Identification of an epilepsy-linked gut microbiota signature in a pediatric rat model of acquired epilepsy

A dysfunctional gut microbiota-brain axis is emerging as a potential pathogenic mechanism in epilepsy, particularly in pediatric forms of epilepsy. To add new insights into gut-related changes in acquired epilepsy that develops early in life, we used a multi-omics approach in a rat model with a 56% incidence of epilepsy. The presence of spontaneous seizures was assessed in adult rats (n = 46) 5 months after status epilepticus induced by intra-amygdala kainate at postnatal day 13, by 2 weeks (24/7) ECoG monitoring. Twenty-six rats developed epilepsy (Epi) while the remaining 20 rats (No-Epi) did not show spontaneous seizures. At the end of ECoG monitoring, all rats and their sham controls (n = 20) were sacrificed for quantitative histopathological and immunohistochemical analyses of the gut structure, glia and macrophages, as well as RTqPCR analysis of inflammation/oxidative stress markers. By comparing Epi, No-Epi rats, and sham controls, we found structural, cellular, and molecular alterations reflecting a dysfunctional gut, which were specifically associated with epilepsy. In particular, the villus height-to-crypt depth ratio and number of Goblet cells were reduced in the duodenum of Epi rats vs both No-Epi rats and sham controls (p < 0.01). Villus height and crypt depth in the duodenum and jejunum (p < 0.01) were increased in No-Epi vs both Epi and sham controls. We also detected enhanced Iba1-positive macrophages, together with increased IL1b and NFE2L2 transcripts and TNF protein, in the small intestine of Epi vs both No-Epi and sham control rats (p < 0.01), denoting the presence of inflammation and oxidative stress. Astroglial GFAP-immunostaining was similar in all experimental groups. Metagenomic analysis in the feces collected 5 months after status epilepticus showed that the ratio of two dominant phyla (Bacteroidota-to-Firmicutes) was similarly increased in Epi and No-Epi rats vs sham control rats. Notably, the relative abundance of families, genera and species associated with SCFA production differed in Epi vs No-Epi rats, describing a bacterial imprint associated with epilepsy. Furthermore, Epi rats showed a blood metabolic signature characterized by changes in lipid metabolism compared to both No-Epi and sham control rats. Our study provides new evidence of long-term gut alterations, along with microbiota-related metabolic changes, occurring specifically in rats that develop epilepsy after brain injury early in life.