Spectrum of Organic Aciduria Diseases in Tunisia: A 35-year Retrospective Study.

Background: Organic aciduria diseases (OADs) occur worldwide, with differences in prevalence and patterns between populations. Objectives: To describe the spectrum of OADs identified in Tunisia over a 35-years period. Materials and Methods: This retrospective study included patients who were diagnosed with OADs between 1987 and 2022 in the Laboratory of Biochemistry, Rabta Hospital, Tunisia. Organic acids were analyzed using gas chromatography-mass spectrometry. Results: A total of 30,670 urine samples were analyzed for OADs, of which 471 were positive for OADs. The estimated incidence of OADs in Tunisia was 6.78 per 100,000 live births. Methylmalonic (n = 146) and propionic (n = 90) acidurias were the most common OADs (estimated incidence: 2.10 and 1.30 per 100,000 live births, respectively). There were 54 cases of L-2-hydroxyglutatric acidurias and 30 cases of pyroglutamic acidurias, which makes it one of the highest in the world. The main clinical features were hypotonia (65%) and feeding difficulties (41%). Age at diagnosis was highly variable, ranging from 1 day to 49 years. Only 27% of the patients were diagnosed within the first month of life. The prevalence of OADs was highest in the Center-East and Southeast regions. Conclusions: In Tunisia, OADs are relatively frequent, but there are shortcomings regarding the diagnosis of these disorders. The frequency and health/social impact of these disorders warrant the need for implementing newborn screening programs and suitable patient management.

Possible role of tryptophan metabolism along the microbiota-gut-brain axis on cognitive & behavioral aspects in Phenylketonuria.

Cognitive and psychiatric disorders are well documented across the lifetime of patients with inborn errors of metabolism (IEMs). Gut microbiota impacts behavior and cognitive functions through the gut-brain axis (GBA). According to recent research, a broad spectrum of GBA disorders may be influenced by a perturbed Tryptophan (Trp) metabolism and are associated with alterations in composition or function of the gut microbiota. Furthermore, early-life diets may influence children's neurodevelopment and cognitive deficits in adulthood. In Phenylketonuria (PKU), since the main therapeutic intervention is based on a life-long restrictive diet, important alterations of gut microbiota have been observed. Studies on PKU highlight the impact of alterations of gut microbiota on the central nervous system (CNS), also investigating the involvement of metabolic pathways, such as Trp and kynurenine (KYN) metabolisms, involved in numerous neurodegenerative disorders. An alteration of Trp metabolism with an imbalance of the KYN pathway towards the production of neurotoxic metabolites implicated in numerous neurodegenerative and inflammatory diseases has been observed in PKU patients supplemented with Phe-free amino acid medical foods (AA-MF). The present review investigates the possible link between gut microbiota and the brain in IEMs, focusing on Trp metabolism in PKU. Considering the evidence collected, cognitive and behavioral well-being should always be monitored in routine IEMs clinical management. Further studies are required to evaluate the possible impact of Trp metabolism, through gut microbiota, on cognitive and behavioral functions in IEMs, to identify innovative dietetic strategies and improve quality of life and mental health of these patients.

Knowledge and perception of inborn errors of metabolism (IEMs) among healthcare students at a selected public university in Klang Valley, Malaysia.

Healthcare providers play an important role in improving the health of Inborn Error of Metabolism (IEM) patients. However, IEM knowledge level among local healthcare students has yet to be determined. Thus, the aim of this study is to assess the knowledge and perception of IEM among local healthcare students. An online self-administered questionnaire was distributed to 378 students across the Faculty of Health Science, Pharmacy and Dentistry from a selected public university in Lembah Klang, Malaysia. For knowledge, a score of 1 is assigned to each correct answer with a maximum total score of 14. Likert scale was used to determine their perception of IEM. The total mean score of IEM knowledge among healthcare students is 5.8. There was no significant difference of mean score of IEM knowledge among the students from the Faculty of Health Science (6.1 ± 2.7), Pharmacy (5.5 ± 2.6) and Dentistry (5.8 ± 2.8). However, the score of knowledge is observed to be significantly different by ethnicity, religion and family history of IEM (p < 0.05). Furthermore, students with experience of meeting an IEM patient and attending IEM classes scored higher than those with no experience (p < 0.05). Most of the healthcare students (89.5%) perceived their knowledge to be insufficient and very poor. Majority of the students from faculty of pharmacy (70.8%) agreed that the IEM course should be mandatory compared to health sciences and dentistry (p < 0.05). This study identified an overall inadequacy of knowledge of IEM among healthcare students. There is a pressing need to improve the IEM-related knowledge and awareness of Malaysian healthcare students. This can be accomplished by incorporating online classes that emphasizes the treatment and management of IEMs in the university curriculum.

Challenging the status quo: A comparison of ion exchange chromatography with liquid chromatography-mass spectrometry and liquid chromatography-tandem mass spectrometry methods for the measurement of amino acids in human plasma.

BACKGROUND: Plasma amino acid analysis is key to the diagnosis and monitoring of inherited disorders of amino acid synthesis, catabolism and transport. Ion exchange chromatography (IEC) is widely accepted as the gold standard method of analysis, but with the introduction of liquid chromatography tandem mass spectrometry (LC-MS/MS) and liquid chromatography mass spectrometry (LC-MS) methods, this should now be questioned. METHODS: The analytical performance of three commercially available reagent kits, Waters AccQ Tag™ ULTRA LC-MS, SpOtOn Amino Acids LC-MS/MS and Chromsystems MassChrom® Amino Acid Analysis LC-MS/MS, were evaluated and compared with Biochrom Physiological Amino Acids ion exchange chromatography. Correlation with IEC was assessed by Passing-Bablok regression, concordance correlation coefficients (CCC) and Bland-Altman analysis for 21 common amino acids. Calculation of the total error from imprecision and bias was also used to benchmark performance. RESULTS: The MassChrom® and SpOtOn kits demonstrated acceptable inter-batch imprecision (CV < 10%) and accuracy (mean bias < 10%), whereas the AccQ Tag™ ULTRA kit did not. Good correlation (CCC > 0.95) with Biochrom IEC was demonstrated for 10/21 analytes in both the MassChrom® and SpOtOn kits and 6/21 in the AccQ Tag™ ULTRA kit. CONCLUSIONS: The LC-MS assay demonstrated variable analytical performance and correlated poorly with ion exchange chromatography. Both LC-MS/MS assays demonstrated comparable analytical performance and reasonable correlation with ion exchange chromatography. They also confer practical advantages which cannot be realized by ion exchange chromatography, superior specificity and significantly faster analysis time, suggesting that ion exchange chromatography should no longer be described as the gold standard method for plasma amino acid analysis.

Acidemia propiónica: una causa sumamente rara de linfohistiocitosis hemofagocítica en un lactante / Propionic acidemia: an extremely rare cause of hemophagocytic lymphohistiocytosis in an infant

La linfohistiocitosis hemofagocítica (LHH) puede ser primaria (hereditaria) o secundaria a infecciones, tumores malignos, trastornos reumatológicos, síndromes de inmunodeficiencia y metabolopatías. Se informaron casos de intolerancia a la proteína lisinúrica, deficiencia de múltiples sulfatasas, galactosemia, enfermedad de Gaucher, síndrome de Pearson y galactosialidosis. No se sabe cómo se desencadena la LHH en las metabolopatías. Se diagnosticó LHH en un lactante de 2 meses con letargo, palidez, alimentación deficiente, hepatoesplenomegalia, fiebre y pancitopenia, y se instauró el protocolo HLH-2004. Se realizaron, en conjunto, análisis para detectar mutaciones genéticas y pruebas metabólicas; los resultados fueron negativos para las mutaciones genéticas de LHH primaria, pero se detectaron hiperamoniemia y concentración elevada de metilcitrato. Se diagnosticó acidemia propiónica. Aquí informamos sobre un caso de LHH secundaria a acidemia propiónica. Es posible la realización simultánea de pruebas de detección de trastornos metabólicos y de mutaciones genéticas para el diagnóstico temprano en los lactantes con LHH

Hemophagocytic lymphohystiocytosis (HLH) may be primary (inherited/familial) or secondary to infections, malignancies, rheumatologic disorders, immune deficiency syndromes and metabolic diseases. Cases including lysinuric protein intolerance, multiple sulfatase deficiency, galactosemia, Gaucher disease, Pearson syndrome, and galactosialidosis have previously been reported. It is unclear how the metabolites trigger HLH in metabolic diseases. A 2-month-old infant with lethargy, pallor, poor feeding, hepatosplenomegaly, fever and pancytopenia, was diagnosed with HLH and the HLH-2004 treatment protocol was initiated. Analysis for primary HLH gene mutations and metabolic screening tests were performed together; primary HLH gene mutations were negative, but hyperammonemia and elevated methyl citrate were detected. Propionic acidemia was diagnosed with tandem mass spectrometry in neonatal dried blood spot. We report this case of HLH secondary to propionic acidemia. Both metabolic disorder screening tests and gene mutation analysis may be performed simultaneously especially for early diagnosis in infants presenting with HLH.

Conformational analysis of the riboflavin-responsive ETF:QO-p.Pro456Leu variant associated with mild multiple acyl-CoA dehydrogenase deficiency.

Multiple-CoA dehydrogenase deficiency (MADD) is an inborn disorder of fatty acid and amino acid metabolism caused by mutations in the genes encoding for human electron transfer flavoprotein (ETF) and its partner electron transfer flavoprotein:ubiquinone oxidoreductase (ETF:QO). Albeit a rare disease, extensive newborn screening programs contributed to a wider coverage of MADD genotypes. However, the impact of non-lethal mutations on ETF:QO function remains scarcely understood from a structural perspective. To this end, we here revisit the relatively common MADD mutation ETF:QO-p.Pro456Leu, in order to clarify how it affects enzyme structure and folding. Given the limitation in recombinant expression of human ETF:QO, we resort to its bacterial homologue from Rhodobacter sphaeroides (Rs), in which the corresponding mutation (p.Pro389Leu) was inserted. The in vitro biochemical and biophysical investigations of the Rs ETF:QO-p.Pro389Leu variant showed that, while the mutation does not significantly affect the protein α/ß fold, it introduces some plasticity on the tertiary structure and within flavin interactions. Indeed, in the p.Pro389Leu variant, FAD exhibits a higher thermolability during thermal denaturation and a faster rate of release in temperature-induced dissociation experiments, in comparison to the wild type. Therefore, although this clinical mutation occurs in the ubiquinone domain, its effect likely propagates to the nearby FAD binding domain, probably influencing electron transfer and redox potentials. Overall, our results provide a molecular rational for the decreased enzyme activity observed in patients and suggest that compromised FAD interactions in ETF:QO might account for the known riboflavin responsiveness of this mutation.

Ampliación del tamizaje de errores innatos del metabolismo en Perú: reporte de caso con trastorno del metabolismo de cobalamina / Widened screening for innate metabolism disorders in Peru: report of a case with cobalamin metabolism disorder

RESUMEN El tamizaje neonatal de los errores innatos del metabolismo se instauró hace más de 50 años en el mundo. En Latinoamérica, Uruguay, Costa Rica, Chile, Brasil y Colombia han implementado esta política de salud pública de manera sostenida. La tecnología para detectar estas enfermedades ha ido progresando con un mejor costo/efectividad, haciendo que sea de acceso casi universal. Los trastornos del metabolismo intracelular de la cobalamina es un grupo heterogéneo clasificados en tres fenotipos bioquímicos. Reportamos al primer paciente en Perú con diagnóstico tardío de una variante homocigota c.394 C>T en el gen MMACHC, el cual pertenece al grupo de complementación cblC el cual produce aciduria metilmalónica y homocistinuria, caracterizado por talla baja, hipotonía, retraso del desarrollo psicomotor, convulsiones, anemia megaloblástica, trombocitopenia y neutropenia ondulantes; con homocisteína elevada, acidemia metilmalónica, y contradictoriamente aumento de vitamina B12 en sangre. Es importante el diagnóstico oportuno de enfermedades potencialmente tratables, evitando o disminuyendo la severidad del fenotipo, a través de la implementación de nuevas tecnologías en nuestro país.

ABSTRACT Neonatal screening for innate metabolism disorders was instituted more than 50 years ago. In Latin America, countries like Uruguay, Costa Rica, Chile, Brazil, and Colombia have implemented this public health measurement in a sustained fashion. Technology for detecting these conditions has been steadily progressing, achieving a good cost/effectiveness ratio, so access for such test is practically universal. Intracellular cobalamin metabolism disorders constitute a heterogeneous group that is subdivided in three biochemical phenotypes. We report the first patient in Peru with a late diagnosis of a homozygous c.394 C>T variant in the MMACHC gene, which belongs to the cbIC complementation group, which leads to methyl-malonic aciduria and homocystinuria, characterized by low height, retardation of psychomotor development, seizures, megaloblastic anemia, and variable thrombocytopenia and neutropenia. Also, homocysteine levels are high, there is methyl-malonic academia, and there is a paradoxical vitamin B12 increase in peripheral blood. This paper emphasizes the importance of making a timely diagnosis of potentially treatable conditions, avoiding or reducing the severity of the implied phenotype, with the implementation of new technologies in our country.

Metabolic screening and metabolomics analysis in the Intellectual Developmental Disorders Mexico Study / Tamiz bioquímico y metabolómico en el estudio de los trastornos del desarrollo intelectual en México

Abstract: Objective: Inborn errors of metabolism (IEM) are genetic conditions that are sometimes associated with intellectual developmental disorders (IDD). The aim of this study is to contribute to the metabolic characterization of IDD of unknown etiology in Mexico. Materials and methods: Metabolic screening using tandem mass spectrometry and fluorometry will be performed to rule out IEM. In addition, target metabolomic analysis will be done to characterize the metabolomic profile of patients with IDD. Conclusion: Identification of new metabolomic profiles associated with IDD of unknown etiology and comorbidities will contribute to the development of novel diagnostic and therapeutic schemes for the prevention and treatment of IDD in Mexico.

Resumen: Objetivo: Los errores innatos del metabolismo (EIM) son condiciones genéticas que pueden asociarse con trastornos del desarrollo intelectual (TDI). El objetivo de este estudio es contribuir a la caracterización metabólica de los pacientes con TDI de etiología desconocida. Material y métodos: Se realizará un tamiz metabólico mediante espectrometría de masas-tándem y fluorometría para descartar EIM; además, se analizará el perfil metabolómico de los pacientes con TDI. Conclusión: La identificación de perfiles metabolómicos asociados con los TDI de etiología desconocida contribuirá al desarrollo de nuevos esquemas diagnósticos y terapéuticos para la prevención y tratamiento de los TDI en México.

Reversal of Pathologic Lipid Accumulation in NPC1-Deficient Neurons by Drug-Promoted Release of LAMP1-Coated Lamellar Inclusions.

UNLABELLED: Aging and pathologic conditions cause intracellular aggregation of macromolecules and the dysfunction and degeneration of neurons, but the mechanisms are largely unknown. Prime examples are lysosomal storage disorders such as Niemann-Pick type C (NPC) disease, where defects in the endosomal-lysosomal protein NPC1 or NPC2 cause intracellular accumulation of unesterified cholesterol and other lipids leading to neurodegeneration and fatal neurovisceral symptoms. Here, we investigated the impact of NPC1 deficiency on rodent neurons using pharmacologic and genetic models of the disease. Improved ultrastructural detection of lipids and correlative light and electron microscopy identified lamellar inclusions as the subcellular site of cholesterol accumulation in neurons with impaired NPC1 activity. Immunogold labeling combined with transmission electron microscopy revealed the presence of CD63 on internal lamellae and of LAMP1 on the membrane surrounding the inclusions, indicating their origins from intraluminal vesicles of late endosomes and of a lysosomal compartment, respectively. Lamellar inclusions contained cell-intrinsic cholesterol and surface-labeled GM1, indicating the incorporation of plasma membrane components. Scanning electron microscopy revealed that the therapeutic drug candidate ß-cyclodextrin induces the subplasmalemmal location of lamellar inclusions and their subsequent release to the extracellular space. In parallel, ß-cyclodextrin mediated the NPC1-independent redistribution of cholesterol within neurons and thereby abolished a deleterious cycle of enhanced cholesterol synthesis and its intracellular accumulation, which was indicated by neuron-specific transcript analysis. Our study provides new mechanistic insight into the pathologic aggregation of macromolecules in neurons and suggests exocytosis as cellular target for its therapeutic reversal. SIGNIFICANCE STATEMENT: Many neurodegenerative diseases involve pathologic accumulation of molecules within neurons, but the subcellular location and the cellular impact are often unknown and therapeutic approaches lacking. We investigated these questions in the lysosomal storage disorder Niemann-Pick type C (NPC), where a defect in intracellular cholesterol transport causes loss of neurons and fatal neurovisceral symptoms. Here, we identify lamellar inclusions as the subcellular site of lipid accumulation in neurons, we uncover a vicious cycle of cholesterol synthesis and accretion, which may cause gradual neurodegeneration, and we reveal how ß-cyclodextrin, a potential therapeutic drug, reverts these changes. Our study provides new mechanistic insight in NPC disease and uncovers new targets for therapeutic approaches.

Adolescent presentations of inborn errors of metabolism.

Several studies have shown that a large percentage of inborn errors of metabolism is present in adolescent patients. Individually, each diagnosis in this category of diseases is rare; therefore, there is often a significant delay in determining the etiology of a patient's complaints. These disorders can have a wide variety of multisystemic presentations, several of which overlap with more common disorders of adolescence. This review highlights the red-flag findings on history and physical examination indicating a possible inborn error of metabolism. In addition, a systematic approach for evaluating and categorizing these disorders is introduced and demonstrated through case examples. Primary care physicians play a crucial role in the early detection and prompt treatment of patients with late-onset inborn errors of metabolism.

Animal models of intellectual disability: towards a translational approach

Intellectual disability is a prevalent form of cognitive impairment, affecting 2-3 percent of the general population. It is a daunting societal problem characterized by significant limitations both in intellectual functioning and in adaptive behavior as expressed in conceptual, social and practical adaptive skills. Intellectual disability is a clinically important disorder for which the etiology and pathogenesis are still poorly understood. Moreover, although tremendous progress has been made, pharmacological intervention is still currently non-existent and therapeutic strategies remain limited. Studies in humans have a very limited capacity to explain basic mechanisms of this condition. In this sense, animal models have been invaluable in intellectual disability investigation. Certainly, a great deal of the knowledge that has improved our understanding of several pathologies has derived from appropriate animal models. Moreover, to improve human health, scientific discoveries must be translated into practical applications. Translational research specifically aims at taking basic scientific discoveries and best practices to benefit the lives of people in our communities. In this context, the challenge that basic science research needs to meet is to make use of a comparative approach to benefit the most from what each animal model can tell us. Intellectual disability results from many different genetic and environmental insults. Taken together, the present review will describe several animal models of potential intellectual disability risk factors.