Applications of NMR spectroscopy to study muscle glycogen metabolism in man

Prior to the advent of nuclear magnetic resonance (NMR) spectroscopy, human glucose metabolism was studied through tracer and tissue biopsy methodolog y. NMR spectroscopy now provides a noninvasive means to monitor metabolic f lux and intracellular metabolite concentrations continuously. C-13 NMR spec troscopy has shown that muscle glycogen synthesis accounts for the majority of insulin-stimulated muscle glucose uptake in normal volunteers and that defects in this process are chiefly responsible for insulin resistance in t ype 1 and type 2 diabetes mellitus, as well as in other insulin resistant s tates (obesity, insulin-resistant offspring of type 2 diabetic parents, ele vation of plasma FFA concentrations). Furthermore, using P-31 NMR spectrosc opy to measure intracellular glucose-6-phosphate, it has been shown that de fects in insulin-stimulated glucose transport/phosphorylation activity are primarily responsible for the insulin resistance in these states.