Biliary bile acids in cholelithiasis and colon cancer

Thermodynamic interference with bile acid demicelleization reduces systemic entry and injury during cholestasis

Bile acids (BA), with their large hydrophobic steroid nucleus and polar groups are amphipathic molecules. In bile, these exist as micelles above their critical micellar concentration (CMC). In blood at low concentrations, these exist as monomers, initiating cellular signals. This micellar to monomer transition may involve complex thermodynamic interactions between bile salts alone or with phospholipids, i.e. mixed micelles and the aqueous environment. We therefore went on to test if therapeutically relevant changes in temperature could influence micellar behavior of bile salts, and in turn whether this affected the biological responses in cells, and in vivo. Sodium taurocholate (STC) belongs to a major class of bile salts. STC has a CMC in the 5–8 mM range and its infusion into the pancreatic duct is commonly used to study pancreatitis. We thus studied micellar breakdown of STC using isothermal titration calorimetry (ITC), dynamic light scattering and cryogenic transmission electron microscopy. Under conditions relevant to the in vivo environment (pH 7.4, Na 0.15 M), ITC showed STC to have a U shaped reduction in micellar breakdown between 37 °C and 15 °C with a nadir at 25 °C approaching ≈90% inhibition. This temperature dependence paralleled pancreatic acinar injury induced by monomeric STC. Mixed micelles of STC and 1-palmitoyl, 2-oleyl phosphatidylcholine, a phospholipid present in high proportions in bile, behaved similarly, with ≈75% reduction in micellar breakdown at 25 °C compared to 37 °C. In vivo pancreatic cooling to 25 °C reduced the increase in circulating BAs after infusion of 120 mM (5%) STC into the pancreatic duct, and duct ligation. Lower BA levels were associated with improved cardiac function, reduced myocardial damage, shock, lung injury and improved survival independent of pancreatic injury. Thus micellar breakdown of bile salts is essential for their entry into the systemic circulation, and thermodynamic interference with this may reduce their systemic entry and consequent injury during cholestasis, such as from biliary pancreatitis.

Gallstone disease is associated with rectal cancer: a meta-analysis

BACKGROUND

Increased levels of secondary bile acids after cholecystectomy and cholelithiasis are believed to increase the risk of colorectal cancer, and several studies have suggested that the risk of colorectal cancer may be the greatest proximally. Numerous conflicting studies have been published and it remains unclear whether the risk is apparent in the rectum. This meta-analysis aims to determine the risk of developing rectal cancer following gallstone disease or cholecystectomy.

METHODS

The prospective protocol included a literature search of PubMed, MEDLINE, EMBASE, and Current Contents (1950-2011). Selection criteria were developed to sort for studies exploring the relationship between cholelithiasis, cholecystectomy, and rectal cancer in an adult population. A random-effects model was used to generate pooled odds ratios (OR) and 95% confidence intervals (CI). Publication bias and heterogeneity were assessed.

RESULTS

Of the 2358 studies identified, 42 were suitable for final analysis. There were 1,547,506 subjects in total, 14,226 diagnosed with rectal cancer, and 496,552 with gallstones or cholecystectomy. There was a statistically significant risk of rectal cancer following cholelithiasis (OR = 1.33; 95% CI = 1.02-1.73), though no risk was apparent following cholecystectomy (OR = 1.14; 95% CI = 0.92-1.41).

CONCLUSIONS

Cholelithiasis increases the risk of rectal cancer. No association exists between cholecystectomy and rectal cancer.

Bile acid analysis in biliary tract cancer

The etiology of biliary tract cancer is obscure, but there are evidences that bile acid plays a role in carcinogenesis. To find the association between biliary tract cancer and bile acid, this study compared the bile acid concentration and composition among patients with biliary cancer, biliary tract stones, and no biliary disease. Bile was compared among patients with biliary tract cancer (n = 26), biliary tract stones (n = 29), and disease free controls (n = 9). Samples were obtained by percutaneous transhepatic biliary drainage, endoscopic nasobiliary drainage, or gallbladder puncture, and analyzed for cholic, deoxycholic, chenodeoxycholic, lithocholic, and ursodeoxycholic acid composition. Total bile acid concentration was lower in the cancer group than the biliary stone and control groups; the proportions of deoxycholic (2.2% vs. 10.2% and 23.6%, p < 0.001 and p < 0.001, respectively) and lithocholic acid (0.3% vs. 0.6% and 1.0%, p = 0.065 and p < 0.001, respectively) were also lower. This result was similar when disease site was limited to bile duct or gallbladder. Analysis of cases with bilirubin <or= 2.0 mg/dL also showed lower total bile acid concentration and deoxycholic acid composition in the cancer group compared to controls (5.7% vs. 23.6%, p = 0.003). Although the presence of bile duct obstruction explains some of the difference in total concentration and composition of bile acid, there are other contributing mechanisms. We suspect the alteration of bile acid transport might decrease bile acid excretion and cause the accumulation of carcinogenic bile acid in bile duct epithelium.

Risk factors for gallbladder cancer: a reappraisal

Carcinoma of the gallbladder has a very unusual geographical distribution with pockets of high incidence seen in Chile, Poland, India, Japan and Israel; it occurs rarely in the rest of the world. It is a common malignancy in the Western Bihar and Eastern Uttar Pradesh regions of India. Patients present with extremes of clinical symptoms, indicating benign biliary diseases on the one hand and incurable malignant disease on the other. Laboratory and roentgenographic data tend to confirm the clinical diagnosis of the advanced incurable disease at presentation, in most cases. Various aetiopathological agents have been proposed but none has stood the test of time. In this article, we have reviewed the aetiopathological agents proposed from time to time over the past two centuries, with special emphasis on the developments made in the last 25 years.

Modification of mutagenic activities of pro-mutagens by glyco-ursodeoxycholic acid in the Ames assay

Mutagenicity, co-mutagenicity and anti-mutagenicity of glycoursodeoxycholic acid (GUDCA) were examined by the Ames assay using Salmonella typhimurium strain TA98 with S9. As pro-mutagens, 2-aminoanthracene (2AA), Benzo[a]pyrene (BaP), 3-amino-1-dimethyl-5H-pyrido[4, 3-b]indole (Trp-P-2), 2-amino-3-methylimidazo[4, 5-f]quinoline (IQ) and 2-amino-3, 4-dimethylimidazo[4, 5-f]quinoline (MeIQ) were used. In addition to these pro-mutagens, blue-chitin extracts of human gallbladder bile (BCE) collected from the cholecystectomized patients with cholelithiasis were used in order to investigate the role of GUDCA on mutagen(s) actually existing in human bile. It was found that GUDCA did not show mutagenicity in this test system. Concerning the modification of mutagenic activities of pro-mutagens, GUDCA showed the different directions. GUDCA acted as co-mutagen, since it enhanced the mutagenic activities of 2AA and BaP. But, acted as anti-mutagen, since it suppressed the activities of Trp-P-2, IQ and MeIQ, all of which were classified as heterocyclic amines. GUDCA also suppressed the mutagen(s) in human bile. Because of the use of blue-chitin absorbed method for testing bile mutagenicity, the chemicals involved were considered to be heterocyclic amines and other polycyclic compounds. In these we suspect the bile mutagens are heterocyclic amines. Further examination should be directed towards the investigation into the mechanism of anti-mutagenic effects of GUDCA on mutagen(s) actually existing in human bile.

Co-mutagenicity of glyco- and tauro-deoxycholic acids in the Ames test

Mutagenicity and co-mutagenicity of glyco- and tauro-deoxycholic acids (GDCA and TDCA), which are abundant in human bile, were examined by the Ames test. The two chemicals were not mutagenic for themselves to Salmonella typhimurium TA98 and TA100, with and without S9 mix. They enhanced, however, the mutagenic activities of the pro-mutagens, 2-aminoanthracene (2AA) and benzo[a]pyrene (BaP), for both TA98 and TA100 with S9 mix. They were more co-mutagenic for the pro-mutagens on TA98 than on TA100. On TA98, the mutagenic activities of 2AA with GDCA (5 mumol/plate) and with TDCA (5 mumol/plate) were 9.7-fold and 11.8-fold as high as that of the corresponding control (2AA only), respectively. BaP with GDCA (2.5 mumol/plate) and with TDCA (2.5 mumol/plate) showed 2.8-fold and 3.0-fold increases over the corresponding control level (BaP only), respectively. It is hence concluded that GDCA and TDCA may enhance the activity of some mutagens existing in bile.

Is there a causal connection between bile acids and colorectal cancer?

Bile acid composition was assessed in 50 patients with colorectal cancer as compared to that in a control group of 50 subjects. The two groups were age- and sex-matched. The overall bile acid values were similar in both groups, while the relative concentrations of primary and secondary bile acids were different, a significant increase in the patients with colorectal cancer being observed. This finding thus seems to confirm the existence of a link between colorectal cancer and cholelithiasis. Both conditions share common risk factors, such as alterations in cholesterol metabolism and bile acid composition.

Geographical variations in mutagenicity of blue rayon extracts of Japanese human bile

The mutagenicity of human bile was investigated in the Ames test after blue rayon treatment. In the present study, 52 and 59 bile samples were collected from the high and the low risk population for gallbladder cancer (GBC), respectively. The bile mutagenicity was detected only when the blue rayon extracts of bile were assayed with Salmonella typhimurium TA98 in the presence of S9 mix. Thirty-two (61.5%) of 52 samples obtained from the high risk population were mutagenic. In our previous study (Mano et al., 1993), the mutagenicity was observed in 14 (58.3%) of 24 samples. After combining this data with the results of the present study, 46 (60.5%) of 76 samples revealed the mutagenicity. On the other hand, the mutagenicity was detected in only 7 (11.9%) of 59 samples collected from the low risk population. Therefore, we found a significant geographical difference in the bile mutagenicity.

Mutagenicity of blue rayon extracts of human bile in the Ames test

The mutagenicity of human bile was examined in the Ames Salmonella/microsome assay. Bile samples were obtained from the gallbladders resected from patients with cholelithiasis, choledocholithiasis, gallbladder cancer, extrahepatic bile duct cancer and other diseases. For extraction of mutagenic components, the bile samples were treated with blue rayon and the adsorbed materials were assayed with Salmonella typhimurium TA98 in the presence of S9 mix. Twenty-four bile samples were tested and positive mutagenic activity was found in 14 samples. A 200-microliter bile equivalent material gave 6.3 times as many revertant colonies as the solvent control. With several samples that had undergone two cycles of blue rayon extraction, clear dose-response relationships in mutagenicity were demonstrated.

Faecal unconjugated bile acids in patients with colorectal cancer or polyps

The unconjugated faecal bile acid profiles of 14 patients with colorectal cancer, nine patients with polyps and 10 controls were compared using gas liquid chromatography, controlling for such confounding variables as cholecystectomy, gall stones and hepatic function. Patients with adenomatous polyps had a higher concentration of faecal bile acids (5.23 mumol/g, 2.16-13.67 (median, range) v 1.96, 0.91-6.97; p = 0.016) lithocholic acid (2.41, 0.88-3.22 v 1.07, 0.38-2.03; p = 0.013) and total secondary bile acids (5.23, 2.16-13.4 v 1.96, 0.73-6.63; p = 0.02) compared with control subjects. Patients with colorectal cancer had an increased (p = 0.029) proportion of secondary faecal bile acids (mol%) compared with controls (100, 96.5-100 v 95.19, 81.73-100) and the ratios of the primary bile acids, cholic and chenodeoxycholic acid, to their respective derivatives (secondary bile acids) were significantly lower in cancer patients compared with control and patients with polyps (p = 0.034 to 0.004). This study lends further support to the theory that bile acids may play a role in the development of polyps and colorectal cancer.

Gallstones and colorectal cancer--there is a relationship, but it is hardly due to cholecystectomy

The prevalence of gallstone disease in 145 consecutive patients with colorectal cancer was compared with gallstone prevalence in 4,159 subjects randomly selected from a population. The group of patients had a significantly higher prevalence of gallstone disease than the population (odds ratio = 1.59; 95 percent confidence limits 1.04-2.45), whereas cholecystectomies occurred with equal frequency in the two groups. There was a nonsignificant trend toward more right-sided cancers in patients with gallstones than in patients without. These results, together with available literature, give substantial evidence for an association between gallstones and colorectal cancer, an association which is not due to cholecystectomy being a predisposing factor to colorectal cancer. Sporadic findings of an association between cholecystectomy and colorectal cancer can be explained by the above relationship.

Biliary bile acid profiles in familial adenomatous polyposis

Patients with familial adenomatous polyposis have an excess risk for adenomas and cancers of the upper and lower gastrointestinal tract. In the upper intestine these lesions occur mainly around the ampulla of Vater and they parallel mucosal exposure to bile. In view of this finding and of evidence that bile acids play a role in colorectal carcinogenesis, biliary bile acid profiles were determined in 29 patients with familial adenomatous polyposis (12 before colectomy, 17 after colectomy) and in 28 patients without familial adenomatous polyposis (all with colons in situ). Patients with familial adenomatous polyposis had a higher total biliary bile acid concentration than the others. The bile of patients with polyposis had a greater proportion of chenodeoxycholic acid and a lower proportion of deoxycholic acid than did the bile of patients without polyposis. The ratio of chenodeoxycholic acid and its metabolite lithocholic acid to cholic acid and its metabolite deoxycholic acid, which is related to subsequent bile acid profiles in the colon, was higher in patients with polyposis. Because bile acids influence cellular proliferation, these findings may be of importance with respect to intestinal adenoma and cancer growth.