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

TL;DR

This study demonstrates the feasibility of simultaneously using interleaved 1H and 31P MRSI at 7T to monitor brain energy metabolism responses to hyperglycemia in humans.

Contribution

It introduces a novel interleaved multinuclear 7T MRS protocol to noninvasively track brain fuel handling during glucose level changes.

Findings

1H Glc+Tau increased with blood glucose levels.

31P high-energy phosphate ratios showed significant glycemia-linked responses.

The protocol enables concurrent measurement of brain energy metabolism at 7T.

Abstract

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 1H signal alongside 31P 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 approx. 120 min. Short-block, short-TE 1H single-voxel spectroscopy (STEAM, TE = 11 ms; mean block duration 5.71 (SD:0.62 min)) was acquired in frontal cortex and quantified using the composite Glucose+Taurine (Glc+Tau) measure. 31P was acquired with rapid 3D PETALUTE MRSI using an ultrashort echo time (UTE; TE = 65 micros; 381 s per block), and high-energy phosphate ratios were derived from a posterior cortical region of interest. Across participants, 1H Glc+Tau increased with blood glucose and showed significant elevations from baseline into hyperglycemia. In parallel, 31P 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 1H and 31P MRS(I) can be interleaved at 7 T to measure energy metabolism within a single session