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Biomedical subjects

E H Mosbach

Publications and source records attributed to E H Mosbach.

At least 73 records · Page 4Linked to original sources
PubMed1984

New bile acid analogs: 3 alpha, 7 alpha-dihydroxy-7 beta-methyl-5 beta-cholanoic acid, 3 alpha, 7 beta-dihydroxy-7 alpha-methyl-5 beta-cholanoic acid, and 3 alpha-hydroxy-7 xi-methyl-5 beta-cholanoic acid.

Methods are described for the chemical synthesis of three new bile acid analogs, namely, 3 alpha, 7 alpha-dihydroxy-7 beta-methyl-5 beta-cholanoic acid, 3 alpha, 7 beta-dihydroxy-7 alpha-methyl-5 beta-cholanoic acid and 3 alpha-hydroxyl-7 xi-methyl-5 beta-cholanoic acid. The starting material, 2-(3 alpha, 7 xi-dihydroxy-7 xi-methyl-24-nor-5 beta- cholanyl )-4, 4-dimethyl-2-oxazoline upon mild hydrolysis in aqueous HCl yields the two epimeric 3 alpha, 7-dihydroxy-7-methyl-5 beta-cholanoic acids which can be separated as the methyl esters by silica gel column chromatography. More rigorous hydrolysis in boiling methanolic HCl yields a mixture of unsaturated compounds which can be separated as their methyl esters into three fractions by silica gel-AgNO3 column chromatography. The fractions containing 3 alpha-hydroxy-7-methyl-5 beta-chol-6-enoic acid and 3 alpha-hydroxy-7-methylene-5 beta-cholanoic acid when subjected to catalytic hydrogenation yield 3 alpha-hydroxy-7 xi-methyl-5 beta-cholanoic acid.

Bile Acids and Salts↗
PubMed1984

Role of hydrophilic bile acids and of sterols on cholelithiasis in the hamster.

The effect of various dietary additions such as cholesterol, beta-sitosterol, bile acids, and bile acid analogs on gallstone formation was studied in the hamster. Gallstones were formed in 50% of the animals fed a high glucose, fat-free diet. Administration of 0.2% cholesterol or 1% beta-sitosterol had no effect on the incidence of gallstones. Ursodeoxycholic acid (0.5%) and its analog ursodeoxy-oxazoline [2-(3 alpha, 7 beta-dihydroxy-24-nor-5 beta-cholanyl)-4,4-dimethyl-2- oxazoline] were ineffective in preventing gallstones. Hyodeoxycholic acid and hyodeoxy-oxazoline [2-(3 alpha,6 alpha-dihydroxy-24-nor-5 beta-cholanyl)-4,4-dimethyl-2- oxazoline] at the same dosage effectively prevented gallstones, while the trihydroxy bile acid, hyocholic acid, was not effective. Of all the dietary regimens tested, only hyodeoxycholic acid significantly lowered serum cholesterol. The lithogenic diet produced a five-fold increase in hepatic HMG-CoA reductase activity; this activity was not affected by dietary cholesterol or beta-sitosterol. Hyodeoxycholic acid and hyocholic acid feeding increased the reductase activity by an additional 50% while the other bile acids had no effect. beta-Sitosterol doubled the cholesterol 7 alpha-hydroxylase activity whereas hyodeoxy-oxazoline lowered it. Hyodeoxycholic acid-fed animals had significantly lower cholesterol absorption than the animals on the lithogenic diet alone. Biliary cholesterol content increased dramatically in the animals fed the lithogenic diet and was increased still further by ursodeoxycholic acid, hyodeoxycholic acid, and hyodeoxy-oxazoline. These data show that hyodeoxycholic acid and hyodeoxy-oxazoline do not prevent gallstones by inhibiting hepatic cholesterol synthesis or biliary cholesterol secretion.

Animals↗
PubMed1984

Prevention of cholesterol-induced gallstones by hyodeoxycholic acid in the prairie dog.

Prairie dogs of both sexes were fed a semisynthetic diet containing 0.35% cholesterol for a period of 8 weeks. This lithogenic diet induced cholesterol gallstones in ten "lithogenic control animals", five males and five females. Three animals maintained with a high glucose, fat-free diet did not develop gallstones although the cholesterol saturation of their bile approached unity. The formation of gallstones was prevented in four out of five males and all five females fed the lithogenic diet plus 0.1% hyodeoxycholic acid (30 mg per kg body weight per day). The biles of the prairie dogs receiving hyodeoxycholic acid were abnormally colored, cloudy, and highly saturated with cholesterol but contained neither cholesterol crystals nor gallstones (with the exception of one male). Feeding the relatively hydrophilic bile acid, hyodeoxycholic acid, was associated with an increase in hepatic microsomal HMG-CoA reductase activity. Cholesterol 7 alpha-hydroxylase, on the other hand, was inhibited by the administered bile acid. The dietary hyodeoxycholic acid was transformed, in part, to 3 alpha, 6 beta-dihydroxy-5-beta-cholanoic acid and hyocholic acid. It is concluded that hyodeoxycholic acid and its metabolites did not prevent the induced cholelithiasis by causing a decrease in the concentration of biliary cholesterol. Instead, this hydrophilic bile acid apparently increases the amount of cholesterol in the bile, probably in the form of a liquid crystalline mesophase. Hyodeoxycholic acid apparently prevents gallstones by preventing the nucleation and aggregation of cholesterol crystals. The lithogenic diet induced moderate to marked bile duct proliferation together with portal fibrosis and inflammatory infiltration. The addition of hyodeoxycholic acid to the lithogenic diet reduced all of the portal tract changes.

Animals↗
PubMed1983

Hydroxylation of secondary bile acids in the perfused prairie dog liver.

Taurolithocholic acid and deoxycholic acid were perfused into isolated prairie dog livers. Taurolithocholic acid was 7 alpha-hydroxylated to form taurochenodeoxycholic acid, whereas deoxycholic acid was conjugated and 7 alpha-hydroxylated to form taurocholic acid. The low concentrations of secondary bile acids observed in prairie dog bile are due, at least in part, to active bile acid 7 alpha-hydroxylase(s) in the liver of these animals.

Animals↗
PubMed1983

Metabolism of bile acid oxazoline derivatives by hepatocyte monolayer cultures and intestinal anaerobic bacteria.

Certain bile acid oxazoline derivatives (100 microM), but not corresponding unconjugated bile acids (100 microM), were found to inhibit the growth of Eubacterium sp. V.P.I. 12708. The growth inhibition was correlated with the polarity of the steroid portion of the bile acid oxazoline. Primary cultures of adult rat hepatocyte monolayer cultures converted [7 epsilon-14C]methylchenooxazoline3 into MeOH-H2O soluble derivatives. Certain intestinal bacteria were capable of metabolizing [17 epsilon-14C]methylchenooxazoline as well as the MeOH-soluble hepatocyte derivative(s). These results suggest that bile acid oxazoline derivatives may undergo hepatic, as well as bacterial metabolism during enterohepatic circulation.

Anaerobiosis↗
PubMed1983

Inactivation of contraceptive steroid hormones by human intestinal clostridia.

Steroid hormones reduced in ring-A are devoid of hormonal activity. In metabolic experiments we found that human fecal flora reduced the delta 4-3-keto structure of natural progestins to 3 alpha-hydroxy, 5 beta-steroid metabolites (3 alpha,5 beta) and of synthetic progestins to a mixture of 3 alpha,5 beta and 3 beta,5 beta compounds. 3 alpha,5 beta-Reductase was synthesized by Clostridium paraputrificum and had a strong affinity for natural progestins such as progesterone. 3 beta,5 beta-Reductase was synthesized by Clostridium innoculin and had a stronger affinity for synthetic progestins. A third enzyme, 3 beta,5 alpha-reductase, was synthesized by St. Luke's strain 209 (Clostridium species "J-1") but was only observed when pure cultures were used. Ring-A reduction of synthetic progestins was 3 to 10 times slower than that of natural progestins, thus explaining the pharmacological superiority of synthetic progestins over naturally occurring analogs.

Clostridium↗
PubMed1983

Effect of bile acid oxazoline derivatives on microorganisms participating in 7 alpha-hydroxyl epimerization of primary bile acids.

We tested bile acid oxazoline derivatives of chenodeoxycholic (CDC-OX), 7-ketolithocholic (7-KLC-OX), ursodeoxycholic (UDC-OX), and deoxycholic (DC-OX) as inhibitors of the 7-epimerization of the primary bile acids cholic acid (CA) and CDC in cultures of four species of bacteria and the human fecal flora. The organisms tested elaborate a 7 alpha- and/or 7 beta-hydroxysteroid dehydrogenase (HSDH); they were Escherichia coli (7 alpha-HSDH), Bacteroides fragilis (7 alpha-HSDH), Clostridium absonum (7 alpha- and 7 beta-HSDH) and Eubacterium aerofaciens (7 beta-HSDH). None of the oxazolines affected 7 alpha-OH oxidation of CA or CDC by E. coli or the growth of the organism. All the oxazolines (except UDC-OX) inhibited the growth of B. fragilis and its 7 alpha-HSDH. In contrast, only DC-OX blocked 7 alpha-OH epimerization of CA by C. absonum. Surprisingly, the other three oxazolines enhanced 7 alpha-OH epimerization of CA, but not that of CDC, which was inhibited (CDC-OX greater than 7-KLC-OX much greater than UDC-OX). Enzymic data suggest that CDC-OX in the presence of CA can induce a greater level of both 7 alpha- and 7 beta-HSDH than CA or CDC-OX alone, CDC-OX being more toxic in the presence of CDC. Formation of urso-bile acid from 7-keto substrates by E. aerofaciens is totally blocked by the oxazolines (except UDC-OX). Similarly, suppression of urso-bile acid formation from primary bile acids by the human fecal flora was evident with DC-OX greater than 7-KLC-OX greater than CDC-OX much greater than UDC-OX, the last being ineffective. The inhibitory activity of the oxazolines on the 7-dehydroxylation of primary bile acids by human fecal flora followed the same order.

Bacteria↗
PubMed1983

Fecal steroid 21-dehydroxylase, a potential marker for colorectal cancer.

Eubacterium lentum and phenotypically similar organisms synthesize a steroid 21-dehydroxylase which converts biliary tetrahydrodeoxycorticosterone to pregnanolone. Tetrahydrodeoxycorticosterone, in contrast to pregnanolone, is carcinogenic for hamster embryonic cells (HECT test). In patients with recently diagnosed, untreated sigmoidal or rectal cancer the fecal concentration of 21-dehydroxylating organisms is reduced by more than 99% as compared with age-matched controls. The lack of fecal 21-dehydroxylating organisms, therefore, is a potential marker for the disorder. The role of steroid 21-dehydroxylase in the pathogenesis of colorectal cancer is unknown.

Adult↗
PubMed1983

Regulation of bile acid 7-dehydroxylase activity by NAD+ and NADH in cell extracts of Eubacterium species V.P.I. 12708.

The 7 alpha-dehydroxylation of primary bile acids by Eubacterium sp. V.P.I. 12708 required a cell extract prepared from a cholic acid-induced culture and NAD+. NADH (0.5 mM) inhibited bile acid 7-dehydroxylase activity more than 50% when added to reaction mixtures containing NAD+ (0.5 mM). Saturation kinetics and double reciprocal plots of NADH inhibition were consistent with negative cooperativity. 7-Dehydroxylase activity was modulated by the molar ratio of NAD+-NADH with maximal activity at a NAD+ mole fraction of 0.75 to 0.85. NADH stimulated 7-dehydroxylase activity (30% to 50%) at low concentration (less than 0.15 mM) and inhibited at higher concentrations. Reduction of the proposed delta 6-intermediate (3 alpha-hydroxy-5 beta-6-cholen-24-oic acid) to lithocholic acid required a cell extract from a cholic acid-induced culture and was stimulated by the addition of NAD+. Reduced flavin nucleotides stimulated (32% to 62%) and NADH (0.5 mM) inhibited (78%) the reduction of the delta 6-intermediate to lithocholic acid. 7-Dehydroxylase was highly specific for bile acid substrates and required a free C-24 carboxyl group and an unhindered 7 alpha- or 7 beta-hydroxy group on the B-ring of the steroid nucleus for activity. Bile acid 7 alpha- and 7 beta-dehydroxylase and delta 6-reductase activities all co-eluted from an anaerobic high performance liquid chromatography gel filtration column. However, approximately 80% to 96% of the total units of activity were lost. A substantial portion (20% to 30%) of the total activity was recovered when material from low molecular weight (8,000 to 14,000 Mr) eluting fractions was added back to fractions containing enzyme activity. These studies show that 7-dehydroxylase is highly specific for substrates and its activity may be regulated by the NAD+-NADH ratio in the bacterial cell.

Carbon Radioisotopes↗
PubMed1982

Distribution of 25-hydroxycholesterol in plasma lipoproteins and its role in atherogenesis. A study in squirrel monkeys.

Oxidation products of cholesterol have been shown to be potent inhibitors of cholesterol biosynthesis and also highly toxic to cultured aortic smooth muscle cells. In rabbit experiments, these compounds produced arterial injury resulting in arteriosclerosis. Purified cholesterol only minimally inhibited cholesterol biosynthesis and had no effect on cultured aortic smooth muscle cells. This raises the possibility that plasma lipoproteins containing beta-apoprotein (i.e. LDL and VLDL), which are considered to be atherogenic, may carry more oxidation products than HDL which is not atherogenic [3H]25-hydroxycholesterol and [14C]cholesterol were given only orally to 10 squirrel monkeys (Saimiri sciureus) and blood samples were collected via femoral puncture 24 h after administration. Lipoproteins were separated by ultracentrifugation and the radioactivity in each fraction was counted. Results show that the distribution of labeled cholesterol in VLDL, LDL, and HDL was almost identical to that of unlabeled cholesterol. Most of the radio-activity of 25-hydroxycholesterol was located in LDL & VLDL (55.1% and 34.7%, respectively), only 10.2% was present in HDL. If the radioactivity of 25-hydroxycholesterol were calculated on the basis of the apoprotein content of the lipoprotein micelle, the relative capacity of VLDL and LDL to carry 25-hydroxycholesterol was even greater and more significant than that of HDL (90 X and 42 X, respectively).

Animals↗
PubMed1982

The preparation of bile acid amides and oxazolines. II. The synthesis of the amides and oxazolines of ursodeoxycholic acid, deoxycholic acid, hyodeoxycholic acid and cholic acid.

Bile acid amides and oxazolines were synthesized by a sequence of steps involving the reaction of the free bile acid with formic acid to yield the formyloxy derivative, preparation of the formyloxy acid chloride, condensation of the acid chloride with 2-amino-2-methyl-1-propanol to give the amide and, finally, cyclization of the amide with thionyl chloride to give the oxazoline. The oxazolines were characterized by physical constants, thin layer and gas-liquid chromatography and identified by elemental analysis and gas-liquid chromatography-mass spectrometry. Some of the bile acid oxazoline derivatives alter the activity of bacterial 7-dehydroxylases in vitro, and inhibit the growth of certain anaerobic bacteria in pure culture.

Amides↗
PubMed1982

Antibacterial properties of bile acid oxazoline compounds.

Chenooxazoline (50-100 microM) inhibited (greater than 50%) both 7 alpha and 7 beta-dehydroxylase activities in whole cells and cell extracts of Eubacterium sp. V.P.I. 12708. Chenooxazoline (greater than or equal to 50 microM) and methylchenooxazoline (greater than 25 microM) but not lithooxazoline (less than or equal to 100 microM) inhibited growing cultures of Eubacterium sp. V.P.I. 12708. Chenooxazoline (100 microM) also inhibited the growth of certain members of the genera Eubacterium, Clostridium, Bacteroides and Staphylococcus but not Pseudomonas, Escherichia, Salmonella or the eucaryotic microorganism, Saccharomyces cerevisiae (less than or equal to 400 microM).

Bacteria↗
PubMed1982

Tissue bile acids in patients with colon cancer and colonic polyps.

The purpose of this study was to determine whether in man unusual types of concentrations or bile acids were present in colonic polyps, colon carcinomas, or the adjacent, apparently normal tissue. Methods for the determination of soluble and tissue-bound bile acids were validated. Of 14 polyps analyzed, eight contained detectable levels of bile acid, predominantly chenodeoxycholic acid; no lithocholic acid was observed in either the tissue-bound or soluble bile acid fractions. Bile acids were found in four of nine samples of colon carcinoma; in one tumor, tissue-bound lithocholic acid was present. Bile acids were similarly found in seven of 10 samples of normal bowel taken adjacent to the carcinoma. In the soluble bile acid fraction, cholic acid was more abundant than chenodeoxycholic acid. There was no correlation between tissue histology and bile acid composition or concentration. Under the conditions used, this study did not disclose a relationship between tissue bile acids and colorectal histology.

Adenocarcinoma↗
PubMed1981

Side-chain cleavage of cortisol by fecal flora.

The side chain of certain C-21 steroids may be removed by an enzyme, desmolase, synthesized by intestinal bacteria. With a view to isolate these organisms we examined the conditions required for their multiplication and function. The model substrate, cortisol (11 beta, 17 alpha, 21-trihydroxy-4-pregnene-3,20-dione), was metabolized by mixed fecal flora of humans and rats to a number of C-21 and C-19 compounds. The major C-21 metabolites were 21-deoxycortisol, tetrahydro-21-deoxycortisol, and tetrahydrocortisol. The C-19 metabolites obtained were identified as 5 beta-androstane-3 alpha, 11 beta-triol and 5 xi-androstane-3 alpha, 11 beta-diol-17-one. The prevalence of converting microorganisms was approximately 10(6)/g feces in both humans and rats. Conversion required an Eh below -130 mV, and an initial pH of 7.0. Optimal yield of C-19 products occurred with a fecal dilution of 10(5), though C-19 metabolites were evident from 10(1) through 10(8) fecal dilutions. Preliminary investigation indicates that the ability of converting organisms to form colonies varied with the composition of the media and the gaseous environment.

Aerobiosis↗
PubMed1981

Identification of acidic steroids in feces of monkeys fed beta-sitoserol.

Vervet monkeys were fed a suspension of beta-sitoseterol in corn oil. Acidic steroids were separated from a 4-day pool of feces and subjected, after fractionation, to gas liquid chromatography and mass spectrometry. Evidence for the presence of derivatives of 27-carboxysitosterol, 27-carboxysitostanol and 7-hydroxy, 27-carboxysitostanol is adduced.

Animals↗
PubMed1981

Effect of candicidin on cholesterol and bile acid metabolism in the rat.

Sterol metabolism studies were carried out in rats maintained on a diet containing a polyene antibiotic, candicidin, (30 mg/kg/day) for 2-1/2 months. Compared to the controls, the candicidin-treated animals had a smaller food intake and weight gain during this period. There was no difference between the 2 groups in serum cholesterol levels, biliary cholesterol or bile acid concentrations. However, in the experimental group, liver cholesterol content decreased by 27% and hepatic HMG-CoA reductase increased by 36%. Candicidin administration produced an 84% increase in neutral sterol output without change in bile acid output. Cholesterol absorption was reduced 80% by candicidin feeding. The weight of ventral prostate was reduced 33% by candicidin administration. Prostatic HMG-CoA reductase levels were 3 times higher than those of the liver, but enzyme activity was unchanged by candicidin treatment.

Animals↗