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Introduction Guanidinoacetate methyltransferase (GAMT) deficiency is an inherited metabolic disorder that impairs the synthesis of creatine (CRE). Lack of CRE in the brain can cause intellectual disability, autistic-like behavior, seizures, and movement disorders. Identification at birth and immediate therapy can prevent intellectual disability and seizures. Here we report the first two cases of GAMT deficiency identified at birth by newborn screening (NBS) in Utah and New York. Methods NBS dried blood spots were analyzed by tandem mass spectrometry (MS/MS) using either derivatized or non-derivatized assays to detect guanidinoacetate (GUAC) and CRE. For any positive samples, a second-tier test using a more selective method, ultra-performance liquid chromatography (UPLC) combined with MS/MS, was performed to separate GUAC from potential isobaric interferences. Results NBS for GAMT deficiency began in Utah on June 1, 2015 using a derivatized method for the detection of GUAC and CRE. In May 2019, the laboratory and method transitioned to a non-derivatized method. GAMT screening was added to the New York State NBS panel on October 1, 2018 using a derivatized method. In New York, a total of 537,408 babies were screened, 23 infants were referred and one newborn was identified with GAMT deficiency. In Utah, a total of 273,902 infants were screened (195,425 with the derivatized method, 78,477 with the non-derivatized method), three infants referred and one was identified with GAMT deficiency. Mean levels of GUAC and CRE were similar between methods (Utah derivatized: GUAC = 1.20 ± 0.43 μmol/L, CRE = 238 ± 96 μmol/L; Utah non-derivatized: GUAC = 1.23 ± 0.61 μmol/L, CRE = 344 ± 150 μmol/L, New York derivatized: GUAC = 1.34 ± 0.57 μmol/L, CRE = 569 ± 155 μmol/L). With either Utah method, similar concentrations of GUAC are observed in first (collected around 1 day of age) and the second NBS specimens (routinely collected at 7–16 days of age), while CRE concentrations decreased in the second NBS specimens. Both infants identified with GAMT deficiency started therapy by 2 weeks of age and are growing and developing normally at 7 (Utah) and 4 (New York) months of age. Conclusions Newborn screening allows for the prospective identification of GAMT deficiency utilizing elevated GUAC concentration as a marker. First-tier screening may be incorporated into existing methods for amino acids and acylcarnitines without the need for new equipment or staff. Newborn screening performed by either derivatized or non-derivatized methods and coupled with second-tier testing, has a very low false positive rate and can prospectively identify affected children. SummaryCerebral creatine deficiency syndromes caused by defects in creatine synthesis can result in intellectual disability, and are preventable if therapy is initiated early in life. This manuscript reports the identification of two infants with GAMT deficiency (one of the cerebral creatine deficiency syndromes) by newborn screening and demonstrates NBS feasibility using a variety of methods.

Guanidinoacetate methyltransferase (GAMT) deficiency is a creatine deficiency disorder and an inborn error of metabolism presenting with progressive intellectual and neurological deterioration. As most cases are identified and treated in early childhood, adult phenotypes that can help in understanding the natural history of the disorder are rare. We describe two adult cases of GAMT deficiency from a consanguineous family in Pakistan that presented with a history of global developmental delay, cognitive impairments, excessive drooling, behavioral abnormalities, contractures and apparent bone deformities initially presumed to be the reason for abnormal gait. Exome sequencing identified a homozygous nonsense variant in GAMT: NM_000156.5:c.134G>A (p.Trp45*). We also performed a literature review and compiled the genetic and clinical characteristics of all adult cases of GAMT deficiency reported to date. When compared to the adult cases previously reported, the musculoskeletal phenotype and the rapidly progressive nature of neurological and motor decline seen in our patients is striking. This study presents an opportunity to gain insights into the adult presentation of GAMT deficiency and highlights the need for in-depth evaluation and reporting of clinical features to expand our understanding of the phenotypic spectrum.

Purpose Guanidinoacetate methyltransferase (GAMT) deficiency is an autosomal recessive disorder caused by pathogenic variants in GAMT. Brain creatine depletion and guanidinoacetate accumulation cause developmental delay, seizures and movement disorder. Treatment consists of creatine, ornithine and arginine-restricted diet. We initiated an international treatment registry using Research Electronic Data Capture (REDCap) software to evaluate treatment outcome. Methods Physicians completed an online REDCap questionnaire. Clinical severity score applied pre-treatment and on treatment. Results There were 22 patients. All had developmental delay, 18 had seizures and 8 had movement disorder. Based on the clinical severity score, 5 patients had a severe, 14 patients had a moderate and 3 patients had a mild phenotype. All patients had pathogenic variants in GAMT. The phenotype ranged from mild to moderate in patients with the most common c.327G > A variant. The phenotype ranged from mild to severe in patients with truncating variants. All patients were on creatine, 18 patients were on ornithine and 15 patients were on arginine- or protein-restricted diet. Clinical severity score improved in 13 patients on treatment. Developmental delay improved in five patients. One patient achieved normal development. Eleven patients became seizure free. Movement disorder resolved in four patients. Conclusion In our small patient cohort, there seems to be no phenotype–genotype correlation. Creatine and ornithine and/or arginine- or protein-restricted diet were the most useful treatment to improve phenotype.Purpose Guanidinoacetate methyltransferase (GAMT) deficiency is an autosomal recessive disorder caused by pathogenic variants in GAMT. Brain creatine depletion and guanidinoacetate accumulation cause developmental delay, seizures and movement disorder. Treatment consists of creatine, ornithine and arginine-restricted diet. We initiated an international treatment registry using Research Electronic Data Capture (REDCap) software to evaluate treatment outcome. Methods Physicians completed an online REDCap questionnaire. Clinical severity score applied pre-treatment and on treatment. Results There were 22 patients. All had developmental delay, 18 had seizures and 8 had movement disorder. Based on the clinical severity score, 5 patients had a severe, 14 patients had a moderate and 3 patients had a mild phenotype. All patients had pathogenic variants in GAMT. The phenotype ranged from mild to moderate in patients with the most common c.327G > A variant. The phenotype ranged from mild to severe in patients with truncating variants. All patients were on creatine, 18 patients were on ornithine and 15 patients were on arginine- or protein-restricted diet. Clinical severity score improved in 13 patients on treatment. Developmental delay improved in five patients. One patient achieved normal development. Eleven patients became seizure free. Movement disorder resolved in four patients. Conclusion In our small patient cohort, there seems to be no phenotype–genotype correlation. Creatine and ornithine and/or arginine- or protein-restricted diet were the most useful treatment to improve phenotype.

The urea cycle generates arginine that is one of the major precursors for creatine biosynthesis. Here we evaluate levels of creatine and guanidinoacetate (the precursor in the synthesis of creatine) in plasma samples (ns = 207) of patients (np = 73) with different types of urea cycle disorders (ornithine transcarbamylase deficiency (ns = 22; np = 7), citrullinemia type 1 (ns = 60; np = 22), argininosuccinic aciduria (ns = 81; np = 31), arginase deficiency (ns = 44; np = 13)). The concentration of plasma guanidinoacetate positively correlated (p, Graphical abstract Unlabelled Image

Guanidinoacetate methyltransferase (GAMT) deficiency is a rare inherited disorder characterized by creatine (Cr) depletion and guanidinoacetate (GAA) accumulation in body fluids. We report the first identified Chinese case, diagnosed in a 4-year-old girl with onset of global developmental. Low Cr and high GAA levels were detected in her serum and urine, and low Cr level in her brain. Compound heterozygous variants in GAMT gene were found, including a previously reported variant at c.491dupG which was inherited from her mother and a novel variant at c.564G>T, which was inherited from her father. The Cr and GAA levels returned back to normal after 3 months of treatment. After one year of treatment, the patient stopped taking antiepileptic drugs and her electroencephalogram (EEG) was also back to normal. The girl was followed up for five years and exhibited good results beyond our expectation. The results have shown that protein restriction with high-dose ornithine and creatine supplements have strong therapeutic potential for our patient.

Arginine:glycine amidinotransferase- and guanidinoacetate methyltransferase deficiency are severe neurodevelopmental disorders. It is not known whether mouse models of disease express a neuroanatomical phenotype. High-resolution magnetic resonance imaging (MRI) with advanced image analysis was performed in perfused, fixed mouse brains encapsulated with the skull from male, 10-12 week old Agat -exc and B6J.Cg-Gamt tm1Isb mice (n = 48; n = 8 per genotype, strain). T2-weighted MRI scans were nonlinearly aligned to a 3D atlas of the mouse brain with 62 structures identified. Local differences in brain shape related to genotype were assessed by analysis of deformation fields. Creatine (Cr) and guanidinoacetate (GAA) were measured with high-performance liquid chromatography (HPLC) in brain homogenates (n = 24; n = 4 per genotype, strain) after whole-body perfusion. Cr was decreased in the brain of Agat- and Gamt mutant mice. GAA was decreased in Agat-/- and increased in Gamt-/- . Body weight and brain volume were lower in Agat-/- than in Gamt-/- . The analysis of entire brain structures revealed corpus callosum, internal capsule, fimbria and hypothalamus being different between the genotypes in both strains. Eighteen and fourteen significant peaks (local areas of difference in relative size) were found in Agat- and Gamt mutants, respectively. Comparing Agat-/- with Gamt-/- , we found changes in three brain regions, lateral septum, amygdala, and medulla. Intra-strain differences in four brain structures can be associated with Cr deficiency, while the inter-strain differences in three brain structures of the mutant mice may relate to GAA. Correlating these neuroanatomical findings with gene expression data implies the role of Cr metabolism in the developing brain and the importance of early intervention in patients with Cr deficiency syndromes.

Guanidinoacetate Methyltransferase deficiency is an inborn error of metabolism that results in decreased creatine and increased guanidinoacetate (GAA) levels. Patients present neurological symptoms whose mechanisms are unclear. We investigated the effects of an intrastriatal administration of 10 μM of GAA (0.02 nmol/striatum) on energy metabolism, redox state, inflammation, glutamate homeostasis, and activities/immunocontents of acetylcholinesterase and Na+,K+-ATPase, as well as on memory acquisition. The neuroprotective role of creatine was also investigated. Male Wistar rats were pretreated with creatine (50 mg/kg) or saline for 7 days underwenting stereotactic surgery. Forty-eight hours after surgery, the animals (then sixty-days-old) were divided into groups: Control, GAA, GAA + Creatine, and Creatine. Experiments were performed 30 min after intrastriatal infusion. GAA decreased SDH, complexes II and IV activities, and ATP levels, but had no effect on mitochondrial mass/membrane potential. Creatine totally prevented SDH and complex II, and partially prevented COX and ATP alterations. GAA increased dichlorofluorescein levels and decreased superoxide dismutase and catalase activities. Creatine only prevented catalase and dichlorofluorescein alterations. GAA increased cytokines, nitrites levels and acetylcholinesterase activity, but not its immunocontent. Creatine prevented such effects, except nitrite levels. GAA decreased glutamate uptake, but had no effect on the immunocontent of its transporters. GAA decreased Na+,K+-ATPase activity and increased the immunocontent of its α3 subunit. The performance on the novel object recognition task was also impaired. Creatine partially prevented the changes in glutamate uptake and Na+,K+-ATPase activity, and completely prevented the memory impairment. This study helps to elucidate the protective effects of creatine against the damage caused by GAA.

Background Guanidinoacetate methyltransferase (GAMT) deficiency is a rare disorder (prevalence Purpose The objective was to report our experience, in order to focus on the importance of galenic preparations, unique resources to treat paediatric patients and orphan diseases. Material and methods The best regimen was established by a multidisciplinary approach in a function of patients’ weight and laboratory data (creatine and guanidinoacetate levels). An appropriate formulation was chosen according to active substance solubility and mucous membranes irritancy. Follow-up data were recorded retrospectively through medical records. Results Two Egyptian patients, 13 and 19 years’ old, weight 56 and 94 kg respectively, in 2012 were diagnosed with GAMT deficiency by the Paediatric Unit. We chose unitary solid formulation: ornithine maps of 5 g for the first patient (10 g/die), maps of 2 g for the second (7 g/die) (106 mg/kg/die). Creatine had been given as powder, with a specific doser, considering high daily amount: 11 gx2/die for the first patient and 12 gx3/die for the second patient (382 mg/Kg/die). Concerning sodium benzoate, an irritant for mucosa, a 20% liquid formulation was chosen, to be administered with fruit juice. Clinicians decided a posology of 59 mg/kg/die, so 9 mLx2/die were administered to the first patient, and 14 mLx2/die were administered to the second patient. Patients since 2012 have not manifested adverse drug reactions and therapy has brought a stable clinical picture: optimal creatine level, measured as peak at MR, and low levels of gaunidinoacetate on spot (8.3 mcM/L), indicative of good metabolic control. Conclusion GAMT deficiency is a rare cerebral disorder, with a high impact on patients’ quality of life. A palliative approach is possible only through galenic preparations. Personalised therapies allow these patients to manage intellectual and movement disability in a better way, contributing to improving and/or stabilising the clinical picture. Reference and/or acknowledgements Viau, et al. evidence-based-treatment of guanidinoacetate methyltransferase deficiency, 2013, Elsevier. No conflict of interest.

Guanidinoacetate methyltransferase (GAMT) deficiency is the second most common defect in the creatine metabolism pathway resulting in cerebral creatine deficiency syndrome (CCDS). We report three patients from two unrelated families, diagnosed with GAMT deficiency on next-generation sequencing. All the probands had happy predisposition as a predominant manifestation in addition to the reported features of global developmental delay, seizures, and microcephaly. This further expands the phenotype of CCDS. The workup for creatine deficiency disorder should be included in the diagnostic algorithm for children with nonsyndromic intellectual disability, especially in those with a happy demeanor. These cases exemplify the utility of magnetic resonance spectroscopy of the brain in the workup of nonsyndromic intellectual disability to diagnose a potentially treatable disorder. In addition, documentation of low serum creatinine may be supportive. Early diagnosis and treatment is essential for better prognosis.

Among cerebral creatine deficiency syndromes, guanidinoacetate methyltransferase (GAMT) deficiency can present the most severe symptoms, and is characterized by neurocognitive dysfunction due to creatine deficiency and accumulation of guanidinoacetate in the brain. So far, every patient was found with negligible GAMT activity. However, GAMT deficiency is thought under-diagnosed, in particular due to unforeseen mutations allowing sufficient residual activity avoiding creatine deficiency, but enough guanidinoacetate accumulation to be toxic. With poorly known GAA-specific neuropathological mechanisms, we developed an RNAi-induced partial GAMT deficiency in organotypic rat brain cell cultures. As expected, the 85% decrease of GAMT protein was insufficient to cause creatine deficiency, but generated guanidinoacetate accumulation causing axonal hypersprouting and decrease in natural apoptosis, followed by induction of non-apoptotic cell death. Specific guanidinoacetate-induced effects were completely prevented by creatine co-treatment. We show that guanidinoacetate accumulation without creatine deficiency is sufficient to affect CNS development, and suggest that additional partial GAMT deficiencies, which may not show the classical brain creatine deficiency, may be discovered through guanidinoacetate measurement.

Hyperargininaemia is a disorder of the last step of the urea cycle. It is an autosomal recessive disease caused by deficiency of liver arginase-1 and usually presents later in childhood with progressive neurological symptoms including marked spasticity. In contrast with other urea cycle disorders, hyperammonaemia is not usually present but can be a feature. A number of guanidine compounds may accumulate in the blood and cerebrospinal fluid of these patients, which could play an important pathophysiological role. Guanidinoacetate is of particular interest as a well-known potent epileptogenic compound in guanidinoacetate methyltransferase deficiency. We found markedly elevated guanidinoacetate levels in a patient with arginase deficiency, which dropped significantly in response to dietary and medical treatment. Measurement of guanidinoacetate and other guanidino compounds may, therefore, be important for therapeutic monitoring in arginase deficiency.

Background Guanidinoacetate methyltransferase (GAMT) deficiency causes cerebral creatine deficiency. Patients can have autistic behavior, seizures, intellectual disability, and severe speech delay. The goal of therapy is to increase creatine while reducing potentially neurotoxic guanidinoacetate concentrations. Here we evaluate how different therapies affect plasma guanidinoacetate levels in patients with GAMT deficiency. Methods Retrospective analysis of data from five new patients with GAMT deficiency (four with delays and seizures, one diagnosed at birth). Results The four symptomatic patients had decreased brain creatine by magnetic resonance spectroscopy and three also had abnormal globi pallidi by MRI. GAMT sequencing identified four previously reported mutations and one novel missense mutation (c.233T>A/p.V78E). Treatment with creatine (250–1000 mg/kg/day), ornithine (100–800 mg/kg/day), and sodium benzoate (50–135 mg/kg/day) supplements along with dietary protein restriction (0.8–1.5 g/kg/day) improved seizures and development with all patients becoming verbal. The patient treated at birth remains developmentally normal. Reduction in glycine and increase in ornithine levels significantly decreased plasma guanidinoacetate, with glycine levels being the best predictor of guanidinoacetate levels. In contrast, arginine levels were not significantly correlated with plasma guanidinoacetate. Conclusions Our results show that supplements of creatine, sodium benzoate (to reduce glycine) and ornithine reduce guanidinoacetate levels in patients with GAMT deficiency (dietary therapy was not evaluated in our study). Normal development with early therapy renders GAMT deficiency an ideal candidate for inclusion in newborn screening panels.

Creatine (Cr) plays an important role in muscle energy homeostasis by its participation in the ATP–phosphocreatine phosphoryl exchange reaction mediated by creatine kinase. Given that the consequences of Cr depletion are incompletely understood, we assessed the morphological, metabolic and functional consequences of systemic depletion on skeletal muscle in a mouse model with deficiency of l-arginine:glycine amidinotransferase (AGAT−/−), which catalyses the first step of Cr biosynthesis. In vivo magnetic resonance spectroscopy showed a near-complete absence of Cr and phosphocreatine in resting hindlimb muscle of AGAT−/− mice. Compared with wild-type, the inorganic phosphate/β-ATP ratio was increased fourfold, while ATP levels were reduced by nearly half. Activities of proton-pumping respiratory chain enzymes were reduced, whereas F1F0-ATPase activity and overall mitochondrial content were increased. The Cr-deficient AGAT−/− mice had a reduced grip strength and suffered from severe muscle atrophy. Electron microscopy revealed increased amounts of intramyocellular lipid droplets and crystal formation within mitochondria of AGAT−/− muscle fibres. Ischaemia resulted in exacerbation of the decrease of pH and increased glycolytic ATP synthesis. Oral Cr administration led to rapid accumulation in skeletal muscle (faster than in brain) and reversed all the muscle abnormalities, revealing that the condition of the AGAT−/− mice can be switched between Cr deficient and normal simply by dietary manipulation. Systemic creatine depletion results in mitochondrial dysfunction and intracellular energy deficiency, as well as structural and physiological abnormalities. The consequences of AGAT deficiency are more pronounced than those of muscle-specific creatine kinase deficiency, which suggests a multifaceted involvement of creatine in muscle energy homeostasis in addition to its role in the phosphocreatine–creatine kinase system.

Creatine metabolism disorders include guanidinoacetate methyltransferase (GAMT) deficiency, arginine:glycine amidinotransferase (AGAT) deficiency, and the creatine transporter (CT1-encoded by SLC6A8 gene) deficiency. Epilepsy is one of the main symptoms in GAMT and CT1 deficiency, whereas the occurrence of febrile convulsions in infancy is a relatively common presenting symptom in all the three above-mentioned diseases. GAMT deficiency results in a severe early onset epileptic encephalopathy with development arrest, neurologic deterioration, drug-resistant seizures, movement disorders, mental disability, and autistic-like behavior. In this disorder, epilepsy and associated abnormalities on electroencephalography (EEG) are more responsive to substitutive treatment with creatine monohydrate than to conventional antiepileptic drugs. AGAT deficiency is mainly characterized by mental retardation and severe language disorder without epilepsy. In CT1 deficiency epilepsy is generally less severe than in GAMT deficiency. All creatine disorders can be investigated through measurement of creatine metabolites in body fluids, brain proton magnetic resonance spectroscopy ((1) H-MRS), and molecular genetic techniques. Blood guanidinoacetic acid (GAA) assessment and brain H-MRS examination should be part of diagnostic workup for all patients presenting with epileptic encephalopathy of unknown origin. In girls with learning and/or intellectual disabilities with or without epilepsy, SLC6A8 gene assessment should be part of the diagnostic procedures. The aims of this review are the following: (1) to describe the electroclinical features of epilepsy occurring in inborn errors of creatine metabolism; and (2) to delineate the metabolic alterations associated with GAMT, AGAT, and CT1 deficiency and the role of a substitutive therapeutic approach on their clinical and electroencephalographic epileptic patterns.

Background: GAMT deficiency is an autosomal recessive disorder of creatine biosynthesis resulting in severe neurological complications in untreated patients. Currently available treatment is only successful to stop disease progression, but is not sufficient to reverse neurological complications occurring prior to diagnosis. Normal neurodevelopmental outcome in a patient, treated in the newborn period, highlights the importance of early diagnosis. Methods: Targeted mutation analysis (c.59G>C and c.327G>A) in the GAMT gene by the QIAxcel system and GAA measurement by a novel two-tier method were performed in 3000 anonymized newborn blood dot spot cards. Results: None of the targeted mutations were detected in any newborn. Two novel heterozygous variants (c.283_285dupGTC; p.Val95dup and c.278_283delinsCTCGATGCAC; p.Asp93AlafsX35) were identified by coincidence. Carrier frequency for these insertion/deletion types of GAMT mutations was 1/1475 in this small cohort of newborns. GAA levels were at or above the 99th percentile (3.12μmol/l) in 4 newborns. Second-tier testing showed normal results for 4 newborns revealing 0.1% false positive rate. No GAMT mutations were identified in 4 of the newborns with elevated GAA levels in the first tier testing. Conclusion: This is the first two-tier study to investigate carrier frequency of GAMT deficiency in the small cohort of newborn population to establish evidence base for the first steps toward newborn screening for this treatable neurometabolic disorder. © 2012 Elsevier Inc.

Creatine deficiency syndromes, which have only recently been described, represent a group of inborn errors of creatine synthesis (L-arginine-glycine amidinotransferase deficiency and guanidinoacetate methyltransferase deficiency) and transport (creatine transporter deficiency). Patients with creatine deficiency syndromes present with mental retardation expressive speech and language delay, and epilepsy. Patients with guanidinoacetate methyltransferase deficiency or creatine transporter deficiency may exhibit autistic behavior. The common denominator of these disorders is the depletion of the brain creatine pool, as demonstrated by in vivo proton magnetic resonance spectroscopy. For diagnosis, laboratory investigations start with analysis of guanidinoacetate, creatine, and creatinine in plasma and urine. Based on these findings, enzyme assays or DNA mutation analysis may be performed. The creatine deficiency syndromes are underdiagnosed, so the possibility should be considered in all children affected by unexplained mental retardation, seizures, and speech delay. Guanidinoacetate methyltransferase deficiency and arginine-glycine amidinotransferase deficiency are treatable by oral creatine supplementation, but patients with creatine transporter deficiency do not respond to this type of treatment.

Guanidinoacetate methyltransferase (GAMT) deficiency is a disorder of creatine biosynthesis, characterized by excessive amounts of guanidinoacetate in body fluids, deficiency of creatine in the brain, and presence of mutations in the GAMT gene. We present here 8 new patients with GAMT deficiency along with their clinical, biochemical and molecular data. The age at diagnosis of our patients ranges from 0 to 14 years. The age of onset of seizures usually ranges from infancy to 3 years. However, one of our patients developed seizures at age 5; progressing to myoclonic epilepsy at age 8 years and another patient has not developed seizures at age 17 years. Five novel mutations were identified: c.37ins26 (p.G13PfsX38), c.403G>T (p.D135Y), c.507_521dup15 (p.C169_S173dup), c.402C>G (p.Y134X) and c.610_611delAGinsGAA (p.R204EfsX63). Six patients had the c.327G>A (last nucleotide of exon 2) splice-site mutation which suggests that this is one of the most common mutations in the GAMT gene, second only to the known Portuguese founder mutation, c.59G>C (p.W20S). Our data suggests that the clinical presentation can be variable and the diagnosis may be overlooked due to unawareness of this disorder. Therefore, GAMT deficiency should be considered in the differential diagnosis of progressive myoclonic epilepsy as well as in unexplained developmental delay or regression with dystonia, even if the patient has no history of seizures. As more patients are reported, the prevalence of GAMT deficiency will become known and guidelines for prenatal diagnosis, newborn screening, presymptomatic testing and treatment, will need to be formulated.

Guanidinoacetate methyltransferase deficiency (GAMT-deficiency) is an inborn error of metabolism biochemically characterized by accumulation of guanidinoacetate (GAA) and depletion of creatine; the pathogenesis of brain dysfunction in this disorder is not yet established. In the present study we investigated the effect of intrastriatal administration of GAA on acetylcholinesterase (AChE) activity and on memory acquisition, consolidation and retrieval of step-down inhibitory avoidance task in rat. Results showed that GAA significantly increased AChE activity in rat striatum 30 min (50%) and 3 h (25%), but not 6 h after drug administration. GAA impaired test session performance when applied 30 min before training or after training, and before testing sessions, i.e., impaired memory acquisition, consolidation and retrieval. When injected with a 6 hour interval, GAA affected only memory retrieval. Although the mechanisms of action of GAA on AChE activity and on memory are unclear, these findings suggest that the accumulation of GAA found in patients with GAMT-deficiency may be one of the mechanisms involved in neural dysfunction. Further studies are necessary to evaluate these mechanisms.

Deficiency of guanidinoacetate methyltransferase (GAMT) causes creatine depletion and guanidinoacetate accumulation in brain with the latter deemed to be responsible for the severe seizure disorder seen in affected patients. We studied electrical brain activity and GABAA mediated mechanisms of B6J.Cg-Gamt(tm1Isb) mice. Electrocorticographic (ECoG) monitoring of pharmacological treatments with ornithine (5 % in drinking water for 5-18 days) and/or Picrotoxin (PTX) (a GABAA receptor antagonist) (1.5 mg/kg, I.P.) in Gamt(MUT) and Gamt(WT) groups [n = 3, mean age (SEM) = 6.9 (0.2) weeks]. Mice were fitted with two frontal and two parietal epidural electrodes under ketamine/xylazine anesthesia. Baseline and test recordings were performed for determination of seizure activity over a 2 h period. The ECoG baseline of Gamt(MUT) exhibited an abnormal monotonous cortical rhythm (7-8 Hz) with little variability during awake and sleep states compared to wild type recordings. Ornithine treatment and also PTX administration led to a relative normalization of the Gamt(MUT) ECoG phenotype. Gamt(WT) on PTX exhibited electro-behavioral seizures, whereas the Gamt(MUT) did not have PTX induced seizures at the same PTX dose. Gamt(MUT) treated with both ornithine and PTX did not show electro-behavioral seizures while ornithine elevated the PTX seizure threshold of Gamt(MUT) mice even further. These data demonstrate: (1) that there is expression of electrical seizure activity in this Gamt-deficient transgenic mouse strain, and (2) that the systemic availability of guanidinoacetate affects GABAA receptor function and seizure thresholds. These findings are directly and clinically relevant for patients with a creatine-deficiency syndrome due to genetic defects in GAMT and provide a rational basis for a combined ornithine/picrotoxin therapeutic intervention.

Guanidinoacetate methyltransferase deficiency (GAMT deficiency) is an inherited neurometabolic disorder clinically characterized by epilepsy and mental retardation and biochemically by accumulation of guanidinoacetate (GAA) and depletion of creatine. Although this disease is predominantly characterized by severe neurological findings, the underlying mechanisms of brain injury are not yet established. In the present study, we investigated the effect of intrastriatal administration of GAA on Na+, K+-ATPase activity, total (tCK), cytosolic (Cy-CK), and mitochondrial (Mi-CK) creatine kinase (CK) activities in rat striatum. We verified that Na+, K+-ATPase, tCK, and Mi-CK activities were significantly inhibited by GAA, in contrast to Cy-CK which was not affected by this guanidino compound. Since these enzyme activities can be affected by reactive species, we also investigated the effect of intrastriatal administration of GAA on thiobarbituric acid reactive substances (TBARS), an index of lipid peroxidation in rats. We found that this metabolite significantly increased this oxidative stress parameter. Considering the importance of Na+, K+-ATPase and CK activities for brain metabolism homeostasis, our results suggest that the inhibition of these enzymes by increased intracerebral levels of GAA may contribute to the neuropathology observed in patients with GAMT-deficiency.

The diagnosis of creatine deficiencies, a paediatric application of magnetic resonance spectroscopy that has already become a diagnostic tool in clinical practice, is reviewed and illustrated with results from recent examinations

Our study describes the adult clinical and biochemical spectrum of guanidinoacetate methyltransferase (GAMT) deficiency, a recently discovered inborn error of metabolism. The majority of the previous reports dealt with pediatric patients, in contrast to the present study. A total of 180 institutionalized patients with a severe mental handicap were investigated for urine and plasma uric acid and creatinine. Patients with an increased urinary uric acid/creatinine ratio and/or decreased creatinine were subjected to the analysis of guanidinoacetate (GAA). Four patients (three related and one from an unrelated family) were identified with GAMT-deficiency. A fifth patient had died before a biochemical diagnosis could be made. They all had shown a normal psychomotor development for the first year of life, after which they developed a profound mental retardation. Three out of four had convulsions and all four totally lacked the development of speech. Their GAMT activity in lymphoblasts was impaired and two novel mutations were identified: the 59 G > C and 506 G > A missense mutations. Urinary GAA was increased, but highly variable 347-1,624 mmol/mol creat (Controls

Guanidinoacetate methyltransferase (GAMT) deficiency is a good candidate disorder for newborn screening because early treatment appears to improve outcomes. We report elevation of guanidinoacetate in archived newborn dried blood spots for 3 cases (2 families) of GAMT deficiency compared with an unaffected carrier and controls. We also report a new case of a patient treated from birth with normal developmental outcome at the age of 42 months.

In this study, measurements of guanidinoacetate (GAA) and creatine (Cr) in urine, plasma, and cerebrospinal fluid (CSF) were performed using stable isotope dilution gas chromatography-mass spectrometry. Both compounds were analyzed in a single analysis. Reference values were established for GAA and Cr. These values were age dependent. No differences with gender were observed. Eight guanidinoacetate methyltransferase (GAMT) deficient patients and eight creatine transporter SLC6A8 deficient patients were investigated. In urine, plasma, and CSF of GAMT deficient patients increased levels of GAA are present. The SLC6A8 deficient patients all show increased creatine/creatinine (Cr/Crn) ratio in urine demonstrating the importance of the Cr/Crn ratio as a pathognomonic marker of the SLC6A8 deficiency.

Guanidinoacetate methyltransferase (GAMT) deficiency is an autosomal recessively inherited disorder of creatine biosynthesis. The disease occurs in early life with developmental delay or arrest and several neurological symptoms, e.g., seizures and dyskinesia. Both the deficiency of high-energy phosphates in neurons and the neurotoxic action of the accumulated metabolite guanidinoacetate (GAA) are candidate mechanisms for the pathophysiology of this disease. To examine a potential role of GAA accumulation, we analyzed the electrophysiological responses of neurons induced by GAA application in primary culture and acute murine brain slices. GAA evoked picrotoxin- and bicuculline-sensitive GABA(A) receptor-mediated chloride currents with an EC(50) of 167 microM in cortical neurons. Pathophysiologically relevant GAA concentrations hyperpolarized globus pallidus neurons and reduced their spontaneous spike frequency with an EC(50) of 15.1 microM. Furthermore, GAA acted as a partial agonist at heterologously expressed GABA(A) but not GABA(B) receptors. The interaction of GAA with neuronal GABA(A) receptors represents a candidate mechanism explaining neurological dysfunction in GAMT deficiency.

Phosphocreatine can to some extent compensate for the lack of ATP synthesis that is caused in the brain by deprivation of oxygen or glucose. Treatment of in vitro rat hippocampal slices with creatine increases the neuronal store of phosphocreatine. In this way it increases the resistance of the tissue to anoxic or ischemic damage. In in vitro brain slices pretreatment with creatine delays anoxic depolarization (AD) and prevents the irreversible loss of evoked potentials that is caused by transient anoxia, although it seems so far not to be active against milder, not AD- mediated, damage. Although creatine crosses poorly the blood-brain barrier, its administration in vivo at high doses through the intracerebroventricular or the intraperitoneal way causes an increase of cerebral phosphocreatine that has been shown to be of therapeutic value in vitro. Accordingly, preliminary data show that creatine pretreatment decreases ischemic damage in vivo.

Guanidinoacetate methyltransferase (GAMT) deficiency (McKusick 601240), an inborn error of creatine biosynthesis, is characterized by creatine depletion and accumulation of guanidinoacetate (GAA) in the brain. Treatment by oral creatine supplementation had no effect on the intractable seizures. Based on the possible role of GAA as an epileptogenic agent, we evaluated a dietary treatment with arginine restriction and ornithine supplementation in order to achieve reduction of GAA. In an 8-year-old Kurdish girl with GAMT deficiency arginine intake was restricted to 15 mg/kg/day (0.4 g natural protein/kg/day) and ornithine was supplemented with 100 mg/kg/day over a period of 14 months. The diet was enriched with 0.4 g/kg/day of arginine-free essential amino acid mixture and creatine treatment remained unchanged (1.1 g/kg/day). Guanidino compounds in blood, urine, and CSF were measured by means of cation-exchange chromatography. The combination of arginine restriction and ornithine supplementation led to a substantial and permanent decrease of arginine without disturbance of nitrogen detoxification. Formation of GAA was effectively reduced after 4 weeks of treatment and sustained thereafter. Biochemical effects were accompanied by a marked clinical improvement. Distinctly reduced epileptogenic activities in electroencephalography accompanied by almost complete disappearance of seizures demonstrates the positive effect of GAA reduction. This indicates for the first time that GAA may exert an important epileptogenic potential in man. Arginine restriction in combination with ornithine supplementation represents a new and rationale therapeutic approach in GAMT deficiency.

Background Guanidinoacetate methyltransferase deficiency is an autosomal recessively inherited disorder of creatine biosynthesis. We report a new patient with guanidinoacetate methyltransferase deficiency and her >3-year treatment outcome. Patient This is a 6-year-old girl who was diagnosed with guanidinoacetate methyltransferase deficiency at the age of 28 months. She presented with moderate global developmental delay, one afebrile seizure, and hypotonia between 6 and 18 months of life. She was treated with creatine and ornithine supplementation and a strict arginine-restricted diet for 42 months. Results Mutation analysis (compound heterozygous mutations, a known c.327G>A and a novel c.58dupT [p.Trp20LeufsX65]) and enzyme studies in primary fibroblasts confirmed the diagnosis. After 33 months of therapy, her cerebrospinal fluid guanidinoacetate level decreased from 47 to 5.3 times the normal level. Brain creatine by proton magnetic resonance spectroscopy increased by >75% but did not normalize in the basal ganglia and white matter after 3 years of therapy. Additional treatment with sodium benzoate for 17 months did not further improve plasma guanidinoacetate levels, which questions the relevance of this therapy. Conclusion Treatment did not improve moderate intellectual disability or normalize guanidinoacetate accumulation in the central nervous system.

The goal of this review is to present a comprehensive survey of the many intriguing facets of creatine (Cr) and creatinine metabolism, encompassing the pathways and regulation of Cr biosynthesis and degradation, species and tissue distribution of the enzymes and metabolites involved, and of the inherent implications for physiology and human pathology. Very recently, a series of new discoveries have been made that are bound to have distinguished implications for bioenergetics, physiology, human pathology, and clinical diagnosis and that suggest that deregulation of the creatine kinase (CK) system is associated with a variety of diseases. Disturbances of the CK system have been observed in muscle, brain, cardiac, and renal diseases as well as in cancer. On the other hand, Cr and Cr analogs such as cyclocreatine were found to have antitumor, antiviral, and antidiabetic effects and to protect tissues from hypoxic, ischemic, neurodegenerative, or muscle damage. Oral Cr ingestion is used in sports as an ergogenic aid, and some data suggest that Cr and creatinine may be precursors of food mutagens and uremic toxins. These findings are discussed in depth, the interrelationships are outlined, and all is put into a broader context to provide a more detailed understanding of the biological functions of Cr and of the CK system.

Recently, 3 patients with a creatine synthesis defect have been described. They presented with developmental regression, extrapyramidal movement abnormalities, and intractable epilepsy, and they improved with treatment of creatine monohydrate. We report 2 unrelated boys with a creatine synthesis defect and nonspecific presenting signs of psychomotor retardation, behavioral problems, and, in 1, mild epilepsy. Metabolic urine screening revealed elevations in all metabolites, expressed as millimoles per mole of creatinine, which suggests decreased creatinine excretion. This finding led to the correct diagnosis. We propose to include the assessment of the overall concentrations of amino acids and organic acids relative to creatinine in routine metabolic urine screening.

In gyrate atrophy of the choroid and retina with hyperornithinaemia (GA), a genetically determined deficiency of ornithine delta-aminotransferase activity leads to high ornithine concentrations in body fluids. GA is characterized by centripetally progressing retinal and choroidal destruction and selective atrophy with tubular aggregates in type II skeletal muscle fibres. These findings have been suggested to be mediated by hyperornithinaemia-induced deficiency of high-energy creatine phosphate. As abnormal brain magnetic resonance images and electroencephalograms are found in another disorder of creatine metabolism, guanidinoacetate methyltransferase deficiency, we investigated the central nervous system involvement in GA, which seems to be associated with a milder degree of phosphocreatine deficiency. We compared 23 untreated GA patients with age-matched healthy controls, and with 9 patients who had received creatine or creatine precursor supplementation daily for several years. The mean age of the patients (32 +/- 18 years) was similar to that of the controls (36 +/- 22 years). The MRI or EEG findings of the patients on creatine supplementation did not differ from those of the untreated group. Brain MRI revealed degenerative lesions in the white matter in 50% of the GA patients, and 70% of the patients had premature atrophic changes, with a striking increase in the number of Virchow's spaces. Of the patients whose EEG was recorded, 58% had abnormal slow background activity, focal lesions or high-amplitude beta rhythm (50 microV). The EEG findings were not associated with the MRI changes or with the age or the sex of the patients. Early degenerative and atrophic brain changes and abnormal EEG are thus features of GA, in addition to the well-characterized eye and muscle manifestations.

Hepatic guanidinoacetate methyltransferase deficiency induces a deficiency of creatine/phosphocreatine in muscle and brain and an accumulation of guanidinoacetic acid (GAA), the precursor of creatine. We describe a patient with this defect, a 4-year-old girl with a dystonic-dyskinetic syndrome in addition to developmental delay and therapy-resistant epilepsy. Several methods were used in the diagnosis of the disease: (1) the creatinine excretion in 24-hour urine was significantly lowered, whereas the creatinine concentration in plasma and in randomly collected urine was not strikingly different from control values; (2) the Sakaguchi staining reaction of guanidino compounds in random urine samples indicated an enhanced GAA excretion; (3) GAA excretion measured quantitatively by guanidino compound analysis using an amino acid analyzer was markedly elevated in random urine samples; (4) in vivo 1H magnetic resonance spectroscopy (MRS) revealed a strong depletion of creatine and an accumulation of GAA in brain; (5) in vivo phosphorus 31 MRS showed a strong decrease of the phosphocreatine resonance and a resonance identified as guanidinoacetate phosphate; and (6) in vitro 1H MRS showed an absence of creatine and creatinine resonances in cerebrospinal fluid and the occurrence of GAA in urine. For early detection of this disease, we recommend the Sakaguchi staining reaction of urine from patients with dystonic-dyskinetic syndrome, seizures, and psychomotor retardation. Positive results should result in further investigations including quantitative guanidino compound analysis and both in vivo and in vitro MRS. Although epilepsy was not affected by orally administered creatine (400 to 500 mg/kg per day), this treatment resulted in clinical improvement and an increase of creatine in cerebrospinal fluid and brain tissue.

Aim. Describe the seizure-related manifestations of guanidinoacetate methyltransferase (GAMT) deficiency in two new cases and compare these to the related literature. Methods. We reviewed the clinical and electroencephalographic manifestations of two siblings with GAMT deficiency. We also performed a thorough literature review of all cases of GAMT deficiency, using the PubMed database, and compared our findings to those previously reported. Results. One sibling presented with Lennox-Gastaut syndrome while the second had manifestations of late-onset West syndrome. Based on a literature search, we found that the clinical picture of GAMT deficiency has been described in a total of 58 cases, including our two patients, 45 of whom had at least some description of EEG and/or seizure manifestation. Epilepsy was present in 81%, with age at onset usually between 10 months and 3 years. Drug resistance was observed in approximately 45%. Initial seizures were febrile, tonic, or tonic-clonic. Drop attacks and generalised seizures were the most frequent seizure type. Absence and febrile seizures also occurred. Less frequently, focal seizures and late-onset infantile spasms (one prior case) were observed. Multifocal spikes and generalised

We collected data on 48 patients from 38 families with guanidinoacetate methyltransferase (GAMT) deficiency. Global developmental delay/intellectual disability (DD/ID) with speech/language delay and behavioral problems as the most affected domains was present in 44 participants, with additional epilepsy present in 35 and movement disorder in 13. Treatment regimens included various combinations/dosages of creatine-monohydrate, L-ornithine, sodium benzoate and protein/arginine restricted diets. The median age at treatment initiation was 25.5 and 39 months in patients with mild and moderate DD/ID, respectively, and 11 years in patients with severe DD/ID. Increase of cerebral creatine and decrease of plasma/CSF guanidinoacetate levels were achieved by supplementation with creatine-monohydrate combined with high dosages of t-ornithine and/or an arginine-restricted diet (250 mg/kg/d L-arginine). Therapy was associated with improvement or stabilization of symptoms in all of the symptomatic cases. The 4 patients treated younger than 9 months had normal or almost normal developmental outcomes. One with inconsistent compliance had a borderline IQ at age 8.6 years. An observational GAMT database will be essential to identify the best treatment to reduce plasma guanidinoacetate levels and improve long-term outcomes. (C) 2013 The Authors. Published by Elsevier Inc. All rights reserved.

Guanidinoacetate methyltransferase (GAMT) deficiency is a rare disorder of creatine synthesis resulting in cerebral creatine depletion. We present a 38-year-old patient, the first Japanese case of GAMT deficiency. Developmental delay started after a few months of age with a marked delay in language, which resulted in severe intellectual deficit. She showed hyperactivity and trichotillomania from childhood. Epileptic seizures appeared at 18 months and she had multiple types of seizures including epileptic spasms, brief tonic seizures, atypical absences, complex partial seizures with secondary generalization, and “drop” seizures. They have been refractory to multiple antiepileptic drugs. Although there have been no involuntary movements, magnetic resonance imaging revealed T2 hyperintense lesions in bilateral globus pallidi. Motor regression started around 30 years of age and the patient is now able to walk for only short periods. Very low serum creatinine levels measured by enzymatic method raised a suspicion of GAMT deficiency, which was confirmed by proton magnetic resonance spectroscopy and urinary guanidinoacetate assay. GAMT gene analysis revealed that the patient is a compound heterozygote of c.578A>G, p.Gln193Arg and splice site mutation, c.391G>C, p.Gly131Arg, neither of which have been reported in the literature. We also identified two aberrant splice products from the patient’s cDNA analysis. The patient was recently started on supplementation of high-dose creatine and ornithine, the effects of which are currently under evaluation. Although rare, patients with developmental delay, epilepsy, behavioral problems, and movement disorders should be vigorously screened for GAMT deficiency, as it is a treatable disorder.

The lack of creatine in the central nervous system causes a severe but treatable neurological disease. Three inherited defects, AGAT, GAMT, and CrT deficiency, compromising synthesis and transport of creatine have been discovered recently. Together these so-called creatine deficiency syndromes (CDS) might represent the most frequent metabolic disorders with a primarily neurological phenotype. Patients with CDS present with global developmental delays, mental retardation, speech impairment especially affecting active language, seizures, extrapyramidal movement disorder, and autism spectrum disorder. The two defects in the creatine synthesis, AGAT and GAMT, are autosomal recessive disorders. They can be diagnosed by analysis of the creatine, guanidinoacetate, and creatinine in body fluids. Treatment is available and, especially when introduced in infancy, has a good outcome. The defect of creatine transport, CrT, is an X-linked condition and perhaps the most frequent reasons for X-linked mental retardation. Diagnosis is made by an increased ratio of creatine to creatinine in urine, but successful treatment still needs to be explored. CDS are under-diagnosed because easy to miss in standard diagnostic workup. Because CDS represent a frequent cause of cognitive and neurological impairment that is treatable they warrant consideration in the workup for genetic mental retardation syndromes, for intractable seizure disorders, and for neurological diseases with a predominant lack of active speech.

Creatine in the human body is derived from two sources: the diet and endogenous synthesis. Biosynthesis involves two enzymes: l-arginine:glycine amidinotransferase (EC 2.1.4.1) and guanidinoacetate N -methyltransferase (GAMT; EC 2.1.1.2). Defects in both of these enzymes lead to inborn errors of metabolism (1)(2). Deficiency of l-arginine:glycine amidinotransferase has been reported very recently in two patients by Item et al. (3) and Bianchi et al. (4). GAMT deficiency was first described in 1994 (1)(5). The clinical presentation of the disease varies widely (2)(6). Some patients present with intractable epilepsy, extrapyramidal movement disorder, and severe retardation, whereas other patients have much milder symptoms and show only mild retardation and autistic behavior. The aspecific clinical picture of GAMT deficiency and the relatively good treatment options makes a good diagnostic strategy important. Magnetic resonance spectroscopy of the brains of affected patients shows absence of the creatine/creatine phosphate peak. However, magnetic resonance spectroscopy may not be performed on all patients with mild symptoms. Screening for metabolic disorders may also aid in the diagnosis because generalized increases in amino acids, organic acids, and other metabolites can be found when their concentrations are calculated relative to the creatinine concentration (2). The relatively low creatinine excretion in GAMT patients, which is attributable to the creatine deficiency, gives falsely increased values for a range of metabolites when they are calculated relative to creatinine. When GAMT deficiency is suspected, analysis of guanidinoacetate in plasma should be performed (7)(8). Confirmation of the defect can be obtained by enzymatic and DNA analysis (9)(10). Ilas et al. (11) described an assay for the determination of GAMT in fibroblasts and lymphoblasts. This method uses 14C-labeled guanidinoacetate as substrate. Product formation ([14C]creatine) is determined by HPLC with detection …

Creatine (Cr) and phosphocreatine play an essential role in energy storage and transmission. Maintenance of creatine pool is provided by the diet and by de novo synthesis, which utilizes arginine, glycine and s-adenosylmethionine as substrates. Three primary Cr deficiencies exists: arginine:glycine amidinotransferase deficiency, guanidinoacetate methyltransferase deficiency and the defect of Cr transporter SLC6A8. Secondary Cr deficiency is characteristic of ornithine-aminotransferase deficiency, whereas non-uniform Cr abnormalities have anecdotally been reported in patients with urea cycle defects (UCDs), a disease category related to arginine metabolism in which Cr must be acquired by de novo synthesis because of low dietary intake. To evaluate the relationships between ureagenesis and Cr synthesis, we systematically measured plasma Cr in a large series of UCD patients (i.e., OTC, ASS, ASL deficiencies, HHH syndrome and lysinuric protein intolerance). Plasma Cr concentrations in UCDs followed two different trends: patients with OTC and ASS deficiencies and HHH syndrome presented a significant Cr decrease, whereas in ASL deficiency and lysinuric protein intolerance Cr levels were significantly increased (23.5 vs. 82.6 μmol/L; p < 0.0001). This trend distribution appears to be regulated upon cellular arginine availability, highlighting its crucial role for both ureagenesis and Cr synthesis. Although decreased Cr contributes to the neurological symptoms in primary Cr deficiencies, still remains to be explored if an altered Cr metabolism may participate to CNS dysfunction also in patients with UCDs. Since arginine in most UCDs becomes a semi-essential aminoacid, measuring plasma Cr concentrations might be of help to optimize the dose of arginine substitution.

A 4-year-old female with history of developmental regression and autistic features was diagnosed with guanidinoacetate methyltransferase deficiency at age 21 months. Upon treatment, she showed improvements in her developmental milestones, sensorial-neural hearing loss and brain atrophy on cranial-MRI. The creatine/choline ratio increased 82% in basal ganglia and 88% in white matter on cranial MR-spectroscopy. The CSF guanidinoacetate decreased 80% after six months of ornithine and creatine supplementation and an additional 8% after 18 months of additional arginine restricted diet. We report the most favorable clinical and biochemical outcome on treatment in our patient.

In a patient with extrapyramidal movement disorder and extremely low creatinine concentrations in serum and urine, in vivo proton magnetic resonance spectroscopy disclosed a generalized depletion of creatine in the brain. Oral substitution of arginine, a substrate for creatine synthesis, resulted in an increase of brain guanidinoacetate as the immediate precursor of creatine but did not elevate cerebral creatine levels. In contrast, oral substitution of creatine-monohydrate led to a significant increase of brain creatine, a decrease of brain guanidinoacetate, and a nor-malization of creatinine in serum and urine. Phosphorus magnetic resonance spectroscopy of the brain revealed no detectable creatine-phosphate before oral substitution of creatine and a significant increase afterward. Partial restoration of cerebral creatine concentrations was accompanied by improvement of the patient's neurologic symptoms. This is the first report of a patient with complete creatine deficiency in the brain. Magnetic resonance spectroscopy during arginine and creatine treatment point to an inborn error of creatine biosynthesis at the level of guanidinoacetete-methyltransferase.

Guanidinoacetate methyltransferase (GAMT) deficiency is a disorder of creatine biosynthesis, characterized by early-onset learning disability and epilepsy in most affected children. Severe expressive language delay is a constant feature even in the mildest clinical phenotypes. We report the clinical, biochemical, imaging, and treatment data of two female siblings (18y and 13y) with an unusual phenotype of GAMT deficiency. The oldest sibling had subacute onset of a movement disorder at age 17 years, later than has been previously reported. The younger sibling had better language skills than previously described in this disorder. After treatment with creatine, arginine restriction and ornithine-supplemented diet, seizure severity and movement disorder were reduced but cognition did not improve. This report confirms that GAMT deficiency, a heterogeneous, potentially treatable disorder, detected by increased levels of guanidinoacetate in body fluids (e.g. plasma or urine) or by an abnormal creatine peak on magnetic resonance spectroscopy, should be considered in patients of any age with unexplained, apparently static learning disability and epilepsy.

An increasing number of disorders of metabolism are becoming amenable to the treatment, and GAMT deficiency is one of them. The symptoms and signs are reviewed, emphasising that delayed language development is a particular feature. Other symptoms include learning disorders, autistic behaviour, epileptic seizures, and movement disorders. The condition is inherited in an autosomal recessive manner, and mutations in the GAMT gene severely affect the activity of guanidinoacetate. The MRI scan shows an increased signal in the globus pallidus, and the diagnosis is confirmed by finding increased guanidinoacetate in the urine and a low plasma creatine. Other methods of diagnosis are discussed. Treatment is based on giving creatine supplementation orally and a low-protein diet with restricted arginine and increased ornithine. This results in improvement of many of the symptoms, especially of the epileptic seizures and the abnormal movements. It is justifiable to consider this condition in any patient with unexplained learning disorders.

Cerebral creatine deficiency syndromes (CCDSs) are a group of inborn errors of creatine metabolism comprising two autosomal recessive disorders that affect the biosynthesis of creatine – i.e. arginine:glycine amidinotransferase deficiency (AGAT; MIM 602360) and guanidinoacetate methyltransferase deficiency (GAMT; MIM 601240) – and an X-linked defect that affects the creatine transporter, SLC6A8 deficiency (SLC6A8; MIM 300036). The biochemical hallmarks of these disorders include cerebral creatine deficiency as detected in vivo by 1H magnetic resonance spectroscopy (MRS) of the brain, and specific disturbances in metabolites of creatine metabolism in body fluids. In urine and plasma, abnormal guanidinoacetic acid (GAA) levels are found in AGAT deficiency (reduced GAA) and in GAMT deficiency (increased GAA). In urine of males with SLC6A8 deficiency, an increased creatine/creatinine ratio is detected. The common clinical presentation in CCDS includes mental retardation, expressive speech and language delay, autistic like behaviour and epilepsy. Treatment of the creatine biosynthesis defects has yielded clinical improvement, while for creatine transporter deficiency, successful treatment strategies still need to be discovered. CCDSs may be responsible for a considerable fraction of children and adults affected with mental retardation of unknown etiology. Thus, screening for this group of disorders should be included in the differential diagnosis of this population. In this review, also the importance of CCDSs for the unravelling of the (patho)physiology of cerebral creatine metabolism is discussed

Guanidinoacetate methyltransferase deficiency typically presents with muscular hypotonia, global developmental delay, extrapyramidal signs, and seizures during infancy and childhood. The authors report a 5-year-old child with guanidinoacetate methyltransferase deficiency who presented with severe speech delay, emphasizing the importance of an early screening for disorders of creatine synthesis and transport in every infant or child with isolated speech delay of unknown cause.

Prospective observation in a neonate with guanidinoacetate methyltransferase deficiency (GAMT-D), a severe neurometabolic disorder, revealed increased guanidinoacetate levels at birth. After 14-month treatment with creatine, high-dose ornithine, benzoate, and an arginine-restricted diet, the patient's development is normal and she does not present any symptoms of GAMT-D. The authors' observation indicates that early detection of GAMT-D is possible in the neonatal period, and presymptomatic treatment may prevent its manifestation.

Guanidinoacetate methyltransferase (GAMT; EC 2.1.1.2) deficiency (OMIM 601240) is an autosomal recessive disorder of creatine biosynthesis, characterized clinically by mental retardation, language delay, extrapyramidal movements, epilepsy, and autistic behavior (1). Biochemically, GAMT deficiency is characterized by depletion of creatine and accumulation of guanidinoacetate (GAA) in the brain and body fluids (2). Treatment by creatine supplementation (combined with arginine restriction and ornithine supplementation) partially restores (∼70%) cerebral creatine, reduces seizures, and improves behavior, but it does not reverse the mental retardation (3). We have described a method to measure GAA and creatine in plasma and urine by liquid chromatography–tandem mass spectrometry (LC-MS/MS) (4). In the present study, we validated this method for measurement of GAA and creatine in amniotic fluid, and we report the first GAMT prenatal diagnosis based on a combination of molecular and biochemical investigations. We …

Cerebral creatine and guanidinoacetate and blood and urine metabolites were studied in four patients with argininosuccinate synthetase (ASS) or argininosuccinate lyase (ASL) deficiency receiving large doses of arginine. Urine and blood metabolites varied largely. Cerebral guanidinoacetate was increased in all patients, while cerebral creatine was low in ASS and high in ASL deficiency. Because high cerebral guanidinoacetate might be toxic, lowering the arginine supplementation with additional creatine supplementation might be important. (c) 2006 Elsevier Inc. All rights reserved.

Guanidinoacetate methyltransferase deficiency is a recently described inborn error of creatine biosynthesis that responds to treatment with oral creatine supplementation. The previously reported clinical features consist of developmental arrest and an extrapyramidal movement disorder. We describe a patient who presented with epilepsy, global developmental delay, and a persistently low plasma creatinine level. The diagnosis was established by measuring urinary guanidinoacetate and by demonstrating absence of the creatine/phosphocreatine peak in the patient's basal ganglia in 1H magnetic resonance spectroscopy. The clinical and biochemical abnormalities responded to creatine replacement.

A novel disease of the metabolism of creatine and guanidinoacetate (GUAC) in a 22-month-old child has been reported recently from our department (Stockler et al 1994). Following an uneventful development in the first 3 months, the boy developed muscular hypotonia, weakness and a distinct extrapyramidal disorder with hemiballistic-dystonic movements. In magnetic resonance spectroscopy of the brain the absence of a creatine signal and a massively increased GUAC signal eventually led to the diagnosis of guanidinoacetate methyltransferase deficiency. The boy was successfully treated with oral creatine monohydrate. Standard laboratory results were not very specific, so that the need has arisen for a readily available method to screen for the elevated levels of guanidinoacetate seen in this disease. Presently HPLC is the established method (Marescau et al 1985). We have developed a simple mass fragmentographic method for the determination of GUAC in urine and plasma. The reaction of the guanidino group of GUAC with hexafluoroacetylacetone (Malcolm and Marten 1976) results in the formation of a bis(trifluoromethyl)pyrimidine derivative and the carboxyl group is then converted to the trimethylsilyl ester. 2-Phenylbutyrate is used as the internal standard since this has a suitable retention time and is widely available.

Deficiency of guanidinoacetate methyltransferase (GAMT), the first described creatine biosynthesis defect, leads to depletion of creatine and phosphocreatine, and accumulation of guanidinoacetate in brain. This results in epilepsy, mental retardation, and extrapyramidal movement disorders. Investigation of skeletal muscle by proton and phosphorus magnetic resonance spectroscopy before therapy demonstrated the presence of considerable amounts of creatine and phosphocreatine, and accumulation of phosphorylated guanidinoacetate in a 7-year-old boy diagnosed with GAMT deficiency, suggesting separate mechanisms for creatine uptake and synthesis in brain and skeletal muscle. The combination of creatine supplementation and a guanidinoacetate-lowering therapeutic approach resulted in improvement of clinical symptoms and metabolite concentrations in brain, muscle, and body fluids.