The emerging role of microbiota-derived short-chain fatty acids in immunometabolism

Exploring the significance of microbiota metabolites in rheumatoid arthritis: uncovering their contribution from disease development to biomarker potential

Rheumatoid arthritis (RA) is a multifaceted autoimmune disorder characterized by chronic inflammation and joint destruction. Recent research has elucidated the intricate interplay between gut microbiota and RA pathogenesis, underscoring the role of microbiota-derived metabolites as pivotal contributors to disease development and progression. The human gut microbiota, comprising a vast array of microorganisms and their metabolic byproducts, plays a crucial role in maintaining immune homeostasis. Dysbiosis of this microbial community has been linked to numerous autoimmune disorders, including RA. Microbiota-derived metabolites, such as short-chain fatty acids (SCFAs), tryptophan derivatives, Trimethylamine-N-oxide (TMAO), bile acids, peptidoglycan, and lipopolysaccharide (LPS), exhibit immunomodulatory properties that can either exacerbate or ameliorate inflammation in RA. Mechanistically, these metabolites influence immune cell differentiation, cytokine production, and gut barrier integrity, collectively shaping the autoimmune milieu. This review highlights recent advances in understanding the intricate crosstalk between microbiota metabolites and RA pathogenesis and also discusses the potential of specific metabolites to trigger or suppress autoimmunity, shedding light on their molecular interactions with immune cells and signaling pathways. Additionally, this review explores the translational aspects of microbiota metabolites as diagnostic and prognostic tools in RA. Furthermore, the challenges and prospects of translating these findings into clinical practice are critically examined.

Tolerogenic probiotics Lactobacillus delbrueckii and Lactobacillus rhamnosus promote anti-inflammatory profile of macrophages-derived monocytes of newly diagnosed patients with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is known as an autoimmune disorder that is characterized by the breakdown of self-tolerance, resulting in disease onset and progression. Macrophages have been implicated as a factor in the development of SLE through faulty phagocytosis of dead cells or an imbalanced M1/M2 ratio. The study aimed to investigate the immunomodulatory effects of Lactobacillus delbrueckii and Lactobacillus rhamnosus on M1 and M2 macrophages in new case lupus patients. For this purpose, blood monocytes were collected from lupus patients and healthy people and were cultured for 5 days to produce macrophages. For 48 h, the macrophages were then cocultured with either probiotics or lipopolysaccharides (LPS). Flow cytometry and real-time polymerase chain reaction were then used to analyze the expression of cluster of differentiation (CD) 14, CD80, and human leukocyte antigen - DR (HLADR) markers, as well as cytokine expression (interleukin [IL]1-β, IL-12, tumor necrosis factor α [TNF-α], IL-10, and transforming growth factor beta [TGF-β]). The results indicated three distinct macrophage populations, M0, M1, and M2. In both control and patient-derived macrophage-derived monocytes (MDMs), the probiotic groups showed a decrease in CD14, CD80, and HLADR expression compared to the LPS group. This decrease was particularly evident in M0 and M2 macrophages from lupus patients and M1 macrophages from healthy subjects. In addition, the probiotic groups showed increased levels of IL-10 and TGF-β and decreased levels of IL-12, IL1-β, and TNF-α in MDMs from both healthy and lupus subjects compared to the LPS groups. Although there was a higher expression of pro-inflammatory cytokines in lupus patients, there was a higher expression of anti-inflammatory cytokines in healthy subjects. In general, L. delbrueckii and L. rhamnosus could induce anti-inflammatory effects on MDMs from both healthy and lupus subjects.

Role of traditional Chinese medicine in age-related macular degeneration: exploring the gut microbiota's influence

The pathogenesis of age-related macular degeneration (AMD), a degenerative retinopathy, remains unclear. Administration of anti-vascular endothelial growth factor agents, antioxidants, fundus lasers, photodynamic therapy, and transpupillary warming has proven effective in alleviating symptoms; however, these interventions cannot prevent or reverse AMD. Increasing evidence suggests that AMD risk is linked to changes in the composition, abundance, and diversity of the gut microbiota (GM). Activation of multiple signaling pathways by GM metabolites, including lipopolysaccharides, oxysterols, short-chain fatty acids (SCFAs), and bile acids (BAs), influences retinal physiology. Traditional Chinese medicine (TCM), known for its multi-component and multi-target advantages, can help treat AMD by altering GM composition and regulating the levels of certain substances, such as lipopolysaccharides, reducing oxysterols, and increasing SCFA and BA contents. This review explores the correlation between GM and AMD and interventions for the two to provide new perspectives on treating AMD with TCM.

Gut microbiota bridges dietary nutrients and host immunity

Dietary nutrients and the gut microbiota are increasingly recognized to cross-regulate and entrain each other, and thus affect host health and immune-mediated diseases. Here, we systematically review the current understanding linking dietary nutrients to gut microbiota-host immune interactions, emphasizing how this axis might influence host immunity in health and diseases. Of relevance, we highlight that the implications of gut microbiota-targeted dietary intervention could be harnessed in orchestrating a spectrum of immune-associated diseases.

Vaccination with an HIV T-Cell Immunogen (HTI) Using DNA Primes Followed by a ChAdOx1-MVA Boost Is Immunogenic in Gut Microbiota-Depleted Mice despite Low IL-22 Serum Levels

Despite the important role of gut microbiota in the maturation of the immune system, little is known about its impact on the development of T-cell responses to vaccination. Here, we immunized C57BL/6 mice with a prime-boost regimen using DNA plasmid, the Chimpanzee Adenovirus, and the modified Vaccinia Ankara virus expressing a candidate HIV T-cell immunogen and compared the T-cell responses between individuals with an intact or antibiotic-depleted microbiota. Overall, the depletion of the gut microbiota did not result in significant differences in the magnitude or breadth of the immunogen-specific IFNγ T-cell response after vaccination. However, we observed marked changes in the serum levels of four cytokines after vaccinating microbiota-depleted animals, particularly a significant reduction in IL-22 levels. Interestingly, the level of IL-22 in serum correlated with the abundance of Roseburia in the large intestine of mice in the mock and vaccinated groups with intact microbiota. This short-chain fatty acid (SCFA)-producing bacterium was significantly reduced in the vaccinated, microbiota-depleted group. Therefore, our results indicate that, although microbiota depletion reduces serum levels of IL-22, the powerful vaccine regime used could have overcome the impact of microbiota depletion on IFNγ-producing T-cell responses.

Development and Validation of a Propionate Metabolism-Related Gene Signature for Prognostic Prediction of Hepatocellular Carcinoma

Background

Studies have demonstrated that propionate metabolism-related genes (PMRGs) are associated with cancer progression. PMRGs are not known to be involved in Hepatocellular carcinoma (HCC).

Methods

In this study, The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases were accessed for HCC-related transcriptome data and clinical information. First, DE-PMRGs were derived by intersecting PMRGs and DEGs between HCC tissues and normal controls. The clusterProfiler R package was then used to enrich DE-PMRGs. In addition, biomarkers of HCC were identified, and a prognostic model was developed. Using functional analysis and tumor microenvironment analysis, new insights were obtained into HCC. The expression of biomarkers was validated using quantitative real-time polymerase chain reaction (qRT-PCR).

Results

132 DE-PMRGs were obtained by intersecting 3690 DEGs and 291 PMRGs. Steroid and organic acid metabolism were associated with these genes. For the construction of the risk model for HCC samples, five biomarkers were identified, including Acyl-CoA dehydrogenase short chain (ACADS), CYP19A1, formiminotransferase cyclodeaminase (FTCD), glucose-6-phosphate dehydrogenase (G6PD), and glutamic-oxaloacetic transaminase (GOT2). ACADS, FTCD, and GOT2 were positive factors, whereas CYP19A1 and G6PD were negative. HCC patients with AUC greater than 0.6 were predicted to survive 1/2/3/4/5 years, indicating decent efficiency of the model. The probability of 1/3/5-survival for HCC was also predicted by the nomogram using the risk score, pathologic T stage, and cancer status. Moreover, functional enrichment analysis revealed the high-risk genes were associated with invasion and epithelial-mesenchymal transition. Significantly, immune cell infiltration and immune checkpoint expression were linked to HCC development.

Conclusion

This study identified five biomarkers of propionate metabolism that can predict HCC prognosis. This finding may provide a deeper understanding of PMRG function in HCC.

Roles of gut microbes in metabolic-associated fatty liver disease

Metabolic-associated fatty liver disease (MAFLD) is the most common chronic liver disease. Gut dysbiosis is considered a significant contributing factor in disease development. Increased intestinal permeability can be induced by gut dysbiosis, followed by the entry of lipopolysaccharide into circulation to reach peripheral tissue and result in chronic inflammation. We reviewed how microbial metabolites push host physiology toward MAFLD, including short-chain fatty acids (SCFAs), bile acids, and tryptophan metabolites. The effects of SCFAs are generally reported as anti-inflammatory and can improve intestinal barrier function and restore gut microbiota. Gut microbes can influence intestinal barrier function through SCFAs produced by fermentative bacteria, especially butyrate and propionate producers. This is achieved through the activation of free fatty acid sensing receptors. Bile is directly involved in lipid absorption. Gut microbes can alter bile acid composition by bile salt hydrolase-producing bacteria and bacterial hydroxysteroid dehydrogenase-producing bacteria. These bile acids can affect host physiology by activating farnesoid X receptor Takeda G protein-coupled receptor 5. Gut microbes can also induce MAFLD-associated symptoms by producing tryptophan metabolites kynurenine, serotonin, and indole-3-propionate. A summary of bacterial genera involved in SCFAs production, bile acid transformation, and tryptophan metabolism is provided. Many bacteria have demonstrated efficacy in alleviating MAFLD in animal models and are potential therapeutic candidates for MAFLD.

Association of cigarette smoking with risk of colorectal cancer subtypes classified by gut microbiota

INTRODUCTION

Both cigarette smoking and gut microbiota play important roles in colorectal carcinogenesis. We explored whether the association between smoking and colorectal cancer (CRC) risk varies by gut microbial enterotypes and how smoking-related enterotypes promote colorectal carcinogenesis.

METHODS

A case-control study was conducted. Fecal microbiota was determined by 16S rDNA sequencing. The cases with CRC or adenoma were subclassified by gut microbiota enterotypes. Multivariate analyses were used to test associations between smoking and the odds of colorectal neoplasm subtypes. Mann-Whitney U tests were used to find differential genera, genes, and pathways between the subtypes.

RESULTS

Included in the study were 130 CRC patients (type I: n=77; type II: n=53), 120 adenoma patients (type I: n=66; type II: n=54), and 130 healthy participants. Smoking increased the odds for type II tumors significantly (all p for trend <0.05) but not for type I tumors. The associations of smoking with increased odds of colorectal neoplasm significantly differed by gut microbiota enterotypes (p<0.05 for heterogeneity). An increase in carcinogenic bacteria (genus Escherichia shigella) and a decrease in probiotics (family Lachnospiraceae and Ruminococcaceae) in type II tumors may drive disease progression by upregulating oncogenic signaling pathways and inflammatory/oxidative stress response pathways, as well as protein phospholipase D1/2, cytochrome C, and prostaglandin-endoperoxide synthase 2 expression.

CONCLUSIONS

Smoking was associated with a higher odds of type II colorectal neoplasms but not type I tumors, supporting a potential role for the gut microbiota in mediating the association between smoking and colorectal neoplasms.

Role of Polysaccharides from Marine Seaweed as Feed Additives for Methane Mitigation in Ruminants: A Critical Review

Given the increasing concerns regarding greenhouse gas emissions associated with livestock production, the need to discover effective strategies to mitigate methane production in ruminants is clear. Marine algal polysaccharides have emerged as a promising research avenue because of their abundance and sustainability. Polysaccharides, such as alginate, laminaran, and fucoidan, which are extracted from marine seaweeds, have demonstrated the potential to reduce methane emissions by influencing the microbial populations in the rumen. This comprehensive review extensively examines the available literature and considers the effectiveness, challenges, and prospects of using marine seaweed polysaccharides as feed additives. The findings emphasise that marine algal polysaccharides can modulate rumen fermentation, promote the growth of beneficial microorganisms, and inhibit methanogenic archaea, ultimately leading to decreases in methane emissions. However, we must understand the long-term effects and address the obstacles to practical implementation. Further research is warranted to optimise dosage levels, evaluate potential effects on animal health, and assess economic feasibility. This critical review provides insights for researchers, policymakers, and industry stakeholders dedicated to advancing sustainable livestock production and methane mitigation.

A steroid-resistant cockroach allergen model is associated with lung and cecal microbiome changes

The pathogenesis of asthma has been partially linked to lung and gut microbiome. We utilized a steroid-resistant chronic model of cockroach antigen-induced (CRA) asthma with corticosteroid (fluticasone) treatment to examine lung and gut microbiome during disease. The pathophysiology assessment demonstrated that mucus and airway hyperresponsiveness were increased in the chronic CRA with no alteration in the fluticasone (Flut)-treated group, demonstrating steroid resistance. Analysis of mRNA from lungs showed no decrease of MUC5AC or Gob5 in the Flut-treated group. Furthermore, flow-cytometry in lung tissue showed eosinophils and neutrophils were not significantly reduced in the Flut-treated group compared to the chronic CRA group. When the microbiome profiles were assessed, data showed that only the Flut-treated animals were significantly different in the gut microbiome. Finally, a functional analysis of cecal microbiome metabolites using PiCRUSt showed several biosynthetic pathways were significantly enriched in the Flut-treated group, with tryptophan pathway verified by ELISA with increased kynurenine in homogenized cecum samples. While the implications of these data are unclear, they may suggest a significant impact of steroid treatment on future disease pathogenesis through microbiome and associated metabolite pathway changes.

Oligosaccharides as Potential Regulators of Gut Microbiota and Intestinal Health in Post-COVID-19 Management

The COVID-19 pandemic has had a profound impact worldwide, resulting in long-term health effects for many individuals. Recently, as more and more people recover from COVID-19, there is an increasing need to identify effective management strategies for post-COVID-19 syndrome, which may include diarrhea, fatigue, and chronic inflammation. Oligosaccharides derived from natural resources have been shown to have prebiotic effects, and emerging evidence suggests that they may also have immunomodulatory and anti-inflammatory effects, which could be particularly relevant in mitigating the long-term effects of COVID-19. In this review, we explore the potential of oligosaccharides as regulators of gut microbiota and intestinal health in post-COVID-19 management. We discuss the complex interactions between the gut microbiota, their functional metabolites, such as short-chain fatty acids, and the immune system, highlighting the potential of oligosaccharides to improve gut health and manage post-COVID-19 syndrome. Furthermore, we review evidence of gut microbiota with angiotensin-converting enzyme 2 expression for alleviating post-COVID-19 syndrome. Therefore, oligosaccharides offer a safe, natural, and effective approach to potentially improving gut microbiota, intestinal health, and overall health outcomes in post-COVID-19 management.

Biomaterial types, properties, medical applications, and other factors: a recent review

Biomaterial research has been going on for several years, and many companies are heavily investing in new product development. However, it is a contentious field of science. Biomaterial science is a field that combines materials science and medicine. The replacement or restoration of damaged tissues or organs enhances the patient’s quality of life. The deciding aspect is whether or not the body will accept a biomaterial. A biomaterial used for an implant must possess certain qualities to survive a long time. When a biomaterial is used for an implant, it must have specific properties to be long-lasting. A variety of materials are used in biomedical applications. They are widely used today and can be used individually or in combination. This review will aid researchers in the selection and assessment of biomaterials. Before using a biomaterial, its mechanical and physical properties should be considered. Recent biomaterials have a structure that closely resembles that of tissue. Anti-infective biomaterials and surfaces are being developed using advanced antifouling, bactericidal, and antibiofilm technologies. This review tries to cover critical features of biomaterials needed for tissue engineering, such as bioactivity, self-assembly, structural hierarchy, applications, heart valves, skin repair, bio-design, essential ideas in biomaterials, bioactive biomaterials, bioresorbable biomaterials, biomaterials in medical practice, biomedical function for design, biomaterial properties such as biocompatibility, heat response, non-toxicity, mechanical properties, physical properties, wear, and corrosion, as well as biomaterial properties such surfaces that are antibacterial, nanostructured materials, and biofilm disrupting compounds, are all being investigated. It is technically possible to stop the spread of implant infection.

Short-Chain Fatty Acids Attenuate 5-Fluorouracil-Induced THP-1 Cell Inflammation through Inhibiting NF-κB/NLRP3 Signaling via Glycerolphospholipid and Sphingolipid Metabolism

5-Fluorouracil (5-FU) is a common anti-tumor drug, but there is no effective treatment for its side effect, intestinal mucositis. The inflammatory reaction of macrophages in intestinal mucosa induced by 5-FU is an important cause of intestinal mucositis. In this study, we investigated the anti-inflammatory effects of the three important short-chain fatty acids (SCFAs), including sodium acetate (NaAc), sodium propionate (NaPc), and sodium butyrate (NaB), on human mononuclear macrophage-derived THP-1 cells induced by 5-FU. The expressions of intracellular ROS, pro-inflammatory/anti-inflammatory cytokines, as well as the nuclear factor-κB/NLR family and pyrin domain-containing protein 3 (NF-κB/NLRP3) signaling pathway proteins were determined. Furthermore, the cell metabolites were analyzed by untargeted metabolomics techniques. Our results revealed that the three SCFAs inhibited pro-inflammatory factor expressions, including IL-1β and IL-6, when treated with 5-FU (p < 0.05). The ROS expression and NF-κB activity of 5-FU-treated THP-1 cells were inhibited by the three SCFAs pre-incubated (p < 0.05). Moreover, NLRP3 knockdown abolished 5-FU-induced IL-1β expression (p < 0.05). Further experiments showed that the three SCFAs affected 20 kinds of metabolites that belong to amino acid and phosphatidylcholine metabolism in THP-1 cells. These significantly altered metabolites were involved in amino acid metabolism and glycerolphospholipid and sphingolipid metabolism. It is the first time that three important SCFAs (NaAc, NaPc, and NaB) were identified as inhibiting 5-FU-induced macrophage inflammation through inhibiting ROS/NF-κB/NLRP3 signaling pathways and regulating glycerolphospholipid and sphingolipid metabolism.

Intestine microbiota and SCFAs response in naturally Cryptosporidium-infected plateau yaks

Diarrhea is a severe bovine disease, globally prevalent in farm animals with a decrease in milk production and a low fertility rate. Cryptosporidium spp. are important zoonotic agents of bovine diarrhea. However, little is known about microbiota and short-chain fatty acids (SCFAs) changes in yaks infected with Cryptosporidium spp. Therefore, we performed 16S rRNA sequencing and detected the concentrations of SCFAs in Cryptosporidium-infected yaks. Results showed that over 80,000 raw and 70,000 filtered sequences were prevalent in yak samples. Shannon (p<0.01) and Simpson (p<0.01) were both significantly higher in Cryptosporidium-infected yaks. A total of 1072 amplicon sequence variants were shared in healthy and infected yaks. There were 11 phyla and 58 genera that differ significantly between the two yak groups. A total of 235 enzymes with a significant difference in abundance (p<0.001) were found between healthy and infected yaks. KEGG L3 analysis discovered that the abundance of 43 pathways was significantly higher, while 49 pathways were significantly lower in Cryptosporidium-infected yaks. The concentration of acetic acid (p<0.05), propionic acid (p<0.05), isobutyric acid (p<0.05), butyric acid (p<0.05), and isovaleric acid was noticeably lower in infected yaks, respectively. The findings of the study revealed that Cryptosporidium infection causes gut dysbiosis and results in a significant drop in the SCFAs concentrations in yaks with severe diarrhea, which may give new insights regarding the prevention and treatment of diarrhea in livestock.

Gut microbiome modulation by probiotics, prebiotics, synbiotics and postbiotics: a novel strategy in food allergy prevention and treatment

Food allergy has caused lots of global public health issues, particularly in developed countries. Presently, gut microbiota has been widely studied on allergy, while the role of dysbiosis in food allergy remains unknown. Scientists found that changes in gut microbial compositions and functions are strongly associated with a dramatic increase in the prevalence of food allergy. Altering microbial composition is crucial in modulating food antigens' immunogenicity. Thus, the potential roles of probiotics, prebiotics, synbiotics, and postbiotics in affecting gut bacteria communities and the immune system, as innovative strategies against food allergy, begins to attract high attention of scientists. This review briefly summarized the mechanisms of food allergy and discussed the role of the gut microbiota and the use of probiotics, prebiotics, synbiotics, and postbiotics as novel therapies for the prevention and treatment of food allergy. The perspective studies on the development of novel immunotherapy in food allergy were also described. A better understanding of these mechanisms will facilitate the development of preventive and therapeutic strategies for food allergy.

Exposure to Antibiotics and Neurodevelopmental Disorders: Could Probiotics Modulate the Gut-Brain Axis?

In order to develop properly, the brain requires the intricate interconnection of genetic factors and pre-and postnatal environmental events. The gut-brain axis has recently raised considerable interest for its involvement in regulating the development and functioning of the brain. Consequently, alterations in the gut microbiota composition, due to antibiotic administration, could favor the onset of neurodevelopmental disorders. Literature data suggest that the modulation of gut microbiota is often altered in individuals affected by neurodevelopmental disorders. It has been shown in animal studies that metabolites released by an imbalanced gut-brain axis, leads to alterations in brain function and deficits in social behavior. Here, we report the potential effects of antibiotic administration, before and after birth, in relation to the risk of developing neurodevelopmental disorders. We also review the potential role of probiotics in treating gastrointestinal disorders associated with gut dysbiosis after antibiotic administration, and their possible effect in ameliorating neurodevelopmental disorder symptoms.

Microbiota Modulation in Patients with Metabolic Syndrome

Metabolic syndrome (MS) comprises a vast range of metabolic dysfunctions, which can be associated to cardiovascular disease risk factors. MS is reaching pandemic levels worldwide and it currently affects around 25% in the adult population of developed countries. The definition states for the diagnosis of MS may be clear, but it is also relevant to interpret the patient data and realize whether similar criteria were used by different clinicians. The different criteria explain, at least in part, the controversies on the theme. Several studies are presently focusing on the microbiota changes according to the components of MS. It is widely accepted that the gut microbiota is a regulator of metabolic homeostasis, being the gut microbiome in MS described as dysbiotic and certain taxonomic groups associated to metabolic changes. Probiotics, and more recently synbiotics, arise as promising therapeutic alternatives that can mitigate some metabolic disturbances, namely by correcting the microbiome and bringing homeostasis to the gut. The most recent studies were revised and the promising results and perspectives revealed in this review.