The microbiome-gut-brain axis in epilepsy: pharmacotherapeutic target from bench evidence for potential bedside applications

Unraveling the nutritional challenges in epilepsy: Risks, deficiencies, and management strategies: A systematic review

BACKGROUND

Malnutrition and epilepsy share a complex bidirectional relationship, with malnutrition serving as a potential risk factor for epilepsy development, while epilepsy, in turn, often exerts profound effects on nutritional status. Nutritional interventions have emerged as a critical adjunctive approach in epilepsy management.

AIM

To explore the multifaceted associations between malnutrition and epilepsy, structured into three primary sections: (1) Elucidating the impact of malnutrition as a risk factor for epilepsy onset; (2) Examining the reciprocal influence of epilepsy on nutritional status, and (3) Evaluating diverse nutritional interventions in the management of epilepsy.

METHODS

A systematic search was conducted across PubMed, Scopus, and Web of Science databases utilizing defined keywords related to malnutrition, epilepsy, and nutritional interventions. Inclusion criteria encompassed various study types, including clinical trials, animal models, cohort studies, case reports, meta-analyses, systematic reviews, guidelines, editorials, and review articles. Four hundred sixteen pertinent references were identified, with 198 review articles, 153 research studies, 21 case reports, 24 meta-analyses, 14 systematic reviews, 4 guidelines, and 2 editorials meeting the predefined criteria.

RESULTS

The review revealed the intricate interplay between malnutrition and epilepsy, highlighting malnutrition as a potential risk factor in epilepsy development and elucidating how epilepsy often leads to nutritional deficiencies. Findings underscored the importance of nutritional interventions in managing epilepsy, showing their impact on seizure frequency, neuronal function, and overall brain health.

CONCLUSION

This systematic review emphasizes the bidirectional relationship between malnutrition and epilepsy while emphasizing the critical role of nutritional management in epilepsy treatment. The multifaceted insights underscore the need for a holistic approach to addressing nutritional aspects alongside conventional epilepsy management strategies.

Impact of Oxidative Stress and Neuroinflammation on Sarco/Endoplasmic Reticulum Ca2+-ATPase 2b Downregulation and Endoplasmic Reticulum Stress in Temporal Lobe Epilepsy

Epilepsy is one of the most common neurological disorders. Calcium dysregulation and neuroinflammation are essential and common mechanisms in epileptogenesis. Sarco/endoplasmic reticulum (ER) Ca2+-ATPase 2b (SERCA2b), a crucial calcium regulatory pump, plays pathological roles in various calcium dysregulation-related diseases. However, the link between SERCA2b and neuroinflammation in epilepsy remains undetermined. This study aimed to establish the relationship between SERCA2b, oxidative stress, and neuroinflammation in epilepsy to elucidate the underlying molecular mechanism in epileptogenesis. Neuroinflammation and oxidative stress were induced in N2a cells using lipopolysaccharide (LPS) and hydrogen peroxide (H2O2). However, experimental temporal lobe epilepsy (TLE) was induced in mice using pilocarpine. Further, effects of oxidative stress and neuroinflammation on SERCA2b and ER stress markers were assessed at protein and mRNA levels. Calcium imaging was employed to determine intracellular calcium levels. SERCA2b expression significantly decreased after LPS, H2O2, and pilocarpine exposure at both mRNA and protein levels, mediated by upregulating neuroinflammation. This downregulation of SERCA2b was associated with increased production of reactive oxygen species and elevated intracellular calcium levels, leading to elevated ER stress markers. Our findings highlight a link between oxidative stress, neuroinflammation and SERCA2b in TLE. The results suggest that targeting SERCA2b could restore calcium homeostasis and ER stress processes, potentially providing a therapeutic option for TLE. This study underscores the importance of SERCA2b in the pathophysiology of epilepsy and its potential as a therapeutic target.

Gut-microbiota-brain Axis and post-traumatic epilepsy

There has been growing evidence that perturbations in gut-microbiota-brain axis (GMBA) are involved in mechanisms of chronic sequelae of traumatic brain injury (TBI). This review discusses the connection between GMBA and post-traumatic epilepsy (PTE), the latter being a common outcome of TBI. The focus is on two aspects of post-TBI GMBA dysfunction that are relevant to epilepsy. First are impairments in intestinal permeability with subsequent translocation of gut bacteria into the bloodstream. Specifically, endotoxemia following TBI may have a serendipitous protective effect against PTE through lipopolysaccharide conditioning, which may be leveraged for the development of therapeutic interventions. Second are changes in microbial composition (i.e., dysbiosis). Here, the GMBA-PTE connection is explored from predictive biomarker perspective, whereby the risk of PTE can be stratified based on specific microbial profiles. Finally, microbiota transplantation is discussed both as a tool to examine the role of gut microbiota in PTE and as a prelude to novel approaches for PTE therapy and prevention.

A Comprehensive Overview of the Current Status and Advancements in Various Treatment Strategies against Epilepsy

Epilepsy affects more than 70 million individuals of all ages worldwide and remains one of the most severe chronic noncommunicable neurological diseases globally. Several neurotransmitters, membrane protein channels, receptors, enzymes, and, more recently noted, various pathways, such as inflammatory and mTORC complexes, play significant roles in the initiation and propagation of seizures. Over the past two decades, significant developments have been made in the diagnosis and treatment of epilepsy. Various pharmacological drugs with diverse mechanisms of action and other treatment options have been developed to control seizures and treat epilepsy. These options include surgical treatment, nanomedicine, gene therapy, natural products, nervous stimulation, a ketogenic diet, gut microbiota, etc., which are in various developmental stages. Despite a plethora of drugs and other treatment options, one-third of affected individuals are resistant to current medications, while the majority of approved drugs have severe side effects, and significant changes can occur, such as pharmacoresistance, effects on cognition, long-term problems, drug interactions, risks of poor adherence, specific effects for certain medications, and psychological complications. Therefore, the development of new drugs and other treatment options that have no or minimal adverse effects is needed to combat this deadly disease. In this Review, we comprehensively summarize and explain all of the treatment options that have been approved or are in developmental stages for epilepsy as well as their status in clinical trials and advancements.

Role of Human Milk Microbiota in Infant Neurodevelopment: Mechanisms and Clinical Implications

BACKGROUND

Human milk (HM) is recognized as an ideal source of nutrition for newborns; as a result, its multiple bioactive molecules can support the growth of healthy newborns and reduce the risk of mortality and diseases such as asthma, respiratory infections, diabetes (type 1 and 2), and gastrointestinal disorders such as ulcerative colitis and Crohn's disease. Furthermore, it can reduce the severity of necrotizing enterocolitis (NEC) in preterm infants. Moreover, human milk oligosaccharides (HMOs) present in breast milk show an immunomodulatory, prebiotic, and neurodevelopmental effect that supports the microbiota-gut-brain axis.

MATERIAL AND METHODS

This study examined the state-of-the-art research, using keywords such as "breastfeeding", "human milk oligosaccharides", "microbiota-gut-brain axis", "infants", and "malnutrition". The literature review was conducted by selecting articles between 2013 and 2024, as the most recent ones. The databases used were Web Science, PubMed, and Scopus.

RESULTS

We found multiple studies examining the composition of HM and infant formula (IF). However, further longitudinal studies and randomized control trials (RCTs) are needed to better understand the clinical outcomes that bioactive components exert on healthy and hospitalized children and how, in conditions of malnutrition, it is necessary to support the growth of the newborn.

CONCLUSIONS

In this review, we affirm the importance of human milk and, through it, the modulation of the microbiota and the neuroprotective role in newborns, determining the health of the following years of life.

Diet composition and sterilization modifies intestinal microbiome diversity and burden of Theiler's virus infection-induced acute seizures

OBJECTIVE

Brain infection with Theiler's murine encephalomyelitis virus (TMEV) in C57BL/6J mice can induce acquired epileptogenesis. Diet alters acute seizure incidence in TMEV-infected mice; yet it is unclear whether intestinal dysbiosis may also impact acute or chronic behavioral comorbidities. This study thus assessed the impact of diet formulation and sterilization on acute seizure presentation, gut microbiome composition, and epilepsy-related chronic behavioral comorbidities.

METHODS

Baseline fecal samples were collected from male C57BL/6J mice (4- to 5-weeks-old; Jackson Labs) upon facility arrival. Mice were randomized to either autoclaved (AC) or irradiated diet (IR) (Prolab RMH 3000) or IR (Picolab 5053). Three days later, mice underwent intracerebral TMEV or phosphate-buffered saline (PBS) injection. Fecal samples were collected from a subset of mice at infection (Day 0) and Day 7 post-infection. Epilepsy-related working memory deficits and seizure threshold were assessed 6 weeks post-infection. Gut microbiome diversity was determined by 16S rRNA amplicon sequencing of fecal samples.

RESULTS

TMEV-infected mice displayed acute handling-induced seizures, regardless of diet: 28 of 57 IR Picolab 5053 (49.1%), 30 of 41 IR Prolab RMH 3000 (73.2%), and 47 of 77 AC Prolab RMH 3000 (61%) mice displayed seizures. The number of observed seizures differed significantly by diet: IR Picolab 5053 diet-fed mice had 2.2 ± 2.8 seizures (mean ± standard deviation), IR Prolab RMH 3000 diet-fed mice had 3.5 ± 2.9 seizures, and AC Prolab RMH 3000 diet-fed mice had 4.4 ± 3.8 seizures during the 7-day monitoring period. Gut microbiome composition differed significantly in TMEV-infected mice fed the AC Prolab RMH 3000 diet, with measured differences in gram-positive bacteria. These mice also displayed worsened long-term working memory deficits.

SIGNIFICANCE

Diet-induced differences in intestinal dysbiosis in the TMEV model are associated with marked changes in acute seizure presentation, symptomatic recovery, and onset of chronic behavioral comorbidities of epilepsy. Our study reveals a novel disease-modifying impact of dietary manipulation on intestinal bacterial species after TMEV-induced acute seizures.

Effect of dietary supplementation with Lactobacillus helveticus R0052 on seizure thresholds and antiseizure potency of sodium valproate in mice

OBJECTIVE

Both animal and human studies, though limited, showed that multi-strain probiotic supplementation may reduce the number of seizures and/or seizure severity. Here, we evaluated the effect of a single strain probiotic supplementation on seizure susceptibility, antiseizure efficacy of sodium valproate, and several behavioral parameters in mice.

METHODS

Lactobacillus helveticus R0052 was given orally for 28 days. Its influence on seizure thresholds was evaluated in the ivPTZ- and electrically-induced seizure tests. The effect on the antiseizure potency of valproate was assessed in the scPTZ test. We also investigated the effects of probiotic supplementation on anxiety-related behavior (in the elevated plus maze and light/dark box tests), motor coordination (in the accelerating rotarod test), neuromuscular strength (in the grip-strength test), and spontaneous locomotor activity. Serum and brain concentrations of valproate as well as cecal contents of SCFAs and lactate were determined using HPLC method.

RESULTS

L. helveticus R0052 significantly increased the threshold for the 6 Hz-induced psychomotor seizure. There was also a slight increase in the threshold for myoclonic and clonic seizure in the ivPTZ test. L. helveticus R0052 did not affect the threshold for tonic seizures both in the maximal electroshock- and ivPTZ-induced seizure tests. No changes in the antiseizure potency of valproate against the PTZ-induced seizures were reported. Interestingly, L. helveticus R0052 increased valproate concentration in serum, but not in the brain. Moreover, L. helveticus R0052 did not produce any significant effects on anxiety-related behavior, motor coordination, neuromuscular strength, and locomotor activity. L. helveticus R0052 supplementation resulted in increased concentrations of total SCFAs, acetate, and butyrate.

CONCLUSIONS

Altogether, this study shows that a single-strain probiotic - L. helveticus R0052 may decrease seizure susceptibility and this effect can be mediated, at least in part, by increased production of SCFAs. In addition, L. helveticus R0052 may affect bioavailability of valproate, which warrants further investigations.

The interplay between microbiota and brain-gut axis in epilepsy treatment

The brain-gut axis plays a vital role in connecting the cognitive and emotional centers of the brain with the intricate workings of the intestines. An imbalance in the microbiota-mediated brain-gut axis extends far beyond conditions like Irritable Bowel Syndrome (IBS) and obesity, playing a critical role in the development and progression of various neurological disorders, including epilepsy, depression, Alzheimer's disease (AD), and Parkinson's disease (PD). Epilepsy, a brain disorder characterized by unprovoked seizures, affects approximately 50 million people worldwide. Accumulating evidence suggests that rebuilding the gut microbiota through interventions such as fecal microbiota transplantation, probiotics, and ketogenic diets (KD) can benefit drug-resistant epilepsy. The disturbances in the gut microbiota could contribute to the toxic side effects of antiepileptic drugs and the development of drug resistance in epilepsy patients. These findings imply the potential impact of the gut microbiota on epilepsy and suggest that interventions targeting the microbiota, such as the KD, hold promise for managing and treating epilepsy. However, the full extent of the importance of microbiota in epilepsy treatment is not yet fully understood, and many aspects of this field remain unclear. Therefore, this article aims to provide an overview of the clinical and animal evidence supporting the regulatory role of gut microbiota in epilepsy, and of potential pathways within the brain-gut axis that may be influenced by the gut microbiota in epilepsy. Furthermore, we will discuss the recent advancements in epilepsy treatment, including the KD, fecal microbiota transplantation, and antiseizure drugs, all from the perspective of the gut microbiota.

The Role of the Vagus Nerve in the Microbiome and Digestive System in Relation to Epilepsy

The Enteric Nervous System (ENS) is described as a division of the Peripheral Nervous System (PNS), located within the gut wall and it is formed by two main plexuses: the myenteric plexus (Auerbach's) and the submucosal plexus (Meissner's). The contribution of the ENS to the pathophysiology of various neurological diseases such as Parkinson's or Alzheimer's disease has been described in the literature, while some other studies have found a connection between epilepsy and the gastrointestinal tract. The above could be explained by cholinergic neurons and neurotransmission systems in the myenteric and submucosal plexuses, regulating the vagal excitability effect. It is also understandable, as the discharges arising in the amygdala are transmitted to the intestine through projections the dorsal motor nucleus of the vagus, giving rise to efferent fibers that stimulate the gastrointestinal tract and consequently the symptoms at this level. Therefore, this review's main objective is to argue in favor of the existing relationship of the ENS with the Central Nervous System (CNS) as a facilitator of epileptogenic or ictogenic mechanisms. The gut microbiota also participates in this interaction; however, it depends on many individual factors of each human being. The link between the ENS and the CNS is a poorly studied epileptogenic site with a big impact on one of the most prevalent neurological conditions such as epilepsy.

Diet composition and sterilization modifies intestinal microbiome diversity and burden of Theiler's virus infection-induced acute seizures

Objective

Central nervous system infection with Theiler's murine encephalomyelitis virus (TMEV) in C57BL/6J mice can model acquired epileptogenesis. Diet alters the acute seizure incidence in TMEV-infected mice; yet it is unclear whether intestinal dysbiosis may also impact acute or chronic behavioral comorbidities. This study thus assessed the impact of diet sterilization in a specific pathogen-free vivarium on acute seizure presentation, the composition of the gut microbiome, and chronic behavioral comorbidities of epilepsy.

Methods

Baseline fecal samples were collected from male C57BL/6J mice (4-5 weeks-old; Jackson Labs) upon arrival. Mice were randomized to either autoclaved (AC) or irradiated (IR) diet (Prolab RMH 3000 - UU diets) or IR (Picolab 5053 - UW IR diet). Mice then underwent intracerebral TMEV or PBS injection three days later. Fecal samples were collected from a subset of mice at infection (Day 0) and Day 7 post-infection. Epilepsy-related working memory deficits and seizure threshold were assessed 6 weeks post-infection. Gut microbiome diversity was determined by 16S rRNA amplicon sequencing of fecal samples.

Results

TMEV-infected mice displayed acute handling-induced seizures, regardless of diet: 28/57 UW IR (49.1%), 30/41 UU IR (73.2%), and 47/77 UU AC (61%) mice displayed seizures. The number of observed seizures significantly differed: UW IR mice had 2.2±2.8 seizures (mean±standard deviation), UU IR mice had 3.5±2.9 seizures, and UU AC mice had 4.4±3.8 seizures during the 7-day monitoring period. The composition of the gut microbiome significantly differed in TMEV-infected mice fed the UU AC diet, with most measured differences occurring in Gram-positive bacteria. TMEV-infected mice fed the UU AC diet displayed worsened chronic working memory.

Significance

Intestinal dysbiosis evokes stark differences in acute seizure presentation in the TMEV model and vastly influences the trajectory of post-TMEV infection-induced behavioral comorbidities of epilepsy. Our study reveals a novel disease-modifying contribution of intestinal bacterial species after TMEV-induced acute seizures.