Intestinal barrier function in patients undergoing colectomy.

AIM: The aim of this pilot study was to determine whether the type of approach (open or laparoscopic) and the order of devascularization during laparoscopic colectomy affect intestinal barrier function, local inflammatory response and clinical outcome. METHOD: Twenty-two patients undergoing elective colectomy from April 2006 to July 2008 were randomized to two sequences of vascular ligation, starting with either the inferior mesenteric artery or the ileocolic artery. Eighteen patients scheduled for open surgery served as a prospective control group. To assess the intestinal barrier function, release of intestinal fatty-acid binding protein (I-FABP; a marker of mucosal injury and ischaemia) was measured pre- and postoperatively. Mesenteric lymph nodes were harvested to assess the expression of inflammatory mediator-related genes using multiplex ligation probe amplification. The study was registered under NTR1025. RESULTS: Laparoscopic devascularization starting at the ileocolic artery resulted in a significantly increased excretion of I-FABP over time (P = 0.002). In this group, the I-FABP levels were significantly increased on postoperative days 1 and 3 compared with preoperative values (P = 0.011 and P = 0.001, respectively). There were no differences in expression of inflammatory mediator-related genes or postoperative morbidity among the groups. CONCLUSIONS: In this pilot study, devascularization commencing at the ileocolic artery during laparoscopic colectomy was associated with prolonged intestinal mucosal ischaemia.

Indomethacin enhances bile salt detergent activity: relevance for NSAIDs-induced gastrointestinal mucosal injury.

Gastroduodenal toxicity of nonsteroidal anti-inflammatory drugs (NSAIDs) is partly independent from cyclooxygenase inhibition, possibly related to increased intermixed micellar-vesicular (nonphospholipid-associated) bile salt concentrations thought to be responsible for bile salt cytotoxicity. We evaluated the effects of indomethacin on bile salt cytotoxicity with complementary in vitro and ex vivo systems. In the erythrocyte model, indomethacin alone did not induce hemolysis. In contrast, indomethacin enhanced and phospholipids decreased hemolysis induced by hydrophobic taurodeoxycholate (TDC). Hydrophilic tauroursodeoxycholate (TUDC) enhanced rather than decreased TDC-induced hemolysis in the presence of indomethacin. Indomethacin did not affect intermixed micellar-vesicular bile salt concentrations or compositions. Indomethacin also increased TDC-induced lactate dehydrogenase release in CaCo-2 cells and bile salt-induced rat colonic mucosal injury, and prevented potential protective effects of TUDC in these systems. Our data show that indomethacin enhances bile salt-induced cytotoxicity without affecting intermixed micellar-vesicular bile salt concentrations or compositions. These findings may be relevant for gastroduodenal injury during NSAID therapy.

Small intestinal glucose absorption and duodenal motility in type 1 diabetes mellitus.

OBJECTIVE: Small intestinal glucose absorption is increased in animal models of diabetes mellitus, but little data are available in humans. Small intestinal motility is reported to be frequently abnormal in patients with diabetes and could potentially affect glucose absorption. Our aim was to evaluate small intestinal glucose absorption and duodenal motor responses to intraduodenal nutrients, in patients with type 1 diabetes and controls. METHODS: Eight type 1 patients (two with autonomic neuropathy) and nine controls were studied during euglycemia. A manometric catheter was positioned across the pylorus, and nutrient infused intraduodenally (90 kcal over 30 min), followed by a bolus of 3-O-methylglucose (3-OMG). Blood was sampled to measure glucose and 3-OMG concentrations. RESULTS: During nutrient infusion, the number of duodenal waves did not differ between patients and controls. After the infusion, patients with diabetes had more propagated duodenal wave sequences (p < 0.05). The area under the plasma 3-OMG curve did not differ between the groups but correlated with both the blood glucose concentration at the time of 3-OMG administration (r = 0.64, p < 0.005) and the number of duodenal waves (r = 0.52, p < 0.05) and antegrade propagated duodenal sequences (r = 0.51, p < 0.05) preceding the 3-OMG bolus. CONCLUSIONS: During euglycemia, duodenal motor responses to small intestinal nutrient are comparable in patients with relatively uncomplicated type 1 diabetes and healthy subjects, but duodenal motility after nutrient infusion is increased in patients. Small intestinal glucose absorption is similar in patients and controls, but may be dependent on the blood glucose concentration and duodenal motor activity.

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.

Accurate separation of vesicles, micelles and cholesterol crystals in supersaturated model biles by ultracentrifugation, ultrafiltration and dialysis.

Gel filtration with bile salts at intermixed micellar/vesicular concentrations (IMC) in the eluant has been proposed to isolate vesicles and micelles from supersaturated model biles, but the presence of vesicular aggregates makes this method unreliable. We have now validated a new method for isolation of various phases. First, aggregated vesicles and - if present - cholesterol crystals are pelleted by short ultracentrifugation. Cholesterol contained in crystals and vesicular aggregates can be quantitated from the difference of cholesterol contents in the pellets before and after bile salt-induced solubilization of the vesicular aggregates. Micelles are then isolated by ultrafiltration of the supernatant through a highly selective 300 kDa filter and unilamellar vesicles by dialysis against buffer containing bile salts at IMC values. Lipids contained in unilamellar vesicles are also estimated by subtraction of lipid contents in filtered micelles from lipid contents in (unilamellar vesicle+micelle containing) supernatant ('subtraction method'). 'Ultrafiltration-dialysis' and 'subtraction' methods yielded identical lipid solubilization in unilamellar vesicles and identical vesicular cholesterol/phospholipid ratios. In contrast, gel filtration yielded much more lipids in micelles and less in unilamellar vesicles, with much higher vesicular cholesterol/phospholipid ratios. When vesicles obtained by dialysis were analyzed by gel filtration, vesicular cholesterol/phospholipid ratios increased strongly, despite correct IMC values for bile salts in the eluant. Subsequent extraction of column material showed significant amounts of lipids. In conclusion, gel filtration may underestimate vesicular lipids and overestimate vesicular cholesterol/phospholipid ratios, supposedly because of lipids remaining attached to the column. Combined ultracentrifugation-ultrafiltration-dialysis should be considered state-of-the-art methodology for quantification of cholesterol carriers in model biles.

Improved healing of extraperitoneal intestinal anastomoses in the early phase when surrounded by omentum.

BACKGROUND: The extra-anatomical position of a cervical oesophagogastrostomy is a reason for impaired anastomotic healing, but transposition of the omentum that is covered with mesothelial cells may be a way to improve that. METHOD: This hypothesis was tested in a rat model. An end-to-end jejuno-jejunostomy was placed subcutaneously in group I (n = 29), subcutaneously surrounded by omentum in group II (n = 29) and intra-abdominally surrounded by omentum in group III (n = 20). After 3, 7 or 14 days, the rats were sacrificed and bursting pressure (BP) of the anastomosis or jejunum was measured and the hydroxyproline (HP) level was determined. RESULTS: In group I 5/29, in group II 2/29 and in group III 0/20 rats died following anastomotic leakage (nonsignificant) and were excluded from other measurements. BP was decreased after 3 days in group I (60+/-9 mm Hg) compared with group II (101+/-8 mm Hg) and group III (107+/-11 mm Hg) (p = 0.002). After 7 days, BP in groups I (122+/-10 mm Hg) and II (132+/-10 mm Hg) were lower as compared with group III (230+/-8 mm Hg) (p<0.001). Differences in HP levels were not statistically significant between the groups after 3, 7 and 14 days. CONCLUSION: The healing of intestinal anastomoses in an extraperitoneal position is improved in the early phase only when surrounded by omentum.

Lipid solubilization in human gallbladder versus hepatic biles.

BACKGROUND/AIMS: Cholesterol crystallizes more rapidly in gallbladder than in hepatic biles, supposedly due to formation of cholesterol-supersaturated vesicles in concentrated gallbladder biles because of preferential micellization of phospholipids compared to cholesterol. We therefore aimed to compare lipid solubilization in hepatic and gallbladder biles. METHODS: Mixed micellar and vesicular phases were separated from hepatic and associated gallbladder biles of seven cholesterol gallstone patients by using state-of-the-art gel filtration with bile salts at intermixed micellar/intervesicular compositions and concentrations in the eluant. RESULTS: Vesicles were found in 6 out of 7 hepatic biles, but only in 2 of the corresponding gallbladder biles. Both percentage (7.8+/-5.1 vs. 36.3+/-7.6%; p = 0.01) and amount (0.9+/-0.2 vs. 1.7+/-0.3 mM; p = 0.06) of vesicular cholesterol were lower in gallbladder biles. Similar results were found for vesicular phospholipids (1.3+/-0.8 vs. 11.6+/-6.0%; p = 0.05; and 0.3+/-0.1 vs. 1.1+/-0.5 mM; p = 0.07). The vesicular cholesterol/ phospholipid ratio was 1.7+/-0.5 in hepatic bile but 4.3 and 1.8 in the 2 gallbladder biles which contained vesicles. Mixed micelles in gallbladder biles had a higher cholesterol saturation index than mixed micelles in hepatic biles (1.43+/-0.11 vs. 1.15+/-0.07; p = 0.02). CONCLUSIONS: Concentration of bile in the gallbladder leads to decreased vesicular lipid contents. The finding of supersaturated mixed micelles in the absence of vesicles in a significant number of patients points to the possibility of non-vesicular modes of crystallization.

Asymmetric distribution of phosphatidylcholine and sphingomyelin between micellar and vesicular phases. Potential implications for canalicular bile formation.

Both phosphatidylcholine (PC) and sphingomyelin (SM) are the major phospholipids in the outer leaflet of the hepatocyte canalicular membrane. Yet, the phospholipids secreted into bile consist principally (>95%) of PC. In order to understand the physical;-chemical basis for preferential biliary PC secretion, we compared interactions with bile salts (taurocholate) and cholesterol of egg yolk (EY)SM (mainly 16:0 acyl chains, similar to trace SM in bile), buttermilk (BM)SM (mainly saturated long (>20 C-atoms) acyl chains, similar to canalicular membrane SM) and egg yolk (EY)PC (mainly unsaturated acyl chains at sn-2 position, similar to bile PC). Main gel to liquid-crystalline transition temperatures were 33. 6 degrees C for BMSM and 36.6 degrees C for EYSM. There were no significant effects of varying phospholipid species on micellar sizes or intermixed-micellar/vesicular bile salt concentrations in taurocholate-phospholipid mixtures (3 g/dL, 37 degrees C, PL/BS + PL = 0.2 or 0.4). Various phases were separated from model systems containing both EYPC and (EY or BM)SM, taurocholate, and variable amounts of cholesterol, by ultracentrifugation with ultrafiltration and dialysis of the supernatant. At increasing cholesterol content, there was preferential distribution of lipids and enrichment with SM containing long saturated acyl chains in the detergent-insoluble pelletable fraction consisting of aggregated vesicles. In contrast, both micelles and small unilamellar vesicles in the supernatant were progressively enriched in PC. Although SM containing vesicles without cholesterol were very sensitive to micellar solubilization upon taurocholate addition, incorporation of the sterol rendered SM-containing vesicles highly resistant against the detergent effects of the bile salt. These findings may have important implications for canalicular bile formation.

Impaired healing of extraperitoneal intestinal anastomoses.

BACKGROUND: The extra-anatomical position of a cervical oesophagogastrostomy might be a reason for impaired anastomotic healing. METHODS: This hypothesis was tested in a rat model. Jejunal resection with an end-to-end jejunojejunostomy was placed intra-abdominally in group 1 (n = 24) and subcutaneously in group 2 (n = 30). Jejunum without anastomosis was placed subcutaneously in group 3 (n = 12). After 3, 7 or 14 days the rats were killed; the bursting pressure of the anastomosis or jejunum was measured and the hydroxyproline level was determined. RESULTS: Two of 24 rats in group 1 and eight of 30 in group 2 died following anastomotic leakage (P not significant) and were excluded from other measurements. Bursting pressure was decreased after 3 days in group 1 (mean(s.e.) 62(10) mmHg) and group 2 (57(10) mmHg) compared with that in group 3 (204(17) mmHg) (P < 0.001). After 7 days, it was in the normal range in group 1 (200(14) mmHg), but lower in group 2 (104(15) mmHg) compared with that in group 3 (230(8) mmHg) (P < 0.001). Differences in hydroxyproline levels were not statistically significant between the groups after 3, 7 and 14 days. CONCLUSION: Healing of jejunojejunostomies is impaired in an extraperitoneal position compared with an intra-abdominal position.

A randomized trial in primary biliary cirrhosis comparing ursodeoxycholic acid in daily doses of either 10 mg/kg or 20 mg/kg. Dutch Multicentre PBC Study Group.

BACKGROUND: Ursodeoxycholic acid (UDCA) prolongs transplantation-free survival in primary biliary cirrhosis (PBC). However, the optimal therapeutic dose has not been established. AIM: To compare the effects of UDCA administered in daily doses of 10 vs. 20 mg/kg on symptoms, liver biochemistry and biliary UDCA enrichment. METHODS: A 6-month multicentre randomized open controlled trial was conducted to assess the effects of an increase in the dose of UDCA to 20 mg/kg/day vs. continuation of 10 mg/kg/day for patients who had not achieved biochemical normalization during treatment for at least 6 months with the 10 mg/kg dose. Clinical and laboratory evaluations were performed at entry and at 3-month intervals. The percentage UDCA in duodenal bile was assessed at entry and at 6 months. RESULTS: Sixty-one patients were enrolled. No side-effects of UDCA were observed. Within the 20 mg/kg/day group significant decreases were found for alkaline phosphatase (- 8%; P = 0.003), aspartate aminotransferase (- 11%; P = 0.01), alanine aminotransferase (- 17%; P < 0.001), gamma-glutamyl transferase (- 34%; P < 0.001), immunoglobulin M (- 11%; P = 0.002) and cholesterol (- 8.1%; P < 0.001). In the 10 mg/kg group none of these parameters differed significantly from baseline. No significant differences between dose groups for symptom scores or serum bilirubin were found. Biliary enrichment with UDCA increased from 37% to 46% in the 20 mg/kg group (P = 0.02) while remaining stable in the 10 mg/kg group. CONCLUSIONS: Liver biochemistry improved in PBC patients receiving UDCA 20 mg/kg/day compared to a dose of 10 mg/kg/day. Both doses were equally well tolerated. These results indicate that UDCA 10 mg/kg/ day is a suboptimal dose for treating PBC.

Quantitation of cholesterol-carrying particles in human gallbladder bile.

The inter-mixed micellar/vesicular (non-phospholipid-associated) bile salt concentration (IMC) can be rapidly measured in model biles by centrifugal ultrafiltration, thus allowing reliable separation of vesicular and micellar cholesterol carriers by gel filtration with an elution buffer containing bile salts at the correct IMC (Donovan, J. M., and A. A. Jackson. 1993. J. Lipid Res. 34: 1121-1129). We adapted this method to the more complex human gallbladder bile and examined the relationship between cholesterol solubilization and crystallization in gallbladder biles from 10 cholesterol gallstone patients. The IMC (mean +/- SEM) was 9.67 +/- 1.97 (range 3.56-35.02) mM with significant enrichment with hydrophilic bile salt species. Upon gel filtration of these biles with an eluant buffer containing 10 major bile salts at concentrations according to their IMC, cholesterol was found to be solubilized mainly in mixed micelles. Vesicles were detected in all 10 biles after separation by KBr density gradient ultracentrifugation but in only 5 of these biles with the IMC method. Biles without vesicles had a lower CSI (1.15 +/- 0.12 vs. 1.90 +/- 0.28, P < 0.05), a higher total lipid concentration (11.9 +/- 2.3 vs. 5.9 +/- 1.1, P < 0.05), and a higher bile salt/ (bile salt + phospholipid) ratio (0.83 +/- 0.01 vs. 0.74 +/- 0.04, P = 0.07). For both IMC and ultracentrifugation methods, vesicular cholesterol concentration showed a negative correlation with crystal observation time and a positive correlation with cumulative crystal score during 21 days. Our data indicate that methods such as density gradient ultracentrifugation overestimate vesicular cholesterol solubilization in human biles.

Quantifying vesicle/mixed micelle partitioning of phosphatidylcholine in model bile by using radiolabeled phosphatidylcholine species.

Phospholipid in vesicles and mixed micelles of (model) bile has been traced or quantitated (or both) by adding radioactively labeled phosphatidylcholine species. The question is whether these labeled species mix homogeneously with the phosphatidylcholine species mixture present, such that the label distribution reflects the already established mass partitioning of species. In this study, model bile containing egg yolk phosphatidylcholine was incubated with radioactive phosphatidylcholine species. Vesicle and mixed micelle fractions were separated by gel filtration. Radiochemical analysis of the species distribution confirmed chemical analysis: 1,2-di(14C)palmitoyl-phosphatidylcholine was enriched in the vesicles, the 1-palmitoyl-2-(14C)oleoyl species evenly distributed, and the 1-palmitoyl-2-(14C)linoleoyl species more expressed in mixed micelles. This indicates that the distribution of an added radioactive phosphatidylcholine species represents the vesicle/mixed micelle distribution of that particular phosphatidylcholine species. Consequently, the label distribution of a particular added radioactive phosphatidylcholine species can be used to calculate the vesicle/mixed micelle partitioning of total phosphatidylcholine only after it has been established that the radioactive species reaches the same partitioning as total phosphatidylcholine.

Gastric mucosal phospholipids in dogs with familial stomatocytosis-hypertrophic gastritis.

In dogs, hypertrophic gastritis, which resembles Ménétrier's disease in man, has been demonstrated to be part of a hereditary syndrome called familial stomatocytosis-hypertrophic gastritis. In addition to hypertrophic gastritis, affected dogs exhibit abnormal blood phospholipid composition. Phospholipids may play a role in maintaining gastric mucosal integrity, and this may be compromised in gastritis. The question arises whether the differences in blood phospholipids may result from a disorder that might also be revealed in the composition of gastric mucosal phospholipids. We analysed the phospholipid composition of gastric mucosa from four dogs with familial stomatocytosis-hypertrophic gastritis. The general phospholipid composition and the molecular composition of phosphatidylcholine from mucosal tissue in the corpus of the stomach where hypertrophic gastritis was evident were not different from that of the antrum, where the tissue was normal. These results do not corroborate a relation between the gastric mucosal phospholipid composition and hypertrophic gastritis.

Effects of bile salt hydrophobicity on crystallization of cholesterol in model bile.

Precipitation of cholesterol crystals is an essential step in gallstone formation. In the present study we found much faster and more extensive precipitation of various cholesterol crystal shapes in whole model biles containing the hydrophobic bile salt taurodeoxycholate than in biles containing the relatively hydrophilic taurocholate. Addition of taurodeoxycholate to isolated cholesterol-phospholipid vesicles also induced more crystallization than taurocholate. Crystallization behaviour in whole model biles and in vesicles after addition of corresponding bile salts was very similar. The very hydrophilic bile salts tauroursodeoxycholate and taurohyodeoxycholate never induced crystallization from vesicles, and crystallization in corresponding whole model biles did not occur. These bile salts also reduced crystallization dose dependently after addition of taurodeoxycholate to vesicles. Ultracentrifugation experiments suggested a higher vesicular cholesterol-phospholipid bile salts. These findings indicate that bile salt hydrophobicity influences shape of cholesterol crystals and extent of crystallization, possibly by modulating the vesicular cholesterol-phospholipid ratio.

Behavior of various cholesterol crystals in bile from patients with gallstones.

Besides classical plate-like cholesterol monohydrate crystals, a variety of crystal shapes have recently been described in model biles but their relevance for human gallstone formation is unknown. We therefore studied crystallization behavior in gallbladder bile from cholesterol stone patients (54 untreated, 13 ursodeoxycholate-treated) and 6 pigment stone patients. Bile preparation by ultrafiltration or ultracentrifugation left biliary lipid composition unchanged but plates and their aggregates, and arcs and needles crystallized more extensively while spirals and tubules crystallized less extensively in ultra-centrifuged bile than in ultrafiltered bile. Plates, aggregates, and arcs/needles were seen in 90 percent, 36 percent, and 18 percent of the cases respectively of fresh unfiltered biles of untreated cholesterol stone patients, while spirals and tubules were always absent. In ultrafiltered biles arcs/needles, plates and aggregates progressively developed as persistent forms. Spirals and tubules occurred transiently and were associated with increased deoxycholic acid (+41 percent, P = .039) and with more extensive cholesterol crystallization. Rate/extent of crystallization of all crystal forms was higher (P < .0001) for multiple than solitary cholesterol stone patients. Ursodeoxycholate-treated patients had atypical platelike cholesterol crystals in fresh unfiltered biles that decreased in size at prolonged observation and in 2 cases even dissolved after 15 and 20 days. No crystals ever developed in ultra-filtered bile of ursodeoxycholic acid (UDCA)-treated patients during 21 days. Pigment stone patients seldom developed crystals. Thus, plates, aggregates and arcs/needles are persistent forms with high crystallization rate in multiple cholesterol stone patients. Tubules and spirals are transient forms that are associated with more extensive crystallization. Patients treated with ursodeoxycholate often have atypical crystals in their fresh bile.

Effects of simvastatin and cholestyramine on bile lipid composition and gall bladder motility in patients with hypercholesterolaemia.

Although the effects of 3-hydroxy, 3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors and bile acid sequestrants on bile lipid composition have been studied separately, no data are available on combination therapy of these drugs. Moreover, the effects of prolonged (four weeks) administration of these drugs on gall bladder motility, an important determinant of cholesterol gall stone formation, have not been studied so far. A prospective study was therefore performed with eight patients who had hypercholesterolaemia (age 53 (5) (SEM), body mass index 27.4 (1.1) kg m-2, low density lipoprotein cholesterol 5.9 (0.3) mmol/l). They received treatment during three periods of four weeks with simvastatin 20 mg/day, cholestyramine 4 g twice daily, and a combination of both in random order, each treatment period separated by a two week wash out period. Before treatment and after each treatment period, postprandial gall bladder motility was studied with ultrasound, followed by duodenal bile sampling. Serum cholesterol decreased in all subjects in any treatment period illustrating good compliance. Molar percentages in duodenal bile of cholesterol, phospholipids, and bile salts were unchanged during simvastatin and cholestyramine treatment. During combined therapy percentage bile salts was lower (72.5 (2.9)% v 77.8 (1.7)% at baseline, p < 0.05) whereas phospholipids were higher (21.2 (2.4)% v 16.4 (1.3)% at baseline, p < 0.05). As a result cholesterol saturation index (CSI) did not change in any treatment period. No cholesterol crystals were detected in any bile sample, taken at baseline and after each treatment period. Bile salt hydrophobicity index during cholestyramine (0.19 (0.02)) and combined treatment (0.22 (0.01)) decreased strongly compared with baseline (0.34 (0.01), p < 0.001, p < 0.01, respectively), resulting from increased proportions of glycocholate (59.4 (3.9)% (cholestyramine), 55.6 (2.4)% (combination), and 28.2 (2.2) (baseline), p < 0.001)) and decreased proportions of deoxycholic acid and chenodeoxycholic acid. Fasting gall bladder volume was increased during simvastatin (28.7 (2.8) ml) v baseline (23.2 (2.3) ml, p < 0.01) whereas, residual volume did not differ (5.7 (0.9) ml (simvastatin) v 5.9 (0.7) (baseline). During cholestyramine and combined treatment, no significant differences in gall bladder motility were seen. In conclusion, this study suggests that HMG-CoA reductase inhibitors alone and combined with cholestyramine do not affect major determinants of cholesterol gall stone formation, for example, CSI and gall bladder emptying. In addition cholestyramine alone and combined with simvastatin leads to a strong decrease of bile salt hydrophobicity, which may be beneficial in the prevention of nucleation of cholesterol crystals.

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.

The effects of the 3-hydroxy, 3-methylglutaryl coenzyme A reductase inhibitor pravastatin on bile composition and nucleation of cholesterol crystals in cholesterol gallstone disease.

3-hydroxy,3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors reduce biliary cholesterol saturation index (CSI) in duodenal bile in hypercholesterolemic patients and might be useful for gallstone dissolution. However, preliminary data suggest that these drugs are not effective in this respect. We therefore studied 33 patients with radiolucent gallstones in an opacifying gallbladder who were scheduled for elective cholecystectomy. Patients were treated with 40 mg pravastatin day-1 or placebo during the 3 weeks before surgery. Six patients could not be evaluated. Baseline characteristics (age, sex, body mass index, serum cholesterol, and the solitary/multiple gallstone ratio) were similar in both groups. Serum cholesterol fell by 39% in the pravastatin group (P < .001) and remained unchanged in the placebo group. Biliary cholesterol (9.5 +/- 1.3 vs. 14.3 +/- 1.5 mmol/L, P = .026), and phospholipid concentrations (24.8 +/- 3.9 vs. 36.7 +/- 3.9 mmol/L, P = .043) were lower in the pravastatin group. Although bile salt concentrations were lower in the pravastatin group (114 +/- 21 vs. 152 +/- 15 mmol/L), this difference was not significant. CSI was not different between both groups (142 +/- 27% [pravastatin] vs. 113 +/- 6% [placebo], P = NS). Cholesterol crystals were present in fresh bile in 7 of 13 patients in the pravastatin group and in 11 of 14 controls (P = NS). Nucleation time was comparable between the 2 groups (13 +/- 3 vs. 9 +/- 3 days, P = NS). Bile salt species and molecular species of phospholipids determined with high-performance liquid chromatography did not differ either between both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of bile salt and phospholipid hydrophobicity on lithogenicity of human gallbladder bile.

Increased biliary bile salt and phospholipid hydrophobicity may promote nucleation of cholesterol crystals and gallstone formation. We therefore compared bile salt composition (determined by gas-liquid chromatography) in patients with cholesterol (n = 35) and pigment (n = 16) gallstones (group A). Bile salt composition and cumulative bile salt hydrophobicity index were not different between both stone types. Hydrophobicity index or % of individual bile salts did not correlate with cholesterol saturation index or nucleation time. In an additional 21 cholesterol stone patients (group B) biliary bile salt and phospholipid hydrophobicity as determined by high-pressure liquid chromatography did not correlate with cholesterol saturation index or nucleation time. In both group A and group B, cholesterol stone patients with cholesterol crystals in their fresh biles had a higher % deoxycholic acid, a lower % cholic acid and a higher bile salt hydrophobicity index than crystal-negative patients. This study indicates the need for further research on the role of bile salt hydrophobicity in the pathogenesis of gallstones.

Normal cations and abnormal membrane lipids in the red blood cells of dogs with familial stomatocytosis-hypertrophic gastritis.

Examination of the red blood cells (RBCs) of eight dogs with familial stomatocytosis-hypertrophic gastritis (FS-HG), a multiorgan disease associated with hemolytic anemia, hereditary stomatocytosis (HSt), and hypertrophic gastritis resembling Ménétrier's disease in man, showed abnormal osmotic fragility, normal mean corpuscular volume, slightly increased cell water, and normal cation content and cation fluxes. Cholesterol was decreased in RBC and increased in plasma. In both RBCs and plasma, total phospholipid (PL) was normal, phosphatidylcholine (PC) decreased, and sphingomyelin increased. The palmitic acid content of PC was increased, and the stearic acid content of PC was decreased. Sodium dodecyl sulfate electrophoresis of RBC membrane proteins was normal. These findings have not been described previously in HSt. They suggest that in FS-HG, abnormal composition of the PL in RBCs secondary to abnormal PL in plasma causes defective membrane function and stomatocytic shape-change. This conclusion was supported by a shortened half-life of 51Cr-labeled RBCs from normal dogs after transfusion in dogs with FS-HG. It was concluded (1) that not all hereditary forms of stomatocytosis are necessarily associated with an intrinsic structural defect of the RBC membrane, but that the change in shape of RBC may also be induced by abnormal composition of the plasma; (2) that stomatocytosis may be caused by loss of membrane surface area rather than by the increased cation uptake such as has been shown in some human kindreds with HSt, (3) that FS-HG is a disorder of lipid metabolism, and by consequence, (4) that abnormal lipid metabolism might be involved in the pathogenesis of Ménétrier's disease.