Anticonvulsant effects of a triheptanoin diet in two mouse chronic seizure models

Abstract

We hypothesized that in epileptic brains citric acid cycle intermediate levels may be deficient leading to hyperexcitability. Anaplerosis is the metabolic refilling of deficient metabolites. Our goal was to determine the anticonvulsant effects of feeding triheptanoin, the triglyceride of anaplerotic heptanoate. CF1 mice were fed 0-35% calories from triheptanoin. Body weights and dietary intake were similar in mice fed triheptanoin vs. standard diet. Triheptanoin feeding increased blood propionyl-carnitine levels, signifying its metabolism. 35%, but not 20%, triheptanoin delayed development of corneal kindled seizures. After pilocarpine-induced status epilepticus (SE), triheptanoin feeding increased the pentylenetetrazole tonic seizure threshold during the chronically epileptic stage. Mice in the chronically epileptic stage showed various changes in brain metabolite levels, including a reduction in malate. Triheptanoin feeding largely restored a reduction in propionyl-CoA levels and increased methylmalonyl-CoA levels in SE mice. In summary, triheptanoin was anticonvulsant in two chronic mouse models and increased levels of anaplerotic precursor metabolites in epileptic mouse brains. The mechanisms of triheptanoin's effects and its efficacy in humans suffering from epilepsy remain to be determined.

Copyright © 2010 Elsevier Inc. All rights reserved.

Figures

Fig. 1

The 35% triheptanoin diet is calorically equivalent to the standard diet. (A) No significant difference in the growth curves of CF1 mice on standard and triheptanoin diets for 52 days (A, n=7; mean +/- SEM). (B) Similar daily energy intake per body weight (kcal/g/day) of standard and triheptanoin diets, showing the caloric equivalence of the two diets. The food intake was averaged for 4 days (n=6 mice per diet group).

Fig. 2

The development of corneal kindling-induced seizures is delayed by 35% triheptanoin feeding. (A) Timeline of experiments B and C indicating that the experimental diets were initiated three weeks before the first corneal stimulation. (B, C) The median seizure thresholds of each diet group are plotted against the stimulation number, showing significant differences in seizure development with 35% triheptanoin feeding during the kindling process (comparisons of areas under the curve B pP=0.006 one way ANOVA; P<0.01 35% triheptanoin vs. standard diet, Newman-Keuls test **). (D) Triheptanoin and standard diets were initiated in fully kindled mice. No significant differences in the severity of behavioral seizures were found between diets in fully kindled mice.

Fig. 3

Lowered PTZ seizure thresholds in the chronic stage of the pilocarpine model. (A) Timeline of the experiment. (B) Twenty-three days after pilocarpine injection, SE mice were more sensitive than no SE and “sham control” mice to PTZ-induced clonic generalized and tonic seizures (p0.05, Newman-Keuls post-test).

Fig. 4

Triheptanoin feeding increases the lowered PTZ tonic extension threshold in the chronic stage of the pilocarpine SE model. (A) Timeline of the experiment showing that experimental diets were given immediately after pilocarpine injection. (B, C) Three weeks after pilocarpine injection, SE mice were more sensitive than no SE and non-injected control mice to PTZ-induced clonic generalized and tonic seizures (p

Fig. 5

Quantification of CoA metabolites in brain shows that triheptanoin feeding increases the levels of anaplerotic molecules in SE mice. (A) Timeline of the experiment. After pilocarpine injection, SE mice and no SE mice were first fed standard diet for two weeks, then divided into groups of equal average weight and received either standard or 35% triheptanoin-containing diet for following three weeks until metabolite quantification. (B, C) The brain levels of CoA-coupled metabolites are plotted for the different mouse groups in nmol/g wet brain weight, white bars - no SE mice, black bars -SE mice, clear bars – standard diet, striped bars – 35% triheptanoin diet. BHB - β-hydroxybutyrate, HMG – 3-hydroxy-3-methylglutaryl, Me-malonyl – methylmalonyl.