AUTHOR=Krumpolec Patrik , Klepochová Radka , Just Ivica , Tušek Jelenc Marjeta , Frollo Ivan , Ukropec Jozef , Ukropcová Barbara , Trattnig Siegfried , Krššák Martin , Valkovič Ladislav 

TITLE=Multinuclear MRS at 7T Uncovers Exercise Driven Differences in Skeletal Muscle Energy Metabolism Between Young and Seniors

JOURNAL=Frontiers in Physiology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2020.00644

DOI=10.3389/fphys.2020.00644

ISSN=1664-042X

ABSTRACT=<p><bold>Purpose:</bold> Aging is associated with changes in muscle energy metabolism. Proton (<sup>1</sup>H) and phosphorous (<sup>31</sup>P) magnetic resonance spectroscopy (MRS) has been successfully applied for non-invasive investigation of skeletal muscle metabolism. The aim of this study was to detect differences in adenosine triphosphate (ATP) production in the aging muscle by <sup>31</sup>P-MRS and to identify potential changes associated with buffer capacity of muscle carnosine by <sup>1</sup>H-MRS.</p><p><bold>Methods:</bold> Fifteen young and nineteen elderly volunteers were examined. <sup>1</sup>H and <sup>31</sup>P-MRS spectra were acquired at high field (7T). The investigation included carnosine quantification using <sup>1</sup>H-MRS and resting and dynamic <sup>31</sup>P-MRS, both including saturation transfer measurements of phosphocreatine (PCr), and inorganic phosphate (Pi)-to-ATP metabolic fluxes.</p><p><bold>Results:</bold> Elderly volunteers had higher time constant of PCr recovery (τ<sub><italic>PCr</italic></sub>) in comparison to the young volunteers. Exercise was connected with significant decrease in PCr-to-ATP flux in both groups. Moreover, PCr-to-ATP flux was significantly higher in young compared to elderly both at rest and during exercise. Similarly, an increment of Pi-to-ATP flux with exercise was found in both groups but the intergroup difference was only observed during exercise. Elderly had lower muscle carnosine concentration and lower postexercise pH. A strong increase in phosphomonoester (PME) concentration was observed with exercise in elderly, and a faster Pi:PCr kinetics was found in young volunteers compared to elderly during the recovery period.</p><p><bold>Conclusion:</bold> Observations of a massive increment of PME concentration together with high Pi-to-ATP flux during exercise in seniors refer to decreased ability of the muscle to meet the metabolic requirements of exercise and thus a limited ability of seniors to effectively support the exercise load.</p>