Short Chain Fatty Acids (SCFAs)-Mediated Gut Epithelial and Immune Regulation and Its Relevance for Inflammatory Bowel Diseases

Strengthening the Immune System and Reducing Inflammation and Oxidative Stress through Diet and Nutrition: Considerations during the COVID-19 Crisis

The coronavirus-disease 2019 (COVID-19) was announced as a global pandemic by the World Health Organization. Challenges arise concerning how to optimally support the immune system in the general population, especially under self-confinement. An optimal immune response depends on an adequate diet and nutrition in order to keep infection at bay. For example, sufficient protein intake is crucial for optimal antibody production. Low micronutrient status, such as of vitamin A or zinc, has been associated with increased infection risk. Frequently, poor nutrient status is associated with inflammation and oxidative stress, which in turn can impact the immune system. Dietary constituents with especially high anti-inflammatory and antioxidant capacity include vitamin C, vitamin E, and phytochemicals such as carotenoids and polyphenols. Several of these can interact with transcription factors such as NF-kB and Nrf-2, related to anti-inflammatory and antioxidant effects, respectively. Vitamin D in particular may perturb viral cellular infection via interacting with cell entry receptors (angiotensin converting enzyme 2), ACE2. Dietary fiber, fermented by the gut microbiota into short-chain fatty acids, has also been shown to produce anti-inflammatory effects. In this review, we highlight the importance of an optimal status of relevant nutrients to effectively reduce inflammation and oxidative stress, thereby strengthening the immune system during the COVID-19 crisis.

The Role of the Microbiome in Food Allergy: A Review

Food allergies are common and estimated to affect 8% of children and 11% of adults in the United States. They pose a significant burden—physical, economic and social—to those affected. There is currently no available cure for food allergies. Emerging evidence suggests that the microbiome contributes to the development and manifestations of atopic disease. According to the hygiene hypothesis, children growing up with older siblings have a lower incidence of allergic disease compared with children from smaller families, due to their early exposure to microbes in the home. Research has also demonstrated that certain environmental exposures, such as a farming environment, during early life are associated with a diverse bacterial experience and reduced risk of allergic sensitization. Dysregulation in the homeostatic interaction between the host and the microbiome or gut dysbiosis appears to precede the development of food allergy, and the timing of such dysbiosis is critical. The microbiome affects food tolerance via the secretion of microbial metabolites (e.g., short chain fatty acids) and the expression of microbial cellular components. Understanding the biology of the microbiome and how it interacts with the host to maintain gut homeostasis is helpful in developing smarter therapeutic approaches. There are ongoing trials evaluating the benefits of probiotics and prebiotics, for the prevention and treatment of atopic diseases to correct the dysbiosis. However, the routine use of probiotics as an intervention for preventing allergic disease is not currently recommended. A new approach in microbial intervention is to attempt a more general modification of the gut microbiome, such as with fecal microbiota transplantation. Developing targeted bacterial therapies for food allergy may be promising for both the treatment and prevention of food allergy. Similarly, fecal microbiota transplantation is being explored as a potentially beneficial interventional approach. Overall, targeted bacterial therapies for food allergy may be promising for both the treatment and prevention of food allergy.

Co-Culture with Bifidobacterium catenulatum Improves the Growth, Gut Colonization, and Butyrate Production of Faecalibacterium prausnitzii: In Vitro and In Vivo Studies

Faecalibacterium prausnitzii is a major commensal bacterium in the human gut. It produces short-chain fatty acids that promote intestinal health. However, the bacterium is extremely oxygen-sensitive, making it difficult to develop as a probiotic. To facilitate practical application of F. prausnitzii, we investigated factors that affect its growth and mammalian gut colonization. We evaluated cross-feeding interactions between F. prausnitzii and seven Bifidobacterium strains, and the anti-inflammatory properties of bacterial metabolites produced in co-culture, in vitro and in vivo. Co-culture of F. prausnitzii and Bifidobacterium catenulatum, with fructooligosaccharides as an energy source, resulted in the greatest viable cell-count and butyrate production increases. Further, the co-culture supernatant reduced the amount of proinflammatory cytokines produced by HT-29 cells and RAW 264.7 macrophages, an effect that was similar to that of butyrate. Furthermore, feeding mice both Faecalibacterium and Bifidobacterium enhanced F. prausnitzii gut colonization. Finally, feeding the co-culture supernatant decreased interleukin 8 levels in the colon and increased butyrate levels in the cecum in the dextran sodium sulfate-induced colitis mouse model. These observations indicate that the Faecalibacterium-Bifidobacterium co-culture exerts an anti-inflammatory effect by promoting F. prausnitzii survival and short-chain fatty acid production, with possible implications for the treatment of inflammatory bowel disease.

Hypoxia Inducible Factor-1α: The Curator of Gut Homeostasis

The human gut microbiome is a stratified and resilient ecosystem co-inhabited by a diverse and dynamic pool of microorganisms. Microbial selection, establishment, and colonization are modulated through a complex molecular network of host-microbial interactions. These molecular bioprocesses ensure the taxonomic composition of the mature human gut microbiome. The human gut microbiome plays a vital role in host health; otherwise, any microbial dysbiosis could predispose to the onset of physiological and metabolic disorder/s. Focussed research are being carried out to identify key molecular agents defining gut homeostasis. These molecules hold the potential to develop effective therapeutic solutions for microbial dysbiosis-associated human disorders. Of these, Hypoxia-inducible factor-1α (HIF-1α) is a central player in host-microbial crosstalk to maintain gut homeostasis. Human gut microbial metabolites regulate its cellular stability, which in turn regulates various cellular processes required for the stable gut microbiome. In the present review, an effort has been made to summarize the key role of HIF-1α to maintain gut homeostasis.

Connecting the Dots Between Inflammatory Bowel Disease and Metabolic Syndrome: A Focus on Gut-Derived Metabolites

The role of the microbiome in health and disease has gained considerable attention and shed light on the etiology of complex diseases like inflammatory bowel disease (IBD) and metabolic syndrome (MetS). Since the microorganisms inhabiting the gut can confer either protective or harmful signals, understanding the functional network between the gut microbes and the host provides a comprehensive picture of health and disease status. In IBD, disruption of the gut barrier enhances microbe infiltration into the submucosae, which enhances the probability that gut-derived metabolites are translocated from the gut to the liver and pancreas. Considering inflammation and the gut microbiome can trigger intestinal barrier dysfunction, risk factors of metabolic diseases such as insulin resistance may have common roots with IBD. In this review, we focus on the overlap between IBD and MetS, and we explore the role of common metabolites in each disease in an attempt to connect a common origin, the gut microbiome and derived metabolites that affect the gut, liver and pancreas.

Molecular mechanisms of postbiotics in colorectal cancer prevention and treatment

The occurrence of colorectal cancer (CRC) has been rising expeditiously and anticipated that 2.4 million new occasions of CRC will be detected yearly around the world until the year 2035. Due to some side-effects and complications of conventional CRC therapies, bioactive components such as microbial-derived biomolecules (postbiotics) have been attaining great significance by researchers for adjuvant therapy in CRC patients. The term 'postbiotics' encompasses an extensive range of complex micro- and macro-molecules (<50, 50-100, and 100< kDa) such as inactivated microbial cells, cell fractions or metabolites, which confer various physiological health benefits to the host when administered in adequate amounts. Postbiotics modulate the composition of the gut microbiota and the functionality of the immune system, as well as promote the CRC treatment effectiveness and reduces its side-effects in CRC patients due to possessing anti-oxidant, anti-proliferative, anti-inflammatory, and anti-cancer activities. Presently scientific literature confirms that postbiotics with their unique characteristics in terms of clinical (safe origin), technological (stability), and economic (low production costs) aspects can be used as promising tools for both prevent and adjuvant treat strategies in CRC patients without any serious undesirable side-effects. This review provides an overview of the concept and safety issues regarding postbiotics, with emphasis on their biological role in the prevention and treatment of CRC.

The Rundown of Dietary Supplements and Their Effects on Inflammatory Bowel Disease-A Review

Inflammatory bowel diseases, including Crohn's disease and ulcerative colitis, are a life-long, chronic, and relapsing problem affecting 11.2 million people worldwide. To date, there is pharmacological therapy to treat symptoms such as diarrhea, constipation, and abdominal cramping/pain. These medications also help to alleviate everyday discomfort; however, there are no curative therapies. Recent studies have investigated the combination of pharmacological treatment along with nutritional interventions to improve quality of life and risk of disease relapse. Dietary supplements, specifically probiotics, polyphenols, fibers, fatty acids and low fermentable oligosaccharide, disaccharide, monosaccharide, and polyol diets (FODMAP diets), have been closely looked at to determine their effect, if any, on the development of inflammatory bowel disease and its course of progression. Approximately 30 studies were carefully reviewed and analyzed to appreciate the value of these above-mentioned supplements and their influence on this gastrointestinal disease. After analysis, it has been demonstrated that by implementing fibers, polyphenols, and fatty acids, as well as keeping a low-saccharide diet for those patients with Crohn's disease and ulcerative colitis can improve quality of life and invoke clinical remission. Some polyphenols, specifically curcumin and resveratrol, have proved to decrease disease activity in studies reviewed. Although these studies have become a topic of recent interest, it would be of great value to doctors and patients alike, to continue in this direction of research and to improve the findings for best treatment substances and dosages. This would lead to increased quality of life and disease control leading to fewer complications in the future.

The Rundown of Dietary Supplements and Their Effects on Inflammatory Bowel Disease-A Review

Inflammatory bowel diseases, including Crohn's disease and ulcerative colitis, are a life-long, chronic, and relapsing problem affecting 11.2 million people worldwide. To date, there is pharmacological therapy to treat symptoms such as diarrhea, constipation, and abdominal cramping/pain. These medications also help to alleviate everyday discomfort; however, there are no curative therapies. Recent studies have investigated the combination of pharmacological treatment along with nutritional interventions to improve quality of life and risk of disease relapse. Dietary supplements, specifically probiotics, polyphenols, fibers, fatty acids and low fermentable oligosaccharide, disaccharide, monosaccharide, and polyol diets (FODMAP diets), have been closely looked at to determine their effect, if any, on the development of inflammatory bowel disease and its course of progression. Approximately 30 studies were carefully reviewed and analyzed to appreciate the value of these above-mentioned supplements and their influence on this gastrointestinal disease. After analysis, it has been demonstrated that by implementing fibers, polyphenols, and fatty acids, as well as keeping a low-saccharide diet for those patients with Crohn's disease and ulcerative colitis can improve quality of life and invoke clinical remission. Some polyphenols, specifically curcumin and resveratrol, have proved to decrease disease activity in studies reviewed. Although these studies have become a topic of recent interest, it would be of great value to doctors and patients alike, to continue in this direction of research and to improve the findings for best treatment substances and dosages. This would lead to increased quality of life and disease control leading to fewer complications in the future.

Tryptophan as a Central Hub for Host/Microbial Symbiosis

Amino acid catabolism occurs during inflammation and regulates innate and adaptive immunity. The role of commensal bacteria in amino acid catabolism and the production of metabolites able to regulate the development and function of the innate immune system is increasingly being recognized. Therefore, commensal bacteria are key players in the maintenance of immune homeostasis. However, the intestinal microbiota also contributes to susceptibility and response to infectious diseases. This is self-evident for fungal infections known to occur as a consequence of weakened immune system and broad-spectrum antibiotic use or abuse. Thus, diseases caused by opportunistic fungi can no longer be viewed as dependent only on a weakened host but also on a disrupted microbiota. Based on these premises, the present review focuses on the role of amino acid metabolic pathways in the dialogue between the mammalian host and its microbiota and the potential implications in fungal commensalism and infectivity.

Inflammatory Bowel Diseases: Host-Microbial-Environmental Interactions in Dysbiosis

Crohn's Disease (CD) and Ulcerative Colitis (UC) are world-wide health problems in which intestinal dysbiosis or adverse functional changes in the microbiome are causative or exacerbating factors. The reduced abundance and diversity of the microbiome may be a result of a lack of exposure to vital commensal microbes or overexposure to competitive pathobionts during early life. Alternatively, many commensal bacteria may not find a suitable intestinal niche or fail to proliferate or function in a protective/competitive manner if they do colonize. Bacteria express a range of factors, such as fimbriae, flagella, and secretory compounds that enable them to attach to the gut, modulate metabolism, and outcompete other species. However, the host also releases factors, such as secretory IgA, antimicrobial factors, hormones, and mucins, which can prevent or regulate bacterial interactions with the gut or disable the bacterium. The delicate balance between these competing host and bacteria factors dictates whether a bacterium can colonize, proliferate or function in the intestine. Impaired functioning of NOD2 in Paneth cells and disrupted colonic mucus production are exacerbating features of CD and UC, respectively, that contribute to dysbiosis. This review evaluates the roles of these and other the host, bacterial and environmental factors in inflammatory bowel diseases.

The gallbladder and vermiform appendix influence the assemblage of intestinal microorganisms

Surgical procedures for the symptomatic removal of the gallbladder and the vermiform appendix have been posited to adversely shift the assemblage of the intestinal microbiome increasing the risk of disease. The associated mechanisms have been linked with dysbiosis of the gut microbiota. Cholecystectomy causes changes of bile acid compositions and bile secretion patterns as bile acids interact with the intestinal microbiota in a bidirectional capacity. An appendectomy precludes the further recolonization of the proximal colon with a commensal biofilm that could maintain a stable intestinal microbiome. Epidemiological studies indicate that there is an increased risk of disease rather than causality following a cholecystectomy and appendectomy. This narrative review summarizes studies that report on the role that bile salts and the appendix, contribute to the assemblage of the intestinal microbiome in health and disease.

Indigo Naturalis Alleviates Dextran Sulfate Sodium-Induced Colitis in Rats via Altering Gut Microbiota

Ulcerative colitis is a gastrointestinal disorder intricately associated with intestinal dysbiosis, but effective treatments are currently limited. Indigo naturalis, a traditional Chinese medicine derived from indigo plants, has been widely used in the treatment of ulcerative colitis. However, the specific mechanisms have not yet been identified. Accordingly, in this study, we evaluated the effects and mechanisms of indigo naturalis on dextran sulfate sodium (DSS)-induced colitis in rats. Our results showed that indigo naturalis potently alleviated DSS-induced colitis in rats, and reversed DSS-induced intestinal dysbiosis using bacterial 16S rRNA amplicon sequencing. The protective effects of indigo naturalis were gut microbiota dependent, as demonstrated by antibiotic treatments and fecal microbiota transplantation. Depletion of the gut microbiota through a combination of antibiotic treatments blocked the anti-inflammatory effect of indigo naturalis on the DSS-induced colitis, and the recipients of the gut microbiota from indigo naturalis-treated rats displayed a significantly attenuated intestinal inflammation, which was actively responsive to therapeutic interventions with indigo naturalis. Notably, supplement with indigo naturalis greatly increased the levels of feces butyrate, which was positively correlated with the relative abundances of Ruminococcus_1 and Butyricicoccus. We further showed that indigo naturalis-dependent attenuation of colitis was associated with elevated expression of short-chain fatty acid-associated receptors GPR41 and GPR43. Collectively, these results suggested that indigo naturalis alleviates DSS-induced colitis in rats through a mechanism of the microbiota-butyrate axis, particularly alterations in Ruminococcus_1 and Butyricicoccus abundances, and target-specific microbial species may have unique therapeutic promise for ulcerative colitis.

Applying mass spectrometry-based assays to explore gut microbial metabolism and associations with disease

The workings of the gut microbiome have gained increasing interest in recent years through the mounting evidence that the microbiota plays an influential role in human health and disease. A principal focus of this research seeks to further understand the production of metabolic by-products produced by bacteria resident in the gut, and the subsequent interaction of these metabolites on host physiology and pathophysiology of disease. Gut bacterial metabolites of interest are predominately formed via metabolic breakdown of dietary compounds including choline and ʟ-carnitine (trimethylamine N-oxide), amino acids (phenol- and indole-containing uremic toxins) and non-digestible dietary fibers (short-chain fatty acids). Investigations have been accelerated through the application of mass spectrometry (MS)-based assays to quantitatively assess the concentration of these metabolites in laboratory- and animal-based experiments, as well as for direct circulating measurements in clinical research populations. This review seeks to explore the impact of these metabolites on disease, as well as to introduce the application of MS for those less accustomed to its use as a clinical tool, highlighting pertinent research related to its use for measurements of gut bacteria-mediated metabolites to further understand their associations with disease.

The Anti-Inflammatory and Antioxidant Effects of Sodium Propionate

The major end-products of dietary fiber fermentation by gut microbiota are the short-chain fatty acids (SCFAs) acetate, propionate, and butyrate, which have been shown to modulate host metabolism via effects on metabolic pathways at different tissue sites. Several studies showed the inhibitory effects of sodium propionate (SP) on nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway. We carried out an in vitro model of inflammation on the J774-A1 cell line, by stimulation with lipopolysaccharide (LPS) and H₂O₂, followed by the pre-treatment with SP at 0.1, 1 mM and 10 mM. To evaluate the effect on acute inflammation and superoxide anion-induced pain, we performed a model of carrageenan (CAR)-induced rat paw inflammation and intraplantar injection of KO₂ where rats received SP orally (10, 30, and 100 mg/kg). SP decreased in concentration-dependent-manner the expression of cicloxigenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) following LPS stimulation. SP was able to enhance anti-oxidant enzyme production such as manganese superoxide dismutase (MnSOD) and heme oxygenase-1 (HO-1) following H₂O₂ stimulation. In in vivo models, SP (30 and 100 mg/kg) reduced paw inflammation and tissue damage after CAR and KO₂ injection. Our results demonstrated the anti-inflammatory and anti-oxidant properties of SP; therefore, we propose that SP may be an effective strategy for the treatment of inflammatory diseases.

Interactions of probiotics and prebiotics with the gut microbiota

The gut microbiota (GM) composition varies among individuals and is influenced by intrinsic (genetics, age) and extrinsic (environment, diet, lifestyle) factors. An imbalance or dysbiosis is directly associated with the development of several illnesses, due to the potential increase in intestinal permeability leading to a systemic inflammation triggered by higher levels of circulating lipopolysaccharides and changes in the immune response caused by an overgrowth of a specific genus or of pathogens. These mechanisms may increase symptoms in gastrointestinal disorders or reduce glucose tolerance in metabolic diseases. Diet also has a significant impact on GM, and functional foods, namely prebiotics and probiotics, are a novel approach to reestablish the indigenous microbiota. Prebiotics, like inulin and polyphenols, are selectively utilized by GM, releasing short-chain fatty acids (SCFA) and other metabolites which may reduce the intestinal lumen pH, inhibit growth of pathogens, and enhance mineral and vitamin bioavailability. Probiotic microorganism may increase the microbial diversity of GM and improve the integrity of the intestinal barrier, leading to an improvement of baseline and pathologic inflammation. In this chapter, we will discuss the potential roles of prebiotics and probiotics in health and diseases throughout an individual's lifetime and proposed mechanisms of action.

Enteral Nutrition Supplemented with Transforming Growth Factor-β, Colostrum, Probiotics, and Other Nutritional Compounds in the Treatment of Patients with Inflammatory Bowel Disease

Enteral nutrition seems to play a significant role in the treatment of both adults and children with active Crohn's disease, and to a lesser degree in the treatment of patients with active ulcerative colitis. The inclusion of some special factors in the enteral nutrition formulas might increase the rate of the efficacy. Actually, enteral nutrition enriched in Transforming Growth Factor-β reduced the activity index and maintained remission in patients with Crohn's disease. In addition, a number of experimental animal studies have shown that colostrum exerts a significantly positive result. Probiotics of a special type and a certain dosage could also reduce the inflammatory process in patients with active ulcerative colitis. Therefore, the addition of these factors in an enteral nutrition formula might increase its effectiveness. Although the use of these formulas is not supported by large clinical trials, it could be argued that their administration in selected cases as an exclusive diet or in combination with the drugs used in patients with inflammatory bowel disease could benefit the patient. In this review, the authors provide an update on the role of enteral nutrition, supplemented with Transforming Growth Factor-β, colostrum, and probiotics in patients with inflammatory bowel disease.

Effects of alternate-day fasting, time-restricted fasting and intermittent energy restriction DSS-induced on colitis and behavioral disorders

Intermittent fasting (IF) has been reported to have beneficial effects on improving gut function via lowering gut inflammation and altering the gut microbiome diversity. In this study, we aimed to investigate the differential effects of three different common IF treatments, alternate day fasting (ADF), time-restricted fasting (TRF), and intermittent energy restriction (IER), on a dextran sodium sulfate (DSS)-induced colitis mouse model. The results indicated that TRF and IER, but not ADF improved the survival rates of the colitis mice. TRF and IER, but not ADF, reversed the colitis pathological development by improving the gut barrier integrity and colon length. Importantly, TRF and IER suppressed the inflammatory responses and oxidative stress in colon tissues. Interestingly, TRF and IER also attenuated colitis-related anxiety-like and obsessive-compulsive disorder behavior and alleviated the neuroinflammation and oxidative stress. TRF and IER also altered the gut microbiota composition, including the decrease of the enrichments of colitis-related microbes such as Shigella and Escherichia Coli, and increase of the enrichments of anti-inflammatory-related microbes. TRF and IER also improved the short chain fatty acid formation in colitis mice. In conclusion, the TRF and IER but not ADF exhibited the protective effects against colitis and related behavioral disorders, which could be partly explained by improving the gut microbiome compositions and preventing gut leak, and consequently suppressing the inflammation and oxidative damages in both colon and brain. The current research indicates that proper IF regimens could be effective strategies for nutritional intervention for the prevention and treatment of colitis.

Microphysiological Engineering of Immune Responses in Intestinal Inflammation

The epithelial barrier in the gastrointestinal (GI) tract is a protective interface that endures constant exposure to the external environment while maintaining its close contact with the local immune system. Growing evidence has suggested that the intercellular crosstalk in the GI tract contributes to maintaining the homeostasis in coordination with the intestinal microbiome as well as the tissue-specific local immune elements. Thus, it is critical to map the complex crosstalks in the intestinal epithelial-microbiome-immune (EMI) axis to identify a pathological trigger in the development of intestinal inflammation, including inflammatory bowel disease. However, deciphering a specific contributor to the onset of pathophysiological cascades has been considerably hindered by the challenges in current in vivo and in vitro models. Here, we introduce various microphysiological engineering models of human immune responses in the EMI axis under the healthy conditions and gut inflammation. As a prospective model, we highlight how the human “gut inflammation-on-a-chip” can reconstitute the pathophysiological immune responses and contribute to understanding the independent role of inflammatory factors in the EMI axis on the initiation of immune responses under barrier dysfunction. We envision that the microengineered immune models can be useful to build a customizable patient's chip for the advance in precision medicine.

Expression of Free Fatty Acid Receptor 2 by Dendritic Cells Prevents Their Expression of Interleukin 27 and Is Required for Maintenance of Mucosal Barrier and Immune Response Against Colorectal Tumors in Mice

BACKGROUND & AIMS

Intestinal microbes and their metabolites affect the development of colorectal cancer (CRC). Short-chain fatty acids are metabolites generated by intestinal microbes from dietary fiber. We investigated the mechanisms by which free fatty acid receptor 2 (FFAR2), a receptor for short-chain fatty acids that can affect the composition of the intestinal microbiome, contributes to the pathogenesis of CRC.

METHODS

We performed studies with ApcMin/+ mice, ApcMin/+Ffar2-/- mice, mice with conditional disruption of Ffar2 in dendritic cells (DCs) (Ffar2fl/flCD11c-Cre mice), ApcMin/+Ffar2fl/flCD11c-Cre mice, and Ffar2fl/fl mice (controls); some mice were given dextran sodium sulfate to induce colitis, with or without a FFAR2 agonist or an antibody against interleukin 27 (IL27). Colon and tumor tissues were analyzed by histology, quantitative polymerase chain reaction, and 16S ribosomal RNA gene sequencing; lamina propria and mesenteric lymph node tissues were analyzed by RNA sequencing and flow cytometry. Intestinal permeability was measured after gavage with fluorescently labeled dextran. We collected data on colorectal tumors from The Cancer Genome Atlas.

RESULTS

ApcMin/+Ffar2-/- mice developed significantly more spontaneous colon tumors than ApcMin/+ mice and had increased gut permeability before tumor development, associated with reduced expression of E-cadherin. Colon tumors from ApcMin/+Ffar2-/- mice had a higher number of bacteria than tumors from ApcMin/+ mice, as well as higher frequencies of CD39+CD8+ T cells and exhausted or dying T cells. DCs from ApcMin/+Ffar2-/- mice had an altered state of activation, increased death, and higher production of IL27. Administration of an antibody against IL27 reduced the numbers of colon tumors in ApcMin/+ mice with colitis. Frequencies of CD39+CD8+ T cells and IL27+ DCs were increased in colon lamina propria from Ffar2fl/flCD11c-Cre mice with colitis compared with control mice or mice without colitis. ApcMin/+Ffar2fl/flCD11c-Cre mice developed even more tumors than ApcMin/+Ffar2fl/fl mice, and their tumors had even higher numbers of IL27+ DCs. ApcMin/+ mice with colitis given the FFAR2 agonist developed fewer colon tumors, with fewer IL27+ DCs, than mice not given the agonist. DCs incubated with the FFAR2 agonist no longer had gene expression patterns associated with activation or IL27 production.

CONCLUSIONS

Loss of FFAR2 promotes colon tumorigenesis in mice by reducing gut barrier integrity, increasing tumor bacterial load, promoting exhaustion of CD8+ T cells, and overactivating DCs, leading to their death. Antibodies against IL27 and an FFAR2 agonist reduce tumorigenesis in mice and might be developed for the treatment of CRC.

Engineered Probiotics for Detection and Treatment of Inflammatory Intestinal Diseases

Inflammatory intestinal diseases such as Crohn's disease and ulcerative colitis have seen an increase in their prevalence in developing countries throughout the current decade. These are caused by a combination of genetic and environmental factors, altered immune response, intestinal epithelium disruption and dysbiosis in the gut microbiome. Current therapies are mainly focused on treating symptoms and are often expensive and ineffective in the long term. Recently, there has been an increase in our understanding of the relevance of the gut microbiome and its impact on human health. Advances in the use of probiotics and synthetic biology have led to the development of intestinal biosensors, bacteria engineered to detect inflammation biomarkers, that work as diagnostic tools. Additionally, live biotherapeutics have been engineered as delivery vehicles to produce treatment in situ avoiding common complications and side effects of current therapies. These genetic constructs often express a therapeutic substance constitutively, but others could be regulated externally by specific substrates, making the production of their treatment more efficient. Additionally, certain probiotics detecting specific biomarkers in situ and responding by generating a therapeutic substance are beginning to be developed. While most studies are still in the laboratory stage, a few modified probiotics have been tested in humans. These advances indicate that live biotherapeutics could have great potential as new treatments for inflammatory intestinal diseases.

Proteobacteria Overgrowth and Butyrate-Producing Taxa Depletion in the Gut Microbiota of Glycogen Storage Disease Type 1 Patients

A life-long dietary intervention can affect the substrates’ availability for gut fermentation in metabolic diseases such as the glycogen-storage diseases (GSD). Besides drug consumption, the main treatment of types GSD-Ia and Ib to prevent metabolic complications is a specific diet with definite nutrient intakes. In order to evaluate how deeply this dietary treatment affects gut bacteria, we compared the gut microbiota of nine GSD-I subjects and 12 healthy controls (HC) through 16S rRNA gene sequencing; we assessed their dietary intake and nutrients, their microbial short chain fatty acids (SCFAs) via gas chromatography and their hematic values. Both alpha-diversity and phylogenetic analysis revealed a significant biodiversity reduction in the GSD group compared to the HC group, and highlighted profound differences of their gut microbiota. GSD subjects were characterized by an increase in the relative abundance of Enterobacteriaceae and Veillonellaceae families, while the beneficial genera Faecalibacterium and Oscillospira were significantly reduced. SCFA quantification revealed a significant increase of fecal acetate and propionate in GSD subjects, but with a beneficial role probably reduced due to unbalanced bacterial interactions; nutritional values correlated to bacterial genera were significantly different between experimental groups, with nearly opposite cohort trends.

Human Intestinal Mononuclear Phagocytes in Health and Inflammatory Bowel Disease

Inflammatory bowel disease (IBD), including Crohn's disease and ulcerative colitis, is a complex immune-mediated disease of the gastrointestinal tract that increases morbidity and negatively influences the quality of life. Intestinal mononuclear phagocytes (MNPs) have a crucial role in maintaining epithelial barrier integrity while controlling pathogen invasion by activating an appropriate immune response. However, in genetically predisposed individuals, uncontrolled immune activation to intestinal flora is thought to underlie the chronic mucosal inflammation that can ultimately result in IBD. Thus, MNPs are involved in fine-tuning mucosal immune system responsiveness and have a critical role in maintaining homeostasis or, potentially, the emergence of IBD. MNPs include monocytes, macrophages and dendritic cells, which are functionally diverse but highly complementary. Despite their crucial role in maintaining intestinal homeostasis, specific functions of human MNP subsets are poorly understood, especially during diseases such as IBD. Here we review the current understanding of MNP ontogeny, as well as the recently identified human intestinal MNP subsets, and discuss their role in health and IBD.

Modulation of the intestinal microbiota and the metabolites produced by the administration of ice cream and a dietary supplement containing the same probiotics

The aim of the present work was to compare the capacity to modulate the intestinal microbiota and the production of metabolites after 14 d administration of a commercial dietary supplement and a manufactured ice cream, both containing the same quantity of inulin and the same viable counts of Lactobacillus acidophilus LA-5 and Bifidobacterium animalis BB-12, using the Simulator of the Human Intestinal Microbial Ecosystem (SHIME®) model. Samples of the colonic contents were evaluated microbiologically by real-time quantitative PCR (qRT-PCR) and next-generation sequencing and chemically by the production of SCFA (acetate, propionate and butyrate) and ammonium ions ($\text{NH}_4^ + $). Statistical analyses were carried out for all the variables using the two-way ANOVA followed by the Tukey multiple comparisons test (P < 0·05) for metabolite production, qRT-PCR and the bioinformatics analysis for microbiota diversity. Dietary supplement and ice cream were able to deliver the probiotic L. acidophilus and B. animalis to the simulated colon and modulate the microbiota, increasing beneficial micro-organisms such as Bifidobacterium spp., Bacteroides spp. and Faecalibacterium spp. for dietary supplement administration, and Lactobacillus spp. for ice cream supplementation. However, the ice cream matrix was probably more favourable for the maintenance of the metabolic activity of the probiotics in the SHIME® model, due to the larger amounts of acetate, propionate, butyrate and ammonium ions obtained after 14 d of supplementation. In conclusion, both ways of probiotic supplementation could be efficient, each with its own particularities.

Propionate supplementation promotes the expansion of peripheral regulatory T-Cells in patients with end-stage renal disease

Patients with end-stage renal disease (ESRD) suffer from a progressively increasing low-grade systemic inflammation, which is associated with higher morbidity and mortality. Regulatory T cells (Tregs) play an important role in regulation of the inflammatory process. Previously, it has been demonstrated that short-chain fatty acids reduce inflammation in the central nervous system in a murine model of multiple sclerosis through an increase in tissue infiltrating Tregs. Here, we evaluated the effect of the short-chain fatty acid propionate on the chronic inflammatory state and T-cell composition in ESRD patients. Analyzing ESRD patients and healthy blood donors before, during, and 60 days after the propionate supplementation by multiparametric flow cytometry we observed a gradual and significant expansion in the frequencies of CD25^highCD127^- Tregs in both groups. Phenotypic characterization suggests that polarization of naïve T cells towards Tregs is responsible for the observed expansion. In line with this, we observed a significant reduction of inflammatory marker CRP under propionate supplementation. Of interest, the observed anti-inflammatory surroundings did not affect the protective pathogen-specific immunity as demonstrated by the stable frequencies of effector/memory T cells specific for tetanus/diphtheria recall antigens. Collectively, our data suggest that dietary supplements with propionate have a beneficial effect on the elevated systemic inflammation of ESRD patients. The effect can be achieved through an expansion of circulating Tregs without affecting the protective pathogen-reactive immunity.

What is the collective effect of aging and HIV on the gut microbiome?

PURPOSE OF REVIEW

Aging and HIV share features of intestinal damage and alterations in the communities of enteric bacteria, termed dysbiosis. The purpose of this review is to highlight the various features of the gut microbiome in aging and in people with HIV (PWH) and to discuss how aging and HIV converge to impact the gut microbiome. The term microbiome reflects the combined genetic material of micro-organisms present including bacteria, viruses, bacteriophages, and fungi. To date, the majority of studies investigating the impact of aging and HIV on the gut microbiome have focused on bacteria, and therefore, for the purposes of this review, the term 'microbiome' is used to reflect enteric bacterial communities.

RECENT FINDINGS

Aging is associated with alterations in the gut bacterial microbiome. Although changes vary by the age of the population, lifestyle (diet, physical activity) and geographic location, the age-associated dysbiosis is typically characterized by an increase in facultative anaerobes with inflammatory properties and a decrease in obligate anaerobes that play critical roles in maintaining intestinal homeostasis and in regulating host immunity. PWH also have dysbiotic gut microbiomes, many features of which reflect those observed in elderly persons. In one study, the age effect on the gut microbiome differed based on HIV serostatus in older adults.

SUMMARY

HIV and age may interact to shape the gut microbiome. Future studies should investigate relationships between the gut microbiome and age-associated comorbidities in older PWH populations. Identifying these links will provide new avenues for treatments and interventions to improve the healthspan and lifespan of older PWH.

NUTRITION AND HEALTH: COMPANION ANIMAL APPLICATIONS: Functional nutrition in livestock and companion animals to modulate the immune response

Advances in the understanding of how the immune system functions in response to diet have altered the way we think about feeding livestock and companion animals on both the short (weeks/months) and long-term (years) timelines; however, depth of research in each of these species varies. Work dedicated to understanding how immune function can be altered with diet has revealed additional functions of required nutrients such as vitamins D and E, omega-3 polyunsaturated fatty acids (PUFA), and minerals such as zinc, while feed additives such as phytogenics and probiotics add an additional layer of immunomodulating potential to modern diets. For certain nutrients such as vitamin D or omega-3 PUFA, inclusion above currently recommended levels may optimize immune function and reduce inflammation, while for others such as zinc, additional pharmacological supplementation above requirements may inhibit immune function. Also to consider is the potential to over-immunomodulate, where important functions such as clearance of microbial infections may be reduced when supplementation reduces the inflammatory action of the immune system. Continued work in the area of nutritional immunology will further enhance our understanding of the power of nutrition and diet to improve health in both livestock and companion animals. This review collects examples from several species to highlight the work completed to understand how nutrition can be used to alter immune function, intended or not.

The Role of Glycosaminoglycans in Protection from Neonatal Necrotizing Enterocolitis: A Narrative Review

Necrotizing enterocolitis, a potentially fatal intestinal inflammatory disorder affecting primarily premature infants, is a significant cause of morbidity and mortality in neonates. While the etiology of the disease is, as yet, unknown, a number of risk factors for the development of necrotizing enterocolitis have been identified. One such risk factor, formula feeding, has been shown to contribute to both increased incidence and severity of the disease. The protective influences afforded by breastfeeding are likely attributable to the unique composition of human milk, an extremely potent, biologically active fluid. This review brings together knowledge on the pathogenesis of necrotizing enterocolitis and current thinking on the instrumental role of one of the more prominent classes of bioactive components in human breast milk, glycosaminoglycans.

Gastrointestinal (GI) Tract Microbiome-Derived Neurotoxins-Potent Neuro-Inflammatory Signals From the GI Tract via the Systemic Circulation Into the Brain

The microbiome of the human gastrointestinal (GI)-tract is a rich and dynamic source of microorganisms that together possess a staggering complexity and diversity. Collectively these microbes are capable of secreting what are amongst the most neurotoxic and pro-inflammatory biopolymers known. These include lipopolysaccharide (LPS), enterotoxins, microbial-derived amyloids and small non-coding RNA (sncRNA). One of the major microbial species in the human GI-tract microbiome, about ~100-fold more abundant than Escherichia coli, is Bacteroides fragilis, an anaerobic, rod-shaped Gram-negative bacterium that secretes: (i) a particularly potent, pro-inflammatory LPS glycolipid subtype (BF-LPS); and (ii) a hydrolytic, extracellular zinc metalloproteinase known as B. fragilis toxin (BFT) or fragilysin. Ongoing studies support multiple observations that BF-LPS and BFT (fragilysin) disrupt paracellular barriers by cleavage of intercellular proteins, such as E-cadherin, between epithelial cells, resulting in 'leaky' barriers. These defective barriers, which also become more penetrable with age, in turn permit entry of microbiome-derived neurotoxic biopolymers into the systemic circulation from which they can next transit the blood-brain barrier (BBB) and gain access into the brain. This short communication will highlight some recent advances in this extraordinary research area that links the pro-inflammatory exudates of the GI-tract microbiome with innate-immune disturbances and inflammatory signaling within the human central nervous system (CNS) with reference to Alzheimer's disease (AD) wherever possible.

Consumption of a baked corn and bean snack reduced chronic colitis inflammation in CD-1 mice via downregulation of IL-1 receptor, TLR, and TNF-α associated pathways

Ulcerative colitis (UC) is a condition that has been rising in the number of cases around the world. Food products made from natural ingredients such as corn and common bean might serve as alternatives for the treatment of UC. This study aimed to assess the anti-inflammatory effect of the consumption of a baked corn and bean snack (CBS) in an in vivo model of UC using 2% dextran sodium sulfate (DSS) as inductor of colitis. CD-1 mice (45, n = 9/group) were randomly separated into 5 groups, treated for 6-weeks as follows: G1 (basal diet, BD), G2 (2% DSS), G3 (20 g CBS/body weight BW/day + BD), G4 (40 g CBS/BW/day + BD) and G5 (60 g CBS/BW/day + BD). BW, Disease Activity Index (DAI), and feces were collected throughout the treatment. After euthanasia, organs (spleen, liver, and colon) were excised and weighed. Feces were analyzed for β-glucuronidase (β-GLUC) activity and gas-chromatography. The colons were analyzed for histopathology, myeloperoxidase (MPO) activity, and gene analysis. At the end of treatments, among the DSS-induced groups, G3 exhibited the lowest BW losses (11.5%), MPO activity (10.4%) and β-GLUC (8.6%). G4 presented the lowest DAI (0.88), relative spleen weight, and histological inflammation score (p < 0.05). Compared to G2, CBS consumption significantly (p < 0.05) reduced serum TNF-α, IL-10, and MCP-1 levels. The fecal metabolome analysis ranked 9-decenoic acid, decane, and butyric acid as the main contributors of pathways associated with the β-oxidation of fatty acids. G4 showed the highest fecal/cecal contents of short-chain fatty acids among all the DSS-induced groups. For the gene expression, G4 was clustered with G1, showing a differential inhibition of the pro-inflammatory genes Il1r1, Il1a, Tlr4, Tlr2, and Tnfrsf1b. In conclusion, CBS consumption decreased the inflammatory state and reduced the expression of the IL-1 receptor, TLR, and TNF-α-associated pathways in DSS-induced UC in CD-1 mice.

Lactobacillus salivarius BP121 prevents cisplatin‑induced acute kidney injury by inhibition of uremic toxins such as indoxyl sulfate and p‑cresol sulfate via alleviating dysbiosis

The gut microbiota is important for maintaining the integrity of the intestinal barrier, promoting immunological tolerance and carrying out metabolic activities that have not evolved in hosts. Intestinal dysbiosis is associated with chronic kidney disease and probiotic supplementation has been shown to be beneficial. However, it is not known whether gut microorganisms‑specifically, lactic acid bacteria (LAB) can protect against acute kidney injury (AKI). To address this issue, the present study investigated the effects of Lactobacillus salivarius BP121, an intestinal LAB isolated from the feces of newborns, in a rat model of cisplatin‑induced AKI and also in Caco‑2 human intestinal epithelial cells. BP121 prevented cisplatin‑induced AKI in rats, as demonstrated by decreases in inflammation and oxidative stress in kidney tissue and in serum levels of uremic toxins such as indoxyl sulfate (IS) and p‑cresol sulfate (PCS). BP121 also reduced intestinal permeability, as determined using fluorescein isothiocyanate‑dextran by immunohistochemical detection of tight junction (TJ) proteins such as zona occludens‑1 and occludin. The abundance of Lactobacillus spp., which are beneficial intestinal flora, was increased by BP121; this was accompanied by an increase in the concentrations of short‑chain fatty acids in feces. Additionally, H2O2‑induced TJ protein damage was reduced in Caco‑2 cells treated with BP121 culture supernatant, an effect that was reversed by the 5' AMP‑activated protein kinase (AMPK) inhibitor Compound C and Toll‑like receptor (TLR)4 inhibitor TLR4‑IN‑C34. In conclusion, this study demonstrated that L. salivarius BP121 protects against cisplatin‑induced AKI by decreasing inflammation and oxidative stress and this renoprotective effect is partially mediated by modulating the gut environment and thereby suppressing IS and PCS production as well as by regulating AMPK and TLR4 dependent TJ assembly.

Gut microbiome of a porcine model of metabolic syndrome and HF-pEF

Metabolic syndrome (MetS) is a composite of cardiometabolic risk factors, including obesity, dyslipidemia, hypertension, and insulin resistance, with a range of secondary sequelae such as nonalcoholic fatty liver disease and diastolic heart failure. This syndrome has been identified as one of the greatest global health challenges of the 21st century. Herein, we examine whether a porcine model of diet- and mineralocorticoid-induced MetS closely mimics the cardiovascular, metabolic, gut microbiota, and functional metataxonomic phenotype observed in human studies. Landrace pigs with deoxycorticosterone acetate-induced hypertension fed a diet high in fat, salt, and sugar over 12 wk were assessed for hyperlipidemia, hyperinsulinemia, and immunohistologic, echocardiographic, and hemodynamic parameters, as well as assessed for microbiome phenotype and function through 16S rRNA metataxonomic and metabolomic analysis, respectively. All MetS animals developed obesity, hyperlipidemia, insulin resistance, hypertension, fatty liver, structural cardiovascular changes including left ventricular hypertrophy and left atrial enlargement, and increased circulating saturated fatty acid levels, all in keeping with the human phenotype. A reduction in α-diversity and specific microbiota changes at phylum, family, and genus levels were also observed in this model. Specifically, this porcine model of MetS displayed increased abundances of proinflammatory bacteria coupled with increased circulating tumor necrosis factor-α and increased secondary bile acid-producing bacteria, which substantially impacted fibroblast growth factor-19 expression. Finally, a significant decrease in enteroprotective bacteria and a reduction in short-chain fatty acid-producing bacteria were also noted. Together, these data suggest that diet and mineralocorticoid-mediated development of biochemical and cardiovascular stigmata of metabolic syndrome in pigs leads to temporal gut microbiome changes that mimic key gut microbial population signatures in human cardiometabolic disease.NEW & NOTEWORTHY This study extends a prior porcine model of cardiometabolic syndrome to include systemic inflammation, fatty liver, and insulin sensitivity. Gut microbiome changes during evolution of porcine cardiometabolic disease recapitulate those in human subjects with alterations in gut taxa associated with proinflammatory bacteria, bile acid, and fatty acid pathways. This clinical scale model may facilitate design of future interventional trials to test causal relationships between gut dysbiosis and cardiometabolic syndrome at a systemic and organ level.

Cocoa diet modulates gut microbiota composition and improves intestinal health in Zucker diabetic rats

Cocoa supplementation improves glucose metabolism in Zucker diabetic fatty (ZDF) rats via multiple mechanisms. Furthermore, cocoa rich-diets modify the intestinal microbiota composition both in humans and rats in healthy conditions. Accordingly, we hypothesized that cocoa could interact with the gut microbiota (GM) in ZDF rats, contributing to their antidiabetic effects. Therefore, here we investigate the effect of cocoa intake on gut health and GM in ZDF diabetic rats. Male ZDF rats were fed with standard (ZDF-C) or 10% cocoa-rich diet (ZDF-Co) during 10 weeks. Zucker Lean animals (ZL) received the standard diet. Colon tissues were obtained to determine the barrier integrity and the inflammatory status of the intestine and faeces were analysed for microbial composition, short-chain fatty acids (SCFA) and lactate levels. We found that cocoa supplementation up-regulated the levels of the tight junction protein Zonula occludens-1 (ZO-1) and the mucin glycoprotein and reduced the expression of pro-inflammatory cytokines such as tumour necrosis factor-α (TNF-α), interleukin-6 (IL-6) and monocyte chemoattractant protein 1 (MCP-1) in the colon of ZDF diabetic animals. Additionally, cocoa modulated the microbial composition of the ZDF rats to values similar to those of the lean group. Importantly, cocoa treatment increased the relative abundance of acetate-producing bacteria such as Blautia and prevented the increase in the relative amount of lactate-producing bacteria (mainly Enterococcus and Lactobacillus genera) in ZDF diabetic animals. Accordingly, the total levels of SCFA (mainly acetate) increased significantly in the faeces of ZDF-Co diabetic rats. Finally, modified GM was closely associated with improved biochemical parameters related to glucose homeostasis and intestinal integrity and inflammation. These findings demonstrate for the first time that cocoa intake modifies intestinal bacteria composition towards a healthier microbial profile in diabetic animals and suggest that these changes could be associated with the improved glucose homeostasis and gut health induced by cocoa in ZDF diabetic rats.

Berberine regulates fecal metabolites to ameliorate 5-fluorouracil induced intestinal mucositis through modulating gut microbiota

Berberine (BBR) is an isoquinoline alkaloid, which has been used in the treatment of intestinal mucositis. However, BBR on chemotherapy-induced mucositis in cancer patients remains largely unknown. Here, we investigated the effect of BBR on intestinal mucositis induced by 5-fluorouracil (5-Fu) using rat model. We detected the degree of intestinal mucosal damage and inflammatory response in 5-Fu treated rats with or without BBR administration, and investigated the changes of fecal metabolites and gut microbiota using ¹H NMR spectroscopy and 16S rRNA. The mechanism was further explored by fecal microbiota transplantation (FMT). Results showed that BBR treated rats displayed less weight loss, lower diarrhea score and longer colon length in 5-Fu treated rats. Meanwhile, BBR treatment significantly increased the expression of Occludin in ileum and decreased the d-lactate content in serum. Moreover, the expression of IL-1β, IL-6 and TNF-α in ileum were suppressed by BBR treatment. The pattern of fecal metabolism changed obviously after treated with 5-Fu, which was reversed by BBR. Importantly, BBR significantly increased the levels of butyrate and glutamine in feces from 5-Fu treated rats. In terms of gut microbiota, BBR enriched the relative abundance of Firmicutes and decreased Proteobacteria at the phylum level. Meanwhile, BBR increased the propotion of unclassified_f_ Porphyromonadaceae, unclassified_f_ Lachnospiraceae, Lactobacillus, unclassified_o_ Clostridiales, Ruminococcus, Prevotella, Clostridium IV, and decreased Escherichia/Shigella at the genera level. Furthermore, principal component analysis (PCA) showed that fecal transplantation led to changes in fecal metabolites. Fecal transplantation from BBR treated rats had low diarrhea score, reduced inflammatory response in ileum, and relieved intestinal mucosal injury, which may be caused by the increased of butyrate level in fecal metabolites. In conclusion, our study provides evidence that BBR regulates fecal metabolites to ameliorate 5-Fu induced intestinal mucositis by modifying gut microbiota.

Metabolite Sensing by Colonic ILC3s: How Far Is Too Ffar2 Go?

It is poorly understood how group 3 innate lymphoid cells (ILC3s) recognize metabolites produced by the gut microbiota. In this issue of Immunity, Chun et al. show that short-chain fatty acids sensed through the G protein-coupled receptor Ffar2 promote ILC3 function in the colon.

Neonatal intestinal dysbiosis

The initial colonization of the neonatal intestinal tract is influenced by delivery mode, feeding, the maternal microbiota, and a host of environmental factors. After birth, the composition of the infant's microbiota undergoes a series of significant changes particularly in the first weeks and months of life ultimately developing into a more stable and diverse adult-like population in childhood. Intestinal dysbiosis is an alteration in the intestinal microbiota associated with disease and appears to be common in neonates. The consequences of intestinal dysbiosis are uncertain, but strong circumstantial evidence and limited confirmations of causality suggest that dysbiosis early in life can influence the health of the infant acutely, as well as contribute to disease susceptibility later in life.

Manipulating resident microbiota to enhance regulatory immune function to treat inflammatory bowel diseases

Altered intestinal microbial composition (dysbiosis) and metabolic products activate aggressive mucosal immune responses that mediate inflammatory bowel diseases (IBD). This dysbiosis impairs the function of regulatory immune cells, which normally promote mucosal homeostasis. Normalizing and maintaining regulatory immune cell function by correcting dysbiosis provides a promising approach to treat IBD patients. However, existing microbe-targeted therapies, including antibiotics, prebiotics, probiotics, and fecal microbial transplantation, provide variable outcomes that are not optimal for current clinical application. This review discusses recent progress in understanding the dysbiosis of IBD and the basis for therapeutic restoration of homeostatic immune function by manipulating an individual patient's microbiota composition and function. We believe that identifying more precise therapeutic targets and developing appropriate rapid diagnostic tools will guide more effective and safer microbe-based induction and maintenance treatments for IBD patients that can be applied in a personalized manner.

A sensitive method for the quantification of short-chain fatty acids by benzyl chloroformate derivatization combined with GC-MS

Short-chain fatty acids (SCFAs) were identified as critical markers in the diagnosis of chronic and metabolic diseases, but a sensitive and stable method to determine SCFAs in feces is a challenge for analysts due to the high volatility.

Dietary Fatty Acids and Microbiota-Brain Communication in Neuropsychiatric Diseases

The gut-brain axis is a multimodal communication system along which immune, metabolic, autonomic, endocrine and enteric nervous signals can shape host physiology and determine liability, development and progression of a vast number of human diseases. Here, we broadly discussed the current knowledge about the either beneficial or deleterious impact of dietary fatty acids on microbiota-brain communication (MBC), and the multiple mechanisms by which different types of lipids can modify gut microbial ecosystem and contribute to the pathophysiology of major neuropsychiatric diseases (NPDs), such as schizophrenia (SCZ), depression and autism spectrum disorders (ASD).

Facilitation of Gastrointestinal (GI) Tract Microbiome-Derived Lipopolysaccharide (LPS) Entry Into Human Neurons by Amyloid Beta-42 (Aβ42) Peptide

Human gastrointestinal (GI)-tract microbiome-derived lipopolysaccharide (LPS): (i) has been recently shown to target, accumulate within, and eventually encapsulate neuronal nuclei of the human central nervous system (CNS) in Alzheimer's disease (AD) brain; and (ii) this action appears to impede and restrict the outward flow of genetic information from neuronal nuclei. It has previously been shown that in LPS-encased neuronal nuclei in AD brain there is a specific disruption in the output and expression of two AD-relevant, neuron-specific markers encoding the cytoskeletal neurofilament light (NF-L) chain protein and the synaptic phosphoprotein synapsin-1 (SYN1) involved in the regulation of neurotransmitter release. The biophysical mechanisms involved in the facilitation of the targeting of LPS to neuronal cells and nuclei and eventual nuclear envelopment and functional disruption are not entirely clear. In this "Perspectives article" we discuss current advances, and consider future directions in this research area, and provide novel evidence in human neuronal-glial (HNG) cells in primary culture that the co-incubation of LPS with amyloid-beta 42 (Aβ42) peptide facilitates the association of LPS with neuronal cells. These findings: (i) support a novel pathogenic role for Aβ42 peptides in neurons via the formation of pores across the nuclear membrane and/or a significant biophysical disruption of the neuronal nuclear envelope; and (ii) advance the concept that the Aβ42 peptide-facilitated entry of LPS into brain neurons, accession of neuronal nuclei, and down-regulation of neuron-specific components such as NF-L and SYN1 may contribute significantly to neuropathological deficits as are characteristically observed in AD-affected brain.

Microbiota-mediated mucosal inflammation in arthritis

Mucosal surfaces are a unique symbiotic environment between a host and a vast and diverse ecology of microbes. These microbes have great immunomodulatory potential with respect to the host organism. Indeed, the mucosal immune system strikes a delicate balance between tolerance of commensal organisms and overt inflammation to ward off pathogens. Disruptions of the microbial ecology at mucosal surfaces has been described in a vast number of different human disease processes including many forms of arthritis, and the resulting implications are still being understood to their fullest. Herein, we review the current state of knowledge in microbe-host interactions as it relates to the development of arthritis through bacterial translocation, bacterial metabolite production, education of the immune response, and molecular mimicry.

Mucosal Metabolomic Profiling and Pathway Analysis Reveal the Metabolic Signature of Ulcerative Colitis

The onset of ulcerative colitis (UC) is characterized by a dysregulated mucosal immune response triggered by several genetic and environmental factors in the context of host–microbe interaction. This complexity makes UC ideal for metabolomic studies to unravel the disease pathobiology and to improve the patient stratification strategies. This study aims to explore the mucosal metabolomic profile in UC patients, and to define the UC metabolic signature. Treatment- naïve UC patients (n = 18), UC patients in deep remission (n = 10), and healthy volunteers (n = 14) were recruited. Mucosa biopsies were collected during colonoscopies. Metabolomic analysis was performed by combined gas chromatography coupled to time-of-flight mass spectrometry (GC-TOF-MS) and ultra-high performance liquid chromatography coupled with mass spectrometry (UHPLC-MS). In total, 177 metabolites from 50 metabolic pathways were identified. The most prominent metabolome changes among the study groups were in lysophosphatidylcholine, acyl carnitine, and amino acid profiles. Several pathways were found perturbed according to the integrated pathway analysis. These pathways ranged from amino acid metabolism (such as tryptophan metabolism) to fatty acid metabolism, namely linoleic and butyrate. These metabolic changes during UC reflect the homeostatic disturbance in the gut, and highlight the importance of system biology approaches to identify key drivers of pathogenesis which prerequisite personalized medicine.

Exacerbation of Chikungunya Virus Rheumatic Immunopathology by a High Fiber Diet and Butyrate

Chikungunya virus (CHIKV) is a mosquito transmitted alphavirus associated with a robust systemic infection and an acute inflammatory rheumatic disease. A high fiber diet has been widely promoted for its ability to ameliorate inflammatory diseases. Fiber is fermented in the gut into short chain fatty acids such as acetate, propionate, and butyrate, which enter the circulation providing systemic anti-inflammatory activities. Herein we show that mice fed a high fiber diet show a clear exacerbation of CHIKV arthropathy, with increased edema and neutrophil infiltrates. RNA-Seq analyses illustrated that a high fiber diet, in this setting, promoted a range of pro-neutrophil responses including Th17/IL-17. Gene Set Enrichment Analyses demonstrated significant similarities with mouse models of inflammatory psoriasis and significant depression of macrophage resolution phase signatures in the CHIKV arthritic lesions from mice fed a high fiber diet. Supplementation of the drinking water with butyrate also increased edema after CHIKV infection. However, the mechanisms involved were different, with modulation of AP-1 and NF-κB responses identified, potentially implicating deoptimization of endothelial barrier repair. Thus, neither fiber nor short chain fatty acids provided benefits in this acute infectious disease setting, which is characterized by widespread viral cytopathic effects and a need for tissue repair.

Therapeutic effect of n-butanol fraction of Huang-lian-Jie-du Decoction on ulcerative colitis and its regulation on intestinal flora in colitis mice

Huang-lian-Jie-du Decoction (HLJDD) is a classical prescription for clearing away heat and detoxification. In order to screen the effective fraction of HLJDD in the treatment of ulcerative colitis (UC) in mice and explore its effects on intestinal flora in UC mice, we prepared different polar fractions of HLJDD by system solvent extraction method. Subsequently, the contents of 13 active compounds in different polar fractions of HLJDD were determined by HPLC. Further, the UC model induced by dextran sodium sulfate was used to evaluate the therapeutic effects of different polar fractions of HLJDD. Finally, cecal contents were used for sequencing and analysis of bacterial 16S rRNA genes. The results showed that the yield of HLJDD-n-butanol (HLJDD-NBA) fraction was the highest, and the content or proportion of 13 active compounds in HLJDD-NBA fraction were the most similar to HLJDD. In addition, in vivo pharmacodynamic experiments showed that HLJDD-NBA intervention not only significantly alleviated the clinical symptoms of UC mice and ameliorated the pathological damage of colon tissue, but also showed significant anti-inflammatory and antioxidative effects (p < 0.05), which were comparable to HLJDD (p > 0.05). Moreover, both HLDD and HLJDD-NBA treatments can restore the intestinal flora homeostasis of UC mice by inhibiting the growth of intestinal pathogens and preventing the decrease of beneficial bacteria. Meanwhile, they can also significantly correct the dysfunction of intestinal flora in UC mice. In conclusion, we proved that HLJDD-NBA fraction is an effective fraction of HLJDD in treating UC in mice, and it can maintain the intestinal flora homeostasis of UC mice, which increases our understanding of the mechanism of HLJDD in treating UC and lays a foundation for the development of new anti-ulcer drugs.

Keep calm: the intestinal barrier at the interface of peace and war

Epithelial barriers have to constantly cope with both harmless and harmful stimuli. The epithelial barrier therefore serves as a dynamic and not static wall to safeguard its proper physiological function while ensuring protection. This is achieved through multiple defence mechanisms involving various cell types - epithelial and non-epithelial - that work in an integrated manner to build protective barriers at mucosal sites. Damage may nevertheless occur, due to pathogens, physical insults or dysregulated immune responses, which trigger a physiologic acute or a pathologic chronic inflammatory cascade. Inflammation is often viewed as a pathological condition, particularly due to the increasing prevalence of chronic inflammatory (intestinal) diseases. However, inflammation is also necessary for wound healing. The aetiology of chronic inflammatory diseases is incompletely understood and identification of the underlying mechanisms would reveal additional therapeutic approaches. Resolution is an active host response to end ongoing inflammation but its relevance is under-appreciated. Currently, most therapies aim at dampening inflammation at damaged mucosal sites, yet these approaches do not efficiently shut down the inflammation process nor repair the epithelial barrier. Therefore, future treatment strategies should also promote the resolution phase. Yet, the task of repairing the barrier can be an arduous endeavour considering its multiple integrated layers of defence - which is advantageous for damage prevention but becomes challenging to repair at multiple levels. In this review, using the intestines as a model epithelial organ and barrier paradigm, we describe the consequences of chronic inflammation and highlight the importance of the mucosae to engage resolving processes to restore epithelial barrier integrity and function. We further discuss the contribution of pre-mRNA alternative splicing to barrier integrity and intestinal homeostasis. Following discussions on current open questions and challenges, we propose a model in which resolution of inflammation represents a key mechanism for the restoration of epithelial integrity and function.

Association between Irritable Bowel Syndrome and Allergic Diseases: To Make a Case for Aeroallergen

Irritable bowel syndrome (IBS) is a functional gastrointestinal disease and the most common cause of prolonged abdominal pain and bowel disturbances in the developed world. While initially thought to be functional or psychosomatic in nature, IBS is now recognized as a heterogeneous group of conditions. A subset of IBS patients and patients with allergic diseases share some characteristic inflammatory features. In fact, atopic children show an increased likelihood of developing IBS as adults. Given these findings, a subset of IBS may be suffering from allergy-related gut diseases. In this review, we present the allergy-related comorbidities of IBS, including genetic, environmental, and immunologic factors. We discuss studies demonstrating an increased sensitization of IBS patients to aeroallergens compared to food allergens. We then postulate potential pathophysiological mechanisms underlying both IBS and aeroallergens in the gut, followed by potential implications in the screening and treatment of allergies in IBS patients.

"Photobiomics": Can Light, Including Photobiomodulation, Alter the Microbiome?

Objective: The objective of this review is to consider the dual effects of microbiome and photobiomodulation (PBM) on human health and to suggest a relationship between these two as a novel mechanism. Background: PBM describes the use of low levels of visible or near-infrared (NIR) light to heal and stimulate tissue, and to relieve pain and inflammation. In recent years, PBM has been applied to the head as an investigative approach to treat diverse brain diseases such as stroke, traumatic brain injury (TBI), Alzheimer's and Parkinson's diseases, and psychiatric disorders. Also, in recent years, increasing attention has been paid to the total microbial population that colonizes the human body, chiefly in the gut and the mouth, called the microbiome. It is known that the composition and health of the gut microbiome affects many diseases related to metabolism, obesity, cardiovascular disorders, autoimmunity, and even brain disorders. Materials and methods: A literature search was conducted for published reports on the effect of light on the microbiome. Results: Recent work by our research group has demonstrated that PBM (red and NIR light) delivered to the abdomen in mice, can alter the gut microbiome in a potentially beneficial way. This has also now been demonstrated in human subjects. Conclusions: In consideration of the known effects of PBM on metabolomics, and the now demonstrated effects of PBM on the microbiome, as well as other effects of light on the microbiome, including modulating circadian rhythms, the present perspective introduces a new term "photobiomics" and looks forward to the application of PBM to influence the microbiome in humans. Some mechanisms by which this phenomenon might occur are considered.

Targeting the Aryl Hydrocarbon Receptor With Indole-3-Aldehyde Protects From Vulvovaginal Candidiasis via the IL-22-IL-18 Cross-Talk

Vulvovaginal candidiasis (VVC) is a common mucosal infection caused by Candida spp., most frequently by Candida albicans, which may become recurrent and severely impacting the quality of life of susceptible women. Although it is increasingly being recognized that mucosal damage is mediated by an exaggerated inflammatory response, current therapeutic approaches are only based on antifungals that may relieve the symptomatology, but fail to definitely prevent recurrences. The unrestrained activation of the NLRP3 inflammasome with continuous production of IL-1β and recruitment of neutrophils is recognized as a pathogenic factor in VVC. We have previously shown that IL-22 is required to dampen pathogenic inflammasome activation in VVC via the NLRC4/IL-1Ra axis. However, IL-22 also regulates IL-18, a product of the inflammasome activity that regulates IL-22 expression. Here we describe a cross-regulatory circuit between IL-18 and IL-22 in murine VVC that is therapeutically druggable. We found that IL-18 production was dependent on IL-22 and NLRC4, and that IL-18, in turn, contributes to IL-22 activity. Like in IL-22 deficiency, IL-18 deficiency was associated with an increased susceptibility to VVC and unbalanced Th17/Treg response, suggesting that IL-18 can regulate both the innate and the adaptive responses to the fungus. Administration of the microbial metabolite indole-3-aldehyde, known to stimulate the production of IL-22 via the aryl hydrocarbon receptor (AhR), promoted IL-18 expression and protection against Candida infection. Should low levels of IL-18 be demonstrated in the vaginal fluids of women with recurrent VVC, targeting the AhR/IL-22/IL-18 pathway could be exploited for future therapeutic approaches in VVC. This study suggests that a deeper understanding of the mechanisms regulating inflammasome activity may lead to the identification of novel targets for intervention in VVC.

Low-protein diets supplemented with casein hydrolysate favor the microbiota and enhance the mucosal humoral immunity in the colon of pigs

Background

High-protein diets can increase the colonic health risks. A moderate reduction of dietary crude-protein (CP) level can improve the colonic bacterial community and mucosal immunity of pigs. However, greatly reducing the dietary CP level, even supplemented with all amino acids (AAs), detrimentally affects the colonic health, which may be due to the lack of protein-derived peptides. Therefore, this study evaluated the effects of supplementation of casein hydrolysate (peptide source) in low-protein (LP) diets, in comparison with AAs supplementation, on the colonic microbiota, microbial metabolites and mucosal immunity in pigs, aiming to determine whether a supplementation of casein hydrolysate can improve colonic health under very LP level. Twenty-one pigs (initial BW 19.90 ± 1.00 kg, 63 ± 1 days of age) were assigned to three groups and fed with control diet (16% CP), LP diets (13% CP) supplemented with free AAs (LPA) or casein hydrolysate (LPC) for 4 weeks.

Results

Compared with control diet, LPA and LPC diet decreased the relative abundance of Streptococcus and Escherichia coli, and LPC diet further decreased the relative abundance of Proteobacteria. LPC diet also increased the relative abundance of Lactobacillus reuteri. Both LP diets decreased concentrations of ammonia and cadaverine, and LPC diet also reduced concentrations of putrescine, phenol and indole. Moreover, LPC diet increased total short-chain fatty acid concentration. In comparison with control diet, both LP diets decreased protein expressions of Toll-like receptor-4, nuclear factor-κB, interleukin-1β and tumor necrosis factor-α, and LPC diet further decreased protein expressions of nucleotide-binding oligomerization domain protein-1 and interferon-γ. LPC diet also increased protein expressions of G-protein coupled receptor-43, interleukin-4, transforming growth factor-β, immunoglobulin A and mucin-4, which are indicators for mucosal defense activity.

Conclusions

The results showed that supplementing casein hydrolysate showed beneficial effects on the colonic microbiota and mucosal immunity and barrier function in comparison with supplementing free AAs in LP diets. These findings may provide new framework for future nutritional interventions for colon health in pigs.

Electronic supplementary material

The online version of this article (10.1186/s40104-019-0387-9) contains supplementary material, which is available to authorized users.