The liver may act as a firewall mediating mutualism between the host and its gut commensal microbiota

Intestinal bacteria-derived extracellular vesicles in metabolic dysfunction-associated steatotic liver disease: From mechanisms to therapeutics

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a progressive disease that affects the health of approximately one-third of the world's population. It is the primary cause of end-stage liver disease, liver malignancy, and liver transplantation, resulting in a great medical burden. No medications have yet been approved by the US Food and Drug Administration for treating MASLD without liver inflammation or scarring. Therefore, the development of specific drugs to treat MASLD remains a key task in the ongoing research objective. Extracellular vesicles (EVs) play an important role in the communication between organs, tissues, and cells. Recent studies have found that intestinal microbiota are closely related to the pathogenesis and progression of MASLD. EVs produced by bacteria (BEVs) play an indispensable role in this process. Thus, this study provides a new direction for MASLD treatment. However, the mechanism by which BEVs affect MASLD remains unclear. Therefore, this study investigated the influence and function of intestinal microbiota in MASLD. Additionally, we focus on the research progress of BEVs in recent years and explain the relationship between BEVs and MASLD from the perspectives of glucose and lipid metabolism, immune responses, and intestinal homeostasis. Finally, we summarized the potential therapeutic value of BEVs and EVs from other sources, such as adipocytes, immunocytes, stem cells, and plants.

Intermittent fasting and metabolic dysfunction-associated steatotic liver disease: the potential role of the gut-liver axis

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a growing public health concern linked to the increasing prevalence of metabolic syndrome, including obesity and type 2 diabetes (T2D). MASLD remains a significant clinical challenge due to the absence of effective therapeutic interventions. Intermittent fasting (IF) has emerged as a promising non-pharmacological strategy for managing MASLD. Although the exact mechanisms underpinning the possible beneficial effects of IF on MASLD are not yet fully elucidated, the gut microbiota and its metabolic byproducts are increasingly recognized as potential mediators of these effects. The gut-liver axis may act as an important conduit through which IF exerts its beneficial influence on hepatic function. This review comprehensively examines the impact of various IF protocols on gut microbiota composition, investigating the resultant alterations in microbial diversity and metabolomic profiles, and their potential implications for liver health and the improvement of MASLD.

Hepatic stellate cells: balancing homeostasis, hepatoprotection and fibrogenesis in health and disease

In the past decades, the pathogenic role of hepatic stellate cells (HSCs) in the development of liver fibrosis and its complications has been deeply characterized, rendering HSCs a primary target for antifibrotic therapies. By contrast, the beneficial roles of HSCs in liver homeostasis and liver disease are only beginning to emerge, revealing critical regulatory and fibrosis-independent functions in hepatic zonation, metabolism, injury, regeneration and non-parenchymal cell identity. Here, we review how HSC mediators, such as R-spondin 3, hepatocyte growth factor and bone morphogenetic proteins, regulate critical and homeostatic liver functions in health and disease via cognate receptors in hepatocytes, Kupffer cells and endothelial cells. We highlight how the balance shifts from protective towards fibropathogenic HSC mediators during the progression of chronic liver disease (CLD) and the impact of this shifted balance on patient outcomes. Notably, the protective roles of HSCs are not accounted for in current therapeutic concepts for CLD. We discuss the concept that reverting the HSC balance from fibrogenesis towards hepatoprotection might represent a novel holistic treatment approach to inhibit fibrogenesis and restore epithelial health in CLD simultaneously.

The role of heme in sepsis induced Kupffer cell PANoptosis and senescence

Elevated heme levels, a consequence of hemolysis, are strongly associated with increased susceptibility to bacterial infections and adverse sepsis outcomes, particularly in older populations. However, the underlying mechanisms remain poorly understood. Using a cecal ligation and puncture (CLP) model of sepsis, we demonstrate that elevated heme levels correlate with Kupffer cell loss, increased bacterial burden, and heightened mortality. Mechanistically, we identify mitochondrial damage as a key driver of heme- and bacterial-induced Kupffer cell PANoptosis, a form of cell death integrating pyroptosis, apoptosis, and necroptosis, as well as cellular senescence. Specifically, heme activates phospholipase C gamma (PLC-γ), facilitating the translocation of cleaved gasdermin D (c-GSDMD) to mitochondria, resulting in GSDMD pore formation, mitochondrial dysfunction, and the release of mitochondrial DNA (mtDNA) during bacterial infection. This mitochondrial damage amplifies PANoptosis and triggers the cGAS-STING signaling pathway, further driving immune senescence. Notably, PLC-γ inhibition significantly reduces mitochondrial damage, cell death, and senescence caused by heme and bacterial infection. Furthermore, we show that hemopexin, a heme scavenger, effectively mitigates sepsis-induced Kupffer cell death and senescence, enhances bacterial clearance, and improves survival outcomes in both young and aged mice. These findings establish mitochondrial damage as a central mediator of heme induced Kupffer cell loss and highlight PLC-γ inhibition and hemopexin administration as promising therapeutic strategies for combating sepsis associated immune dysfunction.

Role of metabolic dysfunction-associated fatty liver disease in atrial fibrillation and heart failure: molecular and clinical aspects

Metabolic dysfunction-associated fatty liver disease (MASLD) is a rising global health concern. In addition to direct hepatic complications, extra-hepatic complications, including cardiovascular diseases (CVD), type 2 diabetes (T2D), gastroesophageal reflux disease, chronic kidney disease and some malignancies, are increasingly recognized. CVD, including atrial fibrillation (AF) and heart failure (HF), is the leading cause of death in patients with MASLD. External factors, including excess energy intake, sedentary lifestyle and xenobiotic use, induce inflammation-related complications. MASLD, AF, and HF are associated with immune system activation, including the reprogramming of immune cells and the establishment of immune memory. Emerging evidence suggests that the heart and the liver cross-talk with each other through the diverse spectrum of autocrine, paracrine and endocrine mechanisms. Pro-inflammatory cytokines produced from the liver and the heart circulate systemically to orchestrate metabolic derangements that promote the systematic immune dysregulation in the heart-liver axis and the development of end-organ complications. Cardio-hepatic syndrome describes the clinical and biochemical evidence of hepatic dysfunction and cardiac pathology due to the interaction between the heart and the liver. Activation of inflammatory cascades, oxidative stress and immune system dysregulation underlie key mechanisms in bringing about such pathological changes. This review focuses on the current clinical and molecular evidence about the heart-liver cross-talk. It summarizes the epidemiological and pathophysiological associations of MASLD, AF and HF. In addition, we will discuss how repurposing currently available and emerging pharmacotherapies may help tackle the cardiovascular risks resulting from MASLD.

Hepatic stellate cells control liver zonation, size and functions via R-spondin 3

Hepatic stellate cells (HSCs) have a central pathogenetic role in the development of liver fibrosis. However, their fibrosis-independent and homeostatic functions remain poorly understood1-5. Here we demonstrate that genetic depletion of HSCs changes WNT activity and zonation of hepatocytes, leading to marked alterations in liver regeneration, cytochrome P450 metabolism and injury. We identify R-spondin 3 (RSPO3), an HSC-enriched modulator of WNT signalling, as responsible for these hepatocyte-regulatory effects of HSCs. HSC-selective deletion of Rspo3 phenocopies the effects of HSC depletion on hepatocyte gene expression, zonation, liver size, regeneration and cytochrome P450-mediated detoxification, and exacerbates alcohol-associated and metabolic dysfunction-associated steatotic liver disease. RSPO3 expression decreases with HSC activation and is inversely associated with outcomes in patients with alcohol-associated and metabolic dysfunction-associated steatotic liver disease. These protective and hepatocyte-regulating functions of HSCs via RSPO3 resemble the R-spondin-expressing stromal niche in other organs and should be integrated into current therapeutic concepts.

The gut-organ axis: Clinical aspects and immune mechanisms

The gut-brain axis exemplifies the bidirectional connection between the intestines and the brain, as evidenced by the impact of severe stress on gastrointestinal symptoms including abdominal pain and diarrhea, and conversely, the influence of abdominal discomfort on mood. Clinical observations support the notion of the gut-brain connection, including an increased prevalence of inflammatory bowel disease (IBD) in patients with depression and anxiety, as well as the association of changes in the gut microbiota with neurological disorders such as multiple sclerosis, Parkinson's disease, stroke and Alzheimer's disease. The gut and brain communicate via complex mechanisms involving inflammatory cytokines, immune cells, autonomic nerves, and gut microbiota, which contribute to the pathogenesis in certain gut and brain diseases. Two primary pathways mediate the bidirectional information exchange between the intestinal tract and the brain: signal transduction through bloodstream factors, such as bacterial metabolites and inflammatory cytokines, and neural pathways, such as neurotransmitters and inflammatory cytokines within the autonomic nervous system through the interaction between the nerve cells and beyond. In recent years, the basic mechanisms of the pathophysiology of the gut-brain axis have been gradually elucidated. Beyond the gut-brain interaction, emerging evidence suggests the influence of the gut extends to other organs, such as the liver and lungs, through intricate inter-organ communication pathways. An increasing number of reports on this clinical and basic cross-organ interactions underscore the potential for better understanding and novel therapeutic strategies targeting inter-organs networks. Further clarification of interactions between multiorgans premises transformative insights into cross-organ therapeutic strategies.

Hepatocyte Toll-like receptors contribute to the hepcidin inflammatory response to pathogens and pathogen-derived ligands

Iron restriction is a critical pathomechanism underlying the Anemia of Inflammation and an innate immune response limiting the replication of extracellular pathogens. During infections, innate immune cells detect pathogen-associated molecular patterns (PAMPs) and produce proinflammatory cytokines. Among these, interleukin (IL)-6 is detected by hepatocytes, where it activates the production of the iron-regulated hormone hepcidin that inhibits iron export from macrophages. Consequently, macrophages accumulate iron and hypoferremia (low plasma iron) develops. Whether Toll-like receptors (TLRs) expressed on hepatocytes directly recognize PAMPs and contribute to hepcidin upregulation is still an open question. Stimulation of primary murine hepatocytes with a panel of PAMPs targeting TLRs 1-9 revealed that the TLR5 ligand flagellin and the TLR2:TLR6 ligand FSL1 upregulated hepcidin. Hepcidin was also induced upon treatment with heat-killed Staphylococcus aureus (HKSA) and Brucella abortus (HKBA). The hepcidin response to flagellin, FSL1, HKSA, and HKBA started at an early time point, was independent of autocrine regulation by IL-6, and occurred through the TLR-mitogen-activated protein kinase (MAPK) axis. By analyzing a macrophage:hepatocyte co-culture, we additionally show that the hepcidin response was dependent on TLR2:TLR6 expression in hepatocytes and independent of macrophage cytokine secretion. Ex vivo liver perfusion of mice with FSL1 and HKSA further revealed that PAMPs and pathogens can pass the sinusoidal barrier and reach hepatocytes to cause hepcidin upregulation in a TLR2:TLR6-dependent manner. We conclude that hepatocytes can directly recognize PAMPs and pathogens and promote hepcidin upregulation in a macrophage and cytokine-independent manner. This positions hepatocytes in the spotlight as potential direct drivers of iron restriction.

Colonic goblet cell-associated antigen passages mediate physiologic and beneficial translocation of live gut bacteria in preweaning mice

Gut-resident microorganisms have time-limited effects in distant tissues during early life. However, the reasons behind this phenomenon are largely unknown. Here, using bacterial culture techniques, we show that a subset of live gut-resident bacteria translocate and disseminate to extraintestinal tissues (mesenteric lymph nodes and spleen) in preweaning (day of life 17), but not adult (day of life 35), mice. Translocation and dissemination in preweaning mice appeared physiologic as it did not induce an inflammatory response and required host goblet cells, the formation of goblet cell-associated antigen passages, sphingosine-1-phosphate receptor-dependent leukocyte trafficking and phagocytic cells. One translocating strain, Lactobacillus animalisWU, showed antimicrobial activity against the late-onset sepsis pathogen Escherichia coli ST69 in vitro, and its translocation was associated with protection from systemic sepsis in vivo. While limited in context, these findings challenge the idea that translocation of gut microbiota is pathological and show physiologic and beneficial translocation during early life.

Splenic red pulp macrophages eliminate the liver-resistant Streptococcus pneumoniae from the blood circulation of mice

Invasive infections by encapsulated bacteria are the major cause of human morbidity and mortality. The liver resident macrophages, Kupffer cells, form the hepatic firewall to clear many encapsulated bacteria in the blood circulation but fail to control certain high-virulence capsule types. Here we report that the spleen is the backup immune organ to clear the liver-resistant serotypes of Streptococcus pneumoniae (pneumococcus), a leading human pathogen. Asplenic mice failed to control the growth of the liver-resistant pneumococci in the blood circulation. Immunologic and genetic analyses identified splenic red pulp (RP) macrophages as the major phagocytes for bacterial clearance. Furthermore, the plasma natural antibodies against the cell wall phosphocholine and the complement system were necessary for RP macrophage-mediated immunity. These findings have provided a conceptual framework for the innate defense against blood bacterial infections, a mechanistic explanation for the hyper-susceptibility of asplenic individuals to S. pneumoniae, and a proof of concept for developing vaccines and therapeutic antibodies against encapsulated pathogens.

Role of Intestinal Barrier Disruption to Acute-on-Chronic Liver Failure

Acute-on-chronic liver failure (ACLF) is a severe condition in patients with decompensated liver cirrhosis, marked by high short-term mortality. Recent experimental and clinical evidence has linked intestinal dysfunction to both the initiation of ACLF as well as disease outcome. This review discusses the significant role of the gut-liver axis in ACLF pathogenesis, highlighting recent advances. Gut mucosal barrier disruption, gut dysbiosis, and bacterial translocation emerge as key factors contributing to systemic inflammation in ACLF. Different approaches of therapeutically targeting the gut-liver axis via farnesoid X receptor agonists, nonselective beta receptor blockers, antibiotics, and probiotics are discussed as potential strategies mitigating ACLF progression. The importance of understanding the distinct pathophysiology of ACLF compared with other stages of liver cirrhosis is highlighted. In conclusion, research findings suggest that disruption of intestinal integrity may be an integral component of ACLF pathogenesis, paving the way for novel diagnostic and therapeutic approaches to manage this syndrome more effectively.

How oxygenation shapes immune responses: emerging roles for physioxia and pathological hypoxia

Most eukaryotes require oxygen for their survival and, with increasing multicellular complexity, oxygen availability and delivery rates vary across the tissues of complex organisms. In humans, healthy tissues have markedly different oxygen gradients, ranging from the hypoxic environment of the bone marrow (where our haematopoietic stem cells reside) to the lungs and their alveoli, which are among the most oxygenated areas of the body. Immune cells are therefore required to adapt to varying oxygen availability as they move from the bone marrow to peripheral organs to mediate their effector functions. These changing oxygen gradients are exaggerated during inflammation, where oxygenation is often depleted owing to alterations in tissue perfusion and increased cellular activity. As such, it is important to consider the effects of oxygenation on shaping the immune response during tissue homeostasis and disease conditions. In this Review, we address the relevance of both physiological oxygenation (physioxia) and disease-associated hypoxia (where cellular oxygen demand outstrips supply) for immune cell functions, discussing the relevance of hypoxia for immune responses in the settings of tissue homeostasis, inflammation, infection, cancer and disease immunotherapy.

Translocating gut pathobiont Enterococcus gallinarum induces TH17 and IgG3 anti-RNA-directed autoimmunity in mouse and human

Chronic autoimmune diseases often lead to long-term sequelae and require lifelong immunosuppression because of an incomplete understanding of the triggers and drivers in genetically predisposed patients. Gut bacteria that escape the gut barrier, known as translocating gut pathobionts, have been implicated as instigators and perpetuators of extraintestinal autoimmune diseases in mice. The gut microbial contributions to autoimmunity in humans remain largely unclear, including whether specific pathological human adaptive immune responses are triggered by such pathobionts. Here, we show that the translocating pathobiont Enterococcus gallinarum can induce both human and mouse interferon-γ+ T helper 17 (TH17) differentiation and immunoglobulin G3 (IgG3) subclass switch of anti-E. gallinarum RNA antibodies, which correlated with anti-human RNA autoantibody responses in patients with systemic lupus erythematosus (SLE) and autoimmune hepatitis, two extraintestinal autoimmune diseases. E. gallinarum RNA, but not human RNA, triggered Toll-like receptor 8 (TLR8), and TLR8-mediated human monocyte activation promoted human TH17 induction by E. gallinarum. Translocation of the pathobiont triggered increased anti-RNA autoantibody titers that correlated with renal autoimmune pathophysiology in murine gnotobiotic lupus models and with disease activity in patients with SLE. These studies elucidate cellular mechanisms of how a translocating gut pathobiont induces systemic human T cell- and B cell-dependent autoimmune responses and provide a framework for developing host- and microbiota-derived biomarkers and targeted therapies in autoimmune diseases.

Natural antibodies to polysaccharide capsules enable Kupffer cells to capture invading bacteria in the liver sinusoids

The interception of blood-borne bacteria in the liver defines the outcomes of invasive bacterial infections, but the mechanisms of this antibacterial immunity are not fully understood. This study shows that natural antibodies (nAbs) to capsules enable liver macrophage Kupffer cells (KCs) to rapidly capture and kill blood-borne encapsulated bacteria in mice. Affinity pulldown with serotype-10A capsular polysaccharides (CPS10A) of Streptococcus pneumoniae (Spn10A) led to the identification of CPS10A-binding nAbs in serum. The CPS10A-antibody interaction enabled KCs to capture Spn10A bacteria from the bloodstream, in part through complement receptors on KCs. The nAbs were found to recognize the β1-6-linked galactose branch of CPS10A and similar moieties of serotype-39 S. pneumoniae and serotype-K50 Klebsiella pneumoniae capsules. More importantly, the nAbs empowered KCs to capture serotype-39 S. pneumoniae and serotype-K50 K. pneumoniae in the liver. Collectively, our data have revealed a highly effective immune function of nAb against encapsulated bacteria and emphasize the concept of treating septic encapsulated bacterial diseases with monoclonal antibodies.

Inducible antibacterial responses in macrophages

Macrophages destroy bacteria and other microorganisms through phagocytosis-coupled antimicrobial responses, such as the generation of reactive oxygen species and the delivery of hydrolytic enzymes from lysosomes to the phagosome. However, many intracellular bacteria subvert these responses, escaping to other cellular compartments to survive and/or replicate. Such bacterial subversion strategies are countered by a range of additional direct antibacterial responses that are switched on by pattern-recognition receptors and/or host-derived cytokines and other factors, often through inducible gene expression and/or metabolic reprogramming. Our understanding of these inducible antibacterial defence strategies in macrophages is rapidly evolving. In this Review, we provide an overview of the broad repertoire of antibacterial responses that can be engaged in macrophages, including LC3-associated phagocytosis, metabolic reprogramming and antimicrobial metabolites, lipid droplets, guanylate-binding proteins, antimicrobial peptides, metal ion toxicity, nutrient depletion, autophagy and nitric oxide production. We also highlight key inducers, signalling pathways and transcription factors involved in driving these different antibacterial responses. Finally, we discuss how a detailed understanding of the molecular mechanisms of antibacterial responses in macrophages might be exploited for developing host-directed therapies to combat antibiotic-resistant bacterial infections.

Exploring the association between pro-inflammatory diets and chronic liver diseases: evidence from the UK Biobank

Background

Chronic liver diseases (CLD) continue to pose a significant global burden, potentially exacerbated by pro-inflammatory diets. This study explores the relationship between the Dietary Inflammatory Index (DII), a measure of dietary inflammatory potential, and CLD risk.

Methods

Utilizing data from the UK Biobank cohort, we assessed the dietary information and calculated the DII for each participant. Cox proportional hazards models and Fine-Gray competing risk models were employed to evaluate the association between DII and CLD incidence, adjusting for potential confounders.

Results

Our analysis included 121,329 participants with a median follow-up of 604.43 weeks, during which 4,018 developed CLD. A higher DII, indicating a more inflammatory diet, was associated with a 16% increased risk of CLD [hazard ratio (HR) = 1.162, P = 0.001], with each unit increase in DII elevating the risk by 3.3% (HR: 1.033, P < 0.001). A significant linear association between DII and CLD was observed. Competing risk analyses, which accounted for cirrhosis, liver cancer, and death, supported these findings. Subgroup analyses confirmed the robustness of the DII's association across various demographic and lifestyle factors. Moreover, a higher DII was positively associated with the progression of CLD to cirrhosis. Sensitivity analyses, including energy-adjusted DII and typical dietary DII, reinforced our results. Additionally, adherence to anti-inflammatory dietary patterns, as indicated by higher Healthy Eating Index 2020 and Mediterranean Diet Score values, was inversely associated with CLD risk.

Conclusion

Our study highlights the potential benefits of adopting anti-inflammatory diets as a strategy for the prevention and management of CLD. Comprehensive dietary interventions may play a pivotal role in mitigating the global burden of CLD.

Bacillus coagulans alleviates hepatic injury caused by Klebsiella pneumoniae in rabbits

BACKGROUND

As an opportunistic bacterial pathogen, Klebsiella pneumoniae (KP) is prone to causing a spectrum of diseases in rabbits when their immune system is compromised, which poses a threat to rabbit breeding industry. Bacillus coagulans (BC), recognized as an effective probiotic, confers a variety of benefits including anti-inflammatory and antioxidant properties.

AIM

The purpose of this study was to investigate whether dietary BC can effectively alleviate hepatic injury caused by KP.

METHODS

In this study, the rabbits were initially pretreated with varying doses of BC (1×106, 5×106, and 1×107 CFU/g), followed by a challenge with KP at a concentration of 1011 CFU/mL. Liver tissues were harvested and processed for histological assessment using H&E and VG stains to assess structural alterations. Biochemical assays were employed to quantify the enzymatic activities of T-SOD and GSH-Px, as well as the MDA content. Furthermore, ELISA was utilized to detect the levels of inflammatory cytokine (IL-10, IL-6, IL-1β and TNF-α) and apoptotic-related gene (Bcl-2, Bax).

RESULTS

Morphological observation indicated that BC can effectively mitigate KP-induced hepatic sinusoidal dilatation and congestion, as well as ameliorate the degree of hepatic fibrosis. Further analysis showed that BC significantly lowered MDA level in KP-treated rabbits, while enhanced the activities of T-SOD and GSH-Px. Additionally, ELISA result showed that BC pretreatment significantly reduced the levels of pro-inflammatory cytokines TNF-a, IL-6, IL-1β and pro-apoptotic gene Bax, while increasing the levels of anti-inflammatory cytokine IL-10 and anti-apoptotic gene Bcl-2 in KP-treated rabbits.

CONCLUSION

Above data indicate that BC supplementation effectively attenuated oxidative stress and inflammatory response induced by KP through augmenting the activities of antioxidant enzymes and diminishing the levels of pro-inflammatory factors. Furthermore, it reduced the Bax/Bcl-2 ratio in the liver, thereby inhibiting KP-induced apoptosis. The treatment group receiving 5x106 CFU/g BC benefitted most from the protective effect.

Modulating the microbiome in chronic liver diseases - current evidence on the role of fecal microbiota transplantation

INTRODUCTION

The gut microbiota has a complex relationship with the human host and is key to maintaining health. Disruption of the healthy diverse gut microbial milieu plays an important role in the pathogenesis of several diseases including Clostridioides difficile infection (CDI), inflammatory bowel disease, irritable bowel syndrome, alcohol-related liver disease and metabolic-dysfunction associated steatotic liver disease (MASLD). Fecal microbiota transplantation (FMT) is highly effective in treating CDI, though its utility in other diseases is still being explored.

AREAS COVERED

In this narrative review, we explore the role of gut microbiota in liver diseases, focusing on key changes in the microbial composition and function. We summarize current evidence on the role of FMT, identifying gaps in current research and outlining future directions for investigation. We comprehensively searched PubMed through 15 October 2024 to identify relevant studies.

EXPERT OPINION

While data from available studies shows promise, more research is necessary before we can use FMT for liver diseases. Key areas that require further study are - determining the optimal FMT regimen for each disease, establishing efficacy and safety with larger clinical trials, ensuring safe and equitable access to the FMT product and mechanistic insights into the reasons for success or failure of FMT.

Klebsiella pneumoniae capsular polysaccharide: Mechanism in regulation of synthesis, virulence, and pathogenicity

Hypervirulent Klebsiella pneumoniae exhibits strong pathogenicity and can cause severe invasive infections but is historically recognized as antibiotic-susceptible. In recent years, the escalating global prevalence of antibiotic-resistant hypervirulent K. pneumoniae has raised substantial concerns and created an urgent demand for effective treatment options. Capsular polysaccharide (CPS) is one of the main virulence determinants contributing to the hypervirulent phenotype. The structure of CPS varies widely among strains, and both the structure and composition of CPS can influence the virulence of K. pneumoniae. CPS possesses various immune evasion mechanisms that promote the survival of K. pneumoniae, as well as its colonization and dissemination. Given the proven viability of therapies that target the capsule, improving our understanding of the CPS structure is critical to effectively directing treatment strategies. In this review, the structure and typing of CPS are addressed as well as genes related to synthesis and regulation, relationships with virulence, and pathogenic mechanisms. We aim to provide a reference for research on the pathogenesis of K. pneumoniae.

Non-alcoholic fatty liver disease and the gut microbiota in adolescents: is there a relationship?

BACKGROUND

Despite the increasing prevalence of nonalcoholic fatty liver disease (NAFLD), the pathophysiology is still not fully understood. Recent evidence suggests that the gut microbiota may play a role in the pathophysiology of NAFLD and may also offer new therapeutic options.

METHODS

This prospective cross-sectional study included 100 consecutive newly diagnosed obese patients (BMI ≥ 95th percentile), aged 14-18 years with NAFLD (confirmed by ultrasound), persistently elevated levels of alanine aminotransferase (ALT) greater than 60 U/L for 1-6 months, and 100 healthy controls. We evaluated changes in the gut microbiota in NAFLD adolescents compared with healthy controls.

RESULTS

According to the multiple logistic regressions, the variables associated with NAFLD were the presence of Clostridium difficile, the presence of Salmonella spp., a greater abundance of Bifidobacterium and Prevotella, and a lower abundance of Lactobacillus.

CONCLUSION

Changes in the gut microbiota occur in adolescents with NAFLD compared with healthy individuals, which may be useful for identifying youths who are amenable to gut microbiota-based interventions.

CLINICAL TRIAL NUMBER

Not applicable.

recAP administration ameliorates sepsis outcomes through modulation of gut and liver inflammation

Sepsis, broadly described as a systemic infection, is one of the leading causes of death and long-term disability worldwide. There are limited therapeutic options available that either improve survival and/or improve the quality of life in survivors. Ilofotase alfa, also known as recombinant alkaline phosphatase (recAP), has been associated with reduced mortality in a subset of patients with sepsis-associated acute kidney injury. However, whether recAP exhibits any therapeutic benefits in other organ systems beyond the kidney is less clear. The objective of this study was to evaluate the effects of recAP on survival, behavior, and intestinal inflammation in a mouse model of sepsis, cecal ligation and puncture (CLP). Following CLP, either recAP or saline vehicle was administered via daily intraperitoneal injections to determine its treatment efficacy from early through late sepsis. We found that administration of recAP suppressed indices of inflammation in the gut and liver but did not improve survival or behavioral outcomes. These results demonstrate that recAP's therapeutic efficacy in the gut and liver may provide a valuable treatment to improve long-term outcomes in sepsis survivors.

Surface nanocoating-based universal platform for programmed delivery of microorganisms in complicated digestive tract

Microbial therapies have promising applications in the treatment of a broad range of diseases. However, effective colonization of the target region by therapeutic microorganisms remains a significant challenge owing to the complexity of the intestinal system. Here, we developed surface nanocoating-based universal platform (SNUP), which enabled the manipulation of controlled release and targeted colonization of therapeutic microbes in the digestive tract without the utilization of any targeting molecules. The system controlled the decomposition time of SNUP in the gut by regulating different modification layers and modification sequences on the microorganism's surface, so that the microorganism was released at a predetermined time and space. With the SNUP nanomodification technology, we could effectively deliver therapeutic microorganisms to specific complex intestinal regions such as the small intestine and colon, and protect the bioactivity of therapeutic microorganisms from destruction by both strong acids and digestive enzymes. In this study, we found that two layers SNUP-encapsulated Liiliilactobacillus salivarius (LS@CCMC) could efficiently colonize the small intestine and significantly improve the symptoms of a mouse model of Parkinson's disease through sustained secretion of γ-aminobutyric acid (GABA). This surface nanocoating-based universal platform system does not require the design of specific targeting molecules, providing a simple and universal method for colonized microbial therapy, target theranostics, precision medicine, and personalized medicine.

The role of the gut microbiome in the development of hepatobiliary cancers

Hepatobiliary cancers, including hepatocellular carcinoma and cancers of the biliary tract, share high mortality and rising incidence rates. They may also share several risk factors related to unhealthy western-type dietary and lifestyle patterns as well as increasing body weights and rates of obesity. Recent data also suggest a role for the gut microbiome in the development of hepatobiliary cancer and other liver pathologies. The gut microbiome and the liver interact bidirectionally through the "gut-liver axis," which describes the interactive relationship between the gut, its microbiota, and the liver. Here, we review the gut-liver interactions within the context of hepatobiliary carcinogenesis by outlining the experimental and observational evidence for the roles of gut microbiome dysbiosis, reduced gut barrier function, and exposure to inflammatory compounds as well as metabolic dysfunction as contributors to hepatobiliary cancer development. We also outline the latest findings regarding the impact of dietary and lifestyle factors on liver pathologies as mediated by the gut microbiome. Finally, we highlight some emerging gut microbiome editing techniques currently being investigated in the context of hepatobiliary diseases. Although much work remains to be done in determining the relationships between the gut microbiome and hepatobiliary cancers, emerging mechanistic insights are informing treatments, such as potential microbiota manipulation strategies and guiding public health advice on dietary/lifestyle patterns for the prevention of these lethal tumors.

Blood MAIT cells phenotype in patients with Opisthorchis felineus invasion depending on the severity of liver fibrosis

Introduction. MAIT cells are a new subpopulation of T cells that protect mucous barriers against penetration of foreign substances. There are practically no studies devoted to the participation of these cells in the pathogenesis of parasitic diseases.

Aim. To study the phenotype of blood MAIT cells in patients with Opisthorchis felineus (O. felineus) invasion depending on the severity of liver fibrosis.

Materials and methods. A total of 78 patients with O. felineus invasion (42 men and 36 women) and 26 control group individuals (14 men and 12 women) were examined. Opisthorchiasis was diagnosed using coproovoscopy and duodenal contents microscopy. All patients underwent liver elastometry using Aixplorer (France) or Siemens Acuson S2000 (Germany) systems with determination of the liver fibrosis degree according to METAVIR. The phenotype composition of lymphocytes was investigated using a Navios flow cytometer (Beckman Coulter, USA). T cells, T helpers, and T cytotoxic lymphocytes were isolated and the presence of NCR Va7.2 and CD161 on the surface of these cells was assessed.

Results. The content of MAIT T-helpers was decreased in patients with O. felineus invasion compared to healthy individuals (p < 0.001). In MAIT T-cytotoxic cells, a similar pattern was not detected (p = 0.5). In patients with liver fibrosis F2 according to METAVIR compared to individuals with F0 according to METAVIR, a decrease in the total number of T-cells, T-helpers and T-cytotoxic cells, as well as MAIT T-helpers and MAIT T-cytotoxic cells was observed. Thus, the content of CD161+ NCR Va7.2+ T-helpers was 0.020% [0.004–0.042%] in patients with opisthorchiasis with F0 according to METAVIR and 0.0% [0.0–0.003%] in individuals with liver fibrosis F2 according to METAVIR (p = 0.001). For CD161+ NCR Va7.2+ T-cytotoxic cells, these indicators were, respectively, 1.47% [0.41–2.49%] and 0.12% [0.07–0.31%] (p < 0.001).

Conclusion. Further study of MAIT cells in patients with liver pathology has undoubted prospects for the creation of new therapeutic and diagnostic technologies.

Role of microbiome in autoimmune liver diseases

The microbiome plays a crucial role in integrating environmental influences into host physiology, potentially linking it to autoimmune liver diseases, such as autoimmune hepatitis, primary biliary cholangitis, and primary sclerosing cholangitis. All autoimmune liver diseases are associated with reduced diversity of the gut microbiome and altered abundance of certain bacteria. However, the relationship between the microbiome and liver diseases is bidirectional and varies over the course of the disease. This makes it challenging to dissect whether such changes in the microbiome are initiating or driving factors in autoimmune liver diseases, secondary consequences of disease and/or pharmacological intervention, or alterations that modify the clinical course that patients experience. Potential mechanisms include the presence of pathobionts, disease-modifying microbial metabolites, and more nonspecific reduced gut barrier function, and it is highly likely that the effect of these change during the progression of the disease. Recurrent disease after liver transplantation is a major clinical challenge and a common denominator in these conditions, which could also represent a window to disease mechanisms of the gut-liver axis. Herein, we propose future research priorities, which should involve clinical trials, extensive molecular phenotyping at high resolution, and experimental studies in model systems. Overall, autoimmune liver diseases are characterized by an altered microbiome, and interventions targeting these changes hold promise for improving clinical care based on the emerging field of microbiota medicine.

The association between the gut microbiota metabolite trimethylamine N-oxide and heart failure

This systematic review explores the relationship between the gut microbiota metabolite trimethylamine N-oxide (TMAO) and heart failure (HF), given the significant impact of TMAO on cardiovascular health. A systematic search and meta-analysis of peer-reviewed studies published from 2013 to 2024 were conducted, focusing on adult patients with heart failure and healthy controls. The review found that elevated levels of TMAO are associated with atherosclerosis, endothelial dysfunction, and increased cardiovascular disease risk, all of which can exacerbate heart failure. The analysis also highlights that high TMAO levels are linked to reduced left ventricular ejection fraction (LVEF) and glomerular filtration rate (GFR), further supporting TMAO's role as a biomarker in heart failure assessment. The findings suggest that interventions targeting gut microbiota to reduce TMAO could potentially benefit patients with heart failure, although further research is needed to evaluate the effectiveness of such approaches.

The gut microbiota and diabetes: research, translation, and clinical applications - 2023 Diabetes, Diabetes Care, and Diabetologia Expert Forum

This article summarises the state of the science on the role of the gut microbiota (GM) in diabetes from a recent international expert forum organised by Diabetes, Diabetes Care, and Diabetologia, which was held at the European Association for the Study of Diabetes 2023 Annual Meeting in Hamburg, Germany. Forum participants included clinicians and basic scientists who are leading investigators in the field of the intestinal microbiome and metabolism. Their conclusions were as follows: (1) the GM may be involved in the pathophysiology of type 2 diabetes, as microbially produced metabolites associate both positively and negatively with the disease, and mechanistic links of GM functions (e.g. genes for butyrate production) with glucose metabolism have recently emerged through the use of Mendelian randomisation in humans; (2) the highly individualised nature of the GM poses a major research obstacle, and large cohorts and a deep-sequencing metagenomic approach are required for robust assessments of associations and causation; (3) because single time point sampling misses intraindividual GM dynamics, future studies with repeated measures within individuals are needed; and (4) much future research will be required to determine the applicability of this expanding knowledge to diabetes diagnosis and treatment, and novel technologies and improved computational tools will be important to achieve this goal.

Changes of bacterial communities and bile acid metabolism reveal the potential "intestine-hepatopancreas axis" in shrimp

The interaction between the gut and the liver plays a significant role in individual health and diseases. Mounting evidence supports that bile acids are important metabolites in the bidirectional communication between the gut and the liver. Most of the current studies on the "gut-liver axis" have focused on higher vertebrates, however, few was reported on lower invertebrates such as shrimp with an open circulatory system. Here, microbiomic and metabolomic analyses were conducted to investigate the bacterial composition and bile acid metabolism in intestine, hemolymph and hepatopancreas of Penaeus vannamei fed diets supplemented with octanoic acid and oleic acid. After six days of feeding, the bacterial composition in intestine, hemolymph and hepatopancreas changed at different stages, with significant increases in the relative abundance of several genera such as Pseudomonas and Rheinheimera in intestine and hepatopancreas. Notably, there was a more similar bacterial composition in intestine and hepatopancreas at the genus level, which indicated the close communication between shrimp intestine and hepatopancreas. Meanwhile, higher content of some bile acids such as lithocholic acid (LCA) and α-muricholic acid (α-MCA) in intestine and lower content of some bile acids such as taurohyocholic acids (THCA) and isolithocholic acid (IsoLCA) in hepatopancreas were detected. Furthermore, Spearman correlation analysis revealed a significant correlation between bacterial composition and bile acid metabolism in intestine and hepatopancreas. The microbial source tracking analysis showed that there was a high proportion of intestine and hepatopancreas bacterial community as the source of each other. Collectively, these results showed a strong crosstalk between shrimp intestine and hepatopancreas, which suggests a unique potential "intestine-hepatopancreas axis" in lower invertebrate shrimp with an open circulatory system. Our finding contributed to the understanding of the interplay between shrimp intestine and hepatopancreas in the view of microecology and provided new ideas for shrimp farming and disease control.

Rejuvenating bone marrow hematopoietic reserve prevents regeneration failure and hepatic decompensation in animal model of cirrhosis

Background and aim

Bone marrow stem cells (BM-SCs) and their progeny play a central role in tissue repair and regeneration. In patients with chronic liver failure, bone marrow (BM) reserve is severally compromised and they showed marked defects in the resolution of injury and infection, leading to liver failure and the onset of decompensation. Whether BM failure is the cause or consequence of liver failure during cirrhosis is not known. In this study, we aimed to determine the underlying relationship between BM failure and regeneration failure in cirrhosis.

Methodology

C57Bl/6(J) mice were used to develop chronic liver injury through intra-peritoneal administration of carbon tetrachloride (CCl4) for 15 weeks (0.1-0.5 ml/kg). Animals were sacrificed to study the transition of cirrhosis and BM defects. To restore the BM-SC reserve; healthy BM cells were infused via intra-BM infusion and assessed for changes in liver injury, regeneration, and BM-SC reserve.

Results

Using a CCl4-induced animal - model of cirrhosis, we showed the loss of BM-SCs reserve occurred before regeneration failure and the onset of non-acute decompensation. Intra-BM infusion of healthy BM cells induced the repopulation of native hematopoietic stem cells (HSCs) in cirrhotic BM. Restoring BM-HSCs reserve augments liver macrophage-mediated clearance of infection and inflammation dampens neutrophil-mediated inflammation, accelerates fibrosis regression, enhances hepatocyte proliferation, and delays the onset of non-acute decompensation.

Conclusion

These findings suggest that loss of BM-HSCs reserve underlies the compromised innate immune function of the liver, drives regeneration failure, and the onset of non-acute decompensation. We further provide the proof-of-concept that rejuvenating BM-HSC reserve can serve as a potential therapeutic approach for preventing regeneration failure and transition to decompensated cirrhosis.

The profile of blood microbiome in new-onset type 1 diabetes children

Blood microbiome signatures in patients with type 1 diabetes (T1D) remain unclear. We profile blood microbiome using 16S rRNA gene sequencing in 77 controls and 64 children with new-onset T1D, and compared it with the gut and oral microbiomes. The blood microbiome of patients with T1D is characterized by increased diversity and perturbed microbial features, with a significant increase in potentially pathogenic bacteria compared with controls. Thirty-six representative genera of blood microbiome were identified by random forest analysis, providing strong discriminatory power for T1D with an AUC of 0.82. PICRUSt analysis suggested that bacteria capable of inducing inflammation were more likely to enter the bloodstream in T1D. The overlap of the gut and oral microbiome with the blood microbiome implied potential translocation of bacteria from the gut and oral cavity to the bloodstream. Our study raised the necessity of further mechanistic investigations into the roles of blood microbiome in T1D.

Tissue-resident bacteria in metabolic diseases: emerging evidence and challenges

Although the impact of the gut microbiome on health and disease is well established, there is controversy regarding the presence of microorganisms such as bacteria and their products in organs and tissues. However, recent contamination-aware findings of tissue-resident microbial signatures provide accumulating evidence in support of bacterial translocation in cardiometabolic disease. The latter provides a distinct paradigm for the link between microbial colonizers of mucosal surfaces and host metabolism. In this Perspective, we re-evaluate the concept of tissue-resident bacteria including their role in metabolic low-grade tissue and systemic inflammation. We examine the limitations and challenges associated with studying low bacterial biomass samples and propose experimental and analytical strategies to overcome these issues. Our Perspective aims to encourage further investigation of the mechanisms linking tissue-resident bacteria to host metabolism and their potentially actionable health implications for prevention and treatment.

A review of MASLD-related hepatocellular carcinoma: progress in pathogenesis, early detection, and therapeutic interventions

The incidence of metabolic dysfunction-associated steatotic liver disease (MASLD) is continuously rising, evolving into a global health challenge. Concurrently, cases of hepatocellular carcinoma (HCC) associated with MASLD are also on the increase. Although traditional risk factors such as age, gender, and metabolic factors play significant roles in the development of HCC, it cannot be overlooked that MASLD, triggered by changes in modern lifestyle and dietary habits, may also exacerbate the risk of HCC, and this phenomenon is common even among non-obese individuals. Regrettably, MASLD often fails to receive timely diagnosis, resulting in a limited number of patients receiving HCC surveillance. Moreover, there is currently a lack of clear definition for the target population for surveillance beyond patients with cirrhosis. Consequently, MASLD-related HCC is often detected at a late stage, precluding the optimal timing for curative treatment. However, our understanding of the pathogenesis and progression of HCC remains limited. Therefore, this paper reviews relevant literature from recent years, delving into multiple dimensions such as pathogenesis, surveillance and diagnosis, prevention, and treatment, aiming to provide new ideas and directions for the prevention and treatment of MASLD-related HCC.

Digestive dynamics: Unveiling interplay between the gut microbiota and the liver in macronutrient metabolism and hepatic metabolic health

Although the liver is the largest metabolic organ in the body, it is not alone in functionality and is assisted by "an organ inside an organ," the gut microbiota. This review attempts to shed light on the partnership between the liver and the gut microbiota in the metabolism of macronutrients (i.e., proteins, carbohydrates, and lipids). All nutrients absorbed by the small intestines are delivered to the liver for further metabolism. Undigested food that enters the colon is metabolized further by the gut microbiota that produces secondary metabolites, which are absorbed into portal circulation and reach the liver. These microbiota-derived metabolites and co-metabolites include ammonia, hydrogen sulfide, short-chain fatty acids, secondary bile acids, and trimethylamine N-oxide. Further, the liver produces several compounds, such as bile acids that can alter the gut microbial composition, which can in turn influence liver health. This review focuses on the metabolism of these microbiota metabolites and their influence on host physiology. Furthermore, the review briefly delineates the effect of the portosystemic shunt on the gut microbiota-liver axis, and current understanding of the treatments to target the gut microbiota-liver axis.

Periportal macrophages protect against commensal-driven liver inflammation

The liver is the main gateway from the gut, and the unidirectional sinusoidal flow from portal to central veins constitutes heterogenous zones, including the periportal vein (PV) and the pericentral vein zones1-5. However, functional differences in the immune system in each zone remain poorly understood. Here intravital imaging revealed that inflammatory responses are suppressed in PV zones. Zone-specific single-cell transcriptomics detected a subset of immunosuppressive macrophages enriched in PV zones that express high levels of interleukin-10 and Marco, a scavenger receptor that sequesters pro-inflammatory pathogen-associated molecular patterns and damage-associated molecular patterns, and consequently suppress immune responses. Induction of Marco+ immunosuppressive macrophages depended on gut microbiota. In particular, a specific bacterial family, Odoribacteraceae, was identified to induce this macrophage subset through its postbiotic isoallolithocholic acid. Intestinal barrier leakage resulted in inflammation in PV zones, which was markedly augmented in Marco-deficient conditions. Chronic liver inflammatory diseases such as primary sclerosing cholangitis (PSC) and non-alcoholic steatohepatitis (NASH) showed decreased numbers of Marco+ macrophages. Functional ablation of Marco+ macrophages led to PSC-like inflammatory phenotypes related to colitis and exacerbated steatosis in NASH in animal experimental models. Collectively, commensal bacteria induce Marco+ immunosuppressive macrophages, which consequently limit excessive inflammation at the gateway of the liver. Failure of this self-limiting system promotes hepatic inflammatory disorders such as PSC and NASH.

Blood defense system - Proposal for a new concept of an immune system against blood borne pathogens comprising the liver, spleen and bone marrow

Blood-borne pathogen (BBP) infections can rapidly progress to life-threatening sepsis and must therefore be promptly eliminated by the host's immune system. Intravascular macrophages of the liver sinusoid, splenic marginal zone and red pulp and perisinusoidal macrophage protrusions in the bone marrow (BM) directly phagocytose BBPs in the blood as an innate immune response. The liver, spleen and BM thereby work together as the blood defence system (BDS) in response to BBPs by exerting their different immunological roles. The liver removes the vast majority of these invading organisms via innate immunity, but their complete elimination is not possible without the actions of antibodies. Splenic marginal zone B cells promptly produce IgM and IgG antibodies against BBPs. The splenic marginal zone transports antigenic information from the innate to the adaptive immune systems. The white pulp of the spleen functions as adaptive immune tissue and produces specific and high-affinity antibodies with an immune memory against BBPs. The BM works to maintain immune memory by supporting the survival of memory B cells, memory T cells and long-lived plasma cells (LLPCs), all of which have dedicated niches. Furthermore, BM perisinusoidal naïve follicular B cells promptly produce IgM antibodies against BBPs in the BM sinusoid and the IgG memory B cells residing in the BM rapidly transform to plasma cells which produce high-affinity IgG antibodies upon reinfection. This review describes the complete immune defence characteristics of the BDS against BBPs through the collaboration of the liver, spleen and BM with combined different immunological roles.

The double roles of T cell-mediated immune response in the progression of MASLD

Metabolic dysfunction-associated steatotic liver disease(MASLD), formerly known as non-alcoholic fatty liver disease(NAFLD), has become a major cause of chronic liver disease and a significant risk factor for hepatocellular carcinoma, which poses a huge burden on global public health and economy. MASLD includes steatotic liver disease, steatohepatitis, and cirrhosis, and the latter two cause great harm to human health and life, even complicated with liver cancer. Immunologic mechanism plays a major role in promoting its development into hepatitis and cirrhosis. Now more and more evidences show that T cells play an important role in the progression of MASLD. In this review, we discuss the double roles of T cells in MASLD from the perspective of T cell response pathways, as well as new evidences regarding the possible application of immunomodulatory therapy in MASH.

Enterobacteriaceae and Enterococcaceae are the dominant bacterial families translocating to femur heads in broiler chicks

RESEARCH HIGHLIGHTS

Large number of bacteria isolated from femoral heads of clinically healthy broilers.The prevailing taxa in femoral heads were Escherichia/Shigella and Enterococcus spp.Continuous presence of bacteria in blood and liver of clinically healthy broilers.Enterobacteriaceae, Enterococcaceae, and Staphylococcaceae prevail in blood and liver.

A protective effect of inflammatory bowel disease on the severity of sclerosing cholangitis

Background

Primary sclerosing cholangitis (PSC) is a chronic liver disease marked by inflammation of the bile ducts and results in the development of strictures and fibrosis. A robust clinical correlation exists between PSC and inflammatory bowel disease (IBD). At present, published data are controversial, and it is yet unclear whether IBD drives or attenuates PSC.

Methods

Mdr2-deficient mice or DDC-fed mice were used as experimental models for sclerosing cholangitis. Additionally, colitis was induced in mice with experimental sclerosing cholangitis, either through infection with Citrobacter rodentium or by feeding with DSS. Lastly, fibrosis levels were determined through FibroScan analysis in people with PSC and PSC-IBD.

Results

Using two distinct experimental models of colitis and two models of sclerosing cholangitis, we found that colitis does not aggravate liver pathology, but rather reduces liver inflammation and liver fibrosis. Likewise, people with PSC-IBD have decreased liver fibrosis compared to those with PSC alone.

Conclusions

We found evidence that intestinal inflammation attenuates liver pathology. This study serves as a basis for further research on the pathogenesis of PSC and PSC-IBD, as well as the molecular mechanism responsible for the protective effect of IBD on PSC development. This study could lead to the discovery of novel therapeutic targets for PSC.

Endotoxemia and Platelets: 2 Players of Intrahepatic Microthrombosis in NAFLD

Gut dysbiosis-related intestinal barrier dysfunction with increased translocation of bacterial products such as lipopolysaccharide (LPS) into systemic circulation is emerging as pathogenic factor of nonalcoholic fatty liver disease (NAFLD). Experimental and clinical studies suggested a potential role of LPS as a trigger eliciting in situ liver inflammation upon interaction with its receptor toll-like receptor 4. Also, LPS has been reported to prime platelets to respond to the common agonists indicating that it behaves as a prothrombotic molecule. Of note, recent studies suggested platelet-related intrahepatic thrombosis triggered by LPS as a mechanism implicated in the process of liver inflammation. This review describes: 1) the impact of gut barrier dysfunction and endotoxemia in the process of NAFLD; 2) the relationship between endotoxemia and platelet activation in NAFLD; 3) clinical evidence for the use of antiplatelet drugs in NAFLD/nonalcoholic steatohepatitis patients; and 4) the potential therapeutic approach to modulate endotoxemia and eventually platelet activation.

Probiotics as Potential Therapeutic Agents: Safeguarding Skeletal Muscle against Alcohol-Induced Damage through the Gut-Liver-Muscle Axis

Probiotics have shown the potential to counteract the loss of muscle mass, reduce physical fatigue, and mitigate inflammatory response following intense exercise, although the mechanisms by which they work are not very clear. The objective of this review is to describe the main harmful effects of alcohol on skeletal muscle and to provide important strategies based on the use of probiotics. The excessive consumption of alcohol is a worldwide problem and has been shown to be crucial in the progression of alcoholic liver disease (ALD), for which, to date, the only therapy available is lifestyle modification, including cessation of drinking. In ALD, alcohol contributes significantly to the loss of skeletal muscle, and also to changes in the intestinal microbiota, which are the basis for a series of problems related to the onset of sarcopenia. Some of the main effects of alcohol on the skeletal muscle are described in this review, with particular emphasis on the "gut-liver-muscle axis", which seems to be the primary cause of a series of muscle dysfunctions related to the onset of ALD. The modulation of the intestinal microbiota through probiotics utilization has appeared to be crucial in mitigating the muscle damage induced by the high amounts of alcohol consumed.

Gut-Liver Axis as a Therapeutic Target for Drug-Induced Liver Injury

Drug-induced liver injury (DILI) is a liver disease that remains difficult to predict and diagnose, and the underlying mechanisms are yet to be fully clarified. The gut-liver axis refers to the reciprocal interactions between the gut and the liver, and its homeostasis plays a prominent role in maintaining liver health. It has been recently reported that patients and animals with DILI have a disrupted gut-liver axis, involving altered gut microbiota composition, increased intestinal permeability and lipopolysaccharide translocation, decreased short-chain fatty acids production, and impaired bile acid metabolism homeostasis. The present review will summarize the evidence from both clinical and preclinical studies about the role of the gut-liver axis in the pathogenesis of DILI. Moreover, we will focus attention on the potential therapeutic strategies for DILI based on improving gut-liver axis function, including herbs and phytochemicals, probiotics, fecal microbial transplantation, postbiotics, bile acids, and Farnesoid X receptor agonists.

The nuclear factor ID3 endows macrophages with a potent anti-tumour activity

Macrophage activation is controlled by a balance between activating and inhibitory receptors1-7, which protect normal tissues from excessive damage during infection8,9 but promote tumour growth and metastasis in cancer7,10. Here we report that the Kupffer cell lineage-determining factor ID3 controls this balance and selectively endows Kupffer cells with the ability to phagocytose live tumour cells and orchestrate the recruitment, proliferation and activation of natural killer and CD8 T lymphoid effector cells in the liver to restrict the growth of a variety of tumours. ID3 shifts the macrophage inhibitory/activating receptor balance to promote the phagocytic and lymphoid response, at least in part by buffering the binding of the transcription factors ELK1 and E2A at the SIRPA locus. Furthermore, loss- and gain-of-function experiments demonstrate that ID3 is sufficient to confer this potent anti-tumour activity to mouse bone-marrow-derived macrophages and human induced pluripotent stem-cell-derived macrophages. Expression of ID3 is therefore necessary and sufficient to endow macrophages with the ability to form an efficient anti-tumour niche, which could be harnessed for cell therapy in cancer.

Liver cirrhosis and complications from the perspective of dysbiosis

The gut-liver axis refers to the intimate relationship and rigorous interaction between the gut and the liver. The intestinal barrier's integrity is critical for maintaining liver homeostasis. The liver operates as a second firewall in this interaction, limiting the movement of potentially dangerous compounds from the gut and, as a result, contributing in barrier management. An increasing amount of evidence shows that increased intestinal permeability and subsequent bacterial translocation play a role in liver damage development. The major pathogenic causes in cirrhotic individuals include poor intestinal permeability, nutrition, and intestinal flora dysbiosis. Portal hypertension promotes intestinal permeability and bacterial translocation in advanced liver disease, increasing liver damage. Bacterial dysbiosis is closely related to the development of cirrhosis and its related complications. This article describes the potential mechanisms of dysbiosis in liver cirrhosis and related complications, such as spontaneous bacterial peritonitis, hepatorenal syndrome, portal vein thrombosis, hepatic encephalopathy, and hepatocellular carcinoma, using dysbiosis of the intestinal flora as an entry point.

The gut-liver axis in hepatobiliary diseases

Recent advances in the analysis of intestinal bacteria have led to reports of variations in intestinal bacterial levels among hepatobiliary diseases. The mechanisms behind the changes in intestinal bacteria in various hepatobiliary diseases include the abnormal composition of intestinal bacteria, weakening of the intestinal barrier, and bacterial translocation outside the intestinal tract, along with their metabolites, but many aspects remain unresolved. Further research employing clinical studies and animal models is expected to clarify the direct relationship between intestinal bacteria and hepatobiliary diseases and to validate the utility of intestinal bacteria as a diagnostic biomarker and potential therapeutic target. This review summarizes the involvement of the microbiota in the pathogenesis of hepatobiliary diseases via the gut-liver axis.

System failure: Systemic inflammation following spinal cord injury

Spinal cord injury (SCI) affects hundreds of thousands of people in the United States, and while some effects of the injury are broadly recognized (deficits to locomotion, fine motor control, and quality of life), the systemic consequences of SCI are less well-known. The spinal cord regulates systemic immunological and visceral functions; this control is often disrupted by the injury, resulting in viscera including the gut, spleen, liver, bone marrow, and kidneys experiencing local tissue inflammation and physiological dysfunction. The extent of pathology depends on the injury level, severity, and time post-injury. In this review, we describe immunological and metabolic consequences of SCI across several organs. Since infection and metabolic disorders are primary reasons for reduced lifespan after SCI, it is imperative that research continues to focus on these deleterious aspects of SCI to improve life span and quality of life for individuals with SCI.

Gut-bacteria derived membrane vesicles and host metabolic health: a narrative review

The intestinal microbiota, consisting of an estimated 10^10-10^11 organisms, regulate physiological processes involved in digestion, metabolism, and immunity. Surprisingly, these intestinal microorganisms have been found to influence tissues that are not directly in contact with the gut, such as adipose tissue, the liver, skeletal muscle, and the brain. This interaction takes place even when intestinal barrier function is uncompromised. An increasing body of evidence suggests that bacterial membrane vesicles (bMVs), in addition to bacterial metabolites such as short-chain fatty acids, are able to mediate effects of the microbiota on these host tissues. The ability of bMVs to dissipate from the intestinal lumen into systemic circulation hereby facilitates the transport and presentation of bacterial components and metabolites to host organs. Importantly, there are indications that the interaction between bMVs and tissues or immune cells may play a role in the etiology of (chronic metabolic) disease. For example, the gut-derived bMV-mediated induction of insulin resistance in skeletal muscle cells and pro-inflammatory signaling by adipocytes possibly underlies diseases such as type 2 diabetes and obesity. Here, we review the current knowledge on bMVs in the microbiota's effects on host energy/substrate metabolism with a focus on etiological roles in the onset and progression of metabolic disease. We furthermore illustrate that vesicle production by bacterial microbiota could potentially be modulated through lifestyle intervention to improve host metabolism.

Liver macrophages and sinusoidal endothelial cells execute vaccine-elicited capture of invasive bacteria

Vaccination has substantially reduced the morbidity and mortality of bacterial diseases, but mechanisms of vaccine-elicited pathogen clearance remain largely undefined. We report that vaccine-elicited immunity against invasive bacteria mainly operates in the liver. In contrast to the current paradigm that migrating phagocytes execute vaccine-elicited immunity against blood-borne pathogens, we found that invasive bacteria are captured and killed in the liver of vaccinated host via various immune mechanisms that depend on the protective potency of the vaccine. Vaccines with relatively lower degrees of protection only activated liver-resident macrophage Kupffer cells (KCs) by inducing pathogen-binding immunoglobulin M (IgM) or low amounts of IgG. IgG-coated pathogens were directly captured by KCs via multiple IgG receptors FcγRs, whereas IgM-opsonized bacteria were indirectly bound to KCs via complement receptors of immunoglobulin superfamily (CRIg) and complement receptor 3 (CR3) after complement C3 activation at the bacterial surface. Conversely, the more potent vaccines engaged both KCs and liver sinusoidal endothelial cells by inducing higher titers of functional IgG antibodies. Endothelial cells (ECs) captured densely IgG-opsonized pathogens by the low-affinity IgG receptor FcγRIIB in a "zipper-like" manner and achieved bacterial killing predominantly in the extracellular milieu via an undefined mechanism. KC- and endothelial cell-based capture of antibody-opsonized bacteria also occurred in FcγR-humanized mice. These vaccine protection mechanisms in the liver not only provide a comprehensive explanation for vaccine-/antibody-boosted immunity against invasive bacteria but also may serve as in vivo functional readouts of vaccine efficacy.

Interorgan communication with the liver: novel mechanisms and therapeutic targets

The liver is a multifunctional organ that plays crucial roles in numerous physiological processes, such as production of bile and proteins for blood plasma, regulation of blood levels of amino acids, processing of hemoglobin, clearance of metabolic waste, maintenance of glucose, etc. Therefore, the liver is essential for the homeostasis of organisms. With the development of research on the liver, there is growing concern about its effect on immune cells of innate and adaptive immunity. For example, the liver regulates the proliferation, differentiation, and effector functions of immune cells through various secreted proteins (also known as "hepatokines"). As a result, the liver is identified as an important regulator of the immune system. Furthermore, many diseases resulting from immune disorders are thought to be related to the dysfunction of the liver, including systemic lupus erythematosus, multiple sclerosis, and heart failure. Thus, the liver plays a role in remote immune regulation and is intricately linked with systemic immunity. This review provides a comprehensive overview of the liver remote regulation of the body's innate and adaptive immunity regarding to main areas: immune-related molecules secreted by the liver and the liver-resident cells. Additionally, we assessed the influence of the liver on various facets of systemic immune-related diseases, offering insights into the clinical application of target therapies for liver immune regulation, as well as future developmental trends.

Fecal microbiota transplantation for the management of autoimmune diseases: Potential mechanisms and challenges

Autoimmune diseases (AIDs) are a series of immune-mediated lethal diseases featured by over-activated immune cells attacking healthy self-tissues and organs due to the loss of immune tolerance, which always causes severe irreversible systematical organ damage and threatens human health heavily. To date, there are still no definitive cures for the treatment of AIDs due to their pathogenesis has not been clearly understood. Besides, the current clinical treatments of AIDs majorly rely on glucocorticoids and immune suppressors, which can lead to serious side effects. In the past years, there are increasing studies demonstrating that an imbalance of gut microbiota is intimately related to the pathogenesis of various AIDs, shedding light on the development of therapeutics by targeting the gut microbiota for the management of AIDs. Among all the approaches targeting the gut microbiota, fecal microbiota transplantation (FMT) has attracted increasing interest, and it has been proposed as a possible strategy to intervene in the homeostasis of gut microbiota for the treatment of various diseases. However, despite the reported good curative effects and clinical studies conducted on FMT, the detailed mechanisms of FMT for the effective treatment of those diseases have not been figured out. To fully understand the mechanisms of the therapeutic effects of FMT on AIDs and improve the therapeutic efficacy of FMT treatment, a systematic review of this topic is necessary. Hence, in this review paper, the potential mechanisms of FMT for the treatment of various AIDs were summarized, including promotion, shaping, activation, or inhibition of the host immune system via the interactions between the microorganisms and the gut immune system, gut-brain, gut-liver, gut-kidney axis, and so on. Then, applications of FMT for the treatment of various AIDs were detailed presented. Finally, the current challenges and potential solutions for the development of FMT formulations and FMT therapeutics were comprehensively discussed.