Abstracts

Rationale: Ketogenic diets (KetoD) are an underutilized option for patients with medically intractable epilepsy. New types of KetoD have been introduced (lab & clinic) over the last 15 years. The initial observation that fasting protects against seizures was noted during the time of Hippocrates. The rationale for the composition of the high-fat, low-carbohydrate form of the KetoD was that it mimicked biochemical changes noted during fasting, particularly ketosis. Exogenous ketone bodies have been shown to protect against seizures. However, our group showed that a murine KetoD and intermittent fasting (using a conventional diet) have opposite effects in the 6 Hz electroshock and kainic acid tests, implying that their antiseizure mechanisms are not identical. In our prior work, seizure outcomes were examined the day after feeding and therefore, mice were not in ketosis. Our hypothesis is that induction of ketosis by intermittent fasting (i.e., seizure testing on the day after a fast), will protect more profoundly against seizures than testing the day after feeding (intermittent fast) or with the KetoD.Methods: Male NIH Swiss mice (4 weeks of age) were fed a KetoD or a control diet matched to the KetoD for protein content. The control diet was administered either ad lib or on an intermittent fasting schedule (alternating days of ad lib feeds or fast). After ~2 weeks of their respective diets, mice were subjected to the kainic acid (KA) seizure test. In cohort #1, mice were injected with KA based on weight (23.5 mg/kg). In cohort #2, KA was injected at the same dose, regardless of weight (to remove the potential confounder of weight, which differed between diet groups). Cell counts were performed histologically to evaluate hippocampal neuron death. Immunoblots were used to evaluate levels of mitochondrial proteins. Blood levels of beta-hydroxybutyrate were determined on the day of seizure testing.Results: In cohort #1, mice were protected more profoundly against seizures on the day after a fast, compared to an ad lib control diet (P < 0.001). Mice fed a KetoD had worse scores than those in the post-feed and post-fast groups, consistent with our prior findings (P < 0.001). In cohort #2, mice fed control diets (all schedules) fared better than the KetoD group (which paradoxically, received the lowest dose of KA). Levels of ketosis were comparable in the KetoD and intermittent fasting (post-fast) groups (P < 0.001). No statistically significant differences were noted between mice treated with different diets on histology but surprisingly, there was a trend of less cell death in mice treated with a KetoD, despite substantially worse test scores. No differences between groups were noted in levels of mitochondrial proteins.Conclusions: Intermittent fasting protected against kainic acid-induced seizures more potently than the KetoD despite similar levels of ketosis, suggesting that food-supplemented ketosis alone does not protect against seizures. These data lend further support to the investigation of intermittent fasting as a dietary treatment for seizures. Study funding: K08NS070931 (NINDS/NIH), University of Calgary