Does acute caffeine ingestion alter brain metabolism in young adults?

Abstract

Caffeine, as the most commonly used stimulant drug, improves vigilance and, in some cases, cognition. However, the exact effect of caffeine on brain activity has not been fully elucidated. Because caffeine has a pronounced vascular effect which is independent of any neural effects, many hemodynamics-based methods such as fMRI cannot be readily applied without a proper calibration. The scope of the present work is two-fold. In Study 1, we used a recently developed MRI technique to examine the time-dependent changes in whole-brain cerebral metabolic rate of oxygen (CMRO2) following the ingestion of 200mg caffeine. It was found that, despite a pronounced decrease in CBF (p<0.001), global CMRO2 did not change significantly. Instead, the oxygen extraction fraction (OEF) was significantly elevated (p=0.002) to fully compensate for the reduced blood supply. Using the whole-brain finding as a reference, we aim to investigate whether there are any regional differences in the brain’s response to caffeine. Therefore, in Study 2, we examined regional heterogeneities in CBF changes following the same amount of caffeine ingestion. We found that posterior brain regions such as posterior cingulate cortex and superior temporal regions manifested a slower CBF reduction, whereas anterior brain regions including dorsolateral prefrontal cortex and medial frontal cortex showed a faster rate of decline. These findings have a few possible explanations. One is that caffeine may result in a region-dependent increase or decrease in brain activity, resulting in an unaltered average brain metabolic rate. The other is that caffeine’s effect on vasculature may be region-specific. Plausibility of these explanations is discussed in the context of spatial distribution of the adenosine receptors.

The neuroprotective effects of caffeine in neurodegenerative diseases

“…Caffeine (1,3,7‐trimethylxanthine) is the most widely used psychostimulant in Western countries . It is contained in coffee, tea, energy drinks, several soft drinks and cocoa .…”

Benchmarking transverse spin relaxation based oxygenation measurements in the brain during hypercapnia and hypoxia

“…All were screened for history of cerebrovascular disease, anemia, heart disease, or lung diseases that might affect blood and brain oxygenation. Volunteers were instructed to abstain from consuming caffeine for 12 h before the scan, given the known effects of caffeine on cerebral blood flow (CBF) . Volunteers were not instructed to abstain from smoking before the scan, although all scans took place on a tobacco‐free campus.…”

Volume‐localized measurement of oxygen extraction fraction in the brain using MRI

“…The sensitivity of TRUST to changes in OEF has been demonstrated using hypercapnia, hyperoxia, hypoxia, and caffeine challenges. [12][13][14][15] The robustness and applicability of the method has been demonstrated further in a number of single and multi-site studies and in a variety of cerebrovascular conditions. [16][17][18] Overall, the TRUST method has been highly influential, however, a key limitation of the method is its lack of spatial specificity.…”

“…Because of a known relationship between blood T 2 and blood oxygen saturation levels, this then allows calculation of tissue OEF. The sensitivity of TRUST to changes in OEF has been demonstrated using hypercapnia, hyperoxia, hypoxia, and caffeine challenges . The robustness and applicability of the method has been demonstrated further in a number of single and multi‐site studies and in a variety of cerebrovascular conditions .…”