Publications by authors named "Bruce A Barshop"

61 Publications

Tumor Metabolism and Neurocognition in CNS Lymphoma.

Neuro Oncol 2021 Feb 24. Epub 2021 Feb 24.

Helen Diller Family Comprehensive Cancer Center, UCSF.

Background: The mechanistic basis for neurocognitive deficits in CNS lymphoma and other brain tumors is incompletely understood. We tested the hypothesis that tumor metabolism impairs neurotransmitter pathways and neurocognitive function.

Methods: We performed serial cerebrospinal fluid (CSF) metabolomic analyses using liquid chromatography-electrospray tandem mass spectrometry to evaluate changes in the tumor microenvironment in 14 patients with recurrent CNS lymphoma, focusing on 18 metabolites involved in neurotransmission and bioenergetics. These were paired with serial mini-mental state examinations (MMSE) and MRI studies for tumor volumetric analyses. Patients were analyzed in the setting of the phase I trial of lenalidomide/rituximab. Associations were assessed by Pearson and Spearman correlation coefficient. Generalized estimating equation (gee) models were also established, adjusting for within-subject repeated measures.

Results: Of 18 metabolites, elevated CSF lactate correlated most strongly with lower MMSE score (p<8E-8, rho=-0.67). High lactate was associated with lower GABA, higher glutamate/GABA ratio and dopamine. Conversely, high succinate correlated with higher MMSE score. Serial analysis demonstrated a reproducible, time-dependent, reciprocal correlation between changes in lactate and GABA concentrations. While high lactate and low GABA correlated with tumor contrast enhancing volume, they correlated more significantly with lower MMSE scores than tumor volumes.

Conclusions: We provide evidence that lactate production and Warburg metabolism may impact neurotransmitter dysregulation and neurocognition in CNS lymphomas. We identify novel metabolomic biomarkers that may be applied in future studies of neurocognition in CNS lymphomas. Elucidation of mechanistic interactions between lymphoma metabolism, neurotransmitter imbalance and neurocognition may promote interventions that preserve cognitive function.
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http://dx.doi.org/10.1093/neuonc/noab045DOI Listing
February 2021

Cardiac tissue citric acid cycle intermediates in exercised very long-chain acyl-CoA dehydrogenase-deficient mice fed triheptanoin or medium-chain triglyceride.

J Inherit Metab Dis 2020 11 4;43(6):1232-1242. Epub 2020 Aug 4.

Department of Molecular and Medical Genetics, Oregon Health & Science University, Portland, Oregon, USA.

Anaplerotic odd-chain fatty acid supplementation has been suggested as an approach to replenish citric acid cycle intermediate (CACi) pools and facilitate adenosine triphosphate (ATP) production in subjects with long-chain fatty acid oxidation disorders, but the evidence that cellular CACi depletion exists and that repletion occurs following anaplerotic substrate supplementation is limited. We exercised very long-chain acyl-CoA dehydrogenase-deficient (VLCAD-/-) and wild-type (WT) mice to exhaustion and collected cardiac tissue for measurement of CACi by targeted metabolomics. In a second experimental group, VLCAD-/- and WT mice that had been fed chow prepared with either medium-chain triglyceride (MCT) oil or triheptanoin for 4 weeks were exercised for 60 minutes. VLCAD-/- mice exhibited lower succinate in cardiac muscle at exhaustion than WT mice suggesting lower CACi in VLCAD-/- with prolonged exercise. In mice fed either MCT or triheptanoin, succinate and malate were greater in VLCAD-/- mice fed triheptanoin compared to VLCAD-/- animals fed MCT but lower than WT mice fed triheptanoin. Long-chain odd acylcarnitines such as C19 were elevated in VLCAD-/- and WT mice fed triheptanoin suggesting some elongation of the heptanoate, but it is unknown what proportion of heptanoate was oxidized vs elongated. Prolonged exercise was associated with decreased cardiac muscle succinate in VLCAD-/- mice in comparison to WT mice. VLCAD-/- fed triheptanoin had increased succinate compared to VLCAD-/- mice fed MCT but lower than WT mice fed triheptanoin. Cardiac CACi were higher following dietary ingestion of an anaplerotic substrate, triheptanoin, in comparison to MCT.
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http://dx.doi.org/10.1002/jimd.12284DOI Listing
November 2020

Dairy Fat Intake, Plasma C15: 0 and Plasma Iso-C17: 0 are Inversely Associated with Liver Fat in Children.

J Pediatr Gastroenterol Nutr 2020 Dec 30;Publish Ahead of Print. Epub 2020 Dec 30.

Division of Gastroenterology, Hepatology and Nutrition, Department of Pediatrics; University of California San Diego; La Jolla, California Department of Gastroenterology, Rady Children's Hospital San Diego, San Diego, California Department of Bioengineering, University of California, San Diego, La Jolla, California Boston University College of Health & Rehabilitation Sciences: Sargent College, Boston, Massachusetts Altman Clinical and Translational Research Institute, School of Medicine, University of California, San Diego, La Jolla Division of Genetics, Biochemical Genetics and Metabolomics Laboratory, Department of Pediatrics; University of California San Diego; La Jolla, California Liver Imaging Group, Department of Radiology, University of California San Diego, La Jolla, California.

Objectives: We sought to evaluate the relevance of pediatric dairy fat recommendations for children at risk for nonalcoholic fatty liver disease (NAFLD) by studying the association between dairy fat intake and the amount of liver fat. The effects of dairy fat may be mediated by odd chain fatty acids (OCFA), such as pentadecanoic acid (C15:0), and monomethyl branched chain fatty acids (BCFA), such as iso-heptadecanoic acid (iso-C17:0). Therefore, we also evaluated the association between plasma levels of OCFA and BCFA with the amount of liver fat.

Methods: Observational, cross-sectional, community-based sample of 237 children ages 8-17. Dairy fat intake was assessed by three 24-hour dietary recalls. Plasma fatty acids were measured by gas chromatography-mass spectrometry. Main outcome was hepatic steatosis measured by whole liver magnetic resonance imaging proton density fat fraction (MRI-PDFF).

Results: Median dairy fat intake was 10.6 grams/day (range 0.0 - 44.5 g/d). Median liver MRI-PDFF was 4.5% (range 0.9% - 45.1%). Dairy fat intake was inversely correlated with liver MRI-PDFF (r = - 0.162; p = .012). In multivariable log linear regression, plasma C15:0 and iso-C17:0 were inverse predictors of liver MRI-PDFF (B = -0.247, p = 0.048; and B = -0.234, p = 0.009).

Conclusions: Dairy fat intake, plasma C15:0, and plasma iso-C17:0 were inversely correlated with hepatic steatosis in children. These hypothesis-generating findings should be tested through clinical trials to better inform dietary guidelines.
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http://dx.doi.org/10.1097/MPG.0000000000003040DOI Listing
December 2020

Person Ability Scores as an Alternative to Norm-Referenced Scores as Outcome Measures in Studies of Neurodevelopmental Disorders.

Am J Intellect Dev Disabil 2020 11;125(6):475-480

Judith S. Miller, University of Pennsylvania.

Although norm-referenced scores are essential to the identification of disability, they possess several features which affect their sensitivity to change. Norm-referenced scores often decrease over time among people with neurodevelopmental disorders who exhibit slower-than-average increases in ability. Further, the reliability of norm-referenced scores is lower at the tails of the distribution, resulting in floor effects and increased measurement error for people with neurodevelopmental disorders. In contrast, the person ability scores generated during the process of constructing a standardized test with item response theory are designed to assess change. We illustrate these limitations of norm-referenced scores, and relative advantages of ability scores, using data from studies of autism spectrum disorder and creatine transporter deficiency.
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http://dx.doi.org/10.1352/1944-7558-125.6.475DOI Listing
November 2020

Identification of pathognomonic purine synthesis biomarkers by metabolomic profiling of adolescents with obesity and type 2 diabetes.

PLoS One 2020 26;15(6):e0234970. Epub 2020 Jun 26.

Department of Pediatrics, University of California San Diego, La Jolla, CA, United States of America.

The incidence of type 2 diabetes is increasing more rapidly in adolescents than in any other age group. We identified and compared metabolite signatures in obese children with type 2 diabetes (T2D), obese children without diabetes (OB), and healthy, age- and gender-matched normal weight controls (NW) by measuring 273 analytes in fasting plasma and 24-hour urine samples from 90 subjects by targeted LC-MS/MS. Diabetic subjects were within 2 years of diagnosis in an attempt to capture early-stage disease prior to declining renal function. We found 22 urine metabolites that were uniquely associated with T2D when compared to OB and NW groups. The metabolites most significantly elevated in T2D youth included members of the betaine pathway, nucleic acid metabolism, and branched-chain amino acids (BCAAs) and their catabolites. Notably, the metabolite pattern in OB and T2D groups differed between urine and plasma, suggesting that urinary BCAAs and their intermediates behaved as a more specific biomarker for T2D, while plasma BCAAs associated with the obese, insulin resistant state independent of diabetes status. Correlative analysis of metabolites in the T2D signature indicated that betaine metabolites, BCAAs, and aromatic amino acids were associated with hyperglycemia, but BCAA acylglycine derivatives and nucleic acid metabolites were linked to insulin resistance. Of major interest, we found that urine levels of succinylaminoimidazole carboxamide riboside (SAICA-riboside) were increased in diabetic youth, identifying urine SAICA-riboside as a potential biomarker for T2D.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0234970PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7319336PMC
September 2020

Cystathionine beta synthase deficiency and brain edema associated with methionine excess under betaine supplementation: Four new cases and a review of the evidence.

JIMD Rep 2020 Mar 8;52(1):3-10. Epub 2020 Jan 8.

Department of Pediatrics, Division of Biochemical Genetics, Rady Children's Hospital-San Diego University of California San Diego California.

CBS deficient individuals undergoing betaine supplementation without sufficient dietary methionine restriction can develop severe hypermethioninemia and brain edema. Brain edema has also been observed in individuals with severe hypermethioninemia without concomitant betaine supplementation. We systematically evaluated reports from 11 published and 4 unpublished patients with CBS deficiency and from additional four cases of encephalopathy in association with elevated methionine. We conclude that, while betaine supplementation does greatly exacerbate methionine accumulation, the primary agent causing brain edema is methionine rather than betaine. Clinical signs of increased intracranial pressure have not been seen in patients with plasma methionine levels below 559 μmol/L but occurred in one patient whose levels did not knowingly exceed 972 μmol/L at the time of manifestation. While levels below 500 μmol/L can be deemed safe it appears that brain edema can develop with plasma methionine levels close to 1000 μmol/L. Patients with CBS deficiency on betaine supplementation need to be regularly monitored for concordance with their dietary plan and for plasma methionine concentrations. Recurrent methionine levels above 500 μmol/L should alert clinicians to check for clinical signs and symptoms of brain edema and review dietary methionine intake. Levels approaching 1000 μmol/L do increase the risk of complications and levels exceeding 1000 μmol/L, despite best dietetic efforts, should be acutely addressed by reducing the prescribed betaine dose.
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http://dx.doi.org/10.1002/jmd2.12092DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7052692PMC
March 2020

A post glycosylphosphatidylinositol (GPI) attachment to proteins, type 2 (PGAP2) variant identified in Mabry syndrome index cases: Molecular genetics of the prototypical inherited GPI disorder.

Eur J Med Genet 2020 Apr 2;63(4):103822. Epub 2019 Dec 2.

Department of Pediatrics, College of Medicine, University of Kentucky, United States.

We report that recessive inheritance of a post-GPI attachment to proteins 2 (PGAP2) gene variant results in the hyperphosphatasia with neurologic deficit (HPMRS) phenotype described by Mabry et al., in 1970. HPMRS, or Mabry syndrome, is now known to be one of 21 inherited glycosylphosphatidylinositol (GPI) deficiencies (IGDs), or GPI biosynthesis defects (GPIBDs). Bi-allelic mutations in at least six genes result in HPMRS phenotypes. Disruption of four phosphatidylinositol glycan (PIG) biosynthesis genes, PIGV, PIGO, PIGW and PIGY, expressed in the endoplasmic reticulum, result in HPMRS 1, 2, 5 and 6; disruption of the PGAP2 and PGAP3 genes, necessary for stabilizing the association of GPI anchored proteins (AP) with the Golgi membrane, result in HPMRS 3 and 4. We used exome sequencing to identify a novel homozygous missense PGAP2 variant NM_014489.3:c.881C > T, p.Thr294Met in two index patients and targeted sequencing to identify this variant in an unrelated patient. Rescue assays were conducted in two PGAP2 deficient cell lines, PGAP2 KO cells generated by CRISPR/Cas9 and PGAP2 deficient CHO cells, in order to examine the pathogenicity of the PGAP2 variant. First, we used the CHO rescue assay to establish that the wild type PGAP2 isoform 1, translated from transcript 1, is less active than the wild type PGAP2 isoform 8, translated from transcript 12 (alternatively spliced to omit exon 3). As a result, in our variant rescue assays, we used the more active NM_001256240.2:c.698C > T, p.Thr233Met isoform 8 instead of NM_014489.3:c.881C > T, p.Thr294Met isoform 1. Flow cytometric analysis showed that restoration of cell surface CD59 and CD55 with variant PGAP2 isoform 8, driven by the weak (pTA FLAG) promoter, was less efficient than wild type isoform 8. Therefore, we conclude that recessive inheritance of c.881C > T PGAP2, expressed as the hypomorphic PGAP2 c.698C > T, p.Thr233Met isoform 8, results in prototypical Mabry phenotype, HPMRS3 (GPIBD 8 [MIM: 614207]). This study highlights the need for long-term follow up of individuals with rare diseases in order to ensure that they benefit from innovations in diagnosis and treatment.
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http://dx.doi.org/10.1016/j.ejmg.2019.103822DOI Listing
April 2020

Thiamine phosphokinase deficiency and mutation in TPK1 presenting as biotin responsive basal ganglia disease.

Clin Chim Acta 2019 Dec 9;499:13-15. Epub 2019 Aug 9.

Department of Pediatrics, University of California San Diego and Rady Children's Hospital, San Diego, CA, USA.

The product of thiamine phosphokinase is the cofactor for many enzymes, including the dehydrogenases of pyruvate, 2-ketoglutarate and branched chain ketoacids. Its deficiency has recently been described in a small number of patients, some of whom had a Leigh syndrome phenotype. The patient who also had a Leigh phenotype was initially found to have a low concentration of biotin in plasma and massive urinary excretion of biotin. Despite treatment with biotin and thiamine, her disease was progressive. Mutations c.311delG and c.426G > C were found in the TPK1 gene.
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http://dx.doi.org/10.1016/j.cca.2019.07.034DOI Listing
December 2019

Biallelic loss of human CTNNA2, encoding αN-catenin, leads to ARP2/3 complex overactivity and disordered cortical neuronal migration.

Nat Genet 2018 08 16;50(8):1093-1101. Epub 2018 Jul 16.

Department of Neuroscience, Rady Children's Institute for Genomic Medicine, Howard Hughes Medical Institute, University of California, San Diego, San Diego, CA, USA.

Neuronal migration defects, including pachygyria, are among the most severe developmental brain defects in humans. Here, we identify biallelic truncating mutations in CTNNA2, encoding αN-catenin, in patients with a distinct recessive form of pachygyria. CTNNA2 was expressed in human cerebral cortex, and its loss in neurons led to defects in neurite stability and migration. The αN-catenin paralog, αE-catenin, acts as a switch regulating the balance between β-catenin and Arp2/3 actin filament activities. Loss of αN-catenin did not affect β-catenin signaling, but recombinant αN-catenin interacted with purified actin and repressed ARP2/3 actin-branching activity. The actin-binding domain of αN-catenin or ARP2/3 inhibitors rescued the neuronal phenotype associated with CTNNA2 loss, suggesting ARP2/3 de-repression as a potential disease mechanism. Our findings identify CTNNA2 as the first catenin family member with biallelic mutations in humans, causing a new pachygyria syndrome linked to actin regulation, and uncover a key factor involved in ARP2/3 repression in neurons.
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http://dx.doi.org/10.1038/s41588-018-0166-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6072555PMC
August 2018

Brain Magnetic Resonance Imaging Findings in Poorly Controlled Homocystinuria.

J Radiol Case Rep 2018 Jan 31;12(1):1-8. Epub 2018 Jan 31.

Department of Radiology, Rady Children's Hospital-San Diego, San Diego, USA.

Homocystinuria is an inherited metabolic disorder most commonly caused by cystathionine β-synthase deficiency. Severe cases can cause white matter abnormalities that can mimic other vascular, toxic and metabolic disorders on computed tomography and magnetic resonance imaging. We present such a case which demonstrates not only extensive white matter abnormalities on magnetic resonance imaging, but also previously unreported basal ganglia signal abnormalities and imaging manifestations of increased intracranial pressure, likely caused by elevated methionine and betaine therapy. We also review the literature and discuss the potential underlying biologic mechanisms of these imaging findings.
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http://dx.doi.org/10.3941/jrcr.v12i1.3207DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5965393PMC
January 2018

Promises and pitfalls of untargeted metabolomics.

J Inherit Metab Dis 2018 05 13;41(3):355-366. Epub 2018 Mar 13.

Biochemical Genetics and Metabolomics Laboratory, Department of Pediatrics, University of California San Diego, 9500 Gilman Dr. La Jolla, CA, 92093-0830, USA.

Metabolomics is one of the newer omics fields, and has enabled researchers to complement genomic and protein level analysis of disease with both semi-quantitative and quantitative metabolite levels, which are the chemical mediators that constitute a given phenotype. Over more than a decade, methodologies have advanced for both targeted (quantification of specific analytes) as well as untargeted metabolomics (biomarker discovery and global metabolite profiling). Untargeted metabolomics is especially useful when there is no a priori metabolic hypothesis. Liquid chromatography coupled to mass spectrometry (LC-MS) has been the preferred choice for untargeted metabolomics, given the versatility in metabolite coverage and sensitivity of these instruments. Resolving and profiling many hundreds to thousands of metabolites with varying chemical properties in a biological sample presents unique challenges, or pitfalls. In this review, we address the various obstacles and corrective measures available in four major aspects associated with an untargeted metabolomics experiment: (1) experimental design, (2) pre-analytical (sample collection and preparation), (3) analytical (chromatography and detection), and (4) post-analytical (data processing).
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http://dx.doi.org/10.1007/s10545-017-0130-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5960440PMC
May 2018

A study on the safety and efficacy of reveglucosidase alfa in patients with late-onset Pompe disease.

Orphanet J Rare Dis 2017 08 24;12(1):144. Epub 2017 Aug 24.

BioMarin Pharmaceutical, 105 Digital Drive, Novato, CA, 94949, USA.

Background: Late-onset Pompe disease is a rare genetic neuromuscular disorder caused by lysosomal acid alpha-glucosidase (GAA) deficiency that ultimately results in mobility loss and respiratory failure. Current enzyme replacement therapy with recombinant human (rh)GAA has demonstrated efficacy in subjects with late-onset Pompe disease. However, long-term effects of rhGAA on pulmonary function have not been observed, likely related to inefficient delivery of rhGAA to skeletal muscle lysosomes and associated deficits in the central nervous system. To address this limitation, reveglucosidase alfa, a novel insulin-like growth factor 2 (IGF2)-tagged GAA analogue with improved lysosomal uptake, was developed. This study evaluated the pharmacokinetics, safety, and exploratory efficacy of reveglucosidase alfa in 22 subjects with late-onset Pompe disease who were previously untreated with rhGAA.

Results: Reveglucosidase alfa plasma concentrations increased linearly with dose, and the elimination half-life was <1.2 h. Eighteen of 22 subjects completed 72 weeks of treatment. The most common adverse events were hypoglycemia (63%), dizziness, fall, headache, and nausea (55% for each). Serious adverse events included hypersensitivity (n = 1), symptomatic hypoglycemia (n = 2), presyncope (n = 1), and acute cardiac failure (n = 1). In the dose-escalation study, all treated subjects tested positive for anti-reveglucosidase alfa, anti-rhGAA, anti-IGF1, and anti-IGF2 antibodies at least once. Subjects receiving 20 mg/kg of reveglucosidase alfa demonstrated increases in predicted maximum inspiratory pressure (13.9%), predicted maximum expiratory pressure (8.0%), forced vital capacity (-0.4%), maximum voluntary ventilation (7.4 L/min), and mean absolute walking distance (22.3 m on the 6-min walk test) at 72 weeks.

Conclusions: Additional studies are needed to further assess the safety and efficacy of this approach. Improvements in respiratory muscle strength, lung function, and walking endurance in subjects with LOPD may make up for the risk of hypersensitivity reactions and hypoglycemia. Reveglucosidase alfa may provide a new treatment option for patients with late-onset Pompe disease.

Trial Registration: ISRCTN01435772 and ISRCTN01230801 , registered 27 October 2011.
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http://dx.doi.org/10.1186/s13023-017-0693-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5571484PMC
August 2017

The mPEG-PCL Copolymer for Selective Fermentation of Staphylococcus lugdunensis Against Candida parapsilosis in the Human Microbiome.

J Microb Biochem Technol 2016 Aug 19;8(4):259-265. Epub 2016 Jun 19.

Department of Dermatology, University of California, San Diego, CA, USA; Moores Cancer Center; University of California, San Diego, CA, USA.

Many human skin diseases, such as seborrheic dermatitis, potentially occur due to the over-growth of fungi. It remains a challenge to develop fungicides with a lower risk of generating resistant fungi and non-specifically killing commensal microbes. Our probiotic approaches using a selective fermentation initiator of skin commensal bacteria, fermentation metabolites or their derivatives provide novel therapeutics to rein in the over-growth of fungi. () bacteria and () fungi coexist in the scalp microbiome. interfered with the growth of via fermentation. A methoxy poly(ethylene glycol)--poly-caprolactone) (mPEG-PCL) copolymer functioned as a selective fermentation initiator of , selectively triggering the fermentation to produce acetic and isovaleric acids. The acetic acid and its pro-drug diethyleneglycol diacetate (Ac-DEG-Ac) effectively suppressed the growth of and impeded the fungal expansion in the human dandruff. We demonstrate for the first time that is a skin probiotic bacterium that can exploit mPEG-PCL to yield fungicidal short-chain fatty acids (SCFAs). The concept of bacterial fermentation as a part of skin immunity to re-balance the dysbiotic microbiome warrants a novel avenue for studying the probiotic function of the skin microbiome in promoting health.
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http://dx.doi.org/10.4172/1948-5948.1000295DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5243119PMC
August 2016

Paracentric Inversion of Chromosome 21 Leading to Disruption of the HLCS Gene in a Family with Holocarboxylase Synthetase Deficiency.

JIMD Rep 2017 13;34:55-61. Epub 2016 Aug 13.

Department of Human Genetics, University of Michigan Medical School, Ann Arbor, MI, USA.

Holocarboxylase synthetase (HLCS) deficiency is a rare autosomal recessive disorder that presents with multiple life-threatening metabolic derangements including metabolic acidosis, ketosis, and hyperammonemia. A majority of HLCS deficiency patients respond to biotin therapy; however, some patients show only a partial or no response to biotin therapy. Here, we report a neonatal presentation of HLCS deficiency with partial response to biotin therapy. Sequencing of HLCS showed a novel heterozygous mutation in exon 5, c.996G>C (p.Gln332His), which likely abolishes the normal intron 6 splice donor site. Cytogenetic analysis revealed that the defect of the other allele is a paracentric inversion on chromosome 21 that disrupts HLCS. This case illustrates that in addition to facilitating necessary family testing, a molecular diagnosis can optimize management by providing a better explanation of the enzyme's underlying defect. It also emphasizes the potential benefit of a karyotype in cases in which molecular genetic testing fails to provide an explanation.
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http://dx.doi.org/10.1007/8904_2016_9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5509548PMC
August 2016

Controversies and research agenda in nephropathic cystinosis: conclusions from a "Kidney Disease: Improving Global Outcomes" (KDIGO) Controversies Conference.

Kidney Int 2016 06;89(6):1192-203

Department of Pediatric Nephrology, University Hospitals Leuven, Belgium; Department of Development and Regeneration, Katholieke Universiteit Leuven, Belgium. Electronic address:

Nephropathic cystinosis is an autosomal recessive metabolic, lifelong disease characterized by lysosomal cystine accumulation throughout the body that commonly presents in infancy with a renal Fanconi syndrome and, if untreated, leads to end-stage kidney disease (ESKD) in the later childhood years. The molecular basis is due to mutations in CTNS, the gene encoding for the lysosomal cystine-proton cotransporter, cystinosin. During adolescence and adulthood, extrarenal manifestations of cystinosis develop and require multidisciplinary care. Despite substantial improvement in prognosis due to cystine-depleting therapy with cysteamine, no cure of the disease is currently available. Kidney Disease: Improving Global Outcomes (KDIGO) convened a Controversies Conference on cystinosis to review the state-of-the-art knowledge and to address areas of controversies in pathophysiology, diagnostics, monitoring, and treatment in different age groups. More importantly, promising areas of investigation that may lead to optimal outcomes for patients afflicted with this lifelong, systemic disease were discussed with a research agenda proposed for the future.
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http://dx.doi.org/10.1016/j.kint.2016.01.033DOI Listing
June 2016

Diagnosis and Monitoring of Cystinosis Using Immunomagnetically Purified Granulocytes.

Clin Chem 2016 05 15;62(5):766-72. Epub 2016 Mar 15.

Biochemical Genetics and Metabolomics Laboratory, Department of Pediatrics, University of California, San Diego, La Jolla, CA.

Background: Cystine determination is a critical biochemical test for the diagnosis and therapeutic monitoring of the lysosomal storage disease cystinosis. The classical mixed-leukocyte cystine assay requires prompt specialized recovery/isolation following blood drawing, providing cystine concentrations normalized to total protein from assorted types of white blood cells, each with varying cystine content.

Methods: We present a new workflow for cystine determination using immunomagnetic granulocyte purification, and new reference ranges established from 47 patient and 27 obligate heterozygote samples assayed. Samples were collected in acid-citrate dextrose tubes and their stability was proven to allow for overnight shipping before analysis. Cystine was quantified by LC-MS/MS.

Results: The new method was reproducible (<15% root mean square error) and specific, assaying purified granulocytes from blood samples that no longer required immediate preparation and therefore allowing for up to 30 h before processing. There was a nearly a 2-fold increase in the therapeutic target (1.9 nmol half-cystine/mg protein) range, established using distributions of patient, obligate heterozygote, and control samples. The 2.5-97.5 percentile ranges (-2 SD to +2 SD around mean) for these cohorts were 0.67-6.05 nmol/mg protein for patients, 0.33-1.35 nmol/mg protein for obligate heterozygotes, and 0.09-0.35 nmol/mg protein for controls.

Conclusions: The intracellular cystine determination method using immunopurified granulocytes followed by LC-MS/MS analysis improves the inherent variability of mixed leukocyte analysis and eliminates the need for immediate sample preparation following blood draw.
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http://dx.doi.org/10.1373/clinchem.2015.252494DOI Listing
May 2016

p300 is not required for metabolic adaptation to endurance exercise training.

FASEB J 2016 Apr 28;30(4):1623-33. Epub 2015 Dec 28.

*Department of Orthopaedic Surgery and Department of Pediatrics, School of Medicine, University of California, San Diego, La Jolla, California, USA; School of Sport, Exercise, and Rehabilitation Sciences, University of Birmingham, Edgbaston, United Kingdom; and Department of Human Physiology, University of Oregon, Eugene, Oregon, USA

The acetyltransferase, E1a-binding protein (p300), is proposed to regulate various aspects of skeletal muscle development, metabolism, and mitochondrial function,viaits interaction with numerous transcriptional regulators and other proteins. Remarkably, however, the contribution of p300 to skeletal muscle function and metabolism,in vivo, is poorly understood. To address this, we used Cre-LoxP methodology to generate mice with skeletal muscle-specific knockout of E1a-binding protein (mKO). mKO mice were indistinguishable from their wild-type/floxed littermates, with no differences in lean mass, skeletal muscle structure, fiber type, respirometry flux, or metabolites of fatty acid and amino acid metabolism.Ex vivomuscle function in extensor digitorum longus and soleus muscles, including peak stress and time to fatigue, as well asin vivorunning capacity were also comparable. Moreover, expected adaptations to a 20 d voluntary wheel running regime were not compromised in mKO mice. Taken together, these findings demonstrate that p300 is not required for the normal development or functioning of adult skeletal muscle, nor is it required for endurance exercise-mediated mitochondrial adaptations.-LaBarge, S. A., Migdal, C. W., Buckner, E. H., Okuno, H., Gertsman, I., Stocks, B., Barshop, B. A., Nalbandian, S. R., Philp, A., McCurdy, C. E., Schenk, S. p300 is not required for metabolic adaptation to endurance exercise training.
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http://dx.doi.org/10.1096/fj.15-281741DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4799503PMC
April 2016

In vivo monitoring of urea cycle activity with (13)C-acetate as a tracer of ureagenesis.

Mol Genet Metab 2016 Jan 14;117(1):19-26. Epub 2015 Nov 14.

Division of Neuropediatrics and Pediatric Metabolic Medicine, University Children's Hospital Heidelberg, Germany. Electronic address:

Background: The hepatic urea cycle is the main metabolic pathway for detoxification of ammonia. Inborn errors of urea cycle function present with severe hyperammonemia and a high case fatality rate. Long-term prognosis depends on the residual activity of the defective enzyme. A reliable method to estimate urea cycle activity in-vivo does not exist yet. The aim of this study was to evaluate a practical method to quantify (13)C-urea production as a marker for urea cycle function in healthy subjects, patients with confirmed urea cycle defect (UCD) and asymptomatic carriers of UCD mutations.

Methods: (13)C-labeled sodium acetate was applied orally in a single dose to 47 subjects (10 healthy subjects, 28 symptomatic patients, 9 asymptomatic carriers).

Results: The oral (13)C-ureagenesis assay is a safe method. While healthy subjects and asymptomatic carriers did not differ with regards to kinetic variables for urea cycle flux, symptomatic patients had lower (13)C-plasma urea levels. Although the (13)C-ureagenesis assay revealed no significant differences between individual urea cycle enzyme defects, it reflected the heterogeneity between different clinical subgroups, including male neonatal onset ornithine carbamoyltransferase deficiency. Applying the (13)C-urea area under the curve can differentiate between severe from more mildly affected neonates. Late onset patients differ significantly from neonates, carriers and healthy subjects.

Conclusion: This study evaluated the oral (13)C-ureagenesis assay as a sensitive in-vivo measure for ureagenesis capacity. The assay has the potential to become a reliable tool to differentiate UCD patient subgroups, follow changes in ureagenesis capacity and could be helpful in monitoring novel therapies of UCD.
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http://dx.doi.org/10.1016/j.ymgme.2015.11.007DOI Listing
January 2016

Perturbations of tyrosine metabolism promote the indolepyruvate pathway via tryptophan in host and microbiome.

Mol Genet Metab 2015 Mar 29;114(3):431-7. Epub 2015 Jan 29.

Biochemical Genetics and Metabolomics Laboratory, Department of Pediatrics, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093, United States.

The drug nitisinone (NTBC) is used to treat tyrosinemia type I, and more recently has been also used for the treatment of another disorder of tyrosine metabolism, alkaptonuria. While studying the dose effects of NTBC treatment on alkaptonuria, untargeted metabolomics revealed perturbations in a completely separate pathway, that of tryptophan metabolism. Significant elevations in several indolic compounds associated with the indolepyruvate pathway of tryptophan metabolism were present in NTBC-treated patient sera and correlated with elevations of an intermediate of tyrosine metabolism. Indolic compounds of this pathway have long been associated with commensal bacterial and plant metabolism. These exogenous sources of indoles have been more recently implicated in affecting mammalian cell function and disease. We studied the correlation of these indolic compounds in other disorders of tyrosine metabolism including tyrosinemia types I and II as well as transient tyrosinemia, and demonstrated that 4-hydroxyphenylpyruvate (4-HPP) was directly responsible for the promotion of this pathway. We then investigated the regulation of the indolepyruvate pathway and the role of 4-HPP further in both mammalian cells and intestinal microbial cultures. We demonstrated that several of the indolic products, including indolepyruvate and indolelactate, were in fact generated by human cell metabolism, while the downstream indole metabolite, indolecarboxaldehyde, was produced exclusively by microbial cultures of human gut flora. This study describes a symbiotic perturbation in host and microbiome tryptophan metabolism in response to elevations related to defects of tyrosine metabolism and concomitant drug treatment.
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http://dx.doi.org/10.1016/j.ymgme.2015.01.005DOI Listing
March 2015

Metabolic Effects of Increasing Doses of Nitisinone in the Treatment of Alkaptonuria.

JIMD Rep 2015 10;24:13-20. Epub 2015 Feb 10.

Biochemical Genetics and Metabolomics Laboratory, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA.

Alkaptonuria is an autosomal recessive disease involving a deficiency of the enzyme homogentisate dioxygenase, which is involved in the tyrosine degradation pathway. The enzymatic deficiency results in high concentrations of homogentisic acid (HGA), which results in orthopedic and cardiac complications, among other symptoms. Nitisinone (NTBC) has been shown to effectively treat alkaptonuria by blocking the conversion of 4-hydroxyphenylpyruvate to HGA, but there have been concerns that using doses higher than about 2 mg/day could cause excessively high levels of tyrosine, resulting in crystal deposition and corneal pathology. We have enrolled seven patients in a study to determine whether higher doses of NTBC were effective at further reducing HGA levels while maintaining tyrosine at acceptable levels. Patients were given varying doses of NTBC (ranging from 2 to 8 mg/day) over the course of between 0.5 and 3.5 years. Urine HGA, plasma tyrosine levels, and plasma NTBC were then measured longitudinally at various doses. We found that tyrosine concentrations plateaued and did not reach significantly higher levels as NTBC doses were increased above 2 mg/day, while a significant drop in HGA continued from 2 to 4 mg/day, with no significant changes at higher doses. We also demonstrated using untargeted metabolomics that elevations in tyrosine from treatment resulted in proportional elevations in alternative tyrosine metabolic products, that of N-acetyltyrosine and γ-glutamyltyrosine.
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http://dx.doi.org/10.1007/8904_2014_403DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4582031PMC
September 2015

Validation of a dual LC-HRMS platform for clinical metabolic diagnosis in serum, bridging quantitative analysis and untargeted metabolomics.

Metabolomics 2014 Apr;10(2):312-323

Biochemical Genetics Lab, University of California, San Diego. 9500 Gilman Dr. La Jolla, CA 92093.

Mass spectrometry-based metabolomics is a rapidly growing field in both research and diagnosis. Generally, the methodologies and types of instruments used for clinical and other absolute quantification experiments are different from those used for biomarkers discovery and untargeted analysis, as the former requires optimal sensitivity and dynamic range, while the latter requires high resolution and high mass accuracy. We used a Q-TOF mass spectrometer with two different types of pentafluorophenyl (PFP) stationary phases, employing both positive and negative ionization, to develop and validate a hybrid quantification and discovery platform using LC-HRMS. This dual-PFP LC-MS platform quantifies over 50 clinically relevant metabolites in serum (using both MS and MS/MS acquisitions) while simultaneously collecting high resolution and high mass accuracy full scans to monitor all other co-eluting non-targeted analytes. We demonstrate that the linearity, accuracy, and precision results for the quantification of a number of metabolites, including amino acids, organic acids, acylcarnitines and purines/pyrimidines, meets or exceeds normal bioanalytical standards over their respective physiological ranges. The chromatography resolved highly polar as well as hydrophobic analytes under reverse-phase conditions, enabling analysis of a wide range of chemicals, necessary for untargeted metabolomics experiments. Though previous LC-HRMS methods have demonstrated quantification capabilities for various drug and small molecule compounds, the present study provides an HRMS quant/qual platform tailored to metabolic disease; and covers a multitude of different metabolites including compounds normally quantified by a combination of separate instrumentation.
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http://dx.doi.org/10.1007/s11306-013-0582-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4234038PMC
April 2014

Consanguinity and rare mutations outside of MCCC genes underlie nonspecific phenotypes of MCCD.

Genet Med 2015 Aug 6;17(8):660-7. Epub 2014 Nov 6.

1] Department of Pediatrics, Rady Children's Hospital, University of California, San Diego, La Jolla, California, USA [2] Clinical and Translational Research Institute, University of California, San Diego, La Jolla, California, USA [3] Institute for Genomic Medicine, University of California, San Diego, La Jolla, California, USA.

Purpose: 3-Methylcrotonyl-CoA carboxylase deficiency (MCCD) is an autosomal recessive disorder of leucine catabolism that has a highly variable clinical phenotype, ranging from acute metabolic acidosis to nonspecific symptoms such as developmental delay, failure to thrive, hemiparesis, muscular hypotonia, and multiple sclerosis. Implementation of newborn screening for MCCD has resulted in broadening the range of phenotypic expression to include asymptomatic adults. The purpose of this study was to identify factors underlying the varying phenotypes of MCCD.

Methods: We performed exome sequencing on DNA from 33 cases and 108 healthy controls. We examined these data for associations between either MCC mutational status, genetic ancestry, or consanguinity and the absence or presence/specificity of clinical symptoms in MCCD cases.

Results: We determined that individuals with nonspecific clinical phenotypes are highly inbred compared with cases that are asymptomatic and healthy controls. For 5 of these 10 individuals, we discovered a homozygous damaging mutation in a disease gene that is likely to underlie their nonspecific clinical phenotypes previously attributed to MCCD.

Conclusion: Our study shows that nonspecific phenotypes attributed to MCCD are associated with consanguinity and are likely not due to mutations in the MCC enzyme but result from rare homozygous mutations in other disease genes.Genet Med 17 8, 660-667.
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http://dx.doi.org/10.1038/gim.2014.157DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4422778PMC
August 2015

Infants suspected to have very-long chain acyl-CoA dehydrogenase deficiency from newborn screening.

Mol Genet Metab 2014 Apr 23;111(4):484-92. Epub 2014 Jan 23.

Genomics Section, Hawai'i Department of Health, Honolulu, HI, USA.

Very long-chain acyl-CoA dehydrogenase deficiency (VLCADD) is a fatty acid oxidation disorder with widely varying presentations that has presented a significant challenge to newborn screening (NBS). The Western States Regional Genetics Services Collaborative developed a workgroup to study infants with NBS positive for VLCADD. We performed retrospective analysis of newborns with elevated C14:1-acylcarnitine on NBS in California, Oregon, Washington, and Hawai'i including available confirmatory testing and clinical information. Overall, from 2,802,504 children screened, there were 242 cases screen-positive for VLCADD. There were 34 symptomatic true positive cases, 18 asymptomatic true positives, 112 false positives, 55 heterozygotes, 11 lost to follow-up, and 12 other disorders. One in 11,581 newborns had an abnormal NBS for suspected VLCADD. Comparison of analytes and analyte ratios from the NBS demonstrated statistically significant differences between true positive and false positive groups for C14:1, C14, C14:1/C2, and C14:1/C16. The positive predictive value for all true positive cases was 94%, 54%, and 23% when C14:1 was ≥2.0 μM, ≥1.0 μM, and ≥0.7 μM, respectively. Sequential post-analytical analysis could reduce the referral rate in 25.8% of cases. This study is the largest reported follow-up of infants with NBS screen-positive results for suspected VLCADD and demonstrates the necessity of developing comprehensive and consistent long-term follow-up NBS systems. Application of clinical information revealed differences between symptomatic and asymptomatic children with VLCADD. Comparison of NBS analytes and analyte ratios may be valuable in developing more effective diagnostic algorithms.
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http://dx.doi.org/10.1016/j.ymgme.2014.01.009DOI Listing
April 2014

A model-driven quantitative metabolomics analysis of aerobic and anaerobic metabolism in E. coli K-12 MG1655 that is biochemically and thermodynamically consistent.

Biotechnol Bioeng 2014 Apr 19;111(4):803-15. Epub 2013 Nov 19.

Department of Bioengineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, California, 92093-0412.

The advent of model-enabled workflows in systems biology allows for the integration of experimental data types with genome-scale models to discover new features of biology. This work demonstrates such a workflow, aimed at establishing a metabolomics platform applied to study the differences in metabolomes between anaerobic and aerobic growth of Escherichia coli. Constraint-based modeling was utilized to deduce a target list of compounds for downstream method development. An analytical and experimental methodology was developed and tailored to the compound chemistry and growth conditions of interest. This included the construction of a rapid sampling apparatus for use with anaerobic cultures. The resulting genome-scale data sets for anaerobic and aerobic growth were validated by comparison to previous small-scale studies comparing growth of E. coli under the same conditions. The metabolomics data were then integrated with the E. coli genome-scale metabolic model (GEM) via a sensitivity analysis that utilized reaction thermodynamics to reconcile simulated growth rates and reaction directionalities. This analysis highlighted several optimal network usage inconsistencies, including the incorrect use of the beta-oxidation pathway for synthesis of fatty acids. This analysis also identified enzyme promiscuity for the pykA gene, that is critical for anaerobic growth, and which has not been previously incorporated into metabolic models of E coli.
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http://dx.doi.org/10.1002/bit.25133DOI Listing
April 2014

Cysteamine modulates oxidative stress and blocks myofibroblast activity in CKD.

J Am Soc Nephrol 2014 Jan 5;25(1):43-54. Epub 2013 Sep 5.

Seattle Children's Hospital Research Institute, University of Washington, Seattle, Washington;

Therapy to slow the relentless expansion of interstitial extracellular matrix that leads to renal functional decline in patients with CKD is currently lacking. Because chronic kidney injury increases tissue oxidative stress, we evaluated the antifibrotic efficacy of cysteamine bitartrate, an antioxidant therapy for patients with nephropathic cystinosis, in a mouse model of unilateral ureteral obstruction. Fresh cysteamine (600 mg/kg) was added to drinking water daily beginning on the day of surgery, and outcomes were assessed on days 7, 14, and 21 after surgery. Plasma cysteamine levels showed diurnal variation, with peak levels similar to those observed in patients with cystinosis. In cysteamine-treated mice, fibrosis severity decreased significantly at 14 and 21 days after unilateral ureteral obstruction, and renal oxidized protein levels decreased at each time point, suggesting reduced oxidative stress. Consistent with these results, treatment of cultured macrophages with cysteamine reduced cellular generation of reactive oxygen species. Furthermore, treatment with cysteamine reduced α-smooth muscle actin-positive interstitial myofibroblast proliferation and mRNA levels of extracellular matrix proteins in mice and attenuated myofibroblast differentiation and proliferation in vitro, but did not augment TGF-β signaling. In a study of renal ischemia reperfusion, cysteamine therapy initiated 10 days after injury and continued for 14 days decreased renal fibrosis by 40%. Taken together, these data suggest previously unrecognized antifibrotic actions of cysteamine via TGF-β-independent mechanisms that include oxidative stress reduction and attenuation of the myofibroblast response to kidney injury and support further investigation into the potential benefit of cysteamine therapy in the treatment of CKD.
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http://dx.doi.org/10.1681/ASN.2012090962DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3871767PMC
January 2014

Metabolomics reveals signature of mitochondrial dysfunction in diabetic kidney disease.

J Am Soc Nephrol 2013 Nov 10;24(11):1901-12. Epub 2013 Oct 10.

Institute of Metabolomic Medicine.

Diabetic kidney disease is the leading cause of ESRD, but few biomarkers of diabetic kidney disease are available. This study used gas chromatography-mass spectrometry to quantify 94 urine metabolites in screening and validation cohorts of patients with diabetes mellitus (DM) and CKD(DM+CKD), in patients with DM without CKD (DM-CKD), and in healthy controls. Compared with levels in healthy controls, 13 metabolites were significantly reduced in the DM+CKD cohorts (P≤0.001), and 12 of the 13 remained significant when compared with the DM-CKD cohort. Many of the differentially expressed metabolites were water-soluble organic anions. Notably, organic anion transporter-1 (OAT1) knockout mice expressed a similar pattern of reduced levels of urinary organic acids, and human kidney tissue from patients with diabetic nephropathy demonstrated lower gene expression of OAT1 and OAT3. Analysis of bioinformatics data indicated that 12 of the 13 differentially expressed metabolites are linked to mitochondrial metabolism and suggested global suppression of mitochondrial activity in diabetic kidney disease. Supporting this analysis, human diabetic kidney sections expressed less mitochondrial protein, urine exosomes from patients with diabetes and CKD had less mitochondrial DNA, and kidney tissues from patients with diabetic kidney disease had lower gene expression of PGC1α (a master regulator of mitochondrial biogenesis). We conclude that urine metabolomics is a reliable source for biomarkers of diabetic complications, and our data suggest that renal organic ion transport and mitochondrial function are dysregulated in diabetic kidney disease.
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http://dx.doi.org/10.1681/ASN.2013020126DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3810086PMC
November 2013

Changes in plasma and urine globotriaosylceramide levels do not predict Fabry disease progression over 1 year of agalsidase alfa.

Genet Med 2013 Dec 16;15(12):983-9. Epub 2013 May 16.

Institute of Metabolic Disease, Baylor Research Institute, Dallas, Texas, USA.

Purpose: Globotriaosylceramide concentrations were assessed as potential predictors of change from baseline after 12 months by estimated glomerular filtration rate and left-ventricular mass index using pooled data from three randomized, placebo-controlled agalsidase alfa trials and open-label extensions of patients with Fabry disease.

Methods: Males (aged 18 years or older) with Fabry disease received agalsidase alfa (0.2 mg/kg every other week for 12 months). A backward-elimination approach evaluated potential predictors (baseline estimated glomerular filtration rate and left-ventricular mass index; age at first dose; baseline and change from baseline at 12 months of globotriaosylceramide (urine, plasma); urine protein excretion; and systolic and diastolic blood pressure). Subgroups included patients randomized to placebo or agalsidase alfa (double-blind phase), then to agalsidase alfa (open-label extensions; placebo→agalsidase alfa or agalsidase alfa→agalsidase alfa, respectively) and stage 2/3 chronic kidney disease patients.

Results: Baseline estimated glomerular filtration rate, age at first dose, baseline urine globotriaosylceramide excretion, and baseline and change from baseline urine protein excretion significantly predicted change from baseline estimated glomerular filtration rate in the analysis population (N = 73; all P<0.05), although not in all subgroups. Change from baseline urine and plasma globotriaosylceramide (baseline and change from baseline) concentrations did not predict change from baseline estimated glomerular filtration rate. No predictors of left-ventricular mass index were significant.

Conclusion: Changes in globotriaosylceramide concentrations do not appear to be useful biomarkers for prediction of Fabry disease-related changes in estimated glomerular filtration rate or left-ventricular mass index.
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http://dx.doi.org/10.1038/gim.2013.56DOI Listing
December 2013

Elevation of guanidinoacetate in newborn dried blood spots and impact of early treatment in GAMT deficiency.

Mol Genet Metab 2013 Jun 16;109(2):215-7. Epub 2013 Mar 16.

Department of Pediatrics, Division of Medical Genetics, Duke University Medical Center, Durham, NC, USA.

Guanidinoacetate methyltransferase (GAMT) deficiency is a good candidate disorder for newborn screening because early treatment appears to improve outcomes. We report elevation of guanidinoacetate in archived newborn dried blood spots for 3 cases (2 families) of GAMT deficiency compared with an unaffected carrier and controls. We also report a new case of a patient treated from birth with normal developmental outcome at the age of 42 months.
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http://dx.doi.org/10.1016/j.ymgme.2013.03.003DOI Listing
June 2013

Pharmacokinetics of cysteamine bitartrate following intraduodenal delivery.

Fundam Clin Pharmacol 2014 Apr 31;28(2):136-43. Epub 2012 Oct 31.

Department of Pediatric, University of California, San Diego, CA, USA; Rady Children's Hospital, San Diego, CA, USA.

Cysteamine is approved for the treatment of cystinosis and is being evaluated for Huntington's disease and non-alcoholic fatty liver disease. Little is known about the bioavailability and biodistribution of the drug. The aim was to determine plasma, cerebrospinal fluid (CSF), and tissue (liver, kidney, muscle) cysteamine levels following intraduodenal delivery of the drug in rats pretreated and naïve to cysteamine and to estimate the hepatic first-pass effect on cysteamine. Healthy male rats (n = 66) underwent intraduodenal and portal (PV) or jugular (JVC) venous catheterization. Half were pretreated with cysteamine, and half were naïve. Following intraduodenal cysteamine (20 mg/kg), serial blood samples were collected from the PV or the JVC. Animals were sacrificed at specific time points, and CSF and tissue were collected. Cysteamine levels were determined in plasma, CSF, and tissue. The Cmax was achieved in 5-10 min from PV and 5-22.5 min from JVC. The PV-Cmax (P = 0.08), PV-AUC0-t (P = 0.16), JVC-Cmax (P = 0.02) and JVC-AUC0-t (P = 0.03) were higher in naive than in pretreated animals. Plasma cysteamine levels returned to baseline in ≤120 min. The hepatic first-pass effect was estimated at 40%. Peak tissue and CSF cysteamine levels occurred ≤22.5 min, but returned to baseline levels ≤180 min. There was no difference in CSF and tissue cysteamine levels between naïve and pretreated groups, although cysteamine was more rapidly cleared in the pretreated group. Cysteamine is rapidly absorbed from the small intestine, undergoes significant hepatic first-pass metabolism, crosses the blood brain barrier, and is almost undetectable in plasma, CSF, and body tissues 2 h after ingestion. Sustained-release cysteamine may provide prolonged tissue exposure.
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http://dx.doi.org/10.1111/fcp.12009DOI Listing
April 2014

Biochemical, molecular, and clinical characteristics of children with short chain acyl-CoA dehydrogenase deficiency detected by newborn screening in California.

Mol Genet Metab 2012 May 9;106(1):55-61. Epub 2012 Feb 9.

Department of Pediatrics, University of California at Los Angeles, Los Angeles, CA, USA.

Background: Short-chain acyl-CoA dehydrogenase deficiency (SCADD) is an autosomal recessive inborn error of mitochondrial fatty acid oxidation with highly variable biochemical, genetic, and clinical characteristics. SCADD has been associated with accumulation of butyryl-CoA byproducts, including butyrylcarnitine (C4), butyrylglycine, ethylmalonic acid (EMA), and methylsuccinic acid (MS) in body fluid and tissues. Differences in genotype frequencies have been shown between patients diagnosed clinically versus those diagnosed by newborn screening. Moreover, while patients diagnosed clinically have a variable clinical presentation including developmental delay, ketotic hypoglycemia, epilepsy and behavioral disorders, studies suggest patients diagnosed by newborn screening are largely asymptomatic. Scant information is published about the biochemical, genetic and clinical outcome of SCADD patients diagnosed by newborn screening.

Methods: We collected California newborn screening, follow-up biochemical levels, and ACADS mutation data from September, 2005 through April, 2010. We retrospectively reviewed available data on SCADD cases diagnosed by newborn screening for clinical outcomes.

Results: During the study period, 2,632,058 newborns were screened and 76 confirmed SCADD cases were identified. No correlations between initial C4 value and follow-up biochemical markers (C4, EMA or MS levels) were found in the 76 cases studied. We found significant correlation between urine EMA versus MS, and correlation between follow-up C4 versus urine EMA. Of 22 cases where ACADS gene sequencing was performed: 7 had two or more deleterious mutations; 8 were compound heterozygotes for a deleterious mutation and common variant; 7 were homozygous for the common variant c.625G>A; and 1 was heterozygous for c.625G>A. Significant increases in mean urine EMA and MS levels were noted in patients with two or more deleterious mutations versus mutation heterozygotes or common polymorphism homozygotes. Clinical outcome data was available in 31 patients with follow-up extending from 0.5 to 60 months. None developed epilepsy or behavioral disorders, and three patients had isolated speech delay. Hypoglycemia occurred in two patients, both in the neonatal period. The first patient had concomitant meconium aspiration; the other presented with central apnea, poor feeding, and hypotonia. The latter, a c.625G>A homozygote, has had persistent elevations in both short- and medium-chain acylcarnitines; diagnostic workup in this case is extensive and ongoing.

Conclusions: This study examines the largest series to date of SCADD patients identified by newborn screening. Our results suggest that confirmatory tests may be useful to differentiate patients with common variants from those with deleterious mutations. This study also provides evidence to suggest that, even when associated with deleterious mutations, SCADD diagnosed by newborn screening presents largely as a benign condition.
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http://dx.doi.org/10.1016/j.ymgme.2012.02.007DOI Listing
May 2012