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Heather LC, Gopal K, Srnic N, Ussher JR. Redefining Diabetic Cardiomyopathy: Perturbations in Substrate Metabolism at the Heart of Its Pathology. Diabetes 2024; 73:659-670. [PMID: 38387045 PMCID: PMC11043056 DOI: 10.2337/dbi23-0019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Accepted: 02/15/2024] [Indexed: 02/24/2024]
Abstract
Cardiovascular disease represents the leading cause of death in people with diabetes, most notably from macrovascular diseases such as myocardial infarction or heart failure. Diabetes also increases the risk of a specific form of cardiomyopathy, referred to as diabetic cardiomyopathy (DbCM), originally defined as ventricular dysfunction in the absence of underlying coronary artery disease and/or hypertension. Herein, we provide an overview on the key mediators of DbCM, with an emphasis on the role for perturbations in cardiac substrate metabolism. We discuss key mechanisms regulating metabolic dysfunction in DbCM, with additional focus on the role of metabolites as signaling molecules within the diabetic heart. Furthermore, we discuss the preclinical approaches to target these perturbations to alleviate DbCM. With several advancements in our understanding, we propose the following as a new definition for, or approach to classify, DbCM: "diastolic dysfunction in the presence of altered myocardial metabolism in a person with diabetes but absence of other known causes of cardiomyopathy and/or hypertension." However, we recognize that no definition can fully explain the complexity of why some individuals with DbCM exhibit diastolic dysfunction, whereas others develop systolic dysfunction. Due to DbCM sharing pathological features with heart failure with preserved ejection fraction (HFpEF), the latter of which is more prevalent in the population with diabetes, it is imperative to determine whether effective management of DbCM decreases HFpEF prevalence. ARTICLE HIGHLIGHTS
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Affiliation(s)
- Lisa C. Heather
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, U.K
| | - Keshav Gopal
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta, Canada
- Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
- Cardiovascular Research Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Nikola Srnic
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, U.K
| | - John R. Ussher
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta, Canada
- Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
- Cardiovascular Research Institute, University of Alberta, Edmonton, Alberta, Canada
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2
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Mapping the Metabolic Niche of Citrate Metabolism and SLC13A5. Metabolites 2023; 13:metabo13030331. [PMID: 36984771 PMCID: PMC10054676 DOI: 10.3390/metabo13030331] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2023] [Revised: 02/17/2023] [Accepted: 02/20/2023] [Indexed: 02/26/2023] Open
Abstract
The small molecule citrate is a key molecule that is synthesized de novo and involved in diverse biochemical pathways influencing cell metabolism and function. Citrate is highly abundant in the circulation, and cells take up extracellular citrate via the sodium-dependent plasma membrane transporter NaCT encoded by the SLC13A5 gene. Citrate is critical to maintaining metabolic homeostasis and impaired NaCT activity is implicated in metabolic disorders. Though citrate is one of the best known and most studied metabolites in humans, little is known about the consequences of altered citrate uptake and metabolism. Here, we review recent findings on SLC13A5, NaCT, and citrate metabolism and discuss the effects on metabolic homeostasis and SLC13A5-dependent phenotypes. We discuss the “multiple-hit theory” and how stress factors induce metabolic reprogramming that may synergize with impaired NaCT activity to alter cell fate and function. Furthermore, we underline how citrate metabolism and compartmentalization can be quantified by combining mass spectrometry and tracing approaches. We also discuss species-specific differences and potential therapeutic implications of SLC13A5 and NaCT. Understanding the synergistic impact of multiple stress factors on citrate metabolism may help to decipher the disease mechanisms associated with SLC13A5 citrate transport disorders.
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3
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Ketone Bodies and Cardiovascular Disease: An Alternate Fuel Source to the Rescue. Int J Mol Sci 2023; 24:ijms24043534. [PMID: 36834946 PMCID: PMC9962558 DOI: 10.3390/ijms24043534] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Revised: 02/04/2023] [Accepted: 02/07/2023] [Indexed: 02/12/2023] Open
Abstract
The increased metabolic activity of the heart as a pump involves a high demand of mitochondrial adenosine triphosphate (ATP) production for its mechanical and electrical activities accomplished mainly via oxidative phosphorylation, supplying up to 95% of the necessary ATP production, with the rest attained by substrate-level phosphorylation in glycolysis. In the normal human heart, fatty acids provide the principal fuel (40-70%) for ATP generation, followed mainly by glucose (20-30%), and to a lesser degree (<5%) by other substrates (lactate, ketones, pyruvate and amino acids). Although ketones contribute 4-15% under normal situations, the rate of glucose use is drastically diminished in the hypertrophied and failing heart which switches to ketone bodies as an alternate fuel which are oxidized in lieu of glucose, and if adequately abundant, they reduce myocardial fat delivery and usage. Increasing cardiac ketone body oxidation appears beneficial in the context of heart failure (HF) and other pathological cardiovascular (CV) conditions. Also, an enhanced expression of genes crucial for ketone break down facilitates fat or ketone usage which averts or slows down HF, potentially by avoiding the use of glucose-derived carbon needed for anabolic processes. These issues of ketone body utilization in HF and other CV diseases are herein reviewed and pictorially illustrated.
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Dolan LC, Karikachery AR, Thipe VC, Arceneaux BG, Katti KK, Katti KV, Chesne AM. Toxicity Investigations of (R)-3-Hydroxybutyrate Glycerides In Vitro and in Male and Female Rats. Nutrients 2022; 14:nu14204426. [PMID: 36297110 PMCID: PMC9610502 DOI: 10.3390/nu14204426] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Revised: 10/19/2022] [Accepted: 10/19/2022] [Indexed: 11/05/2022] Open
Abstract
TCN006, a formulation of (R)-3-Hydroxybutyrate glycerides, is a promising ingredient for enhancing ketone intake of humans. Ketones have been shown to have beneficial effects on human health. To be used by humans, TCN006 must be determined safe in appropriately designed safety studies. The results of a bacterial reverse mutation assay, an in vitro mammalian micronucleus study, and 14-and 90-day repeat dose toxicity studies in rats are reported herein. In the 14- and 90-day studies, male and female Wistar rats had free access to drinking water containing 0, 75,000, 125,000 or 200,000 ppm TCN006 for 92 and 93 days, respectively. TCN006 tested negative for genotoxicity and the no observed adverse effect level (NOAEL) for toxicity in the 14- and 90-day studies was 200,000 ppm, the highest dose administered. In the longer term study, the mean overall daily intake of TCN006 in the 200,000 ppm groups was 14,027.9 mg/kg bw/day for males and 20,507.0 mg/kg bw/day for females. At this concentration, palatability of water was likely affected, which led to a decrease in water consumption in both males and females compared to respective controls. This had no effect on the health of the animals. Although the rats were administered very high levels of (R)-3-Hydroxybutyrate glycerides, there were no signs of ketoacidosis.
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Affiliation(s)
- Laurie C. Dolan
- GRAS Associates, LLC., 11810 Grand Park Avenue, Suite 500, North Bethesda, MD 20852, USA
| | - Alice Raphael Karikachery
- Department of Radiology, Institute of Green Nanotechnology, University of Missouri, Columbia, MO 65212, USA
| | - Velaphi C. Thipe
- Department of Radiology, Institute of Green Nanotechnology, University of Missouri, Columbia, MO 65212, USA
| | - Benjamin G. Arceneaux
- GRAS Associates, LLC., 11810 Grand Park Avenue, Suite 500, North Bethesda, MD 20852, USA
| | - Kavita K. Katti
- Department of Radiology, Institute of Green Nanotechnology, University of Missouri, Columbia, MO 65212, USA
| | - Kattesh V. Katti
- Department of Radiology, Institute of Green Nanotechnology, University of Missouri, Columbia, MO 65212, USA
| | - Alton M. Chesne
- Tecton Group, LLC., 370 River Rd., Alexandria, LA 71302, USA
- Correspondence:
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5
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Yurista SR, Eder RA, Kwon DH, Farrar CT, Yen YF, Tang WHW, Nguyen CT. Magnetic resonance imaging of cardiac metabolism in heart failure: how far have we come? Eur Heart J Cardiovasc Imaging 2022; 23:1277-1289. [PMID: 35788836 PMCID: PMC10202438 DOI: 10.1093/ehjci/jeac121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Revised: 06/06/2022] [Accepted: 06/10/2022] [Indexed: 11/12/2022] Open
Abstract
As one of the highest energy consumer organs in the body, the heart requires tremendous amount of adenosine triphosphate (ATP) to maintain its continuous mechanical work. Fatty acids, glucose, and ketone bodies are the primary fuel source of the heart to generate ATP with perturbations in ATP generation possibly leading to contractile dysfunction. Cardiac metabolic imaging with magnetic resonance imaging (MRI) plays a crucial role in understanding the dynamic metabolic changes occurring in the failing heart, where the cardiac metabolism is deranged. Also, targeting and quantifying metabolic changes in vivo noninvasively is a promising approach to facilitate diagnosis, determine prognosis, and evaluate therapeutic response. Here, we summarize novel MRI techniques used for detailed investigation of cardiac metabolism in heart failure including magnetic resonance spectroscopy (MRS), hyperpolarized MRS, and chemical exchange saturation transfer based on evidence from preclinical and clinical studies and to discuss the potential clinical application in heart failure.
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Affiliation(s)
- Salva R Yurista
- Cardiovascular Research Center, Corrigan Minehan Heart Center, Massachusetts General Hospital, Harvard Medical School, 149 13th St, Charlestown, MA 02129, USA
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, 149 13th St, Charlestown, MA 02129, USA
| | - Robert A Eder
- Cardiovascular Research Center, Corrigan Minehan Heart Center, Massachusetts General Hospital, Harvard Medical School, 149 13th St, Charlestown, MA 02129, USA
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, 149 13th St, Charlestown, MA 02129, USA
| | - Deborah H Kwon
- Department of Cardiovascular Medicine, Heart, Vascular, and Thoracic Institute, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, USA
| | - Christian T Farrar
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, 149 13th St, Charlestown, MA 02129, USA
| | - Yi Fen Yen
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, 149 13th St, Charlestown, MA 02129, USA
| | - W H Wilson Tang
- Department of Cardiovascular Medicine, Heart, Vascular, and Thoracic Institute, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, USA
| | - Christopher T Nguyen
- Cardiovascular Research Center, Corrigan Minehan Heart Center, Massachusetts General Hospital, Harvard Medical School, 149 13th St, Charlestown, MA 02129, USA
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, 149 13th St, Charlestown, MA 02129, USA
- Division of Health Science Technology, Harvard-Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139, USA
- Cardiovascular Innovation Research Center, Heart, Vascular, and Thoracic Institute, Cleveland Clinic, Cleveland, 9500 Euclid Avenue, Cleveland, OH 44195, USA
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6
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Sharma G, Wen X, Maptue NR, Hever T, Malloy CR, Sherry AD, Khemtong C. Co-Polarized [1- 13C]Pyruvate and [1,3- 13C 2]Acetoacetate Provide a Simultaneous View of Cytosolic and Mitochondrial Redox in a Single Experiment. ACS Sens 2021; 6:3967-3977. [PMID: 34761912 DOI: 10.1021/acssensors.1c01225] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Cellular redox is intricately linked to energy production and normal cell function. Although the redox states of mitochondria and cytosol are connected by shuttle mechanisms, the redox state of mitochondria may differ from redox in the cytosol in response to stress. However, detecting these differences in functioning tissues is difficult. Here, we employed 13C magnetic resonance spectroscopy (MRS) and co-polarized [1-13C]pyruvate and [1,3-13C2]acetoacetate ([1,3-13C2]AcAc) to monitor production of hyperpolarized (HP) lactate and β-hydroxybutyrate as indicators of cytosolic and mitochondrial redox, respectively. Isolated rat hearts were examined under normoxic conditions, during low-flow ischemia, and after pretreatment with either aminooxyacetate (AOA) or rotenone. All interventions were associated with an increase in [Pi]/[ATP] measured by 31P NMR. In well-oxygenated untreated hearts, rapid conversion of HP [1-13C]pyruvate to [1-13C]lactate and [1,3-13C2]AcAc to [1,3-13C2]β-hydroxybutyrate ([1,3-13C2]β-HB) was readily detected. A significant increase in HP [1,3-13C2]β-HB but not [1-13C]lactate was observed in rotenone-treated and ischemic hearts, consistent with an increase in mitochondrial NADH but not cytosolic NADH. AOA treatments did not alter the productions of HP [1-13C]lactate or [1,3-13C2]β-HB. This study demonstrates that biomarkers of mitochondrial and cytosolic redox may be detected simultaneously in functioning tissues using co-polarized [1-13C]pyruvate and [1,3-13C2]AcAc and 13C MRS and that changes in mitochondrial redox may precede changes in cytosolic redox.
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Affiliation(s)
- Gaurav Sharma
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas 75390, United States
| | - Xiaodong Wen
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas 75390, United States
| | - Nesmine R. Maptue
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas 75390, United States
| | - Thomas Hever
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas 75390, United States
| | - Craig R. Malloy
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas 75390, United States
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390, United States
- Department of Radiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, United States
| | - A. Dean Sherry
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas 75390, United States
- Department of Radiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, United States
- Department of Chemistry, University of Texas at Dallas, Richardson, Texas 75080, United States
| | - Chalermchai Khemtong
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas 75390, United States
- Department of Radiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, United States
- Department of Medicine, Division of Endocrinology, Diabetes and Metabolism, University of Florida, Gainesville, Florida 32610, United States
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida 32610, United States
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7
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Singh J, Suh EH, Sharma G, Chen J, Hackett EP, Wen X, Sherry AD, Khemtong C, Malloy CR, Park JM, Kovacs Z. 13C-Labeled Diethyl Ketoglutarate Derivatives as Hyperpolarized Probes of 2-Ketoglutarate Dehydrogenase Activity. ANALYSIS & SENSING 2021; 1:156-160. [PMID: 35669533 PMCID: PMC9165698 DOI: 10.1002/anse.202100021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Indexed: 11/11/2022]
Abstract
The TCA cycle is a central metabolic pathway for energy production and biosynthesis. A major control point of metabolic flux through the cycle is the decarboxylation of 2-ketoglutarate by the TCA cycle enzyme 2-ketoglutarate dehydrogenase (2-KGDH). In this project, we developed 13C labeled 2-ketoglutarate derivatives to monitor 2-KGDH activity in vivo. 13C NMR analysis of liver extracts revealed that uniformly 13C labeled 2-ketogutarate, in its cell permeable ester form, was rapidly taken up and hydrolyzed in liver and underwent extensive metabolism to produce labeled glutamate, succinate, lactate and other metabolites. Diethyl [1,2-13C2]-2-ketoglutarate was successfully polarized by dynamic nuclear polarization and within seconds after injection into rats, the probe produced hyperpolarized [13C]bicarbonate in the liver reflecting flux through the TCA cycle. These experiments demonstrate that this tracer offers the possibility of directly monitoring flux through 2-KGDH in vivo.
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Affiliation(s)
- Jaspal Singh
- Advanced Imaging Research Center, University of Texas South-western Medical Center, Dallas, TX
| | - Eul Hyun Suh
- Advanced Imaging Research Center, University of Texas South-western Medical Center, Dallas, TX
| | - Gaurav Sharma
- Advanced Imaging Research Center, University of Texas South-western Medical Center, Dallas, TX
| | - Jun Chen
- Advanced Imaging Research Center, University of Texas South-western Medical Center, Dallas, TX
| | - Edward P Hackett
- Advanced Imaging Research Center, University of Texas South-western Medical Center, Dallas, TX
| | - Xiaodong Wen
- Advanced Imaging Research Center, University of Texas South-western Medical Center, Dallas, TX
| | - A Dean Sherry
- Advanced Imaging Research Center, University of Texas South-western Medical Center, Dallas, TX
| | - Chalermchai Khemtong
- Department of Medicine, Division of Endocrinology, Diabetes and Metabolism, University of Florida, Gainesville, FL and Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL
| | - Craig R Malloy
- Advanced Imaging Research Center, University of Texas South-western Medical Center, Dallas, TX
| | - Jae Mo Park
- Advanced Imaging Research Center, University of Texas South-western Medical Center, Dallas, TX
| | - Zoltan Kovacs
- Advanced Imaging Research Center, University of Texas South-western Medical Center, Dallas, TX
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8
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Savic D, Ball V, Holzner L, Hauton D, Timm KN, Curtis MK, Heather LC, Tyler DJ. Hyperpolarized magnetic resonance shows that the anti-ischemic drug meldonium leads to increased flux through pyruvate dehydrogenase in vivo resulting in improved post-ischemic function in the diabetic heart. NMR IN BIOMEDICINE 2021; 34:e4471. [PMID: 33458907 PMCID: PMC8609426 DOI: 10.1002/nbm.4471] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Revised: 11/20/2020] [Accepted: 12/20/2020] [Indexed: 05/07/2023]
Abstract
The diabetic heart has a decreased ability to metabolize glucose. The anti-ischemic drug meldonium may provide a route to counteract this by reducing l-carnitine levels, resulting in improved cardiac glucose utilization. Therefore, the aim of this study was to use the novel technique of hyperpolarized magnetic resonance to investigate the in vivo effects of treatment with meldonium on cardiac metabolism and function in control and diabetic rats. Thirty-six male Wistar rats were injected either with vehicle, or with streptozotocin (55 mg/kg) to induce a model of type 1 diabetes. Daily treatment with either saline or meldonium (100 mg/kg/day) was undertaken for three weeks. in vivo cardiac function and metabolism were assessed with CINE MRI and hyperpolarized magnetic resonance respectively. Isolated perfused hearts were challenged with low-flow ischemia/reperfusion to assess the impact of meldonium on post-ischemic recovery. Meldonium had no significant effect on blood glucose concentrations or on baseline cardiac function. However, hyperpolarized magnetic resonance revealed that meldonium treatment elevated pyruvate dehydrogenase flux by 3.1-fold and 1.2-fold in diabetic and control animals, respectively, suggesting an increase in cardiac glucose oxidation. Hyperpolarized magnetic resonance further demonstrated that meldonium reduced the normalized acetylcarnitine signal by 2.1-fold in both diabetic and control animals. The increase in pyruvate dehydrogenase flux in vivo was accompanied by an improvement in post-ischemic function ex vivo, as meldonium elevated the rate pressure product by 1.3-fold and 1.5-fold in the control and diabetic animals, respectively. In conclusion, meldonium improves in vivo pyruvate dehydrogenase flux in the diabetic heart, contributing to improved cardiac recovery after ischemia.
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Affiliation(s)
- Dragana Savic
- Cardiac Metabolism Research Group (CMRG), Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUK
- Oxford Centre for Clinical Magnetic Resonance Research (OCMR), Division of Cardiovascular Medicine, Radcliffe Department of MedicineUniversity of OxfordOxfordUK
| | - Vicky Ball
- Cardiac Metabolism Research Group (CMRG), Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUK
| | - Lorenz Holzner
- Department of Physiology, Development and NeuroscienceUniversity of CambridgeCambridgeUK
| | - David Hauton
- Cardiac Metabolism Research Group (CMRG), Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUK
- Metabolomics Research Group, Department of ChemistryUniversity of OxfordOxfordUK
| | - Kerstin N. Timm
- Cardiac Metabolism Research Group (CMRG), Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUK
| | - M. Kate Curtis
- Cardiac Metabolism Research Group (CMRG), Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUK
| | - Lisa C. Heather
- Cardiac Metabolism Research Group (CMRG), Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUK
| | - Damian J. Tyler
- Cardiac Metabolism Research Group (CMRG), Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUK
- Oxford Centre for Clinical Magnetic Resonance Research (OCMR), Division of Cardiovascular Medicine, Radcliffe Department of MedicineUniversity of OxfordOxfordUK
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9
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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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10
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Gropler RJ. Imaging Myocardial Metabolism. Mol Imaging 2021. [DOI: 10.1016/b978-0-12-816386-3.00083-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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11
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Abstract
One of the characteristics of the failing human heart is a significant alteration in its energy metabolism. Recently, a ketone body, β-hydroxybutyrate (β-OHB) has been implicated in the failing heart’s energy metabolism as an alternative “fuel source.” Utilization of β-OHB in the failing heart increases, and this serves as a “fuel switch” that has been demonstrated to become an adaptive response to stress during the heart failure progression in both diabetic and non-diabetic patients. In addition to serving as an alternative “fuel,” β-OHB represents a signaling molecule that acts as an endogenous histone deacetylase (HDAC) inhibitor. It can increase histone acetylation or lysine acetylation of other signaling molecules. β-OHB has been shown to decrease the production of reactive oxygen species and activate autophagy. Moreover, β-OHB works as an NLR family pyrin domain-containing protein 3 (Nlrp3) inflammasome inhibitor and reduces Nlrp3-mediated inflammatory responses. It has also been reported that β-OHB plays a role in transcriptional or post-translational regulations of various genes’ expression. Increasing β-OHB levels prior to ischemia/reperfusion injury results in a reduced infarct size in rodents, likely due to the signaling function of β-OHB in addition to its role in providing energy. Sodium-glucose co-transporter-2 (SGLT2) inhibitors have been shown to exert strong beneficial effects on the cardiovascular system. They are also capable of increasing the production of β-OHB, which may partially explain their clinical efficacy. Despite all of the beneficial effects of β-OHB, some studies have shown detrimental effects of long-term exposure to β-OHB. Furthermore, not all means of increasing β-OHB levels in the heart are equally effective in treating heart failure. The best timing and therapeutic strategies for the delivery of β-OHB to treat heart disease are unknown and yet to be determined. In this review, we focus on the crucial role of ketone bodies, particularly β-OHB, as both an energy source and a signaling molecule in the stressed heart and the overall therapeutic potential of this compound for cardiovascular diseases.
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Affiliation(s)
- Yuxin Chu
- Department of Medicine, Division of Cardiovascular Disease, University of Alabama at Birmingham, Birmingham, AL, United States.,The Key Laboratory of Cardiovascular Remodeling and Function Research, Chinese Ministry of Education, Chinese National Health Commission and Chinese Academy of Medical Sciences, the State and Shandong Province Joint Key Laboratory of Translational Cardiovascular Medicine, Qilu Hospital of Shandong University, Jinan, China
| | - Cheng Zhang
- The Key Laboratory of Cardiovascular Remodeling and Function Research, Chinese Ministry of Education, Chinese National Health Commission and Chinese Academy of Medical Sciences, the State and Shandong Province Joint Key Laboratory of Translational Cardiovascular Medicine, Qilu Hospital of Shandong University, Jinan, China
| | - Min Xie
- Department of Medicine, Division of Cardiovascular Disease, University of Alabama at Birmingham, Birmingham, AL, United States
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Greenwell AA, Gopal K, Ussher JR. Myocardial Energy Metabolism in Non-ischemic Cardiomyopathy. Front Physiol 2020; 11:570421. [PMID: 33041869 PMCID: PMC7526697 DOI: 10.3389/fphys.2020.570421] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2020] [Accepted: 08/26/2020] [Indexed: 12/12/2022] Open
Abstract
As the most metabolically demanding organ in the body, the heart must generate massive amounts of energy adenosine triphosphate (ATP) from the oxidation of fatty acids, carbohydrates and other fuels (e.g., amino acids, ketone bodies), in order to sustain constant contractile function. While the healthy mature heart acts omnivorously and is highly flexible in its ability to utilize the numerous fuel sources delivered to it through its coronary circulation, the heart’s ability to produce ATP from these fuel sources becomes perturbed in numerous cardiovascular disorders. This includes ischemic heart disease and myocardial infarction, as well as in various cardiomyopathies that often precede the development of overt heart failure. We herein will provide an overview of myocardial energy metabolism in the healthy heart, while describing the numerous perturbations that take place in various non-ischemic cardiomyopathies such as hypertrophic cardiomyopathy, diabetic cardiomyopathy, arrhythmogenic cardiomyopathy, and the cardiomyopathy associated with the rare genetic disease, Barth Syndrome. Based on preclinical evidence where optimizing myocardial energy metabolism has been shown to attenuate cardiac dysfunction, we will discuss the feasibility of myocardial energetics optimization as an approach to treat the cardiac pathology associated with these various non-ischemic cardiomyopathies.
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Affiliation(s)
- Amanda A Greenwell
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, AB, Canada.,Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada.,Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, AB, Canada
| | - Keshav Gopal
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, AB, Canada.,Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada.,Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, AB, Canada
| | - John R Ussher
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, AB, Canada.,Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada.,Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, AB, Canada
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Abstract
The term diabetic cardiomyopathy is defined as the presence of abnormalities in myocardial structure and function that occur in the absence of, or in addition to, well-established cardiovascular risk factors. A key contributor to this abnormal structural-functional relation is the complex interplay of myocardial metabolic remodeling, defined as the loss the flexibility in myocardial substrate metabolism and its downstream detrimental effects, such as mitochondrial dysfunction, inflammation, and fibrosis. In parallel with the growth in understanding of these biological underpinnings has been developmental advances in imaging tools such as positron emission tomography and magnetic resonance imaging and spectroscopy that permit the detection and in many cases quantification, of the processes that typifies the myocardial metabolic remodeling in diabetic cardiomyopathy. The imaging readouts can be obtained in both preclinical models of diabetes mellitus and patients with diabetes mellitus facilitating the bi-directional movement of information between bench and bedside. Moreover, imaging biomarkers provided by these tools are now being used to enhance discovery and development of therapies designed to reduce the myocardial effects of diabetes mellitus through metabolic modulation. In this review, the use of these imaging tools in the patient with diabetes mellitus from a mechanistic, therapeutic effect, and clinical management perspective will be discussed.
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Affiliation(s)
- Linda R Peterson
- From the Cardiovascular Division, Department of Medicine (L.R.P.), Washington University School of Medicine, St Louis, MO
| | - Robert J Gropler
- Division of Radiological Sciences, Edward Mallinckrodt Institute of Radiology (R.J.G.), Washington University School of Medicine, St Louis, MO
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14
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Effects of a Ketogenic Diet Containing Medium-Chain Triglycerides and Endurance Training on Metabolic Enzyme Adaptations in Rat Skeletal Muscle. Nutrients 2020; 12:nu12051269. [PMID: 32365746 PMCID: PMC7284751 DOI: 10.3390/nu12051269] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Revised: 04/26/2020] [Accepted: 04/27/2020] [Indexed: 01/20/2023] Open
Abstract
Long-term intake of a ketogenic diet enhances utilization of ketone bodies, a particularly energy-efficient substrate, during exercise. However, physiological adaptation to an extremely low-carbohydrate diet has been shown to upregulate pyruvate dehydrogenase kinase 4 (PDK4, a negative regulator of glycolytic flux) content in skeletal muscle, resulting in impaired high-intensity exercise capacity. This study aimed to examine the effects of a long-term ketogenic diet containing medium-chain triglycerides (MCTs) on endurance training-induced adaptations in ketolytic and glycolytic enzymes of rat skeletal muscle. Male Sprague-Dawley rats were placed on either a standard diet (CON), a long-chain triglyceride-containing ketogenic diet (LKD), or an MCT-containing ketogenic diet (MKD). Half the rats in each group performed a 2-h swimming exercise, 5 days a week, for 8 weeks. Endurance training significantly increased 3-oxoacid CoA transferase (OXCT, a ketolytic enzyme) protein content in epitrochlearis muscle tissue, and MKD intake additively enhanced endurance training–induced increases in OXCT protein content. LKD consumption substantially increased muscle PDK4 protein level. However, such PDK4 increases were not observed in the MKD-fed rats. In conclusion, long-term intake of ketogenic diets containing MCTs may additively enhance endurance training–induced increases in ketolytic capacity in skeletal muscle without exerting inhibitory effects on carbohydrate metabolism.
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Yoshihara HAI, Bastiaansen JAM, Karlsson M, Lerche MH, Comment A, Schwitter J. Detection of myocardial medium-chain fatty acid oxidation and tricarboxylic acid cycle activity with hyperpolarized [1- 13 C]octanoate. NMR IN BIOMEDICINE 2020; 33:e4243. [PMID: 31904900 DOI: 10.1002/nbm.4243] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 11/22/2019] [Accepted: 11/27/2019] [Indexed: 05/05/2023]
Abstract
Under normal conditions, the heart mainly relies on fatty acid oxidation to meet its energy needs. Changes in myocardial fuel preference are noted in the diseased and failing heart. The magnetic resonance signal enhancement provided by spin hyperpolarization allows the metabolism of substrates labeled with carbon-13 to be followed in real time in vivo. Although the low water solubility of long-chain fatty acids abrogates their hyperpolarization by dissolution dynamic nuclear polarization, medium-chain fatty acids have sufficient solubility to be efficiently polarized and dissolved. In this study, we investigated the applicability of hyperpolarized [1-13 C]octanoate to measure myocardial medium-chain fatty acid metabolism in vivo. Scanning rats infused with a bolus of hyperpolarized [1-13 C]octanoate, the primary metabolite observed in the heart was identified as [1-13 C]acetylcarnitine. Additionally, [5-13 C]glutamate and [5-13 C]citrate could be respectively resolved in seven and five of 31 experiments, demonstrating the incorporation of oxidation products of octanoate into the tricarboxylic acid cycle. A variable drop in blood pressure was observed immediately following the bolus injection, and this drop correlated with a decrease in normalized acetylcarnitine signal (acetylcarnitine/octanoate). Increasing the delay before infusion moderated the decrease in blood pressure, which was attributed to the presence of residual gas bubbles in the octanoate solution. No significant difference in normalized acetylcarnitine signal was apparent between fed and 12-hour fasted rats. Compared with a solution in buffer, the longitudinal relaxation of [1-13 C]octanoate was accelerated ~3-fold in blood and by the addition of serum albumin. These results demonstrate the potential of hyperpolarized [1-13 C]octanoate to probe myocardial medium-chain fatty acid metabolism as well as some of the limitations that may accompany its use.
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Affiliation(s)
- Hikari A I Yoshihara
- Division of Cardiology, Lausanne University Hospital (CHUV), Lausanne, Switzerland
- Institute of Physics, Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland
| | - Jessica A M Bastiaansen
- Institute of Physics, Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland
- Department of Diagnostic and Interventional Radiology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
| | - Magnus Karlsson
- Albeda Research ApS, Copenhagen, Denmark
- Department of Health Technology, Technical University of Denmark, Kgs. Lyngby, Denmark
| | - Mathilde H Lerche
- Albeda Research ApS, Copenhagen, Denmark
- Department of Health Technology, Technical University of Denmark, Kgs. Lyngby, Denmark
| | - Arnaud Comment
- Institute of Physics, Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge, UK
- General Electric Healthcare, Chalfont St Giles, UK
| | - Juerg Schwitter
- Division of Cardiology, Lausanne University Hospital (CHUV), Lausanne, Switzerland
- Cardiac MR Center, Lausanne University Hospital (CHUV), Lausanne, Switzerland
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Staňková P, Kučera O, Peterová E, Lotková H, Maseko TE, Nožičková K, Červinková Z. Adaptation of Mitochondrial Substrate Flux in a Mouse Model of Nonalcoholic Fatty Liver Disease. Int J Mol Sci 2020; 21:ijms21031101. [PMID: 32046101 PMCID: PMC7036817 DOI: 10.3390/ijms21031101] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Revised: 02/02/2020] [Accepted: 02/05/2020] [Indexed: 12/30/2022] Open
Abstract
Maladaptation of mitochondrial oxidative flux seems to be a considerable feature of nonalcoholic fatty liver disease (NAFLD). The aim of this work was to induce NAFLD in mice fed a Western-style diet (WD) and to evaluate liver mitochondrial functions. Experiments were performed on male C57BL/6J mice fed with a control diet or a WD for 24 weeks. Histological changes in liver and adipose tissue as well as hepatic expression of fibrotic and inflammatory genes and proteins were evaluated. The mitochondrial respiration was assessed by high-resolution respirometry. Oxidative stress was evaluated by measuring lipoperoxidation, glutathione, and reactive oxygen species level. Feeding mice a WD induced adipose tissue inflammation and massive liver steatosis accompanied by mild inflammation and fibrosis. We found decreased succinate-activated mitochondrial respiration and decreased succinate dehydrogenase (SDH) activity in the mice fed a WD. The oxidative flux with other substrates was not affected. We observed increased ketogenic capacity, but no impact on the capacity for fatty acid oxidation. We did not confirm the presence of oxidative stress. Mitochondria in this stage of the disease are adapted to increased substrate flux. However, inhibition of SDH can lead to the accumulation of succinate, an important signaling molecule associated with inflammation, fibrosis, and carcinogenesis.
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Affiliation(s)
- Pavla Staňková
- Department of Physiology, Faculty of Medicine in Hradec Králové, Charles University, Šimkova 870, 500 03 Hradec Králové, Czech Republic; (P.S.); (H.L.); (T.E.M.); (K.N.); (Z.Č.)
| | - Otto Kučera
- Department of Physiology, Faculty of Medicine in Hradec Králové, Charles University, Šimkova 870, 500 03 Hradec Králové, Czech Republic; (P.S.); (H.L.); (T.E.M.); (K.N.); (Z.Č.)
- Correspondence: ; Tel.: +420-495-816-186
| | - Eva Peterová
- Department of Medical Biochemistry, Faculty of Medicine in Hradec Králové, Charles University, Šimkova 870, 500 03 Hradec Králové, Czech Republic;
| | - Halka Lotková
- Department of Physiology, Faculty of Medicine in Hradec Králové, Charles University, Šimkova 870, 500 03 Hradec Králové, Czech Republic; (P.S.); (H.L.); (T.E.M.); (K.N.); (Z.Č.)
| | - Tumisang Edward Maseko
- Department of Physiology, Faculty of Medicine in Hradec Králové, Charles University, Šimkova 870, 500 03 Hradec Králové, Czech Republic; (P.S.); (H.L.); (T.E.M.); (K.N.); (Z.Č.)
| | - Kateřina Nožičková
- Department of Physiology, Faculty of Medicine in Hradec Králové, Charles University, Šimkova 870, 500 03 Hradec Králové, Czech Republic; (P.S.); (H.L.); (T.E.M.); (K.N.); (Z.Č.)
| | - Zuzana Červinková
- Department of Physiology, Faculty of Medicine in Hradec Králové, Charles University, Šimkova 870, 500 03 Hradec Králové, Czech Republic; (P.S.); (H.L.); (T.E.M.); (K.N.); (Z.Č.)
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17
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Zhao G, Liu C, Li S, Wang X, Yao Y. Exploring the flavor formation mechanism under osmotic conditions during soy sauce fermentation in Aspergillus oryzae by proteomic analysis. Food Funct 2020; 11:640-648. [PMID: 31895399 DOI: 10.1039/c9fo02314c] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2023]
Abstract
Aspergillus oryzae is a common starter in the soy sauce industry and struggles to grow under complex fermentation conditions. However, little is known about the flavor formation mechanism under osmotic conditions (low-temperature and high-salt) in A. oryzae. This work investigated the flavors and the relative protein expression patterns by gas chromatography-mass spectrometry (GC-MS) and proteomic analysis. Low-temperature and a high-salt content are unfavorable to the secretion of hydrolases and the formation of fragrant aldehydes. The aldehyde contents under osmotic conditions were reduced to 1.4-3.7 times lower than that of the control. Besides, copper amine oxidases which decreased under low-temperature stress and salt stress were shown to be important in catalyzing the oxidative deamination of several amine substrates to fragrant aldehydes. Furthermore, alcohol dehydrogenase and polyketide synthase are beneficial to the formation of alcohols and aromatic flavors under low-temperature stress and salt stress. Particularly, the ethanol content under 16 °C stress was 3.5 times higher than that under 28 °C.
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Affiliation(s)
- Guozhong Zhao
- State Key Laboratory of Food Nutrition and Safety, Key Laboratory of Food Nutrition and Safety, Ministry of Education, College of Food Science and Engineering, Tianjin University of Science & Technology, Tianjin 300457, China.
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More Than One HMG-CoA Lyase: The Classical Mitochondrial Enzyme Plus the Peroxisomal and the Cytosolic Ones. Int J Mol Sci 2019; 20:ijms20246124. [PMID: 31817290 PMCID: PMC6941031 DOI: 10.3390/ijms20246124] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Revised: 11/27/2019] [Accepted: 11/29/2019] [Indexed: 12/27/2022] Open
Abstract
There are three human enzymes with HMG-CoA lyase activity that are able to synthesize ketone bodies in different subcellular compartments. The mitochondrial HMG-CoA lyase was the first to be described, and catalyzes the cleavage of 3-hydroxy-3-methylglutaryl CoA to acetoacetate and acetyl-CoA, the common final step in ketogenesis and leucine catabolism. This protein is mainly expressed in the liver and its function is metabolic, since it produces ketone bodies as energetic fuels when glucose levels are low. Another isoform is encoded by the same gene for the mitochondrial HMG-CoA lyase (HMGCL), but it is located in peroxisomes. The last HMG-CoA lyase to be described is encoded by a different gene, HMGCLL1, and is located in the cytosolic side of the endoplasmic reticulum membrane. Some activity assays and tissue distribution of this enzyme have shown the brain and lung as key tissues for studying its function. Although the roles of the peroxisomal and cytosolic HMG-CoA lyases remain unknown, recent studies highlight the role of ketone bodies in metabolic remodeling, homeostasis, and signaling, providing new insights into the molecular and cellular function of these enzymes.
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