Oral bile acids reduce bacterial overgrowth, bacterial translocation, and endotoxemia in cirrhotic rats

Novel prevention strategies for bacterial infections in cirrhosis

INTRODUCTION

Bacterial infections are a serious complication of cirrhosis, as they can lead to decompensation, multiple organ failure, and/or death. Preventing infections is therefore very relevant. Because gut bacterial translocation is their main pathogenic mechanism, prevention of infections is mostly based on the use of orally administered poorly absorbed antibiotics such as norfloxacin (selective intestinal decontamination). However, antibiotic prophylaxis leads to antibiotic resistance, limiting therapy and increasing morbidity and mortality. Prevention of bacterial infections in cirrhosis should therefore move away from antibiotics.

AREAS COVERED

This review focuses on various potentially novel methods to prevent infections in cirrhosis focusing on non-antibiotic strategies. The use of probiotics, nonselective intestinal decontamination with rifaximin, prokinetics and beta-blockers or fecal microbiota transplant as means of targeting altered gut microbiota, bile acids and FXR agonists are all potential alternatives to selective intestinal decontamination. Prokinetics and beta-blockers can improve intestinal motility, while bile acids and FXR agonists help by improving the intestinal barrier. Finally, granulocyte colony stimulating factor (G-CSF) and statins are emerging therapeutic strategies that may improve immune dysfunction in cirrhosis.

EXPERT OPINION

Evidence for these strategies has been restricted to animal studies and proof-of concept studies but we expect this to change in coming years.

Gut epithelial barrier dysfunction in human immunodeficiency virus-hepatitis C virus coinfected patients: Influence on innate and acquired immunity

Even in cases where viral replication has been controlled by antiretroviral therapy for long periods of time, human immunodeficiency virus (HIV)-infected patients have several non-acquired immunodeficiency syndrome (AIDS) related co-morbidities, including liver disease, cardiovascular disease and neurocognitive decline, which have a clear impact on survival. It has been considered that persistent innate and acquired immune activation contributes to the pathogenesis of these non-AIDS related diseases. Immune activation has been related with several conditions, remarkably with the bacterial translocation related with the intestinal barrier damage by the HIV or by hepatitis C virus (HCV)-related liver cirrhosis. Consequently, increased morbidity and mortality must be expected in HIV-HCV coinfected patients. Disrupted gut barrier lead to an increased passage of microbial products and to an activation of the mucosal immune system and secretion of inflammatory mediators, which in turn might increase barrier dysfunction. In the present review, the intestinal barrier structure, measures of intestinal barrier dysfunction and the modifications of them in HIV monoinfection and in HIV-HCV coinfection will be considered. Both pathogenesis and the consequences for the progression of liver disease secondary to gut microbial fragment leakage and immune activation will be assessed.

Targeting gut-liver axis for the treatment of nonalcoholic steatohepatitis: translational and clinical evidence

Nonalcoholic fatty liver disease (NAFLD) is widely emerging as the most prevalent liver disorder and is associated with increased risk of liver-related and cardiovascular mortality. Recent experimental and clinical studies have revealed the pivotal role played by the alteration of gut-liver axis in the onset of fatty liver and related metabolic disturbances. Gut-liver cross talk is implicated not only in the impairment of lipid and glucose homeostasis leading to steatogenesis, but also in the initiation of inflammation and fibrogenesis, which characterize nonalcoholic steatohepatitis (NASH), the evolving form of NAFLD. The gut microbiota has been recognized as the key player in the gut-liver liaison and because of its complexity can act as a villain or a victim. Gut microbiota not only influences absorption and disposal of nutrients to the liver, but also conditions hepatic inflammation by supplying toll-like receptor ligands, which can stimulate liver cells to produce proinflammatory cytokines. Thus, the modification of intestinal bacterial flora by specific probiotics has been proposed as a therapeutic approach for the treatment of NASH. In this review, we summarized the evidence regarding the role of gut-liver axis in the pathogenesis of NASH and discussed the potential therapeutic role of gut microbiota modulation in the clinical setting.

Interactions between the intestinal microbiota and bile acids in gallstones patients

Cholecystectomy, surgical removal of the gallbladder, changes bile flow to the intestine and can therefore alter the bidirectional interactions between bile acids (BAs) and the intestinal microbiota. We quantified and correlated BAs and bacterial community composition in gallstone patients scheduled for cholecystectomy before and after the procedure, using gas-liquid chromatography and 16S rRNA amplicon sequencing, followed by quantitative real-time polymerase chain reaction of the phylum Bacteroidetes. Gallstone patients had higher overall concentrations of faecal BAs and a decreased microbial diversity, accompanied by a reduction in the beneficial genus Roseburia and an enrichment of the uncultivated genus Oscillospira, compared with controls. These two genera may thus serve as biomarkers for symptomatic gallstone formation. Oscillospira was correlated positively with secondary BAs and negatively with primary BAs, while the phylum Bacteroidetes showed an opposite trend. Cholecystectomy resulted in no substantial change in patients' faecal BAs. However, bacterial composition was significantly altered, with a significant increase in the phylum Bacteroidetes. Given that cholecystectomy has been associated with a higher risk of colorectal cancer and that members of the Bacteroidetes are increased in that disease, microbial consequences of cholecystectomy should be further explored.

Gut Microbiota and Host Reaction in Liver Diseases

Although alcohol feeding produces evident intestinal microbial changes in animals, only some alcoholics show evident intestinal dysbiosis, a decrease in Bacteroidetes and an increase in Proteobacteria. Gut dysbiosis is related to intestinal hyperpermeability and endotoxemia in alcoholic patients. Alcoholics further exhibit reduced numbers of the beneficial Lactobacillus and Bifidobacterium. Large amounts of endotoxins translocated from the gut strongly activate Toll-like receptor 4 in the liver and play an important role in the progression of alcoholic liver disease (ALD), especially in severe alcoholic liver injury. Gut microbiota and bacterial endotoxins are further involved in some of the mechanisms of nonalcoholic fatty liver disease (NAFLD) and its progression to nonalcoholic steatohepatitis (NASH). There is experimental evidence that a high-fat diet causes characteristic dysbiosis of NAFLD, with a decrease in Bacteroidetes and increases in Firmicutes and Proteobacteria, and gut dysbiosis itself can induce hepatic steatosis and metabolic syndrome. Clinical data support the above dysbiosis, but the details are variable. Intestinal dysbiosis and endotoxemia greatly affect the cirrhotics in relation to major complications and prognosis. Metagenomic approaches to dysbiosis may be promising for the analysis of deranged host metabolism in NASH and cirrhosis. Management of dysbiosis may become a cornerstone for the future treatment of liver diseases.

The Gut Microbiota as a Therapeutic Target in IBD and Metabolic Disease: A Role for the Bile Acid Receptors FXR and TGR5

The gut microbiota plays a crucial role in regulating many physiological systems of the host, including the metabolic and immune system. Disturbances in microbiota composition are increasingly correlated with disease; however, the underlying mechanisms are not well understood. Recent evidence suggests that changes in microbiota composition directly affect the metabolism of bile salts. Next to their role in digestion of dietary fats, bile salts function as signaling molecules for bile salt receptors such as Farnesoid X receptor (FXR) and G protein-coupled bile acid receptor (TGR5). Complementary to their role in metabolism, FXR and TGR5 are shown to play a role in intestinal homeostasis and immune regulation. This review presents an overview of evidence showing that changes in bile salt pool and composition due to changes in gut microbial composition contribute to the pathogenesis of inflammatory bowel disease and metabolic disease, possibly through altered activation of TGR5 and FXR. We further discuss how dietary interventions, such as pro- and synbiotics, may be used to treat metabolic disease and inflammatory bowel disease (IBD) through normalization of bile acid dysregulation directly or indirectly through normalization of the intestinal microbiota.

Small Intestinal Bacterial Overgrowth Diagnosed by Glucose Hydrogen Breath Test in Post-cholecystectomy Patients

BACKGROUND/AIMS

Patients undergoing cholecystectomy may have small intestinal bacterial overgrowth (SIBO). We investigated the prevalence and characteristics of SIBO in patients with intestinal symptoms following cholecystectomy.

METHODS

Sixty-two patients following cholecystectomy, 145 with functional gastrointestinal diseases (FGIDs), and 30 healthy controls undergoing hydrogen (H2)-methane (CH4) glucose breath test (GBT) were included in the study. Before performing GBT, all patients were interrogated using bowel symptom questionnaire. The positivity to GBT indicating the presence of SIBO, gas types and bowel symptoms were surveyed.

RESULTS

Post-cholecystectomy patients more often had SIBO as evidenced by a positive (+) GBT than those with FGID and controls (29/62, 46.8% vs 38/145, 26.2% vs 4/30, 13.3%, respectively; P = 0.010). In the gas types, the GBT (H2) + post-cholecystectomy patients was significantly higher than those in FGIDs patients (P = 0.017). Especially, positivity to fasting GBT (H2) among the GBT (H2)+ post-cholecystectomy patients was high, as diagnosed by elevated fasting H2 level. The GBT+ group had higher symptom scores of significance or tendency in abdominal discomfort, bloating, chest discomfort, early satiety, nausea, and tenesmus than those of the GBT negative group. The status of cholecystectomy was the only significant independent factor for predicting SIBO.

CONCLUSIONS

The SIBO with high levels of baseline H2 might be the important etiologic factor of upper GI symptoms for post-cholecystectomy patients.

Clinical and pathophysiological consequences of alterations in the microbiome in cirrhosis

Cirrhosis is a major cause of mortality worldwide. Exponential rises in prevalence have been observed secondary to increases in obesity and alcohol consumption. Multiple lines of evidence implicate gut-derived bacteria and bacterial ligands as a central driver of pathogenesis. Recent developments in culture-independent techniques have facilitated a more accurate description of microbiome composition in cirrhosis and led to the description of measures of dysbiosis shown to be associated with disease. More importantly, metagenomic studies are adding to an understanding of the functional contribution of the microbiota and may prove to be a more clinically relevant biomarker than phylogenetic studies. Much like other dysbiotic states such as inflammatory bowel disease, the microbiota in cirrhosis is characterized by a low microbial and genetic diversity. Therapeutic strategies to diminish this process are currently limited to selective intestinal decontamination with antibiotics. This review summarizes the available data and develops a framework for the use of current and future treatment strategies to diminish the consequences of dysbiosis in cirrhosis. Interventional strategies to bind bacterial products in the gut lumen and blood, and modulate the magnitude of host sensing mechanisms remain an unmet clinical need. A greater understanding of the host-microbiota interaction in cirrhosis is of key importance to inform future interventional strategies to diminish the currently escalating burden of the disease.

Role and molecular mechanism of farnesoid X receptor in obstructive jaundice

Obstructive jaundice is a common and frequently occurring disease, which can result in multiple organ dysfunction syndrome in serious conditions due to the abnormal accumulation of bile acids in blood. Farnesoid X receptor (FXR), a nuclear receptor for bile acid, plays a significant role in bile acid metabolism. Recent research demonstrates that FXR also participates in the regulation of the pathological and physiological processes during obstructive jaundice. In this article, we review the latest research about the role and molecular mechanism of FXR in obstructive jaundice, in order to explore new methods and strategies for curing the disease.

Gut-liver axis in liver cirrhosis: How to manage leaky gut and endotoxemia

A “leaky gut” may be the cutting edge for the passage of toxins, antigens or bacteria into the body, and may play a pathogenic role in advanced liver cirrhosis and its complications. Plasma endotoxin levels have been admitted as a surrogate marker of bacterial translocation and close relations of endotoxemia to hyperdynamic circulation, portal hypertension, renal, cardiac, pulmonary and coagulation disturbances have been reported. Bacterial overgrowth, increased intestinal permeability, failure to inactivate endotoxin, activated innate immunity are all likely to play a role in the pathological states of bacterial translocation. Therapeutic approach by management of the gut-liver axis by antibiotics, probiotics, synbiotics, prebiotics and their combinations may improve the clinical course of cirrhotic patients. Special concern should be paid on anti-endotoxin treatment. Adequate management of the gut-liver axis may be effective for prevention of liver cirrhosis itself by inhibiting the progression of fibrosis.

Bile acid nuclear receptor FXR and digestive system diseases

Bile acids (BAs) are not only digestive surfactants but also important cell signaling molecules, which stimulate several signaling pathways to regulate some important biological processes. The bile-acid-activated nuclear receptor, farnesoid X receptor (FXR), plays a pivotal role in regulating bile acid, lipid and glucose homeostasis as well as in regulating the inflammatory responses, barrier function and prevention of bacterial translocation in the intestinal tract. As expected, FXR is involved in the pathophysiology of a wide range of diseases of gastrointestinal tract, including inflammatory bowel disease, colorectal cancer and type 2 diabetes. In this review, we discuss current knowledge of the roles of FXR in physiology of the digestive system and the related diseases. Better understanding of the roles of FXR in digestive system will accelerate the development of FXR ligands/modulators for the treatment of digestive system diseases.

VSL#3 probiotic treatment decreases bacterial translocation in rats with carbon tetrachloride-induced cirrhosis

BACKGROUND & AIMS

Probiotics can prevent pathological bacterial translocation in cirrhosis by modulating intestinal microbiota and improving gut barrier and immune disturbances. To evaluate the effect of probiotic VSL#3 on bacterial translocation, intestinal microbiota, gut barrier and inflammatory response in rats with experimental cirrhosis.

METHODS

Forty-six Sprague-Dawley rats with CCl4 -induced cirrhosis were randomized into two groups: VSL#3 group (n = 22) that received VSL#3 in drinking water, and water group (n = 24) that received water only. Treatment began at week 6 of cirrhosis induction and continued until laparotomy, performed 1 week after development of ascites or at week 20. A control group included 11 healthy rats. At this study end, we evaluated bacterial translocation, intestinal flora, intestinal barrier (ileal claudin-2 and 4, β-defensin-1, occludin and malondialdehyde as index of oxidative damage) and serum cytokines.

RESULTS

Mortality during this study was similar in the VSL#3 group (10/22, 45%) and the water group (10/24, 42%) (P = 1). The incidence of bacterial translocation was 1/12 (8%) in the VSL#3 group, 7/14 (50%) in the water group (P = 0.03 vs. VSL#3 group) and 0/11 in the control group (P = 0.008 vs. water group). The concentration of ileal and caecal enterobacteria and enterococci was similar in the two groups of cirrhotic rats. The ileal occludin concentration was higher and ileal malondialdehyde and serum levels of TNF-α were lower in the VSL#3 group than in the water group (P < 0.05).

CONCLUSIONS

VSL#3 decreases bacterial translocation, the pro-inflammatory state and ileal oxidative damage and increases ileal occludin expression in rats with experimental cirrhosis.

Bile acid malabsorption in inflammatory bowel disease

Bile acid malabsorption (BAM) is a common but an underestimated and often neglected sign of inflammatory bowel diseases (IBDs), especially those affecting the distal ileum. Clinically relevant BAM is most often present in patients with Crohn's ileitis and particularly in ileal-resected Crohn's disease patients. However, deterioration of bile acid (BA) metabolism occurs also in patients with IBD without ileal disease or in those in clinical remission, and the role of BAM in these patients is not well appreciated by clinicians. In a majority of cases, BAM in IBD is caused by impaired conjugated BA reabsorption, mediated by apical sodium/BA cotransporting polypeptide, localized at the luminal surface of the ileal enterocytes. As a consequence, numerous pathological sequelae may occur, including the malfunction of lipid digestion with clinical steatorrhea, impaired intestinal motility, and/or significant changes in the intestinal microflora environment. In this review, a detailed description of the pathophysiological mechanisms of BAM-related diarrhea is presented. Although BAM is present in a significant number of patients with Crohn's disease, its laboratory assessment is not routinely included in diagnostic workups, partially because of costs, logistical reasons, or the unavailability of the more sophisticated laboratory equipment needed. Simultaneously, novel findings related to the effects of the BA signaling pathways on immune functions (mediated through TGR5, cell membrane G protein-coupled BA receptor 1, nuclear farnesoid X receptor, nuclear pregnane X receptor, or nuclear vitamin D receptor) are discussed along with intestinal metabolism in its relationship to the pathogenesis of IBD.

Bile acid signaling through farnesoid X and TGR5 receptors in hepatobiliary and intestinal diseases

BACKGROUND

The well-known functions of bile acids (BAs) are the emulsification and absorption of lipophilic xenobiotics. However, the emerging evidences in the past decade showed that BAs act as signaling molecules that not only autoregulate their own metabolism and enterohepatic recirculation, but also as important regulators of integrative metabolism by activating nuclear and membrane-bound G protein-coupled receptors. The present review was to get insight into the role of maintenance of BA homeostasis and BA signaling pathways in development and management of hepatobiliary and intestinal diseases.

DATA SOURCES

Detailed and comprehensive search of PubMed and Scopus databases was carried out for original and review articles.

RESULTS

Disturbances in BA homeostasis contribute to the development of several hepatobiliary and intestinal disorders, such as non-alcoholic fatty liver disease, liver cirrhosis, cholesterol gallstone disease, intestinal diseases and both hepatocellular and colorectal carcinoma.

CONCLUSION

Further efforts made in order to advance the understanding of sophisticated BA signaling network may be promising in developing novel therapeutic strategies related not only to hepatobiliary and gastrointestinal but also systemic diseases.

Effect of probiotic supplementation on bacterial translocation in common bile duct obstruction

OBJECTIVE

To investigate the effects of probiotics on bacterial translocation in the obstructive common bile duct with comparison to an enteral product containing arginine and glutamine.

MATERIAL AND METHOD

In our study, 40 Sprague-Dawley rats each weighing 250-300 g were used. Animals in Group 1 (sham) were laparatomized and fed standard chow supplemented with physiologic saline at daily doses of 2 ml through orogastric tube for 7 days. Common bile ducts of the animals in the other groups were ligated with 3/0 silk sutures. Group 2 (control group) was fed standard chow supplemented with daily doses of 2 ml physiologic saline. Group 3 (probiotic group) was fed standard chow supplemented with a probiotic solution (Acidophilus plus) containing strains of Lactobacillus acidophilus, Bifidobacterium bifidum and Lactobacillus bulgaricus at a daily doses of 2 × 10(9) colony forming units (CFU). Group 4 (formula group) was fed only an enteral solution (Stresson Multi Fiber) containing glutamine, arginine and a medium-chain fatty acid at daily doses of 2 g/kg. At the end of the 7th day, all animals were relaparatomized, and to determine bacterial translocation, aerobic, and anaerobic cultures were obtained from the specimens of mesenteric lymph nodes, intestinal mucosa, and blood samples. Smear cultures prepared from caecum were examined to determine the number of CFU. Finally, for histological examination specimens were excised from terminal ileum, and oxidative damage was assessed in liver tissues. Afterwards all animals were killed.

RESULTS

Moderately lesser degrees of bacterial translocation, and mucosal damage were seen in Groups 3, and 4 relative to Group 2 (p < 0.05). In Group 4, any difference was not seen in the number of cecal bacteria relative to baseline values, while in Group 3, significant decrease in cecal colonization was seen. Among all groups, a significant difference between levels of malondialdehyde, and glutathione was not observed.

CONCLUSION

At the end of our study, we have concluded that both probiotics, and enteral diets which contain immunomodulators such as glutamine, and arginine alleviate bacterial translocation, and impairment of intestinal mucosa.

The role of intestinal bacteria overgrowth in obesity-related nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease worldwide. It is a progressive disorder involving a spectrum of conditions that include pure steatosis without inflammation, nonalcoholic steatohepatitis (NASH), fibrosis and cirrhosis. The key factor in the pathophysiology of NAFLD is insulin resistance that determines lipid accumulation in the hepatocytes, which may be followed by lipid peroxidation, production of reactive oxygen species and consequent inflammation. Recent studies suggest that the characteristics of the gut microbiota are altered in NAFLD, and also, that small intestinal bacterial overgrowth (SIBO) contributes to the pathogenesis of this condition. This review presents the chief findings from all the controlled studies that evaluated SIBO, gut permeability and endotoxemia in human NAFLD. We also discuss the possible mechanisms involving SIBO, lipid accumulation and development of NASH. The understanding of these mechanisms may allow the development of new targets for NASH treatment in the future.

Prostaglandin F₂α modulates atrial chronotropic hyporesponsiveness to cholinergic stimulation in endotoxemic rats

Endotoxemia induces various physiological adaptive responses such as tachycardia. There is evidence to show that inflammatory tachycardia might be linked to a direct action of prostanoids on the cardiac pacemaker cells. Recent reports have indicated that systemic inflammation may uncouple of cardiac pacemaker from cholinergic neural control in experimental animals; however, the exact mechanism of this phenomenon is uncertain. This study was aimed to explore the hypothesis that prostanoids modulate atrial chronotropic hyporesponsiveness to cholinergic stimulation in endotoxemic rats. Male albino rats were given intraperitoneal injection of either saline or lipopolysaccharide (LPS, 1 mg/kg). 3 h after saline or LPS injection, the atria were isolated and chronotropic responsiveness to cholinergic stimulation was evaluated in an organ bath. The expression of atrial cyclooxygenases (COX)-1, COX-2 and COX-3 mRNA was assessed by quantitative real-time RT-PCR and cytosocalcium-dependent phospholipase A₂ (cPLA₂) activity was measured in the atria. The expression of atrial COX-2 mRNA and cPLA₂ activity increased significantly in endotoxemic atria (P<0.05). Incubation with prostaglandin F₂α (PGF₂α, 100 pM) could significantly decrease chronotropic response to cholinergic stimulation in vitro. Likewise, LPS injection could induce a significant hyporesponsiveness to cholinergic stimulation, and incubation of isolated atria with either indomethacin (5 µM) or AL-8810 (a PGF₂α antagonist, 10 µM) could reverse it (P<0.01, P<0.05, respectively), while SQ29548 (a thromboxane A₂ antagonist, 10 nM) was failed (P>0.05). Our data showed that PGF₂α may contribute to the atrial chronotropic hyporesponsiveness to cholinergic stimulation in endotoxemic rats.

Intestinal transport and metabolism of bile acids

In addition to their classical roles as detergents to aid in the process of digestion, bile acids have been identified as important signaling molecules that function through various nuclear and G protein-coupled receptors to regulate a myriad of cellular and molecular functions across both metabolic and nonmetabolic pathways. Signaling via these pathways will vary depending on the tissue and the concentration and chemical structure of the bile acid species. Important determinants of the size and composition of the bile acid pool are their efficient enterohepatic recirculation, their host and microbial metabolism, and the homeostatic feedback mechanisms connecting hepatocytes, enterocytes, and the luminal microbiota. This review focuses on the mammalian intestine, discussing the physiology of bile acid transport, the metabolism of bile acids in the gut, and new developments in our understanding of how intestinal metabolism, particularly by the gut microbiota, affects bile acid signaling.

Design and evaluation of a novel trifluorinated imaging agent for assessment of bile acid transport using fluorine magnetic resonance imaging

Previously, we developed a trifluorinated bile acid, CA-lys-TFA, with the objective of noninvasively assessing bile acid transport in vivo using (19) F magnetic resonance imaging (MRI). CA-lys-TFA was successfully imaged in the mouse gallbladder, but was susceptible to deconjugation in vitro by choloylglycine hydrolase (CGH), a bacterial bile acid deconjugating enzyme found in the terminal ileum and colon. The objective of the present study was to develop a novel trifluorinated bile acid resistant to deconjugation by CGH. CA-sar-TFMA was designed, synthesized, and tested for in vitro transport properties, stability, imaging properties, and its ability to differentially accumulate in the gallbladders of normal mice, compared with mice with known impaired bile acid transport (deficient in the apical sodium-dependent bile acid transporter, ASBT). CA-sar-TFMA was a potent inhibitor and substrate of ASBT and the Na(+) /taurocholate cotransporting polypeptide. Stability was favorable in all conditions tested, including the presence of CGH. CA-sar-TFMA was successfully imaged and accumulated at 16.1-fold higher concentrations in gallbladders from wild-type mice compared with those from Asbt-deficient mice. Our results support the potential of using MRI with CA-sar-TFMA as a noninvasive method to assess bile acid transport in vivo.

Bacterial infections in cirrhosis: a position statement based on the EASL Special Conference 2013

Bacterial infections are very common and represent one of the most important reasons of progression of liver failure, development of liver-related complications, and mortality in patients with cirrhosis. In fact, bacterial infections may be a triggering factor for the occurrence of gastrointestinal bleeding, hypervolemic hyponatremia, hepatic encephalopathy, kidney failure, and development of acute-on-chronic liver failure. Moreover, infections are a very common cause of repeated hospitalizations, impaired health-related quality of life, and increased healthcare costs in cirrhosis. Bacterial infections develop as a consequence of immune dysfunction that occurs progressively during the course of cirrhosis. In a significant proportion of patients, infections are caused by gram-negative bacteria from intestinal origin, yet gram-positive bacteria are a frequent cause of infection, particularly in hospitalized patients. In recent years, infections caused by multidrug-resistant bacteria are becoming an important clinical problem in many countries. The reduction of the negative clinical impact of infections in patients with cirrhosis may be achieved by a combination of prophylactic measures, such as administration of antibiotics, to reduce the occurrence of infections in high-risk groups together with early identification and management of infection once it has developed. Investigation on the mechanisms of altered gut microflora, translocation of bacteria, and immune dysfunction may help develop more effective and safe methods of prevention compared to those that are currently available. Moreover, research on biomarkers of early infection may be useful in early diagnosis and treatment of infections. The current manuscript reports an in-depth review and a position statement on bacterial infections in cirrhosis.

Interactions between the intestinal microbiome and liver diseases

The human intestine harbors a diverse community of microbes that promote metabolism and digestion in their symbiotic relationship with the host. Disturbance of its homeostasis can result in disease. We review factors that disrupt intestinal homeostasis and contribute to nonalcoholic fatty liver disease, steatohepatitis, alcoholic liver disease, and cirrhosis. Liver disease has long been associated with qualitative and quantitative (overgrowth) dysbiotic changes in the intestinal microbiota. Extrinsic factors, such as the Western diet and alcohol, contribute to these changes. Dysbiosis results in intestinal inflammation, a breakdown of the intestinal barrier, and translocation of microbial products in animal models. However, the contribution of the intestinal microbiome to liver disease goes beyond simple translocation of bacterial products that promote hepatic injury and inflammation. Microbial metabolites produced in a dysbiotic intestinal environment and host factors are equally important in the pathogenesis of liver disease. We review how the combination of liver insult and disruptions in intestinal homeostasis contribute to liver disease.

Bile salts act as effective protein-unfolding agents and instigators of disulfide stress in vivo

Commensal and pathogenic bacteria must deal with many different stress conditions to survive in and colonize the human gastrointestinal tract. One major challenge that bacteria encounter in the gut is the high concentration of bile salts, which not only aid in food absorption but also act as effective physiological antimicrobials. The mechanism by which bile salts limit bacterial growth is still largely unknown. Here, we show that bile salts cause widespread protein unfolding and aggregation, affecting many essential proteins. Simultaneously, the bacterial cytosol becomes highly oxidizing, indicative of disulfide stress. Strains defective in reducing oxidative thiol modifications, restoring redox homeostasis, or preventing irreversible protein aggregation under disulfide stress conditions are sensitive to bile salt treatment. Surprisingly, cholate and deoxycholate, two of the most abundant and very closely related physiological bile salts, vary substantially in their destabilizing effects on proteins in vitro and cause protein unfolding of different subsets of proteins in vivo. Our results provide a potential mechanistic explanation for the antimicrobial effects of bile salts, help explain the beneficial effects of bile salt mixtures, and suggest that we have identified a physiological source of protein-unfolding disulfide stress conditions in bacteria.

Risk factors and outcome of bacterial infections in cirrhosis

Viable and non-viable pathological bacterial translocation promote a self-perpetuating circle of dysfunctional immune activation and systemic inflammation facilitating infections and organ failure in advanced cirrhosis. Bacterial infections and sepsis are now recognized as a distinct stage in the natural progression of chronic liver disease as they accelerate organ failure and contribute to the high mortality observed in decompensated cirrhosis. The increasing knowledge of structural, immunological and hemodynamic pathophysiology in advanced cirrhosis has not yet translated into significantly improved outcomes of bacterial infections over the last decades. Therefore, early identification of patients at the highest risk for developing infections and infection-related complications is required to tailor the currently available measures of surveillance, prophylaxis and therapy to the patients in need in order to improve the detrimental outcome of bacterial infections in cirrhosis.

Effect of treatment with compound Lactobacillus acidophilus on complements and T lymphocyte subsets in patients with compensated liver cirrhosis

AIM: To explore the effect of early oral compound Lactobacillus acidophilus on complements and T lymphocyte subsets in patients with compensated liver cirrhosis.

METHODS: Sixty-six patients with compensated liver cirrhosis were randomly divided into either a control group or a treatment group. The control group received conventional symptomatic treatment, while the treatment group was treated with compound Lactobacillus acidophilus (1.0 g, three times per day) for 12 wk on the basis of conventional symptomatic treatment. The changes in serum complements and T lymphocyte subsets between before and after treatment were observed and compared between the two groups of patients.

RESULTS: After treatment, the levels of complements C3 and C4 (0.97 g/L ± 0.16 g/L vs 0.85 g/L ± 0.24 g/L, 0.22 g/L ± 0.05 g/L vs 0.15 g/L ± 0.07 g/L, both P < 0.05) and the percentages of CD4⁺ and CD4⁺/CD8⁺ T lymphocyte subsets (37.9% ± 6.5% vs 33.8% ± 8.6%, 1.6% ± 0.5% vs 1.3% ± 0.7%, both P < 0.05) were significantly increased in the treatment group.

CONCLUSION: Oral compound Lactobacillus acidophilus can regulate intestinal flora imbalance and modulate immunity in patients with compensated liver cirrhosis.

Metabolomic analyses of faeces reveals malabsorption in cirrhotic patients

BACKGROUND

The study of faeces offers a unique opportunity to observe cooperation between the microbiome and the metabolism of mammalian hosts, an essential element in the study of the human metabolome. In the present study, a global metabolomics approach was used to identify metabolites differentially excreted in the faeces of cirrhotic patients compared to controls.

METHODS

Seventeen cirrhotic patients and 24 healthy individuals were recruited. Faecal metabolites were detected through non-targeted reversed-phase ultra-performance liquid chromatography coupled to electrospray ionization quadrupole time-of-flight mass spectrometry.

RESULTS

A total of 9215 peaks were detected. Using unequal variance t-tests, 2393 peaks were observed with P≤0.05, approximately 74.0% of which were due to decreased faecal metabolite concentrations in liver cirrhosis vs. healthy controls. Integrating multivariate data analyses, we identified six major groups of metabolites. Relative levels of identified metabolites were as follows: strong increase in lysophosphatidylcholines, aromatic amino acids, fatty acids, and acylcarnitines, and a dramatic decrease in bile acids and bile pigments.

CONCLUSION

With severe hepatic injury in patients with liver cirrhosis, malabsorption occurs along with disorders of fatty acid metabolism, potentially due to changes in gut microflora.

Targeting the gut-liver axis in cirrhosis: antibiotics and non-selective β-blockers

The gut-liver axis in cirrhosis and portal hypertension is gaining increasing attention as a key pathophysiological mechanism responsible for progression of liver failure and development of complications such as spontaneous infections and hepatocellular carcinoma. Antibiotics and non-selective β-blockers (NSBB) intercept this axis and each drug has proven efficacy in clinical trials. A synergistic effect is a hitherto unproven possibility. There is an increasing body of evidence supporting improved outcome with expanded use of NSBB and antibiotic therapy beyond current indications. This review addresses the issue of pharmacological treatment of cirrhosis and portal hypertension with antibiotics and NSBB. We discuss their mechanism of action and suggest that combining the two treatment modalities could potentially reduce the risk of complications.

Nuclear receptors as drug targets in cholestatic liver diseases

Cholestatic liver diseases encompass a wide spectrum of disorders with different causes, resulting in impaired bile flow and accumulation of bile acids and other potentially hepatotoxic cholephils. The understanding of the molecular mechanisms of bile formation and cholestasis has recently improved significantly through new insights into nuclear receptor (patho)biology. Nuclear receptors are ligand-activated transcription factors, which act as central players in the regulation of genes responsible for elimination and detoxification of biliary constituents accumulating in cholestasis. They also control other pathophysiologic processes such as inflammation, fibrogenesis, and carcinogenesis involved in the pathogenesis and disease progression of cholestasis liver diseases.

A review of enteral strategies in infant short bowel syndrome: evidence-based or NICU culture?

INTRODUCTION

Short bowel syndrome (SBS) is an increasingly common condition encountered across neonatal intensive care units. Improvements in parenteral nutrition (PN), neonatal intensive care and surgical techniques, in addition to an improved understanding of SBS pathophysiology, have contributed in equal parts to the survival of this fragile subset of infants. Prevention of intestinal failure associated liver disease (IFALD) and promotion of intestinal adaptation are primary goals of all involved in the care of these patients. While enteral nutritional and pharmacological strategies are necessary to achieve these goals, there remains great variability in the application of therapeutic strategies in units that are not necessarily evidence-based.

MATERIALS AND METHODS

A search of major English language medical databases (SCOPUS, Index Medicus, Medline, and the Cochrane database) was conducted for the key words short bowel syndrome, medical management, nutritional management and intestinal adaptation. All pharmacological and nutritional agents encountered in the literature search were classified based on their effects on absorptive capacity, intestinal adaptation and bowel motility that are the three major strategies employed in the management of SBS. The Oxford Center for Evidence-Based Medicine (CEBM) classification for levels of evidence was used to develop grades of clinical recommendation for each variable studied.

RESULTS

We reviewed various medications used and nutritional strategies included soluble fiber, enteral fat, glutamine, probiotics and sodium supplementation. Most interventions have scientific rationale but little evidence to support their role in the management of infant SBS. While some of these agents symptomatically improve diarrhea, they can adversely influence pancreatico-biliary function or actually impair intestinal adaptation. Surgical anatomy and liver function are two important variables that should determine the selection of pharmacological and nutritional interventions.

DISCUSSION

There is a paucity of research investigating optimal clinical practice in infant SBS and the little evidence available is consistently of lower quality, resulting in a wide variation of clinical practices among NICUs. Prospective trials should be encouraged to bridge the evidence gap between research and clinical practice to promote further progress in the field.

Bile acid-induced expression of farnesoid X receptor as the basis for superiority of internal biliary drainage in experimental biliary obstruction

AIMS AND OBJECTIVES

The aim is to determine the efficacy of internal and external biliary drainage (ED) with special reference to the effect of bile acid on intestinal epithelium during experimental biliary obstruction. Methods. A total of 59 male Sprague Dawley rats were randomly assigned to four groups: (I) sham operation (SH); (II) obstructive jaundice (OJ); (III) OJ and ED; and (IV) OJ and internal biliary drainage (ID). The animals underwent surgical ligation of the bile duct on day 1. They were reoperated on day 8 for biliary drainage procedure. Blood cultures were obtained from portal vein and inferior vena cava on day 15. Samples were also drawn for serum total bile acid (TBA) and white blood cell (WBC) counts. The terminal ileum was harvested to study the tight junction-associated protein ("occludin") and bile acid receptor ("farnesoid X receptor" [FXR]) using immunohistochemical method.

RESULTS

Serum TBA (118.9 ± 39.0 μmol/L) and WBC (11.4 ± 2.7 × 10(9)/L) were significantly increased (p = 0.001) after bile duct ligation as compared with SH rats (38.0 ± 15.0 μmol/L and 5.5 ± 1.0 × 10(9)/L, respectively; p = 0.001). The resulting mucosal lesion was high grade and the expressions of FXR and Occludin were decreased. After ED, there was slight decrease in total WBCs, whereas TBA levels declined significantly. The expression of FXR was minimal and Occludin showed no change (ED vs. OJ: p = 0.533). However, both WBC and TBA decreased after ID. The ileal structure, grade of mucosal lesion, and expression of FXR/Occludin were comparable with SH group (p > 0.05). The rate of bacterial translocation was: 57.1% (OJ); 62.5% (ID); and 80% (ED) with identical strains in cultures from the portal vein and inferior vena cava.

CONCLUSION

Downregulation of TBA/FXR expression during biliary obstruction results in damage to intestinal epithelium. Unlike ED, ID restores FXR/Occludin expression in the terminal ileum through reappearance of intestinal bile acid, which thus appears to be a key factor in maintaining integrity of the epithelial barrier.

Microbial biotransformations of bile acids as detected by electrospray mass spectrometry

Many current experiments investigating the effects of diet, dietary supplements, and pre- and probiotics on the intestinal environments do not take into consideration the potential for using bile salts as markers of environmental change. Intestinal bacteria in vertebrates can metabolize bile acids into a number of different structures, with deamidation, hydroxyl group oxidation, and hydroxyl group elimination. Fecal bile acids are readily available to sample and contain a considerable structural complexity that directly relates to intestinal morphology, bile acid residence time in the intestine, and the species of microbial forms in the intestinal tract. Here we offer a classification scheme that can serve as an initial guide to interpret the different bile acid patterns expressed in vertebrate feces.

Pathological bacterial translocation in cirrhosis: pathophysiology, diagnosis and clinical implications

Bacterial translocation (BT) is defined by the passage of viable indigenous bacteria from the intestinal lumen to mesenteric lymph nodes (MLNs) and other territories, and its diagnostic criteria rely on the isolation of viable bacteria in MLNs. Small intestinal overgrowth, increased intestinal permeability and immunological alterations are the main factors involved in its pathogenesis. BT is obviously difficult to identify in patients with cirrhosis, and alternative methods have been proposed instead. Bacterial DNA detection and species identification in serum or ascitic fluid has been proposed as a reliable marker of BT. Bacterial products, such as endotoxin, or bacterial DNA can translocate to extra-intestinal sites and promote an immunological response similar to that produced by viable bacteria. Therefore, pathological BT plays an important role in the pathogenesis of the complications of cirrhosis, not only in infections, but by exerting a profound inflammatory state and exacerbating the haemodynamic derangement. This may promote in turn the development of hepatorenal syndrome, hepatic encephalopathy and other portal hypertension-related complications. Therapeutic approaches for the prevention of BT in experimental and human cirrhosis are summarized. Finally, new investigations are needed to better understand the pathogenesis and consequences of translocation by viable bacteria (able to grow in culture), or non-viable BT (detection of bacterial fragments with negative culture) and open new therapeutic avenues in patients with cirrhosis.

The intestinal microbiome and the leaky gut as therapeutic targets in alcoholic liver disease

Alcoholic liver disease (ALD) encompasses hepatic steatosis, which may progress to alcoholic hepatitis, fibrosis, and cirrhosis. It remains a leading cause of morbidity and mortality in the US and worldwide. The severity of liver disease correlates with plasma levels of bacterial products in patients, and experimental ALD depends on the level of gut derived bacterial products in rodents. Since intestinal decontamination and deficiency of bacterial product receptors or their downstream signaling molecules protect from alcohol-induced liver disease, bacterial translocation (BT), qualitative, and quantitative changes of the enteric microbiome are considered as being of fundamental importance in the pathogenesis of ALD. Recent enhancements in diagnostic technologies provide a better insight into these shifts. This review highlights vital events in ALD such as BT, the importance of Toll-like receptor (TLR) signaling, intestinal bacterial overgrowth (IBO), and changes in the intestinal microbiome. Furthermore, a treatment trial section of patients reviews possible future options of therapy for ALD modifying the enteric microbiome.

Dipeptidyl peptidase IV inhibition potentiates amino acid- and bile acid-induced bicarbonate secretion in rat duodenum

Intestinal endocrine cells release gut hormones, including glucagon-like peptides (GLPs), in response to luminal nutrients. Luminal L-glutamate (L-Glu) and 5'-inosine monophosphate (IMP) synergistically increases duodenal HCO3- secretion via GLP-2 release. Since L cells express the bile acid receptor TGR5 and dipeptidyl peptidase (DPP) IV rapidly degrades GLPs, we hypothesized that luminal amino acids or bile acids stimulate duodenal HCO3- secretion via GLP-2 release, which is enhanced by DPPIV inhibition. We measured HCO3- secretion with pH and CO2 electrodes using a perfused rat duodenal loop under isoflurane anesthesia. L-Glu (10 mM) and IMP (0.1 mM) were luminally coperfused with or without luminal perfusion (0.1 mM) or intravenous (iv) injection (3 μmol/kg) of the DPPIV inhibitor NVP728. The loop was also perfused with a selective TGR5 agonist betulinic acid (BTA, 10 μM) or the non-bile acid type TGR5 agonist 3-(2-chlorophenyl)-N-(4-chlorophenyl)-N,5-dimethylisoxazole-4-carboxamide (CCDC; 10 μM). DPPIV activity visualized by use of the fluorogenic substrate was present on the duodenal brush border and submucosal layer, both abolished by the incubation with NVP728 (0.1 mM). An iv injection of NVP728 enhanced L-Glu/IMP-induced HCO3- secretion, whereas luminal perfusion of NVP728 had no effect. BTA or CCDC had little effect on HCO3- secretion, whereas NVP728 iv markedly enhanced BTA- or CCDC-induced HCO3- secretion, the effects inhibited by a GLP-2 receptor antagonist. Coperfusion of the TGR5 agonist enhanced L-Glu/IMP-induced HCO3- secretion with the enhanced GLP-2 release, suggesting that TGR5 activation amplifies nutrient sensing signals. DPPIV inhibition potentiated luminal L-Glu/IMP-induced and TGR5 agonist-induced HCO3- secretion via a GLP-2 pathway, suggesting that the modulation of the local concentration of the endogenous secretagogue GLP-2 by luminal compounds and DPPIV inhibition helps regulate protective duodenal HCO3- secretion.

Potential mechanisms for the emerging link between obesity and increased intestinal permeability

Recently, increased attention has been paid to the link between gut microbial composition and obesity. Gut microbiota is a source of endotoxins whose increase in plasma is related to obesity and insulin resistance through increased intestinal permeability in animal models; however, this relationship still needs to be confirmed in humans. That intestinal permeability is subject to change and that it might be the interface between gut microbiota and endotoxins in the core of metabolic dysfunctions reinforce the need to understand the mechanisms involved in these aspects to direct more efficient therapeutic approaches. Therefore, in this review, we focus on the emerging link between obesity and increased intestinal permeability, including the possible factors that contribute to increased intestinal permeability in obese subjects. We address the concept of intestinal permeability, how it is measured, and the intestinal segments that may be affected. We then describe 3 factors that may have an influence on intestinal permeability in obesity: microbial dysbiosis, dietary pattern (high-fructose and high-fat diet), and nutritional deficiencies. Gaps in the current knowledge of the role of Toll-like receptors ligands to induce insulin resistance, the routes for lipopolysaccharide circulation, and the impact of altered intestinal microbiota in obesity, as well as the limitations of current permeability tests and other potential useful markers, are discussed. More studies are needed to reveal how changes occur in the microbiota. The factors such as changes in the dietary pattern and the improvement of nutritional deficiencies appear to influence intestinal permeability, and impact metabolism must be examined. Also, additional studies are necessary to better understand how probiotic supplements, prebiotics, and micronutrients can improve stress-induced gastrointestinal barrier dysfunction and the influence these factors have on host defense. Hence, the topics presented in this review may be beneficial in directing future studies that assess gut barrier function in obesity.

The impact of farnesoid X receptor activation on intestinal permeability in inflammatory bowel disease

The most important function of the intestinal mucosa is to form a barrier that separates luminal contents from the intestine. Defects in the intestinal epithelial barrier have been observed in several intestinal disorders such as inflammatory bowel disease (IBD). Recent studies have identified a number of factors that contribute to development of IBD including environmental triggers, genetic factors, immunoregulatory defects and microbial exposure. The current review focuses on the influence of the farnesoid X receptor (FXR) on the inhibition of intestinal inflammation in patients with IBD. The development and investigation of FXR agonists provide strong support for the regulatory role of FXR in mucosal innate immunity. Activation of FXR in the intestinal tract decreases the production of proinflammatory cytokines such as interleukin (IL) 1-beta, IL-2, IL-6, tumour necrosis factor-alpha and interferon-gamma, thus contributing to a reduction in inflammation and epithelial permeability. In addition, intestinal FXR activation induces the transcription of multiple genes involved in enteroprotection and the prevention of bacterial translocation in the intestinal tract. These data suggest that FXR agonists are potential candidates for exploration as a novel therapeutic strategy for IBD in humans.

Microbial translocation in chronic liver diseases

The intestinal microflora is not only involved in the digestion of nutrients, but also in local immunity, forming a barrier against pathogenic microorganisms. The derangement of the gut microflora may lead to microbial translocation, defined as the passage of viable microorganisms or bacterial products (i.e., LPS, lipopeptides) from the intestinal lumen to the mesenteric lymph nodes and other extraintestinal sites. The most recent evidence suggests that microbial translocation (MT) may occur not only in cirrhosis, but also in the early stage of several liver diseases, including alcoholic hepatopathy and nonalcoholic fatty liver disease. Different mechanisms, such as small intestinal bacterial overgrowth, increased permeability of intestinal mucosa, and impaired immunity, may favor MT. Furthermore, MT has been implicated in the pathogenesis of the complications of cirrhosis, which are a significant cause of morbidity and mortality in cirrhotic subjects. Therapeutic strategies aiming at modulating the gut microflora and reducing MT have focused on antibiotic-based options, such as selective intestinal decontamination, and nonantibiotic-based options, such as prokinetics and probiotics. In particular, probiotics may represent an attractive strategy, even though the promising results of experimental models and limited clinical studies need to be confirmed in larger randomized trials.

Enteropathogenic Escherichia coli inhibits ileal sodium-dependent bile acid transporter ASBT

Apical sodium-dependent bile acid transporter (ASBT) is responsible for the absorption of bile acids from the intestine. A decrease in ASBT function and expression has been implicated in diarrhea associated with intestinal inflammation. Whether infection with pathogenic microorganisms such as the enteropathogenic Escherichia coli (EPEC) affect ASBT activity is not known. EPEC is a food-borne enteric pathogen that translocates bacterial effector molecules via type three secretion system (TTSS) into host cells and is a major cause of infantile diarrhea. We investigated the effects of EPEC infection on ileal ASBT function utilizing human intestinal Caco2 cells and HEK-293 cells stably transfected with ASBT-V5 fusion protein (2BT cells). ASBT activity was significantly inhibited following 60 min infection with EPEC but not with nonpathogenic E. coli. Mutations in bacterial escN, espA, espB, and espD, the genes encoding for the elements of bacterial TTSS, ablated EPEC inhibitory effect on ASBT function. Furthermore, mutation in the bacterial BFP gene encoding for bundle-forming pili abrogated the inhibition of ASBT by EPEC, indicating the essential role for bacterial aggregation and the early attachment. The inhibition by EPEC was associated with a significant decrease in the V(max) of the transporter and a reduction in the level of ASBT on the plasma membrane. The inhibition of ASBT by EPEC was blocked in the presence of protein tyrosine phosphatase inhibitors. Our studies provide novel evidence for the alterations in the activity of ASBT by EPEC infection and suggest a possible effect for EPEC in influencing intestinal bile acid homeostasis.

Influence of a high-fat diet on gut microbiota, intestinal permeability and metabolic endotoxaemia

Lipopolysaccharide (LPS) may play an important role in chronic diseases through the activation of inflammatory responses. The type of diet consumed is of major concern for the prevention and treatment of these diseases. Evidence from animal and human studies has shown that LPS can diffuse from the gut to the circulatory system in response to the intake of high amounts of fat. The method by which LPS move into the circulatory system is either through direct diffusion due to intestinal paracellular permeability or through absorption by enterocytes during chylomicron secretion. Considering the impact of metabolic diseases on public health and the association between these diseases and the levels of LPS in the circulatory system, this review will mainly discuss the current knowledge about high-fat diets and subclinical inflammation. It will also describe the new evidence that correlates gut microbiota, intestinal permeability and alkaline phosphatase activity with increased blood LPS levels and the biological effects of this increase, such as insulin resistance. Although the majority of the studies published so far have assessed the effects of dietary fat, additional studies are necessary to deepen the understanding of how the amount, the quality and the structure of the fat may affect endotoxaemia. The potential of food combinations to reduce the negative effects of fat intake should also be considered in future studies. In these studies, the effects of flavonoids, prebiotics and probiotics on endotoxaemia should be investigated. Thus, it is essential to identify dietetic strategies capable of minimising endotoxaemia and its postprandial inflammatory effects.

Effects of pentoxifylline on intestinal bacterial overgrowth, bacterial translocation and spontaneous bacterial peritonitis in cirrhotic rats with ascites

BACKGROUND

Prophylaxis of spontaneous bacterial peritonitis with norfloxacin has been associated to development of antibiotic resistance. We investigated whether pentoxifylline compared to norfloxacin reduces bacterial translocation and spontaneous bacterial peritonitis in rats with CCl(4)-induced cirrhosis and ascites.

METHOD

After development of cirrhosis and ascites, animals were randomly allocated to receive pentoxifylline (16 mg/kg/d every 8h, oral route, n=13) or placebo (n=12) for 15 days. An additional group of 8 cirrhotic rats was given norfloxacin (5mg/kg/d for 15 days). Six healthy rats served as controls. Cecal flora and the prevalence of bacterial translocation and spontaneous bacterial peritonitis were analysed. Serum and ascitic fluid levels of TNF-alpha and cecal levels of malondialdehyde were also measured.

RESULTS

Pentoxifylline in comparison to placebo reduced intestinal bacterial overgrowth (21% vs. 67%, p=0.04), bacterial translocation to cecal lymph nodes (23% vs. 75%, p=0.03) and prevented spontaneous bacterial peritonitis (0% vs. 33%, p=0.04) by Enterobacteriaceae. Norfloxacin administration induced similar results. Pentoxifylline (0.18 ± 0.10 nmol/mg), but not norfloxacin (0.25 ± 0.13; p=0.02), significantly reduced cecal mucosal levels of malondialdehyde compared to placebo (0.33 ± 0.16; p=0.03).

CONCLUSION

In cirrhotic rats with ascites: (a) pentoxifylline as well as norfloxacin reduced intestinal bacterial overgrowth and bacterial translocation and prevented spontaneous bacterial peritonitis; (b) pentoxifylline, but not norfloxacin, reduced oxidative stress in cecal mucosal.

The intestinal microbiota and chronic disorders of the gut

Mucosal surfaces of the gut are colonized by large numbers of heterogeneous bacteria that contribute to intestinal health and disease. In genetically susceptible individuals, a 'pathogenic community' may arise, whereby abnormal gut flora contributes to alterations in the mucosa and local immune system leading to gastrointestinal disease. These diseases include enteric infections, such as Clostridium difficile infection, small intestinal bacterial overgrowth, functional gastrointestinal disorders (including IBS), IBD and colorectal cancer. Prebiotics, probiotics and synbiotics (a combination of prebiotics and probiotics) have the capacity to reverse pathologic changes in gut flora and local immunity. Intestinal health and disease need to be thoroughly characterized to understand the interplay between the indigenous microbiota, the immune system and genetic host factors. This Review provides a broad overview of the importance of the intestinal microbiota in chronic disorders of the gut.

Gut microbiota and probiotics in chronic liver diseases

There is a strong relationship between liver and gut: the portal system receives blood from the gut, and intestinal blood content activates liver functions. The liver, in turn, affects intestinal functions through bile secretion into the intestinal lumen. Alterations of intestinal microbiota seem to play an important role in induction and promotion of liver damage progression, in addition to direct injury resulting from different causal agents. Bacterial overgrowth, immune dysfunction, alteration of the luminal factors, and altered intestinal permeability are all involved in the pathogenesis of complications of liver cirrhosis, such as infections, hepatic encephalopathy, spontaneous bacterial peritonitis, and renal failure. Probiotics have been suggested as a useful integrative treatment of different types of chronic liver damage, for their ability to augment intestinal barrier function and prevent bacterial translocation. This review summarizes the main literature findings about the relationships between gut microbiota and chronic liver disease, both in the pathogenesis and in the treatment by probiotics of the liver damage.

Nuclear receptors as new perspective for the management of liver diseases

Nuclear receptors (NRs) are ligand-activated transcription factors that act as sensors for a broad range of natural and synthetic ligands and regulate several key hepatic functions including bile acid homeostasis, bile secretion, lipid and glucose metabolism, as well as drug deposition. Moreover, NRs control hepatic inflammation, regeneration, fibrosis, and tumor formation. Therefore, NRs are key for understanding the pathogenesis and pathophysiology of a wide range of hepatic disorders. Finally, targeting NRs and their alterations offers exciting new perspectives for the treatment of liver diseases.

Proteomics for the discovery of nuclear bile acid receptor FXR targets

Nuclear receptors (NRs) are important pharmacological targets for a number of diseases, including cancer and metabolic disorders. To unmask the direct role of NR function it is fundamental to find the NR targets. During the last few years several NRs have been shown to affect microRNA expression, thereby modulating protein levels. The farnesoid X receptor (FXR), the main regulator of bile acid (BA) homeostasis, also regulates cholesterol, lipid and glucose metabolism. Here we used, for the first time, a proteomics approach on mice treated with a FXR ligand to find novel hepatic FXR targets. Nineteen spots with a more than two-fold difference in protein amounts were found by 2D-DIGE and 20 proteins were identified by MALDI-TOF MS as putative novel FXR targets. The most striking feature of the protein list was the great number of mitochondrial proteins, indicating a substantial impact of FXR activation on mitochondrial function in the liver. To examine if the differences found in the proteomics assay reflected differences at the mRNA level, a microarray assay was generated on hepatic samples from wild type and FXR^−/− mice treated with a FXR ligand and compared to vehicle treatment. At least six proteins were shown to be regulated only at a post-transcriptional level. In conclusion, our study provides the impetus to include proteomic analysis for the identification of novel targets of transcription factors, such as NRs. This article is part of a Special Issue entitled: Translating nuclear receptors from health to disease.

Fecal metabolome profiling of liver cirrhosis and hepatocellular carcinoma patients by ultra performance liquid chromatography-mass spectrometry

Fecal metabolome of healthy humans and patients suffering from liver cirrhosis and hepatocellular carcinoma (HCC) were studied using ultra performance liquid chromatography coupled to quadrupole-time-of-flight mass spectrometry (UPLC/Q-TOF MS). Metabolic features detected by the method were then statistically treated using partial least squares to latent structure-discriminant analysis (PLS-DA) models to discriminate between healthy and diseased states. PLS-DA was also used to discriminate between cirrhosis and HCC stressed fecal metabolomes and to identify potential biomarkers for cirrhosis and HCC that are expressed at significantly different amounts in fecal metabolomes. Score plots of pattern recognition analysis distinguished liver cirrhosis and HCC patients from healthy humans. Based on the variable of importance in the project (VIP) values and S-plots, six metabolites were considered as potential biomarkers with a strong increase in lysophosphatidylcholines and a dramatic decrease in bile acids and bile pigments in patients with liver cirrhosis and HCC in comparison with healthy humans. Results demonstrate the potential of UPLC-MS as an efficient and convenient method that can be applied to screen fecal samples and aid in the early diagnosis of cirrhosis and hepatocellular carcinoma.

Severe hepatitis and intestinal mucosal barrier

Besides digestion and absorption of nutrients, another important feature of the intestine is epithelial mucosal barrier. Intestinal epithelial mucosal barrier consists of mechanical, immune, chemical, and biological barriers. Although different barriers have different structures and functions, they can interact with each other in a complicated manner. Severe hepatitis is the most serious form of hepatitis. Some studies have demonstrated that severe hepatitis is closely related to intestinal mucosal injury. Therefore, intestinal mucosal injury has become an important topic for research of severe hepatitis. In this paper, we review the relationship between severe hepatitis and intestinal mucosal barrier.