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

The LCHADD Mouse Model Recapitulates Early-Stage Chorioretinopathy in LCHADD Patients

Purpose

Recent studies have shown that the retinal pigment epithelium (RPE) relies on fatty acid oxidation (FAO) for energy, however, its role in overall retinal health is unknown. The only FAO disorder that presents with chorioretinopathy is long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHADD). Studying the molecular mechanisms can lead to new treatments for patients and elucidate the role of FAO in the RPE. This paper characterizes the chorioretinopathy progression in a recently reported LCHADD mouse model.

Methods

Visual assessments, such as optokinetic tracking and fundus imaging, were performed in wildtype (WT) and LCHADD mice at 3, 6, 10, and 12 months of age. Retinal morphology was analyzed in 12-month retinal cross-sections using hematoxylin and eosin (H&E), RPE65, CD68, and TUNEL staining, whereas RPE structure was assessed using transmission electron microscopy (TEM). Acylcarnitine profiles were measured in isolated RPE/sclera samples to determine if FAO was blocked. Bulk RNA-sequencing of 12 month old male WT mice and LCHADD RPE/sclera samples assessed gene expression changes.

Results

LCHADD RPE/sclera samples had a 5- to 7-fold increase in long-chain hydroxyacylcarnitines compared to WT, suggesting an impaired LCHAD step in long-chain FAO. LCHADD mice have progressively decreased visual performance and increased RPE degeneration starting at 6 months. LCHADD RPE have an altered structure and a two-fold increase in macrophages in the subretinal space. Finally, LCHADD RPE/sclera have differentially expressed genes compared to WT, including downregulation of genes important for RPE function and angiogenesis.

Conclusions

Overall, this LCHADD mouse model recapitulates early-stage chorioretinopathy seen in patients with LCHADD and is a useful model for studying LCHADD chorioretinopathy.

Cardiac phenotype in adolescents and young adults with long-chain 3-hydroxyacyl CoA dehydrogenase (LCHAD) deficiency

PURPOSE

Long-chain 3-hydroxyacyl-coenzyme A dehydrogenase deficiency (LCHADD) is a rare fatty acid oxidation disorder characterized by recurrent episodes of metabolic decompensation and rhabdomyolysis, as well as retinopathy, peripheral neuropathy, and cardiac involvement, such as infantile dilated cardiomyopathy. Because LCHADD patients are surviving longer, we sought to characterize LCHADD-associated major cardiac involvement in adolescence and young adulthood.

METHODS

A retrospective cohort of 16 adolescent and young adult participants with LCHADD was reviewed for cardiac phenotype.

RESULTS

Major cardiac involvement occurred in 9 of 16 participants, including sudden death, out-of-hospital cardiac arrest, acute cardiac decompensations with heart failure and/or in-hospital cardiac arrest, end-stage dilated cardiomyopathy, and moderate restrictive cardiomyopathy. Sudden cardiac arrest was more common in males and those with a history of infant cardiomyopathy.

CONCLUSION

The cardiac manifestations of LCHADD in adolescence and early adulthood are complex and distinct from the phenotype seen in infancy. Life-threatening arrhythmia occurs at substantial rates in LCHADD, often in the absence of metabolic decompensation or rhabdomyolysis. The potential risk factors identified here-male sex and history of infant cardiomyopathy-may hint at strategies for risk stratification and possibly the prevention of these events.

Early diagnosis and treatment by newborn screening (NBS) or family history is associated with improved visual outcomes for long-chain 3-hydroxyacylCoA dehydrogenase deficiency (LCHADD) chorioretinopathy

Long chain 3-hydroxyacyl-CoA dehydrogenase (LCHADD) is the only fatty acid oxidation disorder to develop a progressive chorioretinopathy resulting in vision loss; newborn screening (NBS) for this disorder began in the United States around 2004. We compared visual outcomes among 40 participants with LCHADD or trifunctional protein deficiency diagnosed symptomatically to those who were diagnosed via NBS or a family history. Participants completed ophthalmologic testing including measures of visual acuity, electroretinograms (ERG), fundal imaging, contrast sensitivity, and visual fields. Records were reviewed to document medical and treatment history. Twelve participants presented symptomatically with hypoglycemia, failure to thrive, liver dysfunction, cardiac arrest, or rhabdomyolysis. Twenty eight were diagnosed by NBS or due to a family history of LCHADD. Participants diagnosed symptomatically were older but had similar percent males and genotypes as those diagnosed by NBS. Treatment consisted of fasting avoidance, dietary long-chain fat restriction, MCT, C7, and/or carnitine supplementation. Visual acuity, rod- and cone-driven amplitudes on ERG, contrast sensitivity scores, and visual fields were all significantly worse among participants diagnosed symptomatically compared to NBS. In mixed-effects models, both age and presentation (symptomatic vs. NBS) were significant independent factors associated with visual outcomes. This suggests that visual outcomes were improved by NBS, but there was still lower visual function with advancing age in both groups. Early diagnosis and treatment by NBS is associated with improved visual outcomes and retinal function compared to participants who presented symptomatically. Despite the impact of early intervention, chorioretinopathy was greater with advancing age, highlighting the need for novel treatments.

A proposal for an updated staging system for LCHADD retinopathy

OBJECTIVE

To develop an updated staging system for long-chain 3-hydroxyacyl coenzyme A dehydrogenase deficiency (LCHADD) chorioretinopathy based on contemporary multimodal imaging and electrophysiology.

METHODS

We evaluated forty cases of patients with genetically confirmed LCHADD or trifunctional protein deficiency (TFPD) enrolled in a prospective natural history study. Wide-field fundus photographs, fundus autofluorescence (FAF), optical coherence tomography (OCT), and full-field electroretinogram (ffERG) were reviewed and graded for severity.

RESULTS

Two independent experts first graded fundus photos and electrophysiology to classify the stage of chorioretinopathy based upon an existing published system. With newer imaging modalities and improved electrophysiology, many patients did not fit cleanly into a single traditional staging group. Therefore, we developed a novel staging system that better delineated the progression of LCHADD retinopathy. We maintained the four previous delineated stages but created substages A and B in stages 2 to 3 to achieve better differentiation.

DISCUSSION

Previous staging systems of LCHADD chorioretinopathy relied on only on the assessment of standard 30 to 45-degree fundus photographs, visual acuity, fluorescein angiography (FA), and ffERG. Advances in recordings of ffERG and multimodal imaging with wider fields of view, allow better assessment of retinal changes. Following these advanced assessments, seven patients did not fit neatly into the original classification system and were therefore recategorized under the new proposed system.

CONCLUSION

The new proposed staging system improves the classification of LCHADD chorioretinopathy, with the potential to lead to a deeper understanding of the disease's progression and serve as a more reliable reference point for future therapeutic research.

Structural insights into the pathogenicity of point mutations in human acyl-CoA dehydrogenase homotetramers

Acyl-CoA dehydrogenase deficiency (ACAD) is an inherited and potentially fatal disorder with variable clinical symptoms. The relationship between pathogenicity and deleterious point mutations is investigated here in ACAD structures of short (SCAD) and medium-chain (MCAD) types. Structures and dynamic features of native and mutant forms of enzymes models were compared. A total of 2.88 µs molecular dynamics simulations were performed at four different temperatures. Total energy, RMSD, protein ligand interactions and affinity, RMSF measures, secondary structure changes, and important interactions were studied. Mutations in the three main domains of ACADs are pathogenic, while those located at linker turns are not. Mutations affect mostly tetramer formations, secondary structures, and many contacts and interactions. In R206H (MCAD mutant) which is experimentally known to cause a huge turnover decrease, the lack of a single H-bond between substrate and FAD was observed. Secondary structures showed temperature-dependent changes, and SCAD activity was found to be highly correlated to the enzyme helix 3-10 content. Finally, RMSF patterns pointed to one important loop that maintains the substrate close to the active site and is a cause of substrate wobbling upon mutation. Despite similar structure, function, and cellular location, SCAD and MCAD may have different optimum temperatures that are related to the structure taken at that specific temperature. In conclusion, new insight has been provided on the effect of various SCAD and MCAD pathogenic mutations on the structure and dynamical features of the enzymes.

Integrated Transcriptome Analysis of miRNAs and mRNAs in the Skeletal Muscle of Wuranke Sheep

MicroRNAs (miRNAs) are regarded as important regulators in skeletal muscle development. To reveal the regulatory roles of miRNAs and their target mRNAs underlying the skeletal muscle development of Wuranke sheep, we investigated the miRNA and mRNA expression profiles in the biceps femoris of these sheep at the fetal (3 months of gestation) and 3- and 15-month-old postnatal stages. Consequently, a total of 1195 miRNAs and 24,959 genes were identified. Furthermore, 474, 461, and 54 differentially expressed miRNAs (DEMs) and 6783, 7407, and 78 differentially expressed genes (DEGs) were detected among three comparative groups. Functional analysis demonstrated that the target mRNAs of the DEMs were enriched in multiple pathways related to muscle development. Moreover, the interactions among several predicted miRNA-mRNA pairs (oar-miR-133-HDAC1, oar-miR-1185-5p-MYH1/HADHA/OXCT1, and PC-5p-3703_578-INSR/ACTG1) that potentially affect skeletal muscle development were verified using dual-luciferase reporter assays. In this study, we identified the miRNA and mRNA differences in the skeletal muscle of Wuranke sheep at different developmental stages and revealed that a series of candidate miRNA-mRNA pairs may act as modulators of muscle development. These results will contribute to future studies on the function of miRNAs and their target mRNAs during skeletal muscle development in Wuranke sheep.

The Physiological and Pathological Role of Acyl-CoA Oxidation

Fatty acid metabolism, including β-oxidation (βOX), plays an important role in human physiology and pathology. βOX is an essential process in the energy metabolism of most human cells. Moreover, βOX is also the source of acetyl-CoA, the substrate for (a) ketone bodies synthesis, (b) cholesterol synthesis, (c) phase II detoxication, (d) protein acetylation, and (d) the synthesis of many other compounds, including N-acetylglutamate-an important regulator of urea synthesis. This review describes the current knowledge on the importance of the mitochondrial and peroxisomal βOX in various organs, including the liver, heart, kidney, lung, gastrointestinal tract, peripheral white blood cells, and other cells. In addition, the diseases associated with a disturbance of fatty acid oxidation (FAO) in the liver, heart, kidney, lung, alimentary tract, and other organs or cells are presented. Special attention was paid to abnormalities of FAO in cancer cells and the diseases caused by mutations in gene-encoding enzymes involved in FAO. Finally, issues related to α- and ω- fatty acid oxidation are discussed.

A G1528C Hadha knock-in mouse model recapitulates aspects of human clinical phenotypes for long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency

Long chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHADD) is a fatty acid oxidation disorder (FAOD) caused by a pathogenic variant, c.1528 G > C, in HADHA encoding the alpha subunit of trifunctional protein (TFPα). Individuals with LCHADD develop chorioretinopathy and peripheral neuropathy not observed in other FAODs in addition to the more ubiquitous symptoms of hypoketotic hypoglycemia, rhabdomyolysis and cardiomyopathy. We report a CRISPR/Cas9 generated knock-in murine model of G1528C in Hadha that recapitulates aspects of the human LCHADD phenotype. Homozygous pups are less numerous than expected from Mendelian probability, but survivors exhibit similar viability with wildtype (WT) littermates. Tissues of LCHADD homozygotes express TFPα protein, but LCHADD mice oxidize less fat and accumulate plasma 3-hydroxyacylcarnitines compared to WT mice. LCHADD mice exhibit lower ketones with fasting, exhaust earlier during treadmill exercise and develop a dilated cardiomyopathy compared to WT mice. In addition, LCHADD mice exhibit decreased visual performance, decreased cone function, and disruption of retinal pigment epithelium. Neurological function is affected, with impaired motor function during wire hang test and reduced open field activity. The G1528C knock-in mouse exhibits a phenotype similar to that observed in human patients; this model will be useful to explore pathophysiology and treatments for LCHADD in the future.

Successful management of rhabdomyolysis with triheptanoin in a child with severe long-chain 3-hydroxyacyl-coenzyme A dehydrogenase (LCHAD) deficiency

Early-onset long-chain 3-hydroxyacyl-coenzyme A dehydrogenase (LCHAD) deficiency is a fatty acid β-oxidation disorder with a poor prognosis. Triheptanoin, an anaplerotic oil with odd-chain fatty acids can improve the disease course. The female patient presented here was diagnosed at the age of 4 months, and treatment was started as fat restriction, frequent feeding, and standard medium-chain triglyceride supplementation. In follow-up, she had frequent rhabdomyolysis episodes (∼8 per year). At the age of six, she had 13 episodes in 6 months, and triheptanoin was started as part of a compassionate use program. Following unrelated hospital stays due to multisystem inflammatory syndrome in children and a bloodstream infection, she had only 3 rhabdomyolysis episodes, and hospitalized days decreased from 73 to 11 during her first year with triheptanoin. Triheptanoin drastically decreased the frequency and severity of rhabdomyolysis, but progression of retinopathy was not altered.

Mitochondrial pyruvate carrier influences ganoderic acid biosynthesis in Ganoderma lucidum

Mitochondrial pyruvate carriers (MPCs), located in the inner membrane of mitochondria, are essential carriers for pyruvate to enter mitochondria. MPCs regulate a wide range of intracellular metabolic processes, such as glycolysis, the tricarboxylic acid cycle (TCA cycle), fatty acid metabolism, and amino acid metabolism. However, the metabolic regulation of MPCs in macrofungi is poorly studied. We studied the role of MPCs in Ganoderma lucidum (GlMPC) on ganoderic acid (GA) biosynthesis regulation in G. lucidum. In this study, we found that the mitochondrial/cytoplasmic ratio of pyruvate was downregulated about 75% in GlMPC1- and GlMPC2-silenced transformants compared with wild type (WT). In addition, the GA content was 17.72 mg/g and increased by approximately 50% in GlMPC1- and GlMPC2-silenced transformants compared with WT. By assaying the expression levels of three key enzymes and the enzyme activities of isocitrate dehydrogenase (IDH) and α-ketoglutarate dehydrogenase (α-KGDH) of the TCA cycle in GlMPC1- and GlMPC2-silenced transformants, it was found that the decrease in GlMPCs activity did not significantly downregulate the TCA cycle rate, and the enzyme activity of IDH increased by 44% compared with WT. We then verified that fatty acid β-oxidation (FAO) supplements the TCA cycle by detecting the expression levels of key enzymes involved in FAO. The results showed that compared with WT, the GA content was 1.14 mg/g and reduced by approximately 40% in co-silenced transformants. KEY POINTS: • GlMPCs affects the distribution of pyruvate between mitochondria and the cytoplasm. • Acetyl-CoA produced by FAO maintains the TCA cycle. • Acetyl-CoA produced by FAO promotes the accumulation of GA.

Abnormal expression of HADH, an enzyme of fatty acid oxidation, affects tumor development and prognosis (Review)

Tumor occurrence and progression are closely associated with abnormal energy metabolism and energy metabolism associated with glucose, proteins and lipids. The reprogramming of energy metabolism is one of the hallmarks of cancer. As a form of energy metabolism, fatty acid metabolism includes fatty acid uptake, de novo synthesis and β‑oxidation. In recent years, the role of abnormal fatty acid β‑oxidation in tumors has gradually been recognized. Mitochondrial trifunctional protein (MTP) serves an important role in fatty acid β‑oxidation and HADH (two subtypes: α subunit, HADHA and β subunit, HADHB) are important subunits of MTP. HADH participates in the steps of 2, 3 and 4 fatty acid β‑oxidation. However, there is no review summarizing the specific role of HADH in tumors. Therefore, the present study focused on HADH as the main indicator to explore the changes in fatty acid β‑oxidation in several types of tumors. The present review summarized the changes in HADH in 11 organs (cerebrum, oral cavity, esophagus, liver, pancreas, stomach, colorectum, lymph, lung, breast, kidney), the effect of up‑ and downregulation and the relationship of HADH with prognosis. In summary, HADH can be either a suppressor or a promoter depending on where the tumor is located, which is closely associated with prognostic assessment. HADHA and HADHB have similar prognostic roles in known and comparable tumors.

Genetic diversity in Kashubs: the regional increase in the frequency of several disease-causing variants

Differential distribution of genetic variants’ frequency among human populations is caused by the genetic drift in isolated populations, historical migrations, and demography. Some of these variants are identical by descent and represent founder mutations, which — if pathogenic in nature — lead to the increased frequency of otherwise rare diseases. The detection of the increased regional prevalence of pathogenic variants may shed light on the historical processes that affected studied populations and can help to develop effective screening and diagnostic strategies as a part of personalized medicine. Here, we discuss the specific genetic diversity in Kashubs, the minority group living in northern Poland, reflected in the biased distribution of some of the repetitively found disease-causing variants. These include the following: (1) c.662A > G (p.Asp221Gly) in LDLR, causing heterozygous familial hypercholesterolemia; (2) c.3700_3704del in BRCA1, associated with hereditary breast and ovarian cancer syndrome; (3) c.1528G > C (p.Glu510Gln) in HADHA, seen in long-chain 3-hydroxy acyl-CoA dehydrogenase (LCHAD) deficiency, and (4) c.1032delT in NPHS2, associated with steroid-resistant nephrotic syndrome.

Genetic, biochemical, and clinical spectrum of patients with mitochondrial trifunctional protein deficiency identified after the introduction of newborn screening in the Netherlands

Long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHADD) is included in many newborn screening (NBS) programs. Acylcarnitine-based NBS for LCHADD not only identifies LCHADD, but also the other deficiencies of the mitochondrial trifunctional protein (MTP), a multi-enzyme complex involved in long-chain fatty acid β-oxidation. Besides LCHAD, MTP harbors two additional enzyme activities: long-chain enoyl-CoA hydratase (LCEH) and long-chain ketoacyl-CoA thiolase (LCKAT). Deficiency of one or more MTP activities causes generalized MTP deficiency (MTPD), LCHADD, LCEH deficiency (not yet reported), or LCKAT deficiency (LCKATD). To gain insight in the outcomes of MTP-deficient patients diagnosed after the introduction of NBS for LCHADD in the Netherlands, a retrospective evaluation of genetic, biochemical, and clinical characteristics of MTP-deficient patients, identified since 2007, was carried out. Thirteen patients were identified: seven with LCHADD, five with MTPD, and one with LCKATD. All LCHADD patients (one missed by NBS, clinical diagnosis) and one MTPD patient (clinical diagnosis) were alive. Four MTPD patients and one LCKATD patient developed cardiomyopathy and died within 1 month and 13 months of life, respectively. Surviving patients did not develop symptomatic hypoglycemia, but experienced reversible cardiomyopathy and rhabdomyolysis. Five LCHADD patients developed subclinical neuropathy and/or retinopathy. In conclusion, patient outcomes were highly variable, stressing the need for accurate classification of and discrimination between the MTP deficiencies to improve insight in the yield of NBS for LCHADD. NBS allowed the prevention of symptomatic hypoglycemia, but current treatment options failed to treat cardiomyopathy and prevent long-term complications. Moreover, milder patients, who might benefit from NBS, were missed due to normal acylcarnitine profiles.

Management of pregnancy in a patient with long‐chain 3‐hydroxyacyl CoA dehydrogenase deficiency

Long‐chain 3‐hydroxyacyl‐CoA dehydrogenase deficiency (LCHADD) is a rare mitochondrial defect of β‐oxidation of long‐chain fatty acids. Patients may present with muscle pain, hypotonia, peripheral neuropathy, cardiomyopathy, recurrent rhabdomyolysis and sudden death. Dietary management of LCHADD aims at preventing prolonged fasting and decreasing energy production from long‐chain fatty acids compensated by an increase in medium‐chain triglyceride fat. Herein, we present medical and dietetic management of a successful pregnancy in a LCHADD female patient and the delivery of a healthy baby boy.

Impact of newborn screening on the reported incidence and clinical outcomes associated with medium- and long-chain fatty acid oxidation disorders

Fatty acid oxidation disorders (FAODs) are potentially fatal inherited disorders for which management focuses on early disease detection and dietary intervention to reduce the impact of metabolic crises and associated spectrum of clinical symptoms. They can be divided functionally into long-chain (LC-FAODs) and medium-chain disorders (almost exclusively deficiency of medium-chain acyl-coenzyme A dehydrogenase). Newborn screening (NBS) allows prompt identification and management. FAOD detection rates have increased following the addition of FAODs to NBS programs in the United States and many developed countries. NBS-identified neonates with FAODs may remain asymptomatic with dietary management. Evidence from numerous studies suggests that NBS-identified patients have improved outcomes compared with clinically diagnosed patients, including reduced rates of symptomatic manifestations, neurodevelopmental impairment, and death. The limitations of NBS include the potential for false-negative and false-positive results, and the need for confirmatory testing. Although NBS alone does not predict the consequences of disease, outcomes, or management needs, subsequent genetic analyses may have predictive value. Genotyping can provide valuable information on the nature and frequency of pathogenic variants involved with FAODs and their association with specific phenotypes. Long-term follow-up to fully understand the clinical spectrum of NBS-identified patients and the effect of different management strategies is needed.

Generation of an induced pluripotent stem cell line, ICGi028-A, by reprogramming peripheral blood mononuclear cells of a patient suffering from hypertrophic cardiomyopathy and carrying a heterozygous p.E510Q mutation in HADHA

Hypertrophic cardiomyopathy (HCM) is a frequent cardiovascular pathology caused by a huge number of mutations in sarcomere-associated proteins. This genetic diversity leads to differences in pathogenetic mechanisms and hampers HCM therapy. Cardiomyocytes derived from patient-specific induced pluripotent stem cells give new opportunities for studying underlying HCM mechanisms. We generated an iPSC line from peripheral blood mononuclear cells of an HCM patient with a heterozygous p.E510Q mutation in HADHA using non-integrating episomal vectors. The iPSC line showed typical morphology, expression of pluripotency markers, capacity to be differentiated into derivatives of three germ layers, and presence of the patient-specific mutation.

Mitochondrial morphology, bioenergetics and proteomic responses in fatty acid oxidation disorders

Mutations in nuclear genes encoding for mitochondrial proteins very long-chain acyl-CoA dehydrogenase (VLCAD) and trifunctional protein (TFP) cause rare autosomal recessive disorders. Studies in fibroblasts derived from patients with mutations in VLCAD and TFP exhibit mitochondrial defects. To gain insights on pathological changes that account for the mitochondrial deficits we performed quantitative proteomic, biochemical, and morphometric analyses in fibroblasts derived from subjects with three different VLCAD and three different TFP mutations. Proteomic data that was corroborated by antibody-based detection, indicated reduced levels of VLCAD and TFP protein in cells with VLCAD and TFP mutations respectively, which in part accounted for the diminished fatty acid oxidation capacity. Decreased mitochondrial respiratory capacity in cells with VLCAD and TFP mutations was quantified after glucose removal and cells with TFP mutations had lower levels of glycogen. Despite these energetic deficiencies, the cells with VLCAD and TFP mutations did not exhibit changes in mitochondria morphology, distribution, fusion and fission, quantified by either confocal or transmission electron microscopy and corroborated by proteomic and antibody-based protein analysis. Fibroblasts with VLCAD and to a lesser extend cells with TFP mutations had increased levels of mitochondrial respiratory chain proteins and proteins that facilitate the assembly of respiratory complexes. With the exception of reduced levels of catalase and glutathione S-transferase theta-1 in cells with TFP mutations, the levels of 45 proteins across all major intracellular antioxidant networks were similar between cells with VLCAD and TFP mutations and non-disease controls. Collectively the data indicate that despite the metabolic deficits, cells with VLCAD and TFP mutations maintain their proteomic integrity to preserve cellular and mitochondria architecture, support energy production and protect against oxidative stress.

Long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency and progressive retinopathy: one case report followed by ERGs, VEPs, EOG over a 17-year period

BACKGROUND

LCHAD (long-chain 3-hydroxyacyl-CoA dehydrogenase) deficiency is a rare genetic disorder of mitochondrial long-chain fatty acid oxidation inherited as a recessive trait. Affected patients can present with hypoglycaemia, rhabdomyolysis and cardiomyopathy. About half of the patients may suffer from retinopathy.

CASE REPORT

A 19-year-old girl was diagnosed as suffering from LCHAD deficiency with recurrent rhabdomyolysis episodes at the age of 7 months by an inaugural coma with hypoglycaemia and hepatomegaly. Appropriate dietary management with carnitine supplementation was initiated. Retinopathy was diagnosed at age two. Ophthalmological assessments including visual acuity, visual field, OCT, flash ERGs, P-ERG, flash VEPs and EOG recordings were conducted over a 17-year period.

RESULTS

Visual acuity was decreased. Fundi showed a progressive retinopathy and chorioretinopathy. Photophobia was noticed 2 years before the decrease in photopic-ERG amplitude with normal scotopic-ERGs. Scotopic-ERG amplitude decreased 10 years after the decrease in photopic-ERG amplitude. No EOG light rise was observed. Flash VEPs remained normal. These results suggest that the cone system dysfunction occurs largely prior to the rod system dysfunction with a relative preservation of the macula function.

COMMENTS

This dysfunction of cones prior to the dysfunction of rods was not reported previously. This could be related to mitochondrial energy failure in cones as cones are greater consumers of ATP than rods. This hypothesis needs to be further confirmed as other long-chain fatty oxidation defective patients (VLCAD and CPT2 deficiencies) do not exhibit retinopathy.

Fatal COVID-19 infection in a patient with long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency: A case report

Long-chain fatty-acyl CoA dehydrogenase deficiency (LCHADD) is an inborn error of long chain fatty acid oxidation with various features including hypoketotic hypoglycemia, recurrent rhabdomyolysis, pigmentary retinopathy, peripheral neuropathy, cardiomyopathy, and arrhythmias. Various stresses trigger metabolic decompensation. Coronavirus disease 2019 (COVID-19) is a pandemic caused by the RNA virus SARS-CoV-2 with diverse presentations ranging from respiratory symptoms to myocarditis. We report a case of a patient with LCHADD who initially presented with typical metabolic decompensation symptoms including nausea, vomiting, and rhabdomyolysis in addition to mild cough, and was found to have COVID-19. She developed acute respiratory failure and refractory hypotension from severe cardiomyopathy which progressed to multiple organ failure and death. Our case illustrates the need for close monitoring of cardiac function in patients with a long-chain fatty acid oxidation disorder.

Deep geno- and phenotyping in two consanguineous families with CMT2 reveals HADHA as an unusual disease-causing gene and an intronic variant in GDAP1 as an unusual mutation

BACKGROUND

Charcot-Marie-Tooth (CMT) disease is a prevalent and heterogeneous peripheral neuropathy. Most patients affected with the axonal form of CMT (CMT2) do not harbor mutations in the approximately 90 known CMT-associated genes. We aimed to identify causative genes in two CMT2 pedigrees.

METHODS

Neurologic examination, laboratory tests and brain MRIs were performed. Genetic analysis included exome sequencing of four patients from the two pedigrees. The predicted effect of a deep intronic mutation on splicing was tested by regular and real-time PCR and sequencing.

RESULTS

Clinical data were consistent with CMT2 diagnosis. Inheritance patterns were autosomal recessive. Exome data of CMT2-101 did not include mutations in known CMT-associated genes. Sequence data, segregation analysis, bioinformatics analysis, evolutionary conservation, and information in the literature strongly implicated HADHA as the causative gene. An intronic variation positioned 23 nucleotides away from following intron/exon border in GDAP1 was ultimately identified as cause of CMT in CMT2-102. It was shown to affect splicing.

CONCLUSION

The finding of a HADHA mutation as a cause of CMT is of interest because its encoded protein is a subunit of the mitochondrial trifunctional protein (MTP) complex, a mitochondrial enzyme involved in long chain fatty acid oxidation. Long chain fatty acid oxidation is an important source of energy for skeletal muscles. The mutation found in CMT2-102 is only the second intronic mutation reported in GDAP1. The mutation in the CMT2-102 pedigree was outside the canonical splice site sequences, emphasizing the importance of careful examination of available intronic sequences in exome sequence data.

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.

Crystal structure of human mitochondrial trifunctional protein, a fatty acid β-oxidation metabolon

Membrane-bound mitochondrial trifunctional protein (TFP) catalyzes β-oxidation of long chain fatty acyl-CoAs, employing 2-enoyl-CoA hydratase (ECH), 3-hydroxyl-CoA dehydrogenase (HAD), and 3-ketothiolase (KT) activities consecutively. Inherited deficiency of TFP is a recessive genetic disease, manifesting in hypoketotic hypoglycemia, cardiomyopathy, and sudden death. We have determined the crystal structure of human TFP at 3.6-Å resolution. The biological unit of the protein is α₂β₂ The overall structure of the heterotetramer is the same as that observed by cryo-EM methods. The two β-subunits make a tightly bound homodimer at the center, and two α-subunits are bound to each side of the β₂ dimer, creating an arc, which binds on its concave side to the mitochondrial innermembrane. The catalytic residues in all three active sites are arranged similarly to those of the corresponding, soluble monofunctional enzymes. A structure-based, substrate channeling pathway from the ECH active site to the HAD and KT sites is proposed. The passage from the ECH site to the HAD site is similar to those found in the two bacterial TFPs. However, the passage from the HAD site to the KT site is unique in that the acyl-CoA intermediate can be transferred between the two sites by passing along the mitochondrial inner membrane using the hydrophobic nature of the acyl chain. The 3'-AMP-PPi moiety is guided by the positively charged residues located along the "ceiling" of the channel, suggesting that membrane integrity is an essential part of the channel and is required for the activity of the enzyme.

Sex-specific regulation of cardiac microRNAs targeting mitochondrial proteins in pressure overload

Background

Maladaptive remodeling in pressure overload (PO)-induced left ventricular hypertrophy (LVH) may lead to heart failure. Major sex differences have been reported in this process. The steroid hormone 17β-estradiol, along with its receptors ERα and ERβ, is thought to be crucial for sex differences and is expected to be protective, but this may not hold true for males. Increasing evidence demonstrates a major role for microRNAs (miRNAs) in PO-induced LVH. However, little is known about the effects of biological sex and ERβ on cardiac miRNA regulation and downstream mitochondrial targets. We aimed at the analysis of proteins involved in mitochondrial metabolism testing the hypothesis that they are the target of sex-specific miRNA regulation.

Methods

We employed the transverse aortic constriction model in mice and assessed the levels of five mitochondrial proteins, i.e., Auh, Crat, Decr1, Hadha, and Ndufs4.

Results

We found a significant decrease of the mitochondrial proteins primarily in the male overloaded heart compared with the corresponding control group. Following computational analysis to identify miRNAs putatively targeting these proteins, our in vitro experiments employing miRNA mimics demonstrated the presence of functional target sites for miRNAs in the 3′-untranslated region of the messenger RNAs coding for these proteins. Next, we assessed the levels of the functionally validated miRNAs under PO and found that their expression was induced only in the male overloaded heart. In contrast, there was no significant effect on miRNA expression in male mice with deficient ERβ.

Conclusion

We put forward that the male-specific induction of miRNAs and corresponding downregulation of downstream protein targets involved in mitochondrial metabolism may contribute to sex-specific remodeling in PO-induced LVH.

HADHA and HADHB gene associated phenotypes - Identification of rare variants in a patient cohort by Next Generation Sequencing

The heterooctameric mitochondrial trifunctional protein (MTP), composed of four α- and β-subunits harbours three enzymes that each perform a different function in mitochondrial fatty acid β-oxidation. Pathogenic variants in the MTP genes (HADHA and HADHB) cause MTP deficiency, a rare autosomal recessive metabolic disorder characterized by phenotypic heterogeneity ranging from severe, early-onset, cardiac disease to milder, later-onset, myopathy and neuropathy. Since metabolic myopathies and neuropathies are a group of rare genetic disorders and their associated muscle symptoms may be subtle, the diagnosis is often delayed. Here we evaluated data of 161 patients with myopathy and 242 patients with neuropathy via next generation sequencing (NGS) and report the diagnostic yield in three patients of this cohort by the detection of disease-causing variants in the HADHA or HADHB gene. The mitigated phenotypes of this treatable disease were missed by the newborn screening, highlighting the importance of phenotype-based NGS analysis in patients with rare and clinically very variable disorders such as MTP deficiency.

Fatal pitfalls in newborn screening for mitochondrial trifunctional protein (MTP)/long-chain 3-Hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency

Background

Mitochondrial trifunctional protein (MTP) and long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency are long-chain fatty acid oxidation disorders with particularly high morbidity and mortality. Outcome can be favorable if diagnosed in time, prompting the implementation in newborn screening programs. Sporadic cases missed by the initial screening sample have been reported. However, little is known on pitfalls during confirmatory testing resulting in fatal misconception of the diagnosis.

Results

We report a series of three patients with MTP and LCHAD deficiency, in whom diagnosis was missed by newborn screening, resulting in life-threatening metabolic decompensations within the first half year of life. Two of the patients showed elevated concentrations of primary markers C16-OH and C18:1-OH but were missed by confirmatory testing performed by the maternity clinic. A metabolic center was not consulted. Confirmatory testing consisted of analyses of acylcarnitines in blood and organic acids in urine, the finding of normal excretion of organic acids led to rejection and underestimation of the diagnosis, respectively. The third patient, a preterm infant, was not identified in the initial screening sample due to only moderate elevations of C16-OH and C18:1-OH and normal secondary markers and analyte ratios.

Conclusion

Our observations highlight limitations of newborn screening for MTP/LCHAD deficiency. They confirm that analyses of acylcarnitines in blood and organic acids in urine alone are not suitable for confirmatory testing and molecular or functional analysis is crucial in diagnosing MTP/LCHAD deficiency. Mild elevations of primary biomarkers in premature infants need to trigger confirmatory testing. Our report underscores the essential role of specialized centers in confirming or ruling out diagnoses in suspicious screening results.

Regulation of mitochondrial trifunctional protein modulates nonalcoholic fatty liver disease in mice

Mitochondrial trifunctional protein (MTP) plays a critical role in the oxidation of long-chain fatty acids. We previously reported that aging mice (>9 months old) heterozygous for an MTP defect (MTP+/-) develop nonalcoholic fatty liver disease (NAFLD). We tested whether a high-fat diet (HFD) accelerates NAFLD in young MTP+/-mice, and whether overexpression of the nicotinamide adenine dinucleotide (NAD+)-dependent deacetylase sirtuin 3 (SIRT3) deacetylates MTP and improves mitochondrial function and NAFLD. Three-month-old WT and MTP+/- mice were fed HFD (60% cal fat) for 16 weeks and livers were assessed for fatty acid oxidation (FAO) and NAFLD. Compared with WT, MTP+/- mice displayed reduced hepatic SIRT3 levels and reduced FAO, with increased hepatic steatosis and the inflammatory marker CD68. Hepatic overexpression of SIRT3 in HFD-fed MTP+/- mice increased hepatic MTP protein levels at the posttranscriptional level. Immunoprecipitation of MTP from liver mitochondria followed by Western blot with acetyl-lysine antibody showed higher acetylation of MTP in MTP+/- compared with WT mice. Overexpression of SIRT3 in MTP+/- mice significantly reduced the acetylation of MTP compared with β-galactosidase controls, increased mitochondrial FAO, and reduced hepatic steatosis, CD68, and serum ALT levels. Taken together, our data indicate that deacetylation of MTP by SIRT3 improves mitochondrial function and rescues NAFLD in MTP+/- mice.

Disorders of mitochondrial long-chain fatty acid oxidation and the carnitine shuttle

Mitochondrial fatty acid oxidation is an essential pathway for energy production, especially during prolonged fasting and sub-maximal exercise. Long-chain fatty acids are the most abundant fatty acids in the human diet and in body stores, and more than 15 enzymes are involved in long-chain fatty acid oxidation. Pathogenic mutations in genes encoding these enzymes result in a long-chain fatty acid oxidation disorder in which the energy homeostasis is compromised and long-chain acylcarnitines accumulate. Symptoms arise or exacerbate during catabolic situations, such as fasting, illness and (endurance) exercise. The clinical spectrum is very heterogeneous, ranging from hypoketotic hypoglycemia, liver dysfunction, rhabdomyolysis, cardiomyopathy and early demise. With the introduction of several of the long-chain fatty acid oxidation disorders (lcFAOD) in newborn screening panels, also asymptomatic individuals with a lcFAOD are identified. However, despite early diagnosis and dietary therapy, a significant number of patients still develop symptoms emphasizing the need for individualized treatment strategies. This review aims to function as a comprehensive reference for clinical and laboratory findings for clinicians who are confronted with pediatric and adult patients with a possible diagnosis of a lcFAOD.

High prevalence of carriers of variant c.1528G>C of HADHA gene causing long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHADD) in the population of adult Kashubians from North Poland

Background/Objectives

The mitochondrial β-oxidation of fatty acids is a complex catabolic pathway. One of the enzymes of this pathway is the heterooctameric mitochondrial trifunctional protein (MTP), composed of four α- and β-subunits. Mutations in MTP genes (HADHA and HADHB), both located on chromosome 2p23, cause MTP deficiency, a rare autosomal recessive metabolic disorder characterized by decreased activity of MTP. The most common MTP mutation is long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency caused by the c.1528G>C (rs137852769, p.Glu510Gln) substitution in exon 15 of the HADHA gene.

Subjects/Methods

We analyzed the frequency of genetic variants in the HADHA gene in the adults of Kashubian origin from North Poland and compared this data in other Polish provinces.

Results

We found a significantly higher frequency of HDHA c.1528G>C (rs137852769, p.Glu510Gln) carriers among Kashubians (1/57) compared to subjects from other regions of Poland (1/187). We found higher frequency of c.652G>C (rs71441018, pVal218Leu) polymorphism in the HADHA gene within population of Silesia, southern Poland (1/107) compared to other regions.

Conclusion

Our study indicate described high frequency of c.1528G>C variant of HADHA gene in Kashubian population, suggesting the founder effect. For the first time we have found high frequency of rs71441018 in the South Poland Silesian population.

RETINAL PHENOTYPE IN A CASE OF LCHAD/TFP DEFICIENCY WITH LATE-STAGE DIAGNOSIS

PURPOSE

To report the retinal phenotype of a rare case of long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD)/trifunctional protein (TFP) deficiency diagnosed in his late 40s with ocular findings of diffuse chorioretinal atrophy and bilateral retinoschisis.

METHODS

An acylcarnitine profile assay revealed LCHAD/TFP deficiency in a 45-year-old man with a history of high myopia, bilateral decreased vision, episodic rhabdomyolysis, and peripheral neuropathy. Ocular findings were evaluated with spectral domain optical coherence tomography (Spectralis OCT; Heidelberg Engineering, Heidelberg, Germany) and color fundus photography.

RESULTS

Spectral domain optical coherence tomography revealed severe bilateral macular retinoschisis. Subretinal fibrosis was noted in the left temporal macula with an associated lamellar macular hole. Fundus photographs demonstrated diffuse, symmetric chorioretinal atrophy characteristic of end-stage retinopathy, as previously reported in younger patients. Myopic staphylomas were evident in the posterior pole of both eyes. A trial of topical dorzolamide for 3 months resulted in no change in the retinal profile.

CONCLUSION

We report the retinal phenotype of a patient with LCHAD/TFP deficiency diagnosed later in life. To date, this is the oldest patient reported with LCHAD/TFP-associated retinopathy. Macular retinoschisis may represent a feature of the end-stage retinopathy due to the progressive myopia. The diagnosis of LCHAD/TFP deficiency should be considered in adult patients with a history rhabdomyolysis, neuropathy, and retinopathy, as they would not have undergone routine newborn screening before the late 90s.

Mitochondrial trifunctional protein deficiency in human cultured fibroblasts: effects of bezafibrate

Mitochondrial trifunctional protein (MTP) deficiency caused by HADHA or HADHB gene mutations exhibits substantial molecular, biochemical, and clinical heterogeneity and ranks among the more severe fatty acid oxidation (FAO) disorders, without pharmacological treatment. Since bezafibrate has been shown to potentially correct other FAO disorders in patient cells, we analyzed its effects in 26 MTP-deficient patient fibroblasts representing 16 genotypes. Overall, the patient cell lines exhibited variable, complex, biochemical profiles and pharmacological responses. HADHA-deficient fibroblasts showed markedly reduced alpha subunit protein levels together with decreased beta-subunit abundance, exhibited a -86 to -96% defect in LCHAD activity, and produced large amounts of C14 and C16 hydroxyacylcarnitines. In control fibroblasts, exposure to bezafibrate (400 μM for 48 h) increased the abundance of HADHA and HADHB mRNAs, immune-detectable alpha and beta subunit proteins, activities of LCHAD and LCKAT, and stimulated FAO capacities, clearly indicating that MTP is pharmacologically up-regulated by bezafibrate in human fibroblasts. In MTP-deficient patient fibroblasts, which were found markedly FAO-deficient, bezafibrate improved FAO capacities in six of 26 (23%) cases, including three cell lines heterozygous for the common c1528G > C mutation. Altogether, our results strongly suggest that, due to variable effects of HADHA and HADHB mutations on MTP abundance and residual activity, improvement of MTP deficiency in response to bezafibrate was achieved in a subset of responsive genotypes.

The investigation and management of metabolic myopathies

Metabolic myopathies (MM) are rare inherited primary muscle disorders that are mainly due to abnormalities of muscle energy metabolism resulting in skeletal muscle dysfunction. These diseases include disorders of fatty acid oxidation, glyco(geno)lytic muscle disorders and mitochondrial respiratory chain (MRC) disease. Clinically these disorders present with a range of symptoms including infantile hypotonia, myalgia/exercise tolerance, chronic or acute muscle weakness, cramps/spasms/stiffness or episodic acute rhabdomyolysis. The precipitant may be fasting, infection, general anaesthesia, heat/cold or most commonly, exercise. However, the differential diagnosis includes a wide range of both acquired and inherited conditions and these include exposure to drugs/toxins, inflammatory myopathies, dystrophies and channelopathies. Streamlining of existing diagnostic protocols has now become a realistic prospect given the availability of second-generation sequencing. A diagnostic pathway using a ‘rhabdomyolysis’ gene panel at an early stage of the diagnostic process is proposed. Following detailed clinical evaluation and first-line investigations, some patients will be identified as candidates for McArdle disease/glycogen storage disease type V or MRC disease and these will be referred directly to the specialised services. However, for the majority of patients, second-line investigation is best undertaken through next-generation sequencing using a ‘rhabdomyolysis’ gene panel. Following molecular analysis and careful evaluation of the findings, some patients will receive a clear diagnosis. Further functional or specific targeted testing may be required in other patients to evaluate the significance of uncertain/equivocal findings. For patients with no clear diagnosis, further investigations will be required through a specialist centre.

Metabolic neuropathies and myopathies

Inborn errors of metabolism may impact on muscle and peripheral nerve. Abnormalities involve mitochondria and other subcellular organelles such as peroxisomes and lysosomes related to the turnover and recycling of cellular compartments. Treatable causes are β-oxidation defects producing progressive neuropathy; pyruvate dehydrogenase deficiency, porphyria, or vitamin B12 deficiency causing recurrent episodes of neuropathy or acute motor deficit mimicking Guillain-Barré syndrome. On the other hand, lysosomal (mucopolysaccharidosis, Gaucher and Fabry diseases), mitochondriopathic (mitochondrial or nuclear mutations or mDNA depletion), peroxisomal (adrenomyeloneuropathy, Refsum disease, sterol carrier protein-2 deficiency, cerebrotendinous xanthomatosis, α-methylacyl racemase deficiency) diseases are multisystemic disorders involving also the heart, liver, brain, retina, and kidney. Pathophysiology of most metabolic myopathies is related to the impairment of energy production or to abnormal production of reactive oxygen species (ROS). Main symptoms are exercise intolerance with myalgias, cramps and recurrent myoglobinuria or limb weakness associated with elevation of serum creatine kinase. Carnitine palmitoyl transferase deficiency, followed by acid maltase deficiency, and lipin deficiency, are the most common cause of isolated rhabdomyolysis. Metabolic myopathies are frequently associated to extra-neuromuscular disorders particularly involving the heart, liver, brain, retina, skin, and kidney.

Mutations in long-chain 3-hydroxyacyl coenzyme a dehydrogenase are associated with placental maternal floor infarction/massive perivillous fibrin deposition

Maternal floor infarction/massive perivillous fibrin deposition (MFI/MPVFD) of the placenta has an unclear etiology. The placenta of an 8-month-old child diagnosed with long-chain 3-hydroxyacyl coenzyme A dehydrogenase (LCHAD) deficiency reportedly showed MFI, but no further evidence of a direct association between MFI/MPVFD and LCHAD deficiency has been documented. Three cases of MFI/MPVFD were studied. Paraffin blocks of placental tissue were retrieved, tissue scrolls were harvested, and DNA was extracted. The alpha-subunit of the mitochondrial trifunctional protein containing the LCHAD coding region (HADHA) was subsequently amplified using specific primer sets and directly sequenced by the dideoxy chain termination method. All 3 placentas demonstrated heterozygous mutations in the HADHA gene. A sample from a 25-4/7 week gestation growth-restricted female infant revealed a heterozygous mutation in exon 11, 1072C>A (glutamine to lysine, Qln358Lys) with a heterozygous sequence difference in the intron following exon 6 (insertion of a T at position +9, +9insT). The 2nd sample from a 32-4/7 week gestation stillborn fetus revealed a heterozygous mutation (+3A>G after exon 3) and a clear homozygous sequence difference in exon 17. The 3rd sample from a 31 weeks gestation infant revealed heterozygosity for the+3A>G mutation after exon 3. All 3 placentas with MFI/MPVFD demonstrated heterozygous mutations in the HADHA gene, and 2 of the 3 placentas had 2 DNA changes. Given a background incidence of heterozygosity for LCHAD mutations of approximately 1 in 220, these findings lend support to the hypothesis that LCHAD mutations may be directly associated with and potentially causative of MFI/MPVFD.

Growth in Long-Chain 3-Hydroxyacyl-CoA Dehydrogenase Deficiency

Long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency is an inborn error of fatty acid metabolism that affects the degradation of long chain fatty acids and causes insufficient energy production and accumulation of toxic intermediates. The treatment consists of a diet low in fat, with supplementation of medium-chain triglycerides that bypass the metabolic block. In addition, frequent feeds and extra carbohydrates are given during febrile illnesses to reduce lipolysis. Hence, this diet differs from the general dietary recommendations for growing children. Furthermore, the Swedish dietary instructions for fat intake in LCHAD deficiency are given in grams, which differ from most guidelines that recommend fat intake as percentage shares of total caloric intake.

AIMS

To assess growth in patients with LCHAD deficiency, in relation to dietary treatment and to evaluate if overweight/obesity is more common than in the normal population.

RESULTS

The growth velocity showed acceleration after diagnosis and the start of treatment, followed by a period of stable or decelerated growth. The majority of the patients developed overweight to a greater extent than children without LCHAD deficiency. Several patients also went through a phase of obesity. Data on final height (FH) showed that three out of five patients had grown according to their genetic potential.

CONCLUSIONS

Regular and frequent follow-up and careful monitoring of weight are essential to avoid the development of overweight and obesity. The Swedish dietary instructions defining fat intake in total grams per day may be an alternative approach to achieve a moderate total caloric intake.

Observations regarding retinopathy in mitochondrial trifunctional protein deficiencies

Although the retina is thought to primarily rely on glucose for fuel, inherited deficiency of one or more activities of mitochondrial trifunctional protein results in a pigmentary retinopathy leading to vision loss. Many other enzymatic deficiencies in fatty acid oxidation pathways have been described, none of which results in retinal complications. The etiology of retinopathy among patients with defects in trifunctional protein is unknown. Trifunctional protein is a heteroctomer; two genes encode the alpha and beta subunits of TFP respectively, HADHA and HADHB. A common mutation in HADHA, c.1528G>C, leads to a single amino acid substitution, p. Glu474Gln, and impairs primarily long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) activity leading to LCHAD deficiency (LCHADD). Other mutations in HADHA or HADHB often lead to significant reduction in all three enzymatic activities and result in trifunctional protein deficiency (TFPD). Despite many similarities in clinical presentation and phenotype, there is growing evidence that they can result in different chronic complications. This review will outline the clinical similarities and differences between LCHADD and TFPD, describe the course of the associated retinopathy, propose a genotype/phenotype correlation with the severity of retinopathy, and discuss the current theories about the etiology of the retinopathy.

Comprehensive cDNA study and quantitative analysis of mutant HADHA and HADHB transcripts in a French cohort of 52 patients with mitochondrial trifunctional protein deficiency

BACKGROUND

Deficiency of mitochondrial trifunctional protein (MTP) is caused by mutations in the HADHA and HADHB genes, which have been mostly delineated at the genomic DNA level and have not been always elucidated.

AIM

To identify mutations in a French cohort of 52 MTP deficient patients and the susceptibility of mutations generating premature termination codons (PTCs) to the nonsense mRNA mediated decay (NMD).

METHODS

Mutation screening in fibroblasts was performed at the cDNA level and real-time RT-PCR was used to compare the levels of the different PTC-bearing mRNAs before and after a treatment of fibroblasts by emetine, a translation inhibitor.

RESULTS

A mutation detection rate of 100% was achieved. A total of 22 novel mutations were identified, including a large-sized genomic deletion in HADHB gene. A high proportion of all identified mutations were non-sense, frameshift and splicing mutations, generating (PTCs), distributed essentially on HADHA coding regions. We could demonstrate that the majority of mutations resulting in PTCs conform to the established rules governing the susceptibility to NMD.

CONCLUSION

Our results emphasize the value of cDNA analysis in the characterization of HADHA and HADHB mutations and further strengthen the model of haploinsufficiency as a major pathomechanism in MTP defects.

Urgent metabolic service improves survival in long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency detected by symptomatic identification and pilot newborn screening

Long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHADD) is a fatty acid oxidation disorder with especially high mortality and uncertain long-term outcome. The aim of the study was to analyze the influence of diagnostic approach on survival in 59 affected children. Referral to a metabolic center was replaced over time by urine/blood testing in centralized metabolic laboratory (selective screening) and by pilot tandem mass spectrometry newborn screening (NBS). Molecular analysis revealed the prevalent mutation in the HADHA gene in all 58 examined cases. Twenty patients died. The number of detections and number of deaths were respectively 9 and 4 (44%) in the patients recognized by differential diagnosis, 28 and 9 (32%) - by selective screening, and 11 and 1 (9%) - by NBS. In 80% of cases the death occurred before or within 3 weeks from the identification. Urgent and active metabolic service remarkably influenced the surviving. The current age of 39 survivors is 0.5 to 23 yrs (mean 7.2 yrs). The disease frequency estimated on the patients number was 1: 115 450, whereas in the pilot NBS - 1: 109 750 (658 492 neonates tested). Interestingly, the phenylalanine level in asymptomatic neonates frequently exceeded the cut-off values.

CONCLUSIONS

1) Urgent metabolic intervention decreases mortality of LCHAD-deficient patients, but the prognosis is still uncertain. 2) Emergent metabolic reporting and service are crucial also for the survival of neonates detected by NBS. 3) The nationwide selective screening appeared efficient in LCHADD detection in the country. 4) Transient mild hyperphenylalaninaemia may occur in LCHAD-deficient newborns.

A comprehensive HADHA c.1528G>C frequency study reveals high prevalence of long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency in Poland

Isolated long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHADD) is associated with c.1528G>C substitution in the HADHA gene, since most patients have the prevalent mutation on at least one allele. As it is known that the disease is relatively frequent in Europe, especially around the Baltic Sea, and that the majority of Polish LCHADD patients originate from the coastal Pomeranian province, partly inhabited by an ancient ethnic group, the Kashubians, we aimed to determine the carrier frequency of the prevalent HADHA mutation in various districts of Poland with special focus on the Kashubian district. A total of 6,854 neonatal dried blood samples from the entire country, including 2,976 Pomeranian neonates of Kashubian origin, were c.1528G>C genotyped. Fifty-nine heterozygous carriers for the prevalent c.1528G>C substitution (41 Pomeranian children) were detected in the studied group. Our data reveal a geographically skewed distribution of the c.1528C allele in the Polish population; in the northern Pomeranian province the carrier frequency is 1:73, which is the highest frequency ever reported, whereas in the remaining regions it is 1:217. Hence, the incidence of LCHADD in Poland is predicted to be 1:118,336 versus 1:16,900 in the Pomeranian district. Despite the relative rarity of the disease, screening for LCHADD in neonates born in the northern part of Poland, especially those of Kashubian origin, is justified. Our data allow us to suggest a probable Kashubian origin of the prevalent c.1528G>C mutation.

Paternal isodisomy of chromosome 2 as a cause of long chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency

Long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency is an autosomal recessive disorder affecting mitochondrial fatty acid oxidation due to mutations in the HADHA gene. We report on a 22-month-old child who was identified on expanded newborn screening with an abnormal acylcarnitine pattern and increased C14OH. Molecular analysis showed that the child was homozygous for the common mutation, c.1526G > C (p.Glu510Gln) in the HADHA gene. Carrier testing on the parental samples revealed that the father was heterozygous for the mutation whereas the mother did not carry the mutation. Short tandem repeat testing with markers covering both short and long arms of chromosome 2 showed that the child has paternal uniparental isodisomy. We highlight the importance of parental testing in cases of homozygosity in autosomal recessive disorders and its impact on genetic counseling of the family.

Genetic and cellular studies of oxidative stress in methylmalonic aciduria (MMA) cobalamin deficiency type C (cblC) with homocystinuria (MMACHC)

Methylmalonic aciduria (MMA) cobalamin deficiency type C (cblC) with homocystinuria (MMACHC) is the most frequent genetic disorder of vitamin B(12) metabolism. The aim of this work was to identify the mutational spectrum in a cohort of cblC-affected patients and the analysis of the cellular oxidative stress and apoptosis processes, in the presence or absence of vitamin B(12). The mutational spectrum includes nine previously described mutations: c.3G>A (p.M1L), c.217C>T (p.R73X), c.271dupA (p.R91KfsX14), c.331C>T (p.R111X), c.394C>T (p.R132X), c.457C>T (p.R153X), c.481C>T (p.R161X), c.565C>A (p.R189S), and c.615C>G (p.Y205X), and two novel changes, c.90G>A (p.W30X) and c.81+2T>G (IVS1+2T>G). The most frequent change was the known c.271dupA mutation, which accounts for 85% of the mutant alleles characterized in this cohort of patients. Owing to its high frequency, a real-time PCR and subsequent high-resolution melting (HRM) analysis for this mutation has been established for diagnostic purposes. All cell lines studied presented a significant increase of intracellular reactive oxygen species (ROS) content, and also a high rate of apoptosis, suggesting that elevated ROS levels might induce apoptosis in cblC patients. In addition, ROS levels decreased in hydroxocobalamin-incubated cells, indicating that cobalamin might either directly or indirectly act as a scavenger of ROS. ROS production might be considered as a phenotypic modifier in cblC patients, and cobalamin supplementation or additional antioxidant drugs might suppress apoptosis and prevent cellular damage in these patients.

EFFECT OF FEEDING, EXERCISE AND GENOTYPE ON PLASMA 3-HYDROXYACYLCARNITINES IN CHILDREN WITH LCHAD DEFICIENCY

Chronic complications observed in patients with long-chain 3-hydroxyacylCoA dehydrogenase (LCHAD) or trifunctional protein (TFP) deficiency may be mediated by the accumulation of 3-hydroxy fatty acids or 3-hydroxyacylcarnitines. To understand variation in metabolite accumulation, their concentrations were measured by tandem mass spectrometry before and after a mixed meal and moderate intensity exercise. Subjects who were homozygous or heterozygous for the common mutation (c.1528G>C) in the TFP alpha subunit (LCHAD deficiency) had significantly higher 3-hydroxyacylcarnitines than subjects with TFP deficiency. Feeding a mixed meal significantly suppressed and exercise significantly increased plasma 3-hydroxyacylcarnitines concentrations.

Mitochondrial trifunctional protein deficiency with recurrent rhabdomyolysis

Rhabdomyolysis is an important clinical diagnosis. The differential diagnosis is extensive and includes various etiologies, such as infection, inflammation, trauma, endocrinopathies, and congenital muscular and metabolic disorders. Reported here is the case of an infant with recurrent rhabdomyolysis diagnosed as suffering from mitochondrial trifunctional protein deficiency -- a rare beta oxidation defect. The clinical course was unique, and a new mutation in the mitochondrial trifunctional protein gene was identified.

The paradox of the carnitine palmitoyltransferase type Ia P479L variant in Canadian Aboriginal populations

Investigation of seven patients from three families suspected of a fatty acid oxidation defect showed mean CPT-I enzyme activity of 5.9+/-4.9 percent of normal controls. The families, two Inuit, one First Nation, live in areas of Canada geographically very distant from each other. The CPT1 and CPT2 genes were fully sequenced in 5 of the patients. All were homozygous for the same P479L mutation in a highly conserved region of the CPT1 gene. Two patients from the first family were also homozygous for the CPT2 F352C polymorphism in the CPT2 gene. Genotyping the patients and their family members confirmed that all seven patients were homozygous for the P479L variant allele in the CPT1 gene, as were 27 of 32 family members. Three of the seven patients and two cousins had hypoketotic hypoglycemia attributable to CPT-Ia deficiency, but adults homozygous for the variant denied hypoglycemia. We screened 422 consecutive newborns from the region of one of the Inuit families for this variant; 294 were homozygous, 103 heterozygous, and only 25 homozygous normal; thus the frequency of this variant allele is 0.81. There was an infant death in one family and at least 10 more deaths in those infants (7 homozygous, 3 heterozygous) consecutively tested for the mutation at birth. Thus there is an astonishingly high frequency of CPT1 P479L variant and, judging from the enzyme analysis in the seven patients, also CPT-I deficiency in the areas of Canada inhabited by these families. Despite the deficiency of CPT-Ia which is the major rate-limiting enzyme for long chain fatty acid oxidation, clinical effects, with few exceptions, were slight or absent. One clue to explaining this paradox is that, judging from the fatty acid oxidation studies in whole blood and fibroblasts, the low residual activity of CPT-Ia is sufficient to allow a reasonable flux through the mitochondrial oxidation system. It is likely that the P479L variant is of ancient origin and presumably its preservation must have conveyed some advantage.

Genes and the preeclampsia syndrome

Preeclampsia is specific to pregnancy and is still a leading cause of maternal and perinatal mortality and morbidity, affecting about 3% of women, but the underlying pathogenetic mechanisms still remain unclear. Immune maladaptation, placental ischemia and increased oxidative stress represent the main components discussed to be of etiologic importance, and they all may have genetic implications. Since the familial nature of preeclampsia is known for many years, extensive research on the genetic contribution to the pathogenesis of this severe pregnancy disorder has been performed. In this review, we will overview the linkage and candidate gene studies carried out so far as well as summarize important historical notes on the genetic hypotheses generated in preeclampsia research. Moreover, the influence of maternal and fetal genes and their interaction as well as the role of genomic imprinting in preeclampsia will be discussed.

[Recurrent acute fatty liver of pregnancy]

Acute fatty liver of pregnancy (AFLP) is a rare liver disease unique to pregnancy potentially fatal for both mother and child. Only a few cases of recurrence have been published. We report a new case. A 27-year-old primiparous patient presented a first episode of AFLP in 1991 at 37 week's gestation. Diagnosis was suspected because of vomiting, thrombocytopenia, and liver function tests abnormalities. It was confirmed by liver ultrasonography and abdominal computed tomography. Clinical and biological improvement was observed after caesarean delivery. Six years later, the woman began a second pregnancy. Liver function tests and complete blood count were regularly checked. At 30 weeks' gestation, recurrent AFLP occurred and caesarean section was performed. Again, diagnosis was confirmed by both ultrasonography and abdominal computed tomography. In 2006, the mother and the two girls, 15 and 8-year-old respectively, were in good health. The study of the HADHA gene, coding alpha subunit long chain 3-hydroxyacyl coenzyme A dehydrogenase (LCHAD) in the patient failed to find mutations, particularly the common mutation c.1528G>C (Glu474-Gln, p.E474Q). In conclusion, after an episode of AFLP, women should be clearly warned of the risk of recurrence and regularly monitored during the next pregnancy, even if the search of HADHA gene mutation is negative.