The physicochemical basis of cholesterol gallstone formation in man

Effect of glycerophosphate on lithogenic bile. A new approach to treatment of cholelithiasis

Previous studies in animals showed a twofold increase of bile-phospholipids when glycerophosphate, a precursor of phospholipids, was incorporated in chow diet. The present study evaluates the effect of short-term administration of beta-glycerophosphate on bile composition in patients with lithogenic bile. 10 patients with lithogenic bile were selected for study; 9 had cholelithiasis. Fasting hepatic and gallbladder bile before and after treatment with beta-glycerophosphate (6 g. daily for six days) was analysed for molar ratios of cholesterol (Ch.), total bile-salts (B.S.), and total phospholipids (P.L.). The molar ratios of Ch. divided by B.S. + P.L. in hepatic bile decreased in 9 of the 10 patients (P less than 0.01). Thus in all but 1 of the 10 patients the hepatic bile became less lithogenic. This observation was confirmed by plotting the molar percentages on triangular coordinates. The results suggest no change in cholesterol concentrations but an increase of phospholipid and bile-salt concentrations. The composition of the gallbladder bile did not change. These preliminary studies indicate that beta-glycerophosphate should be evaluated as a potential new therapeutic agent for dissolution of cholesterol gallstones in man.

Occurrence of cholesterol crystals in human bile

The occurrence of cholesterol crystals was studied in 20 consecutive gallstone patients with functioning gallbladders. The frequency with which crystals were found rose sharply with the number of stones. Gallbladder bile was found more often to contain cholesterol crystals than hepatic bile of the same individual. Such crystals were absent in T tube drain bile from 10 consecutive choledochostomy patients, studied after the reestablishment of the enterohepatic circulation for at least five days. In gallstone patients in whom the gallbladder was visualized at cholecystography the hepatic bile contained cholesterol crystals more often than in patients with gallbladders not so visualized. In the latter patients the crystals tended to disappear after prolonged fasting. Bile analysis showed hepatic bile of patients with non-functioning gallbladders to be less lithogenic than bile in cases with functioning gallbladders. In the former group bile contained relatively more chenodeoxycholic acid than in the latter. The composition of bile with cholesterol crystals did not differ significantly from that of bile without crystals. In the final analysis it is important to identify possible factors responsible for the precipitation of cholesterol from supersaturated bile.

The control of bile acid pool size: effect of jejunal resection and phenobarbitone on bile acid metabolism in the rat

In patients with cholesterol gallstones, there is a diminished bile acid pool and the bile becomes supersaturated with cholesterol. Medical treatment has been aimed at re-expanding the pool to improve cholesterol solubility in bile but as yet the factors controlling the size of the bile acid pool' are unknown. Therefore the role of the liver and intestine in controlling bile acid pool size in the rat was studied and the effect of experimental expansion of the pool on bile acid metabolism and bile lipid composition examined. Bile acid absorption was increased from ileum made hyperplastic by previous jejunectomy and hepatic bile acid synthesis was increased by phenobarbitone treatment. Both jejunal resection and phenobarbitone significantly increased the size of the bile acid pool from 32.2 +/- SEM 0.94 mumoles/100 g body weight to 42.2 +/- 1.71 and 44.4 +/- 2.03 respectively. However, the effects of these experimental manipulations on bile acid secretion rate, enterohepatic cycling frequency, and synthesis rates were quite different. Jejunectomy caused a 56% increase in bile acid secretion and more rapid cycling of the bile acid pool but the enhanced absorption did not depress bile acid synthesis. In contrast, phenobarbitone markedly increased synthesis from 14.5 +/- 1.42 mumoles.100 g BW(-1). 24 hr(-1) to 25.9 +/- 3.19 but there was no significant change in bile acid secretion and the choleresis seen after phenobarbitone was mainly due to an increase in the bile acid-independent fraction of bile flow. In these experimental studies in the rat, expansion of the bile acid pool did not significantly change bile lipid composition or cholesterol solubility in bile.

Studies of the hepatic excretory defects in essential fatty acid deficiency. Their possible relationship to the genesis of cholesterol gallstones

Male hamsters were fed normal and essential fatty acid (EFA)-deficient diets for at least 12 wk before bile duct cannulation. With [32P]phosphate, hepatic synthesis of lecithin was similar, but biliary excretion of newly synthesized lecithin was significantly reduced in EFA-deficient compared to that in normal hamsters. Hepatic uptake of intravenously infused taurocholate (TC) and taurochenodeoxycholate (TCDC) were similar in both groups of animals. However, biliary excretion of intravenously infused TC was significantly reduced in EFA-deficient hamsters, whereas that of TCDC-was unchanged. The absolute rate of biliary cholesterol excretion was similar in both groups. Canalicular bile flow, as measured by [14C]erythritol clearance after functional nephrectomy, was significantly lower, with both the bile salt-dependent and independent fractions of this flow being diminished in EFA-deficient hamsters infused with TC. It is concluded that EFA deficiency leads to impaired biliary excretion of taurocholate, lecithin, and water, while cholesterol transport is unaffected, and thus results in supersaturation of bile with respect to cholesterol and production of lithogenic bile.

The effect of phenobarbital on cholesterol gallstones in hamsters

This experimental study was undertaken to follow the influence of phenobarbital on bile chemistry and gallstone formation. Phenobarbital (400 mg/kg/day) was administered to golden hamsters receiving a diet known to induce cholesterol gallstones. After a 28-day period none of the control animals had gallstones whereas five of 12 animals with added phenobarbital developed stones. Ten of 19 animals on the lithogenic diet formed gallstones but when phenobarbital was added gallstones occurred in 16 of 19 hamsters. The administration of phenobarbital resulted in the production of bile which was relatively more saturated with cholesterol, the bile salt + phospholipid: cholesterol of 24.8 +/- 12.7 in control animals altering to 9.1 +/- 6.2 in animals receiving phenobarbital. Hepatic bilirubin uridine diphosphate-glucuronyl transferase activity was not increased in animals on phenobarbital. It was concluded that, in the hamster at least, there is no indication that large doses of phenobarbital will reduce the potential for gallstone formation.

Effect of oral chenodeoxycholic acid on bile acid kinetics and biliary lipid composition in women with cholelithiasis

Bile acid kinetics and biliary lipid composition were characterized in six women with gallstones before and after 6 mo of oral therapy with chenodeoxycholic acid, an agent that induces dissolution of cholesterol gallstones in man. Over a dosage range of 1-4 g/day, absorption varied from 0.8 to 2.3 g/day. The chenodeoxycholic acid pool expanded two-to sixfold, and bile became composed predominantly (> 90%) of chenodeoxycholic acid conjugated chiefly with glycine. Cholic acid and deoxycholic acid pools decreased markedly, so that the total bile acid pool expanded much less, about twofold on the average. Cholic acid synthesis decreased in five of the six patients, consistent with negative feedback inhibition of cholic acid synthesis by chenodeoxycholic acid. In four patients whose bile was above or close to saturation with cholesterol, the bile became unsaturated; in two patients, whose bile was unsaturated, it remained so. In five patients with radiolucent gallstones, chenodeoxycholic acid therapy was continued after completion of kinetic and composition measurements; the stones decreased in size or dissolved entirely during the subsequent 6 to 18 mo. Similar measurements of bile acid kinetics and biliary lipid composition were made before and after a 6-mo period without medication in a control group of six healthy women; no changes occurred.

Serum lipids in cholelithiasis: effect of chenodeoxycholic acid therapy

Hypercholesterolaemia has been predicted as a possible complication of chenodeoxycholic acid treatment for gall stones. To exclude this, fasting serum lipids were measured in patients with stones before and at monthly intervals for six months after starting chenodeoxycholic acid. Before treatment half of a group of 36 patients with presumed cholesterol gall stones had serum cholesterol levels exceeding 260 mg/100 ml or serum triglyceride values greater than 160 mg/100 ml or both; these lipid levels were significantly greater than those in control subjects matched for age and sex. Treatment with chenodeoxycholic acid (0.5-1.5 g/day by mouth) did not change serum cholesterol levels but did significantly reduce serum triglyceride concentrations from a pretreatment level of 118 (+/- S.E. of mean 11.7) mg/100 ml to 95 (+/- 7.2) mg/100 ml after six months of therapy. The mechanism of this triglyceride-lowering action of chenodeoxycholic acid is not known, but it may have therapeutic value in patients with hypertriglyceridaemia.

Sex differences in the bile acid composition of human bile: studies in patients with and without gallstones

The bile acid composition of human gallbladder bile was studied in 83 subjects, 20 of each sex without discernible hepatobiliary disease, and 20 men and 23 women with cholelithiasis. The bile acids were measured by combined thin-layer and gas-liquid chromatography.In the bile of patients without cholelithiasis the molar percent of cholic acid was significantly greater in men while that of chenodeoxycholic acid was significantly greater in women.In the bile of patients with cholelithiasis the concentration of total bile acids was reduced in both sexes but there was no sex difference in the molar percent of any of the bile acids. The molar percent of CDCA (both glycine and taurine conjugates) was reduced in women, while the molar percent of CA (only the glycine conjugate) was reduced in men.

Cholesterol solubility in bile. Evidence that supersaturated bile is frequent in healthy man

The development and validation of a direct method for measuring maximum cholesterol solubility in bile is described. Application of this method to five large mammalian species, including man, produced a micellar zone significantly smaller than that previously reported. Further studies on in vitro model solutions patterned after bile confirmed this new micellar zone. Thus, direct evidence demonstrates that the micellar zone boundary derived in vitro from model solutions is applicable to human gallbladder bile. Using the present criteria, normal human bile, in contrast to bile from other mammalian species, is commonly supersaturated with cholesterol. A male-female difference in bile composition is not demonstrable despite the well-established female preponderance of cholelithiasis. Bile from patients with cholesterol cholelithiasis has a micellar zone similar to normals but differs compositionally in that there is a greater excess of cholesterol above saturation. We conclude that cholesterol supersaturation may be a necessary but not solely sufficient cause for gallstone formation.

Regulation of bile salt pool size in man

When the enterohepatic circulation is intact the size of the bile salt pool is largely determined by the frequency of its enterohepatic circulation. This hypothesis, derived from studies of cholate kinetics in coeliac, cholecystectomy, and gall stone patients, represents the simplest interpretation of the data. A corollary is that daily cholate secretion is likely to be normal in these conditions and that therefore the propensity of bile to form cholesterol gall stones is not likely to be directly related to bile salt pool size.

Effect of glycine-conjugated bile acids with and without lecithin on water and glucose absorption in perfused human jejunum

Perfusion studies were performed in healthy volunteers to test whether the secretory effect of conjugated bile acids, previously shown for the colon, was also present in the jejunum. A perfusion system with a proximal occlusive balloon (and continuous aspiration of duodenal secretions) was used; isotonic test solutions contained glycine-conjugated bile acids with or without lecithin. Fluid movement was measured by changes in the concentration of polyethylene glycol (PEG, mol wt 4,000). Conjugated dihydroxy bile acids inhibited electrolyte and fluid absorption and, at higher concentrations, evoked secretion of an isotonic fluid. Glucose absorption continued, despite fluid secretion, but its rate decreased. The secretory effects of bile acids were abolished by the addition of lecithin to the bile acid solutions. A trihydroxy bile acid (cholylglycine) had no effect on jejunal absorption. Small amounts (6-9%) of conjugated bile acids were absorbed in the jejunum; lecithin was well absorbed (72-90%). The results indicate that dihydroxy bile acids influence salt and water transport in the human jejunum but that this effect may be abolished when a polar lipid such as lecithin is present. We speculate that this effect of bile acids may modify fluid movement in the small intestine postprandially after fat absorption has occurred.