Diurnal variation in biliary lipid composition. Possible role in cholesterol gallstone formation

Benign gallbladder disease is a risk factor for colorectal cancer, but cholecystectomy is not: A propensity score matching analysis

Background

Previous studies reported controversial results on the relationship between cholecystectomy (CHE) and colorectal cancer (CRC). We hypothesized that gallbladder disease (GBD), instead of cholecystectomy, increased the risk of CRC. We aimed to investigate the incidence of benign gallbladder disease (BGBD) and CHE in CRC patients and local adults undergoing annual health examination by analyzing large data from a tertiary hospital in southwest China.

Methods

A propensity score matching (PSM) analyzed, retrospective study from January 1, 2013, to August 31, 2020, including 7,471 pathologically confirmed CRC patients and 860,160 local annual health examination adults in the First Affiliated Hospital of Chongqing Medical University, was conducted. The prevalence of BGBD and the CHE rate were analyzed before and after a 1:1 PSM.

Results

Of the 7,471 CRC patients, 7,160 were eligible for the case group. In addition, 860,160 local health examination adults were included for comparison. The incidence of BGBD was higher in the CRC patients than in the local adults (19.2% vs. 11.3%, P < 0.001), but no significant difference in CHE rate existed between the case group and the control group (5.0% vs. 4.8%, P = 0.340). In the subgroup analysis, patients with BGBD had a higher risk of colon cancer than rectal cancer (20.4% vs. 18.2%, P = 0.024) and more significantly in the right colon (P = 0.037). A weakly positive correlation between CHE and right colon cancer was observed before PSM but no longer existed after PSM (P = 0.168).

Conclusions

Benign gallbladder disease was positively correlated with colorectal cancer, especially right colon cancer. Cholecystectomy did not increase the risk of colorectal cancer.

Beneficial Gut Microbiome Remodeled During Intermittent Fasting in Humans

Intermittent fasting (IF) is the practice of restricting food intake for 12-48 hours per fasting cycle over a prolonged period of time. Previous study shows beneficial health effects such as weight loss and lower risk for cardiometabolic diseases. Although reduced calorie intake may account for some of the observed benefits of IF, exact mechanisms are still unclear. Recent evidence indicates that IF may lead to remodeling and increased taxonomic diversity in the human gut microbiome. In particular, the Lachnospiraceae family of anaerobic bacteria increased during fasting. This family, in the order Clostridiales, promotes butryogenesis in the gut, a process that is associated with healthful metabolic and prolongevity effects. IF-associated alterations to the microbiome may play a key role in the metabolic and potential healthspan-enhancing benefits of IF and dietary restriction.

An Intermittent Fasting Mimicking Nutrition Bar Extends Physiologic Ketosis in Time Restricted Eating: A Randomized, Controlled, Parallel-Arm Study

There has been increasing interest in time-restricted eating to attain intermittent fasting's metabolic benefits. However, a more extended daily fast poses many challenges. This study was designed to evaluate the effects of a 200-calorie fasting-mimicking diet (FMD) energy bar formulated to prolong ketogenesis and mitigate fasting-associated side effects. A randomized, controlled study was conducted comparing the impact of consuming an FMD bar vs. continued water fast, after a 15-h overnight fast. Subjects in the FMD group showed a 3-h postprandial beta-hydroxybutyrate (BHB) level and 4-h postprandial BHB area under the curve (AUC0-4) that were non-inferior to those who continued with the water fast (p = 0.891 and p = 0.377, respectively). The postprandial glucose AUC0-4 in the FMD group was non-inferior to that in the water fast group (p = 0.899). A breakfast group served as a control, which confirmed that the instrument used in home glucose and ketone monitoring functioned as expected. The results indicate that FMD bar consumption does not interfere with the physiological ketogenesis associated with overnight fasting and could be used to facilitate the practice of time-restricted eating or intermittent fasting.

Metformin and AMP Kinase Activation Increase Expression of the Sterol Transporters ABCG5/8 (ATP-Binding Cassette Transporter G5/G8) With Potential Antiatherogenic Consequences

OBJECTIVE

The mechanisms underlying the cardiovascular benefit of the anti-diabetic drug metformin are poorly understood. Recent studies have suggested metformin may upregulate macrophage reverse cholesterol transport. The final steps of reverse cholesterol transport are mediated by the sterol transporters, ABCG5 (ATP-binding cassette transporter G5) and ABCG8 (ATP-binding cassette transporter G8), which facilitate hepato-biliary transport of cholesterol. This study was undertaken to assess the possibility that metformin induces Abcg5 and Abcg8 expression in liver and to elucidate the underlying mechanisms.

APPROACH AND RESULTS

Metformin-treated mouse or human primary hepatocytes showed increased expression of Abcg5/8 and the bile salt export pump, Bsep. Administration of metformin to Western-type diet-fed mice showed significant upregulation of Abcg5/8 and Bsep. This resulted in increased initial clearance of ³H-cholesteryl ester HDL (high-density lipoprotein) from plasma. However, fecal ³H-cholesterol output was only marginally increased, possibly reflecting increased hepatic Ldlr (low-density lipoprotein receptor) expression, which would increase nonradiolabeled cholesterol uptake. Abcg5/8 undergo strong circadian variation. Available chromatin immunoprecipitation-Seq data suggested multiple binding sites for Period 2, a transcriptional repressor, within the Abcg5/8 locus. Addition of AMPK (5' adenosine monophosphate-activated protein kinase) agonists decreased Period 2 occupancy, suggesting derepression of Abcg5/8. Inhibition of ATP citrate lyase, which generates acetyl-CoA from citrate, also decreased Period 2 occupancy, with concomitant upregulation of Abcg5/8. This suggests a mechanistic link between feeding-induced acetyl-CoA production and decreased cholesterol excretion via Period 2, resulting in inhibition of Abcg5/8 expression.

CONCLUSIONS

Our findings provide partial support for the concept that metformin may provide cardiovascular benefit via increased reverse cholesterol transport but also indicate increased Ldlr expression as a potential additional mechanism. AMPK activation or ATP citrate lyase inhibition may mediate antiatherogenic effects through increased ABCG5/8 expression.

Gallstone formation and weight loss

Obesity is associated with increased bile stasis and cholesterol saturation, and an increased risk of gallstone development. Conversely, bile composition is normalized following reduction in body weight. It would appear advantageous to promote weight loss in obesity, which would reduce the predisposition to gallstone formation. Despite the potential health benefits of weight reduction, very-low-calorie diets appear to increase the risk for cholesterol crystal and gallstone formation. The incidence of gallstone formation seems to be dependent on the degree of caloric restriction, the rate of weight loss, and the duration of the dietary intervention. Thus, faster rates of weight loss for longer periods of time are associated with increased risk. Available data obtained from prospective studies of subjects during active weight loss suggest that newly formed gallstones occur within 4 weeks and with incidence rates 15 to 25-fold higher than in the general obese population. The stones produce symptoms in approximately one-third of the subjects, of whom approximately one-half will undergo surgery. Proposed mechanisms underlying gallstone formation during weight reduction include bile stasis due to reduced caloric intake, increased biliary cholesterol saturation secondary to increased cholesterol mobilization, and increased nucleation due to changes in bile arachidonate and glycoprotein concentrations. Data are lacking on the effects of gradual rates of weight loss and risk of gallstone formation.

Gallbladder motility and gut hormone plasma levels in subjects with and without gallstones

Hormonal control of gallbladder motility is still unclear in patients with cholelithiasis. In a case-control study, we determined the characteristics of gallbladder emptying evaluated sonographically and the hormone levels of somatostatin, gastrin, and pancreatic polypeptide, before and after a fatty meal in 10 gallstone patients compared with 20 healthy subjects. Patients with lithiasis had a larger residual volume (median 12,0 ml vs 6,5 ml; P = 0.01) and a lower gallbladder ejection fraction (43% vs 70%, P = 0.02) than healthy subjects. During fasting, plasma pancreatic polypeptide concentrations were significantly higher in lithiasis patients (P < 0.03). In contrast, no differences between the two groups of patients were observed during the post prandial period. Somatostatin and gastrin plasma levels were similar in the two groups. Lastly, the serum bile salt levels were in the normal range and were not different between groups both during fasting and postprandial states. We conclude that large basal plasma concentrations of pancreatic polypeptide, a gut peptide inducing gallbladder relaxation, may constitute a factor facilitating lithogenesis.

Pathways of cholesterol crystallization in model bile and native bile

Hypersecretion of hepatic cholesterol, chronic supersaturation of bile with cholesterol and rapid precipitation of cholesterol crystals in the gallbladder from cholesterol-enriched vesicles represent the primum movens in cholesterol gallstone formation. Physical-chemical factors and pathways leading to cholesterol crystallization can be investigated in artificial model biles and ex vivo in fresh human bile. Depending on modulatory factors (i.e., lipid concentration, bile salt or phospholipid species, humidity, mucins, etc.), cholesterol can precipitate in several forms (i.e., monohydrate, anhydrous) and habits (i.e., plate-like, needle-like, intermediate arcs, filaments, tubules, spirals). Careful analysis of biliary cholesterol crystals includes biochemical analysis of precipitated crystals, polarizing quantitative light microscopy, and turbidimetric methods. In this paper, recent concepts on cholesterol crystallization in artificial model biles as well as in human bile will be reviewed.

Effect of the prokinetic agent, erythromycin, in the Richardson ground squirrel model of cholesterol gallstone disease

Impaired gallbladder motility and delayed intestinal transit contribute to cholesterol gallstone formation by impeding the enterohepatic circulation of bile salts and causing gallbladder stasis. The therapeutic value of erythromycin, a prokinetic motilin analog, was evaluated in an animal model of gallstone formation. Eighty ground squirrels were fed either a trace- (control) or a high- (1%) cholesterol diet. Half of each diet group received either erythromycin stearate or placebo orally twice daily for 4 weeks. Biliary lipid secretion and bile salt pool size were determined via common duct cannulation. Gallbladder contractile response to cholecystokinin (CCK) was studied in vitro. Intestinal transit was evaluated in vivo by 51Cr marker. In the placebo-treated group, fed the high- versus the trace-cholesterol diet, bile salt secretion decreased (trace-cholesterol + placebo, 21.0 +/- 1.8 nmol/min/g liver vs. high-cholesterol + placebo, 9.3 +/- 1.4 nmol/min/g liver), cholesterol saturation index (CSI) doubled (trace-cholesterol + placebo, 0.61 +/- 0.06 vs. high-cholesterol + placebo, 1.30 +/- 0.04), nucleation time shortened (trace-cholesterol + placebo, > 21 days vs. high-cholesterol + placebo, 6.4 +/- 1.0 days), cholesterol crystals formed, gallbladder contractility diminished, and intestinal transit was delayed (each P < .05). Erythromycin treatment of animals on the high-cholesterol diet restored gallbladder contractility and intestinal transit to control levels, increased bile salt secretion, reduced the total bile salt pool, lowered the cholesterol saturation of bile, lengthened the nucleation time, and so reduced crystal formation (each P < .05). Erythromycin enhances gallbladder motility and hastens intestinal transit, promoting more rapid enterohepatic cycling of bile salts. This increases bile salt secretion, improves cholesterol solubility, and reduces crystal development.

Cholesterol gallstone formation in man and potential treatments of the gallbladder motility defect

Cholelithiasis affects 10-15% of the adult population in Western society, and about 75% of gallstones are of cholesterol type. Hepatic hypersecretion of cholesterol with the formation of instable cholesterol-rich vesicles in bile, an imbalance between nucleation-inhibiting and nucleation-promoting proteins with further aggregation of cholesterol crystals in a gallbladder with a motility defect (stasis), all play a role in the pathogenesis of cholesterol gallstones. Experimental animal models suggest that gallstone formation can be prevented by improving gallbladder emptying. Thus, a better understanding of the causes underlying the impaired gallbladder motor function in patients with gallstones might lead to the selection of therapeutic approaches for those individuals who are at increased risk for the formation or recurrence of gallstones. The present article focuses on current concepts and theories on the pathogenesis of cholesterol gallstones with emphasis on the gallbladder motility defect. Several treatment strategies for the correction of gallbladder hypomotility are also discussed.

Effects of dietary fat and fatty acids on sterol balance in hamsters

Sterol balance studies, using both isotopic and chromatographic techniques, were carried out in hamsters fed semipurified diets to detect changes in sterol metabolism during the early period of the lithogenic stimulus. The balance studies examined animals in the first two weeks on the experimental lithogenic diets. The variables were as follows: dose of cholesterol (group 1, 0.05% vs. group 2, 0.2%); dietary fat (fatty acid) (group 2, butterfat vs. group 4, palmitic acid); source of hamster [group 2, Sasco (Omaha, NE) vs. group 3, Charles River (Wilmington, MA)]; average weight of animals (group 4, 60 g vs. group 5, 119 g). Animals in groups 1, 2, 3 and 5 maintained almost constant weight throughout the two-week balance study. Liver and plasma cholesterol levels increased in groups 2-5 with increasing dose of dietary cholesterol. The highest levels were found in group 4 (liver cholesterol, 32.7 mg/g; plasma cholesterol, 367 mg/dL). Sterol balance measurements showed that bile acid synthesis remained low (range 0.55-1.01 mg/d) for all groups regardless of the intake of dietary cholesterol (range, 3.27-20.90 mg/d). The dietary cholesterol absorbed from the intestine (range, 2.91-18.91 mg/d) was stored in the liver; this storage was reflected in the negative values for cholesterol balance for all groups (range, -0.70 to -14.97 mg/d). These studies did not reveal any correlations between parameters of sterol balance and cholelithiasis.

Cisapride improves gallbladder contractility and bile lipid composition in an animal model of gallstone disease

BACKGROUND

The hepatic secretion of supersaturated bile and gallbladder stasis are key events in cholesterol gallstone formation. The therapeutic value of cisapride, a prokinetic agent, was assessed in ground squirrels on a 1% cholesterol diet.

METHODS

Biliary lipid secretion was measured directly and bile salt pool size assessed by isotope dilution ([14C]cholic acid). Gallbladder contraction was measured in vitro in response to cholecystokinin (CCK).

RESULTS

Cholesterol-fed animals had a combined hepatic secretory defect (a 53% decrease in bile salt secretion and also a 31% increase in cholesterol secretion). Adding cisapride restored bile salt secretion to control levels but did not affect cholesterol secretion. In cholesterol-fed animals, the cholesterol saturation index of gallbladder bile more than doubled and cholesterol crystals developed; cisapride markedly reduced cholesterol saturation, thus preventing crystal formation. Gallbladder contractility, measured in vitro in response to CCK, decreased 23% in animals on the 1% cholesterol diet; cisapride restored the CCK dose-response curve to normal. The bile salt pool as assessed by isotope dilution was similar in all groups.

CONCLUSIONS

Thus, lithogenic bile develops in this model because of reduced bile salt secretion and increased cholesterol secretion. Cisapride renders biliary lipid composition towards normal by enhancing gallbladder (and possibly intestinal) motility and cycling of the bile salt pool, thereby increasing bile salt secretion.

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.

Pathogenesis of gallstones

Gallstones form as a result of many disorders. Unphysiologic supersaturation, generally from hypersecretion of cholesterol, is essential for the formation of cholesterol gallstones. The other common abnormalities of the hepatobiliary system in gallstone patients are accelerated nucleation, gallbladder hypomotility, and the accumulation of mucin gel. An attempt is made here to relate hypersecretion of cholesterol and biliary supersaturation to the molecular basis of the associated phenomena. Supersaturation of bile with calcium hydrogen bilirubinate, the acid calcium salt of unconjugated bilirubin, is essential for pigment gallstone formation, but its magnitude remains undefined in model systems. Nucleation and the precipitation of calcium hydrogen bilirubinate with the polymerization of the pigment in the gallbladder, together with the deposition of the inorganic salts, calcium carbonate and phosphate, result in black pigment gallstone formation. On the basis of ex vivo muscle studies, gallbladder hypomotility is unlikely in patients with black pigment stones but is invariably present in patients with cholesterol stones. Pigment supersaturation in the gallbladder is the result of hepatic hypersecretion of bilirubin conjugates in hemolytic disorders and possibly enterohepatic cycling of unconjugated bilirubin in nonhemolytic states. Less common is bile salt hyposecretion from impaired synthesis in constitutional disorders and cirrhosis, and uncompensated interruption of the enterohepatic circulation in ileal dysfunction syndromes. Bile salt deficiency causes incomplete solubilization of unconjugated bilirubin and impaired binding of calcium ions. Stasis and anaerobic bacterial infection are responsible for brown pigment stones, which usually form in the bile ducts. In addition to the precipitation of calcium hydrogen bilirubinate that remains unpolymerized, there is also the deposition of the calcium salts of saturated fatty acids and free bile acids, both of which are the result of bacterial enzymatic hydrolysis of biliary lipids.

Effect of dietary fat composition on biliary cholesterol saturation index in dogs

In dogs, the effect of dietary fat on bile cholesterol saturation index and the evolution of molar percentages of biliary lipids have been studied in both fasting and postprandial periods after a long-term adaptation period to diets which only differ in their lipidic source (olive oil and sunflower oil). It has been observed that for similar bile cholesterol saturation indexes in both groups, dietary fat altered differently biliary lipid composition through a double mechanism which involved bile acids and phospholipids. Dietary fat is postulated to affect differently the lipidic composition of bile as well as the biliary tree motility both during interdigestive and postprandial periods.

Diurnal variation in cholesterol metastability of hepatic bile and its acute modulation with ursodeoxycholic acid in humans

We studied the alteration of cholesterol metastability of hepatic bile caused by diurnal variations in hepatic biliary lipid excretions and acutely induced changes following ursodeoxycholic acid (UCDA) administration. Hepatic bile was collected at 6-h intervals for 24 h from 6 patients with an indwelling choledochal drainage before and after UDCA administration. A basal diurnal variation showed the highest cholesterol saturation index (p < 0.05) and cholesterol distribution in vesicles (p < 0.01) and the shortest nucleation time (p < 0.05) in the early morning. After the ingestion of ursodeoxycholic acid for 1 day, early morning biliary cholesterol concentrations were reduced. Interestingly, significant decreases in vesicular cholesterol concentrations (1.0 +/- 0.2 to 0.1 +/- 0.04 mM, p < 0.01) and in the vesicular cholesterol/phospholipid ratio (1.6 +/- 0.1 to 0.7 +/- 0.1, p < 0.05) were associated with prolongation of the nucleation time (11.5 +/- 1.2 to 18.7 +/- 1.5 days, p < 0.01). Biliary protein had no diurnal variations and did not decrease significantly with UCDA. These results indicate that during a day the early morning hepatic bile is the most unstable and that UCDA acutely enhances hepatic biliary metastability mainly by decreasing the rate of vesicular cholesterol saturation.

Interrelationships of bile acid and phospholipid fatty acid species with cholesterol saturation of duodenal bile in health and gallstone disease

The relative amount of cholesterol and the fatty acid composition of phosphatidylcholines in bile can be influenced by the bile acid species secreted. To search for a contribution of secondary bile acids and of phosphatidylcholines to supersaturation of bile in gallstone disease, we compared the relative amount of cholesterol and the biliary composition of bile acids and of phospholipid fatty acids in cholecystokinin-stimulated duodenal bile of 22 female gallstone patients and 16 healthy controls and analyzed the interrelationships of these bile constituents. Gallstone patients had higher molar percentages of cholesterol than did controls (10.2 +/- 3.2 vs. 6 +/- 1.5 mol%; p less than 0.001) and demonstrated a trend toward larger fractions of deoxycholic and lithocholic acids. By linear models, variation of cholesterol saturation could be predicted (p less than 0.001) up to 53% by the bile acid pattern and up to 81% by the fatty acid pattern of phospholipids. Linear path analysis (goodness-of-fit index = 0.973) confirmed the tight relationship between phospholipid fatty acids (positive: oleic, arachidonic; negative: linoleic, palmitoleic) and the relative amount of cholesterol; more than half the influence of cholic, deoxycholic and lithocholic acids on the relative amount of cholesterol could be explained indirectly by their influence on the phospholipid fatty acid pattern. We conclude that the relationships examined by path analysis support the working hypothesis that secondary bile acids contribute to supersaturation of bile mainly by changing the fatty acid pattern of the secreted phospholipids (presumably the pattern of phosphatidylcholines), which increases the molar ratio of cholesterol/phospholipids in bile.

A prospective study of hospitalization with gallstone disease among women: role of dietary factors, fasting period, and dieting

BACKGROUND

Dietary risk factors for the development of gallstones have not been clearly established. We analyzed data from a population-based prospective study to determine dietary risk factors for hospitalization with gallstone disease.

METHODS

We evaluated the role of dietary constituents, fasting, and dieting on subsequent hospitalization with gallstone disease among 4,730 women, ages 25 to 74 years, who participated in the first follow-up of the first National Health and Nutrition Examination Survey. Baseline dietary variables were established through a 24-hour dietary recall and a medical history. Proportional hazards models were used to calculate the effects of dietary variables while controlling for baseline risk factors.

RESULTS

After an average of 10 years follow-up, gallstone disease was confirmed by hospital records among 216 women who denied gallstone disease at the baseline examination. The hazard rate of hospitalization with gallstone disease increased with increasing overnight fasting period and with dieting. Intake of fiber showed a small protective effect. The effect of energy intake was significant only among women younger than age 50 years at baseline. Results were not affected by adjustment for known risk factors for gallstone disease or other dietary factors.

CONCLUSION

A long overnight fasting period, dieting, and low fiber intake may increase the risk of hospitalization with gallstone disease.

Characteristics of biliary lipid metabolism after liver transplantation

Biliary lipid metabolism was studied after 10 liver transplantations with continuous drainage of bile. Within 3 wk after transplantation, the new liver produced bile with concentrations of biliary lipids in agreement with those reported for T-tube bile in cholecystectolized nontransplanted subjects. Although changes in biliary lipid composition occurred swiftly in response to various forms of disturbed liver function, they did not provide substantially more information than did standard serum tests or simple measurements of bile flow in most patients. Secretion rates of phospholipids and cholesterol were found to be completely bile acid dependent. For each micromole of bile acids, 0.22 and 0.08 mumol of phospholipids and cholesterol were secreted, respectively. When bile flow was related to bile acid output, a linear relationship was found (r = 0.89), with a positive intercept indicating a bile acid-independent bile flow of approximately 44 microliters/min. Analysis of individual bile acids showed almost exclusively primary bile acids. The relative proportion of chenodeoxycholic acid was more prominent during the first days after transplantation. Different explanations for this are discussed.

Pathophysiology and treatment of gallstones

Spurred on by the discovery of "lithogenic bile" as a precursor, there has been much attention focused on the pathophysiology and treatment of gallstones. The article reviews the progress to date regarding the epidemiology, pathophysiology, diagnosis, therapy, and recurrence/prevention of gallstones.

Periodic gallbladder contraction maintains bile acid circulation during the fasting period: a canine study

Using a canine model we have studied the relationship between the interdigestive cycle in the small intestine, motility changes in the biliary tract and bile acid output into the duodenum from direct hepatic secretion and gallbladder emptying. Under anaesthesia catheters were inserted into the gallbladder, common bile duct and duodenum, and electrodes were attached to the small intestine in five dogs. These animals were subsequently studied conscious and fasting. A double marker technique was used to measure bile acid output from the gallbladder and liver while pressure in the gallbladder and common bile duct and electrical activity in the small intestine were monitored. Four complete interdigestive cycles were recorded in each dog. Output of bile acids from the gallbladder fluctuated with the phases of the cycle: being lowest in phase I (3.9 +/- 0.7 mumol/min); increasing significantly (P less than 0.005) in phase II (9.8 +/- 1.0 mumol/min); remaining elevated in phase III (13.9 +/- 1.7 mumol/min); and falling significantly (P less than 0.05) in phase IV (8.4 +/- 1.8 mumol/min). In contrast, hepatic secretion of bile acids directly into the duodenum remained fairly constant. Intraluminal pressure in the biliary tract paralleled the fluctuation in gallbladder bile acid output, being significantly increased (P less than 0.05) in phases II and III. Periodic contraction of the gallbladder would, therefore, appear to be the principal mechanism for the phasic output of bile during fasting.

Distribution of biliary cholesterol between mixed micelles and nonmicelles in relation to fasting and feeding in humans

To further investigate the nonmicelle mode of cholesterol transport in human bile, we examined its levels in relation to fasting and feeding. T-tube bile samples were collected (for 30 min) every 4 h over a 24-h period. All patients (3 with cholesterol gallstones; 1 with pigment stone) had their T tube clamped for a minimum of 4 days before the study to allow the bile acid pool to replete. Biliary lipid concentrations in all patients increased with feeding and decreased with fasting. However, because of a greater decrease in bile acid concentration relative to cholesterol concentration during the fasting period, fasting bile was consistently more saturated than bile obtained while feeding. Associated with the increase in lithogenic index with fasting was a decrease in the micelle solubilized cholesterol and an increase in nonmicelle solubilized cholesterol. At low bile acid concentrations (fasting) most biliary cholesterol is therefore transported as a nonmicelle complex, whereas at high bile acid concentrations (feeding) most of the cholesterol is transported in the mixed micelle. No nucleation of the biliary samples was observed in any of the patients over a 10-day period of observation. Thus the biliary nonmicelle complex (presumably vesicles) has a major cholesterol transport function especially at low bile acid concentrations.

Gall stone disease without gall stones--bile acid and bile lipid metabolism after complete gall stone dissolution

Although bile acid and bile lipid metabolism have been studied in established cholelithiasis, little is known about them in patients destined to develop gall stones, but in whom the stones have not yet appeared (prestone gall stone disease). After confirmed complete gall stone dissolution and withdrawal of treatment, gall stones recur frequently. Before the stones reappear, these patients have 'poststone gall stone disease'. In 13 such patients we confirmed complete gall stone dissolution with two normal cholecystograms and in 11 of the 13 by normal ultrasonography, measured bile acid and bile lipid composition in fasting duodenal bile, bile acid synthesis from marker corrected three day faecal bile acid excretion, bile acid pool size using an abbreviated isotope dilution technique, 'steady-state' bile lipid secretion using a duodenal amino acid perfusion system and then calculated the enterohepatic cycling frequency of the bile acid pool and the relationship between pool size and body weight. The results confirm that after withdrawal of treatment the biliary cholesterol saturation index reverts to levels (1.6 +/- SEM 0.4) comparable with those before dissolution therapy first began (1.6 +/- 0.2; NS). The mean bile acid pool size in the 13 patients of 4.4 +/- 0.5 mmol was comparable with that in untreated gall stone patients. Pool size was significantly smaller in the nine non-obese patients (3.5 +/- 0.3), than in the four obese (6.0 +/- 0.8; p less than 0.05). It also correlated significantly with body weight (r = 0.72) and with %IBW (r = 0.79). The coefficients of variation for biliary bile acid, phospholipid and cholesterol secretion were high, but the mean hourly secretion rates were of the same order as those seen in untreated gall stone patients studied with the amino acid duodenal perfusion stimulus. These results provide a baseline for assessing the response to postdissolution treatment and may indicate metabolic events leading to gall stone formation.

Gallbladder emptying in man related to fasting duodenal migrating motor contractions

Animal studies have shown that the gallbladder (GB) empties partially during fasting in relation to phase II of the interdigestive motor cycle (IDMC). It has been assumed that in man the GB remains inert during fasting, although there have been no studies in which repeated sequential measurements of gallbladder volume have been made and related to the IDMC. In this study the possibility of linkage between the IDMC and GB volume has been examined in nine fasting human volunteers (five males/four females). A multilumen constantly perfused manometry catheter was positioned in the duodenum and motor activity recorded continuously. Phase III of the IDMC was characterized by phasic contractions, with a frequency of 10-12/min for at least 2 min, which had a distal propagative pattern and were followed by a motor quiescence (Phase I). GB volume was calculated at 15 min intervals from ultrasound measurements of the maximal length and diameter of the GB by the summation of cylinders method, and related to the time of onset of each phase III of the IDMC. In all nine subjects GB volume decreased prior to the onset of phase III and increased following its passage (P less than 0.01). GB volume decrease ranged between 6 and 56% of maximal GB volume (median 18%) and subsequent filling ranged from 14 to 53% (median 27%). The maximal volume decrease occurred 30 min prior to the onset of phase III (P less than 0.02). These studies have demonstrated that the human GB empties partially during phase II of the IDMC.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of rat biliary cholesterol secretion by agents that alter intrahepatic cholesterol metabolism. Evidence for a distinct biliary precursor pool

Propensity for cholesterol gallstone formation is determined in part by biliary cholesterol content relative to bile salts and phospholipid. We examined the hypothesis that the rate of biliary cholesterol secretion can be controlled by availability of an hepatic metabolically active free cholesterol pool whose size is determined in part by rates of sterol synthesis, as reflected by activity of the primary rate-limiting enzyme 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase and of sterol esterification, as reflected by the activity of the enzyme acyl coenzyme A/cholesterol acyltransferase (ACAT). Rats were prepared with biliary, venous, and duodenal catheters. The enterohepatic circulation of biliary lipids was maintained constant by infusion of a bile salt, lecithin, cholesterol replacement solution. Administration of 25-hydroxycholesterol decreased HMG CoA reductase activity, increased ACAT activity, and decreased biliary cholesterol output 26% by 1 h. By 2 h, ACAT activity and biliary cholesterol secretion were at control levels. Administration of mevinolin, a competitive inhibitor of HMG CoA reductase, had no effect on ACAT activity and decreased biliary cholesterol secretion 16%. Administration of progesterone, an inhibitor of ACAT, had no effect on HMG CoA reductase and increased biliary cholesterol output 32% at 1 h. By 2 h, all parameters were near control levels. None of these agents had any significant effect on biliary bile salt or phospholipid secretion. Thus, acutely altering rates of esterification and/or synthesis can have profound effects on biliary cholesterol secretion independent of the other biliary lipids. These experiments suggest the existence of a metabolically active pool of free cholesterol that serves as a precursor pool for biliary cholesterol secretion. Furthermore, the size of this precursor pool is determined in part both by rates of cholesterol synthesis and esterification and is a key determinant of biliary cholesterol secretion.

Effects of fenofibrate on bile lipid composition

In humans, clofibrate increases the degree of bile cholesterol saturation and predisposes patients to cholesterol gallstone formation. To determine if this activity extends to the related hypolipidemic agent fenofibrate, duodenal bile lipid composition was studied in 15 subjects before they participated in a double-blind study of that drug. Eight subjects were studied again on fenofibrate and six on placebo; five placebo patients were also studied later on open-label fenofibrate. The results were similar in the double-blind and open-label studies, and changes in bile lipid composition were comparable to those seen in studies of clofibrate. Fenofibrate caused a significant decrease in the molar percentage of bile acids and increases in the molar percentage of phospholipids and cholesterol. The changes in bile acids and phospholipids had opposing effects on the cholesterol-holding capacity of bile. A statistically significant increase in the cholesterol saturation index was only apparent when all fenofibrate bile analyses were compared with all untreated bile analyses. The results demonstrated that fenofibrate has clear effects on bile lipid composition that may be associated with an increased propensity for gallstone formation, and when fenofibrate is used, patients should be monitored for this possibility.

Diurnal rhythm of bile lipid composition after cholecystectomy and papillotomy. Postpapillotomy biliary lithogenicity

The influence of the gallbladder and the sphincter of Oddi on the diurnal rhythm of bile lipid composition was assessed by determining the lithogenic index at 4-h intervals over a period of 24 h in 29 cholecystectomized and papillotomized patients with a nasobiliary tube receiving a normal hospital diet and in 9 during 1-day fast. With a normal diet, biliary cholesterol concentrations dropped during the daytime (p less than 0.05), and total biliary lipid, bile acid, phospholipid, and cholesterol concentrations rose at night (p less than 0.05). During fasting, total biliary lipid, phospholipid, and cholesterol concentrations rose continuously (p less than 0.01). Even with loss of function of the gallbladder and sphincter of Oddi, a diurnal rhythm of biliary lithogenicity persisted, caused mainly by cholesterol increases during fasting. Concomitant increases in phospholipids and, to a lesser extent, bile acids modulated these changes.

Gall bladder sludge formation during prolonged fasting after gastrointestinal tract surgery

In this study we have ultrasonographically assessed the prevalence of sludge in a group of 48 fasting patients after gastrointestinal tract surgery. Ultrasound examinations were carried out daily in each patient, beginning on the day before surgery. The period of fasting lasted from seven to 10 days. The presence of sludge was demonstrated within the seventh day in seven out of the 48 patients. In 38 cases fast lasted for a further three days. The total number of sludge-positive patients after 10 days was 12 out of 38. Ultrasound controls were performed after six and 12-24 month interval and showed the presence of gall stones with different ultrasonographic patterns in three sludge positive patients. We conclude that in the early postoperative period there is a high risk for sludge development and that in some cases sludge may subsequently evolve into gall stones.

Diurnal variation in cholesterol saturation of gall-bladder bile

In order to determine whether a diurnal variation in cholesterol saturation index is present in gall-bladder bile, samples of bile were taken by nasoduodenal intubation and cholecystokinin infusion at 9 am after the conventional 12 hour fast, and also at 5 pm five hours after a meal containing no cholesterol or phospholipid. In healthy controls saturation index (mean +/- SEM) fell from 1.02 +/- 0.08 at 9 am to 0.86 +/- 0.08 at 5 pm (n = 8, p less than 0.05). In untreated cholesterol gall-stone patients saturation index fell from 1.30 +/- 0.07 to 1.04 +/- 0.07 (n = 8, p less than 0.05); on chenodeoxycholic acid 15 mg/kg/day it fell from 0.91 +/- 0.06 to 0.78 +/- 0.07 (n = 16, p less than 0.01). The degree of diurnal variation was similar in those taking chenodeoxycholic acid at bedtime and in those taking it at mealtimes. The 9 am sample was supersaturated in three non-responders (showing no evidence of gall stone dissolution on oral cholecystogram after at least six months treatment) and in four responders. The 5 pm sample was a better predictor of treatment failure, being supersaturated in all four non-responders but in only one out of the 12 responders (p less than 0.01).

Management of stones in the biliary tree

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Gallbladder and small intestinal regulation of biliary lipid secretion during intraduodenal infusion of standard stimuli

The gallbladder and small intestine are reservoirs for the bile acid pool during its enterohepatic circulation and, as such, may regulate biliary secretion of bile acid. During studies of biliary bile acid secretion, a stimulus to gallbladder contraction is continuously infused into the duodenum. Under these conditions, it is assumed that the gallbladder is tonically contracted and that the rate of bile acid secretion into the duodenum equals the hepatic bile acid secretion rate. However, secretion rates vary by as much as 100%, depending upon which of two standard stimuli is used. Therefore, we studied the role of gallbladder emptying and small intestinal transit in determining biliary lipid secretion rate and composition during infusion of these stimuli in five healthy subjects. Each subject was studied with a liquid formula containing 40% of calories as fat, and with an amino acid solution for 10 h. Bile acid, phospholipid, cholesterol, and markers were measured in duodenal bile and hourly secretion rates were calculated by marker dilution technique. Real-time gallbladder sonographs and serum pancreatic polypeptide levels were obtained every 30 min. Small bowel transit time was estimated levels were obtained every 30 min. Small bowel transit time was estimated by the breath hydrogen response after giving lactulose intraduodenally.During liquid formula infusion, gallbladder emptying was more complete, small intestinal transit was faster, and pancreatic polypeptide levels were higher. Secretion rates of all lipids were greater and molar percent cholesterol was lower. For the combined data from both infusions, the secretory relationships of cholesterol to bile acid, cholesterol to phospholipid, and phospholipid to bile acid were curvilinear. We conclude that more complete gallbladder emptying and faster intestinal transit increase the enterohepatic cycling of bile acids and lower the molar percent cholesterol of bile. Some of the fluctuation observed in biliary lipid secretion rates, especially during amino acid infusion, is due to gallbladder refilling and emptying.

Changes in gallbladder motor function during the female cycle--a risk factor leading to gallstone formation?

The gallbladder volume of eight women with stable cycles was determined by sonography. Furthermore, gallbladder contraction--following an orally administered fatty meal and the spontaneous refilling of the empty gallbladder--was quantitatively examined. The formula of a rotation ellipsoid, which has been proven to be adequately accurate in in vitro studies, was used for calculating the gallbladder volume. In the gestagen phase (21st or 22nd day) the intraindividual studies showed greater fasting volumes, higher residual volumes after contraction, slower gallbladder emptying, and retarded refilling of the empty gallbladder as compared to the estrogen phase (12th or 13th day). The hormonally modified contraction behavior and the differing course of gallbladder filling may play a major role in the pathogenesis of gallstone formation.

Is recurrence inevitable after gallstone dissolution by bile-acid treatment?

Gallstone dissolution was observed on 60 occasions in 54 patients; in 6, recurrent stones were dissolved by a second course of medical treatment. When complete gallstone dissolution was confirmed (by two consecutive cholecystograms, 3 months apart) bile-acid treatment was stopped, and the patients were followed for up to 71/2 years with oral cholecystograms taken annually (or sooner if symptoms suggested early recurrence). Recurrence was detected 30 times after the 60 episode of gallstone dissolution (50%), in 25 of the 54 patients (46%), and in 25 of 46 patients who had had at least one post-dissolution X-ray before recurrence (54%). In 21 of these 25 patients (84%) the recurrence was observed within 2 years of treatment being stopped. There were no significant differences in clinical details and pre-treatment gallstone characteristics between the 25 gallstone-recurrent (at any time) and the 29 gallstone-free (at the time of study) patients, nor between a subgroup of patients in whom recurrent stones developed rapidly (less than or equal to 1 year) and a subgroup who remained gallstone-free for 3 years. It is concluded that long-term follow-up is advisable and that post-dissolution treatment will be necessary to prevent gallstone recurrence.

Diurnal variation in biliary lipids and serum VLDL before and during treatment with cloribrate

Biliary lipid composition and serum VLDL triglyceride (VLDL-TG) level were determined intermittently over 24 h in 5 previously cholecystectomized hypertriglyceridaemic patients. The study was repeated when the patients had been treated with clofibrate for 2 months. Before and during treatment the molar cholesterol concentration in duodenal bile showed marked diurnal variations. It dropped after the first meal in the morning, remained depressed until the end of the evening, increased early at night and dropped back slightly between 2 and 8 a.m. A diurnal variation was also recorded for bile acid composition, as the contribution of cholic acid (C) increased in 4 of the subjects at night. During treatment with clofibrate, the molar concentration of cholesterol remained unchanged during the day but was significantly elevated in samples obtained at night. The contribution of C increased during both the day and the night. As a general tendency, changes in the curve representing the molar level of cholesterol in bile were mirrored by reversed changes in the VLDL level in plasma. The possibility of a causal relationship between these two parameters is discussed.

Bile acid content of gallbladder bile and stones in type IIb and IV hyperlipoproteinemia

We examined the bile acid composition of gallbladder bile using reversed-phase high performance liquid chromatography (HPLC), in normolipemic and hyperlipidemic (types IIb and IV) patients with cholelithiasis and compared them with normal subjects. Similarly, bile acid composition was determined n the gallstones of these patients. No free bile acids were found in any of the samples examined. We observed that gallbladder bile and gallstones of patients with type IV hyperlipidemia showed a significant increase in the percentage of glyco-conjugated bile acids and reduction in taurine conjugates. Based on this finding we postulate that in addition to biliary lipid composition bile acid composition may also play a role in the pathogenesis of cholesterol gallstone formation.

[Causes, shape and chemistry of gallstones]

Gallstones are precipitations of oversaturated bile fluid. They can develop in the gallbladder and in the efferent bile ducts; they are very often correlated with diseases of the gallbladder, bile ducts and neighboring organs. The gallstone disease (cholelithiasis) is increasing continually, especially in developed countries with overcaloric nourished population. Surgical interventions on the biliary tract are the most frequent abdominal operations at present.