The gut-brain axis and cognitive control: A role for the vagus nerve

Enterococcus faecalis Exerts Neuroprotective Effects via the Vagus Nerve in a Mouse Model of Parkinson's Disease

Parkinson's disease (PD) is a common neurodegenerative disease worldwide. Current treatment methods for PD are unable to halt disease progression. The gut microbiota contributes to the neurodevelopment of PD; however, the gut-brain connections and underlying neural bases that regulate this complex behavior are not yet clear. Enterococcus faecalis (EF) is a common commensal bacterium of the gut and a common pathogen associated with hospital-acquired infections. Here, we demonstrated the significant therapeutic effects of a non-pathogenic strain of EF (EF ATCC19433) on PD. In this study, we established a mouse model of PD by intraperitoneal injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). We found that EF treatment alleviated behavioral impairment, dopaminergic neuronal loss, blood-brain barrier damage, and neuroinflammation induced by MPTP in the mice. Additionally, 16S rRNA sequencing revealed that dysbiosis of PD-related microbial communities induced by MPTP was reversed by EF treatment. Moreover, EF treatment relieved gastrointestinal dysfunction in the mice. The therapeutic efficacy of EF in MPTP-induced PD mice is markedly diminished when the activity of EF is lost. Further mechanistic studies indicated that the neuroprotective effects of EF in PD were associated with the vagus nerve pathway. Following the surgical severance of the vagus nerve through subdiaphragmatic vagotomy, the protective effects of EF on PD were markedly diminished. Our study suggests that EF can alleviate neurofunctional impairments and gastrointestinal disorders associated with PD, indicating that gut-derived microbes influence brain function through the vagus nerve pathway.

The role of brain-liver-gut Axis in neurological disorders

In recent years, with the increasing volume of related research, it has become apparent that the liver and gut play important roles in the pathogenesis of neurological disorders. Considering the interactions among the brain, liver, and gut, the brain-liver-gut axis has been proposed and gradually recognized. In this article, we summarized the complex network of interactions within the brain-liver-gut axis, encompassing the vagus nerve, barrier permeability, immunity and inflammation, the blood-brain barrier, gut microbial metabolites, the gut barrier, neurotoxic metabolites, and beta-amyloid (Aβ) metabolism. We also elaborated on the impact of the brain-liver-gut axis on various neurological disorders. Furthermore, we outline several therapies aimed at modulating the brain-liver-gut axis, including antibiotics, probiotics and prebiotics, fecal microbiota transplantation (FMT), vagus nerve stimulation (VNS), and dietary interventions. The focus is on elucidating possible mechanisms underlying neurological disorders pathogenesis and identifying effective treatments that are based on our understanding of the brain-liver-gut axis.

Case Report: Peripheral combined central dual-target magnetic stimulation for non- motor symptoms of Parkinson's disease

This case report describes an innovative study using central combined vagus dual-target magnetic stimulation for treating non-motor symptoms of Parkinson's disease (PD). PD is a common neurodegenerative disease, and almost all PD patients experience varying degrees of non-motor symptoms. However, there aren't many targeted drugs for non-motor symptoms. Based on this clinical, we used left dorsolateral prefrontal cortex (DLPFC) and vagus nerve dual-target magnetic stimulation to treat PD non-motor symptoms. The choice of this combined stimulation method is based on the closed-loop rehabilitation theory of central-peripheral-central. Stimulation of DLPFC promoted the activation of brain functional areas and improved neuroplasticity, while stimulation of vagus nerve further enhanced the positive feedback and input to the central nervous system, forming a closed-loop information feedback, and synergically promoted the recovery of PD non-motor symptoms. The patient in this paper had non-motor symptoms such as constipation, short-term memory impairment, insomnia, depression, hallucinations. We had 10 sessions in total. The DLPFC stimulation was performed at 10Hz, 120% resting motor threshold (RMT) intensity, 1000 pulses per sequence for 10 minutes. The vagus nerve stimulation was performed at 10Hz, 100%RMT, with a total of 2000 pulses and a duration of 14 minutes. Assessment before treatment, after treatment, and at one month follow-up showed improvements in cognitive function, mood, and constipation symptoms. Therefore, we believe this treatment approach may represent a promising new option for treating non-motor symptoms of PD.

From Physiology to Psychiatry: Key role of vagal interoceptive pathways in emotional control

Interoception is the awareness of bodily sensations, conveyed by both hormonal and neural signals. The vagus nerve is the primary neural interoceptive conduit, responsible for transmitting information from peripheral organs to the brain. It is widely accepted that vagal signals are essential for purely physiological functions like blood pressure maintenance, or nutrient intake homeostasis. However, a growing body of evidence, taking advantage of new technological advances, suggests that the vagus nerve also orchestrates or tunes emotions. Disruption of vagal interoceptive feedback prevents normal emotional control in rodents. Importantly, accumulating evidence indicates that pathological disruption of vagal afferent signals also occurs in humans and may constitute an important risk factor for emotional disorders. Hence, alleviating vagal interoceptive deficits may constitute a new therapeutic avenue for neurotic and affective disorders. Considering the technical and safety challenges for direct stimulation of brain regions relevant to emotionality disorders, the vagus nerve offers a safer and more practical route of potentially achieving similar outcomes. Here we will highlight the earliest studies which examined the consequences of manipulations of the vagal afferent neurons on anxiety, fear, and mood, and integrate these older findings with new research investigating the necessity of vagal afferent neurons in mediating the anxiety or mood-altering effects of physiological signals. We will also discuss the evolutionary significance of vagal control over emotional states within the boundaries of "normal" physiology and conclude by discussing the challenges of engaging the vagal interoception as novel therapeutics in mental health disorders.

Gastric-filling ultrasonography to evaluate gastric motor function in patients long-term bedridden undergoing stroke

Objectives

Gastric motor dysfunction is a common symptom in patients with stroke, yet lacks objective evaluation methods. This study aimed to assess the feasibility of using gastric filling ultrasonography to evaluate gastric motor function in patients undergoing stroke, and to explore the relationship between gastric ultrasound indicators and clinical features.

Methods

We conducted a case-control study where all participants underwent a 60-minute ultrasound examination after consuming a 300 mL test meal. The cross-sectional area (CSA) of the gastric antrum was measured at four-time points: fasting for six to eight hours (T0), immediately after the test meal (T1), and at 30 (T30) and 60 (T60) minutes. Using CSA, we calculated the gastric emptying rate (GER) at T30 and T60 (GER30, GER60). Additionally, we measured the frequency (ACF) and amplitude (ACA) of antral contractions, as well as the motor index (MI). We compared these ultrasound parameters between the two groups and evaluated their correlation with clinical features such as bed rest time, consciousness level, albumin or hemoglobin levels.

Results

We recruited 37 stroke patients and 31 healthy controls. Stroke patients exhibited lower GER compared to controls, particularly evident at T30. Additionally, stroke patients showed significantly reduced ACA, ACF, and MI at T1 and T30, with ACA being the only measure showing statistical differences at T60. Correlation analysis revealed negative associations between ACA, GER30, GER60, MIT1 and bed rest time. For predicting anemia, GER30 had a cut-off of 31.52 (88% specificity, 50% sensitivity), while ACAT60's cut-off was 23.64 (76% specificity, 75% sensitivity).

Conclusion

Ultrasound measurement of gastric filling shows promise as a valuable screening tool for detecting reduced gastric motor function in patients with stroke.

Investigating the modulation of gastric sensations and disposition toward food with taVNS

Interoception, the perception of visceral sensations, is key for several survival functions, including those related to feeding behavior. Sensations of hunger and satiety are mediated by gastric signals transmitted via the vagus nerve to the Nucleus of Solitary Tract. Transcutaneous auricular vagus nerve stimulation (taVNS) has been shown to modulate brain-viscera communication and to impact interoceptive processing in the cardiac domain. Yet, its effect on gastric interoception remains unclear. The aim of this study was to investigate taVNS' modulatory effects on gastric interoception using the Water Load Test-II (WLT-II) and its impact on food-related dispositions through a disposition and willingness to eat task (DWET). Participants underwent active or sham taVNS while performing the WLT-II and DWET. Results showed no significant difference in gastric interoceptive accuracy and amount of water ingested between taVNS groups. However, we found a significant reduction in food liking after the fullness phase of the WLT-II in the active (vs sham) taVNS group, suggesting an influence of vagal activation in the inhibition of food enjoyment when satiated. These findings suggest that, while taVNS may not directly enhance gastric interoceptive accuracy at a conscious level, it influences food-related dispositions, likely by modulating the processing of gastric signals. Further research exploring the intricate relationship between vagal modulation, interoceptive abilities and eating behaviors is warranted to elucidate the underlying mechanisms and, possibly, develop targeted interventions for eating disorders.

The complex relationship between gut microbiota and Alzheimer's disease: A systematic review

Alzheimer's disease (AD) is a progressive, degenerative disorder of the central nervous system. Despite extensive research conducted on this disorder, its precise pathogenesis remains unclear. In recent years, the microbiota-gut-brain axis has attracted considerable attention within the field of AD. The gut microbiota communicates bidirectionally with the central nervous system through the gut-brain axis, and alterations in its structure and function can influence the progression of AD. Consequently, regulating the gut microbiota to mitigate the progression of AD has emerged as a novel therapeutic approach. Currently, numerous studies concentrate on the intrinsic relationship between the microbiota-gut-brain axis and AD. In this paper, we summarize the multifaceted role of the gut microbiota in AD and present detailed therapeutic strategies targeting the gut microbiota, including the treatment of AD with Traditional Chinese Medicine (TCM), which has garnered increasing attention in recent years. Finally, we discuss potential therapeutic strategies for modulating the gut microbiota to alleviate the progression of AD, the current challenges in this area of research, and provide an outlook on future research directions in this field.

Interaction of the Vagus Nerve and Serotonin in the Gut-Brain Axis

The gut-brain axis represents an important bidirectional communication network, with the vagus nerve acting as a central conduit for peripheral signals from the various gut organs to the central nervous system. Among the molecular mediators involved, serotonin (5-HT), synthesized predominantly by enterochromaffin cells in the gut, plays a pivotal role. Gut-derived serotonin activates vagal afferent fibers, transmitting signals to the nucleus tractus solitarius (NTS) and modulating serotonergic neurons in the dorsal raphe nucleus (DRN) as well as the norepinephrinergic neurons in the locus coeruleus (LC). This interaction influences emotional regulation, stress responses, and immune modulation. Emerging evidence also highlights the role of microbial metabolites, particularly short-chain fatty acids (SCFAs), in enhancing serotonin synthesis and vagal activity, thereby shaping gut-brain communication. This review synthesizes the current knowledge on serotonin signaling, vagal nerve pathways, and central autonomic regulation, with an emphasis on their implications for neuropsychiatric and gastrointestinal disorders. By elucidating these pathways, novel therapeutic strategies targeting the gut-brain axis may be developed to improve mental and physical health outcomes.

Beyond digestion: Exploring how the gut microbiota modulates human social behaviors

For a long time, traditional medicine has acknowledged the gut's impact on general health. Contemporary science substantiates this association through investigations of the gut microbiota, the extensive community of microorganisms inhabiting our gastrointestinal system. These microscopic residents considerably improve digestive processes, nutritional absorption, immunological function, and pathogen defense. Nevertheless, a variety of gastrointestinal and extra-intestinal disorders can result from dysbiosis, an imbalance of the microbial composition of the gut microbiota. A groundbreaking discovery is the gut-brain axis, a complex communication network that links the enteric and central nervous system (CNS). This bidirectional communication allows the brain to influence gut activities and vice versa, impacting mental health and mood disorders like anxiety and depression. The gut microbiota can influence this communication by creating neurotransmitters and short-chain fatty acids, among other biochemical processes. These factors may affect our mental state, our ability to regulate our emotions, and the hypothalamic-pituitary-adrenal (HPA) axis. This study aimed to explore the complex interrelationships between the brain and the gut microbiota. We also conducted a thorough examination of the existing understanding in the area of how microbiota affects social behaviors, including emotions, stress responses, and cognitive functions. We also explored the potential of interventions that focus on the connection between the gut and the brain, such as using probiotics to treat diseases of the CNS. This research opens up new possibilities for addressing mental health and neurological conditions in an innovative manner.

Gut-brain axis as a bridge in obesity and depression: Mechanistic exploration and therapeutic prospects

A recent study by Wang et al, published in the World Journal of Psychiatry, provided preventative and therapeutic strategies for the comorbidity of obesity and depression. The gut-brain axis, which acts as a two-way communication system between the gastrointestinal tract and the central nervous system, plays a pivotal role in the pathogenesis of these conditions. Evidence suggests that metabolic byproducts, such as short-chain fatty acids, lipopolysaccharide and bile acids, which are generated by the gut microbiota, along with neurotransmitters and inflammatory mediators within the gut-brain axis, modulate the host's metabolic processes, neuronal regulation, and immune responses through diverse mechanisms. The interaction between obesity and depression via the gut-brain axis involves disruptions in the gut microbiota balance, inflammatory immune responses, and alterations in the neuroendocrine system. Modulating the gut-brain axis, for example, through a ketogenic diet, the use of probiotics, and the supplementation of antioxidants, offers new remedial approaches for obesity and depression. Future research that explores the mechanisms of the gut-brain axis is needed to provide more evidence for clinical treatment.

Transcutaneous vagus nerve stimulation for Parkinson's disease: a systematic review and meta-analysis

Background

Transcutaneous vagus nerve stimulation (tVNS) has emerged as a novel noninvasive adjunct therapy for advanced Parkinson's disease (PD), yet no quantitative analysis had been conducted to assess its therapeutic effect.

Objectives

This review aimed to investigate the efficacy of tVNS on motor function, other potential clinical targets and its safety in various treatment conditions.

Methods

We searched six databases for randomized controlled trials (RCTs) that involved treating PD patients with tVNS. Primary outcome was motor functions, including severity of motor signs, functional mobility and balance, and gait parameters. Secondary outcomes were cognition, emotion, sleep related impairments, patient reported non-motor outcomes, and any adverse events. All outcomes were classified and analyzed according to the treatment duration and medication condition of an included study. Risk of bias was evaluated by referencing Cochrane risk of bias tool 1.0. Data was analyzed by Revman 5.4.

Results

6 RCTs with 176 PD patient were included. Several motor functions and non-motor functions measured during on-medication condition (severity of motor signs -0.48 [95% CI -0.93, -0.04], gait -0.48 [95% CI -0.85, -0.1], patients reported non-motor outcomes -0.4 [95% CI -0.78, -0.03]), improved significantly. However, verbal fluency, sleep-related impairment, and fatigue were negatively impacted by tVNS during on-medication condition. No distinct adverse events were reported.

Conclusion

tVNS is a relatively safe adjunct treatment for PD. It has small to moderate therapeutic effects on motor functions and may negatively impact on a few other outcomes. Quality level of the evidence is low and further research is warranted.

Systematic review registration

https://www.crd.york.ac.uk/prospero/#recordDetails, identifier CRD42024503322 (PROSPERO).

Body as First Teacher: The Role of Rhythmic Visceral Dynamics in Early Cognitive Development

Embodied cognition-the idea that mental states and processes should be understood in relation to one's bodily constitution and interactions with the world-remains a controversial topic within cognitive science. Recently, however, increasing interest in predictive processing theories among proponents and critics of embodiment alike has raised hopes of a reconciliation. This article sets out to appraise the unificatory potential of predictive processing, focusing in particular on embodied formulations of active inference. Our analysis suggests that most active-inference accounts invoke weak, potentially trivial conceptions of embodiment; those making stronger claims do so independently of the theoretical commitments of the active-inference framework. We argue that a more compelling version of embodied active inference can be motivated by adopting a diachronic perspective on the way rhythmic physiological activity shapes neural development in utero. According to this visceral afferent training hypothesis, early-emerging physiological processes are essential not only for supporting the biophysical development of neural structures but also for configuring the cognitive architecture those structures entail. Focusing in particular on the cardiovascular system, we propose three candidate mechanisms through which visceral afferent training might operate: (a) activity-dependent neuronal development, (b) periodic signal modeling, and (c) oscillatory network coordination.

IUPHAR themed review: The gut microbiome in schizophrenia

Gut microbial dysbiosis or altered gut microbial consortium, in schizophrenia suggests a pathogenic role through the gut-brain axis, influencing neuroinflammatory and neurotransmitter pathways critical to psychotic, affective, and cognitive symptoms. Paradoxically, conventional psychotropic interventions may exacerbate this dysbiosis, with antipsychotics, particularly olanzapine, demonstrating profound effects on microbial architecture through disruption of bacterial phyla ratios, diminished taxonomic diversity, and attenuated short-chain fatty acid synthesis. To address these challenges, novel therapeutic strategies targeting the gut microbiome, encompassing probiotic supplementation, prebiotic compounds, faecal microbiota transplantation, and rationalised co-pharmacotherapy, show promise in attenuating antipsychotic-induced metabolic disruptions while enhancing therapeutic efficacy. Harnessing such insights, precision medicine approaches promise to transform antipsychotic prescribing practices by identifying patients at risk of metabolic side effects based on their microbial profiles. This IUPHAR review collates the current literature landscape of the gut-brain axis and its intricate relationship with schizophrenia while advocating for integrating microbiome assessments and therapeutic management. Such a fundamental shift in proposing microbiome-informed psychotropic prescriptions to optimise therapeutic efficacy and reduce adverse metabolic impacts would align antipsychotic treatments with microbiome safety, prioritising 'gut-neutral' or gut-favourable drugs to safeguard long-term patient outcomes in schizophrenia therapy.

The emerging roles of neuroactive components produced by gut microbiota

BACKGROUND

As a multifunctional ecosystem, the human digestive system contains a complex network of microorganisms, collectively known as gut microbiota. This consortium composed of more than 1013 microorganisms and Firmicutes and Bacteroidetes are the dominant microbes. Gut microbiota is increasingly recognized for its critical role in physiological processes beyond digestion. Gut microbiota participates in a symbiotic relationship with the host and takes advantage of intestinal nutrients and mutually participates in the digestion of complex carbohydrates and maintaining intestinal functions.

METHOD AND RESULT

We reviewed the neuroactive components produced by gut microbiota. Interestingly, microbiota plays a crucial role in regulating the activity of the intestinal lymphatic system, regulation of the intestinal epithelial barrier, and maintaining the tolerance to food immunostimulating molecules. The gut-brain axis is a two-way communication pathway that links the gut microbiota to the central nervous system (CNS) and importantly is involved in neurodevelopment, cognition, emotion and synaptic transmissions. The connections between gut microbiota and CNS are via endocrine system, immune system and vagus nerve.

CONCLUSION

The gut microbiota produces common neurotransmitters and neuromodulators of the nervous system. These compounds play a role in neuronal functions, immune system regulation, gastrointestinal homeostasis, permeability of the blood brain barrier and other physiological processes. This review investigates the essential aspects of the neurotransmitters and neuromodulators produced by gut microbiota and their implications in health and disease.

Microglia and gut microbiota: A double-edged sword in Alzheimer's disease

The strong association between gut microbiota (GM) and brain functions such as mood, behaviour, and cognition has been well documented. Gut-brain axis is a unique bidirectional communication system between the gut and brain, in which gut microbes play essential role in maintaining various molecular and cellular processes. GM interacts with the brain through various pathways and processes including, metabolites, vagus nerve, HPA axis, endocrine system, and immune system to maintain brain homeostasis. GM dysbiosis, or an imbalance in GM, is associated with several neurological disorders, including anxiety, depression, and Alzheimer's disease (AD). Conversely, AD is sustained by microglia-mediated neuroinflammation and neurodegeneration. Further, GM and their products also affect microglia-mediated neuroinflammation and neurodegeneration. Despite the evidence connecting GM dysbiosis and AD progression, the involvement of GM in modulating microglia-mediated neuroinflammation in AD remains elusive. Importantly, deciphering the mechanism/s by which GM regulates microglia-dependent neuroinflammation may be helpful in devising potential therapeutic strategies to mitigate AD. Herein, we review the current evidence regarding the involvement of GM dysbiosis in microglia activation and neuroinflammation in AD. We also discuss the possible mechanisms through which GM influences the functioning of microglia and its implications for therapeutic intervention. Further, we explore the potential of microbiota-targeted interventions, such as prebiotics, probiotics, faecal microbiota transplantation, etc., as a novel therapeutic strategy to mitigate neuroinflammation and AD progression. By understanding and exploring the gut-brain axis, we aspire to revolutionize the treatment of neurodegenerative disorders, many of which share a common theme of microglia-mediated neuroinflammation and neurodegeneration.

Microbiota-gut-brain axis: Natural antidepressants molecular mechanism

BACKGROUND

Major depressive disorder (MDD) is a severe mental health condition characterized by persistent depression, impaired cognition, and reduced activity. Increasing evidence suggests that gut microbiota (GM) imbalance is closely linked to the emergence and advancement of MDD, highlighting the potential significance of regulating the "Microbiota-Gut-Brain" (MGB) axis to impact the development of MDD. Natural products (NPs), characterized by broad biological activities, low toxicity, and multi-target characteristics, offer unique advantages in antidepressant treatment by regulating MGB axis.

PURPOSE

This review was aimed to explore the intricate relationship between the GM and the brain, as well as host responses, and investigated the mechanisms underlying the MGB axis in MDD development. It also explored the pharmacological mechanisms by which NPs modulate MGB axis to exert antidepressant effects and addressed current research limitations. Additionally, it proposed new strategies for future preclinical and clinical applications in the MDD domain.

METHODS

To study the effects and mechanism by which NPs exert antidepressant effects through mediating the MGB axis, data were collected from Web of Science, PubMed, ScienceDirect from initial establishment to March 2024. NPs were classified and summarized by their mechanisms of action.

RESULTS

NPs, such as flavonoids,alkaloids,polysaccharides,saponins, terpenoids, can treat MDD by regulating the MGB axis. Its mechanism includes balancing GM, regulating metabolites and neurotransmitters such as SCAFs, 5-HT, BDNF, inhibiting neuroinflammation, improving neural plasticity, and increasing neurogenesis.

CONCLUSIONS

NPs display good antidepressant effects, and have potential value for clinical application in the prevention and treatment of MDD by regulating the MGB axis. However, in-depth study of the mechanisms by which antidepressant medications affect MGB axis will also require considerable effort in clinical and preclinical research, which is essential for the development of effective antidepressant treatments.

The role of gut-derived short-chain fatty acids in Parkinson's disease

The emerging function of short-chain fatty acids (SCFAs) in Parkinson's disease (PD) has been investigated in this article. SCFAs, which are generated via the fermentation of dietary fiber by gut microbiota, have been associated with dysfunction of the gut-brain axis and, neuroinflammation. These processes are integral to the development of PD. This article examines the potential therapeutic implications of SCFAs in the management of PD, encompassing their capacity to modulate gastrointestinal permeability, neuroinflammation, and neuronal survival, by conducting an extensive literature review. As a whole, this article emphasizes the potential therapeutic utility of SCFAs as targets for the management and treatment of PD.

Heart-Brain Axis: A Narrative Review of the Interaction between Depression and Arrhythmia

Arrhythmias and depression are recognized as diseases of the heart and brain, respectively, and both are major health threats that often co-occur with a bidirectional causal relationship. The autonomic nervous system (ANS) serves as a crucial component of the heart-brain axis (HBA) and the pathway of interoception. Cardiac activity can influence emotional states through ascending interoceptive pathways, while psychological stress can precipitate arrhythmias via the ANS. However, the HBA and interoception frameworks are often considered overly broad, and the precise mechanisms underlying the bidirectional relationship between depression and arrhythmias remain unclear. This narrative review aims to synthesize the existing literature, focusing on the pathological mechanisms of the ANS in depression and arrhythmia while integrating other potential mechanisms to detail heart-brain interactions. In the bidirectional communication between the heart and brain, we emphasize considering various internal factors such as genes, personality traits, stress, the endocrine system, inflammation, 5-hydroxytryptamine, and behavioral factors. Current research employs multidisciplinary knowledge to elucidate heart-brain relationships, and a deeper understanding of these interactions can help optimize clinical treatment strategies. From a broader perspective, this study emphasizes the importance of considering the body as a complex, interconnected system rather than treating organs in isolation. Investigating heart-brain interactions enhance our understanding of disease pathogenesis and advances medical science, ultimately improving human quality of life.

Cognitive and Emotional Effect of a Multi-species Probiotic Containing Lactobacillus rhamnosus and Bifidobacterium lactis in Healthy Older Adults: A Double-Blind Randomized Placebo-Controlled Crossover Trial

As the population ages, cognitive decline becomes more common. Strategies targeting the gut-brain axis using probiotics are emerging to achieve improvements in neuropsychiatric and neurological disorders. However, the beneficial role of probiotics on brain function in healthy older adults remains unclear. Our aim was to evaluate a multi-species probiotic formulation as a therapeutic approach to reduce emotional and cognitive decline associated with aging in healthy adults. A randomized double-blind placebo-controlled crossover trial was conducted. The study involved a 10-week intervention where participants consumed the assigned probiotic product daily, followed by a 4-week washout period before the second condition started. Cognitive function was assessed using the Mini-Mental State Examination (MMSE) and the Psychological Experiments Construction Language Test Battery. At the emotional level, the Beck Depression Inventory (BDI) and the State-Trait Anxiety Inventory (STAI) were used. Thirty-three participants, recruited between July 2020 and April 2022, ingested a multispecies probiotic (Lactobacillus rhamnosus and Bifidobacterium lactis). After the intervention, noticeable enhancements were observed in cognitive function (mean difference 1.90, 95% CI 1.09 to 2.70, p < 0.005), memory (mean difference 4.60, 95% CI 2.91 to 6.29, p < 0.005) by MMSE and digit task, and depressive symptoms (mean difference 4.09, 95% CI 1.70 to 6.48, p < 0.005) by BDI. Furthermore, there were significant improvements observed in planning and problem-solving skills, selective attention, cognitive flexibility, impulsivity, and inhibitory ability. Probiotics administration improved cognitive and emotional function in older adults. Limited research supports this, requiring more scientific evidence for probiotics as an effective therapy for cognitive decline. This study has been prospectively registered at ClinicalTrials.gov (NCT04828421; 2020/July/17).

The Phytoneuroendocrine System: Connecting Plants to Human Systems Biology

Traditional medicine, exemplified by systems such as Ayurveda, inherently adopts a holistic framework. This framework extends beyond mere consideration of the human body to encompass broader systems of health, integrating elements of nature, particularly plants. Over time, there has been a notable integration between traditional medical philosophies and modern scientific methodologies. This integration is evident in published works that blend these disciplines, resulting in the creation of innovative terminology, such as «Ayurnutrigenomics». Concurrently, the lexicon within medical science has evolved to highlight the connection of body systems, as illustrated by terms like «gut-brain axis», which emphasize the relationship between physiological and psychological factors. This integration of perspectives is further demonstrated by terms such as «psychoneuroendocrine» and «mind-heart-body», reflecting a holistic approach to health. Alongside the emergence of these novel terms, there has been a proliferation of literature exploring the diverse functions of plants, particularly focusing on phytonutrients such as those found in the polyphenol category of compounds. In many ways, these emerging findings suggest a fundamental relationship between humans and plants, aligning with the principles of traditional medicine and indicating a profound connection between the two. Thus, in harmony with the increasing recognition of the interconnectedness between human systems biology, the study of phytochemicals, and the ability of plants to influence neuroendocrine responses, this article proposes a new term: the phytoneuroendocrine system.

Transcutaneous vagus nerve stimulation: a new strategy for Alzheimer's disease intervention through the brain-gut-microbiota axis?

Transcutaneous vagus nerve stimulation (tVNS) is an emerging non-invasive technique designed to stimulate branches of the vagus nerve distributed over the body surface. Studies suggest a correlation between the brain-gut-microbiota (BGM) axis and the pathogenesis of Alzheimer's disease (AD). The BGM axis represents a complex bidirectional communication system, with the vagus nerve being a crucial component. Therefore, non-invasive electrical stimulation of the vagus nerve might have the potential to modify-most of the time probably in a non-physiological way-the signal transmission within the BGM axis, potentially influencing the progression or symptoms of AD. This review explores the interaction between percutaneous vagus nerve stimulation and the BGM axis, emphasizing its potential effects on AD. It examines various aspects, such as specific brain regions, gut microbiota composition, maintenance of intestinal environmental homeostasis, inflammatory responses, brain plasticity, and hypothalamic-pituitary-adrenal (HPA) axis regulation. The review suggests that tVNS could serve as an effective strategy to modulate the BGM axis and potentially intervene in the progression or treatment of Alzheimer's disease in the future.

Gut microbiota and metabolite variations in a migraine mouse model

Migraine is a prevalent clinical disorder characterized by recurrent unilateral throbbing headache episodes accompanied by symptoms such as nausea, vomiting, photophobia, and phonophobia. Despite its common occurrence, the diagnosis, pathophysiology, and treatment of migraine remain controversial. Extensive research has implicated the gut microbiota in various central nervous system disorders, including anxiety disorders, depression, and Parkinson's disease. Some studies have also suggested that migraine may stem from disruptions to neurohormones and metabolism. This study aimed to investigate the disparities in gut microbiota and metabolites between migraine mice model and normal mice to shed light on the underlying mechanisms and potential therapeutic approaches. Distinct differences in gut microbial composition were observed between the migraine mouse model and normal mouse, indicating a potential correlation between these variations and the pathogenesis of migraine. This study provides evidence of differences in gut microbiota composition and metabolites between a migraine mouse model and normal mice, which showed that Akkermansiaceae constituted the most abundant taxon in the sham injection mouse group, while Lachnospiraceae constituted the most prevalent group in the migraine mouse model group. The associations between the abundances of Akkermansia muciniphila and Lachnospiraceae bacteria and metabolites suggested their potential roles in the pathogenesis of migraine. The altered abundance of Lachnospiraceae observed in migraine-afflicted mice and its correlations with changes in metabolites suggest that it may affect the host's health. Thus, probiotic therapy emerges as a possible treatment for migraine. Moreover, significant disparities in gut metabolites were observed between the migraine mouse model and normal mice. These alterations encompass multiple metabolic pathways, suggesting that metabolic disturbances may also contribute to the development of migraines.

Insular dysfunction of interoception in major depressive disorder: from the perspective of neuroimaging

Interoception plays a crucial role in maintaining bodily homeostasis and promoting survival, and is considered the basis of human emotion, cognition, and self-formation. A malfunction of interoception is increasingly suggested to be a fundamental component of different mental health conditions, and depressive disorders have been especially closely associated. Interoceptive signaling and processing depends on a system called the "interoceptive pathway," with the insula, located in the deep part of the lateral fissure, being the most important brain structure in this pathway. Neuroimaging studies have revealed alterations in the structure and function of the insula in a large number of individuals with depression, yet the precise relationship between these alterations and interoceptive dysfunction remains unclear. The goal of this review is to examine the evidence that exists for dysfunction of interoception in people with Major Depressive Disorder (MDD), and to determine the associated specific alterations in the structure and function of the insula revealed by neuroimaging. Overall, three aspects of the potential relationship between interoceptive dysfunction and alterations in insular function in people with depression have been assessed, namely clinical symptoms, quantitative measures of interoceptive function and ability, and interoceptive modulation. To conclude, several specific limitations of the published studies and important lines of enquiry for future research are offered.

Influence of Food Type on Human Psychological-Behavioral Responses and Crime Reduction

The purpose of this narrative review is to emphasize the importance of food consumption and meal selection on mental health and brain function, including psychological and behavioral reactions such as mood, loving relationships, violence, and criminal activity. Additionally, by being aware of the link between food and mental health, the community can be encouraged to make informed food choices in order to avoid unfavorable outcomes like criminality. Food behaviors are shifting significantly over the world. There are also significant changes in mood, sadness, happiness, and violence, as well as the spread of the variety and severity of mental diseases that lead to violent acts. Food intake and meal selection have evolved over the last ten years as the variety and accessibility of food options have become easier and more diverse. These modifications might have both beneficial and bad consequences. This article examines the relationship between food intake and its impact on marital satisfaction. The goal of this review is to support or refute the claim that food influences mood, love, or criminal behavior, or vice versa. Various diets can have an impact on one's mental health and brain, influencing psychological reactions and behavioral responses such as mood, loving relationships, violence, and even criminal activity. Food insecurity has been demonstrated in various studies to have a negative impact on health and psychological well-being, leading to despair, loss of happiness, marital conflict, and violence. For example, herbal extracts and flavonoids have the potential to improve gut microbiota and treat mood disorders. Understanding how the gut-brain axis communicates might help guide interventions for mood and cognitive function. Since the root of most diseases and behaviors is significantly related to the type of food consumed, this research addresses this issue in order to reduce the cost of treatment and prevention of crime and delinquency at the community level by consciously choosing the food consumed by the society. In other words, prevention is always better than cure.

Neuroimmunomodulation of vagus nerve stimulation and the therapeutic implications

Vagus nerve stimulation (VNS) is a technology that provides electrical stimulation to the cervical vagus nerve and can be applied in the treatment of a wide variety of neuropsychiatric and systemic diseases. VNS exerts its effect by stimulating vagal afferent and efferent fibers, which project upward to the brainstem nuclei and the relayed circuits and downward to the internal organs to influence the autonomic, neuroendocrine, and neuroimmunology systems. The neuroimmunomodulation effect of VNS is mediated through the cholinergic anti-inflammatory pathway that regulates immune cells and decreases pro-inflammatory cytokines. Traditional and non-invasive VNS have Food and Drug Administration (FDA)-approved indications for patients with drug-refractory epilepsy, treatment-refractory major depressive disorders, and headaches. The number of clinical trials and translational studies that explore the therapeutic potentials and mechanisms of VNS is increasing. In this review, we first introduced the anatomical and physiological bases of the vagus nerve and the immunomodulating functions of VNS. We covered studies that investigated the mechanisms of VNS and its therapeutic implications for a spectrum of brain disorders and systemic diseases in the context of neuroimmunomodulation.

Possible Signaling Pathways in the Gut Microbiota-Brain Axis for the Development of Parkinson's Disease Caused by Chronic Consumption of Food Additives

It is well-known that consumption of synthetic and natural food additives has both positive and negative effects in the human body. However, it is not clear yet how food additives are related to the development of Parkinson's disease. Therefore, in this review work, the food additive effects related to the gut microbiota-brain axis and the processes that are carried out to develop Parkinson's disease are studied. To this end, a systematic literature analysis is performed with the selected keywords and the food additive effects are studied to draw possible routes of action. This analysis leads to the proposition of a model that explains the pathways that relate the ingestion of food additives to the development of Parkinson's disease. This work motivates further research that ponders the safety of food additives by measuring their impacts over the gut microbiota-brain axis.

Probiotics for the treatment of depression and its comorbidities: A systemic review

Depression is one of the most common psychiatric conditions, characterized by significant and persistent depressed mood and diminished interest, and often coexists with various comorbidities. The underlying mechanism of depression remain elusive, evidenced by the lack of an appreciate therapy. Recent abundant clinical trials and animal studies support the new notion that the gut microbiota has emerged as a novel actor in the pathophysiology of depression, which partakes in bidirectional communication between the gut and the brain through the neuroendocrine, nervous, and immune signaling pathways, collectively known as the microbiota-gut-brain (MGB) axis. Alterations in the gut microbiota can trigger the changes in neurotransmitters, neuroinflammation, and behaviors. With the transition of human microbiome research from studying associations to investigating mechanistic causality, the MGB axis has emerged as a novel therapeutic target in depression and its comorbidities. These novel insights have fueled idea that targeting on the gut microbiota may open new windows for efficient treatment of depression and its comorbidities. Probiotics, live beneficial microorganisms, can be used to modulate gut dysbiosis into a new eubiosis and modify the occurrence and development of depression and its comorbidities. In present review, we summarize recent findings regarding the MGB axis in depression and discuss the potential therapeutic effects of probiotics on depression and its comorbidities.