RESUMO
The white matter is an important constituent of the central nervous system, containing axons, oligodendrocytes, and its progenitor cells, astrocytes, and microglial cells. Oligodendrocytes are central for myelin synthesis, the insulating envelope that protects axons and allows normal neural conduction. Both, oligodendrocytes and myelin, are highly vulnerable to toxic factors in many neurodevelopmental and neurodegenerative disorders associated with disturbances of myelination. Here we review the main alterations in oligodendrocytes and myelin observed in some organic acidurias/acidemias, which correspond to inherited neurometabolic disorders biochemically characterized by accumulation of potentially neurotoxic organic acids and their derivatives. The yet incompletely understood mechanisms underlying the high vulnerability of OLs and/or myelin in glutaric acidemia type I, the most prototypical cerebral organic aciduria, are particularly discussed.
Assuntos
Erros Inatos do Metabolismo dos Aminoácidos , Encefalopatias Metabólicas , Glutaril-CoA Desidrogenase , Oligodendroglia , Substância Branca , Oligodendroglia/metabolismo , Oligodendroglia/patologia , Erros Inatos do Metabolismo dos Aminoácidos/patologia , Erros Inatos do Metabolismo dos Aminoácidos/metabolismo , Glutaril-CoA Desidrogenase/deficiência , Glutaril-CoA Desidrogenase/metabolismo , Humanos , Animais , Substância Branca/patologia , Substância Branca/metabolismo , Encefalopatias Metabólicas/patologia , Encefalopatias Metabólicas/metabolismo , Bainha de Mielina/metabolismo , Bainha de Mielina/patologiaRESUMO
Glutaric Aciduria Type 1 (GA1) is a serious inborn error of metabolism with no pharmacological treatments. A novel strategy to treat this disease is to divert the toxic biochemical intermediates to less toxic or nontoxic metabolites. Here, we report a putative novel target, succinyl-CoA:glutarate-CoA transferase (SUGCT), which we hypothesize suppresses the GA1 metabolic phenotype through decreasing glutaryl-CoA and the derived 3-hydroxyglutaric acid. SUGCT is a type III CoA transferase that uses succinyl-CoA and glutaric acid as substrates. We report the structure of SUGCT, develop enzyme- and cell-based assays, and identify valsartan and losartan carboxylic acid as inhibitors of the enzyme in a high-throughput screen of FDA-approved compounds. The cocrystal structure of SUGCT with losartan carboxylic acid revealed a novel pocket in the active site and further validated the high-throughput screening approach. These results may form the basis for the future development of new pharmacological intervention to treat GA1.
Assuntos
Erros Inatos do Metabolismo dos Aminoácidos , Encefalopatias Metabólicas , Humanos , Erros Inatos do Metabolismo dos Aminoácidos/tratamento farmacológico , Erros Inatos do Metabolismo dos Aminoácidos/metabolismo , Erros Inatos do Metabolismo dos Aminoácidos/enzimologia , Erros Inatos do Metabolismo dos Aminoácidos/genética , Encefalopatias Metabólicas/tratamento farmacológico , Encefalopatias Metabólicas/metabolismo , Encefalopatias Metabólicas/enzimologia , Glutaratos/metabolismo , Glutaratos/química , Losartan/farmacologia , Losartan/química , Coenzima A-Transferases/metabolismo , Coenzima A-Transferases/antagonistas & inibidores , Coenzima A-Transferases/genética , Coenzima A-Transferases/química , Valsartana , Inibidores Enzimáticos/farmacologia , Inibidores Enzimáticos/química , Cristalografia por Raios X , Domínio Catalítico , Acil Coenzima A/metabolismo , Acil Coenzima A/química , Modelos Moleculares , Ensaios de Triagem em Larga Escala , Glutaril-CoA Desidrogenase/deficiênciaRESUMO
GCDH encodes for the enzyme catalyzing the sixth step of the lysine degradation pathway. Autosomal recessive variants in GCDH are associated with glutaric aciduria type I (GA1), of which a wide genotypic spectrum of pathogenic variants have been described. In this study, hiPSC lines derived from four GA1 patients with different genotypes were generated and fully characterized. Two patients carry compound heterozygous variants in GCDH, while the other two patients carry a variant in homozygosis. These hiPSC lines can significantly contribute to better understand the molecular mechanism underlying GA1 and provide excellent models for the development of new therapeutic strategies.
Assuntos
Erros Inatos do Metabolismo dos Aminoácidos , Encefalopatias Metabólicas , Glutaril-CoA Desidrogenase , Células-Tronco Pluripotentes Induzidas , Humanos , Erros Inatos do Metabolismo dos Aminoácidos/genética , Erros Inatos do Metabolismo dos Aminoácidos/patologia , Erros Inatos do Metabolismo dos Aminoácidos/metabolismo , Glutaril-CoA Desidrogenase/deficiência , Glutaril-CoA Desidrogenase/genética , Glutaril-CoA Desidrogenase/metabolismo , Encefalopatias Metabólicas/genética , Encefalopatias Metabólicas/patologia , Encefalopatias Metabólicas/metabolismo , Células-Tronco Pluripotentes Induzidas/metabolismo , Feminino , Masculino , Alelos , Linhagem CelularRESUMO
The neurometabolic disorder succinic semialdehyde dehydrogenase (SSADH) deficiency leads to great neurochemical imbalances and severe neurological manifestations. The cause of the disease is loss of function of the enzyme SSADH, leading to impaired metabolism of the principal inhibitory neurotransmitter GABA. Despite the known identity of the enzymatic deficit, the underlying pathology of SSADH deficiency remains unclear. To uncover new mechanisms of the disease, we performed an untargeted integrative analysis of cerebral protein expression, functional metabolism, and lipid composition in a genetic mouse model of SSADH deficiency (ALDH5A1 knockout mice). Our proteomic analysis revealed a clear regional vulnerability, as protein alterations primarily manifested in the hippocampus and cerebral cortex of the ALDH5A1 knockout mice. These regions displayed aberrant expression of proteins linked to amino acid homeostasis, mitochondria, glial function, and myelination. Stable isotope tracing in acutely isolated brain slices demonstrated an overall maintained oxidative metabolism of glucose, but a selective decrease in astrocyte metabolic activity in the cerebral cortex of ALDH5A1 knockout mice. In contrast, an elevated capacity of oxidative glutamine metabolism was observed in the ALDH5A1 knockout brain, which may serve as a neuronal compensation of impaired astrocyte glutamine provision. In addition to reduced expression of critical oligodendrocyte proteins, a severe depletion of myelin-enriched sphingolipids was found in the brains of ALDH5A1 knockout mice, suggesting degeneration of myelin. Altogether, our study highlights that impaired astrocyte and oligodendrocyte function is intimately linked to SSADH deficiency pathology, suggesting that selective targeting of glial cells may hold therapeutic potential in this disease.
Assuntos
Astrócitos , Encéfalo , Camundongos Knockout , Oligodendroglia , Succinato-Semialdeído Desidrogenase , Ácido gama-Aminobutírico , Animais , Oligodendroglia/metabolismo , Oligodendroglia/patologia , Astrócitos/metabolismo , Astrócitos/patologia , Succinato-Semialdeído Desidrogenase/deficiência , Succinato-Semialdeído Desidrogenase/metabolismo , Succinato-Semialdeído Desidrogenase/genética , Camundongos , Ácido gama-Aminobutírico/metabolismo , Encéfalo/metabolismo , Encéfalo/patologia , Camundongos Endogâmicos C57BL , Erros Inatos do Metabolismo dos Aminoácidos/metabolismo , Erros Inatos do Metabolismo dos Aminoácidos/patologia , Erros Inatos do Metabolismo dos Aminoácidos/genética , Deficiências do DesenvolvimentoRESUMO
Succinic semialdehyde dehydrogenase (SSADH) is a mitochondrial enzyme involved in the catabolism of the neurotransmitter γ-amino butyric acid. Pathogenic variants in the gene encoding this enzyme cause SSADH deficiency, a developmental disease that manifests as hypotonia, autism, and epilepsy. SSADH deficiency patients usually have family-specific gene variants. Here, we describe a family exhibiting four different SSADH variants: Val90Ala, Cys93Phe, and His180Tyr/Asn255Asp (a double variant). We provide a structural and functional characterization of these variants and show that Cys93Phe and Asn255Asp are pathogenic variants that affect the stability of the SSADH protein. Due to the impairment of the cofactor NAD+ binding, these variants show a highly reduced enzyme activity. However, Val90Ala and His180Tyr exhibit normal activity and expression. The His180Tyr/Asn255Asp variant exhibits a highly reduced activity as a recombinant species, is inactive, and shows a very low expression in eukaryotic cells. A treatment with substances that support protein folding by either increasing chaperone protein expression or by chemical means did not increase the expression of the pathogenic variants of the SSADH deficiency patient. However, stabilization of the folding of pathogenic SSADH variants by other substances may provide a treatment option for this disease.
Assuntos
Erros Inatos do Metabolismo dos Aminoácidos , Deficiências do Desenvolvimento , Succinato-Semialdeído Desidrogenase , Feminino , Humanos , Masculino , Erros Inatos do Metabolismo dos Aminoácidos/genética , Erros Inatos do Metabolismo dos Aminoácidos/metabolismo , Erros Inatos do Metabolismo dos Aminoácidos/patologia , Deficiências do Desenvolvimento/genética , Deficiências do Desenvolvimento/metabolismo , Deficiências do Desenvolvimento/patologia , Variação Genética , Mutação , Linhagem , Dobramento de Proteína , Succinato-Semialdeído Desidrogenase/deficiência , Succinato-Semialdeído Desidrogenase/genética , Succinato-Semialdeído Desidrogenase/química , Succinato-Semialdeído Desidrogenase/metabolismoRESUMO
Although both localized nuclear magnetic resonance spectroscopy (MRS) and non-localized nuclear magnetic resonance spectroscopy (NMR) generate the same information, i.e., spectra generated by various groups from the structure of metabolites, they are rarely employed in the same study or by the same research group. As our review reveals, these techniques have never been applied in the same study of methylmalonic acidemia (MMA), propionic acidemia (PA) or vitamin B12 deficiency patients. On the other hand, MRS and NMR provide complementary information which is very valuable in the assessment of the severity of disease and efficiency of its treatment. Thus, MRS provides intracellular metabolic information from localized regions of the brain, while NMR provides extracellular metabolic information from biological fluids like urine, blood or cerebrospinal fluid. This paper presents an up-to-date review of the NMR and MRS studies reported to date for methylmalonic and propionic acidemias. Vitamin B12 deficiency, although in most of its cases not inherited, shares similarities in its metabolic effects with MMA and it is also covered in this review.
Assuntos
Erros Inatos do Metabolismo dos Aminoácidos , Espectroscopia de Ressonância Magnética , Acidemia Propiônica , Humanos , Acidemia Propiônica/diagnóstico , Acidemia Propiônica/metabolismo , Erros Inatos do Metabolismo dos Aminoácidos/diagnóstico , Erros Inatos do Metabolismo dos Aminoácidos/metabolismo , Espectroscopia de Ressonância Magnética/métodos , Deficiência de Vitamina B 12/diagnóstico , Deficiência de Vitamina B 12/metabolismo , Ácido Metilmalônico/metabolismoRESUMO
BACKGROUND: Succinic semialdehyde dehydrogenase deficiency (SSADHD) represents a model neurometabolic disease at the fulcrum of translational research within the Boston Children's Hospital Intellectual and Developmental Disabilities Research Centers (IDDRC), including the NIH-sponsored natural history study of clinical, neurophysiological, neuroimaging, and molecular markers, patient-derived induced pluripotent stem cells (iPSC) characterization, and development of a murine model for tightly regulated, cell-specific gene therapy. METHODS: SSADHD subjects underwent clinical evaluations, neuropsychological assessments, biochemical quantification of γ-aminobutyrate (GABA) and related metabolites, electroencephalography (standard and high density), magnetoencephalography, transcranial magnetic stimulation, magnetic resonance imaging and spectroscopy, and genetic tests. This was parallel to laboratory molecular investigations of in vitro GABAergic neurons derived from induced human pluripotent stem cells (hiPSCs) of SSADHD subjects and biochemical analyses performed on a versatile murine model that uses an inducible and reversible rescue strategy allowing on-demand and cell-specific gene therapy. RESULTS: The 62 SSADHD subjects [53% females, median (IQR) age of 9.6 (5.4-14.5) years] included in the study had a reported symptom onset at ⼠6 months and were diagnosed at a median age of 4 years. Language developmental delays were more prominent than motor. Autism, epilepsy, movement disorders, sleep disturbances, and various psychiatric behaviors constituted the core of the disorder's clinical phenotype. Lower clinical severity scores, indicating worst severity, coincided with older age (R= -0.302, p = 0.03), as well as age-adjusted lower values of plasma γ-aminobutyrate (GABA) (R = 0.337, p = 0.02) and γ-hydroxybutyrate (GHB) (R = 0.360, p = 0.05). While epilepsy and psychiatric behaviors increase in severity with age, communication abilities and motor function tend to improve. iPSCs, which were differentiated into GABAergic neurons, represent the first in vitro neuronal model of SSADHD and express the neuronal marker microtubule-associated protein 2 (MAP2), as well as GABA. GABA-metabolism in induced GABAergic neurons could be reversed using CRISPR correction of the pathogenic variants or mRNA transfection and SSADHD iPSCs were associated with excessive glutamatergic activity and related synaptic excitation. CONCLUSIONS: Findings from the SSADHD Natural History Study converge with iPSC and animal model work focused on a common disorder within our IDDRC, deepening our knowledge of the pathophysiology and longitudinal clinical course of a complex neurodevelopmental disorder. This further enables the identification of biomarkers and changes throughout development that will be essential for upcoming targeted trials of enzyme replacement and gene therapy.
Assuntos
Erros Inatos do Metabolismo dos Aminoácidos , Deficiências do Desenvolvimento , Células-Tronco Pluripotentes Induzidas , Succinato-Semialdeído Desidrogenase , Adolescente , Animais , Criança , Pré-Escolar , Feminino , Humanos , Masculino , Camundongos , Erros Inatos do Metabolismo dos Aminoácidos/terapia , Erros Inatos do Metabolismo dos Aminoácidos/fisiopatologia , Erros Inatos do Metabolismo dos Aminoácidos/genética , Erros Inatos do Metabolismo dos Aminoácidos/complicações , Erros Inatos do Metabolismo dos Aminoácidos/metabolismo , Encéfalo/metabolismo , Encéfalo/fisiopatologia , Modelos Animais de Doenças , Neurônios GABAérgicos/metabolismo , Ácido gama-Aminobutírico/metabolismo , Células-Tronco Pluripotentes Induzidas/metabolismo , Transtornos do Neurodesenvolvimento/metabolismo , Transtornos do Neurodesenvolvimento/etiologia , Transtornos do Neurodesenvolvimento/genética , Succinato-Semialdeído Desidrogenase/deficiência , Succinato-Semialdeído Desidrogenase/metabolismo , Succinato-Semialdeído Desidrogenase/genéticaAssuntos
Erros Inatos do Metabolismo dos Aminoácidos , Descarboxilases de Aminoácido-L-Aromático/deficiência , Doenças Metabólicas , Humanos , Prevalência , Erros Inatos do Metabolismo dos Aminoácidos/epidemiologia , Erros Inatos do Metabolismo dos Aminoácidos/genética , Erros Inatos do Metabolismo dos Aminoácidos/metabolismoRESUMO
Isovaleric acidemia (IVA; OMIM ID#243500) is an inborn error of leucine metabolism caused by a deficiency of isovaleryl-CoA dehydrogenase (IVD). In this study, we generated a human induced pluripotent stem cell line (hiPSCs) SDQLCHi057-A from a 2-year-7-month old boy with IVA carrying two heterozygous missense mutations c.215A > G (p.N72S) and c.883A > G (p.M295V) of the IVD gene. Patient-specific hiPSCs provide a proper model for further understanding this rare disease.
Assuntos
Erros Inatos do Metabolismo dos Aminoácidos , Células-Tronco Pluripotentes Induzidas , Isovaleril-CoA Desidrogenase/deficiência , Masculino , Humanos , Lactente , Mutação/genética , Células-Tronco Pluripotentes Induzidas/metabolismo , Erros Inatos do Metabolismo dos Aminoácidos/genética , Erros Inatos do Metabolismo dos Aminoácidos/metabolismo , Isovaleril-CoA Desidrogenase/genéticaRESUMO
A distinct adipose tissue distribution pattern was observed in patients with methylmalonyl-CoA mutase deficiency, an inborn error of branched-chain amino acid (BCAA) metabolism, characterized by centripetal obesity with proximal upper and lower extremity fat deposition and paucity of visceral fat, that resembles familial multiple lipomatosis syndrome. To explore brown and white fat physiology in methylmalonic acidemia (MMA), body composition, adipokines, and inflammatory markers were assessed in 46 patients with MMA and 99 matched controls. Fibroblast growth factor 21 levels were associated with acyl-CoA accretion, aberrant methylmalonylation in adipose tissue, and an attenuated inflammatory cytokine profile. In parallel, brown and white fat were examined in a liver-specific transgenic MMA mouse model (Mmut-/- TgINS-Alb-Mmut). The MMA mice exhibited abnormal nonshivering thermogenesis with whitened brown fat and had an ineffective transcriptional response to cold stress. Treatment of the MMA mice with bezafibrates led to clinical improvement with beiging of subcutaneous fat depots, which resembled the distribution seen in the patients. These studies defined what we believe to be a novel lipodystrophy phenotype in patients with defects in the terminal steps of BCAA oxidation and demonstrated that beiging of subcutaneous adipose tissue in MMA could readily be induced with small molecules.
Assuntos
Erros Inatos do Metabolismo dos Aminoácidos , Fatores de Crescimento de Fibroblastos , Lipodistrofia , Animais , Humanos , Camundongos , Erros Inatos do Metabolismo dos Aminoácidos/complicações , Erros Inatos do Metabolismo dos Aminoácidos/genética , Erros Inatos do Metabolismo dos Aminoácidos/metabolismo , Camundongos TransgênicosRESUMO
PURPOSE: Serine (Ser) and glycine (Gly) levels were reported to differ between patients with macular telangiectasia type 2 (MacTel) compared with healthy controls. Because they are closely related to methylation metabolism, this report investigates methylation-associated metabolite levels in patients with MacTel and retinal changes in monogenetic methylation disorders. METHODS: Prospective, monocentric study on patients with MacTel and healthy controls underwent a standardized protocol including a blood draw. Methylation-associated metabolite levels in plasma were determined using targeted quantitative metabolomics. Furthermore, patient records of cystathionine beta-synthase, methylenetetrahydrofolate reductase, and methylmalonic aciduria and homocystinuria type C protein (MMACHC) deficiency were screened for reported retinal changes. RESULTS: In total, 29 patients with MacTel and 27 healthy controls were included. Patients with MacTel showed lower plasma Ser ( P = 0.02 and P = 0.01) and Gly ( P = 0.11 and P = 0.11) levels than controls. Principal component analyses revealed that methylation-associated metabolite, especially homocysteine, contributed to a distinct clustering of patients with MacTel. No retinal changes were seen in cystathionine beta-synthase (n = 1) and methylenetetrahydrofolate reductase (n = 2) deficiency, while two patients with MMACHC (n = 4) deficiency displayed extensive macular dystrophy. CONCLUSION: Patients with MacTel show distinct clustering of methylation-associated metabolite compared with controls. Of the three homocystinurias, only MMACHC resulted in macular dystrophy, possibly due to distinct compensatory pathways.
Assuntos
Telangiectasia Retiniana , Humanos , Feminino , Masculino , Estudos Prospectivos , Telangiectasia Retiniana/diagnóstico , Telangiectasia Retiniana/metabolismo , Telangiectasia Retiniana/genética , Pessoa de Meia-Idade , Tomografia de Coerência Óptica , Adulto , Idoso , Metilação , Erros Inatos do Metabolismo dos Aminoácidos/genética , Erros Inatos do Metabolismo dos Aminoácidos/complicações , Erros Inatos do Metabolismo dos Aminoácidos/metabolismo , Erros Inatos do Metabolismo dos Aminoácidos/diagnóstico , Angiofluoresceinografia/métodos , Glicina , Homocistinúria/genética , Homocistinúria/complicações , Homocistinúria/diagnósticoRESUMO
Succinic semialdehyde dehydrogenase deficiency (SSADHD) is a neurometabolic disorder caused by ALDH5A1 mutations presenting with autism and epilepsy. SSADHD leads to impaired GABA metabolism and results in accumulation of GABA and γ-hydroxybutyrate (GHB), which alter neurotransmission and are thought to lead to neurobehavioral symptoms. However, why increased inhibitory neurotransmitters lead to seizures remains unclear. We used induced pluripotent stem cells from SSADHD patients (one female and two male) and differentiated them into GABAergic and glutamatergic neurons. SSADHD iGABA neurons show altered GABA metabolism and concomitant changes in expression of genes associated with inhibitory neurotransmission. In contrast, glutamatergic neurons display increased spontaneous activity and upregulation of mitochondrial genes. CRISPR correction of the pathogenic variants or SSADHD mRNA expression rescue various metabolic and functional abnormalities in human neurons. Our findings uncover a previously unknown role for SSADHD in excitatory human neurons and provide unique insights into the cellular and molecular basis of SSADHD and potential therapeutic interventions.
Assuntos
Erros Inatos do Metabolismo dos Aminoácidos , Células-Tronco Pluripotentes Induzidas , Humanos , Masculino , Feminino , Células-Tronco Pluripotentes Induzidas/metabolismo , Erros Inatos do Metabolismo dos Aminoácidos/tratamento farmacológico , Erros Inatos do Metabolismo dos Aminoácidos/genética , Erros Inatos do Metabolismo dos Aminoácidos/metabolismo , Neurônios/metabolismo , Ácido gama-Aminobutírico/metabolismo , Succinato-Semialdeído Desidrogenase/genéticaRESUMO
To investigate the genotype-to-protein-to-phenotype correlations of succinic semialdehyde dehydrogenase deficiency (SSADHD), an inherited metabolic disorder of γ-aminobutyric acid catabolism. Bioinformatics and in silico mutagenesis analyses of ALDH5A1 variants were performed to evaluate their impact on protein stability, active site and co-factor binding domains, splicing, and homotetramer formation. Protein abnormalities were then correlated with a validated disease-specific clinical severity score and neurological, neuropsychological, biochemical, neuroimaging, and neurophysiological metrics. A total of 58 individuals (1:1 male/female ratio) were affected by 32 ALDH5A1 pathogenic variants, eight of which were novel. Compared to individuals with single homotetrameric or multiple homo and heterotetrameric proteins, those predicted not to synthesize any functional enzyme protein had significantly lower expression of ALDH5A1 (p = 0.001), worse overall clinical outcomes (p = 0.008) and specifically more severe cognitive deficits (p = 0.01), epilepsy (p = 0.04) and psychiatric morbidity (p = 0.04). Compared to individuals with predictions of having no protein or a protein impaired in catalytic functions, subjects whose proteins were predicted to be impaired in stability, folding, or oligomerization had a better overall clinical outcome (p = 0.02) and adaptive skills (p = 0.04). The quantity and type of enzyme proteins (no protein, single homotetramers, or multiple homo and heterotetramers), as well as their structural and functional impairments (catalytic or stability, folding, or oligomerization), contribute to phenotype severity in SSADHD. These findings are valuable for assessment of disease prognosis and management, including patient selection for gene replacement therapy. Furthermore, they provide a roadmap to determine genotype-to-protein-to-phenotype relationships in other autosomal recessive disorders.
Assuntos
Erros Inatos do Metabolismo dos Aminoácidos , Criança , Humanos , Masculino , Feminino , Erros Inatos do Metabolismo dos Aminoácidos/genética , Erros Inatos do Metabolismo dos Aminoácidos/metabolismo , Erros Inatos do Metabolismo dos Aminoácidos/patologia , Deficiências do Desenvolvimento/genética , Fenótipo , Succinato-Semialdeído Desidrogenase/genética , Succinato-Semialdeído Desidrogenase/metabolismoRESUMO
Inherited disorders of mitochondrial metabolism, including isolated methylmalonic aciduria, present unique challenges to energetic homeostasis by disrupting energy-producing pathways. To better understand global responses to energy shortage, we investigated a hemizygous mouse model of methylmalonyl-CoA mutase (Mmut)-type methylmalonic aciduria. We found Mmut mutant mice to have reduced appetite, energy expenditure and body mass compared with littermate controls, along with a relative reduction in lean mass but increase in fat mass. Brown adipose tissue showed a process of whitening, in line with lower body surface temperature and lesser ability to cope with cold challenge. Mutant mice had dysregulated plasma glucose, delayed glucose clearance and a lesser ability to regulate energy sources when switching from the fed to fasted state, while liver investigations indicated metabolite accumulation and altered expression of peroxisome proliferator-activated receptor and Fgf21-controlled pathways. Together, these shed light on the mechanisms and adaptations behind energy imbalance in methylmalonic aciduria and provide insight into metabolic responses to chronic energy shortage, which may have important implications for disease understanding and patient management.
Assuntos
Erros Inatos do Metabolismo dos Aminoácidos , Camundongos , Animais , Erros Inatos do Metabolismo dos Aminoácidos/genética , Erros Inatos do Metabolismo dos Aminoácidos/metabolismo , Metabolismo Energético/genética , Fígado/metabolismoRESUMO
Glutaric aciduria type 1 (GA1) is a rare neurometabolic disease caused by pathogenic variants in the gene encoding the enzyme glutaryl-CoA dehydrogenase (GCDH). We performed an extensive literature search to collect data on GA1 patients, together with unpublished cases, to provide an up-to-date genetic landscape of GCDH pathogenic variants and to investigate potential genotype-phenotype correlation, as this is still poorly understood. From this search, 421 different GCDH pathogenic variants have been identified, including four novel variants; c.179T>C (p.Leu60Pro), c.214C>T (p.Arg72Cys), c.309G>C (p.Leu103Phe), and c.665T>C (p.Phe222Ser).The variants are mostly distributed across the entire gene; although variant frequency in GA1 patients is relatively high in the regions encoding for active domains of GCDH. To investigate potential genotype-phenotype correlations, phenotypic descriptions of 532 patients have been combined and evaluated using novel combinatorial analyses. To do so, various clinical phenotypes were determined for each pathogenic variant by combining the information of all GA1 patients reported with this pathogenic variant, and subsequently mapped onto the 2D and 3D GCDH protein structure. In addition, the predicted pathogenicity of missense variants was analyzed using different in silico prediction score models. Both analyses showed an almost similar distribution of the highly pathogenic variants across the GCDH protein, although some hotspots, including the active domain, were observed. Moreover, it was demonstrated that highly pathogenic variants are significantly correlated with lower residual enzyme activity and the most accurate estimation was achieved by the REVEL score. A clear correlation of the genotype and the clinical phenotype however is still lacking.
Assuntos
Erros Inatos do Metabolismo dos Aminoácidos , Encefalopatias Metabólicas , Humanos , Glutaril-CoA Desidrogenase/genética , Glutaril-CoA Desidrogenase/metabolismo , Encefalopatias Metabólicas/metabolismo , Mutação de Sentido Incorreto , Erros Inatos do Metabolismo dos Aminoácidos/metabolismoRESUMO
Glutaric aciduria type 1 (GA1) is caused by inherited deficiency of glutaryl-CoA dehydrogenase (GCDH). To further understand the unclear genotype-phenotype correlation, we transfected mutated GCDH into COS-7 cells resembling known biallelic GCDH variants of 47 individuals with GA1. In total, we modeled 36 genotypes with 32 missense variants. Spectrophotometry demonstrated an inverse correlation between residual enzyme activity and the urinary concentration of glutaric acid and 3-hydroxyglutaric acid, confirming previous studies (Pearson correlation, r = -0.34 and r = -0.49, p = 0.045 and p = 0.002, respectively). In silico modeling predicted high pathogenicity for all genotypes, which caused a low enzyme activity. Western blotting revealed a 2.6-times higher GCDH protein amount in patients with an acute encephalopathic crisis (t-test, p = 0.015), and high protein expression correlated with high in silico protein stability (Pearson correlation, r = -0.42, p = 0.011). The protein amount was not correlated with the enzyme activity (Pearson correlation, r = 0.09, p = 0.59). To further assess protein stability, proteolysis was performed, showing that the p.Arg88Cys variant stabilized a heterozygous less stable variant. We conclude that an integration of different data sources helps to predict the complex clinical phenotype in individuals with GA1.
Assuntos
Erros Inatos do Metabolismo dos Aminoácidos , Encefalopatias Metabólicas , Humanos , Glutaril-CoA Desidrogenase , Encefalopatias Metabólicas/genética , Encefalopatias Metabólicas/metabolismo , Mutação de Sentido Incorreto , Erros Inatos do Metabolismo dos Aminoácidos/genética , Erros Inatos do Metabolismo dos Aminoácidos/metabolismo , Fenótipo , Glutaratos/metabolismoRESUMO
OBJECTIVE: Succinic semialdehyde dehydrogenase deficiency (SSADHD) is a rare inherited metabolic disorder caused by a defect of γ-aminobutyrate (GABA) catabolism. Despite the resultant hyper-GABAergic environment facilitated by the metabolic defect, individuals with this disorder have a paradoxically high prevalence of epilepsy. We aimed to study the characteristics of epilepsy in SSADHD and its concordance with GABA-related metabolites and neurophysiologic markers of cortical excitation. METHODS: Subjects in an international natural history study of SSADHD underwent clinical assessments, electroencephalography, transcranial magnetic stimulation (TMS), magnetic resonance spectroscopy for GABA/N-acetyl aspartate quantification, and plasma GABA-related metabolite measurements. RESULTS: A total of 61 subjects with SSADHD and 42 healthy controls were included in the study. Epilepsy was present in 49% of the SSADHD cohort. Over time, there was an increase in severity in 33% of the subjects with seizures. The presence of seizures was associated with increasing age (p = .001) and lower levels of GABA (p = .002), γ-hydroxybutyrate (GHB; p = .004), and γ-guanidinobutyrate (GBA; p = .003). Seizure severity was associated with increasing age and lower levels of GABA-related metabolites as well as lower TMS-derived resting motor thresholds (p = .04). The cutoff values with the highest discriminative ability to predict seizures were age > 9.2 years (p = .001), GABA < 2.57 µmol·L-1 (p = .002), GHB < 143.6 µmol·L-1 (p = .004), and GBA < .075 µmol·L-1 (p = .007). A prediction model for seizures in SSADHD was comprised of the additive effect of older age and lower plasma GABA, GHB, and GBA (area under the receiver operating characteristic curve of .798, p = .008). SIGNIFICANCE: Epilepsy is highly prevalent in SSADHD, and its onset and severity correlate with an age-related decline in GABA and GABA-related metabolite levels as well as TMS markers of reduced cortical inhibition. The reduction of GABAergic activity in this otherwise hyper-GABAergic disorder demonstrates a concordance between epileptogenesis and compensatory responses. These findings may furthermore inform the timing of molecular interventions for SSADHD.
Assuntos
Erros Inatos do Metabolismo dos Aminoácidos , Epilepsia , Oxibato de Sódio , Humanos , Criança , Erros Inatos do Metabolismo dos Aminoácidos/complicações , Erros Inatos do Metabolismo dos Aminoácidos/metabolismo , Deficiências do Desenvolvimento , Epilepsia/metabolismo , Ácido gama-Aminobutírico/metabolismo , Aminobutiratos , ConvulsõesRESUMO
Organic acidurias, such as glutaric aciduria type 1 (GA1), methylmalonic (MMA), and propionic aciduria (PA) are a prominent group of inherited metabolic diseases involving accumulation of eponymous metabolites causing endogenous intoxication. For all three conditions, guidelines for diagnosis and management have been developed and revised over the last years, resulting in three revisions for GA1 and one revision for MMA/PA. The process of clinical guideline development in rare metabolic disorders is challenged by the scarcity and limited quality of evidence available. The body of literature is often fragmentary and where information is present, it is usually derived from small sample sizes. Therefore, the development of guidelines for GA1 and MMA/PA was initially confronted with a poor evidence foundation that hindered formulation of concrete recommendations in certain contexts, triggering specific research projects and initiation of longitudinal, prospective observational studies using patient registries. Reversely, these observational studies contributed to evaluate the value of newborn screening, phenotypic diversities, and treatment effects, thus significantly improving the quality of evidence and directly influencing formulation and evidence levels of guideline recommendations. Here, we present insights into interactions between guideline development and (pre)clinical research for GA1 and MMA/PA, and demonstrate how guidelines gradually improved from revision to revision. We describe how clinical studies help to unravel the relative impact of therapeutic interventions on outcome and conclude that despite new and better quality of research data over the last decades, significant shortcomings of evidence regarding prognosis and treatment remain. It appears that development of clinical guidelines can directly help to guide research, and vice versa.
Assuntos
Erros Inatos do Metabolismo dos Aminoácidos , Encefalopatias Metabólicas , Doenças Metabólicas , Acidemia Propiônica , Recém-Nascido , Humanos , Erros Inatos do Metabolismo dos Aminoácidos/diagnóstico , Erros Inatos do Metabolismo dos Aminoácidos/terapia , Erros Inatos do Metabolismo dos Aminoácidos/metabolismo , Encefalopatias Metabólicas/diagnóstico , Acidemia Propiônica/diagnósticoRESUMO
Tumour dependency on specific metabolic signals has been demonstrated and often guided numerous therapeutic approaches. We identify melanoma addiction to the mitochondrial protein glutaryl-CoA dehydrogenase (GCDH), which functions in lysine metabolism and controls protein glutarylation. GCDH knockdown induced cell death programmes in melanoma cells, an activity blocked by inhibition of the upstream lysine catabolism enzyme DHTKD1. The transcription factor NRF2 mediates GCDH-dependent melanoma cell death programmes. Mechanistically, GCDH knockdown induces NRF2 glutarylation, increasing its stability and DNA binding activity, with a concomitant transcriptional upregulation of ATF4, ATF3, DDIT3 and CHAC1, resulting in cell death. In vivo, inducible inactivation of GCDH effectively inhibited melanoma tumour growth. Correspondingly, reduced GCDH expression correlated with improved survival of patients with melanoma. These findings identify melanoma cell addiction to GCDH, limiting apoptotic signalling by controlling NRF2 glutarylation. Inhibiting the GCDH pathway could thus represent a therapeutic approach to treat melanoma.