Acetate attenuates inflammasome activation through GPR43-mediated Ca2+-dependent NLRP3 ubiquitination

Gut microbiota-derived acetate attenuates lung injury induced by influenza infection via protecting airway tight junctions

BACKGROUND

Gut microbiota (GM) have been implicated as important regulators of gastrointestinal symptom which is commonly occurred along with respiratory influenza A virus (IAV) infection, suggesting the involvement of the gut-to-lung axis in a host's response to IAV. IAV primarily destroys airway epithelium tight junctions (TJs) and consequently causes acute respiratory disease syndrome. It is known that GM and their metabolism produce an anti-influenza effect, but their role in IAV-induced airway epithelial integrity remains unknown.

METHODS

A mouse model of IAV infection was established. GM were analyzed using 16S rRNA gene sequencing, and short-chain fatty acids (SCFAs) levels were measured. GM depletion and fecal microbiota transplantation (FMT) were conducted to validate the role of GM in IAV infection. A pair-feeding experiment was conducted to reveal whether IAV-induced GM dysbiosis is attributed to impaired food intake. Furthermore, human bronchial epithelial (HBE) cells were cocultured with IAV in the presence or absence of acetate. TJs function was analyzed by paracellular permeability and transepithelial electronic resistance (TEER). The mechanism of how acetate affects TJs integrity was evaluated in HBE cells transfected with G protein-coupled receptor 43 (GPR43) short hairpin RNA (shRNA).

RESULTS

IAV-infected mice exhibited lower relative abundance of acetate-producing bacteria (Bacteroides, Bifidobacterium, and Akkermansia) and decreased acetate levels in gut and serum. These changes were partly caused by a decrease in food consumption (due to anorexia). GM depletion exacerbated and FMT restored IAV-induced lung inflammatory injury. IAV infection suppressed expressions of TJs (occludin, ZO-1) leading to disrupted airway epithelial barrier function as evidenced by decreased TEER and increased permeability. Acetate pretreatment activated GPR43, partially restored IAV-induced airway epithelial barrier function, and reduced inflammatory cytokines levels (TNF-α, IL-6, and IL-1β). Such protective effects of acetate were absent in HBE cells transfected with GPR43 shRNA. Acetate and GPR43 improved TJs in an AMP-activated protein kinase (AMPK)-dependent manner.

CONCLUSION

Collectively, our results demonstrated that GM protected airway TJs by modulating GPR43-AMPK signaling in IAV-induced lung injury. Therefore, improving GM dysbiosis may be a potential therapeutic target for patients with IAV infection.

Sex-dependent effects of carbohydrate source and quantity on caspase-1 activity in the mouse central nervous system

BACKGROUND

Mounting evidence links glucose intolerance and diabetes as aspects of metabolic dysregulation that are associated with an increased risk of developing dementia. Inflammation and inflammasome activation have emerged as a potential link between these disparate pathologies. As diet is a key factor in both the development of metabolic disorders and inflammation, we hypothesize that long term changes in dietary factors can influence nervous system function by regulating inflammasome activity and that this phenotype would be sex-dependent, as sex hormones are known to regulate metabolism and immune processes.

METHODS

5-week-old male and female transgenic mice expressing a caspase-1 bioluminescent reporter underwent cranial window surgeries and were fed control (65% complex carbohydrates, 15% fat), high glycemic index (65% carbohydrates from sucrose, 15% fat), or ketogenic (1% complex carbohydrates, 79% fat) diet from 6 to 26 weeks of age. Glucose regulation was assessed with a glucose tolerance test following a 4-h morning fast. Bioluminescence in the brain was quantified using IVIS in vivo imaging. Blood cytokine levels were measured using cytokine bead array. 16S ribosomal RNA gene amplicon sequencing of mouse feces was performed to assess alterations in the gut microbiome. Behavior associated with these dietary changes was also evaluated.

RESULTS

The ketogenic diet caused weight gain and glucose intolerance in both male and female mice. In male mice, the high glycemic diet led to increased caspase-1 biosensor activation over the course of the study, while in females the ketogenic diet drove an increase in biosensor activation compared to their respective controls. These changes correlated with an increase in inflammatory cytokines present in the serum of test mice and the emergence of anxiety-like behavior. The microbiome composition differed significantly between diets; however no significant link between diet, glucose tolerance, or caspase-1 signal was established.

CONCLUSIONS

Our findings suggest that diet composition, specifically the source and quantity of carbohydrates, has sex-specific effects on inflammasome activation in the central nervous system and behavior. This phenotype manifested as increased anxiety in male mice, and future studies are needed to determine if this phenotype is linked to alterations in microbiome composition.

Lactococcus cremoris D2022 alleviates hyperuricemia and suppresses renal inflammation via potential gut-kidney axis

Hyperuricemia (HUA) is a widespread metabolic disorder. Probiotics have drawn increasing attention as an adjunctive treatment with fewer side effects. However, thus far the effective strains are limited and the mechanisms for their serum uric acid (SUA)-lowering effect are not well understood. Along this line, we conducted the current study using a hyperuricemia mouse model induced by potassium oxonate and adenine. A novel strain of Lactococcus cremoris named D2022 was identified to have significant SUA-lowering capability. Lactococcus cremoris D2022 significantly reduced SUA levels by inhibiting uric acid synthesis and regulating uric acid transportation. It was also found that Lactococcus cremoris D2022 alleviated HUA-induced renal inflammatory injury involving multiple signaling pathways. By focusing on the expression of NLRP3-related inflammatory genes, we found correlations between the expression levels of these genes and free fatty acid receptors (FFARs). In addition, oral administration of Lactococcus cremoris D2022 increased short-chain fatty acids (SCFAs) in cecal samples, which may be one of the mechanisms by which oral probiotics alleviate renal inflammation. Serum untargeted metabolomics showed changes in a variety of serum metabolites associated with purine metabolism and inflammation after oral administration of Lactococcus cremoris D2022, further confirming its systemic bioactivity. Finally, it was proved that Lactococcus cremoris D2022 improved intestinal barrier function. In conclusion, Lactococcus cremoris D2022 can alleviate HUA and HUA-induced nephropathy by increasing the production of SCFAs in the gut and systemic metabolism.

Promising dawn in the management of pulmonary hypertension: The mystery veil of gut microbiota

The gut microbiota is a complex community of microorganisms inhabiting the intestinal tract, which plays a vital role in human health. It is intricately involved in the metabolism, and it also affects diverse physiological processes. The gut-lung axis is a bidirectional pathway between the gastrointestinal tract and the lungs. Recent research has shown that the gut microbiome plays a crucial role in immune response regulation in the lungs and the development of lung diseases. In this review, we present the interrelated factors concerning gut microbiota and the associated metabolites in pulmonary hypertension (PH), a lethal disease characterized by elevated pulmonary vascular pressure and resistance. Our research team explored the role of gut-microbiota-derived metabolites in cardiovascular diseases and established the correlation between metabolites such as putrescine, succinate, trimethylamine N-oxide (TMAO), and N, N, N-trimethyl-5-aminovaleric acid with the diseases. Furthermore, we found that specific metabolites, such as TMAO and betaine, have significant clinical value in PH, suggesting their potential as biomarkers in disease management. In detailing the interplay between the gut microbiota, their metabolites, and PH, we underscored the potential therapeutic approaches modulating this microbiota. Ultimately, we endeavor to alleviate the substantial socioeconomic burden associated with this disease. This review presents a unique exploratory analysis of the link between gut microbiota and PH, intending to propel further investigations in the gut-lung axis.

Limosilactobacillus fermentum Strains as Novel Probiotic Candidates to Promote Host Health Benefits and Development of Biotherapeutics: A Comprehensive Review

Fruits and their processing by-products are sources of potentially probiotic strains. Limosilactobacillus (L.) fermentum strains isolated from fruit processing by-products have shown probiotic-related properties. This review presents and discusses the results of the available studies that evaluated the probiotic properties of L. fermentum in promoting host health benefits, their application by the food industry, and the development of biotherapeutics. The results showed that administration of L. fermentum for 4 to 8 weeks promoted host health benefits in rats, including the modulation of gut microbiota, improvement of metabolic parameters, and antihypertensive, antioxidant, and anti-inflammatory effects. The results also showed the relevance of L. fermentum strains for application in the food industry and for the formulation of novel biotherapeutics, especially nutraceuticals. This review provides evidence that L. fermentum strains isolated from fruit processing by-products have great potential for promoting host health and indicate the need for a translational approach to confirm their effects in humans using randomized, double-blind, placebo-controlled trials.

Bacterial acetate metabolism and its influence on human epithelia

Short-chain fatty acids are known modulators of host-microbe interactions and can affect human health, inflammation, and outcomes of microbial infections. Acetate is the most abundant but least well-studied of these modulators, with most studies focusing on propionate and butyrate, which are considered to be more potent. In this mini-review, we summarize current knowledge of acetate as an important anti-inflammatory modulator of interactions between hosts and microorganisms. This includes a summary of the pathways by which acetate is metabolized by bacteria and human cells, the functions of acetate in bacterial cells, and the impact that microbially derived acetate has on human immune function.

Host microbiome associated low intestinal acetate correlates with progressive NLRP3-dependent hepatic-immunotoxicity in early life microcystin-LR exposure

BACKGROUND

Microcystins (MCs), potent hepatotoxins pose a significant health risk to humans, particularly children, who are more vulnerable due to higher water intake and increased exposure during recreational activities.

METHODS

Here, we investigated the role of host microbiome-linked acetate in modulating inflammation caused by early-life exposure to the cyanotoxin Microcystin-LR (MC-LR) in a juvenile mice model.

RESULTS

Our study revealed that early-life MC-LR exposure disrupted the gut microbiome, leading to a depletion of key acetate-producing bacteria and decreased luminal acetate concentration. Consequently, the dysbiosis hindered the establishment of a gut homeostatic microenvironment and disrupted gut barrier function. The NOD-like receptor family pyrin domain - containing 3 (NLRP3) inflammasome, a key player in MC-induced hepatoxicity emerged as a central player in this process, with acetate supplementation effectively preventing NLRP3 inflammasome activation, attenuating hepatic inflammation, and decreasing pro-inflammatory cytokine production. To elucidate the mechanism underlying the association between early-life MC-LR exposure and the progression of metabolic dysfunction associated steatotic liver disease (MASLD), we investigated the role of acetate binding to its receptor -G-protein coupled receptor 43 (GPR43) on NLRP3 inflammasome activation. Our results demonstrated that acetate-GPR43 signaling was crucial for decreasing NLRP3 protein levels and inhibiting NLRP3 inflammasome assembly. Further, acetate-induced decrease in NLRP3 protein levels was likely mediated through proteasomal degradation rather than autophagy. Overall, our findings underscore the significance of a healthy gut microbiome and its metabolites, particularly acetate, in the progression of hepatotoxicity induced by early life toxin exposure, crucial for MASLD progression.

CONCLUSIONS

This study highlights potential therapeutic targets in gut dysbiosis and NLRP3 inflammasome activation for mitigating toxin-associated inflammatory liver diseases.

Alleviation of adipose-hepatic glycolipid dysregulation by acetate in experimental PCOS model is associated with NF-κB/NLRP3 repression

This study hypothesized that acetate breaks the vicious cycle driving adipose-hepatic metabolic dysregulation in a rat model of polycystic ovarian syndrome (PCOS), possibly by suppression of nuclear factor-kappaB (NF-κB)/NOD-like receptor protein 3 (NLRP3) inflammasome. Female Wistar rats (8-week-old) were randomly allocated into four groups of n =6/group, which received vehicle, sodium acetate (200 mg), letrozole (1 mg/kg), and letrozole plus sodium acetate, respectively. The animals were treated by oral gavage, once daily for a period of 21 days. The PCOS animals were insulin-resistant, hyperandrogenic, and hypoestrogenic with decreased sex-hormone binding globulin. In addition, the hepatic tissue had increased lipid profile and decreased glycogen synthesis, while the adipose tissue showed decreased lipid profile with elevated glycogen synthesis. Besides, the results also showed increased malondialdehyde, γ-glutamyl transferase, lactate dehydrogenase, and inflammatory mediators with corresponding decrease in antioxidant defense in the hepatic and adipose tissues. Immunohistochemical evaluation also demonstrated severe expression with Bcl2-associated X protein/NLRP3 antibodies. Nonetheless, concomitant acetate supplementation attenuated these derangements. The present data collectively suggest that acetate ameliorates adipose-hepatic glycolipid dysregulation in experimental PCOS model by attenuating androgen excess and NF-κB/NLRP3 immunoreactivity.

Effects of tris (2-chloroethyl) phosphate exposure on gut microbiome using the simulator of the human intestinal microbial ecosystem (SHIME)

Tris (2-chloroethyl) phosphate (TCEP) has been widely used, and its health risk has received increasing attention. However, the rare research has been conducted on the effects of TCEP exposure on changes in the structure of the human gut microbiome and metabolic functions. In this experiment, Simulator of the human intestinal microbial ecosystem (SHIME) was applied to explore the influences of TCEP on the human gut bacteria community and structure. The results obtained from high-throughput sequencing of 16S rRNA gene have clearly revealed differences among control and exposure groups. High-dose TCEP exposure increased the Shannon and Simpson indexes in the results of α-diversity of the gut microbiome. At phylum level, Firmicutes occupied a higher proportion of gut microbiota, while the proportion of Bacteroidetes decreased. In the genus-level analysis, the relative abundance of Bacteroides descended with the TCEP exposure dose increased in the ascending colon, while the abundances of Roseburia, Lachnospira, Coprococcus and Lachnoclostridium were obviously correlated with exposure dose in each colon. The results of short chain fatty acids (SCFAs) showed a remarkable effect on the distribution after TCEP exposure. In the ascending colon, the control group had the highest acetate concentration (1.666 ± 0.085 mg⋅mL-1), while acetate concentrations in lose-dose medium-dose and high-doseTCEP exposure groups were 1.119 ± 0.084 mg⋅mL-1, 0.437 ± 0.053 mg⋅mL-1 and 0.548 ± 0.106 mg⋅mL-1, respectively. TCEP exposure resulted in a decrease in acetate and propionate concentrations, while increasing butyrate concentrations in each colon. Dorea, Fusicatenibacter, Kineothrix, Lachnospira, and Roseburia showed an increasing tendency in abundance under TCEP exposure, while they had a negatively correlation with acetate and propionate concentrations and positively related with butyrate concentrations. Overall, this study confirms that TCEP exposure alters both the composition and metabolic function of intestinal microbial communities, to arouse public concern about its negative health effects.

3, 4-Benzopyrene (Bap) aggravated abdominal aortic aneurysm formation by targeting pyroptosis in smooth muscle cells through ET-1 mediated NLRP3-inflammasome activation

According to epidemiological studies, smoking is one of the leading causes of the high incidence of abdominal aortic aneurysms (AAA).3,4-Benzopyrene (Bap) is a by-product of coal tar and tobacco combustion produced by the incomplete combustion of organic fuels. It is an essential component of both automobile exhaust and tobacco smoke, it is also an important member of the air pollutants. However, the exact mechanism by which Bap can worsen the condition of patients with AAA and increase the mortality of patients with AAA remains unknown. This research aims to investigate the role of Bap in inducing pyroptosis in AAA. In vitro experiments, we revealed that pyroptosis-Gasdermin D (GSDMD) increased when Bap was used. Additionally, the release of inflammatory factors, such as IL-1β and IL-18 were also rising. An mRNA sequencing analysis revealed that macrophages expressed a high level of the endothelin gene when cells were stimulated by Bap. It seemed that smooth muscle cells pyroptosis was related to macrophages. Experiments revealed that endothelin could increase the calcium ion concentration in smooth muscle cells, resulting in a large amount of ROS and activation of NLRP3 inflammasomes. We discovered that treatment with endothelin receptor antagonist (ABT-546) in vivo and calcium ion chelator (BAPTA) in vitro decreased AAA diameter, downregulated NLRP3 inflammasomes and ROS, and significantly reduced the number of activated GSDMD. Inflammatory mediators were released at a lower level. These findings suggest that Bap-induced pyroptosis may be mediated by the ET-1-Ca2+-inflammasome pathway, providing a new way to reduce mortality in AAA patients.

Tissue immunoexpression of IL-6 and IL-18 in aging men with BPH and MetS and their relationship with lipid parameters and gut microbiota-derived short chain fatty acids

Recent studies indicate that inflammation is one of the causes of the development of benign prostatic hyperplasia (BPH). Inflammation may result from past infections, metabolic disorders, but also from the state of functioning of the intestinal microbiota. The aim of the study was to assess whether the diagnostic lipid parameters for metabolic syndrome and short-chain fatty acids (SCFAs) are related to the immunoexpression of interleukins in prostate tissue with benign hyperplasia. The study involved 103 men with BPH, who were divided into two groups depending on the presence of MetS. We analysed tissue immunoexpression of two proinflammatory interleukins: IL-6, which is known to be involved in the development of BPH, and IL-18, which has not been analysed so far. The results of our study indicate that men with BPH + MetS in the stroma of the prostate have a significantly higher overall percentage of IL-6+ cells compared to men without MetS (p = 0.034). The analysis of IL-18 immunoexpression in prostate tissue indicated that in men with BPH + MetS, the glandular part of the prostate had a significantly higher percentage of cells with strong IL-18 expression (p = 0.040). We also noticed a relationship between tissue expression of IL-6 and IL-18 and lipid parameters (TG and HDL). We conclude that lipid disorders occurring in men with BPH increase inflammation in the prostate gland. Moreover, it has also been demonstrated for the first time that, indirectly, through SCFAs, the gut microbiota can act to prevent or create an inflammatory microenvironment in the prostate gland.

The impact of microbiota-derived short-chain fatty acids on macrophage activities in disease: Mechanisms and therapeutic potentials

Short-chain fatty acids (SCFAs) derived from the fermentation of carbohydrates by gut microbiota play a crucial role in regulating host physiology. Among them, acetate, propionate, and butyrate are key players in various biological processes. Recent research has revealed their significant functions in immune and inflammatory responses. For instance, butyrate reduces the development of interferon-gamma (IFN-γ) generating cells while promoting the development of regulatory T (Treg) cells. Propionate inhibits the initiation of a Th2 immune response by dendritic cells (DCs). Notably, SCFAs have an inhibitory impact on the polarization of M2 macrophages, emphasizing their immunomodulatory properties and potential for therapeutics. In animal models of asthma, both butyrate and propionate suppress the M2 polarization pathway, thus reducing allergic airway inflammation. Moreover, dysbiosis of gut microbiota leading to altered SCFA production has been implicated in prostate cancer progression. SCFAs trigger autophagy in cancer cells and promote M2 polarization in macrophages, accelerating tumor advancement. Manipulating microbiota- producing SCFAs holds promise for cancer treatment. Additionally, SCFAs enhance the expression of hypoxia-inducible factor 1 (HIF-1) by blocking histone deacetylase, resulting in increased production of antibacterial effectors and improved macrophage-mediated elimination of microorganisms. This highlights the antimicrobial potential of SCFAs and their role in host defense mechanisms. This comprehensive review provides an in-depth analysis of the latest research on the functional aspects and underlying mechanisms of SCFAs in relation to macrophage activities in a wide range of diseases, including infectious diseases and cancers. By elucidating the intricate interplay between SCFAs and macrophage functions, this review aims to contribute to the understanding of their therapeutic potential and pave the way for future interventions targeting SCFAs in disease management.

Role of microbiota short-chain fatty acid chains in the pathogenesis of autoimmune diseases

There is emerging evidence that microbiota and its metabolites play an important role in helath and diseases. In this regard, gut microbiota has been found as a crucial component that influences immune responses as well as immune-related disorders such as autoimmune diseases. Gut bacterial dysbiosis has been shown to cause disease and altered microbiota metabolite synthesis, leading to immunological and metabolic dysregulation. Of note, microbiota in the gut produce short-chain fatty acids (SCFAs) such as acetate, butyrate, and propionate, and remodeling in these microbiota metabolites has been linked to the pathophysiology of a number of autoimmune disorders such as type 1 diabetes, multiple sclerosis, inflammatory bowel disease, rheumatoid arthritis, celiac disease, and systemic lupus erythematosus. In this review, we will address the most recent findings from the most noteworthy studies investigating the impact of microbiota SCFAs on various autoimmune diseases.

Serum metabolomic profiling identifies potential biomarkers in arthritis in older adults: an exploratory study

BACKGROUND

Seronegative elderly-onset rheumatoid arthritis (EORA)neg and polymyalgia rheumatica (PMR) have similar clinical characteristics making them difficult to distinguish based on clinical features. We hypothesized that the study of serum metabolome could identify potential biomarkers of PMR vs. EORAneg.

METHODS

Arthritis in older adults (ARTIEL) is an observational prospective cohort with patients older than 60 years of age with newly diagnosed arthritis. Patients' blood samples were compared at baseline with 18 controls. A thorough clinical examination was conducted. A Bruker Avance 600 MHz spectrometer was used to acquire Nuclear Magnetic Resonance (NMR) spectra of serum samples. Chenomx NMR suite 8.5 was used for metabolite identification and quantification.Student t-test, one-way ANOVA, binary linear regression and ROC curve, Pearson's correlation along with pathway analyses were conducted.

RESULTS

Twenty-eight patients were diagnosed with EORAneg and 20 with PMR. EORAneg patients had a mean disease activity score (DAS)-Erythrocyte Sedimentation Rate (ESR) of 6.21 ± 1.00. All PMR patients reported shoulder pain, and 90% reported pelvic pain. Fifty-eight polar metabolites were identified. Of these, 3-hydroxybutyrate, acetate, glucose, glycine, lactate, and o-acetylcholine (o-ACh), were significantly different between groups. Of interest, IL-6 correlated with different metabolites in PMR and EORAneg suggesting different inflammatory activated pathways. Finally, lactate, o-ACh, taurine, and sex (female) were identified as distinguishable factors of PMR from EORAneg with a sensitivity of 90%, specificity of 92.3%, and an AUC of 0.925 (p < 0.001).

CONCLUSION

These results suggest that EORAneg and PMR have different serum metabolomic profiles that might be related to their pathobiology and can be used as biomarker to discriminate between both diseases.

Butyrate potentiates Enterococcus faecalis lipoteichoic acid-induced inflammasome activation via histone deacetylase inhibition

Enterococcus faecalis, a Gram-positive opportunistic pathogen having lipoteichoic acid (LTA) as a major virulence factor, is closely associated with refractory apical periodontitis. Short-chain fatty acids (SCFAs) are found in the apical lesion and may affect inflammatory responses induced by E. faecalis. In the current study, we investigated inflammasome activation by E. faecalis LTA (Ef.LTA) and SCFAs in THP-1 cells. Among SCFAs, butyrate in combination with Ef.LTA markedly enhanced caspase-1 activation and IL-1β secretion whereas these were not induced by Ef.LTA or butyrate alone. Notably, LTAs from Streptococcus gordonii, Staphylococcus aureus, and Bacillus subtilis also showed these effects. Activation of TLR2/GPCR, K⁺ efflux, and NF-κB were necessary for the IL-1β secretion induced by Ef.LTA/butyrate. The inflammasome complex comprising NLRP3, ASC, and caspase-1 was activated by Ef.LTA/butyrate. In addition, caspase-4 inhibitor diminished IL-1β cleavage and release, indicating that non-canonical activation of the inflammasome is also involved. Ef.LTA/butyrate induced Gasdermin D cleavage, but not the release of the pyroptosis marker, lactate dehydrogenase. This indicated that Ef.LTA/butyrate induces IL-1β production without cell death. Trichostatin A, a histone deacetylase (HDAC) inhibitor, enhanced Ef.LTA/butyrate-induced IL-1β production, indicating that HDAC is engaged in the inflammasome activation. Furthermore, Ef.LTA and butyrate synergistically induced the pulp necrosis that accompanies IL-1β expression in the rat apical periodontitis model. Taken all these results together, Ef.LTA in the presence of butyrate is suggested to facilitate both canonical- and non-canonical inflammasome activation in macrophages via HDAC inhibition. This potentially contributes to dental inflammatory diseases such as apical periodontitis, particularly associated with Gram-positive bacterial infection.

Acute and chronic inflammation alter immunometabolism in a cutaneous delayed-type hypersensitivity reaction (DTHR) mouse model

T-cell-driven immune responses are responsible for several autoimmune disorders, such as psoriasis vulgaris and rheumatoid arthritis. Identification of metabolic signatures in inflamed tissues is needed to facilitate novel and individualised therapeutic developments. Here we show the temporal metabolic dynamics of T-cell-driven inflammation characterised by nuclear magnetic resonance spectroscopy-based metabolomics, histopathology and immunohistochemistry in acute and chronic cutaneous delayed-type hypersensitivity reaction (DTHR). During acute DTHR, an increase in glutathione and glutathione disulfide is consistent with the ear swelling response and degree of neutrophilic infiltration, while taurine and ascorbate dominate the chronic phase, suggesting a switch in redox metabolism. Lowered amino acids, an increase in cell membrane repair-related metabolites and infiltration of T cells and macrophages further characterise chronic DTHR. Acute and chronic cutaneous DTHR can be distinguished by characteristic metabolic patterns associated with individual inflammatory pathways providing knowledge that will aid target discovery of specialised therapeutics.

Nuclear magnetic resonance spectroscopy-based tissue metabolomics is used to define detailed temporal signatures of acute and chronic inflammation in cutaneous delayed-type hypersensitivity reaction.

Selenium-Enriched Black Soybean Protein Prevents Benzo(a)pyrene-Induced Pyroptotic Colon Damage and Gut Dysbacteriosis

Selenium-enriched black soybean protein (SeBSP) is a kind of high-quality selenium resource with many physiological functions. Benzo(a)pyrene (BaP) is a well-known injurant that widely exists in high-temperature processed food and has been previously found to cause colon injury. In this study, the effects of SeBSP on colonic damage induced by BaP in BALB/C mice were investigated by comparing it with normal black soybean protein (BSP). SeBSP inhibited the BaP-induced reductions on body weight, food intake, and water intake. Moreover, metabolic enzymes, including AhR, CYP1A1, CYP1B1, and GST-P1, that were promoted by BaP were downregulated by SeBSP, reducing oxidative damage caused by BaP in the metabolic process. The classical pyroptosis indexes (i.e., NLRP3, ASC, Caspase-1, GSDMD) and inflammatory factors (i.e., TNF-α, IL-1β, IL-18, iNOS, COX-2) were downregulated by SeBSP in BaP-treated mice, suggesting the benefits of SeBSP in reducing colonic toxicity. Notably, SeBSP enhanced microbial diversity of gut microbiota and increased relative abundances of prebiotic bacteria, for example, Lactobacillus reuteri, Bacteroides thetaiotaomicron, and genera Bifidobacterium, and Blautia, along with the promotion of short-chain fatty acids. Integrative analysis showed strong links between the antioxidant and anti-inflammatory effects of SeBSP and its altered gut microbiota. Collectively, our study demonstrates the pronounced benefits of Se-enriched black soybean in preventing the colonic toxicity of BaP, and such effects could be mediated by gut microbiota.

The relationship between gut microbiota, chronic systemic inflammation, and endotoxemia in patients with heart failure with preserved ejection fraction

Aim. To study the relationship between the abundance of the genera in the gut microbiota (GM) and levels of serum biomarkers of chronic systemic inflammation and endotoxemia in patients with HFpEF.

Material and methods. The composition of GM among 42 patients with HFpEF (men, 57,1%) was assessed by 16S rRNA sequencing. The median age was 67,0 years, interquartile range [64,0; 71,5] years. Correlation and multivariate regression analysis (with adjustments for sex and age) of relationships between the relative abundance of intestinal bacteria and the concentrations of serum biomarkers including high-sensitivity C-reactive protein (hsCRP), interleukins (IL) 1β and 6, the soluble suppressor of tumorigenicity (sST2), and the level of lipopolysaccharide (LPS) was carried out.

Results. According to multivariate regression analysis, the relative abundance of Haemophilus was directly related to the concentration of IL-1β (odds ratio (ОR) 32,37, 95% confidence interval (CI) 2,071237,69, p=0,025), Coriobacteriaceae (unclassified) — with IL-6 (ОR 6,27, (1,42-36,74), p=0,024), Porphyromonadaceae (unclassified) — with sST2 (ОR 5,96, (1,33-34,39), p=0,028), and the relative abundance of the genera Pseudomonas (ОR 7,09, (1,45-42,39), p=0,020), Parasutterella (ОR 4,55, (1,07-22,76), p=0,047) and Clostridiaceae (unclassified) (ОR 4,85, (1,06-24,7), p=0,045) was directly associated with LPS levels.

Conclusion. In patients with HFpEF, the relative abundance of some GM genera (e.g., Haemophilus, Coriobacteriaceae (unclassified), Porphyromonadaceae (unclassified), Pseudomonas, Parasutterella, Clostridiaceae (unclassified)) is statistically significantly associated with the concentration of biomarkers of chronic systemic inflammation and endotoxemia.

Propionate and butyrate attenuate macrophage pyroptosis and osteoclastogenesis induced by CoCrMo alloy particles

BACKGROUND

Wear particles-induced osteolysis is a major long-term complication after total joint arthroplasty. Up to now, there is no effective treatment for wear particles-induced osteolysis except for the revision surgery, which is a heavy psychological and economic burden to patients. A metabolite of gut microbiota, short chain fatty acids (SCFAs), has been reported to be beneficial for many chronic inflammatory diseases. This study aimed to investigate the therapeutic effect of SCFAs on osteolysis.

METHODS

A model of inflammatory osteolysis was established by applying CoCrMo alloy particles to mouse calvarium. After two weeks of intervention, the anti-inflammatory effects of SCFAs on wear particle-induced osteolysis were evaluated by Micro-CT analysis and immunohistochemistry staining. In vitro study, lipopolysaccharide (LPS) primed bone marrow-derived macrophages (BMDMs) and Tohoku Hospital Pediatrics-1 (THP-1) macrophages were stimulated with CoCrMo particles to activate inflammasome in the presence of acetate (C2), propionate (C3), and butyrate (C4). Western blotting, Enzyme-linked immunosorbent assay, and immunofluorescence were used to detect the activation of NLRP3 inflammasome. The effects of SCFAs on osteoclasts were evaluate by qRT-PCR, Western blotting, immunofluorescence, and tartrate-resistant acid phosphatase (TRAP) staining. Additionally, histone deacetylase (HDAC) inhibitors, agonists of GPR41, GPR43, and GPR109A were applied to confirm the underlying mechanism of SCFAs on the inflammasome activation of macrophages and osteoclastogenesis.

RESULTS

C3 and C4 but not C2 could alleviate wear particles-induced osteolysis with fewer bone erosion pits (P < 0.001), higher level of bone volume to tissue volume (BV/TV, P < 0.001), bone mineral density (BMD, P < 0.001), and a lower total porosity (P < 0.001). C3 and C4 prevented CoCrMo alloy particles-induced ASC speck formation and nucleation-induced oligomerization, suppressing the cleavage of caspase-1 (P < 0.05) and IL-1β (P < 0.05) stimulated by CoCrMo alloy particles. C3 and C4 also inhibited the generation of Gasdermin D-N-terminal fragment (GSDMD-NT) to regulate pyroptosis. Besides, C3 and C4 have a negative impact on osteoclast differentiation (P < 0.05) and its function (P < 0.05), affecting the podosome arrangement and morphologically normal podosome belts formation.

CONCLUSION

Our work showed that C3 and C4 are qualified candidates for the treatment of wear particle-induced osteolysis.

Global research trends in atherosclerosis: A bibliometric and visualized study

Background

Increasing evidence has spurred a considerable evolution of concepts related to atherosclerosis, prompting the need to provide a comprehensive view of the growing literature. By retrieving publications in the Web of Science Core Collection (WoSCC) of Clarivate Analytics, we conducted a bibliometric analysis of the scientific literature on atherosclerosis to describe the research landscape.

Methods

A search was conducted of the WoSCC for articles and reviews serving exclusively as a source of information on atherosclerosis published between 2012 and 2022. Microsoft Excel 2019 was used to chart the annual productivity of research relevant to atherosclerosis. Through CiteSpace and VOSviewer, the most prolific countries or regions, authors, journals, and resource-, intellectual-, and knowledge-sharing in atherosclerosis research, as well as co-citation analysis of references and keywords, were analyzed.

Results

A total of 20,014 publications were retrieved. In terms of publications, the United States remains the most productive country (6,390, 31,93%). The most publications have been contributed by Johns Hopkins Univ (730, 3.65%). ALVARO ALONSO produced the most published works (171, 0.85%). With a betweenness centrality of 0.17, ERIN D MICHOS was the most influential author. The most prolific journal was identified as Atherosclerosis (893, 4.46%). Circulation received the most co-citations (14,939, 2.79%). Keywords with the ongoing strong citation bursts were “nucleotide-binding oligomerization (NOD), Leucine-rich repeat (LRR)-containing protein (NLRP3) inflammasome,” “short-chain fatty acids (SCFAs),” “exosome,” and “homeostasis,” etc.

Conclusion

The research on atherosclerosis is driven mostly by North America and Europe. Intensive research has focused on the link between inflammation and atherosclerosis, as well as its complications. Specifically, the NLRP3 inflammasome, interleukin-1β, gut microbiota and SCFAs, exosome, long non-coding RNAs, autophagy, and cellular senescence were described to be hot issues in the field.

Comparison of Metabolites and Gut Microbes between Patients with Ulcerative Colitis and Healthy Individuals for an Integrative Medicine Approach to Ulcerative Colitis—A Pilot Observational Clinical Study (STROBE Compliant)

Ulcerative colitis (UC) is an intractable disease associated with high morbidity and healthcare costs. Metabolites and gut microbes are areas of interest for mainstream and complementary and alternative medicine. We, therefore, aimed to contribute to the discovery of an integrative medicine for UC by comparing and analyzing gut microbes and metabolites in patients with UC and in healthy individuals. This was an observational case-control study. Blood and stool samples were collected from the participants, and metabolite and gut microbial studies were performed. Among metabolites, formate, glycolate, trimethylamine, valine, and pyruvate levels were significantly different between the two groups. Among gut microbes, the abundance of Bacteroidetes at the phylum level; Bacteroidia at the class level; Bacteroidales and Actinomycetales at the order level; Prevotellaceae, Acidaminococcaceae, and Leptotrichiaceae at the family level; and Prevotella, Roseburia, Paraprevotella, Phascolarctobacterium, Ruminococcus, Coprococcus, Clostridium_XIVB, Atopobium, and Leptotrichia at the genus level was also significantly different. Most of the metabolites and gut microbes significantly different between the two groups were involved in energy metabolism and inflammatory processes, respectively. The results of this study could be helpful for the identification of targets for integrative medicine approaches for UC.

The crosstalk between NLRP3 inflammasome and gut microbiome in atherosclerosis

Atherosclerosis (AS) is chronic pathological process based on the inflammatory reaction associated with factors including vascular endothelial dysfunction, inflammation, and autoimmunity. Inflammasomes are known to be at the core of the inflammatory response. As a pattern recognition receptor of innate immunity, the NLRP3 inflammasome mediates the secretion of inflammatory factors by activating the Caspase-1, which is important for maintaining the immune system and regulating the gut microbiome, and participates in the occurrence and development of AS. The intestinal microecology is composed of a large number of complex structures of gut microbiota and its metabolites, which play an important role in AS. The gut microbiota and its metabolites regulate the activation of the NLRP3 inflammasome. Targeting the NLRP3 inflammasome and regulating intestinal microecology represent a new direction for the treatment of AS. This paper systematically reviews the interaction between the NLRP3 inflammasome and gut microbiome in AS, strategies for targeting the NLRP3 inflammasome and gut microbiome for the treatment of AS, and provides new ideas for the research and development of drugs for the treatment of AS.

GPR43 activation-mediated lipotoxicity contributes to podocyte injury in diabetic nephropathy by modulating the ERK/EGR1 pathway

Background: G-protein-coupled receptor 43 (GPR43) is a posttranscriptional regulator involved in cholesterol metabolism. This study aimed to investigate the possible roles of GPR43 activation in podocyte lipotoxicity in diabetic nephropathy (DN) and explore the potential mechanisms.

Methods: The experiments were conducted by using diabetic GPR43-knockout mice and a podocyte cell culture model. Lipid deposition and free cholesterol levels in kidney tissues were measured by BODIPY staining and quantitative cholesterol assays, respectively. The protein expression of GPR43, LC3II, p62, beclin1, low-density lipoprotein receptor (LDLR) and early growth response protein 1 (EGR1) in kidney tissues and podocytes was measured by real-time PCR, immunofluorescent staining and Western blotting.

Results: There were increased LDL cholesterol levels in plasma and cholesterol accumulation in the kidneys of diabetic mice. However, GPR43 gene knockout inhibited these changes. An in vitro study further demonstrated that acetate treatment induced cholesterol accumulation in high glucose-stimulated podocytes, which was correlated with increased cholesterol uptake mediated by LDLR and reduced cholesterol autophagic degradation, as characterized by the inhibition of LC3 maturation, p62 degradation and autophagosome formation. Gene knockdown or pharmacological inhibition of GPR43 prevented these effects on podocytes. Furthermore, GPR43 activation increased extracellular regulated protein kinases 1/2 (ERK1/2) activity and EGR1 expression in podocytes, which resulted in an increase in cholesterol influx and autophagy inhibition. In contrast, after GPR43 deletion, these changes in podocytes were improved, as shown by the in vivo and in vitro results.

Conclusion: GPR43 activation-mediated lipotoxicity contributes to podocyte injury in DN by modulating the ERK/EGR1 pathway.

Ginkgo biloba extract ameliorates atherosclerosis via rebalancing gut flora and microbial metabolism

The Ginkgo biloba leave extract (GbE) is widely applied in the prevention and treatment of atherosclerotic cardiovascular diseases in clinical practice. However, its mechanism of actions has not been totally elucidated. In this study, we confirmed the beneficial effects of GbE in alleviating hypercholesterolemia, inflammation and atherosclerosis in Ldlr^-/- mice, which were fed 12 weeks of Western diet (WD). Moreover, 16S rRNA sequencing revealed that GbE treatment reshaped the WD-perturbed intestinal microbiota, particularly decreased the Firmicutes/Bacteroidetes ratio and elevated the abundance of Akkermansia, Alloprevotella, Alistipes, and Parabacteroides. Furthermore, GbE treatment downregulated the intestinal transcriptional levels of proinflammatory cytokines and enhanced the expression of tight junction proteins, exerting the roles of attenuating the intestinal inflammation as well as repairing the gut barrier. Meanwhile, the targeted metabolomic analysis displayed that GbE treatment significantly reversed the dysfunction of the microbial metabolic phenotypes, including promoting the production of short chain fatty acids, indole-3-acetate and secondary bile acids, which were correlated with the atherosclerotic plaque areas. Finally, we confirmed GbE-altered gut microbiota was sufficient to alleviate atherosclerosis by fecal microbiota transplantation. In summary, our findings provide important insights into the pharmacological mechanism underlying the antiatherogenic efficacy of GbE.

Acetate Improves the Killing of Streptococcus pneumoniae by Alveolar Macrophages via NLRP3 Inflammasome and Glycolysis-HIF-1α Axis

Short-chain fatty acids (SCFAs) are metabolites produced mainly by the gut microbiota with a known role in immune regulation. Acetate, the major SCFA, is described to disseminate to distal organs such as lungs where it can arm sentinel cells, including alveolar macrophages, to fight against bacterial intruders. In the current study, we explored mechanisms through which acetate boosts macrophages to enhance their bactericidal activity. RNA sequencing analyses show that acetate triggers a transcriptomic program in macrophages evoking changes in metabolic process and immune effector outputs, including nitric oxide (NO) production. In addition, acetate enhances the killing activity of macrophages towards Streptococcus pneumoniae in an NO-dependent manner. Mechanistically, acetate improves IL-1β production by bacteria-conditioned macrophages and the latter acts in an autocrine manner to promote NO production. Strikingly, acetate-triggered IL-1β production was neither dependent of its cell surface receptor free-fatty acid receptor 2, nor of the enzymes responsible for its metabolism, namely acetyl-CoA synthetases 1 and 2. We found that IL-1β production by acetate relies on NLRP3 inflammasome and activation of HIF-1α, the latter being triggered by enhanced glycolysis. In conclusion, we unravel a new mechanism through which acetate reinforces the bactericidal activity of alveolar macrophages.

GPR40 agonist inhibits NLRP3 inflammasome activation via modulation of nuclear factor-κB and sarco/endoplasmic reticulum Ca2+-ATPase

The NOD-like receptor pyrin domain-containing protein 3 (NLRP3) inflammasome is a multi-protein intracellular complex that activates proinflammatory cytokines, including interleukin (IL)-1β and IL-18. Inflammasome activation is related to metabolic inflammation, such as the progression of non-alcoholic steatohepatitis. Fasiglifam (TAK875), a selective G-protein coupled receptor 40 (GPR40) agonist with high affinity, significantly improves glucose-dependent insulin secretion and weight gain without hypoglycemia. Interestingly, we found that two GPR40 agonists, TAK875 and AMG1638, suppressed activation of the NLRP3 inflammasome in bone marrow-derived macrophages (BMDMs). TAK875 inhibited inflammasome activation by blocking formation of apoptosis-associated speck-like protein containing a CARD (ASC), an inflammasome component. TAK875 also suppressed NLRP3 inflammasome-induced pyroptosis of BMDMs. Moreover, nuclear factor-kappa B (NF-κB)-dependent priming of the NLRP3 inflammasome was partially inhibited by TAK875 and AMG1638. The intracellular Ca²⁺ increase caused by ATP, nigericin (pore-forming toxin), or endoplasmic reticulum stress activates the NLRP3 inflammasome. Pre-exposure of BMDMs to TAK875 suppressed the ATP-induced intracellular Ca²⁺ increase, which was reversed by thapsigargin, a sarco/endoplasmic reticulum Ca²⁺-ATPase inhibitor. Oral administration of mice with TAK875 suppressed the increase in serum IL-1β in mice treated with lipopolysaccharide/D-galactosamine in vivo. These findings indicate that the free fatty acid-sensing GPR40 plays a key role in the NLRP3 inflammasome pathway.

Limosilactobacillus fermentum Strains with Claimed Probiotic Properties Exert Anti-oxidant and Anti-inflammatory Properties and Prevent Cardiometabolic Disorder in Female Rats Fed a High-Fat Diet

This study assessed the effects of a mixed formulation containing Limosilactobacillus (L.) fermentum 139, L. fermentum 263, and L. fermentum 296 on cardiometabolic parameters, inflammatory markers, short-chain fatty acid (SCFA) fecal contents, and oxidative stress in colon, liver, heart, and kidney tissues of female rats fed a high-fat diet (HFD). Female Wistar rats were allocated into control diet (CTL, n = 6), HFD (n = 6), and HFD receiving L. fermentum formulation (HFD-LF, n = 6). L. fermentum formulation (1 × 10⁹ CFU/mL of each strain) was administered two twice a day for 4 weeks. Administration of L. fermentum increased acetate and succinate fecal contents and reduced hyperlipidemia and hyperglycemia in rats fed a HFD (p < 0.05). Administration of L. fermentum decreased low-grade inflammation and improved antioxidant capacity along the gut, liver, heart, and kidney tissues in female rats fed a HFD (p < 0.05). Administration of L. fermentum prevented dyslipidemia, inflammation, and oxidative stress in colon, liver, heart, and kidney in female rats fed a HFD.

Dietary fiber-derived short-chain fatty acids: A potential therapeutic target to alleviate obesity-related nonalcoholic fatty liver disease

Over the past several decades, increasing global prevalence of obesity-related nonalcoholic fatty liver disease (NAFLD) has been one of main challenges to human health. Recently, increasing evidence has validated connections among short chain fatty acids (SCFAs), a physiologically relevant concentration, the intestinal microbiota, and host metabolism. In this review, we summarized crosstalk between SCFAs and host metabolism in relation to NAFLD pathophysiology, focusing on recent advances. Firstly, how SCFAs are generated and absorbed under different nutritional conditions in the gut. Secondly, how SCFAs maintain gut barrier and alleviate hepatic inflammatory responses. Thirdly, how SCFAs maintain hepatic energy balance through controlling appetite and mediating the glucose homeostasis at the systemic level. Fourthly, G-protein-coupled receptors (GPRs) are widely involved in the above metabolic processes regulated by SCFAs. Overall, this review aimed to provide new insights into the prospects of SCFAs as a potential therapeutic target in management of liver diseases.

Resolvin D2 suppresses NLRP3 inflammasome by promoting autophagy in macrophages

Inflammasome, a multiprotein complex that regulates interleukin (IL)-1β secretion and pyroptosis, participates in numerous inflammatory diseases, including sepsis, atherosclerosis and type-2 diabetes. Investigating the inflammasome regulation is therefore crucial to understand the inflammasome activation and develop treatment for the related diseases. In addition, it remains unknown how the inflammasome is naturally suppressed during the inflammatory process. The present study aimed to investigate the role of resolvin D2 (RvD2), an innate suppressor of inflammation produced from essential ω3-polyunsaturated fatty acids, in the activation of the inflammasome via in vitro and in vivo experiments. The effects of RvD2 on the cytokine production of inflammasome-related peritonitis were determined, and the NLRP3 inflammasome activation was investigated in the presence of RvD2. Moreover, the potential mechanisms underlying RvD2 in NLRP3 inflammasome regulation through autophagy and proteasome were investigated. The results of the present study demonstrated that RvD2 suppressed inflammasome-mediated peritonitis in vivo and regulated the NLR family pyrin domain containing 3 (NLRP3) inflammasome, but not in absent in melanoma 2 (AIM2), NLR family CARD domain containing 4 (NLRC4) inflammasomes. Mechanistically, RvD2 was found to promote the degradation of NLRP3 through autophagy, and the inhibition of autophagy could reverse the RvD2-mediated suppression of NLRP3 inflammasome in vitro and partially reverse the inflammasome-mediated peritonitis in vivo. In summary, the present study reported the negative regulation of NLRP3 inflammasome activation by RvD2. The findings from this study may extend the knowledge of the innate regulation of inflammasome and highlight a possible target for inflammasome-related diseases.

GPR43 regulation of mitochondrial damage to alleviate inflammatory reaction in sepsis

Sepsis is a common critical illness in ICU and always a great difficulty in clinical treatment. GPR43 (G protein-coupled receptor 43) participates in regulating appetite and gastrointestinal peptide secretion to modulate fat decomposition and formation. However, the biological contribution of GPR43 on inflammation of sepsis has not been previously investigated. We investigated the mechanisms of GPR43 gene, which plays a possible role in distinguishing sepsis and contributes to the pathogenesis of sepsis-induced inflammatory reaction. Furthermore, we performed studies with mice induced to sepsis by Cecal Ligation and Puncture (CLP), Knockout GPR43 (GPR43-/-) mice, and Wild Type (WT) mice induced with CLP. In addition, lung tissues and cell samples were analyzed by histology, Quantitative Polymerase Chain Reaction (Q-PCR), Enzyme-linked Immunosorbent (ELISA) Assay, and western blot. GPR43 agonist could significantly reduce inflammation reactions and trigger lung injury in mice with sepsis. As for GPR43-/- mice, the risks of sepsis-induced inflammatory reactions and corresponding lung injury were promoted. On the one hand, the up-regulation of GPR43 gene reduced ROS mitochondrial damage to inhibit inflammatory reactions via the inactivation of NLRP3 Inflammasome by PPARγ/ Nox1/EBP50/ p47phox signal channel. On the other hand, the down-regulation of GPR43 promoted inflammatory reactions in vitro model through the acceleration of ROS-dependently mitochondrial damage by PPARγ/ Nox1/EBP50/ p47phox/ NLRP3 signal channel. These findings indicate that the inhibition of GPR43 as a possible important factor of sepsis may shed lights on the mechanism of sepsis-induced inflammation reaction.

Altered synthesis of genes associated with short-chain fatty acids in the gut of patients with atrial fibrillation

BACKGROUND

The gut microbiota provides health benefits in humans by producing short-chain fatty acids (SCFAs), whose deficiency causes multiple disorders and inflammatory diseases. However, gut bacteria producing SCFAs in patients with atrial fibrillation (AF), an arrhythmia with increasing prevalence, have not been reported. To investigate major gut microbial organisms related to SCFA synthesis, SCFAs-associated KEGG orthologues (KOs), enzymatic genes, and potential producers were examined according to metagenomic data-mining in a northern Chinese cohort comprising 50 non-AF control and 50 AF patients.

RESULTS

Compared with non-AF controls, individuals with AF had marked differences in microbial genes involved in SCFA-related synthesis, including 125 KOs and 5 SCFAs-related enzymatic genes. Furthermore, there were 10 species that harbored SCFA-synthesis related enzymatic genes, and were markedly decreased in the gut of AF patients. Notably, discriminative features about SCFA-synthesis related function, including 8 KOs (K01752, K01738, K00175, K03737, K01006, K01653, K01647 and K15023), 4 genes (menI, tesB, yciA and CO dehydrogenase acetyl-CoA synthase complex) and 2 species (Coprococcus catus and Firmicutes bacterium CAG:103), were selected as key factors based on LASSO analysis. Furthermore, PLS-SEM analysis showed that 72.8 and 91.14 % of the overall effects on gut microbiota diversity and key species on AF, respectively, were mediated by the key KOs. Meanwhile, 46.31 % of the total effects of SCFA-synthesis related function on left atrial enlargement was mediated by hsCRP. Upon incorporation of clinical properties in AF, the KO score was still significantly associated with AF incidence (OR = 0.004, P = 0.001).

CONCLUSIONS

The current study revealed that dysbiotic gut microbiota in AF is coupled with disrupted SCFA-synthesis related genes, characterized by decreased abundances of KEGG orthologues, synthesis enzymatic genes and harboring species.

Eubacterium rectale Attenuates HSV-1 Induced Systemic Inflammation in Mice by Inhibiting CD83

The purpose of this study was to determine whether administration of the microorganism Eubacterium rectale (E. rectale) could regulate dendritic cell (DC) activation and systemic inflammation in herpes simplex virus type 1-induced Behçet's disease (BD). E. rectale, butyrate-producing bacteria, was administered to BD mice. Peripheral blood leukocytes (PBL) and lymph node cells were isolated and analyzed by flow cytometry. 16S rRNA metagenomic analysis was performed in the feces of mice to determine the differences in the composition of the microbial population between normal and BD mice. Serum cytokine levels were measured by enzyme-linked immunosorbent assay. The frequency of DC activation marker CD83 positive cells was significantly increased in PBL of BD mice. Frequencies of CD83+ cells were also significantly increased in patients with active BD. 16S rRNA metagenomic analysis revealed different gut microbiota composition between normal and BD mice. The administration of E. rectale to BD mice reduced the frequency of CD83+ cells and significantly increased the frequency of NK1.1+ cells with the improvement of symptoms. The co-administration of colchicine and E. rectale also significantly reduced the frequency of CD83+ cells. Differences in gut microbiota were observed between normal mice and BD mice, and the administration of E. rectale downregulated the frequency of CD83, which was associated with BD deterioration. These data indicate that E. rectale could be a new therapeutic adjuvant for BD management.

Low-Dose Lactulose as a Prebiotic for Improved Gut Health and Enhanced Mineral Absorption

Although medium and high doses of lactulose are used routinely for the treatment of constipation and hepatic encephalopathy, respectively, a wealth of evidence demonstrates that, at low doses, lactulose can also be used as a prebiotic to stimulate the growth of health-promoting bacteria in the gastrointestinal tract. Indeed, multiple preclinical and clinical studies have shown that low doses of lactulose enhance the proliferation of health-promoting gut bacteria (e.g., Bifidobacterium and Lactobacillus spp.) and increase the production of beneficial metabolites [e.g., short-chain fatty acids (SCFAs)], while inhibiting the growth of potentially pathogenic bacteria (e.g., certain clostridia). SCFAs produced upon microbial fermentation of lactulose, the most abundant of which is acetate, are likely to contribute to immune regulation, which is important not only within the gut itself, but also systemically and for bone health. Low-dose lactulose has also been shown to enhance the absorption of minerals such as calcium and magnesium from the gut, an effect which may have important implications for bone health. This review provides an overview of the preclinical and clinical evidence published to date showing that low-dose lactulose stimulates the growth of health-promoting gut bacteria, inhibits the growth of pathogenic bacteria, increases the production of beneficial metabolites, improves mineral absorption, and has good overall tolerability. Implications of these data for the use of lactulose as a prebiotic are also discussed.

Sugar Fructose Triggers Gut Dysbiosis and Metabolic Inflammation with Cardiac Arrhythmogenesis

Fructose is a main dietary sugar involved in the excess sugar intake-mediated progression of cardiovascular diseases and cardiac arrhythmias. Chronic intake of fructose has been the focus on the possible contributor to the metabolic diseases and cardiac inflammation. Recently, the small intestine was identified to be a major organ in fructose metabolism. The overconsumption of fructose induces dysbiosis of the gut microbiota, which, in turn, increases intestinal permeability and activates host inflammation. Endotoxins and metabolites of the gut microbiota, such as lipopolysaccharide, trimethylamine N-oxide, and short-chain fatty acids, also influence the host inflammation and cardiac biofunctions. Thus, high-fructose diets cause heart-gut axis disorders that promote cardiac arrhythmia. Understanding how gut microbiota dysbiosis-mediated inflammation influences the pathogenesis of cardiac arrhythmia may provide mechanisms for cardiac arrhythmogenesis. This narrative review updates our current understanding of the roles of excessive intake of fructose on the heart-gut axis and proposes potential strategies for inflammation-associated cardiac vascular diseases.

Metabolic regulators of enigmatic inflammasomes in autoimmune diseases and crosstalk with innate immune receptors

Nucleotide‐binding domain and leucine‐rich repeat receptor (NLR)‐mediated inflammasome activation is important in host response to microbes, danger‐associated molecular patterns (DAMPs) and metabolic disease. Some NLRs have been shown to interact with distinct cell metabolic pathways and cause negative regulation, tumorigenesis and autoimmune disorders, interacting with multiple innate immune receptors to modulate disease. NLR activation is therefore crucial in host response and in the regulation of metabolic pathways that can trigger a wide range of immunometabolic diseases or syndromes. However, the exact mode by which some of the less well‐studied NLR inflammasomes are activated, interact with other metabolites and immune receptors, and the role they play in the progression of metabolic diseases is still not fully elucidated. In this study, we review up‐to‐date evidence regarding NLR function in metabolic pathways and the interplay with other immune receptors involved in GPCR signalling, gut microbiota and the complement system, in order to gain a better understanding of its link to disease processes.

Coronavirus disease–2019 and the intestinal tract: An overview

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection can progress to a severe respiratory and systemic disease named coronavirus disease–2019 (COVID-19). The most common symptoms are fever and respiratory discomfort. Nevertheless, gastrointestinal infections have been reported, with symptoms such as diarrhea, nausea, vomiting, abdominal pain, and lack of appetite. Importantly, SARS-CoV-2 can remain positive in fecal samples after nasopharyngeal clearance. After gastrointestinal SARS-CoV-2 infection and other viral gastrointestinal infections, some patients may develop alterations in the gastrointestinal microbiota. In addition, some COVID-19 patients may receive antibiotics, which may also disturb gastrointestinal homeostasis. In summary, the gastrointestinal system, gut microbiome, and gut-lung axis may represent an important role in the development, severity, and treatment of COVID-19. Therefore, in this review, we explore the current pieces of evidence of COVID-19 gastrointestinal manifestations, possible implications, and interventions.

Bicarbonate, carbon dioxide and pH sensing via mammalian bicarbonate-regulated soluble adenylyl cyclase

Soluble adenylyl cyclase (sAC; ADCY10) is a bicarbonate (HCO3 -)-regulated enzyme responsible for the generation of cyclic adenosine monophosphate (cAMP). sAC is distributed throughout the cell and within organelles and, as such, plays a role in numerous cellular signalling pathways. Carbonic anhydrases (CAs) nearly instantaneously equilibrate HCO3 -, protons and carbon dioxide (CO2); because of the ubiquitous presence of CAs within cells, HCO3 --regulated sAC can respond to changes in any of these factors. Thus, sAC can function as a physiological HCO3 -/CO2/pH sensor. Here, we outline examples where we have shown that sAC responds to changes in HCO3 -, CO2 or pH to regulate diverse physiological functions.

The NLRP3 inflammasome: Multiple activation pathways and its role in primary cells during ventricular remodeling

Inflammasomes are a group of multiprotein signaling complexes located in the cytoplasm. Several inflammasomes have been identified, including NLRP1, NLRP2, NLRP3, AIM2, and NLRC4. Among them, NLRP3 was investigated in most detail, and it was reported that it can be activated by many different stimuli. Increased NLRP3 protein expression and inflammasome assembly lead to caspase-1 mediated maturation and release of IL-1β, which triggers inflammation and pyroptosis. The activation of the NLRP3 inflammasome has been widely reported in studies of tumors and neurological diseases, but relatively few studies on the cardiovascular system. Ventricular remodeling (VR) is an important factor contributing to heart failure (HF) after myocardial infarction (MI). Consequently, delaying VR is of great significance for improving heart function. Studies have shown that the NLRP3 inflammasome plays an essential role in the process of VR. Here, we reviewed the latest studies on the activation pathway of the NLRP3 inflammasome, focusing on the effects of the NLRP3 inflammasome in primary cells during VR, and finally discuss future research directions in this field.

Sophocarpine attenuates septic liver injury through suppression of the NLRP3 inflammasome via autophagy-mediated degradation

Septic liver injury remains a challenge in sepsis treatment. Nucleotide-binding oligomerization domain, leucine rich repeat and pyrin domain containing 3 (NLRP3) inflammasome activation has been suggested to be a major cause of hepatocyte cell death in liver diseases. However, insufficient research has been performed to explore the underlying mechanisms associated with this. In the present study, sophocarpine, a pharmaceutical monomer originally isolated from Sophora flavescens, was suggested to attenuate septic liver injury in a mouse cecal ligation and puncture (CLP) model. By utilizing western blotting, ELISA, H&E staining and immunohistochemistry, the results demonstrated that sophocarpine treatment reversed CLP-induced elevations in serum aspartate transaminase, alanine transaminase, interleukin (IL)-6 and IL-1β levels. Additionally, sophocarpine appeared to have suppressed the activation of the NLRP3 inflammasome, as indicated by observed reductions in liver IL-1β, NLRP3, caspase 1-p20 and gasdermin D-p30 protein levels. Further investigation suggested that sophocarpine-induced autophagy was essential for this suppression of NLRP3 inflammasome activation, the inhibition of which reversed the protective effects of sophocarpine on CLP-induced liver injury. Collectively, results from the present study suggested a protective role for sophocarpine against septic liver injury, where sophocarpine may suppress NLRP3 inflammasome activation by autophagy-mediated degradation.

Acetate Revisited: A Key Biomolecule at the Nexus of Metabolism, Epigenetics, and Oncogenesis - Part 2: Acetate and ACSS2 in Health and Disease

Acetate, the shortest chain fatty acid, has been implicated in providing health benefits whether it is derived from the diet or is generated from microbial fermentation of fiber in the gut. These health benefits range widely from improved cardiac function to enhanced red blood cell generation and memory formation. Understanding how acetate could influence so many disparate biological functions is now an area of intensive research. Protein acetylation is one of the most common post-translational modifications and increased systemic acetate strongly drives protein acetylation. By virtue of acetylation impacting the activity of virtually every class of protein, acetate driven alterations in signaling and gene transcription have been associated with several common human diseases, including cancer. In part 2 of this review, we will focus on some of the roles that acetate plays in health and human disease. The acetate-activating enzyme acyl-CoA short-chain synthetase family member 2 (ACSS2) will be a major part of that focus due to its role in targeted protein acetylation reactions that can regulate central metabolism and stress responses. ACSS2 is the only known enzyme that can recycle acetate derived from deacetylation reactions in the cytoplasm and nucleus of cells, including both protein and metabolite deacetylation reactions. As such, ACSS2 can recycle acetate derived from histone deacetylase reactions as well as protein deacetylation reactions mediated by sirtuins, among many others. Notably, ACSS2 can activate acetate released from acetylated metabolites including N-acetylaspartate (NAA), the most concentrated acetylated metabolite in the human brain. NAA has been associated with the metabolic reprograming of cancer cells, where ACSS2 also plays a role. Here, we discuss the context-specific roles that acetate can play in health and disease.

HIPK2 sustains inflammatory cytokine production by promoting endoplasmic reticulum stress in macrophages

Uncontrolled inflammatory cytokine production by macrophages contributes to numerous conditions, including infection, endotoxemia and sepsis. A previous study proposed that endoplasmic reticulum (ER) stress acts as an essential process in inflammatory cytokine production by macrophages. The present study used a mouse sepsis model and in vitro macrophages to demonstrate that homeodomain-interacting protein kinase 2 (HIPK2) sustained cytokine production in an ER stress-dependent manner. HIPK2 expression was upregulated in the early phase of lipopolysaccharide stimulation. HIPK2 knockdown attenuated IL-6 and TNF-α production, and p65 phosphorylation in macrophages. Furthermore, the attenuated cytokine production was abolished by the ER stress agonist tunicamycin. The activation of ER stress increased the levels of IL-6 and TNF-α, and the phosphorylation of p65, in macrophages following knockdown of HIPK2. Furthermore, HIPK2 inhibition attenuated the production of IL-6 and TNF-α in vitro and in vivo. Therefore, HIPK2 sustained inflammatory cytokine production by promoting ER stress in macrophages. Targeting HIPK2 may be a potential strategy for the management of uncontrolled inflammation in clinical settings.

Acetate Downregulates the Activation of NLRP3 Inflammasomes and Attenuates Lung Injury in Neonatal Mice With Bronchopulmonary Dysplasia

Background: Bronchopulmonary dysplasia (BPD) is a common pulmonary complication in preterm infants. Acetate is a metabolite produced by the gut microbiota, and its anti-inflammatory function is well known. The role of acetate in BPD has not been studied. Here, we investigate the effects of acetate on lung inflammation and damage in mice model of BPD. Objective: To investigate the role of acetate in the development of BPD. Methods: C57BL/6 mice were randomly divided into three groups on the 3rd day after birth: room air group, hyperoxia group, and hyperoxia + acetate (250 mM, 0.02 ml/g) group. The expression of inflammatory factors was determined by ELISA and RT-PCR, and NLRP3 and caspase-1 were detected by Western blot. High-throughput sequencing was used to detect bacterial communities in the mice intestines. Results: After acetate treatment, the expression levels of TNF-α, IL-1β, IL-18, NLRP3, and caspase-1 were significantly reduced, while the expression of GPR43 was increased. In the BPD mice treated with acetate, the proportion of Escherichia-Shigella was lower than in placebo-treated BPD mice, while the abundance of Ruminococcus was increased. Conclusions: These results indicate that acetate may regulate intestinal flora and reduce inflammatory reactions and lung injury in BPD. Therefore, acetate may be an effective drug to protect against neonatal BPD.

Ets2 suppresses inflammatory cytokines through MAPK/NF-κB signaling and directly binds to the IL-6 promoter in macrophages

Proper activation of Toll-like receptor (TLR)-mediated signaling and production of proinflammatory cytokines are critical for the initiation of innate immunity, while the specific mechanism maintaining inflammatory homeostasis remains mostly unknown. Here, we show that Ets2 is upregulated following LPS and VSV stimulation. Ets2 knockdown or knockout leads to increased IL-6, TNF-α, and IFN-β production in macrophages. Consistently, Ets2-deficient mice show exacerbated inflammatory cytokine production and are more susceptible to CLP-induced sepsis. Mechanistically, Ets2 inhibits the LPS- and VSV-induced activation of ERK1/2, JNK, p38, and p65. Ets2 also binds to the promoter of IL-6 to inhibit transcription. Collectively, the results of the present study show the negative regulatory role of Ets2 in LPS- and VSV-induced inflammation through the suppression of MAPK/NF-κB signaling, direct binding to the IL-6 promoter and inhibition of transcription.