MR-Based Metabolic Characterization of Skeletal Muscle: Methods and Applications

Assessment of the tissue metabolism gained a new opportunity with advent and dissemination of the in vivo magnetic resonance spectroscopy (MRS) and imaging methods. Skeletal muscle is readily accessible for non-invasive investigation. While MRI allows for the assessment macroscopic fat distribution, MRS allows for the quantification of ectopic of fat compartments and metabolic profiling of skeletal muscle. Volume selected proton MRS can be applied for the assessment of intramyocellular lipids, creatine, acetylcarnitine, and carnosine. Characterization of glucose fluxes from biopsy specimen could have been replaced by 13C and 31P MRS, which was able to quantify defects of glucose metabolism in diabetes and other insulin resistant states. Basal and stimulated intracellular energy metabolism can be monitored by 31P MRS and combination of spectroscopy and physiologic examinations of the skeletal muscle function and energetic metabolism can help to identify the links between impaired metabolism, function, aging and or training status. Selected issues with respect to methodological issues of skeletal muscle MRS and research oriented applications will be presented and discussed.