Stasis before gallstone formation: Altered gallbladder compliance or cystic duct resistance?

Gallbladder stasis occurs before gallstone formation and provides the link between the hepatic secretion of supersaturated bile and cholesterol cholelithiasis. We recently observed that cystic duct resistance increases while sphincter of Oddi resistance is unchanged in the presence of lithogenic bile without gallstones. Whether alterations in gallbladder function also lead to gallbladder stasis has been unclear. Therefore, we tested the hypothesis that before gallstone formation, stasis results from increased cystic duct resistance and altered gallbladder compliance. Adult, male prairie dogs were fed either a trace cholesterol (control) or a 0.4 percent cholesterol-enriched diet. Cystic duct resistance increased but gallbladder compliance was unchanged before gallstone formation. A significant correlation (p < 0.001) was found between the lithogenic index and cystic duct resistance in pregallstone animals. We conclude that increased resistance to flow across the cystic duct, and not altered gallbladder compliance, is etiologically related to bile stasis, an important event in gallstone formation.     

Effects of cholecystokinin on gallbladder stasis and cholesterol gallstone formation

Recent studies suggest an etiologic role for gallbladder stasis in the genesis of cholesterol gallstones. The effect of periodic gallbladder emptying on stone prevention is not clear. Using the prairie dog model, we tested the hypothesis that daily cholecystokinin-octapeptide (CCK-OP) prevents gallbladder stasis and cholesterol gallstone formation. Prairie dogs were fed either a control or a 0.4% cholesterol-enriched chow for 6 weeks. Cholesterol-fed animals received a daily intramuscular injection of either saline, CCK-OP, 0.2 μg/kg or CCK-OP, 1.0 μg/kg. Gallbladder bile lithogenic index (LI), bile salt pool size (BSPS), and the degree of radioisotope equilibration between gallbladder and hepatic bile (Rsa-an index of stasis) were determined. The more physiologic dose of CCK-OP (0.2) significantly reduced BSPS and bile lithogenicity, prevented stasis and reduced the incidence of gallstones. Our data suggest that (1) periodic gallbladder emptying decreases bile lithogenicity, prevents stasis, and reduces the incidence of cholelithiasis, (2) stasis is essential to gallstone formation and (3) daily physiologic doses of CCK-OP may be useful for gallstone prophylaxis in high-risk patients.     

Gallbladder contractility and mucus secretion after cholesterol feeding in the prairie dog

The purpose of our study was to evaluate changes in gallbladder contractility and mucus secretion in vitro during the early stages of gallstone formation in prairie dogs. Thirty-two animals were divided into five groups. Control animals were fed a trace cholesterol diet. Experimental animals were fed a high-cholesterol diet for 3, 6, 8, and 14 days, respectively. Muscle stress was measured in response to cholecystokinin octapeptide in each of the groups. The maximal stresses in the 8-day diet (68 +/- 7 gm/cm2) (mean +/- SEM) and 14-day diet animals (83 +/- 7 gm/cm2) were found to be significantly lower than those of the control animals (137 +/- 12 gm/cm2). The stress in 3-day diet animals was significantly greater (224 +/- 23 gm/cm2). A significant increase in mucus secretion was observed only in 14-day diet animals (11.0 +/- 0.5 X 10(6) dpm/gm dry wt) compared with the control animals (6.4 +/- 1.0 X 10(6) dpm/gm). The decrease in contractility may be the initial event in cholesterol stone formation, and the prolonged exposure of the gallbladder epithelium to crystals may stimulate the release of mucus into the bile.     

The relationship of cholecystectomy and taurocholic acid feeding to bile composition and hepatocyte function in prairie dogs

The prairie dog was used as a model for human gallstone formation. Stones formed in the gallbladder of all animals on a lithogenic diet. Hepatic bile was nonlithogenic, whereas gallbladder bile promoted cholesterol precipitation. Addition of taurocholate to the diet reduced the number of stones and lithogenicity. Cholecystectomy resulted in an increased bile flow and reduced secretion of cholesterol in the animals on a high cholesterol diet. Reduction of cholesterol and bile acid synthesis by negative feedback was demonstrated in isolated hepatocyte culture. The shift of bile salt production to chenodeoxycholates on a high cholesterol intake was demonstrated both in vivo and in vitro. A theory of gallstone formation is presented which hypothesizes a defect in hepatocyte storage of cholesterol rather than bile acid synthesis as the primary effect, relegating the problems to one of a disease of lipid metabolism.     

Ileal resection-induced gallstones: altered bilirubin or cholesterol metabolism?

Ileal resection has been shown to increase the risk of cholelithiasis. Earlier studies in humans suggested that ileal resection increases the cholesterol saturation index. Recent data from patients on long-term parenteral nutrition and from animals, however, have suggested that ileal resection predisposes to pigment gallstone formation. We therefore tested the hypothesis that ileal resection alters bile calcium and bilirubin metabolism without affecting the cholesterol saturation index. Adult male prairie dogs underwent either sham laparotomy (eight prairie dogs) or ileal resection (16 prairie dogs). All animals were fed a trace cholesterol (nonlithogenic) diet before and for 4 weeks after operation. Pigment gallstones were present in 44% of the ileal-resected animals and in none of the sham animals (p less than 0.05). Calcium bilirubinate crystals were present in 94% of the ileal-resected animals and in none of the sham animals (p less than 0.01). Gallbladder bile calcium (25.6 +/- 2.4 versus 17.2 +/- 1.1 mg/dl; p less than 0.05) and total bilirubin (29.3 +/- 4.0 versus 9.4 +/- 1.8 mg/dl; p less than 0.01) concentrations were significantly greater in ileal-resected animals. The cholesterol saturation index of gallbladder bile, however, was no different in ileal-resected (0.53 +/- 0.04) and in sham-operated animals (0.50 +/- 0.04). Although initial studies suggested that the cholesterol saturation index of hepatic bile was increased after ileal resection, a second set of experiments demonstrated that this phenomenon resulted from washout of bile salts that were already in extremely low concentrations in hepatic bile. We conclude that alterations in bilirubin, but not cholesterol, metabolism result in pigment gallstone formation after ileal resection.     

The role of cystic duct resistance in the pathogenesis of cholesterol gallstones

Several recent clinical and laboratory observations suggest that impaired gallbladder emptying is important in the pathogenesis of cholesterol cholelithiasis. However, the exact mechanism by which gallbladder stasis occurs in the majority of patients who form gallstones has not been clear. We tested the hypothesis that impaired gallbladder emptying antedates cholelithiasis and results from increased resistance to bile flow. Using the prairie dog gallstone model, resistance to flow through the cystic duct (CD) and sphincter of Oddi (SO) was measured in control and cholesterol-fed animals. Prairie dogs were fed either a control (trace cholesterol) or a 0.4% cholesterol-enriched diet known to induce gallstones in 6 weeks. Resistance across the CD and SO was measured at 4 weeks (pregallstone) and 16 weeks (gallstone). Resistance was measured by infusing lactated Ringer's solution through the CD and SO at four separate flow rates while gallbladder and distal common bile duct pressures were recorded. Resistance to flow through the cystic duct increased prior to gallstone formation and continued to increase during the 16 weeks of cholesterol feeding. In comparison, sphincter of Oddi resistance remained normal despite chronic exposure to lithogenic bile and formation of stones within the gallbladder. The increased cystic duct resistance observed prior to gallstone formation provides a mechanism for diminished gallbladder emptying and suggests an etiological role for increased cystic duct resistance in the pathogenesis of cholesterol gallstones.     

Effect of dietary ethanol on gallbladder absorption and cholesterol gallstone formation in the prairie dog

Dietary ethanol has been reported to protect against cholesterol gallstone formation. Because enhanced gallbladder absorption of water is important in cholesterol cholelithiasis, we examined the hypothesis that ethanol acts by inhibiting the absorptive function of the gallbladder. Eighteen adult male prairie dogs were fed a lithogenic liquid diet containing 0.4% cholesterol. Half of the animals received 30% of total calories as ethanol, whereas their pair-fed controls received equicaloric amounts of maltose-dextrin. After 3 months, the gallbladders were inspected for gallstones and crystals, and gallbladder and hepatic bile were analyzed. Cholesterol stones and crystals were present in all nine controls. None of the alcohol-fed animals had stones, but four had cholesterol crystals. Gallbladder cholesterol, phospholipids, and total calcium were significantly decreased in alcohol-fed animals. In both gallbladder and hepatic bile, the cholesterol saturation index was significantly lower in alcohol-fed animals, as was the ratio of trihydroxy to dihydroxy bile salts. The ethanol-supplemented diet produced a significant decrease in the absorption of water by the gallbladder as indicated by changes in the gallbladder bile to hepatic bile ratios of the total bile salt concentration (7.29 +/- 1.25 versus 3.84 +/- 0.56; p less than 0.05) and the total calcium (3.37 +/- 0.24 versus 2.43 +/- 0.29; p less than 0.05). These findings indicate that the protective effect of ethanol may be related to its ability both to inhibit gallbladder absorption of water and to alter the composition of biliary lipids.     

Hyodeoxycholic acid: a new approach to gallstone prevention

Hyodeoxycholic acid and its isomer, 6 beta-hyodeoxycholic acid, when added to a lithogenic diet prevented the formation of cholesterol gallstones and crystals in prairie dogs. This beneficial effect occurred in the presence of bile supersaturated with cholesterol. Hyodeoxycholic acid abolished the feedback inhibition of hepatic hydroxymethylglutaryl coenzyme A reductase activity, the rate-limiting enzyme of cholesterol synthesis, and prevented elevations in serum and liver cholesterol observed in animals fed a 0.4 percent cholesterol diet. The gallbladder bile of the animals fed hyodeoxycholic acid and 6 beta-hyodeoxycholic acid contained abundant liquid crystals. This suggests that these bile acids prevented the transition of cholesterol from its liquid crystalline phase to solid crystals and stones.     

An experimental study on preventing gallstone formation by exogenous cholecystokinin

It is well known that stasis of lithogenic bile in the gallbladder is an important factor in cholesterol gallstone formation. In this study, hamsters fed with standard lithogenic diet were given physiologic dose of exogenous cholecystokinin-octapeptide daily to facilitate emptying of the gallbladder. It was found that there was significant reduction in the gallstone formation. This study suggests that gallbladder motility is closely correlated with cholesterol gallstone formation, and administration of exogenous cholecystokinin-octapeptide can effectively prevent gallbladder stasis and reduce the incidence of cholelithiasis. This method may be useful for gallstone prophylaxis in high-risk individuals.     

The Use of Simvastatin for the Prevention of Gallstones in the Lithogenic Prairie Dog Model

Background: Surgery for morbid obesity is rapidly increasing. Patients undergoing bariatric surgery are prone to gallstone development during the rapid weight loss. These patients are often given medications such as ursodeoxycholic acid to prevent gallstone formation; however, these medications are often poorly tolerated by patients, who subsequently discontinue them. We performed a study in a lithogenic animal model to assess the effectiveness of a potential alternate medication for gallstone prevention. Methods: 20 male prairie dogs were randomly separated into 2 groups and fed a lithogenic diet for 28 days. The study group animals were given 2.5 mg of the HMG-CoA reductase inhibitor simvastatin. Total cholesterol and triglycerides were measured and an open cholecystectomy was performed on each animal at the conclusion of the study period. The gallbladder was visually inspected for gallstones and microscopic biliary cholesterol crystal formation. Results: There was a decrease of 36% in the total cholesterol of the study animals compared to controls. The animals treated with simvastatin showed gallstone formation in 5/10 (50%) of animals, compared with 6/10 (60%) of control animals. The study animals demonstrated microscopic cholesterol crystal formation in 80%, identical to the number found in the control animals. Conclusion: Despite a reduction in cholesterol, simvastatin prevented neither gallstone formation nor biliary cholesterol crystals in this animal model. Given the rapid increase in the number of bariatric surgical procedures coupled with the poor tolerance of ursodeoxycholic acid, viable alternatives should continue to be sought for these patients.     

Bilirubin monoglucuronide promotes cholesterol gallstone formation

Recent evidence suggests that cholesterol (Ch) solubility in bile is determined by a complex interaction of mixed micelles and lecithin-cholesterol vesicles. Bilirubin monoglucuronide (BMG), which binds to bile salts and incorporates into mixed micelles, may displace cholesterol from micelles into vesicles, thus favoring cholesterol monohydrate crystal precipitation. Therefore, we designed an experiment to test the hypothesis that BMG may enhance cholesterol gallstone formation without inducing cholesterol supersaturation. For 8 weeks, 28 adult male prairie dogs were fed either a control, nonlithogenic diet (0.03% Ch), a high carbohydrate diet (CHO) which has no cholesterol but increases hepatic bilirubin secretion, or the same CHO diet plus 0.03% Ch. Cholecystectomy was then performed, and bile was examined microscopically for stones or crystals and analyzed for BMG and biliary lipids. Cholesterol saturation index was calculated. Cholesterol gallstones were found in none of the control animals and in 13% of the CHO-fed animals. However, the addition of trace cholesterol to the CHO diet resulted in an 88% incidence of cholesterol gallstones (P less than 0.001 vs control, P less than 0.01 vs CHO, respectively). Gallbladder bile was unsaturated with cholesterol in all groups. (control = 0.65 +/- 0.05, CHO = 0.46 +/- 0.05, CHO + 0.03% Ch = 0.70 +/- 0.03). CHO feeding alone or with trace cholesterol significantly elevated gallbladder bilirubin monoglucuronide, phospholipid, and cholesterol concentrations when compared to controls. These data suggest that in the prairie dog a high carbohydrate diet with only trace amounts of cholesterol increases bilirubin monoglucuronide in gallbladder bile and causes cholesterol gallstone formation without inducing cholesterol supersaturation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Interaction of chenodeoxycholic acid and dietary cholesterol in the treatment of cholesterol gallstones

Standard doses of chenodeoxycholic acid (15 mg/kg/day) fail to dissolve gallstones in 30 to 50 percent of patients with radiolucent gallstones in a functioning gallbladder. In humans, increasing dietary cholesterol produces increased biliary secretion of cholesterol. Restriction of dietary cholesterol reduces the minimum effective dose of chenodeoxycholic acid and speeds gallstone dissolution. In this study we investigated the interaction of dietary cholesterol and chenodeoxycholic acid in the prevention of gallstones in the prairie dog gallstone model. In animals fed a moderately lithogenic diet, standard doses of chenodeoxycholic acid failed to prevent gallstones. Reduction of the cholesterol stimulus or doubling the dose of chenodeoxycholic acid prevented the formation of gallstones. These findings support the hypothesis that the formation and dissolution of cholesterol gallstones are an expression of the relative strengths of saturating and desaturating stimuli. Therefore, rational therapy for cholesterol gallstone dissolution and prevention requires both reduction of lithogenic stimuli and optimal titration of chenodeoxycholic acid.     

Gallbladder absorption increases during early cholesterol gallstone formation

The hypothesis that the presence of cholelithogenic bile during the early stages of cholesterol gallstone formation promotes gallbladder absorption of water and electrolytes was tested in a prairie dog gallstone model. An increase in gallbladder transport of water and sodium was observed in cholesterol-fed prairie dogs at a time when cholesterol crystals were present, but before gallstone formation. These data suggest that in the presence of cholesterol-saturated bile, in vivo gallbladder absorption is increased during the early stages of cholesterol gallstone formation. The resulting increase in the solute concentration may promote nucleation and, therefore, be an important etiologic factor in cholesterol gallstone formation.     

Altered biliary prostaglandins and cholesterol gallstones: an in vivo study

Recent investigations suggest that biliary prostaglandin metabolism is altered during cholesterol gallstone formation. Most of the available data, however, has been obtained from in vitro studies. The purpose of the present study was to define the effects of cholesterol gallstone formation on in vivo biliary prostaglandin metabolism. Male prairie dogs were fed either a control chow for 21 days or a 1.2% cholesterol-enriched chow for 14-21 days. Cholecystectomy was performed and gallbladder tissue and bile were collected for analysis of prostaglandin concentrations using radioimmunoassay techniques. Gallbladder bile was examined for the presence of crystals and stones. No control animals but all cholesterol-fed animals developed either cholesterol crystals or gallstones (P less than 0.001). Concentrations of prostaglandin E2, prostaglandin F2 (PGF2 alpha), and the stable metabolic products of prostacyclin and thromboxane A2, 6-keto-PGF1 alpha and thromboxane B2 (TXB2), respectively, were decreased 60-85% in the gallbladder tissue of animals with crystals and gallstones compared to controls. Additionally, gallstone containing animals and those with crystals demonstrated a significant increase in the gallbladder bile concentrations of PGF2 alpha, 6-keto-PGF1 alpha, and TXB2. These findings lend support to previously reported in vitro studies suggesting that prostaglandin synthesis increases at an early stage of experimentally induced cholesterol gallstone formation.     

The effects of amiloride on biliary calcium and cholesterol gallstone formation.

Recent studies indicate that gallbladder absorption increases during the early stages of experimentally-induced cholesterol gallstone formation. The purpose of the present study was to ascertain whether pharmacologic inhibition of gallbladder ion transport and absorption reduces the incidence of experimentally-induced cholesterol gallstones. Prairie dogs were fed either a control chow or a 1.2% cholesterol-enriched chow for 15 days. One group of cholesterol-fed animals received saline via an orogastric tube; another group received amiloride, a drug known to inhibit in vitro ion transport in the prairie dog gallbladder. The incidence of gallstones in cholesterol-fed animals was reduced from 83% to 13% (p less than 0.025) when the animals were treated with amiloride; this occurred despite a cholesterol-saturation index comparable to that observed in gallstone animals. Additionally, although biliary calcium decreased in the gallbladder, hepatic bile did not in the amiloride-treated animals. These data provide further evidence that altered gallbladder absorption and increased biliary calcium are important factors in the pathogenesis of cholesterol gallstones.     

Caffeine prevents cholesterol gallstone formation

Methylxanthines are known to inhibit in vitro gallbladder absorption. Increased gallbladder absorption has been observed during formation of cholesterol gallstones. Therefore we tested the hypothesis that caffeine would inhibit in vivo gallbladder absorption and thus prevent formation of cholesterol gallstones. Sixteen adult male prairie dogs received a control nonlithogenic diet, and 16 were fed a diet containing 1.2% cholesterol. Half of the animals in each group received caffeine in their drinking water. Gallbladder and hepatic bile were examined microscopically and analyzed for biliary lipids and electrolytes. The gallbladder/hepatic bile ratios of bile acids and sodium were calculated as indices of gallbladder absorption. All eight animals receiving the 1.2% cholesterol diet formed cholesterol gallstones, whereas none of the eight animals fed the cholesterol diet plus caffeine formed gallstones. The cholesterol saturation index was similar, however, in both groups. In animals fed a control diet, the administration of caffeine significantly increased hepatic bile flow and decreased the gallbladder/hepatic bile ratio for both bile acids (5.4 +/- 0.9 vs 3.6 +/- 0.3; p less than 0.05) and sodium (1.26 +/- 0.03 vs 1.12 +/- 0.03; p less than 0.01). In animals fed the high-cholesterol diet, caffeine significantly decreased the ratios for both bile acids (9.0 +/- 1.6 vs 5.3 +/- 0.6; p less than 0.05) and sodium (1.37 +/- 0.06 vs 1.21 +/- 0.01; p less than 0.05), lowered gallbladder bile protein levels, normalized gallbladder stasis, and lowered serum cholesterol levels. In summary, caffeine prevented formation of cholesterol gallstones in this experimental model. The effect of caffeine may be the result of alterations in multiple biliary parameters including the inhibition of gallbladder absorption.     

小鼠胆囊胆固醇结石模型的建立

目的建立简单、可靠、高效的小鼠胆囊胆固醇结石模型,为研究胆石成因及防治提供重要手段。方法C57BL／6小鼠随机分为对照组和模型组,对照组喂饲基础饲料,模型组喂饲致石饲料（基础饲料加10％猪油、1％胆固醇及0．5％胆酸）。两组小鼠分别于喂养4周和8周后,计算小鼠存活率,同时各取一半数量小鼠在乙醚吸入麻醉下手术取胆囊及血液标本,分别检测成石率、血脂浓度及胆汁胆固醇饱和度。结果对照组小鼠8周存活率100％,模型组小鼠死亡1只,存活率95％。对照组8周成石率为零,模型组4周成石率80％,8周成石率100％。血脂分析表明,与对照组比较,模型组4周和8周总胆固醇及低密度脂蛋白显著升高（P〈0．01）,甘油三酯浓度轻度升高（P〈0．05）,高密度脂蛋白显著降低（P〈0．01）。4周和8周时胆汁胆固醇饱和度测定,对照组分别为0．48±0．29和0．58±0．21,模型组分别为1．36±0．36和1．52±0．37,模型组胆固醇浓度处于过饱和状态。结论本模型方法简单、成石率高、动物死亡率低,可作为研究胆石成因及防治的备选模型。     

Cholecystokinin prophylaxis of parenteral nutrition-induced gallbladder disease.

Recent studies indicate that long-term total parenteral nutrition (TPN) induces gallstone formation and acalculous cholecystitis in humans. Cholecystectomy is hazardous for these patients because they frequently have multiple medical problems and have undergone numerous abdominal operations. The present study was designed to develop a method to prevent TPN-induced gallbladder disease. The authors tested the hypothesis that a single daily intravenous infusion of cholecystokinin-octapeptide (CCK-OP) will prevent TPN-induced gallbladder stasis. Eleven prairie dogs received TPN for 10 days. Six of these animals were given a daily infusion of CCK-OP. Control animals were fed ad lib. Each animal's bile salt pool was labeled with intravenous 3H-cholic acid 16 hours prior to acute terminal experiments. The ratio of gallbladder to hepatic bile 3H-cholic acid specific activity (Rsa) provides an index of gallbladder stasis. A Rsa of less than 1.0 indicates gallbladder stasis. TPN animals had a Rsa of 0.54 +/- 0.13 (p less than 0.01 vs. controls), indicating stasis of bile in the gallbladder. Daily CCK-OP infusions resulted in a Rsa of 0.92 +/- 0.10 (p less than 0.05 vs. TPN without CCK-OP), indicating that TPN-induced gallbladder stasis is prevented by daily CCK-OP. Control animals had a Rsa of 1.03 +/- 0.06. The cholesterol saturation indices of gallbladder and hepatic bile were not increased by TPN or CCK-OP. These data indicate that 1) TPN induces gallbladder stasis but does not increase bile lithogenic index; and 2) daily injections of CCK-OP prevent TPN-induced gallbladder stasis.     

The effects of lithogenic bile on gallbladder epithelium.

Prairie dogs were fed a 1.2% cholesterol diet for up to 24 weeks to evaluate the effects of lithogenic bile on the mucosa of the gallbladder. There was a progressive increase in the lithogenic index of the gallbladder bile (1.44 +/- 0.15 at 4 weeks, p less than 0.05). Fifty-five of 70 animals developed gallstones between the second and fourth week. Increasing stone burden was associated with a 27% (p less than 0.05) decrease in the electrical resistance of the epithelium and a 60% (p less than 0.05) decrease in net sodium transport when measured isotopically in an Ussing chamber (3 weeks). After 4 months, seven of ten animals developed inflammatory mucosal polyps characterized by a heavy infiltration of plasma cells into an expanded matrix. Cellular infiltration began as early as 2 weeks. These changes occurred without alterations in the ultrastructural appearance of the epithelium.     

豚鼠胆汁中胃肠激素含量及其在成石过程中的变化△

To investigate the origin and releasing relation of motilin (MTL), vasoactive intestinal peptide (VIP) and somatostatin (SS) in guinea pig bile as well as its effects during gallstone formation. Guinea pig were divided into three groups control group (50 animals), on normal diet; lithogenic group (70 animals), fed with low-protein low fat; and recovering group (50 animals), fed with low-protein low fat and recovering normal food after the experiment of gallstone formation. MTL, VIP and SS in the bile gallbladder tissue and portal vein plasma of the normal control group were measured with radioimmunoassay. Meanwhile the changes of the gut peptides in the bile and the bile components from different groups were also compared. Results In control group the levels of MTL, VIP and SS in the bile were higher than those in the plasma, but, obviously lower than those in the tissues, the concentration relationship between in the bile and in the tissue was a positive correlation. In contrast to the control group, MTL concentration decreased but VIP and SS increased in the bile of the lithogenic group, the physicochemical nature of the bile also became lithogenic. In the recovering group the bile also became lithogenic, but, the concentration of those peptides and the nature of the bile all got normal. Conclusion MTL, VIP and SS in guinea pig bile originate mainly form the gallbladder wall tissues. Food components affect the levels of the gut peptides in bile, which promote the bile lithogenic changes and gallstone formation.