Bile acids, neutral steroids, and bacteria in feces as affected by a mixed, a lacto-ovovegetarian, and a vegan diet.
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In a metabolic ward 12 healthy male subjects consumed mixed Western (M), lacto-ovovegetarian (L), and vegan (V) diets in a randomized order for 20 d each. The concentrations of deoxycholic acid, isolithocholic acid, and total bile acids in 4-d composites of feces on the L and V diets were significantly lower than on the M diet. The chenodeoxycholic-to-isolithocholic plus lithocholic acid ratio was significantly higher on the V diet. The concentrations of coprostanol and of coprostanol plus cholesterol were highest on M diet and lowest on V diet. The number of fecal lactobacilli and enterococci on the V diet was significantly lower than on the M or the L diets. This study showed a decrease in the concentration of fecal (secondary) bile acids by the L and the V diets and an alteration of the fecal flora composition by the V diet. (+info)
Establishment of a biochemically active intestinal ecosystem in ex-germfree rats.
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A time course study for the establishment of some biochemical microbial intestinal functions was undertaken in ex-germfree rats conventionalized, i.e., colonized with conventional flora, in three different ways: untreated (group 1); contact with visitor rats (group 2); inoculated with intestinal contents from conventional rats (group 3). The first two groups of rats were inoculated with the intestinal contents from conventional rats after being out of the germfree isolators for 4 weeks. The biochemical parameters studied were degradation of mucin, inactivation of tryptic activity, conversion of cholesterol to coprostanol and of bilirubin to urobilinogen, degradation of beta-aspartylglycine, and formation of short-chain fatty acids. The results showed that the way in which the microbes were introduced and the microbial biochemical functions themselves were of importance. In several cases, social contacts, i.e., contact with visitor rats, were just as effective for the functionally adequate establishment of microbial intestinal functions as was inoculation with intestinal contents from conventional rats. Some of the biochemical parameters studied were established after a few days, whereas the establishment of others was markedly delayed. When inoculated after 4 weeks, all rats in the first two groups were colonized with conventional flora within 1 week. The results indicate that the model system described is suitable when studying buildup mechanisms in intestinal ecosystem(s). (+info)
Competitive inhibition of bile acid synthesis by endogenous cholestanol and sitosterol in sitosterolemia with xanthomatosis. Effect on cholesterol 7 alpha-hydroxylase.
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The 7 alpha-hydroxylation of two cholesterol analogues, sitosterol and cholestanol, and their effect on the 7 alpha-hydroxylation of cholesterol were measured in rat and human hepatic microsomes. In untreated rat liver microsomes, the 7 alpha-hydroxylation of cholesterol was higher than that of cholestanol (1.4-fold) and sitosterol (30-fold). After removal of endogenous sterols from the microsomes by acetone treatment, the 7 alpha-hydroxylation of cholesterol was similar to that of cholestanol and only fourfold higher than that of sitosterol. Cholestanol and sitosterol competitively inhibited cholesterol 7 alpha-hydroxylase in both rat and human liver microsomes, with cholestanol the more potent inhibitor. Patients with sitosterolemia with xanthomatosis, who have elevated microsomal cholestanol and sitosterol, showed reduced cholesterol 7 alpha-hydroxylase activity relative to the activity in control subjects (13.9 and 14.7 vs. 20.3 +/- 0.9 pmol/nmol P-450 per min, P less than 0.01). Enzyme activity in these patients was 40% higher when measured in microsomes from which competing sterols had been removed. Ileal bypass surgery in one sitosterolemic patient decreased plasma cholestanol and sitosterol concentrations and resulted in a 30% increase in hepatic microsomal cholesterol 7 alpha-hydroxylase activity. Cholesterol 7 alpha-hydroxylase appears to have a specific apolar binding site for the side chain of cholesterol and is affected by the presence of cholestanol and sitosterol in the microsomal substrate pool. Reduced bile acid synthesis in sitosterolemia with xanthomatosis may be related to the inhibition of cholesterol 7 alpha-hydroxylase activity by endogenous cholesterol analogues. (+info)
Effect of citrus pectin on blood lipids and fecal steroid excretion in man.
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Citrus pectin (15 g/day) was added for 3 weeks to metabolically controlled diets in nine subjects. Pectin was consumed with fruit and sugar as a gel in divided doses with meals. Plasma cholesterol concentrations were reduced by a mean of 13% (P less than 0.001). Fecal fat excretion increased by 44% (P less than 0.001); neutral steroids by 17% (P less than 0.001) and fecal bile acids by 33% (P less than 0.02). Plasma triglyceride levels did not change. (+info)
Fecal bile acids and cholesterol metabolites of patients with ulcerative colitis, a high-risk group for development of colon cancer.
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Patients with chronic ulcerative colitis are at increased risk of developing carcinoma of the colon. It has been shown that the concentration of fecal bile acids and neutral sterols was higher in cancer patients than in the comparable healthy controls. Fecal neutral steroids and bile acids were measured in patients with ulcerative colitis, family controls who were immediate relatives of patients, patients with other digestive diseases, and healthy unrelated controls. The fecal excretion of cholesterol, coprostanol, and cholestane-3beta, 5alpha, 6beta-triol was higher in patients with ulcerative colitis than in other groups. Patients with other diseases, family controls, and unrelated controls excreted comparable levels of neutral sterols. Patients with ulcerative colitis excreted levels of bile acids in their feces comparable to those excreted by other groups. These findings suggest that possible interactions between cholesterol metabolites and colonic epithelial cells may be relevant in colon carcinogenesis. (+info)
Cholesterol-reducing bacterium from human feces.
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An anaerobic, gram-positive diplobacillus that reduces cholesterol to coprostanol was isolated from human feces and rat cecal contents. The isolates closely resemble a cholesterol-reducing organism isolated by Eyssen et al. (H. Eyssen et al., Eur. J. Biochem. 36:412-421, 1973) from a rat's cecum. These organisms would not form colonies and were isolated and cultivated in an anaerobic medium containing homogenized pork brains (naturally high in cholesterol). These organisms require free or esterified cholesterol for growth. They were isolated by serially diluting feces or cecal contents and inoculating brain medium. Colony-forming organisms, which did not reduce cholesterol, were eliminated by addition of inhibitory agents to the brain medium cultures. This serial dilution procedure was performed until a pure culture of a cholesterol-reducing organism was obtained. (+info)
Some effects of deoxycholate administration on the metabolism of cholesterol in man.
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Hypercholesterolemic subjects in a metabolic ward were kept under uniform dietary conditions until constant levels of serum cholesterol were observed. Oral dosage with deoxycholate (1.5 to 3 g daily for a period of 4 to 10 weeks) resulted in a marked reduction of serum cholesterol concentration. Studies with 14C-labeled cholesterol demonstrated that deoxycholate administration decreased absorption of cholesterol from the human intestinal tract. In these subjects, the turnover rate of serum cholesterol was more rapid during therapy with deoxycholate than during control periods. Deoxycholate appeared to influence the intestinal flora as assessed indirectly by analysis of the types of neutral sterols eliminated with the feces. Decreased synthesis of cholesterol during deoxycholate administration uas demonstrated in a study with 14C-mevalonate. It is concluded that deoxycholic acid can have an important role in the regulation of cholesterol metabolism in humans. (+info)
Dihydrocholesterol-induced gallstones in the rabbit: evidence that bile acids cause gallbladder epithelial injury.
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Rabbits fed a diet containing 0.75% dihydrocholesterol for 7 days develop bile acid allodeoxycholic (ADCA) and deoxycholic acid (DCA) stones in the gallbladder. In this model, inflammatory changes in the gallbladder mucosa are often observed even before stones are formed. Within 3 days of the lithogenic diet, abnormalities of platelet function were detectable. Platelet aggregation upon addition of adenosine diphosphate (ADP) was impaired. At the same time the red cells became crenated and developed thorny spicules (echinocytes). This morphological changes was associated with intracellular dehydration and excessive loss of potassium. These changes coincided with a rise in serum ADCA and DCA and preceded a slow rise in serum cholesterol. In vitro incubation studies also suggested that the bile acids had probably caused membrane injury to the platelets and red cells. It is concluded that changes in the bile ADCA and DCA probably induce gallbladder epithelial injury in this model of experimental cholelithiasis. (+info)