Abstracts

Rationale: The Citric Acid Cycle (CAC) is critical for oxidative metabolism in the brain. Also, CAC intermediates are the precursor of neurotransmitters. We hypothesize that impaired CAC activity may lead to decreases in GABA and ATP and could lead to generation/progression of epileptic disorders. Anaplerosis is the metabolic replenishment of CAC catalytic intermediates. Here we researched if an anaplerotic diet may be anti-convulsant and/or anti-epileptogenic in mice. Methods: Mice were fed ad libitum either control diet or diet containing 35% calories from triheptanoin - the triglyceride of heptanoate, an anaplerotic molecule. Body weight and metabolites in blood and brain were monitored to assess metabolism of triheptanoin. To assess anti-epileptic activity of the diet acute and chronic mouse seizure models in CD1 and CF1 mice were employed; namely the fluorothyl, pentylenetetrazole and 6 Hertz acute models, a chronic corneal kindling model and the pilocarpine model with a second hit pentylenetetrazole seizure threshold test. Results: There was no statistically significant difference in body weights or kilocalories consumed/kg body weight/day on either diet, indicating that the diets are calorically equivalent. Blood levels of heptanoyl-, pentanoyl- and propionyl-carnitine were elevated three to ten-fold in mice on the triheptanoin diet, demonstrating metabolism of triheptanoin. The triheptanoin diet showed no significant effects on seizure thresholds in three acute seizure models; the pentylenetetrazole, 6 Hertz, or the fluorothyl models, indicating that it is not anti-convulsant in healthy mice. In the chronic pilocarpine model, mice that developed SE in response to pilocarpine were subsequently fed triheptanoin or control diet for three weeks. Brain metabolite analysis of SE mice on the C7 diet showed statistically significant increases in the levels of β-hydroxybutyrate and the anaplerotic CAC precursors, propionyl-CoA and methylmalonyl-CoA compared to SE mice on control diet. SE mice were significantly more sensitive than non-SE mice to pentylenetetrazole-induced seizures signifying epileptogenesis. SE mice fed triheptanoin diet had an increase in pentylenetetrazole seizure threshold compared to SE mice fed the control diet (p=0.03; ANOVA, with post-hoc Student-Newman-Keuls test), indicating an anti-epileptogenic and/or anti-convulsant effect of triheptanoin. Ongoing experiments will assess if hippocampal neurodegeneration was also reduced by the diet. In the second chronic model, mice on either diet were kindled by corneal electroshock twice a day. The anaplerotic diet produced a statistically significant delay in kindling. Conclusions: Taken together, we found that triheptanoin increased CAC precursor levels in mouse brains and was anti-epileptogenic and/or anti-convulsant in two chronic epilepsy models. The mechanism of the anti-epileptic effect remains to be examined and future human trials are warranted. We thank CURE for funding.