[Clinical and genetic analysis of two children with 3-hydroxy-3-methylglutaryl-CoA lyase deficiency].

OBJECTIVE: To explore the clinical characteristics and genetic variants of two children with 3-hydroxy-3-methylglutaryl-coenzyme A lyase deficiency (HMGCLD). METHODS: Two children with HMGCLD diagnosed at Henan Provincial Children's Hospital respectively in December 2019 and June 2022 were selected as the study subjects. Clinical data and results of laboratory testing were analyzed retrospectively. RESULTS: Both children had manifested with repeated convulsions, severe hypoglycemia, metabolic acidosis and liver dysfunction. Blood amino acids and acylcarnitine analysis showed increased 3-hydroxy-isovalyl carnitine (C5OH) and 3-hydroxy-isovalyl carnitine/capryloyl carnitine ratio (C5OH/C8), and urinary organic acid analysis showed increased 3-hydroxyl-3-methyl glutaric acid, 3-methyl glutaric acid, 3-methyl glutaconic acid, 3-hydroxyisoglycine and 3-methylprotarylglycine. Child 1 was found to harbor homozygous c.722C>T variants of the HMGCL gene, which was rated as uncertain significance (PM2_Supporting+PP3). Child 2 was found to harbor homozygous c.121C>T variants of the HMGCL gene, which was rated as pathogenic variant (PVS1+PM2_Supporting+PP4). CONCLUSION: Acute episode of HMGCLD is usually characterized by metabolic disorders such as hypoglycemia and metabolic acidosis, and elevated organic acids in urine may facilitate the differential diagnosis, though definite diagnosis will rely on genetic testing.

3-hydroxy-3-methylglutaryl-coenzyme A lyase deficiency: one disease - many faces.

BACKGROUND: 3-hydroxy-3-methylglutaryl-coenzyme A lyase deficiency (HMGCLD) is an autosomal recessive disorder of ketogenesis and leucine degradation due to mutations in HMGCL. METHOD: We performed a systematic literature search to identify all published cases. Two hundred eleven patients of whom relevant clinical data were available were included in this analysis. Clinical course, biochemical findings and mutation data are highlighted and discussed. An overview on all published HMGCL variants is provided. RESULTS: More than 95% of patients presented with acute metabolic decompensation. Most patients manifested within the first year of life, 42.4% already neonatally. Very few individuals remained asymptomatic. The neurologic long-term outcome was favorable with 62.6% of patients showing normal development. CONCLUSION: This comprehensive data analysis provides a systematic overview on all published cases with HMGCLD including a list of all known HMGCL mutations.

Bayesian multiple hypotheses testing in compositional analysis of untargeted metabolomic data.

Clinical metabolomics aims at finding statistically significant differences in metabolic statuses of patient and control groups with the intention of understanding pathobiochemical processes and identification of clinically useful biomarkers of particular diseases. After the raw measurements are integrated and pre-processed as intensities of chromatographic peaks, the differences between controls and patients are evaluated by both univariate and multivariate statistical methods. The traditional univariate approach relies on t-tests (or their nonparametric alternatives) and the results from multiple testing are misleadingly compared merely by p-values using the so-called volcano plot. This paper proposes a Bayesian counterpart to the widespread univariate analysis, taking into account the compositional character of a metabolome. Since each metabolome is a collection of some small-molecule metabolites in a biological material, the relative structure of metabolomic data, which is inherently contained in ratios between metabolites, is of the main interest. Therefore, a proper choice of logratio coordinates is an essential step for any statistical analysis of such data. In addition, a concept of b-values is introduced together with a Bayesian version of the volcano plot incorporating distance levels of the posterior highest density intervals from zero. The theoretical background of the contribution is illustrated using two data sets containing samples of patients suffering from 3-hydroxy-3-methylglutaryl-CoA lyase deficiency and medium-chain acyl-CoA dehydrogenase deficiency. To evaluate the stability of the proposed method as well as the benefits of the compositional approach, two simulations designed to mimic a loss of samples and a systematical measurement error, respectively, are added.

Prevention by L-carnitine of DNA damage induced by 3-hydroxy-3-methylglutaric and 3-methylglutaric acids and experimental evidence of lipid and DNA damage in patients with 3-hydroxy-3-methylglutaric aciduria.

3-hydroxy-3-methylglutaric aciduria (HMGA) is an inherited disorder of the leucine catabolic pathway in which occurs a deficiency of the 3-hydroxy-3-methylglutaryl-CoA lyase enzyme. Therefore, the organic acids 3-hydroxy-3-methylglutaric (HMG) and 3-methylglutaric (MGA), mainly, accumulate in tissues of affected patients. Lately, much attention has been focused on free radicals as mediators of tissue damage in human diseases, causing lipid peroxidation, protein oxidation and DNA damage. The treatment of this disease is based in a restricted protein ingest and supplementation with l-carnitine (LC), an antioxidant and detoxifying agent. In the present work, we investigated the in vitro oxidative damage to DNA induced by the accumulation of organic acids and oxidative stress parameters in vivo of patients with 3-HMG, as well as the effect of the recommended therapy. The in vitro DNA damage was analyzed by the alkaline comet assay in leukocytes incubated with HMG and MGA (1 mM, 2.5 mM and 5 mM) and co-incubated with LC (90 µM and 150 µM). The in vivo urinary 15-F2t-isoprostane levels and urinary oxidized guanine species were measured by ELISA kits in patient's urine before and after the treatment with LC. HMG and MGA induced a DNA damage index (DI) significantly higher than that of the control group. The DI was significantly reduced in the presence of LC. It was also verified a significant increase of oxidized guanine species and urinary isoprostane levels, biomarker of oxidative DNA damage and lipid peroxidation respectively, in patients before treatment. After the treatment and supplementation with LC, patients presented significantly lower levels of those biomarkers. Analyzing the data together, we can conclude that HMGA patients present oxidative lipid and DNA damage, which is induced by HMG and MGA, and the antioxidant therapy with LC can prevent that kind of injuries.

Newborn screening for 3-hydroxy-3-methylglutaric aciduria using direct analysis in real-time mass spectrometry.

A novel method utilizing ambient thermal desorption ionization with a direct analysis in real-time source integrated with mass spectrometry (DART-MS) was established and applied to the rapid analysis of 3-hydroxy-3-methylglutaric (3-HMG) acid in the neonatal urine. Instrument parameter settings were optimized to obtain high sensitive and accurate determination of 3-HMG acid. The use of helium gas heated to temperature of 400°C was observed to permit deprotonation, 3-HMG acid producing an abundant (M-H)- (m/z 161) in the negative ion mode. The calibration curve was determined to be linear over the range of 0.05-5 mg/L, with the correlation coefficient r = 0.9988 and the relative standard deviations (n = 6) in the range of 1.5-11.8%. The limit of detection was 0.002 mg/L, and the limit of quantitation was 0.007 mg/L. The recoveries ranged from 88.0% to 123.1%. Four urine samples from patients and four simulated urine samples were investigated. The results of DART-MS were in agreement with the values determined using established methods at the hospitals. The proposed method demonstrated significant potential in the application of the high-throughput screening in newborn screening.

Inflammasome Activation Aggravates Cutaneous Xanthomatosis and Atherosclerosis in ACAT1 (Acyl-CoA Cholesterol Acyltransferase 1) Deficiency in Bone Marrow.

Objective- ACAT1 (Acyl-CoA cholesterol acyltransferase 1) esterifies cellular free cholesterol, thereby converting macrophages to cholesteryl ester-laden foam cells in atherosclerotic lesions and cutaneous xanthoma. Paradoxically, however, loss of ACAT1 in bone marrow causes the aggravation of atherosclerosis and the development of severe cutaneous xanthoma in hyperlipidemic mice. Recently, it has been reported that cholesterol crystals activate NLRP3 (NACHT, LRR [leucine-rich repeats], and PYD [pyrin domain] domain-containing protein 3) inflammasomes, thereby contributing to the development of atherosclerosis. The present study aimed to clarify the role of NLRP3 inflammasomes in the worsening of atherosclerosis and cutaneous xanthoma induced by ACAT1 deficiency. Approach and Results- Ldlr-null mice were transplanted with bone marrow from WT (wild type) mice and mice lacking ACAT1, NLRP3, or both. After the 4 types of mice were fed high-cholesterol diets, we compared their atherosclerosis and skin lesions. The mice transplanted with Acat1-null bone marrow developed severe cutaneous xanthoma, which was filled with numerous macrophages and cholesterol clefts and had markedly increased expression of inflammatory cytokines, and increased atherosclerosis. Loss of NLRP3 completely reversed the cutaneous xanthoma, whereas it improved the atherosclerosis only partially. Acat1-null peritoneal macrophages showed enhanced expression of CHOP (C/EBP [CCAAT/enhancer binding protein] homologous protein) and TNF-α (tumor necrosis factor-α) but no evidence of inflammasome activation, after treatment with acetylated LDL (low-density lipoprotein). Conclusions- Elimination of ACAT1 in bone marrow-derived cells aggravates cutaneous xanthoma and atherosclerosis. The development of cutaneous xanthoma is induced mainly via the NLRP3 inflammasome activation.

[3-hydroxy-3-methylglutaryl-CoA lyase deficiency: a case report and literature review]. / Anorexia nerviosa como causa de fallo hepático agudo. A propósito de un caso.

INTRODUCTION: 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) lyase deficiency is an autosomal recessive disorder that usually presents in the neonatal period with vomiting, metabolic acidosis, hypoglycemia and absent ketonuria. Few cases are reported in the literature, and optimal dietary management and long term outcome are not fully understood. CASE REPORT: We report a 2 year old girl with HMG-CoA-lyase deficiency who had limited fasting tolerance on a low protein diet, with several recurrent hospital admissions with severe hypoketotic hypoglycaemia and metabolic acidosis. We also review the dietary management and outcome of other reported cases in the literature. DISCUSSION: In order to define optimal dietary treatment, it is important to collect higher numbers of case studies with detailed dietary management, fasting times and outcome.

Structural elucidation of novel biomarkers of known metabolic disorders based on multistage fragmentation mass spectra.

Specific diagnostic markers are the key to effective diagnosis and treatment of inborn errors of metabolism (IEM). Untargeted metabolomics allows for the identification of potential novel diagnostic biomarkers. Current separation techniques coupled to high-resolution mass spectrometry provide a powerful tool for structural elucidation of unknown compounds in complex biological matrices. This is a proof-of-concept study testing this methodology to determine the molecular structure of as yet uncharacterized m/z signals that were significantly increased in plasma samples from patients with phenylketonuria and 3-hydroxy-3-methylglutaryl-CoA lyase deficiency. A hybrid linear ion trap-orbitrap high resolution mass spectrometer, capable of multistage fragmentation, was used to acquire accurate masses and product ion spectra of the uncharacterized m/z signals. In order to determine the molecular structures, spectral databases were searched and fragmentation prediction software was used. This approach enabled structural elucidation of novel compounds potentially useful as biomarkers in diagnostics and follow-up of IEM patients. Two new conjugates, glutamyl-glutamyl-phenylalanine and phenylalanine-hexose, were identified in plasma of phenylketonuria patients. These novel markers showed high inter-patient variation and did not correlate to phenylalanine levels, illustrating their potential added value for follow-up. As novel biomarkers for 3-hydroxy-3-methylglutaryl-CoA lyase deficiency, three positional isomers of 3-methylglutaconyl carnitine could be detected in patient plasma. Our results highlight the applicability of current accurate mass multistage fragmentation techniques for structural elucidation of unknown metabolites in human biofluids, offering an unprecedented opportunity to gain further biochemical insights in known inborn errors of metabolism by enabling high confidence identification of novel biomarkers.

3-Hydroxy-3-methylglutaryl-coenzyme A lyase deficiency: Clinical presentation and outcome in a series of 37 patients.

3-Hydroxy-3-methylglutaryl-coenzyme A lyase deficiency (HMGCLD) is a rare inborn error of ketone body synthesis and leucine degradation, caused by mutations in the HMGCL gene. In order to obtain a comprehensive view on this disease, we have collected clinical and biochemical data as well as information on HMGCL mutations of 37 patients (35 families) from metabolic centers in Belgium, Germany, The Netherlands, Switzerland, and Turkey. All patients were symptomatic at some stage with 94% presenting with an acute metabolic decompensation. In 50% of the patients, the disorder manifested neonatally, mostly within the first days of life. Only 8% of patients presented after one year of age. Six patients died prior to data collection. Long-term neurological complications were common. Half of the patients had a normal cognitive development while the remainder showed psychomotor deficits. We identified seven novel HMGCL mutations. In agreement with previous reports, no clear genotype-phenotype correlation could be found. This is the largest cohort of HMGCLD patients reported so far, demonstrating that HMGCLD is a potentially life-threatening disease with variable clinical outcome. Our findings suggest that the clinical course of HMGCLD cannot be predicted accurately from HMGCL genotype. The overall outcome in HMGCLD appears limited, thus rendering early diagnosis and strict avoidance of metabolic crises important.

A novel mutation (c.121­13T>A) in the polypyrimidine tract of the splice acceptor site of intron 2 causes exon 3 skipping in mitochondrial acetoacetyl-CoA thiolase gene.

Mitochondrial acetoacetyl-CoA thiolase (T2) (gene symbol: ACAT1) deficiency is an autosomal recessive disorder affecting isoleucine catabolism and ketone body utilization. In this study, mutational analysis of an Indian T2-deficient patient revealed a homozygous mutation (c.121­13T>A) located at the polypyrimidine tract of the splice acceptor site of intron 2, and exon 3 skipping was identified by cDNA analysis using cycloheximide. We made three mutant constructs (c.121­13T>A, T>C, and T>G substitutions) followed by making a wild-type minigene construct that included an ACAT1 segment from exon 2 to 4 for a splicing experiment. The minigene splicing experiment demonstrated that exon 3 skipping was induced not only by c.121­13T>A mutation, but also by the other two substitutions. It was difficult to predict the effect of these mutations on splicing using in silico tools, as predictions of different tools were inconsistent with each other. The minigene splicing experiment remains the most reliable method to unravel splicing abnormalities.

Coupled brain and urine spectroscopy - in vivo metabolomic characterization of HMG-CoA lyase deficiency in 5 patients.

BACKGROUND: 3-Hydroxy-3-Methylglutaryl-Coenzyme A (HMG-CoA) lyase deficiency is a rare inborn error of leucine metabolism and ketogenesis. Despite recurrent hypoglycemia and metabolic decompensations, most patients have a good clinical and neurological outcome contrasting with abnormal brain magnetic resonance imaging (MRI) signals and consistent abnormal brain proton magnetic resonance spectroscopy (1H-MRS) metabolite peaks. Identifying these metabolites could provide surrogate markers of the disease and improve understanding of MRI-clinical discrepancy and follow-up of affected patients. METHODS: Urine samples, brain MRI and 1H-MRS in 5 patients with HMG-CoA lyase deficiency (4 boys and 1 girl aged from 25days to 10years) were, for each patient, obtained on the same day. Brain and urine spectroscopy were performed at the same pH by studying urine at pH 7.4. Due to pH-induced modifications in chemical shifts and because reference 1H NMR spectra are obtained at pH 2.5, spectroscopy of normal urine added with the suspected metabolite was further performed at this pH to validate the correct identification of compounds. RESULTS: Mild to extended abnormal white matter MRI signals were observed in all cases. Brain spectroscopy abnormal peaks at 0.8-1.1ppm, 1.2-1.4ppm and 2.4ppm were also detected by urine spectroscopy at pH 7.4. Taking into account pH-induced changes in chemical shifts, brain abnormal peaks in patients were formally identified to be those of 3-hydroxyisovaleric, 3-methylglutaconic, 3-methylglutaric and 3-hydroxy-3-methylglutaric acids. CONCLUSION: 3-Methylglutaric, 3-hydroxyisovaleric and 3-hydroxy-3-methylglutaric acids identified on urine 1H-NMR spectra of 5 patients with HMG-CoA lyase deficiency are responsible for the cerebral spectroscopy signature seen in these patients, validating their local involvement in brain and putative contribution to brain neuropathology.

Mitochondrial acetoacetyl-CoA thiolase deficiency: basal ganglia impairment may occur independently of ketoacidosis.

BACKGROUND: Mitochondrial acetoacetyl-CoA thiolase (T2) deficiency affects ketone body and isoleucine catabolism. Neurological impairment may occur secondary to ketoacidotic episodes. However, we observed neuromotor abnormalities without ketoacidotic events in two T2-deficient families. We hypothesized that the neurological signs were related to the genetic defect and may occur independently of ketoacidotic episodes. We therefore conducted a retrospective review on a French T2-deficient patient series searching for neuromotor impairment. METHODS: In total, 26 cases were retrospectively analysed for clinical, biological and neuroimaging data. RESULTS: Neurological findings were observed for 6/26 (23%) patients. Among these, two had never experienced ketoacidotic episodes, though they developed extrapyramidal signs with putamen involvement. Two of the other four patients developed neurological abnormalities before the first ketoacidotic crisis, with putamen involvement in one case. The third patient developed extrapyramidal symptoms more than 10 years after the initial decompensation with globus pallidus involvement. The last patient developed extrapyramidal signs immediately after a severe ketoacidotic crisis with putaminal lesions. CONCLUSIONS: Most T2-deficient patients achieved normal neurodevelopment. However, on account of the role of T2 in isoleucine catabolism, these patients are potentially exposed to accumulation of toxic isoleucine-derived metabolites, which may contribute to neurological impairment. Our findings confirm previous observations that neurological symptoms in T2 deficiency may occur unrelated to ketoacidosis. The role of protein restriction as a preventive measure against neurological symptoms could not be established in this study and deserves further evaluation. Long-term follow-up data on children diagnosed by newborn screening may clarify the pathogenesis of this neurometabolic association.

Management and long-term evolution of a patient with 3-hydroxy-3-methylglutaryl-coenzyme A lyase deficiency.

BACKGROUND: 3-Hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) lyase deficiency is a rare inborn error of metabolism characterized by recurrent metabolic crises caused by fasting, intercurrent illness and excessive physical exercise. Non ketotic hypoglycemia is normally the cause of primary symptoms but without an immediate treatment the illness can evolve into a worsening metabolic state resembling the Reye's syndrome that may cause the patient's death. We report a case with some clinical and therapeutic features not previously described. CASE PRESENTATION: Patient with HMG-CoA lyase deficiency whom after diagnosis at 2 years of age was re-admitted 12 years later, after severe metabolic decompensation following consumption of alcohol. Despite a quick correction of hypoglycemia, within the following few hours, the patient fell into a coma. Suspecting intracranial hypertension (ICH), the patient required mechanical ventilation. Although liver cytolysis was minimal, hyperamoniemia reached 1394 µmol/L, returning to normal, a few hours after administering sodium phenylacetate and sodium benzoate, whose use has not been reported in these patients. Brain edema was evidenced in the computed tomography and by the magnetic resonance imaging that determined that the edema was cytotoxic, as quantified with the restriction of diffusion in the apparent diffusion coefficient map. During the recovery of the ICH, we belatedly, detected vasospasm moderate-severe that was treated with nimodipine. Currently, the patient maintains clinical normality. CONCLUSIONS: The alcohol consumption must be avoided in patients with HMG-CoA lyase deficiency. In our patient hyperamoniemia was effectively treated with sodium phenylacetate and sodium benzoate. Magnetic resonance imaging showed and quantified the cytotoxic brain edema. Belatedly, a cerebral vasospasm was an additional mechanism of cerebral injury. None of these observations has been previously reported.

The management of pregnancy and delivery in 3-hydroxy-3-methylglutaryl-CoA lyase deficiency.

3-hydroxy-3-methylglutaric (HMG)-CoA lyase is required for ketogenesis and leucine degradation. Patients with HMG-CoA lyase deficiency typically present with hypoketotic hypoglycemia and metabolic acidosis, which can be fatal if untreated. The patient is a 28-year-old female with HMG-CoA lyase deficiency who presented at 4 weeks gestation for prenatal care. Protein intake as well as carnitine supplementation were gradually increased to support maternal and fetal demands up to 65 g per day for protein and 80 mg/kg/day for carnitine. Fetal growth was appropriate. At 36 5/7 weeks, she presented with spontaneous rupture of membranes. Twice maintenance 10% glucose-containing intravenous fluids were initiated. During labor, vomiting and metabolic acidosis developed. Delivery was by cesarean. Preeclampsia developed postpartum. The patient recovered well and was discharged home on postpartum day 5. Stress of pregnancy and labor and delivery can lead to metabolic decompensation in HMG-CoA lyase deficiency. Patients should be monitored closely by a biochemical geneticist, dietitian, and high-risk obstetrician at a tertiary care center during their pregnancy. Fasting should be avoided. Intravenous 10% glucose-containing fluids should be provided to prevent catabolism and metabolic decompensation during labor and delivery. © 2016 Wiley Periodicals, Inc.

Potentiating the antitumour response of CD8(+) T cells by modulating cholesterol metabolism.

CD8(+) T cells have a central role in antitumour immunity, but their activity is suppressed in the tumour microenvironment. Reactivating the cytotoxicity of CD8(+) T cells is of great clinical interest in cancer immunotherapy. Here we report a new mechanism by which the antitumour response of mouse CD8(+) T cells can be potentiated by modulating cholesterol metabolism. Inhibiting cholesterol esterification in T cells by genetic ablation or pharmacological inhibition of ACAT1, a key cholesterol esterification enzyme, led to potentiated effector function and enhanced proliferation of CD8(+) but not CD4(+) T cells. This is due to the increase in the plasma membrane cholesterol level of CD8(+) T cells, which causes enhanced T-cell receptor clustering and signalling as well as more efficient formation of the immunological synapse. ACAT1-deficient CD8(+) T cells were better than wild-type CD8(+) T cells at controlling melanoma growth and metastasis in mice. We used the ACAT inhibitor avasimibe, which was previously tested in clinical trials for treating atherosclerosis and showed a good human safety profile, to treat melanoma in mice and observed a good antitumour effect. A combined therapy of avasimibe plus an anti-PD-1 antibody showed better efficacy than monotherapies in controlling tumour progression. ACAT1, an established target for atherosclerosis, is therefore also a potential target for cancer immunotherapy.

Induction of a Proinflammatory Response in Cortical Astrocytes by the Major Metabolites Accumulating in HMG-CoA Lyase Deficiency: the Role of ERK Signaling Pathway in Cytokine Release.

3-Hydroxy-3-methylglutaric aciduria (HMGA) is an inherited metabolic disorder caused by 3-hydroxy-3-methylglutaryl-CoA lyase deficiency. It is biochemically characterized by predominant tissue accumulation and high urinary excretion of 3-hydroxy-3-methylglutarate (HMG) and 3-methylglutarate (MGA). Affected patients commonly present acute symptoms during metabolic decompensation, including vomiting, seizures, and lethargy/coma accompanied by metabolic acidosis and hypoketotic hypoglycemia. Although neurological manifestations are common, the pathogenesis of brain injury in this disease is poorly known. Astrocytes are important for neuronal protection and are susceptible to damage by neurotoxins. In the present study, we investigated the effects of HMG and MGA on important parameters of redox homeostasis and cytokine production in cortical cultured astrocytes. The role of the metabolites on astrocyte mitochondrial function (thiazolyl blue tetrazolium bromide (MTT) reduction) and viability (propidium iodide incorporation) was also studied. Both organic acids decreased astrocytic mitochondrial function and the concentrations of reduced glutathione without altering cell viability. In contrast, they increased reactive species formation (2'-7'-dichlorofluorescein diacetate (DCFHDA) oxidation), as well as IL-1ß, IL-6, and TNF α release through the ERK signaling pathway. Taken together, the data indicate that the principal compounds accumulating in HMGA induce a proinflammatory response in cultured astrocytes that may possibly be involved in the neuropathology of this disease.

NMDA Receptors and Oxidative Stress Induced by the Major Metabolites Accumulating in HMG Lyase Deficiency Mediate Hypophosphorylation of Cytoskeletal Proteins in Brain From Adolescent Rats: Potential Mechanisms Contributing to the Neuropathology of This Disease.

Neurological symptoms and cerebral abnormalities are commonly observed in patients with 3-hydroxy-3-methylglutaryl-CoA lyase (HMG lyase) deficiency, which is biochemically characterized by predominant tissue accumulation of 3-hydroxy-3-methylglutaric (HMG), 3-methylglutaric (MGA), and 3-methylglutaconic (MGT) acids. Since the pathogenesis of this disease is poorly known, the present study evaluated the effects of these compounds on the cytoskeleton phosphorylating system in rat brain. HMG, MGA, and MGT caused hypophosphorylation of glial fibrillary acidic protein (GFAP) and of the neurofilament subunits NFL, NFM, and NFH. HMG-induced hypophosphorylation was mediated by inhibiting the cAMP-dependent protein kinase (PKA) on Ser55 residue of NFL and c-Jun kinase (JNK) by acting on KSP repeats of NFM and NFH subunits. We also evidenced that the subunit NR2B of NMDA receptor and Ca(2+) was involved in HMG-elicited hypophosphorylation of cytoskeletal proteins. Furthermore, the antioxidants L-NAME and TROLOX fully prevented both the hypophosphorylation and the inhibition of PKA and JNK caused by HMG, suggesting that oxidative damage may underlie these effects. These findings indicate that the main metabolites accumulating in HMG lyase deficiency provoke hypophosphorylation of cytoskeleton neural proteins with the involvement of NMDA receptors, Ca(2+), and reactive species. It is presumed that these alterations may contribute to the neuropathology of this disease.

Disturbance of redox homeostasis as a contributing underlying pathomechanism of brain and liver alterations in 3-hydroxy-3-methylglutaryl-CoA lyase deficiency.

3-Hydroxy-3-methylglutaryl-CoA lyase (HL) deficiency is an inherited disorder of organic acid metabolism biochemically characterized by tissue accumulation and high urinary excretion of 3-hydroxy-3-methylgutarate, 3-methylglutarate, 3-methylglutaconate and 3-hydroxyisovalerate. Affected patients predominantly present neurological symptoms that are accompanied by mild hepatopathy during episodes of catabolic crisis. The pathophysiology of this disease is poorly known, although recent animal and human in vitro and in vivo studies have suggested that oxidative stress caused by the major accumulating organic acids may represent a pathomechanism of brain and liver damage in HL deficiency. In this review we focus on the deleterious effects of these carboxylic acids on redox homeostasis in rat and human tissues that may offer new perspectives for potential novel adjuvant therapeutic strategies in this disorder.

Molecular insights into HSD10 disease: impact of SDR5C1 mutations on the human mitochondrial RNase P complex.

SDR5C1 is an amino and fatty acid dehydrogenase/reductase, moonlighting as a component of human mitochondrial RNase P, which is the enzyme removing 5'-extensions of tRNAs, an early and crucial step in tRNA maturation. Moreover, a subcomplex of mitochondrial RNase P catalyzes the N(1)-methylation of purines at position 9, a modification found in most mitochondrial tRNAs and thought to stabilize their structure. Missense mutations in SDR5C1 cause a disease characterized by progressive neurodegeneration and cardiomyopathy, called HSD10 disease. We have investigated the effect of selected mutations on SDR5C1's functions. We show that pathogenic mutations impair SDR5C1-dependent dehydrogenation, tRNA processing and methylation. Some mutations disrupt the homotetramerization of SDR5C1 and/or impair its interaction with TRMT10C, the methyltransferase subunit of the mitochondrial RNase P complex. We propose that the structural and functional alterations of SDR5C1 impair mitochondrial RNA processing and modification, leading to the mitochondrial dysfunction observed in HSD10 patients.

3-HMG Coenzyme A Lyase Deficiency: Macrocephaly and Left Ventricular Noncompaction with a Novel Mutation.

3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) lyase deficiency, an inborn error of ketone body synthesis and leucine degradation, is a rare autosomal recessive disease. There are a few reports demonstrating clinical and neuroradiologic findings of this condition. The authors report case of an 8-mo-old infant with HMG-CoA lyase deficiency, who presented with macrocephaly, left ventricular noncompaction, recurrent pulmonary infections, nonketotic hypoglycemia, seizure and metabolic acidosis. There was no significant difference in brain magnetic resonance imaging after leucine-restricted diet and carnitine therapy and neurologic deterioration was not observed. Left ventricular noncompaction is an interesting finding for HMG-CoA lyase deficiency which has not been reported in the literature. The genetic analysis revealed a novel homozygote deletion in exon 3 and 4 in HMGCL gene. HMG-CoA lyase deficiency should be thought in the patients with hypoketotic hypoglycemia, hyperammonemia, elevated liver function tests, noncompaction left ventricle and characteristic white matter changes and in the differential diagnosis of macrocephaly.