The beneficial effect of probiotics as a supplementary treatment in drug-resistant epilepsy: a pilot study

The Beneficial Effect of Probiotics Supplementation on Penicillin-Induced Focal Seizure in Rats

The focal epilepsy is a chronic neurological brain disorder which affects millions of people in the world. There is emerging evidence that changes in the gut microbiota may have effects on epileptic seizures. In the present study, we examined the effect of probiotics on penicillin-induced focal seizure model in rats. Male Wistar Albino rats (n: 21) were randomly divided into three groups: control (no medication), penicillin and penicillin + probiotic. Probiotic VSL#3 (12.86 bn living bacteria/kg/day) was given by gavage for 30 days. The seizures were induced by intracortical injection of penicillin G (500 IU) into the cortex. An ECoG recordings were made for 180 min after penicillin G application. The spike frequency and the amplitude were used to assess the severity of seizures. Tumor necrosis factor (TNF-α), nitric oxide (NO) and interleukin (IL-6) levels in the brain were studied biochemically. Our results indicated that probiotic supplementation improved focal seizures through increasing the latency (p < 0.001) and decreasing the spike frequency (p < 0.01) compared to the penicillin group. Penicillin-induced seizure in rats significantly enhanced TNF-α (p < 0.01), NO (p < 0.01) and IL-6 (p < 0.05) compared to the control. Probiotic supplementation significantly decreased IL-6 (p < 0.05), TNF-α (p < 0.01) and NO (p < 0.001) compared to the penicillin group. When the body weights were compared before and after the experiment, there was no difference between the control and penicillin groups, but it was observed that the body weight decreased after probiotic supplementation in the penicillin + probiotic group. Probiotic supplementation may have anti-seizure effect by reducing proinflammatory cytokine and NO levels in epileptic rat brain.

Polysaccharides, Next Potential Agent for the Treatment of Epilepsy?

Epilepsy is a chronic neurological disorder. Current pharmacological therapies for epilepsy have limited efficacy that result in refractory epilepsy (RE). Owing to the limitations of conventional therapies, it is needed to develop new anti-epileptic drugs. The beneficial effects of polysaccharides from Chinese medicines, such as Lycium barbarum polysaccharides (COP) and Ganoderma lucidum polysaccharides (GLP), for treatment of epilepsy include regulation of inflammatory factors, neurotransmitters, ion channels, and antioxidant reactions. Especially, polysaccharides could be digested by intestinal microbial flora, referred as “intestinal brain organ” or “adult’s second brain”, may be the target for treatment of epilepsy. Actually, polysaccharides can effectively improve the type and quantity of intestinal flora such as bifidobacteria and lactic acid bacteria and achieve the purpose of treating epilepsy. Therefore, polysaccharides are hypothesized and discussed as potential agent for treatment of epilepsy.

Probiotic supplementation alleviates absence seizures and anxiety- and depression-like behavior in WAG/Rij rat by increasing neurotrophic factors and decreasing proinflammatory cytokines

AIM

Epilepsy is one of the most common chronic brain disorders that affect millions of people worldwide. In the present study, we investigated the effects of probiotic supplementation on absence epilepsy and anxiety-and depression-like behavior in WAG/Rij rats.

MATERIAL AND METHOD

Fourteen male WAG/Rij rats (absence-epileptic) and seven male Wistar rats (nonepileptic) were used. The effects of probiotic VSL#3 (12.86 bn living bacteria/kg/day for 30 day/gavage) on absence seizures, and related psychiatric comorbidities were evaluated in WAG/Rij rats. Anxiety-like behavior was evaluated by the open-field test and depression-like behavior by the forced swimming test. In addition, the brain tissues of rats were evaluated histopathologically for nerve growth factor [NGF], brain-derived neurotrophic factor [BDNF], SRY sex-determining region Y-box 2 [SOX2] and biochemically for nitric oxide [NO], tumor necrosis factor-alpha [TNF-α] ,and Interleukin-6 [IL-6].

RESULTS

Compared to Wistar rats, WAG/Rij rats exhibited anxiety- and depression-like behavior, and had lower BDNF, NGF and SOX2 immunoreactivity, and higher TNF-α, IL-6 levels in brain tissue. VSL#3 supplementation reduced the duration and number of spike-wave discharges (SWDs) and exhibited anxiolytic or anti-depressive effect. VSL#3 supplement also increased the NGF immunoreactivity while decreasing IL-6, TNF-α and NO levels in WAG/Rij rat brain.

CONCLUSION

The findings of the present study showed that neurotrophins, SOX2 deficiency, and pro-inflammatory cytokines may play a role in the pathogenesis of absence epilepsy. Our data support the hypothesis that the probiotics have anti-inflammatory effect. The present study is the first to show the positive effects of probiotic bacteria on absence seizures and anxiety- and depression-like behavior.

The Microbiota-Gut-Brain Axis and Epilepsy

Honoured as the second genome in humans, the gut microbiota is involved in a constellation of physiological and pathological processes, including those related to the central nervous system. The communication between the gut microbiota and the brain is realized by a complex bidirectional connection, known as the "microbiota-gut-brain axis", via neuroendocrine, immunological, and direct neural mechanisms. Recent studies indicate that gut dysfunction/dysbiosis is presumably involved in the pathogenesis of and susceptibility to epilepsy. In addition, the reconstruction of the intestinal microbiome through, for example, faecal microbiota transplantation, probiotic intervention, and a ketogenic diet, has exhibited beneficial effects on drug-resistant epilepsy. The purposes of this review are to provide a brief overview of the microbiota-gut-brain axis and to synthesize what is known about the involvement of the gut microbiota in the pathogenesis and treatment of epilepsy, to bring new insight into the pathophysiology of epilepsy and to present a preliminary discussion of novel therapeutic options for epilepsy based on the gut microbiota.

Gut Microbial Characteristics of Adult Patients With Epilepsy

Objective

To characterize the intestinal flora of patients with epilepsy and its correlation with epilepsy.

Methods

Patients with ages &gt; 18 years were consecutively enrolled from the outpatient department, Affiliated Hospital of Guizhou Medical University from January 2018 to December 2019. A total of 71 subjects were recruited, including epilepsy patients (n = 41) as an observation group and patient family members (n = 30) as a control group. Fresh stool specimens of all the subjects were collected. The 16S ribosomal RNA sequencing was analyzed to determine changes in intestinal flora composition and its correlation with epilepsy. Subgroup analysis was then conducted. All patients with epilepsy were divided into an urban group (n = 21) and a rural group (n = 20) according to the region, and bioinformatics analyses were repeated between subgroups.

Results

LEfSe analysis showed that Fusobacterium, Megasphaera, Alloprevotella, and Sutterella had relatively increased abundance in the epilepsy group at the genus level. Correlation analysis suggested that Fusobacterium sp. (r = 0.584, P &lt; 0.01), Fusobacterium mortiferum (r = 0.560, P &lt; 0.01), Ruminococcus gnavus (r = 0.541, P &lt; 0.01), and Bacteroides fragilis (r = 0.506, P &lt; 0.01) were significantly positively correlated with the occurrence of epilepsy (r ≥ 0.5, P &lt; 0.05). PICRUSt function prediction analysis showed that there were significant differences in 16 pathways between the groups at level 3. Comparing the rural group with the urban group, Proteobacteria increased at the phylum level and Escherichia coli, Fusobacterium varium, Prevotella stercorea, and Prevotellaceae bacterium DJF VR15 increased at the species level in the rural group.

Conclusion

There were significant differences in the composition and functional pathways of gut flora between epilepsy patients and patient family members. The Fusobacterium may become a potential biomarker for the diagnosis of epilepsy.

The effect of a novel anticonvulsant chemical Q808 on gut microbiota and hippocampus neurotransmitters in pentylenetetrazole-induced seizures in rats

Background

The gut microbiota can modulate brain function and behavior and is increasingly recognized as an important factor in mediating the risk of epilepsy and the effects of seizure interventions. Drug therapy is one of the factors that influence the composition of the intestinal microbiota. Q808 is an innovative chemical with strong anticonvulsant activity and low neurotoxicity. However, studies evaluating the effect of Q808 on gut microbial communities are lacking. In this study, we aimed to evaluate the anticonvulsant activity of Q808 on a pentylenetetrazol (PTZ)—induced seizure model and analyze and compare the intestinal microbiota composition of non-PTZ vehicle control group, the PTZ-induced seizure model rats with and without Q808, through 16S rDNA sequencing. Neurotransmitter levels in the hippocampus were quantitatively estimated using HPLC–MS.

Results

The results suggest that Q808 effectively alleviates seizures in chronic PTZ-kindled model rats. Additionally, based on the analyzed abundance of the gut microbiota, dysbacteriosis of model rats was found to be corrected after Q808 treatment at the phylum level. The unique bacterial taxa (e.g., Lactobacillus) that are associated with acetylcholine production, were significantly increased. Several short-chain fatty acids (SCFAs)-producing bacteria, including Roseburia, Alloprevptella, Prevotellaceae_NK3B31_group, Prevotellaceae_UCG-001, and Prevotella_9, were enriched. In the hippocampus, the contents of acetylcholine increased, whereas the levels of 3-methoxytyramine, glutamine, and 5-hydroxyindole acetic acid (5-HIAA) decreased after Q808 treatment.

Conclusions

This study demonstrates that Q808 can be used to remodel the dysbiosis of the gut microbiome and influence neurotransmitter levels in the hippocampus of PTZ-induced seizure model rats. We hope that these novel findings prompt further research on the interaction between gut microbiota and seizures and the mechanism of Q808.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12868-022-00690-3.

Gut microbiome in neuropsychiatric disorders

ABSTRACT Background: Neuropsychiatric disorders are a significant cause of death and disability worldwide. The mechanisms underlying these disorders include a constellation of structural, infectious, immunological, metabolic, and genetic etiologies. Advances in next-generation sequencing techniques have demonstrated that the composition of the enteric microbiome is dynamic and plays a pivotal role in host homeostasis and several diseases. The enteric microbiome acts as a key mediator in neuronal signaling via metabolic, neuroimmune, and neuroendocrine pathways. Objective: In this review, we aim to present and discuss the most current knowledge regarding the putative influence of the gut microbiome in neuropsychiatric disorders. Methods: We examined some of the preclinical and clinical evidence and therapeutic strategies associated with the manipulation of the gut microbiome. Results: targeted taxa were described and grouped from major studies to each disease. Conclusions: Understanding the complexity of these ecological interactions and their association with susceptibility and progression of acute and chronic disorders could lead to novel diagnostic biomarkers based on molecular targets. Moreover, research on the microbiome can also improve some emerging treatment choices, such as fecal transplantation, personalized probiotics, and dietary interventions, which could be used to reduce the impact of specific neuropsychiatric disorders. We expect that this knowledge will help physicians caring for patients with neuropsychiatric disorders.

Epilepsy-associated comorbidities among adults: A plausible therapeutic role of gut microbiota

Epilepsy is a debilitating disorder that affects about 70 million people in the world currently. Most patients with epilepsy (PWE) often reported at least one type of comorbid disorder. These may include neuropsychiatric disorders, cognitive deficits, migraine, cardiovascular dysfunction, systemic autoimmune disorders and others. Current treatment strategies against epilepsy-associated comorbidities have been based on targeting each disorder separately with either anti-seizure medications (ASMs), anti-inflammatories or anti-depressant drugs, which have often given inconsistent and ineffective results. Gut dysbiosis may be a common pathological pathway between epilepsy and its comorbid disorders, and thus may serve as a possible intervention target. Therefore, this narrative review aimed to elucidate the potential pathological and therapeutic role of the gut microbiota in adult epilepsy-associated comorbidities. This review noticed a scarcity in the current literature on studies investigating the direct role of the gut microbiota in relation to epilepsy-associated comorbidities. Nevertheless, gut dysbiosis have been implicated in both epilepsy and its associated comorbidities, with similarities seen in the imbalance of certain gut microbiota phyla (Firmicutes), but differences seen in the mechanism of action. Current gut-related interventions such as probiotics have been consistently reported across studies to provide beneficial effects in correcting gut dysbiosis and improving various disorders, independent of epilepsy. However, whether these beneficial effects may translate towards epilepsy-associated comorbidities have yet to be determined. Thus, future studies determining the therapeutic potential of gut microbiota interventions in PWE with epilepsy-associated comorbidities may effectively improve their quality of life.

A Comprehensive Review on the Role of the Gut Microbiome in Human Neurological Disorders

The human body is full of an extensive number of commensal microbes, consisting of bacteria, viruses, and fungi, collectively termed the human microbiome. The initial acquisition of microbiota occurs from both the external and maternal environments, and the vast majority of them colonize the gastrointestinal tract (GIT). These microbial communities play a central role in the maturation and development of the immune system, the central nervous system, and the GIT system and are also responsible for essential metabolic pathways. Various factors, including host genetic predisposition, environmental factors, lifestyle, diet, antibiotic or nonantibiotic drug use, etc., affect the composition of the gut microbiota. Recent publications have highlighted that an imbalance in the gut microflora, known as dysbiosis, is associated with the onset and progression of neurological disorders. Moreover, characterization of the microbiome-host cross talk pathways provides insight into novel therapeutic strategies. Novel preclinical and clinical research on interventions related to the gut microbiome for treating neurological conditions, including autism spectrum disorders, Parkinson's disease, schizophrenia, multiple sclerosis, Alzheimer's disease, epilepsy, and stroke, hold significant promise. This review aims to present a comprehensive overview of the potential involvement of the human gut microbiome in the pathogenesis of neurological disorders, with a particular emphasis on the potential of microbe-based therapies and/or diagnostic microbial biomarkers. This review also discusses the potential health benefits of the administration of probiotics, prebiotics, postbiotics, and synbiotics and fecal microbiota transplantation in neurological disorders.

Gut microbiome effects on neuronal excitability & activity: Implications for epilepsy

It is now well established that the bacterial population of the gastrointestinal system, known as the gut microbiome, is capable of influencing the brain and its dependent functions. Links have been demonstrated between the microbiome and a variety of normal and pathological neural functions, including epilepsy. Many of these microbiome-brain links involve the direct or indirect modulation of the excitability and activity of individual neurons by the gut microbiome. Such links may be particularly significant when it comes to microbiome modulation of epilepsy, often considered a disorder of neuronal excitability. In this review we consider the current evidence of a relationship between the gut microbiome and the excitability or activity of neurons in the context of epilepsy. The review focuses particularly on evidence of direct, causal microbiome effects on neuronal excitability or activity, but also considers demonstrations of microbiome to host interactions that are likely to have an indirect influence. While we identify a few common themes, it is apparent that deriving general mechanistic principles of microbiome influence on these parameters in epilepsy will require considerable further study to tease out the many interacting factors, systems, and conditions.

Using integrated meta-omics to appreciate the role of the gut microbiota in epilepsy

The way the human microbiota may modulate neurological pathologies is a fascinating matter of research. Epilepsy is a common neurological disorder, which has been largely investigated in correlation with microbiota health and function. However, the mechanisms that regulate this apparent connection are scarcely defined, and extensive effort has been conducted to understand the role of microbiota in preventing and reducing epileptic seizures. Intestinal bacteria seem to modulate the seizure frequency mainly by releasing neurotransmitters and inflammatory mediators. In order to elucidate the complex microbial contribution to epilepsy pathophysiology, integrated meta-omics could be pivotal. In fact, the combination of two or more meta-omics approaches allows a multifactorial study of microbial activity within the frame of disease or drug treatments. In this review, we provide information depicting and supporting the use of multi-omics to study the microbiota-epilepsy connection. We described different meta-omics analyses (metagenomics, metatranscriptomics, metaproteomics and metabolomics), focusing on current technical challenges in stool collection procedures, sample extraction methods and data processing. We further discussed the current advantages and limitations of using the integrative approach of multi-omics in epilepsy investigations.

Gut microbiota modulation by prednisolone in a rat kindling model of pentylenetetrazol (PTZ)-induced seizure

The gut microbiota is a complex community composed by several microorganisms that interact in the maintenance of homeostasis and contribute to physiological processes, including brain function. The relationship of the taxonomic composition of the gut microbiota with neurological diseases such as autism, Parkinson's, Alzheimer's, anxiety, and depression is widely recognized. The immune system is an important intermediary between the gut microbiota and the central nervous system, being one of the communication routes of the gut-brain axis. Although the complexity of the relationship between inflammation and epilepsy has not yet been elucidated, inflammatory processes are similar in many ways to the consequences of dysbiosis and contribute to disease progression. This study aimed to analyze the taxonomic composition of the gut microbiota of rats treated with prednisolone in a kindling model of epilepsy. Male Wistar rats (90 days, n = 24) divided into four experimental groups: sodium chloride solution 0.9 g%, diazepam 2 mg/kg, prednisolone 1 mg/kg, and prednisolone 5 mg/kg administered intraperitoneally (i.p.) for 14 days. The kindling model was induced by pentylenetetrazole (PTZ) 25 mg/kg i.p. on alternate days. The taxonomic profile was established by applying metagenomic DNA sequencing. There was no change in alpha diversity, and the composition of the gut microbiota between prednisolone and diazepam was similar. The significant increase in Verrucomicrobia, Saccharibacteria, and Actinobacteria may be related to the protective activity against seizures and inflammatory processes that cause some cases of epilepsy. Further studies are needed to investigate the functional influence that these species have on epilepsy and the inflammatory processes that trigger it.

A High-Tryptophan Diet Reduces Seizure-Induced Respiratory Arrest and Alters the Gut Microbiota in DBA/1 Mice

Background and Aims: Central 5-hydroxytryptamine (5-HT) defects are responsible for the occurrence of sudden unexpected death in epilepsy (SUDEP). The DBA/1 mouse is an animal model of SUDEP since the mouse exhibits audiogenic seizure-induced respiratory arrest (S-IRA). The synthesis of central 5-HT is closely related to the gut microbiota. Moreover, emerging studies suggest a possible role for the microbiota in mitigating seizure likelihood. Based on this, we aimed to explore the effect of a high-tryptophan diet (HTD) on SUDEP as well as the synthesis and metabolism of central 5-HT. Furthermore, we investigated the involvement of the gut microbiota in this process.

Methods: All DBA/1 mice were subjected to acoustic stimulation to induce seizures. Only those mice that exhibited S-IRA were randomly assigned to the normal diet (ND) group (n = 39) or HTD group (n = 53). After 1 month of dietary intervention, (1) S-IRA rates were evaluated, (2) the concentrations of 5-HT and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) in the plasma and brain were determined by ultra-high-pressure liquid chromatography, and (3) the fecal flora biodiversity and species composition were analyzed by 16S rDNA microbiota profiling.

Results: The S-IRA rate in DBA/1 mice was significantly reduced in the HTD group compared with that in the control group. HTD increased the levels of 5-HT and 5-HIAA in both the telencephalon and midbrain. HTD significantly elevated the species richness and diversity of the gut microbiota. Moreover, there was a significant difference in the gut microbiota composition between the two groups, and the intestinal flora was dominated by Proteobacteria and Actinobacteria after HTD.

Conclusions: HTD is efficient in lowering S-IRA rates and elevating the central 5-HT level in DBA/1 mice. The gut microbiota was altered after HTD intervention. The significant increase in Proteobacteria and Actinobacteria may be related to the SUDEP-protective effect of HTD. Our findings shed light on a candidate choice of dietary prevention for SUDEP.

Analysis of gut microbiota in patients with epilepsy treated with valproate: Results from a three months observational prospective cohort study

BACKGROUND

Growing evidence implicates the potential effect of microbiota on the pathogenesis and course of epilepsy. However, the effects of valproate (VPA), a broad spectrum anti-epileptic drugs, on gut microbiota have not been investigated in humans. This study aimed to analyze fecal microbiota in patients with epilepsy treated with valproate.

METHODS

A total of 10 participants, who were newly diagnosed of cryptogenic epilepsy with treatment naïve and received 1000 mg daily doses of VPA, were recruited in our prospective study. Microbiota compositions were evaluated at baseline and after three months of VPA treatment using 16S rDNA sequencing.

RESULTS

VPA treatment was associated with clinical improvements in all patients, but not changes in gut microbiota richness and complexity (Shannon: p = 0.82). Microbiome composition structure differences also revealed no statistical difference in dissimilarity (Adonis: p = 0.90). No statistical difference taxa were found between two groups. However, the ratio of phyla Firmicutes to Bacteriodetes (ANOVA: p = 0.037) markedly raised after three months of VPA-treatment. A correlation matrix based on the spearman correlation distance confirmed associations between specific fecal taxa and VPA-related clinical metabolic parameters, including drug concentration in the blood, total cholesterol, triglyceride, lactate dehydrogenase, alanine aminotransferase, aspartate aminotransferase and weight gain. (p < 0.05) CONCLUSIONS: Among those patients treated with VPA, characterization of the gut microbiota altered, and gut microbiota associated with weight gain and clinical biochemical indexes, suggesting that microbiome composition data might involve in the mechanisms of VPA induced metabolic disorder.

The Emerging Scenario of the Gut-Brain Axis: The Therapeutic Actions of the New Actor Kefir against Neurodegenerative Diseases

The fact that millions of people worldwide suffer from Alzheimer’s disease (AD) or Parkinson’s disease (PD), the two most prevalent neurodegenerative diseases (NDs), has been a permanent challenge to science. New tools were developed over the past two decades and were immediately incorporated into routines in many laboratories, but the most valuable scientific contribution was the “waking up” of the gut microbiota. Disturbances in the gut microbiota, such as an imbalance in the beneficial/pathogenic effects and a decrease in diversity, can result in the passage of undesired chemicals and cells to the systemic circulation. Recently, the potential effect of probiotics on restoring/preserving the microbiota was also evaluated regarding important metabolite and vitamin production, pathogen exclusion, immune system maturation, and intestinal mucosal barrier integrity. Therefore, the focus of the present review is to discuss the available data and conclude what has been accomplished over the past two decades. This perspective fosters program development of the next steps that are necessary to obtain confirmation through clinical trials on the magnitude of the effects of kefir in large samples.

Gut Microbiota in Canine Idiopathic Epilepsy: Effects of Disease and Treatment

Simple Summary

There is evidence that supports the existence of a gut-brain axis system through which bi-directional communication occurs between gut bacteria and the brain. Epilepsy is one of the most common neurological disorders in humans and dogs. The role of microbiota in epilepsy remains unknown but it has been suggested that it is a possible influence of gut bacteria in controlling seizures. The aim of this study was to investigate the changes in gut microbiota from dogs with idiopathic epilepsy and the possible effect of antiepileptic drugs on the modulation of the composition of this microbiota. In comparison with control dogs, drug-naive epileptic individuals showed a significantly reduced abundance of GABA and SCFAs-producing bacteria, as well as bacteria associated with reduced risk for brain disease. Moreover, the use of phenobarbital or imepitoin monotherapy during one month in epileptic dogs did not modify the gut microbiota composition. These results open up the possibility of studying probiotic interventions in epilepsy. Considering the phylogenetic and metabolic similarities in intestinal microbiome between humans and dogs, this study contributes to the understanding of epilepsy both in human and veterinary medicine.

Abstract

Epilepsy is one of the most common neurological disorders in humans and dogs. The structure and composition of gut microbiome associated to this disorder has not yet been analyzed in depth but there is evidence that suggests a possible influence of gut bacteria in controlling seizures. The aim of this study was to investigate the changes in gut microbiota associated to canine idiopathic epilepsy (IE) and the possible influence of antiepileptic drugs (AEDs) on the modulation of this microbiota. Faecal microbiota composition was analyzed using sequencing of bacterial 16S rRNA gene in a group of healthy controls (n = 12) and a group of epileptic dogs both before (n = 10) and after a 30-day single treatment with phenobarbital or imepitoin (n = 9). Epileptic dogs showed significantly reduced abundance of GABA (Pseudomonadales, Pseudomonadaceae, Pseudomonas and Pseudomona_graminis) and SCFAs-producing bacteria (Peptococcaceae, Ruminococcaceae and Anaerotruncus) as well as bacteria associated with reduced risk for brain disease (Prevotellaceae) than control dogs. The administration of AEDs during 30 days did not modify the gut microbiota composition. These results are expected to contribute to the understanding of canine idiopathic epilepsy and open up the possibility of studying new therapeutic approaches for this disorder, including probiotic intervention to restore gut microbiota in epileptic individuals.

Microbiota-Gut-Brain Axis and Epilepsy: A Review on Mechanisms and Potential Therapeutics

The gut-brain axis refers to the bidirectional communication between the gut and brain, and regulates intestinal homeostasis and the central nervous system via neural networks and neuroendocrine, immune, and inflammatory pathways. The development of sequencing technology has evidenced the key regulatory role of the gut microbiota in several neurological disorders, including Parkinson's disease, Alzheimer's disease, and multiple sclerosis. Epilepsy is a complex disease with multiple risk factors that affect more than 50 million people worldwide; nearly 30% of patients with epilepsy cannot be controlled with drugs. Interestingly, patients with inflammatory bowel disease are more susceptible to epilepsy, and a ketogenic diet is an effective treatment for patients with intractable epilepsy. Based on these clinical facts, the role of the microbiome and the gut-brain axis in epilepsy cannot be ignored. In this review, we discuss the relationship between the gut microbiota and epilepsy, summarize the possible pathogenic mechanisms of epilepsy from the perspective of the microbiota gut-brain axis, and discuss novel therapies targeting the gut microbiota. A better understanding of the role of the microbiota in the gut-brain axis, especially the intestinal one, would help investigate the mechanism, diagnosis, prognosis evaluation, and treatment of intractable epilepsy.

The role of microbiota-gut-brain axis in neuropsychiatric and neurological disorders

Emerging evidence indicates that the gut microbiota play a crucial role in the bidirectional communication between the gut and the brain suggesting that the gut microbes may shape neural development, modulate neurotransmission and affect behavior, and thereby contribute to the pathogenesis and/or progression of many neurodevelopmental, neuropsychiatric, and neurological conditions. This review summarizes recent data on the role of microbiota-gut-brain axis in the pathophysiology of neuropsychiatric and neurological disorders including depression, anxiety, schizophrenia, autism spectrum disorders, Parkinson's disease, migraine, and epilepsy. Also, the involvement of microbiota in gut disorders co-existing with neuropsychiatric conditions is highlighted. We discuss data from both in vivo preclinical experiments and clinical reports including: (1) studies in germ-free animals, (2) studies exploring the gut microbiota composition in animal models of diseases or in humans, (3) studies evaluating the effects of probiotic, prebiotic or antibiotic treatment as well as (4) the effects of fecal microbiota transplantation.

Functional Gastrointestinal Disorders in Patients With Epilepsy: Reciprocal Influence and Impact on Seizure Occurrence

Introduction: The complex relationship between the microbiota-gut-brain axis (MGBA) and epilepsy has been increasingly investigated in preclinical studies. Conversely, evidence from clinical studies is still scarce. In recent years, the pivotal role of MGBA dysregulation in the pathophysiology of functional gastrointestinal disorders (FGID) has been recognized. With this background, we aimed to investigate the prevalence of FGID in patients with epilepsy (PWE) and the possible impact of bowel movement abnormalities on seizure recurrence. Methods: A total of 120 PWE and 113 age-, sex-, and BMI-matched healthy subjects (HS) were consecutively enrolled. A questionnaire to evaluate the presence of FGID (according to Rome III diagnostic criteria) was administrated to all participants. In a subgroup of drug-resistant patients, we administered an ad-hoc questionnaire combining Bristol stool charts and seizure diaries to evaluate seizure trends and bowel movement changes. Results: A higher prevalence of FGID in PWE (62.5%) than in HS (39.8%) was found (p < 0.001). The most frequently observed disorder was constipation, which was significantly higher in PWE than in HS (43.3 vs. 21.2%, p < 0.001), and was not associated with anti-seizure medication intake according to multivariable analysis. In drug-resistant patients, most seizures occurred during periods of altered bowel movements, especially constipation. A significant weak negative correlation between the number of days with seizures and the number of days with normal bowel movements was observed (p = 0.04). According to multivariable logistic regression analysis, FGID was significantly associated with temporal lobe epilepsy as compared with other lobar localization (p = 0.03). Conclusions: Our clinical findings shed new light on the complex relationship between epilepsy and the MGBA, suggesting a bidirectional link between bowel movement abnormalities and seizure occurrence. However, larger studies are required to better address this important topic.

Ciprofloxacin for treatment of drug-resistant epilepsy

PURPOSE

To investigate the efficacy of short-term treatment with ciprofloxacin in alteration of gut microbiota pattern and reduction of seizure frequency in adult patients with drug-resistant epilepsy.

METHODS

In a prospective study, we investigated the effect of a 5-day course of treatment with ciprofloxacin on gut microbiota pattern and seizure frequency of 23 adults with drug-resistant epilepsy. Fecal samples were collected before and after treatment and were analyzed for microbial load and species. Changes in seizure frequency were registered for 12 weeks. Responders were defined as patients who experienced ≥50 % seizure reduction in comparison to baseline. Outcome measures were specified as alteration in fecal microbial burden in days 5-7 and responder rate in 4th and 12th weeks.

RESULTS

The mean baseline frequency of seizures was5.6 ±7.7 per week. All patients were on polytherapy with a mean of 3 ± 1.2 anti-seizure medications. Microbial analysis showed a considerable increase in Bacteroidetes/Firmicutes ratio after treatment. Seizure frequency significantly decreased at the end of first week and the therapeutic effect continued to week 12 (P < 0.001). The responder rate at 4th and 12th weeks were 69.6 % and 73.9 % respectively with a more prominent response in patients with symptomatic generalized epilepsy (P:0.06).

CONCLUSION

Alteration of abnormal gut microbiota pattern by methods such as short-course antibiotic therapy, prescription of probiotics and fecal microbiota transplant might be effective in treatment of drug-resistant epilepsy.

Gut metabolite S-equol ameliorates hyperexcitability in entorhinal cortex neurons following Theiler murine encephalomyelitis virus-induced acute seizures

Objective

A growing body of evidence indicates a potential role for the gut–brain axis as a novel therapeutic target in treating seizures. The present study sought to characterize the gut microbiome in Theiler murine encephalomyelitis virus (TMEV)‐induced seizures, and to evaluate the effect of microbial metabolite S‐equol on neuronal physiology as well as TMEV‐induced neuronal hyperexcitability ex vivo.

Methods

We infected C57BL/6J mice with TMEV and monitored the development of acute behavioral seizures 0–7 days postinfection (dpi). Fecal samples were collected at 5–7 dpi and processed for 16S sequencing, and bioinformatics were performed with QIIME2. Finally, we conducted whole‐cell patch‐clamp recordings in cortical neurons to investigate the effect of exogenous S‐equol on cell intrinsic properties and neuronal hyperexcitability.

Results

We demonstrated that gut microbiota diversity is significantly altered in TMEV‐infected mice at 5–7 dpi, exhibiting separation in beta diversity in TMEV‐infected mice dependent on seizure phenotype, and lower abundance of genus Allobaculum in TMEV‐infected mice regardless of seizure phenotype. In contrast, we identified specific loss of S‐equol‐producing genus Adlercreutzia as a microbial hallmark of seizure phenotype following TMEV infection. Electrophysiological recordings indicated that exogenous S‐equol alters cortical neuronal physiology. We found that entorhinal cortex neurons are hyperexcitable in TMEV‐infected mice, and exogenous application of microbial‐derived S‐equol ameliorated this TMEV‐induced hyperexcitability.

Significance

Our study presents the first evidence of microbial‐derived metabolite S‐equol as a potential mechanism for alteration of TMEV‐induced neuronal excitability. These findings provide new insight for the novel role of S‐equol and the gut–brain axis in epilepsy treatment.

Neuroinflammation: A Signature or a Cause of Epilepsy?

Epilepsy can be both a primary pathology and a secondary effect of many neurological conditions. Many papers show that neuroinflammation is a product of epilepsy, and that in pathological conditions characterized by neuroinflammation, there is a higher probability to develop epilepsy. However, the bidirectional mechanism of the reciprocal interaction between epilepsy and neuroinflammation remains to be fully understood. Here, we attempt to explore and discuss the relationship between epilepsy and inflammation in some paradigmatic neurological and systemic disorders associated with epilepsy. In particular, we have chosen one representative form of epilepsy for each one of its actual known etiologies. A better understanding of the mechanistic link between neuroinflammation and epilepsy would be important to improve subject-based therapies, both for prophylaxis and for the treatment of epilepsy.

Evidences for a Role of Gut Microbiota in Pathogenesis and Management of Epilepsy

Epilepsy as a chronic neurological disorder is characterized by recurrent, unprovoked epileptic seizures. In about half of the people who suffer from epilepsy, the root cause of the disorder is unknown. In the other cases, different factors can cause the onset of epilepsy. In recent years, the role of gut microbiota has been recognized in many neurological disorders, including epilepsy. These data are based on studies of the gut microbiota–brain axis, a relationship starting by a dysbiosis followed by an alteration of brain functions. Interestingly, epileptic patients may show signs of dysbiosis, therefore the normalization of the gut microbiota may lead to improvement of epilepsy and to greater efficacy of anticonvulsant drugs. In this descriptive review, we analyze the evidences for the role of gut microbiota in epilepsy and hypothesize a mechanism of action of these microorganisms in the pathogenesis and treatment of the disease. Human studies revealed an increased prevalence of Firmicutes in patients with refractory epilepsy. Exposure to various compounds can change microbiota composition, decreasing or exacerbating epileptic seizures. These include antibiotics, epileptic drugs, probiotics and ketogenic diet. Finally, we hypothesize that physical activity may play a role in epilepsy through the modulation of the gut microbiota.

Does modern research validate the ancient wisdom of gut flora and brain connection? A literature review of gut dysbiosis in neurological and neurosurgical disorders over the last decade

The connection between gastrointestinal microbiota and the brain has been described in ancient medical texts and is now well established by research. It is a bidirectional communication which plays a critical role in regulating not only the gastrointestinal homeostasis but has also been linked to higher emotional and cognitive functions. Recent studies have sought to expand on this concept by providing concrete evidence of the influence of gut microbiome on a wide array of diseases and disorders of the central nervous system. This article reviews the most recent literature published on this subject, over the previous decade and aims to establish the role of a healthy gut microbiome and probiotics as an effective adjunct in health and management of diseases of the nervous system. A literature search on PubMed database was conducted using keywords including "gut brain-axis," "gut dysbiosis," "neuropsychiatric disorders," "neurodegenerative disorders," "probiotic," and "traumatic brain injury." The search was performed without any publication date restrictions. Both animal and human studies evaluating the role of gut dysbiosis on various neurological and neurosurgical diseases, published in peer-reviewed journals, were reviewed. Current studies do not provide conclusive evidence of a direct origin of CNS disorders from gut dysbiosis, but a possible modulatory role of gut microbiota in certain neurological disorders has been implicated. An understanding of this connection can aid in finding novel therapeutic strategies for the management of neurological disorders associated with memory dysfunctions and brain and spinal cord injuries.

Investigation of the association between imbalance of the intestinal flora and infantile spasms: a pilot case-control study

BACKGROUND

The intestinal flora (IF) regulates brain function via the neuroendocrine and neuroimmune systems and influences the development of several neuropsychiatric diseases, including epilepsy. Here, we investigated the specific relationship between the IF and infantile spasms (IS), a specific form of epilepsy.

METHODS

Twenty-three children suffering from IS were recruited from the Chinese PLA General Hospital. According to patient response to adrenocorticotropic hormone (ACTH) treatment, the cohort was subdivided into 2 groups: an ACTH-response group and an ACTH-no response (NR) group. A total of 21 healthy children were recruited as a control group (healthy controls: HCs) during the same time period. Fecal samples were collected from infants in the IS and HC groups, and the population of fecal microorganisms was analyzed by 16s ribosomal DNA sequencing. The α and β diversity of the fecal microflora was determined, and the relative abundance of each species was classified. Tax4Fun2 was used to analyze the metabolic pathways utilized by the microflora, and the Kyoto Encyclopedia of Genes and Genomes database was used to analyze differentially expressed genes and pathways.

RESULTS

No significant differences existed in α or β diversity when compared between the IS and HC groups, nor between the ACTH-response and ACTH-NR groups which were separated before and after ACTH treatment. Although there was no significant difference between the ACTH-response and ACTH-NR groups with respect to α diversity, there was a significant difference in β diversity. Compared with that of the HCs, the IF of the IS group featured lower proportions of Lactobacillus, Roseburia, and Lachnospira, and a higher proportion of Clostridium. In the IS group, the proportion of Staphylococcus in the IF was higher before treatment than after treatment. Compared with the ACTH-NR group, the ACTH-response group had reduced populations of Odoribacter, Phascolarctobacterium, Anaerotruncus, Mitsuakella, and Robinsoniella. However, an increase was observed in the population of Bifidobacterium. A significant difference was also identified between the IS and HC groups with regard to the expression levels of genes associated with lipoic acid synthesis.

CONCLUSIONS

Our analysis demonstrated that imbalance of the IF may be involved in the pathogenesis of IS and is related to response to ACTH. Regulating the composition of the IF may pave the way to developing a potential adjuvant therapy for patients with IS.

A comparison of the gut microbiota among adult patients with drug-responsive and drug-resistant epilepsy: An exploratory study

BACKGROUND

Approximately one-third of epilepsy patients suffer from drug-resistant epilepsy. The gut microbiome, which is the total genetic makeup of all of the total microbes inhabiting the gut, can affect the CNS through various mechanisms. However, there are only limited studies about the relationship between the gut microbiome and epilepsy. We investigated the composition and characteristics of the gut microbiota among adult patients who have drug-responsive and drug-resistant epilepsy.

METHODS

We prospectively included 44 adult epilepsy patients and classified them into drug-responsive and drug-resistant groups. We collected fecal samples for the next-generation sequencing analysis. We statistically estimated the bacterial differences and alpha and beta diversities in each category.

RESULTS

Although there was no difference in demographic factors between the drug-responsive and drug-resistant groups, there was a significant difference in the composition of the gut microbiota. While the relative abundance of Bacteroides finegoldii and Ruminococcus_g2 increased in the drug-responsive group, the relative abundance of Negativicutes, which belong to Firmicutes increased in the drug-resistant group. Bifidobacterium was relatively abundant in epilepsy patients with a normal electroencephalogram. There was no significant difference between the two groups in analyses of alpha and beta diversities.

CONCLUSIONS

We found a significant difference in the composition of the gut microbiota among adult patients with drug-responsive and drug-resistant epilepsy. Difference in gut microbiota can be used as a novel biomarker to predict prognosis and evaluate treatment response in epilepsy patients. In addition, modification of gut microbiome can be an effective treatment strategy for patient with drug-resistant epilepsy.

The gut microbiome in drug-resistant epilepsy

Drug-resistant epileptic patients make up approximately one-third of the global epilepsy population. The pathophysiology of drug resistance has not been fully elucidated; however, current evidence suggests intestinal dysbiosis, as a possible etiopathogenic factor. Ketogenic diet, whose effect is considered to be mediated by alteration of gut microbiota synthesis, has long been administered in patients with medically refractory seizures, with positive outcomes. In this review, we present data derived from clinical studies regarding alterations of gut microbiome profile in drug-resistant epileptic patients. We further attempt to describe the mechanisms through which the gut microbiome modification methods (including ketogenic diet, pre- or probiotic administration) improve drug-resistant epilepsy, by reporting findings from preclinical and clinical studies. A comprehensive search of the published literature on the PubMed, Embase, and Web of science databases was performed. Overall, the role of gut microbiome in drug-resistant epilepsy is an area which shows promise for the development of targeted therapeutic interventions. More research is required to confirm the results from preliminary studies, as well as safety and effectiveness of altering gut bacterial composition, through the above-mentioned methods.

Fecal Microbiota Transplantation: A New Therapeutic Attempt from the Gut to the Brain

Gut dysbacteriosis is closely related to various intestinal and extraintestinal diseases. Fecal microbiota transplantation (FMT) is a biological therapy that entails transferring the gut microbiota from healthy individuals to patients in order to reconstruct the intestinal microflora in the latter. It has been proved to be an effective treatment for recurrent Clostridium difficile infection. Studies show that the gut microbiota plays an important role in the pathophysiology of neurological and psychiatric disorders through the microbiota-gut-brain axis. Therefore, reconstruction of the healthy gut microbiota is a promising new strategy for treating cerebral diseases. We have reviewed the latest research on the role of gut microbiota in different nervous system diseases as well as FMT in the context of its application in neurological, psychiatric, and other nervous system-related diseases (Parkinson's disease, Alzheimer's disease, multiple sclerosis, epilepsy, autism spectrum disorder, bipolar disorder, hepatic encephalopathy, neuropathic pain, etc.).

First evidence of altered microbiota and intestinal damage and their link to absence epilepsy in a genetic animal model, the WAG/Rij rat

OBJECTIVE

A large number of studies have highlighted the important role of the gut microbiota in the pathophysiology of neurological disorders, suggesting that its manipulation might serve as a treatment strategy. We hypothesized that the gut microbiota participates in absence seizure development and maintenance in the WAG/Rij rat model and tested this hypothesis by evaluating potential gut microbiota and intestinal alterations in the model, as well as measuring the impact of microbiota manipulation using fecal microbiota transplantation (FMT).

METHODS

Initially, gut microbiota composition and intestinal histology of WAG/Rij rats (a well-recognized genetic model of absence epilepsy) were studied at 1, 4, and 8 months of age in comparison to nonepileptic Wistar rats. Subsequently, in a second set of experiments, at 6 months of age, untreated Wistar or WAG/Rij rats treated with ethosuximide (ETH) were used as gut microbiota donors for FMT in WAG/Rij rats, and electroencephalographic (EEG) recordings were obtained over 4 weeks. At the end of FMT, stool and gut samples were collected, absence seizures were measured on EEG recordings, and microbiota analysis and histopathological examinations were performed.

RESULTS

Gut microbiota analysis showed differences in beta diversity and specific phylotypes at all ages considered and significant variances in the Bacteroidetes/Firmicutes ratio between Wistar and WAG/Rij rats. FMT, from both Wistar and ETH-treated WAG/Rij donors to WAG/Rij rats, significantly decreased the number and duration of seizures. Histological results indicated that WAG/Rij rats were characterized by intestinal villi disruption and inflammatory infiltrates already at 1 month of age, before seizure occurrence; FMT partially restored intestinal morphology while also significantly modifying gut microbiota and concomitantly reducing absence seizures.

SIGNIFICANCE

Our results demonstrate for the first time that the gut microbiota is modified and contributes to seizure occurrence in a genetic animal model of absence epilepsy and that its manipulation may be a suitable therapeutic target for absence seizure management.

Clinical Management of Drug Resistant Epilepsy: A Review on Current Strategies

Drug resistant epilepsy (DRE) is defined as the persistence of seizures despite at least two syndrome-adapted antiseizure drugs (ASD) used at efficacious daily dose. Despite the increasing number of available ASD, about a third of patients with epilepsy still suffer from drug resistance. Several factors are associated with the risk of evolution to DRE in patients with newly diagnosed epilepsy, including epilepsy onset in the infancy, intellectual disability, symptomatic epilepsy and abnormal neurological exam. Pharmacological management often consists in ASD polytherapy. However, because quality of life is driven by several factors in patients with DRE, including the tolerability of the treatment, ASD management should try to optimize efficacy while anticipating the risks of drug-related adverse events. All patients with DRE should be evaluated at least once in a tertiary epilepsy center, especially to discuss eligibility for non-pharmacological therapies. This is of paramount importance in patients with drug resistant focal epilepsy in whom epilepsy surgery can result in long-term seizure freedom. Vagus nerve stimulation, deep brain stimulation or cortical stimulation can also improve seizure control. Lastly, considering the effect of DRE on psychologic status and social integration, comprehensive care adaptations are always needed in order to improve patients' quality of life.

Towards Tailored Gut Microbiome-Based and Dietary Interventions for Promoting the Development and Maintenance of a Healthy Brain

Mental health is determined by a complex interplay between the Neurological Exposome and the Human Genome. Multiple genetic and non-genetic (exposome) factors interact early in life, modulating the risk of developing the most common complex neurodevelopmental disorders (NDDs), with potential long-term consequences on health. To date, the understating of the precise etiology underpinning these neurological alterations, and their clinical management pose a challenge. The crucial role played by diet and gut microbiota in brain development and functioning would indicate that modulating the gut-brain axis may help protect against the onset and progression of mental-health disorders. Some nutritional deficiencies and gut microbiota alterations have been linked to NDDs, suggesting their potential pathogenic implications. In addition, certain dietary interventions have emerged as promising alternatives or adjuvant strategies for improving the management of particular NDDs, at least in particular subsets of subjects. The gut microbiota can be a key to mediating the effects of other exposome factors such as diet on mental health, and ongoing research in Psychiatry and Neuropediatrics is developing Precision Nutrition Models to classify subjects according to a diet response prediction based on specific individual features, including microbiome signatures. Here, we review current scientific evidence for the impact of early life environmental factors, including diet, on gut microbiota and neuro-development, emphasizing the potential long-term consequences on health; and also summarize the state of the art regarding the mechanisms underlying diet and gut microbiota influence on the brain-gut axis. Furthermore, we describe the evidence supporting the key role played by gut microbiota, diet and nutrition in neurodevelopment, as well as the effectiveness of certain dietary and microbiome-based interventions aimed at preventing or treating NDDs. Finally, we emphasize the need for further research to gain greater insight into the complex interplay between diet, gut microbiome and brain development. Such knowledge would help towards achieving tailored integrative treatments, including personalized nutrition.

Can change in gut microbiota composition be used as a surrogate marker of treatment efficacy of ketogenic diet in patients with drug-resistant epilepsy?

To answer the question posed in the title of the manuscript, we critically examined the connection between ketogenic diet (KD), gut microbiota (GM), and epilepsy. We conclude that although the evidence for a KD-GM-epilepsy link is fairly robust in rodent epilepsy models, it is very hard to draw meaningful conclusions in humans. The limitations of human studies that have investigated the KD-microbiota-epilepsy relationship include small sample size, a heterogeneous patient population with regard to age and epilepsy type, failure to account for the effect of dietary habits, antiseizure drugs (ASDs) and comedications on GM composition, variability in the KD administered and in the duration of the intervention, and different approaches used in sequencing the microbiome. Although alteration in the GM composition may be a potential indicator of responsiveness/resistance to a KD, we need well-designed randomized case-control and cohort studies involving a large number of a fairly homogenous population of patients with epilepsy adjusted to their habitual dietary habits and region of residence before labeling it as a surrogate marker. Research in this direction may also help us to unravel the mysteries of GM-brain axis not only concerning epilepsy but also in other neurological diseases.

Cross talk between drug-resistant epilepsy and the gut microbiome

One-third of epilepsy patients have drug-resistant epilepsy (DRE), which is often complicated by polydrug toxicity and psychiatric and cognitive comorbidities. Advances in understanding the microbiome and gut-brain-axis are likely to shed light on epilepsy pathogenesis, anti-seizure medication (ASM) resistance, and potential therapeutic targets. Gut dysbiosis is associated with inflammation, blood-brain barrier disruption, and altered neuromodulators. High-throughput and metagenomic sequencing has advanced the characterization of microbial species and functional pathways. DRE patients show altered gut microbiome composition compared to drug-sensitive patients and healthy controls. The ketogenic and modified Atkins diets can reduce seizures in some patients with DRE. These low-carbohydrate dietary therapies alter the taxonomic and functional composition of the gut microbiome, and composition varies between diet responders and nonresponders. Murine models suggest that specific phyla are necessary to confer efficacy from the diet, and antibiotic treatment may eliminate efficacy. The impact of diet might involve alterations in microbiota, promotion of select microbial interactions, and variance in brain neurotransmitter levels that then influence seizures. Understanding the mechanics of how diet manipulates seizures may suggest novel therapies. Most ASMs act on neuronal transmission via effects on ion channels and neurotransmitters. However, ASMs may also assert their effects via the gut microbiota. In animal models, the microbiota composition (eg, abundance of certain phyla) can vary with ASM active drug metabolites. Given the developing understanding of the gut microbiome in DRE, probiotics are another potential therapy. Probiotics alter the microbiota composition, and small studies suggest that these supplements can reduce seizures in some patients. DRE has enormous consequences to patients and society, and the gut microbiome holds promise as a potential therapeutic target. However, the exact mechanism and recognition of which patients are likely to be responders remain elusive. Further studies are warranted.

Nutrition, Microbiota and Role of Gut-Brain Axis in Subjects with Phenylketonuria (PKU): A Review

The composition and functioning of the gut microbiota, the complex population of microorganisms residing in the intestine, is strongly affected by endogenous and exogenous factors, among which diet is key. Important perturbations of the microbiota have been observed to contribute to disease risk, as in the case of neurological disorders, inflammatory bowel disease, obesity, diabetes, cardiovascular disease, among others. Although mechanisms are not fully clarified, nutrients interacting with the microbiota are thought to affect host metabolism, immune response or disrupt the protective functions of the intestinal barrier. Similarly, key intermediaries, whose presence may be strongly influenced by dietary habits, sustain the communication along the gut-brain-axis, influencing brain functions in the same way as the brain influences gut activity. Due to the role of diet in the modulation of the microbiota, its composition is of high interest in inherited errors of metabolism (IEMs) and may reveal an appealing therapeutic target. In IEMs, for example in phenylketonuria (PKU), since part of the therapeutic intervention is based on chronic or life-long tailored dietetic regimens, important variations of the microbial diversity or relative abundance have been observed. A holistic approach, including a healthy composition of the microbiota, is recommended to modulate host metabolism and affected neurological functions.

Physical exercise and seizure activity

Neuroprotective and antiepileptogenic therapies have been extensively investigated for epilepsy prevention and treatment. This review gives an overview of the promising contribution of the ketogenic diet, a complementary treatment, on the intestinal microbiota to reduce seizure susceptibility. Next, the relevance of physical exercise is extensively addressed as a complementary therapy to reduce seizure susceptibility, and thereby impact beneficially on the epilepsy condition. In this context, particular attention is given to the potential risks and benefits of physical exercise, possible precipitant factors related to exercise and proposed mechanisms by which exercise can reduce seizures, and its antiepileptogenic effects. Finally, this review points to emerging evidence of exercise reducing comorbidities from epilepsy and improving the quality of life of people with epilepsy. Based on evidence from current literature, physical or sport activities represent a potential non-pharmacological intervention that can be integrated with conventional therapy for epilepsy.

Evaluation of fecal Lactobacillus populations in dogs with idiopathic epilepsy: a pilot study

Background

Idiopathic epilepsy is a common neurological disorder of dogs characterized by recurrent seizures for which no underlying basis is identified other than a presumed genetic predisposition. The pathogenesis of the disorder remains poorly understood, but environmental factors are presumed to influence the course of disease. Within the growing body of research into the microbiota-gut-brain axis, considerable attention has focused on the protective role of Lactobacilli in the development and progression of neurological disease. Investigations into the association between the gut microbiome and epilepsy are in their infancy, but some preliminary findings support a role for Lactobacilli in drug resistant epilepsy. To date, there are no published studies evaluating the gut microbiome in dogs with epilepsy. This pilot study was undertaken to evaluate fecal Lactobacillus populations in dogs with idiopathic epilepsy compared to healthy dogs.

Results

Fecal samples were obtained from 13 pairs of dogs, consisting of a drug-naïve epileptic dog and a healthy dog from the same household and maintained on the same diet. Evaluation of large-scale microbial patterns based on 16S rRNA gene amplicon sequencing identified a household effect in the study population. Differential prevalence testing at the 16S rRNA gene sequence variant and genus levels did not identify any statistically significant differences between epileptic and control dogs. Quantitative PCR of Lactobacillus species isolated through culture revealed no statistically significant difference between the epileptic and control dogs (median concentration, 3.8 log₁₀ CFU/g feces and 4.6 log₁₀ CFU/g feces, respectively). Lactobacillus in culture was not killed by exposure to phenobarbital, potassium bromide, zonisamide, or levetiracetam.

Conclusions

This pilot study did not identify any difference in large-scale microbial patterns or relative or absolute abundance of Lactobacillus species in drug-naïve epileptic dogs compared to healthy dogs. Further studies are warranted to evaluate the role of the gut microbiome in disease progression and treatment response in dogs with epilepsy. Lactobacilli in culture were not killed or inhibited from growing when exposed to phenobarbital, potassium bromide, zonisamide or levetiracetam, suggesting that antiepileptic drug administration is less likely to be a confounding factor in future studies evaluating the role of Lactobacillus in epilepsy.

The potential role of interventions impacting on gut-microbiota in epilepsy

INTRODUCTION

The gut microbiota seems to be implicated in the functioning and development of basic physiological processes and might also influence central neural processes, through the microbiota-gut-brain (MGB) axis. Pre- and clinical studies support the role of the microbiome in seizure modulation and in the pathogenesis of epilepsy. Acting through different interventions (e.g. diet, supplementations, drugs) could perturb directly and indirectly the MGB axis. Investigating the effects of these interventions might possibly allow better understanding of epilepsy itself, identify biomarkers, or providing new therapeutic options.

AREAS COVERED

PubMed and Google Scholar searches were used to compile a list of relevant publications until January 2020, using data from preclinical studies and clinical trials and gut microbiome/microbiota projects. Furthermore, we evaluate the impact of the antiepileptic drugs on gut microbiota and the influence of intestinal alterations on seizures occurrence.

EXPERT OPINION

Investigating the MGB axis and the role of gut supplementation in epilepsy is challenging due to the numerous potential pathways and variables involved. Few studies have been performed so far and all have been limited making speculation still premature. Studies designed with the similar strictness of pharmaceutical drug development trials, performing taxa, and metabolomic analyses with standard methodologies are needed.

The Gut-Brain-Axis on the Manifestation of Depressive Symptoms in Epilepsy: An Evidence-Driven Hypothesis

Epilepsy is a severe neurological disorder involving 70 million people around the globe. Epilepsy-related neuropsychiatric comorbidities such as depression, which is the most common, is an additional factor that negatively impacts the living quality of epilepsy patients. There are many theories and complexities associated with both epilepsy and associated comorbidities, one of which is the gut-brain-axis influence. The gut microbiome is hypothesized to be linked with many neurological disorders; however, little conclusive evidence is available in this area. Thus, highlighting the role will create interest in researchers to conduct detailed research in comprehending the influence of gut-brain-axis in the manifestation of depressive symptoms in epilepsy. The hypothesis which is explored in this review is that the gut-brain-axis do play an important role in the genesis of epilepsy and associated depression. The correction of this dysbiosis might be beneficial in treating both epilepsy and related depression. This hypothesis is illustrated through extensive literature discussion, proposed experimental models, and its applicability in the field. There is indirect evidence which revealed some specific bacterial strains that might cause depression in epilepsy.

Fecal Microbiota Transplantation in Neurological Disorders

Background: Several studies suggested an important role of the gut microbiota in the pathophysiology of neurological disorders, implying that alteration of the gut microbiota might serve as a treatment strategy. Fecal microbiota transplantation (FMT) is currently the most effective gut microbiota intervention and an accepted treatment for recurrent Clostridioides difficile infections. To evaluate indications of FMT for patients with neurological disorders, we summarized the available literature on FMT. In addition, we provide suggestions for future directions.

Methods: In July 2019, five main databases were searched for studies and case descriptions on FMT in neurological disorders in humans or animal models. In addition, the ClinicalTrials.gov website was consulted for registered planned and ongoing trials.

Results: Of 541 identified studies, 34 were included in the analysis. Clinical trials with FMT have been performed in patients with autism spectrum disorder and showed beneficial effects on neurological symptoms. For multiple sclerosis and Parkinson's disease, several animal studies suggested a positive effect of FMT, supported by some human case reports. For epilepsy, Tourette syndrome, and diabetic neuropathy some studies suggested a beneficial effect of FMT, but evidence was restricted to case reports and limited numbers of animal studies. For stroke, Alzheimer's disease and Guillain-Barré syndrome only studies with animal models were identified. These studies suggested a potential beneficial effect of healthy donor FMT. In contrast, one study with an animal model for stroke showed increased mortality after FMT. For Guillain-Barré only one study was identified. Whether positive findings from animal studies can be confirmed in the treatment of human diseases awaits to be seen. Several trials with FMT as treatment for the above mentioned neurological disorders are planned or ongoing, as well as for amyotrophic lateral sclerosis.

Conclusions: Preliminary literature suggests that FMT may be a promising treatment option for several neurological disorders. However, available evidence is still scanty and some contrasting results were observed. A limited number of studies in humans have been performed or are ongoing, while for some disorders only animal experiments have been conducted. Large double-blinded randomized controlled trials are needed to further elucidate the effect of FMT in neurological disorders.

Probiotics and Nigella sativa extract supplementation improved behavioral and electrophysiological effects of PTZ-induced chemical kindling in rats

INTRODUCTION

Epilepsy is a most common neurological disorder that has negative effects on cognition. In the present study, we investigated the protective effect of Nigella sativa (NS) and probiotics on seizure activity, cognitive performance, and synaptic plasticity in pentylenetetrazole (PTZ) kindling model of epilepsy.

METHODS

One hundred and forty-four rats were divided into 2 experiments: In experiment 1, animals were grouped and treated as follows: 1) control (PTZ + saline), 2) NS treatment, 3) probiotic treatment, and 4) NS and probiotic treatment. Six weeks after the treatment, PTZ kindling were performed, and 48 h after kindling, spatial learning and memory were measured in Morris water maze (MWM) test. Animals in experiment 2 received the same treatment as experiment 1: in control nonkindled groups, control animals were treated with probiotics, NS, and probiotics + NS. Six weeks after the treatment, PTZ kindling were performed, and 48 h after kindling, field potentials were recorded from the dentate gyrus area of the hippocampus; synaptic transmission and long-term potentiation (LTP) was measured.

RESULTS

The results showed that the probiotic and NS supplementation significantly reduces kindling development so that animals in PTZ + NS + probiotic did not show full kindling. In MWM test, the escape latency and traveled path in the kindled group were significantly higher than the control group. In PTZ + NS + probiotics, these parameters were significantly lower than those in the PTZ + saline group. Adding probiotic and NS supplementation significantly reduced population spike (PS)-LTP as compared with the PTZ + saline group.

CONCLUSION

Probiotic and NS supplementation have some protection against seizure, seizure-induced cognitive impairment, and hippocampal LTP in kindled rats.

Emerging roles for the intestinal microbiome in epilepsy

The gut microbiome is emerging as a key regulator of brain function and behavior and is associated with symptoms of several neurological disorders. There is emerging evidence that alterations in the gut microbiota are seen in epilepsy and in response to seizure interventions. In this review, we highlight recent studies reporting that individuals with refractory epilepsy exhibit altered composition of the gut microbiota. We further discuss antibiotic treatment and infection as microbiome-related factors that influence seizure susceptibility in humans and animal models. In addition, we evaluate how the microbiome may mediate effects of the ketogenic diet, probiotic treatment, and anti-epileptic drugs on reducing both seizure frequency and severity. Finally, we assess the open questions in interrogating roles for the microbiome in epilepsy and address the prospect that continued research may uncover fundamental insights for understanding risk factors for epilepsy, as well as novel approaches for treating refractory epilepsy.

Can we 'seize' the gut microbiota to treat epilepsy?

The gut-microbiota, the complex intestinal microbial ecosystem essential to health, is an emerging concept in medicine. Several studies demonstrate a microbiota-gut-brain bidirectional connection via neural, endocrine, metabolic and immune pathways. Accordingly, the gut microbiota has a crucial role in modulating intestinal permeability, to alter local/peripheral immune responses and in production of essential metabolites and neurotransmitters. Its alterations may consequently influence all these pathways that contribute to neuronal hyper-excitability and mirrored neuroinflammation in epilepsy and similarly other neurological conditions. Indeed, pre- and clinical studies support the role of the microbiome in pathogenesis, seizure modulation and responses to treatment in epilepsy. Up to now, researchers have focussed attention above all on the brain to develop antiepileptic treatments, but considering the microbiome, could extend our possibilities for developing novel therapies in the future. We provide here a comprehensive overview of the available data on the potential role of gut microbiota in the physiopathology and therapy of epilepsy and the supposed underlying mechanisms.

Rett Syndrome and Other Neurodevelopmental Disorders Share Common Changes in Gut Microbial Community: A Descriptive Review

In this narrative review, we summarize recent pieces of evidence of the role of microbiota alterations in Rett syndrome (RTT). Neurological problems are prominent features of the syndrome, but the pathogenic mechanisms modulating its severity are still poorly understood. Gut microbiota was recently demonstrated to be altered both in animal models and humans with different neurodevelopmental disorders and/or epilepsy. By investigating gut microbiota in RTT cohorts, a less rich microbial community was identified which was associated with alterations of fecal microbial short-chain fatty acids. These changes were positively correlated with severe clinical outcomes. Indeed, microbial metabolites can play a crucial role both locally and systemically, having dynamic effects on host metabolism and gene expression in many organs. Similar alterations were found in patients with autism and down syndrome as well, suggesting a potential common pathway of gut microbiota involvement in neurodevelopmental disorders.

Microbiota-gut brain axis involvement in neuropsychiatric disorders

Introduction: The microbiota-gut brain (MGB) axis is the bidirectional communication between the intestinal microbiota and the brain. An increasing body of preclinical and clinical evidence has revealed that the gut microbial ecosystem can affect neuropsychiatric health. However, there is still a need of further studies to elucidate the complex gene-environment interactions and the role of the MGB axis in neuropsychiatric diseases, with the aim of identifying biomarkers and new therapeutic targets, to allow early diagnosis and improving treatments. Areas covered: To review the role of MGB axis in neuropsychiatric disorders, prediction and prevention of disease through exploitation, integration, and combination of data from existing gut microbiome/microbiota projects and appropriate other International '-Omics' studies. The authors also evaluated the new technological advances to investigate and modulate, through nutritional and other interventions, the gut microbiota. Expert opinion: The clinical studies have documented an association between alterations in gut microbiota composition and/or function, whereas the preclinical studies support a role for the gut microbiota in impacting behaviors which are of relevance to psychiatry and other central nervous system (CNS) disorders. Targeting MGB axis could be an additional approach for treating CNS disorders and all conditions in which alterations of the gut microbiota are involved.

Crosstalk between the Ketogenic Diet and Epilepsy: From the Perspective of Gut Microbiota

Given the association between a range of neurological disorders and changes in the gut microbiota, interest in the gut microbiota has recently increased. In particular, the significant involvement of the autoimmune processes in the development of epilepsy, one of the most serious and widespread neurological diseases, has led to a suggested link with the gut microbiome. Because the constitution of the gut microbiome can be influenced by diet, dietary therapy has been shown to have a positive impact on a wide range of conditions via alteration of the gut microbiota. An example of one such diet is the ketogenic diet (KD), which promotes a diet that contains high levels of fat, adequate levels of protein, and low levels of carbohydrate. Due to the near-total elimination of carbohydrates from the individual's food in this ultra-high-fat diet, ketone bodies become an important source of energy. Although the ketogenic diet has proven successful in the treatment of refractory epilepsy and other illnesses, the underlying mechanisms of its neuroprotective effects have yet to be fully elucidated. Nevertheless, recent studies strongly indicate a role for the gut microbiota in the effective treatment of epilepsy with the ketogenic diet. The latest advances regarding the links between the ketogenic diet, gut microbiota, and epilepsy are reviewed in this article, with a particular focus on the role of the gut microbiota in the treatment outcome.