Lactobacillus reuteri enhances excitability of colonic AH neurons by inhibiting calcium-dependent potassium channel opening

Microbiota and the gut-brain axis

Changes in gut microbiota can modulate the peripheral and central nervous systems, resulting in altered brain functioning, and suggesting the existence of a microbiota gut-brain axis. Diet can also change the profile of gut microbiota and, thereby, behavior. Effects of bacteria on the nervous system cannot be disassociated from effects on the immune system since the two are in constant bidirectional communication. While the composition of the gut microbiota varies greatly among individuals, alterations to the balance and content of common gut microbes may affect the production of molecules such as neurotransmitters, e.g., gamma amino butyric acid, and the products of fermentation, e.g., the short chain fatty acids butyrate, propionate, and acetate. Short chain fatty acids, which are pleomorphic, especially butyrate, positively influence host metabolism by promoting glucose and energy homeostasis, regulating immune responses and epithelial cell growth, and promoting the functioning of the central and peripheral nervous systems. In the future, the composition, diversity, and function of specific probiotics, coupled with similar, more detailed knowledge about gut microbiota, will potentially help in developing more effective diet- and drug-based therapies.

Prevention of Necrotizing Enterocolitis Through Manipulation of the Intestinal Microbiota of the Premature Infant

PURPOSE

In spite of four decades of research, necrotizing enterocolitis (NEC) remains the most common gastrointestinal complication in premature infants with high mortality and long-term morbidity. The composition of the intestinal microbiota of the premature infant differs dramatically from that of the healthy term infant and appears to be an important risk factor for NEC.

METHODS

We review the evidence of an association between intestinal dysbiosis and NEC and summarize published English language clinical trials and cohort studies involving attempts to manipulate the intestinal microbiota in premature infants.

FINDINGS

Promising NEC prevention strategies that alter the intestinal microbiota include probiotics, prebiotics, synbiotics, lacteroferrin, and human milk feeding.

IMPLICATIONS

Shaping the intestinal microbiota of the premature infant through human milk feeding and dietary supplements decreases the risk of NEC. Further studies to identify the ideal microbial composition and the most effective combination of supplements are indicated.

The role of the gut-brain axis in alcohol use disorders

Neuroimmune and inflammatory processes have been locally associated with the amygdala in alcohol exposure and withdrawal. We and others have suggested that this inflammation in the amygdala may cause disturbance of neural function observed as anxiety and autonomic distress in withdrawal. Despite the potential importance of the robust neuroinflammatory response, the mechanisms contributing to this response are not well understood. We review literature that suggests the effects of alcohol, and other substances of abuse, cause dysbiosis of the gut microbiome. This peripheral response may modulate neuroprotective vagal afferent signaling that permits and exacerbates a neuroinflammatory response in the amygdala. We will examine the mounting evidence that suggests that (1) gut dysbiosis contributes to neuroinflammation, especially in the context of alcohol exposure and withdrawal, (2) the neuroinflammation in the amygdala involves the microglia and astrocytes and their effect on neural cells, and (3) amygdala neuroinflammation itself contributes directly to withdrawal behavior and symptoms. The contribution of the gut to an anxiogenic response is a promising therapeutic target for patients suffering with withdrawal symptoms given the safe and well-established methods of modulating the gut microbiome.

Epigenetic Regulation of Enteric Neurotransmission by Gut Bacteria

The Human Microbiome Project defined microbial community interactions with the human host, and provided important molecular insight into how epigenetic factors can influence intestinal ecosystems. Given physiological context, changes in gut microbial community structure are increasingly found to associate with alterations in enteric neurotransmission and disease. At present, it is not known whether shifts in microbial community dynamics represent cause or consequence of disease pathogenesis. The discovery of bacterial-derived neurotransmitters suggests further studies are needed to establish their role in enteric neuropathy. This mini-review highlights recent advances in bacterial communications to the autonomic nervous system and discusses emerging epigenetic data showing that diet, probiotic and antibiotic use may regulate enteric neurotransmission through modulation of microbial communities. A particular emphasis is placed on bacterial metabolite regulation of enteric nervous system function in the intestine.

Gut microbiota regulates key modulators of social behavior

Social behavior plays a pivotal role in the mental well-being of an individual. Continuous efforts in the past have led to advancements in the area of how the brain regulates emotion and cognition, while the understanding of human social behavior still remains eluded. A major breakthrough in understanding the etiology of neurological disorders is the recent insight on the role of the gut microbiota (GM). Human GM also referred to as the "forgotten organ" is home to 10(13-14) microorganisms, which is 10 times the number of cells present in the human body. In addition, the gut microbiome (total genome of GM) is 150 times greater as compared to the human genome. An emerging concept gaining worldwide focus and acceptance is that, this much big genome can potentially control human behavior and other biological functions. Herein we hypothesize on the basis of GM's ability to modify brain and behavior and that it can directly or indirectly control social behavior. This review focuses on the association of GM with various domains of social behavior like stress, cognition and anxiety.

Protective Role of Postbiotic Mediators Secreted by Lactobacillus rhamnosus GG Versus Lipopolysaccharide-induced Damage in Human Colonic Smooth Muscle Cells

BACKGROUND

Some beneficial effects of probiotics may be due to secreted probiotic-derived factors, identified as "postbiotic" mediators. The aim of this study was to evaluate whether supernatants harvested from Lactobacillus rhamnosus GG (LGG) cultures (ATCC53103 strain) protect colonic human smooth muscle cells (HSMCs) from lipopolysaccharide (LPS)-induced myogenic damage.

MATERIALS AND METHODS

LGG was grown in de Man, Rogosa, Share medium at 37°C and samples were collected in middle and late exponential, stationary, and overnight phases. Supernatants were recovered by centrifugation, filtered, and stored at -20°C. The primary HSMCs culture was exposed for 24 hours to purified LPS of a pathogen strain of Escherichia coli (O111:B4) (1 μg/mL) with and without supernatants. Postbiotic effects were evaluated on the basis of HSMCs morphofunctional alterations and interleukin-6 (IL-6) production. Data are expressed as mean±SE (P<0.05 significant).

RESULTS

LPS induced persistent, significant, 20.5%±0.7% cell shortening and 34.5%±2.2% decrease in acetylcholine-induced contraction of human HSMCs. These morphofunctional alterations were paralleled to a 365.65%±203.13% increase in IL-6 production. All these effects were dose-dependently reduced by LGG supernatants. Supernatants of the middle exponential phase already partially restored LPS-induced cell shortening by 57.34%±12.7% and IL-6 increase by 145.8%±4.3% but had no effect on LPS-induced inhibition of contraction. Maximal protective effects were obtained with supernatants of the late stationary phase with LPS-induced cell shortening restored by 84.1%±4.7%, inhibition of contraction by 85.5%±6.4%, and IL-6 basal production by 92.7%±1.2%.

CONCLUSIONS

LGG-derived products are able to protect human SMCs from LPS-induced myogenic damage. Novel insights have been provided for the possibility that LGG-derived products could reduce the risk of progression to postinfective motor disorders.

Probiotics and Innate and Adaptive Immune Responses in Premature Infants

Premature infants are at increased risk for morbidity and mortality due to necrotizing enterocolitis (NEC) and sepsis. Probiotics decrease the risk of NEC and death in premature infants; however, mechanisms of action are unclear. A wide variety of probiotic species have been evaluated for potential beneficial properties in vitro, in animal models, and in clinical trials of premature infants. Although there is variation by species and even strain, common mechanisms of protection include attenuation of intestinal inflammation, apoptosis, dysmotility, permeability, supplanting other gut microbes through production of bacteriocins, and more effective use of available nutrients. Here, we review the most promising probiotics and what is known about their impact on the innate and adaptive immune response.

Diabetes-related dysfunction of the small intestine and the colon: focus on motility

In contrast to gastric dysfunction, diabetes-related functional impairments of the small and large intestine have been studied less intensively. The gastrointestinal tract accomplishes several functions, such as mixing and propulsion of luminal content, absorption and secretion of ions, water, and nutrients, defense against pathogens, and elimination of waste products. Diverse functions of the gut are regulated by complex interactions among its functional elements, including gut microbiota. The network-forming tissues, the enteric nervous system) and the interstitial cells of Cajal, are definitely impaired in diabetic patients, and their loss of function is closely related to the symptoms in diabetes, but changes of other elements could also play a role in the development of diabetes mellitus-related motility disorders. The development of our understanding over the recent years of the diabetes-induced dysfunctions in the small and large intestine are reviewed in this article.

The TRPV1 channel in rodents is a major target for antinociceptive effect of the probiotic Lactobacillus reuteri DSM 17938

Certain probiotic bacteria have been shown to reduce distension-dependent gut pain, but the mechanisms involved remain obscure. Live luminal Lactobacillus reuteri (DSM 17938) and its conditioned medium dose dependently reduced jejunal spinal nerve firing evoked by distension or capsaicin, and 80% of this response was blocked by a specific TRPV1 channel antagonist or in TRPV1 knockout mice. The specificity of DSM action on TRPV1 was further confirmed by its inhibition of capsaicin-induced intracellular calcium increases in dorsal root ganglion neurons. Another lactobacillus with ability to reduce gut pain did not modify this response. Prior feeding of rats with DSM inhibited the bradycardia induced by painful gastric distension. These results offer a system for the screening of new and improved candidate bacteria that may be useful as novel therapeutic adjuncts in gut pain. Certain bacteria exert visceral antinociceptive activity, but the mechanisms involved are not determined. Lactobacillus reuteri DSM 17938 was examined since it may be antinociceptive in children. Since transient receptor potential vanilloid 1 (TRPV1) channel activity may mediate nociceptive signals, we hypothesized that TRPV1 current is inhibited by DSM. We tested this by examining the effect of DSM on the firing frequency of spinal nerve fibres in murine jejunal mesenteric nerve bundles following serosal application of capsaicin. We also measured the effects of DSM on capsaicin-evoked increase in intracellular Ca(2+) or ionic current in dorsal root ganglion (DRG) neurons. Furthermore, we tested the in vivo antinociceptive effects of oral DSM on gastric distension in rats. Live DSM reduced the response of capsaicin- and distension-evoked firing of spinal nerve action potentials (238 ± 27.5% vs. 129 ± 17%). DSM also reduced the capsaicin-evoked TRPV1 ionic current in DRG neuronal primary culture from 83 ± 11% to 41 ± 8% of the initial response to capsaicin only. Another lactobacillus (Lactobacillus rhamnosus JB-1) with known visceral anti-nociceptive activity did not have these effects. DSM also inhibited capsaicin-evoked Ca(2+) increase in DRG neurons; an increase in Ca(2+) fluorescence intensity ratio of 2.36 ± 0.31 evoked by capsaicin was reduced to 1.25 ± 0.04. DSM releasable products (conditioned medium) mimicked DSM inhibition of capsaicin-evoked excitability. The TRPV1 antagonist 6-iodonordihydrocapsaicin or the use of TRPV1 knock-out mice revealed that TRPV1 channels mediate about 80% of the inhibitory effect of DSM on mesenteric nerve response to high intensity gut distension. Finally, feeding with DSM inhibited perception in rats of painful gastric distension. Our results identify a specific target channel for a probiotic with potential therapeutic properties.

Gut microbiota and the development of pediatric diseases

The human gut harbors a huge number of microbes, which are collectively named "microbiota." The dynamic composition of the human gut microbiota is determined by multiple factors, including mode of delivery, diet, environment, and antibiotics. A healthy gut microbiota is helpful to the host in many aspects, including providing nutrients, protection from pathogens, and maturation of immune responses. Dysbiosis plays important roles in various diseases in infancy and later life: necrotizing enterocolitis, inflammatory bowel disease, obesity, and atopic diseases are some examples. Studies of functional metagenomics by newly developed techniques, such as next-generation sequencing, will not only elucidate the molecular mechanisms underlying gut microbiota-host interactions but will also provide new possibilities for disease prevention and treatment.

The gut microbiome restores intrinsic and extrinsic nerve function in germ-free mice accompanied by changes in calbindin

BACKGROUND

The microbiome is essential for normal myenteric intrinsic primary afferent neuron (IPAN) excitability. These neurons control gut motility and modulate gut-brain signaling by exciting extrinsic afferent fibers innervating the enteric nervous system via an IPAN to extrinsic fiber sensory synapse. We investigated effects of germ-free (GF) status and conventionalization on extrinsic sensory fiber discharge in the mesenteric nerve bundle and IPAN electrophysiology, and compared these findings with those from specific pathogen-free (SPF) mice. As we have previously shown that the IPAN calcium-dependent slow afterhyperpolarization (sAHP) is enhanced in GF mice, we also examined the expression of the calcium-binding protein calbindin in these neurons in these different animal groups.

METHODS

IPAN sAHP and mesenteric nerve multiunit discharge were recorded using ex vivo jejunal gut segments from SPF, GF, or conventionalized (CONV) mice. IPANs were excited by adding 5 μM TRAM-34 to the serosal superfusate. We probed for calbindin expression using immunohistochemical techniques.

KEY RESULTS

SPF mice had a 21% increase in mesenteric nerve multiunit firing rate and CONV mice a 41% increase when IPANs were excited by TRAM-34. For GF mice, this increase was barely detectable (2%). TRAM-34 changed sAHP area under the curve by -77 for SPF, +3 for GF, or -54% for CONV animals. Calbindin-immunopositive neurons per myenteric ganglion were 36% in SPF, 24% in GF, and 52% in CONV animals.

CONCLUSIONS & INFERENCES

The intact microbiome is essential for normal intrinsic and extrinsic nerve function and gut-brain signaling.

Visceral pain and gastrointestinal microbiome

A complex set of interactions between the microbiome, gut and brain modulate responses to visceral pain. These interactions occur at the level of the gastrointestinal mucosa, and via local neural, endocrine or immune activity; as well as by the production of factors transported through the circulatory system, like bacterial metabolites or hormones. Various psychological, infectious and other stressors can disrupt this harmonious relationship and alter both the microbiome and visceral pain responses. There are critical sensitive periods that can impact visceral pain responses in adulthood. In this review we provide a brief background of the intestinal microbiome and emerging concepts of the bidirectional interactions between the microbiome, gut and brain. We also discuss recent work in animal models, and human clinical trials using prebiotics and probiotics that alter the microbiome with resultant alterations in visceral pain responses.

The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems

The gut-brain axis (GBA) consists of bidirectional communication between the central and the enteric nervous system, linking emotional and cognitive centers of the brain with peripheral intestinal functions. Recent advances in research have described the importance of gut microbiota in influencing these interactions. This interaction between microbiota and GBA appears to be bidirectional, namely through signaling from gut-microbiota to brain and from brain to gut-microbiota by means of neural, endocrine, immune, and humoral links. In this review we summarize the available evidence supporting the existence of these interactions, as well as the possible pathophysiological mechanisms involved. Most of the data have been acquired using technical strategies consisting in germ-free animal models, probiotics, antibiotics, and infection studies. In clinical practice, evidence of microbiota-GBA interactions comes from the association of dysbiosis with central nervous disorders (i.e. autism, anxiety-depressive behaviors) and functional gastrointestinal disorders. In particular, irritable bowel syndrome can be considered an example of the disruption of these complex relationships, and a better understanding of these alterations might provide new targeted therapies.

Bifidobacteria modulate cognitive processes in an anxious mouse strain

Increasing evidence suggests that a brain-gut-microbiome axis exists, which has the potential to play a major role in modulating behaviour. However, the role of this axis in cognition remains relatively unexplored. Probiotics, which are commensal bacteria offering potential health benefit, have been shown to decrease anxiety, depression and visceral pain-related behaviours. In this study, we investigate the potential of two Bifidobacteria strains to modulate cognitive processes and visceral pain sensitivity. Adult male BALB/c mice were fed daily for 11 weeks with B. longum 1714, B. breve 1205 or vehicle treatment. Starting at week 4, animals were behaviourally assessed in a battery of tests relevant to different aspects of cognition, as well as locomotor activity and visceral pain. In the object recognition test, B. longum 1714-fed mice discriminated between the two objects faster than all other groups and B. breve 1205-fed mice discriminated faster than vehicle animals. In the Barnes maze, B. longum 1714-treated mice made fewer errors than other groups, suggesting a better learning. In the fear conditioning, B. longum 1714-treated group also showed better learning and memory, yet presenting the same extinction learning profile as controls. None of the treatments affected visceral sensitivity. Altogether, these data suggest that B. longum 1714 had a positive impact on cognition and also that the effects of individual Bifidobacteria strains do not generalise across the species. Clinical validation of the effects of probiotics on cognition is now warranted.

Induction of rhythmic transient depolarizations associated with waxing and waning of slow wave activity in intestinal smooth muscle

Cannon described in 1902 the segmentation motor activity of the small intestine (Canon WB. J Med Res 7: 72-75, 1902). This motor pattern can arise when low-frequency transient depolarizations are evoked in the interstitial cells of Cajal associated with the deep muscular plexus (ICC-DMP) network, which then affect the omnipresent slow wave activity: changing its regular amplitude into a waxing and waning pattern. The objective of the present study was to investigate physiological stimuli that could induce the low-frequency component. Intracellular recordings were obtained from circular muscle with or without attached mucosa. Decanoic acid (1 mM) and butyric acid (10 mM) both evoked low-frequency transient depolarizations but through different mechanisms. Decanoic acid-induced waxing and waning was initiated by purely myogenic means when perfused onto exposed circular muscle. Butyric acid required the intact mucosa and uninhibited neural activity to elicit the low-frequency response. Evidence is provided that the transient rhythmic depolarizations occur in the absence of interstitial cells of Cajal associated with the myenteric plexus (ICC-MP). Onset of the slow transient depolarizations was stimulated by addition of N(ω)-nitro-l-arginine (l-NNA; 100 μM); thus the low-frequency component seems to be under chronic inhibition by nitric oxide. Excitatory tachykinergic stimulation induced the low-frequency component since substance P (0.5 μM) evoked it in the presence of neural blockade. In summary, interplay between two networks of myogenic pacemakers, neural activity, and nutrient factors such as fatty acids plays a role in the generation of the rhythmic low-frequency component that is essential for the development of the checkered segmentation motor pattern.

Intestinal microbiota as modulators of the immune system and neuroimmune system: impact on the host health and homeostasis

Many immune-based intestinal disorders, such as ulcerative colitis and Crohn's disease, as well as other illnesses, may have the intestines as an initial cause or aggravator in the development of diseases, even apparently not correlating directly to the intestine. Diabetes, obesity, multiple sclerosis, depression, and anxiety are examples of other illnesses discussed in the literature. In parallel, importance of the gut microbiota in intestinal homeostasis and immunologic conflict between tolerance towards commensal microorganisms and combat of pathogens is well known. Recent researches show that the immune system, when altered by the gut microbiota, influences the state in which these diseases are presented in the patient directly and indirectly. At the present moment, a considerable number of investigations about this subject have been performed and published. However, due to difficulties on correlating information, several speculations and hypotheses are generated. Thus, the present review aims at bringing together how these interactions work-gut microbiota, immune system, and their influence in the neuroimmune system.

Gut/brain axis and the microbiota

Tremendous progress has been made in characterizing the bidirectional interactions between the central nervous system, the enteric nervous system, and the gastrointestinal tract. A series of provocative preclinical studies have suggested a prominent role for the gut microbiota in these gut-brain interactions. Based on studies using rodents raised in a germ-free environment, the gut microbiota appears to influence the development of emotional behavior, stress- and pain-modulation systems, and brain neurotransmitter systems. Additionally, microbiota perturbations by probiotics and antibiotics exert modulatory effects on some of these measures in adult animals. Current evidence suggests that multiple mechanisms, including endocrine and neurocrine pathways, may be involved in gut microbiota-to-brain signaling and that the brain can in turn alter microbial composition and behavior via the autonomic nervous system. Limited information is available on how these findings may translate to healthy humans or to disease states involving the brain or the gut/brain axis. Future research needs to focus on confirming that the rodent findings are translatable to human physiology and to diseases such as irritable bowel syndrome, autism, anxiety, depression, and Parkinson's disease.

Microbiota regulation of the Mammalian gut-brain axis

The realization that the microbiota-gut-brain axis plays a critical role in health and disease has emerged over the past decade. The brain-gut axis is a bidirectional communication system between the central nervous system (CNS) and the gastrointestinal tract. Regulation of the microbiota-brain-gut axis is essential for maintaining homeostasis, including that of the CNS. The routes of this communication are not fully elucidated but include neural, humoral, immune, and metabolic pathways. A number of approaches have been used to interrogate this axis including the use of germ-free animals, probiotic agents, antibiotics, or animals exposed to pathogenic bacterial infections. Together, it is clear that the gut microbiota can be a key regulator of mood, cognition, pain, and obesity. Understanding microbiota-brain interactions is an exciting area of research which may contribute new insights into individual variations in cognition, personality, mood, sleep, and eating behavior, and how they contribute to a range of neuropsychiatric diseases ranging from affective disorders to autism and schizophrenia. Finally, the concept of psychobiotics, bacterial-based interventions with mental health benefit, is also emerging.

Psychobiotics and the gut-brain axis: in the pursuit of happiness

The human intestine houses an astounding number and species of microorganisms, estimated at more than 10(14) gut microbiota and composed of over a thousand species. An individual's profile of microbiota is continually influenced by a variety of factors including but not limited to genetics, age, sex, diet, and lifestyle. Although each person's microbial profile is distinct, the relative abundance and distribution of bacterial species is similar among healthy individuals, aiding in the maintenance of one's overall health. Consequently, the ability of gut microbiota to bidirectionally communicate with the brain, known as the gut-brain axis, in the modulation of human health is at the forefront of current research. At a basic level, the gut microbiota interacts with the human host in a mutualistic relationship - the host intestine provides the bacteria with an environment to grow and the bacterium aids in governing homeostasis within the host. Therefore, it is reasonable to think that the lack of healthy gut microbiota may also lead to a deterioration of these relationships and ultimately disease. Indeed, a dysfunction in the gut-brain axis has been elucidated by a multitude of studies linked to neuropsychological, metabolic, and gastrointestinal disorders. For instance, altered microbiota has been linked to neuropsychological disorders including depression and autism spectrum disorder, metabolic disorders such as obesity, and gastrointestinal disorders including inflammatory bowel disease and irritable bowel syndrome. Fortunately, studies have also indicated that gut microbiota may be modulated with the use of probiotics, antibiotics, and fecal microbiota transplants as a prospect for therapy in microbiota-associated diseases. This modulation of gut microbiota is currently a growing area of research as it just might hold the key to treatment.

The impact of microbiota on brain and behavior: mechanisms & therapeutic potential

There is increasing evidence that host-microbe interactions play a key role in maintaining homeostasis. Alterations in gut microbial composition is associated with marked changes in behaviors relevant to mood, pain and cognition, establishing the critical importance of the bi-directional pathway of communication between the microbiota and the brain in health and disease. Dysfunction of the microbiome-brain-gut axis has been implicated in stress-related disorders such as depression, anxiety and irritable bowel syndrome and neurodevelopmental disorders such as autism. Bacterial colonization of the gut is central to postnatal development and maturation of key systems that have the capacity to influence central nervous system (CNS) programming and signaling, including the immune and endocrine systems. Moreover, there is now expanding evidence for the view that enteric microbiota plays a role in early programming and later response to acute and chronic stress. This view is supported by studies in germ-free mice and in animals exposed to pathogenic bacterial infections, probiotic agents or antibiotics. Although communication between gut microbiota and the CNS are not fully elucidated, neural, hormonal, immune and metabolic pathways have been suggested. Thus, the concept of a microbiome-brain-gut axis is emerging, suggesting microbiota-modulating strategies may be a tractable therapeutic approach for developing novel treatments for CNS disorders.

Vagal pathways for microbiome-brain-gut axis communication

There is now strong evidence from animal studies that gut microorganism can activate the vagus nerve and that such activation plays a critical role in mediating effects on the brain and behaviour. The vagus appears to differentiate between non-pathogenic and potentially pathogenic bacteria even in the absence of overt inflammation and vagal pathways mediate signals that can induce both anxiogenic and anxiolytic effects, depending on the nature of the stimulus. Certain vagal signals from the gut can instigate an anti-inflammatory reflex with afferent signals to the brain activating an efferent response, releasing mediators including acetylcholine that, through an interaction with immune cells, attenuates inflammation. This immunomodulatory role of the vagus nerve may also have consequences for modulation of brain function and mood.What is currently lacking are relevant data on the electrophysiology of the system. Certainly, important advances in our understanding of the gut-brain and microbiome- gut-brain axis will come from studies of how distinct microbial and nutritional stimuli activate the vagus and the nature of the signals transmitted to the brain that lead to differential changes in the neurochemistry of the brain and behaviour.Understanding the induction and transmission of signals in the vagus nerve may have important implications for the development of microbial-or nutrition based therapeutic strategies for mood disorders.

Gut commensal microvesicles reproduce parent bacterial signals to host immune and enteric nervous systems

Ingestion of a commensal bacteria, Lactobacillus rhamnosus JB-1, has potent immunoregulatory effects, and changes nerve-dependent colon migrating motor complexes (MMCs), enteric nerve function, and behavior. How these alterations occur is unknown. JB-1 microvesicles (MVs) are enriched for heat shock protein components such as chaperonin 60 heat-shock protein isolated from Escherichia coli (GroEL) and reproduce regulatory and neuronal effects in vitro and in vivo. Ingested labeled MVs were detected in murine Peyer's patch (PP) dendritic cells (DCs) within 18 h. After 3 d, PP and mesenteric lymph node DCs assumed a regulatory phenotype and increased functional regulatory CD4(+)25(+)Foxp3+ T cells. JB-1, MVs, and GroEL similarly induced phenotypic change in cocultured DCs via multiple pathways including C-type lectin receptors specific intercellular adhesion molecule-3 grabbing non-integrin-related 1 and Dectin-1, as well as TLR-2 and -9. JB-1 and MVs also decreased the amplitude of neuronally dependent MMCs in an ex vivo model of peristalsis. Gut epithelial, but not direct neuronal application of, MVs, replicated functional effects of JB-1 on in situ patch-clamped enteric neurons. GroEL and anti-TLR-2 were without effect in this system, suggesting the importance of epithelium neuron signaling and discrimination between pathways for bacteria-neuron and -immune communication. Together these results offer a mechanistic explanation of how Gram-positive commensals and probiotics may influence the host's immune and nervous systems.

Bifidobacteria exert strain-specific effects on stress-related behavior and physiology in BALB/c mice

BACKGROUND

Accumulating evidence suggests that commensal bacteria consumption has the potential to have a positive impact on stress-related psychiatric disorders. However, the specific bacteria influencing behaviors related to anxiety and depression remain unclear. To this end, we compared the effects of two different Bifidobacteria on anxiety and depression-like behavior; an antidepressant was also used as a comparator.

METHODS

Innately anxious BALB/c mice received daily Bifidobacterium longum (B.) 1714, B. breve 1205, the antidepressant escitalopram or vehicle treatment for 6 weeks. Behavior was assessed in stress-induced hyperthermia test, marble burying, elevated plus maze, open field, tail suspension test, and forced swim test. Physiological responses to acute stress were also assessed.

KEY RESULTS

Both Bifidobacteria and escitalopram reduced anxiety in the marble burying test; however, only B. longum 1714 decreased stress-induced hyperthermia. B. breve 1205 induced lower anxiety in the elevated plus maze whereas B. longum 1714 induced antidepressant-like behavior in the tail suspension test. However, there was no difference in corticosterone levels between groups.

CONCLUSIONS & INFERENCES

These data show that these two Bifidobacteria strains reduced anxiety in an anxious mouse strain. These results also suggest that each bacterial strain has intrinsic effects and may be beneficially specific for a given disorder. These findings strengthen the role of gut microbiota supplementation as psychobiotic-based strategies for stress-related brain-gut axis disorders, opening new avenues in the field of neurogastroenterology.

Synbiotic in the management of infantile colic: a randomised controlled trial

AIM

Infant colic is a frequent problem affecting up to 10-30% of infants in first 3 months of life. Results from previous trials have shown that manipulation of gut microbiota can lead to symptomatic improvements. In a randomised clinical trial, we aimed to determine efficacy of synbiotic in reducing average infant crying time at day 7 and day 30 after starting intervention.

METHODS

Fifty breastfed infants aged 15-120 days with infantile colic randomly assigned to receive either the synbiotic sachet containing 1 billion CFU of: Lactobacillus casei, L. rhamnosus, Streptococcus thermophilus, Bifidobacterium breve, L. acidophilus, B. infantis, L. bulgaricus and fructooligosacharide (Protexin Healthcare, Somerset, UK), or placebo daily for 30 days. Parents were asked to record details of crying times in a symptoms diary. The primary outcome measure was the treatment success (reduction in the daily crying time >50%) and the secondary outcome measure was symptom resolution (reduction in the daily crying time >90%).

RESULTS

The treatment success was significantly higher in synbiotic group (82.6%) compared with placebo (35.7%) at day 7 (P < 0.005). At day30, treatment success was 87% and 46% in synbiotic and placebo group, respectively (P < 0.01). Symptom resolution was also higher in synbiotic group (39%) compared with placebo (7%) at day 7 (P < 0.03) but not at day 30 (56% vs.36%, P = 0.24). We encountered no complication related to synbiotic use.

CONCLUSION

This synbiotic (a mixture of seven probiotic strains plus FOS) significantly improved colic symptoms in comparison with placebo.

Probiotics in human milk and probiotic supplementation in infant nutrition: a workshop report

Probiotics in human milk are a very recent field of research, as the existence of the human milk microbiome was discovered only about a decade ago. Current research is focusing on bacterial diversity and the influence of the maternal environment as well as the mode of delivery on human milk microbiota, the pathways of bacterial transfer to milk ducts, possible benefits of specific bacterial strains for the treatment of mastitis in mothers, and disease prevention in children. Recent advances in the assessment of early host-microbe interactions suggest that early colonisation may have an impact on later health. This review article summarises a scientific workshop on probiotics in human milk and their implications for infant health as well as future perspectives for infant feeding.

Disturbance of the gut microbiota in early-life selectively affects visceral pain in adulthood without impacting cognitive or anxiety-related behaviors in male rats

Disruption of bacterial colonization during the early postnatal period is increasingly being linked to adverse health outcomes. Indeed, there is a growing appreciation that the gut microbiota plays a role in neurodevelopment. However, there is a paucity of information on the consequences of early-life manipulations of the gut microbiota on behavior. To this end we administered an antibiotic (vancomycin) from postnatal days 4-13 to male rat pups and assessed behavioral and physiological measures across all aspects of the brain-gut axis. In addition, we sought to confirm and expand the effects of early-life antibiotic treatment using a different antibiotic strategy (a cocktail of pimaricin, bacitracin, neomycin; orally) during the same time period in both female and male rat pups. Vancomycin significantly altered the microbiota, which was restored to control levels by 8 weeks of age. Notably, vancomycin-treated animals displayed visceral hypersensitivity in adulthood without any significant effect on anxiety responses as assessed in the elevated plus maze or open field tests. Moreover, cognitive performance in the Morris water maze was not affected by early-life dysbiosis. Immune and stress-related physiological responses were equally unaffected. The early-life antibiotic-induced visceral hypersensitivity was also observed in male rats given the antibiotic cocktail. Both treatments did not alter visceral pain perception in female rats. Changes in visceral pain perception in males were paralleled by distinct decreases in the transient receptor potential cation channel subfamily V member 1, the α-2A adrenergic receptor and cholecystokinin B receptor. In conclusion, a temporary disruption of the gut microbiota in early-life results in very specific and long-lasting changes in visceral sensitivity in male rats, a hallmark of stress-related functional disorders of the brain-gut axis such as irritable bowel disorder.

Converging effects of a Bifidobacterium and Lactobacillus probiotic strain on mouse intestinal physiology

Evidence has grown to support the efficacy of probiotics in the management of gastrointestinal disorders, many of which are associated with dysregulated fluid and electrolyte transport. A growing body of evidence now suggests that the host microbiota and probiotics can influence intestinal ion transport and that these effects often occur in a strain-dependent manner. In this study, we sought to investigate the effects of two therapeutically relevant organisms, Bifidobacterium infantis 35,624 and Lactobacillus salivarius UCC118, on small intestinal transit, fecal output and water content, transepithelial resistance (TER), and colonic secretomotor function. Mice fed either strain displayed significantly reduced small intestinal transit in vivo, though neither strain influenced fecal pellet output or water content. Colon from mice fed both organisms displayed increased colonic TER, without a concomitant change in the gene expression of the tight junction proteins claudin 1 and occludin. However, L. salivarius UCC118 selectively inhibited neurally evoked ion secretion in tissues from animals fed this particular probiotic. Consistent with this finding, the neurotoxin tetrodotoxin (TTx) significantly inhibited the short-circuit current response induced by L. salivarius UCC118 following addition to colonic preparations in Ussing chambers. Responses to B. infantis 35,624 also displayed sensitivity to TTx, although to a significantly lesser degree than L. salivarius UCC118. Both strains similarly inhibited cholinergic-induced ion transport after addition to Ussing chambers. Taken together, these data suggest that B. infantis 35,624 and L. salivarius UCC118 may be indicated in disorders associated with increased small intestinal transit, and, in particular for L. salivarius UCC118, neurally mediated diarrhea.

Enteric GFAP expression and phosphorylation in Parkinson's disease

Enteric glial cells (EGCs) are in many respects similar to astrocytes of the central nervous system and express similar proteins including glial fibrillary acidic protein (GFAP). Changes in GFAP expression and/or phosphorylation have been reported during brain damage or central nervous system degeneration. As in Parkinson's disease (PD) the enteric neurons accumulate α-synuclein, and thus are showing PD-specific pathological features, we undertook the present survey to study whether the enteric glia in PD become reactive by assessing the expression and phosphorylation levels of GFAP in colonic biopsies. Twenty-four PD, six progressive supranuclear palsy (PSP), six multiple system atrophy (MSA) patients, and 21 age-matched healthy controls were included. The expression levels and the phosphorylation state of GFAP were analyzed in colonic biopsies by western blot. Additional experiments were performed using real-time PCR for a more precise analysis of the GFAP isoforms expressed by EGCs. We showed that GFAPκ was the main isoform expressed in EGCs. As compared to control subjects, patients with PD, but not PSP and MSA, had significant higher GFAP expression levels in their colonic biopsies. The phosphorylation level of GFAP at serine 13 was significantly lower in PD patients compared to control subjects. By contrast, no change in GFAP phosphorylation was observed between PSP, MSA and controls. Our findings provide evidence that enteric glial reaction occurs in PD and further reinforce the role of the enteric nervous system in the initiation and/or the progression of the disease. We showed that GFAP is over-expressed and hypophosphorylated in the enteric glial cells (EGCs) of Parkinson's disease (PD) patients as compared to healthy subjects and patients with atypical parkinsonism (MSA, multiple system atrophy and PSP, progressive supranuclear palsy). Our findings provide evidence that enteric glial reaction occurs in PD but not in PSP and MSA and further reinforce the role of the enteric nervous system in the pathophysiology of PD.

The role of microbiome in central nervous system disorders

Mammals live in a co-evolutionary association with the plethora of microorganisms that reside at a variety of tissue microenvironments. The microbiome represents the collective genomes of these co-existing microorganisms, which is shaped by host factors such as genetics and nutrients but in turn is able to influence host biology in health and disease. Niche-specific microbiome, prominently the gut microbiome, has the capacity to effect both local and distal sites within the host. The gut microbiome has played a crucial role in the bidirectional gut-brain axis that integrates the gut and central nervous system (CNS) activities, and thus the concept of microbiome-gut-brain axis is emerging. Studies are revealing how diverse forms of neuro-immune and neuro-psychiatric disorders are correlated with or modulated by variations of microbiome, microbiota-derived products and exogenous antibiotics and probiotics. The microbiome poises the peripheral immune homeostasis and predisposes host susceptibility to CNS autoimmune diseases such as multiple sclerosis. Neural, endocrine and metabolic mechanisms are also critical mediators of the microbiome-CNS signaling, which are more involved in neuro-psychiatric disorders such as autism, depression, anxiety, stress. Research on the role of microbiome in CNS disorders deepens our academic knowledge about host-microbiome commensalism in central regulation and in practicality, holds conceivable promise for developing novel prognostic and therapeutic avenues for CNS disorders.

The gut-brain axis rewired: adding a functional vagal nicotinic "sensory synapse"

It is generally accepted that intestinal sensory vagal fibers are primary afferent, responding nonsynaptically to luminal stimuli. The gut also contains intrinsic primary afferent neurons (IPANs) that respond to luminal stimuli. A psychoactive Lactobacillus rhamnosus (JB-1) that affects brain function excites both vagal fibers and IPANs. We wondered whether, contrary to its primary afferent designation, the sensory vagus response to JB-1 might depend on IPAN to vagal fiber synaptic transmission. We recorded ex vivo single- and multiunit afferent action potentials from mesenteric nerves supplying mouse jejunal segments. Intramural synaptic blockade with Ca(2+) channel blockers reduced constitutive or JB-1-evoked vagal sensory discharge. Firing of 60% of spontaneously active units was reduced by synaptic blockade. Synaptic or nicotinic receptor blockade reduced firing in 60% of vagal sensory units that were stimulated by luminal JB-1. In control experiments, increasing or decreasing IPAN excitability, respectively increased or decreased nerve firing that was abolished by synaptic blockade or vagotomy. We conclude that >50% of vagal afferents function as interneurons for stimulation by JB-1, receiving input from an intramural functional "sensory synapse." This was supported by myenteric plexus nicotinic receptor immunohistochemistry. These data offer a novel therapeutic target to modify pathological gut-brain axis activity.-Perez-Burgos, A., Mao, Y.-K., Bienenstock, J., Kunze, W. A. The gut-brain axis rewired: adding a functional vagal nicotinic "sensory synapse."

Probiotic gut effect prevents the chronic psychological stress-induced brain activity abnormality in mice

BACKGROUND

A probiotic formulation (Lactobacillus helveticus R0052 and Bifidobacterium longum R0175 combination, Probio'Stick(®) ) displays anxiolytic-like activity and reduces apoptosis in the lymbic system in animal models of depression. Based on the hypothesis that modulation of gut microbiota by this probiotic formulation has beneficial effects on brain activity in stress conditions, we report a set of probiotic-evoked physiological, cellular, and molecular events in the brain of Probio'Stick(®) pretreated mice submitted to chronic psychological stress.

METHODS

Water avoidance stress (WAS) was applied or not (sham). Hypothalamic-pituitary-adrenal (HPA) axis and autonomic nervous system (ANS) responses to the chronic stress were assessed through plasma corticosterone and catecholamine measurements. Specific markers for neuronal activity, neurogenesis, and synaptic plasticity were used to assess brain activity. In addition, gut permeability and tight junction (TJ) proteins levels were also determinated.

KEY RESULTS

We observed that a pretreatment with the probiotic formulation attenuated HPA axis and ANS activities in response to WAS, and reduced cFos expression in different brain areas but Lactobacillus salivarius (a negative control) treatment was ineffective on these parameters. Moreover, probiotic pretreatment prevented the WAS-induced decrease hippocampal neurogenesis and expression changes in hypothalamic genes involved in synaptic plasticity. These central effects were associated with restoration of TJ barrier integrity in stressed mice.

CONCLUSIONS & INFERENCES

These data suggest that chronic stress-induced abnormal brain plasticity and reduction in neurogenesis can be prevented by a pretreatment with the Probio'Stick(®) formulation, suggesting that probiotics modulate neuroregulatory factors and various signaling pathways in the central nervous system involved in stress response.

The early administration of Lactobacillus reuteri DSM 17938 controls regurgitation episodes in full-term breastfed infants

Forty breastfed full-term infants were randomly, double blind assigned to receive orally Lactobacillus reuteri (L. reuteri) DSM 17938, 5 drops/daily (10(8) colony-forming units), for 4 weeks (n = 20) or an identical placebo (n = 20), starting before third day of life. They underwent basal and final visit to monitor growth parameters and gastrointestinal (GI) disease. Parents registered daily: crying minutes, stool frequency and consistency, numbers of regurgitations, adverse events. Secretory IgA (sIgA) has been measured in saliva on 28th day. Treated infants demonstrated a reduction in daily regurgitations at the end of treatment (p = 0.02), three neonates in the placebo group only needed simethicone for GI pain, sIgA level was similar in both groups. Random casualty produced an unbalanced gender distribution in the groups, but this bias did not affect the results. Therefore, early administration of L. reuteri DSM 17938 resulted beneficial in preventing regurgitation episodes during the first month of life.

Reprint of: Role of enteric neurotransmission in host defense and protection of the gastrointestinal tract

Host defense is a vital role played by the gastrointestinal tract. As host to an enormous and diverse microbiome, the gut has evolved an elaborate array of chemical and physicals barriers that allow the digestion and absorption of nutrients without compromising the mammalian host. The control of such barrier functions requires the integration of neural, humoral, paracrine and immune signaling, involving redundant and overlapping mechanisms to ensure, under most circumstances, the integrity of the gastrointestinal epithelial barrier. Here we focus on selected recent developments in the autonomic neural control of host defense functions used in the protection of the gut from luminal agents, and discuss how the microbiota may potentially play a role in enteric neurotransmission. Key recent findings include: the important role played by subepithelial enteric glia in modulating intestinal barrier function, identification of stress-induced mechanisms evoking barrier breakdown, neural regulation of epithelial cell proliferation, the role of afferent and efferent vagal pathways in regulating barrier function, direct evidence for bacterial communication to the enteric nervous system, and microbial sources of enteric neurotransmitters. We discuss these new and interesting developments in our understanding of the role of the autonomic nervous system in gastrointestinal host defense.

Intestinal microbiota influence the early postnatal development of the enteric nervous system

BACKGROUND

Normal gastrointestinal function depends on an intact and coordinated enteric nervous system (ENS). While the ENS is formed during fetal life, plasticity persists in the postnatal period during which the gastrointestinal tract is colonized by bacteria. We tested the hypothesis that colonization of the bowel by intestinal microbiota influences the postnatal development of the ENS.

METHODS

The development of the ENS was studied in whole mount preparations of duodenum, jejunum, and ileum of specific pathogen-free (SPF), germ-free (GF), and altered Schaedler flora (ASF) NIH Swiss mice at postnatal day 3 (P3). The frequency and amplitude of circular muscle contractions were measured in intestinal segments using spatiotemporal mapping of video recorded spontaneous contractile activity with and without exposure to lidocaine and N-nitro-L-arginine (NOLA).

KEY RESULTS

Immunolabeling with antibodies to PGP9.5 revealed significant abnormalities in the myenteric plexi of GF jejunum and ileum, but not duodenum, characterized by a decrease in nerve density, a decrease in the number of neurons per ganglion, and an increase in the proportion of myenteric nitrergic neurons. Frequency of amplitude of muscle contractions were significantly decreased in the jejunum and ileum of GF mice and were unaffected by exposure to lidocaine, while NOLA enhanced contractile frequency in the GF jejunum and ileum.

CONCLUSIONS & INFERENCES

These findings suggest that early exposure to intestinal bacteria is essential for the postnatal development of the ENS in the mid to distal small intestine. Future studies are needed to investigate the mechanisms by which enteric microbiota interact with the developing ENS.

Role of enteric neurotransmission in host defense and protection of the gastrointestinal tract

Host defense is a vital role played by the gastrointestinal tract. As host to an enormous and diverse microbiome, the gut has evolved an elaborate array of chemical and physicals barriers that allow the digestion and absorption of nutrients without compromising the mammalian host. The control of such barrier functions requires the integration of neural, humoral, paracrine and immune signaling, involving redundant and overlapping mechanisms to ensure, under most circumstances, the integrity of the gastrointestinal epithelial barrier. Here we focus on selected recent developments in the autonomic neural control of host defense functions used in the protection of the gut from luminal agents, and discuss how the microbiota may potentially play a role in enteric neurotransmission. Key recent findings include: the important role played by subepithelial enteric glia in modulating intestinal barrier function, identification of stress-induced mechanisms evoking barrier breakdown, neural regulation of epithelial cell proliferation, the role of afferent and efferent vagal pathways in regulating barrier function, direct evidence for bacterial communication to the enteric nervous system, and microbial sources of enteric neurotransmitters. We discuss these new and interesting developments in our understanding of the role of the autonomic nervous system in gastrointestinal host defense.

Lactobacillus rhamnosus protects human colonic muscle from pathogen lipopolysaccharide-induced damage

BACKGROUND

Lactobacillus species might positively affect gastrointestinal motility. These Gram-positive bacteria bind Toll-like receptor 2 (TLR2) that elicits anti-inflammatory activity and exerts protective effects on damage induced by lipopolysaccharide (LPS). Whether such effect occurs in gastrointestinal smooth muscle has not been established yet. Aim of this study was to characterize the effects of Lactobacillus rhamnosus GG (LGG) and of supernatants harvested from LGG cultures on human colonic smooth muscle and to explore their protective activity against LPS-induced myogenic morpho-functional alterations.

METHODS

The effects of LGG (ATCC 53103 strain) and of supernatants have been tested on both human colonic smooth muscle strips and isolated cells in the absence or presence of LPS obtained from a pathogenic strain of Escherichia coli. Their effects on myogenic morpho-functional properties, on LPS-induced NFκB activation, and on cytokine production have been evaluated. Toll-like receptor 2 expression has been analyzed by qPCR and flow cytometry.

KEY RESULTS

Lactobacillus rhamnosus GG exerted negligible transient effects per se whereas it was capable of activating an intrinsic myogenic response counteracting LPS-induced alterations. In particular, both LGG and supernatants significantly reduced the LPS-induced morpho-functional alterations of muscle cells, i.e. cell shortening and inhibition of contractile response. They also hindered LPS-induced pro-inflammatory effects by decreasing pro-inflammatory transcription factor NFκB activation and pro-inflammatory cytokine IL-6 secretion, and restored the secretion levels of anti-inflammatory cytokine IL10.

CONCLUSIONS & INFERENCES

Taken together these data demonstrate that LGG protects human colonic smooth muscle from LPS-induced myogenic damage and might be beneficial on intestinal motor disorders due to bacterial infection.

The microbiome: stress, health and disease

Bacterial colonisation of the gut plays a major role in postnatal development and maturation of key systems that have the capacity to influence central nervous system (CNS) programming and signaling, including the immune and endocrine systems. Individually, these systems have been implicated in the neuropathology of many CNS disorders and collectively they form an important bidirectional pathway of communication between the microbiota and the brain in health and disease. Regulation of the microbiome-brain-gut axis is essential for maintaining homeostasis, including that of the CNS. Moreover, there is now expanding evidence for the view that commensal organisms within the gut play a role in early programming and later responsivity of the stress system. Research has focused on how the microbiota communicates with the CNS and thereby influences brain function. The routes of this communication are not fully elucidated but include neural, humoral, immune and metabolic pathways. This view is underpinned by studies in germ-free animals and in animals exposed to pathogenic bacterial infections, probiotic agents or antibiotics which indicate a role for the gut microbiota in the regulation of mood, cognition, pain and obesity. Thus, the concept of a microbiome-brain-gut axis is emerging which suggests that modulation of the gut microflora may be a tractable strategy for developing novel therapeutics for complex stress-related CNS disorders where there is a huge unmet medical need.

Intestinal microbiota and immune function in the pathogenesis of irritable bowel syndrome

The pathophysiology of irritable bowel syndrome (IBS) is believed to involve alterations in the brain-gut axis; however, the etiological triggers and mechanisms by which these changes lead to symptoms of IBS remain poorly understood. Although IBS is often considered a condition without an identified "organic" etiology, emerging evidence suggests that alterations in the gastrointestinal microbiota and altered immune function may play a role in the pathogenesis of the disorder. These recent data suggest a plausible model in which changes in the intestinal microbiota and activation of the enteric immune system may impinge upon the brain-gut axis, causing the alterations in gastrointestinal function and the clinical symptoms observed in patients with IBS. This review summarizes the current evidence for altered intestinal microbiota and immune function in IBS. It discusses the potential etiological role of these factors, suggests an updated conceptual model for the pathogenesis of the disorder, and identifies areas for future research.

Bifidobacterium longum NCC3001 inhibits AH neuron excitability

BACKGROUND

Bifidobacterium longum (B. longum) NCC3001 can affect behavior and brain biochemistry, but identification of the cellular targets needs further investigation. Our hypothesis was that the communication with the brain might start with action on enteric sensory neurons.

METHODS

Ileal segments from adult mice were used to create a longitudinal muscle-myenteric-plexus preparation to expose sensory after-hyperpolarizing (AH) neurons in the myenteric plexus to allow access with microelectrodes. The intrinsic excitability of AH neurons was tested in response to the perfusion of conditioned media (B. longum culture supernatant) or unconditioned media (growth medium, MRS).

KEY RESULTS

B. longum conditioned medium significantly reduced the excitability of AH neurons compared to perfusion with the unconditioned medium. Specifically, a reduction was seen in the number of action potentials fired per depolarizing test pulse, the instantaneous and time-dependent input resistances and the magnitude of the hyperpolarization-activated cationic current (Ih ).

CONCLUSIONS & INFERENCES

The probiotic B. longum reduces excitability of AH sensory neurons likely via opening of potassium channels and closing of hyperpolarization-activated cation channels.

Bacteroides fragilis polysaccharide A is necessary and sufficient for acute activation of intestinal sensory neurons

Symbionts or probiotics are known to affect the nervous system. To understand the mechanisms involved, it is important to measure sensory neuron responses and identify molecules responsible for this interaction. Here we test the effects of adding Lactobacillus rhamnosus (JB-1) and Bacteroides fragilis to the epithelium while making voltage recordings from intestinal primary afferent neurons. Sensory responses are recorded within 8 s of applying JB-1 and excitability facilitated within 15 min. Bacteroides fragilis produces similar results, as does its isolated, capsular exopolysaccharide, polysaccharide A. Lipopolysaccharide-free polysaccharide A completely mimics the neuronal effects of the parent organism. Experiments with a mutant Bacteroides fragilis devoid of polysaccharide A shows that polysaccharide A is necessary and sufficient for the neuronal effects. Complex carbohydrates have not been reported before as candidates for such signalling between symbionts and the host. These observations indicate new neuronal targets and invite further study of bacterial carbohydrates as inter-kingdom signalling molecules between beneficial bacteria and sensory neurons.

An update on the use and investigation of probiotics in health and disease

Probiotics are derived from traditional fermented foods, from beneficial commensals or from the environment. They act through diverse mechanisms affecting the composition or function of the commensal microbiota and by altering host epithelial and immunological responses. Certain probiotic interventions have shown promise in selected clinical conditions where aberrant microbiota have been reported, such as atopic dermatitis, necrotising enterocolitis, pouchitis and possibly irritable bowel syndrome. However, no studies have been conducted that can causally link clinical improvements to probiotic-induced microbiota changes. Whether a disease-prone microbiota pattern can be remodelled to a more robust, resilient and disease-free state by probiotic administration remains a key unanswered question. Progress in this area will be facilitated by: optimising strain, dose and product formulations, including protective commensal species; matching these formulations with selectively responsive subpopulations; and identifying ways to manipulate diet to modify bacterial profiles and metabolism.

Spatiotemporal maps reveal regional differences in the effects on gut motility for Lactobacillus reuteri and rhamnosus strains

BACKGROUND

Commensal bacteria such as probiotics that are neuroactive acutely affect the amplitudes of intestinal migrating motor complexes (MMCs). What is lacking for an improved understanding of these motility effects are region specific measurements of velocity and frequency. We have combined intraluminal pressure recordings with spatiotemporal diameter maps to analyze more completely effects of different strains of beneficial bacteria on motility.

METHODS

Intraluminal peak pressure (PPr) was measured and video recordings made of mouse ex vivo jejunum and colon segments before and after intraluminal applications of Lactobacillus rhamnosus (JB-1) or Lactobacillus reuteri (DSM 17938). Migrating motor complex frequency and velocity were calculated.

KEY RESULTS

JB-1 decreased jejunal frequencies by 56% and 34% in colon. Jejunal velocities increased 171%, but decreased 31% in colon. Jejunal PPr decreased by 55% and in colon by 21%. DSM 17938 increased jejunal frequencies 63% and in colon 75%; jejunal velocity decreased 57%, but increased in colon 146%; jejunal PPr was reduced 26% and 12% in colon. TRAM-34 decreased frequency by 71% and increased velocity 200% for jejunum, but increased frequency 46% and velocity 50% for colon; PPr was decreased 59% for jejunum and 39% for colon.

CONCLUSIONS & INFERENCES

The results show that probiotics and other beneficial bacteria have strain and region-specific actions on gut motility that can be successfully discriminated using spatiotemporal mapping of diameter changes. Effects are not necessarily the same in colon and jejunum. Further research is needed on the detailed effects of the strains on enteric neuron currents for each gut region.

New insights into probiotic mechanisms: a harvest from functional and metagenomic studies

There has been continued and expanding recognition of probiotic approaches for treating gastrointestinal and systemic disease, as well as increased acceptance of probiotic therapies by both the public and the medical community. A parallel development has been the increasing recognition of the diverse roles that the normal gut microbiota plays in the normal biology of the host. This advance has in turn has been fed by implementation of novel investigative technologies and conceptual paradigms focused on understanding the fundamental role of the microbiota and indeed all commensal bacteria, on known and previously unsuspected aspects of host physiology in health and disease. This review discusses current advances in the study of the host-microbiota interaction, especially as it relates to potential mechanisms of probiotics. It is hoped these new approaches will allow more rational selection and validation of probiotic usage in a variety of clinical conditions.

Gut-brain axis: how the microbiome influences anxiety and depression

Within the first few days of life, humans are colonized by commensal intestinal microbiota. Here, we review recent findings showing that microbiota are important in normal healthy brain function. We also discuss the relation between stress and microbiota, and how alterations in microbiota influence stress-related behaviors. New studies show that bacteria, including commensal, probiotic, and pathogenic bacteria, in the gastrointestinal (GI) tract can activate neural pathways and central nervous system (CNS) signaling systems. Ongoing and future animal and clinical studies aimed at understanding the microbiota-gut-brain axis may provide novel approaches for prevention and treatment of mental illness, including anxiety and depression.