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Inducible Systemic Gcn1 Deletion in Mice Leads to Transient Body Weight Loss upon Tamoxifen Treatment Associated with Decrease of Fat and Liver Glycogen Storage. Int J Mol Sci 2022; 23:ijms23063201. [PMID: 35328622 PMCID: PMC8949040 DOI: 10.3390/ijms23063201] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Revised: 03/09/2022] [Accepted: 03/15/2022] [Indexed: 02/06/2023] Open
Abstract
GCN1 is an evolutionarily-conserved ribosome-binding protein that mediates the amino acid starvation response as well as the ribotoxic stress response. We previously demonstrated that Gcn1 mutant mice lacking the GCN2-binding domain suffer from growth retardation and postnatal lethality via GCN2-independent mechanisms, while Gcn1-null mice die early in embryonic development. In this study, we explored the role of GCN1 in adult mice by generating tamoxifen-inducible conditional knockout (CKO) mice. Unexpectedly, the Gcn1 CKO mice showed body weight loss during tamoxifen treatment, which gradually recovered following its cessation. They also showed decreases in liver weight, hepatic glycogen and lipid contents, blood glucose and non-esterified fatty acids, and visceral white adipose tissue weight with no changes in food intake and viability. A decrease of serum VLDL suggested that hepatic lipid supply to the peripheral tissues was primarily impaired. Liver proteomic analysis revealed the downregulation of mitochondrial β-oxidation that accompanied increases of peroxisomal β-oxidation and aerobic glucose catabolism that maintain ATP levels. These findings show the involvement of GCN1 in hepatic lipid metabolism during tamoxifen treatment in adult mice.
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Transcriptome analysis suggests a compensatory role of the cofactors coenzyme A and NAD + in medium-chain acyl-CoA dehydrogenase knockout mice. Sci Rep 2019; 9:14539. [PMID: 31601874 PMCID: PMC6787083 DOI: 10.1038/s41598-019-50758-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Accepted: 09/13/2019] [Indexed: 12/12/2022] Open
Abstract
During fasting, mitochondrial fatty-acid β-oxidation (mFAO) is essential for the generation of glucose by the liver. Children with a loss-of-function deficiency in the mFAO enzyme medium-chain acyl-Coenzyme A dehydrogenase (MCAD) are at serious risk of life-threatening low blood glucose levels during fasting in combination with intercurrent disease. However, a subset of these children remains asymptomatic throughout life. In MCAD-deficient (MCAD-KO) mice, glucose levels are similar to those of wild-type (WT) mice, even during fasting. We investigated if metabolic adaptations in the liver may underlie the robustness of this KO mouse. WT and KO mice were given a high- or low-fat diet and subsequently fasted. We analyzed histology, mitochondrial function, targeted mitochondrial proteomics, and transcriptome in liver tissue. Loss of MCAD led to a decreased capacity to oxidize octanoyl-CoA. This was not compensated for by altered protein levels of the short- and long-chain isoenzymes SCAD and LCAD. In the transcriptome, we identified subtle adaptations in the expression of genes encoding enzymes catalyzing CoA- and NAD(P)(H)-involving reactions and of genes involved in detoxification mechanisms. We discuss how these processes may contribute to robustness in MCAD-KO mice and potentially also in asymptomatic human subjects with a complete loss of MCAD activity.
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Frazier AE, Thorburn DR, Compton AG. Mitochondrial energy generation disorders: genes, mechanisms, and clues to pathology. J Biol Chem 2017; 294:5386-5395. [PMID: 29233888 DOI: 10.1074/jbc.r117.809194] [Citation(s) in RCA: 150] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Inherited disorders of oxidative phosphorylation cause the clinically and genetically heterogeneous diseases known as mitochondrial energy generation disorders, or mitochondrial diseases. Over the last three decades, mutations causing these disorders have been identified in almost 290 genes, but many patients still remain without a molecular diagnosis. Moreover, while our knowledge of the genetic causes is continually expanding, our understanding into how these defects lead to cellular dysfunction and organ pathology is still incomplete. Here, we review recent developments in disease gene discovery, functional characterization, and shared pathogenic parameters influencing disease pathology that offer promising avenues toward the development of effective therapies.
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Affiliation(s)
- Ann E Frazier
- From the Murdoch Children's Research Institute, Royal Children's Hospital and Department of Paediatrics, University of Melbourne, and
| | - David R Thorburn
- From the Murdoch Children's Research Institute, Royal Children's Hospital and Department of Paediatrics, University of Melbourne, and.,Victorian Clinical Genetic Services, Royal Children's Hospital, Melbourne, Victoria 3052, Australia
| | - Alison G Compton
- From the Murdoch Children's Research Institute, Royal Children's Hospital and Department of Paediatrics, University of Melbourne, and
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Lin DS, Kao SH, Ho CS, Wei YH, Hung PL, Hsu MH, Wu TY, Wang TJ, Jian YR, Lee TH, Chiang MF. Inflexibility of AMPK-mediated metabolic reprogramming in mitochondrial disease. Oncotarget 2017; 8:73627-73639. [PMID: 29088732 PMCID: PMC5650287 DOI: 10.18632/oncotarget.20617] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Accepted: 08/17/2017] [Indexed: 01/17/2023] Open
Abstract
Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome is most commonly caused by the A3243G mutation of mitochondrial DNA. The capacity to utilize fatty acid or glucose as a fuel source and how such dynamic switches of metabolic fuel preferences and transcriptional modulation of adaptive mechanism in response to energy deficiency in MELAS syndrome have not been fully elucidated. The fibroblasts from patients with MELAS syndrome demonstrated a remarkable deficiency of electron transport chain complexes I and IV, an impaired cellular biogenesis under glucose deprivation, and a decreased ATP synthesis. In situ analysis of the bioenergetic properties of MELAS cells demonstrated an attenuated fatty acid oxidation that concomitantly occurred with impaired mitochondrial respiration, while energy production was mostly dependent on glycolysis. Furthermore, the transcriptional modulation was mediated by the AMP-activated protein kinase (AMPK) signaling pathway, which activated its downstream modulators leading to a subsequent increase in glycolytic flux through activation of pyruvate dehydrogenase. In contrast, the activities of carnitine palmitoyltransferase for fatty acid oxidation and acetyl-CoA carboxylase-1 for fatty acid synthesis were reduced and transcriptional regulation factors for biogenesis were not altered. These results provide novel information that MELAS cells lack the adaptive mechanism to switch fuel source from glucose to fatty acid, as glycolysis rates increase in response to energy deficiency. The aberrant secondary cellular responses to disrupted metabolic homeostasis mediated by AMPK signaling pathway may contribute to the development of the clinical phenotype.
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Affiliation(s)
- Dar-Shong Lin
- Department of Pediatrics, Mackay Memorial Hospital, Taipei, Taiwan.,Department of Medicine, Institute of Biomedical Sciences, Mackay Medical College, New Taipei, Taiwan
| | - Shu-Huei Kao
- School of Medical Laboratory Science and Biotechnology, Taipei Medical University, Taipei, Taiwan
| | - Che-Sheng Ho
- Department of Pediatrics, Mackay Memorial Hospital, Taipei, Taiwan
| | - Yau-Huei Wei
- Department of Medicine, Institute of Biomedical Sciences, Mackay Medical College, New Taipei, Taiwan.,Center for Mitochondrial Medicine and Free Radical Research, Changhua Christian Hospital, Changhua, Taiwan
| | - Pi-Lien Hung
- Department of Pediatric Neurology, Kaohsiung Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Kaohsiung, Taiwan
| | - Mei-Hsin Hsu
- Department of Pediatric Neurology, Kaohsiung Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Kaohsiung, Taiwan
| | - Tsu-Yen Wu
- Department of Medical Research, Mackay Memorial Hospital, Taipei, Taiwan
| | - Tuan-Jen Wang
- Department of Laboratory Medicine, Mackay Memorial Hospital, Taipei, Taiwan
| | - Yuan-Ren Jian
- Department of Medical Research, Mackay Memorial Hospital, Taipei, Taiwan
| | - Tsung-Han Lee
- Department of Medical Research, Mackay Memorial Hospital, Taipei, Taiwan
| | - Ming-Fu Chiang
- Department of Neurosurgery, Mackay Memorial Hospital, Taipei, Taiwan.,Mackay Medicine, Nursing and Management College, Taipei, Taiwan.,Graduate Institute of Injury Prevention and Control, Taipei Medical University, Taipei, Taiwan
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Zandberg L, van Dyk HC, van der Westhuizen FH, van Dijk AA. A 3-methylcrotonyl-CoA carboxylase deficient human skin fibroblast transcriptome reveals underlying mitochondrial dysfunction and oxidative stress. Int J Biochem Cell Biol 2016; 78:116-129. [PMID: 27417235 DOI: 10.1016/j.biocel.2016.07.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Revised: 07/07/2016] [Accepted: 07/11/2016] [Indexed: 01/03/2023]
Abstract
Isolated 3-methylcrotonyl-CoA carboxylase (MCC) deficiency is an autosomal recessive inherited metabolic disease of leucine catabolism with a highly variable phenotype. Apart from extensive mutation analyses of the MCCC1 and MCCC2 genes encoding 3-methylcrotonyl-CoA carboxylase (EC 6.4.1.4), molecular data on MCC deficiency gene expression studies in human tissues is lacking. For IEMs, unbiased '-omics' approaches are starting to reveal the secondary cellular responses to defects in biochemical pathways. Here we present the first whole genome expression profile of immortalized cultured skin fibroblast cells of two clinically affected MCC deficient patients and two healthy individuals generated using Affymetrix(®)HuExST1.0 arrays. There were 16191 significantly differentially expressed transcript IDs of which 3591 were well annotated and present in the predefined knowledge database of Ingenuity Pathway Analysis software used for downstream functional analyses. The most noticeable feature of this MCCA deficient skin fibroblast transcriptome was the typical genetic hallmark of mitochondrial dysfunction, decreased antioxidant response and disruption of energy homeostasis, which was confirmed by mitochondrial functional analyses. The MCC deficient transcriptome seems to predict oxidative stress that could alter the complex secondary cellular response that involve genes of the glycolysis, the TCA cycle, OXPHOS, gluconeogenesis, β-oxidation and the branched-chain fatty acid metabolism. An important emerging insight from this human MCCA transcriptome in combination with previous reports is that chronic exposure to the primary and secondary metabolites of MCC deficiency and the resulting oxidative stress might impact adversely on the quality of life and energy levels, irrespective of whether MCC deficient individuals are clinically affected or asymptomatic.
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Affiliation(s)
- L Zandberg
- Biochemistry Division, Centre for Human Metabolomics, North-West University, Private Bag X6001, Potchefstroom, 2520, South Africa
| | - H C van Dyk
- Biochemistry Division, Centre for Human Metabolomics, North-West University, Private Bag X6001, Potchefstroom, 2520, South Africa
| | - F H van der Westhuizen
- Biochemistry Division, Centre for Human Metabolomics, North-West University, Private Bag X6001, Potchefstroom, 2520, South Africa
| | - A A van Dijk
- Biochemistry Division, Centre for Human Metabolomics, North-West University, Private Bag X6001, Potchefstroom, 2520, South Africa.
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Hofker MH, Fu J, Wijmenga C. The genome revolution and its role in understanding complex diseases. Biochim Biophys Acta Mol Basis Dis 2014; 1842:1889-1895. [DOI: 10.1016/j.bbadis.2014.05.002] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Revised: 04/30/2014] [Accepted: 05/06/2014] [Indexed: 12/26/2022]
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