Domino liver transplantation for maple syrup urine disease in children: A single-center case series

BACKGROUND

Domino liver transplant (DLT) represents another type of liver donor to expand the donor pool. Recent reports of successful DLT in children with maple syrup urine disease (MSUD) show promising long-term outcomes.

METHODS

It was a retrospective study. All children with MSUD were paired with either recipients with end-stage liver disease (ESLD) or non-MSUD metabolic disease. Each pair underwent simultaneous liver transplant (LT), where the MSUD recipient received the graft from a living-related donor and the liver explanted from the MSUD donor was transplanted to the respective paired domino recipient. We report our experience regarding the techniques and outcomes of DLT at our center.

RESULTS

Eleven children with MSUD and 12 respective DLT recipients were enrolled, one of which was domino split-liver transplantation. DLT recipients included seven ESLD, two propionic acidemia (PA), one glycogen storage disease(GSD) type-1, one GSD type-3, and one Citrullinemia. Post-LT ICU and hospital stays were comparable (p > .05). Patient and graft survival was 100% and 66.6% in the MSUD group and DLT recipients at a mean follow-up of 13.5 and 15 months. There was no death in the MSUD group as compared to four in the DLT group. The amino acid levels rapidly normalized after the LT in the children with MSUD and they tolerated the normal unrestricted diet. No vascular, biliary, or graft-related complications were seen in the post-transplant period. No occurrence of MSUD was noted in DLT recipients.

CONCLUSION

DLTs have excellent post-surgical outcomes. DLT should be strongly considered and adopted by transplant programs worldwide to circumvent organ shortage.

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.

Acyl-CoA dehydrogenase substrate promiscuity: Challenges and opportunities for development of substrate reduction therapy in disorders of valine and isoleucine metabolism

Toxicity of accumulating substrates is a significant problem in several disorders of valine and isoleucine degradation notably short-chain enoyl-CoA hydratase (ECHS1 or crotonase) deficiency, 3-hydroxyisobutyryl-CoA hydrolase (HIBCH) deficiency, propionic acidemia (PA), and methylmalonic aciduria (MMA). Isobutyryl-CoA dehydrogenase (ACAD8) and short/branched-chain acyl-CoA dehydrogenase (SBCAD, ACADSB) function in the valine and isoleucine degradation pathways, respectively. Deficiencies of these acyl-CoA dehydrogenase (ACAD) enzymes are considered biochemical abnormalities with limited or no clinical consequences. We investigated whether substrate reduction therapy through inhibition of ACAD8 and SBCAD can limit the accumulation of toxic metabolic intermediates in disorders of valine and isoleucine metabolism. Using analysis of acylcarnitine isomers, we show that 2-methylenecyclopropaneacetic acid (MCPA) inhibited SBCAD, isovaleryl-CoA dehydrogenase, short-chain acyl-CoA dehydrogenase and medium-chain acyl-CoA dehydrogenase, but not ACAD8. MCPA treatment of wild-type and PA HEK-293 cells caused a pronounced decrease in C3-carnitine. Furthermore, deletion of ACADSB in HEK-293 cells led to an equally strong decrease in C3-carnitine when compared to wild-type cells. Deletion of ECHS1 in HEK-293 cells caused a defect in lipoylation of the E2 component of the pyruvate dehydrogenase complex, which was not rescued by ACAD8 deletion. MCPA was able to rescue lipoylation in ECHS1 KO cells, but only in cells with prior ACAD8 deletion. SBCAD was not the sole ACAD responsible for this compensation, which indicates substantial promiscuity of ACADs in HEK-293 cells for the isobutyryl-CoA substrate. Substrate promiscuity appeared less prominent for 2-methylbutyryl-CoA at least in HEK-293 cells. We suggest that pharmacological inhibition of SBCAD to treat PA should be investigated further.

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.

Newborn Screening Conditions: Early Intervention and Probability of Developmental Delay

OBJECTIVES

The purpose of this study is to explore which newborn screening (NBS) conditions are automatically eligible for early intervention (EI) across states and to determine the extent to which each disorder should automatically qualify for EI because of a high probability of developmental delay.

METHODS

We examined each state's EI eligibility policy and reviewed the literature documenting developmental outcomes for each NBS condition. Using a novel matrix, we assessed the risk of developmental delay, medical complexity, and risk of episodic decompensation, revising the matrix iteratively until reaching consensus. Three NBS conditions (biotinidase deficiency, severe combined immunodeficiency, and propionic acidemia) are presented in detail as examples.

RESULTS

Most states (88%) had Established Conditions lists to autoqualify children to EI. The average number of NBS conditions listed was 7.8 (range 0-34). Each condition appeared on average in 11.7 Established Conditions lists (range 2-29). After the literature review and consensus process, 29 conditions were likely to meet national criteria for an Established Condition.

CONCLUSION

Despite benefiting from NBS and timely treatment, many children diagnosed with NBS conditions are at risk for developmental delays and significant medical complexity. The results demonstrate a need for more clarity and guidance regarding which children should qualify for EI. We suggest that most NBS conditions should automatically qualify based on the probability of resulting in a developmental delay. These findings suggest a future opportunity for collaboration between NBS and EI programs to create a consistent set of Established Conditions, potentially expediate referrals of eligible children, and streamline children's access to EI services.

Altered gut microbiome diversity and function in patients with propionic acidemia

Propionic acidemia (PA) is an inherited metabolic disorder of propionate metabolism, where the gut microbiota may play a role in pathophysiology and therefore, represent a relevant therapeutic target. Little is known about the gut microbiota composition and activity in patients with PA. Although clinical practice varies between metabolic treatment centers, management of PA requires combined dietary and pharmaceutical treatments, both known to affect the gut microbiota. This study aimed to characterize the gut microbiota and its metabolites in fecal samples of patients with PA compared with healthy controls from the same household. Eight patients (aged 3-14y) and 8 controls (4-31y) were recruited from Center 1 (UK) and 7 patients (11-33y) and 6 controls (15-54y) from Center 2 (Austria). Stool samples were collected 4 times over 3 months, alongside data on dietary intakes and medication usage. Several microbial taxa differed between patients with PA and controls, particularly for Center 1, e.g., Proteobacteria levels were increased, whereas butyrate-producing genera, such as Roseburia and Faecalibacterium, were decreased. Most measured microbial metabolites were lower in patients with PA, and butyrate was particularly depleted in patients from Center 1. Furthermore, microbiota profile of these patients showed the lowest compositional and functional diversity, and lowest stability over 3 months. As the first study to map the gut microbiota of patients with PA, this work represents an important step forward for developing new therapeutic strategies to further improve PA clinical status. New dietary strategies should consider microbial propionate production as well as butyrate production and microbiota stability.

Metabolomics-based safety evaluation of acute exposure to electronic cigarettes in mice

INTRODUCTION

A growing number of epidemiological evidence reveals that electronic cigarettes (E-cigs) were associated with pneumonia, hypertension and atherosclerosis, but the toxicological evaluation and mechanism of E-cigs were largely unknown.

OBJECTIVE

Our study was aimed to explore the adverse effects on organs and metabolomics changes in C57BL/6J mice after acute exposure to E-cigs.

METHODS AND RESULTS

Hematoxylin and eosin (H&E) staining found pathological changes in tissues after acute exposure to E-cigs, such as inflammatory cell infiltration, nuclear pyknosis, and intercellular interstitial enlargement. E-cigs could increase apoptosis-positive cells in a time-dependent way using Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) assay. Oxidative damage indicators of reactive oxygen species (ROS), malondialdehyde (MDA) and 4-hydroxynonena (4-HNE) were also elevated after E-cigs exposure. There was an increasing trend of total glycerol and cholesterol in serum, while the glucose and liver enzymes including alanine aminotransferase (ALT), aspartate transaminase (AST), gamma-glutamyltranspeptidase (γ-GT) had no significant change compared to that of control. Further, Q Exactive high field (HF) mass spectrometer was used to conduct metabolomics, which revealed that differential metabolites including l-carnitine, Capryloyl glycine, etc. Trend analysis showed the type of compounds that change over time. Pathway enrichment analysis indicated that E-cigs affected 24 metabolic pathways, which were mainly regulated amino acid metabolism, further affected the tricarboxylic acid (TCA) cycle. Additionally, metabolites-diseases network analysis found that the type 2 diabetes mellitus, propionic acidemia, defect in long-chain fatty acids transport and lung cancer may be related to E-cigs exposure.

CONCLUSIONS

Our findings provided important clues for metabolites biomarkers of E-cigs acute exposure and are beneficial for disease prevention.

An investigation of different intracellular parameters for Inborn Errors of Metabolism: Cellular stress, antioxidant response and autophagy

Oxidative stress is associated with various disease pathologies including Inborn Errors of Metabolism (IEMs), among the most important causes of childhood morbidity and mortality. At least as much as oxidative stress in cells, reductive stress poses a danger to the disruption of cell homeostasis. p62/SQSTM1, protects cells from stress by activation of Nrf2/Keap1 and autophagy pathways. In this study, we tested the role of cellular stress, mitochondrial dysfunction and autophagy via Nrf2/Keap1/p62 pathway in the pathophysiology of three main groups of IEMs. Our results showed that antioxidant and oxidant capacity alone would not be sufficient to reflect the true clinical picture of these diseases. ATP, ROS and mitochondrial membrane potantial (MMP) measurements demonstrated increased cellular stress and bioenergetic imbalance in methylmalonic acidemia (MMA), indicating mild mitochondrial dysfunction. In isovaleric acidemia (IVA), no major change was detected in ATP, ROS and MMP values. Propionic acidemia (PA), mitochondrial diseases (MIT) and mucopolysaccharidosis IV (MPS IV) might point out mitohormesis to cope with chronic reductive stress. Induction of Nrf2/Keap1/p62 pathway and increased expression of HMOX1 were detected in all IEMs. LC3B-II and p62 expression results indicated an impaired autophagic flux in MIT and MPS IV and an induction of autophagic flux in MMA, PA and IVA, but also partial expression of Beclin1, enables autophagy activation, was detected in all IEMs. We conclude that individual diagnosis and treatments are of great importance in IEMs. In addition, we assume that the application of therapeutic antioxidant or preventive treatments without determining the cellular stress status in IEMs may disrupt the sensitive oxidant-antioxidant balance in the cell, leading to the potential to further disrupt the clinical picture, especially in patients with reductive stress. To the best of our knowledge, this is the first study to simultaneously relate IEMs with cellular stress, mitochondrial dysfunction, and autophagy.

Determining ideal balance among branched-chain amino acids in medical formula for Propionic Acidemia: A proof of concept study in healthy children

BACKGROUND

Propionic Acidemia (PROP) is an inherited metabolic disorder, with defect in the enzyme propionyl-CoA carboxylase (PCC) which catalyzes catabolism of two of the branched-chain amino acids (BCAA), valine, isoleucine. Nutritional management in PROP depends on dietary protein restriction and consumption of medical formula depleted of the offending amino acids. Recently, concerns have been raised about medical formula due to imbalanced content of BCAA (high leucine - another BCAA, and no valine/isoleucine), which negatively impacts plasma concentrations of BCAA, and growth in children with PROP.

OBJECTIVES AND METHODS

To determine an optimal BCAA ratio at which total body protein synthesis is optimized in healthy children using the indicator amino acid oxidation method (oxidation of L-¹³C-Phenylalanine to ¹³CO₂). This was accomplished by reducing leucine intake gradually from the current high dose in medical formula, in order to compare protein synthesis, under different BCAA ratios.

RESULTS

A total of 8 healthy children were studied, completing 42 study days. Significant differences in F¹³CO₂ with different BCAA ratios were found. BCAA ratio (leucine: isoleucine: valine) 1:0:0 was associated with the highest F¹³CO₂ (low protein synthesis) compared to other ratios. By reducing leucine intake, and isoleucine and valine at minimum PROP recommendations, BCAA ratio between1:0.26:0.28 to 1:0.35:0.4 was associated with optimal protein synthesis.

CONCLUSION

BCAA ratio of 1:0:0, present in medical formula limited total body protein synthesis. A balanced BCAA ratio was found between 1:0.26:0.28 and 1:0.35:0.4 (leucine:isoleucine:valine). Future research is needed to test this optimal BCAA ratio for optimizing protein synthesis in patients with PROP.

SYNOPSIS

The article describes a proof-of-concept study done on healthy school-aged children testing different ratios of branched chain amino acid (BCAA, leucine:isoleucine:valine), in order to determine an optimal ratio at which total body protein synthesis is improved and has implications for dietary management of children with Propionic Acidemia (PROP).

Selective screening for inborn errors of metabolism by tandem mass spectrometry at Sohag University Hospital, Egypt

BACKGROUND

Inborn errors of metabolism (IEMs) comprise a group of inherited diseases that can have devastating consequences and cause irreversible damage to different body systems and even lead to death. Newborn screening helps in the presymptomatic diagnosis of many medical disorders including IEMs. Early diagnosis and management of IEMs helps reduce morbidity and mortality.

OBJECTIVE

This study aimed to estimate the prevalence of IEMs among at-risk children and contribute toward early diagnosis and management in order to minimize morbidity and mortality.

METHODS

This prospective study was conducted at the Pediatrics and Neonatology Department, Sohag University Hospital, Egypt. The study enrolled 308 participants suspected of having IEMs. Cases were included based on the presence of any of the following: unexplained convulsions, persistent metabolic acidosis, persistent hypoglycemia, disturbed consciousness, delayed milestones, or family history of previous sibling death with IEMs or sibling death with a history suggestive of IEMs. All participants in the study were subjected to metabolic screening by tandem mass spectrometry (MS/MS).

RESULTS

Out of 308 neonates, 93 (30.2%) were diagnosed with IEMs. The most common diagnosis was phenylketonuria, followed by glutaric aciduria type 1 and maple syrup urine disease (43%, 19.4%, and 14%, respectively). Five patients had Canavan disease, four had medium-chain acyl CoA dehydrogenase deficiency, three had congenital lactic acidosis, two had methylmalonic acidemia, and two had primary carnitine deficiency. Propionic acidemia, isovaleric acidemia, homocystinuria, short-chain acyl CoA dehydrogenase deficiency, B-ketothiolase deficiency, and ketone body utilization defect were diagnosed in one patient each. Most patients improved (73.1%) following proper specific management.

CONCLUSION

We recommend newborn screening for IEMs using MS/MS, which may help with the early diagnosis and management of this group of disorders.

Espasmos infantiles como primera manifestación de la acidemia propiónica

Propionic acidemia is a disorder of branch-chain amino acids, the side chain of cholesterol and odd-chain fatty acid metabolism that leads to the accumulation of toxic acid metabolites. The clinical features typically begin shortly after birth, although they can also appear in young adulthood. We report the case of a 3-year-old boy with atypical onset, who at 6 months presented bursts of infantile spasms and a hypsarrhythmic electroencephalogram. He was treated with vigabatrin. At 8 months magnetic resonance imaging showed a wider than normal subarachnoidal space, and hyperintense thalamus, globus pallidus and subthalamic nucleus. Biochemical and genetic analysis confirmed propionic acidemia. Specific therapy was started and the patient is not currently under anti-epileptic treatment and his electroencephalogram is normal. This onset of propionic acidemia is unusual, and we believe that treatment with vigabatrin protected the basal ganglia from irreversible excitotoxic damage.

Prenatal diagnosis of propionic acidemia

In this report we summarize our experience in prenatal diagnosis of propionic acidemia (PA) since 1987. Overall, we have investigated 25 pregnancies at risk from 19 unrelated families. Until genetic structure of the genes involved in PA was elucidated, prenatal diagnosis has been successfully performed by means of metabolite quantitation and/or enzymatic assays in foetal issue. Today, direct propionyl-CoA carboxylase activity assay in combination with molecular analysis in chorion villi can be regarded as a fast and reliable method of choice for prenatal diagnosis of this organic acidemia.

Living-donor liver transplantation for propionic acidaemia

Three patients with the severe form of propionic acidaemia were treated with living-donor liver transplantation (LDLT). The procedure was successful for all patients and the incidence of metabolic decompensation was reduced dramatically even without protein restriction. Biochemically, however, the improvement was not significant and the patients continued to excrete large amounts of propionic acid metabolites. One of the patients experienced a severe acidaemic episode 3 years after transplantation. LDLT has a beneficial effect on the care of severely affected patients since it reduces the risk of metabolic decompensation and improves the quality of life with less strict dietary control. Adequate protein restriction and medication need to be maintained even after successful transplantation.

The relationship of plasma glutamine to ammonium and of glycine to acid-base balance in propionic acidaemia

Hyperammonaemia is a common and serious complication of propionic acidaemia. Treatment of hyperammonaemia with sodium phenylacetate or phenylbutyrate has not been well studied in this disorder. We reviewed the medical records of 5 patients with propionic acidaemia over a 16-year period. We collected information on events where plasma amino acids and ammonium, plasma acids and acid-base balance, or all 3 parameters were obtained simultaneously. All patients were on protein-restricted diet and carnitine throughout the period. In contrast to hyperammonaemia in patients with a urea cycle disorder, plasma glutamine levels were below the normal mean and there was no correlation between plasma ammonium and glutamine levels. The absence of positive correlation between plasma glutamine and ammonium suggests that the routine use of sodium phenylacetate or phenylbutyrate to treat hyperammonaemia in propionic acidaemia should be questioned until further studies are done. Throughout follow-up of our propionic acidaemia patients, we have observed that plasma glycine levels correlated positively with serum bicarbonate. The association of high plasma glycine with good acid-base balance might have a potential role in management and warrants further investigation.

Infantile mitochondrial DNA depletion syndrome associated with methylmalonic aciduria and 3-methylcrotonyl-CoA and propionyl-CoA carboxylase deficiencies in two unrelated patients: a new phenotype of mtDNA depletion syndrome

Mitochondrial DNA (mtDNA) depletion refers to a quantitative defect in mtDNA and is heterogeneous with regard to causal genotypes and the associated clinical phenotypes. We report two unrelated infants with mtDNA depletion. A diagnosis of methylmalonic aciduria was initially raised in both on the basis of high urine methylmalonic acid and related organic acids and elevated propionylcarnitine and methylmalonylcarnitine. Carboxylase assay with skin fibroblasts revealed low propionyl-CoA and 3-methylcrotonyl-CoA carboxylase and normal pyruvate carboxylase activities. Quantitative Southern blot analysis of mitochondrial and nuclear DNA with muscle tissues revealed the patients' mtDNA to be depleted to 24% and 39% of normal controls. Our two patients showed multiple mitochondrial dysfunction including respiratory chain defects and deficiencies in the two nuclear DNA encoded carboxylases resulting in abnormal urine organic acids. To our knowledge, there is no obvious connection between the defective pathways other than their mitochondrial locations. These two cases may represent a new entity of mitochondrial disease that might be due to a defective common mechanism, such as assembly, maintenance and transport, affecting various mitochondrial enzymes and functions. Mitochondrial depletion should be considered in infants with atypical organic aciduria that may resemblemethylmalonicaciduria, propionicacidaemia, or 3-methylcrotonyl-CoA carboxylase deficiency.