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.

Heptanoate as a Neural Fuel: Energetic and Neurotransmitter Precursors in Normal and Glucose Transporter I-Deficient (G1D) Brain

“…29 Particularly, GABA C3 and C4 contained a doublet (D3,4) that derives from glutamate labeled in carbons 2,3 and in carbons 1,2 and 3. Although this labeling pattern is consistent with metabolism of [5,6,[7][8][9][10][11][12][13] C 3 ]heptanoate to [1,2,3-13 C 3 ]propionyl-CoA followed by entry into the TCA cycle, the identical pattern could occur as a consequence of carboxylation of [1,2,3-13 C 3 ]pyruvate derived from glucose.…”

“…However, the spectra of glutamate (specifically, the doublet due to J 45 ) demonstrates that pyruvate in the brain was multiply labeled. Therefore, an alternative interpretation of both the 13 C-NMR spectra in Figure 3 and the mass spectrometry observations is simply that 13 The measured 13 C enrichment in plasma glucose shown in Figure 2 fixes the upper limit on the amount of either [2,[3][4][5][6][7][8][9][10][11][12][13] C]pyruvate or [1,2,3-13 C]pyruvate that can be present in the brain (as these are the two labeling patterns that can be metabolized to [1,2-13 C 2 ]acetyl-CoA).…”

“…Mass isotopomers of 13 C-glucose in plasma. Plasma 13 Cglucose was enriched from [5,6,[7][8][9][10][11][12][13] C 3 ]heptanoate in both normal and mutant (glucose transporter type I deficiency, G1D) animal groups. Data were corrected for the natural abundance of 13 C. Glucose was mostly enriched in M þ 2 (Control: 4.63%±1.5%; G1D: 5.28%±1.22%) and M þ 3 (Control: 3.65%±0.86%; G1D: 3.45%±0.69%).…”

“…In this work, we sought to characterize the metabolism of [5,6,7-13 C 3 ]heptanoate in the brain of normal conscious mice and of a transgenic antisense mouse model of G1D that exhibits the common epileptic phenotype typical of the human glucose transporter defect. 14 Administration of heptanoate labeled in this fashion is followed by oxidation of [5,6,7-13 C 3 ]heptanoate or [3,4,[5][6][7][8][9][10][11][12][13] C 3 ]C5-ketone derivatives in the brain without generation of [1,2-13 C 2 ]acetyl-CoA, and, consequently, without enrichment of carbons 4 or 5 of glutamine or glutamate. Using this approach, we demonstrate that plasma glucose becomes enriched with 13 C in the presence of intravenously infused [5,6,7-13 C 3 ]heptanoate as expected, indicating that the understanding of any effects of heptanoate therapy must consider its effects on glucose production.…”

“…In patients with glucose transporter type I deficiency (G1D), ketogenic diet fat (a source only of acetyl-CoA) reduces seizures, but other symptoms persist, providing the motivation for studying heptanoate metabolism. In this work, metabolism of infused [5,6,[7][8][9][10][11][12][13] C 3 ]heptanoate was examined in the normal mouse brain and in G1D by 13 C-nuclear magnetic resonance spectroscopy, gas chromatography-mass spectrometry (GC-MS), and liquid chromatography-mass spectrometry (LC-MS). In both groups, plasma glucose was enriched in 13 C, confirming gluconeogenesis from heptanoate.…”