The human gut microbiota is neither an organ nor a commensal

Gut dysbiosis impacts the immune system and promotes prostate cancer

The gut microbiota is a system of microorganisms in the human gastrointestinal (GI) system, consisting of trillions of microorganisms residing in epithelial surfaces of the body. Gut microbiota are exposed to various external and internal factors and form a unique gut-associated immunity maintained through a balancing act among diverse groups of microorganisms. The role of microbiota in dysbiosis of the gut in aiding prostate cancer development has created an urgency for extending research toward comprehension and preventative measures. The gut microbiota varies among persons based on diet, race, genetic background, and geographic location. Bacteriome, mainly, has been linked to GI complications, metabolism, weight gain, and high blood sugar. Studies have shown that manipulating the microbiome (bacteriome, virome, and mycobiome) through the dietary intake of phytochemicals positively influences physical and emotional health, preventing and delaying diseases caused by microbiota. In this review, we discuss the wealth of knowledge about the GI tract and factors associated with dysbiosis-mediated compromised gut immunity. This review also focuses on the relationship of dysbiosis to prostate cancer, the impact of microbial metabolites short-chain fatty acids (SCFAs) on host health, and the phytochemicals improving health while inhibiting prostate cancer.

The Role of the Gut and Airway Microbiota in Chronic Rhinosinusitis with Nasal Polyps: A Systematic Review

In recent years, there has been growing interest in understanding the potential role of microbiota dysbiosis or alterations in the composition and function of human microbiota in the development of chronic rhinosinusitis with nasal polyposis (CRSwNP). This systematic review evaluated the literature on CRSwNP and host microbiota for the last ten years, including mainly nasal bacteria, viruses, and fungi, following the PRISMA guidelines and using the major scientific publication databases. Seventy original papers, mainly from Asia and Europe, met the inclusion criteria, providing a comprehensive overview of the microbiota composition in CRSwNP patients and its implications for inflammatory processes in nasal polyps. This review also explores the potential impact of microbiota-modulating therapies for the CRSwNP treatment. Despite variability in study populations and methodologies, findings suggest that fluctuations in specific taxa abundance and reduced bacterial diversity can be accepted as critical factors influencing the onset or severity of CRSwNP. These microbiota alterations appear to be implicated in triggering cell-mediated immune responses, cytokine cascade changes, and defects in the epithelial barrier. Although further human studies are required, microbiota-modulating strategies could become integral to future combined CRSwNP treatments, complementing current therapies that mainly target inflammatory mediators and potentially improving patient outcomes.

A new lexicon in the age of microbiome research

At a rapid pace, biologists are learning the many ways in which resident microbes influence, and sometimes even control, their hosts to shape both health and disease. Understanding the biochemistry behind these interactions promises to reveal completely novel and targeted ways of counteracting disease processes. However, in our protocols and publications, we continue to describe these new results using a language that originated in a completely different context. This language developed when microbial interactions with hosts were perceived to be primarily pathogenic, as threats that had to be vanquished. Biomedicine had one dominating thought: winning this war against microorganisms. Today, we know that beyond their defensive roles, host tissues, especially epithelia, are vital to ensuring association with the normal microbiota, the communities of microbes that persistently live with the host. Thus, we need to adopt a language that better encompasses the newly appreciated importance of host-microbiota associations. We also need a language that frames the onset and progression of pathogenic conditions within the context of the normal microbiota. Such a reimagined lexicon should make it clear, from the very nature of its words, that microorganisms are primarily vital to our health, and only more rarely the cause of disease. This article is part of the theme issue 'Sculpting the microbiome: how host factors determine and respond to microbial colonization'.

Characterisation of Indian gut microbiome for B-vitamin production and its comparison with Chinese cohort

The human gut microbiota can biosynthesize essential micronutrients such as B-vitamins and is also known for its metabolic cooperative behaviour. The present study characterises such B-vitamin biosynthesizers, their biosynthetic pathways, explores their prevalence and abundance, examines how lifestyle or diet affects them in multiple Indian cohorts and compares it with the Chinese cohort. To achieve this, publicly available faecal metagenome data of healthy individuals from multiple Indian (two urban and three tribal populations) and a Chinese cohort were analysed. The distribution of prevalence and abundance of B-vitamin biosynthesizers showed similar profiles to that of the entire gut community of the Indian cohort, and there were 28 B-vitamin biosynthesizers that had modest or higher prevalence and abundance. The omnivorous diet affected only the prevalence of a few B-vitamin biosynthesizers; however, lifestyle and/or location affected both prevalence and abundance. A comparison with the Chinese cohort showed that fourteen B-vitamin biosynthesizers were significantly more prevalent and abundant in Chinese as compared with Indian samples (False Discovery Rate (FDR) <= 0·05). The metabolic potential of the entire gut community for B-vitamin production showed that within India, the tribal cohort has a higher abundance of B-vitamin biosynthesis pathways as compared with two urban cohorts namely, Bhopal and Kasargod, and comparison with the Chinese cohort revealed a higher abundance in the latter group. Potential metabolic cooperative behaviour of the Indian gut microbiome for biosynthesis of the B-vitamins showed multiple pairs of species showed theoretical complementarity for complete biosynthetic pathways genes of thiamine, riboflavin, niacin and pantothenate.

Bones and guts - Why the microbiome matters

The importance of the gut microbiota in human health has become increasingly apparent in recent years, especially when the relationship between microbiota and host is no longer symbiotic. It has long been appreciated that gut dysbiosis can be detrimental to human health and is associated with numerous disease states. Only within the last decade, however, was the gut microbiota implicated in bone biology. Dubbed osteomicrobiology, this emerging field aims to understand the relationship between the gut microbiome and the bone microenvironment in both health and disease. Importantly, the key to one of the major clinical challenges facing both bone and cancer biologists: bone metastasis, may lie in the field of osteomicrobiology; however the link between gut bacteria and bone metastasis is only beginning to be explored. This review will discuss (i) osteomicrobiology as an emerging field, and (ii) the current understanding of osteomicrobiology in the context of cancer in bone.

Microbial Dysbiosis and Male Infertility: Understanding the Impact and Exploring Therapeutic Interventions

The human microbiota in the genital tract is pivotal for maintaining fertility, but its disruption can lead to male infertility. This study examines the relationship between microbial dysbiosis and male infertility, underscoring the promise of precision medicine in this field. Through a comprehensive review, this research indicates microbial signatures associated with male infertility, such as altered bacterial diversity, the dominance of pathogenic species, and imbalances in the genital microbiome. Key mechanisms linking microbial dysbiosis to infertility include inflammation, oxidative stress, and sperm structural deterioration. Emerging strategies like targeted antimicrobial therapies, probiotics, prebiotics, and fecal microbiota transplantation have shown potential in adjusting the genital microbiota to enhance male fertility. Notably, the application of precision medicine, which customizes treatments based on individual microbial profiles and specific causes of infertility, emerges as a promising approach to enhance treatment outcomes. Ultimately, microbial dysbiosis is intricately linked to male infertility, and embracing personalized treatment strategies rooted in precision medicine principles could be the way forward in addressing infertility associated with microbial factors.

Microbiotoxicity: antibiotic usage and its unintended harm to the microbiome

PURPOSE OF REVIEW

Antibiotic use is associated with development of antimicrobial resistance and dysregulation of the microbiome (the overall host microbial community). These changes have in turn been associated with downstream adverse health outcomes. This review analyses recent important publications in a rapidly evolving field, contextualizing the available evidence to assist clinicians weighing the potential risks of antibiotics on a patient's microbiome.

RECENT FINDING

Although the majority of microbiome research is observational, we highlight recent interventional studies probing the associations between antibiotic use, microbiome disruption, and ill-health. These studies include germ-free mouse models, antibiotic challenge in healthy human volunteers, and a phase III study of the world's first approved microbiome-based medicine.

SUMMARY

The growing body of relevant clinical and experimental evidence for antibiotic-mediated microbiome perturbation is concerning, although further causal evidence is required. Within the limits of this evidence, we propose the novel term 'microbiotoxicity' to describe the unintended harms of antibiotics on a patient's microbiome. We suggest a framework for prescribers to weigh microbiotoxic effects against the intended benefits of antibiotic use.

Gut Microbiota Interventions to Retain Residual Kidney Function

Residual kidney function for patients with chronic kidney disease (CKD) is associated with better quality of life and outcome; thus, strategies should be implemented to preserve kidney function. Among the multiple causes that promote kidney damage, gut dysbiosis due to increased uremic toxin production and endotoxemia need attention. Several strategies have been proposed to modulate the gut microbiota in these patients, and diet has gained increasing attention in recent years since it is the primary driver of gut dysbiosis. In addition, medications and faecal transplantation may be valid strategies. Modifying gut microbiota composition may mitigate chronic kidney damage and preserve residual kidney function. Although various studies have shown the influential role of diet in modulating gut microbiota composition, the effects of this modulation on residual kidney function remain limited. This review discusses the role of gut microbiota metabolism on residual kidney function and vice versa and how we could preserve the residual kidney function by modulating the gut microbiota balance.

Epigenetic effects of short-chain fatty acids from the large intestine on host cells

Adult humans harbor at least as many microbial cells as eukaryotic ones. The largest compartment of this diverse microbial population, the gut microbiota, encompasses the collection of bacteria, archaea, viruses, and eukaryotic organisms that populate the gastrointestinal tract, and represents a complex and dynamic ecosystem that has been increasingly implicated in health and disease. The gut microbiota carries ∼100-to-150-times more genes than the human genome and is intimately involved in development, homeostasis, and disease. Of the several microbial metabolites that have been studied, short-chain fatty acids emerge as a group of molecules that shape gene expression in several types of eukaryotic cells by multiple mechanisms, which include DNA methylation changes, histone post-translational modifications, and microRNA-mediated gene silencing. Butyric acid, one of the most extensively studied short-chain fatty acids, reaches higher concentrations in the colonic lumen, where it provides a source of energy for healthy colonocytes, and its concentrations decrease towards the bottom of the colonic crypts, where stem cells reside. The lower butyric acid concentration in the colonic crypts allows undifferentiated cells, such as stem cells, to progress through the cell cycle, pointing towards the importance of the crypts in providing them with a protective niche. In cancerous colonocytes, which metabolize relatively little butyric acid and mostly rely on glycolysis, butyric acid preferentially acts as a histone deacetylase inhibitor, leading to decreased cell proliferation and increased apoptosis. A better understanding of the interface between the gut microbiota metabolites and epigenetic changes in eukaryotic cells promises to unravel in more detail processes that occur physiologically and as part of disease, help develop novel biomarkers, and identify new therapeutic modalities.

Clarifying the effect of gut microbiota on allergic conjunctivitis risk is instrumental for predictive, preventive, and personalized medicine: a Mendelian randomization analysis

Background

Allergic conjunctivitis is an ocular immune disease which affects the conjunctiva, eyelids, and cornea. Growing evidence implicates the gut microbiota in balancing and modulating immunity response, and in the pathogenesis of allergic disease. As a result, gut microbial imbalance could be a useful indicator for allergic conjunctivitis. From the perspective of predictive, preventive, and personalized medicine (PPPM), clarifying the role of gut microbial imbalance in the development of allergic conjunctivitis could provide a window of opportunity for primary prediction, targeted prevention, and personalized treatment of the disease.

Working hypothesis and methodology

In our study, we hypothesized that individuals with microbial dysbiosis may be more susceptible to allergic conjunctivitis due to an increased inflammatory response. To verify the working hypothesis, our analysis selected genetic variants linked with gut microbiota features (N = 18,340) and allergic conjunctivitis (4513 cases, 649,376 controls) from genome-wide association studies. The inverse-variance weighted (IVW) estimate, Mendelian randomization (MR)-Egger, weighted median estimator, maximum likelihood estimator (MLE), and MR robust adjusted profile score (MR.RAPS) were employed to analyze the impact of gut microbiota on the risk of allergic conjunctivitis and identify allergic conjunctivitis-related gut microbes. Ultimately, these findings may enable the identification of individuals at risk of allergic conjunctivitis through screening of gut microbial imbalances, and allow for new targeted prevention and personalized treatment strategies.

Results

Genetic liability to Ruminococcaceae_UCG_002 (OR, 0.83; 95% CI, 0.70-0.99; P = 4.04×10^-2), Holdemanella (OR, 0.78; 95% CI, 0.64-0.96; P = 2.04×10^-2), Catenibacterium (OR, 0.69; 95% CI, 0.56-0.86; P = 1.09×10^-3), Senegalimassilia (OR, 0.71; 95% CI, 0.55-0.93; P = 1.23×10^-2) genus were associated with a low risk of allergic conjunctivitis with IVW. Besides, we found suggestive associations of a genetic-driven increase in the Oscillospira (OR, 1.41; 95% CI, 1.00-2.00; P = 4.63×10^-2) genus with a higher risk of allergic conjunctivitis. Moreover, MLE and MR.RAPS show consistent results with IVW after further validation and strengthened confidence in the true causal associations. No heterogeneity and pleiotropy was detected.

Conclusions

Our study suggests that gut microbiota may play a causal role in the development of allergic conjunctivitis and provides new insights into the microbiota-mediated mechanism of the disease. Gut microbiota may serve as a target for future predictive diagnostics, targeted prevention, and individualized therapy in allergic conjunctivitis, facilitating the transition from reactive medical services to PPPM in the management of the disease.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13167-023-00321-9.

Anthocyanin-rich blue potato meals protect against polychlorinated biphenyl-mediated disruption of short-chain fatty acid production and gut microbiota profiles in a simulated human digestion model

Background

Polychlorinated biphenyls (PCBs) are ubiquitous environmental pollutants associated with a wide variety of adverse human health outcomes. PCB 126 and PCB 153 are among the most prevalent congeners associated with human exposure. Emerging studies have suggested that PCB exposure leads to lower gut microbial diversity although their effects on microbial production of health promoting short-chain fatty acids (SCFAs) has been scarcely studied. Blue potatoes are rich in anthocyanins (ACNs), which is a class of polyphenols that promote the growth of beneficial intestinal bacteria such as Bifidobacterium and Lactobacillus and increase the generation of SCFAs. A batch-culture, pH-controlled, stirred system containing human fecal microbial communities was utilized to assess whether human gut microbiota composition and SCFA production are affected by: (a) PCB 126 and PCB 153 exposure; and (b) ACN-rich digests in the presence and absence of the PCB congeners.

Methods

Anthocyanin-rich blue potato meals (11.03 g) were digested over 12 h with and without PCB 126 (0.5 mM) and PCB 153 (0.5 mM) using an in vitro simulated gut digestion model involving upper gastrointestinal digestion followed by metabolism by human fecal microbiota. Fecal digests were collected for analysis of gut microbial and SCFA profiles.

Results

Polychlorinated biphenyl-exposed fecal samples showed a significant (p < 0.05) decrease in species richness and a significantly (p < 0.05) different microbial community structure. PCB treatment was associated with an increased (p < 0.05) relative abundance of Akkermansia, Eggerthella, and Bifidobacterium and a decreased (p < 0.05) relative abundance of Veillonella, Streptococcus, and Holdemanella. ACN digests counteracted the altered abundances of Akkermansia and Bifidobacterium seen with the PCB treatment. PCB exposure was associated with a significant (p < 0.05) decrease in total SCFA and acetate concentrations. ACN digests were associated with significantly (p < 0.05) higher SCFA and acetate concentrations in the presence and absence of PCBs.

Conclusion

Human fecal matter exposed to PCB 126 and PCB 153 led to decreased abundance and altered gut microbiota profiles as well as lowered SCFA and acetate levels. Importantly, this study showed that prebiotic ACN-rich potatoes counteract PCB-mediated disruptions in human gut microbiota profiles and SCFA production.

Role of the Microbiome in Gut-Heart-Kidney Cross Talk

Homeostasis is a prerequisite for health. When homeostasis becomes disrupted, dysfunction occurs. This is especially the case for the gut microbiota, which under normal conditions lives in symbiosis with the host. As there are as many microbial cells in and on our body as human cells, it is unlikely they would not contribute to health or disease. The gut bacterial metabolism generates numerous beneficial metabolites but also uremic toxins and their precursors, which are transported into the circulation. Barrier function in the intestine, the heart, and the kidneys regulates metabolite transport and concentration and plays a role in inter-organ and inter-organism communication via small molecules. This communication is analyzed from the perspective of the remote sensing and signaling theory, which emphasizes the role of a large network of multispecific, oligospecific, and monospecific transporters and enzymes in regulating small-molecule homeostasis. The theory provides a systems biology framework for understanding organ cross talk and microbe-host communication involving metabolites, signaling molecules, nutrients, antioxidants, and uremic toxins. This remote small-molecule communication is critical for maintenance of homeostasis along the gut-heart-kidney axis and for responding to homeostatic perturbations. Chronic kidney disease is characterized by gut dysbiosis and accumulation of toxic metabolites. This slowly impacts the body, affecting the cardiovascular system and contributing to the progression of kidney dysfunction, which in its turn influences the gut microbiota. Preserving gut homeostasis and barrier functions or restoring gut dysbiosis and dysfunction could be a minimally invasive way to improve patient outcomes and quality of life in many diseases, including cardiovascular and kidney disease.

Feed additives of bacterial origin as an immunoprotective or imunostimulating factor

Since January 2006 when using antibiotics as growth promoters in animal feed have been banned scientists are looking for the best resolution to apply alternative substances. Extensive research into the health-promoting properties of probiotics and prebiotics has led to significant interest in the mechanisms of action of the combined administration of these feed additives as a synbiotic. Subsequent research has led to the development of new products. Among the most important health benefits of additives are, inhibiting the growth of pathogenic bacteria in the GI tract, maintenance of homeostasis, treatment of inflammatory bowel diseases, and increase in immunity. Specific immunomodulatory mechanisms of action are not well understood and the effect is not always positive, though there are no reports of adverse effects of these substances found in the literature. For this reason, research is still being conducted on their proper application. However, due to the difficulties of carrying out research on humans, evidence of the beneficial effect of these additives comes mainly from experiments on animals. The objective of the present work was to assess the effect of probiotics, prebiotics, and synbiotics, as well as new additives including postbiotics, proteobiotics, nutribiotics, and pharmabiotics, on specific immunomodulatory mechanisms of action, increase in immunity, the reduction of a broad spectrum of diseases.

How Do Diet Patterns, Single Foods, Prebiotics and Probiotics Impact Gut Microbiota?

The human gastrointestinal tract hosts a complex and dynamic population of commensal bacterial species, which have coevolved with the host, generating a symbiotic relationship. Some compounds present in foods, such as polyols, prebiotic fibers, or phenolic compounds, are poorly metabolized and absorbed by the host before the transformation guided by the colonic microbiota. By influencing gut microbiota, diet plays a fundamental role in understanding the beneficial effects of the gut microbiota on the host, including its long-term metabolism. The idea that probiotics can act not only by influencing the colonizing microbiota opens the door to a wider range of probiotic possibilities, encouraging innovation in the field. Furthermore, it has been shown both that some probiotics increase phagocytosis or the activity of natural killer cells. Current prebiotics are mainly based on carbohydrates, but other substances, such as polyphenols and polyunsaturated fatty acids, could exert prebiotic effects. A prebiotic substance has been defined as ‘a substrate that is selectively used by host microorganisms that confer a health benefit’, and so can interact with the gut microbiota through competition for nutrients, antagonism, cross-feeding, and support for microbiota stability. Influencing its composition in terms of richness and diversity, food components have a key impact on the intestinal microbiota. Eating habits can strongly influence the composition of the intestinal microbiota. A healthy intestinal microbiota is essential for maintaining general health, and diet is one of the major modulators of this fascinating world of microorganisms. This must give us one more reason to adopt a healthy lifestyle.

An in vitro analysis of how lactose modifies the gut microbiota structure and function of adults in a donor-independent manner

Introduction

Following consumption of milk, lactose, a disaccharide of glucose and galactose, is hydrolyzed and absorbed in the upper gastrointestinal tract. However, hydrolysis and absorption are not always absolute, and some lactose will enter the colon where the gut microbiota is able to hydrolyze lactose and produce metabolic byproducts.

Methods

Here, the impact of lactose on the gut microbiota of healthy adults was examined, using a short-term, in vitro strategy where fecal samples harvested from 18 donors were cultured anaerobically with and without lactose. The data were compiled to identify donor-independent responses to lactose treatment.

Results and discussion

Metagenomic sequencing found that the addition of lactose decreased richness and evenness, while enhancing prevalence of the β-galactosidase gene. Taxonomically, lactose treatment decreased relative abundance of Bacteroidaceae and increased lactic acid bacteria, Lactobacillaceae, Enterococcaceae, and Streptococcaceae, and the probiotic Bifidobacterium. This corresponded with an increased abundance of the lactate utilizers, Veillonellaceae. These structural changes coincided with increased total short-chain fatty acids (SCFAs), specifically acetate, and lactate. These results demonstrated that lactose could mediate the gut microbiota of healthy adults in a donor-independent manner, consistent with other described prebiotics, and provided insight into how dietary milk consumption may promote human health through modifications of the gut microbiome.

Characterization of Gut Microbiota Composition in Type 2 Diabetes Patients: A Population-Based Study

(1) Background: A clinical laboratory index to assess gut dysbiosis is the F/B ratio < 0.8. In fact, an elevated proportion of Firmicutes and a reduced population of Bacteroides in diabetes type 2 (T2D) subjects has been observed. This study aimed to detail the dysbiosis status in the Italian population, focusing on some pathogenic spectra (T2D) or metabolic disorders. (2) Material and methods: A quantity of 334 fecal samples was analyzed in order to perform genetic testing and sequencing. (3) Results: A trend in over imbalance was observed in the percentage of Proteobacteria (median value: 6.75%; interquartile range (IQR): 3.57−17.29%). A statistically significant association (χ2p = 0.033) was observed between type of dysbiosis and T2D, corresponding to an Odds Ratio (OR) of 1.86. It was noted that females with cystitis/candidiasis are significantly prevalent in T2D patients (p < 0.01; OR: 3.59; 95% CI: 1.43−8.99). Although, in non-diabetic males, a sugar craving is significantly associated with the rate of dysbiosis in non-diabetic males (p < 0.05; OR 1.07; 95% CI 1.00−1.16). (4) Conclusion: In T2D patients, the Bacteroidetes/Firmicutes ratio was biased in favor of Proteobacteria, to be expected due to the nutritional habits of the patients. Thus, T2D females had altered gut permeability favoring the development of infections in the vaginal tract.

Colicins of Escherichia coli Lead to Resistance against the Diarrhea-Causing Pathogen Enterotoxigenic E. coli in Pigs

Gut microbes can affect host adaptation to various environment conditions. Escherichia coli is a common gut species, including pathogenic strains and nonpathogenic strains. This study was conducted to investigate the effects of different E. coli strains in the gut on the health of pigs. In this study, the complete genomes of two E. coli strains isolated from pigs were sequenced. The whole genomes of Y18J and the enterotoxigenic E. coli strain W25K were compared to determine their roles in pig adaptation to disease. Y18J was isolated from feces of healthy piglets and showed strong antimicrobial activity against W25K in vitro. Gene knockout experiments and complementation analysis followed by modeling the microbe-microbe interactions demonstrated that the antagonistic mechanism of Y18J against W25K relied on the bacteriocins colicin B and colicin M. Compared to W25K, Y18J is devoid of exotoxin-coding genes and has more secondary-metabolite-biosynthetic gene clusters. W25K carries more genes involved in genome replication, in accordance with a shorter cell cycle observed during a growth experiment. The analysis of gut metagenomes in different pig breeds showed that colicins B and M were enriched in Laiwu pigs, a Chinese local breed, but were scarce in boars and Duroc pigs. IMPORTANCE This study revealed the heterogeneity of E. coli strains from pigs, including two strains studied by both in silico and wet experiments in detail and 14 strains studied by bioinformatics analysis. E. coli Y18J may improve the adaptability of pigs toward disease resistance through the production of colicins B and M. Our findings could shed light on the pathogenic and harmless roles of E. coli in modern animal husbandry, leading to a better understanding of intestinal-microbe-pathogen interactions in the course of evolution.

The Role of Psychobiotics to Ensure Mental Health during the COVID-19 Pandemic-A Current State of Knowledge

Psychobiotics are defined as probiotics, mainly of the genus Lactobacillus and Bifidobacterium, that confer mental health benefits to the host when consumed in a particular quantity through the interaction with commensal gut microbiota. The gut microbiota, which means a diverse and dynamic population of microorganisms harboring the gastrointestinal tract, communicates with the brain and vice versa through the brain-gut axis. The mechanisms of action of psychobiotics may be divided into four groups: synthesis of neurotransmitters and neurochemicals, regulation of the HPA axis, influence on the immune system, and synthesis of metabolites. Recent years showed that the COVID-19 pandemic affected not only physical, but also mental health. Social isolation, fear of infection, the lack of adequate vaccine, disinformation, increased number of deaths, financial loss, quarantine, and lockdown are all factors can cause psychiatric problems. The aim of this review was to discuss the potential role of psychobiotic in light of the current problems, based on in vitro and in vivo studies, meta-analyses, clinical trials evidence, and registered studies assessing probiotics' therapeutic administration in the prevention or treatment of symptoms or side effects of COVID-19.

The Impact of Plant Phytochemicals on the Gut Microbiota of Humans for a Balanced Life

The gastrointestinal tract of humans is a complex microbial ecosystem known as gut microbiota. The microbiota is involved in several critical physiological processes such as digestion, absorption, and related physiological functions and plays a crucial role in determining the host’s health. The habitual consumption of specific dietary components can impact beyond their nutritional benefits, altering gut microbiota diversity and function and could manipulate health. Phytochemicals are non-nutrient biologically active plant components that can modify the composition of gut microflora through selective stimulation of proliferation or inhibition of certain microbial communities in the intestine. Plants secrete these components, and they accumulate in the cell wall and cell sap compartments (body) for their development and survival. These compounds have low bioavailability and long time-retention in the intestine due to their poor absorption, resulting in beneficial impacts on gut microbiota population. Feeding diets containing phytochemicals to humans and animals may offer a path to improve the gut microbiome resulting in improved performance and/or health and wellbeing. This review discusses the effects of phytochemicals on the modulation of the gut microbiota environment and the resultant benefits to humans; however, the effect of phytochemicals on the gut microbiota of animals is also covered, in brief.

Gut microbiome-produced metabolites in pigs: a review on their biological functions and the influence of probiotics

The gastrointestinal tract is a complex ecosystem that contains a large number of microorganisms with different metabolic capacities. Modulation of the gut microbiome can improve the growth and promote health in pigs. Crosstalk between the host, diet, and the gut microbiome can influence the health of the host, potentially through the production of several metabolites with various functions. Short-chain and branched-chain fatty acids, secondary bile acids, polyamines, indoles, and phenolic compounds are metabolites produced by the gut microbiome. The gut microbiome can also produce neurotransmitters (such as γ-aminobutyric acid, catecholamines, and serotonin), their precursors, and vitamins. Several studies in pigs have demonstrated the importance of the gut microbiome and its metabolites in improving growth performance and feed efficiency, alleviating stress, and providing protection from pathogens. The use of probiotics is one of the strategies employed to target the gut microbiome of pigs. Promising results have been published on the use of probiotics in optimizing pig production. This review focuses on the role of gut microbiome-derived metabolites in the performance of pigs and the effects of probiotics on altering the levels of these metabolites.

Human Adult Microbiota in a Static Colon Model: AhR Transcriptional Activity at the Crossroads of Host–Microbe Interaction

Functional symbiotic intestinal microbiota regulates immune defense and the metabolic processing of xenobiotics in the host. The aryl hydrocarbon receptor (AhR) is one of the transcription factors mediating host–microbe interaction. An in vitro static simulation of the human colon was used in this work to analyze the evolution of bacterial populations, the microbial metabolic output, and the potential induction of AhR transcriptional activity in healthy gut ecosystems. Fifteen target taxa were explored by qPCR, and the metabolic content was chromatographically profiled using SPME-GC-MS and UPLC-FLD to quantify short-chain fatty acids (SCFA) and biogenic amines, respectively. Over 72 h of fermentation, the microbiota and most produced metabolites remained stable. Fermentation supernatant induced AhR transcription in two of the three reporter gene cell lines (T47D, HepG2, HT29) evaluated. Mammary and intestinal cells were more sensitive to microbiota metabolic production, which showed greater AhR agonism than the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) used as a positive control. Some of the SCFA and biogenic amines identified could crucially contribute to the potent AhR induction of the fermentation products. As a fundamental pathway mediating human intestinal homeostasis and as a sensor for several microbial metabolites, AhR activation might be a useful endpoint to include in studies of the gut microbiota.

Implementation of the gut microbiota prevents anastomotic leaks in laparoscopic colorectal surgery for cancer:the results of the MIRACLe study

The aim of this pilot study was to evaluate the effects of a novel perioperative treatment for the implementation of the gut microbiota, to prevent anastomotic fistula and leakage (AL) in patients undergoing laparoscopic colorectal resections for cancer. A series of 60 patients who underwent elective colorectal surgery at S. Eugenio Hospital (Rome-Italy) between December 1, 2020 and November 30, 2021 and received a novel perioperative preparation following the MIRACLe (Microbiota Implementation to Reduce Anastomotic Colorectal Leaks) protocol (oral antibiotics, mechanical bowel preparation and perioperative probiotics), was compared to a group of 500 patients (control group) operated on between March 2015 and November 30, 2020, who received a standard ERAS protocol. In the MIRACLe Group only 1 anastomotic leak was registered. In this group the incidence of AL was just 1.7% vs. 6.4% in the control group (p = 0.238) and the incidence of surgical site infections (1.7% vs. 3.6%; p = 0.686), reoperations (1.7% vs. 4.2%; p = 0.547) and postoperative mortality (0% vs. 2.2%; p = 0.504) were lower. The postoperative outcomes were also better: the times to first flatus, to first stool and to oral feeding were shorter (1 vs. 2, 2 vs. 3 and 2 vs. 3 days, respectively; p < 0.001). Additionally, the postoperative recovery was faster, with a shorter time to discharge (4 vs. 6 days; p < 0.001). In this pilot study, the MIRACLe protocol appeared to be safe and considerably reduced anastomotic leaks in elective laparoscopic colorectal surgery for cancer, even if not statistically significant, due to the small number of cases.

Maternal Gut Microbiome Decelerates Fetal Endochondral Bone Formation by Inducing Inflammatory Reaction

To investigate the effect of the maternal gut microbiome on fetal endochondral bone formation, fetuses at embryonic day 18 were obtained from germ-free (GF) and specific-pathogen-free (SPF) pregnant mothers. Skeletal preparation of the fetuses’ whole bodies did not show significant morphological alterations; however, micro-CT analysis of the tibiae showed a lower bone volume fraction in the SPF tibia. Primary cultured chondrocytes from fetal SPF rib cages showed a lower cell proliferation and lower accumulation of the extracellular matrix. RNA-sequencing analysis showed the induction of inflammation-associated genes such as the interleukin (IL) 17 receptor, IL 6, and immune-response genes in SPF chondrocytes. These data indicate that the maternal gut microbiome in SPF mice affects fetal embryonic endochondral ossification, possibly by changing the expression of genes related to inflammation and the immune response in fetal cartilage. The gut microbiome may modify endochondral ossification in the fetal chondrocytes passing through the placenta.

Contribution of Gut Microbiota to Immune Tolerance in Infants

The prevalence of food allergy has increased in recent years, especially among the pediatric population. Differences in the gut microbiota composition between children with FA and healthy children have brought this topic into the spotlight as a possible explanation for the increase in FA. The gut microbiota characteristics are acquired through environmental interactions starting early in life, such as type of delivery during birth and breastfeeding. The microbiota features may be shaped by a plethora of immunomodulatory mechanisms, including a predominant role of Tregs and the transcription factor FOXP3. Additionally, a pivotal role has been given to vitamin A and butyrate, the main anti-inflammatory metabolite. These observations have led to the study and development of therapies oriented to modifying the microbiota and metabolite profiles, such as the use of pre- and probiotics and the determination of their capacity to induce tolerance to allergens that are relevant to FA. To date, evidence supporting these approaches in humans is scarce and inconclusive. Larger cohorts and dose-titration studies are mandatory to evaluate whether the observed changes in gut microbiota composition reflect medical recovery and increased tolerance in pediatric patients with FA. In this article, we discuss the establishment of the microbiota, the immunological mechanisms that regulate the microbiota of children with food allergies, and the evidence in research focused on its regulation as a means to achieve tolerance to food allergens.

Exploring the Gut-Brain Axis for the Control of CNS Inflammatory Demyelination: Immunomodulation by Bacteroides fragilis' Polysaccharide A

The symbiotic relationship between animals and their resident microorganisms has profound effects on host immunity. The human microbiota comprises bacteria that reside in the gastrointestinal tract and are involved in a range of inflammatory and autoimmune diseases. The gut microbiota's immunomodulatory effects extend to extraintestinal tissues, including the central nervous system (CNS). Specific symbiotic antigens responsible for inducing immunoregulation have been isolated from different bacterial species. Polysaccharide A (PSA) of Bacteroides fragilis is an archetypical molecule for host-microbiota interactions. Studies have shown that PSA has beneficial effects in experimental disease models, including experimental autoimmune encephalomyelitis (EAE), the most widely used animal model for multiple sclerosis (MS). Furthermore, in vitro stimulation with PSA promotes an immunomodulatory phenotype in human T cells isolated from healthy and MS donors. In this review, we discuss the current understanding of the interactions between gut microbiota and the host in the context of CNS inflammatory demyelination, the immunomodulatory roles of gut symbionts. More specifically, we also discuss the immunomodulatory effects of B. fragilis PSA in the gut-brain axis and its therapeutic potential in MS. Elucidation of the molecular mechanisms responsible for the microbiota's impact on host physiology offers tremendous promise for discovering new therapies.