Prophylactic tributyrin treatment mitigates chronic-binge ethanol-induced intestinal barrier and liver injury

Gut microbiota-derived short-chain fatty acids and their role in human health and disease

Short-chain fatty acids (SCFAs) are a group of organic compounds produced by the fermentation of dietary fibre by the human gut microbiota. They play diverse roles in different physiological processes of the host with implications for human health and disease. This Review provides an overview of the complex microbial metabolism underlying SCFA formation, considering microbial interactions and modulating factors of the gut environment. We explore the multifaceted mechanistic interactions between SCFAs and the host, with a particular focus on the local actions of SCFAs in the gut and their complex interactions with the immune system. We also discuss how these actions influence intestinal and extraintestinal diseases and emerging therapeutic strategies using SCFAs.

Se-containing compounds with different Se species alleviate alcoholic liver injury through regulating liver metabolism and modulating gut microbiota composition

Alcoholic liver injury is primarily caused by long-term excessive alcohol consumption and has become a global public health concern. It is well known that selenium (Se) has excellent beneficial effects in regulating oxidative stress and protecting liver function. However, the effects of different species of Se compounds on alcohol-induced liver injury and their underlying mechanisms remain unclear. Hence, this study investigated the intervention of three different species of Se compounds-Se-enriched Cardamine violifolia peptides (CV), Se-enriched soybean peptides (SO), and sodium selenite (SS)-in an alcohol-induced liver injury mice model. The results of serum biochemical indices and hepatic oxidative stress indexes showed that although both Se-enriched peptides and SS exhibited protective effects against alcohol-induced liver injury, Se-enriched peptides exerted a better effect than SS. Liver metabolomics studies revealed that 30, 15, and 30 metabolites with significant differences were identified in the comparisons of CV vs. model group (MC), SO vs. MC, and SS vs. MC groups, respectively. Common differential metabolites in the three comparison groups were dopamine glucuronide, docosahexaenoic acid, glycerophosphocholine, galactinol and sclareol. KEGG analysis indicated that the differential metabolites between the SS vs. MC groups were enriched in the glycerophospholipid metabolism pathway. The significant metabolic pathways enriched in the SO vs. MC groups were α-linolenic acid metabolism, citric acid cycle, and glucagon signaling pathway. In the CV vs. MC groups, metabolic pathways related to insulin secretion, carbohydrate digestion and absorption, inositol phosphate metabolism, and C-type lectin receptor signaling pathway were also identified. In addition, the intervention of Se-enriched peptides regulated alcohol-induced dysbiosis of the gut microbiota and upgraded the levels of short-chain fatty acids. In the CV group, differential taxa included unidentified_Bacteria, unidentified_Bacteria family and unidentified_Bacteria genus. The dominant species in the SO group included the Atopobiaceae and Turicibiacter. In conclusion, these findings revealed the important role of the gut-liver axis in the protective effects of Se-containing compounds against alcoholic liver injury. Se-enriched peptides, particularly those from CV with selenocystine as the main Se specie, hold great promise as a novel functional food ingredient for the prevention of alcoholic liver injury.

The Impact of Liver Graft Preservation Method on Longitudinal Gut Microbiome Changes Following Liver Transplant: A Proof-of-concept Study

Background and Aims

End-stage liver disease is associated with disruptions in gut microbiota composition and function, which may facilitate gut-to-liver bacterial translocation, impacting liver graft integrity and clinical outcomes following liver transplantation. This study aimed to assess the impact of two liver graft preservation methods on fecal microbiota and changes in fecal and breath organic acids following liver transplantation.

Methods

This single-center, non-randomized prospective pilot study enrolled liver transplant patients whose grafts were preserved using either static cold storage or ex situ normothermic machine perfusion (NMP). Fresh stool and breath samples were collected immediately before surgery and at postoperative months 3, 6, and 12. Stool microbiota was profiled via 16S rRNA gene sequencing, stool short-chain fatty acids were measured using gas chromatography/-mass spectrometry, and breath volatile organic compounds (VOCs) were analyzed with selected-ion flow-tube mass spectrometry.

Results

Both cohorts experienced a loss of microbiota diversity and dominance by single taxa. The NMP cohort demonstrated enrichment of several beneficial gut taxa, while the static cold storage cohort showed depletion of such taxa. Various gut bacteria were found to correlate with stool short-chain fatty acids (e.g., lactic acid, butyric acid) and several VOCs.

Conclusions

Fecal microbiota alterations associated with end-stage liver disease do not fully normalize to a healthy control profile following liver transplantation. However, notable differences in microbiota composition and function were observed between liver graft preservation methods. Future research with larger randomized cohorts is needed to explore whether the NMP-associated shift in gut microbiota impacts clinical outcomes and if breath VOCs could serve as biomarkers of the clinical trajectory in liver transplant patients.

Preparation, Structural Characterization, and In Vitro Modulation of the Gut Microbiota Activity of a Novel α-Glucan in Hericium erinaceus

Hericium erinaceus (H. erinaceus) is a kind of medicinal and edible fungus that contains polysaccharide as the most studied effective component at present. In this paper, a novel α-glucan was successfully isolated from H. erinaceus fruiting bodies by hot water extraction combined with the fractional ethanol precipitation method. To analyze the monosaccharide composition, methylation and nuclear magnetic resonance spectroscopy were performed, and the polysaccharide was identified having α-(1→4)-glycosidic bonds with a single unit α-D-Glcp branch attached at the O-6 position (Mw, 1.43 × 107 g/mol, branching ratio of 9:1). Furthermore, the aqueous solution analysis demonstrated that this α-glucan adopts a rigid spherical conformation. The polysaccharide exhibited resistance to simulated gastrointestinal digestion but was effectively degraded by gut microbiota (GM), leading to significant changes in total polysaccharide content, reducing sugar, and pH value. Notably, the α-glucan was beneficial to increase the contents of acetic and propionic acids in metabolites, stimulated the growth of beneficial bacteria (Lactobacillus and Bifidobacterium), and inhibited the proliferation of harmful bacteria (Fusobacterium). Overall, the study deepened the regulatory effects of α-glucan with different ratios of main and branch chains from H. erinaceus fruiting bodies on GM, which provides theoretical support for developing of GM-targeted foods.

The Gut-Lung Axis During Ethanol Exposure and a Pseudomonas aeruginosa Bacterial Challenge

Background: Susceptibility to and severity of pulmonary infections increase with ethanol consumption. We have previously shown that ethanol-induced changes in the gut microbiome disrupt gut homeostasis, allowing for the translocation of proinflammatory mediators into the circulation and eliciting an immune response in the lung. Additionally, targeting the gut with butyrate supplementation not only rescues ethanol-induced disruptions to gut health but also reverses aspects of immune dysregulation in the lungs. Here, we assessed the impact of this connection on a subsequent infectious challenge. Methods: To assess if ethanol-induced alterations to the gut microbiome could also impact the host response to a pulmonary infectious challenge, we employed a chronic-binge ethanol-feeding mouse model followed by a nasal instillation of Pseudomonas aeruginosa. Results: In addition to altering gut microbiome composition and metabolism, ethanol consumption also disrupted the local immune response as demonstrated by suppressed cecal SIgA levels, a decreased presence of CD3+CD8a+ cytotoxic T cells in the proximal colon mucosa, and depleted CD3+CD8a+ T cells and CD11c+CD8a+ dendritic cells in the mesenteric lymph nodes. Circulatory Ly6G+CD11b+ neutrophils increased, indicating a systemic change in immune-cell presence with ethanol exposure. Ethanol exposure increased CD11c+CD64+ macrophages and Ly6G+CD11b+ neutrophils in the lungs, with neutrophil populations being further exacerbated during a bacterial challenge with Pseudomonas aeruginosa. Lipocalin 2, a marker of oxidative stress, was also elevated with ethanol consumption, though not with infection. Conclusions: These data suggest that ethanol-induced changes in the gut microbiome and immune environment are linked to dysfunctional immune responses in the intestine, blood, and the lungs, compromising the pulmonary immune response during an infectious challenge in mice.

Gut-liver axis: Recent concepts in pathophysiology in alcohol-associated liver disease

The growing recognition of the role of the gut microbiome's impact on alcohol-associated diseases, especially in alcohol-associated liver disease, emphasizes the need to understand molecular mechanisms involved in governing organ-organ communication to identify novel avenues to combat alcohol-associated diseases. The gut-liver axis refers to the bidirectional communication and interaction between the gut and the liver. Intestinal microbiota plays a pivotal role in maintaining homeostasis within the gut-liver axis, and this axis plays a significant role in alcohol-associated liver disease. The intricate communication between intestine and liver involves communication between multiple cellular components in each organ that enable them to carry out their physiological functions. In this review, we focus on novel approaches to understanding how chronic alcohol exposure impacts the microbiome and individual cells within the liver and intestine, as well as the impact of ethanol on the molecular machinery required for intraorgan and interorgan communication.

Green Radish Polysaccharide Prevents Alcoholic Liver Injury by Interfering with Intestinal Bacteria and Short-Chain Fatty Acids in Mice

This study aimed to ascertain the potential benefits of green radish polysaccharide (GRP) in treating alcoholic liver disease (ALD) in mice and explore its mechanism of action. Using biochemical analysis, high-throughput sequencing of gut microbiota, and gas chromatography-mass spectrometry to measure short-chain fatty acids (SCFAs) in feces, we found that GRP intervention significantly improved lipid metabolism and hepatic function in mice subjected to excessive alcohol intake. The GRP intervention reduced malondialdehyde levels by 66% and increased total superoxide dismutase levels by 22%, thereby mitigating alcohol-induced oxidative stress. Furthermore, GRP intervention in mice with alcohol consumption resulted in a reduction in tumor necrosis factor, interleukin 6, and lipopolysaccharide levels by 12%, 9%, and 25%, respectively, effectively attenuating alcoholic liver inflammation. 16S rRNA amplicon sequencing demonstrated that excessive alcohol consumption markedly altered the gut microbiota composition in mice. The GRP treatment resulted in a significant reduction in the number of beneficial bacteria (Lactobacillus and Lachnospiraceae_NK4A136_group) and an increase in the proportion of harmful bacteria (Muribaculaceae and Verrucomicrobiota). The metabolomic analyses of the SCFAs demonstrated an increase in the contents of SCFAs, acetic acid, propionic acid, and butyric acid, following GRP supplementation. Furthermore, the metabolic levels of cholinergic synapses and glycolysis/gluconeogenesis were found to be modulated. In conclusion, these findings suggest that GRP may attenuate alcohol-induced oxidative damage in the liver by modulating the gut microbiota and hepatic metabolic pathways. This may position GRP as a potential functional component for ALD prevention.

Gut Bacteria in Alcohol-Associated Liver Disease

Alcohol-associated liver disease (ALD) poses a significant global public health challenge, with high patient mortality rates and economic burden. The gut microbiome plays an important role in the onset and progression of alcohol-associated liver disease. Excessive alcohol consumption disrupts the intestinal barrier, facilitating the entry of harmful microbes and their products into the liver, exacerbating liver damage. Dysbiosis, marked by imbalance in gut bacteria, correlates with ALD severity. Promising microbiota-centered therapies include probiotics, phages, and fecal microbiota transplantation. Clinical trials demonstrate the potential of these interventions to improve liver function and patient outcomes, offering a new frontier in ALD treatment.

DHA-enriched phosphatidylserine ameliorates cyclophosphamide-induced liver injury via regulating the gut-liver axis

OBJECTIVE

This study explores the therapeutic effects and mechanisms of DHA-enriched phosphatidylserine (DHA-PS) on liver injury induced by cyclophosphamide (CTX) in mice, focusing on the gut-liver axis.

METHODS

A mouse model was established by administering CTX (80 mg/kg) intraperitoneally for 5 days. DHA-PS (50 or 100 mg/kg) was administered for the next 7 days to assess its reparative impact on liver damage.

RESULTS

The findings revealed significant improvements in liver biochemical indices, inflammatory markers, and oxidative stress levels in the mice treated with DHA-PS. Through non-targeted metabolomics analysis, DHA-PS mitigated CTX-induced metabolic disruptions by modulating lipid, amino acid, and pyrimidine metabolism. Immunofluorescence analysis further confirmed that DHA-PS reduced the expression of liver-associated inflammatory proteins by inhibiting the TLR4/NF-κB pathway. Additionally, DHA-PS restored the intestinal barrier, evidenced by adjustments in the levels of intestinal lipopolysaccharide (LPS), secretory immunoglobulin A (sIgA), and tight junction proteins (Claudin-1, Occludin, and ZO-1). It also improved gut microbiota balance by enhancing microbial diversity, increasing beneficial bacteria, and altering community structures.

CONCLUSION

These results suggest that DHA-PS could be a potential therapeutic agent or functional food for CTX-induced liver injury through its regulation of the gut-liver axis.

Impact of High-Temperature Feeds on Gut Microbiota and MAFLD

The purpose of this study is to investigate the effects of non-obese MAFLD on the gut microbiota and metabolic pathways caused by high-temperature processed meals. It was decided to divide the eighteen male Sprague-Dawley rats into three groups: the control group, the dry-fried soybeans (DFS) group, and the high-fat diet (HFD) group. Following the passage of twelve weeks, a series of physical, biochemical, histological, and microbiological examinations were carried out. There were distinct pathological abnormalities brought about by each diet. The DFS diet was found to cause the development of fatty liver and to demonstrate strong relationships between components of the gut microbiota, such as Akkermansia and Mucispirillum, and indices of liver health. Diet-induced changes in the gut microbiome have a significant impact on liver pathology in non-obese patients with metabolically altered liver disease (MAFLD), which suggests that dietary interventions that target gut microbiota could be used to manage or prevent the illness.

Therapeutic manipulation of the microbiome in liver disease

Myriad associations between the microbiome and various facets of liver physiology and pathology have been described in the literature. Building on descriptive and correlative sequencing studies, metagenomic studies are expanding our collective understanding of the functional and mechanistic role of the microbiome as mediators of the gut-liver axis. Based on these mechanisms, the functional activity of the microbiome represents an attractive, tractable, and precision medicine therapeutic target in several liver diseases. Indeed, several therapeutics have been used in liver disease even before their description as a microbiome-dependent approach. To bring successful microbiome-targeted and microbiome-inspired therapies to the clinic, a comprehensive appreciation of the different approaches to influence, collaborate with, or engineer the gut microbiome to coopt a disease-relevant function of interest in the right patient is key. Herein, we describe the various levels at which the microbiome can be targeted-from prebiotics, probiotics, synbiotics, and antibiotics to microbiome reconstitution and precision microbiome engineering. Assimilating data from preclinical animal models, human studies as well as clinical trials, we describe the potential for and rationale behind studying such therapies across several liver diseases, including metabolic dysfunction-associated steatotic liver disease, alcohol-associated liver disease, cirrhosis, HE as well as liver cancer. Lastly, we discuss lessons learned from previous attempts at developing such therapies, the regulatory framework that needs to be navigated, and the challenges that remain.

Tributyrin Supplementation Rescues Chronic-Binge Ethanol-Induced Oxidative Stress in the Gut-Lung Axis in Mice

Excessive alcohol consumption increases the severity and worsens outcomes of pulmonary infections, often due to oxidative stress and tissue damage. While the mechanism behind this relationship is multifaceted, recent evidence suggests ethanol-induced changes to the gut microbiome impact the gut-lung axis. To assess this, a chronic-binge ethanol feeding mouse model was used to determine how ethanol altered the gut microbiome, small intestinal epithelial barrier, and immune responses, as well as neutrophil abundance and oxidative stress in the lungs, and how supporting gut health with tributyrin supplementation during chronic-binge ethanol exposure affected these responses. We found that ethanol consumption altered gut bacterial taxa and metabolic processes, distorted small intestinal immune responses, and induced both bacteria and endotoxin translocation into the lymphatic and circulatory systems. These changes were associated with increased neutrophil (Ly6G) presence and markers of oxidative stress, lipocalin-2 and myeloperoxidase, in the lungs. Importantly, tributyrin supplementation during ethanol exposure rescued gut bacterial function (p < 0.05), small intestinal barrier integrity, and immune responses, as well as reducing both Ly6G mRNA (p < 0.05) and lipocalin-2 mRNA (p < 0.01) in the lungs. These data suggest ethanol-associated disruption of gut homeostasis influenced the health of the lungs, and that therapeutics supporting gut health may also support lung health.

Dietary sodium acetate and sodium butyrate improve high-carbohydrate diet utilization by regulating gut microbiota, liver lipid metabolism, oxidative stress, and inflammation in largemouth bass (Micropterus salmoides)

BACKGROUND

Adequate level of carbohydrates in aquafeeds help to conserve protein and reduce cost. However, studies have indicated that high-carbohydrate (HC) diet disrupt the homeostasis of the gut-liver axis in largemouth bass, resulting in decreased intestinal acetate and butyrate level.

METHOD

Herein, we had concepted a set of feeding experiment to assess the effects of dietary sodium acetate (SA) and sodium butyrate (SB) on liver health and the intestinal microbiota in largemouth bass fed an HC diet. The experimental design comprised 5 isonitrogenous and isolipidic diets, including LC (9% starch), HC (18% starch), HCSA (18% starch; 2 g/kg SA), HCSB (18% starch; 2 g/kg SB), and HCSASB (18% starch; 1 g/kg SA + 1 g/kg SB). Juvenile largemouth bass with an initial body weight of 7.00 ± 0.20 g were fed on these diets for 56 d.

RESULTS

We found that dietary SA and SB reduced hepatic triglyceride accumulation by activating autophagy (ATG101, LC3B and TFEB), promoting lipolysis (CPT1α, HSL and AMPKα), and inhibiting adipogenesis (FAS, ACCA, SCD1 and PPARγ). In addition, SA and SB decreased oxidative stress in the liver (CAT, GPX1α and SOD1) by activating the Keap1-Nrf2 pathway. Meanwhile, SA and SB alleviated HC-induced inflammation by downregulating the expression of pro-inflammatory factors (IL-1β, COX2 and Hepcidin1) through the NF-κB pathway. Importantly, SA and SB increased the abundance of bacteria that produced acetic acid and butyrate (Clostridium_sensu_stricto_1). Combined with the KEGG analysis, the results showed that SA and SB enriched carbohydrate metabolism and amino acid metabolism pathways, thereby improving the utilization of carbohydrates. Pearson correlation analysis indicated that growth performance was closely related to hepatic lipid deposition, autophagy, antioxidant capacity, inflammation, and intestinal microbial composition.

CONCLUSIONS

In conclusion, dietary SA and SB can reduce hepatic lipid deposition; and alleviate oxidative stress and inflammation in largemouth bass fed on HC diet. These beneficial effects may be due to the altered composition of the gut microbiota caused by SA and SB. The improvement effects of SB were stronger than those associated with SA.

Gut-brain communication mediates the impact of dietary lipids on cognitive capacity

Cognitive impairment, as a prevalent symptom of nervous system disorders, poses one of the most challenging aspects in the management of brain diseases. Lipids present in the cell membranes of all neurons within the brain and dietary lipids can regulate the cognition and memory function. In recent years, the advancements in gut microbiome research have enabled the exploration of dietary lipids targeting the gut-brain axis as a strategy for regulating cognition. This present review provides an in-depth overview of how lipids modulate cognition via the gut-brain axis depending on metabolic, immune, neural and endocrine pathways. It also comprehensively analyzes the effects of diverse lipids on the gut microbiota and intestinal barrier function, thereby affecting the central nervous system and cognitive capacity. Moreover, comparative analysis of the positive and negative effects is presented between beneficial and detrimental lipids. The former encompass monounsaturated fatty acids, short-chain fatty acids, omega-3 polyunsaturated fatty acids, phospholipids, phytosterols, fungal sterols and bioactive lipid-soluble vitamins, as well as lipid-derived gut metabolites, whereas the latter (detrimental lipids) include medium- or long-chain fatty acids, excessive proportions of n-6 polyunsaturated fatty acids, industrial trans fatty acids, and zoosterols. To sum up, the focus of this review is on how gut-brain communication mediates the impact of dietary lipids on cognitive capacity, providing a novel theoretical foundation for promoting brain cognitive health and scientific lipid consumption patterns.

The Postbiotic Butyrate Mitigates Gut Mucosal Disruption Caused by Acute Ethanol Exposure

We aimed to test how the postbiotic butyrate impacts select gut bacteria, small intestinal epithelial integrity, and microvascular endothelial activation during acute ethanol exposure in mice and primary human intestinal microvascular endothelial cells (HIMECs). Supplementation during an acute ethanol challenge with or without tributyrin, a butyrate prodrug, was delivered to C57BL/6 mice. A separate group of mice received 3 days of clindamycin prior to the acute ethanol challenge. Upon euthanasia, blood endotoxin, cecal bacteria, jejunal barrier integrity, and small intestinal lamina propria dendritic cells were assessed. HIMECs were tested for activation following exposure to ethanol ± lipopolysaccharide (LPS) and sodium butyrate. Tributyrin supplementation protected a butyrate-generating microbe during ethanol and antibiotic exposure. Tributyrin rescued ethanol-induced disruption in jejunal epithelial barrier, elevated plasma endotoxin, and increased mucosal vascular addressin cell-adhesion molecule-1 (MAdCAM-1) expression in intestinal microvascular endothelium. These protective effects of tributyrin coincided with a tolerogenic dendritic response in the intestinal lamina propria. Lastly, sodium butyrate pre- and co-treatment attenuated the direct effects of ethanol and LPS on MAdCAM-1 induction in the HIMECs from a patient with ulcerative colitis. Tributyrin supplementation protects small intestinal epithelial and microvascular barrier integrity and modulates microvascular endothelial activation and dendritic tolerizing function during a state of gut dysbiosis and acute ethanol challenge.

Viral Liver Disease and Intestinal Gut–Liver Axis

The intestinal microbiota is closely related to liver diseases via the intestinal barrier and bile secretion to the gut. Impairment of the barrier can translocate microbes or their components to the liver where they can contribute to liver damage and fibrosis. The components of the barrier are discussed in this review along with the other elements of the so-called gut–liver axis. This bidirectional relation has been widely studied in alcoholic and non-alcoholic liver disease. However, the involvement of microbiota in the pathogenesis and treatment of viral liver diseases have not been extensively studied, and controversial data have been published. Therefore, we reviewed data regarding the integrity and function of the intestinal barrier and the changes of the intestinal microbioma that contribute to progression of Hepatitis B (HBV) and Hepatitis C (HCV) infection. Their consequences, such as cirrhosis and hepatic encephalopathy, were also discussed in connection with therapeutic interventions such as the effects of antiviral eradication and the use of probiotics that may influence the outcome of liver disease. Profound alterations of the microbioma with significant reduction in microbial diversity and changes in the abundance of both beneficial and pathogenic bacteria were found.

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.

Ethanol-induced changes to the gut microbiome compromise the intestinal homeostasis: a review

The intestine is the largest organ in terms of surface area in the human body. It is responsible not only for absorbing nutrients but also for protection against the external world. The gut microbiota is essential in maintaining a properly functioning intestinal barrier, primarily through producing its metabolites: short-chain fatty acids, bile acids, and tryptophan derivatives. Ethanol overconsumption poses a significant threat to intestinal health. Not only does it damage the intestinal epithelium, but, maybe foremostly, it changes the gut microbiome. Those ethanol-driven changes shift its metabolome, depriving the host of the protective effect the physiological gut microbiota has. This literature review discusses the impact of ethanol consumption on the gut, the gut microbiota, and its metabolome, providing a comprehensive overview of the mechanisms through which ethanol disrupts intestinal homeostasis and discussing potential avenues for new therapeutic intervention.

The gut-liver axis and gut microbiota in health and liver disease

The trillions of microorganisms in the human intestine are important regulators of health, and disruptions in the gut microbial communities can cause disease. The gut, liver and immune system have a symbiotic relationship with these microorganisms. Environmental factors, such as high-fat diets and alcohol consumption, can disrupt and alter microbial communities. This dysbiosis can lead to dysfunction of the intestinal barrier, translocation of microbial components to the liver and development or progression of liver disease. Changes in metabolites produced by gut microorganisms can also contribute to liver disease. In this Review, we discuss the importance of the gut microbiota in maintenance of health and the alterations in microbial mediators that contribute to liver disease. We present strategies for modulation of the intestinal microbiota and/or their metabolites as potential treatments for liver disease.

Tributyrin Mitigates Ethanol-Induced Lysine Acetylation of Histone-H3 and p65-NFκB Downregulating CCL2 Expression and Consequent Liver Inflammation and Injury

PURPOSE

Chemokine-driven leukocyte infiltration and sustained inflammation contribute to alcohol-associated liver disease (ALD). Elevated hepatic CCL2 expression, seen in ALD, is associated with disease severity. However, mechanisms of CCL2 regulation are not completely elucidated. Post-translational modifications (PTMs) of proteins, particularly acetylation, modulate gene expression. This study examined the acetylation changes of promoter-associated histone-H3 and key transcription factor-NFκB in regulating hepatic CCL2 expression and subsequent inflammation and injury. Further, the effect of therapeutic modulation of the acetylation state by tributyrin (TB), a butyrate prodrug, was assessed.

METHODS

Hepatic CCL2 expression was assessed in mice fed control (PF) or an ethanol-containing Lieber-DeCarli (5% v/v, EF) diet for 7 weeks with or without oral administration of tributyrin (TB, 2 g/kg, 5 days/week). A chromatin immunoprecipitation (ChIP) assay evaluated promoter-associated modifications. Nuclear association between SIRT1, p300, and NFκB-p65 and acetylation changes of p65 were determined using immunoprecipitation and Western blot analyses. A Student's t-test and one-way ANOVA determined the significance.

RESULTS

Ethanol significantly increased promoter-associated histone-H3-lysine-9 acetylation (H3K9Ac), reflecting a transcriptionally permissive state with a resultant increase in hepatic CCL2 mRNA and protein expression. Moreover, increased lysine-310-acetylation of nuclear RelA/p65 decreased its association with SIRT1, a class III HDAC, but concomitantly increased with p300, a histone acetyltransferase. This further led to enhanced recruitment of NF-κB/p65 and RNA polymerase-II to the CCL2 promoter. Oral TB administration prevented ethanol-associated acetylation changes, thus downregulating CCL2 expression, hepatic neutrophil infiltration, and inflammation/ injury.

CONCLUSION

The modulation of a protein acetylation state via ethanol or TB mechanistically regulates hepatic CCL2 upregulation in ALD.

The Role of Gut Microbiome-Derived Short-Chain Fatty Acid Butyrate in Hepatobiliary Diseases

The short-chain fatty acid butyrate, produced from fermentable carbohydrates by gut microbiota in the colon, has multiple beneficial effects on human health. At the intestinal level, butyrate regulates metabolism, helps in the transepithelial transport of fluids, inhibits inflammation, and induces the epithelial defense barrier. The liver receives a large amount of short-chain fatty acids via the blood flowing from the gut via the portal vein. Butyrate helps prevent nonalcoholic fatty liver disease, nonalcoholic steatohepatitis, inflammation, cancer, and liver injuries. It ameliorates metabolic diseases, including insulin resistance and obesity, and plays a direct role in preventing fatty liver diseases. Butyrate has different mechanisms of action, including strong regulatory effects on the expression of many genes by inhibiting the histone deacetylases and modulating cellular metabolism. The present review highlights the wide range of beneficial therapeutic and unfavorable adverse effects of butyrate, with a high potential for clinically important uses in several liver diseases.

Essential oil from Artemisia argyi alleviated liver disease in zebrafish (Danio rerio) via the gut-liver axis

The popularity of intensive fish farming has led to the emergence of fish diseases characterized by hepatobiliary syndrome. Artemisia argyi (A. argyi) essential oils have anti-inflammatory and anti-oxidant effects. However, their alleviating effects and mechanism on liver disease in fish are still unclear. Thus, adult zebrafish were used to construct an animal model to observe histopathological damages, determine biochemical parameters and expression of inflammatory cytokines and mRNAs in the PPAR-γ/NF-κB pathway, and conduct 16 S sequencing of intestinal microbiota. The results found that after treatment with A. argyi essential oil, the histopathological damage caused by ethanol was relieved; the CAT, SOD, and GSH levels were remarkably elevated, while the MDA level was obviously lowered (P < 0.05); the expression levels of IL-10 and IFN-γ mRNAs were enhanced, but the levels of IL-1β, IL-6, PPAR-γ, NF-κB, and TNF-α mRNAs were reduced (P < 0.05) relative to the EtOH group. A. argyi essential oil remarkably attenuated the damage to intestinal tissue structure, and elevated the levels of Muc2, ZO-1, Claudin-1, and Occludin mRNA (P < 0.05). Sequencing of the gut flora showed that A. argyi essential oil significantly altered the composition of gut microbes compared with the EtOH group. In addition, KEGG and COG analyses also showed significant (P < 0.05) changes in acetate cycling metabolism in the EtOH group, catechol 2, 3-dioxygenase and nitroreductase were significantly increased (P < 0.001), and lipid metabolism and terpenoid synthesis were significantly elevated (P < 0.001) in A. argyi essential oil group. The results indicate that A. argyi essential oil could effectively relieve ethanol-caused histopathological damage of livers by modulating the composition of gut microbiota, thus inhibiting the level of IL-1β and mRNAs in the PPAR-γ/NF-κB pathway, increasing the IL-10 level, reducing the oxidative stress. This may offer a rationale for further research on the rationality of A. argyi as a substitute for feed antibiotics in aquaculture.

Gut microbiota in alcohol-related liver disease: pathophysiology and gut-brain cross talk

Alcohol-related liver disease (ALD) from excessive alcohol intake has a unique gut microbiota profile. The disease progression-free survival in ALD patients has been associated with the degree of gut dysbiosis. The vicious cycles between gut dysbiosis and the disease progression in ALD including: an increase of acetaldehyde production and bile acid secretion, impaired gut barrier, enrichment of circulating microbiota, toxicities of microbiota metabolites, a cascade of pro-inflammatory chemokines or cytokines, and augmentation in the generation of reactive oxygen species. The aforementioned pathophysiology process plays an important role in different disease stages with a spectrum of alcohol hepatitis, ALD cirrhosis, neurological dysfunction, and hepatocellular carcinoma. This review aims to illustrate the pathophysiology of gut microbiota and clarify the gut-brain crosstalk in ALD, which may provide the opportunity of identifying target points for future therapeutic intervention in ALD.

Healthy regulation of Tibetan Brassica rapa L. polysaccharides on alleviating hyperlipidemia: A rodent study

Hyperlipidemia is a common metabolic disorder, which can lead to obesity, hypertension, diabetes, atherosclerosis and other diseases. Studies have shown that polysaccharides absorbed by the intestinal tract can regulate blood lipids and facilitate the growth of intestinal flora. This article aims to investigate whether Tibetan turnip polysaccharide (TTP) plays a protective role in blood lipid and intestinal health via hepatic and intestinal axes. Here we show that TTP helps to reduce the size of adipocytes and the accumulation of liver fat, playing a dose-dependent effect on ADPN levels, suggesting an effect on lipid metabolism regulation. Meantime, TTP intervention results in the downregulation of intercellular cell adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and serum inflammatory factors (interleukin-6 (IL-6), interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α)), implying that TTP suppresses the progression of inflammation in the body. The expression of key enzymes associated with cholesterol and triglyceride synthesis, such as 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR), cholesterol 7α-hydroxylase (CYP7A1), peroxisome proliferator-activated receptors γ (PPARγ), acetyl-CoA carboxylase (ACC), fatty acid synthetase (FAS) and sterol-regulatory element binding proteins-1c (SREBP-1c), can be modulated by TTP. Furthermore, TTP also alleviates the damage to intestinal tissues caused by high-fat diet, restores the integrity of the intestinal barrier, improves the composition and abundance of the intestinal flora and increases the levels of SCFAs. This study provides a theoretical basis for the regulation of body rhythm by functional foods and potential intervention in patients with hyperlipidemia.

Innovative Therapeutic Approaches in Non-Alcoholic Fatty Liver Disease: When Knowing Your Patient Is Key

Non-alcoholic fatty liver disease (NAFLD) encompasses a spectrum of disorders ranging from simple steatosis to non-alcoholic steatohepatitis (NASH). Hepatic steatosis may result from the dysfunction of multiple pathways and thus multiple molecular triggers involved in the disease have been described. The development of NASH entails the activation of inflammatory and fibrotic processes. Furthermore, NAFLD is also strongly associated with several extra-hepatic comorbidities, i.e., metabolic syndrome, type 2 diabetes mellitus, obesity, hypertension, cardiovascular disease and chronic kidney disease. Due to the heterogeneity of NAFLD presentations and the multifactorial etiology of the disease, clinical trials for NAFLD treatment are testing a wide range of interventions and drugs, with little success. Here, we propose a narrative review of the different phenotypic characteristics of NAFLD patients, whose disease may be triggered by different agents and driven along different pathophysiological pathways. Thus, correct phenotyping of NAFLD patients and personalized treatment is an innovative therapeutic approach that may lead to better therapeutic outcomes.

Label-Free Imaging Techniques to Evaluate Metabolic Changes Caused by Toxic Liver Injury in PCLS

Abuse with hepatotoxic agents is a major cause of acute liver failure. The search for new criteria indicating the acute or chronic pathological processes is still a challenging issue that requires the selection of effective tools and research models. Multiphoton microscopy with second harmonic generation (SHG) and fluorescence lifetime imaging microscopy (FLIM) are modern label-free methods of optical biomedical imaging for assessing the metabolic state of hepatocytes, therefore reflecting the functional state of the liver tissue. The aim of this work was to identify characteristic changes in the metabolic state of hepatocytes in precision-cut liver slices (PCLSs) under toxic damage by some of the most common toxins: ethanol, carbon tetrachloride (CCl4) and acetaminophen (APAP), commonly known as paracetamol. We have determined characteristic optical criteria for toxic liver damage, and these turn out to be specific for each toxic agent, reflecting the underlying pathological mechanisms of toxicity. The results obtained are consistent with standard methods of molecular and morphological analysis. Thus, our approach, based on optical biomedical imaging, is effective for intravital monitoring of the state of liver tissue in the case of toxic damage or even in cases of acute liver injury.

Gut-liver axis: barriers and functional circuits

The gut and the liver are characterized by mutual interactions between both organs, the microbiome, diet and other environmental factors. The sum of these interactions is conceptualized as the gut-liver axis. In this Review we discuss the gut-liver axis, concentrating on the barriers formed by the enterohepatic tissues to restrict gut-derived microorganisms, microbial stimuli and dietary constituents. In addition, we discuss the establishment of barriers in the gut and liver during development and their cooperative function in the adult host. We detail the interplay between microbial and dietary metabolites, the intestinal epithelium, vascular endothelium, the immune system and the various host soluble factors, and how this interplay establishes a homeostatic balance in the healthy gut and liver. Finally, we highlight how this balance is disrupted in diseases of the gut and liver, outline the existing therapeutics and describe the cutting-edge discoveries that could lead to the development of novel treatment approaches.

Gut microbiota regulation and prebiotic properties of polysaccharides from Oudemansiella raphanipes mushroom

Oudemansiella raphanipes is a type of fungus used as both medicine and food. Fungal polysaccharides have demonstrated various bioactivities, involving the adjust and control of gut microbiota, but no such studies on O. raphanipes polysaccharides (OrPs) have been reported. It is by extracting and purifying that OrPs was obtained from O. raphanipes crude polysaccharide and study their effects in mice. The sample contents of total sugar was 97.26%, and the monosaccharide content comprised mannose, rhamnose, glucose, and xylose in a molar ratio of 35.2:2.8:21.2:40.8. The effects of OrPs on body weight (BW), gut microbiota, fecal short-chain fatty acids (SCFAs), and the correlation between fecal SCFAs and gut microbes, in mice were investigated. The results of the experiment found that OrPs significantly (P < 0.01) inhibited the increase in BW, altered the constitution of the gut microbiota, and significantly (P < 0.05) enhanced the content of fecal SCFAs in mice. Moreover, among the top ten bacteria in terms of relative abundance, the Lachnospiraceae and Lachnospiraceae NK4A136 groups were positively associated with the increased production of SCFAs. Other bacteria, such as Atopobiaceae and Bifidobacterium of Actinobacteriota, and Faecalibaculum, Dubosiella, and Clostridium sensu stricto 5 of Firmicutes, were also positively associated with higher content of fecal SCFAs. The results of the experiment suggest that OrPs have a potential prebiotic effect on gut microbiota and may prevent BW gain. Furthermore, the major producers of SCFAs were Firmicutes and Actinobacteriota.

Evaluation of tributyrin supplementation in milk replacer on diarrhoea occurrence in pre-weaning Holstein calves

Neonatal calf diarrhoea is one of the most important health challenges in cattle herds causing substantial economic losses and antimicrobial use. Due to the raising problem of antimicrobial resistance, effective alternatives are urgently required, in line with European policies. The aim of this study was to evaluate the effect of tributyrin supplementation in milk replacer on diarrhoea, performance and metabolic status in preweaning Holstein calves. Twelve newborn calves, after colostrum administration, were randomly allotted in two experimental groups for 42 days: control (CTRL) fed milk replacer, tributyrin (TRIB) fed milk replacer supplemented with 0.3% of liquid tributyrin on milk powder weight. Calves BW was recorded on a weekly basis from day 7 to day 42, and feed intake was recorded daily to calculate zootechnical performance. Faecal consistency was assessed daily through the faecal score (0-3 scale; considering diarrhoea moderate = 2 and severe = 3). Faecal samples were collected weekly from rectal ampulla for microbiological analysis by plate counting method evaluating the number of total bacteria, lactic acid bacteria and coliform bacteria. On day 0 and day 42, individual blood samples were collected from jugular vein for metabolic profile analysis. Serum samples of day 42 were also evaluated for the antioxidant barrier using a colorimetric test, while glucagon-like peptide 2 and diamine oxidase concentrations were measured through immunoenzymatic assays. Tributyrin supplementation did not influence the zootechnical performance of calves over 42 days of trial. Diarrhoea frequency was significantly lower in TRIB compared to CTRL group (27.91 and 38.37%; P < 0.01) considering the whole experimental period. In particular, the major effect was observed for moderate diarrhoea in TRIB group that showed a significantly reduced frequency compared to CTRL (P < 0.01) thus suggesting a preventive effect of tributyrin. Faecal total bacterial, lactic acid and coliform bacteria counts did not show differences between groups. Urea serum concentrations tended to be lower in TRIB compared to CTRL, indicating an efficient utilisation of dietary protein. Antioxidant barrier and glucagon-like peptide 2 were comparable between CTRL and TRIB on day 42. Diamine oxidase concentrations were significantly decreased in TRIB compared to CTRL group after 42 days of trial (P < 0.01), suggesting a higher gut epithelial integrity probably due to lower diarrhoea frequency and the nourish effect of tributyrin on enterocytes. In conclusion, tributyrin could be considered as a valuable bioactive feed additive to decrease the neonatal diarrhoea occurrence and support intestinal integrity in preweaning calves.

Modulating phenylalanine metabolism by L. acidophilus alleviates alcohol-related liver disease through enhancing intestinal barrier function

BACKGROUND

Impaired metabolic functions of gut microbiota have been demonstrated in alcohol-related liver disease (ALD), but little is known about changes in phenylalanine metabolism.

METHODS

Bacterial genomics and fecal metabolomics analysis were used to recognize the changes of phenylalanine metabolism and its relationship with intestinal flora. Intestinal barrier function was detected by intestinal alkaline phosphatase (IAP) activity, levels of tight junction protein expression, colonic inflammation and levels of serum LPS. Lactobacillus acidophilus was chosen to correct phenylalanine metabolism of ALD mice by redundancy analysis and Pearson correlation analysis.

RESULTS

Using 16S rRNA sequencing and ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) methods, we identified elevated levels of phenylalanine and its' metabolites in the gut of alcohol-fed mice compared to control mice and were negatively correlated with the abundance of Lactobacillus, which mainly metabolized phenylalanine. The intestinal phenylalanine level was positively correlated with the colon inflammatory factors TNF-α and IL-6, and negatively correlated with ZO-1 and Occludin. While intestinal alkaline phosphatase (IAP) activity was negatively correlated with the colon inflammatory factors TNF-α, IL-6 and MCP-1, and positively correlated with ZO-1 and Occludin. Increased phenylalanine inhibited IAP activity, blocked LPS dephosphorylation, increased colonic inflammation and bacterial translocation. Phenylalanine supplementation aggravated alcohol-induced liver injury and intestinal barrier dysfunction. Among the 37 Lactobacillus species, the abundance of Lactobacillus acidophilus was most significantly decreased in ALD mice. Supplementation with L. acidophilus recovered phenylalanine metabolism and protected mice from alcohol-induced steatohepatitis.

CONCLUSIONS

Recovery of phenylalanine metabolism through the oral supplementation of L. acidophilus boosted intestinal barrier integrity and ameliorated experimental ALD.

Fecal microbiota transplantation compared with prednisolone in severe alcoholic hepatitis patients: a randomized trial

BACKGROUND

Severe alcoholic hepatitis (SAH) has high 90-day mortality. Prednisolone therapy has shown modest survival benefits over placebo at 28 but not 90 days. Fecal microbial transplantation (FMT) has shown promise in these patients. We compared the efficacy and safety of the two therapies in SAH patients.

METHODS

Steroid eligible SAH patients were randomized in an open-label study to prednisolone (n = 60) 40 mg/day for 28 days (assessed at day-7 for continuation) or healthy donor FMT (n = 60) through naso-duodenal tube, daily for seven days. Primary outcome of study was day-90 survival.

RESULTS

Patients in prednisolone and FMT arms were comparable at baseline (discriminant function score 65 ± 16.2 and 68 ± 14, MELD score 17.1 and 16.5, respectively). Of 120 patients, 112 [prednisolone-57; FMT-55] completed trial. As per intention-to-treat analysis, 90-day survival was achieved by 56.6% (34/60) patients in prednisolone and 75% (45/60) in FMT group (p = 0.044, FMT HR = 0.528, 95%CI 0.279-0.998). Secondary outcome of 28-day survival [78.33% (47/60) and 88.33% (53/60) (p = 0.243, FMT HR = 0.535, 95%CI 0.213-1.34)] with comparable severity scores over time between both arms. Infections accounted for 11 (19.3%) and 2 (3.6%) deaths in prednisolone and FMT groups, respectively (p = 0.01). Path-tracing showed a slow establishment of microbiota and alpha diversity (Shannon index) improvement by day-28 (p = 0.029). FMT resulted in 23 new taxa by day-28, reduction from baseline in pathogenic taxa [Campylobacter (19-fold, p = 0.035), anaerobes (Parcubacteria, Weisella and Leuconostocaceae)], and increase of Alphaproteobacteria [~ sevenfold, p = 0.047] and Thaumarcheota (known ammonia oxidizer, p = 0.06). Lachnospiraceae (p = 0.008), Prevotella and Viellonella communities in gut favored survival (p < 0.05).

CONCLUSION

In severe alcoholic hepatitis, FMT is safe and improves 90-day survival and reduces infections by favorably modulating microbial communities. It can be a useful alternative to prednisolone therapy.

Butyrate producers, "The Sentinel of Gut": Their intestinal significance with and beyond butyrate, and prospective use as microbial therapeutics

Gut-microbial butyrate is a short-chain fatty acid (SCFA) of significant physiological importance than the other major SCFAs (acetate and propionate). Most butyrate producers belong to the Clostridium cluster of the phylum Firmicutes, such as Faecalibacterium, Roseburia, Eubacterium, Anaerostipes, Coprococcus, Subdoligranulum, and Anaerobutyricum. They metabolize carbohydrates via the butyryl-CoA: acetate CoA-transferase pathway and butyrate kinase terminal enzymes to produce most of butyrate. Although, in minor fractions, amino acids can also be utilized to generate butyrate via glutamate and lysine pathways. Butyrogenic microbes play a vital role in various gut-associated metabolisms. Butyrate is used by colonocytes to generate energy, stabilizes hypoxia-inducible factor to maintain the anaerobic environment in the gut, maintains gut barrier integrity by regulating Claudin-1 and synaptopodin expression, limits pro-inflammatory cytokines (IL-6, IL-12), and inhibits oncogenic pathways (Akt/ERK, Wnt, and TGF-β signaling). Colonic butyrate producers shape the gut microbial community by secreting various anti-microbial substances, such as cathelicidins, reuterin, and β-defensin-1, and maintain gut homeostasis by releasing anti-inflammatory molecules, such as IgA, vitamin B, and microbial anti-inflammatory molecules. Additionally, butyrate producers, such as Roseburia, produce anti-carcinogenic metabolites, such as shikimic acid and a precursor of conjugated linoleic acid. In this review, we summarized the significance of butyrate, critically examined the role and relevance of butyrate producers, and contextualized their importance as microbial therapeutics.

The central role of the gut in intensive care

Critically ill patients undergo early impairment of their gut microbiota (GM) due to routine antibiotic therapies and other environmental factors leading to intestinal dysbiosis. The GM establishes connections with the rest of the human body along several axes representing critical inter-organ crosstalks that, once disrupted, play a major role in the pathophysiology of numerous diseases and their complications. Key players in this communication are GM metabolites such as short-chain fatty acids and bile acids, neurotransmitters, hormones, interleukins, and toxins. Intensivists juggle at the crossroad of multiple connections between the intestine and the rest of the body. Harnessing the GM in ICU could improve the management of several challenges, such as infections, traumatic brain injury, heart failure, kidney injury, and liver dysfunction. The study of molecular pathways affected by the GM in different clinical conditions is still at an early stage, and evidence in critically ill patients is lacking. This review aims to describe dysbiosis in critical illness and provide intensivists with a perspective on the potential as adjuvant strategies (e.g., nutrition, probiotics, prebiotics and synbiotics supplementation, adsorbent charcoal, beta-lactamase, and fecal microbiota transplantation) to modulate the GM in ICU patients and attempt to restore eubiosis.

Effects of Tributyrin Supplementation on Liver Fat Deposition, Lipid Levels and Lipid Metabolism-Related Gene Expression in Broiler Chickens

The objective of this study was to investigate the effects of tributyrin supplementation on liver fat metabolism in broiler chickens. Two hundred and forty broilers were randomly allocated into two experimental groups (6 replicates per treatment; 20 chickens in each replicate): the control group (CN), which received a basal diet, and the tributyrin group (TB), which received a basal diet supplemented with 1 g/kg of tributyrin. The experimental period lasted 37 days. The results showed that in the liver, broilers supplemented with tributyrin had higher content of high-density lipoprotein cholesterol (HDL-C) (p < 0.05). Liver hepatic lipase (HL), lipoprotein lipase (LPL) and total lipid (TL) activity were significantly lower than in the TB group than that in the NC group. Meanwhile, the diet supplemented with tributyrin had more lipid droplets than the NC group, whereas the TB and NC groups showed no histological abnormalities in the liver. Furthermore, the mRNA expression levels of peroxisome proliferators-activated receptor α (PPARα), proliferators-activated receptor γ (PPARγ), fatty acid synthase (FAS), LPL and adipose triglyceride lipase (ATGL) in the liver were significantly upregulated in the TB group (p < 0.05), while those of the long-chain acyl-CoA-synthetase 1 (ACSL1) mRNA between the TB group and the NC group were not different (p > 0.05). These findings indicated that the diet supplemented with tributyrin could increase fat deposition appropriately by promoting fat synthesis without causing liver tissue damage, which demonstrated that tributyrin can be considered a valid feed additive for broiler chickens.

Anthocyanins from Opuntia ficus-indica Modulate Gut Microbiota Composition and Improve Short-Chain Fatty Acid Production

Opuntia ficus-indica is rich in a variety of active substances, such as anthocyanins, flavonoids, and polysaccharides. Some studies have shown that anthocyanins extracted from natural plants can regulate intestinal flora. The fruit was used as raw material, and anthocyanins were extracted from it. In vivo experiments were used to study the effect of Opuntia ficus-indica anthocyanins on the mouse intestine by 16S rRNA high-throughput sequencing (NovaSeq 6000 platform) and gas chromatography (hydrogen flame ionization detector (FID)) methods. Microbiota and effects of short-chain fatty acids (SCFAs). The results showed that after feeding anthocyanins, the diversity of intestinal microorganisms in mice was significantly increased (p < 0.05), the ratio of Firmicutes/Bacteroidetes (F/B value) was significantly decreased (p < 0.05), the relative abundances of beneficial bacteria Lactobacillus, Bifidobacterium, Prevotella, and Akkermansia in the intestinal tract of mice were significantly increased (p < 0.05), and the relative abundance of pathogenic bacteria Escherichia-Shigella and Desulfovibrio decreased significantly (p < 0.05). Furthermore, anthocyanins significantly increased the content of short-chain fatty acids in the cecum of mice, among which the content of acetic acid, propionic acid, and butyric acid increased the most. Opuntia ficus-indica anthocyanins can change the microbial diversity and flora composition of the mouse gut and promote the production of short-chain fatty acids. The findings provide a theoretical basis for the use of Opuntia ficus-indica anthocyanins as dietary supplements to regulate human intestinal flora.

The gut-liver axis in immune remodeling of hepatic cirrhosis

In healthy settings, the gut-liver axis allows host-microbiota communications and mediates immune homeostasis through bidirectional regulation. Meanwhile, in diseases, gut dysbiosis, combined with an impaired intestinal barrier, introduces pathogens and their toxic metabolites into the system, causing massive immune alternations in the liver and other extrahepatic organs. Accumulating evidence suggests that these immune changes are associated with the progression of many liver diseases, especially hepatic cirrhosis. Pathogen-associated molecular patterns that originated from gut microbes directly stimulate hepatocytes and liver immune cells through different pattern recognition receptors, a process further facilitated by damage-associated molecular patterns released from injured hepatocytes. Hepatic stellate cells, along with other immune cells, contribute to this proinflammatory and profibrogenic transformation. Moreover, cirrhosis-associated immune dysfunction, an imbalanced immune status characterized by systemic inflammation and immune deficiency, is linked to gut dysbiosis. Though the systemic inflammation hypothesis starts to link gut dysbiosis to decompensated cirrhosis from a clinical perspective, a clearer demonstration is still needed for the role of the gut-liver-immune axis in cirrhosis progression. This review discusses the different immune states of the gut-liver axis in both healthy and cirrhotic settings and, more importantly, summarizes the current evidence about how microbiota-derived immune remodeling contributes to the progression of hepatic cirrhosis via the gut-liver axis.

Acetate reprograms gut microbiota during alcohol consumption

Liver damage due to chronic alcohol use is among the most prevalent liver diseases. Alcohol consumption frequency is a strong factor of microbiota variance. Here we use isotope labeled [1-13C] ethanol, metagenomics, and metatranscriptomics in ethanol-feeding and intragastric mouse models to investigate the metabolic impacts of alcohol consumption on the gut microbiota. First, we show that although stable isotope labeled [1-13C] ethanol contributes to fatty acid pools in the liver, plasma, and cecum contents of mice, there is no evidence of ethanol metabolism by gut microbiota ex vivo under anaerobic conditions. Next, we observe through metatranscriptomics that the gut microbiota responds to ethanol-feeding by activating acetate dissimilation, not by metabolizing ethanol directly. We demonstrate that blood acetate concentrations are elevated during ethanol consumption. Finally, by increasing systemic acetate levels with glyceryl triacetate supplementation, we do not observe any impact on liver disease, but do induce similar gut microbiota alterations as chronic ethanol-feeding in mice. Our results show that ethanol is not directly metabolized by the gut microbiota, and changes in the gut microbiota linked to ethanol are a side effect of elevated acetate levels. De-trending for these acetate effects may be critical for understanding gut microbiota changes that cause alcohol-related liver disease.

Garlic oil alleviates high triglyceride levels in alcohol-exposed rats by inhibiting liver oxidative stress and regulating the intestinal barrier and intestinal flora

Garlic oil (GO) is a kind of natural extract extracted from garlic, which has strong antioxidant activity. This study elucidates the protective mechanism of GO against alcohol-induced high triglyceride levels. Sixty male Sprague Dawley rats were assigned to five groups, including a control group (CON), a model group (MOD) treated with alcohol 56% v/v at 8 ml kg-1 day-1 for 2 weeks then 10 ml kg-1 day-1 for 8 weeks, a low-dose GO group (GO-L) given GO at 20 mg kg-1 day-1, a high-dose GO group (GO-H) given GO at 40 mg kg-1 day-1, and a positive group (POS) given diammonium glycyrrhizinate at 200 mg kg-1 day-1. The results showed that GO could significantly reduce the serum and liver triglyceride levels caused by alcohol exposure (p < .05). The GO-H group significantly reduced MDA level, increased SOD and GSH-Px levels in serum, liver, and colon (p < .05), significantly increased the levels of Sirt1 and PGC-1α proteins and reduced FoxO1 protein level in liver (p < .05), and significantly increased the levels of ZO-1 and Claudin1 proteins in the colon compared to the MOD group (p < .05). The 16S rRNA sequencing showed that the intestinal flora of the GO-H group was significantly changed compared with the MOD group. In summary, GO has the potential to improve high triglyceride levels in serum and liver induced by alcohol exposure, which may be related to the inhibition of oxidative stress regulation of Sirt1 and its downstream proteins, and to the restoration of the intestinal barrier and intestinal flora.

The effect of increasing intestinal short-chain fatty acid concentration on gut permeability and liver injury in the context of liver disease: A systematic review

BACKGROUND AND AIM

The gut barrier protects the liver through tight junctions, which are disrupted in liver disease either from dysbiosis, inflammation, or the effects of ingested compounds such as alcohol. Strengthening of the gut barrier may ameliorate liver injury of varying etiologies. Short chain fatty acids (SCFAs) have been shown to improve gut barrier function. This systematic review aims to synthesize all studies that have trialed SCFA supplementation as a therapy for liver disease.

METHODS

A systematic review assessing the impact of SCFA supplementation on liver injury and intestinal permeability was conducted. All forms of intervention that specifically increased intestinal SCFA concentration and measured both liver injury and permeability were eligible. Two independent reviewers assessed each study for outcomes, risk of bias, and quality using checklists relevant to the study's methodology.

RESULTS

Seventeen studies were identified; two utilized a human model (15 murine). Fifty-eight markers of liver injury were identified, with 26 different measures of permeability. Given the numerous designs, no meta-analysis was possible. SCFA supplements included oral and enteral butyrate, probiotics, and prebiotics. Fourteen studies demonstrated improved permeability. All studies showed a significant amelioration of liver injury.

CONCLUSIONS

Short chain fatty acid supplementation to reduce intestinal permeability represents a potential therapy in a variety of liver disease models. A large number of outcome measures were reported however not all are practical in human studies. Future work should evaluate methods to increase luminal SCFA concentrations and the effect of this on gut permeability and liver inflammation in people with liver disease.

Ameliorative effects of chlorogenic acid on alcoholic liver injury in mice via gut microbiota informatics

Chlorogenic acid (CGA) is a functional phenolic acid widely used in food and medicine-related fields. It has been proved to be effective in the treatment of alcoholic liver disease (ALD). However, the exact mechanism by which CGA prevents ALD, especially from the crosstalk between gut and liver, has not been previously reported. This work was aimed to explore the protective effects of CGA against ALD and its relationships to gut-liver axis abnormalities. Experimental results showed the increased (p < 0.05) serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), low density lipoprotein (LDL), total cholesterol (TC) and triglyceride (TG) levels of mice fed with ethanol were ameliorated by supplementing with CGA. Moreover, CGA promoted the production of n-butyric acid by nearly 3 times (1.78 vs 0.62 nM, p < 0.01), a short-chain fatty acid that helps maintain the integrity of the intestinal barrier. Furthermore, CGA alleviated microbial dysbiosis, evidenced by the increased relative abundances of beneficial bacteria Muribaculaceae, Bacteroides, Alloprevotella, and Parabacteroides, and decreased that of opportunistic pathogens Eubacterium_nodatum, Eubacterium_ruminantium, and Anaerotruncus. Correlation analysis further elucidated the microbiota altered after CGA intervention was positively correlated with short-chain fatty acids and antioxidant indexes, while negatively correlated with inflammatory cytokines. In summary, these findings suggested the hepatoprotective effect of CGA was ascribed to the modulation of gut-liver axis homeostasis.

In-depth investigation of the mechanisms of Echinacea purpurea polysaccharide mitigating alcoholic liver injury in mice via gut microbiota informatics and liver metabolomics

Accumulating evidence suggests that the pathogenesis of alcoholic liver disease (ALD) is strongly correlated with abnormalities of the gut-liver axis. Echinacea purpurea polysaccharide (EPP) is a homogeneous polysaccharide, which has been shown to mitigate ALD. However, the effects of EPP on gut microbiome and consequently on hepatic metabolism have yet to be explored. In this study, the microbiome and metabolomics were combined to explore the effects of EPP on gut microbiota and hepatic metabolism, and the relationship between both was further revealed by Spearman correlation analysis. Results exhibited EPP reversed alcohol-induced disturbances in gut microbiota, evidenced by increased abundance of Muribaculaceae, Lactobacillus, and Bacteroides and decreased abundance of Escherichia_Shigella and Enterococcus. Besides, EPP promoted the production of n-butyric acid, a short-chain fatty acid that maintains the integrity of the intestinal barrier. Moreover, EPP improved alterations in hepatic metabolites, and characteristic metabolites such as Berberine and Ponasterone as well as key metabolic pathways, particularly Nitrogen metabolism, were identified. Furthermore, correlation analysis suggested significant associations between gut microbes and hepatic metabolites, which in turn confirmed EPP alleviated ALD via the gut-liver axis. Therefore, these findings elucidated in-depth mechanisms of EPP against ALD and provided a new target for intervention in alcohol-related diseases.

Drugs and Bugs: The Gut-Brain Axis and Substance Use Disorders

Substance use disorders (SUDs) represent a significant public health crisis. Worldwide, 5.4% of the global disease burden is attributed to SUDs and alcohol use, and many more use psychoactive substances recreationally. Often associated with comorbidities, SUDs result in changes to both brain function and physiological responses. Mounting evidence calls for a precision approach for the treatment and diagnosis of SUDs, and the gut microbiome is emerging as a contributor to such disorders. Over the last few centuries, modern lifestyles, diets, and medical care have altered the health of the microbes that live in and on our bodies; as we develop, our diets and lifestyle dictate which microbes flourish and which microbes vanish. An increase in antibiotic treatments, with many antibiotic interventions occurring early in life during the microbiome's normal development, transforms developing microbial communities. Links have been made between the microbiome and SUDs, and the microbiome and conditions that are often comorbid with SUDs such as anxiety, depression, pain, and stress. A better understanding of the mechanisms influencing behavioral changes and drug use is critical in developing novel treatments for SUDSs. Targeting the microbiome as a therapeutic and diagnostic tool is a promising avenue of exploration. This review will provide an overview of the role of the gut-brain axis in a wide range of SUDs, discuss host and microbe pathways that mediate changes in the brain's response to drugs, and the microbes and related metabolites that impact behavior and health within the gut-brain axis.

The Impact of Alcohol-Induced Dysbiosis on Diseases and Disorders of the Central Nervous System

The human digestive tract contains a diverse and abundant microbiota that is important for health. Excessive alcohol use can disrupt the balance of these microbes (known as dysbiosis), leading to elevated blood endotoxin levels and systemic inflammation. Using QIAGEN Ingenuity Pathway Analysis (IPA) bioinformatics tool, we have confirmed that peripheral endotoxin (lipopolysaccharide) mediates various cytokines to enhance the neuroinflammation signaling pathway. The literature has identified alcohol-mediated neuroinflammation as a possible risk factor for the onset and progression of neurodegenerative diseases, including Alzheimer's disease (AD) and Parkinson's disease (PD), and psychiatric disorders such as addiction to alcohol and other drugs. In this review, we discuss alcohol-use-induced dysbiosis in the gut and other body parts as a causal factor in the progression of Central Nervous System (CNS) diseases including neurodegenerative disease and possibly alcohol use disorder.

Propionate Ameliorates Alcohol-Induced Liver Injury in Mice via the Gut-Liver Axis: Focus on the Improvement of Intestinal Permeability

Alcohol-related liver disease (ALD) is a major cause of chronic liver disease worldwide with limited therapeutic options. Here, we first revealed the promising beneficial effect of gut microbiota-derived propionate on alcoholic liver injury in mice. This effect was dependent on the modulation of homeostasis of the gut-liver axis, especially the improvement of intestinal permeability. Dietary supplementation with propionate protected against ethanol-induced loss of hepatic function and hepatic steatosis in mice. Meanwhile, propionate treatment attenuated intestinal epithelial barrier dysfunction, restored the expression of intestinal mucus layer components, suppressed intestinal inflammation, and altered intestinal microbiota dysbiosis, which inhibited the intestinal hyperpermeability and subsequently reduced lipopolysaccharide leakage in ALD mice. Furthermore, as a consequence of endotoxemia amelioration, the liver inflammation-related TLR4-NF-κB pathway was inhibited. Collectively, our results suggested that propionate supplementation may be a promising option for the prevention and treatment of ALD.

The gut barrier and chronic diseases

PURPOSE OF REVIEW

The purpose of this review is to provide an update regarding the gut barrier and its involvement with chronic diseases, as well as to review biomarkers for identification of gut barrier integrity. This review is timely and relevant as our knowledge is increasing regarding the role of the gut microbiome and the gut barrier in health and disease.

RECENT FINDINGS

This review provides an overview of: the gut barrier, which is complex and comprised of the mucus layer and the intestinal apical junctional protein complex; the gut microbiome in its relation to regulating the integrity of the gut barrier; select acute and chronic conditions that are known to be associated with gut dysbiosis and impaired gut integrity or 'leaky gut'; and current means for identifying loss in gut barrier integrity.

SUMMARY

Many chronic conditions are associated with gut dysbiosis and systemic inflammation. Identifying whether the gut barrier is compromised in these conditions could help to inform potential therapeutics as a means to correct losses in gut barrier integrity and mitigate associated medical conditions.

Gut Microbiota Targeted Approach in the Management of Chronic Liver Diseases

The liver is directly connected to the intestines through the portal vein, which enables the gut microbiota and gut-derived products to influence liver health. There is accumulating evidence of decreased gut flora diversity and alcohol sensitivity in patients with various chronic liver diseases, including non-alcoholic/alcoholic liver disease, chronic hepatitis virus infection, primary sclerosing cholangitis and liver cirrhosis. Increased intestinal mucosal permeability and decline in barrier function were also found in these patients. Followed by bacteria translocation and endotoxin uptake, these will lead to systemic inflammation. Specific microbiota and microbiota-derived metabolites are altered in various chronic liver diseases studies, but the complex interaction between the gut microbiota and liver is missing. This review article discussed the bidirectional relationship between the gut and the liver, and explained the mechanisms of how the gut microbiota ecosystem alteration affects the pathogenesis of chronic liver diseases. We presented gut-microbiota targeted interventions that could be the new promising method to manage chronic liver diseases.

Polysaccharides from the leaves of Polygonatum sibiricum Red. regulate the gut microbiota and affect the production of short-chain fatty acids in mice

Polysaccharides from the rhizome of Polygonatum sibiricum display a variety of biological activities, including the regulation of intestinal microbiota, but the polysaccharides from the leaves of P. sibiricum have not been studied extensively. Here, we extracted crude polysaccharides from the leaves of P. sibiricum and further separated and purified them to study the effects of P. sibiricum polysaccharides (PsPs) on intestinal microbes and short-chain fatty acids (SCFAs). The PsPs had a total sugar content of 97.48% and a monosaccharide composition comprising mannose, rhamnose, galacturonic acid, glucose, xylose, and arabinose, with molar ratios of 6.6:15.4:4.5:8.8:40.7:24, respectively. The effects of PsPs on intestinal microflora in mice were also studied, with 16S sequencing results showing an increase in the relative abundance of Firmicutes and a decrease in Bacteroidetes at the phylum level. The abundance of Lactobacillus increased, while those of Lachnospiraceae and Bacteroides reduced (at the genus level) by PsPs treatment. The composition of microbes changed. Levels of SCFAs in the PsPs group were significantly increased compared with control mice, including acetic acid, propionic acid, and butyric acid. These results suggest that PsPs can act as prebiotics, regulating the intestinal tract probiotics.