Novel biomarkers and age-related metabolite correlations in plasma and dried blood spots from patients with succinic semialdehyde dehydrogenase deficiency.

BACKGROUND: Previous work has identified age-related negative correlations for γ-hydroxybutyric acid (GHB) and γ-aminobutyric acid (GABA) in plasma of patients with succinic semialdehyde dehydrogenase deficiency (SSADHD). Using plasma and dried blood spots (DBS) collected in an ongoing natural history study, we tested the hypothesis that other biomarkers would follow a similar age-related negative correlation as seen for GHB/GABA. Samples (mixed sex) included: patients (n = 21 unique samples, 1-39.5 yrs) and parallel controls (n = 9 unique samples, 8.4-34.8 yrs). Archival control data (DBS only; n = 171, 0.5-39.9 yrs) was also included. RESULTS: Metabolites assessed included amino acids (plasma, DBS) and acylcarnitines, creatine, creatinine, and guanidinoacetate (DBS only). Age-related negative correlations for glycine (plasma, DBS) and sarcosine (N-methylglycine, plasma) were detected, accompanied by elevated proline and decreased levels of succinylacetone, argininosuccinate, formaminoglutamate, and creatinine. Significantly low acylcarnitines were detected in patients across all chain lengths (short-, medium- and long-chain). Significant age-dependent positive correlations for selected acylcarnitines (C6-, C12DC(dicarboxylic)-, C16-, C16:1-, C18:1-, C18:2OH-carnitines) were detected in patients and absent in controls. Receiver operating characteristic (ROC) curves for all binary comparisons revealed argininosuccinate and succinylacetone to be the most discriminating biomarkers (area > 0.92). CONCLUSIONS: Age-dependent acylcarnitine correlations may represent metabolic compensation responsive to age-related changes in GHB and GABA. Our study highlights novel biomarkers in SSADHD and expands the metabolic pathophysiology of this rare disorder of GABA metabolism.

Temporal metabolomics in dried bloodspots suggests multipathway disruptions in aldh5a1-/- mice, a model of succinic semialdehyde dehydrogenase deficiency.

Succinic semialdehyde dehydrogenase (SSADH) deficiency (SSADHD; OMIM 271980) is a rare disorder featuring accumulation of neuroactive 4-aminobutyric acid (GABA; γ-aminobutyric acid, derived from glutamic acid) and 4-hydroxybutyric acid (γ-hydroxybutyric acid; GHB, a short-chain fatty acid analogue of GABA). Elevated GABA is predicted to disrupt the GABA shunt linking GABA transamination to the Krebs cycle and maintaining the balance of excitatory:inhibitory neurotransmitters. Similarly, GHB (or a metabolite) is predicted to impact ß-oxidation flux. We explored these possibilities employing temporal metabolomics of dried bloodspots (DBS), quantifying amino acids, acylcarnitines, and guanidino- metabolites, derived from aldh5a1+/+, aldh5a1+/- and aldh5a1-/- mice (aldehyde dehydrogenase 5a1 = SSADH) at day of life (DOL) 20 and 42 days. At DOL 20, aldh5a1-/- mice had elevated C6 dicarboxylic (adipic acid) and C14 carnitines and threonine, combined with a significantly elevated ratio of threonine/[aspartic acid + alanine], in comparison to aldh5a1+/+ mice. Conversely, at DOL 42 aldh5a1-/- mice manifested decreased short chain carnitines (C0-C6), valine and glutamine, in comparison to aldh5a1+/+ mice. Guanidino species, including creatinine, creatine and guanidinoacetic acid, evolved from normal levels (DOL 20) to significantly decreased values at DOL 42 in aldh5a1-/- as compared to aldh5a1+/+ mice. Our results provide a novel temporal snapshot of the evolving metabolic profile of aldh5a1-/- mice while highlighting new pathomechanisms in SSADHD.

Gamma-Hydroxybutyrate content in dried bloodspots facilitates newborn detection of succinic semialdehyde dehydrogenase deficiency.

Increased gamma-hydroxybutyric acid in urine and blood are metabolic hallmarks of succinic semialdehyde dehydrogenase deficiency, a defect of 4-aminobutyric acid metabolism. Here, we examined the hypothesis that succinic semialdehyde dehydrogenase deficiency could be identified via measurement of gamma-hydroxybutyric acid in newborn and post-newborn dried bloodspots. Quantitation of gamma-hydroxybutyric acid using liquid chromatography-tandem mass spectrometry in twelve archival newborn patient dried bloodspots was 360 ±â€¯57 µM (mean, standard error; range 111-767), all values exceeding the previously established cutoff for newborn detection of 78 µΜ established from 2831 dried bloodspots derived from newborns, neonates and children. Gamma-hydroxybutyric acid in post-newborn dried bloodspots (n = 19; ages 0.8-38 years) was 191 ±â€¯65 µM (mean, standard error; range 20-1218), exceeding the aforementioned GHB cutoff for patients approximately 10 years of age or younger. Further, gamma-hydroxybutyric acid in post-newborn dried bloodspots displayed a significant (p < .0001) inverse correlation with age. This preliminary study suggests that succinic semialdehyde dehydrogenase deficiency may be identified in newborn and post-newborn dried bloodspots via quantitation of gamma-hydroxybutyric acid, while forming the platform for more extensive studies in affected and unaffected dried bloodspots.

Maternal glutamine supplementation in murine succinic semialdehyde dehydrogenase deficiency, a disorder of γ-aminobutyric acid metabolism.

Murine succinic semialdehyde dehydrogenase deficiency (SSADHD) manifests with high concentrations of γ-aminobutyric acid (GABA) and γ-hydroxybutyrate (GHB) and low glutamine in the brain. To understand the pathogenic contribution of central glutamine deficiency, we exposed aldh5a1-/- (SSADHD) mice and their genetic controls (aldh5a1+/+ ) to either a 4% (w/w) glutamine-containing diet or a glutamine-free diet from conception until postnatal day 30. Endpoints included brain, liver and blood amino acids, brain GHB, ataxia scores, and open field testing. Glutamine supplementation did not improve aldh5a1-/- brain glutamine deficiency nor brain GABA and GHB. It decreased brain glutamate but did not change the ratio of excitatory (glutamate) to inhibitory (GABA) neurotransmitters. In contrast, glutamine supplementation significantly increased brain arginine (30% for aldh5a1+/+ and 18% for aldh5a1-/- mice), and leucine (12% and 18%). Glutamine deficiency was confirmed in the liver. The test diet increased hepatic glutamate in both genotypes, decreased glutamine in aldh5a1+/+ but not in aldh5a1-/- , but had no effect on GABA. Dried bloodspot analyses showed significantly elevated GABA in mutants (approximately 800% above controls) and decreased glutamate (approximately 25%), but no glutamine difference with controls. Glutamine supplementation did not impact blood GABA but significantly increased glutamine and glutamate in both genotypes indicating systemic exposure to dietary glutamine. Ataxia and pronounced hyperactivity were observed in aldh5a1-/- mice but remained unchanged by the diet intervention. The study suggests that glutamine supplementation improves peripheral but not central glutamine deficiency in experimental SSADHD. Future studies are needed to fully understand the pathogenic role of brain glutamine deficiency in SSADHD.

Age-related phenotype and biomarker changes in SSADH deficiency.

Objective: Succinic Semialdehyde Dehydrogenase (SSADH) deficiency is a disorder of elevated gamma-amino butyric acid (GABA) and gamma hydroxybutyric acid (GHB) and a complex neuropsychiatric profile. Adult reports suggest worsening epilepsy and high SUDEP risk. Methods: Subjects with confirmed SSADH deficiency were recruited into a longitudinal study. Plasma thyroid hormone and total GABA/GHB were quantified by standard clinical chemistry methodologies and mass spectrometry, respectively. Results: A total of 133 subjects with SSADH deficiency are enrolled in the registry; 49 participated in the longitudinal study. The age range of the population is 8 weeks to 63 years (median 7.75 year; 44% male). There is a significant difference in proportions among the age groups in subjects affected with hypotonia, compulsive behavior, sleep disturbances, and seizures. Epilepsy is present in 50% of the total population, and more prevalent in subjects 12 years and older (P = 0.001). The median age of onset for absence seizures was 2 years, and 12 years for generalized tonic-clonic seizures (P < 0.01). The SUDEP rate in adults was 12% (4/33). There was a significant age-dependent negative correlation between GABA and T3 levels. Interpretation: There is an age-dependent association with worsening of epilepsy, behavioral disturbances including obsessive-compulsive behavior, and sleep disturbances with age in SSADH deficiency. There is a high risk of SUDEP. We have observed more absence seizures in younger patients, compared to tonic-clonic in the older cohort, which correlates with age-related changes in GABA and GHB concentration and thyroid function, as well as the natural history of seizures in the murine model.

Correlation of blood biomarkers with age informs pathomechanisms in succinic semialdehyde dehydrogenase deficiency (SSADHD), a disorder of GABA metabolism.

We hypothesized that blood levels of γ-aminobutyric acid (GABA) and γ-hydroxybutyric acid (GHB), biomarkers of succinic semialdehyde dehydrogenase deficiency (SSADHD), would correlate with age. GABA and GHB were quantified in plasma and red blood cells (RBCs) from 18 patients (age range 5-41 years; median 8). Both metabolites negatively correlated with age (P < 0.05). Plasma and RBC GHB declined with age, reaching a nadir and approximate steady state by 10 years. Declining plasma GABA achieved this approximate steady state at 30-40 years of age. These biomarker relationships may reflect further GABA- and GHB-ergic neurotransmission imbalances that correlate with the onset of adolescent/adulthood neuropsychiatric morbidity and epilepsy in SSADHD.

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.

Effect of genetically caused excess of brain gamma-hydroxybutyric acid and GABA on sleep.

BACKGROUND: Exogenous gamma-hydroxybutyrate (GHB) increases slow-wave sleep and reduces daytime sleepiness and cataplexy in patients with primary narcolepsy. OBJECTIVE: To examine nighttime sleep and daytime sleepiness in a 13-year-old girl homozygous for succinic semialdehyde dehydrogenase (SSADH) deficiency, a rare recessive metabolic disorder that disrupts the normal degradation of 4-aminobutyric acid (GABA), and leads to an accumulation of GHB and GABA within the brain. METHODS: Sleep interview, nighttime polysomnography, Multiple Sleep Latency Tests, and continuous 24-hour in-lab recordings in the patient; overnight polysomnography in her recessive mother and in a 13-year-old female control. RESULTS: During quiet wakefulness, background electroencephalographic activity was slow and composed of 7-Hz activity. Sleep stage 3/4 was slightly increased (28.1% of total sleep period, norms 15%-28%), and the daytime mean sleep latency was short in the patient (3 minutes 42 seconds, norms > 8 minutes). Stage 2 spindles were infrequent in the child (0.18/minute, norms: 1.2-9.2/minute) and her mother (0.65/minute) but normal (4.6/minute) in the control. At the beginning of the second night, a tonic-clonic seizure occurred, followed by a dramatic increase in stage 3/4 sleep, that lasted 46.3 % of the total sleep period, double the normal value. The mother showed a reduced total sleep time and rapid eye movement sleep percentage. DISCUSSION: This suggests that a chronic excess of GABA and GHB induces subtle sleep abnormalities, whereas increased slow-wave sleep evoked by a sudden event (here an epileptic seizure) may be caused by a supplementary increase in GABA and GHB.