1
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Caldwell HG, Hoiland RL, Bain AR, Howe CA, Carr JMJR, Gibbons TD, Durrer CG, Tymko MM, Stacey BS, Bailey DM, Sekhon MS, MacLeod DB, Ainslie PN. Evidence for direct CO 2-mediated alterations in cerebral oxidative metabolism in humans. Acta Physiol (Oxf) 2024:e14197. [PMID: 38958262 DOI: 10.1111/apha.14197] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Revised: 06/18/2024] [Accepted: 06/20/2024] [Indexed: 07/04/2024]
Abstract
AIM How the cerebral metabolic rates of oxygen and glucose utilization (CMRO2 and CMRGlc, respectively) are affected by alterations in arterial PCO2 (PaCO2) is equivocal and therefore was the primary question of this study. METHODS This retrospective analysis involved pooled data from four separate studies, involving 41 healthy adults (35 males/6 females). Participants completed stepwise steady-state alterations in PaCO2 ranging between 30 and 60 mmHg. The CMRO2 and CMRGlc were assessed via the Fick approach (CBF × arterial-internal jugular venous difference of oxygen or glucose content, respectively) utilizing duplex ultrasound of the internal carotid artery and vertebral artery to calculate cerebral blood flow (CBF). RESULTS The CMRO2 was altered by 0.5 mL × min-1 (95% CI: -0.6 to -0.3) per mmHg change in PaCO2 (p < 0.001) which corresponded to a 9.8% (95% CI: -13.2 to -6.5) change in CMRO2 with a 9 mmHg change in PaCO2 (inclusive of hypo- and hypercapnia). The CMRGlc was reduced by 7.7% (95% CI: -15.4 to -0.08, p = 0.045; i.e., reduction in net glucose uptake) and the oxidative glucose index (ratio of oxygen to glucose uptake) was reduced by 5.6% (95% CI: -11.2 to 0.06, p = 0.049) with a + 9 mmHg increase in PaCO2. CONCLUSION Collectively, the CMRO2 is altered by approximately 1% per mmHg change in PaCO2. Further, glucose is incompletely oxidized during hypercapnia, indicating reductions in CMRO2 are either met by compensatory increases in nonoxidative glucose metabolism or explained by a reduction in total energy production.
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Affiliation(s)
- Hannah G Caldwell
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Ryan L Hoiland
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
- Department of Anesthesiology, Pharmacology and Therapeutics, Vancouver General Hospital, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada
- International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, British Columbia, Canada
- Collaborative Entity for REsearching Brain Ischemia (CEREBRI), University of British Columbia, Vancouver, British Columbia, Canada
| | - Anthony R Bain
- Department of Kinesiology, Faculty of Human Kinetics, University of Windsor, Windsor, Ontario, Canada
| | - Connor A Howe
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Jay M J R Carr
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Travis D Gibbons
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Cody G Durrer
- Centre for Physical Activity Research, Rigshospitalet, Copenhagen, Denmark
| | - Michael M Tymko
- Division of Critical Care Medicine, Department of Medicine, Faculty of Medicine, Vancouver General Hospital, University of British Columbia, Vancouver, British Columbia, Canada
- Human Cerebrovascular Physiology Laboratory, Department of Human Health and Nutritional Sciences, College of Biological Science, University of Guelph, Guelph, Ontario, Canada
| | - Benjamin S Stacey
- Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales, Pontypridd, UK
| | - Damian M Bailey
- Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales, Pontypridd, UK
| | - Mypinder S Sekhon
- International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, British Columbia, Canada
- Collaborative Entity for REsearching Brain Ischemia (CEREBRI), University of British Columbia, Vancouver, British Columbia, Canada
- Division of Critical Care Medicine, Department of Medicine, Faculty of Medicine, Vancouver General Hospital, University of British Columbia, Vancouver, British Columbia, Canada
- Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, British Columbia, Canada
| | - David B MacLeod
- Human Pharmacology and Physiology Lab, Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina, USA
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
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2
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Gunawan F, Matson BC, Coppoli A, Jiang L, Ding Y, Perry R, Sanchez-Rangel E, DeAguiar RB, Behar KL, Rothman DL, Mason GF, Hwang JJ. Deficits in brain glucose transport among younger adults with obesity. Obesity (Silver Spring) 2024; 32:1329-1338. [PMID: 38764181 DOI: 10.1002/oby.24034] [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: 12/15/2023] [Revised: 03/05/2024] [Accepted: 03/13/2024] [Indexed: 05/21/2024]
Abstract
OBJECTIVE Obesity is associated with alterations in eating behavior and neurocognitive function. In this study, we investigate the effect of obesity on brain energy utilization, including brain glucose transport and metabolism. METHODS A total of 11 lean participants and 7 young healthy participants with obesity (mean age, 27 years) underwent magnetic resonance spectroscopy scanning coupled with a hyperglycemic clamp (target, ~180 mg/dL) using [1-13C] glucose to measure brain glucose uptake and metabolism, as well as peripheral markers of insulin resistance. RESULTS Individuals with obesity demonstrated an ~20% lower ratio of brain glucose uptake to cerebral glucose metabolic rate (Tmax/CMRglucose) than lean participants (2.12 ± 0.51 vs. 2.67 ± 0.51; p = 0.04). The cerebral tricarboxylic acid cycle flux (VTCA) was similar between the two groups (p = 0.64). There was a negative correlation between total nonesterified fatty acids and Tmax/CMRglucose (r = -0.477; p = 0.045). CONCLUSIONS We conclude that CMRglucose is unlikely to differ between groups due to similar VTCA, and, therefore, the glucose transport Tmax is lower in individuals with obesity. These human findings suggest that obesity is associated with reduced cerebral glucose transport capacity even at a young age and in the absence of other cardiometabolic comorbidities, which may have implications for long-term brain function and health.
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Affiliation(s)
- Felona Gunawan
- Section of Endocrinology and Metabolism, Department of Internal Medicine, Yale School of Medicine, Yale University, New Haven, Connecticut, USA
| | - Brooke C Matson
- Division of Endocrinology and Metabolism, Department of Medicine, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA
| | - Anastasia Coppoli
- Yale Magnetic Resonance Research Center, Department of Radiology and Biomedical Imaging, Yale School of Medicine, Yale University, New Haven, Connecticut, USA
| | - Lihong Jiang
- Yale Magnetic Resonance Research Center, Department of Radiology and Biomedical Imaging, Yale School of Medicine, Yale University, New Haven, Connecticut, USA
| | - Yuyan Ding
- Section of Endocrinology and Metabolism, Department of Internal Medicine, Yale School of Medicine, Yale University, New Haven, Connecticut, USA
| | - Rachel Perry
- Section of Endocrinology and Metabolism, Department of Internal Medicine, Yale School of Medicine, Yale University, New Haven, Connecticut, USA
| | - Elizabeth Sanchez-Rangel
- Section of Endocrinology and Metabolism, Department of Internal Medicine, Yale School of Medicine, Yale University, New Haven, Connecticut, USA
| | - Renata Belfort DeAguiar
- Section of Endocrinology and Metabolism, Department of Internal Medicine, Yale School of Medicine, Yale University, New Haven, Connecticut, USA
| | - Kevin L Behar
- Yale Magnetic Resonance Research Center, Department of Radiology and Biomedical Imaging, Yale School of Medicine, Yale University, New Haven, Connecticut, USA
- Department of Psychiatry, Yale School of Medicine, Yale University, New Haven, Connecticut, USA
| | - Douglas L Rothman
- Yale Magnetic Resonance Research Center, Department of Radiology and Biomedical Imaging, Yale School of Medicine, Yale University, New Haven, Connecticut, USA
- Department of Biomedical Engineering, Yale University, New Haven, Connecticut, USA
| | - Graeme F Mason
- Yale Magnetic Resonance Research Center, Department of Radiology and Biomedical Imaging, Yale School of Medicine, Yale University, New Haven, Connecticut, USA
- Department of Psychiatry, Yale School of Medicine, Yale University, New Haven, Connecticut, USA
- Department of Biomedical Engineering, Yale University, New Haven, Connecticut, USA
| | - Janice J Hwang
- Section of Endocrinology and Metabolism, Department of Internal Medicine, Yale School of Medicine, Yale University, New Haven, Connecticut, USA
- Division of Endocrinology and Metabolism, Department of Medicine, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA
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3
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DiNuzzo M, Dienel GA, Behar KL, Petroff OA, Benveniste H, Hyder F, Giove F, Michaeli S, Mangia S, Herculano-Houzel S, Rothman DL. Neurovascular coupling is optimized to compensate for the increase in proton production from nonoxidative glycolysis and glycogenolysis during brain activation and maintain homeostasis of pH, pCO 2, and pO 2. J Neurochem 2024; 168:632-662. [PMID: 37150946 PMCID: PMC10628336 DOI: 10.1111/jnc.15839] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Revised: 04/22/2023] [Accepted: 05/02/2023] [Indexed: 05/09/2023]
Abstract
During transient brain activation cerebral blood flow (CBF) increases substantially more than cerebral metabolic rate of oxygen consumption (CMRO2) resulting in blood hyperoxygenation, the basis of BOLD-fMRI contrast. Explanations for the high CBF versus CMRO2 slope, termed neurovascular coupling (NVC) constant, focused on maintenance of tissue oxygenation to support mitochondrial ATP production. However, paradoxically the brain has a 3-fold lower oxygen extraction fraction (OEF) than other organs with high energy requirements, like heart and muscle during exercise. Here, we hypothesize that the NVC constant and the capillary oxygen mass transfer coefficient (which in combination determine OEF) are co-regulated during activation to maintain simultaneous homeostasis of pH and partial pressure of CO2 and O2 (pCO2 and pO2). To test our hypothesis, we developed an arteriovenous flux balance model for calculating blood and brain pH, pCO2, and pO2 as a function of baseline OEF (OEF0), CBF, CMRO2, and proton production by nonoxidative metabolism coupled to ATP hydrolysis. Our model was validated against published brain arteriovenous difference studies and then used to calculate pH, pCO2, and pO2 in activated human cortex from published calibrated fMRI and PET measurements. In agreement with our hypothesis, calculated pH, pCO2, and pO2 remained close to constant independently of CMRO2 in correspondence to experimental measurements of NVC and OEF0. We also found that the optimum values of the NVC constant and OEF0 that ensure simultaneous homeostasis of pH, pCO2, and pO2 were remarkably similar to their experimental values. Thus, the high NVC constant is overall determined by proton removal by CBF due to increases in nonoxidative glycolysis and glycogenolysis. These findings resolve the paradox of the brain's high CBF yet low OEF during activation, and may contribute to explaining the vulnerability of brain function to reductions in blood flow and capillary density with aging and neurovascular disease.
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Affiliation(s)
| | - Gerald A Dienel
- Department of Neurology, University of Arkansas for Medical Sciences, Little Rock, AR, 72205 USA
- Department of Cell Biology and Physiology, University of New Mexico School of Medicine, Albuquerque, NM, 87131 USA
| | - Kevin L Behar
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, 06511 USA
| | - Ognen A Petroff
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, 06511 USA
| | - Helene Benveniste
- Department of Anesthesiology, Yale University, New Haven, CT, 06520 USA
- Department of Biomedical Engineering, Yale University, New Haven, CT, 06520 USA
| | - Fahmeed Hyder
- Department of Biomedical Engineering, Yale University, New Haven, CT, 06520 USA
- Department of Radiology, Magnetic Resonance Research Center (MRRC), Yale University, New Haven, CT, 06520 USA
| | - Federico Giove
- Centro Ricerche Enrico Fermi, Rome, RM, 00184 Italy
- Fondazione Santa Lucia IRCCS, Rome, RM, 00179 Italy
| | - Shalom Michaeli
- Department of Radiology, Center for Magnetic Resonance Research (CMRR), University of Minnesota, Minneapolis, MN, 55455 USA
| | - Silvia Mangia
- Department of Radiology, Center for Magnetic Resonance Research (CMRR), University of Minnesota, Minneapolis, MN, 55455 USA
| | - Suzana Herculano-Houzel
- Department of Psychology, Vanderbilt University, Nashville, TN
- Department of Biological Sciences, Vanderbilt University, Nashville, TN
- Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN
| | - Douglas L Rothman
- Department of Biomedical Engineering, Yale University, New Haven, CT, 06520 USA
- Department of Radiology, Magnetic Resonance Research Center (MRRC), Yale University, New Haven, CT, 06520 USA
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4
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Salvagno M, Geraldini F, Coppalini G, Robba C, Gouvea Bogossian E, Annoni F, Vitali E, Sterchele ED, Balestra C, Taccone FS. The Impact of Inotropes and Vasopressors on Cerebral Oxygenation in Patients with Traumatic Brain Injury and Subarachnoid Hemorrhage: A Narrative Review. Brain Sci 2024; 14:117. [PMID: 38391692 PMCID: PMC10886736 DOI: 10.3390/brainsci14020117] [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: 01/06/2024] [Revised: 01/17/2024] [Accepted: 01/22/2024] [Indexed: 02/24/2024] Open
Abstract
Traumatic brain injury (TBI) and subarachnoid hemorrhage (SAH) are critical neurological conditions that necessitate specialized care in the Intensive Care Unit (ICU). Managing cerebral perfusion pressure (CPP) and mean arterial pressure (MAP) is of primary importance in these patients. To maintain targeted MAP and CPP, vasopressors and/or inotropes are commonly used. However, their effects on cerebral oxygenation are not fully understood. The aim of this review is to provide an up-to date review regarding the current uses and pathophysiological issues related to the use of vasopressors and inotropes in TBI and SAH patients. According to our findings, despite achieving similar hemodynamic parameters and CPP, the effects of various vasopressors and inotropes on cerebral oxygenation, local CBF and metabolism are heterogeneous. Therefore, a more accurate understanding of the cerebral activity of these medications is crucial for optimizing patient management in the ICU setting.
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Affiliation(s)
- Michele Salvagno
- Department of Intensive Care, Hôpital Universitaire de Bruxelles (HUB), 1070 Brussels, Belgium
| | - Federico Geraldini
- Department of Anesthesia and Intensive Care, Ospedale Università di Padova, 35128 Padova, Italy
| | - Giacomo Coppalini
- Department of Anesthesia and Intensive Care, Humanitas Clinical and Research Center, 20089 Milano, Italy
- Department of Biomedical Sciences, Humanitas University, Pieve Emanuele, 20072 Milano, Italy
| | - Chiara Robba
- Anaesthesia and Intensive Care, IRCCS Policlinico San Martino, 16132 Genova, Italy
- Dipartimento di Scienze Chirurgiche Diagnostiche e Integrate, Università di Genova, 16132 Genova, Italy
| | - Elisa Gouvea Bogossian
- Department of Intensive Care, Hôpital Universitaire de Bruxelles (HUB), 1070 Brussels, Belgium
| | - Filippo Annoni
- Department of Intensive Care, Hôpital Universitaire de Bruxelles (HUB), 1070 Brussels, Belgium
| | - Eva Vitali
- Department of Intensive Care, Hôpital Universitaire de Bruxelles (HUB), 1070 Brussels, Belgium
| | - Elda Diletta Sterchele
- Department of Intensive Care, Hôpital Universitaire de Bruxelles (HUB), 1070 Brussels, Belgium
| | - Costantino Balestra
- Department Environmental, Occupational, Aging (Integrative) Physiology Laboratory, Haute Ecole Bruxelles-Brabant (HE2B), 1160 Brussels, Belgium
- Anatomical Research and Clinical Studies, Vrije Universiteit Brussels (VUB), 1090 Brussels, Belgium
- DAN Europe Research Division (Roseto-Brussels), 1160 Brussels, Belgium
- Motor Sciences Department, Physical Activity Teaching Unit, Université Libre de Bruxelles (ULB), 1050 Brussels, Belgium
| | - Fabio Silvio Taccone
- Department of Intensive Care, Hôpital Universitaire de Bruxelles (HUB), 1070 Brussels, Belgium
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5
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Goyal MS, Blazey T, Metcalf NV, McAvoy MP, Strain JF, Rahmani M, Durbin TJ, Xiong C, Benzinger TLS, Morris JC, Raichle ME, Vlassenko AG. Brain aerobic glycolysis and resilience in Alzheimer disease. Proc Natl Acad Sci U S A 2023; 120:e2212256120. [PMID: 36745794 PMCID: PMC9963219 DOI: 10.1073/pnas.2212256120] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Accepted: 01/04/2023] [Indexed: 02/08/2023] Open
Abstract
The distribution of brain aerobic glycolysis (AG) in normal young adults correlates spatially with amyloid-beta (Aβ) deposition in individuals with symptomatic and preclinical Alzheimer disease (AD). Brain AG decreases with age, but the functional significance of this decrease with regard to the development of AD symptomatology is poorly understood. Using PET measurements of regional blood flow, oxygen consumption, and glucose utilization-from which we derive AG-we find that cognitive impairment is strongly associated with loss of the typical youthful pattern of AG. In contrast, amyloid positivity without cognitive impairment was associated with preservation of youthful brain AG, which was even higher than that seen in cognitively unimpaired, amyloid negative adults. Similar findings were not seen for blood flow nor oxygen consumption. Finally, in cognitively unimpaired adults, white matter hyperintensity burden was found to be specifically associated with decreased youthful brain AG. Our results suggest that AG may have a role in the resilience and/or response to early stages of amyloid pathology and that age-related white matter disease may impair this process.
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Affiliation(s)
- Manu S. Goyal
- Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO63110
- Department of Neurology, Washington University School of Medicine, St. Louis, MO63110
- Neuroimaging Labs Research Center, Washington University School of Medicine, St. Louis, MO63110
- Knight Alzheimer Disease Research Center, Washington University School of Medicine, St. Louis, MO63108
- Department of Neuroscience, Washington University School of Medicine, St. Louis, MO63110
| | - Tyler Blazey
- Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO63110
- Neuroimaging Labs Research Center, Washington University School of Medicine, St. Louis, MO63110
| | - Nicholas V. Metcalf
- Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO63110
- Neuroimaging Labs Research Center, Washington University School of Medicine, St. Louis, MO63110
| | - Mark P. McAvoy
- Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO63110
- Neuroimaging Labs Research Center, Washington University School of Medicine, St. Louis, MO63110
- Program in Occupational Therapy, Washington University School of Medicine, St. Louis, MO63108
| | - Jeremy F. Strain
- Department of Neurology, Washington University School of Medicine, St. Louis, MO63110
- Neuroimaging Labs Research Center, Washington University School of Medicine, St. Louis, MO63110
| | - Maryam Rahmani
- Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO63110
- Neuroimaging Labs Research Center, Washington University School of Medicine, St. Louis, MO63110
| | - Tony J. Durbin
- Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO63110
- Neuroimaging Labs Research Center, Washington University School of Medicine, St. Louis, MO63110
| | - Chengjie Xiong
- Knight Alzheimer Disease Research Center, Washington University School of Medicine, St. Louis, MO63108
| | - Tammie L.-S. Benzinger
- Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO63110
- Neuroimaging Labs Research Center, Washington University School of Medicine, St. Louis, MO63110
- Knight Alzheimer Disease Research Center, Washington University School of Medicine, St. Louis, MO63108
| | - John C. Morris
- Department of Neurology, Washington University School of Medicine, St. Louis, MO63110
- Knight Alzheimer Disease Research Center, Washington University School of Medicine, St. Louis, MO63108
| | - Marcus E. Raichle
- Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO63110
- Department of Neurology, Washington University School of Medicine, St. Louis, MO63110
- Neuroimaging Labs Research Center, Washington University School of Medicine, St. Louis, MO63110
- Knight Alzheimer Disease Research Center, Washington University School of Medicine, St. Louis, MO63108
- Department of Neuroscience, Washington University School of Medicine, St. Louis, MO63110
- Department of Biomedical Engineering, Washington University School of Medicine, St. Louis, MO63130
- Department of Psychology & Brain Science, Washington University School of Medicine, St. Louis, MO63130
| | - Andrei G. Vlassenko
- Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO63110
- Neuroimaging Labs Research Center, Washington University School of Medicine, St. Louis, MO63110
- Knight Alzheimer Disease Research Center, Washington University School of Medicine, St. Louis, MO63108
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6
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Herculano-Houzel S, Rothman DL. From a Demand-Based to a Supply-Limited Framework of Brain Metabolism. Front Integr Neurosci 2022; 16:818685. [PMID: 35431822 PMCID: PMC9012138 DOI: 10.3389/fnint.2022.818685] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Accepted: 01/10/2022] [Indexed: 12/20/2022] Open
Abstract
What defines the rate of energy use by the brain, as well as per neurons of different sizes in different structures and animals, is one fundamental aspect of neuroscience for which much has been theorized, but very little data are available. The prevalent theories and models consider that energy supply from the vascular system to different brain regions is adjusted both dynamically and in the course of development and evolution to meet the demands of neuronal activity. In this perspective, we offer an alternative view: that regional rates of energy use might be mostly constrained by supply, given the properties of the brain capillary network, the highly stable rate of oxygen delivery to the whole brain under physiological conditions, and homeostatic constraints. We present evidence that these constraints, based on capillary density and tissue oxygen homeostasis, are similar between brain regions and mammalian species, suggesting they derive from fundamental biophysical limitations. The same constraints also determine the relationship between regional rates of brain oxygen supply and usage over the full physiological range of brain activity, from deep sleep to intense sensory stimulation, during which the apparent uncoupling of blood flow and oxygen use is still a predicted consequence of supply limitation. By carefully separating "energy cost" into energy supply and energy use, and doing away with the problematic concept of energetic "demands," our new framework should help shine a new light on the neurovascular bases of metabolic support of brain function and brain functional imaging. We speculate that the trade-offs between functional systems and even the limitation to a single attentional spot at a time might be consequences of a strongly supply-limited brain economy. We propose that a deeper understanding of brain energy supply constraints will provide a new evolutionary understanding of constraints on brain function due to energetics; offer new diagnostic insight to disturbances of brain metabolism; lead to clear, testable predictions on the scaling of brain metabolic cost and the evolution of brains of different sizes; and open new lines of investigation into the microvascular bases of progressive cognitive loss in normal aging as well as metabolic diseases.
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Affiliation(s)
- Suzana Herculano-Houzel
- Department of Psychology, Vanderbilt University, Nashville, TN, United States,Department of Biological Sciences, Vanderbilt University, Nashville, TN, United States,Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN, United States,*Correspondence: Suzana Herculano-Houzel,
| | - Douglas L. Rothman
- Department of Radiology and Biomedical Imaging, Yale University, New Haven, CT, United States,Department of Biomedical Engineering, Yale University, New Haven, CT, United States,Magnetic Resonance Research Center, Yale University, New Haven, CT, United States
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7
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Faria-Pereira A, Morais VA. Synapses: The Brain's Energy-Demanding Sites. Int J Mol Sci 2022; 23:3627. [PMID: 35408993 PMCID: PMC8998888 DOI: 10.3390/ijms23073627] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Revised: 03/16/2022] [Accepted: 03/22/2022] [Indexed: 02/04/2023] Open
Abstract
The brain is one of the most energy-consuming organs in the mammalian body, and synaptic transmission is one of the major contributors. To meet these energetic requirements, the brain primarily uses glucose, which can be metabolized through glycolysis and/or mitochondrial oxidative phosphorylation. The relevance of these two energy production pathways in fulfilling energy at presynaptic terminals has been the subject of recent studies. In this review, we dissect the balance of glycolysis and oxidative phosphorylation to meet synaptic energy demands in both resting and stimulation conditions. Besides ATP output needs, mitochondria at synapse are also important for calcium buffering and regulation of reactive oxygen species. These two mitochondrial-associated pathways, once hampered, impact negatively on neuronal homeostasis and synaptic activity. Therefore, as mitochondria assume a critical role in synaptic homeostasis, it is becoming evident that the synaptic mitochondria population possesses a distinct functional fingerprint compared to other brain mitochondria. Ultimately, dysregulation of synaptic bioenergetics through glycolytic and mitochondrial dysfunctions is increasingly implicated in neurodegenerative disorders, as one of the first hallmarks in several of these diseases are synaptic energy deficits, followed by synapse degeneration.
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Affiliation(s)
| | - Vanessa A. Morais
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, 1649-028 Lisboa, Portugal;
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8
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Tamayo A, Siepmann T. Regulation of Blood Flow in the Cerebral Posterior Circulation by Parasympathetic Nerve Fibers: Physiological Background and Possible Clinical Implications in Patients With Vertebrobasilar Stroke. Front Neurol 2021; 12:660373. [PMID: 34777191 PMCID: PMC8585859 DOI: 10.3389/fneur.2021.660373] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Accepted: 09/23/2021] [Indexed: 01/14/2023] Open
Abstract
Posterior circulation involves the vertebrobasilar arteries, which supply oxygen and glucose to vital human brainstem structures and other areas. This complex circulatory- perfusion system is not homogenous throughout the day; rather, its hemodynamic changes rely on physiological demands, ensuring brainstem perfusion. This dynamic autoregulatory pattern maintains cerebral perfusion during blood pressure changes. Accumulative evidence suggests that activity within the autonomic nervous system is involved in the regulation of cerebral blood flow. Neither the sympathetic nor parasympathetic nervous systems work independently. Functional studies have shown a tight and complicated cross talk between these systems. In pathological processes where sympathetic stimulation is present, systemic vasoconstriction is followed, representing the most important CNS parasympathetic trigger that will promote local vasodilation. Stroke is a clear example of this process. The posterior circulation is affected in 30% of strokes, causing high morbidity and mortality outcomes. Currently, the management of ischemic stroke is focused on thrombolytic treatment and endovascular thrombectomy within an overall tight 4.5 to 6 h ischemic time window. Therefore, the autonomic nervous system could represent a potential therapeutic target to modulate reperfusion after cerebral ischemia through vasodilation, which could potentially decrease infarct size and increase the thrombolytic therapeutic ischemic window. In addition, shifting the autonomic nervous system balance toward its parasympathetic branch has shown to enhance neurogenesis and decrease local inflammation. Regretfully, the vast majority of animal models and human research on neuromodulation during brain ischemia have been focused on anterior circulation with disappointing results. In addition, the source of parasympathetic inputs in the vertebrobasilar system in humans is poorly understood, substantiating a gap and controversy in this area. Here, we reviewed current available literature regarding the parasympathetic vascular function and challenges of its stimulation in the vertebrobasilar system.
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Affiliation(s)
- Arturo Tamayo
- The Max Rady Faculty of Health Sciences, Department of Medicine, Section of Neurology, WRHA, Winnipeg and Brandon Regional Health Centre, University of Manitoba, Winnipeg, MB, Canada.,Department of Health Care Sciences, Center for Clinical Research and Management Education, Dresden International University, Dresden, Germany
| | - Timo Siepmann
- Department of Health Care Sciences, Center for Clinical Research and Management Education, Dresden International University, Dresden, Germany.,Department of Neurology, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
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Early Life Stress and Metabolic Plasticity of Brain Cells: Impact on Neurogenesis and Angiogenesis. Biomedicines 2021; 9:biomedicines9091092. [PMID: 34572278 PMCID: PMC8470044 DOI: 10.3390/biomedicines9091092] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Revised: 08/15/2021] [Accepted: 08/23/2021] [Indexed: 12/15/2022] Open
Abstract
Early life stress (ELS) causes long-lasting changes in brain plasticity induced by the exposure to stress factors acting prenatally or in the early postnatal ontogenesis due to hyperactivation of hypothalamic-pituitary-adrenal axis and sympathetic nervous system, development of neuroinflammation, aberrant neurogenesis and angiogenesis, and significant alterations in brain metabolism that lead to neurological deficits and higher susceptibility to development of brain disorders later in the life. As a key component of complex pathogenesis, ELS-mediated changes in brain metabolism associate with development of mitochondrial dysfunction, loss of appropriate mitochondria quality control and mitochondrial dynamics, deregulation of metabolic reprogramming. These mechanisms are particularly critical for maintaining the pool and development of brain cells within neurogenic and angiogenic niches. In this review, we focus on brain mitochondria and energy metabolism related to tightly coupled neurogenic and angiogenic events in healthy and ELS-affected brain, and new opportunities to develop efficient therapeutic strategies aimed to restore brain metabolism and reduce ELS-induced impairments of brain plasticity.
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Bennett JP, Onyango IG. Energy, Entropy and Quantum Tunneling of Protons and Electrons in Brain Mitochondria: Relation to Mitochondrial Impairment in Aging-Related Human Brain Diseases and Therapeutic Measures. Biomedicines 2021; 9:225. [PMID: 33671585 PMCID: PMC7927033 DOI: 10.3390/biomedicines9020225] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Revised: 02/18/2021] [Accepted: 02/18/2021] [Indexed: 11/16/2022] Open
Abstract
Adult human brains consume a disproportionate amount of energy substrates (2-3% of body weight; 20-25% of total glucose and oxygen). Adenosine triphosphate (ATP) is a universal energy currency in brains and is produced by oxidative phosphorylation (OXPHOS) using ATP synthase, a nano-rotor powered by the proton gradient generated from proton-coupled electron transfer (PCET) in the multi-complex electron transport chain (ETC). ETC catalysis rates are reduced in brains from humans with neurodegenerative diseases (NDDs). Declines of ETC function in NDDs may result from combinations of nitrative stress (NS)-oxidative stress (OS) damage; mitochondrial and/or nuclear genomic mutations of ETC/OXPHOS genes; epigenetic modifications of ETC/OXPHOS genes; or defects in importation or assembly of ETC/OXPHOS proteins or complexes, respectively; or alterations in mitochondrial dynamics (fusion, fission, mitophagy). Substantial free energy is gained by direct O2-mediated oxidation of NADH. Traditional ETC mechanisms require separation between O2 and electrons flowing from NADH/FADH2 through the ETC. Quantum tunneling of electrons and much larger protons may facilitate this separation. Neuronal death may be viewed as a local increase in entropy requiring constant energy input to avoid. The ATP requirement of the brain may partially be used for avoidance of local entropy increase. Mitochondrial therapeutics seeks to correct deficiencies in ETC and OXPHOS.
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Affiliation(s)
| | - Isaac G. Onyango
- International Clinical Research Center, St. Anne’s University Hospital, CZ-65691 Brno, Czech Republic;
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Effect of Hydroxyethyl Starch Loading on Glycocalyx Shedding and Cerebral Metabolism During Surgery. J Surg Res 2020; 246:274-283. [DOI: 10.1016/j.jss.2019.09.030] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2019] [Revised: 08/04/2019] [Accepted: 09/13/2019] [Indexed: 12/24/2022]
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12
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Abstract
People with bipolar disorder (BD) all too often have suboptimal long-term outcomes with existing treatment options. They experience relapsing episodes of depression and mania and also have interepisodic mood and anxiety symptoms. We need to have a better understanding of the pathophysiology of BD if we are to make progress in improving these outcomes. This chapter will focus on the critical role of mitochondria in human functioning, oxidative stress, and the biological mechanisms of mitochondria in BD. Additionally, this chapter will present the evidence that, at least for some people, BD is a product of mitochondrial dysregulation. We review the modulators of mitochondria, the connection between current BD medication treatments and mitochondria, and additional medications that have theoretical potential to treat BD.
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