Bile acids and bile alcohols in a child with hepatic 3 beta-hydroxy-delta 5-C27-steroid dehydrogenase deficiency: effects of chenodeoxycholic acid treatment

Prognosis and clinical characteristics of patients with 3β-hydroxy-Δ5-C27-steroid dehydrogenase deficiency diagnosed in childhood: A systematic review of the literature

OBJECTIVES

3β-hydroxy-Δ5-C27-steroid dehydrogenase deficiency is a rare autosomal recessive condition. So far fewer than 100 cases have been reported and the factors affecting the prognosis are not yet established. The objective of this study is to explore a possible prediction of the outcome of this rare condition.

METHODS

This review was undertaken and reported in accordance with the preferred reporting items for systematic review and meta-analyses guidelines. Demographics, clinical features, gene data, treatment strategies and prognoses at the last follow-up were extracted and summarized. Patients were divided into 2 groups (alive with native liver and liver transplantation/died). Risk factors for the different clinical features were identified.

RESULTS

87 patients that were taken from 7 case reports and 9 case series were included. 38 (38/63, 63.0%) of them presented initial symptoms when they were younger than 1 month and 55 (55/63, 87.3%) less than 1 year. There is a larger proportion of patients younger than 1 month or 1 year at the age of symptom onset in the liver transplantation /died group than patients in alive with the native liver group. The majority of patients (53/62, 85.5%) were diagnosed before the age of 5 year. In all cases, 65 (predicted) pathogenic variants have been identified. Over 70% of patients carried an HSD3B7 variant on exon 1, 4, 5 or 6. 71 (81.6%) were alive at the last follow-up, 16 (18.4%) underwent liver transplantation or died. No significance was found between the group alive with native liver and group liver transplantation /died.

CONCLUSION

Age of onset of the symptoms may be a potential factor that determines the outcome of patients with 3β-HSD deficiency, patients presented with symptoms and signs at an age younger than 1 month or even 1 year may have a worse prognosis. Since there is no difference between clinical outcome and zygosity of gene mutation, we recommend a further study about any possible relationship between mutation site and clinical characteristics or prognosis.

Genetic spectrum and clinical characteristics of 3β-hydroxy-Δ5-C27-steroid oxidoreductase (HSD3B7) deficiency in China

BACKGROUND

Biallelic variants in HSD3B7 cause 3β-hydroxy-Δ5-C27-steroid oxidoreductase (HSD3B7) deficiency, a life-threatening but treatable liver disease. The goal of this study was to obtain detailed information on the correlation between the genotype and phenotype of HSD3B7 deficiency and to report on responses to primary bile acid therapy.

METHODS

The medical records of a cohort of 39 unrelated patients with genetically and biochemically confirmed HSD3B7 deficiency were examined to determine whether there exist genotype-phenotype relationships in this bile acid synthesis disorder.

RESULTS

In all, 34 of the 44 variants identified in HSD3B7 were novel. A total of 32 patients presented early with neonatal cholestasis, and 7 presented after 1-year of age with liver failure (n = 1), liver cirrhosis (n = 3), cholestasis (n = 1), renal cysts and abnormal liver biochemistries (n = 1), and coagulopathy from vitamin K1 deficiency and abnormal liver biochemistries (n = 1). Renal lesions, including renal cysts, renal stones, calcium deposition and renal enlargement were observed in 10 of 35 patients. Thirty-three patients were treated with oral chenodeoxycholic acid (CDCA) resulting in normalization of liver biochemistries in 24, while 2 showed a significant clinical improvement, and 7 underwent liver transplantation or died. Remarkably, renal lesions in 6 patients resolved after CDCA treatment, or liver transplantation. There were no significant correlations between genotype and clinical outcomes.

CONCLUSIONS

In what is the largest cohort of patients with HSD3B7 deficiency thus far studied, renal lesions were a notable clinical feature of HSD3B7 deficiency and these were resolved with suppression of atypical bile acids by oral CDCA administration.

The effectiveness of correcting abnormal metabolic profiles

Inborn errors of metabolism cause disease because of accumulation of a metabolite before the blocked step or deficiency of an essential metabolite downstream of the block. Treatments can be directed at reducing the levels of a toxic metabolite or correcting a metabolite deficiency. Many disorders have been treated successfully first in a single patient because we can measure the metabolites and adjust treatment to get them as close as possible to the normal range. Examples are drawn from Komrower's description of treatment of homocystinuria and the author's trials of treatment in bile acid synthesis disorders (3β-hydroxy-Δ⁵ -C₂₇ -steroid dehydrogenase deficiency and Δ⁴ -3-oxosteroid 5β-reductase deficiency), neurotransmitter amine disorders (aromatic L-amino acid decarboxylase [AADC] and tyrosine hydroxylase deficiencies), and vitamin B6 disorders (pyridox(am)ine phosphate oxidase deficiency and pyridoxine-dependent epilepsy [ALDH7A1 deficiency]). Sometimes follow-up shows there are milder and more severe forms of the disease and even variable clinical manifestations but by measuring the metabolites we can adjust the treatment to get the metabolites into the normal range. Biochemical measurements are not subject to placebo effects and will also show if the disorder is improving spontaneously. The hypothesis that can then be tested for clinical outcome is whether getting metabolite(s) into a target range leads to an improvement in an outcome parameter such as abnormal liver function tests, hypokinesia, epilepsy control etc. The metabolite-guided approach to treatment is an example of personalized medicine and is a better way of determining efficacy for disorders of variable severity than a randomized controlled clinical trial.

Lipidomics of human umbilical cord serum: identification of unique sterol sulfates

Aim:

There are currently limited lipidomics data for human umbilical cord blood. Therefore, the lipidomes of cord sera from six newborns and sera from six nonpregnant females were compared.

Materials & methods:

Sera lipidomics analyses were conducted using a high-resolution mass spectrometry analytical platform.

Results:

Cord serum contained a diverse array of glycerophospholipids, albeit generally at lower concentrations than monitored in adult serum. The unexpected observations were that cord serum contained several neurosteroid sulfates and bile acid sulfates that were not detectable in adult serum.

Conclusion:

Our data are the first to demonstrate that cord serum contains bile acid sulfates that are synthesized early in the hydroxylase, neutral and acidic pathways of primary bile acid biosynthesis and support previous publications of cord blood perfluoralkyl toxins in newborns.

Umbilical cord blood offers the potential to increase our understanding of fetal development during pregnancy and during development after delivery. Our studies of complex sterols in umbilical cord blood (bile acid sulfates) suggest that with further studies these may be useful biomarkers of abnormal fetal liver development.

Bile acid analysis in human disorders of bile acid biosynthesis

Bile acids facilitate the absorption of lipids in the gut, but are also needed to maintain cholesterol homeostasis, induce bile flow, excrete toxic substances and regulate energy metabolism by acting as signaling molecules. Bile acid biosynthesis is a complex process distributed across many cellular organelles and requires at least 17 enzymes in addition to different metabolite transport proteins to synthesize the two primary bile acids, cholic acid and chenodeoxycholic acid. Disorders of bile acid synthesis can present from the neonatal period to adulthood and have very diverse clinical symptoms ranging from cholestatic liver disease to neuropsychiatric symptoms and spastic paraplegias. This review describes the different bile acid synthesis pathways followed by a summary of the current knowledge on hereditary disorders of human bile acid biosynthesis with a special focus on diagnostic bile acid profiling using mass spectrometry.

Tandem Mass Spectrometric Determination of Atypical 3β-Hydroxy-Δ5-Bile Acids in Patients with 3β-Hydroxy-Δ5-C27-Steroid Oxidoreductase Deficiency: Application to Diagnosis and Monitoring of Bile Acid Therapeutic Response

BACKGROUND

3β-Hydroxy-Δ5-C27-steroid oxidoreductase (HSD3B7) deficiency, a progressive cholestatic liver disease, is the most common genetic defect in bile acid synthesis. Early diagnosis is important because patients respond to oral primary bile acid therapy, which targets the negative feedback regulation for bile acid synthesis to reduce the production of hepatotoxic 3β-hydroxy-Δ5-bile acids. These atypical bile acids are highly labile and difficult to accurately measure, yet a method for accurate determination of 3β-hydroxy-Δ5-bile acid sulfates is critical for dose titration and monitoring response to therapy.

METHODS

We describe a electrospray ionization LC-MS/MS method for the direct measurement of atypical 3β-hydroxy-Δ5-bile acid sulfates in urine from patients with HSD3B7 deficiency that overcomes the deficiencies of previously used GC-MS methods.

RESULTS

Separation of sulfated 3β-hydroxy-Δ5-bile acids was achieved by reversed-phase HPLC in a 12-min analytical run. The mean (SE) urinary concentration of the total 3β-sulfated-Δ5-cholenoic acids in patients with HSD3B7 deficiency was 4650 (1711) μmol/L, approximately 1000-fold higher than in noncholestatic and cholestatic patients with intact primary bile acid synthesis. GC-MS was not reliable for measuring 3β-hydroxy-Δ5-bile acid sulfates; however, direct analysis of urine by fast atom bombardment mass spectrometry yielded meaningful semiquantitative assessment of urinary excretion.

CONCLUSIONS

The tandem mass spectrometry method described here for the measurement of 3β-hydroxy-Δ5-bile acid sulfates in urine can be applied to the diagnosis and accurate monitoring of responses to primary bile acid therapy in HSD3B7 patients.

Focused metabolomics using liquid chromatography/electrospray ionization tandem mass spectrometry for analysis of urinary conjugated cholesterol metabolites from patients with Niemann-Pick disease type C and 3β-hydroxysteroid dehydrogenase deficiency

BACKGROUND

Various conjugated cholesterol metabolites are excreted in urine of the patients with metabolic abnormalities and hepatobiliary diseases. We aimed to examine the usefulness of precursor ion scan and neutral loss scan for the characterization of conjugated cholesterol metabolites in urine.

METHODS

A mixture of authentic standards of conjugated cholesterol metabolites was used for investigating the performance of the present method. The urine of patients with Niemann-Pick diseases type C and 3β-hydroxysteroid dehydrogenase deficiency were analysed by precursor ion scan of m/z 97, 74, and 124.

RESULTS

A precursor ion scan of m/z 97 was effective for identifying conjugates with ester sulphates on hydroxyl groups whereas ester sulphates on phenolic alcohols were signalled by a neutral loss scan of 80 Da. Monosaccharide-conjugated cholesterol metabolites were signalled by a precursor ion scan of m/z 113. Although precursor ion scan of m/z 74 and 124 was effective for finding glycine- and taurine-conjugated metabolites, high intensity of product ions (m/z 74 and 124) disturbed measurement of other multiply conjugated metabolites. The urine samples contained many conjugated cholesterol metabolites, and there were several disease-specific intense peaks. We found several unknown intense peaks with three known peaks in urine of the Niemann-Pick type C patient. In the patient with 3β-hydroxysteroid dehydrogenase deficiency, intense peaks that were tentatively identified as 5-cholenoic acid sulphates and their glycine and taurine conjugates were present.

CONCLUSION

The method should lead to the discovery of new urinary biomarkers for these disturbances of cholesterol catabolism and transport.

Homozygosity mapping identifies a bile acid biosynthetic defect in an adult with cirrhosis of unknown etiology

The most common inborn error of bile acid metabolism is 3β-hydroxy-Δ(5)-C(27)-steroid oxidoreductase (3β-HSD) deficiency, a disorder that usually presents in early childhood with hepatic dysfunction. Timely diagnosis of this disorder is crucial because it can be effectively treated with primary bile acid replacement. Here we describe a 24-year-old woman from Iran with cirrhosis of unknown etiology. Her sister and a first cousin died of cirrhosis (ages 19 and 6 years) and another 32-year-old first cousin had a self-limited liver disorder in childhood that resolved at age 9 years. The family history suggested that the affected family members were homozygous for a mutant allele inherited identical-by-descent. A genome-wide analysis of 2.4 million single nucleotide polymorphisms was performed to identify regions of homozygosity that were present in the proband and the 32-year-old first cousin, but not in a healthy relative. One of these regions contained the gene encoding 3β-HSD (HSD3B7). Sequence analysis of HSD3B7 revealed that the proband and her 32-year-old cousin were homozygous for a frameshift mutation (c.45_46del AG, p.T15Tfsx27) in exon 1. The diagnosis of 3β-HSD deficiency was confirmed by documenting high levels of 3β-hydroxy-Δ(5) bile acids in the serum of the proband and the 32-year-old first cousin using mass spectrometry. To our knowledge, the 32-year-old relative in this family represents the oldest asymptomatic patient with this disorder.

CONCLUSION

This study highlights the clinical utility of homozygosity mapping in diagnosing autosomal recessive metabolic disorders. This family illustrates the wide variation in expressivity that occurs in 3β-HSD deficiency and underscores the need to consider a bile acid synthetic defect as a possible cause of liver disease in adults.

Disorders of bile acid synthesis

Inborn errors of bile acid synthesis can produce life-threatening cholestatic liver disease (which usually presents in infancy) and progressive neurological disease presenting later in childhood or in adult life. Both types of disease can often be treated very effectively with bile acid replacement therapy and it is therefore important to diagnose these disorders as early as possible. The cholestatic disease in infancy is characterised by conjugated hyperbilirubinaemia with raised transaminases but normal γ-glutamyl transpeptidase and a biopsy showing a giant cell hepatitis. There is usually evidence of fat-soluble vitamin malabsorption. The neurological presentation often includes signs of upper motor neurone damage (spastic paraparesis). The most useful screening test for many of these disorders is analysis of urinary cholanoids (bile acids and bile alcohols); this is usually now achieved by electrospray ionisation tandem mass spectrometry. The disorders that are discussed in this review are: 3β-hydroxysteroid-Δ5-C27-steroid dehydrogenase deficiency, Δ4-3-oxosteroid 5β-reductase deficiency, sterol 27-hydroxylase deficiency (cerberotendinous xanthomatosis, CTX), oxysterol 7α-hydroxylase deficiency (including one form of hereditary spastic paraparesis) and the amidation defects, bile acid-CoA: aminoacid N-acyltransferase (BAAT) deficiency and bile acid-CoA ligase deficiency. The disorders of peroxisome biogenesis and peroxisomal β-oxidation that affect bile acid synthesis will be covered in the review by Ferdinandusse et al.

Molecular genetic and bile acid profiles in two Japanese patients with 3beta-hydroxy-DELTA5-C27-steroid dehydrogenase/isomerase deficiency

We report definitive diagnosis and effective chenodeoxycholic acid (CDCA) treatment of two Japanese children with 3[beta]-hydroxy-[DELTA]5-C27-steroid dehydrogenase/isomerase deficiency. Findings of cholestasis with normal serum [gamma]-glutamyltransferase activity and total bile acid concentration indicated the need for definitive bile acid analysis. Large amounts of 3[beta]-hydroxy-[DELTA]5 bile acids were detected by gas chromatography-mass spectrometry. HSD3B7 gene analysis using peripheral lymphocyte genomic DNA from the patients and their parents identified four novel mutations of the HSD3B7 gene in the patients. One had a homozygous mutation, 314delA; the other had compound heterozygous mutations: V132F, T149I, and 973_974insCCTGC. Interestingly, the second patient's mother had V132F and T149I mutations in one allele. Excessive 3[beta]-hydroxy-[DELTA]5-bile acids such as 3[beta],7[alpha]-dihydroxy- and 3[beta],7[alpha],12[alpha]-trihydroxy-5-cholenoic acids were detected in the first patient's urine; the second patient's urine contained large amounts of 3[beta]-hydroxy-5-cholenoic acid. Liver dysfunction in both patients decreased with ursodeoxycholic acid treatment, but unusual bile acids were still detected. Normalization of the patients' liver function and improvement of bile acid profiles occurred with CDCA treatment. Thus, we found mutations in the HSD3B7 gene accounting for autosomal recessive neonatal cholestasis caused by 3[beta]-hydroxy-[DELTA]5-C27-steroid dehydrogenase/isomerase deficiency. Early neonatal diagnosis permits initiation of CDCA treatment at this critical time, before the late cholestatic stage.

Analytical strategies for characterization of bile acid and oxysterol metabolomes

Cholesterol is the precursor of many compounds with functions in the physiology and metabolism of the organism. Methods for the multicomponent analysis of these compounds and their metabolites (metabolomics) are needed to improve our understanding of their roles in different species, organs, cells and metabolic situations and to clarify structure/activity relationships. This review discusses methods based on combinations of ion exchange and reversed-phase separations for sample preparation with derivatization and "charge-tagging" for chromatography-mass spectrometry in qualitative and quantitative characterizations of oxysterol, bile alcohol, bile acid, and steroid hormone metabolomes. Advantages, disadvantages and potential improvements for high-throughput applications are briefly discussed.

Characterization of disease-related 5beta-reductase (AKR1D1) mutations reveals their potential to cause bile acid deficiency

Bile acid deficiency is a serious syndrome in newborns that can result in death if untreated. 5beta-Reductase deficiency is one form of bile acid deficiency and is characterized by dramatically decreased levels of physiologically active 5beta-reduced bile acids. AKR1D1 (aldo-keto reductase 1D1) is the only known human enzyme that stereo-specifically reduces the Delta(4) double bond in 3-keto steroids and sterols to yield the 5beta-hydrogenated product. Analysis of the AKR1D1 gene in five patients with 5beta-reductase deficiency revealed five different mutations resulting in an amino acid substitution in the protein. To investigate a causal role for these observed point mutations in AKR1D1 in 5beta-reductase deficiency, we characterized their effect on enzymatic properties. Attempts to purify mutant enzymes by overexpression in Escherichia coli only yielded sufficient amounts of the P133R mutant for further characterization. This enzyme displayed a highly reduced K(m) and V(max) reminiscent of uncompetitive kinetics with 4-cholesten-7alpha-ol-3-one as substrate. In addition, this mutant displayed no change in cofactor affinity but was more thermolabile in the absence of NADPH as judged by CD spectroscopy. All mutants were compared following expression in HEK 293 cells. Although these enzymes were equally expressed based on mRNA levels, protein expression and functional activity were dramatically reduced. Cycloheximide treatment also revealed that several of the expressed mutants were less stable. Our findings show that the reported mutations in AKR1D1 in patients with 5beta-reductase lead to significantly decreased levels of active enzyme and could be causal in the development of bile acid deficiency syndrome.

Titration of bile acid supplements in 3beta-hydroxy-Delta 5-C27-steroid dehydrogenase/isomerase deficiency

OBJECTIVES

3beta-Hydroxy-Delta 5-C27-steroid dehydrogenase/isomerase deficiency is a bile acid synthesis defect responsive to primary bile acids. We reviewed its clinical features and response to treatment with a mixture of ursodeoxycholic (UDCA) and chenodeoxycholic acid (CDCA) to titrate the dose of supplements required for disease control.

PATIENTS AND METHODS

We studied our patients by liquid chromatography-tandem mass spectrometry, liver function tests, and histology. After diagnosis all of the patients received a balanced mixture of UDCA/CDCA and the dose was titrated according to urinary levels of 3beta,7 alpha-dihydroxy-5-cholenoic acid (u-3beta-D-OH-5C).

RESULTS

Five patients presenting with giant cell hepatitis, biliary cirrhosis, and cryptogenic cirrhosis (1 each), and picked up by neonatal screening (2 patients) were diagnosed at a median age of 2.5 years (range 0.1-5.5). Normal levels of u-3beta-D-OH-5C were achieved after 4 months (range 3-28 months) from the start of the treatment. The minimum dose of UDCA/CDCA required to maintain normal u-3beta-D-OH-5C levels was 5/5 mg x kg(-1) x day(-1). A follow-up biopsy in 2 patients showed no progression of liver disease.

CONCLUSIONS

A mixture of UDCA/CDCA can effectively control 3beta-hydroxy-Delta 5-C27-steroid dehydrogenase/isomerase deficiency. Dose titration by liquid chromatography-tandem mass spectrometry warrants the maintenance of negative feedback on the abnormal synthetic pathway and avoids disease progression.

Variable clinical spectrum of the most common inborn error of bile acid metabolism--3beta-hydroxy-Delta 5-C27-steroid dehydrogenase deficiency

OBJECTIVE

We studied the clinical features of children with 3beta-hydroxy-Delta 5-C27-steroid dehydrogenase (3beta-HSDH) deficiency presenting to King's College and Great Ormond Street hospitals between 1989 and 2005. The diagnosis was made biochemically by detection of sulphated dihydroxycholenoic acids and trihydroxycholenoic acids in urine by fast atom bombardment mass spectrometry or electrospray ionisation tandem mass spectrophotometry and a plasma bile acid profile showing absent or low cholic and chenodeoxycholic acid levels and high concentrations of 3beta-7 alpha-dihydroxy-5-cholenoic acid and 3beta-7 alpha-12 alpha-trihydroxy-5-cholenoic acid.

RESULTS

Eighteen children (12 male) with 3beta-HSDH deficiency were identified and diagnosed at a median age of 1.35 years (range 8 weeks-11 years). The presenting features included neonatal cholestasis (n = 11), rickets (n = 8, 1 of whom also had hypocalcaemic tetany, seizures, and normal liver biochemical markers), hepatomegaly (n = 7), pruritus (n = 3), and steatorrhoea and failure to thrive (n = 3). Ten children had low serum 25-OH vitamin D levels, of whom 8 also had low vitamin E and 6 had low vitamin A serum levels. Liver histology showed giant cell change and hepatocyte disarray in all with added features of cholestasis in 11, bridging fibrosis in 6, micronodular cirrhosis in 1, fatty change in 1, and active lobular and portal inflammation in 1. Five patients were treated with cholic acid and chenodeoxycholic acid (7 mg x kg(-1) x day(-1) of each), 7 with chenodeoxycholic acid only (7-18 mg x kg(-1) x day(-1)), and 1 with cholic acid (8 mg x kg(-1) x day(-1)) only. Repeated liver biopsies performed in 4 patients 6 months after starting replacement therapy showed improved histological changes. Three children died untreated before 5 years of age. After a median follow-up of 5.5 years (range 1-17 years) 12 out of 13 treated children have no clinical signs of liver disease or of fat-soluble vitamin deficiency.

CONCLUSIONS

3beta-HSDH deficiency is a rare inborn error of metabolism with diverse clinical features. Early replacement treatment leads to clinical and biochemical control and prevents chronic liver and bone disease, at least in the medium term.

Mechanisms of disease: Inborn errors of bile acid synthesis

Inborn errors of bile acid synthesis are rare genetic disorders that can present as neonatal cholestasis, neurologic disease or fat-soluble-vitamin deficiencies. There are nine known defects of bile acid synthesis, including oxysterol 7alpha-hydroxylase deficiency, Delta(4)-3-oxosteroid-5beta-reductase deficiency, 3beta-hydroxy-Delta(5)-C(27)-steroid dehydrogenase deficiency, cerebrotendinous xanthomatosis (also known as sterol 27-hydroxylase deficiency), alpha-methylacyl-CoA racemase deficiency, and Zellweger syndrome (also known as cerebrohepatorenal syndrome). These diseases are characterized by a failure to produce normal bile acids and an accumulation of unusual bile acids and bile acid intermediaries. Individuals with inborn errors of bile acid synthesis generally present with the hallmark features of normal or low serum bile acid concentrations, normal gamma-glutamyl transpeptidase concentrations and the absence of pruritus. Failure to diagnose any of these conditions can result in liver failure or progressive chronic liver disease. If recognized early, many patients can have a remarkable clinical response to oral bile acid therapy.

Cholestatic liver disease in adults may be due to an inherited defect in bile acid biosynthesis

BACKGROUND

An increasing number of treatable inborn errors of bile acid synthesis have been described, primarily in infants with severe cholestatic liver disease.

RESULTS

The present patient, whose two older siblings had died from progressive cholestatic liver disease, developed neonatal cholestasis and rickets but recovered during the childhood years and follow-up was terminated at 12 years of age. The patient presented again at 26 years of age with jaundice and pathological liver function tests. This was normalized upon treatment with ursodeoxycholic acid. Electrospray mass spectrometry of urine showed predominance of unsaturated bile acids, characteristic of 3beta-hydroxy-Delta5-C27-steroid dehydrogenase/isomerase (HSD3B7) deficiency. The activity of HSD3B7 in cultured fibroblasts was less than 5% of normal. A single homozygous mutation was found in exon 4 leading to an amino acid exchange (S162R) and loss of enzyme activity.

CONCLUSION

This case illustrates that infants with an inherited absence of HSD3B7 may survive the neonatal period of life and childhood without treatment with bile acids. A low level of sulphation of the abnormal trihydroxy bile acid formed as a result of enzyme deficiency may be of importance for survival. The possibility that liver disease presenting in the adult may be due to a mutation in the HSD3B7 gene should be considered, especially in cases with familial occurrence of liver disease and earlier periods of liver dysfunction.

The farnesoid X receptor: a novel drug target?

Bile acids are end products of cholesterol metabolism. They are exclusively synthesised by the liver and subsequently secreted via the bile duct into the intestine to facilitate the absorption of dietary fat and fat-soluble vitamins. Nuclear receptors are ligand-activated transcription factors. The farnesoid X receptor (FXR) has recently been identified as a bile acid-activated nuclear receptor. FXR controls bile-acid synthesis, conjugation and transport, as well as lipid metabolism. Recent advances in FXR biology demonstrate that FXR may represent a valuable target for the identification of novel drugs to treat dyslipidaemia and cholestasis. However, for therapeutic purposes the development of selective FXR modulators, which only activate or inhibit specific FXR target genes and as such induce specific responses, will be required.

Fifty years with bile acids and steroids in health and disease

Cholesterol and its metabolites, e.g., steroid hormones and bile acids, constitute a class of compounds of great biological importance. Their chemistry, biochemistry, and regulation in the body have been intensely studied for more than two centuries. The author has studied aspects of the biochemistry and clinical chemistry of steroids and bile acids for more than 50 years, and this paper, which is an extended version of the Schroepfer Medal Award lecture, reviews and discusses part of this work. Development and application of analytical methods based on chromatography and mass spectrometry (MS) have been a central part of many projects, aiming at detailed characterization and quantification of metabolic profiles of steroids and bile acids under different conditions. In present terminology, much of the work may be termed steroidomics and cholanoidomics. Topics discussed are bile acids in human bile and feces, bile acid production, bacterial dehydroxylation of bile acids and steroids during the enterohepatic circulation, profiles of steroid sulfates in plasma of humans and other primates, development of neutral and ion-exchanging lipophilic derivatives of Sephadex for sample preparation and group separation of steroid and bile acid conjugates, profiles of steroids and bile acids in human urine under different conditions, hydroxylation of bile acids in liver disease, effects of alcohol-induced redox changes on steroid synthesis and metabolism, alcohol-induced changes of bile acid biosynthesis, compartmentation of bile acid synthesis studied with 3H-labeled ethanol, formation and metabolism of sulfated metabolites of progesterone in human pregnancy, abnormal patterns of these in patients with intrahepatic cholestasis of pregnancy corrected by ursodeoxycholic acid, inherited and acquired defects of bile acid biosynthesis and their treatment, conjugation of bile acids and steroids with N-acetylglucosamine, sulfate-glucuronide double conjugates of hydroxycholesterols, extrahepatic 7alpha-hydroxylation and 3-dehydrogenation of hydroxycholesterols, and extrahepatic formation of C27 bile acids. The final part discusses analysis of free and sulfated steroids in brain tissue by capillary liquid chromatography-electrospray MS and suggests a need for reevaluation of the function of steroid sulfates in rat brain.

3beta-hydroxy-delta5 -C27-steroid dehydrogenase deficiency: diagnosis and treatment

The aim of this study was to evaluate the effects of bile acid treatment and to obtain further information about the pathway of bile acid biosynthesis in a patient with 3beta-hydroxy-delta5-C27-steroid dehydrogenase/isomerase (3beta-HSD) deficiency by gas chromatography-mass spectrometry. Results showed that at 2 months of age, 3beta-hydroxy-5-cholen-24-oic acid (3.0 micromol/mmol Cr, 7.9%) was detected in the urine in essentially the same relative amount as 3beta,7alpha-dihydroxy- and 3beta,7alpha,12alpha-trihydroxy-5-cholen-24-oic acids (3.7 micromol/mmol Cr, 9.8%) during ursodeoxycholic acid treatment combined with prednisolone. As a result, diagnosis was delayed until 18 months of age. One month later with substitution of chenodeoxycholic acid treatment, urinary 3beta,7alpha-dihydroxy- and 3beta,7alpha,12alpha-trihydroxy-5-cholen-24-oic acids decreased significantly, and subsequent improvement of liver dysfunction was accelerated. Chenodeoxycholic acid treatment is useful in 3beta-HSD deficiency. However, in the diagnosis of this disease in early life, it should be noted that the acidic pathway may be the major route for bile acid biosynthesis in the neonatal period. Diagnosis of 3beta-HSD deficiency may have been delayed by administration of ursodeoxycholic acid, resulting in prolonged diagnostic investigation in this child with cholestasis. Further, use of prednisolone may have been contraindicated.

The bile acid synthetic gene 3beta-hydroxy-Delta(5)-C(27)-steroid oxidoreductase is mutated in progressive intrahepatic cholestasis

We used expression cloning to isolate cDNAs encoding a microsomal 3beta-hydroxy-Delta(5)-C(27)-steroid oxidoreductase (C(27) 3beta-HSD) that is expressed predominantly in the liver. The predicted product shares 34% sequence identity with the C(19) and C(21) 3beta-HSD enzymes, which participate in steroid hormone metabolism. When transfected into cultured cells, the cloned C(27) 3beta-HSD cDNA encodes an enzyme that is active against four 7alpha-hydroxylated sterols, indicating that a single C(27) 3beta-HSD enzyme can participate in all known pathways of bile acid synthesis. The expressed enzyme did not metabolize several different C(19/21) steroids as substrates. The levels of hepatic C(27) 3beta-HSD mRNA in the mouse are not sexually dimorphic and do not change in response to dietary cholesterol or to changes in bile acid pool size. The corresponding human gene on chromosome 16p11.2-12 contains six exons and spans 3 kb of DNA, and we identified a 2-bp deletion in the C27 3beta-HSD gene of a patient with neonatal progressive intrahepatic cholestasis. This mutation eliminates the activity of the enzyme in transfected cells. These findings establish the central role of C(27) 3beta-HSD in the biosynthesis of bile acids and provide molecular tools for the diagnosis of a third type of neonatal progressive intrahepatic cholestasis associated with impaired bile acid synthesis.

Inborn errors of bile acid biosynthesis and transport. Novel forms of metabolic liver disease

Defective bile acid biosynthesis, metabolism, and transport can now be delineated in a wide variety of disease states. This ability to recognize specific aberrations, such as the documented inborn errors in bile acid biosynthesis manifesting as neonatal cholestasis, offers new opportunities for therapeutic intervention. Future studies should determine the incidence of bile acid biosynthetic and transport defects in patients with enigmatic and unexplained liver diseases.

Other hereditary diseases and the liver

In this chapter, an abbreviated account is presented on the subject of hereditary diseases and the liver. However, it is incomplete because Alagille syndrome, storage disorders, alpha-1-antitrypsin deficiency and Wilson disease are not included as they appear in other chapters of this volume. Biliary atresia is omitted because all available evidence does not support any significant genetic association. Molecular biological techniques have enabled linkage of several liver cholestatic disorders to chromosomal loci, and further characterization of the canalicular bile salt transporter (cBST) will advance our understanding of pathogenetic mechanisms involved in benign and progressive cholestatic syndromes. Disorders that have been treated as separate entities may have common 'roots', exemplified by the concept of the ductal plate malformation in fibropolycystic disease. Whereas the majority of disorders referred to in this chapter present early in life, there are several that are associated with liver failure in the neonatal period, which makes early recognition particularly important. Liver transplantation offers a cure for many hereditary disorders affecting the liver but it is not applicable to all.

A method for the quantitation of conjugated bile acids in dried blood spots using electrospray ionization-mass spectrometry

Bile acid concentrations are elevated in the blood of neonates with cholestatic hepatobiliary disorders providing a possible means of screening for treatable conditions including biliary atresia. A method is described for the determination of concentrations of conjugated bile acids in dried blood spots using electrospray ionization mass spectrometry. Bile acids were eluted from the blood spots using methanol containing, as internal standards, the taurine and glycine conjugates of D4-chenodeoxycholic acid and D4-cholic acid. The samples were then reconstituted in acetonitrile/water and injected by autosampler into the electrospray source operating in negative ion mode. Optimal conditions were determined for both single quadrupole and tandem mass spectrometry analysis. Blood spot bile acid profiles were studied in two groups of infants (< 1 y), a cholestatic group (conjugated bilirubin > 25 mumol/L; n = 49), and a control group (n = 96). The best discrimination between the two groups was provided by measurements of taurodihydroxycholanoates (normal < 5 mumol/L; cholestatic group 18-94 mumol/L) and glycodihydroxycholanoates (normal < 5 mumol/L; cholestatic group 11-66 mumol/L). The method can also be adapted to detect unusual bile acids which are diagnostic of inborn errors of bile acid synthesis and peroxisomal disorders. The method is fast, reliable, reproducible, and relatively cheap; however, much more work is required to determine whether it can be used for mass screening for cholestasis. It will be necessary to show that measurement of bile acid concentrations in blood spots obtained at 7-10 d can be used to detect infants who currently present with jaundice, pale stools, and dark urine during the first 6 mo of life.

7alpha-Hydroxylation and 3-dehydrogenation abolish the ability of 25-hydroxycholesterol and 27-hydroxycholesterol to induce apoptosis in thymocytes

Oxygenated derivatives of sterols (oxysterols), including 25-hydroxycholesterol and 27-hydroxycholesterol, have immunosuppressive effects. Oxysterols can directly induce apoptosis in immature thymocytes, cells which are inherently sensitive to induction of programmed cell death. For that reason, the metabolism of 25-hydroxycholesterol and 27-hydroxycholesterol in mouse thymus has been studied. When incubated with thymic tissue, both oxysterols were found to be 7alpha-hydroxylated with subsequent oxidation to 7alpha-hydroxy-3-oxo-delta4 steroids. A minor fraction of 27-hydroxycholesterol was also metabolised to 3beta-hydroxy-5-cholestenoic, 3beta,7alpha-dihydroxy-5-cholestenoic and 7alpha-hydroxy-3-oxo-4-cholestenoic acids. The 7alpha-hydroxylase was found to be localised to the thymic epithelial cells and the reaction was stimulated by interleukin-1beta and inhibited by metyrapone and RU486. In contrast to 25-hydroxycholesterol and 27-hydroxycholesterol, the 7alpha-hydroxylated metabolites, 7alpha,25-dihydroxycholesterol, 7alpha,25-dihydroxy-4-cholesten-3-one and 7alpha,27-dihydroxy-4-cholesten-3-one did not induce thymocyte apoptosis. The results suggest that 7alpha-hydroxylation may be of regulatory importance, possibly by protecting the developing thymocytes against toxic effects by oxysterols.

Analysis of bile acids and bile alcohols in urine by capillary column liquid chromatography-mass spectrometry using fast atom bombardment or electrospray ionization and collision-induced dissociation

Solid-phase extraction and group separation by anion exchange chromatography were combined with capillary column liquid chromatography-mass spectrometry (LC/MS) to permit a thorough characterization of bile acids and intact conjugates of bile alcohols in human urine. Groups of compounds were separated according to acid strength and were analysed on a capillary column, 0.25 x 500 mm, packed with 5 microns particles of Chromasil C18, and connected via a fused silica capillary to the continuous-flow fast atom bombardment (CF-FAB) or electrospray (ES) sources of an AutoSpec-TOFFPD hybrid mass spectrometer. Acetonitrile:water mixtures containing 30 mM ammonium acetate pH 7.2 were used as mobile phases, with 5% glycerol added for FAB Ionisation. Bile acids were analysed directly or after derivatization of carboxyl groups with 4-aminobenzenesulphonic acid. Negative-ion spectra (m/z 1000 or 800 to 300 or 100) were recorded using the point detector or, in the case of ES ionization, the focal plane array detector (FPD). Deprotonated molecules of bile acids containing a sulphonic acid group were detected with a spectral signal to noise ratio of 5:1 when about 90 fmol were injected onto the column of the LC/CF-FAB system. The corresponding peak in the reconstructed ion chromatogram gave a signal-to-noise ratio of about 25:1. The sensitivity could be increased 20-50 times by using ES ionization and the FPD. Bile acids without a sulphonic acid group gave about 70% of the signal of sulphonic acids using ES ionization. The capillary column LC/MS systems were evaluated by analyses of urine from an infant with cholestatic liver disease. More than 150 different bile acids and bile alcohol conjugates were detected, some of which were partially characterized using collision induced dissociation (CID) of the deprotonated molecules and B/E linked scans. A number of compounds were detected for the first time, e.g. di-, tri-, and tetra-hydroxycholestanoic acids conjugated with N-acetylhexosamine and cholestenediol, cholestenetriol and cholestanetriol doubly conjugated with sulphuric acid and glucuronic acid. The relative merits of ES and FAB ionization are discussed.

Studies on the relationships between 7 alpha-hydroxylation and the ability of 25- and 27-hydroxycholesterol to suppress the activity of HMG-CoA reductase

The metabolism of 25-hydroxycholesterol in different cell types was studied and the role of 7 alpha-hydroxylation for the effect of 25-hydroxycholesterol on the activity of HMG-CoA reductase was determined. Human diploid fibroblasts (HDF) and the human melanoma cell line SK-MEL-2 converted 25-hydroxycholesterol into 7 alpha,25-dihydroxycholesterol and 7 alpha,25-dihydroxy-4-cholesten-3-one while the virus-transformed fibroblast line 90VA-VI, the colon carcinoma cell line WiDr and the breast cancer cell line MDA-231 did not express 7 alpha-hydroxylase activity. The 7 alpha-hydroxylation of 25-hydroxycholesterol in HDF could be stimulated by dexamethasone and cortisol and inhibited by metyrapone. An unidentified, possibly 4-hydroxylated, metabolite was formed by 90VA-VI cells and a polar, probably conjugated, metabolite was formed by WiDr cells. The 7 alpha-hydroxylated metabolites of 25-hydroxycholesterol suppressed the activity of HMG-CoA reductase to a similar extent as 25-hydroxycholesterol in HDF but not in 90VA-VI cells, while the 7 alpha-hydroxylated metabolites of 27-hydroxycholesterol suppressed the activity of HMG-CoA reductase also in 90VA-VI cells. The suppression of HMG-CoA reductase activity by 25- and 27-hydroxycholesterol was decreased or abolished by dehydroepiandrosterone or pregnenolone which have little or no effect on the 7 alpha-hydroxylation. The results indicate that 7 alpha-hydroxylation is not directly involved, positively or negatively, in the action of 25- or 27-hydroxycholesterol as suppressors of HMG-CoA reductase activity.

Differential interaction of bile acids from patients with inborn errors of bile acid synthesis with hepatocellular bile acid transporters

People with genetic or acquired defects in the biosynthesis of bile acids may suffer from cholestasis. Patients with a deficiency of 3 beta-hydroxy-delta 5-C27-steroid dehydrogenase/isomerase from 3 beta, 7 alpha-dihydroxy- and 3 beta, 7 alpha, 12 alpha-trihydroxy-5-cholenoic acids, the sulfated and partially glycine-conjugated forms of which are found in their urine and bile. 3-Oxo-delta 4 bile acids are detected in the urine of patients with a deficiency of 5 beta-reductase. It has been postulated that these unusual bile acids might act as cholestatic agents in these patients. The aim of the present study was to test this hypothesis in an in vitro system, since the abnormal bile acids would be metabolized in in vivo experiments. Basolateral (sinusoidal) and canalicular plasma membrane vesicles were isolated from rat liver. A rapid filtration method was used to determine transport of cholyltaurine in the presence of model bile acids into the isolated vesicles. It was found that 3 beta, 7 alpha-dihydroxy-5-cholenoic acid and 7 alpha-hydroxy-3-oxo-4-cholenoic acid both inhibited the apical, ATP-dependent transport system for cholyltaurine in a competitive manner with K(m) values of 15 microM and 16 microM, respectively. Radioactively labeled 3 beta, 7 alpha-dihydroxy-5-cholenoyltaurine and 7 alpha-hydroxy-3-oxo-4-cholenoyltaurine were not transported by the same transport system. The same types of experiments were performed with basolateral plasma membrane vesicles. It was found that, in contrast to the canalicular ATP-dependent bile acid transport system, only 7 alpha-hydroxy-3-oxo-4-cholenoyltaurine was a competitive inhibitor of the sodium-dependent transport system for cholyltaurine with a K(m) of 16 microM. Studies with radioactively labeled 7 alpha-hydroxy-3-oxo-4-cholenoyltaurine and 3 beta, 7 alpha-dihydroxy-5-cholenoyltaurine revealed that 7 alpha-hydroxy-3-oxo-4-cholenoyltaurine was transported in a sodium-dependent manner into basolateral rat liver plasma membrane vesicles, whereas 3 beta, 7 alpha-dihydroxy-5-cholenoyltaurine was not transported in a sodium-dependent way. These results support the hypothesis that the unusual bile acids found in patients with defects in bile acid biosynthesis might act as cholestatic agents by inhibiting the canalicular ATP-dependent transport system for bile acids which constitutes the rate-limiting step in the overall process of bile acid transport across hepatocytes. Furthermore, the experiments demonstrated that, despite similar substrate specificities, the basolateral sodium-dependent and the apical ATP-dependent transport system for cholyltaurine might have different recognition sites for bile acids.

Method for combined analysis of profiles of conjugated progesterone metabolites and bile acids in serum and urine of pregnant women

A method for analysis of profiles of conjugated progesterone metabolites and bile acids in 10 ml of urine and 1-4 ml of serum from pregnant women is described. Total bile acids and neutral steroids from serum and urine were extracted with octadecylsilane-bonded silica. Groups of conjugates were separated on the lipophilic ion-exchanger triethylaminohydroxypropyl Sephadex LH-20 (TEAP-LH-20). Fractions were divided for steroid or bile acid analyses. Sequences of hydrolysis/solvolysis and separations on TEAP-LH-20 permitted separate analyses of steroid glucuronides, monosulfates and disulfates and bile acid aminoacyl amidates, sulfates, glucuronides and sulfate-glucuronides. Radiolabelled compounds were added at different steps to monitor recoveries and completeness of separation, and hydrolysis/solvolysis of conjugates was monitored by fast-atom bombardment mass spectrometry. The extraction and solvolysis of steroid disulfates in urine were studied in detail, and extraction recoveries were found to be pH-dependent. Following methylation of bile acids, all compounds were analysed by capillary gas chromatography and gas chromatography-mass spectrometry of their trimethylsilyl ether derivatives. Semiquantification of individual compounds in each profile by gas-liquid chromatography had a coefficient of variation of less than 30%. The total analysis required 3 days for serum and 4 days for urine.

Purification of a 3beta-hydroxy-delta5-C27-steroid dehydrogenase from pig liver microsomes active in major and alternative pathways of bile acid biosynthesis

A 3beta-hydroxy-Delta5-C27-steroid dehydrogenase active in bile acid biosynthesis was purified from pig liver microsomes by solubilization with sodium cholate and by chromatography on DEAE-Sepharose, aminohexyl-Sepharose, and blue Sepharose. The last step in the purification procedure was preparative isoelectric focusing in a Rotofor cell. The final enzyme preparation showed only one protein band upon SDS-polyacrylamide gel electrophoresis. The isoelectric point was estimated to about 7.0 and the apparent Mr was 36,000. The purified enzyme catalyzed the conversion of 7alpha-hydroxycholesterol, 7alpha,25-dihydroxycholesterol, 7alpha, 27-dihydroxycholesterol, and 3beta,7alpha-dihydroxy-5-cholestenoic acid into the corresponding 3-oxo-Delta4 compounds. The enzyme was inactive with C19 and C21 steroids as substrates. The enzyme was also inactive with C27 steroids having the 7-hydroxy group in beta- instead of alpha-position. The Km was found to be 0.30 and 0.32 microM with 7alpha-hydroxycholesterol and 7alpha, 27-dihydroxycholesterol as substrates, respectively. NAD+ was the preferred cofactor. A monoclonal antibody raised against the 3beta-hydroxy-delta5-C27-steroid dehydrogenase was prepared. After coupling to Sepharose, the antibody was able to bind the dehydrogenase and to decrease the conversion of 7alpha-hydroxycholesterol into 7alpha-hydroxy-4-cholest-3-one by more than 90%. The N-terminal amino acid sequence was determined and found to be similar but not identical with those of known 3beta-hydroxy-Delta5-steroid dehydrogenases active in steroid hormone biosynthesis. Thus, the purified enzyme active toward C27 steroids in bile acid biosynthesis appears to represent a novel type of 3beta-hydroxy-delta5-steroid dehydrogenase.

The identification of novel steroid N-acetylglucosaminides in the urine of pregnant women

A series of pregnanediols and pregnanetriols doubly conjugated with N-acetylglucosamine and glucuronic or sulfuric acid has been identified in urine from pregnant women. Steroid conjugates were separated by ion-exchange chromatography and the glucuronide and monosulfate fractions were analysed by fast atom bombardment mass spectrometry. After removal of the acid moiety, the neutral steroids were isolated, derivatized, and analysed by gas chromatography-mass spectrometry (GC-MS). The analyses revealed the presence of steroids conjugated with N-acetylhexosamine both in the glucuronide and the monosulfate fractions. Following enzyme hydrolysis, the sugar was identified by GC-MS as N-acetylglucosamine (GlcNAc). The major steroid conjugated with GlcNAc both in the glucuronide and monosulfate fractions was identified as 5alpha-pregnane-3alpha,20alpha-diol. 5beta-Pregnane-3alpha,2Oalpha-diol was also present as a GlcNAc conjugate in both fractions whereas a GlcNAc conjugate of 5alpha-pregnane-3beta,20alpha-diol was only found in the sulfate fraction. 5alpha-Pregnane-3alpha,20alpha,21-triol was a double conjugate with GlcNAc in the sulfate fraction whereas a pregnane-2,3,20-triol was a double conjugate in the glucuronide fraction. The positions of conjugation were determined by collision-induced dissociation of the pseudomolecular anions produced by fast atom bombardment ionization. The sulfate and glucuronic acid moieties were located at C-3 and N-acetylglucosamine at C-20. An alternative localization of GlcNAc at C-21 of 5alpha-pregnane-3alpha,20alpha,21-triol cannot be excluded. Judging from the enzymatic hydrolysis of the conjugates, the sugar was attached in beta-glycosidic linkage. The mean excretion of N-acetylglucosaminides of the pregnanediols and pregnanetriols was 32.2 micromol/g creatinine (range 17.9-49.1 micromol) in five healthy women in the 38th-39th week of pregnancy. The mean excretion of 5beta-pregnane-3alpha,20alpha-diol glucuronide in the same women was 71 micromol/g creatinine, (range 27-127 micromol). This indicates that conjugation with N-acetylglucosamine constitutes a quantitatively important pathway of progesterone metabolism in human pregnancy.

Delta 4-3-oxosteroid 5 beta-reductase deficiency: failure of ursodeoxycholic acid treatment and response to chenodeoxycholic acid plus cholic acid

BACKGROUND

In some infants with liver disease, 3-oxo-delta 4 bile acids are the major bile acids in urine, a phenomenon attributed to reduced activity of the delta 4-3-oxosteroid 5 beta-reductase required for synthesis of chenodeoxycholic acid and cholic acid. These patients form a heterogeneous group. Many have a known cause of hepatic dysfunction and plasma concentrations of chenodeoxycholic acid and cholic acid that are actually greater than those of the 3-oxo-delta 4 bile acids. It is unlikely that these patients have a primary genetic deficiency of the 5 beta-reductase enzyme.

AIMS

To document the bile acid profile, clinical phenotype, and response to treatment of an infant with cholestasis, increased plasma concentrations of 3-oxo-delta 4 bile acids, low plasma concentrations of chenodeoxycholic acid and cholic acid, and no other identifiable cause of liver disease.

PATIENTS

This infant was compared with normal infants and infants with cholestasis of known cause.

METHODS

Analysis of bile acids by liquid secondary ionisation mass spectrometry and gas chromatography-mass spectrometry.

RESULTS

The plasma bile acid profile of the patient was unique. She had chronic cholestatic liver disease associated with malabsorption of vitamins D and E and a normal gamma-glutamyltranspeptidase when the transaminases were increased. The liver disease failed to improve with ursodeoxycholic acid but responded to a combination of chenodeoxycholic acid and cholic acid.

CONCLUSION

Treatment of primary 5 beta-reductase deficiency requires the use of bile acids that inhibit cholesterol 7 alpha-hydroxylase.

7 alpha-Hydroxylation of 25-hydroxycholesterol and 27-hydroxycholesterol in human fibroblasts

The metabolism of 27-hydroxycholesterol and 25-hydroxycholesterol was studied in cultures of human diploid fibroblasts. Both steroids underwent 7 alpha-hydroxylation with subsequent oxidation to 7 alpha-hydroxy-3-oxo-delta 4 steroids. A minor fraction of the 27-hydroxysteroids was oxidized to acids. Competition experiments indicated that both hydroxycholesterols were hydroxylated by the same enzyme, different from cholesterol 7 alpha-hydroxylase. 7 alpha,25-Dihydroxycholesterol suppressed the activity of HMG-CoA reductase at least as effectively as 25-hydroxycholesterol whereas 7 alpha,25-dihydroxy-4-cholesten-3-one was a less effective suppressor. The results suggest that cholesterol might be converted to 7 alpha-hydroxylated bile acid precursors in extrahepatic tissues in vivo and that the regulation of the activity of HMG-CoA reductase by oxysterols might be modulated by 7 alpha-hydroxylation and subsequent oxidation by 3 beta-hydroxy-delta 5-C27-steroid dehydrogenase/isomerase.

Delta 4-3-oxosteroid 5 beta-reductase deficiency causing neonatal liver failure and hemochromatosis

Neonatal liver failure was evaluated in two infants. Neither infant had evidence of congenital infection, galactosemia, alpha 1-antitrypsin deficiency, tyrosinemia, Zellweger syndrome, or hemophagocytic lymphohistiocytosis. Abnormal levels of iron were detected in the minor salivary glands of the first infant and in the explanted liver of the second. Analyses of urinary bile salts by fast-atom bombardment ionization mass spectrometry and gas chromatography-mass spectrometry revealed a paucity of primary bile acids and a predominance of 7 alpha-hydroxy-3-oxo-4-cholenoic and 7 alpha,12 alpha-dihydroxy-3-oxo-4-cholenoic acids. These findings are consistent with delta 4-3-oxosteroid 5 beta-reductase deficiency, a primary genetic defect in bile acid synthesis. Postmortem evaluation of the first infant revealed significant iron deposition in the liver, pancreas, thyroid, adrenal glands, myocardium, stomach, and submucosal glands of the respiratory tract. In both infants examination of the liver revealed extensive loss of hepatic parenchyma. These cases expand the clinical spectrum of bile acid metabolism defects to include neonatal liver failure with associated hemochromatosis.

Inborn errors of metabolism with consequences for bile acid biosynthesis. A minireview

Five inborn errors with consequences for bile acid biosynthesis have been described: 7-dehydrocholesterol 7-reductase deficiency, 3 beta-hydroxysteroid delta 5-oxidoreductase/isomerase deficiency, 3-oxo-delta 4-steroid 5 beta-reductase deficiency, sterol 27-hydroxylase deficiency (cerebrotendinous xanthomatosis), and peroxisomal disease(s) with absence of peroxisomes. Diagnosis and treatment of these very rare disorders are discussed. Bile acid therapy is important in most of these disorders and in the case of 3 beta-hydroxysteroid delta 5-oxidoreductase/isomerase deficiency and 3-oxo-delta 4-steroid 5 beta-reductase deficiency such therapy may save the life of the affected cholestatic infant. In the case of sterol 27-hydroxylase deficiency, early treatment with chenodeoxycholic acid may prevent the development of progressive neurological dysfunction, dementia, and ataxia. In the latter three cases early diagnosis and treatment is of utmost importance.

3 beta-hydroxy-delta 5-C27-steroid dehydrogenase deficiency; effect of chenodeoxycholic acid therapy on liver histology

The second step in the pathway for synthesis of bile acids from cholesterol is catalysed by the enzyme 3 beta-hydroxy-delta 5-C27-steroid dehydrogenase. Deficiency of this enzyme has been reported to produce cholestatic liver disease with progressive cirrhosis. Treatment with chenodeoxycholic acid led to clinical and biochemical improvement in one patient. We report a further child with this disorder who presented with prolonged neonatal jaundice followed by symptoms of malabsorption of fat-soluble vitamins. Bile acid replacement therapy resulted in clinical and biochemical improvement; it was also possible to demonstrate improvement in the histological appearance of the liver biopsy 4 months after commencing treatment.