Abstracts

Rationale:
There is increasing evidence that changes in the gut microbiota are linked to diseases such as depression, anxiety, and epilepsy. For example, supplementation with probiotics has been associated with a decrease in the seizure frequency of patients with epilepsy, and the antiseizure effect of the ketogenic diet appears to be mediated, in part, by the gut microbiota.   However, very little is known about the effect of seizures and epilepsy on the gut microbiota.     In this study, we aimed to investigate the effects of epilepsy development (epileptogenesis) on the gut microbiota in a translationally relevant animal model of temporal lobe epilepsy.
Method:
The epilepsy model was created by chronically infusing the glutamine synthetase inhibitor methionine sulfoximine (MSO) in the right hippocampus of Sprague Dawley rats (n = 5). Phosphate buffered saline was injected in the hippocampus of another cohort of rats, to serve as controls (n = 5). To evaluate the effect of epileptogenesis on the gut microbiota, feces from all animals were collected at the time of model creation and on days 7, 14, and 21 thereafter.   Bacterial DNA was isolated from the fecal samples using a DNA extraction kit (DNeasy®, Qiagen). The specific regions of the 16S rRNA gene were amplified using barcoded primers. Pooled samples were sequenced by paired-end sequencing with dual indexing on an Illumina MiSeq instrument. The data were analyzed for relative changes in bacterial abundance using the linear discriminant analysis effect size (LEfSe), a well-established metagenomic biomarker discovery method (https://huttenhower.sph.harvard.edu/galaxy/)
Results:
Seven days after the induction of epileptogenesis, there was an overabundance of Prevotella speciescompared to the controls. Fourteen days after induction, Bacteroides and Clostridales predominated, whereas 21 days after, Bacteroides and Anaeroplasma species were overabundant.
Conclusion:
We found significant changes in several gut bacteria in epileptic animals as the disease developed over week. These changes suggest the presence of a regulatory pathway from the epileptic brain to the gut.  The altered gut microbiota may suggest a novel mechanism by which the body   modulates epileptogenesis. Notably, treatment with a ketogenic diet causes an increase in the diversity of Prevotella species in infants with refractory epilepsy. The increase in Prevotella species in our model raises the possibility that this species may be implicated in the epileptogenic process.   Additional studies are required to investigate the role of these and other bacteria in epileptogenesis and whether targeting these bacteria therapeutically may slow or prevent epileptogenesis.
Funding:
:CURE Epilepsy