Constituents of human meconium: II. Identification of steroidal acids with 21 and 22 carbon atoms

Differences in testosterone and its precursors by sex of the offspring in meconium

Prenatal metabolism exerts profound effects on development. The first stool of the newborn, meconium, provides a window into the prenatal metabolic environment. The objective of this study was to examine the feasibility of meconium as a novel matrix to quantify prenatal steroid levels. We quantified parameters of analytical interest regarding the use of meconium, including sample stability. We hypothesized that meconium steroid content would differ by sex, prompting analysis of meconium to test effects of prenatal steroid metabolism. Meconium from 193 newborns enrolled in the Early Autism Risk Longitudinal Investigation (EARLI) study, including 107 males, and 86 females, were analyzed by isotope dilution-liquid chromatography-high resolution mass spectrometry (ID-LC-HRMS) while blinded to identity for testosterone (T), androstenedione (AD), and dehydroepiandrosterone (DHEA). Steroid levels were compared by sex, and investigations of potential trends resulting from sample storage or processing was conducted. The unconjugated steroid content of meconium in ng/g (mean, standard deviation) was for males: T (2.67, 8.99), AD (20.01, 28.12), DHEA (13.96, 23.57) and for females: T (0.82, 1.63), AD (22.32, 24.38), DHEA (21.06, 43.49). T was higher in meconium from males (p=0.0333), and DHEA was higher in meconium from females (p=0.0202). 6 female and 3 male T values were below the limit of detection. No extreme variability in hydration or trend in steroid levels by storage time was detected. Sexually dimorphic levels of hormones may reflect gestational differentiation, and future studies should consider meconium analysis.

A convenient synthesis of dinorbile acids: oxidative hydrolysis of norbile acid nitriles

We report a convenient method for the synthesis of dinorbile acids (23,24-dinor-5beta-cholan-22-oic acids, pregnane-20-carboxylic acids) in fair to good yields from norbile acid nitriles in one step by oxidative hydrolysis with oxygen in the presence of potassium-t-butoxide. The method results in stepwise overall removal of two carbon atoms in bile acid side chains in two steps. Dinorbile acids corresponding to several common bile acids have been prepared and their structures confirmed by spectroscopic methods. This simple method for synthesis of dinorbile acids may facilitate their study metabolically.

Hepatic metabolism of 3-oxoandrost-4-ene-17 beta-carboxylic acid in the adult rat: formation of carboxyl-linked glucuronides both in vivo and in vitro

The hepatic metabolism of 3-oxoandrost-4-ene-17 beta-carboxylic acid (etienic acid), a probable acidic catabolite of deoxycorticosterone, was investigated using rats prepared with an external biliary fistula. Metabolic products were identified by GC-MS after hydrolysis with beta-glucuronidase and by proton nuclear magnetic resonance after chromatographic purification of protected glucuronides. About 80% of the injected dose was secreted into bile in 20 hours. Three fully reduced etianic acids (3 alpha-hydroxy-5 alpha-, 3 beta-hydroxy-5 alpha-, 3 alpha-hydroxy-5 beta-androstan-17 beta-carboxylic acids) were identified as were several of their di- and trihydroxylated congeners. Glucuronides of these reduced and/or hydroxylated metabolites constituted over half of the recovered dose, with carboxyl-linked glucuronides predominating over 3-hydroxyl-linked glucuronides. The mode of glucuronidation correlated well with the ability of liver microsomes to form the corresponding compounds in vitro from the set of four 3,5-diastereomeric etianic acids.

Biosynthesis and chemical synthesis of carboxyl-linked glucuronide of lithocholic acid

The glucuronidation of lithocholic acid (LA) by phenobarbital-induced male Fischer 344 rat liver microsomes supplemented with UDP-glucuronic acid was studied. A single radioactive metabolite was formed and its structure was determined by high pressure liquid chromatography/particle beam/mass spectrometry (HPLC/PB/MS), both with and without prior methylation and acetylation of the sample. The reaction product was rigorously identified as the 1-O-acyl-beta-D-glucuronide of LA by comparison with a chemically synthesized standard. The chemical synthesis of the acyl glucuronide of LA was accomplished via a condensation reaction using benzyl 2,3,4-tri-O-benzyl-D-glucopyranuronate. The latter compound was prepared in two steps from benzyl 2,3,4-tri-O-benzyl-1-O-methyl-alpha-D-glucopyranuronate via the 1-O-acetyl derivative. The stereoselective beta coupling of LA with 2,3,4-tri-O-benzyl-D-glucopyranuronate was achieved by the Mitsunobu reaction, in the presence of the free hydroxyl function of LA, using triphenylphosphine and diisopropyl azodicarboxylate in THF followed by preparative TLC. The benzylic ester and ether groups were cleaved by hydrogenation with Pd on charcoal as the catalyst. Positive identification of the glucuronide was established by HPLC/PB/MS and 1H-NMR spectra. No side products formed by acyl migration were detected, but the free acyl glucuronide underwent rapid transesterification in methanol.

Human liver steroid sulphotransferase sulphates bile acids

The sulphation of bile acids is an important pathway for the detoxification and elimination of bile acids during cholestatic liver disease. A dehydroepiandrosterone (DHEA) sulphotransferase has been purified from male and female human liver cytosol using DEAE-Sepharose CL-6B and adenosine 3',5'-diphosphate-agarose affinity chromatography [Falany, Vazquez & Kalb (1989) Biochem. J. 260, 641-646]. Results in the present paper show that the DHEA sulphotransferase, purified to homogeneity, is also reactive towards bile acids, including lithocholic acid and 6-hydroxylated bile acids, as well as 3-hydroxylated short-chain bile acids. The highest activity towards bile acids was observed with lithocholic acid (54.3 +/- 3.6 nmol/min per mg of protein); of the substrates tested, the lowest activity was detected with hyodeoxycholic acid (4.2 +/- 0.01 nmol/min per mg of protein). The apparent Km values for the enzyme are 1.5 +/- 0.31 microM for lithocholic acid and 4.2 +/- 0.73 microM for taurolithocholic acid. Lithocholic acid also competitively inhibits DHEA sulphation by the purified sulphotransferase (Ki 1.4 microM). No evidence was found for the formation of bile acid sulphates by sulphotransferases different from the DHEA sulphotransferase during purification work. The above results suggest that a single steroid sulphotransferase with broad specificity encompassing neutral steroids and bile acids exists in human liver.

Constituents of human meconium--III. Identification of 3,20-dihydroxypregnan-21-oic acids

Seven 3,20-dihydroxypregnan-21-oic acids (C21) were detected by capillary gas chromatography-mass spectrometry in the acid fraction isolated from human meconium after solvolysis and mild alkaline hydrolysis. The two major acids were isolated and identified by nmr as 3 alpha, 20 alpha-dihydroxy-5 alpha-and 3 alpha, 20 alpha-dihydroxy-5 beta-pregnan-21-oic acids. Two minor C21 components were identified as 3 alpha, 20 beta-dihydroxy-5 beta-pregnan-21-oic and 3 beta, 20 alpha-dihydroxypregn-5-en-21-oic acids. A trace amount of 3 alpha, 20 beta-dihydroxy-5 alpha-, 3 beta, 20 alpha-dihydroxy-5 alpha-pregnan-21-oic, and 3 beta, 20 beta-dihydroxypregn-5-en-21-oic acids were also detected. The identification of these C21 acids was confirmed by mass spectral and chromatographic comparison with standards of eight saturated and two 5-unsaturated 3, 20-dihydroxylated C21 acids. The decisive predominance of 20 alpha isomers confirmed the native presence of C21 acids in meconium. Six acids, with an exception of 3 beta, 20 beta-dihydroxy-pregn-5-en-21-oic acid, were detected in the extract of meconium prepared in the presence of large excess of sodium borohydride; this minor acid, together with a part of its 20-epimer, was evidently formed as result of the artefactual oxidation of 21-hydroxypregnenolone, the known constituent of meconium. The co-occurrence of relatively high concentrations of C21 acids and monohydroxylated C20 acids, previously detected in human meconium, pointed to the significance of the oxidative catabolism of neutral C21 steroids in the case of feto-placental-maternal unit.

Constituents of human meconium--I. Identification of 3-hydroxy-etianic acids

The monohydroxylated fraction of bile acids of human meconium was analyzed by capillary GC-MS. In the sulfate-glucuronide fraction three saturated, and one unsaturated C20 steroidal acids were found. These acids were identified as 3 alpha-hydroxy-5 alpha-, 3 alpha-hydroxy-5 beta-,3 beta-hydroxy-5 alpha-androstane-17 beta-carboxylic, and 3 beta-hydroxyandrost-5-ene-17 beta-carboxylic based on the unequivocal GC-MS comparison with standards of all possible epimers at C-3, 5 and 17. The amount of the major C20 acid, 3 alpha-hydroxy-5 alpha-androstane-17 beta-carboxylic, in meconium was 0.2 nmol/g, i.e. 5 to 10 times the amount of lithocholic acid. To prevent the oxidation of 21-hydroxy-20-oxopregnanes to C20 acids meconium was extracted in the presence of sodium borohydride. In the absence of this reducing agent the amount of 3 beta-hydroxyandrost-5-ene-17 beta-carboxylic acid was increased and its 17 alpha-epimer could be detected. This indicates partial artifactual formation of this C20 acid from 21-hydroxypregnenolone, which is known to be present in human meconium. The amount of the saturated C20 acids was unaffected by the presence of sodium borohydride in the extraction medium, and their native occurence in human meconium was further confirmed by the absence of their 17 alpha-epimers in extracts obtained both with and without borohydride. The probable metabolic origin of C20 acids in the fetal-placental-maternal unit is discussed.

Hepatic metabolism of 3 alpha-hydroxy-5 beta-etianic acid (3 alpha-hydroxy-5 beta-androstan-17 beta-carboxylic acid) in the adult rat

Normal human meconium has been shown to contain short-chain (C20-C22) bile acids and, recently, these compounds have been identified in sera of patients with cholestasis. This suggests that shortchain bile acids may be secreted in bile. We have examined this point by studying the hepatic metabolism and biliary secretion of one naturally occurring C20 bile acid, 3 alpha-hydroxy-5 beta-etianic acid (3 alpha-hydroxy-5 beta-androstan-17 beta-carboxylic acid). [3-3H]-3 alpha-hydroxy-5 beta-etianic acid was prepared and administered intravenously to rats prepared with an external biliary fistula. 85.5 +/- 1.2% of the administered dose was recovered in bile over 20 h with 71.5 +/- 1.3% appearing in the first hour. 11.9 +/- 1.6% of the dose was estimated to be distributed in body water and 0.6 +/- 0.2% was recovered as organic matter in urine. Total recovery of label was 98.0 +/- 2.6%. Administration of milligram quantities of 3 alpha-hydroxy-5 beta-etianic acid produced an increase in bile flow (58.9 +/- 7.1% over basal levels) within 20 min after injection of the steroid. The radiolabeled material in bile was shown by thin-layer chromatography (TLC) to be a polar conjugate which, after beta-glucuronidase hydrolysis, cochromatographed with authentic free 3 alpha-hydroxy-5 beta-etianic acid. After purification, and derivatization, the steroid moiety was proven by gas chromatography-mass spectrometry to be identical to 3 alpha-hydroxy-5 beta-etianic acid. Characterization of the conjugate by TLC and by 3 alpha-hydroxysteroid dehydrogenase assay, before and after beta-glucuronidase hydrolysis, indicated that the steroid was secreted in bile as the 3-O-beta-glucuronide. It is concluded that 3 alpha-hydroxy-5 beta-etianic acid is cleared from the plasma, conjugated with glucuronic acid, and secreted into bile rapidly and in high concentration. The choleretic properties of this shortchain bile acid contrast with the cholestatic effects of lithocholic acid, its C24 analog. Both the form of conjugation of etianic acid and its effect on bile flow suggest that the shortened side chain of this steroid markedly alters its hepatic metabolism and physiology.