Nitric Oxide Impacts Human Gut Microbiota Diversity and Functionalities

In vitro colonic fermentation of clean label ham formulations: Gut microbiota modulation and metabolite production

Consumer wishes for "clean label" products have prompted the rise of these products available in the market. With dietary choices directly influencing market trends, developing novel meat products with natural nitrate and nitrite alternatives is a sought-after premise. Cured meats like ham have been under scrutiny due to their potential harm to human health, having sodium nitrite been theorised to trigger dysbiosis of the gut microbiota and impair faecal short-chain fatty acids (SCFAs) production. Four novel ham formulations with a natural nitrate source coupled with nitrate-reducing starter cultures were subjected to an in vitro gastrointestinal digestion simulation (INFOGEST) and followed by in vitro colonic fermentation. The impact of each novel ham formulation on the gut microbiota and their fermentation metabolites, namely SCFAs, was assessed by quantitative Next Generation Sequencing and High-Performance Liquid Chromatography, respectively. No significant differences have been found for SCFAs levels or microbial communities throughout colonic fermentation. Further research should provide insight into how these alternatives can be associated with nitrosamine formation. The potential benefits of "clean label" alternatives need to be thoroughly demonstrated. While these solutions are often considered preferable to traditional nitrite-containing products, their implementation should be approached with caution. In addition to their antimicrobial efficacy and consumer acceptance, it is essential to assess their impact on product cost and compare their performance and health impact (positive or negative) with that of traditional nitrite formulations. Extensive research is needed to ensure that any move to "clean label" formulations is based on solid evidence rather than market trends.

Metabolomics Insights into Gut Microbiota and Functional Constipation

Background: The composition and metabolic activity of the gut microbiota play a crucial role in various health conditions, including the occurrence and development of chronic constipation. Recent metabolomic advances reveal that gut microbiota-derived metabolites-such as SCFAs, bile acids, neurotransmitters, and microbial gases-play critical roles in regulating intestinal function. Methods: We systematically analyzed the current literature on microbial metabolomics in chronic constipation. This review consolidates findings from high-throughput metabolomic techniques (GC-MS, LC-MS, NMR) comparing metabolic profiles of constipated patients with healthy individuals. It also examines diagnostic improvements and personalized treatments, including fecal microbiota transplantation and neuromodulation, guided by these metabolomic insights. Results: This review shows that reduced SCFA levels impair intestinal motility and promote inflammation. An altered bile acid metabolism-with decreased secondary bile acids like deoxycholic acid-disrupts receptor-mediated signaling, further affecting motility. Additionally, imbalances in amino acid metabolism and neurotransmitter production contribute to neuromuscular dysfunction, while variations in microbial gas production (e.g., methane vs. hydrogen) further modulate gut transit. Conclusions: Integrating metabolomics with gut microbiota research clarifies how specific microbial metabolites regulate gut function. These insights offer promising directions for precision diagnostics and targeted therapies to restore microbial balance and improve intestinal motility.

Nitric Oxide Inhibition of Glycyl Radical Enzymes and Their Activases

Innate immune response cells produce high concentrations of the free radical nitric oxide (NO) in response to pathogen infection. The antimicrobial properties of NO include nonspecific damage to essential biomolecules and specific inactivation of enzymes central to aerobic metabolism. However, the molecular targets of NO in anaerobic metabolism are less understood. Here, we demonstrate that the Escherichia coli glycyl radical enzyme pyruvate formate lyase (PFL), which catalyzes the anaerobic metabolism of pyruvate, is irreversibly inhibited by NO. Using electron paramagnetic resonance and site-directed mutagenesis we show that NO destroys the glycyl radical of PFL. The activation of PFL by its cognate radical S-adenosyl-l-methionine-dependent activating enzyme (PFL-AE) is also inhibited by NO, resulting in the conversion of the essential iron-sulfur cluster to dinitrosyl iron complexes. Whole-cell EPR and metabolic flux analyses of anaerobically growing E. coli show that PFL and PFL-AE are inhibited by physiologically relevant levels of NO in bacterial cell cultures, resulting in diminished growth and a metabolic shift to lactate fermentation. The class III ribonucleotide reductase (RNR) glycyl radical enzyme and its corresponding RNR-AE are also inhibited by NO in a mechanism analogous to those observed in PFL and PFL-AE, which likely contributes to the bacteriostatic effect of NO. Based on the similarities in reactivity of the PFL/RNR and PFL-AE/RNR-AE enzymes with NO, the mechanism of inactivation by NO appears to be general to the respective enzyme classes. The results implicate an immunological role of NO in inhibiting glycyl radical enzyme chemistry in the gut.

Inflammatory Microenvironment-Responsive Microsphere Vehicles Modulating Gut Microbiota and Intestinal Inflammation for Intestinal Stem Cell Niche Remodeling in Inflammatory Bowel Disease

Intestinal stem cells (ISCs) engage in proliferation to maintain a stable stem cell population and differentiate into functional epithelial subpopulations. This intricate process is upheld by various signals derived from the host and gut microbiota, establishing an ISC niche. However, during inflammatory bowel disease (IBD), this signaling niche undergoes dramatic changes, leading to impaired ISC and hindered restoration of the damaged intestinal epithelial barrier. This study introduces intestinal inflammatory microenvironment-responsive microsphere vehicles designed to remodel the ISC niche, offering an approach to treat IBD. Using an advanced emulsion technique, these microsphere vehicles specifically target colonic inflammation sites, delivering a responsive release of MXene and l-arginine. This delivery system is formulated to modulate intestinal flora and immune responses effectively. l-arginine is converted into nitric oxide to regulate the gut microbiome, while MXene serves as a nanoimmunomodulator to stabilize immune homeostasis. Our findings demonstrate that the anti-inflammatory properties of the microspheres are key to promoting epithelial repair and remodeling of the ISC niche. This study highlights the role of antioxidant microspheres as anti-inflammatory agents that indirectly support ISC function and gut regeneration.

Children who develop celiac disease are predicted to exhibit distinct metabolic pathways among their gut microbiota years before diagnosis

Celiac disease (CD) is an autoimmune disease caused by a loss of gluten tolerance in genetically predisposed individuals. While 30%-40% of people possess the predisposing alleles, only 1%-2% are diagnosed with CD, suggesting that environmental factors are involved in disease pathogenesis. To determine an association between pediatric CD and the gut microbiome, we analyzed fecal samples from a prospective cohort study (ABIS). These samples were collected from children who later developed CD (CD progressors) and age-matched healthy children (at ages 1, 2.5, and 5) with similar HLA genotypes, breastfeeding durations, and gluten exposure times. We previously reported gut microbiome differences at ages 2.5 and 5 in this cohort; here, we present findings from samples collected at age 1 (n = 5). We identified 14 ASVs differing significantly between CD progressors and controls, including taxa linked to CD pathogenesis. CD progressors had increased Firmicutes and higher alpha diversity in IgA- bacteria. Using PICRUSt, we analyzed metabolic pathways enriched in CD progressors compared to controls at ages 1, 2.5, and 5 (n = 5-16), revealing enriched inflammatory and pathogenic pathways potentially contributing to CD-related immune dysregulation. While results are based on the primary EdgeR analysis, we also applied a non-parametric method of statistical analysis, reporting those results with supplementary figures. In conclusion, our findings suggest distinct metabolic pathways enriched in the gut microbiome of CD progressors years before diagnosis, which could inform targeted therapeutics for CD. As discussed in the limitations section, this small pilot study should be replicated with larger sample sizes for broader generalization.

IMPORTANCE

We analyzed gut microbiome data from children who later developed celiac disease (CD progressors) compared to healthy children in the first 5 years of life. Using fecal samples corresponding to the three phases of gut microbiome development, we uncovered enriched functional microbial pathways in CD progressors at age 1. Some of these pathways, implicated in bacterial pathogenesis, microbiota modulation, and inflammation, have been correlated with CD. We also identified taxa in CD progressors at age 1 including Lachnospiraceae, Alistipes, and Bifidobacterium dentium that were previously associated with CD. These findings suggest a potential role for these taxa and enriched pathways in pediatric CD onset years before diagnosis, highlighting potential for early interventions. While the findings of this exploratory study should be validated with larger sample sizes, our study suggests microbial metabolic pathways related to CD onset, enhancing our understanding of CD pathogenesis and the role of gut microbiome-mediated early alterations.

Nitric Oxide Inhibition of Glycyl Radical Enzymes and Their Activases

Innate immune response cells produce high concentrations of the free radical nitric oxide (NO) in response to pathogen infection. The antimicrobial properties of NO include non-specific damage to essential biomolecules and specific inactivation of enzymes central to aerobic metabolism. However, the molecular targets of NO in anaerobic metabolism are less understood. Here, we demonstrate that the Escherichia coli glycyl radical enzyme pyruvate formate lyase (PFL), which catalyzes the anaerobic metabolism of pyruvate, is irreversibly inhibited by NO. Using electron paramagnetic resonance and site-directed mutagenesis we show that NO destroys the glycyl radical of PFL. The activation of PFL by its cognate radical S-adenosyl-L-methionine-dependent activating enzyme (PFL-AE) is also inhibited by NO, resulting in the conversion of the essential iron-sulfur cluster to dinitrosyl iron complexes. Whole-cell EPR and metabolic flux analyses of anaerobically growing Escherichia coli show that PFL and PFL-AE are inhibited by physiologically relevant levels of NO in bacterial cell cultures, resulting in diminished growth and a metabolic shift to lactate fermentation. The class III ribonucleotide reductase (RNR) glycyl radical enzyme and its corresponding RNR-AE are also inhibited by NO in a mechanism analogous to those observed in PFL and PFL-AE, which likely contributes to the bacteriostatic effect of NO. Based on the similarities in reactivity of the PFL/RNR and PFL-AE/RNR-AE enzymes with NO, the mechanism of inactivation by NO appears to be general to the respective enzyme classes. The results implicate an immunological role of NO in inhibiting glycyl radical enzyme chemistry in the gut.

In vitro cellular model systems provide a promising alternative to animal experiments for studying the intestine-organ axis

Limiting animal experiments is essential for ethical issues and also because scientific evidence highlights the discrepancies between human and animal metabolism. This review aims to provide a critical discussion of the strengths and limitations of the most appropriate in vitro intestine model to answer complex research questions in pharmaceutical and nutraceutical fields. This review describes the components contributing to the definition of the gut barrier structure, from the outer mucus layer to the inner part of lamina propria, including endothelial and neuronal networks. We conclude that the main advantage of these co-culture models is their versatility since they are modulable systems in which each component can be added, changed, or removed to reproduce a specific physiological condition each time. Additionally, we compare intestinal organoid models and microfluidic systems with well-established co-culture models.

Carbon dioxide enhances Akkermansia muciniphila fitness and anti-obesity efficacy in high-fat diet mice

Numerous studies and clinical applications have underscored the therapeutic potential of the indigenous gut bacterium Akkermansia muciniphila in various diseases. However, our understanding of how Akkermansia muciniphila senses and responds to host gastrointestinal signals remains limited. Here, we demonstrate that A. muciniphila exhibits rapid growth, facilitated by its self-produced carbon dioxide (CO₂), with key enzymes such as glutamate decarboxylase, carbonic anhydrase, and pyruvate ferredoxin oxidoreductase playing pivotal roles. Additionally, we design a novel delivery system, comprising calcium carbonate, inulin, A. muciniphila, and sodium alginate, which enhances A. muciniphila growth and facilitates the expression of part probiotic genes in mice intestinal milieu. Notably, the administration of this delivery system induces weight loss in mice fed high-fat diets. Furthermore, we elucidate the significant impact of CO₂ on the composition and functional genes of the human gut microbiota, with genes encoding carbonic anhydrase and amino acid metabolism enzymes exhibiting heightened responsiveness. These findings reveal a novel mechanism by which gut commensal bacteria sense and respond to gaseous molecules, thereby promoting growth. Moreover, they suggest the potential for designing rational therapeutic strategies utilizing live bacterial delivery systems to enhance probiotic growth and ameliorate gut microbiota-related diseases.

Pediatric migraine is characterized by traits of ecological and metabolic dysbiosis and inflammation

BACKGROUND

Recently, there has been increasing interest in the possible role of the gut microbiota (GM) in the onset of migraine. Our aim was to verify whether bacterial populations associated with intestinal dysbiosis are found in pediatric patients with migraine. We looked for which metabolic pathways, these bacteria were involved and whether they might be associated with gut inflammation and increased intestinal permeability.

METHODS

Patients aged between 6 and 17 years were recruited. The GM profiling was performed by the 16S rRNA metataxonomics of faecal samples from 98 patients with migraine and 98 healthy subjects. Alpha and beta diversity analyses and multivariate and univariate analyses were applied to compare the gut microbiota profiles between the two group. To predict functional metabolic pathways, we used phylogenetic analysis of communities. The level of indican in urine was analyzed to investigate the presence of metabolic dysbiosis. To assess gut inflammation, increased intestinal permeability and the mucosal immune activation, we measured the plasmatic levels of lipopolysaccharide, occludin and IgA, respectively.

RESULTS

The α-diversity analysis revealed a significant increase of bacterial richness in the migraine group. The β-diversity analysis showed significant differences between the two groups indicating gut dysbiosis in patients with migraine. Thirty-seven metabolic pathways were increased in the migraine group, which includes changes in tryptophan and phenylalanine metabolism. The presence of metabolic dysbiosis was confirmed by the increased level of indican in urine. Increased levels of plasmatic occludin and IgA indicated the presence of intestinal permeability and mucosal immune activation. The plasmatic LPS levels showed a low intestinal inflammation in patients with migraine.

CONCLUSIONS

Pediatric patients with migraine present GM profiles different from healthy subjects, associated with metabolic pathways important in migraine.

The role of fiber in modulating plant protein-induced metabolic responses

The rising consumption of plant protein foods and the emergence of meat alternatives have prompted interest in the health benefits of such products, which contain fiber in addition to protein. This review investigates the effect of fiber on plant-based protein metabolism and evaluates its contribution to gut-derived health impacts. Plant proteins, which often come with added fiber, can have varying health outcomes. Factors such as processing and the presence of fiber and starch influence the digestibility of plant proteins, potentially leading to increased proteolytic fermentation in the gut and the production of harmful metabolites. However, fermentable fiber can counteract this effect by serving as a primary substrate for gut microbes, decreasing proteolytic activity. The increased amount of fiber, rather than the protein source itself, plays a significant role in the observed health benefits of plant-based diets in human studies. Differences between extrinsic and intrinsic fiber in the food matrix further impact protein fermentation and digestibility. Thus, in novel protein products without naturally occurring fiber, the health impact may differ from conventional plant protein sources. The influence of various fibers on plant-based protein metabolism throughout the gastrointestinal tract is not fully understood, necessitating further research.

Gastroprotective and microbiome-modulating effects of ubiquinol in rats with radiation-induced enteropathy

Radiation enteritis is a frequently encountered issue for patients receiving radiotherapy and has a significant impact on cancer patients' quality of life. The gut microbiota plays a pivotal role in intestinal function, yet the impact of irradiation on gut microorganisms is not fully understood. This study explores the gastroprotective effect and gut microbiome-modulating potential of ubiquinol (Ubq), the reduced form of the powerful antioxidant CoQ-10. For this purpose, male albino rats were randomly assigned to four groups: Control, IRR (acute 7 Gy γ-radiation), Ubq_Post (Ubq for 7 days post-irradiation), and Ubq_Pre/Post (Ubq for 7 days pre and 7 days post-irradiation). The fecal microbiomes of all groups were profiled by 16S rRNA amplicon sequencing followed by bioinformatics and statistical analysis. Histopathological examination of intestinal tissue indicated severe damage in the irradiated group, which was mitigated by ubiquinol with enhanced regeneration, goblet cells, and intestinal alkaline phosphatase expression. Compared to the irradiated group, the Ubq-treated groups had a significant recovery of intestinal interleukin-1β, caspase-3, nitric oxide metabolites, and thio-barbituric reactive substances to near-healthy levels. Ubq_Pre/Post group displayed elevated peroxisome proliferator-activated receptor (PPAR-γ) level, suggesting heightened benefits. Serum insulin reduction in irradiated rats improved post-Ubq treatment, with a possible anti-inflammatory effect on the pancreatic tissue. Fecal microbiota profiling revealed a dysbiosis state with a reduction of bacterial diversity post-irradiation, which was re-modulated in the Ubq treated groups to profiles that are indistinguishable from the control group. These findings underscore Ubq's gastroprotective effects against radiation-induced enteritis and its potential in restoring the gut microbiota's diversity and balance.

Applied physiology: gut microbiota and antimicrobial therapy

The gut microbiota plays an important role in maintaining human health and in the pathogenesis of several diseases. Antibiotics are among the most commonly prescribed drugs and have a significant impact on the structure and function of the gut microbiota. The understanding that a healthy gut microbiota prevents the development of many diseases has also led to its consideration as a potential therapeutic target. At the same time, any factor that alters the gut microbiota becomes important in this approach. Exercise and antibacterial therapy have a direct effect on the microbiota. The review reflects the current state of publications on the mechanisms of intestinal bacterial involvement in the pathogenesis of cardiovascular, metabolic, and neurodegenerative diseases. The physiological mechanisms of the influence of physical activity on the composition of the gut microbiota are considered. The mechanisms of the common interface between exercise and antibacterial therapy will be considered using the example of several socially important diseases. The aim of the study is to show the physiological relationship between the effects of exercise and antibiotics on the gut microbiota.

Effects of Inducible Nitric Oxide Synthase (iNOS) Gene Knockout on the Diversity, Composition, and Function of Gut Microbiota in Adult Zebrafish

The gut microbiota constitutes a complex ecosystem that has an important impact on host health. In this study, genetically engineered zebrafish with inducible nitric oxide synthase (iNOS or NOS2) knockout were used as a model to investigate the effects of nos2a/nos2b gene single knockout and nos2 gene double knockout on intestinal microbiome composition and function. Extensive 16S rRNA sequencing revealed substantial changes in microbial diversity and specific taxonomic abundances, yet it did not affect the functional structure of the intestinal tissues. Notably, iNOS-deficient zebrafish demonstrated a decrease in Vibrio species and an increase in Aeromonas species, with more pronounced effects observed in double knockouts. Further transcriptomic analysis of the gut in double iNOS knockout zebrafish indicated significant alterations in immune-related and metabolic pathways, including the complement and PPAR signaling pathways. These findings underscore the crucial interplay between host genetics and gut microbiota, indicating that iNOS plays a key role in modulating the gut microbial ecology, host immune system, and metabolic responses.

Species-level characterization of saliva and dental plaque microbiota reveals putative bacterial and functional biomarkers of periodontal diseases in dogs

Periodontal diseases are among the most common bacterial-related pathologies affecting the oral cavity of dogs. Nevertheless, the canine oral ecosystem and its correlations with oral disease development are still far from being fully characterized. In this study, the species-level taxonomic composition of saliva and dental plaque microbiota of 30 healthy dogs was investigated through a shallow shotgun metagenomics approach. The obtained data allowed not only to define the most abundant and prevalent bacterial species of the oral microbiota in healthy dogs, including members of the genera Corynebacterium and Porphyromonas, but also to identify the presence of distinct compositional motifs in the two oral microniches as well as taxonomical differences between dental plaques collected from anterior and posterior teeth. Subsequently, the salivary and dental plaque microbiota of 18 dogs affected by chronic gingival inflammation and 18 dogs with periodontitis were compared to those obtained from the healthy dogs. This analysis allowed the identification of bacterial and metabolic biomarkers correlated with a specific clinical status, including members of the genera Porphyromonas and Fusobacterium as microbial biomarkers of a healthy and diseased oral status, respectively, and genes predicted to encode for metabolites with anti-inflammatory properties as metabolic biomarkers of a healthy status.

Shifts in the functional capacity and metabolite composition of the gut microbiome during recovery from enteric infection

While enteric pathogens have been widely studied for their roles in causing foodborne infection, their impacts on the gut microbial community have yet to be fully characterized. Previous work has identified notable changes in the gut microbiome related to pathogen invasion, both taxonomically and genetically. Characterization of the metabolic landscape during and after enteric infection, however, has not been explored. Consequently, we investigated the metabolome of paired stools recovered from 60 patients (cases) during and after recovery from enteric bacterial infections (follow-ups). Shotgun metagenomics was applied to predict functional microbial pathways combined with untargeted metametabolomics classified by Liquid Chromatography Mass Spectrometry. Notably, cases had a greater overall metabolic capacity with significantly higher pathway richness and evenness relative to the follow-ups (p<0.05). Metabolic pathways related to central carbon metabolism, amino acid metabolism, and lipid and fatty acid biosynthesis were more highly represented in cases and distinct signatures for menaquinone production were detected. By contrast, the follow-up samples had a more diverse metabolic landscape with enhanced richness of polar metabolites (p<0.0001) and significantly greater richness, evenness, and overall diversity of nonpolar metabolites (p<0.0001). Although many metabolites could not be annotated with existing databases, a marked increase in certain clusters of metabolites was observed in the follow-up samples when compared to the case samples and vice versa. These findings suggest the importance of key metabolites in gut health and recovery and enhance understanding of metabolic fluctuations during enteric infections.

The association of dietary nitrates/nitrites intake and the gut microbial metabolite trimethylamine N-oxide and kynurenine in adults: a population-based study

Background

Dietary nitrate and nitrite may affect the gut microbiota and its metabolites, such as trimethylamine N-oxide (TMAO) and kynurenine (KYN). However, this association and the exact mechanism are still unclear. Therefore, this study aimed to assess the association between dietary consumption of nitrite and nitrate on TMAO and KYN levels in adults.

Methods

This cross-sectional study was employed on a subsample baseline phase of the Tehran University of Medical Sciences (TUMS) Employee's Cohort Study (TEC). A total of 250 adults aged 18 years or older were included in the current analysis. Data on the dietary intakes were collected using a validated dish-based food frequency questionnaire (FFQ), and dietary intakes of nitrite and nitrate were estimated using the FFQ with 144 items. Serum profiles and TMAO and KYN were measured using a standard protocol.

Results

The findings of this study demonstrate a significant association between the intake of animal sources of nitrate and nitrite and the likelihood of having elevated levels of TMAO and KYN. Specifically, after adjustment, individuals with the highest intake adherence to nitrates from animal sources exhibited increased odds of having the highest level of TMAO (≥51.02 pg/ml) (OR = 1.51, 95% CI = 0.59-3.88, P = 0.03) and KYN (≥417.41 pg/ml) (OR = 1.75, 95% CI = 0.73-4.17, P = 0.02). Additionally, subjects with the highest animal intake from nitrite sources have 1.73 and 1.45 times higher odds of having the highest levels of TMAO and KYN. These results emphasize the potential implications of animal-derived nitrate and nitrite consumption on the levels of TMAO and KYN.

Conclusion

The present evidence indicates that a high level of nitrate and nitrite intake from animal sources can increase the odds of high levels of TMAO and KYN. Further studies suggest that we should better evaluate and understand this association.

Boosting Fitness Costs Associated with Antibiotic Resistance in the Gut: On the Way to Biorestoration of Susceptible Populations

The acquisition and expression of antibiotic resistance implies changes in bacterial cell physiology, imposing fitness costs. Many human opportunistic pathogenic bacteria, such as those causing urinary tract or bloodstream infections, colonize the gut. In this opinionated review, we will examine the various types of stress that these bacteria might suffer during their intestinal stay. These stresses, and their compensatory responses, probably have a fitness cost, which might be additive to the cost of expressing antibiotic resistance. Such an effect could result in a disadvantage relative to antibiotic susceptible populations that might replace the resistant ones. The opinion proposed in this paper is that the effect of these combinations of fitness costs should be tested in antibiotic resistant bacteria with susceptible ones as controls. This testing might provide opportunities to increase the bacterial gut stress boosting physiological biomolecules or using dietary interventions. This approach to reduce the burden of antibiotic-resistant populations certainly must be answered empirically. In the end, the battle against antibiotic resistance should be won by antibiotic-susceptible organisms. Let us help them prevail.

Postnatal development of the enteric neurons expressing neuronal nitric oxide synthase

Neurons, expressing neuronal nitric oxide synthase (nNOS) in the enteric ganglia are inhibitory motor neurons or interneurons. The aim of the study was to identify the percentage, cross-sectional area of nNOS-immunoreactive (IR) neurons and their colocalization with choline acetyltransferase (ChAT), vasoactive intestinal polypeptide (VIP), and neuropeptide Y in the intramural ganglia of the myenteric (MP) and submucous plexus (SP) of the small intestine (SI) and large intestine (LI) of rats of different age groups using immunohistochemical methods. In the intramural ganglia of the MP, the largest percentage of nNOS-IR neurons was detected in newborn rats in the LI (81 ± 0.9%) and SI (48 ± 4.1%). Subsequently, it decreased in ontogenesis up to 60 days of life (26 ± 0.9% LI, 29 ± 3.2% SI), and did not change until senescence. In the SP, abundant nNOS-IR neurons were also detected in newborns (82 ± 7.0% SI, 85 ± 3.2% LI), while their percentage decreased significantly in the next 20 days. Furthermore, a very small number of nNOS-IR neurons was detected in 30-day- and 2-month-old animals, but they again appeared in large numbers in aged rats. In the MP, the highest percentage of nNOS+/ChAT+ neurons was in 1-day-old, 10-day-old, and 2-year-old rats. In the SP, the largest number of nNOS-IR neurons colocalized ChAT regardless of age. In the MP of all rats, many nNOS-IR neurons colocalized VIP, and the maximal percentage of nNOS+/VIP+ neurons was found in 2-year-old rats, minimal-in newborns. In conclusion, nNOS expression in neurons of the gut is decreased in early postnatal ontogenesis and subsequently increased in aged rats.

Microbiome Alterations Driven by Trypanosoma cruzi Infection in Two Disjunctive Murine Models

Alterations caused by Trypanosoma cruzi in the composition of gut microbiome may play a vital role in the host-parasite interactions that shapes physiology and immune responses against infection. Thus, a better understanding of this parasite-host-microbiome interaction may yield relevant information in the comprehension of the pathophysiology of the disease and the development of new prophylactic and therapeutic alternatives. Therefore, we implemented a murine model with two mice strains (BALB/c and C57BL/6) to evaluate the impact of Trypanosoma cruzi (Tulahuen strain) infection on the gut microbiome utilizing cytokine profiling and shotgun metagenomics. Higher parasite burdens were observed in cardiac and intestinal tissues, including changes in anti-inflammatory (interleukin-4 [IL-4] and IL-10) and proinflammatory (gamma interferon, tumor necrosis factor alpha, and IL-6) cytokines. Bacterial species such as Bacteroides thetaiotaomicron, Faecalibaculum rodentium, and Lactobacillus johnsonii showed a decrease in relative abundance, while Akkermansia muciniphila and Staphylococcus xylosus increased. Likewise, as infection progressed, there was a decrease in gene abundances related to metabolic processes such as lipid synthesis (including short-chain fatty acids) and amino acid synthesis (including branched-chain amino acids). High-quality metagenomic assembled genomes of L. johnsonii and A. muciniphila among other species were reconstructed, confirming, functional changes associated with metabolic pathways that are directly affected by the loss of abundance of specific bacterial taxa. IMPORTANCE Chagas disease (CD) is caused by the protozoan Trypanosoma cruzi, presenting acute and chronic phases where cardiomyopathy, megaesophagus, and/or megacolon stand out. During the course of its life cycle, the parasite has an important gastrointestinal tract transit that leads to severe forms of CD. The intestinal microbiome plays an essential role in the immunological, physiological, and metabolic homeostasis of the host. Therefore, parasite-host-intestinal microbiome interactions may provide information on certain biological and pathophysiological aspects related to CD. The present study proposes a comprehensive evaluation of the potential effects of this interaction based on metagenomic and immunological data from two mice models with different genetic, immunological, and microbiome backgrounds. Our findings suggest that there are alterations in the immune and microbiome profiles that affect several metabolic pathways that can potentially promote the infection's establishment, progression, and persistence. In addition, this information may prove essential in the research of new prophylactic and therapeutic alternatives for CD.

Different Approaches to Ergogenic, Pre-, and Probiotic Supplementation in Sports with Different Metabolism Characteristics: A Mini Review

Sport disciplines with different metabolic characteristics require different dietary approaches. Bodybuilders or sprinters ("anaerobic" athletes) need a high-protein diet (HPD) in order to activate muscle protein synthesis after exercise-induced muscle damage and use nitric oxide enhancers (such as citrulline and nitrates) to increase vasodilatation, whereas endurance athletes, such as runners or cyclists ("aerobic" athletes), prefer a high-carbohydrate diet (HCHD), which aims to restore the intramuscular glycogen, and supplements containing buffering agents (such as sodium bicarbonate and beta-alanine). In both cases, nutrient absorption, neurotransmitter and immune cell production and muscle recovery depend on gut bacteria and their metabolites. However, there is still insufficient data on the impact of an HPD or HCHD in addition to supplements on "anaerobic" and "aerobic" athletes' gut microbiota and how this impact could be affected by nutritional interventions such as pre- and probiotic therapy. Additionally, little is known about the role of probiotics in the ergogenic effects of supplements. Based on the results of our previous research on an HPD in amateur bodybuilders and an HCHD in amateur cyclists, we reviewed human and animal studies on the effects of popular supplements on gut homeostasis and sport performance.

Associations between the Gut Microbiome and Migraines in Children Aged 7-18 Years: An Analysis of the American Gut Project Cohort

BACKGROUND

The gut microbiome seems to play a role in migraines through increasing intestinal epithelial permeability and pro-inflammatory processes. The associations between the gut microbiome and migraines are uncertain in children.

AIM

The purpose of this quantitative study was to examine the associations between the gut microbiome and migraines in children aged 7-18 years from the American Gut Project (AGP).

METHOD

A cohort of children aged 7-18 years from the AGP was analyzed. 16S rRNA V4 gene sequences for the gut microbiome, migraines, and demographics were obtained from the AGP Public Repository. After quality control of 16S rRNA gene sequences, α-diversity (Shannon, Faith's_PD, and evenness) and β-diversity metrics (Bray-Curtis and weighted-UniFrac distances), taxonomy, and abundance analyses were implemented using QIIME 2.

RESULTS

In total, 381 children (341 without migraines; 40 with professional or self-diagnosed migraines) were analyzed with a mean age of 11.5 years. Compared with those without migraines, children with migraines showed lower estimates in Shannon and Faith's_PD (p < .01). Both Bray-Curtis and weighted-UniFrac distances displayed the gut microbial dissimilarities between these two groups (p = .001). Children with migraines had higher abundances in genus of phylum Bacteroidetes (Bacteroides, Parabacteroides, Odoribacter), Actinobacteria (Eggerthella, Varibaculum), Firmicutes (SMB53, Lachnospira, Dorea, Veillonella, Anaerotruncus, Butyricicoccus, Coprobacillus, Eubacterium), and Proteobacteria (Sutterella) than children without migraines.

CONCLUSIONS

Associations of the gut microbiome diversity and abundances with migraines in children indicated potential biological mechanisms of migraines. Future work needs to confirm our findings in children.

The Role of Gut Bacteriome in Asthma, Chronic Obstructive Pulmonary Disease and Obstructive Sleep Apnoea

The human body contains a very complex and dynamic ecosystem of bacteria. The bacteriome interacts with the host bi-directionally, and changes in either factor impact the entire system. It has long been known that chronic airway diseases are associated with disturbances in the lung bacteriome. However, less is known about the role of gut bacteriome in the most common respiratory diseases. Here, we aim to summarise the evidence concerning the role of the intestinal bacteriome in the pathogenesis and disease course of bronchial asthma, chronic obstructive pulmonary disease, and obstructive sleep apnea. Furthermore, we discuss the consequences of an altered gut bacteriome on the most common comorbidities of these lung diseases. Lastly, we also reflect on the therapeutic potential of influencing the gut microbiome to improve disease outcomes.

Role, Relevance, and Possibilities of In vitro fermentation models in human dietary, and gut-microbial studies

Dietary studies play a crucial role in determining the health-benefiting effects of most food substances, including prebiotics, probiotics, functional foods, and bioactive compounds. Such studies involve gastrointestinal digestion and colonic fermentation of dietary substances. In colonic fermentation, any digested food is further metabolized in the gut by the residing colonic microbiota, causing a shift in the gut microenvironment and production of various metabolites, such as short-chain fatty acids (SCFA). These diet-induced shifts in the microbial community and metabolite production, which can be assessed through in vitro fermentation models using a donor's fecal microbiota, are well known to impact the health of the host. Although in vivo or animal experiments are the gold standard in dietary studies, recent advancements using different in vitro systems, like artificial colon (ARCOL), mini bioreactor array (MBRA), TNO in vitro model of the colon (TIM), Simulator of the Human Intestinal Microbial Ecosystem (SHIME), M-SHIME, CoMiniGut, and Dynamic Gastrointestinal Simulator (SIMGI) make it easy to study the dietary impact in terms of the gut microbiota and metabolites. Such a continuous in vitro system can have multiple compartments corresponding to different parts of the colon, i.e., proximal, transverse, and distal colon, making the findings physiologically more significant. Further, post-fermentation samples can be analyzed using metagenomic, metabolomic, qPCR and flow cytometry approaches. Moreover, studies have shown that in vitro results are in accordance with the in vivo findings, supporting their relevance in dietary studies and giving confidence that shifts in metabolites are only due to microbes. This review meticulously describes the recent advancements in various fermentation models and their relevance in dietary studies. This article is protected by copyright. All rights reserved.

Nutraceuticals and Physical Activity as Antidepressants: The Central Role of the Gut Microbiota

Major depressive disorder (MDD) is a common mental illness. Evidence suggests that the gut microbiota play an essential role in regulating brain functions and the pathogenesis of neuropsychiatric diseases, including MDD. There are numerous mechanisms through which the gut microbiota and brain can exchange information in a continuous, bidirectional communication. Current research emphasizes the interexchange of signals influenced by the gut microbiota that are detected and transduced in information from the gut to the nervous system involving neural, endocrine, and inflammatory mechanisms, suggesting a relationship between oxidative stress and the pathophysiology of MDD via the hyperactivation of inflammatory responses. Potential sources of inflammation in the plasma and hippocampus of depressed individuals could stem from increases in intestinal permeability. Some nutraceuticals, such as specific probiotics, namely psychobiotics, polyphenols, carotenoids, butyrate, and prebiotics, have been demonstrated to exert an antidepressant activity, but most of them need to be metabolized and activated by gut microorganisms. By inducing changes in the gut microbiota composition, physical exercise might also exert a role in alleviating depression-like symptoms. The mutual relationships among nutraceuticals, exercise, and depression will be discussed, and the potential role of the gut microbiota as a therapeutic target to treat depression will be explored.

The pathogenic biomarker alcohol dehydrogenase protein is involved in Bacillus cereus virulence and survival against host innate defence

Bacillus cereus is a spore forming bacteria recognized among the leading agents responsible for foodborne outbreaks in Europe. B. cereus is also gaining notoriety as an opportunistic human pathogen inducing local and systemic infections. The real incidence of such infection is likely underestimated and information on genetic and phenotypic characteristics of the incriminated strains is generally scarce. We have recently analyzed a large strain collection of varying pathogenic potential. Screening for biomarkers to differentiate among clinical and non-clinical strains, a gene encoding an alcohol dehydrogenase-like protein was identified among the leading candidates. This family of proteins has been demonstrated to be involved in the virulence of several bacterial species. The relevant gene was knocked out to elucidate its function with regards to resistance to host innate immune response, both in vitro and in vivo. Our results demonstrate that the adhB gene plays a significant role in resistance to nitric oxide and oxidative stress in vitro, as well as its pathogenic ability with regards to in vivo toxicity. These properties may explain the pathogenic potential of strains carrying this newly identified virulence factor.