Ketones suppress brain glucose consumption.
Level 5 - mechanism / opinion, no new human data
Animal experimental study
PubMed 19227486 · doi:10.1007/978-0-387-85998-9_45
What was done
Local cerebral metabolic rate of glucose consumption (CMRglu; µM/min/100g) was measured in the frontal cortex and cerebellum of control and ketotic rats using Patlak analysis of 90-minute dynamic 18F-FDG PET coregistered with 7-Tesla MRI. Blood radioactivity was sampled from the tail vein, and plasma glucose and beta-hydroxybutyrate (BHB) concentrations were measured.
What was found
Local CMRglu decreased linearly with increasing plasma BHB: - Frontal cortex: CMRglu = -3.93*[BHB] + 42.7 (r2 = 0.5) - Cerebellum: CMRglu = -4.07*[BHB] + 61.4 (r2 = 0.3) These data indicate that glucose consumption is reduced by approximately 10% per 1 mM of plasma ketone bodies.
Why it matters
It provides in vivo imaging evidence that circulating ketones dose-dependently substitute for glucose in rodent brain metabolism, suppressing regional cerebral glucose consumption.
Limits
The experiment was conducted exclusively in rats, and the abstract omits sample size, variance, and p-values. Correlations were modest (r2 = 0.3 to 0.5), and findings may not directly translate to human physiology.
Cited by
- supports During prolonged fasting, brain glucose consumption drops from nearly 100% to roughly 40-50%, with the remainder supplied by ketone bodies.