Ramon Bartolí

Effect of olive oil on early and late events of colon carcinogenesis in rats: modulation of arachidonic acid metabolism and local prostaglandin E2 synthesis

BACKGROUND Animal model studies have shown that the colon tumour promoting effect of dietary fat depends not only on the amount but on its fatty acid composition. With respect to this, the effect of n9 fatty acids, present in olive oil, on colon carcinogenesis has been scarcely investigated. AIMS To assess the effect of an n9 fat diet on precancer events, carcinoma development, and changes in mucosal fatty acid composition and prostaglandin (PG)E2 formation in male Sprague-Dawley rats with azoxymethane induced colon cancer. METHODS Rats were divided into three groups to receive isocaloric diets (5% of the energy as fat) rich in n9, n3, or n6 fat, and were administered azoxymethane subcutaneously once a week for 11 weeks at a dose rate of 7.4 mg/kg body weight. Vehicle treated groups received an equal volume of normal saline. Groups of animals were colectomised at weeks 12 and 19 after the first dose of azoxymethane or saline. Mucosal fatty acids were assessed at 12 and 19 weeks. Aberrant crypt foci and the in vivo intracolonic release of PGE2 were assessed at week 12, and tumour formation at week 19. RESULTS Rats on the n6 diet were found to have colonic aberrant crypt foci and adenocarcinomas more often than those consuming either the n9 or n3 diet. There were no differences between the rats on the n9 and n3 diets. On the other hand, administration of both n9 and n3 diets was associated with a decrease in mucosal arachidonate concentrations as compared with the n6 diet. Carcinogen treatment induced an appreciable increase in PGE2 formation in rats fed the n6 diet, but not in those fed the n3 and n9 diets. CONCLUSIONS Dietary olive oil prevented the development of aberrant crypt foci and colon carcinomas in rats, suggesting that olive oil may have chemopreventive activity against colon carcinogenesis. These effects may be partly due to modulation of arachidonic acid metabolism and local PGE2synthesis.

Translocated intenstinal bacteria cause spontaneous bacterial peritonitis in cirrhotic rats: molecular epidemiologic evidence

BACKGROUND/AIMS Intestinal bacterial translocation is common in cirrhotic rats with spontaneous bacterial peritonitis, and it is thought to play a major pathogenic role. There has so far been no evidence for clonality between bacteria isolated from intestine and ascites. This study aimed to use molecular epidemiology techniques to show that spontaneous bacterial peritonitis is due to translocated intestinal bacteria. METHODS Samples of ascitic fluid, portal blood, mesenteric lymph nodes and ileal contents from healthy (n=10) and ascitic cirrhotic rats with (n=12) or without (n=15) spontaneous bacterial peritonitis were cultured. In six infected rats, DNA macrorestriction fragments of 30 bacterial isolates [Escherichia coli (n=13), Enterococcus faecalis (n=12) and Proteus mirabilis (n=5)] from ascites (n=8), mesenteric lymph nodes (n=7), portal blood (n=6), and ileal flora (n=9) were compared. RESULTS Bacterial translocation was more frequent in animals with (58%) than in those without spontaneous bacterial peritonitis (20%, p=0.049) or controls (10%, p=0.026). The same bacterial strain was simultaneously isolated in ascites and in mesenteric lymph nodes and/or ileum in 7/8 (87%) instances. The identity rate for bacteria present in both ascites and mesenteric lymph nodes was 80% (4/5). Likewise, identity was demonstrated in 3/4 instances of bacteria found in both ascites and portal blood. CONCLUSIONS These results indicate that spontaneous bacterial peritonitis in cirrhotic rats is mainly due to intestinal bacteria translocated to mesenteric lymph nodes. Portal blood could be a less frequent route.

Bacterial translocation in cirrhotic rats. Its role in the development of spontaneous bacterial peritonitis.

Bacterial translocation occurs in ascitic cirrhotic rats, but its association with ascites infection is unknown. The aim of this study was to assess the relation between bacterial translocation and ascites infection in cirrhotic rats. Male Sprague-Dawley rats were induced to cirrhosis with intragastric CCl4. Ascitic fluid, portal and peripheral blood, mesenteric lymph nodes, liver and spleen samples were cultured before death in those cirrhotic rats with less (group A) or more (group B) than 250 polymorphonuclear neutrophils/mm3 in ascitic fluid, as well as in healthy control rats. Histological examination of jejunum, ileum, and caecum was also performed. Bacterial translocation occurred in 45% of ascitic rats (without differences between groups A and B), but in 0% controls (p = 0.01). Bacterial translocation was associated with positive ascitic fluid culture in 60% of the cases. In all of them the same bacterial species was isolated in both mesenteric lymph node and ascitic fluid. Submucosal caecal oedema (100%), ileal lymphangiectasia (41%), and caecal inflammatory infiltrate (41%) occurred in ascitic rats, the last being associated with ascitic fluid positive culture (p = 0.04). These results suggests that bacterial translocation occurs frequently in ascitic cirrhotic rats, and may play a permissive, but not unique, part in a number of ascites infections. Whether histological changes seen in cirrhotic ascitic rats favour bacterial translocation remains to be elucidated.

Insulin-like growth factor-I improves intestinal barrier function in cirrhotic rats

Background and aims: In liver cirrhosis, disruption of the intestinal barrier facilitates bacterial translocation and spontaneous bacterial peritonitis. Insulin-like growth factor I (IGF-I) is an anabolic hormone synthesised by hepatocytes that displays hepatoprotective activities and trophic effects on the intestine. The aim of this study was to investigate the effect of IGF-I on intestinal barrier function in cirrhotic rats. Methods: In rats with carbon tetrachloride induced cirrhosis, we investigated the effect of IGF-I therapy on: (a) portal pressure; (b) intestinal histology and permeability to endotoxin and bacteria; (c) intestinal expression of cyclooxygenase 2 (COX-2) and tumour necrosis factor α (TNF-α), two factors that influence in a positive and negative manner, respectively, the integrity of the intestinal barrier; (d) intestinal permeability to 3H-mannitol in rats with bile duct ligation (BDL); and (e) transepithelial electrical resistance (TER) of polarised monolayers of rat small intestine epithelial cells. Results: IGF-I therapy reduced liver collagen expression and portal pressure in cirrhotic rats, induced improvement in intestinal histology, and caused a reduction in bacterial translocation and endotoxaemia. These changes were associated with diminished TNF-α expression and elevated COX-2 levels in the intestine. IGF-I reduced intestinal permeability in BDL rats and enhanced barrier function of the monolayers of epithelial intestinal cells where lipopolysaccharide (LPS) caused a decrease in TER that was reversed by IGF-I. This effect of IGF-I was associated with upregulation of COX-2 in LPS treated enterocytes. Conclusions: IGF-I enhances intestinal barrier function and reduces endotoxaemia and bacterial translocation in cirrhotic rats. IGF-I therapy might be useful in the prevention of spontaneous bacterial peritonitis in liver cirrhosis.

Rifaximin, but not growth factor 1, reduces brain edema in cirrhotic rats

AIM To compare rifaximin and insulin-like growth factor (IGF)-1 treatment of hyperammonemia and brain edema in cirrhotic rats with portal occlusion. METHODS Rats with CCl₄-induced cirrhosis with ascites plus portal vein occlusion and controls were randomized into six groups: Cirrhosis; Cirrhosis + IGF-1; Cirrhosis + rifaximin; Controls; Controls + IGF-1; and Controls + rifaximin. An oral glutamine-challenge test was performed, and plasma and cerebral ammonia, glucose, bilirubin, transaminases, endotoxemia, brain water content and ileocecal cultures were measured and liver histology was assessed. RESULTS Rifaximin treatment significantly reduced bacterial overgrowth and endotoxemia compared with cirrhosis groups, and improved some liver function parameters (bilirubin, alanine aminotransferase and aspartate aminotransferase). These effects were associated with a significant reduction in cerebral water content. Blood and cerebral ammonia levels, and area-under-the-curve values for oral glutamine-challenge tests were similar in rifaximin-treated cirrhotic rats and control group animals. By contrast, IGF-1 administration failed to improve most alterations observed in cirrhosis. CONCLUSION By reducing gut bacterial overgrowth, only rifaximin was capable of normalizing plasma and brain ammonia and thereby abolishing low-grade brain edema, alterations associated with hepatic encephalopathy.

Determination of the ideal preparation for colonoscopy in a rat model.

Background: Quality bowel preparation is essential to examine the entire colon adequately. No trials comparing different purgative regimens are available in animal models. The aim was to compare 5 methods for bowel cleansing to develop a rat model to study therapeutic colonoscopy. Methods: Twenty-five rats were assigned to one of 5 regimens: (1) high-volume polyethylene glycol electrolyte solution (HV-PEG-ES, 40 mL); (2) low-volume PEG-ES (LV-PEG-ES, 20 mL); (3) high-volume PEG-ES+ascorbic acid (HV-PEG-ES+AA, 20 mL); (4) LV-PEG-ES+AA, 10 mL; (5) rectal enema with saline solution (RE-SS). Bowel preparation quality was rated by total colonoscopy. Results: RE-SS is the best regime for left colon cleansing, whereas HV-PEG-ES and HV-PEG-ES+AA solutions resulted in significantly better cleansing in the whole colon. HV-PEG-ES+AA regimen needed less volume, and administration was easier. Conclusions: A total of 20 mL of PEG-ES+AA before colonoscopy is the best regimen to explore the whole colon, whereas to explore the left colon RE-SS is adequate.

Colonoscopy in rats: An endoscopic, histological and tomographic study.

AIM To describe colon anatomy with colonoscopy and computed tomography (CT) to develop a rat model for future studies of therapeutic colonoscopy. METHODS Eighteen male Sprague-Dawley rats, on average 400-420 g, underwent total colonoscopy, CT and histological examination. Colonoscopy was performed after bowel preparation with a baby upper gastrointestinal endoscopy with an outer diameter of 6.7 mm. CT obtained a 3D image of total colon after a rectal enema with radiological contrast. Macroscopic and microscopic examinations were examined with a conventional technique (hematoxylin and eosin). Colonic wall thickness, length and diameter measurements were taken from the anus, 3, 7, 14 and 20 cm from the anal margin. RESULTS The median colonoscope depth was 24 cm (range 20-28 cm). Endoscopic and tomographic study of colon morphology showed an easy access with tubular morphology in the entire left colon (proximal left colon and rectum). Transverse colon was unapparent on colonoscopy. Right colon, proximal to the splenic flexure, was the largest part of the colon and assumed saccular morphology with tangential trabecula. Radiological measurements of the colonic length and diameter substantiate a subdivision of the right colon into two parts, the cecum and distal right colon. In addition, histological measurement of the colonic wall thickness confirmed a progressive decrease from rectum to cecum. The muscular layer was thinner in the proximal left colon. CONCLUSION The combination of colonoscopy, tomography and histology leads to a better characterization of the entire colon. These data are important for deciding when to perform endoscopic resections or when to induce perforations to apply endoscopic treatments.

Rat CCl4‐induced cirrhosis plus total portal vein ligation: a new model for the study of hyperammonaemia and brain oedema

Introduction: Animal models used to study hyperammonaemic disorders related to chronic liver disease are unsatisfactory. These animals only develop hyperammonaemia and brain oedema when fed with diets supplemented with amonium acetate.

Early hospital readmission in decompensated cirrhosis: Incidence, impact on mortality, and predictive factors

BACKGROUND & AIMS The early hospital readmission of patients with decompensated cirrhosis is a current problem. A study is presented on the incidence, the impact on mortality, and the predictive factors of early hospital readmission. PATIENTS AND METHODS On the study included 112 cirrhotic patients, discharged after some decompensation between January 2013 and May 2014. Multivariate analyses were performed to identify predictors of early readmission and mortality. RESULTS The early readmission rate was 29.5%. The predictive factors were male gender (OR: 2.81; 95% CI: 1.07-7.35), Model for End-Stage Liver Disease-sodium score ≥15 (OR: 3.79; 95% CI 1.48-9.64), and Charlson index ≥7 (OR: 4.34, 95% CI 1.65-11.4). This model enabled patients to be classified into low or high risk of early readmissions (13.6% vs. 52.2%). The mortality rate was significantly higher among patients with early readmission (73% vs. 35%) (p<.0001). After adjusting for the Model for End-Stage Liver Disease-sodium score, Charlson index, dependence in activities of daily living, educational status, and number of medications on discharge, the early readmission was independently associated with mortality. CONCLUSIONS Early hospital readmission is common, and is independently associated with mortality. Male gender, MELD-Na ≥15, and Charlson index ≥7 are predictors of early readmission. These results could be used to develop future strategies to reduce early readmission.

Efficacy of platelet-rich plasma as a shielding technique after endoscopic mucosal resection in rat and porcine models

Background and study aims: The aims were to assess the efficacy of endoscopic application of Platelet-rich plasma (PRP) to prevent delayed perforation and to induce mucosal healing after endoscopic resections. Patients and methods: Colonic induced lesions were performed in rats (n = 16) and pigs (n = 4). Animals were randomized to receive onto the lesions saline (control) or PRP. Animals underwent endoscopic follow-up. Thermal injury was assessed with a 1 – 4 scale: (1) mucosal necrosis; (2) submucosal necrosis; (3) muscularis propria necrosis; and (4) serosal necrosis Results: Saline treatment showed 50 % of mortality in rats (P = 0.02). Mean ulcerated area after 48 hours and 7 days was significantly smaller with PRP than with saline (0.27 ± 0.02 cm2 and 0.08 ± 0.01 cm2 vs. 0.56 ± 0.1 cm2 and 0.40 ± 0.06 cm2; P < 0.001). The incidence of thermal injury was significantly lower with PRP (1.25 ± 0.46) than in controls (2.25 ± 0.50); P = 0.006. The porcine model showed a trend toward higher mucosal restoration in animals treated with PRP than with saline at weeks 1 and 2 (Median area in cm2: 0.55 and 0.40 vs. 1.32 and 0.79) Conclusions: Application of PRP to colonic mucosal lesions showed strong healing properties in rat and porcine models.