Bifidobacterium breve with α-linolenic acid and linoleic acid alters fatty acid metabolism in the maternal separation model of irritable bowel syndrome

Bifidobacterium longum S3 alleviates loperamide-induced constipation by modulating intestinal acetic acid and stearic acid levels in mice

Constipation is a major gastrointestinal (GI) symptom worldwide, with diverse causes of formation, and requires effective and safe therapeutic measures. In the present study, we used loperamide hydrochloride to establish a constipation model and assessed the effect of Bifidobacterium on constipation and its possible mechanism of relief. The results showed that B. longum S3 exerted a constipation-relieving effect primarily by improving the gut microbiota, enriching genera including Lactobacillus, Alistipes, and Ruminococcaceae UCG-007, and decreasing the bacteria Lachnospiraceae NK4B4 group. These changes may thereby increase acetic acid and stearic acid (C18:0) levels, which significantly increase the expression levels of ZO-1 and MUC-2, repair intestinal barrier damage and reduce inflammation (IL-6). Furthermore, it also inhibited oxidative stress levels (SOD and CAT), decreased the expression of water channel proteins (AQP4 and AQP8), significantly elevated the Gas, 5-HT, PGE2, and Ach levels, and reduced nNOS and VIP levels to improve the intestinal luminal transit time and fecal water content. Collectively, these changes resulted in the alleviation of constipation.

Molecular signalling during cross talk between gut brain axis regulation and progression of irritable bowel syndrome: A comprehensive review

Irritable bowel syndrome (IBS) is a chronic functional disorder which alters gastrointestinal (GI) functions, thus leading to compromised health status. Pathophysiology of IBS is not fully understood, whereas abnormal gut brain axis (GBA) has been identified as a major etiological factor. Recent studies are suggestive for visceral hyper-sensitivity, altered gut motility and dysfunctional autonomous nervous system as the main clinical abnormalities in IBS patients. Bidirectional signalling interactions among these abnormalities are derived through various exogenous and endogenous factors, such as microbiota population and diversity, microbial metabolites, dietary uptake, and psychological abnormalities. Strategic efforts focused to study these interactions including probiotics, antibiotics and fecal transplantations in normal and germ-free animals are clearly suggestive for the pivotal role of gut microbiota in IBS etiology. Additionally, neurotransmitters act as communication tools between enteric microbiota and brain functions, where serotonin (5-hydroxytryptamine) plays a key role in pathophysiology of IBS. It regulates GI motility, pain sense and inflammatory responses particular to mucosal and brain activity. In the absence of a better understanding of various interconnected crosstalks in GBA, more scientific efforts are required in the search of novel and targeted therapies for the management of IBS. In this review, we have summarized the gut microbial composition, interconnected signalling pathways and their regulators, available therapeutics, and the gaps needed to fill for a better management of IBS.

Hybridization altered the gut microbiota of pigs

Mammalian gut microbiota plays an important role in the host's nutrient metabolism, growth, and immune regulation. Hybridization can enable a progeny to acquire superior traits of the parents, resulting in the hybridization advantage. However, studies on the effects of hybridization on the pigs' gut microbiota are lacking. Therefore, this study used multi-omics technologies to compare and analyze the gut microbiota of the primary wild boar and its offspring. The 16S rRNA gene sequencing results revealed that the gut microbiota of F4 exhibited a host-like dominance phenomenon with a significant increase in the abundance of Lactobacillus and Bifidobacterium. The beta diversity of Duroc was significantly different from those of F0, F2, and F4; after the host hybridization, the similarity of the beta diversity in the progeny decreased with the decrease in the similarity of the F0 lineage. The metagenomic sequencing results showed that the significantly enriched metabolic pathways in F4, such as environmental, circulatory system, fatty acid degradation adaptation, and fatty acid biosynthesis, were similar to those in F0. Moreover, it also exhibited similar significantly enriched metabolic pathways as those in Duroc, such as carbohydrate metabolism, starch and sucrose metabolism, starch-degrading CAZymes, lactose-degrading CAZymes, and various amino acid metabolism pathways. However, the alpha-amylase-related KOs, lipid metabolism, and galactose metabolism in F4 were significantly higher than those in Duroc and F0. Non-targeted metabolome technology analysis found that several metabolites, such as docosahexaenoic acid, arachidonic acid, and citric acid were significantly enriched in the F4 pigs as compared to those in F0. Based on Spearman correlation analysis, Lactobacillus and Bifidobacterium were significantly positively correlated with these metabolites. Finally, the combined metagenomic and metabolomic analysis suggested that the metabolic pathways, such as valine, leucine, and isoleucine biosynthesis and alanine aspartate and glutamate metabolism were significantly enriched in F4 pigs. In conclusion, the gut microbiota of F4 showed a similar host "dominance" phenomenon, which provided reference data for the genetics and evolution of microbiota and the theory of microbial-assisted breeding.

Perinatal transmission of a probiotic Bifidobacterium strain protects against early life stress-induced mood and gastrointestinal motility disorders

Early life stress can considerably interfere in gut microbiome formation and nervous system development. Specific probiotic strains have been proved to exert anti-stress effects by modulating the gut-brain axis. However, little is known about whether probiotic treatment during pregnancy can protect the offspring from early life stress. In this study, Bifidobacterium breve CCFM1025, previously proven to exert microbial and neurobiological regulation effects, was given to pregnant mice. The offspring's gut and brain functions were evaluated when challenged with maternal separation. Intriguingly, treatment with probiotics during pregnancy protected the offspring from maternal separation-induced neurobiological and gastrointestinal disorders such as depression-like behaviour and delayed defecation. Quantification of CCFM1025 was performed, and perinatal transmission of CCFM1025 was further validated, which also explained the reason for increased levels of colonic 5-hydroxytryptamine and caecal short-chain fatty acids in the offspring. Our findings indicated that the effects of probiotics can be perinatally transmitted through gut microbes and that probiotic treatment during pregnancy may have great potential in managing health risks in early life.

Faecal microbiota transplantation alleviates early-life antibiotic-induced gut microbiota dysbiosis and mucosa injuries in a neonatal piglet model

Faecal microbiota transplantation (FMT) is a promising approach to modulate the gut microbiota. Gut microbiota dysbiosis caused by antibiotic administration is a universal problem. This study aimed to evaluate the effect of FMT on the dysbiosis of gut microbiota and metabolic profiles and injury of the intestinal barrier induced by antibiotics and used a neonatal piglet model. Neonatal piglets were administered ampicillin for 3 days, and antibiotic-induced dysbiosis was evaluated by the occurrence of diarrhoea and alteration of gut microbiota. Then, FMT was conducted for 3 days to rebuild the gut microbiota. High-throughput sequencing and a mass spectrometry platform were used for integrated microbiome-metabolome analysis. The results showed that antibiotics led to a decline in the diversity of gut microbiota. Furthermore, there was an increase in the relative abundance of potential pathogenic bacteria, such as Oscillibacter, Pseudomonas and Eubacterium, and an increase in the relative abundance of tetracycline resistance genes (tet genes). FMT restored the diversity and promoted the relative abundance of beneficial bacteria, such as Parabacteroides, Dorea and Parasutterella, while decreasing the relative abundance of tet genes. Untargeted metabolomics analysis found that alpha linolenic acid and linoleic acid metabolism were the key metabolic pathways utilized in the FMT group, and targeted metabolomics analysis further verified the variation in the associated metabolites arachidonic acid and conjugated linoleic acid. FMT also significantly enhanced the relative expression of tight junction (ZO-1, claudin-1 and occludin) and adherens junction (β-catenin, E-cadherin) proteins and anti-inflammatory cytokines (IL-10, TGF-β1) and reduced the production of proinflammatory cytokines (IL-6, IL-1β, TNF-α and IFN-γ) in the colon. FMT not only modulated the gut microbiota composition and microbial metabolism but also reduced the relative abundance of tet genes, improving the intestinal barrier function and inflammatory responses in antibiotic-treated piglets.

Infant gut microbiota characteristics generally do not modify effects of lipid-based nutrient supplementation on growth or inflammation: secondary analysis of a randomized controlled trial in Malawi

An unhealthy gut microbial community may act as a barrier to improvement in growth and health outcomes in response to nutritional interventions. The objective of this analysis was to determine whether the infant microbiota modified the effects of a randomized controlled trial of lipid-based nutrient supplements (LNS) in Malawi on growth and inflammation at 12 and 18 months, respectively. We characterized baseline microbiota composition of fecal samples at 6 months of age (n = 506, prior to infant supplementation, which extended to 18 months) using 16S rRNA gene sequencing of the V4 region. Features of the gut microbiota previously identified as being involved in fatty acid or micronutrient metabolism or in outcomes relating to growth and inflammation, especially in children, were investigated. Prior to correction for multiple hypothesis testing, the effects of LNS on growth appeared to be modified by Clostridium (p-for-interaction = 0.02), Ruminococcus (p-for-interaction = 0.007), and Firmicutes (p-for-interaction = 0.04) and effects on inflammation appeared to be modified by Faecalibacterium (p-for-interaction = 0.03) and Streptococcus (p-for-interaction = 0.004). However, after correction for multiple hypothesis testing these findings were not statistically significant, suggesting that the gut microbiota did not alter the effect of LNS on infant growth and inflammation in this cohort.

The Therapeutic Effect of Exercise on Anxiety and Bowel Oxidative Stress in the Maternal Separation Animal Model

Introduction:

According to evidence, Early-Life Stress (ELS), mood disorders, and medical comorbidities, i.e. Irritable Bowel Syndrome (IBS), are correlated; however, the direct contribution of ELS to IBS manifestations is less understood. The current study aimed at evaluating the effect of voluntary exercise on the mitochondrial dysfunction of the bowel fibroblasts, following the confirmation of anxiety behavior.

Methods:

In this study, Postnatal Day (PND) rats underwent Maternal Separation (MS), as a valid animal model of the brain-gut axis dysfunction, in the days 2–14; three hours daily. On day 21, the study animals were divided into 4 groups, as follows: control, Running Wheel (RW) exercise, MS, and MS+RW groups. The study groups were housed in separate cages (4 rats per cage) until the onset of intervention. On day 60, the elevated plusmaze was used to assess anxiety-like behaviors; the level of oxidative stress biomarkers, i.e. Reactive Oxygen Species (ROS), Glutathione (GSH), as well as Adenosine Triphosphate (ATP) was measured to determine the gut mitochondrial function.

Results:

Findings revealed that ELS affected the gut energy metabolism in the studied rats; the negative effects of MS on anxiety and the gut mitochondrial dysfunction decreased via RW exercise during adolescence.

Conclusion:

Overall, anxiety behaviors and ROS production, leading to increased GSH and ATP levels, improved after RW exercise; this significantly impacts the function of colon secretory mitochondria. According to the positive effects of RW exercise on mitochondrial dysfunction in an ELS animal model, a potential relationship was found between the brain and gut in the study rats.

Toxicity Studies of Lactobacillus plantarum PS128TM Isolated from Spontaneously Fermented Mustard Greens

Probiotics are extensively available to consumers; however, the use of probiotics may not always be safe, and there are few reports on their side effects, including those of Lactobacillus. Lactobacillus plantarum strain PS128^TM isolated from spontaneously fermented mustard greens in Taiwan was recently reported to exhibit probiotic properties. In this study, we aimed to assess the safety of strain PS128^TM for use in humans via examining genotoxic and oral toxic effects using in vitro and in vivo testing. Five strains of Salmonella typhimurium were evaluated by the Ames test; no signs of increased reverse mutation were observed following exposure to PS128^TM. Additional testing of Chinese hamster ovary (CHO) cells exposed to PS128^TM revealed that the incidence of chromosomal aberrations in CHO cells had not increased. PS128^TM treatment also did not affect the proportion of immature to total erythrocytes or the number of micronuclei in the immature erythrocytes of ICR mice. Moreover, following a 28 day study involving repeated oral dose toxicity tests (2400, 400, and 40 mg/kg body weight) utilizing an ICR mouse model, no observable adverse level (NOAEL) was found at any of the doses. PS128^TM was sensitive to antibiotics; however, genes related to the production of biogenic amines were absent. While further research is required, these toxicological assessments suggest that PS128^TM could be safe for human consumption.

Maternal separation in rodents: a journey from gut to brain and nutritional perspectives

The developmental period constitutes a critical window of sensitivity to stress. Indeed, early-life adversity increases the risk to develop psychiatric diseases, but also gastrointestinal disorders such as the irritable bowel syndrome at adulthood. In the past decade, there has been huge interest in the gut-brain axis, especially as regards stress-related emotional behaviours. Animal models of early-life adversity, in particular, maternal separation (MS) in rodents, demonstrate lasting deleterious effects on both the gut and the brain. Here, we review the effects of MS on both systems with a focus on stress-related behaviours. In addition, we discuss more recent findings showing the impact of gut-directed interventions, including nutrition with pre- and probiotics, illustrating the role played by gut microbiota in mediating the long-term effects of MS. Overall, preclinical studies suggest that nutritional approaches with pro- and prebiotics may constitute safe and efficient strategies to attenuate the effects of early-life stress on the gut-brain axis. Further research is required to understand the complex mechanisms underlying gut-brain interaction dysfunctions after early-life stress as well as to determine the beneficial impact of gut-directed strategies in a context of early-life adversity in human subjects.

Transcriptomics-driven lipidomics (TDL) identifies the microbiome-regulated targets of ileal lipid metabolism

The gut microbiome and lipid metabolism are both recognized as essential components in the maintenance of metabolic health. The mechanisms involved are multifactorial and (especially for microbiome) poorly defined. A strategic approach to investigate the complexity of the microbial influence on lipid metabolism would facilitate determination of relevant molecular mechanisms for microbiome-targeted therapeutics. E. coli is associated with obesity and metabolic syndrome and we used this association in conjunction with gnotobiotic models to investigate the impact of E. coli on lipid metabolism. To address the complexities of the integration of the microbiome and lipid metabolism, we developed transcriptomics-driven lipidomics (TDL) to predict the impact of E. coli colonization on lipid metabolism and established mediators of inflammation and insulin resistance including arachidonic acid metabolism, alterations in bile acids and dietary lipid absorption. A microbiome-related therapeutic approach targeting these mechanisms may therefore provide a therapeutic avenue supporting maintenance of metabolic health.

Microbes multifactorially impact host lipid metabolism bearing a significant impact in health and disease. A team led by Mojgan Masoodi and Scott Parkinson at Nestlé Institute of Health Sciences (NIHS) developed an integrative data driven approach for predictive lipidomics investigations of host-microbial impacts on lipid metabolism. Results of in-vivo studies with germ-free mice inoculated with E. coli and in-vitro studies demonstrated the multifactorial nature of the impact of E. coli on arachidonic acid metabolism in the ileum and altered host inflammation and lipid absorption. The findings provide insights into understanding the host-microbiome interactions and identifying microbiome-related solutions for maintaining health and tackling disease. The systems approach presented is applicable to investigate broad range of microbiome dependent and independent alterations in host lipid metabolism.

Bifidobacterium breve with α-linolenic acid alters the composition, distribution and transcription factor activity associated with metabolism and absorption of fat

This study focused on the mechanisms that fatty acid conjugating strains - Bifidobacterium breve NCIMB 702258 and Bifidobacterium breve DPC 6330 - influence lipid metabolism when ingested with α-linolenic acid (ALA) enriched diet. Four groups of BALB/c mice received ALA enriched diet (3% (w/w)) either alone or in combination with B. breve NCIMB 702258 or B. breve DPC 6330 (10⁹ CFU/day) or unsupplemented control diet for six weeks. The overall n-3 PUFA score was increased in all groups receiving the ALA enriched diet. Hepatic peroxisomal beta oxidation increased following supplementation of the ALA enriched diet with B. breve (P < 0.05) and so the ability of the strains to produce c9t11 conjugated linoleic acid (CLA) was identified in adipose tissue. Furthermore, a strain specific effect of B. breve NCIMB 702258 was found on the endocannabinoid system (ECS). Liver triglycerides (TAG) were reduced following ALA supplementation, compared with unsupplemented controls (P < 0.01) while intervention with B. breve further reduced liver TAG (P < 0.01), compared with the ALA enriched control. These data indicate that the interactions of the gut microbiota with fatty acid metabolism directly affect host health by modulating n-3 PUFA score and the ECS.

Impact of Lactobacillus fermentum and dairy lipids in the maternal diet on the fatty acid composition of pups' brain and peripheral tissues

The aim of the study was to determine the effect of maternal diets administered since day 1 of gestation and containing dairy lipids or vegetable oils differing in the supply of n-3 polyunsaturated fatty acids (n-3 PUFAs) (equilibrated or deficient) and of Lactobacillus fermentum (L. fermentum) on the docosahexaenoic acid (DHA) accretion in the pups at postnatal day 14 in the prefrontal cortex (PFC) and hippocampus (HC) for brain structures and in the liver and adipose tissue for peripheral tissues. Maternal milk fatty acid composition was also assessed by analyzing the fatty acid composition of the gastric content of the pups. DHA was higher in mice supplemented with L. fermentum than in mice in the deficient group in HC and PFC and also in liver and adipose tissue. This increase could be linked to the slight but significant increase in C18:3n-3 in the maternal milk. This proportion was comparable in the dairy lipid group for which the brain DHA level was the highest. L. fermentum may have a key role in the protection of the brain during the perinatal period via the neuronal accretion of n-3 PUFAs, especially during n-3 PUFA deficiency.

Polyunsaturated Fatty Acids and Their Derivatives: Therapeutic Value for Inflammatory, Functional Gastrointestinal Disorders, and Colorectal Cancer

Polyunsaturated fatty acids (PUFAs) are bioactive lipids which modulate inflammation and immunity. They gained recognition in nutritional therapy and are recommended dietary supplements. There is a growing body of evidence suggesting the usefulness of PUFAs in active therapy of various gastrointestinal (GI) diseases. In this review we briefly cover the systematics of PUFAs and their metabolites, and elaborate on their possible use in inflammatory bowel disease (IBD), functional gastrointestinal disorders (FGIDs) with focus on irritable bowel syndrome (IBS), and colorectal cancer (CRC). Each section describes the latest findings from in vitro and in vivo studies, with reports of clinical interventions when available.

Gut Microbiome: What We Do and Don't Know

Within the last decade, research regarding the human gut microbiome has exploded. While the gastrointestinal tract was once regarded simply as a digestive organ, new technologies have led the science world to wonder about the impact that the gut microbiota may have on human health and disease. The gut microbiome is now becoming known for its role in metabolism, immune defense, and behavior. From in utero variations to those that rapidly occur post partum, our gut microbiome changes with age, environment, stress, diet, and health status as well as medication exposure. This article reviews what is currently known regarding various influences on the gut microbiome and is meant to encourage the reader to further explore the unknown.

Psychotropic effects of Lactobacillus plantarum PS128 in early life-stressed and naïve adult mice

Ingestion of specific probiotics, namely "psychobiotics", produces psychotropic effects on behavior and affects the hypothalamic-pituitary-adrenal axis and neurochemicals in the brain. We examined the psychotropic effects of a potential psychobiotic bacterium, Lactobacillus plantarum strain PS128 (PS128), on mice subjected to early life stress (ELS) and on naïve adult mice. Behavioral tests revealed that chronic ingestion of PS128 increased the locomotor activities in both ELS and naïve adult mice in the open field test. In the elevated plus maze, PS128 significantly reduced the anxiety-like behaviors in naïve adult mice but not in the ELS mice; whereas the depression-like behaviors were reduced in ELS mice but not in naïve mice in forced swimming test and sucrose preference test. PS128 administration also reduced ELS-induced elevation of serum corticosterone under both basal and stressed states but had no effect on naïve mice. In addition, PS128 reduced inflammatory cytokine levels and increased anti-inflammatory cytokine level in the serum of ELS mice. Furthermore, the dopamine level in the prefrontal cortex (PFC) was significantly increased in PS128 treated ELS and naïve adult mice whereas serotonin (5-HT) level was increased only in the naïve adult mice. These results suggest that chronic ingestion of PS128 could ameliorate anxiety- and depression-like behaviors and modulate neurochemicals related to affective disorders. Thus PS128 shows psychotropic properties and has great potential for improving stress-related symptoms.

Animal models of gastrointestinal and liver diseases. Animal models of visceral pain: pathophysiology, translational relevance, and challenges

Visceral pain describes pain emanating from the thoracic, pelvic, or abdominal organs. In contrast to somatic pain, visceral pain is generally vague, poorly localized, and characterized by hypersensitivity to a stimulus such as organ distension. Animal models have played a pivotal role in our understanding of the mechanisms underlying the pathophysiology of visceral pain. This review focuses on animal models of visceral pain and their translational relevance. In addition, the challenges of using animal models to develop novel therapeutic approaches to treat visceral pain will be discussed.

Brain and liver fatty acid composition changes upon consumption of Lactobacillus rhamnosus LA68

Recent reports suggest that the metabolic activity of the enteric microbiota may influence the fatty acid composition of the host tissue. There are many studies dealing with the influence of lactobacilli on various pathological conditions, and some of the effects are strain-specific. This study was designed to test the effects of a particular Lactobacillus strain, Lactobacillus rhamnosus LA68 on fatty acid composition of the liver and the brain of C57BL/6 mice in the absence of an underlying pathological condition. Female mice were supplemented with live L. rhamnosus LA68 bacteria for the duration of 1 month. Serum biochemistry was analyzed and liver and brain fatty acid composition was assessed by gas-liquid chromatography. Significant changes in liver and brain fatty acid composition were detected. In the liver tissue we detected an increase in palmitoleic acid (p = 0.038), while in the brain compartment we found an increase in palmitic (p = 0.042), stearic (p = 0.017), arachidonic acid (p = 0.009) and docosahexaenoic acid (p = 0.004) for control versus experimental group. These results show discrete changes caused by LA68 strain consumption. Even short duration of administration of LA68 influences the fatty acid composition of the host which adds to the existing knowledge about Lactobacillus host interaction, and adds to the growing knowledge of metabolic intervention possibilities.

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.

Microbes central to human reproduction

As studies uncover the breadth of microbes associated with human life, opportunities will emerge to manipulate and augment their functions in ways that improve health and longevity. From involvement in the complexities of reproduction and fetal/infant development, to delaying the onset of disease, and indeed countering many maladies, microbes offer hope for human well-being. Evidence is emerging to suggest that microbes may play a beneficial role in body sites traditionally viewed as being sterile. Although further evidence is required, we propose that much of medical dogma is about to change significantly through recognition and understanding of these hitherto unrecognized microbe–host interactions. A meeting of the International Scientific Association for Probiotics and Prebiotics held in Aberdeen, Scotland (June 2014), presented new views and challenged established concepts on the role of microbes in reproduction and health of the mother and infant. This article summarizes some of the main aspects of these discussions.

Gut microbiota, the pharmabiotics they produce and host health

A healthy gut microbiota plays many crucial functions in the host, being involved in the correct development and functioning of the immune system, assisting in the digestion of certain foods and in the production of health-beneficial bioactive metabolites or 'pharmabiotics'. These include bioactive lipids (including SCFA and conjugated linoleic acid) antimicrobials and exopolysaccharides in addition to nutrients, including vitamins B and K. Alterations in the composition of the gut microbiota and reductions in microbial diversity are highlighted in many disease states, possibly rendering the host susceptible to infection and consequently negatively affecting innate immune function. Evidence is also emerging of microbially produced molecules with neuroactive functions that can have influences across the brain-gut axis. For example, γ-aminobutyric acid, serotonin, catecholamines and acetylcholine may modulate neural signalling within the enteric nervous system, when released in the intestinal lumen and consequently signal brain function and behaviour. Dietary supplementation with probiotics and prebiotics are the most widely used dietary adjuncts to modulate the gut microbiota. Furthermore, evidence is emerging of the interactions between administered microbes and dietary substrates, leading to the production of pharmabiotics, which may directly or indirectly positively influence human health.

The microbiota-gut-brain axis in gastrointestinal disorders: stressed bugs, stressed brain or both?

The gut-brain axis is the bidirectional communication between the gut and the brain, which occurs through multiple pathways that include hormonal, neural and immune mediators. The signals along this axis can originate in the gut, the brain or both, with the objective of maintaining normal gut function and appropriate behaviour. In recent years, the study of gut microbiota has become one of the most important areas in biomedical research. Attention has focused on the role of gut microbiota in determining normal gut physiology and immunity and, more recently, on its role as modulator of host behaviour ('microbiota-gut-brain axis'). We therefore review the literature on the role of gut microbiota in gut homeostasis and link it with mechanisms that could influence behaviour. We discuss the association of dysbiosis with disease, with particular focus on functional bowel disorders and their relationship to psychological stress. This is of particular interest because exposure to stressors has long been known to increase susceptibility to and severity of gastrointestinal diseases.

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.

Novel n-3 immunoresolvents: structures and actions

Resolution of inflammation is now held to be an active process where autacoids promote homeostasis. Using functional-metabololipidomics and in vivo systems, herein we report that endogenous n-3 docosapentaenoic (DPA) acid is converted during inflammation-resolution in mice and by human leukocytes to novel n-3 products congenerous to D-series resolvins (Rv), protectins (PD) and maresins (MaR), termed specialized pro-resolving mediators (SPM). The new n-3 DPA structures include 7,8,17-trihydroxy-9,11,13,15E,19Z-docosapentaenoic acid (RvD1_{n-3 DPA}), 7,14-dihydroxy-8,10,12,16Z,19Z-docosapentaenoic acid (MaR1_{n-3 DPA}) and related bioactive products. Each n-3 DPA-SPM displayed protective actions from second organ injury and reduced systemic inflammation in ischemia-reperfusion. The n-3 DPA-SPM, including RvD1_{n-3 DPA} and MaR1_{n-3 DPA}, each exerted potent leukocyte directed actions in vivo. With human leukocytes each n-3 DPA-SPM reduced neutrophil chemotaxis, adhesion and enhanced macrophage phagocytosis. Together, these findings demonstrate that n-3 DPA is converted to novel immunoresolvents with actions comparable to resolvins and are likely produced in humans when n-3 DPA is elevated.