Nonalcoholic fatty liver disease aggravates acute pancreatitis through bacterial translocation and cholesterol metabolic dysregulation in the liver and pancreas in mice

Background:Nonalcoholic fatty liver disease(NAFLD)is an independent risk factor for severe acute pancreatitis(AP).The underlying mechanism remains unclear.We sought to determine how bacterial translocation and cholesterol metabolism in the liver and pancreas affect the severity of AP in NAFLD mice.Methods:C57BL/6N mice were fed on a high-fat diet(HFD)to generate the NAFLD model,and mice in the control group were provided with a normal diet(ND).After being anesthetized with ketamine/xylazine,mice got a retrograde infusion of taurocholic acid sodium into the pancreatic duct to induce AP,and sham operation(SO)was used as control.Serum amylase and Schmidt’s pathological score system were used to evaluate AP severity.Bacterial loads,total cholesterol level,and cholesterol metabolic-associated molecules[low-density lipoprotein receptor(LDLR)and ATP-binding cassette transporter A1(ABCA1)]were analyzed in the liver and pancreas.Results:Compared with the ND-AP group,mice in the HFD-AP group had severer pancreatitis,manifested with higher serum amylase levels and higher AP pathologic scores,especially the inflammation and hemorrhage scores.Compared with the HFD-SO group and ND-AP group,bacterial loads in the liver and pancreas were significantly higher in the HFD-AP group.Mice in the HFD-AP group showed a decreased LDLR expression and an increased ABCA1 expression in the pancreas,although there was no significant difference in pancreas total cholesterol between the HFD-AP group and the ND-AP group.Conclusions:NAFLD aggravates AP via increasing bacterial translocation in the liver and pancreas and affecting pancreas cholesterol metabolism in mice.

Microbiota and the gut-liver axis:Bacterial translocation,inflammation and infection in cirrhosis

Liver disease is associated with qualitative and quantitative changes in the intestinal microbiota. In cirrhotic patients the alteration in gut microbiota is characterized by an overgrowth of potentially pathogenic bacteria (i.e., gram negative species) and a decrease in autochthonous familiae. Here we summarize the available literature on the risk of gut dysbiosis in liver cirrhosis and its clinical consequences. We therefore described the features of the complex interaction between gut microbiota and cirrhotic host, the so called “gut-liver axis”, with a particular attention to the acquired risk of bacterial translocation, systemic inflammation and the relationship with systemic infections in the cirrhotic patient. Such knowledge might help to develop novel and innovative strategies for the prevention and therapy of gut dysbiosis and its complication in liver cirrhosis.

Gut flora and bacterial translocation in chronic liver disease

Increasing evidence suggests that derangement of gut flora is of substantial dinical relevance to patients with cirrhosis. Intestinal bacterial overgrowth and increased bacterial translocation of gut flora from the intestinal lumen, in particular, predispose to an increased potential for bacterial infection in this group. Recent studies suggest that, in addition to their role in the pathogenesis of overt infective episodes and the clinical consequences of sepsis, gut flora contributes to the pro-inflammatory state of cirrhosis even in the absence of overt infection. Furthermore, manipulation of gut flora to augment the intestinal content of lactic acid-type bacteria at the expense of other gut flora species with more pathogenic potential may favourably influence liver function in cirrhotic patients. Here we review current concepts of the various inter-relationships between gut flora, bacterial translocation, bacterial infection, pro-inflammatory cytokine production and liver function in this group.

Early intrajejunal nutrition: bacterial translocation and gut barrier function of severe acute pancreatitis in dogs

Objective: To evaluate the effect of early intrajejunalnutrition in attenuating bacterial and/or endotoxintranslocation and improving gut barrier function ofsevere acute pancreatitis (SAP) in dogs.Methods: 15 dogs were divided into parenteral nutrition(PN) group(7 dogs)and early intrajejunal nutrition(EIN) group(8). EIN was delivered nutrients via a nee-dle jejunostomy catheter feeding at 48h after operation.SAP model was induced by injecting 1 ml/kg of com-bined solution of 5% sodium taurocholate and 8000-10000 BAEE units trypsin/ml into the pancreas via thepancreatic duct. Systemic blood samples were ob-tained before and 1, 3, 5, 7 d following SAP, and culturedby aerobic as well as anaerobic bacterial growth. Systemicplasma and portal vein endotoxin levels were quantifiedby the chromogenic limulus amebocyte lysate (LAL)technique. Portal vein blood and specimens of tissuefrom the mesenteriolum and mesocolon lymph nodes,lung, pulmonary portal lymph nodes, pancreatitis tissueand periopancreas tissue were adopted before the experi-ment was finished. Aliquots of the homogenata were cul-tured as blood mentioned above to determine the magnitudeof the bacteria DNA, protein and the villi, the thickness ofmucosa, and the whole bowel wall of the ileum and trans-verse colon were measured.Results: The study showed that the levels of systemicplasma endotoxin and the magnitude of bacterialtranslocation to the portal and systemic blood and dis-tant organ were reduced significantly in the EINgroup as compared with the TPN group. The contentsof protein and DNA, the height of villi, the thicknessof mucosa and whole bowel wall of the ileum andtransverse colon in the EIN group were higher thanthose in the PN group.Conclusion: Our results suggested that EIN is safe andeffective to be adopted by intrajejunal delivery of nu-trients in SAP, decreases the occurrence of gut bacterialtranslocation, and improves the gut barrier function.

Using the polymerase chain reaction coupled with denaturing gradient gel electrophoresis to investigate the association between bacterial translocation and systemic inflammatory response syndrome in predicted acute severe pancreatitis

AIM: To investigate the use of PCR and DGGE to investigate the association between bacterial translocation and systemic inflammatory response syndrome in predicted severe AP.METHODS: Patients with biochemical and clinical evidence of acute pancreatitis and an APACHE Ⅱ score ≥8 were enrolled. PCR and DGGE were employed to detect bacterial translocation in blood samples collected on d1,3, and 8 after the admission. Standard microbial blood cultures were taken when there was clinical evidence of sepsis or when felt to be clinically indicated by the supervising team.RESULTS: Six patients were included. Of all the patients investigated, only one developed septic complications;the others had uneventful illness. Bacteria were detected using PCR in 4 of the 17 collected blood samples. The patient with sepsis was PCR-positive in two samples (taken on d 1 and 3), despite three negative blood cultures. Using DGGE and specific primers, the bacteria in all blood specimens which tested positive for the presence of bacterial DNA were identified as E coli.CONCLUSION: Our study confirmed thatunlike traditional microbiological techniques, PCR can detect the presence of bacteria in the blood of patients with severe AP. Therefore, this latter method in conjunction with DGGE is potentially an extremely useful tool in predicting septic morbidity and evaluating patients with the disease. Further research using increased numbers of patients, in particular those patients with necrosis and sepsis, is required to assess the reliability of PCR and DGGE in the rapid diagnosis of infection in AP.

Effect of honey on bacterial translocation and intestinal morphology in obstructive jaundice

AIM:To evaluate the effects of honey on bacterial translocation and intestinal villus histopathology in experimental obstructive jaundice.METHODS:Thirty Wistar-Albino rats were randomly divided into three groups each including 10 animals:group Ⅰ,sham-operated;group Ⅱ,ligation and section of the common bile duct(BDL);group Ⅲ,bile duct ligation followed by oral supplementation of honey(BDL+honey) 10 g/kg per day.Liver,blood,spleen,mesenteric lymph nodes,and ileal samples were taken for microbiological,light and transmission electrone microscopic examination.RESULTS:Although the number of villi per centimeter and the height of the mucosa were higher in sham group,there was no statistically significant difference between sham and BDL + honey groups(P>0.05).On the other hand,there was a statistically significant difference between BDL group and other groups(P<0.05).The electron microscopic changes werealso different between these groups.Sham and honey groups had similar incidence of bacterial translocation(P>0.05).BDL group had significantly higher rates of bacterial translocation as compared with sham and honey groups.Bacterial translocation was predominantly detected in mesenteric lymph nodes.CONCLUSION:Supplementation of honey in presence of obstructive jaundice ameliorates bacterial translocation and improves ileal morphology.

Effects of glutamine and curcumin on bacterial translocation in jaundiced rats

AIM: To investigate the effect of curcumin on bacterial translocation and oxidative damage in an obstructive jaundice model and compare the results to glutamine, an agent known to be effective and clinically used. METHODS: Twenty-four female Wistar-Albino rats, weighing 200-250 g, were randomly divided into three groups (8 in each group). After ligation of the common bile duct in all animals, GroupⅠ received oral normal saline, Group Ⅱ received oral glutamine and Group Ⅲ received oral curcumin for seven days. Blood samples via cardiac puncture, tissue samples (terminal ileum, liver and mesenteric lymph node) and peritoneal fluid were obtained from the animals at the time of death to investigate bacterial translocation and oxidative damage. RESULTS: We observed that both glutamine and curcumin reduced bacterial translocation in blood, hepatocellular damage, plasma cytokine levels, oxidative tissue damage and apoptosis significantly compared to the control group. Additionally, glutamine showed protective effects on ileal epithelium and reduced villus atrophy. CONCLUSION: On the basis of these findings, both curcumin and glutamine are thought to be effective in preventing or reducing bacterial translocation and oxidative damage in obstructive jaundice.

Melatonin reduces bacterial translocation and apoptosis in trinitrobenzene sulphonic acid-induced colitis of rats

AIM: To investigate the effects of exogenous melatonin on bacterial translocation and apoptosis in a rat ulcerati-ve colitis model. METHODS: Rats were randomly assigned to three groups: groupⅠ: control, group Ⅱ: experimental colitis, group Ⅲ: colitis plus melatonin treatment. On d 11 after colitis, plasma tumor necrosis factor-α, portal blood endotoxin levels, colon tissue myeloperoxidase and caspase-3 activity were measured. Bacterial translocation was quantified by blood, lymph node, liver and spleen culture. RESULTS: We observed a significantly reduced inciden-ce of bacterial translocation to the liver, spleen, mesen-teric lymph nodes, portal and systemic blood in animals treated with melatonin. Treatment with melatonin signifi-cantly decreased the caspase-3 activity in colonic tissues compared to that in trinitrobenzene sulphonic acid-trea-ted rats (16.11 ± 2.46 vs 32.97 ± 3.91, P < 0.01). CONCLUSION: Melatonin has a protective effect on ba-cterial translocation and apoptosis.

Role of pregnane X-receptor in regulating bacterial translocation in chronic liver diseases

Bacterial translocation(BT) has been impeccably implicated as a driving factor in the pathogenesis of a spectrum of chronic liver diseases(CLD). Scientific evidence accumulated over the last four decades has implied that the disease pathologies in CLD and BT are connected as a loop in the gut-liver axis and exacerbate each other. Pregnane X receptor(PXR) is a ligandactivated transcription factor and nuclear receptor that is expressed ubiquitously along the gut-liver-axis. PXR has been intricately associated with the regulation of various mechanisms attributed in causing BT. The importance of PXR as the mechanistic linker molecule in the gutliver axis and its role in regulating bacterial interactions with the host in CLD has not been explored. Pub Med was used to perform an extensive literature search using the keywords PXR and bacterial translocation, PXR and chronic liver disease including cirrhosis. In an adequate expression state, PXR acts as a sensor for bile acid dysregulation and bacterial derived metabolites, and in response shapes the immune profile beneficial to the host. Activation of PXR could be therapeutic in CLD as it counter-regulates endotoxin mediated inflammation and maintains the integrity of intestinal epithelium. This review mainly focuses PXR function and its regulation in BT in the context of chronic liver diseases.

Protective effects of terminal ileostomy against bacterial translocation in a rat model of intestinal ischemia/reperfusion injury

AIM: To investigate the effects of terminal ileostomy on bacterial translocation (BT) and systemic inflammation after intestinal ischemia/reperfusion (I/R) injury in rats.

Leaky gut and the liver: A role for bacterial translocation in nonalcoholic steatohepatitis

Gut flora and bacterial translocation (BT) play important roles in the pathogenesis of chronic liver disease, including cirrhosis and its complications. Intestinal bacterial overgrowth and increased bacterial translocation of gut flora from the intestinal lumen predispose patients to bacterial infections, major complications and also play a role in the pathogenesis of chronic liver disorders. Levels of bacterial lipopolysaccharide, a component of gram-negative bacteria, are increased in the portal and/or systemic circulation in several types of chronic liver disease. Impaired gut epithelial integrity due to alterations in tight junction proteins may be the pathological mechanism underlying bacterial translocation. Preclinical and clinical studies over the last decade have suggested a role for BT in the pathogenesis of nonalcoholic steatohepatitis (NASH). Bacterial overgrowth, immune dysfunction, alteration of the luminal factors, and altered intestinal permeability are all involved in the pathogenesis of NASH and its complications. A better understanding of the cell-specific recognition and intracellular signaling events involved in sensing gut-derived microbes will help in the development of means to achieve an optimal balance in the gut-liver axis and ameliorate liver diseases. These may suggest new targets for potential therapeutic interventions for the treatment of NASH. Here, we review some of the mechanisms connecting BT and NASH and potential therapeutic developments.

EPIDERMAL GROWTH FACTOR PREVENTS INCREASED PERMEABILITY AND BACTERIAL TRANSLOCATION IN RATS WITH ACUTE PANCREATITIS

To evaluate the effects of epidermal growth factor (EGF) on intestinal permeability and bacterial translocation in rats with acute pancreatitis during total parenteral nutrition (TPN). Methods. Thirty- two male Sprague- Dawley rats that underwent injection of 3.5％ sodium taurocholate solution into the pancreatic duct were randomly divided into one of the following two groups: (1) received only TPN (control group) or (2) received TPN with EGF at a dose of 0.2 mg· kg- 1· day- 1 (Egf group). On fifth day of total parenteral nutrition, samples from mesenteric lymph nodes, pancreas, liver and spleen were harvested for cultures. Water, protein and DNA content in jejunal mucosa were determined. D- xylose and fluorescein isothiocyanate (FITC)- dextran were instilled into the lumen of a ligated segament of small intestine. Thirty minutes later, superior mesenteric vein D- xylose and plasma FITC- dextran concentration were measured. Results. Positive cultures in liver and spleen, as well as FITC- dextran concentration in the Egf group were significantly lower than in the control group. Protein and DNA content in jejunal mucosa in the Egf group were significantly higher than in the control group. Conclusion. The results indicate that EGF may prevent increased intestinal permeability and bacterial translocation in rats with acute pancreatitis during TPN.

Bacterial Translocation and Change in Intestinal Permeability in Patients after Abdominal Surgery

The purpose of this study was to investigate bacterial translocation and change in intestinal permeability in patients after abdominal surgery. Sixty-three patients undergoing elective abdominal surgery were enrolled in the study. Blood samples were collected prior to operation and 2, 24, 48 h after surgery for bacterial culture, microbial DNA extraction, plasma D-lactate and endotoxin measurement. PCR analysis was performed after DNA extraction, with β-lactosidase gene of E. coli and 16S rRNA gene as target genes. All patients were observed for a period of 30 days for infectious complications. Our results showed that no bacterial DNA was detected before surgery, but after operation it was found in 12 patients （19.0%）. Bacterial DNA was detected in 41.7% （10/24） of SIRS patients and 5.1% （2/39） of non-SIRS patients （P〈0.01）. About 83.3% of PCR-positive patients developed systemic inflammatory response syndrome （SIRS）, but only 27.5% of PCR-negative patients did so （P〈0.01）. Two thirds of PCR-positive patients developed infectious complications, while none of PCR-negative patients did （P〈0.01）. The blood culture was positive only in 3 patients （4.8%）, who were all PCR-positive. E. coli DNA was found in 66.7% of the PCR-positive patients. The plasma levels of D-lactate and endotoxin were elevated significantly 2, 24 and 48 h after operation in PCR-positive patients, with a significant positive correlation found between them （r=0.91, P〈0.01）. It is concluded that increased intestinal permeability was closely related with bacterial translocation. Intestinal bacterial translocation （most commonly E. coli） might occur at early stage （2 h） after abdominal surgery. Postoperative SIRS and infection might bear a close relationship with bacterial translocation.

Effects of granulocyte-colony stimulating factor on peritoneal defense mechanisms and bacterial translocation after administration of systemic chemotherapy in rats

AIM： To investigate the effects of granulocyte-colony stimulating factor （G-CSF） on peritoneal defense mechanisms and bacterial translocation after systemic 5-Fluorouracil （5-FU） administration. METHODS： Thirty Wistar albino rats were divided into three groups; the control, 5-FU and 5-FU ＋ G-CSF groups. We measured bactericidal activity of the peritoneal fluid, phagocytic activity of polymorphonuclear leucocytes in the peritoneal fluid, total peritoneal cell counts and cell types of peritoneal washing fluid. Bacterial translocation was quantified by mesenteric lymph node, liver and spleen tissue cultures. RESULTS： Systemic 5-FU reduced total peritoneal cell counts, neutrophUs and macrophage numbers. It also altered bactericidal activity of the peritoneal fluid and phagocytic activity of polymorphonuclear leucocytes in the peritoneal fluid. 5-FU also caused significant increase in frequencies of bacterial translocation at the liver and mesenteric lymph nodes. G-CSF decreased bacterial translocation, it significantly enhanced bactericidal activity of the peritoneal fluid and phagocytic activity of polymorphonuclear leucocytes in the peritoneal fluid. It also increased total peritoneal cell counts, neutrophils and macrophage numbers. CONCLUSION： Systemic 5-FU administration caused bacterial translocation, decreased the bactericidal activity of peritoneal fluid and phagocytic activity of polymorphonuclear leucocytes in the peritoneal fluid. G-CSF increased both bactericidal activity of the peritoneal fluid and phagocytic activity of polymorphonuclear leucocytes in the peritoneal fluid, and prevented the bacterial translocation. We conclude that intraperitoneal GCSF administration protects the effects of systemic 5-FU on peritoneal defense mechanisms.

Propolis reduces bacterial translocation and intestinal villus atrophy in experimental obstructive jaundice

AIM： To investigate the effects of propolis on bacterial translocation and ultrastructure of intestinal morphology in experimental obstructive jaundice. METHODS： Thirty Wistar-Albino male rats were randomly divided into three groups, each including 10 animals： group Ⅰ, sham-operated; group Ⅱ, ligation and division of the common bile duct （BDL）; group Ⅲ, BDL followed by oral supplementation of propolis 100 mg/kg per day. Liver, blood, spleen, mesenteric lymph nodes, and ileal samples were taken for microbiological, light and transmission electron microscopic examination on postoperative 7^th d after sacrification. RESULTS： The mean number of villi per centimeter and mean mucosal height of the propolis group were significantly different in the BDL group （P = 0.001 and 0.012, respectively）. The electron microscopic changes were also different between these groups. Sham and BDL＋propolis groups had similar incidence of bacterial translocation （BT）. The BDL group had significantly higher rates of BT as compared with sham and BDL ＋ propolis groups. BT was predominantly detected in MLNs and the most commonly isolated bacteria was Escherichia coil CONCLUSION： Propolis showed a significant protective effect on ileal mucosa and reduced bacterial translocation in the experimental obstructive jaundice model. Further studies should be carried out to explain the mechanisms of these effects,

Bacterial translocation in patients undergoing major gastrointestinal surgery and its role in postoperative sepsis

Bacteria of the human intestinal microflora have a dual role.They promote digestion and are part of a defense mechanism against pathogens.These bacteria could become potential pathogens under certain circumstances.The term“bacterial translocation”describes the passage of bacteria of the gastrointestinal tract through the intestinal mucosa barrier to mesenteric lymph nodes and other organs.In some cases,the passage of bacteria and endotoxins could result in blood stream infections and in multiple organ failure.Open elective abdominal surgery more frequently results in malfunction of the intestinal barrier and subsequent bacterial translocation and blood stream infections than laparoscopic surgery.Postoperative sepsis is a common finding in patients who have undergone non-elective abdominal surgeries,including trauma patients treated with laparotomy.Postoperative sepsis is an emerging issue,as it changes the treatment plan in surgical patients and prolongs hospital stay.The association between bacterial translocation and postoperative sepsis could provide novel treatment options.

Liver Cirrhosis and Intestinal Bacterial Translocation

Intestinal barrier dysfunction, facilitating translocation of bacteria and bacterial products, plays an important role in the pathophysiology of liver cirrhosis and its complications. Intestinal defense system including microbial barrier, immunologic barrier, mechanical barrier, chemical barrier, plays an important role in the maintenance of intestinal function. Under normal circumstances, the intestinal barrier can prevent intestinal bacteria through the intestinal wall from spreading to the body. Severe infection, trauma, shock, cirrhosis, malnutrition, immune suppression conditions, intestinal bacteria and endotoxin translocation, can lead to multiple organ dysfunction. 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 from the intestinal lumen to the mesenteric lymph nodes and other extraintestinal sites. In patients with cirrhosis, primary and intestinal flora imbalance, intestinal bacterial overgrowth, intestinal mucosal barrier dysfunction, endotoxemia is associated with weakened immunity.

Inhibitory effects of high-dose methylprednisolone on bacterial translocation from gut and endotoxin release following acute spinal cord injury-induced paraplegia in rats

BACKGROUND： Previous studies have shown that autonomic dysfunction results in gastrointestinal motility disorders and ultimately results in bacterial translocation following acute spinal cord injury （SCI）. Intensive methylprednisolone dosing improves neurological recovery in SCI patients. However, it remains uncertain whether high-dose methylprednisolone inhibits bacterial translocation and endotoxin release following acute SCI. OBJECTIVE： To investigate the inhibitory effect of methylprednisolone on bacterial translocation and endotoxin release from the gut in paraplegic rats. DESIGN, TIME AND SETTING： The randomized, controlled study was performed at the Orthopedic Lab, First Affiliated Hospital, Nanchang University, China, from April to December 2008. MATERIALS： Methylprednisolone （Pfizer, USA）, automatic microbial identification instrument ATB Expression and reagent ID 32 system （BioMerieux, France）, Limulus test kit （ACC, USA）, and optical microscope （Olympus, Japan） were used in this study. METHODS： A paraplegia model was established following SCI in 48 Wistar rats, aged 7 weeks. The rats were equally and randomly assigned to saline and methylprednisolone groups. Immediately post-injury, the methylprednisolone group was administered 30 mg/kg methylprednisolone via caudal intravenous infusion, followed by a 23-hour infusion of 5.4 mg/kg per hour. The saline group received an equal volume of saline as placebo. MAIN OUTCOME MEASURES： At 24 hours, 72 hours, and 1 week after SCI, blood samples were collected for bacterial cultures, and bacteria and endotoxin were identified using ATB Expression and Limulus test kits. In addition, mesenteric lymph node, spleen, and liver samples were collected for bacterial cultures. Histological examinations of mesenteric lymph node, spleen, liver, jejunum, and ileum were performed 1 week post-injury. Locomotor function in the hind limb was evaluated using the Basso, Beattie, and Bresnahan score at pre-injury time point, as well as 24 hours, 72 hours, and 1 week post-injury. RESULTS： Endotoxemia and bacterial growth were identified at 24 hours post-injury in both groups. However, plasma endotoxin levels were significantly decreased in the methylprednisolone group compared with the saline group at 72 hours and 1 week post-injury （P 〈 0.05）. Translocated bacteria mainly comprised Bacillus coli, Enterobacter cloacae, Escherichia coli, Proteus vulgaris, and Enterococcus faecalis following SCI combined with paraplegia. Histological changes were not as severe in the methylprednisolone group compared with the saline group 1 week after injury. Basso, Beattie, and Bresnahan scores were significantly better in the methylprednisolone group compared with the saline group 1 week after injury （P 〈 0.05）. CONCLUSION： High-dose methylprednisolone inhibited bacterial translocation from the gut and endotoxin release in rats with SCI.