Abstracts

Rationale: The ketogenic diet, a high fat, low protein and low carbohydrate diet, is used to treat drug resistant/intractable epilepsy in children. The diet is also considered to be neuroprotective in some neurodegenerative disease models. To understand the mechanism of the ketogenic diet, we first reassessed the anticonvulsive and neuroprotective effects of the ketogenic diet in two mouse seizure models. Second, we are currently defining the composition of the brain extracellular fluid using in vivo microdialysis. These data are necessary to be able to research the anticonvulsant mechanism of the ketogenic diet in vitro and in vivo. Methods: Ketogenic and control diets balanced in vitamin and mineral content relative to their caloric densities were fed ad lib to adolescent C3H/FeBJ mice for 1-3 weeks. The fluorothyl and the kainate models were used to compare seizure susceptibilities. Hippocampal cell death was visualized by Fluorojade staining. The zero-flow method of in vivo microdialysis was used to determine hippocampal extracellular fluid concentrations of glucose and lactate.Results: As expected, ketogenic diet-fed mice showed about 2 mM blood β-hydroxybutyrate levels, which demonstrates ketosis. The ketogenic diet-fed mice exhibited a significant 10-22% delay in the latency to fluorothyl-induced tonic seizures when compared to the control mice (n=10 each diet group). After injection of 35 mg/kg kainate i.p., mice on the ketogenic diet showed more severe seizure behavior and higher mortality rate than mice on the control diet. In order to compare kainate status epilepticus-induced neuronal damage, ketogenic diet-fed mice were injected with a dose of 25 mg/kg kainate, i.p.. They experienced seizures with similar severity as the control-fed mice injected with 35 mg/kg kainate, i.p.. The extent of Fluorojade staining in the hippocampus among both diet groups was similar, which shows that the ketogenic diet is not neuroprotective in this mouse kainate model. Using the zero-flow microdialysis method, we found that ketogenic diet-fed mice had about one third lower glucose levels in the hippocampal extracellular fluid than control diet-fed mice (p<0.05 unpaired two-sided t-test, n=6-8). This may be a result of a lower blood glucose level, which may contribute to the anticonvulsant effect of the ketogenic diet.Conclusions: 1)The balanced ketogenic diet was anticonvulsant in the mouse fluorothyl model, but not the kainate model, indicating that the ketogenic diet is only anticonvulsant in certain mouse seizure models. 2) There was no neuroprotective effect in the mouse kainate model, indicating that the ketogenic diet is not neuroprotective in all models of neurodegeneration. 3) The extracellular brain environment in mice on the ketogenic diet contained reduced glucose levels, which may contribute to the anticonvulsant effect of the ketogenic diet. The composition of the brain extracellular fluid of ketogenic diet-fed mice, specifically the β-hydroxybutyrate level, is currently being further characterized by our laboratory. This project was funded by the Epilepsy Foundation.