Willem Renooij

Farnesoid X receptor activation inhibits inflammation and preserves the intestinal barrier in inflammatory bowel disease

Background & aims Inflammatory bowel disease (IBD) is characterised by chronic intestinal inflammation, resulting from dysregulation of the mucosal immune system and compromised intestinal epithelial barrier function. The bile salt, nuclear farnesoid X receptor (FXR), was recently implicated in intestinal antibacterial defence and barrier function. The aim of this study was to investigate the therapeutic potential of FXR agonists in the treatment of intestinal inflammation in complementary in vivo and in vitro models. Methods Colitis was induced in wild-type (WT) and Fxr-null mice using dextran sodium sulfate, and in WT mice using trinitrobenzenesulfonic acid. Mice were treated with vehicle or the FXR agonist INT-747, and colitis symptoms were assessed daily. Epithelial permeability assays and cytokine expression analysis were conducted in mouse colon and enterocyte-like cells (Caco-2/HT29) treated with medium or INT-747. Inflammatory cytokine secretion was determined by ELISA in various human immune cell types. Results INT-747-treated WT mice are protected from DSS- and TNBS-induced colitis, as shown by significant reduction of body weight loss, epithelial permeability, rectal bleeding, colonic shortening, ulceration, inflammatory cell infiltration and goblet cell loss. Furthermore, Fxr activation in intestines of WT mice and differentiated enterocyte-like cells downregulates expression of key proinflammatory cytokines and preserves epithelial barrier function. INT-747 significantly decreases tumour necrosis factor α secretion in activated human peripheral blood mononuclear cells, purified CD14 monocytes and dendritic cells, as well as in lamina propria mononuclear cells from patients with IBD. Conclusions FXR activation prevents chemically induced intestinal inflammation, with improvement of colitis symptoms, inhibition of epithelial permeability, and reduced goblet cell loss. Furthermore, FXR activation inhibits proinflammatory cytokine production in vivo in the mouse colonic mucosa, and ex vivo in different immune cell populations. The findings provide a rationale to explore FXR agonists as a novel therapeutic strategy for IBD.

Long-term Study of Large Ceramic Implants (Porous Hydroxyapatite) in Dog Femora

Blocks of porous ceramic hydroxyapatite (dimensions, 2.5 X 1.25 X 0.5 cm; sintering temperature, 1300 degrees; macroporosity, 56%; average pore size 0.18 mm2) were implanted into surgically created defects in dog femora. The implants were retrieved up to 3.5 years after implantation. The implants were 3.5 years after implantation. The implants were firmly attached to the bone. Histologic evaluation suggests that optimal contact between bone and implant should be provided to accelerate bone ingrowth. Bone growth in the pores reached a maximum level after 35 weeks, at which time about one-third of the pore space was filled with bone. When measuring the relative surface areas of bone and ceramic on histologic slides, no change in ceramic mass could be detected, indicating that hydroxyapatite ceramics are not affected by biodegradation processes. The implants effectively provided a scaffold for bone growth bridging a larger bone defect.

Intestinal barrier dysfunction in a randomized trial of a specific probiotic composition in acute pancreatitis

Objectives:To determine the relation between intestinal barrier dysfunction, bacterial translocation, and clinical outcome in patients with predicted severe acute pancreatitis and the influence of probiotics on these processes. Summary of Background data:Randomized, placebo-controlled, multicenter trial on probiotic prophylaxis (Ecologic 641) in patients with predicted severe acute pancreatitis (PROPATRIA). Methods:Excretion of intestinal fatty acid binding protein (IFABP, a parameter for enterocyte damage), recovery of polyethylene glycols (PEGs, a parameter for intestinal permeability), and excretion of nitric oxide (NOx, a parameter for bacterial translocation) were assessed in urine of 141 patients collected 24 to 48 h after start of probiotic or placebo treatment and 7 days thereafter. Results:IFABP concentrations in the first 72 hours were higher in patients who developed bacteremia (P = 0.03), infected necrosis (P = 0.01), and organ failure (P = 0.008). PEG recovery was higher in patients who developed bacteremia (PEG 4000, P = 0.001), organ failure (PEG 4000, P < 0.0001), or died (PEG 4000, P = 0.009). Probiotic prophylaxis was associated with an increase in IFABP (median 362 vs. 199 pg/mL; P = 0.02), most evidently in patients with organ failure (P = 0.001), and did not influence intestinal permeability. Overall, probiotics decreased NOx (P = 0.05) but, in patients with organ failure, increased NOx (P = 0.001). Conclusions:Bacteremia, infected necrosis, organ failure, and mortality were all associated with intestinal barrier dysfunction early in the course of acute pancreatitis. Overall, prophylaxis with this specific combination of probiotic strains reduced bacterial translocation, but was associated with increased bacterial translocation and enterocyte damage in patients with organ failure.

Preferential incorporation of fatty acids at the inside of human erythrocyte membranes

1. 1.Phospholipase A2 isolated from Naja naja venom was used as a tool to discriminate between the outer and inner lipid monolayer of the membranes of human erythrocytes. 2. 2.Incubation of human erythorcytes with radioactive fatty acids resulted in the formation of labelled lecithin in the membrane. The label was found predominantly in that pool of lecithin which is localized in the inner monolayer of the membrane. 3. 3.Lecithins isolated from the total erythrocyte membrane and from the inner monolayer of the membrane possess identical fatty acid patterns and identical positional distributions of their fatty acyl constituents.

Small gallstones, preserved gallbladder motility, and fast crystallization are associated with pancreatitis†‡

Acute pancreatitis is a severe complication of gallstones with considerable mortality. We sought to explore the potential risk factors for biliary pancreatitis. We compared postprandial gallbladder motility (via ultrasonography) and, after subsequent cholecystectomy, numbers, sizes, and types of gallstones; gallbladder bile composition; and cholesterol crystallization in 21 gallstone patients with previous pancreatitis and 30 patients with uncomplicated symptomatic gallstones. Gallbladder motility was stronger in pancreatitis patients than in patients with uncomplicated symptomatic gallstones (minimum postprandial gallbladder volumes: 5.8 ± 1.0 vs. 8.1 ± 0.7 mL; P = .005). Pancreatitis patients had more often sludge (41% vs. 13%; P = .03) and smaller and more gallstones than patients with symptomatic gallstones (smallest stone diameters: 2 ± 1 vs. 8 ± 2 mm; P = .001). Also, crystallization occurred much faster in the bile of pancreatitis patients (1.0 ± 0.0 vs. 2.5 ± 0.4 days; P < .001), possibly because of higher mucin concentrations (3.3 ± 1.9 vs. 0.8 ± 0.2 mg/mL; P = .04). No significant differences were found in types of gallstones, relative biliary lipid contents, cholesterol saturation indexes, bile salt species composition, phospholipid classes, total protein or immunoglobulin (G, M, and A), haptoglobin, and α‐1 acid glycoprotein concentrations. In conclusion, patients with small gallbladder stones and/or preserved gallbladder motility are at increased risk of pancreatitis. The potential benefit of prophylactic cholecystectomy in this patient category has yet to be explored. (HEPATOLOGY 2005.)

Systemic inflammation increases intestinal permeability during experimental human endotoxemia.

Although the gut is often considered the motor of sepsis, the relation between systemic inflammation and intestinal permeability in humans is not clear. We analyzed intestinal permeability during experimental endotoxemia in humans. Before and during experimental endotoxemia (Escherichia coli LPS, 2 ng/kg), using polyethylene glycol (PEG) as a permeability marker, intestinal permeability was analyzed in 14 healthy subjects. Enterocyte damage was determined by intestinal fatty acid binding protein. Endotoxemia induced an inflammatory response. Urinary PEGs 1,500 and 4,000 recovery increased from 38.8 ± 6.3 to 63.1 ± 12.5 and from 0.58 ± 0.31 to 3.11 ± 0.93 mg, respectively (P < 0.05). Intestinal fatty acid binding protein excretion was not affected by endotoxemia. The peak serum IL-10 concentrations correlated with the increase in PEG 1,500 recovery (r = 0.48, P = 0.027). Systemic inflammation results in an increased intestinal permeability. The increase in intestinal permeability is most likely caused by inflammation-induced paracellular permeability, rather than ischemia-mediated enterocyte damage.

The transposition of molecular classes of phosphatidylcholine across the rat erythrocyte membrane and their exchange between the red cell membrane and plasma lipoproteins

1. The molecular composition of phosphatidylcholine is similar in the inner and the outer layer of the rat erythrocyte membrane. 2. The rate of exchange of the various molecular classes of phosphatidylcholine between rat plasma and the red cell membrane does not depend on the degree of unsaturation of the different classes. 3. The transposition of the molecular classes of phosphatidylcholine between the inner and the outer layer of the rat erythrocyte membrane is more pronounced for the more unsaturated classes.

Bacterial infections in cirrhosis: role of proton pump inhibitors and intestinal permeability

Eur J Clin Invest 2012; 42 (7): 760–767

Gallbladder emptying in vivo, bile composition, and nucleation of cholesterol crystals in patients with cholesterol gallstones

BACKGROUND/AIMS Impaired postprandial gallbladder emptying may provide time for progressive bile concentration with formation of instable cholesterol-rich vesicles and fast nucleation of cholesterol crystals. The aim of this study was to assess postprandial gallbladder emptying, bile composition, and nucleation of cholesterol crystals in the same patient. METHODS In 30 patients with cholesterol gallstones, postprandial gallbladder emptying was measured ultrasonographically. In each patient, gallbladder bile composition (obtained at cholecystectomy) and nucleation of cholesterol crystals was determined. Patients were divided in 22 strong contractors (> 50% postprandial gallbladder emptying) and 8 weak contractors. RESULTS In weak contractors, bile salt and phospholipid concentrations were much higher than in strong contractors (234.6 +/- 24.7 vs. 130.3 +/- 10.8 mmol/L [P < 0.001] and 44.5 +/- 3.5 vs. 30.2 +/- 3.1 mmol/L [P < 0.05], respectively). Cholesterol concentrations were comparable in strong and weak contractors. Consequently, total lipid concentration was significantly higher (15.5 +/- 1.4 and 9.2 +/- 0.7 g/dL; P < 0.001) and cholesterol saturation index significantly lower (0.90 +/- 0.08 and 1.61 +/- 0.17; P < 0.001) in weak contractors. Nucleation time, percentage of cholesterol in vesicles, bile salt species, and molecular species of phosphatidylcholine were not significantly different. CONCLUSION Differences in bile composition can be linked to different patterns of postprandial gallbladder emptying and may point to two different pathways of gallstone formation.

Hydrophilic bile salts enhance differential distribution of sphingomyelin and phosphatidylcholine between micellar and vesicular phases: potential implications for their effects in vivo

BACKGROUND/AIMS The hepatocyte canalicular membrane outer leaflet contains both phosphatidylcholine (PC) and sphingomyelin (SM). Normally, PC is the exclusive phospholipid in bile. We examined effects of bile salt hydrophobicity on cytotoxicity and on differential SM and PC distribution between detergent-resistant aggregated vesicles (model for detergent-resistant canalicular membrane) and mixed micelles or small unilamellar vesicles (representing lipid phases in bile). METHODS Aggregated vesicles were obtained by ultracentrifugation of cholesterol-supersaturated model systems containing SM, PC and various bile salts, micelles by ultrafiltration and unilamellar vesicles by dialysis of the supernatant. Erythrocyte hemolysis and lactate dehydrogenase release from CaCo-2 cells upon incubation with various micelles were quantified. RESULTS Preferential SM distribution and lipid solubilization in aggregated vesicles increased in rank order taurodeoxycholate < taurocholate < tauroursodeoxycholate < taurohyodeoxycholate, with reciprocal PC enrichment in micelles and small unilamellar vesicles. Including small amounts of PC within taurohyodeoxycholate micelles increased cytotoxicity with more erythrocyte hemolysis and LDH release from CaCo-2 cells upon incubation, but decreased cytotoxicity in case of tauroursodeoxycholate micelles. CONCLUSIONS Hydrophilic but not hydrophobic bile salts preserve integrity of pathophysiologically relevant phosphatidylcholine plus sphingomyelin-containing bilayers. Enhanced biliary phospholipid secretion during taurohyodeoxycholate but not during tauroursodeoxycholate therapy (Hepatology 25 (1997) 1306) may relate to different interactions of these bile salts with phospholipids.