The Unfolded Protein Response in Breast Cancer (2018)

Eoghan McGrath Susan Logue Katarzyna Mnich Shane Deegan Richard Jäger Adrienne Gorman Afshin Samali

In 2018, in the US alone, it is estimated that 268,670 people will be diagnosed with breast cancer, and that 41,400 will die from it. Since breast cancers often become resistant to therapies, and certain breast cancers lack therapeutic targets, new approaches are urgently required. A cell-stress response pathway, the unfolded protein response (UPR), has emerged as a promising target for the development of novel breast cancer treatments. This pathway is activated in response to a disturbance in endoplasmic reticulum (ER) homeostasis but has diverse physiological and disease-specific functions. In breast cancer, UPR signalling promotes a malignant phenotype and can confer tumours with resistance to widely used therapies. Here, we review several roles for UPR signalling in breast cancer, highlighting UPR-mediated therapy resistance and the potential for targeting the UPR alone or in combination with existing therapies.

Utilizing ethacrynic acid and ciclopirox olamine in liver cancer (2018)

Ahmad Al‑Dali Hans Weiher Ingo Schmidt‑Wolf

Once aberrantly activated, the Wnt/βcatenin pathway may result in uncontrolled proliferation and eventually cancer. Efforts to counter and inhibit this pathway are mainly directed against βcatenin, as it serves a role on the cytoplasm and the nucleus. In addition, speciallygenerated lymphocytes are recruited for the purpose of treating liver cancer. Peripheral blood mononuclear lymphocytes are expanded by the timely addition of interferon γ, interleukin (IL)1β, IL2 and anticluster of differentiation 3 antibody. The resulting cells are called cytokineinduced killer (CIK) cells. The present study utilised these cells and combine them with drugs inhibiting the Wnt pathway in order to examine whether this resulted in an improvement in the killing ability of CIK cells against liver cancer cells. Drugs including ethacrynic acid (EA) and ciclopirox olamine (CPX) were determined to be suitable candidates, as determined by previous studies. Drugs were administered on their own and combined with CIK cells and then a cell viability assay was performed. These results suggest that EAtreated cells demonstrated apoptosis and were significantly affected compared with untreated cells. Unlike EA, CPX killed normal and cancerous cells even at low concentrations. Subsequent to combining EA with CIK cells, the potency of killing was increased and a greater number of cells died, which proves a synergistic action. In summary, EA may be used as an antihepatocellular carcinoma drug, while CPX possesses a high toxicity to cancerous as well as to normal cells. It was proposed that EA should be integrated into present therapeutic methods for cancer.

Amino Acids and Inherited Amino Acid-Related Disorders (2018)

Ina Knerr Laurie Bernstein Ellen Crushell Siobhan O’Sullivan Jörn Oliver Sass

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.

Tekrarlayan ketoasidoz atakları: Keton metabolizma bozuklukluğu olabilir mi? (2018)

Ebru Canda Havva Yazici E. R. Esra Sema Kalkan Ucar Corinne Gemperle-Britschgi Sara Habif Huseyin Onay Jorn Oliver Sass Mahmut Coker

Amaç: Keton cisim oluşumu (ketogenez) bozuklukları; mitokondriyel 3-hidroksi-3metil glutaril CoA sentaz (Mhs) ve 3-hidroksi-3-metil glutaril CoA liyaz (HL) enzim eksiklikleri sonucu oluşur. Keton cisim yıkımı (ketoliz) bozuklukları ise suksinil CoA: 3 oksoasit CoA transferaz (SCOT) ve asetoasetil CoA thiolaz-beta ketotiolaz (MAT) enzim eksiklikleri sonucu oluşmaktadır. Keton metabolizma bozukluğu tanısıyla izlenen hastaların klinik ve laboratuvar bulguları ile değerlendirilmesi amaçlandı. Yöntem: Keton metabolizması bozukluğu tanısıyla izlenen hasta verileri retrospektif olarak incelendi. Bulgular: Dört hastada HL eksikliği, 3 hastada MAT eksikliği ve 2 hastada SCOT eksikliği tanısı mevcuttu. Hastaların ortanca yaşı 5 yıl (6 ay-15,5 yıl), ilk metabolik dekompanzasyon atak yaşı ortalama 7,7 ay (22 gün-19 ay) idi. MAT eksikliği olan bir hasta, kardeş taraması ile asemptomatik dönemde tanı aldı. İki hastada spastik tetraparezi gibi ağır nörolojik defisit gelişti. Dekompanzasyon ataklarının beslenememe, kusma ve gastroenterit gibi infeksiyon sonrası geliştiği görüldü. Sonuç: Açıklanamayan metabolik asidoz atakları durumunda keton metabolizma bozuklukları akılda tutulmalıdır. Akut dekompanzasyon değişik yaşlarda ortaya çıkabilir, klinik şiddeti değişken olabilir. Erken tanı ve uygun tedavi mortalite ve morbidite açısından çok önemlidir.

Laughing Gas in a Pediatric Emergency Department-Fun for All Participants: Vitamin B12 Status Among Medical Staff Working With Nitrous Oxide (2016)

Georg Staubli Matthias Baumgartner Jörn Oliver Sass Martin Hersberger

The efficiency of nitrous oxide in an equimolar mixture with oxygen or in concentrations up to 70% is approved for short painful procedures. Evaluation of the vitamin B12 levels in anesthetic staff applying nitrous oxide showed reduced vitamin B12 plasma levels. This study examines the vitamin B12 status of medical staff working with nitrous oxide in a pediatric emergency department (ED). Medical staff of the ED at the University Children's Hospital Zurich participated. The vitamin B12 status was evaluated by measuring homocysteine, methylmalonic acid, vitamin B12, blood count, and the MTHFR C677T genotype. As a control group, medical personnel working in the “nitrous oxide–free” pediatric intensive care unit were recruited.

Amino acids regulate transgene expression in MDCK cells (2014)

Marta Torrente Adriano Guetg Jörn Oliver Sass Lisa Arps Lisa Ruckstuhl Simone M. R. Camargo François Verrey

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.

HIBCH deficiency in a patient with phenotypic characteristics of mitochondrial disorders (2014)

Miriam S. Reuter Jörn Oliver Sass Thomas Leis Julia Köhler Johannes A. Mayr René G. Feichtinger Manfred Rauh Ina Schanze Luzy Bähr Regina Trollmann Steffen Uebe Arif B. Ekici André Reis

HIBCH (3-hydroxyisobutyryl-CoA hydrolase) deficiency (MIM #250620) is a rare autosomal recessive inborn error of metabolism, leading to a block in the catabolic pathway of the amino acid valine and presumably to accumulation of toxic valine metabolites in mitochondria. Only three families with HIBCH deficiency and biallelic HIBCH mutations have been described. We report on a further patient, first child of healthy consanguineous parents, with severe developmental delay, seizures, hyperintensities of the basal ganglia on magnetic resonance imaging (MRI), progressive brain atrophy, optic nerve atrophy, repeatedly elevated blood lactate, and respiratory chain complexes I, I + III and cytochrome c oxidase deficiencies with borderline depletion of mitochondrial DNA in muscle tissue. Laboratory findings in blood and skeletal muscle were inconsistent and did not allow a definite diagnosis, but supported the hypothesis of mitochondrial dysfunction. Homozygosity mapping and whole-exome sequencing revealed a homozygous one-base pair insertion in HIBCH. Deficiency of enzyme activity was confirmed in cultured fibroblasts. Although relatively unspecific, the clinical features were similar to those of the previously reported cases. Given the clinical variability and large number of differential diagnoses, the prevalence of HIBCH deficiency is probably underestimated. Next-generation sequencing approaches are an effective tool for identifying the underlying genetic basis in patients suspected of mitochondrial disorders.

Propionic acidemia in a previously healthy adolescent with acute onset of dilated cardiomyopathy (2014)

Alexander Laemmle Christian Balmer Carsten Doell Jörn Oliver Sass Johannes Häberle Matthias R. Baumgartner

Propionic acidemia (PA) is a rare autosomal recessive organic aciduria resulting from defects in propionyl-CoA-carboxylase (PCC), a key enzyme of intermediate energy metabolism. PA mostly manifests during the neonatal period, when affected newborns develop severe metabolic acidosis and hyperammonemia. We present a previously healthy teenager, who suffered from acute fatigue and breathlessness. The patient was tachycardic, displayed a precordial heave and a systolic murmur. Cardiac investigations revealed severe dilated cardiomyopathy (DCM). Biochemical work up led to the diagnosis of PA. Remarkably, this patient of consanguineous Hispanic origin was in a good general health condition before the acute onset of DCM. Diagnosis of PA was confirmed by enzymatic and molecular genetic analysis, the latter revealing a novel homozygous mutation in the PCCB gene (c.1229G > A; p.R410Q). Residual PCC enzyme activity of approximately 14 % of normal was detected in patient’s lymphocytes and fibroblasts, thereby providing a possible explanation for the hitherto asymptomatic phenotype. Conclusion: Isolated DCM, although rare, can be the leading and/or sole symptom of late-onset PA. Therefore, patients with DCM should receive a comprehensive diagnostic evaluation including selective screening for inborn errors of metabolism.

Prolonged survival upon ultrasound-enhanced doxorubicin delivery in two syngenic glioblastoma mouse models (2014)

Zsofia Kovacs Beat Werner Anahita Rassi Jörn Oliver Sass Ernst Martin-Fiori Michele Bernasconi

Glioblastoma multiforme (GBM) is the most common and most aggressive malignant primary brain tumor in humans with a very poor prognosis. Chemotherapeutical treatment of GBMs is limited by the blood-brain barrier (BBB). This physical and metabolic barrier separates the blood from the brain parenchyma and prevents the entry of toxins but also of potentially useful chemotherapeutics from the blood into the brain. Microbubble-enhanced focused ultrasound (MB-FUS) has been proposed to disrupt locally and reversibly the BBB to facilitate diffusion of drugs from the micro vasculature into brain tissue. The present study investigates the feasibility and the safety of such an approach in two syngenic mouse models of GBM (GL261 and SMA-560). Local doxorubicin (DOX) concentration in MB-FUS sonicated normal brain tissue as well as in brain tumor tissue was increased as compared to the unsonicated control tissue in the contralateral hemisphere. Moreover, ultrasound mediated BBB disruption, in combination with DOX therapy, resulted in a significant increase of survival and in a slower disease progression in the two syngenic GBM mouse models. In conclusion, our results confirm that MB-ultrasound might ultimately be an effective technology to improve the therapy of GBM, and they provide for the first time evidence that combining MB-FUS with DOX treatment is effective in syngenic mouse models for GBM which can serve as preclinical models to study the impact of immune system on the therapeutic application of MB-FUS chemotherapy.

Ketone body metabolism and its defects (2014)

Toshiyuki Fukao Grant Mitchell Jörn Oliver Sass Tomohiro Hori Kenji Orii Yuka Aoyama

Acetoacetate (AcAc) and 3-hydroxybutyrate (3HB), the two main ketone bodies of humans, are important vectors of energy transport from the liver to extrahepatic tissues, especially during fasting, when glucose supply is low. Blood total ketone body (TKB) levels should be evaluated in the context of clinical history, such as fasting time and ketogenic stresses. Blood TKB should also be evaluated in parallel with blood glucose and free fatty acids (FFA). The FFA/TKB ratio is especially useful for evaluation of ketone body metabolism. Defects in ketogenesis include mitochondrial HMG-CoA synthase (mHS) deficiency and HMG-CoA lyase (HL) deficiency. mHS deficiency should be considered in non-ketotic hypoglycemia if a fatty acid beta-oxidation defect is suspected, but cannot be confirmed. Patients with HL deficiency can develop hypoglycemic crises and neurological symptoms even in adolescents and adults. Succinyl-CoA-3-oxoacid CoA transferase (SCOT) deficiency and beta-ketothiolase (T2) deficiency are two defects in ketolysis. Permanent ketosis is pathognomonic for SCOT deficiency. However, patients with "mild" SCOT mutations may have nonketotic periods. T2-deficient patients with "mild" mutations may have normal blood acylcarnitine profiles even in ketoacidotic crises. T2 deficient patients cannot be detected in a reliable manner by newborn screening using acylcarnitines. We review recent data on clinical presentation, metabolite profiles and the course of these diseases in adults, including in pregnancy.

Proposed guidelines for the diagnosis and management of methylmalonic and propionic acidemia (2014)

Matthias R. Baumgartner Friederike Hörster Carlo Dionisi-Vici Goknur Haliloglu Daniela Karall Kimberly A. Chapman Martina Huemer Michel Hochuli Murielle Assoun Diana Ballhausen Alberto Burlina Brian Fowler Sarah C. Grünert Stephanie Grünewald Tomas Honzik Begoña Merinero Celia Pérez-Cerdá Sabine Scholl-Bürgi Flemming Skovby Frits Wijburg Anita MacDonald Diego Martinelli Jörn Oliver Sass Vassili Valayannopoulos Anupam Chakrapani

Methylmalonic and propionic acidemia (MMA/PA) are inborn errors of metabolism characterized by accumulation of propionic acid and/or methylmalonic acid due to deficiency of methylmalonyl-CoA mutase (MUT) or propionyl-CoA carboxylase (PCC). MMA has an estimated incidence of ~ 1: 50,000 and PA of ~ 1:100'000 -150,000. Patients present either shortly after birth with acute deterioration, metabolic acidosis and hyperammonemia or later at any age with a more heterogeneous clinical picture, leading to early death or to severe neurological handicap in many survivors. Mental outcome tends to be worse in PA and late complications include chronic kidney disease almost exclusively in MMA and cardiomyopathy mainly in PA. Except for vitamin B12 responsive forms of MMA the outcome remains poor despite the existence of apparently effective therapy with a low protein diet and carnitine. This may be related to under recognition and delayed diagnosis due to nonspecific clinical presentation and insufficient awareness of health care professionals because of disease rarity.

3-Methylglutaconic aciduria--lessons from 50 genes and 977 patients (2013)

Saskia B. Wortmann Leo A. J. Kluijtmans Richard J. Rodenburg Jörn Oliver Sass Jessica Nouws Edwin P. van Kaauwen Tjitske Kleefstra Lisbeth Tranebjaerg Maaike C. de Vries Pirjo Isohanni Katharina Walter Fowzan S. Alkuraya Izelle Smuts Carolus J. Reinecke Francois H. van der Westhuizen David Thorburn Jan A. M. Smeitink Eva Morava Ron A. Wevers

Elevated urinary excretion of 3-methylglutaconic acid is considered rare in patients suspected of a metabolic disorder. In 3-methylglutaconyl-CoA hydratase deficiency (mutations in AUH), it derives from leucine degradation. In all other disorders with 3-methylglutaconic aciduria the origin is unknown, yet mitochondrial dysfunction is thought to be the common denominator. We investigate the biochemical, clinical and genetic data of 388 patients referred to our centre under suspicion of a metabolic disorder showing 3-methylglutaconic aciduria in routine metabolic screening. Furthermore, we investigate 591 patients with 50 different, genetically proven, mitochondrial disorders for the presence of 3-methylglutaconic aciduria. Three percent of all urine samples of the patients referred showed 3-methylglutaconic aciduria, often in correlation with disorders not reported earlier in association with 3-methylglutaconic aciduria (e.g. organic acidurias, urea cycle disorders, haematological and neuromuscular disorders). In the patient cohort with genetically proven mitochondrial disorders 11% presented 3-methylglutaconic aciduria. It was more frequently seen in ATPase related disorders, with mitochondrial DNA depletion or deletion, but not in patients with single respiratory chain complex deficiencies. Besides, it was a consistent feature of patients with mutations in TAZ, SERAC1, OPA3, DNAJC19 and TMEM70 accounting for mitochondrial membrane related pathology. 3-methylglutaconic aciduria is found quite frequently in patients suspected of a metabolic disorder, and mitochondrial dysfunction is indeed a common denominator. It is only a discriminative feature of patients with mutations in AUH, TAZ, SERAC1, OPA3, DNAJC19 TMEM70. These conditions should therefore be referred to as inborn errors of metabolism with 3-methylglutaconic aciduria as discriminative feature.

A structural mapping of mutations causing succinyl-CoA:3-ketoacid CoA transferase (SCOT) deficiency (2013)

Naeem Shafqat Kate L. Kavanagh Jörn Oliver Sass Ernst Christensen Toshiyuki Fukao Wen Hwa Lee Udo Oppermann Wyatt W. Yue

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 .

Genetic basis of hyperlysinemia (2013)

Sander M. Houten Heleen te Brinke Simone Denis Jos Pn Ruiter Alida C. Knegt Johannis Bc de Klerk Persephone Augoustides-Savvopoulou Johannes Häberle Matthias R. Baumgartner Turgay Coşkun Johannes Zschocke Jörn Oliver Sass Bwee Tien Poll-The Ronald Ja Wanders Marinus Duran

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.

Ornithine transcarbamylase deficiency combined with type 1 diabetes mellitus - a challenge in clinical and dietary management (2013)

Sarah C. Grünert Pablo Villavicencio-Lorini Bendicht Wermuth Willy Lehnert Jörn Oliver Sass K. Otfried Schwab

Ornithine transcarbamylase (OTC) deficiency is the most common urea cycle defect. The clinical presentation in female manifesting carriers varies both in onset and severity. We report on a female with insulin dependent diabetes mellitus and recurrent episodes of hyperammonemia. Since OTC activity measured in a liver biopsy sample was within normal limits, OTC deficiency was initially excluded from the differential diagnoses of hyperammonemia. Due to moderately elevated homocitrulline excretion, hyperornithinemia-hyperammonemia-homocitrullinuria-syndrome was suggested, but further assays in fibroblasts showed normal ornithine utilization. Later, when mutation analysis of the OTC gene became available, a known pathogenic missense mutation (c.533C>T) in exon 5 leading to an exchange of threonine-178 by methionine (p.Thr178Met) was detected. Skewed X-inactivation was demonstrated in leukocyte DNA. In the further clinical course the girl developed marked obesity. By initiating physical activities twice a week, therapeutic control of both diabetes and OTC deficiency improved, but obesity persisted. In conclusion, our case confirms that normal hepatic OTC enzyme activity measured in a single liver biopsy sample does not exclude a clinical relevant mosaic of OTC deficiency because of skewed X-inactivation. Mutation analysis of the OTC gene in whole blood may be a simple way to establish the diagnosis of OTC deficiency. The joint occurrence of OTC deficiency and diabetes in a patient has not been reported before.

Propionic acidemia: clinical course and outcome in 55 pediatric and adolescent patients (2013)

Sarah C. Grünert Stephanie Müllerleile Linda de Silva Michael Barth Melanie Walter Kerstin Walter Thomas Meissner Martin Lindner Regina Ensenauer René Santer Olaf A. Bodamer Matthias R. Baumgartner Michaela Brunner-Krainz Daniela Karall Claudia Haase Ina Knerr Thorsten Marquardt Julia B. Hennermann Robert Steinfeld Skadi Beblo Hans-Georg Koch Vassiliki Konstantopoulou Sabine Scholl-Bürgi Agnes van Teeffelen-Heithoff Terttu Suormala Wolfgang Sperl Jan P. Kraus Andrea Superti-Furga Karl Otfried Schwab Jörn Oliver Sass

BACKGROUND Propionic acidemia is an inherited disorder caused by deficiency of propionyl-CoA carboxylase. Although it is one of the most frequent organic acidurias, information on the outcome of affected individuals is still limited. STUDY DESIGN/METHODS Clinical and outcome data of 55 patients with propionic acidemia from 16 European metabolic centers were evaluated retrospectively. 35 patients were diagnosed by selective metabolic screening while 20 patients were identified by newborn screening. Endocrine parameters and bone age were evaluated. In addition, IQ testing was performed and the patients' and their families' quality of life was assessed. RESULTS The vast majority of patients (>85%) presented with metabolic decompensation in the neonatal period. Asymptomatic individuals were the exception. About three quarters of the study population was mentally retarded, median IQ was 55. Apart from neurologic symptoms, complications comprised hematologic abnormalities, cardiac diseases, feeding problems and impaired growth. Most patients considered their quality of life high. However, according to the parents' point of view psychic problems were four times more common in propionic acidemia patients than in healthy controls. CONCLUSION Our data show that the outcome of propionic acidemia is still unfavourable, in spite of improved clinical management. Many patients develop long-term complications affecting different organ systems. Impairment of neurocognitive development is of special concern. Nevertheless, self-assessment of quality of life of the patients and their parents yielded rather positive results.

Diurnal variation of phenylalanine and tyrosine concentrations in adult patients with phenylketonuria: subcutaneous microdialysis is no adequate tool for the determination of amino acid concentrations (2013)

Sarah C. Grünert Corinna M. Brichta Andreas Krebs Hans-Willi Clement Reinhold Rauh Christian Fleischhaker Klaus Hennighausen Jörn Oliver Sass K. Otfried Schwab

BACKGROUND Metabolic control and dietary management of patients with phenylketonuria (PKU) are based on single blood samples obtained at variable intervals. Sampling conditions are often not well-specified and intermittent variation of phenylalanine concentrations between two measurements remains unknown. We determined phenylalanine and tyrosine concentrations in blood over 24 hours. Additionally, the impact of food intake and physical exercise on phenylalanine and tyrosine concentrations was examined. Subcutaneous microdialysis was evaluated as a tool for monitoring phenylalanine and tyrosine concentrations in PKU patients. METHODS Phenylalanine and tyrosine concentrations of eight adult patients with PKU were determined at 60 minute intervals in serum, dried blood and subcutaneous microdialysate and additionally every 30 minutes postprandially in subcutaneous microdialysate. During the study period of 24 hours individually tailored meals with defined phenylalanine and tyrosine contents were served at fixed times and 20 min bicycle-ergometry was performed. RESULTS Serum phenylalanine concentrations showed only minor variations while tyrosine concentrations varied significantly more over the 24-hour period. Food intake within the patients' individual diet had no consistent effect on the mean phenylalanine concentration but the tyrosine concentration increased up to 300% individually. Mean phenylalanine concentration remained stable after short-term bicycle-exercise whereas mean tyrosine concentration declined significantly. Phenylalanine and tyrosine concentrations in dried blood were significantly lower than serum concentrations. No close correlation has been found between serum and microdialysis fluid for phenylalanine and tyrosine concentrations. CONCLUSIONS Slight diurnal variation of phenylalanine concentrations in serum implicates that a single blood sample does reliably reflect the metabolic control in this group of adult patients. Phenylalanine concentrations determined by subcutaneous microdialysis do not correlate with the patients' phenylalanine concentrations in serum/blood.

Metabolic stroke in a late-onset form of isolated sulfite oxidase deficiency (2013)

Monica Del Rizzo Alessandro P. Burlina Jörn Oliver Sass Frauke Beermann Chiara Zanco Chiara Cazzorla Andrea Bordugo Laura Giordano Renzo Manara Alberto B. Burlina

We report the first case of late-onset isolated sulfite oxidase deficiency (ISOD) presenting with a stroke-like episode. Clinical, biochemical and neuroradiological features at diagnosis and during follow-up after dietary treatment intervention are described. Furthermore, pathogenic mechanisms possibly leading to stroke in ISOD are discussed.

Functional redundancy of mitochondrial enoyl-CoA isomerases in the oxidation of unsaturated fatty acids (2012)

Michel van Weeghel Heleen te Brinke Henk van Lenthe Wim Kulik Paul E. Minkler Maria S. K. Stoll Jörn Oliver Sass Uwe Janssen Wilhelm Stoffel K. Otfried Schwab Ronald J. A. Wanders Charles L. Hoppel Sander M. Houten

Mitochondrial enoyl-CoA isomerase (ECI1) is an auxiliary enzyme involved in unsaturated fatty acid oxidation. In contrast to most of the other enzymes involved in fatty acid oxidation, a deficiency of ECI1 has yet to be identified in humans. We used wild-type (WT) and Eci1-deficient knockout (KO) mice to explore a potential presentation of human ECI1 deficiency. Upon food withdrawal, Eci1-deficient mice displayed normal blood β-hydroxybutyrate levels (WT 1.09 mM vs. KO 1.10 mM), a trend to lower blood glucose levels (WT 4.58 mM vs. KO 3.87 mM, P=0.09) and elevated blood levels of unsaturated acylcarnitines, in particular C12:1 acylcarnitine (WT 0.03 μM vs. KO 0.09 μM, P<0.01). Feeding an olive oil-rich diet induced an even greater increase in C12:1 acylcarnitine levels (WT 0.01 μM vs. KO 0.04 μM, P<0.01). Overall, the phenotypic presentation of Eci1-deficient mice is mild, possibly caused by the presence of a second enoyl-CoA isomerase (Eci2) in mitochondria. Knockdown of Eci2 in Eci1-deficient fibroblasts caused a more pronounced accumulation of C12:1 acylcarnitine on incubation with unsaturated fatty acids (12-fold, P<0.05). We conclude that Eci2 compensates for Eci1 deficiency explaining the mild phenotype of Eci1-deficient mice. Hypoglycemia and accumulation of C12:1 acylcarnitine might be diagnostic markers to identify ECI1 deficiency in humans.

Delayed-onset adenosine deaminase deficiency: strategies for an early diagnosis (2012)

Carsten Speckmann Carla Neumann Stephan Borte Giancarlo La Marca Jörn Oliver Sass Elisabeth Wiech Paul Fisch Klaus Schwarz Bernd Buchholz Michael Schlesier Kerstin Felgentreff Bodo Grimbacher Ines Santisteban Pawan Bali Michael S. Hershfield Stephan Ehl

Expression of aspartoacylase (ASPA) and Canavan disease (2012)

Anke Sommer Jörn Oliver Sass

Canavan disease (CD) is a neurodegenerative disorder usually presenting in the first six months of life. CD patients can be identified via elevated levels of N-acetyl-l-aspartate in the pattern of urinary organic acids assessed by gas chromatography-mass spectrometry. They are characterized by deficiency of aspartoacylase (aminoacylase 2; ASPA) due to mutations in the ASPA gene. Information on the molecular basis of CD is rather sparse. A lack of expression studies of ASPA mutant proteins in appropriate expression systems has prompted this investigation. Studies with overexpressed ASPA mutant proteins were carried out in the HEK293 cell line, which provides the authentic human machinery for posttranslational modifications. All ASPA mutants tested (ASPA Arg168His, ASPA Pro181Thr, ASPA Tyr288Cys, ASPA Phe295Ser, and ASPA Ala305Glu) showed loss of ASPA activity, which can be explained by the intramolecular effects of the mutations in the enzyme. The mutation p.Phe295Ser even leads to absent ASPA mRNA expression, as revealed by quantitative real-time PCR. Using this approach, ASPA gene expression analysis yielded high levels of human ASPA gene expression not only in brain and kidney, but also in lung and liver. More information of ASPA localization in human organs and detailed characterization of mutations leading to a deficiency of ASPA can contribute to a better understanding of this inborn error of metabolism.

Amino acid metabolism in patients with propionic acidaemia (2012)

Sabine Scholl-Bürgi Jörn Oliver Sass Johannes Zschocke Daniela Karall

Propionic acidaemia (PA) is an inborn error of intermediary metabolism caused by deficiency of propionyl-CoA carboxylase. The metabolic block leads to a profound failure of central metabolic pathways, including the urea and the citric acid cycles. This review will focus on changes in amino acid metabolism in this inborn disorder of metabolism. The first noted disturbance of amino acid metabolism was hyperglycinaemia, which is detectable in nearly all PA patients. Additionally, hyperlysinaemia is a common observation. In contrast, concentrations of branched chain amino acids, especially of isoleucine, are frequently reported as decreased. These non-proportional changes of branched-chain amino acids (BCAAs) compared with aromatic amino acids are also reflected by the Fischer's ratio (concentration ratio of BCAAs to aromatic amino acids), which is decreased in PA patients. As restricted dietary intake of valine and isoleucine as precursors of propionyl-CoA is part of the standard treatment in PA, decreased plasma concentrations of BCAAs may be a side effect of treatment. The concentration changes of the nitrogen scavenger glutamine have to be interpreted in the light of ammonia levels. In contrast to other hyperammonaemic syndromes, in PA plasma glutamine concentrations do not increase in hyperammonaemia, whereas CSF glutamine concentrations are elevated. Despite lactic acidaemia in PA patients, hyperalaninaemia is only rarely reported. The mechanisms underlying the observed changes in amino acid metabolism have not yet been elucidated, but most of the changes can be at least partly interpreted as consequence of disturbance of anaplerosis.

3-Hydroxyisobutyrate aciduria and mutations in the ALDH6A1 gene coding for methylmalonate semialdehyde dehydrogenase (2012)

Jörn Oliver Sass Melanie Walter Julian P. H. Shield Andrea M. Atherton Uttam Garg David Scott C. Geoffrey Woods Laurie D. Smith

3-hydroxyisobutyric aciduria is an organic aciduria with a poorly understood biochemical basis. It has previously been assumed that deficiency of 3-hydroxyisobutyrate dehydrogenase (HIBADH) in the valine catabolic pathway is the underlying enzyme defect, but more recent evidence makes it likely that individuals with 3-hydroxyisobutyryic aciduria represent a heterogeneous group with different underlying mechanisms, including respiratory chain defects or deficiency of methylmalonate semialdehyde dehydrogenase. However, to date methylmalonate semialdehyde dehydrogenase deficiency has only been demonstrated at the gene level for a single individual. We present two unrelated patients who presented with developmental delay and increased urinary concentrations of 3-hydroxyisobutyric acid. Both children were products of consanguineous unions and were of European or Pakistani descent. One patient developed a febrile illness and subsequently died from a hepatoencephalopathy at 2 years of age. Further studies were initiated and included tests of the HIBADH enzyme in fibroblast homogenates, which yielded normal activities. Sequencing of the ALDH6A1 gene (encoding methylmalonate semialdehyde dehydrogenase) suggested homozygosity for the missense mutation c.785 C > A (S262Y) in exon 7 which was not found in 210 control alleles. Mutation analysis of the ALDH6A1 gene of the second patient confirmed the presence of a different missense mutation, c.184 C > T (P62S), which was also identified in 1/530 control chromosomes. Both mutations affect highly evolutionarily conserved amino acids of the methylmalonate semialdehyde dehydrogenase protein. Mutation analysis in the ALDH6A1 gene can reveal a cause of 3-hydroxyisobutyric aciduria, which may present with only slightly increased urinary levels of 3-hydroxyisobutyric acid, if a patient is metabolically stable.

Inborn errors of ketogenesis and ketone body utilization (2012)

Jörn Oliver Sass

Ketone bodies acetoacetate and 3-hydroxy-n-butyric acid are metabolites derived from fatty acids and ketogenic amino acids such as leucine. They are mainly produced in the liver via reactions catalyzed by the ketogenic enzymes mitochondrial 3-hydroxy-3-methylglutary-coenzyme A synthase and 3-hydroxy-3-methylglutary-coenzyme A lyase. After prolonged starvation, ketone bodies can provide up to two-thirds of the brain's energy requirements. The rate-limiting enzyme of ketone body utilization (ketolysis) is succinyl-coenzyme A:3-oxoacid coenzyme A transferase. The subsequent step of ketolysis is catalyzed by 2-methylactoacetyl-coenzyme A thiolase, which is also involved in isoleucine catabolism. Inborn errors of metabolism affecting those four enzymes are presented and discussed in the context of differential diagnoses. While disorders of ketogenesis can present with hypoketotic hypoglycemia, inborn errors of ketolysis are characterized by metabolic decompensations with ketoacidosis. If those diseases are considered early and appropriate treatment is initiated without delay, patients with inborn errors of ketone body metabolism often have a good clinical outcome.

Disorders of the degradation of branched chain amino acids: what is new in clinics and laboratories? (2012)

Jörn Oliver Sass