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A ketogenic diet mitigates the hippocampal astrogliosis in the Epileptic Brain

ABSTRACT: The ketogenic diet (KD) is an established treatment for patients with medically intractable epilepsy and is chiefly characterized by the production of ketone bodies (KB) such as β-hydroxybutyrate (BHB). However, after more than a century of clinical use, the mechanisms underlying its efficacy remain unclear. While prior investigations have examined the effects of the KD and its metabolic substrates on synaptic transmission, few studies have explored a potential connection between astrocytic ion channels and seizure genesis. One essential function of astrocytes is spatial potassium buffering which influences passive potassium conductance (PPC), and when impaired, can result in neuronal hyperexcitability. In the present study, we demonstrate that the KD can mitigate hippocampal astrogliosis in the Kcna1-null (KO) mouse model of developmental epilepsy. Specifically, we observed a significant increase in GFAP expression in KO mice fed a control diet compared to wild-type (WT) animals, and that the KD prevented this change. Furthermore, we noted a reduction in hippocampal astrocytic PPC in epileptic mice, whereas KD-treated KO animals exhibited nearly normal passive conductance levels. In this regard, we also provide evidence for the role of Kir4.1 channels in mediating astrocytic PPC, and the activation of these inwardly rectifying potassium channels by BHB. To further explore these findings at a molecular level, we conducted bulk RNA-seq analysis which revealed down-regulation of factors linked to hippocampal astrogliosis, notably those involved with neuroinflammation, consistent with earlier reports highlighting the anti-inflammatory effects of the KD and its metabolic substrates such as BHB. Our findings indicate that the KD protects against epilepsy-associated astrogliosis and astrocytic PPC changes, underscoring a novel mechanism of KD action, and the potential functional role of extracellular potassium in neuronal-glial interactions in the epileptic brain.

ORGANISM(S): Mus musculus

PROVIDER: GSE264537 | GEO | 2025/04/16

REPOSITORIES: GEO

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Project description:<h4><strong>INTRODUCTION: </strong>Approximately 1% of the world's population is impacted by epilepsy, a chronic neurological disorder characterized by seizures. One-third of epileptic patients are resistant to AEDs, or have medically refractory epilepsy (MRE). One non-invasive treatment that exists for MRE includes the ketogenic diet, a high-fat, low-carbohydrate diet. Despite the KD's success in seizure attenuation, it has a few risks and its mechanisms remain poorly understood. The KD has been shown to improve metabolism and mitochondrial function in epileptic phenotypes. Potassium channels have implications in epileptic conditions as they have dual roles as metabolic sensors and control neuronal excitation.</h4><h4><strong>OBJECTIVES: </strong>The goal of this study was to explore changes in the lipidome in hippocampal and cortical tissue from Kv1.1-KO model of epilepsy.</h4><h4><strong>METHODS: </strong>FT-ICR/MS analysis was utilized to examine nonpolar metabolome of cortical and hippocampal tissue isolated from a Kv1.1 channel knockout mouse model of epilepsy (n = 5) and wild-type mice (n = 5).</h4><h4><strong>RESULTS: </strong>Distinct metabolic profiles were observed, significant (p < 0.05) features in hippocampus often being upregulated (FC ≥ 2) and the cortex being downregulated (FC ≤ 0.5). Pathway enrichment analysis shows lipid biosynthesis was affected. Partition ratio analysis revealed that the ratio of most metabolites tended to be increased in Kv1.1-/-. Metabolites in hippocampal tissue were commonly upregulated, suggesting seizure initiation in the hippocampus. Aberrant mitochondrial function is implicated by the upregulation of cardiolipin, a common component in the mitochondrial membrane.</h4><h4><strong>CONCLUSION: </strong>Generally, our study finds that the lipidome is changed in the hippocampus and cortex in response to Kv1.1-KO indicating changes in membrane structural integrity and synaptic transmission.</h4>

Project description:Beta-hydroxybutyrate (BHB) is a ketone body synthesized during fasting or strenuous exercise. Our previous study demonstrated that a cyclic ketogenic diet (KD), which induces BHB levels similar to fasting every other week, reduces midlife mortality and improves memory in aging mice. BHB actively regulates gene expression and inflammatory activation through non-energetic signaling pathways. Neither of these activities has been well-characterized in the brain and they may represent mechanisms by which BHB affects brain function during aging. First, we analyzed hepatic gene expression in an aging KD-treated mouse cohort using bulk RNA-seq. In addition to the downregulation of TOR pathway activity, cyclic KD reduces inflammatory gene expression in the liver. We observed via flow cytometry that KD also modulates age-related systemic T cell functions. Next, we investigated whether BHB affects brain cells transcriptionallyin vitro. Gene expression analysis in primary human brain cells (microglia, astrocytes, neurons) using RNA-seq shows that BHB causes a mild level of inflammation in all three cell types. However, BHB inhibits the more pronounced LPS-induced inflammatory gene activation in microglia. Furthermore, we confirmed that BHB similarly reduces LPS-induced inflammation in primary mouse microglia and bone marrow-derived macrophages (BMDMs). BHB is recognized as an inhibitor of histone deacetylase (HDAC), an inhibitor of NLRP3 inflammasome, and an agonist of the GPCR Hcar2. Nevertheless, in microglia, BHB's anti-inflammatory effects are independent of these known mechanisms. Finally, we examined the brain gene expression of 12-month-old male mice fed with one-week and one-year cyclic KD. While a one-week KD increases inflammatory signaling, a one-year cyclic KD reduces neuroinflammation induced by aging. In summary, our findings demonstrate that BHB mitigates the microglial response to inflammatory stimuli, like LPS, possibly leading to decreased chronic inflammation in the brain after long-term KD treatment in aging mice.

Project description:Inherited mutations of calcium ion channels exhibit neurological defects, such as epilepsy, ataxia, and migraine, and these phenotypes are shared among humans and mouse models. Absence epilepsy and ataxic phenotypes are present in the calcium channelopathy mutants stargazer (stg-gamma2 subunit), tottering (tg-alpha1 subunit), and lethargic (lh-beta4 subunit). These mutations of high-voltage-activated (HVA) calcium channel subunits initiate increases in membrane excitability of low-voltage-activated (LVA) calcium channels in thalamic neurons, thus enhancing LVA currents. Elevated LVA currents, produced from T-type calcium channels, induce rhythmic thalamocortical burst firing and spike-wave seizures. The changes in gene expression originating from the different mutations result in similar T-type channel function; however, the network of gene modifications causing altered molecular plasticity and the emergence of pathological phenotypes remain unknown. We would like to understand how loss of 3 different subunits of a calcium ion channel differentially alter gene expression in the brain. Characterizing the gene expression profiles of the mutant stg, tg, and lh mice will provide evidence of the epileptic and ataxic mechanisms, which may identify potential therapeutic targets. We will compare the gene expression profiles among adult mutant stg, tg, and lh mice, which display the ataxic and epileptic phenotypes, along with their wildtype, litter-mate controls, in the cerebellum and brain (without cerebellum). We propose that the neuronal dysfunction associated with the ataxic and epileptic phenotypes develops from a common network of interacting gene alterations within the mutant stg, tg, and lh brain. The changes dictated by the initial mutations leading to the ataxic and epileptic phenotypes are hypothesized to be localized to the cerebellum and the remaining areas of the brain, including the thalamus and cortex, respectively. Adult mutant stg, tg, and lh mice, between 2 and 5 months of age, along with wildtype, litter-mate controls, will be sacrificed. Two brain regions responsible for two phenotypes will be examined. The cerebellum (ataxia) will be dissected from remainder of the forebrain (generalized epilepsy). Each tissue set will be collected in triplicate (3 separate mice per set) to account for biological variance, and total RNA isolated via standard Trizol procedure (Invitrogen) and purified with the RNeasy cleanup kit (Qiagen). RNA samples will be stored at -80 C until sent for analysis using the Affymetrix GeneChip Mouse Genome 430 2.0 whole genome array.

Project description:The epilepsies represent one of the most common neurological disorders. Mesial temporal lobe epilepsies (MTLE) are the most frequent form of partial epilepsies and display frequent resistance to anti-epileptic drugs thus representing a major health care problem. In TLE, the origin of seizure activity typically involves the hippocampal formation, which displays major neuropathological features, described with the term hippocampal sclerosis (HS). HS is the most frequent pathological substrate of refractory mesial temporal lobe epilepsy. Complex partial seizures (CPS) are the predominant seizure type associated with medial temporal lobe epilepsy. MTLE is commonly due to mesial temporal sclerosis (MTS). The biology underlying the epilepstic seizures and the transcriptome associated to the seizure in intractable medial temporal lobe epilepsy is ill understood. The aim of the study was to identify potential biomarkers that could identify epileptic seizure. Thus we performed transcriptome profiling of ten medial temporal lobe epilepsy cases which are resistant to the drug and underwent temporal lobectomy. The cases constitutes of patients with intractable complex partial seizure, treated medically and have undergone detailed presurgical evaluation and subjected to surgery for standard temporal lobectomy and amygdalo-hippocampectomy. The spiking areas identified after the electrocorticography will form the test tissues, which compared with the nonspiking areas removed during the surgery, from the same patient. This could probably form one of the appropriate controls, as test and control are from same patient, which eliminates the genome variations that could incur due to the comparison with the tissues from the another patient. Also this could get rid of expression changes due to the treatments undergone by the patient. We performed two color microarray wherein we labled seizure focus (spiking area) with Cy5 and non-seizure region tissues (non-spiking) with Cy3. As a strategy to test the possibility of potential diagnostic biomarkers we are intended to test the differentially regulated molecules in an independent set of epilepsy samples. Two color experiment

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A ketogenic diet mitigates the hippocampal astrogliosis in the Epileptic Brain

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