...HACE1 is considered to act as a tumour suppressor whose downregulation could enhance tumour growth and progression, whereas its overexpression could inhibit tumour development.2 However, the ...implication of HACE1 in human disease is not limited to cancer. The molecular mechanisms underlying HACE1 deficiency have not been completely elucidated, but several studies performed in cellular and animal models provided some insights pointing to altered regulation of autophagy and oxidative stress response pathways.9,10 On the other hand, a recent study performed in SPPRS primary fibroblasts reported significant abnormalities affecting mitochondrial morphology and network branching. ...SPPRS cells showed a strong reduction of the mitophagic flux and a marked accumulation of both the overall and the intramitochondrial oxidative damage due to defective activation of Nrf2-dependent pathways.7 The mitochondrial defects observed in SPPRS patients together with the fact that HACE1 is required for cyclin C mitochondrial translocation reinforces the role of HACE1 in the regulation of mitochondrial physiology.
Lipoic acid biosynthesis defects Mayr, Johannes A.; Feichtinger, René G.; Tort, Frederic ...
Journal of inherited metabolic disease,
July 2014, Letnik:
37, Številka:
4
Journal Article, Conference Proceeding
Recenzirano
Lipoate is a covalently bound cofactor essential for five redox reactions in humans: in four 2-oxoacid dehydrogenases and the glycine cleavage system (GCS). Two enzymes are from the energy ...metabolism, α-ketoglutarate dehydrogenase and pyruvate dehydrogenase; and three are from the amino acid metabolism, branched-chain ketoacid dehydrogenase, 2-oxoadipate dehydrogenase, and the GCS. All these enzymes consist of multiple subunits and share a similar architecture. Lipoate synthesis in mitochondria involves mitochondrial fatty acid synthesis up to octanoyl-acyl-carrier protein; and three lipoate-specific steps, including octanoic acid transfer to glycine cleavage H protein by lipoyl(octanoyl) transferase 2 (putative) (LIPT2), lipoate synthesis by lipoic acid synthetase (LIAS), and lipoate transfer by lipoyltransferase 1 (LIPT1), which is necessary to lipoylate the E2 subunits of the 2-oxoacid dehydrogenases. The reduced form dihydrolipoate is reactivated by dihydrolipoyl dehydrogenase (DLD). Mutations in
LIAS
have been identified that result in a variant form of nonketotic hyperglycinemia with early-onset convulsions combined with a defect in mitochondrial energy metabolism with encephalopathy and cardiomyopathy.
LIPT1
deficiency spares the GCS, and resulted in a combined 2-oxoacid dehydrogenase deficiency and early death in one patient and in a less severely affected individual with a Leigh-like phenotype. As
LIAS
is an iron–sulphur-cluster-dependent enzyme, a number of recently identified defects in mitochondrial iron–sulphur cluster synthesis, including
NFU1
,
BOLA3
,
IBA57
,
GLRX5
presented with deficiency of
LIAS
and a
LIAS
-like phenotype. As in
DLD
deficiency, a broader clinical spectrum can be anticipated for lipoate synthesis defects depending on which of the affected enzymes is most rate limiting.
An immersed quartz crystal resonator (QCR) was employed to assess the effectiveness of a modified alkylphenol resin in reducing asphaltene deposition on metal surfaces under various temperature and ...pressure conditions. The QCR response to asphaltene flocculation was first monitored during isothermal n-heptane titration experiments of dead crude oils with different contents of the asphaltene inhibitor (AI). In addition, the effect of the AI presence on the morphology of asphaltene deposits was analyzed by atomic force microscopy (AFM). Then, constant mass expansion experiments were carried out to determine whether the presence of the AI influenced the asphaltene instability pressure and the deposition rate of asphaltenes in a dead oil + CH4 system with various CH4 contents. The results of all these investigations in the nanometer range shed new light on the AI technology and clearly demonstrate that the presence of the AI can reduce the asphaltene deposition rate and modify the viscoelastic properties of the asphaltene solution in oil production conditions.
Lipoic acid (LA) is an essential cofactor required for the activity of five multienzymatic complexes that play a central role in the mitochondrial energy metabolism: four 2-oxoacid dehydrogenase ...complexes pyruvate dehydrogenase (PDH), branched-chain ketoacid dehydrogenase (BCKDH), 2-ketoglutarate dehydrogenase (2-KGDH), and 2-oxoadipate dehydrogenase (2-OADH) and the glycine cleavage system (GCS). LA is synthesized in a complex multistep process that requires appropriate function of the mitochondrial fatty acid synthesis (mtFASII) and the biogenesis of iron–sulphur (Fe-S) clusters. Defects in the biosynthesis of LA have been reported to be associated with multiple and severe defects of the mitochondrial energy metabolism. In recent years, disease-causing mutations in genes encoding for proteins involved in LA metabolism have been reported:
NFU1
,
BOLA3
,
IBA57
,
LIAS
,
GLRX5
,
LIPT1
,
ISCA2
, and
LIPT2
. These studies represented important progress in understanding the pathophysiology and molecular bases underlying these disorders. Here we review current knowledge regarding involvement of LA synthesis defects in human diseases with special emphasis on the diagnostic strategies for these disorders. The clinical and biochemical characteristics of patients with LA synthesis defects are discussed and a workup for the differential diagnosis proposed.
CCDC186 protein is involved in the maturation of dense-core vesicles (DCVs) in the trans-Golgi network in neurons and endocrine cells. Mutations in genes involved in DCV regulation, other than
, have ...been described in patients with neurodevelopmental disorders. To date, only one patient, within a large sequencing study of 1000 cases, and a single case report with variants in
, had previously been described. However, no functional studies in any of these two cases had been performed. We identified three patients from two gypsy families, unrelated to each other, with mutations in the
gene. Clinically, all patients presented with seizures, frontotemporal atrophy, hypomyelination, recurrent infections, and endocrine disturbances such as severe non-ketotic hypoglycemia. Low levels of cortisol, insulin, or growth hormone could only be verified in one patient. All of them had a neonatal onset and died between 7 months and 4 years of age. Whole exome sequencing identified a homozygous variant in the
gene (c.2215C>T, p.Arg739Ter) in the index patients of both families. Protein expression studies demonstrated that CCDC186 was almost undetectable in fibroblasts and muscle tissue. These observations correlated with the transcriptomic analysis performed in fibroblasts in one of the patients, which showed a significant reduction of
mRNA levels. Our study provides functional evidence that mutations in this gene have a pathogenic effect on the protein and reinforces CCDC186 as a new disease-associated gene. In addition, mutations in
could explain the combined endocrine and neurologic alterations detected in our patients.
Peroxisomal biogenesis disorders (PBDs) are a heterogeneous group of genetic diseases. Multiple peroxisomal pathways are impaired, and very long chain fatty acids (VLCFA) are the first line ...biomarkers for the diagnosis. The clinical presentation of PBDs may range from severe, lethal multisystemic disorders to milder, late-onset disease. The vast majority of PBDs belong to Zellweger Spectrum Disordes (ZSDs) and represents a continuum of overlapping clinical symptoms, with Zellweger syndrome being the most severe and Heimler syndrome the less severe disease. Mild clinical conditions frequently present normal or slight biochemical alterations, making the diagnosis of these patients challenging. In the present study we used a combined WES and RNA-seq strategy to diagnose a patient presenting with retinal dystrophy as the main clinical symptom. Results showed the patient was compound heterozygous for mutations in PEX1. VLCFA were normal, but retrospective analysis of lysosphosphatidylcholines (LPC) containing C22:0–C26:0 species was altered. This simple test could avoid the diagnostic odyssey of patients with mild phenotype, such as the individual described here, who was diagnosed very late in adult life. We provide functional data in cell line models that may explain the mild phenotype of the patient by demonstrating the hypomorphic nature of a deep intronic variant altering PEX1 mRNA processing.
Alteration of vitamin B.sub.12 metabolism can be genetic or acquired, and can result in anemia, failure to thrive, developmental regression and even irreversible neurologic damage. Therefore, early ...diagnosis and intervention is critical. Most of the neonatal cases with acquired vitamin B.sub.12 deficiency have been detected by clinical symptoms and only few of them trough NBS programs. We aim to assess the usefulness of the second-tier test: methylmalonic acid (MMA), methylcitric acid (MCA) and homocysteine (Hcys) in our newborn screening program and explore the implications on the detection of cobalamin (vitamin B.sub.12) related disorders, both genetic and acquired conditions. A screening strategy using the usual primary markers followed by the analysis of MMA, MCA and Hcys as second tier-test in the first dried blood spot (DBS) was developed and evaluated. During the period 2015-2018 a total of 258,637 newborns were screened resulting in 130 newborns with acquired vitamin B.sub.12 deficiency (incidence 1:1989), 19 with genetic disorders (incidence 1:13,613) and 13 were false positive. No false negatives were notified. Concerning the second-tier test, the percentage of cases with MMA above the cut-off levels, both for genetic and acquired conditions was very similar (58% and 60%, respectively). Interestingly, the percentage of cases with increased levels of Hcys was higher in acquired conditions than in genetic disorders (87% and 47%, respectively). In contrast, MCA was high only in 5% of the acquired conditions versus in 53% of the genetic disorders, and it was always very high in all patients with propionic acidemia. When screening for methylmalonic acidemia and homocystinuria, differential diagnosis with acquired vitamin B.sub.12 deficiency should be done. The results of our strategy support the inclusion of this acquired condition in the NBS programs, as it is easily detectable and allows the adoption of corrective measures to avoid the consequences of its deficiency.
We report the case of a 10-year-old Spanish girl with mutations in NADK2 Prenatal central nervous system abnormalities showed ventriculomegaly, colpocephaly, and hypoplasia of the corpus callosum. At ...birth, axial hypotonia, uncoordinated movements, microcephaly, and generalized cerebellar atrophy were detected. Metabolic investigations revealed high lysine, lactate, and pipecolic acid levels in blood and cerebrospinal fluid. Pyruvate carboxylase and pyruvate dehydrogenase activity in fibroblasts were normal. Beginning at birth she received biotin, thiamine, and carnitine supplementation. A lysine-restricted diet was started when she was 1 month old. Because pipecolic acid was high, pyridoxine was added to treatment. At 3 years old, astatic myoclonic epilepsy appeared, with no response to levetiracetam. We switched pyridoxine to pyridoxal phosphate, with electroclinical improvement. Because the activity of mitochondrial respiratory chain complexes III and IV was slightly low in muscle, other cofactors such as ubidecarenone, idebenone, vitamin E, and creatine were added to the treatment. At 8 years old, plasma acylcarnitine testing was performed, and high levels of 2-trans, 4-cis-decadienoylcarnitine were found. Whole exome sequencing identified a homozygous splice site mutation in NADK2 (c.956+6T>C; p.Trp319Cysfs*21). This substitution generates exon skipping, leading to a truncated protein. In fact, NADK2 messenger RNA and the corresponding protein were almost absent. Now, at 10 years of age she presents with ataxia and incoordination. She has oromotor dysphasia but is able to understand fluid language and is a very friendly girl. We hypothesize that the patient's clinical improvement could be due to her lysine-restricted diet together with cofactors and pyridoxal phosphate administration.
Glutaric aciduria type 1 (GA1) is a rare inherited metabolic disorder caused by a deficiency of glutaryl-coenzyme A dehydrogenase (GCDH), with accumulation of neurotoxic metabolites, resulting in a ...complex movement disorder, irreversible brain damage, and premature death in untreated individuals. While early diagnosis and a lysine restricted diet can extend survival, they do not prevent neurological damage in approximately one-third of treated patients, and more effective therapies are required. Here we report the efficacy of adeno-associated virus 9 (AAV9)-mediated systemic delivery of human GCDH at preventing a high lysine diet (HLD)-induced phenotype in Gcdh−/− mice. Neonatal treatment with AAV-GCDH restores GCDH expression and enzyme activity in liver and striatum. This treatment protects the mice from HLD-aggressive phenotype with all mice surviving this exposure; in stark contrast, a lack of treatment on an HLD triggers very high accumulation of glutaric acid, 3-hydroxyglutaric acid, and glutarylcarnitine in tissues, with about 60% death due to brain accumulation of toxic lysine metabolites. AAV-GCDH significantly ameliorates the striatal neuropathology, minimizing neuronal dysfunction, gliosis, and alterations in myelination. Magnetic resonance imaging findings show protection against striatal injury. Altogether, these results provide preclinical evidence to support AAV-GCDH gene therapy for GA1.
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Fillat and colleagues present preclinical evidence supporting gene therapy for GA1, a genetic disease of the lysine catabolism that lacks effective treatment. They demonstrate that gene replacement of GCDH by a single intravascular administration of AAV-GCDH in newborn GCDH-deficient mice ameliorates the murine phenotype.
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