Fatty acid breakdown does not occur to any great extent in the brain because of the low activity of an enzyme in the beta-oxidation pathway limits the pathway’s activity1. Compared to the extrahepatic tissues as a whole, in the brain the following pathways are not performed or are not important:
Glycogen synthesis and breakdown
Fatty acid synthesis and breakdown
Triglyceride synthesis and breakdown
Protein synthesis and breakdown
These pathways are crossed out on the figure below.
Fatty acid breakdown does not occur to any great extent in the brain because low activity of an enzyme in the beta-oxidation pathway limits the activity of this pathway2.
By removing those pathways the only pathways left are:
Ketone body breakdown
Thus, due to its limited metabolic capabilities, the brain needs to receive either glucose or ketone bodies to use as an energy source.
References & Links
1. Yang SY, He XY, Schulz H (1987) Fatty acid oxidation in rat brain is limited by the low activity of 3-ketoacyl-coenzyme A thiolase. J BIol Chem 262 (27): 13027-13032.