Propionic Acidemia Research Articles

Screening for Methylmalonic and Propionic Acidemia: Clinical Outcomes and Follow-Up Recommendations.

Wisconsin’s newborn screening program implemented second-tier testing on specimens with elevated propionylcarnitine (C3) to aid in the identification of newborns with propionic and methylmalonic acidemias. The differential diagnosis for elevated C3 also includes acquired vitamin B12 deficiency, which is currently categorized as a false positive screen. The goal of this study was to summarize screening data and evaluate their effectiveness at establishing diagnoses and categorizing false positive cases. All Wisconsin newborns born between 2013 and 2019 with a positive first-tier screen for C3 were included in this study. For each case the first- and second-tier newborn screening data and confirmatory test results were compiled. The clinical determination for each case was reviewed and categorized into groups: inborn error of metabolism, maternal B12 deficiency, infant B12 deficiency, and false positive. A review of the screening data showed a significant overlap in the concentration of biomarkers for newborns with genetic versus acquired disease. Additionally, a review of confirmatory test results showed incomplete ascertainment of maternal vitamin B12 status. The Wisconsin newborn screening program recommended a confirmatory testing algorithm to aid in the diagnosis of inborn errors of metabolism and acquired vitamin B12 deficiency.

Interorgan amino acid interchange in propionic acidemia: the missing key to understanding its physiopathology

BackgroundPropionic acidemia is an inborn error of metabolism caused by a deficiency in the mitochondrial enzyme propionyl-CoA carboxylase that converts the propionyl CoA to methyl malonyl CoA. This leads to profound changes in distinct metabolic pathways, including the urea cycle, with consequences in ammonia detoxification. The implication of the tricarboxylic acid cycle is less well known, but its repercussions could explain both some of the acute and long-term symptoms of this disease.Materials and methodsThe present observational study investigates the amino acid profiles of patients with propionic acidemia being monitored at the Hospital Ramón y Cajal (Madrid, Spain), between January 2015 and September 2017, comparing periods of metabolic stability with those of decompensation with ketosis and/or hyperammonemia.ResultsThe concentrations of 19 amino acids were determined in 188 samples provided by 10 patients. We identified 40 metabolic decompensation episodes (22 only with ketosis and 18 with hyperammonemia). Plasma glutamine and alanine levels were reduced during these metabolic crises, probably indicating deficiency of anaplerosis (p < 0.001 for both alanine and glutamine). Hypocitrulllinemia and hypoprolinemia were also detected during hyperammonemia (p < 0.001 and 0.03, respectively).ConclusionsThe amino acid profile detected during decompensation episodes suggests deficient anaplerosis from propionyl-CoA and its precursors, with implications in other metabolic pathways like synthesis of urea cycle amino acids and ammonia detoxification.

Diagnosis of inborn errors of metabolism within the expanded newborn screening in the Madrid region.

We present the results of our experience in the diagnosis of inborn errors of metabolism (IEM) since the Expanded Newborn Screening was implemented in our Region. Dried blood samples were collected 48 h after birth. Amino acids and acylcarnitines were quantitated by mass spectrometry (MS)/MS. Newborns with alterations were referred to the clinical centers for follow‐up. Biochemical and molecular genetic studies for confirmation of a disease were performed. In the period 2011 to 2019, 592 822 children were screened: 902 of them were referred for abnormal results. An IEM was confirmed in 222 (1/2670): aminoacidopathies: 89 hyperphenylalaninemia (HPA) (51 benign HPA, 32 phenylketonuria, 4 DNAJC12 defect, and 2 primapterinuria), 6 hypermethioninemia, 3 tyrosinemia type 1 (TYR‐1), 1 TYR‐3, 4 maple syrup urine disease (MSUD), 2 branched‐chain amino acid transferase 2 deficiency, 2 homocystinuria, 1 cystinuria, 2 ornithine transcarbamylase (OTC) deficiency, 2 citrullinemia type I (CTLN1); FAO defects: 43 medium‐chain acyl‐CoA dehydrogenase deficiency (MCADD), 13 very long‐chain acyl‐CoA dehydrogenase deficiency, 2 long‐chain 3‐hydroxyacyl‐CoA dehydrogenase deficiency (LCHADD), 1 multiple acyl‐coA dehydrogenation deficiency, 11 systemic primary carnitine deficiency, 2 carnitine palmitoyltransferase type 2 (CPT‐II) deficiency, 1 CPT‐I deficiency; organic acidurias: 12 glutaric aciduria type 1 (GA‐1), 4 methylmalonic acidemia (MMA), 7 MMA including combined cases with homocystinuria (MMAHC), 6 propionic acidemia (PA), 7 3‐methylcrotonyl‐CoA carboxylase, 1 3‐hydroxy‐3‐methylglutaryl‐CoA lyase deficiency lyase deficiency. Only 19 infants (8.5%) were symptomatic at newborn screening result (1 LCHADD, 5 PA, 1 CPT‐II deficiency, 1 MMA, 3 MMAHC, 2 MSUD, 2 OTC deficiency, 1 CTLN1, 1 MCADD, 2 TYR‐1). No false negative cases were identified. Genetic diagnosis was conclusive in all biochemically confirmed cases, except for two infants with HPA, identifying pathogenic variants in 32 different genes. The conditions with the highest incidence were HPA (1/6661) and MCAD deficiencies (1/13 787).

Biomarkers for drug development in propionic and methylmalonic acidemias.

There is an unmet need for the development and validation of biomarkers and surrogate endpoints for clinical trials in propionic acidemia (PA) and methylmalonic acidemia (MMA). This review examines the pathophysiology and clinical consequences of PA and MMA that could form the basis for potential biomarkers and surrogate endpoints. Changes in primary metabolites such as methylcitric acid (MCA), MCA:citric acid ratio, oxidation of 13C‐propionate (exhaled 13CO2), and propionylcarnitine (C3) have demonstrated clinical relevance in patients with PA or MMA. Methylmalonic acid, another primary metabolite, is a potential biomarker, but only in patients with MMA. Other potential biomarkers in patients with either PA and MMA include secondary metabolites, such as ammonium, or the mitochondrial disease marker, fibroblast growth factor 21. Additional research is needed to validate these biomarkers as surrogate endpoints, and to determine whether other metabolites or markers of organ damage could also be useful biomarkers for clinical trials of investigational drug treatments in patients with PA or MMA. This review examines the evidence supporting a variety of possible biomarkers for drug development in propionic and methylmalonic acidemias.

Inborn error of metabolism patients after liver transplantation: Outcomes of 35 patients over 27 years in one pediatric quaternary hospital.

Liver transplantation (LT) has been used for many years as a therapeutic option for certain inborn errors of metabolism (IEMs). Here we present one institution's 27 years of experience with LT in IEMs. Our objective is to assess the outcomes of IEM patients who have undergone LT, which we hypothesize to be generally successful for prevention of metabolic decompensation. A retrospective chart review was performed on patients with urea cycle defects, organic acidemias, and amino acidopathies who underwent LT at the Children's Hospital of Philadelphia. Thirty-five patients with the following conditions have undergone LT: tyrosinemia (8), methylmalonic acidemia (7), maple syrup urine disease (6), citrullinemia (6), ornithine transcarbamylase deficiency (4), propionic acidemia (2), and argininosuccinate lyase deficiency (2). Average age at transplantation was 3.6 years. Three patients are now deceased. One patient suffered a metabolic stroke posttransplant. No episodes of metabolic decompensation have been noted. Thirty-five patients received LT with generally favorable outcome. None sustained metabolic decompensation posttransplant. As has been reported previously, LT does not ameliorate pre-existing developmental differences or risk to other organ systems. Further research is needed to aid in standardization of care and follow-up, as most patients no longer follow with a geneticist.

Neonatal genetic metabolic disease entities ought to be included in tandem mass spectrometry screening in China

Objective To systematically retrieve and sort out the information on neonatal genetic metabolic disease entities included in tandem mass spectrometry (MS/MS) screening in some countries and to provide a reference for entity expansion in the screening on neonatal genetic metabolic diseases with MS/MS in China. Methods With literature analysis and expert consultation, we assessed the priority order of the neonatal genetic metabolic diseases to be included in screening with MS/MS using a comprehensive score. Results Totally 53 neonatal genetic metabolic diseases were identified with the practicability of to be screened with MS/MS; of which, 23, 16, and 14 were aminoacidopathies, organic acidemias and fatty amino acid metabolic diseases, respectively. The diseases with top ten comprehensive scores in descending order are isovaleric acidemia, glutaric acidemia type Ⅰ, medium-chain acyl-CoA dehydrogenase deficiency, maple syrup urine disease, homocystinuria, propionic acidemia, methyl malonic acidemia, phenylketonuria, citrullinemia type Ⅰ, and very long-chain acyl-CoA dehydrogenase deficiency. Conclusion Based on the study results, we recommend that the ten neonatal genetic metabolic diseases with higher comprehensive scores ought to be included in MS/MS screening and the subsequent disease entities for the screening could be adjusted timely according to screening detection outcomes and the incidences of neonatal genetic metabolic diseases.

Obituary for Charles Rider Roe, MD

Early in his career at Duke University, Charlie pioneered the development and application of creatine phosphokinase isoenzymes and creatine kinase myocardial band analysis for cardiac injury. His interest in isoenzymes in Reye syndrome led him to sabbatical studies of organic acidurias at the Medical Research Council with Alec Lawson and Ron Chalmers. Upon returning to Duke, he created the Mass Spectrometry Facility with David Millington. This led to the discovery of propionylcarnitine in methylmalonic acidemia and propionic acidemia and many other disease-specific acylcarnitines. He also helped to pioneer the application of tandem mass spectrometry to newborn screening. He recruited other geneticists (Y-T Chen, SG Kahler) and genetic counselors, who together created a medical genetics training program. He collaborated with scientists and trainees from around the world. Work with Henri Brunengraber and others began the development of triheptanoin as a truly new therapy for long-chain fatty acid disorders. When he left Duke in 1995 to direct the Summers Metabolic Institute he concentrated on his work with triheptanoin, and expanded newborn screening. He was a member of numerous scientific societies and support organizations for fatty acid disorders and organic acidemias. He is survived by his wife Diane, five children from two marriages, and eight grandchildren.

Inborn errors of metabolism and coronavirus disease 2019: Evaluation of the metabolic outcome.

BackgroundInfectious diseases can result in a catabolic state and possibly trigger an acute metabolic decompensation in inborn errors of metabolism (IEM), which could be life threatening. Studies regarding the course of severe acute respiratory syndrome coronavirus 2 infections in patients with IEM are generally limited to case reports. Here, we aimed to evaluate the clinical findings of coronavirus disease 2019 (COVID‐19) and describe the impact of severe acute respiratory syndrome coronavirus 2 infections on metabolic outcomes in IEM patients.MethodsPatients who were diagnosed with different types of IEM and developed microbiologically confirmed COVID‐19 infection were included. Clinical findings and laboratory results were recorded retrospectively in terms of both IEM and COVID‐19.ResultsEleven patients with diagnosis of intoxication type metabolic disorders, five patients with energy metabolism disorders, and six patients with complex molecular disorders were enrolled. The most frequent clinical finding was fever (52.1%) followed by fatigue/myalgia (47.8%). None of the patients was younger than 1 year. None of the patients presented severe or critical disease. In terms of metabolic decompensation, two patients diagnosed with propionic acidemia, one patient with methylmalonic acidemia and one patient with 3‐hydroxy‐3‐methylglutaryl‐CoA lyase deficiency presented clinical and biochemical findings of an acute metabolic attack.ConclusionsBased on our results, IEM are not found to be an additional risk factor for severe COVID‐19 infection. However, patients with intoxication type and energy metabolism disorders should be considered as a vulnerable population for COVID‐19 and have a major risk of developing acute metabolic decompensation that can lead to life‐threatening complications.

Altered immune response in organic acidemia.

Most patients with organic acidemia suffer from recurrent infections. Although neutropenia has been reported in multiple studies, other components of the immune system have not been evaluated thoroughly. This study was conducted to assess the immune status of patients with organic acidemia (OA). Thirty-three patients with OA who were followed up in Istanbul University-Cerrahpasa, Cerrahpasa School of Medicine, Nutrition and Metabolism Department and a total of 32 age- and sex-matched healthy controls were enrolled to the study. The demographic and clinical data were recorded retrospectively from patient files. Complete blood counts, immunoglobulins, and lymphocyte immunophenotyping were recorded prospectively in a symptom- (infection-) free period. Of the 33 patients enrolled to the study, 21 (88%) were diagnosed with methylmalonic acidemia, 10 (33%) with propionic acidemia, and two (6.6%) with isovaleric acidemia. The mean age of the patients with OA and healthy subjects were 5.89 ± 4.11 years and 5.34 ± 4.36, respectively (P = 0.602). Twenty-nine (88%) of the patients had experienced frequent hospital admission, 13 (39%) were admitted to pediatric intensive care unit, and 18 (55%) suffered from sepsis. Naïve helper T cells and recent thymic emigrants were significantly lower in OAs (P < 0.001). Various defects in humoral immunity have also been documented including memory B cells and immunoglobulins. Patients with OAs may show adaptive immune defects rendering them susceptible to infections. Metabolic reprogramming based on nutritional modifications may be a promising therapeutic option in the future.

The Management of Methylmalonic Aciduria, Propionic Aciduria and Isovaleric Aciduria in Italy: Real-Life Experience with Carbaglu®

The Management of Methylmalonic Aciduria, Propionic Aciduria and Isovaleric Aciduria in Italy: Real-Life Experience with Carbaglu®

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

BackgroundPropionic 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 methodsTo 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. ResultsA 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. ConclusionBCAA 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. SynopsisThe 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).

Propionic acidemia in mice: Liver acyl-CoA levels and clinical course

Propionic acidemia (PA) is a severe autosomal recessive metabolic disease caused by deficiency of propionyl-CoA carboxylase (PCC). We studied PA transgenic (Pat) mice that lack endogenous PCC but express a hypoactive human PCCA cDNA, permitting their survival. Pat cohorts followed from 3 to 20 weeks of age showed growth failure and lethal crises of lethargy and hyperammonemia, commoner in males (27/50, 54%) than in females (11/52, 21%) and occurring mainly in Pat mice with the most severe growth deficiency. Groups of Pat mice were studied under basal conditions (P-Ba mice) and during acute crises (P-Ac). Plasma acylcarnitines in P-Ba mice, compared to controls, showed markedly elevated C3- and low C2-carnitine, with a further decrease in C2-carnitine in P-Ac mice. These clinical and biochemical findings resemble those of human PA patients. Liver acyl-CoA measurements showed that propionyl-CoA was a minor species in controls (propionyl-CoA/acetyl-CoA ratio, 0.09). In contrast, in P-Ba liver the ratio was 1.4 and in P-Ac liver, 13, with concurrent reductions of the levels of acetyl-CoA and other acyl-CoAs. Plasma ammonia levels in control, P-Ba and P-Ac mice were 109 ± 10, 311 ± 48 and 551 ± 61 μmol/L respectively. Four-week administration to Pat mice, of carglumate (N-carbamyl-L-glutamic acid), an analogue of N-carbamylglutamate, the product of the only acyl-CoA-requiring reaction directly related to the urea cycle, was associated with increased food consumption, improved growth and absence of fatal crises. Pat mice showed many similarities to human PA patients and provide a useful model for studying tissue pathophysiology and treatment outcomes.

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

BackgroundInborn 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. ObjectiveThis 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. MethodsThis 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). ResultsOut 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. ConclusionWe recommend newborn screening for IEMs using MS/MS, which may help with the early diagnosis and management of this group of disorders.

Fully Automated Quantitative Measurement of Serum Organic Acids via LC-MS/MS for the Diagnosis of Organic Acidemias: Establishment of an Automation System and a Proof-of-Concept Validation.

Gas chromatography-mass spectrometry has been widely used to analyze hundreds of organic acids in urine to provide a diagnostic basis for organic acidemia. However, it is difficult to operate in clinical laboratories on a daily basis due to sample pretreatment processing. Therefore, we aimed to develop a fully automated system for quantifying serum organic acids using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The pretreatment CLAM-2030 device was connected to an LC-MS/MS system for processing serum under optimized conditions, which included derivatizing serum organic acids using 3-Nitrophenylhydrazine. The derivatized organic acids were separated on a reverse-phase Sceptor HD-C column and detected using negative-ion electrospray ionization multiple reaction monitoring MS. The automated pretreatment-LC-MS/MS system processed serum in less than 1 h and analyzed 19 serum organic acids, which are used to detect organic acidemias. The system exhibited high quantitative sensitivity ranging from approximately 2 to 100 µM with a measurement reproducibility of 10.4% CV. Moreover, a proof-of-concept validation of the system was performed using sera from patients with propionic acidemia (n = 5), methylmalonic acidemia (n = 2), and 3-methylcrotonylglycinuria (n = 1). The levels of marker organic acids specific to each disease were significantly elevated in the sera of the patients compared to those in control samples. The automated pretreatment-LC-MS/MS system can be used as a rapid in-hospital system to measure organic acid levels in serum for the diagnosis of organic acidemias.

Functional neurologic disorders in an adult with propionic acidemia: a case report

BackgroundInborn errors of metabolism are often characterized by various psychiatric syndromes. Previous studies tend to classify psychiatric manifestations into clinical entities. Among inborn errors of metabolism, propionic acidemia (PA) is a rare inherited organic aciduria that leads to neurologic disabilities. Several studies in children with PA demonstrated that psychiatric disorders are associated to neurological symptoms. To our knowledge, no psychopathological description in adult with propionic acidemia is available.Case presentationWe aimed to compare the case of a 53-year-old woman with PA, to the previous psychiatric descriptions in children with PA and in adults with other inborn errors of metabolism. Our patient presented a large variety of signs: functional neurologic disorders, borderline personality traits (emotional dyregulation, dissociative and alexithymic trends, obsessive-compulsive disorders), occurring in a context of neurodevelopmental disorder.ConclusionClinical and paraclinical examinations are in favor of a mild mental retardation since childhood and disorders of behavior and personality without any definite psychiatric syndrome, as already described in other metabolic diseases (group 3). Nonetheless, further studies are needed to clarify the psychiatric alterations within adult patients with PA.

Long-term effectiveness of carglumic acid in patients with propionic acidemia (PA) and methylmalonic acidemia (MMA): a randomized clinical trial

BackgroundPropionic acidemia (PA) and methylmalonic acidemia (MMA) are rare, autosomal recessive inborn errors of metabolism that require life-long medical treatment. The trial aimed to evaluate the effectiveness of the administration of carglumic acid with the standard treatment compared to the standard treatment alone in the management of these organic acidemias.MethodsThe study was a prospective, multicenter, randomized, parallel-group, open-label, controlled clinical trial. Patients aged ≤ 15 years with confirmed PA and MMA were included in the study. Patients were followed up for two years. The primary outcome was the number of emergency room (ER) admissions because of hyperammonemia. Secondary outcomes included plasma ammonia levels over time, time to the first episode of hyperammonemia, biomarkers, and differences in the duration of hospital stay.ResultsThirty-eight patients were included in the study. On the primary efficacy endpoint, a mean of 6.31 ER admissions was observed for the carglumic acid arm, compared with 12.76 for standard treatment, with a significant difference between the groups (p = 0.0095). Of the secondary outcomes, the only significant differences were in glycine and free carnitine levels.ConclusionUsing carglumic acid in addition to standard treatment over the long term significantly reduces the number of ER admissions because of hyperammonemia in patients with PA and MMA.

Metabolic perturbations mediated by propionyl-CoA accumulation in organs of mouse model of propionic acidemia

Propionic acidemia (PA) is an autosomal recessive metabolic disorder after gene encoding propionyl-CoA carboxylase, Pcca or Pccb, is mutated. This genetic disorder could develop various complications which are ascribed to dysregulated propionyl-CoA metabolism in organs. However, the effect of attenuated PCC on propionyl-CoA metabolism in different organs remains to be fully understood. We investigated metabolic perturbations in organs of Pcca−/−(A138T) mice (a mouse model of PA) under chow diet and acute administration of [13C3]propionate to gain insight into pathological mechanisms of PA. With chow diet, the metabolic alteration is organ dependent. l-Carnitine reduction induced by propionylcarnitine accumulation only occurs in lung and liver of Pcca−/− (A138T) mice. [13C3]Propionate tracing data demonstrated that PCC activity was dramatically reduced in Pcca−/−(A138T) brain, lung, liver, kidney, and adipose tissues, but not significantly changed in Pcca−/−(A138T) muscles (heart and skeletal muscles) and pancreas, which was largely supported by PCCA expression data. The largest expansion of propionylcarnitine in Pcca−/−(A138T) heart after acute administration of propionate indicated the vulnerability of heart to high circulating propionate. The overwhelming propionate in blood also stimulated ketone production from the increased fatty acid oxidation in Pcca−/−(A138T) liver by lowering malonyl-CoA, which has been observed in cases where metabolic decompensation occurs in PA patients. This work shed light on organ-specific metabolic alternations under varying severities of PA.

Liver Transplantation for Propionic Acidemia: Evidence From a Systematic Review and Meta-analysis.

The worldwide experience of liver transplantation (LT) in the treatment of propionic acidemia (PA) remains limited and fragmented. This review aims to provide a comprehensive and quantitative understanding of posttransplant clinical outcomes in PA patients. MEDLINE, Embase, and the Cochrane Library databases were searched for studies focusing on PA patients who underwent LT. The pooled estimate rates and 95% confidence intervals (CIs) were calculated using a random-effects model with Freeman-Tukey double arcsine transformation. Twenty-one studies involving 70 individuals were included. The pooled estimate rates were 0.95 (95% CI, 0.80-1.00) for patient survival and 0.91 (95% CI, 0.72-1.00) for allograft survival. The pooled estimate rates were 0.20 (95% CI, 0.05-0.39) for rejection, 0.08 (95% CI, 0.00-0.21) for hepatic artery thrombosis, 0.14 (95% CI, 0.00-0.37) for cytomegalovirus/Epstein-Barr virus infection, and 0.03 (95% CI, 0.00-0.15) for biliary complications. The pooled estimate rates were 0.98 (95% CI, 0.88-1.00) for metabolic stability, 1.00 (95% CI, 0.79-1.00) for reversal of preexisting cardiomyopathy, and 0.97 (95% CI, 0.78-1.00) for improvement of neurodevelopmental delay. A large proportion of patients achieved liberalization of protein intake posttransplant (pooled estimate rate 0.66 [95% CI, 0.35-0.93]). Despite the risk of transplant-related complications, LT is a viable therapeutic option in PA patients with satisfactory survival rates and clinical outcomes. Given the diversity in neurological assessment methods and the inconsistency in the achievement of dietary protein liberalization across different studies, consensus on neurological evaluation methods and posttransplant protein intake is necessary. Longer-term clinical outcomes of LT for PA warrants further investigation.

Pediatric Liver Transplantation as Enzyme Replacement Therapy for Rare Metabolic Diseases with No Structural Liver Damage

Objective: Very rare monogenic metabolic diseases without structural liver damage can be cured by liver transplantation. This process is a surgical enzyme replacement therapy, and defective enzymes may or may not be confined to the liver. The aims of this single center study of children with metabolic diseases showing structurally normal liver parenchyma were to analyze the indications and post-operative outcomes of liver transplantation, identification of developmental and metabolic benefits of the procedure with recognition of peri-operative difficulties to improve the success rate.&#x0D; Materials and Methods: Patients under the age of 19-year-old who underwent liver transplantation for metabolic disorders with no structural liver injury between January 2015 and June 2021 analyzed retrospectively. Patient and graft survivals, indications for transplantation, presence of extra-hepatic enzyme deficiency causing other organ damage, inclusion of simultaneous or sequential kidney transplantation, immunosuppressive protocols, post-transplant complications, and metabolic outcomes were identified.&#x0D; Results: Eight children with primary hyperoxaluria type 1 (n = 4), Maple syrup urine disease (n = 1), Crigler-Najjar syndrome type 1 (n=1), familial hypercholesterolemia (n=1) and propionic acidemia (n = 1) received left lobe (n=6) and left lateral segment (2) allografts from living donors. The median age of 4 girls and 4 boys at time of transplantation was 6.8 years (range 2.2-12.7 years). The median follow-up time was 3.3 years (range 1.5-5.7 years). The most common post-transplant complications were biliary system complications and infections and, two patients died because of sepsis. Six patients are alive with normal functioning allografts and metabolically stable on unrestricted diet.&#x0D; Conclusion: Liver transplantation is a lifesaving treatment and improves patient’s and parent’s life quality for metabolic disorders with no parenchymal injury despite strict dietary restrictions and medical therapies. Especially, living donor liver transplantation is very important for populations with very low organ donation rates.