Adenylosuccinate lyase deficiency--first British case

Microplastic-induced gut microbiota and serum metabolic disruption in Sprague-Dawley rats

Toxic effects of exposure to microplastics (MPs) on living organisms and humans have attracted global concern. However, most previous studies exposed animals to only one type of MP (mainly polystyrene) to assess the health risk of MPs for animals. Therefore, we conducted a laboratory gavage experiment on rats based on the types and concentration of MPs to which humans are exposed in their daily life. The purpose of this study is to use Sprague-Dawley (SD) rat models to assess the potential health risks in mammals from co-exposure to various MPs. In the present study, SD rats were exposed to 12 mg/kg bw/day mixed-MPs (containing 10 types of MPs) for 42 days, and then examined the alteration of gut microbes and serum metabolites. The results showed that 6 gut microbes at the family level (f_Muribaculaceae, f_Oscillospiraceae, f_Bacteroidaceae, f_Neisseriaceae, f_Prevotellaceae, and f_Veillonellaceae) were significantly perturbed (t-test, p < 0.05) in rats after MP exposure. After MP intervention, 47 metabolites significantly regulated in SD rat serum, mainly including lipids and lipid-like molecules (e.g., fatty acids), organic acids and derivatives (e.g., phosphoric acids), and isoflavonoids (e.g., daidzein). These findings contribute to assessing the health risks of various MP co-exposure in mammals in the actual environment and provide a novel insight into the toxicity mechanism of MPs.

Diagnosis of adenylosuccinate lyase deficiency by metabolomic profiling in plasma reveals a phenotypic spectrum

Adenylosuccinate lyase (ADSL) deficiency is a rare autosomal recessive neurometabolic disorder that presents with a broad-spectrum of neurological and physiological symptoms. The ADSL gene produces an enzyme with binary molecular roles in de novo purine synthesis and purine nucleotide recycling. The biochemical phenotype of ADSL deficiency, accumulation of SAICAr and succinyladenosine (S-Ado) in biofluids of affected individuals, serves as the traditional target for diagnosis with targeted quantitative urine purine analysis employed as the predominate method of detection. In this study, we report the diagnosis of ADSL deficiency using an alternative method, untargeted metabolomic profiling, an analytical scheme capable of generating semi-quantitative z-score values for over 1000 unique compounds in a single analysis of a specimen. Using this method to analyze plasma, we diagnosed ADSL deficiency in four patients and confirmed these findings with targeted quantitative biochemical analysis and molecular genetic testing. ADSL deficiency is part of a large a group of neurometabolic disorders, with a wide range of severity and sharing a broad differential diagnosis. This phenotypic similarity among these many inborn errors of metabolism (IEMs) has classically stood as a hurdle in their initial diagnosis and subsequent treatment. The findings presented here demonstrate the clinical utility of metabolomic profiling in the diagnosis of ADSL deficiency and highlights the potential of this technology in the diagnostic evaluation of individuals with neurologic phenotypes.

Adenylosuccinate lyase deficiency

Adenylosuccinate lyase ADSL) deficiency is a defect of purine metabolism affecting purinosome assembly and reducing metabolite fluxes through purine de novo synthesis and purine nucleotide recycling pathways. Biochemically this defect manifests by the presence in the biologic fluids of two dephosphorylated substrates of ADSL enzyme: succinylaminoimidazole carboxamide riboside (SAICAr) and succinyladenosine (S-Ado). More than 80 individuals with ADSL deficiency have been identified, but incidence of the disease remains unknown. The disorder shows a wide spectrum of symptoms from slowly to rapidly progressing forms. The fatal neonatal form has onset from birth and presents with fatal neonatal encephalopathy with a lack of spontaneous movement, respiratory failure, and intractable seizures resulting in early death within the first weeks of life. Patients with type I (severe form) present with a purely neurologic clinical picture characterized by severe psychomotor retardation, microcephaly, early onset of seizures, and autistic features. A more slowly progressing form has also been described (type II, moderate or mild form), as having later onset, usually within the first years of life, slight to moderate psychomotor retardation and transient contact disturbances. Diagnosis is facilitated by demonstration of SAICAr and S-Ado in extracellular fluids such as plasma, cerebrospinal fluid and/or followed by genomic and/or cDNA sequencing and characterization of mutant proteins. Over 50 ADSL mutations have been identified and their effects on protein biogenesis, structural stability and activity as well as on purinosome assembly were characterized. To date there is no specific and effective therapy for ADSL deficiency.

Early diagnosis of adenylosuccinate lyase deficiency using a high-throughput screening method and a trial of oral S-adenosyl-l-methionine as a treatment method

AIM

The aim of this study was to develop a high-throughput urine screening technique for adenylosuccinate lyase (ADSL) deficiency and to evaluate S-adenosyl-l-methionine (SAMe) as a potential treatment for this disorder.

METHOD

Testing for succinyladenosine (S-Ado), a marker of ADSL deficiency, was incorporated into a screening panel for urine biomarkers for inborn errors of metabolism using electrospray tandem mass spectrometry. Liquid chromatography-mass spectrometry and high-performance liquid chromatography were used to confirm and monitor the response of metabolites to oral SAMe treatment.

RESULTS

Increased levels of S-Ado were detected in a 3-month-old male infant with hypotonia and seizures. ADSL gene sequencing revealed a previously described c.-49T>C mutation and a novel c.889_891dupAAT mutation, which was likely to disrupt enzyme function. After 9 months of SAMe treatment, there was no clear response evidenced in urine metabolite levels or clinical parameters.

INTERPRETATION

These results demonstrate proof of the principle for the high-throughput urine screening technique, allowing earlier diagnosis of patients with ADSL deficiency. However, early treatment with SAMe does not appear to be effective in ADSL deficiency. It is suggested that although SAMe treatment may ameliorate purine nucleotide deficiency, it cannot correct metabolic syndromes in which a toxic nucleotide is present, in this case presumed to be succinylaminoimidazole carboxamide ribotide.

Magnetic resonance imaging of the brain in adenylosuccinate lyase deficiency: a report of seven cases and a review of the literature

Adenylosuccinate lyase (ADSL) deficiency is a rare autosomal recessive disorder of purine metabolism. Patients may present with a wide range of neurological symptoms. Head imaging abnormalities have been reported only rarely in the scientific literature and include atrophy of the cerebral cortex, corpus callosum, cerebellar vermis, lack of myelination, delayed myelination, anomalies of the white matter, and lissencephaly. The pathogenesis of abnormalities remains unknown. To further the understanding of the spectrum of brain abnormalities associated with ADSL deficiency, we examined the magnetic resonance findings in seven Polish patients with different clinical phenotypes and genotypes. Head MRI showed impaired white matter myelination with various degrees of global supra- and infratentorial white matter loss including widening of the lateral ventricles, enlargement of the subarachnoid spaces, atrophy of the cerebrum, hypoplasia of the cerebellar hemispheres and enlargement of the cisterna magna, and white matter abnormal hyperintense signal on T(2)-weighted sequences. We recommend performing a detailed analysis of urine and plasma purine metabolites in patients who have neurological findings, including developmental delay, microcephaly, autistic features, neonatal encephalopathy, and seizures especially if MRI findings such as delayed or lack of myelination, white matter abnormal signal, and atrophy of the cerebrum and/or cerebellum are also present. Greater awareness of adenylosuccinate lyase deficiency among general pediatricians, neonatologists, pediatric neurologists, and also radiologists is the key to identifying the disorder at an early stage.

Adenylosuccinate lyase deficiency in the United Kingdom pediatric population: first three cases

Adenylosuccinate lyase deficiency is an autosomal recessive disorder of purine metabolism resulting from mutations in the ADSL gene on chromosome subband 22q13.1 and associated with a wide range of clinical manifestations. Although there is currently no effective treatment of ADSL deficiency, recognition of the condition is important, because prenatal genetic diagnosis can be offered to affected families. Reported here are the cases of the only three children diagnosed to date in the United Kingdom with adenylosuccinate lyase deficiency, to further delineate the clinical phenotype and to raise awareness of this disorder.

Clinical, biochemical and molecular findings in seven Polish patients with adenylosuccinate lyase deficiency

Adenylosuccinate lyase (ADSL) catalyzes two steps in purine nucleotide metabolism-the 8th step in the de novo pathway: conversion of succinylaminoimidazole carboxamide ribotide (SAICAR) to aminoimidazole carboxamide ribotide (AICAR), and conversion of adenylosuccinate (S-AMP) to adenylate (AMP) in the purine nucleotide cycle. To date, over 50 patients have been reported suffering from ADSL deficiency. We report all seven so far diagnosed Polish patients with this defect. Most of our patients shared intractable seizures and psychomotor retardation since the neonatal period and had biochemical evidence of severe (type I) deficiency. Two patients with type II suffered only from mild/moderate psychomotor retardation and showed a transientvisual contact disturbance. One patient had a fatal neonatal form of ADSL deficiency with lack of spontaneous movement, respiratory failure, severe encephalopathy and intractable seizures. Analysis of the ADSL gene showed that four apparently unrelated patients carried a R426H mutation (two homozygous and two compound heterozygous). With the exception of the latter mutation, a Y114H mutation that had been reported previously, and a novel mutation T242I, all other mutations (including D268H and three novel S23R, D215H and I351T mutations) were found only in single families in single alleles. A search for this disorder should be included in the screening program of all infants with unexplained neonatal seizures, severe infantile epileptic encephalopathy, developmental delay, hypotonia, and/or autistic features.

Adenylosuccinate lyase deficiency: the first identified polish patient

Adenylosuccinate lyase (ADSL) deficiency is a rare disease of de novo purine synthesis. The main symptoms are psychomotor retardation, epilepsy, autistic features, occasionally associated with muscular hypotonia. Diagnosis is made by detection of abnormal purine metabolites (succinyladenosine - S-Ado and succinylaminoimidazole carboxamide riboside - SAICAr) in body fluids. The severity of the clinical features correlates with low S-Ado/SAICAr ratio. We report clinical, biochemical and brain MRI findings of a female infant with severe early epilepsy and hypotonia, who died at the age of 10 weeks.

Lethal fetal and early neonatal presentation of adenylosuccinate lyase deficiency: observation of 6 patients in 4 families

OBJECTIVE

To characterize a new lethal fetal and early postnatal variant of adenylosuccinate lyase (ADSL) deficiency.

STUDY DESIGN

This was a retrospective analysis of 6 patients with very early presentation of ADSL deficiency.

RESULTS

Most of the 6 patients had impaired intrauterine growth, microcephaly, fetal hypokinesia, and a lack of fetal heart rate variability. Postnatally, they shared severe muscular hypotonia necessitating mechanical ventilation, intractable seizures, and early death. All 6 patients had biochemical evidence of severe (type 1) disease and low residual ADSL activities. All were compound heterozygous for mutations that, based on expression studies, have a pronounced effect on ADSL activity and/or stability.

CONCLUSIONS

ADSL deficiency may present with prenatal growth restriction, fetal and neonatal hypokinesia, and rapidly fatal neonatal encephalopathy. This clinical presentation is associated with genotypes resulting in very low residual enzyme activity.

Expression, purification, and characterization of stable, recombinant human adenylosuccinate lyase

The full length human adenylosuccinate lyase gene was generated by a PCR method using a plasmid encoding a truncated human enzyme as template, and was cloned into a pET-14b vector. Human adenylosuccinate lyase was overexpressed in Escherichia coli Rosetta 2(DE3)pLysS as an N-terminal histidine-tagged protein and was purified to homogeneity by a nickel-nitriloacetic acid column at room temperature. The histidine tag was removed from the human enzyme by thrombin digestion and the adenylosuccinate lyase was purified by Sephadex G-100 gel filtration. The histidine-tagged and non-tagged adenylosuccinate lyases exhibit similar values of Vmax and Km for S-AMP. Analytical ultracentrifugation and circular dichroism revealed, respectively, that the histidine-tagged enzyme is in tetrameric form with a molecular weight of 220 kDa and contains predominantly alpha-helical structure. This is the first purification procedure to yield a stable form of human adenylosuccinate lyase. The enzyme is stable for at least 5 days at 25 degrees C, and upon rapid freezing and thawing. Temperature as well as reducing agent (DTT) play critical roles in determining the stability of the human adenylosuccinate lyase.