The hypersensitivity to colonic distension of IBS patients can be transferred to rats through their fecal microbiota

Lactose intolerance but not lactose maldigestion is more frequent in patients with irritable bowel syndrome than in healthy controls: A meta-analysis

BACKGROUND AND PURPOSE

Irritable bowel syndrome (IBS) affects 10%-20% of the adult population and is characterized by abdominal symptoms without relevant organic disease. There are numerous clinical trials available investigating the relationship between IBS, lactose maldigestion (LM), and lactose intolerance (LI), but there have been no meta-analyses on this topic yet. We aimed to assess the prevalence of LM, objective and subjective (self-reported) LI in IBS patients compared to healthy controls (HC) without IBS.

METHODS

A systematic literature search was conducted up to 24 April 2018 in PubMed, Embase, and Cochrane Library. Adult IBS patients had to be diagnosed according to the Rome criteria or other well-defined criteria system. We enrolled controlled studies including healthy adult participants without IBS, as control group. Odds ratios with 95% confidence intervals were calculated.

KEY RESULTS

Altogether 14 articles were suitable for statistical analyses. IBS patients reported themselves significantly more frequently lactose intolerant than HCs (odds ratio [OR] = 3.499; 95% confidence interval [CI] = 1.622-7.551). Generally, there was no significant difference in the prevalence of LM based on ingested lactose dose (OR = 1.122; 95% CI = 0.929-1.356) and test type (OR = 1.156; 95% CI = 0.985-1.356). However, significantly more IBS patients had objective LI (OR = 2.521; 95% CI = 1.280-4.965).

CONCLUSIONS AND INFERENCES

Lactose intolerance, but not LM is more frequent among patients with IBS compared to HCs. According to our results, IBS among other functional bowel disorders is a possible contributing factor of LI in people with LM.

Pharmacological restoration of gut barrier function in stressed neonates partially reverses long-term alterations associated with maternal separation

RATIONALE

Intestinal permeability plays an important role in gut-brain axis communication. Recent studies indicate that intestinal permeability increases in neonate pups during maternal separation (MS).

OBJECTIVES

The present study aims to determine whether pharmacological inhibition of myosin light chain kinase (MLCK), which regulates tight junction contraction and controls intestinal permeability, in stressed neonates, protects against the long-term effects of MS.

METHODS

Male Wistar rats were exposed to MS (3 h per day from post-natal day (PND)2 to PND14) or left undisturbed and received daily intraperitoneal injection of a MLCK inhibitor (ML-7, 5 mg/kg) or vehicle during the same period. At adulthood, emotional behaviors, corticosterone response to stress, and gut microbiota composition were analyzed.

RESULTS

ML-7 restored gut barrier function in MS rats specifically during the neonatal period. Remarkably, ML-7 prevented MS-induced sexual reward-seeking impairment and reversed the alteration of corticosterone response to stress at adulthood. The effects of ML-7 were accompanied by the normalization of the abundance of members of Lachnospiraceae, Clostridiales, Desulfovibrio, Bacteroidales, Enterorhabdus, and Bifidobacterium in the feces of MS rats at adulthood.

CONCLUSIONS

Altogether, our work suggests that improvement of intestinal barrier defects during development may alleviate some of the long-term effects of early-life stress and provides new insight on brain-gut axis communication in a context of stress.

Social Stress Affects Colonic Inflammation, the Gut Microbiome, and Short-chain Fatty Acid Levels and Receptors

OBJECTIVES

Gastrointestinal disorders, such as inflammatory bowel diseases (IBDs) and functional gastrointestinal disorders (FGIDs), involve disrupted homeostatic interactions between the microbiota and the host. Both disorders are worsened during stress, and in laboratory mice, stress exposure has been shown to change the composition of the gut microbiome. Stress-induced changes to the microbiome exacerbate intestinal inflammation and alter intestinal motility in mice. It is, however, not yet known whether microbiota-derived short-chain fatty acids (butyrate, propionate, and acetate) and their receptors contribute to this effect.

METHODS

Mice were exposed to a social disruption stress, or left undisturbed as a control. After the first stress exposure, mice were orally challenged with Citrobacter rodentium or with vehicle. The levels of short-chain fatty acids (SCFAs) were measured using gas chromatography-mass spectrometry. SCFA receptors were measured via real-time polymerase chain reaction. Microbial community composition was assessed using 16S rRNA gene sequencing.

RESULTS

Stress exposure reduced colonic SCFA levels. Stress exposure and C rodentium, however, significantly increased SCFA levels and changed the expression of SCFA receptors. The levels of SCFAs did not correlate with the severity of colonic inflammation, but the colonic expression of the SCFA receptor GPR41 was positively associated with inflammatory cytokines and colonic histopathology scores. The relative abundances of several taxa of colonic bacteria were significantly changed by stress exposure, including SCFA producers.

CONCLUSIONS

Social stress can have a significant effect on infection-induced colonic inflammation, and stress-induced changes in microbial-produced metabolites and their receptors may be involved.

The Effect of Allogenic Versus Autologous Fecal Microbiota Transfer on Symptoms, Visceral Perception and Fecal and Mucosal Microbiota in Irritable Bowel Syndrome: A Randomized Controlled Study

OBJECTIVES

Fecal microbiota transfer (FMT) is suggested as a potential treatment for patients with irritable bowel syndrome (IBS). We aimed to study the effect of allogenic and autologous FMT on IBS symptoms, visceral sensitivity, and compositional changes in fecal and mucosa-adherent microbiota.

METHODS

Seventeen patients with IBS were randomized either to receive fecal material from a healthy donor (allogenic) or to receive their own fecal material (autologous). The fecal material was administered into the cecum by whole colonoscopy after bowel cleansing.

RESULTS

No significant differences were found between the allogenic and the autologous FMT regarding symptom scores. However, symptom scores of patients receiving allogenic fecal material significantly decreased after FMT compared with baseline (P = 0.02), which was not the case in the autologous group (P = 0.16). Visceral sensitivity was not affected except for a small beneficial effect on urge scores in the autologous group (P < 0.05). While both fecal and mucosa-adherent microbiota of some patients shifted to their respective donor's fecal microbiota, some patients showed no relevant microbial changes after allogenic FMT. Large compositional shifts in fecal and mucosa-adherent microbiota also occurred in the autologous group.

CONCLUSIONS

This study showed that a single FMT by colonoscopy may have beneficial effects in IBS; however, the allogenic fecal material was not superior to the autologous fecal material. This suggests that bowel cleansing prior to the colonoscopy and/or processing of the fecal material as part of the FMT routine contribute to symptoms and gut microbiota composition changes in IBS.

Glutamatergic Signaling Along The Microbiota-Gut-Brain Axis

A complex bidirectional communication system exists between the gastrointestinal tract and the brain. Initially termed the “gut-brain axis” it is now renamed the “microbiota-gut-brain axis” considering the pivotal role of gut microbiota in maintaining local and systemic homeostasis. Different cellular and molecular pathways act along this axis and strong attention is paid to neuroactive molecules (neurotransmitters, i.e., noradrenaline, dopamine, serotonin, gamma aminobutyric acid and glutamate and metabolites, i.e., tryptophan metabolites), sustaining a possible interkingdom communication system between eukaryota and prokaryota. This review provides a description of the most up-to-date evidence on glutamate as a neurotransmitter/neuromodulator in this bidirectional communication axis. Modulation of glutamatergic receptor activity along the microbiota-gut-brain axis may influence gut (i.e., taste, visceral sensitivity and motility) and brain functions (stress response, mood and behavior) and alterations of glutamatergic transmission may participate to the pathogenesis of local and brain disorders. In this latter context, we will focus on two major gut disorders, such as irritable bowel syndrome and inflammatory bowel disease, both characterized by psychiatric co-morbidity. Research in this area opens the possibility to target glutamatergic neurotransmission, either pharmacologically or by the use of probiotics producing neuroactive molecules, as a therapeutic approach for the treatment of gastrointestinal and related psychiatric disorders.

Altered gut microbiota and short chain fatty acids in Chinese children with autism spectrum disorder

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that is characterized by impairments in social interactions and communication, restricted interests and repetitive behaviors. Several studies report a high prevalence of gastrointestinal (GI) symptoms in autistic individuals. Cumulative evidence reveals that the gut microbiota and its metabolites (especially short-chain fatty acids, SCFAs) play an important role in GI disorders and the pathogenesis of ASD. However, the composition of the gut microbiota and its association with fecal SCFAs and GI symptoms of autistic children remain largely unknown. In the present study, we sequenced the bacterial 16S rRNA gene, detected fecal SCFAs, assessed GI symptoms and analyzed the relationship between the gut microbiome and fecal SCFAs in autistic and neurotypical individuals. The results showed that the compositions of the gut microbiota and SCFAs were altered in ASD individuals. We found lower levels of fecal acetic acid and butyrate and a higher level of fecal valeric acid in ASD subjects. We identified decreased abundances of key butyrate-producing taxa (Ruminococcaceae, Eubacterium, Lachnospiraceae and Erysipelotrichaceae) and an increased abundance of valeric acid associated bacteria (Acidobacteria) among autistic individuals. Constipation was the only GI disorder in ASD children in the present study. We also found enriched Fusobacterium, Barnesiella, Coprobacter and valeric acid-associated bacteria (Actinomycetaceae) and reduced butyrate-producing taxa in constipated autistic subjects. It is suggested that the gut microbiota contributes to fecal SCFAs and constipation in autism. Modulating the gut microbiota, especially butyrate-producing bacteria, could be a promising strategy in the search for alternatives for the treatment of autism spectrum disorder.

The Gut Microbiome in Adult and Pediatric Functional Gastrointestinal Disorders

The importance of gut microbiota in gastrointestinal (GI) physiology was well described, but our ability to study gut microbial ecosystems in their entirety was limited by culture-based methods prior to the sequencing revolution. The advent of high-throughput sequencing opened new avenues, allowing us to study gut microbial communities as an aggregate, independent of our ability to culture individual microbes. Early studies focused on association of changes in gut microbiota with different disease states, which was necessary to identify a potential role for microbes and generate novel hypotheses. Over the past few years the field has moved beyond associations to better understand the mechanistic implications of the microbiome in the pathophysiology of complex diseases. This movement also has resulted in a shift in our focus toward therapeutic strategies, which rely on better understanding the mediators of gut microbiota-host cross-talk. It is not surprising the gut microbiome has been implicated in the pathogenesis of functional gastrointestinal disorders given its role in modulating physiological processes such as immune development, GI motility and secretion, epithelial barrier integrity, and brain-gut communication. In this review, we focus on the current state of knowledge and future directions in microbiome research as it pertains to functional gastrointestinal disorders. We summarize the factors that help shape the gut microbiome in human beings. We discuss data from animal models and human studies to highlight existing paradigms regarding the mechanisms underlying microbiota-mediated alterations in physiological processes and their relevance in human interventions. While translation of microbiome science is still in its infancy, the outlook is optimistic and we are advancing in the right direction toward precise mechanism-based microbiota therapies.

Endocrine regulation of gut function - a role for glucagon-like peptide-1 in the pathophysiology of irritable bowel syndrome

NEW FINDINGS

What is the topic of this review? Pathophysiological changes linked to irritable bowel syndrome (IBS) include stress and immune activation, changes in gastrointestinal microbial and bile acid profiles and sensitization of extrinsic and intrinsic gut neurons. This review explores the potential role for L-cells in these pathophysiological changes. What advances does it highlight? L-cells, which secrete glucagon-like peptide-1 in response to nutrients, microbial factors, bile acids and short-chain fatty acids, may sense IBS-related changes in the luminal environment. Glucagon-like peptide-1 can act as a hormone, a paracrine factor or a neuromodulatory factor and, through its actions on central or peripheral neurons, may play a role in gastrointestinal dysfunction.

ABSTRACT

The prevalent and debilitating functional bowel disorder, irritable bowel syndrome (IBS), is characterized by symptoms that include abdominal pain, bloating, diarrhoea and/or constipation. The heterogeneity of IBS underscores a complex multifactorial pathophysiology, which is not completely understood but involves dysfunction of the bi-directional signalling axis between the brain and the gut. This axis incorporates efferent and afferent branches of the autonomic nervous system, circulating endocrine hormones and immune factors, local paracrine and neurocrine factors and microbial metabolites. L-cells, which are electrically excitable biosensors embedded in the gastrointestinal epithelium, secrete glucagon-like peptide-1 (GLP-1) in response to nutrients in the small intestine. However, they appear to function in a different manner more distally in the gastrointestinal tract, where they are activated by luminal factors including short-chain fatty acids, bile acids and microbial metabolic products, all of which are altered in IBS patients. Glucagon-like peptide-1 can also interact with the hypothalamic-pituitary-adrenal stress axis and the immune system, both of which are activated in IBS. Given that a GLP-1 mimetic has been found to alleviate acute pain symptoms in IBS patients, GLP-1 might be important in the manifestation of IBS symptoms. This review assesses the current knowledge about the role of GLP-1 in IBS pathophysiology and its potential role as a signal transducer in the microbiome-gut-brain signalling axis.

Mixed mucosal-parenteral immunizations with the broadly conserved pathogenic Escherichia coli antigen SslE induce a robust mucosal and systemic immunity without affecting the murine intestinal microbiota

Emergence and dissemination of multidrug resistance among pathogenic Escherichia coli have posed a serious threat to public health across developing and developed countries. In combination with a flexible repertoire of virulence mechanisms, E. coli can cause a vast range of intestinal (InPEC) and extraintestinal (ExPEC) diseases but only a very limited number of antibiotics still remains effective against this pathogen. Hence, a broad spectrum E. coli vaccine could be a promising alternative to prevent the burden of such diseases, while offering the potential for covering against several InPEC and ExPEC at once. SslE, the Secreted and Surface-associated Lipoprotein of E. coli, is a widely distributed protein among InPEC and ExPEC. SslE functions ex vivo as a mucinase capable of degrading mucins and reaching the surface of mucus-producing epithelial cells. SslE was identified by reverse vaccinology as a protective vaccine candidate against an ExPEC murine model of sepsis, and further shown to be cross-effective against other ExPEC and InPEC models of infection. In this study, we aimed to gain insight into the immune response to antigen SslE and identify an immunization strategy suited to generate robust mucosal and systemic immune responses. We showed, by analyzing T cell and antibody responses, that mice immunized with SslE via an intranasal prime followed by two intramuscular boosts developed an enhanced overall immune response compared to either intranasal-only or intramuscular-only protocols. Importantly, we also report that this regimen of immunization did not impact the richness of the murine gut microbiota, and mice had a comparable cecal microbial composition, whether immunized with SslE or PBS. Collectively, our findings further support the use of SslE in future vaccination strategies to effectively target both InPEC and ExPEC while not perturbing the resident gut microbiota.

Effect of a prebiotic galactooligosaccharide mixture (B-GOS®) on gastrointestinal symptoms in adults selected from a general population who suffer with bloating, abdominal pain, or flatulence

BACKGROUND

Prebiotics exert beneficial effects upon gastrointestinal (GI) environment, but this is not always accompanied with a positive effect on GI symptoms. B-GOS® is a prebiotic with high selectivity toward bifidobacteria and a variety of other beneficial effects in humans. Here, we investigated its effect on GI symptoms in adults who suffer with bloating, abdominal pain, and flatulence.

METHODS

In a double-blind, placebo-controlled, crossover study, 83 subjects from the general population who presented with GI symptoms during screening period and had a predicted probability of functional bowel disorder of more than 75% were randomized to receive either a placebo or the B-GOS® treatment (2.75 g/d). Subjects were screened for the presence of GI symptoms for 1 week, they consumed the treatments for 2 weeks, and then went through a 2-week washout period, before switching to the other treatment for the final 2 weeks. GI symptoms, bowel movements, and stool consistency were assessed in daily and weekly questionnaires. Quality of life was assessed weekly and depression and anxiety at the end of each treatment period.

RESULTS

B-GOS® resulted in significantly (P < 0.001) lower scores for bloating, flatulence, and abdominal pain both from baseline and placebo at the end of first week. The effect was sustained at the end of second week. It had no effect on the number of bowel movements, consistency of stools, quality of life, or mood throughout the study.

CONCLUSION

Results suggest that B-GOS® could possibly be used in the management of bloating, flatulence, or abdominal pain and warrant further investigation.

Visceral pain: gut microbiota, a new hope?

BACKGROUND

Visceral pain is a complex and heterogeneous disorder, which can range from the mild discomfort of indigestion to the agonizing pain of renal colic. Regulation of visceral pain involves the spinal cord as well as higher order brain structures. Recent findings have linked the microbiota to gastrointestinal disorders characterized by abdominal pain suggesting the ability of microbes to modulate visceral hypersensitivity and nociception to pain.

MAIN BODY

In this review we describe the neuroanatomical basis of visceral pain signaling and the existing evidence of its manipulation exerted by the gut microbiota. We included an updated overview of the potential therapeutic effects of dietary intervention, specifically probiotics and prebiotics, in alleviating hypersensitivity to visceral pain stimuli.

CONCLUSIONS

The gut microbiota dramatically impacts normal visceral pain sensation and affects the mechanisms mediating visceral nociception. Furthermore, manipulation of the gut microbiota using prebiotics and probiotics plays a potential role in the regulation of visceral pain disorders.

Fermentable Sugar Ingestion, Gas Production, and Gastrointestinal and Central Nervous System Symptoms in Patients With Functional Disorders

BACKGROUND & AIMS

Functional gastrointestinal disorders (FGID) are defined by broad phenotypic descriptions and exclusion of recognizable disease. FGIDs cause multi-organ symptoms and abnormal results in a wide range of laboratory tests, indicating broad mechanisms of pathogenesis. Many patients with FGID develop symptoms following ingestion of fermentable sugars; we investigated the associations between symptoms and intestinal gas production following sugar provocation tests to elucidate mechanisms of FGID.

METHODS

We performed fructose and lactose breath tests in 2042 patients with a diagnosis of FGID (based on Rome III criteria), referred to a gastroenterology practice from January 2008 through December 2011. Medical and diet histories were collected from all subjects. Breath samples were collected before and each hour after, for 5 hours, subjects ingested fructose (35 g) and lactose (50 g) dissolved in 300 mL water. Hydrogen and methane gas concentrations were measured and GI and non-GI symptoms were registered for 5 hours following sugar ingestion. Symptom and gas time profiles were compared, treelet transforms were used to derive data-related symptom clusters, and the symptom severity of the clusters were analyzed for their association with breath gas characteristics.

RESULTS

We identified 11 GI and central nervous system (CNS) symptom profiles and hydrogen and methane breath concentrations that changed significantly with time following sugar ingestion. Treelet transform analysis identified 2 distinct clusters, based on GI and CNS symptoms. The severity scores for the GI and CNS symptoms correlated following ingestion of sugars (all, P < .0001). However, only the GI symptoms associated with hydrogen and methane gas production (all, P < .0001).

CONCLUSIONS

In an analysis of breath test results from more than 2000 patients with FGIDs, we identified clusters of GI and CNS symptoms in response to fructose of lactose ingestion. The association between specific symptoms and breath gas concentrations indicate distinct mechanisms of FGID pathogenesis, such as changes in the microbiome or mechanical and chemical sensitization. ClinicalTrials.gov ID: NCT02085889.

Focus on the use of antidepressants to treat pediatric functional abdominal pain: current perspectives

Chronic abdominal pain is frequently encountered in pediatric practice. A large proportion of cases meet Rome criteria for abdominal pain-functional gastrointestinal disorders (AP-FGIDs). These disorders are costly and, in some cases, lead to impairment of daily functioning and overall quality of life. Pathophysiologic mechanisms include early stressful events, visceral hypersensitivity, dysmotility, changes in intestinal microbiota, and altered central nervous system processing. They are considered disorders of the brain-gut interaction. The diagnosis is made on clinical grounds using symptom-based criteria (Rome criteria). Anxiety and depressive symptoms are more prevalent in patients with AP-FGIDs. Therefore, attention has been directed to the use of neuromodulators as potential interventions for AP-FGIDs. Antidepressants are one type of neuromodulators, and one of the most studied drugs for the management of AP-FGIDs in adult and pediatric population. Data available in pediatric population have significant limitations including nonuniform methodology with different study designs and primary endpoints. Evidence of the efficacy of antidepressants in the management of pediatric AP-FGIDs is not consistent. There is an urgent need for well-designed randomized clinical trials using age-appropriate validated outcome measures. Careful consideration must be given to adverse effects, particularly increased suicidal ideation.

Neuropsychiatric Disorders: Influence of Gut Microbe to Brain Signalling

The microbiome gut brain (MGB) axis consists of bidirectional routes of communication between the gut and the brain. It has emerged as a potential therapeutic target for multiple medical specialties including psychiatry. Significant numbers of preclinical trials have taken place with some transitioning to clinical studies in more recent years. Some positive results have been reported secondary to probiotic administration in both healthy populations and specific patient groups. This review aims to summarise the current understanding of the MGB axis and the preclinical and clinical findings relevant to psychiatry. Significant differences have been identified between the microbiome of patients with a diagnosis of depressive disorder and healthy controls. Similar findings have occurred in patients diagnosed with bipolar affective disorder and irritable bowel syndrome. A probiotic containing Lactobacillus acidophilus, Lactobacillus casei, and Bifidobacterium bifidum produced a clinically measurable symptom improvement in patients with depressive disorder. To date, some promising results have suggested that probiotics could play a role in the treatment of stress-related psychiatric disease. However, more well-controlled clinical trials are required to determine which clinical conditions are likely to benefit most significantly from this novel approach.

Microbiota dysbiosis and its pathophysiological significance in bowel obstruction

Bowel obstruction (OB) causes local and systemic dysfunctions. Here we investigated whether obstruction leads to alterations in microbiota community composition and total abundance, and if so whether these changes contribute to dysfunctions in OB. Partial colon obstruction was maintained in rats for 7 days. The mid colon and its intraluminal feces - proximal to the obstruction - were studied. OB did not cause bacterial overgrowth or mucosa inflammation, but induced profound changes in fecal microbiota composition and diversity. At the phylum level, the 16S rRNA sequencing showed a significant decrease in the relative abundance of Firmicutes with corresponding increases in Proteobacteria and Bacteroidetes in OB compared with sham controls. Daily treatment using broad spectrum antibiotics dramatically reduced total bacterial abundance, but increased the relative presence of Proteobacteria. Antibiotics eliminated viable bacteria in the spleen and liver, but not in the mesentery lymph node in OB. Although antibiotic treatment decreased muscle contractility in sham rats, it had little effect on OB-associated suppression of muscle contractility or inflammatory changes in the muscle layer. In conclusion, obstruction leads to marked dysbiosis in the colon. Antibiotic eradication of microbiota had limited effects on obstruction-associated changes in inflammation, motility, or bacterial translocation.

Role of Gut Microbiota-Gut Hormone Axis in the Pathophysiology of Functional Gastrointestinal Disorders

Gut microbiota exert a pivotal influence on various functions including gastrointestinal (GI) motility, metabolism, nutrition, immunity, and the neuroendocrine system in the host. These effects are mediated by not only short-chain fatty acids produced by microbiota but also gut hormones and inflammatory signaling by enteroendocrine and immune cells under the influence of the microbiota. GI motility is orchestrated by the enteric nervous system and hormonal networks, and disturbance of GI motility plays an important role in the pathophysiology of functional gastrointestinal disorders (FGIDs). In this context, microbiota-associated mediators are considered to act on specific receptors, thus affecting the enteric nervous system and, subsequently, GI motility. Thus, the pathophysiology of FGIDs is based on alterations of the gut microbiota/gut hormone axis, which have crucial effects on GI motility.

Irritable bowel syndrome in children: Current knowledge, challenges and opportunities

Irritable bowel syndrome (IBS) is a common and troublesome disorder in children with an increasing prevalence noted during the past two decades. It has a significant effect on the lives of affected children and their families and poses a significant burden on healthcare systems. Standard symptom-based criteria for diagnosis of pediatric IBS have changed several times during the past two decades and there are some differences in interpreting symptoms between different cultures. This has posed a problem when using them to diagnose IBS in clinical practice. A number of potential patho-physiological mechanisms have been described, but so far the exact underlying etiology of IBS is unclear. A few potential therapeutic modalities have been tested in children and only a small number of them have shown some benefit. In addition, most of the described patho-physiological mechanisms and treatment options are based on adult studies. These have surfaced as challenges when dealing with pediatric IBS and they need to be overcome for effective management of children with IBS. Recently suggested top-down and bottom-up models help integrating reported patho-physiological mechanisms and will provide an opportunity for better understanding of the diseases process. Treatment trials targeting single treatment modalities are unlikely to have clinically meaningful therapeutic effects on IBS with multiple integrating patho-physiologies. Trials focusing on multiple combined pharmacological and non-pharmacological therapies are likely to yield more benefit. In addition to treatment, in the future, attention should be paid for possible prevention strategies for IBS.

Altered Intestinal Microbiota with Increased Abundance of Prevotella Is Associated with High Risk of Diarrhea-Predominant Irritable Bowel Syndrome

Alterations in gut microbiota are postulated to be an etiologic factor in the pathogenesis of irritable bowel syndrome (IBS). To determine whether IBS patients in China exhibited differences in their gut microbial composition, fecal samples were collected from diarrhea-predominant IBS (IBS-D) and healthy controls and evaluated by 16S ribosomal RNA gene sequence and quantitative real-time PCR. A mouse model of postinfectious IBS (PI-IBS) was established to determine whether the altered gut microbiota was associated with increased visceral hypersensitivity. The results indicated that there were significant differences in the bacterial community profiles between IBS-D patients and healthy controls. Prevotella was more abundant in fecal samples from IBS-D patients compared with healthy controls (p < 0.05). Meanwhile, there were significant reductions in the quantity of Bacteroides, Bifidobacteria, and Lactobacillus in IBS-D patients compared with healthy controls (p < 0.05). Animal models similarly showed an increased abundance of Prevotella in fecal samples compared with control mice (p < 0.05). Finally, after the PI-IBS mice were cohoused with control mice, both the relative abundance of Prevotella and visceral hypersensitivity of PI-IBS mice were decreased. In conclusion, the altered intestinal microbiota is associated with increased visceral hypersensitivity and enterotype enriched with Prevotella may be positively associated with high risk of IBS-D.

Functional abdominal pain disorders in children

Chronic abdominal pain is a common problem in pediatric practice. The majority of cases fulfill the Rome IV criteria for functional abdominal pain disorders (FAPDs). At times, these disorders may lead to rather serious repercussions. Area covered: We have attempted to cover current knowledge on epidemiology, pathophysiology, risk factors related to pathophysiology, clinical evaluation and management of children with FAPDs. Expert commentary: FAPDs are a worldwide problem with a pooled prevalence of 13.5%. There are a number of predisposing factors and pathophysiological mechanisms including stressful events, child maltreatment, visceral hypersensitivity, altered gastrointestinal motility and change in intestinal microbiota. It is possible that the environmental risk factors intricately interact with genes through epigenetic mechanisms to contribute to the pathophysiology. The diagnosis mainly depends on clinical evaluation. Commonly used pharmacological interventions do not play a major role in relieving symptoms. Centrally directed, nonpharmacological interventions such as hypnotherapy and cognitive behavioral therapy have shown both short and long term efficacy in relieving pain in children with FAPDs. However, these interventions are time consuming and need specially trained staff and therefore, not currently available at grass root level. Clinicians and researchers should join hands in searching for more pragmatic and effective therapeutic modalities to improve overall care of children with FAPDs.

Butyrate promotes visceral hypersensitivity in an IBS-like model via enteric glial cell-derived nerve growth factor

BACKGROUND

Altered visceral sensation is common in irritable bowel syndrome (IBS) and nerve growth factor (NGF) participates in visceral pain development. Sodium butyrate (NaB) could induce colonic hypersensitivity via peripheral up-regulation of NGF in animals. Enteric glial cells (EGCs) appear to be an important source of NGF. Whether butyrate could induce visceral hypersensitivity via increased EGC-derived NGF is still unknown.

METHODS

CRL-2690 cells were used for transcriptome analyses after butyrate treatment. Rats received butyrate enemas to induce colonic hypersensitivity. Colorectal distention test was performed to assess visceral sensitivity. Immunofluorescence studies were used to evaluate the co-expression of glial fibrillary acidic protein (GFAP) and NGF or growth associated protein 43 in animal model. NGF expression in rat colon was also investigated. In vitro, CRL-2690 cells were stimulated with NaB or trichostatin A (TSA). NGF or GFAP expression was also examined.

KEY RESULTS

Transcriptome analyses showed that butyrate induced marked changes of genes expression related to neurotrophic signaling pathways. NaB-treated rats showed increased visceral sensitivity. An improved NGF expression level was observed in NaB-treated rats. Meanwhile, a 2.1-fold increase in co-expression of GFAP and NGF was also determined in rats received NaB enemas. In cultured cells, both NaB and TSA treatment could cause obvious NGF expression. Thus, butyrate might regulate EGC function via histone deacetylase inhibition.

CONCLUSIONS & INFERENCES

Butyrate-EGC interplay may play a pivotal role in regulation of NGF expression and the development of colonic hypersensitivity in IBS-like animal model.

Irritable bowel syndrome and endometriosis: New insights for old diseases

Irritable bowel syndrome and endometriosis are two diseases affecting a significant part of the female population, either together or individually, with remarkable consequences in the quality of life. Several studies suggest an epidemiological association between them. Their association may not be just an epidemiological phenomenon, but the manifestation of a pathophysiological correlation, which probably generates a mutual promotion phenomenon. In particular, both clinical entities share the presence of a chronic low-grade inflammatory state at the basis of the disease persistence. Recognizing this association is highly significant due to their prevalence and the common clinical manifestation occurring with a chronic abdominal pain. A further multi disciplinary approach is suggested in these patients' management in order to achieve an adequate diagnostic work up and a targeted therapy. This paper analyses some common pathophysiological mechanisms, such as activation of mast cell line, neuronal inflammation, dysbiosis and impaired intestinal permeability. The aim was to investigate their presence in both IBS and endometriosis, and to show the complexity of their relationship in the generation and maintenance of chronic inflammation.

A Review of Microbiota and Irritable Bowel Syndrome: Future in Therapies

Irritable bowel syndrome (IBS), one of the most frequent digestive disorders, is characterized by chronic and recurrent abdominal pain and altered bowel habit. The origin seems to be multifactorial and is still not well defined for the different subtypes. Genetic, epigenetic and sex-related modifications of the functioning of the nervous and immune-endocrine supersystems and regulation of brain-gut physiology and bile acid production and absorption are certainly involved. Acquired predisposition may act in conjunction with infectious, toxic, dietary and life event-related factors to enhance epithelial permeability and elicit mucosal microinflammation, immune activation and dysbiosis. Notably, strong evidence supports the role of bacterial, viral and parasitic infections in triggering IBS, and targeting microbiota seems promising in view of the positive response to microbiota-related therapies in some patients. However, the lack of highly predictive diagnostic biomarkers and the complexity and heterogeneity of IBS patients make management difficult and unsatisfactory in many cases, reducing patient health-related quality of life and increasing the sanitary burden. This article reviews specific alterations and interventions targeting the gut microbiota in IBS, including prebiotics, probiotics, synbiotics, non-absorbable antibiotics, diets, fecal transplantation and other potential future approaches useful for the diagnosis, prevention and treatment of IBS.

Volatile Organic Compounds in Feces Associate With Response to Dietary Intervention in Patients With Irritable Bowel Syndrome

BACKGROUND & AIMS

Dietary interventions are effective in management of patients with irritable bowel syndrome (IBS), although responses vary. We investigated whether fecal levels of volatile organic compounds (VOCs) associate with response to dietary interventions in patients with IBS.

METHODS

Adults who fulfilled the Rome III criteria for IBS were recruited to a 2x2 factorial randomized controlled trial. Patients were randomly assigned to a group counselled to follow a diet low in fructans, galacto-oligosaccharides, lactose, fructose, and polyols (low-FODMAP diet, n = 46) or a group that received placebo dietary advice (sham diet, n = 47) for 4 weeks. Patients from each group were also given either a multi-strain probiotic or placebo supplement. Response was defined as a reduction of 50 points or more on the validated IBS symptom scoring system. Fecal samples were collected from participants at baseline and end of the 4-week study period; VOCs were analyzed by a gas-chromatography sensor device. VOC profiles were determined using a pipeline involving wavelet transformation followed by feature selection based on random forest. A partial least squares classifier was constructed to classify VOC profiles by response and accuracies were determined using 10-fold cross-validation.

RESULTS

Data from 93 patients who completed the study (63 female) were used in the final analysis. More patients responded to the low-FODMAP diet (37/46, 80%) than the sham diet (21/47, 45%) (P < .001), but there was no difference in response between patients given the probiotic (31/49, 63%) vs the placebo (27/44, 61%) (P = .850), with no interaction between the diet and supplement interventions. At baseline, VOC profiles contained 15 features that classified response to the low-FODMAP diet with a mean accuracy of 97% (95% CI, 96%-99%) and 10 features that classified response to probiotic with a mean accuracy of 89% (95% CI, 86%-92%). End of treatment models achieved similar predictive powers and accuracies.

CONCLUSION

Fecal VOC profiling is a low cost, non-invasive tool that might be used to predict responses of patients with IBS to low-FODMAP diet and probiotics and identify their mechanisms of action. ISRCTN registry no: 02275221.

Gut Microbiota-Based Therapies for Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a common, heterogeneous disorder characterized by abdominal pain associated with changes in bowel habits. The pathogenesis of IBS is multifactorial and may relate to alterations in the gut microbiota, changes in visceral sensation and motility, and genetic and environmental factors. Administration of systemic antibiotics may increase the risk of IBS by altering gastrointestinal homeostasis. Therapeutic interventions for IBS with diarrhea that are thought to target alterations in the gut microbiota include the nonsystemic antibiotic rifaximin, the medical food serum-derived bovine immunoglobulin, prebiotics, probiotics, and dietary modification. SYN-010 is a modified-release statin formulation that reduces methane production by Methanobrevibacter smithii and is currently in development for the treatment of patients with constipation-predominant IBS. Use of these interventions in the management of patients with IBS may function to restore a healthy gut microbiota and ameliorate symptoms of IBS.

Bifidobacterium longum and Lactobacillus helveticus Synergistically Suppress Stress-related Visceral Hypersensitivity Through Hypothalamic-Pituitary-Adrenal Axis Modulation

Background/Aims

Visceral pain and hypothalamic-pituitary-adrenal axis (HPA) dysregulation is a common characteristic in irritable bowel syndrome (IBS) patients. Previously, we reported that a probiotic formulation (Lactobacillus helveticus R0052 and Bifidobacterium longum R0175) prevents chronic stress-mediated brain function abnormalities by attenuating the HPA axis response. Here, we compared the effect between different probiotic treatments on the perception of visceral pain during colorectal distension (CRD) following a chronic stress and the consequences to the activity of the HPA axis.

Methods

After a 2-week treatment with a combined probiotic formulation, or L. helveticus or B. longum alone in stressed mice, the visceral pain in response to CRD was recorded. The expression of glucocorticoid receptors was determined in the different brain areas involved in the stress response (hypothalamus, hippocampus, and prefrontal cortex). The plasma levels of stress hormones were also measured.

Results

A pretreatment using the combination of probiotic formulation significantly reduces the chronic stress-induced visceral hypersensitivity respectively at 0.06, 0.08, and 0.10 mL CRD volume. However, a single probiotic (B. longum or L. helveticus) administration is less effective in reducing visceral pain in stressed mice. Moreover, the expression of the glucocorticoid receptor mRNA was consistently up-regulated in several brain areas after pretreatment with a combined probiotic, which correlated with the normalization of stress response compared to the inconsistent effects of a single probiotic.

Conclusion

The combination of L. helveticus and B. longum is more effective in regulating glucocorticoid negative feedback on the HPA axis than probiotic alone and subsequently in treating stress-induced visceral pain.

Fecal Microbiota Transplantation Is Effective in Relieving Visceral Hypersensitivity in a Postinfectious Model

Aim

To investigate the effect of fecal microbiota transplantation on visceral hypersensitivity compared with Bifidobacterium longum.

Methods

Mice visceral hypersensitivity was induced by Trichinella spiralis. After 8 weeks, they were divided into three groups (controls, Bifidobacterium longum, and fecal microbiota transplantation) and were daily treated by gavage with 0.2 ml PBS, Bifidobacterium longum HB55020, or fecal microbiota for 7 days. Visceral hypersensitivity was tested with abdominal withdrawal reflex. Permeability of colon epithelium was assessed with Ussing chamber.

Results

After administration of Bifidobacterium longum, compared with mice in postinfectious group, mice had higher pain threshold (p < 0.05). After administration of fecal microbiota, compared with mice in postinfectious group, mice had higher pain threshold (p < 0.05). Fecal microbiota transplantation was as effective as Bifidobacterium in relieving visceral hypersensitivity. Administration of Bifidobacterium longum or fecal microbiota transplantation improved colon epithelium permeability. Expression of occluding-1 was increased.

Conclusion

Manipulation of microbiota is effective in relieving visceral hypersensitivity. Fecal microbiota transplantation is as effective as Bifidobacterium longum administration.

The Role of Bacteria, Probiotics and Diet in Irritable Bowel Syndrome

Irritable bowel syndrome is a highly prevalent gastrointestinal disorder that threatens the quality of life of millions and poses a substantial financial burden on healthcare systems around the world. Intense research into the human microbiome has led to fascinating discoveries which directly and indirectly implicate the diversity and function of this occult organ in irritable bowel syndrome (IBS) pathophysiology. The benefit of manipulating the gastrointestinal microbiota with diet and probiotics to improve symptoms has been demonstrated in a wealth of both animal and human studies. The positive and negative mechanistic roles bacteria play in IBS will be explored and practical probiotic and dietary choices offered.

Gut dysbiosis and irritable bowel syndrome: The potential role of probiotics

OBJECTIVE

To discuss the role of gut dysbiosis in the development of irritable bowel syndrome (IBS) and the impact of probiotics as a potential therapeutic measure.

METHODS

PubMed was used to search for all of the studies published over the last 15 years using the key words: "irritable bowel syndrome" and "gut dysbiosis" or "probiotic". More than 800 articles were found, but only those published in English or providing evidence-based data were included in the evaluation.

RESULTS

IBS is a common disease for which no resolutive therapy is presently available. In recent years, strong evidence of a possible relationship between modifications of the gut microbiota composition and development of IBS has been collected. Moreover, the evidence showed that attempts to treat acute infectious and post-antibiotic gastroenteritis with some probiotics were significantly effective in a great number of patients, leading many experts to suggest the use of probiotics to address all of the clinical problems associated with IBS.

CONCLUSION

The available data are promising, but presently, a precise definition of which probiotic or which mixture of probiotics is effective cannot be made. Moreover, the dose and duration of treatment has not been established. Finally, we do not know whether probiotic treatment should be different according to the type of IBS. Further studies are needed before probiotics can be considered a reliable treatment for IBS.

[Therapeutic modulation of intestinal microbiota in irritable bowel syndrome. From probiotics to fecal microbiota therapy]

BACKGROUND

An abnormal intestinal microbiota (dysbiosis) plays a central role in the pathogenesis of the irritable bowel syndrome.

METHOD

An overview of four current options for the treatment of irritable bowel syndrome, which are characterized by modulation of intestinal microbiota, is given.

RESULTS AND CONCLUSIONS

Probiotics have very different effects on the individual symptoms of the irritable bowel. The choice of the appropriate preparation should therefore be based on the clinical symptomatology. The antibiotic rifaximin is effective in selected patients. Some patients also benefit from the repetition of this therapy. A FODMAP-reduced diet has shown significant alleviation of irritable bowel symptoms in studies. The fecal microbiota therapy (FMT) is a promising treatment option. At present, however, there are no such placebo-controlled studies to assess the effectiveness of this method.

Biomarkers for visceral hypersensitivity in patients with irritable bowel syndrome

BACKGROUND

Increased visceral sensitivity is observed in up to 60% of patients with Irritable Bowel Syndrome (IBS). Mucosal inflammation, altered neuroendocrine activity and intraluminal metabolic processes may contribute to the development of visceral hypersensitivity. Previously, we demonstrated that biomarkers, indicative for these biological processes, were altered in IBS patients compared to healthy controls. However, how these processes relate to visceral hypersensitivity is unknown.

AIM

The aim of this study was to provide insight in biological processes associated with visceral hypersensitivity. Fecal and plasma biomarkers were measured in normosensitive and hypersensitive IBS patients.

METHODS

A total of 167 IBS patients underwent a rectal barostat procedure to assess visceral sensitivity to pain. Based on the outcome, patients were classified into a normosensitive or hypersensitive group. Calprotectin, human β-defensin 2 (HBD2), chromogranin A (CgA), and short chain fatty acids (SCFAs) were measured in feces, citrulline in plasma, and serotonin and its main metabolite 5-hydroxyindoleacetic acid (5-HIAA) in platelet-poor plasma.

KEY RESULTS

Fecal markers and plasma citrulline were measured in 83 hypersensitive and 84 normosensitive patients, while platelet-poor plasma for the assessment of serotonin and 5-HIAA was available for a subgroup, i.e. 53 hypersensitive and 42 normosensitive patients. No statistically significant differences were found in concentrations of biomarkers between groups. Adjustment of the analyses for potential confounders, such as medication use, did not alter this conclusion.

CONCLUSIONS & INFERENCES

Our findings do not support a role for the biological processes as ascertained by biomarkers in visceral hypersensitivity in IBS patients. This study is registered in the US National Library of Medicine (clinicaltrials.gov, NCT00775060).

Role of microbiota in the pathogenesis of functional disorders of the lower GI tract: Work in progress

Functional bowel disorders affect a significant proportion of people word wide. Patients suffer from longstanding symptoms of abdominal pain or discomfort in combination with abnormal bowel habits. The evidence for role of microbiota is currently contradictory and descriptive. This review aims to summarize the reasons which include methodological differences in DNA extraction and sample handling along with other factors such as diet, prior antibiotic use and transit, all important major determinants of microbiota which are difficult to control. Randomized studies of specific intervention in which such factors are varied may improve reproducibility and consistency of findings in future research.

Intestinal Fungal Dysbiosis Is Associated With Visceral Hypersensitivity in Patients With Irritable Bowel Syndrome and Rats

BACKGROUND & AIMS

Visceral hypersensitivity is one feature of irritable bowel syndrome (IBS). Bacterial dysbiosis might be involved in the activation of nociceptive sensory pathways, but there have been few studies of the role of the mycobiome (the fungal microbiome) in the development of IBS. We analyzed intestinal mycobiomes of patients with IBS and a rat model of visceral hypersensitivity.

METHODS

We used internal transcribed spacer 1-based metabarcoding to compare fecal mycobiomes of 18 healthy volunteers with those of 39 patients with IBS (with visceral hypersensitivity or normal levels of sensitivity). We also compared the mycobiomes of Long-Evans rats separated from their mothers (hypersensitive) with non-handled (normally sensitive) rats. We investigated whether fungi can cause visceral hypersensitivity using rats exposed to fungicide (fluconazole and nystatin). The functional relevance of the gut mycobiome was confirmed in fecal transplantation experiments: adult maternally separated rats were subjected to water avoidance stress (to induce visceral hypersensitivity), then given fungicide and donor cecum content via oral gavage. Other rats subjected to water avoidance stress were given soluble β-glucans, which antagonize C-type lectin domain family 7 member A (CLEC7A or DECTIN1) signaling via spleen-associated tyrosine kinase (SYK), a SYK inhibitor to reduce visceral hypersensitivity, or vehicle (control). The sensitivity of mast cells to fungi was tested with mesenteric windows (ex vivo) and the human mast cell line HMC-1.

RESULTS

α diversity (Shannon index) and mycobiome signature (stability selection) of both groups of IBS patients differed from healthy volunteers, and the mycobiome signature of hypersensitive patients differed from that of normally sensitive patients. We observed mycobiome dysbiosis in rats that had been separated from their mothers compared with non-handled rats. Administration of fungicide to hypersensitive rats reduced their visceral hypersensitivity to normal levels of sensitivity. Administration of cecal mycobiomes from rats that had been separated from their mothers (but not non-handled mycobiome) restored hypersensitivity to distension. Administration of soluble β-glucans or a SYK inhibitor reduced visceral hypersensitivity, compared with controls. Particulate β-glucan (a DECTIN-1 agonist) induced mast cell degranulation in mesenteric windows and HMC-1 cells responded to fungal antigens by release of histamine.

CONCLUSIONS

In an analysis of patients with IBS and controls, we associated fungal dysbiosis with IBS. In studies of rats, we found fungi to promote visceral hypersensitivity, which could be reduced by administration of fungicides, soluble β-glucans, or a SYK inhibitor. The intestinal fungi might therefore be manipulated for treatment of IBS-related visceral hypersensitivity.

The microbiome and disorders of the central nervous system

Alterations of the gut microbiota have been associated with stress-related disorders including depression and anxiety and irritable bowel syndrome (IBS). More recently, researchers have started investigating the implication of perturbation of the microbiota composition in neurodevelopmental disorders including autism spectrum disorders and Attention-Deficit Hypersensitivity Disorder (ADHD). In this review we will discuss how the microbiota is established and its functions in maintaining health. We also summarize both pre and post-natal factors that shape the developing neonatal microbiota and how they may impact on health outcomes with relevance to disorders of the central nervous system. Finally, we discuss potential therapeutic approaches based on the manipulation of the gut bacterial composition.

Early-life adversity, epigenetics, and visceral hypersensitivity

Abdominal pain is associated with many gastrointestinal dysfunctions, such as irritable bowel syndrome (IBS), functional dyspepsia, and inflammatory bowel disease (IBD). Visceral hypersensitivity is a key reason for development of abdominal pain that presents in these gastrointestinal disorders/diseases. The pathogenesis of visceral hypersensitivity is complex and still far from being fully understood. In animal studies, visceral hypersensitivity has been linked to several early-life adverse (ELA) events. In humans, IBD, functional dyspepsia, and IBS can have adult onset, though the adverse events that lead to visceral hypersensitivity are largely uncharacterized. In this issue of the journal, Aguirre et al. report the interesting finding that epigenetics underlies the effects of ELA events on visceral hypersensitivity. This mini-review examines models of ELA events leading to visceral hypersensitivity and the potential role of epigenetics, as reported by Aguirre et al. and others.

Dialysis membrane-enforced microelectrode array measurement of diverse gut electrical activity

A variety of electrical activities occur depending on the functional state in each section of the gut, but the application of microelectrode array (MEA) is rather limited. We thus developed a dialysis membranes-enforced technique to investigate diverse and complex spatio-temporal electrical activity in the gut. Muscle sheets isolated from the gastrointestinal (GI) tract of mice along with a piece of dialysis membrane were woven over and under the strings to fix them to the anchor rig, and mounted on an 8×8 MEA (inter-electrode distance=150µm). Small molecules (molecular weight <12,000) were exchanged through the membrane, maintaining a physiological environment. Low impedance MEA was used to measure electrical signals in a wide frequency range. We demonstrated the following examples: 1) pacemaker activity-like potentials accompanied by bursting spike-like potentials in the ileum; 2) electrotonic potentials reflecting local neurotransmission in the ileum; 3) myoelectric complex-like potentials consisting of slow and rapid oscillations accompanied by spike potentials in the colon. Despite their limited spatial resolution, these recordings detected transient electric activities that optical probes followed with difficulty. In Addition, propagation of pacemaker-like potential was visualized in the stomach and ileum. These results indicate that the dialysis membrane-enforced technique largely extends the application of MEA, probably due to stabilisation of the access resistance between each sensing electrode and a reference electrode and improvement of electric separation between sensing electrodes. We anticipate that this technique will be utilized to characterise spatio-temporal electrical activities in the gut in health and disease.

Microbiota regulates visceral pain in the mouse

The perception of visceral pain is a complex process involving the spinal cord and higher order brain structures. Increasing evidence implicates the gut microbiota as a key regulator of brain and behavior, yet it remains to be determined if gut bacteria play a role in visceral sensitivity. We used germ-free mice (GF) to assess visceral sensitivity, spinal cord gene expression and pain-related brain structures. GF mice displayed visceral hypersensitivity accompanied by increases in Toll-like receptor and cytokine gene expression in the spinal cord, which were normalized by postnatal colonization with microbiota from conventionally colonized (CC). In GF mice, the volumes of the anterior cingulate cortex (ACC) and periaqueductal grey, areas involved in pain processing, were decreased and enlarged, respectively, and dendritic changes in the ACC were evident. These findings indicate that the gut microbiota is required for the normal visceral pain sensation.

DOI:http://dx.doi.org/10.7554/eLife.25887.001

The human gut is home to over 100 trillion microbes collectively known as the gut microbiota. These microbes help us to digest food and absorb the nutrients effectively. A diverse and stable community of gut microbes is believed to be important for good health. Recently, it has also become clear that the microbiota can also influence the brain and how we behave. For example, many studies suggest that gut microbiota can alter how an individual perceives pain, but it is not clear how this works.

Rodents are often used in experiments as models of human biology. One of the most frequently used rodent models in studies of gut microbes is the “germ-free” mouse. These mice grow up in laboratory environments that are completely free of microbes, making it possible to study how having no gut microbes affects the health and behaviour of the mice. Luczynski, Tramullas et al. used germ-free mice to study how the gut microbiota influences an animal’s sensitivity to pain.

The experiments show that, compared to mice with normal gut microbiota, the germ-free mice were more sensitive to pain from internal organs especially the gut. These mice also produced larger amounts of specific proteins involved in immune responses, which contributed to the animal’s increased sensitivity to pain. Allowing the germ-free mice to be colonised with gut microbes could reverse these changes.

The experiments also show that the germ-free mice had changes in the size of two areas of the brain involved in sensing pain: an area called the anterior cingulate cortex was smaller, while the periaqueductal grey region was enlarged. There were also differences in individual nerve cells within the anterior cingulate cortex compared to normal mice.

The findings of Luczynski, Tramullas et al. reinforce the idea that the gut microbiota is involved in the sensation of pain from internal organs, and show that hypersensitivity to this form of pain can be reversed later in life by colonising the gut with microbes. Continuing to study the impact of microbes on this type of pain could aid the development of new therapies for the treatment of pain disorders in humans.

DOI:http://dx.doi.org/10.7554/eLife.25887.002

Serial Frozen Fecal Microbiota Transplantation in the Treatment of Chronic Intestinal Pseudo-obstruction: A Preliminary Study

Background/Aims

Chronic intestinal pseudo-obstruction (CIPO) is a serious, life-threatening motility disorder that is often related to bacterial overgrowth. Fecal microbiota transplantation (FMT) results in restoration of the normal intestinal microbial community structure. We investigated the efficacy of FMT in the treatment of CIPO patients.

Methods

Nine patients (age 18–53 years) with CIPO were enrolled in this prospective, open-label study. Patients received FMT for 6 consecutive days through nasojejunal (NJ) tubes and were followed up for 8 weeks after treatment. We evaluated the rate of clinical improvement and remission, feeding tolerance of enteral nutrition, and CT imaging scores of intestinal obstructions. Lactulose hydrogen breath tests were performed before FMT and 8 weeks after FMT to evaluate for the presence small intestinal bacterial overgrowth (SIBO).

Results

FMT significantly alleviated bloating symptoms, and symptoms of pain were relieved 2 weeks after FMT. Enteral nutrition administered through a NJ tube after FMT was well-tolerated by 66.7% (6/9) of patients. CT scores of intestinal obstructions were significantly reduced after FMT (P = 0.014). SIBO was eliminated in 71.0% (5/7) of patients.

Conclusions

This pilot study demonstrated the safety of using FMT. FMT may relieve symptoms in selected patients with CIPO. FMT may also improve patient tolerance of enteral nutrition delivered via a NJ tube.

Microbiota Is Involved in Post-resection Adaptation in Humans with Short Bowel Syndrome

Short bowel syndrome (SBS) is characterized by severe intestinal malabsorption following restrictive surgery. The objective of this study was to determine the functional contribution of SBS-microbiota after resection. It is well-known that SBS-microbiota displayed specific features with a prevalence of Lactobacillus, a low amount of some anaerobic microbes (Clostridium leptum) and an accumulation of fecal lactate in some patients. Patients with jejuno-colonic anastomosis were stratified according to the presence of lactate in their feces and, we observe that the lactate-producing bacteria were predominant in the sub-group of patients accumulating fecal lactate. One case of D-encephalopathy crisis occurred when the D-lactate isoform accumulated in the feces and plasma bicarbonate levels decreased. The fecal sample at the time of the encephalopathy was transferred to germ free rats (SBS-H rats). The SBS-H microbiota conserved some characteristics of the SBS donnor, predominated by lactate-producing bacteria (mainly Lactobacillus), a low level of lactate-consuming bacteria and undetectable C. leptum. However, lactate did not accumulate in feces of recipient rats and the D-encephalopathy was not reproduced in SBS-H rats. This suggests that the intact small bowel of the recipient rats protected them from lactate accumulation and that D-lactate encephalopathy can occur only in the absence of small intestine. After fecal transfer, we also show that gnotobiotic rats exhibited high levels of circulating GLP-1 and ghrelin, two hormones that are known to be induced in SBS patients. Therefore, the microbiota of SBS is a reservoir of biological signals involved in post-resection adaptation.

Luminal contents from the gut of colicky infants induce visceral hypersensitivity in mice

BACKGROUND

The pathophysiology of infantile colic is poorly understood, though various studies report gut microbiota dysbiosis in colicky infants. We aimed to test the hypothesis that colic-related dysbiosis is associated with visceral hypersensitivity triggered by an altered luminal milieu.

METHODS

Fecal samples from seven colicky and seven non-colicky infants were studied. Fecal supernatants (FS) were infused into the colons of C57/Bl6 mice (n=10/specimen). Visceral sensitivity was subsequently assessed in the animals by recording their abdominal muscle response to colorectal distension (CRD) by electromyography (EMG). Serine and cysteine protease activities were assessed in FS with specific substrates. Infant fecal microbiota composition was analyzed by DNA extraction and 16S rRNA gene pyrosequencing.

KEY RESULTS

FS from colicky infants triggered higher EMG activity than FS from non-colicky infants in response to both the largest CRD volumes and overall, as assessed by the area under the curve of the EMG across all CRD volumes. Infant crying time strongly correlated with mouse EMG activity. Microbiota richness and phylogenetic diversity were increased in the colicky group, without showing prominent microbial composition alterations. Only Bacteroides vulgatus and Bilophila wadsworthia were increased in the colicky group. Bacteroides vulgatus abundance positively correlated with visceral sensitivity. No differences were found in protease activities.

CONCLUSIONS & INFERENCES

Luminal contents from colicky infants trigger visceral hypersensitivity, which may explain the excessive crying behavior of these infants. Additional studies are required to determine the nature of the compounds involved, their mechanism of action, and the potential implications of intestinal microbiota in their generation.

Panic Disorder Comorbidity with Medical Conditions and Treatment Implications

Panic disorder (PD) is unique among the anxiety disorders in that panic symptoms are primarily of a physical nature. Consequently, comorbidity with medical illness is significant. This review examines the association between PD and medical illness. We identify shared pathophysiological and psychological correlates and illustrate how physiological activation in panic sufferers underlies their symptom experience in the context of the fight-or-flight response and beyond a situation-specific response pattern. We then review evidence for bodily symptom perception accuracy in PD. Prevalence of comorbidity for PD and medical illness is presented, with a focus on respiratory and cardiovascular illness, irritable bowel syndrome, and diabetes, followed by an outline for potential pathways of a bidirectional association. We conclude by illustrating commonalities in mediating mechanistic pathways and moderating risk factors across medical illnesses, and we discuss implications for diagnosis and treatment of both types of conditions.

Stress & the gut-brain axis: Regulation by the microbiome

The importance of the gut–brain axis in regulating stress-related responses has long been appreciated. More recently, the microbiota has emerged as a key player in the control of this axis, especially during conditions of stress provoked by real or perceived homeostatic challenge. Diet is one of the most important modifying factors of the microbiota-gut-brain axis. The routes of communication between the microbiota and brain are slowly being unravelled, and include the vagus nerve, gut hormone signaling, the immune system, tryptophan metabolism, and microbial metabolites such as short chain fatty acids. The importance of the early life gut microbiota in shaping later health outcomes also is emerging. Results from preclinical studies indicate that alterations of the early microbial composition by way of antibiotic exposure, lack of breastfeeding, birth by Caesarean section, infection, stress exposure, and other environmental influences - coupled with the influence of host genetics - can result in long-term modulation of stress-related physiology and behaviour. The gut microbiota has been implicated in a variety of stress-related conditions including anxiety, depression and irritable bowel syndrome, although this is largely based on animal studies or correlative analysis in patient populations. Additional research in humans is sorely needed to reveal the relative impact and causal contribution of the microbiome to stress-related disorders. In this regard, the concept of psychobiotics is being developed and refined to encompass methods of targeting the microbiota in order to positively impact mental health outcomes. At the 2016 Neurobiology of Stress Workshop in Newport Beach, CA, a group of experts presented the symposium “The Microbiome: Development, Stress, and Disease”. This report summarizes and builds upon some of the key concepts in that symposium within the context of how microbiota might influence the neurobiology of stress.

The Gut Microbiome in Irritable Bowel Syndrome and Other Functional Bowel Disorders

Emerging data from epidemiologic, microbiome, and physiology research in patients with functional bowel disorders (FBDs) provide evidence for a linkage between alterations in the intestinal microbiota and FBDs. However, currently most of the data is based on association studies, and the causality role of the microbiota in these disorders is not established. Growing evidence for compositional changes and the increasing recognition of the association between the intestinal microbiota and gut-brain functions that are relevant to the pathophysiology and/or clinical symptoms of FBDs have led to increased interest in manipulating the intestinal microbiota for the treatment of these disorders.

Emerging studies of human visceral nociceptors

Animal studies have led to significant advances in our understanding of pain mechanisms in the intestine that could lead to altered signaling in disorders such as irritable bowel syndrome. However, how these translate to the human afferent nervous system is unclear. Recent studies have demonstrated that it is possible to use a variety of techniques, including electrophysiological recordings, to begin to examine these concepts in humans. This mini-review examines these studies to explore how well animal studies translate to humans suffering from irritable bowel syndrome, highlights some of the advantages and technical limitations of these approaches, and identifies some priorities for future studies using human tissues.

Fecal microbiota transplantation in patients with slow-transit constipation: A randomized, clinical trial

Fecal microbiota transplantation has been proposed as a therapeutic approach for chronic constipation. This randomized, controlled trial aimed to compare the effects of conventional treatment alone (control) with additional treatment with FMT (intervention) in patients with slow-transit constipation (STC). Adults with STC were randomized to receive intervention or control treatment. The control group received education, behavioral strategies, and oral laxatives. The intervention group was additionally provided 6 days of FMT. The primary endpoint was the clinical cure rate (proportion of patients achieving a mean of ≥ three complete spontaneous bowel movements [CSBMs] per week]. Secondary outcomes and safety parameters were assessed throughout the study. Sixty patients were randomized to either conventional treatment alone (n = 30) or FMT (n = 30) through a nasointestinal tube. There were significant differences between the intervention group and control group in the clinical improvement rate (intention-to-treat [ITT]: 53.3% vs. 20.0%, P = 0.009), clinical cure rate (ITT: 36.7% vs. 13.3%, P = 0.04), mean number of CSBMs per week (ITT: 3.2 ± 1.4 vs. 2.1 ± 1.2, P = 0.001), and the Wexner constipation score (ITT: 8.6 ± 1.5 vs. 12.7 ± 2.5, P < 0.00001). Compared with the control group, the intervention group showed better results in the stool consistency score (ITT: 3.9 vs. 2.4, P < 0.00001) and colonic transit time (ITT: 58.5 vs. 73.6 h, P < 0.00001). The intervention group had more treatment-related adverse events than did the control group (50 vs. 4 cases). FMT was significantly more effective (30% higher cure rate) for treatment of STC than conventional treatment. No serious adverse events were observed.

Effects of scFOS on the composition of fecal microbiota and anxiety in patients with irritable bowel syndrome: a randomized, double blind, placebo controlled study

BACKGROUND

Short-chain fructooligosaccharides (scFOS) have beneficial effects in subjects with minor digestive complaints, but the potential mechanisms involved have not been elucidated. The aim of the study was to evaluate changes in rectal sensitivity related to the clinical effects of scFOS in a selected group of patients with irritable bowel syndrome (IBS) and rectal hypersensitivity.

METHODS

In 79 IBS patients (defined by Rome III criteria) with rectal hypersensitivity (defined as discomfort threshold ≤44 g) a parallel, placebo-controlled, randomized, and double-blind study was performed to assess the effects of dietary supplementation (5 g d^-1 ) with scFOS vs placebo for 4 weeks on rectal sensitivity (primary outcome: tolerance to increasing wall tension applied by a tensostat), clinical outcomes (IBS, anxiety/depression and quality of life scores) and composition of fecal microbiota.

KEY RESULTS

Rectal discomfort threshold, and IBS and quality of life scores, significantly improved during treatment, but in a similar manner in both scFOS and placebo groups; a post-hoc analysis showed that the effect of scFOS on rectal sensitivity was more pronounced in constipation-predominant-IBS patients (P=.051 vs placebo). Contrary with placebo, scFOS significantly reduced anxiety scores and increased fecal Bifidobacteria (P<.05 for both) without modifying other bacterial groups.

CONCLUSIONS & INTERFENCES

The effect of scFOS on anxiety may be related to modulation of the gut microbiota; demonstration of effects of scFOS on rectal sensitivity may require higher doses and may depend on the IBS subgroup.