Quantitative acylcarnitine determination by UHPLC-MS/MS--Going beyond tandem MS acylcarnitine "profiles"

Tandem MS "profiling" of acylcarnitines and amino acids was conceived as a first-tier screening method, and its application to expanded newborn screening has been enormously successful. However, unlike amino acid screening (which uses amino acid analysis as its second-tier validation of screening results), acylcarnitine "profiling" also assumed the role of second-tier validation, due to the lack of a generally accepted second-tier acylcarnitine determination method. In this report, we present results from the application of our validated UHPLC-MS/MS second-tier method for the quantification of total carnitine, free carnitine, butyrobetaine, and acylcarnitines to patient samples with known diagnoses: malonic acidemia, short-chain acyl-CoA dehydrogenase deficiency (SCADD) or isobutyryl-CoA dehydrogenase deficiency (IBD), 3-methyl-crotonyl carboxylase deficiency (3-MCC) or ß-ketothiolase deficiency (BKT), and methylmalonic acidemia (MMA). We demonstrate the assay's ability to separate constitutional isomers and diastereomeric acylcarnitines and generate values with a high level of accuracy and precision. These capabilities are unavailable when using tandem MS "profiles". We also show examples of research interest, where separation of acylcarnitine species and accurate and precise acylcarnitine quantification is necessary.

Allelic diversity in MCAD deficiency: the biochemical classification of 54 variants identified during 5 years of ACADM sequencing

Medium-chain acyl-coA dehydrogenase (MCAD) deficiency is a commonly detected fatty acid oxidation disorder and its diagnosis relies on both biochemical and molecular analyses. Over a 5-year period, sequencing all 12 exons of the MCAD gene (ACADM) in our laboratory revealed a total of 54 variants in 549 subjects analyzed. As most molecular ACADM testing is referred for the follow-up of an abnormal newborn screening result obtained from an asymptomatic newborn, the identification of a novel DNA variant, or "variant of unknown significance (VUS)," presents clinicians with a dilemma. Frequently, the results of molecular analyses are correlated to biochemical findings, such as the concentration of octanoylcarnitine (C8) in plasma and the excretion of hexanoylglycine (HG) in urine. Here, we describe the classification of genotypes harboring at least one VUS through the comparison of C8 and HG values measured in individuals who are carriers of, or affected with, MCAD deficiency on the basis of the following genotypes: c.985A>G/wildtype, c.199T>C/c.985A>G and c.985A>G/c.985A>G. Our findings emphasize the importance of obtaining both plasma and urine when following up positive newborn screening results and may influence the way physicians counsel their asymptomatic patients about MCAD deficiency after genetic analysis.

Wolcott-Rallison syndrome with 3-hydroxydicarboxylic aciduria and lethal outcome

Wolcott-Rallison syndrome (WRS) (OMIM 226980) is a rare, autosomal recessive disorder with infancy-onset diabetes mellitus, multiple epiphyseal dysplasia, osteopenia, mental retardation or developmental delay, and hepatic and renal dysfunction as main clinical findings. Patients with WRS have mutations in the EIF2AK3 gene, which encodes the pancreatic eukaryotic translation initiation factor 2-alpha kinase 3. We report a female patient who developed insulin-requiring diabetes at 2.5 months of age. Multiple epiphyseal dysplasia was diagnosed at age 2 years. At age 5.5 years she developed a Reye-like syndrome with hypoketotic hypoglycaemia and renal and hepatic insufficiency and died. A partial autopsy showed fat infiltration in the liver and kidneys. Examination of urine by gas chromatography and mass spectrometry showed large amounts of C(6)-dicarboxylic acid (adipic acid), 3-hydroxy-C(8)-dicarboxylic acid, 3-hydroxy-C(10)-dicarboxylic acid, and 3-hydroxydecenedioic acid. Acetoacetate and 3-hydroxybutyrate were absent. The findings suggested a metabolic block in mitochondrial fatty acid oxidation, but lack of material precluded enzyme analyses. The clinical diagnosis of WRS was suggested in retrospect, and confirmed by sequencing of DNA extracted from stored autopsy material. The patient was compound heterozygous for the novel EIF2AK3 mutations c.1694_1695delAT (Y565X) and c.3044T > C (F1015S). Our data suggest that disruption of the EIF2AK3 gene may lead to defective mitochondrial fatty acid oxidation and hypoglycaemia, thus adding to the heterogeneous phenotype of WRS.

Glutaric aciduria type II: a case report

We report a case of a newborn with Glutaric aciduria type II. Pregnancy was complicated by polyhidramnios and fetal bradycardia. Cardiomegaly was detected by fetal echocardiography. The baby was admitted to the Neonatal Intensive Care Unit of Chieti with respiratory distress syndrome immediately after delivery. He showed head and neck edema, micrognathia, paucity of movement, pronounced hypotonia, bilateral cryptorchidism, micropenis, small hands, skin hyperelasticity and joint hypermobility. Serum and urine analysis showed a fatty acid beta-oxidation disorder. He died at 7 days of age for cardiac arrest and autopsy showed marked hepatic and cardiac vacuolisation, lipid storage myopathy and glial cells vacuolisation. Based upon these findings, we speculate that this infant may be suffering from inborn metabolic disease.

Rhabdomyolysis in glutaric aciduria type I

Recurrent rhabdomyolysis has previously been reported in one patient with glutaric aciduria type I. We report rhabdomyolysis in a second, unrelated patient, suggesting that there may be a specific association with thismetabolic disorder.

Strategies for the diagnosis of mitochondrial fatty acid beta-oxidation disorders

Mitochondrial fatty acid beta-oxidation disorders (FAOD) are a group of clinically and biochemically heterogeneous inherited metabolic defects. The spectrum of phenotypes has expanded from hepatic encephalopathy to encompass myopathy, cardiomyopathy, peripheral neuropathy, sudden death and pregnancy complicated by fetal FAOD. Pre-symptomatic diagnosis is important to prevent morbidity and this is now achievable through newborn screening using tandem mass spectrometry (MS/MS). Moreover, most of the diagnosed defects are treatable and the prognosis is generally favourable. This article reviews the features of FAOD, critically evaluates methods of investigation including metabolite analyses in body fluids, in vitro oxidation rates and acylcarnitine profiling studies, enzymatic and mutational tests, and discusses genotype-phenotype correlation, treatment and monitoring options. Based on this knowledge, strategies for the biochemical investigation and differential diagnosis of patients presenting clinically, asymptomatic neonates detected by newborn screening, infants born after complications during late pregnancy, and cases of sudden death with suspected FAOD are presented. Laboratory investigation commonly begins with a search for diagnostic metabolites in physiological fluids, followed by in vitro functional studies if the initial findings are inconclusive, and confirmation by enzymology and molecular analyses. Occasionally a stress test in vivo may be required. At other times there may be no firm diagnosis achieved.

Analysis of 3-hydroxydodecanedioic acid for studies of fatty acid metabolic disorders: preparation of stable isotope standards

Current diagnostic tests to detect disorders of fatty acids metabolism, such as long-chain hydroxyacyl CoA dehydrogenase deficiency (LCHAD), are hampered by insensitivity or a long delay time required for results. Children with LCHAD deficiency are known to excrete 3-hydroxydicarboxylic acids with chain lengths of 10-16 carbons, but a quantitative method to measure excretion of these potentially diagnostically important compounds has not been reported. We report synthetic schemes for synthesis of 3-hydroxydodecanedioic acid and a di-deuterated analog, suitable for use in a stable-isotope dilution mass spectrometric analytical approach. Evaluation of several common derivatization protocols to produce a volatile derivative for gas chromatography determined that trimethylsyl derivatives produced the best efficiency and stability. Positive-ion chemical ionization mass spectrometry provided the greatest yield of characteristic ions. These results indicate the basic reagents needed to develop sensitive and accurate 3-hydroxydodecanedioic acid measurements for diagnosis of LCHAD deficiency and other fatty acid oxidation disorders.

Genetic disorders of cholesterol biosynthesis in mice and humans

Over the past few years, the number of identified inborn errors of cholesterol biosynthesis has increased significantly. The first inborn error of cholesterol biosynthesis to be characterized, in the mid 1980s, was mevalonic aciduria. In 1993, Irons et al. ( 1 ) (M. Irons, E. R. Elias, G. Salen, G. S. Tint, and A. K. Batta, Lancet 341:1414, 1993) reported that Smith-Lemli-Opitz syndrome, a classic autosomal recessive malformation syndrome, was due to an inborn error of cholesterol biosynthesis. This was the first inborn error of postsqualene cholesterol biosynthesis to be identified, and subsequently additional inborn errors of postsqualene cholesterol biosynthesis have been characterized to various extent. To date, eight inborn errors of cholesterol metabolism have been described in human patients or in mutant mice. The enzymatic steps impaired in these inborn errors of metabolism include mevolonate kinase (mevalonic aciduria as well as hyperimmunoglobulinemia D and periodic fever syndrome), squalene synthase (Ss-/- mouse), 3beta-hydroxysteroid Delta14-reductase (hydrops-ectopic calcification-moth-eaten skeletal dysplasia), 3beta-hydroxysteroid dehydrogenase (CHILD syndrome, bare patches mouse, and striated mouse), 3beta-hydroxysteroid Delta8,Delta7-isomerase (X-linked dominant chondrodysplasia punctata type 2, CHILD syndrome, and tattered mouse), 3beta-hydroxysteroid Delta24-reductase (desmosterolosis) and 3beta-hydroxysteroid Delta7-reductase (RSH/Smith-Lemli-Opitz syndrome and Dhcr7-/- mouse). Identification of the genetic and biochemical defects which give rise to these syndromes has provided the first step in understanding the pathophysiological processes which underlie these malformation syndromes.

Identification of undescribed medium-chain acylcarnitines present in urine of patients with propionic and methylmalonic acidemias

In urine of patients with propionyl-CoA carboxylase deficiency or with methylmalonic acidemia, carnitine esters of 2-methyl-branched fatty acids of all chain lengths between 4 and 9 atoms of carbon were identified during the acute phase of the diseases. The chemical structure of these compounds was obtained by gas chromatography-mass spectrometry analysis of their fatty acid moieties in their free and picolinyl ester forms. We suggest mechanisms for the biosynthesis of these branched fatty acids, and their accumulation in urine during episodes of caloric imbalance.

Unique electroencephalographic change of acute encephalopathy in glutaric aciduria type 1

We report the peculiar serial electroencephalographic (EEG) findings in a 7-year-old boy with glutaric aciduria type 1 during an episode of acute encephalopathy. The patient developed Reye-like syndrome triggered by cellulitis. Cranial magnetic resonance imaging demonstrated diffuse softening of cerebral hemisphere. The EEG on the day following onset of acute encephalopathy showed suppression burst pattern including continuous 14-15 Hz rhythmic waves at first. Then, periodic synchronous discharge appeared and lasted for about 40 minutes. Periodic synchronous discharge finally disappeared and nearly total electrocerebral silence continued. There have been no reports indicating such a change of EEG in a short period. The serial EEG changes probably reflect the process of electrical death of neurons in cerebral hemispheres.

High cognitive outcome in an adolescent with mut- methylmalonic acidemia

Methylmalonic acidemia is an inborn error of metabolism known to be a cause of ketoacidosis and mental retardation. The less severe mut(-) form of the disorder, however, has been described with only mild to moderate cognitive deficits or, rarely, with normal neurodevelopment in asymptomatic cases. Nevertheless, there has been no detailed documentation of long-term neuropsychological function in the mut(-) form and relatively few IQ scores. We performed longitudinal developmental and neuropsychological assessments on a girl with symptomatic mut(-) methylmalonic acidemia whose biochemical abnormalities were in the moderately severe range and who had had recurrent episodes of ketoacidosis. At almost 12 years of age, her full scale IQ on the Wechsler Intelligence Scale, third edition, was 129 with very superior and superior scores on nonverbal and verbal skills, respectively. On the National Achievement Test she scored above the 99th percentile in the Basic Battery and is considered to be a gifted student. This outcome suggests that the spectrum of cognitive attainment in mut(-) methylmalonic acidemia is wide and that even a moderate degree of biochemical severity with ketoacidotic episodes may not result in cognitive deficit. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:192-195, 2000.

Quantitative analysis of urinary acylglycines for the diagnosis of beta-oxidation defects using GC-NCI-MS

The analysis of acylglycines is an important biochemical tool for the diagnosis of inherited disorders of mitochondrial fatty acid beta-oxidation. A stable isotope dilution gas chromatography negative chemical ionisation mass spectrometry method for the quantitative analysis of short- and medium-chain acylglycines as their bis(trifluoromethyl)benzyl (BTFMB) ester derivatives is described. The diagnostic usefulness of the method was demonstrated in nine patients with medium-chain acyl-coenzyme A (CoA) dehydrogenase (MCAD) deficiency, and seven patients with multiple acyl-CoA dehydrogenation defect (MAD). The urinary acylglycine profiles in these patients were compared to those in controls (n = 19), children on a medium-chain triglyceride (MCT) supplemented diet (n = 4), and patients with various other diseases (n = 5).

Dietary management of long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHADD). A case report and survey

Current dietary management of long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD; long-chain-(S)-3-hydroxyacyl-CoA:NAD+ oxido-reductase, EC 1.1.1.211) deficiency (LCHADD) is based on avoiding fasting, and minimizing energy production from long-chain fatty acids. We report the effects of various dietary manipulations on plasma and urinary laboratory values in a child with LCHADD. In our patient, a diet restricted to 9% of total energy from long-chain fatty acids and administration of 1.5 g medium-chain triglyceride oil per kg body weight normalized plasma acylcarnitine and lactate levels, but dicarboxylic acid excretion remained approximately ten times normal. Plasma docosahexaenoic acid (DHA, 22:6n-3) was consistently low over a 2-year period; DHA deficiency may be related to the development of pigmentary retinopathy seen in this patient population. We also conducted a survey of metabolic physicians who treat children with LCHADD to determine current dietary interventions employed and the effects of these interventions on symptoms of this disease. Survey results indicate that a diet low in long-chain fatty acids, supplemented with medium-chain triclyceride oil, decreased the incidence of hypoketotic hypoglycaemia, and improved hypotonia, hepatomegaly, cardiomyopathy, and lactic acidosis. However, dietary treatment did not appear to effect peripheral neuropathy, pigmentary retinopathy or myoglobinuria.

Molecular basis of hepatic carnitine palmitoyltransferase I deficiency

Mitochondrial fatty acid beta-oxidation is important for energy production, which is stressed by the different defects found in this pathway. Most of the enzyme deficiencies causing these defects are well characterized at both the protein and genomic levels. One exception is carnitine palmitoyltransferase I (CPT I) deficiency, of which until now no mutations have been reported although the defect is enzymatically well characterized. CPT I is the key enzyme in the carnitine-dependent transport across the mitochondrial inner membrane and its deficiency results in a decreased rate of fatty acid beta-oxidation. Here we report the first delineation of the molecular basis of hepatic CPT I deficiency in a new case. cDNA analysis revealed that this patient was homozygous for a missense mutation (D454G). The effect of the identified mutation was investigated by heterologous expression in yeast. The expressed mutant CPT IA displayed only 2% of the activity of the expressed wild-type CPT IA, indicating that the D454G mutation is the disease-causing mutation. Furthermore, in patient's fibroblasts the CPT IA protein was markedly reduced on immunoblot, suggesting that the mutation renders the protein unstable.

Proton NMR spectroscopic analysis of multiple acyl-CoA dehydrogenase deficiency--capacity of the choline oxidation pathway for methylation in vivo

Proton NMR spectra of urine from subjects with multiple acyl-CoA dehydrogenase deficiency, caused by defects in either the electron transport flavoprotein or electron transport flavoprotein ubiquinone oxidoreductase, provide a characteristic and possibly diagnostic metabolite profile. The detection of dimethylglycine and sarcosine, intermediates in the oxidative degradation of choline, should discriminate between multiple acyl-CoA dehydrogenase deficiency and related disorders involving fatty acid oxidation. The excretion rates of betaine, dimethylglycine (and sarcosine) in these subjects give an estimate of the minimum rates of both choline oxidation and methyl group release from betaine and reveal that the latter is comparable with the calculated total body methyl requirement in the human infant even when choline intake is very low. Our results provide a new insight into the rates of in vivo methylation in early human development.

A new case of malonyl coenzyme A decarboxylase deficiency presenting with cardiomyopathy

A new case of mitochondrial malonyl coenzyme A decarboxylase deficiency is described. The patient presented with an initial episode of metabolic acidosis, seizures, hypoglycemia, and cardiac failure at 2 months of age which slowly resolved. Subsequent evaluations at 4 years of age for developmental delay revealed a prominent elevation of malonic acid in urine. Malonyl carnitine was also elevated. The activity of Malonyl CoA decarboxylase in cultured fibroblasts was 7% of normal.

CONCLUSION

Malonyl CoA decarboxylase deficiency may result in inhibition of fatty acid oxidation, which may account for the cardiomyopathy.

Abnormal bile acids in the Smith-Lemli-Opitz syndrome

The urinary bile acids from four patients with Smith-Lemli-Opitz (SLO) syndrome were analyzed by continuous flow fast atom bombardment mass spectrometry. Two types of abnormalities were noted: (1) a deficiency of normal bile acids (cholenoates) and (2) the presence of abnormal species postulated to be cholenoates and cholestenoates. The finding of abnormal urinary bile acids in children with SLO syndrome led to further investigation of the cholesterol metabolic pathway and to the delineation of a new inborn error of metabolism, deficient conversion of 7-dehydrocholesterol to cholesterol [Irons et al., 1993]. The abnormalities of urinary bile acids, if confirmed by further structural analyses and studies of additional patients, provide an explanation for various aspects of the gastro-intestinal abnormalities and growth retardation noted in SLO syndrome and suggest that exogenous bile acid replacement may play an important role in the therapy of patients with this syndrome.

Determination of orotic acid in urine

Orotic acid was separated from other urinary constituents by ion-pair formation with tetrabutylammonium, and isocratic elution from a reversed-phase column. Absorbance at 280 nm was recorded for quantitation. Owing to the better column characteristics the separations are somewhat faster, and the sensitivity of the method is higher than those of analogous methods using anion-exchange columns. The method was used for the determination of orotic acid in human urine, in urine of rats with portacaval shunts and in small (30 microliters) urine samples from sparse fur mice. Shunted rats excreted ca. 100% more orotic acid per 24 h than sham-operated controls, in spite of their considerably lower body weight. Excessive orotic acid in urine indicates a conditional deficiency of ornithine. Sparse fur mice are congenitally hyperammonemic because of a defective hepatic ornithine carbamoyltransferase. Determination of orotic acid in the urine is a suitable method to identify those animals among litter mates which have the hereditary enzyme defect.

A new case of short-chain acyl-CoA dehydrogenase deficiency with isolated ethylmalonic aciduria

A 28-month-old Turkish girl presented with recurrent bronchopneumonia and severe muscular hypotonia. Urinary excretion of ethylmalonic acid was persistently elevated, methylsuccinate appearing only in stress situations. Studies in cultured fibroblasts showed a deficiency of short-chain acyl-CoA dehydrogenase.

Determination of acylcarnitines in urine of patients with inborn errors of metabolism using high-performance liquid chromatography after derivatization with 4'-bromophenacylbromide

A high-performance liquid chromatographic method is presented for the determination of urinary acylcarnitines. After solid phase extraction on silica columns the acylcarnitines are converted to 4'-bromophenacyl esters with 4'-bromophenacylbromide in the presence of N,N-diisopropylethylamine. Complete derivatization was achieved at 37 degrees C within 30 min. The 4'-bromophenacyl esters were separated by high-performance liquid chromatography on a Hypersil BDS C8 reversed-phase column with a binary gradient containing varying proportions of acetonitrile, water and 0.1 M triethylamine phosphate buffer. Essentially baseline separation was obtained with a standard mixture containing 4'-bromophenacyl esters of carnitine and synthetic acylcarnitines of increasing chain length ranging from acetyl- to palmitoylcarnitine. The method was used to obtain urinary acylcarnitine profiles from patients with propionic, methylmalonic and isovaleric acidemia and with medium-chain and multiple acyl-CoA dehydrogenase deficiency. Quantification of the acylcarnitines was achieved using undecanoylcarnitine as internal standard.

3-Hydroxydicarboxylic and 3-ketodicarboxylic aciduria in three patients: evidence for a new defect in fatty acid oxidation at the level of 3-ketoacyl-CoA thiolase

Three patients presented with evidence of a fatty acid oxidation disorder. Analysis of urinary organic acids by gas chromatography/mass spectrometry demonstrated the presence of medium-chain (C6-C12) dicarboxylic, 3-hydroxydicarboxylic, and 3-ketodicarboxylic acids in all three urines. 3-Ketodicarboxylic aciduria is reported for the first time here, as are the mass spectra for 3-ketosuberic, 3-ketosebacic, and 3-ketododecanedioic acids and the oximated spectrum for 3-ketoadipic acid. The presence of 3-ketodicarboxylic acids suggests a defect at the level of a long-chain 3-ketoacyl-CoA thiolase, an enzyme for which a deficiency state has not previously been described. Our patients may represent the first cases of a long-chain thiolase defect.

Urinary medium-chain acylcarnitines in medium-chain acyl-CoA dehydrogenase deficiency, medium-chain triglyceride feeding and valproic acid therapy: sensitivity and specificity of the radioisotopic exchange/high performance liquid chromatography method

To determine the sensitivity and specificity of detecting urinary medium-chain acylcarnitines for the diagnosis of MCAD deficiency, 114 urine specimens from 75 children with metabolic diseases and controls were analyzed in a blinded fashion using a radioisotopic exchange/HPLC method. All 47 patients with MCAD deficiency were correctly diagnosed using the criterion hexanoylcarnitine or octanoylcarnitine peak areas larger than those of other medium-chain acylcarnitines. The majority of them were tested during the asymptomatic state without L-carnitine loading. Four patients with other defects of fatty acid oxidation and three patients receiving valproic acid had a similar acylcarnitine excretion pattern. To further examine the specificity of the method, eight infants receiving a diet enriched with medium-chain triglycerides and 13 additional patients receiving valproic acid were studied. Most of these also tested positive for MCAD deficiency by the above criterion. Analysis by a new gas chromatographic-mass spectrometric procedure revealed that octanoylcarnitine, not valproylcarnitine, was the most abundant medium-chain carnitine ester excreted by a patient treated with valproic acid. Quantitation of urinary hexanoylcarnitine and octanoylcarnitine showed considerable overlap among patients with MCAD deficiency and those receiving valproic acid or a medium-chain triglyceride-enriched diet. MCAD deficiency can be reliably detected in urine specimens by this method without the need for prior carnitine loading. However, other defects in fatty acid oxidation must be differentiated from MCAD deficiency, and a history of medium-chain triglyceride or valproic acid administration must be considered if the diagnosis of MCAD deficiency is sought through analysis of urinary acylcarnitines.

Analysis of acylcarnitines as their N-demethylated ester derivatives by gas chromatography-chemical ionization mass spectrometry

A novel approach to the analysis of acylcarnitines has been developed. It involves a direct esterification using propyl chloroformate in aqueous propanol followed by ion-pair extraction with potassium iodide into chloroform and subsequent on-column N-demethylation of the resulting acylcarnitine propyl ester iodides. The products, acyl N-demethylcarnitine propyl esters, are volatile and are easily analyzed by gas chromatography-chemical ionization mass spectrometry. For medium-chain-length (C4-C12) acylcarnitine standards, detection limits are demonstrated to be well below 1 ng starting material using selected ion monitoring. Well-separated gas chromatographic peaks and structure-specific mass spectra are obtained with samples of synthetic and biological origin. Seven acylcarnitines have been characterized in the urine of a patient suffering from medium-chain acyl-CoA dehydrogenase deficiency.

Abnormal urinary excretion of unsaturated dicarboxylic acids in patients with medium-chain acyl-CoA dehydrogenase deficiency

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is the most frequently described metabolic disorder of fatty acid oxidation in humans. Acute episodes are usually characterized biochemically by the appearance of nonketotic dicarboxylic aciduria. In addition, other abnormal metabolites, such as suberylglycine, n-hexanoylglycine, 3-phenylpropionylglycine, and octanoylcarnitine, are excreted in the urine. Urinary organic acids were determined using dual capillary column gas-liquid chromatography and gas-liquid chromatography/mass spectrometry. In three cases of MCAD deficiency we observed a disproportionate increase in the excretion of unsaturated dicarboxylic acids compared to either fasting control children with expected ketotic dicarboxylic aciduria or patients with nonketotic dicarboxylic aciduria not associated with MCAD deficiency. The most significant increase was in the urinary excretion of cis-4-decendioic acid. Additionally, the urinary excretions of cis-3-octenedioic and cis-5-decenedioic acids were slightly decreased whereas the excretion of cis-5-dodecenedioic acid was increased. These data are consistent with the notion that as a result of MCAD deficiency the metabolic oxidation of unsaturated fatty acids such as linoleate and oleate is inhibited more than saturated fatty acids.

Urinary sediment in storage diseases: differential diagnosis of Nieman-Pick disease by cytologic means

Renal involvement in lipid storage diseases is well recognized. Electron microscopy or chemical analysis of urinary sediment has been used for the diagnosis of these diseases. Urine cytology, supplemented by cytochemistry, polarization, and autofluorescence, helped us in the diagnosis of Niemann-Pick disease in an infant. The unique findings are described, and the differential diagnosis of storage cells by cytochemical stains is discussed.

Short-chain acyl-coenzyme A dehydrogenase deficiency. Clinical and biochemical studies in two patients

We describe two patients with short-chain acyl-coenzyme A (CoA) dehydrogenase (SCADH) deficiency. Neonate I excreted large amounts of ethylmalonate and methylsuccinate; ethylmalonate excretion increased after a medium-chain triglyceride load. Neonate II died postnatally and excreted ethylmalonate, butyrate, 3-hydroxybutyrate, adipate, and lactate. Both neonates' fibroblasts catabolized [1-14C]butyrate poorly (29-64% of control). Neonate I had moderately decreased [1-14C]octanoate catabolism (43-60% of control), while neonate II oxidized this substrate normally; both catabolized radiolabeled palmitate, succinate, and/or leucine normally. Cell sonicates from neonates I and II dehydrogenated [2,3-3H]butyryl-CoA poorly (41 and 53% of control) and [2,3-3H]octanoyl-CoA more effectively (59 and 95% of control). Mitochondrial acyl-CoA dehydrogenase (ADH) activities with butyryl- and octanoyl-CoAs were 37 and 56% of control in neonate I, and 47 and 81% of control in neonate II, respectively. Monospecific medium-chain ADH (MCADH) antisera inhibited MCADH activity towards both butyryl- and octanoyl-CoAs, revealing SCADH activities to be 1 and 11% of control for neonates I and II, respectively. Fibroblast SCADH and MCADH activities were normal in an adult female with muscular SCADH deficiency.

Spin-echo and 2-dimensional 1H nuclear magnetic resonance studies on urinary metabolites from patients with 2-methylacetoacetyl CoA thiolase deficiency

Spin-echo 1H nuclear magnetic resonance (nmr) spectra of urine from two unrelated patients with 3-oxoacylthiolase deficiency are presented. The metabolite profile revealed by these spectra is probably of diagnostic value. Two of the major abnormal metabolites known to accumulate in this disorder (tiglylglycine and 2-methyl-3-hydroxybutyrate) can both be detected in the spectra. The technique offers the advantage over combined gas chromatography/mass spectrometry that no pre-treatment of the sample is required and that the data can be obtained in less than 2 min. In addition 2-dimensional nmr techniques (J-resolved and chemical shift correlated) were used to further characterise the spectra. This allowed assignment of resonances which could not be detected in the spin-echo spectra, in particular 2-methylacetoacetate and butanone, which are known to accumulate in this disease.

Evaluation of urinary cells in acid cholesteryl ester hydrolase deficiency

Deficiency in the lysosomal enzyme responsible for cholesteryl ester hydrolysis, acid cholesteryl ester hydrolase (E.C. 3.1.1.13), leads to two clinically recognized diseases: Wolman disease and cholesteryl ester storage including leukocytes, fibroblasts and liver. Analysis of urinary sediment from well characterized cases of Wolman disease and CESD also revealed the shedding of lipid enriched renal tubular cells. Morphologic, enzymic and lipid compositional studies of these cells indicate that the enzyme deficiency observed in fibroblasts and leukocytes from these individuals are reflected in these cells shed in the urine. These findings in renal tubular cells confirm and extend those made in other cell types. These studies indicate that analysis of urinary sediment in suspected cases of acid cholesteryl ester deficiency may provide a meaningful approach for monitoring therapeutic attempts involving enzyme infusion and gene therapy.

Octanoylglucuronide excretion in patients with a defective oxidation of medium-chain fatty acids

Octanoyl-beta-D-glucuronide was identified in the urine of five patients with hypoketotic hypoglycemia and dicarboxylic aciduria due to a defective beta-oxidation of medium-chain fatty acids. Two subjects who ingested large amounts of medium-chain triglycerides also excreted large amounts of the glucuronide. The substance was extracted from the urine with ethyl acetate and analyzed by: (1) gas chromatography/mass spectrometry (GC-MS) of the trimethylsilyl derivative and (2) preparative one-dimensional thin-layer chromatography followed by enzymatic hydrolysis with beta-glucuronidase and again GC-MS. A quantitative analysis was performed indirectly by measuring the urinary bound octanoate after the removal of octanoylcarnitine. Octanoylglucuronide represents an additional mechanism for the detoxification of octanoate; its formation may be of help for the maintenance of carnitine homeostasis in patients with medium-chain acyl-CoA dehydrogenase deficiency.

Compilation of gas chromatographic retention indices of 163 metabolically important organic acids, and their use in detection of patients with organic acidurias

Gas chromatographic retention indices have been compiled for 163 metabolically important compounds (mostly organic acids) in the form of methylene units, as trimethylsilyl derivatives, on 10% OV-1 and 10% OV-17 columns. Comprehensive references on metabolic diseases that can be diagnosed by detection of these metabolites are cross-indexed to facilitate the use of the methylene-unit list. The gas chromatographic method, which utilizes extraction of urine with ethyl acetate and trimethylsilylations, is described. Modified methods, one for neutral compounds and one for highly polar organic acids, both of which utilize appropriate ion exchange and lyophilization, are also described. Practical applications of these methods and the use of the methylene-unit in the diagnosis of eleven patients with various metabolic disorders are also shown.

Structure of the side chain of the C29 dicarboxylic bile acid occurring in infants with coprostanic acidemia

The structure of the side chain of the 3 alpha, 7 alpha, 12 alpha-trihydroxy-5 beta-C29 dicarboxylic bile acid occurring in body fluids of infants with coprostanic acidemia was investigated by means of mass spectrometry and nuclear magnetic resonance spectroscopy. The findings identified this bile acid as 3 alpha, 7 alpha, 12 alpha-trihydroxy-27a, 27b-dihomo-5 beta-cholestane-26,27b-dioic acid (3 alpha, 7 alpha, 12 alpha-trihydroxy-27-carboxymethyl-5 beta-cholestan-26-oic acid).

Urinary levels of blood group A trisaccharide: observations in two siblings with neuronal ceroid lipofuscinosis

A readily detectable carbohydrate in the urine of two siblings with neuronal ceroid lipofuscinosis was found to be the blood group A trisaccharide. One child expired before blood typing was done while the other sibling was AB. This latter child excreted greater amounts of the trisaccharide than a group of blood type A subjects with different diagnoses when all the subjects were receiving whole or skim milk by nasogastric feedings. While the relevance of this observation to neuronal ceroid lipofuscinosis is unknown, it has been shown that the trisaccharide may be a major urinary carbohydrate depending on diet and blood type.

Non-ketotic C6-C10-dicarboxylic aciduria: biochemical investigations of two cases

Two boys, who are not related, with hypoglycemia and C6-C10-dicarboxylic aciduria were investigated. Besides substantial amounts of adipic, suberic and sebacic acids, the urinary metabolic profile of organic acids contained 5-OH-caproic acid and caproylglycine. During acute attacks the concentrations of adipic, suberic and sebacic acids were 300--530, 160--200 and 35--200 micrograms/mg creatinine, respectively, and the excretions of 5-OH-caproic acid and caproylglycine were 75--330 and 41--260 micrograms/mg creatinine, respectively. It is argued that the biosynthesis of adipic acid passes through an omega-oxidation, that the production of 5-OH-caproic acid is caused by an omega-1-oxidation, and that caproylglycine formation passes through a glycine-N-acylase catalysed conjugation of accumulated caproic acid in the patients. Suberic acid and sebacic acid are in the same way omega-oxidation products of accumulated caprylic acid and capric acid, respectively. From the excretion pattern presented it is hypothesized that the patients suffer from a defect in the dehydrogenation of fatty acids in the beta-oxidation pathway. The biological significance of the findings is discussed.

Simultaneous estimation of urinary steroids by semi-automated gas chromatography. Investigation of neo-natal infants and children with abnormal steroid synthesis

Development of a method for multicomponent analysis of urinary steroids on open-tubular columns is described. The urinary steroid conjugates were hydrolysed enzymatically, extracted on Amberlite XAD-2 columns, purified on columns of Sephadex LH-20, then analysed as methyloxime trimethylsilyl ethers on a gas chromatograph on which up to 24 samples may be automatically injected. All major urinary steroids from 17-oxosteroids to cortisol metabolites were analysed and these were quantified relative to internal standards, 5alpha-androstane-3alpha, 17alpha-diol and cholesteryl butyrate added to the samples prior to derivatisation. The precision of the full technique and reproducibility of repetitive automatic solid injection was found to be acceptable for the purpose of profile analysis. Examples of urinary steroid profiles in normal infants and infants with disorders of adrenal steroid production and excretion are given.