Triheptanoin reduces seizure susceptibility in a syndrome-specific mouse model of generalized epilepsy

Therapeutic potential of triheptanoin in metabolic and neurodegenerative diseases

In the past 15 years the potential of triheptanoin for the treatment of several human diseases in the area of clinical nutrition has grown considerably. Use of this triglyceride of the odd-chain fatty acid heptanoate has been proposed and applied for the treatment of several conditions in which the energy supply from citric acid cycle intermediates or fatty acid degradation are impaired. Neurological diseases due to disturbed glucose metabolism or metabolic diseases associated with impaired β-oxidation of long chain fatty acid may especially take advantage of alternative substrate sources offered by the secondary metabolites of triheptanoin. Epilepsy due to deficiency of the GLUT1 transporter, as well as diseases associated with dysregulation of neuronal signalling, have been treated with triheptanoin supplementation, and very recently the advantages of this oil in long-chain fatty acid oxidation disorders have been reported. The present review summarises the published literature on the metabolism of triheptanoin including clinical reports related to the use of triheptanoin.

Open-label long-term treatment of add-on triheptanoin in adults with drug-resistant epilepsy

Objective

To investigate feasibility, safety, and tolerability of long‐term (48 weeks) add‐on treatment with triheptanoin (UX007), the triglyceride of heptanoate, in adults with drug‐resistant epilepsy.

Methods

This extension study was offered to adult participants with drug‐resistant epilepsy who completed a 12‐week randomized controlled trial of add‐on medium‐chain triglycerides (MCT) vs triheptanoin. Participants were asked to titrate triheptanoin to their maximum tolerated dose over 3 weeks, followed by 48‐week maintenance before tapering or treatment extension. The primary aims were to assess retention and safety of the triheptanoin treatment, and secondary aims to assess the tolerated doses and changes in seizure frequency.

Results

Eleven adults were enrolled and ten people were analyzed (because one patient was diagnosed as having nonepileptic seizures while on the study). Two adults finished the study and extended their treatment. Eight participants withdrew from the study, due to lack of efficacy (n = 3), unknown reasons (n = 2), belief of weight gain (n = 1), wanting to try a different treatment (n = 1), and a colonoscopy (n = 1). Diarrhea in two people and bloating in one person were deemed possibly related to treatment, but other adverse events were not. The duration of maintenance treatment dose was 27‐513 days (median 247 days, range 27‐513 days), and 0.49 ‐1.1 mL/kg triheptanoin was taken per day (0.77 ± 0.19 mL/kg, mean ± standard deviation, 40‐100 mL/d). Two participants experienced >90% and three people >50% reduction in seizure frequency, and all had focal seizures. The median seizure reduction was 48% (average 38%).

Significance

Our results indicate antiseizure effects of triheptanoin on focal seizures in 5 out of 10 adults. However, only two people finished and extended the 48‐week add‐on treatment phase, despite lack of safety or tolerability issues.

More studies focused on improved treatment formulations, the potential of lower dosages, and efficacy are needed. Trial registration number: ACTRN12615000406505.

Triheptanoin alters [U-13C6]-glucose incorporation into glycolytic intermediates and increases TCA cycling by normalizing the activities of pyruvate dehydrogenase and oxoglutarate dehydrogenase in a chronic epilepsy mouse model

Triheptanoin is anticonvulsant in several seizure models. Here, we investigated changes in glucose metabolism by triheptanoin interictally in the chronic stage of the pilocarpine mouse epilepsy model. After injection of [U-¹³C₆]-glucose (i.p.), enrichments of ¹³C in intermediates of glycolysis and the tricarboxylic acid (TCA) cycle were quantified in hippocampal extracts and maximal activities of enzymes in each pathway were measured. The enrichment of ¹³C glucose in plasma was similar across all groups. Despite this, we observed reductions in incorporation of ¹³C in several glycolytic intermediates compared to control mice suggesting glucose utilization may be impaired and/or glycogenolysis increased in the untreated interictal hippocampus. Triheptanoin prevented the interictal reductions of ¹³C incorporation in most glycolytic intermediates, suggesting it increased glucose utilization or - as an additional astrocytic fuel - it decreased glycogen breakdown. In the TCA cycle metabolites, the incorporation of ¹³C was reduced in the interictal state. Triheptanoin restored the correlation between ¹³C enrichments of pyruvate relative to most of the TCA cycle intermediates in "epileptic" mice. Triheptanoin also prevented the reductions of hippocampal pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase activities. Decreased glycogen breakdown and increased glucose utilization and metabolism via the TCA cycle in epileptogenic brain areas may contribute to triheptanoin's anticonvulsant effects.

Randomized trial of add-on triheptanoin vs medium chain triglycerides in adults with refractory epilepsy

OBJECTIVE

To investigate the feasibility, safety, and tolerability of add-on treatment of the triglycerides of heptanoate (triheptanoin) vs the triglycerides of octanoate and decanoate (medium chain triglycerides [MCTs]) in adults with treatment-refractory epilepsy.

METHODS

After an 8-week prospective baseline period, people with drug-resistant epilepsy were randomized in a double-blind fashion to receive triheptanoin or MCTs. Treatment was titrated over 3 weeks to a maximum of 100 mL/d to be distributed over 3 meals and mixed into food, followed by 12-week maintenance before tapering. The primary aims were to assess the following: (a) safety by comparing the number of intervention-related adverse events with triheptanoin vs MCT treatment and (b) adherence, measured as a percentage of the prescribed treatment doses taken.

RESULTS

Thirty-four people were randomized (17 to MCT and 17 to triheptanoin). There were no differences regarding (a) the number of participants completing the study (11 vs 9 participants), (b) the time until withdrawal, (c) the total number of adverse events or those potentially related to treatment, (d) median doses of oils taken (59 vs 55 mL/d, P = 0.59), or (e) change in seizure frequency (54% vs 102%, P = 0.13). Please note that people with focal unaware seizures were underrepresented in the triheptanoin treatment arm (P = 0.04). The most common adverse events were gastrointestinal disturbances (47% and 62.5% of participants). Five people taking on average 0.73 mL/kg body weight MCTs (0.64 mL/kg median) and one person taking 0.59 mL/kg triheptanoin showed >50% reduction in seizure frequency, specifically focal unaware seizures.

SIGNIFICANCE

Add-on treatment with MCTs or triheptanoin was feasible, safe, and tolerated for 12 weeks in two-thirds of people with treatment-resistant epilepsy. Our results indicate a protective effect of MCTs on focal unaware seizures. This warrants further study.

Current Perspectives On The Role Of The Ketogenic Diet In Epilepsy Management

Drug-refractory epilepsy is a commonly prevalent pediatric neurological illness of global significance. Ketogenic diet (KD) is a time-tested therapeutic modality for refractory epilepsy, which has reemerged as a robust alternative to anti-epileptic pharmacotherapy. There is a growing body of evidence which supports the anti-seizure efficacy, safety profile and feasibility of KD use in childhood epilepsy. In addition, this modality has been recognized to reduce anti-epileptic exposure, improve cognition and behavioral profile of patients as well as improve the quality-of-life of care-givers. Current indications of KD include refractory epilepsy syndromes, selected metabolic disorders (such as pyruvate dehydrogenase deficiency) and a host of varied neurological entities. KD research has broadened the knowledge-base about its mechanisms of action. Four types of KD are in vogue currently with varying nutritional constitution, palatability, administration protocols and comparable efficacy. KD initiation and maintenance are the result of concerted effort of a team of pediatric neurologist/epileptologist, nutritionist and patient's primary care-giver. Consensus is being formulated about various practical aspects of KD such as patient-selection, parental counseling, baseline work-up, dietary prescription, nutritional supplementation, concurrent anti-epileptic drug administration, follow-up and treatment-duration. Novel applications of KD include its use in neonatal epilepsy and super-refractory status epilepticus and tailor-made formulations such as cooking oil-based KD in predominantly rice-fed populations. Increasing body of clinical experience, improved nutritional designs and translational research are promoting KD as a major therapeutic modality. Currently, KD forms a core essence in the armamentarium against refractory epilepsy. In this review, we summarize the recent advances and current perspectives in the use of KD in refractory epilepsy.

A pilot study of add-on oral triheptanoin treatment for children with medically refractory epilepsy

AIM

Despite antiepileptic medication and dietary treatment options available about 45% of children with epilepsy still suffer from uncontrolled seizures. Triheptanoin is an anaplerotic treatment designed to improve energy generation via the Krebs cycle.

METHOD

For the first time, we evaluated the feasibility, tolerability and efficacy of add-on triheptanoin in 12 patients with medically refractory epilepsy (seven males, five females; min-max: 3-18yr, median 13.5 yr).

RESULTS

Eight out of a total of 12 children (67%), who tested the treatment, finished the trial and tolerated between 30 and 100 ml of triheptanoin per day for >12 weeks (median 55 ml, 20.5% caloric intake). The most common adverse effects were diarrhea and other gastro-intestinal effects in seven kids. One child experienced leaking and another child had an infected percutaneous endoscopic gastrostomy button. Five children (62.5%), who all had been on the ketogenic diet previously, showed sustained >50% reductions in seizure frequency, including one patient who became seizure free for 30 weeks. Four patients extended their treatment to a total of 201-909 days, until seizure frequency or severity increased.

INTERPRETATION

In this small trial, triheptanoin was safe and tolerable in children with epilepsy. As some children showed reductions in seizure numbers and/or severity, larger randomized controlled studies are now needed for further evaluation of safety and efficacy.

Impairments in Oxidative Glucose Metabolism in Epilepsy and Metabolic Treatments Thereof

There is mounting evidence that oxidative glucose metabolism is impaired in epilepsy and recent work has further characterized the metabolic mechanisms involved. In healthy people eating a traditional diet, including carbohydrates, fats and protein, the major energy substrate in brain is glucose. Cytosolic glucose metabolism generates small amounts of energy, but oxidative glucose metabolism in the mitochondria generates most ATP, in addition to biosynthetic precursors in cells. Energy is crucial for the brain to signal "normally," while loss of energy can contribute to seizure generation by destabilizing membrane potentials and signaling in the chronic epileptic brain. Here we summarize the known biochemical mechanisms that contribute to the disturbance in oxidative glucose metabolism in epilepsy, including decreases in glucose transport, reduced activity of particular steps in the oxidative metabolism of glucose such as pyruvate dehydrogenase activity, and increased anaplerotic need. This knowledge justifies the use of alternative brain fuels as sources of energy, such as ketones, TCA cycle intermediates and precursors as well as even medium chain fatty acids and triheptanoin.

Metabolic perturbations associated with the consumption of a ketogenic medium-chain TAG diet in dogs with idiopathic epilepsy

Consumption of diets containing medium-chain TAG (MCT) has been shown to confer neuroprotective effects. We aim to identify the global metabolic perturbations associated with consumption of a ketogenic diet (medium-chain TAG diet (MCTD)) in dogs with idiopathic epilepsy. We used ultra-performance liquid chromatography-MS (UPLC-MS) to generate metabolic and lipidomic profiles of fasted canine serum and made comparisons between the MCTD and standardised placebo diet phases. We identified metabolites that differed significantly between diet phases using metabolite fragmentation profiles generated by tandem MS (UPLC-MS/MS). Consumption of the MCTD resulted in significant differences in serum metabolic profiles when compared with the placebo diet, where sixteen altered lipid metabolites were identified. Consumption of the MCTD resulted in reduced abundances of palmitoylcarnitine, octadecenoylcarnitine, stearoylcarnitine and significant changes, both reduced and increased abundances, of phosphatidylcholine (PC) metabolites. There was a significant increase in abundance of the saturated C17 : 0 fatty acyl moieties during the MCTD phase. Lysophosphatidylcholine (17 : 0) (P=0·01) and PC (17:0/20:4) (P=0·03) were both significantly higher in abundance during the MCTD. The data presented in this study highlight global changes in lipid metabolism, and, of particular interest, in the C17 : 0 moieties, as a result of MCT consumption. Elucidating the global metabolic response of MCT consumption will not only improve the administration of current ketogenic diets for neurological disease models but also provides new avenues for research to develop better diet therapies with improved neuroprotective efficacies. Future studies should clarify the involvement and importance of C17 : 0 moieties in endogenous MCT metabolic pathways.

Individualizing Treatment Approaches for Epileptic Patients with Glucose Transporter Type1 (GLUT-1) Deficiency

Monogenic and polygenic mutations are important contributors in patients suffering from epilepsy, including metabolic epilepsies which are inborn errors of metabolism with a good respond to specific dietetic treatments. Heterozygous variation in solute carrier family 2, facilitated glucose transporter member 1 (SLC2A1) and mutations of the GLUT1/SLC2A2 gene results in the failure of glucose transport, which is related with a glucose type-1 transporter (GLUT1) deficiency syndrome (GLUT1DS). GLUT1 deficiency syndrome is a treatable disorder of glucose transport into the brain caused by a variety of mutations in the SLC2A1 gene which are the cause of different neurological disorders also with different types of epilepsy and related clinical phenotypes. Since patients continue to experience seizures due to a pharmacoresistance, an early clinical diagnosis associated with specific genetic testing in SLC2A1 pathogenic variants in clinical phenotypes could predict pure drug response and might improve safety and efficacy of treatment with the initiation of an alternative energy source including ketogenic or analog diets in such patients providing individualized strategy approaches.

Triheptanoin protects against status epilepticus-induced hippocampal mitochondrial dysfunctions, oxidative stress and neuronal degeneration

Triheptanoin, the triglyceride of heptanoate, is anaplerotic (refills deficient tricarboxylic acid cycle intermediates) via the propionyl-CoA carboxylase pathway. It has been shown to be neuroprotective and anticonvulsant in several models of neurological disorders. Here, we investigated the effects of triheptanoin against changes of hippocampal mitochondrial functions, oxidative stress and cell death induced by pilocarpine-induced status epilepticus (SE) in mice. Ten days of triheptanoin pre-treatment did not protect against SE, but it preserved hippocampal mitochondrial functions including state 2, state 3 ADP, state 3 uncoupled respiration, respiration linked to ATP synthesis along with the activities of pyruvate dehydrogenase complex and oxoglutarate dehydrogenase complex 24 h post-SE. Triheptanoin prevented the SE-induced reductions of hippocampal mitochondrial superoxide dismutase activity and plasma antioxidant status as well as lipid peroxidation. It also reduced neuronal degeneration in hippocampal CA1 and CA3 regions 3 days after SE. In addition, heptanoate significantly reduced hydrogen peroxide-induced cell death in cultured neurons. In situ hybridization localized the enzymes of the propionyl-CoA carboxylase pathway, specifically Pccα, Pccβ and methylmalonyl-CoA mutase to adult mouse hippocampal pyramidal neurons and dentate granule cells, indicating that anaplerosis may occur in neurons. In conclusion, triheptanoin appears to have anaplerotic and antioxidant effects which contribute to its neuroprotective properties.

Alternative Fuels in Epilepsy and Amyotrophic Lateral Sclerosis

This review summarises the recent findings on metabolic treatments for epilepsy and Amyotrophic Lateral Sclerosis (ALS) in honour of Professor Ursula Sonnewald. The metabolic impairments in rodent models of these disorders as well as affected patients are being discussed. In both epilepsy and ALS, there are defects in glucose uptake and reduced tricarboxylic acid (TCA) cycling, at least in part due to reduced amounts of C4 TCA cycle intermediates. In addition there are impairments in glycolysis in ALS. A reduction in glucose uptake can be addressed by providing the brain with alternative fuels, such as ketones or medium-chain triglycerides. As anaplerotic fuels, such as the triglyceride of heptanoate, triheptanoin, refill the TCA cycle C4/C5 intermediate pool that is deficient, they are ideal to boost TCA cycling and thus the oxidative metabolism of all fuels.

Mechanisms of Action of Antiseizure Drugs and the Ketogenic Diet

Antiseizure drugs (ASDs), also termed antiepileptic drugs, are the main form of symptomatic treatment for people with epilepsy, but not all patients become free of seizures. The ketogenic diet is one treatment option for drug-resistant patients. Both types of therapy exert their clinical effects through interactions with one or more of a diverse set of molecular targets in the brain. ASDs act by modulation of voltage-gated ion channels, including sodium, calcium, and potassium channels; by enhancement of γ-aminobutyric acid (GABA)-mediated inhibition through effects on GABAA receptors, the GABA transporter 1 (GAT1) GABA uptake transporter, or GABA transaminase; through interactions with elements of the synaptic release machinery, including synaptic vesicle 2A (SV2A) and α2δ; or by blockade of ionotropic glutamate receptors, including α-amino-3-hydroxy-5-methyl-4-isoxazole-propionate (AMPA) receptors. The ketogenic diet leads to increases in circulating ketones, which may contribute to the efficacy in treating pharmacoresistant seizures. Production in the brain of inhibitory mediators, such as adenosine, or ion channel modulators, such as polyunsaturated fatty acids, may also play a role. Metabolic effects, including diversion from glycolysis, are a further postulated mechanism. For some ASDs and the ketogenic diet, effects on multiple targets may contribute to activity. Better understanding of the ketogenic diet will inform the development of improved drug therapies to treat refractory seizures.

Triheptanoin dramatically reduces paroxysmal motor disorder in patients with GLUT1 deficiency

OBJECTIVE

On the basis of our previous work with triheptanoin, which provides key substrates to the Krebs cycle in the brain, we wished to assess its therapeutic effect in patients with glucose transporter type 1 deficiency syndrome (GLUT1-DS) who objected to or did not tolerate ketogenic diets.

METHODS

We performed an open-label pilot study with three phases of 2 months each (baseline, treatment and withdrawal) in eight patients with GLUT1-DS (7-47 years old) with non-epileptic paroxysmal manifestations. We used a comprehensive patient diary to record motor and non-motor paroxysmal events. Functional (31)P-NMR spectroscopy was performed to quantify phosphocreatine (PCr) and inorganic phosphate (Pi) within the occipital cortex during (activation) and after (recovery) a visual stimulus.

RESULTS

Patients with GLUT1-DS experienced a mean of 30.8 (± 27.7) paroxysmal manifestations (52% motor events) at baseline that dropped to 2.8 (± 2.9, 76% motor events) during the treatment phase (p = 0.028). After withdrawal, paroxysmal manifestations recurred with a mean of 24.2 (± 21.9, 52% motor events; p = 0.043). Furthermore, brain energy metabolism normalised with triheptanoin, that is, increased Pi/PCr ratio during brain activation compared to the recovery phase (p = 0.021), and deteriorated when triheptanoin was withdrawn.

CONCLUSIONS

Treatment with triheptanoin resulted in a 90% clinical improvement in non-epileptic paroxysmal manifestations and a normalised brain bioenergetics profile in patients with GLUT1-DS.

TRIAL REGISTRATION NUMBER

NCT02014883.

Anaplerosis for Glutamate Synthesis in the Neonate and in Adulthood

A central task of the tricarboxylic acid (TCA, Krebs, citric acid) cycle in brain is to provide precursors for biosynthesis of glutamate, GABA, aspartate and glutamine. Three of these amino acids are the partners in the intricate interaction between astrocytes and neurons and form the so-called glutamine-glutamate (GABA) cycle. The ketoacids α-ketoglutarate and oxaloacetate are removed from the cycle for this process. When something is removed from the TCA cycle it must be replaced to permit the continued function of this essential pathway, a process termed anaplerosis. This anaplerotic process in the brain is mainly carried out by pyruvate carboxylation performed by pyruvate carboxylase. The present book chapter gives an introduction and overview into this carboxylation and additionally anaplerosis mediated by propionyl-CoA carboxylase under physiological conditions in the adult and in the developing rodent brain. Furthermore, examples are given about pathological conditions in which anaplerosis is disturbed.

Reduced severity of ischemic stroke and improvement of mitochondrial function after dietary treatment with the anaplerotic substance triheptanoin

Triheptanoin, an oily substance, consists of glycerol bound to three molecules of heptanoic acid, a C7 odd-chain fatty acid. A triheptanoin-rich diet has anaplerotic effects because heptanoate metabolism yields succinate which delivers substrates to the Krebs cycle. While previous studies on the effects of triheptanoin focused on metabolic disorders and epilepsy, we investigated triheptanoin's effect on ischemic stroke. Mice were fed a triheptanoin-enriched diet for 14days; controls received soybean oil. Only mice fed triheptanoin had measurable quantities of odd-numbered fatty acids in the plasma and brain. Transient ischemia was induced in the brain by occlusion of the middle cerebral artery (MCAO) for 60min. One day later, mice were tested for neurological function (chimney, rotarod and corner tests) which was found to be better preserved in the triheptanoin group. Microdialysis demonstrated that the strong, neurotoxic increase of extracellular glutamate, which was observed in the mouse striatum during MCAO, was strongly reduced in triheptanoin-fed mice while glucose levels were not affected. Triheptanoin diet reduced the infarct area in stroked mice by about 40%. In ex vivo-experiments with isolated mitochondria, ischemia was found to cause a reduction of mitochondrial respiratory activity. This reduction was attenuated by triheptanoin diet in complex II and IV. In parallel measurements, ATP levels and mitochondrial membrane potential were reduced in control animals but were preserved in triheptanoin-fed mice. We conclude that triheptanoin-fed mice which sustained an experimental stroke had a significantly improved neurological outcome. This beneficial effect is apparently due to an improvement of mitochondrial function and preservation of the cellular energy state. Our findings identify triheptanoin as a promising new dietary agent for neuroprotection.

Anaplerotic triheptanoin diet enhances mitochondrial substrate use to remodel the metabolome and improve lifespan, motor function, and sociability in MeCP2-null mice

Rett syndrome (RTT) is an autism spectrum disorder (ASD) caused by mutations in the X-linked MECP2 gene that encodes methyl-CpG binding protein 2 (MeCP2). Symptoms range in severity and include psychomotor disabilities, seizures, ataxia, and intellectual disability. Symptom onset is between 6-18 months of age, a critical period of brain development that is highly energy-dependent. Notably, patients with RTT have evidence of mitochondrial dysfunction, as well as abnormal levels of the adipokines leptin and adiponectin, suggesting overall metabolic imbalance. We hypothesized that one contributor to RTT symptoms is energy deficiency due to defective nutrient substrate utilization by the TCA cycle. This energy deficit would lead to a metabolic imbalance, but would be treatable by providing anaplerotic substrates to the TCA cycle to enhance energy production. We show that dietary therapy with triheptanoin significantly increased longevity and improved motor function and social interaction in male mice hemizygous for Mecp2 knockout. Anaplerotic therapy in Mecp2 knockout mice also improved indicators of impaired substrate utilization, decreased adiposity, increased glucose tolerance and insulin sensitivity, decreased serum leptin and insulin, and improved mitochondrial morphology in skeletal muscle. Untargeted metabolomics of liver and skeletal muscle revealed increases in levels of TCA cycle intermediates with triheptanoin diet, as well as normalizations of glucose and fatty acid biochemical pathways consistent with the improved metabolic phenotype in Mecp2 knockout mice on triheptanoin. These results suggest that an approach using dietary supplementation with anaplerotic substrate is effective in improving symptoms and metabolic health in RTT.

Epilepsy, energy deficiency and new therapeutic approaches including diet

Metabolic dysfunction leading to epilepsy is well recognised. Dietary therapy, in particular the ketogenic diet, is now considered an effective option. Recent genetic studies have highlighted the central role that metabolism can play in setting seizure susceptibility. Here we discuss various metabolic disorders implicated in epilepsy focusing on energy deficiency due to genetic and environmental causes. We argue that low, uncompensated brain glucose levels can precipitate seizures. We will also explore mechanisms of disease and therapy in an attempt to identify common metabolic pathways involved in modulating seizure susceptibility. Finally, newer therapeutic approaches based on diet manipulation in the context of energy deficiency are discussed.

Dietary Treatments and New Therapeutic Perspective in GLUT1 Deficiency Syndrome

OPINION STATEMENT

GLUT1 deficiency syndrome (GLUT1DS) results from impaired glucose transport into the brain: awareness of its wide phenotypic spectrum is a prerequisite in order to ensure an early diagnosis, treating the patients is the subsequent challenge to allow prompt compensation for the brain's lack of fuel. The ketogenic diet (KD) plays a primary role in the treatment of GLUT1DS because it provides ketone bodies as an alternative source to meet the demands of energy of the brain. Therefore, we recommend early initiation of the KD based on the assumption that early diagnosis and treatment improves the long term neurological outcome: the classic KD (4:1 or 3:1) at the present time is the most proven and effective in GLUT1DS. A KD should be continued at least until adolescence, although there are reports of good tolerability even in adulthood, possibly with a less rigorous ratio; in our experience seizure and movement disorder control can be achieved by a 2:1 ketogenic ratio but the relationship between ketosis and neurodevelopmental outcome remains undetermined. Other types of KDs can, therefore, be considered. The Modified Atkins diet, for example, is also well tolerated and provides effective symptom control; furthermore, this diet has the advantage of being easy to prepare and more palatable, which are important requirements for good compliance. Nevertheless, about 20 % of these patients have compliance trouble or the same diet loses its effectiveness over time; for these reasons, new therapeutic strategies are currently under investigation but further studies on pathophysiological mechanisms and potential effects of novel "diets" or "therapies" are needed for this new pathology.

Alterations of hippocampal glucose metabolism by even versus uneven medium chain triglycerides

Medium chain triglycerides (MCTs) are used to treat neurologic disorders with metabolic impairments, including childhood epilepsy and early Alzheimer's disease. However, the metabolic effects of MCTs in the brain are still unclear. Here, we studied the effects of feeding even and uneven MCTs on brain glucose metabolism in the mouse. Adult mice were fed 35% (calories) of trioctanoin or triheptanoin (the triglycerides of octanoate or heptanoate, respectively) or a matching control diet for 3 weeks. Enzymatic assays and targeted metabolomics by liquid chromatography tandem mass spectrometry were used to quantify metabolites in extracts from the hippocampal formations (HFs). Both oils increased the levels of β-hydroxybutyrate, but no other significant metabolic alterations were observed after triheptanoin feeding. The levels of glucose 6-phosphate and fructose 6-phosphate were increased in the HF of mice fed trioctanoin, whereas levels of metabolites further downstream in the glycolytic pathway and the pentose phosphate pathway were reduced. This indicates that trioctanoin reduces glucose utilization because of a decrease in phosphofructokinase activity. Trioctanoin and triheptanoin showed similar anticonvulsant effects in the 6 Hz seizure model, but it remains unknown to what extent the anticonvulsant mechanism(s) are shared. In conclusion, triheptanoin unlike trioctanoin appears to not alter glucose metabolism in the healthy brain.

Triheptanoin partially restores levels of tricarboxylic acid cycle intermediates in the mouse pilocarpine model of epilepsy

Triheptanoin, the triglyceride of heptanoate, is anticonvulsant in various epilepsy models. It is thought to improve energy metabolism in the epileptic brain by re-filling the tricarboxylic acid (TCA) cycle with C4-intermediates (anaplerosis). Here, we injected mice with [1,2-(13) C]glucose 3.5-4 weeks after pilocarpine-induced status epilepticus (SE) fed either a control or triheptanoin diet. Amounts of metabolites and incorporations of (13) C were determined in extracts of cerebral cortices and hippocampal formation and enzyme activity and mRNA expression were quantified. The percentage enrichment with two (13) C atoms in malate, citrate, succinate, and GABA was reduced in hippocampal formation of control-fed SE compared with control mice. Except for succinate, these reductions were not found in triheptanoin-fed SE mice, indicating that triheptanoin prevented a decrease of TCA cycle capacity. Compared to those on control diet, triheptanoin-fed SE mice showed few changes in most other metabolite levels and their (13) C labeling. Reduced pyruvate carboxylase mRNA and enzyme activity in forebrains and decreased [2,3-(13) C]aspartate amounts in cortex suggest a pyruvate carboxylation independent source of C-4 TCA cycle intermediates. Most likely anaplerosis was kept unchanged by carboxylation of propionyl-CoA derived from heptanoate. Further studies are proposed to fully understand triheptanoin's effects on neuroglial metabolism and interaction.