The Antiepileptic Effect of the Glycolytic Inhibitor 2-Deoxy-d-Glucose is Mediated by Upregulation of KATP Channel Subunits Kir6.1 and Kir6.2

A novel hydrogen sulfide donor reduces neuroinflammation and seizures by activating ATP-sensitive potassium channels

Epilepsy is a common neurological disorder worldwide. Hydrogen sulfide (H2S) has been found to have anti-seizure effects. However, its mechanism remains to be explored. In the present study, we showed that a novel H2S donor attenuated neuroinflammation by up-regulating ATP-sensitive potassium channel (KATP) expression to reduce seizures. The novel H2S donor significantly reduced the expression of TNF-α and increased the expression of IL-10 in LPS-treated BV2 cells and the hippocampus of pilocarpine-induced epileptic mice. The modulatory effects of the H2S donor on inflammatory cytokines were prevented by glibenclamide, a common KATP channels blocker. The H2S donor promoted the expression of KATP channel subunits SUR2 and Kir6.1 in LPS-treated BV2 cells and the hippocampus of pilocarpine-induced epileptic mice. In addition, the H2S donor reduced the electroencephalography amplitude of hippocampal epileptic waves and reduced seizures in pilocarpine-induced epileptic mice, which were also attenuated by glibenclamide. These results indicated that the novel H2S donor reduced seizures and regulated microglial inflammatory cytokines by activating KATP channels, which may provide a prospective therapeutic strategy for the anti-seizure effects of H2S donor.

2-Deoxy-D-glucose administration after seizures has disease-modifying effects on kindling progression

2-deoxy-D-glucose (2DG) is a glucose analog and reversible inhibitor of glycolysis with anticonvulsant and antiepileptic effects in multiple seizure models. 2DG at a dose of 250 mg/kg intraperitoneally (IP) delays progression of repeated seizures evoked by kindling in rats when administered 30 min prior to twice daily kindling stimulation. As toxicological studies have demonstrated that repeated daily oral administration of 2DG at doses of 60-375 mg/kg/day in rats induces dose-dependent, reversible cardiac myocyte vacuolation, it was of interest to determine if 2DG also slowed kindling progression when administered at or below doses causing cardiac toxicity and at various time points after evoked seizures. We found that: (1) 2DG slowed kindling progression nearly 2-fold when administered at a dose of 37.5 mg/kg given IP 30 min prior to kindling stimulation, and (2) 2DG 37.5 mg/kg IP also slowed kindling progression when given immediately after, and for as long as 10 min after evoked (kindled) seizures. These observations suggest potential clinical usefulness of post-seizure administration of 2DG to reduce seizure clusters and long-term consequences of repeated seizures at human equivalent doses that are likely to be safe and well tolerated in patients.

Glycolysis inhibition partially resets epilepsy-induced alterations in the dorsal hippocampus-basolateral amygdala circuit involved in anxiety-like behavior

Pharmacoresistant temporal lobe epilepsy affects millions of people around the world with uncontrolled seizures and comorbidities, like anxiety, being the most problematic aspects calling for novel therapies. The intrahippocampal kainic acid model of temporal lobe epilepsy is an appropriate rodent model to evaluate the effects of novel interventions, including glycolysis inhibition, on epilepsy-induced alterations. Here, we investigated kainic acid-induced changes in the dorsal hippocampus (dHPC) and basolateral amygdala (BLA) circuit and the efficiency of a glycolysis inhibitor, 2-deoxy D-glucose (2-DG), in resetting such alterations using simultaneous local field potentials (LFP) recording and elevated zero-maze test. dHPC theta and gamma powers were lower in epileptic groups, both in the baseline and anxiogenic conditions. BLA theta power was higher in baseline condition while it was lower in anxiogenic condition in epileptic animals and 2-DG could reverse it. dHPC-BLA coherence was altered only in anxiogenic condition and 2-DG could reverse it only in gamma frequency. This coherence was significantly correlated with the time in which the animals exposed themselves to the anxiogenic condition. Further, theta-gamma phase-locking was lower in epileptic groups in the dHPC-BLA circuit and 2-DG could considerably increase it.

2-Deoxy-D-Glucose: A Novel Pharmacological Agent for Killing Hypoxic Tumor Cells, Oxygen Dependence-Lowering in Covid-19, and Other Pharmacological Activities

The nonmetabolizable glucose analog 2-deoxy-D-glucose (2-DG) has shown promising pharmacological activities, including inhibition of cancerous cell growth and N-glycosylation. It has been used as a glycolysis inhibitor and as a potential energy restriction mimetic agent, inhibiting pathogen-associated molecular patterns. Radioisotope derivatives of 2-DG have applications as tracers. Recently, 2-DG has been used as an anti-COVID-19 drug to lower the need for supplemental oxygen. In the present review, various pharmaceutical properties of 2-DG are discussed.

2DG and glycolysis as therapeutic targets for status epilepticus

2-deoxy-D-glucose (2DG) is a glucose analog differing from glucose only by removal of an oxygen atom at the 2 position, which prevents the isomerization of glucose-6-phosphate to fructose-6-phosphate, and thereby reversibly inhibits glycolysis. PET studies of regional brain glucose utilization positron-emitting 18F-2DG demonstrate that brain regions generating seizures have diminished glucose utilization during interictal conditions, but rapidly transition to markedly increased glucose delivery and utilization during seizures, particularly in status epilepticus (SE). 2-deoxy-D-glucose has acute antiseizure actions in multiple in vivo and in vitro seizure models, including models of SE induced by the chemo convulsants pilocarpine and kainic acid, suggesting that focal enhanced delivery of 2DG to ictal brain circuits is a potential novel anticonvulsant intervention for the treatment of SE.

The Glycolysis Inhibitor 2-Deoxy-D-Glucose Exerts Different Neuronal Effects at Circuit and Cellular Levels, Partially Reverses Behavioral Alterations and does not Prevent NADPH Diaphorase Activity Reduction in the Intrahippocampal Kainic Acid Model of Temporal Lobe Epilepsy

Temporal lobe epilepsy is the most drug-resistant type with the highest incidence among the other focal epilepsies. Metabolic manipulations are of great interest among others, glycolysis inhibitors like 2-deoxy D-glucose (2-DG) being the most promising intervention. Here, we sought to investigate the effects of 2-DG treatment on cellular and circuit level electrophysiological properties using patch-clamp and local field potentials recordings and behavioral alterations such as depression and anxiety behaviors, and changes in nitric oxide signaling in the intrahippocampal kainic acid model. We found that epileptic animals were less anxious, more depressed, with more locomotion activity. Interestingly, by masking the effect of increased locomotor activity on the parameters of the zero-maze test, no altered anxiety behavior was noted in epileptic animals. However, 2-DG could partially reverse the behavioral changes induced by kainic acid. The findings also showed that 2-DG treatment partially suppresses cellular level alterations while failing to reverse circuit-level changes resulting from kainic acid injection. Analysis of NADPH-diaphorase positive neurons in the CA1 area of the hippocampus revealed that the number of positive neurons was significantly reduced in dorsal CA1 of the epileptic animals and 2-DG treatment did not affect the diminishing effect of kainic acid on NADPH-d+ neurons in the CA1 area. In the control group receiving 2-DG, however, an augmented NADPH-d+ cell number was noted. These data suggest that 2-DG cannot suppress epileptiform activity at the circuit-level in this model of epilepsy and therefore, may fail to control the seizures in temporal lobe epilepsy cases.

Anticonvulsant effects of ivermectin on pentylenetetrazole- and maximal electroshock-induced seizures in mice: the role of GABAergic system and KATP channels

Introduction

Ivermectin (IVM) is an antiparasitic medicine that exerts its function through glutamate-gated chloride channels and GABA_A receptors predominantly. There is paucity of information on anti-seizure activity of IVM. Moreover, the probable pharmacological mechanisms underlying this phenomenon have not been identified.

Materials and methods

In this study, pentylenetetrazole (PTZ)-induced clonic seizures and maximal electroshock (MES)-induced tonic-clonic seizure models, respectively in mice was utilized to inquire whether IVM could alter clonic seizure threshold (CST) and seizure susceptibility. To assess the underlying mechanism behind the anti-seizure activity of IVM, we used positive and negative allosteric modulators of GABA_A (diazepam and flumazenil, respectively) as well as K_ATP channel opener and closer (cromakalim and glibenclamide, respectively). Data are provided as mean ± S.E.M. After the performance of the variance homogeneity test, a one-way and two-way analysis of variance was used. Fisher's exact test was performed in case of MES. P-value less than 0.05 considered statistically significant.

Results

and Discussion: Our data showed that IVM (0.5, 1, 5, and 10 mg/kg, i.p.) increased CST. Furthermore, flumazenil 0.25 mg/kg, i.p. and glibenclamide 1 mg/kg, i.p., could inhibit the anticonvulsant effects of IVM. Supplementary, an ineffective dose of diazepam 0.02 mg/kg, i.p. or cromakalim 10 μg/kg, i.p. were able to enhance the anticonvulsant effects of IVM. Besides, we figure out that the IVM (1 and 5 mg/kg, i.p.) could delay the onset of first clonic seizure and also might decrease the frequency of clonic seizures induced by PTZ (85 mg/kg, i.p.). Finally, IVM could prevent the incidence and death in MES-induced tonic-clonic seizures.

Conclusion

Based on the obtained results, it can be concluded that IVM may exert anticonvulsant effects against PTZ- and MES-induced seizures in mice that might be mediated by GABA_A receptors and K_ATP channels.

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Ivermectin exerts anticonvulsant effects on PTZ-induced clonic seizures.

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Ivermectin prevents MES-induced tonic-clonic seizures in mice.

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Ivermectin has the most anticonvulsant effects in doses of 1 and 5 mg/kg in mice.

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These anticonvulsant effects may be mediated through the GABAergic system.

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ATP-sensitive potassium channels could play a role in these anti-seizure effects.

Dietary effects on antiseizure drug metabolism and management of epilepsy

In recent years, there has been growing interest in the influences of food-drug interactions on the metabolism of antiseizure medications (ASM) and the management of epilepsy. Studies have proven the effectiveness of the ketogenic diet (KD) in controlling refractory epilepsy. However, dietary interventions such as the KD or its variants may induce significant changes in serum drug concentrations which counteracts the anticonvulsive effects of ASMs, leading to an increased risk of developing seizures. Interactions with enzymes within the cytochrome P450 system may also explain the dietary influences on serum concentrations of antiseizure drugs. The bioavailability of ASMs is also affected by several foods and nutritional supplements. Nevertheless, more studies are warranted to explore the mechanisms underlying food-drug interactions and the risks and benefits of combined drug-diet therapy.

Envisioning the role of inwardly rectifying potassium (Kir) channel in epilepsy

Epilepsy is a devastating neurological disorder characterized by recurrent seizures attributed to the disruption of the dynamic excitatory and inhibitory balance in the brain. Epilepsy has emerged as a global health concern affecting about 70 million people worldwide. Despite recent advances in pre-clinical and clinical research, its etiopathogenesis remains obscure, and there are still no treatment strategies modifying disease progression. Although the precise molecular mechanisms underlying epileptogenesis have not been clarified yet, the role of ion channels as regulators of cellular excitability has increasingly gained attention. In this regard, emerging evidence highlights the potential implication of inwardly rectifying potassium (Kir) channels in epileptogenesis. Kir channels consist of seven different subfamilies (Kir1-Kir7), and they are highly expressed in both neuronal and glial cells in the central nervous system. These channels control the cell volume and excitability. In this review, we discuss preclinical and clinical evidence on the role of the several subfamilies of Kir channels in epileptogenesis, aiming to shed more light on the pathogenesis of this disorder and pave the way for future novel therapeutic approaches.

The Pharmacology of ATP-Sensitive K+ Channels (KATP)

ATP-sensitive K⁺ channels (K_ATP) are inwardly-rectifying potassium channels, broadly expressed throughout the body. K_ATP is regulated by adenine nucleotides, characteristically being activated by falling ATP and rising ADP levels thus playing an important physiological role by coupling cellular metabolism with membrane excitability. The hetero-octameric channel complex is formed of 4 pore-forming inward rectifier Kir6.x subunits (Kir6.1 or Kir6.2) and 4 regulatory sulfonylurea receptor subunits (SUR1, SUR2A, or SUR2B). These subunits can associate in various tissue-specific combinations to form functional K_ATP channels with distinct electrophysiological and pharmacological properties. K_ATP channels play many important physiological roles and mutations in channel subunits can result in diseases such as disorders of insulin handling, cardiac arrhythmia, cardiomyopathy, and neurological abnormalities. The tissue-specific expression of K_ATP channel subunits coupled with their rich and diverse pharmacology makes K_ATP channels attractive therapeutic targets in the treatment of endocrine and cardiovascular diseases.

Kv7 and Kir6 Channels Shape the Slow AHP in Mouse Dentate Gyrus Granule Cells and Control Burst-like Firing Behavior

The slow afterhyperpolarizing potential (sAHP) can silence a neuron for hundreds of milliseconds. Thereby, the sAHP determines the discharge behavior of many types of neurons. In dentate granule cells (DGCs), serving as a filter into the hippocampal network, mostly tonic or adapting discharge properties have been described. As under standard whole-cell recording conditions the sAHP is inhibited, we reevaluated the intrinsic functional phenotype of DGCs and the conductances underlying the sAHP, using gramicidine-perforated patch-clamp technique. We found that in 97/113 (86%) of the DGCs, a burst of action potentials (APs) to excitation ended by a large sAHP, despite continued depolarization. This result suggests that burst-like firing is the default functional phenotype of DGCs and that sAHPs are important for it. Indeed, burst-like firing DGCs showed a significantly higher sAHP-current (I_sAHP) amplitude compared to spike-frequency adapting cells (16/113 = 14%). The I_sAHP was mediated by K_v7 and K_ir6 channels by pharmacological inhibition using XE991 and tolbutamide, although heterogeneously among DGCs. The percent inhibition of I_sAHP by these compounds also correlated with the AP number and AP burst length. Application of 100 µM nickel after XE991 and tolbutamide detected a third conductance contributing to burst-like firing and the sAHP, most likely mediated by T-type calcium channels. Lastly, medial perforant path-dentate gyrus long-term potentiation was amplified by XE991 and tolbutamide. In conclusion, the sAHP shapes intrinsic burst-like firing which, under physiological circumstances, could be controlled via cholinergic afferents and ATP metabolism.

The expression of ATP-sensitive potassium channels in human umbilical arteries with severe pre-eclampsia

The aim of this study is to establish the expression of ATP-sensitive potassium channels(KATP) in human umbilical arteries with severe pre-eclampsia. Real-time quantitative PCR and western blotting were used to detect the mRNA and protein expression levels of KATP channel subunits Kir6.1 and SUR2B in human umbilical arteries from normal pregnant and those with severe pre-eclampsia, early onset severe pre-eclampsia and late onset severe pre-eclampsia. The mRNA and protein levels of SUR2B in the severe pre-eclampsia group were lower than those in the normal group (P < 0.001), and the expression of Kir6.1 was not statistically significant between the two groups (P > 0.05). The mRNA and protein levels of SUR2B in early onset severe pre-eclampsia group were lower than those in late onset severe pre-eclampsia group (P < 0.001). There was no significant difference in expression of Kir6.1 between the two groups (P > 0.05). The mRNA and protein expression levels of SUR2B in pregnant women with severe pre-eclampsia were lower than those in normal pregnant women, suggesting that the expression of the SUR2B of the KATP channel may be related to the occurrence and development of severe pre-eclampsia. Compared with late onset severe pre-eclampsia, the mRNA and protein expression levels of SUR2B were lower in the umbilical arteries of women with early onset severe pre-eclampsia, suggesting that the occurrence time of severe pre-eclampsia may be related to the extent reduced expression of the SUR2B of the KATP channel.

Role of Modulation of Hippocampal Glucose Following Pilocarpine-Induced Status Epilepticus

Status epilepticus (SE) is defined as continuous and self-sustaining seizures, which trigger hippocampal neurodegeneration, mitochondrial dysfunction, oxidative stress, and energy failure. During SE, the neurons become overexcited, increasing energy consumption. Glucose uptake is increased via the sodium glucose cotransporter 1 (SGLT1) in the hippocampus under epileptic conditions. In addition, modulation of glucose can prevent neuronal damage caused by SE. Here, we evaluated the effect of increased glucose availability in behavior of limbic seizures, memory dysfunction, neurodegeneration process, neuronal activity, and SGLT1 expression. Vehicle (VEH, saline 0.9%, 1 μL) or glucose (GLU; 1, 2 or 3 mM, 1 μL) were administered into hippocampus of male Wistar rats (Rattus norvegicus) before or after pilocarpine to induce SE. Behavioral analysis of seizures was performed for 90 min during SE. The memory and learning processes were analyzed by the inhibitory avoidance test. After 24 h of SE, neurodegeneration process, neuronal activity, and SGLT1 expression were evaluated in hippocampal and extrahippocampal regions. Modulation of hippocampal glucose did not protect memory dysfunction followed by SE. Our results showed that the administration of glucose after pilocarpine reduced the severity of seizures, as well as the number of limbic seizures. Similarly, glucose after SE reduced cell death and neuronal activity in hippocampus, subiculum, thalamus, amygdala, and cortical areas. Finally, glucose infusion elevated the SGLT1 expression in hippocampus. Taken together our data suggest that possibly the administration of intrahippocampal glucose protects brain in the earlier stage of epileptogenic processes via an important support of SGLT1.

2-Deoxyglucose terminates pilocarpine-induced status epilepticus in neonatal rats

OBJECTIVE

Neonatal status epilepticus (SE) is a life-threatening medical emergency. Unfortunately, up to 50% of neonates with SE are resistant to current antiseizure drugs, highlighting the need for better treatments. This study aims to explore a novel metabolic approach as a potential alternative treatment to control neonatal SE, using the glycolytic inhibitor 2-deoxyglucose (2-DG).

METHODS

SE was induced by pilocarpine (300 mg/kg, intraperitoneally [ip]) in neonatal Sprague Dawley rats (postnatal day 10 [P10]-P17) and was monitored by video-electroencephalography (V-EEG). After 30 minutes of SE, 2-DG or one of two conventional antiseizure drugs with different mechanisms of action, phenobarbital or levetiracetam, was administrated ip, and V-EEG recording was continued for ~60 additional minutes. The time to seizure cessation after drug injection, EEG scores, and power spectra before and after drug or saline treatment were used to assess drug effects.

RESULTS

Once SE became sustained, administration of 2-DG (50, 100, or 500 mg/kg, ip) consistently stopped behavioral and electrographic seizures within 10-15 minutes; lower doses took longer (25-30 minutes) to stop SE, demonstrating a dose-dependent effect. Administration of phenobarbital (30 mg/kg, ip) or levetiracetam (100 mg/kg, ip) also stopped SE within 10-15 minutes in neonatal rats.

SIGNIFICANCE

Our results suggest that the glycolysis inhibitor 2-DG acts quickly to reduce neuronal hyperexcitability and effectively suppress ongoing seizure activity, which may provide translational value in the treatment of neonatal SE.

Attenuation of epileptogenesis by 2-deoxy-d-glucose is accompanied by increased cerebral glucose supply, microglial activation and reduced astrocytosis

RATIONALE

Neuronal excitability and brain energy homeostasis are strongly interconnected and evidence suggests that both become altered during epileptogenesis. Pharmacologic modulation of cerebral glucose metabolism might therefore exert anti-epileptogenic effects. Here we provide mechanistic insights into effects of the glycolytic inhibitor 2-deoxy-d-glucose (2-DG) on experimental epileptogenesis by longitudinal 2-deoxy-2[¹⁸F]fluoro-d-glucose positron emission tomography ([¹⁸F]FDG PET) and histology.

METHODS

To imitate epileptogenesis, 6 Hz-corneal kindling was performed in male NMRI mice by twice daily electrical stimulation for 21 days. Kindling groups were treated i.p. 1 min after each stimulation with either 250 mg/kg 2-DG (CoKi_2-DG) or saline (CoKi_vehicle). A separate group of unstimulated mice was treated with 2-DG (2-DG_only). Dynamic 60-min [¹⁸F]FDG PET/CT scans were acquired at baseline and interictally on days 10 and 17 of kindling. [¹⁸F]FDG uptake (%injected dose/cc) was quantified in predefined regions of interest (ROI) using a MRI-based brain atlas, and kinetic modelling was performed to evaluate glucose net influx rate K_i and glucose metabolic rate MR_Glu. Furthermore, statistical parametric mapping (SPM) analysis was applied on kinetic brain maps. For histological evaluation, brain sections were stained for glucose transporter 1 (GLUT1), astrocytes, microglia, as well as dying neurons.

RESULTS

Post-stimulation 2-DG treatment attenuated early kindling progression, indicated by a reduction of fully-kindled mice, and a lower overall percentage of type five seizures. While 2-DG treatment alone led to globally increased K_i and MR_Glu values at day 17, kindling progression per se did not influence glucose turnover. Kindling accompanied by 2-DG treatment, however, resulted in regionally elevated [¹⁸F]FDG uptake as well as increased K_i at days 10 and 17 compared both to baseline and to the 2-DG_only group. In hippocampus and thalamus, higher MR_Glu values were found in the CoKi_2-DG vs. the CoKi_vehicle group at day 17. t maps resulting from SPM analysis generally confirmed the results of the ROI analysis, and additionally revealed increased MR_Glu restricted to the ventral hippocampus when comparing the CoKi_2-DG and the 2-DG_only group both at days 10 and, more distinct, day 17. Immunohistochemical staining showed an attenuated kindling-induced regional activation of astrocytes in the CoKi_2-DG group. Interestingly, 2-DG treatment alone (and also in combination with kindling, but not kindling alone) led to increased microglial activation scores, whereas neither staining of GLUT1 nor of dying neurons revealed any differences to untreated controls.

CONCLUSIONS

Post-stimulation treatment with 2-DG exerts disease-modifying effects in the mouse 6 Hz corneal kindling model. The observed local increase in glucose supply and turnover, the alleviation of astroglial activation and the activation of microglia by 2-DG might contribute separately or in combination to its positive interference with epileptogenesis.

Glycolytic inhibitor 2-deoxyglucose prevents cortical hyperexcitability after traumatic brain injury

Traumatic brain injury (TBI) causes cortical dysfunction and can lead to post-traumatic epilepsy. Multiple studies demonstrate that GABAergic inhibitory network function is compromised following TBI, which may contribute to hyperexcitability and motor, behavioral, and cognitive deficits. Preserving the function of GABAergic interneurons, therefore, is a rational therapeutic strategy to preserve cortical function after TBI and prevent long-term clinical complications. Here, we explored an approach based on the ketogenic diet, a neuroprotective and anticonvulsant dietary therapy which results in reduced glycolysis and increased ketosis. Utilizing a pharmacologic inhibitor of glycolysis (2-deoxyglucose, or 2-DG), we found that acute in vitro application of 2-DG decreased the excitability of excitatory neurons, but not inhibitory interneurons, in cortical slices from naïve mice. Employing the controlled cortical impact (CCI) model of TBI in mice, we found that in vitro 2-DG treatment rapidly attenuated epileptiform activity seen in acute cortical slices 3 to 5 weeks after TBI. One week of in vivo 2-DG treatment immediately after TBI prevented the development of epileptiform activity, restored excitatory and inhibitory synaptic activity, and attenuated the loss of parvalbumin-expressing inhibitory interneurons. In summary, 2-DG may have therapeutic potential to restore network function following TBI.

2-Deoxyglucose and Beta-Hydroxybutyrate: Metabolic Agents for Seizure Control

Current anti-seizure drugs (ASDs) are believed to reduce neuronal excitability through modulation of ion channels and transporters that regulate excitability at the synaptic level. While most patients with epilepsy respond to ASDs, many remain refractory to medical treatment but respond favorably to a high-fat, low-carbohydrate metabolism-based therapy known as the ketogenic diet (KD). The clinical effectiveness of the KD has increasingly underscored the thesis that metabolic factors also play a crucial role in the dampening neuronal hyperexcitability that is a hallmark feature of epilepsy. This notion is further amplified by the clinical utility of other related metabolism-based diets such as the modified Atkins diet and the low-glycemic index treatment (LGIT). Traditional high-fat diets are characterized by enhanced fatty acid oxidation (which produces ketone bodies such as beta-hydroxybutyrate) and a reduction in glycolytic flux, whereas the LGIT is predicated mainly on the latter observation of reduced blood glucose levels. As dietary implementation is not without challenges regarding clinical administration and patient compliance, there is an inherent desire and need to determine whether specific metabolic substrates and/or enzymes might afford similar clinical benefits, hence validating the concept of a “diet in a pill.” Here, we discuss the evidence for one glycolytic inhibitor, 2-deoxyglucose (2DG) and one metabolic substrate, β-hydroxybutyrate (BHB) exerting direct effects on neuronal excitability, highlight their mechanistic differences, and provide the strengthening scientific rationale for their individual or possibly combined use in the clinical arena of seizure management.

Ketogenic and anaplerotic dietary modifications ameliorate seizure activity in Drosophila models of mitochondrial encephalomyopathy and glycolytic enzymopathy

Seizures are a feature not only of the many forms of epilepsy, but also of global metabolic diseases such as mitochondrial encephalomyopathy (ME) and glycolytic enzymopathy (GE). Modern anti-epileptic drugs (AEDs) are successful in many cases, but some patients are refractory to existing AEDs, which has led to a surge in interest in clinically managed dietary therapy such as the ketogenic diet (KD). This high-fat, low-carbohydrate diet causes a cellular switch from glycolysis to fatty acid oxidation and ketone body generation, with a wide array of downstream effects at the genetic, protein, and metabolite level that may mediate seizure protection. We have recently shown that a Drosophila model of human ME (ATP6¹) responds robustly to the KD; here, we have investigated the mechanistic importance of the major metabolic consequences of the KD in the context of this bioenergetics disease: ketogenesis, reduction of glycolysis, and anaplerosis. We have found that reduction of glycolysis does not confer seizure protection, but that dietary supplementation with ketone bodies or the anaplerotic lipid triheptanoin, which directly replenishes the citric acid cycle, can mimic the success of the ketogenic diet even in the presence of standard carbohydrate levels. We have also shown that the proper functioning of the citric acid cycle is crucial to the success of the KD in the context of ME. Furthermore, our data reveal that multiple seizure models, in addition to ATP6¹, are treatable with the ketogenic diet. Importantly, one of these mutants is TPI^sugarkill, which models human glycolytic enzymopathy, an incurable metabolic disorder with severe neurological consequences. Overall, these studies reveal widespread success of the KD in Drosophila, further cementing its status as an excellent model for studies of KD treatment and mechanism, and reveal key insights into the therapeutic potential of dietary therapy against neuronal hyperexcitability in epilepsy and metabolic disease.

2-Deoxy-D-Glucose Exhibits Anti-seizure Effects by Mediating the Netrin-G1-KATP Signaling Pathway in Epilepsy

Epilepsy is a disorder of the brain characterized by an enduring predisposition to generate epileptic seizures. The glycolytic inhibitor 2-deoxy-D-glucose (2-DG) has been reported to exert antiepileptic effects by upregulating KATP subunits (kir6.1 and kir6.2). We evaluated whether 2-DG exhibits anti-seizure effect by mediating the netrin-G1-KATP signaling pathway in epilepsy. In a mouse epilepsy model induced by lithium chloride-pilocarpine, 2-DG intervention increased the mRNA and protein expression levels of kir6.1 and kir6.2, and these increases were significantly reversed after knocking down netrin-G1 expression. Similarly, in cultured neurons with a magnesium-free medium, we found that the frequency of spontaneous postsynaptic potentials (SP) was increased, and in the meanwhile, expression levels of kir6.1 and kir6.2 were increased after pretreatment with 2DG. These effects were remarkably reversed after knocking down netrin-G1. Thus, our findings show that 2DG exhibits anti-seizure effects through the netrin-G1-KATP signaling pathway.

Dysregulated Glucose Metabolism as a Therapeutic Target to Reduce Post-traumatic Epilepsy

Traumatic brain injury (TBI) is a significant cause of disability worldwide and can lead to post-traumatic epilepsy. Multiple molecular, cellular, and network pathologies occur following injury which may contribute to epileptogenesis. Efforts to identify mechanisms of disease progression and biomarkers which predict clinical outcomes have focused heavily on metabolic changes. Advances in imaging approaches, combined with well-established biochemical methodologies, have revealed a complex landscape of metabolic changes that occur acutely after TBI and then evolve in the days to weeks after. Based on this rich clinical and preclinical data, combined with the success of metabolic therapies like the ketogenic diet in treating epilepsy, interest has grown in determining whether manipulating metabolic activity following TBI may have therapeutic value to prevent post-traumatic epileptogenesis. Here, we focus on changes in glucose utilization and glycolytic activity in the brain following TBI and during seizures. We review relevant literature and outline potential paths forward to utilize glycolytic inhibitors as a disease-modifying therapy for post-traumatic epilepsy.

Glycolytic inhibition: A novel approach toward controlling neuronal excitability and seizures

Conventional antiseizure medications reduce neuronal excitability through effects on ion channels or synaptic function. In recent years, it has become clear that metabolic factors also play a crucial role in the modulation of neuronal excitability. Indeed, metabolic regulation of neuronal excitability is pivotal in seizure pathogenesis and control. The clinical effectiveness of a variety of metabolism‐based diets, especially for children with medication‐refractory epilepsy, underscores the applicability of metabolic approaches to the control of seizures and epilepsy. Such diets include the ketogenic diet, the modified Atkins diet, and the low‐glycemic index treatment (among others). A promising avenue to alter cellular metabolism, and hence excitability, is by partial inhibition of glycolysis, which has been shown to reduce seizure susceptibility in a variety of animal models as well as in cellular systems in vitro. One such glycolytic inhibitor, 2‐deoxy‐d‐glucose (2DG), increases seizure threshold in vivo and reduces interictal and ictal epileptiform discharges in hippocampal slices. Here, we review the role of glucose metabolism and glycolysis on neuronal excitability, with specific reference to 2DG, and discuss the potential use of 2DG and similar agents in the clinical arena for seizure management.

Opposing effects of 2-deoxy-d-glucose on interictal- and ictal-like activity when K+ currents and GABAA receptors are blocked in rat hippocampus in vitro

The ketogenic diet (KD), a high-fat, carbohydrate-restricted diet, is used as an alternative treatment for drug-resistant epileptic patients. Evidence suggests that compromised glucose metabolism has a significant role in the anticonvulsant action of the KD; however, it is unclear what part of the glucose metabolism that is important. The present study investigates how selective alterations in glycolysis and oxidative phosphorylation influence epileptiform activity induced by blocking K+ currents and GABAA and NMDA receptors in the hippocampal slice preparation. Blocking glycolysis with the glucose derivative 2-deoxy-d-glucose (2-DG; 10 mM) gave a fast reduction of the frequency of interictal discharge (IED) consistent with findings in other in vitro models. However, this was followed by the induction of seizure-like discharges in area CA1 and CA3. Substituting glucose with sucrose (glucopenia) had effects similar to those of 2-DG, whereas substitution with l-lactate or pyruvate reduced the IED but had a less proconvulsant effect. Blockade of ATP-sensitive K+ channels, glycine or adenosine 1 receptors, or depletion of the endogenous anticonvulsant compound glutathione did not prevent the actions of 2-DG. Baclofen (2 μM) reproduced the effect of 2-DG on IED activity. The proconvulsant effect of 2-DG could be reproduced by blocking the oxidative phosphorylation with the complex I toxin rotenone (4 μM). The data suggest that inhibition of IED, induced by 2-DG and glucopenia, is a direct consequence of impairment of glycolysis, likely exerted via a decreased recurrent excitatory synaptic transmission in area CA3. The accompanying proconvulsant effect is caused by an excitatory mechanism, depending on impairment of oxidative phosphorylation.

NEW & NOTEWORTHY This study reveals two opposing effects of 2-deoxy-d-glucose (2-DG) and glucopenia on in vitro epileptiform discharge observed during combined blockade of K+ currents and GABAA receptors. Interictal-like activity is inhibited by a mechanism that selectively depends on impairment of glycolysis and that results from a decrease in the strength of excitatory recurrent synaptic transmission in area CA3. In contrast, 2-DG and glucopenia facilitate ictal-like activity by an excitatory mechanism, depending on impairment of mitochondrial oxidative phosphorylation.

The ATP-sensitive K channel is seizure protective and required for effective dietary therapy in a model of mitochondrial encephalomyopathy

Effective therapies are lacking for mitochondrial encephalomyopathies (MEs). MEs are devastating diseases that predominantly affect the energy-demanding tissues of the nervous system and muscle, causing symptoms such as seizures, cardiomyopathy, and neuro- and muscular degeneration. Even common anti-epileptic drugs which are frequently successful in ameliorating seizures in other diseases tend to have a lower success rate in ME, highlighting the need for novel drug targets, especially those that may couple metabolic sensitivity to neuronal excitability. Furthermore, alternative epilepsy therapies such as dietary modification are gaining in clinical popularity but have not been thoroughly studied in ME. Using the Drosophila ATP6¹ model of ME, we have studied dietary therapy throughout disease progression and found that it is highly effective against the seizures of ME, especially a high fat/ketogenic diet, and that the benefits are dependent upon a functional K_ATP channel complex. Further experiments with K_ATP show that it is seizure-protective in this model, and that pharmacological promotion of its open state also ameliorates seizures. These studies represent important steps forward in the development of novel therapies for a class of diseases that is notoriously difficult to treat, and lay the foundation for mechanistic studies of currently existing therapies in the context of metabolic disease.

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.