Improved spectral resolution and high reliability of in vivo super(1)H MRS at 7 T allow the characterization of the effect of acute exercise on carnosine in skeletal muscle

• Published in: NMR in biomedicine 2016-01, Vol.29 (1), p.24-32
• Main Authors: Just Kukurova, Ivica, Valkovic, Ladislav, Ukropec, Jozef, Courten, Barbora, Chmelik, Marek, Ukropcova, Barbara, Trattnig, Siegfried, Krssak, Martin
• Format: Article
• Language: English
• ISSN: 0952-3480; 1099-1492
• DOI: 10.1002/nbm.3447

The aims of this study were to observe the behavior of carnosine peaks in human soleus (SOL) and gastrocnemius (GM) muscles following acute exercise, to determine the relaxation times and to assess the repeatability of carnosine quantification by super(1)H MRS at 7 T. Relaxation constants in GM and SOL were measured by a stimulated echo acquisition mode (STEAM) localization sequence. For T sub(1) measurement, an inversion recovery sequence was used. The repeatability of the measurement and the absolute quantification of carnosine were determined in both muscles in five healthy volunteers. For absolute quantification, an internal water reference signal was used. The effect of acute exercise on carnosine levels and resonance lines was tested in eight recreational runners/cyclists. The defined carnosine measurement protocol was applied three times - before and twice after (approximately 20 and 40 min) a 1-h submaximal street run and additional toe-hopping. The measured T sub(1) relaxation times for the C2-H carnosine peak at 7 T were 2002 plus or minus 94 and 1997 plus or minus 259 ms for GM and SOL, respectively, and the T sub(2) times were 95.8 plus or minus 9.4 and 81.0 plus or minus 21.8 ms for GM and SOL, respectively. The coefficient of variation of the carnosine quantification measurement was 9.1% for GM and 6.3% for SOL, showing high repeatability, and the intraclass correlation coefficients (ICCs) of 0.93 for GM and 0.98 for SOL indicate the high reliability of the measurement. Acute exercise did not change the concentration of carnosine in the muscle, but affected the shape of the resonance lines, in terms of the shifting and splitting into doublets. Carnosine measurement by super(1)H MRS at 7 T in skeletal muscle exhibits high repeatability and reliability. The observed effects of acute exercise were more prominent in GM, probably as a result of the larger portion of glycolytic fibers in this muscle and the more pronounced exercise-induced change in pH. Our results support the application of the MRS-based assessment of carnosine for pH measurement in muscle compartments. copyright 2015 The Authors. NMR in Biomedicine published by John Wiley & Sons Ltd. Relaxation times of carnosine in the soleus and gastrocnemius muscles were measured and the repeatability of carnosine measurement by super(1)H MRS at 7T was determined. Observation of the effect of acute exercise, by a 1-h-long run, on carnosine showed no changes in concentration, but affected the s