Dynamic Regulation of Long-Chain Fatty Acid Oxidation by a Noncanonical Interaction between the MCL-1 BH3 Helix and VLCAD.

MCL-1 is a BCL-2 family protein implicated in the development and chemoresistance of human cancer. Unlike its anti-apoptotic homologs, Mcl-1 deletion has profound physiologic consequences, indicative of a broader role in homeostasis. We report that the BCL-2 homology 3 (BH3) α helix of MCL-1 can directly engage very long-chain acyl-CoA dehydrogenase (VLCAD), a key enzyme of the mitochondrial fatty acid ß-oxidation (FAO) pathway. Proteomic analysis confirmed that the mitochondrial matrix isoform of MCL-1 (MCL-1Matrix) interacts with VLCAD. Mcl-1 deletion, or eliminating MCL-1Matrix alone, selectively deregulated long-chain FAO, causing increased flux through the pathway in response to nutrient deprivation. Transient elevation in MCL-1 upon serum withdrawal, a striking increase in MCL-1 BH3/VLCAD interaction upon palmitic acid titration, and direct modulation of enzymatic activity by the MCL-1 BH3 α helix are consistent with dynamic regulation. Thus, the MCL-1 BH3 interaction with VLCAD revealed a separable, gain-of-function role for MCL-1 in the regulation of lipid metabolism.

Specifications of the ACMG/AMP guidelines for ACADVL variant interpretation.

Very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency (VLCADD) is a relatively common inborn error of metabolism, but due to difficulty in accurately predicting affected status through newborn screening, molecular confirmation of the causative variants by sequencing of the ACADVL gene is necessary. Although the ACMG/AMP guidelines have helped standardize variant classification, ACADVL variant classification remains disparate due to a phenotype that can be nonspecific, the possibility of variants that produce late-onset disease, and relatively high carrier frequency, amongst other challenges. Therefore, an ACADVL-specific variant curation expert panel (VCEP) was created to facilitate the specification of the ACMG/AMP guidelines for VLCADD. We expect these guidelines to help streamline, increase concordance, and expedite the classification of ACADVL variants.

Very long chain fatty acid metabolism is required in acute myeloid leukemia.

Acute myeloid leukemia (AML) cells have an atypical metabolic phenotype characterized by increased mitochondrial mass, as well as a greater reliance on oxidative phosphorylation and fatty acid oxidation (FAO) for survival. To exploit this altered metabolism, we assessed publicly available databases to identify FAO enzyme overexpression. Very long chain acyl-CoA dehydrogenase (VLCAD; ACADVL) was found to be overexpressed and critical to leukemia cell mitochondrial metabolism. Genetic attenuation or pharmacological inhibition of VLCAD hindered mitochondrial respiration and FAO contribution to the tricarboxylic acid cycle, resulting in decreased viability, proliferation, clonogenic growth, and AML cell engraftment. Suppression of FAO at VLCAD triggered an increase in pyruvate dehydrogenase activity that was insufficient to increase glycolysis but resulted in adenosine triphosphate depletion and AML cell death, with no effect on normal hematopoietic cells. Together, these results demonstrate the importance of VLCAD in AML cell biology and highlight a novel metabolic vulnerability for this devastating disease.

The frequencies of very long-chain acyl-CoA dehydrogenase deficiency genetic variants in Japan have changed since the implementation of expanded newborn screening.

Very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency has been a target of expanded newborn screening (ENBS) using tandem mass spectrometry in Japan. Since the implementation of ENBS, a number of novel ACADVL variants responsible for VLCAD deficiency have been identified. In this study, genotypic differences in Japanese patients with VLCAD deficiency were investigated before and after ENBS. The ACADVL variants in 61 subjects identified through ENBS (ENBS group) and in 40 patients who subsequently developed clinical symptoms without undergoing ENBS (pre-ENBS group) were compared. Subjects in the ENBS group underwent genetic testing and/or VLCAD enzyme activity measurements. Patients in the pre-ENBS group were stratified into three clinical phenotypes and underwent genetic testing. This study revealed that the variants p.K264E, p.K382Q and c.996dupT were found in both groups, but their frequencies were lower in the ENBS group (5.2%, 3.1% and 4.2%, respectively) than in the pre-ENBS group (16.5%, 12.7% and 10.1%, respectively). In addition, p.C607S, p.T409M, p.M478I, p.G289R, p.C237R, p.T260M, and p.R229* were exclusively identified in the ENBS group. Among these variants, p.C607S exhibited the highest frequency (18.8%). The patients who were heterozygous for p.C607S demonstrated 7-42% of control enzyme activity. p.C607S is suspected to be unique to Japanese individuals. According to a comparison of enzyme activity, patients with the p.C607S variant may exhibit higher enzyme activity than those with the p.A416T, p.A180T, p.R450H, and p.K264E variants, which are responsible for the myopathic form of the disease. The VLCAD deficiency genotypes have changed since the initiation of ENBS in Japan.

Characterization of exonic variants of uncertain significance in very long-chain acyl-CoA dehydrogenase identified through newborn screening.

Very long-chain acyl-CoA dehydrogenase deficiency (VLCADD) is an autosomal recessive disease resulting from mutations in the ACADVL gene and is among the disorders tested for in newborn screening (NBS). Confirmatory sequencing following suspected VLCADD NBS results often identifies variants of uncertain significance (VUS) in the ACADVL gene, leading to uncertainty of diagnosis and providing effective treatment regimen. Currently, ACADVL has >300 VUSs in the ClinVar database that requiring characterization to determine potential pathogenicity. In this study, CRISPR/Cas9 genome editing was used to knock out ACADVL in HEK293T cells, and targeted deletion was confirmed by droplet digital polymerase chain reaction (PCR). No VLCAD protein was detected and an 84% decrease in enzyme activity using the electron transfer flavoprotein fluorescence reduction assay and C21-CoA as substrate was observed compared to control. Plasmids containing control or variant ACADVL coding sequence were transfected into the ACADVL null HEK293T. While transfection of control ACADVL restored VLCAD protein and enzyme activity, cells expressing the VLCAD Val283Ala mutant had 18% VLCAD enzyme activity and reduced protein compared to control. VLCAD Ile420Leu, Gly179Arg, and Gln406Pro produced protein comparable to control but 25%, 4%, and 5% VLCAD enzyme activity, respectively. Leu540Pro and Asp570_Ala572dup had reduced VLCAD protein and 10% and 3% VLCAD enzyme activity, respectively. VLCADD fibroblasts containing the same variations had decreased VLCAD protein and activity comparable to the transfection experiments. Generating ACADVL null HEK293T cell line allowed functional studies to determine pathogenicity of ACADVL exonic variants. This approach can be applied to multiple genes for other disorders identified through NBS.

Very Long-Chain Acyl-CoA Dehydrogenase Deficiency Presenting as Rhabdomyolysis.

Presentation A 20 year old female attended the Emergency Department by ambulance following a collapse at a concert. On arrival she was complaining of generalised muscular pain. She had not eaten for over 12 hours and had been dancing for approximately 6 hours. The patient was known to have Very-long-chain acyl-CoA dehydrogenase deficiency (VLCAD). She had a normal exam, and normal vital signs. Diagnosis A diagnosis of rhabdomyolysis was made after her creatinine kinase (CK) was found to be >100000 units/litre (Normal range < 170U/L). Her urine was dark brown with urinalysis positive for blood. Treatment The patient was admitted to the high dependency unit, where she was treated with intravenous fluids. Her urine output and renal function were closely monitored. She made a full recovery and was discharged home four days later. Conclusion (VLCAD) is an inherited, autosomal recessive, metabolic disorder caused by mutations in the ACADVL gene. Management includes treatment of manifestation, primary prevention of manifestation, and prevention of secondary complications.

Clinical outcomes in a series of 18 patients with long chain fatty acids oxidation disorders treated with triheptanoin for a median duration of 22 months.

INTRODUCTION: Triheptanoin provides long-chain fatty acid oxidation disorder (LC-FAOD) patients with an alternative to medium-even-chain triglycerides therapy. MATERIAL-METHODS: Retrospective analysis of 18 French LC-FAOD patients benefiting from early access to triheptanoin treatment. RESULTS: Eight female and 10 male patients with LC-FAOD (VLCAD, LCHAD, CACT, CPTII and MTP) were treated with triheptanoin for a median duration of 22 months (range: 9-228 months). At last consultation, triheptanoin accounted for 15-35% of their daily caloric intake. In the year following the introduction of triheptanoin, patients reported a reduction of intermittent snacking and nocturnal meals. Three patients, including 1 adult, became free of severe hypoglycaemic events. Ten of 12 paediatric patients and 4 of 6 adult patients reported reduced fatigue with reductions in the number and severity of episodes of myalgia. Of 6 patients, including 1 adult, that had required the use of a wheelchair in the year prior to triheptanoin, all but one no longer required its use. The number of emergency hospitalizations decreased, and none were recorded for paediatric patients during these 12 months. Cumulative annual days of emergency care in the home were reduced from 286 to 51 days in the year before and after initiation, respectively, and 13 patients required no such interventions. Adverse events were limited to digestive issues that dissipated over time. CONCLUSIONS: Our case-series suggests that long-term treatment of LC-FAOD paediatric and adult patients with triheptanoin is safe and leads to marked improvement of symptoms and an improved quality of life.

Defects in long-chain 3-hydroxy acyl-CoA dehydrogenase lead to hepatocellular carcinoma: A novel etiology of hepatocellular carcinoma.

The incidence of both nonalcoholic fatty liver disease (NAFLD) and hepatocellular carcinoma (HCC) have been increasing at an alarming rate. Little is known about NAFLD without cirrhosis as a risk for HCC. Here we report, for the first time, generation of a mouse model with a defect in long-chain 3-hydoxy acyl-CoA dehydrogenase (LCHAD). The LCHAD exon 15 deletion was embryonic lethal to the homozygous mice whereas heterozygous mice (HT) develop significant hepatic steatosis starting at young age (3 months old) and HCC at older age (>13 months old) without any evidence of fibrosis or cirrhosis. None of the wild-type (WT) mice developed steatosis and HCC (n = 39), whereas HT-LCHAD mice (n = 41) showed steatosis and ~20% (8/41) developed liver masses with histological features of HCC. Proteomic analysis of liver tissues from WT-mice and HT-mice with no signs of HCC was conducted. Proteins with significant changes in abundance were identified by mass spectrometry. Abundance of 24 proteins was significantly different (p < 0.01) between WT and HT-LCHAD mice. The proteins found to vary in abundance are associated with different cellular response processes ranging from intermediary metabolism of carbohydrate, protein and lipid to oxidative stress, signal transduction and the process of tumorigenesis. Protein expression pattern of the HT-LCHAD mouse liver indicates predisposition to HCC and suggests that impaired hepatic mitochondrial fatty acid oxidation plays an important role in the development and progression of HCC. To assess the implication of these studies in human disease, we demonstrated significant downregulation of HADHA transcripts in HCC patients.

The common K333Q polymorphism in long-chain acyl-CoA dehydrogenase (LCAD) reduces enzyme stability and function.

The fatty acid oxidation enzyme long-chain acyl-CoA dehydrogenase (LCAD) is expressed at high levels in human alveolar type II (ATII) cells in the lung. A common polymorphism causing an amino acid substitution (K333Q) was previously linked to a loss of LCAD antigen in the lung tissue in sudden infant death syndrome. However, the effects of the polymorphism on LCAD function has not been tested. The present work evaluated recombinant LCAD K333Q. Compared to wild-type LCAD protein, LCAD K333Q exhibited significantly reduced enzymatic activity. Molecular modeling suggested that K333 is within interacting distance of the essential FAD cofactor, and the K333Q protein showed a propensity to lose FAD. Exogenous FAD only partially rescued the activity of LCAD K333Q. LCAD K333Q protein was less stable than wild-type when incubated at physiological temperatures, likely explaining the observation of dramatically reduced LCAD antigen in primary ATII cells isolated from individuals homozygous for K333Q. Despite the effect of K333Q on activity, stability, and antigen levels, the frequency of the polymorphism was not increased among infants and children with lung disease.

Nutrition management guideline for very-long chain acyl-CoA dehydrogenase deficiency (VLCAD): An evidence- and consensus-based approach.

The nutrition management guideline for very-long chain acyl-CoA dehydrogenase deficiency (VLCAD) is the fourth in a series of web-based guidelines focusing on the diet treatment for inherited metabolic disorders and follows previous publication of guidelines for maple syrup urine disease (2014), phenylketonuria (2016) and propionic acidemia (2019). The purpose of this guideline is to establish harmonization in the treatment and monitoring of individuals with VLCAD of all ages in order to improve clinical outcomes. Six research questions were identified to support guideline development on: nutrition recommendations for the healthy individual, illness management, supplementation, monitoring, physical activity and management during pregnancy. This report describes the methodology used in its development including review, critical appraisal and abstraction of peer-reviewed studies and unpublished practice literature; expert input through two Delphi surveys and a nominal group process; and external review from metabolic physicians and dietitians. It includes the summary statements of the nutrition management recommendations for each research question, followed by a standardized rating based on the strength of the evidence. Online, open access of the full published guideline allows utilization by health care providers, researchers and collaborators who advise, advocate and care for individuals with VLCAD and their families and can be accessed from the Genetic Metabolic Dietitians International (https://GMDI.org) and Southeast Regional Genetics Network (https://southeastgenetics.org/ngp) websites.

Mitochondrial energetic impairment in a patient with late-onset glutaric acidemia Type 2.

Glutaric acidemia type 2 (GA2), also called multiple acyl-CoA dehydrogenase deficiency, is an autosomal recessive disorder of fatty acid, amino acid, and choline metabolism resulting in excretion of multiple organic acids and glycine conjugates as well as elevation of various plasma acylcarnitine species (C4-C18). It is caused by mutations in the ETFA, ETFB, or ETFDH genes which are involved in the transfer of electrons from 11 flavin-containing dehydrogenases to Coenzyme Q10 (CoQ10 ) of the mitochondrial electron transport chain (ETC). We report a patient who was originally reported as the first case with primary myopathic CoQ10 deficiency when he presented at 11.5 years with exercise intolerance and myopathy that improved after treatment with ubiquinone and carnitine. At age 23, his symptoms relapsed despite increasing doses of ubiquinone and he was shown to have biallelic mutations in the ETFDH gene. Treatment with riboflavin was started and ubiquinone was changed to ubiquinol. After 4 months, the patient recovered his muscle strength with normalization of laboratory exams and exercise tolerance. Functional studies on fibroblasts revealed decreased levels of ETFDH as well as of very long-chain acyl-CoA dehydrogenase and trifunctional protein α. In addition, the mitochondrial mass was decreased, with increased formation of reactive oxygen species and oxygen consumption rate, but with a decreased spared respiratory capacity, and decreased adenosine triphosphate level. These findings of widespread dysfunction of fatty acid oxidation and ETC enzymes support the impairment of a larger mitochondrial ETC supercomplex in our patient.

Cardiac tissue citric acid cycle intermediates in exercised very long-chain acyl-CoA dehydrogenase-deficient mice fed triheptanoin or medium-chain triglyceride.

Anaplerotic odd-chain fatty acid supplementation has been suggested as an approach to replenish citric acid cycle intermediate (CACi) pools and facilitate adenosine triphosphate (ATP) production in subjects with long-chain fatty acid oxidation disorders, but the evidence that cellular CACi depletion exists and that repletion occurs following anaplerotic substrate supplementation is limited. We exercised very long-chain acyl-CoA dehydrogenase-deficient (VLCAD-/-) and wild-type (WT) mice to exhaustion and collected cardiac tissue for measurement of CACi by targeted metabolomics. In a second experimental group, VLCAD-/- and WT mice that had been fed chow prepared with either medium-chain triglyceride (MCT) oil or triheptanoin for 4 weeks were exercised for 60 minutes. VLCAD-/- mice exhibited lower succinate in cardiac muscle at exhaustion than WT mice suggesting lower CACi in VLCAD-/- with prolonged exercise. In mice fed either MCT or triheptanoin, succinate and malate were greater in VLCAD-/- mice fed triheptanoin compared to VLCAD-/- animals fed MCT but lower than WT mice fed triheptanoin. Long-chain odd acylcarnitines such as C19 were elevated in VLCAD-/- and WT mice fed triheptanoin suggesting some elongation of the heptanoate, but it is unknown what proportion of heptanoate was oxidized vs elongated. Prolonged exercise was associated with decreased cardiac muscle succinate in VLCAD-/- mice in comparison to WT mice. VLCAD-/- fed triheptanoin had increased succinate compared to VLCAD-/- mice fed MCT but lower than WT mice fed triheptanoin. Cardiac CACi were higher following dietary ingestion of an anaplerotic substrate, triheptanoin, in comparison to MCT.

Slc22a5 haploinsufficiency does not aggravate the phenotype of the long-chain acyl-CoA dehydrogenase KO mouse.

Secondary carnitine deficiency is commonly observed in inherited metabolic diseases characterised by the accumulation of acylcarnitines such as mitochondrial fatty acid oxidation (FAO) disorders. It is currently unclear if carnitine deficiency and/or acylcarnitine accumulation play a role in the pathophysiology of FAO disorders. The long-chain acyl-CoA dehydrogenase (LCAD) KO mouse is a model for long-chain FAO disorders and is characterised by decreased levels of tissue and plasma free carnitine. Tissue levels of carnitine are controlled by SLC22A5, the plasmalemmal carnitine transporter. Here, we have further decreased carnitine availability in the LCAD KO mouse through a genetic intervention by introducing one defective Slc22a5 allele (jvs). Slc22a5 haploinsufficiency decreased free carnitine levels in liver, kidney, and heart of LCAD KO animals. The resulting decrease in the tissue long-chain acylcarnitines levels had a similar magnitude as the decrease in free carnitine. Levels of cardiac deoxycarnitine, a carnitine biosynthesis intermediate, were elevated due to Slc22a5 haploinsufficiency in LCAD KO mice. A similar increase in heart and muscle deoxycarnitine was observed in an independent experiment using Slc22a5jvs/jvs mice. Cardiac hypertrophy, fasting-induced hypoglycemia and increased liver weight, the major phenotypes of the LCAD KO mouse, were not affected by Slc22a5 haploinsufficiency. This may suggest that secondary carnitine deficiency does not play a major role in the pathophysiology of these phenotypes. Similarly, our data do not support a major role for toxicity of long-chain acylcarnitines in the phenotype of the LCAD KO mouse.

Adult-onset very-long-chain acyl-CoA dehydrogenase deficiency (VLCADD).

BACKGROUND AND PURPOSE: Very-long-chain acyl-CoA dehydrogenase deficiency (VLCADD) is a hereditary disorder of mitochondrial long-chain fatty acid oxidation that has variable presentations, including exercise intolerance, cardiomyopathy and liver disease. The aim of this study was to describe the clinical and genetic manifestations of six patients with adult-onset VLCADD. METHODS: In this study, the clinical, pathological and genetic findings of six adult patients (four from Iran and two from Serbia) with VLCADD and their response to treatment are described. RESULTS: The median (range) age of patients at first visit was 31 (27-38) years, and the median (range) age of onset was 26.5 (19-33) years. Parental consanguinity was present for four patients. Four patients had a history of rhabdomyolysis, and the recorded CK level ranged between 67 and 90 000 IU/l. Three patients had a history of exertional myalgia, and one patient had a non-fluctuating weakness. Through next-generation sequencing analysis, we identified six cases with variants in the ACADVL gene and a confirmed diagnosis of VLCADD. Of the total six variants identified, five were missense, and one was a novel frameshift mutation identified in two unrelated individuals. Two variants were novel, and three were previously reported. We treated the patients with a combination of L-carnitine, Coenzyme Q10 and riboflavin. Three patients responded favorably to the treatment. CONCLUSION: Adult-onset VLCADD is a rare entity with various presentations. Patients may respond favorably to a cocktail of L-carnitine, Coenzyme Q10, and riboflavin.

[Genetic analysis of a child with very long chain acyl-CoA dehydrogenase deficiency].

OBJECTIVE: To analyze the clinical and molecular characteristics of a child with very long chain acyl-CoA dehydrogenase deficiency (VLCADD). METHODS: Peripheral blood sample of the patient was collected for the extraction of genomic DNA. Next generation sequencing (NGS) was carried out for the proband. Suspected mutations were validated by Sanger sequencing. RESULTS: The patient, a 12-month-old girl, was admitted for diarrhea, vomiting, fever, poor spirit and decreased blood pressure. During the course of the disease, she also manifested hypertrophic cardiomyopathy, cardiogenic shock, elevated myocardial enzyme kinase, fever and metabolic acidosis, and had died after three days due to ventricular tachycardia and respiratory failure. Genetic testing showed that she has carried heterozygous mutations of of the ACADVL gene, namely c.664G>A (exon 8) and c.1056_1057del (exon 10). Blood screening for metabolic genetic diseases showed increased C12, C14, C16, C18, C14:1, C14:2, C16:1, C4/C3 and C8/C3, accompanied with decreased C0, C0/C16 and C8/C10. VLCADD and secondary carnitine deficiency could not be excluded, which was in keeping with the result of genetic testing. CONCLUSION: The child was diagnosed with VLCADD, which may be attributed to the compound heterozygous c.664G>A and c.1056_1057del variants of the ACADVL gene.

Clinical and biochemical outcome of patients with very long-chain acyl-CoA dehydrogenase deficiency.

BACKGROUND: Very-Long-Chain Acyl-CoA Dehydrogenase (VLCAD) deficiency is a disorder of fatty acid oxidation included in the recommended uniform newborn screening (NBS) panel in the USA. It can have variable clinical severity and there is limited information on the natural history of this condition, clinical presentation according to genotype and effectiveness of newborn screening. METHODS: Retrospective data (growth parameters, morbidity, biochemical and genetic testing results) were collected from patients with VLCAD deficiency, to evaluate biochemical and clinical outcomes. Descriptive statistics was used for qualitative variables, while linear regression analysis was used to correlate continuous variables. RESULTS: VLCAD deficiency (screened by measuring elevated levels of C14:1-carnitine in blood spots) was more frequent in Utah than the national average (1:27,617 versus 1:63,481) in the first ten years of screening. Twenty-six patients had a confirmed diagnosis of VLCAD deficiency using DNA testing or functional studies. The c.848T>C (p.V283A) variant in the ACADVL gene was the most frequent in our population. Novel variants (c.623-21A>G (IVS7-21A>G); c.1052C>T (p.T351I); c.1183-7A>G (IVS11-7A>G); c.1281G>C (p.W427C); c.1923G>C (p.L641F); c.1924G>A (p.V642M)) were identified in this study, with their pathogenicity remaining unclear in most cases. C14:1-carnitine levels decreased with age and significantly correlated with CK levels as index of muscle involvement. There were no cases of HELLP syndrome nor liver disease during pregnancies in the mothers of VLCAD patients. None of our patients developed cardiac involvement after birth and all patients had normal growth parameters while on treatment. Clinical manifestations were related to concomitant infections and altered biochemical parameters. DISCUSSION: VLCAD deficiency can be identified by neonatal screening. Most patients compliant with therapy normalized biochemical parameters and had no major clinical manifestations. Complications were completely prevented with a relatively low number of pre-emptive ER visits or hospital admissions. It remains unclear whether neonatal screening is now identifying less severely affected patient or if complications will arise as subjects become older. Observation beyond puberty is necessary to fully understand the impact of VLCAD deficiency on morbidity in patients with VLCAD deficiency.

Changes in adipose tissue physiology during the first two weeks posthatch in chicks from lines selected for low or high body weight.

Chickens from lines selected for low (LWS) or high (HWS) body weight (BW) differ in appetite and adiposity. Mechanisms associated with the predisposition to becoming obese are unclear. The objective of the experiment was to evaluate developmental changes in depot-specific adipose tissue during the first 2 wk posthatch. Subcutaneous (SQ), clavicular (CL), and abdominal (AB) depots were collected at hatch (DOH) and days 4 (D4) and 14 (D14) posthatch for histological and mRNA measurements. LWS chicks had decreased SQ fat mass on a BW basis with reduced adipocyte size from DOH to D4 and increased BW and fat mass with unchanged adipocyte size from D4 to D14. HWS chicks increased in BW from DOH to D14 and increased in fat mass in all three depots with enlarged adipocytes in the AB depot from D4 to D14. Meanwhile, CCAAT/enhancer-binding protein-α, neuropeptide Y, peroxisome proliferator-activated receptor-γ, and acyl-CoA dehydrogenase mRNAs differed among depots between lines at different ages. Plasma nonesterified fatty acids were greater in LWS than HWS at D4 and D14. From DOH to D4, LWS chicks mobilized SQ fat and replenished the reservoir through hyperplasia, whereas HWS chicks were dependent on hyperplasia and hypertrophy to maintain adipocyte size and depot mass. From D4 to D14, adipose tissue catabolism and adipogenesis slowed. Whereas LWS fat depots and adipocyte sizes remained stable, HWS chicks rapidly accumulated fat in CL and AB depots. Chicks predisposed to be anorexic or obese have different fat development patterns during the first 2 wk posthatch.

Impact of newborn screening for very-long-chain acyl-CoA dehydrogenase deficiency on genetic, enzymatic, and clinical outcomes.

Most infants with very-long-chain acyl-CoA dehydrogenase deficiency (VLCADD) identified by newborn screening (NBS) are asymptomatic at the time of diagnosis and remain asymptomatic. If this outcome is due to prompt diagnosis and initiation of therapy, or because of identification of individuals with biochemical abnormalities who will never develop symptoms, is unclear. Therefore, a 10-year longitudinal national cohort study of genetically confirmed VLCADD patients born before and after introduction of NBS was conducted. Main outcome measures were clinical outcome parameters, acyl-CoA dehydrogenase very long chain gene analysis, VLCAD activity, and overall capacity of long-chain fatty acid oxidation (LC-FAO flux) in lymphocytes and cultured skin fibroblasts. Median VLCAD activity in lymphocytes of 54 patients, 21 diagnosed pre-NBS and 33 by NBS was, respectively, 5.4% (95% confidence interval [CI]: 4.0-8.3) and 12.6% (95% CI: 10.7-17.7; P < 0.001) of the reference mean. The median LC-FAO flux was 33.2% (95% CI: 22.8-48.3) and 41% (95% CI: 40.8-68; P < 0.05) of the control mean, respectively. Clinical characteristics in 23 pre-NBS and 37 NBS patients revealed hypoglycemic events in 12 vs 2 patients, cardiomyopathy in 5 vs 4 patients and myopathy in 14 vs 3 patients. All patients with LC-FAO flux <10% developed symptoms. Of the patients with LC-FAO flux >10% 7 out of 12 diagnosed pre-NBS vs none by NBS experienced hypoglycemic events. NBS has a clear beneficial effect on the prevention of hypoglycemic events in patients with some residual enzyme activity, but does not prevent hypoglycemia nor cardiac complications in patients with very low residual enzyme activity. The effect of NBS on prevalence and prevention of myopathy-related complications remains unclear.

AAV9 gene replacement therapy for respiratory insufficiency in very-long chain acyl-CoA dehydrogenase deficiency.

Very-long chain acyl-CoA dehydrogenase (VLCAD) deficiency (VLCADD) is an autosomal recessive disorder of fatty acid oxidation. Fatty acids are a major source of energy during catabolic stress, so the absence of VLCAD can result in a metabolic crises and respiratory insufficiency. The etiology of this respiratory insufficiency is unclear. Thus, our aims were: (1) to characterize respiratory pathophysiology in VLCADD mice (VLCAD-/- ), and (2) to determine if AAV9-mediated gene therapy improves respiratory function. For the first aim, VLCAD-/- and wild-type (WT) mice underwent an exercise/fast "stress protocol" and awake spontaneous breathing was evaluated using whole-body plethysmography (WBP) both at baseline and during a hypercapnic respiratory challenge (FiO2 : 0.21; FiCO2 : 0.07; nitrogen balance). During hypercapnia, VLCAD -/- mice had a significantly lower frequency, tidal volume, minute ventilation, and peak inspiratory and expiratory flow, all of which indicate respiratory insufficiency. Histologically, the cardiac and respiratory muscles of stressed VLCAD -/- animals had an accumulation of intramyocellular lipids. For the second aim, a single systemic injection of AAV9-VLCAD gene therapy improved this respiratory pathology by normalizing breathing frequency and enhancing peak inspiratory flow. In addition, following gene therapy, there was a moderate reduction of lipid accumulation in the respiratory muscles. Furthermore, VLCAD protein expression was robust in cardiac and respiratory muscle. This was confirmed by immuno-staining with anti-human VLCAD antibody. In summary, stress with exercise and fasting induces respiratory insufficiency in VLCAD-/- mice and a single injection with AAV9-VLCAD gene therapy ameliorates breathing.

Sideroblastic anemia associated with multisystem mitochondrial disorders.

BACKGROUND: Sideroblastic anemia represents a heterogeneous group of inherited or acquired diseases with disrupted erythroblast iron utilization, ineffective erythropoiesis, and variable systemic iron overload. In a cohort of 421 patients with multisystem mitochondrial diseases, refractory anemia was found in 8 children. RESULTS: Five children had sideroblastic anemia with increased numbers of ring sideroblasts >15%. Two of the children had a fatal course of MLASA1 syndrome (mitochondrial myopathy, lactic acidosis, and sideroblastic anemia [SA]) due to a homozygous, 6-kb deletion in the PUS1 gene, part of the six-member family of pseudouridine synthases (pseudouridylases). Large homozygous deletions represent a novel cause of presumed PUS1-loss-of-function phenotype. The other three children with SA had Pearson syndrome (PS) due to mtDNA deletions of 4 to 8 kb; two of these children showed early onset of PS and died due to repeated sepsis; the other child had later onset of PS and survived as the hematological parameters normalized and the disease transitioned to Kearns-Sayre syndrome. In addition, anemia without ring sideroblasts was found in three other patients with mitochondrial disorders, including two children with later onset of PS and one child with failure to thrive, microcephaly, developmental delay, hypertrophic cardiomyopathy, and renal tubular acidosis due to the heterozygous mutations c.610A>G (p.Asn204Asp) and c.674C>T (p.Pro225Leu) in the COX10 gene encoding the cytochrome c oxidase assembly factor. CONCLUSIONS: Sideroblastic anemia was found in fewer than 1.2% of patients with multisystem mitochondrial disease, and it was usually associated with an unfavorable prognosis.