Lactobacillus GG and tributyrin supplementation reduce antibiotic-induced intestinal injury

Akkermansia muciniphila Protects Against Antibiotic-Associated Diarrhea in Mice

Probiotics are used to prevent antibiotic-associated diarrhea (AAD) via the restoration of the gut microbiota. However, the precise effects of Akkermansia muciniphila (Akk), which is a promising probiotics, on AAD are unknown. Here, AAD models were established via the administration of lincomycin and ampicillin with or without pasteurized Akk or Amuc_1100 treatment. A diffusion test revealed that Akk was susceptible to the majority of the antibiotics, such as ampicillin. These effects were confirmed by the reduced Akk abundance in AAD model mice. Pasteurized Akk or Amuc_1100 significantly decreased the diarrhea status score and colon injury of AAD model mice. Additionally, these treatments significantly decreased the relative abundance of Citrobacter at genus level and reshaped the metabolic function of gut microbiota. Notably, pasteurized Akk or Amuc_1100 significantly changed the serum metabolome of AAD model mice. In addition, pasteurized Akk or Amuc_1100 suppressed intestinal inflammation by upregulating the expression of GPR109A and SLC5A8 and downregulating the expression of TNFα, IFNγ, IL1β, and IL6. Furthermore, they enhanced water and electrolyte absorption by upregulating AQP4, SLC26A3, and NHE3. Pasteurized Akk or Amuc_1100 also restored intestinal barrier function by ameliorating the downregulation of ZO-1, OCLN, CLDN4, and Muc2 in AAD model mice. In summary, optimizing intestinal health with pasteurized Akk or Amuc_1100 may serve as an approach for preventing AAD.

Prevention and treatment of antibiotics-associated adverse effects through the use of probiotics: A review

BACKGROUND

The human gut hosts a diverse microbial community, essential for maintaining overall health. However, antibiotics, commonly prescribed for infections, can disrupt this delicate balance, leading to antibiotic-associated diarrhea, inflammatory bowel disease, obesity, and even neurological disorders. Recognizing this, probiotics have emerged as a promising strategy to counteract these adverse effects.

AIM OF REVIEW

This review aims to offer a comprehensive overview of the latest evidence concerning the utilization of probiotics in managing antibiotic-associated side effects.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Probiotics play a crucial role in preserving gut homeostasis, regulating intestinal function and metabolism, and modulating the host immune system. These mechanisms serve to effectively alleviate antibiotic-associated adverse effects and enhance overall well-being.

Two Enterococcus faecium Isolates Demonstrated Modulating Effects on the Dysbiosis of Mice Gut Microbiota Induced by Antibiotic Treatment

Broad-spectrum antibiotics are frequently used to treat bacteria-induced infections, but the overuse of antibiotics may induce the gut microbiota dysbiosis and disrupt gastrointestinal tract function. Probiotics can be applied to restore disturbed gut microbiota and repair abnormal intestinal metabolism. In the present study, two strains of Enterococcus faecium (named DC-K7 and DC-K9) were isolated and characterized from the fecal samples of infant dogs. The genomic features of E. faecium DC-K7 and DC-K9 were analyzed, the carbohydrate-active enzyme (CAZyme)-encoding genes were predicted, and their abilities to produce short-chain fatty acids (SCFAs) were investigated. The bacteriocin-encoding genes in the genome sequences of E. faecium DC-K7 and DC-K9 were analyzed, and the gene cluster of Enterolysin-A, which encoded a 401-amino-acid peptide, was predicted. Moreover, the modulating effects of E. faecium DC-K7 and DC-K9 on the gut microbiota dysbiosis induced by antibiotics were analyzed. The current results demonstrated that oral administrations of E. faecium DC-K7 and DC-K9 could enhance the relative abundances of beneficial microbes and decrease the relative abundances of harmful microbes. Therefore, the isolated E. faecium DC-K7 and DC-K9 were proven to be able to alter the gut microbiota dysbiosis induced by antibiotic treatment.

Gut-liver axis: Recent concepts in pathophysiology in alcohol-associated liver disease

The growing recognition of the role of the gut microbiome's impact on alcohol-associated diseases, especially in alcohol-associated liver disease, emphasizes the need to understand molecular mechanisms involved in governing organ-organ communication to identify novel avenues to combat alcohol-associated diseases. The gut-liver axis refers to the bidirectional communication and interaction between the gut and the liver. Intestinal microbiota plays a pivotal role in maintaining homeostasis within the gut-liver axis, and this axis plays a significant role in alcohol-associated liver disease. The intricate communication between intestine and liver involves communication between multiple cellular components in each organ that enable them to carry out their physiological functions. In this review, we focus on novel approaches to understanding how chronic alcohol exposure impacts the microbiome and individual cells within the liver and intestine, as well as the impact of ethanol on the molecular machinery required for intraorgan and interorgan communication.

Autoinducer-2 promotes the colonization of Lactobacillus rhamnosus GG to improve the intestinal barrier function in a neonatal mouse model of antibiotic-induced intestinal dysbiosis

BACKGROUND

Human health is seriously threatened by antibiotic-induced intestinal disorders. Herein, we aimed to determine the effects of Autoinducer-2 (AI-2) combined with Lactobacillus rhamnosus GG (LGG) on the intestinal barrier function of antibiotic-induced intestinal dysbiosis neonatal mice.

METHODS

An antibiotic-induced intestinal dysbiosis neonatal mouse model was created using antibiotic cocktails, and the model mice were randomized into the control, AI-2, LGG, and LGG + AI-2 groups. Intestinal short-chain fatty acids and AI-2 concentrations were detected by mass spectrometry and chemiluminescence, respectively. The community composition of the gut microbiota was analyzed using 16S rDNA sequencing, and biofilm thickness and bacterial adhesion in the colon were assessed using scanning electron microscopy. Transcriptome RNA sequencing of intestinal tissues was performed, and the mRNA and protein levels of HCAR2 (hydroxycarboxylic acid receptor 2), claudin3, and claudin4 in intestinal tissues were determined using quantitative real-time reverse transcription PCR and western blotting. The levels of inflammatory factors in intestinal tissues were evaluated using enzyme-linked immunosorbent assays (ELISAs). D-ribose, an inhibitor of AI-2, was used to treat Caco-2 cells in vitro.

RESULTS

Compared with the control, AI-2, and LGG groups, the LGG + AI-2 group showed increased levels of intestinal AI-2 and proportions of Firmicutes and Lacticaseibacillus, but a reduced fraction of Proteobacteria. Specifically, the LGG + AI-2 group had considerably more biofilms and LGG on the colon surface than those of other three groups. Meanwhile, the combination of AI-2 and LGG markedly increased the concentration of butyric acid and promoted Hcar2, claudin3 and claudin4 expression levels compared with supplementation with LGG or AI-2 alone. The ELISAs revealed a significantly higher tumor necrosis factor alpha (TNF-α) level in the control group than in the LGG and LGG + AI-2 groups, whereas the interleukin 10 (IL-10) level was significantly higher in the LGG + AI-2 group than in the other three groups. In vitro, D-ribose treatment dramatically suppressed the increased levels of Hcar2, claudin3, and claudin4 in Caco-2 cells induced by AI-2 + LGG.

CONCLUSIONS

AI-2 promotes the colonization of LGG and biofilm formation to improve intestinal barrier function in an antibiotic-induced intestinal dysbiosis neonatal mouse model.

The Postbiotic Butyrate Mitigates Gut Mucosal Disruption Caused by Acute Ethanol Exposure

We aimed to test how the postbiotic butyrate impacts select gut bacteria, small intestinal epithelial integrity, and microvascular endothelial activation during acute ethanol exposure in mice and primary human intestinal microvascular endothelial cells (HIMECs). Supplementation during an acute ethanol challenge with or without tributyrin, a butyrate prodrug, was delivered to C57BL/6 mice. A separate group of mice received 3 days of clindamycin prior to the acute ethanol challenge. Upon euthanasia, blood endotoxin, cecal bacteria, jejunal barrier integrity, and small intestinal lamina propria dendritic cells were assessed. HIMECs were tested for activation following exposure to ethanol ± lipopolysaccharide (LPS) and sodium butyrate. Tributyrin supplementation protected a butyrate-generating microbe during ethanol and antibiotic exposure. Tributyrin rescued ethanol-induced disruption in jejunal epithelial barrier, elevated plasma endotoxin, and increased mucosal vascular addressin cell-adhesion molecule-1 (MAdCAM-1) expression in intestinal microvascular endothelium. These protective effects of tributyrin coincided with a tolerogenic dendritic response in the intestinal lamina propria. Lastly, sodium butyrate pre- and co-treatment attenuated the direct effects of ethanol and LPS on MAdCAM-1 induction in the HIMECs from a patient with ulcerative colitis. Tributyrin supplementation protects small intestinal epithelial and microvascular barrier integrity and modulates microvascular endothelial activation and dendritic tolerizing function during a state of gut dysbiosis and acute ethanol challenge.

Multiomics Strategy Reveals the Mechanism of Action and Ameliorating Effect of Deer Velvet Antler Water Extracts on DSS-Induced Colitis

Velvet antler is a precious traditional Chinese medicine used for thousands of years. This study investigated the anti-colitis effects of water extracts of Formosan sambar deer (SVAE) and red deer (RVAE) to identify the possible mechanisms and the bioactive compounds using a dextran sulfate sodium (DSS)-induced colitis mouse model. The mechanism of action and the ameliorating effects of SVAE and RVAE on DSS-induced colitis were evaluated using a mouse model. Ultra-high performance liquid chromatography-mass/mass and gas chromatography-mass/mass were applied to identify the bioactive components of the SVAE and RVAE water extracts. The results revealed that both high-dose SVAE and RVAE could ameliorate the symptoms of colitis due to reduced systemic inflammatory responses, enhanced intestinal barrier integrity by restoration of tight junction proteins, and improved gut dysbiosis. The potentially bioactive components of SVAE and RVAE were identified as small molecules (<3 kDa). Further identification by untargeted metabolomics analysis suggested that l-carnitine, hypoxanthine, adrenic acid, creatinine, gamma-aminobutyric-lysine, oleic acid, glycine, poly-γ-glutamic acid, and eicosapentaenoic acid in VAWEs might be involved in ameliorating the symptoms of colitis. This study provided evidence for the potential usage of SVAE and RVAE as anti-colitis agents.

Lacticaseibacillus rhamnosus ATCC 53103 and Limosilactobacillus reuteri ATCC 53608 Synergistically Boost Butyrate Levels upon Tributyrin Administration Ex Vivo

Modulation of the gut microbiota is a trending strategy to improve health. While butyrate has been identified as a key health-related microbial metabolite, managing its supply to the host remains challenging. Therefore, this study investigated the potential to manage butyrate supply via tributyrin oil supplementation (TB; glycerol with three butyrate molecules) using the ex vivo SIFR® (Systemic Intestinal Fermentation Research) technology, a highly reproducible, in vivo predictive gut model that accurately preserves in vivo-derived microbiota and enables addressing interpersonal differences. Dosing 1 g TB/L significantly increased butyrate with 4.1 (±0.3) mM, corresponding with 83 ± 6% of the theoretical butyrate content of TB. Interestingly, co-administration of Limosilactobacillus reuteri ATCC 53608 (REU) and Lacticaseibacillus rhamnosus ATCC 53103 (LGG) markedly enhanced butyrate to levels that exceeded the theoretical butyrate content of TB (138 ± 11% for REU; 126 ± 8% for LGG). Both TB + REU and TB + LGG stimulated Coprococcus catus, a lactate-utilizing, butyrate-producing species. The stimulation of C. catus with TB + REU was remarkably consistent across the six human adults tested. It is hypothesized that LGG and REU ferment the glycerol backbone of TB to produce lactate, a precursor of butyrate. TB + REU also significantly stimulated the butyrate-producing Eubacterium rectale and Gemmiger formicilis and promoted microbial diversity. The more potent effects of REU could be due to its ability to convert glycerol to reuterin, an antimicrobial compound. Overall, both the direct butyrate release from TB and the additional butyrate production via REU/LGG-mediated cross-feeding were highly consistent. This contrasts with the large interpersonal differences in butyrate production that are often observed upon prebiotic treatment. Combining TB with LGG and especially REU is thus a promising strategy to consistently supply butyrate to the host, potentially resulting in more predictable health benefits.

Advances in Lactobacillus Restoration for β-Lactam Antibiotic-Induced Dysbiosis: A System Review in Intestinal Microbiota and Immune Homeostasis

A balanced gut microbiota and their metabolites are necessary for the maintenance of the host's health. The antibiotic-induced dysbiosis can cause the disturbance of the microbial community, influence the immune homeostasis and induce susceptibility to metabolic- or immune-mediated disorders and diseases. The Lactobacillus and their metabolites or components affect the function of the host's immune system and result in microbiota-mediated restoration. Recent data have indicated that, by altering the composition and functions of gut microbiota, antibiotic exposure can also lead to a number of specific pathologies, hence, understanding the potential mechanisms of the interactions between gut microbiota dysbiosis and immunological homeostasis is very important. The Lactobacillus strategies for detecting the associations between the restoration of the relatively imbalanced microbiome and gut diseases are provided in this discussion. In this review, we discuss the recently discovered connections between microbial communities and metabolites in the Lactobacillus treatment of β-lactam antibiotic-induced dysbiosis, and establish the relationship between commensal bacteria and host immunity under this imbalanced homeostasis of the gut microbiota.

The Relationship Between Atrial Fibrillation and Intestinal Flora With Its Metabolites

Atrial fibrillation (AF) is characterized by high morbidity and disability rate. The incidence of AF has rapidly increased due to increased aging population, causing a serious burden on society and patients. Therefore, it is necessary to determine the prevention and treatment of AF. Several studies have assessed the occurrence, development mechanism, and intervention measures of AF. The human gut has several non-pathogenic microorganisms forming the gut flora. The human gut microbiota plays a crucial role in the construction and operation of the metabolic system and immune system. Emerging clinical studies and basic experiments have confirmed that intestinal flora and its metabolites have a role in some metabolic disorders and chronic inflammatory diseases. Moreover, the gut microbiota has a role in cardiovascular diseases, such as hypertension and heart failure. However, the relationship between AF and gut microbiota is unclear. This review summarizes the relevant literature on the relationship between AF and intestinal flora with its metabolites, including Trimethylamine N-Oxide, short-chain fatty acids, lipopolysaccharide and bile acids. Therefore, this review may enhance further development of related research.

Review of glucose oxidase as a feed additive: production, engineering, applications, growth-promoting mechanisms, and outlook

The regulation and prohibition of antibiotics used as growth promoters (AGP) in the feed field are increasing because they cause antimicrobial resistance and drug residue issues and threaten community health. Recently, glucose oxidase (GOx) has attracted increasing interest in the feed industry as an alternative to antibiotics. GOx specifically catalyzes the production of gluconic acid (GA) and hydrogen peroxide (H₂O₂) by consuming molecular oxygen, and plays an important role in relieving oxidative stress, preserving health, and promoting animal growth. To expand the application of GOx in the feed field, considerable efforts have been made to mine new genetic resources. Efforts have also been made to heterologously overexpress relevant genes to reduce production costs and to engineer proteins by modifying enzyme properties, both of which are bottleneck problems that limit industrial feed applications. Herein, the: different sources, diverse biochemical properties, distinct structural features, and various strategies of GOx engineering and heterologous overexpression are summarized. The mechanism through which GOx promotes growth in animal production, including the improvement of antioxidant capacity, maintenance of intestinal microbiota homeostasis, and enhancement of gut function, are also systematically addressed. Finally, a new perspective is provided for the future development of GOx applications in the feed field.

Targeting the Gut Microbiota and Host Immunity with a Bacilli-Species Probiotic during Antibiotic Exposure in Mice

Antibiotic therapy is necessary for the treatment of bacterial infections; however, it can also disrupt the balance and function of commensal gut microbes and negatively affect the host. Probiotics have been tested as a means to counteract the negative effects of antibiotic therapy, but many probiotics are also likely destroyed by antibiotics when taken together. Here we aimed to test the efficacy of a non-pathogenic spore-forming Bacillus-species containing a probiotic blend provided during antibiotic therapy on host immune defenses in mice. Mice were exposed to antibiotics and supplemented with or without the probiotic blend and compared to control mice. Fecal and cecal contents were analyzed for gut microbes, and intestinal tissue was tested for the expression of key enzymes involved in vitamin A metabolism, serum amyloid A, and inflammatory markers in the intestine. The probiotic blend protected against antibiotic-induced overgrowth of gram-negative bacteria and gammaproteobacteria in the cecum which correlated with host immune responses. Regional responses in mRNA expression of enzymes involved with vitamin A metabolism occurred between antibiotic groups, and intestinal inflammatory markers were mitigated with the probiotic blend. These data suggest prophylactic supplementation with a spore-forming Bacillus-containing probiotic may protect against antibiotic-induced dysregulation of host immune responses.

The Impact of Tributyrin on Performance and Intestinal Health of Broiler Chickens Post Coccidiosis Vaccination

Coccidiosis is a major intestinal disease affecting broiler chickens. Tributyrin (TB) is a valid alternative to butyrate acid, which was associated with the improvement of performance and attenuation of intestinal inflammation in animal production. However, there are few reports on TB as a prophylactic treatment against coccidiosis in broilers. The aim of the study was to investigate the effects of TB supplementation on performance and intestinal health of broiler chickens post coccidiosis vaccination with a mixed-species Eimeria. In the first experiment, 612 broiler chicks were randomly assigned to two treatments with six replicates. Treatments included no TB supplementation and coccidiosis vaccination (CV1), or TB supplementation (400 mg/kg) and coccidiosis vaccination (TBCV1). On day 5, all broilers received a single vaccine dose. Performance, intestinal histopathology, clinical severity, and fecal oocyst counts were evaluated from day 1 to day 63. TB supplementation resulted in a nonsignificant effect on body weight gain (BWG), feed intake (FI), and mortality-corrected feed conversion ratio (FCR), except in increased FI on days 22-42 (P < 0.05). The TBCV1 group had increased (P < 0.05) villi heights in the duodenum and increased (P < 0.05) villi widths in the ileum on day 63 of age and reduced oocyst shedding on days 19-26 compared to CV1(P < 0.05). The route of administration in the second experiment was different from the first experiment in which the seeder birds (half of birds from each pen) received a tenfold dose on day 5. TB supplementation in broilers resulted in increased (P < 0.05) BWG and reduced (P < 0.05) FCR on days 22-42, and increased (P < 0.05) villi heights in the duodenum and increased (P < 0.05) villi widths in the ileum on day 63 of age, as well as a lower frequency (P < 0.05) of intestinal hemorrhage on days 13-62 and reduced (P < 0.001) oocyst shedding on day 5 post-Eimeria challenge. In conclusion, the study demonstrated that TB can be considered as a feed additive for protecting broilers from coccidiosis on days 22-42.

Regulation of Oxygen Homeostasis at the Intestinal Epithelial Barrier Site

The unique biology of the intestinal epithelial barrier is linked to a low baseline oxygen pressure (pO₂), characterised by a high rate of metabolites circulating through the intestinal blood and the presence of a steep oxygen gradient across the epithelial surface. These characteristics require tight regulation of oxygen homeostasis, achieved in part by hypoxia-inducible factor (HIF)-dependent signalling. Furthermore, intestinal epithelial cells (IEC) possess metabolic identities that are reflected in changes in mitochondrial function. In recent years, it has become widely accepted that oxygen metabolism is key to homeostasis at the mucosae. In addition, the gut has a vast and diverse microbial population, the microbiota. Microbiome–gut communication represents a dynamic exchange of mediators produced by bacterial and intestinal metabolism. The microbiome contributes to the maintenance of the hypoxic environment, which is critical for nutrient absorption, intestinal barrier function, and innate and/or adaptive immune responses in the gastrointestinal tract. In this review, we focus on oxygen homeostasis at the epithelial barrier site, how it is regulated by hypoxia and the microbiome, and how oxygen homeostasis at the epithelium is regulated in health and disease.

Encapsulated Mixture of Methyl Salicylate and Tributyrin Modulates Intestinal Microbiota and Improves Growth Performance of Weaned Piglets

Tributyrin and essential oils have been used as alternatives to antimicrobials to improve gut health and growth performance in piglets. This study was to evaluate the effects of a dietary supplement with two encapsulated products containing different combinations of tributyrin with oregano or with methyl salicylate on growth performance, serum biochemical parameters related to the physiological status, intestinal microbiota and metabolites of piglets. A total of 108 weaned crossbred piglets (Yorkshire × Landrace, 21 ± 1 d, 8.21 ± 0.04 kg) were randomly divided into three groups. Piglets were fed with one of the following diets for 5 weeks: a basal diet as the control (CON); the control diet supplemented with an encapsulated mixture containing 30% of methyl salicylate and tributyrin at a dosage of 3 kg/t (CMT); and the control diet supplemented with an encapsulated mixture containing 30% of oregano oil and tributyrin at a dosage of 3 kg/t (COT). At the end of the feeding trial, six piglets from each group were slaughtered to collect blood and gut samples for physiological status and gut microbiological analysis. The study found that the CMT group was larger in feed intake (FI) (p < 0.05), average daily gain (ADG) (p = 0.09), total protein (TP), albumin (ALB), glutathione peroxidase (GSH-PX) (p < 0.05), blood total antioxidant capacity (T-AOC) (p < 0.05), and crypt depth in the ileum (p < 0.05) compared with the CON group. The genus abundance of Tissierella and Campylobacter in the CMT group was significantly decreased compared with the CON group. The CMT group also resulted in significantly higher activity in amino acid metabolism and arginine biosynthesis compared with the CON group. The COT group was larger in T-AOC, and the genus abundance of Streptophyta and Chlamydia was significantly increased in the ileum compared with the CON group. Data analysis found a significantly high correlation between the genus abundance of Chlamydia and that of Campylobacter in the ileum. The genus abundance of Campylobacter was also positively correlated with the sorbitol level. In general, the results indicated that the supplementation of both encapsulated mixtures in diet of weaned piglets could improve the animal blood antioxidant capacity. Additionally, the encapsulated mixture of methyl salicylate plus tributyrin improved the growth performance and resulted in certain corresponding changes in nutrient metabolism and in the genus abundance of ileum microbial community.

Use of Short-Chain Fatty Acids for the Recovery of the Intestinal Epithelial Barrier Affected by Bacterial Toxins

Short-chain fatty acids (SCFAs) are carboxylic acids produced as a result of gut microbial anaerobic fermentation. They activate signaling cascades, acting as ligands of G-protein-coupled receptors, such as GPR41, GPR43, and GPR109A, that can modulate the inflammatory response and increase the intestinal barrier integrity by enhancing the tight junction proteins functions. These junctions, located in the most apical zone of epithelial cells, control the diffusion of ions, macromolecules, and the entry of microorganisms from the intestinal lumen into the tissues. In this sense, several enteric pathogens secrete diverse toxins that interrupt tight junction impermeability, allowing them to invade the intestinal tissue and to favor gastrointestinal colonization. It has been recently demonstrated that SCFAs inhibit the virulence of different enteric pathogens and have protective effects against bacterial colonization. Here, we present an overview of SCFAs production by gut microbiota and their effects on the recovery of intestinal barrier integrity during infections by microorganisms that affect tight junctions. These properties make them excellent candidates in the treatment of infectious diseases that cause damage to the intestinal epithelium.

Postbiotics, Metabolic Signaling, and Cancer

Postbiotics are health-promoting microbial metabolites delivered as a functional food or a food supplement. They either directly influence signaling pathways of the body or indirectly manipulate metabolism and the composition of intestinal microflora. Cancer is the second leading cause of death worldwide and even though the prognosis of patients is improving, it is still poor in the substantial part of the cases. The preventable nature of cancer and the importance of a complex multi-level approach in anticancer therapy motivate the search for novel avenues of establishing the anticancer environment in the human body. This review summarizes the principal findings demonstrating the usefulness of both natural and synthetic sources of postbotics in the prevention and therapy of cancer. Specifically, the effects of crude cell-free supernatants, the short-chain fatty acid butyrate, lactic acid, hydrogen sulfide, and β-glucans are described. Contradictory roles of postbiotics in healthy and tumor tissues are highlighted. In conclusion, the application of postbiotics is an efficient complementary strategy to combat cancer.

Myelin as a regulator of development of the microbiota-gut-brain axis

Myelination in the peripheral and central nervous systems is critical in regulating motor, sensory, and cognitive functions. As myelination occurs rapidly during early life, neonatal gut dysbiosis during early colonization can potentially alter proper myelination by dysregulating immune responses and neuronal differentiation. Despite common usage of antibiotics (Abx) in children, the impact of neonatal Abx-induced dysbiosis on the development of microbiota, gut, brain (MGB) axis, including myelination and behavior, is unknown. We hypothesized that neonatal Abx-induced dysbiosis dysregulates host-microbe interactions, impairing myelination in the brain, and altering the MGB axis. Neonatal C57BL/6 mice were orally gavaged daily with an Abx cocktail (neomycin, vancomycin, ampicillin) or water (vehicle) from postnatal day 7 (P7) until weaning (P23) to induce gut dysbiosis. Behavior (cognition; anxiety-like behavior), microbiota sequencing, and qPCR (ileum, colon, hippocampus and pre-frontal cortex [PFC]) were performed in adult mice (6-8 weeks). Neonatal Abx administration led to intestinal dysbiosis in adulthood, impaired intestinal physiology, coupled with perturbations of bacterial metabolites and behavioral alterations (cognitive deficits and anxiolytic behavior). Expression of myelin-related genes (Mag, Mog, Mbp, Mobp, Plp) and transcription factors (Sox10, Myrf) important for oligodendrocytes were significantly increased in the PFC region of Abx-treated mice. Increased myelination was confirmed by immunofluorescence imaging and western blot analysis, demonstrating increased expression of MBP, SOX10 and MYRF in neonatally Abx-treated mice compared to sham controls in adulthood. Finally, administration of the short chain fatty acid butyrate following completion of the Abx treatment restored intestinal physiology, behavior, and myelination impairments, suggesting a critical role for the gut microbiota in mediating these effects. Taken together, we identified a long-lasting impact of neonatal Abx administration on the MGB axis, specifically on myelin regulation in the PFC region, potentially contributing to impaired cognitive function and bacterial metabolites are effective in reversing this altered phenotype.

A Spore-Forming Probiotic Supplement Improves the Intestinal Immune Response and Protects the Intestinal Health During Recurrent Clostridioides difficile Colonization in Mice

BACKGROUND

Around 15%-30% of patients develop recurrent Clostridioides difficile infection (CDI) as conventional therapies disrupt protective gut microbiota. We tested if supplementation with a spore-forming probiotic would protect intestinal health in a mouse model of recurrent CD colonization.

METHODS

Methods: Female CF-1 mice were exposed to CD spores (4-log₁₀ colony-forming units/10 μL) and then randomly assigned to receive either saline (CD-S) or probiotic (CD-PRO). Control mice received only saline (control). Following confirmation of initial CD colonization, mice were treated with vancomycin (10 days). After 5 days, mice recolonized with CD were treated again with vancomycin (10 days) and euthanized 5 days later. Fecal samples were collected at select time points for bacterial analysis. Following euthanasia, blood samples, cecum contents, and the intestine were collected for analysis.

RESULTS

Probiotic supplementation mitigated the antibiotic-induced changes in cecum weight (P < .001). Probiotic-supplemented mice had increased messenger RNA expression of several immune parameters, accompanied by lower serum iron levels compared with CD-S mice (P < .05). Lower expressions of TNF α and calprotectin (P ≤ .05) were observed in CD-PRO mice compared with CD-S. The probiotics also supported the expression of intestinal tight junction proteins, which were diminished in the proximal colon of CD-S mice (P < .05).

CONCLUSION

Mice supplemented with targeted spore-forming probiotics exhibited improved immune responses and nutrition immunity properties, which were linked with less inflammation and enhanced intestinal barrier proteins during recurrent CD colonization.

Lactobacillus rhamnosus GG Attenuates Lipopolysaccharide-Induced Inflammation and Barrier Dysfunction by Regulating MAPK/NF-κB Signaling and Modulating Metabolome in the Piglet Intestine

BACKGROUND

Probiotic Lactobacillius rhamnosus GG (LGG) shows beneficial immunomodulation on cultured cell lines in vitro and in mouse models.

OBJECTIVE

The aim was to investigate the effects of LGG on intestinal injury and the underlying mechanisms by elucidating inflammatory signaling pathways and metabolomic response to LPS stimulation in the piglet intestine.

METHODS

Piglets (Duroc × Landrace × Large White, including males and female; 8.6 ± 1.1 kg) aged 28 d were assigned to 3 groups (n = 6/group): oral inoculation with PBS for 2 wk before intraperitoneal injection of physiological saline [control (CON)] or LPS (25 μg/kg body weight; LPS) or oral inoculation with LGG for 2 wk before intraperitoneal injection of LPS (LGG+LPS). Piglets were killed 4 h after LPS injection. Systemic inflammation, intestinal integrity, inflammation signals, and metabolomic characteristics in the intestine were determined.

RESULTS

Compared with CON, LPS stimulation significantly decreased ileal zonula occludens 1 (ZO-1; 44%), claudin-3 (44%), and occludin (41%) expression; increased serum diamineoxidase (73%), D-xylose (19%), TNF-α (43%), and IL-6 (55%) concentrations; induced p38 mitogen-activated protein kinase (p38 MAPK; 85%), extracellular signal-regulated kinase (ERK; 96%), and NF-κB p65 phosphorylation (37%) (P < 0.05). Compared with LPS stimulation alone, LGG pretreatment significantly enhanced the intestinal barrier by upregulating expressions of tight junction proteins (ZO-1, 73%; claudin-3, 55%; occludin, 67%), thereby decreasing serum diamineoxidase (26%) and D-xylose (28%) concentrations, and also reduced serum TNF-α expression (16%) and ileal p38 MAPK (79%), ERK (43%) and NF-κB p65 (37%) phosphorylation levels (P < 0.05). Metabolomic analysis showed clear separation between each group. The concentrations of caprylic acid [fold-change (FC) = 2.39], 1-mono-olein (FC = 2.68), erythritol (FC = 4.62), and ethanolamine (FC = 4.47) significantly increased in the intestine of LGG + LPS piglets compared with the LPS group (P < 0.05).

CONCLUSIONS

These data suggest that LGG alleviates gut inflammation, improves intestinal barrier function, and modulates the metabolite profile of piglets challenged with LPS. This trial was registered at the Zhejiang University (http://www.lac.zju.edu.cn) as ZJU20170529.

Molecular mechanisms of probiotic prevention of antibiotic-associated diarrhea

Antibiotic-associated diarrhea (AAD) is a common and unintended adverse effect of antibiotic treatment. It is characterized by the disruption of the gut microbiota, decreased intestinal short chain fatty acid (SCFA) concentrations, accumulation of luminal carbohydrates and colonic bile acids, altered water absorption, and ultimately diarrhea. Probiotics were shown to prevent AAD in numerous clinical trials. This review examines what is currently known about how probiotics reduce the risk for AAD via modulating the gut microbiota, altering nutrient and bile acid metabolism, inducing epithelial solute transporter activity, supporting intestinal barrier function, and influencing the immune system. Although probiotics are frequently prescribed with antibiotic use, mechanistic evidence verifying how they confer protection against AAD is extremely limited. This information is urgently needed for improving recommendations for sustaining probiotic development and for implementing probiotics in clinical settings.

The Methyltransferase AflSet1 Is Involved in Fungal Morphogenesis, AFB1 Biosynthesis, and Virulence of Aspergillus flavus

The filament fungal pathogen, Aspergillus flavus, spreads worldwide and contaminates several important crops. Histone posttranslational modifications are deeply involved in fungal development and virulence, but the biological function of the histone methyltransferase AflSet1 in A. flavus is still unknown. In the study, Aflset1 deletion strain was constructed through homologous recombination, and it was found that AflSet1 up-regulates hyphae growth, and promotes conidiation by sporulation regulation genes: abaA and brlA. It was also found that AflSet1 involves in sclerotia formation and AFB1 biosynthesis via sclerotia related transcriptional factors and orthodox AFB1 synthesis pathway, respectively. Crop models revealed that AflSet1 plays critical roles in colonization and AFB1 production on crop kernels. Lipase activity analysis suggested that AflSet1 affects fungal virulence to crops via digestive enzymes. Stresses tests revealed that AflSet1 is deeply involved in fungal resistance against osmotic, oxidative and cell membrane stress. The preparation of N_SET, SET domain deletion mutants and H988K mutant revealed that both domains play critical roles in fungal development and AFB1 production, and that H988 is very important in executing biological functions on morphogenesis and AFB1 synthesis. Subcellular location analysis revealed that AflSet1 is stably accumulated in nuclei in both spore germination and hyphae growth stages, even under the stress of SDS. Through immunoblot analysis, it was found that AflSet1 methylates H3K4me2 and me3 as well as H3K9me2. This study provides a solid evidence to discover the biological functions of histone methyltransferase in pathogenic fungi.

Targeted Approaches for In Situ Gut Microbiome Manipulation

The 2019 Dudrick Research Symposium, entitled "Targeted Approaches for In Situ Gut Microbiome Manipulation," was held on March 25, 2019, at the American Society for Parenteral and Enteral Nutrition (ASPEN) 2019 Nutrition Science & Practice Conference in Phoenix, AZ. The Dudrick Symposium honors the many pivotal and innovative contributions to the development and advancement of parenteral nutrition (PN) made by Dr Stanley J. Dudrick, physician scientist, academic leader, and a founding member of ASPEN. As the 2018 recipient of the Dudrick award, Dr Gail Cresci organized and chaired the symposium. The symposium addressed the evolving field of nutrition manipulation of the gut microbiome as a means to mitigate disease and support health. Presentations focused on (1) the role of prebiotics as a means to beneficially support gut microbiome composition and function and health; (2) designer synbiotics targeted to support metabolic by-products altered by ethanol exposure and microbial effectors that manipulate host metabolic outcomes; and, lastly, (3) types of intervention designs used to study diet-gut microbiome interactions in humans and a review of findings from recent interventions, which tested the effects of diet on the microbiome and the microbiome's effect on dietary exposures. New molecular techniques and multiomic approaches have improved knowledge of the structure and functional activity of the gut microbiome; however, challenges remain in establishing causal relationships between changes in the gut microbial-community structure and function and health outcomes in humans.

Indole-3-carbinol prevents colitis and associated microbial dysbiosis in an IL-22-dependent manner

Colitis, an inflammatory bowel disease, is caused by a variety of factors, but luminal microbiota are thought to play crucial roles in disease development and progression. Indole is produced by gut microbiota and is believed to protect the colon from inflammatory damage. In the current study, we investigated whether indole-3-carbinol (I3C), a naturally occurring plant product found in numerous cruciferous vegetables, can prevent colitis-associated microbial dysbiosis and attempted to identify the mechanisms. Treatment with I3C led to repressed colonic inflammation and prevention of microbial dysbiosis caused by colitis, increasing a subset of gram-positive bacteria known to produce butyrate. I3C was shown to increase production of butyrate, and when mice with colitis were treated with butyrate, there was reduced colonic inflammation accompanied by suppression of Th17 and induction of Tregs, protection of the mucus layer, and upregulation in Pparg expression. Additionally, IL-22 was increased only after I3C but not butyrate administration, and neutralization of IL-22 prevented the beneficial effects of I3C against colitis, as well as blocked I3C-mediated dysbiosis and butyrate induction. This study suggests that I3C attenuates colitis primarily through induction of IL-22, which leads to modulation of gut microbiota that promote antiinflammatory butyrate.

Lactobacillus rhamnosus GG components, SLP, gDNA and CpG, exert protective effects on mouse macrophages upon lipopolysaccharide challenge

The aim of this study was to determine whether Lactobacillus rhamnosus GG (LGG) components (surface layer protein, SLP; genomic DNA, gDNA; unmethylated cytosine-phosphate-guanine-containing oligodeoxynucleotide, CpG-ODN), alone or in combination, could affect immunomodulation, and evaluate the signalling mechanism in mouse macrophage RAW264.7 cells challenged with lipopolysaccharide (LPS). LGG components were used to treat cells before LPS stimulation. Cytokine and Toll-like receptor (TLR) expression were assessed using real-time quantitative PCR (RT-qPCR). Mitogen-activated protein kinase (MAPK), extracellular regulated protein kinase (ERK) and nuclear factor-kappa B (NF-κB) signalling pathways were evaluated using immunoblots and immunofluorescence. SLP or SLP + gDNA pre-treatment significantly reduced the LPS-induced mRNA expression of tumour necrosis factor alpha (TNF-α). Pre-treatment with LGG single components (SLP, gDNA or CpG) or their combinations (SLP + gDNA or SLP + CpG) significantly decreased the LPS-induced interleukin-6 (IL-6) mRNA level (P < 0·05). Pre-treatment with SLP or gDNA, alone or in combination, significantly suppressed LPS-induced TLR2 and TLR4 mRNA levels (P < 0·05). SLP pre-treatment also significantly decreased the LPS-induced expression of TLR9 (P < 0·05). Pre-treatment with LGG single components or combinations significantly suppressed the LPS-induced phosphorylation levels of ERK (P > 0·05). In conclusion, pre-incubation with LGG components, singly or in combination, generally inhibited the activation of TLR, MAPK and NF-κB signalling pathways in LPS-stimulated cells, leading to attenuated inflammatory cytokine TNF-α and IL-6 production. These results indicate that nonviable probiotic LGG components exert an anti-inflammation effect on epithelial cells. SIGNIFICANCE AND IMPACT OF THE STUDY: Lactobacillus rhamnosus GG (LGG) is widely used as probiotics. However, its main components are not well known for affecting immunomodulation. This study investigated the effects of pre-treatments with different components such as surface layer protein, genomic DNA and unmethylated cytosine-phosphate-guanine-containing oligodeoxynucleotides, alone or in combination on immunomodulation, and evaluated the signalling mechanism in mouse macrophage RAW264.7 cells challenged with lipopolysaccharide. Pre-incubation with components alone or in combination generally inhibited the activation of Toll-like receptor, mitogen-activated protein kinases, extracellular regulated protein kinases and nuclear factor-kappa B signalling pathways in lipopolysaccharide-stimulated cells, which generally leads to attenuated inflammatory cytokine interleukin-6 and tumour necrosis factor alpha production. These results indicate that nonviable probiotic LGG components exert an anti-inflammation effect on epithelial cells.

Tributyrin Supplementation Protects Immune Responses and Vasculature and Reduces Oxidative Stress in the Proximal Colon of Mice Exposed to Chronic-Binge Ethanol Feeding

Excessive ethanol consumption causes adverse effects and contributes to organ dysfunction. Ethanol metabolism triggers oxidative stress, altered immune function, and gut dysbiosis. The gut microbiome is known to contribute to the maintenance of intestinal homeostasis, and disturbances are associated with pathology. A consequence of gut dysbiosis is also alterations in its metabolic and fermentation byproducts. The gut microbiota ferments undigested dietary polysaccharides to yield short-chain fatty acids, predominantly acetate, propionate, and butyrate. Butyrate has many biological mechanisms of action including anti-inflammatory and immunoprotective effects, and its depletion is associated with intestinal injury. We previously showed that butyrate protects gut-liver injury during ethanol exposure. While the intestine is the largest immune organ in the body, little is known regarding the effects of ethanol on intestinal immune function. This work is aimed at investigating the effects of butyrate supplementation, in the form of the structured triglyceride tributyrin, on intestinal innate immune responses and oxidative stress following chronic-binge ethanol exposure in mice. Our work suggests that tributyrin supplementation preserved immune responses and reduced oxidative stress in the proximal colon during chronic-binge ethanol exposure. Our results also indicate a possible involvement of tributyrin in maintaining the integrity of intestinal villi vasculature disrupted by chronic-binge ethanol exposure.

Faecalibacterium prausnitzii and a Prebiotic Protect Intestinal Health in a Mouse Model of Antibiotic and Clostridium difficile Exposure

BACKGROUND

Clostridium difficile (CD) infection (CDI) increases patient morbidity, mortality and healthcare costs. Antibiotic treatment induces gut dysbiosis and is both a major risk factor for CD colonization and treatment of CDI. Probiotics have been trialed to support commensal gut microbiota and reduce CDI. This study investigated commensal microbe Faecalibacterium prausnitzii (FP) and a prebiotic, both known to yield butyrate and be anti-inflammatory and immunomodulatory, on CD colonization and gut integrity in mice.

METHODS

Mice were randomly grouped and supplemented daily with FP, prebiotic, FP + prebiotic, FP/prebiotic supernatant, or saline throughout the entire study. Following treatment with clindamycin for 3 days, mice were exposed to CD. Feces were collected at baseline, the day after antibiotic, and 1, 3, and 5 days after CD exposure and cultured for bacterial overgrowth and CD colonization. On days 1 and 5 after CD exposure, mice were randomly euthanized, and proximal colon was dissected for histological analysis and preparation of RNA for analysis of proinflammatory and anti-inflammatory cytokines.

RESULTS

Although all mice exhibited bacterial overgrowth and CD colonization, bacterial burden resolved quicker in the FP + prebiotic group. This was associated with induction and resolution of innate immune responses, anion exchanger, and tight junction protein preservation in proximal colon. CD toxin virulence potential was questionable as expression of CD toxin B receptor was depleted in the FP + prebiotic group.

CONCLUSION

Supplementation with anti-inflammatory butyrate-supporting commensal bacteria and prebiotic may support innate immune responses and minimize bacterial burden and negative effects during antibiotic and CD exposure.

Short-Chain Fatty Acid Transporters: Role in Colonic Homeostasis

Short-chain fatty acids (SCFA; acetate, propionate, and butyrate) are generated in colon by bacterial fermentation of dietary fiber. Though diffusion in protonated form is a significant route, carrier-mediated mechanisms constitute the major route for the entry of SCFA in their anionic form into colonic epithelium. Several transport systems operate in cellular uptake of SCFA. MCT1 (SLC16A1) and MCT4 (SLC16A3) are H+-coupled and mediate electroneutral transport of SCFA (H+: SCFA stoichiometry; 1:1). MCT1 is expressed both in the apical membrane and basolateral membrane of colonic epithelium whereas MCT4 specifically in the basolateral membrane. SMCT1 (SLC5A8) and SMCT2 (SLC5A12) are Na+-coupled; SMCT1-mediated transport is electrogenic (Na+: SCFA stoichiometry; 2:1) whereas SMCT2-mediated transport is electroneutral (Na+: SCFA stoichiometry; 1:1). SMCT1 and SMCT2 are expressed exclusively in the apical membrane. An anion-exchange mechanism also operates in the apical membrane in which SCFA entry in anionic form is coupled to bicarbonate efflux; the molecular identity of this exchanger however remains unknown. All these transporters are subject to regulation, notably by their substrates themselves; this process involves cell-surface receptors with SCFA as signaling molecules. There are significant alterations in the expression of these transporters in ulcerative colitis and colon cancer. The tumor-associated changes occur via transcriptional regulation by p53 and HIF1α and by promoter methylation. As SCFA are obligatory for optimal colonic health, the transporters responsible for the entry and transcellular transfer of these bacterial products in colonic epithelium are critical determinants of colonic function under physiological conditions and in disease states. © 2018 American Physiological Society. Compr Physiol 8:299-314, 2018.

Prophylactic tributyrin treatment mitigates chronic-binge ethanol-induced intestinal barrier and liver injury

BACKGROUND AND AIM

Impaired gut-liver axis is a potential factor contributing to alcoholic liver disease. Ethanol depletes intestinal integrity and causes gut dysbiosis. Butyrate, a fermentation byproduct of gut microbiota, is altered negatively following chronic ethanol exposure. This study aimed to determine whether prophylactic tributyrin could protect the intestinal barrier and liver in mice during combined chronic-binge ethanol exposure.

METHODS

C57BL/6J mice exposed to 5% v/v ethanol-containing diet for 10 days received a single ethanol gavage (5 g/kg) 9 h before euthanasia. Control mice were isocalorically pair-fed maltose dextrin for ethanol. Diets were supplemented (5 mM) with tributyrin or glycerol. Intestine and liver disease activity was assessed histologically. Protein and mRNA expression of tight junction (TJ) proteins, toll-like receptors, and tumor necrosis factor-alpha were assessed. Caco-2 monolayers with or without ethanol exposure and/or sodium butyrate were used to test butyrate's direct effects on intestinal integrity.

RESULTS

Chronic-binge ethanol feeding impaired intestinal TJ protein co-localization staining; however, tributyrin co-treatment mitigated these effects. Ethanol depleted TJ and transepithelial electrical resistance in Caco-2 monolayers, but butyrate co-treatment reduced these effects. Hepatic toll-like receptor mRNA expression and tumor necrosis factor-alpha protein expression was induced by ethanol; however, the response was significantly dampened in mice co-treated with tributyrin. Tributyrin altered localization of both neutrophils and single hepatocyte death: Leukocytes and apoptotic hepatocytes localized predominantly around the portal tract in ethanol-only treated mice, whereas localization predominated around the central vein in ethanol-tributyrin mice.

CONCLUSIONS

Prophylactic tributyrin supplementation mitigated effects of combined chronic-binge ethanol exposure on disruption of intestinal TJ localization and intestinal permeability and liver injury.

Hypoxia and Mucosal Inflammation

Sites of inflammation are defined by significant changes in metabolic activity. Recent studies have suggested that O2 metabolism and hypoxia play a prominent role in inflammation so-called "inflammatory hypoxia," which results from a combination of recruited inflammatory cells (e.g., neutrophils and monocytes), the local proliferation of multiple cell types, and the activation of multiple O2-consuming enzymes during inflammation. These shifts in energy supply and demand result in localized regions of hypoxia and have revealed the important function off the transcription factor HIF (hypoxia-inducible factor) in the regulation of key target genes that promote inflammatory resolution. Analysis of these pathways has provided multiple opportunities for understanding basic mechanisms of inflammation and has defined new targets for intervention. Here, we review recent work addressing tissue hypoxia and metabolic control of inflammation and immunity.

Oxygen metabolism and innate immune responses in the gut

Epithelial cells of the mucosa provide a first line of defense to prevent the inappropriate translocation of luminal antigens, and therefore contribute significantly to nonspecific innate immunity. In the gastrointestinal (GI) tract, barrier is provided by multiple components of the mucosa, including mucus production, epithelial junctional complexes, and the production of antimicrobial molecules. In recent years, it is better appreciated that tissue oxygen metabolism is key to homeostasis in the mucosa. The intestine, for example, maintains a low baseline Po₂ level due to high rates of metabolism, countercurrent blood flow, and the presence of a steep oxygen gradient across the luminal aspect of tissue surface. As a result, hypoxia and hypoxia-inducible factor (HIF)-dependent signaling exists even in the healthy, unperturbed intestinal mucosa. In a number of examples, HIF has been demonstrated both to promote barrier function during homeostasis and to promote resolution of active inflammation. Hypoxia-elicited factors that contribute to innate responses in the mucosa include the transcriptional regulation of mucin genes, junction proteins, and autophagic flux. Here, we review current literature related to hypoxia and innate immunity in health and during mucosal inflammation.

Effect of butyrate and Lactobacillus GG on a butyrate receptor and transporter during Campylobacter jejuni exposure

Campylobacter jejuni frequently infects humans causing many gastrointestinal symptoms, fever, fatigue and several long-term debilitating diseases. Current treatment for campylobacteriosis includes rehydration and in some cases, antibiotic therapy. Probiotics are used to treat several gastrointestinal diseases. Butyrate is a short-chain fatty acid known to promote intestinal health. Interaction of butyrate with its respective receptor (HCAR2) and transporter (SLC5A8), both expressed in the intestine, is associated with water and electrolyte absorption as well as providing defense against colon cancer and inflammation. Alterations in gut microbiota influence the presence of HCAR2 and SLC5A8 in the intestine. We hypothesized that adherence and/or invasion of C. jejuni and alterations in HCAR2 and SLC5A8 expression would be minimized with butyrate or Lactobacillus GG (LGG) pretreatment of Caco-2 cells. We found that both C. jejuni adhesion but not invasion was reduced with butyrate pretreatment. While LGG pretreatment did not prevent C. jejuni adhesion, it did result in reduced invasion which was associated with altered cell supernate pH. Both butyrate and LGG protected HCAR2 and SLC5A8 protein expression following C. jejuni infection. These results suggest that the first stages of C. jejuni infection of Caco-2 cells may be minimized by LGG and butyrate pretreatment.

Tissue metabolism and host-microbial interactions in the intestinal mucosa

In recent years, studies in the gastrointestinal (GI) mucosa have taught us a number of important lessons related to tissue oxygenation and metabolism in health and disease. The highly vascularized mucosa lies immediately adjacent to an anaerobic lumen containing trillions of metabolically active microbes (i.e. the microbiome) that results in one of the more austere tissue microenvironments in the body. These studies have also implicated a prominent role for oxygen metabolism and hypoxia in inflammation, so called "inflammatory hypoxia", that results from the activation of multiple oxygen consuming enzymes. Inflammation-associated shifts in the composition of the microbiome and microbial-derived metabolites have revealed a prominent role for the transcription factor hypoxia-inducible factor (HIF) in the regulation of key target genes that promote inflammatory resolution. Analyses of these pathways have provided a multitude of opportunities for understanding basic mechanisms of both homeostasis and disease and have defined new targets for intervention. Here, we review recent advances in our understanding of metabolic influences on host-microbe interactions in the GI mucosa.

Oxygen metabolism and barrier regulation in the intestinal mucosa

Mucosal surfaces are lined by epithelial cells and provide an important barrier to the flux of antigens from the outside. This barrier is provided at a number of levels, including epithelial junctional complexes, mucus production, and mucosa-derived antimicrobials. Tissue metabolism is central to the maintenance of homeostasis in the mucosa. In the intestine, for example, baseline pO2 levels are uniquely low due to counter-current blood flow and the presence of large numbers of bacteria. As such, hypoxia and HIF signaling predominates normal intestinal metabolism and barrier regulation during both homeostasis and active inflammation. Contributing factors that elicit important adaptive responses within the mucosa include the transcriptional regulation of tight junction proteins, metabolic regulation of barrier components, and changes in autophagic flux. Here, we review recent literature around the topic of hypoxia and barrier function in health and during disease.

Food, nutrients and nutraceuticals affecting the course of inflammatory bowel disease

Inflammatory bowel diseases (ulcerative colitis; Crohn's disease) are debilitating relapsing inflammatory disorders affecting the gastrointestinal tract, with deleterious effect on quality of life, and increasing incidence and prevalence. Mucosal inflammation, due to altered microbiota, increased intestinal permeability and immune system dysfunction underlies the symptoms and may be caused in susceptible individuals by different factors (or a combination of them), including dietary habits and components. In this review we describe the influence of the Western diet, obesity, and different nutraceuticals/functional foods (bioactive peptides, phytochemicals, omega 3-polyunsaturated fatty acids, vitamin D, probiotics and prebiotics) on the course of IBD, and provide some hints that could be useful for nutritional guidance. Hopefully, research will soon offer enough reliable data to slow down the spread of the disease and to make diet a cornerstone in IBD therapy.

Alcoholic liver disease: the gut microbiome and liver cross talk

Alcoholic liver disease (ALD) is a leading cause of morbidity and mortality worldwide. Alcoholic fatty liver disease can progress to steatohepatitis, alcoholic hepatitis, fibrosis, and cirrhosis. Patients with alcohol abuse show quantitative and qualitative changes in the composition of the intestinal microbiome. Furthermore, patients with ALD have increased intestinal permeability and elevated systemic levels of gut-derived microbial products. Maintaining eubiosis, stabilizing the mucosal gut barrier, or preventing cellular responses to microbial products protect from experimental ALD. Therefore, intestinal dysbiosis and pathological bacterial translocation appear fundamental for the pathogenesis of ALD. This review highlights causes for intestinal dysbiosis and pathological bacterial translocation, their relationship, and consequences for ALD. We also discuss how the liver affects the intestinal microbiota.

Benefits of short-chain fatty acids and their receptors in inflammation and carcinogenesis

Epidemiological studies have linked increased incidence of inflammatory diseases and intestinal cancers in the developed parts of the world to the consumption of diets poor in dietary fibers and rich in refined carbohydrates. Gut bacteria residing in the intestinal lumen exclusively metabolize dietary fibers. Butyrate, propionate and acetate, which are collectively called short-chain fatty acids (SCFAs), are generated by fermentation of dietary fibers by gut microbiota. Evidences indicate that SCFAs are key players in regulating beneficial effect of dietary fibers and gut microbiota on our health. SCFAs interact with metabolite-sensing G protein-coupled receptors GPR41, GPR43 and GPR109A expressed in gut epithelium and immune cells. These interactions induce mechanisms that play a key role in maintaining homeostasis in gut and other organs. This review summarizes the protective roles of GPR41, GPR43 and GPR109A in dietary fibers-, gut microbiota- and SCFAs-mediated suppression of inflammation and carcinogenesis in gut and other organs.

Therapeutic Potential to Modify the Mucus Barrier in Inflammatory Bowel Disease

Recently, numerous studies have shown that disruption of the mucus barrier plays an important role in the exacerbation of inflammatory bowel disease, particularly in ulcerative colitis. Alterations in the mucus barrier are well supported by published data and are widely accepted. The use of fluorescence in situ hybridization and Carnoy’s fixation has revealed the importance of the mucus barrier in maintaining a mutualistic relationship between host and bacteria. Studies have raised the possibility that modulation of the mucus barrier may provide therapies for the disease, using agents such as short-chain fatty acids, prebiotics and probiotics. This review describes changes in the mucus barrier of patients with inflammatory bowel disease and in animal models of the disease. We also review the involvement of the mucus barrier in the exacerbation of the disease and explore the therapeutic potential of modifying the mucus barrier with short-chain fatty acids, prebiotics, probiotics, fatty acid synthase, H₂S, neutrophil elastase inhibitor and phophatidyl choline.

Gut Microbiome: What We Do and Don't Know

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

Symbiotic maple saps minimize disruption of the mice intestinal microbiota after oral antibiotic administration

This study was undertaken to evaluate the in vivo impact of new symbiotic products based on liquid maple sap or its concentrate. Sap and concentrate, with or without inulin (2%), were inoculated with Bifidobacterium lactis Bb12 and Lactobacillus rhamnosus GG valio at initial counts of 2-4 × 10(8) cfu mL(-1). The experiments started with intra-gastric administration of antibiotic (kanamycin 40 mg in 0.1 cc) (to induce microbiota disturbance and/or diarrhea) to 3-to-5-week-old C57BL/6 female mice followed by a combination of prebiotic and probiotics included in the maple sap or its concentrate for a week. The combination inulin and probiotics in maple sap and concentrate appeared to minimize the antibiotic-induced breakdown of mice microbiota with a marked effect on bifidobacterium and bacteroides levels, thus permitting a more rapid re-establishment of the baseline microbiota levels. Results suggest that maple sap and its concentrate represent good candidates for the production of non-dairy functional foods.

Crosstalk between Microbiota-Derived Short-Chain Fatty Acids and Intestinal Epithelial HIF Augments Tissue Barrier Function

Interactions between the microbiota and distal gut are fundamental determinants of human health. Such interactions are concentrated at the colonic mucosa and provide energy for the host epithelium through the production of the short-chain fatty acid butyrate. We sought to determine the role of epithelial butyrate metabolism in establishing the austere oxygenation profile of the distal gut. Bacteria-derived butyrate affects epithelial O2 consumption and results in stabilization of hypoxia-inducible factor (HIF), a transcription factor coordinating barrier protection. Antibiotic-mediated depletion of the microbiota reduces colonic butyrate and HIF expression, both of which are restored by butyrate supplementation. Additionally, germ-free mice exhibit diminished retention of O2-sensitive dyes and decreased stabilized HIF. Furthermore, the influences of butyrate are lost in cells lacking HIF, thus linking butyrate metabolism to stabilized HIF and barrier function. This work highlights a mechanism where host-microbe interactions augment barrier function in the distal gut.

Discovering probiotic microorganisms: in vitro, in vivo, genetic and omics approaches

Over the past decades the food industry has been revolutionized toward the production of functional foods due to an increasing awareness of the consumers on the positive role of food in wellbeing and health. By definition probiotic foods must contain live microorganisms in adequate amounts so as to be beneficial for the consumer’s health. There are numerous probiotic foods marketed today and many probiotic strains are commercially available. However, the question that arises is how to determine the real probiotic potential of microorganisms. This is becoming increasingly important, as even a superficial search of the relevant literature reveals that the number of proclaimed probiotics is growing fast. While the vast majority of probiotic microorganisms are food-related or commensal bacteria that are often regarded as safe, probiotics from other sources are increasingly being reported raising possible regulatory and safety issues. Potential probiotics are selected after in vitro or in vivo assays by evaluating simple traits such as resistance to the acidic conditions of the stomach or bile resistance, or by assessing their impact on complicated host functions such as immune development, metabolic function or gut–brain interaction. While final human clinical trials are considered mandatory for communicating health benefits, rather few strains with positive studies have been able to convince legal authorities with these health claims. Consequently, concern has been raised about the validity of the workflows currently used to characterize probiotics. In this review we will present an overview of the most common assays employed in screening for probiotics, highlighting the potential strengths and limitations of these approaches. Furthermore, we will focus on how the advent of omics technologies has reshaped our understanding of the biology of probiotics, allowing the exploration of novel routes for screening and studying such microorganisms.

Monosodium L-glutamate and dietary fat exert opposite effects on the proximal and distal intestinal health in growing pigs

The Chinese population has undergone rapid transition to a high-fat diet. Furthermore, monosodium L-glutamate (MSG) is widely used as a flavour enhancer in China. Previous studies have reported that high-fat diet modifies intestinal metabolism and physiology. However, little information is available on the effects of oral MSG on intestine, and no study focus on the interaction of dietary fat and MSG for intestinal health. The aim of the present study was to evaluate the effects of MSG and dietary fat on intestinal health in growing pigs, and to try to identify possible interactions between these 2 nutrients for such effects. A total of 32 growing pigs were used and fed with 4 isonitrogenous and isocaloric diets (basal diet, high-fat diet, basal diet with 3% MSG and high fat diet with 3% MSG). Parameters related to reactive oxygen species metabolism, epithelial morphology, pro-inflammation factors and tight junction protein expression and several species of intestinal microbe were measured. Overall, dietary fat and MSG had detrimental effects on several of the physiological and inflammatory parameters measured in the proximal intestine, while exerting beneficial effects on the distal intestine in growing pigs, with generally antagonistic effects. These results may be of particular relevance for nutritional concerns in patients with intestinal diseases.

Tributyrin supplementation protects mice from acute ethanol-induced gut injury

BACKGROUND

Excessive alcohol consumption leads to liver disease. Interorgan crosstalk contributes to ethanol (EtOH)-induced liver injury. EtOH exposure causes gut dysbiosis resulting in negative alterations in intestinal fermentation byproducts, particularly decreased luminal butyrate concentrations. Therefore, in the present work, we investigated the effect of butyrate supplementation, in the form of trybutyrin, as a prophylactic treatment against EtOH-induced gut injury.

METHODS

C57BL/6J mice were treated with 3 different EtOH feeding protocols: chronic feeding (25 days, 32% of kcal), short-term (2 days, 32%), or acute single gavage (5 g/kg). Tributyrin (0.83 to 10 mM) was supplemented either into the liquid diet or by oral gavage. Intestinal expression of tight junction (TJ) proteins and a butyrate receptor and transporter were evaluated, as well as liver enzymes and inflammatory markers.

RESULTS

All 3 EtOH exposure protocols reduced the expression and co-localization of TJ proteins (ZO-1, occludin) and the expression of a butyrate receptor (GPR109A) and transporter (SLC5A8) in the ileum and proximal colon. Importantly, tributyrin supplementation protected against these effects. Protection of the intestine with tributyrin supplementation was accompanied by mitigation of EtOH-induced increases in aspartate aminotransferase and inflammatory measures in the short-term and acute EtOH exposure protocols, but not after chronic EtOH feeding.

CONCLUSIONS

These findings suggest that tributyrin supplementation could serve as a prophylactic treatment against gut injury caused by short-term EtOH exposure.

Tributyrin supplementation protects mice from acute ethanol-induced gut injury

BACKGROUND

Excessive alcohol consumption leads to liver disease. Interorgan crosstalk contributes to ethanol (EtOH)-induced liver injury. EtOH exposure causes gut dysbiosis resulting in negative alterations in intestinal fermentation byproducts, particularly decreased luminal butyrate concentrations. Therefore, in the present work, we investigated the effect of butyrate supplementation, in the form of trybutyrin, as a prophylactic treatment against EtOH-induced gut injury.

METHODS

C57BL/6J mice were treated with 3 different EtOH feeding protocols: chronic feeding (25 days, 32% of kcal), short-term (2 days, 32%), or acute single gavage (5 g/kg). Tributyrin (0.83 to 10 mM) was supplemented either into the liquid diet or by oral gavage. Intestinal expression of tight junction (TJ) proteins and a butyrate receptor and transporter were evaluated, as well as liver enzymes and inflammatory markers.

RESULTS

All 3 EtOH exposure protocols reduced the expression and co-localization of TJ proteins (ZO-1, occludin) and the expression of a butyrate receptor (GPR109A) and transporter (SLC5A8) in the ileum and proximal colon. Importantly, tributyrin supplementation protected against these effects. Protection of the intestine with tributyrin supplementation was accompanied by mitigation of EtOH-induced increases in aspartate aminotransferase and inflammatory measures in the short-term and acute EtOH exposure protocols, but not after chronic EtOH feeding.

CONCLUSIONS

These findings suggest that tributyrin supplementation could serve as a prophylactic treatment against gut injury caused by short-term EtOH exposure.

Effects of medicated diet to eradicate Helicobacter spp. on growth, pathology, and infection status in Rag1-/- and nude mice

The use of a commercial 4-drug diet has been shown to eradicate Helicobacter spp. from immunocompetent mice and those with innate immunodeficiencies. However the efficacy of this diet has not been confirmed in mice with altered adaptive immunity. We hypothesized that an 8-wk treatment with medicated diet would eradicate H. hepaticus and H. typhlonius from young naturally infected nude and Rag1 mice lacking functional T cells (Foxn1(nu)) or T and B cells (B6.129S7-Rag1(tm1Mom)/J), respectively. We evaluated helicobacter status, body weight, and gross and histologic changes between medicated and control diet in groups of infected and uninfected mice throughout treatment and at 8 wk after treatment completion. Initial infection status was confirmed by fecal PCR at weaning and 3 wk later, with study initiation in 7-wk-old mice. PCR testing demonstrated that independent of strain and sex, all treated mice tested negative for Helicobacter spp. after 4 wk of treatment and remained negative for the duration of the study. Irrespective of infection status, nude and Rag1 mice fed 8 wk of medicated diet gained less weight than did their untreated controls. Both strains normalized body weight while on control diet for the 8 wk after treatment. Mice fed medicated diet developed severe gastroesophageal hyperkeratosis, suggestive of reduced feed consumption, and enlarged ceca. These conditions improved or resolved after the return to control diet. This report is the first to demonstrate the efficacy and physical effects of providing medicated diet for the eradication of Helicobacter spp. from mice with adaptive immune deficiencies.