Refine
Departments, institutes and facilities
Document Type
- Article (124)
- Part of a Book (3)
- Preprint (2)
Year of publication
Keywords
- Organic aciduria (5)
- Inborn error of metabolism (4)
- Ketolysis (4)
- organic aciduria (4)
- Ketogenesis (3)
- Ketone body (3)
- Metabolic acidosis (3)
- metabolic acidosis (3)
- 3-hydroxyisobutyrate dehydrogenase (2)
- 3-hydroxyisobutyric aciduria (2)
Dihydropyrimidine dehydrogenase (DPD) deficiency is an infrequently described autosomal recessive disorder of the pyrimidine degradation pathway and can lead to mental and motor retardation and convulsions. DPD deficiency is also known to cause a potentially lethal toxicity following administration of the antineoplastic agent 5-fluorouracil. In an ongoing study of 72 DPD deficient patients, we analysed the molecular background of 5 patients in more detail in whom initial sequence analysis did not reveal pathogenic mutations. In three patients, a 13.8 kb deletion of exon 12 was found and in one patient a 122 kb deletion of exon 14–16 of DPYD. In the fifth patient, a c.299_302delTCAT mutation in exon 4 was found and also loss of heterozygosity of the entire DPD gene. Further analysis demonstrated a de novo deletion of approximately 14 Mb of chromosome 1p13.3–1p21.3, which includes DPYD. Haploinsufficiency of NTNG1, LPPR4, GPSM2, COL11A1 and VAV3 might have contributed to the severe psychomotor retardation and unusual craniofacial features in this patient. Our study showed for the first time the presence of genomic deletions affecting DPYD in 7% (5/72) of all DPD deficient patients. Therefore, screening of DPD deficient patients for genomic deletions should be considered.
Dihydropyrimidinase deficiency: Phenotype, genotype and structural consequences in 17 patients
(2010)
Gene expression and cell growth rely on the intracellular concentration of amino acids, which in metazoans depends on extracellular amino acid availability and transmembrane transport. To investigate the impact of extracellular amino acid concentrations on the expression of a concentrative amino acid transporter, we overexpressed the main kidney proximal tubule luminal neutral amino acid transporter B0AT1-collectrin (SLC6A19-TMEM27) in MDCK cell epithelia. Exogenously expressed proteins co-localized at the luminal membrane and mediated neutral amino acid uptake. However, the transgenes were lost over few cell culture passages. In contrast, the expression of a control transgene remained stable. To test whether this loss was due to inappropriately high amino acid uptake, freshly transduced MDCK cell lines were cultivated either with physiological amounts of amino acids or with the high concentration found in standard cell culture media. Expression of exogenous transporters was unaffected by physiological amino acid concentration in the media. Interestingly, mycoplasma infection resulted in a significant increase in transgene expression and correlated with the rapid metabolism of L-arginine. However, L-arginine metabolites were shown to play no role in transgene expression. In contrast, activation of the GCN2 pathway revealed by an increase in eIF2α phosphorylation may trigger transgene derepression. Taken together, high extracellular amino acid concentration provided by cell culture media appears to inhibit the constitutive expression of concentrative amino acid transporters whereas L-arginine depletion by mycoplasma induces the expression of transgenes possibly via stimulation of the GCN2 pathway.
A structural mapping of mutations causing succinyl-CoA:3-ketoacid CoA transferase (SCOT) deficiency
(2013)
Succinyl-CoA:3-ketoacid CoA transferase (SCOT) deficiency is a rare inherited metabolic disorder of ketone metabolism, characterized by ketoacidotic episodes and often permanent ketosis. To date there are ~20 disease-associated alleles on the OXCT1 gene that encodes the mitochondrial enzyme SCOT. SCOT catalyzes the first, rate-limiting step of ketone body utilization in peripheral tissues, by transferring a CoA moiety from succinyl-CoA to form acetoacetyl-CoA, for entry into the tricarboxylic acid cycle for energy production. We have determined the crystal structure of human SCOT, providing a molecular understanding of the reported mutations based on their potential structural effects. An interactive version of this manuscript (which may contain additional mutations appended after acceptance of this manuscript) may be found on the web address:
http://www.thesgc.org/jimd/SCOT
Rescue of lethal molybdenum cofactor deficiency by a biosynthetic precursor from Escherichia coli
(2004)
Changes in plasma amino acid concentrations with increasing age in patients with propionic acidemia
(2010)
Gamma-hydroxybutyric acid
(2005)
In memoriam Willy Lehnert
(2023)
Screening in clinical trials
(2002)
Mutations in ACY1, the gene encoding aminoacylase 1, cause a novel inborn error of metabolism
(2006)
Major progress occurred in understanding inborn errors of ketone body transport and metabolism between the International Congresses on Inborn Errors of Metabolism in Barcelona (2013) and Rio de Janeiro (2017). These conditions impair either ketogenesis (presenting as episodes of hypoketotic hypoglycemia) or ketolysis (presenting as ketoacidotic episodes); for both groups, immediate intravenous glucose administration is the most critical and (mHGGCS, HMGCS2) effective treatment measure.
3-Hydroxy-3-methylglutaryl-coenzyme A lyase (HMGCL, HMGCL) deficiency is a rare inborn error of ketogenesis. Even if the ketogenic enzyme is fully disrupted, an elevated signal for the ketone body acetoacetic acid is a frequent observation in the analysis of urinary organic acids, at least if derivatization is performed by methylation. We provide an explanation for this phenomenon and trace it back to degradation of the derivatized 3-hydroxy-3-methylglutaric acid and high temperature of the injector of the gas chromatograph.
Disorders of the degradation of branched chain amino acids: what is new in clinics and laboratories?
(2012)
Selective screening for inborn errors of metabolism--assessment of metabolites in body fluids
(2011)
Mutations in SELENBP1, encoding a novel human methanethiol oxidase, cause extraoral halitosis
(2017)
Beta-ketothiolase deficiency, also known as mitochondrial acetoacetyl-CoA thiolase (T2) deficiency, is an autosomal recessive disease caused by mutations in the acetylCoA acetyltransferase 1 (ACAT1) gene. A German T2deficient patient that developed a severe ketoacidotic episode at the age of 11 months, was revealed to be a compound heterozygote of a previously reported null mutation, c.472A>G (p.N158D) and a novel mutation, c.949G>A (p.D317N), in ACAT1. The c.949G>A mutation was suspected to cause aberrant splicing as it is located within an exonic splicing enhancer sequence (c. 947CTGACGC) that is a potential binding site for serine/argininerich splicing factor 1. A mutation in this sequence, c.951C>T, results in exon 10 skipping. A minigene construct was synthesized that included exon 9truncated intron 9exon 10truncated intron 10exon 11, and the splicing of this minigene revealed that the c.949G>A mutant construct caused exon 10 skipping in a proportion of the transcripts. Furthermore, additional substitution of G for C at the first nucleotide of exon 10 (c.941G>C) abolished the effect of the c.949G>A mutation. Transient expression analysis of the c.949G>A mutant cDNA revealed no residual T2 activity in the mutated D317N enzyme. Therefore, c.949G>A (D317N) is a pathogenic missense mutation, and diminishes the effect of an exonic splicing enhancer and causes exon 10 skipping. The present study demonstrates that a missense mutation, or even a synonymous substitution, may disrupt enzyme function by interference with splicing.
2-Methyl-3-hydroxybutyryl-CoA dehydrogenase deficiency is caused by mutations in the HADH2 gene
(2003)
Toshiyuki Fukao
(2020)
3-Hydroxyisobutyrate Dehydrogenase (HIBADH) deficiency - a novel disorder of valine metabolism
(2021)
3-Hydroxyisobutyric acid (3HiB) is an intermediate in the degradation of the branched-chain amino acid valine. Disorders in valine degradation can lead to 3HiB accumulation and its excretion in the urine. This article describes the first two patients with a new metabolic disorder, 3-hydroxyisobutyrate dehydrogenase (HIBADH) deficiency, its phenotype and its treatment with a low-valine diet. The detected mutation in the HIBADH gene leads to nonsense-mediated mRNA decay of the mutant allele and to a complete loss-of-function of the enzyme. Under strict adherence to a low-valine diet a rapid decrease of 3HiB excretion in the urine was observed. Due to limited patient numbers and intrafamilial differences in phenotype with one affected and one unaffected individual, the clinical phenotype of HIBADH deficiency needs further evaluation.
Background: Atypical myopathy (AM), an acquired multiple acyl-CoA dehydrogenase deficiency (MADD) in horses, induce changes in mitochondrial metabolism. Only few veterinary laboratories offer diagnostic testing for this disease. Inborn and acquired MADD exist in humans, therefore determination of organic acids (OA) in urine and acylcarnitines (AC) in blood by assays available in medical laboratories can serve as AM diagnostics. The evolution of OA and AC profiles in surviving horses is unreported.
Methods: AC profiles using electrospray ionization tandem mass spectrometry (ESI-MS/MS) and OA in urine using gas chromatography mass spectrometry (GC–MS) were determined in dried blot spots (DBS, n = 7) and urine samples (n = 5) of horses with AM (n = 7) at disease presentation and in longitudinal samples from 3/4 survivors and compared to DBS (n = 16) and urine samples (n = 7) from control horses using the Wilcoxon test.
Results: All short- (C2-C5) and medium-chain (C6-C12) AC in blood differed significantly (p < 0.008) between horses with AM and controls, except for C5:1 (p = 0.45) and C5OH + C4DC (p = 0.06). In AM survivors the AC concentrations decreased over time but were still partially elevated after 7 days. 14/62 (23%) of OA differed significantly between horses with AM and control horses. Concentrations of ethylmalonic acid, 2-hydroxyglutaric acid and the acylglycines (butyryl-, valeryl-, and hexanoylglycine) were highly elevated in the urine of all horses with AM at the day of disease presentation. In AM survivors, concentrations of those metabolites were initially lower and decreased during remission to approach normalization after 7 days.
Conclusion: OA and AC profiling by specialized human medical laboratories was used to diagnose AM in horses. Elevation of specific metabolites were still evident several days after disease presentation, allowing diagnosis via analysis of samples from convalescent animals.
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.
Propionic acidemia in a previously healthy adolescent with acute onset of dilated cardiomyopathy
(2014)
Isovaleric acidemia (IVA), due to isovaleryl-CoA dehydrogenase (IVD) deficiency, results in the accumulation of isovaleryl-CoA, isovaleric acid and secondary metabolites. The increase in these metabolites decreases mitochondrial energy production and increases oxidative stress. This contributes to the neuropathological features of IVA. A general assumption in the literature exists that glycine N-acyltransferase (GLYAT) plays a role in alleviating the symptoms experienced by IVA patients through the formation of N-isovalerylglycine. GLYAT forms part of the phase II glycine conjugation pathway in the liver and detoxifies excess acyl-CoA’s namely benzoyl-CoA. However, very few studies support GLYAT as the enzyme that conjugates isovaleryl-CoA to glycine. Furthermore, GLYATL1, a paralogue of GLYAT, conjugates phenylacetyl-CoA to glutamine. Therefore, GLYATL1 might also be a candidate for the formation of N-isovalerylglycine. Based on the findings from the literature review, we proposed that GLYAT or GLYATL1 can form N-isovalerylglycine in IVA patients. To test this hypothesis, we performed an in-silico analysis to determine which enzyme is more likely to conjugate isovaleryl-CoA with glycine using AutoDock Vina. Thereafter, we performed in vitro validation using purified enzyme preparations. The in-silico and in vitro findings suggested that both enzymes could form N-isovaleryglycine albeit at lower affinities than their preferred substrates. Furthermore, an increase in glycine concentration does not result in an increase in N-isovalerylglycine formation. The results from the critical literature appraisal, in-silico, and in vitro validation, suggest the importance of further investigating the reaction kinetics and binding behaviors between these substrates and enzymes in understanding the pathophysiology of IVA.
Amino acids perform multiple essential physiological roles in humans, and accordingly, their importance to health has been the subject of extensive attention. In this special issue of the Journal of Nutrition and Metabolism, we focus on the various inborn errors of amino acid metabolism, their diagnostic challenges, new treatment approaches, and recent advances in patient monitoring as well as clinical outcomes.
BACKGROUND
Hyperlysinemia is an autosomal recessive inborn error of L-lysine degradation. To date only one causal mutation in the AASS gene encoding α-aminoadipic semialdehyde synthase has been reported. We aimed to better define the genetic basis of hyperlysinemia.
METHODS
We collected the clinical, biochemical and molecular data in a cohort of 8 hyperlysinemia patients with distinct neurological features.
RESULTS
We found novel causal mutations in AASS in all affected individuals, including 4 missense mutations, 2 deletions and 1 duplication. In two patients originating from one family, the hyperlysinemia was caused by a contiguous gene deletion syndrome affecting AASS and PTPRZ1.
CONCLUSIONS
Hyperlysinemia is caused by mutations in AASS. As hyperlysinemia is generally considered a benign metabolic variant, the more severe neurological disease course in two patients with a contiguous deletion syndrome may be explained by the additional loss of PTPRZ1. Our findings illustrate the importance of detailed biochemical and genetic studies in any hyperlysinemia patient.
Background 3-hydroxy-3-methylglutaryl-coenzyme A lyase deficiency (HMGCLD) is an autosomal recessive disorder of ketogenesis and leucine degradation due to mutations in HMGCL .
Method We performed a systematic literature search to identify all published cases. 211 patients of whom relevant clinical data were available were included in this analysis. Clinical course, biochemical findings and mutation data are highlighted and discussed. An overview on all published HMGCL variants is provided.
Results More than 95% of patients presented with acute metabolic decompensation. Most patients manifested within the first year of life, 42.4% already neonatally. Very few individuals remained asymptomatic. The neurologic long-term outcome was favorable with 62.6% of patients showing normal development.
Conclusion This comprehensive data analysis provides a systematic overview on all published cases with HMGCLD including a list of all known HMGCL mutations.
2-methylacetoacetyl-coenzyme A thiolase (beta-ketothiolase) deficiency: one disease - two pathways
(2019)
Background: 2-methylacetoacetyl-coenzyme A thiolase deficiency (MATD; deficiency of mitochondrial acetoacetyl-coenzyme A thiolase T2/ “beta-ketothiolase”) is an autosomal recessive disorder of ketone body utilization and isoleucine degradation due to mutations in ACAT1.
Methods: We performed a systematic literature search for all available clinical descriptions of patients with MATD. 244 patients were identified and included in this analysis. Clinical course and biochemical data are presented and discussed.
Results: For 89.6 % of patients at least one acute metabolic decompensation was reported. Age at first symptoms ranged from 2 days to 8 years (median 12 months). More than 82% of patients presented in the first two years of life, while manifestation in the neonatal period was the exception (3.4%). 77.0% (157 of 204 patients) of patients showed normal psychomotor development without neurologic abnormalities.
Conclusion: This comprehensive data analysis provides a systematic overview on all cases with MATD identified in the literature. It demonstrates that MATD is a rather benign disorder with often favourable outcome, when compared with many other organic acidurias.