Long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency

Exercise testing and prescription in patients with inborn errors of muscle energy metabolism

Skeletal muscle is a dynamic organ requiring tight regulation of energy metabolism in order to provide bursts of energy for effective function. Several inborn errors of muscle energy metabolism (IEMEM) affect skeletal muscle function and therefore the ability to initiate and sustain physical activity. Exercise testing can be valuable in supporting diagnosis, however its use remains limited due to the inconsistency in data to inform its application in IEMEM populations. While exercise testing is often used in adults with IEMEM, its use in children is far more limited. Once a physiological limitation has been identified and the aetiology defined, habitual exercise can assist with improving functional capacity, with reports supporting favourable adaptations in adult patients with IEMEM. Despite the potential benefits of structured exercise programs, data in paediatric populations remain limited. This review will focus on the utilisation and limitations of exercise testing and prescription for both adults and children, in the management of McArdle Disease, long chain fatty acid oxidation disorders, and primary mitochondrial myopathies.

Characterization of Chorioretinopathy Associated with Mitochondrial Trifunctional Protein Disorders: Long-Term Follow-up of 21 Cases

PURPOSE

To assess long-term effects of genotype on chorioretinopathy severity in patients with mitochondrial trifunctional protein (MTP) disorders.

DESIGN

Retrospective case series.

PARTICIPANTS

Consecutive patients with MTP disorders evaluated at a single center from 1994 through 2015, including 18 patients with long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHADD) and 3 patients with trifunctional protein deficiency (TFPD).

METHODS

Local records from all visits were reviewed. Every participant underwent a complete ophthalmic examination and was evaluated by a metabolic physician and dietitian. Nine patients underwent ancillary funduscopic imaging including optical coherence tomography (OCT) and OCT angiography.

MAIN OUTCOME MEASURES

The primary outcome measure was best-corrected visual acuity at the final visit. Secondary outcome measures included spherical equivalent refraction, visual fields, electroretinography B-wave amplitudes, and qualitative imaging findings.

RESULTS

Participants were followed up for a median of 5.6 years (range 0.3-20.2 years). The median age of LCHADD participants at initial and final visits was 2.3 and 11.9 years, whereas that for TFPD participants at initial and final visits was 4.7 and 15.5 years, respectively. Four long-term survivors older than 16 years were included (3 with LCHADD and 1 with TFPD). The LCHADD participants demonstrated a steady decline in visual acuity from an average of 0.23 logarithm of the minimum angle of resolution (logMAR; Snellen equivalent, 20/34) at baseline to 0.42 logMAR (Snellen equivalent, 20/53) at the final visit, whereas TFPD patients maintained excellent acuity throughout follow-up. Participants with LCHADD, but not TFPD, showed an increasing myopia with a mean decrease in spherical equivalent refraction of 0.24 diopters per year. Visual fields showed sensitivity losses centrally associated with defects on OCT. Multimodal imaging demonstrated progressive atrophy of the outer retina in LCHADD, often preceded by the formation of outer retinal tubulations and choriocapillaris dropout. Electroretinography findings support the more severe clinical profile of LCHADD patients compared with TFPD patients; the function of both rods and cones are attenuated diffusely in LCHADD patients, but are within normal limits for TFPD patients.

CONCLUSIONS

Despite improved survival with early diagnosis, medical management, and dietary treatment, participants with the LCHADD subtype of MTP disorder continue to demonstrate visually disabling chorioretinopathy. Multimodal imaging is most consistent with choriocapillaris loss exceeding photoreceptor loss.

Ocular characteristics in 10 children with long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency: a cross-sectional study with long-term follow-up

PURPOSE

To present long-term ocular complications and electroretinographic (ERG) findings in children with long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency - a life-threatening metabolic disease - and the relation to age at diagnosis, treatment and other clinical parameters.

METHODS

Ten children with LCHAD deficiency underwent repeated ophthalmological evaluations including ERG.

RESULTS

All 10 children developed chorioretinal pathology. Regardless of age at diagnosis, initiation of treatment and age at examination, inter-individual differences were present. Profound chorioretinal atrophy, severe visual impairment and progressive myopia had developed in two teenagers. Milder chorioretinopathy with or without subnormal visual acuity was present in all other children. ERG was pathological in seven children. The chorioretinopathy often started in the peripapillary or perimacular areas. In one patient, unilateral visual impairment was associated with fibrosis.

CONCLUSION

Early diagnosis and adequate therapy might delay but not prevent the progression of retinal complications. Late diagnosis with severe symptoms at diagnosis, neonatal hypoglycaemia and frequent decompensations may increase the progression rate of the chorioretinopathy. LCHAD deficiency, a potentially lethal disease, is sometimes difficult to diagnose. Unusual chorioretinal findings should alert the ophthalmologist to the long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency, especially if there is a history of neonatal hypoglycaemia or failure to thrive.

Long-chain L-3-hydroxyacyl-coenzyme a dehydrogenase deficiency: a molecular and biochemical review

Since the first report of long-chain L-3-hydroxyacyl-coenzyme A dehydrogenase deficiency a little more than a decade ago, its phenotypic and genotypic heterogeneity in individuals homozygous for the enzyme defect has become more and more evident. Even more interesting is its association with pregnancy-specific disorders, including preeclampsia, HELLP syndrome (hemolysis, elevated liver enzymes, low platelets), hyperemesis gravidarum, acute fatty liver of pregnancy, and maternal floor infarct of the placenta. In this review we discuss the biochemical and molecular basis, clinical features, diagnosis, and management of long-chain L-3-hydroxyacyl-coenzyme A dehydrogenase deficiency.

Long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency: clinical presentation and follow-up of 50 patients

OBJECTIVES

To assess the mode of presentation, biochemical abnormalities, clinical course, and effects of therapy in patients of long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency.

BACKGROUND

LCHAD deficiency is a rare, autosomal recessive inborn error of fatty acid oxidation. Although case reports and small series of patients have been published, these may not give a true picture of the clinical and biochemical spectrum associated with this disorder. To improve the early recognition and management of this potentially lethal disorder, we have reviewed a large cohort of LCHAD-deficient patients.

METHODS

A questionnaire was sent to the referring physicians of 61 unselected patients with LCHAD deficiency diagnosed in our center. The standardized questionnaire requested information about the clinical signs and symptoms at presentation, the clinical history, family history, pregnancy, biochemical parameters at presentation, treatment, and clinical outcome.

RESULTS

Questionnaires on 50 patients (82%) were returned and included in this study. The mean age of clinical presentation was 5.8 months (range: 1 day-26 months). Seven (15%) of the patients presented in the neonatal period. Thirty-nine patients (78%) presented with hypoketotic hypoglycemia, the classical features of a fatty acid oxidation disorder. Eleven patients (22%) presented with chronic problems, consisting of failure to thrive, feeding difficulties, cholestatic liver disease, and/or hypotonia. In retrospect, most (82%) of the patients presenting with an acute metabolic derangement also suffered from a combination of chronic nonspecific symptoms before the metabolic crises. Mortality in this series was high (38%), all dying before or within 3 months after diagnosis. Morbidity in the surviving patients is also high, with recurrent metabolic crises and muscle problems despite therapy.

CONCLUSIONS

LCHAD deficiency often presents with a combination of chronic nonspecific symptoms. Early diagnosis is difficult in the absence of the classical metabolic derangement. Survival can be improved by prompt diagnosis, but morbidity remains alarmingly high despite current therapeutic regimes.

Inborn errors of mitochondrial fatty acid oxidation

Inborn errors of the mitochondrial beta-oxidation of long-chain fatty acids represent an evolving field of inherited metabolic disease. Fatty acid oxidation defects demonstrate an abnormal response to the process of fasting adaptation and affect those tissues that utilize fatty acids as an energy source. These tissues include cardiac and skeletal muscle and liver. Muscle directly uses fatty acids as an energy source whilst hepatic metabolism of fatty acids is mostly directed toward the synthesis of ketone bodies for energy utilization by tissues such as brain. The clinical phenotypes of fatty acid oxidation disorders include disease of one or more of these fatty acid-metabolizing tissues. In this review, we provide an overview of the pathway, discuss the disorders that are well established, and describe recent advances in the field. Currently available diagnostic procedures are critically evaluated.

Ophthalmologic findings in long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency caused by the G1528C mutation: a new type of hereditary metabolic chorioretinopathy

OBJECTIVE

The purpose of the study was to determine the nature and course of ophthalmic abnormalities in long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency, a recently discovered disorder of mitochondrial fatty acid beta-oxidation.

STUDY DESIGN

The study design was a cohort (case series).

PARTICIPANTS

A retrospective review of the records of 15 children who had died during their first 2 years was performed. Also performed were a longitudinal reanalysis and cross-sectional clinical examination of four long-term survivors aged 5 to 31 years.

MAIN OUTCOME MEASURES

Visual acuity, refraction, visual fields, ophthalmoscopy, fluorescein angiography, biometry, corneal topography, electroretinography (ERG), visual-evoked potentials (VEPs), color vision, and dark adaptation were measured.

RESULTS

In seven children, ophthalmoscopic findings were within normal limits at 3 days to 13 months of age (median, 4.8 months). In 11 children, a granular retinal pigment epithelium (RPE), with or without pigment clumping in the macula, was seen at 4 months to 5 years of age (median, 9 months). Two long-term survivors, 16 and 31 years of age, eventually had circumscribed atrophy of the choroid, RPE, and retina, which coincided with a posterior staphyloma type 1. They had progressive axial myopia starting at 6 and 12 years of age and later paracentral scotomas leading to poor central vision. They suffered from early difficulty with mesopic vision, glare, and a severe generalized color vision deficiency that started as a tritanomaly. A third survivor was mildly myopic at 5 years of age. All four surviving patients had visually insignificant, flake-like supranuclear opacities in the lens. The ERG initially was normal but deteriorated during the first decade and later was unrecordable. The VEP responses remained fairly normal. Initially, angiography showed no blockade of the choroidal fluorescence because of the thin RPE. Filling of choroidal vessels was delayed, and the choriocapillaris and, later, larger choroidal vessels in the posterior pole became nonperfused.

CONCLUSIONS

In LCHAD deficiency, the fundus is normal at birth (stage 1). Soon, however, pigment dispersion occurs in the RPE (stage 2), followed by circumscribed chorioretinal atrophy, occlusion of choroidal vessels, and deterioration of central vision, often with relative sparing of the peripheral fundus (stage 3). Finally, posterior staphylomas and central scotomas may develop (stage 4). Developmental cataract, progressive myopia, and deterioration of visual fields and color vision are new findings in LCHAD deficiency. The chorioretinopathy and abnormal ERG precede the development of myopia and posterior staphyloma, which, in turn, coincide with the loss of macular vision. The authors postulate that the RPE or choriocapillaris is primarily affected. Awareness of the characteristic ocular features is important because of an opportunity for dietary treatment, genetic counseling, and prenatal diagnosis.

Retinal dystrophy in long chain 3-hydroxy-acyl-coA dehydrogenase deficiency

BACKGROUND

Long chain 3-hydroxyacyl-CoA-dehydrogenase (LCHAD) is one of the enzymes involved in the breakdown of fatty acids. A deficiency of this enzyme is associated with life threatening episodes of hypoketotic hypoglycaemia during prolonged fasting. Neuropathy and retinopigmentary changes were mentioned in only a few cases.

METHODS

The case histories of two girls, aged 8 and 15 years, with LCHAD deficiency are reported.

RESULTS

Both children with LCHAD deficiency exhibited extensive macular pigmentary depositions and a 'salt and pepper' scattering of pigment in their retinas. The patients have decreasing visual acuity.

CONCLUSION

The early recognition of LCHAD deficiency can increase the life expectancy in these patients through avoiding catabolism and through appropriate diets. Patients tend to be free of symptoms between attacks, however. Testing for the disorder, therefore, should be included in the diagnostic process for children with retinal dystrophy, in particular when other clinical symptoms are known to have occurred.

Stability of long-chain and short-chain 3-hydroxyacyl-CoA dehydrogenase activity in postmortem liver

Inherited enzyme defects in mitochondrial fatty acid oxidation (FAO) are associated with acute metabolic crisis and sudden death. Necropsy findings may be subtle, yielding no diagnosis and precluding genetic counseling. Preliminary identification of an FAO disorder requires the use of sophisticated tools (e.g., GC/MS) and specific body fluids, and the diagnosis rests on molecular analysis or enzyme assay. At present, confirmation of long-chain or short-chain 3-hydroxyacyl-CoA dehydrogenase deficiency relies on measurement of enzyme activity. Here, we report our examination of the effect of storage temperature (25, 4, −20, and −70 °C) and the postmortem interval on enzyme activities in rat and human liver. Enzyme activity decreases 50% in 30 h in samples stored at 25 °C, whereas 55 h at 4 °C is required to reach this value; freezing minimizes this loss. Regardless of rate of degradation, however, the short-chain to long-chain activity ratio remains constant—which should make it possible to differentiate postmortem degradation from enzyme deficiency.

Long-chain 3-hydroxyacyl-coenzyme A dehydrogenase deficiency with the G1528C mutation: clinical presentation of thirteen patients

Long-chain 3-hydroxyacyl-coenzyme A (CoA) dehydrogenase is one of three enzyme activities of the mitochondrial trifunctional protein. We report the clinical findings of 13 patients with long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency. At presentation the patients had had hypoglycemia, cardiomyopathy, muscle hypotonia, and hepatomegaly during the first 2 years of life. Seven patients had recurrent metabolic crises, and six patients had a steadily progressive course. Two patients had cholestatic liver disease, which is uncommon in beta-oxidation defects. One patient had peripheral neuropathy, and six patients had retinopathy with focal pigmentary aggregations or retinal hypopigmentation. All patients were homozygous for the common mutation G1528C. However, the enoyl-CoA hydratase and 3-ketoacyl-CoA thiolase activities of the mitochondrial trifunctional protein were variably decreased in skin fibroblasts. Dicarboxylic aciduria was detected in 9 of 10 patients, and most patients had lactic acidosis, increased serum creatine kinase activities, and low serum carnitine concentration. Neuroradiologically there was bilateral periventricular or focal cortical lesions in three patients, and brain atrophy in one. Only one patient, who has had dietary treatment for 9 years, is alive at the age of 14 years; all others died before they were 2 years of age. Recognition of the clinical features of long-chain 3-hydroxyacyl-CoA deficiency is important for the early institution of dietary management, which may alter the otherwise invariably poor prognosis.

Trifunctional enzyme deficiency: adult presentation of a usually fatal beta-oxidation defect

Disorders of mitochondrial fatty acid oxidation are a common cause of exercise-induced rhabdomyolysis and myoglobinuria. We report three adult patients from a family with symptoms of recurrent exercise-induced rhabdomyolysis. This presentation closely resembles adult-type carnitine palmitoyltransferase II deficiency except that these patients had an associated peripheral neuropathy. Investigation of fatty acid oxidation in the patients revealed a deficiency of the mitochondrial trifunctional enzyme of beta-oxidation, a newly described fatty acid oxidation disorder with multiorgan involvement and a usually fatal outcome in early childhood. Our cases therefore represent a new phenotype of the disease, which is characterized by recurrent rhabdomyolysis and peripheral neuropathy, but without involvement of other organs, and which is associated with prolonged survival beyond the fourth decade. A low-fat/high-carbohydrate diet proved beneficial in one of the patients, drastically reducing the frequency of rhabdomyolytic episodes. Our findings suggest that mitochondrial trifunctional enzyme deficiency should be considered in patients with recurrent episodes of myoglobinuria and peripheral neuropathy presenting in later life.

Common missense mutation G1528C in long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency. Characterization and expression of the mutant protein, mutation analysis on genomic DNA and chromosomal localization of the mitochondrial trifunctional protein alpha subunit gene

Mitochondrial trifunctional protein (MTP) is a recently identified enzyme involved in mitochondrial beta-oxidation, harboring long-chain enoyl-CoA hydratase, long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) and long-chain 3-ketothiolase activity. A deficiency of this protein is associated with impaired oxidation of long-chain fatty acids which can lead to sudden infant death. Furthermore, it is clear that this inborn error of fatty acid oxidation is very frequent, second to medium chain acyl-CoA dehydrogenase deficiency. In most patients only the LCHAD activity of MTP is deficient with near normal activity of the two other enzyme activities of the complex. We recently described the occurrence of a frequent G1528C mutation in the cDNA coding for the a subunit of MTP. Using S. cerevisiae for expression of wild type and mutant protein we show that the G1528C mutation is directly responsible for the loss of LCHAD activity. Furthermore, we describe a newly developed method allowing identification of the G1528C mutation in genomic DNA. The finding of an 87% allele frequency of the G1528C mutation in 34 LCHAD deficient patients makes this a valuable test for prenatal diagnosis. Finally, we show that the gene encoding the alpha subunit of MTP is located on chromosome 2p24.1-23.3.

The clinical spectrum of long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency

Four patients with long-chain 3-hydroxyacyl-coenzyme A dehydrogenase deficiency are presented. Clinical onset in the form of acute encephalopathy occurred between the ages of 9 months and 3 years. The clinical course included recurrent metabolic crises in 4 patients, cardiac involvement and retinopathy in 3, and myopathy in 2. None had signs of peripheral neuropathy. Three patients died and one is currently well. Hypoketotic hypoglycemia with C6-C14 3-hydroxy-dicarboxylic aciduria during metabolic crises associated with decreased plasma carnitine levels was the main biochemical finding. Enzymologic studies disclosed long-chain 3-hydroxyacyl-coenzyme A dehydrogenase deficiency in all patients. Homozygosity for a G to C mutation at position 1528 in the encoding region of the enzyme was found in 2 patients. Histologic and electron microscopic studies of liver biopsy specimens revealed steatosis in 3 patients and mitochondrial abnormalities in 2. Skeletal muscle biopsies disclosed nonspecific degenerative changes in 2 patients and were normal in the remaining 2. Ultrastructural abnormalities in mitochondria were found in 3 patients. A review of the literature combined with the data from our series (total 22 patients) disclosed acute clinical onset in 77% of cases and subacute in 23%. In the combined series, the average age at onset was 11 months, family history was positive in 32% of patients and overall mortality was 50%. We describe the clinical spectrum of this disease and emphasize that, among patients with suspected beta-oxidation defects the finding of pigmentary retinopathy should lead to the suspicion of long-chain 3-hydroxyacyl-coenzyme A-dehydrogenase deficiency.

Clinical and neurophysiologic response of myopathy and neuropathy in long-chain L-3-hydroxyacyl-CoA dehydrogenase deficiency to oral prednisone

The purpose of this study was to evaluate the clinical and neurophysiologic responses to oral prednisone therapy in a boy with enzymatically confirmed long-chain L-3-hydroxyacyl-CoA dehydrogenase deficiency in biopsied muscle and cultured skin fibroblasts. This boy presented with progressive limb girdle myopathy, recurrent myoglobinuria, peripheral sensorimotor axonopathy, and intraventricular conduction delays. Prior to prednisone therapy, at age 8 years, he exhibited marked distal weakness greater than proximal weakness with a waddling and high-steppage gait, Gowers' maneuver (10 s to rise from the floor), fatigue after 3-20 yards of walking and the ability to climb only 2 stairs. Serum levels of creatine kinase rose from 34 to 4,124 U/L following mild exertion. Nerve conduction studies revealed progressive axonopathy with secondary demyelination. Four weeks after initiation of oral prednisone (0.75 mg/kg/day) therapy, there was approximately a 100% increase in power and endurance. He was able to walk at least 100 yards before tiring, could rise from sitting on the floor in 3-4 s, and was able to climb 20 steps in 30 s. There was concurrent improvement in nerve conduction studies. Prednisone was gradually withdrawn over the next 4 months to 0.19 mg/kg/day; lower doses of 0.08 mg/kg/day resulted in a marked deterioration in power to the prior state. Although 0.19 mg/kg/day did not maintain the peak power achieved at 0.75 mg/kg/day, it provided adequate baseline power and endurance. It is concluded that there was a significant clinical and neurophysiologic response to prednisone at a dosage > or = 0.16 mg/kg/day. Prednisone may stabilize muscle and neuronal plasma membranes, as well as the fatty acid oxidation enzyme complex in the mitochondrial membrane.

Mitochondrial trifunctional protein deficiency. Catalytic heterogeneity of the mutant enzyme in two patients

We examined the enzyme protein and biosynthesis of human trifunctional protein harboring enoyl-CoA hydratase, 3-hydroxyacyl-CoA dehydrogenase, and 3-ketoacyl-CoA thiolase activity in cultured skin fibroblasts from two patients with long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency. The following results were obtained. (a) In cells from patient 1, immunoblot analysis and pulse-chase experiments indicated that the content of trifunctional protein was < 10% of that in control cells, due to a very rapid degradation of protein newly synthesized in the mitochondria. The diminution of trifunctional protein was associated with a decreased activity of enoyl-CoA hydratase, 3-hydroxyacyl-CoA dehydrogenase, and 3-ketoacyl-CoA thiolase, when measured using medium-chain to long-chain substrates. (b) In cells from patient 2, the rate of degradation of newly synthesized trifunctional protein was faster than that in control cells, giving rise to a trifunctional protein amounting to 60% of the control levels. The 3-hydroxy-acyl-CoA dehydrogenase activity with medium-chain to long-chain substrates was decreased drastically, with minor changes in activities of the two other enzymes. These data suggest a subtle abnormality of trifunctional protein in cells from patient 2. Taken together, the results obtained show that in both patients, long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency is caused by an abnormality in the trifunctional protein, even though there is a heterogeneity in both patients.

Long-chain 3-hydroxyacyl-CoA dehydrogenase in chorionic villi, fetal liver and fibroblasts and prenatal diagnosis of 3-hydroxyacyl-CoA dehydrogenase deficiency

Prenatal diagnosis of long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency was performed by analysis of the enzyme activity in a chorionic villus biopsy obtained in the 10th week of pregnancy. The diagnosis was confirmed in liver tissue and cultured fibroblasts from the aborted fetus.

New developments in the diagnosis and investigation of mitochondrial fatty acid oxidation disorders

Since the discovery of muscle carnitine palmitoyltransferase deficiency in 1973, a dozen separate defects of mitochondrial fatty acid beta-oxidation in man have been identified. With the exception of medium-chain acyl-CoA dehydrogenase (MCAD) deficiency, which occurs with a frequency approaching 1:10,000 among Caucasians of Northern European origin, the other defects are quite rare. Collectively, however, they are common causes of disease resembling Reye syndrome in early life, and some have a later and more chronic presentation with cardiomyopathy and skeletal muscle weakness. They also represent a small, but significant, proportion of cases of sudden and unexplained death within the first 2 years of life. Diagnosis of these disorders has become increasingly sophisticated, with the advent of new analytical technologies and an increased awareness of the appropriate clinical and laboratory investigations needed in order to evaluate potential defects of this pathway. The combination of provocative testing (e.g., carnitine loading, phenylpropionic acid loading, long-chain fat loading) and advanced analytical techniques for the measurement of blood and urinary metabolites (e.g., tandem fast atom bombardment-mass spectrometry, stable isotope dilution gas chromatography-mass spectrometry) permits a specific diagnosis in the case of several, although not all, of the disorders of this pathway. Methods for the measurement of all of the enzymes of beta-oxidation are now available to enhance this diagnostic capability. There remain, however, many patients in whom clinical and laboratory signs point to a defect in beta-oxidation, but in whom no specific diagnosis has yet been made.(ABSTRACT TRUNCATED AT 250 WORDS)

First report of prenatal diagnosis of long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency in a pregnancy at risk

Prenatal diagnosis of long-chain 3-hydroxyacyl-CoA dehydrogenase (3-HAD) deficiency was performed in a family at risk. The diagnosis of an affected fetus was carried out by enzyme assay in cultured chorionic villus cells.

Beta-oxidation of unsaturated fatty acids in humans. Isoforms of delta 3, delta 2-enoyl-CoA isomerase

This investigation was undertaken in order to elucidate the human enzymes which participate in metabolism of the double bonds of unsaturated fatty acids during beta-oxidation. The results indicate that the human monofunctional delta 3, delta 2-enoyl-CoA isomerase (EC 5.3.3.8) with the native M(r) of 70,000 differed significantly from its rat counterpart [Palosaari et al. (1990) J. Biol. Chem. 265, 3347-3353]; the isoelectric point of the human isoform was over three pH-units more acidic, it showed different chromatographic behaviour, the human enzyme did not show any clear-cut substrate chain-length specificity and only a weak immunological cross-reactivity was detected with the antibody to rat liver mitochondrial short-chain enzyme. This explains the failure of attempts to apply the rat data directly to human beings. Another isomerase activity from human liver was found to be a part of the isomerase-hydratase-dehydrogenase polypeptide showing immunological cross-reactivity with the previously characterized peroxisomal multifunctional enzyme (MFE) from rat liver.

Long-chain 3-hydroxyacyl-coenzyme A dehydrogenase deficiency--diagnosis, plasma carnitine fractions and management in a further patient

Long-chain 3-hydroxyacyl-coenzyme A dehydrogenase (LCHAD), the third enzyme of the mitochondrial beta-oxidation pathway, carries out the dehydrogenation of 3-hydroxyacyl-CoA compounds of 12-18 carbon length. To date only nine cases of LCHAD deficiency have been documented. We report a further patient who as a neonate developed non-specific gastrointestinal symptoms and at 5 months of age cardiomyopathy, recurrent hypoketotic hypoglycaemia and gross alterations of plasma carnitine fractions. Dietary management with medium chain triglycerides led rapidly to clinical improvement. There was a close correlation between the clinical condition, plasma carnitine fractions and cardiac function. At 2 years of age she is developing normally.

Marked elevation of urinary 3-hydroxydecanedioic acid in a malnourished infant with glycogen storage disease, mimicking long-chain L-3-hydroxyacyl-CoA dehydrogenase deficiency

An infant with glycogen storage disease and prolonged malnourishment showed a urinary organic acid profile during an episode of fasting hypoglycaemia with inappropriate hypoketotic dicarboxylic aciduria that was indistinguishable from that reported in long-chain L-3-hydroxyacyl-CoA dehydrogenase deficiency. Although there was a striking elevation of urinary 3-hydroxydecanedioic acid, the ratios between hydroxydicarboxylic acids were consistent with values reported to be indicate of medium-chain acyl-CoA dehydrogenase deficiency. We suspect that the fasting 3-hydroxydicarboxylic aciduria was attributable to secondarily impaired enzyme activities, the consequence of malnutrition, early infancy, and/or glycogen storage disease. Caution is advised in the interpretation of urinary organic acid patterns that indicate a 3-hydroxydicarboxylic aciduria, as well as an inappropriate hypoketotic dicarboxylic aciduria, as they may represent non-specific findings.

Human trifunctional protein deficiency: a new disorder of mitochondrial fatty acid beta-oxidation

In this paper we report the identification of a new disorder of mitochondrial fatty acid beta-oxidation in a patient which presented with clear manifestations of a mitochondrial beta-oxidation disorder. Subsequent studies in fibroblasts revealed an impairment in palmitate beta-oxidation and in addition, a combined deficiency of long-chain enoyl-CoA hydratase, long-chain 3-hydroxyacyl-CoA-dehydrogenase and long-chain 3-oxoacyl-CoA thiolase. The recent identification of a multifunctional, membrane-bound beta-oxidation enzyme protein catalyzing all these three enzyme activities (Carpenter et al. (1992) Biochem. Biophys. Res. Commun. 183, 443-448; Uchida et al. (1992) J. Biol. Chem. 267, 1034-1041) suggested an underlying basis for this peculiar combination of three enzyme deficiencies. We show by means of size-exclusion chromatography that there is, indeed, a deficiency of the multifunctional beta-oxidation enzyme protein in this patient.

Clinical and biochemical aspects of carnitine deficiency and insufficiency: transport defects and inborn errors of beta-oxidation

Carnitine is required for entry of long chain fatty acids into mitochondria where beta-oxidation occurs. Primary carnitine deficiency, due to a generic defect in cellular carnitine transport, exists in myopathic and systemic forms. Secondary carnitine deficiency may be due to multiplicity of inherited abnormalities, including deficiencies in carnitine palmitoyl-transferase acyl-CoA dehydrogenases, electron transfer flavoprotein, and 3-ketoacyl-CoA-thiolase. The clinical features, diagnosis, and treatment of these conditions are described.