Β-oxidation Deficiency Research Articles

Plasma C24:0- and C26:0-lysophosphatidylcholines are reliable biomarkers for the diagnosis of peroxisomal β-oxidation disorders

The gold-standard diagnostic test for peroxisomal disorders (PDs) is plasma concentration analysis of very long-chain fatty acids (VLCFAs). However, this method’s time-consuming nature and limitations in cases which present normal VLCFA levels necessitates alternative approaches. The analysis of C26:0-lysophosphatydylcholine (C26:0-LPC) in dried blood spot samples by tandem-mass spectrometry (MS/MS) has successfully been implemented in certain newborn screening programs to diagnose X-linked adrenoleukodystrophy (ALD). However, the diagnostic potential of very long-chain LPCs concentrations in plasma remains poorly understood. This study sought to evaluate the diagnostic performance of C26:0-LPC and other very long-chain LPCs, comparing them to VLCFA analysis in plasma. The study, which included 330 individuals affected by a peroxisomal β-oxidation deficiency and 407 control individuals, revealed that C26:0- and C24:0-LPC concentrations demonstrated the highest diagnostic accuracy (98.8% and 98.4%, respectively), outperforming VLCFA when C26:0/C22:0 and C24:0/C22:0 ratios were combined (98.1%). Combining C24:0- and C26:0-LPC gave the highest sensitivity (99.7%), with ALD females exhibiting notably higher sensitivity compared with the VLCFA ratio combination (98.7% vs. 93.5%, respectively). In contrast, C22:0-LPC exhibited suboptimal performance, primarily due to its low sensitivity (75%), but we identified a potential use to help distinguish between ALD and Zellweger spectrum disorders. In summary, MS/MS analysis of plasma C24:0- and C26:0-LPC concentrations represents a rapid and straightforward approach to diagnose PDs, demonstrating superior diagnostic accuracy, particularly in ALD females, compared with conventional VLCFA biomarkers. We strongly recommend integrating very-long chain LPC plasma analysis in the diagnostic evaluation of individuals suspected of having a PD.

DHA Shortage Causes the Early Degeneration of Photoreceptors and RPE in Mice With Peroxisomal β-Oxidation Deficiency.

Patients deficient in peroxisomal β-oxidation, which is essential for the synthesis of docosahexaenoic acid (DHA, C22:6n-3) and breakdown of very-long-chain polyunsaturated fatty acids (VLC-PUFAs), both important components of photoreceptor outer segments, develop retinopathy present with retinopathy. The representative mouse model lacking the central enzyme of this pathway, multifunctional protein 2 (Mfp2-/-), also show early-onset retinal decay and cell-autonomous retinal pigment epithelium (RPE) degeneration, accompanied by reduced plasma and retinal DHA levels. In this study, we investigated whether DHA supplementation can rescue the retinal degeneration of Mfp2-/- mice. Mfp2+/- breeding pairs and their offspring were fed a 0.12% DHA or control diet during gestation and lactation and until sacrifice. Offspring were analyzed for retinal function via electroretinograms and for lipid composition of neural retina and plasma with lipidome analysis and gas chromatography, respectively, and histologically using retinal sections and RPE flatmounts at the ages of 4, 8, and 16 weeks. DHA supplementation to Mfp2-/- mice restored retinal DHA levels and prevented photoreceptor shortening, death, and impaired functioning until 8 weeks. In addition, rescue of retinal DHA levels temporarily improved the ability of the RPE to phagocytose outer segments and delayed the RPE dedifferentiation. However, despite the initial rescue of retinal integrity, DHA supplementation could not prevent retinal degeneration at 16 weeks. We reveal that the shortage of a systemic supply of DHA is pivotal for the early retinal degeneration in Mfp2-/- mice. Furthermore, we report that adequate retinal DHA levels are essential not only for photoreceptors but also for RPE homeostasis.

Maternal and neonatal outcomes and prognostic factors in acute fatty liver of pregnancy

ObjectiveTo report complications of Acute Fatty Liver of pregnancy (AFLP), a rare liver disease of pregnancy, and identify prognostic factors for mothers and children. Study DesignWe conducted a retrospective descriptive study over 18 years in three French maternities. Demographic, clinical, biological data, and outcomes of patients and their infants were reviewed. Results142,450 pregnancies from centers were studied. Eighteen patients with AFLP were identified The prevalence of AFLP was estimated as 1/7,914 pregnancies. Prolonged prothrombin time was identified as a risk factor of maternal complications (OR = 0.86, p = 0.0493). Gestational age at delivery was the only risk factor associated with fetal or neonate complications (OR = 0.37, p = 0.0417). One boy died of previously undiagnosed β-oxidation deficiency at eight months. ConclusionIn AFLP, prothrombin time must be carefully monitored to anticipate major maternal complications. Infants born to mothers with ALFP should be screened as early as possible for mitochondrial fatty acid oxidation deficiency.

Subclinical effects of long-chain fatty acid β-oxidation deficiency on the adult heart: A case-control magnetic resonance study.

Cardiomyopathy can be a severe complication in patients with long‐chain fatty acid β‐oxidation disorders (LCFAOD), particularly during episodes of metabolic derangement. It is unknown whether latent cardiac abnormalities exist in adult patients. To investigate cardiac involvement in LCFAOD, we used proton magnetic resonance imaging (MRI) and spectroscopy (1H‐MRS) to quantify heart function, myocardial tissue characteristics, and myocardial lipid content in 14 adult patients (two with long‐chain 3‐hydroxyacyl‐CoA dehydrogenase deficiency (LCHADD); four with carnitine palmitoyltransferase II deficiency (CPT2D); and eight with very long‐chain acyl‐CoA dehydrogenase deficiency (VLCADD)) and 14 gender‐, age‐, and BMI‐matched control subjects. Examinations included cine MRI, MR tagging, native myocardial T1 and T2 mapping, and localized 1H‐MRS at 3 Tesla. Left ventricular (LV) myocardial mass (P = .011) and the LV myocardial mass‐to‐volume ratio (P = .008) were higher in patients, while ejection fraction (EF) was normal (P = .397). LV torsion was higher in patients (P = .026), whereas circumferential shortening was similar compared with controls (P = .875). LV hypertrophy was accompanied by high myocardial T1 values (indicative of diffuse fibrosis) in two patients, and additionally a low EF in one case. Myocardial lipid content was similar in patients and controls. We identified subclinical morphological and functional differences between the hearts of LCFAOD patients and matched control subjects using state‐of‐the‐art MR methods. Our results suggest a chronic cardiac disease phenotype and hypertrophic LV remodeling of the heart in LCFAOD, potentially triggered by a mild, but chronic, energy deficiency, rather than by lipotoxic effects of accumulating lipid metabolites.

Tissue acylcarnitine status in a mouse model of mitochondrial β-oxidation deficiency during metabolic decompensation due to influenza virus infection

Despite judicious monitoring and care, patients with fatty acid oxidation disorders may experience metabolic decompensation due to infection which may result in rhabdomyolysis, cardiomyopathy, hypoglycemia and liver dysfunction and failure. Since clinical studies on metabolic decompensation are dangerous, we employed a preclinical model of metabolic decompensation due to infection. By infecting mice with mouse adapted influenza and using a pair-feeding strategy in a mouse model of long-chain fatty acid oxidation (Acadvl−/−), our goals were to isolate the effects of infection on tissue acylcarnitines and determine how they relate to their plasma counterparts. Applying statistical data reduction techniques (Partial Least Squares-Discriminant Analysis), we were able to identify critical acylcarnitines that were driving differentiation of our experimental groups for all the tissues studied. While plasma displayed increases in metabolites directly related to mouse VLCAD deficiency (e.g. C16 and C18), organs like the heart, muscle and liver also showed involvement of alternative pathways (e.g. medium-chain FAO and ketogenesis), suggesting adaptive measures. Matched correlation analyses showed strong correlations (r > 0.7) between plasma and tissue levels for a small number of metabolites. Overall, our results demonstrate that infection as a stress produces perturbations in metabolism in Acadvl−/− that differ greatly from WT infected and Acadvl−/− pair-fed controls. This model system will be useful for studying the effects of infection on tissue metabolism as well as evaluating interventions aimed at modulating the effects of metabolic decompensation.

Neuronal Dysfunction and Behavioral Abnormalities Are Evoked by Neural Cells and Aggravated by Inflammatory Microglia in Peroxisomal β-Oxidation Deficiency.

It is becoming evident that microglia, the resident immune cells of the central nervous system (CNS), are active contributors in neurological disorders. Nevertheless, the impact of microgliosis on neuropathology, behavior and clinical decline in neuropathological conditions remains elusive. A mouse model lacking multifunctional protein-2 (MFP2), a pivotal enzyme in peroxisomal β-oxidation, develops a fatal disorder characterized by motor problems similar to the milder form of human disease. The molecular mechanisms underlying neurological decline in men and mice remain unknown. The hallmark of disease in the mouse model is chronic proliferation of microglia in the brain without provoking neuronal loss or demyelination. In order to define the contribution of Mfp2−/− neural cells to development of microgliosis and clinical neuropathology, the constitutive Mfp2−/− mouse model was compared to a neural selective Nestin-Mfp2−/− mouse model. We demonstrate in this study that, in contrast to early-onset and severe microgliosis in constitutive Mfp2−/− mice, Mfp2+/+ microglia in Nestin-Mfp2−/− mice only become mildly inflammatory at end stage of disease. Mfp2−/− microglia are primed and acquire a chronic and strong inflammatory state in Mfp2−/− mice whereas Mfp2+/+ microglia in Nestin-Mfp2−/− mice are not primed and adopt a minimal activation state. The inflammatory microglial phenotype in Mfp2−/− mice is correlated with more severe neuronal dysfunction, faster clinical deterioration and reduced life span compared to Nestin-Mfp2−/− mice. Taken together, our study shows that deletion of MFP2 impairs behavior and locomotion. Clinical decline and neural pathology is aggravated by an early-onset and excessive microglial response in Mfp2−/− mice and strongly indicates a cell-autonomous role of MFP2 in microglia.

Mitochondrial disruption in peroxisome deficient cells is hepatocyte selective but is not mediated by common hepatic peroxisomal metabolites

The structural disruption of the mitochondrial inner membrane in hepatocytes lacking functional peroxisomes along with selective impairment of respiratory complexes and depletion of mitochondrial DNA was previously reported. In search for the molecular origin of these mitochondrial alterations, we here show that these are tissue selective as they do neither occur in peroxisome deficient brain nor in peroxisome deficient striated muscle. Given the hepatocyte selectivity, we investigated the potential involvement of metabolites that are primarily handled by hepatic peroxisomes. Levels of these metabolites were manipulated in L-Pex5 knockout mice and/or compared with levels in different mouse models with a peroxisomal β-oxidation deficiency. We show that neither the deficiency of docosahexaenoic acid nor the accumulation of branched chain fatty acids, dicarboxylic acids or C27 bile acid intermediates are solely responsible for the mitochondrial anomalies. In conclusion, we demonstrate that peroxisomal inactivity differentially impacts mitochondria depending on the cell type but the cause of the mitochondrial destruction needs to be further explored.

Myocardial energy shortage and unmet anaplerotic needs in the fasted long-chain acyl-CoA dehydrogenase knockout mouse

The aim of this animal study is to assess fasting-induced changes in myocardial substrate metabolism and energy status as a consequence of mitochondrial long-chain fatty acid β-oxidation deficiency, using magnetic resonance spectroscopy (MRS). Carbon-13 ((13)C) MRS of hyperpolarized [1-(13)C]pyruvate was used to assess in vivo pyruvate dehydrogenase (PDH) activity in fed and fasted wild-type (WT) mice and long-chain acyl-CoA dehydrogenase knockout (LCAD KO) mice. PDH activity decreased after fasting in both genotypes, but was 2.7-fold higher in fasted LCAD KO mice compared with fasted WT mice. Incorporation of the (13)C label into the myocardial malate and aspartate pools in fasted LCAD KO mice demonstrates enhanced activity of anaplerotic pathways in fasted LCAD KO hearts. These findings were corroborated by ex vivo assays revealing partially depleted pools of citric acid cycle intermediates in fasted LCAD KO myocardium, suggesting an increased, but unmet need for anaplerosis. The in vivo myocardial energy status, assessed using phosphorous-31 ((31)P) MRS, was lower in fasted LCAD KO mice than in fasted WT mice. This study revealed that the heart of fasted LCAD KO mice has an elevated reliance on glucose oxidation, in combination with an unmet demand for myocardial anaplerosis. Due to a lack of substrate availability, the sustained myocardial glucose uptake and PDH activity in LCAD KO mice are ineffective to maintain metabolic homeostasis during fasting, which is reflected by an impaired myocardial energy status in fasted LCAD KO mice.

Peroxisomes contribute to the acylcarnitine production when the carnitine shuttle is deficient

Fatty acid β-oxidation may occur in both mitochondria and peroxisomes. While peroxisomes oxidize specific carboxylic acids such as very long-chain fatty acids, branched-chain fatty acids, bile acids, and fatty dicarboxylic acids, mitochondria oxidize long-, medium-, and short-chain fatty acids. Oxidation of long-chain substrates requires the carnitine shuttle for mitochondrial access but medium-chain fatty acid oxidation is generally considered carnitine-independent. Using control and carnitine palmitoyltransferase 2 (CPT2)- and carnitine/acylcarnitine translocase (CACT)-deficient human fibroblasts, we investigated the oxidation of lauric acid (C12:0). Measurement of the acylcarnitine profile in the extracellular medium revealed significantly elevated levels of extracellular C10- and C12-carnitine in CPT2- and CACT-deficient fibroblasts. The accumulation of C12-carnitine indicates that lauric acid also uses the carnitine shuttle to access mitochondria. Moreover, the accumulation of extracellular C10-carnitine in CPT2- and CACT-deficient cells suggests an extramitochondrial pathway for the oxidation of lauric acid. Indeed, in the absence of peroxisomes C10-carnitine is not produced, proving that this intermediate is a product of peroxisomal β-oxidation. In conclusion, when the carnitine shuttle is impaired lauric acid is partly oxidized in peroxisomes. This peroxisomal oxidation could be a compensatory mechanism to metabolize straight medium- and long-chain fatty acids, especially in cases of mitochondrial fatty acid β-oxidation deficiency or overload.

29. Enzyme reduction therapy as adjunct to cord cell transplant in Hurler syndrome

Peroxisomal disorders include a complex spectrum of diseases, characterized by a high heterogeneity from both the clinical and the biochemical points of view. Specific assays are required for the study of peroxisome metabolism. Among these, pipecolic acid evaluation is considered as a supplementary test. We have established the diagnostic role of pipecolic acid in 30 patients affected by a peroxisomal defect (5 Zellweger syndromes, 10 Infantile Refsum diseases, 1 neonatal adrenoleukodystrophy, 6 patients affected by a peroxisomal biogenesis disorder with unclassified phenotype, 1 case of rhizomelic chondrodysplasia punctata (RCDP), 2 acyl-CoA oxidase deficiencies, 2 bifunctional enzyme deficiencies, 2 Refsum diseases, and 1 β-oxidation deficiency). Pipecolic acid was increased in all generalized peroxisomal disorders, while normal pipecolic acid with abnormal very long chain fatty acid concentrations was strong evidence for a single peroxisomal enzyme deficiency. Unexpectedly, hyperpipecolic acidaemia was found also in a child affected by RCDP and in two patients with Refsum disease. In six patients the suggestion of a peroxisomal disorder was raised by the fortuitous finding of a pipecolic acid peak in amino acid chromatography, routinely performed as a general metabolic screening. For all patients, pipecolic acid proved to be a useful parameter in the biochemical classification of peroxisomal disorders.

Hyperpipecolic acidaemia: a diagnostic tool for peroxisomal disorders

Peroxisomal disorders include a complex spectrum of diseases, characterized by a high heterogeneity from both the clinical and the biochemical points of view. Specific assays are required for the study of peroxisome metabolism. Among these, pipecolic acid evaluation is considered as a supplementary test. We have established the diagnostic role of pipecolic acid in 30 patients affected by a peroxisomal defect (5 Zellweger syndromes, 10 Infantile Refsum diseases, 1 neonatal adrenoleukodystrophy, 6 patients affected by a peroxisomal biogenesis disorder with unclassified phenotype, 1 case of rhizomelic chondrodysplasia punctata (RCDP), 2 acyl-CoA oxidase deficiencies, 2 bifunctional enzyme deficiencies, 2 Refsum diseases, and 1 β-oxidation deficiency). Pipecolic acid was increased in all generalized peroxisomal disorders, while normal pipecolic acid with abnormal very long chain fatty acid concentrations was strong evidence for a single peroxisomal enzyme deficiency. Unexpectedly, hyperpipecolic acidaemia was found also in a child affected by RCDP and in two patients with Refsum disease. In six patients the suggestion of a peroxisomal disorder was raised by the fortuitous finding of a pipecolic acid peak in amino acid chromatography, routinely performed as a general metabolic screening. For all patients, pipecolic acid proved to be a useful parameter in the biochemical classification of peroxisomal disorders.

Analysis of cysteinyl leukotrienes and their metabolites in bile of patients with peroxisomal or mitochondrial β-oxidation defects

Cysteinyl leukotrienes (LTs) are potent lipid mediators which are predominantly eliminated via bile. Their metabolic inactivation and degradation proceeds by β-oxidation. However, although bile is the optimal material for analysis of LTs in man, only very sparse data on bile LT concentration under normal or pathophysiological conditions exist. The aim of the present study was to present for the first time a complete profile of endogenous LTs in human bile and to investigate the importance of bile LT analysis in peroxisomal and mitochondrial β-oxidation deficiency. Cysteinyl LTs and their oxidation metabolites were analysed after HPLC separation by specific immunoassays or gas chromatography-mass spectrometry. Under physiological conditions, LTs are found in human bile ( n=8) in the nanomolar range with LTD 4 predominating, whereas the other LTs were present in similar amounts. In bile of a patient with a peroxisome biogenesis disorder (Zellweger syndrome, ZS) LTE 4 was found to be slightly increased, whereas both ω-oxidation metabolites of LTE 4, ω-hydroxy-LTE 4 and ω-carboxy-LTE 4, were highly increased (about 12–18 times). The β-oxidation metabolite ω-carboxy-tetranor-LTE 3 was below the detection limit (<0.1 nmol/l; controls 1.4±1.2 nmol/l). This abnormal profile demonstrates an impaired degradation of LTs in ZS. In contrast, patients with X-linked adrenoleukodystrophy (X-ALD), medium-chain acyl CoA dehydrogenase deficiency (MCAD) as well as very long-chain acyl CoA dehydrogenase deficiency (VLCAD) did not show any differences in their biliary profile of LTs compared to controls. Increased levels of the biologically active cysteinyl LTs in the bile of patients with ZS might be of pathophysiological significance in the course of the disease, e.g. contributing to liver injury. In addition, our data confirm that the β-oxidation of cysteinyl LTs in vivo occurs in peroxisomes and not in mitochondria.

Stereochemistry of the peroxisomal branched-chain fatty acid α- and β-oxidation systems in patients suffering from different peroxisomal disorders

Phytanic acid (3,7,11,15-tetramethylhexadecanoic acid) is a branched-chain fatty acid derived from dietary sources and broken down in the peroxisome to pristanic acid (2,6,10,14-tetramethylpentadecanoic acid) via α-oxidation. Pristanic acid then undergoes β-oxidation in peroxisomes. Phytanic acid naturally occurs as a mixture of (3S,7R,11R)- and (3R,7R,11R)-diastereomers. In contrast to the α-oxidation system, peroxisomal β-oxidation is stereospecific and only accepts (2S)-isomers. Therefore, a racemase called α-methylacyl-CoA racemase is required to convert (2R)-pristanic acid into its (2S)-isomer. To further investigate the stereochemistry of the peroxisomal oxidation systems and their substrates, we have developed a method using gas-liquid chromatography-mass spectrometry to analyze the isomers of phytanic, pristanic, and trimethylundecanoic acid in plasma from patients with various peroxisomal fatty acid oxidation defects. In this study, we show that in plasma of patients with a peroxisomal β-oxidation deficiency, the relative amounts of the two diastereomers of pristanic acid are almost equal, whereas in patients with a defect of α-methylacyl-CoA racemase, (2R)-pristanic acid is the predominant isomer. Furthermore, we show that in α-methylacyl-CoA racemase deficiency, not only pristanic acid accumulates, but also one of the metabolites of pristanic acid, (2,6,10)-trimethylundecanoic acid, providing direct in vivo evidence for the requirement of this racemase for the complete degradation of pristanic acid. —Ferdinandusse, S., H. Rusch, A. E. M. van Lint, G. Dacremont, R. J. A. Wanders, and P. Vreken. Stereochemistry of the peroxisomal branched-chain fatty acid α- and β-oxidation systems in patients suffering from different peroxisomal disorders.

Specific and rapid quantification of 8-iso-prostaglandin F 2α in urine of healthy humans and patients with Zellweger syndrome by gas chromatography–tandem mass spectrometry

8-iso-Prostaglandin F 2α (8-iso-PGF 2α) is currently discussed as a potential index parameter of oxidative stress in vivo. We describe in this article a fully validated gas chromatographic–tandem mass spectrometric method for the quantitative determination of 8-iso-PGF 2α in human urine. The method is highly specific and requires a single thin-layer chromatographic step for sample purification. Inter- and intraday imprecision were below 8%. Mean inaccuracy was 5.3% for added levels of 8-iso-PGF 2α up to 2000 pg/ml of urine. We measured highly elevated excretion of 8-iso-PGF 2α in the urine of children with peroxisomal β-oxidation deficiency, i.e. Zellweger syndrome, (63.3±16.6 ng/mg creatinine) compared to that of healthy children (0.51±0.16 ng/mg creatinine) (mean±S.D., both n=5). The method could be useful for diagnosing Zellweger syndrome and for investigating the utility of 8-iso-PGF 2α as a novel marker for oxidative stress in vivo in man.

Fatty acid β-oxidation deficiency masquerading as fulminant myocarditis

We present a 9-month-old child presenting with acute cardiomyopathy and fever following a viral illness. He was diagnosed to have acute myocarditis, was proposed for an external hemodynamic assistance but died of ventricular tachycardia. Post-mortem data revealed a very-long-chain acylcoenzyme A dehydrogenase deficiency. Our report raises awareness on the interest for preserving tissue samples and for performing a metabolic screening in acute childhood cardiomyopathy.

Metabolic studies in a patient with severe carnitine palmitoyltransferase type II deficiency

Here we report on a patient with severe (“non-classic”) carnitine palmitoyltransferase type II (CPT II) deficiency. Hypoglycemia prompted by an infectious episode and associated with non-ketotic dicarboxylic aciduria orientated diagnosis towards β-oxidation deficiency disorders. Blood carnitine levels revealed a secondary carnitine deficiency that was responsive to oral l-carnitine supplementation. Blood acylcarnitine profiles were abnormal and included acetyl (C2:0), butyryl/isobutyryl (C4:0), isovaleryl/2-methylbutyryl (C5:0), hexanoyl (C6:0), myristoyl (C14:0), palmitoyl (C16:0), hexadecenoyl (C16:1), oleyl (C18:1) and stearoyl (C18:0) carnitine. In urine, excess excretion of dicarboxylylcarnitines, mainly dodecanedioylcarnitine, was noticed. Upon carnitine supplementation, C8 to C12 fatty acylcarnitines, with decanoylcarnitine as well as C10 to C14 dicarboxylylcarnitines being prominent, were observed in urine. Biochemical measurements disclosed a severe reduction of mitochondrial CPT II activity (7% of normal values). Correlations of metabolic findings in the patient and physiological roles of CPT II are briefly discussed.

Acylcarnitine removal in a patient with acyl-CoA β-oxidation deficiency disorder: effect of l-carnitine therapy and starvation

Carnitine levels and acylcarnitine profiles in a patient with mild multiple acyl-CoA dehydrogenase deficient β-oxidation were compared with control results. Whereas blood and urine total carnitine levels were moderately decreased, blood esterified carnitine levels in the patient were about 2-fold higher than in controls. Urinary acylcarnitine profiles presented with a larger variety of carnitine esters than in controls and included propionyl-carnitine, butyrylcarnitine, 2-methylbutyrylcarnitine, hexanoylcarnitine and octanoylcarnitine. Total carnitine levels in body fluids were similarly affected by chronic oral l-carnitine administration in patient and controls. By contrast, esterified carnitine level increase was 2-fold more important in controls than in patient. Whereas no qualitative changes in urinary acylcarnitine profiles were induced by l-carnitine therapy in controls, several alterations of these profiles were observed in the patient. The effect of starvation on metabolites was also studied, especially β-oxidation rates assessed by free fatty acids to 3-hydroxybutyric acid ratios in blood from the patient in the untreated and l-carnitine treated states. In the l-carnitine-supplemented patient, the effect of starvation on the time course of carnitine levels and acylcarnitine profiles could also be documented. The ability of chronic oral l-carnitine administration to remove relatively less important amounts of acylcarnitines in the patient than in controls is further discussed, as well as qualitative alterations of acylcarnitine profiles induced by this therapy in the pathological condition.