1
|
Abstract
Ketone bodies play significant roles in organismal energy homeostasis, serving as oxidative fuels, modulators of redox potential, lipogenic precursors, and signals, primarily during states of low carbohydrate availability. Efforts to enhance wellness and ameliorate disease via nutritional, chronobiological, and pharmacological interventions have markedly intensified interest in ketone body metabolism. The two ketone body redox partners, acetoacetate and D-β-hydroxybutyrate, serve distinct metabolic and signaling roles in biological systems. We discuss the pleiotropic roles played by both of these ketones in health and disease. While enthusiasm is warranted, prudent procession through therapeutic applications of ketogenic and ketone therapies is also advised, as a range of metabolic and signaling consequences continue to emerge. Organ-specific and cell-type-specific effects of ketone bodies are important to consider as prospective therapeutic and wellness applications increase.
Collapse
Affiliation(s)
- Patrycja Puchalska
- Department of Medicine, Division of Molecular Medicine, University of Minnesota, Minneapolis, Minnesota 55455, USA; ,
| | - Peter A Crawford
- Department of Medicine, Division of Molecular Medicine, University of Minnesota, Minneapolis, Minnesota 55455, USA; , .,Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, USA
| |
Collapse
|
2
|
Schmidt CA, Fisher-Wellman KH, Neufer PD. From OCR and ECAR to energy: Perspectives on the design and interpretation of bioenergetics studies. J Biol Chem 2021; 297:101140. [PMID: 34461088 PMCID: PMC8479256 DOI: 10.1016/j.jbc.2021.101140] [Citation(s) in RCA: 71] [Impact Index Per Article: 23.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Revised: 08/25/2021] [Accepted: 08/26/2021] [Indexed: 12/12/2022] Open
Abstract
Biological energy transduction underlies all physiological phenomena in cells. The metabolic systems that support energy transduction have been of great interest due to their association with numerous pathologies including diabetes, cancer, rare genetic diseases, and aberrant cell death. Commercially available bioenergetics technologies (e.g., extracellular flux analysis, high-resolution respirometry, fluorescent dye kits, etc.) have made practical assessment of metabolic parameters widely accessible. This has facilitated an explosion in the number of studies exploring, in particular, the biological implications of oxygen consumption rate (OCR) and substrate level phosphorylation via glycolysis (i.e., via extracellular acidification rate (ECAR)). Though these technologies have demonstrated substantial utility and broad applicability to cell biology research, they are also susceptible to historical assumptions, experimental limitations, and other caveats that have led to premature and/or erroneous interpretations. This review enumerates various important considerations for designing and interpreting cellular and mitochondrial bioenergetics experiments, some common challenges and pitfalls in data interpretation, and some potential "next steps" to be taken that can address these highlighted challenges.
Collapse
Affiliation(s)
- Cameron A Schmidt
- East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, North Carolina, USA; Departments of Physiology, Brody School of Medicine, East Carolina University, Greenville, North Carolina, USA
| | - Kelsey H Fisher-Wellman
- East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, North Carolina, USA; Departments of Physiology, Brody School of Medicine, East Carolina University, Greenville, North Carolina, USA.
| | - P Darrell Neufer
- East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, North Carolina, USA; Departments of Physiology, Brody School of Medicine, East Carolina University, Greenville, North Carolina, USA; Departments of Biochemistry and Molecular Biology, Brody School of Medicine, East Carolina University, Greenville, North Carolina, USA.
| |
Collapse
|
3
|
Hansen C, Olsen K, Pilegaard H, Bangsbo J, Gliemann L, Hellsten Y. High metabolic substrate load induces mitochondrial dysfunction in rat skeletal muscle microvascular endothelial cells. Physiol Rep 2021; 9:e14855. [PMID: 34288561 PMCID: PMC8290479 DOI: 10.14814/phy2.14855] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Revised: 03/01/2021] [Accepted: 03/03/2021] [Indexed: 12/21/2022] Open
Abstract
The influence of glucose and palmitic acid (PA) on mitochondrial respiration and emission of hydrogen peroxide (H2 O2 ) was determined in skeletal muscle-derived microvascular endothelial cells. Measurements were assessed in intact and permeabilized (cells treated with 0.025% saponin) low passage endothelial cells with acute-or prolonged (3 days) incubation with regular (1.7 mM) or elevated (2.2 mM) PA concentrations and regular (5 mM) or elevated (11 mM) glucose concentrations. In intact cells, acute incubation with 1.7 mM PA alone or with 1.7 mM PA + 5 mM glucose (p < .001) led to a lower mitochondrial respiration (p < 0.01) and markedly higher H2 O2 /O2 emission (p < 0.05) than with 5 mM glucose alone. Prolonged incubation of intact cells with 1.7 mM PA +5 mM glucose led to 34% (p < 0.05) lower respiration and 2.5-fold higher H2 O2 /O2 emission (p < 0.01) than incubation with 5 mM glucose alone. Prolonged incubation of intact cells with elevated glucose led to 60% lower (p < 0.05) mitochondrial respiration and 4.6-fold higher H2 O2 /O2 production than incubation with 5 mM glucose in intact cells (p < 0.001). All effects observed in intact cells were present also in permeabilized cells (State 2). In conclusion, our results show that acute and prolonged lipid availability, as well as prolonged hyperglycemia, induces mitochondrial dysfunction as evidenced by lower mitochondrial respiration and enhanced H2 O2/ O2 emission. Elevated plasma substrate availability may lead to microvascular dysfunction in skeletal muscle by impairing endothelial mitochondrial function.
Collapse
Affiliation(s)
- Camilla Hansen
- Department of Nutrition, Exercise and SportsCardiovascular Physiology GroupSection of Integrative PhysiologyUniversity of CopenhagenCopenhagenDenmark
| | - Karina Olsen
- Department of Nutrition, Exercise and SportsCardiovascular Physiology GroupSection of Integrative PhysiologyUniversity of CopenhagenCopenhagenDenmark
| | - Henriette Pilegaard
- Department of BiologySection of Cell Biology and PhysiologyUniversity of CopenhagenCopenhagenDenmark
| | - Jens Bangsbo
- Department of Nutrition, Exercise and SportsSection of Integrative PhysiologyUniversity of CopenhagenCopenhagenDenmark
| | - Lasse Gliemann
- Department of Nutrition, Exercise and SportsCardiovascular Physiology GroupSection of Integrative PhysiologyUniversity of CopenhagenCopenhagenDenmark
| | - Ylva Hellsten
- Department of Nutrition, Exercise and SportsCardiovascular Physiology GroupSection of Integrative PhysiologyUniversity of CopenhagenCopenhagenDenmark
| |
Collapse
|
4
|
Smith CD, Lin CT, McMillin SL, Weyrauch LA, Schmidt CA, Smith CA, Kurland IJ, Witczak CA, Neufer PD. Genetically increasing flux through β-oxidation in skeletal muscle increases mitochondrial reductive stress and glucose intolerance. Am J Physiol Endocrinol Metab 2021; 320:E938-E950. [PMID: 33813880 PMCID: PMC8238127 DOI: 10.1152/ajpendo.00010.2021] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Elevated mitochondrial hydrogen peroxide (H2O2) emission and an oxidative shift in cytosolic redox environment have been linked to high-fat-diet-induced insulin resistance in skeletal muscle. To test specifically whether increased flux through mitochondrial fatty acid oxidation, in the absence of elevated energy demand, directly alters mitochondrial function and redox state in muscle, two genetic models characterized by increased muscle β-oxidation flux were studied. In mice overexpressing peroxisome proliferator-activated receptor-α in muscle (MCK-PPARα), lipid-supported mitochondrial respiration, membrane potential (ΔΨm), and H2O2 production rate (JH2O2) were increased, which coincided with a more oxidized cytosolic redox environment, reduced muscle glucose uptake, and whole body glucose intolerance despite an increased rate of energy expenditure. Similar results were observed in lipin-1-deficient, fatty-liver dystrophic mice, another model characterized by increased β-oxidation flux and glucose intolerance. Crossing MCAT (mitochondria-targeted catalase) with MCK-PPARα mice normalized JH2O2 production, redox environment, and glucose tolerance, but surprisingly, both basal and absolute insulin-stimulated rates of glucose uptake in muscle remained depressed. Also surprising, when placed on a high-fat diet, MCK-PPARα mice were characterized by much lower whole body, fat, and lean mass as well as improved glucose tolerance relative to wild-type mice, providing additional evidence that overexpression of PPARα in muscle imposes more extensive metabolic stress than experienced by wild-type mice on a high-fat diet. Overall, the findings suggest that driving an increase in skeletal muscle fatty acid oxidation in the absence of metabolic demand imposes mitochondrial reductive stress and elicits multiple counterbalance metabolic responses in an attempt to restore bioenergetic homeostasis.NEW & NOTEWORTHY Prior work has suggested that mitochondrial dysfunction is an underlying cause of insulin resistance in muscle because it limits fatty acid oxidation and therefore leads to the accumulation of cytotoxic lipid intermediates. The implication has been that therapeutic strategies to accelerate β-oxidation will be protective. The current study provides evidence that genetically increasing flux through β-oxidation in muscle imposes reductive stress that is not beneficial but rather detrimental to metabolic regulation.
Collapse
Affiliation(s)
- Cody D Smith
- East Carolina Diabetes and Obesity Institute, Brody School of Medicine, East Carolina University, Greenville, North Carolina
- Department of Physiology, Brody School of Medicine, East Carolina University, Greenville, North Carolina
| | - Chien-Te Lin
- East Carolina Diabetes and Obesity Institute, Brody School of Medicine, East Carolina University, Greenville, North Carolina
- Department of Physiology, Brody School of Medicine, East Carolina University, Greenville, North Carolina
| | - Shawna L McMillin
- East Carolina Diabetes and Obesity Institute, Brody School of Medicine, East Carolina University, Greenville, North Carolina
- Department of Biochemistry & Molecular Biology, Brody School of Medicine, East Carolina University, Greenville, North Carolina
| | - Luke A Weyrauch
- East Carolina Diabetes and Obesity Institute, Brody School of Medicine, East Carolina University, Greenville, North Carolina
- Department of Biochemistry & Molecular Biology, Brody School of Medicine, East Carolina University, Greenville, North Carolina
| | - Cameron A Schmidt
- East Carolina Diabetes and Obesity Institute, Brody School of Medicine, East Carolina University, Greenville, North Carolina
- Department of Physiology, Brody School of Medicine, East Carolina University, Greenville, North Carolina
| | - Cheryl A Smith
- East Carolina Diabetes and Obesity Institute, Brody School of Medicine, East Carolina University, Greenville, North Carolina
- Department of Physiology, Brody School of Medicine, East Carolina University, Greenville, North Carolina
| | - Irwin J Kurland
- Department of Medicine, Albert Einstein College of Medicine, Bronx, New York
| | - Carol A Witczak
- East Carolina Diabetes and Obesity Institute, Brody School of Medicine, East Carolina University, Greenville, North Carolina
- Department of Physiology, Brody School of Medicine, East Carolina University, Greenville, North Carolina
- Department of Biochemistry & Molecular Biology, Brody School of Medicine, East Carolina University, Greenville, North Carolina
- Department of Kinesiology, East Carolina University, Greenville, North Carolina
| | - P Darrell Neufer
- East Carolina Diabetes and Obesity Institute, Brody School of Medicine, East Carolina University, Greenville, North Carolina
- Department of Physiology, Brody School of Medicine, East Carolina University, Greenville, North Carolina
- Department of Biochemistry & Molecular Biology, Brody School of Medicine, East Carolina University, Greenville, North Carolina
- Department of Kinesiology, East Carolina University, Greenville, North Carolina
| |
Collapse
|