Clinical, biochemical, and molecular characterization of patients with glutathione synthetase deficiency

Novel COVID-19 biomarkers identified through multi-omics data analysis: N-acetyl-4-O-acetylneuraminic acid, N-acetyl-L-alanine, N-acetyltriptophan, palmitoylcarnitine, and glycerol 1-myristate

This study aims to apply machine learning models to identify new biomarkers associated with the early diagnosis and prognosis of SARS-CoV-2 infection.Plasma and serum samples from COVID-19 patients (mild, moderate, and severe), patients with other pneumonia (but with negative COVID-19 RT-PCR), and healthy volunteers (control) from hospitals in four different countries (China, Spain, France, and Italy) were analyzed by GC-MS, LC-MS, and NMR. Machine learning models (PCA and PLS-DA) were developed to predict the diagnosis and prognosis of COVID-19 and identify biomarkers associated with these outcomes.A total of 1410 patient samples were analyzed. The PLS-DA model presented a diagnostic and prognostic accuracy of around 95% of all analyzed data. A total of 23 biomarkers (e.g., spermidine, taurine, L-aspartic, L-glutamic, L-phenylalanine and xanthine, ornithine, and ribothimidine) have been identified as being associated with the diagnosis and prognosis of COVID-19. Additionally, we also identified for the first time five new biomarkers (N-Acetyl-4-O-acetylneuraminic acid, N-Acetyl-L-Alanine, N-Acetyltriptophan, palmitoylcarnitine, and glycerol 1-myristate) that are also associated with the severity and diagnosis of COVID-19. These five new biomarkers were elevated in severe COVID-19 patients compared to patients with mild disease or healthy volunteers.The PLS-DA model was able to predict the diagnosis and prognosis of COVID-19 around 95%. Additionally, our investigation pinpointed five novel potential biomarkers linked to the diagnosis and prognosis of COVID-19: N-Acetyl-4-O-acetylneuraminic acid, N-Acetyl-L-Alanine, N-Acetyltriptophan, palmitoylcarnitine, and glycerol 1-myristate. These biomarkers exhibited heightened levels in severe COVID-19 patients compared to those with mild COVID-19 or healthy volunteers.

Case report: A Chinese patient with glutathione synthetase deficiency and a novel glutathione synthase mutation

Glutathione synthetase deficiency (GSSD) is an autosomal-recessive metabolic disorder caused by glutathione synthetase (GSS) gene mutations. No more than 90 cases of GSSD have been reported worldwide; thus, the spectrum of GSS mutations and the genotype-phenotype association remain unclear. Here, we present a severely affected infant carrying a compound heterozygous GSS variation, c.491G > A, and a novel variant of c.1343_1348delTACTTC. We also summarize the clinical manifestations, treatment protocol, prognosis, and genetic characteristics of previously reported GSSD cases in China. In this case study, our patient presented with tachypnea, jaundice, intractable metabolic acidosis, and hemolytic anemia. Urinary-organic acid analysis revealed elevated 5-oxoproline levels. Further, this patient showed improved outcomes owing to early diagnosis and the timely administration of vitamins C and E. Therefore, our study indicates that in clinical cases of unexplained hemolytic anemia and metabolic acidosis, GSSD should be considered. Additionally, genetic testing and antioxidant application might help identify GSSD and improve the prognosis.

Metabolomics analysis identifies glutamic acid and cystine imbalances in COVID-19 patients without comorbid conditions. Implications on redox homeostasis and COVID-19 pathophysiology

It is well known that the presence of comorbidities and age-related health issues may hide biochemical and metabolic features triggered by SARS-CoV-2 infection and other diseases associated to hypoxia, as they are by themselves chronic inflammatory conditions that may potentially disturb metabolic homeostasis and thereby negatively impact on COVID-19 progression. To unveil the metabolic abnormalities inherent to hypoxemia caused by COVID-19, we here applied gas chromatography coupled to mass spectrometry to analyze the main metabolic changes exhibited by a population of male patients less than 50 years of age with mild/moderate and severe COVID-19 without pre-existing comorbidities known to predispose to life-threatening complications from this infection. Several differences in serum levels of particular metabolites between normal controls and patients with COVID-19 as well as between mild/moderate and severe COVID-19 were identified. These included increased glutamic acid and reduced glutamine, cystine, threonic acid, and proline levels. In particular, using the entire metabolomic fingerprint obtained, we observed that glutamine/glutamate metabolism was associated with disease severity as patients in the severe COVID-19 group presented the lowest and higher serum levels of these amino acids, respectively. These data highlight the hypoxia-derived metabolic alterations provoked by SARS-CoV-2 infection in the absence of pre-existing co-morbidities as well as the value of amino acid metabolism in determining reactive oxygen species recycling pathways, which when impaired may lead to increased oxidation of proteins and cell damage. They also provide insights on new supportive therapies for COVID-19 and other disorders that involve altered redox homeostasis and lower oxygen levels that may lead to better outcomes of disease severity.

Blood transcriptome analysis: Ferroptosis and potential inflammatory pathways in post-traumatic stress disorder

BACKGROUND

Transcriptome-wide analysis of peripheral blood in post-traumatic stress disorder (PTSD) indicates widespread changes in immune-related pathways and function. Ferroptosis, an iron-dependent regulated cell death, is closely related to oxidative stress. However, little is known as to whether ferroptosis plays a role in PTSD.

METHODS

We conducted a comprehensive analysis of combined data from six independent peripheral blood transcriptional studies in the Gene Expression Omnibus (GEO) database, covering PTSD and control individuals. Differentially expressed genes (DEGs) were extracted by comparing PTSD patients with control individuals, from which 29 ferroptosis-related genes (FRGs) were cross-matched and obtained. The weighted gene co-expression network analysis (WGCNA), the Extreme Gradient Boosting (XGBoost) model with Bayesian Optimization, and the least absolute shrinkage and selection operator (LASSO) Cox regression were utilized to construct a PTSD prediction model. Single-sample Gene Set Enrichment Analysis (ssGSEA) and CIBERSORT revealed the disturbed immunologic state in PTSD high-risk patients.

RESULTS

Three crucial FRGs (ACSL4, ACO1, and GSS) were identified and used to establish a predictive model of PTSD. The receiver operating characteristic (ROC) curve verifies its risk prediction ability. Remarkably, ssGSEA and CIBERSORT demonstrated changes in cellular immunity and antigen presentation depending on the FRGs model.

CONCLUSION

These findings collectively provide evidence that ferroptosis may change immune status in PTSD and be related to the occurrence of PTSD, which may help delineate mechanisms and discover treatment biomarkers for PTSD.

Glutathione synthetase deficiency: a novel mutation with femur agenesis

Introduction: Glutathione synthetase (GSS) deficiency is an autosomal recessive disorder (frequency < 1/1,000,000) with different varyingly severe clinical manifestations that include metabolic acidosis, hemolytic anemia, hyperbilirubinemia, neurological disorders and sepsis. Case report: This infant was small for gestational age, had hemolytic anemia, metabolic acidosis, bilateral subependymal pseudocysts and increased echogenicity of the basal ganglia. GSS deficiency was confirmed by genetic analysis. The patient also had unilateral right femur agenesis. Conclusion: By using next generation sequencing analysis, we identified a novel homozygous variant c.800G > A, p.Arg267Gln in the GSS gene of this patient. Femur agenesis had not previously been associated with GSS.

Neuroimaging Findings of Organic Acidemias and Aminoacidopathies

Although individual cases of inherited metabolic disorders are rare, overall they account for a substantial number of disorders affecting the central nervous system. Organic acidemias and aminoacidopathies include a variety of inborn errors of metabolism that are caused by defects in the intermediary metabolic pathways of carbohydrates, amino acids, and fatty acid oxidation. These defects can lead to the abnormal accumulation of organic acids and amino acids in multiple organs, including the brain. Early diagnosis is mandatory to initiate therapy and prevent permanent long-term neurologic impairments or death. Neuroimaging findings can be nonspecific, and metabolism- and genetics-based laboratory investigations are needed to confirm the diagnosis. However, neuroimaging has a key role in guiding the diagnostic workup. The findings at conventional and advanced magnetic resonance imaging may suggest the correct diagnosis, help narrow the differential diagnosis, and consequently facilitate early initiation of targeted metabolism- and genetics-based laboratory investigations and treatment. Neuroimaging may be especially helpful for distinguishing organic acidemias and aminoacidopathies from other more common diseases with similar manifestations, such as hypoxic-ischemic injury and neonatal sepsis. Therefore, it is important that radiologists, neuroradiologists, pediatric neuroradiologists, and clinicians are familiar with the neuroimaging findings of organic acidemias and aminoacidopathies. ^©RSNA, 2018.

A case of severe glutathione synthetase deficiency with novel GSS mutations

Glutathione synthetase deficiency (GSSD) is a rare inborn error of glutathione metabolism with autosomal recessive inheritance. The severe form of the disease is characterized by acute metabolic acidosis, usually present in the neonatal period with hemolytic anemia and progressive encephalopathy. A case of a male newborn infant who had severe metabolic acidosis with high anion gap, hemolytic anemia, and hyperbilirubinemia is reported. A high level of 5-oxoproline was detected in his urine and a diagnosis of generalized GSSD was made. DNA sequence analysis revealed the infant to be compound heterozygous with two mutations, c.738dupG in exon 8 of GSS gene resulting in p.S247fs and a repetitive sequence in exon 3 of GSS gene. Treatment after diagnosis of GSSD included supplementation with antioxidants and oral sodium hydrogen bicarbonate. However, he maintained a variable degree of metabolic acidosis and succumbed shortly after his parents requested discontinuation of therapy because of dismal prognosis and medical futility when he was 18 days old.

Controlled Growth of Gold Nanostars: Effect of Spike Length on SERS Signal Enhancement

Two different types of gold nanostars (Au NS), namely, short-spiked nanostars (SSNS) and long-spiked nanostars (LSNS), are prepared by using a hexagonal lyotropic liquid-crystalline (LLC) phase as a template. The formation, size and length of spikes or arms of the resultant Au NS are controlled by preparation in either a hexagonal LLC phase or an isotropic phase. These NS are anchored onto indium tin oxide (ITO) electrodes through a self-assembled monolayer of 3-mercaptopropyltrimethoxysilane, which acts as a linker molecule. Structural and morphological characterisations of SSNS- and LSNS-anchored ITO electrodes are performed by means of microscopic and spectroscopic analyses. Further electrochemical techniques, namely, cyclic voltammetry and electrochemical impedance spectroscopy, are also used to confirm the immobilisation of these Au NS on ITO electrodes and to study the electrochemical characteristics. These studies clearly reveal the formation of star-shaped, branched, anisotropic nanostructures of gold during the template preparation method and these Au NS are successfully anchored onto ITO electrodes through a covalent immobilisation strategy. Furthermore, the SERS activity of these Au NS is analysed by using glutathione and crystal violet as analytes and by employing glass and ITO as substrates. It is interesting to note that SSNS show a significant enhancement in SERS signals relative to those of LSNS.

Five Chinese patients with 5-oxoprolinuria due to glutathione synthetase and 5-oxoprolinase deficiencies

OBJECTIVE

5-Oxoprolinuria is a rare inherited metabolic disorder caused by a defective gamma-glutamyl cycle resulting from mutations in the genes encoding 5-oxoprolinase (OPLAH) and glutathione synthetase (GSS). No inherited 5-oxoprolinuria case has been reported in mainland China until now. In this study, clinical, biochemical, and genetic aspects of five Chinese 5-oxoprolinuria patients with OPLAH or GSS gene mutations were investigated.

METHODS

Three boys and two girls from five unrelated Chinese families with symptomatic 5-oxoprolinuria were identified within the past 3years in Peking University First Hospital. OPLAH and GSS genes were analyzed.

RESULTS

Patients were hospitalized between the age of 13days to 1year and 3months for hypersomnia, developmental retardation, feeding deficiency, vomiting, icterus and recurrent pneumonia. All patients had significantly elevated urine 5-oxoproline. Three novel mutations (c.1904G>A and c.2813_2815delGGG in Patient 1, c.2978G>T in Patient 2) on OPLAH, on GSS, one novel mutation (c.1252C>T in Patient 3) and a reported mutation (c.491G>A in Patients 3-5) were detected. Patient 4 has homozygous mutation c.491G>A, the others are heterozygous. After treatment by l-carnitine, vitamin E, B1, B2 and coenzyme Q10, three patients with GSS deficiency improved, but the two 5-oxoprolinase-deficient patients did not respond to treatment.

CONCLUSIONS

5-Oxoprolinase deficiency and GSS deficiency share some clinical and biochemical features. Genetic analysis is important for the deferential diagnosis. In this study, five Chinese patients had severe central nervous system damage. Antioxidant treatments were proved effective for the three patients with GSS deficiency but not for the two patients with 5-oxoprolinase deficiency.

5-Oxoprolinuria in Heterozygous Patients for 5-Oxoprolinase (OPLAH) Missense Changes

The inherited 5-oxoprolinuria is primarily suggestive of genetic defects in two enzymes belonging to the gamma-glutamyl cycle in the glutathione (GSH) metabolism: the glutathione synthetase (GSS) and the 5-oxoprolinase (OPLAH). The GSS deficiency is the best characterized of the inborn errors of GSH metabolism, whereas the OPLAH deficiency is questioned whether it is a disorder or just a biochemical condition with no adverse clinical effects. Recently, the first human OPLAH mutation (p.H870Pfs) was reported in homozygosis in two siblings who suffered from 5-oxoprolinuria with a benign clinical course. We report two unrelated patients who manifested massive excretion of 5-oxoproline in urine. In both probands, the blood GSH levels were normal and no mutations were found in the GSS gene. The mutational screening of the OPLAH gene, which included the codified sequences, the intronic flanking sequences, the promoter sequence, and a genetic analysis in order to detect large deletions and/or duplications, showed that each patient only harbors one missense mutation in heterozygosis. The in silico analyses revealed that each one of these OPLAH mutations, p.S323R and p.V1089I, could alter the proper function of this homodimeric enzyme. In addition, clinical symptoms manifest in these two probands were not related to GSH cycle defects and, therefore, this study provides further evidence that oxoprolinuria may present as epiphenomenon in several pathological conditions and confound the final diagnosis.

Alternative RNA splicing in expression of the glutathione synthetase gene in human cells

Ubiquitous free radical production occurs continuously in cells and tissues. Glutathione is the most abundant mammalian antioxidant, and is synthesized by glutathione synthetase (GSS). Therefore, GSS plays an important role in defending the cell against reactive oxygen species. The expression of GSS has been studied in human cells; however, sequence information about alternative splicing variants of GSS mRNA has not been reported. In the present study, we identified a novel alternative splicing variant (ASV) of the GSS gene in 10 human normal tissues and five human cancer cell lines. The deleted transcript of GSS was characterized by an in-frame deletion of 333 bp, corresponding to the complete loss of exons 4 and 5. Thus this GSS ASV causes protein truncation. We quantified the mRNA of GSS ASV in human normal tissues using real-time PCR. The ASV was detected in colon, kidney, lung, liver, placenta, peripheral blood and uterus, but not in heart, skeletal muscle and spleen tissue. Our results provide a basis for more detailed studies on the regulation of GSS, and for further evaluation of this and other possible roles of GSS. Understanding the regulation of GSS expression is very important for the development of new strategies for controlling the development of GSH-based redox homeostasis.

The central role of glutathione in the pathophysiology of human diseases

Reduced glutathione (L-gamma-glutamyl-L-cysteinyl-glycine, GSH) is the prevalent low-molecular-weight thiol in mammalian cells. It is formed in a two-step enzymatic process including, first, the formation of gamma-glutamylcysteine from glutamate and cysteine, by the activity of the gamma-glutamylcysteine synthetase; and second, the formation of GSH by the activity of GSH synthetase which uses gamma-glutamylcysteine and glycine as substrates. While its synthesis and metabolism occur intracellularly, its catabolism occurs extracellularly by a series of enzymatic and plasma membrane transport steps. Glutathione metabolism and transport participates in many cellular reactions including: antioxidant defense of the cell, drug detoxification and cell signaling (involved in the regulation of gene expression, apoptosis and cell proliferation). Alterations in its concentration have also been demonstrated to be a common feature of many pathological conditions including diabetes, cancer, AIDS, neurodegenerative and liver diseases. Additionally, GSH catabolism has been recently reported to modulate redox-sensitive components of signal transduction cascades. In this manuscript, we review the current state of knowledge on the role of GSH in the pathogenesis of human diseases with the aim to underscore its relevance in translational research for future therapeutic treatment design.

Genotype, enzyme activity, glutathione level, and clinical phenotype in patients with glutathione synthetase deficiency

Glutathione synthetase (GS) deficiency is a rare autosomal recessive disorder. The clinical phenotype varies widely, and nearly 30 different mutations in the GSS gene have been identified. In the present study, genotype, enzyme activity, metabolite levels and clinical phenotype were evaluated in 41 patients from 33 families. From some of the patients, data on glutathione (GSH) levels and gamma-glutamylcysteine levels in cultured fibroblasts were also available. Twenty-seven different mutations were found: 14 missense, 9 splice, 2 deletions, 1 insertion and 1 nonsense mutation. Twenty-three patients were homozygous and 18 were compound heterozygous. The moderate and severe clinical phenotypes could not be distinguished based on enzyme activity, GSH or gamma-glutamylcysteine levels in cultured fibroblasts. However, in fibroblasts, the residual GS activity was correlated with the GSH level. All mutations causing frameshifts, premature stop codons or aberrant splicing were associated with moderate or severe clinical phenotypes including haemolytic anaemia, 5-oxoprolinuria, and (in several forms) neurodevelopmental signs. The data indicate that additional genetic or environmental factors modify at least the moderate and severe phenotypes and that the clinical classification given to the patients may be influenced by variation in follow-up. The type of mutation involved can, to some extent, predict a mild versus a more severe phenotype.

Physiological and pathological aspects of GSH metabolism

The antioxidant glutathione is found in low levels in diseases in which increasing evidence implicate oxidative stress in the development of the disease, for example retinopathy of prematurity, necrotizing enterocolitis, bronchopulmonary dysplasia, patent ductus arteriosus and asthma. Glutathione is metabolized in the gamma-glutamyl cycle, which involves six different enzymes. The synthesis of glutathione is a two-step process in which the first step is catalysed by gamma-glutamylcysteine synthetase and the second step by glutathione synthetase. Glutathione synthetase deficiency is an autosomal recessive disease and the most common inborn error of the gamma-glutamyl cycle. Approximately 25% of patients with hereditary glutathione synthetase deficiency die during childhood. Patients present with a clinical picture ranging from compensated haemolytic anaemia to a complex disorder with additional symptoms like 5-oxoprolinuria, metabolic acidosis and central nervous system impairment. Even though the correlation between phenotype and genotype in these patients is complex, an indication of the phenotype can be based on the type of mutation involved. Also, there is a correlation between the glutathione synthetase activity and the level of glutathione in cultured fibroblasts. Inborn errors have also been described in three additional steps of the y-glutamyl cycle, namely gamma-glutamyl-transpeptidase, 5-oxoprolinase and gamma-glutamylcysteine synthetase.

CONCLUSION

The range of disorders in patients with inborn errors in the metabolism of glutathione illustrates the intricate metabolism of glutathione and its involvement in numerous essential processes in the cell. By studying these patients, further insight into the functions and metabolism of glutathione can be achieved.

Trial of erythropoietin treatment in a boy with glutathione synthetase deficiency

We report a 3-year-old boy with glutathione synthetase deficiency, who in the newborn period developed severe persistent haemolytic anaemia. Treatment with erythropoietin was introduced with good clinical and haematological response.

Human hereditary glutathione synthetase deficiency: kinetic properties of mutant enzymes

Patients with hereditary glutathione synthetase deficiency suffer from haemolytic anaemia, 5-oxoprolinuria, metabolic acidosis, recurrent bacterial infections and various degrees of central nervous system dysfunction. To investigate the molecular basis of the mutations associated with this disease, seven naturally occurring missense mutations [L188P (Leu188-->Pro), D219A, D219G, Y270C, Y270H, R283C and P314L] were expressed using a His-tagged, Escherichia coli-based expression system. Effects of the mutations on kinetic properties, including negative co-operative binding of gamma-glutamyl substrate, were evaluated. The mutation P314L did not have any major effect on these parameters and was classified as a neutral mutation. The remaining mutations decreased V(max) to 2-27% of wild-type activity. Negative co-operativity for gamma-gluABA (L-gamma-glutamyl-L-alpha-aminobutyric acid) was abolished in five mutant recombinant enzymes, whereas for one mutant enzyme, this co-operativity changed from negative to positive. The structural consequences of the mutations were interpreted on the basis of the known structure of the wild-type enzyme.

Clinical acid-base pathophysiology: disorders of plasma anion gap

The plasma anion gap is a frequently used parameter in the clinical diagnosis of a variety of conditions. The commonest application of the anion gap is to classify cases of metabolic acidosis into those that do and those that do not leave unmeasured anions in the plasma. While this algorithm is useful in streamlining the diagnostic process, it should not be used solely in this fashion. The anion gap measures the difference between the unmeasured anions and unmeasured cations and thus conveys much more information to the clinician than just quantifying anions of strong acids. In this chapter, the significance of the anion gap is emphasized and several examples are given to illustrate a more analytic approach to using the clinical anion gap; these include disorders of low anion gap, respiratory alkalosis and pyroglutamic acidosis.

Kinetic properties of missense mutations in patients with glutathione synthetase deficiency

Patients with hereditary glutathione synthetase (GS) (EC 6.3.2.3) deficiency present with variable clinical pictures, presumably related to the nature of the mutations involved. In order to elucidate the relationship between genotype, enzyme function and clinical phenotype, we have characterized enzyme kinetic parameters of missense mutations R125C, R267W, R330C and G464V from patients with GS deficiency. One of the mutations predominantly affected the K(m) value, with decreased affinity for glycine, two mutations influenced both K(m) and V(max) values, and one mutation reduced the stability of the enzyme. This characterization agrees well with predictions based on the recently reported crystal structure of human GS. Thus our data indicate that different mutations can affect the catalytic capacity of GS by decreasing substrate affinity, maximal velocity or enzyme stability.