Antibiotics prevent liver injury in rats following long-term exposure to ethanol

The role of probiotics on the roadmap to a healthy microbiota: a symposium report

The ninth International Yakult Symposium was held in Ghent, Belgium in April 2018. Keynote lectures were from Professor Wijmenga on using biobanks to understand the relationship between the gut microbiota and health; and Professor Hill on phage-probiotic interactions. Session one included talks from Professor Plӧsch on epigenetic programming by nutritional and environmental factors; Professor Wilmes on the use of "omics" methodologies in microbiome research and Professor Rescigno on the gut vascular barrier. Session two explored the evidence behind Lactobacillus casei Shirota with Dr Nanno explaining the plasticity in immunomodulation that enables the strain to balance immune functions; Dr Macnaughtan outlining its potential therapeutic use in cirrhosis and Professor Nishida detailing effects in subjects under stress. The third session saw Professor Marchesi describing that both the host genes and the gut microbiota can play a role in cancer; Professor Bergheim highlighting crosstalk between the gut and the liver and Professor Cani describing the relationship between the gut microbiota and the endocrine system. The final session explored probiotic mechanisms, with Professor Lebeer dissecting the challenges in conducting mechanistic studies; Professor Wehkamp describing the mucosal defence system and Professor Van de Wiele detailing methods for modelling the gut microbiota in vitro.

Microbial Products and Metabolites Contributing to Alcohol-Related Liver Disease

As a serious public health concern, alcohol-related liver disease is associated with dysregulations in the intestinal barrier function and the gut microbiota. The liver and gut communicate via the gut-liver axis, through which microbial products and metabolites translocate to the liver. Here, the current knowledge of various microbial products and metabolites which contribute to the alcohol-related liver diseases, including bile acids, indole-3-acetic acid, butyrate, long-chain fatty acids, endotoxin, cytolysin, β-glucan, and candidalysin is reviewed. Some of these might serve as therapeutic targets for alcohol-related liver disease.

Changes in the Intestinal Microbiome during a Multispecies Probiotic Intervention in Compensated Cirrhosis

Probiotics have been used in trials to therapeutically modulate the gut microbiome and have shown beneficial effects in cirrhosis. However, their effect on the microbiome of cirrhosis patients is not fully understood yet. Here, we tested the effects of a multispecies probiotic on microbiome composition in compensated cirrhosis. The gut microbiome composition of 58 patients with compensated cirrhosis from a randomized controlled trial who received a daily dose of multispecies probiotics or placebo for six months was analysed by 16S rRNA gene sequencing. Microbiome composition of patients who received probiotics was enriched with probiotic strains and the abundance of Faecalibacterium prausnitzii, Syntrophococcus sucromutans, Bacteroides vulgatus, Alistipes shahii and a Prevotella species was increased in the probiotic group compared to the placebo group. Patients who had microbiome changes in response to probiotic treatment also showed a significant increase in neopterin and a significant decrease in faecal zonulin levels after intervention, which was not observed in placebo-treated patients or patients with unchanged microbiome compositions. In conclusion, multispecies probiotics may enrich the microbiome of compensated cirrhotic patients with probiotic bacteria during a six-month intervention and beneficially change the residential microbiome and gut barrier function.

Lemon balm and dandelion leaf extract synergistically alleviate ethanol-induced hepatotoxicity by enhancing antioxidant and anti-inflammatory activity

We investigated the effect of a 2:1 (w/w) mixture of lemon balm and dandelion extracts (LD) on ethanol (EtOH)-mediated liver injury and explored the underlying mechanisms. Administration of LD synergistically reduced relative liver weight and decreased the levels of serum biomarkers of hepatic injury. Histopathological and biochemical analyses indicated that LD synergistically attenuated hepatic accumulation of triacylglycerides (TGs) and restored the levels of mRNAs related to fatty acid metabolism. In addition, LD significantly reduced EtOH-induced hepatic oxidative stress by attenuating the reduction in levels of nuclear factor E2-related factor 2 (Nrf2) mRNA and enhancing antioxidant activity. Moreover, LD decreased the EtOH-mediated increase in levels of hepatic tumor necrosis factor-α (TNF-α) mRNA. In vitro, LD significantly scavenged free radicals, increased cell viability against tert-butylhydroperoxide (tBHP), and transactivated Nrf2 target genes in HepG2 cells. Furthermore, LD decreased levels of pro-inflammatory mediators in lipopolysaccharide-stimulated Raw264.7 cells. Therefore, LD shows promise for preventing EtOH-mediated liver injury. PRACTICAL APPLICATIONS: There were no approved therapeutic agents for preventing and/or treating alcoholic liver diseases. In this study, a 2:1 (w/w) mixture of lemon balm and dandelion leaf extract (DL) synergistically ameliorated EtOH-induced hepatic injury by inhibiting lipid accumulation, oxidative stress, and inflammation. Our findings will enable the development of a novel food supplement for the prevention or treatment of alcohol-mediated liver injury.

Intestinal and hepatic microbiota changes associated with chronic ethanol administration in mice

Alcohol-induced liver disease is closely related to translocation of bacterial products and bacteria from the intestine to the liver. However, it is not known whether bacterial translocation to the liver depends on certain intestinal microbiota changes that would predispose bacteria to translocate to the liver. In this study, we investigated the microbiota in the jejunum, ileum, cecum, feces and liver of mice subjected to chronic ethanol feeding using a Lieber DeCarli diet model of chronic ethanol feeding for 8 weeks. We demonstrate that chronic ethanol administration changes alpha diversity in the ileum and the liver and leads to compositional changes especially in the ileum. This is largely driven by an increase in gram-negative phyla - the source of endotoxins. Moreover, gram-negative Prevotella not only increased in the mucus layer of the ileum but also in liver samples. These results suggest that bacterial translocation to the liver might be associated with microbiota changes in the distal gastrointestinal tract.

A story of liver and gut microbes: how does the intestinal flora affect liver disease? A review of the literature

Each individual is endowed with a unique gut microbiota (GM) footprint that mediates numerous host-related physiological functions, such as nutrient metabolism, maintenance of the structural integrity of the gut mucosal barrier, immunomodulation, and protection against microbial pathogens. Because of increased scientific interest in the GM, its central role in the pathophysiology of many intestinal and extraintestinal conditions has been recognized. Given the close relationship between the gastrointestinal tract and the liver, many pathological processes have been investigated in the light of a microbial-centered hypothesis of hepatic damage. In this review we introduce to neophytes the vast world of gut microbes, including prevalent bacterial distribution in healthy individuals, how the microbiota is commonly analyzed, and the current knowledge of the role of GM in liver disease pathophysiology. Also, we highlight the potentials and downsides of GM-based therapy.

Pro- and Anti-fibrogenic Functions of Gram-Negative Bacterial Lipopolysaccharide in the Liver

Extensive research performed over several decades has identified cells participating in the initiation and progression of fibrosis, and the numerous underlying inter- and intra-cellular signaling pathways. However, liver fibrosis continues to be a major clinical challenge as the precise targets of treatment are still elusive. Activation of physiologically quiescent perisinusoidal hepatic stellate cells (HSCs) to a myofibroblastic proliferating, contractile and fibrogenic phenotype is a critical event in the pathogenesis of chronic liver disease. Thus, elucidation of the mechanisms of the reversal to quiescence or inhibition of activated HSCs, and/or their elimination via apoptosis has been the focus of intense investigation. Lipopolysaccharide (LPS), a gut-resident Gram-negative bacterial endotoxin, is a powerful pro-inflammatory molecule implicated in hepatic injury, inflammation and fibrosis. In both acute and chronic liver injury, portal venous levels of LPS are elevated due to increased intestinal permeability. LPS, via CD14 and Toll-like receptor 4 (TLR4) and its adapter molecules, stimulates macrophages, neutrophils and several other cell types to produce inflammatory mediators as well as factors that can activate HSCs and stimulate their fibrogenic activity. LPS also stimulates synthesis of pro- and anti-inflammatory cytokines/chemokines, growth mediators and molecules of immune regulation by HSCs. However, LPS was found to arrest proliferation of activated HSCs and to convert them into non-fibrogenic phenotype. Interestingly, LPS can elicit responses in HSCs independent of CD14 and TLR4. Identifying and/or developing non-inflammatory but anti-fibrogenic mimetics of LPS could be relevant for treating liver fibrosis.

Allicin Modifies the Composition and Function of the Gut Microbiota in Alcoholic Hepatic Steatosis Mice

The intestinal microbiome plays an important role in the pathogenesis of liver diseases. Alcohol intake induces gut microbiota dysbiosis and alters its function. This study investigated the antibiotic effect of allicin in mice with hepatic steatosis. Male C57BL/6 mice were administered an ethanol diet supplemented with allicin (5 and 20 mg/(kg bw day)) for 4 weeks. Allicin modified the gut microbiota composition. Cecal microbiota exhibited a positive correlation with alcohol and hepatic triacylglycerol, but were suppressed with allicin. Ethanol diet with 5 mg of allicin induced a lower intestinal permeability compared to the ethanol diet alone. Allicin mediated the lipopolysaccharide (LPS)-CD14-toll-like receptor 4 (TLR4)-induced hepatic inflammation pathway by reducing LPS, CD14, TLR4, and pro-inflammatory cytokines-tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6. However, hepatic inflammation primarily resulted from alcohol toxicity rather than LPS production in the gut. The prediction of functional profiles from metagenomic 16S ribosomal RNA (rRNA) data revealed different functional profiles in each group. The predicted aldehyde dehydrogenase tended to increase in alcoholic mice administered allicin. The predicted LPS-related pathway and LPS biosynthesis protein results exhibited a similar trend as plasma LPS levels. Thus, alcohol and allicin intake shapes the gut microbiota and its functional profile and improves the CD14-TLR4 pathway to alleviate inflammation in the liver.

Odontogenic infection by Porphyromonas gingivalis exacerbates fibrosis in NASH via hepatic stellate cell activation

Odontogenic infection of Porphyromonas gingivalis (P.g.), a major periodontal pathogen, exacerbates pathological progression of non-alcoholic steatohepatitis (NASH). In this study, we aimed to clarify the detailed mechanism in which P.g. induced hepatic stellate cells (HSCs; key effector cells in liver fibrosis) activation. In the liver of high fat diet-induced NASH mouse model with P.g. odontogenic infection, immunolocalization of P.g. was detected. The number of hepatic crown-like structure, which was macrophage aggregation and related to liver fibrosis, was drastically increased and fibrosis area was also increased through upregulating immunoexpression of Phosphorylated Smad2 (key signaling molecule of TGF-β1) and Galectin-3. P.g.-secreted trypsin-like enzyme [gingipain; an activator of protease-activated receptor 2 (PAR2)] stimulated HSC proliferation and differentiation through Smad and ERK signaling induced by TGF-β1 produced from HSCs with P.g.-infection. Further, Galectin-3 produced from HSCs with P.g. infection and P.g.-derived LPS/lipoprotein stimulation stabilized TGFβ-receptor II resulting in increasing sensitivity for TGF-β1, finally leading to HSC differentiation via activating Smad and ERK signaling. In addition to them, hepatocytes (main component cells of liver) contributed to HSC activation through TGF-β1 and Galectin-3 production in paracrine manner. Collectively, P.g.-odontogenic infection exacerbates fibrosis of NASH by HSC activation through TGF-β1 and Gal-3 production from HSCs and hepatocytes.

The mechanism of dysbiosis in alcoholic liver disease leading to liver cancer

Currently, alcoholic liver disease (ALD) is one of the most prevalent chronic liver diseases worldwide, representing one of the main etiologies of cirrhosis and hepatocellular carcinoma (HCC). Although we do not know the exact mechanisms by which only a selected group of patients with ALD progress to the final stage of HCC, the role of the gut microbiota within the progression to HCC has been intensively studied in recent years. To date, we know that alcohol-induced gut dysbiosis is an important feature of ALD with important repercussions on the severity of this disease. In essence, an increased metabolism of ethanol in the gut induced by an excessive alcohol consumption promotes gut dysfunction and bacterial overgrowth, setting a leaky gut. This causes the translocation of bacteria, endotoxins, and ethanol metabolites across the enterohepatic circulation reaching the liver, where the recognition of the pathogen-associated molecular patterns via specific Toll-like receptors of liver cells will induce the activation of the nuclear factor kappa-B pathway, which releases pro-inflammatory cytokines and chemokines. In addition, the mitogenic activity of hepatocytes will be promoted and cellular apoptosis will be inhibited, resulting in the development of HCC. In this context, it is not surprising that microbiota-regulating drugs have proven effectiveness in prolonging the overall survival of patients with HCC, making attractive the implementation of these drugs as co-adjuvant for HCC treatment.

Role of gut microbiota in liver disease

The gut microbiome is the natural intestinal inhabitant that has been recognized recently as a major player in the maintenance of human health and the pathophysiology of many diseases. Those commensals produce metabolites that have various effects on host biological functions. Therefore, alterations in the normal composition or diversity of microbiome have been implicated in various diseases, including liver cirrhosis and nonalcoholic fatty liver disease. Moreover, accumulating evidence suggests that progression of dysbiosis can be associated with worsening of liver disease. Here, we review the possible roles for gut microbiota in the development, progression, and complication of liver disease.

Microbiome dysbiosis and alcoholic liver disease☆

Microbiome dysbiosis is strongly associated with alcoholic liver disease (ALD). Recent studies on comprehensive analyses of microbiome compositional and functional changes have begun to uncover the mechanistic relation between microbiome and the pathogenesis of ALD. Importantly, targeting the microbiome has become a potential strategy for the prevention and treatment of ALD. In this review, we summarize the clinical evidence of microbiome dysbiosis in ALD patients, and experimental advances in microbiome and metabolomic functional changes in animals with different species and genetic backgrounds in ALD. We also summarize the studies in humanized intestinal microbiome and fecal microbiota transplantation in mice. We introduce new developments in the studies on the role of the circulating bacterial microbiome, oral bacterial microbiome and fungal microbiome in the development of ALD. We highlight the potential mechanisms by which microbiome dysbiosis contributes to ALD, including short chain fatty acid changes, bile acid metabolism, intestinal barrier function, release of bacterial and fungal products, and inflammation. In addition, we summarize the recent developments targeting the microbiome in prevention and treatment of ALD, including dietary nutrient interference, herbal medicine, antibiotics, anti-fungal agents, probiotics, engineered bacterial therapy, fecal transplantation and oral hygiene. Although recent preclinical studies have advanced our understanding of the microbiome and ALD, clinical studies, especially prospective studies with large samples, are needed to better understand the cause-effect of microbiome dysbiosis in ALD. Identifying new precision-based strategies targeting the microbiome are expected to be developed as more effective therapies in ALD.

The Role of Gut-Derived Microbial Antigens on Liver Fibrosis Initiation and Progression

Intestinal dysbiosis has recently become known as an important driver of gastrointestinal and liver disease. It remains poorly understood, however, how gastrointestinal microbes bypass the intestinal mucosa and enter systemic circulation to enact an inflammatory immune response. In the context of chronic liver disease (CLD), insults that drive hepatic inflammation and fibrogenesis (alcohol, fat) can drastically increase intestinal permeability, hence flooding the liver with gut-derived microbiota. Consequently, this may result in exacerbated liver inflammation and fibrosis through activation of liver-resident Kupffer and stellate cells by bacterial, viral, and fungal antigens transported to the liver via the portal vein. This review summarizes the current understanding of microbial translocation in CLD, the cell-specific hepatic response to intestinal antigens, and how this drives the development and progression of hepatic inflammation and fibrosis. Further, we reviewed current and future therapies targeting intestinal permeability and the associated, potentially harmful anti-microbial immune response with respect to their potential in terms of limiting the development and progression of liver fibrosis and end-stage cirrhosis.

Gut Microbiota and Metabolome Response of Decaisnea insignis Seed Oil on Metabolism Disorder Induced by Excess Alcohol Consumption

This study investigated the modulatory effects of Decaisnea insignis seed oil (DISO), which was rich in palmitoleic acid (55.25%), palmitic acid (12.25%), and oleic acid (28.74%), on alcohol-induced metabolism disorder in mice. Fifty mice were orally administered with 38% alcohol (0.4 mL/day) and without or with DISO (3, 6, and 12 g/kg) for consecutive 12 weeks. DISO inhibited the alcohol-induced weight loss and liver function abnormality (p < 0.01) and shifted the profiles of cecal microbiome: elevating the abundance of Lactobacillus, Ruminoccoceae_UCG_004 (p < 0.05) and decreasing abundance of Parabacteroides (p < 0.05). This treatment also regulated metabolome response of amino acid and lipid metabolism in cecal content: upregulating 5-hydroxyindole-3-acetic acid (p < 0.05), 6-hydroxynicotinic acid, 5-methoxytryptamine, nicotinamide, and nicotinic acid (p < 0.1) and downregulating androsterone, tryptophan, and indole-3-acetamide (p < 0.05). DISO protected against alcoholic liver injury and gut microbiota dysbiosis by enriching the relative abundance of Lactobacillus, which was positively associated with the improvement of intestinal permeability and tryptophan metabolism.

Alcohol or Gut Microbiota: Who Is the Guilty?

Alcoholic liver disease (ALD), a disorder caused by excessive alcohol intake represents a global health care burden. ALD encompasses a broad spectrum of hepatic injuries including asymptomatic steatosis, alcoholic steatohepatitis (ASH), fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). The susceptibility of alcoholic patients to develop ALD is highly variable and its progression to more advanced stages is strongly influenced by several hits (i.e., amount and duration of alcohol abuse). Among them, the intestinal microbiota and its metabolites have been recently identified as paramount in ALD pathophysiology. Ethanol abuse triggers qualitative and quantitative modifications in intestinal flora taxonomic composition, mucosal inflammation, and intestinal barrier derangement. Intestinal hypermeability results in the translocation of viable pathogenic bacteria, Gram-negative microbial products, and pro-inflammatory luminal metabolites into the bloodstream, further corroborating the alcohol-induced liver damage. Thus, the premise of this review is to discuss the beneficial effect of gut microbiota modulation as a novel therapeutic approach in ALD management.

Intestinal Microbial Products From Alcohol-Fed Mice Contribute to Intestinal Permeability and Peripheral Immune Activation

BACKGROUND

Alcohol use causes significant disruption of intestinal microbial communities, yet exactly how these dysbiotic communities interact with the host is unclear. We sought to understand the role of microbial products associated with alcohol dysbiosis in mice on intestinal permeability and immune activation in an in vitro model system.

METHODS

Microbiota samples from binge-on-chronic alcohol-fed and pair-fed male and female mice were cultured in Gifu Anaerobic Broth for 24 hours under anaerobic conditions. Live/whole organisms were removed, and microbial products were collected and added to human peripheral blood mononuclear cells (PBMCs) or polarized C2BBe1 intestinal epithelial monolayers. Following stimulation, transepithelial electrical resistance (TEER) was measured using a volt/ohm meter and immune activation of PBMC was assessed via flow cytometry.

RESULTS

Microbial products from male and female alcohol-fed mice significantly decreased TEER (mean percentage change from baseline alcohol-fed 0.86 Ω/cm² vs. pair-fed 1.10 Ω/cm² ) compared to microbial products from control mice. Following ex vivo stimulation, immune activation of PBMC was assessed via flow cytometry. We found that microbial products from alcohol-fed mice significantly increased the percentage of CD38+ CD4+ (mean alcohol-fed 17.32% ± 0.683% standard deviation (SD) vs. mean pair-fed 14.2% ± 1.21% SD, p < 0.05) and CD8+ (mean alcohol-fed 20.28% ± 0.88% SD vs. mean pair-fed 12.58% ± 3.59% SD, p < 0.05) T cells.

CONCLUSIONS

Collectively, these data suggest that microbial products contribute to immune activation and intestinal permeability associated with alcohol dysbiosis. Further, utilization of these ex vivo microbial product assays will allow us to rapidly assess the impact of microbial products on intestinal permeability and immune activation and to identify probiotic therapies to ameliorate these defects.

Transplantation of fecal microbiota rich in short chain fatty acids and butyric acid treat cerebral ischemic stroke by regulating gut microbiota

The gut microbiota and its short chain fatty acid (SCFA) metabolites have been established to play an important protective role against neurodegenerative diseases. Our previous study demonstrated that cerebral ischemic stroke triggers dysfunctional gut microbiota and increased intestinal permeability. In this study, we aimed to clarify the mechanism by which gut microbiota and SCFAs can treat cerebral ischemic stroke in rat middle cerebral artery occlusion models and use the information to develop new therapies. Our results show that oral administration of non-absorbable antibiotics reduced neurological impairment and the cerebral infarct volume, relieved cerebral edemas, and decreased blood lipid levels by altering the gut microbiota. We also found that ischemic stroke decreased intestinal levels of SCFAs. And that transplanting fecal microbiota rich in these metabolites was an effective means of treating the condition. Compared with other SCFAs, butyric acid showed the highest negative correlation with ischemic stroke. Supplementation with butyric acid treated models of ischemic stroke effectively by remodeling the gut microbiota, enriching the beneficial Lactobacillus, and repairing the leaky gut. In conclusion, interfering with the gut microbiota by transplanting fecal bacteria rich in SCFAs and supplementing with butyric acid were found to be effective treatments for cerebral ischemic stroke.

Probiotics for Alleviating Alcoholic Liver Injury

Many animal experiments and clinical trials showed that probiotics are effective for the treatment of alcoholic liver disease. Alcohol disrupts the composition of intestinal flora; probiotics modulate the gut microbiota and reverse alcohol-associated intestinal barrier dysfunction by decreasing intestinal mucosal permeability and preventing intestinal bacteria from translocating. Probiotics enhance immune responses and reduce the levels of alcohol-induced inflammatory cytokines and reactive oxygen species (ROS) production in the liver and intestine. Probiotics also increase fatty acid β-oxidation and reduce lipogenesis, combating alcohol-induced hepatic steatosis. In this review, we summarize the current knowledge regarding the mechanism of action of probiotics for reducing the effects of alcoholic liver disease.

Role of Gut Microbiota in Hepatocarcinogenesis

Hepatocellular carcinoma (HCC), one of the leading causes of death worldwide, has a causal nexus with liver injury, inflammation, and regeneration that accumulates over decades. Observations from recent studies have accounted for the involvement of the gut–liver axis in the pathophysiological mechanism responsible for HCC. The human intestine nurtures a diversified colony of microorganisms residing in the host ecosystem. The intestinal barrier is critical for conserving the normal physiology of the gut microbiome. Therefore, a rupture of this barrier or dysbiosis can cause the intestinal microbiome to serve as the main source of portal-vein endotoxins, such as lipopolysaccharide, in the progression of hepatic diseases. Indeed, increased bacterial translocation is a key sign of HCC. Considering the limited number of clinical studies on HCC with respect to the microbiome, we focus on clinical as well as animal studies involving the gut microbiota, with the current understandings of the mechanism by which the intestinal dysbiosis promotes hepatocarcinogenesis. Future research might offer mechanistic insights into the specific phyla targeting the leaky gut, as well as microbial dysbiosis, and their metabolites, which represent key pathways that drive HCC-promoting microbiome-mediated liver inflammation and fibrosis, thereby restoring the gut barrier function.

A combination of Pueraria lobata and Silybum marianum protects against alcoholic liver disease in mice

BACKGROUND

Excess alcohol exposure leads to alcoholic liver disease (ALD). Pueraria lobata (PUE) and Silybum marianum (SIL) are two well-known hepatoprotective herbal remedies with various activities. The possible effect of combination of PUE and SIL on ALD has not been elucidated yet.

PURPOSE

We aimed to demonstrate that the combination of PUE and SIL prevents against alcoholic liver injury in mice using a model of chronic-plus-single-binge ethanol feeding.

STUDY DESIGN

Male C57BL/6 mice were randomly divided into five groups (n = 8-10), namely the control group (CON), ethanol-induced liver injury group (ETH), 150 mg/kg PUE treated group (PUE), 60 mg/kg SIL treated group (SIL), 210 mg/kg PUE+SIL treatment group (PUE+SIL). Except control group, all animals were fed a modified Lieber-DeCarli ethanol liquid diet for 10 days. While, control group received Lieber-DeCarli control diet containing isocaloric maltose dextrin substituted for ethanol. On day 11, the mice orally received a single dose of 31.5% (v/v) ethanol (5 g/kg BW) or an isocaloric maltose solution.

RESULTS

Ethanol exposure caused liver injury, as demonstrated by remarkably increased plasma parameters, histopathological changes, the increased lipid accumulation, oxidative stress and inflammation in liver. These alterations were ameliorated by the treatments of PUE, SIL and PUE+SIL. While, the PUE+SIL treatment showed the most effective protection, which was associated with reducing alcohol-induced hepatic steatosis via upregulating LKB1/AMPK/ACC signaling, and inhibiting hepatic inflammation via LPS-triggered TLR4-mediated NF-κB signaling pathway. Our results also indicated that the hepatoprotective effects of SIL+PUE might mainly attribute to the protection of SIL and PUE alone in alcohol-induced hepatic steatosis and hepatic inflammation, respectively.

CONCLUSION

These findings also suggest that the combination of PUE and SIL has a potential to be developed as a functional food for the management of ALD.

Gut microbiota in liver disease: too much is harmful, nothing at all is not helpful either

The intestinal microbiome plays a major role in the pathogenesis of liver disease, with a hallmark event being dysbiosis, or an imbalance of pathobionts and beneficial bacteria with the associated deleterious effects on their host. Reducing the number of intestinal bacteria with antibiotic treatment is generally advantageous in experimental liver diseases. Complete absence of intestinal microbiota as in germ-free rodents can be protective in autoimmune hepatitis and hepatic tumors induced by chemicals, or it can exacerbate disease as in acute toxic liver injury and liver fibrosis/cirrhosis. In alcoholic liver disease, nonalcoholic fatty liver disease, and autoimmune cholangiopathies, germ-free status can be associated with worsened or improved hepatic phenotype depending on the experimental model and type of rodent. Some of the unexpected outcomes can be explained by the limitations of rodents raised in a germ-free environment including a deficient immune system and an altered metabolism of lipids, cholesterol, xenobiotics/toxins, and bile acids. Given these limitations and to advance understanding of the interactions between host and intestinal microbiota, simplified model systems such as humanized gnotobiotic mice, or gnotobiotic mice monoassociated with a single bacterial strain or colonized with a defined set of microbes, are unique and useful models for investigation of liver disease in a complex ecosystem.

Suppression of Gut Bacterial Translocation Ameliorates Vascular Calcification through Inhibiting Toll-Like Receptor 9-Mediated BMP-2 Expression

Aims

Vascular calcification (VC) is a primary risk factor for cardiovascular mortality in chronic renal failure (CRF) patients; thus, effective therapeutic targets are urgently needed to be explored. Here, we identified the role of intestinal bacterial translocation in CRF-related VC.

Methods and Results

Antibiotic supplementation by oral gavage significantly suppressed intestinal bacterial translocation, CRF-related VC, and aortic osteogenic gene and Toll-like receptor (TLR) gene expression in CRF rats. Furthermore, TLR4 and TLR9 activation in vascular smooth muscle cells (VSMCs) aggravated inorganic phosphate- (Pi-) induced calcification. TLR9 inhibition, but not TLR4 inhibition, by both a pharmacological inhibitor and genetic methods could significantly reduce CRF rats' serum or CRF-induced VC. Interestingly, bone morphogenic protein-2 (BMP-2) levels were increased in the aorta and sera from CRF rats. Increased BMP-2 levels were also observed in VSMCs treated with TLR9 agonist, which was blocked by NF-κB inhibition. Both siRNA knockdown of BMP-2 and NF-κB inhibitor significantly blocked TLR9 agonist-induced VSMC calcification.

Conclusions

Gut bacterial translocation inhibited by oral antibiotic significantly reduces CRF-related VC through inhibition of TLR9/NF-κB/BMP-2 signaling.

A literature review for the mechanisms of stress-induced liver injury

INTRODUCTION

Experimental studies and clinical observations have shown that stress can damage hepatic tissue both directly and indirectly. Many studies have partially revealed the contributors of stress-induced liver injury; however, the whole process has not yet been uncovered. This review aims to summarize the mechanisms that have been proposed to be involved.

METHODS

A literature search was conducted using PubMed (http://www.ncbi.nlm.nih.gov/pubmed) in its entirety up to March 2018, and analyzed the animal-derived mechanistic studies on stress-induced liver injury.

RESULTS

The liver is the organ that meets and filters a mass of alien material, and then maintains immune tolerance under physiological conditions. Under stress conditions, however, immune tolerance is interrupted, which results in the induction of inflammation in the liver. Contributors to this process can be categorized as follows: hypoxia-reoxygenation, over-activation of Kupffer cells and oxidative stress, influx of gut-derived lipopolysaccharide and norepinephrine, and over-production of stress hormones and activation of the sympathetic nerve.

CONCLUSIONS

Psychological stress is associated with a variety of pathological conditions resulting in liver injury through multiple systems, including the sympathetic nervous and adrenocortical system. Mechanistic understanding of this phenomenon is important for the clinical practice of managing patients with hepatic disorders and should be explored further in the future.

Microbiome as a therapeutic target in alcohol-related liver disease

Alcohol-related liver disease is associated with significant changes in gut microbial composition. The transmissibility of ethanol-induced liver disease has been demonstrated using faecal microbiota transfer in preclinical models. This technique has also led to improved survival in patients with severe alcoholic hepatitis, suggesting that changes in the composition and function of the gut microbiota are causatively linked to alcohol-related liver disease. A major mechanism by which gut microbiota influence the development of alcohol-related liver disease is through a leaky intestinal barrier. This permits translocation of viable bacteria and microbial products to the liver, where they induce and promote inflammation, as well as contribute to hepatocyte death and the fibrotic response. In addition, gut dysbiosis is associated with changes in the metabolic function of the intestinal microbiota, bile acid composition and circulation, immune dysregulation during onset and progression of alcohol-related liver disease. Findings from preclinical and human studies will be used to demonstrate how alcohol causes intestinal pathology and contributes to alcohol-related liver disease and how the latter is self-perpetuating. Additionally, we summarise the effects of untargeted treatment approaches on the gut microbiota, such as diet, probiotics, antibiotics and faecal microbial transplantation in alcohol-related liver disease. We further discuss how targeted approaches can restore intestinal homeostasis and improve alcohol-related liver disease. These approaches are likely to add to the therapeutic options for alcohol-related liver disease independently or in conjunction with steroids.

Gut microbial dysbiosis associates hepatocellular carcinoma via the gut-liver axis

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most common malignancies in the world. Gut microbiota has been demonstrated to play a critical role in liver inflammation, chronic fibrosis, liver cirrhosis, and HCC development through the gut-liver axis.

DATA SOURCES

Recently there have been several innovative studies investigating gut microbial dysbiosis-mediated enhancement of HCC through the gut-liver axis. Literatures from January 1998 to January 2018 were searched in the PubMed database using the keywords "gut microbiota" and "hepatocellular carcinoma" or "liver cancer", and the results of experimental and clinical studies were analyzed.

RESULTS

Gut microbial dysbiosis accompanies the progression of alcoholic liver disease, non-alcoholic fatty liver disease and liver cirrhosis, and promotes HCC progression in an experimental mouse model. The immune system and key factors such as Toll-like receptor 4 are involved in the process. There is evidence for gut microbial dysbiosis in hepatitis virus-related HCC patients.

CONCLUSIONS

Gut microbial dysbiosis is closely associated with hepatic inflammation disease and HCC through the gut-liver axis. With the enhanced understanding of the interactions between gut microbiota and liver through the gut-liver axis, new treatment strategies for HCC are being developed.

Pathogenesis of Alcoholic Liver Disease: An Update

Apart from the classic knowledge that ethanol mediates its hepatotoxicity through its metabolism to acetaldehyde, a well-known hepatotoxic molecule, recent research has elucidated several key mechanisms that potentiate ethanol's damage to the liver parenchyma, such as generation of free radicals, activation of Kupffer cells, and alterations to the human bacterial and fungal microbiome. Genetic studies have suggested the role of PNPLA3 and TM6SF2 gene mutations in the progression of alcoholic liver disease.

n-3 Polyunsaturated fatty acids for the management of alcoholic liver disease: A critical review

Excess alcohol exposure leads to alcoholic liver disease (ALD), a predominant cause of liver-related morbidity and mortality worldwide. In the past decade, increasing attention has been paid to understand the association between n-3 polyunsaturated fatty acids (n-3 PUFAs) and ALD. In this review, we summarize the metabolism of n-3 PUFAs, animal model of ALD, and the findings from recent studies determining the role of n-3 PUFAs in ALD as a possible treatment. The animal models of acute ethanol exposure, chronic ethanol exposure and chronic-plus-single binge ethanol feeding have been widely used to explore the impact of n-3 PUFAs. Although the results of studies regarding the role of n-3 PUFAs in ALD have been inconsistent or controversial, increasing evidence has demonstrated that n-3 PUFAs may be useful in alleviating alcoholic steatosis and alcohol-induced liver injury through multiple mechanisms, including decreased de novo lipogenesis and lipid mobilization from adipose tissue, enhanced mitochondrial fatty acid β-oxidation, reduced hepatic inflammation and oxidative stress, and promoted intestinal homeostasis, positively suggesting that n-3 PUFAs might be promising for the management of ALD. The oxidation of n-3 PUFAs ex vivo in an experimental diet was rarely considered in most n-3 PUFA-related studies, likely contributing to the inconsistent results. Thus, the role of n-3 PUFAs in ALD deserves greater research efforts and remains to be evaluated in randomized, placebo-controlled clinic trial. ABBREVIATION AA arachidonic acid ACC acetyl-CoA carboxylase ACLY ATP-citrate lyase ACO acyl-CoA oxidase ALA α-linolenic acid ALD alcoholic liver disease ALP alkaline phosphatase ALT alanine aminotransferase AMPK AMP-activated protein kinase AST aspartate aminotransferase ATGL adipose triglyceride lipase cAMP cyclic adenosine 3',5'-monophosphate COX cyclooxygenases CPT1 carnitine palmitoyltransferase 1 CYP2E1 cytochrome P450 2E1 DGAT2 diacylglycerol acyltransferase 2 DGLA dihomo-γ-linolenic acid DHA docosahexaenoic acid DPA docosapentaenoic acid DTA docosatetraenoic acid EPA eicosapentaenoic acid ER endoplasmic reticulum ETA eicosatetraenoic acid FAS fatty acid synthase FATPs fatty acid transporter proteins GLA,γ linolenic acid GPR120 G protein-coupled receptor 120 GSH glutathione; H&E haematoxylin-eosin; HO-1 heme oxygenase-1; HSL hormone-sensitive lipase; IL-6 interleukin-6 iNOS nitric oxide synthase LA linoleic acid LBP lipopolysaccharide binding protein LOX lipoxygenases LXR liver X receptor LXREs LXR response elements MCP-1 monocyte chemotactic protein-1 MTP microsomal triglyceride transfer protein MUFA monounsaturated fatty acids MyD88 myeloid differentiation factor 88 n-3 PUFAs omega-3 polyunsaturated fatty acid NAFLD nonalcoholic fatty liver disease NASH nonalcoholic steatohepatitis NF-κB transcription factor nuclear factor κB PDE3B phosphodiesterase 3B PPAR peroxisome proliferator-activated receptor ROS reactive oxygen species RXR retinoid X receptor SCD-1 stearyl CoA desaturase-1 SDA stearidonic acid SFA saturated fatty acids SIRT1 sirtuin 1 SOD superoxide dismutase SREBP sterol regulatory element-binding protein TB total bilirubin TC total cholesterol TG triacylglycerol TLR4 Toll-like receptor-4 TNF-α tumor necrosis factor-α VLDLR very low-density lipoprotein receptor WT wild type; ZO-1 zonula occludens-1.

Alcoholic liver disease: A current molecular and clinical perspective

Heavy alcohol use is the cause of alcoholic liver disease (ALD). The ALD spectrum ranges from alcoholic steatosis to steatohepatitis, fibrosis, and cirrhosis. In Western countries, approximately 50% of cirrhosis-related deaths are due to alcohol use. While alcoholic cirrhosis is no longer considered a completely irreversible condition, no effective anti-fibrotic therapies are currently available. Another significant clinical aspect of ALD is alcoholic hepatitis (AH). AH is an acute inflammatory condition that is often comorbid with cirrhosis, and severe AH has a high mortality rate. Therapeutic options for ALD are limited. The established treatment for AH is corticosteroids, which improve short-term survival but do not affect long-term survival. Liver transplantation is a curative treatment option for alcoholic cirrhosis and AH, but patients must abstain from alcohol use for 6 months to qualify. Additional effective therapies are needed. The molecular mechanisms underlying ALD are complex and have not been fully elucidated. Various molecules, signaling pathways, and crosstalk between multiple hepatic and extrahepatic cells contribute to ALD progression. This review highlights established and emerging concepts in ALD clinicopathology, their underlying molecular mechanisms, and current and future ALD treatment options.

[Gut-liver axis: How intestinal bacteria affect the liver]

BACKGROUND

Liver and intestine are in close contact with each other. The risk of damage to the liver increases, when the intestinal barrier is damaged ("leaky gut") .

METHOD

The review article describes how intestinal bacteria influence the pathogenesis of chronic liver diseases and what treatment options are available.

RESULTS AND CONCLUSIONS

Intestinal dysbiosis plays an important role in the development of chronic liver diseases such as alcoholic liver disease, nonalcoholic fatty liver disease, primary biliary cholangitis, primary sclerosing cholangitis, and cirrhosis. Intestinal microbial modulating therapy with probiotics, prebiotics or synbiotics shows positive effects. The more precise meaning of this therapeutic approach needs to be clarified in further studies.

Reduced gut microbiome protects from alcohol-induced neuroinflammation and alters intestinal and brain inflammasome expression

Background

The end-organ effects of alcohol span throughout the entire body, from the gastrointestinal tract to the central nervous system (CNS). In the intestine, alcohol use changes the microbiome composition and increases gut permeability allowing translocation of microbial components into the circulation. Gut-derived pathogen-associated signals initiate inflammatory responses in the liver and possibly elsewhere in the body. Because previous studies showed that the gut microbiome contributes to alcohol-induced liver disease, we hypothesized that antibiotic administration to reduce the gut microbiome would attenuate alcohol-induced inflammation in the brain and small intestine (SI).

Methods

Six- to 8-week-old C57BL/6J female mice were fed alcohol in a liquid diet or a calorie-matched control diet for 10 days with an acute alcohol binge or sugar on the final day (acute-on-chronic alcohol administration). Some mice were treated with oral antibiotics daily to diminish the gut microbiome. We compared serum levels of TNFα, IL-6, and IL-1β by ELISA; expression of cytokines Tnfα, Mcp1, Hmgb1, Il-17, Il-23, Il-6, and Cox2; and inflammasome components Il-1β, Il-18, Casp1, Asc, and Nlrp3 in the CNS and SI by qRT-PCR. Microglial morphology was analyzed using immunohistochemical IBA1 staining in the cortex and hippocampus.

Results

Antibiotics dramatically reduced the gut microbiome load in both alcohol- and pair-fed mice. Alcohol-induced neuroinflammation and increase in SI cytokine expression were attenuated in mice with antibiotic treatment. Acute-on-chronic alcohol did not induce serum TNFα, IL-6, and IL-1β. Alcohol feeding significantly increased the expression of proinflammatory cytokines such as Tnfα, Mcp1, Hmgb1, Il-17, and Il-23 in the brain and intestine. Reduction in the gut bacterial load, as a result of antibiotic treatment, attenuated the expression of all of these alcohol-induced proinflammatory cytokines in both the brain and SI. Alcohol feeding resulted in microglia activation and morphologic changes in the cortex and hippocampus characterized by a reactive phenotype. These alcohol-induced changes were abrogated following an antibiotic-induced reduction in the gut microbiome. Unexpectedly, antibiotic treatment increased the mRNA expression of some inflammasome components in both the brain and intestine.

Conclusions

Our data show for the first time that the acute-on-chronic alcohol administration in mice induces both neuroinflammation and intestinal inflammation and that reduction in the intestinal bacterial load can attenuate alcohol-associated CNS and gut inflammation. Gut microbiome-derived signals contribute to neuroinflammation in acute-on-chronic alcohol exposure.

Intestinal HIF-1α deletion exacerbates alcoholic liver disease by inducing intestinal dysbiosis and barrier dysfunction

BACKGROUND & AIMS

Alcoholic liver disease (ALD) is characterized by gut dysbiosis and increased gut permeability. Hypoxia inducible factor 1α (HIF-1α) has been implicated in transcriptional regulation of intestinal barrier integrity and inflammation. We aimed to test the hypothesis that HIF-1α plays a critical role in gut microbiota homeostasis and the maintenance of intestinal barrier integrity in a mouse model of ALD.

METHODS

Wild-type (WT) and intestinal epithelial-specific Hif1a knockout mice (IEhif1α^-/-) were pair-fed modified Lieber-DeCarli liquid diet containing 5% (w/v) alcohol or isocaloric maltose dextrin for 24 days. Serum levels of alanine aminotransferase and endotoxin were determined. Fecal microbiota were assessed. Liver steatosis and injury, and intestinal barrier integrity were evaluated.

RESULTS

Alcohol feeding increased serum levels of alanine aminotransferase and lipopolysaccharide, hepatic triglyceride concentration, and liver injury in the WT mice. These deleterious effects were exaggerated in IEhif1α^-/- mice. Alcohol exposure resulted in greater reduction of the expression of intestinal epithelial tight junction proteins, claudin-1 and occludin, in IEhif1α^-/- mice. In addition, cathelicidin-related antimicrobial peptide and intestinal trefoil factor were further decreased by alcohol in IEhif1α^-/- mice. Metagenomic analysis showed increased gut dysbiosis and significantly decreased Firmicutes/Bacteroidetes ratio in IEhif1α^-/- mice compared to the WT mice exposed to alcohol. An increased abundance of Akkermansia and a decreased level of Lactobacillus in IEhif1α^-/- mice were also observed. Non-absorbable antibiotic treatment reversed the liver steatosis in both WT and IEhif1α^-/- mice.

CONCLUSION

Intestinal HIF-1α is essential for the adaptative response to alcohol-induced changes in intestinal microbiota and barrier function associated with elevated endotoxemia and hepatic steatosis and injury.

LAY SUMMARY

Alcohol consumption alters gut microbiota and multiple intestinal barrier protecting factors that are regulated by intestinal hypoxia-inducible factor 1α (HIF-1α). Absence of intestinal HIF-1α exacerbates gut leakiness leading to an increased translocation of bacteria and bacterial products to the liver, consequently causing alcoholic liver disease. Intestinal specific upregulation of HIF-1α could be developed as a novel approach for the treatment of alcoholic liver disease.

National Early Warning Score Accurately Discriminates the Risk of Serious Adverse Events in Patients With Liver Disease

BACKGROUND & AIMS

The National Early Warning Score (NEWS) is used to identify deteriorating adult hospital inpatients. However, it includes physiological parameters frequently altered in patients with cirrhosis. We aimed to assess the performance of the NEWS in acute and chronic liver diseases.

METHODS

We collected vital signs, recorded in real time, from completed consecutive admissions of patients 16 years or older to a large acute-care hospital in Southern England, from January 1, 2010, through October 31, 2014. Using International Classification of Diseases, 10th revision, codes, we categorized patients as having primary liver disease, secondary liver disease, or none. For patients with liver disease, 2 analysis groups were developed: the first was based on clinical group (such as acute or chronic, alcohol-induced, or associated with portal hypertension), and the second was based on a summary of liver-related, hospital-level mortality indicator diagnoses. For each, we compared the abilities of the NEWS and 34 other early warning scores to discriminate 24-hour mortality, cardiac arrest, or unanticipated admission to the intensive care unit using the area under the receiver operating characteristic (AUROC) curve and early warning score efficiency curve analyses.

RESULTS

The NEWS identified patients with primary, nonprimary, and no diagnoses of liver disease with AUROC values of 0.873 (95% CI, 0.860-0.886), 0.898 (95% CI, 0.891-0.905), and 0.879 (95% CI, 0.877-0.881), respectively. High AUROC values were also obtained for all clinical subgroups; the NEWS identified patients with alcohol-related liver disease with an AUROC value of 0.927 (95% CI, 0.912-0.941). The NEWS identified patients with liver diseases with higher AUROC values than other early warning scoring systems.

CONCLUSIONS

The NEWS accurately discriminates patients at risk of death, admission to the intensive care unit, or cardiac arrest within a 24-hour period for a range of liver-related diagnoses. Its widespread use provides a ready-made, easy-to-use option for identifying patients with liver disease who require early assessment and intervention, without the need to modify parameters, weightings, or escalation criteria.

Gut⁻Liver Axis: How Do Gut Bacteria Influence the Liver?

Chronic liver diseases are a major cause of morbidity and mortality worldwide. Recently, gut dysbiosis was identified as an important factor in the pathogenesis of liver diseases. The relationship between gut microbiota and the liver is still not well understood; however, dysfunction of the gut mucosal barrier ("leaky gut") and increased bacterial translocation into the liver via the gut⁻liver axis probably play crucial roles in liver disease development and progression. The liver is an important immunological organ, and, after exposure to gut-derived bacteria via portal circulation, it responds with activation of the innate and adaptive immune system, leading to hepatic injury. A better understanding of the pathophysiological links among gut dysbiosis, the integrity of the gut barrier, and the hepatic immune response to gut-derived factors is essential for the development of new therapies to treat chronic liver diseases.

Targeting Nrf-2 is a promising intervention approach for the prevention of ethanol-induced liver disease

Alcoholic liver disease (ALD) remains to be a worldwide health problem. It is generally accepted that oxidative stress plays critical roles in the pathogenesis of ALD, and antioxidant therapy represents a logical strategy for the prevention and treatment of ALD. Nuclear factor erythroid-derived 2-like 2 (NFE2L2 or Nrf-2) is essential for the antioxidant responsive element (ARE)-mediated induction of endogenous antioxidant enzymes such as heme oxygenase 1 (HO-1) and glutamate-cysteine ligase [GCL, the rate-limiting enzyme in the synthesis of glutathione (GSH)]. Activation of Nrf-2 pathway by genetic manipulation or pharmacological agents has been demonstrated to provide protection against ALD, which suggests that targeting Nrf-2 may be a promising approach for the prevention and treatment of ALD. Herein, we review the relevant literature about the potential hepatoprotective roles of Nrf-2 activation against ALD.

Young alcohol binge drinkers have elevated blood endotoxin, peripheral inflammation and low cortisol levels: neuropsychological correlations in women

Alcohol binge drinking is a pattern of heavy alcohol consumption that is increasingly practiced by adolescents and young adults. Evidence indicates that alcohol binges induce peripheral inflammation and an exacerbated neuroimmune response that may participate in alcohol-induced cognitive/behavioral dysfunctions. Here, we recruited 20-year-old male and female university students who were identified as binge drinkers for at least 2 years. Compared with controls, young alcohol binge drinkers had elevated levels of blood endotoxin and upregulated markers of the toll-like receptor 4/NF-κB inflammatory pathway in peripheral blood mononuclear cells, together with pro-inflammatory cytokine/chemokine release, oxidative stress and lipid peroxidation. These changes positively correlate with the estimated blood alcohol levels achieved during alcohol binge intoxication and negatively correlate with the time elapsed from the last alcohol consumption. The immune/inflammatory changes were more prominent in female drinkers, who showed elevated levels of alcohol danger-associated molecules, such as high mobility group box 1, indicating that there are sex-related differences in the peripheral inflammatory response to alcohol. In contrast, cortisol levels were decreased in alcohol binge drinkers. Finally, higher levels of inflammatory markers, mainly monocyte chemoattractant protein-1, as well as LPS, high mobility group box 1, toll-like receptor 4, IL-6 and ciclooxygenase-2, correlated with worse scores on episodic memory and executive functioning tasks in female binge drinkers but not in male binge drinkers. These results emphasize possible risky consequences of alcohol use in binge episodes during young adulthood and call attention to sex-related differences in the alcohol-induced immune/inflammatory and neurocognitive responses.

Alcoholic liver disease

Alcoholic liver disease (ALD) is the most prevalent type of chronic liver disease worldwide. ALD can progress from alcoholic fatty liver (AFL) to alcoholic steatohepatitis (ASH), which is characterized by hepatic inflammation. Chronic ASH can eventually lead to fibrosis and cirrhosis and in some cases hepatocellular cancer (HCC). In addition, severe ASH (with or without cirrhosis) can lead to alcoholic hepatitis, which is an acute clinical presentation of ALD that is associated with liver failure and high mortality. Most individuals consuming >40 g of alcohol per day develop AFL; however, only a subset of individuals will develop more advanced disease. Genetic, epigenetic and non-genetic factors might explain the considerable interindividual variation in ALD phenotype. The pathogenesis of ALD includes hepatic steatosis, oxidative stress, acetaldehyde-mediated toxicity and cytokine and chemokine-induced inflammation. Diagnosis of ALD involves assessing patients for alcohol use disorder and signs of advanced liver disease. The degree of AFL and liver fibrosis can be determined by ultrasonography, transient elastography, MRI, measurement of serum biomarkers and liver biopsy histology. Alcohol abstinence achieved by psychosomatic intervention is the best treatment for all stages of ALD. In the case of advanced disease such as cirrhosis or HCC, liver transplantation may be required. Thus, new therapies are urgently needed.

Mesenchymal stem cell transplantation improves chronic colitis-associated complications through inhibiting the activity of toll-like receptor-4 in mice

Background

A variety of extra-intestinal manifestations (EIMs), including hepatobiliary complications, are associated with inflammatory bowel disease (IBD). Mesenchymal stem cells (MSCs) have been shown to play a potential role in the therapy of IBD. This study was designed to investigate the effect and mechanism of MSCs on chronic colitis-associated hepatobiliary complications using mouse chronic colitis models induced by dextran sulfate sodium (DSS).

Methods

DSS-induced mouse chronic colitis models were established and treated with MSCs. Severity of colitis was evaluated by disease activity index (DAI), body weight (BW), colon length and histopathology. Serum lipopolysaccharide (LPS) levels were detected by limulus amebocyte lysate test (LAL-test). Histology and liver function of the mice were checked correspondingly. Serum LPS levels and bacterial translocation of mesenteric lymph nodes (MLN) were detected. Pro-inflammatory cytokines including tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), interleukin-1β (IL-1β), interleukin-17A (IL-17A), Toll receptor 4 (TLR4), TNF receptor-associated factor 6 (TRAF6) and nuclear factor kappa B (NF-κB) were detected by immunohistochemical staining, western blot analysis and real-time PCR, respectively.

Results

The DSS-induced chronic colitis model was characterized by reduced BW, high DAI, worsened histologic inflammation, and high levels of LPS and E. coli. Liver histopathological lesions, impaired liver function, enhanced proteins and mRNA levels of TNF-α, IFN-γ, IL-1β, IL-17A, TLR4, TRAF6 and NF-κB were observed after DSS administration. MSCs transplantation markedly ameliorated the pathology of colon and liver by reduction of LPS levels and proteins and mRNA expressions of TNF-α, IFN-γ, IL-1β, IL-17A, TLR4, TRAF6 and NF-κB.

Conclusions

MSCs can improve chronic colitis-associated hepatobiliary complications, probably by inhibition of enterogenous endotoxemia and hepatic inflammation through LPS/TLR4 pathway. MSCs may represent a novel therapeutic approach for chronic colitis-associated hepatobiliary complications.

Bletilla striata polysaccharide has a protective effect on intestinal epithelial barrier disruption in TAA-induced cirrhotic rats

It has been reported that intestinal epithelial barrier dysfunction serves an important role in the development of liver cirrhosis. However, at present there is no satisfactory treatment for intestinal mucosal lesions and ulcers associated with cirrhosis. The aim of the present study was to investigate the effect of Bletilla striata polysaccharide (BSP) on intestinal epithelial barrier disruption in rats with thioacetamide (TAA)-induced liver cirrhosis. Rats were randomly divided into 5 groups (n=10): BSP low dosage (15 mg/kg), BSP middle dosage (30 mg/kg), BSP high dosage (60 mg/kg), experiment and control groups. All groups except control group were administered with TAA (200 mg/kg/day) to induce liver cirrhosis. Following modeling, rats in the low, middle and high-dose BSP groups received BSP. ELISA kits were used to measure the endotoxin, alanine transaminase (ALT) and aspartate transaminase (AST) levels in the portal vein, while interleukin (IL)-6 and tumor necrosis factor (TNF)-α expression in the ileal tissue was measured. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blotting were used to detect the expression of zonula occludens (ZO)-1 and occludin mRNA and protein, respectively. Intestinal epithelial tissue pathology was detected using hematoxylin-eosin (HE) staining. Immunohistochemistry was performed to assess the expression of ZO-1 and occludin in intestinal epithelial tissues. Following treatment with BSP, ALT, AST and endotoxin levels in the portal vein, as well as IL-6 and TNF-α expression in ileal tissues, were significantly decreased compared with model group (P<0.05 or 0.01). Furthermore, BSP treatment upregulated the expression of ZO-1 and occludin mRNA and protein compared with the model group (P<0.05 or 0.01) and cytoplasmic staining for these proteins was increased. The degree of intestinal epithelial tissue pathological damage was significantly reduced in the BSP groups. In conclusion, BSP is able to reduce endotoxin levels, inhibit the inflammatory cytokines IL-6 and TNF-α and elevate expression of ZO-1 and occludin at tight junctions. Together, these results suggest a novel protective agent for the restoration of intestinal epithelial barrier disruption.

Outside the liver box: The gut microbiota as pivotal modulator of liver diseases

The gut microbiota affects host physiology and has evolved as an important contributor to health and disease. Gut and liver are closely connected and communicate via the portal vein and the biliary system so the liver is constantly exposed to gut-derived bacterial products and metabolites. The intestinal barrier is important for maintaining physical and functional separation between microbes in the gut and the interior of the host and disruption of the barrier function can lead to bacterial translocation and increased leakage of bacterial metabolites. Liver diseases have been associated with dysbiotic changes in the gut microbiota and impaired gut barrier integrity, thus a future strategy to treat liver disease may be to target the gut microbiota and thereby restore the gut barrier function. This review will summarize and discuss studies that have shown a link between the gut microbiota and liver disease with the main focus on non-alcoholic fatty liver disease and alcoholic liver disease.

Modulation of the intestinal bile acid/farnesoid X receptor/fibroblast growth factor 15 axis improves alcoholic liver disease in mice

Alcoholic liver disease (ALD) is associated with changes in the intestinal microbiota. Functional consequences of alcohol-associated dysbiosis are largely unknown. The aim of this study was to identify a mechanism of how changes in the intestinal microbiota contribute to ALD. Metagenomic sequencing of intestinal contents demonstrated that chronic ethanol feeding in mice is associated with an over-representation of bacterial genomic DNA encoding choloylglycine hydrolase, which deconjugates bile acids in the intestine. Bile acid analysis confirmed an increased amount of unconjugated bile acids in the small intestine after ethanol administration. Mediated by a lower farnesoid X receptor (FXR) activity in enterocytes, lower fibroblast growth factor (FGF)-15 protein secretion was associated with increased hepatic cytochrome P450 enzyme (Cyp)-7a1 protein expression and circulating bile acid levels. Depletion of the commensal microbiota with nonabsorbable antibiotics attenuated hepatic Cyp7a1 expression and reduced ALD in mice, suggesting that increased bile acid synthesis is dependent on gut bacteria. To restore intestinal FXR activity, we used a pharmacological intervention with the intestine-restricted FXR agonist fexaramine, which protected mice from ethanol-induced liver injury. Whereas bile acid metabolism was only minimally altered, fexaramine treatment stabilized the gut barrier and significantly modulated hepatic genes involved in lipid metabolism. To link the beneficial metabolic effect to FGF15, a nontumorigenic FGF19 variant-a human FGF15 ortholog-was overexpressed in mice using adeno-associated viruses. FGF19 treatment showed similarly beneficial metabolic effects and ameliorated alcoholic steatohepatitis.

CONCLUSION

Taken together, alcohol-associated metagenomic changes result in alterations of bile acid profiles. Targeted interventions improve bile acid-FXR-FGF15 signaling by modulation of hepatic Cyp7a1 and lipid metabolism, and reduce ethanol-induced liver disease in mice. (Hepatology 2018;67:2150-2166).

Current State of Knowledge on Implications of Gut Microbiome for Surgical Conditions

The role of the microbiome in human health has become a central tenant of current medical research, infiltrating a diverse disciplinary base whereby microbiology, computer science, ecology, gastroenterology, immunology, neurophysiology and psychology, metabolism, and cardiovascular medicine all intersect. Traditionally, commensal gut microbiota have been assumed to play a significant role only in the metabolic processing of dietary nutrients and host metabolites, the fortification of gut epithelial barrier function, and the development of mucosal immunity. However, over the last 20 years, new technologies and renewed interest have uncovered a considerably broader influence of the microbiota on health maintenance and disease development, many of which are of particular relevance for surgeons. This article provides a broad overview of the current state of knowledge and a review of the technology that helped in their formation.

Microbiota, a key player in alcoholic liver disease

Alcoholic liver disease (ALD) is a major cause of morbidity and mortality worldwide. Only 20% of heavy alcohol consumers develop alcoholic liver cirrhosis. The intestinal microbiota (IM) has been recently identified as a key player in the severity of liver injury in ALD. Common features of ALD include a decrease of gut epithelial tight junction protein expression, mucin production, and antimicrobial peptide levels. This disruption of the gut barrier, which is a prerequisite for ALD, leads to the passage of bacterial products into the blood stream (endotoxemia). Moreover, metabolites produced by bacteria, such as short chain fatty acids, volatile organic compounds (VOS), and bile acids (BA), are involved in ALD pathology. Probiotic treatment, IM transplantation, or the consumption of dietary fiber, such as pectin, which all alter the ratio of bacterial species, have been shown to improve liver injury in animal models of ALD and to be associated with an improvement in gut barrier function. Although the connections between the microbiota and the host in ALD are well established, the underlying mechanisms are still an active area of research. Targeting the microbiome through the use of prebiotic, probiotic, and postbiotic modalities could be an attractive new approach to manage ALD.

"Immune Gate" of Psychopathology-The Role of Gut Derived Immune Activation in Major Psychiatric Disorders

Interaction between the gastrointestinal tract (GI) and brain functions has recently become a topic of growing interest in psychiatric research. These multidirectional interactions take place in the so-called gut-brain axis or more precisely, the microbiota-gut-brain axis. The GI tract is the largest immune organ in the human body and is also the largest surface of contact with the external environment. Its functions and permeability are highly influenced by psychological stress, which are often a precipitating factor in the first episode, reoccurrence and/or deterioration of symptoms of psychiatric disorders. In recent literature there is growing evidence that increased intestinal permeability with subsequent immune activation has a major role in the pathophysiology of various psychiatric disorders. Numerous parameters measured in this context seem to be aftermaths of those mechanisms, yet at the same time they may be contributing factors for immune mediated psychopathology. For example, immune activation related to gut-derived bacterial lipopolysaccharides (LPS) or various food antigens and exorphins were reported in major depression, schizophrenia, bipolar disorder, alcoholism and autism. In this review the authors will summarize the evidence and roles of such parameters and their assessment in major psychiatric disorders.

Association of mRNA expression of iron metabolism-associated genes and progression of non-alcoholic steatohepatitis in rats

Background

Excess iron is associated with non-alcoholic steatohepatitis (NASH).

Results

mRNA expression of duodenal cytochrome b, divalent metal transporter 1, ferroportin 1, hepcidin, hephaestin and transferrin receptor 1 in liver were higher in high fat, high cholesterol-containing diet (HFCD) group than in normal diet (ND) group. mRNA levels of divalent metal transporter 1 and transferrin receptor 1, which stimulate iron absorption and excretion, were enhanced in small intestine. Epithelial mucosa of small intestine in HFCD group was characterized by plasma cell and eosinophil infiltration and increased vacuoles. Iron absorption was enhanced in this NASH model in the context of chronic inflammation of small intestinal epithelial cells, consequences of intestinal epithelial cell impairment caused by HFCD. Iron is transported to hepatocytes via portal blood, and abnormalities in iron absorption and excretion occur in small intestine from changes in iron transporter expression, which also occurs in NASH liver. Knockdown of hepcidin antimicrobial peptide led to enhanced heavy chain of ferritin expression in human hepatocytes, indicating association between hepcidin production and iron storage in hepatocytes.

Conclusions

Iron-related transporters in liver and lower/upper portions of small intestine play critical roles in NASH development.

Methods

Expression of iron metabolism-related genes in liver and small intestine was analyzed in stroke-prone spontaneously hypertensive rats (SHR-SP), which develop NASH. Five-week-old SHR-SP fed ND or HFCD were examined. mRNA and protein levels of iron metabolism-related genes in liver and small intestine from 12- and 19-week-old rats were evaluated by real-time RT-PCR and immunohistochemistry or Western blot.

Hepatocyte toll-like receptor 4 deficiency protects against alcohol-induced fatty liver disease

Objective

Recent studies have suggested a critical role for toll-like receptor 4 (TLR4) in the development of alcoholic liver disease. As TLR4 is widely expressed throughout the body, it is unclear which TLR4-expressing cell types contribute to alcohol-induced liver damage.

Methods

We selectively ablated TLR4 in hepatocytes and myeloid cells. Male mice were fed a liquid diet containing either 5% alcohol or pair-fed a control diet for 4 weeks to examine chronic alcohol intake-induced liver damage and inflammation. In addition, mice were administered a single oral gavage of alcohol to investigate acute alcohol drinking-associated liver injury.

Results

We found that selective hepatocyte TLR4 deletion protected mice from chronic alcohol-induced liver injury and fatty liver. This result was in part due to decreased expression of endogenous lipogenic genes and enhanced expression of genes involved in fatty acid oxidation. In addition, mice lacking hepatocyte TLR4 exhibited reduced mRNA expression of inflammatory genes in white adipose tissue. Furthermore, in an acute alcohol binge model, hepatocyte TLR4 deficient mice had significantly decreased plasma alanine transaminase (ALT) levels and attenuated hepatic triglyceride content compared to their alcohol-gavaged control mice. In contrast, deleting TLR4 in myeloid cells did not affect the development of chronic-alcohol induced fatty liver, despite the finding that mice lacking myeloid cell TLR4 had significantly reduced circulating ALT concentrations.

Conclusions

These findings suggest that hepatocyte TLR4 plays an important role in regulating alcohol-induced liver damage and fatty liver disease.

•

Hepatocyte TLR4 ablated mice were protected from both chronic and acute alcohol-induced hepatic triglyceride accumulation.

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Hepatocyte TLR4 ablated mice showed attenuated inflammation in the fat pad and the circulation after chronic alcohol intake.

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Loss of TLR4 in myeloid cells did not affect alcohol-induced development of fatty liver.

Different Sex-Based Responses of Gut Microbiota During the Development of Hepatocellular Carcinoma in Liver-Specific Tsc1-Knockout Mice

Gut microbial dysbiosis is correlated with the development of hepatocellular carcinoma (HCC). Therefore, analyzing the changing patterns in gut microbiota during HCC development, especially before HCC occurrence, is essential for the diagnosis and prevention of HCC based on gut microbial composition. However, these changing patterns in HCC are poorly understood, especially considering the sex differences in HCC incidence and mortality. Here, with an aim to determine the relationship between gut microbiota and HCC development in both sexes, and to screen potential microbial biomarkers for HCC diagnosis, we studied the changing patterns in the gut microbiota from mice of both sexes with liver-specific knockout of Tsc1 (LTsc1KO) that spontaneously developed HCC by 9–10 months of age and compared them to the patterns observed in their wide-type Tsc1^fl/fl cohorts using high-throughput sequencing. Using the LTsc1KO model, we were able to successfully exclude the continuing influence of diet on the gut microbiota. Based on gut microbial composition, the female LTsc1KO mice exhibited gut microbial disorder earlier than male LTsc1KO mice during the development of HCC. Our findings also indicated that the decrease in the relative abundance of anaerobic bacteria and the increase in the relative abundance of facultative anaerobic bacteria can be used as risk indexes of female HCC, but would be invalid for male HCC. Most of the changes in the gut bacteria were different between female and male LTsc1KO mice. In particular, the increased abundances of Allobaculum, Erysipelotrichaceae, Neisseriaceae, Sutterella, Burkholderiales, and Prevotella species have potential for use as risk indicators of female HCC, and the increased abundances of Paraprevotella, Paraprevotellaceae, and Prevotella can probably be applied as risk indicators of male HCC. These relationships between the gut microbiota and HCC discovered in the present study may serve as a platform for the identification of potential targets for the diagnosis and prevention of HCC in the future.

Recovery of ethanol-induced Akkermansia muciniphila depletion ameliorates alcoholic liver disease

OBJECTIVE

Alcoholic liver disease (ALD) is a global health problem with limited therapeutic options. Intestinal barrier integrity and the microbiota modulate susceptibility to ALD. Akkermansia muciniphila, a Gram-negative intestinal commensal, promotes barrier function partly by enhancing mucus production. The aim of this study was to investigate microbial alterations in ALD and to define the impact of A. muciniphila administration on the course of ALD.

DESIGN

The intestinal microbiota was analysed in an unbiased approach by 16S ribosomal DNA (rDNA) sequencing in a Lieber-DeCarli ALD mouse model, and faecal A. muciniphila abundance was determined in a cohort of patients with alcoholic steatohepatitis (ASH). The impact of A. muciniphila on the development of experimental acute and chronic ALD was determined in a preventive and therapeutic setting, and intestinal barrier integrity was analysed.

RESULTS

Patients with ASH exhibited a decreased abundance of faecal A. muciniphila when compared with healthy controls that indirectly correlated with hepatic disease severity. Ethanol feeding of wild-type mice resulted in a prominent decline in A. muciniphila abundance. Ethanol-induced intestinal A. muciniphila depletion could be restored by oral A. muciniphila supplementation. Furthermore, A. muciniphila administration when performed in a preventive setting decreased hepatic injury, steatosis and neutrophil infiltration. A. muciniphila also protected against ethanol-induced gut leakiness, enhanced mucus thickness and tight-junction expression. In already established ALD, A. muciniphila used therapeutically ameliorated hepatic injury and neutrophil infiltration.

CONCLUSION

Ethanol exposure diminishes intestinal A. muciniphila abundance in both mice and humans and can be recovered in experimental ALD by oral supplementation. A. muciniphila promotes intestinal barrier integrity and ameliorates experimental ALD. Our data suggest that patients with ALD might benefit from A. muciniphila supplementation.