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Wongkittichote P, Cunningham G, Summar ML, Pumbo E, Forny P, Baumgartner MR, Chapman KA. Tricarboxylic acid cycle enzyme activities in a mouse model of methylmalonic aciduria. Mol Genet Metab 2019; 128:444-451. [PMID: 31648943 PMCID: PMC6903684 DOI: 10.1016/j.ymgme.2019.10.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Revised: 09/19/2019] [Accepted: 10/15/2019] [Indexed: 02/05/2023]
Abstract
Methylmalonic acidemia (MMA) is a propionate pathway disorder caused by dysfunction of the mitochondrial enzyme methylmalonyl-CoA mutase (MMUT). MMUT catalyzes the conversion of methylmalonyl-CoA to succinyl-CoA, an anaplerotic reaction which feeds into the tricarboxylic acid (TCA) cycle. As part of the pathological mechanisms of MMA, previous studies have suggested there is decreased TCA activity due to a "toxic inhibition" of TCA cycle enzymes by MMA related metabolites, in addition to reduced anaplerosis. Here, we have utilized mitochondria isolated from livers of a mouse model of MMA (Mut-ko/ki) and their littermate controls (Ki/wt) to examine the amounts and enzyme functions of most of the TCA cycle enzymes. We have performed mRNA quantification, protein semi-quantitation, and enzyme activity quantification for TCA cycle enzymes in these samples. Expression profiling showed increased mRNA levels of fumarate hydratase in the Mut-ko/ki samples, which by contrast had reduced protein levels as detected by immunoblot, while all other mRNA levels were unaltered. Immunoblotting also revealed decreased protein levels of 2-oxoglutarate dehydrogenase and malate dehydrogenase 2. Interesting, the decreased protein amount of 2-oxoglutarate dehydrogenase was reflected in decreased activity for this enzyme while there is a trend towards decreased activity of fumarate hydratase and malate dehydrogenase 2. Citrate synthase, isocitrate dehydrogenase 2/3, succinyl-CoA synthase, and succinate dehydrogenase are not statistically different in terms of quantity of enzyme or activity. Finally, we found decreased activity when examining the function of methylmalonyl-CoA mutase in series with succinate synthase and succinate dehydrogenase in the Mut-ko/ki mice compared to their littermate controls, as expected. This study demonstrates decreased activity of certain TCA cycle enzymes and by corollary decreased TCA cycle function, but it supports decreased protein quantity rather than "toxic inhibition" as the underlying mechanism of action. SUMMARY: Methylmalonic acidemia (MMA) is an inborn metabolic disorder of propionate catabolism. In this disorder, toxic metabolites are considered to be the major pathogenic mechanism for acute and long-term complications. However, despite optimized therapies aimed at reducing metabolite levels, patients continue to suffer from late complications, including metabolic stroke and renal insufficiency. Since the propionate pathway feeds into the tricarboxylic acid (TCA) cycle, we investigated TCA cycle function in a constitutive MMA mouse model. We demonstrated decreased amounts of the TCA enzymes, Mdh2 and Ogdh as semi-quantified by immunoblot. Enzymatic activity of Ogdh is also decreased in the MMA mouse model compared to controls. Thus, when the enzyme amounts are decreased, we see the enzymatic activity also decreased to a similar extent for Ogdh. Further studies to elucidate the structural and/or functional links between the TCA cycle and propionate pathways might lead to new treatment approaches for MMA patients.
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Affiliation(s)
- Parith Wongkittichote
- Children's National Rare Disease Institute, Children's National Health System, Washington DC 20010, United States; Department of Pediatrics, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Bangkok 10400, Thailand; Department of Pediatrics, St. Louis Children's Hospital, Washington University School of Medicine, St. Louis, MO, USA
| | - Gary Cunningham
- Children's National Rare Disease Institute, Children's National Health System, Washington DC 20010, United States
| | - Marshall L Summar
- Children's National Rare Disease Institute, Children's National Health System, Washington DC 20010, United States
| | - Elena Pumbo
- Children's National Rare Disease Institute, Children's National Health System, Washington DC 20010, United States
| | - Patrick Forny
- Division of Metabolism, the Children's Research Center, The Swiss Newborn Screening Laboratory, University Children's Hospital Zurich, 8032 Zurich, Switzerland; The radiz-Rare Disease Initiative Zurich, Clinical Research Priority Program for Rare Diseases, the Center for Integrative Human Physiology, University of Zurich, 8006 Zurich, Switzerland
| | - Matthias R Baumgartner
- Division of Metabolism, the Children's Research Center, The Swiss Newborn Screening Laboratory, University Children's Hospital Zurich, 8032 Zurich, Switzerland; The radiz-Rare Disease Initiative Zurich, Clinical Research Priority Program for Rare Diseases, the Center for Integrative Human Physiology, University of Zurich, 8006 Zurich, Switzerland
| | - Kimberly A Chapman
- Children's National Rare Disease Institute, Children's National Health System, Washington DC 20010, United States.
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Kiykim E, Zubarioglu T, Cansever MS, Celkan T, Häberle J, Aktuglu Zeybek AC. Coagulation Disturbances in Patients with Argininemia. Acta Haematol 2018; 140:221-225. [PMID: 30355940 DOI: 10.1159/000493678] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Accepted: 09/06/2018] [Indexed: 12/31/2022]
Abstract
BACKGROUND Argininemia is an autosomal recessive urea cycle disorder (UCD). Unlike other UCD, hyperammonemia is rarely seen. Patients usually present in childhood with neurological symptoms. Uncommon presentations like neonatal cholestasis or cirrhosis have been reported. Although transient elevations of liver transaminases and coagulopathy have been reported during hyperammonemia episodes, a permanent coagulopathy has never been reported. METHODS In this retrospective study, coagulation disturbances are examined in 6 argininemia patients. All of the patients were routinely followed up for hepatic involvement due to argininemia. Laboratory results, including liver transaminases, albumin, prothrombin time (PT), international normalized ratio (INR), activated partial thromboplastin time (aPTT), and clotting factor levels, were assessed in all of the patients. RESULTS All of the patients had a prolonged PT and an increased INR, while none of the patients had a prolonged aPTT. Five patients had slightly elevated liver transaminases. A liver biopsy was performed in 1 patient but neither cirrhosis nor cholestasis was documented. Five of the 6 patients had low factor VII and factor IX levels, while other clotting factors were normal. CONCLUSIONS Argininemia patients should be investigated for coagulation disorders even if there is no apparent liver dysfunction or major bleeding symptoms.
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Affiliation(s)
- Ertugrul Kiykim
- Division of Nutrition and Metabolism, Department of Pediatrics, Cerrahpasa Medical Faculty, Istanbul University, Istanbul, Turkey
| | - Tanyel Zubarioglu
- Division of Nutrition and Metabolism, Department of Pediatrics, Cerrahpasa Medical Faculty, Istanbul University, Istanbul,
| | - Mehmet Serif Cansever
- Central Laboratory, Cerrahpasa Medical Faculty, Istanbul University, Istanbul, Turkey
| | - Tiraje Celkan
- Division of Hematology and Oncology, Department of Pediatrics, Cerrahpasa Medical Faculty, Istanbul University, Istanbul, Turkey
| | - Johannes Häberle
- Division of Metabolism, University Children's Hospital, Zurich, Switzerland
| | - Ayse Cigdem Aktuglu Zeybek
- Division of Nutrition and Metabolism, Department of Pediatrics, Cerrahpasa Medical Faculty, Istanbul University, Istanbul, Turkey
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