New Cases of Maleylacetoacetate Isomerase Deficiency with Detection by Newborn Screening and Natural History over 32 Years: Experience from a German Newborn Screening Center.

Newborn screening (NBS) for hepatorenal tyrosinemia type I (HT1) based on a determination of succinylacetone is performed in countries worldwide. Recently, biallelic pathogenic variants in GSTZ1 underlying maleylacetoacetate isomerase (MAAI) deficiency have been described as a differential diagnosis in individuals with slightly elevated succinylacetone detected by NBS. We report the experience with NBS for HT1 over 53 months in a large German NBS center and the identification and characterization of additional cases with MAAI deficiency, including one individual with a natural history over 32 years. A total of 516,803 children underwent NBS for HT1 at the NBS center in Heidelberg between August 2016 and December 2020. Of 42 children with elevated succinylacetone, HT1 was confirmed in two cases (1 in 258.401). MAAI deficiency was suspected in two cases and genetically confirmed in one who showed traces of succinylacetone in urine. A previously unreported pathogenic GSTZ1 variant was found in the index in a biallelic state. Segregation analysis revealed monoallelic carriership in the index case's mother and homozygosity in his father. The 32-year-old father had no medical concerns up to that point and the laboratory work-up was unremarkable. MAAI has to be considered a rare differential diagnosis in NBS for HT1 in cases with slight elevations of succinylacetone to allow for correct counselling and treatment decisions. Our observation of natural history over 32 years adds evidence for a benign clinical course of MAAI deficiency without specific treatment.

Neuron-astrocyte metabolic coupling facilitates spinal plasticity and maintenance of inflammatory pain.

Long-lasting pain stimuli can trigger maladaptive changes in the spinal cord, reminiscent of plasticity associated with memory formation. Metabolic coupling between astrocytes and neurons has been implicated in neuronal plasticity and memory formation in the central nervous system, but neither its involvement in pathological pain nor in spinal plasticity has been tested. Here we report a form of neuroglia signalling involving spinal astrocytic glycogen dynamics triggered by persistent noxious stimulation via upregulation of the Protein Targeting to Glycogen (PTG) in spinal astrocytes. PTG drove glycogen build-up in astrocytes, and blunting glycogen accumulation and turnover by Ptg gene deletion reduced pain-related behaviours and promoted faster recovery by shortening pain maintenance in mice. Furthermore, mechanistic analyses revealed that glycogen dynamics is a critically required process for maintenance of pain by facilitating neuronal plasticity in spinal lamina 1 neurons. In summary, our study describes a previously unappreciated mechanism of astrocyte-neuron metabolic communication through glycogen breakdown in the spinal cord that fuels spinal neuron hyperexcitability.

Newborn screening for aromatic l-amino acid decarboxylase deficiency - Strategies, results, and implication for prevalence calculations.

BACKGROUND: Aromatic l-amino acid decarboxylase deficiency (AADCD) is a rare, autosomal-recessive neurometabolic disorder caused by variants in dopa decarboxylase (DDC) gene, resulting in a severe combined deficiency of serotonin, dopamine, norepinephrine, and epinephrine. Birth prevalence of AADCD varies by population. In pilot studies, 3-O-methyldopa (3-OMD) was shown to be a reliable biomarker for AADCD in high-throughput newborn screening (NBS) allowing an early diagnosis and access to gene therapy. To evaluate the usefulness of this method for routine NBS, 3-OMD screening results from the largest three German NBS centers were analyzed. METHODS: A prospective, multicenter (n = 3) NBS pilot study evaluated screening for AADCD by quantifying 3-OMD in dried blood spots (DBS) using tandem mass spectrometry (MS/MS). RESULTS: In total, 766,660 neonates were screened from January 2021 until June 2023 with 766,647 with unremarkable AADCD NBS (766,443 by 1st-tier analysis and 204 by 2nd-tier analysis) and 13 with positive NBS result recalled for confirmatory diagnostics (recall-rate about 1:59,000). Molecular genetic analysis confirmed AADCD (c.79C > T p.[Arg27Cys] in Exon 2 und c.215 A > C p.[His72Pro] in Exon 3) in one infant. Another individual was highly suspected with AADCD but died before confirmation (overall positive predictive value 0.15). False-positive results were caused by maternal L-Dopa use (n = 2) and prematurity (30th and 36th week of gestation, n = 2). However, in 63% (n = 7) the underlying etiology for false positive results remained unexplained. Estimated birth prevalence (95% confidence interval) was 1:766,660 (95% CI 1:775,194; 1:769,231) to 1:383,330 (95% CI 1:384,615; 1:383,142). The identified child remained asymptomatic until last follow up at the age of 9 months. CONCLUSIONS: The proposed screening strategy with 3-OMD detection in DBS is feasible and effective to identify individuals with AADCD. The estimated birth prevalence supports earlier estimations and confirms AADCD as a very rare disorder. Pre-symptomatic identification by NBS allows a disease severity adapted drug support to diminish clinical complications until individuals are old enough for the application of the gene therapy.

Influence of Season, Storage Temperature and Time of Sample Collection in Pancreatitis-Associated Protein-Based Algorithms for Newborn Screening for Cystic Fibrosis.

Newborn screening (NBS) for cystic fibrosis (CF) based on pancreatitis-associated protein (PAP) has been performed for several years. While some influencing factors are known, there is currently a lack of information on the influence of seasonal temperature on PAP determination or on the course of PAP blood concentration in infants during the first year of life. Using data from two PAP studies at the Heidelberg NBS centre and storage experiments, we compared PAP determinations in summer and winter and determined the direct influence of temperature. In addition, PAP concentrations measured in CF-NBS, between days 21-35 and 36-365, were compared. Over a 7-year period, we found no significant differences between PAP concentrations determined in summer or winter. We also found no differences in PAP determination after 8 days of storage at 4 °C, room temperature or 37 °C. When stored for up to 3 months, PAP samples remained stable at 4 °C, but not at room temperature (p = 0.007). After birth, PAP in neonatal blood showed a significant increasing trend up to the 96th hour of life (p < 0.0001). During the first year of life, blood PAP concentrations continued to increase in both CF- (36-72 h vs. 36-365 d p < 0.0001) and non-CF infants (36-72 h vs. 36-365 d p < 0.0001). Seasonal effects in central Europe appear to have a limited impact on PAP determination. The impact of the increase in blood PAP during the critical period for CF-NBS and beyond on the applicability and performance of PAP-based CF-NBS algorithms needs to be re-discussed.

Severity-adjusted evaluation of liver transplantation on health outcomes in urea cycle disorders.

PURPOSE: Liver transplantation (LTx) is performed in individuals with urea cycle disorders when medical management (MM) insufficiently prevents the occurrence of hyperammonemic events. However, there is a paucity of systematic analyses on the effects of LTx on health-related outcome parameters compared to individuals with comparable severity who are medically managed. METHODS: We investigated the effects of LTx and MM on validated health-related outcome parameters, including the metabolic disease course, linear growth, and neurocognitive outcomes. Individuals were stratified into "severe" and "attenuated" categories based on the genotype-specific and validated in vitro enzyme activity. RESULTS: LTx enabled metabolic stability by prevention of further hyperammonemic events after transplantation and was associated with a more favorable growth outcome compared with individuals remaining under MM. However, neurocognitive outcome in individuals with LTx did not differ from the medically managed counterparts as reflected by the frequency of motor abnormality and cognitive standard deviation score at last observation. CONCLUSION: Whereas LTx enabled metabolic stability without further need of protein restriction or nitrogen-scavenging therapy and was associated with a more favorable growth outcome, LTx-as currently performed-was not associated with improved neurocognitive outcomes compared with long-term MM in the investigated urea cycle disorders.

ASS1 deficiency is associated with impaired neuronal differentiation in zebrafish larvae.

Citrullinemia type 1 (CTLN1) is a rare autosomal recessive urea cycle disorder caused by deficiency of the cytosolic enzyme argininosuccinate synthetase 1 (ASS1) due to pathogenic variants in the ASS1 gene located on chromosome 9q34.11. Even though hyperammenomia is considered the major pathomechanistic factor for neurological impairment and cognitive dysfunction, a relevant subset of individuals presents with a neurodegenerative course in the absence of hyperammonemic decompensations. Here we show, that ASS1 deficiency induced by antisense-mediated knockdown of the zebrafish ASS1 homologue is associated with defective neuronal differentiation ultimately causing neuronal cell loss and consecutively decreased brain size in zebrafish larvae in vivo. Whereas ASS1-deficient zebrafish larvae are characterized by markedly elevated concentrations of citrulline - the biochemical hallmark of CTLN1, accumulation of L-citrulline, hyperammonemia or therewith associated secondary metabolic alterations did not account for the observed phenotype. Intriguingly, coinjection of the human ASS1 mRNA not only normalized citrulline concentration but also reversed the morphological cerebral phenotype and restored brain size, confirming conserved functional properties of ASS1 across species. The results of the present study imply a novel, potentially non-enzymatic (moonlighting) function of the ASS1 protein in neurodevelopment.

High Throughput Newborn Screening for Sickle Cell Disease - Application of Two-Tiered Testing with a qPCR-Based Primary screen.

BACKGROUND: Sickle cell disease (SCD) is a group of hemoglobinopathies with a common point mutation causing the production of sickle cell hemoglobin (HbS). In high-throughput newborn screening (NBS) for SCD, a two-step procedure is suitable, in which qPCR first pre-selects relevant samples that are differentiated by a second method. METHODS: Three NBS centers using qPCR-based primary screening for SCD performed a laboratory comparison. Methods using tandem MS or HPLC were used for differentiation. RESULTS: In a benchmarking test, 450 dried blood samples were analyzed. Samples containing HbS were detected as reliably by qPCR as by methods established for hemoglobinopathy testing. In a two-step screening approach, the 2nd-tier-analyses have to distinguish the carrier status from pathological variants. In nine months of regular screening, a total of 353,219 samples were analyzed using two-stage NBS procedures. The 1st-tier screening by qPCR reduced the number of samples for subsequent differentiation by>99.5%. Cases with carrier status or other variants were identified as inconspicuous while 78 cases with SCD were revealed. The derived incidence of 1:4,773, is in good agreement with previously published incidences. CONCLUSION: In high-throughput NBS for SCD, qPCR is suitable to focus 2nd-tier analyses on samples containing HbS, while being unaffected by factors such as prematurity or transfusions. The substantial reduction of samples numbers positively impacts resource conservation, sustainability, and cost-effectiveness. No false negative cases came to attention.

Kidney urinary biomarkers in patients with branched-chain amino acid and cobalamin metabolism defects.

There is a clinical need for early detection of chronic kidney disease (CKD) in patients with organic acidurias. We measured kidney markers in a longitudinal study over 5 years in 40 patients with methylmalonic aciduria (Mut0 ), propionic aciduria (PA), cobalamin A (CblA), and cobalamin C (CblC) deficiencies. Neutrophil gelatinase-associated lipocalin (NGAL), calprotectin (CLP), kidney injury molecule-1 (KIM-1), dickkopf-3 (DKK-3), albumin and beta-2-microglobulin (B2MG) in urine, as well as cystatin C (CysC) in serum were quantified. In Mut0 patients, mean concentrations of B2MG, KIM-1, and DKK-3 were elevated compared with healthy controls, all markers indicative of proximal tubule damage. In PA patients, mean B2MG, albumin, and CLP were elevated, indicating signs of proximal tubule and glomerulus damage and inflammation. In CblC patients, mean B2MG, NGAL, and CLP were increased, and considered as markers for proximal and distal tubule damage and inflammation. B2MG, was elevated in all three diseases, and correlated with DKK-3 in Mut0 /CblA and with eGFR(CysC) and KIM-1 in PA patients, respectively. None of the markers were elevated in CblA patients. Significant deterioration of kidney function, as determined by steady increase in CysC concentrations was noted in seven patients within the observation period. None of the investigated biomarker profiles showed a clear increase or added value for early detection. In conclusion, we identified disease-specific biomarker profiles for inflammation, tubular, and proximal damage in the urine of Mut0 , PA, and CblC patients. Whether these biomarkers can be used for early detection of CKD requires further investigation, as significant kidney function deterioration was observed in only a few patients.

Collaborative evaluation study on 18 candidate diseases for newborn screening in 1.77 million samples.

Analytical and therapeutic innovations led to a continuous but variable extension of newborn screening (NBS) programmes worldwide. Every extension requires a careful evaluation of feasibility, diagnostic (process) quality and possible health benefits to balance benefits and limitations. The aim of this study was to evaluate the suitability of 18 candidate diseases for inclusion in NBS programmes. Utilising tandem mass spectrometry as well as establishing specific diagnostic pathways with second-tier analyses, three German NBS centres designed and conducted an evaluation study for 18 candidate diseases, all of them inherited metabolic diseases. In total, 1 777 264 NBS samples were analysed. Overall, 441 positive NBS results were reported resulting in 68 confirmed diagnoses, 373 false-positive cases and an estimated cumulative prevalence of approximately 1 in 26 000 newborns. The positive predictive value ranged from 0.07 (carnitine transporter defect) to 0.67 (HMG-CoA lyase deficiency). Three individuals were missed and 14 individuals (21%) developed symptoms before the positive NBS results were reported. The majority of tested candidate diseases were found to be suitable for inclusion in NBS programmes, while multiple acyl-CoA dehydrogenase deficiency, isolated methylmalonic acidurias, propionic acidemia and malonyl-CoA decarboxylase deficiency showed some and carnitine transporter defect significant limitations. Evaluation studies are an important tool to assess the potential benefits and limitations of expanding NBS programmes to new diseases.

Combined Newborn Screening Allows Comprehensive Identification also of Attenuated Phenotypes for Methylmalonic Acidurias and Homocystinuria.

Newborn screening (NBS) programs are effective measures of secondary prevention and have been successively extended. We aimed to evaluate NBS for methylmalonic acidurias, propionic acidemia, homocystinuria, remethylation disorders and neonatal vitamin B12 deficiency, and report on the identification of cofactor-responsive disease variants. This evaluation of the previously established combined multiple-tier NBS algorithm is part of the prospective pilot study "NGS2025" from August 2016 to September 2022. In 548,707 newborns, the combined algorithm was applied and led to positive NBS results in 458 of them. Overall, 166 newborns (prevalence 1: 3305) were confirmed (positive predictive value: 0.36); specifically, methylmalonic acidurias (N = 5), propionic acidemia (N = 4), remethylation disorders (N = 4), cystathionine beta-synthase (CBS) deficiency (N = 1) and neonatal vitamin B12 deficiency (N = 153). The majority of the identified newborns were asymptomatic at the time of the first NBS report (total: 161/166, inherited metabolic diseases: 9/14, vitamin B12 deficiency: 153/153). Three individuals were cofactor-responsive (methylmalonic acidurias: 2, CBS deficiency: 1), and could be treated by vitamin B12, vitamin B6 respectively, only. In conclusion, the combined NBS algorithm is technically feasible, allows the identification of attenuated and severe disease courses and can be considered to be evaluated for inclusion in national NBS panels.

Complex metabolic disharmony in PMM2-CDG paves the way to new therapeutic approaches.

PMM2-CDG is the most common defect among the congenital disorders of glycosylation. In order to investigate the effect of hypoglycosylation on important cellular pathways, we performed extensive biochemical studies on skin fibroblasts of PMM2-CDG patients. Among others, acylcarnitines, amino acids, lysosomal proteins, organic acids and lipids were measured, which all revealed significant abnormalities. There was an increased expression of acylcarnitines and amino acids associated with increased amounts of calnexin, calreticulin and protein-disulfid-isomerase in combination with intensified amounts of ubiquitinylated proteins. Lysosomal enzyme activities were widely decreased as well as citrate and pyruvate levels indicating mitochondrial dysfunction. Main lipid classes such as phosphatidylethanolamine, cholesterol or alkyl-phosphatidylcholine, as well as minor lipid species like hexosylceramide, lysophosphatidylcholines or phosphatidylglycerol, were abnormal. Biotinidase and catalase activities were severely reduced. In this study we discuss the impact of metabolite abnormalities on the phenotype of PMM2-CDG. In addition, based on our data we propose new and easy-to-implement therapeutic approaches for PMM2-CDG patients.

A high-throughput newborn screening approach for SCID, SMA, and SCD combining multiplex qPCR and tandem mass spectrometry.

Early diagnosis of severe combined immunodeficiency (SCID), spinal muscular atrophy (SMA), and sickle cell disease (SCD) improves health outcomes by providing a specific treatment before the onset of symptoms. A high-throughput nucleic acid-based method in newborn screening (NBS) has been shown to be fast and cost-effective in the early detection of these diseases. Screening for SCD has been included in Germany's NBS Program since Fall 2021 and typically requires high-throughput NBS laboratories to adopt analytical platforms that are demanding in terms of instrumentation and personnel. Thus, we developed a combined approach applying a multiplexed quantitative real-time PCR (qPCR) assay for simultaneous SCID, SMA, and 1st-tier SCD screening, followed by a tandem mass spectrometry (MS/MS) assay for 2nd-tier SCD screening. DNA is extracted from a 3.2-mm dried blood spot from which we simultaneously quantify T-cell receptor excision circles for SCID screening, identify the homozygous SMN1 exon 7 deletion for SMA screening, and determine the integrity of the DNA extraction through the quantification of a housekeeping gene. In our two-tier SCD screening strategy, our multiplex qPCR identifies samples carrying the HBB: c.20A>T allele that is coding for sickle cell hemoglobin (HbS). Subsequently, the 2nd tier MS/MS assay is used to distinguish heterozygous HbS/A carriers from samples of patients with homozygous or compound heterozygous SCD. Between July 2021 and March 2022, 96,015 samples were screened by applying the newly implemented assay. The screening revealed two positive SCID cases, while 14 newborns with SMA were detected. Concurrently, the qPCR assay registered HbS in 431 samples which were submitted to 2nd-tier SCD screening, resulting in 17 HbS/S, five HbS/C, and two HbS/ß thalassemia patients. The results of our quadruplex qPCR assay demonstrate a cost-effective and fast approach for a combined screening of three diseases that benefit from nucleic-acid based methods in high-throughput NBS laboratories.

Neonatal screening for isovaleric aciduria: Reducing the increasingly high false-positive rate in Germany.

Newborn screening (NBS) for isovaleric acidemia (IVA) is performed by flow injection tandem mass spectrometry quantifying C5 carnitines (C5). Isovalerylcarnitine, however, is isomeric with pivaloylcarnitine which can be present in blood due to maternal use of pivaloylester-containing antibiotics, available in Germany since late 2016. During a 36-month period (January 19-December 21), all newborns screened in Hamburg with a C5 above cutoff (NeoGram®: 0.50 µmol/L or Neobase®2: 0.45 µmol/L) were included in the study. As a second-tier test, a simple ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed to differentiate the C5 isomers pivaloyl-, 2-methylbutyryl-, isovaleryl-, and valerylcarnitine. Out of 156 772 newborns tested, one turned out to have genetically proven IVA while 99 were false positive (C5: 0.5-8.2 µmol/L) due to the presence of pivaloylcarnitine. These cases have increased year by year and show local clusters. Retrospective analysis of another 39 cases from 287 206 neonates tested at the NBS center in Heidelberg with C5 elevation (0.9-10.6 µmol/L) but clinical and biochemical exclusion of IVA yielded evidence of pivaloylcarnitine in all cases. Inclusion of a second-tier test into NBS significantly reduces the high and increasing false-positive rate of IVA screening. This avoids further diagnostic steps, prevents unnecessary stress and anxiety of parents in a remarkably high number of cases. If Hamburg data of 2021 are extrapolated to all of Germany, one can assume around 800 (1‰) false-positive cases in comparison to an average of two classic IVA cases per year. Unless licensing of pivaloylester-containing drugs for use during pregnancy is reconsidered, a second-tier test for C5 determination is indispensable.

Recommendations for diagnosing and managing individuals with glutaric aciduria type 1: Third revision.

Glutaric aciduria type 1 is a rare inherited neurometabolic disorder of lysine metabolism caused by pathogenic gene variations in GCDH (cytogenic location: 19p13.13), resulting in deficiency of mitochondrial glutaryl-CoA dehydrogenase (GCDH) and, consequently, accumulation of glutaric acid, 3-hydroxyglutaric acid, glutaconic acid and glutarylcarnitine detectable by gas chromatography/mass spectrometry (organic acids) and tandem mass spectrometry (acylcarnitines). Depending on residual GCDH activity, biochemical high and low excreting phenotypes have been defined. Most untreated individuals present with acute onset of striatal damage before age 3 (to 6) years, precipitated by infectious diseases, fever or surgery, resulting in irreversible, mostly dystonic movement disorder with limited life expectancy. In some patients, striatal damage develops insidiously. In recent years, the clinical phenotype has been extended by the finding of extrastriatal abnormalities and cognitive dysfunction, preferably in the high excreter group, as well as chronic kidney failure. Newborn screening is the prerequisite for pre-symptomatic start of metabolic treatment with low lysine diet, carnitine supplementation and intensified emergency treatment during catabolic episodes, which, in combination, have substantially improved neurologic outcome. In contrast, start of treatment after onset of symptoms cannot reverse existing motor dysfunction caused by striatal damage. Dietary treatment can be relaxed after the vulnerable period for striatal damage, that is, age 6 years. However, impact of dietary relaxation on long-term outcomes is still unclear. This third revision of evidence-based recommendations aims to re-evaluate previous recommendations (Boy et al., J Inherit Metab Dis, 2017;40(1):75-101; Kolker et al., J Inherit Metab Dis 2011;34(3):677-694; Kolker et al., J Inherit Metab Dis, 2007;30(1):5-22) and to implement new research findings on the evolving phenotypic diversity as well as the impact of non-interventional variables and treatment quality on clinical outcomes.

Identification of potential interferents of methylmalonic acid: A previously unrecognized pitfall in clinical diagnostics and newborn screening.

OBJECTIVES: Determination of methylmalonic acid (MMA) from dried blood spots (DBS) is commonly performed in clinical diagnostics and newborn screening for propionic acidemia (PA) and methylmalonic acidemia. Isobaric compounds of MMA having the same mass can affect diagnostic reliability and quantitative results, which represents a previously unrecognized pitfall in clinical assays for MMA. We set out to identify interfering substances of MMA in DBS, serum and urine samples from confirmed patients with PA and methylmalonic acidemia. METHODS: Techniques included quadrupole time-of-flight high-resolution mass spectrometry (QTOF HR-MS), nuclear magnetic resonance (NMR) spectroscopy, liquid chromatography (LC) and tandem mass spectrometry (MS/MS). RESULTS: The five isobaric metabolites detected in DBS, serum and urine from PA and methylmalonic acidemia patients were confirmed as 2-methyl-3-hydroxybutyrate, 3-hydroxyisovalerate, 2-hydroxyisovalerate, 3-hydroxyvalerate and succinate using a series of experiments. An additional unknown substance with low abundance remained unidentified. CONCLUSIONS: The presented results facilitate the diagnostic and quantitative reliability of the MMA determination in clinical assays. Isobaric species should be investigated in assays for MMA to eliminate possible interference in a wide range of conditions including PA, methylmalonic acidemia, a vitamin B12 deficiency, ketosis and lactic acidosis.

Predicting the disease severity in male individuals with ornithine transcarbamylase deficiency.

OBJECTIVE: Ornithine transcarbamylase deficiency (OTC-D) is an X-linked metabolic disease and the most common urea cycle disorder. Due to high phenotypic heterogeneity, ranging from lethal neonatal hyperammonemic events to moderate symptoms and even asymptomatic individuals, the prediction of the disease course at an early disease stage is very important to individually adjust therapies such as medical treatment or liver transplantation. In this translational study, we developed a severity-adjusted classification system based on in vitro residual enzymatic OTC activity. METHODS: Applying a cell-based expression system, residual enzymatic OTC activities of 71 pathogenic OTC variants were spectrophotometrically determined and subsequently correlated with clinical and biochemical outcome parameters of 119 male individuals with OTC-D (mOTC-D) as reported in the UCDC and E-IMD registries. RESULTS: Integration of multiple data sources enabled the establishment of a robust disease prediction model for mOTC-D. Residual enzymatic OTC activity not only correlates with age at first symptoms, initial peak plasma ammonium concentration and frequency of metabolic decompensations but also predicts mortality. The critical threshold of 4.3% residual enzymatic activity distinguishes a severe from an attenuated phenotype. INTERPRETATION: Residual enzymatic OTC activity reliably predicts the disease severity in mOTC-D and could thus serve as a tool for severity-adjusted evaluation of therapeutic strategies and counselling patients and parents.

Validated UPLC-MS/MS method for the analysis of vitamin B6 pyridoxal 5́-phosphate, pyridoxal, pyridoxine, pyridoxamine, and pyridoxic acid in human cerebrospinal fluid.

Vitamin B6 and its metabolites play a crucial role in the development and interaction of brain metabolism. Following diagnostic improvements additional inherited disorders in vitamin B6 metabolism have been identified, most of them leading to a severe epileptic disorder accompanied by progressive neurological deficits including intellectual disability and microcephaly. Since early treatment can improve the outcome, fast and reliable detection of metabolic biomarkers is important. Therefore, the analysis of vitamin B6 metabolites has become increasingly important, but is, however, still challenging and limited to a few specialized laboratories. Until today, vitamin B6 metabolites are measured by liquid chromatography tandem mass spectrometry (LC-MS/MS) using trichloroacetic acid for protein precipitation. In this work, we present the development and validation of a new, accurate and reliable method for analysis and quantification of the vitamin B6 vitamers pyridoxal 5́-phosphate (PLP), pyridoxal (PL), pyridoxine (PN), pyridoxamine (PM) and pyridoxic acid (PA) in human CSF samples using acetonitrile for protein precipitation. The method is based on ultra-performance liquid chromatography-tandem mass spectrometry using electrospray ionization (UPLC-ESI-MS/MS). The calibration was performed in surrogate matrix Ringer solution and metabolites were quantified by their corresponding isotopically labelled internal standards. A protein precipitation by acetonitrile was applied greatly improving chromatographic separation of the metabolites in a 4.7 min chromatographic run. The method was validated following the European Medical Agency (EMA) and Food and Drug Administration (FDA) guidelines for bioanalytical method validation. The metabolites were quantified from 5 to 200 nmol/L with a seven-point calibration curve and minimum coefficient of regression of 0.99. The validation was performed with quality control samples at four concentration levels with surrogate matrix ringer solution and pooled CSF material. Within- and inter-day accuracy and precision in Ringer solution were within 85.4 % (PLP) and 114.5 % (PM) and from 2.6 % (PA) to 16.5 % (PLP). Within- and inter-day accuracy and precision in pooled CSF material were within 90.5 % (PN) and 120.1 % (PL) and from 1.7 % (PA) to 19.0 % (PM). The method was tested by measuring of 158 CSF samples to determine reference ranges. The B6 vitamers PLP and PL were determined in all CSF samples above 5 nmol/L while PN, PM and PA showed concentrations below or near LOQ. Probable supplementation of PLP was detected in eight CSF samples, which revealed high concentrations of PM, PN, PL, or PA, whereas PLP was in the reference range or slightly elevated. The method is suitable for the application within a routine diagnostic laboratory.

mRNA-based therapy proves superior to the standard of care for treating hereditary tyrosinemia 1 in a mouse model.

Hereditary tyrosinemia type 1 is an inborn error of amino acid metabolism characterized by deficiency of fumarylacetoacetate hydrolase (FAH). Only limited treatment options (e.g., oral nitisinone) are available. Patients must adhere to a strict diet and face a life-long risk of complications, including liver cancer and progressive neurocognitive decline. There is a tremendous need for innovative therapies that standardize metabolite levels and promise normal development. Here, we describe an mRNA-based therapeutic approach that rescues Fah-deficient mice, a well-established tyrosinemia model. Repeated intravenous or intramuscular administration of lipid nanoparticle-formulated human FAH mRNA resulted in FAH protein synthesis in deficient mouse livers, stabilized body weight, normalized pathologic increases in metabolites after nitisinone withdrawal, and prevented early death. Dose reduction and extended injection intervals proved therapeutically effective. These results provide proof of concept for an mRNA-based therapeutic approach to treating hereditary tyrosinemia type 1 that is superior to the standard of care.

GFI1B acts as a metabolic regulator in hematopoiesis and acute myeloid leukemia.

Recent studies highlighted the role of transcription factors in metabolic regulation during hematopoiesis and leukemia development. GFI1B is a transcriptional repressor that plays a critical role in hematopoiesis, and its expression is negatively related to the prognosis of acute myeloid leukemia (AML) patients. We earlier reported a change in the metabolic state of hematopoietic stem cells upon Gfi1b deletion. Here we explored the role of Gfi1b in metabolism reprogramming during hematopoiesis and leukemogenesis. We demonstrated that Gfi1b deletion remarkably activated mitochondrial respiration and altered energy metabolism dependence toward oxidative phosphorylation (OXPHOS). Mitochondrial substrate dependency was shifted from glucose to fatty acids upon Gfi1b deletion via upregulating fatty acid oxidation (FAO). On a molecular level, Gfi1b epigenetically regulated multiple FAO-related genes. Moreover, we observed that metabolic phenotypes evolved as cells progressed from preleukemia to leukemia, and the correlation between Gfi1b expression level and metabolic phenotype was affected by genetic variations in AML cells. FAO or OXPHOS inhibition significantly impeded leukemia progression of Gfi1b-KO MLL/AF9 cells. Finally, we showed that Gfi1b-deficient AML cells were more sensitive to metformin as well as drugs implicated in OXPHOS and FAO inhibition, opening new potential therapeutic strategies.

Six-Month Periodic Fasting in Patients With Type 2 Diabetes and Diabetic Nephropathy: A Proof-of-Concept Study.

CONTEXT: Novel fasting interventions have gained scientific and public attention. Periodic fasting has emerged as a dietary modification promoting beneficial effects on metabolic syndrome. OBJECTIVE: Assess whether periodic fasting reduces albuminuria and activates nephropathy-driven pathways. DESIGN/PARTICIPANTS: Proof-of-concept study where individuals with type 2 diabetes (n = 40) and increased albumin-to-creatinine ratio (ACR) were randomly assigned to receive a monthly fasting-mimicking diet (FMD) or a Mediterranean diet for 6 months with 3-month follow-up. MAIN OUTCOMES MEASURES: Change in ACR was assessed by analysis of covariance adjusted for age, sex, weight loss, and baseline value. Prespecified subgroup analysis for patients with micro- vs macroalbuminuria at baseline was performed. Change in homeostatic model assessment for insulin resistance (HOMA-IR), circulating markers of dicarbonyl detoxification (methylglyoxal-derived hydroimidazolone 1, glyoxalase-1, and hydroxyacetone), DNA-damage/repair (phosphorylated histone H2AX), lipid oxidation (acylcarnitines), and senescence (soluble urokinase plasminogen activator receptor) were assessed as exploratory endpoints. RESULTS: FMD was well tolerated with 71% to 95% of the participants reporting no adverse effects. After 6 months, change in ACR was comparable between study groups [110.3 (99.2, 121.5) mg/g; P = 0.45]. FMD led to a reduction of ACR in patients with microalbuminuria levels at baseline [-30.3 (-35.7, -24.9) mg/g; P ≤ 0.05] but not in those with macroalbuminuria [434.0 (404.7, 463.4) mg/g; P = 0.23]. FMD reduced HOMA-IR [-3.8 (-5.6, -2.0); P ≤ 0.05] and soluble urokinase plasminogen activator receptor [-156.6 (-172.9, -140.4) pg/mL; P ≤ 0.05], while no change was observed in markers of dicarbonyl detoxification or DNA-damage/repair. Change in acylcarnitines was related to patient responsiveness to ACR improvement. At follow-up only HOMA-IR reduction [-1.9 (-3.7, -0.1), P ≤ 0.05]) was sustained. CONCLUSIONS: Improvement of microalbuminuria and of markers of insulin resistance, lipid oxidation, and senescence suggest the potential beneficial effects of periodic fasting in type 2 diabetes.