Succinic Semialdehyde Dehydrogenase Deficiency Research Articles

SAXS fingerprints of aldehyde dehydrogenase oligomers.

Enzymes of the aldehyde dehydrogenase (ALDH) superfamily catalyze the nicotinamide adenine dinucleotide-dependent oxidation of aldehydes to carboxylic acids. ALDHs are important in detoxification of aldehydes, amino acid metabolism, embryogenesis and development, neurotransmission, oxidative stress, and cancer. Mutations in genes encoding ALDHs cause metabolic disorders, including alcohol flush reaction (ALDH2), Sjögren–Larsson syndrome (ALDH3A2), hyperprolinemia type II (ALDH4A1), γ-hydroxybutyric aciduria (ALDH5A1), methylmalonic aciduria (ALDH6A1), pyridoxine dependent epilepsy (ALDH7A1), and hyperammonemia (ALDH18A1). We previously reported crystal structures and small-angle X-ray scattering (SAXS) analyses of ALDHs exhibiting dimeric, tetrameric, and hexameric oligomeric states (Luo et al., Biochemistry 54 (2015) 5513–5522; Luo et al., J. Mol. Biol. 425 (2013) 3106–3120). Herein I provide the SAXS curves, radii of gyration, and distance distribution functions for the three types of ALDH oligomer. The SAXS curves and associated analysis provide diagnostic fingerprints that allow rapid identification of the type of ALDH oligomer that is present in solution. The data sets provided here serve as a benchmark for characterizing oligomerization of ALDHs.

Spotlight on the September 8 Issue

#### Notable in Neurology This issue features an article assessing the beneficial effect of ursodeoxycholic acid on mitochondrial dysfunction in LRRK2 G2019S carriers and in vivo models and another identifying the natural history of succinic semialdehyde dehydrogenase deficiency through adulthood. Another article focuses on the pathogenic effects of antibodies on gut and brain neurons in anti-DPPX encephalitis. ### Putaminal serotonergic innervation: Monitoring dyskinesia risk in Parkinson disease The authors acquired 2 PET scans and 3T MRI from 30 patients with Parkinson disease without dementia or depression divided into 3 matched groups. Relative serotonergic innervation of the putamen and …

AB049. Aldehyde dehydrogenases: from cancer stem cells to inborn errors of metabolism

The aldehyde dehydrogenase (ALDH) superfamily comprises NADP-dependent enzymes that catalyze the oxidation of aldehydes to their corresponding carboxylic acids. To date, 19 ALDH genes have been identified in the human genome. In addition to aldehyde metabolizing capacity, ALDHs have additional catalytic (e.g., esterase and reductase) and non-catalytic activities. The latter include functioning as structural elements in the eye (crystallins) and as binding molecules to endobioticsand xenobiotics. Mutations in human ALDH genes are the molecular basis of several diseases, including gamma-hydroxybutyricaciduria, type II hyperprolinemia, Sjogren-Larsson syndrome, pyridoxine-dependent epilepsy as well as osteoporosis and gout. ALDH enzymes also play important roles in embryogenesis and development, neurotransmission, oxidative stress and cancer. One of the most exciting recent discoveries regarding ALDHs is their identification as markers of cancer stem cells and their involvement in cancer cell resistance to chemotherapy and radiotherapy. Thus, therapeutic targeting of ALDHs may represent a novel means of more effectively treating patients with cancer or metabolic disease and improving clinical outcomes.

Inherited Metabolic Epilepsies

Anyone who has struggled with determining the etiology of intractable seizures in a newborn or infant, and then treating the child effectively (each of us!), has undoubtedly bemoaned the absence of a unified source of up-to-date information about the multitude of potential metabolic causes. Rest assured that this information gap has now been filled, admirably, by Dr. Phillip Pearl's multiauthored book, Inherited Metabolic Epilepsies. Dr. Pearl has edited a beautifully written and illustrated volume that brings together international experts to discuss the metabolic seizure diagnoses that “you cannot afford to miss,” many of them eminently treatable if diagnosed accurately and early. The first part of the book covers techniques useful in the evaluation of inherited metabolic epilepsies, including neuroimaging, electrophysiology, and genetic testing. Expanded coverage is then provided about individual disorders of small and large molecules, including organic and amino acid disorders, mitochondrial diseases, pyridoxine-dependent epilepsies, disorders of gamma-amino butyric acid metabolism such as succinic semialdehyde dehydrogenase deficiency, leukodystrophies and peroxisomal disorders, to name a few. The clinical features, pathophysiology, diagnostic workup, and management options for each disorder are presented in a clear fashion. A theme running through the book is the ever-increasing understanding of the genetic basis of these disorders, which might eventually lead to targeted or personalized therapies for some of them. Optimal treatment of seizures in metabolic disorders often requires more than standard antiepileptic drugs. The book concludes with a concise clinical algorithm for approaching a child with suspected metabolic basis for seizures, which is quite helpful, though an expanded version of this approach, including when to consider a metabolic etiology, would be even more useful.

Succinic semialdehyde dehydrogenase deficiency of four Chinese patients and prenatal diagnosis for three fetuses

Succinic semialdehyde dehydrogenase (SSADH) deficiency is a rare autosomal recessive disorder that affects the degradation of γ-aminobutyric acid (GABA). Only a few cases of SSADH deficiency have been documented in mainland China and prenatal diagnosis has not been performed. SSADH deficiency in four patients (three girls and one boy) from four unrelated Chinese families was detected by selective screening at the age of 50days to 1year. Four patients were admitted due to intractable seizures and psychomotor retardation. Their urine 4-hydroxybutyric acid was significantly elevated. Seven mutations in their ALDH5A1 gene were identified, of which the following six were novel: c.127-128insGGCCC (p.L31Pfs*62), c.615delT (p.F206Sfs*5), c.1313T>C (p.L438P), c.1568C>T (p.S523F), 1383-2delA and a 0.15-Mb deletion harboring ALDH5A1. Only one mutation, c.820C>T, had been previously reported. Three mothers of Patients 1–3 underwent amniocentesis during their third pregnancy and the fetuses were not affected by SSADH deficiency. Normal development and urine organic acid levels of the infants confirmed the prenatal diagnosis after birth.

Disorders of GABA metabolism: SSADH and GABA-transaminase deficiencies.

Clinical disorders known to affect inherited gamma-amino butyric acid (GABA) metabolism are autosomal recessively inherited succinic semialdehyde dehydrogenase and GABA-transaminase deficiency. The clinical presentation of succinic semialdehyde dehydrogenase deficiency includes intellectual disability, ataxia, obsessive-compulsive disorder and epilepsy with a nonprogressive course in typical cases, although a progressive form in early childhood as well as deterioration in adulthood with worsening epilepsy are reported. GABA-transaminase deficiency is associated with a severe neonatal-infantile epileptic encephalopathy.

Clinical Evaluation of Gamma Hydroxybutyric Acid (GHB) and its Glucuronide in Biological Matrices of Succinic Semi Aldehyde Dehydrogenase Deficient Patients

Gamma hydroxybutyric acid (GHB), an endogenous metabolite, is an agonist towards both GHB and GABAB receptors. GHB is elevated during illicit drug use and in patients with heritable succinic semialdehyde dehydrogenase (SSADH) deficiency, a disorder of GABA degradation. Previous reports have postulated that the glucuronide conjugate (GHB‐gluc) may represent a urinary biomarker for GHB intoxication. The objective of the present work was to examine the level of GHB‐gluc in SSADH‐deficient patients and its applicability as a potential clinical biomarker. Urine was quantified for GHB and GHB‐gluc on an AB Sciex 6500 mass spectrometer. Semi validation of the urine method was conducted using plasma and cerebrospinal fluid (CSF). SSADH patient urine, plasma and CSF and healthy volunteer control urine and plasma were collected and quantified for GHB and GHB‐gluc using LC‐MS/MS. Absolute quantification of GHB and GHB‐gluc in patient urine samples revealed an inverse correlation between GHB and GHB‐gluc (r2, 0.6; p value<0.05). Relative to control samples, the GHB‐gluc was only moderately elevated in patient samples (~15%). The GHB‐gluc was below the limit of quantification (25 ng/ml) in patient CSF and was not discernible between groups in plasma specimens. This work indicates that GHB‐conjugation may occur primarily in the kidney, or that a fraction of the GHB‐gluc is excreted in the bile.Acknowledgement: The generous support of the SSADH Association (www.ssadh.net) is gratefully acknowledged.

NMR-based urinalysis for rapid diagnosis of inborn errors of metabolism

Aims A rapid diagnosis for patients with suspected inborn errors of metabolism (IEM) is clinically important. However, most urine organic acid analysis (UOA) using GC-MS takes time. Here, we developed a rapid workflow using nuclear magnetic resonance (NMR) spectroscopy-based urinalysis as a complementary diagnostic tool to UOA. Methods Urine samples will be analysed using 1 H-NMR spectroscopy, including 100 urine controls without IEM and urine samples from patients with beta-ketothiolase deficiency (BKD), beta-ureidopropionase deficiency (UPD), propionic acadaemia (PA), multiple carboxylase deficiency (MCD) and succinic semialdehyde dehydrogenase (SSADH) deficiency. A 2-dimension ( 1 H- 13 C heteronuclear single quantum correlation, HSQC) will be performed to provide structural-based evidence on the positive identification of metabolites if necessary. Results Disease-specific markers were identified in all patients with IEM: butanone in BKD, β-ureidoisobutyric and β-ureidopropionic acids in UPD, 3-hydroxypropionic acid in PA, 3-hydroxyisovaleric acid in MCD, and 4-hydroxybutyric acid in SSADH deficiency, and they were not found in excess in unaffected controls. Discussion The operation of NMR is simple and fast; sample preparation is a 2-step procedure without the needs of derivatisation while a usual 1 H-NMR acquisition takes

Biomarkers in a Taurine Trial for Succinic Semialdehyde Dehydrogenase Deficiency.

We tested the hypothesis that patients with succinic semialdehyde dehydrogenase (SSADH) deficiency on taurine would have decreased cortical excitability as measured by transcranial magnetic stimulation (TMS) and improved cognition, due to taurine's partial GABA(A and B) receptor agonist effects and rescue in the null mouse model from status epilepticus and premature lethality. Biomarkers including neuropsychological testing, TMS, and CSF metabolites were studied in a cohort of patients on and off three months' taurine treatment. Seven patients (5M/2F; age range 12-33 years) were enrolled in this open-label crossover study. Baseline average full-scale IQ (FSIQ) was 44.1 (range 34-55). Of six who returned at 6-month follow-up, five completed cognitive testing (3M/2F) on therapy; average FSIQ = 43.4 (range 33-51). CSF biomarkers (n = 4 subjects) revealed elevation in taurine levels but no change in free or total GABA. Baseline cortical excitability measured with TMS agreed with previous findings in this population, with a short cortical silent period and lack of long-interval intracortical inhibition. Patients on taurine showed a decrease in cortical silent period and short-interval intracortical inhibition compared to their off taurine study. TMS demonstrated decreased inhibition in patients on taurine, in contrast to the study hypothesis, but consistent with its failure to produce clinical or cognitive improvement. TMS may be a useful biomarker for therapy in pediatric neurotransmitter disorders.

Single amino acid polymorphism in aldehyde dehydrogenase gene superfamily.

The aldehyde dehydrogenase gene superfamily comprises of 19 genes and 3 pseudogenes. These superfamily genes play a vital role in the formation of molecules that are involved in life processes, and detoxification of endogenous and exogenous aldehydes. ALDH superfamily genes associated mutations are implicated in various diseases, such as pyridoxine-dependent seizures, gamma-hydroxybutyric aciduria, type II Hyperprolinemia, Sjogren-Larsson syndrome including cancer and Alzheimer's disease. Accumulation of large DNA variations data especially Single Amino acid Polymorphisms (SAPs) in public databases related to ALDH superfamily genes insisted us to conduct a survey on the disease associated mutations and predict their function impact on protein structure and function. Overall this study provides an update and highlights the importance of pathogenic mutations in associated diseases. Using KD4v and Project HOPE a computational based platform, we summarized all the deleterious properties of SAPs in ALDH superfamily genes by the providing valuable insight into structural alteration rendered due to mutation. We hope this review might provide a way to define the deleteriousness of a SAP and helps to understand the molecular basis of the associated disease and also permits precise diagnosis and treatment in the near future.

Inherited disorders of gamma-aminobutyric acid metabolism and advances in ALDH5A1 mutation identification.

Inherited disorders of gamma-aminobutyric acid (GABA) metabolism include succinic semialdehyde dehydrogenase (SSADH) and gamma-aminobutyric acid transaminase (GABA-T) deficiencies. The clinical features, pathophysiology, diagnosis, and management of both, and an updated list of mutations in the ALDH5A1 gene, which cause SSADH deficiency, are discussed. A database of 112 individuals (71 children and adolescents, and 41 adults) indicates that developmental delay and hypotonia are the most common symptoms arising from SSADH deficiency. Furthermore, epilepsy is present in two-thirds of SSADH-deficient individuals by adulthood. Research with murine genetic models and human participants, using [11 C] flumazenil positron emission tomography (FMZ-PET) and transcranial magnetic stimulation, have led to therapeutic trials, and the identification of additional disruptions to GABA metabolism. Suggestions for new therapies have arisen from findings of GABAergic effects on autophagy, with enhanced activation of the mammalian target of rapamycin (mTOR) pathway. Details of known pathogenic mutations in the ALDH5A1 gene, three of which have not previously been reported, are summarized here. Investigations into disorders of GABA metabolism provide fundamental insights into the mechanisms underlying epilepsy, and support the importance of developing biomarkers and clinical trials. Comprehensive definition of phenotypes arising as a result of deficiencies in both SSADH and GABA-T may increase our understanding of the neurophysiological consequences of a hyper-GABAergic state.

Screening of Inherited Metabolic Disorders in Infants with Infantile Spasms.

The objective of this study is to explore the incidence of inherited metabolic disorders (IMD) in infants with infantile spasms (IS), with an attempt to improve the early diagnosis and etiological and symptomatic treatment. Urine and blood samples were collected from 60 IS patients and analyzed for the quantification of amino acids, organic acids, and fatty acids by gas chromatography-mass spectrometry and tandem mass spectrum. Routine urine tests, hepatic function tests, blood biochemistry, brain imaging, as well as examinations of the brain stem auditory/visual evoked potentials were also examined. In addition to antiepileptic therapy, etiological and symptomatic treatments were also conducted in infants with confirmed IMD and the follow-up lasted for 6 months in these pediatric patients. Metabolic disorders were found in 28 (46.67 %) of 60 IS infants, among them 13 (21.67 %) were confirmed to be with IMD. Twelve of these 13 IS patients with definite IMD diagnoses (92.31 %) experienced varying degrees of delayed development of intelligence and motor function, 8 patients (61.54 %) had abnormal cranial CT or MRI findings, 11 patients (84.61 %) had abnormal brain stem evoked potentials, 4 patients (30.77 %) had abnormal hepatic functions, 3 patients (23.07 %) had abnormal blood biochemistry, 2 patients (15.38 %) had positive (+ to ++) results for routine urine ketones, and 2 patients (15.38 %) had skin lesions. After treatment in children who were diagnosed IMD, the well controlled epileptic seizures and the satisfactory developments in mental and motor were found in 4 cases of methylmalonic acidemia, 2 cases of classical phenylketonuria, and one case of biotin deficiency disease, glutaric acidemia type I, and 4-hydroxybutyric aciduria in each. IMD is a key biological cause in IS. Early screening for IMD is warranted in IS infants to facilitate the improvement for the prognosis and an early etiological treatment.

Spotlight on the March 18 Issue

The authors assessed quality of life in patients with ischemic stroke or TIA at 3 and 12 months. After accounting for sociodemographic variables, stroke severity, and disability, women had lower quality of life than men after stroke. The reasons could be decreased mobility, pain, and anxiety/depression after stroke. See p. 922 Taurine is an amino acid with potential neuroprotective effects based on effectiveness in an animal model and anecdotal reports in succinic semialdehyde dehydrogenase deficiency. This disorder of GABA metabolism is …

Defects in GABA metabolism affect selective autophagy pathways and are alleviated by mTOR inhibition

In addition to key roles in embryonic neurogenesis and myelinogenesis, γ-aminobutyric acid (GABA) serves as the primary inhibitory mammalian neurotransmitter. In yeast, we have identified a new role for GABA that augments activity of the pivotal kinase, Tor1. GABA inhibits the selective autophagy pathways, mitophagy and pexophagy, through Sch9, the homolog of the mammalian kinase, S6K1, leading to oxidative stress, all of which can be mitigated by the Tor1 inhibitor, rapamycin. To confirm these processes in mammals, we examined the succinic semialdehyde dehydrogenase (SSADH)-deficient mouse model that accumulates supraphysiological GABA in the central nervous system and other tissues. Mutant mice displayed increased mitochondrial numbers in the brain and liver, expected with a defect in mitophagy, and morphologically abnormal mitochondria. Administration of rapamycin to these mice reduced mTOR activity, reduced the elevated mitochondrial numbers, and normalized aberrant antioxidant levels. These results confirm a novel role for GABA in cell signaling and highlight potential pathomechanisms and treatments in various human pathologies, including SSADH deficiency, as well as other diseases characterized by elevated levels of GABA.

Taurine trial in succinic semialdehyde dehydrogenase deficiency and elevated CNS GABA.

The objective of this open-label study was primarily to assess the effect of taurine on adaptive behavior and secondarily to collect safety and tolerability data in patients with succinic semialdehyde dehydrogenase deficiency. In the current study, subjects were titrated weekly from a starting dose of 50 mg/kg/d to a target 200 mg/kg/d, and assessed for safety, tolerability, and adaptive functioning using age-normalized Adaptive Behavior Assessment Scales. Eighteen patients (8 males/10 females, aged 0.5-28 years, mean 12 years) were recruited. Three subjects withdrew because of perceived lack of efficacy. One serious adverse event occurred (hospitalization for hypersomnia) on 16 g/d (200 mg/kg/d), leading to a dose-lowering paradigm with a maximum dose of 10 g/d. Results did not show clinically meaningful improvement in the adaptive domains after taurine therapy. Pre- and posttherapy adaptive scores also demonstrated no statistically significant difference (p > 0.18). Adaptive behavior did not improve significantly with taurine intervention. Further therapeutic clinical trials including an on-off paradigm using biomarkers are planned. This study provides Class IV evidence that for patients with succinic semialdehyde dehydrogenase deficiency, taurine does not significantly improve adaptive behavior. The study is rated Class IV because of the absence of a control group.

Suggestive Association With Ocular Phoria at Chromosome 6p22

We conducted a genome-wide association study to identify genetic factors that contribute to the etiology of heterophoria. We measured near and far vertical and horizontal phorias in 988 healthy adults aged 16 to 40 using the Keystone telebinocular with plates 5218 and 5219. We regressed degree of phoria against genotype at 642758 genetic loci. To control for false positives, we applied the conservative genome-wide permutation test to our data. A locus at 6p22.2 was found to be associated with the degree of near horizontal phoria (P = 2.3 × 10(-8)). The P value resulting from a genome-wide permutation test was 0.014. The strongest association signal arose from an intronic region of the gene ALDH5A1, which encodes the mitochondrial enzyme succinic semialdehyde dehydrogenase (SSADH), an enzyme involved in γ-aminobutyric acid metabolism. Succinic semialdehyde dehydrogenase deficiency, resulting from mutations of ALDH5A1, causes a variety of neural and behavioral abnormalities, including strabismus. Variation in ALDH5A1 is likely to contribute to degree of horizontal phoria.

A novel ALDH5A1 mutation is associated with succinic semialdehyde dehydrogenase deficiency and severe intellectual disability in an Iranian family

Succinic semialdehyde dehydrogenase (SSADH) deficiency is a disorder of the catabolism of the neurotransmitter gamma-aminobutyric acid (GABA) with a very variable clinical phenotype ranging from mild intellectual disability to severe neurological defects. We report here on a large Iranian family with four affected patients presenting with severe intellectual disability, developmental delay and generalized tonic-clonic seizures. Molecular genetic analysis revealed a missense mutation c.901A>G (p.K301E, RefSeq number NM_001080) in ALDH5A1 co-segregating with the disease in the family. The missense mutation affects an amino acid residue that is highly conserved across the animal kingdom. Protein modeling showed that p.K301E most likely leads to a loss of NAD(+) binding and a predicted decrease in the free energy by 6.67 kcal/mol furthermore suggests a severe destabilization of the protein. In line with these in silico observations, no SSADH enzyme activity could be detected in patient lymphoblasts.

Quantitation of gamma-hydroxybutyric acid in dried blood spots: Feasibility assessment for newborn screening of succinic semialdehyde dehydrogenase (SSADH) deficiency

ObjectiveSSADH deficiency, the most prevalent autosomal recessive disorder of GABA degradation, is characterized by elevated gamma-hydroxybutyric acid (GHB). Neurological outcomes may be improved with early intervention and anticipatory guidance. Morbidity has been compounded by complications, e.g. hypotonia, in undiagnosed infants with otherwise routine childhood illnesses. We report pilot methodology on the feasibility of newborn screening for SSADH deficiency. MethodDried blood spot (DBS) cards from patients affected with SSADH deficiency were compared with 2831 archival DBS cards for gamma-hydroxybutyric acid content. Following extraction with methanol, GHB in DBS was separated and analyzed using ultra high-performance liquid chromatography tandem mass spectrometry. ResultsMethodology was validated to meet satisfactory accuracy and reproducibility criteria, including intra-day and inter-day validation. Archival refrigerated dried blood spot samples of babies, infants and children (N=2831) were screened for GHB, yielding a mean+/−S.D. of 8±5nM (99.9%-tile 63nM) (Min 0.0 Max 78nM). The measured mean and median concentrations in blood spots derived from seven SSADH deficient patients were 1182nM and 699nM respectively (Min 124, Max 4851nM). ConclusionsGHB concentration in all 2831 dried blood spot cards was well below the lowest concentration of affected children. These data provide proof-of-principle for screening methodology to detect SSADH deficiency with applicability to newborn screening and earlier diagnosis.

Evidence for treatable inborn errors of metabolism in a cohort of 187 Greek patients with autism spectrum disorder (ASD)

We screened for the presence of inborn errors of metabolism (IEM) in 187 children (105 males; 82 females, ages 4–14 years old) who presented with confirmed features of autism spectrum disorder (ASD). Twelve patients (7%) manifested increased 3-hydroxyisovaleric acid (3-OH-IVA) excretion in urine, and minor to significant improvement in autistic features was observed in seven patients following supplementation with biotin. Five diagnoses included: Lesch Nyhan syndrome (2), succinic semialdehyde dehydrogenase (SSADH) deficiency (2), and phenylketonuria (1) (2.7%). Additional metabolic disturbances suggestive of IEMs included two patients whose increased urine 3-OH-IVA was accompanied by elevated methylcitrate and lactate in sera, and 30 patients that showed abnormal glucose-loading tests. In the latter group, 16/30 patients manifested increased sera beta hydroxybutyrate (b-OH-b) production and 18/30 had a paradoxical increase of sera lactate. Six patients with elevated b-OH-b in sera showed improved autistic features following implementation of a ketogenic diet (KD). Five patients showed decreased serum ketone body production with glucose loading. Twelve of 187 patients demonstrated non-specific MRI pathology, while 25/187 had abnormal electroencephalogram (EEG) findings. Finally, family history was positive for 22/187 patients (1st or 2nd degree relative with comparable symptomatology) and consanguinity was documented for 12/187 patients. Our data provide evidence for a new biomarker (3-OH-IVA) and novel treatment approaches in ASD patients. Concise 1 sentence take-home message: Detailed metabolic screening in a Greek cohort of ASD patients revealed biomarkers (urine 3-hydroxyisovaleric acid and serum b-OH-b) in 7% (13/187) of patients for whom biotin supplementation or institution of a KD resulted in mild to significant clinical improvement in autistic features.

GABA-Ergic Dysfunction in Succinic Semialdehyde Dehydrogenase Deficiency

Investigators at the Clinical Epilepsy and Neurorehabilitation Sections, NIH, Bethesda, MD; Albert Ludwigs University, Freiberg, Germany; and Children's National Medical Center, Washington, DC used transcranial magnetic stimulation (TMS) to quantify the excitation and inhibition in primary motor cortex in 8 patients (mean age 15.4 years) with succinic semialdehyde dehydrogenase (SSADH) deficiency.