Feasibility of in vivo measurement of glucose metabolism in the mouse hypothalamus by (1) H-[(13) C] MRS at 14.1T

PURPOSE: Determine the feasibility of (1) H-[(13) C] MRS in the mouse hypothalamus using a 14.1T magnet. METHODS: We optimized the design of a (1) H-[(13) C] surface coil to maximize the signal-to-noise ratio of (1) H-[(13) C] MRS in the mouse hypothalamus. With enhanced signal, (13) C accumulation in glucose metabolites was measured in a 8.7 microL voxel in the hypothalamus of 5 healthy mice during the continuous administration of [1,6-(13) C2 ]glucose. RESULTS: Accumulation of (13) C label in glucose C6 and lactate C3 was visible in the hypothalamus 11 min after glucose administration. The (13) C fractional enrichment (FE) curves of lactate C3, glutamate and glutamine C4, glutamate+glutamine C3 and C2, GABA C2, C3, and C4, and aspartate C3 were measured with a time resolution of 11 min over 190 min. FE time-courses and metabolic pool sizes were averaged to fit a novel one-compartment model of brain energy metabolism that incorporates the main features of the hypothalamus. CONCLUSION: Dynamic (1) H-[(13) C] MRS is able to measure in vivo brain metabolism in small and deep areas of the mouse brain such as the hypothalamus, and it can be used to calculate metabolic fluxes, including glutamatergic and GABAergic metabolism as well as the contribution of metabolic sources other than glucose.