Abstracts

Rationale: Triheptanoin, the triglyceride of heptanoate (C7 fatty acid), has recently been found to be anticonvulsant in several mouse models. We hypothesized that triheptanoin will alter brain metabolism of some amino acids, energy metabolites and glutathione, which may underlie its anticonvulsant effects. Methods: The pilocarpine mouse model was used. It results in spontaneous recurrent seizures in mice that had experienced pilocarpine-induced status epileptics (SE), but not in mice without SE (no SE mice). After pretreatment with 2 mg/kg methyl-scopolamine (i.p.) 7-8 week old male CD1 mice were injected with pilocarpine (280-360 mg/kg s.c.) and 90 min later with 25 mg/kg pentobarbital (i.p.). All mice were immediately placed on a standard control or 35% (caloric value) triheptanoin diets with matched protein, vitamin and mineral levels. To encourage weight gain in animals with SE, mice were injected with 4% dextrose in saline (s.c) and hand fed, for the first few days after SE. Three weeks later mice were sacrificed by focal 5 KW microwave irradiation on the head. Polar metabolites from the cerebral cortex and hippocampal formations were extracted using methanol/chloroform and then quantified with HPLC using alpha-aminobutyric acid as an internal standard. For each metabolite and brain area One-Way ANOVA's with post-hoc Bonferroni tests with selected comparisons were used to compare SE and no SE mice on standard and triheptanoin diet (n=9-10 mice per group) separately. Only changes that were statistically significant in the ANOVA and post test with p<0.05 are shown. Results: After SE, mice showed 1.5-fold increases in myo-inositol consistent with astrogliosis found in this model (p<0.001). Mice on our standard diet which experienced SE showed reduced hippocampal levels of glutathione (by 20%, p<0.01), glutamate (28%, p<0.01) and alanine (35%, p<0.001) compared to those without SE. Similar changes after SE were seen in mice fed triheptanoin, except that there were no significant decreases in glutathione, indicating that triheptanoin feeding protects against loss of this important antioxidant in the "epileptic" hippocampal formation. Also, triheptanoin decreased hippocampal threonine levels in SE mice (26%, p<0.01) and in the cortex in both SE (36%, p<0.01) and no SE mice (28%, p<0.05), raising the possibility that triheptanoin interferes with threonine uptake or metabolism. Triheptanoin induced no changes in the levels of aspartate, glutamate, serine, glutamine, glycine, taurine, alanine, tyrosine, GABA, lysine and methionine. Currently, we are assessing to which extent triheptanoin alters high energy phosphate levels in the hippocampus and cortex. Conclusions: Triheptanoin feeding did not change any of the measured amino acids in the cerebral cortex and hippocampal formation of healthy and epileptic mice, except for lowering threonine levels. Therefore, it is advisable to monitor this amino acid in our clinical trial of triheptanoin. The inhibition of the decrease of the GSH level in SE mice by triheptanoin may contribute to its protective effect against seizures.