Prophylactic Administration of Gut Microbiome Metabolites Abrogated Microglial Activation and Subsequent Neuroinflammation in an Experimental Model of Japanese Encephalitis.

Short-chain fatty acids (SCFAs) are gut microbial metabolic derivatives produced during the fermentation of ingested complex carbohydrates. SCFAs have been widely regarded to have a potent anti-inflammatory and neuro-protective role and have implications in several disease conditions, such as, inflammatory bowel disease, type-2 diabetes, and neurodegenerative disorders. Japanese encephalitis virus (JEV), a neurotropic flavivirus, is associated with life threatening neuro-inflammation and neurological sequelae in infected hosts. In this study, we hypothesize that SCFAs have potential in mitigating JEV pathogenesis. Postnatal day 10 BALB/c mice were intraperitoneally injected with either a SCFA mixture (acetate, propionate, and butyrate) or PBS for a period of 7 days, followed by JEV infection. All mice were observed for onset and progression of symptoms. The brain tissue was collected upon reaching terminal illness for further analysis. SCFA-supplemented JEV-infected mice (SCFA + JEV) showed a delayed onset of symptoms, lower hindlimb clasping score, and decreased weight loss and increased survival by 3 days (p < 0.0001) upon infection as opposed to the PBS-treated JEV-infected animals (JEV). Significant downregulation of inflammatory cytokines TNF-α, MCP-1, IL-6, and IFN-Υ in the SCFA + JEV group relative to the JEV-infected control group was observed. Inflammatory mediators, phospho-NF-kB (P-NF-kB) and iba1, showed 2.08 ± 0.1 and 3.132 ± 0.43-fold upregulation in JEV versus 1.19 ± 0.11 and 1.31 ± 0.11-fold in the SCFA + JEV group, respectively. Tissue section analysis exhibited reduced glial activation (JEV group─42 ± 2.15 microglia/ROI; SCFA + JEV group─27.07 ± 1.8 microglia/ROI) in animals that received SCFA supplementation prior to infection as seen from the astrocytic and microglial morphometric analysis. Caspase-3 immunoblotting showed 4.08 ± 1.3-fold upregulation in JEV as compared to 1.03 ± 0.14-fold in the SCFA + JEV group and TUNEL assay showed a reduced cellular death post-JEV infection (JEV-6.4 ± 1.5 cells/ROI and SCFA + JEV-3.7 ± 0.73 cells/ROI). Our study critically contributes to the increasing evidence in support of SCFAs as an anti-inflammatory and neuro-protective agent, we further expand its scope as a potential supplementary intervention in JEV-mediated neuroinflammation.

Short-chain fatty acids induced lung tumor cell death and increased peripheral blood CD4+ T cells in NSCLC and control patients ex vivo.

Background: Despite therapy advances, one of the leading causes of cancer deaths still remains lung cancer. To improve current treatments or prevent non-small cell lung cancer (NSCLC), the role of the nutrition in cancer onset and progression needs to be understood in more detail. While in colorectal cancer, the influence of local microbiota derived SCFAs have been well investigated, the influence of SCFA on lung cancer cells via peripheral blood immune system should be investigated more deeply. In this respect, nutrients absorbed via the gut might affect the tumor microenvironment (TME) and thus play an important role in tumor cell growth. Objective: This study focuses on the impact of the short-chain fatty acid (SCFA) Sodium Butyrate (SB), on lung cancer cell survival. We previously described a pro-tumoral role of glucose on A549 lung adenocarcinoma cell line. In this study, we wanted to know if SB would counteract the effect of glucose and thus cultured A549 and H520 in vitro with and without SB in the presence or absence of glucose and investigated how the treatment with SB affects the survival of lung cancer cells and its influence on immune cells fighting against lung cancer. Methods: In this study, we performed cell culture experiments with A549, H520 and NSCLC-patient-derived epithelial cells under different SB levels. To investigate the influence on the immune system, we performed in vitro culture of peripheral mononuclear blood cells (PBMC) from control, smoker and lung cancer patients with increasing SB concentrations. Results: To investigate the effect of SB on lung tumor cells, we first analyzed the effect of 6 different concentrations of SB on A549 cells at 48 and 72 hours cell culture. Here we found that, SB treatment reduced lung cancer cell survival in a concentration dependent manner. We next focused our deeper analysis on the two concentrations, which caused the maximal reduction in cell survival. Here, we observed that SB led to cell cycle arrest and induced early apoptosis in A549 lung cancer cells. The expression of cell cycle regulatory proteins and A549 lung cancer stem cell markers (CD90) was induced. Additionally, this study explored the role of interferon-gamma (IFN-γ) and its receptor (IFN-γ-R1) in combination with SB treatment, revealing that, although IFN-γ-R1 expression was increased, IFN-γ did not affect the efficacy of SB in reducing tumor cell viability. Furthermore, we examined the effects of SB on immune cells, specifically CD8+ T cells and natural killer (NK) cells from healthy individuals, smokers, and NSCLC patients. SB treatment resulted in a decreased production of IFN-γ and granzyme B in CD8+ T cells and NK cells. Moreover, SB induced IFN-γ-R1 in NK cells and CD4+ T cells in the absence of glucose both in PBMCs from controls and NSCLC subjects. Conclusion: Overall, this study highlights the potential of SB in inhibiting lung cancer cell growth, triggering apoptosis, inducing cell cycle arrest, and modulating immune responses by activating peripheral blood CD4+ T cells while selectively inducing IFN-γ-R1 in NK cells in peripheral blood and inhibiting peripheral blood CD8+ T cells and NK cells. Thus, understanding the mechanisms of action of SB in the TME and its influence on the immune system provide valuable insights of potentially considering SB as a candidate for adjunctive therapies in NSCLC.

Modulation of the gut microbiota and short-chain fatty acid production by gac fruit juice and its fermentation in in vitro colonic fermentation.

This study aimed to investigate the effects of gac fruit juice and its probiotic fermentation (FGJ) utilizing Lactobacillus paracasei on the modulation of the gut microbiota and the production of short-chain fatty acids (SCFAs). We conducted a comparison between FGJ, non-fermented gac juice (GJ), and control samples through in vitro digestion and colonic fermentation using the human gut microbiota derived from fecal inoculum. Our findings revealed that both GJ and FGJ led to an increase in the viability of Lactobacilli, with FGJ exhibiting even higher levels compared to the control. The results from the 16S rDNA amplicon sequencing technique showed that both GJ and FGJ exerted positive impact on the gut microbiota by promoting beneficial bacteria, notably Lactobacillus mucosae and Bacteroides vulgatus. Additionally, both GJ and FGJ significantly elevated the levels of SCFAs, particularly acetic, propionic, and n-butyric acids, as well as lactic acid, in comparison to the control. Notably, FGJ exhibited a more pronounced effect on the gut microbiota compared to GJ. This was evident in its ability to enhance species richness, reduce the Firmicutes to Bacteroidetes (F/B) ratio, promote Akkermansia, and inhibit pathogenic Escherichia coli. Moreover, FGJ displayed enhanced production of SCFAs, especially acetic and lactic acids, in contrast to GJ. Our findings suggest that the probiotic fermentation of gac fruit enhances its functional attributes in promoting a balanced gut microbiota. This beverage demonstrates potential as a functional food with potential advantages for sustaining intestinal health.

Reactive oxygen species generation required for autophagy induction during butyrate- or propionate-induced release of damage-associated molecular patterns from dying gingival epithelial Ca9-22 cells.

PURPOSE: Bacterial cells in mature dental plaque produce a high concentration of short-chain fatty acids (SCFAs) such as butyrate and propionate. SCFA-treatment on human gingival epithelial Ca9-22 cells induced cell death. However, the exact mechanism underlying cell death remains unclear. In this study, the relationship between reactive oxygen species (ROS) and autophagy induction during SCFA-induced cell death was examined. METHODS: Human gingival epithelial Ca9-22 cells were treated with butyrate or propionate to induce cell death and the number of dead cells were measured using SYTOX-green dye. A siRNA for ATG5 and N-acetylcysteine (NAC) were used for autophagy reduction and ROS-scavenging, respectively. Release of damage-associated molecular patterns (DAMPs) such as Sin3A-associated protein 130 (SAP130) and high-mobility group box 1 (HMGB1) were detected using western blot. RESULTS: Reducing autophagy significantly suppressed SCFA-induced Ca9-22 cell death. ROS generation was observed upon SCFA treatment, and scavenging ROS with NAC decreased cell death. NAC also reduced the SCFA-induced increase in microtubule-associated protein 1 light chain 3B (LC3B)-I and LC3B-II, and mitigated the release of DAMPs. CONCLUSION: The findings suggest that ROS generation is necessary for autophagy, which is required for SCFA-induced cell death and accompanying DAMP release.

[Effect of Zuogui Jiangtang Jieyu Formula on intestinal flora and short-chain fatty acid metabolism in rats with diabetes mellitus complicated with depression].

This study aimed to investigate the regulatory effects of Zuogui Jiangtang Jieyu Formula(ZJJ) on the intestinal flora, short chain fatty acids(SCFAs), and neuroinflammation in rats with diabetes mellitus complicated depression(DD). The DD model was established in rats and model rats were randomly divided into a model group, a positive drug(metformin + fluoxetine) group, a ZJJ low-dose group, and a ZJJ high-dose group, with eight rats in each group. Another eight rats were assigned to the blank group. Subsequently, depressive-like behavior test was conducted on the rats, and cerebrospinal fluid samples were collected to measure pro-inflammatory cytokines [interleukin-1ß(IL-1ß), interleukin-6(IL-6), and tumor necrosis factor-α(TNF-α)]. Blood serum samples were collected to measure proteins related to the hypothalamic-pituitary-adrenal axis(HPA axis), including corticotropin-releasing hormone(CRH), adrenocorticotropic hormone(ACTH), and cortisol(CORT), as well as glucose metabolism. Gut contents were collected from each group for 16S rRNA sequencing analysis of intestinal flora and SCFAs sequencing. The results indicated that ZJJ not only improved glucose metabolism in DD rats(P<0.01) but also alleviated depressive-like behavior(P<0.05) and HPA axis hyperactivity(P<0.05 or P<0.01). Besides, it also improved the neuroinflammatory response in the brain, as evidenced by a significant reduction in pro-inflammatory cytokines in cerebrospinal fluid(P<0.05 or P<0.01). Additionally, ZJJ improved the intestinal flora, causing the intestinal flora in DD rats to resemble that of the blank group, characterized by an increased Firmicutes abundance. ZJJ significantly increased the levels of SCFAs(acetic acid, butyric acid, valeric acid, and isovaleric acid)(P<0.01). Therefore, it is deduced that ZJJ can effectively ameliorate intestinal flora dysbiosis, regulate SCFAs, and thereby improve both glucose metabolism disturbances and depressive-like behavior in DD.

Possible roles of short-chain fatty acids produced by oral bacteria in the development of alveolar osteitis.

PURPOSE: Alveolar osteitis (dry sockets) is a painful condition characterized by a limited immune response. It is typically caused by the removal of blood clots from extracted tooth sockets, which leads to the fermentation of trapped food remnants by oral bacteria in the cavities, producing high concentrations of short-chain fatty acids (SCFAs). This study examined the effects of SCFAs on immunity and bone metabolism. METHODS: Mouse macrophage Raw264.7 cells were treated with oral bacteria supernatants or SCFA mixtures, and inducible nitric oxide synthase (iNOS) levels were determined by western blot. The same cells were treated with SCFA mixtures in the presence of receptor activator of nuclear factor-kappa B ligand (RANKL), and osteoclast-like cells were counted. MC3T3-E1 cells were treated with SCFA mixtures and stained with alizarin red S. RESULTS: Raw264.7 cells treated with oral bacterial culture supernatants of Porphyromonas gingivalis and Fusobacterium nucleatum inhibited lipopolysaccharide (LPS)-induced iNOS production, likely due to SCFA content. SCFA mixtures mimicking these supernatants inhibited the number of RANKL-induced tartrate-resistant acid phosphatase (TRAP)-positive cells and MC3T3-E1 cell mineralization. CONCLUSION: These data suggest that SCFAs produced by P. gingivalis and F. nucleatum may reduce the inflammatory response and mildly induce mineralization of the alveolar walls. These results may contribute to the understanding of alveolar osteitis.

Hyperbaric oxygen augments susceptibility to C. difficile infection by impairing gut microbiota ability to stimulate the HIF-1α-IL-22 axis in ILC3.

Hyperbaric oxygen (HBO) therapy is a well-established method for improving tissue oxygenation and is typically used for the treatment of various inflammatory conditions, including infectious diseases. However, its effect on the intestinal mucosa, a microenvironment known to be physiologically hypoxic, remains unclear. Here, we demonstrated that daily treatment with hyperbaric oxygen affects gut microbiome composition, worsening antibiotic-induced dysbiosis. Accordingly, HBO-treated mice were more susceptible to Clostridioides difficile infection (CDI), an enteric pathogen highly associated with antibiotic-induced colitis. These observations were closely linked with a decline in the level of microbiota-derived short-chain fatty acids (SCFAs). Butyrate, a SCFA produced primarily by anaerobic microbial species, mitigated HBO-induced susceptibility to CDI and increased epithelial barrier integrity by improving group 3 innate lymphoid cell (ILC3) responses. Mice displaying tissue-specific deletion of HIF-1 in RORγt-positive cells exhibited no protective effect of butyrate during CDI. In contrast, the reinforcement of HIF-1 signaling in RORγt-positive cells through the conditional deletion of VHL mitigated disease outcome, even after HBO therapy. Taken together, we conclude that HBO induces intestinal dysbiosis and impairs the production of SCFAs affecting the HIF-1α-IL-22 axis in ILC3 and worsening the response of mice to subsequent C. difficile infection.

Isocaloric diets with varying protein levels affected energy metabolism in young adult Sprague-Dawley rats via modifying the gut microbes: A lipid imbalance was brought on by a diet with a particularly high protein content.

Protein is the most important macro-nutrient when it comes to maximizing health, body composition, muscle growth, and recovery of body tissue. In recent years, it has been found that protein also plays an important role in metabolism and gut microbiota. This study was performed to investigate the effects of an isocaloric diet with different crude protein contents on the energy metabolism of Sprague-Dawley (SD) rats. Results revealed that compared with the 20% crude protein (CP; control) diet, the 38% CP diet improved serum parameters that are associated with dyslipidemia and glucose metabolic disorders in SD rats, whereas the 50% CP diet increased liver injury indicators and fatty acid synthesis-related genes and protein expression in the liver. Compared with the control diet, the 14% CP diet increased the abundance of colonic short-chain fatty acid-producing bacteria (Lachnospiraceae_NK4A136_group and Ruminiclostridium_9) and promoted colonic microbial cysteine and methionine metabolism, the 38% CP diet up-regulated colonic microbial lysine biosynthesis and degradation pathways, and the 50% CP diet down-regulated colonic mucosal cholesterol metabolism. Furthermore, the increase of multiple colonic enteropathogenic bacteria in the 50% CP group was associated with higher palmitic acid and stearic acid concentrations in the colonic microbes and lower cholesterol and arachidonic acid concentrations in the colonic mucosa. These findings revealed that the 14% CP and 38% CP diets improved rats' energy metabolism, while the 50% CP diet was accompanied by lipid metabolism imbalances and an increase in the abundance of multiple enteropathogenic bacteria.

Enhancement of intestinal calcium transport by short-chain fatty acids: roles of Na+/H+ exchanger 3 and transient receptor potential vanilloid subfamily 6.

Small organic molecules in the intestinal lumen, particularly short-chain fatty acids (SCFAs) and glucose, have long been postulated to enhance calcium absorption. Here, we used 45Ca radioactive tracer to determine calcium fluxes across the rat intestine after exposure to glucose and SCFAs. Confirming previous reports, glucose was found to increase the apical-to-basolateral calcium flux in the cecum. Under apical glucose-free conditions, SCFAs (e.g., butyrate) stimulated the cecal calcium fluxes by approximately twofold, while having no effect on proximal colon. Since SCFAs could be absorbed into the circulation, we further determined whether basolateral SCFA exposure rendered some positive actions. It was found that exposure of duodenum and cecum on the basolateral side to acetate or butyrate increased calcium fluxes. Under butyrate-rich conditions, cecal calcium transport was partially diminished by Na+/H+ exchanger 3 (NHE3) inhibitor (tenapanor) and nonselective transient receptor potential vanilloid subfamily 6 (TRPV6) inhibitor (miconazole). To confirm the contribution of TRPV6 to SCFA-stimulated calcium transport, we synthesized another TRPV6 inhibitor that was demonstrated by in silico molecular docking and molecular dynamics to occlude TRPV6 pore and diminish the glucose- and butyrate-induced calcium fluxes. Therefore, besides corroborating the importance of luminal molecules in calcium absorption, our findings provided foundation for development of more effective calcium-rich nutraceuticals in combination with various absorptive enhancers, e.g., glucose and SCFAs.NEW & NOTEWORTHY Organic molecules in the intestinal lumen, e.g., glucose and short-chain fatty acids (SCFAs), the latter of which are normally produced by microfloral fermentation, can stimulate calcium absorption dependent on transient receptor potential vanilloid subfamily 6 (TRPV6) and Na+/H+ exchanger 3 (NHE3). A selective TRPV6 inhibitor synthesized and demonstrated by in silico docking and molecular dynamics to specifically bind to the pore domain of TRPV6 was used to confirm a significant contribution of this channel. Our findings corroborate physiological significance of nutrients and SCFAs in enhancing calcium absorption.

Effects of short-chain fatty acids on blood glucose and lipid levels in mouse models of diabetes mellitus: A systematic review and network meta-analysis.

Short-chain fatty acids (SCFAs), the main metabolites of gut microbiota, have been associated with lower blood glucose and lipid levels in diabetic mice. However, a comprehensive summary and comparison of the effects of different SCFA interventions on blood glucose and lipid levels in diabetic mice is currently unavailable. This study aims to compare and rank the effects of different types of SCFAs on blood glucose and lipid levels by collecting relevant animal research. A systematic search through PubMed, Embase, Cochrane Library, and Web of Science database was conducted to identify relevant studies from inception to March 17, 2023. Both pairwise meta-analysis and Bayesian network meta-analysis were used for statistical analyses. In total, 18 relevant studies involving 5 interventions were included after screening 3793 citations and 53 full-text articles. Notably, butyrate therapy (mean difference [MD] = -4.52, 95% confidence interval [-6.29, -2.75]), acetate therapy (MD = -3.12, 95% confidence interval [-5.79, -0.46]), and propionate therapy (MD = -2.96, 95% confidence interval [-5.66, -0.26]) significantly reduced the fasting blood glucose levels compared to the control group; butyrate therapy was probably the most effective intervention, with a surface under the cumulative ranking curve (SUCRA) value of 85.5%. Additionally, acetate plus propionate therapy was probably the most effective intervention for reducing total cholesterol (SUCRA = 85.8%) or triglyceride levels (SUCRA = 88.1%). These findings underscore the potential therapeutic implications of SCFAs for addressing metabolic disorders, particularly in type 2 diabetes mellitus.

Melatonin Ameliorates Neuropsychiatric Behaviors, Gut Microbiome, and Microbiota-Derived Metabolites in Rats with Chronic Sleep Deprivation.

With the increasing prevalence of sleep deprivation (SD)-related disorders, the effective treatment of sleep disorders has become a critical health research topic. Thus, we hypothesized and investigated the effectiveness of a 3-week melatonin intervention on neuropsychiatric behavioral responses mediated throughout melatonin receptors, gut microbiota, and lipid metabolites in rats with chronic SD. Eighteen 6-week-old Wistar rats were used and divided into the control grup (C, n = 6), SD group (n = 6), and melatonin-supplemented group (SDM, n = 6). During weeks 0 to 6, animals were provided with the AIN-93M diet and free access to water. Four-week chronic SD was conducted from weeks 7 to 10. Exogenous melatonin administration (10 mg/kg BW) was injected intraperitoneally 1 h before the daily administration of SD for 3 weeks in the SDM group. SD rats exhibited anxiety-like behavior, depression-like behavior, and cognitive impairment. Exogenous melatonin administration ameliorated neuropsychiatric behaviors induced by chronic SD. Analysis of fecal metabolites indicated that melatonin may influence brain messaging through the microbiota-gut-brain axis by increasing the production of short-chain fatty acids (SCFA) and decreasing the production of secondary bile acids (SBA). Four-week SD reduced the cerebral cortex expression of MT1, but not in the colon. Chronic SD led to anxiety and depression-like behaviors and cognitive decline, as well as the reduced intestinal level of SCFAs and the enhanced intestinal level of SBAs in rats. In this work, we confirmed our hypothesis that a 3-week melatonin intervention on neuropsychiatric behavioral response mediated throughout melatonin receptors, gut microbiota, and lipid metabolites in rats with chronic SD.

Functional profiling of gut microbial and immune responses toward different types of dietary fiber: a step toward personalized dietary interventions.

Dietary fiber plays a crucial role in maintaining gut and overall health. The objective of this study was to investigate whether different types of dietary fiber elicited specific changes in gut microbiota composition and the production of short-chain fatty acids. To test this, a longitudinal crossover study design was employed, in which healthy adult women consumed three distinct dietary fiber supplements: Inulin (fructo-oligosaccharide), Vitafiber (isomalto-oligosaccharide), and Fibremax (mixture of different fiber) during a one-week intervention period, followed by a 2-week washout period. A total of 15 g of soluble fiber was consumed daily for each supplement. Samples were collected before and after each intervention to analyze the composition of the gut microbiota by 16S rRNA sequencing and fecal levels of short-chain fatty acids measured using nuclear magnetic resonance. Phenotypic changes in peripheral blood mononuclear cells were studied in subsets of participants with higher SCFA levels post-intervention using spectral flow cytometry. The results revealed substantial stability and resilience of the overall gut bacterial community toward fiber-induced changes. However, each supplement had specific effects on gut bacterial alpha and beta diversity, SCFA production, and immune changes. Inulin consistently exerted the most pronounced effect across individuals and certain taxa were identified as potential indicators of SCFA production in response to inulin supplementation. This distinguishing feature was not observed for the other fiber supplements. Further large-scale studies are required to confirm these findings. Overall, our study implies that personalized dietary fiber intervention could be tailored to promote the growth of beneficial bacteria to maximize SCFA production and associated health benefits.

The role and mechanism of action of microbiota-derived short-chain fatty acids in neutrophils: From the activation to becoming potential biomarkers.

Short-chain fatty acids (SCFAs), such as acetate, propionate, and butyrate, have emerged as critical mediators in the communication between the human microbiota and its host. As the first responder to the inflammatory site, neutrophils play an important role in protecting the host against bacterial infections. Recent investigations revealed that SCFAs generated from microbiota influence various neutrophil activities, including activation, migration, and generation of mediators of inflammatory processes. SCFAs have also been demonstrated to exhibit potential therapeutic benefits in a variety of disorders related to neutrophil dysfunction, including inflammatory bowel disease, viral infectious disorders, and cancer. This study aims to examine the molecular processes behind the complicated link between SCFAs and neutrophils, as well as their influence on neutrophil-driven inflammatory disorders. In addition, we will also provide an in-depth review of current research on the diagnostic and therapeutic value of SCFAs as possible biomarkers for neutrophil-related diseases.

The maca protein ameliorates DSS-induced colitis in mice by modulating the gut microbiota and production of SCFAs.

Maca is a functional food with anti-inflammatory activity, and it is rich in protein. Currently, inflammatory bowel disease (IBD) is a common gastrointestinal disease. However, there is little research focusing on the effect of maca protein (MCP) on IBD. In this study, we extracted MCP from maca root and explored its effect and mechanism on improving dextran sodium sulfate (DSS)-induced IBD in mice. The results indicated that MCP intervention alleviated the clinical symptoms and colon tissue damage of mice with DSS-induced colitis and inhibited the expression of inflammatory factors. Moreover, it can modulate the gut microbiota composition in mice with DSS-induced colitis. The regulation is achieved by reducing the relative abundance of the IBD-exacerbating key bacterial genera: Lachnospiraceae_NK4A136_group, Bacteroides, Desulfovibrio, Prevotella, Helicobacter and Sutterella, while increasing the relative abundance of the IBD-alleviating key bacterial genera: norank_f_Muribaculaceae, Lactobacillus, Oscillospira, Akkermansia and Bifidobacterium. MCP can also promote the production of short-chain fatty acids (SCFAs). The further western blotting results indicated that MCP can regulate the Treg/Th17 immune balance in mice with colitis via the SCFAs-GPR41/43/HDAC1 signaling pathway. Overall, MCP can alleviate colitis by comprehensively regulating the gut microbiota and inflammatory response. It may be a promising functional component that reduces the risk of colitis by maintaining intestinal health.

Akkermansia muciniphila attenuated lipopolysaccharide-induced acute lung injury by modulating the gut microbiota and SCFAs in mice.

Gut microbiota are closely related to lipopolysaccharide (LPS)-induced acute lung injury (ALI). Akkermansia muciniphila (A. muciniphila) maintains the intestinal barrier function and regulates the balance of reduced glutathione/oxidized glutathione. However, it may be useful as a treatment strategy for LPS-induced lung injury. Our study aimed to explore whether A. muciniphila could improve lung injury by affecting the gut microbiota. The administration of A. muciniphila effectively attenuated lung injury tissue damage and significantly decreased the oxidative stress and inflammatory reaction induced by LPS, with lower levels of myeloperoxidase (MDA), enhanced superoxide dismutase (SOD) activity, decreased pro-inflammatory cytokine levels, and reduced macrophage and neutrophil infiltration. Moreover, A. muciniphila maintained the intestinal barrier function, reshaped the disordered microbial community, and promoted the secretion of short-chain fatty acids (SCFAs). A. muciniphila significantly downregulated the expression of TLR2, MyD88 and NF-kappa B (P < 0.05). Butyrate supplementation demonstrated a significant improvement in the inflammatory response (P < 0.05) and mitigation of histopathological damage in mice with ALI, thereby restoring the intestinal butyric acid concentration. In conclusion, our findings indicate that A. muciniphila inhibits the accumulation of inflammatory cytokines and attenuates the activation of the TLR2/Myd88/NF-κB pathway due to exerting anti-inflammatory effects through butyrate. This study provides an experimental foundation for the potential application of A. muciniphila and butyrate in the prevention and treatment of ALI.

Lactic acid enhances vaginal epithelial barrier integrity and ameliorates inflammatory effects of dysbiotic short chain fatty acids and HIV-1.

The vaginal microenvironment is key in mediating susceptibility to sexually transmitted infections. A polymicrobial environment with reduced Lactobacilllus spp. is characteristic of vaginal dysbiosis, associated with increased production of several short chain fatty acids (SCFAs), vaginal inflammation and an increased risk of HIV-1 acquisition. In contrast, a eubiotic vaginal microbiome (VMB), dominated by Lactobacillus spp. correlates with increased production of lactic acid (LA), an acidic milieu and protection against HIV-1. Vaginal metabolites, specifically LA and SCFAs including butyric, succinic and acetic acids are associated with modulation of HIV-1 risk. We assessed the impact of combined and individual SCFAs and LA on vaginal epithelial cells (VK2) grown in air-liquid interface cultures. Treatment of VK2 cells with eubiotic SCFA + LA mixture showed increased epithelial barrier integrity, reduced FITC dextran leakage and enhanced expression of cell-cell adhesion proteins. Treatment with dysbiotic SCFA + LA mixture diminished epithelial barrier integrity, increased NFκB activation and inflammatory mediators: TNF-α, IL-6, IL-8 and RANTES. LA was found to be the primary contributor of the beneficial effects. Eubiotic SCFA + LA mixture ameliorated HIV-1 mediated barrier disruption and HIV-1 leakage, whereas dysbiotic SCFA + LA treatment exacerbated HIV-1 effects. These findings indicate a key role for LA in future prophylactic strategies.

Trans-vaccenic acid reprograms CD8+ T cells and anti-tumour immunity.

Diet-derived nutrients are inextricably linked to human physiology by providing energy and biosynthetic building blocks and by functioning as regulatory molecules. However, the mechanisms by which circulating nutrients in the human body influence specific physiological processes remain largely unknown. Here we use a blood nutrient compound library-based screening approach to demonstrate that dietary trans-vaccenic acid (TVA) directly promotes effector CD8+ T cell function and anti-tumour immunity in vivo. TVA is the predominant form of trans-fatty acids enriched in human milk, but the human body cannot produce TVA endogenously1. Circulating TVA in humans is mainly from ruminant-derived foods including beef, lamb and dairy products such as milk and butter2,3, but only around 19% or 12% of dietary TVA is converted to rumenic acid by humans or mice, respectively4,5. Mechanistically, TVA inactivates the cell-surface receptor GPR43, an immunomodulatory G protein-coupled receptor activated by its short-chain fatty acid ligands6-8. TVA thus antagonizes the short-chain fatty acid agonists of GPR43, leading to activation of the cAMP-PKA-CREB axis for enhanced CD8+ T cell function. These findings reveal that diet-derived TVA represents a mechanism for host-extrinsic reprogramming of CD8+ T cells as opposed to the intrahost gut microbiota-derived short-chain fatty acids. TVA thus has translational potential for the treatment of tumours.

Gut microbiota might mediate the benefits of high-fiber/acetate diet to cardiac hypertrophy mice

Continuously prolonged cardiac hypertrophy results in maladaptive myocardial remodeling, which affects cardiac function and can eventually lead to heart failure. Short-chain fatty acids (SCFAs), including acetate, propionate, and butyrate, have been reported to be associated with cardiovascular diseases (CVD). Gut microbiota may mediate between dietary fiber and SCFA effects on cardiac hypertrophy. The mice model of isoproterenol (ISO)-induced cardiac hypertrophy was constructed and verified for physiological, functional, and fibrotic alterations in this study. Both high-fiber and acetate diet improved physiological indexes, ameliorated cardiac functions, and relieved fibrotic alterations in model mice hearts; collectively, cardiac hypertrophy in mice receiving both high-fiber and acetate diet improved. Following 16s rDNA sequencing and integrative bioinformatics, analyses indicated that both high-fiber and acetate diet caused alterations in mice gut microbiota compared with the ISO group, including OTU composition and abundance. In conclusion, high-fiber and acetate diet improve the physiological status, cardiac functions, and fibrotic alterations in ISO-induced hypertrophic mice. Besides, considering the alterations in mice gut microbiota in response to single ISO, both high-fiber and acetate diet treatment, gut microbiota might mediate the favorable benefits of both high-fiber and acetate diet on cardiac hypertrophy. (AU)

Lychee Pulp-Derived Dietary Fiber-Bound Phenolic Complex Upregulates the SCFAs-GPRs-ENS Pathway and Aquaporins in Loperamide-Induced Constipated Mice by Reshaping Gut Microbiome.

This study aimed to investigate the effects of the lychee pulp-derived dietary fiber-bound phenolic complex (DF-BPC) on a murine model of loperamide-induced constipation and its molecular mechanism associated with gut microbiota modification. DF-BPC supplementation mitigated loperamide-induced dyschezia, intestinal hypomotility, and colonic impairment, as evidenced by the increased gastro-intestinal transit rate and mucus cell counts. By comparison, short-chain fatty acids (SCFAs) contents and relative abundances of associated genera (Butyricimonas, Clostridium, and Lactobacillus) were effectively upregulated following DF-BPC supplementation. Notably, DF-BPC significantly enhanced expressions of G protein-coupled receptor (GPR) 41 and 43, reaching 1.43- and 1.62-fold increase, respectively. Neurotransmitter secretions were simultaneously altered in DF-BPC-treated mice, suggesting upregulation of the SCFAs-GPRs-enteric nervous system pathway. The overexpression of aquaporins (AQP3, 8, and 9) was stimulated partly through GPRs activation. Mild inflammation associated with constipation was inhibited by suppressing LBP-TLR4-NF-κB signaling translocation. These findings suggest that DF-BPC from lychee pulp has the potential to alleviate constipation in mice through modifying the gut microbiome.

Chitosan and its oligosaccharide accelerate colonic motility and reverse serum metabolites in rats after excessive protein consumption.

Excessive protein consumption (EPC) could increase the gastrointestinal burden and impair gut motility. The present study was designed to explore the improvement of chitosan (CTS) and chitosan oligosaccharide (COS) on colonic motility and serum metabolites in rats after EPC. The results of in vivo experiments fully proved that CTS and COS could improve gut motility and reverse the serum metabolites in rats as indicated by LC-MS/MS analysis, and the COS group even showed a better effect than the CTS group. Furthermore, short-chain fatty acids (SCFAs), which could promote gut motility, were also increased to alleviate EPC-induced constipation after supplementation with CTS or COS. In addition, CTS and COS could decrease the concentration of ammonia in serum and down-regulate the levels of H2S and indole. In summary, the present study revealed that CTS and COS could produce SCFAs, improve the colonic motility in rats, reverse the levels of valine, adenosine, cysteine, 1-methyladenosine, indole, and uracil, and enhance aminoacyl-tRNA biosynthesis and valine, leucine and isoleucine degradation. The present study provides novel insights into the potential roles of CTS and COS in alleviating the adverse effects of EPC.