Elevated GHB Research Articles

A False-Positive Gamma-Hydroxy Butyric Acid Urine Screening in a Patient with High Anion Gap Metabolic Acidosis Due to Ethylene Glycol Poisoning.

A young woman with a history of several suicide attempts was admitted to the hospital after suspicion of a new intoxication without definite identification of the causing agent. The patient had a high anion gap metabolic acidosis (HAGMA) with respiratory compensation, a lactate gap and an osmolar gap at admission. Initial toxicological screening showed no abnormalities except for a weak positive gamma-hydroxy butyric acid (GHB) enzymatic screen in urine. This finding could not be confirmed using chromatographic analysis nor be explained by the presence of known cross-reacting substances like ethanol. In this case, falsely elevated urinary GHB screening was caused by the ingestion of ethylene glycol. To confirm that the interference was due to ethylene glycol or its metabolites, we performed a spiking experiment. Cross reactivity was linked to ethylene glycol and was low in our experiments (0.1-0.2%). Substantial amounts of ethylene glycol are required to slightly elevated GHB results, depending on the endogenous cutoff used. We can conclude that ethylene glycol can give rise to falsely elevated urinary GHB levels at ethylene glycol concentrations that are typically found in intoxications.

Author Response: Novel ALDH5A1 Variants and Genotype: Phenotype Correlation in SSADH Deficiency

We thank Dr. Siniscalchi for his interest in our characterization of the phenotype of SSADH deficiency (SSADHD; ALDH5A1)1 and for highlighting the putative role of elevated gamma hydroxybutyric acid (GHB) in abnormal gliotransmission. In vivo exposure of the brain to GHB triggers intracellular calcium spikes, which has long-term impacts on astrocyte function and might contribute to the well-known epileptogenic activity of GHB.2 Other studies3—including our own—underscore the role of activated glial cells (reactive astrogliosis) and ensuing GABA-glutamine-glutamate cycle dysfunction in the phenotype of experimental ADLH5A1 deficiency (aldh5a1-deficient mice). Earlier studies in this model presented evidence for glial dysfunction and reduced glutamate/glutamine cycling.4 Recent studies using stable isotopes revealed that astrocytes extensively metabolize GABA for maintenance of glutamine.5 Metabolic analyses in multiple brain regions of an autopsied patient (age 37 years) with SSADHD verified not only highly elevated GABA and GHB, but strikingly low glutamine.6 As a short chain alcohol, elevated GHB in SSADHD may also affect astrocyte/oligodendrocyte function in a fashion analogous to that of ethanol, which can trigger seizures during withdrawal.7 Targeted knockout of aldh5a1 in mammalian astrocytes may provide additional insight into the role of GHB in astrocyte pathology in SSADHD.

Clinical diagnosis and mutation analysis of four Chinese families with succinic semialdehyde dehydrogenase deficiency

BackgroundSuccinic semialdehyde dehydrogenase (SSADH) deficiency is a rare autosomal recessively-inherited defect of γ-aminobutyric acid (GABA) metabolism. The absence of SSADH, which is encoded by aldehyde dehydrogenase family 5 member A1 (ALDH5A1) gene, leads to the accumulation of GABA and γ-hydroxybutyric acid (GHB). Few cases with SSADH deficiency were reported in China.Case presentationIn this study, four Chinese patients were diagnosed with SSADH deficiency in Tianjin Children’s Hospital. We conducted a multidimensional analysis with magnetic resonance imaging (MRI) of the head, semi quantitative detection of urine organic acid using gas chromatography-mass spectrometry, and analysis of ALDH5A1 gene mutations.Two of the patients were admitted to the hospital due to convulsions, and all patients were associated with developmental delay. Cerebral MRI showed symmetrical hyperintense signal of bilateral globus pallidus and basal ganglia in patient 1; hyperintensity of bilateral frontal-parietal lobe, widened ventricle and sulci in patient 2; and widened ventricle and sulci in patient 4. Electroencephalogram (EEG) revealed the background activity of epilepsy in patient 1 and the disappearance of sleep spindle in patient 2. Urine organic acid analysis revealed elevated GHB in all the patients. Mutational analysis, which was performed by sequencing the 10 exons and flanking the intronic regions of ALDH5A1 gene for all the patients, revealed mutations at five sites. Two cases had homozygous mutations with c.1529C > T and c.800 T > G respectively, whereas the remaining two had different compound heterozygous mutations including c.527G > A/c.691G > A and c.1344-2delA/c.1529C > T. Although these four mutations have been described previously, the homozygous mutation of c.800 T > G in ALDH5A1 gene is a novel discovery.ConclusionSSADH deficiency is diagnosed based on the elevated GHB and 4, 5DHHA by urinary organic acid analysis. We describe a novel mutation p.V267G (c.800 T > G) located in the NAD binding domain, which is possibly crucial for this disease’s severity. Our study expands the mutation spectrum of ALDH5A1 and highlights the importance of molecular genetic evaluation in patients with SSADH deficiency.

Identification of a New Metabolite of GHB: Gamma-Hydroxybutyric Acid Glucuronide

Gamma-hydroxybutyric acid (GHB) is an important analyte in clinical and forensic toxicology with a narrow detection window of 3-6 h. In the search of improved detection methods, the existence in vivo of a glucuronated GHB metabolite (GHB-GLUC) was hypothesized. Chemically pure standards of GHB-GLUC and a deuterated analogue for chromatography were synthesized. Liquid chromatography and tandem mass spectrometry were used for targeted analysis in anonymous clinical urine samples (n = 50). GHB-GLUC was found in concentrations ranging from 0.11 to 5.0 µg/mL (mean: 1.3 ± 1.2 µg/mL). Thus far, this is the first report of a GHB glucuronide detected in biological samples. Given that glucuronides generally have longer half-life values than their corresponding free drugs, GHB-GLUC should theoretically be a biomarker of GHB intoxication. It is also proposed that the hitherto unexplained reports of elevated GHB concentrations in some biological samples, which has caused the setting of a relatively high cutoff value (10 µg/mL), represent total GHB measurements (sum of free GHB and actively chemically hydrolyzed GHB-GLUC). To address these challenges, the present study must be followed by comprehensive pharmacokinetic and stability studies after the controlled administration of GHB.

GABA B -ergic motor cortex dysfunction in SSADH deficiency

Succinic semialdehyde dehydrogenase (SSADH) deficiency is a rare autosomal recessive disorder of GABA degradation leading to elevations in brain GABA and γ-hydroxybutyric acid (GHB). The effect of chronically elevated GABA and GHB on cortical excitability is unknown. We hypothesized that use-dependent downregulation of GABA receptor expression would promote cortical disinhibition rather than inhibition, predominantly via presynaptic GABAergic mechanisms. We quantified the magnitude of excitation and inhibition in primary motor cortex (M1) in patients with SSADH deficiency, their parents (obligate heterozygotes), age-matched healthy young controls, and healthy adults using single and paired pulse transcranial magnetic stimulation (TMS). Long interval intracortical inhibition was significantly reduced and the cortical silent period was significantly shortened in patients with SSADH deficiency compared to heterozygous parents and control groups. Since long interval intracortical inhibition and cortical silent period are thought to reflect GABA(B) receptor-mediated inhibitory circuits, our results point to a particularly GABA(B)-ergic motor cortex dysfunction in patients with SSADH deficiency. This human phenotype is consistent with the proposed mechanism of use-dependent downregulation of postsynaptic GABA(B) receptors in SSADH deficiency animal models. Additionally, the results suggest autoinhibition of GABAergic neurons. This first demonstration of altered GABA(B)-ergic function in patients with SSADH deficiency may help to explain clinical features of the disease, and suggest pathophysiologic mechanisms in other neurotransmitter-related disorders.

Polysomnographic abnormalities in succinic semialdehyde dehydrogenase (SSADH) deficiency.

Patients with SSADH deficiency, a disorder of chronically elevated endogenous GABA and GHB, were studied for sleep symptoms and polysomnography. We hypothesized that patients would have excessive daytime somnolence and decreased REM sleep. Polysomnography and MSLT were performed on patients enrolled for comprehensive clinical studies of SSADH deficiency. Sleep studies were obtained in the sleep laboratories at CNMC and NIH. Sleep recordings were obtained in 10 patients with confirmed SSADH deficiency. Thirteen overnight polysomnograms were obtained in 10 patients (7 male, 3 female, ages 11-27 y). Eleven MSLT studies were completed in 8 patients. Polysomnograms showed prolongation of REM stage latency (mean 272 +/- 89 min) and decreased percent stage REM (mean 8.9%, range 0.3% to 13.8%). Decreased mean sleep latency was present in 6 of 11 MSLTs. SSADH deficiency is associated with prolonged latency to stage REM and decreased percent stage REM. This disorder represents a model of chronic GABA and GHB accumulation associated with suppression of REM sleep.

Explanations for the High Risk of Diabetes-Related Amputation in a Caribbean Population of Black African Descent and Potential for Prevention

Diabetes-related lower-extremity amputation (LEA) rates are elevated in blacks compared with whites in the U.S., but are lower in African Caribbeans in the U.K., whereas anecdotal reports suggest high rates in the Caribbean. We aimed to establish the incidence and risk factors for diabetes-related LEA in a Caribbean population. We conducted an incident and prospective case-control study of case patients (individuals with diabetes having a LEA) and community-based control subjects (individuals with diabetes without a LEA) in Barbados, West Indies. Participants completed an interview and examination of risk factors for amputation, including footwear use. The overall 1-year incidence of LEA (n = 223) was 173 per 10(5) population and 936 per 10(5) population with diabetes (557 per 10(5) for minor amputation and 379 per 10(5) for major amputation). Women had higher amputation rates than those reported in the Global Lower Extremity Amputation Study, apart from the U.S. Navajo population. Independent risk factors for all diabetes-related LEAs were poor footwear (odds ratio [OR] 2.71 [95% CI 1.23-5.97]), elevated GHb (1.40 per percent increase [1.26-1.57]), peripheral neuropathy (1.05 per volt increase [1.03-1.08]), and peripheral vascular disease. Diabetes LEA rates in Barbados are among the highest in the world. Inadequate footwear independently tripled amputation risk. Education of professionals and patients, particularly about footwear and foot care, coupled with improved diabetes clinical care, is key to reducing amputation risk in this population.

Significant behavioral disturbances in succinic semialdehyde dehydrogenase (SSADH) deficiency (Gamma-Hydroxybutyric aciduria)

Background We report two adult patients with succinic semialdehyde dehydrogenase deficiency, manifesting as γ-hydroxybutyric aciduria. For both, the clinical presentation included significant behavioral disturbances and psychosis (hallucinations, disabling anxiety, aggressive behavior, and sleep disorder), leading to multiple therapeutic attempts. Intervention with benzodiazepines appeared most efficacious, resulting in decreased aggression and agitation and improvement in anxiety. A review of 56 published and unpublished studies of SSADH-deficient patients revealed that 42% manifested behavioral disturbances, whereas 13% (predominantly adults) displayed psychotic symptomatology. Methods To explore the potential biochemical basis of these behavioral abnormalities, we studied cerebrospinal fluid derived from 13 patients, which revealed significantly elevated GHB (65- to 230-fold), high free and total GABA (up to threefold), and low glutamine. Results Although within the control range, homovanillic and 5-hydroxyindoleacetic acids (end products of dopamine and serotonin metabolism, respectively) showed a significant linear correlation with increasing GHB concentration, suggesting enhanced dopamine and serotonin turnover. Conclusions We conclude that elevated GABA combined with low glutamine suggest disruption of the glial-neuronal glutamine/GABA/glutamate shuttle necessary for replenishment of neuronal neurotransmitters, whereas altered dopamine and serotonin metabolism may be causally linked to the hyperkinetic movement disorders and behavioral disturbances seen in SSADH-deficient patients.

Therapeutic intervention in mice deficient for succinate semialdehyde dehydrogenase (gamma-hydroxybutyric aciduria).

Therapeutic intervention for human succinic semialdehyde dehydrogenase (SSADH) deficiency (gamma-hydroxybutyric aciduria) has been limited to vigabatrin (VGB). Pharmacologically, VGB should be highly effective due to 4-aminobutyrate-transaminase (GABA-transaminase) inhibition, lowering succinic semialdehyde and, thereby, gamma-hydroxybutyric acid (GHB) levels. Unfortunately, clinical efficacy has been limited. Because GHB possesses a number of potential receptor interactions, we addressed the hypothesis that antagonism of these interactions in mice with SSADH deficiency could lead to the development of novel treatment strategies for human patients. SSADH-deficient mice have significantly elevated tissue GHB levels, are neurologically impaired, and die within 4 weeks postnatally. In the current report, we compared oral versus intraperitoneal administration of VGB, CGP 35348 [3-aminopropyl(diethoxymethyl)phosphinic acid, a GABA(B) receptor antagonist], and the nonprotein amino acid taurine in rescue of SSADH-deficient mice from early death. In addition, we assessed the efficacy of the specific GHB receptor antagonist NCS-382 (6,7,8,9-tetrahydro-5-[H]benzocycloheptene-5-ol-6-ylideneacetic acid) using i.p. administration. All interventions led to significant lifespan extension (22-61%), with NCS-382 being most effective (50-61% survival). To explore the limited human clinical efficacy of VGB, we measured brain GHB and gamma-aminobutyric acid (GABA) levels in SSADH-deficient mice receiving VGB. Whereas high-dose VGB led to the expected elevation of brain GABA, we found no parallel decrease in GHB levels. Our data indicate that, at a minimum, GHB and GABA(B) receptors are involved in the pathophysiology of SSADH deficiency. We conclude that taurine and NCS-382 may have therapeutic relevance in human SSADH deficiency and that the poor clinical efficacy of VGB in this disease may relate to an inability to decrease brain GHB concentrations.

The Performance of a Risk Score in Predicting Undiagnosed Hyperglycemia

Type 2 diabetes is a serious disease that is commonly undetected and for which screening is sometimes advocated. A number of risk factors are associated with prevalent undiagnosed diabetes. The use of routinely available information on these factors has been proposed as a simple and effective way of identifying individuals at high risk for having the disease. The objective of this study was to assess the effectiveness of the Cambridge risk score in a large and representative population. A risk score derived from data in a previous study was tested for its ability to detect prevalent undiagnosed hyperglycemia as measured by a GHb > or = 6.0, 6.5, or 7% in 6,567 subjects aged 39-78 years in the European Prospective Investigation of Cancer-Norfolk cohort. For a specificity of 78%, the risk score predicted a GHb of > or = 7.0% in subjects aged 39-78 years, with a sensitivity of 51% (95% CI 40-62). The areas under the receiver-operating characteristic (ROC) curve for GHb > or = 6.0, 6.5, and 7% were 65.7% (63.8-67.6), 71.2% (68.4-75.2), and 74.2% (69.5-79.0), respectively. The area under the ROC curve was not significantly reduced if data on family and smoking history were unavailable for any of the cut-offs for GHb. The risk score performed as well as other previously reported models in all age groups. We concluded that a simple risk score using data routinely available in primary care can identify people with an elevated GHb with reasonable sensitivity and specificity, and it could therefore form part of a strategy for early detection of type 2 diabetes.

Hyperglycemia, recognized and unrecognized, as a risk factor for stroke and transient ischemic attacks.

Glycosylated hemoglobin concentration (GHb), which is considered an indication of glycemia over the preceding several months, was examined in 50 patients hospitalized for recent stroke or transient ischemic attacks (TIA), and compared to that in several reference populations. Patients with stroke or TIA had GHb (mean %A1 +/- SD, 10.2 +/- 2.3) higher than in hospital controls without cerebrovascular disease (8.3 +/- 0.9, p less than 0.005), and equivalent to values for ambulatory diabetic patients treated with diet or diet plus oral agents (9.5 +/- 2.4) or with insulin (10.7 +/- 2.9). Twenty percent (10/50) of the stroke/TIA group were previously known to have abnormal glucose tolerance or diabetes; when this subgroup was excluded, there remained 42% of the original group (21/50) with abnormal GHb (greater than 10% A1) not previously known to have hyperglycemia, and the difference between GHb values for the stroke/TIA patients not known to have glycemic abnormality and for the hospital control group remained significant (p less than 0.005). Sixty-two percent of stroke/TIA patients (31/50) were under treatment for glycemic abnormality, or had high GHb, or both. The high prevalence of elevated GHb in this population could not be attributed to a relationship to age, sex, smoking history, hypercholesterolemia, or hypertension. We conclude that hyperglycemia commonly precedes stroke and TIA, is usually unrecognized, and has been under-appreciated as a risk factor for cerebrovascular disease.