GABA concentration in sensorimotor cortex following high-intensity exercise and relationship to lactate levels

Abstract

Key points: Magnetic resonance spectroscopy was conducted before and after high-intensity interval exercise. Sensorimotor cortex GABA concentration increased by 20%. The increase was positively correlated with the increase in blood lactate. There was no change in dorsolateral prefrontal cortex. There were no changes in the glutamate-glutamine-glutathione peak.

Abstract: High-intensity exercise increases the concentration of circulating lactate. Cortical uptake of blood borne lactate increases during and after exercise; however, the potential relationship with changes in the concentration of neurometabolites remains unclear. Although changes in neurometabolite concentration have previously been demonstrated in primary visual cortex after exercise, it remains unknown whether these changes extend to regions such as the sensorimotor cortex (SM) or executive regions such as the dorsolateral prefrontal cortex (DLPFC). In the present study, we explored the acute after-effects of high-intensity interval training (HIIT) on the concentration of gamma-Aminobutyric acid (GABA) and the combined glutamate-glutamine-glutathione (Glx) spectral peak in the SM and DLPFC, as well as the relationship with blood lactate levels. Following HIIT, there was a robust increase in GABA concentration in the SM, as evident across the majority of participants. This change was not observed in the DLPFC. Furthermore, the increase in SM GABA was positively correlated with an increase in blood lactate. There were no changes in Glx concentration in either region. The observed increase in SM GABA concentration implies functional relevance, whereas the correlation with lactate levels may relate to the metabolic fate of exercise-derived lactate that crosses the blood-brain barrier.

Keywords: gamma-aminobutyric acid; high-intensity exercise; magnetic resonance spectroscopy.

Figure 1. Overview of experiment

MRS measures were obtained before and after HIIT exercise using MEGA‐PRESS tuned to detect GABA. A, following acquisition of an anatomical image (T1), MRS sequences were repeated for the left SM hand knob region and right DLPFC voxels. Lactate was measured from capillary blood at rest (× 2 baseline measures), during HIIT, as well as at the cessation of exercise. B and C, positioning of the SM and DLPFC voxels, respectively. The post‐exercise voxel (green) is overlaid upon the pre exercise voxel (yellow). D, difference spectra for all participants and timepoints are shown for each voxel (black lines). Model fit for each acquired difference spectrum is superimposed (red lines) for the GABA peak at 3.0 ppm and the Glx peak at 3.75 ppm. [Color figure can be viewed at wileyonlinelibrary.com]

Figure 2. Blood lactate measures are displayed relative to exercise onset

The second baseline measure was obtained within the 5 min prior to exercise commencing. During exercise, measures were obtained at the end of the third and fourth high‐intensity epochs.

Figure 3. SM voxel GABA and Glx ratios

Concentrations are shown for pre‐ and post‐HIIT exercise, depicting the main contrast of interest. Metabolite concentrations are shown relative to water (A and B) and creatine (C and D). Squares depict the mean and 95% confidence interval. Circles show individual subject data.

Figure 4. Exercise‐induced change in Lactate and GABA

Correlation between increase in blood lactate and the percent increase in GABA concentration in the SM voxel following HIIT (r = 0.63, P = 0.034).