Sensory neuropathy as a manifestation of multiple acyl-coenzyme A dehydrogenase deficiency.

Multiple acyl-coenzyme A dehydrogenase deficiency (MADD) is a rare metabolic disorder which typically manifests with muscle weakness. However, despite late-onset MADD being treatable, it is often misdiagnosed, due in part to the heterogeneity of presentations. We report a case of late-onset MADD manifesting first as a sensory neuropathy before progressing to myopathic symptoms and acute metabolic decompensation. Early diagnostic workup with acylcarnitine profiling and organic acid analysis was critical in patient outcome; metabolic decompensation and myopathic symptoms were completely reversed with riboflavin supplementation and dietary modification, although sensory neuropathy persisted. Clinical consideration of MADD as part of the differential diagnosis of neuropathy with myopathy is crucial for a timely diagnosis and treatment of MADD.

S1P defects cause a new entity of cataract, alopecia, oral mucosal disorder, and psoriasis-like syndrome.

In this report, we discovered a new entity named cataract, alopecia, oral mucosal disorder, and psoriasis-like (CAOP) syndrome in two unrelated and ethnically diverse patients. Furthermore, patient 1 failed to respond to regular treatment. We found that CAOP syndrome was caused by an autosomal recessive defect in the mitochondrial membrane-bound transcription factor peptidase/site-1 protease (MBTPS1, S1P). Mitochondrial abnormalities were observed in patient 1 with CAOP syndrome. Furthermore, we found that S1P is a novel mitochondrial protein that forms a trimeric complex with ETFA/ETFB. S1P enhances ETFA/ETFB flavination and maintains its stability. Patient S1P variants destabilize ETFA/ETFB, impair mitochondrial respiration, decrease fatty acid ß-oxidation activity, and shift mitochondrial oxidative phosphorylation (OXPHOS) to glycolysis. Mitochondrial dysfunction and inflammatory lesions in patient 1 were significantly ameliorated by riboflavin supplementation, which restored the stability of ETFA/ETFB. Our study discovered that mutations in MBTPS1 resulted in a new entity of CAOP syndrome and elucidated the mechanism of the mutations in the new disease.

Hypoketotic hypoglycemia without neuromuscular complications in patients with SLC25A32 deficiency.

Mitochondrial flavin adenine dinucleotide (FAD) transporter deficiencies are new entities recently reported to cause a neuro-myopathic phenotype. We report three patients from two unrelated families who presented primarily with hypoketotic hypoglycemia. They all had acylcarnitine profiles suggestive of multiple acyl-CoA dehydrogenase deficiency (MADD) with negative next-generation sequencing of electron-transfer flavoprotein genes (ETFA, ETFB, and ETFDH). Whole exome sequencing revealed a homozygous c.272 G > T (p.Gly91Val) variant in exon 2 of the SLC25A32 gene. The three patients shared the same variant, and they all demonstrated similar clinical and biochemical improvement with riboflavin supplementation. To date, these are the first patients to be reported with hypoketotic hypoglycemia without the neuromuscular phenotype previously reported in patients with SLC25A32 deficiency.

Clinical, pathological and genetic features and follow-up of 110 patients with late-onset MADD: a single-center retrospective study.

To observe a long-term prognosis in late-onset multiple acyl-coenzyme-A dehydrogenation deficiency (MADD) patients and to determine whether riboflavin should be administrated in the long-term and high-dosage manner, we studied the clinical, pathological and genetic features of 110 patients with late-onset MADD in a single neuromuscular center. The plasma riboflavin levels and a long-term follow-up study were performed. We showed that fluctuating proximal muscle weakness, exercise intolerance and dramatic responsiveness to riboflavin treatment were essential clinical features for all 110 MADD patients. Among them, we identified 106 cases with ETFDH variants, 1 case with FLAD1 variants and 3 cases without causal variants. On muscle pathology, fibers with cracks, atypical ragged red fibers (aRRFs) and diffuse decrease of SDH activity were the distinctive features of these MADD patients. The plasma riboflavin levels before treatment were significantly decreased in these patients as compared to healthy controls. Among 48 MADD patients with a follow-up of 6.1 years on average, 31 patients were free of muscle weakness recurrence, while 17 patients had episodes of slight muscle weakness upon riboflavin withdrawal, but recovered after retaking a small-dose of riboflavin for a short-term. Multivariate Cox regression analysis showed vegetarian diet and masseter weakness were independent risk factors for muscle weakness recurrence. In conclusion, fibers with cracks, aRRFs and diffuse decreased SDH activity could distinguish MADD from other genotypes of lipid storage myopathy. For late-onset MADD, increased fatty acid oxidation and reduced riboflavin levels can induce episodes of muscle symptoms, which can be treated by short-term and small-dose of riboflavin therapy.

Riboflavin in Neurological Diseases: A Narrative Review.

Riboflavin is classified as one of the water-soluble B vitamins. It is part of the functional group of flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) cofactors and is required for numerous flavoprotein-catalysed reactions. Riboflavin has important antioxidant properties, essential for correct cell functioning. It is required for the conversion of oxidised glutathione to the reduced form and for the mitochondrial respiratory chain as complexes I and II contain flavoprotein reductases and electron transferring flavoproteins. Riboflavin deficiency has been demonstrated to impair the oxidative state of the body, especially in relation to lipid peroxidation status, in both animal and human studies. In the nervous system, riboflavin is essential for the synthesis of myelin and its deficiency can determine the disruption of myelin lamellae. The inherited condition of restricted riboflavin absorption and utilisation, reported in about 10-15% of world population, warrants further investigation in relation to its association with the main neurodegenerative diseases. Several successful trials testing riboflavin for migraine prevention were performed, and this drug is currently classified as a Level B medication for migraine according to the American Academy of Neurology evidence-based rating, with evidence supporting its efficacy. Brown-Vialetto-Van Laere syndrome and Fazio-Londe diseases are now renamed as "riboflavin transporter deficiency" because these are autosomal recessive diseases caused by mutations of SLC52A2 and SLC52A3 genes that encode riboflavin transporters. High doses of riboflavin represent the mainstay of the therapy of these diseases and high doses of riboflavin should be rapidly started as soon as the diagnosis is suspected and continued lifelong. Remarkably, some mitochondrial diseases respond to supplementation with riboflavin. These include multiple acyl-CoA-dehydrogenase deficiency (which is caused by ETFDH gene mutations in the majority of the cases, or mutations in the ETFA and ETFB genes in a minority), mutations of ACAD9 gene, mutations of AIFM1 gene, mutations of the NDUFV1 and NDUFV2 genes. Therapeutic riboflavin administration has been tried in other neurological diseases, including stroke, multiple sclerosis, Friedreich's ataxia and Parkinson's disease. Unfortunately, the design of these clinical trials was not uniform, not allowing to accurately assess the real effects of this molecule on the disease course. In this review we analyse the properties of riboflavin and its possible effects on the pathogenesis of different neurological diseases, and we will review the current indications of this vitamin as a therapeutic intervention in neurology.

ETF dehydrogenase advances in molecular genetics and impact on treatment.

Electron transfer flavoprotein dehydrogenase, also called ETF-ubiquinone oxidoreductase (ETF-QO), is a protein localized in the inner membrane of mitochondria, playing a central role in the electron-transfer system. Indeed, ETF-QO mediates electron transport from flavoprotein dehydrogenases to the ubiquinone pool. ETF-QO mutations are often associated with riboflavin-responsive multiple acyl-CoA dehydrogenase deficiency (RR-MADD, OMIM#231680), a multisystem genetic disease characterized by various clinical manifestations with different degrees of severity. In this review, we outline the clinical features correlated with ETF-QO deficiency and the benefits obtained from different treatments, such as riboflavin, L-carnitine and/or coenzyme Q10 supplementation, and a diet poor in fat and protein. Moreover, we provide a detailed summary of molecular and bioinformatic investigations, describing the mutations identified in ETFDH gene and highlighting their predicted impact on enzymatic structure and activity. In addition, we report biochemical and functional analysis, performed in HEK293 cells and patient fibroblasts and muscle cells, to show the relationship between the nature of ETFDH mutations, the variable impairment of enzyme function, and the different degrees of RR-MADD severity. Finally, we describe in detail 5 RR-MADD patients carrying different ETFDH mutations and presenting variable degrees of clinical symptom severity.

Clinical characteristics and gene mutation analysis of an adult patient with ETFDH­related multiple acyl­CoA dehydrogenase deficiency.

Multiple acyl­CoA dehydrogenase deficiency (MADD) is a rare autosomal recessive disorder of fatty acid metabolism caused by defects in electron transfer flavoprotein (ETF) or electron transfer flavoprotein dehydrogenase (ETFDH). These defects are mainly classified into the neonatal and late­onset types, based on their clinical manifestations. ETFDH gene mutations are generally considered to be associated with the late­onset type. The present study reported an adult woman with late­onset MADD accompanied with biochemical and muscle biopsy findings indicating metabolic disorders. Gene sequencing analysis showed that the c.1514T>C homozygous mutation in the region of the 12th exon of the ETFDH gene, which led to the amino acid substitution p.I505T (isoleucine > threonine), resulting in defective ETFDH protein function. The results of family verification revealed that the homozygous mutation originated from her parents. The female patient was treated with a large dose of vitamin B2, L­carnitine and coenzyme Q10, and the symptoms were significantly relieved. The c.1514T>C mutation in the ETFDH gene, was considered as a novel pathogenic mutation that had not been previously reported. Therefore, it was hypothesized that this mutation was responsible for the clinical characteristics of the adult female patient. Overall, this novel mutation could expand the spectrum of the ETFDH gene mutation and provide the basis for the etiological and prenatal diagnosis of MADD.

Neonatal-onset multiple acyl-CoA dehydrogenase deficiency (MADD) in the ETFDH gene: A case report and a literature review.

RATIONALE: Multiple acyl-CoA dehydrogenase deficiency (MADD) is a rare inborn error of metabolism affecting fatty acid, amino acid, and choline metabolism. The clinical manifestation of MADD is heterogeneous, from severe neonatal forms to mild late-onset forms. PATIENT CONCERNS: Here, we report a patient who presented with severe hypoglycemia and exercise intolerance suggestive of MADD. Serum tandem mass spectrometry analysis indicated elevated levels of various acyl carnitines at 25 days of age. Exome sequencing of the proband revealed compound heterozygous mutations, c. 413T>G (p.Leu138Arg) and c.1667C > G (p.Pro556Arg), in the ETFDH gene as the probable causative mutations. DIAGNOSES: Based on the patient's clinical presentation and test results, the patient was diagnosed with MADD. INTERVENTIONS: A high-calorie and reduced-fat diet was given together with oral supplements of L-carnitine (150 mg/day). OUTCOMES: He passed away at the age of 4 months because of severe respiratory distress accompanied by muscle weakness. LESSONS: He passed away at the age of 4 months because of severe respiratory distress accompanied by muscle weakness. Clinicians should consider MADD in the differential diagnosis when patients present with muscle weakness and biochemical abnormalities. Gene testing plays a critical role in confirming the diagnosis of MADD and may not only prevent the need for invasive testing but also allow for timely initiation of treatment.

A case report of a mild form of multiple acyl-CoA dehydrogenase deficiency due to compound heterozygous mutations in the ETFA gene.

BACKGROUND: Multiple acyl-CoA dehydrogenase deficiency (MADD), previously called glutaric aciduria type II, is a rare congenital metabolic disorder of fatty acids and amino acids oxidation, with recessive autosomal transmission. The prevalence in the general population is estimated to be 9/1,000,000 and the prevalence at birth approximately 1/200,000. The clinical features of this disease are divided into three groups of symptoms linked to a defect in electron transfer flavoprotein (ETF) metabolism. In this case report, we present new pathogenic variations in one of the two ETF protein subunits, called electron transfer flavoprotein alpha (ETFA), in a childhood-stage patient with no antecedent. CASE PRESENTATION: A five-year-old child was admitted to the paediatric emergency unit for seizures without fever. He was unconscious due to hypoglycaemia confirmed by laboratory analyses. At birth, he was a eutrophic full-term new-born with a normal APGAR index (score for appearance, pulse, grimace, activity, and respiration). He had one older brother and no parental consanguinity was reported. A slight speech acquisition delay was observed a few months before his admission, but he had no schooling problems. MADD was suspected based on urinary organic acids and plasma acylcarnitine analyses and later confirmed by genetic analysis, which showed previously unreported ETFA gene variations, both heterozygous (c.354C > A (p.Asn118Lys) and c.652G > A (p.Val218Met) variations). Treatment was based on avoiding fasting and a slow carbohydrate-rich evening meal associated with L-carnitine supplementation (approximately 100 mg/kg/day) for several weeks. This treatment was maintained and associated with riboflavin supplementation (approximately 150 mg/day). During follow up, the patient exhibited normal development and normal scholastic performance, with no decompensation. CONCLUSION: This case report describes new pathogenic variations of the ETFA gene. These compound heterozygous mutations induce the production of altered proteins, leading to a mild form of MADD.

Adolescent Hyperuricemia with Lipid Storage Myopathy: A Clinical Study.

BACKGROUND In this study, we investigated the clinical and pathological features of patients with lipid storage myopathy (LSM) complicated with hyperuricemia, to improve clinicians' understanding of metabolic multi-muscular disorder with metabolic disorders, and to reduce the risk of missed diagnosis of LSM. MATERIAL AND METHODS From January 2005 to December 2017, 8 patients underwent muscle biopsy and diagnosed by muscle pathology and genetic testing in our hospital. All 8 patients were in compliance with LSM diagnosis. We collected data on the patient's clinical performance, adjuvant examination, treatment, and outcomes to provide a comprehensive report and description of LSM patients with hyperuricemia. RESULTS All patients were diagnosed as having ETFDH gene mutations. The main clinical manifestations of patients were chronic limb and trunk weakness, limb numbness, and muscle pain. The serum creatine kinase (CK) values in all patients were higher than normal values. Electromyography showed 3 cases of simple myogenic damage and 3 cases of neurogenic injury. Hematuria metabolic screening showed that 2 patients had elevated glutaric aciduria, and 1 patient had elevated fatty acyl carnitine in the blood. All patients were given riboflavin treatment, and the clinical symptoms were significantly improved, and 3 patients returned to normal uric acid levels after treatment. Pathological staining showed an abnormal deposition of lipid droplets in muscle fibers. CONCLUSIONS If an adolescent hyperuricemia patient has abnormal limb weakness, exercise intolerance, and elevated serum CK values, clinicians need to be highly alert to the possibility of LSM. Early diagnosis and treatment of LSM should improve the clinical symptoms and quality of life and reduce complications.

Molecular and Clinical Investigations on Portuguese Patients with Multiple acyl-CoA Dehydrogenase Deficiency.

BACKGROUND: Multiple Acyl-CoA Dehydrogenase Deficiency (MADD) is a congenital rare metabolic disease with broad clinical phenotypes and variable evolution. This inborn error of metabolism is caused by mutations in the ETFA, ETFB or ETFDH genes, which encode for the mitochondrial ETF and ETF:QO proteins. A considerable group of patients has been described to respond positively to riboflavin oral supplementation, which constitutes the prototypic treatment for the pathology. OBJECTIVES: To report mutations in ETFA, ETFB and ETFDH genes identified in Portuguese patients, correlating, whenever possible, biochemical and clinical outcomes with the effects of mutations on the structure and stability of the affected proteins, to better understand MADD pathogenesis at the molecular level. METHODS: MADD patients were identified based on the characteristic urinary profile of organic acids and/or acylcarnitine profiles in blood spots during newborn screening. Genotypic, clinical and biochemical data were collected for all patients. In silico structural analysis was employed using bioinformatic tools carried out in an ETF:QO molecular model for the identified missense mutations. RESULTS: A survey describing clinical and biochemical features of eight Portuguese MADD patients was made. Genotype analysis identified five ETFDH mutations, including one extension (p.X618QextX*14), two splice mutations (c.34+5G>C and c.405+3A>T) and two missense mutations (ETF:QO-p.Arg155Gly and ETF:QO-p.Pro534Leu), and one ETFB mutation (ETFß- p.Arg191Cys). Homozygous patients containing the ETFDH mutations p.X618QextX*14, c.34+5G>C and ETF:QO-p.Arg155Gly, all presented severe (lethal) MADD phenotypes. However, when any of these mutations are in heterozygosity with the known ETF:QO-p.Pro534Leu mild variant, the severe clinical effects are partly and temporarily attenuated. Indeed, the latter destabilizes an ETF-interacting loop, with no major functional consequences. However, the position 155 in ETF:QO is localized at the ubiquinone binding and membrane interacting domain, and is thus expected to perturb protein structure and membrane insertion, with severe functional effects. Structural analysis of molecular models is therefore demonstrated to be a valuable tool to rationalize the effects of mutations in the context of the clinical phenotype severity. CONCLUSION: Advanced molecular diagnosis, structural analysis and clinical correlations reveal that MADD patients harboring a severe prognosis mutation in one allele can actually revert to a milder phenotype by complementation with a milder mutation in the other allele. However, such patients are nevertheless in a precarious metabolic balance which can revert to severe fatal outcomes during catabolic stress or secondary pathology, thus requiring strict clinical follow-up.

ETF-QO Mutants Uncoupled Fatty Acid ß-Oxidation and Mitochondrial Bioenergetics Leading to Lipid Pathology.

The electron-transfer flavoprotein dehydrogenase gene (ETFDH) that encodes the ETF-ubiquinone oxidoreductase (ETF-QO) has been reported to be the major cause of multiple acyl-CoA dehydrogenase deficiency (MADD). ETF-QO is an electron carrier that mainly functions in mitochondrial fatty acid ß-oxidation and the delivery of electrons to the ubiquinone pool in the mitochondrial respiratory chain. A high frequency of c.250G>A has been found in Taiwanese patients with late-onset MADD. We postulated that the ETFDH c.250G>A mutation may concomitantly impair fatty acid ß-oxidation and mitochondrial function. Using MADD patient-derived lymphoblastoid cells and specifically overexpressed ETFDH c.92C>T, c.250G>A, or coexisted c.92C>T and c.250G>A (c.92C>T + c.250G>A) mutated lymphoblastoid cells, we addressed the genotype-phenotype relationship of ETFDH variation in the pathogenesis of MADD. The decreased adenosine triphosphate synthesis, dissipated mitochondrial membrane potentials, reduced mitochondrial bioenergetics, and increased neutral lipid droplets and lipid peroxides were found in the MADD patient-derived lymphoblastoid cells. Riboflavin and/or coenzyme Q10 supplementation rescued cells from lipid droplet accumulation. All three mutant types, c.92C>T, c.250G>A, or c.92C>T + c.250G>A, had increased lipid droplet accumulation after treatment with palmitic acid. These results help to clarify the molecular pathogenesis of MADD as a result of the high frequency of the ETFDH c.250G>A and c.92C>T mutations.

Acute-onset multiple acyl-CoA dehydrogenase deficiency mimicking Guillain-Barré syndrome: two cases report.

BACKGROUND: Multiple acyl-CoA dehydrogenase deficiency (MADD) showed great clinical heterogeneity and poses a challenge to diagnosis. Guillain-Barré syndrome (GBS) is an acute-onset autoimmune-mediated peripheral neuropathy. However, no patients of acute-onset MADD mimicking the GBS phenotype are reported previously. CASE PRESENTATION: Two patients displayed acute-onset limb weakness, areflexia, and length-dependent sensory disturbances, which clinically indicate the diagnosis of GBS, but electrophysiological and cerebrospinal fluid results threw doubtful points to the initial diagnosis. The muscle biopsy showed lipid storage disorder; and compound heterozygous mutations in the electron transfer flavoprotein dehydrogenase (ETFDH) gene were found in the two patients through targeted next generation sequencing, which provided the definite diagnostic evidences of late-onset MADD. Muscle weakness was quickly improved by riboflavin supplementation, but sensory disturbances required a long-term treatment. DISCUSSION: The present two cases have demonstrated that MADD can mimic GBS. Taking into consideration the significant differences of therapeutic regimen and prognosis, MADD should be included in the differential diagnosis of GBS.

Characterization of two ETFDH mutations in a novel case of riboflavin-responsive multiple acyl-CoA dehydrogenase deficiency.

BACKGROUND: Deficiency of electron transfer flavoprotein dehydrogenase (ETFDH) is associated with multiple acyl-CoA dehydrogenase deficiency (MADD). This disorder is an autosomal recessive lipid storage myopathy (LSM) that exhibits a wide range of clinical features, including myopathy, weakness and multisystem dysfunctions. Many patients with late onset of MADD improve when treated with riboflavin and are also referred to as RR-MADD (riboflavin-responsive multiple Acyl-CoA dehydrogenase disorder). METHODS: In this study, we report the clinical and genetic characterization of a novel RR-MADD patient. Biochemical data were obtained from analysis of muscle and plasma samples. DNA and RNA were extracted from peripheral blood, and sequence analysis and expression study of ETFDH gene were performed. Finally, the impact of mutations on ETFDH folding was evaluated using bioinformatic tools. RESULTS: Patient initially presented with vomiting, muscle weakness, and acidosis. Muscle biopsy revealed typical myopathological patterns of lipid storage myopathy and blood acylcarnitine profiles showed a combined elevation of long and medium chain acylcarnitines, supporting the diagnosis of RR-MADD. Molecular analysis of ETFDH gene revealed two heterozygous mutations, a novel splice variation in intron 10, c.1285 + 1G > A, and the previously reported c.560C > T missense mutation. RT-PCR analysis showed an alteration of ETFDH RNA splicing which in turn should lead to the production of a truncated protein. The in silico prediction analysis of ETFDH tridimensional structure demonstrated that the missense mutation resulted in instability and loss of protein activation, while the splice site variation induced a dramatic conformational change of the truncated protein. After MCT diet supplemented with carnitine and riboflavin, the patient showed significant biochemical and clinical improvement, in spite of severe molecular defect. CONCLUSION: This case report extends the spectrum of ETFDH mutations in MADD, providing further evidence that patients presenting at least one missense mutation in the FAD-binding domain may respond to either carnitine or riboflavin treatment, due to the recovery of some enzymatic activity.

ETFDH Mutations and Flavin Adenine Dinucleotide Homeostasis Disturbance Are Essential for Developing Riboflavin-Responsive Multiple Acyl-Coenzyme A Dehydrogenation Deficiency.

OBJECTIVE: Riboflavin-responsive multiple acyl-coenzyme A dehydrogenation deficiency (RR-MADD) is an inherited fatty acid metabolism disorder mainly caused by genetic defects in electron transfer flavoprotein-ubiquinone oxidoreductase (ETF:QO). The variant ETF:QO protein folding deficiency, which can be corrected by therapeutic dosage of riboflavin supplement, has been identified in HEK-293 cells and is believed to be the molecular mechanism of this disease. To verify this hypothesis in vivo, we generated Etfdh (h)A84T knockin (KI) mice. METHODS: Tissues from these mice as well as muscle biopsies and fibroblasts from 7 RR-MADD patients were used to examine the flavin adenine dinucleotide (FAD) concentration and ETF:QO protein amount. RESULTS: All of the homozygous KI mice (Etfdh (h)A84T/(h)A84T , KI/KI) were initially normal. After being given a high-fat and vitamin B2 -deficient (HF-B2 D) diet for 5 weeks, they developed weight loss, movement ability defects, lipid storage in muscle and liver, and elevated serum acyl-carnitine levels, which are clinically and biochemically similar to RR-MADD patients. Both ETF:QO protein and FAD concentrations were significantly decreased in tissues of HF-B2 D-KI/KI mice and in cultured fibroblasts from RR-MADD patients. After riboflavin treatment, ETF:QO protein increased in proportion to elevated FAD concentrations, but not related to mRNA levels. These results were further confirmed in cultured fibroblasts from RR-MADD patients. INTERPRETATION: For the first time, we successfully developed a RR-MADD mice model and confirmed that FAD homeostasis disturbances played a crucial role on the pathomechanism of RR-MADD in this mouse model and culture cells from patients. Supplementation of riboflavin may stabilize variant ETF:QO protein by rebuilding FAD homeostasis. Ann Neurol 2018;84:667-681.

Coenzyme Q10 serves to couple mitochondrial oxidative phosphorylation and fatty acid ß-oxidation, and attenuates NLRP3 inflammasome activation.

Multiple acyl-CoA dehydrogenase deficiency (MADD), an autosomal recessive metabolic disorder of fatty acid metabolism, is mostly caused by mutations in the ETFA, ETFB or ETFDH genes that result in dysfunctions in electron transfer flavoprotein (ETF) or electron transfer flavoprotein-ubiquinone dehydrogenase (ETFDH). In ß-oxidation, fatty acids are processed to generate acyl-CoA, which is oxidised by flavin adenine dinucleotide and transfers an electron to ETF and, through ETFDH, to mitochondrial respiratory complex III to trigger ATP synthesis. Coenzyme Q10 (CoQ10) is believed to be a potential treatment that produces symptom relief in some MADD patients. CoQ10 acts as a key regulator linking ETFDH and mitochondrial respiratory complex III. Our aim is to investigate the effectiveness of CoQ10 in serving in the ETF/ETFDH system to improve mitochondrial function and to reduce lipotoxicity. In this study, we used lymphoblastoid cells with an ETFDH mutation from MADD patients. ETFDH dysfunction caused insufficient ß-oxidation, leading to increasing lipid droplet and lipid peroxide accumulation. In contrast, supplementation with CoQ10 significantly recovered mitochondrial function and concurrently decreased the generation of reactive oxygen species and lipid peroxides, inhibited the accumulation of lipid droplets and the formation of the NOD-like receptor family pyrin domain-containing three (NLRP3) inflammasome, and reduced interleukin-1ß release and cell death. These results clarify the causal role of CoQ10 in coupling the electron transport chain with ß-oxidation, which may promote the development of CoQ10-directed therapies for MADD patients.

[Clinical features and ETFDH mutations of children with late-onset glutaric aciduria type II: a report of two cases].

OBJECTIVE: To investigate the clinical and genetic features of two families with late-onset glutaric aciduria type II caused by ETFDH mutations. METHODS: Target gene sequence capture and next generation sequencing were used for sequencing of suspected patients and their family members. The patients' clinical features were retrospectively analyzed and literature review was performed. RESULTS: The probands of the two families had a clinical onset at the ages of 10 years and 5.5 years respectively, with the clinical manifestations of muscle weakness and muscle pain. Laboratory examinations revealed significant increases in the serum levels of creatine kinase, creatine kinase-MB, and lactate dehydrogenase. Tandem mass spectrometry showed increases in various types of acylcarnitines. The analysis of urine organic acids showed an increase in glutaric acid. Electromyography showed myogenic damage in both patients. Gene detection showed two novel mutations in the ETFDH gene (c.1331T>C from the mother and c.824C>T from the father) in patient 1, and the patient's younger brother carried the c.1331T>C mutation but had a normal phenotype. In patient 2, there was a novel mutation (c.177insT from the father) and a known mutation (c.1474T>C from the mother) in the ETFDH gene. Several family members carried such mutations. Both patients were diagnosed with glutaric aciduria type II. Their symptoms were improved after high-dose vitamin B2 treatment. CONCLUSIONS: For patients with unexplained muscle weakness and pain, serum creatine kinase, acylcarnitines, and urinary organic acids should be measured, and the possibility of glutaric aciduria type II should be considered. Genetic detection is helpful to make a confirmed diagnosis.

Neurite growth could be impaired by ETFDH mutation but restored by mitochondrial cofactors.

INTRODUCTION: c.250G>A (p.Ala84Thr) in ETFDH is the most common mutation that causes later-onset multiple acyl-coenzyme A dehydrogenase deficiency (MADD) in the southern Chinese population. No functional study has targeted this mutation. METHODS: Using cells expressing ETFDH-wild-type (WT) or ETFDH-mutant (p.Ala84Thr), reactive oxygen species (ROS) production and neurite length were analyzed, followed by pathomechanism exploration and drug screening. RESULTS: Increased ROS production and marked neurite shortening were observed in the cells expressing the ETFDH-mutant, compared with WT. Further studies demonstrated that suberic acid, an accumulated intermediate metabolite in MADD, could significantly impair neurite outgrowth of NSC34 cells, but neurite shortening could be restored by supplementation with carnitine, riboflavin, or Coenzyme Q10. CONCLUSIONS: Neurite shortening caused by the c.250G>A mutation in ETFDH suggests that neural defects could be underdiagnosed in human patients with MADD. This impairment might be treatable with mitochondrial cofactor supplementation. Muscle Nerve 56: 479-485, 2017.

[Clinical features and gene mutations in a patient with multiple aeyl-CoA dehydrogenase deficiency with severe fatty liver].

OBJECTIVE: To analyze the clinical features and gene mutations in an adolescent patient affected with late-onset multiple aeyl-CoA dehydrogenase deficiency (MADD) with severe fatty liver. METHODS: Potential mutations of the ETFDH gene were detected with polymerase chain reaction (PCR) and DNA sequencing. RESULTS: The 13-year-and-10-month girl has presented with weakness without any other special manifestation. Laboratory tests demonstrated an elevation of myocardial enzyme levels, total cholesterol, lactic acid and abnormal serum free fatty acids. H magnetic resonance spectroscopy revealed severe fatty liver. An increase in multiple plasma acyl-carnitines was detected by gas chromatography/mass spectrometry and isobutyrylglycine in urine by screening with tandem mass spectrometry. Genetic analysis demonstrated 2 heterozygous missense mutations c.250G>A (p.Ala84Thr) and c.353G>T (p.Cys118Phe) in the ETFDH gene. The diagnosis of MADD was confirmed. The patient was given large dose of vitamin B2, which resulted in rapid clinical and biochemical improvement. CONCLUSION: A common mutation c.250G>A and a novel mutation c.353G>T in the ETFDH gene were identified in the patient. The pathogenic role of c.353G>T (p.Cys118Phe) deserves further study. Early diagnosis of MADD and appropriate therapy is crucial for the prognosis.