Role of intestinal transit in the pathogenesis of gallbladder stones.

Increasing evidence implicates prolonged intestinal transit (slow transit constipation) in the pathogenesis of conventional gallbladder stones (GBS), and that of gallstones induced by long term octreotide (OT) treatment. Both groups of GBS patients have multiple abnormalities in the lipid composition and physical chemistry of their gallbladder bile-associated with, and possibly due to, an increased proportion of deoxycholic acid (DCA) (percentage of total bile acids). In turn, this increase in the percentage of DCA seems to be a consequence of prolonged colonic transit. Thus, in acromegalic patients OT treatment significantly prolongs large bowel transit time (LBTT) and leads to an associated increase of the percentage of DCA in fasting serum (and, by implication, in gallbladder bile). LBTT is linearly related to the percentage of DCA in fasting serum and correlates significantly with DCA input (into the enterohepatic circulation) and DCA pool size. However, these adverse effects of OT can be overcome by the concomitant use of the prokinetic drug cisapride, which normalizes LBTT and prevents the rise in the percentage of serum DCA. Therefore, in OT-treated patients and other groups at high risk of developing stones, it may be possible to prevent GBS formation with the use of intestinal prokinetic drugs.

Octreotide induced prolongation of colonic transit increases faecal anaerobic bacteria, bile acid metabolising enzymes, and serum deoxycholic acid in patients with acromegaly.

BACKGROUND: Acromegalic patients have slow colonic transit, increased rates of deoxycholic acid formation, and an increased prevalence of cholesterol gall stones, especially during long term octreotide treatment. However, the effects of this prolonged large bowel transit time on the numbers of faecal anaerobes and the activities of the enzyme systems which biotransform conjugated cholic acid into unconjugated deoxycholic acid (cholylglycine hydrolase and 7alpha-dehydroxylase) are unknown. METHODS: Therefore, in 10 non-acromegalic controls, 11 acromegalic patients not treated with octreotide, and 11 acromegalics on long term (8-48 months) octreotide (100-200 mug three times daily subcutaneously), we measured large bowel transit time and, in freshly voided faeces, the activities of the two bile acid metabolising enzymes, and related the results to the proportion of deoxycholic acid in fasting serum. Moreover, in patients with acromegaly, we measured quantitative bacteriology in faeces. RESULTS: Mean large bowel transit time in acromegalics not treated with octreotide (35 (SEM 6.5) hours) was 66% longer than that in non-acromegalic controls (21 (3.1) hours; NS) and became further prolonged during octreotide treatment (48 (6.6) hours; p<0.001). These octreotide induced changes in transit were associated, in acromegalic patients, with more total (15.0 (2.5) v 6.3 (1.3)x10(9) colony forming units (cfu)/g; p<0.05) and Gram positive (6.3 (2.3) v 3.2 (1.0)x10(9) cfu/g; p<0.05) faecal anaerobes. Mean faecal cholylglycine hydrolase activity in the long term octreotide group (22.0 (6.0)x10(-2) U/mg protein) was 138% greater than that in non-acromegalic controls (12.0 (6.0)x10(-2); p<0.01). Similarly, mean 7alpha-dehydroxylase activity in octreotide treated acromegalics (11.1 (1.18)x10(-4) U/mg protein) was 78% greater than that in patients not receiving long term octreotide (6.3 (0.5)x10(-4); p<0.001). The mean proportion of deoxycholic acid in fasting serum also increased from 18.0 (2.88)% in the untreated group to 29.6 (2.3)% during long term octreotide (p<0.05). There were significant linear relationships between large bowel transit time and: (i) faecal 7alpha-dehydroxylase activity; and (ii) the proportion of deoxycholic acid in fasting serum and between 7alpha-dehydroxylase activity and the proportion of deoxycholic acid in serum.Summary/interpretation: These data suggest that increased deoxycholic acid formation seen in acromegalics during octreotide treatment is due not only to the greater numbers of faecal anaerobes but also to increased activity of the rate limiting enzyme pathway (7alpha-dehydroxylation) converting cholic acid to deoxycholic acid.

Influence of pH on the phase distribution of nascent deoxycholic acid in fresh human cecal aspirates.

Prolonged large bowel transit time and an associated increase in the proportion of deoxycholic acid (DCA) in serum and bile have been implicated in the development of cholesterol-rich gallstones and colon cancer. Prolongation of intestinal transit also increases intracolonic pH that, we hypothesized, should favor the solubilization and absorption of newly formed DCA within the colon. To test this hypothesis, we performed in vitro studies on homogenized cecal aspirates (obtained at colonoscopy) that were incubated anaerobically with [14C]cholic acid for 16 h after which the pH was adjusted to between 4.0 and 7.0 in 0.5-pH unit steps. The resultant reaction mixtures were centrifuged to separate the supernatant from the precipitate, and the specific activity of [14C]DCA was quantitated in both phases. As the pH in the aspirates was manipulated from 4.0 to 7.0, the proportion of newly formed, labeled DCA increased in the supernatant and fell in the precipitate, particularly at a hydrogen ion concentration of <100 x 10(-7) (equivalent to pH 5.0-7.0). These results show that the solubility of DCA in colonic contents increases with increasing pH. If solubility is rate limiting, this should lead to increased absorption that, in turn, would explain why the proportion of DCA in serum and bile increases with the prolongation of large bowel transit time.

Gallstone dissolution with oral bile acid therapy. Importance of pretreatment CT scanning and reasons for nonresponse.

In patients with cholesterol-rich gallbladder stones and a patent cystic duct, complete stone clearance rates of 65-90% have been reported with oral bile acids (OBAs) alone or with adjuvant lithotripsy (extracorporeal shock-wave lithotripsy; ESWL). The aims of the present study were to analyze pretreatment gallstone characteristics that predict the speed and completeness of dissolution with OBAs +/- ESWL, and to assess, in patients with incomplete dissolution, the reasons for the poor response. We compared pretreatment gallstone characteristics in 43 patients who became stone-free after a median of 9 months OBAs +/- ESWL with those in 43 age- and sex-matched patients whose stones failed to dissolve after two years of treatment. In those with incomplete gallstone dissolution, we repeated the oral cholecystogram and computed tomogram (CT) and, in selected patients, obtained gallbladder bile by percutaneous fine-needle puncture. In patients who became stone-free, those with stones that were isodense with bile and/or had CT scores of < 75 Hounsfield units had the fastest dissolution rates. In the 43 nonresponders, the main causes for treatment failure were impaired gallbladder contractility and acquired stone calcification. CT-lucent, noncholesterol stones, or failure of desaturation of bile with the prescribed bile acids, occurred in a minority. We conclude that the pretreatment CT attenuation score predicts both the speed and completeness of gallstone dissolution. In patients with incomplete stone dissolution, the combination of oral cholecystography, CT, and analysis of gallbladder bile will determine the underlying reasons for treatment failure in most, but not all, cases.

Bile acid metabolism by fresh human colonic contents: a comparison of caecal versus faecal samples.

BACKGROUND: Deoxycholic acid (DCA), implicated in the pathogenesis of gall stones and colorectal cancer, is mainly formed by bacterial deconjugation (cholylglycine hydrolase (CGH)) and 7 alpha-dehydroxylation (7 alpha-dehydroxylase (7 alpha-DH)) of conjugated cholic acid (CA) in the caecum/proximal colon. Despite this, most previous studies of CGH and 7 alpha-DH have been in faeces rather than in caecal contents. In bacteria, CA increases 7 alpha-DH activity by substrate-enzyme induction but little is known about CA concentrations or CA/7 alpha-DH induction in the human colon. AIMS AND METHODS: Therefore, in fresh "faeces", and in caecal aspirates obtained during colonoscopy from 20 patients, we: (i) compared the activities of CGH and 7 alpha-DH, (ii) measured 7 alpha-DH in patients with "low" and "high" percentages of DCA in fasting serum (less than and greater than the median), (iii) studied CA concentrations in the right and left halves of the colon, and examined the relationships between (iv) 7 alpha-DH activity and CA concentration in caecal samples (evidence of substrate-enzyme induction), and (v) 7 alpha-DH and per cent DCA in serum. RESULTS: Although mean CGH activity in the proximal colon (18.3 (SEM 4.40) x10(-2) U/mg protein) was comparable with that in "faeces" (16.0 (4.10) x10(- 2) U/mg protein), mean 7 alpha-DH in the caecum (8.54 (1.08) x10(-4) U/mg protein) was higher (p<0.05) than that in the left colon (5.72 (0.85) x10(-4) U/mg protein). At both sites, 7 alpha-DH was significantly greater in the "high" than in the "low" serum DCA subgroups. CA concentrations in the right colon (0.94 (0.08) micromol/ml) were higher than those in the left (0.09 (0.03) micromol/ml; p<0.001) while in the caecum (but not in the faeces) there was a weak (r=0.58) but significant (p<0.005) linear relationship between 7 alpha-DH and CA concentration. At both sites, 7 alpha-DH was linearly related (p<0.005) to per cent DCA in serum. INTERPRETATION/SUMMARY: These results: (i) confirm that there are marked regional differences in bile acid metabolism between the right and left halves of the colon, (ii) suggest that caecal and faecal 7 alpha-DH influence per cent DCA in serum (and, by inference, in bile), and (iii) show that the substrate CA induces the enzyme 7 alpha-DH in the caecum.

Mechanism for the transit-induced increase in colonic deoxycholic acid formation in cholesterol cholelithiasis.

BACKGROUND & AIMS: Many patients with cholesterol gallbladder stones (GBS) have a high percentage of deoxycholic acid (DCA) in gallbladder bile (all of which are in the conjugated form), probably as a result of prolonged large bowel transit times (LBTT). However, whether the prolonged LBTT increases DCA formation, solubilization, or absorption (or all 3) is not known. METHODS: In 40 subjects (20 with GBS; age range, 24-74 years), we measured LBTT using radiopaque markers, and intestinal luminal pH by radiotelemetry. We also measured quantitative anaerobic bacteriology and the activities of 2 bile acid-metabolizing enzymes in fresh cecal aspirates obtained during clinically indicated unprepared colonoscopy, and related these results to the percentage of DCA in fasting serum measured by gas chromatography-mass spectrometry. RESULTS: Compared with controls, GBS patients had longer LBTT (mean 23.1 +/- SEM 2.8 h vs. 36.5 +/- 3.3 h; P < 0.01); more total (2.7 +/- 0.6 x 10(9) vs. 5.9 +/- 1.5 x 10(9) cfu/mL) and Gram-positive (9.5 +/- 3.1 x 10(8) vs. 18.0 +/- 4.1 x 10(8) cfu/mL; P < 0.05) anaerobes; and greater 7alpha-dehydroxylating (7alpha-DH) activity (3.39 +/- 0.59 vs. 10.37 +/- 1.15 x 10(-4) U/mg protein) in the cecal aspirates. They also had higher intracolonic pH values (P < 0.02) and increased percentages of DCA in fasting serum (13.4% +/- 1.52% vs. 21.8% +/- 2. 19%; P < 0.005). Results of univariate and multivariate analyses confirmed that LBTT was critical in determining the percentage of DCA in serum and showed that 7alpha-DH activity and apparent distal colonic pH were also significant independent variables. CONCLUSIONS: Slow colonic transit (more time), increased Gram-positive anaerobes (more bacteria), and greater 7alpha-DH activity (more enzyme) favor enhanced DCA formation; transit-induced increases in distal colonic luminal pH favor enhanced DCA solubilization/bioavailability; and increases in LBTT (more time) again favor DCA absorption.

Prolonged large bowel transit increases serum deoxycholic acid: a risk factor for octreotide induced gallstones.

BACKGROUND: Treatment of acromegaly with octreotide increases the proportion of deoxycholic acid in, and the cholesterol saturation of, bile and induces the formation of gallstones. Prolongation of intestinal transit has been proposed as the mechanism for the increase in the proportion of deoxycholic acid in bile. AIMS: To study the effects of octreotide on intestinal transit in acromegalic patients during octreotide treatment, and to examine the relation between intestinal transit and bile acid composition in fasting serum. METHODS: Mouth to caecum and large bowel transit times, and the proportion of deoxycholic acid in fasting serum were measured in non-acromegalic controls, acromegalic patients untreated with octreotide, acromegalics on long term octreotide, and patients with simple constipation. Intestinal transit and the proportion of deoxycholic acid were compared in acromegalic patients before and during octreotide. RESULTS: Acromegalics untreated with octreotide had longer mouth to caecum and large bowel transit times than controls. Intestinal transit was further prolonged by chronic octreotide treatment. There were significant linear relations between large bowel transit time and the proportion of deoxycholic acid in the total, conjugated, and unconjugated fractions of fasting serum. CONCLUSIONS: These data support the hypothesis that, by prolonging large bowel transit, octreotide increases the proportion of deoxycholic acid in fasting serum (and, by implication, in bile) and thereby the risk of gallstone formation.

Roles of gall bladder emptying and intestinal transit in the pathogenesis of octreotide induced gall bladder stones.

BACKGROUND: Octreotide treatment of acromegalic patients increases the % deoxycholic acid conjugates and the cholesterol saturation of gall bladder bile, and induces gall stone formation. AIMS: To study the roles of gall bladder emptying and intestinal transit in these phenomena. METHODS AND PATIENTS: Gall bladder emptying and mouth to caecum transit was measured in (a) control subjects and acromegalic patients given saline or 50 micrograms of octreotide, and (b) acromegalic patients taking long term octreotide. In the second group, large bowel transit was also measured. RESULTS: A single dose of octreotide inhibited meal stimulated gall bladder emptying, the ejection fraction falling from mean (SEM) 66.0 (2.3)% to 7.0 (5.3)% in controls (p < 0.001); from 72.5 (2.1) to 16.6 (5.1)% in untreated acromegalic patients (p < 0.001), and to 30.4 (9.5)% in acromegalic patients taking long term octreotide (p < 0.001 v untreated acromegalic group). Octreotide prolonged mouth to caecum transit time, from 112 (15) min to 237 (13) min in controls (p < 0.001), from 170 (13) min to 282 (11) min in untreated acromegalic patients (p < 0.001), and to 247 (10) min in acromegalic patients taking long term octreotide (p < 0.001 v untreated acromegalic patients). The mean large bowel transit in octreotide untreated compared with treated acromegalic patients remained unchanged (40 (6) h v 47 (6) h). CONCLUSIONS: Prolongation of intestinal transit and impaired gall bladder emptying may contribute to lithogenic changes in bile composition and gall stone formation in patients receiving long term octreotide.

Effects of cisapride on gall bladder emptying, intestinal transit, and serum deoxycholate: a prospective, randomised, double blind, placebo controlled trial.

BACKGROUND: Octreotide inhibits gall bladder emptying and prolongs intestinal transit. This leads to increases in the proportion of deoxycholic acid in, and cholesterol saturation of, gall bladder bile, factors that contribute to the pathogenesis of octreotide induced gall stones. AIMS: To see if an intestinal prokinetic, cisapride, could overcome these adverse effects of octreotide and if so, be considered as a candidate prophylactic drug for preventing iatrogenic gall bladder stones. METHODS: A randomised, double blind, placebo controlled, crossover design was used to examine the effects of cisapride (10 mg four times daily) on gall bladder emptying, mouth to caecum and large bowel transit times, and the proportions of deoxycholic acid and other bile acids, in fasting serum from: (i) control subjects (n=6), (ii) acromegalic patients not treated with octreotide (n=6), (iii) acromegalics on long term octreotide (n=8), and (iv) patients with constipation (n=8). RESULTS: Cisapride had no prokinetic effect on the gall bladder. In fact, it significantly increased both fasting and postprandial gall bladder volumes. However, it shortened mouth to caecum (from 176 (13) to 113 (11) minutes; p<0.001) and large bowel (from 50 (3.0) to 31 (3.4) h; p<0.001) transit times. It also reduced the proportion of deoxycholic acid in serum from 26 (2.3) to 15 (1.8)% (p<0.001), with a reciprocal increase in the proportion of cholic acid from 40 (3.5) to 51 (3.8)% (p<0.01). There were significant linear relationships between large bowel transit time and the proportions of deoxycholic acid (r=0.81; p<0.001) and cholic acid (r=-0.53; p<0.001) in fasting serum. INTERPRETATION/SUMMARY: Cisapride failed to overcome the adverse effects of octreotide on gall bladder emptying but it countered octreotide induced prolongation of small and large bowel transit. Therefore, if changes in intestinal transit contribute to the development of octreotide induced gall bladder stones, enterokinetics such as cisapride may prevent their formation.

Colonic transit influences deoxycholic acid kinetics.

BACKGROUND & AIMS: Prolonged large bowel transit, and an increase in the proportion of deoxycholic acid (DCA), have been implicated in the pathogenesis of cholesterol gallstones-including those developing in acromegalics treated with octreotide. However, there are few data on the effects of intestinal transit on bile acid kinetics. METHODS: We therefore measured the kinetics of DCA and cholic acid (CA) using stable isotopes, serum sampling, and mass spectrometry. The results were related to mouth-to-caecum (MCTT) and large bowel transit times (LBTTs) in 4 groups of 8 individuals: (1) non-acromegalic controls, (2) acromegalics untreated with octreotide, (3) acromegalics on long-term octreotide, and (4) patients with constipation. Paired, before and during octreotide, studies were performed in 5 acromegalics. RESULTS: In the unpaired and paired studies, octreotide significantly prolonged MCTT and LBTT. In the paired studies, the octreotide-induced prolongation of LBTT caused an increase in the DCA input rate (6.4 +/- 2.8 to 12 +/- 2.6 micromol. kg. d, P < 0.05) and pool size (18 +/- 12 to 40 +/- 13 micromol/kg, P < 0.05), and a decrease in CA pool size (45 +/- 15 to 25 +/- 11 micromol/kg, P < 0.05). Furthermore, during octreotide treatment, the mean conversion of 13C-CA to 13C-DCA (micromoles) was greater (P < 0.05) on study days 3, 4, and 5. There were also positive linear relationships between LBTT and DCA input rate (r = 0.78), pool size (r = 0.82, P < 0.001), and a weak (r = -0.49) negative linear relationship between LBTT and CA pool size (P < 0.01). CONCLUSIONS: These data support the hypothesis that, by increasing DCA formation and absorption, prolongation of large bowel transit is a pathogenic factor in the formation of octreotide-induced gallstones.