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

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.

Bile acids and progesterone metabolites in intrahepatic cholestasis of pregnancy

The pathogenesis of intrahepatic cholestasis of pregnancy (ICP) can be related to abnormalities in the metabolism and disposition of sex hormones and/or bile acids, determined by a genetic predisposition interacting with environmental factors. The total amount of oestrogens and progesterone circulating in the blood or excreted in the urine of ICP patients is similar to normal pregnancies. Thus, the search for the cause has been focused on abnormal hormone metabolites. The cholestatic potential of some D-ring oestrogen metabolites is supported by experimental and clinical data. Similar observations with regard to bile acids and progesterone metabolites are still scarce. This article reviews current knowledge in this field, including our own data. Bile acid synthesis appears to be reduced in patients with ICP, in whom primary conjugated bile acids are retained in blood. The major bile acid in blood and urine of these patients is cholic acid instead of chenodeoxycholic acid present in normal pregnancies. Hydroxylation and sulfation of bile acids are enhanced, while glucuronidation appears to be of lesser importance. The synthesis of progesterone appears unimpaired, while the profiles of progesterone metabolites in plasma and urine are different from normal pregnancies, with a larger proportion of mono- and disulfated metabolites, mainly 3alpha,5alpha isomers. Glucuronidated metabolites, however, are unchanged. With the administration of ursodeoxycholic acid (UDCA) to patients with ICP, pruritus and serum liver values are improved, the concentration of bile acids in blood is diminished and the proportion of their conjugated metabolites returned to normal. Simultaneously, the concentration of sulfated progesterone metabolites in blood and their urinary excretion are reduced. The serum levels of bile acids and progesterone metabolites before UDCA administration and their decrease during treatment do not correlate with each other. We propose that patients with ICP have a selective defect in the secretion of sulfated progesterone metabolites into bile and speculate that this may be caused by genetic polymorphism of canalicular transporter(s) for steroid sulfates or their regulation. Interaction with oestrogen metabolites and/or some exogenous compounds may further enhance the process triggering ICP in genetically predisposed individuals.

Profiles of bile acids and progesterone metabolites in the urine and serum of women with intrahepatic cholestasis of pregnancy

BACKGROUND/AIMS AND METHODS

The etiology of intrahepatic cholestasis of pregnancy (JCP) is unknown. We have performed comprehensive chromatographic and mass spectrometric analyses of progesterone metabolites and bile acids in serum and urine of six patients in order to characterize changes that might be of importance for the development of the disease.

RESULTS

Conjugated bile acids were increased in serum and urine of patients with ICP while the levels of unconjugated bile acids were similar in healthy pregnancies and ICP. Unconjugated and conjugated 7 alpha, 12 alpha-dihydroxy-3-oxo-4-cholenoic acid was excreted in urine both in healthy pregnancies and in ICP, possibly indicating a rate limitation of 3-oxo-delta 4-steroid 5 beta-reductase in pregnancy. The serum levels and urinary excretion of total sulfated progesterone metabolites were increased in ICP while the glucuronides were unchanged or low. Confirming previous results, the fraction of metabolites with 3 alpha-hydroxy-5 alpha(H) configuration was increased. The urinary excretion of 5 alpha-pregnane-3 alpha, 20 alpha-diol 3-sulfate, 20-N-acetylglucosaminide was greatly increased in ICP, as was that of 3 alpha-hydroxy-5 alpha-androstane-17 beta-carboxylic acid, assumed to be a progesterone metabolite.

CONCLUSIONS

The combined results of this and previous studies are compatible with a primary change in the reductive metabolism of progesterone in ICP, resulting in increased formation of metabolites with a 3 alpha-hydroxy-5 alpha(H) configuration and a larger fraction of sulfates. There also seems to be a selective defect in the biliary secretion of sulfated metabolites, particularly disulfates.

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.

Identification of a new Sertoli cell metabolite of testosterone: 5 alpha-androstane-3 alpha,16 alpha,17 beta-triol, by HPLC and GC-MS

Testosterone metabolism by isolated rat Sertoli cells cultured in vitro was investigated using HPLC and GC-MS techniques. Monolayer cultures of Sertoli cells (greater than 90% pure and free of Leydig cells) were incubated for 3-day periods with a stable labeled [2,2,4,6,6-d5]testosterone prepared and used in a 1:1 proportion with unlabeled testosterone as the substrate (5 X 10(-7)M). After incubation, the metabolites were extracted from the media and reacted with oestradiol-antibodies. The antibody-bound components were separated on reverse phase HPLC and the fraction corresponding to oestradiol was analyzed by GC-MS in the form of TMS-ether. One of the metabolites whose mass spectrum contained d0 + d5 species was detected and interpreted to be a triol with a mol. wt of 308. Mass spectra data indicated that this testosterone metabolite is one of the sixteen possible isomers of 3,16,17-trihydroxy androstane. This substance was identified based on the Vm value (27.81) closely resembling that of 5 alpha-androstane-3 alpha,16 alpha,17 beta-triol TMS-ether (Vm reported = 27.78) [1] and when compared directly with synthesized compounds [2-3]. Recently we have demonstrated that similar Sertoli cell preparations contain two 16 alpha-hydroxylases by their ability to convert oestradiol to oestriol [4] and 5 alpha-androstane-3 alpha,17 beta-diol to 5 alpha-androstane-3 alpha,16 alpha,17 beta-triol [3], where the former conversion is not affected by FSH, the latter is significantly stimulated by the presence of FSH. Presence of this new product represents the first example of testosterone conversion to 5 alpha-androstane-3 alpha,16 alpha,17 beta-triol and confirms our previous observation that 16 alpha-hydroxylation of 5 alpha-reduced androgens can occur in the rat testis.

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.

Lithocholate glucuronide is a cholestatic agent

Lithocholic acid and its taurine, glycine, and sulfate derivatives are potent cholestatic agents. Lithocholate glucuronide is present in the plasma and urine of patients with cholestatic syndromes, but little is known of its metabolism, excretion, and cholestatic potential. [3 beta-3H]lithocholate 3-O-beta-D-glucuronide was synthesized, and chemical and radiochemical purity were established. The aqueous solubility of lithocholate glucuronide was determined and found to be greater than that of lithocholic acid or several of its derivatives. In the range of concentrations examined, calcium ions precipitated lithocholate glucuronide stoichiometrically. The material was administered to rats prepared with an external biliary fistula. When 17-25 micrograms quantities were administered, 89.1 +/- 4.5% (mean +/- SEM) of the radiolabel was secreted in bile within the first 20 h after administration, the major fraction being secreted in less than 20 min. Four-fifths of the radiolabeled material in bile was the administered unaltered parent compound, while a minor fraction consisted of a more polar derivative(s). We showed that increasing biliary concentrations of more polar derivatives were observed with milligram doses of [3H]lithocholate glucuronide, and with time after the administration of these loading doses. Milligram doses of [3H]lithocholate glucuronide resulted in partial or complete cholestasis. When induced cholestasis was partial, secretion in bile remained the primary excretory route (82.5-105.6% recovery in bile), while, when complete cholestasis was induced, wide tissue distribution of radiolabel was observed. Cholestasis developed rapidly during infusion of [3H]lithocholate glucuronide. Bile flow was diminished within 10-20 min of the start of an infusion of 0.05 mumol, 100 g-1 body weight, minute-1, administered concomitantly with an equimolar infusion of taurocholate. The results establish that lithocholate glucuronide exerts cholestatic effects comparable to those exerted by unconjugated lithocholic acid.