Seasonal Variations in Femoral Gland Secretions Reveals some Unexpected Correlations Between Protein and Lipid Components in a Lacertid Lizard

Animals modulate intraspecific signal shape and intensity, notably during reproductive periods. Signal variability typically follows a seasonal scheme, traceable through the expression of visual, acoustic, chemical and behavioral patterns. The chemical channel is particularly important in lizards, as demonstrated by well-developed epidermal glands in the cloacal region that secrete lipids and proteins recognized by conspecifics. In males, the seasonal pattern of gland activity is underpinned by variation of circulating androgens. Changes in the composition of lipid secretions convey information about the signaler's quality (e.g., size, immunity). Presumably, individual identity is associated with a protein signature present in the femoral secretions, but this has been poorly investigated. For the first time, we assessed the seasonal variability of the protein signal in relation to plasma testosterone level (T), glandular activity and the concentration of provitamin D₃ in the lipid fraction. We sampled 174 male common wall lizards (Podarcis muralis) over the entire activity season. An elevation of T was observed one to two months before the secretion peak of lipids during the mating season; such expected delay between hormonal fluctuation and maximal physiological response fits well with the assumption that provitamin D₃ indicates individual quality. One-dimensional electrophoretic analysis of proteins showed that gel bands were preserved over the season with an invariant region; a result in agreement with the hypothesis that proteins are stable identity signals. However, the relative intensity of bands varied markedly, synchronously with that of lipid secretion pattern. These variations of protein secretion suggest additional roles of proteins, an issue that requires further studies.

Profiling and Imaging Ion Mobility-Mass Spectrometry Analysis of Cholesterol and 7-Dehydrocholesterol in Cells Via Sputtered Silver MALDI

Profiling and imaging of cholesterol and its precursors by mass spectrometry (MS) are important in a number of cholesterol biosynthesis disorders, such as in Smith-Lemli-Opitz syndrome (SLOS), where 7-dehydrocholesterol (7-DHC) is accumulated in affected individuals. SLOS is caused by defects in the enzyme that reduces 7-DHC to cholesterol. However, analysis of sterols is challenging because these hydrophobic olefins are difficult to ionize for MS detection. We report here sputtered silver matrix-assisted laser desorption/ionization (MALDI)-ion mobility-MS (IM-MS) analysis of cholesterol and 7-DHC. In comparison with liquid-based AgNO3 and colloidal Ag nanoparticle (AgNP), sputtered silver NP (10-25 nm) provided the lowest limits-of-detection based on the silver coordinated [cholesterol + Ag](+) and [7-DHC + Ag](+) signals while minimizing dehydrogenation products ([M + Ag-2H](+)). When analyzing human fibroblasts that were directly grown on poly-L-lysine-coated ITO glass plates with this technique, in situ, the 7-DHC/cholesterol ratios for both control and SLOS human fibroblasts are readily obtained. The m/z of 491 (specific for [7-DHC + (107)Ag](+)) and 495 (specific for [cholesterol + (109)Ag](+)) were subsequently imaged using MALDI-IM-MS. MS images were co-registered with optical images of the cells for metabolic ratio determination. From these comparisons, ratios of 7-DHC/cholesterol for SLOS human fibroblasts are distinctly higher than in control human fibroblasts. Thus, this strategy demonstrates the utility for diagnosing/assaying the severity of cholesterol biosynthesis disorders in vitro.

Differences between predicted and established diagnoses of Smith-Lemli-Opitz syndrome in the Polish population: underdiagnosis or loss of affected fetuses?

Smith-Lemli-Opitz syndrome (SLOS) is a metabolic disorder in which an error in cholesterol biosynthesis results in congenital anomalies/mental deficits. The results of our previous newborn screening, based on the carrier frequency of the two most common SLOS-causing mutations in Poland (p.W151X and p.V326L), would make SLOS one of the most frequent recessive disorders in our country (with an incidence of 1:2,300 - 1:3,937). This prompted us to carry out a 3-year (2006-2008) national surveillance program in which about 2,000 physicians were asked to identify potential SLOS patients pre- and postnatally based on clinical identification forms. The incidence of SLOS in Poland was estimated to be from 1:60,941 to 1:105,395 (1: 83,168 ± 22,227) live births, and its 3-year prevalence 1:866,273 ± 16,242. The mean carrier frequency was calculated to be from 1:123 to 1:165. The notable discrepancy between our previous carrier newborn screening and these prospective data may result from reduced fertility in SLOS carriers, intrauterine death of affected fetuses, or underdiagnosis in postnatal life. Since we did not notice significant data supporting the first two aspects, our study may support the suggestion that screening for the most frequent DHCR7 alleles does not reflect the true disease rates in the Polish population. Hence, further studies in which maternal urinary steroids (7-dehydroestriol/estriol and 8-dehydropregnanetriol/pregnanetriol ratios) would serve as screening markers in early pregnancies may be justified.

Identification of an overabundant cholesterol precursor in hepatitis B virus replicating cells by untargeted lipid metabolite profiling

Viruses rely upon host lipid metabolic pathways for successful replication, and there is increasing interest in these pathways as novel therapeutic targets for antiviral drug discovery. Despite this, relatively little is known about the impact of viral infection on cellular lipid metabolism, and the specific lipid metabolites utilized by viruses have not yet been examined. We have applied liquid chromatography-mass spectroscopy (LC-MS) based untargeted metabolite profiling to identify lipid metabolites whose steady-state abundance is significantly altered by replication of hepatitis B virus (HBV), a major human pathogen. Untargeted metabolite profiling indicated that although major lipid classes were unaffected by HBV, an ion of 367 m/z was overabundant in HBV+ cells by 18-fold. As shown by ion fragmentation mass spectrometry and coinjection with standard, the identity of this ion is 7-dehydrocholesterol (7-DHC), an immediate dehydrogenated precursor to cholesterol. While cholesterol has previously been demonstrated to be essential in the replication of many viruses, this is the first to show that viral replication is associated with the selective accumulation of 7-DHC. Most virological studies to date have relied upon methods that deplete all sterols and preclude the observation of any selectivity in sterol utilization by viral pathogens. Our study suggests that HBV may selectively utilize 7-DHC versus other sterols and prompts experiments investigating the functional significance of this enrichment and the elucidation of the mechanism by which it is achieved. The results also highlight the value of untargeted metabolite profiling as a method for identifying critical metabolites for viral infection.

Precholesterol sterols accumulate in lipid rafts of patients with Smith-Lemli-Opitz syndrome and X-linked dominant chondrodysplasia punctata

Systemic fetal dysmorphogenesis in disorders of postsqualene cholesterol biosynthesis is thought to be caused by disruption of Hedgehog signaling. Because precholesterol sterols such as 7-dehydrocholesterol and lathosterol can replace cholesterol in the activation of Hedgehog proteins, it is currently believed that cholesterol deficiency-related Hedgehog signaling block occurs further downstream, probably at the level of Smoothened. Experimentally, such a block in Hedgehog signaling occurs at sterol levels of <40 mug/mg protein. Recently, we studied autopsy material from 2 infants with fatal cholesterol biosynthetic disorders (Smith-Lemli-Opitz syndrome and X-linked dominant chondrodysplasia punctata) in which the hepatic cholesterol levels were far greater. In this study, we demonstrate abnormal accumulation of sterol precursors of cholesterol in membrane lipid rafts (detergent resistance membranes) prepared from liver tissues of these 2 infants: 8-dehydrocholesterol and 7-dehydrocholesterol in lipid rafts of the infant with Smith-Lemli-Opitz syndrome and cholest-8(9)-ene-3beta-ol in lipid rafts of the infant with X-linked dominant chondrodysplasia punctata. We suggest that such alterations in the lipid raft sterol environment may affect the biology of cells and the development of fetuses with cholesterol biosynthetic disorders.

Sterol profiling of amniotic fluid: a routine method for the detection of distal cholesterol synthesis deficit

OBJECTIVES

Smith Lemli Opitz syndrome (SLOS) caused by a deficit of 3beta-hydroxysterol-Delta7 reductase was the first sterol deficit described with multiple malformations. The lack of specificity of many morphological abnormalities detected by ultrasound and their frequency have justified routine screening of amniotic fluid (AF) for sterols by GC-MS. The examination contributes to an improved knowledge of the sterol status in the fluid.

METHODS

A series of sterol profiles is collated here. Accumulation of 7- and 8-dehydrocholesterol are diagnostic for SLOS. However, a number of other sterols have also been detected by GC-MS in control AF and their presence may be confusing.

RESULTS AND CONCLUSIONS

In addition to cholesterol, the level of which varies as function of the gestational age, lathosterol is present together with trace amounts of 7- and 8-dehydrocholesterol and other precursors such as desmosterol, lanosterol, and dimethylsterol. Phytosterols are also present in 70% of AF samples that have been tested. Besides SLOS, GC-MS examination of amniotic fluid can detect various sterol deficits associated with malformations (lathosterolosis, desmosterolosis, X-linked chondrodysplasia, and particular Antley-Bixler syndrome). Practical conclusions support GC-MS as a routine method to investigate skeletal and central nervous system malformations.

Sterol composition of gonad, muscle and digestive gland of Pecten maximus from Málaga (South Spain)

Sterol composition and content and their seasonal variations over 18 months were investigated in adductor muscle, digestive gland and gonads of Pecten maximus. Sterols were isolated by Silicagel 60 thin layer chromatography and identified by gas chromatography/mass spectrometry. Eleven sterols were identified, with cholesterol, brassicasterol, 24-methylenecholesterol and 22-trans-dehydrocholesterol being the principal components. The same sterols were found in all three tissues independent of season. The relative amounts of each sterol present in each tissue differed. Total sterol levels in gonad and muscle were higher than in digestive gland. Statistically significant differences (P<0.05) were found between the concentrations of each of the sterols isolated from the gonad or muscle and digestive gland. The seasonal variations in the sterol content of the gonad seem be related to the reproductive cycle, while the sterol content of the digestive gland appears to be linked to diet, mainly diatoms or dinoflagellates. The muscle sterol content showed minor changes throughout the year.

Neutral sterols of rat epididymis. High concentrations of dehydrocholesterols in rat caput epididymidis

Phospholipids and sterols are known to have multiple functions in reproductive tissue of mammals. High concentrations of the cholesterol precursor desmosterol have been described in testis, epididymis, and spermatozoa of various species. These findings and the recent discovery of some cholesterol precursors as meiosis-activating sterols suggest important functions of cholesterol precursors in fertility. Many sterol intermediates appear from the 19-step conversion of lanosterol, the first sterol synthesized in the cascade of cholesterol synthesis, to cholesterol. The biochemical basis of the genetically inherited Smith-Lemli-Opitz syndrome has been described as a defective conversion of 7-dehydrocholesterol to cholesterol. Since this discovery, interest has focused on this special cholesterol precursor. Here, we report high concentrations of 7- and 8-dehydrocholesterol in caput epididymidis and spermatozoa derived from caput epididymidis of Sprague-Dawley and Wistar rats, which comprised up to 30% of total sterols. In contrast to caput epididymidis, 7- and 8-dehydrocholesterol were barely detected in cauda epididymidis or testis. Desmosterol increased several times from caput to cauda epididymidis. This is the first report of the natural appearance of high concentrations of dehydrocholesterols in mammalian tissue, and it underlines the putative importance of cholesterol precursors in reproductive tissue.

Difficult prenatal diagnosis in mild Smith-Lemli-Opitz syndrome

Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive disorder of cholesterol biosynthesis caused by mutations of the 7-dehydrocholesterol (7DHC) reductase gene (DHCR7). We present our experience with prenatal diagnosis of an affected fetus with a very mild form of SLOS. The mother underwent prenatal diagnosis by chorionic villus (CV) sampling at 11 2/7 weeks because of having two prior affected sons with SLOS. The 7DHC/total-sterol ratio in the fetus was higher than in normal control fetuses but lower than the ratio observed in CV of three other fetuses in whom SLOS was diagnosed prenatally. The pregnancy was terminated at 13 2/7 weeks. The level of 7DHC in amniotic fluid (AF) obtained at the time of pregnancy termination was unequivocally elevated, confirming the diagnosis of SLOS. This report illustrates the difficulties with the interpretation of biochemical prenatal diagnosis based on the determination of 7DHC/total-sterol ratio in CV sample in a case of mild SLOS, whereas biochemical testing of amniotic fluid clearly manifests the biochemical defects of SLOS as early as 13 weeks of gestation.

Fetal demise with Smith-Lemli-Opitz syndrome confirmed by tissue sterol analysis and the absence of measurable 7-dehydrocholesterol Delta(7)-reductase activity in chorionic villi

Smith-Lemli-Opitz syndrome (SLOS), an autosomal recessive condition with multiple malformations, mental retardation, and growth failure, results from markedly reduced activity of the final enzyme in the cholesterol biosynthetic pathway, 7-dehydrocholesterol Delta(7)-reductase (DHCR7). We diagnosed SLOS in a fetus following intrauterine demise at 32 weeks' gestation. Chorionic villus (CV) sampling had been performed at 30 weeks because oligohydramnios and atrioventricular septal defect were noted on fetal ultrasound. On fetal post-mortem examination, a midline U-shaped soft palate cleft, micrognathia, postaxial polydactyly of the fingers with single transverse palmar creases bilaterally, and cutaneous syndactyly of toes two-three bilaterally suggested SLOS. We hypothesized that SLOS could be confirmed by analysis of tissue sterols despite extensive autolysis, and by measurement of enzyme activity in CV cells. Measurement of DHCR7 activity in CV cells was undertaken using ergosterol as a substrate. CV cells were unable to convert any ergosterol to brassicasterol after a 72 h incubation period while control CV cells reduced 12.6-71.8% of ergosterol to brassciasterol in a 72 h period. SLOS was confirmed by measurement of elevated 7-dehydrocholesterol (7-DHC) in the CV cells. Measurements of sterols were made in multiple fetal tissues. All tissues analysed showed elevated 7-DHC with markedly increased 7-DHC/cholesterol ratios.

Prenatal diagnosis of Smith-Lemli-Opitz syndrome in a pregnancy with low maternal serum oestriol and a sex-reversed fetus

A cytogenetically normal male fetus was subsequently found to have female external genitalia, a cardiac malformation and mid-trimester intra-uterine growth retardation by ultrasound examination. The maternal serum oestriol level was low. The combination of low oestriol and sonographic findings suggested Smith Lemli Opitz syndrome (SLO), which was confirmed by a markedly increased amniotic fluid level of 7-dehydrocholesterol. We review the differential diagnosis of apparent sex reversal in a fetus and low maternal serum oestriol level. To further examine the specificity of low maternal oestriol level as a marker for SLO a follow-up study of 12141 pregnancies screened for Down syndrome using three biochemical markers: alpha-fetoprotein, beta-human chorionic gonadotrophin and oestriol was performed. 26 pregnancies had an oestriol level that was 0.25 MoM or less. SLO was not diagnosed clinically in any of the liveborn children ascertained through a low maternal oestriol level. Nine of the pregnancies ended in spontaneous miscarriage. Although the frequency of SLO in pregnancies with low maternal oestriol levels or sex-reversed fetuses is unknown, the diagnosis of SLO should, nevertheless, be considered in both clinical settings.

Identification of 7-dehydrocholesterol, vitamin D3, 25(OH)-vitamin D3 and 1,25(OH)2-vitamin D3 in Solanum glaucophyllum cultures grown in absence of light

Solanum glaucophyllum contains the calciotropic hormone 1, 25-dihydroxy-vitamin D3 (1,25(OH)2D3). The metabolic pathway leading to the formation of 1,25(OH)2D3 in the plant is largely unknown. Specifically, there is controversy about the participation of a photolytic reaction in the generation of vitamin D3 and its metabolites. To investigate the requirement for light, S. glaucophyllum tissue (callus) and cell suspension cultures grown under strict conditions of darkness were extracted with chloroform/methanol (1:2, v/v) followed by purification of the lipidic fraction by Sephadex LH-20 and high-performance liquid chromatography. HPLC peaks with elution times similar to those of authentic samples of 7-dehydrocholesterol, vitamin D3, 25(OH)D3 and 1,25(OH)2D3 were detected. The presence of 1,25(OH)2D3 was also evidenced by [3H]1,25(OH)2D3 competitive binding analysis using the chick hormone intestinal receptor. Furthermore, 7-dehydrocholesterol, vitamin D3, 25(OH)D3 and 1,25(OH)2D3 were unequivocally identified by mass spectrometry. Incubation of control samples of 7-dehydrocholesterol under the same conditions as S. glaucophyllum cultures did not result in vitamin D3 formation, excluding the influence of light in these experiments. The results suggest that a synthetic route of vitamin D3 compounds independent of light operates in Solanum glaucophyllum cultured in vitro.

Fetal Smith-Lemli-Opitz syndrome can be detected accurately and reliably by measuring amniotic fluid dehydrocholesterols

The Smith-Lemli-Opitz syndrome, characterized by limb, face and organ abnormalities, and mental retardation, is caused by an inherited block in the step of cholesterol biosynthesis in which the delta 7 double bond of 7-dehydrocholesterol is reduced. It is diagnosed by the presence of markedly elevated levels of 7-dehydrocholesterol and 8-dehydrocholesterol in plasma and tissue. We measured amniotic fluid sterols in 15 pregnancies in 13 women who had previously carried an affected fetus. Cholesterol, 7-dehydrocholesterol and 8-dehydrocholesterol concentrations averaged 18 +/- 3, 9.8 +/- 2.9 and 5.0 +/- 1.7 micrograms/ml, respectively, in seven pregnancies with an affected fetus or child. In contrast, these levels were 19 +/- 3, 0.05 +/- 0.01 and < 0.005 micrograms/ml, respectively, in eight increased-risk pregnancies with normal outcomes and 16 +/- 2, 0.07 +/- 0.01 and < 0.005 micrograms/ml in normal controls. 7-dehydrocholesterol concentrations, 2.2-26 and 0.05-0.10 micrograms/ml in pregnancies with an affected and unaffected fetus, respectively, did not overlap. Thus, abnormally elevated amniotic fluid dehydrocholesterol concentrations are an accurate predictor of fetal Smith-Lemli-Opitz syndrome. A false-positive or a false-negative result is highly unlikely.

Skin content of 7-dehydrocholesterol in patients with malabsorption

The mechanism for the development of vitamin D deficiency in patients with malabsorption remains unclear. We wished to examine the hypothesis that one factor was a reduced skin content of 7-dehydrocholesterol, the precursor for the formation of vitamin D in the presence of ultraviolet radiation. We measured 7-dehydrocholesterol in skin samples from 9 patients who had previously had vitamin D deficiency due to malabsorption (6 with Crohn's disease, 2 with primary biliary cirrhosis, and 1 with idiopathic pseudo-obstruction). We found no evidence of reduced levels of 7-dehydrocholesterol in the skin in these patients. Lack of 7-dehydrocholesterol does not contribute to vitamin D deficiency in malabsorption.

First-trimester diagnosis of Smith-Lemli-Opitz syndrome

We report here the prenatal diagnosis of Smith-Lemli-Opitz (SLO) syndrome in the first trimester by direct measurement of 7-dehydrocholesterol (7-DHC) in a chorionic villus (CV) biopsy. The proband was diagnosed clinically at birth and the diagnosis was confirmed biochemically by demonstrating elevated 7-DHC in plasma. The family pursued prenatal diagnosis in their fourth, fifth, and sixth pregnancies. The fourth pregnancy spontaneously miscarried at 9 weeks' gestation. Analysis in both direct and cultured curetting tissue (identified as similar to CV tissue) showed an abnormal tissue neutral sterol pattern with an elevated 7-DHC concentration. The fifth pregnancy also miscarried spontaneously at 9 weeks but no tissue of unequivocal fetal origin could be identified to allow biochemical investigation. In the sixth pregnancy, ultrasound examination at the time of CV sampling showed a thickened nuchal fold. Direct analysis of the CV sample revealed elevated levels of 7-DHC consistent with the diagnosis of SLO. The pregnancy was terminated and both fetal tissue and cultured fetal cells showed marked increases in 7-DHC, confirming the prenatal diagnosis.

Increased first trimester nuchal translucency as a prenatal manifestation of Smith-Lemli-Opitz syndrome

Routine ultrasound examination at 11 weeks of gestation in a woman with no family history of genetic disease demonstrated increased accumulation of fluid in the fetal nuchal region. In view of the association of this defect with chromosomal abnormalities, fetal karyotyping was performed by chorion villus sampling and this demonstrated a normal 46,XY karyotype. Subsequent scans showed resolution of the nuchal fluid, and at the 20-week scan the fetal genitalia appeared to be female. Fetal blood sampling confirmed a normal male karyotype and fetoscopy confirmed the presence of female external genitalia. The parents elected to terminate the pregnancy, and postmortem findings were indicative of Smith-Lemli-Opitz syndrome. This was confirmed by the finding of increased levels of 7-dehydrocholesterol in cultured skin fibroblasts.

Prenatal diagnosis of Smith-Lemli-Opitz syndrome is possible by measurement of 7-dehydrocholesterol in amniotic fluid

Amniocentesis was performed at 17.3 weeks in a pregnancy with severe intrauterine growth retardation. Cytogenetic studies on amniocytes were normal, 46,XX, and the pregnancy was continued. The diagnosis of Smith-Lemli-Opitz syndrome was suspected in the neonatal period and confirmed by the presence of 7-dehydrocholesterol (7-DHC) in the plasma (0.4 mmol/l, normal = not detectable) associated with a low total cholesterol concentration (0.4 mmol/l, normal = 2.56 +/- 0.23). Retrospective analysis of the amniotic fluid sample revealed an elevated level of 7-DHC (0.022 mmol/l; normal = undetectable). Therefore measurement of 7-DHC levels in amniotic fluid during the second trimester of pregnancy is useful for the prenatal diagnosis of Smith-Lemli-Opitz syndrome in families at risk and should be considered in cases of severe growth retardation of unknown aetiology for which amniotic fluid is available and in which a normal chromosomal pattern in amniocytes is present.

Diagnosis of Smith-Lemli-Opitz syndrome by gas chromatography/mass spectrometry of 7-dehydrocholesterol in plasma, amniotic fluid and cultured skin fibroblasts

A method is described for quantification of 7-dehydrocholesterol (7DHC) and other neutral sterols by gas chromatography/mass spectrometry for diagnosis of Smith-Lemli-Opitz syndrome, an apparent primary defect of cholesterol biosynthesis associated with low plasma levels of cholesterol and high levels of its precursor, 7DHC. Results are summarized for specimens from normal controls and from 40 patients with Smith-Lemli-Opitz syndrome (SLOS). Whereas the concentration of 7DHC (as a combined peak of 7DHC and iso-7DHC) in normal infant plasma was found to be 0.10 +/- 0.05 (S.D.) microgram/ml, the level in patients with SLOS ranged from 2.7 to 470 micrograms/ml, or from 10 to more than 2000 times the upper limit of normal. Patients with milder type I SLOS as well as those with the more severe type II SLOS were found to have the same sterol abnormality. Although most infants with SLOS had plasma cholesterol levels lower than 400 micrograms/ml (40 mg/dl), several older children with only mildly increased levels of 7DHC had normal plasma cholesterol levels. Diagnostically useful, comparably increased levels of 7DHC were found in amniotic fluid and cultured skin fibroblasts from patients with SLOS. More mildly increased levels of 7DHC were also found in both plasma and cultured skin fibroblasts of SLOS heterozygotes. The method described uses capillary columns and GC/MS instrumentation available in most biochemical genetics laboratories and should prove useful not only for diagnosis and prenatal diagnosis of Smith-Lemli-Opitz syndrome, but also for identification of other possible inborn errors of sterol biosynthesis.

Smith-Lemli-Opitz syndrome: prenatal diagnosis by quantification of cholesterol precursors in amniotic fluid

Until recently, the diagnosis of Smith-Lemli-Opitz syndrome (SLOS), an autosomal recessive malformation/mental retardation syndrome, was made on the basis of clinical criteria alone. As a result, prenatal diagnosis has been possible only if sonography disclosed distinct fetal malformations in a subsequent pregnancy. However, the recent description of increased levels of 7-dehydrocholesterol (cholesta-5,7-dien-3 beta-ol) in patients with SLOS, most likely caused by a deficiency of 3 beta-hydroxysteroid-delta 7-reductase, has provided an apparently reliable biochemical marker for diagnosis of SLOS. To determine if this abnormality of sterol metabolism has utility for prenatal diagnosis of SLOS, we measured the levels of neutral sterols in stored amniotic fluid samples from two SLOS pregnancies. In both cases, the diagnosis of SLOS was made in the neonatal period by clinical criteria and the finding of markedly increased levels of 7-dehydrocholesterol in plasma. Quantitative analysis by gas chromatography of sterols extracted from the amniotic fluid of both pregnancies revealed similar, markedly increased levels of 7-dehydrocholesterol and its precursor, lathosterol (cholest-7-en-3 beta-ol), both of which were undetectable in reference amniotic fluids. These findings suggest that abnormalities of cholesterol biosynthesis in SLOS may be sufficiently expressed in fetal life to permit prenatal diagnosis of this disorder by measurement of 7-dehydrocholesterol in amniotic fluid.

Prenatal detection of the cholesterol biosynthetic defect in the Smith-Lemli-Opitz syndrome by the analysis of amniotic fluid sterols

The Smith-Lemli-Opitz (SLO or RSH) syndrome is an autosomal recessive disorder characterized by a recognizable pattern of minor facial anomalies, congenital anomalies of many organs, failure to thrive, and mental retardation. Its cause is a defect in cholesterol biosynthesis characterized by abnormally low plasma cholesterol levels and concentrations of the cholesterol precursor 7-dehydrocholesterol (7DHC) elevated up to several thousand-fold above normal. We used capillary column gas-chromatography to quantify sterols in amniotic fluid, amniotic cells, plasma, placenta, and breast milk from a heterozygous mother who had previously given birth to an affected son and in cord blood and plasma from her affected newborn daughter. The cholesterol concentration in amniotic fluid at 16 weeks gestation was normal, but 7DHC, normally undetectable, was greatly elevated. In cultured amniocytes, the level of 7DHC was 11% of total cholesterol, similar to cultured fibroblasts from patients with SLO syndrome. At 38 weeks, a girl with phenotype consistent with the syndrome was born. Cholesterol concentrations were abnormally low in cord blood and in the baby's plasma at 12 weeks, while levels of 7DHC were grossly elevated, confirming the prenatal diagnosis. The mother's plasma cholesterol increased steadily during gestation but remained below the lower 95% limit reported for normal control women. We conclude that it is now possible to detect the SLO syndrome at 16 weeks gestation by analyzing amniotic fluid sterols.

Prenatal diagnosis of Smith-Lemli-Opitz syndrome

An abnormality in cholesterol synthesis was described recently in the Smith-Lemli-Opitz (SLO) syndrome. Here we describe how the application of this finding has enabled an accurate prenatal diagnosis. We also discuss the possible use of this test in detecting heterozygotes.

Quantification of 7-dehydrocholesterol in plasma and amniotic fluid by liquid chromatography/particle beam-mass spectrometry as a biochemical diagnostic marker for the Smith-Lemli-Opitz syndrome

The qualitative and quantitative determination of cholesterol and 7-dehydrocholesterol (7-DHC) in plasma as a biochemical diagnostic marker for the Smith-Lemli-Opitz syndrome by liquid chromatography/particle beam interface-mass spectrometry (LC/PB-MS) is presented. Baseline separation of cholesterol and 7-DHC is achieved on a silica column with hexane+ethanol (99: 1 v/v) as mobile phase within a 10 min analysis. Recoveries of cholesterol and 7-DHC in a simple two-phase extraction system are nearly 100%. The absolute limit of detection using LC/PB-MS is approximately 10 ng. The method presented allows extraction, analysis and quantification of cholesterol and 7-DHC within 15 min without the necessity of sample derivatization.

Defective cholesterol biosynthesis associated with the Smith-Lemli-Opitz syndrome

BACKGROUND

The Smith-Lemli-Opitz syndrome (frequency, 1:20,000 to 1:40,000) is defined by a constellation of severe birth defects affecting most organ systems. Abnormalities frequently include profound mental retardation, severe failure to thrive, and a high infant-mortality rate. The syndrome has heretofore been diagnosed only from its clinical presentation.

METHODS

Using capillary-column gas chromatography-mass spectrometry, we measured the sterol composition of plasma, erythrocytes, lens, cultured fibroblasts, and feces from five children with the syndrome (three girls and two boys).

RESULTS

Plasma cholesterol levels were abnormally low (8 to 101 mg per deciliter [0.20 to 2.60 mmol per liter]) in every patient, being well below the 5th percentile for age- and sex-matched controls. Concentrations of the cholesterol precursor 7-dehydrocholesterol (cholesta-5,7-dien-3 beta-ol), which was not detectable in most of our controls, were elevated (11 to 31 mg per deciliter) more than 2000-fold above normal and were similar to the levels of cholesterol in all tissues from all patients. An isomeric dehydrocholesterol with a structure similar to that of 7-dehydrocholesterol was also detected.

CONCLUSIONS

The combination of abnormally low plasma cholesterol levels and a high concentration of the cholesterol precursor 7-dehydrocholesterol points to a major block in cholesterol biosynthesis at the step in which the C-7(8) double bond of 7-dehydrocholesterol is reduced, forming cholesterol. The block may be sufficient to deprive an embryo or fetus of cholesterol and prevent normal development, whereas the incorporation of 7-dehydrocholesterol into all membranes may interfere with proper membrane function.

Lipid composition of hamster epididymal spermatozoa

The lipid composition of hamster epididymal spermatozoa was examined. Caput epididymal spermatozoa were isolated by Percoll density gradient centrifugation without contamination by other cells and they had a specific gravity of 1.10-1.12 g cm-3. Caput and cauda epididymal spermatozoa showed little difference in the amounts of total fatty acid and total sterol. However, sterol composition changed markedly during the transit of spermatozoa through the epididymis: the amount of cholesterol decreased, while the amount of desmosterol and cholesta-7,24-dien-3 beta-ol increased. No significant change in fatty acid composition was observed during the transit, although there was a tendency for an increase in chain length. Both 22:5 and 22:6 represented high percentages in fatty acids of hamster spermatozoa. Some difference in lipids was detected between the upper fraction (1.04 g cm-3) and the lower fraction (1.10 g cm-3) obtained by the density gradient centrifugation of cauda epididymal spermatozoa. Total fatty acid content of the upper fraction was 1.4-fold higher than that of the lower fraction, and the percentage of 18:0 was lower in the latter fraction with a higher percentage of 18:2. The total sterol:total phospholipid ratio in hamster cauda epididymal spermatozoa was 0.21.

Teratogenic effect of the cholesterol synthesis inhibitor AY 9944 on rat embryos in vitro

AY 9944 [trans-1,4-bis(2-chlorobenzylaminomethyl) cyclohexane dihydrochloride] is an amphiphilic cationic molecule. This chemical is an established inhibitor of cholesterol synthesis and is teratogenic in rats. The mechanisms of this teratogenicity remain to be clarified. This study used cultured rat whole embryos to ascertain whether AY 9944 had a direct effect on embryos, or whether its action was indirect, via the maternal cholesterol metabolism. Four experimental conditions were investigated: (A) controls; (B) 10 day untreated embryos were cultured in serum of treated rats; (C) 10 day untreated embryos were cultured in serum containing added AY 9944 (0-1,000 micrograms/ml); and (D) 10 day embryos from females treated on day 4 of gestation were cultured in normal serum. In group B there was no growth retardation; some slight nonspecific abnormalities were not significant. In group C, direct addition of AY 9944 to culture medium retarded growth and differentiation in a dose-dependent manner. No malformation was observed, but histological examinations showed numerous areas of cell necrosis, especially in the CNS. In group D, not only was growth retardation observed, but also characteristic malformations of AY 9944 teratogenesis, including pituitary agenesis. These results show that AY 9944 teratogenicity is initiated prior to day 10.

Determination of 7-dehydrocholesterol in human skin by high-performance liquid chromatography

A two-stage chromatographic procedure has been devised for the measurement of 7-dehydrocholesterol in human skin. Extracts containing ergosterol as internal standard underwent preparative chromatography on a Spherisorb S5W column using hexane-1% isopropanol as solvent, and an eluted fraction was analysed with an Ultrasphere 5-microns ODS column with methanol-tetrahydrofuran-17.5 mM KH2PO4 (95:1:4, v/v) as solvent and using an amperometric detector at 1.7 V. 7-Dehydrocholesterol could be reliably assayed in human skin samples as small as 5 mm in diameter. In hospital patients skin 7-dehydrocholesterol concentrations ranged from 12 to 81 micrograms/g dry weight.

Effects of steroid molecules on the dynamical structure of dioleoylphosphatidylcholine and digalactosyldiacylglycerol bilayers

The ESR spectra of cholestane spin labels (CSL) in dioleoylphosphatidylcholine (DOPC) bilayers containing 20 wt% of cholesterol, 7-dehydrocholesterol, beta-sitosterol, stigmasterol and lanosterol exhibit a marked similarity, thus indicating that these steroids induced the same effects on the lipid bilayer over the temperature range 21-55 degrees C. The incorporation of these steroids into the DOPC bilayers enhances the orientational order of the CSL molecules at every temperature studied, but only induces a pronounced slow-down in their rotational motions at temperatures above 35 degrees C. Similar results were obtained in DOPC/ergosterol multilamellar liposomes, but the changes are now less pronounced than in the other five DOPC/steroid systems. In contrast, the addition of stigmasterol to digalactosyldiacylglycerol (DGDG) bilayers appears to increase the order parameter mean value of P2, without affecting the diffusion coefficients. Furthermore, the incorporation of 7-dehydrocholesterol to DGDG bilayers causes a large enhancement in the orientational order, but has only a small effect on D perpendicular of the CSL molecules. Importantly, this latter effect appears to be independent of temperature. The marked changes in the rates of the rotational motion brought about by the addition of steroids, contrasts with the lack of a significant effect of unsaturation on the bilayer dynamics reported by us previously (Korstanje et al. (1989), Biochim. Biophys. Acta 980, 225-233, and 982, 196-204).

HPLC analysis of desmosterol, 7-dehydrocholesterol, and cholesterol

A simple and sensitive method to analyze mixtures of desmosterol, 7-dehydrocholesterol and cholesterol is described. The method involves the oxidative conversion of the sterols with cholesterol oxidase, followed by high performance liquid chromatographic (HPLC) analysis. A C18 reversed phase column (3 microns, 75 X 4.6 mm) and a mixture of methanol and acetonitrile (1:1, v/v) at a rate of 1 ml/min are used to separate the sterols. The eluted sterols are quantified by measuring UV absorption at 240 nm. As little as 10 pmoles of sterol can be quantified under these conditions.

Identification of cholesta-7,24-dien-3 beta-ol and desmosterol in hamster cauda epididymal spermatozoa

The sterol composition of hamster cauda epididymal spermatozoa was remarkably different from that of several other mammalian spermatozoa. Desmosterol and cholesta-7,24-dien-3 beta-ol account for as much as 90% of the total sterols. Cholesterol and desmosterol are the major components of mouse cauda epididymal spermatozoa, and rabbit, boar and bull ejaculated spermatozoa. Cholesta-7,24-dien-3 beta-ol was not detected. Furthermore, cholesterol was the main sterol in hamster caput epididymal spermatozoa, while only a trace amount of desmosterol was detected and cholesta-7,24-dien-3 beta-ol was hardly detected at all. The sterol content of cauda and caput epididymal spermatozoa was 0.17 +/- 0.05 mumol/10(8) spermatozoa. During maturation, the desmosterol and cholesta-7,24-dien-3 beta-ol levels increase and the cholesterol level decreases. Cholesta-7,24-dien-3 beta-ol appears as a sterol in mature spermatozoa and seems to be a characteristic sterol of hamster cauda epididymal spermatozoa.

Separation and identification of triglycerides, cholesteryl esters, cholesterol, 7-dehydrocholesterol, dolichol, ubiquinone, alpha-tocopherol, and retinol by high performance liquid chromatography with a diode array detector

A simple isocratic high performance liquid chromatography (HPLC) system is described that allows separation and identification of cholesteryl esters, triglycerides, ubiquinone, alpha-tocopherol, dolichol, cholesterol, 7-dehydrocholesterol, and retinol. This consisted of a normal phase cyanopropyl column with 0.1% isopropanol in heptane as the solvent. The effluent was monitored with an LKB model 2140 diode array detector which enabled the lipids to be identified by their characteristic absorption spectra. This system was applied to a sample of dog liver in which cholesteryl esters, retinyl esters, triglycerides, ubiquinone, dolichol, cholesterol, and retinol were identified. Retinyl esters and vitamin D esters were identified by their similarity in absorption spectra to retinol and vitamin D. A system to transfer and store the chromatograms on the VAX PDP-11 or an optical disc is also described.

The cholecalciferol sulphate system in mammals

7-Dehydrocholesterol sulphate has been identified in human and rat skin. The compound was isolated by anion exchange chromatography and following hydrolysis it was characterized by high-performance liquid chromatography and gas chromatography-mass spectrometry. Experiments with rats showed that 7-dehydrocholesterol sulphate can serve as a precursor of cholecalciferol sulphate and 25-hydroxy-cholecalciferol 3-sulphate, the latter compound being present in significant amounts in human blood. The sulphated sterols identified represent a previously unknown secosteroid system in mammals.

24-Methyl-23-dehydrocholesterol: a new sterol intermediate in C-24 demethylation from the nematodes Panagrellus redivivus and Caenorhabditis elegans?

Panagrellus redivivus produced 24-methyl-23-dehydrocholesterol as 4.0% of the 4-desmethylsterols when propagated in a medium containing campesterol as the dietary sterol. The re-examination of previous data revealed that Caenorhabditis elegans produced 1.8% 24-methyl-23-dehydrocholesterol when propagated in medium containing campesterol. 24-Methyl-23-dehydrocholesterol was not detected when the nematodes were propagated in medium containing 22-dihydrobrassicasterol or 24-methylenecholesterol. This may be a result of the greater efficiency of dealkylation of the latter two sterols. This is the first report of the natural occurrence of this sterol in a non-photosynthetic organism, and the first report in organisms that dealkylate 24-alkylsterols.

Measurement of blood levels of 7-dehydrocholesterol in man by high-performance liquid chromatography

A high-performance liquid chromatography procedure was established to measure 7-dehydrocholesterol (7DHC) in the blood. Interference studies were performed using 20 similar compounds likely to give analytical errors. 7DHC was extracted with a methanol chloroform mixture. Extraction recoveries were reproducible and acceptable, with low methodological variations from batch-to-batch. Results show that 7DHC is not detectable in the blood, contrary to the previous reports. Possible explanations for its absence in the blood are: (1) it is confined to the skin and is not present in the blood in this form; (2) because the molecule is labile, it is destroyed by the methods applied; (3) previous reports on 7DHC levels were based on non-specific methods.

Tissue distribution of 7-dehydrocholesterol, vitamin D3 and 25-hydroxyvitamin D3 in several species of fishes

A high-performance liquid chromatographic (HPLC) method for simultaneous determination of 7-dehydrocholesterol (7-DHC), vitamin D3 and 25-hydroxyvitamin D3 (25-OH-D3) in tissues of fishes was established, and using this method the tissue distribution of the sterols in lamprey (Entosphenus japonicus), great blue shark (Prionace glauca), skipjack (Katsuwonus pelamis) and albacore (Thunnus alalunga) was investigated. The results are summarized in the following: Although the alimentary canal, gall bladder and roe of lamprey and the alimentary canal of great blue shark contained comparatively high levels of 7-DHC (higher than 2,000 ng/wet tissue g), the other tissues of lamprey and great blue shark and all tissues of skipjack and albacore contained only low levels of 7-DHC (lower than 1,000 ng/g). There was no significant correlation between the levels of 7-DHC and vitamin D3. The contents of 7-DHC in the skin of skipjack and albacore were only 1/1,000 of those in the skin of rats. Although the contents of vitamin D3 in the liver of skipjack and albacore were extremely high (41,240 and 21,000 ng/g, respectively), those in the skin were very low (454 and 257 ng/g, respectively). 25-OH-D3 was detected in the viscera of skipjack, but the levels were not very high (lower than 150 ng/g). These levels were not significantly correlated with those of vitamin D3. The results suggest that large quantities of vitamin D3 in the liver of skipjack and albacore are supplied by other biosynthetic routes or by intake of vitamin D3 rather than by photochemical biosynthesis.

Aging decreases the capacity of human skin to produce vitamin D3

An evaluation of surgically obtained skin (age range, 8-92 yr) revealed that there is an age-dependent decrease in the epidermal concentrations of provitamin D3 (7-dehydrocholesterol). To ascertain that aging indeed decreased the capacity of human skin to produce vitamin D3, some of the skin samples were exposed to ultraviolet radiation and the content of previtamin D3 was determined in the epidermis and dermis. The epidermis in the young and older subjects was the major site for the formation of previtamin D3, accounting for greater than 80% of the total previtamin D3 that was produced in the skin. A comparison of the amount of previtamin D3 produced in the skin from the 8- and 18-yr-old subjects with the amount produced in the skin from the 77- and 82-yr-old subjects revealed that aging can decrease by greater than twofold the capacity of the skin to produce previtamin D3. Recognition of this difference may be extremely important for the elderly, who infrequently expose a small area of skin to sunlight and who depend on this exposure for their vitamin D nutritional needs.

A histochemical method suitable to discriminate free cholesterol from its esters and both from 7-dehydrocholesterol and vitamins D

The peracetic acid-toluidine blue and the peracetic acid-Schiff reactions as well as the failure of HgCl2-formalin fixative for inhibiting these reactions appears as a very useful method for free cholesterol histochemical detection and to discriminate it from its esters and from some of its metabolic products such as 7-dehydrocholesterol and vitamins D. The cholesterol histochemical detection provided by those reactions appears specific taking into account the findings afforded by spot tests. The peracetic acid-toluidine blue reaction is very suitable for histochemical purposes on tissue sections, since it does not produces tissues damages, it is sensitive and the stained end product is almost insoluble in the solvents frequently used in histological techniques. The previous ribonuclease treatment and methylation are very useful in avoiding the basophil substances interference on the peracetic acid-toluidine blue reaction. The 2,4-dinitrophenylhydrazine carbonyl group blockade is useful to decrease the influence of carbonyl group on the peracetic acid-histological techniques. The previous ribonuclease treatment and methylation are very useful in avoiding the basophil substances interference on the peracetic acid-toluidine blue reaction. The 2,4-dinitrophenylhydrazine carbonyl group blockade is useful to decrease the influence of carbonyl group on the peracetic acid-histological techniques. The previous ribonuclease treatment and methylation are very useful in avoiding the basophil substances interference on the peracetic acid-toluidine blue reaction. The 2,4-dinitrophenylhydrazine carbonyl group blockade is useful to decrease the influence of carbonyl group on the peracetic acid-Schiff reaction. The peracetic acid-toluidine blue reaction is more sensitive and more specific than peracetic acid-Schiff reaction, since the tissues do contain Schiff reactive products unable to be 2,4-dinitrophenylhydrazine blocked which interfere on the results of the latter reaction decreasing its specificity and its sensitivity. The cholesterol histochemical detection based on the peracetic acid-toluidine blue and peracetic acid-Schiff reaction as it is suitable in discriminating free cholesterol from its esters as well as from some of its metabolic products it appears very useful for metabolic studies on tissue sections.

Application of high-performance liquid chromatography to the study of esterified 7-dehydrocholesterol in rat skin

A novel and precise method for determining free and esterified 7-dehydrocholesterol in rat skin was developed by using a two-step high-performance liquid chromatography system. This method involves initial lipid extraction, separation of the free and esterified 7-dehydrocholesterol by, firstly, preparative high-performance liquid chromatography, saponification, and determination by, secondly, analytical high-performance liquid chromatography. This method was applied to the study of the 7-dehydrocholesterol in rat skin. Almost all of the 7-dehydrocholesterol in rat skin was present in an esterified form (78-93%). Ultraviolet exposure of the skin increased total 7-dehydrocholesterol content, however, the percentage of esterified 7-dehydrocholesterol was not altered appreciably. Application of this method to the study of the photo-metabolism of 7-dehydrocholesterol in rat skin revealed that almost all of the vitamin D3 produced by ultraviolet rays was in the esterified form.

Identification of vitamin D3 and 7-dehydrocholesterol in cow's milk by gas chromatography-mass spectrometry and their quantitation by high-performance liquid chromatography

Identification of vitamin D3 and 7-dehydrocholesterol (7-DHC) in cow's milk by gas chromatography-mass spectrometry (GC-MS) and their quantitation by high-performance liquid chromatography (HPLC) were investigated. When vitamin D and provitamin D fractions purified from a sample of commercial cow's milk were applied to GC-MS, the results showed that the fractions contained vitamin D3 and 7-DHC, respectively, while neither vitamin D2 nor ergosterol could be detected in the milk. HPLC methods for the determination of vitamin D3 and 7-DHC in cow's milk were then proposed as routine methods. The method for assaying vitamin D3 included the isolation of lipids from milk according to the directions of Bell and Christie (5), saponification, isolation of unsaponifiable matter, digitonin-Celite column chromatography, preparative thin-layer chromatography (TLC) and application to HPLC. On the other hand, 7-DHC in milk could be simultaneously determined without the purification by digitonin-Celite column chromatography. The peak corresponding to either vitamin D3 or 7-DHC in the respective HPL-chromatograms was clearly separated from possible interfering substances and the recovery experiments for both vitamin D3 and 7-DHC gave satisfactory results. When the proposed methods were applied to 10 samples of commercial cow's milk, the assayed values of vitamin D3 and 7-DHC were 19--79 I.U./liter and 14--56 microgram/liter, respectively.

Occurrence of 7-dehydrocholesterol in the uropygial gland of domestic fowls

Histochemical studies on the uropygial gland of domestic fowls have shown the presence of sterols (among which cholesterol and its esters) in the lipidic fraction of the gland secret. beta-Glucuronidase activity beside A5 3beta- and 17beta-hydroxysteroid dehydrogenase activities suggests that uropygial gland might be involved in sterols metabolism. By thin layer chromatography cholesterol and 7-dehydrocholesterol can be separated from the uropygial extracts and these compounds can be identified in gas liquid chromatography.