Human beta-glucuronidase. Measurement of its activity in gallbladder bile devoid of intrinsic interference

Pathophysiological preconditions promoting mixed "black" pigment plus cholesterol gallstones in a DeltaF508 mouse model of cystic fibrosis

Gallstones are frequent in patients with cystic fibrosis (CF). These stones are generally "black" pigment (i.e., Ca bilirubinate) with an appreciable cholesterol admixture. The pathophysiology and molecular mechanisms for this "mixed" gallstone in CF are unknown. Here we investigate in a CF mouse model with no overt liver or gallbladder disease whether pathophysiological changes in the physical chemistry of gallbladder bile might predict the occurrence of "mixed" cholelithiasis. Employing a DeltaF508 mouse model with documented increased fecal bile acid loss and induced enterohepatic cycling of bilirubin (Am J Physiol Gastrointest Liver Physiol 294: G1411-G1420, 2008), we assessed gallbladder bile chemistry, morphology, and microscopy in CF and wild-type mice, with focus on the concentrations and compositions of the common biliary lipids, bilirubins, Ca(2+), and pH. Our results demonstrate that gallbladder bile of CF mice contains significantly higher levels of all bilirubin conjugates and unconjugated bilirubin with lower gallbladder bile pH values. Significant elevations in Ca bilirubinate ion products in bile of CF mice increase the likelihood of supersaturating bile and forming black pigment gallstones. The risk of potential pigment cholelithogenesis is coupled with higher cholesterol saturations and bile salt hydrophobicity indexes, consistent with a proclivity to cholesterol phase separation during pigment gallstone formation. This is an initial step toward unraveling the molecular basis of CF gallstone disease and constitutes a framework for investigating animal models of CF with more severe biliary disease, as well as the human disease.

Gallbladder sludge: what is its clinical significance?

Biliary sludge is a mixture of particulate solids that have precipitated from bile. Such sediment consists of cholesterol crystals, calcium bilirubinate pigment, and other calcium salts. Sludge is usually detected on transabdominal ultrasonography. Microscopy of aspirated bile and endoscopic ultrasonography are far more sensitive. Biliary sludge is associated with pregnancy; with rapid weight loss, particularly in the obese; with critical illness involving low or absent oral intake and the use of total parenteral nutrition (TPN); and following gastric surgery. It is also associated with biliary stones with common bile duct obstruction; with certain drugs, such as ceftriaxone and octreotide; and with bone marrow or solid organ transplantation. The clinical course of biliary sludge varies. It often vanishes, particularly if the causative event disappears; other cases wax and wane, and some go on to gallstones. Complications caused by biliary sludge include biliary colic, acute cholangitis, and acute pancreatitis. Asymptomatic patients with sludge or microlithiasis require no therapy. When patients are symptomatic or if complications arise, cholecystectomy is indicated. For the elderly or those at risk from the surgery, endoscopic sphincterotomy can prevent recurrent episodes of pancreatitis. Medical therapy is limited, although some approaches may show promise in the future.

beta-Glucuronidase in common duct bile, methodological aspects, variation of pH optima and relation to gallstones

beta-Glucuronidase of human or bacterial origin may deconjugate bilirubin diglucuronide, causing pigment gallstones. Intrinsic interference by biliary compounds must be minimized for accurate assay of beta-glucuronidase. We report a modified ion-pair extraction of interfering substances by tetrahexylammonium chloride (THAC) in ethyl acetate in the presence of albumin, and a microtitre plate assay for biliary beta-glucuronidase activity in bile with the substrate p-nitrophenol-glucuronide. Adding albumin improved the recovery of beta-glucuronidase activity to 99.8% (CV 1.9%), and 92.2% of the bilirubin in bile samples was extracted in one step. Competitive inhibition was overcome by increasing the substrate concentration. In endoscopically obtained common duct bile from 44 patients, five different beta-glucuronidase activity peaks were identified, at pH 3.9, 4.8, 5.3, 5.8 and 7.2. The pH profiles were classified into one bacterial pattern and five patterns for presumed human beta-glucuronidase. Of the latter patterns, four displayed dual activity peaks. In a second sample, obtained at follow up in four patients, their original pH profile was maintained. In conclusion, using the modified purification and assay system, we found functionally diverse subcategories of human beta-glucuronidase with respect to activity at variable pH. Our results indicate that several pH optima have to be taken into consideration in order to clarify the role of human biliary beta-glucuronidase in the pathogenesis of pigment gallstones. Bacterial beta-glucuronidase activity was associated with duodenal diverticula (p < 0.05) and common duct stones (p < 0.05).

Biliary manometry, bacterial characteristics, bile composition, and histologic changes fifteen to seventeen years after endoscopic sphincterotomy

AIM

To evaluate the function of the biliary sphincter 15 to 17 years after endoscopic sphincterotomy and to investigate if loss of sphincter function is associated with bacterial colonization, changes in bile composition, or inflammation of the biliary system.

METHODS

Eight patients who had undergone endoscopic sphincterotomy for bile duct stones 15 to 17 years previously underwent ERCP with biliary manometry, bile sampling, and biopsy. Manometry was performed using a perfused triple-lumen manometry catheter and a station pull-through technique. Bile samples were cultured and analyzed for biliary lipids, bile salts, bacterial beta-glucuronidase, and phospholipase A2. Biopsy specimens were taken from the proximal common heptic duct for histologic examination.

RESULTS

Manometry demonstrated absent basal sphincter pressure and no choledochoduodenal pressure gradient in all patients. Phasic contractions were observed in two patients. Cholangiography showed stones in one patient. Positive cultures were obtained in three patients, including the patient with stones. All bile samples showed a high content of biliary lipids and cholesterol. Some samples contained considerable amounts of hydrophobic bile salts. Five samples contained very high levels of phospholipase A2 activity. Significant bacterial beta-glucuronidase activity was found in one patient, the patient with stones. Biopsy specimens of the proximal common hepatic duct in three patients showed chronic inflammation with fibrosis and reactive epithelial changes.

CONCLUSIONS

After endoscopic sphincterotomy for bile duct stones, the function of the biliary sphincter is permanently lost. This is associated with bacterial colonization, presence of cytotoxic components in the bile, and chronic inflammation of the biliary system.

Biliary electrolytes and enzymes in patients with and without gallstones

pH, osmolarity, various electrolytes, nine enzymes, and bile acid were determined in hepatic and gallbladder biles from 108 and 100 patients, respectively, relating to various types of gallstones. The pH, osmolarity, and electrolytes were essentially identical in all groups of patients except for slightly higher Ca and Mg in the hepatic bile in patients with muddy pigment stones. The gallbladder bile contained much higher inorganic cations yet remained isosmotic as a result of their sequestration into bile acid micelles. Excluding extremely high values, the activities of nine enzymes in the bile showed only minor differences among four groups of patients except for a high beta-glucuronidase activity in the hepatic bile in patients with muddy pigment stones. The biliary baseline activities of various enzymes and the relation to their serum levels were determined by their sources and subcellular localization in the hepatocytes. We concluded that biliary electrolytes and enzymes were basically similar in patients with and without gallstones except for higher levels of Ca, Mg, and beta-glucuronidase in hepatic bile in patients with muddy pigment stones.

Cholelithiasis in Taiwan. Gallstone characteristics, surgical incidence, bile lipid composition, and role of beta-glucuronidase

The nature and occurrence of gallstones in Taiwan and their etiologic factors might not be the same as in Western countries and warranted a systematic investigation. Gallbladder biles and gallstones were obtained at surgery from 100 and 74 patients, respectively. Common duct bile and stones were either drained through an indwelling common duct T-tube or aspirated through a nasobiliary catheter in 108 patients. Gallstones were analyzed for bilirubin, cholesterol, bile acid, calcium, and residue, and biles for bile acid, cholesterol, phospholipid, bilirubin, and beta-glucuronidase. There were four major kinds of gallstones in Taiwan: cholesterol/mixed stones, high-residue black formed pigment stones, low-residue brown formed pigment stones, and muddy pigment stones. The surgical incidence of all types of stones increased steadily during the past four decades. During the past 15 years the relative frequencies for mixed, formed pigment, and muddy pigment stones had been roughly 40, 40, and 20%, respectively, with a further increase in the mixed stones and a decrease in the muddy pigment stones in recent years. Improvement of nutritional status and living standards might contribute to such changes. Cholesterol content in the common duct and gallbladder biles was higher in the mixed stone group than in other groups. Bacterial beta-glucuronidase activity was detected in 53% of patients with muddy pigment stones. Endogenous beta-glucuronidase activity and concentration were also highest in this group, intermediate in the formed pigment and mixed stone group, and lowest in the control. We concluded that hypercholesterobilia was responsible for increasing incidence of mixed stones during the past two decades, while both bacterial and human beta-glucuronidase might contribute to pigment cholelithiasis.

Primary and secondary prevention of gallstone disease: implications for patient management and research priorities

Primary prevention is defined as the prevention of gallstone formation; secondary prevention is defined as the prevention of clinical manifestations of gallstones--symptoms or more severe complications. For primary prevention, general "wellness" measures can be recommended from a theoretic standpoint. These include elimination of obesity (to decrease excessive cholesterol biosynthesis or mobilization of tissue cholesterol during rapid weight loss); a high-fiber, high-calcium diet (to diminish input of deoxycholic acid); ingestion of meals at regular intervals (to diminish gallbladder storage and interruption of the enterohepatic circulation of bile acids); and vigorous exercise (to permit frequent meals without excessive caloric intake). In addition, based on animal studies, intake of low saturated fatty acids may diminish the nucleation of supersaturated bile. Secondary prevention is recommended only when gallstones become symptomatic because of the benign natural history of asymptomatic gallstones, the intrinsic limitations of medical therapy, and the absence of predictors that would enable selection of asymptomatic patients at high risk for becoming symptomatic. Secondary prevention involves nonsurgical approaches (dissolution with ursodiol, extracorporeal shock-wave lithotripsy plus adjuvant bile acids, and, rarely, contact dissolution with organic solvents). For patients with symptomatic gallstones, nonsurgical therapy will be used by those patients who cannot or will not have surgery, as well as those patients who wish to explore a trial of nonsurgical therapy before having surgery. Because of the intrinsic limitations of nonsurgical therapy in comparison to the efficacy and safety of surgery, most patients will undergo surgery. Future research priorities include elucidation of factors responsible for: (1) bile that is supersaturated in cholesterol; (2) elevated biliary deoxycholic acid levels in patients with cholesterol gallstones; (3) rapid nucleation in patients with multiple cholesterol gallstones; (4) precipitation of calcium bilirubinate; and (5) impaired gallbladder motility in gallbladder stone disease.

Biliary D-glucaric acid: its quantitation and preventive role in gallstone formation

A method for quantitation of D-glucaric acid in bile has been developed involving extraction with tetrahexylammonium chloride, boiling for 40-60 min, and determination of the percentage inhibition of beta-glucuronidase activity at 56 degrees C and pH 4. D-glucaric acid, bilirubin, bile acid, and protein were determined in 106 human gallbladder biles obtained at autopsy, including 20 with gallstones. The mean D-glucaric acid content was 1125 +/- 159 microM (mean +/- SE). Biliary beta-glucuronidase activity was not affected by D-glucaric acid because of 1) no difference in biliary D-glucaric acid content, either absolute or corrected for per unit of bilirubin, bile acid, or protein, between those with and those without gallstones; 2) no negative correlation between D-glucaric acid content and beta-glucuronidase activity in the bile; and 3) minimal conversion of D-glucaric acid to D-glucaro-1,4-lactone at the usual pH of bile. We conclude that biliary D-glucaric acid plays no role in the prevention of gallstone formation.

D-glucaro-1,4-lactone: its excretion in the bile and urine and effect on the biliary secretion of beta-glucuronidase after oral administration in rats

This experiment was designed to test the hypothesis that orally administered D-glucaro-1,4-lactone might be excreted in the bile and thus suppress the activity of biliary beta-glucuronidase, which is believed to play a key role in the development of pigment gallstones. D-Glucaro-1,4-lactone, 50 to 2,600 mu moles, was fed to adult Sprague-Dawley rats which had a bile fistula and were kept in metabolic cages for bile and urine collection. A total of 21 feeding experiments were carried out. Quantitation of D-glucaro-1,4-lactone and total D-glucaric acid as the sum of D-glucaric acid and its lactones in the bile and urine involved extraction of bile with tetrahexylammonium chloride, adjustment of pH, boiling and determination of percentage inhibition of beta-glucuronidase activity. The maximal velocity of beta-glucuronidase in the bile was also determined by the enzyme kinetic method. The results showed that 11% of administered D-glucaro-1,4-lactone was excreted in the urine and only 0.2% in the bile, with D-glucaro-1,4-lactone accounting for 20% of the total excreted D-glucaric acid. The concentration and excretory rate of total D-glucaric acid and D-glucaro-1,4-lactone in the urine, but not in the bile, were proportional to the amount of D-glucaro-1,4-lactone fed. The mean concentration of D-glucaro-1,4-lactone in the bile after feeding was 0.06 mM, which was capable of suppression of 75% of beta-glucuronidase activity. Oral administration of D-glucaro-1,4-lactone decreased biliary beta-glucuronidase concentration, slowed bile flow rate and hence decreased biliary beta-glucuronidase secretion.(ABSTRACT TRUNCATED AT 250 WORDS)