Feasibility of Concurrent 1 H MRS and 31 P MRSI at 7 T: Brain Energy Metabolism Responses to Hyperglycemia

How the human brain adjusts fuel handling and its bioenergetic state during changing glucose levels remains difficult to assess noninvasively. In this study, we established an interleaved multinuclear 7 T MR spectroscopy protocol to track a glucose-related ${}^1$ H signal alongside ${}^{31}$ P measures of high-energy phosphate metabolism during a hyperglycemic clamp. Five healthy adults completed a morning, fasted infusion experiment consisting of baseline, ramp-up, and hyperglycemic stages over $\sim$ 120 min. Short-block, short-TE ${}^1$ H single-voxel spectroscopy (STEAM, TE = 11 ms; mean block duration $5.71\pm 0.62$  min) was acquired in frontal cortex and quantified using the composite glucose $+$ taurine (Glc $+$ Tau) measure. ${}^{31}$ P was acquired with rapid 3D PETALUTE MRSI using an ultrashort echo time (UTE; TE = 65  $\mu$ s; 381 s per block), and high-energy phosphate ratios were derived from a posterior cortical region of interest. Across participants, ${}^1$ H Glc $+$ Tau increased with blood glucose and showed significant elevations from baseline into hyperglycemia. In parallel, ${}^{31}$ P ratios exhibited smaller but significant glycemia-linked responses: both PCr/Pi and $\gamma$ ATP/Pi increased with blood glucose and differed across glucose clamp stages. These findings show that ${}^1$ H and ${}^{31}$ P MRS(I) can be interleaved at 7 T to measure energy metabolism within a single session.