, pages 1368–1375, November 2012
How to Cite
Boss, A., Kreis, R., Saillen, P., Zehnder, M., Boesch, C. and Vermathen, P. (2012), Skeletal muscle 1H MRSI before and after prolonged exercise. II. visibility of free carnitine. Magn Reson Med, 68: 1368–1375. doi: 10.1002/mrm.24167
- Issue published online: 22 OCT 2012
- Article first published online: 27 JAN 2012
- Manuscript Accepted: 30 DEC 2011
- Manuscript Revised: 29 NOV 2011
- Manuscript Received: 3 AUG 2011
- Swiss National Science Foundation. Grant Numbers: 310000-118219, 31003A-132935
- 1H magnetic resonance spectroscopic imaging;
Carnitine (Car) buffers excess acetyl-CoA through the formation of acetylCar (AcCar). AcCar's acetyl group (AG-AcCar) gives rise to a peak at 2.13 ppm in 1H MR spectra of skeletal muscle, whereas the trimethylammonium (TMA) groups of both, AcCar and Car, are thought to contribute to the TMA peak at 3.23 ppm. Surprisingly, in previous studies both resonances, AG-AcCar and TMA, increased after exercise. The aim of this study was to assess if the exercise-related TMA increase correlated with AcCar production. Magnetic resonance spectroscopic imaging (pulse repetition time/echo time = 1200/35 ms) was performed before and after prolonged exercise in the lower leg and thigh of eight runners and eight cyclists, respectively. TMA and AG-AcCar increased after exercise (P < 0.001). TMA's increase correlated with the AG-AcCar increase (R2 = 0.73, P < 0.001, lower leg; R2 = 0.28, P < 0.001, thigh). The correlation of ΔTMA with ΔAG-AcCar suggests that the TMA increase is due to AcCar formation. As total Car (Car + AcCar) remains unchanged with exercise, these findings suggest that the contribution of free Car to the TMA peak is limited and, therefore, is partly invisible in muscle 1H MR spectra. This indicates that the biochemically relevant cytosolic content of free Car is considerably lower than the overall concentration determined by radioisotopic assays, a potentially important result with respect to regulation of substrate oxidation. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc.