B. Marescau

Creatine deficiency syndrome caused by guanidinoacetate methyltransferase deficiency: Diagnostic tools for a new inborn error of metabolism

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.

Guanidino compound levels in brain regions of non-dialyzed uremic patients

Guanidino compounds have been suggested to contribute to the complex neurological complications associated with uremia. Several of them have previously been reported to accumulate in physiological fluids of renal insufficient subjects. We report on guanidino compound levels in 28 brain regions in control and uremic brains. In all brain regions studied, in controls as well as in uremic patients, concentrations of alpha-keto-delta-guanidinovaleric acid, alpha-N-acetylarginine and beta-guanidinopropionic acid remained below detection limits. Creatine, guanidinoacetic acid, argininic acid, gamma-guanidinobutyric acid, arginine and homoarginine were not increased in uremic patients. Argininic acid and homoarginine were detectable in some brain regions only. Creatine concentrations varied from 2500 +/- 2100 nmol/g tissue in hypophysis to 10500 +/- 1200 nmol/g tissue in cerebellar cortex. Even more pronounced regional differences were found for gamma-guanidinobutyric acid with the lowest concentration in the caudate nucleus (0.6 +/- 0.3 nmol/g tissue) and highest in substantia nigra, pallidum and cerebellar dentate nucleus (8.3 +/- 2.8 nmol/g tissue). The guanidinosuccinic acid levels were below detection limit in controls in the majority of brain regions. Taking into account the detection limit of guanidinosuccinic acid for a certain amount of tissue applied to the analytical system, important increases (approx. up to > 100 fold) were observed in all brain regions of uremic patients. Accumulation of guanidinosuccinic acid increased with increasing degree of renal failure with levels up to 65 nmol/g tissue in the hypophysis. Creatinine concentrations were also found to be increased in uremic brain regions but increases seemed to be less strictly related to serum urea levels. Guanidine and methylguanidine were found only occasionally in brain regions of controls while respectively 100- and 30-fold increases were found in brain regions of uremic subjects. Levels of guanidinosuccinic acid and creatinine in uremic brain were comparable to those previously observed in brain of experimental animals displaying convulsions following intraperitoneal injection of the respective compounds. Our findings further establish guanidino compounds as probable uremic toxins contributing to the neurological complications in uremia.

Guanidino compounds in uraemic dialysed patients

The concentrations of guanidino compounds in blood are raised in uraemic patients and may have toxic effects. The concentrations of 13 guanidino compounds in serum were measured in 29 patients with chronic renal failure treated by chronic intermittent haemodialysis using liquid cation exchange chromatography with a highly sensitive fluorescence detection method. For taurocyamine we used another column system. Substantial increases in guanidinosuccinic acid, creatine, N-alpha-acetylarginine, creatinine, guanidine and methylguanidine were found. The values obtained for taurocyamine and beta-guanidinoproprionic acid were much lower than those reported by others: a much smaller increase was observed for beta-guanidinoproprionic acid and taurocyamine was only doubled in 4 of 29 uraemic patients. The concentrations of other guanidino compounds such as arginine and guanidinoacetic acid were normal. No differences were found between the polycystic renal disease, the chronic glomerulonephritis and the interstitial nephritis subgroups.

Guanidino Compound Analysis as a Complementary Diagnostic Parameter for Hyperargininemia: Follow-Up of Guanidino Compound Levels during Therapy

ABSTRACT: The aim of this collaborative study was to investigate whether guanidino compound analyses in the biologic fluids can be used as a complementary diagnostic parameter for hyperargininemia. Guanidino compounds were determined in the biologic fluids of all known living hyperargininemic patients using a cation exchange Chromatographie system with a fluorescence detection method. The serum arginine, homoarginine, α-keto-δ-guanidino-valeric acid, argininic acid, and N-α-acetylarginine levels of all the hyperargininemic patients are higher than the normal range. Similar increases were seen for the urinary excretion of α-keto-δ-guanidinovaleric acid and argininic acid. Untreated hyperargininemic patients have the highest guanidino compound levels in cerebrospinal fluid. However, even under therapy, the arginine, homoarginine, α-keto-δ-guanidinovaleric acid, and argininic acid levels in cerebrospinal fluid are still increased. Protein restriction alone is not sufficient to normalize the hyperargininemia, but protein restriction together with supplementation of essential amino acids with or without sodium benzoate decreases further the arginine levels. However, whereas the argininemia can be normalized, the catabolites of arginine are still increased. We conclude that the urinary amino acid levels may remain normal in hyperargininemia, whereas consistent increases of the guanidino compounds are observed. Thus, guanidino compound analyses can be used as a complementary biochemical diagnostic parameter for hyperargininemia. Although the argininemia can be normalized by therapy, the levels of the catabolites of arginine are still elevated.

Impaired cognitive performance in ornithine transcarbamylase-deficient mice on arginine-free diet.

Sparse-fur (spf) mice are a model for the congenital deficiency of ornithine transcarbamylase (OTC), the most common inborn error of urea synthesis in man. In this study, performance of clinically stable spf and control mice (8-10-weeks-old) on two learning tests was assessed under normal Arg(+) or arginine-free Arg(-) diet conditions. Used as an indicator of the metabolic status of the animals, plasma ammonia concentrations were significantly higher in spf than in controls on normal diet, and increased even more during the Arg(-) diet episode. Behaviourally, we found no difference in passive avoidance learning between control and spf mice on Arg(+) diet, whereas in spf mice receiving Arg(-) diet during training, retention performance was significantly reduced. In the hidden-platform water maze, spf mice on Arg(+) diet only showed decreased swimming velocity compared to controls. In mice on Arg(-) diet during the first week of acquisition training, performance on acquisition and retention (probe) trials showed that spf mice experienced more difficulties in actually locating the platform. Visible-platform control experiments only showed a reduction in swimming velocity in spf mice on either diet. We conclude that cognitive performance is impaired in spf mice as a consequence of Arg(-) diet-induced neurochemical alterations.

Effects of α-keto-δ-guanidinovaleric acid on inhibitory amino acid responses on mouse neurons in cell culture

Abstract The experimentally proven convulsant α-keto-δ-guanidinovaleric acid (α-K-δ-GVA) was applied to mouse spinal cord neurons in primary dissociated cell culture to assess its effects on postsynaptic γ-aminobutyric acid (GABA)- and glycine (GLY)-responses. Intracellular microelectrode recording techniques were used. α-K-δ-GVA reversibly inhibited both GABA- and GLY-responses in a concentration-dependent manner. The effect of α-K-δ-GVA on GABA-responses was not antagonized by co-application of the benzodiazepine receptor antagonist CGS 9896. The results suggest that α-K-δ-GVA inhibited responses to the inhibitory neurotransmitters GABA and GLY by blocking the chloride channel. This action might underlie the convulsant effect of this compound in rabbit. The possible pathophysiological importance of α-K-δ-GVA in hyperargininemic patients is discussed.

Hyperargininemia: intellectual and motor improvement related to changes in biochemical data.

Hyperargininemia is an inherited urea cycle disorder resulting from deficiency of arginase (EC 3.5.3.1). The clinical picture includes progressive spastic diplegia, mental retardation, and epilepsy. Acute episodes of vomiting, ataxia, and lethargy or agitation can also occur. Since the disorder was first described in 1969,1 various treatments have been proposed, including restriction of protein intake, oral administration of an amino acid mixture, therapy with sodium benzoate or sodium phenylacetate or both, and enzyme replacement. However, only five patients have been described who have shown sustained improvement in motor and mental abilities during therapy. 2-4 Another patient had improvement in auditory brain-stem evoked potentials during treatment. 5 The mechanisms responsible for neurologic damage are unknown but are unlikely to be due to hyperammonemia alone. Arginine and its guanidino metabolites are candidate neurotoxins. 6,7 A disturbance of central monoamine metabolism has also been described in one patient.8, 9 In this article, we describe the clinical course of a girl with hyperargininemia whose condition progressively improved during a 24-month period of strict metabolic control. We also present the results of serial determinations of ammonium, arginine, and its guanidino metabolites and of neuro-

Biochemical, Histological and Behavioral Consequences of Nephrectomy in Young and Aged Mice

Background: This study investigates the effect of nephrectomy in young and aged mice on some biochemical, histological and behavioural aspects. Methods: Each age group, 2- and 12-months-old, comprised a sham-operated group, a unilaterally nephrectomized group and a subtotally nephrectomized group. Consequences of nephrectomy were examined 10 days postsurgery on urea and guanidino compound levels in body fluids and brain; the remaining kidney by light-microscopic examination; and learning and memory abilities using the Morris water maze task. Results: Effect of nephrectomy on urea and guanidino compound levels in plasma, urine and brain was significantly more pronounced in the young age group. Some guanidino compounds show a tendency to decrease with aging in the sham-operated group and the two nephrectomized groups. Higher compensatory kidney hypertrophy was found in younger nephrectomized mice whereas in older mice glomerular mesangial expansion was a common feature. Finally, young mice with subtotal nephrectomy displayed a slight but significant impairment in memory and learning; whilst old nephrectomized mice manifested no impairment. Conclusions: Nephrectomy induces more changes in younger mice than in older mice as observed in higher variation of urea and guanidino compound levels, glomerular volume and kidney hypertrophy and decline in spatial learning and memory.

Disturbed metabolism of guanidino compounds characterized by elevated excretion of β-guanidinopropionic acid and γ-guanidinobutyric acid – An effect of vigabatrin treatment?

compounds are in part neurotoxic substances, especially acting as epilepGuanidino togenics et al Disturbed metabolism of guanidino compounds has (DÏHooge 1992). been reported in hyperargininaemic patients et al in renal insuffi(Marescau 1990), ciency Deyn et al after experimental subtotal nephrectomy in rats (De 1987), et al and in creatine deÐciency syndrome (McKusick 601240) (Levillain 1995), et al We report on a 8-month-old patient presenting with a neuro(Schulze 1997). degenerative disorder mainly characterized by seizures, psychomotor retardation and brain atrophy. Biochemical investigations revealed so far unreported abnormalities in guanidino compound metabolism, probably caused by vigabatrin treatment.

Determination of Guanidino Compounds in Plasma and Urine of Patients with Argininemia before and during Therapy

The first clinical and biochemical description of two sisters affected with argininemia, last of the five primary disorders of the urea cycle, was published in 19691–3. A third sister homozygote was described shortly after birth five years later4. Five other families including eight cases have been reported in the literature5–10. The first clinical symptoms seen in patients with argininemia are irritability, coma and epilepsy. The children show also pyramidal spasticity and mental retardation. All the patients described are still alive. The patient’s biochemistry is characterized by an arginase deficiency in liver shown after biopsy as well as in erythrocytes and leucocytes. As a consequence to this arginase deficiency, the patients accumulate arginine in their cells and biological fluids. The arginine accumulation leads to an increase of its catabolites: the guanidino compounds. Already in 1972 it was reported that guanidinoacetic acid, N-α-acetylarginine, argininic acid, γ-guanidinobutyric acid, arginine and an unknown guanidino compound (later identified as being γ-keto-δ-guanidinovaleric acid11) were elevated in urine of these patients12. These determinations were done applying the colorimetric Sakaguchi detection method.