NUCLEAR-MAGNETIC-RESONANCE STUDIES OF MUSCLE AND APPLICATIONS TO EXERCISE AND DIABETES

Natural-abundance C-13 nuclear magnetic resonance (NMR) spectroscopy i s a noninvasive technique that enables in vivo assessments of muscle a nd/or liver glycogen concentrations. When directly compared with the t raditional needle biopsy technique, NMR was found to be more precise, Over the last several years, we have developed and used C-13-NMR to ob tain information about human glycogen metabolism both under conditions of altered blood glucose and/or insulin and with exercise. Because NM R is noninvasive, we have been able to obtain more data points over a specified time course, thereby dramatically improving the time resolut ion. This improved time resolution has enabled us to document subtleti es of the resynthesis of muscle glycogen after severe exercise that ha ve not been observed previously. An added advantage of NMR is that we are able to obtain information simultaneously about other nuclei, such as P-31. With interleaved C-13- and P-31-NMR techniques, we have been able to follow simultaneous changes in muscle glucose-6-phosphate and muscle glycogen. In this article, we review some of the work that has been reported by our laboratory and discuss the relevance of our find ings for the management of diabetes.