Interdependence of central stearic and oleic acids. Due to its unsaturated structure oleic acid (C18:1n-9) moves more readily than stearic acid (C18:0) across the BBB. Within the CNS oleic acid can inhibit both Δ9-D and ACC resulting in decreased de novo synthesis of both itself and steric acid. Simultaneously a decrease in melonyl CoA and it’s inhibition of CPT1 can promote an increase in central fatty acid β-oxidation. Oleic acid also increases the expression of genes linked to fatty acid β-oxidation by a SIRT1/PGC1 dependent mechanism. (Abbreviations; ACC, acetyl CoA; FAS, fatty acid synthase; ELO, elongase; Δ9-D, Δ9-desaturase; CPT1, carnitine palmitoyltransferase-1; cAMP/PKA, cyclic adenosine monophosphate/protein kinase A; pSIRT1, phosphorylated sirtuin 1; PGC1α peroxisome proliferator-activated receptor gamma co-activator).