Prebiotic reduction of brain histone deacetylase (HDAC) activity and olanzapine-mediated weight gain in rats, are acetate independent.

The intestinal microbiome is emerging as a novel therapeutic target owing to the wide range of potential health benefits that could result by manipulating the microbiota composition through relatively simple interventions. Ingestion of the prebiotic Bimuno™ galacto-oligosaccharide (B-GOS®) is one such intervention that has been shown to attenuate olanzapine-induced weight gain and improve cognitive flexibility in rats, potentially through mechanisms involving acetate, the major short-chain fatty acid (SCFA) that is produced by B-GOS® fermentation. The present study investigated the individual influences of B-GOS® and sodium acetate intake on brain histone acetyltransferase (HAT) and histone deacetylase (HDAC) activities, cortical and hippocampal expression of HDAC1-4 and N-methyl-d-aspartate receptor subunits in saline or olanzapine injected female rats. The effect of sodium acetate on olanzapine-induced weight gain was also investigated. Daily ingestion of B-GOS® for 21 days, reduced HDAC activity and hippocampal HDAC-4, and elevated levels of cortical HDAC-1 and HDAC-3 mRNAs. Sodium acetate supplementation significantly decreased HAT, but not HDAC, activity and increased hippocampal HDAC-3 and HDAC-4 mRNAs. Olanzapine-induced weight gain and fourteen genera of intestinal bacteria, were not influenced by sodium acetate intake. Together these data suggests the effects of B-GOS® in rats cannot be replicated by acetate ingestion, and that mechanisms beyond the production of this SCFA are likely to underlie the psychotropic and metabolic actions of this prebiotic.