Abstracts

Rationale: Medium chain triglycerides (MCTs) are used as a treatment for several metabolic disorders, and one MCT, triheptanoin, a triglyceride of heptanoate (7-carbon fatty acid) has recently been shown to be anticonvulsant in four rodent seizure models. We hypothesised that both the even and odd chain triglycerides, trioctanoin and triheptanoin, will alter brain glucose metabolism, and that this contributes to their anticonvulsant effects.Methods: Seven week old CD1 mice were fed a standard, 35% trioctanoin or 35% triheptanoin (caloric value) diet with matched protein, vitamins and mineral levels. The 6 Hz seizure model was performed on the same mice on days two, seven and twenty one after diet initiation. The critical current required to induce seizures in 50% of mice (CC50) was determined using the up-and down-method varying electrical current intensities at 2 mA intervals. Another group of 7-8 week old male CD1 males were sacrificed by focal 5 KW microwave irradiation to the head after three weeks of feeding the diets. Polar metabolites from the hippocampal formation were extracted using methanol/chloroform extraction and quantified with liquid chromatography tadem mass spectrometry. All statistics were performed using One-Way ANOVA with post-hoc Newmann-Keuls test (n=8-10 mice per group). Results: Both the 35% trioctanoin and triheptanoin diets increased the seizure threshold in the 6Hz seizure model. At the 7 day time point the CC50 was increased by 3.79 mA (p<0.05) and 5.09mA (p<0.01) in trioctanoin and triheptanoin fed mice, respectively compared to controls. Furthermore, trioctanoin raised the CC50 value by 4.3 mA (p<0.01) and triheptanoin by 5.2 mA (p<0.001) in comparison to controls after 21 days of feeding each diet. Glucose levels were similar amongst the different treatment groups, however the -hydroxybutyrate levels were 1.6- (p<0.05) and 1.7-fold (p<0.05) higher in trioctanoin and triheptanoin fed mice compared to standard diet. In mice fed trioctanoin compared to controls, a 1.6- fold(p<0.05), and 1.5(p<0.05) increase was observed in the levels of glucose 6-phosphate and fructose-6 phosphate, respectively. Furthermore between these two groups fructose-1,6-bisphosphate, dihydroxyacetone phosphate and 2- and 3-phosphoglycerate were reduced by 40%, 67% and 48% (p<0.05) indicating that glycolysis is inhibited through phosphofructokinase inhibition. Metabolites in the pentose phosphate pathway (PPP) were also reduced in mice fed trioctanoin, ribulose-5-phosphate and xylulose-5-phosphate both by 60% (p<0.05) compared to controls. This indicates that either the activity of the PPP is reduced, or these metabolites are used to supplement the loss of glycolytic intermediates. No significant differences were found between triheptanoin and control groups. Conclusions: Overall we found that trioctanoin but not triheptanoin reduced glucose utilisation in the hippocampal formation of CD1 mice. As the seizure threshold is increased by similar amounts by both triglycerides in healthy brains, it indicates that the anticonvulsant effects may be through separate mechanisms or are dependent on BHB levels.