Elevated preoptic brain activity in zebrafish glial glycine transporter mutants is linked to lethargy-like behaviors and delayed emergence from anesthesia.

Delayed emergence from anesthesia was previously reported in a case study of a child with Glycine Encephalopathy. To investigate the neural basis of this delayed emergence, we developed a zebrafish glial glycine transporter (glyt1 - / -) mutant model. We compared locomotor behaviors; dose-response curves for tricaine, ketamine, and 2,6-diisopropylphenol (propofol); time to emergence from these anesthetics; and time to emergence from propofol after craniotomy in glyt1-/- mutants and their siblings. To identify differentially active brain regions in glyt1-/- mutants, we used pERK immunohistochemistry as a proxy for brain-wide neuronal activity. We show that glyt1-/- mutants initiated normal bouts of movement less frequently indicating lethargy-like behaviors. Despite similar anesthesia dose-response curves, glyt1-/- mutants took over twice as long as their siblings to emerge from ketamine or propofol, mimicking findings from the human case study. Reducing glycine levels rescued timely emergence in glyt1-/- mutants, pointing to a causal role for elevated glycine. Brain-wide pERK staining showed elevated activity in hypnotic brain regions in glyt1-/- mutants under baseline conditions and a delay in sensorimotor integration during emergence from anesthesia. Our study links elevated activity in preoptic brain regions and reduced sensorimotor integration to lethargy-like behaviors and delayed emergence from propofol in glyt1-/- mutants.

Nonketotic Hyperglycinemia in Tunisia. Report upon a Series of 69 Patients.

AIM: The aim of the study is to report on epidemiological, clinical, and biochemical characteristics of nonketotic hyperglycinemia (NKH) in Tunisia. METHODS: Patients diagnosed with NKH in Laboratory of Biochemistry at Rabta hospital (Tunis, Tunisia) between 1999 and 2018 were included. Plasma and cerebrospinal fluid (CSF) free amino acids were assessed by ion exchange chromatography. Diagnosis was based on family history, patient's clinical presentation and course, and increased CSF to plasma glycine ratio. RESULTS: During 20 years, 69 patients were diagnosed with NKH, with 25 patients originating from Kairouan region. Estimated incidences were 1:55,641 in Tunisia and 1:9,684 in Kairouan. Consanguinity was found for 73.9% of the patients and 42% of the families have history of infantile death due to a disease of similar clinical course than the propositus. Clinical symptoms initiated within the first week of life in 75% of the patients and within the first 3 months in 95.7% ones. The phenotype was severe in 76.8% of the patients. Main symptoms were hypotonia, feeding difficulties, coma, apnea, and seizures. Most patients died within few days to months following diagnosis. CSF to plasma glycine ratio was increased in all patients. CSF and plasma glycine levels were negatively correlated with age of disease onset and severity. CONCLUSION: NKH is quite frequent in Tunisia. Kairouan region has the highest NKH incidence rate, worldwide. However, due to lack of confirmatory enzymatic and genetic tests, NKH diagnosis was based on first-line biochemical tests. Characterization of causal mutations is needed for accurate diagnosis and prenatal diagnosis of this devastating life-threatening disease.

Nonketotic hyperglycinemia: Clinical range and outcome of a rare neurometabolic disease in a single-center.

BACKGROUND: Nonketotic hyperglycinemia (NKH) is an autosomal recessive severe life-threatening catostrophic metabolic disorder. MATERIALS AND METHODS: The present study was conducted in a tertiary reference center in Turkey for six years period. The accurate diagnosis of six NKH patients was based on clinical history of the patients, neurological examinations, seizure semiology, serial electroencephalography (EEG) recordings, neuroimaging findings, metabolic tests and genetic analysis. RESULTS: The common clinical findings were hypotonia with severe head lag, poor feeding, poor sucking, and intractable seizures. The starting age of the symptoms was between birth and 45 days of age (median: 8 days). The starting age of the seizures was between 30 min of age and 45 days of age (median: 18 days). The age of accurate diagnosis was between 1 month of age and 5.5 months of age (mean: 3.75 ±â€¯1.69 months). The cerebrospinal fluid (CSF) to plasma GLY ratio of the patients was between 0.031 and 0.21 (median: 0.16). The EEG patterns of the patients were suppression-burst, hypsarrhythmia, multifocal epileptic activity, and right centro-occipital epileptic activity on admission. The neuroimaging findings were diffuse hypomyelination, corpus callosum (CC) hypoplasia, CC agenesis and brainstem hypoplasia on the magnetic resonance imaging and glycine peak was evidenced on magnetic resonance spectroscopy. Four of the patients were mutation-positive. CONCLUSIONS: If a child is encephalopathic and/or hypotonic with severe head lag, early evaluation of the EEG records should be made even without a history of clinical seizures. The disease has a heterogenous course and the clinical outcome depends on the mutation type.

Glycine Administration Alters MAPK Signaling Pathways and Causes Neuronal Damage in Rat Brain: Putative Mechanisms Involved in the Neurological Dysfunction in Nonketotic Hyperglycinemia.

High glycine (GLY) levels have been suggested to induce neurotoxic effects in the central nervous system of patients with nonketotic hyperglycinemia (NKH). Since the mechanisms involved in the neuropathophysiology of NKH are not totally established, we evaluated the effect of a single intracerebroventricular administration of GLY on the content of proteins involved in neuronal damage and inflammatory response, as well as on the phosphorylation of the MAPK p38, ERK1/2, and JNK in rat striatum and cerebral cortex. We also examined glial fibrillary acidic protein (GFAP) staining, a marker of glial reactivity. The parameters were analyzed 30 min or 24 h after GLY administration. GLY decreased Tau phosphorylation in striatum and cerebral cortex 30 min and 24 h after its administration. On the other hand, synaptophysin levels were decreased in striatum at 30 min and in cerebral cortex at 24 h after GLY injection. GLY also decreased the phosphorylation of p38, ERK1/2, and JNK 30 min after its administration in both brain structures. Moreover, GLY-induced decrease of p38 phosphorylation in striatum was attenuated by N-methyl-D-aspartate receptor antagonist MK-801. In contrast, synuclein, NF-κB, iκB, inducible nitric oxide synthase and nitrotyrosine content, and GFAP immunostaining were not altered by GLY infusion. It may be presumed that the decreased phosphorylation of MAPK associated with alterations of markers of neuronal injury induced by GLY may contribute to the neurological dysfunction observed in NKH.

[Hemichorea with Contralateral High Signal Intensity Putaminal Lesion on T1-Weighted Images in Non-Ketotic Hyperglycemia]. / Hemichorea mit T1-hyperintenser Signalalteration im kontralateralen Putamen bei nichtketotischer Hyperglykämie.

A 64-year-old diabetic female patient presented with involuntary unilateral hyperkinetic movements of the left limbs. Cranial MRI showed a contralateral high signal intensity putaminal lesion on T1-weighted images without any signal changes in the T2-weighted images. This finding is characteristic for hemichorea-hemiballism associated with insufficiently treated diabetes mellitus. Additionally, proton MR spectroscopy was performed and revealed a decreased N-acetylaspartate/creatine and N-acetylaspartate/choline ratio, indicating neuronal damage of the contralateral putamen.

[Amplitude-integrated electroencephalography in non-ketotic hyperglycinaemia]. / Electroencefalograma de amplitud integrada en la hiperglicinemia no cetósica.

TITLE: Electroencefalograma de amplitud integrada en la hiperglicinemia no cetosica.

Epileptic encephalopathy with suppression-bursts and nonketotic hyperglycinemia.

Bursts of paroxysmal activity alternating with lack of activity define the suppression-burst (SB) pattern that may be acute, in hypoxic-ischemic encephalopathy and barbiturate intoxication, or chronic in the course of early epileptic and neonatal myoclonic (NME) encephalopathies. Malformations, namely Aicardi syndrome and hemimegalencephaly, gene mutations - of ARX and MUNC18 -, and inborn errors of metabolism, namely glycine encephalopathy, are the main causes, with spasms indicating more likely a malformation whereas myoclonus indicates metabolic disorders. Although glycine encephalopathy has a very severe outcome in its classical expression, it may be transient in the neonatal period, for reasons yet not identified. Although glycine encephalopathy is the main identified cause of NME, the disorder may not cause SB, especially in cases with later onset. The biochemical bases, due to changes in one of the four proteins that compose the enzyme, are well understood, but there is no phenotype-genotype correlation. Prenatal diagnosis is based on villous biopsy. The mechanism of SB partly depends on glutamate - or glycine, the co-neurotransmitter for NMDA transmission - overflow, mainly in the immature brain but also in cases due to barbiturate intoxication. Energy supply defect may also be involved in some inborn errors of metabolism.

Nonketotic hyperglycinemia presenting as pulmonary hypertensive vascular disease and fatal pulmonary edema in response to pulmonary vasodilator therapy.

The association of pulmonary hypertensive vascular disease with nonketotic hyperglycinemia is rare. We describe 5 infants diagnosed with nonketotic hyperglycinemia, in whom pulmonary hypertensive vascular disease was the main presenting feature, and who developed severe pulmonary edema in response to pulmonary vasodilators.

Hyperglycemic nonketotic states and other metabolic imbalances.

Hemichorea and generalized chorea are well-recognized syndromes associated with nonketotic hyperglycemia. This condition usually occurs in older age, affects females more than men, and often heralds a new diagnosis of diabetes, usually type 2. It may resolve over days with treatment of the underlying hyperglycemia or persist for years. Magnetic resonance imaging is very characteristic, and shows T1 hyperdensity in the striatum. The underlying pathophysiology is not clear, but recent evidence suggests that the imaging may represent zinc, as opposed to calcium. Tetrabenazine has worked well when symptomatic treatment is required. Other rare causes of metabolic choreas include hypoparathyroid abnormalities, hypoglycemia, and hypernatremia.

Crisis occipitales con alteraciones electroencefalográficas como manifestación inicial de diabetes mellitus / Occipital seizures with electroencephalographic alterations as the initial manifestation of diabetes mellitus

La aparición de crisis motoras parciales en la hiperglucemia no cetósica es frecuente; sin embargo, es excepcional que el síntoma inicial de diabetes mellitus sea la aparición de crisis occipitales. Son escasísimas las descripciones electroencefalográficas de este cuadro. Un paciente varón de 56 años de edad acudió al servicio de urgencias por presentar, tres o cuatro veces al día desde hacía 4 días, episodios intermitentes de 30 min de duración y consistentes en visión de una luz de color azul-amarillo en el cuadrante inferior izquierdo de su campo visual. La valoración oftalmológica fue normal. En el interrogatorio dirigido refería tener desde hacía 4 meses poliuria, polidipsia y ganancia de peso. El estado general era bueno y el resto de la exploración neurológica fue normal. En la analítica se detectó una hiperglucemia de 339 mg/dl, leve elevación de la osmolaridad plasmática de 302 mOsm/kg y cetonuria negativa. En la resonancia cerebral se detectaron mínimas alteraciones no relacionadas con los síntomas visuales. En el electroencefalograma, coincidiendo con la aparición de los síntomas visuales, se registró una crisis occipital derecha. El paciente fue tratado con hidratación e insulina, con lo que desaparecieron completamente los síntomas visuales al cabo de 48 h (AU)

Focal motor seizures are common in nonketotic hyperglycemia but occipital seizures as the initial symptom of hyperglycemia are exceptional. Sporadic electroencephalographic description has rarely been reported. A 56-year-old man presented to the emergency department with a 4-day history of intermittent, 30-minute episodes of flashing lights (blue-yellow color), 3-4 times per day in his left lower temporal visual field. His past medical history was significant for hypercholesterolemia and hypertension. The results of the ophthalmology examination were normal. When asked, the patient reported polyuria, polydipsia and weight gain for the previous 4 months. His general state was good and no other neurological symptoms were present. Among the laboratory tests, non-ketonic hyperglycemia of 339 mg/dl and mild plasma hyperosmolarity of 302 mOsm/kg were found. The results of visual campimetry were normal. Brain magnetic resonance imaging showed minimal alterations unrelated to the visual symptoms. An electrographic seizure in the right occipital region associated with visual symptoms was recorded. The patient was treated with hydration and insulin and was completely asymptomatic after 48 hours (AU)

Early myoclonic encephalopathy and nonketotic hyperglycinemia.

Early myoclonic encephalopathy is an epileptic syndrome with different etiologies. Nonketotic hyperglycinemia is one cause. We describe two cases of early myoclonic encephalopathy, secondary to nonketotic hyperglycinemia, with fatal evolution in the neonatal period. These two cases may better clarify clinical findings that can be associated with impairment of glycine metabolism. Distinguishing features include agenesis of the corpus callosum in patient 1, and weight loss exceeding 10%, associated with metabolic acidosis, in patient 2. The burst-suppression electroencephalography pattern is relatively common in neonatal encephalopathies, and is frequently associated with seizures. Nonketotic hyperglycinemia is an inborn error of metabolism caused by mutations in genes encoding protein in the mitochondrial glycine cleavage system. The neonatal form is a severe, frequently lethal neurologic disease. When associated with electro-clinical features, progressive lethargy and hypotonia occur in the first days of life, progressing to apnea and often death. Prospective treatment with oral sodium benzoate, the N-methyl-d-aspartate receptor antagonist ketamine, and dextromethorphan can favorably modify the early neonatal course of severe nonketotic hyperglycinemia, but does not prevent poor long-term outcomes.

Nonketotic hyperglycinemia and acquired hydrocephalus.

Nonketotic hyperglycinemia is an autosomal recessive disorder of glycine metabolism. Patients generally present in the neonatal period with lethargy, feeding difficulty, hypotonia, apnea, poorly controlled convulsions, and coma. Myoclonic seizures and burst suppression pattern on electroencephalography are major findings of disease, but development of hydrocephalus is not an expected finding. The present case is that of an infant with acquired hydrocephalus, psychomotor retardation, and myoclonic seizures in whom the final diagnosis was nonketotic hyperglycinemia.

Glycine provokes lipid oxidative damage and reduces the antioxidant defenses in brain cortex of young rats.

Patients affected by nonketotic hyperglycinemia (NKH) usually present severe neurological symptoms and suffer from acute episodes of intractable seizures with leukoencephalopathy. Although excitotoxicity seems to be involved in the brain damage of NKH, the mechanisms underlying the neuropathology of this disease are not fully established. The objective of the present study was to investigate the in vitro effects of glycine (GLY), that accumulate at high concentrations in the brain of patients affected by this disorder, on important parameters of oxidative stress, such as lipid peroxidation (thiobarbituric acid-reactive substances (TBA-RS) and chemiluminescence) and the most important non-enzymatic antioxidant defense reduced glutathione (GSH) in cerebral cortex from 30-day-old rats. GLY significantly increased TBA-RS and chemiluminescence values, indicating that this metabolite provokes lipid oxidative damage. Furthermore, the addition of high doses of the antioxidants melatonin, trolox (soluble vitamin E) and GSH fully prevented GLY-induced increase of lipid peroxidation, indicating that free radicals were involved in this effect. GLY also decreased GSH brain concentrations, which was totally blocked by melatonin treatment. Finally, GLY significantly reduced sulfhydryl group content from a commercial GSH solution, but did not oxidize reduced cytochrome C. Our data indicate that oxidative stress elicited in vitro by GLY may possibly contribute at least in part to the pathophysiology of the neurological dysfunction in NKH.

Glycine decarboxylase mutations: a distinctive phenotype of nonketotic hyperglycinemia in adults.

Three unrelated adult patients with mild hyperglycinemia, infantile hypotonia, mental retardation, behavioral hyperirritability, and aggressive outbursts were screened for glycine decarboxylase (GLDC) mutations; two novel missense mutations (A389V and R739H) were found. Both mutations had a 6 to 8% of normal GLDC activities when expressed in COS7 cells.

Control of puberty by excitatory amino acid neurotransmitters and its clinical implications.

Excitatory amino acids, glutamate in particular, have a marked stimulatory effect on the reproductive axis, particularly at puberty. Glutamate, N-methyl-D-aspartate (NMDA), and kainate stimulate gonadotropin-releasing hormone (GnRH) secretion in immature mammals and NMDA receptor stimulation results in precocious puberty in rats and monkeys. Puberty is characterized by an increased sensitivity of GnRH to glutamate as well as an increase in glutaminase activity in the hypothalamus. Glutamatergic and GABAergic regulation of GnRH secretion seem strongly interdependent around puberty. In addition to the transsynaptic glutamatergic regulation of GnRH secretion, a coordinated activity of glutamatergic neurons and astroglial cells has been shown to play an active role in puberty. The participation of kainate receptors in the estradiol-induced advancement of puberty suggest that these receptors may be involved in the estradiol-mediated activation of GnRH secretion at puberty. A case of precocious puberty associated with hyperglycinemia illustrates the NMDA involvement in puberty in humans. In this patient, the occurrence of precocious puberty was thought to result from excessive stimulation by glycine of the NMDA receptors linked to the GnRH neurons. Glutamate plays several roles in the hypothalamic mechanism of puberty as it has been shown in animal models, but there are still few clinical data supporting the role of glutamate in human puberty.

[Clinical progress of neonatal non-ketotic hyperglycinemia under treatment]. / Evolución de la hiperglicinemia no cetósica neonatal en tratamiento.

INTRODUCTION: Non-ketotic hyperglycinemia is a congenital error in the breakdown of glycine. The most common type is the classical neonatal form, which begins at the age of a few days with symptoms of lethargy, hypotonia, myoclonia, convulsions, apneas and, frequently, ends in death. Survivors usually develop intractable epilepsy and mental retardation. There is no effective treatment for this condition, but trials have been carried out with a therapy that diminishes the levels of glycine, benzoate (BZ), and another that blocks the excitatory effect in N-methyl-D-aspartate receptors: dextromethorphan (DTM). CASE REPORT: We report on the progress of a classical neonatal case, which began at the age of a few hours with hypotonia and stupor, without myoclonias or seizures, but with a suppression wave trace on the electroencephalogram (EEG). Cerebrospinal fluid (CSF) showed glycine levels of 141 micromol/L (the normal level is 6.66 +/- 2.66 micromol/L), with a CSF/plasma ratio of 0.19 (the normal ratio is < 0.02). Treatment was started on the thirteenth day with BZ and DTM, and alertness and eye fixation improved in just three days; at the same time the EEG readings become normal. The glycine level in plasma returned to normal at two months and that in CSF was considerably reduced, although with CSF/plasma levels that were still high. At present the patient is 4 years old, has never had convulsions, EEG results have always been normal, and continues with BZ, DTM, carnitine and diet. The patient has presented a high degree of hypermotoric behaviour, but is currently more attentive and more sociable, has been walking from the age of 35 months and has a quotient in the different areas of development of 40-50. CONCLUSIONS: The clinical progress made by our patient could be said to be anything but negligible, and we therefore recommend that treatment should be started as early as possible after diagnosis.