1
|
Smith ME, Bazinet RP. Unraveling brain palmitic acid: Origin, levels and metabolic fate. Prog Lipid Res 2024; 96:101300. [PMID: 39222711 DOI: 10.1016/j.plipres.2024.101300] [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: 03/26/2024] [Revised: 08/26/2024] [Accepted: 08/28/2024] [Indexed: 09/04/2024]
Abstract
In the human brain, palmitic acid (16:0; PAM) comprises nearly half of total brain saturates and has been identified as the third most abundant fatty acid overall. Brain PAM supports the structure of membrane phospholipids, provides energy, and regulates protein stability. Sources underlying the origin of brain PAM are both diet and endogenous synthesis via de novo lipogenesis (DNL), primarily from glucose. However, studies investigating the origin of brain PAM are limited to tracer studies utilizing labelled (14C/11C/3H/2H) PAM, and results vary based on the model and tracer used. Nevertheless, there is evidence PAM is synthesized locally in the brain, in addition to obtained directly from the diet. Herein, we provide an overview of brain PAM origin, entry to the brain, metabolic fate, and factors influencing brain PAM kinetics and levels, the latter in the context of age, as well as neurological diseases and psychiatric disorders. Additionally, we briefly summarize the role of PAM in signaling at the level of the brain. We add to the literature a rudimentary summary on brain PAM metabolism.
Collapse
Affiliation(s)
- Mackenzie E Smith
- Department of Nutritional Sciences, University of Toronto, 1 King's College Circle, Toronto, Ontario M5S 1A8, Canada
| | - Richard P Bazinet
- Department of Nutritional Sciences, University of Toronto, 1 King's College Circle, Toronto, Ontario M5S 1A8, Canada.
| |
Collapse
|
2
|
Seeger DR, Schofield B, Besch D, Golovko SA, Kotha P, Parmer M, Solaymani-Mohammadi S, Golovko MY. Exogenous oxygen is required for prostanoid induction under brain ischemia as evidence for a novel regulatory mechanism. J Lipid Res 2023; 64:100452. [PMID: 37783389 PMCID: PMC10630775 DOI: 10.1016/j.jlr.2023.100452] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Revised: 09/25/2023] [Accepted: 09/28/2023] [Indexed: 10/04/2023] Open
Abstract
Previously, we and others reported a rapid and dramatic increase in brain prostanoids (PG), including prostaglandins, prostacyclins, and thromboxanes, under ischemia that is traditionally explained through the activation of esterified arachidonic acid (20:4n6) release by phospholipases as a substrate for cyclooxygenases (COX). However, the availability of another required COX substrate, oxygen, has not been considered in this mechanism. To address this mechanism for PG upregulation through oxygen availability, we analyzed mouse brain PG, free 20:4n6, and oxygen levels at different time points after ischemic onset using head-focused microwave irradiation (MW) to inactivate enzymes in situ before craniotomy. The oxygen half-life in the ischemic brain was 5.32 ± 0.45 s and dropped to undetectable levels within 12 s of ischemia onset, while there were no significant free 20:4n6 or PG changes at 30 s of ischemia. Furthermore, there was no significant PG increase at 2 and 10 min after ischemia onset compared to basal levels, while free 20:4n6 was increased ∼50 and ∼100 fold, respectively. However, PG increased ∼30-fold when ischemia was followed by craniotomy of nonMW tissue that provided oxygen for active enzymes. Moreover, craniotomy performed under anoxic conditions without MW did not result in PG induction, while exposure of these brains to atmospheric oxygen significantly induced PG. Our results indicate, for the first time, that oxygen availability is another important regulatory factor for PG production under ischemia. Further studies are required to investigate the physiological role of COX/PG regulation through tissue oxygen concentration.
Collapse
Affiliation(s)
- Drew R Seeger
- Department of Biomedical Sciences, School of Medicine and Health Science, University of North Dakota, Grand Forks, ND, USA
| | - Brennon Schofield
- Department of Biomedical Sciences, School of Medicine and Health Science, University of North Dakota, Grand Forks, ND, USA
| | - Derek Besch
- Department of Biomedical Sciences, School of Medicine and Health Science, University of North Dakota, Grand Forks, ND, USA
| | - Svetlana A Golovko
- Department of Biomedical Sciences, School of Medicine and Health Science, University of North Dakota, Grand Forks, ND, USA
| | - Peddanna Kotha
- Department of Biomedical Sciences, School of Medicine and Health Science, University of North Dakota, Grand Forks, ND, USA
| | - Meredith Parmer
- Department of Biomedical Sciences, School of Medicine and Health Science, University of North Dakota, Grand Forks, ND, USA
| | - Shahram Solaymani-Mohammadi
- Department of Biomedical Sciences, School of Medicine and Health Science, University of North Dakota, Grand Forks, ND, USA
| | - Mikhail Y Golovko
- Department of Biomedical Sciences, School of Medicine and Health Science, University of North Dakota, Grand Forks, ND, USA.
| |
Collapse
|
3
|
Seeger DR, Golovko SA, Golovko MY. Blood-Brain Barrier Is the Major Site for a Rapid and Dramatic Prostanoid Increase upon Brain Global Ischemia. Lipids 2019; 55:79-85. [PMID: 31814137 DOI: 10.1002/lipd.12205] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Revised: 11/12/2019] [Accepted: 11/15/2019] [Indexed: 12/17/2022]
Abstract
We and others have demonstrated a rapid and dramatic increase in brain prostanoids upon decapitation-induced brain global ischemia and injury. However, the mechanism for this induction, including the cell types involved, are unknown. In the present study, we have validated and applied a pharmacological approach to inhibit prostanoid synthesis in the blood-brain barrier including endothelial cells. Our results indicate that a nonspecific cyclooxygenase (COX) inhibitor, ketorolac, does not pass the blood-brain barrier and does not enter red blood cells but penetrates endothelial cells. Ketorolac treatment did not affect basal prostanoid levels but completely prevented prostanoid induction upon global ischemia. These data indicate that basal prostanoids are synthesized in brain parenchyma cells, while inducible prostanoids are synthesized in the blood-brain barrier, most likely in endothelial cells. However, future studies with cell and COX isoform-specific gene ablation are needed to further validate this conclusion. These findings identify endothelial cells as a possible target for the development of pharmacological approaches to selectively attenuate inducible prostanoid pools without affecting basal levels under brain ischemia, trauma, surgery, and other related conditions.
Collapse
Affiliation(s)
- Drew R Seeger
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, 1301 N. Columbia Rd., Grand Forks, ND, 58202-9037, USA
| | - Svetlana A Golovko
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, 1301 N. Columbia Rd., Grand Forks, ND, 58202-9037, USA
| | - Mikhail Y Golovko
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, 1301 N. Columbia Rd., Grand Forks, ND, 58202-9037, USA
| |
Collapse
|
4
|
Fiandaca MS, Gross TJ, Johnson TM, Hu MT, Evetts S, Wade-Martins R, Merchant-Borna K, Bazarian J, Cheema AK, Mapstone M, Federoff HJ. Potential Metabolomic Linkage in Blood between Parkinson's Disease and Traumatic Brain Injury. Metabolites 2018; 8:metabo8030050. [PMID: 30205491 PMCID: PMC6161135 DOI: 10.3390/metabo8030050] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Revised: 09/01/2018] [Accepted: 09/04/2018] [Indexed: 12/17/2022] Open
Abstract
The etiologic basis for sporadic forms of neurodegenerative diseases has been elusive but likely represents the product of genetic predisposition and various environmental factors. Specific gene-environment interactions have become more salient owing, in part, to the elucidation of epigenetic mechanisms and their impact on health and disease. The linkage between traumatic brain injury (TBI) and Parkinson's disease (PD) is one such association that currently lacks a mechanistic basis. Herein, we present preliminary blood-based metabolomic evidence in support of potential association between TBI and PD. Using untargeted and targeted high-performance liquid chromatography-mass spectrometry we identified metabolomic biomarker profiles in a cohort of symptomatic mild TBI (mTBI) subjects (n = 75) 3⁻12 months following injury (subacute) and TBI controls (n = 20), and a PD cohort with known PD (n = 20) or PD dementia (PDD) (n = 20) and PD controls (n = 20). Surprisingly, blood glutamic acid levels in both the subacute mTBI (increased) and PD/PDD (decreased) groups were notably altered from control levels. The observed changes in blood glutamic acid levels in mTBI and PD/PDD are discussed in relation to other metabolite profiling studies. Should our preliminary results be replicated in comparable metabolomic investigations of TBI and PD cohorts, they may contribute to an "excitotoxic" linkage between TBI and PD/PDD.
Collapse
Affiliation(s)
- Massimo S Fiandaca
- Translational Laboratory and Biorepository, Department of Neurology, University of California Irvine School of Medicine, Irvine, CA 92697-3910, USA.
- Department of Neurological Surgery, University of California Irvine School of Medicine, Irvine, CA 92697-3910, USA.
- Department of Anatomy & Neurobiology, University of California Irvine School of Medicine, Irvine, CA 92697-3910, USA.
| | - Thomas J Gross
- Translational Laboratory and Biorepository, Department of Neurology, University of California Irvine School of Medicine, Irvine, CA 92697-3910, USA.
- Department of Anatomy & Neurobiology, University of California Irvine School of Medicine, Irvine, CA 92697-3910, USA.
| | - Thomas M Johnson
- Intrepid Spirit Concussion Recovery Center, Naval Medical Center Camp Lejeune, Jacksonville, NC 28540, USA.
| | - Michele T Hu
- Nuffield Department of Clinical Neurosciences, University of Oxford, 01865 Oxford, UK.
- Department of Neurology, John Radcliffe Hospital, Oxford University Hospitals Trust, Oxford 01865, UK.
| | - Samuel Evetts
- Nuffield Department of Clinical Neurosciences, University of Oxford, 01865 Oxford, UK.
| | - Richard Wade-Martins
- Department of Physiology, Anatomy and Genetics, Oxford Parkinson's Disease Centre, University of Oxford, Oxford 01865, UK.
| | - Kian Merchant-Borna
- Department of Emergency Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY 14604, USA.
| | - Jeffrey Bazarian
- Department of Emergency Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY 14604, USA.
| | - Amrita K Cheema
- Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, DC 20001, USA.
- Department of Biochemistry and Molecular & Cellular Biology, Georgetown University Medical Center, Washington, DC 20001, USA.
| | - Mark Mapstone
- Translational Laboratory and Biorepository, Department of Neurology, University of California Irvine School of Medicine, Irvine, CA 92697-3910, USA.
| | - Howard J Federoff
- Translational Laboratory and Biorepository, Department of Neurology, University of California Irvine School of Medicine, Irvine, CA 92697-3910, USA.
| |
Collapse
|
5
|
Chen CT, Domenichiello AF, Trépanier MO, Liu Z, Masoodi M, Bazinet RP. The low levels of eicosapentaenoic acid in rat brain phospholipids are maintained via multiple redundant mechanisms. J Lipid Res 2013; 54:2410-22. [PMID: 23836105 PMCID: PMC3735939 DOI: 10.1194/jlr.m038505] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Revised: 06/26/2013] [Indexed: 12/19/2022] Open
Abstract
Brain eicosapentaenoic acid (EPA) levels are 250- to 300-fold lower than docosahexaenoic acid (DHA), at least partly, because EPA is rapidly β-oxidized and lost from brain phospholipids. Therefore, we examined if β-oxidation was necessary for maintaining low EPA levels by inhibiting β-oxidation with methyl palmoxirate (MEP). Furthermore, because other metabolic differences between DHA and EPA may also contribute to their vastly different levels, this study aimed to quantify the incorporation and turnover of DHA and EPA into brain phospholipids. Fifteen-week-old rats were subjected to vehicle or MEP prior to a 5 min intravenous infusion of (14)C-palmitate, (14)C-DHA, or (14)C-EPA. MEP reduced the radioactivity of brain aqueous fractions for (14)C-palmitate-, (14)C-EPA-, and (14)C-DHA-infused rats by 74, 54, and 23%, respectively; while it increased the net rate of incorporation of plasma unesterified palmitate into choline glycerophospholipids and phosphatidylinositol and EPA into ethanolamine glycerophospholipids and phosphatidylserine. MEP also increased the synthesis of n-3 docosapentaenoic acid (n-3 DPA) from EPA. Moreover, the recycling of EPA into brain phospholipids was 154-fold lower than DHA. Therefore, the low levels of EPA in the brain are maintained by multiple redundant pathways including β-oxidation, decreased incorporation from plasma unesterified FA pool, elongation/desaturation to n-3 DPA, and lower recycling within brain phospholipids.
Collapse
Affiliation(s)
- Chuck T. Chen
- Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Toronto, ON, Canada M5S 3E2; and
| | - Anthony F. Domenichiello
- Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Toronto, ON, Canada M5S 3E2; and
| | - Marc-Olivier Trépanier
- Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Toronto, ON, Canada M5S 3E2; and
| | - Zhen Liu
- Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Toronto, ON, Canada M5S 3E2; and
| | - Mojgan Masoodi
- Nestlé Institute of Health Sciences SA, Campus EPFL, Quartier de l'innovation, bâtiment G, 1015 Lausanne, Switzerland
| | - Richard P. Bazinet
- Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Toronto, ON, Canada M5S 3E2; and
| |
Collapse
|
6
|
Igarashi M, Kim HW, Gao F, Chang L, Ma K, Rapoport SI. Fifteen weeks of dietary n-3 polyunsaturated fatty acid deprivation increase turnover of n-6 docosapentaenoic acid in rat-brain phospholipids. BIOCHIMICA ET BIOPHYSICA ACTA 2012; 1821:1235-43. [PMID: 22142872 PMCID: PMC3348251 DOI: 10.1016/j.bbalip.2011.11.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2011] [Revised: 10/25/2011] [Accepted: 11/02/2011] [Indexed: 11/23/2022]
Abstract
Docosapentaenoic acid (DPAn-6, 22:5n-6) is an n-6 polyunsaturated fatty acid (PUFA) whose brain concentration can be increased in rodents by dietary n-3 PUFA deficiency, which may contribute to their behavioral dysfunction. We used our in vivo intravenous infusion method to see if brain DPAn-6 turnover and metabolism also were altered with deprivation. We studied male rats that had been fed for 15 weeks post-weaning an n-3 PUFA adequate diet containing 4.6% alpha-linolenic acid (α-LNA, 18:3n-3) or a deficient diet (0.2% α-LNA), each lacking docosahexaenoic acid (22:6n-3) and arachidonic acid (AA, 20:4n-6). [1-(14)C]DPAn-6 was infused intravenously for 5min in unanesthetized rats, after which the brain underwent high-energy microwaving, and then was analyzed. The n-3 PUFA deficient compared with adequate diet increased DPAn-6 and decreased DHA concentrations in plasma and brain, while minimally changing brain AA concentration. Incorporation rates of unesterified DPAn-6 from plasma into individual brain phospholipids were increased 5.2-7.7 fold, while turnover rates were increased 2.1-4.7 fold. The observations suggest that increased metabolism and brain concentrations of DPAn-6 and its metabolites, together with a reduced brain DHA concentration, contribute to behavioral and functional abnormalities reported with dietary n-3 PUFA deprivation in rodents. (196 words).
Collapse
Affiliation(s)
- Miki Igarashi
- National Institute on Aging, National Institutes of Health, Bethesda, MD, USA.
| | | | | | | | | | | |
Collapse
|
7
|
Ramadan E, Chang L, Chen M, Ma K, Hall FS, Uhl GR, Rapoport SI, Basselin M. Knocking out the dopamine reuptake transporter (DAT) does not change the baseline brain arachidonic acid signal in the mouse. Int J Neurosci 2012; 122:373-80. [PMID: 22376027 PMCID: PMC3464054 DOI: 10.3109/00207454.2012.665972] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
BACKGROUND Dopamine transporter (DAT) homozygous knockout (DAT(-/-)) mice have a 10-fold higher extracellular (DA) concentration in the caudate-putamen and nucleus accumbens than do wildtype (DAT(+/+)) mice, but show reduced presynaptic DA synthesis and fewer postsynaptic D(2) receptors. One aspect of neurotransmission involves DA binding to postsynaptic D(2)-like receptors coupled to cytosolic phospholipase A(2) (cPLA(2)), which releases the second messenger, arachidonic acid (AA), from synaptic membrane phospholipid. We hypothesized that tonic overactivation of D(2)-like receptors in DAT(-/-) mice due to the excess DA would not increase brain AA signaling, because of compensatory downregulation of postsynaptic DA signaling mechanisms. METHODS [1-(14)C]AA was infused intravenously for 3 min in unanesthetized DAT(+/+), heterozygous (DAT(+/-)), and DAT(-/-) mice. AA incorporation coefficients k* and rates J(in), markers of AA metabolism and signaling, were imaged in 83 brain regions using quantitative autoradiography; brain cPLA(2)-IV activity also was measured. RESULTS Neither k* nor J(in) for AA in any brain region, or brain cPLA(2)-IV activity, differed significantly among DAT(-/-), DAT(+/-), and DAT(+/+) mice. CONCLUSIONS These results differ from reported increases in k* and J(in) for AA, and in brain cPLA(2) expression, in serotonin reuptake transporter (5-HTT) knockout mice, and suggest that postsynaptic dopaminergic neurotransmission mechanisms involving AA are downregulated despite elevated DA in DAT(-/-) mice.
Collapse
Affiliation(s)
- Epolia Ramadan
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, MD 20892, USA.
| | | | | | | | | | | | | | | |
Collapse
|
8
|
Chen CT, Liu Z, Bazinet RP. Rapid de-esterification and loss of eicosapentaenoic acid from rat brain phospholipids: an intracerebroventricular study. J Neurochem 2010; 116:363-73. [DOI: 10.1111/j.1471-4159.2010.07116.x] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
|
9
|
Rahman T, Taha AY, Song BJ, Orr SK, Liu Z, Chen CT, Bazinet RP. The very low density lipoprotein receptor is not necessary for maintaining brain polyunsaturated fatty acid concentrations. Prostaglandins Leukot Essent Fatty Acids 2010; 82:141-5. [PMID: 20106645 DOI: 10.1016/j.plefa.2009.11.003] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2009] [Accepted: 11/05/2009] [Indexed: 12/23/2022]
Abstract
Polyunsaturated fatty acids (PUFA), especially docosahexaenoic and arachidonic acids, as well as cholesterol are important for neural development and maintaining brain function. However, in contrast to cholesterol, the brain is unable to synthesize the required amounts of these PUFA de novo and requires a constant supply from plasma. Suggested pools of uptake include plasma unesterified PUFA or the uptake of PUFA-containing lipoproteins via lipoprotein receptors into endothelial cells of the blood brain barrier. Our study tested whether the very low density lipoprotein receptor (VLDLr) is necessary for maintaining brain PUFA and cholesterol concentrations. Moreover, since VLDLr knockout (VLDLr(-/-)) mice have been reported to have behavioural deficits, this study asked the question whether altered brain PUFA and cholesterol concentrations might be related to these deficits. VLDLr(-/-) and wild-type mice had ad libitum access to chow. At 7 weeks of age the mice were sacrificed, and the cortex, cerebellum, hippocampus, and the remainder of the brain were isolated for total fatty acid and cholesterol analyses. There were no differences in total lipid PUFA or cholesterol concentrations in any of the four brain regions between VLDLr(-/-) and wild-type mice. These findings demonstrate that the VLDLr is not necessary for maintaining brain PUFA concentrations and suggest that other mechanisms to transport PUFA into the brain must exist.
Collapse
Affiliation(s)
- Tupur Rahman
- Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, FitzGerald Building, 150 College Street, Room 306, Toronto, ON, Canada
| | | | | | | | | | | | | |
Collapse
|
10
|
Chang L, Rapoport SI, Nguyen HN, Greenstein D, Chen M, Basselin M. Acute nicotine reduces brain arachidonic acid signaling in unanesthetized rats. J Cereb Blood Flow Metab 2009; 29:648-58. [PMID: 19142197 PMCID: PMC2704339 DOI: 10.1038/jcbfm.2008.159] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Nicotine exerts its central effects by activating pre- and postsynaptic nicotinic acetylcholine receptors (nAChRs). Presynaptic nAChRs modulate the release of many neurotransmitters that bind to postsynaptic receptors. These may be coupled to the activation of cytosolic phospholipase A(2) (cPLA(2)), which hydrolyzes arachidonic acid (AA) from membrane phospholipids. We hypothesized that nicotine would modify brain signaling involving AA by binding to nAChRs. Nicotine (0.1 mg/kg, subcutaneously) or saline was injected 2 or 10 mins before infusing [1-(14)C]AA in unanesthetized rats. The AA incorporation coefficient k(*) (a marker of the AA signal) was measured in 80 brain regions by quantitative autoradiography. Nicotine, compared to saline, when administrated 2 mins before [1-(14)C]AA infusion, significantly decreased k(*) for AA in 26 regions, including cerebral cortex, thalamus, and habenula-interpeduncular regions, by 13% to 45%. These decreases could be entirely prevented by pretreatment with mecamylamine (1.0 mg/kg, subcutaneously). When administered 10 mins before [1-(14)C]AA infusion, nicotine did not alter any value of k(*). In summary, nicotine given to unanesthetized rats rapidly reduces signaling involving AA in brain regions containing nAChRs, likely by modulating the presynaptic release of neurotransmitters. The effect shows rapid desensitization and is produced at a nicotine dose equivalent to smoking one cigarette in humans.
Collapse
Affiliation(s)
- Lisa Chang
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, Maryland 20892, USA
| | | | | | | | | | | |
Collapse
|
11
|
Kaduce TL, Chen Y, Hell JW, Spector AA. Docosahexaenoic acid synthesis from n-3 fatty acid precursors in rat hippocampal neurons. J Neurochem 2008; 105:1525-35. [DOI: 10.1111/j.1471-4159.2008.05274.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
|
12
|
Gruetter R. Principles of the measurement of neuro-glial metabolism using in vivo 13C NMR spectroscopy. ACTA ACUST UNITED AC 2003. [DOI: 10.1016/s1569-2558(03)31018-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
|
13
|
Giovacchini G, Chang MCJ, Channing MA, Toczek M, Mason A, Bokde ALW, Connolly C, Vuong BK, Ma Y, Der MG, Doudet DJ, Herscovitch P, Eckelman WC, Rapoport SI, Carson RE. Brain incorporation of [11C]arachidonic acid in young healthy humans measured with positron emission tomography. J Cereb Blood Flow Metab 2002; 22:1453-62. [PMID: 12468890 DOI: 10.1097/01.wcb.0000033209.60867.7a] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Arachidonic acid (AA) is an important second messenger involved in signal transduction mediated by phospholipase A2. The goal of this study was to establish an in vivo quantitative method to examine the role of AA in this signaling process in the human brain. A simple irreversible uptake model was derived from rat studies and modified for positron emission tomography (PET) to quantify the incorporation rate K* of [11C]AA into brain. Dynamic 60-minute three-dimensional scans and arterial input functions were acquired in 8 young healthy adults studied at rest. Brain radioactivity was corrected for uptake of the metabolite [11C]CO2. K* and cerebral blood volume (Vb) were estimated pixel-by-pixel and were calculated in regions of interest. K* equaled 5.6+/-1.2 and 2.6+/-0.5 microL x min(-1) x mL(-1) in gray and white matter, respectively. K* and Vb values were found to be unchanged with data analysis periods from 20 to 60 minutes. Thus, PET can be used to obtain quantitative images of the incorporation rate K* of [11C]AA in the human brain. As brain incorporation of labeled AA has been shown in awake rats to be increased by pharmacological activation associated with phospholipase A2-signaling, PET and [11C]AA may be useful to measure signal transduction in the human brain.
Collapse
Affiliation(s)
- Giampiero Giovacchini
- Brain Physiology and Metabolism Section, National Institute on Aging, Bethesda, Maryland, U.S.A
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
14
|
Choi IY, Lei H, Gruetter R. Effect of deep pentobarbital anesthesia on neurotransmitter metabolism in vivo: on the correlation of total glucose consumption with glutamatergic action. J Cereb Blood Flow Metab 2002; 22:1343-51. [PMID: 12439292 DOI: 10.1097/01.wcb.0000040945.89393.46] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The effect of deep barbiturate anesthesia on brain glucose transport, TCA cycle flux, and aspartate, glutamate, and glutamine metabolism was assessed in the rat brain using 13C nuclear magnetic resonance spectroscopy at 9.4 T in conjunction with [1-13C] glucose infusions. Brain glucose concentrations were elevated, consistent with a twofold reduced cerebral metabolic rate for glucose (CMRglc) compared with light alpha-chloralose anesthesia. Using a mathematical model of neurotransmitter metabolism, several metabolic reaction rates were extracted from the rate of label incorporation. Total oxidative glucose metabolism, CMRglc(ox), was 0.33 +/- 0.03 micromol x g(-1) x min(-1). The neuronal TCA cycle rate was similar to that in the glia, 0.35 +/- 0.03 micromol x g(-1) x min(-1) and 0.26 +/- 0.06 micromol x g(-1) x min(-1), respectively, suggesting that neuronal energy metabolism was mainly affected. The rate of pyruvate carboxylation was 0.03 +/- 0.01 micromol x g(-1) x min(-1). The exchange rate between cytosolic glutamate and mitochondrial 2-oxoglutarate, Vx, was equal to the rate of neuronal pyruvate dehydrogenase flux. This indicates that Vx is coupled to CMRglc(ox), implying that the malate-aspartate shuttle is the major mechanism that facilitates label exchange across the inner mitochondrial membrane. The apparent rate of glutamatergic neurotransmission, V(NT), was 0.04 +/- 0.01 micromol x g x min, consistent with strong reductions in electrical activity. However, the rates of cerebral oxidative glucose metabolism and glutamatergic neurotransmission, CMRglc(ox)/V(NT), did not correlate with a 1:1 stoichiometry.
Collapse
Affiliation(s)
- In-Young Choi
- Department of Radiology, University of Minnesota, Center for MR Research, Minneapolis 55455, USA
| | | | | |
Collapse
|
15
|
Contreras MA, Greiner RS, Chang MC, Myers CS, Salem N, Rapoport SI. Nutritional deprivation of alpha-linolenic acid decreases but does not abolish turnover and availability of unacylated docosahexaenoic acid and docosahexaenoyl-CoA in rat brain. J Neurochem 2000; 75:2392-400. [PMID: 11080190 DOI: 10.1046/j.1471-4159.2000.0752392.x] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We applied our in vivo fatty acid method to examine concentrations, incorporation, and turnover rates of docosahexaenoic acid (22:6 n-3) in brains of rats subject to a dietary deficiency of alpha-linolenic acid (18:3 n-3) for three generations. Adult deficient and adequate rats of the F3 generation were infused intravenously with [4, 5-(3)H]docosahexaenoic acid over 5 min, after which brain uptake and distribution of tracer were measured. Before infusion, the plasma 22:6 n-3 level was 0.2 nmol ml(-1) in 18:3 n-3-deficient compared with 10.6 nmol ml(-1) in control rats. Brain unesterified 22:6 n-3 was not detectable, whereas docosahexaenoyl-CoA content was reduced by 95%, and 22:6 n-3 content in different phospholipid classes was reduced by 83-88% in deficient rats. Neither plasma or brain arachidonic acid (20:4 n-6) level was significantly changed with diet. Docosapentaenoic acid (22:5 n-6) reciprocally replaced 22:6 n-3 in brain phospholipids. Calculations using operational equations from our model indicated that 22:6 n-3 incorporation from plasma into brain was reduced 40-fold by 18:3 n-3 deficiency. Recycling of 22:6 n-3 due to deacylation-reacylation within phospholipids was reduced by 30-70% with the deficient diet, but animals nevertheless continued to produce 22:6 n-3 and docosahexaenoyl-CoA for brain function. We propose that functional brain effects of n-3 deficiency reflect altered ratios of n-6 to n-3 fatty acids.
Collapse
Affiliation(s)
- M A Contreras
- Section on Brain Physiology and Metabolism, National Institute on Aging, Bethesda 20892, USA.
| | | | | | | | | | | |
Collapse
|
16
|
Rapoport SI. In vivo fatty acid incorporation into brain phospholipids in relation to signal transduction and membrane remodeling. Neurochem Res 1999; 24:1403-15. [PMID: 10555781 DOI: 10.1023/a:1022584707352] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
A method and model are described to quantify in vivo turnover rates and half-lives of fatty acids within brain phospholipids. These "kinetic" parameters can be calculated by operational equations from measured rates of incorporation of intravenously injected fatty acid radiotracers into brain phospholipids. To do this, it is necessary to determine a "dilution factor" lambda, which estimates the contribution to the brain precursor acyl-CoA pool of fatty acids released from phospholipids through the action of PLA1 or PLA2. Some calculated fatty acid half-lives are minutes to hours, consistent with active participation of phospholipids in brain function and structure. The fatty acid method can be used to identify enzyme targets of drugs acting on phospholipid metabolism. For example, a reduced brain turnover of arachidonate by chronic lithium, demonstrated in rats by the fatty acid method, suggests that this agent, which is used to treat bipolar disorder, has for its target an arachidonate-specific PLA2. In another context, when combined with in vivo imaging by quantitative autoradiography in rodents or positron emission tomography in macaques or humans, the fatty acid method can localize and quantify normal and modified PLA2-mediated signal transduction in brain.
Collapse
Affiliation(s)
- S I Rapoport
- Laboratory of Neurosciences National Institute on Aging, National Institutes of Health, Bethesda, Maryland 20892, USA.
| |
Collapse
|