Serotonin, tryptophan metabolism and the brain-gut-microbiome axis. Behav Brain Res. 2015;277:32-48. [PMID: 25078296 DOI: 10.1016/j.bbr.2014.07.027]

Integrative metabolic and microbial profiling on patients with Spleen-yang-deficiency syndrome

Gut microbiota is recognized as an indispensable "metabolic organ" that plays crucial roles in maintaining human health or initiating diseases. Spleen-yang-deficiency syndrome (SYDS) is a common syndrome of Traditional Chinese Medicine (TCM) clinic. It is a complex phenotype reflecting the overall changes of metabolism which are mainly caused by digestive disorders. However, little is known about the changes of gut microbiota and metabolism in patients with SYDS, as well as the crosstalk between gut microbiota and host metabolism. In the current study, an integrative metabolic and microbial profiling was performed on plasma, urine and feces from recruited SYDS and healthy individuals by using a LC-QTOFMS-based metabolomic and 16 s rRNA sequencing approaches. Our results showed a potentially significant contribution of gut dysbiosis to the metabolic disorders in SYDS. By integrating the differential gut bacteria with the metabolites, the results revealed some active bacterium of norank_f_CFT112H7, f_lachnospiraceae and bacteroides were closely involved in host mucosal integrity, bile acid metabolism and polysaccharides decomposition. Therefore, our results indicated the probable involvement of gut microbiota in mediating the metabolic changes, which warrants a further investigation on the role of gut microbiota in modulating the pathogenesis of SYDS.

The hologenome concept of evolution after 10 years

The holobiont (host with its endocellular and extracellular microbiome) can function as a distinct biological entity, an additional organismal level to the ones previously considered, on which natural selection operates. The holobiont can function as a whole: anatomically, metabolically, immunologically, developmentally, and during evolution. Consideration of the holobiont with its hologenome as an independent level of selection in evolution has led to a better understanding of underappreciated modes of genetic variation and evolution. The hologenome is comprised of two complimentary parts: host and microbiome genomes. Changes in either genome can result in variations that can be selected for or against. The host genome is highly conserved, and genetic changes within it occur slowly, whereas the microbiome genome is dynamic and can change rapidly in response to the environment by increasing or reducing particular microbes, by acquisition of novel microbes, by horizontal gene transfer, and by mutation. Recent experiments showing that microbiota can play an initial role in speciation have been suggested as an additional mode of enhancing evolution. Some of the genetic variations can be transferred to offspring by a variety of mechanisms. Strain-specific DNA analysis has shown that at least some of the microbiota can be maintained across hundreds of thousands of host generations, implying the existence of a microbial core. We argue that rapid changes in the microbiome genome could allow holobionts to adapt and survive under changing environmental conditions thus providing the time necessary for the host genome to adapt and evolve. As Darwin wrote, "It is not the strongest of the species that survives but the most adaptable".

Indole, a Signaling Molecule Produced by the Gut Microbiota, Negatively Impacts Emotional Behaviors in Rats

Gut microbiota produces a wide and diverse array of metabolites that are an integral part of the host metabolome. The emergence of the gut microbiome-brain axis concept has prompted investigations on the role of gut microbiota dysbioses in the pathophysiology of brain diseases. Specifically, the search for microbe-related metabolomic signatures in human patients and animal models of psychiatric disorders has pointed out the importance of the microbial metabolism of aromatic amino acids. Here, we investigated the effect of indole on brain and behavior in rats. Indole is produced by gut microbiota from tryptophan, through the tryptophanase enzyme encoded by the tnaA gene. First, we mimicked an acute and high overproduction of indole by injecting this compound in the cecum of conventional rats. This treatment led to a dramatic decrease of motor activity. The neurodepressant oxidized derivatives of indole, oxindole and isatin, accumulated in the brain. In addition, increase in eye blinking frequency and in c-Fos protein expression in the dorsal vagal complex denoted a vagus nerve activation. Second, we mimicked a chronic and moderate overproduction of indole by colonizing germ-free rats with the indole-producing bacterial species Escherichia coli. We compared emotional behaviors of these rats with those of germ-free rats colonized with a genetically-engineered counterpart strain unable to produce indole. Rats overproducing indole displayed higher helplessness in the tail suspension test, and enhanced anxiety-like behavior in the novelty, elevated plus maze and open-field tests. Vagus nerve activation was suggested by an increase in eye blinking frequency. However, unlike the conventional rats dosed with a high amount of indole, the motor activity was not altered and neither oxindole nor isatin could be detected in the brain. Further studies are required for a comprehensive understanding of the mechanisms supporting indole effects on emotional behaviors. As our findings suggest that people whose gut microbiota is highly prone to produce indole could be more likely to develop anxiety and mood disorders, we addressed the issue of the inter-individual variability of indole producing potential in humans. An in silico investigation of metagenomic data focused on the tnaA gene products definitively proved this inter-individual variability.

Fecal bacterial communities of wild-captured and stranded green turtles (Chelonia mydas) on the Great Barrier Reef

Green turtles (Chelonia mydas) are endangered marine herbivores that break down food particles, primarily sea grasses, through microbial fermentation. However, the microbial community and its role in health and disease is still largely unexplored. In this study, we investigated and compared the fecal bacterial communities of eight wild-captured green turtles to four stranded turtles in the central Great Barrier Reef regions that include Bowen and Townsville. We used high-throughput sequencing analysis targeting the hypervariable V1-V3 regions of the bacterial 16S rRNA gene. At the phylum level, Firmicutes predominated among wild-captured green turtles, followed by Bacteroidetes and Proteobacteria. In contrast, Proteobacteria (Gammaproteobacteria) was the most significantly dominant phylum among all stranded turtles, followed by Bacteroidetes and Firmicutes. In addition, Fusobacteria was also significantly abundant in stranded turtles. No significant differences were found between the wild-captured turtles in Bowen and Townsville. At the family level, the core bacterial community consisted of 25 families that were identified in both the wild-captured and stranded green turtles, while two unique sets of 14 families each were only found in stranded or wild-captured turtles. The predominance of Bacteroides in all groups indicates the importance of these bacteria in turtle gut health. In terms of bacterial diversity and richness, wild-captured green turtles showed a higher bacterial diversity and richness compared with stranded turtles. The marked differences in the bacterial communities between wild-captured and stranded turtles suggest the possible dysbiosis in stranded turtles in addition to potential causal agents.

Psychosocial Stress and Immunity-What Can We Learn From Pig Studies?

Psychosocial stress may impair immune functions and provoke the development of pathologies. The underlying communication between the brain and the immune system is being studied predominantly in rodents. However, pigs offer several advantages as preclinical models for humans because pigs are more similar to humans than rodents in many anatomical and physiological characteristics. Unlike in rodents, the main stress-induced glucocorticoid in humans and pigs is cortisol with a similar circadian rhythm. In this study, we summarize data on short-term and long-term effects of social stress in pigs for their immunity and neuroendocrine regulation with consequences for their health and well-being. As typical social stressors, regrouping, crowding, social isolation, and maternal deprivation have been studied. Psychosocial stress in pigs may affect various reactions of innate and adaptive immunity, such as leukocyte distribution, cytokine secretion, lymphocyte proliferation, and antibody production as well as immune responses to viral infection or vaccination. Furthermore, social stress may induce or promote gastrointestinal diseases through dysregulation of inflammatory processes. In piglets, psychosocial stress may also result in glucocorticoid resistance of lymphocytes, which has been discussed as a cause of allergic asthma in humans. Stress-related neuroendocrine alterations in the cortico-limbic structures, such as the prefrontal cortex, amygdala, hippocampus and hypothalamus, have been demonstrated in pigs at different ages. Based on these data, we propose using pigs as models for psychosocial stress in humans to study the mechanisms of brain-to-immune and immune-to-brain communication from the systemic level down to the cellular and subcellular levels.

Assessment of tryptophan metabolism and signs of depression in individuals with carbohydrate malabsorption

This prospective cross-sectional study aimed to investigate the potential association between primary-adult lactose malabsorption, fructose malabsorption, tryptophan (TRP) metabolism and the presence of depressive signs. Overall 251 patients, who were referred for lactase gene C/T_-13910 polymorphism genotyping and fructose hydrogen/methane breath testing, were included. All participants filled out the Beck Depression Inventory (BDI II). Serum concentrations of tryptophan (TRP), kynurenine (KYN), kynuric acid (KYNA), and TRP competing amino acids (leucine, isoleucine, valine, phenylalanine, tyrosine) were measured by high-pressure liquid-chromatography. Logistic regression analysis was performed with lactose malabsorption, fructose malabsorption and all potential biomarkers of TRP metabolism to assess the effect on signs of depression, defined as a BDI II score > 13. Primary-adult lactose malabsorption and fructose malabsorption was detected in 65 (25.90%) and 65 (25.90%) patients, respectively. Fructose malabsorption was significantly associated with BDI II score, whereas no such relationship was found for lactose malabsorption. Serum levels of TRP and TRP metabolites were no predictors of depression. The authors suggest to conduct further prospective longitudinal studies in order to get further insight of associations between carbohydrate malabsorption, biomarkers and mood disorders.

Serotonin as a link between the gut-brain-microbiome axis in autism spectrum disorders

Autism-spectrum disorder (ASD) is a neurodevelopmental disorder characterized by persistent deficits in social communication and repetitive patterns of behavior. ASD is, however, often associated with medical comorbidities and gastrointestinal (GI) dysfunction is among the most common. Studies have demonstrated a correlation between GI dysfunction and the degree of social impairment in ASD. The etiology of GI abnormalities in ASD is unclear, though the association between GI dysfunction and ASD-associated behaviors suggest that overlapping developmental defects in the brain and the intestine and/or a defect in communication between the enteric and central nervous systems (ENS and CNS, respectively), known as the gut-brain axis, could be responsible for the observed phenotypes. Brain-gut abnormalities have been increasingly implicated in several disease processes, including ASD. As a critical modulator of ENS and CNS development and function, serotonin may be a nexus for the gut-brain axis in ASD. This paper reviews the role of serotonin in ASD from the perspective of the ENS. A murine model that has been demonstrated to possess brain, behavioral and GI abnormalities mimicking those seen in ASD harbors the most common serotonin transporter (SERT) based mutation (SERT Ala56) found in children with ASD. Discussion of the gut-brain manifestations in the SERT Ala56 mice, and their correction with developmental administration of a 5-HT₄ agonist, are also addressed in conjunction with other future directions for diagnosis and treatment.

Exploration of the association between dietary fiber intake and depressive symptoms in adults

OBJECTIVE

Current evidence on the association between dietary fiber intake and the risk of depressive symptoms is inconsistent. Thus, the purpose of the present study was to explore their association.

METHODS

Data from the National Health and Nutrition Examination Survey 2007 to 2014 were used in this cross-sectional study. Dietary data were obtained through two 24-h dietary recall interviews. Depressive symptoms were assessed using Patient Health Questionnaire. Logistic regression models and restricted cubic spline models were applied to evaluate the associations among dietary intakes of total, cereal, vegetable, and fruit fiber and depressive symptoms.

RESULTS

A total of 16 807 adults ages 20 y or older were included in this study. Dietary intakes of total, cereal, vegetable, and fruit fiber were inversely associated with depressive symptoms in unadjusted model and multivariate-adjusted model 1. In multivariate-adjusted model 2, the odds ratios (95% confidence intervals) of depressive symptoms were 0.59 (0.44-0.79), 0.90 (0.69-1.19), 0.58 (0.45-0.76), and 0.64 (0.45-0.92) for the highest versus lowest quartile of total, cereal, vegetable, and fruit fiber intakes, respectively. Dose-response analyses found that the risk of depressive symptoms was associated with total fiber intake in a nonlinear manner, whereas the relationships were linear with cereal, vegetable, and fruit fiber intakes.

CONCLUSIONS

Our study suggested that intakes of total fiber, vegetable fiber, and fruit fiber were inversely associated with depressive symptoms. Further larger prospective studies are needed to confirm our findings.

Nutritional preferences of human gut bacteria reveal their metabolic idiosyncrasies

Bacterial metabolism plays a fundamental role in gut microbiota ecology and host-microbiome interactions. Yet the metabolic capabilities of most gut bacteria have remained unknown. Here we report growth characteristics of 96 phylogenetically diverse gut bacterial strains across 4 rich and 15 defined media. The vast majority of strains (76) grow in at least one defined medium, enabling accurate assessment of their biosynthetic capabilities. These do not necessarily match phylogenetic similarity, thus indicating a complex evolution of nutritional preferences. We identify mucin utilizers and species inhibited by amino acids and short-chain fatty acids. Our analysis also uncovers media for in vitro studies wherein growth capacity correlates well with in vivo abundance. Further value of the underlying resource is demonstrated by correcting pathway gaps in available genome-scale metabolic models of gut microorganisms. Together, the media resource and the extracted knowledge on growth abilities widen experimental and computational access to the gut microbiota.

The Continuum of Aging and Age-Related Diseases: Common Mechanisms but Different Rates

Geroscience, the new interdisciplinary field that aims to understand the relationship between aging and chronic age-related diseases (ARDs) and geriatric syndromes (GSs), is based on epidemiological evidence and experimental data that aging is the major risk factor for such pathologies and assumes that aging and ARDs/GSs share a common set of basic biological mechanisms. A consequence is that the primary target of medicine is to combat aging instead of any single ARD/GSs one by one, as favored by the fragmentation into hundreds of specialties and sub-specialties. If the same molecular and cellular mechanisms underpin both aging and ARDs/GSs, a major question emerges: which is the difference, if any, between aging and ARDs/GSs? The hypothesis that ARDs and GSs such as frailty can be conceptualized as accelerated aging will be discussed by analyzing in particular frailty, sarcopenia, chronic obstructive pulmonary disease, cancer, neurodegenerative diseases such as Alzheimer and Parkinson as well as Down syndrome as an example of progeroid syndrome. According to this integrated view, aging and ARDs/GSs become part of a continuum where precise boundaries do not exist and the two extremes are represented by centenarians, who largely avoided or postponed most ARDs/GSs and are characterized by decelerated aging, and patients who suffered one or more severe ARDs in their 60s, 70s, and 80s and show signs of accelerated aging, respectively. In between these two extremes, there is a continuum of intermediate trajectories representing a sort of gray area. Thus, clinically different, classical ARDs/GSs are, indeed, the result of peculiar combinations of alterations regarding the same, limited set of basic mechanisms shared with the aging process. Whether an individual will follow a trajectory of accelerated or decelerated aging will depend on his/her genetic background interacting lifelong with environmental and lifestyle factors. If ARDs and GSs are manifestations of accelerated aging, it is urgent to identify markers capable of distinguishing between biological and chronological age to identify subjects at higher risk of developing ARDs and GSs. To this aim, we propose the use of DNA methylation, N-glycans profiling, and gut microbiota composition to complement the available disease-specific markers.

Interplay Between Peripheral and Central Inflammation in Autism Spectrum Disorders: Possible Nutritional and Therapeutic Strategies

Pre- and post-natal factors can affect brain development and function, impacting health outcomes with particular relevance to neurodevelopmental diseases, such as autism spectrum disorders (ASDs). Maternal obesity and its associated complications have been related to the increased risk of ASDs in offspring. Indeed, animals exposed to maternal obesity or high fat diets are prone to social communication impairment and repetitive behavior, the hallmarks of autism. During development, fatty acids and sugars, as well as satiety hormones, like insulin and leptin, and inflammatory factors related to obesity-induced low grade inflammation, could play a role in the impairment of neuroendocrine system and brain neuronal circuits regulating behavior in offspring. On the other side, post-natal factors, such as mode of delivery, stress, diet, or antibiotic treatment are associated to a modification of gut microbiota composition, perturbing microbiota-gut-brain axis. Indeed, the interplay between the gastrointestinal tract and the central nervous system not only occurs through neural, hormonal, and immune pathways, but also through microbe-derived metabolic products. The modification of unhealthy perinatal and postnatal environment, manipulation of gut microbiota, nutritional, and dietary interventions could represent possible strategies in preventing or limiting ASDs, through targeting inflammatory process and gut microbiota.

Of Microbes and Minds: A Narrative Review on the Second Brain Aging

In recent years, an extensive body of literature focused on the gut-brain axis and the possible role played by the gut microbiota in modulating brain morphology and function from birth to old age. Gut microbiota has been proposed as a relevant player during the early phases of neurodevelopment, with possible long-standing effects in later life. The reduction in gut microbiota diversity has also become one of the hallmarks of aging, and disturbances in its composition are associated with several (age-related) neurological conditions, including depression, Alzheimer's disease, and Parkinson's disease. Several pathways have been evoked for gut microbiota-brain communication, including neural connections (vagus nerve), circulating mediators derived by host-bacteria cometabolism, as well as the influence exerted by gut microbiota on host gut function, metabolism, and immune system. Although the most provoking data emerged from animal studies and despite the huge debate around the possible epiphenomenal nature of those findings, the gut microbiota-brain axis still remains a fascinating target to be exploited to attenuate some of the most burdensome consequences of aging.

A gut feeling: Microbiome-brain-immune interactions modulate social and affective behaviors

The expression of a wide range of social and affective behaviors, including aggression and investigation, as well as anxiety- and depressive-like behaviors, involves interactions among many different physiological systems, including the neuroendocrine and immune systems. Recent work suggests that the gut microbiome may also play a critical role in modulating behavior and likely functions as an important integrator across physiological systems. Microbes within the gut may communicate with the brain via both neural and humoral pathways, providing numerous avenues of research in the area of the gut-brain axis. We are now just beginning to understand the intricate relationships among the brain, microbiome, and immune system and how they work in concert to influence behavior. The effects of different forms of experience (e.g., changes in diet, immune challenge, and psychological stress) on the brain, gut microbiome, and the immune system have often been studied independently. Though because these systems do not work in isolation, it is essential to shift our focus to the connections among them as we move forward in our investigations of the gut-brain axis, the shaping of behavioral phenotypes, and the possible clinical implications of these interactions. This review summarizes the recent progress the field has made in understanding the important role the gut microbiome plays in the modulation of social and affective behaviors, as well as some of the intricate mechanisms by which the microbiome may be communicating with the brain and immune system.

Angiotensin receptor blocker irbesartan reduces stress-induced intestinal inflammation via AT1a signaling and ACE2-dependent mechanism in mice

Stress is associated with pathophysiology of both irritable bowel syndrome (IBS) and hypertension. Angiotensin receptor blockers (ARB) have anti-inflammatory properties via inhibition of angiotensin II (Ang II)/Ang II type I receptor axis (AT1). Inhibition of the classical RAS pathway is also involved in upregulation of angiotensin converting enzyme-2 (ACE2), which activates the Ang-(1-7)/Mas pathway to counteract inflammatory signaling and acts as a partner of the amino acid transporter, B⁰AT-1, to absorb tryptophan for regulation of microbiota-gut-brain axis. In this study, we determined the effects of ARB irbesartan on stress-induced intestinal inflammation. C57BL/6J mice were subjected to 2-week intermittent restraint stress. They were orally treated during the stress with either vehicle, 3 or 10 mg/kg/day irbesartan. Restraint stress resulted in colon inflammation with higher histological damage scores, increased expression of Nox4, TLR-4 and IL1-β, accumulation of reactive oxygen species (ROS), and activation of the ACE-angiotensin II-AT1 receptor axis. Stress also downregulated intestinal amino acid transporter, ACE2/B⁰AT-1, and activity of intestinal mammalian target of rapamycin (mTOR) and p70 S6 kinase (p70S6K), resulting in decrease in α-defensins, changes in intestinal microbial contents, and perturbation of tryptophan metabolism with activation of the kynurenine pathway. Administration of irbesartan inhibited activation of stress-induced AT1 pathway to reduce intestinal ROS accumulation and inflammation, restored expression of ACE2/B⁰AT-1, activity of mTOR and p70S6K, dysbiosis and tryptophan metabolism. Our results suggest that AT1 is a potentially suitable therapeutic target in stress-induced intestinal inflammation, and that irbesartan could be beneficially suitable for the treatment of stressed patients with IBS.

Dysbiosis of gut microbiota by chronic coexposure to titanium dioxide nanoparticles and bisphenol A: Implications for host health in zebrafish

Gut microbiota is of critical relevance to host health. However, toxicological understanding of environmental pollutants on gut microbiota is limited, not to mention their combined effects. In the present study, adult zebrafish (Danio rerio) were exposed to titanium dioxide nanoparticles (nano-TiO₂; 100 μg/L), bisphenol A (BPA; 0, 2, and 20 μg/L) or their binary mixtures for three months. Sequencing of 16S rRNA amplicons found that nano-TiO₂ and BPA coexposure shifted the intestinal microbial community, interacting in an antagonistic manner when the BPA concentration was low but in a synergistic manner at a higher BPA concentration. Sex- and concentration-dependent responses to the coexposure regime were also observed for zebrafish growth and intestinal health (e.g. neurotransmission, epithelial barrier permeability, inflammation, and oxidative stress). Correlation analysis showed that oxidative stress after nano-TiO₂ and BPA coexposure was tightly associated with the imbalanced ratio of pathogenic Lawsonia and normal metabolic Hyphomicrobium, where higher abundance of Lawsonia but lower abundance of Hyphomicrobium were induced concurrently. A positive relationship was observed between zebrafish body weight and the abundance of Bacteroides in the gut, which was also closely associated with the genera of Anaerococcus, Finegoldia, and Peptoniphilus. This study revealed, for the first time, the combined effects of nano-TiO₂ and BPA coexposure on the dynamics of the gut microbiome, which proved to have toxicological implications for zebrafish host health.

Gut : liver : brain axis: the microbial challenge in the hepatic encephalopathy

Hepatic encephalopathy (HE) is a debilitating neuropsychiatric condition often associated with acute liver failure or cirrhosis. Advanced liver diseases are characterized by a leaky gut and systemic inflammation. There is strong evidence that the pathogenesis of HE is linked to a dysbiotic gut microbiota and to harmful microbial by-products, such as ammonia, indoles, oxindoles and endotoxins. Increased concentrations of these toxic metabolites together with the inability of the diseased liver to clear such products is thought to play an important patho-ethiological role. Current first line clinical treatments target microbiota dysbiosis by decreasing the counts of pathogenic bacteria, blood endotoxemia and ammonia levels. This review will focus on the role of the gut microbiota and its metabolism in HE and advanced cirrhosis. It will critically assess data from different clinical trials measuring the efficacy of the prebiotic lactulose, the probiotic VSL#3 and the antibiotic rifaximin in treating HE and advanced cirrhosis, through gut microbiota modulation. Additionally data from Randomised Controlled Trials using pre-, pro- and synbiotic will be also considered by reporting meta-analysis studies. The large amount of existing data showed that HE is a clear example of how an altered gut microbiota homeostasis can influence and impact on physiological functions outside the intestine, with implication for host health at the systems level. Nevertheless, a strong effort should be made to increase the information on gut microbiota ecology and its metabolic function in liver diseases and HE.

Dysregulation of Intestinal Health by Environmental Pollutants: Involvement of the Estrogen Receptor and Aryl Hydrocarbon Receptor

To determine how environmental pollutants induce dysbiosis of the gut microbiota, we exposed adult zebrafish to model pollutants with varied modes of action (atrazine, estradiol, polychlorinated biphenyl [PCB]126, and PCB153) for 7 days. Subsequently, metagenomic sequencing of the intestines was performed to compare the gut microbiomes among the groups. We observed clear compound- and sex-specific responses to xenobiotic stress. Principal component analysis revealed involvement of the aryl hydrocarbon receptor (AhR) and, to a lesser extent, the estrogen receptor (ER) in the dysregulation of the intestinal microbiota. The model pollutants differentially impaired intestinal and hepatic physiological activities, as indicated by assessments of gut motility, epithelial permeability, inflammation, and oxidative stress. Correlation analysis showed that abnormal Aeromonas reproduction, especially in the PCB126 groups, was significantly positively associated with oxidative damage. Aeromonas closely interacted with Mannheimia and Blastococcus to regulate intestinal permeability. In summary, we demonstrated that ER and AhR signaling regulated the dynamics of the gut microbiota. Our findings provide new mechanistic insight into the complex interactions between the host metabolism and gut microbiota, which may contribute to the grouped assessment of environmental pollutants in future.

Open-label pilot for treatment targeting gut dysbiosis in myalgic encephalomyelitis/chronic fatigue syndrome: neuropsychological symptoms and sex comparisons

BACKGROUND

Preliminary evidence suggests that the enteric microbiota may play a role in the expression of neurological symptoms in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Overlapping symptoms with the acute presentation of D-lactic acidosis has prompted the use of antibiotic treatment to target the overgrowth of species within the Streptococcus genus found in commensal enteric microbiota as a possible treatment for neurological symptoms in ME/CFS.

METHODS

An open-label, repeated measures design was used to examine treatment efficacy and enable sex comparisons. Participants included 44 adult ME/CFS patients (27 females) from one specialist medical clinic with Streptococcus viable counts above 3.00 × 105 cfu/g (wet weight of faeces) and with a count greater than 5% of the total count of aerobic microorganisms. The 4-week treatment protocol included alternate weeks of Erythromycin (400 mg of erythromycin as ethyl succinate salt) twice daily and probiotic (D-lactate free multistrain probiotic, 5 × 1010 cfu twice daily). 2 × 2 repeated measures ANOVAs were used to assess sex-time interactions and effects across pre- and post-intervention for microbial, lactate and clinical outcomes. Ancillary non-parametric correlations were conducted to examine interactions between change in microbiota and clinical outcomes.

RESULTS

Large treatment effects were observed for the intention-to-treat sample with a reduction in Streptococcus viable count and improvement on several clinical outcomes including total symptoms, some sleep (less awakenings, greater efficiency and quality) and cognitive symptoms (attention, processing speed, cognitive flexibility, story memory and verbal fluency). Mood, fatigue and urine D:L lactate ratio remained similar across time. Ancillary results infer that shifts in microbiota were associated with more of the variance in clinical changes for males compared with females.

CONCLUSIONS

Results support the notion that specific microorganisms interact with some ME/CFS symptoms and offer promise for the therapeutic potential of targeting gut dysbiosis in this population. Streptococcus spp. are not the primary or sole producers of D-lactate. Further investigation of lactate concentrations are needed to elucidate any role of D-lactate in this population. Concurrent microbial shifts that may be associated with clinical improvement (i.e., increased Bacteroides and Bifidobacterium or decreased Clostridium in males) invite enquiry into alternative strategies for individualised treatment. Trial Registration Australian and New Zealand Clinical Trial Registry (ACTRN12614001077651) 9th October 2014. https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=366933&isReview=true.

Impact of the Gut Microbiota on Intestinal Immunity Mediated by Tryptophan Metabolism

The gut microbiota influences the health of the host, especially with regard to gut immune homeostasis and the intestinal immune response. In addition to serving as a nutrient enhancer, L-tryptophan (Trp) plays crucial roles in the balance between intestinal immune tolerance and gut microbiota maintenance. Recent discoveries have underscored that changes in the microbiota modulate the host immune system by modulating Trp metabolism. Moreover, Trp, endogenous Trp metabolites (kynurenines, serotonin, and melatonin), and bacterial Trp metabolites (indole, indolic acid, skatole, and tryptamine) have profound effects on gut microbial composition, microbial metabolism, the host's immune system, the host-microbiome interface, and host immune system-intestinal microbiota interactions. The aryl hydrocarbon receptor (AhR) mediates the regulation of intestinal immunity by Trp metabolites (as ligands of AhR), which is beneficial for immune homeostasis. Among Trp metabolites, AhR ligands consist of endogenous metabolites, including kynurenine, kynurenic acid, xanthurenic acid, and cinnabarinic acid, and bacterial metabolites, including indole, indole propionic acid, indole acetic acid, skatole, and tryptamine. Additional factors, such as aging, stress, probiotics, and diseases (spondyloarthritis, irritable bowel syndrome, inflammatory bowel disease, colorectal cancer), which are associated with variability in Trp metabolism, can influence Trp-microbiome-immune system interactions in the gut and also play roles in regulating gut immunity. This review clarifies how the gut microbiota regulates Trp metabolism and identifies the underlying molecular mechanisms of these interactions. Increased mechanistic insight into how the microbiota modulates the intestinal immune system through Trp metabolism may allow for the identification of innovative microbiota-based diagnostics, as well as appropriate nutritional supplementation of Trp to prevent or alleviate intestinal inflammation. Moreover, this review provides new insight regarding the influence of the gut microbiota on Trp metabolism. Additional comprehensive analyses of targeted Trp metabolites (including endogenous and bacterial metabolites) are essential for experimental preciseness, as the influence of the gut microbiota cannot be neglected, and may explain contradictory results in the literature.

Molecular dynamics simulation studies suggests unconventional roles of non-secretary laccases from enteropathogenic gut bacteria and Cryptococcus neoformans serotype D

Laccase in Cryptococcus neoformans is covalently linked to the carbohydrate moiety of the cell wall, which allows it to get access to the different substrates for catalyzing their oxidation and therefore plays a vital role in the virulence. The laccase gene (3.0 kb) from C. neoformans serotype D was amplified, cloned and sequenced for protein modeling, docking and simulation studies. The three dimensional homology models of laccase protein from C. neoformans and other pathogenic gut bacteria were docked with selected biomolecules like prostaglandins (PG), membrane phospholipids, neurotransmitters (serotonin) using GOLD software. The GOLDscore values of laccase from C. neoformans docked with prostaglandinH₂ (59.76), prostaglandinG₂ (59.45), prostaglandinE₂ (60.99), phosphatidylinositol (54.95), phosphatidylcholine (46.26), phosphatidylserine (55.26), arachidonic acid (53.08) and serotonin (46.22) were similar to the laccase from enteropathogenic bacteria but showed a better binding affinity as compared to that of the non-pathogenic bacteria (e.g. Bacillus safensis, Bacillus pumilus and Bacillus subtilis). The RMSD of MD simulation study done for 25 ns using laccase protein from C. neoformans complexed with phosphatidylcholine was found to be highly stable, followed by the laccase-PGE₂ and laccase-serotonin complexes. Furthermore, the binding free energy results were found to support the docking and MD simulation results. The present study implies that few candidate ligands can be intermediate substrate in the catalysis of microbial laccases, which can further play some crucial role in the cell signaling and pathogenesis of enteropathogenic gut micro flora and C. neoformans.

Harnessing Gut Microbes for Mental Health: Getting From Here to There

There has been an explosion of interest in the study of microorganisms inhabiting the gastrointestinal tract (gut microbiota) and their impact on host health and physiology. Accumulating data suggest that altered communication between gut microbiota and host systems could participate in disorders such as obesity, diabetes mellitus, and autoimmune disorders as well as neuropsychiatric disorders, including autism, anxiety, and major depressive disorders. The conceptual development of the microbiome-gut-brain axis has facilitated understanding of the complex and bidirectional networks between gastrointestinal microbiota and their host, highlighting potential mechanisms through which this environment influences central nervous system physiology. Communication pathways between gut microbiota and the central nervous system could include autonomic, neuroendocrine, enteric, and immune systems, with pathology resulting in disruption to neurotransmitter balance, increases in chronic inflammation, or exacerbated hypothalamic-pituitary-adrenal axis activity. However, uncertainty remains regarding the generalizability of controlled animal studies to the more multifaceted pattern of human pathophysiology, especially with regard to the therapeutic potential for neuropsychiatric health. This narrative review summarizes current understanding of gut microbial influence over physiological function, with an emphasis on neurobehavioral and neurological impairment based on growing understanding of the gut-brain axis. Experimental and clinical data regarding means of therapeutic manipulation of gut microbiota as a novel treatment option for mental health are described, and important knowledge gaps are identified and discussed.

Steroids, stress and the gut microbiome-brain axis

It is becoming well established that the gut microbiome has a profound impact on human health and disease. In this review, we explore how steroids can influence the gut microbiota and, in turn, how the gut microbiota can influence hormone levels. Within the context of the gut microbiome-brain axis, we discuss how perturbations in the gut microbiota can alter the stress axis and behaviour. In addition, human studies on the possible role of gut microbiota in depression and anxiety are examined. Finally, we present some of the challenges and important questions that need to be addressed by future research in this exciting new area at the intersection of steroids, stress, gut-brain axis and human health.

Alzheimer's disease hypothesis and related therapies

Alzheimer's disease (AD) is a progressive neurodegenerative disorder and the most common cause for dementia. There are many hypotheses about AD, including abnormal deposit of amyloid β (Aβ) protein in the extracellular spaces of neurons, formation of twisted fibers of tau proteins inside neurons, cholinergic neuron damage, inflammation, oxidative stress, etc., and many anti-AD drugs based on these hypotheses have been developed. In this review, we will discuss the existing and emerging hypothesis and related therapies.

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

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

Effects of anti-inflammatory drugs on the expression of tryptophan-metabolism genes by human macrophages

Several lines of evidence link macrophage activation and inflammation with (monoaminergic) nervous systems in the etiology of depression. IFN treatment is associated with depressive symptoms, whereas anti‐TNFα therapies elicit positive mood. This study describes the actions of 2 monoaminergic antidepressants (escitalopram, nortriptyline) and 3 anti‐inflammatory drugs (indomethacin, prednisolone, and anti‐TNFα antibody) on the response of human monocyte‐derived macrophages (MDMs) from 6 individuals to LPS or IFN‐α. Expression profiling revealed robust changes in the MDM transcriptome (3294 genes at P < 0.001) following LPS challenge, whereas a more limited subset of genes (499) responded to IFNα. Contrary to published reports, administered at nontoxic doses, neither monoaminergic antidepressant significantly modulated the transcriptional response to either inflammatory challenge. Each anti‐inflammatory drug had a distinct impact on the expression of inflammatory cytokines and on the profile of inducible gene expression—notably on the regulation of enzymes involved in metabolism of tryptophan. Inter alia, the effect of anti‐TNFα antibody confirmed a predicted autocrine stimulatory loop in human macrophages. The transcriptional changes were predictive of tryptophan availability and kynurenine synthesis, as analyzed by targeted metabolomic studies on cellular supernatants. We suggest that inflammatory processes in the brain or periphery could impact on depression by altering the availability of tryptophan for serotonin synthesis and/or by increasing production of neurotoxic kynurenine.

Potential Impact of Metabolic and Gut Microbial Response to Pregnancy and Lactation in Lean and Diet-Induced Obese Rats on Offspring Obesity Risk

SCOPE

Maternal obesity programs metabolic dysfunction in offspring, increasing their susceptibility to obesity and metabolic diseases in later life. Moreover, pregnancy and lactation are associated with many metabolic adaptations, yet it is unclear how diet-induced maternal obesity may interrupt these processes.

METHODS AND RESULTS

¹ H NMR serum metabolomics analysis was performed on samples collected pre-pregnancy and in pregnant and lactating lean and high fat/sucrose (HFS) diet-induced obese Sprague-Dawley rats to identify maternal metabolic pathways associated with developmental programming of offspring obesity. Gut microbial composition was assessed using qPCR. Offspring of HFS dams had nearly 40% higher adiposity at weaning compared to offspring of lean dams. While pregnancy and lactation were associated with distinct maternal metabolic changes common to both lean and obese dams, we identified several metabolic differences, potentially implicating dysregulated one-carbon and mammary gland metabolism in the metabolic programming of obesity. Gut microbial composition was significantly altered with obesity, and both gestation and lactation were accompanied by changes in gut microbiota.

CONCLUSION

Diet-induced maternal obesity and consumption of an obesogenic maternal diet results in differential metabolic and gut microbial adaptations to pregnancy and lactation; these maladaptations may be directly involved in maternal programming of offspring susceptibility to obesity.

Gut microbiota in cardiovascular disease and heart failure

Accumulating evidence supports a relationship between the complexity and diversity of the gut microbiota and host diseases. In addition to alterations in the gut microbial composition, the metabolic potential of gut microbiota has been identified as a contributing factor in the development of diseases. Recent technological developments of molecular and biochemical analyses enable us to detect and characterize the gut microbiota via assessment and classification of its genomes and corresponding metabolites. These advances have provided emerging data supporting the role of gut microbiota in various physiological activities including host metabolism, neurological development, energy homeostasis, and immune regulation. Although few human studies have looked into the causative associations and underlying pathophysiology of the gut microbiota and host disease, a growing body of preclinical and clinical evidence supports the theory that the gut microbiota and its metabolites have the potential to be a novel therapeutic and preventative target for cardiovascular and metabolic diseases. In this review, we highlight the interplay between the gut microbiota and its metabolites, and the development and progression of hypertension, heart failure, and chronic kidney disease.

The microbiota-gut-brain axis as a key regulator of neural function and the stress response: Implications for human and animal health

The brain-gut-microbiota axis comprises an extensive communication network between the brain, the gut, and the microbiota residing there. Development of a diverse gut microbiota is vital for multiple features of behavior and physiology, as well as many fundamental aspects of brain structure and function. Appropriate early-life assembly of the gut microbiota is also believed to play a role in subsequent emotional and cognitive development. If the composition, diversity, or assembly of the gut microbiota is impaired, this impairment can have a negative impact on host health and lead to disorders such as obesity, diabetes, inflammatory diseases, and even potentially neuropsychiatric illnesses, including anxiety and depression. Therefore, much research effort in recent years has focused on understanding the potential of targeting the intestinal microbiota to prevent and treat such disorders. This review aims to explore the influence of the gut microbiota on host neural function and behavior, particularly those of relevance to stress-related disorders. The involvement of microbiota in diverse neural functions such as myelination, microglia function, neuronal morphology, and blood-brain barrier integrity across the life span, from early life to adolescence to old age, will also be discussed. Nurturing an optimal gut microbiome may also prove beneficial in animal science as a means to manage stressful situations and to increase productivity of farm animals. The implications of these observations are manifold, and researchers are hopeful that this promising body of preclinical work can be successfully translated to the clinic and beyond.

Kynurenines: Tryptophan's metabolites in exercise, inflammation, and mental health

Kynurenine metabolites are generated by tryptophan catabolism and regulate biological processes that include host-microbiome signaling, immune cell response, and neuronal excitability. Enzymes of the kynurenine pathway are expressed in different tissues and cell types throughout the body and are regulated by cues, including nutritional and inflammatory signals. As a consequence of this systemic metabolic integration, peripheral inflammation can contribute to accumulation of kynurenine in the brain, which has been associated with depression and schizophrenia. Conversely, kynurenine accumulation can be suppressed by activating kynurenine clearance in exercised skeletal muscle. The effect of exercise training on depression through modulation of the kynurenine pathway highlights an important mechanism of interorgan cross-talk mediated by these metabolites. Here, we discuss peripheral mechanisms of tryptophan-kynurenine metabolism and their effects on inflammatory, metabolic, oncologic, and psychiatric disorders.

An introduction to the microbiome and MS

The human microbiota is composed of diverse forms of microorganisms that live on or in us and plays a crucial role in the health and development. Commensal species that reside in the intestine particularly influence host physiology at local and systemic levels. Multiple sclerosis (MS) is a debilitating autoimmune disorder of the central nervous system for which there is currently no cure. While the cause of MS is unknown, there is a growing body of evidence suggesting that the microbiota can play both pathogenic and protective roles in disease progression. In this review, we provide a brief overview, based on both animal and clinical studies, of the current understanding by which the microbiota may influence MS and discuss opportunities for therapeutic intervention that may alleviate the symptoms associated with this debilitating neuroimmunological disease.

Microbiome and Gut Dysbiosis

The gastrointestinal (GI) tract is the residence of trillions of microorganisms that include bacteria, archaea, fungi and viruses. The collective genomes of whole microbial communities (microbiota) integrate the gut microbiome. Up to 100 genera and 1000 distinct bacterial species were identified in digestive tube niches. Gut microbiomes exert permanent pivotal functions by promoting food digestion, xenobiotic metabolism and regulation of innate and adaptive immunological processes. Proteins, peptides and metabolites released locally and at distant sites trigger many cell signalling and pathways. This intense crosstalk maintains the host-microbial homeostasis. Diet, age, diet, stress and diseases cause increases or decreases in relative abundance and diversity bacterial specie of GI and other body sites. Studies in animal models and humans have shown that a persistent imbalance of gut's microbial community, named dysbiosis, relates to inflammatory bowel diseases (IBD), irritable bowel syndrome (IBS), diabetes, obesity, cancer, cardiovascular and central nervous system disorders. Notably specific bacterial communities are promising clinical target to treat inflammatory and infectious diseases. In this context, intestinal microbiota transplantation (IMT) is one optional treatment for IBD, in particular to patients with recurrent Clostridium difficile-induced pseudo-membrane colitis. Here we discuss on recent discoveries linking whole gut microbiome dysbiosis to metabolic and inflammatory diseases and potential prophylactic and therapeutic applications of faecal and phage therapy, probiotic and prebiotic diets.

Polyphenols-gut microbiota interplay and brain neuromodulation

Increasing evidence suggests that food ingested polyphenols can have beneficial effects in neuronal protection acting against oxidative stress and inflammatory injury. Moreover, polyphenols have been reported to promote cognitive functions. Biotransformation of polyphenols is needed to obtain metabolites active in brain and it occurs through their processing by gut microbiota. Polyphenols metabolites could directly act as neurotransmitters crossing the blood-brain barrier or indirectly by modulating the cerebrovascular system. The microbiota-gut-brain axis is considered a neuroendocrine system that acts bidirectionally and plays an important role in stress responses. The metabolites produced by microbiota metabolism can modulate gut bacterial composition and brain biochemistry acting as neurotransmitters in the central nervous system. Gut microbiota composition can be influenced by dietary ingestion of natural bioactive molecules such as probiotics, prebiotics and polyphenol. Microbiota composition can be altered by dietary changes and gastrointestinal dysfunctions are observed in neurodegenerative diseases. In addition, several pieces of evidence support the idea that alterations in gut microbiota and enteric neuroimmune system could contribute to onset and progression of these age-related disorders. The impact of polyphenols on microbiota composition strengthens the idea that maintaining a healthy microbiome by modulating diet is essential for having a healthy brain across the lifespan. Moreover, it is emerging that they could be used as novel therapeutics to prevent brain from neurodegeneration.

Loss of Microglia and Impaired Brain-Neurotrophic Factor Signaling Pathway in a Comorbid Model of Chronic Pain and Depression

Major depressive disorder (MDD) and chronic pain are two complex disorders that often coexist. The underlying basis for this comorbidity is unknown. In the current investigation, microglia and the brain-derived neurotrophic factor (BDNF)-cAMP response element-binding protein (CREB) pathway were investigated. A comorbidity model, with characteristics of both MDD and chronic pain, was developed by the administration of dextran sodium sulfate (DSS) and the induction of chronic unpredictable psychological stress (CUS). Mechanical threshold sensory testing and the visceromotor response (VMR) were employed to measure mechanical allodynia and visceral hypersensitivity, respectively. RT-qPCR and western blotting were used to assess mRNA and protein levels of ionized calcium-binding adaptor molecule 1 (Iba-1), nuclear factor-kappa B (NF-κB), nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha (IκBa), BDNF, and CREB. In comorbid animals, mechanical allodynia and visceral hypersensitivities were significant with increased mRNA and protein levels for NF-κB-p65 and IκBa. Furthermore, the comorbid animals had deceased mRNA and protein levels for Iba-1, BDNF, and CREB as well as a reduced number and density of microglia in the medial prefrontal cortex (mPFC). These results together suggest that DSS and CUS can induce the comorbidities of chronic pain and depression-like behavior. The pathology of this comorbidity involves loss of microglia within the mPFC with subsequent activation of NF-κB-p65 and down-regulation of BDNF/p-CREB signaling.

The Microbiome-Gut-Behavior Axis: Crosstalk Between the Gut Microbiome and Oligodendrocytes Modulates Behavioral Responses

Environmental and dietary stimuli have always been implicated in brain development and behavioral responses. The gut, being the major portal of communication with the external environment, has recently been brought to the forefront of this interaction with the establishment of a gut-brain axis in health and disease. Moreover, recent breakthroughs in germ-free and antibiotic-treated mice have demonstrated the significant impact of the microbiome in modulating behavioral responses in mice and have established a more specific microbiome-gut-behavior axis. One of the mechanisms by which this axis affects social behavior is by regulating myelination at the prefrontal cortex, an important site for complex cognitive behavior planning and decision-making. The prefrontal cortex exhibits late myelination of its axonal projections that could extend into the third decade of life in humans, which make it susceptible to external influences, such as microbial metabolites. Changes in the gut microbiome were shown to alter the composition of the microbial metabolome affecting highly permeable bioactive compounds, such as p-cresol, which could impair oligodendrocyte differentiation. Dysregulated myelination in the prefrontal cortex is then able to affect behavioral responses in mice, shifting them towards social isolation. The reduced social interactions could then limit microbial exchange, which could otherwise pose a threat to the survival of the existing microbial community in the host and, thus, provide an evolutionary advantage to the specific microbial community. In this review, we will analyze the microbiome-gut-behavior axis, describe the interactions between the gut microbiome and oligodendrocytes and highlight their role in the modulation of social behavior.

Gut microbiota changes in the extreme decades of human life: a focus on centenarians

The gut microbiota (GM) is a complex, evolutionarily molded ecological system, which contributes to a variety of physiological functions. The GM is highly dynamic, being sensitive to environmental stimuli, and its composition changes over the host's entire lifespan. However, the basic question of how much these changes may be ascribed to variables such as population, diet, genetics and gender, and/or to the aging process per se is still largely unanswered. We argue that comparison among studies on centenarians-the best model of healthy aging and longevity-recruited from different geographical areas/populations (different genetics and dietary habits) can help to disentangle the contribution of aging and non-aging-related variables to GM remodeling with age. The current review focuses on the role of population, gender and host genetics as possible drivers of GM modification along the human aging process. The feedback impact of age-associated GM variation on the GM-brain axis and GM metabolomics is also discussed. We likewise address the role of GM in neurodegenerative diseases such as Parkinson's and Alzheimer's, and its possible therapeutic use, taking advantage of the fact that centenarians are characterized by an extreme (healthy) phenotype versus patients suffering from age-related pathologies. Finally, it is argued that longitudinal studies combining metagenomics sequencing and in-depth phylogenetic analysis with a comprehensive phenotypic characterization of centenarians and patients using up-to-date omics (metabolomics, transcriptomics and meta-transcriptomics) are urgently needed.

Antibiotic-induced microbiota perturbation causes gut endocannabinoidome changes, hippocampal neuroglial reorganization and depression in mice

The microbiota-gut-brain axis (MGBA) regulates the reciprocal interaction between chronic inflammatory bowel and psychiatric disorders. This interaction involves multiple pathways that are highly debated. We examined the behavioural, biochemical and electrophysiological alterations, as well as gut microbiota composition in a model of antibiotic-induced experimental dysbiosis. Inflammation of the small intestine was also assessed. Mice were exposed to a mixture of antimicrobials for 2weeks. Afterwards, they received Lactobacillus casei DG (LCDG) or a vehicle for up to 7days via oral gavage. Perturbation of microbiota was accompanied by a general inflammatory state and alteration of some endocannabinoidome members in the gut. Behavioural changes, including increased immobility in the tail suspension test and reduced social recognition were observed, and were associated with altered BDNF/TrkB signalling, TRPV1 phosphorylation and neuronal firing in the hippocampus. Moreover, morphological rearrangements of non-neuronal cells in brain areas controlling emotional behaviour were detected. Subsequent probiotic administration, compared with vehicle, counteracted most of these gut inflammatory, behavioural, biochemical and functional alterations. Interestingly, levels of Lachnospiraceae were found to significantly correlate with the behavioural changes observed in dysbiotic mice. Our findings clarify some of the biomolecular and functional modifications leading to the development of affective disorders associated with gut microbiota alterations.

Gut Microbiota Are Disease-Modifying Factors After Traumatic Spinal Cord Injury

Spinal cord injury (SCI) disrupts the autonomic nervous system (ANS), impairing its ability to coordinate organ function throughout the body. Emerging data indicate that the systemic pathology that manifests from ANS dysfunction exacerbates intraspinal pathology and neurological impairment. Precisely how this happens is unknown, although new data, in both humans and in rodent models, implicate changes in the composition of bacteria in the gut (i.e., the gut microbiota) as disease-modifying factors that are capable of affecting systemic physiology and pathophysiology. Recent data from rodents indicate that SCI causes gut dysbiosis, which exacerbates intraspinal inflammation and lesion pathology leading to impaired recovery of motor function. Postinjury delivery of probiotics containing various types of "good" bacteria can partially overcome the pathophysiologal effects of gut dysbiosis; immune function, locomotor recovery, and spinal cord integrity are partially restored by a sustained regimen of oral probiotics. More research is needed to determine whether gut dysbiosis varies across a range of clinically relevant variables, including sex, injury level, and injury severity, and whether changes in the gut microbiota can predict the onset or severity of common postinjury comorbidities, including infection, anemia, metabolic syndrome, and, perhaps, secondary neurological deterioration. Those microbial populations that dominate the gut could become "druggable" targets that could be manipulated via dietary interventions. For example, personalized nutraceuticals (e.g., pre- or probiotics) could be developed to treat the above comorbidities and improve health and quality of life after SCI.

Bifidobacterium and Lactobacillus Counts in the Gut Microbiota of Patients With Bipolar Disorder and Healthy Controls

Background: Although the pathophysiology of bipolar disorder remains elusive, growing evidence suggests the beneficial effects of Bifidobacterium and Lactobacillus in the gut microbiota on stress response and depressive symptoms. In the present study, we examined Bifidobacterium and Lactobacillus counts for association with bipolar disorder and serum cortisol levels. Methods: Bacterial counts in fecal samples were examined in 39 patients with bipolar disorder according to the Diagnostic and Statistical Manual of Mental Disorders, 4th edn. and 58 healthy controls using bacterial rRNA-targeted reverse transcription-quantitative polymerase chain reaction. Results: No significant difference was found in either bacterial counts between the two groups. However, we found a significantly negative correlation between Lactobacillus counts and sleep (ρ = -0.45, P = 0.01). Furthermore, a significant negative correlation was found between Bifidobacterium counts and cortisol levels (ρ = -0.39, P = 0.02) in the patients, although such a correlation was not found for Lactobacillus counts. Conclusions: Our results suggest that Bifidobacterium or Lactobacillus counts may not play a major role in the pathophysiology of bipolar disorder in our sample. However, the observed negative correlation between Lactobacillus counts and sleep and that between Bifidobacterium counts and serum cortisol levels point to the possible roles of these bacteria in sleep and stress response of the patients.

The sinonasal microbiota, neural signaling, and depression in chronic rhinosinusitis

BACKGROUND

The complex relationships between the human microbiota, the immune system, and the brain play important roles in both health and disease, and have been of increasing interest in the study of chronic inflammatory mucosal conditions. We hypothesized that the sinonasal microbiota may act as a modifier of interkingdom neural signaling and, subsequently, mental health, in the upper respiratory inflammatory condition chronic rhinosinusitis (CRS). In this study we investigated associations between the sinonasal microbiota; local concentrations of the neurotransmitters serotonin, dopamine, and γ-aminobutyric acid (GABA); and depression severity in a cohort of 14 CRS patients and 12 healthy controls.

METHODS

Subject demographics, clinical severity scores, depression index scores, and sinonasal swab and mucus samples were collected at the time of surgery. Bacterial communities were characterized from swabs by 16S rRNA gene-targeted sequencing and quantified by quantitative polymerase chain reaction. Mucus concentrations of the neurotransmitters serotonin, dopamine, and GABA were quantified by enzyme-linked immunosorbent assay.

RESULTS

Several commonly "health-associated" sinonasal bacterial taxa were positively associated with higher neurotransmitter concentrations and negatively associated with depression severity. In contrast, several taxa commonly associated with an imbalanced sinonasal microbiota negatively associated with neurotransmitters and positively with depression severity. Few significant differences were identified when comparing between control and CRS subject groups, including neurotransmitter concentrations, depression scores, or sinonasal microbiota composition or abundance.

CONCLUSION

The findings obtained lend support to the potential for downstream effects of the sinonasal microbiota on neural signaling and, subsequently, brain function and behavior.

Food-grade cationic antimicrobial ε-polylysine transiently alters the gut microbial community and predicted metagenome function in CD-1 mice

Diet is an important factor influencing the composition and function of the gut microbiome, but the effect of antimicrobial agents present within foods is currently not understood. In this study, we investigated the effect of the food-grade cationic antimicrobial ε-polylysine on the gut microbiome structure and predicted metagenomic function in a mouse model. The relative abundances of predominant phyla and genera, as well as the overall community structure, were perturbed in response to the incorporation of dietary ε-polylysine. Unexpectedly, this modification to the gut microbiome was experienced transiently and resolved to the initial basal composition at the final sampling point. In addition, a differential non-random assembly was observed in the microbiomes characterized from male and female co-housed animals, although their perturbation trajectories in response to diet remain consistent. In conclusion, antimicrobial ε-polylysine incorporated into food systems transiently alters gut microbial communities in mice, as well as their predicted function. This indicates a dynamic but resilient microbiome that adapts to microbial-active dietary components.

Possible role of the gut microbiota-brain axis in the antidepressant effects of (R)-ketamine in a social defeat stress model

Accumulating evidence suggests that the gut microbiota-brain axis plays a role in the pathogenesis of depression, thereby contributing to the antidepressant actions of certain compounds. (R)-ketamine has a greater potency and longer-lasting antidepressant effects than (S)-ketamine. Here, we investigated whether the gut microbiota plays a role in the antidepressant effects of these two ketamine enantiomers. The role of the gut microbiota in the antidepressant effects of ketamine enantiomers in a chronic social defeat stress (CSDS) model of depression was examined using 16S ribosomal RNA gene sequencing of fecal samples. At the phylum level, CSDS-susceptible mice showed alterations in the levels of Tenericutes and Actinobacteria; however, neither ketamine enantiomers influenced these alterations. At the class level, both ketamine enantiomers significantly attenuated the increase in the levels of Deltaproteobacteria in the susceptible mice after CSDS. Furthermore, (R)-ketamine, but not (S)-ketamine, significantly attenuated the reduction in the levels of Mollicutes in the susceptible mice. At the genus level, both ketamine enantiomers significantly attenuated the decrease in the levels of Butyricimonas in the susceptible mice. Notably, (R)-ketamine was more potent than (S)-ketamine at reducing the levels of Butyricimonas in the susceptible mice. In conclusion, this study suggests that the antidepressant effects of two enantiomers of ketamine in CSDS model may be partly mediated by the restoration of the gut microbiota. Furthermore, the specific effect of (R)-ketamine on the levels of Mollicutes and Butyricimonas may explain its robust antidepressant action.

The first model of keeping energy balance and optimal psycho affective development: Breastfed infants

BACKGROUND

Breastfed infants follow a peculiar growth fashion characterized by a rapid weight gain in the first weeks of life, then followed by a fast decrease in growth rates, a capacity to self-regulate the sense of hungry and satiety, and a minor propensity towards overweight and obesity later on, in parallel with a better neurodevelopmental performance.

METHODS

We searched studies investigating the relationship between the feeding mode in infancy and the energy balance, so the possible associations with total energy expenditure and intake regulation. We focused the research on the interaction with the neuropsychological development and the possible role of microbiome in determinating the normal generation and regular functioning of the brain through the so named "gut-brain axis".

RESULTS

Total energy expenditure (TEE) is different for breast-fed and formula-fed infants, in particular the feeding mode seems to affect the sleep organisation. Long-term breastfeeding, is one of the most studied factors of neurodevelopment, several studies reporting beneficial effects on child neuropsychological development. Probably this effect is modulated by genetic variations in fatty acid metabolism. Increasing data also showed that the intestinal microbiome exerts several functions which are able to influence neurodevelopment.

LIMITATIONS

There is considerable controversy over whether nutrition in early life has a long-term influence on neurodevelopment. Other studies are needed to confirm the association between breastfeeding and brain development.

CONCLUSIONS

The key points of energy disposal, the role and effects of the instestinal flora represent promising fields of investigation possibly leading to indications for the wide area of preventive medicine.

Microbiota and Aging. A Review and Commentary

Although there is a consensus that the dominant species that make up the adult microbiota remains unchanged in elderly people, it has been reported that there are significant alterations in the proportion and composition of the different taxa, leading to reduced microbiota diversity, as well as an increase of enteropathogens that may lead to chronic inflammation. The ageing of mucosal immune and motor systems also contributes to these changes. As the individual ages, there is a loss in the number of Peyer's patches, an altered local capacity of T and B cell functions as well as chronic macrophage activation. Also, environment, diet, place of residence and biogeography are regulatory factors of the microbiota. Communication in the gut-brain-axis is regulated by many intermediaries including diverse metabolites of the microbiota. Microbial changes have been observed in several geriatric diseases, like Parkinson's and Alzheimer's. In addition, evidence has shown that individuals with high frailty scores had a significant reduction on lactobacilli species when compared to non-frail individuals. Oral microbiota may be also especially important because of the opportunities for access to the brain through the olfactory nerve at the roof of the nose or through the abundant innervations of the oral cavity by the trigeminal and other cranial nerves. Also, there are an increasing number of reports that have suggested potential mechanisms by which the microbiota promote human health span and aging. The study of the microbiota represents an important advance in the understanding of the aging process.