1
|
Fukui K, Takahashi T, Matsunari H, Uchikura A, Watanabe M, Nagashima H, Ishihara N, Kakuma T, Watanabe Y, Yamashita Y, Yoshino M. Moving towards a novel therapeutic strategy for hyperammonemia that targets glutamine metabolism. J Inherit Metab Dis 2022; 45:1059-1069. [PMID: 35866457 DOI: 10.1002/jimd.12540] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Revised: 07/15/2022] [Accepted: 07/19/2022] [Indexed: 11/11/2022]
Abstract
Patients with urea cycle disorders intermittently develop episodes of decompensation with hyperammonemia. Although such an episode is often associated with starvation and catabolism, its molecular basis is not fully understood. First, we attempted to elucidate the mechanism of such starvation-associated hyperammonemia. Using a mouse embryonic fibroblast (MEF) culture system, we found that glucose starvation increases ammonia production, and that this increase is associated with enhanced glutaminolysis. These results led us to focus on α-ketoglutarate (AKG), a glutamate dehydrogenase inhibitor, and a major anaplerotic metabolite. Hence, we sought to determine the effect of dimethyl α-ketoglutarate (DKG), a cell-permeable AKG analog, on MEFs and found that DKG mitigates ammonia production primarily by reducing flux through glutamate dehydrogenase. We also verified that DKG reduces ammonia in an NH4 Cl-challenged hyperammonemia mouse model and observed that DKG administration reduces plasma ammonia concentration to 22.8% of the mean value for control mice that received only NH4 Cl. In addition, we detected increases in ornithine concentration and in the ratio of ornithine to arginine following DKG treatment. We subsequently administered DKG intravenously to a newborn pig with hyperammonemia due to ornithine transcarbamylase deficiency and found that blood ammonia concentration declined significantly over time. We determined that this effect is associated with facilitated reductive amination and glutamine synthesis. Our present data indicate that energy starvation triggers hyperammonemia through enhanced glutaminolysis and that DKG reduces ammonia accumulation via pleiotropic mechanisms both in vitro and in vivo. Thus, cell-permeable forms of AKG are feasible candidates for a novel hyperammonemia treatment.
Collapse
Affiliation(s)
- Kaori Fukui
- Department of Pediatrics and Child Health, Kurume University School of Medicine, Kurume, Japan
| | - Tomoyuki Takahashi
- Department of Pediatrics and Child Health, Kurume University School of Medicine, Kurume, Japan
- Division of Gene Therapy and Regenerative Medicine, Cognitive and Molecular Research Institute of Brain Diseases, Kurume University, Kurume, Japan
| | - Hitomi Matsunari
- Meiji University International Institute for Bio-Resource Research, Kawasaki, Japan
- Laboratory of Medical Engineering, Meiji University, Kawasaki, Japan
| | - Ayuko Uchikura
- Laboratory of Medical Engineering, Meiji University, Kawasaki, Japan
| | - Masahito Watanabe
- Meiji University International Institute for Bio-Resource Research, Kawasaki, Japan
| | - Hiroshi Nagashima
- Meiji University International Institute for Bio-Resource Research, Kawasaki, Japan
- Laboratory of Medical Engineering, Meiji University, Kawasaki, Japan
| | - Naotada Ishihara
- Department of Protein Biochemistry, Institute of Life Science, Kurume University, Kurume, Japan
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Japan
| | | | - Yoriko Watanabe
- Department of Pediatrics and Child Health, Kurume University School of Medicine, Kurume, Japan
- Research Institute of Medical Mass Spectrometry, Kurume University School of Medicine, Kurume, Japan
| | - Yushiro Yamashita
- Department of Pediatrics and Child Health, Kurume University School of Medicine, Kurume, Japan
| | - Makoto Yoshino
- Division of Gene Therapy and Regenerative Medicine, Cognitive and Molecular Research Institute of Brain Diseases, Kurume University, Kurume, Japan
| |
Collapse
|