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Frisch C, Woyke S, Mair N, Haller T, Ronzani M, Marcher K, Schantl D, Rugg C, Schlager A. The impact of cannabinoids on methemoglobin formation and hemoglobin oxygen affinity: An ex-vivo study. Toxicology 2024; 505:153832. [PMID: 38759720 DOI: 10.1016/j.tox.2024.153832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2024] [Revised: 05/13/2024] [Accepted: 05/14/2024] [Indexed: 05/19/2024]
Abstract
The affinity of hemoglobin (Hb) to oxygen (O2) influences processes of oxygen delivery and extraction at the tissue level. Despite cannabinoids being utilized or ingested in various ways, their possible impact on Hb-O2 affinity has barely been studied. This is an experimental ex-vivo trial. Venous blood samples were drawn from 5 male and 6 female healthy volunteers and subsequently exposed to different cannabinoid types: (delta-9-tetrahydrocannabinol [Δ9-THC], delta-8-tetrahydrocannabinol [Δ8-THC], cannabidiol [CBD]) at different concentrations. Oxygen dissociation curves (ODC) were measured and blood gas analyses were performed for methemoglobin (MetHb) determination. The results revealed no MetHb formation. Besides two statistically significant changes (+1.4 mmHg and -0.9 mmHg) in the female cohort, following Δ9-THC and Δ8-THC exposure, no further P50 changes could be observed. The study demonstrated an in-vitro effect of selected cannabinoids and dosages on P50 values in female participants, with variations not observed at other dosages, leaving the underlying mechanisms open for debate. MetHb formation, as potential mechanism, was not detected in this study. The precise reasons why changes only occurred at specific dosages remain unclear, indicating a need for further in-vivo research to understand the interaction between cannabinoids and Hb-O2 affinity completely.
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Affiliation(s)
- Christoph Frisch
- Department of Anesthesiology and Intensive Care Medicine, Medical University of Innsbruck, Austria
| | - Simon Woyke
- Department of Anesthesiology and Intensive Care Medicine, Medical University of Innsbruck, Austria.
| | - Norbert Mair
- Department of Physiology and Medical Physics, Institute of Physiology, Medical University of Innsbruck, Austria
| | - Thomas Haller
- Department of Physiology and Medical Physics, Institute of Physiology, Medical University of Innsbruck, Austria
| | - Marco Ronzani
- Department of Anesthesiology and Intensive Care Medicine, Medical University of Innsbruck, Austria
| | - Katharina Marcher
- Department of Anesthesiology and Intensive Care Medicine, Medical University of Innsbruck, Austria
| | | | - Christopher Rugg
- Department of Anesthesiology and Intensive Care Medicine, Medical University of Innsbruck, Austria
| | - Andreas Schlager
- Department of Anesthesiology and Intensive Care Medicine, Medical University of Innsbruck, Austria
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Sekyonda Z, An R, Goreke U, Man Y, Monchamp K, Bode A, Zhang Q, El-Gammal Y, Kityo C, Kalfa TA, Akkus O, Gurkan UA. Rapid measurement of hemoglobin-oxygen dissociation by leveraging Bohr effect and Soret band bathochromic shift. Analyst 2024; 149:2561-2572. [PMID: 38501195 PMCID: PMC11056771 DOI: 10.1039/d3an02071a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Accepted: 02/24/2024] [Indexed: 03/20/2024]
Abstract
Oxygen (O2) binds to hemoglobin (Hb) in the lungs and is then released (dissociated) in the tissues. The Bohr effect is a physiological mechanism that governs the affinity of Hb for O2 based on pH, where a lower pH results in a lower Hb-O2 affinity and higher Hb-O2 dissociation. Hb-O2 affinity and dissociation are crucial for maintaining aerobic metabolism in cells and tissues. Despite its vital role in human physiology, Hb-O2 dissociation measurement is underutilized in basic research and in clinical laboratories, primarily due to the technical complexity and limited throughput of existing methods. We present a rapid Hb-O2 dissociation measurement approach by leveraging the Bohr effect and detecting the optical shift in the Soret band that corresponds to the light absorption by the heme group in Hb. This new method reduces Hb-O2 dissociation measurement time from hours to minutes. We show that Hb deoxygenation can be accelerated chemically at the optimal pH of 6.9. We show that time and pH-controlled deoxygenation of Hb results in rapid and distinct conformational changes in its tertiary structure. These molecular conformational changes are manifested as significant, detectable shifts in Hb's optical absorption spectrum, particularly in the characteristic Soret band (414 nm). We extensively validated the method by testing human blood samples containing normal Hb and Hb variants. We show that rapid Hb-O2 dissociation can be used to screen for and detect Hb-O2 affinity disorders and to evaluate the function and efficacy of Hb-modifying therapies. The ubiquity of optical absorption spectrophotometers positions this approach as an accessible, rapid, and accurate Hb-O2 dissociation measurement method for basic research and clinical use. We anticipate this method's broad adoption will democratize the diagnosis and prognosis of Hb disorders, such as sickle cell disease. Further, this method has the potential to transform the research and development of new targeted and genome-editing-based therapies that aim to modify or improve Hb-O2 affinity.
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Affiliation(s)
- Zoe Sekyonda
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA
| | - Ran An
- Department of Mechanical and Aerospace Engineering, Case Western Reserve University, 10900 Euclid Ave., Glennan Building 616B, Cleveland, OH, 44106, USA.
| | - Utku Goreke
- Department of Mechanical and Aerospace Engineering, Case Western Reserve University, 10900 Euclid Ave., Glennan Building 616B, Cleveland, OH, 44106, USA.
| | - Yuncheng Man
- Department of Mechanical and Aerospace Engineering, Case Western Reserve University, 10900 Euclid Ave., Glennan Building 616B, Cleveland, OH, 44106, USA.
| | - Karamoja Monchamp
- Department of Mechanical and Aerospace Engineering, Case Western Reserve University, 10900 Euclid Ave., Glennan Building 616B, Cleveland, OH, 44106, USA.
- Division of Hematology and Oncology, University Hospitals Cleveland Medical Center, Cleveland, OH, USA
| | - Allison Bode
- Department of Mechanical and Aerospace Engineering, Case Western Reserve University, 10900 Euclid Ave., Glennan Building 616B, Cleveland, OH, 44106, USA.
- Division of Hematology and Oncology, University Hospitals Cleveland Medical Center, Cleveland, OH, USA
| | - Qiaochu Zhang
- Department of Mechanical and Aerospace Engineering, Case Western Reserve University, 10900 Euclid Ave., Glennan Building 616B, Cleveland, OH, 44106, USA.
| | - Yasmin El-Gammal
- Division of Hematology, Cancer and Blood Diseases Institute, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Cissy Kityo
- The Joint Clinical Research Center, Kampala, Uganda
| | - Theodosia A Kalfa
- Division of Hematology, Cancer and Blood Diseases Institute, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
- Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Ozan Akkus
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA
- Department of Mechanical and Aerospace Engineering, Case Western Reserve University, 10900 Euclid Ave., Glennan Building 616B, Cleveland, OH, 44106, USA.
- Department of Orthopedics, Case Western Reserve University, Cleveland, OH, USA
| | - Umut A Gurkan
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA
- Department of Mechanical and Aerospace Engineering, Case Western Reserve University, 10900 Euclid Ave., Glennan Building 616B, Cleveland, OH, 44106, USA.
- Department of Orthopedics, Case Western Reserve University, Cleveland, OH, USA
- Case Comprehensive Cancer Center, Case Western Reserve University, Cleveland, OH, USA
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Böning D, Kuebler WM, Vogel D, Bloch W. The oxygen dissociation curve of blood in COVID-19-An update. Front Med (Lausanne) 2023; 10:1098547. [PMID: 36923010 PMCID: PMC10008909 DOI: 10.3389/fmed.2023.1098547] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Accepted: 02/03/2023] [Indexed: 03/02/2023] Open
Abstract
An impressive effect of the infection with SARS-Co-19 is the impairment of oxygen uptake due to lung injury. The reduced oxygen diffusion may potentially be counteracted by an increase in oxygen affinity of hemoglobin. However, hypoxia and anemia associated with COVID-19 usually decrease oxygen affinity due to a rise in [2,3-bisphosphoglycerate]. As such, COVID-19 related changes in the oxygen dissociation curve may be critical for oxygen uptake and supply, but are hard to predict. A Pubmed search lists 14 publications on oxygen affinity in COVID-19. While some investigations show no changes, three large studies found an increased affinity that was related to a good prognosis. Exact causes remain unknown. The cause of the associated anemia in COVID-19 is under discussion. Erythrocytes with structural alterations of membrane and cytoskeleton have been observed, and virus binding to Band 3 and also to ACE2 receptors in erythroblasts has been proposed. COVID-19 presentation is moderate in many subjects suffering from sickle cell disease. A possible explanation is that COVID-19 counteracts the unfavorable large right shift of the oxygen dissociation curve in these patients. Under discussion for therapy are mainly affinity-increasing drugs.
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Affiliation(s)
- Dieter Böning
- Institute of Physiology, Charité Medical University of Berlin, Berlin, Germany
| | - Wolfgang M. Kuebler
- Institute of Physiology, Charité Medical University of Berlin, Berlin, Germany
| | - Dominik Vogel
- Klinik für Interdisziplinäre Intensivmedizin, Vivantes Humboldt-Klinikum, Berlin, Germany
| | - Wilhelm Bloch
- Department of Molecular and Cellular Sport Medicine, Institute of Cardiovascular Research and Sport Medicine, German Sport University Cologne, Cologne, Germany
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Ronzani M, Woyke S, Mair N, Gatterer H, Oberacher H, Plunser D, Haller T, Ströhle M, Rugg C. The effect of desflurane, isoflurane and sevoflurane on the hemoglobin oxygen dissociation curve in human blood samples. Sci Rep 2022; 12:13633. [PMID: 35948604 PMCID: PMC9365211 DOI: 10.1038/s41598-022-17789-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Accepted: 07/31/2022] [Indexed: 11/09/2022] Open
Abstract
Desflurane, isoflurane and sevoflurane, three halogenated ethers, are commonly used inhaled anesthetics, both in the operating room and in the intensive care unit (ICU). The potency and dosage of these drugs is expressed by the MAC value (minimum alveolar concentration). Their interaction with hemoglobin and its affinity for oxygen, best described by the oxygen dissociation curve (ODC), has already been investigated, with conflicting results. Altered by many factors, the ODC can be shifted to the left or to the right, therefore increasing or decreasing hemoglobin oxygen (Hb-O2) affinity. In venous blood samples of 22 healthy participants (11 female, 11 male) ODC were measured with a high-throughput method in vitro. Blood samples were either exposed to control or to three different concentrations of desflurane, isoflurane or sevoflurane prior to and during measurements (low, medium and high corresponding to MAC 0.5, MAC 1.0 and MAC 2.0). With increasing concentrations from control to medium, desflurane and isoflurane significantly decreased Hb-O2 affinity by shifting the ODC to the right (p = 0.016 and p < 0.001) but sevoflurane showed no effects. When further increasing concentrations from medium to high, all three inhaled anesthetics shifted the ODC back to the left (p < 0.001). Comparing only controls to high concentrations, a significant increase in Hb-O2 affinity for desflurane (p = 0.005) and sevoflurane (p < 0.001) was detected. Our study shows a varying effect at different doses of inhaled anesthetics on Hb-O2 affinity. While the underlying mechanisms remain unclear, these results show an effect which needs to be further investigated to determine if patients undergoing anesthesia may potentially benefit or get disadvantage from this slightly increased (e.g. impaired pulmonary oxygen uptake), or decreased Hb-O2 affinity (e.g. arterial vascular disease). Trial registration: This study is registered with clinicaltrials.gov (NCT04612270).
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Affiliation(s)
- Marco Ronzani
- Department of Anesthesiology and Critical Care Medicine, Medical University of Innsbruck, Anichstraße 35, 6020, Innsbruck, Austria
| | - Simon Woyke
- Department of Anesthesiology and Critical Care Medicine, Medical University of Innsbruck, Anichstraße 35, 6020, Innsbruck, Austria.
| | - Norbert Mair
- Institute of Physiology, Medical University of Innsbruck, Innsbruck, Austria
| | - Hannes Gatterer
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Herbert Oberacher
- Institute of Legal Medicine and Core Facility Metabolomics, Medical University of Innsbruck, Innsbruck, Austria
| | - David Plunser
- Institute of Legal Medicine and Core Facility Metabolomics, Medical University of Innsbruck, Innsbruck, Austria
| | - Thomas Haller
- Institute of Physiology, Medical University of Innsbruck, Innsbruck, Austria
| | - Mathias Ströhle
- Department of Anesthesiology and Critical Care Medicine, Medical University of Innsbruck, Anichstraße 35, 6020, Innsbruck, Austria
| | - Christopher Rugg
- Department of Anesthesiology and Critical Care Medicine, Medical University of Innsbruck, Anichstraße 35, 6020, Innsbruck, Austria
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Woyke S, Mair N, Haller T, Ronzani M, Plunser D, Oberacher H, Gatterer H, Rugg C, Ströhle M. The impact of nebulized epoprostenol and iloprost on hemoglobin oxygen affinity: an ex vivo experiment. Am J Physiol Lung Cell Mol Physiol 2022; 322:L898-L903. [PMID: 35503651 PMCID: PMC9169818 DOI: 10.1152/ajplung.00084.2022] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Revised: 04/25/2022] [Accepted: 04/25/2022] [Indexed: 11/22/2022] Open
Abstract
Inhalational prostacyclins act as strong vasodilators, potentially improving oxygenation by reducing shunt fraction and ventilation-perfusion mismatch. As prostacyclin receptors are known to be present on human erythrocytes, possible direct effects on hemoglobin oxygen transport were further explored by examining the sole in vitro influence of prostacyclins on hemoglobin oxygen (Hb-O2) affinity. Venous blood samples from 20 healthy volunteers were exposed in vitro to supramaximal doses of epoprostenol, iloprost, and compared with control. By high-throughput measurements, hemoglobin oxygen dissociation curves (ODCs) were derived. Hb-O2 affinity, expressed by P50 and Hill coefficient, was determined and analyzed for three subgroups: males (n = 10), females not taking oral contraceptives (n = 4), and females taking oral contraceptives (n = 6). Epoprostenol significantly decreased P50 in all (males, females without contraceptives, and females taking oral contraceptives) [27.5 (26.4-28.6) mmHg (control) vs. 24.2 (22.7-25.3) mmHg; P < 0.001. median (interquartile range, IQR)] thereby increasing Hb-O2 affinity. Inversely, iloprost only showed significant effects in females taking oral contraceptives where P50 was markedly increased and therefore Hb-O2 affinity decreased [28.4 (27.9-28.9) mmHg (control) vs. 34.4 (32.2-36.0) mmHg; P < 0.001]. Prostacyclin-receptor stimulation and subsequent cAMP-mediated ATP release from erythrocytes are discussed as a possible underlying mechanism for the effect of epoprostenol on Hb-O2 affinity. The reason for the sex hormone-modified iloprost effect remains unclear. Being aware of potentially differing effects on Hb-O2 affinity might help select the right prostacyclin (epoprostenol vs. iloprost) depending on the patient and the underlying disease (e.g., acute respiratory distress syndrome vs. peripheral arterial disease).
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Affiliation(s)
- Simon Woyke
- Department of Anaesthesiology and Critical Care Medicine, Medical University of Innsbruck, Innsbruck, Austria
| | - Norbert Mair
- Institute of Physiology and Medical Physics, Medical University of Innsbruck, Innsbruck, Austria
| | - Thomas Haller
- Institute of Physiology and Medical Physics, Medical University of Innsbruck, Innsbruck, Austria
| | - Marco Ronzani
- Department of Anaesthesiology and Critical Care Medicine, Medical University of Innsbruck, Innsbruck, Austria
| | - David Plunser
- Institute of Legal Medicine and Core Facility Metabolomics, Medical University of Innsbruck, Innsbruck, Austria
| | - Herbert Oberacher
- Institute of Legal Medicine and Core Facility Metabolomics, Medical University of Innsbruck, Innsbruck, Austria
| | - Hannes Gatterer
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Christopher Rugg
- Department of Anaesthesiology and Critical Care Medicine, Medical University of Innsbruck, Innsbruck, Austria
| | - Mathias Ströhle
- Department of Anaesthesiology and Critical Care Medicine, Medical University of Innsbruck, Innsbruck, Austria
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Er Z, Gong P, Zhou J, Wang Y, Jiang X, Xie L. Dissolved oxygen sensor based on the fluorescence quenching method with optimal modulation frequency. APPLIED OPTICS 2022; 61:4865-4873. [PMID: 36255971 DOI: 10.1364/ao.457805] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Accepted: 05/11/2022] [Indexed: 06/16/2023]
Abstract
Measurement of dissolved oxygen (DO) in liquid samples is of vital importance in both industrial and biomedical fields. In this paper, a DO sensor based on the fluorescence quenching method has been built. The measurement principle is based on fluorescence lifetime detection, which is indicated by the phase difference between an excitation light signal and a fluorescence signal. The nonlinear effect of the fluorescent material has been taken into consideration to obtain a more accurate fitting model. The performance of the system varying with the modulation frequency of excitation light signals is also reported. Modulation frequency mainly affects the sensitivity and phase resolution ratio of the system. The system at the optimized modulation frequency has a good degree of fitting with R2 value of 0.9981 and a small relative error of 0.79%. The study shows that this kind of sensor with optimal modulation frequency has good performance, which can be used in many important fields.
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Woyke S, Brugger H, Ströhle M, Haller T, Gatterer H, Dal Cappello T, Strapazzon G. Effects of Carbon Dioxide and Temperature on the Oxygen-Hemoglobin Dissociation Curve of Human Blood: Implications for Avalanche Victims. Front Med (Lausanne) 2022; 8:808025. [PMID: 35198571 PMCID: PMC8859098 DOI: 10.3389/fmed.2021.808025] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Accepted: 12/20/2021] [Indexed: 11/13/2022] Open
Abstract
Completely avalanche-buried patients are frequently exposed to a combination of hypoxia and hypercapnia with a risk of normothermic cardiac arrest. Patients with a long burial time and an air pocket are exposed to a combination of hypoxia, hypercapnia, and hypothermia which may lead to the development of the “triple H syndrome”. This specific combination has several pathophysiological implications, particularly on the cardiovascular system and oxygen transport (oxygen supply and oxygen consumption). To examine the effects on hemoglobin oxygen affinity, we investigated venous blood samples from 15 female and 15 male healthy subjects. In a factorial design of four different carbon dioxide partial pressure (PCO2) levels (20, 40, 60, and 80 mmHg) and five different temperature levels (13.7°C, 23°C, 30°C, 37°C, and 42°C), 30 unbuffered whole blood samples were analyzed in a newly developed in vitro method for high-throughput oxygen dissociation curve (ODC) measurements. P50s, Hill coefficients, CO2-Bohr coefficients, and temperature coefficients were analyzed using a linear mixed model (LMM). Mean P50 at baseline (37°C, 40 mmHg PCO2) was 27.1 ± 2.6 mmHg. Both CO2-Bohr (p < 0.001) and temperature coefficients (p < 0.001) had a significant effect on P50. The absolute CO2 effect was still pronounced at normothermic and febrile temperatures, whereas at low temperatures, the relative CO2 effect (expressed by CO2-Bohr coefficient; p < 0.001, interaction) was increased. The larger impact of PCO2 on oxygen affinity at low temperature may be caused by the competition of 2,3-BPG with PCO2 and the exothermic binding characteristic of 2,3-BPG. In a model of an avalanche burial, based on published data of CO2 levels and cooling rates, we calculated the resulting P50 for this specific condition based on the here-reported PCO2 and temperature effect on ODC. Depending on the degree of hypercapnia and hypothermia, a potentially beneficial increase in hemoglobin oxygen affinity in the hypoxic condition might ensue.
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Affiliation(s)
- Simon Woyke
- Department of Anaesthesiology and Critical Care Medicine, Medical University of Innsbruck, Innsbruck, Austria
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Hermann Brugger
- Department of Anaesthesiology and Critical Care Medicine, Medical University of Innsbruck, Innsbruck, Austria
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Mathias Ströhle
- Department of Anaesthesiology and Critical Care Medicine, Medical University of Innsbruck, Innsbruck, Austria
- *Correspondence: Mathias Ströhle
| | - Thomas Haller
- Institute of Physiology, Medical University of Innsbruck, Innsbruck, Austria
| | - Hannes Gatterer
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Tomas Dal Cappello
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Giacomo Strapazzon
- Department of Anaesthesiology and Critical Care Medicine, Medical University of Innsbruck, Innsbruck, Austria
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
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Dose- and Sex-Dependent Changes in Hemoglobin Oxygen Affinity by the Micronutrient 5-Hydroxymethylfurfural and α-Ketoglutaric Acid. Nutrients 2021; 13:nu13103448. [PMID: 34684449 PMCID: PMC8537252 DOI: 10.3390/nu13103448] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Revised: 09/23/2021] [Accepted: 09/25/2021] [Indexed: 11/18/2022] Open
Abstract
5-Hydroxymethylfurfural (5-HMF) is known to increase hemoglobin oxygen affinity (Hb–O2 affinity) and to induce a left shift of the oxygen dissociation curve (ODC). It is under investigation as a therapeutic agent in sickle cell anemia and in conditions where pulmonary oxygen uptake is deteriorated or limited (e.g., various clinical conditions or altitude exposure). The combination of 5-HMF and α-ketoglutaric acid (αKG) is commercially available as a nutritional supplement. To further elucidate dose effects, ODCs were measured in vitro in venous whole blood samples of 20 healthy volunteers (10 female and 10 male) after the addition of three different doses of 5-HMF, αKG and the combination of both. Linear regression analysis revealed a strong dose-dependent increase in Hb–O2 affinity for 5-HMF (R2 = 0.887; p < 0.001) and the commercially available combination with αKG (R2 = 0.882; p < 0.001). αKG alone increased Hb–O2 affinity as well but to a lower extent. Both the combination (5-HMF + αKG) and 5-HMF alone exerted different P50 and Hill coefficient responses overall and between sexes, with more pronounced effects in females. With increasing Hb–O2 affinity, the sigmoidal shape of the ODC was better preserved by the combination of 5-HMF and αKG than by 5-HMF alone. Concerning the therapeutic effects of 5-HMF, this study emphasizes the importance of adequate dosing in various physiological and clinical conditions, where a left-shifted ODC might be beneficial. By preserving the sigmoidal shape of the ODC, the combination of 5-HMF and αKG at low (both sexes) and medium (males only) doses might be able to better maintain efficient oxygen transport, particularly by mitigating potentially deteriorated oxygen unloading in the tissue. However, expanding knowledge on the interaction between 5-HMF and Hb–O2 affinity in vitro necessitates further investigations in vivo to additionally assess pharmacokinetic mechanisms.
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