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Stacpoole PW, McCall CE. The pyruvate dehydrogenase complex: Life's essential, vulnerable and druggable energy homeostat. Mitochondrion 2023; 70:59-102. [PMID: 36863425 DOI: 10.1016/j.mito.2023.02.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Revised: 01/30/2023] [Accepted: 02/13/2023] [Indexed: 03/04/2023]
Abstract
Found in all organisms, pyruvate dehydrogenase complexes (PDC) are the keystones of prokaryotic and eukaryotic energy metabolism. In eukaryotic organisms these multi-component megacomplexes provide a crucial mechanistic link between cytoplasmic glycolysis and the mitochondrial tricarboxylic acid (TCA) cycle. As a consequence, PDCs also influence the metabolism of branched chain amino acids, lipids and, ultimately, oxidative phosphorylation (OXPHOS). PDC activity is an essential determinant of the metabolic and bioenergetic flexibility of metazoan organisms in adapting to changes in development, nutrient availability and various stresses that challenge maintenance of homeostasis. This canonical role of the PDC has been extensively probed over the past decades by multidisciplinary investigations into its causal association with diverse physiological and pathological conditions, the latter making the PDC an increasingly viable therapeutic target. Here we review the biology of the remarkable PDC and its emerging importance in the pathobiology and treatment of diverse congenital and acquired disorders of metabolic integration.
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Affiliation(s)
- Peter W Stacpoole
- Department of Medicine (Division of Endocrinology, Metabolism and Diabetes), and Department of Biochemistry and Molecular Biology, University of Florida, College of Medicine, Gainesville, FL, United States.
| | - Charles E McCall
- Department of Internal Medicine and Translational Sciences, and Department of Microbiology and Immunology, Wake Forest University School of Medicine, Winston-Salem, NC, United States
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Ragavan M, McLeod MA, Giacalone AG, Merritt ME. Hyperpolarized Dihydroxyacetone Is a Sensitive Probe of Hepatic Gluconeogenic State. Metabolites 2021; 11:441. [PMID: 34357335 PMCID: PMC8307483 DOI: 10.3390/metabo11070441] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Revised: 06/23/2021] [Accepted: 07/01/2021] [Indexed: 11/25/2022] Open
Abstract
Type II diabetes and pre-diabetes are widely prevalent among adults. Elevated serum glucose levels are commonly treated by targeting hepatic gluconeogenesis for downregulation. However, direct measurement of hepatic gluconeogenic capacity is accomplished only via tracer metabolism approaches that rely on multiple assumptions, and are clinically intractable due to expense and time needed for the studies. We previously introduced hyperpolarized (HP) [2-13C]dihydroxyacetone (DHA) as a sensitive detector of gluconeogenic potential, and showed that feeding and fasting produced robust changes in the ratio of detected hexoses (6C) to trioses (3C) in the perfused liver. To confirm that this ratio is robust in the setting of treatment and hormonal control, we used ex vivo perfused mouse livers from BLKS mice (glucagon treated and metformin treated), and db/db mice. We confirm that the ratio of signal intensities of 6C to 3C in 13C nuclear magnetic resonance spectra post HP DHA administration is sensitive to hepatic gluconeogenic state. This method is directly applicable in vivo and can be implemented with existing technologies without the need for substantial modifications.
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Affiliation(s)
| | | | | | - Matthew E. Merritt
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL 32610, USA; (M.R.); (M.A.M.); (A.G.G.)
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Savic D, Ball V, Curtis MK, Sousa Fialho MDL, Timm KN, Hauton D, West J, Griffin J, Heather LC, Tyler DJ. L-Carnitine Stimulates In Vivo Carbohydrate Metabolism in the Type 1 Diabetic Heart as Demonstrated by Hyperpolarized MRI. Metabolites 2021; 11:metabo11030191. [PMID: 33806953 PMCID: PMC8004902 DOI: 10.3390/metabo11030191] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Revised: 03/15/2021] [Accepted: 03/19/2021] [Indexed: 01/25/2023] Open
Abstract
The diabetic heart is energetically and metabolically abnormal, with increased fatty acid oxidation and decreased glucose oxidation. One factor contributing to the metabolic dysfunction in diabetes may be abnormal handling of acetyl and acyl groups by the mitochondria. L-carnitine is responsible for their transfer across the mitochondrial membrane, therefore, supplementation with L-carnitine may provide a route to improve the metabolic state of the diabetic heart. The primary aim of this study was to use hyperpolarized magnetic resonance imaging (MRI) to investigate the effects of L-carnitine supplementation on the in vivo metabolism of [1-13C]pyruvate in diabetes. Male Wistar rats were injected with either vehicle or streptozotocin (55 mg/kg) to induce type-1 diabetes. Three weeks of daily i.p. treatment with either saline or L-carnitine (3 g/kg/day) was subsequently undertaken. In vivo cardiac function and metabolism were assessed with CINE and hyperpolarized MRI, respectively. L-carnitine supplementation prevented the progression of hyperglycemia, which was observed in untreated streptozotocin injected animals and led to reductions in plasma triglyceride and ß-hydroxybutyrate concentrations. Hyperpolarized MRI revealed that L-carnitine treatment elevated pyruvate dehydrogenase flux by 3-fold in the diabetic animals, potentially through increased buffering of excess acetyl-CoA units in the mitochondria. Improved functional recovery following ischemia was also observed in the L-carnitine treated diabetic animals.
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Affiliation(s)
- Dragana Savic
- Cardiac Metabolism Research Group, Department of Physiology Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, UK; (V.B.); (M.K.C.); (M.d.L.S.F.); (K.N.T.); (D.H.); (L.C.H.); (D.J.T.)
- Oxford Centre for Clinical Magnetic Resonance Research (OCMR), Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford OX1 3PT, UK
- Correspondence:
| | - Vicky Ball
- Cardiac Metabolism Research Group, Department of Physiology Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, UK; (V.B.); (M.K.C.); (M.d.L.S.F.); (K.N.T.); (D.H.); (L.C.H.); (D.J.T.)
| | - M. Kate Curtis
- Cardiac Metabolism Research Group, Department of Physiology Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, UK; (V.B.); (M.K.C.); (M.d.L.S.F.); (K.N.T.); (D.H.); (L.C.H.); (D.J.T.)
| | - Maria da Luz Sousa Fialho
- Cardiac Metabolism Research Group, Department of Physiology Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, UK; (V.B.); (M.K.C.); (M.d.L.S.F.); (K.N.T.); (D.H.); (L.C.H.); (D.J.T.)
| | - Kerstin N. Timm
- Cardiac Metabolism Research Group, Department of Physiology Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, UK; (V.B.); (M.K.C.); (M.d.L.S.F.); (K.N.T.); (D.H.); (L.C.H.); (D.J.T.)
- Department of Pharmacology, University of Oxford, Oxford OX1 3PT, UK
| | - David Hauton
- Cardiac Metabolism Research Group, Department of Physiology Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, UK; (V.B.); (M.K.C.); (M.d.L.S.F.); (K.N.T.); (D.H.); (L.C.H.); (D.J.T.)
- Metabolomics Research Group, Department of Chemistry, University of Oxford, Oxford OX1 3PT, UK
| | - James West
- Department of Medicine, University of Cambridge, Cambridge CB2 1TN, UK;
| | - Julian Griffin
- Department of Metabolism, Digestion and Reproduction, Faculty of Medicine, Imperial College London, London SW7 2AZ, UK;
| | - Lisa C. Heather
- Cardiac Metabolism Research Group, Department of Physiology Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, UK; (V.B.); (M.K.C.); (M.d.L.S.F.); (K.N.T.); (D.H.); (L.C.H.); (D.J.T.)
| | - Damian J. Tyler
- Cardiac Metabolism Research Group, Department of Physiology Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, UK; (V.B.); (M.K.C.); (M.d.L.S.F.); (K.N.T.); (D.H.); (L.C.H.); (D.J.T.)
- Oxford Centre for Clinical Magnetic Resonance Research (OCMR), Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford OX1 3PT, UK
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