Fecal bile acid metabolic pattern after administration of different types of bread.

Increased concentrations of fecal bile acids have been suggested to be associated with increased risk of colorectal cancer. Fecal bile acid profiles were determined in 12 healthy Finnish women who included in their normal diets for 2-week periods in turn three different types of bread, 200-300 g/day. The breads contained either low-fiber wheat, whole-meal wheat, or whole-grain rye. During consumption of rye bread, the total mean concentration of fecal free bile acids was 4.77 +/- 0.90 mumol/g of dry feces (mean +/- SEM), which was much lower than with the normal omnivorous diet (8.05 +/- 1.56 mumol/g) or during administration of the low-fiber wheat bread (8.83 +/- 1.56 mumol/g) or the whole-meal wheat bread (7.88 +/- 1.34 mumol/g) (P less than 0.05). This decrease was mainly caused by increased proportions of saponifiable bile acids (P less than 0.01). During intake of the whole-grain rye bread, 46% +/- 3% of the fecal bile acids were in their saponifiable forms; this percentage was 30% +/- 3% during the control period, 30% +/- 4% during the low-fiber wheat bread period, and 27% +/- 4% during the whole-meal wheat bread period. It is concluded that the type of bread significantly effects concentrations of cocarcinogenic and comutagenic free lithocholic and deoxycholic acids by changing modes of conjugation in the gut.

Fecal free and conjugated bile acids and neutral sterols in vegetarians, omnivores, and patients with colorectal cancer.

Increased excretion and intestinal bacterial metabolism of bile acids and neutral sterols have been suggested to be associated with an increased risk of colorectal cancer. We determined fecal neutral sterol and bile acid profiles by new capillary column gas-liquid chromatographic methods in 18 patients with colorectal cancer, 10 omnivores, and 10 vegetarians. The methods also determine concentrations of esterified neutral sterols and saponifiable bile acids formed by intestinal bacterial action. Patients with colorectal cancer had the highest concentrations of neutral animal sterols, the lowest degree of esterification of neutral sterols, the lowest relative amount of saponifiable bile acids, and the highest concentrations of unconjugated primary bile acids. These differences were statistically significant (p less than 0.05) and more profound when the patients were compared with vegetarians than with omnivores. Since epidemiologic studies suggest that vegetarians have a lower risk of colorectal cancer than omnivores, these differences are discussed as possible risk factors for colorectal cancer.

Effect of oxytetracycline administration on intestinal metabolism of oestrogens and on plasma sex hormones in healthy men.

The effect of oxytetracycline (1 g/day for five days) on the enterohepatic recycling of oestrogens and on plasma sex hormone concentrations was assessed in healthy men. Plasma oestrone (E1), oestradiol-17 beta (E2), 4-androstenedione (A), 5 alpha-dihydrotestosterone (5 alpha-DHT), total and free testosterone (T and free T), binding capacity of sex hormone binding globulin, luteinizing hormone, dehydroepiandrosterone-sulphate, urinary total E1, E2, and oestriol (E3), and oestriol-3-glucuronide (E3-3G) and faecal unconjugated and conjugated E1, E2, and E3 were measured by radioimmunoassay (RIA). Treatment with the antibiotic significantly increased the excretion of faecal conjugated oestrogens, which parallelled a decrease in urinary oestrogen excretion, especially of E3. The effect on urinary E3 could be explained almost entirely by the simultaneous decrease of urinary E3-3G concentrations. In urine and faeces the E2/E3 and E1 + E2/E3 ratios increased, probably because of the diminished reductive metabolism of oestrogens in the gut. No significant effects on plasma unconjugated oestrogen concentrations were observed. Moreover, in the present study oxytetracycline had no remarkable effect on plasma total, or free T concentrations, nor on other plasma hormones measured. Our results suggest that enterohepatic recycling and intestinal metabolism of oestrogens may be significant in men. The mechanism of action of antibiotics on oestrogen metabolism probably involves decreased hydrolysis by beta-glucuronidase of oestrogen conjugates by the intestinal contents, diminishing the reabsorption of aglycones of oestrogen conjugates and resulting in faecal loss of the steroids.

Multicomponent analysis of bile acids in faeces by anion exchange and capillary column gas-liquid chromatography: application in oxytetracycline treated subjects.

A method is described for the multicomponent analysis of bile acids in faeces. Following homogenization and extraction, bile acids are separated into several groups according to their mode of conjugation by anion exchange chromatography on DEAE-Sephadex A-25 in the acetate form. The different conjugate groups are then processed separately and quantified using capillary column gas-liquid chromatography (GC), the identity of the individual bile acid components being established by gas chromatography-mass spectrometry (GC-MS). The method permits the quantitative determination, with good precision, of unconjugated bile acids, their saponifiable derivatives, and their glycine-, taurine- and sulfated conjugates. In five healthy men the mean daily excretion of bile acids was 472 +/- 21.8 mumol (SEM) and the mean faecal concentration 7.74 +/- 1.07 mumol (SEM)/g dry weight. Free bile acids constituted 74.8% +/- 5.8% (SEM), saponifiable conjugates 23.5% +/- 5.8% (SEM) glycine-conjugates 0.7% +/- 0.2% (SEM), taurine-conjugates 0.2% +/- 0.07% (SEM), and their sulfated conjugates 0.8% +/- 0.1% (SEM) of total faecal bile acids. In addition to a detailed description of the methodology the effect of antibiotics on faecal bile acid profiles is presented. Oxytetracycline consistently decreased faecal concentrations of saponifiable derivatives of bile acids while increasing the taurine- and sulfated conjugates. The concentrations of the primary bile acids, cholic- and chenodeoxycholic acid, were higher during the course of oxytetracycline.

Fecal neutral sterols in omnivorous and vegetarian women.

The purpose of this study was to investigate the effect of a vegetarian diet on human fecal neutral sterol excretion. Free and esterified fecal neutral sterols were analyzed by capillary gas-chromatography in healthy North-American white women who were consuming either a mixed Western diet (n = 19) or a vegetarian diet (n = 20). Vegetarians had lower mean concentrations of bacterial metabolites of cholesterol, coprostanol, and coprostanone, and their relative amounts of esterified neutral sterol metabolism in both populations. Most of the subjects in both groups excreted their neutral sterols mainly as metabolites. However, 25% of the omnivores and 21% of the vegetarians had exceptionally low amounts of these metabolites in their feces. The vegetarians in this study differed only slightly from omnivores with regard to intestinal bacterial metabolism of neutral sterols.

Effect of oxytetracycline on bacterial intestinal metabolism of neutral sterols and on serum lipids.

The effect of oral oxytetracycline administration to five healthy male volunteers on intestinal bacterial metabolism of faecal neutral sterols was studied. A reduction in bacterial transformation of cholesterol to coprostanol and coprostanone was observed which lasted 1-2 weeks after 5 days' intake of oxytetracycline (1000 mg/day). In addition, a reduction in the amount of esterified neutral sterols in faeces was observed. The significant changes in the intestinal metabolism of cholesterol had no effect on the levels of serum cholesterol, HDL-cholesterol, LDL-cholesterol, or triglycerides.

Studies on the role of intestinal bacteria in metabolism of synthetic and natural steroid hormones.

Administration of antimicrobial agents to subjects taking oral contraceptives has been reported to lead to contraceptive failure and subsequent pregnancy. In women taking oral contraceptives antimicrobial agents could have an effect on both endogenous hormone levels and on the metabolism of the exogenously administered steroids. To investigate these possibilities, antimicrobial agents were administered for short periods to normal women taking various steroid drugs: Megestrol acetate (MA), medroxyprogesterone acetate (MPA), norethisterone (NET), a combination of NET and ethinylestradiol (EE) or a combination of lynestrenol and EE. During ampicillin administration the 24-h morning plasma concentrations of MA, MPA and NET were increased compared to the control values. In the MA and MPA experiments the afternoon values were determined and also found to be increased. In the subjects taking oral contraceptives plasma EE concentration showed a tendency to decrease during ampicillin administration on the third, fourth or fifth morning of ampicillin administration, but was never lower than the pretreatment values. In other experiments plasma estrone (E1) and estradiol (E2), urinary total E1, E2 and estriol (E3) and fecal unconjugated and conjugated E1, E2 or E3 were determined by RIA before, during and after administration of oxytetracycline (2 X 500 mg/day for 5 days) to 5 young male subjects. Furthermore urinary and fecal estrogens were determined in 1 male subject after administration of erythromycin for 6 days and in 2 normally menstruating women after tetracycline and trimethoprim administration, respectively. During treatment with antimicrobial drugs an increase in the excretion of fecal conjugated and, with the exception of the oxytetracycline experiments, also of unconjugated estrogens paralleled a decrease in urinary estrogen excretion, especially for E2 and E3. In both urine and feces the E1/E2 and E1 + E2/E3 ratios increased due to diminished reductive metabolism of estrogens in the gut. No significant effects on plasma unconjugated estrogen concentrations were observed. The results suggest that the intestinal bacterial flora plays a significant role in estrogen metabolism. However, further studies are necessary, because our results do not explain why administration of antibiotics may cause contraceptive failure.

PIP: Administration of antimicrobial agents to subjects taking oral contraceptives (OCs) has been reported to lead to contraceptive failure and subsequent pregnancy. In women taking OCs, antimicrobial agents could have an effect on both endogenous hormone levels and on the metabolism of the exogenously administered steroids. To investigate these possibilities, antimicrobial agents were administered for short periods to normal women taking various steroid drugs: megestrol acetate (MA), medroxyprogesterone acetate (MPA), norethisterone (NET), a combination of NET and ethinyl estradiol (EE), or a combination of lynestrenol and EE. During ampicillin administration, the 24 hour morning plasma concentrations of MA, MPA, and NET were increased compared to control values. In the MA and MPA experiments, the afternoon values were determined and also found to be increased. In the subjects taking OCs, plasma EE concentration showed a tendency to decrease during ampicillin administration on the 3rd, 4th, or 5th mornings of ampicillin administration, but was never lower than the pretreatment values. In other experiments, plasma estrone (E1) and estradiol (E2), urinary total E1, E2, and estriol (E3) and fecal unconjugated and conjugated E1, E2, or E3 were determined by RIA before, during, and after administration of oxytetracycline (2x500 mcg/day for 5 days) to 5 young male subjects. Furthermore, urinary and fecal estrogens were determined in 1 male subject after erythromycin administration for 6 days and in 2 normally menstruating women after tetracycline and trimethoprim administration respectively. During treatment with antimicrobial drugs, an increase in the excretion of fecal conjugated and, with the exception of oxytetracycline experiments, also of unconjugated estrogens, paralleled a decrease in urinary estrogen excretion, especially for E2 and E3. In both urine and feces, the E1/E2 and E1+E2/E3 ratios increased due to diminished reductive metabolism of estrogens in the gut. No significant effects on plasma unconjugated estrogen concentrations were observed. The results suggest that the intestinal bacterial flora plays a significant role in estrogen metabolism. However, further studies are necessary since these results do not explain why antibiotic administration causes contraceptive failure.

Capillary gas-liquid chromatography of faecal free and esterified neutral sterols.

A method is described for the analysis of faecal free and esterified neutral sterols by high-resolution capillary gas-liquid chromatography (GC). After homogenization and filtration of the sample, free and esterified sterols are separated by reversed-phase Lipidex-5000 chromatography. The esterified sterols are saponified and analysed by GC. The free sterols are further fractionated on a Lipidex-5000 straight-phase column into oxo- and hydroxysterols, respectively. The GC separation of the compounds is achieved with an SE-30 open-tubular silica capillary column. The mean recoveries of the authentic sterols are 90.0% +/- 5.8% (SD) and the mean within-assay coefficients of variations are 3.7% +/- 2.9% (SD). The method permits determination of (A) the main animal sterols (cholesterol, coprostanol, epicoprostanol, cholestanol, coprostanone and cholestanone), (B) the amount of total plant sterols (beta-sitosterol, campesterol, stigmasterol and their metabolic conversion products) and (C) the degree of esterification of neutral sterols. In addition results obtained in faecal samples from eight healthy young men eating normal Finnish food are presented.