bims-meglyc 2023-10-29 papers

Proteomics Clin Appl. 2023 Oct 24. e2300040

"Hide and seek": Misleading transferrin variants in PMM2-CDG complicate diagnostics.

Alexandre Raynor, Arnaud Bruneel, Pieter Vermeersch, Sophie Cholet, Sebastian Friedrich, Matthias Eckenweiler, Anke Schumann, Simone Hengst, Ali Tunç Tuncel, François Fenaille, Christian Thiel, Daisy Rymen.

PURPOSE: Congenital disorders of glycosylation (CDG) are one of the fastest growing groups of inborn errors of metabolism. Despite the availability of next-generation sequencing techniques and advanced methods for evaluation of glycosylation, CDG screening mainly relies on the analysis of serum transferrin (Tf) by isoelectric focusing, HPLC or capillary electrophoresis. The main pitfall of this screening method is the presence of Tf protein variants within the general population. Although reports describe the role of Tf variants leading to falsely abnormal results, their significance in confounding diagnosis in patients with CDG has not been documented so far. Here, we describe two PMM2-CDG cases, in which Tf variants complicated the diagnostic.
EXPERIMENTAL DESIGN: Glycosylation investigations included classical screening techniques (capillary electrophoresis, isoelectric focusing and HPLC of Tf) and various confirmation techniques (two-dimensional electrophoresis, western blot, N-glycome, UPLC-FLR/QTOF MS with Rapifluor). Tf variants were highlighted following neuraminidase treatment. Sequencing of PMM2 was performed.
RESULTS: In both patients, Tf screening pointed to CDG-II, while second-line analyses pointed to CDG-I. Tf variants were found in both patients, explaining these discrepancies. PMM2 causative variants were identified in both patients.
CONCLUSION AND CLINICAL RELEVANCE: We suggest that a neuraminidase treatment should be performed when a typical CDG Tf pattern is found upon initial screening analysis.

Keywords: CDG; PMM2-CDG; congenital disorder of glycosylation; transferrin variant

DOI: https://doi.org/10.1002/prca.202300040

Nutrients. 2023 Oct 16. pii: 4376. [Epub ahead of print]15(20):

Endogenous Fructose Production and Metabolism Drive Metabolic Dysregulation and Liver Disease in Mice with Hereditary Fructose Intolerance.

Ana Andres-Hernando, David J Orlicky, Masanari Kuwabara, Christina Cicerchi, Michelle Pedler, Mark J Petrash, Richard J Johnson, Dean R Tolan, Miguel A Lanaspa.

Excessive intake of sugar, and particularly fructose, is closely associated with the development and progression of metabolic syndrome in humans and animal models. However, genetic disorders in fructose metabolism have very different consequences. While the deficiency of fructokinase, the first enzyme involved in fructose metabolism, is benign and somewhat desirable, missense mutations in the second enzyme, aldolase B, causes a very dramatic and sometimes lethal condition known as hereditary fructose intolerance (HFI). To date, there is no cure for HFI, and treatment is limited to avoiding fructose and sugar. Because of this, for subjects with HFI, glucose is their sole source of carbohydrates in the diet. However, clinical symptoms still occur, suggesting that either low amounts of fructose are still being consumed or, alternatively, fructose is being produced endogenously in the body. Here, we demonstrate that as a consequence of consuming high glycemic foods, the polyol pathway, a metabolic route in which fructose is produced from glucose, is activated, triggering a deleterious mechanism whereby glucose, sorbitol and alcohol induce severe liver disease and growth retardation in aldolase B knockout mice. We show that generically and pharmacologically blocking this pathway significantly improves metabolic dysfunction and thriving and increases the tolerance of aldolase B knockout mice to dietary triggers of endogenous fructose production.

Keywords: HFI; aldolase b; endogenous fructose; metabolic dysfunction; polyol pathway

DOI: https://doi.org/10.3390/nu15204376

J Biol Chem. 2023 Oct 19. pii: S0021-9258(23)02403-1. [Epub ahead of print] 105375

Loss of Muscle PDH Induces Lactic Acidosis and Adaptive Anaplerotic Compensation via Pyruvate-Alanine Cycling and Glutaminolysis.

Keshav Gopal, Abdualrahman Mohammed Abdualkader, Xiaobei Li, Amanda A Greenwell, Qutuba G Karwi, Tariq R Altamimi, Christina Saed, Golam M Uddin, Ahmed M Darwesh, K Lockhart Jamieson, Ryekjang Kim, Farah Eaton, John M Seubert, Gary D Lopaschuk, John R Ussher, Rami Al Batran.

Pyruvate dehydrogenase (PDH) is the rate-limiting enzyme for glucose oxidation that links glycolysis-derived pyruvate with the tricarboxylic acid (TCA) cycle. Although skeletal muscle is a significant site for glucose oxidation and is closely linked with metabolic flexibility, the importance of muscle PDH during rest and exercise has yet to be fully elucidated. Here, we demonstrate that mice with muscle-specific deletion of PDH exhibit rapid weight loss and suffer from severe lactic acidosis, ultimately leading to early mortality under low-fat diet provision. Furthermore, loss of muscle PDH induces adaptive anaplerotic compensation by increasing pyruvate-alanine cycling and glutaminolysis. Interestingly, high-fat diet supplementation effectively abolishes the early mortality and rescues the overt metabolic phenotype induced by muscle PDH deficiency. Despite increased reliance on fatty acid oxidation during high-fat diet provision, loss of muscle PDH worsens exercise performance and induces lactic acidosis. These observations illustrate the importance of muscle PDH in maintaining metabolic flexibility and preventing the development of metabolic disorders.

Keywords: Alanine Cycling; Fatty Acid Oxidation; Glucose Oxidation; Glutaminolysis; Glycolysis

DOI: https://doi.org/10.1016/j.jbc.2023.105375

J Pharmacol Exp Ther. 2023 Oct 24. pii: JPET-AR-2023-001919. [Epub ahead of print]

Pantothenate kinase activation restores brain coenzyme A in a mouse model of pantothenate kinase associated neurodegeneration.

Chitra Subramanian, Matthew W Frank, Rajaa Sukun, Christopher E Henry, Anna Wade, Mallory E Harden, Satish Rao, Rajendra Tangallapally, Mi-Kyung Yun, Stephen W White, Richard E Lee, Uma Sinha, Charles O Rock, Suzanne Jackowski.

Pantothenate kinase associated neurodegeneration (PKAN) is characterized by a motor disorder with combinations of dystonia, parkinsonism and spasticity, leading to premature death. PKAN is caused by mutations in the PANK2 gene that result in loss or reduction of PANK2 protein function. PANK2 is one of three kinases that initiate and regulate coenzyme A biosynthesis from vitamin B5 and the ability of BBP-671, an allosteric activator of pantothenate kinases, to enter the brain and elevate coenzyme A was investigated. The metabolic stability, protein binding and membrane permeability of BBP-671 all suggest it has the physical properties required to cross the blood brain barrier. BBP-671 was detected in plasma, liver, cerebrospinal fluid and brain following oral administration in rodents demonstrating the ability of BBP-671 to penetrate the brain. The pharmacokinetic and pharmacodynamic properties of orally administered BBP-671 evaluated in cannulated rats showed that CoA concentrations were elevated in blood, liver and brain. BBP-671 elevation of whole blood acetyl-CoA served as a peripheral pharmacodynamic marker and provided a suitable method to assess target engagement. BBP-671 treatment elevated brain coenzyme A concentrations, and improved movement and body weight in a PKAN mouse model. Thus, BBP-671 crosses the blood brain barrier to correct the brain CoA deficiency in a PKAN mouse model resulting in improved locomotion and survival, providing a preclinical foundation for the development of BBP-671 as a potential treatment for PKAN. Significance Statement The blood brain barrier represents a major hurdle for drugs targeting brain metabolism. This work describes the pharmacokinetic/pharmacodynamic properties of BBP-671, a pantothenate kinase activator. BBP-671 crosses the blood brain barrier to correct the neuron-specific CoA deficiency and improve motor function in a mouse model of pantothenate kinase associated neurodegeneration. The central role of CoA and acetyl-CoA in intermediary metabolism suggests that pantothenate kinase activators may be useful in modifying neurological metabolic disorders.

Keywords: Drug development; blood-brain barrier; neurodegeneration

DOI: https://doi.org/10.1124/jpet.123.001919

Biochem Biophys Res Commun. 2023 Oct 17. pii: S0006-291X(23)01207-X. [Epub ahead of print]684 149123

N-Acetylglutamate and N-acetylmethionine compromise mitochondrial bioenergetics homeostasis and glutamate oxidation in brain of developing rats: Potential implications for the pathogenesis of ACY1 deficiency.

Vanessa Trindade Bortoluzzi, Rafael Teixeira Ribeiro, Camila Vieira Pinheiro, Ediandra Tissot Castro, Tailine Quevedo Tavares, Guilhian Leipnitz, Jörn Oliver Sass, Roger Frigério Castilho, Alexandre Umpierrez Amaral, Moacir Wajner.

Aminoacylase 1 (ACY1) deficiency is an inherited metabolic disorder biochemically characterized by high urinary concentrations of aliphatic N-acetylated amino acids and associated with a broad clinical spectrum with predominant neurological signs. Considering that the pathogenesis of ACY1 is practically unknown and the brain is highly dependent on energy production, the in vitro effects of N-acetylglutamate (NAG) and N-acetylmethionine (NAM), major metabolites accumulating in ACY1 deficiency, on the enzyme activities of the citric acid cycle (CAC), of the respiratory chain complexes and glutamate dehydrogenase (GDH), as well as on ATP synthesis were evaluated in brain mitochondrial preparations of developing rats. NAG mildly inhibited mitochondrial isocitrate dehydrogenase 2 (IDH2) activity, moderately inhibited the activities of isocitrate dehydrogenase 3 (IDH3) and complex II-III of the respiratory chain and markedly suppressed the activities of complex IV and GDH. Of note, the NAG-induced inhibitory effect on IDH3 was competitive, whereas that on GDH was mixed. On the other hand, NAM moderately inhibited the activity of respiratory complexes II-III and GDH activities and strongly decreased complex IV activity. Furthermore, NAM was unable to modify any of the CAC enzyme activities, indicating a selective effect of NAG toward IDH mitochondrial isoforms. In contrast, the activities of citrate synthase, α-ketoglutarate dehydrogenase, malate dehydrogenase, and of the respiratory chain complexes I and II were not changed by these N-acetylated amino acids. Finally, NAG and NAM strongly decreased mitochondrial ATP synthesis. Taken together, the data indicate that NAG and NAM impair mitochondrial brain energy homeostasis.

Keywords: Aminoacylase 1; Brain bioenergetics; Citric acid cycle; N-Acetylglutamate; N-Acetylmethionine; Respiratory chain

DOI: https://doi.org/10.1016/j.bbrc.2023.149123