Role of central vagal 5-HT3 receptors in gastrointestinal physiology and pathophysiology

Antidepressant and anxiolytic effects of activating 5HT2A receptors in the anterior cingulate cortex and the theoretical mechanisms underlying them - A scoping review of available literature

Psychedelic drugs that activate the 5HT2A receptor have long been the target of extensive clinical research, particularly in models of psychiatric illness. The aim of this literature review was to investigate the therapeutic effects of 5HT2A receptor activation in the anterior cingulate cortex (ACC) and the respective mechanisms that underlie them. Based on the available research, I suggest that 5HT2A receptors in the ACC exert profound changes in excitatory neurotransmission and brain network connectivity in a way that reduces anxious preoccupation and obsessional thoughts, as well as promoting cognitive flexibility and long-lasting mood improvements in anhedonia. This is possibly due to a complex interplay with glutamate and gamma-butyric acid neurotransmission, particularly 5HT2A activation enhances α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor signalling, thus altering the ratio of AMPA to N-methyl-D-Aspartate (NMDA) activity in the ACC, which can dismantle previously established neuronal connections and aid the formation of new ones, an effect that may be beneficial for fear extinction and reversal learning. Psychedelics potentially change intra- and internetwork connectivity, strengthening connectivity from the dorsal ACC / Salience Network to the Default Mode Network (DMN) and Central Executive Network (CEN), which correlates with improvements in attentional shifting and anti-anhedonic effects. Additionally, they may decrease inhibitory influence of the DMN over the CEN which may reduce overevaluation of internal states and ameliorate cognitive deficits. Activation of ACC 5HT2A receptors also has important downstream effects on subcortical areas, including reducing amygdala reactivity to threatening stimuli and enhancing mesolimbic dopamine, respectively improving anxiety and the experience of natural rewards.

Progress of Chinese Medicine in Regulating Microglial Polarization against Alzheimer's Disease

Alzheimer's disease (AD), the predominant form of dementia, is a neurodegenerative disorder of the central nervous system (CNS) characterized by a subtle onset and a spectrum of cognitive and functional declines. The clinical manifestation of AD encompasses memory deficits, cognitive deterioration, and behavioral disturbances, culminating in a severe impairment of daily living skills. Despite its high prevalence, accounting for 60-70% of all dementia cases, there remains an absence of curative therapeutics. Microglia (MG), the resident immune cells of the CNS, exhibit a bifurcated role in AD pathogenesis. Functioning in a neuroprotective capacity, MGs express scavenger receptors, facilitating the clearance of [Formula: see text]-amyloid protein (A[Formula: see text]) and cellular debris. Conversely, aberrant activation of MGs can lead to the secretion of pro-inflammatory cytokines, thereby propagating neuroinflammatory responses that are detrimental to neuronal integrity. The dynamics of MG activation and the ensuing neuroinflammation are pivotal in the evolution of AD. Chinese medicine (CM), a treasure trove of traditional Chinese cultural practices, has demonstrated significant potential in the therapeutic management of AD. Over the past triennium, CM has garnered considerable research attention for its multifaceted approaches to AD, including the regulation of MG polarization. This review synthesizes current knowledge on the origins, polarization dynamics, and mechanistic interplay of MG with AD pathology. It further explores the nexus between MG polarization and cardinal pathological hallmarks of AD, such as A[Formula: see text] plaque deposition, hyperphosphorylation of tau, synaptic plasticity impairments, neuroinflammation, and brain-gut-axis dysregulation. The review also encapsulates the therapeutic strategies of CM, which encompass monomers, formulae, and acupuncture. These strategies modulate MG polarization in the context of AD treatment, thereby providing a robust theoretical framework in which to conduct future investigative endeavors in both the clinical and preclinical realms.

A new target for treating intervertebral disk degeneration: gut microbes

Intervertebral disk degeneration (IDD) is a common clinical spinal disease and one of the main causes of low back pain (LBP). Generally speaking, IDD is considered a natural degenerative process with age. However, with the deepening of research, people have discovered that IDD is not only related to age, but also has many factors that can induce and accelerate its progression. In addition, the pathogenesis of IDD remains unclear, resulting in limited traditional treatment methods that cannot effectively prevent and treat IDD. Conservative treatment may lead to patients' dependence on drugs, and the pain relief effect is not obvious. Similarly, surgical treatment is highly invasive, with a longer recovery time and a higher recurrence rate. With the deepening of exploration, people have discovered that intestinal microorganisms are an important symbiotic microbial community in the human body and are closely related to the occurrence and development of various diseases. Changes in intestinal microorganisms and their metabolites may affect the body's inflammatory response, immune regulation, and metabolic processes, thereby affecting the health of the intervertebral disk. In this context, the gut microbiota has received considerable attention as a potential target for delaying or treating IDD. This article first introduces the impact of gut microbes on common distal organs, and then focuses on three potential mechanisms by which gut microbes and their metabolites influence IDD. Finally, we also summarized the methods of delaying or treating IDD by interfering with intestinal microorganisms and their metabolites. Further understanding of the potential mechanisms between intestinal microorganisms and IDD will help to formulate reasonable IDD treatment strategies to achieve ideal therapeutic effects.

Intergenerational neurotoxicity of polystyrene nanoplastics in offspring mice is mediated by dysfunctional microbe-gut-brain axis

Nanoplastics (NPs) are ubiquitous in daily life, posing potential risks to the environment and human. While their negative effects on parental organisms have been extensively studied, intergenerational effects are still in the early stages of investigation. Here, we aimed to investigate the impact of maternal exposure to an environmentally relevant level of polystyrene NPs (PSNPs, 100 nm) during gestation and lactation (∼32 days, 50 μg/mouse/day) on neurotoxicity mediated by the microbe-gut-brain axis in offspring mice. Maternal PSNPs exposure significantly increased brain TNF-α level and microglia by 1.43 and 1.48 folds respectively, compared to control, accompanied by nuclear pyknosis and cell vacuolization in cortex and hippocampus. Targeted neurotransmitter metabolomics analysis revealed dysregulation in dopamine and serotonin metabolism. Specifically, dopamine levels increased significantly from 0.007 ng/L to 0.015 ng/L, while N-acetylseroton and 3,4-dihydroxyphenylacetic acid decreased significantly from 0.002 and 0.929 ng/L to 0.001 and 0.680 ng/L, respectively. Through a combination of 16S rRNA sequencing and biochemical analysis, we discovered that maternal PSNPs exposure led to a depletion of anti-inflammatory bacteria and an enrichment of pro-inflammatory bacteria resulting in intestinal barrier damage, elevated levels of lipopolysaccharide in blood, and subsequent activation of neuroinflammation. Meanwhile, gut bacteria dysbiosis interfered with communication between gut and brain by dysregulating neurotransmitter synthesis, as evidenced by significant associations between neurotransmitter-related bacteria (Akkermansia, Family_XIII_AD3011_group, Lachnoclostridium) and dopamine/serotonin related metabolites. Furthermore, transcriptional alterations in dopamine and serotonin related pathways were observed in the enteric nervous system, suggesting abnormal signal transduction from gut to brain contributes to neurotoxicity. This study provides new insights into NPs-induced neurotoxicity within the context of microbe-gut-brain axis and highlights the risk of cerebral dysfunction in offspring with maternal NPs exposure.

Microbiome composition and central serotonergic activity in patients with depression and type 1 diabetes

The role of gut-brain axis functioning gains growing attention in research on the pathophysiology of major depressive disorders. Here, especially consequences of altered microbiota composition on tryptophan metabolism resulting in altered serotonergic neurotransmission in the central nervous system (CNS) have reached a central position. Previous research, however, mainly focused on either microbiota and peripheral serotonin levels or central serotonergic neurotransmission. The present study aimed to combine the analysis of microbiota composition and central serotonergic activity using a valid neurophysiological indicator. We recruited 19 adult patients with type 1 diabetes and depression (D + D; 7 males), 19 patients with type 1 diabetes (D-; 7 male), and 20 healthy participants (HC; 7 males). Next to the analysis of fecal microbiota regarding α- and β-diversity, the loudness dependence of auditory evoked potential (LDAEP) was investigated, a non-invasive measurement of central serotonergic activity. High α-diversity was associated with high LDAEP, i.e., low serotonergic activity, in patients with diabetes and additional depression. Furthermore, relative abundances of bacterial families belonging to Bacteroidetes, Proteobacteria and Firmicutes were shown to have an impact on central serotonergic activity. This finding was supported by a tendency indicating an association of central serotonergic activity with the Bacteroidetes-Firmicutes ratio in both patients' groups. Together, this data suggests that the guts' microbiota composition might play an important role in regulating the central serotonergic activity in the brain.

Systematic Insights into the Relationship between the Microbiota-Gut-Brain Axis and Stroke with the Focus on Tryptophan Metabolism

Stroke, as a serious cerebral vascular disease with high incidence and high rates of disability and mortality, has limited therapeutic options due to the narrow time window. Compelling evidence has highlighted the significance of the gut microbiota and gut-brain axis as critical regulatory factors affecting stroke. Along the microbiota-gut-brain axis, tryptophan metabolism further acquires increasing attention for its intimate association with central nervous system diseases. For the purpose of exploring the potential role of tryptophan metabolism in stroke and providing systematic insights into the intricate connection of the microbiota-gut-brain axis with the pathological procedure of stroke, this review first summarized the practical relationship between microbiota and stroke by compiling the latest case-control research. Then, the microbiota-gut-brain axis, as well as its interaction with stroke, were comprehensively elucidated on the basis of the basic anatomical structure and physiological function. Based on the crosstalk of microbiota-gut-brain, we further focused on the tryptophan metabolism from the three major metabolic pathways, namely, the kynurenine pathway, serotonin pathway, and microbial pathway, within the axis. Moreover, the effects of tryptophan metabolism on stroke were appreciated and elaborated here, which is scarcely found in other reviews. Hopefully, the systematic illustration of the mechanisms and pathways along the microbiota-gut-brain axis will inspire more translational research from metabolic perspectives, along with more attention paid to tryptophan metabolism as a promising pharmaceutical target in order to reduce the risk of stroke, mitigate the stroke progression, and ameliorate the stroke prognosis.

Overview of growth differentiation factor 15 (GDF15) in metabolic diseases

GDF15 is a stress response cytokine and a distant member of the transforming growth factor beta (TGFβ) superfamily, its levels increase in response to cell stress and certain diseases in the serum. To exert its effects, GDF15 binds to glial-derived neurotrophic factor (GDNF) receptor alpha-like (GFRAL), which was firstly identified in 2017 and highly expressed in the brain stem. Many studies have demonstrated that elevated serum GDF15 is associated with anorexia and weight loss. Herein, we focus on the biology of GDF15, specifically how this circulating protein regulates appetite and metabolism in influencing energy homeostasis through its actions on hindbrain neurons to shed light on its impact on diseases such as obesity and anorexia/cachexia syndromes. It works as an endocrine factor and transmits metabolic signals leading to weight reduction effects by directly reducing appetite and indirectly affecting food intake through complex mechanisms, which could be a promising target for the treatment of energy-intake disorders.

Psilocybin therapy and anorexia nervosa: a narrative review of safety considerations for researchers and clinicians

BACKGROUND

Clinical trials using psilocybin therapy to treat anorexia nervosa (AN) are currently underway. The safety and tolerability of psilocybin is of utmost importance in individuals with AN who may present unique medical vulnerabilities. The purpose of this review is to describe how the common physiologic adverse effects of psilocybin may impact medical complications experienced by individuals with AN in clinical trials of psilocybin therapy.

MAIN BODY

The physiologic underpinnings of common adverse effects following psilocybin administration are described, including tachycardia, hypertension, electrocardiogram changes, nausea, headache, and lightheadedness. These anticipated physiologic changes are described in relation to the common medical correlates seen in individuals with AN. Risk mitigation strategies for each adverse effect are proposed.

CONCLUSION

Early evidence suggests that psilocybin therapy is well-tolerated in individuals with AN. Understanding the unique medical complications of AN, and how they may be impacted by common physiologic adverse effects of psilocybin administration, leads to tailored risk mitigation strategies to enhance safety and tolerability of this novel intervention.

Development and Validation of a High-Performance Liquid Chromatography Method to Quantify Marker Compounds in Lysimachia vulgaris var. davurica and Its Effects in Diarrhea-Predominant Irritable Bowel Syndrome

Irritable bowel syndrome (IBS), a common gastrointestinal disorder worldwide, is characterized by chronic abdominal pain, bloating, and disordered defecation. IBS is associated with several factors, including visceral hypersensitivity, gut motility, and gut-brain interaction disorders. Because currently available pharmacological treatments cannot adequately improve symptoms and may cause adverse effects, the use of herbal therapies for managing IBS is increasing. Lysimachia vulgaris var. davurica (LV) is a medicinal plant used in traditional medicine to treat diarrhea. However, information on whether LV can effectively improve diarrhea-predominant IBS (IBS-D) remains limited. In this study, using an experimental mouse model of IBS-D, we elucidated the effects of the LV extract. The methanol extract of LV decreased fecal pellet output in the restraint stress- or 5-hydroxytryptamine (5-HT)-induced IBS mouse model and inhibited 5-HT-mediated [Ca2+]i increase in a dose-dependent manner. Furthermore, we developed and validated a high-performance liquid chromatography method using two marker compounds, namely, chlorogenic acid and rutin, for quality control analysis. Our study results suggest the feasibility of the methanol extract of LV for developing therapeutic agents to treat IBS-D by acting as a 5-HT3 receptor antagonist.

Do the therapeutic effects of psilocybin involve actions in the gut?

The psychedelic compound psilocybin has recently emerged as a therapeutic intervention for various mental health conditions. Psilocybin is a potent agonist of serotonin (5-HT) receptors (5-HTRs), which are expressed in the brain and throughout peripheral tissues, with particularly high expression in the gastrointestinal (GI) tract. However, no studies have investigated the possibility that peripheral actions of psilocybin may contribute to improvements in mental health outcomes. This is despite strong evidence for disturbed gut-brain signalling in conditions in which psilocybin is being tested clinically. In this Opinion, we highlight the likely actions of psychedelics in the gut and provide initial support for the premise that peripheral actions may be involved in rapid and long-term therapeutic effects. A greater understanding of all sites and modes of action will guide more targeted approaches to drug development.

A vibrating ingestible bioelectronic stimulator modulates gastric stretch receptors for illusory satiety

Effective therapies for obesity require invasive surgical and endoscopic interventions or high patient adherence, making it challenging for patients with obesity to effectively manage their disease. Gastric mechanoreceptors sense distension of the stomach and perform volume-dependent vagal signaling to initiate the gastric phase and influence satiety. In this study, we developed a new luminal stimulation modality to specifically activate these gastric stretch receptors to elicit a vagal afferent response commensurate with mechanical distension. We designed the Vibrating Ingestible BioElectronic Stimulator (VIBES) pill, an ingestible device that performs luminal vibratory stimulation to activate mechanoreceptors and stroke mucosal receptors, which induces serotonin release and yields a hormonal metabolic response commensurate with a fed state. We evaluated VIBES across 108 meals in swine which consistently led to diminished food intake (~40%, P < 0.0001) and minimized the weight gain rate (P < 0.05) as compared to untreated controls. Application of mechanoreceptor biology could transform our capacity to help patients suffering from nutritional disorders.

Subdiaphragmatic vagal nerve stimulation attenuates the development of hypertension and alters nucleus of the solitary tract transcriptional networks in the spontaneously hypertensive rat

Augmented vagal signaling may be therapeutic in hypertension. Most studies to date have used stimulation of the cervical vagal branches. Here, we investigated the effects of chronic intermittent electric stimulation of the ventral subdiaphragmatic vagal nerve branch (sdVNS) on long-term blood pressure, immune markers, and gut microbiota in the spontaneously hypertensive rat (SHR), a rodent model of hypertension characterized by vagal dysfunction, gut dysbiosis, and low-grade inflammation. We evaluated the effects of sdVNS on transcriptional networks in the nucleus of the solitary tract (NTS), a major cardioregulatory brain region with direct gut vagal projections. Male juvenile SHRs were implanted with radiotelemetry transmitters and vagal nerve cuffs for chronic intermittent electric sdVNS, applied three times per day for 7 consecutive weeks followed by 1 wk of no stimulation. Blood pressure was measured once a week using telemetry in the sdVNS group as well as age-matched sham-stimulated SHR controls. At the endpoint, colonic and circulating inflammatory markers, corticosterone, and circulating catecholamines were investigated. Bacterial 16 s sequencing measured gut bacterial abundance and composition. RNA sequencing evaluated the effects of sdVNS on transcriptional networks in the NTS. SHRs that received sdVNS exhibited attenuated development of hypertension compared with sham animals. No changes in peripheral inflammatory markers, corticosterone, or catecholamines and no major differences in gut bacterial diversity and composition were observed following sdVNS, apart from decreased abundance of Defluviitaleaceale bacterium detected in sdVNS SHRs compared with sham animals. RNA sequencing revealed significant sdVNS-dependent modulation of select NTS transcriptional networks, including catecholaminergic and corticosteroid networks.NEW & NOTEWORTHY We show that stimulation of the ventral subdiaphragmatic vagal nerve branch may be a promising potential approach to treating hypertension. The data are especially encouraging given that rodents received only 30 min per day of intermittent stimulation therapy and in view of the potential of long-term blood pressure effects that are not stimulus-locked.

Epstein-Barr virus-acquired immunodeficiency in myalgic encephalomyelitis-Is it present in long COVID?

Both myalgic encephalomyelitis or chronic fatigue syndrome (ME/CFS) and long COVID (LC) are characterized by similar immunological alterations, persistence of chronic viral infection, autoimmunity, chronic inflammatory state, viral reactivation, hypocortisolism, and microclot formation. They also present with similar symptoms such as asthenia, exercise intolerance, sleep disorders, cognitive dysfunction, and neurological and gastrointestinal complaints. In addition, both pathologies present Epstein-Barr virus (EBV) reactivation, indicating the possibility of this virus being the link between both pathologies. Therefore, we propose that latency and recurrent EBV reactivation could generate an acquired immunodeficiency syndrome in three steps: first, an acquired EBV immunodeficiency develops in individuals with "weak" EBV HLA-II haplotypes, which prevents the control of latency I cells. Second, ectopic lymphoid structures with EBV latency form in different tissues (including the CNS), promoting inflammatory responses and further impairment of cell-mediated immunity. Finally, immune exhaustion occurs due to chronic exposure to viral antigens, with consolidation of the disease. In the case of LC, prior to the first step, there is the possibility of previous SARS-CoV-2 infection in individuals with "weak" HLA-II haplotypes against this virus and/or EBV.

Mast cells link immune sensing to antigen-avoidance behaviour

The physiological functions of mast cells remain largely an enigma. In the context of barrier damage, mast cells are integrated in type 2 immunity and, together with immunoglobulin E (IgE), promote allergic diseases. Allergic symptoms may, however, facilitate expulsion of allergens, toxins and parasites and trigger future antigen avoidance1-3. Here, we show that antigen-specific avoidance behaviour in inbred mice4,5 is critically dependent on mast cells; hence, we identify the immunological sensor cell linking antigen recognition to avoidance behaviour. Avoidance prevented antigen-driven adaptive, innate and mucosal immune activation and inflammation in the stomach and small intestine. Avoidance was IgE dependent, promoted by Th2 cytokines in the immunization phase and by IgE in the execution phase. Mucosal mast cells lining the stomach and small intestine rapidly sensed antigen ingestion. We interrogated potential signalling routes between mast cells and the brain using mutant mice, pharmacological inhibition, neural activity recordings and vagotomy. Inhibition of leukotriene synthesis impaired avoidance, but overall no single pathway interruption completely abrogated avoidance, indicating complex regulation. Collectively, the stage for antigen avoidance is set when adaptive immunity equips mast cells with IgE as a telltale of past immune responses. On subsequent antigen ingestion, mast cells signal termination of antigen intake. Prevention of immunopathology-causing, continuous and futile responses against per se innocuous antigens or of repeated ingestion of toxins through mast-cell-mediated antigen-avoidance behaviour may be an important arm of immunity.

Hematochezia caused by tandospirone in a patient with major depressive disorder and anxious distress: a case report

Background

Major depressive disorder (MDD) with anxious distress is a relatively common condition that is often associated with a poor treatment response. In order to enhance the effectiveness of MDD treatment, 5-HT1A agonists like tandospirone are often prescribed in conjunction with antidepressants. While it is known that antidepressants can increase the risk of bleeding, whether tandospirone poses a similar risk remains uncertain.

Case presentation

We presented the case of a 55-year-old Chinese woman diagnosed with MDD and anxious distress. After receiving various types of antidepressants, she experienced hematochezia following the administration of tandospirone, sertraline, and agomelatine. The occurrence of hematochezia ceased after tandospirone was discontinued. The patient was subsequently discharged with a treatment regime consisting of sertraline and agomelatine. During the 1-month follow-up, she reported no hematochezia.

Conclusion

Tandospirone may potentially increase the risk of hematochezia in patients with MDD and anxious distress.

Influence of the gut microbiota on satiety signaling

Recent studies show a link between the gut microbiota and the regulation of satiety and energy intake, processes that contribute to the development and pathophysiology of metabolic diseases. However, this link is predominantly established in animal and in vitro studies, whereas human intervention studies are scarce. In this review we focus on recent evidence linking satiety and the gut microbiome, with specific emphasis on gut microbial short-chain fatty acids (SCFAs). Based on a systematic search we provide an overview of human studies linking the intake of prebiotics with gut microbial alterations and satiety signaling. Our outcomes highlight the importance of in-depth examination of the gut microbiota in relation to satiety and provide insights into recent and future studies in this field.

Three-Dimensional-Printed Electrochemical Multiwell Plates for Monitoring Food Intolerance from Intestinal Organoids

Common symptoms of food intolerance are caused by chemical components within food that have a pharmacological activity to alter the motility of the gastrointestinal tract. Food intolerance is difficult to diagnose as it requires a long-term process of eliminating foods that are responsible for gastrointestinal symptoms. Enterochromaffin (EC) cells are key intestinal epithelium cells that respond to luminal chemical stimulants by releasing 5-HT. Changes in 5-HT levels have been shown to directly alter the motility of the intestinal tract. Therefore, a rapid approach for monitoring the impact of chemicals in food components on 5-HT levels can provide a personalized insight into food intolerance and help stratify diets. Within this study, we developed a three-dimensional (3D)-printed electrochemical multiwell plate to determine changes in 5-HT levels from intestinal organoids that were exposed to varying chemical components found in food. The carbon black/poly-lactic acid (CB/PLA) electrodes had a linear range in physiological concentrations of 5-HT (0.1-2 μM) with a limit of detection of 0.07 μM. The electrodes were stable for monitoring 5-HT overflow from intestinal organoids. Using the electrochemical multiwell plate containing intestinal organoids, increases in 5-HT were observed in the presence of 0.1 mM cinnamaldehyde and 10 mM quercetin but reduction in 5-HT levels was observed in 1 mM sorbitol when compared to control. These changes in the presence of chemicals commonly found in food were verified with ex vivo ileum tissue measurements using chromatography and amperometry with boron-doped diamond electrodes. Overall, our 3D electrochemical multiwell plate measurements with intestinal organoids highlight an approach that can be a high-throughput platform technology for rapid screening of food intolerance to provide personalized nutritional diet.

Effects of Ginger Intake on Chemotherapy-Induced Nausea and Vomiting: A Systematic Review of Randomized Clinical Trials

Nausea and vomiting are the most common side effects of chemotherapy. They must be managed because they can increase the risk of malnutrition in patients, which can adversely affect treatment. The objective of this study was to evaluate the effect of ginger supplementation as an adjuvant treatment for alleviating chemo We checked. therapy-induced nausea and vomiting (CINV). This study searched for randomized controlled trials (RCTs) related to ginger supplement intake for CINV in three electronic databases (i.e., Medline (PubMed), Embase, and Web of Science). The search period ranged from each database's first date of service to 5 November 2021. Two investigators independently performed abstract screenings, full-text screenings, data extraction, and risk of bias analyses (ROB). The Cochrane ROB tool was used for the assessment of ROB. This study systematically reviewed 23 RCTs. The effects of ginger supplementation were compared to those of placebo or antiemetic agents. This study conducted a meta-analysis after classifying the effects of ginger supplementation on acute and delayed CINV into subgroups due to the clinical heterogeneity between these RCTs. The results showed that the incidence of acute nausea (p = 0.53), the incidence of delayed nausea (p = 0.31), the incidence of acute vomiting (p = 0.09), and the incidence of delayed vomiting (p = 0.89) were not significantly different between the ginger supplement intake group and the control group. However, it was found that the ginger supplement intake group, which took not more than 1 g of ginger supplementation per day for above four days, had significantly less acute vomiting than the control group (OR 0.30; 95% CI 0.12 to 0.79; p = 0.02; I2 = 36%). Ginger supplementation may reduce the incidence of acute chemotherapy-induced vomiting. However, this study could not confirm the effects of ginger supplementation on the incidence of chemotherapy-induced nausea and delayed vomiting. Therefore, it will be necessary to conduct additional studies with sufficient sample sizes using high-quality RCTs to evaluate the effects of ginger supplementations based on the results of this study.

Zhizhu Kuanzhong, a traditional Chinese medicine, alleviates gastric hypersensitivity and motor dysfunction on a rat model of functional dyspepsia

Ethnopharmacological relevance: Zhizhu Kuanzhong (ZZKZ) is a traditional Chinese medicine modified from classic formula Zhizhu decoction in "Synopsis of Golden Chamber" (Han Dynasty in the 3rd century) and the Zhizhu pill in "Differentiation on Endogenous" in Jin Dynasty (1,115-1,234). ZZKZ contains four botanical drugs, including Citrus × Aurantium L [Rutaceae; Aurantii Fructus Immaturus], Atractylodes Macrocephala Koidz. [Compositae; Rhizoma Atractylodis Macrocephalae], Bupleurum Chinense DC [Apiaceae; Radix Bupleuri Chinensis], and Crataegus Pinnatifida Bunge [Rosaceae; Fructus Crataegi Pinnatifidae], which have been widely used in clinical therapy for functional dyspepsia (FD). Aim of the study: This study aimed to evaluate the pharmacological effects and mechanisms of action of ZZKZ on gastric hypersensitivity and motor dysfunction in a rat model of FD. Materials and methods: FD was induced in Sprague-Dawley rats by neonatal gastric irritation with 0.1% iodoacetamide. The FD rats were treated with ZZKZ (0.5 g/kg, 1.0 g/kg, or 1.5 g/kg respectively) by gavage for 7 days, while domperidone (3 mg/kg) acted as treatment control. Body weight gain, food intake, gastric emptying, and intestinal propulsion were also measured. Ex vivo gastric smooth muscle activity recordings and greater splanchnic afferent (GSN) firing recordings were employed to evaluate gastric motility and sensation. Particularly, the role of 5-HT in the action of ZZKZ in improving gastric dysmotility and hypersensitivity was explored. Results: ZZKZ promoted weight gain, food intake, gastric emptying, and intestinal propulsion in FD rats. ZZKZ promoted spontaneous and ACh-induced contractions of gastric smooth muscle strips in FD rats, alleviated spontaneous activity, and chemical (acid perfusion) and mechanical (intragastric distension) stimulated GSN firing in FD rats. ZZKZ ameliorated gastric smooth muscle contraction and GSN firing induced by 5-HT in FD rats. ZZKZ stimulated the release of serum 5-HT, with reduced 5-HT3 receptor and increased 5-HT4 receptor mRNA expression in the guts of FD rats. Conclusion: This study demonstrated that ZZKZ improves FD-related gastric hypersensitivity and motor dysfunction and should be an effective compound for relieving FD symptoms. The gastric 5-HT system with lower 5-HT3 activity and increased 5-HT4 distribution is involved in the mechanisms of ZZKZ underlying the treatment of FD.

Central and peripheral regulations mediated by short-chain fatty acids on energy homeostasis

The human gut microbiota influences obesity, insulin resistance, and the subsequent development of type 2 diabetes (T2D). The gut microbiota digests and ferments nutrients resulting in the production of short-chain fatty acids (SCFAs), which generate various beneficial metabolic effects on energy and glucose homeostasis. However, their roles in the central nervous system (CNS)-mediated outputs on the metabolism have only been minimally studied. Here, we explore what is known and future directions that may be worth exploring in this emerging area. Specifically, we searched studies or data in English by using PubMed, Google Scholar, and the Human Metabolome Database. Studies were filtered by time from 1978 to March 2022. As a result, 195 studies, 53 reviews, 1 website, and 1 book were included. One hundred and sixty-five of 195 studies describe the production and metabolism of SCFAs or the effects of SCFAs on energy homeostasis, glucose balance, and mental diseases through the gut-brain axis or directly by a central pathway. Thirty of 195 studies show that inappropriate metabolism and excessive of SCFAs are metabolically detrimental. Most studies suggest that SCFAs exert beneficial metabolic effects by acting as the energy substrate in the TCA cycle, regulating the hormones related to satiety regulation and insulin secretion, and modulating immune cells and microglia. These functions have been linked with AMPK signaling, GPCRs-dependent pathways, and inhibition of histone deacetylases (HDACs). However, the studies focusing on the central effects of SCFAs are still limited. The mechanisms by which central SCFAs regulate appetite, energy expenditure, and blood glucose during different physiological conditions warrant further investigation.

Tryptophan metabolites in depression: Modulation by gut microbiota

Clinical depression is a multifactorial disorder and one of the leading causes of disability worldwide. The alterations in tryptophan metabolism such as changes in the levels of serotonin, kynurenine, and kynurenine acid have been implicated in the etiology of depression for more than 50 years. In recent years, accumulated evidence has revealed that gut microbial communities, besides being essential players in various aspects of host physiology and brain functioning are also implicated in the etiology of depression, particularly through modulation of tryptophan metabolism. Therefore, the aim of this review is to summarize the evidence of the role of gut bacteria in disturbed tryptophan metabolism in depression. We summed up the effects of microbiota on serotonin, kynurenine, and indole pathway of tryptophan conversion relevant for understanding the pathogenesis of depressive behavior. Moreover, we reviewed data regarding the therapeutic effects of probiotics, particularly through the regulation of tryptophan metabolites. Taken together, these findings can open new possibilities for further improvement of treatments for depression based on the microbiota-mediated modulation of the tryptophan pathway.

Ethanol Inhibits Pancreatic Projecting Neurons in the Dorsal Motor Nucleus of the Vagus

Alcohol use disorder (AUD) is a rapidly growing concern in the United States. Current trending escalations of alcohol use are associated with a concurrent rise in alcohol-related end-organ damage, increasing risk for further diseases. Alcohol-related end-organ damage can be driven by autonomic nervous system dysfunction, however studies on alcohol effects on autonomic control of end-organ function are lacking. Alcohol intake has been shown to reduce insulin secretions from the pancreas. Pancreatic insulin release is controlled in part by preganglionic parasympathetic motor neurons residing in the dorsal motor nucleus of the vagus (DMV) that project to the pancreas. How these neurons are affected by alcohol exposure has not been directly examined. Here we investigated the effects of acute ethanol (EtOH) application on DMV pancreatic-projecting neurons with whole-cell patch-clamp electrophysiology. We found that bath application of EtOH (50mM) for greater than 30minutes significantly enhanced the frequency of spontaneous inhibitory post synaptic current (sIPSC) events of DMV pancreatic-projecting neurons suggesting a presynaptic mechanism of EtOH to increase GABAergic transmission. Thirty-minute EtOH application also decreased action potential firing of these neurons. Pretreatment of DMV slices with 20μM fluoxetine, a selective serotonin reuptake inhibitor, also increased GABAergic transmission and decreased action potential firing of these DMV neurons while occluding any further effects of EtOH application, suggesting a critical role for serotonin in mediating EtOH effects in the DMV. Ultimately, decreased DMV motor output may lead to alterations in pancreatic secretions. Further studies are needed to fully understand EtOH's influence on DMV neurons as well as the consequences of changes in parasympathetic output to the pancreas.

Olanzapine-induced lipid disturbances: A potential mechanism through the gut microbiota-brain axis

Objective: Long-term use of olanzapine can induce various side effects such as lipid metabolic disorders, but the mechanism remains to be elucidated. The gut microbiota-brain axis plays an important role in lipid metabolism, and may be related to the metabolic side effects of olanzapine. Therefore, we explored the mechanism by which olanzapine-induced lipid disturbances through the gut microbiota-brain axis.

Methods: Sprague Dawley rats were randomly divided into two groups, which underwent subphrenic vagotomy and sham surgery. Then the two groups were further randomly divided into two subgroups, one was administered olanzapine (10 mg/kg/day) by intragastric administration, and the other was administered normal saline by intragastric administration (4 ml/kg/day) for 2 weeks. The final changes in lipid parameters, gut microbes and their metabolites, and orexin-related neuropeptides in the hypothalamus were investigated among the different groups.

Results: Olanzapine induced lipid disturbances as indicated by increased weight gain, elevated ratio of white adipose tissue to brown adipose tissue, as well as increased triglyceride and total cholesterol. Olanzapine also increased the Firmicutes/Bacteroides (F/B) ratio in the gut, which was even aggravated by subphrenic vagotomy. In addition, olanzapine reduced the abundance of short-chain fatty acids (SCFAs) metabolism related microbiome and 5-hydroxytryptamine (5-HT) levels in the rat cecum, and increased the gene and protein expression of the appetite-related neuropeptide Y/agouti-related peptide (NPY/AgRP) in the hypothalamus.

Conclusion: The abnormal lipid metabolism caused by olanzapine may be closely related to the vagus nerve-mediated gut microbiota-brain axis.

Three Naturally-Occurring Psychedelics and Their Significance in the Treatment of Mental Health Disorders

Classical psychedelics represent a family of psychoactive substances with structural similarities to serotonin and affinity for serotonin receptors. A growing number of studies have found that psychedelics can be effective in treating various psychiatric conditions, including post-traumatic stress disorder, major depressive disorder, anxiety, and substance use disorders. Mental health disorders are extremely prevalent in the general population constituting a major problem for the public health. There are a wide variety of interventions for mental health disorders, including pharmacological therapies and psychotherapies, however, treatment resistance still remains a particular challenge in this field, and relapse rates are also quite high. In recent years, psychedelics have become one of the promising new tools for the treatment of mental health disorders. In this review, we will discuss the three classic serotonergic naturally occurring psychedelics, psilocybin, ibogaine, and N, N-dimethyltryptamine, focusing on their pharmacological properties and clinical potential. The purpose of this article is to provide a focused review of the most relevant research into the therapeutic potential of these substances and their possible integration as alternative or adjuvant options to existing pharmacological and psychological therapies.

Mechanisms of Chemotherapy-Induced Neurotoxicity

Since the first clinical trials conducted after World War II, chemotherapeutic drugs have been extensively used in the clinic as the main cancer treatment either alone or as an adjuvant therapy before and after surgery. Although the use of chemotherapeutic drugs improved the survival of cancer patients, these drugs are notorious for causing many severe side effects that significantly reduce the efficacy of anti-cancer treatment and patients’ quality of life. Many widely used chemotherapy drugs including platinum-based agents, taxanes, vinca alkaloids, proteasome inhibitors, and thalidomide analogs may cause direct and indirect neurotoxicity. In this review we discuss the main effects of chemotherapy on the peripheral and central nervous systems, including neuropathic pain, chemobrain, enteric neuropathy, as well as nausea and emesis. Understanding mechanisms involved in chemotherapy-induced neurotoxicity is crucial for the development of drugs that can protect the nervous system, reduce symptoms experienced by millions of patients, and improve the outcome of the treatment and patients’ quality of life.

The physiological control of eating: signals, neurons, and networks

During the past 30 yr, investigating the physiology of eating behaviors has generated a truly vast literature. This is fueled in part by a dramatic increase in obesity and its comorbidities that has coincided with an ever increasing sophistication of genetically based manipulations. These techniques have produced results with a remarkable degree of cell specificity, particularly at the cell signaling level, and have played a lead role in advancing the field. However, putting these findings into a brain-wide context that connects physiological signals and neurons to behavior and somatic physiology requires a thorough consideration of neuronal connections: a field that has also seen an extraordinary technological revolution. Our goal is to present a comprehensive and balanced assessment of how physiological signals associated with energy homeostasis interact at many brain levels to control eating behaviors. A major theme is that these signals engage sets of interacting neural networks throughout the brain that are defined by specific neural connections. We begin by discussing some fundamental concepts, including ones that still engender vigorous debate, that provide the necessary frameworks for understanding how the brain controls meal initiation and termination. These include key word definitions, ATP availability as the pivotal regulated variable in energy homeostasis, neuropeptide signaling, homeostatic and hedonic eating, and meal structure. Within this context, we discuss network models of how key regions in the endbrain (or telencephalon), hypothalamus, hindbrain, medulla, vagus nerve, and spinal cord work together with the gastrointestinal tract to enable the complex motor events that permit animals to eat in diverse situations.

Potential Roles of Enterochromaffin Cells in Early Life Stress-Induced Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is one of the most common functional gastrointestinal disorders, also known as disorders of the gut–brain interaction; however, the pathophysiology of IBS remains unclear. Early life stress (ELS) is one of the most common risk factors for IBS development. However, the molecular mechanisms by which ELS induces IBS remain unclear. Enterochromaffin cells (ECs), as a prime source of peripheral serotonin (5-HT), play a pivotal role in intestinal motility, secretion, proinflammatory and anti-inflammatory effects, and visceral sensation. ECs can sense various stimuli and microbiota metabolites such as short-chain fatty acids (SCFAs) and secondary bile acids. ECs can sense the luminal environment and transmit signals to the brain via exogenous vagal and spinal nerve afferents. Increasing evidence suggests that an ECs-5-HT signaling imbalance plays a crucial role in the pathogenesis of ELS-induced IBS. A recent study using a maternal separation (MS) animal model mimicking ELS showed that MS induced expansion of intestinal stem cells and their differentiation toward secretory lineages, including ECs, leading to ECs hyperplasia, increased 5-HT production, and visceral hyperalgesia. This suggests that ELS-induced IBS may be associated with increased ECs-5-HT signaling. Furthermore, ECs are closely related to corticotropin-releasing hormone, mast cells, neuron growth factor, bile acids, and SCFAs, all of which contribute to the pathogenesis of IBS. Collectively, ECs may play a role in the pathogenesis of ELS-induced IBS. Therefore, this review summarizes the physiological function of ECs and focuses on their potential role in the pathogenesis of IBS based on clinical and pre-clinical evidence.

Tumor Necrosis Factor Alpha and the Gastrointestinal Epithelium: Implications for the Gut-Brain Axis and Hypertension

The colonic epithelium is the site of production and transport of many vasoactive metabolites and neurotransmitters that can modulate the immune system, affect cellular metabolism, and subsequently regulate blood pressure. As an important interface between the microbiome and its host, the colon can contribute to the development of hypertension. In this critical review, we highlight the role of colonic inflammation and microbial metabolites on the gut brain axis in the pathology of hypertension, with special emphasis on the interaction between tumor necrosis factor α (TNFα) and short chain fatty acid (SCFA) metabolites. Here, we review the current literature and identify novel pathways in the colonic epithelium related to hypertension. A network analysis on transcriptome data previously generated in spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats reveals differences in several pathways associated with inflammation involving TNFα (NF-κB and STAT Expression Targets) as well as oxidative stress. We also identify down-regulation of networks associated with gastrointestinal function, cardiovascular function, enteric nervous system function, and cholinergic and adrenergic transmission. The analysis also uncovered transcriptome responses related to glycolysis, butyrate oxidation, and mitochondrial function, in addition to gut neuropeptides that serve as modulators of blood pressure and metabolic function. We present a model for the role of TNFα in regulating bacterial metabolite transport and neuropeptide signaling in the gastrointestinal system, highlighting the complexity of host-microbiota interactions in hypertension.

The Antiemetic Mechanisms of Gingerols against Chemotherapy-Induced Nausea and Vomiting

Chemotherapy-induced nausea and vomiting (CINV) is a common and painful side effect that occurs in cancer patients receiving chemotherapeutic drugs. Although an abundance of agents are applied to prevent CINV, there is still lack of effective control in delayed nausea and vomiting. Ginger (Zingiber officinale Rosc.), a traditional antiemetic herb, draws attention due to its therapeutic effect in treating acute and delayed CINV. Its main bioactive pungent constituents, gingerols, contribute to the antiemetic effect against CINV primarily. A growing number of reports have made progress in investigating the mechanisms of gingerols and their single ingredients against CINV. In this review, we searched for relevant studies in PubMed database to summarize the mechanism of gingerols in the prevention of CINV and provided a preliminary prediction on the potential targets and signaling pathways using network pharmacology, laying a foundation for further researches.

Electroacupuncture could balance the gut microbiota and improve the learning and memory abilities of Alzheimer's disease animal model

Alzheimer's disease (AD), as one of most common dementia, mainly affects older people from the worldwide. In this study, we intended to explore the possible mechanism of improving cognitive function and protecting the neuron effect by electroacupuncture.

METHOD

We applied senescence-accelerated mouse prone 8 (SAMP8) mice as AD animal model, used Morris water maze, HE staining, 16S rDNA amplicon sequencing of gut microbiota and ELISA to demonstrate our hypothesis.

RESULTS

electroacupuncture improved the learning and memory abilities in SAMP8 mice (P<0.05) and could protect the frontal lobe cortex and hippocampus of SAMP8 mice; electroacupuncture significantly decreased the expression of IL-1β (P<0.01), IL-6 (P<0.01) and TNF-α (P<0.01 in hippocampus, P<0.05 in serum) in serum and hippocampus; electroacupuncture balanced the quantity and composition of gut microbiome, especially of the relative abundance in Delta-proteobacteria (P<0.05) and Epsilon-proteobacteria (P<0.05).

CONCLUSION

electroacupuncture treatment could inhibit the peripheral and central nerve system inflammatory response by balancing the gut microbiota.

Crosstalk Between Intestinal Serotonergic System and Pattern Recognition Receptors on the Microbiota-Gut-Brain Axis

Disruption of the microbiota-gut-brain axis results in a wide range of pathologies that are affected, from the brain to the intestine. Gut hormones released by enteroendocrine cells to the gastrointestinal (GI) tract are important signaling molecules within this axis. In the search for the language that allows microbiota to communicate with the gut and the brain, serotonin seems to be the most important mediator. In recent years, serotonin has emerged as a key neurotransmitter in the gut-brain axis because it largely contributes to both GI and brain physiology. In addition, intestinal microbiota are crucial in serotonin signaling, which gives more relevance to the role of the serotonin as an important mediator in microbiota-host interactions. Despite the numerous investigations focused on the gut-brain axis and the pathologies associated, little is known regarding how serotonin can mediate in the microbiota-gut-brain axis. In this review, we will mainly discuss serotonergic system modulation by microbiota as a pathway of communication between intestinal microbes and the body on the microbiota-gut-brain axis, and we explore novel therapeutic approaches for GI diseases and mental disorders.

A novel CT contrast agent for intestinal-targeted imaging through rectal administration

In this study, a novel CT contrast agent used by rectal administration is developed for targeting intestinal imaging. Iopamidol, an iodinated contrast agent, is loaded in chitosan (CS) nanospheres modified by Anti-5-HT3R (AH) antibody. The obtained AH-CS-I nanospheres (AH-CS-I Ns) would combine to 5-HT3 receptors highly expressed on the gastrointestinal mucosal, enhancing the intestinal-targeting ability of the contrast agent. The AH-CS-I Ns were administered by the rectal route for intestinal CT imaging, and FITC-labeled AH-CS-I Ns were prepared for investigating the in vivo distribution of the contrast agent. As a result, obvious contrast enhancement could still be observed at 6 h post administration because of the poorly absorption of enteral AH-CS-I Ns. Unlike the intravascularly administered agents, AH-CS-I Ns would not accumulate in the kidney and induce adverse reactions. Therefore, this technology has potential applications in the examination of intestinal diseases and could reduce the side effect of commercial iopamidol.

Enteric Microbiota-Mediated Serotonergic Signaling in Pathogenesis of Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a chronic functional disorder that affects the gastrointestinal tract. Details regarding the pathogenesis of IBS remain largely unknown, though the dysfunction of the brain-gut-microbiome (BGM) axis is a major etiological factor, in which neurotransmitters serve as a key communication tool between enteric microbiota and the brain. One of the most important neurotransmitters in the pathology of IBS is serotonin (5-HT), as it influences gastrointestinal motility, pain sensation, mucosal inflammation, immune responses, and brain activity, all of which shape IBS features. Genome-wide association studies discovered susceptible genes for IBS in serotonergic signaling pathways. In clinical practice, treatment strategies targeting 5-HT were effective for a certain portion of IBS cases. The synthesis of 5-HT in intestinal enterochromaffin cells and host serotonergic signaling is regulated by enteric resident microbiota. Dysbiosis can trigger IBS development, potentially through aberrant 5-HT signaling in the BGM axis; thus, the manipulation of the gut microbiota may be an alternative treatment strategy. However, precise information regarding the mechanisms underlying the microbiota-mediated intestinal serotonergic pathway related to the pathogenesis of IBS remains unclear. The present review summarizes current knowledge and recent progress in understanding microbiome–serotonin interaction in IBS cases.

The gut, its microbiome, and the brain: connections and communications

Modern research on gastrointestinal behavior has revealed it to be a highly complex bidirectional process in which the gut sends signals to the brain, via spinal and vagal visceral afferent pathways, and receives sympathetic and parasympathetic inputs. Concomitantly, the enteric nervous system within the bowel, which contains intrinsic primary afferent neurons, interneurons, and motor neurons, also senses the enteric environment and controls the detailed patterns of intestinal motility and secretion. The vast microbiome that is resident within the enteric lumen is yet another contributor, not only to gut behavior, but to the bidirectional signaling process, so that the existence of a microbiota-gut-brain "connectome" has become apparent. The interaction between the microbiota, the bowel, and the brain now appears to be neither a top-down nor a bottom-up process. Instead, it is an ongoing, tripartite conversation, the outline of which is beginning to emerge and is the subject of this Review. We emphasize aspects of the exponentially increasing knowledge of the microbiota-gut-brain "connectome" and focus attention on the roles that serotonin, Toll-like receptors, and macrophages play in signaling as exemplars of potentially generalizable mechanisms.

Bacterial-Induced Blood Pressure Reduction: Mechanisms for the Treatment of Hypertension via the Gut

Hypertension is a major risk factor for the development of cardiovascular disease. As more research into the gut microbiome emerges, we are finding increasing evidence to support that these microbes may have significant positive and negative effects on blood pressure and associated disorders. The bacterial-derived metabolites that are produced in the gut are capable of widespread effects to several tissue types and organs in the body. It is clear that the extensive metabolic function that is lost with gut dysbiosis is unlikely to be replenished with a single metabolite or bacterial strain. Instead, combinations of bacteria and concomitant therapies will provide a more well-rounded solution to manage hypertension. The bioactive molecules that are recognized in this review will inform on ideal characteristics of candidate bacteria and provide direction for future research on the gut microbiome in hypertension.

Motilin Comparative Study: Structure, Distribution, Receptors, and Gastrointestinal Motility

Motilin, produced in endocrine cells in the mucosa of the upper intestine, is an important regulator of gastrointestinal (GI) motility and mediates the phase III of interdigestive migrating motor complex (MMC) in the stomach of humans, dogs and house musk shrews through the specific motilin receptor (MLN-R). Motilin-induced MMC contributes to the maintenance of normal GI functions and transmits a hunger signal from the stomach to the brain. Motilin has been identified in various mammals, but the physiological roles of motilin in regulating GI motility in these mammals are well not understood due to inconsistencies between studies conducted on different species using a range of experimental conditions. Motilin orthologs have been identified in non-mammalian vertebrates, and the sequence of avian motilin is relatively close to that of mammals, but reptile, amphibian and fish motilins show distinctive different sequences. The MLN-R has also been identified in mammals and non-mammalian vertebrates, and can be divided into two main groups: mammal/bird/reptile/amphibian clade and fish clade. Almost 50 years have passed since discovery of motilin, here we reviewed the structure, distribution, receptor and the GI motility regulatory function of motilin in vertebrates from fish to mammals.

[Depression therapy for somatic diseases]

A review of works devoted to the problem of psychopharmacotherapy of depression in general medical practice is presented. The issues of its comorbidity with somatic and neurological diseases, as well as multimorbidity are discussed. Both direct and side-effects of antidepressants, which are important for effective therapy of not only affective disorders proper, but also the symptoms of the leading pathology, are considered in detail for individual organs and systems. The analysis of the preferred pharmacological classes of antidepressants, which are drugs of first choice, taking into account the somatic condition of the patient, is carried out, and drugs are indicated, the appointment of which is undesirable for the treatment of a patient with a certain disease. The presented results are aimed both at increasing the efficiency of therapy for patients with general medical level of health care, and at increasing the safety of treatment of psychiatric patients with concomitant somatic disorders.

Gut Microbiome and Serum Metabolome Alterations Associated with Isolated Dystonia

Dystonia is a complex neurological movement disorder characterized by involuntary muscle contractions. Increasing studies implicate the microbiome as a possible key susceptibility factor for neurological disorders, but the relationship between the gut microbiota and dystonia remains poorly explored. Here, the gut microbiota of 57 patients with isolated dystonia and 27 age- and environment-matched healthy controls was analyzed by 16S rRNA gene amplicon sequencing. Further, integrative analysis of the gut microbiome and serum metabolome measured by high-performance liquid chromatography-mass spectrometry was performed. No difference in α-diversity was found, while β-diversity was significantly different, with a more heterogeneous community structure among dystonia patients than among controls. The most significant changes in dystonia highlighted an increase in Clostridiales, including Blautia obeum, Dorea longicatena, and Eubacterium hallii, and a reduction in Bacteroides vulgatus and Bacteroides plebeius. The functional analysis revealed that genes related to tryptophan and purine biosynthesis were more abundant in gut microbiota from patients with dystonia, while genes linked to citrate cycle, vitamin B₆, and glycan metabolism were less abundant. The evaluation of serum metabolites revealed altered levels of l-glutamic acid, taurine, and d-tyrosine, suggesting changes in neurotransmitter metabolism. The most modified metabolites strongly inversely correlated with the abundance of members belonging to the Clostridiales, revealing the effect of the gut microbiota on neurometabolic activity. This study is the first to reveal gut microbial dysbiosis in patients with isolated dystonia and identified potential links between gut microbiota and serum neurotransmitters, providing new insight into the pathogenesis of isolated dystonia.

IMPORTANCE Dystonia is the third most common movement disorder after essential tremor and Parkinson’s disease. However, the cause for the majority of cases is not known. This is the first study so far that reveals significant alterations of gut microbiome and correlates the alteration of serum metabolites with gut dysbiosis in patients with isolated dystonia. We demonstrated a general overrepresentation of Clostridiales and underrepresentation of Bacteroidetes in patients with dystonia in comparison with healthy controls. The functional analysis found that genes related to the biosynthesis of tryptophan, which is the precursor of the neurotransmitter serotonin, were more active in isolated dystonia patients. Altered levels of several serum metabolites were found to be associated with microbial changes, such as d-tyrosine, taurine, and glutamate, indicating differences in neurotransmitter metabolism in isolated dystonia. Integrative analysis suggests that neurotransmitter system dysfunction may be a possible pathway by which the gut microbiome participates in the development of dystonia. The gut microbiome changes provide new insight into the pathogenesis of dystonia, suggesting new potential therapeutic directions.

The Mechanism of Secretion and Metabolism of Gut-Derived 5-Hydroxytryptamine

Serotonin, also known as 5-hydroxytryptamine (5-HT), is a metabolite of tryptophan and is reported to modulate the development and neurogenesis of the enteric nervous system, gut motility, secretion, inflammation, sensation, and epithelial development. Approximately 95% of 5-HT in the body is synthesized and secreted by enterochromaffin (EC) cells, the most common type of neuroendocrine cells in the gastrointestinal (GI) tract, through sensing signals from the intestinal lumen and the circulatory system. Gut microbiota, nutrients, and hormones are the main factors that play a vital role in regulating 5-HT secretion by EC cells. Apart from being an important neurotransmitter and a paracrine signaling molecule in the gut, gut-derived 5-HT was also shown to exert other biological functions (in autism and depression) far beyond the gut. Moreover, studies conducted on the regulation of 5-HT in the immune system demonstrated that 5-HT exerts anti-inflammatory and proinflammatory effects on the gut by binding to different receptors under intestinal inflammatory conditions. Understanding the regulatory mechanisms through which 5-HT participates in cell metabolism and physiology can provide potential therapeutic strategies for treating intestinal diseases. Herein, we review recent evidence to recapitulate the mechanisms of synthesis, secretion, regulation, and biofunction of 5-HT to improve the nutrition and health of humans.

Capsaicin-Sensitive Vagal Afferent Nerve-Mediated Interoceptive Signals in the Esophagus

Heartburn and non-cardiac chest pain are the predominant symptoms in many esophageal disorders, such as gastroesophageal reflux disease (GERD), non-erosive reflux disease (NERD), functional heartburn and chest pain, and eosinophilic esophagitis (EoE). At present, neuronal mechanisms underlying the process of interoceptive signals in the esophagus are still less clear. Noxious stimuli can activate a subpopulation of primary afferent neurons at their nerve terminals in the esophagus. The evoked action potentials are transmitted through both the spinal and vagal pathways to their central terminals, which synapse with the neurons in the central nervous system to induce esophageal nociception. Over the last few decades, progress has been made in our understanding on the peripheral and central neuronal mechanisms of esophageal nociception. In this review, we focus on the roles of capsaicin-sensitive vagal primary afferent nodose and jugular C-fiber neurons in processing nociceptive signals in the esophagus. We briefly compare their distinctive phenotypic features and functional responses to mechanical and chemical stimulations in the esophagus. Then, we summarize activation and/or sensitization effects of acid, inflammatory cells (eosinophils and mast cells), and mediators (ATP, 5-HT, bradykinin, adenosine, S1P) on these two nociceptive C-fiber subtypes. Lastly, we discuss the potential roles of capsaicin-sensitive esophageal afferent nerves in processing esophageal sensation and nociception. A better knowledge of the mechanism of nociceptive signal processes in primary afferent nerves in the esophagus will help to develop novel treatment approaches to relieve esophageal nociceptive symptoms, especially those that are refractory to proton pump inhibitors.

Gastroprotective effect of fluvoxamine and ondansetron on stress-induced gastric ulcers in mice

OBJECTIVES

The association between stress and gastric ulcers has been well reported. This study is divided into two parts: the first part of this study is consisted of analyzing the effect of fluvoxamine administration by intracerebroventricular (ICV) and intraperitoneal (IP) injections on stress-induced gastric ulcers. The second part investigates the effect of ondansetron in influencing the protection of the gastric mucous by giving fluvoxamine to the mice before being induced with stress.

METHODS

Water immersion restraint stress (WIRS) was used to induce stress. Fluvoxamine 50 and 100 mg/kg by IP injection, fluvoxamine 9.3 µg, and 18.6 µg by ICV injection 30 min before the induction of stress. Meanwhile, single drug and in combination administered to the mice, ondansetron 3 mg/kg was given by IP at 60 min, and fluvoxamine 50, 100 mg/kg orally at 30 min before stress induction.

RESULTS

The obtained results show fluvoxamine 50 and 100 mg/kg by IP, and fluvoxamine 18.6 µg by ICV had significantly reduced ulcer index with p<0.005, p<0.001, and p<0.005 while fluvoxamine 9.3 µg showed the insignificant result. Fluvoxamine 50 mg/kg, fluvoxamine 100 mg/kg, and ondansetron 3 mg/kg monotherapy have a significant reduction in ulcers with p<0.005, p<0.001, and p<0.05, while the combination drugs showed an insignificant reduction in ulcers.

CONCLUSIONS

Fluvoxamine with different administration routes and ondansetron monotherapy before stress reduce the occurrence of gastric ulcers, while the combination drugs did not increase the protective effect of the gastric mucosa.

Selective stimulation of the ferret abdominal vagus nerve with multi-contact nerve cuff electrodes

Dysfunction and diseases of the gastrointestinal (GI) tract are a major driver of medical care. The vagus nerve innervates and controls multiple organs of the GI tract and vagus nerve stimulation (VNS) could provide a means for affecting GI function and treating disease. However, the vagus nerve also innervates many other organs throughout the body, and off-target effects of VNS could cause major side effects such as changes in blood pressure. In this study, we aimed to achieve selective stimulation of populations of vagal afferents using a multi-contact cuff electrode wrapped around the abdominal trunks of the vagus nerve. Four-contact nerve cuff electrodes were implanted around the dorsal (N = 3) or ventral (N = 3) abdominal vagus nerve in six ferrets, and the response to stimulation was measured via a 32-channel microelectrode array (MEA) inserted into the left or right nodose ganglion. Selectivity was characterized by the ability to evoke responses in MEA channels through one bipolar pair of cuff contacts but not through the other bipolar pair. We demonstrated that it was possible to selectively activate subpopulations of vagal neurons using abdominal VNS. Additionally, we quantified the conduction velocity of evoked responses to determine what types of nerve fibers (i.e., Aδ vs. C) responded to stimulation. We also quantified the spatial organization of evoked responses in the nodose MEA to determine if there is somatotopic organization of the neurons in that ganglion. Finally, we demonstrated in a separate set of three ferrets that stimulation of the abdominal vagus via a four-contact cuff could selectively alter gastric myoelectric activity, suggesting that abdominal VNS can potentially be used to control GI function.

Vortioxetine Derivatives with Amino Acid as Promoiety: Synthesis, Activity, Stability and Preliminary Pharmacokinetic Study

Vortioxetine (Vot) is an effective antidepressant with unique mechanisms exerting multi-target effects. However, severe side-effects such as nausea and vomiting are commonly experienced under conditions of long-term administration. Eight amino acid modified Vot derivatives were designed and prepared in this study. Similar or lower binding affinities of the modified compounds to the serotonin transporter (SERT) than Vot was observed in the 4-(4-(dimethylamino)-styrl)-N-methylpyridinium (ASP⁺) uptake assay on RBL-2H3 cells. Additionally, the majority of derivatives remained sufficiently stable in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF), indicating achievement of intestinal absorption in the modified form. Afterwards, all derived compounds exhibited slower hepatic clearance and a longer half-life, compared to the parent drug Vot. Notably, threonine-modified 3f exhibited significantly lower activity to SERT, serine-modified 3e showed the fastest degradation rate in rat plasma, with hydrolysis to an extent of 50% in 10 min, and better pharmacokinetic properties in rat, including C_max, t_1/2, and especially AUC_0-t, which was ~3-fold higher relative to the parent compound. Although, no clear understanding of SARs has been obtained, modification of Vot with amino acids containing hydroxyl groups may be beneficial to reduce the gastrointestinal side effect of Vot or obtain better pharmacokinetic properties, providing some ideas for the further study in the future.

Effects of Palonosetron on Nausea and Vomiting Induced by Multiple-Day Chemotherapy: A Retrospective Study

Patients who undergo multiple-day chemotherapy sessions experience hard-to-treat nausea and vomiting. Currently, there is no effective standard treatment for this condition. This study compared the preventive effect of first-generation 5-hydroxytryptamine 3 receptor antagonists (5-HT₃ RAs) and second-generation 5-HT₃ RAs palonosetron in multiple-day chemotherapy-induced nausea and vomiting. The design of this study was a retrospective case-control study of patients who received a five-day cisplatin-based chemotherapy and were treated with aprepitant, dexamethasone, granisetron, and ramosetron or palonosetron. The patients were divided into two groups: patients given granisetron and ramosetron (the first-generation group), and those given palonosetron (palonosetron group). The percentage of patients with a complete response or total control was assessed. They were divided into three phases: 0-216 h (overall phase), 0-120 h (remedial phase), and 120-216 h (after phase). The remedial phase was further divided into 0-24 h (early phase) and 24-120 h (later phase). Moreover, the nutritional status of each patient was assessed by noting the patients' total calorie-intake per day and total parenteral nutrition. First-generation 5-HT₃ RAs and palonosetron were used for treatment in 18 and 28 patients, respectively. The complete response rate and caloric oral intake of the later phase were higher in the palonosetron group than in the first-generation group. We conclude that palonosetron treatment was more effective than first-generation 5-HT₃ RAs in controlling multiple-day chemotherapy-induced nausea and vomiting.

Colonic 5-HT4 receptors are targets for novel prokinetic drugs

5-HT₄ receptors are G protein-coupled receptors that link to the stimulatory protein Gs which activates adenylate cyclase to increase intracellular cyclic AMP which then activates protein kinase A (PKA). 5-HT₄ receptors are expressed by neurons in the central and peripheral nervous systems especially the enteric nervous system (ENS). In general, 5-HT₄ receptors are stimulatory and their activation in the ENS enhances neurotransmitter release and propulsive motility patterns. 5-HT₄ receptors are expressed by enterochromaffin (EC) cells, Goblet cells, and most enteric neurons. The study by Konen and colleagues in this issue of Neurogastroenterology and Motility features two novel 5-HT₄ receptor agonists (5-HT₄ -LA1 and 5-HT₄ -LA-2) that are not absorbed from the gastrointestinal tract of mice and act locally in the colonic mucosa to stimulate propulsive motility. The authors show that 5-HT₄ -LA1 and 5-HT₄ -LA2 were not absorbed from the colon and that both drugs stimulated colonic transit when administered by gavage. Both agonists stimulated colonic glass bead expulsion, and 5-HT₄ LA1 activation stimulated fecal output and increased fecal water content. These effects were detected in young and aged mice. 5-HT₄ receptors were also localized to the epithelium of the human duodenum, ileum, and colon. These studies highlight novel 5-HT₄ receptor agonists that have prokinetic actions on the GI tract. These drugs are not absorbed and act locally in the gut mucosa to stimulate propulsive motility while minimizing access to systemic 5-HT₄ receptors and avoiding potential unwanted side effects.

A link between gastrointestinal disorders and migraine: Insights into the gut-brain connection

Background

Migraine is a complex, multifaceted, and disabling headache disease that is often complicated by gastrointestinal (GI) conditions, such as gastroparesis, functional dyspepsia, and cyclic vomiting syndrome (CVS). Functional dyspepsia and CVS are part of a spectrum of disorders newly classified as disorders of gut–brain interaction (DGBI). Gastroparesis and functional dyspepsia are both associated with delayed gastric emptying, while nausea and vomiting are prominent in CVS, which are also symptoms that commonly occur with migraine attacks. Furthermore, these gastric disorders are comorbidities frequently reported by patients with migraine. While very few studies assessing GI disorders in patients with migraine have been performed, they do demonstrate a physiological link between these conditions.

Objective

To summarize the available studies supporting a link between GI comorbidities and migraine, including historical and current scientific evidence, as well as provide evidence that symptoms of GI disorders are also observed outside of migraine attacks during the interictal period. Additionally, the importance of route of administration and formulation of migraine therapies for patients with GI symptoms will be discussed.

Methods

A literature search of PubMed for articles relating to the relationship between the gut and the brain with no restriction on the publication year was performed. Studies providing scientific support for associations of gastroparesis, functional dyspepsia, and CVS with migraine and the impact these associations may have on migraine treatment were the primary focus. This is a narrative review of identified studies.

Results

Although the association between migraine and GI disorders has received very little attention in the literature, the existing evidence suggests that they may share a common etiology. In particular, the relationship between migraine, gastric motility, and vomiting has important clinical implications in the treatment of migraine, as delayed gastric emptying and vomiting may affect oral dosing compliance, and thus, the absorption and efficacy of oral migraine treatments.

Conclusions

There is evidence of a link between migraine and GI comorbidities, including those under the DGBI classification. Many patients do not find adequate relief with oral migraine therapies, which further necessitates increased recognition of GI disorders in patients with migraine by the headache community.

Tryptophan Metabolism and Gut-Brain Homeostasis

Tryptophan is an essential amino acid critical for protein synthesis in humans that has emerged as a key player in the microbiota-gut-brain axis. It is the only precursor for the neurotransmitter serotonin, which is vital for the processing of emotional regulation, hunger, sleep, and pain, as well as colonic motility and secretory activity in the gut. Tryptophan catabolites from the kynurenine degradation pathway also modulate neural activity and are active in the systemic inflammatory cascade. Additionally, tryptophan and its metabolites support the development of the central and enteric nervous systems. Accordingly, dysregulation of tryptophan metabolites plays a central role in the pathogenesis of many neurologic and psychiatric disorders. Gut microbes influence tryptophan metabolism directly and indirectly, with corresponding changes in behavior and cognition. The gut microbiome has thus garnered much attention as a therapeutic target for both neurologic and psychiatric disorders where tryptophan and its metabolites play a prominent role. In this review, we will touch upon some of these features and their involvement in health and disease.

Does Intravenous Ondansetron Affect the Intestinal Motility Pattern in Healthy Donkeys (Equus asinus)?

The current study was undertaken to investigate the effect of intravenous administration of ondansetron on the small and large intestinal motility in donkeys (Equus asinus) using non-invasive transabdominal ultrasonography. The current prospective, randomized, placebo-controlled, crossover study was conducted on thirty healthy donkeys (15 males and 15 females). The selected donkeys underwent two trials; the first was performed by intravenous administration of saline solution as a placebo, while the second was carried out by intravenous administration of ondansetron hydrochloride. The contractility of selected portions of both the small intestine (duodenum and jejunum) and the large intestine (left colon, right colon, and cecum) was counted over a period of 3 minutes before administration (zero time) and at 15, 30, 60, 90, 120, 180, and 240 minutes after administration. The results of this study showed that ondansetron significantly altered the small and large intestinal contractility compared to normal saline. Intravenous administration of ondansetron induced a significant decrease in the duodenal, jejunal and cecal contractility compared to placebo at 30, 60, 90, and 120 minutes after administration. Likewise, ondansetron induced a significant decrease in the left colon and right colon contractility when compared with placebo at 30, 60, 90, 120, and 180 minutes following administration. Ondansetron can be used as a highly specific and selective serotonin 5-HT₃ receptor antagonist for reducing the small and large intestinal motility in donkeys, and is therefore highly suggested for treating spasmodic colic in equine.