L-arginine metabolism as pivotal interface of mutual host-microbe interactions in the gut

Arginine depletion-induced autophagy and metabolic dysregulation are involved in the disease severity of hand, foot, and mouth disease

Amino acid metabolism provides significant insight into the development and prevention of many viral diseases. Therefore, the present study aimed to compare the amino acid profiles of hand, foot, and mouth disease (HFMD) patients with those of healthy individuals and to further reveal the molecular mechanisms of HFMD severity. Using UPLC-MS/MS, we determined the plasma amino acid expression profiles of pediatric patients with HFMD (mild, n = 42; severe, n = 43) and healthy controls (n = 25). Brain tissues from CVA6-infected mice were examined using untargeted metabolomics. Several amino acids were significantly different between the three groups. Pathway analysis revealed that arginine, proline, and tryptophan metabolism are implicated in the pathogenesis of HFMD. A similar arginine depletion was observed in the brain tissues of CVA6-infected mice. Importantly, L-arginine supplementation improved the survival rate of CVA6-infected mice, inhibited virus multiplication, and reduced pathological autophagy associated with mTOR-autophagy pathway in the brain. Collectively, arginine, as the hub amino acid metabolite of the mammalian target of rapamycin (mTOR) signaling pathway affecting autophagy, plays an important role in the pathogenesis of severe HFMD. L-arginine supplementation may serve as a potential therapeutic option for critical patients with HFMD.

Exposure to high altitude leads to disturbances in host metabolic homeostasis: study of the effects of hypoxia-reoxygenation and the associations between the microbiome and metabolome

This study investigated alterations in hematological parameters, gut microbiota composition, and fecal and plasma metabolic profiles among high-altitude residents during reoxygenation periods of 1 week, 1 month, and 4 months to elucidate the effects of reoxygenation on human physiology and metabolism. Exposure to high altitudes alters intestinal flora, plasma and fecal metabolites, disrupting their metabolic balance. Distinct differences in amino acid, lipid, energy, immune, cofactor, and vitamin metabolism pathways were detected between high- and low-altitude populations, with a partial recovery of disparities during reoxygenation. Although the gut microbiota exhibited limited adaptive homeostasis to altitude variations, the abundance of microbial taxa and the expression levels of fecal metabolites during the initial reoxygenation phase, particularly during the first week, were sensitive to the reoxygenated environment. Through 16S rRNA gene sequencing and bioinformatics analysis, operational taxonomic units (OTUs) were annotated at the genus level, revealing that the genera Barnesiella, Parabacteroides, and Megasphaera, along with plasma L-arginine, S1P, and alpha-D-glucose, emerged as potential biomarkers for the first week of reoxygenation among high-altitude populations. Notably, a marked change in oxidative stress levels and an increase in antioxidant capacity were observed in high-altitude residents during early reoxygenation. Tyrosine metabolism, which is jointly regulated by the plasma and fecal metabolites and gut microbiota, plays an important role under high-altitude conditions during initial reoxygenation. Additionally, the plasma metabolites pyridoxine and hypoxanthine and the Rothia genus correlated significantly with high-altitude deacclimatization syndrome scores during the first week of reoxygenation.IMPORTANCEOur research focuses on the prompt activation of tyrosine metabolism in plasma following reoxygenation, along with the regulatory mechanisms employed by the intestinal microbiota and the metabolism of feces to modulate this metabolic process. Notably, in the initial stages of reoxygenation, specific microbial genera such as Barnesiella, Parabacteroides, and Megasphaera, alongside plasma biomarkers including L-arginine, S1P, and alpha-D-glucose, emerge as pivotal players. Additionally, our findings reveal a distinct hematological profile characterized by a decrease in the MCHC and increases in the MCV and RDW-SD during the first week of reoxygenation, and this temporal window marked a crucial juncture in the plasma metabolome. Whereas the first month of reoxygenation signified a pivotal phase in the gut microbiome's adaptation to altered environmental conditions, as evidenced by alterations in alpha diversity.

Nutrition-induced changes in the microbiota can cause dysbiosis and disease development

Eukaryotic organisms are associated with complex microbial communities. Changes within these communities have been implicated in disease development. Nonetheless, it remains unclear whether these changes are a cause or a consequence of disease. Here, we report a causal link between environment-induced shifts in the microbiota and disease development. Using the model organism Hydra, we observed changes in microbial composition when transferring laboratory-grown Hydra to natural lake environments. These shifts were caused not only by new colonizers, through the process of community coalescence (merging of previously separate microbial communities), but also by lake water nutrients. Moreover, selective manipulation of the nutrient environment induced compound-specific shifts in the microbiota followed by disease development. Finally, L-arginine supplementation alone caused a transition in Pseudomonas from symbiotic to pathogenic, leading to an upregulation of immune response genes, tissue degradation, and host death. These findings challenge the notion that the host-associated microbiota is exclusively controlled by the host, highlighting the dynamic interplay between host epithelial environment, microbial colonizer pool, and nutrient conditions of the surrounding water. Furthermore, our results show that overfeeding of the microbiota allows for uncontrolled microbial growth and versatile interactions with the host. Environmental conditions may thus render symbionts a potential hazard to their hosts, blurring the divide between pathogenic and non-pathogenic microbes.IMPORTANCEThis study highlights the critical need to understand the dynamic interplay between host-associated microbiota and environmental factors to obtain a holistic view on organismal health. Our results demonstrate that ecosystem-wide microbial trafficking (community coalescence) and environmental nutrient conditions reshape microbial communities with profound implications for host health. By exploring nutrient-driven changes in microbial composition, our research finds experimental support for the "overfeeding hypothesis," which states that overfeeding alters the functionality of the host microbiota such that an overabundance in nutrients can facilitate disease development, transforming non-pathogenic microbes into pathogens. These findings emphasize the critical role of metabolic interactions driving microbial pathogenicity. Furthermore, our research provides empirical evidence for the "pathogenic potential" concept, challenging traditional distinctions between pathogenic and non-pathogenic microbes and supporting the idea that any microbe can become pathogenic under certain conditions.

Fasting-mimicking diet-enriched Bifidobacterium pseudolongum suppresses colorectal cancer by inducing memory CD8+ T cells

BACKGROUND

Fasting-mimicking diet (FMD) boosts the antitumour immune response in patients with colorectal cancer (CRC). The gut microbiota is a key host immunity regulator, affecting physiological homeostasis and disease pathogenesis.

OBJECTIVE

We aimed to investigate how FMD protects against CRC via gut microbiota modulation.

DESIGN

We assessed probiotic species enrichment in FMD-treated CRC mice using faecal metagenomic sequencing. The candidate species were verified in antibiotic-treated conventional and germ-free mouse models. Immune landscape alterations were evaluated using single-cell RNA sequencing and multicolour flow cytometry. The microbiota-derived antitumour metabolites were identified using metabolomic profiling.

RESULTS

Faecal metagenomic profiling revealed Bifidobacterium pseudolongum enrichment in FMD-treated CRC mice. B. pseudolongum mediates the FMD antitumour effects by increasing the tissue-resident memory CD8+ T-cell (TRM) population in CRC mice. The level of L-arginine, a B. pseudolongum functional metabolite, increased in FMD-treated CRC mice; furthermore, L-arginine induced the TRM phenotype in vivo and in vitro. Mechanistically, L-arginine is transported by the solute carrier family 7-member 1 (SLC7A1) receptor in CD8+ T cells. Both FMD and B. pseudolongum improved anti-CTLA-4 efficacy in the orthotopic mouse CRC model. In FMD-treated patients with CRC, the CD8+ TRM cell number increased as B. pseudolongum and L-arginine accumulated. The abundance of CD8+ TRM cells and B. pseudolongum was associated with a better prognosis in patients with CRC.

CONCLUSION

B. pseudolongum contributes to the FMD antitumour effects in CRC by producing L-arginine. This promotes CD8+ T-cell differentiation into memory cells. B. pseudolongum administration is a potential CRC therapeutic strategy.

The role of colonic microbiota amino acid metabolism in gut health regulation

The human gut microbiota plays a critical role in maintaining host homeostasis through metabolic activities. Among these, amino acid (AA) metabolism by the microbiota in the large intestine is highly heterogeneous and relevant to host health. Despite increasing interest, microbial AA metabolism remains relatively unexplored. This review highlights recent advances in colonic microbial AA metabolism, including auxotrophies, AA synthesis, and dissimilatory AA metabolites, and their implications in gut health, focusing on major gastrointestinal diseases including colorectal cancer, inflammatory bowel disease, and irritable bowel syndrome.

Regulation of innate lymphoid cell by microbial metabolites

Innate lymphoid cells (ILCs) are a unique category of immune cell that lack antigen-specific receptors yet possess the capacity to detect signals from the surrounding tissue. The majority of ILCs reside in the lymphoid and mucosal tissues, maintaining close associations with the microbiota. Beyond the contributions of accessory cells and adaptive immune cells, accumulating studies demonstrate that microbial metabolites serve a crucial role in mediating the relationship between ILCs and the microbiota. In this review, we highlight and summarize the roles of microbial metabolites from different sources in modulating ILC subsets, proposing these metabolites as potential therapeutic mechanisms in ILC-mediated diseases.

Improvement in Heat Stress-Induced Damage to Sperm Quality Following Fecal Microbiota Transplantation from L-Arginine-Treated Mice

Heat stress has become a significant concern in animal husbandry, as it adversely affects reproductive performance, particularly sperm quality, through mechanisms that are not fully understood. This study aimed to investigate the protective effects of L-arginine against heat stress-induced sperm damage and explore its potential mechanisms through the modulation of the intestinal microbiota. This study consisted of two experiments. First, in a heat-stressed mouse model, L-arginine was administered to evaluate its effects on the reproductive health of heat-stressed mice. In the second experiment, by transplanting L-arginine-induced changes in the gut microbiota into heat-stressed mice, the protective effects of the microbiota on the sperm of heat-stressed mice were assessed. The findings revealed a significant amelioration of decreased sperm quality and testicular injury induced by heat stress. Post heat stress, mice supplemented with L-arginine presented an increase in seminal vesicle gland weight and index, partial alleviation of testicular tissue morphology, and a substantial increase in testosterone concentration (p < 0.05). Additionally, L-arginine upregulated the expression of testosterone synthesis genes and the mRNA levels of sperm generation-related genes, including 3β-HSD, Stra8, WT1, and Gdnf (p < 0.05). Concurrently, L-arginine-induced microbial communities mitigated heat stress-induced decreases in sperm quality and testicular injury, coupled with increases in the mRNA expression levels of Cyp17a1, 17β-HSD, Plzf, and Gdnf (p < 0.05). Furthermore, there was a reduction in the expression of proinflammatory factors, namely, NFκB, MyD88, TNF-α, and TGF-β3 (p < 0.05). In conclusion, L-arginine may influence the ratio of beneficial bacteria to harmful bacteria in the intestinal microbiota, thereby reducing inflammation caused by heat stress, maintaining intestinal health, and influencing the microenvironment for spermatogenesis.

The impact of sleeve gastrectomy on MASH development by regulating the composition of gut microbiota and metabolic homeostasis

The prevalence of metabolic dysfunction-associated steatohepatitis (MASH) is increasing annually, which is a global public health issue. Although clinical trials are lacking, observational studies indicate that bariatric surgery can alleviate the progression of MASH. Here, we performed sleeve gastrectomy (SG) and Sham surgery on 8-week-old mice, and then fed a AMLN diet for 24 weeks to construct a diet-inducted MASH mice model after 4-week post-surgery recovery. Applying a multi-omics approach combining metagenomics, metabolomics, and transcriptomics, we found that SG prevents the development of hepatic steatosis, inflammation, and fibrosis in MASH mice not only by significantly altering the structure of gut microbiota including s_Akkermansia muciniphila, s_Alistiples dispar, g_Helicobacter and s_uc_Oscillospiraceae, but also by modulating the levels of serum metabolites including l-arginine and taurocholic acid (TCA). These results suggest that SG and the alteration of gut microbiota and its related serum metabolites can be served as the effective therapeutic strategies for MASH.

Encapsulated hesperetin modulates inflammatory responses in an in vitro intestinal immune co-culture model

In vitro cell models are an effective way to evaluate the biological activities of functional compounds. Hesperetin (HST) is a flavanone with various potential health-related benefits, and encapsulation improved its stability and bioavailability. This study aimed to investigate the anti-inflammatory effects of encapsulated HST using different delivery systems, including β-cyclodextrin (CD), nanoliposomes (NL), and NL coated with chitosan (CH) and carrageenan (CGN). A Caco-2 and THP-1 co-culture model characterized by direct cell-to-cell contact was developed, and these delivery systems were digested in vitro and subsequently tested on this model. The addition of lipopolysaccharide (LPS) in the model resulted in high secretion of the pro-inflammatory cytokines (IL-8, TNF-α, and IL-1β), the upregulation of the phenotype genes (CD68 and CD80) and the inflammation-related genes (MYD88, NFκB, and COX-2), marking the differentiation of M0 macrophages into M1 macrophages. Among the delivery systems, HST encapsulated in CH and CGN coated NL (CGN-CH-NL-HST) was the most effective in suppressing the production of IL-8 and expression of MYD88 and COX-2 in the inflammatory co-culture model. Metabolomic data showed that the M1 macrophage metabolic profile was changed by applying free HST and encapsulated HST, mostly in glycolysis and amino acid metabolism. Encapsulated HST in the CGN-CH-NL delivery system showed anti-inflammatory activity in the Caco-2 and THP-1 direct co-culture model, suggesting a potential of encapsulated bioactive compounds in treating inflammatory bowel disease.

Intestinal Microbiota Dysbiosis Role and Bacterial Translocation as a Factor for Septic Risk

The human immune system is closely linked to microbiota such as a complex symbiotic relationship during the coevolution of vertebrates and microorganisms. The transfer of microorganisms from the mother's microbiota to the newborn begins before birth during gestation and is considered the initial phase of the intestinal microbiota (IM). The gut is an important site where microorganisms can establish colonies. The IM contains polymicrobial communities, which show complex interactions with diet and host immunity. The tendency towards dysbiosis of the intestinal microbiota is influenced by local but also extra-intestinal factors such as inflammatory processes, infections, or a septic state that can aggravate it. Pathogens could trigger an immune response, such as proinflammatory responses. In addition, changes in the host immune system also influence the intestinal community and structure with additional translocation of pathogenic and non-pathogenic bacteria. Finally, local intestinal inflammation has been found to be an important factor in the growth of pathogenic microorganisms, particularly in its role in sepsis. The aim of this article is to be able to detect the current knowledge of the mechanisms that can lead to dysbiosis of the intestinal microbiota and that can cause bacterial translocation with a risk of infection or septic state and vice versa.

Optimization of citrulline production from a Bacillus subtilis BH-01 isolated from raw buffalo milk

The main purpose of this study was to optimize the L-citrulline production process using Plackett-Burman and Box-Behnken designs. L-citrulline-producing bacterium BH-01 was isolated from raw buffalo milk. The isolate was tested for probiotic activities such as tolerance to simulated gastric and intestinal juices, antagonistic activity against six antibiotic-resistant bacteria, and temperature tolerance. L-citrulline production and arginine deiminase (ADI) activity were optimized using statistical designs. The bacterial isolate was molecularly identified as Bacillus subtilis strain AUMC B-498 (accession number PP574248.1). The strain exhibited resistance at pH 2.0 and bile salt 0.5% for a two-hour exposure period. It could inhibit the growth of Escherichia coli, Klebsiella pneumonia, Serratia sp., Staphylococcus aureus, methicillin-resistant Staphylococcus aureus (MRSA), and Streptococcus pneumoniae. From the results of statistical optimization, the Plackett-Burman design identified temperature, L-arginine, incubation period, and peptone as the most effective factors among the eight selected variables. Based on these, the Box-Behnken design was used to optimize the factors required to maximize citrulline production. The maximum L-citrulline was 632.5 µg/L, and ADI activity was 1.42 U/mL. Therefore, BH-01 isolated from Buffalo milk might be a promising candidate in food, biotechnological, and pharmaceutical applications due to its dual functionality for citrulline production and probiotic characteristics.

Effects of gut microbiota and metabolites on the host defense peptide expression

The widespread use of antibiotics has led to the emergence of multidrug-resistant bacteria, which pose significant threats to animal health and food safety. Host defense peptides (HDPs) have emerged as promising alternatives because of their unique antimicrobial properties and minimal resistance induction. However, the high costs associated with HDP production and incorporation into animal management practices hinder their widespread application. Alternatively, promoting endogenous HDP expression has gained attention as a sustainable and cost-effective approach. This study summarizes the latest research findings on the modulation of HDP expression by the gut microbiota and its metabolites. By exploring the intricate relationships among the gut microbiota, metabolites, and HDP expression, this study aims to provide a theoretical foundation for the development of targeted strategies to increase endogenous HDP production, thereby promoting animal health and resistance to infectious diseases. KEY POINTS: • Host defense peptides (HDPs) are expressed via various factors, such as nutrients, the gut microbiota, and microbial metabolites. • Recent trends include mechanisms among the gut microbiota, microbiota metabolites, and the intestine on HDP expression. • A comprehensive overview of mechanisms of HDP expression and gut microbiota-host interaction is provided.

Metabolic tug-of-war: Microbial metabolism shapes colonization resistance against enteric pathogens

A widely recognized benefit of gut microbiota is that it provides colonization resistance against enteric pathogens. The gut microbiota and their products can protect the host from invading microbes directly via microbe-pathogen interactions and indirectly by host-microbiota interactions, which regulate immune system function. In contrast, enteric pathogens have evolved mechanisms to utilize microbiota-derived metabolites to overcome colonization resistance and increase their pathogenic potential. This review will focus on recent studies of metabolism-mediated mechanisms of colonization resistance and virulence strategies enteric pathogens use to overcome them, along with how induction of inflammation by pathogenic bacteria changes the landscape of the gut and enables alternative metabolic pathways. We will focus on how intestinal pathogens counteract the protective effects of microbiota-derived metabolites to illustrate the growing appreciation of how metabolic factors may serve as crucial virulence determinants and overcome colonization resistance.

Xiaohuafuning tang intervenes liver-depression-and-spleen-deficiency syndrome chronic-atrophic-gastritis by reshaping amino acid metabolism through gut Microbiota

BACKGROUND

Xiaohua Funing Tang (XHFND) is a decoction formula of traditional Chinese medicine (TCM) and possesses the potential to manage chronic atrophic gastritis (CAG) with liver depression and spleen deficiency (LDSD), but the mechanisms were still unclear.

PURPOSE

Our aim is to reveal the overall synergistic mechanisms of XHFND against CAG with LDSD.

METHODS

Based on a CAG rat model with LDSD, this study combined metabolomics, gut microbiota, and network pharmacology techniques to demonstrate the XHFND mechanisms with multiple components and targets.

RESULTS

Through the integration analysis of gut microbiome and metabolome using metorigin, we found that XHFND regulates arginine metabolism levels in the urea cycle by regulating the gut ecological environment and the host. The XHFND mainly promotes aspartate 1 metabolism by regulating the abundance of odoribacter, bacteroides, phocaeicola, lachnospire, and intestinimonas, intervened in the imbalance of arginine metabolism in CAG rats with LDSD, suppresses the pathogenic Th17 cell differentiation, and inhibits the gastric mucosa damage in rats. Through Cytoscape analysis of network pharmacology and metabolomics integration, we found that XHFND might regulate host phospholipid metabolism through PTEN and PIK3CA to inhibit the PI3K-AKT-TSC axis and then inhibit mTORC1 to control arginine metabolism in the urea cycle and produce polyamines, thereby inhibiting the pathogenic Th17 cell differentiation and preventing rat gastric mucosa damage. Intervention in arginine metabolism in the urea cycle is the primary pathway in which XHFND exerts its therapeutic effects. XHFND may mainly control the pathogenic Th17 cell differentiation in the gastric mucosa of model rats through the pathway.

CONCLUSION

This study indicated that XHFND might intervene in treating CAG with LDSD from multiple levels and perspectives to suppress the pathogenic Th17 cell differentiation, which aligns with the characteristics of TCM treatment. This study presents experimental evidence for the clinical use of XHFND and promotes the development of drugs for the therapy of CAG with LDSD.

MMETHANE: interpretable AI for predicting host status from microbial composition and metabolomics data

Metabolite production, consumption, and exchange are intimately involved with host health and disease, as well as being key drivers of host-microbiome interactions. Despite the increasing prevalence of datasets that jointly measure microbiome composition and metabolites, computational tools for linking these data to the status of the host remain limited. To address these limitations, we developed MMETHANE, an open-source software package that implements a purpose-built deep learning model for predicting host status from paired microbial sequencing and metabolomic data. MMETHANE incorporates prior biological knowledge, including phylogenetic and chemical relationships, and is intrinsically interpretable, outputting an English-language set of rules that explains its decisions. Using a compendium of six datasets with paired microbial composition and metabolomics measurements, we showed that MMETHANE always performed at least on par with existing methods, including blackbox machine learning techniques, and outperformed other methods on >80% of the datasets evaluated. We additionally demonstrated through two cases studies analyzing inflammatory bowel disease gut microbiome datasets that MMETHANE uncovers biologically meaningful links between microbes, metabolites, and disease status.

Randomized Clinical Trials Demonstrate the Safety Assessment of Alkalihalobacillus clausii AO1125 for Use as a Probiotic in Humans

(1) Background: Alkalihalobacillus clausii AO1125 is a Gram-positive, motile, spore-forming bacterium with potential as a probiotic due to its broad-spectrum antimicrobial activity, inhibiting pathogens like Listeria monocytogenes, Staphylococcus aureus, and Clostridium difficile, as well as anti-rotavirus activity. Its resilience in gastrointestinal conditions suggests benefits for gut health. This study evaluates the safety and probiotic potential of A. clausii AO1125. (2) Methods: Genome annotation identified genes linked to probiotic traits such as stress resistance, gut colonization, immune modulation, and antimicrobial production. The genome was screened for antibiotic resistance genes using CARD, bacteriocin clusters using BAGEL4, and virulence factors via VFDB. Cytotoxicity was assessed on Vero cells and erythrocytes, and a Phase I, double-blind, placebo-controlled clinical trial was conducted with 99 healthy volunteers (50 AO1125, 49 placebo). (3) Results: Genomic analysis confirmed minimal antibiotic resistance genes and the absence of virulence factors, supporting safety. A. clausii AO1125 showed no pathogenicity, cytotoxicity, or hemolytic activity and was well-tolerated in clinical settings, with mild, transient abdominal gas as the most common adverse event. (4) Conclusions: The safety profile and genetic basis for probiotic and antimicrobial properties support A. clausii AO1125 as a promising probiotic candidate for gastrointestinal health, warranting further clinical research.

Bacterial amino acid chemotaxis: a widespread strategy with multiple physiological and ecological roles

Chemotaxis is the directed, flagellum-based movement of bacteria in chemoeffector gradients. Bacteria respond chemotactically to a wide range of chemoeffectors, including amino, organic, and fatty acids, sugars, polyamines, quaternary amines, purines, pyrimidines, aromatic hydrocarbons, oxygen, inorganic ions, or polysaccharides. Most frequent are chemotactic responses to amino acids (AAs), which were observed in numerous bacteria regardless of their phylogeny and lifestyle. Mostly chemoattraction responses are observed, although a number of bacteria are repelled from certain AAs. Chemoattraction is associated with the important metabolic value of AAs as growth substrates or building blocks of proteins. However, additional studies revealed that AAs are also sensed as environmental cues. Many chemoreceptors are specific for AAs, and signaling is typically initiated by direct ligand binding to their four-helix bundle or dCache ligand-binding domains. Frequently, bacteria possess multiple AA-responsive chemoreceptors that at times possess complementary AA ligand spectra. The identification of sequence motifs in the binding sites at dCache_1 domains has permitted to define an AA-specific family of dCache_1AA chemoreceptors. In addition, AAs are among the ligands recognized by broad ligand range chemoreceptors, and evidence was obtained for chemoreceptor activation by the binding of AA-loaded solute-binding proteins. The biological significance of AA chemotaxis is very ample including in biofilm formation, root and seed colonization by beneficial bacteria, plant entry of phytopathogens, colonization of the intestine, or different virulence-related features in human/animal pathogens. This review provides insights that may be helpful for the study of AA chemotaxis in other uncharacterized bacteria.

Environmental Driving of Adaptation Mechanism on Rumen Microorganisms of Sheep Based on Metagenomics and Metabolomics Data Analysis

Natural or artificial selection causes animals to adapt to their environment. The adaptive changes generated by the rumen population and metabolism form the basis of ruminant evolution. In particular, the adaptive drive for environmental adaptation reflects the high-quality traits of sheep that have migrated from other places or have been distant from their origins for a long time. The Hu sheep is the most representative sheep breed in the humid and low-altitude environments (Tai Lake region) in East Asia and has been widely introduced into the arid and high-altitude environments (Tibetan Plateau and Hotan region), resulting in environmental adaptive changes in the Hu sheep. In this study, a joint analysis of the rumen microbial metagenome and metabolome was conducted on Hu sheep from different regions (area of origin and area of introduction) with the objective of investigating the quality traits of Hu sheep and identifying microorganisms that influence the adaptive drive of ruminants. The results demonstrated that the growth performance of Hu sheep was altered due to changes in rumen tissue and metabolism following their introduction to the arid area at relatively high altitude. Metagenomic and metabolomic analyses (five ramsper area) revealed that 3580 different microorganisms and 732 different metabolites were identified in the rumen fluid of arid sheep. Among these, the representative upregulated metabolites were 4,6-isocanedione, methanesulfonic acid and N2-succinyl-L-arginine, while the dominant microorganism was Prevotella ruminicola. The downregulated metabolites were identified as campesterol, teprenone and dihydroclavaminic acid, while the disadvantaged microorganisms were Dialister_succinatiphilus, Prevotella_sp._AGR2160, Prevotella_multisaccharivorax and Selenomonas_bovis. The results of the Pearson analysis indicated that the rumen microbiota and metabolite content of sheep were significantly altered and highly correlated following their relocation from a humid lowland to an arid upland. In particular, the observed changes in rumen microorganisms led to an acceleration of body metabolism, rendering sheep highly adaptable to environmental stress. Prevotella_ruminicola was identified as playing an important role in this process. These findings provide insights into the environmental adaptation mechanisms of sheep.

Deciphering relationship between depression and microbial molecules based on multi-omics: A case study of Chaigui Granules

Objective

To decipher the antidepression effect of Chaigui Granules (CGKL) from the relationship between depression and microbial molecules based on multi-omics.

Methods

Male SD rats were subjected to chronic unpredictable mild stress (CUMS) for seven weeks. The antidepressants CGKL extract and CGKL were administered for the following four weeks. The behavior test and the content of monoamine neurotransmitters were used to evaluate the efficacy of CGKL. The 16S rRNA sequencing, LC-MS technology and molecular biological techniques were used to explore the pharmacological mechanism of CGKL.

Results

CGKL treatment obviously alleviated the depressive behavioral indicators and regulated the content of monoamine neurotransmitters, and presented dose-dependent manner. CGKL could also improve the arginine metabolism disorder of gut microbiota in the jejunum. Meanwhile, the contents of arginine and its metabolites in the serum and hippocampus were regulated to normal levels. Further investigation indicated that the expression of related rate-limiting enzyme genes and proteins in the hippocampus was validated by qRT-PCR and Western blotting. The results showed that the gut microbiota, metabolites, and genes or proteins of rate-limiting enzymes involved in the arginine pathway were significantly regulated by CGKL.

Conclusion

The present study demonstrates that CGKL might exert antidepressant effects through regulating arginine metabolism, and its mechanism may be related to modulating the gut microbiota and related metabolic enzyme.

Productive and metabolomic consequences of arginine supplementation in sows during different gestation periods in two different seasons

BACKGROUND

The prolificacy of sows (litter size at birth) has markedly increased, leading to higher post-natal mortality. Heat stress can exacerbate this issue. Arginine plays an important role in several physiological pathways; its effect on gestating sows can depend on the period of supplementation. This study evaluated the effects of arginine supplementation on the productive performance and physiological status of sows during different gestation periods and seasons, using a multi-omics approach.

METHODS

A total of 320 sows were divided into 4 groups over 2 seasons (warm/cold); a control group (CO) received a standard diet (including 16.5 g/d of arginine) and 3 other groups received the standard diet supplemented with 21.8 g/d of arginine (38.3 g/d of arginine) either during the first 35 d (Early35), the last 45 d (Late45) or throughout the entire gestation period (COM). The colostrum was analyzed for nutritional composition, immunoglobulins and metabolomic profile. Urine and feces were analyzed on d 35 and 106 for the metabolomic and microbial profiles. Piglet body weight and mortality were recorded at birth, d 6, d 26, and on d 14 post-weaning.

RESULTS

Interactions between arginine and season were never significant. The Early35 group had a lower percentage of stillborn (P < 0.001), mummified (P = 0.002) and low birthweight (LBW) piglets (P = 0.02) than the CO group. The Late45 group had a lower percentage of stillborn piglets (P = 0.029) and a higher percentage of high birthweight piglets (HBW; P < 0.001) than the CO group. The COM group had a higher percentage of LBW (P = 0.004) and crushed piglets (P < 0.001) than the CO group. Arginine supplementation modifies the metabolome characterization of colostrum, urine, and feces. Creatine and nitric oxide pathways, as well as metabolites related to microbial activity, were influenced in all matrices. A slight trend in the beta diversity index was observed in the microbiome profile on d 35 (P = 0.064).

CONCLUSIONS

Arginine supplementation during early gestation reduced the percentage of stillborn and LBW piglets, while in the last third of pregnancy, it favored the percentage of HBW pigs and reduced the percentage of stillbirths, showing that arginine plays a significant role in the physiology of pregnant sows.

The arginine and nitric oxide metabolic pathway regulate the gut colonization and expansion of Ruminococcous gnavus

Ruminococcus gnavus is a mucolytic commensal bacterium whose increased gut colonization has been associated with chronic inflammatory and metabolic diseases in humans. Whether R. gnavus metabolites can modulate host intestinal physiology remains largely understudied. We performed untargeted metabolomic and bulk RNA-seq analyses using R. gnavus monocolonization in germ-free mice. Based on transcriptome-metabolome correlations, we tested the impact of specific arginine metabolites on intestinal epithelial production of nitric oxide (NO) and examined the effect of NO on the growth of various strains of R. gnavus in vitro and in nitric oxide synthase 2 (Nos2)-deficient mice. R. gnavus produces specific arginine, tryptophan, and tyrosine metabolites, some of which are regulated by the environmental richness of sialic acid and mucin. R. gnavus colonization promotes expression of amino acid transporters and enzymes involved in metabolic flux of arginine and associated metabolites into NO. R. gnavus induced elevated levels of NOS2, while Nos2 ablation resulted in R. gnavus expansion in vivo. The growth of various R. gnavus strains can be inhibited by NO. Specific R. gnavus metabolites modulate intestinal epithelial cell NOS2 abundance and reduce epithelial barrier function at higher concentrations. Intestinal colonization and interaction with R. gnavus are partially regulated by an arginine-NO metabolic pathway, whereby a balanced control by the gut epithelium may restrain R. gnavus growth in healthy individuals. Disruption in this arginine metabolic regulation will contribute to the expansion and blooming of R. gnavus.

Microbiome and metabolome analyses indicate variations in the gut microbiota that disrupt regulation of appetite

The mechanism connecting gut microbiota to appetite regulation is not yet fully understood. This study identifies specific microbial community and metabolites that may influence appetite regulation. In the initial phase of the study, mice were administered a broad-spectrum antibiotic cocktail (ABX) for 10 days. The treatment significantly reduced gut microbes and disrupted the metabolism of arginine and tryptophan. Consequently, ABX-treated mice demonstrated a notable reduction in feed consumption. The hypothalamic expression levels of CART and POMC, two key anorexigenic factors, were significantly increased, while orexigenic factors, such as NPY and AGRP, were decreased. Notably, the levels of appetite-suppressing hormone cholecystokinin in the blood were significantly elevated. In the second phase, control mice were maintained, while the ABX-treated mice received saline, probiotics, and short-chain fatty acids (SCFAs) for an additional 10 days to restore their gut microbiota. The microbiota reconstructed by probiotic and SCFA treatments were quite similar, while microbiota of the naturally recovering mice demonstrated greater resemblance to that of the control mice. Notably, the abundance of Akkermansia and Bacteroides genera significantly increased in the reconstructed microbiota. Moreover, microbiota reconstruction corrected the disrupted arginine and tryptophan metabolism and the abnormal peripheral hormone levels caused by ABX treatment. Among the groups, SCFA-treated mice had the highest feed intake and NPY expression. Our findings indicate that gut microbes, especially Akkermansia, regulate arginine and tryptophan metabolism, thereby influencing appetite through the microbe-gut-brain axis.

Autophagy: Are Amino Acid Signals Dependent on the mTORC1 Pathway or Independent?

Autophagy is a kind of "self-eating" phenomenon that is ubiquitous in eukaryotic cells. It mainly manifests in the damaged proteins or organelles in the cell being wrapped and transported by the autophagosome to the lysosome for degradation. Many factors cause autophagy in cells, and the mechanism of nutrient-deficiency-induced autophagy has been a research focus. It has been reported that amino-acid-deficiency-induced cellular autophagy is mainly mediated through the mammalian rapamycin target protein complex 1 (mTORC1) signaling pathway. In addition, some researchers also found that non-mTORC1 signaling pathways also regulate autophagy, and the mechanism of autophagy occurrence induced by the deficiency of different amino acids is not precisely the same. Therefore, this review aims to summarize the process of various amino acids regulating cell autophagy and provide a narrative review on the molecular mechanism of amino acids regulating autophagy.

Harnessing CD8+ T cell dynamics in hepatitis B virus-associated liver diseases: Insights, therapies and future directions

Hepatitis B virus (HBV) infection playsa significant role in the etiology and progression of liver-relatedpathologies, encompassing chronic hepatitis, fibrosis, cirrhosis, and eventual hepatocellularcarcinoma (HCC). Notably, HBV infection stands as the primary etiologicalfactor driving the development of HCC. Given the significant contribution ofHBV infection to liver diseases, a comprehensive understanding of immunedynamics in the liver microenvironment, spanning chronic HBV infection,fibrosis, cirrhosis, and HCC, is essential. In this review, we focused on thefunctional alterations of CD8+ T cells within the pathogenic livermicroenvironment from HBV infection to HCC. We thoroughly reviewed the roles ofhypoxia, acidic pH, metabolic reprogramming, amino acid deficiency, inhibitory checkpointmolecules, immunosuppressive cytokines, and the gut-liver communication in shapingthe dysfunction of CD8+ T cells in the liver microenvironment. Thesefactors significantly impact the clinical prognosis. Furthermore, we comprehensivelyreviewed CD8+ T cell-based therapy strategies for liver diseases,encompassing HBV infection, fibrosis, cirrhosis, and HCC. Strategies includeimmune checkpoint blockades, metabolic T-cell targeting therapy, therapeuticT-cell vaccination, and adoptive transfer of genetically engineered CD8+ T cells, along with the combined usage of programmed cell death protein-1/programmeddeath ligand-1 (PD-1/PD-L1) inhibitors with mitochondria-targeted antioxidants.Given that targeting CD8+ T cells at various stages of hepatitis Bvirus-induced hepatocellular carcinoma (HBV + HCC) shows promise, we reviewedthe ongoing need for research to elucidate the complex interplay between CD8+ T cells and the liver microenvironment in the progression of HBV infection toHCC. We also discussed personalized treatment regimens, combining therapeuticstrategies and harnessing gut microbiota modulation, which holds potential forenhanced clinical benefits. In conclusion, this review delves into the immunedynamics of CD8+ T cells, microenvironment changes, and therapeuticstrategies within the liver during chronic HBV infection, HCC progression, andrelated liver diseases.

Tributyrin Supplementation Rescues Chronic-Binge Ethanol-Induced Oxidative Stress in the Gut-Lung Axis in Mice

Excessive alcohol consumption increases the severity and worsens outcomes of pulmonary infections, often due to oxidative stress and tissue damage. While the mechanism behind this relationship is multifaceted, recent evidence suggests ethanol-induced changes to the gut microbiome impact the gut-lung axis. To assess this, a chronic-binge ethanol feeding mouse model was used to determine how ethanol altered the gut microbiome, small intestinal epithelial barrier, and immune responses, as well as neutrophil abundance and oxidative stress in the lungs, and how supporting gut health with tributyrin supplementation during chronic-binge ethanol exposure affected these responses. We found that ethanol consumption altered gut bacterial taxa and metabolic processes, distorted small intestinal immune responses, and induced both bacteria and endotoxin translocation into the lymphatic and circulatory systems. These changes were associated with increased neutrophil (Ly6G) presence and markers of oxidative stress, lipocalin-2 and myeloperoxidase, in the lungs. Importantly, tributyrin supplementation during ethanol exposure rescued gut bacterial function (p < 0.05), small intestinal barrier integrity, and immune responses, as well as reducing both Ly6G mRNA (p < 0.05) and lipocalin-2 mRNA (p < 0.01) in the lungs. These data suggest ethanol-associated disruption of gut homeostasis influenced the health of the lungs, and that therapeutics supporting gut health may also support lung health.

Intestine proteomic and metabolomic alterations in dogs infected with Toxocara canis

Toxocariasis is an important zoonotic parasitic disease. Toxocaris canis adults live and reproduce in the intestinal tract of dogs and other canine hosts, and the infectious eggs are continuously excreted in feces, which causes environmental contamination and has an important public health significance. In this study, TMT proteomic and untargeted metabolomic methods were used to explore the physiological and pathological effects on the intestinal tract of dogs which infected with T. canis, and a series of bioinformatics analyses were conducted to identify differentially expressed proteins (DEPs) and differentially expressed metabolites (DEMs). The proteomics results showed that 198 DEPs were mainly enriched in the immune system and signal transduction pathway, and involved in the regulation of the occurrence and development of cancer and infectious diseases. T. canis could disrupt intestinal permeability by increasing the expression of proteins such as zinc finger protein DZIP1L and myosin heavy chain 10. Additionally, T. canis infection could also inhibit the host immune response by decreasing the expression of MHC-II, NF-κB, DLA and other immune-related molecules. While, the metabolomics results revealed that the expression of oxoglutaric acid, glutamate, d-aspartate, arginine, taurochenodeoxycholic acid and taurocholic acid which participated in tricarboxylic acid (TCA) cycle, glycolysis/gluconeogenesis, bile secretion, biosynthesis of amino acids pathway were significantly decreased. The correlation results of proteomics and metabolomics showed that DEPs and DEMs were mainly co-enriched in bile secretion pathway to regulate intestinal peristalsis. Analyzing DEPs and DEMs will not only provide insights into the mechanisms of host parasite interaction, but also aid in identifying potential targets for therapy and diagnosis, thus setting the groundwork for effectively preventing and managing toxocariasis.

Characterizing arginine, ornithine, and putrescine pathways in enteric pathobionts

Arginine-ornithine metabolism plays a crucial role in bacterial homeostasis, as evidenced by numerous studies. However, the utilization of arginine and the downstream products of its metabolism remain undefined in various gut bacteria. To bridge this knowledge gap, we employed genomic screening to pinpoint relevant metabolic targets. We also devised a targeted liquid chromatography-tandem mass spectrometry (LC-MS/MS) metabolomics method to measure the levels of arginine, its upstream precursors, and downstream products in cell-free conditioned media from enteric pathobionts, including Escherichia coli, Klebsiella aerogenes, K. pneumoniae, Pseudomonas fluorescens, Acinetobacter baumannii, Streptococcus agalactiae, Staphylococcus epidermidis, S. aureus, and Enterococcus faecalis. Our findings revealed that all selected bacterial strains consumed glutamine, glutamate, and arginine, and produced citrulline, ornithine, and GABA in our chemically defined medium. Additionally, E. coli, K. pneumoniae, K. aerogenes, and P. fluorescens were found to convert arginine to agmatine and produce putrescine. Interestingly, arginine supplementation promoted biofilm formation in K. pneumoniae, while ornithine supplementation enhanced biofilm formation in S. epidermidis. These findings offer a comprehensive insight into arginine-ornithine metabolism in enteric pathobionts.

Targeted arginine metabolomics combined with metagenomics revealed the potential mechanism of Pueraria lobata extract in treating myocardial infarction

The extraction methods for traditional Chinese medicine (TCM) may have varying therapeutic effects on diseases. Currently, Pueraria lobata (PL) is mostly extracted with ethanol, but decoction, as a TCM extraction method, is not widely adopted. In this study, we present a strategy that integrates targeted metabolomics, 16 s rDNA sequencing technology and metagenomics for exploring the potential mechanism of the water extract of PL (PLE) in treating myocardial infarction (MI). Using advanced analytical techniques like ultra-high performance liquid chromatography with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) and ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), we comprehensively characterized PLE's chemical composition. Further, we tested its efficacy in a rat model of MI induced by ligation of the left anterior descending branch of the coronary artery (LAD). We assessed cardiac enzyme levels and conducted echocardiograms. UPLC-MS/MS was used to compare amino acid differences in serum. Furthermore, we investigated fecal samples using 16S rDNA sequencing and metagenomic sequencing to study intestinal flora diversity and function. This study demonstrated PLE's effectiveness in reducing cardiac injury in LAD-ligated rats. Amino acid metabolomics revealed significant improvements in serum levels of arginine, citrulline, proline, ornithine, creatine, creatinine, and sarcosine in MI rats, which are key compounds in the arginine metabolism pathway. Enzyme-linked immunosorbent assay (ELISA) results showed that PLE significantly improved arginase (Arg), nitric oxide synthase (NOS), and creatine kinase (CK) contents in the liver tissue of MI rats. 16 s rDNA and metagenome sequencing revealed that PLE significantly improved intestinal flora imbalance in MI rats, particularly in taxa such as Tuzzerella, Desulfovibrio, Fournierella, Oscillibater, Harryflintia, and Holdemania. PLE also improved the arginine metabolic pathway in the intestinal microorganisms of MI rats. The findings indicate that PLE effectively modulates MI-induced arginine levels and restores intestinal flora balance. This study, the first to explore the mechanism of action of PLE in MI treatment considering amino acid metabolism and intestinal flora, expands our understanding of the potential of PL in MI treatment. It offers fresh insights into the mechanisms of PL, guiding further research and development of PL-based medicines.

The strain-dependent cytostatic activity of Lactococcus lactis on CRC cell lines is mediated through the release of arginine deiminase

BACKGROUND

Colorectal cancer (CRC) is one of the most commonly diagnosed cancers, posing a serious public health challenge that necessitates the development of new therapeutics, therapies, and prevention methods. Among the various therapeutic approaches, interventions involving lactic acid bacteria (LAB) as probiotics and postbiotics have emerged as promising candidates for treating and preventing CRC. While human-isolated LAB strains are considered highly favorable, those sourced from environmental reservoirs such as dairy and fermented foods are also being recognized as potential sources for future therapeutics.

RESULTS

In this study, we present a novel and therapeutically promising strain, Lactococcus lactis ssp. lactis Lc4, isolated from dairy sources. Lc4 demonstrated the ability to release the cytostatic agent - arginine deiminase (ADI) - into the post-cultivation supernatant when cultured under conditions mimicking the human gut environment. Released arginine deiminase was able to significantly reduce the growth of HT-29 and HCT116 cells due to the depletion of arginine, which led to decreased levels of c-Myc, reduced phosphorylation of p70-S6 kinase, and cell cycle arrest. The ADI release and cytostatic properties were strain-dependent, as was evident from comparison to other L. lactis ssp. lactis strains.

CONCLUSION

For the first time, we unveil the anti-proliferative properties of the L. lactis cell-free supernatant (CFS), which are independent of bacteriocins or other small molecules. We demonstrate that ADI, derived from a dairy-Generally Recognized As Safe (GRAS) strain of L. lactis, exhibits anti-proliferative activity on cell lines with different levels of argininosuccinate synthetase 1 (ASS1) expression. A unique feature of the Lc4 strain is also its capability to release ADI into the extracellular space. Taken together, we showcase L. lactis ADI and the Lc4 strain as promising, potential therapeutic agents with broad applicability.

Oral streptococci S. anginosus and S. mitis induce distinct morphological, inflammatory, and metabolic signatures in macrophages

Oral streptococci, key players in oral biofilm formation, are implicated in oral dysbiosis and various clinical conditions, including dental caries, gingivitis, periodontal disease, and oral cancer. Specifically, Streptococcus anginosus is associated with esophageal, gastric, and pharyngeal cancers, while Streptococcus mitis is linked to oral cancer. However, no study has investigated the mechanistic links between these Streptococcus species and cancer-related inflammatory responses. As an initial step, we probed the innate immune response triggered by S. anginosus and S. mitis in RAW264.7 macrophages. These bacteria exerted time- and dose-dependent effects on macrophage morphology without affecting cell viability. Compared with untreated macrophages, macrophages infected with S. anginosus exhibited a robust proinflammatory response characterized by significantly increased levels of inflammatory cytokines and mediators, including TNF, IL-6, IL-1β, NOS2, and COX2, accompanied by enhanced NF-κB activation. In contrast, S. mitis-infected macrophages failed to elicit a robust inflammatory response. Seahorse Xfe96 analysis revealed an increased extracellular acidification rate in macrophages infected with S. anginosus compared with S. mitis. At the 24-h time point, the presence of S. anginosus led to reduced extracellular itaconate, while S. mitis triggered increased itaconate levels, highlighting distinct metabolic profiles in macrophages during infection in contrast to aconitate decarboxylase expression observed at the 6-h time point. This initial investigation highlights how S. anginosus and S. mitis, two Gram-positive bacteria from the same genus, can prompt distinct immune responses and metabolic shifts in macrophages during infection.IMPORTANCEThe surge in head and neck cancer cases among individuals devoid of typical risk factors such as Human Papilloma Virus (HPV) infection and tobacco and alcohol use sparks an argumentative discussion around the emerging role of oral microbiota as a novel risk factor in oral squamous cell carcinoma (OSCC). While substantial research has dissected the gut microbiome's influence on physiology, the oral microbiome, notably oral streptococci, has been underappreciated during mucosal immunopathogenesis. Streptococcus anginosus, a viridans streptococci group, has been linked to abscess formation and an elevated presence in esophageal cancer and OSCC. The current study aims to probe the innate immune response to S. anginosus compared with the early colonizer Streptococcus mitis as an important first step toward understanding the impact of distinct oral Streptococcus species on the host immune response, which is an understudied determinant of OSCC development and progression.

Integrated gut microbiome and metabolome analysis reveals the inhibition effect of Lactobacillus plantarum CBT against colorectal cancer

The microecological stability of the gut microbiota plays a pivotal role in both preventing and treating colorectal cancer (CRC). This study investigated whether Lactobacillus plantarum CBT (LP-CBT) prevents CRC by inducing alterations in the gut microbiota composition and associated metabolites. The results showed that LP-CBT inhibited colorectal tumorigenesis in azoxymethane/dextran sulfate sodium (AOM/DSS)-treated mice by repairing the intestinal barrier function. Furthermore, LP-CBT decreased pro-inflammatory cytokines and anti-inflammatory cytokines. Importantly, LP-CBT remodeled intestinal homeostasis by increasing probiotics (Coprococcus, Mucispirillum, and Lactobacillus) and reducing harmful bacteria (Dorea, Shigella, Alistipes, Paraprevotella, Bacteroides, Sutterella, Turicibacter, Bifidobacterium, Clostridium, Allobaculum), significantly influencing arginine biosynthesis. Therefore, LP-CBT treatment regulated invertases and metabolites associated with the arginine pathway (carbamoyl phosphate, carboxymethyl proline, L-lysine, 10,11-epoxy-3-geranylgeranylindole, n-(6)-[(indol-3-yl)acetyl]-L-lysine, citrulline, N2-succinyl-L-ornithine, and (5-L-glutamyl)-L-glutamate). Furthermore, the inhibitory effect of LP-CBT on colorectal cancer was further confirmed using the MC38 subcutaneous tumor model. Collectively, these findings offer compelling evidence supporting the potential of LP-CBT as a viable preventive strategy against CRC.

Functional host-specific adaptation of the intestinal microbiome in hominids

Fine-scale knowledge of the changes in composition and function of the human gut microbiome compared that of our closest relatives is critical for understanding the evolutionary processes underlying its developmental trajectory. To infer taxonomic and functional changes in the gut microbiome across hominids at different timescales, we perform high-resolution metagenomic-based analyzes of the fecal microbiome from over two hundred samples including diverse human populations, as well as wild-living chimpanzees, bonobos, and gorillas. We find human-associated taxa depleted within non-human apes and patterns of host-specific gut microbiota, suggesting the widespread acquisition of novel microbial clades along the evolutionary divergence of hosts. In contrast, we reveal multiple lines of evidence for a pervasive loss of diversity in human populations in correlation with a high Human Development Index, including evolutionarily conserved clades. Similarly, patterns of co-phylogeny between microbes and hosts are found to be disrupted in humans. Together with identifying individual microbial taxa and functional adaptations that correlate to host phylogeny, these findings offer insights into specific candidates playing a role in the diverging trajectories of the gut microbiome of hominids. We find that repeated horizontal gene transfer and gene loss, as well as the adaptation to transient microaerobic conditions appear to have played a role in the evolution of the human gut microbiome.

Host-microbiota interaction in intestinal stem cell homeostasis

Intestinal stem cells (ISCs) play a pivotal role in gut physiology by governing intestinal epithelium renewal through the precise regulation of proliferation and differentiation. The gut microbiota interacts closely with the epithelium through myriad of actions, including immune and metabolic interactions, which translate into tight connections between microbial activity and ISC function. Given the diverse functions of the gut microbiota in affecting the metabolism of macronutrients and micronutrients, dietary nutrients exert pronounced effects on host-microbiota interactions and, consequently, the ISC fate. Therefore, understanding the intricate host-microbiota interaction in regulating ISC homeostasis is imperative for improving gut health. Here, we review recent advances in understanding host-microbiota immune and metabolic interactions that shape ISC function, such as the role of pattern-recognition receptors and microbial metabolites, including lactate and indole metabolites. Additionally, the diverse regulatory effects of the microbiota on dietary nutrients, including proteins, carbohydrates, vitamins, and minerals (e.g. iron and zinc), are thoroughly explored in relation to their impact on ISCs. Thus, we highlight the multifaceted mechanisms governing host-microbiota interactions in ISC homeostasis. Insights gained from this review provide strategies for the development of dietary or microbiota-based interventions to foster gut health.

Immunonutrients and intestinal microbiota: a gap in the literature

The human intestinal microbiota is composed of a wide variety of microorganisms that play an important role in intestinal permeability, digestion, and especially, in the maturation of host's immune system. At the same time, effectiveness of immunomodulatory nutrients is known, especially in situations of stress and in strengthening body's defenses. However, the influence of the use of immunonutrients on microbiota's composition and variability is still poorly investigated. Studies indicate that the use of immunomodulators such as omega 3, glutamine, and arginine, can play a role in its modulation, through the immunological enhancement of the hosts. Therefore, this article sought to concentrate the latest evidence on the influence of the use of the main immunonutrients used in clinical practice on human gut microbiota, and their potential benefits.