Medium-chain acyl-CoA Dehydrogenase Deficiency Patients Research Articles

Personalised modelling of clinical heterogeneity between medium-chain acyl-CoA dehydrogenase patients

BackgroundMonogenetic inborn errors of metabolism cause a wide phenotypic heterogeneity that may even differ between family members carrying the same genetic variant. Computational modelling of metabolic networks may identify putative sources of this inter-patient heterogeneity. Here, we mainly focus on medium-chain acyl-CoA dehydrogenase deficiency (MCADD), the most common inborn error of the mitochondrial fatty acid oxidation (mFAO). It is an enigma why some MCADD patients—if untreated—are at risk to develop severe metabolic decompensations, whereas others remain asymptomatic throughout life. We hypothesised that an ability to maintain an increased free mitochondrial CoA (CoASH) and pathway flux might distinguish asymptomatic from symptomatic patients.ResultsWe built and experimentally validated, for the first time, a kinetic model of the human liver mFAO. Metabolites were partitioned according to their water solubility between the bulk aqueous matrix and the inner membrane. Enzymes are also either membrane-bound or in the matrix. This metabolite partitioning is a novel model attribute and improved predictions. MCADD substantially reduced pathway flux and CoASH, the latter due to the sequestration of CoA as medium-chain acyl-CoA esters. Analysis of urine from MCADD patients obtained during a metabolic decompensation showed an accumulation of medium- and short-chain acylcarnitines, just like the acyl-CoA pool in the MCADD model. The model suggested some rescues that increased flux and CoASH, notably increasing short-chain acyl-CoA dehydrogenase (SCAD) levels. Proteome analysis of MCADD patient-derived fibroblasts indeed revealed elevated levels of SCAD in a patient with a clinically asymptomatic state. This is a rescue for MCADD that has not been explored before. Personalised models based on these proteomics data confirmed an increased pathway flux and CoASH in the model of an asymptomatic patient compared to those of symptomatic MCADD patients.ConclusionsWe present a detailed, validated kinetic model of mFAO in human liver, with solubility-dependent metabolite partitioning. Personalised modelling of individual patients provides a novel explanation for phenotypic heterogeneity among MCADD patients. Further development of personalised metabolic models is a promising direction to improve individualised risk assessment, management and monitoring for inborn errors of metabolism.

Free carnitine concentrations and biochemical parameters in medium-chain acyl-CoA dehydrogenase deficiency: Genotype-phenotype correlation.

Biallelic variants in the ACADM gene cause medium-chain acyl-CoA dehydrogenase deficiency (MCADD). This study reports on differences in the occurrence of secondary free carnitine (C0) deficiency and different biochemical phenotypes related to genotype and age in 109 MCADD patients followed-up at a single tertiary care center during 22 years. C0 deficiency occurred earlier and more frequently in c.985A>G homozygotes (genotype A) compared to c.985A>G compound heterozygotes (genotype B) and individuals carrying variants other than c.985A>G and c.199C>T (genotype D) (median age 4.2 vs. 6.6 years; p < 0.001). No patient carrying c.199C>T (genotype C) developed C0 deficiency. A daily dosage of 20-40 mg/kg carnitine was sufficient to maintain normal C0 concentrations. Compared to genotype A as reference group, octanoylcarnitine (C8) was significantly lower in genotypes B and C, whereas C0 was significantly higher by 8.28 μmol/L in genotype C (p < 0.05). In conclusion, C0 deficiency is mainly found in patients with pathogenic genotypes associated with high concentrations of presumably toxic acylcarnitines, while individuals carrying the variant c.199C>T are spared and show consistently mild biochemical phenotypes into adulthood. Low-dose carnitine supplementation maintains normal C0 concentrations. However, future studies need to evaluate clinical benefits on acute and chronic manifestations of MCADD.

Medium-chain Acyl-COA dehydrogenase deficiency: Pathogenesis, diagnosis, and treatment.

Medium-Chain Acyl-CoA Dehydrogenase Deficiency (MCADD) is the most common inherited metabolic disorder of β-oxidation. Patients with MCADD present with hypoketotic hypoglycemia, which may quickly progress to lethargy, coma, and death. Prognosis for MCADD patients is highly promising once a diagnosis has been established, though management strategies may vary depending on the severity of illness and the presence of comorbidities. Given the rapid developments in the world of gene therapy and implementation of newborn screening for inherited metabolic disorders, the provision of concise and contemporary knowledge of MCADD is essential for clinicians to effectively manage patients. Thus, this review aims to consolidate current information for physicians on the pathogenesis, diagnostic tools, and treatment options for MCADD patients. MCADD is a commonly inherited metabolic disease with serious implications for health outcomes, particularly in children, that may be successfully managed with proper intervention.

Oxidized phosphatidylcholines suggest oxidative stress in patients with medium-chain acyl-CoA dehydrogenase deficiency

Inborn errors of metabolism encompass a large group of diseases caused by enzyme deficiencies and are therefore amenable to metabolomics investigations. Medium chain acyl-CoA dehydrogenase deficiency (MCADD) is a defect in β-oxidation of fatty acids, and is one of the most well understood disorders. We report here the use of liquid chromatography–mass spectrometry (LC–MS) based untargeted metabolomics and targeted flow injection analysis–tandem mass spectrometry (FIA–TMS) that lead to discovery of novel compounds of oxidative stress. Dry blood spots of controls (n=25) and patient samples (n=25) were extracted by methanol/water (1/1, v/v) and these supernatants were analyzed by LC–MS method with detection by an Orbitrap Elite MS. Data were processed by XCMS and CAMERA followed by dimension reduction methods. Patients were clearly distinguished from controls in PCA. S-plot derived from OPLS-DA indicated that medium-chain acylcarnitines (octanoyl, decenoyl and decanoyl carnitines) as well as three phosphatidylcholines (PC(16:0,9:0(COOH))), PC(18:0,5:0(COOH)) and PC(16:0,8:0(COOH)) were important metabolites for differentiation between patients and healthy controls. In order to biologically validate these discriminatory molecules as indicators for oxidative stress, a second cohort of individuals were analyzed, including MCADD (n=25) and control (n=250) samples. These were measured by a modified newborn screening method using FIA–TMS (API 4000) in MRM mode. Calculated p-values for PC(16:0,9:0(COOH)), PC(18:0,5:0(COOH)) and PC(16:0,8:0(COOH)) were 1.927×10−14, 2.391×10−15 and 3.354×10−15 respectively. These elevated oxidized phospholipids indeed show an increased presence of oxidative stress in MCADD patients as one of the pathophysiological mechanisms of the disease.

Medium-Chain Acyl-CoA Dehydrogenase Deficiency: Evaluation of Genotype-Phenotype Correlation in Patients Detected by Newborn Screening.

Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is included in many newborn screening programmes worldwide. In addition to the prevalent mutation c.985A>G in the ACADM gene, potentially mild mutations like c.199T>C are frequently found in screening cohorts. There is ongoing discussion whether this mutation is associated with a clinical phenotype. In 37 MCADD patients detected by newborn screening, biochemical phenotype (octanoylcarnitine (C8), ratios of C8 to acetylcarnitine (C2), decanoylcarnitine (C10) and dodecanoylcarnitine (C12) at screening and confirmation) and clinical phenotype (inpatient emergency treatment, metabolic decompensations, clinical assessments, psychometric tests) were assessed in relation to genotype. 16 patients were homozygous for c.985A>G (group 1), 11 compound heterozygous for c.199T>C and c.985A>G/another mutation (group 2) and 7 compound heterozygous for c.985A>G and mutations other than c.199T>C (group 3) and 3 carried neither c.985A>G nor c.199T>C but other known homozygous mutations (group 4). At screening C8/C2 and C8/C10, at confirmation C8/C2, C8/C10 and C8/C12 differed significantly between patients compound heterozygous for c.199T>C (group 2) and other genotypes. C8, C10 and C8/C2 at screening were strongly associated with time of sampling in groups 1 + 3 + 4, but not in group 2. Clinical phenotype did not differ between genotypes. Two patients compound heterozygous for c.199T>C and a severe mutation showed neonatal decompensation with hypoglycaemia. Biochemical phenotype differs between MCADD patients compound heterozygous for c.199T>C with a severe mutation and other genotypes. In patients detected by newborn screening, clinical phenotype does not differ between genotypes following uniform treatment recommendations. Neonatal decompensation can also occur in patients with the presumably mild mutation c.199T>C prior to diagnosis.

Retrospective study of the medium‐chain acyl‐CoA dehydrogenase deficiency in Portugal

Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is the commonest genetic defect of mitochondrial fatty acid β-oxidation. About 60% of MCADD patients are homozygous for the c.985A>G (p.Lys329Glu) mutation in the ACADM gene (G985 allele). Herein, we present the first report on the molecular and biochemical spectrum of Portuguese MCADD population. From the 109 patients studied, 83 were diagnosed after inclusion of MCADD in the national newborn screening, 8 following the onset of symptoms and 18 through segregation studies. Gypsy ancestry was identified in 85/109 patients. The G985 allele was found in homozygosity in 102/109 patients, in compound heterozygosity in 6/109 and was absent in one patient. Segregation studies in the Gypsy families showed that 93/123 relatives were carriers of the G985 allele, suggesting its high prevalence in this ethnic group. Additionally, three new substitutions-c.218A>G (p.Tyr73Cys), c.503A>T (p.Asp168Val) and c.1205G>T (p.Gly402Val)-were identified. Despite the particularity of the MCADD population investigated, the G985 allele was found in linkage disequilibrium with H1(112) haplotype. Furthermore, two novel haplotypes, H5(212) and H6(122) were revealed.

Medium‐Chain Acyl‐CoA Deficiency: Outlines from Newborn Screening, In Silico Predictions, and Molecular Studies

Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is a disorder of fatty acid oxidation characterized by hypoglycemic crisis under fasting or during stress conditions, leading to lethargy, seizures, brain damage, or even death. Biochemical acylcarnitines data obtained through newborn screening by liquid chromatography-tandem mass spectrometry (LC-MS/MS) were confirmed by molecular analysis of the medium-chain acyl-CoA dehydrogenase (ACADM) gene. Out of 324.000 newborns screened, we identified 14 MCADD patients, in whom, by molecular analysis, we found a new nonsense c.823G>T (p.Gly275∗) and two new missense mutations: c.253G>C (p.Gly85Arg) and c.356T>A (p.Val119Asp). Bioinformatics predictions based on both phylogenetic conservation and functional/structural software were used to characterize the new identified variants. Our findings confirm the rising incidence of MCADD whose existence is increasingly recognized due to the efficacy of an expanded newborn screening panel by LC-MS/MS making possible early specific therapies that can prevent possible crises in at-risk infants. We noticed that the “common” p.Lys329Glu mutation only accounted for 32% of the defective alleles, while, in clinically diagnosed patients, this mutation accounted for 90% of defective alleles. Unclassified variants (UVs or VUSs) are especially critical when considering screening programs. The functional and pathogenic characterization of genetic variants presented here is required to predict their medical consequences in newborns.

Cis-4-decenoic acid provokes mitochondrial bioenergetic dysfunction in rat brain

Aims In the present work we investigated the in vitro effect of cis-4-decenoic acid, the pathognomonic metabolite of medium-chain acyl-CoA dehydrogenase deficiency, on various parameters of bioenergetic homeostasis in rat brain mitochondria. Main methods Respiratory parameters determined by oxygen consumption were evaluated, as well as membrane potential, NAD(P)H content, swelling and cytochrome c release in mitochondrial preparations from rat brain, using glutamate plus malate or succinate as substrates. The activities of citric acid cycle enzymes were also assessed. Key findings cis-4-decenoic acid markedly increased state 4 respiration, whereas state 3 respiration and the respiratory control ratio were decreased. The ADP/O ratio, the mitochondrial membrane potential, the matrix NAD(P)H levels and aconitase activity were also diminished by cis-4-decenoic acid. These data indicate that this fatty acid acts as an uncoupler of oxidative phosphorylation and as a metabolic inhibitor. cis-4-decenoic acid also provoked a marked mitochondrial swelling when either KCl or sucrose was used in the incubation medium and also induced cytochrome c release from mitochondria, suggesting a non-selective permeabilization of the inner mitochondrial membrane. Significance It is therefore presumed that impairment of mitochondrial homeostasis provoked by cis-4-decenoic acid may be involved in the brain dysfunction observed in medium-chain acyl-CoA dehydrogenase deficient patients.

Prolonged moderate‐intensity exercise without and with L‐carnitine supplementation in patients with MCAD deficiency

Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is probably the most common inborn error of fatty acid oxidation (FAO). Routine L-carnitine supplementation in the treatment of MCADD is controversial. To establish the effects of L-carnitine supplementation during prolonged moderate-intensity exercise in MCADD, five patients and three control subjects were studied during 2 hours of moderate-intensity exercise after a 12-hour fast. Patients were studied twice, once with and once without L-carnitine supplementation (50 mg/kg per day). Blood samples were collected before, during and after exercise, and analysed for routine parameters, acylcarnitines and carnitine biosynthesis intermediates. Urine was collected before and after exercise, and analysed for acylcarnitines. All patients were able to complete the exercise test without any apparent clinical or biochemical adverse effects, even without L-carnitine supplementation. A significant rise in plasma free fatty acids and octanoylcarnitine levels during exercise was seen in all patients, indicating a substantial increase in FAO during exercise. Octanoylcarnitine levels in plasma were significantly higher in patients with L-carnitine supplementation, suggesting increased clearance of accumulating acylcarnitines. A statistically significant increase of plasma and urinary free carnitine levels, as well as of plasma gamma-butyrobetaine was seen in MCADD patients without L-carnitine supplementation. These data suggest an increase in carnitine biosynthesis. In conclusion, although L-carnitine supplementation may promote clearance of accumulating acylcarnitines during moderate-intensity exercise, no apparent beneficial effect of this supplementation on clinical and biochemical parameters was observed in MCADD patients. Our results suggest that MCADD patients are able to increase carnitine biosynthesis during exercise to compensate for carnitine losses.

Medium-chain acyl-CoA dehydrogenase deficiency: Genotype–biochemical phenotype correlations

The fatty acid oxidation disorder most commonly identified by tandem mass spectrometry newborn screening is the potentially fatal medium-chain acyl-CoA dehydrogenase deficiency (MCAD). In clinically presenting cases, 80% are homozygous for the common mutation, c.985A > G and 18% heterozygous. We screened 592,785 babies and identified 34 with MCAD, 17 homozygous for c.985A > G, 14 with one copy, and 3 with no copy. We sequenced the exons of 19 patients, the 17 carrying one or no copy of c.985A > G, and two with marginal findings, and examined correlations between groups of mutations and biochemical markers. We found two known or putative pathogenic mutations in 18 of the 19 patients. Two mutations appeared more than once: c.199T > C, not recorded in clinically presenting cases ( n = 4), and c.583G > A ( n = 2). Patients homozygous for c.985A > G had the highest levels of neonatal octanoylcarnitine, plasma octanoylcarnitine when asymptomatic, and urinary acylglycines. Compound heterozygotes of c.985A > G and other mutations had intermediate levels, and those without c.985A > G, or heterozygous for that and c.199T > C had the lowest levels of these analytes. There was overlap in all values. The c.985A > G and c.583G > A mutations appear to have functional effects towards the severe end of the spectrum, and the c.199T > C mutation a smaller effect, as has been previously postulated. If these results are confirmed and extended, this could influence the advice given to parents of babies with MCAD detected by newborn screening, and make management more specific. In the meantime, all MCAD patients identified by newborn screening have, by definition, a functional defect and require careful clinical management.

Population spectrum ofACADMgenotypes correlated to biochemical phenotypes in newborn screening for medium-chain acyl-CoA dehydrogenase deficiency

Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is the most frequent inherited defect of fatty acid oxidation, with a significant morbidity and mortality in undiagnosed patients. Adverse outcomes can effectively be prevented by avoiding metabolic stress and following simple dietary measures. Therefore, prospective newborn screening (NBS) is being proposed for this condition. However, technical validation of MCADD population screening and assessment of its overall benefit require broadening of the as-yet-scarce knowledge of the MCADD genetic heterogeneity unraveled by NBS and its phenotypic consequences. Here, we describe the entire spectrum of sequence variations occurring in newborns with MCADD in the population of Bavaria, Germany, in relation to the biochemical phenotype. Among 524,287 newborns, we identified 62 cases of MCADD, indicating a birth incidence of 1 in 8,456. In all of the 57 newborns available for analysis, two alterations within the MCADD gene (ACADM) were identified. The most prevalent alteration c.985A>G (Lys329Glu) occurred in 27 (47%) newborns in the homozygous and in 18 (32%) in the heterozygous state (63% of defective alleles). The mild folding variant c.199T>C (Tyr67His) was identified in nine individuals, six of them being compound heterozygous with c.985A>G (Lys329Glu). Neither of the prevalent alterations were found in the remaining nine newborns. A total of 18 sequence variations were identified; 13 of them were novel: eight missense mutations, one nonsense mutation, two splice variants, and two small deletions. The remaining five were previously reported in MCADD patients. The ACADM heterogeneity uncovered was larger as anticipated from previous c.985A>G (Lys329Glu) carrier screening data. In addition, we show that MCADD appears to occur as frequently in Turkish newborns as in the native German population. Our data validate that biochemical NBS for MCADD is a highly specific procedure for disease detection, with the identification of a significant share of milder biochemical phenotypes, such as c.199T>C (Tyr67His). These show statistically lower acylcarnitine markers, allowing us to distinguish subgroups within the spectrum of ACADM sequence variations that correlate to biochemical MCADD disease expression. Our data might provide technical and medical guidance for decision making in the worldwide efforts to introduce MCADD population screening.

Inhibition of energy metabolism in cerebral cortex of young rats by the medium-chain fatty acids accumulating in MCAD deficiency

Patients affected by medium-chain acyl CoA dehydrogenase (MCAD) deficiency, a frequent inborn error of metabolism, suffer from acute episodes of encephalopathy. However, the mechanisms underlying the neuropathology of this disease are poorly known. In the present study, we investigated the in vitro effect of the medium-chain fatty acids (MCFA), at concentrations varying from 0.01 to 3 mM, accumulating in MCAD deficiency on some parameters of energy metabolism in cerebral cortex of young rats. 14CO 2 production from [U 14] glucose, [1- 14C] acetate and [1,5- 14C] citrate was evaluated by incubating cerebral cortex homogenates from 30-day-old rats in the absence (controls) or presence of octanoic acid, decanoic acid or cis-4-decenoic acid. OA and DA significantly reduced 14CO 2 production from acetate by around 30–40%, and from glucose by around 70%. DA significantly reduced 14CO 2 production from citrate by around 40%, while OA did not affect this parameter. cDA inhibited 14CO 2 production from all tested substrates by around 30–40%. The activities of the respiratory chain complexes and of creatine kinase were also tested in the presence of DA and cDA. Both metabolites significantly inhibited cytochrome c oxidase activity (by 30%) and complex II–III activity (DA, 25%; cDA, 80%). Furthermore, only cDA inhibited complex II activity (by 30%), while complex I–III and citrate synthase were not affected by these MCFA. On the other hand, only cDA reduced the activity of creatine kinase in total homogenates, as well as in mitochondrial and cytosolic fractions from cerebral cortex (by 50%). The data suggest that the major metabolites which accumulate in MCAD deficiency, with particular emphasis to cDA, compromise brain energy metabolism. We presume that these findings may contribute to the understanding of the pathophysiology of the neurological dysfunction of MCAD deficient patients.

Rapid, comprehensive screening of the human medium chain acyl-CoA dehydrogenase gene

Newborn screening by tandem mass spectrometry (MS/MS) identifies patients with medium chain acyl-CoA dehydrogenase (MCAD) deficiency the most frequently observed disorder of fatty acid oxidation. Molecular genetic analysis is becoming a common tool to confirm those identified as affected by prospective screening and for carrier detection in family studies. The A985G (K304E) mutation accounts for approximately 80% of mutant alleles in MCAD deficient patients, presenting symptomatically, while greater variability of mutant alleles is observed among cases identified through prospective screening. Aside from A985G, the mutation spectrum in MCAD deficient patients is heterogeneous such that comprehensive gene analysis is required. Traditionally the MCAD gene is assayed by sequencing the entire coding region. Although effective and definitive, this approach is expensive, turn around time is slow, and is poorly amenable to a clinical service molecular genetics laboratory. Dye-binding/high-resolution thermal denaturation is a rapid and homogeneous method by which to scan a PCR product for evidence of sequence aberration. PCR is performed in capillaries in the presence of the dsDNA-binding dye LCGreen I and subsequently the DNA/dye complexes are analyzed by high-resolution thermal denaturation. DNA sequencing was limited to fragments displaying abnormal melting profiles. Of 18 specimens analyzed, 11 have a genotype consistent with MCAD deficiency and seven have a genotype consistent with carrier status. Clinical and biochemical data corroborate that the genotype results identified the affected patients and differentiates them from carriers. The entire process is homogeneous requiring no post-PCR manipulation and is completed in under 3 h.

437. Developing a Mouse Model of the Mitochondrial NARP Syndrome Using AAV-Ribozymes for ATP6

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is the most commonly diagnosed inborn error of metabolism. Clinical presentation ranges from mild hypotonia and hypoglycemia in children to sudden unexpected death. Current therapies including avoidance of fasting, vitamin supplementation, and dietary management are effective, but may not prevent acute clinical decompensations associated with infectious illnesses. Together, this makes MCAD deficiency a good model disease for a safe and durable gene delivery system. The adeno-associated virus subtype 2 (AAV) is known to be a durable gene delivery system which can transduce non-dividing cells and has minimal toxicity in phase 1 human clinical trials. We report here the development of a recombinant AAV vector that expresses the human MCAD gene (AAV-hMCAD). Preliminary studies with the expression cassette demonstrated localization of the MCAD protein to the mitochondria, and correction of the metabolic block in fibroblasts isolated from MCAD deficient patients. Intact AAV-hMCAD particles were produced by triple plasmid transfection in 293 cells then characterized by electron microscopy and ELISA assay. Real-time PCR quantified viral genome containing particles. Human MCAD transcript was identified after AAV-hMCAD infection of MCAD deficient human and murine fibroblasts by RT-PCR. Acyl-carnitine analysis revealed functional correction of the metabolic block seen in MCAD deficient fibroblasts after infection with AAV-hMCAD. Together, these data provide important preliminary data for future in vivo studies in MCAD deficient mice.

Medium Chain Acyl-CoA Dehydrogenase Deficiency in Pennsylvania: Neonatal Screening Shows High Incidence and Unexpected Mutation Frequencies

Medium chain acyl-CoA dehydrogenase deficiency (MCAD) is a defect in the mitochondrial oxidation of fatty acids. The disorder typically presents with episodes of vomiting and hypoglycemia, sometimes with changes in mental status and hepatic failure. These Reye's-like features may culminate in coma and death. Stress, intercurrent illness, and reaction to childhood immunization have been shown to precipitate acute metabolic episodes in MCAD patients. All cases are caused by mutations of the single MCAD gene on chromosome 1. Most clinically ascertained cases are caused by an A985G transition in exon 11. Here we report the preliminary findings of MCAD patients detected prospectively through a supplemental newborn screening program in Pennsylvania using tandem mass spectrometry. From the first 80,371 newborns screened we prospectively found nine babies with MCAD (1/8930) plus two additional newborns screened because of a previously known family history. Molecular analysis showed 56% of the detected patients to be compound heterozygotes for the A985G and a second mutation. This is in contrast to clinical retrospective studies which have found only 20% to be compound heterozygotes. We have identified two of the other mutations including a novel mutation (DG91/C92, 6-bp deletion) in one of our patients by using single-stranded conformation polymorphism (SSCP) and sequence analysis of conformers. Our results confirm that MCAD is one of the more common inborn errors of metabolism. The different mutation frequencies observed between retrospective clinical studies and our prospective newborn screening study suggest that clinical ascertainment may lead to preferential identification of the A985G mutation.

Plasma cis-dec-4-enoic acid measured by isotope dilution mass spectrometry; an improved assay to diagnose medium-chain acyl-CoA dehydrogenase deficiency.

An isotope dilution mass spectrometric assay for plasma cis-dec-4-enoic acid is described. It is quicker, more reliable and more accurate than previous methods. It confirmed previous findings that cis-dec-4-enoic acid is a reliable indicator for medium-chain acyl-CoA dehydrogenase deficiency (MCAD). The plasma cis-dec-4-enoic acid levels of both asymptomatic and symptomatic MCAD patients (3.5-71 mumol/L) are demonstrably higher than those of normal children (0.2-1.7 mumol/L), MCAD heterozygotes (0.1-1.5 mumol/L), those with other fatty acid oxidation defects (0.2-2.2 mumol/L) or those receiving high doses of valproic acid (0.2-0.4 mumol/L).

Fatty acid β-oxidation in leukocytes from control subjects and medium-chain acyl-CoA dehydrogenase deficient patients

In recent years an increasing number of inherited diseases in man have been identified in which there is an impairment in mitochondrial fatty acid oxidation. Diagnosis is usually done by gas-chromatographic analysis of urine, which may give difficulties, since urinary abnormalities may only be present intermittently. We therefore studied whether leukocytes could be used to study mitochondrial β-oxidation directly. The results described herein show that leukocytes are able to β-oxidize octanoate and palmitate. Furthermore, clear abnormalities in octanoate β-oxidation were found in leukocytes from patients with an established deficiency of medium-chain acyl-CoA dehydrogenase, suggesting that measurement of octanoate and palmitate β-oxidation in leukocytes may contribute to rapid diagnosis of medium-chain acyl-CoA dehydrogenase deficiency and presumably other mitochondrial β-oxidation disorders.

Medium‐chain acyl‐CoA dehydrogenase deficiency: Metabolic effects and therapeutic efficacy of long‐terml‐carnitine supplementation

Medium-chain acyl-CoA dehydrogenase deficiency is a recently described inborn error of metabolism characterized by episodes of coma and hypoketotic hypoglycaemia in response to prolonged fasting. Secondary carnitine deficiency has been documented in these patients as well as the excretion in the urine of medium-chain-length acyl carnitine esters, such as octanoylcarnitine. Based on the potential toxicity of medium-chain fatty acid metabolites and the beneficial responses of patients with other inborn errors of metabolism and secondary carnitine deficiency, oral carnitine has been proposed as treatment for children with medium-chain acyl-CoA dehydrogenase deficiency. We report the results of carefully monitored fasting challenges of an infant with this deficiency both before and after 3 months of oral carnitine therapy. Carnitine supplementation failed to prevent lethargy, vomiting, hypoglycaemia and accumulation of free fatty acids in response to fasting despite normalization of plasma carnitine levels and a marked increase in urinary excretion of acyl-carnitine esters. Potentially toxic medium-chain fatty acids accumulated in the plasma in spite of therapy. Based on this study of one patient, we stress that avoidance of fasting and prompt institution of glucose supplementation in situations when oral intake is interrupted remain the mainstays of therapy for medium-chain acyl-CoA dehydrogenase deficient patients.