Short-chain Fatty Acids Supplementation Research Articles

#885 Combination of medium cut-off dialyzer membrane and diet modification to reduce serum concentrations of p-cresyl sulfate and indoxyl sulfate

Abstract Background and Aims Online hemodiafiltration (ol-HDF) may be considered currently as the best choice for chronic hemodialysis (HD) treatment, but medium cut-off (MCO) membranes may provide similar efficiency for larger and protein-bound toxin removal. P-cresyl sulfate (PCS) and indoxyl-sulfate (IS) concentration depends mainly on residual renal function and diet. Increased dietary fiber intake and short-chain fatty acid (SCFA) supplementation were associated with decreased production of PCS and IS. The aim of this study was to pragmatically combine MCO use with diet modification in an attempt to reduce serum concentration of PCS and IS and compare this strategy to online HDF use. Method We report preliminary results from a subset of a study sample with 42 chronic prevalent HD patients in a prospective randomized controlled interventional study. Two weeks after standard bicarbonate HD (BHD), patients were randomized to hemodialysis with MCO membrane (EXP group) or ol-HDF with a standard "high-flux" (HF) dialyzer membrane (CON group). After 4 weeks, both groups were supplemented by a change in the diet with increase of the daily intake of dietary fiber to 30g and addition of a SCFA propionate in the dose of 1g daily for 8 weeks. Two main outcomes were serum concentrations of PCS and IS. Measurements were taken at baseline (after 2 week wash-in period), after 4 weeks of the first intervention phase (MCO vs. ol-HDF; T1), after 8 weeks of the second intervention phase (fiber and SCFA supplementation; T2) and finally, after 4 weeks of wash-out period with BHD (T3). Results From 42 participants, 38 completed the study (63.2% men, 66.4±10.9 years, Charlson comorbidity index 5.7±2.3). In the CON group, serum concentrations of PCS (in μg/ml) were 36.8±19.6 (baseline), 36.9±20.8 (T1), 32.4±17.4 (T2) and 38.6±22.1 (T3). Serum concentrations of IS (in μg/ml) were 31.8±13.0 (baseline), 32.9±14.7 (T1), 29.5±9.1 (T2) and 35.5±16.8 (T3). In the EXP group, serum concentrations of PCS were 33.5± 16.6 (baseline), 35.9±17.8 (T1), 34.0±16.1 (T2) and 37.4±21.5 (T3). Serum concentrations for IS were 39.6±12.6 (baseline), 37.3±12.9 (T1), 42.3±13.5 (T2) and 41.0±12.8 (T3). Repeated measures ANOVA revealed no significant time*group interaction for PCS (F(1,33)=0.479, p=0.698, ŋ2=0.014) and IS (F(1,33)=2.392, p=0.073, ŋ2=0.068). There was a significant within-group increase in serum IS concentration between T2 and T3 in CON group (p=0.042). There was a trend towards a decrease in PCS concentration between T1 and T2 and increase between T2 and T3 in CON group. Conclusion The results of the study suggest both hemodialysis methods are equivalent in eliminating PCS and IS. Additional fiber and SCFA propionate supplementation did not decrease serum PCS and IS concentrations significantly, although there was a trend towards lower serums concentration of PCS after diet modification in CON group.

Sodium propionate oral supplementation ameliorates depressive-like behavior through gut microbiome and histone 3 epigenetic regulation

Major depressive disorder (MDD) is a global health concern, affecting over 250 million individuals worldwide. In recent years, the gut-brain axis has emerged as a promising field for understanding the pathophysiology of MDD. Microbial metabolites, such as short-chain fatty acids (SCFAs)—acetate, butyrate, and propionate-, have gained attention for their potential to influence epigenetic modifications within the host brain. However, the precise mechanisms through which these metabolites participate in MDD pathophysiology remain elusive. This study was designed to investigate the effects of oral SCFA supplementation in adult male Wistar rats subjected to chronic unpredictable mild stress (CUMS). A subset of control and CUMS-exposed rats received different supplementations: sodium acetate (NaOAc) at a concentration of 60 mM, sodium butyrate (NaB) at 40 mM, sodium propionate (NaP) at 50 mM, or a mixture of these SCFAs. The gut microbiome was assessed through 16S rRNA sequencing, and epigenetic profiling was performed using Western blot analysis. Results demonstrated that NaP supplementation significantly alleviated anhedonia in stressed animals, as evidenced by improved performance in the sucrose consumption test. This ameliorative effect was potentially associated with the modulation of gut bacterial communities, accompanied by the attenuation of the region-specific epigenetic dysregulation in the brain of the animals exposed to chronic stress. These findings suggest a potential association between gut dysbiosis and stress response, and NaP could be a promising target for future MDD interventions. However, further studies are needed to fully elucidate the underlying mechanisms of these effects.

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.

SCFAs Supplementation Rescues Anxiety- and Depression-like Phenotypes Generated by Fecal Engraftment of Treatment-Resistant Depression Rats.

Alteration of gut microbiota and microbial metabolites such as short-chain fatty acids (SCFAs) coexisted with stress-generated brain disorders, including depression. Herein, we investigated the effect of SCFAs in a treatment-resistant depression (TRD) model of rat. Rats were exposed to chronic-unpredictable mild stress (CUMS) and repeated adrenocorticotropic hormone (ACTH) injections to generate a TRD-like phenotype. The cecal contents of these animals were engrafted into healthy-recipient rats and allowed to colonize for 4 weeks (TRD-FMT group). Blood, brain, colon, fecal, and cecal samples were collected for molecular studies. Rats exposed to CUMS + ACTH showed TRD-like phenotypes in sucrose-preference (SPT), forced swim (FST), and elevated plus maze (EPM) tests. The TRD-FMT group also exhibited anxiety- and depression-like behaviors. Administration of SCFAs (acetate, propionate, and butyrate at 67.5, 25, and 40 mM, respectively) for 7 days exerted robust antidepressant and antianxiety effects by restoring the levels of SCFAs in plasma and fecal samples, and proinflammatory cytokines (TNF-α and IL-6), serotonin, GABA, norepinephrine, and dopamine in the hippocampus and/or frontal cortex of TRD and TRD-FMT animals. SCFAs treatment elevated the expression of free-fatty acid receptors 2/3, BDNF, doublecortin, and zonula-occludens, and reduced the elevated plasma levels of kynurenine and quinolinic acid and increased mucus-producing goblet cells in TRD and TRD-FMT animals. In 16S sequencing results, decreased microbial diversity in TRD rats corresponds with differences in the genus of Faecalibacterium, Anaerostipes, Allobaculum, Blautia, Peptococcus, Rombustia, Ruminococcaceae_UCG-014, Ruminococcaceae_UCG-002, Solobacterium, Subdolibacterium, and Eubacterium ventriosum. SCFAs may impart beneficial effects via modulation of tryptophan metabolism, inflammation, neurotransmitters, and microbiota-gut-brain axis in TRD rats.

Mitigation of Osteoclast-Mediated Arthritic Bone Remodeling By Short Chain Fatty Acids.

The objective for this study was to evaluate the effects of short chain fatty acids (SCFAs) on arthritic bone remodeling. We treated a recently described preclinical murine model of psoriatic arthritis (PsA), R26STAT3Cstopfl/fl CD4Cre mice, with SCFA-supplemented water. We also performed in vitro osteoclast differentiation assays in the presence of serum-level SCFAs to evaluate the direct impact of these microbial metabolites on maturation and function of osteoclasts. We further characterized the molecular mechanism of SCFAs by transcriptional analysis. The osteoporosis condition in R26STAT3Cstopfl/fl CD4Cre animals is attributed primarily to robust osteoclast differentiation driven by an expansion of osteoclast progenitor cells (OCPs), accompanied by impaired osteoblast development. We show that SCFA supplementation can rescue the osteoporosis phenotype in this model of PsA. Our in vitro experiments revealed an inhibitory effect of the SCFAs on osteoclast differentiation, even at very low serum concentrations. This suppression of osteoclast differentiation enabled SCFAs to impede osteoporosis development in R26STAT3Cstopfl/fl CD4Cre mice. Further interrogation revealed that bone marrow-derived OCPs from diseased mice expressed a higher level of SCFA receptors than those of control mice and that the progenitor cells in the bone marrow of SCFA-treated mice presented a modified transcriptomic landscape, suggesting a direct impact of SCFAs on bone marrow progenitors in the context of osteoporosis. We demonstrated how gut microbiota-derived SCFAs can regulate distal pathology (ie, osteoporosis) and identified a potential therapeutic option for restoring bone density in rheumatic disease, further highlighting the critical role of the gut-bone axis in these disorders.

Spinal cord injury-induced gut dysbiosis influences neurological recovery partly through short-chain fatty acids

Spinal cord injury (SCI) can reshape gut microbial composition, significantly affecting clinical outcomes in SCI patients. However, mechanisms regarding gut–brain interactions and their clinical implications have not been elucidated. We hypothesized that short-chain fatty acids (SCFAs), intestinal microbial bioactive metabolites, may significantly affect the gut–brain axis and enhance functional recovery in a mouse model of SCI. We enrolled 59 SCI patients and 27 healthy control subjects and collected samples. Thereafter, gut microbiota and SCFAs were analyzed using 16 S rDNA sequencing and gas chromatography–mass spectrometry, respectively. We observed an increase in Actinobacteriota abundance and a decrease in Firmicutes abundance. Particularly, the SCFA-producing genera, such as Faecalibacterium, Megamonas, and Agathobacter were significantly downregulated among SCI patients compared to healthy controls. Moreover, SCI induced downregulation of acetic acid (AA), propionic acid (PA), and butyric acid (BA) in the SCI group. Fecal SCFA contents were altered in SCI patients with different injury course and injury segments. Main SCFAs (AA, BA, and PA) were administered in combination to treat SCI mice. SCFA supplementation significantly improved locomotor recovery in SCI mice, enhanced neuronal survival, promoted axonal formation, reduced astrogliosis, and suppressed microglial activation. Furthermore, SCFA supplementation downregulated NF-κB signaling while upregulating neurotrophin-3 expression following SCI. Microbial sequencing and metabolomics analysis showed that SCI patients exhibited a lower level of certain SCFAs and related bacterial strains than healthy controls. SCFA supplementation can reduce inflammation and enhance nourishing elements, facilitating the restoration of neurological tissues and the improvement of functional recuperation. Trial registration: This study was registered in the China Clinical Trial Registry (www.chictr.org.cn) on February 13, 2017 (ChiCTR-RPC-17010621).

Prebiotic Mannan Oligosaccharide Attenuates Cognitive and Behavioral Disorders in HIV-1 gp120 Transgenic Mouse Via the Microbiota-Gut-Brain Axis

Background The prevalence of HIV-associated neurocognitive disorders (HAND) remains high among HIV-1 infected patients, despite significant advances in antiretroviral therapy (HAART). HAND is characterized by clinical symptoms such as motor and attention deficits, impaired learning and memory, and in severe cases, dementia. The HIV-1 envelope protein gp120 is believed to have a crucial role in the development of these disorders HIV-1-related neurocognitive dysfunction is strongly linked to the host inflammatory regulator α7 nicotinic acetylcholine receptor (A7R) and the signaling of highly reactive oxygen species (ROS). A7R plays a crucial role in regulating calcium ion exchange in nerve cells, immune cells, and endothelial cells. In the brain, antioxidants are present to control and prevent the formation of harmful ROS, which further contribute to the severity of neurodegeneration. Assessing ROS can help predict oxidative tissue damage, including modifications in proteins, lipids, or DNA. ROS tend to accumulate in the small and large intestines, leading to oxidative stress and affecting cognitive function. The prebiotic mangan oligosaccharide (MOS) has been reported to reshape the gut microbiome and increase short-chain fatty acid (SCFAs) production. This, in turn, alters neuronal redox status through the gut-brain axis. There may be a critical role for HIV-1 gp120 (Gp120) protein in these disorders. The microbiota-gut-brain (MGB) axis is bidirectional, and gut microbiota influence brain disorders including HAND, which could be targeted by nutritional interventions. Methods: The HIV-1 gp120 transgenic mice (Gp120 transgenic mice), and wild-type (WT) mice were randomly divided into 4 groups (9 months old, n=6 per group): WT group, WT+MOS group, Gp120 transgenic group, Gp120 transgenic + MOS group. All MOS group mice were administered the prebiotic MOS (0.12% w/v in the drinking water).The drinking water added MOS or was replaced twice a week for 8 weeks and recorded water intake. In the in vitro cell experiment, the cortex of neonatal Sprague-Dawley (SD) rats (1-3 days) was dissected to prepare astrocytes. Cells were identified using Cy3-conjugated GFAP immunostaining. Cultured astrocytes were treated with 300 pM Gp120 protein for 24 hours, and then 0.2, 2, 20 or 200 μM MOS was applied for 24 hours, and different proteins level of expression were detected by Western blot. The ROS level were then analyzed on FACS Calibur-Tangerine flow cytometry in 502 nm. The alteration in mitochondrial membrane potential in astrocytes was assessed through the utilization of the JC-1 Assay Kit in mPMs. Results: As a result of treatment with MOS, the redox status of the brain and the neuroinflammatory responses were significantly balanced. Through correlation analysis, it was observed that a modified gut microbiome and increased butyrate production had a significant impact on behavioral changes and brain oxidative status. Our findings suggest that MOS could mitigate cognitive and behavioral disorders in the Gp120 transgenic mouse. MOS achieves this by suppressing Gp120-induced chronic inflammation and dysregulated production of reactive oxygen species (ROS), thereby improving HIV-1-related neurocognitive dysfunction. This is achieved by targeting A7R and intestinal ROS signaling. Additionally, our results indicate that SCFA supplementation in the brain of HAND mice alleviated behavioral disorders and balanced the HPA-axis and redox status. Conclusion: Overall, the present study demonstrated that MOS significantly reduced cognitive and mental deficits in Gp120 transgenic mice. As prebiotics, MOS could be translated into novel microbiota-targeted approaches to manage metabolic and neurodegenerative diseases. ( Acknowledgements: Natural Science Foundation of Guangdong Province, No. 208059478058 to H.C.; Corresponding author: Hong Cao, gzhcao@smu.edu.cn ) Keywords：HIV-1 gp120, mangan oligosaccharide, α7nAChR, reactive oxygen species

Gut microbiota-derived short-chain fatty acids ameliorate methamphetamine-induced depression- and anxiety-like behaviors in a Sigmar-1 receptor-dependent manner

Methamphetamine (Meth) abuse can cause serious mental disorders, including anxiety and depression. The gut microbiota is a crucial contributor to maintaining host mental health. Here, we aim to investigate if microbiota participate in Meth-induced mental disorders, and the potential mechanisms involved. Here, 15 mg/kg Meth resulted in anxiety- and depression-like behaviors of mice successfully and suppressed the Sigma-1 receptor (SIGMAR1)/BDNF/TRKB pathway in the hippocampus. Meanwhile, Meth impaired gut homeostasis by arousing the Toll-like receptor 4 (TLR4)-related colonic inflammation, disturbing the gut microbiome and reducing the microbiota-derived short-chain fatty acids (SCFAs). Moreover, fecal microbiota from Meth-administrated mice mediated the colonic inflammation and reproduced anxiety- and depression-like behaviors in recipients. Further, SCFAs supplementation optimized Meth-induced microbial dysbiosis, ameliorated colonic inflammation, and repressed anxiety- and depression-like behaviors. Finally, Sigmar1 knockout (Sigmar1−/−) repressed the BDNF/TRKB pathway and produced similar behavioral phenotypes with Meth exposure, and eliminated the anti-anxiety and -depression effects of SCFAs. The activation of SIGMAR1 with fluvoxamine attenuated Meth-induced anxiety- and depression-like behaviors. Our findings indicated that gut microbiota-derived SCFAs could optimize gut homeostasis, and ameliorate Meth-induced mental disorders in a SIGMAR1-dependent manner. This study confirms the crucial role of microbiota in Meth-related mental disorders and provides a potential preemptive therapy.

Early-life noise exposure causes cognitive impairment in a sex-dependent manner by disrupting homeostasis of the microbiota–gut–brain axis

Epidemiological investigations show that noise exposure in early life is associated with health and cognitive impairment. The gut microbiome established in early life plays a crucial role in modulating developmental processes that subsequently affect brain function and behavior. Here, we examined the impact of early-life exposure to noise on cognitive function in adolescent rats by analyzing the gut microbiome and metabolome to elucidate the underlying mechanisms. Chronic noise exposure during early life led to cognitive deficits, hippocampal injury, and neuroinflammation. Early-life noise exposure showed significant difference on the composition and function of the gut microbiome throughout adolescence, subsequently causing axis-series changes in fecal short-chain fatty acid (SCFA) metabolism and serum metabolome profiles, as well as dysregulation of endothelial tight junction proteins, in both intestine and brain. We also observed sex-dependent effects of microbiota depletion on SCFA-related beneficial bacteria in adolescence. Experiments on microbiota transplantation and SCFA supplementation further confirmed the role of intestinal bacteria and related SCFAs in early-life noise-exposure-induced impairments in cognition, epithelial integrity, and neuroinflammation. Overall, these results highlight the homeostatic imbalance of microbiota–gut–brain axis as an important physiological response toward environmental noise during early life and reveals subtle differences in molecular signaling processes between male and female rats.

Gut microbiota-derived short-chain fatty acids promote prostate cancer progression via inducing cancer cell autophagy and M2 macrophage polarization

We have previously demonstrated abnormal gut microbial composition in castration-resistant prostate cancer (CRPC) patients, here we revealed the mechanism of gut microbiota-derived short-chain fatty acids (SCFAs) as a mediator linking CRPC microbiota dysbiosis and prostate cancer (PCa) progression. By using transgenic TRAMP mouse model, PCa patient samples, in vitro PCa cell transwell and macrophage recruitment assays, we examined the effects of CRPC fecal microbiota transplantation (FMT) and SCFAs on PCa progression. Our results showed that FMT with CRPC patients’ fecal suspension increased SCFAs-producing gut microbiotas such as Ruminococcus, Alistipes, Phascolarctobaterium in TRAMP mice, and correspondingly raised their gut SCFAs (acetate and butyrate) levels. CRPC FMT or SCFAs supplementation significantly accelerated mice's PCa progression. In vitro, SCFAs enhanced PCa cells migration and invasion by inducing TLR3-triggered autophagy that further activated NF-κB and MAPK signalings. Meanwhile, autophagy of PCa cells released higher level of chemokine CCL20 that could reprogramme the tumor microenvironment by recruiting more macrophage infiltration and simultaneously polarizing them into M2 type, which in turn further strengthened PCa cells invasiveness. Finally in a cohort of 362 PCa patients, we demonstrated that CCL20 expression in prostate tissue was positively correlated with Gleason grade, pre-operative PSA, neural/seminal vesical invasion, and was negatively correlated with post-operative biochemical recurrence-free survival. Collectively, CRPC gut microbiota-derived SCFAs promoted PCa progression via inducing cancer cell autophagy and M2 macrophage polarization. CCL20 could become a biomarker for prediction of prognosis in PCa patients. Intervention of SCFAs-producing microbiotas may be a useful strategy in manipulation of CRPC.

Disordered gut microbiota and changes in short-chain fatty acids and inflammatory processes in stress-vulnerable mice

Long-term exposure to chronic stress increases the incidence of depression. However, chronic stress is an associated risk factor in only a subset of individuals. Inflammation has been identified as a putative mechanism promoting stress vulnerability. Because of the gut microbiota's potential role as a source of inflammatory substances, short-chain fatty acids (SCFAs) may exert their influence on inflammation, emotional states, and cognition via the gut-brain axis. In this study, Classic behavioral tests were used to categorize C57BL/6 J mice into a CUMS-vulnerable and a CUMS-resilient group after they were exposed to chronic unpredictable mild stress (CUMS). We compared the 16S ribosomal RNA (rRNA) gene sequences retrieved from fecal samples between control, CUMS-vulnerable, and CUMS-resilient mice. SCFAs in fecal samples were detected by liquid chromatography and gas chromatography–mass spectrometry. Hippocampal cytokine production and TLR4/MYD88/NF-κB inflammatory pathway activation were evaluated using enzyme-linked immunosorbent assays (ELISAs) and western blotting. Then, we supplemented SCFAs in CUMS mice. we observed depression-like behavior and the expression of TLR4/MYD88/NF-κB inflammatory pathway in hippocampus of SCFAs supplementation mice. Susceptible mice to CUMS showed more severe symptoms of depression and anxiety, α diversity was significantly different, as well as higher expression of interleukin (IL)-1β and TLR4/MYD88/NF-κB inflammatory pathway components in the hippocampus. SCFA levels in the feces were significantly higher in CUMS-resilient mice than in control mice. Depressive behavior was reversed in CUMS-SCFAs group, and the protein level of TLR4/MYD88/NF-κB in hippocampus was decreased. Overall, these results provide new light on the possible involvement of the microbiome in the gut-brain axis development in depressive disorder and provide a theoretical basis for identifying novel therapeutic targets.

Multi-Omics Reveals the Impact of Exogenous Short-Chain Fatty Acid Infusion on Rumen Homeostasis: Insights into Crosstalk between the Microbiome and the Epithelium in a Goat Model.

Emerging data have underscored the significance of exogenous supplementation of butyrate in the regulation of rumen development and homeostasis. However, the effects of other short-chain fatty acids (SCFAs), such as acetate or propionate, has received comparatively less attention, and the consequences of extensive exogenous SCFA infusion remain largely unknown. In our study, we conducted a comprehensive investigation by infusion of three SCFAs to examine their respective roles in regulating the rumen microbiome, metabolism, and epithelium homeostasis. Data demonstrated that the infusion of sodium acetate (SA) increased rumen index while also promoting SCFA production and absorption through the upregulation of SCFA synthetic enzymes and the mRNA expression of SLC9A1 gene. Moreover, both SA and sodium propionate infusion resulted in an enhanced total antioxidant capacity, an increased concentration of occludin, and higher abundances of specific rumen bacteria, such as "Candidatus Saccharimonas," Christensenellaceae R-7, Butyrivibrio, Rikenellaceae RC9 gut, and Alloprevotella. In addition, sodium butyrate (SB) infusion exhibited positive effects by increasing the width of rumen papilla and the thickness of the stratum basale. SB infusion further enhanced antioxidant capacity and barrier function facilitated by cross talk with Monoglobus and Incertae Sedis. Furthermore, metabolome and transcriptome data revealed distinct metabolic patterns in rumen contents and epithelium, with a particular impact on amino acid and fatty acid metabolism processes. In conclusion, our data provided novel insights into the regulator effects of extensive infusion of the three major SCFAs on rumen fermentation patterns, antioxidant capacity, rumen barrier function, and rumen papilla development, all achieved without inducing rumen epithelial inflammation. IMPORTANCE The consequences of massive exogenous supplementation of SCFAs on rumen microbial fermentation and rumen epithelium health remain an area that requires further exploration. In our study, we sought to investigate the specific impact of administering high doses of exogenous acetate, propionate, and butyrate on rumen homeostasis, with a particular focus on understanding the interaction between the rumen microbiome and epithelium. Importantly, our findings indicated that the massive infusion of these SCFAs did not induce rumen inflammation. Instead, we observed enhancements in antioxidant capacity, strengthening of rumen barrier function, and promotion of rumen papilla development, which were facilitated through interactions with specific rumen bacteria. By addressing existing knowledge gaps and offering critical insights into the regulation of rumen health through SCFA supplementation, our study holds significant implications for enhancing the well-being and productivity of ruminant animals.

The modulatory effects of gut microbes and metabolites on blood-brain barrier integrity and brain function in sepsis-associated encephalopathy.

Intestinal microbiota homeostasis and the gut-brain axis are key players associated with host health and alterations in metabolic, inflammatory, and neurodegenerative disorders. Sepsis-associated encephalopathy (SAE), which is closely associated with bacterial translocation, is a common secondary organ dysfunction and an urgent, unsolved problem affecting patient quality of life. Our study examined the neuroprotective effects of the gut microbiome and short-chain fatty acid (SCFA) metabolites on SAE. Male C57BL/6 mice were administered SCFAs in drinking water, then subjected to cecal ligation and puncture (CLP) surgery to induce SAE. 16S rRNA sequencing was used to investigate gut microbiome changes. The open field test (OFT) and Y-maze were performed to evaluate brain function. The permeability of the blood-brain barrier (BBB) was assessed by Evans blue (EB) staining. Hematoxylin and eosin (HE) staining was used to examine intestinal tissue morphology. The expression levels of tight junction (TJ) proteins and inflammatory cytokines was assessed by western blots and immunohistochemistry. In vitro, bEND.3 cells were incubated with SCFAs and then with lipopolysaccharide (LPS). Immunofluorescence was used to examine the expression of TJ proteins. The composition of the gut microbiota was altered in SAE mice; this change may be related to SCFA metabolism. SCFA treatment significantly alleviated behavioral dysfunction and neuroinflammation in SAE mice. SCFAs upregulated occludin and ZO-1 expression in the intestine and brain in SAE mice and LPS-treated cerebromicrovascular cells. These findings suggested that disturbances in the gut microbiota and SCFA metabolites play key roles in SAE. SCFA supplementation could exert neuroprotective effects against SAE by preserving BBB integrity.

Maternal helminth infection protects offspring from high-fat-diet-induced obesity through altered microbiota and SCFAs.

Helminth-induced Th2 immunity and gut microbiota have been recently shown to be highly effective in modulating metabolic syndromes in animal models. This study aimed to determine whether maternal immunity and microbial factors affect the induction and development of obesity in offspring. Here, Heligomosomoides polygyrus (Hp)-infected or control female C57BL/6J mice mated with normal males and their offspring were fed a high-fat diet (HFD) for 9 weeks after weaning. Our results showed that Hp-induced maternal outcomes during gestation and lactation significantly impacted offspring metabolic phenotypes. This was evidenced by results showing that offspring from helminth-infected mothers on an HFD (Hp-offspring + HFD) gained significantly less body weight than those from uninfected mothers (Cont-offspring + HFD). Hp-offspring + HFD exhibited no Th2 phenotype but displayed a pattern of gut microbiota composition similar to that of Hp-infected mothers. Cross-fostering experiments confirmed that the helminth-induced maternal attenuation of offspring obesity was mediated through both prenatal and postnatal effects. Our results further showed that helminth-infected dams and their offspring had a markedly altered gut microbiome composition, with increased production of short-chain fatty acids (SCFAs). Intriguingly, Hp-infected mothers and Hp-offspring + HFD showed increased SCFA receptor (GPR) expression in adipose and colonic tissues compared to noninfected mothers and Cont-offspring + HFD, respectively. Moreover, SCFA supplementation to the pups of uninfected control mothers during lactation protected against HFD-induced weight gain, which corresponded with changes in gut bacterial colonization. Collectively, our findings provide new insights into the complex interaction of maternal immune status and gut microbiome, Hp infection, and the immunity and gut microbiome in obese-prone offspring in infant life.

Maternal γδ Tcells shape offspring pulmonary type 2 immunity in a microbiota-dependent manner.

Immune development is profoundly influenced by vertically transferred cues. However, little is known about how maternal innate-like lymphocytes regulate offspring immunity. Here, we show that mice born from γδ Tcell-deficient (TCRδ-/-) dams display an increase in first-breath-induced inflammation, with a pulmonary milieu selectively enriched in type 2 cytokines and type 2-polarized immune cells, when compared with the progeny of γδ Tcell-sufficient dams. Upon helminth infection, mice born from TCRδ-/- dams sustain an increased type 2 inflammatory response. This is independent of the genotype of the pups. Instead, the offspring of TCRδ-/- dams harbors a distinct intestinal microbiota, acquired during birth and fostering, and decreased levels of intestinal short-chain fatty acids (SCFAs), such as pentanoate and hexanoate. Importantly, exogenous SCFA supplementation inhibits type 2 innate lymphoid cell function and suppresses first-breath- and infection-induced inflammation. Taken together, our findings unravel a maternal γδ Tcell-microbiota-SCFA axis regulating neonatal lung immunity.

S-44-4: POST-STROKE SUPPLEMENTATION WITH SHORT-CHAIN FATTY ACIDS ACCELERATES RECOVERY IN MICE VIA THE G-PROTEIN COUPLED RECEPTORS

Objective: Dietary fibre intake is negatively associated with stroke and overall mortality. A plausible hypothesis is that this happens via the gut microbiota, producing metabolites known as short-chain fatty acids (SCFAs) during fibre fermentation. Indeed, our unpublished data showed that low-fibre (LF) intake worsens stroke outcomes while high-fibre (HF) intake ameliorates it. Thus, we aimed to investigate whether switching from a LF diet pre-stroke to either a HF diet or supplementation with SCFAs post-stroke can improve functional and histological outcomes. We also aimed to determine if this effect is dependent on SCFAs-sensing G-protein coupled receptors GPR41, GPR43, and GPR109A. Design and methods: Male C57BL/6J mice (8–9 weeks, n = 8/group) were randomized and treated with a LF diet for 4-weeks prior to photothrombotic stroke surgery. Post-stroke, the mice were either fed with LF, HF or SCFAs for 7-days. Results: Using MRI, we observed no difference in the infarct volume at day 1 (D1) post-stroke. However, a HF diet and SCFAs supplementation reduced infarct volume at day 7 (D7) (mean brain infarct volume ± SEM; LF:13.52 ± 2.43 mm3 vs HF:7.71 ± 1.12 mm3 vs SCFAs:5.25 ± 1.18 mm3, P = 0.007), and improved brain recovery rate (LF:64.93 ± 2.94% vs HF:78.06 ± 1.98% vs SCFAs:85.05 ± 2.45%, P &lt; 0.001). High-fibre and SCFAs supplementation improved wire-hanging grip strength and coordination at D7, which measures motor function (mean % improvement ± SEM; LF:12.59 ± 2.66% vs HF:69.77 ± 8.44% vs SCFAs:97.42 ± 1.54%, P &lt; 0.001). Immunofluorescence was performed to access gut barrier integrity, immune cell infiltration and neurogenesis in the brain at D7. HF and SCFAs improved gut barrier integrity (ZO-1, P &lt; 0.001). Moreover, SCFAs-treated mice had fewer neutrophils (MPO+, P = 0.017) and more neuroblasts (DCX+/Tuj1+, P &lt; 0.001) in the infarct core, with a positive correlation between DCX+/Tuj1+ and recovery rate post-stroke (R2 = 0.50, P &lt; 0.001). To identify the receptors by which SCFAs improve stroke recovery, wild-type (WT) and GPR41/43/109a-/- mice (8–9 weeks, n = 8/group) were fed a HF diet pre- and post-stroke. GPR41/43/109a-/- mice showed worse stroke outcomes with larger brain infarct volume at D1 (P = 0.048) and D7 (P = 0.008), and worse recovery rate (P = 0.002). Consistent with this, wire-hanging grip strength was reduced (P &lt; 0.001) at D7. In addition, compared to WT mice, GPR41/43/109a-/- mice had a leaky gut (P &lt; 0.001), more neutrophils (P = 0.007) and very few neuroblasts (P = 0.011) in the infarct core. Conclusions: A high-fibre diet, resulting in the production of SCFAs, targets GPR41/43/109a signalling to reduce stroke-induced brain injury and improve functional recovery post-stroke. This improvement is likely to occur via neurogenesis and the suppression of the inflammatory response in the ischaemic brain.

Short-chain fatty acids ameliorate necrotizing enterocolitis-like intestinal injury through enhancing Notch1-mediated single immunoglobulin interleukin-1-related receptor, toll-interacting protein, and A20 induction.

Single immunoglobulin interleukin-1-related receptor (SIGIRR), toll-interacting protein (TOLLIP), and A20 are major inhibitors of toll-like receptor (TLR) signaling induced postnatally in the neonatal intestine. Short-chain fatty acids (SCFAs), fermentation products of indigestible carbohydrates produced by symbiotic bacteria, inhibit intestinal inflammation. Herein, we investigated the mechanisms by which SCFAs regulate SIGIRR, A20, and TOLLIP expression and mitigate experimental necrotizing enterocolitis (NEC). Butyrate induced NOTCH activation by repressing sirtuin 1 (SIRT1)-mediated deacetylation of the Notch intracellular domain (NICD) in human intestinal epithelial cells (HIECs). Overexpression of NICD induced SIGIRR, A20, and TOLLIP expression. Chromatin immunoprecipitation revealed that butyrate-induced NICD binds to the SIGIRR, A20, and TOLLIP gene promoters. Notch1-shRNA suppressed butyrate-induced SIGIRR/A20 upregulation in mouse enteroids and HIEC. Flagellin (TLR5 agonist)-induced inflammation in HIEC was inhibited by butyrate in a SIGIRR-dependent manner. Neonatal mice fed butyrate had increased NICD, A20, SIGIRR, and TOLLIP expression in the ileal epithelium. Butyrate inhibited experimental NEC-induced intestinal apoptosis, cytokine expression, and histological injury. Our data suggest that SCFAs can regulate the expression of the major negative regulators of TLR signaling in the neonatal intestine through Notch1 and ameliorate experimental NEC. Enteral SCFAs supplementation in preterm infants provides a promising bacteria-free, therapeutic option for NEC.NEW & NOTEWORTHY Short-chain fatty acids (SCFAs), such as propionate and butyrate, metabolites produced by symbiotic gut bacteria are known to be anti-inflammatory, but the mechanisms by which they protect against NEC are not fully understood. In this study, we reveal that SCFAs regulate intestinal inflammation by inducing the key TLR and IL1R inhibitors, SIGIRR and A20, through activation of the pluripotent transcriptional factor NOTCH1. Butyrate-mediated SIGIRR and A20 induction represses experimental NEC in the neonatal intestine.

Short-chain fatty acid metabolism and multiple effects on cardiovascular diseases.

Cardiovascular diseases (CVDs) are the leading cause of mortality worldwide, and fatty acid metabolism has been well studied. Short-chain fatty acids (SCFAs) have been less discussed than long-chain fatty acids (LCFAs) in CVDs. However, increasing evidence indicates the importance of SCFAs in regulating cardiac function. Here, we summarize the current understanding of SCFAs in hypertension, ischaemic reperfusion, myocardial infarction, atherosclerosis and heart failure. Most SCFAs exert positive effects in regulating related diseases. Butyrate and propionate can reduce blood pressure, improve I/R injury and decrease the risk of coronary artery disease (CAD) and atherosclerosis. Acetate can also play a positive role in regulating hypertension and preventing atherosclerosis, and malonate can improve cardiac function after MI. They affect these diseases by regulating inflammation, the immune system and related G protein-coupled receptors, with multiple neurohumoural regulation participation. In contrast, succinate can accelerate IR injury, increasing mitochondrial ROS production. SCFAs ultimately affect the regulation of different pathophysiological processes in heart failure. Here, we clarified the importance of short-chain fatty acids in the cardiovascular system and their multiple effects in various pathophysiological processes, providing new insights into their promising clinical application. More research should be conducted to further elucidate the underlying mechanism and different effects of single or multiple SCFA supplementation on the cardiovascular system.

Microbial and host factors contribute to bloodstream infection in a pediatric acute lymphocytic leukemia mouse model

BackgroundHematological malignancies are the most common cancers in the pediatric population, and T-cell acute lymphocytic leukemia (T-ALL) is the most common hematological malignancy in children. Bloodstream infection (BSI) is a commonly occurring complication in leukemia due to underlying conditions and therapy-induced neutropenia. Several studies identified the gut microbiome as a major source of BSI due to bacterial translocation. This study aimed to investigate changes in the intestinal and fecal microbiome, and their roles in the pathophysiology of BSI in a pediatric T-ALL mouse model using high-throughput shotgun metagenomics sequencing, and metabolomics. ResultsOur results show that BSI in ALL is characterized by an increase of a mucin degrading bacterium (Akkermansia muciniphila) and a decrease of butyrate producer Clostridia spp., along with a decrease in short-chain fatty acid (SCFA) concentrations and differential expression of tight junction proteins in the small intestine. Functional analysis of the small intestinal microbiome indicated a reduced capability of SCFA synthesis, while SCFA supplementation ameliorated the development of BSI in ALL. ConclusionsOur data indicates that changes in the microbiome, and the resulting changes in levels of SCFAs contribute significantly to the pathogenesis of bloodstream infection in ALL. Our study provides tailored preventive or therapeutic approaches to reduce BSI-associated mortality in ALL.

Mesoporous silica nanoparticle-encapsulated Bifidobacterium attenuates brain Aβ burden and improves olfactory dysfunction of APP/PS1 mice by nasal delivery

BackgroundDysbiosis or imbalance of gut microbiota in Alzheimer's disease (AD) affects the production of short-chain fatty acids (SCFAs), whereas exogenous SCFAs supplementation exacerbates brain Aβ burden in APP/PS1 mice. Bifidobacterium is the main producer of SCFAs in the gut flora, but oral administration of Bifidobacterium is ineffective due to strong acids and bile salts in the gastrointestinal tract. Therefore, regulating the levels of SCFAs in the gut is of great significance for AD treatment.MethodsWe investigated the feasibility of intranasal delivery of MSNs-Bifidobacterium (MSNs-Bi) to the gut and their effect on behavior and brain pathology in APP/PS1 mice.ResultsMesoporous silica nanospheres (MSNs) were efficiently immobilized on the surface of Bifidobacterium. After intranasal administration, fluorescence imaging of MSNs-Bi in the abdominal cavity and gastrointestinal tract revealed that intranasally delivered MSNs-Bi could be transported through the brain to the peripheral intestine. Intranasal administration of MSNs-Bi not only inhibited intestinal inflammation and reduced brain Aβ burden but also improved olfactory sensitivity in APP/PS1 mice.ConclusionsThese findings suggested that restoring the balance of the gut microbiome contributes to ameliorating cognitive impairment in AD, and that intranasal administration of MSNs-Bi may be an effective therapeutic strategy for the prevention of AD and intestinal disease.